ENVIRONMENTAL FATES AND IMPACTS OF
MAJOR FOREST USE PESTICIDES
by:
Masood Ghassemi (Program Manager and Technical Director)
and
Linda Fargo, Page Painter, Pam Painter, Sandra Quinlivan, Robert Scofield and Anne Takata
December 1981
1ONMENTAL DIVISION
RE DON DO BEACH, CA 90278
EPA Contract No. 68-02-3174
Work Assignment Nos. 13, 14 and 62
EPA Project Officer: Michael Dellarco
Prepared for:
U.S. Environmental Protection Agency
Office of Pesticides and Toxic Substances
Washington, D.C. 20460
-------
PREFACE AND ACKNOWLEDGEMENTS
This compendium of environmental fate and impact profiles for major
forestry pesticides is one output of the Forest Use Chemicals Project, a
multi-contractor/grantee study sponsored by the Office of Pesticides and
Toxic Substances (OPTS) of the U.S. Environmental Protection Agency and
aimed at developing guidance for the timber production industry and public
on comparative risks and benefits of various chemical and non-chemical
approaches to pest management. Those on the TRW project staff wish to ex-
press their gratitude to the EPA Project Officer, Mr. Michael Dellarco, for
his advice and guidance during the course of the program. Special thanks
are also due to a'number of EPA technical and management staff, specially
to Mrs. Jan Auerbach, Chief of the Regulatory Support Branch, Special Pesti-
cide Review Division of OPTS, who reviewed program progress and provided
constructive suggestions and guidance.
Much of the data used in developing the pesticide profiles were supplied
by individuals/companies engaged in pesticide characterization and related
field studies. The project is deeply indebted to these supporting indivi-
duals/organizations, particularly to those listed in Table 2, and to the
technical experts and pesticide registrants listed in Table 3, who reviewed
and commented on the draft profiles.
At TRW, the Program Manager and Technical Director for the effort was
Dr. Masood Ghassemi. The development of the data base for this compendium
involved review and technical evaluation of a voluminous amount of data
by individuals from several different technical disciplines; Mr. Irving
Zuckerman, the General Manager of TRW Environmental Division, was most in-
strumental in assuring timely availability of appropriate technical talents
to the program. Special thanks are also due to Mrs. Monique Tholke for
typing the compendium and for her invaluable secretarial support to the
proj ect.
ii
-------
CONTENTS
Preface and Acknowledgements 11
Tables iv
1.0 Background, Objectives and Scope 1
2.0 Data Sources, Methodology and Review Procedure 3
2.1 Selection of Specific Pesticides 3
2.2 Data Sources and Data Collection Methodology .... 3
2.3 Data Evaluation and Review Procedure 5
3..0 Overview of the Available Data on Environmental Fate and
Impacts 10
3.1 Scope and Limitations of the Data and Some General
Recommendations 10
3.2 Highlights of the Reported Data 11
3.2.1 General Properties and Use Data 11
3.2.2 Uptake and Metabolism in Plants/Insects ... 18
3.2.3 Fate in Soil 23
3.2.4 Fate in Water 31
3.2.5 Impact on Non-Target Plants and Organisms . . 31
Appendix A-l
I. Herbicides A-l
Amitrole A-2
Atrazine . . . . ' A-17
Dalapon A-46
Dicamba A-80
2,4-D A-101
Fosamine Ammonium A-130
Glyphosate A-149
Hexazinone A-169
MSMA A-195
Picloram . A-221
Simazine A-268
Triclopyr A-299
II. Insecticides A-312
Acephate'. A-312
Carbaryl . . A-331
Trlchlorfon. A-376
III. Biologicals A-398
Bacillus thuringiensis A-398
Nucleopolyhedrosis virus A-411
Pheromones A-423
ill
-------
TABLES
Number Page
1 Pesticides Addressed in the Project
2 Key Individuals/Organizations Contributing to the Data
Base for the Study
3 Pesticide Registrants and Other Technical Experts Who
Provided Review Comments on. the Draft Documents , 8
4 Typical Request for Review of the Draft Documents 9
5 Summary of General Properties and Use Data 12
6 Summary of Data on Uptake and Metabolism in Plants (or
Insects) 19
7 Summary of Data on Fate in Soil 24
8 Summary of Data on Fate in Water 32
9 Impacts on Non-Target Plants and Organisms 35
iv
-------
1.0 BACKGROUND, OBJECTIVES AND SCOPE
In January 1980, the Special Pesticide Review Division of the U.S.
Environmental Protection Agency's Office of Pesticides and Toxic Substances
initiated the "Forest Use Chemicals Project", the objective of which was to
develop guidance for the timber production industry and the public on the
comparative risks and benefits associated with various chemical and non-
chemical approaches to pest control in timber management. A key Impetus for
the project was the ban imposed on the forestry uses of herbicide 2,4,5-T,
thereby precipitating considerable interest in examining chemical and non-
chemical alternatives to the use of 2,4,5-T.
Since the fate in the environment and the potential impacts on non-
target plants and animals are important considerations in assessing the
relative safety and environmental suitability of pesticides, in developing
the data base for risk analysis in the Forest Use Chemicals Project, a con-
siderable effort was devoted to the compilation and review of the available
data on environmental fate and impact of some eighteen pesticides addressed
in the study. The collected data and the results are presented in this
compendium which is also intended as an "information transfer" document,
thereby making available to the practicing foresters, state and local regu-
latory agencies, and the public interested in the safe use of pesticides,
the most up-to-date information on biodegradation and persistence of various
pesticides in plant, air, soil and water environments, and on their poten-
tial hazard to non-target plants and organisms. The document also draws
attention to major gaps and conflicts in the existing data so that appro-
priate testing and field studies can be designed to generate the additional
data. The environmental fate and impact data presented in this document,
in combination with estimates of potential for human exposure (e.g., due to
drift from aerial applications) and animal/human toxicity data, provide the
data base for assessing potential risks associated with the use of a specific
pesticide.
This document is organized in three sections and an Appendix. Section
1 (this section) presents the background for the study and the intended uses
-------
of the document. Section 2 identifies the sources of data and data acquisi-
tion and assessment methodology. Section 3 presents an overall summary of
the collected data and results. Detailed data on the pesticides addressed
are presented in the Appendix which consists of 18 subsections ("separate
documents"), one for each pesticide reviewed. Each review document in the
appendix consists of a summary and several sections which provide, where
available, the following information for the specific pesticide reviewed:
(a) background data on application method/rate, efficacy, extent of use,
mode of action, etc.; (b) physical and chemical properties of the active
ingredient; (c) environmental fate, including uptake, metabolism and persis-
tence in plants (or in insects for the insecticides), degradation, volatili-
zation and adsorption/leaching in soil, and chemical and biochemical alter-
ations in the aqueous environment; (d) impacts on non-target plants and
organisms including crops, fish and other aquatic organisms, wildlife and
beneficial insects, and potential for bioaccumulation; and (e) references
to all data sources used.
-------
2.0 DATA SOURCES, METHODOLOGY AND REVIEW PROCEDURE
2.1 SELECTION OF SPECIFIC PESTICIDES
Table 1 lists the eighteen pesticides for which environmental fate and
Impact profiles are presented in the Appendix. These specific pesticides
were selected from a much larger list of candidates based in part on dis-
cussions with technical experts most familiar with pest management problems
and pesticide usage in the four major U.S. forest production regions covered
in the Forest Use Chemicals Project . Additional considerations in selecting
the pesticides listed in Table 1 were: (1) the project funding and schedule
constraints which limited the total number of pesticides which could be
addressed; (2) representation of major pesticides used; and (3) inclusion of
"problem/controversial" pesticides, newer pesticides with potential for future
large-scale application, and biological pesticides which have often been pro~
moted by environmentalists as viable substitutes for chemical pesticides.
2.2 DATA SOURCES AND DATA COLLECTION METHODOLOGY
The major sources of data used in developing pesticide fate and environ-
mental impact profiles consisted of published literature; data provided by
the Ecological Effects and Environmental Fate Branches of EPA's Office of
Pesticide Programs, based on their review of the EPA's pesticide registration
files; and discussions with technical experts at pesticide manufacturing
companies, academic institutions, timber companies, U.S. Department of Agri-
culture, and State Forest Service agencies. The published literature was
searched via computerized data bases such as Pollution Abstracts, TOXLINE,
MEDLARS, NTIS, and DIALOG. These searches were updated via review of the more
recent issues of pertinent periodicals such as Archives of Environmental
Contamination and Toxicology, Agronomy Journal, Down to Earth, and Journal
of Forestry.
The four production regions are: Northwest, Great Lakes, Northeast (Maine)
and Southeast; these regions were chosen since they collectively account
for close to 70 percent of the total commercial forest land in the U.S. and
cover a spectrum of geographic/climatic conditions, species diversity and
pest management problems.
-------
The Individuals/organizations who contributed to the data base for the
study are too numerous for complete listing in this report. Table 2'provides
a partial listing of those individuals who provided considerable unpublished
data and/or copies of published reports and journal articles for use in the
study. In connection with the Forest Use Chemicals Project, field trips were
also undertaken to the four production systems for the purpose of collecting
"real world" data. These trips, which were of several days duration each,
were most helpful in developing appreciation for the region-specific pest
management problems and provided an opportunity for face-to-face discussions
with individuals most familiar with such problems.
2.3 DATA EVALUATION AND REVIEW PROCEDURE
The literature searches which were conducted identified a relatively
large number of journal articles and published reports as potentially con-
taining environmental fate and impact data for many of the pesticides of
interest. These identified references and other reports and articles which
were obtained from other sources were reviewed and those judged to be of un-
acceptable or questionable quality (e.g., due to inadequate documentation or
assertions without providing supportive technical data) were screened out.
Only those materials which, based on the data and discussions presented,
could be judged to be of adequate technical quality were used in developing
the environmental fate and Impact profiles.
To assure accuracy and completeness and to give the pesticide registrants
an opportunity to provide additional data not available to the study from
other sources, the draft environmental fate and impact documents were for-
warded to pesticide registrants and, in the case of biological pesticides,
to technical experts for review and comment. Table 3 lists the pesticide
registrants and technical experts to whom the draft documents were sent for
review. A copy of the typical request letter accompanying the draft docu-
ments is reproduced as Table 4. Comments received from the reviewers were
evaluated and incorporated, when appropriate, in the revised documents which
appear in this report. In all cases, the reviewers' comments were very
constructive and, In the case of certain newer pesticides such as hexazinone
for which little data were available in the open literature, were substantial,
thus requiring major revisions, substantial expansion, and hence significant
improvement in the accuracy and completeness of the documents.
-------
TABLE 2. KEY INDIVIDUALS/ORGANIZATIONS CONTRIBUTING TO THE DATA BASE FOR THE STUDY
Individual
Affiliation
o»
Prof. Norm Akesson
Dr. Larry Atkins
Mr. William Bedard
Dr. Morton Biskind
Mr. Temple Bowen
Mr. Perry Coy
Dr. Don Dahlsten
Dr. Gary Daterman
Mr. Richard Dunkel
Mr. Richard Duvall
Dr. L. C. Folmar
Dr. Richard Garcia
Mr. Dean Gjerstad
Mr. Dave Graham
Dr. H. Gratkowski
Dr. G. W. Green
Mr. Larry Gross
Dr. Illo Gauditz
Mr. Dan Hartman
Dr. Steve Herman
Mr. Ralph Hodoeh
Dr. E. F. Boiling
Mr. Fred Honning
Dr. Allen Isensee
Dr. Carl Johnson
- Agricultural Experiment Station, University of California, Davis, CA
- Dept. of Entomology, University of California, Riverside, CA
- USFS, Berkeley, CA
- Pharmocologist, Westport, CT
- Maine Bureau of Forestry, Augusta, ME
- Pesticide Use Enforcement, State of California, Berkeley, CA
- University of California (Dlv. of Biological Control), Albany, CA
• Pacific NW Forest and Range Experiment Station, U.S. Forest Service,
Corvallls, OR
• California Department of Food and Agriculture, Sacramento, CA
• California Department of Food and Agriculture, Sacramento, CA
National Marine Fisheries Service, Seattle, WA
University of California (Div. of Biological Control), Albany, CA
Department of Forestry, Auburn University, Auburn, AL
Forest Insect and Disease Management, Forest Service/USDA, Washington,
D.C.
Pacific NW Forest and Range Experiment Station, U.S. Forest Service,
Corvallls, OR
Canada Forestry Service, Forest Management Institute, Sault Ste.
Marie, Ontario
U.S. Forest Service, Milwaukee, WI
Weyerhaeuser Co., Centralla, WA
Consolidated Paper Company, Wisconsin Rapids, WI
Evergreen State College, Olympia, WA
Conrel, Needham Heights, MA
Institute of Animal Research Ecology, University of British Columbia,
Vancouver, Canada
Forest Insect and Disease Management, Forest Service/USDA, Washington,
D.C.
Pesticide Degradation Laboratory, USDA, Bartlesville, HD
Entomology Department, Washington State University, Pullman, WA
-Continued-
-------
TABLE 2. (Continued)
Individual
Affiliation
Dr. Donald Kaufman
Dr. Philip C. Kearney
Mr. Peter Kinsbury
Mr. Robert Kirshner
Mr. Leroy Kline
Dr. Terry Lavy
Dr. William Lawrence
Mr. Jay Maitlen
Dr. Maxwell McCoraack
Mr, William McCredie
Dr, Jerry Michael
Dr, Daniel Beary
Dr, Michael Newton
Dr. David Pimentel
Dr. Steven Radosevich
Mr. Lou Seymour
Dr. Kathy Sheehan
Dr. Robert Spears
Mr. William A. Tuttle
Dr, John Walstad.
Dr. Charles Webb
Dr. David Wood
Dr. Ed Woolson
Prof. Wesley Yates
Mr. Noel Yoho
Pesticide Degradation Laboratory, USDA, Bartlesville, MD
Pesticide Degradation Laboratory, USDA, Bartlesville, MD
Forest Pest Management Institute, Sault Ste. Marie, Ontario, Canada
National Forest Products Association, Washington, D.C.
Oregon Department of Forestry, Salem, OR
Department of Agronomy, Altheimer Laboratory, University of Arkansas,
Fayetteville, AR
Weyerhaeuser Co., Centralia, WA
USDA, Yakima Agricultural Research Laboratory, Yaklraa, WA
School of Forest Resources, University of Maine, Orono, ME
National Forest Products Association, Washington, D.C.
Southern Forestry Experiment Station, Auburn, AL
Forest Service/DSDA, Gainesville, FL
School of Forestry, Oregon State University, Corvallls, OR
Department of Entomology, Cornell University, Ithaca, NY
Department of Botany, University of California, Davis, CA
Sandoz Inc., San Diego, CA
University of California (Div. of Biological Control), Albany, CA
School of Public Health, University of California, Berkeley, CA
Forest Service (USDA), Milwaukee, WI
Department of Forest Science, Oregon State University, Corvallis, OR
International Paper Co., Bangor, ME
Department of Entomology, University of California, Berkeley, CA
Pesticide Degradation Laboratory, USDA, Bartlesville, MD
Agricultural Experiment Station, University of California, Davis, CA
International Paper Co., Mobile, AL
The listing in this table does not Include various divisions and branches of EPA's Office of Pesticides
and Toxic Substances which made their data files available to the project, nor the pesticide registrants
and other technical experts, listed in Table 3, who reviewed the draft documents and provided references
and much supplementary information.
-------
TABLE 3. PESTICIDE REGISTRANTS AND OTHER TECHNICAL EXPERTS WHO PROVIDED
REVIEW COMMENTS ON THE DRAFT DOCUMENTS
Reviewers
Pesticides
Registrants
Chevron Chemical Co.
Ciba-Geigy Corp.
Diamond Shamrock
Dow Chemical
DuPont
Mobay Chemical Corp.
Monsanto
Union Carbide
Velsicol
Other Technical Experts
Acephate
Atrazine, slmazine
MSMA
Dalapon, picloram, 2,4-D, triclopyr
Hexazinone, fosamine ammonium
Trichlorfon
Glyphosate
Carbaryl, amitrole
Dicamba
Dr. Robert Hoist (EPA/OPTS-HED) All 18 pesticides
Dr. Jack Pllamer (USDA) Pheromones
Dr. H. T. Dulmage (USDA) Bacillus thuringiensis
Dr. Franklin Lewis (USDA) Nucleopolyhedrosis virus
Dr. Normand Dubois (USDA) Bacillus thuringiensis
-------
TABLE 4. TYPICAL REQUEST FOR REVIEW OF THE DRAFT DOCUMENTS
TRW
31 July 1980
Itc. Howard Dulmage
SEA-SR
Subtropical Texas Area
Cotton Insect Unit
P. 0. Box 1033
Brownsville, Texas 78520
Dear Dr. Dulmage:
In connection with our EPA-sponsored "Forest Use Chemical Project," w«
have been reviewing the available data on environmental fate and impacts
associated with the use of some eighteen pesticides. One of the pesticides
addressed in this study is Bacillus thuringiensis for which you are a tech-
nical authority. Per suggestion of Dr. Franklin Lewis of USDA-Forest Service
(Banden, Connecticut), I aft enclosing a draft copy of our environmental fate
and impact document on B.t. for your review. Your review of the document
for accuracy and completeness would be nost appreciated. We also would
appreciate receiving any supplementary data which you feel should be in-
corporated in the document.
HO familiarize you with the nature and objectives of our project, I am also
enclosing copies of the Program Plan and Status report {as of June 1980)
Which have been prepared by EPA for the Forest Use Chemical Project. {The
Project Schedule indicated in Appendix 3 of the Program Plan has been some-
what modified to accommodate some delays which have been encountered in data
acquisition.}
W* look forward to receiving your review comments on the enclosed document;
To assure meeting our very stringent project schedule, we would very much
like to receive your review coactents before 29 August 1980.
Sincerely,
*^x^
Masood Ghassemi, Ph.O.,P.E.
Senior Project Engineer
Enclosure
cct Michael Dellarco(EPA)
-------
3.0 OVERVIEW OF THE AVAILABLE DATA ON
ENVIRONMENTAL FATE AND IMPACTS
The available data on environmental fate and impacts for the eighteen
pesticides addressed in this study are presented in the Appendix and are
summarized in Tables 5 through 9. Based on the data presented in the Appen-
dix and in the summary tables, and on the discussions which were held with
forestry organizations, timber companies and technical experts during the
site visits to various forest production regions, the following are the
highlights of the data and some general observations on the nature, signifi-
cance, and limitations of the available data and some recommendations for
future studies.
3.1 SCOPE AND LIMITATIONS OF THE DATA AND SOME GENERAL RECOMMENDATIONS
• Most of the available data have been generated by the pesticide
registrants In support of pesticide registration for specific uses.
Since only a few of the pesticides have the same registrant and are
for the same applications, the data for different pesticides are
not generally on the same bases (e.g., in terms of efficacy, non-
target plants of interest, types of animals tested for toxicity or
soils used in leaching and degradability studies, and experimental
conditions used) and hence the comparison of various pesticides
is often inappropriate or very difficult. Field studies in which
efficacy and environmental persistence and Impacts of pesticides
«rLl°XSJ Tt" *151ia5 application conditions can provide the
real world data needed for comparative assessment of relative
merits and shortcomings of pesticides recommended for the same
applications. "Forestry cooperatives" such as those which have
been recently established and are now operative in the South rlnhum
University Forestry Chemicals Cooperative) and in Maine °Cooper~afe
Forestry Research Unit, University of Maine) would be approprCte
vehicles for carrying out such independent comparative studies?
in the past have
2,
10
-------
all such data would be applicable to forestry applications due to
differences in soil characteristics, climate and sunlight condi-
tions and application rates.
• While extensive data have been generated by the registrants through
systematic and well-designed scientific studies for a few of the
pesticides (particularly the newer herbicides), such comprehensive
data bases do not exist for most of the pesticides addressed in the
study. Many assertions in the literature as to "low" or "moderate"
toxicity, mobility or persistence of certain pesticides appear to
be unsubstantiated; where some quantitative data have been reported
(e.g;, TLso values for toxicity to fish), there appears to be cer-
tain overlapping and inconsistencies in assigning qualitative des-
criptors based on quantitative data. For most pesticides, little
data are reported on fate in the aqueous environment.
• In general, the majority of environmental fate data are from labo-
ratory tests conducted under carefully controlled and simplistic
conditions which do not necessarily reflect the very complex forest
ecological systems.
• Laboratory animal toxicity data which have been reported for many
of the pesticides by themselves do not provide indications of po-
tential risk to aquatic and terrestrial life under actual forest
use conditions. To estimate risks, toxicity data must be used in
conjunction with data on actual exposure (populations exposed,
concentration levels and persistence) in the forest environments.
Data from actual monitoring of forest streams and wildlife food
sources, and of populations and diversities of aquatic and terres-
trial communities prior and subsequent to pesticide application are
needed in developing the data base for risk assessment.
• Up-to-date detailed technical information on various aspects of
pesticide use, such as the data presented in this document on fate
and environmental Impacts of pesticides, are not generally available
to the practicing foresters and local and state agencies who are
interested in the safe use of pesticides. Publication and distri-
bution of "information transfer11 documents such as this document,
and sponsorship of technical workshops and seminars would be valu-
able vehicles for making the latest technical data and research and
development results available to the user community.
3.2 HIGHLIGHTS OF THE REPORTED DATA
3.2.1 General Properties and Use Data (Table 5)
• Primary forestry application of the herbicides addressed in this
study are for site preparation and conifer release; the insecticides
(including biologicals) are used primarily for the control of spruce
budworm, gypsy moth, tussock moth, and other forest insects.
• Aerial broadcast is by far the most prevalent application method
for pesticides; the rate of application varies with the specific
pesticide and use, and is generally less than 4 lb a.i. per acre.
11
-------
TABLE 5. SUMMARY OF GENERAL PROPERTIES AND.HSE DATA
Pesticide
Common
Name
Major Trad*
Names/
Formulations
Major
Registrant
Forestry
Applications
Application Ratt
and Method
Ex tent of
Use
Relevant Physical/
Chemical Properties
of Active Ingredient
Miscellaneous
I. HERBICIDES
Amitrole
Atrazine
Oalapon
Dicamba
Amitrol-T,
Cytrol
Amitrole T.
Weedazol
AAtrex (BOW,
9CW.4L.4CL)
Union Carbide
ICibaGeisv
DOWPON,
DOWPON M.
DOWPON C,
Radapon
Barivel.
Formulated as a
water soluble
tsitt,oil*ok/bt»
Hquid, water
soluble liquid,
emubifiable
concentrate.
Often combined,
with 2.44)
Dow
VeUicol
Chemical
Corp.
I Used on salmonberry
I and etderberry for site
preparation and con-
ifer release
I Col-liter release,
nursery applications of
fir transplants, and
seed orchards/produc-
tion areas
; Site preparation,
release, in seed
orchard/production
areas, and vegetation
control in established
1 plantings
I Primarily for site prep-
I aration to control
deciduous shrub* and
1 trees, certain conifers
and f orbs
Applied as a foliar
spray at the rate of
2 Ib a J. per acre
I Aerial broadcast or
ground spot applica-
tions at 3 to S Ib of
B0%a.i./acrefor
conifer release; 2 Ib
ajjaae in nursery
applications; 2 - 4 Ib
8.L/acre in seed
orchards/production
3 to ISIb/acre
i (DOWPON M) via
ground or aerial spray
Dimethylamine salt
' used undiluted (4 Ibs
acid equivalent per gal)
I or diluted 1:4 in water
for cut surface injec-
tion
Primarily in the coast
range of the Pacific
Northwest
Primarily in the
Pacific Northwest
Used in Pacific North-
west (e.g., 14,354 Ib
applied to 2.900 acres
in BLM Region 5 in
(1976 -1979). Data
unavailable on usage
in other regions
Used in southeastern
pine forests and in the
Pacific Northwest.
Data do not indicate
extensive use
Highly soluble in water
<28g/10Ogat25"C),
and in polar solvents.
Low volatility
Solubility 70 ppm in
water. Low volatility
(l.4x lO^mmHgat
30 °C)
Very soluble in water;
solubility of DOWPON
M I IOa/100 ml at
22 °C, in water
containing 100 ppm
hardness
Soluble in most organ-
ic solvents, poorly
soluble in water (0.45
B/100 ml at 25 °C|.
DMA sail highly
soluble in water (72
g/IOOcnl). Vapor
pressure 3.4 x
mmHgat25*C
Sometimes used in
combination with
dalapon for control of
broadleaf weeds and
grass for Douglas fir
release in the Pacific
Northwest; and with
simazine in the South
Has been used in
combination with
atrazine and 2,4-D for
control of broadleaf
weeds
(Continued)
-------
TABLE 5. (Continued)
Pesticide
Common
Name
2,4D
Fosamine
Ammonium
Glyphosate
Major Trad*
Names/
Weedone LV-4,
Erteron99
Concentrate,
Weedar64.
Verton 2 O.
OMA-4 I
Major
Registrant
Dow Chemical
Company
i
iCrenite brush
control agent;
•Krenite'S
brush control
agent
Roundup
Du Pont
Monsanto
Forestry
Applications
Used as a selective
broadleaf weedkiller
far tite preparation
Site preparation and
conifer release
Site preparation and
release; seed orchards/
production areas, pre-
plan! nursery uses
Application Rat*
and Method
Applied as foliage
sprays by handgun or
Tacfcpadc mist blower.
aerial application or
ground rig applicators;
applied at 2 to 4 Ib
acid equivalent of
active ingredient per
acre
Aerial broadcast (3 to
12lb*.i/acreforsite
preparation, less for
release). Limited
ground application
Ground and aerial
application; 1 to IS
and 3 to 4 qt* per 10
gallon solution/acre
for release and site
preparation, respect-
ively
Extent of
Use
•rimarily in the Pacific
Northwest and Great
Lakes
Primarily in the Pacific
Northwest. Limited
application in the
South; used in exper-
imental plots in the
Northeast. Quan-
titative usage data
unavailable
Primarily in Pacific
Northwest (1979.
4,100 to in USFS
Regions 5 and 6; 3,000
to 5,000 acres of state-
owned forests treated
annually); also, major
uses by private timber
companies. Limited
use in the Northeast
(1970, 6,000 Ib used
in Maine)
Relevant Physical/
Chemical Properties
of Active Ingredient
Varies, depending on
formulation. Water
solubility of 2,4 0 acid
s0.09g/100gal25°C;
vapor pressure is 0.4
mm Hgat 160 "C.
Water solubility of
2.4Damineis300gS
100gat20°C.
Butoxyethanol ester of
2,4 0 insoluble in
water; vapor pressure
4.5 x 10* mm Hg at
25 °C
Highly water soluble
(179g/IOOg).
Low volatility (vapor
pressure 4 x 10* mm
Hgat 26 "C)
Solubility 1.2 percent
in water at 25 °C;
negligible vapor
pressure
Miscellaneous
Relatively new herbicide
(introduced in f 974). Most
effective when applied in late
summer or early fall ar»d does
not show its effects until the
following spring.
Relatively new
herbicide (introduced
In 1971). Primary uses
•re In agriculture and
industrial/recreational
areas
(Continued)
-------
TABLE 5. (Continued)
Pesticide
Common
Nairn
Major Trad*
Names/
Formulations
Major
RegutiMit
Forestry
Applications
Application Raw
and Method
Extent of
UM
Relevant Physical/
Chemical Properties
of Active Ingredient
Miscellaneous
Hexazinone
"Velpar"
1 "Gridball"
| Brush Killer.
"Velpar" Weed
Ou Pont I Site preparation and
I pine release
Dependent on toil
type; 5 to 10 and 7 to
20 Ib/acre "Gridball"
for release and site
To date, primarily in
the South (1979
estimated acreage
treated: 6,500 acres)
Water solubility: 3.3g/
100gat25"C;vapor
pressure: 2 x 10'' r»
Hg at 25 °C; slowly
Very new herbicide;
under evaluation in
large-scale commercial
applications in the
1 Killer, "Velpar1
1 L Weed Killer;
I I preparation, respec-
I tivety;"Gridball"
["Gridball" 1 I pellets applied by
1 pellets available I 1 1 hand or with special
1 as 10% to 20% 1 1 1 aerial equipment.
I ingredient I 1 1 Rain necessary for
I j sokibilization of
f f pellets and movement
I 1 of hexazinone into
I soil
MSMA I Ansar, 1 Diamond I Site preparation and [ Applied by injection
1 Bueno, 1 Shamrock, 1 precommercial 1 or cut surface of tree
I Daconate. I Vinetond I thinning I trunk
Weed-Hoe. I Chemical | J
Valson
Picforam I Tordon (101, 1 Dow 1 Site preparation and 1 Spray solutions
J101R, 10K j 1 conifer release; occa- 1 (2 oz to 3 Ib/acre);
I pellets, K) 1 f sional use in pre- j pellets (2 to 8 Ib/acre};
I for forestry
J use; Tordon
I commercial thinning J stem injection (1 ml/
I j injection of Tordon
|(2K,22K,202 j I 1 101)
1 Mixture. 22SE j j 1
I Mixture. RTh) I 1 1
for non-forestry | |
use;Andon
Approximately 6
metric tons/year used
primarily in the Pacific
Northwest
Primarily in the South
(In 1979. 81.500 acres.
site preparation;
78,510 acres, release).
Also used in Pacific
Northwest and Great
Lakes in smaller
quantities
decomposes in water
Soluble in water.
non-volatile, forms
insoluble salts with
divalent cations
Picloram only slightly
soluble in water (430
mg/£), but potassium
and amine salts highly
water soluble. Vapor
pressure 6.2 x 10''
mm Hg at 35 °C;
slightty higher for
picloram esters
South. Northwest and
upper Midwest .as
possible substitute for
2.4.5T
No photodegradation
reported
Also effective when
used in combination
with triclopyr and
2,4 D for control of
mixed hardwood brush
•
(Continued)
-------
TABLE 5. (Continued)
Pesticide
Common
Nam*
Simazine
Triclopyr
•
II. INSECTICIDES
Acephate
Major Trad*
Names/
Formulatiom
Princep
Garlon3A
Gar loo 4
Orthene
Major
RtQISUUlt
CibaGeigy
Dow
Chevron
Chemical
Company
(Ortho
Division)
Forestry
Applications
Site preparation.
conifer release, nursery
application!
Site preparation;
conifer release
Used in seed orchards
to control cone and
seed insects; used fn
forests for control of
spruce budworm and
gypsy moth
Application Rata
and Method
3 to 4 Ib a,), in 10 gal
water/acre for site
preparation and
conifer release; 1 .6 to
33 Ib a.i. in 10 to 25
gal water/acre for
nursery applications.
Aerial broadcast and
ground spot methods
used
2 to 3 gal/acre
(Carton 3A) by broad-
can application via
low volume ground
spray equipment or
helicopter; 1/2 to
one gal/1 00 gal
water for high volume.
full spray; also by trw
injection
In seed orchards.
applied with ground
spray rigs at 2/3 Ib/
100 gal water/acre.
Aerially applied in
forests at a rate of
2/3 to 1 1/3 to in
1 gal/acre
Extant of
UM
Used primarily in
Pacific Northwest and
to a limited extent in
the South. Quantita-
tive use data unavail-
able
Used on experimental
basis in Pacific North-
west, Northeast and
South (1979. 100
acres in Washington.
Oregon. California)
Has been used to a
limited extent against
spruce budwormsm
Maine
Relevant Physical/
Chemical Properties
of Active Ingredient
Low volatility; vapor
pressure 6.1 x 10 9
mmHgat20°C.
Slightly water soluble
(3.5ppmwat20DC)
Solubility, 4.39/100
mC in water; vapor
pressure 1.3 x 10^>
mmHgat25°C
Highly soluble in water
(65%) and in polar
organic solvents. Low
vapor pressure
(2 K ID"6 mm Hg at
25 'Cl
Miscellaneous
Also used in combina-
tion with atrazine in
both PNW and South
Very new herbicide
only recently register-
ed for use in forestry.
Most current exper-
imental uses in PNW in
ground applications
foe stump treatment
and tree injection
Does not appear to
photodegrade on
surfaces or in water
(Continued!
-------
TABLE 5. (Continued)
Pesticide 1 Major Trade
Common Names/
Nam* Formulation*
CarbaryJ 1 Sevin-4^il
| Sevin SO WP,
80WP.80S
I
J
Trichlorfon |Dylox1.5oil
Dykw4
BIOLOGfCALS I j
I Major Forestry j Application Rate
j Registrant Application* 1 and Method
1 Union Carbide 1 Control of insects such 1 Aerial application
1 I at spruce bod worm, I (I - 2 Ibs a.tVacre
1 gypsy and tussock Sevin-4-oil or Sevin
1 \motitt 1 80S); ground applica-
1 1 tion (2 Ib a.l/acre
I 1 Sevin SOS with mist
1 I I Mower; one Ib a.i./acr
J J j Sevin 80S with
[ 1 1 hydraulic sprayer)
J
I
Mobay j Control of gypsy moth. 1 Applied at 1 Iba.i. per
Chemical spruce bud worm, j acre. Aerial applica-
Corp forest tent caterpillars I tion
Bacillus I Oipel. 1 Abbott 1 For control of spruce I Aerial application of
Extant of
Use
Primarily in Northeast
<8.2 and 2.5 million
acres in Maine in
1975 -79 .wxl 1979,
respectively, for spruce
budworm control" in
1979 42,000 acres in
Northeast for yypsy
moth control). Also
used in Pacific North-
west for Douglas fir
tussock moth and in
Rocky Mountain nates
For Western spruce
ixtdworm; quantitative
usage data unavailable
Registered for use in
Relevant Physical/
Chemical Properties
of Active Ingredient
Slightly water soluble
(WpprnatWC).
Low volatility (0.002
mmHgat40°C)
Solubility in water
Maine and New 1 2.3g/1 OOg. Slightly
Hampshire for gypsy I soluble in paraff ink
moth and spruce bud-
worm; In Louisiana
and Alabama for
orest tent caterpillars.
7.000 acres treated in
Maine in 1979
bit extensive use is
hydrocarbons. Vapor
pressure 7.8 x 1(H*
mm Hg at 20 °C.
Stable in ackf. rapidly
hydrolyzad In alkaline
solutions
Active ingredient
Misceianeous
Widely used to control
insect pests on field
crops, gardens and
range lands
Pbotodegradation
thuringiensb | Thuridde
Laboratories
Sandozfnc.
budworm. gypsy moth,
Douglas fir tussock
moth, forest tent
caterpillars, spring and
fall cankerworms
1.8 to 8 Bill/acre.
depending on target
insect
for control of spruce
budworm in Maine on
•bout 200,000 acres/
year
consists of spores and
parasporal crystals of
the bacterium, approx.
1p in diameter
half-life of 0.3 to 3
days on exposed leaves
(Continued)
-------
TABLE 5. (Continued)
Pertidd*
CofTHIKMI
Name
Nudeopoly-
hedrosis
virus
Pheromones
Major Trade
Names/
Formulations
Gypcheck,
TM-Biocontral 1
Elcartfor
agricultural uie)
Pheromones are
specific for a
particular insect
Some trade
names are Cbek,
Mate, Pherocon
EPSM. Pherocon
GM
Major
Registrant
USDA,
Sandoz Inc.
Hercon.
Conre),
Zoecon
Forestry
Applications
For control of gypsy
moth, Douglas fir
tussock moth. Elcar
for control of cotton
budworm and tobacco
budworm
Current uses primarily
for bkmirveys and
monitoring of forest
insect pests. Limited
use for mating dis-
ruption or mass
trapping
Application Rat*
and Method
Applied at 25 - 125
million units/acre for
gypsy moth; 1 billion
units/acre for tussock
moth. Aerial applica-
tion.
Applied at rates
approximating those
levels which are
naturally present.
Applied as flakes.
kiretape, rubber caps
or wicks, hollow
plastic capillaries
Extant of
lisa
Limited
Used against gypsy
moth, elm bark beetle.
pine shoot moth, elm
bark beetle, spruce
budworm. Western
pine shoot borer.
Much use is still
— i a_i
experimental
Relevant Physical/
Chemical Properties
of Active Ingredient
Active ingredient
consists of polyhedra.
approx.lfi in
diameter
Volatile organic
compounds highly
selective lor a single
species; formulated
to closely represent
the natural insect
pheromone
Miscellaneous
Inactivated by sunlight
on surfaces in 3 — 15
days
^^^
-------
3.2.2
The .ban on forestry use of 2,4,5-T has been a major Impetus for
the recent and current evaluation of several new herbicides (e.g.
hexazinone and glyphosate) and testing of some older herbicides ' '
(e.g., picloram) in forestry applications. Because of the limited
supplies, some of the newer herbicides (e.g., triclopyr) have only
been tested on small experimental plots. Some of the biological
pesticides (specifically pheromones) have also been used only on a
small scale experimental basis.
Some pesticides are more widely used in specific regions than in
others (e.g., use of amitrole in the Pacific Northwest) and for
specific pests (e.g., use of specific pheromones for specific in-
moths)?r USe °f Carbaryl for s*ruce budw°™ ^d gypsy and tussock
l^tor "IT data10;:iqUantitative usa*e of P*"icides by the public
sector are available, very little data are publicly available on
such uses by the private sector. iJ-aoj-e on
tl?e',most herbicide ""age ^ in the Northwest
insecticlde «« i* primarily in the Northeast.
*»* *
Certain herbicides are used in combinations to improve efficacy
(e.g., use of atrazine In combination with dalapon, Z?*!" or sima-
™* amlt«le) • herbicides are
and Metabolism in Plants/Insects (Table 6)
=c«
. <•-.
of herbicides Include ' 86"6"1. 'he modes of action
and v.rs«h «BDO« "^^is proce.s.
chemical Insecti *" !>lai1"- *11 three
tehibittag acetylchteest "" atert thelr
and "
•re behavior modifying agents
'« ««• *ich are,
18
-------
TABLE 6. SUMMARY OF DATA ON UPTAKE AND METABOLISM IN PLANTS (OR INSECTS)
Pesticide
Mod* of Upttke
Mode of Action
Metabolism
I. HERBICIDES
Amitrole
Atraztne
Dalapon
Dicamba
2,4-D
Absorbed through leaves and roots;
readily translocated.
Roots and leaves (minor). Foliar
uptake enhanced by addition of
adjuvents such as mineral oil.
Some accumulation in marginal
zone of leaves.
Roots and foliage. Rapidly trans-
locates throughout the plant and
accumulates in areas of high
metabolic activity (vegetative
buds and fruiting areas).
Absorbed by roots or foliar
tissues; readily translocated.
Absorbed through leaves, stems, or
roots; readily translocated.
Prevents chloroplast development
in new growth.
Inhibits photosynthesis resulting
in defoliation and plant death.
Causes leaf chlorosis and abnormal
growth responses typical of growth
regulators; also displays acute
contact toxicity.
An effective plant growth regulator
which alters root and shoot develop-
ment and causes leaf malformation,
increased branching, petiole and
stem curvature and abnormal
flowering.
Acts as an analog of the growth
hormone, indole-2-acetic acid, to
cause loss of normal growth. Some
tissues are stimulated while others
are inhibited in their development.
Conjugates formed in plants. One
breakdown product is 3 ATAL, which
is less toxic than amitrole.
Four principal degradation
mechanisms: (1) hyd rol ysis to
hydroxy atrazine; (2) conjugation
with glutathione or amino acids at
2-position of triazine ring; (3) N-
dealkylation of side chain group;
(4) s-triazine ring deavtge.
Not metabolized within 2 weeks
following uptake; metabolism beyond
2 weeks not demonstrated.
Species dependent; may involve ring
hydroxylation, formation of conju-
gates, demethoxylation. Half-life of
about two weeks observed for the
amine salt in grasses.
May include side chain degradation or
lengthening, ring hydroxylation or
cleavage, conjugation, metabolite
formation. High residue levels not
expected.
Continued)
-------
TABLE 6. (Continued)
Pesticide I
Mode of Uptake j
Mode of Action
Metabolism
Fosamine
Ammonium
Gtyphosate
10
o
Hexazinone
MSMA
Picloram
Absorbed by fofiage, buds, and
stems; uptake facilitated by
addition of surfactants.
Primarily through foliage; some root
uptake, depending on soil type.
Foliage uptake growth enhanced by
humidfty and surfactants.
Root (pellets) root and foliar (foliar)
spray).
Uptake by roots and leaves.
Roots (spray pellets); foliage (spray)-
less rapid uptake than by root; rapidJy
translocated throughout the plant,
with tendency for accumulation in
new growth.
Interferes with spring bud develop-
ment; produces miniature spindly
chlorotic leaves which do not
photosynthesize adequately.
Not fully understood; may involve
blockage of aromatic amino acid
biosynthesis.
Interference with photosynthesis pro-
I cess resulting in defoliation and
pfant death.
I May interfere with plant phosphorous
f metabolism; causes chlorosis.
Growth regulator; exact mechanism Relatively stable and remains largely
Half-lives of 2-3 weeks in apple seed-
ling leaves arid 7 days in pasture flora.
Metabolites were carbamoyl phos-
phoric acid (CPA) and carboxyphos-
phonic acid, which reached maximum
concentration after 2 weeks. No
residue found in pasture turf twelve
months after application.
No significant degradation in plants
up to 20 days after treatment (long
term data unavailable).
Metabolized in plants, with very low
residue levels after several months;
a number of degradation products
identified.
Data on cotton indicate little meta-
bolism; metabolized to organic arsen-
icals in sensitive plants. Found at
levels of 116 ppm arsenic in pine
needles several months after
application.
not known.
| intact within the plant; small amounts
degrade via decarboxylation, conju-
gate formation with proteins and
other mechanisms.
(Continued)
-------
TABLE 6. (Continued)
Pesticide
Mode of Uptake
Mode of Action
Metabolism
Simazine
Triclopyr
II. INSECTICIDES
Acephate
Carbaryl
Roots; limited foliar uptake when
used with surfactants or when leaves
are physically damaged (e.g., due
to hail).
Roots and leaves. Readily translocat-
ed throughout the plant. Application
to leaves results in accumulation
in shoots.
Penetrates plant tissues within 24
hours. Kills insects on contact or
upon ingestion of treated plants.
By exposure to direct application;
or by ingestion of contaminated
foliage (insects, animals) or root
uptake (plants).
nhibits photosynthesis by arresting
Hill reaction in chloroplasts.
Induces auxin-type responses; affects
ongitudinal cell structure and pro-
itbits bending of stalks and stems
in phototropic response.
Neurotoxicto insects; inhibits
acetycholinesterase.
Nerve poison; inhibits
acetylcholinesterase.
Readily metabolized via 4 major
mechanisms: hydrolysis; N-dealky-
lation of side chains; conjugation
with amino acids; and s-triazine
ring cleaveage.
Data unavailable on metabolic
degradation (if any).
Metabolized in plants to
methamidophos, 0,S-dimethyl-
phosphorothioate, S-methyl
acetylphosphoroamidothioate
and unidentified products.
Readily metabolized by insects to
l-naphthol and N-methylcarbamic
acid, which further decompose.
Metabolized by animals to l-naphthol
and numerous other hydrolysis,
hydroxylation and epoxidation
reactions. Metabolized by plants to
products via oxidation, hydrolysis,
hyroxylation and conjugate
formation.
{Continued)
-------
TABLE 6. (Continued)
Pesticide
Mod. of Uptake
Mode of Action
Metabolism
Trichlorfon
ro
re
III. BIOLOGICALS
BacHfus
thuringtensis
Nucteopolyhedrosis
virus
Pneromones
I Kills insects on contact or by stomach! An organophosphate; inhibits
faction upon ingestion. Available data I acetvlcholinesterase in insects and
[suggests limited uptake by plants. | other organisms.
No evidence for uptake in plants.
Ingested by insects.
No evidence for uptake in plants.
Ingested by insects.
No uptake occurs.
Bacterial toxin attacks midgut
epithelium of insects; bacteria cause
septicemia in insects.
Virus infects susceptible insects.
Disrupts natural insect behavior
e.g., mating or aggregation.
Several metabolites in plants, but only
DDVP is toxic. Two main degrada-
tion pathways in animals: hydrolysis
and dehydrochlorination; DDVP is
formed, hydrolyzed and excreted.
None in plants. Toxin is activated
in the insect gut (requires pH 9.0
to 10.5 and gut enzymes).
Bacteria reproduce in insect tissues.
None in plants. Virus is propagated
in living host farvae; infectious
polyhedra are formed.
Not metabolized.
-------
S UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
f WASHINGTON. D.C. 20460
APR 2! 1987 OFFICEOF
PESTICIDES AND TOXIC SUBSTANCES
Frank Nichols
U.S. Environmental Protection Agency
Region VIII
Emergency Response Branch
999 18th Street
Suite 1300
Denver, CO 80202
Dear Mr. Nichols:
In our recent phone conversation, you requested some
information on the concentration of herbicides in agricultural
runoff from fields. I understand that you want this informa-
tion to help evaluate the significance of the pesticide
contamination which resulted from runoff from a warehouse
fire in Minot, North Dakota.
I have quickly pulled together some information to try
to help you. I am enclosing the following materials:
Herbicide and Insecticide Residues in Tailwater Pits:
Water and Pit Bottom Soil .from Irrigated Corn and
Sorghum Fields. 1978. Kadoum, Ahmed K. , and Mock,
Donald E. J. Aqric. and Food Chem. Vol. 26, No. 1.
The Pesticide Content of Surface Water Draining from
Agricultural Fields — A Review. 1978. Wauchope, R.D.
J. Environ. Qual. Vol. 7, No. 4.
Environmental Fates and Impacts of Major Forest Use
Pesticides. Ghassemi, Masood, et al. 1981. Report
by TRW Environmental Division for U.S. Environmental
Protection Agency, Contract #68-02-3174, Work Assignments
Nos. 13, 14, 62. (Please return)
Please let me know at 557-5734 if I should send further
information on the subject. Good luck on the cleanup.
Sincerely,
Carolyn K. Offutt, Chief
Environmental Processes and
Guidelines Section
Exposure Assessment Branch, RED
(TS-769)
-------
« i . - l ofEitt/innmeatatQuaiity
VOL 7. BO. 4, October -December 1978. Copyright ,c, jflTg. ASA, CSSA SSS
677 Souvh Scgoc fW, M«da«on. \V[ S371J USA
C-1'
'
The Pesticide Content of Surface Water Draining from Agricultural Fields—A Review
R. D. WAUCHOPE
-------
.,.
,<• --•'
. V • ,y
' ' S •"
'' -*
' "• '-f'
.
.£.*'
The Pesticide Content of Surface Water Draining from Agricultural Fields—A Review1
R.D.WAUCHOPE1
ABSTRACT
Tt|e literature on pesticide losses Jn runoff waters from agricultural
field! (j reviewed. For (he majority of commercial pesticides, lolal
losses trc 0.5% or leu of ih« amounts applied, unless severe rain/all
conditions occur within 1-2 weeks after «pulicvi
-------
that burden on the quality of receiving waters, consider-
ing all the subsequent uses for which that water is
needed? The first question can be answered by experi-
ment, and has been the subject of intense research over
the last decade. In this review 1 will attempt to show that
at least the first part of question (i) has, to some extent,
been answered. Unfortunately, rational implementation
of the FWPCA requires answers to question (if). These
answers are and will be slow in coming because water
quality is essentially a social issue arrising from conflicts
over water use.
To assess the state of knowledge of pesticide contami-
nation of agricultural runoff3 waters, I have reviewed
the literature through spring, 1977. An excellent earlier
review on the limited data then available was given by
Pionke and Chesters (1T73). Caro (1977) has given a re-
pent broad overview of the runoff problem as it relates
to water quality and aquatic ecosystems. Wauchope et aJ.
(1977b) reviewed experimental methods. The goals of
the present review were (i) to tabulate "edge-of-field"
concentrations and loads of all pesticides for which data
are available; (ii) to suggest rules of. thumb, fpr csiimat-
ing lossesjyhich may be of use for FWPCA planning;
""and (in) to suggest research areas that need more atten-
tion.
REVIEW OF THE DATA
The nomenclature and relevant chemical properties of
compounds which have been studied are listed in Table
1. For purposes of discussing these results, 1 have classi-
fied experiments into the following categories: (i) sea-
sonal or long-term quantitative measurements of losses
from fields;4 (ii) short-term studies which typically
measure concentrations only, (Hi) simulation studies of
"catastrophic" rainfall situations, in which severe
"rainfall" is artificially applied to plots soon after the
application of a pesticide.
Seasonal and LonR-Term Losses of Pesticides
from Fields
The studies in this category provide a realistic picture
of the runoff losses of pesticides to be expected under
agncuJtural conditions. Results are tabulated in Table 2.
and summarized in Fig.M. Nearly all the data arc from
the central and southeastern states where pesticide usage
and runoff levels are both relatively high (Stewart,
1976). White and coworkers at Watkinsville, Ga., were
pioneers in this research (White et ah, 1967), and the
work at Watkinsville has culminated in a monumental
cooperative EPA/ARS field study of pesticide losses
which is in preparation.'
Several generalizations can be made from the data in
Table 2.
1) Pesticides formulated as wettable powders (all are
herbicides applied to the soil surface) consistently show
the highest long-term losses of any general class of
herbicides. In general, losses of up to 5% can be ex-
pected from fields of moderate slope (10-15<7o), and
losses of up to 2% can be expected from fields of low
slope (3% or less). Losses may be much (typically 3 x)
higher if a large runoff-producing event occurs within
about 2 weeks of application, and is the first event to
•The term runoff will be used to describe both the water and its as-
sociated sediment lost from the surfaces of fields.
'For purposes of this review, the terms watershed, field, and plot
will be used in an experimental sense (Wauchope, 19776). A watershed
is an area where all overland flow is naturally confined to a single out-
let (steam) and may be many square miles in size and contain a diversi-
ty of soils, crops or cover, and even weather. A field is an experiment-
al area of homogeneous crop, pesticide, and cultural practice (in run*
off work these have ranged from several hundred m' to several ha). A
plot is a subsection of a field (used especially for simulated-rainfall
studies), typically several hundred m' or less in area.
•C. N. Smith, R. A. Leonard, O. W. Langdale, and G. W. Bailey.
1978. Transport of agricultural chemicals from small upland pied-
mont watersheds. Draft in preparation. USEPA. Environ. Prot.
Technol. Ser.
Table 1— Nomenclature aad relevant properties of pc*tieide« mentioned IB text or tables, t
Common name
Alacalor
Aldrin
Amitrole
Arienic acid
Atrazine
Benzene
heuchloride
Cvbaryl
Carbofurao
Cyanazine
2.4-DUcid)
2.4-D(*alt>
2.4-D(esUr)
Trade name »nd
manufacturer?
LASSO, Monsanto
AMITROI/TArachem
DESICCANT L-10. Pennwalt
AATREX.CIBA-GEIGY
BHC. Hooker
SEVIN. union Carbide
FURADAN.FMC
BLADEX. Shell
Generally told as tails or
esters
WEEDAR 64. Amchem
ESTERON W.Dow
Chemical notation
2-cbloro-2 ',6 '-diethykWrnethoxynietliyUaeeUnilide
•
1.2.3.4.10.10-heuchlor-1.4.4a.&.8.8a-hexAhydro-M-
«iuto-fxo-5.d-duneth*nonaphthaleiM
3-anuno-s-triaxoIe
Arsenic add
2-ch]oro-4-{ethylamiiioHHi3Opropylainino)-*-triaziiM
1.2.3.4,5,6-hexachlorocyclohexane. consisting of
several isomers and containing a specified
percentage of gamma isoroer
1-naphthyl raethylcarbamaU
2.3-dihydro-2,2-dimcthyl-7-benxofuranyl
methylcarbamate
2-04-chJoro-WethyUmino>-j-tri«iin«-2-ylJaDuno}-2-
melhylpropionithle
|2.4-24
1
>12
12
>36
< 1
< It
12/
< 1
< 1
< 1
(continued on next page)
460 J. Environ. Qual., Vol. 7, no. 4,1978
-------
Tabk 1 —Continued
Common name
Trade namo and
manufacturert
Chemicai notation
Peetiddc
elat* Sohibitilrf
Penutenet
in*oi!1
DDT
Diazinoa
Dieunba (sail)
DichJobenil
Dieldrin
DinitruniM
Dipbenamid
Diuron
Endiin
PeBac(aalt)
Fluometuron
Foao/ca
Heptachlor
LinuroD
MethAxychlor
Methyl panthion
Metribuzin
Moliaate
MSMA
Paraquat
Parathion
Phorate
Protluralin
Prometryn
Propaehlor
SPECTRACIDE. CIBA-
GE1GY
BANVEUVelsicol
CASORON.ThompBoo-
Hayward
COBEXU.S. Borax
DYMID, Elanco
KARMEX DwPont
THIODAN.FMC
FENAC.Amehem
CCTORAN. CIBA-GEIGY
DYFONATE.St*uffer
LOROXDuPont
SENCOR. Chemagro
ORDRAM.Slauffer
ANSAR,AnsuJ
ORTHO PARAQUAT,
Chevron
PHOSKIL, FMC
THIMET. American
Cyan* mid
TORDON.Dow
TOLB AN. CIBA-GEIGY
CAPAROL, CIBA-GEIGY
RAMROD, Monsanto
MILOGARD. CIBA-GEIGY
SUMITOL(G&14254>.
CIBA-GEIGY
PRINCEP.CIBA-GEIGY
l.I.l-trichloro-2.2-bi«(plylhjrea
C^ethyl 5-phenyl ethy IphosphonodithioaU
1.4^,6.7.8,8-hepUcWoro-3a,4.7.7a-tet»hydro-l,7-
metbanoindene
3-(3.<-dichlorophenyl-l-niethory-l-iiiethylurea
ia,Mrichloro-2,2-bi9-«-tri«ane
OrgMMxhloruw
inaecticide
Organophoaphate
inaecticide
Benzoic acid
herbicide
Benxonitril*
berbia'de
Orgenochlorine
inaecticide
Dinitroanilin*
herbicide
AoeUmide
herbicide
Urea herbicide
Organochlorine
insecticide
OTganochlorine
insectide
Phenylacetic acid
herbicide
Urea herbicide'
Phosphate
inaecticide
Orgaaochlorine
isaecticide
Urea herbicide
OrgaBochfartDe
inaecticide
OrgiDOphoaphata
insecticide
Triaiine
herbicide
Thiocarbamate
herbicide
Anenical
herbicide
Bipyridinyl
herbicide
Organophoaphau
insecticide
Picofcuc acid
berbiciue
DuBtroaniliBe
herwaoe
ppmw
v.001
40
aol
18
0.1-0.25
1
260
42
< li
0.23
aol
90
13
< I/
75
0.1-0.25
50
1,220
800
Ml
aol
24
.80-85
sol
0.1
4ft
.
236
3
2
4
>36
•3
6
10
4
< It
>24
4
< 1
6
2
12
>24
< U
< 1
18
12
2
^ ••**»•« ""W « h USDA does it ^ty ^.iration undw Fit RA as
•
In Vmrraluae or typically sold under common name.
Vmrrauae or typicay so uner comm . *.iA«.«i>voL
fts^^
1. EiTiron. Qual., Vol. 7, no. 4, 19TI 46 1
big on climate and soil.
' Aaaumed from properuea o( aimilar compouada.
-------
Table f—Seasonal lessee of pesticide* from agricultural field*.
Site
Compound
Arsenic acid
(DsFl
AlruinefHwSI
Carbaryl |[gl)
CarbofuranUgl)
Cy«nazine(HwS)
g
2.4-D salMHsS)
2.4-D(HeSl
DDTtfeF)
Dieldrinllel)
Diphenamid
(HwS)
DiuronfHISl
EndosuJfan([«Fl
EndrintleP)
EndrintlgS)
FenaeaalUHsS)
Linuron(HwS|
Methocychlor
MelribiuinlHwS)
Methyl
pirathiondeF)
Location
Bie»el,TM.
Coahoeton. Ohio
University Park,
Pt.
Wattinav-ille. Ga.
Caauna. lowt
Coshocton, Ohio
Coshocton, Ohio
Watkinsville, Ga.
Ti/ton, Ga.
Watkinsville. Ga.
Preaquelale,
Mains
Rocky Mount,
N.C.
Lewis ton, N.C.
CUrlcsdeJe. Mis*
Coshocton. Ohio
Watkinsville, Ga.
Ga,
Baton Rouge, La.
Presque Isle.
Maine
Presque Isle.
LJ '»*.
Maine
Baton Rouge. La.
Baton Rouge, La.
Baton Rouge, La.
Coshectcn, Ohio
Stone villa. M is*.
Rocky Mount.
N.C.
Lewiston, N.C.
Area
h«
2.2-8.4
2.7
0.004
1.30
1.38
D.W-1.S4
0.79
O.S9
0.79
1.30
1.38
0.34
1.38
1.30
0.0061
0.0017
O.OW7
1B.6
0.79
1.09
0.68
2.71
J.26
0.045
0.0081
0.0081
0.045
0.045
0.045
0.0081
0.20
0.0017
0.0017
••••••MBMaiMM
Soil Crop or
Slope texture! Cover}
%
1-5 C
_ _
14 SICL
Z SUSCL
3 SUSCL
3 SUSCL
10-15 SiL
9.6 SO.
9.3 SiL
9.6 SiL
2 SCL
3 SL/SCL
3J! LS
3 SUSCL
2 SL/SCL
8 GL
4 LS
2 SL
0.2 SiC
9.6 SiL
14 SiL
14 SiL
2-10 GSL
3 SL/SC
0.2 SICL
S GL
B GL
0.2 SiCL
0.2 SiCL
0.2 SiCI
0.2 -SiL
0.5 SL
4 LS
2 SL
• • ,. •
Cotton
Cora
Com
Com
Cora
Com
Corn
Cora
Corn
Corn
Com
Cora
Com
Com
Corn
Potatoes
Potatoes/
oats
•Cotton
Cotton
Cotton
Corn
Com/whut
Com/wheat
Soybeans
Soybeans
Cotton
Potatoes
Potatoes
Potatoes/
oats
Sujarcant
Sugarcane
Soybeans
Grass
Soybeans
Cotton
Cotton
— IM^— ^^•"•™«^^™
Application
rate
kgrha
6.6
1.12
0.6
1.1
2J
4.5
6.7
9.0
2.24
4.48
$.56
3.8]
1.&4
3.36
4.03
1.46
3.36
3.36
3.36
3.36
6.03
(.41
3.11
4.16
1.61
1.35
0.56
0.56
0.56
1.55
1.68
0.73
0.73
13.4Tt
13.4Tt
13.4tt
isxtt
T.8tT
5.6
5.6
5.6
3.36
3.36
3.36
3.16
316
i*V
0.84
0,84
' 1. 05ft
1.56tt
O.S7tt
C.69TT
0.34
3*36
I.U
2.24
M ttM
24.24
22.5
C.M
ft KA
O.OO
13.4
13.4
13.4
13.4
Period
of
record
mo
36
3
4
4
4
4
4
4
6
E
a
4
9
2
4
1
1
3
3
3
3
8
6
8
3
1
6
y
3
i
2
15
16
3
3
6
f
30{J
4
27
8
3
3
3
3
6
2
3
3
3
15
3
25
10
1
i
3
3
2
14
1
fi
4
4
Runoff
Pesticide
No. of Total %of
events amount applied Total Reference
30
2
13
13
10
1!
'
13
3
7
3
-
•-
6
3
7
17
17
10
10
13
13
60
5
13
14
12
9
4
6
16
5
9
4
9
17
12
17
14
4
4
£
4
6
20
2
7
7
9
14
on
30
—
28-
28
28
28
28
28
32
32
13.3
10.9
8.0
11.1
5.5
2.4
2.8
6.8
0.8
4.1
1.5
2.7
4.1
0.7
0.0
2.4
8.2
7.8
3.3
2.4
8.0
B.4/
EJ5/
7.4
7.3
9.9
10.2
16.2
1.4
29
31
4.8
6.4
5.0
4.3
B.7
0.4
0.6*
3.3
4*1
3.4J
4.21
W/
13.3
3.0
0.6
5.6
0.95
1.1
.3.2
4.C
6.7
2.2
3.4
5.3
9.9
0.91
4.7
1.7
3.7
2.5
2.2
2J
3.0
6.1
4.9
LS
o.w
0.70
0.84
0.19
0.26
15.9
6.4
2.7
2.5
0.15
0.87
U
0.47
1.0
0.07
0.33
0.27
0.04
0.007
1.0
3.2
2.6
0.94H
3.1
l.W
o!o23
0,001
2.1
0.91
7.2
0.59
0.12
2.0
<0,04
<0.03
^0.1
OJ
0.93
0.00
0.77
0.11
0.19
0.0004
2.9
0.02
0.04
0.29
0.004?
2.1
D.9
0.008
0.024
0.13
0.25
g/ha
63
(3
10
40
65
98
160
270
110
220
64
7.2
11
28
7.7
3.8
530
180
91
85
7.3
47
58
20
16
1.0
1.8
1.5
0.22
0.11
•17
23
IS
340
130
420
150
127
1.3
0.4
120
30
240
20
3.8
66
<0.4
<0.2
*c 1*0
3.1
15
5.2
6.3
0.37
0.6
0.01
97
0.4
0.9
6.5
1.1
11
4.8
1.1
3.2
17
33
Richardson et al
H977J
Edwards 11972)
Hall eteL (1972)
Hall (197-1)
*
Smith1
RitteretaL<1974)
C*ro etal (1974)
Caroetal (19731
Smith'
White et aid 976}
Smith'
Epstein and Grant
(1965]
Sheets et alP 972)
Willis ct tL(l 975)
CaroetaL 11972)
Cam and Taylor
BniceetaL(l975)11
Smith'
Willis etaL 11975)
Epstein and Grant
C19MI .
WDUs and
Hamilton (1973)
Willis etaU19?5J
WiUistttL(1975)
Ed wards and Class
(1971)
Wauchopoelal
|1977e»
Shecu et aL 11972)
(continued on n«t page)
462 J. Environ. Qunl., Vol. 7, no. 4,197*
-------
Tables-Continued
* Site
• Compound
and u*ef
MSUAtHaS}
ParaquaMHsS)
Pfctoramaail
(HpS)
Piclorsxn ealt
(HaF)
PropaeUorfHwS)
I>ropazin«(HwS)
SecbunietoD
(HwS)
SaouintfUwS)
2,4.6-TsaJUKaF)
Terbuthylazioe
(HwSI
ToxmpbntOtF)
TriflursJioIHalt
Location
•WtoikCa.
Stone villa. Mis*.
WatlciBaviUe,Ga.
Arizona
Coehocton. Ohio
Button, Tex.
CaldwellTei.
RieseLTex
Castaoa. Icnri.
WatkinsvflJe,Ga.
University Park.
Pa.
Coshocton, Ohio
Coshocton, Ohio
RiestLTax.
University Park,
Pa.
Bocky Mount,
N.C.
Lewijton.N.C.
Ctarkadale,Miu.
WsHtinavai8,Ga.
Rocky Mount,
N.C.
Lewi*um.N.C.
fitonevflle,Mias,
ClaiksdaJe, Mlar,
Baton Rouge, La.
-
Area
ha
0.34
0.20
2.71
2.71
1J4
1*0
1.26
0.S5
0.0008
8.1
34
1.2
O-SJ-l.i*
2.71
0.0040
2.7
0,006
•1.2
0.0040
OM17
04017
1E.6
2.71
IM
0.0017
0.0017
0.20
15.6
16.6
0.045
Soil Crop or Application
Slope teituiet cover} rale
%
3.2 LS
O.S SL
3- 10 GSL
2-10 CSL
3 SUSCL
S . SUSCL
S SUSC
51 CLS
- S£L
- S
2.9 S
6 C
10-15 Stt.
2-10 GSL
14 SiCL
•a. —
- SIL
5 L
14 SiCL
4 LS
2 SL,
02 SSL
2-10 GSL
3 SL'SC
4 LS
3 SL
O.S SL
.
0.2 SiL
OS SiL
0.2 SiCL
Soybeans
Soybeans
Soybeans
Sorghiua
Corn
Corn
Soybeans
Bnui
Grtss
Grass
Grass
Grass
Con
SergBua
AJlsJfa
Corn
Grass
Grass
Con
Cotton
Cotton
Cotton
Soybeui
fjojrbon*
Cottoa
Cotton
Soybeans
Soybeans
Cotton
Cotton or
Sofbau*
kg/ha
2.24
8.96
8.94
1£J4
2.12
J.53
1.66
1.93
1.76
1.63
2.45
:.B3
:.t3
•, r»4
1.94
U3
10.4
1.24
0.56
0.56
tww
6.72 '
1.66
2.2
4.5
2.24
UJ
USfTT
2.24
4.48
£6.9
26.9
26.9
36.9
2&9
Sfi.J
aa.9
36.9
20.16
S0.lt
1.12
1.12
1.12
MX
1.12
1.12
LIJ
1.12
O.B4
0^4
1J2
US
1.40
J.40
L40
Period -
of
Eecord •
mo
4
1
7
6
3
3
1
4
1
2
4
2
2
6
3
3
3
11
2
12
9
1
2
3
3
3
14
6
6
6
3
3
6
6
6
6
4
4
UtTtt
12fTTT
4
3
Z
a
6
a
7
6
1
£
12
13
3
4
4
t See Table 1 (or nomenclature. First ccpiul letter indicates use 1 * inaeetidda. D * defoliant. H
Runoff
No. of
events
10
2
7
12
10
9
S
E
3
9
10
7
10
16
6
4,
13
8
-
-
ID
3
3
7
7
2
-
10
13
13
10
10
0
9
13
IS
13
13
21
39
ft
f
W
4
10
10
31
17
2
7
21
39
6
6
E
Pe*iictd* fc-si
Total %of
amount applied
cm
0.64
4.6
7.1
4.8
17.5
1.4
1A
£.6
2.4
11.1
10J
£.0
13 .3
9J
4J
e.o
-
0.7
-
—
J2.6
24
2.9
Low
Low
-
• ZJ
12.6
4J
4^
7.0
7.3
3i
3.4
10.1
10.2
9.7
9.9
74J
£8.0
4*
6.4
9.2
6J
Jl-8
6.1
1 8.2
13.8
4.6
6.7
745
W.O
Oi
1£.6
3.4
0.1
2.0
U
6.1
18.3
32.0*/
0.91
0.93
2.0
4.0
3.2
9.4
IOJ
4.6
3.0
tjttl
4Jt
ooxn
0.002
0.002
O£3
3,1
6.1
0.02
0.03
3.5
0-067
OJ3
S.O
5.7
OJ1
0^1
0.078
0.13
0.40
0.71
0 !1
O.S2
0.53
0.48
0.12
0.16
4X20
OJ4
0.48
0^7
0.46
0.76
0.12
0.04
oja
0.18
<0.03I
0
0.04
Total
Kfoa
2
1BO
130
780
390
340
IE
18
94
63
79
ISO
17D
710
68
83
470
0.16
0.01
0.01
i.9
210
100
0.44
IX
78
7.6
.
S.9
no
260
83
140
21
36
110
300
34
89
130
97
U
3.9
i3
3.7
S.<
3.0
6-2
&£
1.0
OJ
S.O
2.Q
O.J4
0
04
Refereece
Wauchopaetal
(1977b)
Smith'
Davtta,ndlQgebo
0973)
Glass and Edwards
(1974)
Seifrtsetal(1977)
Bovsyetsi(1974)
Ritteretai.il 9741
Smith'
Hall [1974)
Edwards (19721
Ed ward* sad Glass
U97U
Boveyetai (187*)
Hall 11 974)
Sba*taetaUl972)
Willis etaL (197 6)
Smith'
Sheets «tal. (19731
Waacfcop*
Wjllls M al [1976}
Wi{li*(tsi|197£j
• herbicide; towtr use feucr indicate* lornmlaUoo;
. g - Rr.nulcs, Y " liquid dispersed in wtwr. p - peilel* a * towou aoUrtinii. w » potrd«r«Lfiper»«d in water. Seeood r»»din»iL
t C * clay. Si v ittUyl, L » koamly^ S - sandty). G * eravellly). .
| iDdtMJee COVK emercioff befor* or efcw appiica tioK in the Utur cam. CaJd usually bare at
1 Not pvem by author, »tum»u>d trom other dau.
. I iDcludeeaomepntiMUnenirunott.
tTSiuucf rouHipIo applications. l)-picaUy applied at 1-wmk intcrvala.
J1 Applied witK toiiphene. which (weiiibly ariod *(. ioiifgt "tticitaf", dazmttiof wttbtO.
'
•^ Compleu tiau in Smith'.
ff Probably indudoj nsiduu from 10 x rate applied previous yvar.
ttt CatcuUlions based ea two applicaLoni Jout of live! tK»t were followed by runotf evwta.
f f ff Observations pegu 1 year * i \a a ppticsuoa.
-------
20
10
I •
wettable powders
fra
a>
Q.
O
6
ior organochlorine
10
all others
-3
-2-1
log(%Jost)
Fig. \ — Total long-terra losses (To of applied amounts) of pesticides
vs. the number of experiments (applications) which have shown
such losses.
occur on the site (referred to hereafter as a critical
event — see below).
2) Pesticides that are water insoluble and, therefore,
usually applied as emulsions (most are foliar-applied in-
secticides) show the next worst long-term losses: 1% or
less. An exception is DDT, which, even when compared
to other organochlorine compounds, appears to remain
"available" for washoff for longer periods and consist-
ently shows losses of 2-3%. (As a class, the organo-
chlorine insecticides are the most persistent pesticides
and their season or annual losses are less sensitive to
rainfall timing.)
3) Water-soluble pesticides applied as aqueous solu-
tions and pesticides incorporated into the soil make up
the bulk of the remaining entries in Table 2. These
usually show losses of 0.5% or less. Exceptions are
paraquat and the arsenicals, which will be discussed
later. As with wettable powders, losses can be typically
3 x this, level if a large, early runoff event 'occurs (see
below). Incorporated pesticides are less sensitive to
storm timing, although Caro and Taylor (1971) ob-
served a single early event on incorporated dieldrin in
which the loss exceeded all later events combined. In the
many studies with trifluralin, however and with granu-
lar incorporated materials (Carp et al., 1973), even
severe events soon after application did not drastically
tffect overall losses.
When long-term loss patterns are analyzed in detail, it
becomes obvious that single-storm losses can be very
important. Except for one study on granular, incorpo-
rated carbofuran (Caro ct al., 1973), the exceptions to
the above generalizations on maximum losses were
always a result of a single runoff event that produced
losses that dwarfed those during the rcsi of the season.
Three types of important runoff events may be defined,
and these definitions will clarify the discussion on con-
centration and simulation data below.
A critical runoff event may be defined in terms of
timing and intensity. It is one which qcurs within 2
weeks of pesticide application, has at least a cm of rain
and has a runoff volume.which is 50% or more of the
precipitation. These events almost always produce the
bulk of the runoff losses observed for an entire season
unless the chemical is incorporated or is extremely per-
sistent.
A catastrophic event, defined in terms of pesticide
losses, is an event which produces runoff losses of 2%
or more of the applied amount. This is an arbitrary
definition used to set apart events which move relatively
large amounts of chemicals.
A third type of event that is neither critical or
catastrophic may still have a transient effect on water
quality: A small rain, soon after application, may, be-
cause of low runoff volume combined with high pesti-
cide residues in the field, produce very high concentra-
tions in the runoff even though total losses are small.
These events are observed particularly with wettable
powders.
Concentration of Pesticides in Runoff
•Short-term experiments on large watersheds generally
have been confined to measuring pesticide concentra-
tions. These experiments provide data useful either as a
supplement to the long-term data in Table 1 or provide
data on other compounds or situations, such as forest
sites. While these short-term experiments cannot be
alnne \r\ predict long-|erm losses, they can provide
maximum runoff concentrations from a given
application. These concentrations, along with" concen-
trations maxima from the experiments summarized in
Table 2, are given in Table 3 and summarized in Fig. 2.
Pesticide concentrations in runoff may vary by an
order of magnitude or more during a single runoff
event, and even event averages for a given chemical are
almost unique for each situation, depending on rate of
application, storm intensity and timing, field site, etc.
Add to this complexity all the factors which may
drastically reduce edge-of-field concentrations after
runoff leaves the field (dilution by receiving waters, ad-
sorption by stream sediments -or untreated soil or
vegetation surfaces, etc.), and it is obvious that concen-
tration is a highly transient property. In order to make
some sense of these data, Table 3 has been ordered into
listings by formulation type and application target.
Event averages, rather than instantaneous sample
values, are given since these are usually the values re-
ported. Bulk concentrations are emphasized (/ig pesti-
cide per liter of water-sediment mixture) but some sedi-
ment values arc also given lor comparison; the subtleties
of water/sediment partitioning will be discussed later.
As might be expected, the most soluble pesticides tend
to give the highest runoff concentrations, u/i/es? they
arc applied to bare soil, where leaching into the soil in-
terior lowers the amount available for washoff.
The classification in Table 3 oi experiments on water-
soluble pesticides into "foliar-applied" or "soil-
applied" categories is somewhat arbitrary, as reports
464 J, Environ. Qual., Vol. 7, no. 4, 1978
-------
Table 3—Muiniura observed concentrations of pesticides in runoff (event average), in drainage streams below (rented am-
or in irrigation outflow,
Runoff eoneentra tion in
Application .Sediment
Compound*
Alachlor
2,4-D ester
2,4-D insoL salt
DDT
Dieldrut
Diuron
Endosulfan
Eodria
Methoxyehlor
Methyl para thion
Tozapheae
Arsenic acid
2,4-D salt
Dieamba (salt)
Pjcloram (salt)
2.4,5>T(salt|
2,4-D (acid)
2,4-D (salt)
Dieamba
Fenae
MSMA
Picloram (salt)
2.4.5-TlaaJt) •
Atruiitt
Cyanazine
Dichlobenil
rate
kg/ha
2.24
0.46.4.93
1.68
1.S5
0.73
1.12-4.48
7.84
5.6
0.84
2.06
0.35
0.29
0.34,0.34
22.50
3.4-4.5, 9.0
2.24-22.4
6.6
1-41
2.24
0.56
0.56
0.56-21
1.12,2.24
2.24
0.56
0.66
0.49-21
2.24
0.56
0.56
0.56
2,46
2.24
3.36
2.24. 9
0.28
0.56
1.1
1.12
1.12
2.24
10.4
0.56
2.24
11.2
0.6
1 12
AcA*
1.1, 2.2
1.45
i *>t
4*9*
1.6-3.3
3JJ6
3.36
3.36,3.51
S.36.4.03
A AH
^.^w
4.4-9.0
1.35
1ft*
•91
3.24
6.7-7.0
phase Bulk*. Notes
ppmw Ppbw
Low-so'ubilj ty « 250 ppmw) pesticides applied as emulsions to folia ere or toil surface
1 76-184 Severe storm; 33-m' plots
870{. 1,780 Severe storm; 20-m1 plots
2.1 309 1.3-ha
0.03 1.2 1.38-ha; cone, measured below grass waterway
83 81-m1 plots
S66-743 17-m1 plots
30 15.6-ha. 0.2% slope
12.2 3-120 0.7-ha
0-<10 0.04-ha, 0.2% slope
74 2.5-ha.3-12%slope
18 81-m1 plots
33-49 81-m1 plots
1.2. 2.9 0.04-ha. 0.2% slope
'0.2-0.5 Stream cone in 3.000- ha watershed
9 8-m1 plot
15-30. 274 17-m1 plots
100-543 17-m1 plots
Water-soluble (> 10% wl/voll pesticides applied mainly to foliage
6-40/ 20-250* 2 to 8-ha; cotton defoliation
1,600-4.200 0.5 to 2.2- ha "hilly" watersheds
4.810 9-m' plots
285-353 4 to 8-ha
520 24-m1 plot
1,100-4,200 0.6-ha
1,980-3,810, 9-m1 plots
2,170-5.210
16 6-m* plots; 30 days after aDDlieation
117-160 4t«8-ha
618 24-m1 plot
850-1,380 0.4-to2-ha
3,300 9-m1 plots
Water-soluble (> 10% wt/votl pesticides applied to sparse vegetation or bare soil
1.0 22} Severe storm: 30-m1 plots
3-8 0.34-ha
2.8 25 Severe storm: 30-m1 plots
70-110} Severe storm: 20-m' plots
1,600 9-m1 plot
24-310 0.04-ha, 0.2%
108,450 0.2-,0.3-ha
17 0.2-ha irrigation outflow
12 1^-hit: 72 days after application
105 ha-size range areas
10-28 1.6-to32-ha
2-90 0.56-ha
650 .9-m« plots
370 0-85-ha, 20% slope, cone, diluted by water from
Untreated areas
26 1.2-ha, 72 days after application
2.600 9-m' plot
380 8-m* plot
Wettable powder-forrm)l»'«d .herbicides, applied to soil surface
0.4 400 40-m' plots, 14% slope
180 2.7-ha
1.0.0-1.4 800.800-2.300 40-m' plots. 14% slope
0.5 37 1.38 ha; cone, measured below grass waterway
1.6 109 2.7 ha
2.3-8.8 120-408 Slightly incorporated: severe storm on 20-m1 plots
6.7 627-1.460 Severe storm: 20-m1 plots
900-3.400 0.5-1.2 ha. 10-15% slope
3.2,4.1 200.1.900 1.30. 1.39 ha
0.6, 0.6 160. 330 1.38-hai cone measured below grass waterway
850 2.7-ha
3.8-1 1 1.950-4,700 40-m1 plots. 14% slope
0.2 13 1.38-ha; cone measured below grass waterway
24 193 1.3-ha
1.0 101-275 Severe storm: 33-m' plots
6.9- 17.5 31 1 -634 Severe storm: 33-m1 plots
References
Baker etal. (1976)
Barnttt etol. (19671
Smith*
EpsteinandGrar.t tl96*i
Sheets etol. 11972)
Willis el«L (19761
Caro and Tavlor ( 1 971 )
Willis etal. U975I
Green etal. (1977)
Epstein and Grant ( 1 96r
Epstein and Grant C19BV
Willis and Hamilton 1197:;
Lauer etal. (19661
Edwards and Glass 11971
Sheets ctaL (19721
Sheets etal (19721
Richardson et al. (1978)
Evans and Duscja (1973'
TricheU etaL (1968)
Scifres etal. 11977)
Bovey etal. 11974)
Evans and DuseJH 1197
Trichell etal. 11966)
Gkss and Edwards (19
Scifres etal. (19771
Bovey etal.11974)
Evans and Duseja (1973.
TricheU etaL (19681
Asmussen etal. (1977) •
White etaL (19761
Harriett etol. (1967!
Trichell el a I.(19C8)
Willis elal. (1975)
Wauchopecial. (1977al
Scifres etal. 1)971)
Boveyetal.11974)
Haas etal. (1971)
Evans and Dusrja 1 1 973)
Baur etaL (1972)
Trichell etaL 11968)
Da vis and Ingebo(1973l
Bovey ctaL (1974)
TricheU etal. (19681
Edwards and G lass 1 1 97 1 1
HaUetaL{J972)
Edwards 11972)
Hall etaL (1974)
Smith*
Bailey etal.(l974a)
White etal. I19U7I
Hitter etaL (19741
Smith*
Edwards 11972)
IUltetal.11974)
Smith*
Bskcrttal.fi 976)
Bailey etal. 11 974al
(continued on next page)
J. Environ. Qunl., Vol. 7, no. 4,1978 465
-------
Tables-Continued.
Runoff concentration in
Compoundt
rHpKenf mffl
FhtODBturoB
LiauroD
Metribuiln
Apple* tion
rale
k«/ha
8.36-3.62
2.31-3.36
3.36
2.8
2.24
O.«l
Sediment
phaee
ppmw
*
0.6-0.9
0.6-0.8
1.2
iai
Bulkj
ppbv
123-1.645
23-63
65.000
32«
14-124
10
Not*.
2.71 ha
1.26 ha; cone. BMJurod below gnu waterway
1.25 ha; low-volume 1 it event
Severe t term; 7-mJ ploU
0.4-ha
2-m'ploU
Reference*
Smith1
Baldwin etalfmsb)
Willis etaL (1976)
DuMja (peraetuU
Prometryn
Propacblor
Propazine
SecbumeUm
Terbuthyluioe
Dieldria
Trinuralin
Carbaryl
Carboruran
Diaiinon
Ponofoa
Molina te
Amltrole
Benzene heiachlorid*
2,4-D ester
Dicamba
2,4,6-TaaH
2.4,&-T eater
Paraquat
0.66,0.66
2.8
6.72
1.66
1.68,3.36
2.2.4.4
2.24
2.24.4.43
6.6
0.84
1.12
1.12
1.12
1.40
6.03
4.16,6.41
1.12
1.12
4.48
11.2
4.6
1.12
0.66
2.24.4.46
1.63-2.12
1.63-1.94
1.63
16.34
16.34
2.46
1.9$
21.6
8.30
12.2
0.03-0.04
0.1
1.2
0.6,1.6
. 0.17
0.2-1.0
61-980
34-66
37
224
421
1.470
10,63 0.2-Ha
97{ 7-m'plota
1.702 0.6- to 1.6-ha. 10-16% slope
401 2.7-ha, tone, measured twiow graa* waterway
272.467 37-m>;irrigat!iD outflow
280, 420 40-ra1 plots 14 % slope
300 2.7-ha
900.1,800 40-m'plota
Emulsion sprays, incorporatedI toto sofl
3.2-120 0.7-ha
O.S-2.7 0.2-ha
7.7-23.9 17-m'plot*
7-16 2.71 ha
9-10 1.26 ha.: cone, measured below grass waterway
0-1.9 0.04-ha
Granular peaticidea. incorporated into aoH
0.8 ha. 10% alope
0.8 and 0.6 ha, 10% slope
0.6- to 1.5-ha
Severe storm; 33-m' plots
Irrigation outflow
Otter cases (see teit)
400 Drainage stream cone, below forest
16 Drainage stream cone, below forest
2,000 ft Drainage stream cone, below forest
38 tt Drainage stream cone, below forest
0.100ft Drainage stream cone, below forest
1.000.2.100 0.6-ha, applied in dteael fuel
64-1.000 1.3 to 2.7 ha
$1-254 1.26 to 1.38 ha; eone. measured below grass waterway
1,637 2.7 ha; include* residues from previous year
3.501 2.7 ha; atom 27 days after application
7,965 1.26 ha; storm 2 days after application
7.406 1.3 ha: low-voL 1st event
conunimici, tionj
Bald win ttaL(197Sa)
Hitter etai (1974)
South'
Evans and Duseja (1973)
Hall (1914)
Edwards (1972)
Hall (197 4)
C«roetal<1972)
Wauehope1
Sheets etal (1972)
Smith'
248
1,000.1.400
100
6-60
780
Can etaL (1974)
Caroetal(1974)
Hitter et eld 974)
Baker et aid 976)
Tarrant and Norris (1967)
Jackson et si (1974)
Aldhous(1967)
Norris and Montgomery
(1976)
Montgomery and Norn's
(1970)
Lawaon(1976)
Smith1'
T See Table 1 for nomenclature. ,,.„>•.
f Concentration in water plus suspended sediment, ntfliter. concentrations »epan ted by commas correspond to different application rate* given,
{ From application to dry soil; concentration was touch higher from application to wet toil.
1 RatM adjuetad for partial trnatment ot watershed.
I Concentration aa elemental As: natural As (probably 5 ppn>or more) al»o present in Mdunent
TT Water may have been directly contaoinated by application.
seldom define precisely how deposition of a spray appli-
cation was distributed. Sod and grass sites were placed
in the former category and chapparal, range, and fallow
sites were placed in the latter. Even with this uncertain-
ty, the contrast between soil- and foliar-applied water-
soluble pesticides is apparent. The contrast was also
• specifically shown in an experiment by TricheJl et al.
(1968), who in one case observed almost four times
greater losses of dicamba from sod plots than from
fallow plots.
Wcttable powders also give high runoff concentra-
tions. However, there is an inverse dependence of run-
off concentration on the solubility of the herbicide. Hall
(1974) observed runoff concentrations of 272 and 487
ppb for sccbumcion (solubility 620 ppm) under condi-
tions where concentrations of atrazine and terbuthyla-
zinc (solubilities of 33 and 8.5 ppm, respectively)
reached 2,000 ppm or more. Metribuzin, which is solu-
ble enough such that half of it may be in true solution in
the spray tank, gave a maximum concentration of 53
ppm on flat soil', and might be classified in the water-
soluble category in Table 3.
^Thcrc is considerable discussion among scientists do-
ing this research as to the usefulness of runoff data from
small plots. The data in Table 3 suggests that small plots
are reasonable simulators of larger fields (several ha) as
•R, D. Wauchope. K. E. SavaRt. and E. B. Hollinpswoilh. 1977.
Trinuralin. mciribuiin, and MS MA in surface v,aiei irom » Mtsiu-
»ippi Delta field. Abitr. WecdSci. Soc. Am. 1977:60.
466 J.Eov»r
-------
PESTICIOE APPLICATION
INCORPORATED EMULSIONS
OR GRANULES
INSOLUBLE PESTICIDES. APPLIED
AS EMULSIONS TO SOIL SURFACE
OR CROP FOLIAGE
SOLUBLE PESTICIDES, APPLIED
AS SOLUTIONS TO SOIL SURFACE
WETTABLE POWDERS, APPLIED
TO SOIL SURFACE
SOLUBLE PESTICIOCS. APPLIED
TO CROP FOLIACE
CONCENTRATION OF PESTICIDE
IN RUNOFF --MAXIMUM VALUES
OBSERVED IN DIFFERENT
EXPERIMENTS
log {cone, ppb)
'1- 2—Maximum runoff concentrations (event averages) observed
for pesticides, grouped by application conditions. Each horizontal
bar represents a different compound (active ingredient), and (he
range Is for different applications, site*, tic. Narrow ranges proba-
bly simply reflect a smaller number of experiments. The dark ban
•re for incorporated granular pesticides.
far as concentrations are concerned. Table 2 indicates,
however, that the small plots which have been used
(s 0.005 ha or Jess) can overestimate total long-term
losses (loads) from larger sites by a factor up to i\(see
trifluralin and atrazine data), and the difference may be
larger when considering fields of many hectares. Per-
haps the difference is related in some way to the more
rapid or more complete hydrologic response of the small
sites.
Catastrophic Even Is: Simulation of Worst-Case
Conditions and (he Importance of
Storm Timing
Single-event runoff losses in the range of 1-2*70 are
not uncommon for a wide range of pesticides. Losses
greater than this, however, are usually the result of ex-
treme conditions. 1 have called such events catastrophic,
in terms of the amounts of pesticide (>2"?o) that are
{ost, and alt such events found in the literature are given
in Table 4. A catastrophic event is (he usual result of a
severe-storm simulation experiment on a small plot, but
may also occur, though rarely, on larger fields under
natural conditions (Table 4).
Several generalizations can be made from the data of
Tables 3 and 4.
1) Catastrophic events arc almost without exception
the first event to occur on a site after application. Storm
timing is, in fad, as important as slorm intensity in pro-
ducing a catastrophic event. The exceptions arc, as
might be expected, with the most persistent compounds,
DDT and paraquat. Excluding these two, the average
time between application and a catastrophic event was 3
days.
2) Single-event losses of S^o or more occur almost ex-
clusively in small-plot simulation studies. The excep-
tions are with soil surface-applied wcttable powders and
paraquat to be discussed later.
3) Reference to Tables 3 and 4 will show that cata-
strophic losses are a result of unusually large runoff vol-
umes, not of unusually high concentrations of pesti-
cides. In fact, low-volume events on large watersheds
typically result in the highest concentrations given in
Table 3.
The 15% loss of atrazine from a large watershed re-
ported by Ritter et al. (1974) is apparently an overesti-
mate.' The concentrations used by those authors to cal-
culate losses were based on samples taken early in the
runoff event, when concentrations are high (see discus-
sion on mechanisms of losses of wettable powder).
Later concentrations were estimated from sediment-
toad relationships, which would yield overestimates,
since atrazine is transported mainly early in the water
phase.
What can we conclude about the validity of simulated
catastrophic events on small plots? In fact, they appear
to give realistic results, if we compare them to large-site,
natural-rainfall experiment results extrapolated to the
same conditions. There is no reason to suppose that
single-event losses of, say, 10% of any pesticide cannot
occur, unless it is incorporated. Tint probability of such
losses is, however, extremely small, because a storm of
very low annual probability is required, and it must oc-
cur within a very short time period after application. In
addition, such events arc typically highly localized in na-
ture (however, the probabilities given in Table 4 are for
the occurrence of an event of that intensity over a large
area, and the probability of the intensity occurring
locally is much higher). If an entire basin or large (many
square miles) watershed were subjected to the kind of
rainfall that produces a catastrophic runoff event, pesti-
cide pollution in the resulting runoff would be the least
of local concerns.
SOME GENERAL CONSIDERATIONS
Half Lives and (he Significance of Storm Timing
With the banning of the most persistent organo-
chlorine insecticides, most pesticides now in general use
in agriculture have a persistence lime (defined here as
the time required for soil pesticide concentrations to de-
cline to lO'Vo of initial values) of a year or less (Table 1).
Pesticide dissipation in soils is usually observed to be
approximately exponential in form, i.e., Ct, = CV, x
exp[ - AYJfi - /if], where k is a constant and CV, and Ct,
are the concentration of pesticide in the soil at succcs-
' W. F. Kilter. personal communication. H77, A priming error in
the paper by Kilter et al. (197-t) should also be noted: in Table I. run-
off amounts for the storms of 4-13-70 ;md4OO-70 are reversed lor the
ridded vs. surface-contoured watershed; i.e., runoff losses were higher
from I he latter than from the former.
J. Environ. Qua!., Vol. 7, no. 4,1978 467
-------
Table 4—Single catastrophic event* (losses *2% of applied pesticide).
Compound
aaduaet
AtrazineJHwS)
AlaehlortHeS)
CyanaanefHwS}
2.4-DaodtHsS)
2.4'Daalt(HaS)
2.4-DesUrs(H«S}
DDTtleF)
Dicamba(HsF)
Dichlobenil(HwS)
Diphenamid) H wS)
FenacaalUHsS)
Fonofoadgl)
ParaquaUHsS)
Pidoram(HiF)
PromedyafHwS)
Prop«chI
PropaiiixsfHwSl
2.4.i.TacidfHsF)
2,4.5-Tcst*rtHeS)
RainJiU
Amount!
en
-
1.3 S
3.2 S
6.4 S
14 S
—
21 S
21 5
13 S
IS S
7-13S
3.4. 10 S
4.5.5
1.27 S
14 S
1.9
7.4
20 S
1.9.6.4
5
2-9
1.27 S
1.27 em/
bourS
intensity
_
4.7
1.27 S
6.05
Duration
Bin
-
12
30
60
120
—
tt
n.
30
120
120
30.90
_
60
120
—
_
tt
.
_
_
60
_
M
60
Event
frequency}
year
-
< 1
1
10
100
—
MOO
MOO
MOO
MOO
10- MOO
1.BO
_
< 1
100
—
••
_
_
_
_
< 1
-
_
< 1
Runoff
ere
0.41
0.18
1.6
3.6
9
l.E, 1.3
6-17
e-it
6.10
8-9
4-11
2.7
1.4. 1.3
-0.1.
9
1,4
2.9
6-12
1.4,2.6
4
0.4-8
-0.1
1.0
1.0
2.6
-0.1
0.34
Time after
application
days
7
<1
<1
<1
<1
7,34
2
2
1
• wet soD
Applied in diesel fuel to cleared
forest area
Rafertac*
Rittoetil (1974|
White etal (1967)
Bailey etaL(1974al
Ritlar etaL (1974)
Baker etaL (1976)
Baker etaL (1976)
Asmussenetal
11977]
Baruett etaL (196 7>
Barnett etaL (1967)
Sheets et si (19721
TricheUetaL(19fi8)
Bailey etaL(1974a|
Smith'
Williaetai (1975)
Baker etal (1976)
Smith'
Trichelletal<19€5)
Baldwin at aL
(1875*1
Rltter etal (1974)
Smith'
Tricbell etaL (1968)
Lawsoa (1976)
t Sec Table 1 for nomenclature and symbols.
i S indicates simulated rainfelL
$ Probable period in which given event will occur once, from long-term weather record*.
] Se* Table 3 (or application rates.
I This value proba bly too high: sec text.
tt Total for 3 events iii < 24 hours.
n Runoff from this event may have been contaminated by a 10 x higher rat« application on this site in the prawns year.
sivc times /, and /,.* Half lives, & term often used to dis-
cuss dissipation rates are, (for simple exponential decay)
about 0.3 of the persistence times.
" It might be tempting to use soil persistence times or
halflivcs to estimate the pesticide residues available, for
runoff, as a function of time after application. The situ-
ation is actually more complicated than this; several
other processes appear to be much more important in
determining availability. It is obvious from the data of-
Table 3 that pesticides that are deposited on the surfaces
of foliage and soil are most available for transport.
However, it is these surface residues that are most sub-
ject to rapid volatilization and photodegradation and to
leaching into the body of the soil by rainfall. For these
reasons, while many runoff experiments do show ex-
ponential decreases in pcsiicidc concentration in runoff
water in successive events, the decline is much steeper
lhan for soil concentrations. Data from many of the
long-term experiments give excellent linear plots for log
(pesticide concentration in runoff) vs. lime, extending
to three or more half-lives. Some examples ol ninoIT-
available-pesticide half-lives obtained this way are:
Airazinc: 7-10 days
-------
Pirtilioning of Peslicidcs between rhc Sediment
sod Water Phases of Runoff: Effects of
Erosion Control Practices
If a pesticide is carried off a field primarily in (he
sediment phase of runoff, then its loss should be con-
trollable by soil conservation practices. Sediment is the
most important pollutant in runoff water (McDowell
and Grissingcr, 1976), and efforts to control it remain
inadequate (Carter, 1977). It could be hoped, then, that
eventual better control of erosional losses of soil would
also reduce "piggyback" pesticide losses.
Unfortunately, although pesticide concentrations are
often 2-3 orders of magnitude higher in sediments than
in the associated water (Table 3), most pesticides are still
lost mainly in the water phase, simply because sediment
is usually such a small fraction, by weight or by volume,
of runoff.' In Fig. 1 the ranges of fractions of pesticides
lost in the aqueous phase of runoff reported in the
literature arc plotted as a function of solubility. A sim-
ple S-curve fits the data surprisingly well, considering
the tremendous variety of chemicals, sites, weather etc.
that is represented. The implications are clear: erosion-
control practices, except as they control water as well as
sediment losses, can be expected to have little effect on
runoff losses of pesticides, except those having solubili-
ties of 1 ppm or less or ionic pesticides with extreme
clay-binding capabilities (paraquat and arsenicals).
Several experiments in which low-till or other erosion
control practices have been studied bear this out. Baker
et al. (1976) used six different cultural practices in small-
plot simulation studies; erosion was decreased in some
cases but runoff losses of alachlor and cyanazine were
little affected. Losses of fonofos, a more insoluble com-
pound, were decreased by erosion control. Smith1 found
that losses of atrazine and diphenamid were similar on
terraced and nonterraced watersheds, but the terraced
watersheds gave much lower sediment and paraquat
losses. Ritter ct al. (1974) greatly reduced runoff vol-
umes by use of'ridged corn planting rather than
contour-tillage only, and reductions in atrazine losses
were proportional.'
Several other results of research on sediment-water
partitioning of pesticides may be mentioned briefly. For
the more soluble pesticides, the fraction of pesticide
load that is in the sediment phase increases with suc-
ceeding runoff events (Hall et ah, 1972: Caro et al.,
1974; \Vhite et al., 1976). This observation suggests that,
for these pesticides, the "available" fraction is simply
that fraction of the applied material which is easily dis-
solved by runoff.
Baldwin et al. (1975b) showed that if fluometuron
was surface applied to moist, rather than dry, soil,
losses were significantly higher (Table 3), and the frac-
tion that was lost in the solution phase was higher (98%
vs. 80%). This is an example of the effects of nonre-
versible soil adsorption, an aspect of soil-water parti-
tioning which is beyond the scope of this article. Several
excellent reviews are available on soil-water partitioning
of pesticides: e.g., Bailey and White (1964), Pionkeand
•Of course, if the runoff contains Hide or no sediment, then lasses
will have to be in the waier phase. Under Ihese conditions, however,
the tot*I amouat of JOM, for highJy-sorbed pesticides, is relatively
small.
Chestcrs (1973), Stevenson (1972), and Gucnzi (1974).
Other authors have also reported increased losses when
the spil is moist during the time of application, for 2,4-
D acid, salts, and esters (Asmusscn ct al., 1977; Burnett
ct al., 1967) and for prometryn (Baldwin, 1975a).
Soil Dust and Wcttable Powders as Vehicles
for Runoff Losses
Consider a bare soil that has been cultivated, perhaps
double-disked or harrowed to incorporate a prcplant
herbicide, prepared for planting, and planted. The re-
sulting soil surface is powder-dry and coated with a thin
layer of dust which has been generated by these opera-
tions—a dust composed principally of clay particles. A
pesticide is now applied, forming a thin film of emul-
sion, solution, or dispersed powder at the soil surface.
For paraquat and the arsenical herbicides, the spray is
a true aqueous solution that is absorbed by the soil sur-
face and dust. The water evaporates, and the dust itself
becomes a powdery vehicle for these herbicides, since
they are tenaciously bound to clay surfaces by ionic
bonds (Weber and Weed, 1968; Dickens and Hihbold,
1967.; Wauchope, 1975). If the herbicide is a wettable
powder, the evaporation of spray water simply leaves
this powder at the surface—a powder that is formulated
for easy dispersal in water.
Now let us imagine that a thunderstorm occurs 1 day
later and, say, 5 cm of rain falls rapidly enough so that 1
cm of runoff occurs. The 4 cm of water that infiltrates
into the soil will, to the extent that the herbicide is solu-
ble, leach it downward into the soil body. Paraquat is
essentially immobile and will remain at the soil surface.
Some leaching of the powder-formulated triazines
might be expected (an interesting slurry experiment by
Hance (1976) on the kinetics of herbicide transfer from
wettable powder particles to soil granules throws some
light on this process). The arsenicals apparently lie
somewhere in between. In any case the runoff will pick
up the herbicide-loaded dust, or the wettable powder,
with ease, and losses follow the order paraquat > in-
soluble WP's > arsenicals & soluble WP's, which is
seen in Table 2.
This soil- or formulation-dust scheme seems to offer a
plausible explanation for the uniquely large runoff
losses of wettable powders and paraquat, and there is
other evidence to suggest that dust is important in run-
off losses. Spencer et al. (1975) sampled soil surface
dust under the dripline of-citrus trees treated with
paralhion and found very high concentrations (up to
650 ppm) of the insecticide on the dust. Rainfall dras-
tically reduced these dust concentrations. Low-volume
runoff events have been reported which show very high
concentrations of wettable powders or paraquat, even
under conditions where erosion is not severe; an extreme
example is reported by Smith' for a paraquat- and atra-
zine-treatcd site. In a first event 6 days alter application,
a relatively small (I.57-cm) rain produced only 0.02 cm
of runoff, but this runoff contained 1,900 ppb of atra-
zine (4,100 ppb in the sediment) and the sediment con-
tained 1,500 ppm of paraquat. A second, larcer event 3
weeks Later showed drastically reduced (9SVt) concen-
trations. Early samples taken during large first events
would be expected to show very high pesticide conccn-
J.EnvlK».Qu*l.,Vol.7,no.4,197a 469
-------
trations as pesticide-loaded dust or wettablc powders
come off the field with the water front. This has been
observed for atrazine by White et ah (1967) and for
wettable powders and paraquat by Smith.' A rapid de-
cline in pesticide concentration during a runoff event
may explain why the sediment load calculations used by
Kilter et al. (1974) together with concentrations in sam-
ples taken early in events led to large overestimates of
atrazine losses.
Dusts, however, are obviously not ihe only source of
easily removed residues in a first storm after applica-
tion; high concentrations early in such events are a gen-
eral phenomenon, regardless of the pesticide applied.
The paraquat experiments of Smith3 and the MSMA
experiments of Wauchope et al. (J977a) were artificial
in that the herbicides were applied to bare soil—both are
normally applied to foliage. Losses from foliar applica-
tions might be larger or smaller; prediction is uncertain.
CONCLUSIONS: WATER QUALITY
IMPLICATIONS AND RESEARCH NEEDS
Classification of Pesticides—Some Rules of Thumb
for Predicting Losses
Any rule of thumb that might be proposed for pre-
dicting edge-of-fiefd Josses is like a ruJff of grammar—as
soon as it is stated an exception springs to mind. Never-
theless, there are consistent patterns in Tables 1-3, and I
would like to propose three classes of pesticides by po-
tential annual loss or environmental impact that might
be useful in water-quality planning for large regions or
basins.
FOLIAR-APPLIED ORGANOCHLORJNE INSECTICIDES
These are Jost in reJat?vely large amounts because they
are persistent and because, compared with other pesti-
cides, large quantities are applied. In addition they are
foxic enough lo aquatic life so that runoff can produce
acute effects such as fish kills. 1 suggest an average of
1% per year of the amounts applied be used as an esti-
mate of runoff losses,
Toxaphene is the only remaining compound in this
class still in major use. Like the other organochlorine
pesticides it has the'virtue (as far as runoff losses are
concerned) of very low solubility, and is an important
example of a pesticide for which effective soil conserva-
tion could lower losses,
WETTABLE POWDER FORMULATIONS
The consistently high losses reported for triazine and
other wcttable powder-formulated herbicides, even
though these materials are not particularly persistent,
place them in a class by themselves. 1 suggest loss esti-
mates of 2% for slopes of Wit or less and 5°!o for slopes
over lO^o.
Do these relatively large losses of wcttable powders
reduce water quality? ft appears that little can be said on
this at present. It is obvious, however, that drastic dis-
sipation and dilution processes must occur after these
materials leave the field; they are sddoni detected in
water-monitoring studies of large water bodies (Caro,
1977).
NONORGANOCHLORINE INSECTICIDES, INCORPORATED
PESTICIDES, AND ALL OTHER HERBICIDES
These make up the remainder of the pesticides that
have been studied." Losses are quite varied, but con-
sidering that rather severe-runoff situations have been
the rule in these studies, 1 suggest a 0.5^o loss estimate
for these pesticides. Because many of them are quite
water soluble and not strongly bound to sediment (e.g.,
the phenoxy herbicides, Fig. 3} these losses, though
smalt relative to application amounts, can result in
transient detectable levels in receiving water bodies;
pidoram is a conspicuous example because it is relative-
ly persistent (Caro, 1977).
Implications for Modeling Pesticide Losses in Runoff
An intense effort to mathematically model pesticide
losses in individual runoff events has been going on for
the last 5 years (e.g., Crawford and Donigian, 1973;
Bailey et al., 19T4b; Bruce et al., 1975; Frere, 1975;
Donigian and Crawford, 1976). These models hav« per-
formed well in one of their intended functions—to
identify significant processes leading to pesticide losses
during a runoff event. It remains to be^seen whether
"Paraquat and MSMA are foliar-applied but, as noted previously,
have only been studio: in soil-application experiments.
froction lost in water phase
(% of total loss)
* » 0 O
O OOP
.V-"
•-DDT
"• - ptQmc Iryn
lluomiluron
E -
a.
a.
£ o
_s
"5
o>
£ w
a
• — piclorem
tell
>-2,4.0 M
Fie. 3— Partitioning of ptstirtdes btlwetn wtitr and lediment In run-
off simples, 1 he rutur of wnier friction* reported in the liimturt
urr shown »•, * function of »aiut)i'lil> (plimt* «r mg>liter). Sttlnhili-
lies of very soluble priorities (all urr xaltsl are »ppu>\im:ilr. Rang?
fur MSMA »nd IIIH mnce fur Irillurulin art iniitrrci f.niruK's bused
nn h»i*li ftirreluimns hrlwrrn hulk cunmilraliun ind ivilimtnt
CururrKnifion wrlftr-ifii-nl*. ))i*«Yr/m»«-) li«»trn mflumlin rctulu
of Smith' (upjwr niti* in figure) unu1 oilier iriflur»lin results it un-
nplmncd. L)uu Irum reference* in Tublt 2.
470 J. Environ. Qual., Vol. 7, no. 4,1978
-------
these models can be integrated into large-basin models.
The ultimate limitation of such modcts for prediction
purposes is that they can be no better than the weather
prediction that goes into them. Water-quality planning
will have to be based on long-term predictions recog-
nizing the stochastic nature of weather and pesticide us-
age, combined with single-event modeling. It will be
necessary to determine whether a given single-event
model, when combined with a spectrum of weather pat-
terns over the persistence time of a pesticide, will predict
long-term losses near the rules of thumb suggested
above.
It would also be useful to estimate the effect of dilu-
tion factors alone on pesticide concentrations in surface
waters at a basin outflow, using the rules of thumb,
pesticide use data, and a hydrologic model for the basin.
One could calculate whether dilution alone could
account for the low or undetectable levels of most pesti-
cides found in large water bodies, or whether drastic ad-
sorption/degradation processes are also required.
Research Needs
While it is obvious that everything is not known about
edge-of-field Josses of pesticides, it is clear that reason-
able estimates of these inputs to rivers and lakes can be
made, at least in principle. Where information is most
needed is on the fate of a pesticide load after it leaves
the edge of a field. Present water-quality criteria (Natl.
Acad. of Sci., 1973) are based on toxicity tests with vari-
ous freshwater biota. However, overall assessments of
runoff impact must include judgments on such factors
as the time and distance of impact of a given field run-
off event and the ability of local ecosystems to recover
from temporary high concentrations of a pesticide. The
dynamics of dilution and sediment exchange, and
uptake, transfer, and metabolism by aquatic life of
most of the pesticides presently in use are not known.
Without this knowledge, the impact of a given pesticide
input on the quality of water in a river or lake cannot be
predicted. For instance, several studies suggest that
pesticide levels in runoff begin declining drastically as
soon as the runoff leaves.the treated area and passes
over untreated soil or vegetation (Asmussen et aIM 1977;
Hall, 1974; Smith et al.»). In summary, what we have at
present is a-fair ability to estimate cdge-of-field inputs
to water systems, combined with near-complete
ignorance as to what those inputs mean.
As a final comment, I will reemphasize a point that
has been a major theme of this review—that pesticides
arc different. The only property that these chemicals
have in common is their broad function as tools for crop
protection. Once they leave the spray nozzle they show
vastly different persistences, mobilities, and toxicitics.
Especially important is the distinction that should be
made between the organochlorine pesticides, most of
which are no longer in use, and the later generations of
pesticides now in use. The difference is persistence. To
my knowledge, there is no evidence that nonpcrsistcnt
pesticides have any permanent impaci on aquatic eco-
systems (see also Caro, 1977). This is not lo suggest lhat
such effects cannot exist, or that nonpcrsistcm pesti-
cides might not be dangerous for other reasons—mam-
malian toxicity, carcinogenic!ty. harm to nontarget ter-
restrial species, atmospheric effects, etc. I believe how-
ever, that the major controversy over pesticide use is a
result of the harmful effects exhibited by the extremely
persistent organochlorine insecticides, and that if these
compounds were generally (and correctly) recognized as
distinct in this regard, public debate on the questions of
pesticide use would become considerably more realistic.
ACKNOWLEDGMENTS
The author is indebted 10 J. H. Caro, R. A. Leonard, and A. M.
Heasly for reviewing this manuscript and for considerable htjp in
clarifying the material, and to S. M. Buckner for exceptional per-
formance in the preparaiton of text and tables.
LITERATURE CITED
1. Aldhous, J.R. 1967. 2,4-D residues in water following aerial
spraying in a Scottish forest. Weed Res. 7:239-24!.
2. Aanuisw), L. E.. A. W. White, E. W. Hauser, and J.. A. Sheri-
dan. 1977. Movement of 2.4-D in a vegetated waterway. J. En-
viron. Qual. 6:159-162.
3. Bailey, G. W., A. P. Bamett, W. R. Payne. Jr., and C. X. Smith.
1974a. Herbicide runoff from four coastal plain soil types.
. \ USEPA. Environ.>rot. Technol. Ser., EPA-660/2-7-MJI7.98 p.
[•4 J Bailey, O. W., A. R. Swank. Jr., and H. P. Nicholson. 1974b.
>—' Predicting pesiicide runoff from agricultural land; a conceptual
model. J. Environ. Qual. 3:95-102.
S. Bailey, C. W., and J. L. White. 1964. Review of adsorption and
desorption of organic pesticides by soil colloids, with implica-
tions concerning pesticide bioactivity. J. Agric. Food Chem. 12:
324-332.
6. Baker, J. L., H. P. Johnson, and J. M. Laflen. 1976. Comple-
tion report—effect of tillage systems on runoff losses of pesti-
cides: a simulated rainfall study. Iowa Sute Water Rtsour. Res.
la«. Rep. no. 1SWHRJ.7J, Ames, Iowa, 96 p.
7. Baldwin, F. L.. P. W. Samelmann, and J. M. Davidsca. 1975a.
Prometryne movement across and through soil. Wted Sci. 23:
285-286.
8. Baldwin, F. L., P. W. Samelmann, and J. M. Davidson. I973b.
Movement of fluometuron across and through lie soil. J.
Environ. Quat. 4:191-194.
9. Bainen, A. P., E. W. Mauser, A. W. White, and J. H. Holladay.
1967. Loss of 2,4-D in washoff from cultivated fallow land.
Weeds 15:133-137.
10. Baur, J. R.. R. W. Bovey, and M. 0. Merkle. 1972. Concentre-
lion of picloram in runoff water. Wetd Sci. 20:309-313.
11. Bovey, R. W., E. Burnett, C. Richardson, M. O. Merkle, J. R.
Baur, and W, C. Knisel. 1974. Occurrence of 2,4,3-T and piclor-
am in surface runoff water in the Blacklands of Texas. J. En-
/-v viron. Qual. 3:61-64.
' /12.) Brace, R. R., L. A. Harper, Jr.. R. A. Leonard, W. M. Snydcr.
v_X and A. W. Thomas. I97S. A model for runoff of pesticides from
small upland watersheds. J. Environ. Qual. 4:34|-J46.
^13. Caro. J. H. 1976. Pesticides in agricultural runoff, p. 91-119. In
B. A. Stewart (ed.) Control of water pollution from cropland.
Vol. II—An overview. USEPA "Rep. EPA-600/2-73-C26b or
USDA Rep. no. ARS-H-5-2. p. 187 p.
14. Caro. J. H.. W. M. Edwards. B. L. Glass, and M. H. Frere.
1972. Dieldrin in runoff from treated watersheds, p. 141-160. in
Proc. Symp. Interdisctpl. Aspects Watershed Manage., Am. Soc.
Civil Eng., New York.
15. Caro. J. H.. H. P. Freeman, D. W. Glotfeliy, B. J. Turner,
and W. M. Edwards. 1973. Dissipation of soil-incorporated car*
bofuran in the field. J. Agric. Food Chem. 21:1010-10:5.
16. Caro. J. H...II. P. Freeman, and B. C Turner. 197J. Persistence
in soil and losses in runoff of soil-incorporated carbaryt in a small
watershed, J. Agrie. Food Chem. 22:860-863.
17, Caro, J. H., and A. W. Taylor. 1971. Pathways of loss of di-
tldrin fiocn soils under Held conditions. J. Agric. Food Chem.
19:379-384.
18. Carter, L. J. 1977. Soil erosion: the problem persists itipite the
billions spent on it. Science 196:409-411.
J.EnTtn*.Q«l., Vol. •»,»«. *. 1918 471
-------
21.
22.
19. Chemical Rubber Co. 1966. Handbook of chemistry and physics.
47th ed. Chemical Rubber Co., Cleveland. Ohio. 1838 p.
I Cruwford. N. H.. and A. S. Donician. 1973. Pesticide transport j
and runoff for agriculiural lands. USEPA, Environ. Prot. 1
Technol. Ser., El'A-660/2-74-013. 211 p. —*
Davis, E. A., and P. A. Ingebo. 1973. Picloram movement from
a chapparral watershed. Water Rcsour. Res, 9:1304-1311.
Dickens, R., and A. E. HifttwJd. 1967. Movement and persist-
ence of meihanearsonates in soil. Weeds 15:299-304.
lijian, A. S., and N, H. Crawford. J976. Modeling pesticides
^—'and nutrients on agricultural lands. USEPA. Environ. Prot.
Technol. Ser., EP A-600/2-76-043.3 J 7 p.
24. Edwards, W. M. 1972. Agricultural chemical pollution as af-
fected by reduced tillage systems, p. 30-JO. In Proc. No-Tillage
Systems Symp., 21 Feb. 1972. Ohio State Univ., Columbus.
25. Edwards. W. M.. and B. L. Glass. 1971. Mcthoxychlor and
2,4,5-T in lysimeter percolation and runoff water. Dull. Environ.
Contam. Toxicol. 6:81-84. -—-,
26. Epstein, E., and W. J. Grant. 1968. Chlorinated insecticides in I
runoff water as affected by crop rotation. Soil Sci. Soc. Am. /
Proc. 32:423-426. "^L
27. Evans. J. O., and D. R. Duseja. 1973. Herbicide contamination I
of surface runoff waters. USEPA. Environ. Pfot. Technol. Ser., J
EPA-R2-73-266.99 p. - sugar-cane
fanning in Louisiana. Am. Fisheries Soc. Trans. 95:310-316.
39. Lawscn. E. R. 1976. 2,4,5-T residues in storm runoff from imall
- watersheds. J. Soil Water Conserv. 31:217-219.
40. McDowell, L. L., and E. H. Grissinger, 1976. Erosion and water
cowe, . ., an . . , .
quality, p. 40-56. In Proc. 23rd Natl. Watershed Congr., Biloxi.
41
42.
43.
44.
sources.
McElroy, A. D., S. Y. Chiu, J. W. Nebgen, A. Alrtj.;
Vandergrift. 1975. Water pollution from nonpomt
Water Res. 9:675-681.
ZSS».tt ^£&FffteZk environment.
USDA For. Serv. Res. No«e PN W-l 16.11 p.
National Academy of Sciences. 1973. Water qualif.
a report of the committee on water quality criicna.
EPA-R3-73-033. March 1973.594 p.
Nicholson. H. P. 1975. The needs for mieMtmiiiy models on
agricultural watersheds. J.Environ. Qual. 4:21-23.
45. Norris. L. A., and M. A. Montgomery. 1975. Djcnnha residues
in sircams after forest spraying. UaU. tnvwon. Contam. Twaeol.
13:1-8.
46. Pionke, H. B., and G. Chester*. 1973. PcsiJcide-sediment-waier
interactions. J. Environ. Qual. 2:29-45.
47. Richardson, C. W., J, D. Price, and E. Burned. 1978. Arsenic
concentration in surface runoff from small watersheds in Texas.
J, Environ. Quat. 7:189-192.
Ritter, W. F.. H. P. Johnson, W. G. Lovely, and M. Molnau.
1974. Atrazinc. propaclilor, and diazition residues on small agri-
cultural watersheds. Environ. Sci. Technol. 8:37-42.
Scifres. C. J.. R. R. Harm, J. Dial-Colon, and M. G. Merkle.
1971. Picloram persistence in semiarid rangeland soils and water.
Weed Sci. 19:J8J-384.
Scifres C. J., H. G. McCalt. R. Maxe/, »nd H. Tai. 1977.
Residual properties of 2,4,5-T and picloram in sandy rangeland
soils. J. Environ. Qual. 6:36-42.
Sheets, T. J., J. R. Bradley, Jr., and M. D. Jackson. 1972. Con- .
lamination of surface and ground water with pesticides applied to
cotton Univ. North Carolina Water Kcsour. Res. Inst. Rep. no.
60, Chapel Hill, N.C. 63 p.
Spencer. W. F., M. M. Cliath, K. R. Davis, R. C. Spear, and W.
J. Popendorf. 1975. Persistence of parathion and its oxidation to
paraoxon on the soil surface as related to worker reentry into
treated crops. Bull. Environ. Contam. Toxicol. 14:265-270.
Stevenson, F. J. 1972. Organic matter reactions involving herbi-
cides in soil. J. Environ. Qual. 1:333-343.
Stewart, B. A. 1976. Control of water pollution from cropland.
Vol I A manual for guideline development. USDA Rep. no.
ARS-H-5-1 or USEPA Rep. no. EPA-6CO/2-7S-026a. 111 p.
Tanji, K. K., M. Mchran, J. W. Biggar, and D. W. Henderson.
1974. Herbicide persistence and movement studies w-th molinate
m rice irrigation management. Calif. Agric. May:10-12.
Tanant, R. F.. and L. A. Norris. 1967. Residues of herbicides
and diesef oil carriers in forest waters: a review, p. 94-102. In
Proc. Symp. Herbic. and Vegetation Manage, in Forests, Ranges,
and Noncroplands, 1967. Oregon State Univ., Corvaths.
Trichell, D. W., H. L. Morton, and M. G. Merkle. 1968. Loss of
herbicides in runoff water. Weed Sci. 16:447-449.
U.S. Environmental Protection Agency. 1972. Fed. Water
Pollut. Control Act Amendments PL 92-500.18 Oct. 1972.
59. Wauchope, R. D. 1975. Fixation of arsenical herbicides phos-
phate, and arsonate in aJluviaJ soils. J. Environ. Qual. 4:355-358.
/60 Wauchope, R. D., L. E. Asmussen, and E. W. Mauser |977a.
\. MSMA losses m runoff from small watershed^i in the Mwimppi
Delta and Georgia coastal plain. Proc. South. Weed Sci. Soc. 30:
•s 395-
(61 I Wauchope, R. D., K. E. Savage, and D. G. DeCpursey. 1977b.
\-/ Measurement of herbicides in runoff from agricultural areas, p.
50-58 In B. Truelovc (ed.) Research methods in weed science.
2nd ed.. South. Weed Sci. Soc.
62. Weber, J. B. 1972. Interaeiion of organic pesticides with panicu-
late ma'tter in aquatic and soil systems. B-55-I21-/flf;F-5°"'a
(ed 1 Fate of pesticides in the aquatic environment. Adv. Cnem.
Ser/111, Am. Chem. Soc., Washington, D.C.
Weber, J. B.. and S. B. Weed. 1968. Adsorption andI desorption
of diquat, paraquat, and prometone byB™n«n°?'1°n'"c Md
kaolinic daymincraU. Soil Sci. Soc. Am. Proc. 32:458^87.
Weed Science Society of America. 1974. Herbicide handbook,
3rd ed. Weed Sci. Soc. Am., Champaign, III. 430 p.
White A W.. L. E. Asinussen, E. W. Hauscr. and J. W. Tiirrt-
bulL1976 Loss of 2,4-D in runoff from plots receiving sjmubted
fainfil and from a small agricultural watershed. J. En won.
W,t5A8w'9A'. D.Barneit. B. G. Wri5ht. and J. H. Holladay.
»tt AttVziM losses from fallow land caused by runoff and ero-
sion. Environ. Sci. Technol. 1:740-744. .
Willis G H and R. A. Hamilton. 1973. Agricultural chemicals
fa £f£ nTnS ground water, and soil: endrm. J. Environ^
Qual. 2.463^ . L f paff and c E Murpbree.
Micide wneeniratioiw and yields in runoff amisegment
wssaffis^.*^1^, -
JftSASi »S h;SrS-S,S
water. J. Environ. Qual. 4:399-402.
48.
49.
30.
51.
52.
53.
54.
55.
56.
ۥ
58.
€3.
64.
66
472 J. Environ. Qual., Vol. 7, no. 4,1978
-------
46 J. Agric. Food Cham.. Vol. 26, No. 1. 1978
HEAD oncn OR
WEi.1
PUMP -
J J J J J J J
lAkWATER COLLECTING DITCH
Figure 1. Diagram of an irrigated field, tailwater pit, and tailwater
reuse system. This pit is drawn disproportionately large.
Typically a 160-acre (65-ha) field 0.5 mile (0.8 km) long on each
side is served by a pit 6 to 10 ft (2 or 3 m) deep, 75 to 125 ft (23
to 38 m) wide, and 125 to 200 ft (38 to 61 m) long. The part of
the field irrigated by tailwater can usually be irrigated alternately
by fresh well water. Most irrigation systems are not designed for
controlled miiing of fresh water and tailwater for simultaneous
use on any one pan of the field.
muddy bottom soil from each pit. This soil was primarily
sediment, but in some pits it included original pit bottom
soil. Pit bottom soil (primarily sediment) was collected
ca. 20 to 25 ft (6 to 8 m) from the shore near the inlet
Exceptions occurred when water was depleted from pits
and the body of water was less than 40 ft (12 m) wide. A
collecting device, to obtain pit bottom soil, was made from
a 2-in. (5.08 cm) i.d. iron pipe 13 in. (33 cm) long, which
was threaded and capped on one end. A chain link welded
to the lip of the open end was used to attach a 25-ft (ca.
8 m) rope.
For collecting the samples, the rope was coiled (loose end
secured to the collector's wrist), and the device and coil
were thrown into the pit for retrieval. Bottom soil was
poured from the device into wide-mouth Mason jars (Ken-
Glass Mfg. Corp., Sand Springs, Okla.) until a 1-qt (0.95
L) sample was obtained. Aluminum foil was used to line
the jar lids.
Many of the 1973 samples were stored 2 weeks or longer
at ca. 22 °C before extraction of residues for analysis.
Extractions were made from the 1974 samples within 2.7
± 1.7 days after collection.
Extraction of Sediment. Stones and other large
objects were removed from the sample of pit bottom soil,
and the sample was thoroughly mixed with a spatula on
a sheet of aluminum foil. A portion of the soil sample (150
g) was weighed and placed in a quart jar with 100 mL of
acetone. The mixture was then mixed vigorously for 5* mm
on a mechanical shaker. The slurry (mixture of sediment
and acetone) was then reextracted with three successive
portions of ethyl acetate (100 mL each), and the total
extract of acetone and ethyl acetate was decanted. The
combined extract was placed in a 1000-mL round-bottom
flask and was evaporated to dryness with vacuum in a 45
°C water bath. The extract residue was then dissolved in
5 mL of benzene.
Extraction of Water. Water samples were collected
in clean 1-gal jars for transport to the laboratory. Two
liters of a sample was placed in a separate 1-gal jar for
extraction with 200 mL of 50% ethyl acetate in hexane.
The jar was shaken vigorously for at least 1 min. After
the phases separated, the ethyl acetate-hexane (upper)
layer was decanted into a 1-L round-bottom flask. A
second extraction was then completed, and the upper
layers were combined. The sample was then reextracted
with 400 mL of chloroform, and the extracts were com-
Kadoum. Mock
bined and evaporated to dryness with vacuum in a 45 °C
water bath. The extract residue was dissolved in 5 mL of
benzene.
Cleanup Procedure. Kontes K420280 chromaflex
minicolumn, size 10.5 mm i.d., was packed with a mixture
of 24 g of Celite 545,12 g of MgO, and 15 g of Norit SG
1. The column was capped with a 5-mm glass-wool plug
and the column then flushed with acetone. The extract
in 5 mL of benzene was added to the column and eluted
with 75 mL of 25% ethyl acetate in benzene with the
eluent being collected in a 250-mL round-bottom flask.
The column was flushed dry with nitrogen gas. The eluent
was evaporated to dryness with vacuum in a 45 8C water
bath. The residue was then dissolved in benzene for
injection into the gas chromatograph.
Gas Chromatographic Analysis. The nitrogen
compounds were gas chromatographecl on a dual-column
Tracor 550 with a Coulson conductivity detector in the
nitrogen mode. Both columns were 3 ft X 0.25 in. (91 cm
x 6 mm) Pyrex packed with Chromosorb W HP, 60/80
mesh. One column used a 3% OV-25 liquid phase, the
other, a 1.1% Carbowax 20M. Hydrogen was the carrier
gas at a flow rate of 58 mL/min. Temperatures for the
inlets were 200 °C; outlets, 210 °C; transfer line, 215 °C;
furnace valve block, 220 °C; and the furnace was operated
at 900 °C.
Atrazine and carbofuran (retention times 680 and 1053
s, respectively) were separated on OV-25 at an oven
temperature of 140 °C and a carrier flow of 80 mL/min.
The much larger atrazine peak was vented off before
switching the column onto the detector, to allow the
carbofuran to be observed on the recorder without prior
disturbance.
Propazine and atrazine (retention times of 197 and 275
s, respectively) were separated on the Carbowax column
at an oven temperature of 140 8C and a carrier flow of 58
mL/min. Sensitivity of the detector to nitrogen was 1.2
ng at a peak size equal to twice baseline noise. An Autolab
6300 digital integrator assisted in quantitating peak values.
Organophosphate compounds were determined on a
Bendix 2110X gas chromatograph equipped with a Bendix
flame photometric detector and a 6 ft x 0.25 in. (1.8 m x
6 mm) Pyrex column; 3% OV-1 on 60/80 mesh Gas-Chrom
Q was the packing material. The detector temperature was
150 "C, and the nitrogen carrier flow was 135 mL/min.
The detector gas flows were: hydrogen, 300 mL/min; air,
80 mL/min; and oxygen 10 mL/min. Oven temperature
was set at 185 °C and the inlet was maintained at 215 °C.
Sensitivity to phosphorus was 25 pg at a peak size equal
to twice baseline noise. Preliminary results from the
recovery studies using pure standards of all tested pes-
ticides yielded average recoveries of 99 ± 3% of all pes-
ticides found in tailwater pits. The percentages of the
recoveries from fortified soil and water samples are shown
in Table I.
RESULTS AND DISCUSSION
Pesticide residue data from the samples collected in 1973
were published previously (Kadoum et al., 1975).
Herbicide and insecticide residues found in tailwater pit
samples (Tables II-VII) indicate some residue movement
from fields. Various rates and timing of pesticide ap-
plications, soil pH and organic matter, amount of runoff
water, and tillage and cultivation methods undoubtedly
affected the amounts of residues in the pits.
Residues of seven herbicides and seven insecticides were
detected. The mean number of different pesticides de-
tected in tailwater pits in 1974 alone was 2.3 for pits re-
ceiving runoff from sorghum fields, 3.4 from those serving
-------
Horftckfe ftasttuA* in Tailwaiw
Table 1
Pesticide
Carbofuran
Dimethoate
Disulfoton
EPN
Fonofos
Parathion
Phorate
Recovery0
98 i 3
95 i 5
101 t 2
95 ± 4
101 t 2
100 t 2
102 ± 2
Pesticide
Alachlor
Atrazine
Cyanazine
EPTC
Propachlor
Propazine
Terbutryn
R25788
Recovery0
98 i 3
103 i 2
96 i 4
96 i 5
100 t 2
103 i 2
99 t 3
96 t 4
0 Standard deviation calculated from four replicates.
corn fields, and 4.4 from pits serving both corn and
sorghum. Potential hazard to crops and animals, due to
summary or synergistic effects of different pesticide
residues in the same tailwater pit, should be considered.
Residues of the triazine herbicides, atrazine and pro-
pazine, occurred in both water and bottom soil with far
greater frequency than did other pesticides. Both persisted
throughout the year (Table VII). Atrazine occurred in
greater concentrations than all other residues (Table IV).
Seasonal uses of specific pesticides are reflected in the
chronology of peak concentrations of residues in the
tailwater pits (Table VII). All of the herbicides in this
study were used most heavily as preplant, planting time,
and early postemergent applications in Haskell County.
All were detected in highest concentrations in May or June.
The insecticides carbofuran, fonofos, and phorate were
used mostly in planting time applications against corn
rootworms in corn. Concentrations of their residues
peaked from 4 to 6 weeks later in June and July. Di-
methoate, disulfoton, EPN, and parathion were used
mostly as foliar applications against a complex of sorghum
and com insects in late July and in August and September.
Residues of all these peaked in August, except for para-
thion for which a low peak appeared unaccountably in May
of 1974.
Many pesticides were aerially applied to crops in the
locale of our study. Resultant drift, or even direct ap-
plication over tailwater pits, may account for some of the
pesticide residues detected.
The pesticides most likely to have entered tailwater pits
aerially were atrazine, dimethoate, and EPN applied to
com fields, propazine to sorghum fields, and disulfoton and
parathion applied to both corn and sorghum. Some runoff
occasionally occurred in the study area after heavy rains.
However, rainfall is generally a minor contributor to field
runoff in southwest Kansas. We believe that irrigation
runoff is the primary carrier of pesticide residues into
tailwater pits in the study area.
We may calculate the amount of pesticide which is
applied,to a crop when residue-bearing tailwater is reused
Table II. Frequency and Concentrations of Perticid* Residue* in Samples from 12 Tailwater Pits Serving Sorghum Fields
in Haskell County, Kansas, 1973
Frequency of detection0 _
Pesticidee
Alachlor
Atrazine
Phorate
Propazine
Terbutryn
Atrazine
Cyanazine
Parathion
Phorate
Propazine
Terbutryn
No. of
samples
1
13
1
22
2
22
3
2
3
25
1
No ofpit-r \A>uvfui.
implicated Median
Pit Bottom Soil (40 Samples)
1
6 29.2
1
7 71.6
1 128.1
Tailwater (46 Samples)
7 4.7
2 47.5
2 0.7
2 1.5
7 16.3
1
ration of residues, b ppb
Mean
121.0
47.1
2.3
106.2
128.1
20.4
34.2
0.7
1.6
36.2
4 A
,**
Maximum
132.5
429.0
218.5
128.0
50.7
1.0
20
.4
153.0
0 Some samples contained no residues, others contained several kinds. The sum of residue fluencies is therefore not
- - • • ' * Medians and means were calculated from detectable residue data only.
... « . , it ' J ___.*__* __. ....AI'M ft A nrrrtil U ItA *M
es analyzed. " Meojans ana means were «icuia»u LIWIU Uov=v».u,. '7--~-- , j L L
cs based on all samples analyzed, including those with no detectable residues of a given I«b«^!*«" ^ ""?. ,„
lower. * Analyses ihomdI no detectable residues (<0.1 ppb) for cyanazme and parath.on in bottom soil and for alachlor in
water.
Table HI. "Frequency and Concentrations of Pesticide Residues in Samples from 24 Tailwater Pits Serving Com Fields in
I County, Kansas, 1973
Pesticide
Atrazine
Cyanazine
Fonofos
Phorate
Atrazine
Cyanazine
Fonofos
Phorate
Frequency
No. of
samples
81
1
4
98
4
2
7
of detection"
No. of pits
implicated
Concentration of residues,6 ppb
Median
Pit Bottom Soil (96 Samples)
23 27.2
1
1
2
Tailwater (108
24
1
1
6
4.0
1.7
Samples)
3.5
5.7
0.8
Mean
42.9
21.6
4.4
2.1
13.9
21.1
0.4
1.8
Maximum
369.0
8.4
4.6
250.0
. 73.0
8.7
no
lower,
-------
J. Ayric. Food Cham.. Vol. 26, No. 1, 197B
Kaooum. Mock
Table IV. Frequency and Concentrations of Pesticide Residues in Samples from 26 Tailwater Pits Serving Corn Fields in
Haskell County, Kansas, 1974 ^^
Pesticide6
Alachlor
Atrazine
Carbofuran
Cyanazine
Oisulfoton
EPN
EPTC
F on of os
Phorate
No. of
samples
1
109
2
6
6
2
11
22
7
No. of pits
implicated
Pit Bottom Soil
1
23
2
3
5
2
7
6
5
concentration 01 residues," ppo
Median
(129 Samples)
35.1
50.0
8.7
11.4
33.5
38.1
15.6
1.6
Mean
188.6
90.8
50.0
16.9
13.8
33.5
40.8
130. 9
9.6
Maximum
1068.3
75.9
46.6
32.7
56.2
102.3
771.2
56.9
Alachlor
Atrazine
Carbofuran
Cyanazine
Dimethoate
EPN
EPTC
Fonofos
Parathion
R25788
Tailwater (129 Samples)
5 3 8.6
14 24 6.1
12 10 31.1
5 3 46.0
10 10 1.5
3 3 1.0
17 11 0.3
12 6 0.4
1 1
6 5 1.9
30.3
56.2
35.2
37.7
1.9
1.4
1.7
1.8
6.2
1.6
98.8
1074.1
88.9
54.0
4.3
2.2
11.4
5.9
2.8
**4»tS i W w —
" Some samples contained no residues, others contained several kinds. The sum of residue frequencies is therefore not
equal to the number of samples analyzed. * Medians and means were calculated from detectable residue data only.
Statistics based on all samples analyzed, including those with no detectable residues of a given pesticide, would be much
lower. e Analyses showed no detectable residues (< 0.1 ppb) for dimethoate, parathion, and R25788 in bottom soil and
for disulfoton and phorate in water.
Table V. Frequency and Concentrations of Pesticide Residues in Samples from Five Tailwater Pit* Each Serving Both Corn
and Sorghum Fields in Haskell County, Kansas, 1974
Pesticide6
Atrazine
Carbofuran
Cyanazine
Disulfoton
EPN'
Fonofos
Propazine
Terbutryn
Atrazine
Carbofuran
Cyanazine
Dimethoate
EPTC
Fonofos
Parathion
Phorate
Propazine
Terbutryn
Frequency
No. of
samples
12
2
3
1
1
4
14
3
15
3
4
1
1
3
1
1
15
3
of detection"
No. of pits
implicated
Bottom Soil (25
4
2
1
1
1
1
4
1
Tailwater (25
5
2
1
1
1
1
1
1
5
1
Concentration of residues,6
Median Mean
Samples)
77.6
30.6
124.8
48.4
53.2
30.5
Samples)
6.1
17.0
24.1
0.2
2.4
5.7
133.4
30.6
88.4
11.0
75.0
136.2
65.6
39.1
81.7
24.1
24.1
1.9
0.3
0.2
0.1
0.1
28.5
9.5
ppb
Maximum
468.9
42.4
124.8
428.9
247.8
72.0
766.7
51.7
45.9
0.3
219.4
19.0
0 Some samples contained no residues, others contained several kinds. The sum of residue frequencies is therefore not
«qual to the number of samples analyzed. " Medians and means were calculated from detectable residue data « •
f , iven stiadM "u'd
«qual to the number of samples analyzed. Medians and means were cacuae rom eecae rei
Statistics based on all samples analyzed, including those with no detectable residues of i , given PfstiadjM "?u'd
lower. « Analyses showed no detectable residues (<0.1 ppb) for dimethoate, EPTC, and parathion :n bottom soil and for
disulfoton and EPN in water.
for irrigation. On medium-textured soils such as the silt
loams of our study area, a typical midsummer irrigation
of corn requires 4 acre-inches of water/acre (Hay and Pope,
1976a). Sorghum and alfalfa have similar requirements
for high production. Wheat fields may need irrigations
of similar or greater quantity in the autumn before
planting or in May (Hay and Pope, 1976b).
Relatively few of the pesticide residues in water were
as great as 10 ppb although exceptions skewed the means
upward (Tables II-VII). If tailwater containing 10 ppb
of a pesticide residue was reused to supply cropland with
a 4-inch (10-cm) irrigation, this would equal a pesticide
application of 0.009 Ib/acre (0.001 kg/ha) (Table VIII).
That is an inconsequential amount.
However, water from two pits carried exceptionally high
concentrations of atrazine in 1974, one with 1074 ppb in
May and the other with 739 ppb in June. Such exceptions
may create problems. Again referring to Table VIII, a
4-inch (10-cm) irrigation with water from the pit carrying
1074 ppb atrazine delivers 0.98 Ib/acre (0.18 kg/ha) of the
-------
Herbicide Rescues in Tauwaier Pits
~yr*gnc. food Uwm., Vol. 26. No. J, 1S78 49
Table VI. Frequency and Concentrations ot Pesticide Residues in Samples from Four Tailwater Pits Serving Sorghum
Fields in Haskeli County, Kansas, 1974
Frequency of detection0
Pesticide0
Atrazine
Disulfoton
Propazine
Atrazine
Parathion
Propazine
No. of
samples
13
2
7
15
1
10
.. ... L-oncerurati
fJrj of pit* . ,. ... ,. _.
implicated Median
Bottom Soil (19 Samples)
3 46.2
1 117.2
3 23.5
Tailwater f 19 Samples)
3 6.2
1 0.1
4 6.7
ion of residues,6 ppb
Mean
63.9
117.2
44.8
31.8
0.1
32.9
Maximum
193.7
227.8
183.2
285.0
0.1
269.4
0 Some samples contained no residues, others contained several kinds. The sum of residue frequencies is therefore not
equal to the number of samples analyzed. b Medians and means vere calculated from detectable residue data only.
Statistics based on all samples analyzed, including those with rio detectable residues of a given pesticide, would be much
lower. ' Analyses showed no detectable residues (<0.1 ppb) for parathion in bottom soil and for disulfoton in water.
Table VII. Concentrations (ppb) of Pesticide Residues Occurring in Tailwater Pits in Different Months (Data for Each
Pesticide is the Mean of AH Pits from Which Residues of that Specific Pesticide Were Detected. 1973 and 1974
Data Are Pooled)"
Soil
Water
Pesticide
May
June
July
Aug Nov-Dec May June July Aug Nov-Dec
Alachlor
Atrazine
Cyanazine
EPTC
Propazine
R25788
Terbutryn
Carbofuran
Dimethoate
Disulfoton
EPN
Fonofos
Parathion
Phorate
0
38
0
4
43
0
0
0
0
0
0
9
0
0
47
124
32
26
90
0
117
5
0
0
0
305
0
9
30
65
21
8
81
0
36
7
0
0
0
101
0
3
Herbicides
0
32
2
0
20
0
34
Insecticides
0
0
36
27
14
0
a
o
16
0
0
1
0
0
0
0
11
2
2
0
0
38
47
18
T
25
1
0
6
0
0
0
T
1
0
9
87
30
2
60
1
12
31
0
0
0
2
T
1
0
19
21
T
24
0
3
1
0
0
0
T
0
T
0
7
1
0
5
0
2
0
2
0
1
T
T
0
0
6
T
0
1
0
0
0
0
0
T
0
0
0
Table VIII. Pounds of Pesticide in Irrigation Water from
Tailwater Pits with Indicated Levels of Pesticide Residue"
0 Residue concentrations rounded off to nearest whole ppb, those less than 0.5 ppb are reported as T= trace.
herbicide. This is one-third to one-half the amount
recommended to kill many broadleafed weeds and some
grasses (Niison et al., 1975) and could possibly kill or injure
soybeans, sugarbeets, or wheat. Several irrigations are
usually required each growing season in southwest Kansas.
Multiple irrigations increase the danger of damage, al-
though in our study residue concentrations decreased as
the season progressed.
Evans and Duseja (1973) reported atrazine concentra-
tions of up to 0.86 ppm (860 ppb) in a stream below ex-
perimental applications to stream side plots. They con-
cluded, "The low concentrations that are observed fol-
lowing proper application of the herbicides would not likely
be hazardous to crops or animals". Comparing their results
to ours as discussed in the foregoing paragraph, we must
disagree with their conclusion.
The danger of damage to crops can be minimized in the
following ways: (1) using tailwater on less sensitive crops;
(2) avoiding repeated irrigation of the same area with
tailwater; (3) using tailwater only after several weeks'
degradation time has elapsed; (4) mixing tailwater with
uncontaminated irrigation water. The third method is of
minimal value. because the cost of high capacity pits is
prohibitive. Efficiency in taiiwater use systems depends
upon rapid {even continuous) reuse (Hay and Pope, 1977).
The fourth method is also of limited feasibility because
most irrigation systems are not designed for controlled
mixing of fresh water and tailwater for simultaneous use
on any one part of a field
-------
Trichlorfon and carbaryl are metabolized by insects to various de-
gradates; all three chemical insecticides are also metabolized in
plants.
• Rates of metabolism have not been established for all pesticides,
but are expected to vary with the pesticide and application condi-
tions. Half-life values of 2 weeks for dicamba in grasses and 2-3
weeks and 7 days for fosamine ammonium in apple seedling leaves and
pasture flora, respectively, have been reported. Levels of residue
in plants which are reported for only a few herbicides (e.g., hexa-
zinone, fosamine ammonium, and 2,4-D) indicate low levels several
months after application.
3.2.3 Fate in Soil (Table 7}
• Processes which impact the fate of the pesticides in soil are
adsorption/leaching-runoff, chemical and microbial degradation,
photodegradation and volatilization. The extent that each of these
processes impact the persistence of a pesticide in the soil envi-
ronment is dictated by the physical (particularly water solubility
and vapor pressure) and chemical properties of the pesticides,
soil characteristics (particularly organic content and pH) and
climatic conditions (e.g., rainfall and temperature). Microbial
degradation - and not chemical hydrolysis, volatilization, or
photodegradation - is by far the major route for dissipation of
pesticides from soils.
• Actual field data on the persistence of pesticides (residue levels
and half-life values) in the forest soil have only been reported
for a few pesticides, most notably hexazinone, 2,4-D, and sima-
zine.
• Reported degradation data indicate that, depending on the soil con-
ditions, half-life of pesticides may be very low (e.g., less than
one day for acephate) but is generally in the order of several months;
arsonates which are degradation products of MSMA have a half-life
in soil of about 6 years. Actual tesidue data under actual condi-
tions of use in forestry are available for only selected pesticides.
• Mobility in soil is inversely related to a pesticide's affinity for
adsorption to and/or chemical reaction with soil particles. In
general, pesticides/formulations with low water solubility (e.g.,
atrazine and simazine) and pesticides which have strong chemical
affinity for soil particles (e.g., fosamine ammonium and glyphosate)
are relatively immobile and are not readily leached (or leached to
great depths) in the soils. In general, adsorption is greater
(mobility is lower) in soils containing higher organic content and
at lower pH levels and temperatures.
• In general, some loss of pesticides in runoff is likely if heavy
rainfall occurs soon after application. Actual monitoring of resi^-
due levels in forest streams subsequent to pesticide application
23
-------
TABLE 7. SUMMARY OF DATA ON FATE IN SOIL
Pesticide
Adsorption, Leaching, and Runoff
Chemical and Microbial Degradation
Photodegradation, Volatilization, etc.
f. HERBICIDES
Amitrole
Atrazine
KI
Dalapon
Reversibly adsorbed to soil;
adsorption greater in high organic
soils, and at lower pH. Leaching
occurs in sandy soils, but greatly
reduced in clay soils.
A low mobility herbicide. Readily
and reversibly adsorbed on soil.
Adsorption stronger on soils with high
organic matter, lower pH, moisture
and at lower temperature. Leaching
confined to upper 6 in. of soil in
many soil types. Significant loss in
runoff (5-10%) may occur If heavy
rainfall occur* soon after applica-
tion.
Limited adsorption to soil in labora-
tory studies; however, tittle leaching
observed beyond upper 6 in. of soil
under field conditions due to rapid
microbial degradation. Quantitative
data on runoff rates unavailable.
Degradation is chemical and
microbial; depends on soil moisture,
temperature, pH. Detectable residue
persists from several days to 6
months or more.
May remain at phytotoxic levels
for over one year depending on
soil type and climate conditions.
Degrades via chemical and micro-
bial routes. Principal chemical
degradation route is hydrolysis
to hydroxy atrazine, (half-life 66
days at pH 3,81 days at pH 11).
Microbial degradation occurs via
dealkylation, ring cleavage and
hydroxylation of 2-chtoro group.
Nitrosoatrazines (suspected car-
cinogens) not formed in signifi-
cant amounts when atrazine
(2 ppm in 7,5 cm of soil or
2 Ib/acre) applied with ammon-
ium nitrate fertilizer (100 ppm).
Microbial degradation major route of
dissipation from soil; chemical
hydrolysis minor to negligible. Rate
of microbial degradation dependent
on soil type, temperature, pH,
moisture content and application
rate. Generally persists between 2
weeks and several months at pH>5.
Volatilization expected to be limited
due to amitrole's low volatility.
Amitrole appears stable under UV
light.
Photodegrades if prolonged sunlight
and high temperature follow applica-
tion, but precede precipitation
(47 and 60% losses observed after
exposure to spring sunlight in agri-
cultural fields 25 and 60 days,
respectively). Mechanism and
products of photodegradation
unknown. Volatilization, if any,
would occur 1 to 2 days after
application.
Volatilization considered insignifi-
cant under field conditions. Photo-
degradation considered unlikely due
to poor absorption of light.
(Continued)
-------
TABLE 7. (Continued)
Pesticide
Adsorption, Leaching, and Runoff I Chemical and Microbial Degradation
Photodegradation, Volatilization, etc.
Oicamba
VJi
2,4-D
Fosamine
Ammonium
Considered to be a very mobile
herbicide; mobility greater at higher,
pH, Does not readily adsorb to soil
but can adsorb to clays. Readily
leached from soils; runoff possible
with heavy rainfall after spraying.
No dicamba residues detected in
streams after 11 days following
forest application of 1.12 kg/ha
in 373 liters of water.
Adsorbs more strongly to soils with
higher organic matter; does not
adsorb strongly to clay. Leaching)
generally depends on the formula-
tion, soil properties, and amount of
rainfall; polar salts leach more
readily than esters. Potential for
runoff is greater for esters which do
not leach so readily.
A low mobility herbicide. Strongly
adsorbed to and not readily teachable
in soils high in clay and heavy metals
content. Remained in top 12 inches
of Fallsington soil under simulated
rainfall conditions. Loss in surface
runoff possible especially after heavy
rainfall soon after application.
Degradation is primarily microbial;
extent depends on soil conditions.
Breakdown product is 3,6~DCSA.
Generally does not persist more
than several months in most soils.
Photodecomposition not expected to
be significant. Vapors from soil-
incorporated dimethylamine salt
shown to be phytotoxic to beans.
Degradation depends on soil temper-
ature, moisture, organic matter
content of soil; it ts primarily micro-
bial. Under field conditions, 2,4-D
esters normally hydrolyze to the acid
within a few days. Only 6 percent
remained in forest floor material
35 days after application of 2.24
and 4.48 kg/ha of 2,4-D.
Half-life of one week observed
under field conditions in Florida,
Delaware and Illinois at practical
application rate of 11.3 kg/hr. No
residues detectable after 3-6
months. Half-tife of 10 days
determined in laboratory study.
Undergoes chemical hydrolysis In
soil to carhamoylphosphonic acid.
Is decomposed rapidly by soil
microorganisms.
Volatilization depends on vapor
pressure-acids, salts, amines are less
volatile than esters; greater in soils
with low organic matter and clay
content.
No data available on photodegrada-
tion rates. Has low volatility.
(Continued)
-------
TABLE 7. (Continued)
Pesticide
1 Adsorption, Leaching, and Runoff
1 Chemical and Microbiai Degradation
Photodegradation, Volatilization, etc.
Glyphosate
NJ
Hexazinone
MSMA
Strongly adsorbed to soil via phos-
phoric acid functional group.
Adsorption highest in soils with
high organic content; minimal in
sand. Also binds readily to kaoJinite,]
illite and bentonfte clays. Minimal
mobility via leaching and runoff. No
leachate after elution through soil
columns for 45 days.
Hexazinone and at least some of its
degradation products wash into
the soil with rainwater; classified
as "very mobile", with mobility
dependent on soil type. In a forest
watershed study (application rate
76.8 kg/hr), a series of f 9 storm*
produced a residue loss of 0.5%
of the applied hexazinone.
Converted toarsenate in soil which
tj tightly bound; little leaching.
No residues detected in forest
streams after injection of MSMA
for precommercial thinning;
detection limit was 0.01 ppm.
Decomposed rapidly by soil micro-
organisms under aerobic and
anaerobic conditions. Principal soil
metabolite is amino methylphos-
phonic acid. No appreciable
chemical degradation.
Degrades by soil microorganisms.
Half-life could be as short as 1
month but up to about 6 months,
primarily depending on soil type
and conditions. Several trfazine
compounds identified as degradation
'products.
Converted to a number of organic
and inorganic arsenic compounds;
degradation largely mlcrobitl. De-
gradation products are largely
arsonates which have a half-fife in
soil of about 6 years.
Volatilization negligible due to low
vapor pressure. Does not photo-
degrade under laboratory conditions;
photodegradation in the field
considered negligible.
Will photodegrade on soil surface;
based on laboratory tests, photo-
degradation half-life estimated at
37 days.
None reported.
(Continued)
-------
TABLE 7. (Continued)
Pesticide
Adsorption, Leaching, and Runoff
Chemical and Microbial Degradation I Photodegradation, Volatilization, etc
Picloram
Simazine
Mobility a function of soil type,
pH, application rate and rainfall.
Adsorption greatest in soils high
in organic matter. Seldom leaches
below 20 to 30 cm for most soil
types except sandy soil. Did not
leach below the upper inches of
soil in a forest floor; runoff likely
if heavy rainfall occurs within 1 to
2 months after application.
Low mobility; strongly adsorbed on
soifs high in organic content and in
day soils at low pH. In laboratory
studies leached to depths of one
to two inches in high organic muck
soil; up to 6 inches in other soils
with one inch applied water. Runoff
potential high after heavy rainfall
soon after application.
Reported half-lives varying from
one to over 13 months; rate depen-
ent on soil type and climatic
conditions. Degradation occurs via
microbial and not chemical routes.
Decomposition rate increased under
conditions favoring microbial
growth (i.e., adequate moisture,
temperature, etc). Microbial
degradation thought to involve
decarboxylation and ring cleavage.
Half-life 4 to 6 months depending
on soil type and climatic conditions,
Less persistent in soils high in
organic matter content. Residues
of less than-1 ppm observed in
Woteott, CT forest plot 6 months
after application of 4,8,12 and
16 Ib/acre. Degrades via both
chemical and microbial routes.
Chemical degradation occurs via
hydrolysis to hydroxy simazine;
rate is pH dependent. Hydrolysis
promoted by Fe and Al ions in
soils. N-dealkylation primary
mechanism of microbial degrada-
tion; hydroxylation and ring
cleavage minor mechanisms.
Photodecomposes on soil surfaces,
particularly under intense sunlight
Salt forms less subject to photodc-
composition than ester forms.
Photodegradation may involve
pyridine ring cleavage.
Photodegradation insignificant under
normal climatic conditions. Volatil-
izes only slightly, particularly in
drier soils.
(Continued)
-------
TABLE 7. (Continued)
Pesticide
Adsorption, Leaching, and Runoff I Chemical and Microbial Degradation
Photodegradation, Volatilization, etc.
Triclopyr
00
II. INSECTICIDES
Acephate
Classified a mobile herbicide with
mobility dependent on soil type.
Adsorption greater in soils with high
organic content Principal degrada-
tion product, trichloropyridinol, has
low to intermediate mobility. In
I loam sand, 75 to 80% of applied
triclopyr leached through 12 inch
soil column after 15 days and
7.5 inches applied water. Trichloro-
pyridinol less teachable (13 inches
applied water required for complete
passage through column). Residues
of 6 ppb and 1 ppb in runoff
found 5 and 9 months, respectively,
after application of 3 Ib/acre
triclopyr as TEA salt and 150 cm
rainfall.
Readily leached in soil; not strongly
adsorbed.
Decomposed by soil microorganisms
to 3,5,6-trichloro-2-pyridinol and
trichloromethoxypyridine. Half-life
(average 46 days) dependent on soil
type and climatic conditions. Half-
life of degradation to trichloro-2-
pyridinol 79 to 156 days at 15*C,
<50 days at25 to 35° C. Degrades
5 to 8 times slower under anaerobic
than aerobic conditions at 25°C in
silt loam soils. Does not degrade via
hydrolysis or other chemical routes.
Degradation is microbial; half-life
reported to range from 0.5 to 13
days. The metabolite, Monitor,
is also degraded with a reported
half-life of 2 to 6 days.
Some photodegradation possible
from soil or foliar surfaces. Losses
from volatilization considered
insignificant due to low vapor
pressure.
No photodegradation reported.
Volatility expected to be low.
(Continued)
-------
TABLE 7. (Continued)
Pesticide
Adsorption. Leaching, and Runoff
Chemical and Microbial Degradation
fiotodegradation. Volatilization, etc.
Carbaryl
to
Trichlorfon
Adsorbed readily by organic soils
jut moves rapidly through inorganic
soil. Adsorption completely revers-
ble, due to weak chemical bonding.
In soil teaching study, 72% retained
in upper 20 cm of 100 cm organic
soil column; none detected below
60 cm; only 50% retained in 100 cm
inorganic soil column. Of 8.8 Ib
applied to field test plot, total of
0.14% lost in runoff of which 90%
lost after heavy rainfall soon after
application; concentration in runoff
less than 0.1 ppb after 70 days.
Reversibly adsorbed on soil; greatest
adsorption in high organic soils.
Subject to leaching due to its high
water solubility.
Degradation primarily via microbial
rather than chemical routes. Decom-
posed by bacteria and fungi to
l-naphthol, several hydroxylated pro-
ducts and CO^ Rate dependent
upon soil type, temperature and type
of microorganism. Chemical hydro-
lysis minor degradation route.
Half-life in soil generally <30 days.
Degrades more rapidly in alkaline
soils. Degradation is microbial or
chemical.
Expected to photodegrade on soil
surfaces; photodegradation expected
to be insignificant in the forest system;
no quantitive data available on rates.
Thought to be minimal due to low
volatility, high teachability.
(Continued)
-------
TABLE 7. (Continued)
Pwtiekte
Adsorption, Leaching
and Runoff
Chemical and Microbial
Degradation
Photodagradation,
Volatilization, etc.
Miscellaneous
III. BIOLOGICALS
Bacillus
thuringiensis
OJ
o
Nucleopofyhedrosis
virus
Pheromones
No data available
No data available
Data for oriental fruit fly
pheromone indicates no
leaching.
No data available
No data available
Half-life of pheromones in soil
less than one day. Chemical hydro-
lysis possible. Many application
materials (for e.g., fibers) are
completely biodegradable.
Inactivated by sun-
light on most soils;
in activation more
rapid under moist
conditions.
Inactivated by UV
light.
Highly volatile; not
expected to persist
in soil.
Endospores may
persist in soil for
years.
Viral particles can
persist jn soil for
years.
-------
have been reported for only some of the pesticides (e.g., hexazi-
none, dicaroba, and MSMA) .
• Because of their low vapor pressures, pesticide losses via volatili-
zation are expected to be minimal. Only a few pesticides (e.g.,
atrazine, picloram, triclopyr, Bacillu s t hurlng ien s is . nucleopoly-
hedrosis viruses) would undergo photodegradation/photoinactivat ion
on the soil surface; photodegTadatioTi/pnotoinactivation is expected
to be insignificant in the forest system because of the lack of
intense sunlight and extended exposure.
3.2.4 Fate in Water {Table 8)
• Dilution, adsorption on bettors sediments, chemical breakdown, fflicro-
bial degradation, volatilization and photodegradation are mechanisms
for dissipation of pesticides in the aqueous environment, with
microbial degradation being by far the roost prevalent degradation
route. pH and temperature of the water are the two most important
factors influencing stability and rate of degradation of a pesticide
in water.
« Most of the available data on fate of pesticides in water are from
laboratory studies; actual- monitor in.fc.cf forest streams to determine
rate of dissipation has only been reported for some of the pesticides
(e.g., hexazinone, trichlorfon, amitrole, and Bacillus thurineiensis.
• Except for carbaryl and fosamine ammonium which, at low concentra-
tions, readily hydrolyze in water, chemical pesticides are generally
stable to hydrolysis.
• Quantitative data on Modegradability in the aqueous enviTOnaent
have only been reported for a few pesticides; biodegradabilifcy
appears to vary from that of readily biodegradable (e.g., dalapon
and glyphosate) to considerable persistence (e.g., triclopyr, pic-
loram, and simazine) . Degradation pathways and products have Veen
established for only certain of the pesticides (most notably hexa-
zinone, carbaryl, and acephateK
• Photodegradation can be an Unportant contributor to the dissipation
of hexazinone, piclora*. and triclopyr & the aqueous environment.
nacillus thurineiensis and nucleopolyhedrosis virus would be inac-
Hvated by proloused exposure to sunlight. Although quantitative
data have not beeti reported, the remaining pesticides are expected
to be relatively stable to photodegradation.
3.2.5 impact on KoTi-T&Tget Plants and Organisms (Table 9)
Many of the pesticides have been developed for specif ic applica-
tions (e.g., site preparation and/or release) and specific applica
tion conditions (application rates, time of application, appUca-
ticm method, etc.) against specific target pests. Proper jse is
thus essential to achieve maximum efficacy and minimum damage to
non-target species within the application area.
31
-------
TABLE 8. SUMMARY OF DATA ON FATE IN WATER
Pesticide
Chemical Degradation
HERBICIDES
Amifrok
Alrazine
CO
ro
Dalapon
Dicamba
2.4-D
Fosanune
Ammonium
Glyphosite
Possible chemical degradation, bu
specific mechanism not reported.
No quantitative data available.
Data unavailable; considered negtig
| Me based on rale of chemical degra
dation in soil.
Possible hydrolysis, but specific
I DMdwniwn not reported.
Ener hydrolyzed to the «ctd. Half-
rife shorter at higher pH - ranges
from 0.04 to 220 days depending
on astir formulation and pH.
[ Aqueous solutions of 6 ppm concen-
tration hydrolyzed marly complete-
ly to CPA with 2 weeks at pH 6
(half life, 10 dayjj.no hydrolysis
| after 4 weeks at pH 7 and ». At
7200 ppm (typical ol actual spray
I concentrations) tea than 3X decoro-
{ position observed at pH 5 and 7.
Doe* not degrade via chemical
rout at; no degradation observed of
0.1 ppm at pH 4 to 7.3 alter incuba-
tion 49 day! in the dark; or of 25
or 260 ppm at pH 3,6 and 0 follow-
ing incubation at 5*C and r«*C in
the dark for 32 day*.
Microbral Degradation
Probable aiicrobidl degradation in
water or sediments as in soil, but no
specific data reported.
No quantitative data available.
tojor route ol degradation. BOD/
:OD ratios comparable to readily
Biodegradable susbtances such a*
sucrose and athanoL
Probable microbial degradation in
water or sediments ai in soil, but
no specific data reported.
avored in warm, nutrient-rich
water. Esters hydrolyzed to the
acid. In natural waters, may remain
stable for 8 months or more.
o data available.
Major route ol degradation in natural
waters; naif-life in water approxi-
mately 2 weeks.
Phofodegradation
Amitrofe reported to be stable
under UV light.
Extremely slow, due to lack of
sunlight adsorption. Expected to be
insignificant In the environment.
Miscellaneous
Quantitative data unavailable; con-
sidered insignificant in water based
on behavior in soil
None reported.
Photodegradation not a major
mechanism. Breakdown product«
2,4-dichlorophenol Volatilization
may be important for removal
of some esters under tow pH
conrJitionSk
Extremely slow under laboratory
conditions 12% decomposition in 8
weeks of 6 ppm solution exposed to
irradiation intensity of 1200 watts/
qcml. Expected to be Insigni-
ficant in the enviranmant.
Data unavailable; considered negli-
gible based on rate of pftotodegr*-
dation in soil.
Mechanism for degradation not
reported. Disappearance from water
may be due to dilution or adsorp-
tion to bottom sediments. No
amiirole residue found in streams
3 days after application to 260
acres ol forest land at 2 Ib/acre.
Maximum ol 16.7 ppb detected in
7 rhreri monitored in corn belt;
peak residue occured during month
of heaviest application (May-June).
and declined to < I ppb for rest
of year. Rale of decay in ponds
treated with 0.3 ppm approximately
0 68 ppb/day (attributable to
chemical and/or microbial degrada-
tion routes, uptake by aquatk
organisms, adsorption to bottom
soil, and/or other mechanisms).
Mechanisms lor degradation not
reported. May be hydrolyzed and
slowly transformed to 5-OH dicamba
(about t OK after 32 day.).
Concentrations in forest streams
following spraying are generally
-------
TABLE 8. (Continued)
Pesticide
Chemical Degradation
Photodetndition
Miscellaneous
Hexazinone
Pidoram
Simazine
Tcielopyr
II. INSECTICIDES
Acephate
Carbaryl
Trtchlorton
Relatively stable to chemical hydro-
lysis under natural conditions (l«t
than 1% degradation noted in test
solutions over several weeks).
Expected to be negligible.
Microbial degradation (see Table SI
and photodegradation major causes
of hexazinone reductkm in natural
waters.
Converted to a number ol organic
and inorganic arsenic compounds.
Stable to hydrolysis under natural I Not readily decomposed by micro
t conditions I organisins in water.
Q: ' moderately persistent in
wjlt, '-50 to 70 days, with
99% tu^.. I? months. pHand
temperature dependent; hall lite 4
months at 70°C. pH 7; shorter at
increasing and decreasing pH.
Minor; stable to hymn/sis in bulli
solutions up to 9 months at pH 5,7
and 8 and at 15. 25 and 35'C; less
than 1% converted to 3. S. 6-
trkhloro-pyridine.
Expected to be minimal relative
to microbial degradation.
Hydrolyzes rapidly in water at
pH>7: no decomposition at pH 3-6.
Halt life one month at 3.5'C and
3.5daysat20"CatpH8.
Possible chemical degradation, but
specific mechanism not reported.
Not considered a significant degra
(ion route. Quantitative data
unavailable.
In laboratory test solutions, 30%
degraded in S weeks; rate slower in
natural waters where sediments are
present.
Does not photodegrade.
Readily degraded by UV light and
sunlight in water (photolysis half
life of 5 to 60 days reported).
Degradation thought to follow
pseudo-first order kinetics. Numer-
ous degradation routes possible,
including free radical pathway.
Extremely slow under laboratory
conditions; considered insignificant
in the field. 4.W>is (ethylamino)-s-
triazina major degradation product.
May also adsorb to sediments in
water.
Quantitative data unavailable;
considered negligible relative to dis-1
1 sipation via photodeyradation.
Degrades faster In wanner water
[ with higher pH; degradation faster
when sediments present.
Degrades to t-naphthol, CO2 and
other products.
Probable microbial degradation in
water or sediments as in soil, but
no specific data reported.
Major pathway for dissipation from
aquatic environments. Decomposi-
tion rapid in both natural sunlight
and under laboratory conditions;
hall-life is 10 hrs at 26'C. Degrades
to trkhloropvridinol. which further
degrades to various pyridine polyo
via free radical mechanism.
Does not photodegrade.
Sub|ect to photodecomposition:
raw dependant on pH, level of
Incident radiation and dissolved
oxygen. During summer months
In the field, rate as much as four
times that In winter months.
Half-life shorter with exposure to
sunlight
Residua of 2 to 26O ppb found
2 to 3 hours alter application ol
I Ib/acre Sevin 4 oil to forest
test plots.
Degradation faster under alkaline
conditions and at warm tempera-
tures. Half life
-------
TABLE 8. (Continued)
Pesticide
Chemical Degradation
Microbial Degradation
Photodegradation
Miscellaneous
III. BIOLOGICALS
Bacillus
Nudeopolyhedrosis
virus
Pheromones
None reported.
None reported.
Possible chemical degradation, but
specific mechanism not reported.
None known.
Nona known.
None reported.
Inactivatied by UV light
Inactivatied by UV light
None reported.
No viable spores present in river
water 4 weeks after aerial application
to Canadian forest plots.
Mechanism for degradation not
reported. Pink bollworm pheromone
had half-life in water of 7 days.
-------
TABLE 9. IMPACTS ON NON-TARGET PLANTS AMD ORGANISMS
U9
In
low HnfcMv 10 Mi (uhnon FMd ipplicMioni hnc
ftablndv non-to«ic to boa
rum I Mi ttwi Spirant
M • dov
tram opplicttiofi of 1 ^ftm.
LmbM hnfcitv (onl LDjO
•cuu taridtf ionl LOjo.
1.100 fn^kcm. 14.700
to IM ankwinjc In into
U>wMRioiMrauto»icit«tD Honto.ic n mil mm-
MiiicitrMbMllnd
(LCM>MOD
dudlfM
in «qu«rkm> omomtrMian ol
OMppml. Svno bkHcai
mlMion in
totppm. Madnmlytanc
ft ppm In tnan conuin-
fcf.1t.Jpl*
";«
kw rapidl* ntma vith no
f«Mr •hcitM tat mud/
Low Mwichv w «* lt€so >
.... „ ofwil
initM
obpjrwd «ta JO Ib/Kn
nochHifMIOHrA
MnnpopulMion
lultoconilmHailM
•odium Ml; S,MOiii»*|
m« brti 100 - I WO ppm
for
ol< 1OOppn.du.mf
«nd I ppnmJ
DOWfON md DOMFON Ml
Looubl
toonto.
LovMu
twH LOjo (Mdun. M09
bolMhiu qurt md mritod
dwMM 1.000 to 6.000 PP*.
to* (Ml ol tnieitv ID bMi
terattotllnl
LOy, >1 ffOO "V^t-l"*
nonwiic to b*M « rac-
.•WUBI-, tWH. CMWin Wd
XppmtvnintewtnMl
-------
TABLE 9. (Continued)
Pesticide
Plant*
2.4-D (Harmful to numerous cropi;
may damage conifers
Fish and Other
Aquatic Organisms
Bulyl esters 100 time* mom
toxic than the add*; 96 hr
LCgo'l about l.0mg/t
for trout. Effects on
I [aquatic invertebrate* et
Ieveb 10OO and > 1,000 ppm|soH bacteria end fungi un-
tor MuegUtt. embow trout
and fathead minnow, respec- Jweeks. Uayormsynat
twety- 48-hr tCjo ^ 1 ^2* Ulfect rates ol nitrogen
ppm for Daphnie nwgna. No |fu«io)i by K)M becterie
data available on metabolism
in fish
Gryphotate I Temporary browning of
eonifen observed in release
lkjtion* using I to 3 QU/
acre. No injury sustained by
Icrops after agricultural applic-
|alion at usual rates. Injury to
murgx plena due to drift
from forest eppliratlon
Low to moderate toxicity
(96hrLCso,2Jm»/Ifor
fatrtead minnowf. 43 mgfl
[for mature scuds). Surfactant
lused in Roundup considered
the principal toxic agent In the
(ormulauon (24-hr LCfcg for
rainbow Iraat.tM mg/Tfor
gtypfnsete.2.1 mg/I for
surfactent)
Hat minimal to-nil effect on
under aerobic end
corxiitioai. No
effect* obaerveC) from
•nd 25 ppm on microfaial
ilalions in soil in term* of
fixation; nttriHcation,
and starch, protein or leaf
Htter degradation
served in persons exposed to
2,4 Dal nigh doses;con-
genital malformations seen In
rait or mice, few other
effecttobterved. U>50'»
rings from 300 to 6.000
mg/kg for poultry, mallard,
ducks, phsatants, pigeon*
end quail.
Low toxkity to mammals and
birds (acute on) LDso of
24.000 mgAg for rats. 7,380
mg/kg for guinea pigs.
|> 10.000 mg/kg for mallard
sandbofawhiteouail.) No
aflects except mild
Jdtarrhel noted Irom feeding
[ral* 3^00 moAn/day for 14
NotteratogenicdO^OO
fed to pregnant rattl or
Imutagtnic (Ames test)
Metaboliied and/or excreted
rapidly by animals and con-
sidered non bioaccumulable.
Typically > 85% eliminated in
faces, and > 8% «n urine. Low
eccumulation observed In
catfish exposed to 1 ppm for
4w*eki
Low toxicily to wildlife
and benef kail Insects
fLC$0 m*JJjrd duck and
quail > 4,600 ppm; acute
oral IDgo rat, 4,330 moAg:
LOso bee. 100 ug/bee)
Link lo no bioeocumuUtion
I in fish <0.1 ppm Roundup in
IbNjegilli. trout and basi ex-
jposed to 10 - 12 ppm for 14
Idayt; 80 ug/kg glyphosate in
|f ish tissue and 60 ugAg in lish
> efter exposure to 2.0 mg/I
iRoundup). Rapidly excreted
I in mammals (80% In feces.
11X in urine of rabbin 5 days
[after edministretion of single
jdosel
(Continued)
-------
TABLE 9. (Continued)
Pesticide
Plants
Fish and Other
Aquatic Organism*
Soil Organism*
Birds. BenettciaMntects
and Mammals
Btoaccumulation
Potential
Hexazinone 10 to 15% conifer mortality
I may occur in release applica-
I tions, depending on conifer
I species, soil type and applica-
Uton rate. Residue levels in
I non-target wild fruits under
I study
MSMA. I Toxic to many agricultural
land non-agricultural plants
Picloram I Toxic to young conifers and
(various nontarget species; •
(several incidents of damage
[reported due to spray drift.
I Certain crops injured as long
las S years after application
(due to picloram persistence
"Slightly" toxic to fish and
Daphnia (96-hr TL;>o values of
275 to 420 pom for three
species of fish tested). Ex-
posure to intermittent concen-
trations (6 to 44 ppb) of
hexazinone in a forest stream
did not result in major alter-
ations in species composition
or diversity in aquatic macro
vertebrate community
Low toxicity (964v LCgr/'
f 13 to 1.100 ppm for fish)
10 ppm hexazinone added to
3 agricultural soils did not
reduce fungi or bacterial count
in 8 wks; in lab bioassays. 100
showed no fungal toxicity,
to 20 ppm hexazinone added
to 2 soils had no effect on soil
itrilying bacteria in a 5 wk
test. No major changes noted
in the terrestrial microarthro-
pod samples 8 months after
.treatment in a forest water-
study
Relatively non-toxic
Low toxicity to fish and other
aquatic species (24-hr LC$o
30 ppm. rainbow trout; 64
ppm. fathead minnow).
ncrease in fry mortality in
Salmo clarki observed at
concentrations greater than
1-3mg/*. No adverse effects
n food chain study with algae.
laphnia. goldfish and yuppies.
Inhibitory to growth of
certain spades of algae at
SO to 250 ppm. Picloram
ester f romulations more
toxic to fish than picloram
and picloram salts due to
presence of toxic impurity
2-(3,4.5,6-tetrachloro-2-
pyridyl) - guanidine
Very low toxicity to soil
microorganisms; no adverse
effects noted on treatment of
45 common soil organisms.
Including bacteria and fungi,
with up to 1,000 ppm. Con-
centrations of 1 to 10 ppm
inhibitory to populations of
soil Penicillia but stimulated
growth of AsperaiUa and
Trlchoderma.
Low toxicity to mammals and
birds; acute oral LDgrj of 860.
2.258 and > 3.400 mg/kg for
guinea pig. mallard ducks and
dog, respectively. Not carcin-
ogenic, embryotoxk or terato-
genk (5,000 ppm in diet of
ratl. No effect level in 2-yr rat
feeding study was 200 ppm
Not bioaccutnulative in fish.
No evidence for accumulation
in stream organisms in an
8-mo field study; but residue
levels in terrestrial invertebrate
were a maximum of two
orders of magnitude greater
than 0.01 to 0.18 ppm levels
found in forest floor material
Toxic to some grazing
animals. 48-hr LD$Q for
bees, 24 ug/bee
Low toxicity to birds.
(Acute oral LDso > 2.000
mg/kg for mallard ducks and
pheasants). For bees, LDgo
* 15 ug/bee for both
picloram and a certain
Tordon formulation. Low
toxicity to mammalian
species (oral LDgrj 8,200
mg/kfl, rats; > 1,000 mg/kg.
sheep; > 750 mg/kg, cattle).
No adverse effects in long-
term feeding studies on rats.
Tordon 101 considered more
toxic than picloram to sheep
(feeding 055 mg/kg resulted
in 2 deaths within 10 days)
Bioaccumulation observed in
some aquatic organisms but it
is not expected to become
concentrated in food chains
Excreted rapidly by and does
not bioaccumulate in
mammals (90 percent excreted
in dog urine when fed at
Vivels of 100 mg/kg in the
diet). Not accumulated in
invertebrates or in their food
chains. Accumulation factors
of 0.25 (pidoraml for
Bambresia sp.and 023
(picloram) and 0.050
(6-hydroxy-35-dichloro-4-
aminopicolinic acid metabo-
lite) for catfish
(Continued)
-------
TABLE 9. (Continued)
Petticide
Plants
Fi*h and Other
Aquatic Organisms
Soil Organisms
Bird*. Beneficial Insects
and Mammals
Bioaccumulation
Potential
Simazine I Causes severe injury when
I sprayed directly on young
J pine seedlings {based on
I reported rates of 0.5 and 11b
la.L/acre). Phytotoxic to
I certain non-target agriculture
land orchard species (e.g., oats.
I peach trees). Residues may
[persist at phytoxic levels fnto
(next growing season
Low toxicity to fish and
lower aquatic organisms
(LC5Q> 1,000 ppm Princep
BOW for bluegill and channel
catfish). No effects on
daphnid reproduction at
(US to 3.0 mg/8
u>
00
Triclopyr (Minor injury to conifers at
14.4 kg/hr reported in release
japplication; no injury at 22
|kg/hr. Some inhibiitkm of
[cucumber yields at 0.5 Ib
la.iVacre after 3 months; SOX
(inhibition at 3 and BlbaJY
I acre after 4 months
ow toxicity; 96-hr LCgQ tor
luegilli, 148 ppm (triclopyr)
nd 891 ppm (Garlon 3A); for
inbow trout, 117 ppm
trklopyr}, B52 ppm (Garlon
A); shrimp, 80S ppm (Garlon
A)
Harmless at normal applica-
tion rates. Cellulolytic
organism growth stimulated
i>y normal and higher-ihan-
normal application rates;
nitrogen cycle organisms
unaffected. Fungal popula-
tions in sandy loam soH
stimulated by 2.5, 5.0 and
10.0 pom in one reported
tudy; minor fungicidal
ctivity also reported in
separate study
Considered non-toxic; no
effect observed on 6 soil
icroorganisrns at 500 ppm
tar 72 hrs incubation
Low toxktty to mammals
(acute oral LD$0 > 5.000 -
10rOOO mg/kg for rats, mice,
rabbits). No systemic toxicity
observed in 2-yr rat feeding
study with 100 ppm. Very
low toxicity to birds (no
mortality up to 5,000 ppm
to bobwhite quail and mallard
ducks). No effect on mallard
duck reproduction at dietary
levels of 2.0 and 20.0 ppm.
No insecticidal activity at
normal application rates
Low toxicity to mammals and
birds; acute oral LD^Q rat,
630 mg/kg (triclopyr). 2.140
mg/kg {Garlon 3A), 2,140
mg/kg (Garlon 4); LCsg*
mallard duck, > 5000 ppm
triclopyr), > 10.000 ppm
Garlon 3A), > 10,000 ppm
Garlon 4). Non-carcinogen-
c to mica and rats. Mildly
etotoxic at 200 mg/kg/day.
Data unavailable on insects
Low in fish and other aquatic
organisms. No accumulation
observed in fish, dragonfly
nymphs, midge larvae and
mayflies in four 0.25 acre
ponds'treated with 0.1,0.3
1.0 and 3.0 fig/me. Accumu-
lation of one to four times
the water concentration
observed in other studies.
Metabolized rapidly by
animals and not accumulated
in tissue or milk (80 ppm in
cow diet resulted in 0.01 to
0.02 ppm in milk I. Little
bioaccumulation by micro-
organisms; equilibrium tissue
concentration reached after
24 hours in static studies
No bioaccumulation in fish;
data unavailable for mammals,
birds, etc.
(Continued)
-------
TABLE 9. (Continued)
II. INSECTI-
CIDES
Plants
Fish and Other
Aquatic Organisms
Sol Organisms
Birds. Beneficial Insects
and Mammals
Potential
Acephate (Not expected to harm planu;
I leal burn wid Interveinal
chlorosis hn been reported
Low toxkitv to fish (96-hr
TL50>'.OOOppn>)
(None reported
May inhibit brain cholinester-
«e activity in birds but mort-
ity not expected et recom-
mended application rate*.
Toxic to non-target imectt:
toxic to ben (LDyj
1.2ug/beel. Low toxidty to I
.nek (acute oral LDsQ
700 mg/kg. rat. Low to I
moderate toxkhy to birds I
acute oral LDcQ 350 mg/kg.|
ticks; 825 me/Kg chickens). I
Slight bioaccumulation has
been observed in li«h;
I acephate i* reported to be
I eliminated ai concentration
I in water drops
LJ
VO
Carbaryl |Low phytotoxicity. Some IToxk to fish (96-hr LCgQ
[injury may occur to certain 11—20 ppm) . Degradation
(species (e.g., apples, pears, (product 1 -naphthol also toxic.
(boston hry) if rain/high JToxicity varies with formula
Ihunwttty persist for several Woo (e.g,. 48-hr LCso 28 ppm
(days after application (for Sevin-4-oil 14 ppm for
1
Trichlorfon
.
•
iavin40WP). Toxic to
rrustaceans and mollusks
»8*r LCso 10 ppb - 3 ppm)
ind certain other aquatk
(organisms. 10 ppm lethal to
1 three aperies of marina algae :
No advene effects reported
0.1 ppm lethal to five spedaf
to phytoplankton.
Highly toxic to some aquatk
1 invertebrates (e.g. D. maona.
48hrLC50<1ppb);lMS
.
r
1
1
1
toxk to fish (LCso generally
from 1 to 100 ppm)
Toxk to soil microbes;
decrease in mkroarthropod
population in millet field liner
[observed 3 weeks after traat-
Imentwith2lbs/acre. Degra-
Idation product 1 -naphthol
|»Uo toxk (lethal at 50 ppm to
Ifmafjum solani: 20 — 30 ppm
1 to certain bacterial. Toxk to
1 certain soil microbes
IKB «*_ _ _ *. _ . J _i
INo nractt obMrviid wtitn
(•ppUfx) at Itvf to up to 10 ppm
1
Moderate to low toxwity to 1 Bioaccumulates in aquatic
mammals (LDso't typicallv (biota (accumulation ratio
200-8SQmg/kg|. Low 1 1,064 in trout bile; and 3A
oxicily to birds (LDgo's land 4.0 for lake trout and
780- 2,030 mg/kg>. No (Coho Salmon in aquarium
significant effects on repro- Iconcentrationa of 2j6 ppm).
duction. Toxk to honeybees |L
(LDso13| n.006 for chicken kidney)
Adverse effects on many 1
Insects observed; low I
toxkity to bees (LDgg SO JS3 \
ug/bee). Reduced brain
acetylcholitietterase levels 1
found bi birds but no
mortality observed. Low to
moderate toxkity In
mammals (acute oral LDso
to rats, 184 mg/Vg as techni-
cal formulation: 2500 mg/kg.
as 1 S o»l: depreued cholines-
terase leveb reported: terato-
gank in rats; used in veterin-
ary practice to kill pests on
animal*
Analysis of fish tissues
ndkated no bioaccumulation.
Did not bioaccumulate in
sWWBp.
(Continued)
-------
TABLE 9. (Continued)
Pesticide
Planti
Fish and Other
Aquatic Organism*
Soil Organisms
Bird*. Beneficial Intact*
and Mammals
Bioaccumulation
Potential
III. BIOLOGICAL
Bacillus
thuringiensis
Quantitative data onaval table;
no advene effect! expected
Nucleopolyhedros
virus
Quantitative data unavailable;
no adverse effect! expected
Pheromones
uantitative data unavailable;
no adverse effect! expected
Generally low toxicity; some
toxicity to Coho salmon
juvenile at > 300 -1.800
billion/kg viable spore
count
Non-toxic to fish. Labor-
atory studies with Coho
salmon, Chinook salmon and
steelhead trout showed no
advene effect* from expos-
ure via 3 routes: waterborne
exposure, intraperitoneal
injection arid feeding
No quantitative data avail-
able; no advene effects
expected
Quantitative data unavailable
no advene effects expected
Quantitative data unavailable;
no advene effect! expected
Quantitative data unavailable;
no advene effect* expected
Non-toxic to bees at levels ai
high as 726,000 spores/bee.
Non-toxic to rats up to 24g/
kg body weight. Maybe
harmful to some non-target
Lepidopten
Low toxicity to birds,
mammals, bees. No
advene effects at con-
centration of 10 x 109
polyhedra/bee hive. Non-
carcinogenic to rats
Several pheromones found
non-toxic in laboratory
animals. Flying insects,
>kds, etc. could get caught
n sticky trap*
Quantitative data unavailable;
no bioaccumulation expected
No bioaccumulation in fish.
None expected in other
species
Quantitative data unavailable;
no bioaccumulation expected
-------
» Many of the pesticides are phytotoxic to agricultural crops and
other non-target plants, and hence can potentially cause damage to
such crops and plants if drifted significant distances off-target;
in forestry applications, however, potential for spray drift can
be minimized via strict adherence to label instructions and local
buffer zone requirements. Herbicide formulations which can be used
as large pellets (e.g., "Velpar" "Gridball" formulation of hexazi-
none) or in special devices such as luretape, rubber caps, or wicks
(e.g., in the case of pheromones) present little potential for
drift during the application.
» Certain laboratory bioassay data for aquatic organisms have been re-
ported for nearly all the pesticides addressed. These data indicate:
(a) a range of toxicities with LC5Q values being in the 1 to 100 ppm
range for amitrole, dicamba, 2,4-D (butyl ester), glyphosate, pic-
loram (ester formulations), carbaryl and trichlorfon; (b) for some
pesticides (e.g., 2,4-D, carbaryl, and picloram) toxicity is dif-
ferent for different formulations; (c) toxicity effect is dependent
on the species tested and is generally higher for the organisms in
the lower end of aquatic food chains (e.g., reported 48-hr LC5Q values
for Daphnia are 3 ppm and less than 1 ppb for amitrole and trichlor-
fon, compared to values for fish of 3,250 ppo and 1-100 ppm, respec-
tively) .
Quantitative data on impacts on organisms in the forest soils under
actual application conditions and the long term significance of such
impacts are generally unavailable for many of the pesticides. Short
term toxicity data reported for dalapon, fosamine ammonium, gly-
phosate, hexazinone, picloram, simazine, triclopyr, carbaryl, and
trichlorfon indicate variable impacts (non-toxic to grovth stimi-
lants), depending on the species and the application rate.
Based on data from animal studies, the majority of the pesticides
addressed would be considered to be of low acute toxicity to mammals
and birds; U>5Q values for rats are generally greater than 1,000
mg/kg and tests with atrazine, hexazinone, fosamine ammonium, gly-
phosate, picloram, triclopyr indicate Lt>5o values for mallard duck
ranging from 700-800 mg/kg for atrazine to greater than 10,000 mg/kg
for fosamine ammonium. Quantitative toxicity data for bees indicate
low to high toxicity to bees, with LDso's of 100, 24, 15, 1.3, and
1.2 yg/bee for glyphosate, MSHA, picloram, carbaryl, and acephate,
respectively. Bacillus thuringiensis has been shown to be non-
toxic to bees at levels as high as 726,000 spores/bee.
Bioaccumulation data indicate low or no potential for bioaccumula-
tion in fish for nearly all pesticides for which such data have been
reported, except for carbaryl for which a high bioaccumulation
factor in fish and certain fish organs has been observed. Little
or no bioaccumulation in test birds and mammals has also been noted
for atrazine, dalapon, dicamba, 2,4-D, fosamine ammonium, glyphosate,
picloram simazine, carbaryl, and trichlorfon. Biological insecti-
cides are not expected to accumulate in fish or other organisms.
41
-------
APPENDIX
I. HERBICIDES
II. INSECTICIDES
III. BIOLOGICALS
A-l
-------
I. HERBICIDES
Common Name: Amitrole
Chemical Name: 3-amino-l,2,4-triazole
Major Trade Names: Amitrol-T; Cytrol Amitrole-Tj Weedazol
Major Applications Control of salmonberry and elderberry in the coast
in Forestry: range of Pacific Northwest.
SUMMARY
Amitrole is a non-selective herbicide that is absorbed through leaves
or by roots. In plant tissue, it inhibits chloroplast development, causing
chlorosis and eventual death. It is currently registered for use is a h«?
bicide on non-agricultural sites, and is used primarily to control grasses
broadleaf weeds, poison ivy and aquatic weeds/ In forestry, it is used ?or
site preparation and for conifer release.
Amitrole is highly soluble in water but is not soluble in non-polar
organic solvents such as oils. It is not tightly bound to soils and thus
can be leached readily. In addition, it is microbially or chemicaUy 5e«a
moderate0* *, / * **™i8t?™* °f •»*«*• in soil i8 consider^ low to
an eeral
amitrole is converted to compounds with little o? no known toxicity? imi-
trole^does not accumulate in animal tissues nor is it biomagnif ie^in ftJd
° 0tyow
of
A-2
-------
1.0 INTRODUCTION
Amitrole is a non-selective, systemic herbicide registered under the
Federal Insecticide, Fungicide and Rodenticlde Act in 1956 (1). One of the
early uses of amitrole was on cranberry bogs after harvest. In 1959,
certain lots of cranberries containing amitrole residues were removed from
the market following reports that amitrole induced cancers of the thyroid
in rats (1,2). By 1971, all registered uses of amitrole on food crops were
cancelled (2). Amitrole ie currently registered with the Environmental
Protection Agency for non-crop and aquatic site use (1).
Amitrole's primary use is for control of grasses and broadleaf weeds,
poison ivy, poison oak and aquatic weeds (3). In the forestry industry,
amitrole is applied to salmonberry and elderberry for site preparation and
conifer release in the coast range of the Pacific Northwest (4,5). It is
generally applied as a foliar spray at the rate of about 2 pounds of active
ingredient per acre.
Amitrole is marketed in the United States by Union Carbide, Custom
Chemicals, American Cyanamid, and Fairmont Chemicals under several trade
names, including the following (1,3):
Amerol
Amino Triazole Weedkiller 90
Amitrol-T
Amizol
Azole
Cytrol
Cytrol Amitrole-T
Herbizole
- Weedazol.
It is also available commercially as a mixture of herbicides with simaztae,
diuron, atrazine, bromocil, fenac and linuron (3,6). Formulations are avail-
able as soluble powder and liquid and in pressurized containers. Some ami-
trole formulations contain ammonium thiocyanata, NH4SCN. The NH4SCH repor-
tedly enhances translation of the herbicide inside the target plant by
inhibiting the formation of a less mobile metabolite (2,7).
2.0 PHYSICAL ANT CHEMICAL PROPERTIES OF THE ACTIVE INGREDIENT
The active ingredient of amitrole formulations is 3-amino-l,2,4-
triazole:
A-3
-------
N — N
)l II
HC C-NH
XK' 2
H
It is a weak base which reacts as a typical aromatic amine (2). The ring
structure of amitrole is resistant to hydrolysis and the action of oxidizing
agents (8).
Amitrole is highly soluble in water (28 grams in 100 grams water at
25°C) and in the polar organic solvent ethanol (26 grams in 100 grams at
75°C). It is insoluble in oil or in most other non-polar organic solvents.
Amitrole is reported to have a low volatility although no vapor pressure
values are reported in the literature. Its melting point is 159°C (6).
3.0 ENVIRONMENTAL FATE
Since very little environmental fate data has been published in connec-
tion with the use of amitrole in forests, most of the discussion in this
section is based on data for non-forest applications.
3.1 UPTAKE AND METABOLISM BY PLANTS
Amitrole is absorbed through the leaves and roots of plants and readily
translocated inside the plant (2). Its mode of action is to prevent chloro-
plast development in new growth, possibly by interfering with purine syn-
thesis (9) or by preventing normal carotenoid synthesis and accumulation
(10).
Upon review of the literature, Carter (2) states there is no conclusive
evidence of extensive ring cleavage in plants. The amitrole residues found
in treated plants are in the form of free amitrole or conjugates reversibly
bound to plant constituents. Bondarenko (11), in a field study of treated
soybeans and com, found amitrole throughout the plants eight days after
application. In a laboratory study, amitrole was detected in grafted,
treated tomato plants for up to 3-1/2 months after treatment (12).
More than a dozen compounds derived from amitrole have been isolated
from treated plants (13). Most of these compounds are probably conjugates
(2). One metabolic breakdown product has been identified as 3- (3-amino-s-
tria2Ple-l-yl) 2-aminopropionic acid or 3ATAL (14). The metabolite, 3ATAL,
A-4
-------
appears to be less toxic than amitrole and, therefore, amitrole is considered
to be detoxified when metabolized to 3ATAL. The 3ATAL is also not as mobile
in plants as amitrole. The additive NH^SCN inhibits 3ATAL formation (15,16)
and, thus, may indirectly enhance amitrole mobility (16).
Amitrole in the plant exhibits its phytotoxicity in the form of a
chlorosis or lack of chlorophyl in new growth which is white in color. Phy-
totoxicity is related to the amount of amitrole in the soil, ambient tempera-
ture and soil pH (12,17,18). Muzik (12) has observed higher phototoxicity
to grafted tomato leaves at an ambient temperature of 55°F compared to tem-
peratures of 70°F and 85°F. Phytotoxicity to cucumber plants has been shown
to be maximum at a soil pH of 6.5 (17).
3.2 FATE IN SOIL
In the soil amitrole may be found adsorbed to soil colloids or in the
form of complexes with metallic ions (nickel, cobalt, copper, iron, and
magnesium) (18). Disappearance from soil may be the result of uptake by
plants, volatilization, photodecomposition, leaching, raicrobial degradation
or chemical breakdown. Volatilization is not considered a major factor in
the loss of amitrole from soil because of the low volatility of amitrole
(19,20,21). Photodecomposition is probably also not important because ami-
trole appears to be stable under ultraviolet radiation (21,22). However, in
laboratory experiments, photodecomposition has been shown to occur under uv
light in the presence of riboflavin (2,21).
Persistence of amitrole in soil is dependent, to a large extent on ad-
sorption of the compound on soil colloids and on its chemical/microbial de-
gradation. These factors, which affect the potential for leaching and hence,
for contamination of surface waters, are discussed below.
3.2.1 Adsorption and Leaching
In studies of amitrole fate in soil, adsorption is usually measured as
the change in amitrole concentration before and after addition to soil (23,
24). Day, et al. (20) found that 20-50 percent of the amitrole applied to
55 California soils was reversibly adsorbed to the soil accompanied by a
decrease in amitrole mobility. Repeated percolation of water through the
soil released the bound amitrole. No relationship was found between adsorp-
tion of amitrole and base exchange capacity or soil classification. However,
A-5
-------
Martson, et al. (25) report that araitrole adsorbs rapidly and tightly to
soils with high base exchange capacity and organic matter content. Other
researchers have also found the adsorptive capacity of soil to be related
to organic matter content. Kaufman, et al. (26) found that adsorption of
amitrole in organic soil was as high as 40 percent and in inorganic sandy
soil as low as 3 percent. Nearpass (23) measured amitrole adsorption in a
high organic soil suspension of peat and water. Over 59 percent of the
amitrole applied was adsorbed onto the soil after one minute; over 68 per-
cent was adsorbed in 24 hours. Adsorption also increased with Increasing
acidity in the soil.
In a given soil type, the adsorptive capacity for amitrole appears to
directly affect its leaching characteristics. Leaching of amitrole can
occur in sand or sandy loam but is greatly reduced in clay, clay loam or
high organic soil (27). These latter soil types show stronger affinity for
adsorption of amitrole. Day, et al, (20) studied adsorption and leaching
in several soil types. As expected because of amitrole's high solubility
in water, amitrole moves readily with the leaching water. Repeated passage
of water released more amitrole. Peak concentrations of amitrole recovered
in the first few passages of water were found in those soils exhibiting poor
adsorption. High adsorptive soils required more water to release the bound
amitrole.
3.2.2 Persistence and Degradation
Amitrole is considered to have a low to moderate persistence in soil,
depending on the soil type and conditions. Detectable residues are reported
to persist from several days to six months or more (28,29). In a study
measuring amitrole residues by methanol extraction from forest' litter, ami-
trole was shown to degrade fairly rapidly with a half-life of about 5 days
(28). Kaufman (29) found residues amounting to 36 percent of the applied
amitrole after 18 months in a sandy loam soil. Burschel and Freed (30) re-
port a breakdown rate of 1.31 yg/g soil/day at 29'C for a Chehalis loam soil
and estimate a half-life of about 6 weeks.
Factors influencing persistence of amitrole in soil include soil mois-
ture, temperature, PH, base exchange capacity and soil treatments aimed at
eliminating or inhibiting soil microorganisms (see Table 1). Ercegovich
A-6
-------
TABLE 1. EFFECT OF SOIL PARAMETERS ON PERSISTENCE OF AMITROLE IN SOIL
T
Soil Parameter
Moisture, %
Temperature, °C
pH
Base exchange
capacity, meq/100 gms
Clay content, %
Range of
Parameter Tested
0 - 30%
15 - 100°C
4.3 - 8.0
3-99
2 - 15%
Increasing the Parameter Produces ^
(+) Increase, (-) decrease, (0) no effect
Adsorption CO- Evolution Phytotoxicity
- (12)
- (23) - (31)
+ (2,20)
- (20)
Recoverable
Residues
- (21)
- (21)
- (21)
+ (18)
- (18)
Organic matter
content, Z
Treatment with KN-
Treatment with
ethylene oxide
Autoclave treatment
Addition of free-
radical reagents
Presence of dalapon
in soil
1.5 - 75%
(26)
- (18)
- (26)
- (26)
.- (26)
+ (22)
0 (29)
*
Numbers on the designations refer to the reference for the data source.
-------
and Frear (21) studied the effects of various soil parameters on the persis-
tence of amitrole. They found that increased soil moisture decreases per-
sistence probably by enhancing degradation or leaching. Elevated temperatures
to 1DO°C also shortened residue life. The fact that amitrole steadily dis-
appeared under increasingly high temperatures to an extreme of 100°C indi-
cates that degradation is at least partially a chemical process rather than
strictly microbial decomposition. Deviation of pH much above or below neu-
tral also shortened persistence (21). This observation is consistent with
phytotoxicity studies showing that amitrole has optimum efficiency in soil
with a pH of about 6.5 (17,31). Sund (18) studied the effect of soil type
on amitrole degradation and persistence and discovered that a high base ex-
change capacity (about 100 meq per 100 grams of soil) increased persistence
whereas high clay and organic matter content decreased persistence. This
finding is in agreement with Day, et ai. (20) «bo found that high colloidal
soils were characterized by decreased persistence of amitrole.
Degradation in soil has been mea8ured as: (.) evolution of radioactive
C02 fro* soil containing C-5 amitrole (22,26); (b) loss of phytotoxic
effect, measured in terms of reduced plant growth (29); and (c) reduction
xn the amount of recoverable araitrole aS,I9,21), Evolution of I4CO from
C-5 amitrole containing soil has been taken as evidence .« ring cleavage.
Because CO, or formate is formed from the 5 earbon of amitrole and labelled
amitrole is cotoercially available only as »c-5 amitrole, other degradation
products remain unified and would be difficult to identify and .uantify
Several investigators have found that autoclave treaty of aoll
nearly stops Co, evolutio, frra» a»ir^-cantaining ^
claving also depresses the amitrole degradation raL U°'21'26>-
soil residue depletion over time („ ,3!,. " ^ . T^
that sterilization by ethylene oxide or tr~* / °
substantially. These findings sugg«t that ,.„ , „,
1. not entir^ . .icro.iolcgica! t " "
che.ica! reaction. (see bel», The
'
of free radicals (22.26). " ^ *"" "°* "aitr°U to the
A-e
-------
Plimmer, et al. (22) propose the following scheme to show the possible
pathway of the degradation and adsorption of amitrole.
N
n
N
II
H C14 C N H,
\ /
,14
N
n
H C
N
.H
amitrole
free radical
(e.g. , 0 K-)
N
ii
C N H
X
H
amitrole
free radical
o
H
adsorption
polymerization
urea
cyanamide
The free radical extracts a hydrogen, converting amitrole to a free radical
that can either adsorb to colloidal particles or polymerize. The amitrole
can also be oxidized by the free radical to form CC>2, urea and cyanamide as
primary products that would be readily utilized by soil microorganisms. C02,
urea and cyanamide have been identified as breakdown products in free radi-
cal systems (22).
There has been much debate over whether microorganisms or chemical re-
actions are primarily responsible for degradation (2). Evidence for chemical
lA
decomposition of amitrole stems from success in generating C02 from free
radical systems and the seemingly contradictory results obtained from soil
sterilization studies. As noted previously, sterilization by ethylene oxide
does not completely stop C<>2 evolution as does autoclaving. However, ethylene
oxide is not as damaging to free radical systems or extracellular enzymes as
is autoclaving. Involvement of such enzymes in amitrole degradation could
explain the effects of different methods of soil sterilization.
Efforts to isolate soil organisms that degrade amitrole have been, for
the most part, unsuccessful. Compacci, et al. (33) have isolated several
soil bacteria of the genera Pseudomonas, Bacillus, and Corynebacterium that
will degrade amitrole after a 3-week lag period and sufficient dilution.
Evidence that microorganisms can degrade amitrole in a laboratory setting is
not sufficient proof that microblal degradation occurs to any appreciable
extent in nature. Kaufman, et al. (26) propose that microbes per se are not
A-9
-------
responsible for amitrole degradation but are indirectly involved in enhancing
or providing the conditions that allow for chemical decomposition.
3.3 PERSISTENCE IN WATER
Amitrole persistence in water has not been studied extensively. Norris,
et al. (34) monitored amitrole residues in forest streams before and after
aerial application of 2 Ibs per acre to 260 acres of forest land. Amitrole
residues appeared within an hour of application, peaked in about 2 hours and
could not be detected by the third day. Norris (35) also studied the effects
of rainfall on amitrole concentration in streams flowing by or through
treated forest areas. The area was treated in late March and samples of
creek water were taken in late September and early October with average rain-
fall of 0.63 inches per day. No measurable amitrole residues were detected.
Demint, et al. (36) have determined that amitrole residues in treated irri-
gation canals are less than 1 ppb and hence, insufficient to damage sensitive
crops. (The canal banks had been treated with amitrole for weed control at
about 4 Ibs. per acre.)
A long-term study of amitrole degradation in water and sewage treatment
systems was carried out by Ludazck and Mandia (37). Using 94 percent pure
amitrole, they were unable to detect significant BOD, COD, or any measurable
degradation of amitrole in distilled water, sewage or river water. In res-
piration tests there was a stimulation of CO. production from biodegradable
material in river water but no decrease in the concentration of amitrole.
An inhibitory effect on respiration and nitrification in activated sludge
was observed in the presence of amitrole concentrations between 2.2 and 10
ppm. Disappearance of amitrole in water may be due mainly to dilution and
perhaps to a much lesser extent to adsorption to bottom sediment.
4.0 IMPACTS ON NON-TARGET ORGANISMS
4.1 PLANTS
Amitrole is phytotoxic to many agricultural plants including tomato
plants, cucumber seedlings, citrus and avocado trees, and wheat (20,29,31,
38).
A-10
-------
4.2 ANIMALS
The toxicity of amitrole to animal species has been reviewed by Maier-
Bode (39) and Pimental (40). In mallard ducks, the oral LD5Q was greater
than 2,000 mg/kg (41). The LC5Q for mallards, for pheasants and for Japanese
quail was greater than 5,000 ppm when these birds were given an amitrole-
containing diet for 5 days (42). The 48-hour LC5Q for salmon was estimated
to be 3,250 ppm (43). Bluegill, green sunfish, lake chub-sucker and small-
mouth bass fry have tolerated 50 ppm for 8 days (44).
Daphnia is very sensitive to amitrole with a 48-hour LC,-0 of 3 ppm (4).
The median immobilization concentration for amitrole to Daphnia magna is re-
ported to be 23 ppm (45). The EPA recommended safety measures, based on
Daphnia sensitivity, limit amitrole potable water concentrations to 0.15 to
0.015 ppm and irrigation water concentrations to 0.1 to 0.01 ppm, depending
on stream size (48).
When bees were dusted with amitrole at a dose of 12.09 yg/bee, mortality
was less than 5 percent (46). For comparison with field conditions, an
application rate of 1 kg/ha would give a dose of 1.12 Vg/bee. Therefore, at
recommended application rates, amitrole is considered relatively non-toxic
to bees.
The National Institute of Occupational Safety and Health, data on mamma-
lian toxicity is presented in Table 2. Amitrole has moderate to low acute
oral toxicity to mice and rats. However, it has been reported to be carci-
nogenic in both mice and rats. In addition, mutation studies using a host-
mediated assay test system in which mice were exposed to the test chemical
and SalmQnella tvphimurium was used as the indicator organism, indicate 12
mg/kg as the lowest dose reported to have a mutagenic effect (47).
4.3 MICROORGANISMS
Amitrole's effect on .icroorg.nl— has been studied by several inves-
tigators. Valentine and Bingham (49) cultured three genera of freshwater
algae one of which metabolized the amitrole. producing three cellular and
four extracellular breakdown products. Field.applications of amitrole at
recommended rates of 8, 4, 2. and 1 lb per acre have produced a depressed
of nitrification and decreased numbers of microorganisms (38). In
rate
A-ll
-------
TABLE 2. TOXICITY OF AMITROLE TO MAMMALS (47)
Organism
Toxicity
Comments
Rat
Rat
Mouse
Mouse
Mouse
Rat
Oral LD5Q: 1,100 rag/kg
Oral TDLQ: 122 g/kg
Oral LD5Q: 14,700 mg/kg
Oral TDLQ: 113 g/kg
Ipr LD5Q: 200 mg/kg
Oral TD: 3,670 mg/kg
Toxic effects reported;
carcinogenicity.
Toxic effects reported:
carcinogenicity.
Toxic effects reported:
neoplastic effects.
other studies, amitrole has been found to inhibit microbial respiration and
nitrification in activated sludge (37), nitrifying bacteria in soil (50) and
cellulose decomposition in fungi at concentrations of 500 ppm in buried soil
samples (51).
4.4 BIOACCUMULATION
No major concern has been reported regarding bioaccumulation of ami-
trole, probably because of amitrole's high solubility in water and insolubi-
lity in cellular lipids (6.48). Bioaccumulation of amitrole has not been
studied to any appreciable extent.
5.0 MISCELLANEOUS
The EPA Advisory Committee on amitrole has expressed concern over the
labelling of ammonium thiocyanate as an inert ingredient in commercial ami-
trole formulations (1). Ammonium thiocyanate has an acute oral LD for
rats that is very much lower than that for amitrole (760 mg/kg vs/LoO-llOO
mg/kg) (6). Ammonium thiocyanate is a reactive compound, a gbiterogen and
inhibits the metabolic breakdown at amitrole (1).
A-12
-------
REFERENCES
1. Meissner, W.A., et al. Report of the Amitrole Advisory Committee. EPA,
1971.
2. Carter, M.S. "Amitrole" in Kearney, P.C. and D.D. Kaufman, eds. Her-
bicides: Chemistryf Degradation and Mode of Action, 2nd Edition, Vol.
1, Marcel Dekker, Inc., New York. pp. 377-398, 1975.
3. Farm Chemicals Handbook. Meister Publishing Co., Willoughby, Ohio.
1979.
4. Newton, M. and J.A. Norgren. Silvicultural Chemicals and Protection of
Water Quality. EPA Report 910/9-77-036, 1977.
5. Witt, J.S. and D.M. Baumgartner. A Handbook of Pesticide Chemicals for
Forest Use. Forest Pesticide Shortcourse, Portland, Oregon, March 1980
(1979).
6. Mullison, W.R. Herbicide Handbook. 4th Edition, Weed Science Society
of America, pp. 18-20, 1979.
7. Newton, M. and C.A. Roberts. Brush Control Alternatives for Forest
Site Preparation, Oregon Weed Control Conference. Salem, Oregon, 1979.
8. Melnikov, N.N. Chemistry of Pesticides. In: Residue Reviews, Volume
36, Springer-Verlag, New York, 1971. pp. 428-432.
9. Bartels, P.G. and F.T. Wolf. Phvsiol. Plant. 18: 805, 1965. In Re-
ference 2,
10. Burns, E.R.. G.A. Buchanan, and M.C. Carter. Plant Physiol. 47; 144,
1971. In Reference 2.
11 Bondarenko. D.D. Absorption and Translocation of Amitrole in Corn and
Soybean Plants. Morth Central W^d Control Conference Proceedings,
1958.
12. Muzik, T.J. Effect of Temperature on the Activity and Persistence of.
Amitrole and 2,4-D, Weed Research, 5: 207-212, 1965.
13. Ashton, F.M. Fate of Amitrole in Soil. Weeds, 11: 167-170, 1963.
14. Massini, P. A.ta Bot. Neerl. 12:64,1963. In Reference 2.
15. Smith, L.W., D.E. Bayer, and C.L. Foy. WeecLJ^ 16: 523, 1969. In
Reference 2.
A-13
-------
16, Carter, M.C. Physio I. Plant. 18: 1054, 1965. In Reference 2.
17. Corbin, F.T., R.P. Upchurch, and F.L. Selman. Influence of pH on the
Phytotoxicity of Herbicides in Soil. Weed Science 19(3): 233-239, 1971.
18. Sund, K. 1956. Residual Activity of 3-amino-l,2,4-triazole in Soils.
J. Agr. Food Chem. 4(1): 57-60, 1956.
19. Norris, L.A. Chemical Brush Control: Assessing the Hazard, Journal
of Forestry, 69(10): 715-720, 1971.
20. Day, B.E., et al. The Decomposition of Amitrole in California Soils.
Weeds 9(3): 443-456, 1961.
21. Ercegovich, C.D. and D.E.H. Frear. 1965. The Fate of 3-amino-l,2,4-
triazole in Soils. J. Agric. Food Chem. 12(1): 26-29.
22. Plimmer, J.R., et al. Amitrole Decomposition by Free-Radical Generat-
ing Systems and by Soils. J. Agric. Food Chem. 15(6): 996-999, 1967.
23. Nearpass, B.C. Exchange Adsorption of 3-amino-l,2,4-triazole by an
Organic Soil. Soil Science Society of America Proceedings, 33: 524-528,
J. y o 7 •
24. Nearpass, D.C. 1971. Adsorption Interactions in Soils Between Amitrole
and^S-triazines. Soil Science Society of America Proceedings, 35:
25. Marston, R.B., et al. Pesticides in Water. Pesticides Monitoring
Journal, 2(3): 123-128, 1968.
26. Kaufman, D.D et al. Chemical Versus Microbial Decomposition of Ami-
trole in Soil. Weed Science, 16(2): 266-272, 1968.
-------
33. Campacci, E.F., et al. Isolation of Amitrole-degrading Bacteria,
Nature 266: 164-165, 1977.
34. Norris, L.A., et al. Stream Contamination With Amitrole From Forest
Spray Operations, Research Progress Report. 1967. Western Weed Control
Conference, 1967.
35. Norris, L.A. Stream Contamination by Herbicides After Fall Rains on
Forest Land, Research Progress Report, 1968, Western Society of Weed
Science, 1968.
36. Demint, R.J., et al. 1970. Amitrole Residues and Rate of Dissipation
in Irrigation Water. Weed Science, 18(4): 439-442.
37. Ludzack, F.J. and J.W. Mandia. Behavior of 3-amino-l,2,4-triazole in
Surface Water and Sewage Treatment. Purdue University Engr. Bull.,
Ext. Series No. 109. 1962.
38. Fletcher, W.W. The Effect of Herbicides on Soil Microorganisms. Black-
well Publishing Ltd., Great Britain, 1960.
39. Maier-Bode, H. Residues and Side Effects of Herbicides in Forest Pro-
tection. Anz. Schaedlingsk Pflanzen-Umeltschung, 46(2): 17-24, 1973.
40. Piaentel, D. Ecological Effects of Pesticides on Non-Target Species.
Executive Office of the President, Office of Science and Technology
Report, U.S. Government Printing Office, Washington, D.C. June 1971.
41. Tucker, R.R. and D.G. Crabtree. 1970. Handbook of Toxicity of Pesti-
cides to Wildlife. U.S. Department of Interior; Fish, Wildlife Service,
Bur. Sport Fish. Wildl., Resource Pub. No. 84.
42. Heath, R.G., J.W. Stann, E.F. Hill, and J.F. Kretjer. 1972. Compara-
tive Dietary Toxicities of Pesticide to Birds. Special Scientific
Report — Wildlife No. 152. Washington, D.C.
43. Bohmont, B.L. 1967. Toxicity of Herbicides to Livestock, Fish, Honey
Bees, and Wildlife. 20th Western Weed Control Conf. Proc. 21: 25-27.
44. Hiltibran, R.C. 1967. Effects of Some Herbicides on Fertilized Fish
Eggs and Fry. Trans. Am. Fish. Soc. 96: 414-416.
45. Crosby, D.G. and R.K. Tucker. Toxicity of Aquatic Herbicides to Daphnia
magna. Science 154: 289-291, 1966. In Reference 40.
46. Atkins, E.L., E.A. Greywood, and R.L. MacDonald. Toxicity of Pesticides
and Other Agricultural Chemicals to Honey Bees - Laboratory Studies.
U. of Calif., Division of Agricultural Sciences Leaflet 2287, 1975.
47. Lewis, R.J., Sr. and R.L. Tatken, eds. Registry of Toxic Effects of
Chemical Substances, 1979 Edition. U.S. Dept. of Health and Human
Services, Public Health Service, Center for Disease Control, National
Institute for Occupational Safety and Health. U.S. Government Printing
Office, Washington, D.C. 1980.
A-15
-------
A8. Newton, M. Herbicide and Insecticide Technical Properties and Herbi-
cide Use Guidelines, Oregon State University, 1979.
49. Valentine, J.P. and S.W. Bingham. Influence of Algae on Amitrole and
Atrazine Residues in Water, Can. J. Botany, 54: 2100-2107, 1976.
50. Chandra, P. Herbicidal Effects on Certain Soil Microbial Activities
in Some Brown Soils of Saskatchewan, Weed Research, 5: 54-63, 1964.
51. Grossbard, E. and G.I. Wingfield. 1978. Effects of Paraquat, Amino-
Triazole and Glyphosate on Cellulose Decomposition. Weed Research, 18:
347-353.
A-16
-------
Common Name: Atrazine
Chemical Name: 2-chloro-4-ethylamino-6-isopropylamino-s-triazine
Major Trade Names: AAtrex (SOW, 90W, 4L, ACL)
Major Applications Used primarily in the Pacific Northwest in conifer
in Forestry: release, nursery applications and seed orchards and
production areas for grass and broadleaf weed control.
SUMMARY
Most of the available information on the fate of atrazine in soil and
water is the result of laboratory and/or field studies with agricultural
systems. Very little data are available on or in connection with applica-
tions to forests.
Atrazine is considered a stable, persistent herbicide and may P«sist
in phytotoxic concentrations for over a year in agricultural soils. High
concentrations of soil organic matter, such as may be present in forest
soils, as well as low temperatures, tend to increase its persistence. Atra-
zine degrades via chemical and microbial routes; the extent of and factors
affecting such degradation in forest soils have not been fully investigaed.
The extent of atrazine losses due to volatilization from agricultural soils
is very small. Such losses are expected to be even less from fores soils
due to lower temperatures. Atrazine decomposes by uv light; the extent of
photodecomposition in forest systems is expected to be very low.
Atrazine is considered a low mobility herbicide. Leaching and desorp-
falls. Atrazine degrades to some extent in water.
organisms, and nil in animals.
Inert ingredients present in atrazine formulations are not considered
hazardous.
A-17
-------
1.0 INTRODUCTION
Atrazine is a selective herbicide that has been widely used in crop and
non-crop applications for broadleaf weed and grass control since its disco-
very, as one of a family of s-triazine herbicides, in the early 1950's (1).
It currently leads all other herbicides in the U.S. in volume of use (2).
In the forest industry, atrazine is used in conifer release, nursery
applications of fir transplants, and seed orchards and seed production areas
on Douglas-fir, Noble fir, western hemlock, lodgepole pine and Ponderosa
pine (3,4). These uses are primarily in the Pacific Northwest west of the
crest of the Cascade Range. Usual application rates for atrazine are 3-5 Ib
of 80 percent active ingredient (in 10-20 gallons of water) per acre for
conifer release; 2 Ib a.i./acre in nursery applications; and 2-4 Ib a.i./
acre (3) in seed orchards and production. AAtrex SOW is one of the princi-
pal wettable powder formulations used in all three applications (3). Appli-
cation methods for conifer release are typically the aerial broadcast method
or ground spot applications (3,4). Atrazine is sometimes used in combina-
tion with 2,4-D or Dalapon (3-5 Ib a.i./acre) for more effective control of
broadleaf weeds as well as grass for Douglas-fir release in Pacific North-
west forests (5). Atrazine has also been used to a limited extent in
forests in the southern U.S. in combination with simazine.
Agricultural uses of atrazine are extensive and include application to
corn, sorghum, sugarcane, pineapple and other crops (6). It is al8O used in
vegetation control in rangeland (6). After uptake by plant roots, atrazine
exerts its toxic action on plants by inhibiting photosynthesis with arresta-
t on of the Hill reaction in chloroplasts; atrazine also interferes with
Plant transpiration (7,8). Atrazine is manufactured domestically by Ciba-
Geigy Corp. under the trade name AAtrex, Shell, Farmland and Vicksburg
emica Companies (9). It is also manufactured by foreign producers under
the trade name Atranex (Israel) and Vectral SC (Great Britain) (10).
Atrazine formulations are 50-80 percent wettable powders in 5-lb multi-
walled bags and a 4-lb/gallon flowable concentrate available in 1- and 5-
gallon containers (2). The wettable powder formulations contain one or more
inert materials including: (a) carriers, such as calcium silicates, sodium
aluminum silicates, or precipitated silicic acid; (b) wetting agents, such
A-18
-------
as arylalkyl sulfonates; and (c) dispersing agents, such as lignin sulfonates.
Chalk or clay may also be added to some formulations (1) .
Atrazine is also formulated in combination with several other herbicides,
as (6):
• AAtram 20G (atrazine plus propachlor)
• Atratol 8P (atrazine plus sodium chlorate and sodium metaborate)
• Atratol SOW (atrazine plus prometon)
• Bicep 4.5L (atrazine plus metolachlor)
2.0 PHYSICAL/CHEMICAL PROPERTIES OF ACTIVE INGREDIENT
The chemical nomenclature for atrazine is:
2-chloro-4-ethylamino-6-isopropylamino-s-triazine
N N
C. C^ XCH
NH ' ^ |/ NH-CH
Vs" CH3
It is a white crystalline solid with a melting point of 173-175'C.
Solubility in water is 70 ppm (7, 11,12) j in roethanol, 18,000 ppm (11);
in ether, 12,000 ppm (11); and in chloroform, 52,000 ppm (11).
Vapor pressure data are shown below as a function of temperature (6):
Temperature. °C mm Hi
10
20
30
50
5.7 x
3.0 x
1.4 x
2.3 x
-8
10
io"7
io-6
10
3.0 ENVIRONMENTAL FATE
Based on the literature reviewed in this program, it appears that the
fate of atrazine in the forest environment has not been adequately addressed
Most of the fate information reported and discussed below pertains to non-
forest environments.
A-19
-------
3.1 UPTAKE AND METABOLISM IN PLANTS
Extensive studies have been conducted on the uptake of atrazine from
corn, sorghum, cereals, weeds and other plants. These studies, which have
been reviewed by Kearney (1), have focused on uptake of atrazine from nu-
trient solutions in laboratory experiments and in many cases actual field
conditions have not been adequately simulated. The studies indicate that
the principal mechanism of uptake is through the plant roots, although up-
take through leaves also occurs; root uptake occurred readily in all species
studied. Research using radiolabelled atrazine showed that it is evenly
distributed through the system into all aerial parts of the plants, with some
accumulation in the marginal zones of the leaves, particularly in susceptible
species. Root uptake increases with increasing concentration of atrazine,
time of exposure, higher temperature and lower relative humidity. Foliar
uptake occurs much less readily than root uptake, and is enhanced by addition
of adjuvants such as mineral oil (1). Atrazine exerts its toxic action on
plants by inhibiting photosynthesis, resulting in defoliation and plant death.
Metabolic degradation of atrazine in plants occurs via 4 major mecha-
nisms: (1) hydrolysis of the 2-chloro group to give hydroxy atrazine; (2)
conjugation with glutathione or amino acids at the 2-position of the triazine
ring; <3) N-dealkylation of side chain groups; and (4) s-triazine ring
cleavage (1,13,14). The degradation route and rate vary with plant types,
with stage of growth and with site of entry of atrazine into the plant.
In corn the major metabolite is the 2-hydroxyl hydrolysis product,
formed both in the roots and shoots (1,15). Cleavage of the triazine ring
occurs to only a minor extent in com (as well as in cotton and soybeans)
after 4 days as indicated in a recent study by Davis, et al. (16). However,
the ring cleavage is a difficult and relatively slow process and occurs after
longer periods of time (1). In range grasses, 175 to 270 days after treat-
ment with 16 lb a.i./acre, residues included hydroxyatrazine (<0.04 ppm) and
N-dealkylation products such as deethylated atrazine (0.72-1.15 ppm), de-
isopropylated atrazine (0.17-0.25 ppm), and 2-chloro-4,6-diamino-s-triazine
(0.5 ppm) (14). Residues in range grasses were not determined beyond 270
days.
In general, hydrolysis and conjugation with glutathione and amino acids
occur readily in monocotyledonous plants (i.e., sorghum, cordgrass) (14,17).
A-20
-------
N-dealkylation (deethylation or de-isopropylation) can either precede or
follow formation of hydroxyatrazine in these species (14). Hydrolysis and
conjugation of atrazine result in a complete loss of phytotoxic properties.
Plant species which hydrolyze and/or conjugate atrazine are most resistant
to the herbicide. N-dealkylation of atrazine results in only partial loss
of phytotoxicity, and species using this route of degradation have moderate
resistance to atrazine (1).
3.2 FATE'IN SOIL
The fate of atrazine in soil can be described in terms of six factors:
volatilization, photodecomposition, leaching, adsorption, runoff, and chemi-
cal and microbial degradation. These factors are discussed below.
3.2.1 Volatilization
The extent of atrazine volatilization from soil is not fully known.
Atrazine is known to dissipate from treated areas by volatilization but it
is generally held that this does not take place to a significant extent (2,
6), presumably due to the low vapor pressure of atrazine. Although quantita-
tive results are unavailable, atrazine losses by volatilization have been
measured and were observed to occur in the field most prevalently 1-2 days
after initial application, and occurred to the greatest extent under condi-
tions of high temperature and direct prolonged sunlight prior to rainfall
(6,18). .
Laboratory studies of atrazine on planchets at 25'C and 60«C by Foy
(19) showed significant losses of atrazine even at the lower temperature.
Kearney (1,20) extended this study to .measuring triazine losses from five
soils as a function of soil type. Although insufficient data were obtained
to permit definite conclusions on the relationship between rate of volati-
lization and soil properties, atrazine was observed "to volatilize from all
of the soils. Vapor losses of atrazine from a variety of other surfaces,
including sand, clay, metal and glass, have also been observed and measured
in the lab by Davis (16).
In addition to temperature, volatilization is also affected by soil
moisture, with increased volatilization from drier soils (21,20). In the
forest, the extent of atrazine volatilization from soil due to sunlight
exposure may be less than in the field due to increased shading. Also,
A-21
-------
because atrazine is somewhat amphoteric in nature, the pH of aqueous solu-
tions may be expected to influence its volatility; the extent of this in-
fluence has not been determined (11).
3.2.2 Photodecompos it ion
On the soil surface (and on the surface of vegetation) atrazine under-
goes photodecomposition due to the action of uv radiation in sunlight (22).
The rate of photodecomposition and factors influencing it are not fully un-
derstood (6). Available data indicate that photodecomposition occurs to
some extent in the field if high temperatures and prolonged sunlight follow
application before precipitation (6), but these conditions are not considered
typical of the forest environment. Studies conducted by Comes and Timmons
(23) on agricultural fields indicate losses of 47 percent and 60 percent
during exposure to spring sunlight for 25 and 60 days, respectively. Under
forest conditions the rates of atrazine decomposition on the soil surface
would be less than in the agricultural fields due to increased shading.
The mechanism and products of photodegradation in soil have not been
investigated. The decomposition of atrazine on other surfaces has been
studied in the laboratory. Atrazine exposure to UV light on aluminum plan-
chets at 42°C resulted in a change in the UV absorbance and a color change
from white to light tan (24); the degradation products were not identified.
One possible product is hydroxy atrazine, which is a known photodecomposition
product of atrazine under exposure to light of 253.7 nm in aqueous solution
\£3 ) •
3'2'3 Adsorption and Leaching
Atrazine is generally considered a low solubility, low mobility herbi-
cide (12,26,27). In the soil atr.zine i. readily and rev.r.ibly adsorbed
on soil particles (2,7). The extent of adsorption (and desorption) i. a
function of soil type as well as temperature, moisture, and pH (26.28).
Soil organic matter is the primary sou parameter responsible for adsorp-
tion with increasing organic matter resulting in increased adsorption (29).
in other studies it has been shown that atr.Un. 1. .lso more readily ad-
sorbed on clay soils than on soils with low clay content (6).
Adsorption of atrazine increase, with the lowering of the pK. parti-
cularly in clay soils, since atrazine i. somewhat ba.ic. and at higher PH
A-22
-------
levels it loses its affinity for negatively charged clay particles (14).
High levels of soil moisture facilitate hydrolysis of atrazine adsorbed to
clay soils, and indirectly decrease the amount available for desorption (14).
The extent of adsorption is also higher at lower temperatures.
Adsorption capacity of a given soil type for atrazine affects the po-
tential for leaching of atrazine from soil. The leaching tendency would be
lower with those soil types and under those conditions which promote adsorp-
tion. In general, leaching is more pronounced in sandy and clay soils than
in soils with high organic matter content (30). In agricultural soils with
high organic matter content, atrazine is not normally found below the upper
foot of soil in detectable quantities, even after years of continuous use
(26,27). In a study by Burnside (31), leaching of atrazine in Nebraska soils
was determined to be greater in coarse-textured, low organic matter soil in
western Nebraska even though the rainfall in this region was considerably
less than in regions with high organic content soils (32). Even in sand the
depths to which atrazine penetrates via leaching are not significant. When
atrazine was surface-applied to Plainfield sand at rates of 1, 2, and A lb/
acre and leached, most remained in the first inch of soil when 2, 4, and 8
inches of water were used (27). Some atrazine moved downward to a depth of
6 inches; with application of additional water more atrazine was leached
from the first inch of soil. Even after prolonged leaching, atrazine is not
expected to penetrate the soil to any significant depth. Smith, et al. (33)
observed that atrazine applied to irrigation ditches at a rate of 22.4 kg/ha
did not leach to depths greater than 90 cm after 3 years. Marriage, et al.
(34) found that residues of atrazine applied at a rate of 4.5 kg/ha for 9
consecutive years to the same plots of a peach orchard located on a sandy
loam soil near Harrow, Ontario, were confined to the upper 15 cm of the soil
profile and that the majority of the herbicide remained in the 0-5 cm soil
layer. The maximum residue level found was 0.4 kg/ha of atrazine in the top
15 cm of the soil profile.
Even though leaching of atrazine fro» the forest soil has.not been
studied, based on the data presented above, the extent of such leaching
would be expected to be lo.er than that in agriculture! soil because of the
higher organic content of the forest soil.
A-23
-------
3.2.4 Runoff
Although atrazine is slightly soluble in water, a potential exists for
buildup in high concentrations in local waterways due to runoff after heavy
rainfall (2). This is particularly true if rainfall occurs soon (1-2 weeks)
after application.
In a field study, Leonard, et al. (35) determined the amount of atrazine
in runoff (water plus sediments) from sandy loam soils at a Piedmont water-
shed in Georgia as a function of application rate (1.45 to 4.03 kg/ha) and
time after application (up to 60 days). During the experiment an average
rainfall of 30 cm was observed. The results indicated a nearly exponential
decrease in atrazine concentration with time. The total quantity of atrazine
measured in the runoff ranged from 0.2 to 0.8 percent of the original atra-
zine applied. In a field study by Triplett (36) on 0.4- to 3.5-ha watersheds,
the highest concentrations of atrazine (0.48 ppm) were present in runoff
occurring soon after application and declined rapidly in later events. The
quantity of atrazine transported increased with the amount of rainfall and
was inversely related to the length of time between the application and the
runoff event. A maximum of 6 percent of the applied herbicide was trans-
ported from the field even under the most favorable conditions, and the
average for all watersheds was less than 2 percent.
A summary of other atrazine runoff studies is presented in Table 1.
The results indicate that atrazine runoff is a function of the amount, fre-
quency, and intensity of runoff events.
Based on atrazine runoff data and data on runoff with other pesticides,
Leonard, et al. (35) developed the following empirical relationship (for the
Georgia Piedmont soil tested) which correlates the concentration of herbicide
in runoff (y, mg/1) with the concentration of residual herbicide in the soil
at the time of runoff (x, mg/g): y - 0.05 x1/2. This empirical relationship
has not been tested against other soil types or other concentration ranges.
3.2.5 Chemical and Microbial Degradation
Atrazine is considered to be a stable, persistent compound. The per-
sistence of atrazine in soil was reviewed by Sheets (41) who concluded it is
very persistent, and that residues can persist in agricultural soils at phy-
totoxic levels for over one year. More recent studies by Best, et al. (42),
A-24
-------
TABLE 1. SUMMARY OF SELECTED ATRAZINE RUNOFF STUDIES
Location/Soil Type
Application
Rate
Time Span
Rainfall
Results and Comments Reference
tv>
Ui
Fallow plots of Cecil
soil (6.5% slope)
Field plots of
Hagerstown silty
clay loam growing
corn
Field plots of
Hagerstown silty
clay loam growing
corn and alfalfa
16.4 ha corn field
3 Ibs/acre
0, 0,6,
1.1, 2,2,
4.5, 6.7,
and 9.0
kg/ha
2.2 and
4.5 kg/ha
1.7 kg/ha
96 hrs after
herbicide
application
One growing
season
(1967)
1971 and
1972 growing
seasons
1976 growing
season
10 year frequency
storm (2.5 in/hr)
Rainfall expe-
rienced at Penn-
sylvania test
site in 1967
Rainfall expe-
rienced at Penn-
sylvania test
site in 1971 and
1972
Rainfall expe-
rienced at site
in 1976
Atrazine loss of 7.3% 37
observed.
Average losses for all 38
rates in 1967 in runoff
water and soil sediment
equalled 2.4% and 0.16%
of the total applied,
respectively.
Total losses of atrazine 39
during first growing
season were 5,0 and 4.8%
of application rate; 87
to 93% of the losses
occurred within the first
month following applica-
tion.
First storm event occur- 40
red 11 days after appli-
cation and discharged
55% of the total runoff
loss of the 1976 growing
season and 90% of the
total runoff loss occur-
ring within 2 months of
planting.
-------
Ritter, et al. (43), and Buchanon and Hiltbald (44) have indicated that atra-
zlne rarely persists at phytotoxic levels longer than 1-2 years. The resi-
dual activity of atrazine in soil for many specific soil types is such that
most rotational crops can be planted one year after application, except in
an arid or semi-arid climate. However, broadcast rates needed in heavier,
relatively higher organic matter soils of the North Central states result in
enough residue carryover, under some conditions, to injure small grains,
alfalfa and soybeans planted 12 months later (6,45).
The persistence of atrazine in a soil has been the subject of a large
number of studies, the results of some of which are summarized in Table 2.
These studies show that the persistence is greater in soils with lower or-
ganic content, at greater depths and at lower temperatures.
The atrazine degradation in soil occurs via chemical and/or microbial
routes. In a study of atrazine persistence, Hunter, et al. (50) found atra-
zine residue at phytotoxic levels in desert soil eight years after applica-
tion. The desert soil was characterized by high pH, low moisture, and
extreme surface temperatures - conditions which do not favor chemical and
microbial degradation of atrazine. A brief review of the factors affecting
chemical and microbial degradation of atrazine in soil follows.
Chemical Degradation
Hydrolysis is the major chemical degradation reaction of atrazine in
soil. The reaction is first order and involves hydroxylation of the carbon-
chlorine bond to give hydroxy atrazine (51,52). The activation energy of
the hydrolysis reaction is 10.8 kcal/mole, which corresponds to the energy
required to break the C-C1 bond (22). The rate of hydrolysis is pH depen-
dent and the reaction is both acid and base catalyzed. The following half-
lives have been measured for atrazine hydrolysis as a function of PH (53):
£l Half-life (days')
1-3 5.1
2.2 18.4
3-1 66.4
11-1 81.1
11-9 15.2
12.9 12.9
A-26
-------
TABLE 2. SUMMARY OF SELECTED ATRAZINE PERSISTENCE STUDIES
location/Soil
Typo
IT sit<:s ir. ^i.e U.S..
«~.clut*ing central
Kaphington, Alabama,
Maryland and Minnesota
Eoidin-jton barn field
r.oil (1.*%C, 16» clay,
ilx silt, 73* sand.
Fi: ~.4), and Triangle
S'iolM .'oil (•JiC, 16*.
clay. 16' silt, 68*
SAr.d, rll S.4> . 801
water holding capacity
Sandy icar. soils in;
Colorado
Montana
Nevada
Idaho
Sharpsburg silty
clay loan
K»» soil
Irrigation ditch
soil in Tyron. .
"c-r»skat Valentine
loany fine soil
Alabama
Application
Rate
K.A.
5«*l/9
2 Ib ai/acre
4 Ib ai/acre
1.2.4 Ib ai/
acre
1.2 Ib ai/
acre
2.4 Ib ai/
' acre
1.2 and 2.4
Ib ai/acre
9.6 Ib ai/
acre
0.5-2 ppn
2-20 Ib ai/
acre
2.5 Ib/acre
10 Ib/acre
30 Ib/acre
30 lb/acr«
"
Soil Depths
Measured
3.9 and 15
inches
.A.
0-6 in.
6-12 in.
C-12 in.
0-6 In.
6-12 in.
0-6 in.
6-12 in.
0-6 in.
6-12 in.
0-6 in.
6-12.
0-6 in.
6-12 In.
15,40 and
90 cm
0-1 in.
1-2 in.
2-4 in.
.4-6 in.
6-6 in.
6-18 in.
6-12 in.
1-18 in.
18-36 in.
"
Tine Span
"amples placed at
beginning o. growing
season: retrieved in
fall
Soils were incubated
at 22CC for 3-4 weeks
283 days
Results and forwent
Between <1 ar.ci SR- of the original atrazine
lower depths and was more pcrrxstent in the
northern U.S. (average recoveries showed
61* more at 15-in. level than at 3-in. level)
First order degradation r.ite was used to
describe the results; in Boddington barn soil
the rate was faster at high pll levels but
the reverse occurred on Triar.qle soils, pro-
bably due to increased chemical hydrolysis on
the higher organic content triangle soil
0.09 ppm
283 days 1 0.05 ppn
283 days I 0.5 ppn
130; 320 days I All shoved 0.05 ppn
130i320 days 1
365 days 0.07 ppn
3GS days I 0.05 ppm
365 days 0.25 ppm
365 days 0.15 ppm
365 days 1 0.005 ppm for all
365 days
365 days 1 0.1O ppn
365 days 1 0.05 ppn
0-41 mos. 1 Phytotoxic acids of atrazine dissipated dur-
1 ing tlie first 5 mos. at 15 cm, and during
1 the first 17 mos. at 40 cm. Atrazine resi-
1 dues remained at 90 en depth after 41 mos.
One growing 1 After rainfall of 8.16 in., 85.3% of atraclne
season 1 was in the- 0-1 in. layer; 5.7V in the 1-2 in.
1 layer. After one year the results were the
1 same.
73 days 1 No atrazine detected
319-366 days 1 No atrazine detected
0.05 ppn 1 Persisted one year after application
73 days 1 No appreciable atrazine detected
I Half-Ufa vas measured at 30 days.
Rrforen're
46.1
47
14
32
48
t
18
49
-------
Based on the half-lives data, the average values of the rate constants for
-5 -1 -9
acid and alkaline hydrolysis have been calculated as 3.4 x 10 M sec
and 6.5 x 10~5 M*1 sec"1, respectively (53).
Studies on sterilized soil systems indicate that hydrolysis may be cata-
lyzed by certain soil compounds, Nucleophilic compounds in soil including
Fe/Al ions promote nucleophilic displacement of -Cl with -OH at high pH,
whereas humic acid and various soil colloidal particles catalyze hydrolysis
at low pH. The low pH hydrolysis results from the protonation of ring or
chain nitrogen atoms and subsequent cleavage of the C-C1 bond (54). In gen-
eral, increasing organic matter in soil increases degradation by chemical
hydrolysis (1).
Several studies have been conducted on the formation and stability of
nitrosoatrazines in soils. Results indicate that nitrosoatrazine is not
formed in amounts that are significant at normal rates of field application
of atrazine (2 ppm in the surface 7.5 cm of soil or 2 Ib/acre application
rate), and in the presence of 100 ppm NH^ (14,55). In the presence of
100 ppm NaN02 (as N), nitrosoatrazine formed and increased in concentration
with decreasing pK « of atrazine converted to nitrosoatrazine as a function
of pH were: PH5, 0%; PH4, 0.7%; PH3, 19.3%; pH2, 35.7%) (14,55).
Microbial Degradation
Microbial degradation accounts for the decomposition of a significant
portion of atrazine in soil (6). Factors influencing microbial growth in-
clude soil moisture, temperature, pH, soil type and presence of nutrients,
but very few studies have been performed measuring the effect of these factors
on microbial degradation of atrazine. Three major routes for biological de-
gradation are dealkylation, ring cleavage and hydroxylation of the 2-chloro
group. Dealkylation is the primary mechanism of microbial degradation.
Kaufman and Blake (56) observed atrazine degradation by dealkylation by 12
different fungi in a basal salts medium supplemented with sucrose; some of
the fungi (i.e., Rhizopus stolonifar^ removed the isopropyl group to give 2-
chloro-4-ethylamino-6-amino-s-triazine) while others (i.e., Aspergillus fumi-
£atus) removed the ethyl group to give 2-chloro-4-anino-6-isopropylaIDino-s-
triazine. In a two-week study using chain-labelled atrazine, Skipper, et al.
(57) found ethylamino C in carbon dioxide involved by Aspergillus fumigatus.
A-28
-------
Atrazine degradation by ring cleavage was studied "by Roeth, et al. (58)
14
and McCormick and Hiltbold (59) who observed the evolution of C09 from
14
microbial cultures containing C ring-labelled atrazine. The atrazlne hy-
drolysis product hydroxy atrazine was also observed to undergo ring cleavage.
Skipper, et al. (57) found that mixed microbial populations degraded the hy-
droxy atrazine ring three times more rapidly than it degraded atrazine. Ring
metabolism of hydroxy atrazine was also found in a study with both aerobic
and anaerobic lake sediment samples by Hance and Chesters (60) using ring-
labelled hydroxy atrazine, More labelled carbon dioxide was evolved from
aerobic than anaerobic sediment samples; however, the reverse was true for
soil samples. Microbial degradation of atrazine by hydrolysis to hydroxy
atrazine is known to occur by one microbial species, Fusarlum roseum (22).
Both dealkylated and hydroxylated atrazine degradation products are
subject to further microbial degradation (1). Recent studies have shown that
degradation of both types of products nay give rise to common metabolites,
such as 2-hydroxy-4-araino-6-alkylamino-s-triazine (1,61).
3.3 PERSISTENCE IN WATER
Very limited studies have been conducted on the persistence and degra-
dation of atrazine in water. Klaasen (62) studied the distribution and decay
of atrazine applied to pond water in various components of a pond ecosystem.
The study was carried out in farm ponds near Manhattan, Kansas to which atra-
zine was added to establish an initial concentration in water of 0.3 ppm.
Atrazine levels were monitored in various pond ecosystem components (water,
mud, fish, etc.). Soon after application residues were found st high levels
(165-353 ppb) in all components except tadpoles. Residues decreased slightly
during the growing season, but were still present at fairly high levels at
the end of the growing season. The results of one set of experiments carried
out in 1973 are shown in Table 3. As Indicated In the tables, a rate of de-
cay of 0.676 ± 0.367 ppb/day was calculated for the water.
In an atraaine water monitoring ptogra. conducted in 1975 In seven
major rivers in the central U.S. (i.e., the corn belt), a maximum of 16.7
ppb of atrazine was detected. The peak residues occurred during the months
of heaviest application (i.e., Way-June); residue concentrations declined
after June to <1 ppb for the rest of the year (14).
A-2 9
-------
TABLE 3. ATRAZINE RESIDUES (PPB) AND RATE OF DECAY IN PONDS
TREATED WITH 0.3 PPM ATRAZINE (62)
Sample Type
Surface water
Mud from
shallow area
Mud from deep
area
Zoop lank ton
Clam
Bullfrog tadpole
Small bluegill
Medium bluegill
Large bluegill
Days after Treatment
0
NOT
ND
ND
ND
__*
ND
ND
ND
ND
1
309
323
316
240
—
ND
280
270
290
22
230
314
305
277
—
—
289
237
245
55
237
302
221
213
250
—
307
290
260
120
206
284
204
195
—
—
216
230
211
Slope
std.
.676
.323
1.001
.535
.568
.333
.555
and
dev.
+ .367
+ .022
+ .322
+ .304
+ .358
+ .359
+ .2.14
R2
.63
.99
.83
.61
.56
...17
.77
ND
Not detectable (less than 0.4 ppb)
—= Samples could not be obtained
The rate of atrazine photodecomposition ia water is extremely slow, as
measured under laboratory conditions, and is not expected to be significant
in the environment. This is primarily due to its lack of absorption of sun-
light. Laboratory photolysis of atrazine in water and other hydrolytic sol-
vents (e.g., methanol) at 253.7 nm was shown to result in the formation of
the 2-hydroxy compound, due to nucleophilic displacement of the chlorine
atom (53). In a related study, Jordan, et al. (24) observed that the uv
spectrum of an atrazine solution was altered after irradiation with 253.7 nm
light or with sunlight (292 to 400 nm).
4.0 IMPACTS ON NON-TARGET PLANTS AND. ORGANISMS
4.1 PLANTS
Atrazine has been shown to be phytotoxic to non-target forest species
under certain application conditions. In one study by Kozlowski (27),
atrazine applied in nursery culture as a soil spray at rates of 1, 2, and 4
Ib a.i./acre was extremely toxic to young, recently-emerged (5-week old)
red and white pine seedlings. No harmful effects were reported on older
A-30
-------
seedlings. Atrazine combined with dalapon (3-5 Ib a.i./acre) and used for
conifer release from grass in southwestern Oregon resulted in complete de-
foliation of well-established Ponderosa pines 8 to 15 feet tall (5). The
severity of the damage was believed due to a synergistic effect of atrazine
with dalapon.
Atrazine also exhibits phytotoxicity to a number of nontarget agricul-
tural crops including soybeans, alfalfa, and small grains. It may persist
at phytotoxic levels in agricultural soils for 1-2 years and may cause in-
jury to susceptible species planted in the growing season following applica-
tion (6). However, applications of 3.2, 6.4, 12.8, and 25.6 Ib/acre of
atrazine repeated annually to plots of Emperor variety grapes in Davis, Ca-
lifornia, gave no evidence of adverse effects (63).
Several studies have been conducted on the phytotoxicity to nontarget
organisms of atrazine degradation products. The results indicate that hy-
droxy atrazine is non-phytotoxic. The ability of a plant to hydrolyze atra-
zine is a partial basis for its resistance to the herbicide. K-dealkylation
products are moderately phytotoxic. This was confirmed in a recent study
by Kaufman and Blake using oat seedlings (56). Hydroxy atrazine was shown
to be non-phytotoxic to oat seedlings at 1 and 5 ppm concentrations. The
N-dealkylation products 2-chloro-4-amino-6-isopropylamino-s-triazine and
2-chloro-4-ethylamino-6-amino-s-triazine were phytotoxic to oat seedlings;
the former compound at both 1 and 5 ppm, and the latter compound at 5 ppm.
Recent investigations have shown that the protein content of various
crops may increase when sublethal concentrations of triazine herbicides are
applied. In a study by Singh, et al. (64), foliar application of 0.5 or 1.0
rag/1 atrazine (applied until runoff occurred) increased the protein content
in pods of bush beans and leaves of spinach under field and/or growth room
conditions. Results of quantitative analyses indicated that the soluble
amino acid content was also higher in the treated test species. In addition,'
the Fe content in the bush bean seeds and the Fe, Kg, P and K contents in
spinach leaves were higher in the treated plants than in the controls (64).
In studies conducted on MSMA and cacodylic acid, it has been shown that the
presence of atrazine facilitates uptake of arsenic in green plants (1).
A-31
-------
4.2 FISH AND OTHER AQUATIC ORGANISMS
Atrazine is slightly toxic to most species of, fish and moderately toxic
to lower aquatic organisms (2). Toxicological investigations conducted on
goldfish and bluegill sunfisb have shown atrazine to have very low toxlcity
toward these species (48-hour LC5Q of 118 mg/1 for bluegills) (6,12), How-
ever, atrazine is considerably more toxic to rainbow trout (LC »4,5 mg/1).
Data an the toxicity of atrazine to various lower aquatic organisms were
obtained in a study by Butler (65) in 1965, the results of which are shown
in Table 4. As indicated in the table, shrimp are more sensitive to atra-
zine than fish or oysters and experience 30% mortality at 1.0 ppm atrazine
in 48-hour exposures.
In acute and chronic aquatic toxicity studies by Walker (66) , atrazine
applied to fish ponds at rates of 0.2 to 6.0 ppmw was shovn to be somewhat
toxic to bottom fauna. Among the most sensitive organisms were mayflies
(Ephemeroptera), caddis flies (Tricoptera) .' leeches (Hirudinea) , and gas-
tropods (Musculium). The most significant reduction in bottom fauna occurred
during the period immediately following application. The bottom fauna
appeared to recover four to six months after treatment. Walker (67,68) also
found that an application of 0.5-2.0 ppm of atrazine to pond enclosures re-
duced clams to iy8 of their original numbers, whereas the «*il population
increased by nearly 4 times. Portmann, et al. (69) found LC ' . for the
shore crab (Cascinus maenus) and the cockle (Cardium edul^ to be greater
than 100 ppm, 'while the brown shrimp LC5Q was 10-30 ppm.
Vivier and Nisbet (70) experimented with atrazine in A361(l) and in
GasaPri*e (II) and found that for I, 0.5 ppm was lethal in 72 hours for 20%
of the population of the min»ov Ph^i^s ohox,ntie while ^ ^^ ^ ^
1.25 ppm. The 24-hour and 48-hour ^ values for II were 3.7S and 2.5%p..
respectively. Jones (71) found at least 90% survival for 72 hour exposures,
PP-0 letaluuun (10.0
.
and Lepomis macrochlrus (10.0 ppm). No effect levels at concentrations of
10 ppm were found for Erimvzon sucetta (eggs) , Lepomus macr^-,,... (eggs),
and L. cyanellus after eight to ten day exposures (72). Email-mouth bass
died after 3 days exposure at 10 ppm.
A-32
-------
TABLE 4. TOXICITY OF ATRAZINE TO ESTUARINE ORGANISMS (65)
Oysters
96-hr EC5Q
ppm (mg/1)
no effect at 1.0
Shrimp
48-hr EC50f
ppm (mg/1)
30% at 1.0
Fish§
48-hr LC^*
ppm (mg/1)
no effect at 1.0
Phytoplankton
Percent decrease
at 1.0 ppm
*
Concentration of herbicide in sea water causing a 50% decrease in oyster
shell growth.
Concentration of herbicide in sea water causing mortality or paralysis to
50% of adult shrimp tested.
'Concentration of herbicide in sea water causing 50% mortality to juvenile
fish.
§
Spotfish, Leisetomus Xanthurus.
In field experiments in Kansas, six experimental 1/10 acre ponds were
exposed to 0, 20, and 150 yg/1 of atrazine for 135 days (14). The ponds
contained natural aquatic communities and controlled stocks of fish. Atra-
zine application resulted in an almost immediate decline in rates of photo-
synthesis by aquatic algae. The decline in photosynthesis rate was followed
by increased growth of resistant plant species within a few weeks, resulting
in significant alterations in the plant community during the course of the
study (14). Other results of the study are summarized in Table 5. As indi-
cated in the table, atrazine also reduced the photosynthesis of algae at 20
ug/1 concentration level (14).
Very little data are available on the degradation products of atrazine
in fish or in lower aquatic organisms. In one study on the metabolism of
atrazine in box crabs, various water-soluble metabolites from glutathione
conjugation of atrazine were observed (17).
4.3 WILDLIFE
Atrazine has low toxicity to warm-blooded animals. The acute oral
LD for rats is 3,800 mg/kg and for mice, 1,750 mg/kg (6). Little data are
available in the literature on toxicities of atrazine to birds and wildlife
A-33
-------
TABLE 5. EFFECTS OF ATRAZINE (20 AND 500 yg/liter)
ON POND ECOSYSTEM (14)
A. Water Quality and Algae
• Physical-chemical condition*: not directly affected.
• Oxygen and pH: indirectly lowered for 28 days due Co effects on algal photo-
synthesis.
• Algal photosynthesis: within 2 days - in 500 ug ponds, declined by 96% ---
in 20 ug ponds, declined by 342.
• Algal photosynthesis: in 500 pg ponds, averaged 502 lower than controls —
in 20 ug ponds, similar to controls.
• Algal biomass: within 7 days in 500 ug ponds, declined by 502 --- in 20 ug
ponds, similar to controls.
• Algal biomass: in 500 ug ponds, averaged similar to controls after 15 days.
• Algal composition: affected throughout the 135 days at both atrazine levels.
• Resistant algal species: increasingly dominant in ponds at both atrazine
levels; first noticeable after 15 days.
• Resistant algal communities: in 500 ug ponds by day 56, 7X more resistant
(photosynthesis) than control pond communities to another 500 ug.
• Resistant algal communities: in 20 ug ponds by day 85, no increased photo-
synthesis resistance but 2X more resistant to light energy blockage.
• Persistence of atrazine in the ponds: 75% of the original concentrations on
day 116.
• Persistence of effects of this remaining atrazine demonstrated by exposing
control pond algae to atrazine pond water on day 98.
B. Other Aquatic Organisms
• Aquatic flowering plant (Najas): reduced in biomass by day 15 by 1002 with
500 ug and by 402 with 20 ug.
• ZoopUnkton reproduction rates (Slmocephalus, Daphnia): reduced by 572 and
702 with 500 ug and 92 and 702 with 20 Ug.
reduced by d«y 15 by *><>«* atrazine levels up to 602
* levels1*"" C0mpositlon: a"ected throughout 135 days by both atrazine
. Zooplankton responses: indirect from the effects of .trazlne of algae,
their food source.
• Bottom-dwelling Invertebrates (Fingernail clam, isopod, damselfly): no
mortality response.
* 2OTh3o10^Vf™Zard 8^d> ^hannCl cat£ish. bluegill .unfish): reduced by
202-302 with 500 ug and unaffected with 200 ug.
• Fish mortality: unaffected by atrazine.
bluesl11 Bunfl«h. reduced by 962 at both atrazine
A-3A
-------
species (i.e., deer, beaver, rabbits, etc.). However, a toxicological in-
vestigation conducted on bobwhite quail, pheasants, and mallard ducks showed
atrazine to have very low toxicity to these species; the LD__ values for
mallard ducks were >5,000 ppm; for pheasants, were >5,000 ppm; and for bob-
white quail, were 700 to 800 ppm of atrazine fed for five days, followed by
three days of untreated feed (6,73). Studies conducted on cattle, dogs,
horses fed a diet of 25 ppm atrazine or more over extended periods of time
resulted in no observable ill effects (6).
In subacute toxicity studies (74), administration of daily dosages of
100 ppm of an 80% wettable powder formulation of atrazine to cows for 21
days, or feeding 30 ppm of this formulation in grain to cattle for four
weeks resulted in no observable effects. In acute oral toxicity studies by
Palmer and Radeleff (75), the toxic dosage of atrazine for cattle was found
to be 25 mg/kg after 8 doses by drench and 2 doses by capsule. The toxic
dosage for sheep was 5 mg/kg, although one sheep received 199 consecutive
doses at 50 mg/kg before it was poisoned and died. Chickens administered
10 doses at 50 mg/kg had significant reductions in weight gains (75),
Innes, et el. (76) found no significant indication of tumorigenicity
in rats fed 21.5 mg/kg atrazine at 7-28 days of age and then 82 ppm after
28 days of age. Rats fed 100 and 1000 ppm for two years showed no differen-
ces from controls (77). The administration of atrazine at a level of 46.4
mg/kg to C3H, C57, and AKR mice produced no significant increase in anoma-
lies in offspring (78). Peters and Cook (79) determined that atrazine was
not embryotoxic except when administered at extremely high levels (800 and
2000 mg/kg) to the rat. In addition, atrazine did not affect the number of
pups per litter or weaning weight at levels as high as 1,000 ppm. Innes,
et al. (80) found that oral administration of 83 ppm of atrazine to certain
strains of mice did not cause a significant Increase in tumors.
4.4 BENEFICIAL INSECTS
Limited studies on atrazine have shown no insecticidal activity (6).
The synergistic effects of atrazine with insecticides on bees were studied
by the U.S. Department of Agriculture (81). Bees were fed insecticides and
insecticides fortified with atrazine or other herbicides at dosages which
determined sublethal in preliminary experiments. In no case was the
were
A-35
-------
mortality significantly greater feeding the bees herbicide-insecticide com-
bination than feeding the insecticide alone at the same concentrations.
4.5 MICROFLORA
Atrazine is nontoxic to soil microorganisms (2). A number of studies
conducted in recent years have shown varying results as to the impact of
atrazine on soil microbial populations (82). Atrazine was shown to be a
growth stimulant to microflora in a recent study by Percich (82). Increases
in populations of actinomycetes, bacteria and fungi were observed in Conover
loam soil treated with atrazine at rates of 10, 30, and 100 rag/g; the in-
creases were also sustained for 2-3 months. The results confirmed investiga-
tions performed in the Soviet Union (83,84,85). Increases in populations of
Fusarium, which led to increased root diseases in plants, have also been
observed in atrazine-treated soils (82).
Comparative studies performed by Voets, et al. (86) showed that atra-
zine applied at a rate of 4 kg/ha in an orchard of dwarf apple trees reduced
the populations of anaerobic bacteria, sporeformers, cellulolytic micro-
organisms and nitrifying, amylolytic and denitrifying microbial groups. A
metabolic study has indicated no adverse effects on earthworms.
4.6 BIOACCUMULATION
The bioaccumulation of atrazine in fish, snails, and algae is "low"
(see Table 6); in microorganisms, "moderate"; and in animals, "nil". (7,55).
In a study of atrazine residues in 7 major rivers and tributaries in the
Midwest in 1975, the maximum residues in fish were estimated at 0.5 ppm for
a maximum residue concentration in the waters of 16.7 ppb. For a near-normal
1.0 ppb level in water, the concentration in fish was estimated at 0.02 ppm
(14).
Bioaccumulation of atrazine in microorganisms was demonstrated in a
recent laboratory study of 18 species of actinomycetes and fungi in water,
nutrient broth and loam soil containing 5 ng/ml (mg/g for soil) of atrazine
(82). Among the species studied, there was a large variation in the ability
to accumulate atrazine. Less accumulation occurred in soil than in water,
due to restricted contact of the organisms with the atrazine in soil compared
to the liquid media. The accumulation of atrazine in actinomycetes, fungi
A-36
-------
TABLE 6. CONCENTRATIONS AND BIOACCUMULATION RATIOS (BR) OF
ATRAZINE IN FISH, SNAILS AND ALGAE *t (55)
Species
Fish
Snails
Algae
Day
9
18
18
18
ppb
197
186
98
105
BR
17
16
8
9
Determined in a model aquatic ecosystem. Bottom soil was ini-
tially treated with 0.82 ppm atrazine.
BR ratios agree with those reported by Isensee.
and other organisms growing in soils with high levels of atrazine would
suggest that in the enviornment such accumulation may serve as a vehicle
for the entry of atrazine into certain food chains (55). However, as dis-
cussed below, bioaccumulation in higher forms of life is unlikely due to
metabolic breakdown of atrazine.
Atrazine is metabolized readily by animals and is considered non-bio-
accumulable (7). Very little intact, unmetabolized atrazine is excreted in
either the urine or feces of animals. Feeding goats and cows with I mg/kg
atrazine resulted in transient milk residues which reached a maximum con-
centration between 8 and 24 hours after feeding, then declined rapidly to
the limit of detection within 2 to 4 days (1). The metabolic degradation
products of atrazine in animals include hydroxy atrazine, N-dealkylation
products (i.e., 2-hydroxy-4-amino-6-ethylamino-atrazine and 4,6-diamino-
atrazine), side-chain modified atrazine (i.e., via <* oxidation of the iso-
propyl group'to a carboxylic acid), and glutathione conjugation products
(28 1 88,2016). Hydroxy atrazine and N-dealkylation products are rapidly
excreted in the urine with no bioaccumulation (1). Moreover, these compounds
are nontoxic to mammals, with LD50's of greater than 5000 mg/kg. The glu-
tathione conjugation product rapidly degrades to the corresponding mercap-
turic acid which subsequently undergoes mercapturic acid biosynthesis in a
A-37
-------
path recognized as a general means of detoxification and excretion of
numerous foreign compounds in mammals (89), in birds (90) and in insects
(91).
5.0 MISCELLANEOUS
As indicated in Section 1,0, commercial wettable power formulations of
atrazine contain up to 80% active ingredient and 20% "inerts". None of the
inert materials (see Section 1.0) are expected to be very toxic or hazardous.
A-38
-------
REFERENCES
1, Kearney, P. E. and D. D. Kaufman. Degradation of Herbicides. Vols. 1
and 2. Marcel Dekker, Inc., New York. 1975. 1058 pp.
2. Von Rumker, 0., E.W. Lawless, and A.F. Meiners. Production, Distribu-
tion, Use and Environmental Impact Potential of Selected Pesticides.
EPA 540/1-74-001. U.S. EPA, Office of Pesticide Programs, Washington,
D.C., 1975, pp. 211-217.
3. Pesticide Uses in Forestry. National Forest Products Association,
Forest Chemicals Program, Washington, D.C., 1980. pp. 3, 62, 97.
4, Weyerhaeuser Trip Data; Vegetation Problems, Control Methods for Con-
ifer Release. Weyerhaeuser Company, Tacorna, WA, 1979, 4 pp.
5. Gratkowski, H. Silvicultural Use of Herbicides in Pacific Northwest
Forests. Technical Report No. PNW-37, USDA Forest Service, Pacific
Northwest Forest and Range Experiment Station, Portland, Oregon, 1975.
45 pp.
6. Mullison, W.R. Herbicide Handbook of the Weed Science Society of
America. Weed Science Society of America, Champaign, Illinois, 4th
Edition, 1979. 518 pp.
7 Witt J.S. and D.M. Baumgartner. A Handbook of Pesticide Chemicals
for Forest Use. Forest Pesticide Shortcourse. Washington State Uni-
versity and Oregon State University, 1979. pp. 9-10.
8. Audus, L.J. (ed.). The Physiology and Biochemistry of Herbicides.
Bedford College, London, England, 1964.
9. Information provided to TRW by Ciba-Geigy Corporation, November 18,
1980.
10. 1980 Farm Chemicals Handbook. Meister Publishing Co., Wiloughby, Ohio,
p. D-25.
11 Fox C.L. Volatility and Tracer Studies with Alkylamino-S-Triazines.
Weeds, 12: 103-108, 1964.
10 «.*.„* M and J A Norgren. Silvicultural Chemicals and Protection
12' oi Twa^r Quality.' EPA-910/9-77-036. U.S. EPA, Region X, Seattle,
Washington, June 1977, 240 pp.
J.T. and D.E. David. Metabolic Fate of Atrazine in the
Journal of
Quality, 8(3): 335-338, 1979.
A-39
-------
14. Information provided by EPA, based on review of Ecological Effects
Branch registration files.
15. Hilton, H.W. Pesticides and Food Additives in Sugarcane and Sugar
Products. Sugar Planters Association Exp. Station, Honolulu, HA.
16. Davis, D.E., J.V. Gramlich, and H.R. Funderburk. Weeds, 13: 252, 1965.
In Reference 1.
17. Pillai, P., et al. Atrazine Metabolism in Box Crabs. Journal of En-
vironmental Quality, 8(3): 277-280, 1979..
18. Hammons, R.H. Atrazine Persistence in Valentine Loamy Fine Sand Pro-
file. NTIS PB-291-497. M.S. Thesis, University of Nebraska, Lincoln,
Nebraska. 1977. 55 pp.
19. Foy, C.L. Weeds, 12: 103, 1964. ln Reference 1.
20. Kearney, P.C., T.J. Sheets, and J.W. Smith. Volatility of Seven S-
Triazines. Weeds, 12: 83-87, 1964.
pBNoQ7 ln Groundwater a*d Mobility of Herbicides.
PB No. 239-242. University of Nebraska, Lincoln, Nebraska. 1974.
77 pp.
sSi^JJ'Jl ^'L' Le?iS* Chemical and Mi«obial Degradation of Ten
Selected Pesticides on Aquatic Systems. Residue Reviews, 45: 95-124,
so - Effect °f SunllS*t on the Phytotoxicity
- IT 196? T%af TriaZo?e Herbicid« ^ a Soil Surface. Weeds,
. ei, iy&5. In Reference 22.
' fer«« l!8" J'D' Mann> Md B'E- Dajr' Weeds- »' «• "65. In Re-
- «*
27
s
and Food Chemistry, 12(4): 324-331,
A-40
-------
29. Goring, C.A.I. Physical Aspects of Soil in Relation to the Action of
Soil Fungicides. Ann. Review Phytopathol, 5: 285, 1967. In: Residue
Reviews, "32: 175-210. 1970.
30. Rodgers, E.G. Leaching Characteristics of Four S-Triazine Compounds.
7 pp. (supplied by P. Kearney).
31. Burnside, O.C,, C.R. Fenster, and G.A. Wicks. Dissipation and Leaching
of Monuron, Simazine and Atrazine in Nebraska Soils. Weeds, 11: 209-
213, 1963. In Reference 32.
32. Lavy, T.L., F.W. Roeth, and C.R. Fenster. Degradation of 2,4-D and
Atrazine at Three Soil Depths in the Field. J. Environmental Quality,
2: 132-137, 1963.
33. Smith, A.E., et al. Persistence and Movement of Atrazine, Bromacil,
Monuron and Simazine in Intermittently Filled Irrigation Ditches.
Canadian Journal of Plant Science, 55: 809-816, 1975.
34. Marriage, P.B., et al. Residues of Atrazine, Simazine, Linuron and
Duiron After Repeated Annual Applications in a Peach Orchard. Weed
Research 15: 377-379, 1975.
35. Leonard, R.A. , G.W. Langdale, and W.G. Fleming. Herbicide Runoff From
Upland Piedmont Watershed - Data and Implications for Modelling Pesti-
cide Transport. Journal of Environmental Quality, 8(2): 223-229, 1979.
36. Triplett, G.B., et al. Transport of Atrazine and Simazine in Runoff
From Conventional and No-Tillage Corn. J. Environ. Quality 7(1): 77,
1978.
37. White, A. P., et al. Atrazine Losses From Fallow ^Caused by Runoff
and Erosion. Environmental Science and Technology, 1(9): 740-744, 1967.
38. Hall, J.K., et al. Losses of Atrazine in Runoff Water and Soil Sediment.
J. Environ. Quality, 1(2): 172, 1972.
39. Hall, J.K. Erosional Losses of S-triazine Herbicides. J. Environ.
Quality 3(2): 174, 1974.
40. Wu/T.L. The Distribution of Atrazine in Corn Field Soils at Various
Elevations. Proc. NEWSS, Vol. 33, p. 121, January 1979.
41 Sheets, T.J. Persistence of Triazine Herbicides in Soils. Residue
Reviews, 32: 287-310, 1970.
Reference 50.
Atrazine, Propachlor, and Diazinon Residues on
A-41
-------
44. Buchanon, G.A. and H.E. Hlltbold. Performance and Persistence of
Atrazine. Weed Science, 21: 412-416, 1973. In Reference 50.
45. Vegetation Management With Herbicides: Final Environmental Statement.
Forest Service - USDA, Pacific Northwest Region, 1978.
46. Harris, C.I., E.A. Woolson, and B.E. Hummer. Dissipation of Herbicides
at Three Soil Depths. Weed Science, 17: 27, 1969. In Residue Reviews,
32: 391-399, 1970, •
47. Hance, R.J. Effect of pH on the Degradation of Atrazine, Dichlorprop,
Linuron and Propyzamide in Soil. Pesticide Science, 10; 83-86, 1979.
48. Birk, L.A. and F.E.B. Roadhouse. Penetration of and Persistence in
Soil of the Herbicide Atrazine. Canadian Journal of Plant Science,
44: 21-27, 1962.
49. Hiltbold, A.E. Leaching and Inactivation of Atrazine and Diuron in
the Field. Amer. Soc. Agron. Abstr., p. 90, 1967. In: Residue Reviews,
32: 175-210, 1970.
50. Hunter, R. , A. Wallace, and E.M. Romney. Persistent Atrazine Toxicity
in Mohave Desert Shrub Cotnmunities. Journal of Range Management, 31(3):
199-203, 1978.
51. Zlmdahl, R.L., et al. Weed Research, 10: 18, 1970. In Reference 53.
52. Armstrong, D.E., G. Chesters, and R.F. Harris. Soil Scl. Soc. Amer.
Proc. 31: 61, 1967. In Reference 53.
53. Wolfe, N.L., et al. Chemical and Photochemical Transformation of
Selected Pesticides in Aquatic Systems. EPA-600/3-76-067, U.S. EPA,
Environmental Research Laboratory, Athens, Georgia, 1976, pp. 125-128.
54. Khan, S.V. Kinetics of Hydrolysis of Atrazine in Aqueous Fulvic Acid
Solution. Pesticide Science, 9: 39-43, 1978.
55' Kra!;n«?' P'C*' et al* Distribution, Movement, Persistence and Metabolism
of N-Nitrosoatrazine in Soils: A Model Aquatic Ecosystem. J. Agricul-
tural Food Chemistry, 25(5): 177-181, 1977.
56. Kaufman D.D and J. Blake. Degradation of Atrazine by Soil Fungi.
Soil Biol. Biochem. , 2: 73-80, 1970.
57. Skipper H.D., R. Freeh, and V.V. Volk. Ph.D. Thesis, Oregon State
University, Corvallis, Oregon, 1970. In Reference 1.
58. Roeth F W T.L Lavy, and O.C. Burnside. Atrazine Degradation in Two
Soil Profiles. Weed Science, 17: 202, 1969. In Reference 22.
anrn ' Hil^old' MlcrobUl Decomposition of Atrazine
and Diuron in Soil. Weeds, 14: 77, 1966. In Reference 22.
A-42
-------
60, Hance, R.J. and G. Chesters. The Fate of Hydroxyatrazine in a Soil and
a Lake Sediment. Soil Biochemistry, 1: 309, 1969. In Reference 22.
61. Ramsteiner, K.A., W. Hormann, and D. Eberle. Z. Pflanzenkrankhelten
Sonderheft, 6: 43, 1972. In Reference 1.
62. Klaassen, H.E. and A.M. Kadoum. Distribution and Retention of Atrazine
and Carbofuran in Farm Pond Ecosystems. Archives Environ. Contamin.
Toxicology, 8: 34-353, 1979,
63. Leonard, P.A. and L.A. Lider. Response of Grapes to Several Years'
Application of Soil Applied Herbicides. Abstract of Meeting of Weeds
Society of America, February 1969, p, 51.
64. Singh, B., et al. Effects of Foliar Application of S-Triazines on
Protein, Amino Acids, Carbohydrates, and Mineral Composition of Pea and
Sweet Corn Seeds, Bush Bean Pods, and Spinach Leaves. J. Agr. Food
Chem. 20(6): 1256. 1972.
65. Butler, P.A. Effects of Herbicides on Estuarine Fauna. Presented at
13th Annual Meeting of Southern Weed Conference, January 19-21, 1965.
Dallas, Texas, 6 pp.
66. Walker, C.R. Simazine and Other S-Triazine Compounds as Aquatic
Herbicides in Fish Habitats. Weeds 12(2): 134-9, 1964. In Reference
92.
67. Information provided by EPA, based on review of Environmental Fate
Branch registration files and summaries supplied by OPTS.
68. Walker, C.R. Toxicological Effects of Herbicides on the Fish Environ-
ment? Ann. Air Water Poll. Conf. (November 12, 1962, Columbia, Missouri),
Proc. 8: 17-34, 1962. Summarized in Reference 67.
69. Portmann, J.E. and K.W. Wilson. The Toxicity of 140 Substances to the
Brown S^imp and Other Marine Animals. Ministry Agr Fish Food Fish
Lab., Burnham-on-Crouch, Essex, England, Shelff. Infor. Leafl. 22,
12 p., 1971. Summarized in Reference 67.
70 Vivier P. and M. Nisbet. Toxicity of Some Herbicides, Insecticides,
/U. Viviet, r. »"~ T_ n.1^1 A,,4«n1 PrnKlomS in Water
and Industrial Wastes, p. lo/—ID?.
Pollution. Third Sen., 19oZ. U.S>i
1965. Summarized in Reference 67.
,,
711
R n Tolerance of the Fry of Common Warm-water Fishes to Some
-
73. Heath,
Diet
Spec
F T Hill and J.F. Kreitzer. Comparative
, E.F. Hill, *™'
A-43
-------
74. Anon. 1971a. AAtrex Herbicide Technical Bulletin. Geigy Agricultural
Chemicals. GAG 700-564. 8 p. In Reference 92,
75. Palmer, J.S. and R.D. Radeleff. The Toxicity of Some Organic Herbicides
to Cattle, Sheep, and Chickens. USDA A.K.S. Production Research Report
No. 106. 26 pp. In Reference 92.
76. Innes, J.R.M., B.M. Ulland, et al. Bioassay of Pesticides and Indus-
trial Chemicals for Tumorigenicity in Mice: A Preliminary Note. J.
Nat. Cancer Inst. 42(6): 1101-1114, 1969. Summarized in Reference 67.
77. Spencer, E.Y. Guide to the Chemicals Used in Crop Protection. Research
Branch Agriculture Canada. 1973. 542 p. Summarized in Reference 67.
78. Report of the Secretary's Commission on Pesticides and Their Relation-
ship to Environmental Health, U.S. Dept. of Health, Education and Wel-
fare, December 1969. In: Information supplied to TRW by Ciba Geigy
on June 15, 1979.
79. Peters, J.W. and R.M. Cook. Effects of Atrazine on Reproduction in
Rats. Bulletin of Environmental Contamination and Toxicology, 9(5):
jUJ. • Ly 73 •
80. Innes, J.R., et al. Bioassay of Pesticides and Industrial Chemicals
for Tumorigenicity in Mice: A Preliminary Note. J. National Cancer
Institute 42: 1101-1114. 1969.
81. Sonnet P E. Toxicity of Pesticide Combinations and Pesticide Meta-
bolic Products to Honey Bees. USDA-ARS Bee District Laboratory,
Laramie, WY, May 1979. Abstract.
82. Percich, J A. and J.L. Lockwood. Interaction of Atrazine with Soil
SCMrrg^ f S; *?Pula*ion Chan8es and Accumulation. Canadian Journal
of Microbiology, 24: 1145-1152, 1978.
83. Kozloya, E.I., A.A. Belousova, and V.S. Vandar'era. Effect of
2 2nr277neiQfi7th%I3eri0pment of SOU Mic«or8anisffis, Agrobiologiya,
/. 271-277, 1967. In Reference 82.
G;r*elak' Effect of Atrazine and Simazine on the
13 22 1966 % ? C°nt^1 ±n F°reSt Nurs«i*s. Sylvan, 110(11):
13-22, 1966. (Soils Fert., 32: 387, 1966). In Reference 82.
crofE;J* r?,P;TD- Pashcbenko- Th. Effect of Herbicides on
Aerie Sel n6 ??t i«9der^iZe* ?r°C- VI Conf' Chemicalization
Agric., 1965. p. 179-182. (Weed Abstr. 16: 184 , 1967) . In Reference
Ma™* Microbiol°8i**l and Biochemical Effects of
149!l52 W?" Appllcatiorts- Soil Biology and Biochemistry .6(1) :
A-44
-------
87. Chio, H. and J.R. Sanborn. The Metabolism of Atrazine, Chlorumben, and
Dicamba in Earthworms (Lumbricus terrestris) From Treated and Untreated
Plots. Weed Science 26(4): 331. 1978.
88. Khan, S.U. and T.S. Foster. Residues of Atrazine (2-chloro-4-ethylamino-
6-isopropylamino-s-triazine) and Its Metabolites in Chicken Tissues.
J. Agric. Food Chem. 24(4); 768. 1976.
89. Boyland, E. and L.F. Chasseaud. The Role of Glutathione and Glutathione
s-Transferaces in Mercapturic Acid Biosynthesis. Advances in Enzymolo-
gy, 32: 173-219, 1969. In Reference 17.
90. Wit, J.G. and P. Leeuwaugh. Mercapturic Acid Formation and Enzyme-
Catalyzed Conjugation with Glutathione in Pigeons. Biochem. Biophys.
Acta, 177: 239, 1969. In Reference 17.
91. Cohen, A.J., J.N. Smith, and H. Turbert, Comparative Detoxification.
Biochem. Journal, 90: 457, 1964.
92. USDA Final Environmental Statement on GY'73 Herbicide Use on Vegetation
Management on the Coleville, Kaniksu, Okanogan, Wenatchu, and Umatella
National Forests, Washington. Appendix E. Pacific Northwest Region,
USDA, Forest Service, Portland, Oregon, May 1973.
93. Sanborn, J.R., et al. The Degradation of Selected Pesticides in Soil:
A Review of the Published Literature. Municipal Environmental Research
Laboratory, Concinnati, OH. PB-272 353/4WP, August 1977. 635 pp.
A-45
-------
Common Name: Dalapon
Chemical Name: 2,2-dichloropropionic acid
Major Trade Names: DOWPON, DOWPON M, DOWPON C, Radapon
Major Applications Site preparation, grass control in seed orchards and
in Forestry: seed production areas, release, and vegetation control
in established plantations.
SUMMARY
The fate of dalapon in the environment and its potential effect on non-
target plants and animals have been the subject of extensive studies. These
studies indicate a relatively short environmental persistence and very low-
order toxicity to aquatic and terrestrial organisms for dalapon.
•^K, ?bsorbed via Plant foliage and roots and is apparently not
metabolized by plants to any appreciable extent. Residues on plant surfaces
decrease very rapidly following application. Microbial degradation is the
tion ratf L K 8 t?S* t0 the dissiPation °* ^pon from soil. Degrada-
" l Variable an»o<* ^he soils studied and has ranged
from com.1
™ 8 SiX r^T "^ ** UsS than 2 weeks to two-thirds retention
decomposition is more rapid at warm temperatures, in the
'
,
u of itsM %moisT! and at a slightly less than nu"al ?» Be-
to anv LirL?flM T " solubility« dalaP°n is not adsorbed to soil particles
tteacttonon /8aln8t annual and Perennial grasses and
Crops su^ceptibL to~d^get C!nifer8 &" 6XpeCted in forestry applications
be exp" ef rom possib e'drifHu: T **?< ' T' ^ n° Cr°P d™*** W°Uld
application rates of 5 ll T aPPHcations in forest areas. At
"
of dalapon are ™c expected to ha^e
A-46
-------
reproduction. The LC5Q for dalapon for 12 species of fresh water fish
tested is greater than 100 ppm, thus indicating low order toxicity to fish.
Dalapon at 50 ppm level has been shown to cause no mortality to fish eggs
and fry for several fish species tested. Consistent with its high water
solubility, dalapon does not present potential for bioaccumulation in ani-
mals. In laboratory tests, residues in the tissues of mammals and birds fed
100 to 1000 ppm dalapon in their diet over periods of weeks, months or years
remained below 100 ppm during treatment and soon fell to below one ppm when
removed from exposure to dalapon.
Dalapon has essentially no effect on aerobic or anaerobic organisms in
soil at dosages approximating commercial usage recommendations. A number of
genera and species of algae, fungi, and bacteria tolerate high dosages of
dalapon and are capable of decomposing it.
A-47
-------
1.0 INTRODUCTION
Dalapon is a moderately selective herbicide for grasses. It was first
introduced in 1953 by the Dow Chemical Company and has since gained exten-
sive use for grass control in a wide range of applications including agri-
culture, industry, right-of-way, and forestry (1,2). In forest applications
(primarily in the Northwest), dalapon is used for control of annual and pe-
rennial grasses for site preparation, seed orchard and seed production areas,
release, and vegetation control in established plantings (2). Despite its
general potential uses, dalapon is applied less extensively than other her-
bicides in forestry. The Dow Chemical Company estimates that, in 1979,
dalapon was applied to A,167 acres or about 0.013 percent of the total
forest acres (3).
Dalapon is formulated as the sodium and magnesium salts (4). DOWPON M,
a mixture containing 72.5 percent sodium salt and 12.0 percent magnesium salt
of dalapon, is the major dalapon formulation and appears to be the only form-
ulation used in forestry applications (2,4). Recommended application rates
in forest uses range from 3 to 15 Ibs of DOWPON M per acre. Depending on
the specific target species and whether broadleaf weeds are also to be con-
trolled, dalapon may be applied along with atrazine, Esteron-99 (2,4-D)f or
a surfactant (2,5). Dalapon is applied either by ground or aerial spray
\£,j) i
Data on the amount of dalapon used is very limited. The amount of
dalapon used in Forest Service Regions 5 and 6 and by the Bureau of Land Ma-
nagement in Oregon in the past several years are given in Tables 1, 2, and 3.
TABLE 1.
DALAPON USE IN FOREST SERVICE REGION 5 (5)
Year
1976
1976
1977
1978
1979
1979
1979
:..
Pounds
Applied
25
6252
56
1267
3800
2912
42
—^~^^™^^~«*"^^^^™
•^™""» •— — •
Acres
Treated
— •—
2
744
414
344
997
391
8
Purpose
plantation weed control
site preparation
conifer release
perennial grass control
conifer release
'site preparation
grass control
A-48
-------
TABLE 2. DALAPON USE IN FOREST SERVICE REGION 6 (5)
Year
1975
1975
1976
1976
1977
1977
1978
1978
1979
1979
1979
Pounds
Applied
637
850
1
169
942
60*
40
138
2208
32*
12
Acres
Treated
745
93
0.5
30
230
15
5.25
262
1220
4
3
Purpose
timber management
seed orchard
release
site preparation
site preparation
release
site preparation
release
site preparation
site preparation
release
Dalapon +• atrazine applied.
TABLE 3. DALAPON USE BY THE BLM IN OREGON (5)
Year
1978
1979
1979
1979
1979
Pounds
Applied
none
1750
1000
2160*
9+
Acres
Treated
none
804
200
540
145/60 ml.
Purpose
site preparation
site preparation
site preparation
site preparation
road maintenance
Dalapon + atrazine applied.
f2 Ib dalapon + 7 Ib 2,4-D applied.
Dalapon appears to cause leaf chlorosis and abnormal growth responses
typical of growth regulators. It also displays pronounced contact toxiclty
(6).
2.0 PHYSICAL AND CHEMICAL PROPERTIES
The active ingredient in dalapon is 2,2-dichloropropionic acid
H c - I - " - OH, which is a colorless, odorless liquid with a boiling
A Cl
A-49
-------
point of 185 to 190°C. It is reported to be "very soluble" in water, alkali
solvents and ethanol, and "soluble" in ether (1).
DOWPON M, the formulation of dalapon used in forestry, is a mixture of
sodium (72.5 percent) and magnesium (12.0 percent) salts of dalapon. It is
an off-white powder which is very soluble in water and most organic solvents.
The solubility in water containing 100 ppm hardness is 110 g/100 ml at 22°C
(1).
The sodium salt of dalapon has been shown to hydrolyze slowly in water
to produce pyruvic acid, and the rate of hydrolysis increased with increasing
temperature. After 175 hours, the extent of hydrolysis at 25°C for 1 percent,
5 percent and 18 percent dalapon solutions were 0.41 percent, 0.61 percent,
and 0.8 percent, respectively (7).
3,0 ENVIRONMENTAL FATE
3.1 UPTAKE AND METABOLISM BY PLANTS AND RESIDUES ON PLANT FOLIAGE
Nearly all studies of uptake and metabolism of dalapon by plants have
been in connection with crop production, These studies indicate that dalapon
can be absorbed by either the roots or foliage. Once absorbed it is trans-
located throughout the plant. Based on tests with corn, soybean, sugarbeets,
barley, sorghum and wheat (6,8), accumulation appears to be greatest in
regions of high metabolic activity (e.g., vegetative buds and fruiting areas).
Dalapon does not appear to be metabolized by plants within about 2 weeks
following uptake, and whether it is metabolized at all is not clear.
Blanchard, et al. (8) used 2- C dalapon sodium salt to measure the
distribution of dalapon in corn and soybean plants. Soybeans were treated
by root application in nutrient solution containing 32 ppm of dalapon for
four days and by foliar application and held for three days post-application.
Corn was treated by root application in a nutrient solution of 2.5 ppm of
dalapon for 11 days. Dalapon tended to concentrate in the young tissues as
shown by autoradiograms. Extracts of treated plant tissues showed only a
single spot
-------
Long-term studies are less clear on whether dalapon Is metabolized.
14
Nine to ten weeks after treatment with 2- C dalapon (through severed pe-
tioles), approximately 85-90 percent of the radioactivity was recoverable
14
as dalapon (9). Some dalapon may be slowly degraded and the C incorporated
metabolically into the plant constituents. Smith and Dyer (10), however,
attributed the presence of non-extractable radioactive residues in cotton to
occlusion or trapping of chemically unaltered dalapon. Quantitatively, it
accounted for only a very small percentage of the applied chemical.
The fate of dalapon in plants was also evaluated by Foy (11) who em-
ployed dalapon 2- C and Cl for tracer and metabolic studies in cotton,
corn, and wheat. Dalapon was absorbed, translocated, and accumulated in
plants principally as the intact molecule or its dissociable salt, and re-
mained unchanged for long periods, especially in dormant or quiescent tissues.
O £
Slow metabolic decomposition resulted in some release of Cl or incorpora-
tion of 14C into other compounds indicating eventual breakdown, possibly an
initial dehalogenation followed by normal or modified propionate oxidation.
Slowness of metabolism or the stability of dalapon may also be indicated by
the presence of "dalapon stimulus" in the third generation of seeds after
exposure of the first generation of wheat to pre-plant applications of four
pounds of dalapon per acre in the field (11). This was detected by typical
plant formative effects of dalapon but not by chemical analysis.
Considerable data have been published on residue of crops and grass
following treatment with dalapon. These data indicate a rapid decrease in
residue following application. The amount of residue is generally related
directly to the application rate, is affected by field conditions, and is a
function of plant surface area-to-weight ratio. Plant parts with the largest
ratio such as foliage have the highest residues. Thus, it would be expected
that residues on seeds, stems, fruits, etc., would be lower than for foliage
with the same dosage application (4).
Scholl (12) reported that dalapon residues in seedling alfalfa and
birdsfoot trefoil decreased rapidly and appeared to be insignificant eight
veeks following treatment. This conclusion was supported by Kenaga (4) who
presented a review of the literature and the results of plant residue studies
conducted by the Dow Chemical Company. .Fertig and Schreiber (13) reported
that "early residue studies" on forage legumes, alfalfa, and birdsfoot
A-51
-------
trefoil showed a maximum of approximately 300 ppm of dalapon following use
of a spring application of ten pounds of dalapon per acre to these crops.
Getzendaner (14) reported analyses of dalapon residues at intervals of zero,
one, two, four, six, and eight weeks after application of eight pounds per
acre of DOWPON M (8 Ib/A, equals 6 Ibs of dalapon per acre). Average resi-
dues of the active ingredient, dalapon, per one Ib of the commercial formu-
lation, DOWPON, per acre after the above time intervals were 135, 28 25
21, 6, and 4 ppm, respectively. The average residues of dalapon per one Ib
of the active ingredient, dalapon per acre, after the same time inter-
vals were 182, 38, 34, 28, 8, and 5 ppm, respectively.
3.2 FATE IN SOIL
Microbial degradation is by far the most important process affecting
the fate of dalapon in soil, other processes which are of lesser importance
are adsorption, leaching and runoff, chemical degradation and volatilization.
Based on the light absorption characteristics of aqueous solutions of sodium
salts of dalapon, it has been concluded that photodecomposition of dalapon
in field applications is improbable (15).
3.2.1 Microbial Degradation
The microbial population in soil is capable of degrading dalapon. The
rate . degradation appears to vary with soil type and environmental condi-
„
rates ranged fro* compete disappearance in less than 2 wee! 'to Itl! 0°'
retention of the added dalapon after 8 wee*. The capacity of the so 1 o
decompose dalapon was essentially random with respect to soil serie. tex
ture^ation-exchange capacity, total organic matter, and geographical
The persistence of dalapon in soil appears to be related to the appli-
cation rate, temperature, moisture content. pR and aoil organic conten ' At
low application rates, phytotoxic concentrations of dalapon have be™ hown
A-52
-------
to disappear from soil within 2-4 weeks (17,18,19). At high rates of appli-
cation, dalapon can persist for several months (18). Southwick (20) reported
that, under greenhouse conditions with heavily watered soil, the toxicity
of 40 Ib/A of dalapon persisted for 8 to 12 weeks. Brown (21) reported that
40 Ib/A of dalapon applied in June was still toxic to alfalfa and sweet
clover one year later under field conditions. Wingfield, et al. (22) studied
the effect of temperature on dalapon disappearance from soil and reported
that dalapon disappearance was more rapid at room temperature (19 ± 2°C)
than at 2 to 10°C. At 19 ± 2°C, 50 percent of dalapon applied at a rate of
40 kg/ha to the surface of an undisturbed column of undisturbed sandy loam
disappeared in about 11 days. Laboratory studies by Theigs (23) indicated
that dalapon decomposition was most rapid in warm, moist soil but was very
slow in moist soil at 40"F and dry soil at 100°F. Jensen (24) observed that
dalapon was decomposed only feebly at pH-levels below 5. Kaufman (25) found
with five soils in greenhouse and laboratory studies that dalapon degrada-
tion by effective microorganisms was affected by organic matter level, pH,
cation-exchange capacity, and aeration. Corbin and Upchurch (26) reported
that dalapon was almost 100 percent detoxified within a two-week incubation
period when high-organic-matter soils were buffered to pH 6.5. Soils buffer-
ed to pH 6.5 provided optimum conditions for microbial adaptation and herbi-
cide degradation. Inactivation rate was slower at pH 7.5 and 5.3 and nega-
tive detoxication occurred at pH 4.3. Dalapon phytotoxlcity in high organic
soils increased as pH decreased and reached a maximum at pH 4.3; a change
of one pH unit decreased the phytotoxicity (27).
The biological nature of dalapon degradation in soil has been well
established. Thiegs (23) compared the rates of degradation of dalapon in
autoclaved and non-autoclaved soils. The concentration of dalapon (59 PPm)
in the autoclaved soil did not change after incubation at 100'F for one week
while in the unsterilized soil, dalapon disappeared in four to five weeks
after one application and in one week after the second application of 50 ppm.
Based on the observations that dalapon decomposition is adversely affected
by low soil moisture, low PH, temperatures below 20'-25«C, and large addi-
tions of organic matter, Holstun and Loomis (28) concluded that it was a
function of microbiological activity.
A-53
-------
A wide range of microorganisms are effective in degrading dalapon.
Hirsch and Alexander (29) isolated and characterized strains of Pseudomonas
and five strains of Nocardia which decomposed dalapon, liberating 90-100
percent of the halogen within three weeks. Other workers have reported
additional species of bacteria, fungi, and actinomycetes that have decom-
posed chlorinated aliphatic acids. For example, Magee and Colmer (30) re-
ported Agrobacterium. Thiegs (31) reported FUvobacterium. and Jensen (32,
33) added ?enicillium. Trichoderma. Clonostachys. and Arthrobacter.
Kaufman (34) found that the microbiological degradation of dalapon was
inhibited in the presence of amitrole. Phytotoxic residues of the herbicide
persisted longer in the soils when the herbicides were applied in combina-
tion than when each was used individually.
3.2.2 Adsorption. Leaching and Runoff
Laboratory studies have indicated that dalapon adsorption to soil par-
ticles is very limited. This, which is consistent with the high solubility
of dalapon in water, suggests that dalapon is potentially a highly mobile
compound. The much more limited mobility observed in field studies appears
to be due to microbial degradation proceeding faster than leaching,
Newman and Downing (35) measured the adsorption of herbicide by ascer-
taining the amount of compound required to cause 90 percent inhibition of
crabgrass growth in silica sand, a fin. sandy soll, . sllt ^ & ^ ^
and an old muck. Adsorption was considered to result in Motivation and,
hence, unavailability of the active ingredient to exert its phytotoxic effect.
There was little adsorption of dalapon by any of the soils. (For other
herbicides which were strongly adsorbed, 24 to 90 times as much was required
to cause 90 percent inhibition in old muck as in silica sand.)
Holstun and Loo*is (28) used soil columns to investigate the leachabili-
y of da apon. Preli^ experlments foun
-------
of the maximum dalapon concentration, but did increase the quantity retained
in the upper 2 inches of the soil. Smith, et al. (36) studied the leaching
of dalapon- C at the dosage of one Ib/A through an 8.5 inch deep soil column
of Kawkawlin sandy loam. Nine acre-inches of water applied at one-half inch
increments for wetting accounted for the leaching of 99. A percent of the
dalapon in the effluent from the soil column.
Dalapon adsorption and mobility in soil have been compared with a
number of other pesticides. Warren (37) compared the leachability of dalapon
sodium salt (applied at 8 Ib/A) in four soil types with that of several other
herbicides. Dalapon and trichloroacetic acid (TCA) were the only herbicides
to move readily in all soils tested. Bioassays on crabgrass were used to
measure activity. Helling (38) classified AO pesticides into 5 groups based
on relative mobilities on silty clay loam plates, using soil thin layer
chromatography based on R, values. Only four compounds were classified in
the group of greatest mobility (least adsorption): TCA, dicamba, amiben,
and dalapon. Such materials are among the most likely to leach through or
run off soil among the 40 pesticides tested (4).
Even though the laboratory studies indicate that dalapon is a highly
mobile compound and should be readily leachable from soils, field data show
that under many practical conditions dalapon does not move beyond the first
six-inch depth of soil. This is probably because microbial action proceeds
at a faster rate than leaching under favorable conditions (A). Kenaga (A)
reviewed the literature on dalapon and noted that many of the laboratory
studies (including those mentioned above) have often used "exaggerated"
conditions of rainfall or soil permeability. Miller and Getzendaner (39)
analyzed field soil" samples taken from various locations in the United States
representing different climates, rainfall, soil types, and soil depths.
Samples were taken at intervals of several days to one year after applica-
tion of DOWPON M or DOWPON grass killers at rates of A to Al Ibs/A. No
residues of dalapon were found in the zero-to-six inch layer of soil from
any treatment after AO days. In a Wayside, Mississippi soil treatment using
10 Ibs of DOWPON/A, the residues of dalapon in the zero-to-six inch layer at
7 days were 2.0 to 2.2 PPm, at 14 days 0.11 to 0.28 ppm, at 28 days 0.06 to
0.15 ppm, and at A2 days <0.025 ppm. No residues of dalapon were found in
the 6-to-12 inch layer of soil from any treatment or time interval from
A-55
-------
application. It was concluded that dalapon is unstable in soil under condi-
tions favorable for microbial growth and thus, it will usually be degraded
before appreciable leaching can take place. This conclusion is consistent
with laboratory data presented by Kearney, et al. (15) which indicates that
physical interactions between soil particles and dalapon are relatively un-
important.
It would, however, be possible for leaching of dalapon to occur if
irrigation or rainwater is applied to a site following dalapon application
and before substantial biodegradation occurs. Frank, et al. (AO) studied
the concentrations of dalapon in irrigation water following canal bank appli-
cations of 6.7 to 20 Ib/A. Maximum concentrations of dalapon found were
0.023 and 0.365 ppm when sampled in the treated area within 30 minutes after
application. The treated irrigation canals varied in water flow from 3.4
to 390 cu. ft/second and 0.96 to 2.4 ft/second (2.4 ft/second - 3.65 mph).
After several hours only very low levels of. dalapon (<10 ppb) were present
in waters flowing from the treated area. It should be noted that the highest
concentration of dalapon found in the irrigation water (0.365 ppm) would
deposit only 0.09 Ib of herbicide per acre-inch of water and would be too
low a rate to be likely to injure irrigated crops (4) (see Section 4).
3.2.3 Chemical Degradation
Although dalapon is subject to hydrolysis, under field conditions
chemical degradation is considered to be very slow and is unlikely to be an
important factor in the dissipation of dalapon from soil. Smith, et al. (41)
and Brust (7) demonstrated that dalapon and its sodium salt can undergo
hydrolysis to pyruvate and HC1. Other investigations have shown that hydro-
lysis is more rapid under alkaline pH and at elevated temperatures. Smith,
et al. (41) isolated sodium pyruvate in essentially quantitative yield after
hydrolyzing a dalapon solution containing excess sodium bicarbonate at 110°C
for 15 minutes. Brust (7) observed that dalapon sodium salt was hydrolyzed
only slowly at 25'C in either dilute (1 percent) or concentrated (18 percent)
solutions. At 50-C, the rate of hydrolysis was more.rapid, with approxima-
tely 25 percent hydrolysis in 8 days at initial concentrations ranging from
1 to 18 percent in water (7).
A-56
-------
Hydrolysis of solutions cf either dalapon or dalapon sodium salt are
accelerated at alkaline pH values. For example, hydrolysis of dalapon sodium
salt at 60°C was 20 percent complete in 30 hours at which time the equili-
brium pH was 2.3. In contrast, hydrolysis was 40 percent complete in 30
hours when the pH was maintained at 12 during the experiment (42).
Based on reaction rate studies, Kenaga (4) concluded that both dalapon
salt and dalapon would have chemical hydrolysis half-lives of several months
at temperatures less than 25°C and at initial solution concentrations.of less
than one percent. Considering the more rapid rate of microbial degradation,
Kenaga (4) concluded that it does not appear that chemical hydrolysis of
dalapon is a particularly significant degradative pathway in soils.
3.2.4 Volatilization
Volatilization of dalapon salts used in forestry under field conditions
is expected to be insignificant. In general, volatilization is primarily a
function of temperature and air movement. The vaporization from soil is also
dependent on a substance's chemical form and the extent of its interactions
with the soil particles (15). As was previously discussed, there is little
interaction between dalapon and soil particles. Any volatilization of dala-
pon at a given temperature would then depend primarily on air movement and
the specific chemical form of dalapon. Day (43) and Day, et al. (16) found
that some esters of dalapon were more volatile and others less volatile than
the acid form. In addition, Foy (44) found that at room temperature, dalapon
acid volatilized rapidly from an aluminum surface, whereas only negligible
amounts of the sodium salt form disappeared in 64 hours. Kutschinski (45)
reported that under more severe temperature conditions (63«C), 69 percent of
dalapon applied as the acid to sand disappeared in 6 hours. In comparison,
Kutschinski also applied the sodium salt of dalapon to several moist soils,
also at 63°C, and found that the greatest loss (from silica sand) amounted
to 13.5 percent in 6 hours.
It appears that, when applied to soil, the sodium salt of dalapon will
remain in the relatively non-volatile salt form and will not be converted to
the more volatile acid form. This has been suggested by Kutschinski (45)
who measured dalapon volatility in experiments in which sodium salt of dala-
pon was applied to moist soils at 63'C. On the basis of the results,
A-57
-------
Kutschinski concluded that dalapon hydrolyzed to pyruvate and that the li-
berated H+C1~ caused the formation of the acid of dalapon from the applied
sodium salt. However, conditions favoring formation of the dalapon acid
would not likely occur in most natural soil conditions. This is because the
PKa of dalapon acid is low (1.71) and because most soils have some buffering
capacity which will remove free protons generated by pyruvate formation.
The dalapon acid is only likely to form: (a) in sands where the buffering
capacity is low or nil, and (b) in microareas surrounding concentrated cen-
ters of dalapon in soils where the buffering capacity would be exceeded (15).
Kearney, et al. (15) comment that while Kutschinski's conclusions appear
to be valid, the possibility that the sodium salt of dalapon might also have
volatilized under the conditions of his experiment which were extreme com-
pared to natural conditions, cannot be eliminated since the analytical me-
thodology could not have probably distinguished between the acid and salt of
dalapon trapped in the gas scrubber used.
In summary, the available data indicate that while some volatilization
of the dalapon acid from soils can be expected, very little volatilization
of the dalapon salt can occur under normal forest use conditions.
3.3 FATE IN WATER
Actual field data on oersi«!i-pnra nt ^«i« j
wu persistence of dalapon in water appear to be limi-
ted to the observations by Frank, et al. (40) who reported negligible con-
centrations of dalapon in water downstream of a treatment site after the
water had travelled a distance of 32.2-40.2 km. Based on the laboratory BOD
test results and the observation of the rapid degradation of dalapon in soil
by microorganisms, dalapon is expected to biodegrade readily in the aquatic
environment. Kenaga (4) reported that the BOD/COD ratios for DOWPON M and
dalapon sodium salt (at 3.33 and 1.67 Ppm concentrations) are comparable to
those for such readily biodegradable substances as sucrose, ethanol, and
glutamic acid.
Because of its nl8h water solubility and lack of affinity for .oil par-
ticles, appreciable adsorption of dalapon on suspended or botto. sediMent.
is not expected in nature! ..ters. Baaed on the discussion in the preceding
sections, c epical degradation and volatUlzation probably occur to slowly
to account for substantial loss of dalapon fro, water. Aquatlum studlM
A-58
-------
conducted by Smith, et al. (36) provide further evidence that volatility
is not a route for significant loss of dalapon from water.
4.0 IMPACTS ON NON-TARGET ORGANISMS
4.1 PLANTS
Dalapon is relatively selective against annual and perennial grasses
(6). This selectivity has been attributed to possible differences in the
metabolism between target and non-target species (46). In forest site pre-
paration applications, dalapon is used, at least two weeks before planting
conifers. Tests run by Stewart and Beebe (47) in Wenatchee National Forest
indicated that 5 Ib of dalapon per acre could provide adequate grass control
without damaging ponderosa pine seedlings planted immediately after spraying.
Conifer damage may result, however, when dalapon is used in conjunction with
certain other herbicides. In at least one area in southwestern Oregon, a
combination of atrazine and dalapon resulted in complete defoliation of well-
established ponderosa pines 8 to 15 feet tall (48). No information on the
amount of the mixture applied or the mix ratio in this incident was reported,
but it appears that there is a synergistic effect when these two chemicals
are used in combination which increases their activity and effect upon coni-
fers (48).
Crops susceptible to dalapon damage are few and, in general, no crop
damage would be expected from possible drift due to applications in forest
areas. Dalapon is used for grass control on several agricultural crops in-
cluding sugarcane, sugarbeets, corn, potatoes, asparagus, grapes, flax, new
legume spring seedlings, citrus, and deciduous fruit, coffee, certain stone
fruits and nut trees (1). Cotton is considered to be tolerant to dalapon
while sorghum is considered susceptible (6).
Foy and Miller (49) investigated the effect of dalapon on maturity,
yield, and seed and fiber properties of cotton by applying a basally directed
spray of dalapon during the early square and full flowering stages of deve-
lopment as well as after a full boll load had developed. Application rates
of 3 and 6 pounds per acre during the two flowering stages caused signifi-
cant delay of maturity and reduction of cotton yield, with the high rate
being more severe. Later applications did not produce any observed delete-
rious effects at either rate. Germination of seed from treated cotton was
A-59
-------
measurably retarded (at 48 and 96 hours) but final viability was not reduced.
The effect of retarded germination also was observed in seeds germinated
after two years in storage. Foy and Miller (49) also reported that the in-
fluence on germination was correlated with dosage and with the time of appli-
cation in relation to reproductive development.
To prevent depression of crop yield, Newton and Norgren (50) recommended
an allowable level of 0.02 mg/1 of dalapon in sources of irrigation water
and a maximum of 0.1 mg/1 in smaller streams where maximum concentrations
tend to exist only briefly and would not lead to a harmful accumulation of
dalapon on the crop.
4.2 FAUNA
At application rates of 5 to 15 Ib/acre recommended for forestry uses,
it appears that birds, fish, other aquatic organisms, honey bees, and soil
invertebrates will not be exposed to levels of dalapon which cause observa-
ble toxic effects. Under worst-case conditions (e.g., treatment of a large
area at maximum recommended application rate and no rainfall), it appears
possible that a small browsing mammal (e.g., a rabbit) could consume enough
dalapon to cause an acute toxic reaction. One study, however, indicated
that larger mammals (calves and sheep) grazing on dalapon-treated feed did
not suffer visible harmful effects (51).
Kenaga (4) has reviewed the literature on the toxic effects of dalapon
on mammals, birds, fish and other aquatic animals, honey bees, and soil in-
vertebrates. This section, with only minor modifications, is extracted from
his review.
4.2.1 Effects on Mammals
Some LD50's reported for dalapon sodium salt and two dalapon formula-
tions are presented in Table 4. The high LD50 value indicates very low
acute toxicity to mammals.
Table 5 presents the results of subacute toxicity experiments with
cattle and sheep. The animals were dosed with daily oral capsule or drench
applications of dalapon sodium salt at rates of 15 to 500 mg/kg/day, equiva-
lent to an intake of about 150 to 1,500 ppm in the diet; no mortality
occurred at any of the dosage rates which were given for from 9 to 481
A-60
-------
TABLE 4, ACUTE ORAL TOXICITIES OF DALAPON TO MAMMALS (4)
Species
Rat
Mouse
Guinea pig
Rabbit
Sex
M
F
F
F
F
LD50 <*/»>
Dalapon
sodium
salt
9,300
7,570
>4,600
3,860
3,860
*
DOWPON
5.660
5,660
—
4,930
2,830
DOWPON M
5,660
5,660
— —
2,830
2,140
* Formulation containing 85 percent dalapon sodium salt.
•f Formulation containing 72.5 percent dalapon sodium salt
and 12 percent dalapon magnesium salt.
TABLE 5. TOXICITY OF DALAPON SODIUM SALT TO CATTLE AND SHEEP (4)
No. days
treated
Cattle
10
9
10
Sheep
10
10
10
481
10
10
10
Means of oral I
dosing 1 U
Drench
Drench
Capsure
Drench
Drench
Capsule
Capsule
Drench
Drench
Capsule
Dosage
ng/kg/day)
250
500
500
50
100
100
100
250
500
500
Effects
None
Throat irritation
None
None
None
111 but survived, 6% wt loss
None, 10% wt loss after 80
treatments
None
111 but survived, 17% wt loss
111 after 7 treatments but
survived, 6% wt loss
A-61
-------
successive days. Cattle exhibited some throat irritation at 500 rag/kg with
an oral drench and sheep lost some weight at as low as 100 rag/kg/day when
fed for 10 days. In another study, Paynter, et al. (52) reported the treat-
ment of a heifer and a bull suckling calf with 1,000 mg/kg/day for 10 suc-
cessive days. Some symptoms exhibited were temporary. No mortality occurred.
Macroscopic and microscopic examination of tissues from the animals sacri-
ficed on the eleventh day revealed these tissues to be within normal limits,
with the possible exception of kidney tissues of the bull.
Paynter, et al. (52) also conducted a 97-day dietary feeding study on
rats using diets containing 115, 346,.1150, 3460, and 11,500 ppm. No morta-
lity occurred at any of these dosages. There was no measured effect on male
rats at 1150 ppm (- 115 mg/kg/day) and on female rats at 115 ppm as judged
by food consumption, average body and organ weights, and by hematological,
gross, and histopathological examinations.
Goldstein and Long (51) conducted field tests with dalappn (sodium salt?'
on a grassy pasture using 30 lb/100 gal of water (- approx. 30 Ib/A). Two
calves grazed on the pasture until the vegetation turned brown, with no vis-
ible harmful effects to the calves. Oats treated with 2.5, 5, 10, and 20
lb/100 gal (= approx. same rates/A) were fed on by calves and sheep without
ill effects. Sudan grass treated with 20 lb/100 gal was fed upon by a calf
without ill effect. Goldstein and Long (51) added dalapon sodium salt at
the rate of "a pint of the standard concentration of dalapon spray per five
gallons of drinking water" (probably equivalent to 12,500 ppm); this was the
drinking source for a hog, sheep, and cattle for two weeks without causing
visible ill effects.
Chronic toxicity tests in which dogs were administered capsules daily,
5 days a week for 52 weeks, containing doses of 15, 50, or 100 mg/kg/day of
dalapon sodium salt were conducted by Paynter, et al. (52). The usual ex-
tensive toxicological parameters measured indicated no effect from these
treatments except increases in average kidney weights at 100 mg/kg/day. In
a 2-year dietary feeding test with rats, also conducted by Paynter, et al.
(52), rats consumed diets containing 100, 300, and 1,000 ppm of dalapon
sodium salt for 2 years, equivalent to 5, 15, and 50 mg of dalapon sodium
salt/kg/day, respectively. The usual extensive toxicological parameters
A-62
-------
measured during chronic feeding tests indicated no effect from these treat-
ments except increases in average kidney weights at 50 mg/kg/day.
The effect of dalapon on mammalian reproduction has been investigated
by a number of investigators. In studies by Paynter, et al. (52), young rats
were fed for at least 110 days on diets containing 300, 1,000, or 3,000 ppm
of dalapon sodium salt (- about 30, 100, or 300 mg of dalapon sodium salt/
kg/day) continuously through each of three generations of two litters each,
with no effect on reproduction (fertility, gestation, viability) and lacta-
tion. No adverse effect was seen on body weight, a favorable indicator of
normal growth and maturation. Thompson, et al. (53) administered dalapon by
gavage to pregnant rats from day 6 through 15 of the gestation in a tolerance
study designed to suggest dose levels acceptable for teratogenic studies.
Dosages given were 250, 500, 1,000, 1,500, or 2,000 mg/kg/day. The following
parameters were examined: maternal body weights and gains, food consumption,
number of viable fetuses, fetus resorptions, and corpora lutea, individual
pup weights and sex, and gross external examination of pups. As the result
of these tests, only the following notable observations were made: clinical
signs of toxicity consisted of soft stools and slight appetite depression in
dams from the 2,000 mg/kg dosage group. One rat from the 1,500 mg/kg group
had diarrhea. Weight gains for pregnant dams were lower than controls at
1,500 or 2,000 ing/kg/day. Fetal resorption rate was increased at both the
1,500 and 2,000 mg/kg dosage levels but the increase was not significantly
different from controls. Pup weights from the 2,000 mg/kg dosage level were
significantly lower than controls. No effects were seen at 1,000, 500, or
250 mg/kg/day.
Teratological studies of dalapon in the rat were reported by Emerson,
et al. (54). Dalapon was administered in distilled water once daily, by
gavage, from day 6 through 15 of gestation (sperm positive vaginal smear -
day zero). Four groups of mated females were administered 0, 500, 1,000, or
1,500 mg of dalapon/kg/day, respectively. They were killed pi, gestation day
20 and fetuses were removed by caesarean section. The following tests were
conducted: clinical observations, maternal body weights on days 0, 6, 15,
and 20, food consumption on days 6, 15, and 20, observations on the number
of viable fetuses, resorptions, and corpora lutea, individual fetal weights
A-63
-------
and sex, external examination, and skeletal (two-thirds) and visceral (one-
third) examinations.
All rats treated with dalapon were restless for approximately 10 minutes
following dosing. Focal alopecia, intermittent staining of rear quarters
with urine, and soft stools were observed in some treated. rats. Mean weight
gains and food consumption for dalapon-treated adult rats during the test
interval (days 0 to 20) did not differ significantly from the controls.
However, mean weight gains (500 and 1,500 mg/ kg /day groups) and mean daily
food consumption (1,500 mg/kg/day group) were significantly less than the
controls for the dalapon treatment interval (gestation period, days 6 to 15).
Mean pup weights were significantly less than controls only in groups given
1,000 or 1,500 mg/kg/day. An increased incidence of minor variants such as
retarded ossification of sternebrae was observed in fetuses of treated dams
and was associated with decreased fetal weights. Spontaneous major visceral
abnormalities consisted of unilateral microphthalmia in one fetus each of
the 500 and 1,000 mg/kg/day groups.
Kenaga (4) stated in summary that no major dose-related skeletal or
visceral abnormalities were observed in the fetuses of dams treated with
dalapon and, other than reduced pup weights in the 1,000 and 1,500 mg/kg/day
treatment levels, no untoward effects were detected.
4.2.2 Effects on Birds
Based on reported bioassaj, results, normal uses of dalapon should pre-
sent no adverse impacts on birds and beneficial insects such as bees. The
DLrV?5" " dalapon sodlum salt to chlckens ls "*«"••' MOO ••/
* ««. Pal*er and Radeleff (55) reported that chickens treated »ith lT
dai v repeated oral treatments usi^ capsules contain^ 500 „ dllapon
sodiu. ,alt/kB/da, suffered no .ortalitv and onlv 8llght
tions (0 percent vs. <2 percent, over untreated chickens. No . Lilt,
°"urred undei the sane test
Table 6 presents the
...... „
fed 1,000 to 5,000
A-64
-------
TABLE 6. TOXIC EFFECTS OF DALAPON IN DIET OF
VARIOUS WILD BIRD SPECIES (4)
Species
Pheasant
Japanese quail
Bobwhite
Mallards
Age
Young
Adult
Adult
2-3 wk
2-3 wk
Young
Adult
Young
Young
Adult
Adult
2-3 wk
Amount
in diet
(ppm)
5,000
5,000
5,000
5,000*
5,000*
5,000
5,000
5,000
1,000
2,500
1,000
5,000*
Test
period
(days)
169
10
24
5
5
100
100
100
100
100
100
5
Mor-
tality
%
24
10
90
0
0
40
95
24
68
85
94
0
Toxicant
consumed
(mgAg/day)
431
250
.
_
-
-
610
-
-
230
120
^
*Dalapon sodium $alt.
ppm of dalapon for various periods (10 to 169 days) sustained partial but
not 100 percent mortality. Mallards appeared to be the most sensitive spe-
cies tested.
The potential effects of dalapon on bird reproduction have been evalu-
ated by dalapon injection into eggs and in dietary feeding tests. The ef-
fects of dalapon when injected into eggs represents a severe test, both
because of the mechanical and physiological effects of injecting chemicals
through the shell and because the egg has no external excretory way to dis-
pose of unmetabolized compounds. Dunachie and Fletcher (56,57) injected
from 10 to 500 ppm of dalapon by weight of egg via an acetone solution into
hens eggs. No teratogenic effects were seen at 500 ppm, the highest dosage
tested. Hatchability of eggs was unchanged in treatments at or below 200
ppm and was 63 percent and 70 percent of control at 300, 400, and 500 ppm
levels, respectively.
Dietary feeding reproduction tests conducted on adult pheasants, bob-
whites, and mallards are shown in Table 7. The highest dosages used (1,000
to 5,000 ppm in the diet) were checked for effects on the hatching success
A-65
-------
in terms of chicks per hen. The dosages selected were the highest of those
used in Table 6 for each species and resulted in high adult mortality.
Presumably, part of the adult mortality occurred after the reproduction
tests were finished. In any case, the dosages were in the partially lethal
range for adults. In spite of these high dosages, reproduction was not de-
creased in treated bobwhites and only partially with pheasants and mallards.
Effects on reproduction were those related to number of eggs laid, a common
effect at sublethal dosage levels. There was no effect on the viability
and fertility (hatching success) of the three species compared to the con-
trols (4).
TABLE 7. EFFECTS OF DALAPON SODIUM SALT ON REPRODUCTION OF THE
MALLARD, PHEASANT, AND BOBWHITE (4)
Species
Mallard
Ring-necked
Pheasant
Bobwhite
Dalapon
Sodium
Salt
(ppm)
2,500
1,000
5,000
5,000
Eggs/Female
Con-
trol
(A)
27
21
32
67
Test
(B)
6.8
11
22
82
% Con-
trol/
Test
(B/A)
25
51
68
122
»'!•••! . —
Viable Young
Per Female*
Con-
trol
(C)
5.1
11
12
33
Test
(D)
2.6
4.7
6.3
42
% Con-
trol
Test
(D/C)
51
43
55
128
% Viable
Young Per
Eggt Laid
Con-
trol
(C/A)
19
53
36 .
49
Test
(D/B)
36
45
29
51
Chicks per hen.
Hatching success.
4-2.3 Toxicity to Honey Bees
Research on the toxicity of herbicides to honey bees indicates that the
toxicity depends on the chemical, the formulation, and the carrier used with
the herbicide. In addition, the method of testing seems to have an important
influence on the outcome of the test. Toxicants can kill honey bees by acting
as stomach poisons, as contact poisons, and in the case of herbicides, through
A-66
-------
destruction of the food source. The toxicity of dalapon to honey bees has
been studied as both a contact poison and a stomach poison.
Dalapon is considered to be relatively non-toxic to honey bees (58).
Laboratory tests at the Dow Chemical Company showed that honey bees immersed
and wetted momentarily in dalapon sodium salt solution at a concentration of
20,000 ppm experienced no mortality 24 hours after Immersion (4). Anderson
and Atkins (59) classified 163 pesticides Into three groups on the basis of
field tests and commercial experiences for the more commonly used materials.
Laboratory contact data (LD5Q values) from Atkins and Anderson (59) were
also used as follows: highly toxic <2 ug/bee, moderately toxic 2 to 10 ug/
bee, and relatively non-toxic >10 yg/bee. Dalapon was classified in the
relatively non-toxic group by these researchers who characterize substances
in this category as those that "can be used around bees with a minimum of
injury" (62). Duval (60) made a similar evaluation of toxicity of pesticides
to honey bees, classifying dalapon as relatively non-hazardous among the
many pesticides evaluated. According to Kenaga (4), the available data on
impact of dalapon on bees are in overwhelming contradiction to the statement
by King (61) (reportedly made without supportive data) that dalapon should
not be used in areas of high bee activity because of severe contact toxicity.
The potency of dalapon as a stomach poison was investigated by Morton,
et al. (58) who fed bees 60 percent sucrose solutions containing 0, 10, 100,
and 1000 ppmw dalapon. As a measure of toxicity, the investigators compared
the number of days required for half of the bees to die (half-life) in a
group of bees fed dalapon to that for a control group. All bees tested were
newly emerged adults less than 24 hours old. Significant reductions in the
half-life of the groups fed 10 and 100 ppmw concentrations of dalapon were
not observed. The group fed dalapon at 1000 ppmw did have a slightly shorter
half-life than the control group (37.0 vs. 51.8 days).
4.2.4 Effects on Fish and Other Aquatic Organisms
Various studies have been reported on the acute toxicity of various
dalapon formulations to several species of fish under a range of temperature
and exposure durations. The reported results, as summarized-by Kenaga (4),
are presented in Table 8 for dalapon sodium and magnesium salts for 12 spe-
cies of fresh water fish in static water. As noted in the table, the LC5Q
A-67
-------
for all species is greater than 100 ppm of dalapon, which represents a low
order of toxicity. An acute toxicity test with dalapon in flowing water
has also showed a similar low order of toxicity to large-mouth bass (63).
TABLE 8. TOXICITY OF DALAPON AND FORMULATIONS TO FISH (4)
B .
|^M-
W»tcr
Wmp.
ErpMiirt
(hourlj
KUUritl
tfvtfd*
CwwcnlrktioD
(ppm)
Formu-
PO*
HI w-
lAiify
lUlabow Iraul
Vrewi tiwvl SO*F
ire
we
WF
WK
WF
WK
SOT
Cotw *tW> 6S*F
WF
Blwiill
IZ'C
ire
TI
34QF
SIOF
430X
3DOF
3«SF
300F
WOK
T«h.
Ttch.
SJ51N.)
JIO(N»)
Yelk>«
35*0.
2i*C>
75*F
75;F
7S*F
Iff
7S*F
15'F
l»-2tDty« Tteh.
34
4R
89
34
4S
m
34
43
M
72
n
72
72
73
Bowrox •
•owrow *
Chtnncl ntKth |2'C
OoldfUK IS-C
WTF
108 DOT KIM
IC8 Bowrow
«9 Tteh.
M Twb.
M KJWPUK
5tO(Nt>
1901 N!)
300 F
4MF
3WF
400 F
500F
l.OOOtN.)
1,000(N»J
350(N4)
>8T
352-
155*
318
318
in
*TO
m
»s
2*7
I»
>B7
M
4I«
381
381
443
381
351
US*
IDS*
222
222
300
3TO
n?
867
IIT
>87
200
so*
M'
M
M
CO
M
W.
w
0
M
SO
W
60
M
W
SO
CO
0
100
0
7?
0
100
0
so
M
0
0
0
lnlioa*
• ll.rd.
' Coniunl Ron of »-iUf,
• M»y he M tedium mil.
• M • MH nlut io til
A-68
-------
Table 9 presents data on the toxicity of dalapon to fish eggs and fry. In
tests with four species of fish, 50 ppm of dalapon caused no mortality to
the fry. Green sunfish eggs (embryo) were not affected by 50 ppm of dala-
pon. Two species of salt water fish (longnose killifish and white mullet)
were also tested and found to be very tolerant to dalapon (see Table 10).
The substitute toxicity of dalapon to fish has also been evaluated. Lawrence
(64,65) tested dalapon at 80 ppm for 7 days and at 50 ppm for 15 to 21 days
without causing mortality to bluegills. Folmar (66) reported that rainbow
trout (Salmo ggirdneri) avoided 1.0 ppm of the dalapon sodium salt.
TABLE 9. TOXICITY OF DALAPON TO FISH EGGS AND FRY*(4)
Species
Bluegill
Small
Fry
Green sunfish
Fry
Egg embryo
Lake chubsucker
Fry
Smallmouth bass
Fry
Exposure
(days)
12
8
8
3
8
8
Dalapon
(ppra)
50
50
SO
50
50
50
Mortality
(%)
0
0
0
0
0
0
*At 22° to 25°C water temperature.
Dalapon sodium salt has been tested on a number of species of insects
and other crustaceans, both in fresh water and in salt water in short-exposure
tests. Such tests have also been conducted on snails, oysters, and marine
phytoplankton (see Tables 10 and 11). The no-effect level of dalapon for
snails, dragonflies, stoneflies, and several crustaceans is at least 200 ppm.
Daphnids are more sensitive, being "immobilized" at 11 to 16 ppm. Shrimp
are "immobilized" 40 percent at 0.9 ppm.
The highest concentrations of chemicals which were tested by Butler (67)
(Table 10) in estuaries where shrimp, oysters, and crabs grow, are at low
ppm concentrations since even ppb concentrations are not likely to occur
after herbicidal use because of dilution.
A-69
-------
TABLE 10. THE EFFECT OF DALAPON ON AQUATIC ORGANISMS IN SALT WATER (67)
Organism
Exposure
(hours)
Longnose killifish 48
White mullet
Brown shrimp
Blue crab
Eastern oyster
Phytoplankton
48
48
48
48
96
4
Temp
(°C)
29
20
27
29
24
31
-
Dalapon
(ppm)
37*
0.87T
37
0.87
37
0.87
0.87
Effect
0% mortality
0% mortality
0% mortality
47% immobilization
No effect
0% mortality or shell-
growth effect
0% decrease in carbon
fixation
Dalapon sodium salt tested.
Dalapon sodium salt tested as RADAPON herbicide formulation.
TABLE 11. THE EFFECT OF DALAPON ON AQUATIC INVERTEBRATES (4)
Organisms
Exposure
(hours)
Temp
Dalapon
sodium salt
(ppm)
Effect
Entomostracans
Daphnida (Cladocerans)
Simocephalus serratus
Daphnia pulex
Cyclops sp.
Eubranchipius sp.
Insects
Stoneflies, Pleronarcys
California, naiad
Dragonfly, Aeschna sp.
Snails
Planorbis sp.
Physa. sp.
48
48
24
24
24
24
96
48
60
60
80
80
80
80
60
16
11
400 (a.el)*
200 (a.e.)*
400 (a.e.)*
200 (a.e.)*
100
1,600 (a.e.)*
400
200
400
""50'
EC50f
100% mortality
0% mortality
100% mortality
0% mortality
None apparent
0% mortality
50% mortality
0% mortality
50% mortality
a.e. = acid equivalent
EC50 * 50 Percent immobilization or mortality
A-70
-------
4.2.4 Effects on Soil Invertebrates (Arthropods. Nematodes, and Earthworms)
Fox (68) studied the effect of dalapon sodium salt on the numbers of
wireworms, springtails, mites, earthworms, and millipedes in grassland soil
over a two-year period after application. Since dalapon destroys grass, po-
pulations of invertebrates feeding on grass and succession plants will be
affected by the kind of plants remaining. Dalapon at 40 Ib/A or 20 Ib/A did
not affect wireworm populations, principally those of the genus Agriotes. A
dosage of 20 Ib dalapon/A resulted in slightly increased numbers of milli-
peds and springtails (suborder Arthropleona) in the first year and increase
in numbers of mites (unspecified) in the first and second year (at the 95
percent confidence limits). No significant increase or decrease in numbers
of earthworms (Lumbricidae) occurred.
Courtney, et al. (69) found that dalapon applied at 5 Ib/A to colonial
bentgrass reduced the number of nematodes by 94 percent. On the basis of
unpublished data, Edwards, et al. (70) state that dalapon is "not toxic to
soil animals".
4.3 BIOACCUMULATION POTENTIAL
Data provided by the manufacturers indicate no potential for dalapon
bioaccumulation in mammals, birds, fish, snail or daphnids (4,36). Studies
reported by other investigators also indicate that while residue buildup may
occur in plants, significant accumulation of a permanent nature in animals
is unlikely. The observed low level magnification of dalapon in the aquatic
fauna has been attributed to physical adsorption and not to metabolic pro-
cesses (4). In laboratory tests, residues in the tissues of mammals and
birds fed 100 to 1000 ppm of dalapon in their diet over periods of weeks,
months, or years remained below 100 ppm during treatment and soon fell to
below 1 ppm when removed from exposure to dalapon (4).
Smith, et al. (36) studied the distribution of dalapon sodium salt, in
an aquarium containing water with a concentration of 5 ppb of dalapon and
fish, snails, Daphnia sp., submerged plants (Cabomba caroliniana)t floating
plants (Limna minor), and algae over a three-day exposure period. A second
identically furnished aquarium was used except that instead of using live
organisms, the plants were killed by autoclaving and the animals were killed
by freezing them in Dry Ice prior to putting them in the aquarium. The
A-71
-------
differences with time between residues from organisms in the two aquariums
were essentially that due to adsorption and absorption in the first aquarium
minus that due to adsorption in the second aquarium. Concentrations of dala-
pon in water remained at 5 to 6 ppb throughout the exposures, showing little
or no volatility from water or overall adsorption from water by organisms.
Fish appeared to contain up to 15 ppb on or in tissues of both dead and live
whole fish. Snails and Daphnia sp. contained residues less than that of the
surrounding water environment. Duckweed (Limna minor) contained about 40 to
50 ppb when dead and up to about 180 ppb when alive. Cabomba carolinlana
contained about 20 to 50 ppb when dead, but around 780 ppb when alive and
appeared still to be absorbing residues after 72 hours exposure.
4.4 MICROORGANISMS
Studies conducted on the effect of dalapon on nitrification by soil
bacteria indicate that a significant, but temporary, reduction in nitrifica-
tion would result following application of dalapon at levels recommended
for forest use. Reid (71) studied the effect of dalapon sodium salt on ni-
trification rate as a measure of the changes in soil microflora at 258C
under aerated conditions [nitrifying bacteria are among the most sensitive
microorganisms to herbicides (15)]. At concentrations corresponding to
dalapon application rates of 25, 50, 100, and 150 Ib/A, nitrification rates
were 30, 23, 20, and 2 percent of the control, respectively, 14 days after
treatment and 95, 80, 77, and 48 percent of the control, respectively, after
28 days. Mayeux and Colmer (72) observed that dalapon at concentrations of
up to 700 ppm had little effect on nitrite oxidation.
Several studies have reported the nitrogen fixing Azotobacter to be
very resistant to dalapon and other chlorinated aliphatic herbicides (4).
For example, Magee and Colmer (73) found that the minimum dalapon concentra-
tions necessary to produce maximum inhibition of respiration of Azotobacter
species varied among species from 2,000 to 10,000 ppm. Newman and Downing
(35) reported that at normal rates of treatment, dalapon should not have
adverse effects on Azotobacter. Little is known about the effect of dalapon
on symbiotic nitrogen-fixing bacteria, although Worsham and Giddens (74)
have reported that dalapon had no effect on soybean nodulation at application
rates of 17, 34, and 68 Ib/acre. MacKenzie and Macrae (75) tested the tole-
rance of the nitrogen-fixing system of Azobacter vinelandii to dalapon
A-72
-------
sodium salt. The acetylene reduction and the growth rate of the bacterium
were not affected by 5 and 50 ppm dalapon sodium salt in the growth media.
These concentrations are equal to or in excess of those which would occur
from commercial use of dalapon, even when applied directly to water (4).
The effects of dalapon on soil microorganisms other than nitrogen fixing
bacteria have been evaluated by a number of investigators. Both stimulatory
and inhibitory effects have been observed. In a few instances, initial re-
ductions in growth have been followed by increases in activity. Increases
may be due to either adaptation and proliferation of "effective" microorga-
nisms, or to proliferation of organisms resistant to the effects of the her-
bicide. Magee (76) observed that dalapon stimulated the multiplication of
soil bacteria, actinomycetes, and fungi. Worsham and Giddens (74) also ob-
served an increase in numbers of actinomycetes and bacteria present in
treated soil. Hale, et al., found that low dalapon concentrations (50-150
ppm) increased oxygen uptake by soil microorganisms, whereas higher concen-
trations (600 ppm) slightly inhibited oxygen uptake. Elkan, et al. (78,79)
observed that sodium propionate greatly increased both respiration and total
numbers of soil microorganisms but marketly depressed the numbers of fungi.
Stimulation in this case was attributed to higher bacterial counts arising
subsequent to inhibition of fungi.
Walsh (80) found the sodium and magnesium salts of dalapon to be 4 to
25 times less toxic on the basis of 10 days growth at 20°C than dalapon to
four species of unicellular algae in test tubes containing artificial sea
water at a salinity of 30 parts per thousand. Even greater differences
(around 100-fold) between the acid and salts occurred in regards to decrease
in oxygen production as measured fay a photosynthesis respirometer over a 90-
minute exposure at 20°C. None of the organisms appeared sensitive to dala-
pon or its sodium or magnesium salts at concentrations which would be ex-
pected to occur in natural marine waters. Venkataraman and Rajyalakshmi.
(81) found blue-green algae tolerant to dalapon at dosage rates equivalent
to 200 kg/ha (179 Ib/A) over 15-day period. The species included those in
the genera Aulosira (fertilisslma), Tolvpothrix (tenuis). Anicjrstis,
baena, and Nostpc.
A-73
-------
REFERENCES
1. Mullison, W.R. Herbicide Handbook of the Weed Science Society of Ame-
rica. Weed Science Society of America, Champaign, Illinois, 4th Edi-
tion, 1979. 518 pp.
2. Pesticide Tests in Forestry. National Forest Products Association,
Forest Chemicals Program, Washington, D.C. 1980.
3. Weseloh, J.W. Manager, Product Registrations, Regulatory and Legisla-
tive Issues, Health and Environmental Sciences, The Dow Chemical Company.
Letter to Dr. M. Ghassemi, TRW Inc., August 28, 1981.
4. Kenaga, Eugene E. Toxicological and Residue Data Useful in the Environ-
mental Safety Evaluation of Dalapon, Residue Reviews, Vol. 53, 1974.
5. Stavins, R.N. Raw Data on Pesticide Usage on Public Lands, U.C. Berke-
ley, 1980.
6. Foy, Chester L. The Chlorinated Aliphatic Acids in Kearney, P.C. and
Kaufman, D.D. Herbicides: Chemistry, Degradation and Mode of Action,
2nd Edition, Vol. 1, Marcel Dekker, Inc., Hew York. pp. 399-452. 1975.
7. Brust, H. Hydrolysis of Dalapon Sodium Salt Solutions. E.G. Britton
Research Laboratory, The Dow Chemical Company, Midland, Michigan.
November 4, 1953.' Cited in Reference 4.
8. Blanchard, F.A., W.W. Muelder, and G.N. Smith. Synthesis of Carbon-14
Labelled Dalapon and Trial Applications to Soybean and Com Plants.
J. Agr. Food Chem. 8: 124, 1960. Cited in Reference 4.
9. Foy, C.L. Plant Physiol. 36: 698, 1961. Cited in Reference 6.
10. Smith, G.N. and D.L. Dyer. J. Agr. Food Chem. 9: 155, 1961.
11. Foy, C.L. Absorption, Distribution, and Metabolism of 2,2-Dichloropro-
pionic Acid in Relation to Phytotoxlcity. II. Distribution and Meta-
bolic Fate of Dalapon in Plants. Pi. Physiol. 36: 398, 1961. Cited in
Reference 4.
12. Scholl, J.M. Down to Earth, 25(3): 15, 1969. Cited in Reference 6.
13. Fertig, S.N. and M.M. Schriber, Effect of Dalapon Ingestion on Per-
formance of Dairy Cattle and Levels of Residue in the Milk. J. Agr.
Food Chem. 9: 369, 1961. Cited in Reference 4.
14. Getzendaner, M.E. Residue Study: Dalapon in Grass Treated with DOWPON
M Herbicide. Unpub. Rept. GH-C 526, Agricultural Department, The Dow
Chemical Company, Midland, Michigan. Feb. 16, 1972. Cited in Reference
4.
A-74
-------
15. Kearney, P.C., et al. Behavior and Fate of Chlorinated Aliphatic Acids
in Soils. Adv. Pest. Control Res. 6: 1-30, 1965.
16. Day, B.E., et al. Persistence of Dalapon Residues in California Soils.
Soil Science, 95(5): 326-330, 1963.
17. Warren, G.F. Proc. North Central Weed Control Conf. 11: 5, 1954. Cited
in Reference 6.
18. Crafts, A.S. and H. Drever. Weeds, 8: 12, 1960. Cited in Reference 6.
19. Richards, R.F. Proc. South. Weed Conf. 9: 154, 1956. Cited in Re-
ference 6.
20. Southwick, L. Progress Report on Agricultural Uses of Dalapon. Proc.
Northeastern Weed Control Conf., pp. 251-256, 1954. Cited in Reference
28.
21. Brown, D.A. Residual Effect of CMU, Dalapon, and Urab. Res. Report,
North Central Weed Control Conf., pp. 3, 1954. Cited in Reference 28.
22. Wingfield, G.I., et al. The Effect of Soil Treatment on the Response
of the Soil Microflora to the Herbicide Dalapon. J. Appl. Bact. 43:
39-46, 1977.
23. Thiegs, B.J. The Stability of Dalapon in Soils, Down to Earth, Fall
Issue, 1955. Cited in Referenced,
24. Jensen, H.L. Soils Fert. 23: 60, 1960. Cited in Reference 6.
25. Kaufman, D.D. Can. J. Microbiol. 10: 843, 1964. Cited in Reference 6.
26. Corbin, F.T. and R.P. Upchurch. Weed Sci. 15: 370, 1967. Cited in
Reference 6.
27. Corbin, F.T., R.P. Upchurch, and F.L. Selman. Weed Sci. 19: 233, 1971.
Cited in Reference 6.
28. Holston, J.T. and W.E. Loomis. Leaching and Decomposition of 2,2-
Dichloropropionic Acid in Several Iowa Soils. Weeds, 4: 205-217, 1956.
29. Hirsch, P. and M. Alexander. Can. J. Microbiol. 6: 241, 1960. Cited
in Reference 6.
30. Magee, L.A. and A.R. Colmer. Can. J. Microbiol. 5: 255, 1959. Cited
in Reference 6.
31. Thiegs, B.J. Down to Earth, 18: 7, 1962. Cited in Reference 6.
32. Jensen, H.L. Can. J. Microbiol. 3: 151, 1957. Cited in Reference 6.
33. Jensen, H.L. Nature, 180: 1416, 1957. Cited in Reference 6.
34. Kaufman, D.D. Weeds, 14: 130, 1966. Cited in Reference 6.
A-75
-------
35. Newman, A.S. and C.R. Downing. Herbicides and the Soil. J. Aer Food
Chem. 6: 352-3, 1958.
36. Smith, G.N., Y.S. Taylor, and B.S. Watson. Ecological Studies on
Dalapon (2,2-Dichloropropionic Acid). Unpub. rept. NBE-16, Chemical
Biology Res., The Dow Chemical Company, Midland, Michigan, June 12
1972. Cited in Reference 4. '
37. Warren, G.F. Rate of Leaching and Breakdown of Several Herbicides in
Different Soils. NC Weed Control Conf. Proc., llth Ann. Meeting,
Fargon. N. Dak., 1954. Cited in Reference 4.
38. Helling, C.S. Pesticide Mobility in Soils, I, II, III. proc Soil
Sci. Soc. Amer. 35: 732-748, 1971.
39. Miller, P.W. and M.E. Getzendaner. Residues of Dalapon in Soil Treated
With DOWPON Grass Killer. Unpub. rept. GH-C 658, The Dow Chemical
Company, Midland, Michigan, June 5, 1973. Cited in Reference 4.
40. Frank, P. A., R.J. Demint, and R.D. Comes. Herbicides in Irrigation
Vote!o^0ll°Wing Canal-bank Treatment for Weed Control. Weed Science
18: 687, 1970.
41. Smith, G.N., M.E. Getzendaner, and A.H. Kutschinski. Determination of
s* 25 ^?Pr°S<°n*C Acld (DalaP°n> in Sugar Cane. J. Agr. Food Chem.
5: 675, 1957. Cited in Reference 4.
42. Tracey, W.J. and R.R. Bellinger, Jr. Hydrolysis of Sodium 2 , 2-Dichloro-
n!°P SX? *? W5JeLS°1Uti0n' Mldland Divisi°*. The Dow Chemical Com-
pany, Midland, Michigan. October 16, 1958. Cited in Reference 4.
43. Day, B.E. Weed Res. Is 177, 1961. Cited in Reference 6.
44. Foy, C.L. Hilgardia 30: 153, 1960. Cited in Reference 6.
45. Kutschinski, A.H. Down to Earth, 10(3): 14, 1954. Cited in Reference
46' Chemical t^**** °f ™*™ <*"«tifi* Journal, Dow
47 " ^nTcon^'f*?1 *' I"*!' Burv±™1 of *md«*o.. Pine Seedlings Follow-
ss S8 1 Si rSrje5 I ^ra8se8' ln: ^oc. West. Soc. Weed Sci. 27:
55-50, 1974. Cited in Reference 48.
48. Gratkowskl, H. Silvicultural Use of Herbicides in Pacific Northwest
Forests, Pacific Northwest Forest and Range Experiment Static" U?"
Department of Agriculture, Portland, Oregon, 1975.
49. Foy, C.L. and J.H. Miller. Influence of Dalapon on Maturity Yield
and Seed and Fiber Properties of Cotton. Weeds 11: 31-36, 1963.
A-76
-------
50. Newton, M. and J.A. Norgren. Stlvicultural Chemicals and Protection
of Water Quality. EPA Report 910/9-77-036, 1977.
51. Goldstein, H.E. and J.F. Long. Observations on Cattle, Sheep and Swine
Exposed to 2,4-D, 2,4,5-T, and Dalapon Herbicides. Presented S. Weed
Control Conf., Biloxi, Miss., Jan. 20, 1960. Cited in Reference 4,
52. Paynter, O.E., et al. Toxicology of Dalapon Sodium (2,2-Dichloropro-
pionic Acid, Sodium Salt). J. Agr. Food Chem. 8: 47, 1960.
53. Thompson, D.J., C.G. Gerbig, and J.L. Emerson. Results of Tolerance
Study of 2, 2-Dichloropropionic Acid (Dalapon) in Pregnant Rats. Unpub.
rept. HH-393, Human Health Research and Development Center, The Dow
Chemical Company, Zionsville, Ind. Sept. 29, 1971. Cited in Reference
4.
54. Emerson, J.L., D.J. Thompson, and C.G. Gerbig. Results of Teratologi-
cal Studies in Rats Treated Orally with 2, 2-Dichloropropionic Acid
(Dalapon) During Organogenesis. Rept. HH-417, Human Health Research
and Development Laboratories. -The Dow Chemical Company, Zionsville,
Ind. Dec. 14, 1971.
55. Palmer, J.S. and R.D. Radeleff. The Toxicity of Some Organic Herbicides
to Cattle, Sheep and Chickens. ARS Production Research Report No. 106,
pp. 1-3, and 23. U.S. Department of Agriculture, 1969. Cited in Re-
ference 4.
56. Dunachie, J.F. and W.W. Fletcher. Effect of Some Herbicides on the
Hatching Rate of Hen's Eggs. Nature 215: 1406, 1967. Cited in Re-
ference 4.
57. Dunachie, J.F. and W.W. Fletcher. The Toxicity of Certain Herbicides
to Hen's Eggs Assessed by the Egg Injection Technique. Ann. Applied
Biol. 66: 515, 1970.
58. Morton, H.L., J.O. Moffett, and R.H. MacDonald. Toxicity of Herbicides
to Newly Emerged Honey Bees. Env. Entom. 1: 102-104, 1972.
59. Anderson, L.D. and E.L. Atkins. Toxicity of Pesticides and Other Agri-
cultural Chemicals to Honey Bees. Proc. Reg. Pest. Chem. Applicators.
Riverside, CA. April 3 and 4, 1967. Cited in Reference 4.
60. Duval, C.T. Pesticides and the Honey Bee. PANS 15: 321, 1969. Cited
in Reference 4.
61. King, C.C. Effects of Herbicides on Honey Bees. Gleanings in Bee
Culture, pp. 230-233 and 250-251, April Issue, 1964. Cited in Refe-
rence 4.
62. Atkins, E.L., L.D. Anderson, D. Kellum. and K W Neuman.
Honey Bees From Pesticides.. University of California, Division of
Agricultural Sciences, Leaflet 2883. September 1977. 14 pp.
A-77
-------
63. Dewitt, J.B. Toxicity of Pesticides to Upland Birds and Wildfowl.
Toxicity of Dalapon (Sodium 2,2-Dichloropropionate) . Work Unit D-1.7,
Bureau of Sport Fisheries and Wildlife, U.S.D.A. , Patuxent, MD. 1962.
Cited in Reference 4.
64. Lawrence, J.M. Aquatic Herbicide Data. Agricultural Handbook No. 231,
Agricultural Research Service, U.S. Department of Agriculture, Washing-
ton, D.C. 1962. Cited in Reference 4.
65. Lawrence, J.M. Aquatic Herbicide Data, Supplement I. Agricultural
Experiment Station, Auburn U. , Auburn, Ala. pp. 1-65, 1962. Cited in
Reference 4.
66. Folmar, S.C. Overt Avoidance Reactions of Rainbow Trout Fry to Nine
Herbicides. Bull. Environ. Contam. Toxicol. 15(5): 509-519, 1976.
67. Butler, P. A. Effects of Herbicides on Estuarine Fauna. S. Weed Control
Conf. Proc. 18: 57, 1965. Cited in Reference 4.
68. Fox, C.J.S. The Effects of Five Herbicides on the Numbers of Certain
Invertebrate Animals in Grassland Soil. Can. J. Plant Sci. 44: 405.
1964. Cited in Reference 4.
69. Courtney, W.D., D.V. Peabody, and H.M. Austinson. Effects of Herbi-
cides on Nematodes in Bentgrass. Plant Disease Reporter 42: 256. 1962.
Cited in Reference 4.
70. Edwards. C.A., E.B. Dennis, and D.W. Empson. Pesticides and the Soil
in an Arable Fleld' Ann- APP1' Bl01'
71. Reid, J.J. Bacterial Decompsoition of Herbicides. Proc. NE Weed Con-
trol Conf. 14: 19, 1960. Cited in Reference 4.
72. Mayeux, J.V. and A.R. Colmer. Appl. Microbiol. 10: 206, 1962. Cited
in Reference 15.
73. Magee, L.A. and A.R. Colmer. Appl. Microbiol. 2: 288, 1955. Cited in
Reference 15.
74. Worsham, A.D. and J. Giddens. Weeds, 5: 361, 1957. Cited in Reference
JL j •
75. MacKenzie, K.A. and I.e. Macrae. Tolerance of the Nitrogen-Fixing
System of Azobacter vinelandii for Four Commonly Used Pesticides.
Antonie van Leenmenhoek 38: 529, 1972.
76. Magee, L.A. Dissertation Abstr. 19: 413, 1958. Cited in Reference 15.
77. Hale, M.G., et al. Weeds 5: 331, 1957. Cited in Reference 15.
?8< ?"SsBG'H«,a!; ?l'» !acteri0^ Proc-
-------
79. Elkari, G.H. and W.E.C. Moore. Can. J. Microbiol. 6: 339, 1960. Cited
in Reference 15.
80. Walsh, C.E. Effects of Herbicides on Photosynthesis and Growth of
Marine Unicellular Algae. Hyacinth Control J. 10: 45, 1972. Cited in
Reference 4.
81. Venkataraman, G.S. and B. Rayyalakshini. Tolerance of Bluegreen Algae
to Pesticides. Current Sci. 40: 143, 1971. Cited in Reference 4.
A-79
-------
Common Name: Dicamba
Chemical Name: 3,6-dichloro-o-anisic acid
Major Trade Name: Banvel
Major Applications Dicamba is used primarily for site preparation in
in Forestry: southeastern pine forests and in the Pacific Northwest.
SUMMARY
h,pn f" °Vhe !tUdleS °n the fate of dicamba in th* environment have
been on non-forest systems. There is a limited amount of data available in
connection with application to forests. avaxj-aoie in
matr °f dlCamba 1S faV°red in soils with a hi8" organic
matter and moisture content, and at higher temperatures. Degradation is
primarily due to microbial action. Under field conditions, Scamba will
of di~V°, P6r! SJ m°re thSn S6Veral m°nths in most soils- The products
of dicamba degradation in soil are 3,6-dichlorosalicyclic acid and C02.
Dicamba has been shown to volatilize from soil and leaf surfaces but
.
-
1y
location, and metabolism. Dicamba has a low level of acute toxic ity?o
mammals and birds. The oral LD50 of y
S?
accumulat ave>' n°n-toxic to ^ees. It does not bio
A-80
-------
1.0 INTRODUCTION
Dicamba, 3,6-dichloro-o-anisic acid, was introduced in the early 1960's
as a selective herbicide for preemergence and postemergence control of an-
nual broadleaf and grassy weeds in cereals (1). It is currently registered
for brush control along rights-of-way and for control of both annual and
perennial broadleaf weeds in corn, sorghum, small grains, rangeland, pas-
tures, turf, and noncropland (2). Foliar and soil applications of dicamba
can be used to control phenoxy-tolerant broadleaf weeds and brush species
(3).
In forestry, dicamba is used primarily for site preparation since it
is highly phytotoxic to conifers (4,5,6). It is used to control deciduous
shrubs and trees, conifers and forbs (7). In the Pacific Northwest forests,
dicamba has been effective in controlling western swordfern (A), chinquapin
oak and associated hardwoods, alder, vine maple, and maple stump sprouts
(8).
Complete quantitative data on the extent of dicamba use in forestry
are not available. Based on a survey of major timber companies, no dicamba
was used by these companies in the southwest in 1979. However, USFS has
reported -some use of dicamba in the southeastern pine forests in 1979 (9).
These reported uses are shown in Table 1.
TABLE 1. DICAMBA USE BY THE USFS IN SOUTHEASTERN PINE FORESTS
IN FY 1979 (9)
Amount Used
11 Ibs dicamba
(+23 Ibs 2,4-D)
24 Ibs dicamba
(+48 Ibs 2,4-D)
32 Ibs dicamba
(+64 Ibs 2,4-D)
675 Ibs dicamba
(+1350 Ibs 2,4-D)
394 Ibs dicamba
(+803 Ibs 2,4-D)
Units Treated
23 acres
140 acres
90 miles
(spot treatments)
810 acres
773 acres
Target Pest/Purpose
aquatic weeds
thistle control
weed control for right-
of-way
site preparation
release
A-81
-------
The USFS pesticide use report for FY 1976 indicates that only 0.2 Ibs
of dicamba were used by the USFS in Region 5 (California) to treat 0.3 acres
for release (10). No dicamba use was reported for FY 1977, 1978, or 1979.
In Region 6 (Oregon and Washington) (10), USFS pesticide use for FY 1975-
1979 is shown in Table 2. The data includes the use of dicamba for all
purposes on USFS lands.
The BLM pesticide use report for FY 1979 for the State of Oregon indi-
cates 0.5 Ib/acre of dicamba (combined with one Ib of 2,4-D/acre) was
applied to 51 acres over 21 miles on weeds and grasses for road maintenance.
564 Ibs of 2,4-D + dicamba was used on 937 acres for grass and brush in
site preparation (10).
Dicamba is an effective plant growth regulator which alters root and
shoot development and elicits a number of morphological responses including
leaf malformation, increased branching, petiole and stem curvature, and
abnormal flowering (11,12,13). It has been shown to destroy the phloem,
cambium and associated parenchyma cells in nodal tissues of alligatorweed
(14) and to inhibit mitosis in barley (15).
Dicamba is usually formulated as a highly water-soluble sodium, potas-
sium or dimethylamine salt (16). It is frequently combined with other her-
bicides, particularly with phenoxy herbicides, to give wider spectrum weed
control (17,18). Dicamba is registered for forest use as an oil-soluble
liquid, a water-soluble liquid, and an emulsifiable concentrate (19). The
dimethylamine salt in water and the oil-soluble formulation contain 4 Ibs
acid equivalent/gal (2). The dimethylamine salt can be applied in all
seasons and is used undiluted or diluted 1:4 in water for cut surface in-
jection into hardwoods or conifers (7,19). The dimethylamine salt plus
2,4-D is commonly applied in the spring to mid-summer to the foliage of
shrubs and weed trees in site preparation (7,19). The oil-soluble acid of
dicamba plus the isooctyl ester of 2,4-D is applied in the fall to late
winter for shrub and weed tree control in site preparation (7,19).
The basic producer of dicamba in the U.S. is Velsicol Chemical Corpora-
tion which manufactures dicamba under a variety of trade names. Velsicol
also produces dicamba in combination with other herbicides. For example,
Banvel K and Weedmaster contain dicamba and 2,4-D. MonDak contains dicamba
A-82
-------
TABLE 2. DICAMBA USE ON USFS LANDS IN REGION 6 FOR FY 1975-1979 (10)
FY
1975
1976
L977
.978
979
-
Herbicide
dicamba
dicamba
Banvel 720*
Banvel 520*
Banvel+2,4-D
dicamba
dicamba
dicamba+2,4,5-T
Banvel 120
Banvel 4 WS
Banvel 720*
dicamba
dicamba+2 , 4-D
Banvel 720*
Banvel 4S
dicamba
dicamba
dicamba
Pounds Used
9
28
118.5
unknown
• 300
93
640
—
7.5
176
1.5
25
22 (dicamba)
3 (dicamba)
532
27
180
15
Units Treated
40 acres
35 mi.
116.1 acres
2.5 acres
161.2
23 acres
298.5 acres
27 acres
~
—
—
50 acres
8 si. mi.
3 acres
283 acres
110 acres
20 acres
29 acres
Target Pest/Purpose
For noxious and poison
weed control/range manage
ment on NF* land
Road right-of-way
On brush under powerlines
on FS^ land
On brush under powerlines
On brush under powerlines
For site preparation on
FS land
For right-of-way on FS
land
For right-of-way on FS
land
For right-of-way on FS
land
For right-of-way on FS
land
For right-of-way on FS
land
For noxious weed control
on FS land
Road right-of-way
For powerline right-of-
way on FS land
For powerline right-of-
way on FS land
For noxious weed control
on FS land
For site preparation on
National Forest System
lands
For noxious weed control
NF • National Forest
fFS = Forest service
*dicamba+2,4-D
A-83
-------
and MCPA (4-chloro-2-methyl phenoxyacetic acid) (2). The major formulations
of dicamba are listed in Table 3.
2.0 PHYSICAL AND CHEMICAL PROPERTIES OF THE ACTIVE INGREDIENT
The active ingredient of dicamba is 3,6-dichloro-o-anisic acid (or
2-methoxy-3,6-dichlorobenzoic acid):
COOH
OCH.
It is a white, crystalline solid with a melting point of 114e-116°C. It is
poorly soluble in water but highly soluble in most organic solvents (16).
The solubility at 25eC is as follows (3):
Solvent Solubility, e/100 ml
Ethanol 92.2
Heavy aromatic naphthanes 5.2
Water 0.45
Xylene 7>8
The alkali metal and amine salts of dicamba are highly water soluble (16) .
The dimethylamine salt has a water solubility of greater than 72 g/100 ml.
Dicamba is stable to oxidation and hydrolysis and resistant to acid and
strong alkali (3). Its vapor pressure is 3.41 x 10"5 mm Hg at 25°C (3) and
3.75 x 10~ mm Hg at 100 °C (1).
3.0 ENVIRONMENTAL FATE
3.1 UPTAKE AND METABOLISM IN PLANTS
Dicamba is rapidly absorbed by the roots or foliar tissues of plants
and is readily translocated (21). The rate of absorption, movement and dis-
tribution in the plant may vary with the species (22,23) and with the stage
of growth (12,24). Studies on a variety of plant species (grape, Johnson-
grass, bean, purple nutsedge, Tartary buckwheat, wheat, barley, wild mustard,
Canadian thistle) have shown that root-absorbed dicamba is translocated to
foliar tissues (1). Foliar-absorbed dicamba is translocated both basipetally
A-84
-------
TABLE 3. VELSICOL'S BANVEL FORMULATIONS* (20)
Product
Concentration of
Active Ingredient
Federally Registered Utet
Banvel Herbicide
(water soluble liquid)
4 Ibs/gal dicimba
(DMA i lit)
Field corn. Small grains. Sorghum.
Pastures and Rangeland, Noncropland.
Gran grown (or teed. Tree injection.
Harvest aid-Sofghum, Cropland rotated
to wheat
Banve! 45
(water soluble liquid)
Banvel * 2,4-0
(water soluble liquid)
Banvel K
(water soluble liquid)
Banvel 5G
(granules)
Banvel 4 O.S.
(oil soluble liquid)
Banvel 4 W.S.
(water soluble liquid)
Banvel 520
(oil soluble liquid)
Banvel 10G Granules
Banvel 2% Granules
MonDak
(water soluble liquid)
Provel
Weed master
(water soluble liquid)
Banvel 720
(water soluble liquid)
Banvel X.P.
(pellets)
Brush Buster
(water soluble liquid)
4 Ibs/gal dicamba
(DMA salt)
1.5 Ibs/gal
dicamba + 3 Ibs/gal
2.4- D (DMA salt)
1.25 Ibs/gal
dicamba + 2.5 Ibs/gal
2,4-0 (DMA salt)
5% dicamba
(free acid)
4 Ibs/gal dicamba
(free acid)
4 Ibt/gal dicamba
(DMA salt)
t Ib/gal dicamba
(free acid) 2 Ibs/gal
2.4- D
(isooctyl ester)
10% dicamba (free acid)
2% dicamba
1.25 Ibs/gal dicamba
2.5 Ibs/gal MCPA
(DMA salts)
0.23 tbs/gal dicamba
0.92 Ibs/gal 2.4- D
(DMA salts)
1 Ib/gal dicamba
3 Ibs/gal 2,4-D
(DMA salts)
1 Ib/gal dicamba
2 Ibs/gal 2.4-D
(DMA salts)
10% dicamba
(free acid)
1 Ib/gal dicamba
2 Ibs/gal 2.4-D
(DMA salts)
Lawns and Turf
Lawns and Turf
Field corn, Fall seeded wheat
Pasture, Rangeland, Noncropland
industrial
(tank mix with 2,4-D or 2.4,5-T only)
Industrial
(alone or tank mix with 2.4-D or 2,4,5- T)
Industrial
Brush
Lawns and Turf
Wheat, Noncropland
Lawns and Turf
Pasture and Rangeland, Noncropland
Industrial
Pasture. Rangeland Noncropland
Brush and weed control, Noncropland
_ ' — — •" •
2,4,5-T formulations are excluded from this list.
tank-mixes and combinations are available also.
Many federally approved
A-85
-------
and acropetally. It is continually redistributed from mature leaves to
younger leaves and meristematic tissues. There is a limited amount of basi-
petal translocation to the roots and excretion into the surrounding soil or
nutrient solution (1).
Dicamba metabolism in plants is species dependent (1,25). In wheat,
bluegrass, Tartary buckwheat, wild mustard, barley and corn, the major path-
way of dicamba metabolism appears to involve an initial ring hydroxylation
at the 5 position followed by rapid formation of polar, acid-labile conju-
gates (1). In wheat and Tartary buckwheat, the majority of the 5-hydroxy-
dicamba is probably conjugated as an 0-glucoside (26,27). There are also
minor pathways for dicamba metabolism in plants including demethoxylation
to yield DCSA (3,6-dichlorosalicyclic acid) and DCGA (3,6-dichlorogentisic
acid) which are also conjugated (1). Foy and Penner (30) found that dicamba
inhibited the tricarboxylic acid cycle substrate oxidation by mitochondrial
fractions isolated from etiolated cucumber cotyledons.
The metabolism of dicamba to 5-hydroxy-dicamba and its subsequent con-
jugation appears to be an effective detoxification mechanism in higher
plants (1). Other ways in which residues can be dissipated are by exudation
through the roots or by loss from leaf surfaces (28).
The persistence of dicamba in range forage grasses has been studied by
Morton, et al. (29). Dicamba (DMA salt) labelled in the carboxyl position
was applied at a rate of 1 Ib/acre to pasture consisting of various range
grasses over a three-year period. The amine salt of dicamba had an apparent
half-life of two weeks in green tissues of silver beardgrass, little blue-
stem and dallisgrass. The average half-life of dicamba in the litter
tissues was 2.6 weeks.
3.2 FATE IN SOIL
Processes which may affect the fate of dicamba in soil are volatiliza-
tion, leaching and adsorption, runoff, photodecomposition, and degradation.
Degradation appears to be primarily microbial.
3.2.1 Volatilization
Dicamba has been shown to volatilize from soil and leaf surfaces, but
the extent and significance of losses due to volatility have not been
A-86
-------
determined (1). Centner (31) showed that vapors from the soil-incorporated
dimethylamine salt of dicamba were phytotoxic to beans. Burnside and Lavy
(32), in studies using C-carboxyl labelled dicamba (acid), showed that
very little dicamba was lost over an 8-week period when dicamba-treated
soils autoclaved prior to treatment were incubated at 35°C under various
relative humidities (0-100 percent). On bare planchets, there was a loss
of 48 percent at 35°C over a period of 11 weeks.
In recent studies by Behrens and Lueschen (33), dicamba volatility was
examined in the field and in growth chambers. In the field experiments,
potted soybeans exposed to vapors arising from corn foliarly-treated with
various salts of dicamba developed dicamba injury symptoms. Dicamba vola-
tilization was detected for three days after the application. In the growth
chamber studies, the effects of dicamba volatility on soybeans were reduced
by lowering the temperature or by increasing the relative humidity. Vola-
tilization was influenced by the surface on which dicamba was deposited.
The acid form was the most volatile and inorganic salts were the least
volatile in growth chambers. However, in the field, the use of less volatile
formulations did not eliminate symptoms on soybeans. The volatile component
of the dimethylamine salt of dicamba was identified as free dicamba acid.
3.2.2 Adsorption and Leaching
Dicamba is considered to be a very mobile pesticide (34,35,36). In
studies using soil thin layer chromatography to evaluate the mobility of 40
pesticides on Hagerstown sicl soil (2.5 percent organic matter, 39.5 percent
clay, pH 6.8), Helling (34) found that dicamba was one of the most mobile
pesticides tested with an Rf value of 0.96. Rf values for the pesticides
tested ranged from 0 to 0.96. In further studies on 14 surface soils with
13 pesticides, Helling (35) found that dicamba was the most mobile pesticide
tested. Dicamba mobility was significantly correlated with PH at the 5 per-
cent level with greater mobility occurring at higher pH.
Other studies on the relative mobility of 28 herbicides in silty clay
loam and sandy loam soils using soil columns have shown that dicamba was
second only to 2,3,6-trichlorobenzoic acid (2,3,6-TBA) in mobility (37).
Grover (38) studied the movement of dicamba in five Canadian prairie
soils using soil columns. The relative movement of dicamba indicated an
A-87
-------
inverse relationship between adsorption and mobility in soil. The volume
of water required to leach 50 percent of the dicamba through the soil columns
varied from 13 ml to 35 ml with larger volumes required for soils with
greater amounts of organic matter.
The ready movement of dicamba in soil suggests that there is a limited
amount of adsorption to soil particles or colloids (39). In general, ad-
sorption studies have shown that dicamba is adsorbed onto kaollnite clay but
that there is little adsorption onto other clays and soil types studied (32).
It was suggested that the adsorption onto kaolinite was due to its consider-
able anion adsorption capacity. (Electrophoresis studies have shown that
dicamba behaves as an anion over the pH range 4.1 to 9.4.) Carringer, et al.
(41) studied adsorption and desorption of dicamba on soil organic matter and
Ca-saturated montmorillonite. Dicamba was adsorbed by the montmorillonite
but not by organic matter> Only 9.54 percent of the applied dicamba was de-
sorbed using deionized water while 41.6 percent was desorbed with 1 N CaCl .
This suggests that some dicamba was strongly adsorbed. In studies on adsorp-
tion of dicamba by humic acid, Khan (42) found that humic acid could retain
dicamba in amounts of 44 y moles dicamba per 1 g of humic acid. Prolonged
washing with distilled water did not release any herbicide. It was concluded
that this complexing of dicamba and humic acid could affect the activity,
behavior, bioavailability and survival rate of dicamba in the soil and aqua-
tic environment. Other studies on adsorption of the major degradation pro-
duct of dicamba, 3,6-DCSA, indicate that at least 30 percent is adsorbed to
all soil types (40). The greatest adsorption of DCSA occurred on silty clay
soil (55 percent) while the least amount was adsorbed to the sandy loam soil
(30 percent).
Dicamba is readily leached from soils (43,44). Studies in soil columns
show that the dimethylamine salt of dicamba followed slightly behind the
forward penetration of added water in both loam and sandy loam soils (39).
In studies with dicamba (acid) applied to 1.5 x 1.5 m plots of silt loam soil
in a humid, temperate climate at rates of 1.1, 2.2, and 4.5 kg/ha, small
amounts of dicamba leached to a depth of 10-20 cm (45). None was detected
below 20 cm. However, results obtained with the acid may not be representa-
tive of the more commonly used dimethylamine salt form which is expected to
move readily through the soil when excessive rainfall occurs (32). In
A-88
-------
another study, Banvel D was applied to a lysimeter with silt loam soil at a
rate of 5.6 kg active ingredient/ha (46). Residues of dicamba at 0.7 ppb
were first detected in the percolation water 10 months after application.
Subirrigation and surface evaporation studies by Harris (44) have shown that
dicamba may also move upward in the soil profile, depending on the water
flux and capillary water movement.
3.2.3 Runoff
The salts of dicamba are highly water-soluble and readily enter the
soil. Therefore, contamination of local surface waters due to runoff is un-
likely except in the event of heavy rainfall very shortly after dicamba
application. The loss of dicamba in runoff water was determined on sod and
fallow clay loam soil plots with slopes of 3 percent and 8 percent (47).
The dimethylamine salt was applied at a rate of 1-2 Ib/acre and simulated
rainfall of 0.5 in/hr was applied 24 hours after dicamba application. Of
the 177 L of water applied, 15 L were recovered as runoff. The concentra-
tion of dicamba in the runoff and the total amount of dicamba from sod and
fallow plots with a 3 percent slope are as shown:
Dicamba Concentration, ug/ml Total Dicamba (Ib/A)
Soil Cover Time After Application Time After Application
24 hr. 4 mo. 24 hr. 4 mo.
Sod
Fallow
4.81
1.60
0
0.018
0.065
0.017
0
0.0032
Bean plant bioassays indicated that there was sufficient dicamba in 100 ml
of runoff water obtained 24 hours after application to kill the plants.
Four months after application, the amount was not sufficient to kill the
plants.
In another experiment, Banvel D was applied in May to a lysimeter and
to an adjacent soil plot (4.1 m2) of silt loam soil at a rate of 5.6 kg
active ingredient/ha, a rate 3-10 times the rate commonly used for weed
control (46). Runoff samples collected after storms in August and September
contained 0.23 and 0.54 ppm, respectively.
Norris and Montgomery (48) analyzed stream water samples for dicamba
following forest application of 1.12 kg dicamba per ha in 37.8 liters of
water. Samples of water were collected periodically for nearly 14 months
A-89
-------
after application, but no dicamba residues were found more than 11 days
after application despite the persistence and leaching characteristics of
dicamba and the potential for runoff.
3.2.A Photodecomposition
Photodecoraposition is probably not a major route for dicamba degrada-
tion. Bioassays for aqueous dicamba solutions (0.0625 to 1 ppmw) exposed to
sunlight for up to 16 days indicate that dicamba toxicity remained at a
level sufficient to inhibit growth of cucumber roots (49). Although there
was a slight decrease in toxicity, it could have been due to biological de-
gradation.
3.2.5 Degradation
The degradation of dicamba is favored in soils high in organic and
moisture content, and at higher temperatures. Research suggests that dicam-
ba degradation is, to a large extent, due to microbial breakdown. Burnside
and Lavy (32) applied C-labelled dicamba to silty clay loam, silt loam,
and sandy loam soils and incubated them at moisture levels 13 percent and
18 percent of field capacity at temperatures of 15°, 25°, and 35'C. Soybean
bioassays were used to test the phytotoxicity of dicamba over a 9 month
period. Dedication was found to be greater in soils with more organic
matter, in soils with a higher level of moisture, and at higher temperatures.
In greenhouse studies using five soils, the amount of dicamba initially re-
quired to reduce the fresh weights of snap beans was found to increase as
the clay and organic matter increased (50). Hahn, et al. (49) using cucumber
bioassays, found that dicamba was degraded faster in silty clay loam soil
than in sandy loam soil, faster in surface soil than in subsurface soil, and
faster at higher temperatures. It was suggested that degradation is likely
to occur faster in those soils with the relatively .high organic matter levels
(e.g., the silty clay loam and the top-soil) because of larger microbial
populations.
In laboratory studies on three prairie soils, high organic silty clay,
sandy loam, and heavy clay, Smith (51) found that dicamba disappearance was
most rapid on the silty clay soil. Breakdown of dicamba took 2 weeks at all
moisture levels. In the sandy loam and heavy clay soils, however, degrada-
tion was dependent on the soil moisture. At a high moisture level (35 per-
A-90
-------
cent), less than 10 percent of the applied dicamba was detected after 4 weeks.
At levels near the wilting point, residues were still detected after 6 weeks.
When the three soils were sterilized prior to dicamba application, over 90
percent of the dicamba was recovered after 4 weeks.
14 14
Smith (40) also studied degradation of C-ring and C-carboxyl la-
belled dicamba in moist, non-sterile, heavy clay in flasks at 25°C. Over 50
percent of the dicamba was lost within 4 weeks. The sole degradation products
were 3,6-dichlorosalicyclic acid (3,6-DCSA) and C0_. In additional studies,
14
Smith (40) compared the decomposition of C-ring labelled dicamba in 3
soils: silty clay, heavy clay, and sandy loam. There was a buildup of 3,6-
DCSA as dicamba degraded, followed by a slow loss of DCSA which was complete
in 9 weeks. In steam sterilized soils, there was negligible breakdown of
dicamba.
Burnside, et al. (53) followed the dissipation and detoxification of
dicamba for 6 years at three locations in Nebraska. The soil types and
characteristics were as follows:
Soil Type % Sand
(2-
0.05 mm)
Rosebud loam
Holdrege loam
49
37
% Silt
(0.05-
0.002 mm)
32
41
% Clay pH
(0.002
mm)
19
22
6.8
7.1
Moisture
% at
15 atro
8.6
10.8
Organic
Matter,
%
1.2
2.6
C • E * 0 •
meq/100g
15
20
Sharpsburg
silty clay 2 59 39 5.8 14.3 4.4 24
loam
Dicamba was applied at 5, 10, and 20 Ib/acre and its persistence was deter-
mined by field bioassays growing field beans and soybeans. Field bean yields
were significantly reduced only in rosebud loam sprayed with 20 Ib/acre di-
camba (an average 40 percent reduction in yield). Dicamba apparently did not
persist at other application rates or in the other soils.
Smith and Cullimore (52) studied the effects of temperature variation
on the microbial degradation of ^C-carboxyl labelled dicamba applied at 2
ppm to three prairie soils (sandy loam, silty clay, and heavy clay) at field
capacity moisture levels. No loss of dicamba was observed in any soil at
-5°C In silty clay soil, more than 80 percent of the dicamba was degraded
at temperatures above 15'C after 8 days. In sandy loam and heavy clay soils,
A-91
-------
over 80 percent of the dicamba was degraded between 20° and 35"C after 14
days.
Studies have shown that the pH of the soil also influences the degrada-
tion and/or phytotoxicity of dicamba. Corbin and Upchurch (54), using high
organic matter soils, determined that the optimum pH for detoxification of
dicamba is 5.3. Cucumber seed assays showed complete detoxication of 14.4
ppm within 4 weeks. At pH 7.5, dicamba persisted. Another study indicated
that the phytotoxicity of dicamba increases as the soil pH increases, reach-
ing a maximum at pH 6.5 and 7.5 (55). The reported persistence of toxic
concentrations of dicamba has varied from 30 days (32) to over one year (57).
However, based on the studies reviewed below, under field conditions, dicamba
will probably not persist more than several months in most soils. This is
likely to be the case for forest soils which usually have high levels of
organic matter and moisture. Smith (51) applied 1.1 kg/ha of dicamba to
field plots 20 x 20 cm and analyzed the soil for dicamba residues approxima-
tely six months after application. No residues were recovered at depths up
to 15 cm in soil. Altom and Stritzke (56) applied the dimethylamine salt of
.dicamba in a water solution to forest and grassland soils to give a concen-
tration of 2.47 ppm (W/W). Soil samples were taken over a period of 100 days.
The half-life of dicamba ranged from 17 to 32 days in the soils tested. In
other studies, an amine salt of dicamba was applied to the surface of a silty
loam soil (1.5 x 1.5 m plots) in a humid, temperate climate at the rates 1.1,
2.2, and 4.5 kg acid equivalent/ha (45). After 42 days, about 5 percent of
the applied dicamba remained.
Dicamba was applied to Texas grassland soils with neutral to slightly
basic pH and low organic matter content at application rates of 0.28 0 56
0.84, and 1.12 kg/ha (58). Data indicated that 1.12 kg/ha or less of applied
dicamba will dissipate during the growing season following spring application.
Residues were not found below 180 cm at any time in any soil up to 53 weeks
after application at the rates used.
3.3 PERSISTENCE IN WATER
Few studies have been conducted on the persistence and degradation of
dicamba in water. In one field study, 1.12 kg/ha of dicamba and 2.24 kg/ha
of 2,4-D in 37.8 1 water was aerially applied to 67 ha of a 244 ha forestland
A-92
-------
watershed (48). Residues were found at the first sampling point about two
hours after application. Residue levels rose to a maximum of 37 ppb in
about 5.2 hours and then slowly declined to background levels by 37.5 hours.
No dicamba residues were found more than 11 days after application. The
authors concluded that dicamba could have been adsorbed by stream sediments
or taken up by aquatic biota.
The fate of dicamba in water has also been studied using a model eco-
system containing sand, water, and a series of food chain organisms compa-
tible with conditions in the aquarium (59). Using this model ecosystem,
C-carboxyl labelled dicamba in acetone was applied to the leaves of sorghum
plants (60). The concentration of dicamba and its metabolites in the water
reached a peak the 6th day after application and then slowly decreased, in-
dicating that decarboxylation*of dicamba does not occur rapidly. About 0.2
percent of the radioactive materials could be ether-extracted from raw water.
After hydrolysis with HC1, 98.8 percent could be extracted. It was concluded
that most of the dicamba and its metabolites persisted in conjugated or in
anionic forms in water. After hydrolysis, dicamba was slowly transformed to
5-hydroxydicamba (about 10 percent after 32 days).
4.0 IMPACTS ON NON-TARGET ORGANISMS
4.1 PHYTOTOXICITY
The sensitivity of plants to dicamba varies considerably (61). Dicamba
selectivity depends on differences in its distribution within a plant species
and differences in the rate of absorption, translocation, and metabolism (1).
Rapid metabolism in tolerant plants detoxifies dicamba (26), effectively re-
ducing the concentration of highly mobile unchanged dicamba which is avail-
able for transport to sensitive target sites (1).
Dicamba has been found to be phytotoxic to many deciduous shrubs and
trees, conifers, and forbs (7). Patric and Campbell (62) have categorized
plants in West Virginia according to their susceptibility to dicamba. These
categories are shown in Table 4. These examples illustrate the broad spec-
trum of plant species affected by dicamba.
A-2 TOXICITY TO FISH, BIRDS, WILDLIFE, AND INSECTS
Dicamba has a low order of acute toxicity for oral, dermal and inhala-
tion exposure to mammals (28). Table 5 gives some toxicity values for
A-93
-------
TABLE 4. SENSITIVITY OF PLANTS IN WEST VIRGINIA TO DICAMBA (62)
Least Susceptible
American beech Chestnut oak
Fern Grasses
Hickory Sedge
Striped maple Sugar maple
W111^ ash witch hazel
Intermediate in Susceptibility
Blackberry Black birch
Black cherry Black gum
Chestnut Cucumber tree
Deertongue grass Dock
Fireweed Flowering dogwood
Loosestrife Red maple
Red oak Sassafras
Serviceberry Sourwood
Violet
Most Susceptible
American elder Azalea
Bindweed Black locust
Pin cherry Pokeweed
Puckley ash sh
Smartweed Staghorn sumac
TeaberrV Twisted stalk
specific formulations. Dicamba is not a skin irritant although some formu-
lations are extremely irritating and corrosive to the eyes (28), When fed
to rats as the DMA salt over a period of about 13 weeks, Banvel produced an
overall no-effect level at 500 Ppm. AS indicated in Table 5, dicamba also
has a low level of toxicity to wildfowl. Dicamba is more toxic to fish than
to birds or mammals.
Dicamba has been shown to be relatively non-toxic to bees. When fed to
honeybees in a 60 percent sucrose solution at concentrations of 0, 10, 100,
and 1000 ppmw, dicamba and the dimethylamine salt of dicamba did not cause
any significant differences in the half-life of bees at any concentration
A-94
-------
(66). When bees were dusted with dicamba at a dose of 91 ug/bee, mortality
was 2.6 percent (67).. For comparison with field conditions, an application
rate of 1 kg/ha would give a dose of 1.12 ug/bee. Therefore, at recommended
application rates, dicamba is considered relatively non-toxic to bees.
4.3 BIOACCUMULATION
Dicamba does not tend to bioaccumulate in animals. In rats, it is
rapidly excreted in the urine with approximately 20 percent of the urinary
metabolites in the form of glucuronic acid conjugates (69). Because of its
high solubility, most dicamba residues are in the aqueous parts of the body
rather than in fatty tissues (68). Studies using a model ecosystem have
provided no evidence that dicamba or its metabolites are magnified in the
food chain (60). The total equivalent of radioactivity decreased from 1.6
ppm in algae to 0.02 ppm in fish in the model ecosystem food chain involving
algae to mosquito to fish (60) .
A-96
-------
REFERENCES
1. Frear, D.S. 1976. "The Benzole Acid Herbicides", Ch. 11 in Herbicides
- Chemistry. Degradation and Mode of Action, Kearney, P.C. and Kaufman,
D.D., eds. Marcel Dekker, Inc. N.Y.
2. 1980 Farm Chemicals Handbook. Meister Publishing Co., Willoughby, Ohio.
3. Mullison, W.R. 1979. Herbicide Handbook of the Weed Science Society
of America, WSSA, Champaign, Illinois, 4th Edition, 518 pp.
4. Stewart, R.E. 1976. Herbicides for Control of Western Swordfern and
Western Bracken. USDA Forest Service Research Note PNW-284.
5. Newton, M. and C.A. Roberts. 1979. Brush Control Alternatives for
Forest Site Preparation. Oregon Weed Control Conf., Salem, OR.
6. USFS, 1974. Vegetation Management with Herbicides. EIS-OR-73-1637-D.
7. USDA-States-EPA 2,4,5-T RPAR Assessment Team. 1979. The Biologic and
Economic Assessment of 2,4,5-T, Report of the USDA-States-EPA RPAR Team.
8. BLM, 1978. Vegetation Management with Herbicides, Western Oregon.
Final EIS.
9. Herbicides Used by the USFS, 1979. EPA Forestry Report JEB 1, Job A,
6/3/80. p. 42.
10. USFS Pesticide Use Reports for FY 1975-1979, Region 5. USFS Pesticide
Use Reports for FY 1975-1979, Region 6. U.S. Bureau of Land Manage-
ment Pesticide Use Reports for FY 1978-1979, Oregon and Washington.
11. Leonard, O.A., et al. 1966. Weed Res. 6:37. In Reference 1.
12. Quimby, P.C. and J.D. Nalewaja. 1966. Weeds 14;229. In Reference 1.
13. Wax, L.M., et al. 1969. Weed Sci. 17:388. In Reference 1.
14. Pate, D.A., et al. 1965. Weeds 13:208. In Reference 1.
15. Wuu, K.D. and W.F. Grant. 1966, Can. J. Genet. Cytol. 8:481. In
Reference 1.
16. Melnikov, N.N. 1971. Chemistry of Pesticides. Residue Reviews, Vol.
36.
17. Skaptason, J.S. 1971. Proc. North Central Weed Control Conf. 26:35.
In Reference 1.
A-97
-------
18. Colby, S.R. 1967. Weeds 15:20. In Reference 1.
19. Newton, M. 1979. Herbicide and Insecticide Technical Properties and
Herbicide Use Guidelines.
20. Data provided by Velsicol.
21. Swanson, C.R. 1969. "The Benzoic Acid Herbicides", Ch. 11 in Degrada-
t.10.".-0* Herbicides, Kearney, P.C. and Kaufman, D.D., eds. Marcel Dekker,
Inc. N.Y. '
22. Quimby, P.C. and J.D. Nalewaja. 1961. Weed Sci. 19:598. In Reference
1 *
23. Chang, F.Y. and W.H. Vanden Born. 1971. Weed Sci. 19:113. In Refer-
ence 1. -
24. Magalhaes, A.C., et al. 1968. Weed Sci. 16:240. In Reference 1.
25. Audus, L.J 1976. Herbicides-Phy8iologv. Biochemistry. Ecology. Vol.
2. Academic Press, N.Y., 2nd Edition. - -
26. Chang, F.Y. and W.H. Vanden Born. 1971. Weed Sci. 19:107. In Re-
ference 1. — — __
27. Broadhurst, N.A., et al. 1966. J. Agric. Food Chem. 14:585. In
Reference 1. . -
T,v -T, and dicamba in range forage grasses. Weeds 15:268-271.
30. Foy D.L and D. Penner. 1967. Effect of Inhibitors and Herbicides
°Xi— * ^t- Cu Joer
31. Centner, W.A. 1964. Weeds 12:239. In Reference 1.
32. Burnside^O.C. and T.L. Lavy. 1966. Dissipation of Dicamba. Weeds
33. Behrens.^and W.E. Lueschen. 1979. Dicamba Volatility. Weed Sci.
34* f^rl\ C;S> ^rl1' Pestlcide Ability in Soils II. Applications of
Soil Thin-Layer Chromatography . Soil Sci. Soc. Amer. Proe.. 35: 737-
y H j 9 - ^^^•^""^"^^^•^•"^•«™«^^w«^»»
35. Helling, C.S. 1971 .Pesticide Mobility in Soils III. Influence of
Soil Properties. Soil Sci. Soc. Amer. Proc.. 35:743-748.
A-98
-------
36. Helling, C.S. and B.C. Turner. 1968. Pesticide Mobility: Determina-
tion by Soil Thin-Layer Chromatography. Science 162: 562-563.
37. Harris, C.I. 1967. Movement of Herbicides in Soil. Weeds 15: 214-216.
38. Grover, R. 1977. Mobility of Dicamba, Picloram, and 2,4-D in Soil
Columns. Weed Sci. 25(2): 159-162.
39. Friesen, H.A. 1965. The Movement and Persistence of Dicamba in Soil.
Weeds 13: 30-33.
40. Smith, A.E. 1974. Breakdown of the Herbicide Dicamba and Its Degrada-
tion Product, 3,5-dichlorosalicyclic Acid in Prairie Soils. J. Agric.
Food Chem. 22(4): 601-605.
41. Carringer, R.D., J.B. Weber, and T.J. Monaco. 1975. Adsorption-
Desorption of Selected Pesticides by Organic Matter and Montmorillonite.
J. Agric. Food Chem.. 23: 568-572.
42. Khan, S.U. 1973. Interaction of Humic Acid with Chlorinated Phenoxy-
acetic and Benzoic Acid. Environ. Lett., 4: 141-148.
43. Donaldson, T.W. and C.L. Foy, 1965. Weeds 13:195. In Reference 1.
44. Harris, C.I. 1964. Weeds 12:112. In Reference 1.
45. Stewart, D.K.R. and S.O. Gaul. 1977. Persistence of 2,4-D, 2,4,5-T,
and Dicamba in a Dykeland Soil. Bull. Environ. Contain. Toxicol..
18(2): 210-218.
46. Glass, R.L. and W.M. Edwards. 1979. Dicamba in Lyslmeter Runoff and
Percolation Water. J. Agric. Food Chem.. 27(4): 908-909.
47. Trlchell, D.W., et al. 1968. Loss of Herbicides in Runoff Water.
Weed Sci. 16(4); 447-449.
48 Norris, L.A. and M.L. Montgonery. 1975. Dicamba Residues in Streams
After Forest Spraying. Bull. Environ. Contam. Toxicol. 13(1): 1-8.
49. Hahn, R.R.. O.C. Burnside, and T.L. Lavy. 1969. Dissipation and
Phytotoxicity of Dicamba. Weed Sci. 17(1): 3-8.
50 Sheets T.J. et al. 1968. Persistence of Benzoic and Phenylacetic
Acid in Soils. Weed Sci. 16(2); 217-222.
51. Smith, A.E. 1973. Degradation of Dicamba in Prairie Soils. Weed Res.
13: 373-378.
« Smith A E and D.R. Cullimore. 1975. Microbiological Degradation of
5 the Serticide Dicamba in Moist Soils at Different Temperatures. Weed
Res. 15: 59-62.
C. G.A. Wicks, and C.R. Fenster. 1971. Dissipation of Di-
' L Across Nebraska. Weed Sci. 19(4): 323-325.
A-99
-------
54. Corbin, F.T. and R.P. Upchurch, 1967. Influence of pH on Detoxifica-
tion of Herbicides in Soil. Weeds 15: 370-377.
55. Corbin, F.T., et al. 1971. Influence of pH on the Phytotoxicity of
Herbicides in Soil. Weed Sci. 19(3); 233-239.
56. Altora, J.D. and J.F. Stritzke. 1973. Degradation of Dicamba, Piclo-
ram, and Four Phenoxy Herbicides in Soils. Weed Sci. 21(6): 556-560.
57. Dowler, C.C., et al. 1968. Effect and Persistence of Herbicides
Applied to Soil in Puerto Rican Forests. Weeds 16: 45-50. In Re-
ference 56.
58. Scifres, C.j. and T.J. Allen. 1973. Dissipation of Dicamba From
Grassland Soils of Texas. Weed Sci. 21(5): 393-396.
59. Metcalf, R.L. , O.K. Sangha, and I. P. Kapoor. 1971. Environ. Sci.
Tech. 5<9): 709- Model Ecosystem for the Evaluation of Pesticide Bio-
degradability and Ecological Magnification.
60. Yu, C.C., et al. 1975. Fate of Dicamba in a Model Ecosystem. Bull. •
Environ. Contain. Toxicol. 13: 280-283. -
61. Pond, F.W., et al. 1972. Environmental Statement - Background Docu-
ment - Pesticides. Dicamba, EPA.
^H« and J- cf Pbell. 1970. Some Experiences with Dicamba in
Controlling Revegetation of Deforested Land In West Virginia. NE Weed
Control Conf. Proc., Vol. 24: 61-68. In Reference 61.
"* B±°n!;;/wn,n
-------
Common Name: 2,4-D
Chemical Name: 2,4-dichlorophenoxyacetic acid
Major Trade Names: Weedone LV-4; Esteron 99 Concentrate; Weedar 64;
Verton 2-D
Major Applications Used in the Pacific Northwest and Great Lakes primarily
in Forestry: as a selective broadleaf weedkiller in connection with
site preparation. Has limited use for release.
SUMMARY
Most of the available data on the fate of 2,4-D in soil and water is
the result of laboratory or field studies in non-forest systems. There is
limited data available in connection with applications to forests.
Plants readily absorb, translocate and metabolize 2,4-D. The formula-
tion influences the degree of absorption. Once absorbed, 2,4-D may be
chemically altered by a variety of mechanisms. Since brush usually re-
sprouts within a year after spraying 2,4-D on forest lands, it is believed
that residues at phytotoxic levels do not persist in the vegetation.
2,4-D is considered to be a relatively nonpersistent herbicide. The
most persistent form of 2,4-D in the environment is the acid. Esters and
amines of 2,4-D hydrolyze to the acid within a few days in the soil. Degra-
dation of the acid is primarily microbial. In warm, moist soils with a high
organic content, 2,4-D can degrade within days, but 2,4-D can persist for
many months in the absence of favorable soil conditions. Leaching of 2,4-D
is more extensive in soils with lesser amounts of organic matter and with a
lower pH. Leaching and adsorption are inversely related. In general, 2,4-D
remains within the top foot of the soil surface.
In water esters of 2,4-D are rapidly hydrolyzed to the acid form. The
persistence of the acid depends on the presence of microorganisms adapted to
H-D degradation. In cool, nutrient-poor, natural surface waters, 2,4-D
Jn!?n stable for many months. Photodecomposition has been demonstrated
inytnriaboratory Although the degree of 2,4-D degradation in the field with
natural sunUght is unknown. Volatilization is usually not a major mechanism
for removal of 2,4-D from water.
« / « • h«rntoxic to numerous non-target plant species including some
2,4-D is Phy""xlcc£1£ra are susceptible during periods of rapid
crops and ornamentals. Conlfers p variable depending on the
growth. The toxicity of 2,4^D to t forfflulation. The acute oral LD50
species, the water quality and the ^ ^ ^ ^ generally lfiss
of 2,4-D for some birds ranges tro f 2 A.D to honey bees is low.
A-101
-------
1.0 INTRODUCTION
The compound 2,4-dichlorophenoxyacetic acid (2,4-D) is a phenoxy herbi-
cide related to the herbicides 2,4,5-trichlorophenoxyacetic acid (2,4,5-T)
and 4-chloro-2-methyl phenoxyacetic acid (MCPA). It was introduced as a
selective weedkiller at the end of World War II following the discovery of
its activity as a plant growth regulator CD. The value of 2,4-D lies in
its effectiveness as an herbicide against dicotyledonous, but not monocotyle-
donous plants. Consequently, it has been used to selectively kill broadleaf
weeds in cereal grains, pastures, grasslands, and forests.
Forest uses of 2,4-D have been primarily in connection with site prepa-
ration. Because of possible injury to conifers, 2,4-D has limited applica-
tion for "release" in coniferous forests.
2,4-D is an active analog of the plant growth hormone, indole-2-acetic
acid (IAA) (1). IAA is an auxin, an organic substance which promotes growth
along the longitudinal axis of shoots and inhibits elongation of roots.
2,4-D can take the place of IAA in reactions controlling plant growth, thus
causing loss of normal growth control. The uptake and translocation of
2,4-D from the surface of the plant will result in increased auxin concen-
trations in many plant tissues, including those that normally have low con-
centrations. Normal growth is disrupted as some tissues are stimulated to
regrowth and others are inhibited in their development.
In addition to affecting the activity of enzymes, 2,4-D also affects
cell division and differentiation and synthesis of nucleic acids and pro-
teins (1).
Formulations of 2,4-D recommended for use in forestry and ranges in-
clude (2):
a) Low volatile esters (propylene glycol butyl ether ester, butoxy-
ethanol ester, isooctyl ester);
b) High volatile esters (isopropyl ester, butyl, n-butyl, and isobutyl
esters, ethyl ester);
c) Water soluble amines (dimethylamine, triethanol amine, triisopropyl
amine); * *3
d) Oil soluble amines (dodecyl amine, tetradecyl amine, n-oleyl-1
3-propylene diamine);
A-102
-------
e) The parent acid;
f) Inorganic salts (sodium, potassium, lithium, ammonium).
Water soluble and oil soluble amine salts account for a small propor-
tion of the total use of 2,4-D for forestry and range purposes. Water
soluble amines are generally used for cut surface or injection into indivi-
dual stems. Oil soluble amines are used as foliage sprays in areas where
use of low volatile esters may not be suitable due to potential for vapor
drift and damage to non-target vegetation. Low volatile esters account for
80 to 90 percent of all forest improvement spray projects (2). They are
commonly applied as foliage sprays (by hand gun or backpack mist blower).
Aerial application or ground rig applicators are also used (2). Applica-
tions in forestry are at the rate of 2 to A Ibs acid equivalent of active
ingredient per acre. Once in the environment, all formulations of 2,4-D are
degraded to the parent acid.
In the United States, there are four basic producers of 2,4-D: The Dow
Chemical Co.; Fallek-Lankro Corp.; Rhone-Poulenc, Inc.; and Vertac Chemical
Corp. (3). Some of the manufacturers as well as a number of other companies
formulate and distribute the product. Trade names of some formulations of
2 4-D commonly used in forestry include (3,4):
• Rhodia 2,4-D Low Volatile Ester 46 (isooctyl ester of 2,4-D);
• Weedone 170 (butoxyethanol ester of 2,4-D and 2,4-DP);
• Weedone LV-4 (butoxyethanol ester of 2,4-D);
• Esteron 99 Concentrate (propylene glycol butyl ether ester of 2,4-D);
• Formula 40 (an amine of 2,4-D);
• Weedar 64;
• Verton 2-D;
• DMA-4 (dimethylamine salt of 2,4-D).
2.0 PHYSICAL AND CHEMICAL PROPERTIES OF THE ACTIVE INGREDIENT
Solubility, vapor pressure and chemical structures for some important
formulations of 2,4-D are presented in Table 1.
3.0 ENVIRONMENTAL FATE
3.1 UPTAKE AND METABOLISM IN PLANTS
Studies on the uptake and metabolism of 2,4-D in plants have been re-
A-103
-------
TABLE 1. CHEMICAL AND PHYSICAL PROPERTIES OF 2,4-D (5)
Formulation
2,4-D (acid)
2,4-D amine
(dimethylamine
salt of 2,4-D)
Low volatile
2,4-D ester
(butoxyethanol
ester)
Oil soluble
amine salt
(N-oleyl-1,3
propylene-
diamine salt)
Solubility
0.09 g/lOOg, 25°C, water
85.0g/100g, 25°C, acetone*
300g/100g, 20°C, water soluble
in methyl, ethyl and isopropyl
alcohols and acetone. Insoluble
in kerosene, diesel oil.
Soluble in most organic solvents;
insoluble in water.
Insoluble in water; soluble in
most organic solvents.
Vapor Pressure
0.4 mm Hg,
160°C
—
4.5xlO~6 mm Hg,
25oc957
— —
Structure
CI— /. .\— O-CH,— COOH
CI
c*-(\ \ OCH.COOH-NH /
a (\ /V-O-CH.COCXTH.CH.OCH.CH.CH.CH,
+ -f
OUCH,),CH =CH(CHA NHjtCH,), NH,
o o-
c=o c=o
CH, CH,
^^
>
M
O
*See the source reference for solubility in a number of other solvents.
-------
viewed by Loos (1). 2,4-D is absorbed through leaves, stems, or roots and
translocated throughout the plant. The formulation significantly influences
adsorption. Formulations with a low lipid solubility (e.g., 2,4 -D salts)
penetrate poorly, particularly in an application medium with a high pH (1).
Esters are readily absorbed, although some may damage the translocation
mechanism of the plant. However, esters formed from long chain alcohols
with lipophilic and hydrophilic properties (e.g., butoxyethanol esters) are
effectively absorbed and translocated (1).
Inclusion of surface active compounds as emulsifying agents in 2,4-D
formulations often increases herbicidal activity, probably by increasing
absorption; high humidity also increases uptake.
While 2,4-D is readily absorbed into the roots of plants, translocation
is not as effective as with uptake by the leaves or stem (1). Once absorbed
by plants, 2,4-D may undergo chemical alteration in one or more of the
following ways (1):
a) Degradation of the side chain (observed in many species);
b) Side chain lengthening (a few cases);
c) Hydroxylation of the ring (a well-established metabolic reaction);
d) Conjugation with plant constituents (e.g., glucose ester of 2,4-D,
2,4-dichlorophenoxyacetyl-aspartic acid);
e) Ring cleavage (rare); and
f) Formation of various metabolites.
Norris and Freed (7) studied the metabolism of 2,4-D in bigleaf maple,
a large deciduous woody plant commonly found in forest lands of the Western
U.S. They found that decarboxylation in treated foliage was not an important
detoxification mechanism. In another study, Norris (6) found that brush
usually resprouts within a year following spraying on forest lands with
2,4-D. This suggests that high levels of phytotoxic residues of 2,4-D do
not persist in vegetation.
Morton, et al. (8) sprayed 2,4-D labelled in the carboxyl position on
pasture consisting of various range grasses over a three-year period. The
acid of 2,4-D was applied at rates of 0.5 to 2 Ib/acre while the DMA salt of
2 4-D was applied at. the rate of 1 Ib/acre. Samples were taken up to 16
weeks after treatment. The average half-life of 2,4-D in green and litter
A-105
-------
tissues was 2.3 and 2.8 weeks, respectively. Extracts of green tissue har-
vested one hour after treatment with the acid yielded only the acid of 2,4-D;
tissue harvested one week after treatment contained both acid and unknown
metabolites.
3.2 FATE IN SOIL
Processes which may affect the fate of 2,4-D in soil are photodecompo-
sition, volatilization, leaching, adsorption, runoff and chemical and micro-
bial degradation. However, the extent of photodecomposition of 2,4-D on the
surface of forest soil has not been studied. In water, 2,4-D can undergo
photodecomposition under uv radiation or sunlight but, regardless of whether
this mechanism operates in soil, photodecomposition would not be expected
to significantly contribute to the disappearance of 2,4-D from forest soil
due to minimal exposure to sunlight.
3.2.1 Volatilization
Volatilization will depend on the vapor pressure of the 2,4-D formula-
tion. The acid, salts, and amines are less volatile than the esters, with
the oil soluble amines being the least volatile form (5). Volatility also
occurs to a greater extent in soils with low organic matter and clay con-
tent (9). No studies making quantitative measurements of volatilization
were located. One study, however, on the fate of the 2,4-D dimethylamine
salt (DMA-2,4-0) and 2,4-D isooctyl ester in a fine silty loam soil suggested
volatilization as a means for disappearance of 2,4-D from soil (10). One
hour after 2,4-D was applied under field conditions, considerably more amine
than ester was recovered from the soil. After 6 months, an average of 0.04
ppm of 2,4-D remained in the soil regardless of formulation, application
rate, or cropping scheme. It was suggested that the lower initial recovery
of the ester may be due to its volatilization; however, no measurements were
taken to confirm this.
3.2,2 Adsorption and Leaching
The adsorption capacity of a given soil for 2,4-D affects the potential
for leaching of 2,4-D from soil. The leaching tendency would be lower with
those soil types and under those conditions which promote adsorption.
The extent to which 2,4-D is adsorbed in soil has been correlated with
the organic matter content of the soil and the soil pH. Grover (11) studied
A-106
-------
the movement of 2,4-D in five Canadian soils using soil columns. The rela-
tive movement of 2,4-D in the soil indicated an inverse relationship between
adsorption and mobility. The volume of water required to leach 50 percent
of the 2,4-D through the soil columns varied from 16 to 140 ml. Larger
volumes were required for soils with greater amounts of organic matter.
There was also some correlation with pH; 2,4-D leached more readily in soils
with a higher pH. No correlation was found between leaching and the clay
content of the soil.
Other studies have shown that clay does not strongly adsorb 2,4-D.
Frissel and Bolt (13) observed negative adsorption of 2,4-D on montmoril-
lonite at low salt concentrations and at pH greater than 4.0 and on illite
at pH greater than 7.0.
Aly and Faust (12) determined the sorption of the sodium salt, the iso-
propyl, butyl and isooctyl esters of 2,4-D and 2,4-dichlorophenol on 3 clay
minerals: kaolinite, bentonite (a montmorillonitic clay) and illite. In
general, the sorbed amounts were very small, ranging between 0.02 and 0.14
mg per gram of clay at an applied concentration of 5 mg per liter. Since
natural waters have low salt concentrations and have pH values between 6,0
and 8.0, suspended clays in surface waters are not expected to carry signi-
ficant amounts of 2,4-D.
The kinetics of adsorption and desorption of 2,4-D on forest soil ma-
terial were studied by Norris (14) in laboratory tests. The following data
on percent attainment of equilibrium for adsorption and desorption were
reported as a function of time.
% Attainment of Equilibrium
Time, min. Adsorption Desorption
5
10
15
20
30
60
120
180
The above data indicate a relatively rapid rate for both adsorption and de-
sorption for the system studied.
A-107
44
62
65
56
74
82
79
94
67
—
74
82
89
95
97
-------
Helling and Turner (15) evaluated pesticide movement by comparing R.
values on thin layers of soils (the Rf value is a quantitative indication
of the front of pesticide movement and a reproducible index of mobility).
Pesticides were categorized in classes 1 through 5, in order of increasing
mobility. Based on these studies, 2,4-D is relatively mobile in soil - it
is considered to be a class 4 pesticide.
Despite its potential mobility, 2,4-D usually remains within the top
few inches of soil (16). The extent to which 2,4-D will leach into soil is
determined by the formulation, the soil properties and the amount of water
moving through the soil. Salts of 2,4-D, which are polar, are more readily
leached in sandy soils than esters, which have a lower water solubility (9).
Other soil types have been tested with similar results. In these ex-
periments, 2,4-D in water solutions was applied to tubes of silty clay loam
top soil to determine the effect of flooding conditions on the leaching of
herbicides (17). An alkanolamine salt of 2,4-D (with 100 percent solubility)
leached 15 inches whereas the butoxyethanol ester (solubility of 16 ppm)
leached only 3 inches.
The leaching of 2,4-D has been studied in field plots of silty loam soil
to which simulated rainfall was applied one day after application of 2,4-D
amine and estet to the soil (10). Two days later, 2,4-D was found to a depth
of 24 cm. Five days after application, 2,4-D was found to a depth of 40 cm.
It continued to move downward in the soil for 30 days after herbicide appli-
cation.
3.2.3 Runoff
Studies on runoff from 2,4-D amine and 2,4-D ester-treated agricultural
plots (1.5 m x 4.5 m) with a slope gradient of 16 to 17 percent showed that
2,4-D can be lost from fields within a few days after application if suffi-
cient rainfall occurs (10). The extent of 2,4-D recovered in runoff in-
creased with higher rates of herbicide application. The concentration of
2,4-D araine in the collected runoff was 4.5 ppm and 2.0 ppm for application
rates of 11.2 kg/ha and 1.1 kg/ha, respectively. At these same application
rates, the concentrations of 2,4-D ester in the runoff were 3.4 and 2.0 ppm,
respectively.
A-108
-------
Since the esters of 2,4-D do not leach into the soil as readily as
water soluble formulations, they may have a greater potential for runoff
from soil. At least one study suggests that this is the case. As much as
27 percent of the 2,4-D ester washed from the soil surface of a sandy loam
soil in a test plot in which artificial rain was applied (18). Under similar
conditions, using the more water soluble 2,4-D amine, only 3 percent of the
2,4-D was lost.
3.2.4 Chemical and Microbial Degradation
Degradation of 2,4-D in the soil is to a large degree dependent on the
soil conditions such as organic content, moisture and temperature. Under
favorable conditions (i.e., high organic content, adequate moisture and warm
temperatures), 2,4-D is not expected to persist in soil for an appreciable
length of time. Under such favorable conditions, a half -life of 4 to 5 days
has been reported (19) .
Only limited data on the persistence of 2,4-D in forest soils or under
conditions simulating those in various forests are available. Norris (20)
reports that 2,4-D was readily degraded in forest floor material collected
beneath red alder. Thirty-five days after application of 2.24 kg/ha of 2,4-D
(2 Ib/acre), only 6 percent was recovered in the floor material. Recovery
was similar for 2,4-D applied at 4.48 kg/ha.
Breakdown of 2,4-D in the soil depends on the soil temperature, moisture,
the organic matter content of the soil and the soil aeration. In the late
1940' s, researchers provided evidence for microbial degradation when they de-
monstrated that 2,4-D degradation was stimulated by warm, moist conditions
and the addition of organic matter to the soil. Degradation was inhibited
in air-dried and autoclaved soils. According to Loos (1), Audus was the
first to conclusively demonstrate (in the early 195.0 's) the role of micro-
organisms in the degradation of 2,4-D in soil.
Field studies on the degradation of 2,4-D acid have been recently con-
r .IT::,;:: srr-sr- isr;r,» ;::..
r r :
A-109
-------
whereas in sandy loam soil under anaerobic conditions, a significant amount
o-f 2,4-D remained at all 3 depths. Since soils higher in organic content
(in this case, the silty clay loam) can support a larger microbial popula-
tion, they have a better chance of containing the facultative microorganisms
required to degrade 2,4-D under both aerobic and anaerobic conditions.
The potential for soil organisms to degrade 2,4-D depends on possession
of the enzyme system required to metabolize compounds structurally similar
to 2,4-D. Consequently, a soil that has had sufficient prior exposure to
2,4-D and has developed an appropriate microbial community may be able to
degrade 2,4-D at a faster rate. Pathways for the degradation of 2,4-D have
been demonstrated in Arthrobacter and in Pseudomonas (1). The most important
mechanism involves removal of the acetic acid side chain to yield 2,4-
dichlorophenol. This is followed by ring cleavage and finally degradation
to produce aliphatic acids (e.g., succinic acid). In the soil, ester and
amide forms of 2,4-D are first converted to the parent acid form prior to
degradation. The conversion to the acid form may be brought about through
enzymatic hydrolysis by microorganisms (22).
Isooctyl esters of 2,4-D and mixed amines of 2,4-D were applied to the
surface of a silty loam soil in a humid, temperate climate to determine soil
persistence (23). The following application rates were used:
Active Ingredient Rate, kg/ha AE
Isooctyl esters of 2,4-D 7.8*
and 2,4,5-T 15.7*
31.4*
Mixed amines of 2,4-D 5.6
11.2
22.4
Rate of each ingredient
None of the 2,4-D Isooctyl esters was detectable in the soil after 14
days. The major residue in soil after application of the ester was the free
phenoxy acid which reached a maximum concentration in the 14-day soil
samples. After 70 days, 1 percent of the applied 2,4-D remained in the soil
from the plots treated with 7.8 kg/ha and 31.4 kg/ha; 2 percent remained on
the plots treated with 15.7 kg/ha. No 2,4-D was detected past 55 weeks.
A-110
-------
In plots treated with the amine of 2,4-D, maximum soil residues (free
phenoxy acid) occurred after 14 days. Less than 5 percent of the 2,4-D re-
mained at the end of 70 days. Some 2,4-D penetrated 10-20 cm into the soil
but none was detected below that level.
As noted previously, conversion of esters and amines of 2,4-D to the
parent acid may be brought about by microbial degradation. However, there
is evidence that chemical hydrolysis may be responsible for this conversion
in some cases.
In studies on hydrolysis of 2,4-D esters to 2,4-D in Saskatchewan soils,
the following results were obtained in samples analyzed after 24 hours (24):
Soil Type
Sandy loam
Heavy clay
Loam
Moisture
Content
5%
20%
15%
Ester Recovered
n-butyl
none
none
none
Isopropyl
none
none
none
Isooctyl
25%
28%
20%
Under field conditions, esters of 2,4-D normally hydrolyze to the acid
within a few days providing the moisture levels are adequate. It was sug-
gested that because of the relatively rapid hydrolysis of the n-butyl and
isopropyl esters in soil, hydrolysis by soil microorganisms is unlikely, and
that a soil catalyzed reaction may be responsible for their degradation.
3.3 PERSISTENCE IN WATER
Stream contamination is probably the most important environmental con-
cern in the forest because water is the habitat for many biological species
and because water may be utilized downstream for domestic, industrial, and
agricultural purposes (25). Norris (25) has made several studies on stream
contamination by 2,4-D in western and eastern Oregon. The magnitude of con-
tamination is closely related to the layout of the treatment area with
respect to live streams. Areas having a high water table would have the
greatest potential to contribute to stream contamination. At most of the
sites sampled, concentrations were less than 100 ppb shortly after spraying.
These levels were less than 10 ppb after one week.
Data collected by the U.S. Geological Survey program for monitoring
pesticides in streams of the western U.S. during the period of October 1966-
A-lll
-------
September 1968 indicate that 2,4-D was the most frequently found herbicide
(26). The maximum concentration found was 0.35 jjg/liter (0.35 ppb) .
In an aqueous environment 2,4-D will most likely be found in the free
anion form (27). Salt formulations dissociate to the anion and esters hydro-
lyze to the anion, usually within one day. Therefore, the degradation rate
of the anion is of primary concern in determining the persistence of 2,4-D
in an aquatic environment. Processes which affect 2,4-D persistence in
natural waters are microbial degradation, chemical hydrolysis* photodecom-
position, volatilization and adsorption. A. brief review of these processes
follows.
3.3.1 Microbial Degradat ion
Halter (27) has compiled an extensive review of studies on the persis-
tence of 2,4-D in aquatic environments. In general, laboratory studies show
that warm, nutrient rich, 2,4-D-rich conditions favor 2,4-D degradation in
water. Therefore, it is reasonable to assume that the cool, nutrient-poor
conditions characteristic of many natural surface waters do not promote
microbial degradation of the dilute concentrations of 2,4-D likely to be
encountered.
Several studies indicate that, even in non-sterile water, 2,4-D will
persist if certain microorganisms are absent. My and Faust (12), studying
the fate of 2,4-D and ester derivatives in natural surface waters, showed
that no breakdown of 2,4-D occurred in lake waters aerobically incubated in
the laboratory for 120 days. Although esters of 2,4-D were hydrolyzed bio-
logically to 2,4-D acid and the corresponding alcohol within 9 .days, only
the alcohol moiety was oxidized further. Most of the 2,4-dichlorophenol
disappeared within 30 days under aerobic conditions in laboratory tests with
natural lake waters, indicating the presence of microorganisms capable of
decomposing this compound in natural waters. Under anaerobic conditions,
the phenol persisted longer.
Using dilute salts solutions containing 0.1 and 1.0 mg/1 2,4-D, Schwartz
(28) showed that no more than 37 percent of the acetic acid moiety disappeared
over a period of 3 to 6 months in spite of excellent conditions for biologi-
cal activity. Since a natural waterway could not be expected to provide as
good a microbial environment as the experimental system, it was concluded
A-112
-------
that 2,4-D would not be substantially degraded by microorganisms in natural
waters.
Watson (29) demonstrated that 2,4-D can remain stable in water and mud
samples from rivers for up to 6 months depending on the microorganisms,
nutrient levels, and suspended sediments.
Other studies have demonstrated that 2,4-D will be degraded in an aqua-
tic environment under more favorable conditions. Studies conducted in warm
to temperate water ponds suggest that the majority of 2,4-D persists for a
maximum of 30 to 40 days after application; however, 2,4-D probably persists
at low ppb levels for several months (27).
3.3.2 Chemical Hydrolysis
Non-enzymatic hydrolysis appears to play a major role in the breakdown
of 2,4-D esters to the anion form. Zepp, et al. (30) measured the hydroly-
sis half-lives of 2,4-D esters at pH 6 and 9, pH levels in the range commonly
found in natural waters. The data shown in Table 2 (photolysis and vaporiza-
tion data shown in the table will be discussed later) indicate a much shorter
half-life for all esters at pH 9 than at pH 6. As shown in Table 2,
2-butoxyethyl exhibited the shortest half-life among the 4 formulations
tested.
TABLE 2 COMPARISON OF HYDROLYSIS, PHOTOLYSIS, AND VAPORIZATION
HALF-LIVES FOR SEVERAL 2,4-D ESTERS AT 25°C*
Ester
Methyl
1-Butyl
1-Octyl
2-Butoxyethyl
*
Hydrolysis, days
pH 9
0.04
0.2
0.2
0.02
.
pH 6
44
220
220
26
Direct
Photolysis, *
days
29
~"
16
Vapori zation , *
days
21.7
IT
. X
Uc
895
For water body 1 m deep.
'For September in southern United States
1m deep pure water. Expressed in terms of
^Calculated for a completely mixed water body.
*"
-hr days.
A-113
-------
Other results have corroborated the finding that esters undergo rapid
hydrolysis at a high pH. Smith (24) studied the hydrolysis of the isopropyl,
n-butyl and isooctyl esters of 2,4-D to the free acid in aqueous solutions.
At pH 13.0 (0.1 N NaOH) more than 50 percent of all the esters were hydro-
lyzed in less than one minute. At pH 11.2 (0.1 N Na CO,) the half-lives at
25°C were 5, <5, and 30 minutes for the isopropyl, n-butyl, and isooctyl
esters, respectively.
3.3.3 Photodecomposition
Photodecomposition does not appear to be a major mechanism for 2,4-D
degradation in surface waters, although some photolysis may occur near the
water surface.
Aly and Faust (12) showed that irradiation of aqueous solutions of 2,4-D
compounds with uv light from a mercury lamp results in 2,4-D cleavage at the
ether linkage and production of 2,4-dichlorophenol. Decomposition was faster
at higher pH's. They concluded, however, that Photodecomposition in surface
waters is not expected to be significant due to the character of natural
sunlight (weaker uv radiation) and the presence of suspended and organic
matter which reduces the effects of solar radiation.
Crosby and Tutass (31) also studied Photodecomposition of 2,4-D in
water under uv light and concurred that the major reaction was cleavage at
the ether bond to produce 2,4-dichlorophenol. This was subsequently dehalo-
genated to 4-chlorocatechol; 1,2,4 benzenetriol was then formed and rapidly
air oxidized to polyquinoid humic acids. The proposed reaction mechanisms
are as shown below.
AW*. \ cocoon
-
A-114
-------
Irradiations using sunlight appeared to produce degradation products
similar to those obtained for irradiation with uv light in the laboratory.
2,4-dichlorophenol and 3-hydroxy-4-chlorophenoxy acetic acid which were
identified as degradation products under uv irradiation were also identified
as products under sunlight irradiation. 4-chlorocatechol was not identified
as a degradation product with sunlight irradiation of 2,4-D esters.
Zepp, et al. (30) carried out laboratory photolysis studies in distilled
water, organic solvents, and a natural water sample. In organic solvents,
photoreaction involved replacement of a chlorine by hydrogen. In water, at
concentrations greater than the solubility (>300 ppm), the major photo-
products were monochlorophenoxyacetic acid esters; in dilute (<1 ppm), airr
saturated solutions, the major photoproducts were 2,4-dichlorophenol and
compounds resulting from replacement of one chlorine by hydroxyl. In river
water, the photoproducts were the same as those in distilled water although
more 2,4-dichlorophenol and less hydroxylated phenoxy esters were formed.
Photolysis was twice as fast in river water as in distilled water, probably
due to photosensitiza.tion of substances dissolved in the river water.
Table 2 presents the calculated half-lives for the photolysis of two
esters of 2,4-D under the stated conditions. In natural waters, the rate
of photolysis will depend on the time of the day, the season, and the lati-
tude. The photolysis would be expected to be greater near the water surface
and the half-life to increase with increasing depth due to reduction in
light penetration.
3.3.4 Volatilization
Zepp, et al. (30) calculated volatilization half-lives of 2,4-D esters
based on the fact that volatilization rates of pesticides from completely
mixed water bodies are proportional to their vapor pressures and inversely
proportional to their solubilities. The calculated values given in Table 2
indicate that at a PH of 6.0, vaporization may be a more important mechanism
for removal of some 2,4-D esters from water than hydrolysis since, at this
PH (and perhaps also at lower PH levels) conversion of ester to acid via
hydrolysis takes place at a much slower rate. However, at a PH of 9.0,
hydrolysis is a more important mechanism for removal of the 2,4-D esters
shown in the table.
A-115
-------
3.3.5 Adsorption
Halter (27) has reviewed studies on the sorption of 2,4-D to a variety
of particles and surfaces found in natural waters. Based on these studies,
adsorption does not appear to be a significant factor in the fate of 2,4-D
in an aquatic environment.
3.4 FATE IN AIR
Determination of degradation of 2,4-D in air is complicated by the
occurrence of airborne losses due to drift and volatilization at the time
of application, subsequent vaporization from the treated areas and dispersal
into the atmosphere. No studies were found on the actual rate of degrada-
tion of 2,4-D in the atmosphere.
A number of researchers have measured quantities of 2,4-D in the atmo-
sphere during the spraying season. These measurements indicate that the
levels of 2,4-D in air depend on meteorological conditions and on the formu-
lation used. Farwell, et al. (32), in surveys of airborne 2,4-D in south-
central Washington, were unable to correlate 2,4-D application rates with
subsequent atmospheric concentrations. Daily samples were taken at 8 sta-
tions to determine the average 2,4-D concentration by volatility type. ' High
volatile esters represented the majority of the 2,4-D present in air samples.
Studies on 2,4-D residues in the atmosphere in central and southern
Saskatchewan between 1966 and 1975 showed that residues of 2,4-D were present
in up to 50 percent of the daily samples collected at any location during
the spraying season (33). Atmospheric concentrations were greater for high
volatile esters than for low volatile esters. The maximum level of 2,4-D
measured was. 23.14 ug/m3. In any given year and at any of the sampling sites,
10 percent or less of the samples had 2,4-D levels exceeding 1 ug/m3.
4.0 IMPACTS ON NON-TARGET PLANTS AND ORGANISMS
4.1 PHYTOTOXICITY
A serious hazard in the use of 2,4-D is drift of the herbicide to non-
target plants during or after application. Most established grass species
are not injured by 2,4-D; however, it is extremely harmful to cotton, grapes
tobacco, beans, tomatoes, fruit trees, and some ornamentals (16). Conifers '
are susceptible during periods of rapid growth (34).
A-116
-------
4.2 TOXICITY TO FISH AND AQUATIC ORGANISMS
Halter (27) has made an extensive review of the literature on the
effects of 2,4-D on fish. Acute toxicity of 2,4-D to freshwater fish, as
measured in laboratory tests, varies considerably depending on the species
used, the water quality, and the 2,4-D formulation tested. Most of the
studies have been conducted under laboratory conditions.
The butyl esters of 2,4-D have been found to be 100 times more toxic
than their corresponding acids (35). However, under field conditions they
are quickly hydrolyzed to the acid or salt. Woodward and Mayer (36) studied
acute and chronic toxicity of 2,4-D butyl ester (BE), 2,4-D isooctyl ester
(IE), and 2,4-D propylene glycol butyl ether ester (PGBEE) on cutthroat
trout and lake trout. Acute toxicity data is presented in Table 3. The
2,4-D BE tended to be slightly more toxic than 2,4-D PGBEE. There was also
an increase in susceptibility as temperature decreased. Neither water hard-
ness nor pH significantly influenced toxicity. The 2,4-D IE was not toxic
to either species in 96 hours at concentrations less than 60,000 pg/L. In
chronic toxicity tests, the no effect concentrations were as follows: for
cutthroat trout - 24 pg/L BE and 31 ug/L PGBEE; for lake trout - 33 yg/L BE
and 52 ug/L PGBEE.
Meehan, et al. (37) tested acute toxicity of 2,4-D acid, butyl, and
isooctyl esters to juvenile salmon, char, and rainbow trout. At concentra-
tions less than 50 ppm, 2,4-D acid produced mortality only in pink salmon
fry. The butyl ester was the most toxic, causing nearly complete mortality
in all species at concentrations'greater than 1.0 ppm. The isooctyl ester
was less toxic than the butyl ester.
Folmar (38) reported a 96-hour LC5Q of 100 mg/L for rainbow trout ex-
posed to 2,4-D DMA salt. Fish were found to avoid 2,4-D at concentrations
of 1 mg/L but not at 0.1 mg/L.
Elder, et al. (39) reported that 2,4-D exhibited low toxicity to all
freshwater and marine algal species examined at levels approaching the maxi-
mum solubility of the herbicide in water. Additional acute toxicity data of
various 2,4-D formulations to fish and other aquatic organisms is presented
in Table 4.
A-117
-------
OO
TABLE 3. ACUTE TOXICITY OF 2,4-D BE AND 2,4-D PGBEE TO FINGERLING CUTTHROAT TROUT
AND LAKE TROUT AT DIFFERENT TEMPERATURES (36)
Water Characteristic
Chemical and
Temperature (°C)
2,4-D BE
5
10
15
2,4-D PGBEE
5
10
15
Cutthroat Trout
Water
pH Hardness
7.2 Soft (40 mg/L
as CaC03>
7.2 - Soft
7.2 Soft
7.2 Soft
7.2 Soft
7.2 Soft
96-h LC5Q
(vg/1)
490
540
770
490
1,030
780
95% Confidence
Limits (Mg/D
397-606
460-640
657-902
400-604
920-1,200
663-918
Lake Trout
96-h LC50
(Mg/D
600
640
820
700
630
1,000
95% Confidence
Limits (ug/1)
541-665
569-720
715-940
631-777
542-733
824-1,210
-------
4.3 TOXICITY TO INSECTS
There have been some reports of adverse effects to bees from applica-
tion of 2,4-D, although at normal rates of application there appears to be
little hazard to bees or insects from direct toxicity (2). Morton, et al.
(52), studying the toxicity of herbicides to honey bees, found that the
toxicities of the herbicides studied were relatively unchanged by addition
of solvents and surfactants in the formulation process. The formulation of
2,4-D either as an amine or an ester had little influence on its toxicity
to honey bees as a stomach poison. No formulation of 2,4-D significantly
shortened the half-life of honey bees at concentrations of 10- and 100-ppmw.
The butoxyethanol ester of 2,4-D and the amine salt of 2,4-D caused signi-
ficant reductions in half-life at the 1000-ppmw concentration. When bees
were dusted with 2,4-D sodium salt at a dose of 24.17 ug/bee and 2,4-D low
volatile oil-soluble ester at a dose of 18.13,ug/bee, mortality was 3.7 per-
cent and 6.4 percent, respectively (53). For comparison with field condi-
tions, an application rate of 1 kg/ha would give a dose of 1.12 ug/bee.
Therefore, at recommended application rates, 2,4-D is considered relatively
non-toxic to bees.
4.4 TOXICITY TO BIRDS AND MAMMALS
Phenoxy herbicides are generally less toxic to birds than to mammals
(34) (also see Table 4). The acute oral LD5Q for 2,4-D (and 2,4,5-T) ranges
from 300 to 5000 mg/kg for poultry, mallards, pheasants, pigeons and quail,
with the LC5Q in bird feed greater than 2500 ppm (34).
Chronic toxicity data is available for various domestic birds and
mammals for several 2,4-D formulations and is presented in Table 5. Some
of these effects included locomotory disturbance and depressed growth rate.
In most cases, however, no effects were observed.
Various studies have also been conducted to provide information on
human health hazards of 2,4-D. The 2,4-D isooctyl ester, 2,4-D butyl ester,
and 2 4-D isopropyl ester have been found to produce statistically signifi-
cant higher incidences of congenital malformations in rats or mice (54).
Most mutagenesis studies with 2,4-D are negative, although it has been
in certain test systems (55,56). Further studies are needed to
A-121
-------
TABLE 5. CHRONIC TOXICITY OF 2,4-D (40)
Formulation
Trlethanol-
amine
Triethanol-
amine
Butyl ester
Triethanol-
amine
Triethanol-
amine
Triethanol-
amine
Alkanolamine
Alkanolamine
PGBE ester
EthylViexyl
ester
Ethylhexyl
ester
Ethylhexyl
ester
Not specified
Organism
Swine
Swine
Swine
Swine
Rats
Chicken
Sheep
Cattle
Sheep
Cattle
Sheep
Sheep &
Cattle
Dog
Dose
50
mg/kg/day
50
og/kg/day
50
mg/kg/day
500 ppm
in feed
1000 ppm
in water
1000 ppm
in water
100
mg/kg/day
50
mg/kg/day
100
mg/kg/day
250
rag /kg/day
250
mg/kg/day
100
mg/kg/day
500 ppm
in feed
Duration
3 doses
8-10 doses
<5 doses
1 month
10 months
Daily pro-
duction
reduced
30%
481 days
112 days
481 days
14 days
17 days
10 days
2 years
Effect Reference
None
Minor transient
effects
None
Some locomotory
disturbance,
depressed growth
rate, no gross
pathology
Depressed growth
rate, no gross
pathology
Egg size normal,
from hatching
through first 2
months of egg
production.
No effect
No effect
No effect
111 in 3 days,
9 r
survive & recover
from 9 doses.
14 doses lethal.
Ill in 3 days,
17 doses lethal
None to minor
effects
None
45
45
45
45
45
45
49
49
49
50
50
50
51
•J-^
(Continued)
A-122
-------
TABLE 5. (Continued)
Formulation
Not specified
Not specified
Alkanolamine
PGBE ester
PGBE ester
Acid
Organism
Rat
Rat
Chicken
Chicken
Cattle
Mule
deer
Dose
1250 ppm
in feed
500 ppm
in feed
100
mg/kg/day
50
mg/kg/day
100
mg/kg/day
80 and 240
mg/kg/day
Duration
2 years
2 years
10 days
10 days
10 days
30 days
Effect
No effects on
growth, survival
hermatology or
tumor incidence
No effects in
reproduction
studies
No effect on
weight gain
No effect on
weight gain
No effect
Minor symptoms
no weight loss
Reference
51
51
49
49
49
48
indicate that, with the exception of peripheral neuropathy (there have been
at least six reported cases of persons being deraally exposed to 2,4-D
producing a severe peripheral neuropathy), acute adverse effects of 2,4-D
occur only at high doses (55). The oral LD5Q for humans has been estimated
between 80 and 800 mg/kg (55).
4.5 BIOACCUMULATION
The potential for bioaccumulation and persistence of 2,4-D in fish has
been the subject of a number of studies. The results of these studies in-
dicate that any 2,4-D accumulated is rapidly broken down to hydrocarbon
fragments which are subsequently utilized by the fish for synthesis of the
normal body tissue and/or eliminated.
Rodgers and Stalling (57) examined the uptake of the C labelled
butoxy-ethanol ester of 2,4-D from water by 3 species of fed and fasted fish.
The fish were exposed to either 0.3 or 1.0 mg/1 for up to 168 hours. The
whole body residue, based on 14C measurement, was found to be 7 to 55 times
A-123
-------
greater than the exposure concentration 1 to 6 hours after exposure. The
maximum residue concentrations in fed fish occurred in most of the organs
within 1 or 2 hours of exposure; in fasted fish maximum concentrations were
observed within 1 to 8 hours of exposure. The maximum residue levels for
the fasted fish was 2 to 5 times those for the fed fish. For both the
fasted and the fed fish, the herbicide and its metabolites were eliminated
rapidly after reaching a maximum concentration.
Shultz (58) exposed fish to varying concentrations of 14C labelled DMA-
2,4-D (0.5, 1.0, and 2.0 PPm) for up to 84 days. Radioactive residues as
evidenced by the presence of C, were found in all fish tissues and organs
analyzed, including the muscle. Analysis of the muscle for 2,4-D, however
indicated less than trace amounts in all but 2 samples out of 30 samples
tested, thus indicating that metabolism of 2,4-D had occurred.
Further studies (Stalling and Huckins) (59) on the metabolism of DMA-
2.40 in bluegills showed that residues in fish were not intact 2 4-D 14C
labelled DMA-2.4-D was degraded and "c was found incorporated into fatty
acids, glycogen and protein materials. Since 2,4-D degradation to pools
devoid of fish was also observed, it was speculated that the 2,4-D may have
been degraded by microorganisms in water and the breakdown products accumu-
lated by fish.
Schultz and Whitney (60) monitored 2,4-D residues in fish water and
mud following spraying of over 7,000 acres along a canal in the Loxahatchee
Wildlife Refuge (Florida). The dodecyl-tetradecyl amine salts of 2 4-D were
sprayed at a rate of 4.48 kg/ha.^ The highest 2,4-D residue in water 0 037
mg/L was found on the day following the initial treatment. Among 60 samples
of fish, 3 had herbicide residue levels greater than 0.010 mg/kg 16 ^
less than 0.010 mg/kg, and the rest had no detectable residues. 'Florlda
gallinules had residue levels of 0.30 mg/kg ln breast muscle and 0.675 mg/kg
in liver one day after spraying but no detectable residues 4 days after
spraying.
Numerous studies on the fate of 2,4-D in large animals also indicate
that bioaccumulation is not likely to be of concern. In O08t cases 2 4 D
fed to animals appears to be absorbed readily in the gut and excreted rapid-
ly in urine, largely as unchanged phenoxy acid (2,61).
A-124
-------
REFERENCES
1. Loos, M.A. Phenoxyalkanoic Acids. In Herbicides - Chemistry, Degrada-
tion, and Mode of Action. Kearney, P.C. and Kaufman, D.D., eds. Marcel
Dekker Inc., N.Y. (1975).
2. Schlapfer, T.A. Calendar Year 1973 Herbicide Use on the Olympic Paci-
fic Northwest Region. EIS-WA-73-0608-F. (1973).
3. 1980 Farm Chemicals Handbook. Meister Publishing Co., Wiloughly, Ohio.
4. National Forest Products Assoc., Pesticide Uses in Forestry. NFPA
Forest Ghent. Prog.. Washington. D.C. (1980).
5. Mullison, W.R. Herbicide Handbook of the Weed Science Society of
America, Weed Science Society of America, Champaign, Illinois, 4th
Edition, 1979. 518 pp.
6. Norris, L.A. Chemical Brush Control: Assessing the Hazard, J. Forestry
69(10): 715-720 (1971).
7. Norris, L.A. and V.H. Freed. The Metabolism of a Series of Chloro-
phenoxyalkyl Acid Herbicides in Bigleaf Maple, Acer macrophyllum Pursh.
Weed Res. 6: 212-220, 1966.
8. Morton, H.L., E.D. Robison, and R.E. Meyer. Persistence of 2,4-D,
2,4,5-T, and Dicamba in Range Forage Grasses. Weeds 15: 268-271, 1967.
9. Weidner, C.W. Degradation in Groundwater and Mobility of Herbicides.
NTIS: PB-239 242 (1974).
10. Wilson, R.G., Jr. and H.H. Cheng. Breakdown and Movement of 2,4-D in
the Soil Under Field Conditions. Weed Sci. 24(5): 461-466 (1976).
11. Grover, R. Mobility of Dicamba, Picloram, and 2,4-D in Soil Columns.
Weed Science 25(2); 159-162 (1977).
12. Aly, O.M. and S.D. Faust. Studies on the Fate of 2,4-D and Ester
Derivatives in Natural Surface Waters. J. Agric. Food Chem. 12(6):
541-546 (1964).
13. Frissel, M.J. and G.H. Bolt. Soil Science 94: 284 (1962). In Re-
ference 12.
14. Norris, L.A. The Kinetics of Adsorption and Desorption of 2,4-D,
2,4,5-T, Picloram and Amitrole on Forest Floor Material. Research
Progress Report, Western Society of Weed Science, pp. 103-104 (1970).
15. Helling, C.S. and B.C. Turner. Pesticide Mobility: Determination by
Soil Thin-Layer Chromatography. Science 162: 562-563, 1968.
A-125
-------
16. Draft EIR: Alternative Methods of Plantation Release and Site Prepa-
ration on the Superior National Forest. Superior National Forest
Pesticide Use Committee. (1980).
17. Wiese, A.F. and R.G. Davis. Herbicide Movement in Soil With Various
Amounts of Water. Weeds 12: 101-103 (1964).
18. Tarrant, R.F. and L.A. Norris. Residues of Herbicides and Diesel Oil
Carriers in Forest Waters: A Review. In Symposium Proceedings-
Herbicide and Vegetation Management in Forests. Ranees, and Noncrop
Lands, Oregon State University. (1967) . -
19. Alton J.D. and J.F. Stritzke. Degradation of Dicamba, Picloram, and
Four Phenoxy Herbicides in Soils. Weed Science 21(6): 556-560 (1973).
20. Norris, L.A. Degradation of Herbicides in the Forest Floor In- Tree
Growth and Forest Soils, C.T. Youngberg and C.B. Davey, eds., Oregon
State University Press, 1970. pp. 397-411. uregon
21. Lavy T L et al. Degradation of 2, 4-D and Atrazine at Three Soil
Depths in the Field. J. Environ. Quality 2(11? 132-137 (1973)
22. Norton, T R Metabolism of Toxic Substances, in Toxicology- The Basic
Dou11* j- —
23. Steurt, D.K.R. and S.O. Gaul. Parsistence of 2. 4-D 2 4 5-T and
' 18(2):
ment in Forests. Ranges and Noneron T.ar,^ brecmn ci..Z it ^ ^^ff6
pp. 103-123 (1967). - - P bana^- 0reS°n State University,
26. Manigold, D.B. and J.A. Schulze. Pesticides
- A
27. Halter, M.T. 2,4-D in the Aquatic Environment Sectlm, TT < T4
ture Reviews of Four Selected «—'-«-. Section II in Litera-
Municipality
->0/?LPeSticides in Aqueous
39(10): 1701-1716 (1967).
Biodegradation of 2,4-D in
(1977). in Reference 27.
A-126
-------
30. Zepp, R.G., et al. Dynamics of 2,4-D Esters in Surface Waters: Hy-
drolysis, Photolysis, and Vaporization. Environ. Sci. and Technol.
9: 1144-1150 (1975). :
31. Crosby, D.G. and H.O. Tutass. Photodecomposition of 2,4-Dichloro-
phenoxy-acetic Acid. J. Agric. Food Chem. 14(6); 596-699 (1966).
32. Farwell, S.O., et al. Survey of Airborne 2,4-D in South-Central
Washington. J. Air Pollution Control Association. 26(3): 224-230
(1976). ~
33. Grover, R., et al. Residues of 2,4-D in Air Samples from Saskatchewan.
1966-1975. J. Environ. Sci. Hlth B. 11(4); 331-347 (1976).
34. Anon., The Phenoxy Herbicides. Council for Agricultural Science and
Technology, Report No. 77 (1978).
35. Cameron, J.J. and J.W. Anderson. Results of the Stream Monitoring
Program Conducted During FY 1977 Herbicide Spray Project - Coos Bay
District. USDI/BLM Report, Coos Bay, Oregon, 1977.
36. Woodward, D.F. and F.L. Mayer, Jr. Toxicity of Three Herbicides
(Butyl, Isooctyl, and Propylene Glycol Butyl Ether Esters of 2,4-D) to
Cutthroat Trout and Lake Trout. U.S. Fish and Wildlife Service Tech-
nical Paper Vol. 97, Columbia Nat. Fish Res. Lab., Jackson, Wyoming,
1978. 6 pp.
37. Meehan, W.R., L.A. Norris, and H.S. Sears. Toxicity of Various Formu-
lations of 2,4-D to Salmonids in Southeast Alaska. J. Fish. Res.
Board Canada 31(4): 480-485, 1974.
38. Folmar, L.C. Overt Avoidance Reaction of Rainbow Trout Fry to Nine
Herbicides. Bull. Env. Contain. Toxicol. 15(5): 509-514, 1976.
39. Elder, J.H., C.A. Lembi, and D.J. Morre. Toxicity of 2,4-D and Piclo-
ram to Fresh Water Algae. NTIS PB-199-114, October 1970.
40. Norris, L.A., H. Gratkowski, C. Graham, and W.F. Currier. Phenoxy
Herbicides Background Information. In: Vegetation Management With
Herbicides Program on the Umatilla, Malheur, and Wallowa-Whitman
National Forests, Oregon.
41. Butler, P.A. 1965. Effects of Herbicides on Estuarine Fauna. South-
ern Weed Cont. Conf. Proc. 18: 567. In Reference 40.
42. Rowe, V.K. and T.A. Hymas. 1954. Summary of Toxicological Information
on 2,4-D and 2,4,5-T Type Herbicides and an Evaluation of the Hazards
. to Livestock Associated with Their Use. Am. J. Vet. Res. 15: 622-629.
In Reference 40.
43. Lawrence, J.N. 1964. Aquatic Herbicide Data. USDA. ARS. Agricul-
tural Handbook 231. In Reference 40.
A-127
-------
44. Hughes, J.S. and J.T. Davis. 1966. Toxicity of Pesticides to Bluegill
Sunfish Tested During 1961-1966. Report to Louisiana Wildlife and
Fisheries Commission, Monroe, Louisiana. In Reference 40.
45. Bjorklund, Nils-Erik and Kurt Erne. 1966. Toxicological Studies of
Phenoxyacetic Herbicides in Animals. Acta. Vet. Scand. 7: 364-390.
In Reference 40.
46. Edson, E.F., D.N. Sanderson, and D.N. Nookes. 1964. Acute Toxicity
Data for Pesticides. World Review of Pest Control 4(1) Spring 1965
In Reference 40.
47. Hayes, Wayland J.J. 1963. Clinical Handbook on Economic Poisons
U.S. Department of Health, Education and Welfare. In Reference 40.
48. Tucker, R.K. and D.G. Crabtree. 1970. Handbook of Toxicity of Pesti-
cides to Wildlife. Resource Publication No. 84. Bureau of Sport
Fisheries and Wildlife. U.S. Department of the Interior. In Reference
49. Palmer, J.S. and R.D. Radeleff. 1964. The Toxicologic Effects of
Certain Fungicides and Herbicides on Sheep and Cattle. Ann N Y Acad
Sci. Ill: 729-736. In Reference 40.
50. Hunt, L.M., B.N. Gilbert, and J.S. Palmer. 1970. Effects of a Herbi-
S£i Sr^^^-JS-sa: S£"SE~
tamination and Toxicol. 5: 54-60. In Reference 5.
51. House, W.B., et al. 1967. Assessment of Ecological Effects of Exten
sive or Reoeated Us* of Herbicides. Fi~" -- meets of Exten
3-B Under Dept. of
"•
54. Mrak, E. Report of the Secretarv'
"
55. California Department of Health -,..,-„-.*.*».,.,
lations. 2,4-Dichlorophenoxyacetic Actd «TST V*,Indu8trlal
Human Health Hazards. Hazard Alert Sv^Ji '^Ll,!™1^.1™ of .the
Laboratory Report, Berkeley,
"' '"" " """ i. Larson.
***-**•*•w** *••**• «^^« *-» naawi^XclueQ WlThf-haTT^^^^^t. ~ —- —«—
for the National Forest Products Association^0^ Hfbicides- »«port
Associates,-Inc., Berkeley, Calif. 19^ ,£* Environ»ental Health
* 1^^- PP«
A-128
-------
57. Rodgers, C.A. and D.F. Stalling. Dynamics of an Ester of 2,4-D in
Organs of Three Fish Species. Weed Sci. 20(1): 101-105. (1972).
58. Schultz, D.P. Dynamics of a Salt of (2,4-Dichlorophenoxy) Acetic Acid
in Fish, Water, and Hydrosol. J. Agric. Food Chem. 21(2): 186-192.
(1973).
59. Stalling, D.L. and J.N. Huckins. Metabolism of 2,4-Dichlorophenoxy-
acetic Acid (2,4-D) in Bluegills and Water. J. Agric. Food Chem.
26(2): 447-452. (1978).
60. Schultz, D.F. and E.W. Whitney. Monitoring of 2,4-D Residues at Loxa-
hatchee National Wildlife Refuge. Pest. Monit. J. 7(3/4); 146-152.
1974.
61. Ivie, G.W. and H.W. Dorough, eds. Fate of Pesticides in Large Animals.
ACS Pesticide Chemistry Division, Academic Press, N.Y. (1977).
-------
Common Name: Fosamine ammonium
Chemical Name: Ammonium ethyl carbamoylphosphonate
Major Trade Name: "Krenite" S Brush Control Agent
Major Applications Used primarily in Pacific Northwest for woody brush
in Forestry: and weed control in site preparation and conifer re-
i^h* _In"oduct°7 development work is being conducted
in the South for similar use.
SUMMARY
Fosamine ammonium, or "Krenite", is a relatively new herbicide which
been commercially available only in the past few vJU. TifJ .„.« .JI-J1.
on efficacy and environmental fate and impacts are
and field tests with non-forest systems conducted
sraSSSSlSra^T^
a^vSsSS-a—^SeST
"
and heavy metals content. So.e fosamine occ»r8ln
. forest Md
in spring and su^ner. "Krenite" na" low tox2ijv to fl I'"', partt<:''1«13'
It is excreted and/or metabolized rapidly by anlLu .% , " naimal'-
bloaccumulable. It is considered non-toxic to ^ ? S consld««i non
baen sh=™ to decrease the rate nitrification „"
d
recommended use rates. >-onsiaerea toxic
A-130
-------
1.0 INTRODUCTION
Fosamine ammonium, or "Krenite", is a herbicide/growth regulant suitable
for the control of many undesirable woody plants. It was discovered in 1974
and has been available commercially only in the past few years (1). Species
completely controlled include: birch, blackberry, black locust, bracken
(fern), loblolly pine, pin cherry, quacking aspen, red alder, red oak,
salmonberry, sumac, sweet gum, thimbleberry, vine maple, water oak, white
oak, and Virginia pine (2,3,A,5). American elder, eastern cottonwood,
eastern white pine, multiflora rose, slippery elm, sycamore, tree-of-heaven,
wild grape, and wild plum can be completely controlled with a single foliar
application of 2 to 3 gallons of "Krenite" per acre (2). Brush plants par-
tially controlled and suppressed include bigleaf maple, black cherry, black-
gum, chokecherry, elm, hawthorn, hickory, persimmon, red maple, sassafras,
sourwood, tulip tree (yellow poplar), willow, and white ash (2,6). It does
not control evergreen brush (2,7).
Since it is relatively new, commercial application of fosamine ammonium
has not been extensive in forestry and it apparently has been used to a
greater extent in such other applications as right-of-way and industrial
maintenance. In the forest industry, fosamine ammonium is used in the U.S.
in reforestation areas and is labelled for conifer release (2,8,9,10) in
Washington and Oregon. Data on the extent of use in the region are presented
in Table 1 (11). Application rates commonly range from 3 to 12 Ib a.i./acre
(3/4 to 3 gal product/acre), with lower rates used for conifer release (2).
Fosamine ammonium is applied via aerial broadcast with limited ground appli-
cation reported (4,6). In forestry areas, adequate water is required to
obtain best performance (10-40 gallons by air, 50-100 gallons on the ground).
Krenite has been used in experimental plots in Maine; limited forestry appli-
cation has also been reported in the South (8,12,13,14). In the Northeast,
fosamine ammonium has been recommended (and apparently used) on Christmas
tree stands; the recommended rate is 1-1/2 gallons in 50-100 gallons of
water per acre (14). Although no technical support data have been published,
in application to the forests in the South, fosamine ammonium has been re-
ported to give similar results when injected versus sprayed on certain
species (12).
A-131
-------
TABLE '1. AVAILABLE DATA ON "KRENITE" USAGE IN THE PACIFIC NORTHWEST,
FISCAL YEARS 1977 TO 1979 (11)
Agency
F.Y.
Targets
Units
Treated
Amount Used
State of Washington,
Dept. of Natural
Resources
State of Oregon,
State and
Private Usage
State of Oregon,
Bureau of Land
Management
State of Oregon,
P ermit t ee/grant ee
USDA Region 6,
Oregon and
Washington
1978 Forestry and
non-forestry
1977 Forestry and
non-forestry
1979 Brush road
maintenance
1979 Brush/conifer
release
1979
1979
1978
1978
1978
Broadleaf road
maintenance
Site preparation
Right-of-way
maintenance
Right-of-way
maintenance
659 acres 517 gallons
425 gallons
166 miles 20 pounds
809 acres 809 pounds
Site preparation 643 acres
and conifer re-
lease
3585 pounds
26 acres 104 pounds
960 pounds 310 acres
506 pounds 82 acres
12 pounds
2 acres
Fosamine ammonium is also registered as a foliar spray for control of
field bindweed and brush control on rights-of-way, industrial sites storage
areas, drainage ditch banks, railroad, utilities, and lands adjacent to and
surrounding domestic water supply reservoirs, supply streams, lakes and
ponds (2,3,12,15). Usual application rates are 6 to 12 Ibs/acre on'rights-
of-vay (4>, and application methods include aerial broadcast methods or
ground methods (4,16).
A-132
-------
Fosamine ammonium is usually applied in the late summer or early fall
before leaf coloration occurs; it is quickly absorbed by the plant foliage,
stems and buds (3,6). Browning of the leaves occurs soon after application
in non-deciduous species; no such immediate impact is observed in deciduous
species. In the spring following treatment, bud development is suppressed
in all susceptible species which fail to refoliate and die. However, the
stems of many woody species may remain alive for 1 to 3 years following
application of fosamine ammonium.
Fosamine ammonium is marketed domestically by E.I. DuPont de Nemours
Co., Inc. (15). It is available as the amber-colored water soluble liquid
formulation containing 41.5 percent (4 Ib. minimum/ gal Ion) active ingredient
(15) and is marketed in 1-, 5-, and 30-gallon drums (2,3). Non-ionic sur-
factants such as DuPont Surfactant WK, Tween 20, or Triton X-100 are often
added at a rate of 1 quart per 100 gallons prior to application to promote
plant penetration (16,17).
2.0 PHYSICAL/CHEMICAL PROPERTIES OF ACTIVE INGREDIENT
The active ingredient is ammonium ethyl carbamoylphosphonate:
It is a white crystalline solid melting at 175°C. It is highly water soluble
(179 g/100 g) and slightly soluble in most common organic solvents as indi-
cated below (15,18):
Solubility,
Solvent g/100 g at 25aC
Chloroform 0.004
n-Hexane 0.02
Acetone 0.03
Benzene 0.04
Dimethylformamide 0.14
Ethanol 1.20
Methanol 15.80
A-133
-------
Fosamine ammonium has low volatility, with a vapor pressure of A x 10
mm Hg at 25"C (18).
3.0 ENVIRONMENTAL FATE
Very little environmental fate data have been published in connection
with the use of fosamine ammonium in forests. Host of the discussion in
this section is based on data reported for non-forest applications.
3.1 UPTAKE AND METABOLISM IN PLANTS
Limited studies have been, and are being, conducted on the uptake of
fosamine ammonium in plants (2). The studies indicate that it is absorbed
by foliage, buds and steins with no major visible effect until the following
spring when bud development is either prevented or severely limited by the
production of only miniature, spindly leaves which are chlorotic and do not
photosynthesize adequately (18). (As noted previously, certain non-deciduous
plants such as bindweed and some pines may show browning immediately after
application.) (3,18).
In uptake, translocation and fate studies in greenhouse experiments
14
with apple seedlings using C-labelled fosamine ammonium, slow penetration
and a half-life for the intact material of 2-3 weeks were observed when
fosamine ammonium was applied to leaves; better penetration occurred when
the fosamine ammonium was applied to the stems (18). The use of surfactant
greatly enhanced fosamine ammonium penetration. Once absorbed, foliar-applied
fosamine ammonium rapidly translocated into all leaves, stems and roots.
When applied to the roots via nutrient solution, fosamine ammonium also
translocated rapidly to all parts of the plants. Field studies of fosamine
ammonium efficacy have indicated that complete coverage of all parts of the
woody plants is necessary for effective control under practical use situa-
tions (18).
Limited data are available on the mechanism and products of metabolic
degradation of fosamine ammonium in plants. The metabolism of ^C-labelled
"Krenite" has been studied at 12 Ibs a.i./acre on a pasture area consisting
of a small pin oak surrounded by grass and clover. Fosamine ammonium had an
average half-life of 7 days in the pasture flora. The only metabolites found
were carbamoylphosphonic acid (CPA) and carboxyphosphonic acid which reached
A-134
-------
a maximum concentration after two weeks, then rapidly degraded. Twelve
months after treatment, no fosamine ammonium, CPA, or carboxyphosphonic acid
(<0.05 ppm) were found in pasture turf (19).
3.2 FATE IN SOIL
The fate of fosamine ammonium in soil can be described in terms of 6
factors: volatilization, photodecomposition, adsorption/leaching, runoff,
and chemical and microbial degradation. "Based on limited field data, volati-
lization and photodecomposition are not significant contributors to the loss
of fosamine ammonium following application (2,20).
3.2.1 Adsorption, Leaching and Runoff
Fosamine ammonium is generally considered a low mobility herbicide (3,
20). It is rapidly and reversibly adsorbed on soil particles. On Keyport
silt loam soil, fosamine ammonium has a Freundllch K equilibrium constant of
greater than 20, indicating a high adsorption to the soil (3). The extent
of adsorption (and desorption) is a function of soil type as well as tempera-
ture, moisture and pH. Because of its ionic character, fosamine ammonium is
more strongly adsorbed to soils high in clay and heavy metals content than
to other soils (21). No quantitative data are available on the effects of
soil organic matter, temperature, moisture and pH on fosamine ammonium.
The adsorption capacity of a given soil type for fosamine ammonium
affects the potential for leaching of the herbicide from soil. The leaching
tendency would be lower with those soil types and under those conditions
which promote adsorption. Based on limited data available, it appears that
leaching is less pronounced in soils with high clay and heavy metals content
than in soils with lower clay and heavy metals content. Tables 2 and 3
present the results of laboratory leaching tests with silt loam Keyport soil
(17 percent clay content) and sandy loam Fallsington soil (12 percent clay
content). The data indicate low leaching tendencies for both soils, but
higher leaching for the soil with the lower clay content. The mobility of
fosamine ammonium in soil has been investigated under simulated rainfall
conditions. Table 4 presents the results of a laboratory leaching study
with Fallsington soil in flats 12 x 36 x 3 in., sloped 5 to 10 degrees under
a "rain" application of 25 to 50 ml over a 2-hour period. "Krenite" (15 Ib
a.i./acre) was applied to the top third of the flat before "rain" was applied.
A-135
-------
As shown in Table 4, most of the "Krenite" remained near the surface and in
the upper portion of the flat, thus indicating no appreciable downward or
lateral mobility. This conclusion has been also confirmed in a field study
(20). Other field studies conducted in Florida, Delaware, and Illinois with
14
C-labelled fosamine ammonium have also indicated very little or no down-
ward movement in soil of the herbicide or its degradation products (1,18).
TABLE 2. SHORT TERM LABORATORY LEACHING STUDY WITH
':-LABELLED FOSAMINE AMMONIUM "(1,20)
*
Soil Section
0-2 inch
2-4 inch
4-8 inch
8-12 inch
Total in Soil
Total in Leachate
Total Recovered
— _ —
j.
Activity Recovered, 2
Keyport Soil
43.5
21.5
10.5
3.2
78.7
4.4
83.1
=========
Fallsington Soil
27.3
34.6
13.7
9.5
85.1
9.3
94.3
••" — -.. ...
Columns, 2 inches by 10 inches in length, were packed with soil
-
O
time 7 days, Keyport time 20 days. columns; Fallsington
The role of organic matter in the soil on adsorption and mobility of
fosamine ammonium have not been studied and no actual measurements of these
parameters in the forest soil have been reported.
Because of its low mobility and its strong adsorption to soil particles,
loss of fosamine ammonium via solubilization or subsurface leachate would be
expected to be minimal. Loss in aur-fA.-a
t<4C& tUnOtI of £0&&inin& ammn ^ £
soil surface however, is possible via aobilisatlon of ,osaBine a^onlul-
adsorbed soil particles b, the action of flowing 6ur£ace uater
following a heavy rainfall. ' e8Pecll'115r
A-136
-------
TABLE 3. LONGER-TERM LABORATORY LEACHING STUDY WITH
l^C-LABELLED FOSAMINE AMMONIUM (1,20)
Soil Section
Activity Recovered, %
Keyport Soil
Fallsington Soil
0-2 inch
2 - A inch
A - 8 inch
8 - 12 inch
Total in Soil
Total in Leachate
Total Recovered
A9.6
22.0
5.8
3.9
81.3
2.0 or less
83.3
37.7
3A.8
11.3
6.1
89.9
2.0 or less
91.9
Columns 2" by 12" in length were packed with soil and then 100 gm of
soil treated with -^C fosamine ammonium were added to the top of each
column. After aging for 30 days, water was added at a constant rate
of 0.5 inches per day, for A5 days.
TABLE A. LABORATORY MOBILITY STUDY USING
LABELLED FOSAMINE AMMONIUM (20)
1A.
Soil Layer
Activity Recovered (%) in Increments Along Flat
0-12 inch 12 - 2A inch 2A - 36 inch
First inch
Second inch
Third inch
Total
92.6
1.0
0.2
93.8
2.08
0.33
3.2.2 Chemical and Microbial Degradation
Fosamine ammonium is not considered a persistent compound in soils.
Under field conditions in Florida, Illinois and Delaware, the half-life of
1A
C-labelled fosamine ammonium in soils was approximately one week following
treatment at an application of 11.3 kg/ha (a rate typical of practical use
A-137
-------
levels) (1). The results, shown in Table 5, indicate that fosamine ammonium
and its major metabolite carbamoylphosphonic acid (CPA) had disappeared com-
pletely within 3 to 6 months. Much of the residual 1AC was incorporated
into the soil organic matter (alpha-humus, beta-humus, soluble humin frac-
tions, etc.). Greenhouse soil studies with L C-labelled fosamine ammonium
indicated a half-life of about 10 days, which is in good agreement with the
field study half-life (1,18).
TABLE 5. C RESIDUES FOUND IN 0-5 cm SOIL INCREMENTS IN FIELD STUDIES (1)
Time After
Application
Percentage Detected 14C in
H20
Extractt
*
pH 10
Extract
Unextracted
Residue
Percentage
Detected l2*C as
Fosamine CPA
KEYPORT SILT LOAM
0 day
1 week
2 week
6 week
6 month
1 year
68.3
32.8
27.3
20.8
18.7
3.8
29.1
61.0
64.0
69.3
70.1
82.5
3.1
6.1
8.2
8.9
9.0
9.2
>96 <1
49.3 <1
27.5 26.7
5.6 10.4
<1 <1
FLANAGAN SILT LOAM*
0 week
1 week
6 week
.2.5 month
3 . 5 month
6 month
10 month
12 month
LEON IMMOKALEE
0 week
1 week
2 week
1 month
3 month
6 month
9 month
12 month
*
73.0
52.0
50.1
31.2
21.7
20.9
20.1
18.5
FINE SAND*
90.5
70.1
64.0
47.3
35.7
34.1
29.6
28.7
~ — _
•
19.6
34.9
36.7
55.5
62.4
63.2
62.2
61.7
4.4
8.3
9.5
38.0
48.9
52.3
54.4
52.2
- __
•
1.8
2.6
5 5
•J * J
8.8
8.1
8 0
v • \j
8 3
*•* • J
8.5
1.1
1.8
3.7
3.9 -
L •>
H . f.
4.1
4.4
4.0
•
'
>95 <1
40 5
<1 40
<1 <1
<1 <1
<1 <1
<1 <1
>95 <1
36 60
<5 83
<1 41
! :!
See Table 6 for soil property data.
CPA was major constituent in the water extract.
A-138
-------
TABLE 6. PROPERTIES OF SOILS USED IN FOSAMINE AMMONIUM PERSISTENCE
STUDY SHOWN IN TABLE 5
Constituents,
SOIL
SAND
SILT
CLAY
ORGANIC
MATTER pH
Keyport silt loam,
Newark, Delaware 21
Flanagan silt loam,
Rochelle, Illinois 5
Leon Immokalee Fine Sand,
Bradenton, Florida 99
62
64
17
31
2.8
4.0
1.0
6.4
5.0
6.4
As described below, fosamine ammonium degradation in soil occurs via
both chemical and microbial routes.
Chemical Degradation—
Hydrolysis of fosamine ammonium to carbamoylphosphonic acid (CPA) is
thought to be one of the major chemical degradation routes in soil (1,18).
t
0
HO-P— C-NH.
i 2
OH
CPA
The kinetics of and pH's favorable to hydrolysis have not been determined.
Like fosamine ammonium, CPA is non-volatile and degrades fairly rapidly in
soils (see above). The dependence of the degradation of CPA in soil on soil
type, temperature, moisture and pH have not been determined.
Microbial Degradation —
Laboratory studies by Han (1) have shown that fosamine ammonium is de-
14
composed quickly by soil microorganisms. When C-labelled fosamine ammonium
A-139
-------
was added to Fallsington sandy loam and Keyport silt loam soils in labora-
tory biometer flasks to establish 4 and 20 ppm treatment levels, between 45
and 75 percent of the original weight of the labelled carbon was evolved as
C02 within 90 days (1). As noted in Figures 1 and 2, the degradation was
essentially nil in the sterile soils at least during the first 20 to 30 days
of the experiments; the minimal activity noted subsequently in these soils
is probably due to the loss of complete sterility.
The effects of soil moisture, temperature, pH, soil type and nutrient
levels on microbial degradation of fosamine ammonium have not been studied.
Also not evaluated is the mechanism of degradation of fosamine atnmonium by
soil microorganisms.
3.3 PERSISTENCE IN WATER
Several laboratory studies have been conducted by DuPont [Han (1)] on
fosamine atnmonium persistence and degradation in water. Aqueous solutions
of C-labelled fosamine ammonium at 5 ppm .concentration were found to be
stable in the dark (less than 3 percent decomposition) for 4 weeks at pH 7
and 9, but at pH 5 hydrolyzed nearly completely to CPA within 2 weeks (1).
The half-life for the reaction at pH 5 was approximately 10 days. At 7200
PPm concentration, which is more typical of normal spraying operations, lesa
than 3 percent decomposition was observed at any of the pH's studied. Ac-
cording to Han (1), decomposition under actual field conditions is expected
*.** .k-n _. J —. J—__ 1 *
to be minimal.
The rate of fosamine ammonium photodecomposition in »ater is extremely
.lov. as measured under lavatory conditions, and is not expected to be
significant in the environment (1.20). Laboratory photolysis studies con-
ducted with a Genera! Electric-40BL lamp (300-500 nm) positioned 7 inches
; 0£ the sample° containlnB 5 ppm £oMmlne «ta - «""
Density of 1200 watts/s, cm (about half of the intensity of
an
r.r:
A-140
-------
sH
20
40 60
TIME (DAYS)
80
14 14
Figure 1. C02 Evolved From C Fosamine Ammonium Treated
Fallsington Sandy Loam in Biometer Flasks (1)
£
t
Is
SO
10
-i-
0 10 20 30 40 » 60 70 "0 SO
TIME (DAYS)
14 14
Figure 2. C02 Evolved From C Fosamine Ammonium Treated
Keyport Silt Loam in Biometer Flasks (1)
A-141
-------
4.0 IMPACTS ON NON-TARGET PLANTS AND ORGANISMS
4.1 PLANTS
Fosamine ammonium is considered phytotoxic to most non-target woody
forest and non-forest plants (18,22,23). Pines are the conifers most sus-
ceptible to injury from fosamine ammonium. In a study by Radosevich, et al.
(24) on the seasonal tolerance of 6 coniferous species to fosamine ammonium,
it was determined that conifers were more tolerant after fall dormancy, but
substantial injury and mortality occurred in spring or summer, when rates
of photosynthesis were high and moisture stress was low. The actual results
of the study are summarized in Table 7.
Since fosamine ammonium is rapidly degraded in the soil, there should
not be sufficient residue carry-over to cause injury to susceptible species
in the next growing season.
TABLE 7. SURVIVAL OF SIX CONIFEROUS SPECIES FOLLOWING
FOSAMINE AMMONIUM APPLICATION (24) (4.5 kg/ha)
Species
Ponderosa pine
Jeffrey pine
Sugar pine
Douglas fir
White fir
Red fir
Conifer
April 14
0
4
14
4
6
3
Survival (% of untreated)
Application
July 7
0
6
45
12
17
29
Date
September 23
96
80
85
94
88
97
Average
32
30
55
37
37
43
4.2 FISH
Limited studies conducted on the toxicity of fosamine ammonium to fish
indicate it has a low toxicity to several species (25). LC 's of "Krenitc
for bluegills, rainbow trout, and fathead minnows are 670, >1000, and >1000
.11
A-142
-------
ppm, respectively (2,18). The 48-hour LC in Daphnia magna is 1,524 ppm.
The 96-hour LCSO on salmon is 8,290 ppm in a static bioassay and 9.812 ppm
in a replacement bioassay (2). No data are available on the metabolism of
fosamine ammonium in these species or in fish.
4.2 WILDLIFE
"Krenite" has low toxicity to warm-blooded animals. The acute oral LD-0
of "Krenite" for rats is 24,000 mg/kg; for guinea pigs, 7,380 mg/kg (26). The
approximate lethal dose for dogs is greater than 15,000 mg/kg (2). Little
data are available in the literature on toxicities of fosamine ammonium to
birds and wildlife species (i.e., deer, beaver, etc.). However, a toxicolo-
gical investigation conducted on mallard ducks and bobwhite quail showed
"Krenite" to have very low toxicity to these species (LI>50 greater than 10,000
mg/kg for both species) (18,26). Subacute oral toxicity studies conducted
on rats showed no adverse effects except for mild diarrhea from feeding
2,200 mg/kg/day over a 2-week period. A level of 1,000 ppm in the rat diet
for 3 months also showed no adverse effects except for diarrhea (2). At
high doses (up to 10,000 ppm), rats had kidney tubule cell swelling and dogs
had increased heart and stomach weights (5). In dietary studies conducted
on dogs for 6 months and sheep for 3 months, little evidence of toxicity
was found (2,18). Acute dermal toxicological investigations using rabbits
gave an LC of greater than 4,000 mg/kg (27). Other studies have indicated
"Krenite" has a relatively low acute inhalation toxicity (28). A teratology
study indicated that fosamine ammonium was not teratogenic when pregnant
rats were fed 10,000 ppm in the diet. When rats were fed at the rate of
5,000 to 10,000 ppm, there was no adverse effect on reproduction. In an
Ames test, fosamine ammonium was not mutagenic either with or without acti-
vation (2).
Fosamine ammonium is considered non-toxic to fauna, and is registered
for use along stream banks and other water impoundments (9).
4.4 BENEFICIAL INSECTS
Fosamine ammonium is considered non-toxic to bees. A 10,000 ppm spray
solution produced no greater mortality than that presentamong untreated
controls (2).
A-143
-------
4.5 HICROFLORA
Fosamine ammonium is considered non-toxic to soil microorganisms. Labo-
ratory studies using 3 agricultural soils (Leon Immokalee fine sand from
Bradenton, Florida; Fallsington sandy loam from Glasgow, Delaware; and Flana-
gan silt loam from Rochelle, Illinois) showed that populations and species
of soil bacteria and fungi were unaltered over an 8-week period after treat-
ment with 10 ppm fosamine ammonium (20). In an agar plate bioassay test,
fosamine ammonium showed little or no fungitoxicity at treatment rates up to
100 ppm. The fungi tested were: Aspergillus niger. A. Terreus. Penicillium
citrinum. Gibberella saubinetti, Fusarium sp.. Alternaria sp.. Rhizoctonia
soIani, and Pythium sp.
Several studies have been conducted on the effects of fosamine ammonium
on the activity of various soil microorganisms, with varying results. In
laboratory studies using 2 soils (Fallsington sandy loam and Keyport silt
loam), no effect could be detected on either the population or activities
of soil nitrifying bacteria during a 5-week test period after application of
0.5, 5, and 20 ppm fosamine ammonium (1,20,29). However, results of a labo-
ratory study by Hallborn and Bergen (30) showed that treatment of Nostoe sp_.
algae isolated from Peltigira pratextata lichen with 100 ppm "Krenite" dras-
tically decreased nitrogen fixation rates, with total inhibition occurring
after 8 hours.
4.6 BIOACCUMULATION
Fosamine ammonium is metabolized and/or excreted rapidly by animals
14
and is considered non-bioaccumulable (17). When C-labelled fosamine ammo-
nium was administered as a single oral dose to preconditioned rats by intra-
gastric intubation, the radioactivity was rapidly eliminated in the feces
(87 percent) and urine (13 percent) (31). Trace amounts of radioactivity
were found in the gastrointestinal tract, hide, and exhaled air (0.1-0.2
percent). Less than 0.05 percent radioactivity was found in the body tissues
after 72 hours. Total recovery of applied radioactivity was nearly 100 per"
cent. The eliminated carbon-14 in both urine and feces was 87 percent intact
fosamine ammonium and about 13 percent carbamoylphosphonic acid (CPA). The
degradation of fosamine ammonium to CPA is consistent with known metabolic
pathways of organophosphorous agrichemicals in animals (32).
A-144
-------
In addition, when a lactating nanny goat was given seven consecutive
14
daily doses of C fosamine ammonium, the radioactivity was again rapidly
eliminated in the feces (88.6 percent) and the urine (9 percent). Total
14
C residues of fosamine ammonium and its metabolite, CPA, in all tissue
and organs were less than 0.05 ppm 24 hours after the last dose (19).
Fosamine ammonium and its soil degradation products do not significantly
accumulate in fish. In a laboratory study on catfish exposed to 1 ppm
fosamine ammonium for 4 weeks, the accumulation factor was less than 1 and
50 percent of these residues were eliminated in a two-week withdrawal period
(20,33).
There is no evidence for bioaccumulation of fosamine ammonium in micro-
organisms.
5.0 MISCELLANEOUS
As indicated in Section 1.0, non-ionic surfactants such as DuPont Sur-
factant WK, Tween 20, or Triton X-100 are often added to fosamine ammonium
spray formulations to promote plant penetration* Based on data supplied by
the manufacturer and OSHA "data sheets", these surfactants are not considered
toxic or hazardous.
There are indications in the literature that fosamine ammonium is un-
suitable for killing and dessicating shrubs to prepare brushfield for burning
before reforestation in the Pacific Northwest (22). In the Coast ranges of
Oregon and Washington, foresters prefer to spray brush for site preparation
during late winter or early spring and burn the dry bush in August or Sep-
tember of the same year. Since fosamine ammonium is most effective when
applied during late summer or early fall and does not show its effects on
plants until the following spring, burning may not be possible until at least
1 or even 2 years after spraying. This disadvantage limits the usefulness
of fosamine ammonium for preburn dessication, especially in the Coast Ranges
of the Pacific Northwest.
A-145
-------
REFERENCES
14
1. Han, J.C-Y. Stability of C Fosamine Ammonium in Water and Soils.
J. Agr. Food Chemistry, 27(3): 564-571, 1979.
2. Information supplied to TRW by E. I. DuPont de Nemours, Wilmington,
DE, September 5, 1980.
3. DuPont de Nemours Co., Inc. "Krenite" Brush Control Agent: Technical
Information and Spray Guide. 1975. 6 pp.
4. Lewis, C.R., Jr. 2,4,5-T Use Analysis. U.S. EPA, Plant Sciences
Branch. -Benefits and Field Studies Division, Washington, D.C. Decem-
ber 15, 1979. 17 pp.
5. Information supplied to National Forest Products Association by E. I.
DuPont de Nemours, Wilmington, DE. October 16, 1981.
6. Newton, M. Herbicide and Insecticide Technical Properties and Herbi-
cide Use Guidelines. F-432. September 1979. 22 pp.
7' SliS'T161'/; H«blcideVor s^b and Weed Control in Western Oregon.
USDA Forest Service, Pacific Northwest Forest and Range Experiment
/'a d' 0reS°n- General Technical Report PNW-77. December
*»o pp.
8. Draft Final Report: The Biologic and Economic Assessment of 2 A 5-T.
A Report of the USDA - Status - EPA RPAR Assessment Team. 202 pp.
9. Newton, M. and C.A. Roberts. Brush Control Alternatives for Forest
Site Preparation. Proceedings and Research Progress Report. 28th
Annual Oregon Weed Control Conference, 1979. Salem, Oregon. 10 ppm.
ferR« T«±P Dfa> VeSetation Problems, Control Methods for Coni-
fer Release. Weyerhaeuser Company, Tacoma, Washington. 1979. 4pp.
11. Data provided to TRW by U.S. Forest Service, Washington, D.C. 1980.
12. Status of Some New Herbicides n «?
13.
Bata. Herbicides in Fores«y Data sheet. ^^ 12>
Trees s " *-*»l-*- - B««*
8pp. USDA c<">P«ative Extension Service. 1980.
A-146
-------
15. 1980 Farm Chemicals Handbook. Meister Publishing Co., Willoughby,
Ohio. p. D-25.
16. Draft Environmental Assessment Report: Chippewa National Forest.
Chippewa National Forest Integrated Pest Management Work Group, Cass
ake, MN. 1980. 110 pp.
17. Moore, D.J. Practical Alternatives to 2,4,5-T for Chemical Control of
Brush Along Drainage Ditches and General Watershed Use. Office of
Water Research and Technology, Washington, D.C. PB-262/217/3ST, 1976.
16 pp.
18. Mullison, W.R. Herbicide Handbook of Weed Science Society of America.
Weed Science Society of America, Champaign, Illinois, 4th Edition,
1979. 518 pp.
19. DuPont Report submitted to EPA on 5 December 1979 with Application for
Amended Registration (EPA Reg. No. 352-376). Summarized in Reference
2.
20. Information provided by EPA based on review of the Registration Files
of the Environmental Fate Branch.
21. Personal communication of S. Quinlivan, TRW, to Jerry Han, DuPont,
Biochemicals Dept., Research Division, Wilmington, Delaware. June 4t
1980. In Reference 1.
22. Gratkowski, H.J., et al. Triclopyr and "Krenite" Herbicides Show Pro-
mise for Use in Pacific Northwest Forests. Down to Earth, 34(3): 28-32,
1978.
23. Schlapfer, T.A. Environmental Impact Statement: Vegetation Management
with Herbicides. USDA-FS-RG-DES(ADM) 75-18. USDA, Forest Service,
Portland, Oregon. 1977. pp. 75-96.
24. Radosevich, S.R. Seasonal Tolerance of Six Coniferous Species to Eight
Foliage-Active Herbicides. Forestry, 26(1): 60-66, 1980.
25. Final Environmental Statement. Vegetation Management with Herbicides;
Western Oregon, Volume I. U.S. Dept. of Interior, Bureau of Land
Management, Washington, D.C. 1978. Chapter 3.
26. DuPont de Nemours Co., Inc. Fosamine Ammonium. Technical Data Sheet.
Biochemicals Dept., Wilmington, DE. May 1979. 3 pp.
27. Final Environmental Statement: Vegetation Management With Herbicides.
USDA-FS-R6-FES(ADM) 75-18, U.S. Dept. of Agriculture, Pacific North-
west Region, Forest Service, Portland, Oregon. 1978. p. 132-3.
28. DuPont de Nemours Co., Inc. "Krenite" Brush Control Agent. Technical
Data Sheet. 1976. In Reference 27.
A-147
-------
29. Han, Jerry C-Y and R.L. Krause. Microbial Activity in Soils Treated
with Fosamine Ammonium. Soil Science, 128(1): 23-27, 1979.
30. Hallborn, L. and B. Bergman. Influence of Certain Herbicides and a
Forest Fertilizer on the Nitrogen Fixation by the Lichen Peltigera
praetextata. Oecologia (Berl.) 40: 19-27, 1979.;
31. Chrzanowski, R.L., J.C-Y Han, and C.L. Mclntosh. Metabolism of ^C
Fosamine Ammonium in the Rat. J. Agricultural Food Chemistry, 27(3):
550-554, 1979.
32. Menn, J.J. and J.B. McBain. Residue Reviews, 53(34), 1974. In Re-
ference 31.
33. Han, Jerry C-Y. Residue Studies With 14C Fosamine Ammonium in Channel
Catfish. J. of Toxicology and Environmental Health, 5: 957-963. 1979.
A-148
-------
Common Name: Glyphosate
Chemical Name: N-(phosphonomethyl)glycine
Major Trade Name: Roundup
Major Applications Glyphosate is used for site preparation, conifer re-
in Forestry: lease, post directed sprays, and tree injection.
SUMMARY
Being a relatively new pesticide, the environmental fate and potential
ecological effects of the use of glyphosate in forests have not yet been
adequately studied. The limited data which are currently available are
almost entirely from greenhouse and laboratory studies with agricultural
systems and laboratory animals and have been largely generated by the manu-
facturer. These data indicate high effectiveness, short persistence in
soil and water environments, and very low toxicity to animals for glyphosate.
Because of these features, a great potential exists for future large-scale
use of glyphosate in forestry.
Glyphosate is absorbed almost exclusively via plant foliage and is
translocated throughout the plant. Less than one percent of the glyphosate
in the soil is absorbed via the roots. Glyphosate is apparently not meta-
bolized to a significant degree in plants and its mode of action is believed
to involve inhibition of aromatic amino acid synthesis. It is rapidly and
strongly adsorbed to soil particles; this strong adsorption by soil accounts
for the observed lack of mobility and leaching tendency of glyphosate in soil
and its "unavailability" for root uptake. Adsorption to soil is believed to
be through the phosphonic acid moiety, since phosphate level in the soil in-
fluences the quantity of glyphosate adsorbed and glyphosate adsorption is
greater in soils saturated with Al"*"1"* and Pe"*"1"*" than with Na+ and Ca**.
Dissipation of glyphosate in soil is fairly rapid (half life about 2
months) and is primarily due to microbial degradation. The principal soil
metabolite of glyphosate is aminomethylphosphonic acid (AMPA), which itself
is also highly biodegradable. Glyphosate is subject to biodegradation in
natural waters and has an estimated half-life of 7 to 10 weeks.
Under normal application rates, Roundup™ herbicide (the commercial
formulation of glyphosate) should not be toxic to forest fauna at recommended
application rates. Bioassay tests on several aquatic invertebrates and
fishes have indicated 96-hr LC5Q values ranging from 2.3 mg/L for fathead
minnows to 43 mg/L for mature scuds. Aquatic tests comparing toxicities of
the technical grade glyphosate, Roundup herbicide and the surfactant used in
Roundup herbicide have indicated that the surfactant and not the glyphosate
is the primary toxic agent in Roundup. Animal feeding studies with glyphosate
have indicated low toxicity to rat, mallard duck and quail and little or no
potential for bioaccumulation.
@ Trademark of Monsanto Company.
A-W9
-------
1.0 INTRODUCTION
Glyphosate is a broad-spectrum and relatively non-selective herbicide
introduced in 1971 (1). Its primary uses are in agriculture and on non-
crop areas such as industrial and recreational areas, irrigation canals
and rights-of-way (2). The use of glyphosate in forestry is relatively
new and has been primarily in the Pacific Northwest for control of brush
species such as bigleaf maple, vine maple, alder, salmonberry, thimble-
berry, hazel, and bracken fern (3). Specific forestry applications in-
clude preplant nursery uses for pine seedlings, site preparation, and
conifer release and seed orchards and seed production areas (4). In 1979,
approximately 4100 Ib of glyphosate was used in U.S. Forest Service
Regions 5 and 6 (more specifically, in the Pacific Northwest); of this,
about 3600 Ib were used for conifer release, and the remainder was used for
general weed control, including right-of-way applications (5). According to
the Oregon Department of Forestry (6), use of glyphosate is now an integral
part-of that state's vegetation management; about 3000 to 5000 acres of
state-owned forest land are annually treated with glyphosate, primarily for
conifer release. In the Pacific Northwest, glyphosate has proved considera-
bly more effective than 2,4,5-T for the control of certain specific weed
species (e.g., salmonberry and thimbleberry). For these applications, gly-
phosate may be overall more cost-effective than 2,4,5-T, despite its higher
per acre treatment cost (estimated at about $50/acre). No quantitative data
are available on the extent of usage of glyphosate by private timber compa-
nies, although such uses are reported to be "major" (3). Limited uses of
glyphosate have also been reported in the northeastern United States, prima-
rily in connection with Christmas tree production and in experimental site
preparation/conifer release plots. In Maine, 6,000 Ib of glyphosate were
used for these purposes in 1979, and Georgia Pacific treated 2,400 acres of
its forest plantation in Maine with glyphosate in 1979 (8).
Both ground and aerial application methods have been used in connection
with forestry uses. When applied aerially, use of "raindrop" nozzles signi-
ficantly reduces potential for drift. A typical application rate for conifer
release is 1 to 1.5 quarts of Roundup herbicide per 10 gallons of solution
per acre; somewhat higher rates (about 3-4 quarts of Roundup herbicide per
10 gallons of solution) have been used for site preparation (6)
A-150
-------
Glyphosate is manufactured by Monsanto Co. and the commercial formula-
(R)
tion, Roundup^, is a mixture containing a surfactant and the isopropylamine
salt of glyphosate (24). The role of the surfactant is to increase absorp-
tion and translocation of the herbicide in plants.
2.0 PHYSICAL/CHEMICAL PROPERTIES OF ACTIVE INGREDIENT
Glyphosate is the common name for N-(phosphonomethyl)glycine. Its
structural formulation is:
0 H O
II I I!
HO - C - CH - N - CH - p - OH
2 2 ,
OH
It is a white odorless solid with a melting point of 200°C. The solu-
bility in water is 1.2 percent at 25°C and the solubility in other solvents
is reported as "none" (11). The vapor pressure of glyphosate is reported as
"negligible".
3.0 ENVIRONMENTAL FATE
3.1 UPTAKE AND METABOLISM BY PLANTS
Field and greenhouse studies have indicated that the basic mechanism
for the uptake of glyphosate is through the plant foliage; some root uptake
may also take place, depending on the soil type. Although the mechanism of
glyphosate action is not fully elucidated, it is believed to involve blockage
of aromatic amino acid biosynthesis (12).
Humidity and the presence of surfactants significantly increase the ab-
sorption of glyphosate by the foliage. Foliar absorption experiments con-
ducted in a greenhouse by Gottrup, et al. (13), using Canada thistle (Cirsium
arvense) and leafy spurge (Euphorbia esula) indicated maximum absorption under
conditions of high humidity when glyphosate was applied with surfactant.
Under conditions of low relative humidity (ambient glasshouse conditions),
each species absorbed about 27 percent of the applied herbicide after one
week. Under high relative humidity (plants in plastic bags), absorption was
about 85 percent after one week. Both low and high humidity experiments were
conducted in the presence of surfactants.
Wyrill and Burnside (14) also conducted foliar absorption experiments
on field and greenhouse plants. Tests were conducted on common milkweed
A-151
-------
(Asclepias syriaca) and hemp dogbane (Apocynum cannabinum). The tests found
that neither wax removal, subcuticular cell damage, nor surfactant signifi-
cantly increased diffusion of glyphosate across common milkweed or dogbane
cuticles. Removal of epicuticular wax with chloroform did not appreciably
increase absorption of glyphosate in either species.
The hydrophobic epicuticular wax is probably an effective barrier to
the polar, negatively charged glyphosate molecule. However, since wax re-
moval had little effect on glyphosate absorption, it appears that the cuticle
is also an effective barrier to glyphosate absorption. Wyrill and Burnside
(14) noted that this was possibly because glyphosate was repelled by negati-
vely charged cuticle components. Based on the finding that an effective
surfactant did not increase glyphosate diffusion across the cuticles of
either species, Wyrill and Burnside (14) postulated that the main influence
of the surfactant may be on the plasma membrane and not the leaf cuticle.
Sprankle, et al. (15) investigated the absorption of glyphosate via
roots. Greenhouse studies found that soybean and com grown in Spinks sandy
loam soil absorbed less than 0.8 percent of the glyphosate applied to the
soil. However, glyphosate was readily absorbed from a nutrient solution by
wheat seedlings. This suggests that the absence of glyphosate effect when
applied to the soil is probably due to the unavailability of glyphosphate in
soil for absorption by the roots (see Section 3.2.1) (15).
Once absorbed by plants, glyphosate is translocated to all plant parts
including the underground propagules of perennial species, thus preventing
their regrowth (11). Studies of the metabolism of glyphosphate by Canada
thistle, leafy spurge, milkweed and hemp dogbane have indicated no signifi-
cant degradation in these plants up to 20 days after treatment (13,14). No
data have been reported on persistence in plants over longer time periods.
In one study using C-glyphosate on Canada thistle and leafy spurge foliage
and roots, the examination of autoradiographs of thin layer plates containing
Plant extracts indicated the presence of intact 14C-glypho8ate in both species
with no detectable amount of metabolites of UC-glyphosate one week after
treatment (13).
3.2 FATE IN SOIL
Dissipation of glyphosate in soil ls considered to be rel.tively rapid.
A-152
-------
Rueppel, et al. (10) conducted greenhouse soil dissipation studies in which
glyphosate was applied to soil just prior to the planting of corn. Three
different soil types (Drummer silty clay loam, Norfolk sandy loam, and Ray
silt loam; organic contents: 6 percent, 1.0 percent, and 1.0 percent, res-
pectively) and two different glyphosate concentrations (4 and 8 ppm corres-
ponding to approximately 4.48 and 8.98 kg/ha application rates) were used.
For both application rates, the calculated half-lives were 3, 130, and 27
days for Drummer, Norfolk, and Ray soils, respectively. The relatively
rapid dissipation of glyphosate in soil has been substantiated by the results
of actual field studies (conducted by Monsanto on eleven different soils
covering a full range of soil types and geographic areas) which indicate an
average half-life of 2 months. Other investigators have reported half-lives
of 17 to 19 weeks for sandy soil and 3 weeks in silt loam (16).
Adsorption on soil particles, which influences the potential for leach-
ing, runoff, and degradation by the action of soil microorganisms are the
primary factors in determining the dissipation of glyphosate from soil.
Photodecomposition, volatilization and chemical degradation do not appear
to make significant contributions to glyphosate losses. (As noted in Section
2, glyphosate is reported to have a negligible vapor pressure. Rueppel, et
14
al. (10) investigated the photodecomposition of C-glyphosate in solution
14
using a Crosby photoreactor and found no loss of C content via volatile
degradation products and no change in the composition of the test solution.)
3.2.1 Adsorption. Leaching and Runoff
The strong adsorption of glyphosate on soil has been demonstrated in a
number of studies and is considered the initial step in inactivation (i.e.,
"unavailability" to plant roots) of glyphosate in soil. In a greenhouse
study, Sprankle, et al. (15) measured the effect of glyphpsate on the growth
of 16-day-old wheat plants grown on washed quartz sand, clay loam (3.7 per-
cent organic content) and muck soil (81 percent organic content) treated with
glyphosate at application rates of 4.5, 11, and 56 kg/ha. While no reduction
in plant yield was observed for the two soils, glyphosate treatment signifi-
cantly reduced plant growth in the quartz sand, thus indicating that the
herbicide was adsorbed to the soils and that adsorption to sand was much
less extensive.
A-153
-------
Sprankle, et al. (15) also studied the effect of pH and phosphate on
the adsorption of glyphosate by soil, using plant yield as a measure of gly-
phosate inactivation and, hence, adsorption. While no significant pH effect
was observed at glyphosate application rates of 4.5 and 11 kg/ha, a pronounced
effect was observed at an application rate of 56 kg/ha; at this rate, reduc-
tions in yield of 20 percent, 7.5 percent, 27 percent, 51 percent and 55
percent were observed at pH levels of 4.6, 5.1, 5.6, 6.1 and 6.7, respecti-
vely (see Table 3). These results indicated a decrease in glyphosate adsorp-
tion as the pH was raised. Binding of glyphosate to soil was also determined
to be influenced by phosphate. Glyphosate applied at 11.2 kg/ha with 98 kg/ha
of phosphate gave a significant reduction in plant dry weight, while 11.2
kg/ha of the herbicide alone had no effect. The data also indicated that the
initial glyphosate binding was reversible with phosphate anions competing
with glyphosate for binding sites.
Glyphosate adsorption to the soil begins immediately after application
and increases slowly after one hour (17). Glyphosate rapidly binds to kao-
linite, illlte and bentonite clays and to muck. Fe444 and Al44* saturated
clays and organic matter adsorb more glyphosate than Na* or Ca44" saturated
clays and organic matter. Based on these observations and the fact that the
Phosphate level in the soil is the most important factor in determining the
quantity of glyphosate adsorbed, it has been concluded that glyphosate is
bound to the soil through the phosphonic acid moiety (17).
The strong adsorption of glyphosate to soil reduces its mobility through
leaching and surface washout. The mobility of glyphosate in Ray, Norfolk,
and Drummer soils (aee above) has been examined by Rueppel, et al. (10). Soil
thin-layer plates were spotted with 14C-glyphosate and developed twice with
water; the distribution of «C activity relative to the origin was determined
by beta camera analysis after each development. The parent compound was BO
strongly adsorbed by all three soils that 97-100 percent of the 14C activity
had an Rf of less than 0.09. Similarly, 95-99 percent of the starting UC
activity remained at an Rf of less than 0.09 after the second development.
in no case was any of the radioactivity of an R greater than 0.18. These
values correspond to a Class 1 pesticide (Mobile) in the Helling and Turner
pesticide mobility classification system (18). (class 1, 0.0-0 9 Class 2,
0.1-0.34; Class 3, 0.35-0.64; Class 4. 0.6,0.80; ^ £^
A-154
-------
Comes, et al. (19) investigated leaching of glyphosate from banks of
irrigation canals treated with glyphosate. Neither glyphosate nor its pri-
mary soil metabolite, aminomethyIphosphonic acid (AMPA, see Section 3.2.2),
were detected in the first flow of water through two canals following appli-
cation of Roundup herbicide at 5.6 kg/ha to ditchbanks when the canals were
dry. Soil samples collected the day before canals were filled (about 23
weeks after treatment) contained about 0.35 ppm glyphosate and 0.78 ppm AMPA
in the 0 to 10-cm layer. Soil column leaching studies conducted by the
Monsanto Company have also indicated limited potential for leaching (16).
In these studies, soil columns treated with either glyphosate or its sodium
salt were aged for 30 days prior to eluting with 1/2 acre inch of water for
45 days; leaching of parent compound was insignificant.
Rueppel, et al. (10) also evaluated the runoff potential from Ray,
Drummer, and Norfolk inclined soil beds at 7.5° using a rate of 1.12 kg/ha
applied uniformly to the upper third of the soil surface. The entire soil
surface was then subjected to three artificial rainfalls at 1, 3, and 7-day
intervals after treatment. Each time, rainfall was continued through collec-
tion of two consecutive 50-ml samples of runoff water and sediment. The
14
water was separated from the sediment by centrifugation and the C content
of each determined. In both the sediment and runoff water, the amount of
C activity collected was extremely low, ranging from 6.5 x 10~ down to
/ —^ •» ^
1 x 10 percent of that applied for the water and 3 x 10~ to 1 x 10~ per-
cent for the sediment. These data correspond to a maximum runoff of less
than 2 x 10~ kg/ha. The lack of runoff is not surprising in lieu of the
tight binding of glyphosate to soil discussed above.
3.2.2 Degradation
Studies conducted by Sprankle, et al. (17) and Rueppel, et al. (10)
have indicated that glyphosate degradation in soil is relatively rapid and
takes place microbiologically, and not by chemical action. Rueppel, et al.
(10) conducted soil/water "shake flask" experiments to investigate, under
aerobic and anaerobic, and sterile and non-sterile conditions, the mechanism
and rate of glyphosate degradation and the nature of degradation products.
Each shake flask contained 4.5 g (dry weight) of soil, 1 mg of a C-
glyphosate and 100 ml of distilled water. Three different C-glyphosates
were used: N-phosphono-lAC-methylglycine, N-phosphonomethylglycine-1- C,
A-155
-------
14
and N-phosphonotnethylglycine-2- c. Four agricultural soils studied were
Ray silt loam, Drummer silty clay loam, Lintonia sandy loam, and Norfolk
sandy loam, with organic matter contents of 1.0, 6.0, 1.1, and 1.0 percent,
respectively. The results of these experiments and two other experiments
14 14
using sucrose- C and sucrose- C plus unlabelled glyphosate are presented
in Table 1 for Ray silt loam soil. As shown in the table, all 3 carbons of
glyphosate were rapidly degraded at comparable rates in the presence of Ray
silt loam. In addition, all three l C-labelled compounds were degraded to
nearly the same extent and rate as the natural and general metabolite sucrose.
From the three C labels, 47-55 percent of glyphosate 14C was given off as
1 C02 in 4 weeks, compared to 57.9 percent for sucrose. Experiments using
autoclaved soil/water slurries indicated negligible (less than 1 percent)
evolution of CO,, from the three ^C-labelled glyphosates and the control
sucrose C during a 7-day observation period.
Rueppel, et al. (10) also analyzed the supernatants and soils in shake
flasks to determine the distribution of "c labelled compounds between the
two phases and to identify metabolites. The metabolite distribution was
similar for both the aerobic and anaerobic shake flasks for a given soil.
In general, the same metabolites were observed regardless of the soil type.
The principal soil metabolite observed from the N-phosphonic-^C-methyl
label of glyphosate was aminomethylphosphonic acid (AMPA); as expected, due
to the C-label position, this metabolite was not observed radioactively
from the two glycine- C labels. The maximum amount of AMPA detected in the
supernatant was 15 per-ent of the starting 14C activity. Several other
metabolites were also detected chromatographically in soae cases. These
minor metabolites included H-methylaminomethylphosphonlc acid, glycine, N,-
N-dimethylaminomethylphosphonic acid, hydroxymethylphosphonic acid, and two
unknown metabolites; none of these minor metabolites were normally present
to an extent greater than 1 percent of the applied radioactivity. No meta-
bolic products containing an intact N-(phosPhonomethyl)glycine grouping were
detected in these studies.
Analysis of the shake flask soils, carried out by TLC/b.t. ca»er. ana-
lysis of a soil extract obtained by „„.„,„„ ^ „... _ ^
that the eitractable residue consisted pr^arily oE tlle f^f „
and the ^or metabolite AMPA. As in the case »lth the shake «..k super-
A-156
-------
TABLE 1.
EVOLUTION FROM SHAKE FLASKS AS A FUNCTION OF TIME AND
C LABEL FOR RAY SILT LOAM SOIL (10)
r
M
in
•vj
1AC Label
14 *
N-phdsphono C-methyl
14 *
Glycine 1- C
14 *
Glycine 2- C
Sucrose C
14
Sucrose C plus
Unlabelled glyphosate
Type of
Metabolism^
A
An
A
An
A
An
A
An
A
An
14 14
Percent C Released as CC>2
at 30°C at Day Analyzed
3
13.2
6.2
28.1
12.6
19.0
3.8
41.5
34.3
26.7
22.3
7
16.7
8.2
10.1
14.8
16.2
6.8
5.3
10.1
13.0
9.5
14
10.1
17.8
13.8
18.9
12.8
9.9
4.9
5.3
11.7
7.4
21
4.6
3.7
1.9
4.8
4.0
5.9
3.0
3.1
2.2
11.5
28
2.2
1.4
1.4
1.3
3.3
7.1
2.4
2.5
2.0
10.8
14
Total C
as C0?
46.8
37.3
55.3
51.4
55.3
33.5
57.9
55.3
55.6
61.5
Labelled N-(phosphonomethyl)glycine.
Aerobic (A); anaerobic (An).
-------
natants, several minor metabolites were also observed, and the same general
distribution was observed on both the aerobic and anaerobic soils. Combus-
tion analysis of the soils after extraction with NH.OH indicated that from
14 4
8.5 to 40.3 percent of the applied C activity was bound to soil. Although
the bound residue material could not be identified, the NH,OR non-extractable
residue was considered to represent the extensively metabolized products of
glyphosate and AMPA.
14
Shake flask studies of C-labelled AMPA indicated that this major
metabolite of glyphosate is also highly biodegradable. Aminomethyl-14C-
phosphonic acid shake flask studies with Ray silt loam and Drummer silty clay
loam soils gave 34.8 and 16.1 percent, respectively, of the applied 14C as
C02 in 63 days. The slower degradation of AMPA compared to glyphosate was
explained in terms of its possible tighter binding to soil and/or lower per-
meability through the cell walls of microflora.
Based on shake flask slurry studies and dissipation experiments with
moist soil (which confirmed the shake flask results), Rueppel, et al. (10)
concluded that glyphosate is clearly a biodegradable compound in the presence
of soil microflora and that the rate and extent of metabolism are rapid and
complete.
3.3 PERSISTENCE IN WATER
The stability of glyphosate in water has been studied by Monsanto Com-
pany in laboratory tests conducted under sterile and non-sterile conditions
(25). In these experiments, the sodium salt of glyphosate was incubated in
sterile water at PH values of 3.0, 6.0, and 9.0 at 25 and 250 ppm. The
solutions were incubated in the dark at 5" and 35'C for 32 days. Samples
were taken at Ot 7, 14, 21. and 32 days. In addition, three natural water
samples ranging from PH 4 to pH 7.3 were treated with 0.! ppn and Abated
in the dark for 7, 21, 35, and 49 days. Clyphosate tes 8table in 8terile
conditions with slow biodegradation occurring in natural water.
The data reported indicate the following half-lives i* natural water
systems (25): Sphagnum bogs (pH 4.23), 7 veeks; cattail svamp (pH 6 25)
9 weeks; and pond water (PH 7.33), 10 weeks. Monsanto reports that/as with
soil, microbial breakdown is the major route of degradatlon of
A-158
-------
in water. The material is tightly adsorbed to organic and mineral matter
within the aquatic system and then degraded. Rates of degradation are
slower than in most soils due to the lower numbers of microbes In the aqua-
tic system (21).
4.0 IMPACT ON NON-TARGET ORGANISMS
4.1 PLANTS
In applications in the Northeast for conifer release, some "browning"
of conifers have been observed with glyphosates at normal application rates
of 1 to 2 quarts per acre; this browning, however, has been temporary, and
the conifers (e.g., Jack and red pines) have gradually recovered (8). Mon-
santo has conducted field studies on the potential for drift when Roundup
herbicide is applied by air. Their results show that at wind speeds of 12
mph, damaging drift is not likely to move more than 200 ft outside the
target. With rates of 2 quarts or less per acre, Monsanto recommends a
buffer zone of 75 ft. For rates above 2 quarts, 125 ft is recommended; and
a general restriction of 200 ft around homesteads and recreational areas is
recommended (21).
As discussed previously, once the glyphosate enters soils, it is inac-
tivated relatively rapidly via adsorption and microbial degradation. In
agricultural applications, use of glyphosate at proposed rates has been shown
to have no injurious effects on crops planted immediately after herbicide
treatment (15). In sand cultures where glyphosate adsorption is minimal,
high dosages of glyphosate have been shown to reduce height and shoot growth
in several crops. The effect of 0.57 kg/ha of glyphosate applied in sand
culture on the growth of seven crop species is shown in Table 2. Based on
the data in Table 2, a wide spectrum of sensitivity to glyphosate can be ex-
pected. Of the species tested, flax is the most sensitive; corn, soybean
and bean are less sensitive than flax, while barley, oat and cucumber are
the least sensitive of all. Data presented by Sprankle, et'al. (15) also
indicated that the germination of corn, soybean and wheat is unaffected by
glyphosate application rates of as high as 4.5 kg/ha. Table 3 shows that
the dry weight of young wheat plants was not affected by glyphosate applied
to the soil at rates of 4.48 and 11.2 kg/ha (15). (The highest recommended
application rate for forest uses is about 5 kg/ha of glyphosate.)
A-159
-------
TABLE 2. THE EFFECT OF 0.56 kg/ha OF GLYPHOSATE* APPLIED IN SAND CULTURE
ON THE GROWTH OF SEVERAL CROP SPECIES (15)
Species
Flax
Corn
Soybean
Wheat
Barley
Oats
Cucumber
Percent of Control *
Plant Ht.
14 a
35 b
36 b
56 c
68 d
82 e
75 de
Shoot Fresh Wt.
21 a
48 be
42 ab
55 be
72 cd
116 d
69 cd
Shoot Dry Wt.
20 a
45 b
33 ab
52 b
71 c
100 c
86 c
Mono(dimethylamine) salt of glyphosate.
Means within a column with common letters are not significantly different
at the 5 percent level by Duncan's multiple range test.
The control is the treatment where 0.8 percent surfactant was applied to
the sand. rr
TABLE 3.
4.6
5.1
5.6
6.1
6.7
THE EFFECT OF GLYPHOSATE ON THE DRY WEIGHT PER PLANT OF
16-DAY-OLD WHEAT PLANTS FOLLOWING INCORPORATION INTO
HILLSDALE SANDY CLAY LOAM AT SEVERAL PH LEVELS (15)
20 ab
40 de
44 c
43 de
40 de
15 a
39 de
43 c
43 de
40 de
Isopropylamine salt of glyphosate.
19 ab
A2 de
44 c
43 .de
40 de
56.0 (mg)t
16 ab
37 cd
32 c
21 b
18 ab
A-160
-------
Yates, Akesson, and Bayer (27) looked at the effects of spray drift on
wheat and grape plants. Exposure to plants was measured by measuring the
amount of glyphosate deposited on Mylar plates. Previous studies found an
excellent correlation between deposit on Mylar plates and residues on alfal-
fa. The tests found a rather wide band of injury levels as related to de-
posit levels. For example, some low levels of injury occurred at levels as
low as 0.1 to 1 g/ha while some values as high as 10 g/ha produced no injury.
The authors state that the data from this study can be used to indicate
rough guidelines for the most sensitive conditions. For example, they found
that a 10 g/ha exposure on mylar sheets could result in a 70 percent injury
on wheat at the 4-leaf stage of growth. For grape plants, the band of in-
jury levels were somewhat lower (i.e., less injury) but similar to the
response of wheat plants. The data also showed that the grape plants tended
to grow out of the symptoms in time.
A. 2 FAUNAL IMPACTS
Data on the toxicity and limited data on the effects of Roundup on habi-
tat suitability indicate that Roundup can be used in the forest without re-
sulting in toxic effects to forest fauna.
Folmar, et al. (9) conducted several experiments on the effects of gly-
phosate and glyphosate formulations on aquatic ecosystems. Among the tests
conducted were acute toxicity assays for Roundup on several aquatic inverte-
brates and fishes. As shown in Table A, the 96-hr LCSQ values varied from
2.3 mg/L for fathead minnows to A3 mg/L for mature scuds. In Table 5, it
can be seen that under "worse case" conditions, the LC5Q for rainbow trout
can be as low as l.A mg/L. The toxicities determined for the other organisms
were nearer the values for fathead minnows than for the more resistant scuds.
Tests comparing the toxicities of the technical grade glyphosate, Round-
up and the surfactant used in the Roundup formulation have indicated that the
surfactant, and not the glyphosate, is the primary toxic agent in Roundup
(9) (see Tables 5 and 6). As shown in Table A, the 2A-hr LC5Q for rainbow
trout is 1AO mg/1 for glyphosate and only 2.1 mg/1 for the surfactant. The
data in Table 5 also illustrate the effect of pH on aquatic toxicity of
Roundup and its glyphosate and surfactant components. Except for the gly-
phosate which appears to be more toxic at a pH of 6.5 than at a pH of 9.5,
A-161
-------
TABLE 6. EFFECTS OF pH ON TOXICITY OF ROUNDUP, GLYPHOSATE, AND THE
SURFACTANT TO RAINBOW TROUT AND BLUEGILLS (9)
Chemicals,
Organism, and pH
ROUNDUP
Rainbow trout
6.5
7.5
8.5
9.5
Bluegills
6.5
7.5
8.5
9.5
GLYPHOSATE
Rainbow trout
6.5
9.5
Bluegills
6.5
9.5
SURFACTANT
Rainbow trout
6.5
9.5
Bluegills
6.5
9.5
LCso (mg/L) and 95% Confidence Limits
14
2.4
2.4
2.4
7.6
4.0
3.9
2.4
240
240
240
230
7.4
1.4
4.2
3.0
24 h
(12-17)
(2.0-2.9)
(2.0-2.9)
(2.0-2.9)
(6.4-9.1)
(3.2-5.0)
(3.1-4.9)
(2,0-2.9)
(200-290)
(200-290)
(200-290)
(190-280)
(6.2-8.9)
(1.2-1.7)
(3.1-5.7)
(2.2-4.1)
7.6
1.6
1.4
1.4
4.2
2.4
2.4
1.8
140
240
140
220
7.4
0.65
1.3
1.0
96 h
(6.4-9.1)
(1.2-2.2)
(1.2-1.7)
(1.2-1.7)
(3.5-5.0)
(2.0-2.9)
(2.0-2.9)
(1.3-2.5)
(120-170)
(200-290)
(120-170)
(170-280)
(6.1-9.0)
(0.54-0.78)
(1.1-1.6)
(0.72-1.4)
all three chemicals were less toxic to the species tested at the lower pH
value of 6.5.
Folmar, et al. (9) also investigated the effects of temperature on the
toxicity of Roundup to two species of fish. The results, shown in Table 7,
indicate that Roundup is about twice as toxic to rainbow trout at 17°C than
it is at 7°C, and that it is more toxic to bluegills at 27°C than at 17°C.
A-163
-------
TABLE 7. EFFECTS OF ™RATIJRE ON THE TOXICITY OF ROUNDUP TO TWO
Organism and
Temp. (°C)
Rainbow trout
7°
12°
17°
Bluegills
17°
22°
27°
_
LCsn (ttR/L) and 95% Confidence Limits
T A « -- •"—••—•-—»••—•»•——
24 h
14
(11-17)
(11-17)
7.5 (6.3-9.0)
9.6 (7.9-12.0)
6.4 (4.8-8.6)
4.3 (3.4-5.4)
14 (11-16)
7.5 (6.3-9.0)
7.4 (6.2-8.9)
7.5 (6.3-9.0)
5.0 (3.8-6.6)
4.0 (3.2-5.0)
Fol^r, et al. (9) also conducted experiments on my£ly avoidance of
Roundup and rainbo. trout avoidance of the tsopropyla»i»e sa!t of glyphosate.
n these tests, rainhov trout did not avoid concentrations of the isopropy!-
H /r t"' " m8/L! Myfly ^^ SVOlded "^ « "—ration, of
10 mg/L but not at 1.0 mg/L.
ty
ln
stage
^
de
cant difference was observed at S n
surviva! o£ sac-£ry M8 seet ^ 0
indicate that
dulins seasons
"" " 2'° "8/L" Th"' ""'
i sh e " "" """' '"«" « «
fish are present in th, receiving »ter. (9).
insects). Ceding studies
of neater than ,600 pp. of
bees have indicated an LD
,,„ for 8lyphosate if
(l<1Ullt< "*
««• «- «- -
Experiments with
(20). The
A-164
-------
4.3 BIOACCUMULATION
The limited data available indicate that glyphosate has little to no
potential to bioaccumulate when used in forest systems. Trout, bluegills,
and bass exposed to 10-12 ppm of Roundup for 14 days contained only 0.1 ppm
of glyphosate (20). Upon being placed in clear water, the glyphosate in
the "contaminated" fish was depleted (20). The octanol/water partition co-
efficient for glyphosate is reported to be 0.0017 at 20 ppm and 0.0006 at
100 ppm, indicating virtually no tendency to bioconcentrate in living cells
(26).
Folmar, et al. (9) exposed rainbow trout for 12 hours to 0.02, 0.2, and
2.0 mg/L of either the isopropylamine salt of glyphosate or Roundup as a
simulation of actual field exposures. No residues of glyphosate or the
primary metabolite, AMPA, were detected in either the fillets or eggs of
fish exposed to the isopropylamine salt. However, in fish exposed to 2.0
mg/L of Roundup, the fillets contained 80 ug/kg of glyphosate and the eggs
contained 60 ug/kg. Midge larvae, from both drift and substrate samples,
were collected for 7 days after exposure to Roundup in artificial stream
studies. No glyphosate residues were detected in the midge larvae (9).
14
In another study, rabbits were administered a single oral dose of C-
14
glyphosate. Five days after treatment, more than 80 percent of C were
found in the feces, 7 to 11 percent in urine, less than 1 percent in expired
^ L 14
CO. and most of the unrecovered C was found in the colon (16).
4.4 MICROORGANISMS
Rueppel, et al. (10) investigated the effect of glyphosate on soil
microorganisms by measuring the rate of sucrose degradation in treated and
untreated soil and by conducting plate counts of treated and untreated soil
under aerobic and anaerobic conditions, the rate of degradation of C
sucrose to 14CO_ was similar in both glyphosate-treated and glyphosate-
untreated soils. Plate counts appeared to indicate that glyphosate had no
adverse effect on the total microflora population. Treatment of Norfolk
sandy loam caused a large increase (from 3.8 x 10" to 62.0 x 10~ ) in the
total number of microorganisms per gram of soil. These findings are general-
ly consistent with those of Quilty and Geoghegan (23) who found glyphosate
to have minimal effect on microflora in peat.
A-165
-------
Application of glyphosate to three soils - Drummer silty clay loam,
Lintonia sandy loam, and Ray silt loam - at 5 and 25 ppm (1 and 5 times
normal dose) showed no apparent significant effects on nitrogen fixation
or nitrification by microbes (16). Treatment of the three soils mentioned
above with 5 and 25 ppm of glyphosate resulted in no apparent effect on
cellulose degradation, starch degradation, protein degradation, or leaf
litter degradation (16).
A-166
-------
REFERENCES
1. Baird, D.D., R.P. Upchurch, W.B. Homesley, and J.E. Franz. Introduc-
tion of a New Broad Spectrum Postemergence Herbicide Class with Utility
of Herbaceous Perennial Weed Control. Proc. No. Centr. Weed Contr.
Conf. 26: 64-68, 1971.
2. Farm Chemicals Handbook. Meister Publishing Company, Willoughby, Ohio.
1979.
3. Weyerhaeuser Trip Data; Vegetation Problems, Control Methods for Coni-
fer Release. Weyerhaeuser Company, Tacoma, WA. A pp. 1979.
4. National Forest Products Association, Pesticide Uses for Forestry.
Report prepared by the National Forest Products Association, Washing-
ton, D.C. March I960.
5. Pest Management Group, University of California at Berkeley, Raw Data
on Pesticides Usage on Public Lands (U.S. Forest Service), 1980.
6. Personal communication with Mr. Jerry Chetock, Oregon Department of
Forestry, June 13, 1980 (to M. Ghassemi of TRW).
7. McCormack, W.L. and M. Newton. Aerial Application of Triclopyr, Pheno-
xies, Picloram and Glyphosate for Conifer Release in Spruce-fir Forests
of Maine. Abstracts. Meeting, Weed Science Society of America, Fe-
bruary 5-7, 1980.
8. Personal communication with Mr. Oscar Selin, Georgia Pacific (Woodland,
Maine), May 16, 1980 (to M. Ghassemi of TRW).
9. Folmar, L.C., H.O. Sanders, and A.M. Julin. Toxicity of the Herbicide
Glyphosate and Several of Its Formulations to Fish and Aquatic Inver-
tebrates. Arch. Environ. Contam. Toxicol. 8; 269-78, 1977.
10. Rueppell, M.L., et al. Metabolism and Degradation of Glyphosate in
Soil and Water, J. Agric. Food Chem..25(3): 512-528, 1977.
11. Weed Science Society of America, Herbicide Handbook, Fourth Edition,
pp. 224-228, 1979.
12. Jaworski, E.G. Mode of Action of N-(phosphonomethyl)glycine: Inhibi-
tion of Aromatic Amino Acid Biosynthesis. J. Agr. Food Chem. 20(6):
1195-8, 1972.
13. Gottrup, 0., et al. Uptake, Translocation, Metabolism, and Selectivity
of Glyphosate in Canada Thistle and Leafy Spurge. Weed Research 16:
197-201, 1976.
A-167
-------
14. Wyrill, J.B. and O.C. Burnside. Adsorption, Translation, and Meta
bolism of 2, and Glyphosate in Common Milkweed and Hemp Doebane
Weed Sci. 24(6): 557-566, 1976. uogoane.
15 •
16. Information provided by EPA, based on a review of
18. Helling, C.S. Pesticide
. Proc.
20- - Frank
. prov"ed
22-
- • ,
Protection Agency. Undated. te File' GlvP*«>sate, U.S. Environmental
A-168
-------
Common Name: Hexazinone
Chemical Name: 3-Cyclohexyl-6-(dimethylamino)-l-methyl-l,3,5-triazine-
2,4(lH,3H)-dione
Major Trade Names: Velpar>£ Gridball^ Brush Killer; Velpar ^ Weed Killer;
Velpar^ L Weed Killer
Major Applications Used primarily in the Southeast and Southwest for site
in Forestry: preparation and pine release, and the Northeast to a
lesser extent to control undesirable hardwoods in forest
situations.
SUMMARY
Velpar® Gridball® Brush Killer is a relatively new herbicide which is
being evaluated in large-scale commercial applications in the Southeast,
Southwest, Northeast and upper Midwest as a possible substitute for 2,4,5-T
for site preparation and conifer release. Because of its relative newness,
field trials of "Velpar" to date have primarily emphasized evaluation of
efficacy with environmental fate and impact studies in progress. The data
which are available on soil residues, degradation, and impacts on non-target
organisms are primarily those generated in laboratory, greenhouse, field and
forest studies by the manufacturer or investigators in connection with the
registration of various "Velpar" formulations.
Root untake is the principal mechanism for the absorption of hexazinone
by plants from so Us treated with "Velpar" "Gridball" pellets. . Hexazinone is
translocated to the foliage where it blocks the photosynthesis process. In
translocated to the *°^ag. . is dissipated in soil via photodegrada-
addition to plan "P<^e, J^™^ laboratory tests in which soil films
tion, bf°deSrf f i™' *^iar sunlight yielded a photodegradation half-life of
were subjected to art if *c£^££| and field soil degradation tests using
37 days for hexazinone. Greenhous hexazinone degrades in soil bio-
^C-labelled hexazinone have indicated t±OM. Depending on fleld
logically both under aerobic and an ^ ^ ^^ ^
conditions, half-life of h~Sf!i£e app-arS to be independent of the
in excess of six months. The half ^^ ography-liquid scintillation count-
*a"C
application rate. U^ Jdan"een identified-, hexazinone degradation
ing, several triazine compounds have D ^ indicated that hexazinone
products. ^borf orY±n Bluets would be washed into the soil with the
and some of its d^radf X Ind biological decomposition are the major fac-
tors in reducing hexazinone COMUBI.U*-..—
t »v»lnar" "Gridball" for conifer release, some conifer
In applications of Velpar u ^ ^ Qn speciegf rate> soil
mortality may occur from ° ^l*™tox'ic±ty data indicate that "Velpar" is only
type, and other factors. «qu ^ product also does not bioaccumulate
slightly toxic to Daphnia ana . "Velpar" is of low toxicity to
in fish. Toxicity tests nave xiiuo.*...
birds, wildlife, fish, and mammals.
A-169
-------
1.0 INTRODUCTION
With the suspension of forestry uses of 2,4,5-T, considerable attention
has been focused, particularly in the South, on developing suitable chemical
substitutes for 2.A.5-T. DuPont's "Velpar" "Gridball" Brush Killer, which
is being evaluated in large-scale commercial trials, appears to hold some
promise as a partial replacement for 2,4,5-T. It has been found effective
for control of brush at least two inches in diameter at breast height on
coarse to medium textured soils when applied as spring treatment. Rainfall
is required to dissolve the pellets and move the active ingredient into the
root zone of the species to be controlled. Estimates place the total acreage
treated in the South at about 20 thousand acres per year, mainly for site
preparation (1) and conifer release. Another estimate, based on an industry
survey, indicates the following usage of hexazinone in the Southeast for
1979 (2):
Treatment
Site preparation
- woody vegetation
Pine release
- woody vegetation
Pine release
- herbaceous
Site preparation
- kudzu
Hexazinone
Formulations
"Gridball"
"Gridball"
Soluble powder
Soluble powder
Acres
Treated
160
375
6,006
5
Lb Used
1,900
5,000
6,006
15
Kethod of
Application
Ground and aerial
Ground and aerial
Ground
Ground
"Velpar" "Gridball" is currently registered for forestry use in the U.S.
east of the Rocky Mountains. It has been tested in the Pacific Northwest,
the Southeast, Southwest, upper Midwest, Northeast, and Canada (3). Excel-
lent results have been obtained in tests in Michigan and the Northeast (and
in full scale trials in the Southeast and Southvest); results have not been
as promising for the Northwest (3). Some difficultly have also been encoun-
tered in preliminary tests in the colder elites of Maine and Canada; these,
however, are being investigated and the manufacturer feels that "Velpar"
Gridball may also prove effective in the cold climates.
"Velpar" "Gridball" Brush Killer u Bended for forestry sitc pre-
paration and conifer release where loblolly, long leaf, short leaf, slash
A-170
-------
and Virginia pines are grown. It is effective for the control of many woody
plants including black cherry, hawthorn, oaks (such as blackjack, bluejack,
post, southern red, turkey, water, willow, and white oak), sweetgum, wild
plum, and winged elm. Recommended rates for site preparation usually provide
control of hard-to-kill species, including flowering dogwood, hickory, persim-
mon, red cedar, red maple, and sourwood.
"Velpar" "Gridball" pellets are applied by hand or with appropriate
aerial equipment such as the modified Simplex Airblown Seeder. Simplex Manu-
facturing Co. (Portland, Oregon) has developed an applicator device for heli-
copters for aerial application of "Gridball" pellets. In trials in Oregon
and Alabama, the modified seeder was demonstrated to be capable of effective-
ly and uniformly distributing the 1-inch long "Gridball" pellets (4). For
hand application, the spacing between the pellets determines the rate of
application. For example, to apply 5 Ib per acre, pellets must be spaced
approximately 8 1/2 feet apart in each direction on the soil surface; for 10
Ib per acre, 6 feet apart, etc. The degree of brush control and duration of
the effect vary with the amount of product applied, soil type, rainfall, and
timing of application. The chemical is applied before or during the period
of active brush growth and when rainfall can be expected for soil activation.
Reflecting differences in soil characteristics, the recommended label appli-
cation rates vary somewhat for different states. The recommended label
application rates for various soil textures in Alabama are as follows (5,6):
Pounds Product/Acre
PineSiteSpecies Controlled
Soil Texture Release* Preparation or Suppressed
,„ „„ All species listed
Sand 5-6 7 1/2-10 above
Loamy sand, 7-8 10-15
sandy loam
Sandy clay loam, 10 15-20
silt loam, loam
Silty clay loam, 10 15-20
clay loam
*Pine release rates will not control hard-to-kill species.
According to the label, rates higher than those shown above can cause
injury to pines. Based on field results, however, for some "heavy" soils
A-171
-------
in Alabama, application rates of 30 Ib/acre or higher would be required for
effective site preparation (1). The level of residue in soil and its poten-
tial impact on pine seedlings planted subsequently, however, are not currently
known for these very high application rates (1). Data from field applications
also indicate variable results in release applications; while at some sites
pine mortality has been at acceptable levels, at certain sites a pine mortali-
ty of as high as 38 percent was caused by poor distribution of pellets on
stressed or sensitive species of pines (6). "Velpar" "Gridball" should not
be used on poorly drained sites, on sites dominated by small stemmed brush
(<2" DBH) nor on pines which are suffering from loss of vigor caused by in-
sects, diseases, drought, winter injury or other stresses, as severe injury
may result (6).
"Velpar" "Gridball" pellets are available as 10 percent or 20 percent '
active ingredient (7) hexazinone (also referred to as DPX 3674). Another
"Velpar" formulation, "Velpar'' Weed Killer (also referred to as "Velpar" 90)
is a water soluble formulation containing 90 percent active ingredient and
10 percent inerts, and has been used as a foliar spray for control of certain
weeds in Christmas tree plantations and reforestation areas and for the con-
trol of undesirable woody plant species in non-cropland areas such as rail-
road, highway, utility and pipeline rights-of-way, petroleum tank farm
storage areas and drainage ditchbanks. Other "Velpar" formulations are
"Velpar" L (a water dispersible liquid containing 2 Ibs hexazinone) with
registrations similar to "Velpar" Powder (6). '-Velpar" K products (wettable
powders containing various combinations of hexazinone plus diuron) are re-
gistered for uses outside the U.S. (6,8). E. I. DuPont de Nemours & Co., Inc.
(Wilmington, Delaware) is the sole producer of "Velpar" formulations. The
company indicates that it has sufficient production capacity to meet the
current demand (9). The suggested consumer price for "Velpar" "Gridball" is
3 30 per Ib; conffiercial applicators repQrtedly ^^^ between $4>Qo ^
98.50 per acre to apply "Velpar" "Gridball" (9).
2.0 WTHCU. «D CHEKICAL CWMCIBIB1CS OF THE ACTIVE IHGREDIEKT
3-cyclohexyl-6-(dlmethyUmlno)-l-nethyl-l 3 5
A-172
-------
Hexazinone
Hexazinone is a white crystalline solid with a specific gravity of 1.25,
It has a melting point of 115°-117°C and a vapor pressure 2 x 10 nnn Hg at
25°C (extrapolated from a vapor pressure of 6.4 x 10 mm Hg at 86eC) (8).
It is soluble in water to the extent of 3.3 g/100 g at 25CC. Solubility in
other solvents are as follows (8):
Solvent Solubility, e/100 g at 25°C
Chloroform 388
Methanol 265
Benzene 94
Dimethylfonnamide 83.6
Acetone 79.2
Toluene 38.6
Hexane 0.3
The following data have been reported on the stability and photodecom-
position of hexazinone solutions (6,10). Hexazinone slowly degrades in dis-
tilled water (under "artificial sunlight" about 15 percent in 8 weeks). The
rate of photodegradation is about three times faster when small amounts of
inorganic salts are present and about seven times faster in natural river
water or in distilled water when a photoinitiator is present. In buffered
aqueous solutions in the dark at 5 ppm and 5,990 ppm (representing dilute
and spray tank concentrations), the compound is stable (less than 1 percent
decomposition) for at least 5 to 8 weeks at pH 5, 7, and 9 and temperatures
of 15°C, 35°C, and 37eC (see Section 3.3).
3.0 ENVIRONMENTAL FATE
Since "Velpar" is a new herbicide, most of the interest in this chemical
to date has been in connection with the evaluation of its efficacy and the
optimum conditions to improve effectiveness. Accordingly, field trials of
A-173
-------
"Velpar" use in forestry have not included an evaluation of the environmental
fate of "Velpar", until recently. In general, the data which are available
now on soil residues, degradation in water and potential impacts on non-target
organisms are largely those generated in laboratory and greenhouse studies
by the manufacturer in connection with the registration of various "Velpar"
formulations. A forest ecosystem study is now in progress to better answer
the above questions related to forestry (6).
3.1 UPTAKE AND METABOLISM BY PLANTS
When "Velpar" is used in "Gridball" formulation, the rainfall causes
breakdown of the pellets, thereby releasing the hexazinone. The hexazinone
is moved downward in soil in concentrated columns and is absorbed from the
soil solution by the tree roots and is translocated upward in the conductive
tissue to the foliage where it blocks the photosynthetic process and slowly
causes the susceptible woody tissue to die. When applied as a foliar spray,
the root absorption is supplemented by some direct absorption via foliage.
The first visible symptoms of "Velpar" "Gridball" treatment effects are a
yellowing and browning of the leaves followed by defoliation. Some trees will
defoliate and refoliate in the first growing season after application. Other
trees may follow this pattern and, also, put out new leaves in the second
growing season after application; they will, however, gradually defoliate.
The defoliated trees will ultimately die.
Metabolism studies have been conducted on sugarcane and alfalfa.
alfalfa in the field, treated with 1 lb a.i /aero 14r i v i, * ^
, _ . . _ « «*•!./acre C-labelled hexazinone,
contained 0.5, 0.5, and 0.1 ppm total "c-residues when harvested at two,
three, and six months, respectively. At least 70 percent of the total 14C-
residues in the two-month cutting was identify
«. , . u identified as natural products; about
1 percent of the total c-residues consisted of f«e and conjugated he»-
zlnone net.bolitee (12 percent, mi intact hexa *» | "
total of 84.9 percent identified radioactivity (11).
0 08 onm and fi n^ ""* a^ harvest were 0.07 to
metabolite A, and less
— f «••• ^i
A-174
-------
CH3
HEXAZINONE B
0
,S>-NAN
CH3 CH3
A C
H
H
Figure 1. Structures of Degradation Products of Hexazinone (10,14)
3.2 FATE IN SOIL
The major routes for the dissipation of hexazinone in soil are photo-
degradation, biodegradation, and leaching. Volatilization is not considered
to be a significant contributor to hexazinone losses from the soil because
of the very low vapor pressure of hexazinone (see Section 2.0).
3.2.1 Photodegradation
Hexazinone on the soil surface is subject to photodegradation under the
action of sunlight. In a study by DuPont (13)t Flanagan silt loam (organic
14
matter 4 percent) was treated with 10 ppm of C-parent compound, slurried
and placed in petri dishes. Soil film thickness was about 500 microns. The
photosource was artificial sunlight at six inches from the soil film. Expo-
sure continued for six weeks. Samples were extracted with 90:10 acetone:
water, and analyzed by TLC-LSC (thin layer chromatography-liquid scintilla-
14
tion counting). Non-extractable C was analyzed by total combustion-LSC
A-175
-------
procedures. Material balance over six weeks of exposure was 91-100 percent,
1A
with extractable C compounds comprising 89-90 percent and non-extractable
C declining from 10 percent at 0 interval and 1 percent at six weeks. The
half-life of the parent compound was estimated by simple linear regression
at 37 days, with only 40 percent of the parent remaining at six weeks. The
major photoproducts were 3-cyclohexyl-l-methyl-6-(dimethylamino)-l-methyl-l,
3,5-triazine-2,4(lH,3H)-dione (compound A - see Figure 1) and the triazine
trione (compound D) at 9 percent and 5 percent, respectively, at six weeks
sampling Interval.
Photodegradation of hexazinone on soil surfaces has also been demons-
trated in studies where hexazinone was applied to silica gel plates as a
narrow streak and exposed to artificial light (13). After three weeks of
exposure, the percent activity found at each R value was R 0.00, 13 per-
cent; Rf 0.13, 22 percent; Rf 0.27, 8 percent; Rf 0.40, 41 percent; Rf 0.8,
4 percent; and Rf 0.9, 12 percent.
3.2.2 Biodegradation
Greenhouse soil metabolism tests conducted by DuPont (14) using 14C-
labelled hexazinone have indicated that hexazinone is degraded by the action
of soil microorganisms both under aerobic and anaerobic conditions, although
the rate of degradation is somewhat slower under anaerobic conditions. Two
soil types (Fallsington sandy loam and Flanagan silt loam, 1.4 percent and
4.02 percent organic matter content, respectively) were fortified with 4 PP»
hexazinone. Moisture content was maintained and samples were taken periodi-
cally. Water/acetone extracts of the samples were analyzed by a TLC-LSC
procedure. The results indicated that under aerobic conditions the time re-
quired for 50 percent degradation was less than 4 months in both soil types-
The half-life for total radioactive residues was greater than 6 months; 65
percent and 68 percent of the applied "c was present i* Fallsington sandy
loam and Flanagan silt loam soils, respectively, after a 6-month greenhouse
exposure The ma.or metabolites in the greenhouse soils were compounds A,
B, and D (Figure 1) in contrast to the field studies (see below) where com-
pound C was the major metabolite, No degradation of hexazinone ,r loss of
c
e d .
in YJT e*aZin0ne' ~" -""""d -der anaerobic condi-
tions for a 60-day period.
A-176
-------
Laboratory studies in biometer flasks with the two soil types treated
14
with ( C)-hexazinone (4 and 20 ppm) indicated that hexazinone is degraded
by microbial action. The results (14) show that after an initial lag period
14
of 10-20 days, the rate of CO, evolution increased rapidly. After 80 days,
14
45-75 percent of the applied radioactivity had been evolved as C0?. These
14
data suggest that the triazine ring is totally degraded to liberate C02-
No 14CO. was detected in the treated sterile Fallsington sandy loam, and only
trace amounts were found from the treated sterile Flanagan silt loam.
14
Studies to determine the fate of C hexazinone in soil under actual
field conditions have been conducted on test sites at Newark, DE (Keyport
silt loam); Rochelle, IL (Flanagan silt loam); and Scott, MS (Dundee silt
loam) (14). At each location, cylinders were driven into undisturbed soil
14
and the soil Inside each cylinder was treated with C hexazinone at the rate
corresponding to 3.7 kg/ha. Cylinders from each location were dug up at
regular intervals and depth increments analyzed. The results indicated the
following half-life values for intact C hexazinone: 1 month in Delaware,
2 months in Illinois, and 6 months in Mississippi. The time for 50 percent
loss of total radioactive residues was: 3-4 months in Delaware, 6-7 months
in Illinois, and 10-12 months is Mississippi. The major routes of degrada-
tion of hexazinone in soil were determined to involve both demethylation and
hydroxylation of the 4 position of the cyclohexyl ring. The major metabolite
at each location was metabolite C (Figure 1). Other soil metabolites present
in significant amounts at each location were metabolites A, B, and G. The
soil metabolites have been shown to be degradation products of hexazinone in
the rat and in water.
In a separate study (13)> the above mentioned field experiments with the
Keyport silt loam were extended to include an evaluation of the effect of
application rate on persistence of hexazinone in soil. Four application
rates (1.8, 4.0, 9.2, and 20 Ib a.I./acre) were evaluated. At the highest
application rate of 20 Ib a.i./acre incorporated (15 ppm in soil, calculated),
about 15 percent of hexazinone remained in soil after 6 months as combined
hexazinone and metabolites A and B. Some leaching of the parent compound down
to a depth of 12-18 in. was also observed. When surface applied at a rate
of 9.2 Ib a.i./acre (6.9 ppm, -calculated), the concentration of the parent
A-177
-------
compound after 8 months was 0.12 ppm. Test results indicated that the half-
life of hexazinone was apparently independent of the application rate for
the soil type and dosages tested.
In a more recent field study (15) conducted by the U.S. Forest Service
Southern Forest Experiment Station, "Velpar" 90W, at 2 and 4 kg/ha, was
applied by a tractor-mounted boom sprayer to experimental plots of Pacolet
clay and Uchee loamy sand in Alabama. A composite soil sample consisting of
30 cores (1.9 cm in diameter) was taken from each herbicide-treated plot.
Sampling dates were 0, 4, 8, 16, 24, 36, and 49 weeks after treatment. Each
soil core was divided into 3 increments: 0-8 cm, 8-16 cm, and 16-24 cm.
All soil samples were air dried, screened through a 2 mm sieve, stored in a
glass jar, and refrigerated until analysis. Both oat (Avena fatua var.
Florida 501) shoot dry weight bioassay and gas-liquid chromatographic analy-
sis (GC) were used to determine the concentrations of hexazinone in the
soils. For both oat bioassay and GC analysis, the half-life of hexazinone
was about 4-6 weeks in Pacolet clay. In Uchee loamy sand, the half-life of
hexazinone was less than 4 weeks according to both methods. Hexazinone
metabolites A and B were found in both Pacolet clay and Uchee loamy sand
soils. Metabolite C was found in the Pacolet clay soil only.
In a companion field study by the Southern Forest Experiment Station
where the "Gridball" was used instead of the "90W" (15), a half-life of
approximately 14 weeks was obtained on a deep (100") sandy soils. The
hexazinone was metabolized and metabolites A and B were detected at low
levels.
3.2.3 Leaching and Runoff
As part of the field soil degradation studies mentioned above, DuPont
also evaluated the potential for leaching of hexazlnone from the soils tested.
The results indicated that hexazinone and at least some of its degradation
products are washed into the soil with the rainwater. The distributions of
C as a function of the soil depth and total rainfall were as shown in
Tables 1 and 2 for Keyport silt loam and Flanagan silt loam, respectively.
DuPont (6,13) has also reported on laboratory column leaching studies
with Flanagan silt loam (organic content 4 percent, pH 5.0, and cation ex-
change capacity 23.4 me/100 g) and Fall8ington sandy loam ( c
A-178
-------
1.4 percent, pH 5.6, and cation exchange capacity 4.8 me/100 g). Freshly
14
applied and "aged" (30 days) C-hexazinone was applied at a 4 Ib a. i. /acre
rate. Water was percolated through the prewetted columns at the rate of
0.2 in/hr until a total of 20 inches was collected. 0.2-in increments were
36
collected for analysis. A. sodium chloride- Cl breakthru volume test was
also run.
With the sandy loam 87 percent and 64 percent of the applied radioacti-
vity percolated through the columns for fresh and "aged" soils, respectively,
in 20 inches of water. Highest concentrations occurred at 5 inches for
sodium chloride, 8 inches for freshly treated soil and 10 inches for aged
soil.
With silt loam soil 27 percent and 0.1 percent of applied radioactivity
eluted with 20 inches of water for fresh and "aged" samples, respectively.
Highest concentrations occurred at 18 inches for the unaged sample and 7
inches for sodium chloride.
Two-inch increments of the "aged" samples were removed from the columns
and analyzed. The radioactivity remaining in the column was evenly distri-
buted over the length.
The soil column leaching tests thus indicated that hexazinone is leached
in the soils. Leaching rates are much lower for "aged" samples, indicating
the formation of less water soluble or more highly adsorbed degradation pro-
ducts.
Rhode, (14) reported on soil ILC ^bilUy tests using the techni,ues of
Helling and Turner. Rf values „„ „_„ ^ ^^^ g _„ tot
Flanagan silt loam, 0.75 for KovnoT-f
-------
30 cm H-flumes, equipped with water-level recorders, and Coshocton wheel
flow-proportional samplers. Hexazinone concentrations in a sandy loam typic
hapludlt were monitored by soil samples collected on the lower, mid-, and
upper slopes. A series of 19 storms sampled in the last 8 months of 1979
produced a residue loss in runoff amounting to 0.5 percent of the applied
hexazinone (31 percent of the chemical which fell directly into ephemeral
channels). In the soil, a downslope, concentrating wave of hexazinone resi-
dues was observed in the 0 to 10 cm depth. Concentrations peaked 3 days
after the first rainfall at the upper and mid-slope positions, but continued
to climb at the slope base for 60 days. Hexazinone residues in the soil
fell below detection levels by 90 days after the first storm. During a 17
day period immediately thereafter, two peaks of hexazinone residues were
detected in a first order perennial stream below the treated area. Stream-
flow during this period originated entirely from baseflow as no.rainfall
occurred. The peak stream concentration was 23 ppb, consisting of equal
portions of hexazinone and one metabolite. The subsurface movement of resi-
dues produced an additional loss of 0.02 to 0.05 percent of the chemical
originally applied to the watersheds.
In connection with the above field study, Mayack, et al. (18) and Neary,
et al. (19) reported on hexazinone residue (hexazinone plus metabolites A and
B) in solution in a perennial stream 250 m below the watershed. Metabolite
B was never detected. For much of the experimental period, hexazinone resi-
due was below 1 ppb analytical detection limit. Detectable concentrations
(6 to 44 ppb) consisting of metabolite A and hexazinone occurred during very
short periods, prionarily during the third and fourth months, after herbicide
application. Peak residue levels, however, did not show any direct relation-
ship to the magnitude of storm events, nor did periods of elevated concentra-
tions coincide with all storm events.
In a more recent study by the Southern Forestry Experiment Station (1),
"Velpar" "Gridball" was placed on deep sandy soil in a recently-burned area
(to represent the "worst" case in forestry application). Application was
made in 1979 at a rate of one 2 cc "Gridball" pellet (10 percent hexazinone)
on a 6' x 6' grid. Soil samples were collected at the time of application
and 1 week, 2 weeks, 4 weeks, 2 months, 4 months, 8 months, and 12 months
after application; sampling depths were 0-6 inches, 6-18 inches, and 18-30
A-181
-------
inches directly under pellets and around the periphery of pellets (circles
of 12-, 24-, and 36-inch diameter). Thus, at each sampling time, a total of
90 samples were collected. Preliminary results from analysis of the samples
indicated (15) rapid vertical but little lateral hexazinone movement (less
than 12 inches laterally in any direction).
3.3 PERSISTENCE IN WATER
Rhodes (10) studied the degradation of hexazinone in aqueous systems.
The available data indicate that photodegradation and biological decomposi-
tion are the major contributing factors to the reduction of hexazinone
concentration in natural waters; hydrolysis does not appear to contribute
to hexazinone dissipation.
^ Hydrolysis studies consisted of tests run on the following solutions of
C-labelled hexazinone: (a) 5990 ppm (5 lb/100 gal) in 0.05 M pH 5.7 and 9
aqueous buffers at 15°C; (b) 5 ppm in 0.05 M PH 5.7 and 9 aqueous buffers at
15°C; and (c) 5 ppm in 0.05 M pH 7 buffer at 25'C and 37«C. Solutions were
thermostated and kept in the dark. Samples were taken for analysis at one
week intervals for 8 weeks and applied to silica gel TLC plates, developed
and radioscanned. Less than 1 percent degradation was observed in any sample,
Mass spectrometeric analysis of one of the samples showed it to be the same
as a reference standard. These results thus indicated that hexazinone does
not hydrolyze appreciably in water.
Rhodes (10) reported on photodegradation studies of hexazinone in water
under: (a) artificial sunlight having an average uv intensity at the water
surface of about one-half that of typical sunshine at noon, and (b) summer
sunshine in Wilmington, DE. The following solutions containing 5 ppm 14C
hexazinone were used:
Artificial light studies
Distilled water (pH 6.7)
CpH ••»
"ttutfr """ "th Mth»1"">°« (20 ppm) added a. photo-
a. photo-
A-182
-------
Natural sunlight studies
Standard reference water (pH 8.1)
Standard reference water containing 20 ppra riboflavin
Brandywine River (Delaware) water
Brandywine River water with 2.5 cm of bottom sediments
Each solution (200 ml, 5 cm deep) was placed in a 400-ml jacketed
beaker where the water temperature was maintained close to 15°C for 5 to 8
weeks. At weekly intervals, an aliquot of each sample was analyzed for
1A 14
total C in the solution, and a second aliquot analyzed for C hexazinone
and C degradation products by TLC-scintillation counting.
Tables 3 and 4 present the experimental results for the artificial and
natural sunlight photodegradation tests. The results indicate that in dis-
tilled water exposed to artificial sunlight, hexazinone is slowly degraded
(ca. 10 percent in 5 weeks). On the basis of 5-week data, the amount of de-
composition under both artificial and natural sunlight is about three times
greater in standard reference water and about four to seven times greater in
natural river water or in distilled water containing 20 ppm of riboflavin.
The degree of decomposition in distilled water containing 20 ppm of anthra-
quinone under artificial light and in natural river water with bottom sedi-
ments is about three times the amount in distilled water. At the end of the
5-week exposure period, about 10 percent of the UC in the river water with
sediments was found in the sediments. Extraction of the sediments removed
67 percent of the 1AC. TLC analysis of the extract showed about the same
distribution of 14C compounds that was found in the river water, e.g., 70
percent hexazinone in the sediments and 65 percent in the water.
Based on degradation products identified, the major routes of photo-
degradation appear to involve demethylation to give compounds B and H (Figure
1) and hydroxylation to give compound A. The structures of these major de-
gradation products have been previously confirmed by mass spectroscopy.
4.0 IMPACT ON NON-TARGET ORGANISMS
4.1 PLANTS
In applications of "Velpar" "Gridball" for conifer release, 0 to 15
percent conifer mortality may occur but this depends on species, rates, soil
type and other factors (6). In site preparation applications, use of high
application rates can potentially result in high residue levels in the soil
A-183
-------
TABLE 3. ANALYSIS OF AQUEOUS SOLUTIONS OF (14C)HEXAZINONE EXPOSED TO UV LIGHT
(% DISTRIBITTION OF RADIOACTIVITY APPLIED TO TLC PLATES) (10)
Distilled Water
Exposure, Weeks
1123345
11 9 1 1 A C
100 95 94 91 90 87 87 82
111 1 1
112 2
Standard Reference Water
Exposure, Weeks
1 234567
2 4 5 6 8 10
100 87 82 79 73 68 64
11222
14122
ft
10
23
55
3
2
WC Compd* R t
Origin 0.00
B, H, hexazlnone 0.40
O.Z/
0 0.90
E 0.80
Distilled Water
+ Anthraquinone
Exposure, Weeks
11234
84 80 76 73 68
12 34
9 11 13 10 9
Distilled Water
+ Riboflavin
Exposure, Weeks
8 15 20 25 19
11 1O 91 91 1A
53 43 37 34 31
11 22
57966
See Figure 1 for structures.
TLC systea: ethyl acetate-aetbanol (9:1, v/v).
-------
TABLE 4. ANALYSIS OF AQUEOUS SOLUTIONS OF ( C)HEXAZINONE EXPOSED TO NATURAL SUNLIGHT
(% DISTRIBUTION OF RADIOACTIVITY APPLIED TO TLC PLATES) (10)
Standard,
Reference Water
Exposure, Weeks
12345
114
6366
3 4 11 11 17
2468
97 87 81 73 69
Standard Reference
Water + Ribo flavin
Exposure, Weeks
12345
1174
4 6 6 11 13
6 7 10 13 16
9 10 11 12 15
80 76 66 60 56
14 *
C Compd
Origin
A + C
B
H
D, hexazinone
R +
Rf
0.00
0.40
0.55
0.70
0.80
Brandywine River
Water
Exposure, Weeks
12345
1 79
6 5 14 16
3 14 17 14 18
5798
91 81 70 56 49
Brandywine River
Water and Sediment
Exposure, Weeks
12345
2
176
6.9 12 10 11
5 6 7 10
94 86 81 76 71
T
!-•
00
Ui
See Figure 1 for structures.
TLC system: chloroform-methanol (9:1, v/v)
-------
with possible adverse impact on seedlings planted subsequently into grid
spots. This possibility was evaluated very recently by the U.S. Forest Ser-
vice Southern Forest Experiment Station (15) in field test plot studies with
two soil types (Pacolet clay and Uchee loamy sand) in Alabama. Hexazinone
("Velpar" 90W), at 2 and 4 kg/ha, was applied by a tractor-mounted boom
sprayer. Herbicide treatments vere made in March/April 1978. Immediately
following herbicide treatment and soil sampling, 36 nursery stock ("1-0")
loblolly pine (Pinus taeda L.) seedlings were planted at 1 meter spacings in
half of each plot. A similar planting was made on the remaining half of each
plot in January 1979. Subsequent observation of weed control effectiveness
and pine seedling injury/mortality indicated the following (15)-
'
control. y ' U also Provided good weed
. Hexazinone at A kg/ha did not cause mortality but JM — <
crease growth increments of seconder pines (i e th^L
planted in January 1979) on the clay^oil '
• Hexazinone at both rates caused hish
pine growth of first-year pines in tl
excellent weed control was provided.
• Hexazinone at both rates did not
not significantly increase erovt-h ** P "^ftality and did
sandy soil. B ot second-year pines on the
By virtue of its peUet for. and application method. aerU1 drlft> whlch
»ay impact non-tar8« plants outside tne application areas, i, Mt
to be a probie. .ith the use c£ "Velpar" "Gridball". "Vel ar" Weed
soluble powder formulation
under EUP.,or tteed control n e 'T » ^ "'"
Puerto R^rn A T garcane fields in Florida, Hawaii, Louisiana,
r^r- £- ~— - ~ - —
' ut oaki eouruoodi and hietor>> «« *«
^ °£ hexizl»<»-'- Individual tree.
base, mld-ste*, top and cro»n positions and subdivided into
EUP - Experimental Use Permit.
A-186
-------
bark and wood components for moisture and residue analysis. Hexazinone re-
sidues were primarily in the form of metabolite B. The parent compound and
metabolite A were found in only 7 percent of treated samples and then at
concentrations less than 0.09 and 0.13 ppm, respectively. Metabolite B was
detected in 19 percent of the hexazinone treated steins at maximum concentra-
tions of 0.26 ppm in wood and 1.76 ppm in bark. The weighted total residue
concentrations for both oak species were less than 0.05 ppm at all stem
positions and both sampling times. In sourwood and hickory, the weighted
concentrations were more variable over time and stem position, but were less
than 0.15 ppm. Since the allowable residue for food crops, at which no
adverse health effects will occur, is 0.2 ppm, Bush, et al. (19) concluded
that the lower residues found in firewood samples would likewise produce no
adverse health problems.
The U.S. Forest Service Southern Forestry Experiment Station (Auburn,
AL) is currently engaged in a study to evaluate residues of "Velpar" and
metabolites in non-target fruit plants such as blackberries and blueberries;
these fruits are often picked by people in the wilderness. Samples which
have been collected are currently awaiting laboratory analysis (21).
4.2 AQUATIC ORGANISMS
Indirect exposure to fish and other aquatic organisms may result via
runoff from sites treated with "Velpar". Acute fish toxicity data for
"Velpar" Weed Killer (90 percent a.i.) submitted to EPA by DuPont indicate
96 hour TL5Q values of 274 ppm for fathead minnows, between 370 and 420 ppm
for bluegill sunfish, and between 320 and 420 ppm for rainbow trouts. These
values suggest slight acute toxicity to fish (22). Data on Dapjmia also
suggest that the product is slightly toxic to this organism (48-hour LC50 is
151.6 ppm, 21-day LC50 is >20 and <50 ppm).
Use of "Velpar" Weed Killer in sugarcane fields in coastal areas can
nresent a potential for exposure of shrimp, crab, and oysters. The following
.cute toxicity data have been reported for these organisms: grass shrtop,
56 PPm <96-hour LC5£) <100 PPm; fiddler crab, 96-hour LC50 >100 ppm; and
embryo larvae of oysters, 320 ppm<48-hr LC5£) <560 ppm (22).
Rhodes (10) reported on studies to assess the potential for bioaccumu-
.lation of hexazinone in fish. Hexazinone was labelled in the 2 or 4-carbonyl
position.
A-187 .
-------
The C residues (calculated as ppm hexazinone) in bluegill sutifish
(mean length 63 mm, mean height 3.4 grams) exposed to water treated with
0.01 and 1.0 ppm hexazinone are shown in Table 5. The residue levels in all
tissues were low and were found to plateau after 1-2 weeks of exposure. The
14
maximum accumulation factor ( C residue in fish tissue/concentration in
water) of ca. 5-7 occurred in the viscera at both exposure levels. The
accumulation factors in the liver and carcass were 3-5 and 2, respectively.
The residue levels in all tissues decreased by greater than 90 percent after
a 1-week withdrawal period in fresh water, and no detectable radiolabelled
residues remained after a 2-week withdrawal period.
The major portion of the radioactivity extracted from the fish was un-
changed hexazinone. The extraction procedure removed 80 percent of the 14C
from the fish tissue. TIC analysis showed that 91 percent of the extracted
C was unchanged hexazinone and 9 percent was 3-(4-hydroxycyclohexyl)-6-
dimethylamino-l-methyl-l,3,5-triazine-2,4-(lH,3H)-dione, a major urinary
metabolite (metabolite A) of hexazinone in the rat (Rhodes and Jewell, 1980).
Mayack, et al. (18) evaluated the impact of hexazinone on aquatic macro-
phytes and invertebrate communities within forested watersheds in the Piedmont
region of Georgia. Four replicate watersheds received hexazinone pellets
(10 percent a.t.; pellet size - 2 cm3) on April 23, 1973 and were subsequently
monitored for eight months. Aquatic organisms in a second order perennial
stream were exposed to intermittent concentrations of hexazinone (6 to 44
ppb). Hexazinone and its metabolites were generally not detected ( 0.1 pp»)
in aquatic invertebrates and macrophytes (composed prfcnarily of aquatic
mosses Ecrhynchium rusciforme and Leptodictvum riparium). No major altera-
tions in species composition or diversity were detected in the aquatic macro-
invertebrate community.
4.3 SOIL ORGANISMS
Rhode,, et .1. (23) reported on studies of the effect of hexazinone on
bacterial and fungal populations in agricultural soiU. Adding 10 ppm of
hexazinone to three soils did not reduce the soil population counts of fungi
or bacteria during an 8-weeK test period. In all soils, the distribution of
a given fungus type „. 8intlar ta treated „, ^^ „*,«..«
that hexazinone did not alter the number of an, given fungu. component in
A-188
-------
TABLE 5. TOTAL C RESIDUE IN BLUEGILL SUNFISH (ppm) (10)
I-1
CO
Exposure
Period
3 days
1 week
2 weeks
3 weeks
4 weeks
1 day
3 days
1 week
2 weeks
0 . 01 ppm
Carcass
0.01
0.01
0.02
0.02
0.02
0.01
<0.01
<0.01
<0.01
14
( C) Hexazinone in Water
Liver
0.02
0.03
0.03
0.02
0.02
0.02
<0.01
<0.01
<0.01
Viscera
0.04
0.07
0.07
0.04
0.05
Withdrawal Phase
0.03
<0.01
<0.01
<0. 01
1.0 ppm
Carcass
1.0
1.3
2.1
2.0
1.0
0.5
<0.1
<0.1
<0.1
14
( C) Hexazinone
Liver
1.3
1.6
5.0
2.7
1.9
2.1
0.2
<0.1
<0. 1
in Water
Viscera
2.0
5.3
6.7
5.5
4.6
3.7
0.6
0.2
<0.1
-------
the soil. In an agar plate bioassay test, hexazinone showed little or no
fungitoxicity at treatment rates up to 100 ppm, thus indicating that hexazi-
none would not reduce or modify soil fungus populations at its expected use
rates of 4 to 10 ppm. A nitrification study showed that the addition of 5
and 20 ppm hexazinone to two agricultural soils had no effect on soil-nitri-
fying process during a 5-week test period.
In their forest watershed study (see Section 4.2), Mayack, et al. (18)
analyzed hexazinone residue levels in terrestrial invertebrates. In contrast
to the aquatic biota, hexazinone and its metabolites accumulated in terres-
trial macro invertebrates. Mean levels of hexazinone or at least one of its
metabolites were one to two orders of magnitude greater than comparable
levels (0.01 to 0.18 ppm) found in forest floor material. Although this
suggested an appreciable uptake of hexazinone by the micro invertebrate com-
munity either by active biological uptake or passive accumulation, the signi-
ficance of. the observed accumulations on the invertebrate organisms could
not be established based on the limited data generated, as terrestrial micro-
arthropod samples collected near the end of the study period (8 months after
application) revealed no major community changes.
4.4 ANIMALS
DuPont (24) has carried out extensive toxicological studies of hexazi-
none, using rats, guinea pigs, dogs, mice, hamsters, bobwhite quail, and
mallard duck. The studies included oral acute, subacute, chronic and sub-
chronic toxicity; reproductive effects, teratogenicity; mutagenicity; skin
irritation and sensitization; acute and subacute skin absorption; eye irri-
tation; and acute and subacute inhalation. The results which are sumnarized
in Table 6 indicate that hexazinone is of low toxicity to manuals and birds.
Other data provided by DuPont (7) indicate no carcinogenic effect in a 2-
year feeding study in rats; negative ^ ^^ ^ ^^ ^ ^
tion assays; not embryotoxic or teratogenic at up to 5000 ppm in diet of
rat; not embryotoxic or teratogenic at up to 125 mg/kg by gavage in rabbits;
and a no-effect level of 200 ppm in a 2-year rat feeding study.
A-190
-------
TABLE 6. TOXICOLOGICAL TEST RESULTS FOR HEXAZINONE (24)
Test
Acute oral
Acute oral
Acute oral
Species
Rats (male. ChR-CD)
Guinea pigs -(male)
Dogs (male, beagle)
Test Substance
Unformulated
Unformulated
Formulated 90*!
soluble powder
Test Procedure
Single dose by Intubation
Single dose by Intubation
Single dose In gelatin capsule
Results
U>50 1690 mg/kg
U>50 860 mg/kg
Lethal dose >3*00 mg/kg (the »axlivi:3
feasible dose)
Subacute oral
Subchronlc oral
Subchronlc oral
Subchronlc oral
Subchronlc oral
Chronic oral
Reproductive
Teratogenlc oral
Rats (male. ChR-CD)
Rats (male and
female, ChR-CD)
Dogs (ule and
female, beagle)
Mice (male and
female, ChR-CD-1)
Hamsters (male and
feule eagle)
Rat* (male and
female, ChR-CD)
Hats (male and
female. ChR-CD)
Rats (female,
ChK-CD)
Mutagenlclty (Salmonella Salmonella
tvghlnurluji/micro some typhlnurlum
a ssay)
Unformulated 300 mg/kB/day by intubation, five
times a week for two weeks
Unformulated . Fed to weanlings for 90 days at
dietary levels of 0. 200. 1000 and
5000 pp«
Unformulated Young adults fed dietary levels of
0. 200. 1000. and 5000 ppm for 3
months
Unformulated Fed to weanling* st levels of 0,
250, 500. 1250. 2500. 5000 and
10.000 ppm in diet for 8 weeks
Unformulated Fed to weanling hamsters at levels
of 0. 5000. 7500 and 10.000 ppm in
th« diet for 8 weeks
Formulated 90Z Fed to rats, starting with weanlings
soluble powder for 2 years
Formulated 907. 3-genentlon 3-lltter study with rsts
soluble powder that received 0, 200. 1000 and 2500
. ppm a.l. in diet
Unformulated Fed in the diet to pregnant rats from
day 6 through day 15 of gestation at
levels of 0. 200, 1000, and 5000 ppm
Unformulated Ames procedure
100Z survival, no hlstopathologlcal
changes In tissues examined
1000 ppm no effect level; except for
decreased body weight and food effi-
ciency, 'no other effects at 5000 ppn
1000 ppm no effect level; decreased
body weight and evidence of liver In-
jury at 5000 ppm
No mortality or clinical signs of toxl-
clty; increase in liver weight at lO.noo
PP»
No mortality or clinical signs of toxl-
clty
No effect level 200 ppm; lower average
body weight gains, food efficiency and
food consumption at 2500 and/or 10,000
pom; hematological and urinary evidence
of toxlclty at only the highest level
Except for slightly lower average body
weight of the pups at weaning in the
2500 ppm group, no meaningful differ-
ences among control and test groups with
respect to reproduction and lactation
performance
No evidence of embryotonlclty, terato-
genlclty or clinical signs of toxlclty
Not nutagenlc
(Continued)
-------
TABLE 6. (Continued)
Test
Sf.ln irritation and
sensit ixat ton
Species Test Substance Test Procedure
Guinea pig* Unformul*ted Aqueous solution (25 and 50 JO applied to Intact
skin; Intradermal injection (II) for aensltlza-
tion; challenge applications after 2 week rrst
periods
Results
No skin irritation or sensitizaticn
Acute ikin absorption Rabbits
Subacute I'tln absorption Rabbits
fs»
Eve irritation
L.-K Irritation
Eve Irritation
(repealed exposure)
Subacute inhalation
Acute oral (wildlife)
Rabbits
Rabbits
Rabbits
Rats (male,
Chit-CD)
Rats (nale.
CM-CD)
Bobuhlte quail
(rule and female)
Subacut* oral (wildlife) HalUrd duck
and bOBvhlta
quail
Formulated 90Z
soluble powder
Formulated 901
soluble powder
Unfomulated
Formulated 90Z
soluble powder
Formulated 90S
soluble ponder
Unfomulated
Formulated 90Z
soluble povder
(0.06Z of par-
ticles in th* res-
plrable range)
UnforsHilated
Unformulated
Single dose of 24Z aqueous paste on gauze on
shaved trunk area, covered with wrappings, for
24 "Imur*
Control and teat material applied dally with a
syringe to a 3x3 in. 12-ply gauze pad for 10.
consecutive daya to clipped shoulders and back;
gauze covered with PVC film and wrapping*. After
6 lit. exposure each d&y. the film and wrapping*
removed and ckin washed with water and* dried.
Nominal concentrations were 770 mg/kg/day
Rl|;ht eye* of 2 rabbit* treated with 10 mg
powdered sample; one treated eye washed with
waii-r. the other not waahed. Eye* examined up
to 14 day* after exposure
Right eye* of six rabbit* treated with O.I ml
powdered sample; eye* examined 24, 48, and 72
hours after treatment
Right eyev of rabbit* treated with 1 mg powdered
•ample daily for up to 5 day*. Eyes examined at
one hour and at 1, 2, 3, 4, 5, 7 and 14 day*
One hour exposure in a chamber at 7.48 mg/1
(max. that could be generated under test
condition*)
Head only exposure in a chamber with an average
concentration of 2.5 mg/1 dust, alx hours/day
for IS days vith two day* rest after the Sth
and Ulth exposure
Frd by oral intubation to fasted twenty-week old
males and female* at 0. 39», Ml. 1.000. 1.590
and 2.510 •*/•«; bird* obacrved for mortality
and tonic effect* for 14 daya
Fed in dfat to one-month old duck* and 15-day
old quail at levels of 0, MJ. 1.2 SO, 2.5OO.
5.000 and 10.OOO ppm for the first 5 day* of an
right -day ttudy. Fasal diet only was fed for
the final 3 daya. Dleldrla wa* a positive con-
trol. »ird* ob**rv*d dally for mortality and
toxic •ffact*
Lethal dose >5,278 mg/kg. the
maximum feasible dose
Elevated plasma glucanie-prruvic
transanina*e activity at the
highest concentration level; no
such effect at lower levels; no
evidence of liver or other tissue
injury
Moderate corneal Injury and con-
Jui-ctivities vlth no Iritlc ef:"e:t .
Eire* were normal within 7 days
4/6 rabbits shoved a positive reac-
tion in at least one of the exami-
nation
3 of S rabbit eyes had localised
•mall areas of snail corneal oraci-
ty, which w.-.s reversible. So CU-KI-
lative wcular effects; all eyes
normal within 3 to 14 day*
LCjo >7.4B ng/l; 100" survival; ir-
regular respiration and salivation
during exposure
Rats survived with no significant
clinical or hi*copathological
finding*
U>.n 7,258 mg/tu
°
!£«., >10.000 ppm for both duck and
.n
quill
-------
REFERENCES
1. Personal communication with Dr. Jerry Michael, Southern Forest Experi-
ment Station, USDA Forest Service, Auburn University, Alabama, June 20,
1980 (to M. Ghassemi of TRW).
2. Unpublished forest pesticide use survey data, collected by Dr. Dean
Cjerstad, Auburn University Forestry Chemicals Cooperative, Auburn,
Alabama, June 19BO.
3. Personal communication with Mr. Del Shelton, DuPont Product Manager for
Velpar, June 26, 1930 (to M. Ghassemi of TRW).
A. First Helicopter Applicator. Agrichemical Age, November-December 1979,
p. 16.
5. E. I. DuPont de Nemours and Company, Agricultural Bulletin, Supplemental
labelling for distribution and use only within the State of Alabama, EPA
Reg. No. 352-387, "Velpar" "Gridball" Brush Killer for Control of Un-
desirable Woody Plants in Reforestation Areas in the State of Alabama.
6. DuPont review comments on TRW draft "Velpar" document, September 5,
1980 (from DuPont Product Manager for "Velpar" to M. Ghassemi of TRW).
7. DuPont review comments on the EPA "Preliminary Draft Report on Forest
Use Chemicals Project); October 16, 1981 (from Larry A. Loehr, Agricul-'
tural Marketing Division to William McCredie of API/NFPA).
8. E. I. DuPont de Nemours and Company, Hexazinone Technical Data Sheet,
May 1978.
9. E. I. DuPont de Nemours and Company, letter dated 6/29/79 from Rufus
A. Bastian, Product Sales Manager, to Mr. C. D. Mattson of U.S. EPA.
10. Rhodes, R.C. "Studies With 14C-Labelled Hexazlnone in Water and Blue-
gill Sunfish". Agricultural and Food Chemistry, Vol. 28, No. 2, p. 306.
1980.
11. DuPont report submitted to SPA on 5/14/79 with Pesticide Petition 9G2214.
12. DuPont report submitted to EPA on 3/18/76 with Pesticide Petition 6G1765.
13. Information provided by EPA based on the review of thejjesticide regis-
tration files by the Environmental Fate Branch, BED, OPTS.
14. Rhodes, R.C. "Soil Studies With UC-Labelled Hexazinone". Agricultural
and Food Chemistry, Vol. 28, No. 2, p. 311. 1980.
A-193.
-------
15. Personal communication with Dr. Jerry Michael, Southern Forest Experi-
mental Station, USDA Forest Service, Auburn 1'niversity, Auburn, Alabama
(Letter to M. Ghassemi of TRW; November 17, 1981).
16. Helling, C.S. Pesticide Mobility in Soils. Parameters of Thin-Layer
Chromatography, Proc. Soil Sci. Soc. Amer. 35; 732-748, 1971.
17. Neary, D.G., P.B. Bush, and J.E. Douglas. Subsurface Movement of
Hexazinone in Small Forest Watersheds, Abstracts of the Twenty-First
Meeting of Weed Science Society of America, Las Vegas, Nevada, February
17-19, 1981, p. 45.
18. Mayack, D.T., P.B. Bush, D.G. Neary, and J.E. Douglas. Impact of Hexa-
zinone on Invertebrates After Application to Forested Watersheds, Arch.
Environmental Contamination and Toxicology (in press).
19. Neary, D.G., J.E. Douglas, P.B. Bush, and D.T. Mayack. Hexazinone
Losses in Storm Runoff from Small Forest Watersheds in the Upper Pied-
mont of Georgia, Abstracts of the Twentieth Meeting of Weed Science
Society of America, Toronto, Canada, February 25-27, 1980, p. 53.
20. Bush, P.B,, D.G. Neary, and H.L. Hendricks. Hexazinone Residues in
Firewood: 4 and 16 Month Levels. Proc. South. Weed Sci. Soc. 34: 274,
1981.
21. Personal communication with Dr. Jerry Michael, Southern Forest Experi-
ment Station, USDA Forest Service, Auburn University, Auburn, Alabama,
October 21, 1981 (to M. Ghassemi of TRW).
22. Information provided by EPA, based on the review of the pesticide re-
gistration files by the Ecological Effects Branch, HED, OPTS.
23. Rhodes, R.C R.L. Krause, and M.H. Williams. Microbial Activity in
toy 1980? Wlth Hexazinone- Soil Science, Vol. 120, -No. 5, p. 311,
"xicolo T °rat°ry f°r Toxicol°Sy ™« ^dustry Medicine,
Toxico logical Information: Hexazinone".
A-194
-------
Common Name: MSMA
Chemical Name: Monosodium methanearsonate
Major Trade Names: Ansar; Bueno; Daconate
Major Applications Used in precommercial thinning; applied by injection or
in Forestry: cut surface.
SUMMARY
MSMA is an organic arsenical herbicide that is widely used for weed
control in cotton fields. In forestry, it is used to thin conifers by in-
jection or by application on cut tree surfaces, but the total amount used
in forestry is a small fraction of the agricultural use. The primary envi-
ronmental concern in the use of MSMA is arsenic toxicity. MSMA itself is
less toxic to most animal species than is inorganic arsenate, the primary
breakdown product. MSMA is converted to several other organic and inorganic
arsenicals in the environment. However, MSMA and all of these products
occur naturally in soils, in water and in the tissues of organisms. Further-
more, the amount of MSMA annually produced and used in the United States is
a small fraction of the amount of arsenic that occurs naturally in the soil.
In most surveys, agricultural use of MSMA has not resulted in a signi-
ficant increase above the background arsenic content of soil. The major
breakdown product of MSMA in soil is inorganic arsenate which is relatively
quickly and tightly bound in soil. Therefore, entry of MSMA into soil does
not significantly increase the risk of contamination of drinking water by
the leaching of arsenic from soil. In forestry, arsenic from MSMA use enters
the soil when foliage of treated trees decomposes, and no contamination of
streams by this arsenic has been detected. Arsenic does accumulate in the
tissues of organisms. However, in animals, it tends to achieve the highest
concentrations in species at the bottom of food chains, and it does not
appear to biomagnify in food chains.
MSMA is toxic to some agricultural crops such as soybeans when applied
at the rate used on cotton plants. It is moderately toxic to rabbits and to
cattle. It has low toxicity to fish and birds, and it has moderate toxicity
to honey bees when they are sprayed or when they ingest contaminat edf°°<*-
Proper use of MSMA in forestry is unlikely to harm wildlife or domestic
animals. However, spraying MSMA on foliage accessible to grazing animals
can endanger both domestic and wild species.
A-195
-------
1.0 INTRODUCTION
MSMA is the most widely used organic arsenical herbicide. It is gener-
ally applied at low rates and has the lowest mammalian toxicity of the
arsenical pesticides (1). However, MSMA is a potential hazard to a wide
spectrum of organisms since it breaks down to form inorganic arsenate that
is toxic to both plants and animals.
The biological activity of MSMA was known prior to 1900 but MSMA was
not used as a herbicide until 1951 (1). At present, MSMA is used primarily
in agriculture to control post-emergent weeds in cotton. It is also used as
a nonselective herbicide against grasses in noncrop areas such as ditchbanks,
right-of-way and storage yards (2). Forestry use is by injection or cut
surface application to unwanted trees for site preparation, for brush con-
trol of weed trees over 2 inches in diameter and especially for precommer-
cial thinning of hardwoods and conifers (3,4).
United States consumption of MSMA in 1972 was estimated at 19 million
pounds (5). Industrial and commercial use, which includes forestry applica-
tions, amounted to 4 million pounds, about 21 percent of total use. About
66 percent or 12.5 million pounds were used in agriculture, primarily in the
south-central states; home and garden uses amounted to 1.5 million pounds
and various uses by governmental agencies accounted for 1.0 million pounds.
MSMA is manufactured by several chemical companies. The principal U.S.
producers are Diamond Shamrock Company and Vineland Chemical Company (6).
MSMA is available in several formulations under numerous trade names. Some
of the common formulations are listed in Table 1. The forest induatry gen-
erally uses a 50 percent solution (6 Ibs per gal) with approximately 22 per-
cent total arsenic content (7). Those formulations with surfactants are
used primarily in agriculture as foliar sprays.
MSMA was first used as a foliar spray against crabgrass in turf. It is
now known to be effective against several grasses. In cotton and on noncrop
lands, MSMA is used to control Johnsongrass, nutsedge, watergrass, sandbur,
foxtail, cocklebur, and pigweed (1,6). m forestry, MSMA is applied only in
spot treatment of trees by the cut surface (hack and squirt) or injection
methods. It is effective against Douglas-fir, lodgepole pine, bigleaf maple,
A-196
-------
TABLE 1. SOME COMMON FORMULATIONS OF MSMA (1,2,6,7,10-16)
Trade Name
Ansar 529
Ansar 529 H.C.
Bueno 6
Daconate
Ansar 70 H.C.
gilvisar 550*
Weed-E-Rad+W
Dal-E-Rad+W
Heed-Hoe 120
Weed-Hoe 2X
Check -Mate
Diumate
Broadside
Panther Juice
Valson 6.6
MSMA 4 Plus
MSMA
lb/gal
4.0
6.0
6.0
4.0
8.0
6.0
4.02
4.02
6.67
8.0
4.0
6.6
4.0
%
35%
48%
48%
35%
48%
35%
35%
51%
35%
%
Total
Arsenic
16%
22%
22%
16%
22%
16%
16%
24%
16%
Other Chemicals
Present
surfactant
surfactant
surfactant
surfactant
—
surfactant
surfactant
sodium cacooylate
diuron
.surfactant.
sodium cacoaylate
surfactant
-
surfactant
Manufacturer
Diamond Shamrock
Diamond Shamrock
Diamond Shamrock
Diamond Shamrock
Diamond Shamrock
TSI Company
Vineland Chemical
Vineland Chemical
Vineland Chemical
• Vineland Chemical
Vineland Chemical
Crystal Chemical
MFC Services (AAL)
Valley Chemical
Grower Service
^Discarded name as of 1980 (6).
ponderosa pine, and certain types of alder, ash, cedar, elm, oak and cherry
(4,8). Its major use is in precommercial thinning of overdense stands to
promote more rapid growth of timber (9).
Forest application of MSMA utilizes undiluted herbicide usually at a
concentration of 6 Ibs per gallon, and the cost in 1979 was $14.50 per gallon
(6 Ibs a.i.). Several cuts are made into the cambium of the tree, the number
depending on the size of the trunk (7). One or two ml of KSMA are applied
per cut. The season of application is fall and winter. The MSMA is trans-
located throughout the plant (1). It is slow in killing the tree, producing
first a chlorosis and the cessation of growth. Gradual yellowing of leaves
occurs, then the yellow leaves become brown, followed by dehydration and
death (1). The specific mode of action of MSMA is not known with certainty,
but it appears to interfere with phosphorus metabolism in plants (17). To
A-197
-------
be effective, the chemical must contact leaf surfaces in use as a spray or
be injected into the growing part of the tree.
MSMA has been used in the forests of the Pacific Northwest for precom-
mercial thinning (18). Approximately 41 thousand pounds were used to thin
about 28 thousand acres of U.S. Forest Service land in Oregon, Washington,
and California from 1975 to 1979 (19). MSMA is not used extensively in the
southeastern United States. Some 624 pounds were used to thin 165 acres of
USFS trees in the southeast in 1979 (20). The amounts of reported use and
the mode of application indicate that environmental contamination due to
MSMA in forests should be minimal and generally limited to the immediate
area of the treated trees.
2.0 PHYSICAL AND CHEMICAL PROPERTIES OF THE ACTIVE INGREDIENT
MSMA, monosodium methanearsonate, has the structure:
0 Na
CH, As-OH
3 II
0
It belongs to a group of organic arsenical herbicides that are salts or de-
rivatives of methanearsonic acid. Other members of this group include caco-
dylic acid, disodium methanearsonate, octyldodecyl ammonium methanearsonate
and calcium acid methanearsonate.
Aqueous solutions of MSMA are clear to light yellow and are odorless.
MSMA is an acid in aqueous solution and is in equilibrium with methanearsonic
acid (MAA) at pH 6 to 7. At pH 10 to 11, the equilibria is shifted toward
formation of the disodium salt (21):
CH QI
I 3 pH 6.5,Na+ ,3 pH 10 5 N . CH
0-As-OH , 0-As-ONa • *0-5>Ka+ , 3
I ' 0*As-ONa ,1 C-As-ONa
08 OH I
08 ONa
DSMA
MSMA is highly stable in water, but in the presence of calci™. ^gneslua or
iron, It will form insoluble salts of these ions (6,21).
The effectiveness of MSMA and like compounds is due to the ar.enic .«..
Although often referred to as a heavy Mtal, arsenic is not a heavy aetal or
A-198
-------
a true metal, but is a metalloid with metallic and non-metallic properties
(1). Arsenic can be found in valence states from -1-5 to -3. It is ubiqui-
tous in nature being found in all environmental substrates (1,22). Arsenic
cycles in the environment; it is taken up and released by biota and sediments
and soils; low concentrations are maintained in air and water (22). The
following diagram is a schematic presentation of the arsenic cycle in nature;
solid lines represent natural transfers; dashed lines represent anthropogenic
inputs (22):
I combustion sources
| industrial sources
pesticide use
3.0 ENVIRONMENTAL FATE
The fate of MSMA in the environment has been determined primarily from
field studies measuring total arsenic residues and from laboratory studies
of microbial degradation. Methods are now available to distinguish between
MSMA, cacodylic acid, As+3 and As+5 (21,23). However, due to the difficulty
of separation, the analyses that are normally performed measure all forms of
arsenic, as total arsenic, and do not differentiate between organic and in-
organic arsenic.
Natural arsenic levels in air and water- are generally low; soil resi-
dues, however, can cover a wide range. The following are reported background
levels of total arsenic (22):
1 to 40 ppm, from weathered rock
0.5 to 2.3 ppb, Lake Michigan
0.15 .to 6.0 ppb
10 ugm/m., rural air
30 vgm/nt , urban air
- Freshwater
- Sea Water
- Air
A-199
-------
Background levels can reflect natural and anthropogenic sources of arsenic.
The higher value for urban air is due to pollutant emissions from industrial
and combustion sources (22).
Estimates of the magnitude of various anthropogenic sources of arsenic
are found in Table 2. Emissions from copper smelters are the largest anthro-
pogenic source, but agricultural use is a significant fraction of the total.
The amount of arsenic used in forestry is estimated to be less than 0.1 per-
cent of the total arsenic released by man.
TABLE 2. COMPARISON OF VARIOUS ANTHROPOGENIC SOURCES OF ARSENIC
Metric Tons
Per Year
Total airborne losses from the smelting of
copper ores, nationwide (24) 4800
Total airborne losses from coal burning,
nationwide (24) 650
Total agricultural consumption of MSMA-arsenic
in 1972, nationwide (assuming use of MSMA
with 16% arsenic content) (5) 910
Total industrial and commercial (including
forestry) consumption of MSMA-arsenic in
1972, nationwide (assuming use of MSMA
with 24% arsenic content) (5) 440
Total reported annual use of MSMA-arsenic,
based on USFS reports (19,20)
Total estimated annual forestry use of MSMA-
arsenic (assuming total reported USFS
use is 20% of total forestry use)*
In 1970, USFS lands comprised about 20 percent of all U.S. commercial
forest land (25).
Arsenate and CO., are products of the microbial decomposition of MSMA.
Arsenate is reduced and methylated to volatile compounds by various organisms
in the environment. The components of an environmental fate analysis of
MSMA include arsenate, methylated arsines, cacodylic acid and other organic
arsenicals. All of these compounds are naturally occurring; all of them are
A-200
-------
products of or substrates for natural microbial transformations. The major
pathways in the environmental chemistry of MSMA are shown in the following
diagram (see Section 6.0 for chemical structures):
TMA
TMA oxide
-CH.
DMA
CO.
fungi CA — Methanobacteriuin
bacteria |
animals I
aquatic organisms *_
—CH. anaerobic conditions
-CH,
ASO.
i:
MSMA soil microbes % AS04 Fe,Al ,Ca;day ( insoluble salts
CO.
The major environmental concern in regard to MSMA is the fact that it
is largely"converted to arsonate in soil which cannot be further degraded
and is much more toxic than the organic compound. Toxic trimethylarsine gas
(TMS) can also be produced from the inorganic arsenic. The degradation pro-
ducts of MSMA, .largely arsonates, are very persistent in the soil with a
half-life of approximately 6 years (22).
3.1 UPTAKE AND METABOLISM BY PLANTS
Uptake and metabolism of MSMA by plants have been studied primarily in
agricultural systems. • Information does not appear to be available on the
metabolism of MSMA injected into trees. MSMA in Johnson-grass is rapidly
taken up by the roots and is translocated throughout the plant in A hours
(1). Atrazine has been shown to facilitate the uptake of arsenic by plants.
Temperature is also a factor in translocation and toxicity in plants. MSMA
sprayed on cotton at 3 Ibs per acre caused injury to the plants when applied
A-201
-------
at 13°C or 20°C but not at 31°C (1,25,26). Maximum absorption was observed
at 29°C; translocation out of the cotyledons was faster at 20°C than 29°C.
Some plant species are able to metabolize MSMA. One or more metabolites
containing arsenic were found in target plants possibly involving formation
of a histidine complex (1,27). However, some 40 percent of MSMA in beans
remained unmetabolized and no metabolites were found in cotton 72 hours after
exposure, indicating that most MSMA may remain unmetabolized in non-target
plants.
3.2 FATE IN SOIL
MSMA reaching the soil can undergo several physical, chemical, and mi-
crobial reactions. MSMA in soil is largely broken down to inorganic arsenate.
Formation of insoluble salts, adsorption, ion exchange and microbial trans-
formations are all possible reactions of MSMA in soil. MSMA itself is a
chemically stable compound and is not known to volatilize or photodecompose
(21).
Direct entrance of MSMA into soil due to forest application would re-
sult primarily from splash back in hack and squirt applications and from
leakage of equipment in injection methods. Proper handling to avoid spillage
and care in disposal of wash water and empty containers should minimize the
potential for environmental contamination. Concentrations of arsenic in
forest litter following use of MSMA for tree thinning has been reported to
range from 1.8 to 39 mg per kg (28). Contamination due to splash back and
leakage of MSMA can spread from the area of the treated tree through leaching
and runoff. A substantial source of MSMA-derived arsenic in forest soils
appears to be arsenic-containing foliage that falls to the ground after
treatment. Newton (29) measured 116 ppm arsenic in dead pine needles several
months after application.
3.2.1 Soil Residues
Naturally occurring arsenic residues in soil usually range from 1 to
40 ppm (22). The National Soils Monitoring Program found arsenic in over 99
percent of sites tested in 1969 (30). The range of values was 0.25 to 107.45
ppm. The arsenic appeared to be largely from natural sources; only 0.5 per-
cent of the sites tested reported using MSMA that year.
A-202
-------
Hiltbold, et al. (31) measured soil arsenic residues due to applications
of up to 35.6 Ib per acre of MSMA (10 times the normal rate). MSMA was
applied to cotton as a broadcast spray with a cumulative maximum dose of 100
Ib per acre. Thirty-nine to 67 percent of the applied arsenic was detected
as soil residues in the top 30 cm of soil. The rest of the applied arsenic
was thought to have escaped to the air by formation of volatile arsine gas.
No residues were found below 30 cm. Increased adsorption was observed with
increasing depth and corresponding increases in clay and iron content. Ro-
binson (32) investigated the effects of application of large amounts of MSMA
over a period of 5 years. Soil residues were measured to a depth of 90 cm.
Surface soil residues were not significantly different from the control for
application rates of up to 32 Ib per acre. Rates of 64 Ib per acre and up
resulted in increased surface arsenic residues after the second year of appli-
cation. For the higher application rate of over 250 Ib per acre, 50 percent
of the arsenic applied was recovered in the upper 10 cm of surface soil.
Even after 5 years, arsenic residues below 30 cm were not significantly dif-
ferent from the control. For the soil tested, a sandy loam, use of the
normal field rates of MSMA did not increase soil arsenic residues signifi-
cantly.
A similar study was done by Johnson and Hiltbold (33). MSMA was applied
at cumulative rates of up to approximately 60 Ib of arsenic per acre. Most
of the arsenic applied was recovered in the upper 5 cm of the soil. 85 per-
cent of these surface soil residues were found in the clay fraction of the
soil. Very little organic arsenic was found in the soil.
Woolson, et al. (34) measured arsenic residues in surface soil samples
taken from treated and untreated soils in several states. Soils with a
history of arsenic application averaged 165 ppm; untreated soils averaged
13 ppm. Samples were also taken to a depth of 1.82 m. Most of the arsenic
found was in the first 15 cm of soil but arsenic was found in all of the
samples. Most of the arsenic was associated with iron; lesser amounts were
associated with aluminum and calcium. The recovery of applied arsenic was
least in areas where silting and flooding occur.
3.2.2 Adsorption and Leaching
Morris (35) reported that MSMA is moderately mobile in forest soil and
A-203
-------
forest floor material. About 80 percent of MSMA was not retained in a 6-
inch column of forest floor material; about 50 percent applied to a 3-inch
soil column was not retained.
Arsenic bound to soil is said to be fixed. Physical adsorption, ion
exchange reactions and formation of insoluble salts can all result in the
fixation of arsenic in soil. It is not always possible to determine which
mechanism of fixation is responsible for the observed association of arsenic
with clay or cations as insoluble salts. Arsenic can react with iron and
aluminum oxides which coat clay particles or react with cations in the soil
solution (22). Adsorption of arsenic to clay depends upon soil PH, texture,
iron and aluminum content, and organic matter. There is always some arsenic
present in the soil solution and is likely that which is available for micro-
bial transformations (22). Fixed arsenic is apparently unavailable for up-
take by plants since phytotoxicity is generally reduced by the fixation of
arsenic (1).
3.2.3 Microbial Transformations
Microbial transformations play a major role in the fate of MSMA arsenic
in soil. Soil microorganisms have been shown to degrade MSMA (36). Fungi
and bacteria as well as some animals and aquatic organisms are capable of
producing methylated arsines from inorganic arsenicals (22).
Von Endt, et al. (36) studied microbial degradation in various types of
soil using C02 evolution as the measure of decomposition. After three weeks
incubation, the amount of CO,, evolved was dependent on organic matter content,
About 10 percent was evolved from a 3.9 percent organic soil and only 1.7
percent from a 1.7 percent organic soil. Steam sterilization of the soil
resulted in almost no CO,, evolution, indicating that microbial metabolism
was responsible for MSMA decomposition. A fungus, two actinomycetes and a
bacterium that were isolated from the soil all produced CO, and arsenate as
the sole products of MSMA degradation.
Several organisms in the environment have been shown to methylate ar-
senicals, forming volatile compounds. Cox and Alexander (37) isolated three
sewage fungi capable of producing tria.thylar.in. gas (TMA). McBride and
Wolfe (38) have shown that cell extracts of Methanobactertun, form dimethyl-
arsine (DMA) from arsonate under anaerobic conditions. The requirements
A-204
-------
are the same as those for synthesis of methane gas indicating a competition
between arsenate and substrates for methane synthesis. The methylated
arsines produced are volatile and toxic but also unstable and probably react
to form oxides (22,38,39). The methylation and demethylation of arsenicals
in soil can be illustrated as follows (1,38):
co2
soil microbes
Methanobacterium
cPa
MAA
DMA
Methylated arsenicals have also been found in the environment in places
other than in soil. Bramen and Foreback (39) found low levels of methane-
arsenic acid (MAA) and dimethylarsinic acid (CA) in natural waters* bird
eggshells, seashells and human urine. Because dimethylarsine is easily
oxidized, it could not be determined in.the laboratory. Woolson (22) reports
that MAA and CA have been found in fresh and salt water, aquatic weeds and
shrimp. Di- and trimethyl-arsine gases have been measured in outdoor and
indoor air.
3.3 FATE IN WATER
Many of the arsenic reactions that occur in soil also occur in natural
waters and in bottom sediments. Inorganic arsenic exists in oxygenated water
primarily as arsonate (22). Insoluble salts may form. Adsorption to clay
particles and methylation can also occur in water or sediment. Certain
marine bacteria are capable of reducing arsenate to arsenite (22). Methyl-
ation reactions to form MAA, CA, DMA and TMA occur in both fresh and salt
water.
A-205
-------
Arsenic residues in natural waters are generally low (22). A survey
of U.S. surface waters reported 79 percent of waters sampled had arsenic re-
sidues less than 10 ppb, the recommended drinking water standard, and only
2 percent had residues greater than 50 ppb. The concentration in water is
generally less than that of the sediment. For example, Lake Michigan water
had residues of 0.5 to 2.3 ppb and the sediment had residues of 7.2 to 28.8
ppm (22).
MSMA used at the rate of 5 Ib per acre to control weeds along irrigation
canals was found not to contaminate the water (40). Maximum residues of
0.86 ppm were found immediately after treatment and were reduced to 0.06 ppm
or less in 10 minutes. It was calculated that 0.002 to 0.04 Ib of arsenic
per acre could reach farmland from a 24-hour 6-inch irrigation. These figures
are well within the range of naturally occurring arsenic levels.
Canutt, et al. (18) monitored arsenic in forest streams after injection
of MSMA for precommercial thinning. No residues were detected in stream-
water. The limit of detection was 0.01 ppm.
4.0 IMPACTS ON NON-TARGET ORGANISMS
Concern for non-target organisms exposed to MSMA is due to the presence
of- arsenic. Oral LD^'s in rats range from 700 to 1800 mg/kg, indicating
moderate toxicity (41).
4.1 PLANTS
As noted in Section 1.0, the herbicide MSMA is used against hard-to-
control grasses and weeds. As a tree killer, it is used against hardwoods
and conifers. In agriculture, MSMA is widely used to control weeds in cotton
fields. It is applied when cotton is at least 3 inches high but before first
bloom to avoid arsenic accumulation in the seeds (31). siight turning and a
reddish discoloration of the cotton leaf may occur but the plant develops
normally (2). Wauchope and McWhorter (42) designed a field experiment to
simulate spray drift conditions to which soybeans may be exposed when grown
in fields adjacent to cotton. Injury to soybean plants and a significant
reduction in yield resulted from application of 5 to 20 percent of the normal
application rate of MSMA to cotton (2 Ib per acre applied four tiues per
season). A series of experiments were used to study the effects of MSMA on
grasses of a salt marsh (43). Leaf damage was noted at the higher doses of
A-206
-------
100 and 9000 ppro applied several times as a foliar spray. A flooding exper-
iment simulated actual conditions if MSMA were present in tide water. Doses
of 10,000 and 90,000 ppm caused tissue damage on shoots. The amounts of
MSMA causing plant injury were massive compared to the concentrations likely
to be present in tide water due to runoff from treated areas (43).
Arsenic is normally found in plants at about 4 ppm in dry weight of
plant material (21). The arsenic level in the soil that will be phytotoxic
depends upon the chemical form of the arsenic, the soil fertility, amounts
of iron and arsenic in the soil and plant vigor. In one case, 250 ppm in
the upper 6 inches of soil resulted in a 50 percent reduction in growth of
4-week-old corn plants (21). Residues of 10 ppm of arsenic were measured
in plant material.
Wauchope and McWhorter (42) studied MSMA in soybeans. Foliar applica-
tion of as little as 0.4 Ib per acre for the season resulted in plant injury
and decreased yield. MSMA applied early in the season did not result in
recoverable residues in soybeans. However, MSMA applied late in the season
accumulated in the seeds. This application was only 5 percent of the normal
foliar spray. According to other investigators, a concentration of 120 times
the normal rate would be required in soil to result in residues in seed (42).
4.2 FISH AND OTHER AQUATIC ORGANISMS
MSMA has relatively low toxicity to fish with 96-hour LC^'s ranging
from 13 to 1,100 ppm (21,44). The acute toxicity of MSMA depends upon the
fish species and the amount of arsenic in the formulation. Table 3 lists
LC,. 's for various fish. The movement of large amounts of arsenic from
treated areas to water containing fish is not likely to occur due to fixation
of MSMA in plants, soil and sediment (1).
MSMA appears to have little toxicity to certain aquatic organisms.
Shrimp and oysters were exposed to 1 ppm MSMA in flowing sea water (21). No
adverse effects were observed in shrimp in 48 hours nor in oysters exposed
for 24 hours. A 96-hour exposure to 100 ppm was not toxic to scud, a fresh-
water crustacean (21).
A-207
-------
TABLE 3. ACUTE TOXICITY OF MSMA TO VARIOUS FISH (21,44)
Fish
Bluegill
Channel catfish
Fathead minnow
Goldfish
Rainbow trout
Black bass
Crayfish
% a.i. in
"Formulation
34.7
34.8
34.7
100
100
100
22.6
100
100
LC50, ppm
49.2
>1,000
26.8
1,100
13.3
31.1
96.0
700
3t050
Exposure Time
in Hours
96
48
96
96
96
96
9*
96
96
4.3 WILDLIFE AND DOMESTIC CATTLE
In general, MSMA appears to be relatively non-toxic to wildlife. The
oral LC5Q for ducks is greater than 5000 ppm (45). Mallard ducklings and
bobwhite quail were fed up to 464 ppn of a 51.3 percent MSMA formulation for
5 days; one group was given a single dose of 5000 ppm. No toxicity symptoms
or abnormal behavior were observed.
Wildlife was sampled for tissue residues after forest application of
arsenicals including MSMA (46). The reported results placed the animals in
two groups: those in which there were generally no detectable residues and
those in which low levels of arsenic, were found. Essentially no residues
were detected in several species of birds, mountain beaver, porcupine, ruffled
grouse and one deer known to be a resident of the area. The low level group
consisted of voles, shrews, mice, chipmunks and ground squirrels. About 50
percent of this group had.arsenic residues between 0.5 and 9.8 ppm; most of
the animals had residues below 5.0 ppm. One squirrel had 17 to 30 ppm arse-
nic in various body parts. Animals collected more than 30 days after herbi-
cide injection generally exhibited no detectable residues. Two hares examined
2 and 42 days after forest treatment with arsenicals had no arsenic residue;
A-2Q8
-------
five hares examined 232 days after application had very low levels or no
residues. The MSMA L^en for snowshoe hares is reported as 173 rag/kg (46).
MSMA toxicity to rabbits was investigated more fully by Exon, et al.
(47). Rabbits were fed 50 ppm MSMA (27.5 ppm arsenic) for 17 weeks. This
concentration in the feed resulted in an average dose of 1.5 mg As/kg body
weight. At intervals, rabbits were sacrificed and various tissues examined
for arsenic residues and pathological changes. Table 4 lists the residue
found in various tissues and organs. After 14 days exposure, a 35 percent
decrease in food intake was observed along with intestinal inflammation and
congestion (48). Several rabbits developed toxic hepatitis after 7 weeks
exposure. When the MSMA dose was reduced to 0.74 mg As/kg at 17 weeks,
toxic hepatitis was not found and yet residues in the liver increased. The
toxic hepatitis may have blocked arsenic accumulation in the liver. Tests
on offspring showed no residues at 1 and 20 days of age. A high proportion
(70 percent) of the arsenic was excreted in feces and urine.
TABLE 4. ARSENIC RESIDUES FOUND IN RABBITS, PPM (47)
Tissue or Organ
Liver
Kidney
Muscle
Bone
Hair
Peces
Urine
Weeks of Exposure
0
0.20
0.70
— *
2
0.57
0.56
—
—
11.30
15.10
4
0.37
0.47
0.27
—
1.30
8.10
9.10
7
0.44
0.56
0.26
—
2.42
8.50
13.30
12
0.37
0.49
0.54
—
3.58
8.80
8.40
17
0.78
1.40
0.36
3.52
2.29
8.40
6.20
*--: below the limits of reliable detection
Cattle are often allowed to graze in forested areas treated with MSJ1A.
Exposure to arsenic has been measured as residues in hair and other body
tissues. Norris (49) compared arsenic residues in cattle hair before and
after forest treatment (spring and fall) in a herd with previous exposure
A-209
-------
ro arsenlcals. Arsenic residues in -a. control herd having no previous expo-
sure were also measured in the spring and fall. There was no statistically
significant difference between spring and fall arsenic residues for the test
herd. The spring average was 0.69 ppm and the fall average was 0,48 ppm.
However, there was a statistically significant difference between spring and
fall residues for the control herd (0.16 ppm spring, 0,35 ppm fall). The
cattle grazed in untreated areas over the summer naturally accrued some
arsenic as residue in hair. All the residue values obtained appeared to be
within the normal range of up to 2.7 ppn for cattle as shown by other studies
(49,50).
Dickinson (50) orally administered 10 mg MSMA per kg to cattle for 8 to
10 days. Four of five test steers died; their body tissues were examined for
gross pathology and arsenic residues (see Table 5). The examination revealed
massive kidney damage, evidence of hemorrhagic gastritis and lesions in the
liver of one steer. The steers that were on a regular diet for 2 to 8 days
had reduced arsenic residues in kidney and liver and yet had extensive kidney
tissue damage. The damage to the kidney was apparently irreversible and was
considered to be the cause of death. Cumulative doses of 80 to 100 mg/kg
were fatal to 4 of the 5 cattle; poisoning occurred in all 5 cattle with a
total dose of 50 to 70 mg/kg. Arsenic residues in body tissues did not
always give a true indication of the effect of MSMA on the animals.
TABLE 5. ARSENIC RESIDUES AS PPM IN CATTLE ORALLY ADMINISTERED
10 mg MSMA/kg (50)
Expo-
sure
0
10
10
8
8
Regular
Diet Prior
to Exam
0
0 .
2
0
8
Kidney
0.25-1.1
58
27
46
3.5
Body Tissue
Liver
0.7-0.82
27
27
18
1.6
Brain
0.05
1.8
2.6
Bone
0.03
5.0
2.5
Muscle
0.02
10
7.4
Stomach
0.02
14
Hair
0.81-2.7
3.3
1.4
A-210
-------
Evaluation of the studies to determine the impact of MSMA on cattle
indicate conflicting results. A reliable method to measure exposure of
cattle to MSMA had not yet been developed; measurement of residues in hair
and body tissues appear to be unsatisfactory.
4.4 BENEFICIAL INSECTS
Studies of the toxicity of MSMA to beneficial insects generally deal
with honey bees. There is some controversy over the effects of MSMA on bees.
Some investigators indicate that the main hazard of herbicides including
MSMA to bees is loss of pollen and nectar plants (53). The response of bees
to MSMA in laboratory studies appears to depend upon the formulation and
method of application.
Atkins, et al. (54) report a 48-hour LD5Q for bees of 24 vg MSMA per
bee. Pesticides with LD's of 11 yg or more per bee were considered non-
toxic. MSMA was applied as a dust in this study. Johansen (55) states that
queenless hives observed in the fall have been associated with use of arse-
nicals the preceding summer. Morton, et al. (56) investigated the effects
of arsenicals as stomach poisons fed to bees at 10, 100 and 1000 ppm in 60
percent sucrose for 60 days, A commercial formulation of MSMA, Ansar 170,
was shown to be toxic to bees at all three concentrations. The time necessa-
ry to kill one-half of a given population was as follows for. Ansar 170:
ppm Ansar 170 h/2' days
0 39.5
10 29.5
100 5.4
1000 . 2.5
The toxicity of various arsenicals tested was not affected by addition of
surfactants.
Moffett, et al. (53) studied the effects of MSMA sprayed onto bees in
cages. The bees.were sprayed once with a concentration equivalent to the
normal field application rate of 4 Ib per acre. Dead bees were counted
every day. MSMA was found to be extremely toxic with 65 percent cumulative
mortality in 3 days.
A-211
-------
4.5 MICROORGANISMS
The effects of MSMA on microorganisms are varied. High concentrations
appear to inhibit bacterial growth. Arsenicals as a group are more toxic to
bacteria than fungi with the greatest toxicity exhibited by organic arseni-
cals (57). Bollen, et al. (58) studied the response of bacteria, actino-
mycetes and fungi to MSMA in concentrations up to 10,000 ppm. Bacterial
growth in liquid culture media was inhibited at 10,000 ppm and slightly in-
hibited at 1000 ppm. The rate of microbial decomposition of organic matter
in the soil in the presence of MSMA was also measured as CO, evolution from
soil and forest floor material. The rate of CO, evolution due to microbial
decomposition in soil generally decreased with time. MSMA at 100 ppm inhi-
bited decomposition in soil and forest litter; at 1000 ppm MSMA actually
increased decomposition in soil.
Bollin, et al. (28) investigated the effects of MSMA on nitrogen meta-
bolism in soil and forest floor material. Ammonification was enhanced by
the presence of MSMA. Nitrification, however, was inhibited by as little as
10 tag arsenic per kg soil or forest litter.
5.0 BIOACCUMULATION
Because MSMA is an organic arsenical and is converted to other organic
arsenicals in thb environment, there is concern that these forms will bio-
accumulate in organisms and perhaps biomagnify in food chains. Some marine
organisms, especially algae, accumulate arsenic up to 142 ppm (52). Arsenic
in these organisms is probably incorporated as organic compounds or is bound
to cell walls. Fish and algae are apparently capable of synthesizing Upid-
soluble and water-soluble organic arsenic compounds (52). However, concen-
trations of arsenic are usually highest in lower members of aquatic food
chains, and arsenic does not appear to biomagnify (1).
Isensee, et al. (51) investigated the accumulation of dimethylarsine
(DMA) obtained from soil in algae, snails, Daphnia and fish. Two systems
were used to recover DMA from soil: an oxygen system and a nitrogen system.
DMA is easily converted to the oxidized form, cacodylic acid, in the pre-
sence of oxygen. The nitrogen system was used to minimize this conversion.
Table 6 lists bioaccumulation ratios for both recovery systems. DMA con-
A-212
-------
centration in the aquarium water was 7.0 ppb 24 hours after its addition.
Ratios for lower aquatic organisms were much higher than those for fish.
TABLE 6. BIOACCUMULATION RATIOS FOR AQUATIC ORGANISMS
EXPOSED TO DIMETHYLARSINE (51)
Treatment
DMA
oxygen recovery
DMA
nitrogen recovery
Algae
1605
1248
Snails
446
299
Daphnia
2175
736
Fish
19
49
Woolson, et al. (52) studied bioaccumulation of MSMA and inorganic
arsenic in aquatic organisms. Crayfish were found to store substantial
amounts of arsenic whereas catfish did not. Crayfish placed in water that
was nearly arsenic-free did not lose all the arsenic residue'in body tissues.
Some arsenic was either tightly bound or assimilated into cellular components.
Lipid incorporation was generally higher for MSMA than for inorganic arsenic.
Table 7 presents the data from these experiments. At least four stable ar-
senic compounds were found in body tissues, suggesting that these organisms
metabolized MSMA.
A-213
-------
TABLE 7. BIOACCUMULATION PARAMETERS FROM AQUATIC ORGANISMS EXPOSED TO
MSMA ARSENATE (52)
Parameter
Exposure
Inorganic As in
organism, ppro
BR* for As
As % lip id
soluble
MSMA in
organism, ppm
BR* for MSMA '
MSMA % lipid
soluble
Daphnia
29 days
3.6 ppro
5
20%
8.4 ppm
8
29%
Garobusia
15 days
101.9 ppm
127
86%
108 ppm
110
42%
Algae
27 days
26.9 ppm
34
2.5%
4.2 ppm
4
17%
Crayfish
12-15 days
4.3 ppm
5
20%
1.4 ppm
1
27%
*BR «= bioaccumulation ratio
6.0 GLOSSARY OF CHEMICAL TERMS
Arsenate: inorganic arsenic radical where arsenic has a valence of +5;
AsO/3
4
Arsenite: inorganic arsenic radical where arsenic has a valence of +3-
AS02 .
Cacodylic acid(CA): hydroxydimethylarsine oxide; dimethylarsinic acid;
here arsenic has a valence of +1; (CH^AsO.,!!; an organic arsenical
herbicide, also a naturally occurring compound;
HO - As
I
0
- CH
A-214
-------
Dimethylarsine (DMA) : an alkylarsine where arsenic has a valence
of -3; (CtO-AsH; a naturally occurring compound produced by
organisms from arsenate;
CH, - As - CH
3 I
H
Disodium methanearsonate (DSMA) : at pH 10.5, DSMA is the predominant
sodium salt of methanearsonic acid (MAA); DSMA is an organic
arsenical herbicide, also a naturally occurring compound at high pH;
As - ONa
I
ONa
T3 I'* b I
0 - As - ONa "j * O - As - ONa < J O - As - OH
I pH 10.5 ' PH 6.5 '
ONa OH 0"
DSMA MS*1* MAA
Methanearsonic acid (MAA): methyl arsenic acid; CH3As03H2; an organic
arsenical herbicide; also a naturally occurring compound at low
pH;
r>
0 « AS - OH
I
OH
Monosodium methanearsonate (MSMA)* monosodium acid methanearsonate; the
sodium salt of methanearsonic acid; CH3As03Na; an organic arsenical
herbicide, also a naturally occurring compound;
As - OH
I
ONa
A-215
-------
Trimethylarsine gas (TMA) : here arsenic has a valence of -3; (CHO-As;
a naturally occurring compound produced by organisms, especially
fungi, from arsenate; toxic; volatile; has the odor of garlic;
-3
- As -
A-216
-------
18. Canutt, P.R., et aL. Arsenic Residues in Forest Floor, Soil, Vegetation
and Water After Injecting Conifers with MSMA. In: Studies of the Safe-
ty of Organic Arsenical Herbicides as Precommercial Thinning Agents; A
Progress Report, L.A. Norris, ed. , USFS, Corvallis, Oregon. 1970.
19. Data gathered regarding forestry use of pesticides in the Pacific North-
west for the Forest Use Chemicals Project (OFF, EPA) by DC Berkeley,
1980.
20. Unpublished forest pesticide use survey data collected by Dr. Dean
Gjerstad, Auburn University, Forestry Chemicals Corporative, Auburn,
Alabama. June 1980.
21. Midwest Research Institute. Substitute Chemical Program; Initial
Scientific Review of MSMA/DSMAJ EPA, 540/1-75-020, 1975^ -
22. Woolson, E.A. Fate of Arsenicals in Different Environmental Substrates.
Environmental Health Perspectives 19: 73-81, 1977.
23. Woolson, E.A. and N. Aharonson. Specification of Arsenical Metabolites
by HPLC-GFAA. Paper No. 117, Pesticide Degradation Laboratory, USDA.
Bettsville, ME. 1979.
24. Carton, R. Technical and Microeconoaic Analysis of Arsenic and Its
Compounds. EPA 560/6-76-016, Office of Toxic Substances, Washington.
D.C. 1976. In Reference 22.
25. Keeley, P.E. and R.J, Thullen.. Weed Science 19: 297, 1971. In Re-
ferences 1.
26. Keeley, P.E. and R.J. Thullen. Weed Science 19: 601, 1971. In Re-
ference 1.
27. Sckerl, M.M, and R.E. Frans. Weed Science 17: 421, 1969. In Refer-
STl C £ ,L «
28. Bollen, W.B., et al. Effect of Cacodylic Acid and MSMA on Nitrogen
29. Newton, M. Fate of Organic Arsenical Herbicides in Chemically Thinned
SriLf HerMci/nd ^f ingt°n' ln! StUdleS °f the S*^T ^r
Arsenical Herbicides as Precommercial Thinning Agents; A PrLyae»- p..
£2£t. L.A. Norris, ed. USFS. Corvallis. OregSn.^ 1970. Pr°^eS8 Re
A-218
-------
32. Robinson, E.L. Arsenic In Soil With Five Annual Applications of MSMA.
Weed Science 23(5): 341-343, 1975.
33. Johnson, L.R. and A.E. Hiltbold. Arsenic Content of Soil and Crops
Following Use of Methanearsenate Herbicides. Soil Sci. Soc. Amer.
Proc. 33: 279-282, 1969.
34. Woolson, E.A., et al. The Chemistry and Phytotoxicity of Arsenic in
Soils: 1. Contaminated Field Soils. Soil Sci. Soc. Amer. Proc. 35:
938-943, 1971.
35. Norris, L.A. and W.B. Bollen. Behavior of Cacodylic Acid and MSMA in
Forest Floor Material and Soil. In: Studies of the Safety of Organic
Arsenical Herbicides as Precommercial Thinning Agents, A Progress Re-
port, L.A. Norris, ed. USFS, Corvallis, Oregon. 1970.
36. Von Endt, D.W., et al. Degradation of Monosodium Methanearsonic Acid
by Soil Microorganisms. Journal of Agricultural and Food Chemistry
16(1): 17-20, 1968.
37. Cox, D.P. and M. Alexander. Production of Trimethylarsine Gas From
Various Arsenic Compounds by Three Sewage Fungi. Bulletin of Environ-
mental Contamination and Toxicology 9(2): 84-88, 1973.
38. McBride, B.C. and R.S. Wolfe. Biosynthesis of Dimethylarsine by Methane-
bacterium. Biochemistry 10(23): 4312-4317, 1971.
39. Braman, R.S. and C.C. Foreback. Methylated Forms of Arsenic in the
Environment. Science 182: 1247-1249, 21 December 1973.
40. Salman, H.A., et al. Progress Report of Residues Studies on Organic
Arsenicals Used for Ditchbank Weed Control, USDI, Bureau of Reclamation,
Report REC-ERC-72-37, 1972.
41. Final EIS: Vegetation Management With Herbicides. Pacific Northwest
Region. USFS, 1978.
42 Wauchope, R.D. and C.G, McWhorter. Arsenic Residues in Soybean Seed
From Simulated MSMA Spray Drift. Bulletin of Environmental Contamina-
tion, and Toxicology 17(2): 165-167, 1977.
43 Edwards A C. The Effects of an Organic Arsenical Herbicide on a Salt
* Marsh Ecosystem. MS Thesis, Auburn University. Auburn. Alabama. 1973.
44 Anderson, A.C., A.A. Abdelghani, P.M. Smith, J.W. Mason, and A.J.
Enelande Jr. The Acute Toxicity of MSMA to Black Bass, Crayfish, and
Channel Catfish. Bulletin of Environmental Contamination and Toxicolo-
gy 14: 330-332, 1975.
45 Fletcher D. 8-Dav Dietary LCsp Study with Monosodium Acid Methane-
45' !'!±" in Mallard Ducklings, unpublished report of Industrial Bio-
fest Laboratories, Northbrook, Illinois, 1973.
A-219
-------
46. Schroedel, T., et al. Arsenical Silvicide Effects on Wildlife. In:
Studies of the Safety of Organic Arsenical Herbicides as Precommercial
Thinning Agents: A Progress Report, L.A. Norris, ed. USFS, Corvallis,
Oregon, 1970.
47. Exon, J.H. , et al. The Effects of Long Term Feeding of Monosodium Acid
Me thanear senate (KSMA) to Rabbits. Nutrition Reports International
9(5): 351-357, 1974.
48. Harr, J.R. Functional, Histologic and Residue Effects of MSMA in
Rabbits. In: Studies of the Safety of Organic Arsenical Herbicides as
Precommercial Thinning Agents; A Progress Report, L.A. Norris, ed.
USFS, Corvallis, Oregon, 1970.
49. Norris, L.A. Arsenic in Cattle Hair After Forests Are Precomnercially
Thinned With Organic Arsenical Herbicides. USFS PNW-296, Portland,
Oregon, 1977.
50. Dickinson, J.O. Toxicity of the Arsenical Herbicide Monosodium Acid
Methanear senate in Cattle. American Journal Veterinary Research 33(9):
1889-1892, 1972.
51. Isensee, A.R. , et al. Distribution of Alkyl Arsenicals in Model Eco-
system. Environmental Science and Technology 7(9): 841-845, 1973.
52. Woolson, E.A. , et al. Distribution and Isolation of Radioactivity from
74As-Arsenate and 14C-Methanearsonic Acid in an Aquatic Model Ecosystem.
Pesticide Biochemistry and Physiology 6: 261-269, 1976.
53. Moffett, J.O., et al. Toxicity of Some Herbicidal Sprays to Honey Bees.
Journal of Economic Entomology 65(1): 32-36, 1972.
54. Atkins, E.L. , et al. Toxicity of Pesticides and Other Agricultural
Chemicals to Honey Bees. Division of Agricultural Sciences University
of California Leaflet 2287, 1975.
55. Johansen, C. How to Reduce Bee Poisoning From Pesticides. Western Re-
gional Extension Publication No. 15, Washington State University, 1980.
56. Morton, H.L. , et al. Toxicity of Herbicides to Newly Emerged Honey
Bees. Environmental Entomology 1(1): 102-104, 1972.
57. Zabel, R.A and F.W. O'Neal. The Toxicity of Arsenical Compounds to
Microorganisms. Tappi 40(11) : 911-914, 1957.
58' O«'F;;' S ;3 E"ec* of Cacodylic Acid
Forest Floor and Soil. Weed Science 22(6): 557-562. 1974.
A-220
-------
Common Name: Picloram
Chemical Name: 4-amino-3,5,6-trichloropicolinic acid
Major Trade Names: Tordon; Amdon
Major Applications Used in virtually all geographic regions of the U.S.
in Forestry: primarily in site preparation and occasionally in pre-
commercial thinning and conifer release.
SUMMARY
The fate of picloram in the forest environment has been the subject of
limited studies. Most of the available information on the fate of picloram
in soil and water is the result of laboratory and/or field studies with
agricultural systems.
Picloram is rapidly absorbed by plant roots and less rapidly by foliage.
Once absorbed, it is readily translocated throughout the plant with a ten-
dency for accumulation in new growth. It is very stable and remains largely
intact within the plant, although small amounts degrade via decarboxylation,
conjugate formation and other mechanisms.
Picloram is considered "moderately" to "highly" persistent in soils
under conditions of normal application and may exist at phytotoxic levels for
over one year. Reported half-lives vary from one to over 13 months. Persis-
tence is generally shorter in soils with high organic matter content and
adequate moisture such as may be present in forest soils, and in warm tempe-
ratures. Picloram degradation in soil occurs via microbial rather than chem-
ical routes. .Even under conditions highly favorable to microbial growth
however, amounts of picloram decomposed are small. Picloram undergoes photo-
decomposition on soil surfaces. Photodecomposition on soil occurs to the
Greatest extent under intense sunlight, and hence is not expected to be great
in Jorest^ystems Volatilization is not likely to be a major mechanism for
the dissipation of picloram and its formulations from forest soils because
of their low vapor pressures.
Picloram is considered a mobile herbicide and is reversibly adsorbed on
crt-n Articles Adsorption is greatest in soils high in organic matter, and
increases ^'decreasing PH, particularly in clay soils Leaching occurs
increases witn ° * sandv, light-textured soils and soils poor in
to the «"•"« «*"£ picloram did not leach below the upper few inches
:?H 1 inTfoUs floor i!S the Pacific Northwest Picloram formulation
mL -ff«et its leaching. Studies have shown that the potassium salt of
plclolam is »ore readUy leached than the triisopropanolamine salt.
Because of the water solubility of picloram and its salts and its
leachS tendencies, runoff from treated areas can contain relatively high
A-221
-------
concentrations of picloram. Field monitoring studies conducted on three
forest plots in Oregon and Washington treated with 0.5 to 1 Ib/acre picloram
indicated that runoff of picloram is most likely if heavy rainfall occurs
soon (1-2 months) after application. Picloram rapidly degrades in water in
sunlight.
Picloram is phytotoxic to numerous non-target plant species. It is
very toxic to young pine seedlings. Several incidents of damage to non-
target plants due to picloram spray drift have been reported. Certain
species of plants have been injured as long as five years after application
as a result of the persistence of picloram.
Picloram and its salts are low in toxicity to fish and other aquatic
organisms. It has low toxicity to warm-blooded animals and to soil micro-
organisms. Limited studies on picloram and picloram plus 2,4-D have indi-
cated low toxicities of these compounds to bees. Picloram is rapidly
excreted by and does not bioaccumulate in mammals. Picloram in water is not
accumulated in invertebrates or in food chains.
Recent studies have shown that certain picloram ester formulations may
be more toxic to fish than picloram and its salts due to the presence of the
toxic impurity 2-(3,4,5-6-tetrachloro-2-pyridyl)-guanidine.
A-222
-------
1.0 INTRODUCTION
Picloram, discovered in 1963, is a non-selective, wide-spectrum herbi-
cide which is widely used for control of woody plants and most annual and
perennial broadleaf weeds (1,2). Major non-forest uses are in brush control
along utility rights-of-way, for weed and brush control in pastures and
rangeland, and broadleaf weed control in small grains (2). It is also regis-
tered for use in combination with 2,4,5-T on permanent rangeland and pasture
in Texas, New Mexico, and Oklahoma (3,A).
Picloram alone and/or in combination with 2,4-D (as various "Tordon"
formulations) is used in the forest industry in virtually all geographic re-
gions of the U.S., primarily in site preparation and occasionally in pre-
commercial thinning (5,6). Picloram is occasionally used in combination with
2,4-D for the control of woody vegetations for conifer release; topkills of
90 percent or better have been achieved in such applications (7,8). However,
it is not recommended for conifer release for herbaceous weed control by
broadcast application since it can severely damage young conifers (9,10,11).
Tables 1 and 2 show the usage of picloram formulations for site prepara-
tion (woody vegetation and kudzu control) and pine release in the Southeast
in 1979, respectively. For comparison, use data for all other pesticides
reportedly used in the Southeast are also provided. As indicated in the
table, picloram formulations were used in the site preparation for woody
vegetation control in over 51,500 acres, or 52.8 percent of the total acreage
treated. For pine release, picloram formulations were applied to 78,510
acres, or 68.3 percent of the total acreage treated. Tordon 10K and Tordon
101 wire used almost exclusively in site preparation for kudzu control.
A complete picture of the picloram usage in forestry is not available
for other geographic regions of the country. Data for usage on public lands
in the Pacific Northwest indicate that while picloram usage has been substan-
tial in recent years, picloram is not one of the most widely used pesticides
in that region of the country. Picloram usages by U.S. Bureau of Land Mana-
gement (in Oregon) and by U.S. Forest Service in Regions 5 and 6 are pre-
sented in Tables 3, 4, and 5, respectively. Available data on the use of
picloram formulations by the State of Minnesota, Department of Natural Re-
sources, are presented in Table 6.
A-223
-------
TABLE 1. FOREST HERBICIDE USAGE IN THE SOUTHEAST IN
1979 FOR SITE PREPARATION (12)
Woody Vegetation
2,4~D Anin«
Hexazinone (-Gridball)
Tordon 10L
Tordcn 101R
Tordon 101 +
2,4-DP
Tordon 101 R +
2,4-D Amine
Tordon 101 +
Carlon 3A
Tordon 10K
2,4-DP
2,4-D + 2,4-1)1'
Ueedom; fiii
Weed one 170
Paraquat
Sllvisor
Subtotal ....
Kudzu
Tordon 10K
Tordon 101
Hexazinone (WP)
Subtotal
Acreage
30,000
160
2,425
25,411
9,660
11,581
2,300
160
1,262
1,480
5,250
4,280
2,714
C39
4
2,350
1,578
5
*••*«•,
: -
Amount
12,093 gal
1,900 lb.
3,014 gal.
10,444 gal.
13,702 gal.
16,641 gal
17,515 gal.
17,185 gal
2,300 gal
1,150 gal
4,080 lb
691 gal
1,910 gal
2,620 gal
4,280 gal
72 gal
200 gal
4 gal
Q"7 ^"Jfi
7/1 3^o
54,420
1,537 gal
15 lb
3,933
101,459
"
Method of Application
injection
ground 6 aerial
aerial
injection
aerial
inj action
aerial
aerial
aerial
each aerial
injection
aerial
injection
aerial
injection
ground
ground
ground
'
A-224
-------
TABLE 2. FOREST HERBICIDES USAGE IN THE SOUTHEAST IK 1979 FOR
PINE RELEASE (WOODY VEGETATION) (12)
Chemical
Tordon 101
2,4-D Amititi
Tordon 101
Tordon 101
Hexazinone
2,4-D
2,4-DP
Weedone 170
Formula 40
Deduced 40
TOTAL
TABLE 3.
FY
1979
Acreage
R f 47,562
R 15,316
15,632
(Gridball) 375
4,775
12,000
2,714
9,000
7,665
115,009
Amount
2,400 gal
9,385 gal
2,585 gal
5,000 Ib.
1,925 gal
6,000 Ib
72 gal
?
?
Method of
Application
each injection
injection
injection
aerial & ground
injection
ground
injection
injection
injection
PICLORAM APPLICATIONS IN STATE OF OREGON BY U.S. BUREAU OF
LAND MANAGEMENT, FISCAL YEARS 1978 AND 1979 (13) -
Formulation Target
Picloram Yellow
Pounds
Pest/Purpose Acres Treated . Used
Star Thistle
800 200
1978
Tordon K and
Verzoh 20
Picloram
Picloram
Picloram
Mixed hardwoods,
site preparation
Biological,
Yellow Star Thistle
Yellow Star Thistle
Biological,
Yellow Star Thistle
890
10
692
10
4,450
2.5
.73
2.5
A-225
-------
TABLE 4. PICLORAM APPLICATIONS IN U.S. FOREST SERVICE REGION 5, FISCAL YEARS 1975-1979 (13)
FY Formulation
1979 Picloram
1976 Picloram
1977 Tordon 10K
L976 Piclorant
Target Pest/
Purpose
Fuelbreak
Fuelbreak
Thinning
Noxious weed control
Chapparal ,
conifers
Puelbreak
Noxious weed control
Noxious weeds
Fuelbreak
No. of Sites Acres
Treated Treated
192
199
20
60.25
129
459
23
85
235
Pounds
Used
328
249
7.2
30.6
846
30,323
9
70
213
Application
Method
aerial
aerial
ground
ground
~
-
-
-
—
-------
TABLE 5. PICLORAM APPLICATIONS IN U.S. FOREST SERVICE REGION 6,
FISCAL YEARS 1975-1979 (13)
py
1979
1976
1977
1975
Formulation
Picloram
2,4-C +
Pi do run
2,4-D +
Pi dor am
Picloram
Tordon 10K
Tor don 101
Picloram
Picloram
Picloram
Picloram +
2,4-D
Pidorara
Picloran
Pidoratn
Picloran
Picloran
Picloram
Picloram
Picloran
Tordon 22K
Picloram
Picloran
Tordon 10K
Tordon 101
Tordon 101
Tordon 10X
Tordon 10K
Tordon 101
Target Pest/
Purpose
Vegetation thinning
Vegetation control/
site preparation
Conifer release
Noxious weed control
Vegetation control.
powerline row
Vegetation control,
powerline row
Site preparation
Release
Noxious weed control
Noxious weed control
Right-of-way
Thinning
Site preparation
Site preparation
Site preparation
Release
Noxious weed control
Noxious weed control
Noxious weed control
Road Right-of-way
Powerline Right-of-way
Powerline Right-of-way
Timber management
Mistletoe control/
tree injection
Poison oak
Control of wood,
plants near power lines
Brush under powerlines
So. of Sites
Treated
353
2,109
42
477
7
7
2,609
903
229
52
171
1
495
35
757
1,069
1,701
129.2
47
9
97
45
7,545
412
2
40
326
Pounds
Used
12
10,132
198
148
42
42
11,219
77
389
12
685
2.5
115.5
17.5
379
50
22
295.9
82.5
36
70
13
906
46
5
60
3,988
Application
Method
Crowd
Aerial
Ground
Ground
Ground
Ground
-
-
-
-
'
-
-
-
-
-
-
-
-
-
-
—
m
-
-
»•
^
A-227
-------
TABLE 6. TORDON 101 USAGE BY MINNESOTA DEPARTMENT OF NATURAL RESOURCES (14)
OO
Administrative
District
Target Pest
or Purpose
Amount
Used
Units
Treated
Remarks
A) January 1 - June 30, 1980
Lewiston Area
Lewiston Area
Red Wing District
Lake City District
B) January 1 - June 30
Region V
Region V
Release of black
walnut
Release of pine
Boxelder
Weed trees
, 1979
Weed trees
Boxelder, elm
6.5 gal
20.75 gal
1 gal
7.5 gal
8 gal
25 Ibs
721 acres
41 acres
5 acres
144 acres
41 acres
5 acres
Miscellaneous hardwoods injected with
hack and squirt method
Miscellaneous hardwoods injected with
hack and squirt method
Site preparation for walnut planting
Timber stand Improvement
Winter application not 100% effective;
injection method used
C) July - December, 1979
Red Wing District
Lake City District
Lake City District
Lewiston Area
Lewiston Area
Boxelder, elm
Elm, boxelder
Miscellaneous
hardwoods
Walnut TSI
Release of pine
19 gal
2 gal
1/2 gal
1 gal
15 gal
43 acres
10 acres
10 acres
35 acres
20 acres
Competing trees injected with 2 ml/
diameter inch
Miscellaneous hardwoods injected with
D) July 1 - December 31, 1978
Lewiston Area
Release of black
walnut
1 qt
hack and squirt method. Cut stump
type applications also used.
3 acres Killed competing hardwoods and pruned
walnut
-------
Picloram can be applied as: 1) a spray solution to foliage; 2) injected
as a liquid formulation into tree or brush stems or applied as a cut surface
treatment, or applied as pellets to the ground to be leached into the root
zone by rainfall (15). Liquid formulations are applied aerially, or by means
of ground equipment, knapsack equipment and tree injection. The granular
formulation is applied by hand or with commercial granular applicators (1).
Liquid formulations are usually aqueous solutions and are applied at rates
of 2 oz to 3 Ib/acre of picloram. Pellets are usually applied at a rate of
2 to 8 Ib/acre (1). Tree injection rates are typically 1 ml/injection of
Tordon 101 formulation (7). Applications are usually made from spring to 3
weeks before the first frost (5).
Picloram is a growth regulator, but its exact mode of action has not
been established (16,17). It is absorbed by both roots and foliage, is
translocated throughout the plant, and is accumulated in points of new growth
(16,17).
Major forest weed species which are controlled by picloram include aspen,
blackgum, brambles, buttonbush, Canada thistles, chokecherry, conifers, field
bindweed, gallberry, hickory, juniper sp., kudzu, mulberry, redbud, sassafras
and sourwood (17,18,19). Table 7 presents the relative susceptibility of a
number of woody plants to foliage-applied sprays of picloram and picloram
plus 2,4-D. Picloran, is also effective in eradicating eternise, a chaparral
species (21). A large number of deep-rooted perennial broadleaves such as
bindweed, leafy spurge and larkspur are readily controlled with 2 pounds per
acre of various Tordon formulations (22). Most established perennial grasses
are not affected by rates of 1 to 2 pounds per acre (22).
Formulations of picloram commonly used in forestry, their active in-
gredients and inert carriers are presented in Table 8. Other available for-
mulations for use in rangeland and cropland are listed in Table 9. A number
of formulations which have previously been used in non-forest applications
are no longer produced. These include: Tordon 2S Weedkiller (21.5 percent
picloram as the potassium salt); Tordon 155 (10.3 percent picloram as the
isooctyl ester plus 41.3 percent 2,4.5-T as the propylene glycol butyl ether
ester); and Tordon 212 (10.1 percent picloram as triisopropanolamine salt
plus 20.2 percent 2.4-D as triisopropanolamine salt) (23).
A-229
-------
TABLE 7,
SUSCEPTIBILITY OF VARIOUS WOODY PLANTS TO FOLIAGE-APPLIED
SPRAYS OF PICLORAM AND PICLORAM PLUS 2,4-D* (20)
Common Name
Scientific Name
Picloram
2,4-0(1:4)
Picloraa
Alder
Ash
Barberry, common
Basswood
Beech
Birch
Blackberry
Broom, scotch
Buckthorn, European
Caragana, common
Cherry
Cedar, Western
Cedar, yellow
Currants
Dogwood, red osier
Elderberry
Elm
Fir, balsam
Fir, Douglas
Gorse
Hazel
Hardback
Hawthorn
Hemlock, Western
Honeysuckle, bush
Hornbeam
Lilac
Locust, black
Maple, Manitoba
Maple
Maple vine
Oak
Pines
Poison-ivy*1
Poplar aspen
Poplar, balsam
Raspberry, wild
Rose, wild
Sagebrush, nig
Salmonberry
Saskatoon
Snowberry (buckbrush)
Sumac
Spruce (white,black)
Thimbleberry
Virginia creeper
Willows
Alnue ssp.
Pyrua f, Frasinue ssp.
Berberie vulgarit
Tilia ameriaana
Fagus ssp.
Betula asp.
Kubue gap.
Cytieus saopari+a
Khamnus aatharziaa
Caragana arbortsstnt
Prunus ssp.
Thuja pliaats
Chamaeayparit r.:3tkat»n*iz
Kibes ssp.
Cornue etoloniferz
Sambucue ssp.
Ulmus ssp.
Abies amabalie
Peeudoteuga zzzifolia
(Ilex europae^e
Coi-ylue ssp.
Spiraea tomer.~:ez
Crataegus ssp.
Tang a hetercskftts
Loniaera ssp.
Ostrya wiroinirns
Syringa vulasrie
Robinia pee'+d: uacis
Ao«r negund:
Acer ssp.
Acer ciroinsiu-
Querous ssp.
Pinue
Rkut fadica'.t
Populue tr>e—*:?-:zes
Pzpulue
Kubus sap.
noea ssp.
Artemisia tridentata
/?uus epeatabilie
fiielanchier alnifolia
Symphoriaarpue oaoidentalia
f?'Ji48 ssp.
Piaea ssp.
3:,ou8 parviflorua
Parthenoo-ittut
Salix ssp.
S
I
S
S
S
S
S
S
5
S
S
S
S
S
S
S
S
I
S
S
S
S
S
S
S
S
S
S
S
I
S
S
S
S
S
S
S
S
S
S
S
S
S
S
S
I
S
S
S
S
S
S
S
S
S
S
S
8
S
8
I
S
S
S
S
S
S
S
S
S
S
S
I
S
S
S
S
S
S
S
S
I
S
X
S
S
8
8
S
'Susceptibility classification:
S =
««**• -» th. one
A-230
-------
TABLE 8. PICLORAM FORMULATIONS FOR FORESTRY USE (4,20,23)
Formulation
Active Ingredients
(Percent)
Active Ingredients
(Weight)
Inert Carriers
Tordon 101
N>
Tordon 101R
Mixture"*"
Tordon 10K
Pellets
Tordon K
10.2% picloram -
tr i i sopropanolaraine
sail. 39.6% 2,4-D -
triisopropanolamine
salt.
Appxoximat'ely 5.1%
picloram - triisopro-
panolamine salt.
Approximately 20%
2,4-D - triisopro-
panolamine salt.
11.6% picloram -
potassium salt.
24.0% picloram -
potassium salt.
10 oz acid equivalent (a.I.)/
Imp. gal. triisopropanolamine
salt. 40 oz a.i./Imp. gal.
2,4-D - triisopropanolamine
salt.
5 oz acid equivalent (a.i.)/
Imp. gal. triisopropanolamine
salt. 20 oz a.i./Imp. gal.
2,4-D - triisopropanolamine
salt.
1.6 oz a.i./lb - potassium
salt.
2.0 Ib a.i./gal - potassium
salt.
Tordon 101 mixture also contains
a filycol derivative sequestrant
and glycol wetting agent along
with alcohol and water.
Tordon 101R mixture also contains
a glycol derivative sequestrant
and glycol wetting agent along
with alcohol and water.
Clay.
Applied as a water spray (4).
Applied via tree injection or cut surface treatment methods (4).
-------
TABLE 9. PICLORAM FORMULATIONS FOR NON-FORESTRY USF.S (1,4,16,23)
r\j
to
Is)
Picloram in Formulation
Trade Name
of Product % a . i . *
Tordon 2K + 2.3
Tordon 22K 24.9
Tordon 202 Mixture 1.4
Tordon 22 5E Mixture^ 10.7
g/
liter
-
-
15
120
Other Herbicides in Formulation
Deriva-
tive"1' Name %a.i.*
K salt
K salt
TIPA salt 2,4-D 22.1
TEA salt 2,4,5-T 10.7
as Tordon 101R; see Table 8 —
g/ Deriva-
liter tive^
-
-
240 TIPA salt
120 TEA salt
* a.i, is acid equivalent (picloram, BO, 2,4-D, 2,4,5-T, and MCPA, respectively).
t K is potassium salt. TIPA is triisopropanolamine salt, and TEA is triethylanune salt.
£ This formulation contains ammonium sulfate as the inert ingredient, and has re-
placed Tordon Beads which contained 2.3% picloram as the potassium salt, plus
disodium tetraborate pentahydrate and disodium tetraborate decahydrate as the
in ert ingre dien ts.
# Registered for use only in Texas, Oklahoma and New Mexico for mesquite control
in rangeland and pastureland.
-------
In addition to use with 2,4-D and 2,4,5-T, picloram has been shown to
be efficacious when used in combination with triclopyr (24). In applications
to 1/60-acre plots in central Louisiana, use of picloram at a rate of 1.0 Ib
a.i./acre in combination with triclopyr ester or 2,4,5-T ester at a rate of
3.0 Ib a.i./acre resulted in over 90 percent topkill of mixed hardwood brush
for two growing seasons. Picloram alone applied at a rate of 3.0 Ib a.i./
acre gave only 60 to 66 percent topkill under the same conditions (24).
Picloram is manufactured by the Dow Chemical Company. In addition to
Tordon, it is also known by the trade name Amdon (2).
2.0 PHYSICAL AND CHEMICAL PROPERTIES OF ACTIVE INGREDIENT
The active ingredient of picloram is 4-amino-3,5,6-trichloropicolinic
acid:
Cl
Cl
It is a white colorless crystalline substance which decomposes at 215°C
before melting (16,25). Picloram is a monocarboxylie acid with a dissocia-
tion constant, pKa, of 3.6 (26). It is stable in both acidic and basic
media, but may hydrolyze to the 6-hydroxy derivative in the presence of hot
concentrated alkali (27).
Picloram is only very slightly soluble in water (430 mg/1), but its
potassium and amine salts are highly water soluble (25). Solubility data
for picloram and its salts at 25eC in various solvents are presented in
Table 10.
Vapor pressure data for picloram, picloram methyl ester and picloram
isooctyl ester (the active ingredient in Tordon 155) are shown in Table 11.
Although no vapor pressure data are available for salts of picloram, the
volatility of the salts are expected to be significantly less than the non-
ionic compounds shown in Table 11.
A-233
-------
TABLE 10. SOLUBILITY (in rag/1) OF PICLORAM AND ITS POTASSIUM
AND AMINE SALTS IN VARIOUS SOLVENTS (16,28)
Solvent
Acetone
Ethanol (2B-abs)
Isopropanol
Acetonitrile
Diethyl ether
Methylene chloride
Water
Benzene
Carbon disulphide
Kerosene
Xylene
Picloram
19,800
10,500
5,500
1,600
1,200
600
430
200
50
10
Potassium Salt
100
240
400,000
100
100
Amine Salt
Highly soluble
TABLE 11. VAPOR PRESSURE FOR PICLORAM AND
TWO PICLORAM ESTERS (16,29)
Compound
Picloram
Picloram (methyl ester)
Picloram (isooctyl ester)
Temperature
35
45
40
40
Vapor Pressure
(mm of Hg)
6.16 x 10~,
1.07 x 10
7.4 x 10"6
5.88 x 10~6
A-234
-------
3.0 ENVIRONMENTAL FATE
Only a small body of environmental fate data have been published in
connection with the use of picloram in forests. Most of the available data,
which are included in the discussion in this section, are for non-forest
applications.
3.1 UPTAKE AND METABOLISM BY PLANTS
Picloram is a growth regulator, but its exact mode of operation has not
been established (16,17). Picloram is rapidly absorbed by plant roots and
less rapidly by foliage (17,20,22). Rapid uptake of picloram by roots from
nutrient solutions has been demonstrated in a number of studies using green
ash (Fraxinus Pennsylvania marsh), sweet gum (Liquidombar styracflua L.) and
silver maple (Acer saccharinum L.) seedlings (30); huisache (Acacia farne-
siana L. wild) and honey mesquite (Prosopis juliflora) (31); and oats, soy-
beans (32), and peas (33). Rapid uptake of picloram by roots from soil has
also been demonstrated with young huisache (34) and leafy spurge plants (35).
Picloram sprayed on the leaves of yaupon (Slex vomitoria, Ait) at 4.4 kg/ha
resulted in only 2 percent absorption after 72 hours (36). In studies on
bean seedlings, 7 days were required before 90 percent of the foliage applied
picloram was absorbed.
Once absorbed, picloram is readily translocated throughout the plant
with a tendency for accumulation in new growth (17,22). Relatively little
is known about the metabolism and fate of picloram and its derivatives or
degradation products in plants. Most studies have shown that picloran itself
is very stable and remains largely intact within the plant (37,38). Rede-
mann, et al. (39) reported that the major compounds present in extracts of
84-day-old wheat plants treated at 1.0 kg/ha were: the parent compound, 83
percent; oxalic acid, 8 percent; 4-amino-2,3,5-trichloropyridine, 4 percent;
and 4-amino-3,5-dichloro-6-hydroxypicolinic acid, 5 percent. Decarboxylation
also is suggested as a possible degradation pathway (37). In a study using
cotton, however, the rate of decarboxylation was very slow, indicating that
it was not an important mechanism for picloram metabolism in plants. Resi-
due analysis in this study indicated the presence of no other compound
besides picloram. Picloram has also been reported to form conjugates with
various plant constituents including proteins (37,38,39).
A-235
-------
3.2 FATE IN SOIL
Processes which affect the fate of picloram in soil are volatilization,
photodecomposition, adsorption and leaching, runoff, and chemical and micro-
bial degradation.
Volatilization is not expected to be a major mechanism for dissipation
of picloram from soil because of the low vapor pressure of picloram and its
formulations (see Section 2). This has been indicated in 2 laboratory stu-
dies in which vapor losses from the potassium salt of picloram from open
petri dishes maintained at 55 to 60°C were less than 5 percent over a one-
week period (40,3A). The contributions of the remaining processes to the
fate of picloram in soil are described below.
3.2.1 Photodecomposition
Picloram undergoes photodecomposition on the soil surface and on the
surface of vegetation due to the action of uv radiation in sunlight (1,41,
A2). Photodecomposition occurs to the greatest extent under intense sunlight
(42).
Laboratory studies by Merkle, et al. (40) indicated that 60 percent of
picloram, when spread evenly on a glass surface, was degraded by uv light
within 48 hours, whereas 35 percent was degraded by sunlight in the same time
period. After one week's exposure, over 90 percent was degraded by uv light
and 65 percent by sunlight. Degradation from soil surfaces was slower than
from glass; only 15 percent of the applied picloram was degraded after one
week in sunlight. In studies by Bovey and Scifres (43), salt forms of piclo-
ram were found to be less subject to photodecomposition than ester forms.
The mechanism and.products of picloram photodegradation in soil have not
been fully investigated, although there are recent indications that cleavage
of the pyridine ring occurs (1).
3'2'2 Adsorption and Leachinp;
con-
Picloram is reversibly adsorbed on soil particles and is generally _-
sidered a mobile herbicide (3). The extent of adsorption and hence potentla!
for mob Hty and leaching is dependent on Boil type (primarily organic matter
content , pH appUcation rate, the amount of Water applied (rainfall) and
tbe picloram formulation. Soil organic matter is the principal parameter
A-236
-------
responsible for adsorption and adsorption can be substantial in forest litter
having high organic matter content (3,44). It has been postulated that soil
humic substances retain picloram initially via surface adsorption and subse-
quently via adsorption/occlusion within the internal structures (45).
Picloram adsorption on soils generally increases with decreasing pH,
particularly in clay soils, and is minimimal in neutral and alkaline soil
types (20,46,47,48,49). Picloram is also strongly adsorbed by hydrated
oxides of aluminum and iron (50) and this accounts for some adsorption which
occurs in clay soils.
Consistent with the adsorption properties of various soil types, leach-
ing of picloram occurs to the greatest extent in sandy, light-textured soils
and in soils poor in organic matter (1,3,20). A number of studies have shown
that picloram remains in the upper 20-30 cm of soil for most soil types ex-
cept sandy soils (3). In a study of the leaching of picloram in connection
with its use in powerline rights-of-way weed control in the Pacific Northwest,
no picloram was leached below 30 cm in the soil, and very little leached be-
low 15 cm (6). In a separate study essentially no picloram leached below
the upper inches of soil in a forest floor (6). Norris (51) reported that
picloram applied to a southern Oregon hillside pasture was largely confined
to the surface 6 inches of soil. For most soil types, the extent of picloram
leaching in soil is affected by the amount of water (rainfall) applied and
the picloram application rate.
The extent of picloram leaching is also a function of total amount of
water and the rate of picloram applied. In a recent study by Grover (52),
it was shown that increasing the amount of water applied from 0.25 to 2.5 cm
enhanced the movement of picloram in a heavy clay soil, but had no effect on
a sandy loam. There was little or no difference in movement when the herbi-
cide was applied at 0.2 or 2.0 kg/ha. In a sandy loam, picloram leached to
a greater depth when the soil was initially dry rather than wet. Field
studies have demonstrated that at low rates of application, picloram rarely
moves downward beyond the upper 30 cm of soil, particularly in semi-arid
regions (53,54,55). At high rates of application, picloram readily leaches
downward to over 100 cm, even in a relatively dry area (35). The results of
various field studies reflecting the effects of soil type, pH, rainfall and
application rate on picloram leaching are summarized in Table 12.
A-237
-------
TABLE 12. SUMMARY OF SOIL PROFILES OBTAINED IN VARIOUS FIELD STUDIES
ON LEACHING BEHAVIOR OF PICLORAM (20)
U)
00
Locality
Texas
*j;J tyne
fine s.l.
pH
5.0-6.0
Organic Rain- jtppit. Samp]
•attar fall rate Intel
(f) ten) />„.>>»> f*.m
Texas gravelly s.l. 5.5
Ort ir.
Onio
Ohio
silt; c.
silt 1.
sill 1.
Saskatchewan c. 1.
jaskaicheuar. i.
Alberta
fclberia
Texas
Texas
Nebraska
Nebraaka
Nebraska
Nebraska
Puerto Rico
Puerto Rico
Texas
Texts
Texas
Kansas
.Saskatchewan
Saskatchewan
Manitoba
1.
1.
c.l.
a.
silty c.l.
sllty c.l.
fine s.l.
sllty c.l.
e.
a.
s.l.
l.B.
fine s.l.
B.C.I.
heavy c.
sanely 1.
e.
6.0-6.6
6.1-5.8
6.0-7.1
7.2
5.7
8.0
*-7
_
-
6.6
5.6
7.5
6.8
. -
7.1
7.6
-
-
7.7
7.5
b.*-7.4 8.
4.4-1
15.0
8.6
.1 40.1
2.9-1.0 63.3
3.9-0.9 69.3
4.0
4.0
11.0
11.0
_
-
4.7
2.7
1.8
4.3
-
T.5
-
2.2
4.1
1.8 '
8-2.6
—
-
—
-
- 35.6
33.0
met
«D
69*6
47 ft
*•- * • U
59.9
124,5
53.3
2.5
8.9
-
64.3
r£4.0
73.5
8.96
8.96
4.48
4.48
4.48
4.48
0.56
1.12
0.28
10.08
10.08
2*24 **\
1 • 1 2 <"*'
224 •»'
42
84
280
245
270
350
435
330
435
180
180
f
i-yr
l_*n>
• *** I — J 4
2.24 -1-yr
10. 08
10.08
0.28
0.28
1.12
3.36 3
ISO
ISO
28
36
30
-y
4.49 -C-jrr
0.70 ^
139
i Plclorasi reeovarT at indicated depths (c»J
^.Q-2.5 0-5 Or15 15-30 30-45 45-60 60-7J 75-90 Sg-1P3
,} ^^pob)
60 - 330 !80
60 - 120 60
400 368
232 80
220 146
I~900 — S750— 1424 i
I 38 — ^38 -i-37-I
I 83 —I- 99 -4-38-1J
j ^,60^^ .
I 50 — I - - -
136 39 1* U
m no -
184 104 78 32 -
-
• — — — -
JX — ™ — ~ "*
105-UO
-
—
' -
—
"
-
-
I 49 — H6-J-O— IO-I - - - - -
220 210
30 10
I ~" I
T 17 I
I •" I
T *w* T
883 612
, ' - 0 0
113 - 31 I •
38 - 8 I
93 18
I 229 -t-2*
- 233 156 33
- 70 30
I -80 1 1 10 1 I 0-
I 50 1 1 60 1 I 60-
•y g Y * Jd- T _
* 2 T J y T
T ij T T- 26 - T -
jr j* ^^ * ^*^ j
I — 215 — t I- 62-1
I 0 1 1—0-5
— 0 1 - - -
— 0 1 -
2 - 1
J ; •>"3 ^ 31 I 13
I its 1 I 100 II 28 —
1 6 1 -
1
1
_
_
_
-
J-109-
~
-
—
2
_J
1
1
~"*
s. = sa.ndyt 1> = loa«j e. = els?
Dashe* (-) Indlesta no savplas wsr» taken.
-------
The type of picloram formulation used may or may not affect its leaching
in soil. Hunter and Stobbe (55) reported that the potassium salt of picloram
leached more readily than the triisopropanolamine salt. In a leaching study
conducted by Bovey and Scifres (43), however, the leaching patterns of pi-
cloram salts and esters were found to be similar. Where esters were used,
the unhydrolyzed esters were found in the top 5 cm of soil; only the acid
form was found below 5 cm. It was not possible to distinguish between the
acid and salt formulations.
3.2.3 Runoff
Because of the water solubility of picloram (especially its salts) and
its leaching tendencies, runoff from areas treated with picloram can contain
relatively high concentrations of picloram. Based on field monitoring data
for three forest plots in Oregon and Washington treated with 0.5 to 1 lb/
acre of picloram, in which maximum picloram concentrations of 20 to 78 ppb
occurred in runoff during storm events, Norris (56) concluded that runoff of
picloram can occur after the first heavy autumn rains if application is in
mid or late summer and that the greatest potential for runoff exists when.
the storms are sufficiently intense to cause overland flow rather than infil-
tration. In a separate study, losses of picloram from a Tordon 101-sprayed
podsol in a Great Lakes forest clearcut were measured for 13 months following
spraying (57). A rainfall occurring lees than 24 hours after spraying
released only a very minute amount of picloram and only less than 1 per-
cent of the applied picloram was lost as a result of seven runoff events
which occurred during the monitoring period.
Based on a large number of non-forest and several forest field studies,
it is generally held that a potential exists for high concentrations of pi-
cloram in runoff if heavy rainfall occurs soon after application (58).
Bovey, et al. (34) found that maximum concentrations of picloram were 400 to
800 ppb in surface runoff water if heavy rainfall occurred immediately after
spraying a 1:1 mixture of triethylamine salts at 1.12 kg/ha on grassland
watersheds. However, if major storms occurred within 1 month after applica-
tion, picloram concentrations were less than 5 ppb. Picloram residues in
drainage from a forest plot in Ontario, Canada, sprayed with 0.9 kg/ha were
38 ppb one day after application, 26 ppb after 7 weeks, and 1 ppb after one
year (60).
A-239
-------
The fact that on Iy a very small percentage of the applied picloram from
the treated areas would enter the runoff has been demonstrated in a relative-
ly large number of field studies in non-forest applications. These studies,
summarized in Table 13, indicate maximum picloram losses of less than 3 per-
cent. These studies have also shown that concentration of picloram in runoff
water generally decreases with time, and also with time-lapse from applica-
tion to the first rainfall. In one of the studies (61) where picloram was
applied at a rate of 1.12 kg/ha on an 8-ha site, about 10 ppb of picloram was
present in runoff water adjacent to plots 10-12 weeks after application.
Water sampled 8 days after application at a distance of 1.2 km from the plots
had less than 1 ppb of picloram. With heavy rainfall 2 days after applica-
tion, high amounts of picloram (26.2-89.7 ppb) occurred in runoff waters in
areas adjacent to the plots. Eight months after treatment, the runoff water
contained less than 1 ppb at a distance of 1.6 km from the plots. Applica-
tion of picloram pellets to riparian vegetation at a rate of 9.0 kg/ha on 4.5
percent of a forested watershed in Arizona produced a maximum stream concen-
tration of 370 ppb after one storm of 72 mm (59). In the following 2 months,
ten storm events totalling 103 mm of rainfall produced a maximum picloram
concentration of 52 ppb. Five successive storms totalling 56 cm of rainfall
over the next week resulted in a maximum picloram concentration of 350 ppb
(59). In another study by Trichell (62,63), approximately 5 percent of the
picloram applied to small plots was lost in runoff water when a simulated
rainfall of 1 inch per hour was applied 24 hours after treatment.
The concentration of picloram in runoff water is also affected by slope
and soil compaction. Studies by Scifres (53) and Trichell (64) have demon-
strated that picloram concentration in runoff decreases more as the runoff
passes over untreated compacted soil (especially sod) than over uncompacted
(fallow) soil. .The effects of slope and rate of application on the concen-
tration of picloram in runoff passing over untreated sod is shown in Table
14. As indicated by the data, higher concentrations of picloram are asso-
ciated with higher slopes and in the lower half of the slope.
The runoff potential using picloram pellets has been evaluated and, in
one field study, compared with that using liquid sprays. Bovey, et al. (65)
demonstrated that loss of the potassium salt of picloram from grassland
watersheds in surface runoff water was similar whether the picloram was
A-240
-------
TABLE 13. RESIDUES OF PICLORAM IN SURFACE RUNOFF WATERS AT DIFFERENT TIME INTERVALS
(DAYS IN BRACKETS) AFTER APPLICATION OF PICLORAM AT VARYING RATES (20)
10
Typo of area treated
Rate
applied
Picloram residues in water
at different times after application *
(kg/ha)
Watersheds
Watersheds
Watersheds
Semi -arid
Semi-arid
Semi-arid
Sub-humid
(Texas)
(Arizona)
(Arizona)
rangeland (Texas)
rangeland (Texas)
watershed (Texas)
watershed (Texas)
Grassland (Texas)
Sod (Texas)
Fallow (Texas)
1
1
10
0
1
0.28-2
0.28-2
1
1.12-2
1.12-2
.12
.90
.40
.28
.12
.24
.24
.12
.24
.24
9-168
370
17
26-90
184
55-184
2170
650
(4)
(10)
(10)
(2)
(7)
(14)
(1)
(1)
(ug/l)
<5
(90)
Trace (90)
<1 (30)
10
'o
2-29
27
15
(70)
(180)
(42)
(120)
(120)
0 (300)
<100 (365)
0 (365)
fcl (365)
19 (365)
<1 (365)
All sampling areas located immediately adjacent to treated plots.
-------
TABLE 14. EFFECT OF SLOPE, RATE OF APPLICATION, AND MOVEMENT OVER
UNTREATED SOD ON THE CONCENTRATION OF PICLORAM IN
RUNOFF WATERS (64)
Rate Slope Portion of plot
treated
owA) m
2 8 upper half
1 8 entire
2 3 upper half
1 3 entire
Picloram in runoff
water '
(ppm)
2.1
3.8
13
2.0
Picloram
runoff
(% of applied)
1.6
5.5
0.9
2.8
Picloram applied as potassium salt in water (400 g/A).
Simulated rainfall 0.5 in/hr 24 hours after herbicide application.
applied as an aqueous spray or pellet. Davis, et al. (66) applied pelleted
Picloram (10 percent) at 10.4 kg/ha to a 0.9-ha drainage area in an 18.8-ha
watershed in central Arizona. The highest concentrations of picloram in
runoff collected 7 days after application and a 6.4-cm rainfall was 0.37 ppo.
Only trace amounts of picloram were present after 3 months and picloram was
not detectable after one year.
Burnett, at al. (67) measured and compared picloram concentrations in
runoff from large watersheds in Texas to which either a picloram spray or
picloram formulated in starch xanthate granules were applied. The results
indicated that picloram was slowly released from the starch granules over a
period of several months, and that application of the granule formulation
eliminated the initial large concentration of picloram in runoff water which
occurred with the spray. Immediately after application at a ra.te of 2 kg/ha,
picloram concentrations in the runoff water averaged 112 ppb and 6 ppb, res-
pectively, on watersheds treated with the conventional spray and with starch
xanthate granules. Pi-loram concentrations from the sprayed watershed later
decreased to 0.1 , pb, while concentrations from the watershed treated with
A-242
-------
the starch granule formulation increased for several weeks, remained at 20
ppb for 14 weeks, and then decreased to 4 ppb after 8 months. Cumulative
amounts of picloram lost in nine rainfall events represented 2.5 percent of
that applied as a spray at 2 kg/ha, and 1.5 percent of the herbicide applied
as the starch xanthate granules at 2 and 4 kg/ha. Picloram concentrations
in the upper 15 cm of soil were also greater on plots treated with the slow
release granules than with the spray.
3.2.4 Persistence and Degradation
Picloram is considered "moderately" to "highly" persistent in soils
under conditions of normal application and may exist at phytotoxic levels
for over one year (68). Reported half-lives vary from one to over 13 months
(15,3). Persistence in soil is affected principally by soil type, moisture
and temperature. Persistence is generally shorter in soils with high organic
matter content. In forest soils it has been shown that picloram degrades
within one year after application (9,17). Field studies conducted in the
Pacific Northwest have indicated that Douglas-fir can be planted within 8
months to one year after application of up to 1 Ib picloram plus 4 lb a.i.
of 2,4-D/acre (69). In a study of the persistence of picloram on powerline
rights-of-way in the Pacific Northwest, Norris (70) found that damaging
concentrations of picloram were seldom present more than 12 months after
application.
Picloram is very persistent in clay and sandy loam soils having low
organic matter content, and in cold, dry climates (71). In a field study in
which picloram was applied to fallow Somerset sandy loam soil in the cold,
dry climate of Nova Scotia, it was found that crops susceptible to low con-
centrations of picloram were damaged even after 1,055 days after application
(72). Keys and Friesen (53) reported that residues of picloram applied at
0.6 kg/ha in the fall declined to about 10 percent after 24 months and to
less than 6 percent after 35 months. Residues from picloram application at
3.24 kg/ha to patches of persistent weeds in central Alberta, Canada, crop-
lands were found to be sufficiently high to delay germination of sensitive
crops even in the fifth year after treatment (73). Studies by Fryer, et al.
(74) have shown that 5 to 6 percent of picloram applied at 1.68 hg a.i./acre
to test plots of sandy loam soil in England was recoverable one year after
A-243
-------
application, and that this residue degraded slowly over the following 3 years
to a level of 0.5 percent.
Additional studies by Hunter and Stobbe (55) indicated that dissipation
of picloram was very slow under conditions of low soil moisture, with about
35 percent remaining after 2 years following application of 0.35 kg/ha piclo-
ram. Other field investigations have demonstrated that degradation of piclo-
ram is more rapid in warm humid clinates than in colder drier ones, especial-
ly in light-textured sandy soils (40,55,75). Picloram persistence also de-
creases with decreasing pH (26) and in the presence of plant roots (37).
The kinetics of picloram degradation has been studied and can best be
described as being half to first order under practical application rates
(3). Using a half order reaction kinetics model, Hamaker, et al. (76) cal-
culated rates of picloram loss in soil samples collected from 18 states and
two Canadian provinces (Table 15). The estimated rate constants, kj , varied
from 0.12 for Saskatchewan to 0.79 for Texas soils, and were highly correla-
ted with the observed temperatures, with the rates being faster at higher
temperatures.
Picloram degradation in soil occurs via microbial rather than chemical
routes (77). (There is no breakdown of picloram when it is incubated in
sterile soil at room temperature.) (26,52). Rates of microbial degradation
increase under conditions which favor microbial growth, e.g., adequate
moisture, warm temperature, adequate organic matter content, etc. However,
even under the most favorable conditions, amounts of picloram decomposed are
small (16), and picloram is considered not a good energy source for micro-
organisms but is co-metabolized with other energy sources. In studies by
Meikle, et al. (37), only 4 percent of picloram was degraded in 15 days by
plant-root and rhyzosphere microorganisms. Youngson, et al. (26) found that
breakdown of picloram in nutrient cultures containing many different types
of bacteria and fungi was only 0.24 to 1.21 percent. Naik, et al. (78) re-
ported persistence of picloram in microbial cultures for more than 275 days.
The exact mechanism of picloram degradation in soil is not fully known
and may vary with the organisms. Degradation by most microorganisms is be-
lieved to involve both decarboxylation of the ring carboxylic acid group and
ring cleavage. Laboratory studies have shown that ring-labelled carbons in
A-244
-------
TABLE 15. OBSERVED HALF-ORDER CONSTANTS (
AND STATES OF CANADA AND UNITED
FOR VARIOUS PROVINCES
STATES (76)
State or
Province
Alberta
California
Colorado
Idaho
Illinois
Kansas
Michigan
Minnesota
Montana
Nebraska
Nevada
New Mexico
North Dakota
Oregon
Saskatchewan
South Dakota
Texas
Washington
Number of
Soil Profiles
Analyzed
2
33
4
11
3
3
7
6
34
2
2
2
8
4
6
11
46
22
Average kj
0.40
0.27
0.25
0.47
0.62
0.41
0.17
0.19
0.22
0.19
0.67
0.57
0.37
0.21
0.12
0.37
0.79
0.40
90% Confidence
Limits For
Half-order
Constants
t
0.05
0.13
0.12
t
t
0.05
0.11
0.03
t
t
t
0.05
0.04
0.05
0.20
0.12
0.09
s
where co = rate of application of the herbicide
in ounces/acre (initial concentration)
c ~ final concentration of the herbicide in
the soil at time (final concentration)
t - interval between treatment and analysis
in months.
ka = half-order constant in [ounces per acre]i
per month.
t / 90% Confidence limits not estimated for fewer than four
profiles in a state.
A-245
-------
picloram are emitted as CCL at almost the same rate as carboxyl-labelled
carbon, indicating that the degradation mechanism involves both ring clea-
vage and decarboxylation (79). A reaction sequence for the microbial decom-
position of picloram involving both ring cleavage and decarboxylation was
recently proposed by Meikle, et al. (80) and is presented in Figure 1. Addi-
tional degradation products which have been identified are 4-amino-2,3,5-
trichloropyridine and 6-hydroxy-3,5-dichloro-4-aminopicolinic acid. Rieck
(81) found that Trichoderma growth on broth media containing picloram re-
sulted in the formation of 4-amino-2,3,5-trichloropyridine, the decarboxylated
molecule, and that this metabolite was readily further assimilated by the
fungus via ring cleavage reactions. The 6-hydroxy-3,5-dichloro-4-aminopico-
linic acid reportedly is formed in only very small quantities (82,83).
The fate of picloram in bodies of water in forest areas treated with
picloram has not been investigated. In an area in which 67 percent of a
watershed was sprayed in August, residues up to 0.078 ppm were detected in
nearby streams after an initial one-inch storm (84). A rapid decrease in
the residue was observed subsequently, probably due to dilution and for de-
gradation..
Picloram is not readily degraded by chemical and microbial routes in
water. It is, however, readily degraded by uv light and sunlight. Photo-
degradation is the major degradation route for picloram in water (3,20,62).
Laboratory studies have indicated a photolysis half-life varying from as
little as 5 days in one-inch deep containers to as much as 60 days in non-
circulating 12-foot deep containers (85). Hall, et al. (86) investigated
picloram photolysis in basic aqueous solutions under uv light and sunlight.
Approximately 20 percent of the picloram was degraded by 48-hour exposure
to uv light, with slower and more variable degradation under sunlight.
Research by Hedlund and Youngson (87) indicated that photolysis by sun-
light of picloram in aqueous solutions followed pseudo-first order kinetics
for concentrations up to 4.14 x lO^M and in circulating solutions as deep
as 3.64 meters. Hazy sunlight and water impurities had only a small effect
on the rate of photolysis in the systems studied. Studies by Michel, et al.
(88) have shown that photolysis of picloram by uv light also follows pseudo-
first order kinetics.
A-246
-------
HMUI LJ
rMn2 pi— n
rjn2 w2 v,i >^x c U
Clff^CI V 0-V7iCI / HOOC
—V-»^ I —4—>•
11 I v
cill X^JCOOH A ^ o-JL !JcooH~/^ HOOC^ ^COOH
N / /*N /
FADH2 Cl I H20
H H
^ lIcooH "~~ <^JcooH r
H2N HN /
HoO
HCI
MM c°2 I H2O,O2
NH' \ HC^ \ HOOb
ci y ^ V i
' - I —^—- I
H. NH, H • NH, NH3 N^ C02
Cl J
CHO CHO COOH
Figure 1. Proposed Mechanism for Microbial Decomposition of Picloram in Soil (80)
-------
Numerous studies have been conducted to elucidate the mechanism of pi-
cloram photodegradation in water. The results indicate that picloram degra-
dation may follow several pathways, resulting in different initial products
(see Figure 2) which are further degraded. Studies by Hall, et al. (89) and
Hosier and Guenzi (90) have shown that a free radical mechanism is likely to
be involved in the formation of certain of the initial products. A possible
sequence of reactions for photolysis of picloram to form initial product II
(Figure 2) is as follows (90):
I I —
^ ^^kCQ2H
II
4.0 IMPACTS ON NON-TARGET PLANTS AND ORGANISMS
4.1 PLANTS
As noted in Section 1.0, picloram is not recommended for conifer re-
lease by broadcast application since it can cause damage to young conifers.
Wu, et al. (91) found that picloram was very toxic to young pine seedlings.
At 50 mg/1 applied as nutrient solution, picloram inhibited both root and
shoot growth. Ryker (11) found that picloram used alone or in combination
with 2,4-D damaged 2-year old conifer seedlings. In addition, several inci-
dents of damage to non-target plants due to picloram spray drift have been
reported. In one incident in southern Canada, trees 50 meters from a treated
area were killed (20). In other incidents in Minnesota, drift of picloram
from roadside spraying caused injury to nearby corn and soybean fields (92).
A-2A8
-------
I. 4-amino-3,5,6-trichloropicolinic acid
II. 4-amino-3,5-dichloro-6-hydroxy-picolinic acid
III. 4-amino-2,3,5-trichloropyridine
IV. 4-amino-3,5-dichloro-6-hydroxy-pyridine
V. 3-hydroxy-4-amino-5,6-dichloro-2-picolinic acid
VI. 4-amino-5,6-dichloro-2-picolinic acid
Figure 2. Alternative Pathways for the Photodegradation of Picloram (20)
A-249
-------
Because of its persistence in soil, phytotoxic levels of picloram may
remain in soil long after treatment. Certain species of plants have been
injured as long as five years after application (20). Gesnik, et al. (93)
found that picloram plus 2,4-D (0.6 kg/ha + 2.2 kg/ha) applied to Wyoming
rangeland resulted in injury to certain desirable perennial grasses up to 2
years following application.
4.2 FISH
Picloram and its salts are low in toxicity to fish and other aquatic
species (3,94). LC5Q values for various species of fish to picloram and its
salts are shown in Tables 16 and 17. The median tolerance limits in ppm of
Tordon 101 to various fish are: fathead minnow, 64; brook trout, 240; brown
trout, 250; rainbow trout, 150; and green sunfish, 150. In a laboratory
study using concentrations of picloram simulating field concentrations in
runoff waters and streams, Woodward (95) found that picloram increased fry
mortality in cutthroat trout (Salmo clarki) in concentrations greater than
1,300 ug/1 and reduced fry growth in concentrations above 610 ug/1. Piclo-
ram had no adverse effects on fry concentrations below 290 ug/1.
In a study conducted by Butler (96), shrimp and oysters exhibited no
effects when exposed to picloram at 1.0 ppm for 48 and 96 hours, respective-
ly. Other studies by Butler demonstrated that mollusks were not susceptible
to picloram up to a dose of 380 ppm, but a dose of 530 ppm resulted in 100
percent mortality of the mollusks (97). The estimated LC50 for stonefly
nymphs (Ptesnarye californica) exposed for 27 hours to picloram was 120 ppm
(98). The 48-hour LC50 for amphipods (Gammarus laeustrl^ was 48,000 ppm
(99). Daphnia exposed to 380 ppm of picloram for 24 hours did not show any
ill effects, but when exposed to 530 ppm, 95 percent of the Daphnia did not
survive (100,101).
In a food chain study involving algae, Daphnia. goldfish, and guppies
reared together and exposed to 1 Ppm concentration of picloram over a period
of 10 weeks, no effects were noted in the normal patterns of growth of the
organisms (100). No adverse effects were exhibited by the guppies even after
6-month exposure to a 1 ppm concentration (100).
No data are currently available on the degradation producte of picloram
in fish or in lower aquatic organisms.
A-250
-------
TABLE 16. THE LC,-n FOR VARIOUS FISH TO PICLORAM (16)
Formulation Fish species
Potassium salt Harlequin fish
Acid Fathead minnow
Fathead minnow
Rainbow trout
Green sunfish
Brown trout
Rainbow trout
Brown trout
Brook trout
Brook trout
Green, sunfish
Black bullhead
Rainbow trout
TABLE 17. THE 24-HR LC^ FOR VARIOUS FISH
Formulation Fish species
Acid Bass
Bluegill
Goldfish
Coho salmon
Rainbow trout
Trllsopropanolamine
gait Rainbow trout
Trlethylamine salt Rainbow trout
Channel catfish
Goldfish
Potassium salt Channel catfish
Bluegill
Exposure
time (hr)
24
24
24
24
24
24
24
24
24
24
24
24
48
TO PICLORAM
LCM
(mm)
19.7
26.5
27-36
29.0
34
279.0
43.4
70.5
90.6
41
69
LCjo
(ppm)
66
64
135
150
150
230
230
240
240
420
420
420
2.5
FORMUALTIONS (16)
Temperature
CF)
75
63
75
63?
55
60
60
80
80
80
80
A-251
-------
A.3 WILDLIFE
Picloram has low toxicity to warm-blooded animals (1,3,20). The LD--
values for several mammalian species are presented below (1):
Species LD$0 Value (mgAg)
Rats 8200
Mice 2000-4000
Rabbits 2000
Guinea pigs 3000
Chicks 6000
Sheep > 1000
Cattle > 750
Lynn (102) reported that sheep showed no ill effects from the potassium
salt formulation (25 percent active ingredient) up to 4,650 mg/kg. However,
the Tordon 101 formulation produced toxic effects at 2,530 mg/kg and subse-
quent death in three days. Cattle were more sensitive in showing toxic
effects at a rate of 1,900 mg/kg Tordon.
Chronic exposure to picloram showed little or no effects on test animals
(6). Feeding studies conducted for 90 days with rats resulted in no adverse
effects from dietary levels as high as 1,000 ppm (103). The only effect
noted at 0.3 percent picloram in the diet was an increase in liver/body
weight ratios of the- females (104). Only slight to moderate pathological
changes were observed in the liver and kidneys on a diet containing 1 percent
(1,000 ppm) picloram. No adverse effects were noted in any animals fed a 0.3
percent triisopropanolamine salt picloram diet (104).
In long term feedings, albino rats and beagle dogs were fed picloram at
a rate of 15 to 150 mg/kg of body weight for 2 years (104). No observable
adverse effects were noted in either species in terms of body weight, food
consumption, behavior, mortality, hematological and clinical blood study
results and urine analyses results. Also, no pathological differences were
found in the incidence or kind of tumors found in controlled and treated
animals.
Picloram also exhibits low toxicity to birds (1). Japanese quall
(coturnix coturnix) and bobwhite quail (Colinus vir^in-.^ were fed
A-252
-------
picloram at rates ranging from 100 to 1,000 ppm in their diets without reach-
ing the LC5Q (105). The LD._ was more than 2,000 ppm for young mallard ducks
(anac platyrhynachos) and for young pheasants (Phasianus colchicus) (106).
The LCcn for adult mallard ducks and pheasants exceeded 5,000 ppm (105).
Japanese quail, fed up to 1,000 ppm of picloram in their diet for each of
three successive generations exhibited no effects on mortality, egg produc-
tion, and fertility (105).
A summary of additional feeding studies on birds is presented in Table
18 (108). Toxicological studies conducted on Tordon 101 indicate that it is
more toxic than picloram (101). In a subacute oral toxicity experiment,
Tordon 101 fed to 11 sheep at 0.11 mg/kg resulted in no adverse effects, but
at 0.55 mg/kg resulted in 2 deaths within 10 days (107).
4.4 BENEFICIAL INSECTS
Limited studies on picloram and picloram plus 2,4-D have indicated low
toxicities of these compounds to bees (109.110). The LD5Q for both picloram
and Toxdon (unspecified formulation) is reportedly 15 yg/bee (109). In a
study by Morton, et al. (111),.newly emerged honey bees (Agis mellifera L.)
fed concentrations of 0, 10, 100 and 1,000 pppm by weight of picloram in 60
percent sucrose syrup showed no reduction in half-life at any concentration
tested. In fact, there was an increase noted in the half-life of bees fed
the 100 and 1,000 ppmw concentrations when compared to control bees. In a
study by Moffett, et al. (112), Tordon 22K and Tordon 212 applied at a rate
of 4 Ib a.i./acre to honey bees confined in a small water carrier volume of
20 gal/acre were non-toxic.
4.5 MICROFLORA
Picloram has very low toxicity to soil microorganisms (1,3,20). Experi-
ments conducted by Goring, et al. (113) with 45 common soil microorganisms,
including bacteria and fungi, showed that picloram had little effect on total
numbers at concentrations up to 1,000 ppm. The growth of one organism,
Thiobacillus thiooxidans, was inhibited at 1,000 ppm but not at 100 ppm. In
addition, rates of carbon dioxide evolution, nitrification and urea hydroly-
sis were unaffected.
Arnold, et al. (114) showed that the growth of AsperRillus niRer, as
mycelial dry weight, was not depressed by addition of 0.4-5.0 ppm picloram
A-253
-------
TABLE 18. TOXICITY OF PICLORAM TO GAME BIRDS (108)
Species
Acid .
Equivalent
(ng/kg-feed)
Observations
Japanese quail
Coturnix eoturnix
Japonica
100
1,000
14-day exposure, reproduction stuiiy,
No effect on plumage, feathering,
egg production, fertility, hatcha-
bility, mortality or weight.
lA^day exposure, reproduction
study. No effect on egg produc-
tion, body weight or adult mor-
tality. Egg fertility reduced 55%,
egg hatehability reduced first
week but not second week of treat-
ment. Hatehability and fertility
normal first week after treatment.
Japanese quail
Coturnix eoturnix
Japonica
(5-7-day-old chtcks)
Bobwhite quail
Colinus vlrginianus
Bobwhite quail
Colinus virginianus
(5-7 day old chicks)
Mallard ducklings
Anas platyrhvnchos
100-
1,000
100;
500;
1,000
23,366
10.000
500-
10,000
385,200
—
Dosage increased over a period of
nearly one year. No increased
mortality, no decrease in consump-
tion or body weight; no impaired
reproductive effect compared to
controls.
Reproductive, three-generation
study. F generation fed 20 weeks,
Fj generation fed ,12 weeks, F2
generation fed 8 weeks. No statis-
tically significant difference
between controls and treatments as
measured by food consumption, egg
production, fertility and hateha-
bility, survival and body weight
gain. No adverse symptoms noted
when medicated diets were with-
drawn.
"V
LC50*
OX mortality*
"so*
*5-day feeding, 8-day mortality. VSDI protocol.
A-254
-------
in nutrient solution, although picloram tended to accumulate in the mycelia.
Concentrations of picloram up to 1,000 ppm did not-appreciably affect the
population of the fungus.
Hameed and Foy (115) studied the effects of picloram on the growth of
five soil fungi: Triehoderma virdie. Fusarium oxysporum, Helminthosporium
victoriae. Penicillium lanosum. and Aspergillus flaves. All five species
grew, as indicated by increases in mycelium dry weight, when cultured in mo-
dified soil extract containing 1-1,000 ppm picloram. However, all of the
fungi failed to produce mycelial pads in a synthetic liquid medium lacking
carbon or nitrogen but supplemented with picloram, indicating that picloram
alone is not a favorable sole source growth media for the fungi.
In studies on the effect of picloram on microbial activity in three
Willamette Valley soils, Tu and Collen (116) found that concentrations of 1
and 10 ppm of picloram were inhibitory to populations of Penicillia but
stimulated growth of Aspergilla and Trichoderma. However, the increases in
population were small and not considered important to overall soil fertility.
Investigations by Arvik, et al, (117) indicated that picloram alone or
in combination with 2.A-D can inhibit the growth of certain species of algae
in concentrations of 50 to 250 ppm. In a study by Hardy (118), algae were
unaffected by picloram at 1 ppm in water. In other studies by Elder (119),
picloram exhibited low toxicity to many fresh water and marine algae species
at concentrations approaching its maximum solubility in water.
4.6 BIOACCUMULATION
Picloram is rapidly excreted by and does not bioaccumulate in mammals.
In studies using carboxyl-14C labelled picloram fed to dogs at levels of 100
mg/kg in the diet, 90 percent of the labelled picloram was excreted within
48 hours in the urine (103,120). Studies using rats and steers showed small
residue levels in various tissues (liver, heart, fat, brain) and in blood at
various feeding levels (103,121). Concentrations of 200 to 400 ppm of piclo-
ram were required in the diet of cattle to produce residues of 0.05 to 1.0
ppm in edible tissue such as fat and muscle U22).^ McCollester and Lang
(104) found that mammals eliminate 98 percent of ingested picloram from the
bloodstream and kidneys as an unchanged compound in the urine before it is
A-255
-------
able to be metabolized in the liver. Other investigations have shown that
picloram is not decarboxylated in vivo (22).
Picloram in water is not accumulated in invertebrates or in food chains
(20). Eambusia sp. exposed to 5 ppb of picloram in water for 567 days in a
static test accumulated a concentration of 1.12 ppb. The accumulation factor
(whole body, wet weight) was low at 0.25 (3). In separate experiments, the.
accumulation factors for catfish was 0.023 for piclorara, and 0.050 for the
picloram metabolite 6-hydroxy-3,5-dichloro-4-aminopicolinic acid (3). A
summary of the accumulation factors in several other aquatic and terrestrial
organisms is shown in Table 19.
5.5 MISCELLANEOUS
As indicated in Section 4.2, picloram and its salts exhibit low toxicity
to fish. Recent studies by Sargent, et al. (94) have found that certain
picloram ester formulations may be more toxic to fish than picloram and its
salts, due to the presence of the toxic impurity 2-(3,4,5,6-tetrachloro-2-
pyridyD-guanidine in the ester formulations.
Other known impurities of picloram ester formulations include:
4-amino-3,5,6-trichloropicolinonitrile
4-amino-2,3,5,6-tetrachloropyridine
6-amino-3,4,5-trichloropicolinic acid.
These 3 impurities are not toxic to fish at concentrations of 10~4 M or less.
In view of the phytotoxicity of picloram (see Section 4.1), various
thickening and sequestering agents are often added to picloram formulations
and spray mixes to reduce the potential for drift (20). As indicated in
Table 8, Tordon 101 and Tordon 101K contain a glycol derivative sequestrant.
Data are unavailable on the exact composition and the environmental and
health hazards, if any, of these sequestrants.
A-256
-------
TABLE 19. CONCENTRATION FACTORS OBSERVED FOR PICLORAM IN SOME AQUATIC AND TERRESTRIAL SPECIES (20)
SPECIES MEDIUM COMPOUND
Daphnia Water K-salt
Mosquito Water Acid
fish
Dairy Diet K-salt
Cattle
Steer st Diet Acid
Sheep Diet Acid
TISSUE
whole
body
whole
body
Milk
Blood
muscle &
fat
kidney
Blood
CONC. FACTORS* BASED
ON a.e. OF PICLORAM
1.0
0.02
0.0003
0.001
<0.0005
0.01
0.001
TIME
SCALE
7 weeks
18 days
2 weeks
2 weeks
1 week
REFERENCES
123
124
125
126
126
*/
Concentration in tissue, a.e./concentration in water or diet, a.e. A factor of one or less
means no accumulation greater than that found in the medium of exposure, i.e. diet or water.
over the time scale of the exposure. These numbers are not considered absolutes but only
indicators since time-dose-dependent studies per ee have not generally been carried out.
V
Upon continuous exposure, residues reached a plateau within three days. The concentration
factor, ppm-blood/ppm-diet, was independent of time for the remainder of the study and the
concentrations in the blood are nearly directly proportional to the concentrations in the
feed.
-------
Piclorara and its derivatives have been involved in a number of reported
incidents of environmental contamination (58,92,127). One of the best docu-
mented incidents occurred in 1968 in which picloram used in agriculture
resulted in contaminated ground water near Kimball, Nebraska (92,127). When
the ground water was used for irrigation, major plant damage occurred in
gardens, croplands, and commercial greenhouses in Kimball. Other alleged
incidents have involved damage to agricultural crops, wildlife and domestic
animals (92). Many of these incidents are currently under investigation by
EPA and have not yet been confirmed (92).
A-258
-------
REFERENCES
1. Mullison, W.R. Herbicide Handbook of the Weed Science Society of
America. Weed Science Society of America, Champaign, Illinois, 4th
Edition, 1979, 518 pp.
2. 1980 Farm Chemicals Handbook. Meister Publishing Co., Willoughby,
Ohio, p. D-312.
3. Information provided by EPA, based on review of the registration files
of the Environmental Fate Branch.
4. Personal Communication of S. Quinlivan, TRW, to Mr. R.L. Eischer, Dow
Chemical U.S.A., Midland, MI, July 9, 1980, MDTS Task No. 13, Notebook
001, p. 42.
5. The Biologic and Economic Assessment of 2,4,5-T. Report of the USDA,
State, EPA RPAR Assessment Team, 1979, 202 pp.
6. Final Environmental Statement. Vegetation Management with Herbicides
in the Eastern Region. USDA-FSR9 FES ADM-77-10, 1977.
7. Pesticide Uses in Forestry. National Forest Products Association.
Forest Chemicals Program, Washington, D.C. 1980. pp. 39, 40, 85, 99,
119, 143-145.
8. Williston, H.L., et al. Chemical Control of Vegetation in Southern
Forests. USDA Forest Service, Atlanta, GA. Forest Management Bulletin,
November 1976. 6 pp.
9. Bratkowski, H. Silvicultural Use of Herbicides in Pacific Northwest
Forests. USDA, U.S. Forest Service, Portland, Oregon, Forest Pesticides
Shortcourse, March 1980. pp. 12-13.
10. Newton, M. and C.A. Roberts. Brush Control Alternatives for Forest
Site Preparation, Oregon Weed Control Conference, Salem, Oregon, 1979.
11 Ryker R A Effects of Dicamba and Picloram on Some Northern Idaho
Shrubs and Trees. USDA Forest Service, Intermountain Forest and Range
Experiment Station, Ogden, Utah, USDA Forest Service Research Note INT-
114, 1970, 6 p.
12. Unpublished Forest Pesticide Use Survey Data, collected by Dr. Dean
Gjerstad, Auburn University Forestry Chemicals Cooperative, Auburn,
Alabama, June 1980.
13. Pesticide Usage Data. USDA, U.S., Forest Service Pacific Northwest,
Regions 5 and 6, and Bureau of Land Management, Oregon, 1979.
A-259
-------
14. Minnesota Department of Natural Resources. Report of Pesticides Used.
July 1, 1977 to June 30, 1980. 25 p.
15. Schlapfer, T.A. Environmental Impact Statement: Vegetation Management
with Herbicides. USDA-FS-R6-DES(ADM) 75-18. USDA Forest Service,
Portland, Oregon, 1977. 668 pp.
16. Kearney, P.C. and D.D. Kaufman. Degradation of Herbicides. Vols. 1
and 2. Marcel Dekker, Inc., New York, 1975, 1058 pp.
17. Witt, J.S. and D.M. Baumgartner. A Handbook of Pesticide Chemicals for
Forest Use. Forest Pesticide Shortcourse. Washington State University
and Oregon State University, 1979, pp. 32-33.
18. Lewis, C.R., Jr. 2,4,5-T Use Analysis. Plant Studies Branch, BFSD,
U.S. EPA, Washington, D.C. December 15, 1978, 17 pp.
19. Tordon Specimen Labels. Dow Chemical Company, Midland. MI. 1978, 1979,
1980.
20. Picloram: The Effects of Its Use as a Herbicide on Environmental Qua-
lity. National Research Council of Canada, Subcommittee Report No. 1,
NRCC No. 13684, 1974, 128 pp.
21. Green, L.R., et'al. Picloram Herbicide for Killing Chaparral Species
... A Preliminary Rating. Pacific Southwest Forest and Range Experi-
ment Station, Berkeley, CA. U.S. Forest Service Research Note PSW 122,
1966, 8 pp.
22. Environmental Statement: Region 1, Colville and Kaniksu National Fo-
rests, Region 6, Okanogan, Umatilla, and Wenatchee National Forests,
Calendar Year 1973, Herbicide Program, Washington. T1SDA Forest Service,
EIS-WA-73-0958-F, 15 May 1973. 442 pp.
23. Information supplied to TRW by Dow Chemical Company, September 1981.
24. Haywood, J.D. Combinations of Foliar- and Soil-Applied Herbicides for
Controlling Hardwood Brush. Down to Earth, 36(2): 14-15. 1980.
25. Melnikov, N.N. Chemistry of Pesticides. In: Residue Reviews, Volume
36, Springer-Verlag, New York, 1971, pp. 403-404.
26. Youngson, C.R., et al. Factors Influencing the Decomposition of TORDON
Herbicide in Soils. Down to Earth. 23: 3-8, 10-11. 1967. In Reference
£w •
27. Ramsey, J.C. TORDON. In: Analytical Methods for Pesticides, Plant
Growth Regulators and Food Additives. G. Zweig (Ed.), Vol V Aca-
demic Press, New York, pp. 507-525. 1967. In Reference 20.'
28. Herbicide Handbook, Weed Society of America. Monograph No. 3, p. 76
1970. In Reference 20.
A-260
-------
29. Information supplied by E.E. Kanaga, Dow Chemical Company, 1973. In
Reference 20, p, 75.
30. Webb, W.L. The Differential Response of Green Ash, Sweet Gum, and
Silver Maple to Picloram. Proc. WWCC 21: 46, 1967. In Reference 20.
31. Baur, J.R., R.W. Bovey, and J.D. Smith. Herbicide Concentrations in
Liveoak Treated with Mixtures of Picloram and 2,4,5-T. Weed Sci. 17:
567-570, 1969. In Reference 20.
32. Isensee, A.R., G.E, Jones, and B.C. Turner. Root Absorption and Trans-
location of Picloram by Oats and Soybeans. Weed Sci. 19: 727-731, 1971.
In Reference 20.
33. Scott, P.C. and R.O. Morris. Quantitative Distribution and Metabolism
of Auxin Herbicides in Roots. Plant Physiol. 46: 680-684, 1970. In
Reference 20.
34. Bovey, R.W., F.S. Davis, and M.G. Merkle. Distribution of Picloram in
Huisache After Foliar and Soil Applications. Weeds 15: 245-249, 1967.
In Reference 20.
35. Bowes, G.G. Personal Communication to Dr. R. Grover, National Research
Council of Canada, 1972. In Reference 20.
36. Davis, F.S., R.W. Bovey, and M.G. Merkle. The Role of Light, Concen-
tration and Species in Foliar Uptake of Herbicides in Woody Plants.
Forest Sci. I4j 165-169, 1968. In Reference 20.
37. Meikle, R.W., E.A. Williams, and C.T. Redemann. Metabolism of TORDON
Herbicide (4-Amino-3,5,6-Trichloropicolinic Acid) in Cotton and Decom-
position in Soil. J. Agr. Fd. Chem. 14: 384-387, 1966. In Reference
20.
38. Maroder, H.L. and I.A. Prego. Transformation of Picloram in Prosopis
ruscifolia and Diplotaxis tenuifolia. Weed Res.. 11: 193-195, 1971.
In Reference 20.
39. Redemann, C.T., et al. The Fate of 4-Amino-3,5,6-Trichloropicolinic
Acid in Spring Wheat and Soil. Bull. Environ. Cont. Toxicol. 3: 80-96,
1968. In Reference 20.
40. Merkle, M.G., R.W. Bovey, and F.S. Davis. Factors Affecting the Per-
sistence of Picloram in Soil. Agron. J. 59: 413-415, 1967. In Re-
ference 20.
41. Norris, L.A. and D.G. Moore. The Entry and Fate of Forest Chemicals
in Streams. Presented at Forest Land Uses and Stream Environment Sym-
posium, October 19-21, 1970. 18 pp.
42. Boney, R.W. The Persistence and Movement of Picloram In Texas and
Puerto Rican Soils. Pesticide Monitoring Journal, 3(3): 177, 1968.
A-261
-------
43. Bovey, R.W. and C.J, Scifres. Residual Characteristics of Picloram in
Grassland Ecosystems. Texas Agricultural Experiment Station, B-llll.
1971. 24 p. In Reference 22.
44. Morris, L.A. The Kinetics of Adsorption and Desorption of 2,4-D,
2,4,5-T, Picloram and Amitrole on Forest Floor Material. Research
Progress Report, Western Society of Weed Science, pp. 103-105. 1970.
45. Khan, S.U. Interaction of Humic Acid with Chlorinated Phenoxyacetic
Acid and Benzoic Acid. Environ. Letters 4: 141-148. 1972. In Re-
ference 20.
46. Biggar, J.W. and M.W. Cheung. Adsorption of Picloram (4-Amino-3,5,6-
Trichloropicolinic Acid) on Panoche, Ephrata and Palouse Soils: A
Thermodynamic Approach to the Adsorption Mechanism. Soil Sci. Soc.
Amer. Proc. 37: 863-868, 1973. Summarized in Reference 3.
47. Farmer, W.J. and Y. Aochi. Picloram Sorption by Soils. Soil Sci. Soc.
Amer. Proc. 38: 418-423, 1974. Summarized in Reference 3.
48. Grover, R. Adsorption of Picloram by Soil Colloids and Various Other
Adsorbents. Weed Sci. 19: 417-418, 1971. Summarized in Reference 3.
49. McCall, H.G., R.W. Bovey, M.G. McCully, and M.G. Merkle. Adsorption
and Desorption of Picloram, Trifluralin, and Paraquat by Ionic and
Non-Ionic Exchange Resins. Weed Sci. 20: 250-255, 1972. Summarized
in Reference 3.
50. Hamaker, J.W., et al. A Picolinic Acid Derivative: A Plant Growth
Regulator. Science 141: 363, 1963. In Reference 20.
51. Norris, Logan A., M.L. Montgomery, and Jack Warren. Leaching and Per-
sistence Characteristics of Picloram and 2,4-D on a Small Watershed in
Southwest Oregon. Abstract 81, Abstracts, 1976 Meeting of the Weed
Science Society of America. February 3-5, 1976. Denver, Colorado,
1976. Summarized in Reference 6.
52. Grover, R. Studies on the Degradation of 4-Amino-3,5,6-Trichloropi-
colinic Acid in Soil. Weed Res. 7: 61-67, 1967. In Reference 20?
53. Scifres, C.J., et al. Picloram Persistence in Semi-arid Rangeland
Soils and Water. Weed Sci. 19: 381-384, 1971b. In Reference"?
54. Keys, C.H. and H.A. Friesen. Persistence of Picloram Activltv <
Weeds 16: 341-343, 1968. In Reference 20. "CI°ram Activity *
55. Hunter, J.H. and E.H. Stobbe, Movement and Persistence of Picloram in
Soil. Weed Sci. 20: 486-489, 1972. In Reference 2? "el™ ^
56. Norris L.A. Herbicide Runoff from Forest Lands Sprayed in Summer
Research Progress Report, Western Society of Weed Science.!^ pp.
A-262
-------
57. Suffling, R., D.W. Smith, and G. Sirons. Lateral Loss of Picloram and
2,4-D From a Forest Podsol During Rainstorms, Weed Research, 14: 301-
304, 1964,
58. Gwinn, D. Picloram, Phase I Position Review, Draft. Plant Studies
Branch, BFSD, U.S. EPA, Washington, D.C. 17 October 1975, 28 pp.
59. Davidson, J.M. and R.K. Chang. Transport of Picloram in Relation to
Soil Physical Conditions and Pore-Water Velocity. Soil Science Soc.
Amer. Proc. 36: 257-261, 1972. In: Proc. Southern Weed Science Socie-
ty 32: 182-197, 1979.
60. Suffling, R., et al; Lateral Loss of Picloram and 2,4-D From a Forest
Podsol During Rainstorms. Weed Research 14: 301-304, 1974. In: Proc.
Southern Weed Science Society 32: 182-197, 1979.
61. Baur, J.R., R.W. Bovey, and M.G. Merkle. Concentration of Picloram in
Runoff Water. Weed Science, 20: 309-313, 1972. In Reference 20.
62. Haas, R.H., G.O. Hoffman, and M.G. Merkle. Persistence of Picloram in
Natural Water Sources. Texas Agricultural Experiment Station, Con-
solidated Progress Report, June 1970, p. 86-90.
63 Trichell, D.W., H.L. Morton, and M.G. Merkle. The Loss of Herbicides
in Runoff Water. Weed Science, 16: 447-449, 1968. In Reference 62.
64. Trichell, D.W., H.L. Morton, and M.G. Merkle. Loss of Herbicides in
Runoff Water. Weed Science, 16(4): 447-449, 1968.
65. Bovey, R.W., et al. Loss of Spray and Pelleted Picloram in Surface
Runoff Water. Journal of Environmental Quality, 7(2): 1978-180, 1978.
66. Davis, E.A., P,A. Ingels, and C.P. Pase. Effect of a Watershed Treat-
ment with Picloram on Water Quality. USDA, Forest Service Research Note
RM-100. 4 pp. In Reference 65.
67 Burnett E. and C.W. Richardson. Herbicide Residues in Runoff Water,
Soils and Vegetation. USDA, Grassland Soil and Water Research Labora-
tory, Temple, Texas. 1980. In: Toxicology Research Projects Direc-
tory Research Abstract, Vol. 5, Issue No. 9, 1980.
68. Mitchell, B. Persistence of Picloram Residues. Farm Research News,
10(1): 16, 1969.
69. Finnis, J.M. and J.D. Sund. Planting of Douglas Fir Seedlings Follow-
ing Aerial Application of Tordon 101 Herbicide. Down to Earth, 26(1):
10-11, 1970. In Reference 9.
70 Norris, Logan A., H.L. Montgomery, and Fred Gross. The Behavior of
Picloram and 2,4-D in Soil or, Western Powerline Right.-of-Way. Abstract
19, Abstracts 1976 Meeting of th* Weed Science Society of America.
February 3-5, 1976. Denver, Colorado, 1976. Summarized in Reference 6.
A-263
-------
71. Caro, J.H., H.P. Freeman, and B.C. Turner. Persistence in Soil and
Losses in Runoff of Soil-Incorporated Carbaryl in a Small Watershed.
Journal of Agricultural Food Chemistry, 22(5): 860-863, 1974.
72. Ragab, M.T.H. Residues of Picloram in Soil and Their Effects on Crops.
Canadian Journal of Soil Science, 55: 55-59, 1975. In Reference 58.
73. Vanden Born, W.H. Picloram Residues and Crop Production. Canadian J.
of Plant Science, 49: 628-629, 1969. In Reference 20.
74. Fryer, J.D., P.D. Smith, and J.W. Ludwig. Long-term Persistence of
Picloram in a Sandy Loam Soil. J. Environ. Quality, Vol. 8(1): 83-86,
1979.
75. Herr, D.E., E.W. Stroube, and D.A. Ray. The Movemeat and Persistence
of Picloram in Soil. Weeds 14: 248-250, 1966b. In Reference 20.
76. Hamaker, J.W. Reaction Kinetics for the Detoxification of TORDON in
Soils. The Dow Chemical Co., Bioproducts Dept. Unpublished Report GS
652, 1967. In Reference 20.
77. Hance, R.J. Decomposition of Herbicides in the Soil by Non-Biological
Chemical Processes. J. Science and Field Agriculture, 18: 544-549, 1967.
78. Naik, M.N., et al. Microbial Degradation and Phytotoxicity of Picloram
and Other Substituted Pyridines. Soil Siol. Biochem. 4: 313-323, 1972.
In Reference 20.
79. Meikle, R.W., et al. Decomposition of Picloram by Soil Microorganisms.
A Proposed Reaction Sequence. Weed Science, 22: 263-268, 1974. Summa-
rized in Reference 3.
80. Meikle, R.W., et al. Decomposition of Picloram by Soil Microorganisms.
A Proposed Reaction Sequence. Submitted to Weed Science, May 1973.
In Reference 20. • '
81. Rieck C E Microbial Degradation of 4-Amino-3,5,6-Trichloropicolinic
Acid in Soils and in Pure Cultures of Soil Isolates. Diss. Abstr. Part
B., p. 72, 1969. In Reference 20.
82. Meikle, R.W., et al. Measurement and Prediction of Picloram Disappear-
ance Rates from Soil. Weed Science, 21: 549-555, 1973. Summarized in
Reference 3.
83. Redemann C.T. et al. The Fate of 4-Amino-3,5,6-Trichloropicolinic
Acid in Spring Wheat and Soil. Bulletin of Environmental Contamination
and Toxicology, 3(2): 80-96, 1968. Summarized in Reference 3.
84. Norris, Logan A. Herbicide Runoff from Forest Lands Sprayed in Summer.
Res. Prog. Rpt. West. Soc. of Weed Sci., Las Vegas, pp. 24-26 1969.
Summarized in Reference 6. '
A-264
-------
85. Hedelund, R.T. and C.R. Youngson. The Rates of Photodecomposition of
Picloram in Aqueous Systems. Advances in Chemistry Series. No. Ill:
157-172, 1972. Summarized in Reference 3.
86. Hall, R.C., C.S. Giam, and M.G. Merkle. The Photolytic Degradation of
Picloram. Weed Research, 8: 292-297, 1968.
87. Hedlund, R.T. and C.R. Youngson. The Rates of Photodecomposition of
Picloram in Aqueous Systems. Adv. in Chem. Ser. Ill: 159-172, 1972.
In Reference 20.
88. Michel, J., R. Grover, and J.R. Gear. Kinetics of Picloram Photolysis
in Aqueous Solutions. Froc. Chem. Biochem. Herbicides 1: 12-13, 1973.
In Reference 20.
89. Hall, R.C., C.S. Giam, and M.G. Merkle. The Photolytic Degradation of
Picloram. Weed Res. 8: 292-297, 1968. In Reference 20.
90. Mosier, A.R. and W.D. Buenzi. Picloram Photolytic Decomposition, J.
Agricultural Food Chemistry, 21(5): 835-837, 1973.
91. Wu, C.C., et al. Effects of Direct Contact of Pinus resinosa Seeds and
Young Seedlings with 2,4-D or Picloram on Seedling Development. Can.
J. Bot. 49: 1737-1741, 1971. In Reference 20.
92. Summary for Reported Incidents Involving Picloram. Pesticide Incident
Monitoring System, Report No. 115, EPA, Office of Pesticides Program,
October 1978. In: PIMS Data on 2,4,5-T and Alternatives, U.S. EPA
files.
93. Gesink, R.W., H.P. Alley, and G.A. Lee. Vegetative Response to Chemical
Control of Broom Snakeweed on a Blue Grama Range. J. Range Management
26: 139-143, 1973. In Reference 20.
94. Sargent, M., et al. The Toxicity of 2,4-D and Picloram Herbicides to
Fish. Purdue University and Indiana State Highway Commission, NTIS
PB-201-099, February 1971, 22 pp.
95. Woodward, D.F. Assessing the Hazard of Picloram to Cutthroat Trout.
Journal of Range Management, 32(3): 230-232, 1979.
96. Butter P.A. Effects of Herbicides on Estuarine Fauna. Bureau of Com-
mercial Fisheries, Biological Laboratory. Gulf Breeze, Florida. Pre-
sented at 13th Annual Meeting of the Southern Weed Conference, January
19-21, 1965, Dallas, Texas, 6 pp.
97. Butler, P.A. Proceedings of Southern Weed Conference 18: 576, 1965.
In Reference 16.
98. Sanders, H.O. and O.B. Cope. Ltonological Oceanographies, 13: 112,
1968. In Reference 16.
A-265
-------
99. Sanders, H.O. Toxicity of Pesticides to the Crustacean Gammaries
lacustris. Technical Paper 25, Bureau Sport Fisheries Wildlife, U.S.
Dept. of Interior", 1969, 18 pp. In Reference 16.
100. Lynn, G.E. Down to Earth, 20: 6, 1965. In Reference 16.
101. House, W.B., et al. Assessment of Ecological Effects of Extensive or
Repeated Use of Herbicides. Midwest Research Institute, Kansas City,
Missouri, MRI Project No. 31, 1967, pp. 177-185.
102. Lynn, G.E. A Review of Toxicological Information on Tordon Herbicides.
Down to Earth 20(4): 6-8, 1965. In Reference 22.
103, McCollister, D.D. and M.F, Leng. Toxicology of Picloram and Safety
Evaluation of Tordon Herbicides. Down to Earth 25(2): 5-10 1969.
Summarized in Reference 6. '
104. McCollister, D.D. and M.L. Leng. Toxicology of Picloram and Safety
Evaluation of Tordon Herbicides. Down to Earth 25(2): 5-10 1969.
In Reference 22. '
105. Kenaga, E.E. Down to Earth 25: 5, 1969. In Reference 16.
106. Tucker, R.K. and D.G. Crabtree. Handbook of Toxicity of Pesticides
S^Jit1""' U'S* Fisheries Wildlife Service, Bureau Sports Fisheries
Wildlife, Resource Publication No. 84, 1970, 131 pp. In Reference 16.
107. Weioer J.T., et al. Toxicological Studies Related to the Use of
White (Tordon 101) as a Defoliant. U.S. Army Edgewood Arsenal, Pharm.
Labs, 26 pp., September 1967. In Reference 101.
108. Kenaga, E.E. TORDON Herbicides - Evaluation of Safety to Fish and
Birds, Down to Earth 25: 5-0, 1969. In Reference 20.
109 ' S^SJUlS't' Lf ternRegardin8 Pesticide Toxicity to Bees. Washing-
Say 12* 198? " y' Departnent of ^omology, Pullman, Washington,
110. Toxicity^of Pesticides to Honey Bees. University of California, Divi-
sion of Agricultural Sciences, Leaflet 2286, December 1975. 4 pp.
111. Morton H.L., et al. Toxicity of Herbicides to Newly Emerged Honey
Bees. Environmental Entomology, 1(1). 102-104, 1972.
112. Moffett, J.O., et al. Toxicity of Some Herbicidal Sprays to Honey
Bees. J. of Economic Entomology, 65(1): 32-36, 1972.
113. Goring, C.A.I., et al. Down to Earth, 72: 14, 1967. In Reference 16.
A-266
-------
115. Hameed, K.M. and C.L. Foy. Bulletin of the College of Science, Univer-
sity of Baghdad, Republic of Iraq, Volume 12, Part 2, 1974. In Referen-
ce 16.
116. Tu, C.M. and W.B. Bollen. Effect of Tordon on Microbial Activities in
Three Willamette Valley Soils. Technical Paper No. 2650, Oregon Agri-
cultural Experiment Station, Corvallie, Oregon, 1969, 17 pp.
117. Arvik, V.H., D.L. Wiltson, and L.C. Darlington. Weed Science, 19: 276,
1971. In Reference 16.
118. Hardy, J.L. Down to Earth, 22: 11, 1966. In Reference 16.
119. Elder, J.H., C.A. Lembi, and D.J. Horre. Toxicity of 2,4-D and Piclo-
ram to Fresh Water Algae. Purdue University and Indiana State Highway
Commission, NTIS PB-199-114, October 1970, 10 pp.
120. Redemann, C.T. The Metabolism of 4-Amino-3,5,6-Trichloropicolinic
Acid by the Dog. The Dow Chemical Company, Seal Beach, California.
Unpublished Report GS-609, 1963. In Reference 20.
121. Leasure, J.K. and M.E. Getzander. A Residues Study on Tissues From
Beef Cattle Fed Diets Containing TORDON Herbicide. Bioproducts Labo-
ratory, The Dow Chemical Company, Midland, Michigan. Unpublished
report GS-P 141, 1964. In Reference 20.
122. Kutschinski, A.H. and Van Riley. Residues in Various Tissues of Steers
Fed 4-Amino-3,5,6-Trichloropicolinic Acid. J. Agr. Food Chem. 17:
283-287, 1969. In Reference 22.
123. Hardy, J.L. Effect of TORDON Herbicides on Aquatic Chain Organisms.
Down to Earth 22: 11-13, 1966. In Reference 20.
124. Youngson, C.R. and R.W. Meikle. Residues of Picloram Acquired by a
Mosquito Fish, Gambusia sp. from Treated Water. The Dow Chemical Com-
pany, Walnut Creek, California. Unpublished Report GH-1210, 1972.
In Reference 20.
125. Kutschinski, A.H. Residues in Milk from Cows Fed 4-Amino-3,5,6-
Trichloropicolinic Acid. J. Agr. Fd. Chem. 17: 288-290, 1969. In
Reference 20.
126. Kutschinski, A.H. and V. Riley. Residues in Various Tissues of^Steers
Fed 4-Ajnino-3,5,6-Trichloropicolinic Acid. J. Agr. Fd. Chem. 17: 283-
287, 1969. In Reference 20.
127. Herbicide Contamination in Water Supplies, Kimball, Nebraska. National
Enforcement Investigations Center, Denver, Colorado, and Region VII,
Kansas City, Missouri, EPA-330/2-76-037, December 1976, 19 pp.
A-267
-------
Common Name: Simazine
Chemical Name: 2-chloro-4,6-bis(ethylamino)-s-triazine
Major Trade Name: Princep
Major Applications Used primarily in the Pacific Northwest for site prepa-
in Forestry: ration, conifer release and nursery applications for
grass and broadleaf weed control.
SUMMARY
Most of the available information on the fate of simazine in soil and
water is the result of laboratory and/or field studies with agricultural
systems. Very little data are available on or in connection with applica-
tions to forests.
roots.
The principal mechanism of simazine uptake by plants is through the
. Simazine is considered a stable, persistent herbicide and may persist
in phytotoxic concentrations for over a year in agricultural soils. Simazine
degrades via chemical and microbial routes. High concentrations of soil
organic matter, such as may be present in forest soils, as well as low tem-
SSaTi?1?^18? PH* *e*d to **«•"• its persistence. At PH 4, the degra-
AulS SS M^6 S S°* S 10 year85 " PR 2' 4° days' Simazine losses .
due to volatilization from agricultural soils are very small. Such losses
IXhSK^S-S be,6Ven le88 vr°n f°"8t 80ils due to lower temperatures.
fa SSt SlJ decomposes by uv light, the extent of photodecomposition
in forest systems is expected to be very low.
1M anfdl^rnM con*idf ed a lo« solubility, low mobility herbicide. Leach-
contenl !ndK± J '???"? *" Iwe8t ln 80ils with h^ organic matter
content, and hence should be low fa forest soils. It is very sliahtly so-
luble in water Its half -life fa water is reportedly S-7? Lys, with II
percent loss 12 months after application.
Simazine is phytotoxic to numerous non-target plant aoeciea It is
extremely toxic to very young, recently emerged'red pfae serfage. It is
tion is low fa fish and microorganism
hazarSus! in8tedlent8 P«8ent in Blmazfae formulations are not considered
A-268
-------
1.0 INTRODUCTION
Sima2ine is a selective herbicide and soil sterilant that has been
widely used in crop and noncrop applications since its discovery, along with
atrazine and other s-triazine herbicides, in the early 1950's in Switzerland
(1). It is used in forestry and agricultural applications primarily for
highly effective control of annual and perennial grasses and shallow-rooted
broadleaf weeds; it is less effective on deep-rooted broadleaf weeds such as
Canada thistle, birdweed, and St. Johnswort (2).
In the forest industry simazine is used primarily in the Pacific North-
west for site preparation, in conifer release and in nursery applications
alone or in combination with atrazine (3,4). Usual application rates are
3 to 4 Ib of 80 percent active ingredient in 10 gallons water/acre for site
preparation and conifer release; and 1.6 to 3.8 Ib of 80 percent active in-
gredient in 10 to 25 gallons water/acre in nursery applications (4). Princep
SOW is one of the principal wettable powder formulations used. The primary
method of application is the ground spot method (3), although aerial broad-
cast is also used (3,5). In areas west of the Cascades, applications are
usually recommended for late winter or early spring (2). The most desirable
time to make application is in late February or March. Applications made
after April 1 may not receive enough moisture to carry the materials into the
root zone of the weeds. In areas east of the Cascades, suggested applica-
tions are for early fall (2). Simazine is reportedly also used to a limited
extent in the south in combination with atrazine.
Agricultural uses of simazine include application to corn, established
alfalfa and bermuda grass, fruits, nuts and turf grass (6). At high rates
of application, it is also used for nonselective weed control in industrial
areas, in airports, and railroad rights-of-way (7). Simazine is also used
for algae control in ponds, fountains, recirculating water cooling towers,
and large aquariums and swimming pools (8,5). After uptake by plant roots
or algae, simazine exerts its toxic action by inhibiting photosynthesis by
arrestation of the "Hill" reaction in chloroplasts (9).
Simazine is manufactured domestically by Ciba-Geigy Corporation under
the trade name Princep (6). In the U.S., simazine is also marketed under
the trade name Aquazine for control of algae and aquatic weeds. Simazine
A-269
-------
is also available from foreign producers under the following trade names (5):
Cekusan
Framed
Gesatop
Primatol
Simadex
Simazol
Simazine is formulated as a wettable powder containing various percent-
ages of technical grade active ingredient; th« remainder of the formulation
consists of various diluents such as chalk or kaolin (6,8). Simazine is
also formulated with amitrole as Simazol (6).
2.0 PHYSICAL/CHEMICAL PROPERTIES OF ACTIVE INGREDIENTS
The chemical nomenclature for simazine is 2-chloro-4,6-bis(ethylamino)-
s-triazine:
Cl
I
N. N
I II
C C
Simazine is a white crystalline solid with a melting point of 225 to
227'C. Solubility data in water and organic solvents as a function of tem-
perature are shown below (5):
Temperature, °C ppmw
0 2
20 3.5
85 84
Chloroform 20 goo
Methanol 20 ^
n-Pentane 25
Petroleum ether 20
Simazine exhibits very low volatility. Vapor pressure data are pre-
sented below as a function of temperature (5) :
A-270
-------
Temperature, "C
10 9.2 x 10"10
20 6.1 x 10"9
30 3.6 x 10~8
50 9.0 x 10~7
3.0 ENVIRONMENTAL FATE
Very little environmental fate data have been published in connection
with the use of simazine in forests. Host of the fate information discussed
in this section is based on data reported for non-forest applications.
3.1 UPTAKE AND METABOLISM' IN PLANTS
Laboratory experiments conducted on tha uptake of simazine on corn,
sorghum, cereals, weeds and other plants have shown that the principal me-
chanism of uptake in through the plant roots and that uptake occurs rapidly
in the presence of adequate moisture which carries the herbicide to the root
zone. The studies also indicate that the uptake increases with increasing
concentration of simazine, time of exposure, temperature and decreasing
relative humidity (1). Studies using radiolabelled triazine herbicides have
shown that they translocate rapidly and distribute evenly throughout the
plant system into all aerial parts of the plant, with some accumulation in
the marginal zones of the leaves, particularly in susceptible species (1).
Simazine does not penetrate readily through plant leaves and foliar applica-
tions are generally ineffective; however, studies have shown that foliar
penetration occurs and is enhanced by plant cuticle damage, by hail damage
to leaves, and by surfactants on the leaves or in simazine formulations (10).
Metabolic degradation of simazine in plants occurs via 4 major mecha-
nisma (1,8,11): CD hydrolysis of the 2-chloro group to give hydroxy sima-
zine; (2) N-dealkylation of the side chains; (3) conjugation with glutathione
or amino acid compounds such as Y-glutamylcysteine at the 2-position of the
triazine ring; and (4) s-triazine ring cleavage. Ring cleavage of intact
simazine is a difficult and slow process and occurs to a minor extent over
long periods of time. N-dealkylation is thought to proceed via a free radi-
cal mechanism, as indicated in studies by Plimmer, et al. (12). Ammelide
and ammeline have been reported as products of further degradation following
.A-271
-------
N-dealkylation (8). In general, the route and rate of degradation vary with
plant type, stage of growth and site of entry into the plant. The metabolism
rates are more rapid in tolerant plants than in susceptible plants.
Extensive studies have been conducted by Montgomery and Freed (13),
Castelfranco (14), and Gysin and Knusli (15) on the root uptake and metabo-
lism of simazine in corn and maize; these studies indicate rapid uptake and
decomposition for simazine. Degradation occurs in the presence of a corn
enzyme (thought to be a benzoxazine derivative) (16) via hydrolysis of the
2-chloro group to produce 2-hydroxy simazine followed by ring cleavage and/or
conjugate formation with the plant acids (see Figure 1) (8). The metabolism
of simazine in corn is apparently very rapid and is completed before simazine
is translocated to the leaves.
Hydrolysis and conjugation of simazine result in a complete loss of
phytotoxic properties. Plant species which hydrolyze and/or conjugate sima-
zine are most resistant to the herbicide. N-dealkylation of simazine results
in only partial loss of phytotoxicity, and species using this route of degra-
dation have moderate resistance to simazine (1).
3.2 FATE IN SOIL
The fate of simazine in soil can be described in terms of volatiliza-
tion, photodecomposition, leaching, adsorption, runoff, and chemical and
microbial degradation. These factors are discussed in the sections below.
3.2.1 Volatilization
The extent of simazine volatilization from soil is not fully known.
Simazine is known to dissipate from treated areas by volatilization, but it
is generally held that this does not take place to a significant extent (5),
presumably due to the extremely low vapor pressure of simazine. Laboratory
studies by Foy (17) of simazine on planchets at 25" and 60°C showed very
little loss of simazine, even at the higher temperature. In another labora-
tory study measuring triazine losses from 5 soils as a function of soil type
(18), simazine was observed to volatilize only very slightly and less than
atrazine. This is reasonable due to the fact that simazine has a lower vapor
pressure than atrazine. .
A-272
-------
r ?
// \ corn // \ / \
N K --- «---> N N HN N
i l enzyme . _ _ -----
C C . • N
/\ <~R
{\ «"\
HI "H ^ n| •„ R = Plant acids
N'
H/ \ >
II
Hi »H \x C-NHCH
C H_NC CNC H
5 \ / 5 X K
N H
Figure 1. Metabolism of Slmazine in Corn (8)
-------
In the forest the extent of simazine volatilization from soil due to
sunlight exposure may be less than that in an agricultural field due to in-
creased shading. In addition to temperature, volatilization if also affected
by soil moisture, with increased volatilization from drier soils (18,19).
Also because simazine is somewhat amphoteric in nature, the pH of aqueous
solutions may be expected to influence its volatility; the extent of this
influence has not been determined (10).
3.2.2 Photodecomposition
Siaazine can undergo photodecomposition under uv radiation (20). The
rate of photodecomposition and factors influencing it are not fully under-
stood (5). It is, however, generally held that under normal climatic con-
ditions, loss of simazine from soil and foliage surfaces by photodecomposi-
tion is insignificant (5). It is possible that photodecomposition occurs
to some extent in agricultural fields where high temperatures and prolonged
sunlight may prevail (5), but these conditions are not considered typical of
the forest environment.
The photodecomposition of simazine on metallic and non-metallic surfaces
has been studied to a limited extent in the laboratory (21). In a study by
Jordan in 1965 (22), slma2llie on aluoinun planchfits decOfflposed up
A-274
-------
Consequently, acidic conditions would be expected to promote adsorption on
clay soils. In a study by Sheets (26), sinazine was removed from solution
by a cationic exchange resin and not by an anionic exchange resin, thus in-
dicating that under the conditions tested, simazine exhibited acidic proper-
ties and was electrically positive.
The adsorption capacity of a given soil for sinazine affects its poten-
tial for leaching of simazine. The leaching tendency is lower in those soil
types and under those conditions which promote adsorption. Leaching is known
to be more pronounced in sand and clay-type soils than in soils with high
organic matter content (27). This was confirmed in a laboratory study on 3
Florida soils (i.e., Lakeland fine sand, Greenville fine sand, and Everglade
muck) in which the least penetration (to a one-inch depth) was achieved with
the high organic muck soil (27). In this study simazine was also shown to
leach at much lower rates than atrazine. In a separate study simazine was
shown to migrate to & depth of 6 inches with application of one inch of
water (28). Other tests have indicated that for several months after appli-
cation, the greatest amount of simazine remains in the upper 2 inches of
soil (5). Smith, et al. (29) observed that simazine applied to Canadian
irrigation ditches at a rate of 22.4 kg/ha remained primarily in the top 7.5
cm of soil after 3 growing seasons, whereas atrazine became distributed uni-
formly throughout a 90-cm soil depth. Marriage, et al. (30) found that resi-
dues of simazine applied for 9 consecutive years at a rate of 4.5 kg/ha to
the same plots of a peach orchard located on a sandy loam soil near Harrow,
Ontario, were confined to the upper 15 cm of the soil profile and that the
majority of the herbicide remained in the 0-5 cm soil layer. The maximum
residue level found was 1,6 kg/ha of simazine in the top 15 cm of the soil
profile.
An empirical worst-case model was proposed by Hartley (31) describing
the pattern of leaching of simazine at 2 application rates using soil having
no adsorptive capacity and 20 percent pore volume. At Mb/acre, it was
postulated that one inch of rain could dissolve all of the simazine and pro-
duce a saturation zone in the upper 5 inches of soil. According to the
model, further rain would move the zone downward as a 5-inch band. At 10
Ib/acre, 10 inches of rain would dissolve the simazine and give a 50-inch
band. Soil with increased adsorptive capacity would reduce the leaching
A-275
-------
tendency. Even though leaching of simazine from forest soil has not been
studied, the extent of such leaching is expected to be lower 'than that in
agricultural soil because of the higher organic content of the forest soil.
Limited data are available on rates of simazine runoff resulting from
rainfall after forest or crop applications. In a study performed by the
U.S. Department of Agriculture to determine the pathways and quantities of
simazine and other herbicides transported from Appalachian watersheds (32),
the highest concentration of simazine (1.2 ppm) was present soon after appli-
cation in runoff on 0.4 to 3.5 ha agricultural watersheds and declined ra-
pidly in later rainfall events. A maximum of 6 percent and an average of 2
percent of the applied simazine were transported in the runoff. Less runoff
occurred from no-tillage rather than from conventionally tilled fields.
Several studies have been conducted on atrazine runoff which indicate
that although atrazine is only very slightly soluble in water, a potential
exists for buildup in local streams/rivers due to runoff after heavy rain-
fall (33). Because of the lower solubility of simazine compared to atrazine
(5 ppm vs. 70 ppm at 25°C), runoff via solubilization.would be expected to
be somewhat less for simazine than for atrazine.
3.2.5 Chemical and Microbial Degradation
In soil simazine is considered to be a stable, persistent compound (29).
According to Sheets (34), simazine residues may persist in agricultural soils
at phytotoxic levels to sensitive plants for over one year. Its persistence
also makes it valuable for long term weed control (9). The half-life in soil
is estimated at 4-6 months; 90 percent loss was observed after 10 months at
35°C (28). In a laboratory study using a terrestrial microcosm chamber sim-
ulating a forest ecosystem and containing synthetic soils and vegetation
(Douglas fir and alder seedlings, etc.), total soil residues of simazine were
0.18 ppo after 26 days following application of 0.25 Ib/acre simazine (35).
The persistence of simazine is a function of. soil type, with less per-
sistence in soils with high organic matter content (36,37). Aelbus and
Homburg in 1959 (38) showed simazine to be less persistent in clay and peat
soils than in sandy soil 3, 6, and 11 months after application. Simazine
residues have been monitored in high organic content Woodbridge loam soil in
a young Fraser fir (Abies fraseri pursch pois) plantation plot in Wolcott,
A-276
-------
CT, to which 4, 8, 12, and 16 Ib/acre of simazine were applied (39). The
results, shown in Table 1, indicate that even in the fall after spring appli-
cation, simazine residues were generally less than 1 ppm.
In a study by Walker (40) using sandy loam soil, the time required for
disappearance of 50 percent applied simazine varied from 37 days at 25°C
(13 percent soil moisture) to 243 days at 15°C (7 percent soil moisture).
Simazine persists slightly longer than atrazine in most soils, but in some
soils the two are about equally persistent (41).
In addition to soil type, the persistence of simazine is also a function
of pH, temperature and moisture. In a study of persistence of simazine in
corn and soybean production fields, Slack, et al. (42) determined that the
persistence increased with increasing pH. A number of other laboratory and
field studies by Burnside, et al. (43), Harris and Sheets (44), and Harris,
et al. (45) have shown that simazine is more persistent in colder drier
climates than warmer, wetter ones. A mathematical model was developed by
Walker (46) to describe and predict the effects of soil temperature and
moisture on degradation rates for four herbicides including simazine. In
the model, temperature effects are characterized by the Arrhenius equation:
In k « -E /RT where k is the rate constant of degradation and E is the ex-
a a
perimental activation energy, and moisture effects are characterized by the
empirical equation of the form: H - AM~b where H is the half-life at moist-
ure content M, and A and b are constants derived from laboratory measure-
ments; the constant b gives a measure of the moisture dependence of degrada-
tion. The predicted relative order of persistence of the 4 herbicides was
verified in field experiments on sandy loam soils under various conditions
of temperature and moisture. To date, the model has not been tested against
other soil types.
The persistence of simazine in bottom sediments in ponds has also been
studied in connection with its use for algae control. Mauck, et al. (47)
reported sioazine residues of 0.07 and 0.32 ug/ml in mud residues from 4
ponds after 346 days and application of 1.0 and 3.0 ug/ml, respectively (47).
The concentration of simazine plateaued approximately 35 days after applica-
tion at levels of roughly 0.1 wg/ml and 0.5 ug/ml, respectively.
A-277
-------
Simazine degradation in soil occurs via both chemical and/or tnicrobial
routes. A brief review of the factors affecting each of these degradation
pathways follows.
Chemical Degradation—
Hydrolysis is the major chemical degradation reaction of simazine in
soil, The reaction is first order and involves hydroxylation of the carbon-
chlorine bond to give hydroxy simazine (1,48). The rate of reaction is pH
dependent, with increasing hydrolysis at lower pH. At pH 4, the half-life
of the acid-catalyzed hydrolysis of simazine is 10 years, at pH 2, 40 days
(15).
As with atrazine, hydrolysis may.be catalyzed by certain soil compounds.
Nucleophilic compounds in soil including Fe/Al ions promote nucleophilic
displacement of -Cl with -OH at high pH, whereas humic acid and various soil
colloidal particles catalyze hydrolysis at low pH« The low pH hydrolysis
results from the protonation of ring or chain nitrogen atoms and subsequent
cleavage of the C-C1 bond (49).
Increasing temperature and moisture also favor hydrolysis of simazine
(50,51,52).
In addition to hydrolysis, N-dealkylation of simazine is a possible de-
gradation route in soil; no information has been reported on the rate of this
reaction and factors influencing it. Also not reported are data on subse-
quent degradation of hydroxy and dealkylated simazines.
Microbial Degradation—
Simazine in soil is subject to microbial degradation. A list of micro-
organisms capable of degrading simazine is presented in Table 2. Factors
influencing microbial growth in soil include soil moisture, temperature, pH,
soil type and presence of nutrients (1), but very few studies have been per-
formed measuring the effect of these factors on microbial degradation of
simazine. Three major routes for biological degradation are: N-dealkylation,
hydrolysis, and ring cleavage.
N-dealkylation is one of the primary mechanisms of microbial degradation
and has been studied by a number of investigators in recent years. Studies
by Kearney, et al. (53) have shown that simazine dealkylation by
A-279
-------
TABLE 2. LIST OF MICROORGANISMS WHICH DEGRADE SIMAZINE IN SOIL
^ Name of Microorganism Reference
1. Actinomycetes
Streptomyces sp. 55
2. Fungi
Penicillium
purpurogenum 55
P.cyclopium 57
P.lano-coeruleum 57
Aspergillus ustus 56
Fusarium oxysporum 57
F.avenaceum c-,
Cylindrocarpon radicicola 57
Stachybotrys sp. 57
Xanthochrous pini ea
Coriolus versicolor eg
Penicillium citrinum 58
Penicillium notatum -8
3. Bacteria
Corynebacterium sp. 0
o
Escherichia coli
8
Bacillus mesentericies 59 6Q
Bacillus mycoides eo
59160
Bacillus cereus 59>60
Bacillus agglomeratus -0 ,.
J3»DO
Bacillus idosus
59
Pseudomonas fluorescens
A-280
-------
fumigatus Fres. results in the formation of 2-chloro-4-amino-6-ethylamino-s-
triazine. Recent studies by Plimmer (12,54) have demonstrated that a free
radical mechanism may be involved in the reaction. Subsequent metabolism of
the 2-chloro-4-amino-6-ethylamino-s-triazine results in further dealkylation
or deamination, followed by dehalogenation of the 2-chloro group to give
ammelide. The following degradation pathway has been determined (11,55):
Cl Cl QH
. Aspergillus
fumigatus
X
II — — JI
j-*\ /^N-CLH_ NHr"\ /*
2 ^ / H 2 5 2 ^ /
N N
Simazine 2-chloro 4-amino- Ammelide
6-ethylamino-s-triazine
Limited information is available on hydroxylation and ring cleavage of
simazine by soil microorganisms (50,61,62). Hydroxylation is regarded as an
initial reaction in microbial degradation of simazine and other triazines
(63), Ring cleavage is a minor degradation reaction in soil. In a study by
Ragab and McCollum (64), only a few percent of labelled C02 was produced
from simazine uniformly labelled with 14C in the triazine ring. In a sepa-
rate study by Suss (65), it was noted that microbial degradation reactions
of simazine are lengthy and occur in successive phases. Approximately 2.5
percent of 14C- ring label of simazine was evolved as C02 from different
soils within five weeks. This period was followed by a lag phase of up to
15 weeks, after which a second period of 14C02 evolution started and conti-
nued up to 30 weeks. Depending on the soil type, the cumulative amount of
14CO liberated varied from 6 to 17 percent. In a subsequent study by Suss
(66), when simazine adsorbed to peat was incorporated into various soils, a
substantial increase in the liberation of1 C02 was observed in contrast to
the control in which simazine was added directly.
Both dealkylated and hydroxylated simazine degradation products are
subject to further microbial degradation (1). Recent studies have shown
that degradation of both types of products may give rise to common metabo-
lites, such as 2-hydroXy-4-amino-6-alkylamino-s-triazine (1,67).
A-281
-------
3.3 PERSISTENCE IN WATER
Siinazine is considered to be "moderately" persistent in water. The half-
life in water is reportedly 50-70 days, with 99 percent loss 12 months after
application (28). When applied to ponds for weed and algae control, the
average half-life of simazine is 30 days (5). The hydrolysis of simazine in
aqueous solution has been studied as a function of temperature and pH over a
period of 28 days (8). Based on the results, hydrolysis rate constants and
half-lives were calculated for temperatures of 30, 50, 70°C and pH levels
ranging from 0.1 to 13. The calculated data indicated no significant hydro-
lysis of a simazine over the test period in the pH range 5-9 at any of the
test temperatures. Slow hydrolysis (half-life of about 4 months) occurred at
an elevated temperature of 70«C at pH 7, and the rate of hydrolysis generally
Increased with both increasing or decreasing pH from pH 7.0,
The persistence in ponds is dependent upon many factors including the
level of algae and weed infestation, and pond temperature (5). Mauck, et
al. (47) studied the decay of sinazine applied to four 0.25 acre ponds. The
results, summarized in Table 3, indicate that simazine residues in water were
directly proportional to rates of application, and seldom exceeded one-third
to one-half of the total amount applied. Simazine was still present in the
water 346 days after the first application, and 456 days after the second
application. In a study conducted by Ciba Geigy (8) in 1973, 0.25 ppm active
ingredient simazine was added to the littoral zone of Findley Lake, N.Y.
After 5 days and 15 days, siaazine levels in epillminon (0-15 feet) water was
at about the same level as initially (0.25 ppm); hypoliainon (15-35 feet)
water contained about 0.03-0.04 ppn on both days. Results of a number of
other studies on the persistence of simazine in ponds indicate that the time
for residues to decrease by 90 percent varied widely from 15 to 247 days (8).
The rate of simazine photodecomposition in water is extremely slow, as
measured under laboratory conditions, and is not expected to be significant
in the environment. Laboratory photolysis of siaazine under uv radiation
(2200'A) in water and other hydrolytic solvents (e.g., methanol) was shown
to result in the formation of 4,6-bis(ethylamino)-s-triazine (12)
A-282
-------
4.0 IMPACTS OF RON-TARGET PLANTS AND ORGANISMS
4.1 PLANTS
Slaazine has been shown to be pnytotoxic to non-target forest species
under certain, application conditions. In a study by Kozlowski and Kuntz
<68), simazine (0.5 and 1 Ib active ingredient/acre) sprayed directly on
the foliage of young recently-emerged red pine seedlings resulted in severe
injury including extensive browning and curling and death. No harmful effects
were reported on older seedlings. Simazine applied as a pre-emergence spray
also caused severe damage in terms of seedling growth (SB).
Simaaine has been shown to have significant effects on the form, growth
and color characteristics of balsam fir Christmas trees (68). Firs treated
with 12 Ib a.i./acre simazine or fertilizer-simazine combination displayed
higher crude protein and ash content and were darker green in color and more
succulent than' controls. The treated trees were consequently much oare
attractive to browsing deer than control trees. Results further Indicated
that simazine has the potential to improve the quality of non-commercial
shrubs and trees in peripheral areas to buffer the Impacts of deer on commer-
cial operations.
Slaazine exhibits phytotoxicity to a number of non-target agricultural
and orchard crops, including a wide number of monocotyledonous and dicotyle-
donous plants (9). sfcnazine has caused injury to oats following use on a
previous com crop (9). Crop injuries follovinB application of simaziae in
preceding growing seasons have also been encountered in eastern Europe (69).
In a study by Fischer and Lange <70) on phytotoxic responses of fruit trees
to simazine and other herbicides, 20-year old bearing Elberta peach trees
growing in sandy soil were severely inured at siaazine application rates of
, kt 8, Bnd 16 Ib a.i./acre in the late sprlag followed by flood irrigation
20 acre-inches of water in two months. At and above 4 Ib/acre simazine ««
excessively toxic causing severe chlorosis and bums on the foliage over
most of the trees; 3 Ib/acre caused considerable chlorosis. No simazine re-
sidue was found in the peach fruit up to the highest rates, i.e., 16 iWacre.
Less phytotoxicity was observed in soils with 2.1 percent organic matter con-
tent as opposed to the sandy orchard soil: even above A lb/acre, ooly slight
symptoms were observed. Applications of 3.2, 6,4, 12.8 and 25.6 Ib/acre of
A-284
-------
simazine repeated annually to plots of Emperor variety grapes located in
Davis, California, gave no evidence of adverse effects in studies conducted
by Leonard (71).
Studies by Singh, et al. (72) have shown that protein levels in various
crops is increased when sublethal concentrationf of s-triazine compounds are
applied. Foliar applications of 2 or 5 mg/1 of simazine (generally applied
until runoff occurred) increased the protein content of seeds of peas and
sweet corn growing under field conditions. A similar application of 0.5 or
1.0 mg/1 of simazine increased the protein content in pods of bush beans and
leaves of spinach under field and/or growth room conditions. Results of
quantitative analyses indicated that the soluble amino acid content was
higher in the treated bush bean seeds and spinach leaves. In addition, the
Fe content in the bush bean seeds and the Fe, Mg, P, and K contents in
spinach leaves were higher in the treated plants than in the controls.
4.2 FISH AND OTHER AQUATIC ORGANISMS
Simazine is considered to be only "slightly" toxic to fish and lower
aquatic organisms. Toxicological investigations conducted on rainbow trout
and bluegill sunfish have shown simazine to. have very low toxicity toward
these species (5) (see also Table 4), Results of toxicological investiga-
tions conducted by Mauck, et al. (47) on the distribution of 0.1, 0.3, 1.0,
and 3.0 yg/ml simazine in four 0.25-acre ponds are summarized in Table 5.
The results indicate that simazine may persist in fish for more than one
year. As noted in the table, residue concentrations are highest immediately
after simazine application, but subsequently decline.
The effects of continuous exposures to simazine on: (1) daphnid repro-
duction, (2) midge emergence, and (3) growth, reproduction and survival of
fathead minnows were conducted by Mayer and Sanders (73) using flow-through
diluter systems. A second study was also undertaken with fathead minnows
using a simulated use-pattern exposure. No adverse effects were observed on
daphnid reproduction with simazine concentrations of 0.25 to 3.0 mg/1, but
midge emergence was temporarily delayed in the 0.66 and 2.2 mg/1 simazine
range. Fathead minnow egg hatch and fry growth were reduced in continuous
simazine exposures to a simazine concentration of 1.7 mg/1, and no adverse
effects were found with simazine in the use-pattern exposure.
A-285
-------
TABLE A. FISH TOXICITY OF SIMAZINE (8)
Species
Toxic Effect
Mirror Carp
Rainbow Troup
Bluegill
Bluegill and
Channel Catfish
Fathead Minnows
Oysters
Pink Shrimp and
Mud Crab
First toxic signs were noticed after 8 hours at lg/L
Toxic signs after about 4-8 hours at a concentration
of O.lg/L
Concentrations in small test ponds of up to 5 ppm caused
no noticeable effect when held in this concentration for
a period of 7 weeks. Terbutryn, the positive control,
killed small bluegill at a concentration of 5.0 ppm.
values for Princep SOW were greater than 1000 ppm
for both species at all intervals up to 96 hours after
initial exposure.
No effect level of simazine after 96 hours exposure was
2.5 ppm.
Simazine at 1.0 ppm does not inhibit shell growth nor
cause any mortality. DDT caused 50% reduced shell growth
at 0.24 ppm and 35% mortality at 0.5 ppm.
The no-effect level for Pink Shrimp was 75 mg/L and 1000
mg/L for Mud Crab after 96 hours of contact with simazine.
Very little data are available on the degradation products of siaazine
in fish or lower aquatic organisms. In one study on the metabolism of slaa-
zine in fish (8), the major portion of the extractable residues in fish
tissues consisted of the parent herbicide plus the mono- and dl-deethylated
derivatives. Small amounts of the hydroxy siaazine and its metabolite8 were
also found.
4.3 WILDLIFE
Simazine is considered of "low" toxicity to warm-blooded animals. The
acute oral LD50 for rats, mlce and rabblts ^ ^^ ^ ^
(5,8). Two-year chronic oral feeding studies in which male and female rats
were given daily dosages of simazine at various rates as high as 100 ppm in
A-286
-------
the diet resulted in no observable systemic toxicity due to ingestion (47).
Little data are available in the literature on toxicities of simazine to
wildlife. A toxicological investigation on bobwhite quail and mallard ducks
has reportedly shown simazine to have very low toxicity (5,28); no mortality
was observed at treatment levels as high as 5000 ppm.
Dietary levels of 2.0 and 20.0 ppm simazine given to mallard ducks
before and during normal egg production cycles had no observable ill effects
on reproductive capacities (74).
4.4 BENEFICIAL INSECTS
Limited studies conducted on simazine have shown no insecticidal activi-
ty at usual application rates (5,28). According to Beran (75), simazine is
"harmless" to bees.; In a study by Sonnet (76), addition of simazine to car-
baryl and other insecticides at sublethal insecticide doses fed to bees
showed no increase in mortality.
In an experimental program on the effect of simazine on worms (nematodes,
enchytraea and annelides) and soil mites (acari) in an experimentally planted
forest garden and a grass-covered pine culture near Munich, Germany, Baimber,
et al. (77) found that high dosages of simazine (5 and 7.5 kg/ha) inhibited
the growth of the soil animals in the forest garden but increased the popu-
lation in the pine culture. Other laboratory studies by Baimber (77) of
simazine on moss mites also showed that high dosages can reduce the survival
times of fasted mites.
Results of toxicological investigations conducted by Mauck, et al. (47)
on the distribution of 0.1, 0.3, 1.0, and 3.0 Vg/ml simazine in*various
Insects in four 0.25-acre ponds are summarized in Table 6. The insects sam-
pled were dragonfly nymphs and midge larvae in the control pond and the ponds
treated with 0.1 and 0.3 ug/ml, and mayflies (Hexagenia so.) in the ponds
treated with 1.0 and 3.0 pg/ml. Simazine residues in these organisms were .
directly proportional to the amounts applied, and residues persisted for
more than one year. As noted in the table, residue concentrations are highest
immediately after simazine application but subsequently decline.
A-288
-------
4.5 MICROFLORA
Simazine is relatively harmless to soil microorganisms and at normal
application rates, it generally has no appreciable adverse effects on total
numbers in soil (78,79,80). The effects of simazine on microorganisms active
in the nitrogen cycle and on cellulolytic organisms were studied in the la-
boratory and in the field by Torstensson (81). Although the former organisms
were insensitive to simazine at normal and higher than normal field applica-
tion rates, the latter organisms were stimulated by simazine at both concen-
t rat ions.
Limited studies have shown minor fungicidal activity of simazine (5)
However, in a study by Nayyar, concentrations of 2.5, 5.0, and 10 ppm sima-
zine in sandy loam soil slightly striated the fungal populations (82).
4 . 6 BIOACCUMULATION
The bioaccumulation of ,i»Iln. in fish and other a,uatic invertebrates
»ay be considered ••!„,,••. Littl. „ no
^
ported in fish> dragonfly ny«phs, midge Urvae and BayfHe, in . study on
^ °-1> °'3> 1'°> "* 3'° "8/ml Sta"lM * f°«< ••»-
d
pond, by Mauci, et .1. (.„. rlsh studlM usln ^^
residue, in the range of on. to «. tl»es the concentration in the
(8). Field studies in treated ponds indicated one to four tlW. the
concentration in rater: the higher value «. pO88lbly due to the ingestion
7rr,rr.: r— r: — •
exposure to the simazine (83).
The bioaccumulation of 14C-labell«»H 0^n ^ u
and alBae) in at*M , „ ^belled simazine by microorganisms (daphnids
and algae) in static and flowing aquatic model ecosystems was studied bv
Isensee and Yockia (84)- the remm-* A , studied by
she™ in Table ,. LL t J" o T "— """- """•
reached an e^ukriu. ti . ^ o L ^ H *! "" "'"= '"""
not accurate appreciable additi^ ™«
ratios are lo* and indicate
A-290
-------
TABLE 7. ACCUMULATION OF ^C-SIMAZINE BY DAPHNIDS AND ALGAE IN AQUATIC MODEL ECOSYSTEMS (84)
to
\0
Organism
Daphnids*
Algae**
Experiment
Static
Flowing
Static
Flowing
Treatment*
0.1
1.0
10.0
0.1
L.O
10.0
0,1
1.0
10.0
0.1
1.0
10.0
1 3
os o
(0)»
0.01 0.01
(1)
0.21 0.20
(1)
0.19 0.19
(32)
0.35 0.09
(53)
0.23 0.19
(4)
0 0
(6)
0.02+0.07 0.04+0.02
(4)
0.19+0.09 0.35+0.05
(3)
0 0
(3)
0.10 0.20+0.03
(9)
0.06 0.23+0.03
u7
Days after
7
0.1
(7)
0.03
(2)
0.21
(1)
0
(0)
0.14
(19)
0.17
(*•
0.01
(4)
0.03+0.01
(2)
0.46+0.03
(3)
0.20+0.19
0.18+0.25
(«)
1.15+0.39
(20)
start of
15
0.01
0.02
O.22
0.13
0.17
0.81
0.01
0.06+0.02
0.38+0.06
0.09+0.08
0.22+0.06
1.72+0.64
experiment
30 35f 42
0
0.02
0.31
0.41
1.09
3.11
0.01+0.01 0 0
0.11+0.01 0.05+0.02 0.05+0.02
0.91+0.12 0.40+0.04 0.75+0.39
0.04+0.07 0.04+0.04 0
0.28+0.06 0.06+0.06 0.07
1.54+0.44 1.27+0.31 0.92+0.46
•Concentration of simazine adsorbed to 400 grans soil (static, ppm) and theoretical concentration introduced into its water
(flowing, ppb).
^After day 30 the organisms wete allowed to desorb in untreated water.
baphnta meqna.
tissue concentration (ppn) based on total WC analysis (sinazine plus metabolites).
Bioaccumulatlon ratios (in parenthesis) - tissue concentration/water concentration.
Oedogonium cardiacum.
-------
Based on analysis of urine and feces samples which indicate absence of
intact simazine, it is concluded that simazine is metabolized rapidly by
animals and is non-bioaccumulable (2). Feeding goats and cows with 1 mg/kg
simazine resulted in transient milk residues which reached a maximum concen-
tration between 8 and 24 hours after feeding, then declined rapidly to the
limit of detection within 2 to 4 days (1). Cow feeding studies at levels up
to 80 ppm simazine in the total diet resulted in only trace net residues in
milk (0.01 to 0.02 ppm) (8). The metabolic degradation products of simazine
in animals include hydroxy simazine, N-dealkylation products (e.g., 2-hydroxy-
4-amino-6-ethylamino-s-triazine), side-chain modified simazine (i.e., via
oxidation of the ethyl group to carboxylic acid), and conjugation products
(1,8). Hydroxy simazine, and N-dealkylation and conjugation products are
generally rapidly excreted in the urine with no bioaccumulation (1).
5.0 MISCELLANEOUS
As indicated in Section 1.0, commercial wettable powder formulations of
simazine contain up to 80 percent active ingredient and 20 percent "inerts".
None of the inert materials are considered very toxic or hazardous.
In a study on the effectiveness of the herbicide glyphosate on various
plant species, it was determined that there is an appreciable loss of activi-
ty of glyphosate if wettable powder formulations are mixed and applied with
simazine (85).
A-292
-------
REFERENCES
1. Kearney, P.C. and D.D. Kaufman. Degradation of Herbiciees. Vols. 1
and 2. Marcel Dekker, Inc., Hew York, 1975. 1058 pp.
2. Witt, J.S. and D.M. Baumgartner, A Handbook of Fersticide Chemicals
for Forest Use. Forest Pesticide Shortcourse. Washington State Uni-
versity and Oregon State University, 1979. pp. 9-10.
3. Pesticide Uses in Forestry. National Forest Products Association,
Forest Chemicals Program, Washington, B.C. 1980. pp. 3, 62, 97.
4. Newton, N. Herbicide and Insecticide Technical Properties and Herbi-
cide Use Guidelines. F-432, September 1979, 22 pp.
5. Mullison, W.R. Herbicide Handbook of the Weed Science Society of
America. Weed Science Society of America, Champaign, Illinois, 4th
Edition. 1979. 518 pp.
6. 1980 Faro Chemicals Handbook. Meister Publishing Co., Wllloughby,
Ohio. p. D-25. .
7. Gunther, F,A. and J.A. Gunther, eds. Residue Reviews, 36: 427-440.
1971.
8. Information provided by EPA, based on review of the Registration Files
by the Ecological Effects Branch.
9. Audus, L.J. (ed.) The Physiology and Biochemistry of Herbicides,
Bedford College, London, England. 1964.
10. Foy, C.L. Volatility and Tracer Studies with Alkylamino-s-Triazines.
Weeds, 12: 103-106, 1964.
11. Kearney, P.O. Summary and Conclusions. In: Residue Reviews, 32: 391-
399, 1970.
ti I Klineebiel. A Study of the Mechanism of Deto-
Ss-TrSzinesf Weed Science Society of America,
Abstract, p. 202, 1969. In Reference 55.
13. Montgomery, M. and V.H. Freed. WeedB, 9: 231, 1961. In Reference 1.
14. castelfranco, P.. C.L. Foy, and D.B. Deutsch. Weeds, 9: 580, 1961. In
Reference 1.
•15. Gysin, H. and E. Knulsi. Advances in Pest Control Research, 3: 289,
1960. In Reference 1.
A-293
-------
16. Kaufman, D.D., P.C. Kearney, and T.J. Sheets. Microbial Degradation
of Simazine. J. Agr. and Food Chemistry, 13(3): 238-242, 1965.
17. Foy, C.L. Weeds, 12: 103, 1964. In Reference 1.
18. Kearney, P.C., T.J. Sheets, and J.W. Smith. Volatility of Seven s-
Triazines. Weeds, 12: 83-87, 1964.
19. Weidner, C.W. Degradation in Groundwater and Mobility of Herbicides
NTIS PB-239-242. University of Nebraska, Lincoln, Nebraska, 1974
77 pp.
20. Paris, D.F. and D.L. Lewis. Chemical and Microbial Degradation of Ten
Selected Pesticides on Aquatic Systems. Residue Reviews, 45: 95-124,
21. Mitchell, L.C. J.A.O.A.C., 44: 643, 1961. In Reference 1.
ference l". " J'D* **""' "* ***' ^ W6ed8' 13: 43» 1965' In Re-
'
* Asricultural ™* Food Chemistr -
1964. y* Asricultural ™* Food Chemistry, 12(4) : 324-331,
on revieu
A-294
-------
31. Hartley, G.S. Herbicide Behavior in Soil. I. Physical Factors and
Action Through the Soil. In L.J. Audus (ed.) The Physiology and Bio-
chemistry of Herbicides, p. 111. Bedford College, London, England.
1964. In: Residue Reviews, 32: 175-210, 1970.
32. Owen, L.B. and W.M. Edwards. Relation of Agricultural Practice to
Water Quality in North Appalachian Region. U.S. Dept. of Agriculture,
Watershed Research Station, Coshocton, Ohio. Grant No. 0043388, 1979.
Abstract.
33. Von Rumker, 0., E.W. Lawless, and A.F. Meiners. Production, Distribu-
tion, Use and Environmental Impact Potential of Selected Pesticides.
EPA 540/1-74-001. U.S. EPA, Office of Pesticide Programs, Washington,
D.C. 1975, pp. 211-217.
34. Sheets, T.J. Persistence of Triazine Herbicides in Soils. Residue
Reviews, 32: 287-310, 1970.
35. Gile, J.D., J.C. Collins, and J.W. Gillett. The Fate of Selected Her-
bicides in a Terrestrial Laboratory Microcosm. Corvallis Environmental
Research Laboratory, Corvallis, Oregon, 1979. 21 pp.
36. Burschel, P. Weed Research, 1: 13, 1961. In Reference 9.
37. Roadhouse, F.C.B. and L.A. Birk. Canadian Journal of Plant Science,
4: 252, 1961. In Reference 9.
38. Aelbers, E. and K. Homburg. Die Inactivering en Pentratie van Simazime
in de Grand. Mededel Landbouwhogeschool en Opzoekingsst. Staat Gent.
24: 893, 1959. In Reference 34.
39. McCormack, M.L. Simazine Residue Analyses, Wolcott, CT. 1972. 10 pp.
40. Walker, A. Simulation of Herbicide Persistence in Soil. 1. Simazine
and Prometryne. Pesticide Science, 7(1): 41, 1976. Abstract.
41. Sheets, T.J. Persistence of Triazine Herbicides in Soils. Residue
Reviews, 32: 287-310, 1970. Abstract.
42. Slack, C.H., R.L. Blevins, and C.E. Rieck. Effect of Soil pH and
Tillage on Persistence of Simazine. Weed Science, 26(2): 145-148, 1978.
43. Burnside, O.C., et al. Effect of Soil and Climate on Herbicide Dissi-
pation. Weeds, 17: 241-245, 1969. In Reference 42.
44. Harris, C.I. and T.J. Sheets. Influence of Soil Properties on Absorp-
tion and Phytotoxicity of CIPC, Diuron, and Simazine. Weeds, 13: 215-
218, 1965. In Reference 42.
45 Harris, C.I., E.A. Woolson, and B.E. Hummer. Dissipation of Herbicides
at Three Soil Depths. Weeds, 17: 27-31, 1969. In Reference 42.
A-295
-------
46 Walker A. Simulation of the Persistence of Eight Soil-Applied Herbi-
cides. Weed Research, 18: 305-313, 1978.
47 Mauck, W.L., F.L. Mayer, Jr., and D.D. Hclz. Siaiazine Residue Dynamics
in Small Ponds. Bulletin of Env. Contamination and Toxicology, 16(1):
1-9, 1976.
48. Armstrong, D.E., C. Chesters, and R.F. Harris. Atrazine Hydrolysis in
Soil. Soil Science Society of American Proceedings, 31(1): 61-66, 1967.
49. Khan, S.V. Kinetics of Hydrolysis of Atrazine in Aqueous Fulvic Acid
Solution. Pesticide Science, 9: 39-43, 1978.
50. Armstrong, D.E., G. Chesters, and R.F. Harris. Soil Science Society of
America Proceedings, 31: 6, 1967. In Reference 1.
51. Agundis, 0. Thesis, University of Minnesota, Minneapolis. 1966. In
Reference 1.
52. Obien, S.R. and R.E. Green. Weed Science, 17: 509, 1967, In Reference
1.
53. Kearney, P.O., D.D. Kaufman, and T.J. Sheets. Metabolites of Simazine
bv Aapergillua fumigatus. J. Agr. Food Chemistry, 13: 369-373, 1965.
In: Soil Biol. Biochem. 2: 73-80, 1970.
54. Plimmer, J.R. and P.E. Kearney. Free Radical Oxidation of Pesticides.
Weed Science Society of America, Abstract, p. 20, 1968. In Reference
55.
55. Newton, N. and J.A. Norgren. Silvicultural Chemicals and Protection of
Water Quality. EPA-910/9-77-036. U.S. EPA, Region X, Seattle, Washing-
ton. June 1977, 240 pp.
56. Burnside, O.C., E.L. Schmidt, and R. Behrens. Weeds, 9: 477, 1961.
In Reference 9.
57. Guillemat, J. C.R. Academy of Science, Paris, 250: 1353-4, 1960. In
Reference 9.
58. Strzelec, A. Microbial Degradation of Simazine. Inst. Ubrawy Nawozenia
Blebnzn, Pulawy, Poland. Roczniki Gleboznawcze, 75(2): 31-3, 1973.
Abstract.
59. Yel, R. Decomposition of Konnatural Compounds by Microorganisms. Izv.
Akad. Nauk SSR, Ser. Biology 11(3): 301-312, 1973. Abstract.
60. Voinova, G., Jr. and D. Bakalivanov, Jr. Detoxification of Certain
Herbicide Aminotriazines by Soil Bacteria. Meded. R'yksfac. Landboruv-
wetensch Gent., 35(2): 839-46, 1970. Abstract.
61. Harris, C.I. J. Agricultural Food Chemistry, 15: 157, 1967. In Re-
ference 1.
A-296
-------
62. Skipper, H.D., C.M. Gtlmour, and W.R. Furtick. Soil Science Society
of America Proceedings, 31: 653, 1967. In Reference 1.
63. Strzelec, A. Microbial Degradation of s-Triazine Herbicides in Soil.
Postepy Nauk Roln. 21(2): 23-29, 1974. Abstract.
64. Ragob, M.T.H. and J.P. McCollum. Weeds, 9: 72-84, 1961. In Reference
9.
65. Suss, A. Private communication, Boyer, Landesanstalt fur Bodenkultur,
Pflanzenbau und-schutz, Munich, 1967. In Reference 1.
66. Suss, A., C. Eben, and H. Siegmund. Z. Pflanzenkrankheiten, Sonderheft,
6: 43, 1972. In Reference 1.
67. Ramsteiner, K.A., W. Hermann, and D. Eberle. Z. Pflanzenkrankhelten
Sonderheft, 6: 43, 1972. In Reference 1.
68. Kozlowski, T.T. and J.E. Kuntz. Effects of Simaaine, Atrazine, Propa-
zine and Eptam on Growth and Development of Pine Seedlings. Soil
Science, 95(3): 164-174, 1963.
69. Neururer, H. Zur Kenntis der Auswirkung von Herbizideniia Boden. I.
Mitteilung Untersuchung uber die Fruchtfolge. Pfanzenschutzbevs 28:
145, 1962. In Reference 34.
70. Fischer, B.B. and A.H. Lange. Orchard Weed Control, Irrigation and
Phytotoxicity from Simazine and Diuron. In: Research Progress Report.
Western Society of Weed Science. March 19-21, 1968, Boise, Idaho.
p. 52-54.
71. Leonard, D.A. and L.A. Lider. Response of Grapes to Several Years
Application of Soil Applied Herbicides. Abstract of Meeting of Weed
Society of America, February 1969, p. 51.
72. Singh. B., et al. Effects of Foliar Applications of s-Triazine on
Protein, Amino Acids, Carbohydrates, and Mineral Composition of Pea and
Sweet Corn Seeds, Bush Bean Pods, and Spinach Leaves. J. Agr. Food
Chenu 20(6): 1256, 1972.
73. Mayer, F.L. and H.O. Sanders. Slnazine Effects on Non-Target Aquatic
Organisms: A Preliminary Report. Fish and Wildlife Service U.S. Dept.
of Interior, Columbia, MO. Proceedings of the-30th Annual Meeting of
the Southern Weed Science Society, 1977.
74. Fink, R. The Effect of Simazine on the1ReP"Jucti^RC;pa^"ty °f
Mallard Ducks. Toxicol. Appl. Pharmacal. 31(1): 188-9, 1975.
75 Beran. F. Current Stand of Our Knowledge Concerning the Toxicity and
Health Hazards of our Plant Protection Agents for Bees. Besunde Pflan-
zen, 22: 21-31, 1970. In Reference 48.
A-297
-------
76 Sonnet, P.E. Toxicity of Pesticide Combinations and Pesticide Metabolic
Products to Honey Bees. U.S. Department of Agriculture, Agricultural
Research Service, Bee Disease Laboratory, Laramie, Wyoming. Grant No.
0043737, 1978. Abstract.
77. Baumber, W., et al. The Effects of the Herbicides Paraquat and Sima-
zine on the Fauna in Forest Soils. Anzeiger fur Schadlingskunde, 51(1):
1-5, 1978.
78. Bondarenko, D.D. Dissertation Abstracts, 17: 2109-10, 1967. In Re-
ference 9.
79. Kratochvil, D.E. Weeds, 1: 25-31, 1961. In Reference 9.
80. Ponchon, J., P. Tardieux, and M. Charpentier. C. R. Academy of Science,
Paris, 250: 1555-6, 1960. In Reference 9.
81. Torstensson,.L. Effects of MCPA, 2,4,5-T, Linuron and Simazine.on
Some Functional Groups of Soil Microorganisms. Swedish J. Agricultural
Research, 4(3): 151-160, 1974. Abstract.
82. Navyar, V.K., Jr., N.S. Randhawa, Jr., and S.L. Chopra, Jr. Effects of
Sioazine on Nitrification and Microbial Population in a Sandy Loam Soil.
Indian J. Agricultural Science, 40(5): 445-51, 1970. Abstract.
83. Rodgers, C.A. Uptake and Elimination of Simazine by Green Sunfish
(Lepomis Cyanellus). Weed Science, 18(1); 134-136, 1970. Abstract.
84. Isensee, A.R. and R.S. Yockim. Freshwater Micro-Ecosystem Development
and Testing of Substitute Chemicals. EPA-600/3-80-008, U.S. EPA En-
vironmental Research Laboratory, Duluth, MN( January 1980, 36 pp!
85. Crowning Points, Central Coast Counties. University of California
Cooperative Extension. June 1979. 4 pp.
A-298
-------
Common Name: Triclopyr
Chemical Name: 3,5,6-trichloro-2-pyridinyloxyacetic acid
Major Trade Names: GarIon 3A; GarIon 4
Major Applications Used on an experimental basis in the Northeast, the
in Forestry: Pacific Northwest end the South, primarily in site
preparation and occasionally in conifer release for
woody plant and broadleaf weed control.
SUMMARY
Triclopyr is a relatively new herbicide which has been commercially
available only in the past few years. Accordingly, very little data are
available in connection with its efficacy and environmental fate and impacts.
The limited available data are largely from laboratory and/or field studies
conducted by the manufacturer on non-forest systems.
The mechanism of triclopyr uptake by plants is through both leaves and
roots. It induces characteristic auxin-type responses in plants. Triclopyr
is not considered a persistent compound in soils; it degrades rapidly, with
an average half-life of 46 days. The major route of degradation in soil is
via microbial decomposition. Degradation of triclopyr does not occur to
any appreciable extent via chemical hydrolysis or other chemical routes in
soil. Triclopyr losses due to volatilization are not appreciable.
Triclopyr is considered a mobile, herbicide. Leaching and desorption
are lowest in soils with high organic matter content. Because of its mobi-
lity and rapid desorption from soil particles, some loss of triclopyr due to
solubilization and/or runoff may be expected following field application.
Although it is stable to hydrolysis in aqueous solution, triclopyr photo-
degrades rapidly with a half-life of 10 hours at 25°C.
Triclopyr can cause injury to conifers, particularly at high rates of
application and is not generally recommended for conifer release. When
applied directly, it exhibits phytotoxicity to agricultural crops. Triclopyr
has low toxicity to fish and lower aquatic organisms and does not bioaccumu-
late in these species. It exhibits low toxicity to wildlife and is con-
sidered non-toxic to soil microorganisms.
A-299
-------
1.0 INTRODUCTION
Triclopyr is an auxin-type herbicide for the control of many woody
plants and annual and perennial broadleaf weeds. It has only recently been
registered for use in forestry and it is used primarily on experimental
rather than commercial scales for site preparation (1,2,3) and occasionally
in conifer release (4,5). These uses are in the Northeast, the Pacific
Northwest, and the South (5,6). It is not registered for use in California
(3). No quantitative data are available on the extent of the uses in the
Northeast and South, although it is estimated that about 100 acres in
Washington, Oregon and California were treated with triclopyr in 1979 (about
only 5 of the 100 acres were in California) (3). Due to production capacity
limitation, the use of triclopyr in certain regions has been restricted by
the manufacturer (Dow Chemical Co.) to extend the supply and make it avail-
able to new potential users (3). Most current experimental uses in the
Pacific Northwest are ground applications for stump treatment and tree in-
jection (4,7). Recommended rates for aerial spraying are 2-3 gallons/acre
(Garlon 3A) for broadcast application by low-volume ground or helicopter
equipment, and one-half to one gallon/100 gallons water for high volume,
full spray coverage (4,8). Triclopyr may be used in combination with 2,4-D,
Tordon 101, Esteron 99, or DMA 4 for forest site preparation (1,9,10).
According to the manufacturer, triclopyr is effective for the control
of the following woody species: alder, arrowwood, ash, aspen, beach, birch,
blackberry, blackgum, cascara, chamise, choke cherry, cottonwood, crataegus
(hawthorn), dogwood, elderberry, elm, hazel, hickory, hornbeam, locust,
maples, mulberry, oaks, persimmon, pine, poison oak, poplar, salmonberry,
sassafras, sumac, sweetbay magnolia, sweetgum, sycamore, thimbleberry, tulip
poplar, willow, and winged elm (1,11). Among the annual and perennial broad-
leaf weeds controlled are: burdock, chicory, curled dock, dandelion, field
bindweed, lambsquarters, plantain, ragweed, smartweed, vetch and wild let-
tuce (1). It is not effective for control of most grasses.
Triclopyr is also recommended for the control of woody and herbaceous
weeds'in non-crop areas including industrial manufacturing and storage sites,
and rights-of-way such as electric power lines, communication lines, pipe-
lines, roadsides and railroads. Triclopyr induces characteristic auxin-type
A-300
-------
responses In plants (8); i.e., it regulates longitudinal cell structure so
as to control bending of the stalk or stem in phototropic responses (.12).
It is absorbed by both leaves and roots, and is readily translocated through
the plant (8). Maximum plant response is achieved when application is made
soon after full leaf development (8) .
Triclopyr is manufactured by Dow Chemical USA, Ag-Organics Dept. (13).
It is produced in two major formulations (8): Garlon 3A and Garlon 4.
Garlon 3A contains 44.4 percent active ingredient as the triethylamine (TEA)
salt, which is equivalent to 31.8 percent acid equivalent and is present in
the formulated product at 3 Ibs acid equivalent/gallon. This water-soluble
formulation also contains methanol. Garlon 3A is also available as Experi-
mental Herbicide M-3724 in areas where the Garlon 3A label has not been
approved (8), Garlon 4 is an oil-soluble water-emulsif iable ethylene glycol
butyl ether ester (EGBE) formulation containing 4 Ibs of triclopyr acid
equivalent/gallon (8). Surfactants may be added to Garlon 3A formulations
to improve its effectiveness (1). Water is the usual carrier for foliar
sprays; fuel oil is used for basal sprays (14).
2.0 PHYSICAL/CHEMICAL PROPERTIES OF ACTIVE INGREDIENT
The active ingredient of triclopyr is 3,5,6-trichloro-2-pyridinylOXy-
acetic acid:
It is a white, odorless solid with melting point of 148-150«C. Solubility
in various solvents at 25°C is (14):
Solvent I/Si ^ilveSt */»!
no Q n-hexane 0.041
Acetone **•*
. ., 126 n-octanol 30.7
Acetonitrile 12."
7 73 Xylene 2.79
Benzene Z*'J • •
, 73 Water 0.043
Chloroform 2./J
Vapor pressure data are shown below as a function of temperature (14):
A-301
-------
Temperature mm Hg
25 1.26 x 10~6
40 5.30 x 10~
50 1.03 x 10~5
70 1.04 x 10~A
3.0 ENVIRONMENTAL FATE
Being a very new pesticide, the fate of triclopyr in the environment
(especially the forest environment) following application has not been the
subject of much scientific investigation. The very limited data which have
been reported are from studies performed or sponsored by the manufacturers
and pertain to non-forest environments.
3.1 UPTAKE AND METABOLISM BY PLANTS
Limited studies have been conducted on the uptake of triclopyr by plants.
As noted previously, it induces auxin-type responses in plants. It is ad-
sorbed by both leaves and roots, and is readily translocated throughout the
plant (8).
The effects of photoperiod and temperature on the translocation of tri-
clopyr were studied by Radosevich and Bayer (15) on tanoak, snowbrush ceano-
thus, bigleaf maple, beans and barley. Translocation of triclopyr was
observed to be greatest under warm temperatures and long-day photoperiods.
With colder temperatures and short-day photoperiods, movement was greatly
reduced. Following application directly to leaves, triclopyr was observed
to move readily in the symplasts, with the preponderance remaining in the
shoot. Applications to the roots resulted in very little apoplastic mobili-
ty. In a subsequent study on absorption of triclopyr by tanoak, greater
amounts were absorbed by Immature leaves than mature leaves and by abaxial
surfaces containing large stomatal densities than by axial surfaces (16).
No data are available on the metabolic degradation (if any) of triclo-
pyr in plants.
3.2 FATE IN SOIL
In general the fate of a pesticide in soil can be described in terms of
six factors: volatilization, photodecomposition, adsorption/leaching, run-
off, and chemical and microbial degradation. Although actual field data are
A-302
-------
unavailable, volatilization is not considered to be a significant contributor
to the loss of triclopyr following application because of the very low vola-
tility of triclopyr (see Section 2.0). No data are available on the photo-
degradation (if any) of triclopyr in soil. However, based on photodegradation
data for water (see Section 3.3), it is likely that photodegradation of
triclopyr may occur in soil and from foliar surfaces. The adsorption/leaching
and degradation data which have been submitted by Dow to EPA in support of
registration applications for various uses of triclopyr are discussed in the
following sections.
3.2.1 Adsorption, Leaching and Runoff
Triclopyr is considered a mobile herbicide (9). It is rapidly and re-
versibly adsorbed on soil particles. The extent of adsorption is primarily
a function of soil type. Soil organic matter is the principal soil parameter
responsible for adsorption, with increasing soil organic matter resulting in
increased adsorption (9). Several laboratory studies have been conducted on
the adsorption of the C labelled triethylamine salt of triclopyr by 12
soils (17). The organic carbon content of the soils ranged from 0.081 per-
cent to 21.7 percent. Adsorption coefficients K, and K were measured and
a oc
ranged from 0.016 to 14.5, and 12 to 78, respectively, indicating mobility.
In a study using 3 soil types, the principal degradation product of triclopyr
(trichloropyridinol) was found to have K, and K adsorption coefficients
d oc r
of 0.63 to 5.64 and 114 to 156, respectively, indicating low-to-intermediate
mobility (18). No quantitative data are available on the effects of pH on
triclopyr adsorption; because of its weakly acidic character, however, ad-
sorption is expected to be favored under acidic conditions.
The adsorption capacity of a given soil type affects the potential for
leaching of the herbicide from soil. Based on available limited data, it
appears that triclopyr is leachable but that leaching should be less pro-
nounced in soils with high organic matter content than in soils with lower
organic matter content. Results of a leaching study using a low organic
matter content soil (loam sand, 0.62 percent organic carbon) leached with
0.5 inches of water per day for 45 days showed that 75 percent to 80 percent
of the triclopyr leached through the 12-inch soil column between days 11-15
(19). The trichloropyridinol degradate was found to be significantly less
A-303
-------
leachable; while the triclopyr moved through the column after about 7.5
inches of water were applied, the degradate required 13 inches of applied
water to completely pass through the column. In a study of 6 soils under
test plot field condition in 6 states, small amounts of triclopyr and its
degradates were observed in the 6-12 inch and 12-18 inch soil layers between
28 and 56 days following application of GarIon 3A at a rate of 3 gallons/
acre and normal rainfall conditions (20). The trichloropyridinol degradate
was less leachable and showed maximum residues in the 0 to 6 inch soil layer
between 28 and 56 days after application and declined thereafter. The tri-
chloromethoxy pyridine degradate remained around 0.1 ppm or less at all
sample intervals. The six soil types tested were Tiffon, Georgia loamy sand;
Fargo, ND clay; Corvallis, or hazelaire comples; Benchley, TX clay to clay
loam; Arthurdale, WV unspecified soil; and Laramie, WY Forelli fine sandy
loam.
Because of its mobility and rapid desorption from soil particles, some
loss of triclopyr due to solubilization and/or runoff may be expected fol-
lowing field application after rainfall. This was confirmed by results of
several small-scale water monitoring programs in which residues of 6 ppb
were observed in runoff water 5 months after application and 1 ppb was ob-
served 9 months after application of 3 Ib/acre triclopyr as the triethyl-
amine salt, and after 150 cm of natural rainfall (21).
3>2'2 Chemical and Microbial Degradation
Triclopyr is not considered a persistent compound in soils. Laboratory
studies have shown that triclopyr is decomposed quickly by soil microorgan-
isms (9,14). Microbial degradation results in the formation of 3.5,6-
trichloro-2-pyridinol and trichloromethoxypyridine (9,22). The average
half-life in soil is 46 days with the actual value dependent on soil type
and climatic conditions (14). Studies on the aerobic soil degradation of
radio-labelled triclopyr indicated degradation to trichloro-2-pyridinol with
a half-life between 79 and 156 days at 15°C. and less than 50 days at 25-35'C
(9,22,23). The trichloro-2-pyridinol subsequently degraded to trichloro-
methoxypyridine. and eventually to CO, with 7 to 30 percent evolution of CO,
at 375 days. Half-lives of these secondary reaction products and the degra-
dation mechanisms have not been determined. The microbial degradation of
A-304
-------
triclopyr was shown to be approximately 5 to 8 times slower under anaerobic
conditions (i.e., waterlogging) than under aerobic conditions in a study
using Illinois silty clay loam and Mississippi silt loam at 25°C (24).
Trichloropyridinol degradation has been shown to yield mostly carbon
dioxide and some trichloromethoxypyridine (25). Tests with 15 soils from 10
major agricultural areas have indicated a half-life of 8 to 279 days for
trichloropyridinol. Twelve of the 15 soils showed half-lives of less than
90 days. Two unidentified degradates were found at 1.8 to 6.5 percent of
the initial radiolabelled trichloropyridinol. When the other degradate of
triclopyr, trichloromethoxypyridine, was studied, results showed extensive
degradation to carbon dioxide with estimated half-life of 50 days in two
soils (Commerce silt loam and Flanagan silty clay loam), but more than 300
days in another soil (Yoho loam) (26). Trichloropyridinol was also found as
a degradate of trichloromethoxypyridine.
In a study by Norris, et al. (27) of the fate of triclopyr on small
hillside pastures in southwestern Oregon applied at a rate of 3.36 kg/ha,
triclopyr residues were 350, 172, and 65 ppb at 6, 9, and 12 months after
application, respectively.
'Degradation of triclopyr in soil does not occur to any appreciable
extent via chemical hydrolysis or other chemical routes (9). Laboratory
studies using a silt loam soil have indicated that triclopyr does not degrade
in sterile soil, but does degrade rapidly in the same soil when it is not
sterilized (28).
3.3 PERSISTENCE IN WATER
Several laboratory studies conducted on the persistence and degradation
of triclopyr in water have indicated triclopyr is stable to hydrolysis in
buffered solutions for periods up to 9 months at pH 5, 7, and 8 and at 15,
25, and 35°C (29). Several photodegradation products, including 3,5,6-
trichloro-2-pyridinol and 2-methoxy-3,5,6-trichloropyridine, were formed in
minor amounts (less than one percent). -Chemical hydrolysis is thus not ex-
pected to be a major pathway of triclopyr degradation in the aqueous envi-
ronment.
The rate of triclopyr photodegradation in water is rapid in both natural
sunlight and in the laboratory; half-life is 10 hours in water at 25°C (14,
A-305
-------
30). The first degradation product is trichloropyridinol, which is rapidly
degraded to various pyridine polyols formed via photolytic hydrolysis of the
ring chlorine atoms (30). These primary and secondary photoproducts are
further degraded in the aquatic environment, Thus, photodegradation is a
major pathway for the-dissipation of triclopyr in aquatic environments.
4.0 IMPACTS ON NON-TARGET PLANTS AND ORGANISMS
At high application rates, triclopyr can cause injury to conifers and
is not generally recommended for conifer release. In a study of the aerial
applications of triclopyr and other herbicides in spruce-fir forests of
Maine (31), Garlon 3A applied at a rate of 4.4 kg/ha caused minor injury to
a small percentage of conifers, but at a rate of 2.2 kg/ha caused no injury.
Injury to conifers following triclopyr applications have also been reported
in the Pacific Northwest and in Sweden (5,32).
Triclopyr also exhibits some toxicity to agricultural crops, depending
on application rates. Triclopyr applied at a rate of 0.5 Ib a.i./acre showed
some inhibition of cucumber yields over periods of at least 3 months follow-
ing application, while rates of 3.0 and 9.0 Ibs a.i,/acre showed 50 percent
inhibition of cucumber yields after a period of at least 4 months (33).
Triclopyr applied at a rate of 0.5 and 1 ounce acid equivalents/acre had very
little noticeable effect on wheat and no noticeable effect in bean stands
planted 3, 8, 12, and 17 weeks after treatment (9). In general, most broad-
leaf crops will tolerate small quantities of triclopyr to a greater extent
than other auxin-type herbicides (14).
Since triclopyr is rapidly degraded by soil microorganisms, there would
not be sufficient residue carryover to cause injury to susceptible species
in the next growing season (8).
4.1 FISH .
Both triclopyr and the amine salt formulation Garlon 3A have very low
toxicity to fish and lower aquatic organisms (see Table 1). No data are
available on the fate and degradation products of triclopyr in fish or lower
aquatic organisms.
A-306
-------
TABLE 1. AQUATIC TOXICITY (96-HR AND 48-HR LC50Ts) OF
TRICLOPYR AND GARLON 3A (8,14)
Species
Bluegill
Rainbow trout
Oysters
Shrimp
Crab
Exposure
96 hr
96 hr
48 hr
96 hr
96 hr
Triclopyr
148 ppm
117 ppm
-.••••»
Gar Ion 3A
891 ppm
552 ppm
56-87 ppm
895 ppm
>1,000 ppm
A.2 ANIMALS
Based on tests with laboratory animals, both triclopyr and its formula-
tions are considered to have low toxicities to warm-blooded animals (see
Table 2).
TABLE 2. ACUTE TOXICITY'(ORAL LD50 AND LCSo) OF TRICLOPYR AND
ITS FORMULATIONS TO LABORATORY ANIMALS (8,14,34)
Species
^50
Rat (female)
Rat (male)
Rabbit (mixed)
Guinea pig
LC50 •
Mallard duck
Japanese quail
Bobwhite quail
Triclopyr
630 mg/kg
725 mg/kg
550 mg/kg
310 mg/kg
>5,000 ppa
3,278 ppn
,• i i i i • '•
Garlon 3A
2,140 mg/kg
2,830 mg/kg
- •' — — •
___
>10,000 ppn
— — -
11,622 ppm
Garlon , A
2,140 mg/kg
2,460 mg/kg
"• ~
>10,000 ppm
^**^
9,026 ppm
A-307
-------
Dosages of criclopyr of 30 mg/kg/day produced no carcinogenic effects
in mice and rats (34). Triclopyr was f ound to be non-mutagenic in dominant
lethal and host mediated assay tests (34). It is considered mildly fetotoxic,
exhibiting a reproductive toxicity effect at 200 mg/kg/day (34).
No data are available on the insecticidal activity of triclopyr on bene-
ficial insects.
4.3 SOIL MICROORGANISMS
Triclopyr is non-toxic to soil microorganisms. In a laboratory study
of the effect of 500 ppm of triclopyr on 6 soil microorganisms (Aerobaeter
aerogenes, Pseudomonas aeruginosa, Salmonella typhosa, Staphylococcus aureus.,
Aspergillus terreus,v and Pullularia pullulams), growth of the microorganisms
was compared to controls (35). After 72 hours of incubation, no apparent
effect was observed. The results of laboratory and field studies by Hallborn
and Bergman (36) showed that treatment of Peltigera praetextata lichen and
its free-living pshycobiant algae Nostoc sp. with GarIon 3A at rates typical-
ly used in forestry applications did not significantly affect the rates of
nitrogen fixation by either organism.
4.5 BIOACCUMULATION
Triclopyr and its degradates trichloropyridinol and trichloromethoxy-
pyridine do not accumulate to any appreciable extent in fish. Several labo-
ratory studies have indicated that these compounds do not accumulate in
edible portions of catfish or in fish heads, viscera or skiri8 (37). Mosquito
fish also do not accumulate significant residues of trichloropyridinol (37).
No data are available on the bioaccumulation of triclopyr in animals or
microorganisms.
A-308
-------
REFERENCES
1. Specimen label: Gar Ion 3A Herbicide. Dow Chemical Company, Midland,
MI. May 1979. 2 pp.
2. Stewart, R.E. and H. Weatherly. Aerial Sprays of Triclopyr for Brush
Control. Abstract. In: Research Progress Report, Western Society of
Weed Science, Portland, Oregon. March 1976. p. 41.
3. Telephone communication of Mr. Jack Warren, Technical Representative
for Dow Chemical. Co. in Pacific Northwest, to M. Ghas'semi, TRW. June
27, 1980 (Project Notebook No. 003, pp. 33-34).
4. Pesticide Uses in Forestry. National Forest Products Association.
Forest Chemicals Program, Washington, D.C. 1980. p. 101.
5. Weyerhaeuser Trip Data. Vegetation Problems, Control Methods for Coni-
fer Release. Weyerhaeuser Company, Tacoma, WA. 1979, 4 pp.
6. Northeast Trip Data. Herbicides in Forestry. Northern New England.
4 PP-.
7. Telephone communication of Mr. Doug Bells, State of Washington, Depart-
ment ^Natural Resources, to M. Ghassemi, TRW. June 30, 1980 (Project
Notebook No. 003, p. 35).
8. Dow Chemical USA, Technical Information on
dient of Garlon Herbicides. Technical Data Sheet, 1979, .
9. Information provided by EPA, based on review of Registration Files of
the Ecological Effects Branch.
10. Brooks, W., et al. Control of Undesirably Plants in Brushland Forests
and Rangeland. University of California, 1975. 28 pp.
1977. pp. 188-192.
12. Hawley, -C.C. The Condensed Chemical Dictionary, Van Nostrand Reinhold
Company, New York, 1971. p. 85.
13. 1980 Farm Chemicals Handbook. Meister Publishing Company, Willoughby,
Ohio, pp. 0-317.
-•
Edition, 1979. pp. 445-447
A-309
-------
L5. Radosevich, S.R. and D.E. Bayer. Effect of Temperature and Photoperiod
on Triclopyr, Picloram and 2,4,5-T Translocation. Weed Science, 27(1):
22-27, 1979.
16. King, M.G. and S.R. Radosevich. Tanoak (Lithocarpres densif lorus) Leaf
Surface Characteristics and Absorption of Triclopyr. Weed Science.
27(8): 599-604, 1979.
17. Hamaker, J.W. Adsorption of Triclopyr in Soil. Report No. GS-1390.
February 6, 1975. Summarized in Reference 9.
18. Hamaker, J.W. Adsorption of 3,5,6-Trichloro-2-pyridinol by Soils.
Report No. GS-1354. 1974. Summarized in Reference 9.
19. Hamaker, J.W. A 45-Day Soil Leaching Test on Triclopyr (3,5,6-trichloro-
2-pyridinyl) Oxyacetic Acid. Report No. GS-1469. February 7, 1977.
Summarized in Reference 9.
20. McKellar, R.L. Residues of Triclopyr, 3,5,6-Trichloro-2-pyridinol, and
2-Methoxy-3,5,6-trichloropyridine in Soil Treated With Garlon 3A Herbi-
cide. Report No. GH-C-983. April 11, 1977. Summarized in Reference 9.
21. Norris,. L.A., M.L. Montgomery, and G.D. Savelle, Behavior of Triclopyr
(Dowco 233) in Soil and Stream Water on a Small Watershed, Southwest
Oregon. Presented at Weed Science Society Meeting, 1976 Annual Meeting,
Denver, Colorado. Summarized in Reference 9.
22, Regoli A.J. and D.A. Laskowski. Aerobic Degradation of Ring-labelled
llfil 1
-------
29. Hamaker, J.W. The Hydrolysis of Triclopyr In Buffered Distilled Water.
Report No. GS-1410. Summarized in Reference 9.
30. Hamaker,, J.W. Photolysis of Triclopyr (0,5,6-trichloro-2-pyridinyl)oxy-
acetic Acid). Report No. GS-1467. February 11, 1977. Summarized in
Reference 9.
31. Northeast Trip Data, McCormack, M.L. and M. Newton. Aerial Applications
of Triclopyr, Phenoxys, Picloram, and Glyphoeate for Conifer Release in
Spruce-fir Forests of Maine. Abstract of Annual Meeting of Weed Science
Society of America, February 7, 1980. 8 pp.
32. Barring, V. Results of County-wide Trials in Forestry—Trials Into
Aerial Application of Glyphosate and Triclopyr Amine. Weeds and Weed
Control, 20th Swedish Weed Conference, Uppsala, Sweden, 1979. p. 82-93.
33. Zimdahl, R.L. Column Leaching Studies With Triclopyr and Picloram -
A Report. Colorado State University. Submitted to Dow Chemical Com-
pany, April*14, 1975. Summarized in Reference 9.
34. Data supplied to TRW by Dow Chemical Company, Midland, MI. September
1981.
35. Grittith, J.D. The Effect of Triclopyr on Soil Microorganisms. Report
No. GS-1456. September 28, 1976. Summarized in Reference 9.
36. Hallborn, L. and B. Bergman. Influence of Certain Herbicides and a
Forest Fertilizer on the Nitrogen Fixation by the Lichen Peltigera
praetextata. Oecologia (Berl.) 40: 19-27, 1979.
37. Hedlund, R.T. Determination of the Bioconcentration Potential of 3,5,6-
trichloro-2-pyridinol. Report No. GS-1282. November 24, 1972. Summa-
rized in Reference 9.
A-311
-------
II. INSECTICIDES
Common Name: Acephate
Chemical Name: 0,S-dimethyl acetylphosphoramidothioate
Major Trade Names: Orthene; Ortran; RE 12,420; Ortho 12,420; Ent 27822
Major Applications Control of spruce budworm and gypsy moth
in Forestry:
SUMMARY
Acephate is an organophosphate broad spectrum insecticide utilized in
forestry primarily for the control of spruce budworm and gypsy moth. Ace-
phate is a neurotoxin which kills insects both on contact and through
systemic action on chewing and sucking insect species.
The major pathways for removal of acephate from the environment are
I
acephate. The remaining acephate degrades into innocuous salts.
in soil At21' and 7 e8rfaton of aceP^te in water is slower than
TL50 for trout bgilcafish'SlOoS68 ^ ?°^City t0 flsh
50 r rout gilcafishlOo
ly alter feeding habits Non^^V PPo) althou8h It may temporari-
exposure to acephate ana acephate^ S"!!?* J°^Iati°n8 ~* Decrease after
yg/bee). it. is'considered to^e of low'toxicit^t'0 ^i «** °f l'2°
toxicity data, Monitor is considerably rn^re toxic ^vT^ ^ B^6d °n ^"
LD50 of 7.5 mg/kg for Monitor vs. 700^ S^" *"*
A-312
-------
1.0 INTRODUCTION
Acephate is an organophosphate broad spectrum insecticide manufactured
by Chevron Chemical Company, Qrthc Division, and marketed as Orthene. It
has been registered for commercial use on ornamentals, lawns, and non-crop
bearing trees and has since been registered for use on cotton, beans, celery,
head lettuce and sweet peppers to control a number of agricultural pests
(1). In commercial forestry, acephate is used both in seed orchards and in
forests. In seed orchards, Orthene "Tree and Ornamental Spray" is applied .
by ground spray rigs at a rate of 2/3 lb/100 gal water/acre. It is used on
conifer seed orchards to control Douglas-fir coneworm, gall midge, and other
cone and seed insects (2). In forests, Orthene "Forest Spray" is aerially
applied at a rate of 2/3 to 1-1/3 Ibs in 1 gallon/acre on stands of white
fir and other conifers to control western spruce budworm and Modoc budworm
(2). Orthene "Forest Spray" is also used at a rate of 1/2 to 3/4 Ib a.i./
acre for control of gypsy moth larvae (1), and it has been used to a limited
extent against the spruce budworm in Maine (3).
Acephate is neurotoxic to insects and other animals including man. Its
mode of action is the inhibition of acetylcholinesterase, the enzyme that
breaks down the neurotransmitter acetylcholine. Acephate kills insects on
contact and also passes from leaf surfaces into plant tissue where it gives
some systemic protection against chewing or sucking insects for approximate-
ly one week (4).
2.0 PHYSICAL/CHEMICAL PROPERTIES
Acephate, 0,S-dimethyl acetylphosphoramidothioate, has the following
structure:
CH,0. 0 0
P - NH
3"^ ' -|.
CHjS
It is a white crystalline solid when pure and is off-white in the technical
grade. It has a very low vapor pressure of 2 x 10" mm Hg at 25°C. It is
highly soluble in water (65 percent) and in polar organic solvents (e.g.,
25 percent solubility in methanol), and is slightly soluble in non-polar
A-313
-------
organic solvents (e.g., one percent solubility in benzene and 0.01 percent
olubility in hexane) (5) . The melting point of pure acephate is 92-93 C
and that of the technical grade is 82-89'C. Acephate is stable at 21«C but
decomposes at its melting point. In normal usage and storage, it is not
corrosive (4). Insecticide formulations of acephate contain 75 percent
active ingredient (5).
3.0 ENVIRONMENTAL FATE
The major pathways for removal of acephate from the environment are
uptake in plants, metabolism in soil, and leaching. Acephate does not
appear to photodegrade to an appreciable extent on surfaces or in water (5) .
Most of the breakdown products of acephate appear to have little or no toxi-
city. However, one breakdown product, methamidophos (Monitor) is a regis-
tered pesticide with toxicity and environmental persistence that is largely
similar to that of acephate.
3.1 FATE IN PLANTS
Acephate penetrates plant tissues quickly, within 24 hours (4). Exper-
iments on cotton plants indicate that greater than 80 percent of the acephate
applied disappeared from leaf surfaces within 24 hours; more than 50 percent
of the applied dose was recovered inside the plant after 24 hours (6). Un-
absorbed residues were essentially depleted in 48 hours. A small amount of
the absorbed acephate (about 9 percent of the dose) was metabolized to the
toxic insecticide, methamidophos, while less than 5 percent of the dose was
metabolized to at least four other products. Two of these were identified
as 0,S-dimethylphosphorothioate and S-methyl acetylphosphoramidothioate
which are non-toxic. The structures of these compounds are as follows:
CH.S 0
3 - CH3 SO O
CH O^ 7^ P-NH-6-CH-
3 HO --- 3
S-methyl acetylphosphoramidothioate
°H3S ^ 9
OiS-dimethyl phosphorothioate
A-314
-------
Residues on plant foliage are generally undetectable 70 to 75 days
after application. When acephate was aerially applied in New York for gypsy
moth control at rates of 0.78 and 0.56 kg a.i. per ha, the average residues
of Orthene in leaves after 24 hours were 30.8 and 11.1 ppm, respectively
(7). Residues were 0.21 ppm for the 0.78 kg/ha application rate 18 days
after spraying and were undetectable (0.02 ppm) within 75 days. Residues
from the 0.56 kg/ha application rate were undetectable 20 days after spray-
ing. Devine (7) also reported an average residue in litter of 5.5 ppm one
day after aerial application in Pennsylvania of 0.56 kg a.i./ha for gypsy
moth control. Twenty days after spraying, residues decreased to 0.03 ppm
and were undetectable after 70 days.
Szeto, et al. (8) found that acephate residues could no longer be de-
tected in Douglas-fir needles or in forest litter 60 days following applica-
tion of 1.12 kg/ha.
Half-lives of about 10 days have been reported for acephate and metha-
midophos in the rinds of various citrus plants sprayed with acephate (9).
Maximum penetration of residues in rind and pulp occurred within 7 days after
spraying.
3.2 FATE IN SOIL.
Acephate in soil can be readily leached. In one experiment, an amount
of water equivalent to 10 inches of rainfall was passed through acephate-
containing soil columns. In six tests with different soil types, this quan-
tity of water eluted from 62 percent to 100 percent of the acephate (1).
The smallest amount of leaching was in a muck soil with high organic content
and the highest values were in sandy soil. In separate experiments (1), the
rate of acephate movement through soil relative to the rate of water move-
ment was measured. These relative rates,, called Rf values, were between
0.5 and 1.0 for the six soil types. Furthermore, Rf values for methamidophos
were not significantly different from those of acephate. Therefore, neither
acephate nor methamidophos are tightly bound to soil to a significant extent,
and both are capable of rapid leaching from soil.
Acephate is rapidly degraded in soil. Half-lives of acephate at 1 to
10 ppm initial concentration levels in 9 different soil types have been
A-315
-------
reported to vary from 0.5 to 13 days (see Table 1) with the longest persis-
tence corresponding to a high organic muck soil (1,5). These data are from
laboratory experiments conducted under aerobic conditions with the soils
wetted to about field capacity.
TABLE 1. THE DEGRADATION OF ACEPHATE IN SOIL (5)
Soil Origin
Clarkesburg, Ca.
Fresno, Ca.
Kettleman City, Ca.
Ocoee, Florida
Mt. Holly, N.J.
Norwalk, Iowa
Greenville, Mississippi
Ocoee, Florida
Riverside, Ca.
Soil Type
Clay
Loam
Clay (high pH)
Loamy Sand
Sandy Clay Loam
Silty Clay Loam
Clay (low pH)
Muck
Loamy Sand
Half-life
1 ppm
1-1/2
1-1/2
1/2
1
1/2
—_
6
—
(Days)
10 ppm
1-1/2
3
1/2
1
1
2
1-1/2
13
A*
20 ppm fortification.
Monitor, the potentially toxic metabolite of acephate is also degraded
in soil and has a half-life range of 2 to 6 days based on Chevron studies.
Both acephate and Monitor degrade more rapidly in wet soil than in dry soil
(5).
The decomposition of both acephate and Monitor in soil is primarily due
to the action of soil microorganisms. Figure 1 shows the relative rates of
decomposition of acephate in two different soil types under sterile and non-
sterile (natural) conditions.. As shown in this figure, essentially little
or no acephate decomposition takes place in the sterile soil.
A-316
-------
DAYS
Figure 1. Rates of Decomposition of Acephate in Sterile and Non-sterile Soils (5)
-------
The following routes have been postulated for the degradation of ace-
phate in soil (5):
P-NH Monitor
CH S
?-OH
>)l II
P-NH-C-CH.
j
acephate
P-NH-C-CH
methyl' acetylphosphoramidioate
Further degradation
O,S-dimethylphosphorothioate
3.3 PERSISTENCE IN WATER
While acephate degrades rapidly in soil, its breakdown (hydrolysis)
rate in water is relatively slow. The rate is dependent upon pH and tempera-
ture (see Table 2) and is higher at higher temperature and pH levels.
TABLE 2. HALF-LIVES (IN DAYS) FOR ACEPHATE AND MONITOR IN WATER
AS A FUNCTION OF TEMPERATURE AND pH (5)
PH
3
5
7
9
——————___
Acephate
21° C
———————
65.5
55.2
46. A
16.1
40°C
— — — — _ .
29.4
29.7
16.5
2.5
• .
Monitor
21°C
22.0
107.8
44.0
9.2
i -
.„
40°C
8.4
45.1
9.8
4.8
A-318
-------
Acephate appears to be more susceptible to hydrolysis at high pH. In
a recent study, Szeto, et al. (10) studied the hydrolysis of acephate in
buffered distilled water over a pH range of 4.0 to 8.2 and incubated for 20
days at 20°C and 30°C. Their results are summarized in Table 3. They found
that acephate was quite resistant to hydrolysis between pH 4.0 and 6.9 re-
gardless of temperature; over 80 percent of the acephate was recovered in
this range, with greater recoveries at the lower pH. At pH 8.2, however,
temperature strongly affected hydrolysis - 78 percent was recovered at 20°C
whereas only 18 percent was recovered at 30°C. Higher amounts of monitor
were also detected at higher pH. The maximum level of Monitor was found at
pH 8.2 and 20°C. However, only 4.5 percent of the acephate added was con-
verted to Monitor.
TABLE 3. THE EFFECT OF pH ON THE HYDROLYSIS OF ACEPHATE IN BUFFERED,
DISTILLED WATER, HELD AT 20CC AND 30°C FOR 20 DAYS (10)
PH
Acephate
Recovered (pg)
X ± SD*
Monitor
Recovered (pg)
X ± SD*
Recovery in % of Acephate Added
Acephate Monitor
4.0
5.0
5.6
6.0
6.9
8.2
4.0
5.0
5.6
6.0
6.9
8.2
^^^^•MBNHM
978
927
882
861
842
779
955
902
838
830
825
178
20.8
15.5
17.5
16.1
15.5
8.5
21.0
18.8
15.0
14.1
6.9
13.0
20°C
Tt
T
T
T
10.0 0.4
44.6 0.5
30°C
4.9 0.2
T
T
T
16.7 1.9
43.3 2.9
97.8
92.7
88.2
86.1
84.2
77.9
95.5
90.2
83.8
83.0
82.5
17.8
0.2
0.2
0.2
0.2
1.0
4-5
0.5
0.2
0.2
0.2
1.7
4.3
*N
T (Trace) < 4 pg
Szeto, et al. (10) also studied the persistence of acephate in water
samples from two natural sources, pond water and creek water. The samples
were held at 9CC for 42 and 50 days, respectively. The results are
A-319
-------
presented in Tables 4 and 5. About 83 percent of the acephate was recovered
from pond water after 42 days while 45 percent was recovered from creek
water after 50 days. Rates of degradation increased greatly when sediments
were included in the samples. In the presence of sediments, only 15 percent
of the acephate was recovered from pond water (Table 6) and 25 percent from
creek water (Table 7). Autoclaving creek water prior to incubation with
acephate showed that a major factor in the disappearance of acephate was
microbial breakdown of acephate. In creek water without sediments, auto-
claving increased acephate recovery by over 30 percent; in creek water with
sediments, autoclaving more than doubled the recovery of acephate. Only
quantitatively insignificant amounts of Monitor were found in the samples.
Acephate was not found to escape into the atmosphere from the water
during any of the experiments.
TABLE 4. THE FATE OF 1 PPM ACEPHATE IN POND WATER AT 9'C* (10)
Time, Days
Recovery in % of Acephate Added
AcephateMonitor
pH was 7.5 at day 0 and had changed to 8.0.
Non-detectable.
A-320
-------
TABLE 5. THE FATE OF 1 PPM ACEPHATE IN CREEK WATER AT 9°C,
AND THE EFFECT OF AUTOCLAVING* (10)
Time, Days
0
0
7
7
21
21
34
34
50
50
43
43
50
50
Recovery in /
Ac ep hate
95.5
89.8
Not Autoclaved
80.9
74.3
88.7
87.3
59.8
57.0
45.0
45.5
Autoclaved
75.0
76.5
76.8
76.0
I of Acephate Added
Monitor
NDf
ND
0.4
0.3
0.3
0.4
0.3
0.3
0.4
0.3
0.4
0.4
0.5
0.5
In samples not autoclaved, pH was 7.0 at day 0; after 50 days
it had changed to 7.2 with acephate. In autoclaved samples,
pH was 7.0 at day 0 and remained unchanged.
ND - Not-detectable.
A-321
-------
TABLE 6. THE FATE OF 1 PPM ACEPHATE IN POND WATER AT 9°C
IN THE PRESENCE OF BOTTOM SEDIMENTS* (10)
Time,
Days
0
0
2
2
7
7
14
14
21
21
42
42
Recovery in % of
Ac ep hate
Water
90.2
89.3
56.3
58.7
42.9
50.0
37.8
39.7
31.3
33.7
17.8
15.0
B.S.t
ND*
ND
19.5
20.7
21.3
18.2
22.4
20.5
21.6
17.5
5.7
3.9
Acephate Added
Monitor
Water
ND
ND
0.6
0.8
1.0
1.3
0.7
0.9
0.4
0.5
0.2
0.2
B.S.
ND
ND
0.3
0.3
0.4
0.4
0.4
0.4
0.3
0.3
0.07
0.07
*
pH was 7.5 at day 0 and had changed to 7.9 with both treatments
after 42 days.
B.S. - Bottom sediment.
*ND - Not-detectable.
Based on Chevron data (5), the major hydrolysis product of acephate
is 0,S-dimethylphophorothioate (II, see diagram). In the physiological pH
range, Monitor is not formed. At the extreme pH of 3 and 9, traces of Moni-
tor may be formed. However, it is itself hydrolyzed to II, which is stable
under acid conditions, but degrades under alkaline conditions. At pH 7,
S-methyl-acetyl-phosphoroamidothioate (III) is also formed. The hydrolytic
degradation route for acephate can be shown by the following diagram (5):
A-322
-------
TABLE 7. THE FATE OF 1 PPM ACEPHATE IN CREEK WATER AT 9°C.IN THE PRESENCE
OF BOTTOM SEDIMENTS, AND THE EFFECT OF AUTOCLAVING* (10)
Time,
Days
0
0
7
7
21
21
34
34
50
50
*3
43
50
50
Recovery in 7. of Acephate Added
Acephate
Water
95.5
89.8
36.0
38.0
27.1
31.5
36.5
34.7
25.9
25.1
54.0
52.0
56.8
53.2
B.S.t
ND*
ND
Not Autoclaved
19.2
19.1
16.2
13.3
2.1
2.1
2.5
2.1
Autoclaved
9.7
10.3
9.2
10.2
Monitor
Water
ND
m
0.6
0.6
0.5
0.5
0.5
0.4
0.3
0.4
0.4
0.4
0.6
0.5
B.S.
ND.
ND
0.4
0.4
0.3
0.4
0.1
0.1
0.07
0.07
0.2
0.1
0.3
0.2
*In samples not autoclaved, pH was 7.1 at day 0; after 50 days
it had changed to 7.8 with acephate. In autoclaved samples it
had changed from 7.1 to 7.3.
B.S. - Bottom sediment.
^ND - Not-detectable.
A-323
-------
0
>
II
0 / o
III
Cll
ZI
c:n3s
ii
4.0 IMPACT ON NON-TARGET ORGANISMS
4.1 PLANTS
As noted in Section 3.1, acephate is rapidly picked up and degraded by
plants. According to the manufacturer (4), acephate has been demonstrated
to be safe to a wide range of plants. Only marginal leaf burns or inter-
veinal chlorosis on elm, crabapple, maple, cottonwood, redbud and weigela
has been observed.
4.2 BIRDS
Determination of the effects of Orthene on birds has included observa-
tions on population declines, breeding cycles, and bird activity. The
effect of acephate on birds in forests sprayed with Orthene at 0.56 and 1.4
kg a.i./ha was studied by Buckner and MacLeod (11). NO adverse effects on
birds could be attributed to acephate. Population fluctuations were observed
but were attributed to other factors. The breeding cycle of birds did not
appear to be interrupted.
Further work by Buckner and MacLeod (12) showed that applications of
acephate (0.56 kg/ha) combined with Bacillus thurlnpji^.^ (19.8 BIU/ha) re_
suited in reduced warbler activity. However, this impact was considered
comparable to normal population and activity changes encountered in un-
treated environments.
A-324
-------
Acephate applied to forested plots at a rate of 0.55 kg a.i./ha was
found to cause a decline in song activity of red-eyed vireos (13). There
was also a decline in numbers of vireos on treated plots. However, it was
uncertain whether acephate affected birds directly or indirectly, by de-
pleting their food supply.
Brain -cholinesterase levels have also been studied following forest
spraying in an attempt to correlate cholinesterase levels with dosage and
bird mortality. Based on the limited amount of data currently available,
it appears that brain cholinesterase inhibition of at least 80 percent is
required to kill birds with a single oral dose of an organophosphate insec-
ticide, but they may die with only 50 percent inhibition when continuously
exposed (14).
An evaluation of the effects of Orthene on songbird brain cholinesterase
activity following'application of Orthene at 0.5 Ib/acre to forest land in
Maine showed a significant brain cholinesterase inhibition in evening gros-
beaks and magnolia warblers (15). No mortality or evidence of other delete-
rious effects in songbird populations was found.
Orthene applied to a forest in northeastern Oregon at 1.12 and 2.24
kg/ha caused a 30 to 50 percent inhibition of brain cholinesterase activity
in forest birds for up to at least 33 days for 11 of 12 species collected
(16). Post spray bird census data suggested that two species of birds may
have decreased numbers following spray treatments. One dead grouse was
located on the plot treated with 2.24 kg/ha which may be indicative of a
greater overall mortality, considering the rapidity with which carcasses
disappear due to heat, predators and scavengers. This dose, however, is
significantly higher than the doses recommended for forestry use.
LD5Q data has been reported for a few bird species. The oral LD5Q for
ducks to acephate is 350 mg/kg; for chickens, 852 mg/kg (17). The metabo-
lite, Monitor, is considerably more toxic than acephate - it has an oral
ID5 for chickens of 25 mg/kg.
4.3 FISH AND AQUATIC ORGANISMS
Available data indicate that acephate;is of low toxicity to fish (4).
Rabeni and Stanley (18) studied the effects of acephate on fish following
A-325
-------
aerial spraying in Maine forests. Acephate concentrations in the streams
studied reached a maximum of 140 ppb one hour after spraying and residues
remained for at least two days. Brook trout, landlocked salmon, longnose
sucker, and common sucker were analyzed for brain acetylcholinesterase acti-
vity, effects on feeding, and growth. Suckers were the only fish with
significant depression of acetylcholinesterase activity (up to 29 percent
decrease). Analysis of stomach contents showed that acephate altered feeding
habits. Exposed fish consumed more terrestrial prey (beetles, wasps, moths,
spiders) than unexposed fish (which preyed primarily on immature aquatic
insects). However, these effects were transient. No unusual growth patterns
were observed. Also, population densities of benthic Invertebrates did not
appear to be affected.
Hydorn, et al. (19) also analyzed the stomach content of mature brook
trout from sprayed and unsprayed streams for arthropods. The results, shown
in Table 8, indicate that within 48 hours after exposure to aerial applica-
tions of 0.56 kg/ha acephate, fish consumed many more spiders and other
arthropods.
In another study, Orthene was applied at a rate of 0,56 kg a.i./ha to
a freshwater pond (20). No long-term adverse effects to the pond and stream
ecosystem were observed. No deaths or adverse effects were found in fish or
phytoplankton. The only significant population decrease was obtained for
midges.
Chevron (4) reports that Orthene's toxicity to fish is extremely low.
The 96-hour (TL5Q) of technical Orthene for trout, bluegills, and catfish
is greater than 1000 ppm. Fish continuously exposed to Orthene temporarily
accumulate small amounts In body tissues, but Orthene is rapidly eliminated
as levels of the chemical in water drop.
4.4 BEES AND OTHER INSECTS
Chevron (4) reports that acephate is highly toxic to bees in treatment
areas at the time of application. The mortality of bees reportedly increases
Immediately after acephate spraying at normal application rates (M..O lb/
acre). Nurse bees are particularly affected, with heavy mortality continuing
for 2 days and pollen collection curtailed for as long as five days. The
A-326
-------
TABLE 8. ABUNDANCE OF SPIDERS BY FAMILY IN STOMACHS OF BROOK TROUT CAPTURED FROM STREAMS IN
ACEPHATE-SPRAYED AND UNSPRAYED FOREST (19)
w
to
Unsprayed strewn
Family
Agctcimlac
Anyphaeitidae
Arancidac
ClubionUJae
Dictynidac
Hahniidac
Linyptuidae
Lytiistdae
Phiktdnimidae
Sallkidae
Tclrjgiuthidac
Thcrkliidac
Mean mi. spiders/
fish
IN,, fish)
Prespray
Z-bdays
0
0
0
0
0
0
1
0
1
0
1
0
0.31
IB)
Post -spray
24-48 h
1
O
1)
U
0
0
C
i
2
.11
n
i
0.45
(Ml
Pnsi-*pray
4-8 days
0
0
0
0
0
0
0
0
0
0
C
0
0.00
110)
Prespray
2-6 days
0
0
0
0
0
0
1
0
0
I
0
0
0.2S
(H)
Sprayed stream 1
Post-spray
24-48 h
0
0
Sprayed stream 2
Prespray
2-* days
0
0
0
1
0
3
0
2
0
0
6
1
1.30
(I0|
Pin.t >pf jy
24-4B h
0
i
14
10
1
0
10
0
3
7
41
1
'271
|7»
P.M-pray
4-tttlavs
0
II
n
u
o
it
ii
0
1
I
2
O
ii 411
(III)
-------
LD for Orthene has been reported to be 1.20 ug/bee, which is considered
to be extremely toxic (21).
Laboratory and field studies conducted by Lake Ontario Environmental
Laboratory (22) indicate that several non-target insects are adversely
affected after aerial application of acephate at 0.5 Ibs/acre. Lepidoptera
larvae, Diptera larvae, and Hymenoptera (predominantly Formicidae) were
the most sensitive whereas Coleoptera were least affected. Also, there was
a knockdown immediately after treatment affecting all orders of arthropods
collected. Within one month the populations which were depressed recovered
to pretreatment levels and no species were totally eliminated. Hydorn (19)
has also observed that caged spiders in an acephate-sprayed forest behave
abnormally and have a low survival rate.
4.5 MAMMALS
Acephate is considered to be of very low toxicity to mammals when
applied at recommended levels (3,4,10,23). In field tests, Orthene applied
at 0.56 kg a.i^/ha did not appear to adversely affect small mammals or cause
interruption of their breeding cycle (11). Other studies on the effects of
Orthene on small mammals also did not detect any significant adverse effects
(24). In these studies, mortality, emigration, stomach contents and growth,
juvenile to adult age class ratio, incidence of pregnancy and lactation,
and other reproductive effects were considered. White-footed mice, short-
tailed shrews, and red-backed voles were the primary species analyzed.
Toxicity data for Orthene indicate the oral LD5Q in rats is 700 mg/kg,
while the skin LD5Q in rabbits is 2000 mg/kg (17). Acephate is also re-
ported to irritate rabbit eyes but the eyes appear normal after two weeks
(4). The metabolite, Monitor, is considerably more toxic. Its oral rat
LD5Q is 7.5 mg/kg and the skin U>50 in rabbits is 118 mg/kg (17).
A-328
-------
.REFERENCES
1. Information provided by EPA, based on a review of registration data by
the Ecological Effects Branch.
2. Pesticide Uses for Forestry, National Forest Products Association,
March 1980.
3. Raisch, R.D. Proposed Cooperative Spruce Budworm Suppression Project,
Maine, 1980, USDA Forest Service, NE Area, USDA-FS-80-01.
4. Chevron. Orthene - A New Concept in Insect Control. Chevron Chemical
Company, Richmond," CA. 1975. 19 pp.
5. The Impact of Orthene on the Environment, Chevron Chemical Company,
January 1973.
6. Bull, D.R. Fate and Efficacy of Acephate After Application to Plants
and insects. J. Agri. Food Chem.. 27(2): 268-272, 1979.
7. Devina, J.M. Persistence of Orthene Residues in the Forest and Aquatic
Environment. In: Environmental Impact Study of Aerially Applied
Orthene on a Forest and Aquatic Ecosystem. Lake Ontario Environmental
Laboratory Report 174, Oswego, N.Y. 1975, pp. 48-82.
8, Szeto, S.Y., et al. Residues in Douglas-fir Needles and Forest Litter
Following an Aerial Application of Acephate, J. Environ. Sei. Health
B13C2): 87-103, 1978.
9. Nigg, H.N., J.A. Reinert, G.E. Fitzpatrick. Food and Feed: Acephate
and Methamidophos Residue Behavior in Florida Citrus, 1976 Univ. Fla,
Agric. Res. Center, Ft. Lauderdale and Agrlc. Res. and Ed Center, Lake
Alfred, Fla, Pesticides Monitoring Journal. 12(4); 167-171. IV/*.
10. Szeto, S.Y., et al. The Fate of Acephate and Carbaryl in Water, J.
Env. Sci. Health .B«(6): 635-654, 1979.
11 Buckner C.H. and B.B. MacLeod. Impact of Aerial Applications of
Srthtne'up;" Non-Target Organisms. Chem. Control Research Inst. Report
CC-X-104. Ottowa, Ontario. 1975.
12 Buckner C.H. and B.B. MacLeod. Impact of'Experimental Spruce Budworm
"' lupSessio;Trials Upon Forest Dwelling Birds in Newfoundland in 1977,
Canadian Forest Service, Forest Pest Management Institute Report
FPM-X-9, 1977.
13; Bart, J. The Effects of Acephate and Sevin on Forest Birds, J. Wild-,
life Management. 43(2): 544-549, 1979,
A-329
-------
14. Zinkl, J.G., C.J. Henny, and P.J. Shea. Brain Chollnesterase Activi-
ties of Passerine Birds in Forests Sprayed with Cholinesterase Inhibi-
ting Insecticides. In: Animals as Monitors of Environmental Pollu-
tants, NAS, Washington, D.C. 1979. pp. 356-363.
15. Julin, A.M. and F.J. Gramlich. Effects of Orthene on Songbird Brain
Cholinesterase in Maine, 1977. Forest Insect and Disease Management
Evaluation Report, USDA, Broomall, Pa. June 1978. 5 pp.
16. Richmond, M.L., C.J. Henny, R.L. Floyd, et al. Effects of Sevin-4-
oil, Dimilin and Orthene on Forest Birds in Northeastern Oregon, PSW
Forest and Range Experiment Station, Berkeley, CA. Research Paper
PSW-148, 1979.
17. Lewis, R.J. and R.L. Tatken, eds. Registry of Toxic Effects of Chemical
Substances. 1979 Edition. National Institute for Occupational Safety
and Health, U.S. Government Printing Office, Washington, D.C. 1980.
18. Rabeni, C.F. and J.G. Stanley. Operational Spraying of Acephate to
Suppress Spruce Budworm has Minor Effects on Stream Fishes and Inver-
tebrates. Bull. Env. Contain. Toxicol. 23: 327-334, 1979.
19. Hydorn, S.B., C.F. Rabeni, and D.J. Jennings. Effect of Forest Spray-
ing with Acephate Insecticide on Consumption of Spiders by Brook Trout,
Can. Entomol. Ill: 1185-1192, 1979.
20. Bocsor, J.G. and T.F. O'Connor. Impact on Aquatic Ecosystem. In:
Environmental Impact Study of Aerially Applied Orthene on a Forest
and Aquatic Ecosystem. Lake Ontario Environmental Laboratory Report
174, Oswego, N.Y. 1975, pp. 29-47.
21. Atkins, E.L., E.A. Greywood, and R.L. MacDonald. Toxicity of Pestici-
des and Other Agricultural Chemicals to Honey Bees - Laboratory Studies.
U. of Calif., Div. of Agric. Sciences Leaflet 2287. 1975.
22. Shelby, M. and T. O'Connor. Impact on Non-Target Arthropods. In:
Environmental Impact Study of Aerially Applied Orthene on a Forest
and Aquatic Ecosystem. Lake Ontario Environmental Laboratory Report
174, Oswego, N.Y. 1975, pp. 172-207.
23. Draft Environmental Statement for Cooperative Gypsy Moth Suppression
and Regulatory Program, 1980 activities.
24. Stehn, R. and J. Stone. Impact on Small Mammals. In: Environmental
Impact Study of Aerially Applied Orthene on a Forest and Aquatic Eco-
system. Lake Ontario Environmental Laboratory Report 174, Oswego, N.Y.
1975, pp. 123-171.
A-330
-------
Common Name: Carbaryl
Chemical Name: 1-naphthyl-N-methylcarhamate
Major Trade Names: Sevin-4-oil; Sevin 50WP, 80WP, 80S
Major Applications Used primarily against the defoliating insects, the
in Forestry: gypsy moth, spruce budworm, and tussock moth.
SUMMARY
Carbaryl is a widely used broad spectrum insecticide. Forestry appli-
cations of 0.75 to two pounds a.i. per acre are used to protect mature trees
against defoliating insects such as the gypsy moth, spruce budworm, and
tussock moth. Union Carbide is the sole producer of carbaryl in the United
States. Most of the carbaryl used in this country is for agriculture. In-
dustrial consumption in 1972 was one million pounds, only 4 percent of total
carbaryl consumption. Carbaryl is available in several formulations under
the trade name Sevin. The forest industry utilizes Sevin-4-oil and the
wettable powders primarily.
Carbaryl is a contact and stomach poison in insects with no systemic
effect. Its mode of action is to inhibit acetylcholinesterase. Of the
carbamate insecticides, carbaryl has received the widest distribution.
Carbaryl is only slightly soluble in water and has a low vapor pressure,
It is stable at room temperature at acid pH but readily hydrolyzes to 1-
naphthol, C02, and methylamine in alkaline solutions.
Carbaryl is considered "moderately" persistent in the environment.
Reported half-lives range from a few days to several months depending on
environmental conditions. Degradation is primarily by chemical hydrolysis
in water and microbial decomposition in soil.
Carbaryl is also taken up and metabolized by target and non-target in-
sects, plants and animals. Metabolic products include 1-naphthol, methyl-
amine, formaldehyde, ammonia and hydroxylated ring compounds. Conjugates
are also formed with body substances. These are primarily glucosides in
insects, glucuronides in animals and glycosides in plants.
Most of the carbaryl applied to a forest is deposited on vegetation.
Residues on plants are measured as ppm of plant material and as amounts per
unit surface area. Reported half-lives calculated from surface residues
are 12 to 22 days; reported half-lives based on residues in plant material
are only 3 to 8 days.
Few investigations of carbaryl volatilization were found in the litera-
ture. Carbaryl would not be expected to be readily volatile because of its
low vapor pressure. However, when hydrolysis to 1-naphthol occurs, volati-
lization of 1-naphthol may be a means of dissipation from leaf surfaces.
A-331
-------
The fate of carbaryl in forest soils is determined primarily by the
extent of adsorption, chemical hydrolysis, and microbial decomposition.
Several field studies have measured carbaryl residues in soil. Results vary
from rapid disappearance in a few days to persistence after 16 months. The
amount of carbaryl applied, soil type and depth of sampling appear to in-
fluence residues in soil over time. Adsorption of carbaryl to soil is
reversible and occurs to a greater extent in organic than inorganic soils.
Microbial decomposition appears to be a major contributing factor to carba-
ryl dissipation in soils.
Soil bacteria and fungi have been shown to degrade carbaryl primarily
to 1-naphthol and C02* Several hydroxylated products and some as yet un-
identified compounds are also formed. Soil bacteria and fungi have also
been shown to degrade 1-naphthol to some extent even though it is toxic to
microorganisms. In most soil degradation studies a portion of the carbaryl
added to the system remained in the soil as an unextractable residue. This
unextractable residue could not be chemically analyzed but was found to be
nontoxic.
Carbaryl enters forest streams primarily by direct application as a
consequence of forest spraying. Its persistence in water is dependent on pH
and temperature. At alkaline pH, carbaryl is hydrolyzed to 1-naphthol.
This process is retarded at low temperatures (e.g., 3°C) and enhanced by
higher temperatures (e.g., 28«C). Carbaryl has been shown to undergo photo-
lysis in sunlight under acid conditions. The photolysis rate in water is
influenced by the level of dissolved oxygen, pH and amount of incident ra-
diation (shade, time of day, time of year).
Forestry use of carbaryl can be expected in general to affect insect
and arthropod populations and the aquatic biota in the treated area. Car-
baryl exhibits little phytotoxic effect but has been reported to cause
ue
*n l!LM "rtrin uPlT !' esPeclally if "in or high humidity persists after
application. Carbaryl does cause fruit to fall from apple trees and has
r Uithi8' Carbaryl l8 toxic to *** but •* »t retained
» o l8 toxic to *** but •* »t retained
in muscle tissue. The 96-hour LC50'B range from 1 to 20 ppm; fish are gener
ally even more sensitive to 1-naphthol than to carbaryl. Aquat£ organist
ll\P&l£ " * 8u8«PtibU to the toxic effects of carbaryS. in water?
96-hour LC50's range from 3 to 10 ppb. The natural animal composition of
. .
cholinesterase activity. Temporary territory abandonment and loss o| Toad
supply have been noted Larger doses will produce decreased growth? a"
normal body organs and decreased hatching of eggs. »wwwit . w
Carbaryl adversely affects many beneficial insects/especially aquatic
insects and honey bees. The high toxicity of carbaryl to honey bees is
A-332
-------
probably the major hazard to non-target organisms in forest applications.
Susceptibility of aquatic arthropods that serve as food for fish is also a
problem in forest systems. Small amounts of carbaryl in streams (40 to 80
ppb) will substantially reduce numbers of aquatic insects. Populations of
soil arthropods are reduced by application of one to two pounds per acre
but generally return to normal the following year. The toxicity of carbaryl
to honey bees is extended by the ability of forager bees to collect the
powder formulation along with pollen and carry it back to the hive where it
can remain toxic for up to 8 months. Carbaryl should not be applied at a
time when bees are foraging and hives should be moved out of the area.
Carbaryl has been shown to be toxic to marine and freshwater algae and
to reduce litter decomposition. Its hydrolysis product, 1-naphthol, is
toxic to certain fungi and bacteria. Bioaccumulation studies show carbaryl
does not accumulate in fish or aquatic invertebrates. However, bioaccumula-
tion ratios for algae and duckweed are relatively high. Biomagnification
effects on food chains due to large accumulations of carbaryl in organisms
of the first trophic level is not known.
A number of issues have been raised regarding the real and potential
consequences of carbaryl use in forestry. Some of these issues relate to
environmental fate and environmental impacts. Carbaryl readily hydrolyzes
to 1-naphthol in the environment. There is some evidence the 1-naphthol is
more toxic to certain aquatic organisms than carbaryl. It is possible that
effects attributed to carbaryl are actually due to 1-naphthol. Extensive
aerial spraying of carbaryl is being questioned as a safe, effective means
of insect control. Enhancement of virus production has been demonstrated in
laboratory studies. Although carbaryl has been converted to a nitroso deri-
vative in the laboratory, no formation of nitrosamines was found in soil.
A-333"
-------
1.0 INTRODUCTION
1.1 BACKGROUND
Carbaryl Is a broad spectrum insecticide that is widely used in the
United States and throughout the world. It is applied to control a variety
of insect pests on field crops, forests, rangelands, gardens, poultry and
pests (1,2). Carbaryl was developed as a pesticide in 1956 and first re-
gistered for agricultural use in 1958. It is currently registered for con-
trol of over 545 insects on over 106 different crops in the United States
(3). Carbaryl has been presented as a substitute for DDT that is effective
against insect pests, relatively non-persistent in the environment and gen-
erally of low toxicity to non-target organisms (A,5).
Forest industry uses of carbaryl are primarily to protect mature trees
from defoliating insects such as the spruce budworm, gypsy moth and tussock
moth. The largest forest aerial pesticide spray program in the United States
involves the use of carbaryl against the spruce budworm in northern Maine.
In 1980 the plan called for spraying 1.1 million acres of forest land with
carbaryl and 200 thousand acres with Bacillus thuringiensis at an estimated
total cost of $8 million (6). Table 1 lists forestry uses and application
rates based on recommendations by the National Forest Products Association,
USDA and Union Carbide, the only producer of carbaryl in the United States.
The major agricultural crop uses are against pests on corn, soybeans, cotton,
fruits and vegetables (1).
United States consumption of carbaryl for 1972 was estimated at about
25 million pounds, 19 million pounds of which were used in agriculture (1).
Industrial and commercial use, which would include forestry, totalled one
million pounds; government use was 1.5 million pounds; and home and garden
use was 3.5 million pounds. By area, industrial and commercial use was 0.2
million pounds in the northeastern states, 0.2 million pounds in the south-
eastern states and 0.1 million pounds in the northwestern states.
Union Carbide estimated annual plant capacity is 65 million pounds (1).
Various formulations are available under the trade name Sevin. Foreign pro-
ducers market carbaryl worldwide in several formulations under about a dozen
trade names. Sevin, the basic U.S. product, is sold as wettable powders,
dusts, granules, baits, and sprayable liquids in oil or aqueous suspensions.
A-334
-------
TABLE 1. FORESTRY USES AND APPLICATION RATES FOR CARBARYL (2,7,8,9)
Host Tree
Insect
Application Rate
>
OJ
Eastern hardwoods, hemlocks,
pine, spruce
True fir, Douglas-fir
True fir, spruce
Eastern hardwoods
Aspen, western hardwoods
Beech, maples, northern hardwoods,
eastern hardwoods
Eastern hardwoods, pine
Spruce
Pine
Eastern hardwoods
Eastern hardwoods, western hardwoods
Douglas-fir
Gypsy moth
Western spruce budworm
Spruce budworm
Fall cankerworm
Great Basin tent caterpillar
Saddled prominent cater-
pillar
Bagworm
Spruce needle miner, aphid
Mountain pine beetle
European pine sawfly
Birch leaf miner
Boxelder bug
Eastern tent caterpillar
Forest tent caterpillar
Tussock moth
0.75-1 lb a.i./gal/acre
1 lb a.i. in oil/acre
0.75-1 lb a.i. in oil/acre
0.5 lb a.i./gal/acre
1 lb a.i. in oil/acre
1 lb a.i./gal/acre
1 lb a.i. in 100 gal water
1 lb a.i. in 100 gal water
A Ibs a.i. in 23 gal
water/50 ft2 bark
1 lb a.i. in 100 gal water
1 lb a.i. in 100 gal water
1 lb a.i. in 100 gal water
1 lb a.i. in 100 gal water
1 lb a.i. in oil/acre
2 Ibs a.i./acre
-------
Table 2 lists the names of various formulations and possible uses of Sevin
produced by Union Carbide and foreign manufacturers.
TABLE 2. BASIC SEVIN FORMULATIONS AVAILABLE*
Name
Composition
Active
Ingredient
Possible Use
Sevin-4-oil Sevin in oil
Sevin 50WP Wettable powder
Sevin 80WP
Sevin SOS
Sevin 85S
Sevimol
Sevidol
Sevin
Wettable powder
Sprayable liquid
Wettable powder
Sevin in molasses
Sevin and BHC
Granules
dust
baits
concentrates
49%,
4 Ibs/gal.
50%
80%
80%
85%
40%
8% Sevin,
8% BHC
5-10%,
2-10, 25-50%
5%
50-97%
Forestland (10,12)
rangeland
pasture
agriculture
Forest
agriculture (13)
orchards (apple)(14)
Forest
agriculture (cotton)(15)
orchards (citrus trees)
(16)
Forest (17)
agriculture
Agriculture (cotton)(18)
Agriculture (rice)(10)
Agriculture (18)
agriculture
animal husbandry
animal husbandry
1.2 USES IN-FORESTRY AGAINST DEFOLIATING INSECTS
Carbaryl use in forestry to control tree defoliation by the gypsy
moth utilizes aerial application or ground application with mistblower or
hydraulic spray. Aerial application involves use of one pound a.i. per
A-336
-------
acre of Sevin-4-oil or Sevln 80S with Pinolene or Chevron sticker for longer
residual activity. Ground application uses Sevin SOS with a sticker at two
pounds a.i. per acre for the mistblower and one pound a.i. per acre with the
hydraulic sprayer (19). The chemical is applied against larvae in early
instars and can give a 90 percent kill in one to two days with about 70 per-
cent foliage protection (7). Approximately 42,000 acres of forests, forested
recreation areas and forested communities in Connecticut, Maine, Massachu-
setts, New Hampshire, New Jersey, New York, and Pennsylvania were sprayed
with Sevin in 1979 for gypsy moth control at a cost of about $7 per acre.
Most of the areas were sprayed only once. Carbaryl has been used for con-
trol of the Douglas-fir tussock moth in northwest forests (4,20). Usually
Sevin-4-oil at one to two pounds a.i. per acre is aerially applied. The
chemical is directed against the larval state at early instars. One pound
a.i. per acre of carbaryl can give 72 to 83 percent mortality; two pounds
a.i. per acre can give up to 97 percent mortality in 14 days with measurable
foliage protection (4). Application of two pounds a.i. per acre to forests
in Montana and Idaho in 1976 by the U.S. Forest Service decreased populations
of the tussock moth to the extent that post-treatment egg masses were not in
sufficient quantity to repopulate these forests the next year.
The eastern spruce bud worm has been a pest of northeastern forests,
especially Maine (24). The western spruce budworm has been a problem in
western and Rocky Mountain states (25,26). Spruce budworm control in
forested areas of these states is usually by means of aerial application of
Sevin-4-oil at about one pound a.i. per acre. Almost 2.5 million acres in
Maine were treated with carbaryl for spruce budworm control in 1979 (24).
More than 8.2 million acres in Maine were treated with carbaryl from 1975 to
1979. Carbaryl has been the primary insecticide since 1975 and the termina-
tion of use of DDT. About 78 percent of the treated area in Maine was
sprayed with carbaryl. The reasons for heavy use of carbaryl were its low
cost and consistent effectiveness (24),
1.3 MODE OF ACTION
Carbaryl is a contact and stomach poison in insects with no systemic
effect. Its mode of action is that of a nerve poison in inhibiting acetyl-
cholinesterase (1). Acetylcholine is a major chemical mediator in the
A-337
-------
autonomic and central nervous systems. It facilitates the transfer of nerve
impulses across the synapse at nerve junctions and is controlled by the in-
activating effect of the hydrolytic enzyme, acetylcholinesterase. The inhi-
bition of this enzyme results in prolonged nerve transmission and uncon-
trolled nerve activity (27). Death of insect larvae occurs in one or two
days following application of carbaryl to forest systems (24).
The inhibition of acetylcholinesterase by carbaryl is reported to be
reversible (1,2,24). Short term exposure of organisms to non-lethal doses of
carbaryl would not be expected to result in permanent depression of acetyl-
cholinesterase levels; enzyme activity should return to normal sometime after
the carbaryl has been metabolized and/or excreted. Acetylcholinesterase
inhibition has been used as an indicator of exposure of birds to carbaryl
following forest spraying. Zinkl, et al. (28) measured brain cholinesterase
activity in birds five days after application of carbaryl to forests in
Montana. Richmond, et al. (29) also used brain cholinesterase levels of
collected birds to determine the extent and magnitude of exposure to car-
baryl sprayed in Oregon forests. In both studies measurement of enzyme levels
of 20 percent or more below normal was considered indicative of exposure; 50
percent inhibition was considered diagnostic for cause of death (28,29).
2.0 PHYSICAL AND CHEMICAL PROPERTIES OF THE ACTIVE INGREDIENT
Carbaryl is the common name for 1-naphthyl N-methylcarbamate:
0 - C - NH - CH,
\ II 3
0
Carbaryl is a member of the carbamate group of pesticides. This group
consists of ester derivatives of carbamic acid. Only the esters of N-alkyl-
carbamic acid have insecticidal activity. !„ the N-methylcarbamate series,
carbaryl has received the.widest distribution (11). The technical grade
chemical is 99.5 percent + pure. It is a white crystalline solid with a
melting point at 142'C (10). It is only slightly soluble in water (40 ppm
at 30'C). It is soluble in most polar organic solvents such as acetone and
mixed cresols (10). The vapor pressure of carbaryl is very low, 0.002 mm
A-338
-------
Hg at 40°C. Its density is 1.232 gm/ml at 20°C (10). At room temperature,
carbaryl is nonreactive in acid solution but readily hydrolyzes to CO ,
1-naphthol and methylamine in alkaline solution:
0 - C - NH - CH.
H
0
carbon
1-naphthyl N-methyl carbamate 1-naphthol dioxide methylamine
Thus, carbaryl is not compatible with alkaline compounds such as Bordeaux
mixture, calcium and barium polysulfides or lime. It is reported by Union
Carbide to be stable in light, including ultra violet, unreactive in heat up
to 70°C, and stable in a spray formulation under prolonged storage for up to
five years (2).
3.0 ENVIRONMENTAL FATE
Carbaryl is taken up and metabolized by insects, plants, and animals
exposed by direct application or in the case of insects and animals, by in-
gestion of contaminated foliage. The persistence of carbaryl in the forest
environment is ultimately determined by the extent of volatilization, photo-
decomposition and chemical and microbial degradation that takes place on
plants, in soil and in water. Volatilization following hydrolysis may be
important as a means of carbaryl dissipation on foliar surfaces. Chemical
hydrolysis and photodecomposition may also occur on leaf surfaces but have
been investigated in water and so will be discussed in relation to the fate
of carbaryl in water. Microbial degradation is thought to occur primarily
in soil and so discussion of fate in soil will emphasize this mechanism.
Carbaryl is considered "moderately" persistent in the environment (30).
It contains a readily cleavable carbamoyl group C?N-C-) and is rapidly hy-
drolyzed under alkaline conditions (31,32). Reported $ half-lives range from
a few days to several months. Table 3 lists the half-lives of carbaryl under
various conditions.
3.1 UPTAKE AND METABOLISM IN INSECTS, PLANTS AND ANIMALS
Carbaryl taken up by target and non-target insects, plants and animals
A-339
-------
TABLE 3. HALF-LIVES OF CARBARYL FOR VARIOUS ENVIRONMENTAL CONDITIONS
'1/2
45 hours
1.3 days
4.4 months
8 days
4.5 days
38 days
7-9 days
1-5 days
3-4 days
Environment
Midday sunlight, June,
34°N, distilled water, pH 5.5
Water, pH 8
Water, pH 6
Grass
Doug las- fir
Sea water
Soil
Water
Plant leaves ChaseH r»«
-------
0 - C - NH - CH.
Carbaryl
0 - C - NH - CH.
1-naphthol
N-methylcarbaroate
0
II
O - C - NH - CH.
CO,
CH O
N-methylcarbamate methylamine carbon dioxide formaldehyde
C02H *
formic acid
•Catalase and
peroxidase systems
Conjugation of carbaryl with insect body substances usually takes the form
of glucosides (32). Plants are exposed to carbaryl directly by spray or
dust or through uptake from contaminated soil. Metabolism of carbaryl in
plants invoves oxidation, hydrolysis, hydroxylation and formation of con-
jugates with plant constituents, especially carbohydrates. The primary
plant-carbaryl conjugates formed are glycosides (36). Oxidation involves the
N-methyl group to ultimately form formaldehyde, ammonia and 1-naphthol (11).
Hydroxylation of carbaryl in plants is thought to occur prior to conjugation
and involves the N-methyl group. There is presently no evidence of hydroxy-
lation of the nitrogen atom (37). An example of carbaryl oxidation in plants
is as follows:
- C - NH - CH
3
NADPH.
()„
0 - C - NH - CH2OH
0
carbaryl
1-naphyl N-methylolcarbamate
Although carbaryl is used in animal husbandry as a dust or body wash
for insect control, exposure of animals to carbaryl in forest applications is
likely to involve ingestion of contaminated foliage or insects. Metabolism
A-341
-------
of carbaryl in animals results in numerous products from hydrolysis/ hydroxy-
lation and epoxidation {R - C = C - R' • R - CX-XC - R')(36). The primary
hydrolysis product is 1-naphthol. Glucuronide conjugates are formed, es-
pecially in warm-blooded animals(32), along with sulfates and mercapturic
acids.(36). There is a tendency for some metabolites to concentrate in the
liver and kidneys of mammals. All animal systems are not alike in their
metabolism of carbaryl; for example, the primary metabolic product in man
is 1-naphthol, whereas no 1-naphthol is produced in dogs (36). Ring
hydroxylation can also occur (11):
- CH,
5-hydroxy naphthyl 4-hydroxy naphthyl
N-methylcarbamate N-methylcarbamate
3.2 PERSISTENCE ON FOLIAR SURFACES
Most of the carbaryl applied to a forest is deposited on vegetation.
Persistence of these residues is determined by the extent of volatiliza-
tion, photodecomposition and chemical degradation of carbaryl, none of
which have been measured on foliar surfaces.
3.2.1 Residues on Plants
Several field studies of the persistence of carbaryl on plants have
been done primarily because of the use of carbaryl on crops, including
edible crops, and because of the reliance on ingestion of treated foliage
as a means of exposing target insects to carbaryl in forest applications.
The gypsy moth control program in forests of the northeastern United States
utilizes 0.75 Ibs. a.i. per acre of Sevin-4-oil. Residues have been
found on leaves 60 days after treatment. Rainfall is thought to be a
major factor in reducing residues (7), A Russian study of a forest appli-
cation of 0.5 gm. per square meter (4.46 Ibs. per acre) reported residues
on berries and sprigs of red raspberries, forest strawberries, tree buds
and branches one year after treatment (33). pieper (12) ta a field study of
carbaryl residues on forest foliage calculated a half life on Douglas-fir
A-342
-------
of 4.5 days and on aspen of 8 days. Table 4 lists actual residues recovered
on various plant types for this study.
TABLE 4. PERSISTENCE OF CARBARYL ON FOREST FOLIAGE TREATED WITH
1 LB A.I. PER ACRE SEVIN-4-OIL (ADAPTED FROH REFERENCE 12)
Foliage
Type
Grass
Geranium
Aspen
Douglas-fir
Average
Residue Recovered in
ppm in Days After Treatment*
1/2
Days
8
3
8
4.5
0
Days
70
168
30
138
1
Day
56
99
30
124
3
Days
65
104
17
44
7
Days
46
59
11
67
14
Days
21
24
17
29
28
Days
0.3
2.8
6.7
4.0
47
Days
<0.1
0.2
2.4
4.5
63
Days
<0.1
cO.l
0.5
3.8
Analytical % recoveries were 89.5% for grass, 86.5% for geranium, 75% for
aspen, and 50% for Douglas-fir.
A number of carbaryl plant residue studies have been done for agricul-
tural crops. Measurements of carbaryl residues are in ppn of plant material
or.ygm per square centimeter of plant surface. Union Carbide reports a half
life on plant leaves of 3 to 4 days (2). Table 5 lists some registered uses
of carbaryl on crops, allowable residues and measured residues on these
crops.
TABLE 5. ALLOWABLE AND ACTUAL CARBARYL RESIDUES ON CROPS
(ADAPTED FROM REFERENCE 30}
Registered Use
Citrus
Cotton
Soybeans
Soybean forage
U.S.
Tolerance,
ppm
10
5
5
10
WHO
Tolerance,
ppm
7
1
1
Residue,
ppm
2-8
2-3
0.96
<0.1
Days
After
Application
5
38
85
Application
Rate
1 lb/100 gal
2.5 kg/ha
1-2 Ibs/acre
1-2 Ibs/acre
A-343
-------
A field study done in India measured residues on bajra plants from a
field treated with 13.4,26.8, and 40.2 Ibs a.i./acre of granular carbaryl (18).
samples were taken at 15, 30, 60 and 90 days after treatment. No carbaryl
residues were detected in bajra plants or grain. The detection limit was
<0.07 ppm. Another Indian field study measured residues from four spray
applications of carbaryl on cabbage and eggplant at 0.55, 1.1 and 2.2 Ib.
per acre (13). By the first day after treatment only 55-60% of the carbaryl
applied was recovered. After one week only 15-20% of the carbaryl applied
was detected. Washing the cabbage prior to residue determination decreased
measurements taken the day of application by an average of 95% and measure-
ments taken one day after application by an average of 73% as compared to
residues on unwashed cabbage. The half-life calculated for cabbage was 3
days and for eggplant 3.2 days.
Tilden and van Middlelem 09) measured residues on spinach and chicory.
Four applications of 1 Ib. a.i. per acre resulted in an average residue 8
days after the last application of 3.75 ppm on spinach and 7.1 ppm on chicory.
Four applications of 2 Ibs. a.i. per acre resulted in an average residue 8
days after the last application of 16.5 ppm on spinach and 18 ppm on chicory.
The calculated percent reduction in carbaryl from 1 day to 8 days after
treatment are comparable: 1 Ib. a.i./acre, spinach 88%, chicory 82% and
2 Ib. a.i./acre, spinach 81%, chicory 85%. The rate of dissipation of car-
baryl on plants appears to be independent of initial concentration
Sell and Maitlen (14) measured carbaryl residues on the surface of appl*
leaves from trees treated with an aqueous solution containing 0.5 and 1.0
Ib. a.i. per 100 gallons of water. Each test plot consisted of three apple
trees which were sprayed until insecticide runoff was produced. Average
2
surface residues on leaves measured 0.70 and 1.71 ygn/cm the day of
treatment. By day 31, the average surface residue had decreased by 90%
to 0.07 and 0.18 ygm/cm2. The calculated half-life of carbaryl for
apple leaves for this study was 13.33 days.
Dislodgeable residues on citrus trees were measured by Iwata et al.(16).
Lemon and orange trees were treated with 11.5 Ibs. a.i. per acre of Sevin
80WP. Leaves were sampled 5, 10, 15, 30, 45 and 60 days after applica-
tion. Five days after application surface residues were 5.6 wgm/cm2 on
A-344
-------
2
orange leaves and 2.4 ygm/cm on lemon leaves. By 60 days after appli-
cation these residues were reduced by 94% and 83% to 0.36 and 0.41 Ugm/cm .
The fruit was sampled after 52 and 59 days. Pulp residues ranged from
<0.01 to 0.02 ppm in oranges and 0.01 to 0.09 ppm in lemons. Half-lives
calculated were for orange leaves 14 days and for lemon leaves 22 days.
Depending upon how carbaryl residues in plants have been measured,
reported half-life values range from 3 to 22 days. If residues on the
surface are determined, half-life values are from 13 to 22 days. Reported
half-life values based on residues in plant material are from 3 to 8 days.
3.2.2 Volatilization
Studies of the reduction of carbaryl residues on plant surfaces
measure loss of carbaryl by volatilization as well as by decomposition.
However, no investigations have been made to determine the relative impor-
tance of each mechanism to carbaryl dissipation.
Few investigations of carbaryl volatilization from any medium were
found in the literature. Two studies reported losses of carbaryl from
surfaces. Over 70% of carbaryl on bean leaf surfaces was dissipated in
one day (32). The half-life of carbaryl on glass plates was 14 hours.
Metabolites of carbaryl exhibited half lives of 0.3 to 1.8 hours on glass(32).
In an analysis for carbaryl and its hydrolysis product, 1-naphthol, on
treated apple leaves, only carbaryl could be recovered. The investiga-
tors assumed 1-naphthol was formed by carbaryl hydrolysis on the alkaline
leaf surface but rapidly vaporized and so could not be detected(40). Carbaryl
itself would not be expected to be readily volatile because of its low
vapor pressure. 1-naphthol is volatile in steam(41). Intense sunlight may
produce an effective temperature on the leaf surface that would result in
1-naphthol volatilization. In intense sunlight, however, photodecomposi-
tion of carbaryl may also occur. It is possible that hydrolysis, volatili-
zation and photodecomposition are all responsible for the loss of carbaryl
residues from plant surfaces. Pull evaluation of the volatility of carbaryl
in the forest environment requires further study.
3.3 FATE IN SOIL .
Carbaryl reaches the forest floor directly during application and
indirectly through residues on vegetation that falls to the ground. The fate
A-345
-------
of carbaryl in forest soils is determined primarily by the extent of chemi-
cal and/or microbial decomposition. Photodecomposition is probably not of
major importance in forest soils because of the physical nature of forest
systems. Unlike cultivated fields, forests are characterized by heavy
vegetation that allows little sunlight to reach the ground. Forest soils
are covered by a layer of forest litter. The degradation of carbaryl in
forest soil may be very different from degradation in agricultural soil
due to the presence of the overlying forest litter. The influence of forest
litter on the persistence of carbaryl in forest soil has not been investi-
gated. Investigations into the fate of carbaryl in soil are limited prim-
arily to measurement of residues and laboratory studies of microbial
degradation.
Carbaryl is usually sprayed onto forest trees aerially or with ground
equipment. An aerial application of 2 Ibs. a.i. per 0.75 gal. per acre
of Sevin-4-oil was made to Idaho and Montana forests for control of the
Douglas-fir tussock moth (4). In Montana only about 20% of the carbaryl
applied, 0.15 gal. per acre, actually reached the forest floor. In Idaho
the percentage of carbaryl reaching the forest floor was about 29% or
0.22 gal. per acre (A).
3.3.1 Residues in Soil
Several field studies have measured carbaryl residues in soil over a
range of application rates. The results vary from rapid disappearance in a
few days to persistence after 16 months. The amount of carbaryl applied,
soil type, and depth of sampling appear to influence the residues of car-
baryl in soil over time.
Kuhr, et al. (42) report that two applications of 3 Ibs a.i. per acre
to an orchard soil left no detectable residues 8 days after treatment. The
detection limit for this study was 1 ppm; only the top two inches of soil
was sampled. Residues decreased 93% from 13.8 ppm the day of application to
less than 1 ppm after 8 days.
A field study in India measuring soil persistence associated with
heavier application rates of granular carbaryl showed a slower decline in
residue levels (18). Reductions in soil residues of 62 to 81% after 15 days
and 94-98% after 60 days were measured for application rates of 13.4, 26.8,
A-346
-------
and 40.2 Ibs. a.i. per acre. Residues up to 6.3 ppm were still in the soil
after 90 days. Soil samples were taken to a depth of 10 cm. A heavy appli-
cation of 22.7 Ibs. per acre of carbaryl to a sandy loam soil resulted tn no
residues in the first 20 cm of soil after 4 months (36). The upper 1 meter
soil layer, however, retained 6% of the initial carbaryl applied after 16
months. These application rates, however, are many times higher than those
in current use. At normal application rates, residues are expected to per-
sist for a shorter period of time. Union Carbide reports that commonly used
rates of carbaryl could be expected to have a half-life in field soil of 38
days or less (3).
The National Soils Monitoring Program results for FY 1970 showed soil
residues of carbaryl of about 1 ppm in 2.3% of the sites tested (A3). Those
states sampled that had carbaryl in soil were primarily in the southeast and
the Great Lakes area.
A study by Caro, et al. (44) utilized an artificial watershed consisting
of approximately two acres of a silt loam soil planted with corn. A collec-
tion system beneath the plot allowed measurement of runoff. The plot was
treated with 4.5 Ibs. per acre of carbaryl and 2 Ibs. per acre of atrazine.
The results of residue analysis of soil samples taken to a depth of 20 to 30
cm showed no significant loss of carbaryl in the first 40 days of the test.
The overall value for the watershed for 95% dissipation of the carbaryl from
the soil was 135 days. Previous investigation obtained a half-life of car-
baryl in soil of 8 days which would result in 95% residue reduction in 35
days. There were localized differences in carbaryl dissipation in small
areas throughout the watershed. In all areas there was a lag of 25 to 116
days before any dissipation of carbaryl from the soil. This lag period is
indicative of microbial degradation. Once degradation began, it proceeded
at a fairly rapid rate in all areas of the watershed.
3.3.2 Adsorption. Leaching and Runoff
This persistence of carbaryl in soil is influenced by soil type primari-
ly because of the differences in the adsorptive characteristics of various
soils. Carbaryl adsorbs readily to organic soils but moves rapidly through
inorganic soils. Dissipation of carbaryl from field soils low in organic
matter may not be due entirely to degradation but may be due in part to
leaching.
A-347 i
-------
Leenheer and Ahlrichs (17)studied adsorption of carbaryl on soil organic
surfaces and found that adsorption was completely reversible. The
amount of carbaryl that could be desorbed increased as the soil temperature
increased from 5 to 40°C. The adsorption was thought to be due to weak chemi-
cal bonding between the hydrophobia portions of the pesticide molecule and
soil particle.
The desorption of carbaryl with water was investigated by LaFleur (45) in
soils with 5.16 and 0.15% organic matter. The K. or ratio of the amount of
carbaryl retained to the amount desorbed was 3.7 for the organic soil com-
pared to 0.12 for the inorganic soil. These ratios indicate that organic
soil adsorbs carbaryl more tightly than inorganic soil. Carbaryl residues
were extracted from each soil at various depths of a soil column. Seventy-
two percent of the carbaryl in the organic soil was found in the upper 20 cm;
no carbaryl was found below 60 cm of the 100 cm column. The carbaryl was not
very mobile in the organic soil. Only half of the carbaryl applied to the
inorganic soil was retained in the column. This carbaryl was very mobile
being evenly distributed throughout the column.
A few field studies on the leaching characteristics of carbaryl have been
done. Klein, et al (32) performed lysimeter and field studies of land waste-
water disposal sites. Carbaryl at 0.1 ppm was added to the wastewater efflu-
ents treated in the spray irrigation systems. No residues of carbaryl were
detected in soil samples to a depth of 36 inches during the 14 week stabiliza-
tion period for the disposal system and 26 weeks after addition of carbaryl
to the wastewater. At this low concentration carbaryl is apparently degraded
rapidly enough so that it doesn't translocate with the soil water and would
not accumulate in spray irrigation systems.
in the watershed study by Caro, et al (44) the measurement of runoff after
any rainfall indicated steadily decreasing amounts of carbaryl in runoff and
accompanying sediment. The amount of carbaryl in runoff water and sediment
was reduced substantially in three weeks and measured less than 0.1 ppb 70 days
after application of carbaryl to the soil. Over 90% of the carbaryl detected
in the runoff was found in a single sample taken after a heavy rainfall. Of
the approximately 8.8 pounds of carbaryl applied to the plot, only 0.14% was
recovered in runoff water and sediment. The soil in the watershed was a silt
loam with 1.7% organic matter.
A-348
-------
3.3.3 Microbial Degradation
Microbial degradation appears to be a major contributing factor to
carbaryl dissipation in soils. Bacteria and fungi have been shown.to decompose
carbaryl primarily to CO and 1-naphthol with several hydroxylated products
and some as yet unidentified products also formed. The end products produced
by fungi and bacteria are not identical indicating that degradation occurs
by more than one pathway. Bacteria and fungi have also been shown to degrade
1-naphthol to some extent even though it is toxic to microorganisms. Chemi-
cal hydrolysis will also occur in alkaline soils.
Microbial degradation was studied by Rodriguez and Dorough (46) In soils
receiving varying degrees of carbaryl treatment. Soil A received no pesti-
cide, soil B received a treatment of 4 Ibs per acre of carbaryl six months
previous to the experiments, and soil C had been treated with several pesti-
cides, including carbaryl, over a period of 15 years. Carbaryl was added
to the soils at 10 ppm. The most rapid decrease in carbaryl was observed in
soil B between the first and second day after treatment. On the fourth day
after treatment soils A and C retained over 90% of the carbaryl applied where-
as soil B retained only 28%. At 120 days, however, 14 to 30% of the carbaryl
was still present in-all three soils. Recent application of carbaryl to soil
appeared to facilitate the immediate decomposition of added carbaryl but had
little effect on the long term rate. Autoclaved soils did show reduction in
carbaryl over time but at a slower rate than in nonsterile soils. After 14
days incubation, autoclaved soil B retained 71% of added carbaryl as compared
to 19% for nonsterile soil -B. Also in autoclaved soil B there was no evolu-
tion of C02 or formation of 1-naphthol, which in other studies have been
identified2as microbial degradation products (47,48,49). Carbaryl in culture
media with bacteria, fungi and nonsterile soil retained the following % of
added carbaryl after 14 days incubation (46):
bacteria, ,10 to 0% (one bacterium, 53%)
fungi, 54 to 79%
soil B, 19%
uninoculated control, 76%
Dissipation of carbaryl in the uninoculated control was probably due to chemi-
cal hydrolysis.
A-349
-------
Microbial degradation of carbaryl in soil was demonstrated by Bollag. and
Liu (49) in studies using a fungus and two bacterial strains. The carbaryl
used was radioactively labelled at the terminal methyl group and loss of radio-
activity was used as a measure of degradation. Metabolites were analyzed by
thin layer chromatography; 1-naphthol and several unidentified compounds were
found. CO. evolution was not measured directly. Chemical hydrolysis to 1-
naphthol was not considered to be a possible avenue of degradation in these
experiments because of the end products formed. The lost label was on the
methyl carbon and not the carbonyl carbon that forms CO in chemical hydrolysis.
Uninoculated controls, in which chemical hydrolysis took place, showed no loss
of radioactivity.
Chemical hydrolysis:
0-C-NH-C*H.
Alkaline^
V
CO + C*H NH_
Carbaryl
1-naphthol
carbon
dioxide
(unlabelled)
methy1-
amine
(labelled)
Microbial degradation:
0
II
0-C-NH-C*H,
Microbes
C*°
1-naphthol carbon
dioxide
(labelled)
Unidentified
products
(unlabelled)
In comparison with the bacteria, the fungus, Fusariuro solani. was a more
effective decomposer of carbaryl, decreasing radioactivity by 24% in 5 days
and 82% in 12 days (49). The two bacterial strains degraded 40 and 50% of
the carbaryl in 12 days. Bacterial end products were not the sane as those
of the fungus. Mixed cultures of the three organisms were generally more
effective than pure cultures, degrading from 65 to 80% of added carbaryl in
12 days.
The metabolism of 1-naphthol by these organisms was also studied in the
same series of experiments. Even though 1-naphthol was toxic to the organisms
A-350
-------
in concentrations from 50 to 20 ppm, it was degraded to some extent by all
three microbes. The fungus and the mixed cultures were the most active in
decomposing 1-naphthol compared to pure cultures of the bacteria.
A mechanism of microbial degradation of carbaryl to 1-naphthol was pro-
posed by Bollag and Liu (48):
0
ii
0-C-NH
CH,
CH2OH
CARBARYL
I
t OH
I-NAPHTHYL
/V-HYDROXYMETHYL CARBAMATE
0
n
0-CNH2
1-NAPHTHOL
I-NAPHTHYL CARBAMATE
This study involved degradation of carbaryl by a fungus, Aspergillus terrus.
The metabolism of carbaryl by another fungus, Gliocladium roseuro, resulted
in three hydroxylation breakdown products, two ring hydroxy and one methyl
hydroxy compounds (48):
4-HYDROXY-l-NAPHTHYL
METHYL CARBAMATE
CARBARYL
I-NAPHTHYL
AC-HYDROXYMETHYL CARBAMATE
5-HYDROXY-l-NAPHTHYL
METHYL CARBAMATE
A-351
-------
Kazano, et al (47) studied the degradation of carbaryl in five rice paddy
soils with varying amounts of organic matter. Carbaryl radioactively labelled
at the carbonyl carbon and the ring and labelled 1-naphthol were added sep-
arately to the soils at concentrations of 2 and 200 ppm. Degradation was
measured as evolution of labelled CO . Degradation products were determined
by thin layer chromatography. The CO. evolution measured ranged from 2.2 to
37.4% of the added carbaryl depending upon soil type and carbaryl concentra-
tion. The greatest amount of degradation occurred in the clay soil and the
least in the loamy sand. Hydrolysis was the main pathway of degradation as
determined by analysis of end products. In each soil there was some residual
radioactivity left after solvent extraction. This nonextractable fraction
appeared to be related to soil organic matter content; the soils with rela-
tively high organic matter retained the higher percentage of the residual
label. For example, a 13% organic soil retained 57% of the label in the un-
extractable fraction and soils with 1.5 and 4.1% organic matter retained 17%.
Evolution of C02 from 1-naphthol in soil was dependent upon soil type and
1-naphthol concentration (47). After 60 days incubation an average of about 6%
of the radioactivity in the 1-naphthol evolved as CO , 11% was extracted with
solvents and 78% remained in the soil as nonextractable residues (5% was lost
in analysis).
A bacterium of the genus Pseudomonas was isolated from the rice paddy
soils that metabolized 1-naphthol (47), 7.4% of the label evolved as CO , indi-
2
eating cleavage of the naphthol ring. One of the metabolites identified was
coumarin which is an artifact of a proposed pathway for naphthalene decomposi-
tion. The presence of coumarin indicates that the 1-naphthol pathway could be
similar to that of naphthalene.
Based on the investigations by Kazano, et al(47)and others, Ruhr and
Dorough (50) have proposed the following hypothetical pathway for microbial
degradation of carbaryl in soil (products underlined have been identified as
soil metabolites of carbaryl):
A-352
-------
Unknown
WoUr-tolublti. Ui»«tmctohl«»
Of"
"xA
Cartel
"
O
H
CHj-C-COOM
CO,
Solieytal.
SabcybUyd*
3.4 FATE IN WATER
Carbaryl enters forest streams primarily by direct application as a
consequence of forest spraying. The fate of carbaryl in water is deter-
mined by the effects of dilution, degradation, and adsorption to bottom
sediments. Investigations of carbaryl in water are primarily laboratory
studies of decomposition and measurement of residues.
3.4.1 Residues in Water
Residues of carbaryl were measured in spring and creek water following
application of 1 Ib per acre of Sevin-4-oil to forest test plots (12). An
irregular pattern of carbaryl concentration was found in the water with resi-
dues ranging from 2 to 260 ppb 2 to 3 hours after application. The use of
an oil formulation was thought to produce local accumulations of carbaryl in
floating oil.
The persistence of carbaryl in water has been found to be dependent on
PH and temperature (26). In a study by Szeto, et al (26) creek .and pond water
samples containing 1 ppm of carbaryl were incubated at 9°C with and without
sediment. Autoclaved and non-autoclaved samples were also analyzed. Per-
sistence of carbaryl in the creek water having a PH of 7.0 to 7.1 was greater
than in the slightly alkaline pond water, PH 7.5 to 7.8. After 21 days incu-
bation about 66 to 62% of added carbaryl remained in creek water whereas 46
A-353
-------
to 39% was found in pond water. Autoclaving and the presence of sediment
also increased persistence. In the pond water incubated with sediment there
was a steady decrease in the carbaryl concentration of the water but the sedi-
ment concentration remained about the same from 2 days after inoculation
through day 21 of the experiment.
3.4.2 Photodecomposition in Aquatic Systems
Statements regarding the stability of carbaryl in sunlight indicate con-
flicting views. Some researchers, including those of Union Carbide, report
that carbaryl is stable in daylight including ultra violet light (2,11,36)
Other investigators, however, report photodecomposition of carbaryl and its
metabolites under various conditions (31,33,51). One study involved irradia-
tion of carbaryl in ethanol (33). Several products were formed including 1-
naphthol and methylisocyanate. Some of these products had anticholinesterase
activity. One-naphthol was also a photoproduct in aqueous solution. Wauchope
and Haque (31) state that acidic solutions of carbaryl and 1-naphthol are stable
for weeks at room temperature under laboratory light. However, in basic solu-
tions carbaryl and 1-naphthol decompose forming at least one light sensitive
product. The.carbaryl hydrolyzes in basic solution to 1-naphthol and 1-
naphthol forms 1-naphthoxide ion. This ion appears to be light sensitive,
reacting to give a quinone, lawsone.
Wolfe, et al (33,51) studied photolysis of carbaryl under various labora-
tory conditions. Sunlight was approximated by Pyrex-filtered light from a
mercury lamp. Because chemical hydrolysis does not occur to any appreciable
extent at pH values less than 7, the experiments were carried out in aqueous
solutions of pH 5.5 to 6.9 in order to ensure that observed decomposition was
due primarily to the action of the light. Their results indicate that photo-
lysis of carbaryl in aquatic systems does occur in sunlight. However, 1-
naphthol and methylisocyanate were not products of this photolysis system 03).
The photolysis rate is slowed by the presence of oxygen and is not influenced
by PH in^acid solutions of PH 5 to 7. The calculated half-life for carbaryl
at 30-40 N latitude of 45 to 46 hours agrees with a measured half-life in sun-
light of 45 hours in distilled water buffered to PH 5.5. Table 5 lists the
calculated half-lives in shallow water for carbaryl at various seasons and
latitudes.
A-354
-------
TABLE 5. CALCULATED DIRECT PHOTOLYSIS HALF-LIVES OF CARBARYL AT DIFFERENT
SEASONS AND LATITUDES IN THE NORTHERN HEMISPHERE (33)
Latitude, °N
0
30
40
50
70
Spring
43
51
64
90
292
Half-life,
Summer
45
46
52
61
121
. — ,, ^
hrs*
Fall
41
68
102
186
1760
Winter
43
103
200
571
43800
water
Several factors determine the extent to which sunlight will influence
the decomposition of carbaryl in forest streams. The level of dissolved
oxygen, pH and the amount of incident radiation appear to be important. The
variation of photolysis half-life with season, as determined by Wolfe, et al (51)
indicates that at the time of application in the summer months photolysis rates
can be as much as four times the rate in the winter months.
3.4.3 Chemical Degradation; Hydrolysis in Water
The rate of hydrolysis of carbaryl is rapid enough to be a significant
degradation pathway likely to occur in nature (52). Hydrolysis rates are
affected by temperature and PH (3D. The following are half-lives of carbaryl
in sea water of pH 8 at varying temperatures (31,34):
Temperature, C
3.5
17
20
28
1 month
4.8 days
3.5 days
1.0 days
Carbaryl is stable at PH values from 3 to 6. Wolfe et al (51) observed no
decomposition of carbaryl in 10 days in water at 47 C and PH 5. Rapid hydro-
lysis of carbaryl to 1-naphthol, however, occurs at PH values above 7. The
following are half-lives of carbaryl in water at varying PH levels (33):
9
8
7
6
5
3.2 days
1.3 days
13 days
4.4 months
3.6 years
A-355
-------
A study of the fate of carbaryl in estuarine water and mud was made by
Karinen, et al (34). Carbaryl radioactively labelled at the carbonyl carbon
and at the ring carbon was added at concentrations up to 25 ppm to sea water
(pH 8) and sediment. Two systems were set up, one at 8°C and the other at
20°C. Dissipation of carbaryl and evolution of (X>2 was considered indicative
of degradation.
At 8 C recoverable carbaryl residues in sea water containing sediments
decreased with only a slight increase in the 1-naphthol concentration. A
corresponding increase in carbaryl and 1-naphthol was found in the sediment.
The carbaryl was adsorbed to the mud and slowly degraded. Sea water alone
at 8°C did not degrade the added carbaryl to an appreciable extent; 90% was
still present after 38 days. At 20°C carbaryl quickly dissipated to about
50% of the original concentration in 5 days and then slowly degraded. At 5
days the 1-naphthol formed began to decompose. CO evolution from the car-
• bonyl group began on the first day of the experiment; CO2 from the ring struc-
ture began to appear on day 5. inability to recover more than half of the
label from the 20°C system lead to speculation that a non-reactive gas such
as methane was also a product of degradation, other investigations have
observed the retention of label (e.g., unextractability with solvent) in
soil and sediment (47,53). The results of this study show that carbaryl is
likely to persist in estuarine mud from 2 to 6 weeks (34).
In a laboratory study Pritchard (53) investigated degradation of carbaryl
in experimental ecosystem chambers containing sterile and nonsterile water
and sediment from a salt marsh and from a toxic waste disposal pond. Varying
amounts of unextractable material were found in all systems. This material
may be polymers or cell biomass. Products of carbaryl degradation in non-
sterile water were 1-naphthol and C0r No O>2 was evolved and only 5.3% of
added carbaryl was in the for* of 1-naphthol in the sterile water. Several
other unidentified products were formed in both systems.
4.0 IMPACTS ON NON-TARGET ORGANISMS
Forestry use of carbaryl can be expected in general to affect insect
and arthropod populations and the aquatic biota in the area being sprayed.
Carbaryl exhibits little phytotoxicity and its effect on wildlife, includ-
ing birds, appears to be minimal. The high toxicity of carbaryl to honey
A-356
-------
bees is probably the major hazard to non-target organisms in forest appli-
cations. Some fish and certain aquatic invertebrates, including insects,
have also been shown to be particularly sensitive to earbaryl. Table 6 lists
carbaryl toxicities to various organisms.
Natural waterways in forested areas are the ecosystems most vulnerable
to injury by carbaryl contamination. Protection of sensitive arthropods
that are food for fish is of critical importance in maintaining balance in
the system (54). Chronic exposure of aquatic biota is unlikely because car-
baryl is usually applied to forests only once a year. Newton and Norgren (54)
propose that maintenance of 0.2 ppb in large rivers with somewhat higher con-
centrations in feeder streams should provide adequate prbtection against .
short term damage to aquatic systems due to a single forest application of
carbaryl.
4.1 PLANTS
Carbaryl has very little phytotoxic effect. As noted in Section 1.1,
carbaryl is used directly on a variety of crops for insect control. Under
certain conditions, however, carbaryl can cause injury to some plants. For
example, carbaryl has been reported to cause damage to Boston ivy, water-
melons, apple leaves, apples and pears (2). The manufacturer warns users that
some foliage may be injured if rain or high humidity persist for several
days after application. Carbaryl causes young fruit to fall from apple trees
if applied 10 to 25 days after full bloom and is used for fruit thinning (1).
4.2 FISH AND OTHER AQUATIC ORGANISMS
Carbaryl is toxic to fish with 96-hour median tolerance limits (LC50>
ranging from about 1 to 20 ppm (54). Fish are generally more sensitive to
1-naphthol than to carbaryl. One-naphthol at 1.3 ppm is reported to be
twice as toxic to fish as carbaryl (57). F.ingerling brown trout are less sensi-
tive to carbaryl in soft, acidic water than in hard, alkaline water that
fosters hydrolysis to 1-naphthol (57). The toxicity of carbaryl to fish in-
creases as the water temperature increases. Carbaryl exhibits a corres-
ponding increase in decomposition by hydrolysis with increasing temperature
•and sunlight (57). The formulation used may also intensify toxicity. For
example, the 48-hour LC5Q for goldfish is 28 ppm for Sevin-4-oil and 14 ppm
for Sevin 50 WP (57).
A-357
-------
Carbaryl can also have indirect effects on fish. Non-lethal concentra-
tions of carbaryl have been shown to increase toxicity to trout of other
pesticides, such as 2,4-D and dieldrin(24). Residues of less than 1 ppm in
streams have resulted in the presence of drifting dead insects which could
result in a change in the eating habits of the fish in these streams (24).
Depressed acetylcholinesterase levels of about 10 to 35% were detected
in fish up to B days following forest spraying of 1 Ib per acre carbaryl in
Maine against the spruce budwom (24), No residues were found in fish tissue.
Some dead fish were found in shallow waters after forest application of 0.75
Ib per acre (24).
Korn (60)exposed channel catfish to carbaryl at 0.28 and 2.6 mg per kg
per week in feed and to 0.05 and 0.25 mg/1 in continuously circulating tank
water for up to 56 days. Fish were sampled at intervals to determine resi-
dues of carbaryl and metabolites. Analysis of carbaryl residues in the fish
indicated that carbaryl was metabolized and excreted by the fish and did
not accumulate to any appreciable extent. Less than 1% of the available
carbaryl was retained by fish exposed via diet. Only 0.0001% of carbaryl
was retained by fish exposed via water. Diet exposed fish placed on carbaryl-
free diets rapidly eliminated the carbaryl. Water-exposed fish placed in
carbaryl-free water maintained previous residue levels.
Carlson (56)investigated the effects of long and short-term exposure
to carbaryl on the growth, survival and reproduction of the fathead minnow.
Carbaryl in tank water for 6 to 9 months at about 0.7 ppm adversely affected
survival, egg release, spawning and egg development. Short-term exposure
indicated a 96-hour TL5Q of 9.0 ppm.
Toxicity of carbaryl to aquatic organisms other than fish has been
studied by a number of investigators. Forest use of carbaryl has been re-
ported to reduce populations of aquatic invertebrates in streams and ponds(36).
The toxicity of carbaryl to crustaceans and roollusks is greater than its
toxicity to fish. Most reported 96-hour LC50's range from about 10 ppb to
3 ppm. Some mollusks are especially sensitive to carbaryl; development of
clam eggs is inhibited by 1 ppb (57,58).
Tagatz et al (61) investigated the effects of low concentrations of
carbaryl on the numbers of individuals and species in estuarine communities
A-359
-------
that developed from planktonic larvae in contaminated tanks. One-naphthol
concentrations were not measured. Since sea water is alkaline, hydrolysis
of the carbaryl to 1-naphthol could have occurred in the experimental tanks.
Carbaryl (or 1-naphthol) concentrations of approximately 10 and 100 ppb added
to the tank water after 10 weeks resulted in a decrease of about 50% in the
number of species and a significantly smaller number of species per tank.
At 100 ppb there was a complete absence of nemertan worms and a two-fold
increase in one species of annelid worm. This study demonstrated a distinct
effect of 0.1 ppm carbaryl (or 1-naphthol) on the natural composition of an
estuarine community.
Chaiyarach et al (55) determined carbaryl median tolerance limits for
freshwater and marine animals important in the food webs in areas around
Texas rice fields routinely sprayed with carbaryl. The freshwater animals
tested were mosquitofish, grass shrimp and crayfish, the marine animal
tested was the mactrid clam. Sevin 80WP was used and added both as a powder
and in an acetone solution. The powder was found to be slightly more toxic
than the liquid probably because of its ability to coat the gills and pre-
vent gas exchange. The results of the bioassays with carbaryl powder are
Presented in Table 7. ,3 shown in Table 7, the clam was the £ tolerant
of the species tested perhaps because it can close its shell and avoid
Prolonged exposure to the pesticide (55). The 24-hour TL for grass shrimp
was found to be 0.41 mg/1 for carbary! powder and 0.42 ^ ^ P
" °f °'°42 " 24 hour
TABLE 7. TLm, ing/1 FOR CARBARYL POWDER (55)
mosquitofish
grass shrimp
crayfish
mactrid clam
40
0.41
2.87
>2000
35
0.24
2.66
1860
32.4
0.14
2.43
350
31.8
0.12
2.43
125
A-360
-------
A three-year study was done in New York state on the effects of forest
spraying of 1 Ib per acre of carbaryl on the aquatic environment (59). This
study found no adverse effects on the watershed monitored due to carbaryl.
Residues greater than 0.1 ppm were not detected in water, soil or insects.
No change in the aquatic insect population could be attributed to the spray-
ing.
4.3 WILDLIFE
Few studies have been done on the effects of carbaryl on forest animals.
The toxicity of carbaryl to mammals and birds, however, appears to be less
than that to aquatic organisms. Carbaryl is used on cattle, poultry,
and pets to control insects. Reported LD5Q's for mammals range between
200 and 850 mg/kg indicating moderate toxicity. LD50'§ for birds are
reported to range from 780 to 2300 mg/kg indicating only slight toxicity.
Mammalian carbaryl toxicity studies discuss effects on the survival and
reproduction of small mammals whereas bird studies emphasize measurement
of brain cholinesterase levels and observation of physical effects.
Barrett (62)investigated effects on cotton rats, house mice and old-
field mice feeding in a millet field sprayed with 2 Ib per acre of carbaryl.
The millet contained about 35 ppm carbaryl resulting in a consumption of
about 1.1 mg carbaryl per adult per day. The carbaryl in the diet produced
a four week delay in reproduction of the cotton rat. .The lag in the popu-
lation density growth rate allowed another species to become dominant.
There were no observed effects on the old-field mouse population. The
house mouse population increased somewhat due to the temporary decrease
in cotton rats.
Subsequent laboratory studies on reproduction in the cotton rat and
house mouse gave results similar to the field study (62). The number of
litters born and the number of females giving birth were reduced by more
than 50% in cotton rats fed 1.1 mg per day of carbaryl. Reproduction in
the house mouse was not affected.
A Russian study of a forest application of 4.46 Ib per acre (0.5 gm
per m2) of carbaryl noted decreases in mole and rodent populations without
observable recovery in two years (38). Residues of carbaryl were detected
A-361
-------
in moles. Reproductive organs contained 5 mg/kg, liver contained 3 mg/kg
and muscle tissue contained 1.5 mg/kg. Another study of application of 0.5
Ib per acre to grassland reported observation of several dead deer mice in
the treated area (5) . A Canadian study found no change in small mammal
populations two months after forest spraying of Sevin-4-oil against the
spruce budworm (63).
The reported effect, of carbaryl on birds include temporary territory
abandonment (7), loss of food supply <«»>. decIMSed
relative liver and Mdney weights («,. and depressed brain cho ]
activity US „,. Kurt, and Studholme («, meas»red residues of
in ground eeding songbirds Inhabiting .„ area sprayed with 1 lb per e
of car aryl Three day. after spraying. trace (0.1 to !.o ppm) alun "ere
ound in both exposed and unerased birds, m this study "
vatlons vere made for the presence or absenc
-re mml. Bucteeti „ ^ "«• "^ '«-.— y and weight gain
UP to 3 weeks following carbarT < "° ""^ " "«*« >°*"l"i°"
the spruce budwor,. ^ -W^_.f a Canadian spruce forest against
Cholinesterase inhibition v,= - u
of e^osure o .^ 1 ^T."^ T ' **""" " ^ M8alt"4e
brain choline.tera ^ L L 12 T' ™' " ^^ "8> '"
forest application of 1 iH 8P6 " " bitd8 "' " 5 d^8
""erent specie, show. ^"Z O'on7lT°tl- ""' "^ "
spraying, had entyme level. «.f * Ur ' C°1UCted the da" Of
.-P. Only ,.« of the bir 7^ lb ^ 2°Z "^ ^ """ " «- «-Ol
exposure TO9 ain^. Th. aut. „ "^ MZyne ^"Itlon Indicating that
inhibition could increase suscet "£T" ^ ^'^ "»"»«tera.e .
obtain food (28). lty '° Prai«"on and tapalt ability to
A-362
-------
Richmond et al (29) measured brain cholinesterase levels as well as several
other parameters in forest birds to determine the effects of a carbaryl
forest treatment at 2 Ib per acre (an application rate which would normally
be used against the Douglas-fir tussock moth). Measurements were made of
breeding bird density, species diversity, nesting success (survival of eggs
or nestlings), brain cholinesterase, abnormal behavior, and presence of sick
or dead birds. Two of the 55 birds tested showed enzyme levels depressed by
23 and 27%. All other measurements were normal. No abnormal behavior, sick
or dead birds were observed. Since at the time of spraying there was no in-<
sect outbreak, this study did not measure the effects of carbaryl on birds due
to ingestion of contaminated insects. In another field investigation where
carbaryl was used to control an actual outbreak of gypsy moth, a 55% decrease
in bird population was noted (29).
Laboratory studies of quail exposed to large doses of carbaryl in
daily feed have shown effects on growth and organ weight (65). Increased
length of exposure intensified observed effects. The presence of carbaryl
in parental diet did not effect offspring. Levels in feed of 900 mgAg of
body weight or less for 14 weeks resulted in decreased body weight and
increased brain, liver and kidney weight. Liver and kidney weight gain
and morphological change were thought to be related to detoxification. The
progeny of exposed quail exhibited normal growth, reproduction and
me::tality rates. Another experiment with chick embryos involved exposure to
mixtures of pesticides by injection into the egg (67). Only 40% of eggs
injected with 5 mg of carbaryl hatched. Only 4% hatched of those eggs
injected with 2.5 mg each of phosdrin and carbaryl. No eggs hatched that
were injected with 2.5 mg each of malathion and carbaryl. Doses for these
chick embryos were massive in terms of expected environmental exposure.
4.4 BENEFICIAL INSECTS
Carbaryl is a fairly broad spectrum insecticide and so affects many
beneficial insects as well as target insects, Honey bees are particularly
susceptible to the toxic effects of carbaryl. The LD5Q in vg a.i. per bee
is 1.3 (2). Certain soil insects and various aquatic insects are also very
sensitive to carbaryl. Its lethal effect on aquatic insects serves to de-
crease the supply of fish food in streams and ponds.
A-363
-------
Croft and Brown (68) report an LD^ for the gypsy moth of 0.26 pg
carbaryl per insect. Corresponding LD^'s for parasites of the gypsy moth
range from 1.0 to 0,03 pg per insect. Coster and Bagenovich (69) investi-
gated the effects of carbaryl on 11 species of predators and parasites of
the southern pine beetle, infested pine trees were cut down and sectioned
into four foot bolts. The center bolts were sprayed with 2.2% carbaryl and
caged. Those insects that emerged from the treated bolts were counted and
compared to emergence from untreated bolts. Five of the 11 species counted
showed significant decreases in emergence from treated bolts. Numbers of
the most common beneficial insect were decreased to 1/3 of the control
Spain aO> studied the litter fauna of plots of a Corsican pine forest
sprayed with approximately 10 and 1 lb cer ar™ nf
Mite populations were
^r™ were 8i
normal alica "" °£ °alaiyl (1°
; ::
°rtteopod8 ot
.
determined. All three parameters for 1- and 2- V
after treatment. Total Uom... and ~" "'"
uere
baryl than pradator. «• confer.) and r ""ceptible to car-
opposed to 5 w.ek. for praaat™ ll! tn "
(71) compared the raapoL.
and a ne.ly.planted J
and species di.arsit, .re mealed be,ore
A-364
-------
effects of carbaryl on arthropods for herbivores (1° consumers) was imme-
diate, pronounced and short term, whereas for carnivores (2° consumers) it
was delayed, less pronounced and long-term. Decreases in arthropod density
and biomass were greater and recovery was more rapid in the old field in-
dicating that the more stable, diverse ecosystem was more resilient than the
monoculture.
Pre- and post-spray populations of insects were compared by Dean, et
al. (72) in New York forests aerially treated with 1 Ib per acre of carbaryl
against the gypsy moth. Predator populations were represented by the
Calosoma beetle; soil forming decomposers were represented by mites and
Collembola, springtails. Measurements of the amount of carbaryl actually
reaching the ground indicated large variations with an average of 0.145 Ibs
per acre to the soil. The Calosoma beetle and Collembola populations were
depressed following treatment and for 3 months afterward but returned to
normal the following spring. A significant (30%) increase in mites occurred
probably due to decreases in predator and/or competitor insect populations.
This increase was temporary; the mite population was also back to normal the
following spring.
The effect of carbaryl on aquatic insects has also been investigated.
The application of 1 Ib per acre of carbaryl to a watershed resulted in
stream residues of 40 to 80 ppb carbaryl (24), This concentration produced
drifts of dead stoneflies, mayflies and caddisflies in the stream. In
similar studies the population of aquatic insects was reduced 60 to 100%(24).
Long term effects have also been reported. Some populations of aquatic
insects did not return to normal up to 2 years after exposure (24).
- . - ' . \
Carbaryl is highly toxic to honeybees producing high bee mortality in
sprayed areas 04). Bee poisoning is indicated by agitated behavior, death
of many bees and queenless hives (73). A queenless hive or one severly
damaged will not live through the following winter. Severe poisoning in '
one instance left one-half of the colonies of a sprayed area without queens
within 30 days of exposure (73). Carbaryl applied as a wettable powder can
be collected by the bee along with the pollen and transported back to the
hive (24,73). The carbaryl in the hive can be incorporated into the pollen
stores and fed to newly emerging bees. Thus, carbaryl can be toxic in the
A-365
-------
hive for up to 8 months. The oil formulation is not as easily collected by
bees and its use is thought to reduce the hazard of carbaryl to bees
(20,22,23,24).
The Sevin label contains a warning that spraying will harm bees in the
spray area. To avoid bee poisoning, hives should be moved beyond bee flight
range (3 to 4 miles) until one week after carbaryl application (2,73). Car-
baryl should not be applied at a time when bees are foraging or when ambient
temperatures are unusually low. At low temperatures residues on crops remain
toxic to bees up to 20 times as long (73).
A series of investigations were carried out in the forests of northeastern
Oregon to determine the effects of carbaryl spraying against the Douglas-fir
tussock moth. Application of Sevin-4-oil at 2 Ibs per acre left residues on
foliage of 39 to 145 ppm on the day of spray (20). Residues of 14 ppm were
found in bee pollen one day after spray. Nearly 50% bee mortality was observed
during the first week (22). Three of the 4 hives in the area were dead by the
following January: The following spring, however, the number of foraging bees
returned to normal due to migration of bees into the area. There was no de-
crease the following year in fruit production of wild plants due to lack of
pollination. Predator ant and yellowjacket populations also showed no long
term effects due to the one carbaryl application (23).
4.5 MICROORGANISMS
Carbaryl toxicity has been noted for marine and freshwater algae and for
soil microbes. Carbaryl at 1.0 ppm suppressed growth of two species of marine
algae; 10 Ppm was lethal for three species (61). Five species of phytoplankton
could not tolerate concentrations of carbaryl greater than 0.1 ppm (61),
The effect of carbaryl on freshwater algae varies with the algal genus (35).
Carbaryl at 0.1 ppm is toxic to Chlorella but Scenedesmus appears to thrive on
it. When exposed to carbaryl, Scenedesmus cell biomass increased by 44 to
57% in 6 days (35). Breakdown of carbaryl to CO2 and w provides nitrogen to
aquatic ecosystems; if nitrogen is a limiting nutrient, carbaryl in natural
waters could produce algal blooms.
Barrett (62) in his study oj the .auet field »pr,y.a with 2 Ibs p« acr.
of carbaryl fauna a significant decrease in litter decoction 3 we.*, fcllo.-
m, t™t. ». decrease was attributed to th. change i» the Icroarthro-
pod population.
A-366
-------
The carbaryl hydrolysis product, 1-naphthol, is toxic to microorganisms.
Bollag and Lui (47) in their investigation of carbaryl and 1-naphthol degrada-
tion by soil microorganisms determined that Fusarium solani can tolerate up
to 50 ppm and certain bacteria 20 to 30 ppm of 1-naphthol.
4.6 BIOACCUMULATION
Bioaccumulation has been studied in various organisms but has been observed
primarily in aquatic biota. Carbaryl has been shown to accumulate in trout
bile (30). The ratio of carbaryl and metabolites in bile to carbaryl in aquar-
ium water was measured as 1064. The ratios of fish tissue concentration to
water concentration are not as high. An aquarium concentration of 2.6 ppm
resulted in ratios for lake trout of 3.6 and for Coho salmon of 4.0 (30). Stor-
age factors in animals are reported as the ratio of carbaryl in tissue to car-
baryl in the diet. Animals tested show low ratios; the ratio for the cow
kidney is 0.01 and for the chicken kidney is 0.006 (30).
Kanazawa et al (21) investigated the fate of carbaryl in an experimental
aquatic ecosystem. Carbaryl concentrations were monitored in soil (bottom
mud), water and tissues of various aquatic organisms. The soil or mud was the
major repository for carbaryl in this ecosystem. After 20 days about 68% of
the radioactivity added as labelled carbaryl was found in the soil, 45% as
unextractable residues. The unextractable residues were non-toxic to Daphnia
which is very sensitive to carbaryl. The water in the system contained about
1% and biomass about 0.1% of the added carbary label. Bioaccumulation ratios
(BAR's) were calculated as ppm carbaryl in dry tissue to ppm carbaryl in the
final test water. The results were as follows:
Source ppm Carbaryl BAR
Soil 1.55
Water 0.00945
Algae 37.9 4000
Duckweed 34.2 3600
Snail 2.81 300
Catfish 1.33 140
Crayfish 2.48 260
The ratios for algae and duckweed are relatively high. These results indicate.
that carbaryl can persist and accumulate in the aquatic environment. Bio-
magnification effects on food chains due to large accumulations of carbaryl
in organisms of the first trophic level is not known.
A-367
-------
5.0 MISCELLANEOUS
A number of issues have been raised regarding the real and potential
consequences of carbaryl use in forestry. These topics include the toxicity
and persistence of 1-naphthol, viral enhancement by carbaryl, possible for-
mation of nitrosamines from carbaryl in soil"and the large aerial carbaryl
spray programs. These issues are briefly discussed in this section.
The main product of carbaryl decomposition is 1-naphthol. It is readily
formed in an alkaline environment. There is some evidence that 1-naphthol is
more toxic to fish and certain aquatic organisms than carbaryl itself (59).
1-naphthol is considered toxic by ingestion and skin absorption (41)..Methods
of determining carbaryl residues do not always differentiate between carbaryl
and 1-naphthol (34,44) so that properties attributed to carbaryl may be due to
1-naphthol formed by hydrolysis prior to analysis.
The apparent microbial breakdown of carbaryl in soil to 1-naphthol could
result in a more persistent compound than the original pesticide. Sjoblad
et al (74) have isolated an extracellular fungal enzyme that catalyzes the poly-
merization of 1-naphthol to dimeric, trimeric, tetrameric and pentameric
forms. Polymerization of 1-naphthol and its interaction with naturally occur-
ring compounds could produce substances very resistent to microbial break-
down (47), .
The gypsy moth has been a forest pest in the northeastern United States
since 1869 (7). In these forests one to three years of a high population of
gypsy moths is usually followed by seven years of low population due to the
activity of natural enemies such as wasps, birds, mice, parasites and wilt
disease virus. The use of a non-selective insecticide such as carbaryl can
decrease populations of natural insect enemies as well as the gypsy moth.
The main reason for massive spraying against such defoliating insects is to
preserve the eocnomic value of the forest land. Commercial timber in Massach-
usetts, Rhode Island and Connecticut is minimal so that, in these states,
the value of forested land is primarily in terms of recreational use (75).
There is much controversy, especially in New England, over the effectiveness
and desirability of large carbaryl spray programs. Some residents believe
if no spraying is done, the gypsy moth's natural enemies will control the
pest population as well as carbaryl but without the human and environmental
A-368
-------
exposure to pesticide (75). Some of the local objections to the large
scale spray program against the spruce budworm are similar to the arguments
against use of carbaryl for control of the gypsy moth. Some residents ques-
tion the overall efficiency of carbaryl in actually controlling insect infes-
tations in light of the hazards involved in its use (6).
Abrahamsen and Jerkofsky (76) have recently reported a 2 to 15 fold in-
crease in virus production in cell cultures exposed to carbaryl. Although
human virus and human cell cultures were used in these experiments, the same
phenomenon may be exhibited by animal and plant viruses. Enhancement of viral
disease in non-target organisms would be difficult to determine; viral disease
is not monitored other than in domestic animals and birds.
Nitrosamines are known carcinogens in laboratory animals and have been
found in certain pesticide formulations, excluding carbaryl (77). Carbaryl has
been nitrosated; i.e., converted to a nitroso derivative, in the laboratory.
However, no N-nitrosocarbamates were detected when three soils were tested
with 100 and 1000 ppm nitrite and 20 ppm carbaryl (77).
A-369
-------
REFERENCES
1. Von Rumker, R. , et al. Production. Distribution. Use and Environmental
Impact Potential of Selected Pesticides. EPA 540/1-74-001 QPP -
Washington, D.C. 1975. ' '
2- Recommended Uses for Sevin Carbarvl Insecticide. Union Carbide, no date.
3. Data provided by Union Carbide Agricultural Products Company Inc
Jacksonville, Florida. 1980. ««pany, inc.
4. Ciesla, W. , at al. "Field Efficacy of Aerial Applications of Carbaryl
n " 6?
lo!l?!' W7l!'
Substitute". Environment 13(6)
Battle",
Dynamic, of
10.
HandbooV. Meister Publishing Co . , Willoughby , Ohio.
22: 167-171, 1979!
Contamination and Toxicology
es. Agricultural Worker Exposure
-003, USDA, yaklmaf Washington,
A-370
-------
15. Ware, G.W., B. Estesen, and W.P. Cahill. Dislodgeable Insecticide
Residues on Cotton. Bull. Env. Contam. Toxicol. 14(5): 606-609. 1975.
16. Iwata, Y., et al. "Worker Environment Research: Residues From Carba-
ryl, Chlorobenzilate, Dimethoate, and Trichlorfon Applied to Citrus
Trees", Journal Agricultural and Food Chemistry 27(6): 1141-1145. 1979.
17. Leenheer, J.A. and J.L. Ahlrichs. "A Kinetic and Equilibrium Study of
the Adsorption of Carbaryl and Parathion Upon Soil Organic Matter
Surfaces", Soil Science Society of America Proceedings 35: 700-705,
1971.
18. Gangwar, S.K., et al. "Pestistence of Carbaryl in Sandy Loam Soil and
Its Uptake in Bajra, Pennisetum Typhoides", Annals of the Arid Zone
±7(4): 357-362, 1978.
19. Gypsy Moth and Browntail Moth Control, USDA, 1978.
20. David, E.J., et al. "Impact of Chemical Control Applications for the
Douglas-fir Tussock Moth on Beneficial Insects Including Biological
Studies of Bees, Yellowjackets, and Flesh Flies", in Melanderia, Volume
30, R.D. Akre and C.A. Johansen, ed., Washington State Entomological
Society, 1978. p. 1-8.
21. Kanazawa, J., et al. "Distribution of Carbaryl and 3,5-xylyl Methyl-
carbamate in an Aquatic Model Ecosystem", Journal Agricultural and
Food Chemistry 2.3(4): 760-763, 1975.
22. Robinson, W.S. and C.A. Johansen. "Effects of Control Chemicals for
Douglas-fir Tussock Moth, Orgyia pseudotsugata (McDonnough) on Forest
Pollination (Lepidoptera: Lymantriidae)", in Melanderia, Volume J30,
R.D. Akre and C.A. Johansen, ed., Washington State Entomological So-
ciety, 1978. p. 9-56.
23. Roush, C.F.. and R.D. Akre. "Impact of Chemicals for Control of the
Douglas-fir Tussock Moth Upon Populations of Ants and Yellowjackets
(Hymenoptera: Formicidae, Vespidae)", in Melanderia, Volume 30, R.D.
Akre and C.A. Johansen, ed., Washington State Entomological Society,
1978, p. 95-110.
24. Raisch, R.D. Proposed Cooperative Spruce Budworm Suppression Project.
Maine. 1980, USDA FS-80-01, Forest Service, 1980.
25. Yates, W.E., et al. "Atmospheric Transport of Sprays from Helicopter
Applications in Mountainous Terrain", American Society Agricultural
Engineers Paper No. 78-1504. 1978.
26. Szeto, S.Y., et al. "The Fate of Acephate and Carbaryl in Water",
Journal Environmental Science and Health B14(6): 635-654, 1979.
27. Harper, H.A. Review of Physiological Chemistry. 15th Edition, Lange
Medical Publications, Los Altos, 1975. p. 527.
A-371
-------
28. Zinkl, J.G., et al. "Brain Cholinesterase Activities of Birds from
Forests Sprayed with Trichlorfon (Dylox). and Carbaryl (Sevin-4-oil)",
Bulletin Environmental Contamination and Toxicology j^U): 379-386,
1977.
29. Richmond, M.L., et al. "Effects of Sevin-4-oil, Dimilin and Orthene
on Forest Birds in Northeastern Oregon", USFS Research Paper PSW-148.
Berkeley, 1979.
30. Relative Risks of Dimilin and Alternative Pesticides. Clement Asso-
ciates, Washington, D.C. 1978.
31. Wauchope, R.D. and R. Haque. "Effects of pH, Light and Temperature on
Carbaryl in Aqueous Media", Bulletin Environmental Contamination and
Toxicology 2(5): 257-260, 1973.
32. Klein, S.A., et al. An Evaluation of the Accumulation. Translocation
and Degradation of Pesticides at Land Wastewater Disposal S-tt-gg MTTS
AD/A-006-551, 1974. — ~" K -'
33. Wolfe, N.L., et al. Chemical and Photochemical Transformation of
Selected Pesticides in Aquatic Systems. EPA 600/3-76-067
1976.
34. Karinen F.J. et al. "Persistence of Carbaryl in the Marine Environ-
ment: Chemical and Biological Stability in Aquarium Systems", Journal
Agricultural and Food Chemistry ,15(1) : 148-155, 1967.
Tesel "Cheoical and Microbial Degradation of
1973! pesticides in Aquatic Systems", Residue Reviews 45: 95-124,
36> ^tminary Carbarvl Position iw^.-^,. , , EPA> OPP( Washingtont D>c>
37. Still G.G. and R.A. Herrett. "Methylcarbamates, Carbanilates and
Action Jdr8^ ^ Her^"^ C^Ltrr. »**r^™?"*^* ^
Action» P-C. Kearney and D.D. Kaufman, ed. 1975 - aS~2£
"'
"• •—
A-372
-------
42. Kuhr, R.J., et al. "Dissipation of Guthion, Sevin, Polyram, Phygon and
Systox from Apple Orchard Soil", Bulletin Environmental Contamination
and Toxicology 11(3): 224-230, 1974.
43. Crockett, A.B., et al. "Pesticides in Soil: Pesticide Residue Levels
in Soils and Crops FY-70, National Soils Monitoring Program II", Pesti-
cides Monitoring Journal .8(2): 69-97, 1974.
44. Caro, H.J., et al. "Persistence in Soil and Losses in Runoff of Soil
Incorporated Carbaryl in a Small Watershed", Journal Agricultural and
Food Chemistry 212(5): 860-863, 1974.
45. LaFleur, K.S. "Carbaryl Desorption and Movement in Soil Columns",
Soil Science m.(4): 212-216, 1976.
46. Rodriguez, L.D. and H.W. Dorough. "Degradation of Carbaryl by Soil
Microorganisms", Archives Environmental Contamination and Toxicology
.6: 47-56, 1977.
47. Kazano, H., et al. "Metabolism of Methyl-carbamate Insecticides in
Soil", Journal Agricultural and Food Chemistry ^0(5): 975-979, 1972.
48. Laveglia, J. and P.A. Dahm. "Degradation of Organophosphorous and
Carbamate Insecticides in the Soil and by Soil Microorganisms", Annual
Review Entomology 22: 483-513, 1977.
49. Bollag, J.M. and S.Y. Lui. "Degradation of Sevin by Soil Micro-
organisms", Soil Biology and Biochemistry _3: 337-345. 1971.
50. Kuhr, R.J. and H.W. Dorough. Carbamate Insecticides; Chemistry. Bio-
chemistry and Toxicology. CRC Press, Inc., New York, p. 146-161, 1976.
51. Wolf, N.L., et al. "Carbaryl, Propham and Chlorproham: A Comparison
of the Rates of Hydrolysis and Photolysis with the Rate of Biolysis",
Water Research JL2: 565-571, 1977.
52. Wolf, N.L., et al. "Use of Structure-reactivity Relationships to
Estimate Hydrolytic Persistence of Carbamate Pesticides", Water Research,
12: 561-563, 1977.
53. Pritchard, A Comparative Study of the Fate of Carbaryl. Methyl Parathion
and Pentaehloroohenol in Aquatic Biodeeradation Test Systems (Draft),
EPA, Gulf Breeze/Florida, 1980.
54. Newton, M. and J.A. Norgren. Silvicultural Chemicals and Protection of
Water Quality, EPA 910/9-77-036, Region 5, Seattle, 1977.
55. Chaiyarach, S., et al. "Acute Toxicity of the Insecticides Toxaphene
and Carbaryl and the Herbicides Propanil and Molinate to Four Species
of Aquatic Organisms", Bulletin Environmental Contamination and Toxico-
logy 14(3): 281-284, 1975.
A-373
-------
56. Carlson, A.R. "Effects of Long-term Exposure to Carbaryl (Sevin) on
Survival, Growth.and Reproduction of the Fathead Minnow", Journal
Fisheries Research Board of Canada 29; 583-587, 1971.
57. Booth, D.C. Pesticide Monitoring of State Forest Insect Control Ooei
tions in New York State. NTIS PB 279-833, 1975. ~~
58. Pimentel, D. Ecological Effects of Pesticides on Kon-1-...r.-* Qreanist
Office of Science and Technology, 1971". — ° s °"
59. Reese, C.D., et al. The Movement and
of Pesticides Used 4
6 AqUStiC
60. Kom, S. "The Uptake and Persistence of Carbaryl in Channel Catfish"
Transations of the American Fish Society 102(1) * 137-139 1973 '
Manaitob.
Fotest Blrd8"-
«. "Co.binauoas
Insecticid
Januiry 31>
Ecology 11. 467-481, 194
ComparLon". J<)urMi
A-374
-------
71. Suttman, C.E. and G.W. Barrett. "Effects of Sevin on Arthropods in
an Agricultural and an Old-field Plant Community", Ecology .60(3): 628-
641, 1979.
72. Dean, H.J., et al, "Some Effects of Carbaryl on Mites, Collembola and
Calosoma sp. in an Oak Type Forest", Environmental Entomology ^(4):
793-797, 1975.
73. Johansen, C. How to Reduce Bee Poisoning From Pesticides. Washington
State Western Regional Extension Publication 15, 1980.
74. Sjoblad, R.D., et al. "Polymerization of 1-naphthol and Related
Phenolic Compounds by an Extracellular Fungal Enzyme", Biochemistry
and Physiology .6: 457-463, 1976.
75. Kunz, R.F., ed. "Man vs Gypsy Moth", Connecticut Conservation Reporter
£(6-7), 1971.
76. Abrahamsen, L.H. and M. Jerkofsky. Interaction of Human |a'ricella-
Zoster Virus with Sevin in Cultures of Human Cells, University of Maine,
Orono, 1980. (An abstract).
77. Kearney, P.C. "Nitrosamines and Pesticides: A Special Report", Pure
and Applied Chemistry .52: 499-526, 1979.
A-375
-------
Common Name:
Chemical Name:
Trade Name:
Trichlorfon
0,0-Diaiethyl (2,2,2-trichloro-l-hydroxyethyl) phosphonate
Dylox 1.5 Oil, Dylox 4
Major Applications Control of gypsy moth and spruce budworm
in Forestry:
generally U8S
chlorfon l. tob
solubility. It
under
:
SUMMARY
«•»
30
by
.
ptoces"s- Half lit. In 80ll ls
£rom BoU
water
. Parti=»l.rly
toxic to honey bUs. Trichlorfon has III* "****«**** is relatively non-
ln birds and i* the white-footed mouse as I^T tO,^U8e SUbaCUte effects
cholinesterase activity. There are r^0^ eyfdenced by depressed brain
togenic in mammals. reports that trichlorfon may be tera-
A-376
-------
1.0 INTRODUCTION
Trichlorfon is an organophosphorus insecticide and parasiticide ori-
ginally developed by Farbenfabriken Bayer GmbH, Leverkusen, West Germany (1).
In the United States, trichlorfon is formulated into finished products and
marketed by the Agricultural Chemicals Division of Mobay Chemical Corporation
under the trade name Dylox.
The trichlorfon formulation most commonly used in forest pest control
is formulated in a refined petroleum oil and has the trade name Dylox 1.5
oil. Dylox 1.5 oil is registered and used for gypsy moth control at a dose
of 1 Ib a.i./acre (5.3 pints of formulation) (2). It contains 18.5 percent
active ingredient , 76.2 percent refined petrpleum distillates, and 5.3 per-
cent inert ingredients (2). Dylox 4 is registered and recommended for use
on the gypsy moth, spruce budworm (in Maine and New Hampshire), and forest
tent caterpillars (in Louisiana and Alabama only) (3). It is mixed with
water for application at 1 to 2 pints/acre and contains 39 percent active
ingredient and 61 percent inert ingredients. In the 1979 spruce budworm
suppression program in Maine, approximately 97,000 acres of forestland were
treated with Dylox (4); no Dylox was used in the 1980 program.
Trichlorfon kills insects on contact or by stomach action upon ingestion
by insects. It is registered for use on a wide variety of field crops, ve-
getables, seed crops, and ornamentals, and is effective for the control of
many species of Diptera, Lepidoptera, Hymenoptera, Hemiptera, and Coleoptera
(1).
2.0 PHYSICAL AND CHEMICAL PROPERTIES OF ACTIVE INGREDIENT
The active ingredient of Dylox is 0,0-dimethyl (2,2,2-trichloro-l-
hydroxyethyl) phosphonate:
0 OH
^a^ II I
3 ^** P-CH-CC1
CH ,0
It is a white crystalline powder (determination of molecular weight shows
that it is a bimolecular compound with intermolecular hydrogen bonds) (6)
A-377
-------
with a melting point of 81-82°C and a boiling point of 100°C at 0.1 mm Hg
(18). Its solubility is as follows (7):
• 12.3 g/100 g in water.
• 15.2 g/100 g in benzene.
• 75 g/100 g in chloroform.
It is only slightly soluble in paraffinic hydrocarbons. The vapor pressure
and volatility of trichlorfon are 7.8 x 10~ mm Hg and 0.11 mg/m , respecti-
vely, at 20°C (6). .
Trichlorfon is stable in acid medium and is rapidly hydrolyzed in alka-
line medium. The hydrolysis under different conditions follows two paths.
Under acidic conditions the first product of hydrolysis is 0-methyl-(l-
hydroxy-2,2,2-trichloroethyl) phosphoric acid, which is further hydrolyzed
with mineralization of the molecule (6):
0 OH n n«
II I HOV S ?
(CH30) 2P - CHCC13 + H20 —* CH OH + \ |L •- ^HCCl
0^0' 3
Trichlorfon breaks down very rapidly in the light in dilute solutions. In
alkaline medium trichlorfon is dehydrochlorinated and simultaneously re-
arranged. The principal product of the reaction is 0,0-dimethyl 0-(2,2-
dichlorovinyl) phosphate (dichlorvos, DDVP) (6):
0 OH 0
(CH30)2P - CHCC13 + KOH—*• (0^0) 2POCH = CC12 + KC1 + H 0
Dichloroacetaldehyde, dimethylphosphoric acid, and some other compounds are
formed as products of side reactions.
Prolonged storage of aqueous solutions of trichlorfon leads to partial
hydrolysis of the compound which results in acidification of solutions to-
eluding formation of phosphoric and dimethylphosphoric acids, and HC1.'
3.0 ENVIRONMENTAL FATE
3.1 UPTAKE AND METABOLISM BY PLANTS
Lialted dat. is available re|ardi^ uptake and Mtatolim ta ttmt,
cotton plant, tr^ted rtth "f-trichlor£on „ root uptake
A-378
-------
application for periods up to 9 days were found to contain small amounts of
trichlorfon (7). After 3 days, about 70 percent of the activity was accoun-
ted for as water soluble degradation products. Of this, 60-70 percent was
dimethyl phosphate, 17-24 percent was inorganic phosphate, and less than 5
32
percent was monomethyl phosphate. In another study with P-trichlorfon
applied to individual cotton leaves, dimethyl phosphate was also found as a
major metabolite (7). Minor amounts of 0-dimethyl trichlorfon, DDVP, and
0-dimethyl DDVP were reported. Figure 1 illustrates these possible plant
metabolites of trichlorfon and dichlorvos.
Of all the compounds shown in Figure 1, only trichlorfon (parent com-
pound) and its metabolite DDVP are biologically active and, therefore, of
toxicologic significance (7). It should be noted that DDVP is a considera-
bly more toxic substance than the trichlorfon. The acute oral LD5Q of DDVP
in the rat is 56-80 mg/kg whereas the LD5Q for the Dylox formulation is 450-
630 mg/kg (5).
3.2 PERSISTENCE ON FOLIAR SURFACES
Available data indicates that neither trichlorfon or DDVP presents a
residue problem (5,7). In a 1971 USDA study (8), trichlorfon residues on
Douglas-fir, willow, and grass were monitored at several locations in the
Pike National Forest in Colorado following an aerial application of 1 lb/
acre. The results, presented in Tables 1 and 2 for two test.plots, indicated
a fairly rapid decline on foliage during the first two weeks after applica-
tion. In general, residues taken from grass and willow growing in exposed
areas showed a greater deposit; however, greater exposure also seemed to be
correlated with a faster disappearance of the insecticide. Although the
exact mechanism(s) for the dissipation of trichlorfon on foliar surfaces is
not known, much dissipation is probably due to a combination of chemical de-
gradation and photodecomposition.
Another study performed by the State University College of Forestry at
Syracuse University (9) sought to determine the persistence of trichlorfon
residues in the forest environment via a sampling and analysis of forest
leaves, twigs and litter. Dylox 80% SPA formulation mixed with Sunspray 7N
sumineroil was aerially applied to a forest in New York at the rate of 1 lb/
acre. At the two plots sampled, residue levels on leaves decreased from
A-379
-------
0 OH
CHaOv« t
V-CH-CCIa
CHaO
0,0-dioethy1-tl-hydroxy-2,2,2-trlchloroethy1}-
phosphonate
Parent Coapouna
0 OH
CHsOJI I
>-CH-CCIa
HO' .
0-Methyl-(l-hydroxy-2,2,2-trichloroethyl)-
hydrogen phosphonate
Des nethyl ttl-
ehlorfon
0 OH
HV '
P-CH-CCIa
HO
'l-Hydroxy-2,2,2-trlehloroethyl-dihydrogen
phosphonate
Doubly deaethylated
trichlorfon
CHaO.H
>-0-CH=CC I a
CHaO
0,0-Dl«ethyl-0-(2t2-dichlorwInyl)phosphate
DDV?
0
CHaOvll
)p-0-CH=Clft
HO
0-Hethy 1-0-(2.2-dichlorovinyl)hydrogen. phosphate
peaoetbyl DDVP
0
• CHaOx«
;P-OH
CHaO
0,0-Dimethyl phosphate
DKP
0
CHaOll
HO
Methyl phosphate
Mono aethyl phosphate
Wft HP
Figure 1. Plant Metabolites of Trichlorfon and Dichlorvoe
A-380
-------
TABLE 1. RESIDUE OF TRICHLORFON ON FOLIAGE AND IN WATER AFTER AERIAL
SPRAYING (1 LB/ACRE) BY DAY OF APPLICATION AND DAYS THEREAFTER.
"WEST CREEK" TEST PLOT, PIKE NATIONAL FOREST, COLORADO (8)
Sample
Douglas- fir
Douglas- fir
Douglas- fir
Average
Willow
Willow
Willow
Average
Grass
Grass
Grass
Average
Sainpling
Point
10
11
12
--
13
14
15
—
16
17
18
—
Day 0
Day
1 Day 7 Day 14
ppm*
8.6
11.8
12.8
11.1
80.0
70.7
53.0
63.2
44.1
57.6
27.7
43.1
3.0
7.1
1.2
3.8
48.0
37.9
34.9
40.3
22.8
47.3
19.8
30.0
1.3 0.3
0.5 <0.1
0.6 <0.1
0.8
9.1 <0.1
1.9 0
2.5 0
4.5 <0.1
4.6 2.1
•5.,4 1.9
5.4 <0.1
5.1 <2.1
*Value of one measurement
75 ppm and 105 ppm to 5.93 ppm and 5.76 ppm, respectively, within one week
(see Table 3). Residue levels in twigs and litter samples likewise decreased.
At 106 days postsprey some Dylok was still detectable in all of the samples
analyzed. A follow-up analysis made 343 days postspray showed no measurable
residues of Dylox in the forest soil and samples of current leaves (10).
However, one twig sample showed a small residue, and Dylox residues were
found in all forest litter samples (see Table 4). The levels of residue in
litter, however, were considered too low to be of biological significance.
3.3 FATE IN SOIL
The fate of trichlorfon in the forest soil is determined by physical
processes such.as adsorption, leaching and runoff, and by chemical and
A-381
-------
TABLE 2 RESIDUES OF TRICHLORFON ON FOLIAGE AND IN WATER AFTER AERIAL
' SPRAYING (1 LB/ACRE) BY DAY OF APPLICATION AND DAYS THEREAFTER.
"LONG"TEST PLOT, PIKE NATIONAL FOREST, COLORADO (8)
Sample ,
Douglas -fir
Douglas-fir
Doug las- fir
Average
Willow
Willow
Willow
Average
Grass
Grass
Grass
Average
Sampling
Point
1
2
3
4
5
6
-
7
8
9
-
Day 0
22.4
6.5
8.8
12.6
121.2
87.1
36.9
81.7
101.7
11.3
226.0
113.0
Day 1
ppra
13.5
12.4
5.3
10.4
90.9
80.8
6.6
59.4
39.0
16.4
17.0
24.1
Day 7
1.5
2.2
1.5
1.6
7.3
4.0
0.5
3.9
5.9
12.4
0.5
6.3
Day 14
0.8
0.4
0.8
0.67
0.2
0.0
0.0
0.07
2.9
1.4
2.0
2.1
*Value of one measurement
microbial degradation. Volatilization and photodecomposition are probably
less important because of the low volatility of trichlorfon and minimal
light penetration through the litter layer. Based on the data supplied to
EPA by the manufacturer on the persistence of trichlorfon in various soil
types, half-life values are generally less than 30 days, with most of the
values below 6 days (7).
3-3.1 Adsorption. Leaching aTUj Runoff
Information supplied to EPA by the manufacturer (7) indicates that
trichlorfon is reversibly adsorbed on soil. The extent of adsorption (and
hence, leachability) is dependent on soil type/with high organic soils
exhibiting greatest trichlorfon retention capacity. Table 5 shows the
A-382
-------
TABLE 3. SUMMARY OF DYLOX RESIDUES IN LEAF, TWIG AND
FOREST LITTER SAMPLES (9)
Days Postspray x ppn Dylox t Standard Deviation
Leaves Twigs . Litter
Ward Poundridge Reservation
1 75.0 ± 51.7* 1.73 ± 1.09 5.14 ± 4.52
2 56.7 26.7 1.44 0.94 7.65 7.55
3 34.8 27.5 1.26 0.56 2.85 2.46
4 19.4 14.3 1.33 0.80 3.20 2.87
5 9.57 5.09 1.60 0.63 4.72 3.96
7 5.93 4.87 1.59 0.91 2.14 1.59-
16 1.39 1.66 0.93 0.89 1.13 0.64
28 2.24 1.66 0.93 0.89 1.13 0.64
106 0.73 0.90 0.02 0.04 0.04 0.07
Blue Mountain Reservation
1
2
3
4
5
7
16
•bW
28
*• W
106
105.0
43.4
33.6
13.0
9.49
9.49
0.91
1.90
1.20
121.0
28.2
28.8
8.77
5.21
5.21
0.73
1.66
1.57
3.10
1.27
1.12
2.84
3.29
3.29
0.70
0.66
0.05
1.99
0.67
0.55
1.17
1.97
1.97
0.26
0.24
0.04
6.21
7.44
3.60
9.75
13.7
13.7
6.32
1.38
0.08
7.03
6.32
4.67
9.10
11.6
11.6
3.96
1.31
0.10
Each figure represents the average residue level from
9 sample stations on a specific date postspray.
adsorption coefficients and the estimated amounts of rainfall which would
be required to leach trichlorfon 12 inches into three different soils tested
in the laboratory. As shown in the table, the organic silt loam has the
highest adsorption coefficient and requires the largest volume of water for
leaching.
A-383.,
-------
TABLE 4. SUMMARY OF DYLOX RESIDUE DATA FOR FOREST SAMPLES
COLLECTED 343 DAYS POSTSPRAY FROM BLUE MOUNTAIN
RESERVATION SPRAY PLOT (10)
Sampling
Station
1
2
3
4
5
6
7
8
9
Control
Forest Soil
NM*
"
it
H
M
it
ii
it
"
NM
PPM lyiox
Leaves
NM
ii
"
ii
"
"
"
it
"
NM
TWigs
0.13
NM
11
it
it
it
11
it
it
X -
NM
Forest
Litter
0.81
0.36
0.12
1.18
0.24
0.38
0.20
0.46
0.40
0.46
NM
NM - nonmeasurable peak, equivalent to less than 0.05 ppm.
TABLE 5. TRICHLORFON ADSORPTION AND LEACHING FOR THREE SOILS (7)
Soli lype
Sandy Loam
Silt Loam
Organic Silt Loam
PH
^^•••M
6.4
5.5
5.4
Adsorption
Coefficients
0.25
0.40
0.51
Inches of Water
Required for Leaching
to a Depth of 12 in.
•WMM^
17,4
22.2
25.1
A-384
-------
Because of its high water solubility, trichlorfon is subject to leaching
and washout from soil. The runoff tendency of trichlorfon in leachate was
evaluated in a study where Dylox (4 Ibs/gal) was sprayed on sloping plots of
three soil types (sandy loam, silt loam, and high organic silt loam) (7).
Application was made at 20 Ibs/a.i./acre followed by simulated rainfall
applied once a week for 5 weeks. After the 5-week period, total residues
in the runoff water was analyzed. The amounts of trichlorfon found in the
runoff as percentages of the quantity applied were 2.86 percent, 0.65 percent
and 0.35 percent for silt loam, sandy loam and high organic silt loam, res-
pectively. These results thus confirmed the adsorption results which indi-
cated a higher trichlorfon retention capacity for soils high in organic
matter.
3.3.2 Degradation
Trichlorfon is subject to degradation in soil. The rate of degradation
appears to depend on soil characteristics, including pH. Degradation is
considerably more rapid in alkaline soils than in acid soils (11).
Trichlorfon-l-14C was incubated with wet sandy loam, grey, red and high
organic silt loam soil under aerobic and anaerobic laboratory conditions.
The most important factor contributing to degradation was soil pH. The half-
life in pH 5.3 sandy loam soil was 11 days, while in pH 6.2 soil, it was one
day.
Conflicting data have been reported regarding chemical vs. microbial
routes for the degradation of trichlorfon in soil. In one laboratory study
trrichlorfon degradation was found to be the same in sterile and non-sterile
soils (see Table 6). Other studies (7,12) indicate that trichlorfon degrada-
tion in soil is primarily due to microbial action, with the extent of degra-
dation depending on the species. One study (12) reported that at a trichlor-
fon content of 0.1 to 12.5.mg/ml, 100 percent of the preparation was decom-
posed; 92 percent of the degradation was attributed to microorganisms and
only 8 percent to chemical reactions. At higher concentrations, the tri-
i i Cfor-flization of silty loam soil has
chlorfon was degraded more slowly. Sterilization y
., v, i-hp half-life of trichlorfon while 1 percent sucrose
been shown to double the hair-me 01
added to the soil merged the rate of breakdown, lndic.tlne the ro e of
microorganism In trichlorfon .et.boUs. (7).- In this study, the only
A-385
-------
TABLE 6. TRICHLORFON DEGRADATION IN STERILE AND NON-STERILE SOILS (11)
Concentration
(in mg/kg)
100
100
10
10
Soil
Nonsterile
Sterile
Nonsterile
Sterile
Initial
123.0
123.0
13.0
13.0
Sampling
After
20 Days
22.0
21.6
5.0
5.0
Period
After
30 Days
5.6
5.8
1.04
1.22
After
40 Days
0.52
0.59
0
Traces
metabolic products detected in soil were hydrolytic products resulting from
P-O-CH- rupture.
A laboratory study on forest soils (9), performed at the State Univer-
sity College of Forestry at Syracuse University indicated that Dylox degrades
rapidly in soil (see Table 7). Detectable residues dropped rapidly from the
initial concentration unit. After 13 days, only soil cultures treated with
10 ppm Dylox retained any measurable residues. No DDVP was detected in any
of the samples examined.
TABLE 7. RESIDUES DETECTED AT VARIOUS PERIODS OF TIME FROM
SOIL SAMPLES TREATED WITH KNOWN CONCENTRATIONS OF
DYLOX (ANALYTICAL GRADE) (9)
Initial Dylox Concentration
Days after
treatment 0 (Control
1 PPM
0
3
6
9
13
< 0.05 ppm*
< 0.05 ppm
< 0.05 ppm
< 0.05 ppm
< 0.05 ppm
— — — — — _ _ ___
10 PPM
Sensitivity of analytical procedures: 0.05 ppm.
A-386
-------
3.4 PERSISTENCE IN WATER
The available data indicates that trichlorfon breakdown in natural
water is relatively fast. The breakdown rate is higher under alkaline pH
conditions and at wanner temperatures. Mobay reports that the half-lives
of Dylox in water in the dark at 30°C at pH 5, 7 and 9 are 4.7, 0.6 and 0.1
days, respectively (13). The corresponding half-lives at 50°C are 3.7,.0.2
and 0.03 days, respectively. Dylox in an outdoor pond (pH 7, average tem-
perature 29°C, and exposure to sunlight) showed a half-life of only 0.3 days
(7). A laboratory study performed by McGill University on the chemical sta-
bility of trichlorfon in fresh and salt water concurs that in acidic fresh
water, trichlorfon is relatively stable and may persist long enough to be
absorbed into various levels of the food chain; in contrast, trichlorfon is
unstable in sea water and is readily degraded (14).
The persistence of trichlorfon in forest waters was evaluated in a study
at the State University College of Forestry at Syracuse University (9).
Several forest plots were sprayed with Dylox (1 Ib/acre) without any precau-
tion to avoid direct spraying of the lakes and streams in the study plots.
Dylox residue levels in water samples ranged from 0.40 to 0.06 ppm one hour
after spraying and decreased to a non-detectable level (less than 0.002 ppm)
after 4 days (see Table 8). There were no detectable residues in any of the
mud samples indicating that Dylox does not concentrate in lake and stream
bottom sediments.
TABLE 8. DYLOX RESIDUES IN LAKE AND STREAM WATER SAMPLES (9)
PPM Dylox in Water
Prespray
1 Hour
1 Day Postspray
2 Days Postspray
3 Days Postspray
4 Days Postspray
5 Days Postspray
7 Days Postspray
16 Davs Postspray
Sampling Site; Lake
ND*
0.400
0.071
0.022
0.006
0.002
ND
ND
ND
Lake
ND
0.100
0.041
0.016
0.006
0.002
ND
ND
ND
Lake
ND
0.062
0.085
0.061
0.005
0.004
ND
ND
ND
Stream
ND
0.084
0.034
0.020
0.042
0.002
ND
ND
ND
Stream
ND
0.060
0.036
0.010
0.023
0.004
ND
ND
ND
* \l> * \ot detectable; less than 0.002 ppm.
A-387
-------
Analysis for DDVP (a Dylox metabolite) residues indicated that several of
the water samples contained small amounts of DDVP (see Table 9).
TABLE 9. DDVP RESIDUES IN WATER (9)
Sample
Water
Water
Water
Water
Water
Water
Water
Sampling Site
Lake
Lake
Stream
Stream
Stream
Stream
Stream
Sampling Interval
1 Hour
1 Day Postspray
2 Days Postspray
3 Days Postspray
4 Days Postspray
5 Days Postspray
7 Days Postspray
PPM DDVP
0.010
0.007
ND*
0.002
ND
ND
ND
Not detectable; less than 0.002 ppm for water.
4.0 IMPACTS ON NON-TARGET ORGANISMS
4.1 IMPACTS ON AQUATIC ORGANISMS
Laboratory acute toxicity data indicate that trichlorfon is highly
toxic to certain aquatic organisms, particularly to some aquatic inverte-
brates (Table 10). Field evaluations of the effects of trichlorfon on aqua-
tic insects also indicate that trichlorfon can be lethal to certain species
(e.g., stoneflies and Collembola) even at the recommended application rate
of 1.0 Ib/acre (4).
Trichlorfon is less toxic to fish than to invertebrates (Table 10). In
fact, some fish parasites have been treated with trichlorfon. One trichlor-
fon formulation, Masoten, is registered for the control of fish parasites at
a recommended application rate of 0.5 lb trichlorfon/acre-ft of water (A)
Dylox has also been tested as a control for fairy shrimps in fish hatchery
ponds. It is highly toxic to fairy shrimp at levels of 0.10 and 0.25 mg/L-
mortality exceeded 82 percent in 48 hours in laboratory tests.
In studies exposing rainbow trout and eastern brook trout to continuous
applications of 1 ppm and 10 ppm, respectively, there were no effects ob-
served after 24 and 72 hours of exposure (7). but rainbow trout exposed to
A-388
-------
10 ppm for 24 hours did not survive. However, a level of 10 ppm is much
higher than levels expected from forest spraying. Field investigations of
the impact of trichlorfon on aquatic organisms in forest waters have indi-
cated little adverse effects on fish when Dylox is applied at the recommended
application rate of about 1 Ib/acre (4).
Dylox also does not appear to bioaccumulate in aquatic species. In one
postspray field investigation of trichlorfon residues in fish tissue, resi-
due levels peaked 12 and 24 hours after a 1.0 Ib trichlorfon/acre application
and were at or below detectable limits (<0.02 ppm) after 96 hours, thus in-
dicating that trichlorfon was eliminated and not bioaccumulated (4). In
another field study (9), Dylox was aerially applied at the rate of 1.0 Ib/
acre over forest plots including lakes and streams. No Dylox residues were
detected in fish or snake samples; however, a small residue was found in one
frog sample taken one day postspray (see Table 11). No residues were found
in frog samples taken 3 days postspray. In rooted aquatic plant samples,
Dylox residues were found through the 28th day postspray, but not detected
at 106 days.
In tests for residue accumulation in fish, bluegill and catfish were
exposed to trichlorfon at a concentration of 1 ppm in the water (7). Maximum
residue in edible flesh was 0.02 ppm in samples taken 4 hours after the last
of four applications at 7-day intervals. Samples taken 20 hours later con-
tained <0.01 ppm.
4.2 IMPACTS ON SOIL MICROORGANISMS
As noted previously, microbial degradation is believed to be a major
factor in the degradation of trichlorfon in soil. One laboratory study using
various cultures of soil bacteria and fungi indicated that trichlorfon at
concentrations of 1, 5 and 10 ppm had no apparent effect on the population
of microorganisms (see Table 12) (9).
In another study (7), day loam and silt loam soils were treated with
trichlorfon at 50 and 250 mg/kg and maintained at 50 percent field moisture
capacity for 56 days. No effect was noted on populations of fungi, bacteria,
or actinomycetes due to treatment.
A-390
-------
TABLE 11. DYLOX RESIDUES IN VARIOUS AQUATIC ORGANISM SAMPLES (9)
Sample
Fish*
Fish
Fish
Frogs
Frogs
Frogs
Water Snake
Rooted Aquatics +
Rooted Aquatics
Rooted Aquatics
Rooted Aquatics
Rooted Aquatics
* Composites of small
Sampling Interval
(Days Postspray)
Prespray
3
78
Prespray
1
3
3
Prespray
1
3
28
106
blue gills (Lepomis
PPM Dylox
ND*
ND
ND
ND
0.06
ND
ND
ND
0.24
0.33
0.05
ND
macrochirus) .
f Composite of arrow arum fPeltandra cf. virginica).
* ND - not detectable; less than 0.05 ppm.
4.3 IMPACTS ON NON-TARGET INSECTS
Trichlorfon will reduce populations of some non-target insects even at
recommended application rates. Adverse effects on various insect species
have been reported as a result of trichlorfon treatment for the control of
gypsy moth and spruce budworm (16). In Connecticut, flesh flies, Tacinidae
and true bugs were reduced by 90 percent after trichlorfon treatment. True
flies, ants, wasps, moths and butterflies were reduced after trichlorfon
treatment in New York. In Maine, reduced populations of spiders, gnats,
butterflies and tachinids were reported.
Available data indicate that trichlorfon is relatively non-toxic to
honey bees. One study indicated that bees caged with trichlorfon treated
foliage (sprayed 2 hours previously) sustained only 7 to 18 percent mortali-
ty (4). Trichlorfon residues are not expected to be transported by foraging
bees from contaminated surfaces into hives (A). The toxicity to honey bees
A-391
-------
TABLE 12. NUMBERS OF MICROORGANISMS PER GRAM OF SOIL AT VARIOUS PERIODS
OF TIME AFTER TREATMENT WITH KNOWN CONCENTRATIONS OF DYLOX'
DILUTIONS PLATED ON 3 MEDIA (9). '
Initial
Dylox
cone.
0 ppm
(Control)
1 ppm
5 ppm
10 ppm
Days after
treatment
0
3
6
9
13
0
3
6
9
13
0
13
0
6
13
IT A t
N.A.T
Bacteria
128
272
148
261
303
126
197
189
275
333
146
317
145
181
271
117
202
223
164
381
Microorganisms/gram of soil*
N.F.
Bacteria
96
212
89
84
92
76
80
91
79
--
89
155
139
67
88
68
157
77
74
88
Bacteria
9
515
126
247
245
19
3
142
392
217
680
278
93
222
359
43
195
205
275
259
P.G.A.
fungi
15
85
40
20
46
14
30
44
21
13
70
42
44
41
122
18
58
34
22
53
Total
24
600
166
267
291
33
33
186
413
230
750
320
137
263
481
61
253
239
297
312
for bacteru -
acid
****' "'*' ' nitro**»-f™ agar; P.G.A. - peptone glucose
A-392
-------
has been measured in laboratory studies with an LD of 59.83 ug/bee, a
level considered to be relatively non-toxic (17).
4.4 IMPACT ON BIRDS
No bird mortality has been observed in field observations following
application of trichlorfon at a rate of 1 Ib/acre (19,20). However, tri-
chlorfon may induce certain subacute effects in birds such as depression of
brain cholinesterase levels. Such depression has been used as an indicator
of organophosphate poisoning. Passerine bird species were analyzed for
brain cholinesterase levels following spraying of 1.13 kg/ha of trichlorfon
in forest plots in southwestern Montana (21,22). Sufficient data were
obtained from 10 species to evaluate the effects of trichlorfon on brain
cholinesterase activity. One dark-eyed junco, one evening grosbeak, two
mountain chickadees, and two western tanagers had values which were at least
2 standard deviations below the mean. The western tanagers collected on the
day of spraying had depressed brain cholinesterase activities 21 percent and
27 percent below the mean. The evening grosbeak (collected on day 3) had
19.7 percent inhibition.
In another study (20), trichlorfon was applied to forests in south-
western Montana at a rate of 1 lb a.i. in 1 gallon per acre. No significant
decrease in bird numbers was detected based on breeding-pair estimates and
live bird counts after spraying. No sick or dead birds were found and the
success of nests in sprayed plots did not differ significantly from those
of the control plots.
Messick, et al. (19) found that trichlorfon applied at recommended
application rates does not cause major pheasant losses in southwestern
Idaho. Observations on penned and radio-equipped wild pheasants within the
treatment area revealed no direct mortality from spraying. Penned pheasants
5 to 15 days old exhibited symptoms of organophosphorus poisoning, but re-
covered. Crop analysis indicated that pheasants in the treated area consumed
significantly fewer insects than those birds in the control area, probably
due to decreases in insect availability as a result of spraying.
Songbirds collected from areas sprayed with trichlorfon at a rate of
1 Ib/acre in eastern Pennsylvania contained low, but detectable levels of
trichlorfon (23). The amounts found were 0.001 ppm in a blue jay, 0.003 to
A-393
-------
0.01 ppm in crested flycatchers, and 0.005 to 0.04 ppm in Baltimore orioles.
These residues are considered to be very small and, in most cases, are
within the USDA allowances for residues in beef (0.1 ppm), milk (0.01 ppm),
and many vegetables (0.1 ppm).
Toxicity data is available for some bird species to trichlorfon. In
bobwhite quail, the LD50 is 500 mg/kg in feed (7). A level of 25 ppm In the
diet has been found to reduce reproduction by 25 percent. For ringnecked
pheasant, an oral LD50 of 25 mg/kg in feed has been determined (7). Acute
oral LD5Q values of 28 to 50 mg/kg and 38 to 50 mg/kg have been reported for
redwinged blackbirds and starlings, respectively (7).
4.5 IMPACTS ON MAMMALS
Toxicity of trichlorfon to mammals has been studied since it is used
in veterinary practice to kill pests on animals. In one study (24), sheep
were given 3 or 10 percent aqueous solutions of trichlorfon. Animals re-
ceived levels up to 0.2 g/kg. A slight increase in body temperature as well
as an increase in the number of leukocytes was noted. The highest blood
level reached was 2 mg/kg, 1-2 hours following administration. After 6 hours
only trace levels remained in the blood and none was detected after 30 hours.
Histologic studies of the liver, kidney and cardiac muscle revealed minor
effects which were reversible,
Iri a cow treated orally with trichlorfon and a dog injected with tri-
chlorfon, most of the chemical was metabolized and excreted in the urine (7)
ported
dimethyl phosphate, monomethyl phosphate, demethylated trichlorfon 2 2 2-
trichloro-1-hydroxyethyl phosphate, methanol, formic acid, and CO/ ' '
Table 13 presents the toxicity data reported by Mobay Chemical Corp.
for various trichlorfon formulations.
There have been reports that trichlorfon may be teratogenic in mammals.
ne study has indicated that trichlorfon is te,ato8enic ln rats at doses of
"" ^-d embryonic and
genie effects in rats from an 80 mg/kg dose (4).
In field studies, depressed brain cholinesterase activity has been
observed in the white-footed mouse following an application of 1.0 Ib/acre
A-394
-------
TABLE 13. TOXICITY DATA FOR VARIOUS TRICHLORFON FORMULATIONS (1)
Formulation
Technical
80% soluble
powder
1.5 oil
Liquid
solution
5% granular
bait
Species
Rat
Rabbit
Rat
Rat
Rat
Rat
Sex Oral LD5Q, Dermal LD5Q,
mg/kg mg/kg
M ISA
F 144
M
F Approx, 470
F 2,500
F 950
M
F
>2,000
>2,000
>2,100
>2,000
>2,000
>2,000
Inhalation LC^Q,
yg/1/60 min
>10,000
>20,000
>20,000
>20,000
of trichlorfon (4)., In other studies, however, no impacts on small mammals
have been observed (4). One study reports that inhibition of mammalian
cholinesterase is caused by the dichlorvos formed from trichlorfon (25).
A-395
-------
REFERENCES
1. Dylox Insecticide Technical Information. Mobay Chemical Corp., Agri-
cultural Chemicals Division, Kansas City, Missouri. January 1979.
2. Dylox 1.5 Oil Insecticide. U.S. Label Information, 3/5/79.
3. Dylox A Insecticide. U.S. Label Information, 3/5/79.
4. Raisch, R.D. Proposed Cooperative Spruce Budworm Suppression Project
Maine, USDA Forest Service, N.E. Area, USDA-FS-80-01, 1980.
5. 1980 Farm Chemicals Handbook, Meister Publishing Co., Willoughby, Ohio.
6, Melnikov, N.S. Chemistry of Pesticides. Residue Reviews, Volume 36
Springer-Verlag, N.Y. 1971. ' ¥"'Luaie JD'
of
'?' Ricbmond- ^sidues of Trichlorfon and Lauroyl
After ''1^83' Aspen' F°Ua^. and in Creek
°f Envlr0naen tal Contamination
9. Environmental Impact and Efficacy of Dylox Used for Gypsy Moth Control
ColleL fVt3^' AFcU ReP°rt N°- 10' Stat "
College of Forestry, Syracuse U. , May 1972.
o£
cology Letters, 3: 117-120, 19? nc»iiiMt«taM Potency, Toxi-
A-396
-------
15. Moss, J.L. Toxicity of Selected Chemicals to the Fairy Shrimp, Strep-
tocephalus seali, Under Laboratory and Field Conditions. The Prog.
Fish-Culturist 40(4): 158-160, 1978.
16. USDA. Draft Environmental Statement for Cooperative Gypsy Moth Sup-
pression and Regulatory Program, 1980 Activities.
17. Atkins, E.L., et al. Toxicity of Pesticides and Other Agricultural
Chemicals to Honey Bees - Laboratory Studies. U. of Calif., Division
of Agricultural Sciences Leaflet 2287, 1975.
18. Dylox 1.5 Oil Insecticide. Mobay Chemical Corp. Information Bulletin.
Kansas City, Missouri. Undated.
19. Messick, J.P., et al. Aerial Pesticide Applications and Ring-Necked
Pheasants, U. of Idaho, Moscow, Ida. J. Wildlife Management, 38(4):
679-685, 1974.
20. DeWeese, L.R., et al. Response of Breeding Bird to Aerial Sprays of
Trichlorfon and Carbaryl in Montana Forests, U.S. Fish Wildlife Special
Science Report, 1979.
21. Zinkl, J.F., et al. Brain Cholinesterase Activities of Birds From
Forests Sprayed with Trichlorfon (Dylox) & Carbaryl (Sevin-4-oil),
Bulletin of Environ. Contam. & Toxicol., 17: 379-386, 1977.
22. Zinkl, J.6., C.J. Henny, and P.J. Shea. Brain Cholinesterase Activi-
ties of Passerine Birds in Forests Sprayed with Cholinesterase Inhi-
bit! biting Insecticides. In: Anljnals as Monitors of Environmental Pollu-
tants, National Academy of Sciences, Washington, D.C. 1977.
23. Kurtz, D.A. and G.A. Studholme. Recovery of Trichlorfon (Dylox) and
Carbaryl (Sevin) in Songbirds Following Spraying of Forest for Gypsy
Moth, Bulletin of Environ. Contam. & Toxicol., 11(1): 78-84, 1974.
24. Plaan, 0. Toxicity and Retention of Trichlorfon in the Organism of
Animals, Problem Parazitologii V Pribaltike, 4: 159-161, 1970.
25. Reiner, E. Toxicology of Anticholinesterase Pesticides,
Academy of Science & Arts, Zagreb, EPA Health Effects Research Lab.,
Research Triangle Park, N.C. 1977.
A-397
-------
III. BIOLOGICALS
Common Name: Bacillus thuringiensis
Chemical Name: Bacillus thuringiensis Berliner
Major Trade Names: Dipel; Thuricide
Major Applications Bacillus thuringiensis is used primarily in the North-
in Forestry: east forests for control of the spruce budworm in areas
where chemical insecticides cannot be used.
SUMMARY
Bacillus thuringiensis (B.t.) is a microbial insecticide that is parti-
cularly effective in controlling a number of insect species of the order
Lepidoptera. B.t. is formulated as a suspendible powder which is applied
as a water-based aerosol. The active ingredients of B.t. preparations are
bacterial spores, which infect tissues of sensitive insects, and a crystal-
line protein toxin, which becomes active only in the gut of insects with
alkaline pH and the proper digestive enzymes.
There is limited data available on the fate of B.t. in soil and water.
However, the available studies indicate that the spores of B.t. may persist
in the soil for at least several months. Viable spores of B.t. are not ex-
pected to persist in water for longer than one month. The primary cause of
inactivation of the spores in the environment is probably sunlight. The
susceptibility to solar radiation is enhanced under humid conditions.
In field tests of B.t.. no adverse effects on mammals, birds, fish or
on beneficial insects have been observed. In laboratory tests, B.t. has
toxic effects on a few beneficial invertebrates and vertebrates, but these
effects occur only at levels far higher than those achieved under field
conditions of application. Furthermore, B.t. has never been reported to
cause disease in man or in other vertebrates.
A-398
-------
1.0 INTRODUCTION
Bacillus thuringiensis (B.t.) is a naturally-occurring bacterium which
is pathogenic to a number of insect species primarily in the order Lepidop-
tera. All bacteria in the genus Bacillus form endospores which are a dormant
stage in the life cycle. Endospores are highly resistant to both heat and
dessication. Therefore, they can persist for long periods when the environ-
ment is unfavorable for bacterial growth. The spores in these rod-shaped
bacteria are formed several hours after vegetative growth slows and cells
enter the stationary phase. The mature spores are oval bodies located either
centrally or sub-terminally within the parent cell, the sporangium. A dis-
tinctive feature of Bacillus thuringiensis is the presence of a bipyramidal
crystal, the parasporal body, within the sporangium. This crystal, which
has been called "delta-endotoxin", is the principal active ingredient of
B.t. insecticide formulations. Endospores constitute the second active in-
gredient of B.t. formulations.
B.t. was first isolated in Japan in 1901 from diseased larvae of the
silkworm (2) and reisolated in 1911 from diseased larvae of the Mediterranean
flour moth (3). The first commercial use in the U.S. occurred in 1958 when
application of the B.^ formulation, Thuricide, directly to food and
forage crops under the conditions of a temporary exemption from a tolerance
was authorized. Since that time, B.t. use has expanded to include forest
pests. The cumulative total acreage aerially sprayed in the U.S. between
1958 and 1974 for suppression of forest insect populations was 23,000 acres
(4). In recent years, B.t.'s major use in forestry has been for spruce
budworm control in Maine. B.t. was applied to about 200,000 acres during
the 1980 spray program in Maine (5).
Independent isolations of B.t. have produced a number of varieties or
strains of this bacterium that differ in their pathogenic properties as well
as in their serological reactions. Early formulations of B^ manufactured
in the U.S. were produced from _B- thuringiensis var. thurinfjiensis and con-
tained a second toxin called "beta-exotoxin" which has a broad range of
toxicity to insects including honey bees (7,8). However, damage to bees
occurs only at application rates much higher than the recommended rates.
All B.t. formulations currently manufactured in the U.S. are produced from
strain kurstaki (HD-1) which was selected by Dulmage (9) for its high
A-399
-------
virulence to target lepidoptera. This strain is not toxic to honey bees nor
does it produce beta-exotoxin.
In the U.S., the potency of B.t. preparations is defined in terms of
International Units by a standardized bioassay that determines the potency
of the preparation relative to ths potency of a standard preparation,
HD-l-S-1971, derived from the commercially used strain HD-1 with a deter-
mined potency of 18,000 lU/mg (10). All preparations of B.t. sold in the
U.S. are required to list the number of international Units on their labels.
B.t. is usually applied as a suspension in a water-based formulation.
Spray formulations generally contain additives designed to increase their
effectiveness. Among these additives are thickening agents to keep the
spores, parasporal crystals and other ingredients in a uniform suspension;
wetting agents to obtain better leaf coverage; antievaporants; stickers to
increase the retention of spray deposits on foliages; and protectants to
reduce the adverse effect of solar radiation on the spores and crystals
(11). Field tests have been performed for many years on a variety of formu-
lations to determine their effectiveness against forest insect pests. Se-
lected examples of these experiments are described in Table 1.
The major producers of B.t. in the U.S. are Abbott Laboratories (for
Dipel) and Sandoz Inc. (for Thuricide). There are also foreign producers
which market B.^ in the U.S. under a variety of trade names: Bactospeine,
Leptox, Novabac, Bug Time, and Cekubacilina (18). For forest use, B.t. is
generally aerially applied. Typical application rates for the gypsy moth
are 2 quarts of Dipel LC per acre or 1/2 to 1 Ib of Dipel worm killer in 1
to 5 gallons of water (19). Thuricide 16B and Dipel 4L for the spruce bud-
worm are applied at a dosage of 8 Billion International Units (BIU) per
acre (20).
2.0 PROPERTIES AND MODE OF ACTION
Bacillus thurinfiiensls belongs to a genus of rod-shaped spore-forming
bacteria that grow aerobically or facultatively anaerobically. Its vegeta-
tive cells are approximately 1 um in width and 5 pm in length (21). They
are motile and are propelled by peritrichous flagellae. B^t, can grow in
moist soils deriving nutrients from decaying plants and can grow in the
tissues of infected insects. Several hours after vegetative growth stops
A-400
-------
TABLE 1. FIELD TESTS OF B.t. AGAINST SOME FOREST INSECTS
Hoat
Teat Area
FormulaLion/Dose Applied
Results
Reference
Tliyridopteryx
ephemeraetorula
(bagwora)
Forest tent
caterpillar
Douglas fir
tussock oath
Chori stoneura
Eumlterana
.(spruce budworm)
Chor istonetira
tucnifetana
(spruce budwom)
Lyaantr ta
dlspar L.
(gypsy Both)
Paleacttta vein*
(spring canker-
worm); Alsophlla
pometaria (fall
cantcervrorm)
2 acres of Scotch
Pine in KJ.fjnouri
Each formilation was
applied to a 20-acre
>lnt of water tupelo
Kip forest In
Alabama
20-acre plots in
Hallcwa-Hhitnan
National forest in
Oregon
Two lOO-acre plots
of balsam-fir in .
Quebec
10,000 acres of
balsam-fir forest
in Quebec
Tvo 500 acre plots
of eastern hardwoods
in Pennsylvania
Windbreaks la North
Dakota
Dipel WP having at least 25
billion viable spores/gin in a
solution of 6 gal water plus 2
qts. exude molasses applied at
0.5 Ib/acre.
Dipel WP. 0-25 Ib/acre
Dipel WP, 0.50 Ib/acre •
Thuricide UPC. 1 qt/acre
Dipel WP in a 25% molasses
solution applied at 1 Ib/acre
to the 2nd or 3rd ihstar.
TTiuricide MFC
Thurlcide HPC
chitinase*
Thurlcide HPC + chitlnase in
a formulation containing
adjuvant and sticker applied
at .005 to 1.33 gal/acre
Tliurlcidc 16B and Dipel LC
at 8 Bill/acre
Biotrol W at 3.* BIC/acr«;
Dipel LC at 4.0 BlU/acre;
Thvrlclde 16B at 4.0 BlU/acre
95t reduction in the
nagvorm pojmlation
15-40% average foliaqo loss
30-35* average foliage loss
0-5O% average foliage loss
27 days after treatment.
The control plot had 95-100%
foliage loss
The population reduction
exceeded 95% at 35 days.
Defoliation levels were below
25V
85* larval moftality
93* larval mortality
The control plot had 54*
mortality.
In areas where the spray
deposit vas >C.t gal/acre and
the plate counts were >77
colonies/cm2 for B.t., the
average mortality was B8.2*
80-907 larval reduction und
921 foliage protection
85-95% larval reduction
15
17
16
12
Chltlna.se ttss been shown to accelerate development of disease probably by disruption of the chitinase lining of the
gut linen which would allow better contact of ingested spore* with cells of the gut wall and facilitate penetration
(15).
-------
and cells enter the stationary phase, the process of sporulation-begins.
The first step is the appearance in the cell of a relatively transparent
forespore which gradually changes into the mature spore. The process of
spore maturation is accompanied by the development of the parasporal crystal.
Eventually, the sporangium, the cell containing an endospore and parasporal
crystal, lyses.
B.t. must be ingested by susceptible insects before it can kill. This
normally occurs when larvae feed on foliage sprayed with B.t., thereby in-
gesting both endospores and parasporal crystals. The crystal is comprised
of a protein that is insoluble at acidic or neutral pH but is soluble at
alkaline pH. Those insects that are most susceptible to B.t. have alkaline
gut contents between pH 9.0 and 10.5 (1). The solubilized protein must be
cleaved by digestive enzymes to form the active toxin which works by attack-
ing the gut lining of epithelial cells. This allows molecules in the alka-
line gut to diffuse into the hemolymph, increasing the pH of tissues and
resulting in paralysis (1,22). When the epithelial gut lining has been
sufficiently damaged, ingested spores can pass into the hemolymph and germ-
inate. Here, the bacteria grow vegetatively, producing a fatal septicemia.
Sporulation begins after growth stops and leads to production of endospores
and parasporal crystals within dead insect tissues.
In highly susceptible insects, only the toxin is needed for control,
but in less susceptible insects, the synergistic effect of endospores
together with toxin is required. Since the chitinous layer in the insect
gut is the main barrier that B.t. must pass through in order to invade
tissues, some investigators have added chitinase, an enzyme that hydrolyzes
chitin, to B.t. formulations. This approach appears to increase the viru-
lence of B.t. preparations in laboratory tests (23) but, despite various
field tests (42,43) addition of chitinase has not been universally accepted
as beneficial for field use.
3.0 ENVIRONMENTAL FATE
Most studies of the persistence of B.t. in the environment have been
directed at following viability of B^t.. spores rather than following toxin
activity. This is primarily because the presence of the crystal in nature
is much more difficult to detect than is the presence of spores. Those
A-402
-------
studies that have been carried out to follow persistence of the crystalline
toxin show that it disappears from the environment at a steady rate, although
somewhat slower than the disappearance of B.t. spores (2A).
B.t. spores and vegetative cells occur naturally in a number of envi-
ronments not contaminated by B.t. insecticide formulations. This organism
is commonly found where susceptible insects inhabit the environment. For
example, it is frequently found in stored grain and in the soils of environ-
ments with high concentrations of lepidopterous larvae (24).
When B.t. is applied in nature, the spores rapidly disappear. The pri-
mary cause of inactivation of B.t. spores in the environment is probably
sunlight, although*endospores are generally resistant to heat, shortwave
radiation, and toxic chemicals. It has been shown that moist, unprotected
spores of B.t. are rapidly killed by exposure to sunlight (26). Further
studies also suggest that spores exposed to sunlight are less susceptible
to solar radiation damage under very dry conditions (25). When four commer-
cial B.t. preparations were sprayed on coast live oak at different locations,
the viable spores persisted longer in the hot, dry climate than in the cool,
moist climate. In another study, the persistence of four B.t. formulations
was tested on redbud tree leaves at two sites in California: Auburn (alti-
tude, 374 o) and Sacramento (altitude, 10 m) (27). The rate of decay of
viable spores was not significantly different although the amount of solar
radiation was greater at Auburn. It was concluded that since the relative
humidity at Auburn was lower (21.7 percent vs. 27.5 percent), the drier con-
ditions may have compensated for any difference in solar radiation levels.
Sunlight and humidity are probably not the only factors affecting the
persistence of spores on vegetation. It has been suggested that the initial
B.t. deposit retained on the leaves after application and the subsequent de-
cay or loss of viable spores may be determined to some extent by the leaf
tvpe or species, based on studies measuring, viable spore decay on the leaves
of four different species of trees (California live oak, redbud, eucalyptus,
and walnut) subject to the same climatic conditions (28).
. It is'generally recognized that endospores can remain dormant for a long
period of ti*e. in some cases for many years. ' B^ has been known to remain
active in soil for at least four months (29). In laboratory studies evalua-
A-403
-------
ting some of the factors affecting the survival and competitive growth of
B.t. in soil, Saleh, et al. (30) confirmed that spores of B.t. can remain
viable for long periods of time in soil when germination-inducing stimuli
are absent. Under conditions favorable for the growth of soil bacilli, such
as neutral pH and presence of proteinaceous matter, B.t. can germinate and
compete in the vegetative phase with other soil microorganisms. B.t. can
also sporulate successfully to levels of more than 1 million spores/g soil.
Although few studies are available on the fate of B.t. in water, one
study suggests that B.t. will not persist in aquatic systems based on data
collected from monitoring river'water following aerial applications of
Thuricide to forest plots in Canada (31). The viable spores present in river
water and clams immediately after treatment disappeared within four weeks.
4.0 IMPACTS ON NON-TARGET ORGANISMS
4.1 IMPACT ON TERRESTRIAL INVERTEBRATES
Regardless of the persistence of B.t. in the environment, non-target
invertebrates are not expected to be harmed by exposure to B.t. at levels
commonly encountered after spraying of forests. In field tests in Nova
Scotia where B.t. was the only insecticide applied to an apple orchard over
a four-year period, population levels of lepidopteran insects were reduced
but there was no effect on predaceous .insects (32).
Spruce-fir stands in Algonquin Park, Ontario (Canada) and mixed forest
containing mature spruce stands, poplar bluff, and areas of dense brush and
open fields in Spruce Woods, Manitoba, were sprayed with formulations of
Thuricide 16B or Dipel WP. Although some declines in populations of non-
target insects were observed, comparison with the controls indicated that
the declines would not be attributed to the spraying (31). In these studies,
there was also no significant increase in mortality among foraging bees as
a result of B^t.. treatment. Many other studies have been made on the effects
of B-t.. on honey bees (7,8,33,34,35,36). These studies have found no evi-
dence that bees will be harmed by B.^ at the levels commonly used in spray
operations. B^t,. has been shown to be non-toxic to bees at levels as high
as 726,000 spores per bee (37).
^ One .tudy has shown B^ to be fatal to earthworms at concentrations
10 to 10 times higher than that which would occur in the soil after normal
A-404
-------
application in the field (39). However, these studies were carried out
using B. thuringiensis var. thuringiensis that produces beta-exotoxin which
could have influenced the results. In experiments using Dipel (16>000 lU/mg)
2
at dose rates of 60, 600, and 6,000 mg/m on forest plots and Bactospeine
o
(1000 IU) at a dose rate of 30 g/m , worm density after spraying was not
significantly different from worm density prior to spraying (38).
4.2 IMPACT ON AQUATIC SPECIES
Few toxic effects have been reported in studies on B.t. exposure to
aquatic species. While monitoring aquatic species on Moresby Island, British
Columbia in 1960, Todd and Jackson (40) found no adverse effects on Coho
salmon fry or on aquatic insects in streams within an experimental area
treated with B.t. In studies in Algonquin Park, Ontario, Canada, fish and
bottom fauna suffered no adverse effects up to four weeks after spraying
(31). Data from in vivo tests evaluating the safety of B.t. to fish (Table
2) show B.t. to be either non-toxic or toxic only at very high doses.
4.3 IMPACT ON MAMMALS AND BIRDS
Field tests have not revealed any deleterious effects of B.t. on popu-
lations of birds and mammals. In studies in Algonquin Park and Spruce Woods,
no significant differences were found between the populations of birds and
mammals on the sprayed plots vs. the populations on the untreated plots (31).
In a second test, aerial application of Dipel WP applied at a rate of 0.5
Ib/acre to a Scotch pine plantation containing a large population of nesting
mourning doves apparently did not affect or disturb the birds (13). Twenty-
four hours after spraying, fledglings were observed still in their nests
and adults were flying about the plantation. After 28 days, adults were
still numerous.
Extensive laboratory tests have produced no evidence that B.t. is pa-
thogenic to vertebrates which inhale, ingest, or come into contact with it.
Table 2 summarizes the results of some of these studies. Human volunteers
inhaled 100 mg/day of Thuricide powder for 5 days with no adverse effects
and ingested 1 gm/day for 5 days with no adverse effects (3). Rats were
given a single oral dose up to 24 gm/kg of body weight without adverse
effects. When mice were injested with large numbers of B^ spores and
cells (106-109), some individuals died. This appeared to be the result of
A-405
-------
,£, ^ | *jurii.iru.v^ w*. — »•• - — - — -
THURINGIENSIS PREPARATIONS TO FISHES, BIRDS, AND
Species
Fishes
Rainbow trout, black
bullhead, yellow
perch, mosquito fish
Coho salmon juvenile
Birds
Wild pheasant
Partridge
Cornish chick
Chick
New Hampshire laying
hen
Cockeral , Vantress
cross
Mammals
Mouse
Rat
Guinea pig
Swine, duroc
Human
it\l 4 a Wl A *» MMUM »_. . ._^ _ j?
Numbers
of
Animals
40
20
9
2
190
48
16
60
48
48
48
48
10
10
10
10
100
20
10
• A
10
IP
* /k
10
1 A
10
3
18
5
MAMMALS (41)
Inoculum*
(billion/kg)
<0.01-4.5
300-1800
3600
5800
0.2
300-1900
1000-3000
480-15,800
0.1-0.3 cells
0.04-2 cells
0.8-7.8 spores
20-160 spores
77
15
20,000
2000
7700
0.01-1.0
77
40
4000
0.3
16
185
0.2
0.02
Route**
TE
TE
diet
diet
diet
diet
diet
diet
ip
sc
ip
sc
PO
iP
1h
DO
diet
ip
diet
ip
sc
DA
diet
DO
1h
Results
negative
toxlcity at
higher doses
negative
negative
negative
negative
negative
negative
lethal dose, 50%
lethal dose, 50%
lethal dose, 50%
lethal dose, 501
negative
abdominal Irri-
tation; some
death
negative
negative
negative
negative
negative
negative
negative
localized reaction
at Injection site
slight erythema on
abraded skin
negative
negative
negative
included spores, vege-
sc>
- TE-
A-A06
-------
toxic substances in the B.t. preparations since death also occurred after
injecting heat-killed preparations. No evidence of infection was seen, and
bacteria completely disappeared from the blood by 72 hours after injection
(3).
As a result of the widespread natural occurrence of B.t.. there is
certainly occasional human exposure to this organism through inhalation,
ingestion, and wound contamination. However, there are no reports of human
disease caused by B.t. Furthermore, no adverse effects of occupational
exposure to Thuricide have been noted, nor have adverse effects been detected
following its use (3).
A-407
-------
REFERENCES
1 Falcon, L.A. 1971. Use of Bacteria for Microbial Control. Ch. 3 In
Microbial Control of Insects and Mites. Burges, H.D. and N.W. Hussey,
^ Academic Press, N.Y. pp. 67-95.
2. Heimpel, A.M. and T.A. Angus. 1963. In Insect Pathology - An Advanced
Treatise, E.A. Steinhaus, ed. Vol. 2, pp. 21-73, Academic Press, N.Y.
In Reference 1.
3. Fisher, R. and L. Rosner. 1959. Toxicology of the Microbial Insecti-
cide, Thuricide. J. Agrie. Food Chem. 7(10); 686-688.
4. Miller, R.S., et al. 1975. Forest Pest Control - Vol. IV of Pest
Control: An Assessment of Present and Alternative Technologies. Na-
tional Academy of Sciences.
5. Schneider, R. 1980. Pesticide Use Evaluation: Maine Spruce Budworm
Suppression Project - 1980. EPA 330/2-80-034.
6. Bailey, L. 1971. The Safety of Pest-Insect Pathogens for Beneficial
Insects. Ch. 23 in Microbial Control of Insects and Mites. Burges,
H.D. and N.W. Hussey, eds. Academic Press, N.Y., pp. 491-505.
7. Krieg, A. and W. Herfs. 1962. Entomophaga. Mem, hors Ser. No. 2: 193-
195. In Reference 6.
8. Krieg, A. and W. Herfs. 1963. Entomologia Exp. Appl. 6; 1-9. In Re-
ference 6.
9. Dulmage, H.T. 1970. Insecticidal Activity of HD-1, A New Isolate of
Bacillus thuringiensis var. alesti. I. Invert. Pathol. 15: 232-239.
10. Information provided by EPA based on a review of registration files in
the Ecological Effects Branch.
11. Maksymiuk, B. and J. Neisess. 1975. Physical Properties of Bacillus
thuringiensis Spray Formulations, J. Econ. Entomol. 68(3): 407-410.
12. Harper, J.D. 1974. Forest Inse.ct Control With Bacillus thuringiensis
- Survey of Current Knowledge. University Printing Service, Auburn U.t
Alabama. 64 pp.
13. Kearby, W.H., et al. 1975. Aerial Application of Bacillus thurin-
Riensis fo* Control of the Bagworm in Pine Plantations. J. Forestry
73(1): 29-30. - *•
14. Abrahamson, L.P. and J.D. Harper. 1973. Microbial Insecticides Con-
trol Forest Tent Caterpillar in Southwestern Alabama. USFS Res. Note
SO-157.
A-408
-------
15. Stelzer, M.J., et al. 1975. Aerial Application of a Nucleopolyhedrosis
Virus and Bacillus thurlnglensis Against the Douglas-fir Tussock Moth,
J. Econ. Entomol. 68(2): 269-272.
16. Smirnoff, W.A., et al. 1973. Aerial Spraying of a Bacillus thurin-
glensis - Chitinase Formulation for Control of the Spruce Budworm. Can.
Entomologist 105: 1535-1544.
17. Smirnoff, W.A. 1972. Results of Experimental Aerial Spraying of Ba^
cillus thuringiensis Against Spruce Budworm Larvae, Bi-Mon. Res. Notes.
Pep. Environm. 28:1. In Reference 6.
18. 1980 Farm Chemicals Handbook. Meister Publishing Co., Wiloughby, Ohio.
19. Pesticide Uses in Forestry. National Forest Products Association,
Forest Chemicals Program, Washington, D.C. 1980.
20. Raisch, R.D. Proposed Cooperative Spruce Budworm Suppression Project,
Maine, 1980. USDA-FS-80-01.
21. Stanier, R.Y., et al. 1970. The Microbial World, Prentice-Hall, Inc.,
N.J., third edition.
22. Jaques, R.P. 1973. Methods and 'Effectiveness of Distribution of
Microbial Insecticides. Ann. N.Y. Acad. Sci. Vol. 217. Conf; Reg. of
Insect Populations by Microorganisms. Part III Biological Factors.
L.A. Bulla, Jr.-, ed.
23. Dubois, N.R. 1977. Pathogenicity of Selected Resident Microorganisms
of Lvmantria dispar L. After Induction for Chitinase. PhD Thesis, U.
Massachusetts.
24. Dulmage, H.T. USDA Agricultural Research, Southern Region, Brownsville,
Texas. Letter to TRW, Sept. 15, 1980.
25. Pinnock, D.E., et al. 1971. The Field Persistence of Bacillus thurin-
eiensls spores. J. Invert. Pathol. 18: 405-411.
26. Cantwell, G.E. and B.A. Franklin. 1966. Inactiyation by Irradiation
of Spores of Bacillus thuringiensis var. thurinfiiensis. J. Invert.
Pathol. 8: 256-258. In Reference 25.
27. Pinnock, D.E., et al. 1974. The Field Persistence of Bacillus thurin-
giensis Spores on cerds occidental^ leaves. J. Invert. Pathol. 23;
341-346.
28. Pinnock, D.E., et al. 1975. Effect of Tree Species on the Coverage
and Field Persistence of Bacillus thurineiensis species. J. Invert.
Pathol. 25: 209-214.
29. Hitchings, D.L. 1967. J. Econ. Entomol. 60: 596-597. In Reference
22.
A-409
-------
30. Saleh, S.M., et al. 1970. Fate of Bacillus thuringiensis in Soil:
Effect of Soil pH and Organic Amendment. Can. J. Microbiol. 16: 667-
680.
31. Buckner, C.H., et al. 1974. Evaluation of Commercial Preparations of
Bacillus thuringiensis With and Without Chitinase Against Spruce Bud-
worm. F. Impact of Aerial Treatment on Non-target Organisms, Chem.
Cont. Res. Inst. Infer. Rep. CC-X-59.
32. Jaques, R.P. 1965. Can. Entomol. 97: 795-802. In Reference 22.
33. Burges, H.D. and L. Bailey. 1968. J. Invert. Pathol. 11: 184-195. In
Reference 6.
34. Franz, J.M., et al. 1967. Nachr. Bl. dt. Pfl Schutzdienst Stuttg
19: 36-44. In Reference 6.
35. Cantwell, G.E., et al. 1966. J. Invert. Pathol. 8; 228-233. In Re-
ference 6.
36. Wilson, W.T. 1962. J. Insect Pathol. 4: 269-270. In Reference 6.
37. Atkins, E.L., et al. 1975. Toxicity of Pesticides and Other Agricul-
tural Chemicals to Honey Bees - Laboratory Studies. U. of Calif.,
Division of Agricultural Sciences Leaflet 2287.
38. Benz, G. and A. Altwegg. 1975. Safety of Bacillus thuringiensis for
Earthworms. J. Invert. Pathol. 26: 125^126.
39. Smirnoff, W.A. and A.M. Heimpel. 1961. J. Insect. Pathol. 3; 403-408.
In Reference 38. ! ~~
40. Todd, I.S. and K.J. Jackson. 1961. The Effects on Salmon of a Program
of Forest Insect Control With DDT on Northern Moresby Island, Can.
Fish. Cult. 30: 15-38. In Reference 31.
41. Ignoffo, C.M. 1973. Effects of Entomopathogens on Vertebrates. Ann.
N.Y. Acad. Sci. 217: 141-164.
42. Smirnoff, W.A., et al. 1973. Field Test of the Effectiveness of Chit-
inase Additive to Bacillus thuringiensis Berliner Against Choristoneura
fumiferana (Clem.) Can. J. For. Res. 3: 228-236. In Reference 16.
43. Smirnoff, W.A. 1974. Three Years of Aerial Field Experiments With
Bacillus thuringiensis plus Chitinase Formulation Against the Spruce
Budworm, J. Invert. Pathol. 24: 344-348.
A-410
-------
Common Name: Nucleopolyhedrosis virus
Chemical Name: Nucleopolyhedrosis virus
Major Trade Names: Gypcheck; TM-Biocontrol-1
Major Applications Nucleopolyhedrosis viruses are used as insecticides
in Forestry: against specific forest insects. Current use is very
limited.
SUMMARY
Nucleopolyhedrosis viruses (NPV's) are a group of naturally-occurring
viruses that infect and kill a number of insects in the orders Hymenoptera
and Lepidoptera. Each NPV is host specific, and NPV insecticides are formu-
lated as a suspendible powder containing virus that is active against a
single insect pest. NPV's are currently registered for use against several
agricultural pests and are registered for use by the USFS against the gypsy
moth and Douglas-fir tussock moth.
NPV's invade insect tissues after foliage contaminated with virus has
been ingested, but the virus can also be transmitted transovarially. Tissues
of insects killed by NPV contain large amounts of infectious virus which, in
certain cases, can give some long-term pest control. However, NPV s are
normally not persistent on foliage as they are inactivated within a few days
when exposed directly to sunlight. Soil appears to be a natural reservoir
for NPV's where they can persist, in some cases, for several years. Little
is known about the fate of NPV's in water.
In field studies on the impact of NPV's on the environment, no adverse
effects on non-target animal or plant species have been observed. This is
undoubtedly due to the extreme host-specificity of these viruses. Further-
more, laboratory studies on fish and mammals exposed to NPV s in water, in
food or by intraperitoneal injection have not revealed adverse effects. No
disease of man or other vertebrates are known to be caused or associated with
these viruses.
NPV's are currently used to only a limited extent in forestry in the
U S This is oartly due to the relatively high cost of treatment that, in
some cIses.maKs chemical pesticides more attractive, and it is partly due
to the expend of testing each new NPV before it could be registered for use
against its target.
A-A11
-------
1.0 INTRODUCTION
Nucleopolyhedrosis viruses (NPV's) are naturally-occurring pathogens
of insects. These viruses, sometimes called baculoviruses, are named for
polyhedral inclusion bodies that are visible in the light microscope and
that first appear in the nuclei of infected host cells. Nucleopolyhedrosis
viruses are very host specific - each virus normally infects a single insect
species or a few closely-related species. As a consequence, NPV's are prime
candidates for integrated pest management (IPM) programs since they can kill
insect pests without harming beneficial insects.
A number of NPV's have been isolated from nature and have been deve-
loped for use on a variety of agricultural and forest insect pests. Forest
insects of the orders Hymenoptera (e.g., sawflies) and Lepidoptera (e.g.,
spruce budworm, Douglas fir tussock moth, forest tent caterpillar, and gypsy
moth) are susceptible species. In forestry, the most successful non-chemical
means of pest control has been the use of NPV's against specific sawflies,
which are tree defoliators. In 1950, a low concentration of NPV that was
introduced into a sawfly population in Canada became established and spread
throughout the infested area. Virus epizootics* recurred for ten consecu-
tive years and maintained the population below levels that would have caused
economic damage (1). NPV's have also been used against the Douglas fir
tussock moth with 90-97 percent reductions in pest populations and a signi-
ficant reduction in defoliation (2). There have been many other trial appli-
cations of NPV's against forest defoliators. Table 1 summarizes the hosts,
dosages used, application methods, and results of some early field tests
using NPV's to control forest defoliators in North America. These results
indicate that NPV application can result in high population reductions.
However, the relationship between population reductions and foliage protec-
tion is unclear.
The NPV of Heliothis sea has been used commercially-since 1971 for con-
trol of the cotton bollworm (3). It is formulated as a wettable powder con-
taining at least four billion polyhedral inclusion bodies (PIB) per gram
A-412
-------
TABLE 1. ARTIFICIAL FIELD DISSEMINATION OF VIRUSES AGAINST
SOME NORTH AMERICAN FOREST DEFOLIATORS (1)
IllWt
Lcpidoptcia
Qiontlontun
lumiferjnii (Clemen?)
(Spit'cc budworm)
Htmerocempa
pltudoRugale McDunnoufh
(Douglas-fir
tussock moth)
Hetecosonu
iiatrie Hubner
(forest tent
caterpillar)
Malacotonu
fttgilt (Stretch)
(Great Bjsin
tent nlerpilUr)
I.ymimiria
ditfer L,
<«P*y moil')
.
liivijr ()•»«' Anp"c.tti»*n
lUMti-il tVllirVuiw mf!li.Hlh
KuclVijr-rolvkcdnuis Virus
2 3x,0.v,,cc
3-4 3x10" /acre* A
2 0.1*/12fl tree G
M OlE/J2ftttcc G
M 3xlO*/10fltre« G
4 1x10" /acre A
2-3 1x10" /acre A
JJl ID'/ml G
g ft trees
heavily sprayed
1 l.SxlO'/fee G
1 IJilO'/tree C
3 7JxJO'/«ce G
Jj» 2.5x10' '/acre A
2 2.2x10" /acre A
1-3 l.lxlO1*- G
5x10" /acic
3-4 5.6x10"- G
2.2x10" /acre
2-3 4x10' V»ere 0
•'
1-3 IxlO'V.'KiS ha G
J-3 Ixl0l>/.405 hj G
- ; ^
Ki-Mih.\
BO? population
reduction
6un population
reduction
4(1',:- infection
32 days aftrr spray
75% reduction
9 days alter spray
28% infection
14-20 days
after spray
54-76% population
reduction
Uttle foliage
protection
96-99.8% population
reduction
Foliage protection
90% mortality
24 days after spray
92$ mortality
17-24 days after
»ptay
28% mortality
17-24 days after
•pray
14* mortality
17-24 days after
•pray
no control
70% population
reduction
Some population
reduction
Population
reduction
F~oli*l;*c protection
Iff. rru« reduction
Nn fulure
protection
Slijiht f.ilupc
pnHeriMM
H££ IllUlk ItdUi'ti'tTl
(Continued)
-------
TABLE 1. (Continued)
llml
Hymcnoplcta
Hrodiprion
ttfliftr (Geofl'roy)
(European
pine uwfly)
N. Mail
(Harm)
(BaUamdr
uwfly)
N. pnni
pnnl (Dyar)
(pine tawHy)
N.utdu
iinttns Roa
(Loblolly pint
avfly)
N.nmnti
(Hiddlelon)
(Swaine'sjack
pine owfly)
Upidorten
C fumiftnn.
"
Imur
in-jtcJ
early
inttari
early
initatl
tarly
insurs
1
1
3
tatty
intuit
1-2
1-2
1-2
tarty
instan
3-4
2
34
=====
n»s»- Application
(VlllWunii inclh«xl»>
Nuck'nr-l'olylicJicsu Virm
6x10* */20 tract C
l.SxiO"/S acres C
8.3x1 or /acre A
3.6xlOV2.5m tret C
3.6x10' /2.5m tree c
SxlO'- A
2xlO'
-------
of product and is applied at a rate of 2 to 4 ounces per acre (140-180
grams/hectare) (4). The sole commercial producer of this virus is Sandoz,
Inc., and it is marketed under the trade name Elcar (5).
The gypsy moth NPV and the Douglas-fir tussock moth NPV are currently
registered by public agencies for forest use. They are not yet commercially
produced (6). The NPV of the gypsy moth is known as Gypcheck, and it is
formulated as a 4 percent suspendible powder which is registered for use by
or under the supervision of the U.S. Forest Service. Applications can be
repeated once after 7 to 10 days. The NPV of the tussock moth is registered
for application to forest trees at a rate of 0.50 ounces of formulation per
acre (7). Known as TM-Bio.control-1, it is a 3.5 percent suspendible powder
for U.S. Forest Service use only. Formulations for NPV's commonly include
molasses, stickers, and/or a sunscreen. The pH of the formulation must be
between 5.5 and 7.5 (8).
2.0 PROPERTIES AND MODE OF ACTION
Insect viruses usually enter the host by way of the mouth or trans-
ovarially into the egg (9) . Normally, larvae are infected by NPV when they
feed on foliage contaminated with polyhedral inclusion bodies. .In the mid-
gut, virus invasion depends on favorable pH and digestive enzymes, and host
nutrition plays a role with poor quality foliage increasing the insects'
susceptibility to the virus (9). NPV contains DNA as its genetic material
and multiplies exclusively in the nuclei, mainly in the skin, blood cells,
fat body and trachea (10). However, in a few species, NPV's multiply only
in midgut epithelial cells (10). During the infection, rod-shaped viral
particles become occluded (imbedded) within polyhedral protein crystals,
which are the inclusion bodies. Infected tissues liquefy as the larvae or
pupae die, producing a suspension containing large quantities of infectious
inclusion bodies. These can reach the soil or can contaminate foliage to
give some degree of long-term pest control for some pests (2). There is
considerable evidence that NPV epizootics occur in natural populations
releasing much larger amounts of infectious polyhedra than those introduced
by man (9).
The production of an NPV insecticide involves propagation of the virus
in living host larvae. The insect cadavers can be lyophilized and ground
A-415
-------
to a powder, or they can be triturated in water, often followed by a purifi-.
cation process (11).
3.0 ENVIRONMENTAL FATE
NPV is not persistent on foliage, but may persist in the soil. The
most important factor in the physical environment for inactivating the virus
is sunlight (12). Viruses are largely inactivated within a few days after
application to foliage exposed to direct sunlight. This has been demon-
strated in studies on the NPV of Trichoplusia ni (cabbage looper) which
show that deposits of the virus retain little activity five days after
application to cabbage leaves exposed to sunlight (13,14). Studies on sun-
light protectants indicate that deposits of viruses smeared on plants when
virus-killed larvae decpmpose are protected substantially from sunlight in-
activation because of the protein content and the dark color of the smear
(15,16). Studies on the gypsy moth NPV have shown that, following applica-
tion in eastern hardwood forests, it disappears from bark and foliage in 3-
15 days and that normal rates of application do not significantly increase
the concentration of naturally-occurring NPV in forest soil (17).
Next to sunlight, temperature is an important viral inactivator. Low
mortality has been observed in infected insects exposed to low temperatures
(18,19,20). Relative humidity has little effect on the inactivation of
viruses but it may affect the resistance and behavior of the insect to virus
infections (9). At a pH below 2, infectivity is rapidly lost.
Soil is a major site for virus persistence (9). Polyhedra can protect
virions for a long time, in some cases, for several years. Consequently,
large amounts of infectious polyhedra often exist in the upper layers of
soil. Field tests with the NPV of Trichoplusia ni show that NPV retained
25 percent of its original activity six years after application (21). In
addition, there are indications that the initiation of epizootics of viral
disease in insect populations occurs in the soil (14,22).
No studies have been reported on the fate or persistence of NPV in
water.
4.0 IMPACTS ON NON-TARGET ORGANISMS
Because of the host-specificity exhibited by NPV's, they are not ex-
pected to produce adverse impacts on non-target organisms. Ignoffo (23)
A-416
-------
has reviewed the toxicity of entomopathogenic viruses to vertebrates and
found that out of 51 viruses treated in vivo, including 29 NPV, no toxicity
or pathogenicity has been demonstrated. Furthermore, NPV's have never been
reported to cause disease in man or in any other mammal.
4.1 IMPACTS ON BIRDS, AQUATIC FAUNA, AND HONEY BEES
No apparent adverse impacts have been observed in field studies on the
effects of NPV on birds. Following aerial applications of two formulations
of the gypsy moth NPV to woodland plots in Pennsylvania at a rate of 2.5 x
12
10 PIB/ha, no short-term population changes in wild songbirds could be
attributed to the virus (24). Necropsy and histopathological data on quail
caged on the study plot and on 53 songbirds collected from the study plot
over a 10-week period after application indicated no significant differences
between control birds and treated birds.
In Ontario, Canada, the NPV of the red-headed pine sawfly was aerially
applied in a formulation containing molasses and a sunlight protectant at a
rate of 5.5 billion PIB/ha to two plantations of red pine (13.2 ha and 30.8
ha) (25). No adverse effects on birds, aquatic fauna (Benthic populations
from a stream), or honey bees were observed.
In another study, the NPV of the spruce budworm was aerially applied to
160 hectares of infected forest on Manitoulin Island at the rate of 247.5 x
10 PIB/ha (26). Songbirds, small mammals, honey bees and aquatic inver-
tebrates (bottom-dwelling fauna) were monitored. No immediate or short-term
adverse impacts were detected.
Toxicity studies have also been conducted on various birds, aquatic
invertebrates, and bees. Mallard hens survived five daily oral treatments
with a nucleopolyhedrosis virus preparation containing 18.34 x 10 poly-
hedra/mg (dosage level: 500 mg/kg body weight) (8). The amount received
over the 5-day period corresponded to the amount commonly applied to an
acre of land. In feeding studies conducted using quail, mallard ducks, and
blackbirds, there was no damage or death in any test organisms due to the
virus (8).
Honey bees fed various NPV's in combination with sucrose at concentra-
tions of 1010 polyhedra per hive showed no apparent adverse effects (8).
Feeding studies of the nucleopolyhedrosis virus of H. sea carried out on
A-417
-------
juvenile oysters (Crassostrea virglnica) caused no pathogenicity. Mature
grass shrimp (Paldemopatas pagio) and adult brown shrimp (Penaeus estecus)
were tested with the virus in suspension and showed no adverse effects or
undue mortality (8).
4.2 IMPACTS ON FISH
Based on available data, no pathological effects of NPV have been
observed in fish. In laboratory studies examining the potential effects of
the NPV of the Douglas-fir tussock moth on salmonid fish residing in waters
adjacent to the forest, the virus was found to cause no pathology in two
salmonid cell lines or in three species of salmonid fish (27). The fish,
Coho salmon, Chinook salmon, and steelhead trout, were exposed via three
routes: waterborne exposure, intraperitoneal injection, and feeding. The
virus did not persist in the fish.
Studies on pathomorphological changes in the internal organs of trout
induced by NPV indicate that NPV has no lethal effect on the fish and causes
' no pathological changes in fish orally exposed to the virus (28).
4.3 IMPACTS ON MAMMALS
Laboratory tests have demonstrated the safety of the NPV of the red-
headed pine sawfly to mammals (29). Additional reports have indicated that
other NPV's also have no adverse effects on laboratory animals (31,32,33,34).
Laboratory studies have also been conducted on the responses of three wild
mammalian predators of the gypsy moth, the white-footed mouse, the short-
tailed shrew, and the Virginia opossum, to consumption of the NPV of the
gypsy moth (30). NPV appeared to have no short-term effect on the physical
condition or the reproductive efficiency of the animals. There were no con-
sistent differences in the occurrence of gross or microscopic lesions in any
of the 3 species. The test animals were fed 3 formulations of the virus:
(1) larvae containing between 3.5 x 108 and 6.0 x 108 PIB's; (2) purified
PIB's at the rate of 1.0 x 109 PIB/animal/day for 3 days; and (3) a standard
spray formulation for the gypsy moth NPV (containing Cargil insecticide
base, Chevron spray sticker, IMC 90-001, water, and PIB's) at the rate of
1 x 105 PIB/animal/day for 3 days. The total amount of NPV consumed by each
mouse and shrew was equivalent to more than a 40 ha exposure for a 70 kg
person assuming an application rate of 5.0 x 1011 PIB/ha.
. A-418
-------
Various toxicological tests have also been performed on mammals. In
acute oral toxicity tests to rats, the polyhedra of L. dispar were not toxic
19
when administered by gastric intubation at a dose of 40 x 10 per rat (8).
Acute dermal toxicity tests on guinea pigs, eye irritation tests on rabbits,
primary skin irritation tests on rabbits, and inhalation toxicity studies
on rats produced no evidence of toxicity (8). In a two-year carcinogenicity
study in rats, no increased mortality or tumorgenicity was found (8).
5.0 MISCELLANEOUS
NPV's appear to be good candidates for use against a number of agricul-
tural and forest pests, but they have so far been used to only a, limited
extent. One barrier to the use of NPV insecticides is the host-specific
property of these viruses: each NPV preparation can be expected to be
effective against a single pest species. Thus, a pest must be of consider-
able economic importance in order to justify the large expense of meeting
registration requirements for a new pesticide. A second barrier to use of
NPV's is competition from chemical insecticides. However, this is not a
firm barrier since the NPV insecticide for the cotton bollworm is currently
being produced on a large scale at a cost that is competitive with that of
chemical insecticides (5). Yet, in cases where multiple applications or
high-dose applications of an NPV are required for adequate pest control, use
of the NPV may never be competitive with use of chemicals when judged on
purely economic grounds. Another barrier to NPV use is the expectation
among some pesticide users that insects will "drop dead" immediately after
being sprayed. The fact that NPV cannot produce the rapid and spectacular
insect kills achieved by some chemical pesticides can lead to the perhaps
erroneous perception that NPV's are less effective.
A-419
-------
REFERENCES
1. Kaya, H.K. 1976. Insect Pathogens in Natural and Microbial Control
of Forest Defoliators. In: Perspectives in Forest Entomology. Ander-
son, J.F. and Kaya, H.K. , eds., Academic Press, N.Y.
2. Steizer, M.J., J. Neisess, and C.G. Thompson. 1975. Aerial Applica-
tions of a Nucleopolyhedrosis Virus and Bacillus thuringiensis Against
the Douglas Fir Tussock Moth. J. Econ . Entomol . 68: 269-272.
3. Jaques, R.P. 1973. Methods and Effectiveness of Distribution of Micro-
bial Insecticides. Ann. N.Y. Acad. Sci. Vol. 217, Conf : Reg. of Insect
Populations by Microorganisms. Pt. Ill Biological Factors.
A. 1980 Farm Chemicals Handbook. Meister Publishing Co., Wiloughby, Ohio.
5. Personal communication with Mr. L. Seymour, Sandoz Inc., June 11 1980
.(to P. Painter, TRW).
6. Personal communication with Dr. Franklin Lewis, USDA Forest Service,
June 16, 1980 (to P. Painter, TRW).
7. Nucleopolyhedrosis Virus (NPV) (Gypcheck) . Report from EPA, 8/78.
8. Information provided by EPA based on a review of registration files in
the Ecological Effects Branch.
9. Tanada, Y. 1976. Ecology of Insect Viruses. In: Perspectives in
Forest Entomology. Anderson, J.K. and Kaya, H.K., eds., Academic Press,
M • I •
10. Smith, K.M. 1976. Virus-Insect Relationships. Longman, New York.
n °f VirUSeS f°r Microblal c^trol of Insects.
, .- °nt!01 of Insects and Mttea- Bur*ea' H-D- and
Hussey, N.W., eds., Academic Press, N.Y. pp. 97-123.
12. Yendol, W.G. and R.A. Hamlen. 1973. Ecology of Entomoaenous Viruses
"Re8ullof lnsect
d
, Jr., ed. Ann. H.Y. Acad. Sci. 217. 254 pp.
o£
14.
Can. Entomol. 99: 820-820." In Reference 9'
A-420
-------
15. Jaques, R.P. 1972. The Inactivation of Foliar Deposits of Viruses of
TrichopJLusia ni. and Pier is rapae and Tests on Protectant Additives.
Can. Entomol. 104: 1985-1995. In Reference 9.
16. Jaques, R.P. 1971. Tests on Protectants for Foliar Deposits of a Poly-
hedrosis Virus. J. Invert. Pathol. 17: 9-16. In Reference 9.
17. Podgwaite, J.D.. , K.S. Shields, R.J. Zerillo, and R.B. Bruen. 1979.
Environmental Persistence of the Nucleopolyhedrosis Virus of the Gypsy
Moth, Lymantria dispar. Environ. Entomol. 8: 528-536.
18. David, W.A. , et al. 1971. The Stability of a Purified Granulosis Virus
of the European Cabbageworm, Pieris brassicae in Dry Deposits of Intact
Capsules. J. Invert. Pathol. 17; 228-233. In Reference 9.
19. Morris, O.N. 1971. The Effect of Sunlight, Ultraviolet, and Gamma
Radiations, and Temperature on the Infectivity of a Nuclear Polyhedro-
sis Virus. J. Invert. Pathol. 18: 292-294. In Reference 9.
20. Keller, S. 1973. Mikrobiologische Bekampfung des Apfelwicklers
(Laspeyresia- pomonella L.) mit Spezifischem Granulosis-virus. Z^
Angew. Entomol. 73: 137-181. In Reference 9.
21. Jaques, R.P. and F. Huston. 1967. Virus of the Cabbage Looper in
Soil. Bull. Entomol. Soc. Amer. 13: 158, 194. In Reference 9.
22. Tanada, Y. 1971. Persistence of Entomogenous Viruses in the Insect
Ecosystem. In Entomological essays to commemorate the retirement of
Prof. K. Yasumatsu, pp. 367-379, Hokuryukan Pub. Co. Ltd., Tokyo,
Japan. In Reference 9.
23. Ignoffo, C.M. 1973. Effects of Entomopathogens on Vertebrates. Ann..
N.Y. Acad. Sci. 217: 141-164.
24. Lautenschlager, R.A. , et al. 1978. Effects of Field Application of
Gypsy Moth Nucleopolyhedrosis Virus. J. N.Y. Entomol. Soc, 86(4).
303-304.
in 1977. Report FPM-X-11, Can. Forestry Service.
The Effect of an Experimental Application
Delected Forest F,un,. Che,. Co«r.
Res. Inst. Report CC-X-101.
in-re. •tfffan-a of the Douulas-fir Tussock Moth
27. Banowltz, -G.M., et al. 1976. Effects of tne uou gxa uSDA For
Nucleopolyhedrosis Virus on Three Species of Salmonid fish. USDA For.
Serv. Res. Pap. PNW-214.
-
Khoz. 98; 24-31 (Translation).
A-421
-------
29. Valli, V.E.O., C.M. Forsberg, and P. Dwyer. 1978. Mammalian Patho-
genicity of the Nuclear Polyhedrosis Virus of the Red-headed Pine
Sawfly, Neodiprion lecontei) report prepared under DSS Contract No.
OSU 76-00226, 524 pp. In Reference 23.
30. Anon. 1977. Effect of Nucleopolyhedrosis Virus on Selected Mammalian
Predators of the Gypsy Moth. USDA Northeastern For. Exp. Stn.
31. Ignoffo, C.M., O.F. Batzer, W.M. Baker, and A.G. Ebert. 1970. Fate
of Heliothis Nucleopolyhedrosis Virus Following Oral Administration to
Rats. Proc. IV Int. Colloq. Insect Pathol. pp. 357-362. In Re-
ference 28.
32. Ignoffo, C.M. and A.M. Heimpel. 1965. The Nuclear-Polyhedrosis Virus
of Heliothis zea (Boddie) and Heliothis virescens (Fabricus). V. Toxi-
city-Pathogenicity of Virus to White Mice and Guinea Pigs. J. Inver-
tebr. Pathol. 7: 329-340. In Reference 28.
33. Meinecke, C.F., W.C. McLane, and C.S. Rehnborg. 1970. Toxicity-
Pathogenicity Studies of a Nuclear-Polyhedrosis Virus of Heliothis zea
in White Mice. J. Invertebr. Pathol. 15; 10-14. In Reference 28.
34. Smirnoff, W.A. and C.F. MacLeod. 1964. Apparent Lack of Effects of
Orally Introduced Polyhedrosis Virus on Mice and of Pathogenicity of
Rodent-Passed Virus for Insects. J. Insect. Pathol. 6: 537-538. In
Reference 28.
A-422
-------
Common Name: Pheromones, Behavior-modifying chemicals
Chemical Name: Varies
Major Trade Name: Varies
Major Applications Current uses limited to biosurveys and monitoring of
in Forestry: forest insect pests.
SUMMARY
Pheromones are chemicals secreted by one insect that affect the behavior
of other individuals of the same species. They are highly selective for a
single (and occasionally a few closely-related) species. For forest pest
management, pheromones may be used in survey traps as lures to attract in-
sects or for population reduction and control. They are formulated in fibers
or flakes for aerial application to disrupt mating. In order to be competi-
tive with natural pheromones, synthetic behavior-modifiers must closely re-
present the natural chemical stimuli.
To date, most of the work with pheromones has been on a small-scale
experimental basis. There are currently no operational programs using
pheromones for pest control. Some of the problems associated with the use
of pheromones for insect control relate to mobility of insects, spread of
infestations over large areas, and difficulty in establishing effective
application rates and in correlating changes in insect populations with sub-
sequent reductions in tree damage.
There is very little data available on the environmental fate of the
pheromones of forest insect pests. However, they are designed to volatilize
completely and their use rates are so low that they are not expected to
contaminate plant, soil, or aquatic systems. There is also little data on
the effect of pheromones on non-target organisms, but because of the quanti-
ties used and the way in which the compounds are released, little impact is
expected.
A-423
-------
1.0 INTRODUCTION
1.1 BACKGROUND
Pheromones are chemicals secreted by one insect that affect the behavior
of other individuals of the same species (1). Many insects use chemical
communication systems that depend on the production and release of pheromones
(2). Pheromones can evoke many types of behavioral responses (e.g., alarm,
orientation, aggregation, mating). The sex pheromones, which induce respon-
ses such as orientation, precopulatory behavior, and mating in another indi-
vidual of the same species, are considered most promising for insect control
(1,3).
Basically, there are two approaches for using pheromones in forest pest
management (1,2,3). First, pheromones may be used in survey traps as lures
to attract insects. These traps can be useful for general survey and detec-
tion, for delimiting a population, for predicting population trends, for
timing insecticide spray applications, or for post-spray surveys. Second,
pheromones have been proposed for population reduction and control. This
may include luring males into pheromone-baited traps (mass-trapping) or
permeating the atmosphere with female pheromones which confuse the males and
disrupt mating (mating disruption or "male-confusion").
Synthetic pheromones are formulated to correspond to the compositions
of natural pheromones and are released at rates approximating those of the
natural systems. Any changes in either the ratios of the chemical components
or in the pheromone emission rates can prevent successful orientation of
males to the traps. The effectiveness of a synthetic attractant in luring
males is best determined by comparing the number of males caught in attrac-
tant-baited traps relative to the number of males caught in traps baited
with the virgin female (3).
The forest insects for which controls via use of pheromones are current-
ly being investigated include the spruce budworm, forest tent caterpillar,
spruce coneworm, satin moth, large aspen tortrix, shoot borers, tussock
moths, and gypsy moth (2). To date, most of the work with pheromones and
other behavior-modifying chemicals has been on a small scale experimental
basis. In only a few cases have the pheromones of forest insects been
A-424
-------
registered for use. Tables 1 and 2 list some of the behavior-modifying
chemicals which have been tested for potential application in pest manage-
ment .
1.2 COMMERCIAL AVAILABILITY
Behavior-modifying chemicals are produced and distributed by a number
of companies. Hercon (New York, N.Y.) commercially produces "Chek/Mate", a
controlled-release pheromone used to suppress and control insect pest popu-
lations by mating disruption (5). Chek/Mate consists of small pieces of
laminated multi-layered polymeric dispensers ("flakes") containing the in-
sect sex pheromone or a related behavior-modifying chemical. It is regis-
tered for use against the gypsy moth. Hercon also produces luretape, a
multi-layered polymeric, laminated strip dispenser for controlled release of
sex pheromones or attractants and related behavior-modifying chemicals to be
used in survey and monitoring of insect populations and distributions (5).
The pheromone of the elm bark beetle, multilure, which consists of a-
cubebene, 4-methyl-3-heptanol, and 2,4-dimethyl-5-ethyl-6,8-dioxabicyclo
(3.2.1) octane (multistriatin), and the gypsy moth pheromone, dispaflure
(cis-7,8-epoxy-2-methyloctadecane) are available as luretape.
Pherocon EPSM (trans-9-dodecenyl acetate), a clear liquid used for moni-
toring the European pine shoot moth, is an insect attractant formulated as
a rubber cap or wick by Zoecon Corp. (Palo Alto, CA). Zoecon also formulates
the gypsy moth pheromone, Pherocon GM, as a cotton wick to be used for moni-
toring gypsy moth distributions (5).
Conrel (Needham Heights, MA) manufactures pheromone dispensers for use
as lures in survey trapping and mass trapping. They consist of a parallel
array of hollow plastic capillaries mounted on adhesive tape and filled with
synthetic pheromone. The capillaries are open at one end to allow the attrac-
tant to slowly evaporate in air at a uniform rate (5). Conrel formulates
pheromones for the elm bark beetle, the gypsy moth, and the spruce budworm
(trans-11-tetradecenal: cis-11-tetradecenal) in these dispensers. Conrel
currently has conditional registration on the Western pine shoot borer phero-
mone (6). This pheromone is for aerial application as a hollow fiber encap-
sulated formulation at a rate of 2 g a.i./acre (37 g total/acre) or 2 fibers/
m2.
A-425
-------
TABLE 1. FOREST PEST SPECIES FOR WHICH ATTRACTION TO BMC'S HAS BEEN DEMONSTRATED IN FIELD TESTS (4)
f
Specie*
BMC(.)
tl»e fatten
icpldopteri
tyaantrlldae
Oryyia p**udot*uffata
Cymtria diffar
Olethreutldaei
Rh'jacionia tuolimi
Tar'trlcldae
Chortttonfura fltitfmn*
C. eeaUmtaUt
Celeopcera
Scolytldae
Dcndroatonu* tmvietml*
0, frontaUf
D.
9* rufipamt*
Zft eonftnuf
/. amtlna
I. eeltiffraphu*
I.
Cnattiotrtetm* tuleatui
Sfolyt** mil
cin- 7,«
trana-9-
-------
TABLE 2. FOREST PEST.SPECIES FOR WHICH INTERRUPTION OF MATING
OR AGGREGATION BY BMC'S HAS BEEN DEMONSTRATED IN
FIELD TESTS (4)
BMC(a)
Uee Pattern
Upidoptera
niantrlid
Lymantria. diaper
peeudoteugata
Turtrlcidae
fumffgrorta
Scolytidae
i/iidroctonua breviconrit
D. frontalia
D. patudoteugat
2-nethyl-ci»-7-octadecene;
diaparlure
e£0-6-henelcoaen-ll-one
tran»-ll-tetradecenyl acetate
tron*-ll-tetrad«cenol
sprudamont
mating
• n
tran8-v«rbenon«; A3»-br«vicooin, «(gr«gatien
froncalln, oyrccn*
ero-brevicoEiln and verbcnon*; "
endo- and «so- brevleominj "
frontalura "
3-Bethyl-2-cyclohcxcn-l-oD« (HCH); "
frontalur* "
Ips pcraeonfusia
I. pint
MCH
verbenone
lp»«nol
n
n
footnote ID Table 1.
1.3 TECHNICAL CONSIDERATIONS IN USING PHEROMONES FOR INSECT CONTROL
Although a potential exists for use of pheromones in forestry for in-
sect control, considerable experimental and demonstration work is needed
before pheromones could be deployed on a commercial scale. At the present
time, the western pine shoot borer pheromone is registered for use in mating
disruption in Oregon although it has been determined that the impact of the
insect is not significant, and therefore, pheromone control is not likely to
be extensively used (7). Current uses of pheromones are primarily for bio-
surveys and monitoring, and the EPA has exempted this use from registration
<8)« A number of field tests which have been conducted to determine, the
potential use of pheromones in forest insect control are summarized in
Table 3.
A-427
-------
NJ
00
TABLE 3.
Insect Species
Douglas-fir tussock
SELECTED FIELD TESTS DEMONSTRATING THE USE OF PHEROMONES IN FOREST INSECT CONTROL
Pheronone
Z-6-henelcosen-ll-one
Test Area
1 h» plots
Application
Controlled-release applicators;
Results
Disruption greater for traps baited
Reference
9
not!: (Orygia
pseudosugate)
Douglas-fir tussock Z-6-henelcosen-ll'
Both
2 to 4 ha plots
of white fir and
ponderosa pins
WMte-urked tussock
s»th (KMT),
Pine tussock sioth
(PTM)
Gypsy aoth
("orthetrta dlspar)
Shoot borer
{Eucosaa
sonoaana)
Z-6-hcneicoaen-ll'
Dlsparlure
4:1 els:trans Mixture
of 9-dodecenyl acetate
Western pine beetle
(PenJractonus
brcvlcoals)
Western spruce
bujvora (Cnoristo-
neura occldeotalis)
Mixture of (IR,5S,7R)-W-
exo-brevicoain, (15,5R)-
(-)-frontalln, end ayreene
trans-11-tetradecenal
cls-11-tetradecenal
324 • plots
16 he plota
7SO ha of
ponderosa pine
3 plots.
3.6-8.7 ha
0.25-5 ha of
Ponderosa pine
plantation
2.56 ka plots
on e 65 ka2 area
of Ponderosa pine
350 he
release rate 0.05-5.0 ng/ha/day
PheroBone-fllled Conrel fibers
applied to achieve noalnal do-
sage* of 2.3, 9. and 36 g/ha
Release of 140 Bg/ha/day
froa planclict evaporatora
Release rates of 20-50
•g/ha/day fro* hollow fiber
dispensers
Aerial application In Blcro-
capsules at rates of 5.O and
15.0 g/ha
Hollow fibers containing 10
g a.l./ha; »ean application
rate 3 fibers/a2
Aerially applied hollow
fibers containing 250-300 ug
pheronone; 15 g/he noalnal
dosage
Manually applied in poly-
vinyl chloride strips; noalnal
dosages of 3.5 g/ha end 14
t/ha
Traps containing the attractant
Aerial application in laalnated
plastic flakes at dosages of 2
and 20 g/h.
vlth live females than for traps
baited with synthetic. Dosages >1
Bg/ha/day appeared more effective.
In plots with low population den- 18
sit lea, dosages of 0, 2.3, 9, and
36 g/ha resulted in 0.26, 0.07,
0.02, and 0 egg aasseB/feaale, res-
pectively. At higher population
densities, 36 g/ha dosage resulted
in 0.21 egg xasses/female vs. 0.97
egg aaases/feaale In the untreated
plot.
92-100Z disruption of PTH; 96-1001 10
disruption of WMT
65-96Z disruption of PTH; 76-921
disruption of WMT
Hating suppression still evident as 11
long as 6 weeks after application
Damage to teiatnal shoots reduced 12
69-81Z In treated areas
67Z reduction In damage to terminal 13
shoots; 79Z reduction In all In-
fested shoots. Nearly 100Z disrup-
tion of female to aale sex pheroaone
coBBunlcat ion.
Both treataents 1001 In disorienting 14
aales. At 3.5 g/ha, 83Z control of
shoot daaage and 85Z population re-
duction. At 14 g/ha, 84.21.shoot
daaage control and 87.9Z population
reduction. i
Tree aortallty declined froa 227 15,16
before the test to 73 during the
oppression period
Male orientation to female-baited 17
trapa disrupted at a rate 87Z In
the 20 g/ha treataant.
-------
Some of the potential problems which are associated with the use of
pheromones for insect control relate to mobility of insects, spread of in-
sect infestations over large area.: and difficulties in establishing effective
application rates and correlating changes in insect populations to any subse-
quent reduction in tree damage. Whether or not pheromones can be used to
successfully control an insect pest depends in part on the life cycle and
behavioral characteristics of the insect species. In the case of Eucosma
sonomana (western pine shoot borer), three characteristics make this insect
an excellent candidate for control by mating disruption (12,14): (a) the
shoot borer produces only a single generation per year; (b) adults fly only
2 to 3 months during the spring; and (c) even severely infested stands harbor
only about 100 adults/ha/year. It is easier to disrupt mating in low density
infested areas since when populations are high, especially in a limited area,
vision may be as important as pheromones for locating a mate (1). In spite
of favorable characteristics for pheromone treatment, Eucosma sonomana can
damage forests even in treated areas if moth flight and hence, female mating,
occurs prior to pheromone application. In addition, mated females can fly
into a treated area from nearby untreated areas and lay their eggs (13).
The gypsy moth may be an even better candidate for mating disruption, parti-
cularly in low populations, since the female moths do not fly (19).
No protection effects have been demonstrated for any forest defoliators
using behavior-modifying chemicals to interrupt mating (4). The difficulty
of obtaining adequate mating disruption using pheromones is exemplified in
the case of the spruce budworm. The problem with the spruce budworm is that
it is an insect with a long dispersal flight (8). Some adult females deposit
their eggs near the site where they fed as larvae whereas some females are
dispersed miles away from the larval feeding site and deposit eggs there.
If the pheromone is used at one site, some degree of disruption will occur,
but In' some cases, females with eggs fly in from untreated areas and lay
their eggs in the treated site. In other cases, the females that disperse
out of the treatment area find male moths to mate with in untreated areas
(8). The pheromone would have to be applied before any mating occurred and
to all areas infested with the pest in order to give adequate protection.
For high density pests such as the spruce budworm, pheromones may be most
A-429
-------
effectively used as a preventive strategy in monitoring the population to
determine the best time to treat an area (17).
When behavior-modifying chemicals are used in the field, it is often
very difficult to correlate the resulting changes in the insect population
with any subsequent tree damage (4). Although it is clear that these chemi-
cals influence adult behavior, little information exists on the relationship
between the number of adults and damage levels in the next generation (4).
For some species, the precise role of male and female sex pheromones in the
mating behavior of target species is poorly understood and effective phero-
mone application rates cannot be easily determined (2). A case in point is
the control of bark beetles (D. brevicomis). When attractant release rates
are increased, more bark beetles are caught and they tend to be trapped
farther from the source of the attractant (15). However, higher attractant
release rates also increase the tendency for host trees near the attractant
source to be attacked by the beetle. The release rate, therefore, is cri-
tical - a low rate results in a low catch, whereas a high rate results in
attack of the host near the attractant source (15).
2.0 PHYSICAL AND CHEMICAL PROPERTIES
The composition and the physical and chemical properties of insect
behavior-modifying chemicals are highly variable. These substances are
volatile organic compounds and are highly selective for a single (and occa-
sionally a few closely-related) species (20). In order to be competitive
with natural pheromones, synthetic behavior-modifiers must closely represent
the natural chemical stimuli (4). The chemical structures which produce the
desired response have been determined for some forest pest species and are
illustrated in the following examples.
In Ips pini. only the (-) enantiomer of ipsenol interrupts its response
to the naturally-produced pheromone. No activity is observed with (+)-ipse-
nol. In the case of the western bark beetle, D. brevicomis. no more inter-
ruption or enhancement of attraction is observed for the enantiomers of the
synthetic pheromones than for the racemic compounds (22). For Scolytus
multistriatus. the'elm bark beetle, only one of the 4 enantiomers of syn-
thetic 4-methyl-3-heptanol, and one of the 4 isomers of synthetic multi-
striatin are attractive (with (-)-a-cubebene) (23).
A-430
-------
3.0 ENVIRONMENTAL FATE
There is very little data available on the environmental fate of the
pheromones of forest insect pests. However, pheromones are designed to
volatilize as completely as possible and their use rates are so low (4) that
they are not expected to contaminate plant, animal, soil, or aquatic sys-
tems (15). Pheromones that are applied in hollow fibers or flakes do not
ever come into contact with the environment except as a vapor (6). In
addition, the low dosages and infrequent treatment make buildup of fibers
and flakes unlikely (24). Some of the fibers are completely biodegradable
(6).
Field experiments have demonstrated the volatility characteristics of
specific forest insect pheromones. Disparlure (gypsy moth pheromone) applied
to 1-ha plots as a 2 percent solution in gelatin microcapsules at a rate of
5 g a.i./ha was not detected in the field after 66 days. When a 10 percent
solution was used, measurable amounts were found after 66 days (25). In
aerial applications of the Eucosma sonomana sex attractant formulated in
hollow fibers with 250-300 ug/fiber , the fibers were found to contain an
average of 63 ug of the attractant after 85 days (13).
In studies monitoring atmospheric concentrations of the spruce budworm
pheromone, a very rapid decline in atmospheric concentrations was noted (26).
A hollow fiber formulation was applied at a rate of 500..000 fibers/ha to 100
ha of mixed balsam fir and white spruce in New Brunswick. Atmospheric levels
dropped from greater than 7 nanograms/m3 on the day of application to less
than 1 nanogram/m3 one week following application.
The fate of pheromones in soil and water has been studied in agricultu-
ral applications. Methyl Eugenol, the attractant of the oriented fruit fly,
dissipated rapidly from soil and water (21). The half-life was 6 hours in
both soil and water at 32'C. At 22'C the half-life in soil was 16 hours and
in water, 34 hours. It did not leach in the three soils tested. Only 3.8
percent of the pheromone was recovered'from the surface of field-grown toma-
toes after 24 hours. In another study, gossyplure [(Z,Z) and (Z,E)-7,11-
hexadecadiene-1-ol acetate], the pink bollworm pheromone, was found to have
a half-life in soil of 24 hours (28). The half-life in water was 7 days.
A-431
-------
In soil column tests, no leaching was found. In soil, the acetate was hydro-
lyzed to the corresponding alcohol.
4.0 IMPACTS ON NON-TARGET ORGANISMS
Few studies are available on the effect of pheromones on non-target
organisms. However, because of the amount used and the way in which the com-
pounds are released, very little impact on non-target organisms is expected.
In field tests, application of the Douglas-fir tussock moth pheromone
(Z-6-heneicosen-ll-one) did not result in reduced parasitism of fertile
tussock moth eggs masses by two major egg parasites, Telenomus californicus
and Tetrastichus (29). The pheromone was applied in Conrel fibers to a 4-ha
plot at a rate of 36 g/ha.
Laboratory toxicity evaluations show no adverse effects on test animals
exposed to the Eucosma sonomana pheromone (30). Test animals were exposed
by inhalation to 4 g volatilized pheromone in one hour. This dose is equi-
valent to the total amount of pheromone vaporized in one acre of pine plan-
tation during a 10-week period following application. No adverse effects
were observed. At an oral dose of 15 g/kg, no deaths or abnormalities were
noted in rats. Rabbits had no adverse reactions to a dermal dose of 3 g/kg.
The pheromone was found to be a slight to moderate eye irritant only.
The attractants of the western pine beetle, exo-brevicomin and fronta-
lin, are non-toxic as determined in acute oral and dermal tests, eye and
skin irritation tests, and inhalation tests in laboratory animals (15). In
the field, however, non-target flying insects, bats, and small birds can be
physically caught and die in sticky traps (15).
5.0 MISCELLANEOUS
The progress in developing and using pheromones in forestry has been
slow due to the high cost of research and the complexities involved in re-
search on the dynamics of highly mobile, widely distributed pest populations
(20). The costs involved with trying to develop, register, and introduce a
pheromone for mating disruption on a commercial scale include synthesis,
formulation research development, efficacy testing, development of residue
analytical methods, radiochemical synthesis, study of environmental chemis-
try and effects, toxicology, and process development and manufacturing (31).
A-432
-------
Such costs have been estimated at about $1.5 million (31). In addition,
there are two major problems which seriously hinder large scale use of phe-
romones (31):
1. Risk of failure by the developer to secure government approval
or registration, and
2. Uncertainty of the grower in risking use of a new material for
protection of valuable crops.
A third difficulty is that there is a low market potential because of the
high specificity of a pheromone for a pest (20).
A-433
-------
REFERENCES
1. Marx, J.L. Insect Control I: Use of Pheromones, Science 181: 736-737,
1972.
2. Anon. Organization and Program of the Forest Pest Management Institute,
Canadian Forestry Service, 1980.
3. Roelofs, W.L. and R.T. Corde. Responses of Lepidoptera to Synthetic
Sex Pheromone Chemicals and Their Analogues. Ann. Rev. Entomol., 22:
377-405, 1977.
4. Wood, D.L. Development of Behavior Modifying Chemicals for Use in
Forest Pest Management in the U.S.A., in: Chemical Ecology; Odour
Communication in Animals. F.J. Ritter, ed. Elsevier/North Holland
Biomedical Press, pp. 261-279, 1979.
5. 1980 Farm Chemicals Handbook. Meister Publishing 0., Willoughby, Ohio.
6. Telephone communication with Ralph Hodosh, Conrel, 5/28/80. (To P.
Painter, TRW).
7. Telephone communication with LeRoy Kline, Oregon Forestry Department,
November 10, 1981. (To P. Painter, TRW).
8. Telephone communication with W. Bedard, USFS, 5/28/80. (To P. Painter,
TRW).
9. Sower, L.L. and G.E. Daterman. Evaluation of a Synthetic Sex Phero-
mone as a Control Agent for Douglas-fir Tussock Moths. Environ. Ento-
mol.. 6(6): 889-892, 1977.
10. Grant, G.G. Field Trials on Disruption of Pheromone Communication of
Tussock Moths. J. Econ. Entomol. 71(3); 453-456, 1978.
11. Schwalbe, C.P., et al. Field Tests of Microencapsulated Disparlure
for Suppression of Mating Among Wild and Laboratory-reared Gypsy Moths.
Environ. Entomol. 3(4); 589-592, 1974.
12. Overhulser, D.L. Control of Eucosma sonomana (Lepidoptera) with Aerial-
ly Applied Hollow Fibers Containing Synthetic Sex Attractants. Weyer-
haeuser Techn. Rept. 1979.
13. Overhulser, D.L., et al. Mating Disruption with Synthetic Sex Attrac-
tants Controls Damage by Eucosma sonomana in Pinus ponderosa Planta-
tions. II. Aerially Applied Hollow Fiber Formulation, Can. Entomol.
A-434
-------
14. Sartwell, C., et al. Mating Disruption with Synthetic Sex Attractants
Controls Damage by Eucosma sonomana in Firms ponderosa Plantations. I.
Manually Applied PVC Formulations, Can. Entomol. 112: 163-165, 1980.
15. Bedard, W.D. and D.L. Wood. Suppression of Dendroctonus brevicomis by
Using a Mass-trapping Tactic. For publication in Management of Insect
Pests with Semiochemicals Proceeding From a Colloquium. Plenum Press,
N.Y., 1980.
16. Bedard, W.D. and D.L. Wood. Bark Beetles - The Western Pine Beetle.
In: Pheromones. M.C. Birch, ed., Vol. 32. Frontiers of Biology, North-
Holland Publishing Co., pp. 441-461. 1974.
17. Daterman, G.E. Personal communication, 5/28/80. (With P. Painter, TRW).
18. Sower, L.L., et al. Reduction of Douglas-fir Tussock Moth Reproduction
With Synthetic Sex Pheromone. J. Econ. Entomol. 72(5): 739-742, 1979.
19. Doane, C.C. Flight and Mating Behavior of the Gypsy Moth. In:
Perspectives in Forest Entomology. J. F. Anderson and H.K. Kaya, eds.
Academic Press, N.Y. 1976.
20. Wood, D.L. Manipulation of Forest Insect Pests, Ch. 22 in Chemical
Control of Insect Behavior; Theory and Applications. H.H. Shorey and
J.J. McKelvey, Jr., eds., John Wiley and Sons, Inc., pp. 369-384, 1977.
21. Birch, M.C., et al. Nature 220: 738-739, 1977. In Reference 4.
22. Wood, D.L., et al. Science 192: 896-898, 1976. In Reference 4.
23. Lanier, G.N., et al. J. Chem. Ecol. 3: 1-8, 1977. In Reference 4
24. Daterman, G.E. Personal communication, 5/28/80. (with P. Painter, TRW).
25. Caro, J.H., et al. Disparlure: Volatilization Rates of two Microen-
capsulated Formulations from a Grass Field, Environ. Entomol. 6(6); 877-
881, 1977.
26. Wiesner, C.J., et al. Monitoring of Atmospheric Concentrations of the
Sex Pheromone of the Spruce Budworm, Choristoneura fumigerana. Can.
Entomol.ll2(8): 333-344. 1980.
27. Shaver, T.N. and D.L. Bull. Environmental Fate of Methyl Eugenol.,
Bull Environ. Contam. Toxicol. 24: 619-626, 1980.
28. Benson, R.D. Environmental Fate of Gossyplure. Environ. Entomol. 6:
821-822, 1977.
29. Sower, L.L. and T.R. Torgersen. Field Application of Synthetic Douglas-
fir Tussock Moth Sex Pheromone Did not Reduce Parasitism by Two Hyme-
noptera, Can. Entomol. 751-752, 1979.
A-435
-------
30. USDA Forestry Sciences Laboratory. Toxicity Evaluation - Western Pine
Shoot Borer Pheromone, USDA, 1978.
31. Siddall, J.B. Commercial Production of Insect Pheromones — Problems
and Prospects. In: Chemical Ecology: Odour Communication in Animals
F.J. Ritter, ed., Elsevier/North Holland Biomefical Press. 1979.
A-436