SUBSTITUTE CHEMICAL PROGRAM
INITIAL SCIENTIFIC
AND MINIECONOMIC
REVIEW OF
CARBOFURAN
JULY 1976
U.S. ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF PESTICIDE PROGRAMS
CRITERIA AND EVALUATION DIVISION
WASHINGTON, D.C. 20460
EPA 540/1-76-009
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This report has been compiled by the Criteria and Evaluation
Division, Office of Pesticide Programs, EPA, in conjunction
with other sources listed in the Preface. Mention of trade
names or commercial products does not constitute endorsement
or recommendation for use.
For sale by National Technical Information Service, 5285 Port Royal Road,
Springfield, Virginia 22161
Limited copies are available from EPA Forms and Publications Center,
M-D-41, Research Triangle Park, North Carolina 27711
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SUBSTITUTE CHEMICAL PROGRAM
INITIAL SCIENTIFIC
AND
MINIECONOMIC REVIEW
OF
CARBOFURAN
JULY 1976
U.S. ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF PESTICIDE PROGRAMS
CRITERIA AND EVALUATION DIVISION
WASHINGTON, D.C. 20460
EPA-540/1-76-009
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PREFACE
The Alternative (Substitute) Chemicals Program was initiated under Public
Law 93-135 of October 24, 1973, to "provide research on, and testing of, substi-
tute chemicals." The legislative intent is to avoid the use of substitute chem-
icals that would be even more deleterious to man and his environment than a pes-
ticide that is cancelled or suspended for causing "unreasonable adverse effects
to man or his environment." The major objective of the program is to determine
whether potential substitute chemicals are suitable replacements for cancelled
or suspended pesticides or for pesticides that are under litigation or are can-
didates for Rebuttable Presumption Against Registration (RPAR).
The review of the substitute chemical considers its chemistry, toxicology,
and pharmacology as well as its use patterns, efficacy, and environmental fate
and movement. EPA realizes that, even though a compound is registered, it still
may not be a practical substitute for certain uses of a problem pesticide. There-
fore, the utilitarian value of the "substitute" must be established by reviewing
its biological and economic data.
The reviews of substitute chemicals are carried out in two phases. Phase I
Initial Scientific Review evaluates the "safety and efficacy" of the substitute
chemical based on data readily accessible at the present time. The Phase II
Integrated Use Analysis examines the effects of possible regulatory action
against a hazardous pesticide for each of its major and critical uses. The
examination considers the suitable substitutes in conjunction with alternative
agricultural management practices. Current and projected environmental, health,
and economic impacts are also evaluated.
This report contains the Phase I Initial Scientific Review of carbofuran.
Carbofuran was identified as a registered substitute chemical for certain prob-
lematic uses of chlordane, heptachlor and aldrin which have been cancelled by
EPA. The report covers all uses of carbofuran and is intended to be adaptable
to future needs. Should carbofuran be identified as a substitute for a problem
pesticide other than those mentioned above, the review can be updated and made
readily available for use. The data searches ended in June, 1975. The report
summarizes rather than interprets scientific data reviewed during the course
of the studies. Data from different sources is not correlated, nor are opin-
ions presented on contradictory findings.
A team of EPA scientists in the Criteria and Evaluation Division of the
Office of Pesticide Programs coordinated the review; the team leader provided
guidance and direction and technically reviewed information retrieved during
the course of the study. The following EPA scientists comprised the review
team: E. Neil Pelletier, Ph.D. (Team Leader); Padma Datta, Ph.D., and Hudson
Boyd (Chemistry); Roger Gardner (Pharmacology and Toxicology); Willard Cummings
and Richard Stevens (Fate and Significance in the Environment); Ralph Wright
(Registered Uses); and Gary Ballard and Harry Gaede, Ph.D. (Economics).
iii
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Data research, abstracting, and collection were performed primarily by Mid-
west Research Institute (MRI), Kansas City, Missouri (EPA Contract #68-01-2448)
under the direction of Thomas L. Ferguson. The following MRI scientists were
principal contributors to the report: Alfred F. Meiners, Ph.D.; James V. Dilley,
Ph.D.; Frank E. Wells, Ph.D.; William J. Spangler, Ph.D.; David F. Hahlen; and
Thomas L. Ferguson. Other MRI project team members who contributed to the devel-
opment of this review were John R. Hodgson, Ph.D.; Edward W. Lawless, Ph.D.;
Daniel G. Puzak, and Kathryn Lawrence. Rosmarie von Rumker, Ph.D., and Freda
Horay, both of RvR Consultants, were also contributors.
The scientific staffs of EPA's Environmental Research Laboratories reviewed
draft copies of the report. Comments and supplemental material provided by the
following laboratories were greatly appreciated and have been incorporated into
this report: Gulf Breeze Environmental Research Laboratory, Gulf Breeze,
Florida, and the National Ecological Research Laboratory, Corvallis, Oregon.
FMC Corporation, which manufactures carbofuran, and the Chemagro Division of
Mobay Chemical Corporation, which markets carbofuran under a license from FMC,
both reviewed the draft of this report and made certain comments and additions.
iv
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GENERAL CONTENTS
Page
List of Figures vi
List of Tables vii
Part I. Summary 1
Part II. Initial Scientific Review 15
Subpart A. Chemistry 15
Subpart B. Pharmacology and Toxicology 51
Subpart C. Fate and Significance in the Environment. ... 96
Subpart D. Production and Use 142
Part III. Minieconomic Review 162
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FIGURES
No. Page
1 Manufacturing Process for Carbofuran 3
2 Preparation of Carbofuran from £-Nitrophenol 16
3 Production Schematic for Carbofuran 17
4 Degradation Curves for Carbofuran in Sultan Silt Loam at
4 pH Levels 40
5 Oxidation and Hydrolysis Routes of Carbofuran 44
6 Scheme for Producing Parental and Progeny Stock for a 3-
Generation Study (Rats) 67
7 Proposed Products of Carbofuran Oxidation and Hydrolysis 77
8 Materials Flow Diagram for Carbofuran (1972) 148
vi
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TABLES
1 Method Requirements for Specific Samples .......... 22
2 Other Analytical Methods for Carbofuran Residues ...... 25
3 Residues of Carbofuran on Sugarcane ............ 28
4 Maximum Total Residues (ppm of Carbofuran, Including 3-
hydroxycarbofuran) Found on Field Corn Silage and
Stover .......................... 29
5 Residues of Carbofuran in Alfalfa (ppm Al/acre) ...... 30
6 Residues of Carbofuran on Peanuts ............. 32
7 Residues in Milk of 3 Metabolites of Carbofuran Fed at
200 ppm Total Metabolites ................ 35
8 Residues in Tissue of 3 Metabolites of Carbofuran at End
of 28-Day Feeding Period ................. 36
9 U. S. Tolerances for Carbofuran .............. 37
10 Summary of Acute Toxicity Data for Rats .......... 54
11 Acute Oral Toxicity of Carbofuran Metabolites ....... 55
12 Summary of Acute Toxicity Data for Animals Other than
Rats ........................... 56
13 Changes in Plasma Cholinesterase Activity in Dogs After
Dosing with Carbofuran .................. 57
14 Changes in Erythrocyte Cholinesterase Activity in Dogs
Dosed with Carbofuran .................. 57
15 Survival Indices for a 3-Generation Study on Rats (30 ppm
Carbofuran) ....................... 69
16 Summary of Tumor Incidence During an 18-Month Carcinogenic
Study with Swiss White Mice ............... 71
17 Metabolites of Carbofuran ................. 78
18 Ratios of Carbofuran Metabolite Residues in 6 Major
Crops .......................... 81
vii
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TABLES (Continued)
No. Page
19 Degradation of Labeled Carbofuran by Rat Liver 15,000
G Solubles 86
20 Toxicity of Technical Carbofuran and Its Formulations
to Fish 99
21 Acute Toxicity of Carbofuran to Birds 102
22 Subacute Toxicity of Carbofuran to Birds 105
23 Effect of Furadan 10G on Oxygen Uptake in Field Soil. . . Ill
24 Radioactive Carbofuran Equivalents Recovered as Carbo-
furan, Soil-Bound Residue, and Expired C02 from
Irradiated and Nonirradiated Soils Treated with
14c-Carbonyl-Labeled Insecticide at 20 ug/cm3 120
25 Carbofuran Residues in Soil Samples (mg/m^) 124
26 Runoff-Producing Rainfalls and Carbofuran Losses in
Runoff Water from Carbofuran-Treated Watersheds 133
27 Currently Registered Uses of Carbofuran 149
28 Use of Carbofuran in the U. S. by Crops, 1971 155
29 Use of Carbofuran in the U. S. by Regions, 1971 156
30 Use of Carbofuran in California by Major Crops and Other
Uses, 1970-1974 157
31 Use of Carbofuran in California in 1972, 1973 and 1974
by Crops and Other Uses, Applications, Quantities, and
Acres Treated 158
32 Estimated Uses of Carbofuran in the U. S. by Regions
in 1971, 1972 and 1974 159
33 Summary of Carbofuran Tests on Alfalfa 175
34 Summary of Carbofuran Tests on Corn 176
35 Summary of Carbofuran Tests on Peanuts 177
36 Summary of Carbofuran Tests on Potatoes 178
viii
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TABLES (Continued)
No. Page
37 Summary of Carbofuran Tests on Rice 179
38 Summary of Carbofuran Tests on Sugarcane 179
39 Summary of Carbofuran Tests on Tobacco 180
40 Summary of Carbofuran Tests on Peppers 180
ix
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PART I. SUMMARY
CONTENTS
Page
Production and Use 2
Toxicity and Physiological Effects 2
Food Tolerances and Acceptable Intake 7
Environmental Effects 8
Efficacy and Cost Effectiveness 12
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This section contains a summary of the "Initial Scientific and Minieconomic
Review" conducted on carbofuran (2,3-dihydro-2,2-dimethyl-7-benzofuranyl methyl-
carbamate). The section summarizes rather than interprets data reviewed.
Production and Use
Carbofuran (2,3-dihydro-2,2-dimethyl-7-benzofuranyl methylcarbamate) is a
broad-spectrum insecticide-nematicide, especially effective against corn root-
worms. Carbofuran is manufactured by FMC Corporation (owner of the manufactur-
ing and use patents) at Middleport, New York, and is also marketed under license
by the Chemagro Division of Mobay Chemical Corporation.
Carbofuran is a white crystalline solid that undergoes alkaline hydrolysis
(cleavage at the carbamate linkage), oxidation and photodecomposition. Carbo-
furan is readily metabolized by plants, animals, insects, and soil microorgan-
isms. Oxidation and photodecomposition appear to be minor environmental degra-
dation routes. (See Figure 1.)
Carbofuran is available in 4 granular formulations (2, 3, 5, and 10%)
and a 4 Ib/gal flowable formulation. The only formulations available for domestic
use are those made by the manufacturer; carbofuran is not available in the
United States as a technical active ingredient.
Carbofuran production in 1972 was estimated at 6 million Ib active ingredi-
ent (AI), approximately 1 million Ib of which were exported. Estimated 1974
domestic usage was slightly over 7.0 million Ib. Approximately 6.8 of the 7.0
million pounds were used on corn (6.3 million Ib in the corn belt, lake and
northern plains states; 500,000 Ib in the remaining corn-growing states).
Toxicity and Physiological Effects
Acute Toxicity - In tests with various animal species, chickens appeared to
possess the greatest resistance to carbofuran (LD5Q = 25.0 to 38.9 mg/kg) and
mice, the least resistance (LDso = 2 mg/kg). Dogs were intermediate (U>50 =
1.5.85 mg/kg). Sex differences were not apparent.
In tests with rats the acute toxicity of carbofuran was found to be as
follows:
Route of
administration Formulation Measurement Value
Oral Technical LDso 1-65 mg/kg (newborn)
(98.8%) 3.36 mg/kg (weanling)
6.4 to 14.1 mg/kg (adult)
Intraperitoneal Technical LD5Q 1.37 mg/kg
(98.8%)
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NO,
o-nltrophenol methallyl
chloride
base (-HCl
CH3
o-methallyloxy-
nitrobenzene (I)
rearrangement
heat
175-190'C
HO,
* 0,
-OH
2-nitro-6-raethallylphenol (II)
NO,
OH
-CH=C(CH3)2
2-nltro-6-isobutenylphenol (III)
II and III
cycllzatlon
acid catalyst
(FcCl- preferred)
150-190*C
CH,
2,3-dihydro-2,2-dimethyl-
7-nitrobenzofuran (IV)
hydrogenation
catalyst
7-amino-2,3-dihydro-
2,i -Jiinethylbenzofuran (V)
dlatotization,
room temperature
CH,
SO,
7-dlazonium-2,3-dihydro-
2,2-dimethybenzofuran
+ Na2SOA + H20
H20, heat
catalyst
CH,
2,3-dihydro-2,2-diraethyl-
7-benzofuranol (VI)
VI + CH3NCO
methyl
isocyanate
OCON1ICH
carbofuran
Figure 1. Manufacturing Process for Carbofuran
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The acute dermal LD5Q for rabbits of technical carbofuran in an organic
solvent (Dowanol DPM) was 14.7 mg/kg; however, the acute dermal LD,-n of the
technical carbofuran in water was greater than 10.2 g/kg. A 10% granular for-
mulation (10G) had an LD5Q of 10.2 g/kg. Furadan® 4 flowable had a dermal LDso
value of 6.8 g/kg.
In studies on the effects of carbofuran metabolites on rats, 3-hydroxy-
carbofuran was found to be highly toxic; 2,3-dihydro-7-hydroxy-2,2-dimethyl-3-
oxobenzofuran and 3-ketocarbofuran moderately toxic; and 2,3-dihydro-2,2-
dimethyl-7-hydroxybenzofuran and 2,2-dimethyl-3,7-dihydroxy-2,3-dihydrobenzo-
furan, slightly toxic.
In tests with 1- to 2-week-old calves, a single dose of carbofuran at 1 mg/kg
resulted in death; the same dose in older animals resulted only in salivation,
tearing, hyperactivity and diarrhea.
Sheep exhibited increased salivation, stomach cramps, and frequent micturi-
tion at carbofuran doses higher than 2.5 mg/kg. At 10 mg/kg dosing, death
occurred, even though the animals were treated with atropine sulfate.
Subacute Toxicity - The subacute effects of carbofuran were evaluated in tests
using rats, rabbits, guinea pigs, chickens, and dairy cows.
Rats fed 0.1 to 1,600 ppm carbofuran for 90 days did not exhibit abnormal
changes when compared to controls; comparisons were made of gross pathology,
histopathology, hematology, and urine constituents. Although no deaths were
recorded, animals that received diets containing carbofuran at 1,600 ppm
exhibited slight to moderate, generalized tremors.
Other rats were fed at dietary levels up to 3,000 ppm for 90 days without
significant observable differences between test groups and controls. Comparisons
were made of hematology, urine constituents, blood chemistry, gross pathology,
and histopathology.
As part of a 16-week study, rats were dosed after 13 weeks with carbofuran
at levels of 0, 0.1, 0.3, 1.0, and 3.0 mg/kg/day. A slight reduction in
cholinesterase values at the highest dose occurred.
A study in which female rats were given 3 mg/kg/day for 3 weeks showed that
the time of testing for cholinesterase activity after dosing is important.
Samples taken from 0 to 60 min after administration of carbofuran showed greatest
cholinesterase inhibition a short time after treatment.
At 5 mg/kg/day, cholinesterase activity in dogs treated for 92 days was not
radically reduced (the dogs exhibited frequent coughing and gagging). Daily
exposure to carbofuran resulted in some adaptation to the pesticide. The depres-
sion of cholinesterase activity after a single dose given to rats previously
exposed to carbofuran for 14 to 28 days was not as great as that which occurred
in rats that had not been previously exposed.
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Rabbits fed a diet containing 700 ppm carbofuran for 14 days showed a
slight decrease in body weight. No other effects were noted.
Three metabolites of carbofuran (3-hydroxycarbofuran phenol, 3-ketocarbo-
furan phenol, and carbofuran phenol) were fed to chickens for 28 days without
any apparent adverse changes in appearance, behavior, food consumption, or egg
production. These same metabolites were also fed to dairy cows in combinations
Up to 200 ppm (66.7 ppm dietary for each metabolite) for 28 days. No abnormal
effects were observed in any test animal.
Chronic Toxicity - Two-yr chronic studies were conducted with rats and dogs.
Rats were given carbofuran at dietary levels of 1, 10, and 100 ppm. Both males
and females in the 100 ppm test group exhibited a weight depression, but the
lowered rate of gain was statistically significant in males only (P < 0.05).
In all other measurements, no differences were observed between the untreated
controls and treated animals. Comparisons were made by hematological tests,
tests for urinary constituents, blood chemistry tests, and gross pathology and
histopathology.
An additional study was performed at dietary levels of 25 and 50 ppm. The
only differences noted between treated and control rats was a reduction in food
consumption by males at the 50 ppm level for the first 9 months of the test.
All other comparisons (mortality, behavioral reactions, gross pathology, and
histopathology) did not demonstrate any differences between the untreated con-
trols and the animals fed the 50-ppm diet.
In a 2-yr chronic study with dogs, no abnormal behavioral reactions were
observed in animals fed 1, 2, 10, 20, and 50 ppm carbofuran diets. At 100 ppm,
slight coughing and gagging reactions were observed. At 200 and 400 ppm,
coughing and gagging were observed daily. Muscular tremors and weakness in the
hinquarters were also seen in dogs fed 200 ppm. Death occurred in some animals
at 400 ppm.
Effects on Reproduction - A 3-generation reproduction study with rats fed a 1,
10, and 100 ppm showed a low 5-day survival index for pups and a greater
incidence of stillbirths in the 100 ppm test group. In another test conducted
at 50 ppm, results for Fo parents and F^a and FH, progeny paralleled the 100 ppm
study. The 5-day survival indexes for the progeny from the treated animals
were lower than those of the controls; weanling body weights were also lower
in treated than in untreated animals.
A 3-generation study at 20 and 30 ppm carbofuran suggested that the 30 ppm
treatment level (a) affected the mating of parental animals, and (b) had an
effect on the 5-day survival index of progeny from treated parents.
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Three metabolites of carbofuran fed to .rats at 10 and 50 ppm apparently
did not have any effect on the ability of the animals to mate, conceive, or
to carry their young.
A reproduction study with dogs indicated that dietary levels of carbo-
furan at 20 and 50 ppm for 20 months had no adverse effects on parental animals
with respect to mortality, estrus cycles, mating, parturition or lactation.
Treatment of parents did not affect progeny with respect to litter size,
survival indices, or ability to nurse. When pregnant bitches were fed carbo-
furan at 20 ppm during the last half of gestation, no effects were observed
in the pups or the mother. All pups appeared normal and maintained normal
growth patterns.
Carcinogenicity - The incidence of tumors in rats fed dietary levels of 10 ppm
carbofuran for 2 yr was no different than in untreated controls. Similar
results were observed in a study at 50 ppm.
Mice were fed carbofuran at 30 and 100 ppm for 18 months in a study to
determine whether or not carbofuran was carcinogenic by oral routes. The
percent of mice bearing tumors at the end of the study (10.5%) was the same
for the controls and for the animals treated at 100 ppm. In a positive
control group (treated with urethane) 76% of the animals had tumors.
Mutagenesis - One study with mice indicated that a dose of 0.5 mg/kg carbofuran
did not induce a dominant lethal mutation in mice.
Teratology - Female rabbits were administered carbofuran in gelatin capsules
(0.1 and 0.5 mg/kg/day) beginning on the sixth day of gestation and continuing
through the eighteenth day. On the twenty-ninth day of gestation the does were
sacrificed and the litters recovered by caesarian section. Examination of 120
fetuses failed to reveal any abnormalities that could be attributed to exposure
to carbofuran. It appeared, however, that resorption was twice as high in the
carbofuran test groups as in the controls.
Potentiation - Twelve pesticides were included in a study to determine whether
or not combination with carbofuran resulted in potentiation. No potentiation
as determined by acute oral toxicity was observed.
Signs and Symptoms - Depending on dose, signs and symptoms reported for carbo-
furan intoxication were similar in most animals. These included fibrillary
action, salivation, ataxia, exophthalmos, hyperpnea, tonoclonic convulsions,
labored breathing, affected limbs (weakness, paralysis), depression, prostration,
and death.
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Antidotes - Studies with rats, dogs, rabbits, cattle, and sheep indicated that
treatment of affected animals with atropine sulfate could reverse the toxic
effects of carbofuran if treatment was started early enough. A 50 mg/kg dose
was effective in rats and dogs. A 10 mg dose of atropine sulfate protected
rabbits from lethal effects of carbofuran at 5.3 mg/kg. The results of one
study with rats, however, indicated that 2-pyridine aldoxime methochloride
(2-PAM) was not antidotal.
Eye Irritation - Instillation of 5 mg of technical carbofuran into the conjunc-
tival sac of the eyes of New Zealand white rabbits resulted in miosis for a
period of 2 hr. Thereafter, the condition cleared.
Skin Irritation - Intracutaneous injection of technical carbofuran into the skin
of male guinea pigs every other day for 20 days (0.05 ml initial injection and
all others 0.10 ml) did not elicit a sensitizing reaction.
Neurotoxicity - White leghorn hens dosed with technical carbofuran at concentra-
tion equivalent to the reported LD5Q (38.9 mg/kg) exhibited salivation and
general weakness, but not leg and wing weakness. Surviving birds were given a
second dose at day 21 with similar results. No physical signs of neurotoxicity
were observed.
Metabolism - The main pathway of oxidative metabolism of carbofuran in animals
(and in plants and insects) appears to consist of hydroxylation at the benzylic
carbon to yield 3-hydroxycarbofuran (2,3-dihydro-2,2-dimethyl-3-hydroxybenzo-
furanyl-7-methylcarbamate). The hydroxylated product is further oxidized to give
3-ketocarbofuran (2,3-dihydro-2,2-dimethyl-3-ketobenzofuranyl-7-N-methylcarba-
mate). Hydrolysis and conjugation then result. Carbofuran can also be hydro-
lyzeJ to carbofuran phenol (2,3-dihydro-2,2-dimethyl-7-hydroxybenzofuran). In
addition, hydrolysis can occur following oxidation to 3-hydroxycarbofuran (or
3-ketocarbofuran). The 3-keto compound is hydrolyzed at a much faster rate than
carbofuran.
The available data also indicates that hydrolysis is generally preceded by
oxidative metabolism. The hydroxylated metabolites can be conjugated as gluco-
sides in plants, or glucuronides in animals. Carbofuran metabolites are stored
in plants but are not reported to accumulate or persist in animal tissues or milk.
Food Tolerances and Acceptable Intake
Carbofuran has not been reported as a significant residue in any class of
food, nor is it detected by the Food and Drug Administration analytical system
routinely used to monitor pesticide residues in food.
Tolerances have been established for "carbofuran" (evaluated as carbofuran
plus its 4 major metabolites, and total carbamates) for 24 food and feed
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commodities. These tolerances range from 0.05 ppm (including a maximum 0.02 ppm
carbamates) in meat, fat, and meat by-products to 40 ppm (including a maximum 20
ppm carbamate) in alfalfa hay. See page 37
An acceptable daily intake (ADI) has not yet been proposed for carbofuran.
Environmental Effects
Fish - Ten species of fish were used in laboratory testing of the toxicity of
carbofuran. From all tests, the 96 hr LC5Q ranged from 0.08 to 1.18 ppm. The
toxicity of carbofuran varied considerably depending upon the species of fish
and the physical conditions associated with the tests. For example, the LC5Q
(24 hr) of carbofuran to brown trout was 0.355 mg/1 (ppm) in city water, but
was found to be 0.842 ppm in reconstituted standard water.
The bluegill appeared to be the most sensitive species and the fathead
minnow the most resistant. Intoxicated fish were at first hyperactive, but
this stage was followed by lethargy, body paralysis, scoliosis, loss of equili-
brium, opercular paralysis, and death.
When 3% granular carbofuran was applied to rice fields at the rate of
0.5 Ib Al/acre, some casualties fo mosquitofish (Gambusia affinis) occurred
1 hr after treatment. Heavy mortality of mosquitofish, large-scale menhaden
(Brevoortia patronus), Atlantic croaker (Micropogon undulatus) and European
carp (Cyprinus carpio) was found 24 and 48 hr after treatment. The rice seed
used to plant the fields had been treated with another insecticide. If, and
to what extent, the seed treatment may have influenced the fish mortalities is
unknown.
Lower Aquatic Animals - Carbofuran was of intermediate toxicity (compared to
several other commonly-used insecticides) to lower aquatic animals in one test,
highly toxic in another test. The LC5Q for white river-crawfish and bullfrog
tadpoles was 500 and 2,700 ppb, respectively. The LC5Q for Daphnia magna was
20 ppb. The 24- and 48-hr £059 values for pink shrimp exposed to technical
carbofuran were 0.0068 and 0.0046 ppm, respectively. Technical carbofuran did
not appear to affect the eastern oyster in exposures up to 96 hr at 1.0 ppm.
In a field study, carbofuran granules (0.5 Ib Al/acre) resulted in heavy
mortality of cricket frogs, crayfish, earthworms, and nontarget aquatic insects
between 1 and 45 hr after treatment.
Wildlife - Data on carbofuran''s toxicity to wildlife demonstrates that the oral
1050 to 8 species of adult birds for technical grade carbofuran ranged from
0.238 mg/kg for the fulvous tree duck (Dendrocygna bicolor) to 8.0 mg/kg for
the bobwhite quail (Colinus virginianus). Dermal toxicity was 100 mg/kg in
tests with 2 species (house sparrow, Passer domesticus, and quelea, Quelea quelea.
Oral LD50 for Furadan 10G ranged from 0.71 mg/kg for mallard ducks (Anas
platyrhynchos; to 100 mg/kg for bobwhite quail.
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Subacute toxicity studies indicated that the mallard duck was the most
sensitive of the birds studied (oral LDso = 0.397 mg/kg) and that the bobwhite
quail was the most resistant (oral LDso =8.0 mg/kg) to technical grade carbo-
furan. Toxicity symptoms among the surviving bird species lasted from 5 to 7
days and occurred as soon as 5 min after treatment.
Carbofuran fed to quail for 6 weeks was not highly toxic at levels of 200
ppm or less, but was highly toxic at 400 ppm. Feed efficiency decreased at
dietary levels above 200 ppm.
Although sex differences were not observed with single acute doses, the
males appeared to be more susceptible than females to extended, subacute
dosing.
The fertility of females and the hatchability of eggs were greatly
reduced at levels of 200 ppm and above. However, no abnormal embryos or
hatchlings were observed.
In one field study on the effects of carbofuran on wildlife, an application
of 3% granular carbofuran to rice fields at a rate of 0.5 Ib Al/acre resulted in
bird death or illness at 17 and 24 hr after treatment, with anywhere from 1 to 8
carbofuran granules in their stomachs. In 5 other field studies, no mortality
or significant adverse effects on mallard ducks, bobwhite quail, and ring-neck
pheasant resulted from exposure to various carbofuran formulations.
Beneficial Insects - Carbofuran was highly toxic to honeybees (Apis mellifera)
by direct contact. The LD5Q was 0.16 yg/bee. No label warnings occur on
granular carbofuran formulations since granulars apparently offer little or no
hazard to bees.
Lower Terrestrial Flora - When applied at rates of 1 and 5 yg/g soil, carbofuran
did not drastically reduce the fungal population. However, the higher rate did
depress fungal populations at 1, 2, and 4 weeks, but at 8 and 12 weeks there was
no significant difference between carbofuran-treated plots and untreated controls.
Carbofuran applied at 5 yg/g soil significantly decreased bacterial popula-
tions during the first week. However, bacterial populations soon recovered to
previous levels or levels above controls.
The above studies also showed that carbofuran had no effect on ammonifica-
tion or nitrification of ammonium from soil organic nitrogen. However, oxidation
of elemental sulfur was significantly depressed.
Measurement of soil microbial respiration showed that oxygen consumption
increased as carbofuran concentration increased. The authors concluded that
soil microorganisms are able to tolerate carbofuran.
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Carbofuran applied at 100 ppm and 10 ppm AI had little effect on soil
respiration. Oxygen uptake in carbofuran-treated soil was slightly higher
than the untreated control. Possible degradation of the formulation was
indicated.
Other studies showed that carbofuran had no effect on nitrification at
application rates of 5, 50, and 500 ppm. In addition, growth of the rhizobia
bacteria Rhizobium meliloti and Rhizobium japonicum was not affected.' However,
there was some growth inhibition of Rhizobium leguminosarum and Rhizobium tri-
folii.
Legume seedling growth was studied at the 5, 50, and 500 ppm application
rates using sweet clover and alfalfa. At the field application rate (5 ppm),
carbofuran did not affect seedling growth. However, at 500 ppm, growth was
drastically reduced.
The effects of carbofuran on microflora under field conditions were
studied using field plots designed to approximate actual pesticide applica-
tion and timing in the growing of shade leaf tobacco. Carbofuran depressed
relative numbers of fungi, bacteria, actinomycetes, and algae, although not at
a statistically significant level. Nitrification depression was also not
statistically significant.
Carbofuran had no harmful effect on the Rhizobium species peanut (Arachis
hypogaea) symbiosis when applied at normal field rates.
A study to determine the influence of carbofuran on the growth rate of 2
soil-borne fungi was conducted in vitro. The growth of Fusarium oxysporium f.
lycopersici was slightly inhibited when grown on nutrient media containing 5 ppm
carbofuran. The dry weight of Penicillium digitatum increased slightly.
The effects of 1,000 ppm AI carbofuran on microbial populations was studied.
Twenty-four hr after application the average number of bacteria and fungi per
gram of soil did not differ significantly between the treated.and untreated
samples.
When carbofuran (0.47g AI/100 ml) was added to commercial formulations of
Bacillus thuringiensis, the survival of the bacteria on inert surfaces was not
affected.
Lower Terrestrial Fauna - The effect of 10% granular carbofuran applications on
earthworms (Lumbricus terrestris) was studied. Surface level dead and dying
earthworm counts were made 6 days after application. Earthworms in the immedi-
ate area of 2.0 and 4.0 Ib Al/acre carbofuran banded applications were killed in
large numbers. The LDso for earthworms was 1.3 mg/kg. When carbofuran was
mixed with soil, the LCso over a 5-day test period was 12.2 ppm. Studies using
14d-labeled carbofuran indicated that earthworms metabolize carbofuran initially
in a manner similar to other animals and plants. However, the study suggested
that toxicity to worms was caused by factors other than cholinesterase inhibi-
tion.
10
-------
The reactions of the manure worm (Eisenia foetida) were compared to those
of earthworms (Lumbricus terrestris). Carbofuran appeared to repel E, foetida
while seeming to immobilize I,, terrestris. Carbofuran uptake in a 6-hr period
was similar for both species. However, excretion of this material in 48 hr was
95% and 10%, respectively.
Bioaccumulation and Biomagnification - Bioaccumulation and biomagnification
studies were performed using a terrestrial-aquatic model ecosystem with a 7-
element food chain. The terrestrial phase of the system was treated with l^C-
labeled carbofuran at a rate equivalent to 1 Ib Al/acre and allowed to run 33
days. At the end of the experiment, none of the organisms contained carbofuran,
although several carbofuran metabolites were isolated from a freshwater plant,
Elodea canadensis (maximum concentration 0.035 ppm) .
Carbofuran was highly biodegradable, with low residual activity in the
ecosystem. Detoxification occurred by hydroxylation of the carbofuran mole-
cules. The authors concluded that carbofuran does not present ecological
problems related to food chain accumulation or biomagnification.
Fate in Soil - The fate of carbofuran in soil was studied by incorporating 10%
granules applied at 1.85 ppm (recommended rate) into soils. Soil concentration
of carbofuran after 8 weeks was 20% of the original. Biological activity in
sandy loam soil disappeared within 16 weeks. In muck soils, biological activity
persisted for 24.weeks.
Degradation in soils of pH 7.8 was rapid; a tenfold difference in half-life
was noted between soils of pH 4.3 and 7.8. Rapid chemical hydrolysis is the
primary route of carbofuran degradation in alkaline soils. In acid and neutral
soils, both chemical and microbial degradation mechanisms predominate, but over-
all degradation rates are slower.
Field investigations showed that carbofuran reached maximum insecticidal
toxicity 3 to 5 days after application. Toxicity degradation in the 2 soils
tested (pH 5.2 and 6.4) was approximately equal.
Time periods required for carbofuran toxicity to reach soil surfaces when
incorporated into the soil at depths of 1/2, 3/4 and 1 in were 1, 2 to 3, and
3 to 4 weeks, respectively.
Three soil types were treated with 2.0 and 9.0 ppm -^C-labeled carbofuran.
Dissipation was more rapid in sandy loam soil than in muck soil with half-life
ranging from 20 to 40 days.
Studies of carbofuran dissipation showed no correlation between climate
and dissipation rate. However, dissipation was greater after broadcast appli-
cation than after band or in-furrow application. In addition, studies showed
no indication of soil residue increase with carbofuran applications in successive
years. '
11
-------
Fate in Water - Little data was available on the fate or effects of carbofuran
in water. Maximum carbofuran residues in water from rice fields treated with
0.5 Ib Al/acre were as follows: 0.7 ppm 8 hr after a postflood application
and 0.05 to 0.1 ppm 7 days after a preflood application.
Fate in Air and Nontarget Plants - Limited data was found on the fate or the
effects of carbofuran residues in the air, or on effects of residues in non-
target plants.
Transport - In a test simulating application of carbofuran granules to flooded
rice fields, carbofuran residues in quantities toxic to leafhoppers (test
animal) moved laterally 22.5 cm in 48 hr.
Transport studies showed that carbofuran leaches more slowly in soils
which are high in clay or organic matter. If soils are of the same clay content,
movement is further in soils with lower exchange capacities.
In a lysimeter study, carbofuran residues after 1 yr were negligible in the
top 1.5 ft of 2 heavy soils (high organic matter) but were distributed equally
throughout the top 3 ft of the sandy loam soil. Field studies showed that
carbofuran residues generally remain in the upper 6 in of treated soils. Below
6 in depths, concentrations were less than 0.1 to 0.2 ppm in most instances.
Runoff studies showed that major losses of carbofuran occurred only with
early rainfall events. In an extensive 2-yr study, carbofuran losses
represented only 0.5 to 2.0% of the total applied. Most of the carbofuran which
was lost was found in the water, not the sediment.
Efficacy and Cost Effectiveness
Carbofuran is recommended for control of armyworms, corn borers, corn root-
worms , wireworms, nematodes, flea beetles, thrips, leaf hoppers, aphids,
Colorado potato beetles, rice water weevils, tobacco budworms, hornworms,
mosquito larvae, potato tuberworms, and lygus bugs on crops, and several pests
attacking trees. Crops which are affected by these pests include alfalfa,
bananas, field corn, peanuts, peppers, potatoes, rice, sugarcane, and tobacco.
The efficacy and cost effectiveness of carbofuran in pest control are
summarized below.
12
-------
Alfalfa - The alfalfa weevil was controlled for 28 days when 0.5 Ib/acre of
carbofuran was applied to the crop. Carbofuran at 1.0 Ib/acre gave effective
control of the Egyptian alfalfa weevil when applied 80 days prior to cutting.
Control of lygus bugs was achieved for up to 33 days, but control of aphids
was effective for a shorter period and additional applications were needed.
Corn - Control of corn rootworms, the European and southwestern corn borers,
and the armyworms in field corn was obtained at rates of 1.0 Ib of carbofuran
per acre or less, except for the Illinois region where rates of 2.0 to 3.0 Ib/
acre were needed to control corn borers. Yields were generally increased with
improved control.
In the tests reviewed, control of nematodes in carbofuran-treated field
corn was slightly better than in untreated checks, but yields were significantly
increased. Control of wireworms in the tests reported was poor.
The use of carbofuran on field corn resulted in yield changes ranging from
a loss of 6.6 bu/acre to a gain of 49.4 bu/acre, as compared to untreated test
plots. Economic benefits from these yield changes ranged from a loss of $35.40/
acre to a gain of $90.20/acre from the use of carbofuran.
Peanuts - Carbofuran is effective as a nematicide for control of root-knot,
sting, and stunt nematodes in peanuts. Thrips were also controlled. Control
of ring nematodes, however, was reported as poor. Yield increases were found
to be directly related to control of the root-knot nematode; little relation
was found between thrips control and yield.
Most test plots produced significant yield increases of peanuts when
treated with carbofuran. Compared to untreated plots, yield changes varied
from a loss of 412 Ib/acre to a gain of 2,258 Ib/acre. Economic benefits
ranged from a loss of $70.70/acre to a gain of $293.00/acre.
Potatoes - Carbofuran was found to be effective against potato infestation
caused by the Colorado potato beetle, wireworms, flea beetles, and aphids.
Control was effective for several weeks, with 1 application at rates vary-
ing from 0.5 to 8.0 Ib/acre. Yields increased significantly in all but one
test. Compared to untreated plots, yields varied from a loss of 21 cwt/acre
to a gain of 213 cwt/acre. Economic benefits ranged from a loss of $83.50/
acre to a gain of $625.00/acre.
Rice ~ Carbofuran was found to be effective in controlling the rice water weevil
for up to 6 weeks. Applications made as preplant or up to 5 weeks after flood
were effective. Control of mosquito larvae was reported as excellent with
carbofuran. Rice yields generally increased with the use of carbofuran. Com-
pared to untreated test plots, yields ranged from a loss of 214 Ib/acre to a
gain of 1,302 Ib/acre. Economic benefits ranged from a loss of $24.60/acre to
a gain of $106.50/acre.
13
-------
Tobacco - Carbofuran is used for control of wireworms and the hornworm in
tobacco. It is also reported to be effective in control of the tobacco budworm
and tobacco flea beetle. Control of the hornworm was achieved for 7 weeks
after 1 application. Better control of the budworm was achieved at 4.0 to 6.0
Ib/acre than at lower rates. Control of the flea beetles was greatest with a
pretransplant application followed by a posttransplant application. Tobacco
yield changes ranged from 152 to 161 Ib/acre compared to untreated plots.
Economic benefits varied from $102.00 to $110.00/acre.
Peppers - Carbofuran is recommended for control of the green peach aphid and
European corn borer in peppers. Two applications were successful in control-
ling the borer. Yields increased in all tests reviewed, and some were signi-
ficantly better than untreated test plots. Yield changes varied from a gain
of 22 cwt to 82 cwt/acre, compared to untreated test plots. Economic benefits
range from $269.00 to $l,035.00/acre.
Sugarcane - Carbofuran is considered effective for controlling the sugarcane
borer and wireworms. It also is used in control of nematodes, and it signifi-
cantly increases sugarcane yields. Economic benefits, based on one test, were
$410.00/acre.
14
-------
PART II. INITIAL SCIENTIFIC REVIEW
SUBPART A. CHEMISTRY
CONTENTS
Page
Synthesis and Production Technology 16
Physical Properties. 19
Analytical Methods 21
Multi-Residue Methods 21
Residue Analysis 21
Formulation Analysis 24
Other Residue Methods 24
Occurrence of Residues in Food'and Feed Commodities 27
Acceptable Daily Intake 34
Tolerances ..... 34
Composition and Formulation 38
Chemical Properties 38
Hydrolysis 39
Hydroxylation (oxidation) '*3
Photodecomposition 43
References 45
15
-------
This section contains a detailed review of available data on carbofuran's
chemistry and presence in foods. Eight subject areas have been examined:
Synthesis and Production Technology; Physical Properties of Carbofuran;
Analytical Methods; Composition and Formulation; Chemical Properties,
Degradation Reactions and Decomposition Processes; Occurrence of Residues
in Food and Feed Commodities; Acceptable Daily Intake; and Tolerances. The
section summarizes rather than interprets data reviewed.
Synthesis and Production Technology
Carbofuran (2,3-dihydro-2,2-dimethyl-7-benzofuranyl methylcarbamate) is
manufactured by the Agricultural (formerly Niagara) Chemical Division of the
FMC Corporation. FMC's manufacturing plant for carbofuran is located at
Middleport, New York, but an important intermediate of carbofuran (2,3-dihydro-
2,2-dimethyl-7-benzofuranol) is produced at Baltimore.
The process used for manufacturing carbofuran (FMC, 1975), is described in
patents by Borivoj (1967) and Thorpe (1974). The reactions for this process
are shown in Figure 2. A schematic diagram of this process is shown in
Figure 3.
C1CH CCH
C1CH2CCH3
chloride
CHj
t«Cf.ng««nt
175-190*C
LCH,C-CH,
(II)
,011
-CH-C(CHj)2
2-nlcro-6-tiobuti«iul (III)
nurob«
(ftCL ?r«;«rr«d)
:5C-i?o'c
H2. hydrogttution
catalyit
7-Gicrobanzofuran (IV)
S!'2 . .CH,
2.2-dlMthylb«iuofur»a (V)
+ H.SO. + 3USO, or b.Io
^ •>• HjO
SO,
H,0, hHC
—
4 CuS04
2,3-dlhyd»-2,2-dlB4Chyl-
7-baasofurftaol (VZ)
VI + OijNCO
Figure 2. Preparation of Carbofuran from o-Nitrophenol
Source: FMC (1975).
16
-------
Methallyl Chloride
o-Nitrophenol
Aqueous Base
Ferric Chloride
Sodium Nitrite
Mineral Acid
Cupric Sulfate
Steam
Etherification
Unit
Separation
• Aqueous Waste
1
Rearrangement
and
Cyclization Unit
1
Hydrogen
Catalyst
Hydrogenation
Unit
t
Filter
I
Diazotization
and
Hydrolysis Unit
1
Steam Distillation
1
Methyl Isocyanate
Methylene Chloride
i
Solvent
Rec
Carbofuran Unit
ycle
I
I
Carbofuran
Figure 3. Production Schematic for Carbofuran
Source: FMC (1975).
Catalyst
Recycle
•Aqueous Waste
17
-------
An alternate manufacturing process for carbofuran is described by
Scharpf (1969). The reactions for this process are as follows:
OH CH2 RefluxinS
II (Acetone)
+ C1CH2CCH3
Base,
KI Cat.
Catechol Methallyl
chloride
Methallyloxyphenol
2,3-Dihydro-
2,2-dimethyl-
7-benzofurano1
CH3 + CH3NCO
Methyl
Isocyanate
Ether
OCONHCH3
Triethylamine
(2)
CH-i
Carbofuran
In the laboratory preparation described in the Scharpf patent, the
yield in the step from catechol to methallyloxyphenol was 44%. The yield
for Reaction (2) was 73%. The overall yield could not be calculated
from the data given.
Several other patents issued to FMC describe processes for the manu-
facture of the intermediate 2,3-dihydro-2,2,-dimethyl-7-benzof.uranol.
These processes are described below. Orwoll (1967) describes a process
beginning with £-bromophenol as shown in Equations (3), (4a) , and (4b) .
Re fluxing, several
solvents at
different times
Vacuum distillation
-Bromophenol
Methallyl
chloride
CH3
(3)
2,3-Dihydro-2,2-dimethy1
7-bromobenzofuran (I)
18
-------
+ HOCH2CH2OH
Ethylene
glycol
+ NaOH + Cu(N03)2'3H20
Sodium Copper
hydroxide nitrate
+ NaOH + CU20
Sodium Cuprous
"hydroxide oxide
2,3-Dihydro-
2,2-dimethyl-
7-benzofuranol
(4a)
(4b)
Before the patent to Scharpf (1969) was issued, Borivoj (1967) reported
that catechol is an expensive starting material compared to a-nitrophenol.
Furthermore, the overall yield from o-nitrophenol was reported to be high,
about 50% based upon £-nitrophenol, even though the process involved many
steps. (See Figure 2.)
Physical Properties
Chemical name; 2,3-dihydro-2,2-diraethyl-7-benzofuranyl methylcarba-
mate
Common name: Carbofuran
Other names; Furadan®, XIA. 10242, Em 27164
Pesticide class; Insecticide, acaricide, nematicide; carbaraate
Empirical formula;
Structural formula:
Pi "
>-C-N-CH3
CH-i
Molecular weight; 221.3
Elemental analysis; C, 65.2%; H, 6.8%; N, 6.3%; 0, 21.7%
19
-------
Physical state; White, crystalline solid
Odor; Odorless (Martin, 1971)
Slightly phenolic (FMC, 1971b)
Density; 1.180 at 20/20°C
Melting point; Pure, 153 to 154°C
Technical, 150 to 152°C
Degrades at temperatures in excess of 130°C (FMC,
1971b)
Vapor pressure; 2 x 10" mm Hg at 33°C
1.1 x 10"4 mm Hg at 50°C
Solubility; 7. weight/weight, 25° C (Cook, 1973)
Acetone 15
Acetonitrile 14
Benzene 4
Cyclohexanone 9
Dimethyl formamide 27
Dimethyl sulfoxide 25
Ethanol 4
Kerosene < 1
N-Methyl-2-pyrrolidone 30
Methyl chloride 12
Petroleum ether < 1
Xylene < 1
Water 0.07 (700 ppra)
Carbofuran is essentially insoluble in conventional formulation solvents
employed in agriculture (FMC, 1971b).
Flammability; Not flammable--will support combustion if ignited.
Explosive hazard; Nonhazardous at normal temperatures
Corrosive action: Noncorrosive
20
-------
Analytical Methods
This subsection reviews analytical methods for carbofuran. The review
describes multi-residue methods, residue analysis principles, and formulation
analysis principles. Information on the sensitivity and selectivity of the
methods is also presented.
Multi-Residue Methods - Carbofuran cannot be detected by the multi-residue
methods described in the Pesticide Analytical Manual (PAM, Vol. I, 1971); it
is not obtained in the eluate from the extraction and cleanup procedures.
A procedure has recently been developed by Holden (1973) that can be used
for several methylcarbamate pesticides in plant materials. The procedure calls
for extraction of the crop material with acetonitrile, then partitioning the
extract with petroleum ether. The extract is purified by means of a coagula-
tion procedure using phosphoric acid-ammonium chloride solution. The mixture
is filtered through celite and the filtrate is extracted with methylene
chloride. Phenolic impurities are eliminated by partitioning the methylene
chloride extract with 0.1 N potassium hydroxide. The residue, after evapora-
tion of the methylene chloride, is treated with l-fluoro-2,4-dinitrobenzene
to form an ether derivative. Conversion in this step is essentially complete.
Determination is then made by electron capture gas chromatography. Residues
may be determined as low as 0.05 ppm, with recoveries between 90 and 110%.
This procedure, however, will not detect phenolic metabolites or plant metabo-
lic conjugates such as the 3-hydroxycarbofuran glycosides.
Residue Analysis Principles - There is one basic method for carbofuran residue
analysis. It employs microcoulometric gas chromatography with a nitrogen
detection system. The most important studies all use this basic method,
although there are changes in extraction and cleanup procedures for specific
food products. The method was first published by Cook et al. (1969). The
method is also described in PAM (Vol. II, 1967) and in Residue Reviews (Cassil
et al., 1969). Cook (1973) has summarized previous reports for carbofuran in
40 products, including various plant materials, animal materials, milk, water,
and soil (Table 1). The details of the extraction methods are described below.
The following diagram shows the steps in this method (McCarthy, 1970).
Acid hydrolysis of sample
I
Methylene chloride extraction
J
Concentration
I
Acetonitrile/hexane partition
Methylene chloride extraction
Concentration >
J
Silica gel/nuchar-attaclay cleanup
I
Hexane/ethyl acetate elution
*
Conccntrat ion
Nitrogen analysis by microcoulometric
gas chromatography
Calculation
21
-------
Table 1. Method Requirements for Specific Sample!
Column cleanup
Simple
Alfalfa
Alfalfa, hay
Apple*
Beans, green
Beans, lima
Carrots
Corn, cobs
Corn, grain
Corn, husks
Com, silage
Corn, stover
Eggs
Lettuce
Milk
Peaches
Peanut, hay
Peanut, hull a
Peanut, vines
Peanuts
Pears
Peppers, green
Potatoes
Pumpkins
Rice, grain
Rice, hulls
Rice, green stjrav
Rice, dry strav
Soil
Sugar beets, foliage
Sugar beets, pulp
Sugar beets, roots
Sugar cane
Sugar cane Juice
Tissue, glztards
Tissue, kidney
Tissue, liver
Tissue, muscle
Tobacco, dry
Tobacco, green
Tomatoes
Water
Sample
•lie (g)
25
5
50
50
50
100
50
70
50
50
50
100
SO
100
50
100
20
20
40
50
100
100
50
20
20
40
10
50
50
20
50
40
40
100
100
100
100
10
50
50
100
Nuchar-actaclay (g):
Partition
No
No
No
Yet
Yes
No
No
Yea
Yes
Yes
No
Yes
No
Yes
No
Yes
No
Yes
No
No
Yes
No
Yes
Yes
Yes
No
Yes
No
No
No
No
No
No
No
Yes
Yes
Yes
No
No
No
No
7:
7:
7:
7:
7:
7:
7:
7:
7:
7:
7:
7:
7:
7:
7:
5:
5:
S:
5:
7:
7:
5:
7:
3:
3:
3:
3:
7
7:
7:
7:
5:
5:
7
7:
7:
7:
7:
7:
5:
5:
packing (g)
10 silicic acid
10 silicic acid
5 silica gel
5 silica gel
5 silica gel
5 silica gel
5 silica gel
5 silica gel
5 silica gel
5 silica gel
5 silica gel
5 silica gel
10 silicic acid
5 silica gel
5 silica gel
10 Florlill*-'
10 Florlslli/
10 Florlslli/
10 Florlslli'
5 silica gel
5 silica gel
10 Florlsll
5 silica gel
15 Florlsllf
15 FlorisllV
15 Florlstl^'
15 FlorlsllV
10 aluminum oxlde£'
10 aluminum oxide*-'
10 aluminum oxlde^'
10 PlorlsllS-'
10 Florlsll*y
5 silica gel
5 silica gel
5 silica gel
10 silicic acid
10 silicic acid
10 Florisll
10 Florlsll
ml Ethyl acetate/
hexane (v/v)
125-70/30
125-70/30
100-70/30
100-70/30
100-70/30
300-70/30
100-70/30
100-70/30
150-60/20
150-80/20
100-70/30
150-70/30
125-70/30
150-70/30
100-70/30
100-80/20
100-80/20
100-80/20
100-80/20
100-70/30
200-70/30
150-70/30
100-70
230-100/0
230-100/0
230-100/0
230-100/0
150-80/20
125-100/02.'
125-100/0
125-100/0
100-60/40
100-60/40
150-80/20
150-70/80
150-70/80
150-70/80
125-70/80
125-70/80
100-80/20
110-80/20
Method
sensitivity (pptn)
0.20 ,
0.20
0.10
0.10
0.10
0.05
0.10
0.10
0.10
0.10
0.10
0.05
0.20
0.025
0.10
0.5
0.1
0.5
0.1
0.1
0.05
0.05
0.10
0.20
0.20
0.20
0.20
0.10
0.10
0.10
0.10
0.10
0.10
0.05
0.05
0.05
0.05
0.20
0.20
0.05
0.01
Concentrate the dried ncthylene chlmlde extract (1 ,fiOO ml) In a Ki:dcrn,n-D.inl»h
oncent r
-------
Cook (1973) described extraction methods for plant materials as follows:
Place the appropriate amount of chopped and blended crop in a
1,000-ml round-bottomed flask containing a magnetic stirring
bar. Add 600 ml of 0.25 N hydrochloric acid. Connect the round-
bottomed flask to a Liebig condenser using a 50/50 to 24/40 $
neck adapter. Reflux the crop-acid mixture for 1 hr using a
heating mantle. Swirl the flask contents by hand during the
initial heating period and then continuously stir the mixture
with a magnetic stirring bar. Fortify check crop samples prior
to the addition of acid.
After 1 hr of refluxing, remove the round-bottomed flask from the
heating mantle and filter the hot sample through glass wool into
a 1,000-ml Erlenmeyer flask. Wash the reflux flask and glass wool
with an additional 300 ml of hot 0.25 N hydrochloric acid. Cool
the filtrate for 1 hr at -10°C and transfer into a 2,000-ml
separatory funnel. Add approximately 250 mg of sodium lauryl
sulfate to the filtrate and mix. Extract the aqueous phase 3
times with 600 ml of distilled methylene chloride. Combine the
methylene chloride extracts and dry over anhydrous sodium sulfate.
A modification of this procedure which is suitable for residues in small fruits
is reported in Williams and Brown (1973).
Cook (1973) described extraction methods for milk as follows:
Pour 100 ml (100 g) of milk into a blender. Add 500 ml of dis-
tilled acetone and blend for 3.0 min. Fortify check milk samples
prior to the addition of acetone. Filter the sample in a 1,000-ml
round-bottom flask. Add 100 ml of 0.375 N hydrochloric acid and
2 or 3 glass beads. Connect a. Snyder column to the flask. Place
the sample mixture in the steam bath and evaporate all the acetone,
leaving the sample in the aqueous solution. Reflux the aqueous
solution for 15 min. Remove the round-bottom flask from the steam
bath and rinse the bubble column with 0.375 N hydrochloric acid.
Place the aqueous solution in a freezer (-10°C). Allow the sample
to cool until ice just begins to form (about 1.5 hr) . Remove the
sample from the freezer and filter quickly through glass wool into
a 1,000-ml separatory funnel to remove any oils or waxes which have
solidified during cooling. Rinse the round-bottom flask and glass
wool with about 50 ml of 0.375 N hydrochloric acid. Extract the
aqueous phase 3 times with 200 ml of distilled methylene chloride.
Combine the methylene chloride extracts and dry over anhydrous
sodium sulfate.
Cook (1973) described extraction methods for animal material as follows:
Place the appropriate amount of subsampled diced tissue or eggs
(shells removed) into a blender. Add 300 ml of acetone and
blend for 3.0 min. Filter the blended mixture through a Buchner
23
-------
funnel, using No. 5 filter paper. Retain the filtrate. Return
the filter paper and the tissue residue to the blender. Add
300 ml of acetone and blend again for 30 min. Filter the blended
mixture through a Buchner funnel using No. 5 filter paper. Com-
bine the first and second filtrates.
Allow the combined filtrates to stand in a 1,000-ml separatory
funnel for 0.75 hr. Drain off any oils that settle to the bottom.
(Note: Beef tissue and egg filtrate "oil" will settle out at
room temperature. Chicken tissue filtrate may require cooling to
settle out the "oil.")
Place the acetone filtrate from above into a 1,000-ml round-bottom
flask (24/40 S neck) with a few glass beads. Connect a Snyder
column to the flask and concentrate the acetone to approximately
50% of its initial volume on a steam bath. Remove the flask from
the steam bath and add 150 ml of 0.25 N hydrochloric acid. Replace
the sample mixture in the steam bath and evaporate all the acetone.
Reflux the aqueous solution for an additional 0.25 hr to insure
complete conversion of the conjugated residues to the aglycone form.
Remove the round-bottom flask from the steam bath. Rinse the bubble
column with 0.25 N hydrochloric acid. Place the aqueous solution
in a freezer (-10°C) for 1.5 hr to allow the remaining fats and oils
to solidify. Remove the sample from the freezer and quickly filter
through a small bed of glass wool into a 500-ml separatory funnel.
Rinse the flask and glass wool with 50 ml of 0.25 N hydrochloric
acid. Extract the filtrate 3 times with 100-ml portions of methylene
chloride. Combine the methylene chloride extract and dry over an-
hydrous sodium sulfate.
Cook (1973) described extraction methods for water as follows:
Place the appropriate amount of subsampled water into a 250-ml
separatory funnel. Extract 3 times with 100-ml portions of methylene
chloride. Combine the methylene chloride extracts, dry over sodium
sulfate, and filter. Wash the sodium sulfate and filter paper with
methylene chloride.
Formulation Analysis - "Dhe recommended method for analysis qf carbofuran formu-
lations is by gas chromatography, using an internal standard, comparing the peak
area of the unknown sample to the peak area of the standard (Cook, 1973). Other
analytical methods for identification and/or reference are infrared spectrometry
(Chen and Benson, 1966); nuclear magnetic resource spectrometry, (Keith and Alford,
1970), and spectrometry (Vickers et al., 1973).
Other Residue Methods - Table 2 lists other analytical methods and sensitivities.
24
-------
Table 2. Other Analytical Methods for Carbofuran Residues
Type of method
Sensitivity
Source
Spectrophotofluorometry
0.5 ppm
Gas liquid chromatography 0.04 ppm
Alkaline hydrolysis to phenol,
steam distillation and derivi-
tization as thiophosphoryl
ether followed by fluoro
photometric detection in
phosphorous mode.
Infrared analysis
50 yg
Electron-capture gas chroma- 0.01-0.10 ppm
tography of trichloroacetates
after hydrolysis of carbofuran
residues to phenols
Electron-capture gas liquid
chromatography of trichloro-
acetates of carbamates after
removal of phenolic metabolites
0.01 ppm
Electron-capture gas chroma- 0.1 ppm
tography of dinitrophenyl ethers
High-speed liquid chromatography 2-10 ng/injection
Electron-capture gas chromatography -
Thin-layer chromatography-
spectrophotofluorometry
Thin-layer chromatography-
enzyme inhibition-
Thin-layer chromatography
Phosphorescence
ppb range
ng range
Bowman and Beroza
(1967b)
Bowman and Beroza
(1967a)
Broderick et al.
(1966)
Butler and McDonough
(1968)
Butler and McDonough
(1971)
Caro et al. (1973b)
Frei et al. (1974)
Holden et al. (1969)
Lawrence and Frei
(1972b), Lawrence and
Frei (1972a), Lawrence
et al. (1972)
Mendoza (1972),
Mendoza and Shields
(1970), Mendoza and
Shields (1971)
CWinterlin et al. (1968)
Moye and Winefordner
(1965)
25
-------
Table 2. Other Analytical Methods for Carbofuran Residues (Continued)
Type of method
Sensitivity
Source
Gas chromatography of N-perfluoro-
acyl derivatives
Electron-capture gas chromato-
graphy of various ether
derivatives
Transesterification with methanol
via reaction gas chromatography
to form methyl N-methylcarbamate
with alkali flame detection
Spectrometry (laser excited Ramen
and fluorescence spectra)
Gas chromatography (Review article)
0.05 ppm
Seiber (1972)
Seiber et al. (1972)
Van Middlelem et al.
(1971)
Vickers et al. (1973)
Williams (1970)
In addition to carbofuran itself, 2 types of metabolites are detected by
the method of Cook (1973). These are 3-hydroxycarbofuran and various conjugated
forms of 3-hydroxycarbofuran including glycosides (plant metabolic conjugates)
and glucuronides (conjugated products of animal metabolism).
The water-soluble conjugated forms are converted into the 3-hydroxycarbo-
furan (aglycone) form before extraction. The equation for this acid hydrolysis
reaction is as follows (Cook, 1973):
0
II
OCNHCH3
0-Glucoside
3-Hydroxyglucoside
3-Hydroxycarbofuran
It should be noted that some of the methods listed in Table 2 are not
applicable to the conjugated forms because organic solvent extraction techniques
were used that did not remove the water-soluble conjugated form. These were the
methods of Bowman and Beroza (1967a) and Butler and McDonough (1968).
26
-------
In addition, Ruhr and Casida (1967) and Metcalf (1968) indicate that
certain glycosidic conjugates are difficult to cleave to corresponding
aglycone.
More recently an analytical method has been developed to detect the
phenolic metabolites of carbofuran. These metabolites are carbofuran phenol,
3-ketocarbofuran-7-phenol, and 3-hydroxycarbofuran-7-phenol. The method con-
sists of hydrolyzing possible conjugates, deriving the 3-hydroxy moiety to the
ethoxy or rv-propoxy ether and then deriving the phenol to the 2,4-dinitrophenyl
ether. Analysis is by GC, using a nitrogen-specific detector (FMC^1971a).
Its application to potato tubers, milk, eggs, and cattle and poultry tissue
are reported by Jackson (1973a and 1973b) and Shuttleworth (1973).
It should be noted that all current tolerances include consideration of
both phenolic metabolites (and conjugates) as well as oxidation products still
containing the carbamate functional grouping (see p. 34).
Occurrence of Residues in Food and Feed Commodities
Methods for detecting residues in crops are described in the subsection on
Analytical Methods (see p. 21). Residue tests for various crops are described
below,
Sugarcane - Carbofuran was applied to sugarcane grown in 7 locations in Florida
and Louisiana. Twenty-seven test plots treated with 3 and 4 applications of
carbofuran 3G (total of 3 to 4 Ib Al/acre) were sampled at post-harvest intervals
ranging from 0 to 55 days. There were only 3 instances in which the total resi-
dues from the 4 Ib Al/acre rate measured 0.1 ppm or greater. In one test, at
0 days from last application to harvest, 0.23 ppm residues were found. In a
second test, 18 days after the harvest, residues ranged from 0.1 to 0.2 ppm.
In a third test, also 18 days after the harvest, 0.37 ppm residues were found.
Carbofuran 10G applied at rates to 32 Ib Al/acre, with post-harvest inter-
vals ranging from 212 to 427 days, resulted in no detectable residues.
Applications of carbofuran 75 WP produced variable results, as shown, with
other applications in the following table (FMC, 1969a).
27
-------
Table 3. Residues of Carbofuran on Sugarcane^
Active
ingredient per Number
Formulation
10G
10G
10G
10G
75 WPl/
75 WP
75 WP
75 WP
75 WP
75 WP
75 WP
75 WP
75 WP
75 WP
' 75 WP
75 WP
75 WP
75 WP
3G
3G
3G
3G
3G
3G
3G
3G
3G
application
(Ib/acre)
8
8
8
8
0
0.6
0;6
0.6
0.6
0.6
0.6
1.2
1.2
1.2
1.2
1.2
1.2
1.2
0
0.9
0.9
0.9
0.9
0.9
0.9
0.45
0.45
of
Days from last
application to
applications harvest
1
1
2
2
0
4
4
4
4
4
4
4
4
4
4
4
4
4
0
4
4
4
4
4
4
3
3
356.
356
212
212
2
2
17
17
33
33
2
2
17
17
17
33
33
0
0
18
18
41
41
55
55
Total
residue—
(ppro)
ND
ND
ND
ND
ND
1.03
0.5 to
0.6
< 0.1
< 0.1
< 0.1
< 0.1
0.83
0.48
0.11
0.11
< 0.1
< 0.1
ND
ND
0.23
< 0.1
0.1 to
0.20
0.37
ND
< 0.1
ND
ND
a/ Data from
seven locations in states
l>/ Total residue equals
~~ lytical
method used
a nitrogen detector
c/ ND = None
detectable.
d/ Formulation currently
carbofuran plus
of Florida and Louisiana.
3-hydroxy carbofuran.
The ana-
was microcoulometric gas chromatography with
, corrected for
not available.
recovery.
Source: FMC (1969a).
28
-------
Corn Fields - Table 4 summarizes data for carbofuran tests on field corn grown
in 4 states.
75
76
92
98
101
111
133
133
136
Table 4. Maximum Total Residues (ppm of Carbofuran
Including 3-hydroxycarbofuran) Found on
Field Corn Silage and Stover
Al/acre
Days
lapsed Location
1 Ib
rate
2 Ib
rate
4 Ib
rate
8 Ib
rate
Arkansas
Arkansas
New York
Iowa
Nebraska
New York
Arkansas
Iowa
Nebraska
3.0 (0.8)-/ 5.1 (3.9)
1.0
4.6 (1.9)
2.4
0.5
1.3
3.1
0.8
0.1
0.4
7.3
2.8
a/ Values in parentheses are from the banded treatment (7-in band/40-in row).
All others are in-furrow, 10G formulation.
Note: Carbofuran was found to be nondetectable in corn grain at rates to 8 Ib/
acre harvested from 111 to 133 days after application. The maximum
recommended application rate is 3 Ib Al/acre.
Source: FMC (1971a).
Alfalfa - Dissipation studies (FMC, 1968) were conducted on alfalfa grown in
9 states with carbofuran applied at levels ranging from 0.25 to 2.0 Ib Al/acre.
Total carbamate residues were determined on green alfalfa by a nitrogen specific
microcoulometric gas chromatograph method sensitive to 0.2 ppm carbofuran and
0.2 ppm of the metabolite 3-hydroxycarbofuran. Only carbofuran, 3-hydroxy-
carbofuran, and 3-hydrocarbofuran glucoside were found. The glucoside was hydro-
lized quantitatively and reported as 3-hydroxycarbofuran. All results were
adjusted for 80% moisture in the alfalfa.
29
-------
Wide variations were found in residue dissipation due to the combined
effect of various factors including climatic conditions, metabolism in the
plant, rate of growth, density, and uniformity of the stand. Maximum total
carbamate residues in ppm were as follows:
Table 5. Residues of Carbofuran in Alfalfa
(ppm Al/acre)
0.25
0.50
1.0
2.0
0
7
14
21
28
15.5
0.9
0.5
—
0.5
32.4
20.6
3.8
1.4
1.0
114.0
48.5
6.6
7.4
4.1
145.5
87.0
11.4
8.2
"• —
Source: FMC (1968).
In some of the studies, samples of alfalfa hay were taken to compare residue
values with those in the green alfalfa of the same time interval. Water deter-
mination gave an average of 16% in the hay. A drying method, reducing the mois-
ture from 80% to 15%, would give a factor of 4.25; this theoretical factor was
verified by tests on the green and dried samples of the same interval cuttings.
Studies from 9 states with carbofuran applied at 1.0 Ib Al/acre showed total
residues ranging from 1.4 to 14.5 ppm at zero day and 4.1 to 0.1 ppm Al/acre 28
days posttreatment.
A study was made on the persistence of carbofuran and 3-hydroxycarbofuran
on alfalfa in Massachusetts. When carbofuran was applied to first-cutting al-
falfa at the rate of 0.5 Ib Al/acre, no detectable residue of carbofuran was
found in the green plant 21 days posttreatment; 3-hydroxycarbofuran amounted
to 0.55 ppm. At 1.0 Ib Al/acre, the carbofuran residue was below the sensiti-
vity of the method and the metabolite was measured at 1.26 ppm 21 days posttreat-
ment. Stubble sprays of carbofuran at 0.5 and 1.0 Ib Al/acre resulted in no
detectable residues of carbofuran and a maximum of 1.5 ppm of the metabolite on
the dry hay (Shaw et al., 1969).
Studies of Fahey (1970) on green and dehydrated alfalfa grown in South
Dakota and treated with carbofuran at 0.5 and 1.0 Ib Al/acre showed no measur-
able residues of carbofuran in samples collected 14 and 21 days after treatment.
The loss of carbofuran attributed to dehydration averaged 67% for plots treated
with 1.0 and 0.5 Ib Al/acre and sampled the same day.
•
Rice - Test data was obtained from rice grown in California, Louisiana, and
Texas (FMC 1969b) . When carbofuran was applied as a 2 G formulation at rates
from 0.5 to 2.0 Ib Al/acre, green straw rice harvested from 25 to 148 days
after application contained less than 0.3 ppm carbofuran residues.
30
-------
Whole grain rice grown on soil treated with carbofuran 2G at rates of
0.5 to 2.0 Ib Al/acre and harvested from 110 to 168 days after application
likewise contained less than 0.3 ppm carbofuran residues, with the majority
of samples containing less than 0.2 ppm. Similar results were obtained when
carbofuran 3G was applied at 0.5 to 1.0 Ib Al/acre, with a post-harvest
interval of only 51 days. Hulls, polishings, broken grains, and polished
grain from rice harvested 87 to 92 days after applications of carbofuran 3G
at 0.5 to 1.0 Ib/acre contained less than 0.3 ppm residues.
Total residues equaled carbofuran plus 3-hydroxycarbofuran. The analyti-
cal method used was microcoulometric gas chromatograph (MCGC), with a nitrogen
detector corrected for recovery. It should be noted that, even on samples ta-
ken from rice receiving no treatment, residues were reported as <0.2 ppm.
Peanuts - Table 6 lists the data obtained from tests of carbofuran on peanuts
(FMC,1970). The data listed includes portions of plant, type of application,
amount of active ingredient applied per acre, days lapsed, and total residue
of carbofuran plus 3-hydroxycarbofuran. The maximum residue in the nut por-
tion was less than 0.1 ppm. The maximum residue in the hulls was 0.8 ppm.
The maximum residues in the vines by type of application were: banded at
planting, 1.5 ppm; in-furrow at planting, 20 ppm; banded at pegging, 9 ppm;
and in-furrow at planting plus banded at pegging, 37 ppm.
•
General - A study (Shuttleworth, 1974) was conducted to determine whether or not
a buildup of residues of carbofuran and its metabolite 3-hydroxycarbofuran would
occur in raw agricultural commodities (corn, potatoes, peanuts, and tobacco)
grown on plots treated 4 consecutive years with carbofuran at registered or
proposed rates and use patterns. Plots were located in the south, midwest, and
east. Samples were analyzed by a nitrogen specific microcoulometric gas
chromatograph. Depending upon the crop, method sensitivities ranged from 0.075
ppm to 0.20 total carbamates. Recoveries exceeded 70% for both carbofuran and
the metabolite.
Potato tubers grown in New York and receiving 5 foliar applications of
carbofuran 4F at 1.0 Ib Al/acre yielded no carbamate residues approaching the
sensitivity of the method.
Corn grown in Nebraska and New York on soils treated with carbofuran 10G
(in-furrow and banded) at 3.0 Ib Al/acre contained no detectable residues in
either grain or stalk samples from either location.
Peanuts grown in Arkansas on soil treated with 1.0 and 2.0 Ib Al/acre
(as carbofuran 10G) in-furrow and at pegging, respectively, showed trace
residues (0.025 ppm) of carbofuran and 20.10 ppm of 3-hydroxycarbofuran.
Tobacco samples from Arkansas plots treated with 6.0 Ib Al/acre carbofuran
10G broadcast yielded total carbamate residues of 0.13 ppm. Previous samples
yielded up to 15.0 ppm after 3 yr of consecutive treatments. High variability
from plot to plot was indicated because re-analyses verified prior results.
31
-------
Table 6. Residues of Carbofuran on Peanuts.3./
Portion
of
plant
Nuts
Hulls
Vines
Nuts
Hulls
Vines
Nuts
Hulls
Vines
Nuts
Hulls
Vines
Nuts
Hulls
Vines
Nuts
Hulls
Vines
Active
Type of ingredient
application (Ib/acre)
14-in band 2
on 42-in row
at planting
18-in band 4
on 36-in row
at planting
In-furrow at 1
planting
. In-furrow at 1
planting
1
1
i
In-furrow at 3
planting
t
12-in band 2
on 36-in row
at pegging
Total
Days residue?-/
lapsed (ppm)
166 ND^
< 0.20
NA*/
139 ND
< 0.10
0.26
0.33
1.33
1.47
153 ND
ND
0.81
0.59
15.6
11.9
123 ND
ND
123 0.36
0.32
123 4.1
20.3
123 < 0.10
ND
0.69
37.2
38.8
92 ND
ND
NA
9.09
8.54
32
-------
Table 6. (Continued)
Portion
of
plant
. Type of
application
Active
ingredient
(Ib/acre)
Days
lapsed
Total
residue^/
(ppm)
Nuts
Hulls
Vines
12-in band
on 36-in row
at pegging
79
< 0.10
ND
0.62
0.67
< 1.43,
1.63
> 0.93
Nuts
Hulls
Vines
Dual-in-furrow
at plant plus
banded at pegging
1 and 2
74
< 0.10
< 0.10
0.71
36.6
34.5
a/ Data from five locations in Florida, Georgia, Mississippi, North
Carolina, and Virginia.
b_/ Total residue equals carbofuran plus 3-hydroxycarbofuran. The
analytical, method used was microcoulometric gns chromatogrnphy
with a nitrogen detector, corrected for recovery.
£/ ND =• None detectable.
d/ NA — Not available or not analyzed.
Source: FMC (1970).
It was concluded that carbamate residues above existing or proposed toler-
ances would not occur from annual treatments with carbofuran at registered or
proposed rates.
Meat and Milk - Reno (1973b) fed 3 phenolic metabolites of carbofuran to
cows at a dietary level of 200 ppm. The 3 metabolites were carbofuran phenol,
3-keto-7-phenol-carbofuran and 3-hydroxy-carbofuran phenol. Equal quantities
of each metabolite were fed and the dietary levels were 20, 60, and 200 ppm
total metabolites.
33
-------
The results of the milk residue study are shown in Table 7. Table 7 shows
the results of the 200 ppm study. The results for the average level (of the 4
cows) and the maximum level are given for 2 of the metabolites. The third
metabolite, 3-hydroxy-7-phenol carbofuran, was not detectable (Shuttleworth,
X if / J / •
The results of tissue analyses from this study are shown in Table 8. The
tissue was taken by sacrificing 2 of the test animals at the end of the 28-day
feeding period.
Reno (1973a) conducted a similar feeding test with chickens. Test animals
were fed 2, 6, and 20 ppm total metabolites (one-third each metabolite). Egg
and tissue (liver, fat, and breast) samples from the 20 ppm study were analyzed
by the FMC Corporation using a gas chromatograph equipped with a nitrogen
specific Coulson conductivity detection system (Shuttleworth, 1973). No
phenolic residues were detected at or above 0.05 ppm (method sensitivity).
Other residue data related to carbofuran and its metabolites in milk and
tissue samples from domestic ruminants is discussed in the subsection on toler-
ances .
Acceptable Daily Intake
The acceptable daily intake (ADI) is defined as the daily intake which,
during an entire lifetime, appears to be without appreciable risk on the basis
of all known facts at the time of evaluation (Lu, 1973). It is expressed in
milligrams of the chemical per kilogram of body weight (mg/kg).
The ADI for pesticides is established jointly by the Food and Agricultural
Organization (FAO) Committee on Pesticides in Agriculture and the World Health
Organization (WHO) Expert Committee on Pesticide Residues. However, an ADI for
carbofuran has not yet been established.
Tolerances
The tolerances for carbofuran apply to the total of carbofuran plus the
following 4 metabolites: 3-hydroxycarbofuran (2,3,-dihydro-2,2-dimethyl-3-
hydroxy-7-benzofuranyl-N-methylcarbamate), structure II, p. 38; carbofuran
phenol (2,3-dihydro-2,2-dimethyl-7-benzofuranol), structure VII, p. 38; 3-
hydroxycarbofuran phenol (2,3-dihydro-2,2-dimethyl-3,7-benzofurandiol), struc-
ture IX, p. 38; and 3-ketocarbofuran phenol (2,3-dihydro-2,2-dimethyl-3-oxo-7-
benzofuranol), structure VIII, p. 38.
Official pesticide tolerances are published in the Code of Federal
Regulations, Title 40, and updated in the Federal Register. A summary of
current tolerances for carbofuran is presented in Table 9. A distinction is
made between residues containing a carbamate function (cholinesterase-inhibiting
compounds) and those without this function. Tolerances are based upon the as-
sumption that complete hydrolysis of all conjugates has taken place prior to
analysis.
34
-------
Table 7. Residues in Milk of 3 Metabolites of Carbofuran
Fed at 200 ppm Total Metabolites?/
Residue
Carbofuran phenol
3-Keto-7-phenol
carbofuran
Days lapsed
Pretest (0)
2
4
7
14
18
21
25
28
Recovery day 1
Average£/
ND!/
0.044
0.043
0.025
0.030
0.049
0.052
0.046
0.034
ND
Maximum
ND
0.057
0.069
0.034
0.047
0.060
0.065
0.057
0.046
ND
Average
ND
0.44
0.36
0.37
0.41
0.58
0.49
0.55
0.46
ND
Maximum
ND
0.49
0.55
0.48
0.59
0.77
0.70
0.71
0.54
ND
a,/ Total metabolites, 200 ppm:
66.7 ppm carbofuran phenol,
66.7 ppm 3-keto-7-pnenol-carbofuran, and
66.7 ppm 3-hydroxy-7-phenol-carbofuran
b/ No 3-hydroxycarbofuran phenol was detected at a method sensitivity
of 0.050 ppm. The analytical method used was microcoulometric
g.is chromatography with a nitrogen detector, corrected for in-
strument efficiency and average recovery.
cl Average of 4 cows.
d/ ND = None detectable.
Source: Shuttleworth (1973).
35
-------
Table 8. Residues in Tissues of 3 Metabolites ot
Carbofuran at End of 28-day Feeding Period
Tissue and
Feeding level
Residue, ppro—
Carbofuran phenol
3-Keto-7-phenol
Carbofuran
3-Hydroxy-7-phenol
carbofuran
Muscle
200
200
Liver
200
200
Fat
200
200
Kidney
20
20
60
60
200
200
ND£/
ND
ND
ND
ND
ND
ND
ND
ND
ND
0.15
0.32
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
0.27
0.34
ND
ND
ND
ND
ND
ND
ND
ND
< 0.10
ND
0.32
0.40
a/ Feeding level of 200 pptn:
66.7 ppm carbofuran phenol,
66.7 ppm 3-keto-7-phenol-carbo£uran,
66.7 ppm 3-hydroxy-7-phanol-carbofuran.
Feeding level of 60 ppm:
20 ppm of each of the above.
Feeding level of 20 pptn:
6.7 ppm of rach of the above.
b/ Method sensitivity: muscle, livov, and fat, 0.05 ppm; kidney, 0.10
ppm. Analytical method: micrccoulomctric gas chromntography with
a nitrogen detector, corrected for instrument efficiency and aver-
age recovery.
£/ ND ™ None detrctable.
Source: Shuttleworth (1973).
36
-------
Table 9. U.S. Tolerances for Carbofuran
ppm Crop
10 Alfalfa (fresh) (limited to 5 ppm carbamates)
40 Alfalfa hay (limited to 20 ppm carbamates)
0.1 Bananas
0.05 Cattle (meat, fat, meat by-products) limited to 0.02
ppm carbamates
0.1 Coffee beans
25 Corn fodder and forage (limited to 5 ppm carbamates)
0.2 Corn grain including popcorn (limited to 0.1 ppm carba-
mates)
0.05 Goats (meat, fat, meat by-products) limited to 0.02
ppm carbamates
0.05 Hogs (meat, fat, meat by-products) limited to 0.02 ppm
carbamates
0.05 Horses (meat, fat, meat by-products) limited to 0.02
ppm carbamates
0.1 Milk (limited to 0.02 ppm carbamates)
0.2 Peanuts (limited to 0.1 ppm carbamates)
5 Peanut hulls (limited to 1 ppm carbamates)
1 Peppers (limited to 0.2 ppm carbamates)
2 Potatoes (limited to 1.0 ppm carbamates)
0.2 Rice
1 Rice straw (limited to 0.2 ppm carbamates)
0.05 Sheep (meat, fat, meat by-products) limited to 0.02
ppm carbamates
3 Sorghum fodder and forage (limited to 0.5 ppm carbamates)
0.1 Sorghum grain
0.5 Strawberries (limited to 0.2 ppm carbamates)
0.1 Sugar beets
2 Sugar beet tops (limited to 1 ppm carbamates)
0.1 Sugarcane
Source: Code of Federal Regulations, Title 40, Chapter 1, Part 180, Subpart
C, Section 180.254, July 1975, as amended in Federal Register 41(2):
763. January 5, 1976.
37
-------
Composition and Formulation
According to the manufacturer (FMC, 1972a), technical carbofuran is 98.8% pure.
The other 1.2%, classified as an inert ingredient, is 2,3-dihydro-2,2-dimethyl-
7-benzofuranol, an unreacted raw material from the final processing step (see the
Synthesis and Production Technology section).
Carbofuran is available in 2 principal formulations from the manufacturer,
These are granules, 10, 5, 3, and 2% (designated 10G, 5G, 3G, and 2G), and 4 lb/
gal flowable formulation. Two wettable powder formulations (50 and 75%) have been
used for crop residue studies, but are not currently available.
Chemical Properties
Most of the available information on the chemical degradation of carbofuran
was obtained by researchers concerned with the metabolism of carbofuran and its
degradation in animals and plants. Carbofuran undergoes 3 types of chemical
degradation: hydrolysis, oxidation, and photodecomposition. The structures and
common names of carbofuran and its principal degradation products are given below.
0
n
OCNHCH3
CH3
Carbofuran
I
3-Hydroxycarbofuran
II
3-K.etocarbofiiran
III
OCN1!CH2OH
N-Methyl hydroxycarbofuran 3-keto-N-methyl
hydroxycarbofuran
IV
V
OH
3-Keto-6-hydroxy-
ccrbofurun
VI
CH3
Carbofuran-7-phenol
VII
3-ketocarbofuran-
phenol
VIII
CH,
3-hydroxy-7-phenol
carbofuran
IX
38
-------
Hydrolysis - Cook (1973) states that carbofuran is stable in neutral or
slightly acid solutions, but will hydrolyze under basic or strongly acid
conditions. Cleavage occurs at the carbamate linkage.
Metcalf et al. (1968) studied the hydrolysis rate of carbofuran and
several of its metabolites in alkaline solution at 37.5°C. The various
carbamates were added at 0.1% weight/volume in methanol to phosphate buf-
fer at pH 9.5, and the hydrolysis constants were determined by the rate
of formation of the phenolic hydrolysis products which were measured by
ultraviolet spectrophotometry. The results are shown below.
Khyd, min ~! Tl/2. min
Carbofuran 0.0104 66.9
3-Hydroxycarbofuran 0.0263 26.4
3-Ketocarbofuran 1.715 0.404
N-Methylhydroxycarbofuran 0.130 5.33
3-Keto-N-methylhydroxycarbofuran > 7.0 0.1
Getzin (1973) studied the degradation of carbofuran in soil. Figure
4 shows his results at 4 pH levels in Sultan silt loam, Getzin also studied
carbofuran hydrolysis in alkaline (unstated pH) aqueous solution and obtained
a half life of 8 days at 25°C. The hydrolysis occurred at the carbamate link-
age yielding carbofuran-7-phenol as one product. (Getzin did not report other
hydrolysis products, nor did he describe his experimental method.) Getzin con-
cludes that, in alkaline soils, the primary route of degradation is chemical
hydrolysis, while in acid or neutral soils slow microbial and chemical degra-
dation occurs.
Caro et al. (I973a) primarily studied dissipation of carbofuran in the
soil. They determined the half-life of carbofuran in solution (unspecified
concentration) at pH 6.35 and 5.20. The half-life at pH 6.35 was 140 days and
at pH 5.20, 1,600 days. The results in soil are discussed in the Fate and Sig-
nificance in the Environment Section of this report.
Caro et al. (1973a) also estimated the effect of temperature on hydrolysis
by utilizing the Arrhenius equation:
k = Ae-E*/RT
39
-------
lOOn
0
8
PH4.3
16 24
WEEKS AFTER TREATMENT
32
Figure 4. Degradation Gurves for Carbofuran in
Sultan Silt Loam at 4 pH Levels
Source: Getzin, L.W. (1973). Persistence and degradation of carbofuran
in soil. F.nviron. Entomol. 2(3) :461-467. Reprinted by permis-
sion of Entomological Society of America.
40
-------
Studies were done on the hydrolysis of technical carbofuran, 2 carbofuran
formulations, and 3-hydroxycarbofuran, a major metabolite of carbofuran. In the
first test, the pH levels were 4, 7, and 9.2; only one analysis was taken after
24 hr. The samples were saturated solutions, buffered in water at 25°C. The
results showed little or no hydrolysis at pH 4 and 7, and complete hydrolysis at
PH 9.2 (McDonald, 1972).
McDonald then conducted a further test at pH 9.2, which included intermediate
measurements. The results are as follows:
Timed interval and rate of hydrolysis (%)
Product 0 hr 3 hr 5.5 hr 24 hr
Technical carbofuran 0 39.1 64.4 100
Furadan® 75 WP 0 78.4 79.1 100
Furadan®10 G 0 20.2 62.4 96.6
3-Hydroxycarbofuran 0 67.2 87.6 100
McDonald indicated that the incomplete hydrolysis of the granules was "associated
with water release characteristics or solubility of this formulated product in water."
McDonald then studied several pH levels between 7 and 9.2, using the same
buffering procedure, but only with technical carbofuran. The results are as
follows:
Percent hydrolysis in
24 hr at ?.5°C
7.0 0
7.6 4.6
8.0 18.2
8.6 31.0
9.2 100
41
-------
These values may be plotted on a log percent versus time graph and the half-
life read from the 50% point (FMC,1972b). A different line (with only the ini-
tial and final points) is drawn from each pH value. This method for determining
half-life is valid if an assumption of first-order kenetics is correct. This
assumption is discussed below. Using this method, the above report gave the
following half-lives at 25°C: pH 8.6, 1.9 days; pH 8.0, 3.6 days; pH 7.6,
16.1 days.
The following chemical reaction occurs in hydrolysis under slightly alkaline
conditions (pH 5-10).
C-N-CHc
8 A
CH3
H
methylcarbamic
acid
[CH3NHCOOH]
CH3NH2 + C02
methylamine
In a strongly alkaline solution such as 20% NaOH, and at temperatures above
100°C, the reaction as given by McDonald (1972), would be of second order with
respect to carbofuran.
,u,
0-C-N-C%
o
CH3
CH3 +
Base
CH3NCNCH3
0
2,2-Dimethyl-7-
hydroxy-2,3-
dihydrobenzofuran
1,3-Dime thylurea
42
-------
The rates of hydrolysis under various pH and temperature conditions have
been determined. These findings are summarized below (Cook and Robinson, 1972).
pH Temperature (°C) Results
5 28 No hydrolysis in 28 days
7 28 Stable for 3 days, 48,4%
remaining at 21 days,
erratic step pattern
9
28 19.9% remaining after 1 day
9 26 Half-life of 12 hr (0.46
days) (60% remaining after
7 hr)
9 5 Half-life of 1.5 days (53.8%
remaining after 1 day (0.7%
after 7 days)
Hydroxylation (oxidation) - Metcalf et al. (1968) studied the oxidation of car-
bofuran in plants, insects, mice, and in a model system. Results are depicted
graphically in Figure 5. Major metabolic pathways were: (1) hydroxylation at
carbon position number 3, (2) further oxidation to corresponding 3-ketocarbofuran
compounds and (3) hydrolysis of carbamate moieties to the corresponding phenols.
Photodecomposition - Metcalf et al. (1968) studied the effects of fluorescent
light and sunlight on residues of crystalline carbofuran in Petri dishes. 3-
hydroxycarbofuran was detected by thin-layer chromatography (TLC) after 2 days
in outdoor sunlight, and also on TLC plates exposed to fluorescent light at 70°F
for 1 week. After 2% weeks, 3 other unidentified compounds were detected in the
samples irradiated in sunlight. The authors speculated that one was carbofuran
phenol because it did not inhibit cholinesterase. However, none of these compounds
were analytically identical. The authors also noted that the 3-ketocarbofuran
did not appear.
43
-------
Carbofuran
phenol
Carbofuran
10]
(?)
3-Ke to-6- hydroxycarbofuran
(unconfirmed)
3-Hydroxycarbofuran
Hydrolysis
3-Hydroxycarbofuran-7-phenol
(0)
>
Hydrolysis
3-Ketocarbofuran
3-Ketocarbofuran-7-phenol
Figure 5. Oxidation and Hydrolysis Routes of Carbofuran
Note: Heavy lines indicate major pathways.
Source: Based on data in Metcalf et al. (1968).
-------
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Plants." J. Agr. Food Chem.. 15(5):814-829 (1967).
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-------
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49
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PART II. INITIAL SCIENTIFIC REVIEW
SUBPART B. PHARMACOLOGY AND TOXICOLOGY
CONTENTS
Page
Acute, Subacute, and Chronic Toxicity 53
Acute Oral Toxicity—Rats 53
Acute Oral Toxicity—Dogs 55
Acute Dermal Toxicity—Rabbits 57
Acute Oral Toxicity—Mice 5g
Acute Oral Toxicity—Chickens 53
Acute Oral and Topical Toxicity—Cattle 58
Acute Oral Toxicity—Sheep 59
Subacute Oral Toxicity—Rats 59
Subacute Oral Toxicity—Dogs 62
Subacute Oral Toxicity—Rabbits 62
Subacute Oral Toxicity—Chickens 62
Subacute Oral Toxicity—Cattle 63
Chronic Oral Toxicity—Rats 64
Chronic Oral Toxicity—Dogs 65
Reproduction Studies 66
Effects on Reproduction—Rats 66
Metabolite Study—Rats 68
Effects on Reproduction—Dogs 68
Oncogenic Effects 70
Oncogenic Effects—Mice 70
Oncogenic Effects—Rats 70
Mutagenic Effects 71
Teratogenic Effects 72
Other Toxicity Tests 72
Eye Irritation—Rabbits 72
Skin Sensitivity—Guinea Pigs 73
Neurotoxicity-Chickens 73
Potentiation Studies 73
Symptoraology and Pathology 73
Signs of Toxicity 73
Symptoms of Toxicity 74
51
-------
CONTENTS (Continued)
Page
Treatment of Intoxication 74
Accidential Exposures 75
Metabolism 76
I
Insect Metabolism 76
Plant Metabolism 81
Metabolism in Mammals 85
Cholinesterase Inhibition 88
References 89
52
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This section Is concerned with Information on the acute, subacute, and
chronic toxiclty of carbofuran In laboratory and domestic animals (mice, rats,
dogs, rabbits, cattle, sheep, and chickens). A review is given of the charac-
teristic symptoms and pathology of carbofuran poisoning in mammals, in addition
to possible antidotes. Studies are discussed concerning the effects of carbo-
furan on the reproductive cycles of rats and dogs. Oncogenic effects are also
considered plus a review of mutagenic, teratogenic and potentiation studies.
The section summarizes rather than interprets data reviewed.
Acute, Subacute, and Chronic Toxicity
Acute Oral Toxiclty - Rats - A number of acute oral toxlcity tests have indi-
cated that the oral W$Q for technical carbofuran in the adult rat ranges from
6.4 rag/kg to 14.1 mg/kg (see Table 10). The oral toxicity of a formulation is
proportional to the amount of active ingredient present. For example, the
oral LD5Q for the formulation 10G (10% granular) was reported to be 131.2
mg/kg (Schoenig, 1968h). The intraperitoneal LD5Q of technical grade carbo-
furan was reported as 1.37 mg/kg (Kohn et al., 1967b).
The acute oral toxiclty of different formulations varies with the formu-
lation, but there does not appear to be a sex difference in response. Dif-
ferences in the sensitivity of the newborn, the weanling, and the adult rat
to technical carbofuran are summarized in Table 10.
The acute oral toxlcity of carbofuran metabolites was also evaluated.
Five metabolites were studied in tests on young albino rats (Sprague-Dawley
strain). Selected dosages were given to groups of 4 rats each (2 males and
2 females) by intubation, followed by a 14 day observation period. The
results of the tests are summarized in Table 11.
The effect of acute doses of carhofuran on cholinesterase activity was
studied in Charles River strain rats. Groups of 25 rats were intubated at
dose levels of 0.2, 0.5, 1.0, 3.0, and 10.0 mg/kg. After administration of
the pesticide, blood samples were withdrawn from the orbital sinuses of the
animals. Brain cholinesterase was determined in groups of 5 animals at 1, 2,
4, 6, and 24 hr. The results for the various dose levels were as follows:
At 0.2 mg/kg there was no effect on plasma, red blood cell (RBC) or brain cho-
linesterase at 1, 2, 4, 6, or 24 hr. At 0.5 mg/kg, the only effect seen was a
36% depression of brain cholinsesterase at 6 hr. There was no effect on brain
or blood cholinesterase at other intervals. At 1.0 mg/kg, a 497. depression of
brain cholinesterase was noted at 6 hr, but no depression at 1,2, 4, or 24 hr.
Plasma cholinesterase was depressed at 1, 2, 4, and 6 hr, but returned to normal
at 24 hr. No effect on RBC cholinesterase was observed. At 3.0 mg/kg, there
was a depression of plasma and brain cholinesterase up to 6 hr which reLurned to
normal at 24 hr. No effect on RBC activity was noted at 1, 2, 4, 6, or 24 hr.
At 10.0 mg/kg, there was a significant mean depression of brain cholinester.jse
levels at 1, 2, 4, and 6 or 24 hr. Marginal effects on RBC activity were ob-
served at 2, 4, and 24 hr (Kretchmer, 1972).
53
-------
Table 10. Summary of Acute Toxicity Data for Rats
Animal
Formulation
Administration
Toxicity
Reference
Rat§/
Rat£/
Rat (
Rat (F)*/
Rat (M)*/
Rat (newborn)—
Rat (weanling)—'
Rat§7
Rat*/
Rat*/
Rat£/
Rat£/
Rat£/
Tech.
Tech.
Tech.
Tech.
Tech.
Tech.
Tech.
Tech.
Tech.
10 G
Tech.
Tech.
Tech.
Tech.
Tech.
(PG)*
(PG) _
(PG, CO)**
(CO)
(CO)
(CO)
(CO)
(CO)
(CO)
(PG)
(PG)
(PG)
(PG)
(PG)
Oral
Oral
Oral
Oral
Oral
Oral
Oral
Oral
Oral
Oral
Oral
Oral
Intraperitoneal
Intraperitoneal
Intraperitoneal
in
LD50 =7.1 mg/kg (+ 0.7)
II>5o = 6.4 mg/kg
LD50 =14.1 mg/kg (8.91-22.4)
LD50 =11.9 mg/kg (+ 2.5)
LD50 = 11.34 mg/kg (+ 1.15)
LD50 = 11.34 mg/kg C 2.16)
LD5Q =8.2 mg/kg
LD50 =1.65 mg/kg (± 0.24)
LD50 = 3.36 mg/kg (1 0.64)
LD50 = 131.2 mg/kg (± 13.3)
LDj =5.3 mg/kg (-)
IJ>99 = 9.5 mg/kg (-)
LD50 = 1.37 mg/kg (± 0.17 mg)
W± =1.05 mg/kg
LD99 =1.80 mg/kg
Palazzolo (1963a)
Palazzolo (1963a)
Powers (1964)
Kohn et al. (1967a)
Schoenig (1967f)
Schoenig (1967f)
Schoenig (1966)
Schoenig (1967f)
Schoenig (1967f)
Schoenig (1968b)
Palazzolo (1963a)
Palazzolo (1963a)
Kohn et al. (1967b)
Kohn et al. (1967b)
Kohn et al. (1967b)
* PG = Propylene glycol carrier.
** CO = Corn oil carrier.
a/ Sprague-Dawley strain.
b_/ Unspecified strain.
c_/ Slmonson Laboratory strain.
-------
Table 11. Acute Oral Toxicity of Carbofuran Metabolites
Metabolite LDsn Reference
2,3-Dihydro-2,2-dijnethyl-7- 2.2 1 0.5 g/kgi/ (Schoenig, 1967b)
hydroxybenzofuran 1.8 "t 0.4 g/kgb/
1.8 ± 0.3 g/kg£/
2,3-Dihydro-7-hydroxy-2,2- 295.1 ± 29.96 mg/kgd/ (Schoenig, 1967c)
dimethy1-3-oxobenzofuran
2,2-Dimethyl-3,7-dihydroxy- 1,350 1 158.4 mg/kgl/ (Schoenig, 1967d)
2,3-dihydrobenzofuran
3-Hydroxycarbofuran 17.9 t 4.3 mg/kg®/ (Schoenig, 1967e)
3-Ketocarbofur^n 69.0 ± 14.7 mg/kgl/ (Schoenig, 1967e)
a/ Undiluted.
b/ 25% (w/v) corn oil solution.
c/ 75% (w/v) propylene glycol solution.
d/ 5% (w/v) corn oil suspension.
e/ 0.1% (w/v) suspension in corn oil.
fj 1% (w/v) suspension in corn oil.
Acute Oral Toxicity - Dogs - The results of oral toxicity tests indicated that
dogs were somewhat more resistant than rats to the action of carbofuran. The
U>50 for dogs is reported to be 18.85 mg/kg. However, acute inhalation tests
indicated that the dog was equally susceptible by the respiratory route (see
Table 12).
During an acute toxicity study with beagle dogs, the inhibition of blood
cholinesterase by technical carbofuran was also investigated. The reduction
of cholinesterase activity for plasma and erythrocytes with time and dose is
shown in Tables 13 and 14 (Baran, 1967a). The lowest level of cholinesterase
activity appeared following the first hr of administration. Signs of recovery
were observed at 24 hr (Baran, 1967a).
55
-------
Table 12. Summary of Acute Toxicity Data for Animals Other Than Rats
ON
Animal
Dog*/
Dog*/
Rabbit^/
Rabbit^/
Rabbi tb/
Chicken^/
Chicken!/
Mouse
Formulation
Tech. (GC)*
Tech.
Tech.
Tech.
10 G
Furadan® 4
(flowable,
Tech.
Tech.
Tech.
Administration
Oral
Oral
Oral
Dermal
Dermal
Dermal
paste)
Oral
Oral
Oral
LD50 =
LDgg =
LD50 =
' LD50 -
LD50 =
LD50 =
Lp50 =
Toxicity
18.85 mg/kg (+ 1.02)
16.46 mg/kg (-)
21.55 mg/kg (-)
14.7 mg/kg
10.2 g/kg
6.8 g/kg (+ 0.8)
25.0 mg/kg (12.5-50)
38.9 mg/kg (-)
2 mg/kg
Reference
Baran (1967a)
Baran (1967a)
Baran (1967a)
Palazzolo (1963a)
Schoenig (1967a)
Schoenig (1968a)
Palazzolo (1966)
Jackson (1967)
Fahmy et al. (1970)
* GC = Gelatin capsule.
a/ Beagle.
b/ New Zealand albino strain.
cf English strain.
d_/ White leghorn strain.
-------
Table 13. Changes in Plasma Cholinesterace Activity
in Dogs After Dosing With Carbofuran
Cholinesterase activity?.'
1
2
3
4
Dog
(male)
(female)
(male)
(female)
Dose
(mg/kg)
15.38
15.38
23.07
23.07
Time after dose (hr)
0
0.499
0.471
0.516
0.470
1/2
0.455
0.372
0.291
0.297
1
0.364
0.333
0.184
0.300
2
0.510
0.305
-b/
0.401
24
0.444
0.446
-
0.398
a/ Acetic acid (um/min/ml) of plasma.
b_/ Dog died.
Source: Baran (1967a).
Table 14.
Changes in Erythrocyte Cholinesterase Activity
in Dogs Dosed With Carbofuran
Cholineeterase activity3.'
1
2
3
4
Dog
(male)
(female)
(male)
(female)
Dose
(rag/kg)
15.38
15.38
23.07
23.07
Time after dose (hr)
0
0.328
0.336
0.273
0.361
1/2
0.259
0.312
0.263
0.132
1
0.243
0.277
0.171
0.311
2
0.274
0.243
_b/
0.294
24
0.315
0.296
—
0.321
a/ Acetic acid Qam/min/ml) erythrocytes.
b7 Dog died.
Source: Baran (1967a).
Acute Dermal Toxicity - Rabbits - Furadan (4 Ib/gal) was applied as an aqueous
slurry to the shaved skin of rabbits. Animals were wrapped and a plastic
collar was used to prevent migration of the test material during the 24 hr
exposure. All animals that died, as well as survivors, were necropsied
(Schoenig, 1967a).
Animals that received doses of 4.6, 6.8, and 10.2 g/kg showed hypoactiv-
ity and muscular weakness 1 to 6 hr posttreatment. Reactions continued 1 to 2
days in survivors. Salivation, tremors, fibrillary action and miosis were
noted at 6.8 and 10.2 g/kg, 1 to 6 hr after treatment and continued 6 to 18
hr.
57
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Skin reactions were characterized by pale, red, definable erythema in all
dose groups at termination of the 24 hr contact period. At 7 and 14 days fol-
lowing treatment, only dryness and desquamation of skin were noted at the appli-
cation site. No significant pathological alterations were noted in any animal
at necropsy. The acute dermal LD50 was calculated to be 6.8 g/kg (i 0.8)
(Schoenig, 1968b).
The acute dermal LD5Q of technical carbofuran in an organic solvent (Dowa-
nol DPM) for rabbits was determined to be 14.7 mg/kg; however, the acute dermal
LD50 of the technical carbofuran in water was greater than 10.2 g/kg (FMC, 1963
and 1969).
Acute Oral Toxicity - Mice - The acute oral W$Q for technical carbofuran admini-
stered to Swiss mice was determined to be 2 mg/kg body weight (Fahmy et al.,
1970).
Acute Oral Toxicity - Chickens - The acute oral toxicity for chickens was report-
ed to range from LD5Q 25.0 to 11)50 38.9 mg/kg. This data indicates that chickens
possess more resistance to carbofuran than any other animal for which data is
available (Palazzolo, 1966 and Jackson, 1967). The LD5Qfs reported for domestic
chicken also indicate that this bird is more resistant to the acute toxic effects
of carbofuran than wild birds (see section on Effects on Wildlife).
Acute Oral and Topical Toxicity - Cattle - In a metabolism study, administration
of a single 0.52 mg/kg dose of carbofuran to 1 cow resulted in marked nervous-
ness of the animal for about 3 hr, but no other signs of poisoning appeared.
Another dose of 1.0 mg/kg caused salivation, tearing, hyperactivity, and diar-
rhea within 50 min after dosing. The signs of toxicity were most severe after
2 hr but subsided to an apparent normal condition in 4 hr (Ivie and Dorough,
1968).
In another study, a 635 kg Holstein cow was given a single 5 g (7.9 mg/kg)
oral dose of carbofuran. The animal exhibited extreme signs of distress within
30 min. The signs of poisoning were very rapid breathing and muscular twitching
followed by convulsions. One hr after administration of carbofuran, the animal
was treated with atropine sulfate, and recovery appeared complete within 12 hr
(Miles et al., 1971).
The effects of oral dosage and topical application of carbofuran to 1- to
2-week-old calves and older cattle was studied. The compound was administered
orally as a 75% wettable powder or as 96.7% technical grade carbofuran, in
gelatin capsules, 1 hr after feeding.
Intoxication in the 1- to 2-week-old calves resulted from oral doses of
0.25 mg/kg or greater. At 1 mg/kg, 1 animal died even though it was treated
with atropine sulfate. Necropsy findings (1 mg/kg) were congestion of the lungs
and reddening of the visceral mucosa. In older cattle, the highest oral dose
of carbofuran (1.0 mg/kg) resulted in only mild signs of toxicosis which did
not necessitate administration of atropine sulfate.
58
-------
For topical application, 4 liters of an 0.01, 0.05, or 0.19% spray were admin-
istered. Animals receiving topical applications greater than 0.05% carbofuran
(4 liters of emulsion) showed mild signs of toxicity. Signs of toxicity occurred
within 1 hr after treatment. Animals treated topically with 0.1% emulsion
required atropine sulfate treatment to prevent death.
Two yr-old heifers receiving 0.05% topical applications showed signs of
toxicity but did not require atropine sulfate treatment. At 0.1%, yearlings
exhibited increased salivation, muscular tremors and prostration. Washing
away the residual and atropine sulfate treatment was required to save the
animals. Animals showing indication of toxicosis generally had depressed
blood cholinesterase levels (Palmer and Schlinke, 1973).
Acute Oral Toxicity - Sheep - Carbofuran was administered orally to yearling
crossbred sheep as single 1.0, 5.0, 10.0, and 25.0 mg/kg doses in gelatin
capsules. Doses higher than 2.5 mg/kg body weight resulted in severe toxicosis
requiring atropine treatment to save the animals. One animal receiving a
10.0 mg/kg dose died within 2 hr in spite of atropine treatment. The severity
of toxicosis was generally indicated by reduced blood cholinesterase levels.
The animal that died after treatment with 10 mg/kg carbofuran exhibited pulmo-
nary edema and congestion of internal organs (Palmer and Schlinke, 1973).
Subacute Oral Toxicity - Rats - The subacute toxicity of technical carbofuran
for Sprague-Dawley rats was determined over a period of 90 days (Kohn, 1965).
The test groups established and the feeding schedule for each group are shown
below. Ten males and 10 females were used for each test group and for the
controls. Diets were fed ad libitum:
Carbofuran (ppm) fed for indicated days
0-21 22-35 36-49 50-90
Controls - - -
Test group
I 0.1 0.4 1.6 1.6
II 0.4 1.6 6.4 6.4
III 2.0 8.0 32.0 32.0
IV 10.0 40.0 160.0 160.0
V 25.0 100.0 400.0 1,600.0
After 90 days all animals were sacrificed. Standard gross and microscopic
pathological examinations were conducted on several organs including the liver,
kidney, spleen, gonads, heart, and brain.
59
-------
Some effects on growth were noted in both males and females. Lowered
weight gains were recorded for both sexes in Treatment Groups IV and V. It
was suggested that reduced palatability in the higher treatment groups may
have contributed to the reduced weight gains (192 g weight gain for controls,
171 g for Group IV females and 133 g for Group V females). There were no dif-
ferences between controls and treated animals in hematology, urinalysis,
behavioral effects, gross pathology, microscopic pathology, and in selected
organ weights. No deaths were recorded throughout the study (Kohn, 1965).
In another test, groups of Charles River albino rats (15 males and 15
females per group) were fed carbofuran for 90 days at dose rates of 0, 300,
1,000, and 3,000 ppm. During the feeding period, weight gains were determined
at weekly intervals and food consumption was carefully monitored for 5 animals
of each sex per test group. Mortality and abnormal reactions were recorded
daily. Blood and urine samples were collected from 10 rats of both sexes for
the control and 3,000 ppm test groups after 45 and 84 days of feeding. Hema-
tology, blood chemistry, and urinalysis were monitored.
All animals were sacrificed at the end of 90 days of feeding and each was
subjected to necropsy. Weights of livers, kidneys, spleens, gonads, hearts,
and brains, were recorded. Microscopic examination was carried out on tissues
from 10 rats of each sex for the control and the 3,000-ppm test group.
An examination of the results of all tests indicated no significant dif-
ference between the control and the test group for any parameter compared
(Reyna, 1972). Charles River strain albino rats were dosed at 0.1, 0.3, 1.0,
and 3.0 mg/kg/day for 16 weeks (propylene glycol solutions, intubated) and the
effect of treatment on cholinesterase activity was then determined after 1, 3,
6, and 13 weeks. After 13 weeks, treatment was reported to have caused little
reduction of cholinesterase activity at the highest concentration (3.0 mg/kg)
used.
Some of the 13-week values obtained in this study are shown below:
Cholinesterase activity3/
Plasma Erythrocyte Brain
Controls
Test
- Male
Female
- Male
Female
0.263
0.390
0.275
0.492
0.513
0.383
0.530
0.491
4.277
4.826
5.196
5.080
a./ Acetic acid (um/min/ml) of plasma or erythrocytes and um/min/g for brain.
Source: Wolf (1966a).
60
-------
The effect of time of sampling on cholinesterase activity was shown by
Wolf in a subacute study using female Charles River rats. After dosing at
3.0 mg/kg/day for 3 weeks (technical carbofuran), blood samples were drawn at
intervals from 0 time (after dosing) to 60 min. The following results suggest
that a depression of cholinesterase acitivity is observed if sampling is done
a short time following dosing:
Effect of time of sampling on cholinesterase activity
Time of sampling:
after dosing
0
15 min
30 min
45 min
60 min
Cholinesterase
Erythrocyte
0.482
0.396
0.361
0.370
0.329
activity—/
Plasma
0.323
0.251
0.245
0.205
0.1522
a./ Acetic acid Qim/min/ml)
Source: Wolf (1966a).
A 28-day cholinesterase study was performed using female Charles River
rats (Plank, 1972). A group of 40 rats was administered daily doses of 1.0
mg/kg carbofuran in corn oil by gavage. A control group of 10 animals was
given daily doses of corn oil by gavage. At 14 and 28 days, 5 test animals
were sacrificed 1, 2, 6, and 24 hr following carbofuran administration. Five
control animals were also sacrificed at 14 and 28 days. Plasma, RBC and brain
cholinesterase activity were determined for each animal sacrificed.
In the 14- to 28-day test, only slight depression (less than 15%) of
plasma or RBC cholinesterase was observed 1 to 6 hr after dosing. However,
because a single 1 mg/kg dose resulted in 30% depression in 1 to 6 hr in other
animals, the investigator concluded that daily exposure resulted in some adapta-
tion during the 14- or 28-day exposure periods.
Brain cholinesterase was significantly depressed after 2 and 6 hr at the
14- and 28-day exposure periods. The cholinesterase level returned to normal
within 24 hr. The results suggest there is no adaptive mechanism for brain
cholinesterase depression by carbofuran (Plank, 1972).
Ninety-day subacute tests for oral toxicity were conducted using 3-
hydroxycarbofuran at dietary levels of 10, 30, and 100 ppm (Plank, 1969) and
2,3-dihydro-2,2-dimethyl-7-hydroxybenzofuran at 300, 1,000, and 3,000 ppm
(Reyna, 1972). Charles~River strain rats were used as test animals.
61
-------
At 100 ppm 3-hydroxycarbofuran, no differences in behavior, mortality,
hematologic, biochemical or urologic tests were observed between the treated
animals and the controls. Data from gross pathological examinations indicated
that differences due to treatment could not be identified.
Differences between untreated rats and those fed 2,3-dihydro-2,2-dimethyl-
7-hydroxybenzofuran at 3,000 ppm were not observed for body weight, food con-
sumption, mortality, behavioral reactions, hematological tests, blood chemistry,
urine constituents, or gross pathology. Erythrocyte cholinesterase activity
of treated animals (3,000 ppm, 90 days) was not inhibited as a result of feeding
the metabolite.
Subacute Oral Toxicity - Dogs - In an effort to establish a maximum dose level
that would have no effect on plasma or erythrocyte cholinesterase, a study was
conducted for 92 days by treating beagle dogs with technical carbofuran. Both
male and female pure-bred beagles were used; 3 males and 3 females at each of
5 dose levels. When cholinesterase activity was determined 20 hr after dosing,
no significant differences were reported between controls and animals treated
at the highest concentration, 5 mg/kg/day. Although differences in cholines-
terase activity were not noted, the dogs treated at 5 mg/kg/day exhibited
frequent coughing and gagging, occasional salivation, muscular tremors and
emesis (Baran, 1966).
Subacute Oral Toxicity - Rabbits - A study was conducted to assess possible
hazards to rabbits feeding on alfalfa treated with carbofuran. The dietary
levels were 70, 210, and 700 ppm. Seventy ppm was considered the average 0
day deposition on 8-in alfalfa when applied at the rate of 1.0 Ib/acre. These
3 levels were fed to groups (3 males and 3 females per group) of albino rabbits
for 14 days.
No deaths or untoward behavioral reactions were noted. Slight adverse
effects on body weights were noted among animals in all groups; however, 5 of
6 animals in the 700 ppm group lost weight while only 1 or 2 animals in other
groups lost weight. The weight losses may have been due at least in part to a
slight reduction in food intake (Mastri, 1967).
Subacute Oral Toxicity - Chickens - The effects of 3 phenolic metabolites of
carbofuran were studied in chickens (Hybrid laying hens). Groups of 10 birds
each were fed 3 levels of mixtures of the metabolites 3-hydroxycarbofuran
phenol, 3-ketocarbofuran phenol, and carbofuran phenol as indicated below:
62
-------
Group
No. of animals
Dietary level—
carbofuran
(ppm)
Dietary level-
metabolites
(ppm)
1
2
3
4
10
10
10
10
0
20
60
200
0
6.67
20
66.7
Source: Reno (1973b).
The diets were fed for 28 days to determine the levels of metabolites
which would occur in eggs and body tissue and to determine the rate at which
the metabolites clear the system upon withdrawal from the diet.
After the 28-day feeding period, 5 birds from each of the 4 groups were
sacrificed. Following a 15-day recovery period, the remaining birds were
sacrificed.
Appearance, behavior, body weights, food consumption, and egg production
were observed throughout the feeding and recovery periods. At necropsy,
liver, gizzard, skin, fat, heart, muscle, and kidney were taken for analysis
of residues.
There were no significant differences observed in appearance, behavior,
food consumption, and egg production between the control group and the test
groups. No gross pathological alterations or tissue changes were observed at
the time of sacrifice. No results were reported for the analysis of tissues
and eggs (Reno, 1973b).
Subacute Oral Toxicity - Cattle - The effects of 3 metabolites of carbofuran
were also studied in the lactating Holstein dairy cow, using groups of 10
animals each. They were fed the same levels and dosages of phenolic metabo-
lite mixtures as reported in the chronic study on chickens (Reno, 1973b).
The diets were fed to the cows for 28 days to determine the levels of
metabolites which would occur in milk and tissues and to determine the rate
at which the metabolites clear the system upon withdrawal from the diet.
After being fed the metabolite for 28 days, 2 animals from each of the
4 groups were sacrificed. Following a 15-day recovery period on the basal
diet without metabolites, the remaining animals were sacrificed.
63
-------
Body weights and food consumption were recorded for each animal through-
out the test period and milk samples were taken for residue analysis. At
sacrifice, gross necropsies were performed and samples of muscle, fat, liver,
and kidneys were taken for residue analysis.
Except for 2 injuries and a minor respiratory infection, no untoward
effects were observed in the animals during the test. All but 2 of the cattle
receiving metabolites showed an unexpected decrease in body weight during
feeding. However, these animals began to gain weight during the recovery
period. No gross tissue changes were observed in any of the animals sacrificed
(Reno, 1973a).
Chronic Oral Toxicity - Rats - Long-term chronic toxicity tests (2 yr) with
Charles River albino rats treated at dietary levels of 1, 10, and 100 ppm did
not result in any mortality in the treated groups that could be attributed to
carbofuran consumption (50% of the animals died).
Both males and females in the 10 ppm test group exhibited a weight depres-
sion, but this lowered gain was confirmed statistically (P<:0.05) only in males.
•
Throughout the study no behavioral abnormalities were observed to have
resulted from treatment.
Blood studies were conducted at the end of the treatment period (2 yr) ,
but no difference between controls and the highest treatment level could be
detected for values of hemoglobin concentrations, hematocrits, erythrocyte
counts, leucocyte counts and differentials.
Blood chemistry tests were done for blood urea nitrogen (BUN), serum alka-
line phosphatase activity (SAP), and serum glutamic pyruvic transaminase (SGPT).
Differences could not be detected between the controls and treated animals.
Gross pathological examinations were conducted at 12 months and at 2 yr.
The only abnormality noted was the spleen weight in males treated at 100 ppm for
1 yr (5 males and 5 females from the controls and the 100-ppm group were exam-
ined) . The difference between the control values and the 100-ppm group, how-
ever, was not found to be statistically significant. The author reported that
the finding may be important because of the observed weight loss which occurred
in these males.
All animals that survived for 2 yr were sacrificed and gross and micro-
scopic pathological examinations were conducted.
No differences in gross pathology could be detected between the controls
and the treated rats. Histopathological examination confirmed the absence of
differences between treated groups and controls.
64
-------
Absolute organ weights of liver, kidney, spleen, gonads, heart, and brain
and organ-to-body or organ-to-brain weight ratios did not reveal any consistent
differences between the control animals and those fed carbofuran (Wolf, 1967b).
In another 2 yr chronic study, dietary levels of technical carbofuran of
25 and 50 ppm were fed to Charles River albino rats (Plank, 1968). Seventy
animals (35 males and 35 females) were included in each test group. A total
of 77% of the animals died during the test, but since mortality was randomly
scattered throughout controls and treatment, the deaths were not considered to
have been related to treatment.
A reduction in food consumption was noted only in males at the 50-ppm
level during the first 9 months of the study. Females fed 50 ppm, and both
males and females fed 25 ppm, consumed feed at intakes comparable to untreated
controls.
At the dietary level of 50 ppm, males gained less than controls for the
first 12 months; thereafter, the gain was similar.
No differences were noted in gross pathology between untreated controls
and carbofuran-fed animals (Plank, 1968).
Wolf reported no significant difference between control and test groups
with regard to weight gain, food consumption or behavioral effects. Gross
pathological examination and examination of tissues collected at necropsy re-
vealed no significant differences between the control and test groups at the
end of the 2-yr feeding study (Wolf, 1968).
Chronic Oral Toxicity - Dogs - Pure-bred beagle dogs were fed carbofuran for
2 yr according to the schedule shown below.
Dietary level
Test grou£
I
II
f
III
IV
V
(ppm)
1
2
10
20
50
100
100
200
100
200
400
Days fed
1-267
268-737
1-267
268-737
1-142
143-730
1-267
268-737
1-14
15-267
268-737
65
-------
At the end of the 2-yr period, comparisons of treated and control groups
were made for food consumption, hematology, blood chemistry, liver function,
urine analyses, organ weights, and pathology (gross and microscopic). No sig-
nificant differences were observed between treated and control groups.
Abnormal behavioral reactions were not observed in dogs at 1, 2, 10, 20,
and 50 ppm. At 100 ppm (Groups IV and V), minimal coughing and gagging
were observed. At 200 to 400 ppm (Groups IV and V), dogs showed a slight
coughing and gagging. Slight salivation, emesis, muscular tremors and weakness
in the hindquarters were observed in dogs of Group IV (200 ppm) at 500 to
737 days, and in dogs of Group V (200 to 400 ppm) at days 15 to 737.
Fatalities occurred in the Test Group V animals at 400 ppm (Baran, 1967b and
1967c).
Reproduction Studies
Effects on Reproduction - Rats - A 3-generation reproductive study was con-
ducted with weanling rats (Charles River - Sprague-Dawley derived) which were
fed diets containing 1, 10, or 100 ppm technical carbofuran (Kennedy, 1967b).
Each of the 3 test groups and the control group consisted of 8 males and 16
females which were parents for the first generation of the study. Parental
stock and progeny were produced by following the scheme outlined in Figure 6.
Animals from each generation were maintained on their respective test diets
until sacrifice.
Eight males and 16 females from the second litters of each group were
randomly selected at weaning for use as parental animals for the succeeding
generation. Mating was conducted when the animals were 100 days old. At 100
ppm, a weight depression was noted in the males (10 to 18% below untreated
controls). All deaths that occurred were reported to be due to respiratory
infection and not to treatment with carbofuran.
Mating and fertility indices of the 100 ppm test animals were similar to
those of untreated controls. In all 3 generations most of the 100 ppm females
delivering apparently normal pups lost their entire litters prior to weaning
at 21 days.
A greater incidence of stillbirths was observed for all 3 generations in
the 100 ppm test group than in the controls or in any of the other treatment
groups (Kennedy, 1967b).
A 1-generation reproductive study was conducted with Charles River rats
at dietary levels of 0 and 50 ppm carbofuran (Kennedy, 1967a). The weanling
body weights in the F^a and F^ test groups were lower than the corresponding
control groups. The 5~day survival indices for the treated F^a and F^ groups
were also lower (44.7 for F^a and 30.4 for Flb) than the same indices for the
controls (96.6 for Fla and 76.8 for F^) . These results appear to parallel the
above studies performed at 100 ppm by Kennedy (1967a).
66
-------
c
o
•r4
4J
4J Id
tO »4
iH 0)
C
o
•H
4J
•o rt
C M
CM
-------
A second-generation study on albino Charles River rats used 2 groups of
24 animals each (8 males and 16 females). One group was given 30 ppm carbo-
furan in the diet while the other group was maintained on a diet containing
no carbofuran.
No significant differences in body weights and no untoward behavioral re-
actions were noted in the F]_ parental animals. No gross pathological altera-
tions or histopathological differences were observed in test or control F,
animals.
Mating indices and incidences of pregnancy and parturition were signifi-
cantly lower in the test than in the control groups. The first litter lacta-
tion index was also lower for the test group. The number of pups born and
the number of pups viable at various periods of lactation were lower in both
litters (F2a or ?2b) for the test groups as compared to controls. In the
first litters only the 5-day survival index was lower for the test groups;
however, all survival indices were lower for second litters of the test group.
The only significant differences in weights of weanlings were observed in
second litter females which had lower average body weights than the controls
(Arnold, 1968a).
Feeding carbofuran at 30 ppm generally appeared to have affected the
mating of parental animals and to have had a subsequent effect on the progeny.
The survival indices for all 3 generations are shown in Table 16 (Arnold,
1968b).
Metabolite Study - The compound 3-ketocarbofuran phenol, a metabolite of carbo-
furan, was fed to Charles River albino rats at dietary levels of 10 and 50 ppm.
The animals were mated when they were 100 days old (79 days on test). After
32 weeks, when the F^ litters were weaned, the FQ parents were sacrificed and
subjected to gross pathological examinations.
The results of this study indicated that the metabolite had no effect on
the ability of the animals to mate or on the females' ability to conceive and
carry the young. There were no differences between the treated and the con-
trols in (a) the number of pups delivered; (b) the number of stillborn; (c)
viable pups at birth; (d) number of pups weaned; (e) survival of pups; (f)
weanling body weights; (g) physical reactions; or (h) physical appearances of
pups.
Histopathological examinations indicated that there were no differences
between untreated controls and treated animals (Arnold, 1969).
Effects on Reproduction - Dogs - A reproduction study was carried out with
dogs fed dietary levels of '20 and 50 ppm carbofuran for 20 months. One male
and 4 females were used per group. One control and 2 test groups of 6-month-
old virgin females were fed ad_ libitum for the duration of the study. The
68
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Table 15. Survival Indices for a 3-Generation Study
on Rats (30 ppm Carbofuran)
Controls : F^a
Fib
F2a
F2b
F3a
F3b
30 ppm test: Fia
Fib
F2a
F2b
F3a
F3b
Live birth
index*/
93.5
98.9
92.5
100.0
79.3
92.4
90.5
94.7
90.6
85.7
85.0
84.6
24-Hr survival
indexb/
97.9
98.3
92.6
97.5
82.6
84.5
90.3
96.0
88.5
66.7
100.0
100.0
5-Day survival
index£/
95.1
79.1
89.0
82.5
73.0
47.4
82.1
80.7
70.1
55.6
94.1
36.4
a/ Live birth index: viable pups x 100
total pups
b_/ 24-Hr survival index: pups viable on lactation day 1 x IQO.
viable pups
c/ 5-Day survival index: pups viable on lactation day 5 x IQO.
~~ viable pups born
Source: Adapted from Arnold (1967, 1968a, 1968b).
study was terminated after litters of 3 or 4 females per group were 4 weeks
old. At 1 week, X-rays were taken of each pup to determine any adverse effects
on skeletal development. At 4 weeks, 1 male and 1 female from each litter were
sacrificed and subjected to complete pathological examination.
The results showed no adverse effects on parental animals with respect to
mortality, general reactions, body weight, food consumption, estrus cycles,
mating performance, parturition and lactation. No adverse effects were ob-
served in the progeny of control or test animals with respect to litter size,
survival indices,-general reactions, body weights, ability to nurse, or skele-
tal abnormalities and gross pathological findings (Stephens, 1970).
Three pregnant female beagle dogs were fed carbofuran in the diet at 20
ppm during the last half of the gestation period and continuing through lac-
tation. Initially, the dietary level was 5 ppm but it was increased every 5
days by 5 ppm until 20 ppm was reached.
69
-------
The females did not exhibit any physical signs of intoxication during the
test period. All the pups born of these test animals appeared normal and main-
tained normal growth patterns (Carlson, 1968).
Oncogenic Effects
Oncogenic Effects - Mice - The carcinogenicity of technical carbofuran to
Charles River, random-bred mice was considered in a study by Reyna (1973).
The mice were divided into 4 groups of 100 animals (50 males and 50 females).
One group was held as untreated controls and 2 of the remaining 3 groups were
given carbofuran in the diet at 30 and 100 ppm. The last group was a positive
control and was given urethane at 600 ppm. The mice were fed on their respec-
tive diets for 18 months.
Each animal was examined weekly for signs of tumor formation and complete
gross pathological examinations were conducted on all postmortem animals and
on all animals surviving the treatment.
Tumors were observed in test animals, but they were not different in
number nor in their latent periods from those observed in untreated animals.
Treatment with urethane resulted in an increase in tumor incidence. A summary
of tumor incidence is given in Table 16 (Reyna, 1973).
Oncogenic Effects - Rats - Rats fed 100 ppm dietary carbofuran in a chronic
toxicity study were evaluated after 2 yr for incidence of tumors. The results
indicated that the incidence of tumors in treated animals was not related to
treatment with carbofuran.
Dietary dose Tumor incidence
(ppm) (%}
0 24.2
1 12.5
10 15.6
100 8.8
Source: Wolf (1967a and 1967b).
The tumors found were primarily chromophobe adenomas of the pituitary and mam-
mary adenofibromas (Wolf 1967a and 1967b).
Treated survivors fed up to 50 ppm carbofuran for 2 yr had the same inci-
dence of tumors as untreated controls (Plank, 1968).
70
-------
Table 16. Summary of Tumor Incidence During an 18-Month
Carcinogenic Study With Swiss White Mice
Groups
Number submitted for
histopathologic ex-
amination3.'
Number with tumors
Percent of total examined
with tumors
Type of tumor
Alveologenic adenoma
Alveologenic carcinoma
Hemangioma
Squamous cell carcinoma
Lympho s ar coma
Reticulum cell sarcoma
Total number of tumors
Control
57
6
10.5
4
0
0
0
2
0
Positive
control
25
19
76.0
Carbofuran
30 ppm
31
16.1
Number of tumors
16
1
6
2
0
0
•^••^M
25
4
0
1
0
0
0
100 ppm
39
8
20.5
7
0
2
0
3
0
Mtf^V
12
a/ The number of animals submitted for histopathologic examination included all
animals sacrificed at the conclusion of the investigation and any post-mortem
animal or animals sacrificed in extremis with signs of possible tumor forma-
tion. All other animals were examined grossly and found to be free of tumors
or tumor-like growth.
Source: Reyna (1973).
Mutagenic Effects
Mutagenesis studies have been carried out using Charles River strain albino
mice as test animals. A dominant lethal mutation study was conducted with tech-
nical grade carbofuran by Arnold (1971). An untreated control, a positive con-
trol, methyl methanesulfonate and 2 levels of treatment with carbofuran (0.25
and 0.5 mg/kg) were utilized in the test. Twelve males were included in each
treatment group including the controls. Each male was mated to 3 females per
week for 6 weeks. The females were sacrificed 1 week after removal from the
breeding cage and were examined for implantation sites, resorption sites, and
embryos.
71
-------
Data for the first 2 weeks of the positive control group indicated that
a dominant lethal mutation had occurred. The data from the control and carbo-
furan treatment groups revealed that no dominant lethal mutation was present
in these animals (Arnold, 1971).
Teratogenic Effects
Teratogenesis studies were conducted using New Zealand albino rabbits.
A total of 40 female rabbits were observed for 60 days before testing. Four
groups of 10 females each were placed on test according to the following
protocol:
Group
Control
Positive control
Test Group I
Test Group II
Test material
None3./
Thalidomide
Carbofuran
Carbofuran
Dose level
(mg/kg of body weight)
per day
75.0
o.ib/
0.5
Number of
females per
group
10
10
10
10
a/ Control group females received a sham dose (empty gelatin capsule).
b/ Technical grade carbofuran
Source: Jackson (1968).
Treatments were given on day 6 through day 18 of the gestation period.
On gestation day 29, all females were sacrificed and the litters recovered
by caesarian section. After 24 hr of observation for viability, the fetuses
were sacrificed and examined by dissection. Particular attention was given
to the skeletal tissue and the differences in size, shape, and position of
major organs and blood vessels. A positive thalidomide control group was
included to indicate teratogenic sensitivity of the rabbit strain used.
Examination of 120 fetuses from females treated with carbofuran revealed
no gross abnormalities. Internal structural formation was normal and skeletal
development was well defined. The young were present in normal numbers, were
well formed, and showed good survival during the first 24 hr after Caesarian
delivery. However, the incidence of resorption was twice as high in both
carbofuran test groups as in the control group (Jackson, 1968).
Other Toxicity Tests
Eye Irritation - Rabbits - Palazzolo (1963c) conducted a study on eye irrita-
tion using New Zealand white rabbits. Technical carbofuran (5 rag) was instil-
led into the conjunctival sac of the right eyes of 2 rabbits; the left eyes
were used as controls. Examinations were then made at intervals up to 7 days.
72
-------
After 10 mln, both rabbits exhibited miosis which persisted for 2 hr.
Thereafter, the condition cleared. Only minimal irritation was reported in
this test (Palazzolo, 1963).
Skin Sensitivity - Guinea Pigs - Technical carbofuran injected intracutaneous-
ly into the skin of male guinea pigs did not elicit a sensitizing reaction.
Injections were given every other day for 20 days. The first injection was
0.05 ml and all others were 0.10 ml each. The challenge dose was given 2
weeks following the 10th injection (Schoenig, 1967g).
Neurotoxicity - Chickens - When treated with a concentration of technical
carbofuran equal to the LD5Q concentration of 38.9 mg/kg, white Leghorn hens
dosed with technical carbofuran exhibited salivation and general weakness,
but not leg and wing weakness at a concentration equivalent to the LD5Q (38.9
mg/kg). In surviving birds, the weakness subsided in 24 hr. Surviving birds
were given another acute dose at 21 days with similar results. No physical
signs of delayed neurotoxicity (demyelination) were observed and, therefore,
microscopic examinations were not performed (Jackson, 1967).
Potentiation Studies - Sprague-Dawley rats were the test animals used in po-
tentiation studies. Schoenig (1966) determined the LD5Q of carbofuran and
other pesticides (12 compounds), and then determined the LD5Q of equitoxic
mixtures of carbofuran and each of the other compounds. The results were
compared to theoretical LD5Q values derived from assumption of strictly addi-
tive toxicity. Potentiation of the acute oral toxicity of carbofuran by any
of the other test materials was not observed. For example, the theoretical
LD5Q of an equitoxic mixture of carbofuran and ethion was 104.1 while the
observed LD5Q was 180. The theoretical LDso of a mixture of carbofuran and
Sevin was 129.1 and the observed LD5Q was 111.0. The ratio of theoretical
to observed LD5Q was 0.58 for ethion and carbofuran, and 1.16 for Sevin and
carbofuran (Schoenig, 1966).
Symptomology and Pathology
Signs of Toxicity - Signs of intoxication that developed in rats after an acute
dose of carbofuran were reported by various investigators as follows: fibril-
lary action, salivation, ataxia, lacrimation, exophthalmos, hyperpnea, cyanosis,
hemorrhagic conjunctivitis, tonoclonic convulsions, diuresis, labored breathing,
sprawling of the limbs, and depression. The dosage resulted in the deaths of
some animals. (Palazzolo, 1965; Powers, 1964; and Palazzolo, 1963c).
The signs observed in the dog were similar to those seen in the rat. The
predominant reactions reported for a single acute dose of carbofuran were trem-
ors (lasting 4 to 6 hr) emesis and moderate to severe convulsions. The dose
resulted in the deaths of some animals (Baran, 1967a).
Signs of subacute intoxication are coughing, gagging, salivation, muscu-
lar tremors, and emesis (Baran, 1966).
73
-------
The most frequently observed signs of acute intoxication with carbofuran
in sheep and cattle were reported by Palmer and Schlinke (1973) to be in-
creased salivation, lolling tongue movements, stiff uncoordinated gait,
dyspnea, muscular tremors, ataxia, and prostration. Acute intoxication might
also prove to be fatal.
Signs reported for acute intoxication in chickens include salivation,
general weakness, and a specific extreme leg and wing weakness (Jackson, 1967).
Symptoms of Toxicity - In humans the symptoms of carbofuran intoxication are
assumed to be those produced by other cholinesterase inhibitors: headache,
nervousness, blurred vision, general weakness, nausea and cramps, diarrhea,
sweating, tearing, excessive respiratory tract secretion, cyanosis, convul-
sions, coma, loss of reflexes, loss of sphincter control, and cardiac arrest.
Carbofuran intoxication can also cause death (Hayes, 1963).
Treatment of Intoxication
Sprague-Dawley rats with a body weight of 150 g were administered tech-
nical carbofuran orally at concentrations of 3.5 and 5.3 mg/kg. Within 30
seconds after dosing with the insecticide, atropine sulfate (1.5% solution)
was given intraperitoneally.
Animals which were not given atropine exhibited salivation, lacrimation,
miosis, and generalized tremors. Those treated with atropine exhibited only
generalized tremors. At a dosa of 3.5 mg/kg carbofuran, 25% of the rats died;
animals treated at 3.5 mg/kg carbofuran plus 50 mg/kg atropine had a mortal-
ity of 8.3%. Rats dosed at 5.3 mg/kg of carbofuran followed by treatment with
atropine sulfate at 100 mg/kg had a mortality of 6.2%, while the test animals
at 5.3 mg/kg carbofuran exhibited mortality equal to 69% (Palazzolo, 1963a).
Sprague-Dawley albino rats weighing 175 g were administered technical
carbofuran at 5.3 mg/kg. Thirty seconds after treatment, 2-pyridine aldozime methn-
chloride (2-PAM Cl) was given to 2 groups of carbofuran-treated animals at
100 or 150 mg/kg. Eighty percent of the carbofuran controls and 60% of both
groups given 2-PAM Cl treatment died. These results appeared to indicate that
2-PAM Cl cannot be recommended as treatment for carbofuran intoxication. In
addition, the animals which received only 2-PAM Cl exhibited reactions of
dyspnea, exophthalmos, excitation, and mild generalized tremors 5 to 30 min
following dosing. These symptoms persisted for about 1-1/2 hr (Palazzolo,
1964a).
Treatment of dogs with atropine sulfate was also found to reduce reactions
due to treatment with technical carbofuran (5.3 mg/kg). Two dogs were treated
with atropine sulfate (50 mg) when symptoms of intoxication appeared. Severe
reactions occurred for 3 hr in the absence of an atropine treatment. Dogs
treated with 50 mg atropine sulfate responded immediately (Palazzolo, 1963d).
74
-------
New Zealand strain albino rabbits were given a single dose of technical
carbofuran by gavage and, as soon as signs of intoxication appeared, half of
the test animals were given an injection containing 10 mg of atropine sulfate.
The atropine-treated animals responded immediately. Symptoms of intoxication
persisted in the nontreated animals for 5 hr. Seventy-five percent of the
non-atropine-treated rabbits died, but none of the atropine-treated animals
succumbed (Palazzolo, 1964b).
Calves, 1 to 2 weeks old, were treated orally, with technical carbofuran
at doses from 0.25 mg to 5 mg/kg.
When signs of toxicosis appeared, animals which had received doses of 1
and 5 mg/kg carbofuran were treated with atropine sulfate peritoneally at a
dosage of 0.5 mg/kg body weight. The animal administered 1 mg/kg carbofuran
died even though treated with atropine sulfate; the animal dosed with carbo-
furan at 5 mg/kg and treated with atropine sulfate survived. The authors
did not comment on the results (Palmer and Schlinke, 1973).
Sheep were administered carbofuran at 5 and 10 mg/kg body weight. When
signs of toxicosis were observed, 3 animals treated at 5 mg/kg and 1 animal
treated at 10 mg/kg were treated intravenously with atropine sulfate at a dose
of 0.5 mg/kg body weight. The animals that received 5 mg/kg carbofuran sur-
vived; the animal given 10 mg/kg carbofuran died even though treated with
atropine sulfate (Palmer and Schlinke, 1973).
For treatment of organophosphorus pesticide poisoning in man, Hayes
(1963) recommends a dosage of 1 to 2 mg atropine sulfate at the appearance
of symptoms. In cases where excessive secretions occur, the individual should
be given atropine sulfate every hour up to 50 mg a day.
The recommendation made in the Merck Manual (1966) for organic phosphate
poisoning is 1 to 4 mg of atropine intramuscularly or intravenously, followed
by 1 to 2 mg every 20 min up to a total of 10 to 20 mg/day.
Accidental Exposures
Accidental exposures to carbofuran are recorded by the EPA Pesticide
Episode Review System (PERS). Computerized PERS data for the period 1972
through January 1974 showed carbofuran to be the twenty-sixth most frequently
cited compound in the review system. More recently, a review was conducted
of the PERS data for the period January 1967 to April 1975 (EPA, 1975). This
review indicated that a total of 55 episodes had been reported, including
those involving humans, animals, plants, and contaminated areas. However, in
most cases, carbofuran was not conclusively established as the cause of the
episode. There was substantial evidence to link the pesticide to the episodic
effect for only 3 of the 26 episodes involving accidental human exposure.
The available data was too limited to establish any relationship between the
episodes and any specific method of application or use of carbofuran.
75
-------
The geographical distribution of the 55 episodes, according to EPA
Region, is as follows:
EPA region No. of episodes
1 0
2 1
3 1
4 6
5 4
6 6
7 7
8 13
9 14
10 3
Metabolism
The main pathway of oxidative metabolism of carbofuran in plants,
insects, and animals appears to consist of hydroxylation at the benzylic
carbon to yield 3-hydroxycarbofuran (see Table 19 and Figure 7)« The hy-
droxylated product is further oxidized to give 3-ketocarbofuran. Hydroly-
sis and conjugation then occur. The 3-keto compound is hydrolyzed at a
much faster rate than the parent carbofuran although hydrolysis and con-
jugation can also occur at other stages of metabolism. Carbofuran can be
converted (hydrolyzed) to 2,3-dihydro-2,2-dimethyl-7-hydroxybenzofuran
(carbofuran phenol) or hydroylsis can follow oxidation to 3-hydroxycar-
bofuran .
The available data appears to indicate that hydrolysis is preceded
by oxidative metabolism (Schlagbauer and Schlagbauer, 1972; Metcalf, 1968;
Casida and Lykken, 1969; O'Brien, 1967; and Ryan, 1971).
Numerous studies describing the specific steps in the metabolic path-
ways of carbofuran in plants and animals are cited in Table 17. The pro-
ducts of oxidation and hydrolysis of carbofuran in rats, cows, and in
plants, as proposed by Knaak (1971), are shown in Figure 7.
Insect Metabolism - Microsomal preparations of housefly tissues were used by
Metcalf et al. (1968) to study the effects of mixed function oxidases on
carbofuran. The results of this study suggested that carbofuran is hydroxy-
lated at 4 sites: the 3-position of the furan ring, the 6-position of the
aryl ring, the N-methyl group and the 2-methyl groups. The authors stated,
however, that formation of substantial amounts of metabolites hydroxylated
at the N-methyl or 2-methyl groups does not appear likely.
76
-------
In alfalfa
V
0-Cluco«e
Hydroxylation
OCNHCH3
In rats and eovs
0
Hydrolysis
OH
Hydrolysis
N
cose 0-Gl
' • OSO I!
j
ucose 0-CL /
f \
OS03H
icid 0-GL A
f ^
OS03H
cid 0-GL i
*
1C id
Source: Knaak, G. B. 1971. Biological and nonbiological modifications of carbamates.
Bull. World Health Ore. 44:121-131. Reprinted, by permission of the World
Health'Organization.
Figure 7 . Proposed Products of Carbofur.an Oxidation and Hydrolysis
-------
Table 17. Metabolites of Carbofurun
Name of compound usually
found In the literature
Carbofuran (I)
Formula
3-tfydroxycarbofuran (II)
Probable, metabolic
reaction resulting
In formation
Pesticldal compound
could also be
secondarily re-
leased from (XII)
Aromatic hydroxylatlon
of (1) (Oxldatlve)
00
3-Ketocarbofuran (III)
Oxidation of (II)
Plants and animals
in which metabolite
has been found
KaramulB, blrda, fish
Insects, plants, soil
Rat
Chicken
Cattle
Mouse
Cotton
Alfalfa
Corn
Beans
Tobacco
tine
Insects
Earthworms
Soil
Rat
Cattle
Mouse
Cotton
Alfalfa
Corn
Beans
Tobacco
Insects
Soil
References
Sc'nlagbauer and Schlux'u.iucr (1972)
Catilda and Lykken (19.',9); u'Brlon (1967)
Rynn (1971); Knnak (1971); Fnkuto (1972);
Menzic (1969); WustntT et al. (1974);
Menn (1972); Kiihr (1970)
Lucier (1972); Dorough (1968b)
Hicks et al. (1970)
Ivie and Dorough (196U); Knaak ct al. (1970b);
Miles et al. (1971)
Metcalf (1968)
Hetcalf et al. (1968)
Knaak et al. (1970a)
Turner and Caro (1973); Caro et al. (1973);
Metcalf ct al. (1968)
Dorough (19*<8a)
Ashuortli and Sheets (1972)
Prcc and Saunders (1974)
Black et al. (1973); Shrivastava et •»!. (1971);
Metcalf (1968); Sangha (1971)
Stenersen ct al. (1973)
Cr.ro et al. (1973)
Dorough (1968b); Lucior et al. (1972)
Ivie and Dorough (1968)
Metcalf et al. (1968)
Metcalf et al. (1968)
Knaak et al. (1970b)
Caro et al. (1973); Turner and Caro (1973);
Metcalf ct al. (1968)
Dorough (1968a)
Ashworth and Sheets (1972)
Shrivastava et al. (1971):
Sangha (1971); Metcalf U968)
Caro rt al. (1973)
-------
Table 17. (Continued)
X»M of conpound usually
found jr. the literature
Carbofuran phenol (IV)
formula
OH
Probable metabolic
reaction resulting
in formation
Hydrolysis of (I)
plants -nd ar.irr.al3
in vhic!1' T^cabolite
nas bean found
< o-*\
Cattle
Mouse
Cotton
Alfalfa
. Eeans
Tobacco
Injects
Pine
Rc-forences
Metcalf «t al. (1968)
Dorouih (1968b): Lucier et al. (1972)
Knaak'cc al. (1970b); Ivit a^ Dorough (1968)
Metcalf et al. (1968)
Metcalf et al. (1968)
Knaak et al. U970a)
Dorouf.h (1968&)
Ashworth and Sheets (1972)
Metcalf et al. (1968)
Pree and SaunUe'rs (1974)
3-Hydroxycarbofuran
phtnol (V)
Hydrolyai. of (11)
r-.1C3
Chicken
'.attle
Alfslfa
Beans «ind tobacco
Insects
Earthworms
Cotton
?ine
L-.-er et al. (1972)
Kicks et al. (1970)
Ivle and Dorougb (1968); Knaak et al. (1970b)
Knaak et al. (1970a)
Ashwo-th and Sheets (1972); Dorough (1968a)
hetctlf et al. (1968)
Stcnersen et al. (1973)
Metcalf et »l. (1968)
Pree and Saunders (1974)
3-Katocarbofurcn phanol
(VI)
^rdrolyala of (III)
01 oxidation of
-,a- Dorough (1968o): Lucier et al. (1972)
Chicken Hicks et al. (1970)
Cattle • Ivie .and Dorough (1968); Knaak et al. (1970b)
Souse Metcali et al. (1968)
.Mfalfa Kr.jak et al. 'li'70a)
Lorn Metcalf et ai. U9r-3)
Eeanc Dorough (1963a)
Tobacco Ashworth *nd Sheets (1972)
fine Pree and Saunders (1974)
Insects Metcalf et al. (1968)
Cotton Metcalf et al. (1968)
Carbofuraa phenol con-
jugate (VII)
0-conjugat*
Conjugation of (IV)
Cattle
Mouse
Cotton
.'Ifilfa
Tonacco
insects
Dorouih (196Kb)
Knaak et t.1. (1970b)
Ketcalf et al. (1-J68)
Metcalf et -1. (1968)
Knaak et ai. Ui"0a)
Ashworth and ^eeta (1972); Ketcali et al. (1968)
Metcalf at jl. (1968)
-------
Table 17. (Continued)
00
O
Nane of compound usually
found in the literature Formula
3- Hydroxycarbofuran 0-conjuga:c
conjugate (VIH) I £j.
f/'~V|x ^fC.r|
IVvJ 1^ 3
OH
3-Kctocarbofuran con-
jugate (IX) 0-conjugace
Jl o ^c"3
(QLJ;:^
3-Hydroxy-N-nethylol- 0
carbofuran (X) ixNILIUOII
1 * -xCHi
ff)T' "Y^-CH
x~x"— — ^ 3
\x^ OH
N-ttathylolcarbofuran 0
(xi) OC'NHCHJOH
JL n CHi
oT Yc«3
3-Oxy-carbofuran con- 0
jugate (Xll) OCNHCHj
Prob.ible metabolic
reaction rosultinK
In formation
Conjugation uf (V)
Conjugation of (VI)
Aliphatic hydroxyla-
tion of (II) or
aromatic hydroxy-
lation of (XI)
(oxidatlvc)
Aliphatic hydroxy-
latlon of (1)
(oxidatlva)
Conjugation of (11)
can be metabolized
Plants and aniruls
in which metabolite
has been found
Cattle
Muu jt.'
Alfalfa
Corn
Tobacco
Cattle
Mouse
Alfalfa
Corn
Rat
Chicken
House
Beana
Insects
Cattle
Cotton
Chicken
Mouse
Pine
InaectB
Rat
References
Knaak et al. (1970b)
Metcalf et al. (1968); Black et
Knaak et al. (1970a)
Metcalf et al. (1968)
Aahworth and Sheets (1972)
Knaak et al. (1970b)
Metcalf et al. (1968); Black et
Knaak et al. (1970a)
Metcalf et al. (1968)
Dorough (I968b); Lucier et al.
Hicks et al. (1970)
Black et al. (1973)
Dorough (1968a)
Dorough U°68a) (1968b)
Ivle and Drough (1968)
Metcalf et al. (1968)
Hicks et al. (1970)
Metcalf et al. (1968)
Free and Saundera (1974)
Dorough (1968b); Metcalf et al.
Dorough (1968b)
al. (1973)
al. (1973)
(1972)
(1968)
to (HI)
-eonjugate
-------
Plant Metabolism - The following studies summarize available information on
the metabolism of carbofuran in specific crops. The ratios of major carbo-
furan metabolites in 6 crops are given in Table 18.
Isolated cotton leaves were allowed to imbibe labeled carbofuran and
then, at intervals up to 12 days, representative samples were homogenized,
extracted, and chromatographed. Total recovery of radioactivity ranged from
80 to 94% in the leaf homogenates (Metcalf et al., 1968).
Two-dimensional thin layer chromatography (TLC) of leaf extracts re-
sulted in detection of the following metabolites: carbofuran phenol, 3-
hydroxycarbofuran, 3-hydroxycarbofuran phenol, 3-ketocarbofuran, 3-keto-
carbofuran phenol, and conjugates of the phenolic and alcoholic metabolites.
In this study conjugates of N-methylolcarbofuran were not detected.
Exposure of the conjugates to fi-glucosidase enzymes (emulsion) resulted
in liberation of the aglycones (3-hydroxycarbofuran phenol, 3-ketocarbofuran
phenol) showing that these plant conjugates were glucosides (Metcalf et al.,
1968). Only a small quantity of the 3-hydroxycarbofuran conjugate could be
released by either enzymates or acid digestion.
The metabolites formed by the intact cotton plant were demonstrated to
be similar to those formed in isolated leaves. However, the rate of meta-
bolism in the intact plant was more rapid than in isolated leaves (Metcalf
et al., 1968).
The metabolism of carbofuran was studied in isolated corn leaves and
in corn seedlings. The isolated leaves were allowed to imbibe the insecticide,
but the seedlings-were grown from seeds treated topically.
Table 18. Ratios of Carbofuran Metabolite
Residues in 6 Major Crops
Plant
Major metabolite
Phenol/carbamate
ratio
Potato
Corn (foliage)
Alfalfa
Sugar beet (foliage)
Tomato (vine)
Bean plant (bean)
Carbofuran phenol
Phenols
3-Hydroxycarbofuran
3-Ketocarbofuran phenol
3-Hydroxycarbofuran
3-Hydroxycarbofuran
8/1
3/1
1/1
1/1
1/2
1/16
Source: FMC Corporation (1971).
81
-------
The rate of metabolism in isolated corn leaves was slower than the rate
in isolated cotton leaves, but the conjugate metabolites appeared to be the
same for the 2 plants.
TLC revealed the presence of 3-hydroxycarbofuran and 3-ketocarbofuran
phenol in the leaves together with the phenolic conjugates. The roots were
found to contain large proportions of carbofuran phenol and lesser amounts
of 3-hydroxycarbofuran and 3-ketocarbofuran (Metcalf et al., 1968).
The metabolism of carbofuran in corn plants was also studied by Turner
and Caro (1973). The investigators reported that over 90% of the carbofuran
was converted to 3-hydroxycarbofuran and 3-ketocarbofuran by the time the
plants reached silage stage. Most of the residue in leaves (92 to 93%) was
3-hydroxycarbofuran. The author also reported that, in the corn stalks, the
principal metabolic process was hydrolysis to 3-hydroxycarbofuran with no
accompanying oxidation.
Metabolites of carbofuran were isolated from roots and tops of tobacco
plants by Ashworth and Sheets (1972) in studies on root and foliar uptake of
the insecticide.
Neither carbofuran nor its unconjugated metabolites were found to accumu-
late in the roots of the tobacco plants. In addition, only trace amounts of
glycosidic aglycones (3-hydroxycarbofuran) were detected after acid hydrolysis
of the methanol-soluble root extracts.
Analyses from root-uptake studies of the tops of tobacco plants, however,
showed that the expected metabolites were present— carbofuran phenol, 3-
ketocarbofuran phenol, 3-ketocarbofuran, 3-hydroxycarbofuran, and several un-
identified compounds.
Some differences were noted by these investigators when the results of
analyses from root-uptake studies were compared to foliar-uptake studies.
Carbofuran was not found in plant parts other than the treated leaves. The
hydrolysis product, carbofuran phenol, was the major unconjugated metabolite.
In the root-uptake studies, the oxidation product 3-hydroxycarbofuran
was most abundant. From studies with topically applied material the investi-
gators also concluded that most of the carbofuran does not penetrate plant
cuticle and is therefore not subjected to metabolic processes in the plant.
The half-life of carbofuran absorbed through the root system and in the
leaves of tobacco plants was approximately 4 days. Carbofuran and the oxi-
dation products, 3-hydroxycarbofuran and 3-ketocarbofuran, were hydrolyzed
to their corresponding phenols. The hydroxy compounds were eventually con-
jugated as glycosides.
Bean plants (Dorough, 1968a) and animals (Borough, 1968b) were reported
to produce the same metabolic products of carbofuran. The metabolite present
in highest concentration was 3-hydroxycarbofuran. This material was found
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as the free carbamate, but its concentration never equaled its concentration
as a water-soluble conjugate. The compounds 3-ketocarbofuran and 3-hydroxy-
N-methylolcarbofuran, both free and conjugated, were also detected in the
plants. In a test using ^C ring-labeled carbofuran, the hydrolytic products
carbofuran phenol, 3-hydroxycarbofuran phenol, and 3-ketocarbofuran phenol
were isolated.
Of the hydrolytic products, only carbofuran phenol was found in the
free form, but always at a concentration below the soluble conjugated form.
pie metabolism in the potato of radio-labeled carbofuran (^C ring-labeled
and -"C carboxyl-labeled) was also investigated. Carbofuran was applied to
the soil around 60-day-old field plants and to the soil around greenhouse
plants. The greenhouse potatoes were harvested 7 days later and the field
potatoes 60 days later.
Using greenhouse plants, the following glycosides were found after 7 days:
carbofuran phenol (45% of metabolites); 3-ketocarbofuran phenol (6.8%); 3-hydroxy-
carbofuran phenol (4.2%); and 3-hydroxycarbofuran (26.2%). Carbofuran and
3-hydroxycarbofuran were also found at respective levels of 9.2 and 6.4%.
Using field-grown plants, the following glycosides were found after 60
days: carbofuran phenol (71.5% of metabolites); 3-ketocarbofuran phenol
(8.6%); 3-hydroxycarbofuran phenol (3.8%); and 3-hydroxycarbofuran (11.5%).
Extraction, hydrolysis and chromatographic studies indicated that carbo-
furan was absorbed by the potato roots and was transferred to the tubers
prior to hydrolysis and conjugation. The C carboxyl label remained in the
tubers and became a part of the natural product (Knaak, 1970b) .
The residue content and metabolism of carbofuran was also investigated
in field-grown tomato plants. One-week-old plants were treated with the
equivalent of 2.2 Ib/acre of radio-labeled C-carbofuran and sampled for
analysis at 11 days (immature) and 50 days (mature) after treatment.
Total l^C residues in mature and immature (tomato) vines were 1.15 and
1.58 ppm (ring-l^C) and 0.33 and 1.0 ppm (carbonyl-^C) at the respective
intervals. Total -"-^C-residues in mature and immature fruit were 0.08 and
0.07 ppm (ring-l^C) and 0.04 and 0.18 ppm (carbonyl-l^C). Mature and immature
roots exhibited a total ^C-content of 15.98 and 9.44 ppm (ring-14C) and 26.42
and 7.60 ppm (carbonyl- ^C).
Carbofuran was metabolized in the plant by oxidation to form 3-hydroxy-
carbofuran (33.0% in mature vine and 35.7% in immature vine). More carbofuran
was found in the immature (28.3%) than in the mature (2.6%) vine. The major
phenolic component was 3-ketocarbofuran phenol (19.9% mature and 12.1% immature).
83
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In mature root the major metabolite was 3-hydroxycarbofuran (52.2%); in
immature root, the carbofuran was the major component (46.4%).
In tomato fruit, the ^C levels of activity were too low to permit an
accurate evaluation of possible metabolites (Hunger, 1972).
Twelve 35-day-old sugar beet plants were placed within barriers and, at
65 days, 4 plants were administered 18.0 mg/plant l^C ring-labeled carbofuran
and 4 were administered 18.0 rag/plant carbonyl l^C-carbofuran. Four untreated
plants were selected as controls. One-half of the treated and the control
plants were harvested at 30 days and the remainder at 72 days.
Carbofuran was readily absorbed into the sugar beet roots and was trans-
located to foliage. The major carbamate metabolite identified was 3-hydroxy-
carbofuran while the predominant phenol was 3-ketocarbofuran phenol (Robinson,
1972).
Carbofuran was applied to the soil of potted alfalfa plants (9 mg/pot
of l^C ring-labeled carbofuran), and after a 30-day growth period, the plants
were harvested and analyzed for carbofuran metabolites.
The major metabolites identified (Knaak et al., 1970b) were the glyco-
sides of 3-hydroxycarbofuran (37.3%), 3-hydroxycarbofuran phenol (18.5%), and
3-ketocarbofuran phenol (20%). Total residue uptake expressed as carbofuran
amounted to 76 ppm.
The roots of Mugho pine shrubs (30 to 45 cm in height) were exposed for
24 days to a solution of l^C carbomyl or -^C ring-labeled carbofuran. The
needles were collected at various dates and were analyzed for metabolites
along with the buds, roots, trunk, and current wood growth of the shrubs.
(Free and Saunders, 1974).
An unidentified metabolite and 3-hydroxycarbofuran were the only organo-
soluble metabolites detected in the plant fraction from trees treated with
carbonyl-l^c carbofuran. Accumulation of metabolites was greatest in the
needles.
In the trees treated with -^C ring-labeled carbofuran, carbofuran phenol
was the main organo-soluble in each sample, although 3-hydroxycarbofuran and
3-ketocarbofuran phenol were also found. Two unidentified metabolites were
also present.
The separation of carbofuran and its free metabolites from their con-
jugated forms indicated that most of the metabolites were in the conjugated
form, although all compounds were also present in the free form. Treatment
with /J-glucosidase or /J-glucuronidase converted all of the identified metabo-
lites from the conjugated form to the free form.
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Metabolism in Mammals
Male Swiss white mice were given radio-labeled carbofuran (^H-labeled,
1.68 mc/mmole), and over the following 24-hr period, urine was collected
and analyzed for metabolites. Two mice treated orally with 2 rag/kg of the
3R-labeled carbofuran eliminated 37 and 67% of the administered radioactivity
in the 24-hr period.
The major metabolite, 3-hydroxycarbofuran, was detected in the urine
by an ether extraction procedure. Smaller amounts of 3-ketocarbofuran and
carbofuran phenol were also identified. The major conjugate and aqueous
portion was of 3-ketocarbofuran phenol.
The metabolism of carbofuran in mice was shown to be similar to that
in plants and insects; however, more of the carbofuran dose was metabolized
by mice to the water-soluble 3-hydroxycarbofuran than was true for plants
or insects (Metcalf et al., 1968). In plants, 3-hydroxycarbofuran; in
mice nearly 45% of the radio-label recovered in metabolites was present in
3-hydroxycarbofuran.
Carbofuran metabolites formed by the soluble fraction of rat liver homo-
genates were identified by Dorough (1968b) as 3-hydroxy-N-methylolcarbofuran,
N-methylolcarbofuran, 3-hydroxycarbofuran, 3-hydroxycarbofuran phenol, 3-
ketqcarbofuran phenol and carbofuran phenol. Three unidentified compounds
and other water-soluble complexes were also found. The metabolites formed
and their relative concentrations are shown in Table 19.
The 3-hydroxy-N-methylolcarbofuran, when incubated singly with liver
15,000 g solubles, was largely converted to water-soluble materials (con-
jugates) . Both N-methylolcarbofuran and 3-hydroxycarbofuran were reported
to have been metabolized (a) to an unidentified fraction (2.2 and 0.6%,
respectively), (b) to 3-hydroxy-N-methylolcarbofuran (6.9 and 8.9%), (c)
to 3-hydroxycarbofuran phenol (4.1 and 3.9%, respectively), and (d) to water
soluble materials (23.9 and 23.4%, respectively).
Carbofuran phenol was metabolized by the rat liver enzymes system primarily
to conjugated, water-soluble compounds.
The in vivo metabolism in rats was studied by housing treated animals
in metabolic cages and collecting and analyzing urine and feces separately.
Analysis of the organo-extractable metabolites in urine indicated that
jin vivo metabolism was similar to in vitro metabolism with liver homogenates.
Two metabolites, 3-ketocarbofuran phenol and an unknown, were not detected
in the unconjugated form in the rat urine, but they were present as water-
soluble conjugates. Four additional metabolites were also produced from the
water-soluble conjugates by means of acid hydrolysis: 3-hydroxy-N-methylol-
carbofuran, 3-hydroxycarbofuran, 3-hydroxycarbofuran phenol, and carbofuran
phenol.
Radioactivity in the water fraction from 14C-ring-labeled carbofuran
incubation was about 3 times greater when microsomes from control rats were
85
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used than when microsomes from methylmercury hydroxide-treated rats were
used.
Rats treated with methylmercury hydroxide excreted carbofuran-1^-C
equivalents more rapidly than controls.
The metabolites obtained from the treated animals were identified as
3-hydroxycarbofuran, carbofuran phenol, 3-hydroxycarbofuran phenol, 3-
ketocarbofuran, 3-hydroxy-N-methylolcarbofuran, and N-methylolcarbofuran.
Table 19. Degradation of Labeled Carbofuran by Rat Liver 15,000 C Solubles
% of radioactivity added
Carbonyl-labeled Ring-labeled
14jC 14C
Unknown I 0.07 0.10
Unknown II 0.011 0.09
Unknown III 0.05 0.03
3-OH-N-Methylolcarbofuran 1.76 2.07
N-Methylolcarbofuran 6.40 7.05
3-OH-Carbofuran 21.09 20.13
3-OH-Carbofuran phenol 0.00 0.02
3-ketocarbofuran phenol 0.00 0.02
Carbofuran phenol 0.00 3.82
Water solubles 5.89 7.01
Carbofuran 60.29 58.50
Source: Adapted from Dorough (1968b).
Prior treatment of rats with either methylmercury hydroxide or chlor-
ine affected the rate at which microsomal fractions from the rat's liver
would metabolize carbofuran. However, the treatment did not alter the type
of metabolite which resulted (Lucier et al., 1972).
86
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The excretion of carbofuran metabolites in cows' milk was studied by Dorough
and Ivie (1968). Two percent of an oral dose (gelatin capsule of -^C-carbonyl-
labeled carbofuran, 2.7 mg) was eliminated in milk, but only 0.16% of a ^C-ring
labeled dose was detected. The investigators noted a distinctly different distri-
bution of the radioactivity from that found with other carbamates. Significant
quantities of labeled residues could not be extracted from milk, and most of the
residues extractable by organic solvents could not be extracted from lipid materials
This suggested that some of the radioactivity in milk from cows fed 1^C-carbonyl
labeled carbofuran was not in metabolites, but in naturally occurring chemicals
that had incorporated the -^C atom from the treatment.
Another study by Ivie and Dorough (1968) included only ^C-labeled carbo-
furan, but also l^C-labeled sodium bicarbonate. Results from these tests supported
the earlier idea that the greater 14c-carbonyl-labeled residue resulted from in-
corporation of 14C02 into body chemicals normally found in milk. The authors
calculated that only 0.31% of the radioactive dose of l^C-carbonyl-labeled carbo-
furan was eliminated in the milk as extractable metabolites. With the extract-
able metabolites from milk, traces of parent carbofuran were present along with
3-hydroxycarbofuran, 3-ketocarbofuran, 3-hydroxy-N-methylolcarbofuran, 3-hydroxy-
carbofuran phenol, 3-ketocarbofuran phenol, and one unidentified metabolite.
The 3 metabolites (3-hydroxycarbofuran, 3-ketocarbofuran phenol, and carbofuran
phenol) were the products in highest concentration (70 to 80%).
The metabolism of carbofuran residues in alfalfa fed to cows was studied
by Knaak et al. (1970b). The carbofuran residues present in the alfalfa were
identified as carbofuran and the glycosides of 3-hydroxycarbofuran, carbofuran
phenol, 3-hydroxycarbofuran phenol, and 3-ketocarbofuran phenol. Since these
materials were all present in the alfalfa at the time of feeding, metabolic
pathways could not be defined. These residues were metabolized and excreted
as sulfates of 3-ketocarbofuran phenol, carbofuran phenol, and 3-hydroxycarbofuran
phenol.
The overall process was reported to include hydrolysis of the glycosides
and the carbomates, oxidation of the phenols, and conjugation of the resulting
compounds with sulfuric or glucuronic acid.
Cows were also treated with -^C-carbonyl-labeled carbofuran by Miles et al.
(1971) and the milk from these animals was analyzed for metabolites.
When cows were administered carbofuran, either by gelatin capsule or by
feeding in silage, the only metabolite reported in the milk was 3-hydroxy-
carbofuran. Its concentration ranged from nondetectable to 0.26 ppm in the
milk from 8 cows, averaging 0.13 ppm (Miles et al., 1971). An average of 0.05%
of the administered dose was excreted in the milk as 3-hydroxycarbofuran. Ivie
and Dorough (1968) reported that carbofuran and at least 6 metabolites were
detected in milk from carbofuran-treated cows.
Metabolites excreted in the fecal material of laying hens given ^C-carbonyl-
labeled carbofuran and ^C-ring-labeled carbofuran were detected by Hicks et al.
(1970). The authors found that rapid hydrolytic degradation occured. After 6 hr
54% of the dose had been hydrolyzed; by 24 hr, 72% had been hydrolyzed. Five
unidentified metabolites were detected along with 3-hydroxycarbofuran, N-methylol-
87
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carbofuran, 3-hydroxy-N-methylolcarbofuran, 3-ketocarbofuran, and carbofuran phenol.
The predominant metabolite was 3-hydroxycarbofuran phenol.
The concentration of carbofuran metabolites in eggs was low. Maximum radio-
active residue in eggs from hens treated with l^C-ring-labeled carbofuran was
0.13 ppm.
Samples of liver, kidney, gizzard, heart, breast, thigh, leg, skin, brain,
fat, and blood were collected and were analyzed for radioactive residues. All
tissues at both 6 and 24 hr contained -^C-carbofuran equivalents; none were
detected after this time in hens treated with ^C-ring-labeled carbofuran. However,
some residues were detected in tissues from hens treated with l^C-carbonyl-labeled
carbofuran after 3 days. There was no proof, however, that the radioactivity de-
tected was actually present as label in carbofuran or carbofuran metabolites.
Free and conjugated forms of 3-hydroxy-N-methylolcarbofuran and N-methylol-
carbofuran were found in the liver. Analyses of gizzard tissue revealed the
presence of carbofuran, 3-hydroxycarbofuran, 3-hydroxy-N-methylolcarbofuran and
an unidentified metabolite.
Metabolism in soil - In a study on persistence of carbofuran in soil,
Caro et al. (1973) found that after application of carbofuran to the soil,
partial conversion of the pesticides to the oxidation product, 3-ketocarbo-
furan, occurred. However, only traces of the product, 3-hydroxycarbofuran,
were found in soil samples. In corn grown on the treated soil, over 90% of
the parent carbofuran was detected as 3-hydroxycarbofuran in the stalks.
Cholinesterase Inhibition
A comparative study using carbofuran, 3-hydroxycarbofuran and 3-ketocar-
bofuran as inhibitors of cholinesterase indicated that in rats all compounds
were generally ineffective inhibitors at a concentration of 1 x 10~3 jug/ml
(Lazanas, 1967). However, in dogs, both carbofuran and 3-hydroxycarbofuran
caused greater than 50% inhibition at 1 x 10~3 jjg/mg, while 3-ketocarbofuran
only resulted in 26.9% inhibition.
The concentration of inhibitor (ng/ml) resulting in 50% inhibition of
erythrocyte cholinesterase in dogs was 1 x 10~5 for carbofuran and between
1 x 10~4 and 1 x 10~4 and 1 x 10~5 for 3-hydroxycarbofuran. The results of
these tests are summarized as follows :
% Inhibition of
concentration of erythrocyte
inhibitor cholinesterase
Inhibitor (|ig/ml) Dog Rat
Carbofuran 1 x 10~3 65.5 22.2
3-Hydroxycarbofuran 1 x 10~3 67.2 21.7
3-Ketocarbofuran 1 x 10~3 26.9 21.7
-------
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Sangha, G., "Environmental Effects of Carbamate Insecticides as Assays in the
Model Ecosystem1 - A Comparison with DDT," Ph.D. Thesis, University of
Illinois, Urbana, 111. (1971).
Schlagbauer, B. G. L., and A. W. J. Schlagbauer, "The Metabolism of Carbamate
Pesticides - A Literature Analysis. Part I," Res. Rev., 42:1-91 (1972).
Schoenig, G., "Acute Dermal Toxicity of Furadan® 4 Flowable Paste," FMC
Corporation, Middleport, N.Y. (unpublished, 1968a).
Schoenig, G., "Acute Dermal Toxicity Study on NIA 10242 10G," FMC Corporation
Middleport, N.Y. (unpublished, 1967a).
Schoenig, G., "Acute Oral Toxicity Study on Furadan® 10G," FMC Corporation
Middleport, N.Y. (unpublished 1968b).
Schoenig, G., "Acute Toxicity Studies on NIA 10272," FMC Corporation, Middleport
N.Y., (unpublished, June 27, 1967b).
Schoenig, G., "Acute Toxicity Studies on NIA 16490," FMC Corporation, Middleport
N.Y. (unpublished, November 27, 1967c).
Schoenig, G., "Acute Toxicity Studies on NIA 16497," FMC Corporation, Middleport
N.Y. (unpublished, November 27, 1967d).
Schoenig, G., "Acute Toxicity Studies on NIA 17481 and NIA 18209," FMC Corpora-
tion, Middleport, N.Y. (unpublished, October 5, 1967e).
Schoenig, G., "Comparative Acute Oral Toxicity of NIA 10242," FMC Corporation
Middleport, N.Y. (unpublished, 1967f).
93
-------
Schoenig, G., "Potentiation Studies on NIA 10242," FMC Corporation, Middleport,
N.Y. (unpublished, 1966).
Schoenig, G., "Skin Sensitization Test on NIA 10242 Technical," FMC Corporation,
Middleport, N.Y. (unpublished, 1967g).
Shrivastava, S. P., G. P. Georghio, and T. R. Fukuto, "Metabolism of N-Methyl-
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Stenersen, J., A. Gilman, and A. Vardanis, "Carbofuran: Its Toxicity to and
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171 (1973).
Stephens, J. L., "Reproductive Study with Technical Furadan® in Beagle Dogs,"
FMC Corporation, Middleport, N.Y. (unpublished, 1970).
Turner, B. C., and J. H. Caro, "Uptake and Distribution of Carbofuran and Its
Metabolites in Field-Grown Corn Plants," J. Environ. Quality, 2:245-247
(1973).
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Wolf, C., "Two-Year Chronic Oral Toxicity of NIA 10242 - Albino Rats," FMC
Corporation, Middleport, N.Y. (unpublished, 1967a).
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Wolf, C., "Two-Year Chronic Oral Toxicity of NIA 10242, 25 and 50 ppm - Albino
Rats," FMC Corporation, Middleport, N.Y. (unpublished, 1968).
Wustner, D. A., M. A. Fahmy, and T. R. Fukuto, "New Aspects of Organophosphorus
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Residue Rev.. 53:56-65 (1974).
94
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PART II. INITIAL SCIENTIFIC REVIEW
SUBPART C. FATE AND SIGNIFICANCE
CONTENT
Page
Effects on Aquatic Species 98
Fish '. . . . 98
Lower Aquatic Organisms 100
Effects on Wildlife 102
Laboratory Studies 102
Field Studies 104
Field Investigations 106
Effects on Beneficial Insects . 107
Bees 107
Field Reports on Bee Toxicity 108
Beneficial Parasites and Predators 109
Interactions with Lower Terrestial Organisms 110
Flora 110
Fauna 114
Residues in Soil 117
Laboratory and Greenhouse Studies 117
Field and Combined Field/Laboratory Studies 121
Residues in Water 127
Phytotoxicity 127
Bioaccumulation and Biomagnification 128
96
-------
CONTENTS (Continued)
Page
Environmental Transport Mechanisms 130
Lateral Movement 130
Leaching Studies 131
Runoff Studies 132
References
136
97
-------
This section contains data on the environmental effects of carbofuran,
including its effects on aquatic species, wildlife, and beneficial insects.
The interactions of carbofuran with lower terrestrial organisms and its resi-
dues in soil and water are also discussed. The section summarizes rather than
interprets the data reviewed.
Effects on Aquatic Species
Fish -
Laboratory Studies - The toxicity of technical carbofuran to fish reported
in different tests (see Table 20) appeared to vary depending upon the species
of fish tested and on the conditions prevailing at the time of testing.
Longnose killifish (Fundulus similis) were not affected by doses of tech-
nical carbofuran up to 0.1 ppm, but sheepshead minnow (Cyprinodon variegatus)
were irritated by 0.1 ppm carbofuran. However, the killifish were irritated
when exposed to Furadan 3G at 10 Ib/acre for 48 hr; 10% mortality occurred with-
in 24 hr when exposed to Furadan 3G at 20 Ib/acre. The fish recovered when
placed in clean water (Lowe, 1970).
A study by Schoenig (1967) indicated that rainbow trout, channel catfish,
and bluegill were of about equal sensitivity to technical carbofuran and that
the 96 hr TLm ranged from 0.21 to 0.28 ppm for these 3 species (Table 20).
The 24 hr LC5Q of technical carbofuran to channel catfish was reported to
be 2.03 ppm by Carter and Graves (1973) under static conditions of testing, a
value 10 times higher than that reported by Schoenig (1967) for channel catfish
also tested under static conditions.
In a test conducted by Carter (1971) on channel catfish, it was also re-
ported that the amount of carbofuran required to effect a 50% reduction in
cholinesterase activity was 0.19 ppm. Treated fish showed the following sequen-
tial signs of toxicity: hypoactivity , lethargy, body paralysis, scoliosis,
loss of equilibrium, opercular and mouth paralysis followed by death.
The signs and symptoms of toxicity that appeared in 3 species of fish during
tests to determine the TI^ of a formulation (Furadar£)lOG) were reported by
Schoenig (1967) as follows:
Rainbow trout; 96 hr TLn, -4.0 ppm
Signs at: 1 ppm No signs observed.
1.8 ppm Hypoactivity.
3.2 ppm Hypoactivity, increased respiration, and
intermittent loss of equilibrium.
5.6 ppm Hypoactivity, intermittent loss of equili-
brium, convulsions, gasping mouth, dis-
tended operculum, increased respiration.
Channel catfish; 96 hr TL,,, - 4.1 ppm
Signs at: 1 ppm No signs noted.
98
-------
1.8 ppm Hypoactivity, increased respiration, inter-
mittent loss of equilibrium.
3.2, 5.6, Hypoactivity, increased respiration, intermit-
and 10.OS/ tent loss of equilibrium, flaccidity (inter-
ppm mittent), convulsions, gasping mouth, disten-
ded operculum.
Bluegill; 96 hr TL,,, - 2.3
ppm
Signs at: 1.0 ppm
X • 0 PptD
3.2 and
5.6 ppio
No signs noted.
Hypoactivity, Increased respiration, intermit-
tent loss of equilibrium, intermittent flac-
cidity, intermittent convulsions
Same as 1.8.
£/ At this level, all fish were dead within 3 hr.
Field Studies - The U.S. Department of the Interior's Denver Wildlife Re-
search Center (Flickinger, 1975) studied the effects of carbofuran on fish and
other nontarget organisms in several areas in Texas where it was used to con-
trol larvae of the rice water weevil, Lissorhoptrus oryzophilus.
When carbofuran (as 3% granules) was applied to rice fields at the rate of
0.5 Ib Al/acre, some mortality of mosquito fish (Gambusia affinis) occurred 1
hr after treatment. Heavy mortality of mosquito fish, large-scale menhaden (Bre-
voortia patronus), Atlantic croaker (Micropogon undulatus), and European carp
(Cyprinus carpio) was found 24 and 48 hr after treatment.
In the rice fields where these observations were made, rice seeds were trea-
ted with another insecticide. It is not known if and to what extent the insecti-
cide in seed treatment may have contributed to the fish mortalities observed.
Table 20. Toxiclty of Technical Carbofuran and Its Formulations to Fish
Pllh
ec let
Formulae Ion
tested
Toxiclty
calculation
Toxtcity meaaurcd
Reference*
Channel c«t[Uh (Ict«luru« punctual) T«ch.
Channel catfllh (Ictnlurus punctatua) Tech.
Yellow perch (Perca flaveiceni)
City water Tech.
Yellow perch (Perca flavescens)
City water Tech.
Blueglll (Ixsponili aacrochlrm) Tech.
Mosquito fish (Cambuata aftlnlt) Tech.
Fathead minnow (Ptnephalei prone las)
City water Tech.
Fathead rtlnnow (Ptnephalea pronelai)
City water Tech.
24
24
24
96
96
96
24
96
LCM
"=50
"=50
LC50
LC5o
"=50
1*50
"=50
2.03 pp.. (-)
2,030 ug/i (-)
ISO Mg/i (126-179)
147 MS/1 (115-187)
80 ug/i (-)
300 Mg/Z (-)
Carter (1971)
Carter and Craves (1973)
Mluck (1972)
Mauck (1972)
Carter and Craves (1973)
Carter and Craves (1973)
1,320 ug/i (991-1,760) Mauck (1972)
1,180 pg/i (814-1,710) Hauck (1972)
99
-------
Table 20. Toxlcity of Technical Carbofuran and Ita Formulations to Flah (Continued)
Formulation
tested
Toxlcity
calculation
Toxleltv meaauro.d References
SCeelhead trout (Salno nalrdnerl)
Standard water
Steelhcad trout (Si Imp talrdneri)
Standard water
Brown trout (Salno trutta)
City water
Standard water
Brown trout (Salno trutta)
City water
Lake trout (Salvollnua namaycuah)
Lake trout (Salve I tnua naipavcuehl
Coho lllmon (Oncorhynchua klautch)
Standard water
Coho falmon (Oncorhynchui kllutch)
Standard water
Rainbow trout (Salno gilrdntrl)
Channel catflah (Ictalurua punctatua)
Blutglll (Ltponle macrochlrua)
Rainbow trout (Salno galrdnerl)
Chennel catfleh (Ictalurue ounctatua)
Blueglll (Lepomla imacrochlrua)
Tech.
Tech.
Tech.
Tech.
Tech.
Tech.
Tech.
Tech.
Tech.
Tech.
10 C
10 C
10 C
Tech.
Tech.
Tech.
24
96
24
24
96
Oft
yo
24
96
24
96
96
96
96
96
96
96
1*50
UCjO
"50
IC50
"=50
LC.
"•50
LCjo
LCSO
"=50
"50
TL,,
§
1,020 ug/I (635-1,640)
600 pg/i (436-826)
355 ug/* (242-521)
842 pg/1 (705-1,010)
280 pg/i (205-383)
560 pg/A (475-660)
164 pg/t (119-226)
164 ug/t .(U9-226)
530 wg/t (432-650)
524 tig/Z (-)
«.0 ppca (2.5-6.1)
4.1 pp. (2.4-7.0)
2.3 pp. (1.7-2.9)
0.28 ppei (0.23-0. JS)
0.21 ppa (0.16-0.28)
0.24 ppm (0.18-0.34)
Hauck (1972)
Hauck (1972)
Hauck (1972)
Hauck (1972)
Hauck (1972)
Hauck (1972)
Hauck (1972)
Hauck (1972)
Hauck (1972)
Hauck (1972)
Schoenlg (1967)
Schoenlg (1967)
Schoenlg (1967)
Schoenlg (1967)
Schoenlg (1967)
Schoenlg (1967)
Extensive search of the literature and contacts with several laboratories
known to be engaged in fish toxicity studies with pesticides failed to produce
additional reports on the effects, if any, of carbofuran on fish under field
conditions.
Commercial labels of carbofuran 10% granules carry the following warning
regarding fish toxicity:
This product is toxic to birds, fish, shrimp, crab and other
wildlife. Birds and other wildlife in treated areas may be
killed. Keep out of lakes, streams, ponds, tidal marshes
and estuaries. Cover or incorporate granules which are
spilled during loading and which are exposed on the soil sur-
face in turn areas. Do not apply where runoff is likely to
occur. Do not contaminate water by cleaning of equipment
or disposal of wastes.
A similar warning is included in the labeling of the carbofuran 4 Ib Al/gal
flowable formulations.
Typical labels of carbofuran 2, 3 and 5% granules state: "This product is
toxic to fish and wildlife; keep out of lakes, streams, or ponds. Keep irri-
gation water out of lakes, streams, and ponds for at least 7 days."
Lower Aquatic Organisms -
Laboratory Studies - Carter and Graves (1973) studied the acute toxicity
of several commonly-used insecticides (including carbofuran) to several species
100
-------
of fish, to the white river-crawfish, and to bullfrog tadpoles. The crawfish
were seined from roadside ditches near the Louisiana State University and
placed into large aluminum pans with a capacity of 2.5 1. The bullfrog tad-
poles were obtained by seining ponds of the Louisiana State University Fisher
ies Unit on the Ben Hur Plantation and tested in aquaria lined with polyethy-
lene bags. Statis bioassay tests were carried out in tap water (PH 7.0, hard
ness of 2 to 5 ppm) that was aged and aerated for at least 2 days. The bio-
assay procedures, conditions, and results were as follows:
Procedure, condition Whlte rlver_ Bullfrog
and re3ult9 _ crawfish tadpole
Mean weight of test animals, g 0.7 34
Number of animals per container 3 in'
Replications per dose 5 2
Exposure time, hr 95 96
Test container volume, liters 05 20
Water temperature, C 26 23-26
Dissolved oxygen, ppm 9_U g,9
LC50, ppb 500 2700
™S °f the ®ther insecticides included in these studies ranged from
2 to 50,000 ppb for the crawfish, and from 270 to 185,000 ppb for the bullfrog
tadpole. The crawfish was more sensitive to all insecticides tested than the
bullfrog tadpole. In comparison to the other insecticides, carbofuran ranged
intermediate in toxicity to both test animals.
In model ecosystem studies (reported in greater detail in the section on
Bioaccumulation and Biomagnification) , Sangha (1972) and Yu et al. (1974) found
that carbofuran was highly toxic to the lower aquatic organisms with which the
test tanks were stocked, including fresh water clams (Corbicula manilensis) .
fresh water crabs (Uca minax) , frogs (species not identified) , snails (Physa
species) , and water fleas (Daphnia magna) . Most of these organisms were killed
shortly after sorghum plants growing on the terrestrial part of the system were
treated with carbofuran at a rate equivalent to 1 lb Al/acre. Fresh aquatic
organisms were reintroduced into the test tanks every 5 to 7 days. Those
stocked 20 days after the application of carbofuran survived. The authors did
not report the concentration of carbofuran in the water during this period.
Sangha (1972) stated that the LC50 of carbofuran to Daphnia was found to be
20 ppb. — * -
Technical carbofuran did not appear to affect the eastern oyster (Crasso-
s^trea virginica) in 24-, 48-, and 96-hr tests of up to 1.0 ppm carbofuran.
However, technical carbofuran and Furadan 3G were highly toxic to pink shrimp
(Penaeus duorarum) . The 24-, and 48-hr EC50 values for the shrimp exposed to
technical carbofuran were 0.0068 and 0.0046 ppm, respectively. Furadan 3G at
15 Ib/acre caused 70% paralysis or mortality of the shrimp within 24 hr (Lowe
1970).
Field Studies - In the previously mentioned field studies on the effects
of the use of carbofuran 3% granules on rice (Flickinger, 1975) , there was heavy
101
-------
mortality of cricket frogs, crayfish, earthworms, and nontarget aquatic insects
which occurred generally between 1 and 45 hr after treatment. No details re-
garding the degree of mortality or the nontarget species involved are given in
the unpublished progress reports available at this time.
Effects on Wildlife
Laboratory Studies - The oral 11)50 of carbofuran ranged from 0.238 mg/kg to
5.04 mg/kg in 8 species of adult birds. The fulvous tree duck was most sensi-
tive and the bobwhite quail was most resistent (see summary of toxicity in
Table 21). Dermal toxicity was studied with 2 species (Quelea quelea and Pas-
ser domesticus) and in both cases was reported to be 100 mg/kg (Schafer et al.j
1973).
The age of mallard ducks was shown to affect their response to carbofuran
although the difference in the LD^g between the most sensitive age group and
the most resistant age group was only about twofold (Hudson et al.,1972). The
greatest susceptibility to carbofuran appeared to occur at hatching or shortly
thereafter and decreased to the minimum value around 1 week of age. The sus-
ceptibility then appeared to increase to 30 days of age and began again to ap-
proach maximum susceptibility at 6 months of age.
Table 21. Acute Toxicity of Carbofuran to Birds
Speclea
King-neck phcassnt (3 months)
(Pha» tanus colchlcus)
Mil I lad duck (3-6 months)
(Anas platyrhynchos)
Mallard duck
(Anaa platyrhynochos)
36-hr old
7-days old
30-days old
6-aontha old
Fulvoun trre duck (3-6 months)
(Dcndrocynna blcolor)
lobwhtce quail
(Collnua vlrelnlanus)
Japaneae quail (H) (2 weeks)
(Commit inpinlci)
Japanese quail (F) (2 weeks)
(Coturnlx laponlca)
Qua lea (Quelea quelea)
Houac sparrow
(Paster domc*ttcus)
Red-wing blackbird
(Aaelalus phoenlceus)
Quelea (Quelra ouelca)
House sparrow
(Passer domettlcu»)
Fornulatlon
teated
Tech.
Tech.
Tech.
Tech.
Tech.
Tech.
Tech.
Tech.
Tech.
Tech.
Tech.
Tech.
Tech.
Tech.
Tech.
Toxicity
calculation
Toxlctty meaaured
LDjO (oral) 4.15 mg/kg (2.38-7.22)
Kaierencea
Tucker and Crabtree (1970)
LD50 (oral) 0.397 mg/kg (0.315-0.5r.O) Tucker and Crabtree (1970)
U>i0 (oral) 0.370 mg/kg (0.283-0.484) Hudson et al. (1972)
LD50 (oral) 0.620 mi;/kg (0.530-0.744) Hudson et al. (1972)
LDjo (oral) 0.510 mg/kg (0.410-0.635) Hudson et al. (1972)
(oral) 0.415 mg/kg (0.333-0.516) Hudson et al. (1972)
Tucker and Crabtree (1970)
Tucker and Crabtree (1970)
Sherman and Ross (1969)
Sherman and Ross (1969)
Schafer et al. (1973)
Schafer et al. (1973)
Sctufcr et al. (1973)
Schaiar at al. (1973)
Schafer at al. (1973)
L0jO (oral) 0.238 ng/kg
LDso (oral) 5.04 mg/kg (3.64-6.99)
LDj0 (oral) 1.9 «g/kg (1.7-2.1)
LDjo (oral) 1.7 ng/kg (1.3-1.9)
LOjo (oral) 0.42 ng/kg (-)
LDio (oral) 1.3 ng/kg (-)
I.DJQ (oral) 0.42 me/kg (-)
LD50 (dermal) 100 ng/kg (-)
LOjo (dermal) 100 Kg/kg (-)
102
-------
The sequential signs of poisoning for Japanese quail administered techni-
cal carbofuran were lethargy, ataxla, quivering, and death. When death did not
occur, lethargy usually lasted 24 hr (Sherman and Ross, 1969).
Similar signs and symptoms of acute poisoning were reported for mallards,
pheasants, and bobwhite quail by Tucker and Crabtree (1970). The authors ob-
served the following signs to be associated with acute toxicity: ataxia, wings
crossed high over back, nutation, diarrhea, phonation, salivation, lacrimation,
immobility with wings spread, dyspnea, miosis, terminal wingbeat convulsions or
opisthotonos. Symptoms in survivors persisted up to 7 days. Mortalities oc-
curred as soon as 5 min after treatment.
Subacute toxicity of carbofuran to Japanese quail was studied by Sherman
and Ross (1969). Rations containing 50, 100, 200, 400 and 800 ppm carbofuran
were fed ad libitum to groups of quail (20/group) for 6 weeks. The feed con-
sumption, weight gain, and mortality were recorded over the entire feeding
period. The results indicated that carbofuran was not toxic at dietary levels
of 200 ppm or less, but was highly toxic when fed at 400 ppm or more for the
6-week feeding period. Feed efficiency was affected significantly at levels
greater than 200 ppm.
Although there appeared to be no sex difference in susceptibility to a
single oral dose, the male appeared more susceptible to continued subacute
doses. At the highest level fed (800 ppm) some females survived to the third
week while all males died during the first week. At 400 ppm all males died by
the fourth week while one-third of the females survived the entire 6-week feed-
ing period. During the feeding experiment, eggs were collected from females
over a 17-day period after reaching the egg-producing age. The results indi-
cate that fertility and hatchability were greatly depressed at levels of 200
ppm and higher. No abnormal embryos were observed among the fertile eggs fail-
ing to hatch, and there were no abnormalities observed among the newly hatched
quail.
Hudson (1972) studied subacute toxicity of technical carbofuran adminis-
tered orally by gelatin capsules to ring-necked pheasants. A group of 3 cocks
and 3 hens, 20 or 25 weeks old, were exposed daily for 30 days to 2.10 and
4.20 mg/kg/day. No mortality occurred at the lower rate. At 4.20 mg/kg/day,
1 male died after 8 doses, and 1 female died after 3 doses. Weight loss of
41 g was observed at 2.10 mg/kg/day and 75 g at 4.20 mg/kg/day during the first
week of treatment. The birds began to gain weight by the second week. By the
end of the 30-day period, weight gains in the pheasants were similar to the
controls.
Signs which appeared most severe during the first several days of treat-
ment included ataxia, hyperexcitability, tremors, jerkiness, tenseness, ata-
raxia, high carriage, hypoactivity, running and falling and chronic convulsions,
Brain acetylcholinesterase in the dead birds was inhibited 47.6%; survivors of
both levels showed little or no inhibition.
Symptoms of carbofuran toxicity to bobwhite quail, ring-necked pheasants,
Japanese quail and mallard ducks exposed to technical carbofuran and Furadan
103
-------
10G (Gough and Shellenberger,1972) were mild lethargy, hypoactivity, regurgita-
tion, and lacrimation; at higher levels terminal wing-beat convulsions and par-
tial paralysis were observed prior to death. Following necropsy, mild to moder-
ate hemorrhagic areas in the lung, stomach, esophagus, and crop were observed
in those birds found dead as a result of treatment. Surviving birds generally
appeared normal 3 to 4 days following treatment. The results of other studies
on subacute toxicity are summarized in Table 22. The mallard duck appeared to
be more susceptible to the toxic action of carbofuran than either pheasant or
Japanese quail.
Field Studies - The U.S. Department of Interior's Denver Wildlife Research Cen-
ter (Flickinger,1975) studied the effects of applications of carbofuran to rice
fields on a number of wildlife species, including birds. Observations were made
in 3 Texas study areas in 1970 and 1973 after applications of carbofuran 3% gran-
ules to rice fields at the rate of 0.5 Al/acre. Species of birds found dead or
sick at 17 and 24 hr after treatment were western sandpiper (Ereunetes mauri),
pectoral sandpiper (Erolia melanotos), and red-winged blackbird (Agelaius phoe-
niceus). The western sandpiper was found to be the species most susceptible to
carbofuran. All dead sandpipers contained from 1 to 8 carbofuran granules in
their stomachs. Mortality of all birds thus was believed to be largely the re-
sult of consumption of the carbofuran-treated granules, although it was pointed
out that in the study area, rice seeds were treated with another insecticide.
A field test was conducted by Harris and Applewhite (1969) to assess the
hazard of carbofuran to mallard ducks when applied as Furadan 3G under condi-
tions representing pre-flood rice application. Twelve pairs of adult mallards
(a pair consisting of one drake and one hen) were used for each formulation.
Furadan 2G was applied at the rate of 25 Ib/acre, 16 hr before water was allowed
to enter the field, and Furadan 3G at 20 Ib/acre. Daily feedings consisted of
8 oz of cracked corn scattered in the water. After 14 days of observation no
mortality or adverse affects were seen in any of the mallard ducks.
Furadan 10G was tested under field conditions simulating normal applica-
tion procedure to a prepared seed bed. Its effect upon adult bobwhite quail
at rates of 20, 60 and 200 Ib/acre was studied. After the 5-week experimental
period, no marked adverse effects on body weight of males and females were ob-
served other than fluctuations in weekly average body weights. Two males died
at the 60 Ib/acre level and 2 males at the 200 Ib/acre level. Intestinal enter-
itis was thought to be the cause of these 4 deaths. One-half of the surviving
males and females were necropsied and evidence of an intetstinal enteritis was
observed in several birds of all treatment levels. It was not established
that Furadan 10G was the.cause of the intestinal enteritis (Shellenberger,
1971).
In a field study with 14 pairs of 12-week-old ring-necked pheasants ex-
posed to Furadan 75 WP at a rate of 1.3 Ib/acre (1.0 Al/acre) for 14 days,
Stephens (1969) observed no mortality or adverse effects in any of the test
groups.
In another field- study, Zorb (1971) found similar results with Furadan
75 WP. Sprays of 1.0 Ib/acre were applied directly on pheasants, food or
104
-------
Table 22. Subacute Toxicity of Carbofuran to Birds
Species
Formulation
tested
Ring-neck pheasant 10G
(Phasianus colchicus) Tech.
Tech.
Days
exposure
7
5
5
Toxicity
calculation
LC5Q
LC50
LC
50
Toxicity
measured (ppm)
expressed m
(95% confidence limits)
9,600 (775-13,598)
438 (356-529)
573 (492-666)
References
Jackson (1968)
Hill (1974)
Stickel (1975)
Mallard duck
(Anas platyrhynchos)
10G
Tech.
Tech.
7
5
5
LC50
LC5Q
LC5Q
2,100 (1,455-3,034)
190 (156-230)
190 (156-230)
Jackson (1968)
Hill (1974)
Stickel (1975)
Bobwhite quail
10G
LC
50
10,250
Jackson (1968)
Japanese quail
(Coturnix japonica)
Tech.
Tech.
Tech.
5
5
LC
LC
6 (weeks) LC
50
50
50
438 (356-529)
437 (356-529)
200-400
Hill (1974)
Stickel (1975)
Sherman & Ross (1969)
-------
vegetation, and combinations of these 3 treatments. Pheasants that died had
high infestations of internal parasites. It was not established whether the
Furadan or the parasite killed the birds. There were no apparent effects on
reproduction in the treated birds that had received an application 8 months be-
fore and during egg laying. The author concluded that Furadan 75 WP causes no
ill effects on pheasants.
Carbofuran at 0.2 Ib Al/acre was applied to a 5 acre pond in the Kern
National Wildlife Refuge in California to simulate control of mosquito larvae.
Birds on or around the pond included sandpiper, killdeer, blackbirds, meadow-
larks, horned larks and lark sparrows. On an adjacent pond of the refuge
there were pintail, teal, sandpipers, dowitchers and yellow legs. There was
no evidence of dead or affected wildlife (Hagen,1971).
Field Investigations - The U.S. Environmental Protection Agency's Pesticide
Episode Review System (PERS) contains 3 reports of carbofuran episodes involv-
ing birds during the period January 1967 to April 1975 (EPA, 1975).
In 1972, a "bird kill" (not further defined) in Wisconsin was ascribed
to carbofuran. However, the report on this episode states that no evidence
exists to link carbofuran to the bird kill. A survey of 60 fields revealed
only 1 owl with (unspecified) pesticide residues.
In 1972 in California, 19 geese were found ill, and 15 of them died in an
alfalfa field 24 hr after application of carbofuran (formulation and rate not
given). The episode report states, however, that insufficient evidence exists
to link carbofuran to this incident.
On March 15, 1974, in California, 2,450 widgeon ducks, 2 Canadian geese,
and 1 mallard duck died in an alfalfa field located near a reservoir. The
alfalfa had been treated with carbofuran (4 Ib Al/gal flowable formulation) to
control the Egyptian alfalfa weevil (Hypera brunneipennis). Laboratory analy-
sis revealed that the deaths were not caused by a disease, and carbofuran was
present in the crops of the sample birds. Local officials felt that the pre-
sence of large numbers of birds was due to an unusual delay in migration. It
was concluded that, in this case, substantial evidence existed linking carbo-
furan to the bird kill.
The label of Furadarf^4 flowable, a liquid formulation containing 4 Ib of
carbofuran Al/gal, carries the following warning regarding bird toxicity:
"This product is toxic to fish, birds and other wildlife. Birds feeding on
treated areas may be killed."
The label for carbofuran 10% granular bears the following statement regard-
ing bird toxicify:
This product is toxic to birds, fish, shrimp, crab and other
wildlife. Birds and other wildlife in treated areas may be
killed. Keep out of lakes, streams, ponds, tidal marshes and
estuaries. Cover or incorporate granules which are spilled
during loading and which are exposed on the soil surface in
turned areas.
106
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Labels for carbofuran 2, 3, and 5% granular formulations state: "This
product is toxic to fish and wildlife .... Birds feeding on treated areas
may be killed."
Effects on Beneficial Insects
Bees - Bailey and Swift (1968) and Anderson et al. (1971), based on laboratory
and field data, classified carbofuran as "highly toxic" to honeybees. The term
"highly toxic" was defined as including severe losses which "may be expected if
the pesticide is used when bees are present at treatment time or within a day
thereafter."
These bee toxicity ratings are based on laboratory studies by Atkins et
al. (1973), as well as on more than 120 large-scale field tests on crops in
bloom and highly attractive to honeybees (Anderson et al.,1971). Most tests
were run on alfalfa, and a few were made on ladino clover, cotton, sweet corn,
and in peach and citrus orchards. The test insecticides were applied by air-
plane or by power ground sprayers. The publication by Anderson et al. (1971)
does not include experimental details pertaining specifically to the testing of
carbofuran in this program.
Atkins et al. (1973) summarized the results of toxicity tests in which a
large number of pesticides and other agricultural chemicals were studied with
regard to their effects on the honeybee (Apis mellifera). In a laboratory
procedure which primarily measures a chemical's contact effect, pesticides
were applied in dust form to groups of 25 bees per test dose, 3 replicates per
each of 3 colonies, for a total of 9 replicates per test dose. This procedure
permits determination of an U^Q value for each pesticide in micrograms of
chemical per bee. Honeybees (worker bees of uniform age obtained from the same
colony before treatment) were exposed to carbofuran for 48 hr at 80°F (26.7°C)
and 65% relative humidity. Under these conditions, the LI>50 of carbofuran was
0.15 jig/bee, placing it into Group I, ''highly toxic to honeybees."
In their test procedures, Atkins et al. (1973) also determined the slope
of the dosage-mortality curve for each pesticide tested, and recorded it as a
"slope value" in terms of probit units, Pesticides with a slope value of 4
probits or higher can often be made safer to honeybees by lowering the dosage
only slightly. Conversely, by increasing the dosage only slightly, the pesti-
cide can become highly hazardous to bees. Carbofuran rated a slope value of
4.31, indicative of a moderately steep dosage-mortality curve.
Atkins et al. (1970) studied the effects of a carbofuran application at
the rate of 1.0 Ib Al/acre on seed alfalfa on the Santiaga Ranch in Kern County,
California, in 1968. Carbofuran was applied as a spray in 10 gal of water per
acre by airplane to a non-replicated 16-acre plot in a field in good bloom
which contained 2 to 3 well-established colonies of bees per acre. The treat-
ment was made directly over the unprotected test bee colonies. Effects of the
treatment were determined from records of honeybee kill at the hive and in
field cages, colony strength and behavior, and field bee blossom visitation
rates. Observations were made for several days before, the day of, and for 4
107
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to 5 days after treatment. Dead bee records at the colonies were obtained by
daily counts of bees collected in traps placed on 6 colonies per treatment.
Cages of bees were placed in the fields at fly-over time to measure the initial
contact effect. Other cages of bees were placed in the treated areas at inter-
vals after treatment to study residual fumigation. Average summer weather con-
ditions prevailed during the test period.
Field bee visitation returned to normal after a drastic reduction for 5
days following carbofuran application. There was no significant kill in trapped
colonies placed in the carbofuran-treated field, 4, 7, or 10 days after treat-
ment. The carbofuran treatment killed 100% of the caged bees exposed during
treatment, but there were no fumigation effects at 1 to 2 hr post-treatment.
The authors concluded that bee colonies can be safely placed in carbofuran-
treated fields 4 days after treatment,
Field Reports on Bee Toxicity - The U.S. Environmental Protection Agency's
Pesticide Episode Review System contains several reports of injury to bees at-
tributed to carbofuran during the period January 1967 to April 1975 (EPA,1975).
On June 12, 1972, all honeybees in 36 hives were destroyed in Utah after
the application of carbofuran to a nearby alfalfa field, No further information
was given regarding application details, or how the bees were exposed. The
episode report states that insufficient evidence existed to link carbofuran to
this bee kill.
On March 27, 1973, a bee kill (not further defined) occurred in California,
apparently caused by bees carrying contaminated pollen back to the hives where
a progressive kill occurred. No details are given regarding the crop or type
of carbofuran application involved, and carbofuran was not verified as the
causative agent.
On June 1, 1973, in Wyoming, 192 honeybee colonies were "moderately dam-
aged" (no further details given) after carbofuran had been applied to a nearby
field to control alfalfa weevils. Formulation, method, and rate of application
were not given. Seven apiaries were involved. The episode report states that
insufficient evidence existed to link carbofuran to the bee damage.
Three additional episodes involving damage to bee colonies in Wyoming in
June of 1973 have been reported. In 1 case, 89 honeybee colonies from 2 api-
aries were moderately damaged. In another case, 63 honeybee colonies were
damaged severely, and 11 colonies were damaged moderately; 3 apiaries were in-
volved. In the third case, 33 bee colonies from 1 apiary were moderately dam-
aged. In all 3 instances, carbofuran was applied to nearby fields for the
control of alfalfa weevils. No details regarding the carbofuran applications
or the manner of exposure of the bees were given. Carbofuran was not verified
as the causative agent in any of these episodes.
On August 12, 1974, in Montana, 25 beehives were "affected" when bees had
to pass through a corn field recently treated with carbofuran (treatment details
not given) in order to reach an alfalfa field. There were 300 to 400 dead bees
108
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found lying around each hive. The episode report stated that circumstantial
evidence existed linking carbofuran to the incident.
The commercial label for Furadarr^ 4 flowable (containing 4 Ib of carbo-
furan Al/gal) includes the warning: "Do not move bees into alfalfa fields
within 7 days of application."
No bee toxicity statements are found in the labeling of carbofuran gran-
ular formulations.
Beneficial Parasites and Predators - Croft and Meyer (1973) studied the toxicity
of carbofuran to 3 different strains of the phytoseiid mite, Amblyseius falla-
cis, a common predator of spider mites in commercial fruit orchards in central
and eastern United States and Canada. Carbofuran 75% wettable powder was tested
against an organophosphate-resistant strain from Hartford, Michigan, a strain
selected with carbaryl for 9 yr, and a strain selected with carbofuran for 4
yr. The LC^Q'S of carbofuran as determined by a laboratory leaf-dip technique
were 0.002 Ib for the first strain and 0.006 Ib for the latter 2. This data
indicates that there was no appreciable development of resistance of the predator
to carbofuran.
Elsey (1973) investigated the effects of carbofuran and several other in-
secticides on the spined stilt bug, Jalysus spinosus, a foliage-inhabiting
predator of insect eggs and aphids on tobacco. Carbofuran 10% granules were
applied at the rate of 6 Ib Al/acre as a broadcast treatment before tobacco
was transplanted. Treated and untreated plots were randomized and replicated
3 times. The density of stilt bug adults in the carbofuran-treated plots was
slightly lower than in the check plots throughout the season, though the dif-
ferences were seldom statistically significant at the 5% level by Duncan's
multiple range test. The populations of stilt bug nymphs were much lower, and
nymphs were seldom found in the plots treated with carbofuran. Since some
stilt bug adults and eggs remained in the carbofuran-treated plots throughout
the season, the investigators attributed the lack of nymphs to the poisoning
and death of eggs or newly-hatched nymphs which fed on treated plant tissue or
came in contact with carbofuran residues brought to the leaf surface by tri-
chome exudates. Other predators were present but not abundant in the plots,
and there were no statistical differences between treated and untreated plots.
On 4 different dates in August, each of the test plots was infested with
30 eggs of the tobacco budworm, Heliothis virescens, from a laboratory culture
by gluing 3 eggs per plant to the underside of leaves on 10 plants in the center
2 rows of each plot. The plants were checked after 48 hr for indications of
insect predation, and for missing and normal eggs. Egg losses caused by pre-
dators with chewing mouthparts were not included, In this test, the predation
of budworm eggs in the carbofuran-treated plots was significantly lower than
in the check plots (at the 5% level by Duncan's multiple range test) on 3 of the
4 test dates.
109
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Interactions with Lower Terrestrial Organisms
Flora - The effects of carbofuran and 3 other nematicides on microorganisms in
soil were studied by Tu (1972) in experiments conducted with Delhi loamy sand,
a typical agricultural soil in southwestern Ontario. The soil contained 0.81%
organic matter and 0.03% nitrogen, and had a moisture-holding capacity of 27%,
and pH of 8.2. Carbofuran was added to the soil at the rates of 1 and 5 ug/g of
soil. Reagent grade peptone and elemental sulfur powder were added to the soil
samples at 1,000 ug of nitrogen or sulfur per g to measure ammonification and sul-
fur oxidation, respectively. Oxidation of ammonium from soil organic nigrogen was
studied by nitrification. The experimental mixtures and controls were held in 0.5
pint milk bottles closed with polyethylene film. Soil moisture was maintained at
60% of capacity. The treatments, in duplicate, were incubated 1 week in the lab-
oratory at 28°C for ammonification, 1 and 2 weeks for nitrification, and 4 weeks
for sulfur oxidation. Changes in population of soil microorganisms were deter-
mined after 1, 2, 4, 8, and 12 weeks.
Plate count data indicated that neither carbofuran nor any of the other 3
nematicides affected fungal population drastically. Five ug/g of carbofuran
slightly depressed fungal population 1, 2, and 4 weeks into the experiment. At
8 and 12 weeks, there were no significant differences in the fungal counts be-
tween carbofuran treatments and untreated controls. The higher rate of carbo-
furan significantly decreased bacterial populations during the first week of in-
cubation, but they subsequently recovered to levels at or above those found in the
controls. Plate counts in the controls showed a decrease in fungal and bacterial
populations during the 12-week incubation period. The carbofuran treatments gene-
rally had no significant effects on ammonification or nitrification of ammonium
from soil organic nitrogen. Oxidation of elemental sulfur was depressed signifi-
cantly by both carbofuran treatments.
Tu (1972) also measured the soil microbial respiration using the Warburg
technique. Oxygen consumption from decomposition of native organic matter was
greater in the carbofuran treated soils than in the controls. Oxygen consumption
increased as carbofuran concentrations were increased in soils with and without
supplemented glucose-carbon. The author concluded that indigenous soil microor-
ganisms can tolerate carbofuran and the other nematicides tested.
In further experiments with the same soil and with carbofuran at the same
rates (1 and 5 ppm), Tu (1973) added temperature as another variable. Treated
soil samples were incubated at 5 and 28°C. Fungal and bacterial populations
were counted 2, 14, 28, and 56 days after incubation, soil respiration with and
without glucose was measured, and effects of the treatments on ammonification
and nitrification were determined. Carbofuran again did not significantly affect
bacterial or fungal counts, ammonification, nitrification, mineralization of soil
organic sulfur, or oxidation of mineral sulfur. The carbofuran treatments did
not significantly decrease oxygen consumption from the decomposition of indig-
enous soil organic matter at either temperature. However, there was a marked
respiration increase in soils without supplemental glucose-C at 30°C with the 5
ppm carbofuran concentration. The author ascribed this to readjustments of mi-
croflora and ascendancy of certain groups and species following the depression
of competitors and antagonists, resulting in increased microbial activity.
110
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Harnish and Wendler (1972) investigated the effects of carbofuran on oxygen
uptake by microorganisms in the soil. Topsoil treated with Furadan 10G at a
rate of 100 ppm and 10 ppm AI was added to flasks (100 g of soil per flask).
Sufficient water was introduced to bring the samples to 60% of their moisture-
holding capacity. Using a Gilson Differential Respirometer and standard mano-
metric techniques, oxygen uptake was observed for an incubation period of 85 hr.
The data in Table 23 indicates that Furadan 10G at 100 and 10 ppm AI had no
noticeable influence on soil respiration. Oxygen uptake in both Furadan treat-
ments was slightly higher than the untreated check. The authors suggest this
could indicate "slight degradation of carbofuran or one of the components in the
formulation."
Table 23. Effect of FURADAN 10G on Oxygen Uptake in Field Soil
Oxygen Uptake (ul) at Specified Incubation Period^.'
Substrate8/ 1 Hr 2^5 Hr 4.5 Hr 60 Hr 85 Hr
FURADAN 100 ppm 66 36.4 45,2 43.4 44.2
FURADAN 10 ppm 3.0 32.8 34,0 30.8 32.4
GLUCOSE 200 ppm 30.2 108.4 152.6 172.2 229.8
FURADAN 100 ppm
GLUCOSE 200 ppm 37.8 104.0 139.6 161.6 198.4
FURADAN 10 ppm
GLUCOSE 200 ppm
Untreated
31.2
0.0
92.2
22.2
127.0
24.0
138.6
11.2
186.6
20.5
— FURADAN applied as 102 Granules, rate expressed in ppm active ingredient
carbofuran.
>_/ Incubated at 25°C; 5 g soil.
Source: Harnish, W. N., S. J. Wendler, FMC Corporation, iti Studies of the
impact of carbofuran on the environment, 1972.
When glucose was added to the untreated soil, respiration was stimulated,
indicating metabolism of the substrate by soil microorganisms. The addition of
Furadan 10G to the soil containing glucose had little effect on soil respiration.
Lin et al. (1972) studied the effects of carbofuran and several other in-
secticides on soil nitrification, growth of legume seedlings, and growth of 4
species of rhizobia bacteria. Tests were carried out in a Bearden loam soil
without previous record of insecticide application. Carbofuran was added at
rates of 5, 50, and 500 ppm. Moisture-holding capacity was adjusted to 60%,
and the treatments were incubated in 250 ml flasks capped with plastic film
at 30°C.
Ill
-------
Carbofuran had no effect on nitrification at any of the tested concentra-
tions. Tested by the disc-inhibition method on a yeast-mannitol agar, carbo-
furan at 2 and 20 pi/disc had no effects on the growth of Rhi zobium meliloti or
R. japonic urn, but there was some inhibiting effect on R. legujninosarum and R..
trifolii.
The effect of carbofuran on the growth of legume seedlings was tested by
growing sweet clover and alfalfa in disposable plastic pouches in 25 ml of nu-
trient solution to which carbofuran was added at 5, 50, and 500 ppm AI. After
germination of the seeds, 1 ml of 1:5 (w/v) Nitragin AB, a preparation of nodu-
1.-iting bacteria, was distributed evenly over the seeds as an inoculum. Untreat-
ed control seeds were grown with and without Inoculum. The plants were allowed
co grow for 30 days under artificial light on a 12 hr on, 12 hr off photoperiod.
The average dry weight of all plants was determined at the end of the 30-day
period. The results in the carbofuran series, expressed as average dry weights
ol plants in milligrams, were as follows:
Carbofuran
concentration Alfalfa Sweetclover
5 ppm 11.8 9.2
SO ppm 6.1 5.6
500 ppm 2.6 2.2
0 inoculated 12.6 7.9
0 noninoculated 6.0 5.6
This data indicates that, at the field use rate (5 ppm), carbofuran did not
significantly affect the growth of the seedlings, while at 500 ppm, plant growth
rates were well below those of both controls. Fifty ppm applications of carbo-
furan resulted in growth rates closely comparable to the noninoculated controls.
Hubbell et al. (1973) studied the effects of carbofuran and several other
pesticides on the relative numbers of microbes and on nitrification in soil.
The pesticides, alone and in combinations, had been applied to field plots at
times and rates of application approximating agronomic practices in the growing
of shadeleaf tobacco in the area of Quincy, Florida. The field plots were laid
out on a Norfolk loamy fine sand prepared and fertilized for the growing of
tobacco. Carbofuran was applied at the rate of 10 Ib of Al/acre (11.2 kg/ha).
Numbers of microorganisms and nitrification were monitored at 2-week intervals
for 16 weeks following application.
The carbofuran treatments somewhat depressed the relative numbers of fungi,
bacteria, actinomycetes and algae, although none of these effects were statisti-
cally significant at the 5% level. The rate of nitrification as determined by
nitrate nitrogen appeared to be reduced by about 25% during the first 8 weeks
in the carbofuran-treated plots, but the reduction was not statistically signi-
ficant at the 5% level. In all treatments, there was a drastic reduction in
nitrate nitrogen after 8 weeks. This reduction followed a heavy rainfall and
was apparently due to leaching of the nitrate. There were no significant differ-
ences between treatments during the remainder of the experimental period.
112
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Kulkarni et al. (1974) studied the effects of carbofuran and 3 other insec-
ticides, applied to soil at their recommended rates, on the symbiosis of Rhizo-
biurc species with "groundnuts" (for example, peanuts), Arachis hypogaea. Carbo-
furan (type of formulation not given) at the rate of 16 kg/ha (14.2 Ib/acre) was
applied to red loamy soil of pH 6.8 in pots. (It is not clear whether the appli-
cation rate is given in terms of active ingredient or formulated product.) Pea-
nut seeds inoculated with a 5-day-old culture of Rhizobium species were sown in
plots maintained under greenhouse conditions. Eight weeks after planting, some
plants were removed carefully, and the number and fresh weight of root nodules
were determined. The leghaemoglobin concentration of freshly excised nodules
was determined. At harvest time, pot yield and dry matter weight of plants were
recorded, and the nitrogen content of the plants was determined.
The carbofuran treatment had no significant effect on nodule numbers, but
increased the fresh nodule weight in terms of milligrams per plant, and the
average weight per nodule. Carbofuran had no significant effect on the leghae-
moglobin content in the nodules, nor on the yield of peanut pods per plant, the
dry matter weight, or the nitrogen content of the plant. The authors concluded
that carbofuran, used at normal field rates, has no harmful effect on symbiotic
nitrogen-fixing bacteria and peanut growth.
Harnish and Wendler (1972) conducted a study to determine the influence of
carbofuran on the growth rate of 2 soil-borne fungi, Fusarium oxysporum f. ly_-
coperisici qnd Pencillium digitatum. Carbofuran (5 ppm) was added to 25 ml of
liquid broth medium in a sterile flask. The flasks were inoculated with a 4 mm
block of agar plus mycelium and incubated on a gyratory shaker at room tempera-
ture. The mycelium and spores were harvested daily, washed, dried in a desic-
cator for 48 hr, and then weighed.
The JP._ digitatum grown in the carbofuran-treated medium produced a maximum
amount of growth (208 mg) on the third day, whereas the untreated control reached
a maximum (178 mg) on the second day. Conversely, F. oxysporum f. Ivcopersici
grown in the medium containing 5 ppm carbofuran weighed 160 mg compared to 209
mg in the untreated control. The authors concluded that carbofuran slightly in-
hibits the growth of F. oxysporum f. lycopersici and slightly increased the dry
weight of P^ digitatum.
In another test, Harnish and Wendler (1972) studied the effects of carbo-
furan on microbial populations using a dilution plate technique. Soil was
treated with 1,000 ppm AI carbofuran and then incubated at room temperature for
24 hr. The number of fungi on potato dextrose agar and the number of bacteria
in nutrient agar were reported as follows:
Soil Treatment Average Number of Microbes/g soil x 104
Bacterial? Fungi*?/
Carbofuran 1,000 ppm 114 14
Untreated check H5 13
a/ Isolated on nutrient agar
b/ On potato dextrose agar (PDA)
113
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Counts per gram of treated soil did not differ significantly from the untreated
check.
Chen et al. (1974) conducted a laboratory test to determine the effects of
several organophosphate and carbamate insecticides on 2 commercial preparations
of Bacillus thuringiensis. Carbofuran (75% wettable powder) was added to a
thoroughly mixed suspension of B^ thuringiensis at a concentration of 0.47 g
AI/100 ml. The test surface, a sterile membrane filter of cellulose acetate,
was inoculated with 0.2 ml of the test solution and allowed to incubate. Spore
numbers on the filters were determined at 0, 2, and 4 weeks. Three replicates
were used for each time interval.
Their results indicated that the addition of carbofuran to the commercial
formulations of B. thuringiensis did not affect the survival of the bacteria on
inert surfaces. Several of the insecticides tested, however, adversely affected
the survival of B. thuringiensis.
Fauna - Thompson and Gore (1972) investigated the effects of carbofuran and a
number of other insecticides on springtails, Folsomia Candida, soil-inhabiting
insects of the order Collembola that contribute to the breakdown of organic
matter. To determine the direct contact toxicity of technical-grade carbofuran
(95 to 99% purity), it was applied in a volume to volume ratio of 19:1 acetone:
olive oil solvent mixture in a Potter spray tower. The spray was applied for
15 sec and 15 more sec were allowed for the droplets to settle. Because temper-
ature can greatly affect the toxicity of insecticides, tests were run at 2 dif-
ferent pre treatment and post treatment temperatures, 13 and 24°C. The contact
toxicity of carbofuran to _F. Candida was as follows:
Pre-treatment and post- Average corrected % mortality caused by
treatment temperature (°C) indicated % carbofuran solution
0.001 0.01 0.1 1.0
13 0 45 100 100
24 0 30 95 100
In further tests, Thompson and Gore (1972) determined the toxicity to
springtails of carbofuran applied to a Plainfield sand that contained 6.5% wa-
ter, 0.7% organic matter and, in the mineral fraction, 93.5% sand, 4.9% silt,
and 1.7% clay. Carbofuran was applied to the soil in 9 different concentra-
tions in chromatographically distilled n-pentane at 21 - 2°C. Five g aliquots
of treated soil were kept at 2 different pretreatment temperatures for at least
2 hr before 10 springtails per vial were placed on the treated soil. The test
vials were kept in darkness for 24 hr before dead insects were counted. The
following results were obtained with carbofuran in this test series:
Test Average corrected % mortality caused by indicated carbo-
temperature ("C) furan concentration in soil (ppm dry weight soil)
13
24
114
0.005
5
0
0.01
5
0
0.05
5
20
0.1
35
95
0.5
100
100
1.0-50
100
100
-------
This data shows that the direct contact toxicity of carbofuran to F. candi-
da was not significantly affected by temperature. The carbofuran soil treatments
were more toxic to the test insects at the higher temperature.
Kring (1969) studied the effects of carbofuran on the earthworm (Lumbricus
terrestris). Carbofuran and the other materials were applied in the form of 10%
granules in a band 20 cm wide over the row and raked in lightly. Shade tobacco
was planted in the rows the day following the treatment. Dead and dying earth-
worms on the surface were observed and counted in the fields 6 days after the
treatment. Only earthworms on the surface of the soil in the planted row were
counted. Each plot consisted of a single row 6 m long, and the different treat-
ments were randomized and replicated 4 times. The following numbers of dead
earthworms were found in the carbofuran treatments:
Carbofuran rate
kg/hectare = Ib/acre Number of
(active ingredient) dead earthworms
0 0 0.25
0.56 0.5 8
1.12 1.0 12
2.24 2.0 20
4.48 4.0 20
Observations indicated that all earthworms in the immediate area of the
carbofuran treatments at 2.0 and 4.0 Ib/acre were killed. Blow flies (Lucilia
species) attracted to the decaying earthworms were killed in large numbers in
the plots treated with carbofuran.
Thompson (1971) and Thompson and Sans (1974) studied the effects of carbo-
furan and other insecticides on the numbers and biomass of earthworms (Lumbri-
cidae) in pasture. The experiment was set up in a trefoil pasture that had not
been treated with herbicides or insecticides for at least 5 yr. Carbofuran
(from a wettable powder formulation) was applied at the rate of 4.48 kg of Al/ha
(4.0 Ib/acre) in a Latin square design to plots 10 ft square. Each treatment
was replicated 10 times, and there were untreated strips 6 ft wide between plots
and around the experimental area. Three weeks after treatment, the arithmetic
mean of the number of earthworms found in 20 2 ft square wooden quadrats was 3.1
in the carbofuran-treated soil, compared to 17.9 in the untreated control, a
reduction of 82.7%. In the carbofuran plots, the number of worms found in 20
quadrats ranged from 0 to 7, compared to 9 to 32 in the untreated control. The
difference between the mean number of worms per quadrat between the carbofuran
treatment and the untreated control was significant at p >0.01. When earthworm
counts were taken again 52 weeks after treatment, there were no statistically
significant differences (p = 0.05) between numbers of earthworms in the carbo-
furan-treated and untreated plots.
115
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The biomass of earthworms in the carbofuran-treated plots (in grams of
fresh weight of the worms from 20 quadrats) 3 weeks after treatment was 160.3,
compared to 404.6 in the untreated control, a reduction of 60.4%. The differ-
ence between the carbofuran-treated plots and the untreated control was signifi-
cant at p >0.01. There were no statistically significant differences in the
mean earthworm biomass per quadrat between the carbofuran-treated and the un-
treated plots 52 weeks after treatment.
Chemical analysis of the earthworms obtained 3 weeks after treatment from
the carbofuran-treated plots revealed no residues of carbofuran or its metabo-
lites above the limits of detection of the analytical method. Samples were
analyzed by gas chromatography, but the limits of detection for carbofuran were
not given.
Stenersen et al. (1973 and 1974) studied the toxicity and mechanism of ac-
tion of carbofuran in the earthworm (Lumbricus terrestris), and its metabolism
by this species. Earthworms were obtained from a-live bait dealer who had
collected them largely from London, Ontario area golf courses, which would in-
dicate that the worms had been exposed to many herbicides and insecticides. All
worms used for experiments were sexually mature (showed well-developed clitella)
and weighed between 3 and 5g. Worms were injected with dosages of carbofuran
between 1.0 and 5.0 ug (0.5 to 1.55 mg/kg), and the LD^Q was determined to be
1.3 mg/kg. When carbofuran was mixed in the soil (sterilized moistened loam;
organic content approximately 20%, water content 10%, peat moss added at 1.5
by volume), the LC^Q over a 5-day period was 12.2 ppm.
In in vitro cholinesterase studies of the inhibition of earthworm cholin-
esterase, the carbofuran concentration producing 50% enzyme inhibition was
found to be 10~6-31 (0.5 ppm). Two organophosphates, tested under the same
conditions, depressed earthworm cholinesterase more severely, while a methyl
carbamate insecticide inhibited it less than carbofuran. Cholinesterase recov-
ery in the live carbofuran-treated worms occurred more rapidly than in those
treated with other chemicals tested. Characteristic signs of carbofuran poi-
soning were rigidity, immobility, sores and segmental swellings; only rigidity
and immobility were observed after treatment with the organophosphorus insecti-
cides.
In tests with ring-labeled l^C carbofuran, it was determined that earth-
worms excreted carbofuran mainly as the unchanged parent compound, its hydroxy-
lated analog (3-hydroxycarbofuran), and at least 2 unidentified products. The
earthworms reabsorbed excreted insecticide and its metabolites from a sand
medium. Earthworms excreted less than 10% of the total amount of carbofuran
taken up originally. Comparing these observations with carbofuran metabolism
studies on other organisms by other authors, Stenersen et al. (1973) concluded
that the earthworm would appear to metabolize carbofuran initially in a similar
fashion to both plants and other animals. They further suggested that the toxi-
city of carbofuran to earthworms may be caused by factors other than cholines-
terase inhibition.
Oilman and Vardanis (1974) performed additional studies on the toxicity
and metabolism of carbofuran in the common dew worm (L. terrestris), and a
manure worm. (Eisenia foetida), after seemingly conflicting reports on the
116
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effects of carbofuran on earthworms had been released by the manufacturer (FMC
Corporation). Oilman and Vardanis discovered that the apparent discrepancy was
not valid; FMC had used as its test animal a species that is not strictly an
earthworm, i.e., E. foetida, a worm that inhabits animal dung and manure and
feeds on organic debris without ever surfacing. By injection, carbofuran was
about 6 times more toxic to L,^ terrestris than to E_._ foetida. When applied to
the soil, carbofuran was twice as toxic to L^ terrestris as to E^. foetida.
When placed in soil treated with carbofuran at 4 ppm, coiling was always
observed in both species. Eighty percent of the _L^ terrestris were found coiled
at the soil surface within 24 hr while E_^ foetida showed some coiling, but re-
mained buried in treated soils. In experiments designed to study the ability of
the 2 species to detect carbofuran-treated soils, it was observed that carbo-
furan appeared to repel E^_ foetida but not L^ terrestris. The authors pointed
out that L. terrestris, which comprises a large percent of the detritus feeder
biomass in Ontario, seems to be immobilized by carbofuran, as demonstrated by a
marked inability to leave treated soils, leaving affected earthworms susceptible
to predation and dehydration.
In uptake and excretion tests, the total amount of carbofuran taken up by
both worms after 6 hr was similar when compared on the basis of micrograms per
gram of worm. However, E. foetida excreted 95% of this material in 48 hr com-
pared to only 10% excreted by L^ terrestris. Approximately half of the material
excreted by E. foetida was unchanged insecticide. Of the carbofuran metabolized
by the worms in a 48-hr period, E. foetida retained only 5% as metabolites, where-
as L. terrestris retained 87%.
The authors pointed out that this comparative study emphasizes that great
care must be taken in selecting truly representative species for the evaluation
of the ecological effects of chemicals.
Residues in Soil
Laboratory and Greenhouse Studies - Onsager and Rusk (1969) studied the residual
toxicity of carbofuran and other insecticides to the sugar beet wireworm (Limo-
nius californicus) in a laboratory experiment. Carbofuran 10% granules were
applied at an initial concentration of 1.85 ppm, the field application rate sug-
gested by the manufacturer. The insecticide was thoroughly incorporated into the
soil ("Sagemoor sandy loam soil"). The treated soils were buried outdoors in
specially prepared steel casings in such a manner that the level of soil inside
the casing was flush with the level of the soil outside. The soils were kept
moist by adding water to each casing twice each week. Soil samples were taken
immediately after mixing and at 2, 4, and 6 weeks thereafter. All samples were
subjected to bioassay with field-collected, sugar beet wireworms. The results
observed in the carbofuran treatments were as follows:
Weeks after
treatment Percent mortality after indicated days of expoBure
0
2
4
6
117
6-8
SO
40
34
36
13-15
56
71
38
83
20-22
74
75
91
27-29
100
83
95
>41
85
-------
Chemical analysis of the carbofuran-treated soil showed that under the con-
ditions of this test, carbofuran had an initial half-life of 36 days. About 20%
of the initial concentration of carbofuran was still present in the soil 8 weeks
after application.
Harris (1969b) employed a laboratory bioassay procedure to assess the per-
sistence of biological activity of carbofuran and other insecticides in soils.
Two soil types were used: Beverly fine sandy loam (pH 7.2, 1.5% organic matter,
76.6% sand, 21.1% clay), and a muck soil (pH 6.5; 64.6% organic matter; and 35.4%
mineral content consisting of 14.5% sand, 38.8% silt, 46.7% clay). When treated
with insecticide, the sandy loam contained 12.3 and the muck 164.0% water.
First-instar nymphs of the common field cricket, Acheta (Gryllus) pennsylva-
i-icus, were used as test insects. The LD5Q of carbofuran to this insect was
2.34 ppm in the sandy loam, 74.2 ppm in the muck soil. Equally large differ-
ences in toxicity between the 2 types of soil occurred for the other 9 insecti-
< ides investigated in the same manner. Soil persistence tests were run by ap-
plying carbofuran and the other insecticides to the 2 soils at levels of 4 times
the LD50. Samples were bioassayed at 0, 1, 2, 4, 7, 12, 16, 24, 36, and 48
veeks after treatment. In the sandy loam soil, the biological activity of car-
bofuran disappeared within 16 weeks, placing it into the "moderately residual"
troup ranging in between "highly residual" and "slightly residual" insecticides.
In the muck soil, the biological activity of carbofuran persisted for about 24
weeks.
Campbell et al. (1971) studied the influence of organic matter content of
toils on the efficacy of carbofuran and of several other insecticides on the
wireworm, Melanotus communis, in the laboratory, following up on reports from
' he field about difficulties in controlling this insect. Carbofuran and the
ether insecticides were applied to Bladen silt loam soil (9.0% organic matter),
organic loam soil (7.4% organic matter), and loamy fine sand (3.5% organic mat-
ter) . Late-instar wireworm larvae collected from these soils in problem fields
were placed in their respective native soils which had previously been treated
with the test insecticides, including carbofuran from a 10% granular formulation
at the rate of 1 and 2 Ib Al/acre. Wireworm control of some of the other insec-
ticides tested decreased with an increase in the organic matter content of the
test soils, but carbofuran produced very low or no mortality of wireworms in any
of the soils for reasons which the authors apparently did not investigate.
The persistence of the biological activity of carbofuran and 6 other in-
secticides in soil was studied by Thompson (1973), using Folsomia Candida, a
soil-inhabiting species of Collembola, as test insect. Equitoxic dosage rates
of the test insecticides were thoroughly incorporated into Plainfield sand con-
taining 6.5% water. The mineral fraction consisted of 93.5% sand, 4.9% silt,
1.7% clay, and there was 0.7% organic matter. For each insecticide, the appli-
cation rate was the lowest concentration that would cause 100% mortality of F.
i andida in the soil in 24 hr, that is, 0.5 ppm in the case of carbofuran. Two
parallel sets of the experiment were run at 2 different temperatures, 13 and
24 - 1°C. Soil samples were bioassayed 1, 2, 4, 8, 12, and 16 weeks after
treatment of the soils. Carbofuran killed 100% of the test insects at both
temperatures throughout the entire test period. The author concluded that the
concentration of carbofuran employed was too high, probably twice the LDgg, and
118
-------
that carbofuran did not degrade to less than the LDgg under the conditions of
the experiment. Based on comparative data, the author classified carbofuran
as "moderately persistent."
Getzin (1973) studied the persistence and degradation of ^C-carbofuran in
4 different soil types under laboratory conditions. The physical and chemical
properties of the 4 soils used were as follows:
Soil
Ritzville silt
loam
Sultan silt
loam
Chehalis clay
loam
Organic
(muck)
Organic
matter (%)
1.0
3.0
7.2
40.0
7.8
6.0
6.2
5.9
Cation
exchange
capacity
(meq/100 g)
17.8
13.4
32.8
49.1
Moisture
Bulk equivalent
density (% of dry Clay
(g/cm3) wt) (%)
1.2 20 19
1.2 20 17
1.0 34 36
0.6 79
To determine the extent, if any, of microbial degradation, portions of these
soils were radiation-sterilized. Initially, the irradiated soils were sterile,
but they became contaminated with airborne spores during insecticide application
and subsequent handling procedures. ^-^C-carbonyl carbofuran was applied to ir-
radiated and nonirradiated samples of the 4 soils at the rate of 20 >ig/cm3 and
moisture levels were adjusted. Replicated samples of each soil were put into
wide-mouth pint jars that were then equipped with C02 traps and kept in a con-
stant-temperature room. Water was added periodically to maintain the moisture
content within 5% of the original level. The NaOH in the C02 traps was replaced
at 2- to 4-week intervals, and the absorbed C02 was precipitated and assayed for
14C02. Duplicate 20-cm3 soil samples were removed for analysis at the desired
intervals. Table 24 presents the results of this test in the 4 different soils
at 0, 4, 8, 16 32, and 54 weeks after treatment. The parent compound, expired
C02, and nonextractable residues in the soil accounted for most of the radio-
activity. Water-soluble degradation products amounted to less than 1% of the
extractable radioactivity in all soils throughout the experiment and are not in-
cluded in Table 24. The data showed that the persistence of carbofuran varied
considerably between soils; the approximate times required for 50% loss of carbo-
furan were about 4 weeks in the Ritzville silt loam, 8 weeks in the Chehalis
clay loam, and more than 54 weeks in both the Sultan silt loam and the organic
soil. Sterilization had no effect on the degradation rate of carbofuran in the
Ritzville silt loam, and only a slight effect in the Sultan and organic soils,
but significant effect in the Chehalis clay loam. Most of the -^C from the de-
graded carbonyl-labeled carbofuran was expired as -
In a second test, Ritzville silt loam and Chehalis clay loam were treated
with !*C ring-labeled carbofuran at 5 ug/cm3. The initial half-life of ring-
labeled carbofuran in the 2 soils corresponded closely to the degradation rates
for carbonyl-labeled carbofuran observed with these soils in the previous test.
The breakdown of ring-labeled carbofuran resulted in the accumulation of
119
-------
nonextractable soil-bound radioactivity and a gradual evolution of CC^. Only
small quantities of carbofuran phenol, an expected degradation product of the
insecticide, were recovered from treated soils.
When ^c-carbofuran phenol was added to Ritzville silt loam and Chehalis
clay loam at the rate of 5 ug/cm3, the compound was bound to the soils very rap-
idly. Nonextractable radioactivity amounted to 21 and 24% in the 2 soils imme-
diately after treatment, reaching a maximum of 70 to 80% of the applied rate 2
weeks after treatment. About 25% of the ^C added as carbofuran phenol was ex-
pired as ^002 within the 32-week experimental period. The soil-bound radioac-
tivity and extractable radioactivity decreased gradually at the same time.
The persistence of carbofuran in relation to soil pH was determined in
Sultan silt loam adjusted to 4 different pH levels and treated with carbonyl-
!4c-carbofuran at the rate of 4 mg/400cm3 of soil (10 ug/cm3) . Aliquot samples
were removed at intervals and assayed. Carbofuran was rapidly degraded at pH
7.8; there was a tenfold difference in the time required for 50% breakdown be-
tween the soils at pH 4.3 and 7.8. This data indicates that the short residual
life of carbofuran in the Ritzville silt loam (Table 24) was at least in part
the result of alkaline degradation.
Table 24. Radioactive Carbofuran Equivalents Recovered as Carbofuran,
Soil-Bound Residue, and Expired C(>2 from Irradiated and Honlrradlated
Soils Treated with ^C-Carbonyl-Labeled Insecticide at 20 ug/cn3
Weeks
after
treatment
M( Equivalents/cm3
Nonirradlated soil
Carbofuran
Soil-bound
of soil
Irradiated soil
CO? Carbofuran
Soil-bound
Ritzville silt loam
0
4
8
16
32
54
0
4
8
16
32
54
0
4
8
16
32
54
18.7
10.0
5.5
2.4
0.9
0.4
19.3
13.5
9.2
5.5
3.6
2.5
19.0
17.9
16.0
12.8
12.1
11.1
0.1
0.8
0.9
0.7
1.3
0.9
Chehalis
0
0
0.1
0.4
0.3
0.2
Sultan
0
0
0.1
0.3
0.3
0.2
0
7.1
10.2
13.9
15.6
15.8
clay loam
0
7.3
9.8
11.9
14.4
15.7
silt loam
0
1.2
2.2
3.8
5.9
7.9
18.2
10.8
6.0
2.2
0.9
0.4
19.2
18.4
17.6
15.5
14.0
11.1
18.8
.19.4
17.5
17.3
16.7
12.3
0.2
1.8
3.1
3.4
3.6
3.2
0
0
0.2
0.3
0.7
1.1
0
0
0.1
0.1
0.3
0.5
CO;
0
3.3
5.3
6.8
10.6
11.0
0
0.5
0.8
2.1
5.2
9.4
0
0.3
0.6
1.4
3.7
7.1
Organic soil
0
4
8
16
32
54
22.0 •
19.7
19.5
18.1
16.3
15.3
0
0
0.1
0.2
0.3
0.4
0
1.0
1.5
2.5
3.9
5.4
20.9
20.2
20.1
19.5
17.8
17.3
0
0
0.1
0.2
0.3
0.2
0
0.2
0.3
0.8
2.1
3.4
Source: Getzin (1973). Reprinted from Environmental Entomology by permission
of the publisher.
120
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Getzin (1973) concluded that rapid chemical hydrolysis is the primary route
of degradation of carbofuran in alkaline soils. A slower breakdown occurs in
acid and neutral soils, and is caused by both chemical and microbial degradation
mechanisms.
Stanovick (1968) studied the degradation of carbofuran in 3 soil types
(sandy loam, silt loam, and muck) treated with ^C-ring- and carbonyl-labeled
carbofuran at 2.0 and 9.0 ppm. Moisture content was maintained at 75% of field
capacity in the sandy and silt loam soils, and 85% of field capacity in the muck
soil. The soils were kept in wide-mouthed gallon jars at room temperature for
174 days. Fifty g samples were analyzed at various time intervals during the
study period. The soil was exhaustively extracted with methanol, and the radio-
activity in the extract was determined by liquid scintillation. Samples from the
last time interval were (a) acid-hydrolyzed and extracted with methylene chloride,
and (b) combusted by the Parr Bomb procedure.
The initial half-life of carbofuran under these conditions was 20 to 40
days. Carbofuran degraded fastest in the sandy loam and slowest in the muck
soil; it dissipated 3.0 half-lives in the sandy loam, 2.3 half-lives in the silt
loam, and 1.4 half-lives in the muck soil over the 174-day period.
Carbofuran was the only compound detected in the methanol and methylene
chloride extracts by thin-layer and gas chromatography procedures. At the 174-
day interval, the presence of 2,3-dihydro-7-hydroxy-2,2-dimethylbenzofuran resi-
dues was indicated in the Parr Bomb analysis, but this compound was not extract-
able from the soils by either methanol or acid hydrolysis. Acid hydrolysis,
followed by methylene chloride extraction, was found to be the most efficient
method for extraction of aged carbofuran residues.
Field and Combined Field/Laboratory Studies - Read (1969) studied the persistence
of carbofuran and several other insecticides in acid mineral soils in the labo-
ratory and in microplots in the field by a bioassay technique, using first-instar
larvae of the cabbage maggot, Hylemya brassjlcae. Soils used in the field inves-
tigations were Kildare sandy soil (pH 5.2) and Charlottetown fine sandy loam (pH
6.4). The Kildare soil was also used in the greenhouse study. The tests were
set up to simulate field conditions (banding 3/4 in deep in ridges) as closely
as possible. Carbofuran was applied as a 10% granular formulation.
The activity of carbofuran in the field microplots, measured by percent
mortality of H. brassicae larvae, was as follows:
Daye after Carbofuran concentration placed
carbofuran in the BO 11 (ppm)
application 3. 10 20 50
Kildare sandy soil
2 64 98 100 100
5 85 96 100 100
30 89 100 100 100
45 78 98 100 100
60 73 97 99 100
90 68 97 99 100
120 49 63 94 100
150 0 3 10 22
121
-------
98
98
90
97
88
91
0
100
99
96
99
93
90
0
100
99.9
99
100
100
100
8
4
100
100
100
100
100
100
32
12
Daya after Carbofuran concentration placed
carbofuran In the soil (ppm)
application 1 10 20 50
Charlottetovm fine sandy loam
2
5
30
45
60
90
120
150
Carbofuran, like most of the other insecticides studied, was more toxic to
the larvae 3 to 5 days after application than within the first 24 to 48 hr. Re-
duction in toxicity occurred somewhat more slowly in the greenhouse than in the
field. There was no marked difference in the rate of loss in toxicity in the
sandy or fine sandy loam soils, indicating that the texture of the 2 mineral
soils was not an important factor in toxicity degradation.
Read (1971a and 1971b) reported further observations on the activation,
deactivation, bioactivity and persistence of carbofuran and several other insec-
ticides in 2 other published articles. In the first of these (Readj1971a), field
microplots were set up as described in the earlier studies (Read, 1969, see above).
The test insecticides were spread evenly 3/4 in below the soil surface at a rate
equivalent to 100 ppm in the upper 1 in of soil. This concentration is somewhat
higher than the recommended commercial rate of application for carbofuran in the
area (60 to 70 ppm). At different time intervals after treatment, samples of
the treated soils were taken to the laboratory, mixed thoroughly, and diluted
serially with insecticide-free soil to obtain desired concentrations of toxicants
in a given volume of soil.
Bioassays with first larval stages of the cabbage maggot, H. brassicae,
demonstrated that carbofuran became biologically active soon after application.
It was the most toxic of the compounds tested, and its toxicity persisted longer
than that of several other insecticides tested at a given rate of toxicant per
acre. At 30 ppm, carbofuran produced 100% mortality of H. brassicae larvae for
at least 150 days; at 10 ppm, it remained 100% effective for about 80 days; at
3 ppm, close to 100% larval mortality was reached about 15 days after treatment,
persisting for only about 15 days. At 1.5 ppm, maximum larval mortality (about
50%) occurred 15 days after treatment and declined gradually thereafter, ap-
proaching zero 80 days after treatment.
Carbofuran was the only insecticide in the group that showed readily de-
tectable upward movement in the soil; flies resting on the surface of the car-
bofuran-treated soil were killed. In further studies of this observation, car-
bofuran was band-applied at different depths below the soil surface in ridged
greenhouse microplots. The times required for toxicants of carbofuran to reach
the soil surface were 1 week, 2 to 3 weeks, and 3 to 4 weeks, respectively, for
the 1/2-, 3/4-, and 1 in depth of insecticide placement. In a second greenhouse
test, dead flies were found on carbofuran-treated soil containing as low as 3
ppm of carbofuran.
Evidence that carbofuran toxicants actually moved into the surface soil
was demonstrated by removing the upper \ in of soil and testing it for toxicity
122
-------
by the cabbage maggot bioassay method. At the field recommended rate for cab-
bage maggot control, sufficient toxic components of carbofuran moved from the 1
in depth of application into the upper 1/4 in of the soil to produce 100% mor-
tality of test larvae after 3 to 4 weeks. When the upper 1/4 in of soil was
transferred to a new area over untreated soil, toxicants could be detected by
bioassay for 2 months. However, if left in the original microplots over the
carbofuran-treated band, the upper layer of the soil remained toxic for at
least 200 days. This observation indicates, according to Read (1971a), contin-
ual upward movement of toxic materials into the surface soil from the parent
compound.
In the greenhouse trials, all toxic components of carbofuran decreased to
nondetectable levels (below 0.5 ppm) within 300 days.
In another series of tests (Read, 1971b) on the bioactivity and persistence
of insecticides against the cabbage maggot, H^ brassicae, the performance of
carbofuran essentially confirmed the author's previous findings. Among the in-
secticides included in this experiment, carbofuran was again the most toxic to
the test organisms 30 days after application to field microplots at 100 ppm (in
the manner described previously). Toxicity gradually declined in the carbofuran-
treated soil, and toxic residues were barely detectable the following spring.
Hubbell et al. (1973), in studies on the microbiological effects of carbo-
furan and other pesticides described previously, also made observations on the
persistence of the insecticides investigated. The test pesticides were applied
to field plots at times and rates of application approximating agronomic prac-
tices in the growing of shadeleaf tobacco in northern Florida. Field plots were
established on a Norfolk loamy fine sand prepared and fertilized as for a tobac-
co crop. Carbofuran was applied at the rate of 10 Ib Al/acre (11.2 kg/ha). The
carbofuran-treated soil was sampled 2, 4, 6, 8, and 10 weeks after application.
Carbofuran was extracted from the soil samples and analyzed chemically. Carbo-
furan levels found were as follows:
Weeks after treatment Carbofuran residue
2 0.95
4 0.90
6 1.25
8 1.05
10 0.55
Caro et al. (1973) studied the dissipation of soil-incorporated carbofuran
in a 2-yr field investigation in two small watersheds at Coshocton, Ohio. Water-
shed No. 113 consisted of Keene and Rayne silt loam soil with an average pH of
6.35 and an average slope of 9.3%. Watershed No. 118 consisted of Coshocton
silt loam, average pH 5.2 and average slope 9.6%. Both watersheds were plowed,
disked, harrowed and fertilized in accordance with normal corn growing practices.
Carbofuran 10% granules were applied broadcast at the rate of 4.83 Ib Al/acre
(5.41 kg/ha) to Watershed No. 113, followed within 30 min by disking into the
7.5 cm depth. Watershed No. 118 received carbofuran 10% granules at the rate of
3.71 Ib Al/acre (4.16 kg/ha) applied in-furrow 5 cm deep in rows 1 m apart,
along with the corn seed, without subsequent cultivation. The following year,
123
-------
in May of 1972, an in-furrow application of carbofuran 10% granules at the rate
of 2.77 Ib Al/acre (3.11 kg/ha) was made on Watershed No. 113. Watershed No.
118 was not retreated in 1972.
•;v
Soil samples were taken from numerous sampling points in each watershed on
the day of carbofuran application and at 4 to 8 week intervals throughout both
seasons. Carbofuran persistence in the soil, expressed in milligrams per square
meter after each of the 3 treatments, is shown in Table 25. The disappearance
curve in each case approximated a first-order reaction during the crop season.
In 1971, half-lives were estimated to be 46 and 117 days in the broadcast and
band applications, respectively. In 1972, the band application half-life was 94
days. Disappearance was slower during the cold months of the year. Despite the
use of soil sampling techniques designed to minimize variation, variability in
carbofuran content among samples and standard deviations were quite high. The
irregularities parallel those found in similar experiments by the authors and by
other investigators and are believed to be largely due to a lack of uniformity
in pesticide field application.
Table 25. Carbofuran Residues in Soil Samples (mg/m2)
Days after
_apj> 1 i ca t io n
Range
Mean
Std.
dev.
. Range Mean
Std.'
dev.
0
29
63
113
153
225
337
Watershed No. 113 broad-
cast application, 1971
215-726
1.46-588
65-244
17-140
9-129
4-97
8-59
404
265
147
69
46
30
22
126
102
50
33
31
25
14
Watershed No. 118 band
application, 1971
365-1,508
376-1,558
375-920
126-633
142-551
28-558
51-134
775
743
575
343
311
203
76
353
362
157
143
126
126
28
Band application, 1972
0 .
49
89
138
160
628-1,046
330-866
224-665
116-467
135-537
830
516
392
291
306
177
170
167
126
159
Source: Adapted from Caro et al. (1973).
As reported above, the 2 watersheds had soil pH values of 6.35 and 5.20,
respectively. The half-life of pure carbofuran at these 2 pH levels in solution
124
-------
was determined to be 140 and 1,600 days, respectively. Thus, it is apparent
that carbofuran decomposes more rapidly in soil, but it is not known whether
chemical and/or biological mechanisms are responsible. The authors state that
the observed differences in insecticide half-lives in the 2 watersheds were the
result of differences in both soil pH and management practices.
Carbofuran residues disappeared much faster from certain small areas in
each of the watersheds where the insecticide was banded. The residue values at
these sampling points are not included in the data in Table 25 because these
sites were obviously atypical. The factors causing this decreased persistence
are not known, but moisture regime, soil pH, and physical structure of the soil
are believed to be involved. The "rapid disappearance" areas were characterized
by 1 or more of the following: greater runoff intensity; higher soil pH level
(about 0.4 pH unit above that of the surrounding area); more clay-like soil tex-
ture; and soil moisture content that was higher by approximately 1.2% wet weight
basis.
In an effort to further define the effect of temperature on the rate of de-
composition of carbofuran, Caro et al. (1973) determined the activation energy
of carbofuran hydrolysis and found it to be 38.5 kcal/mol. The mean soil tem-
peratures during the season in Watershed No. 113 were 19.8°C in 1971 and 18.7°
in 1972. Entering these values into the Arrhenius equation3./ indicates that the
hydrolysis of carbofuran is a sensitive function of temperature, and that the
half-life of carbofuran should have been about 50% longer in 1972 than in 1971.
However, the actual half-life was more than twice as long (94 versus 46 days),
suggesting overriding effects of other factors, especially placement. A sub-
stantial increase in persistence apparently occurred as a result of the band
application.
Caro et al. (1973) also studied the losses of carbofuran in the runoff
water from the treated watershed (see subsection on Environmental Transport
Mechanisms, p. 129).
FMC Corporation (1974),in commenting on the studies by Caro et al. (1973)
discussed above, points out that the observed dissipation rates of carbofuran
in soils are not nearly as sensitive to changes in temperature and pH as the
solution kinetic studies predict. From the Climatic Atlas of the United States,
FMC calculated the mean temperatures during a typical growing season, June
through September, for several areas. The Arrhenius equation was then used to
predict the following relative half-lives for the hydrolysis of carbofuran in
these areas during the summer months:
Average Relative
Area temperature (°F) half-life
Caribou, Maine 60.3 1.000
Buffalo, New York 66.0 0.414
Lincoln, Nebraska 74.8 0.156
Amarillo, Texas 77.5 0.111
Memphis, Tennessee 79.0 0.092
Miami, Florida 81.5 0.056
a/ k = Ae E*/RT
125
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FMC analyzed the actual dissipation rates of carbofuran after broadcast
application of 10% granules in a variety of soils from 6 states. The most rap-
id dissipation rate was only about 5 times greater than the slowest rate. No
correlations between climate and dissipation rates were observed. A similar
analysis of the dissipation of carbofuran after in-furrow application of 10%
granules in soils from 8 states again showed no correlation between climate and
dissipation rate. Again, there was approximately a 5-fold difference between
the slowest and fastest dissipation rates.
The discrepancy between theoretical dissipation rates and those observed
was considered to be due to several factors, including microbial action, insuf-
ficient moisture in the soil for true solution kinetics, catalysis of carbofuran
decomposition by 1 or more soil constituent(s) and/or a complex reaction mecha-
nism which does not conform to the Arrhenius equation. (The Arrhenius equation
suggests that catalysis, i.e., lowering of the activation energy, would render
the reaction less sensitive to temperature changes.)
FMC Corporation (1972a and 1974) conducted studies to evaluate the persis-
tence of carbofuran in different soils following single applications, and the
possible buildup of carbofuran residues in soil from repeated applications in
successive years.
In 1 study, carbofuran residues were determined after single broadcast ap-
plications of carbofuran 10% granules in 6 different states, representing a
variety of soils. The analytical results from different rates of application
were normalized to a rate of 6 Ib Al/acre. The average residues (in parts per
million) found were as follows: 6.6 on day of application; 1.9 after 30 days;
0.31 after 75 days; 0.73 after 95 days; 0.21 after 130 days; 0.31 after 160
days; 0.06 after 360 days. The average variation ranged from 24 to 79% for
sampling dates 0 to 130 days after application. There were no correlations be-
tween climate and dissipation rates.
The dissipation of carbofuran following in-furrow treatment with 10% gran-
ules was studied at 10 different sites in 8 states, again representing a vari-
ety of different soils. Analytical results were normalized to a rate of 1 Ib
Al/acre. Average residues (in ppm) found were as follows: 20 on the day of
application; 12 after 40 days; 1.8 after 60 days; 0.52 after 150 days; 0.53
after 190 days; 0.13 after 360 days. The average variation ranged from 42 to
100%.
As other investigators have observed, this data indicates that carbofuran
residues in the soil dissipate more rapidly following broadcast than following
band treatment.
In a third set of studies, FMC Corporation (1974) evaluated carbofuran soil
residues following repeated applications in successive years. The soils were
planted with crops typical for each location. They were sampled twice each
year, once in the fall at the time of harvest of the crop and once in the spring
just prior to the next year's carbofuran application. This sampling schedule
was followed for 4 yr, from the fall of 1970 through the fall of 1973.
126
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There was no indication of an increase in soil residues following repeated
applications of carbofuran in successive years. Treatments monitored included
5.0 (5 x 1.0) Ib of 4 Ib/gal flowable Al/acre/yr applied to potatoes in New
York; 3 Ib of 10% granules Al/acre/yr applied to corn in New York and Nebraska^;
6 Ib of 10% granules Al/acre/yr applied to tobacco in Arkansas; and 3 Ib of 10%
granules Al/acre/yr applied to peanuts in Arkansas. Carbofuran residues in the
New York corn plots snowed greater variations from year to year than those from
Nebraska plots. This might be related to differences in method of application.
Residues from tobacco plots receiving broadcast applications were fairly uniform
from year to year.
Soil samples from these studies were analyzed by a method that included acid
hydrolysis, methylene chloride extraction, Nuchar-atta clay column cleanup, and
detection with a nitrogen-specific microcoulometric gas chromatograph. Carbo-
furan was the only carbamate compound detected above the method sensitivity of
0.10 ppm.
Residues in Water
The dissipation of carbofuran in flooded rice fields is summarized in a
report by the FMC Corporation (1972a). In California, carbofuran residues in
water were determined following postflood at the rate of 1 Ib Al/acre: carbo-
furan residues in the water peaked at 0.7 ppm 8 hr after application. In an-
other postflood test, maximum residues (0.3 ppm) were reached 14 hr after an ap-
plication of carbofuran 2% granules at 0.5 Ib Al/acre. When carbofuran granules
were applied to rice fields preflood at the rate of 0.5 Ib Al/acre, maximum resi-
dues in the water occurred 7 days after treatment, and these maxima were lower,
for example, 0.1 ppm not tilled, and 0.05 ppm tilled.
Similar patterns were observed in tests in Louisiana rice fields. When
carbofuran 2% granules were applied postflood at the rate of 0.5 Ib Al/acre,
carbofuran residues in the water peaked at 0.3 ppm 8 hr after treatment. Fol-
lowing a preflood application of carbofuran 3% granules at 0.5 Ib Al/acre, max-
imum water residues, 0.2 ppm, were reached 2 days after application.
After peaking, carbofuran water residues dissipated with a half-life of 1
day or less. Residues reached nondetectable (0.01 ppm) levels within a few
days. No other carbamate metabolites such as 3-hydroxy-carbofuran or 3-keto-
carbofuran were detected.
Phytotoxicity
Tobacco plant responses to recommended and excessive rates of application
of Furadan® 10G were studied by Tappin (1969). Furadan® 10G was broadcast by
hand on February 25 at rates of 4, 6, and 10 Ib Al/acre and roto-tilled to a
depth of 6 to 8 in. Plots were bedded and transplanted 27 days later. An un-
treated check and a standard dust treatment were included in the randomized
block, 4-replicate experiment. Plant response was evaluated by measuring the
stalk height on the fifteenth and fifty-seventh day and by rating phytotoxicity
on a scale of 0 to 4 weekly intervals from April 16 through June 25.
127
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Plants responded well to Furadan®, as judged by plant height, but the 4
and 6 Ib rates showed slight to moderate injury until early June. Plants treat-
ed at the 10 Ib rate showed symptoms of severe phytotoxicity in May, but again
had outgrown all effects by early June.
The author attaches little, if any, economic importance to the phytoxicity
observed, especially at the 4 and 6 Ib/acre rates. At proposed rates of appli-
cation this has been limited to occasional chlorosis and, in unusually severe
cases, small necrotic spots (flecks) on the lower leaves of the plant. Since
these leaves are normally not harvested and usually drop prematurely due to lack
of adequate sunlight, injury'to these leaves is of no consequence. The improved
growth of treated plants, particularly in the early season, more than offsets
any possible early season injury to the unharvested older leaves.
Bioaccumulation and Biomagnification
The propensity of carbofuran for bioaccumulation and biomagnification was
recently studied by investigators at the University of Illinois at Urbana-
Champaign (Sangha,1972; 53^01^1,1974; and Yu et al., 1974), using a laboratory
terrestrial-aquatic model ecosystem developed by Metcalf et al. (1971). The
model ecosystem consists of a terrestrial-aquatic interface and a 7-element food
chain; it can be used to simulate the application of pesticides to crop plants
and to study contamination of the aquatic environment. The system is housed in
a glass aquarium (25 x 30 x 45 cm) and contains a sand-water interface consist-
ing of 15 kg of sterilized white quartz sand and 7 liters of standard reference
water.
Sorghum (Sorghum halepense) was grown in the sand for 7 days, followed by
treatment with 5 mg (50 uCi) of ring-l^c- and carbonyl-l^C-labeled carbofuran
in 0.5 ml of acetone (rate equivalent to 1 Ib of carbofuran Al/acre). After
treatment of the sorghum, larvae of the saltmarsh caterpillar, Estigmene acrea,
were added to the system and allowed to feed on the treated sorghum plants; the
larvae simulated the first member of a food chain, and acted as an effective
distributing agent for the labeled pesticides within the system. The saltmarsh
caterpillars died after they ate carbofuran-treated sorghum leaves. As a re-
sult, more caterpillars were added for the first 5 days after treatment until
all sorghum leaves were consumed.
The water phase contained several members of a freshwater aquatic food chain,
for example, frogs (species not identified), snails (Physa species), freshwater
clams (Corbicula manilensis), freshwater crabs (Uca minax), water fleas (Daphnia
magna), green filamentous algae (Oedogonium cardiacum), and a freshwater plant
(Elodea canadensis). After 27 days, mosquito larvae were added to the system
to become another member of the food chain, and after 3 more days, mosquito fish
(Gambusia affinis) were added to become the final segment of the system. The
experiment was carried out in 2 aquaria (tanks) each for ring-^C- and carbonyl-
14-c-labeled carbofuran, respectively.
At the end of 33 days, the entire system was taken apart, and the organisms
and water were extracted and analyzed for radioactivity. In addition, extracts
were spotted on TLC plates, developed with appropriate solvents, and exposed to
128
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x-ray film to locate and identify the chemical composition of the solvent ex-
tracts. Metabolites were identified by co-chromatography with proposed metabo-
lites, as well as by infrared, nuclear magnetic resonance, and mass spectrometry
techniques.
At the end of the test period, none of the organisms contained residues of
carbofuran. In the test with carbonyl-labeled carbofuran, several unknown com-
pounds were isolated from E._ canadensis along with 3-ketocarbofuran (35 ppb),
N-hydroxymethyl carbofuran (35 ppb) and 3-hydroxy-carbofuran (11.8 ppb). Fewer
metabolites were isolated from the experiment with ring-labeled carbofuran. As
previously observed with 2 other carbamate insecticides, most of the carbofuran
radioactivity was unextractable by acetone; values for ring- and carbonyl-la-
beled carbofuran were 69 and 77%, respectively. Small amounts of the unchanged
carbonyl-labeled carbofuran (ca. 0.5 ppb) were isolated from the water phase of
the system. Other metabolites found in identifiable quantities in the water
portion were 3-ketocarbofuran, N-hydroxymethyl carbofuran, carbofuran phenol,
and 3-hydroxycarbofuran, none of them in concentrations higher than 10 parts per
trillion. It was concluded from these findings that carbofuran is highly bio-
degradable and has low residual activity in the components of the model ecosys-
tem. Detoxification occurred by hydroxylation of the carbofuran molecule at
several points. Metabolites were found only in the water phase (Sangha,1972).
Sanborn's conclusions from these studies on carbofuran and 2 other carba-
mate insecticides are as follows: "If the data obtained for these carbamates
in this model ecosystem is representative of the behavior of aryl N-methyl car-
bamate insecticides, then it would appear that the use of these insecticides
will not present ecological problems related to persistence and food chain ac-
cumulation" (Sanborn,1974).
Yu et al. (1974) provided additional details in regard to these carbofuran
model ecosystem studies. His paper covers sample preparation and analytical
techniques, and presents detailed, tabular data on the concentration of carbo-
furan metabolites and degradation products in solvent extracts and in residue
fractions for ring-labeled and carbonyl-labeled carbofuran. The authors also
report on the distribution of radioactive metabolites in solvent extracts after
TLC analysis for both types of ^C-carbofuran.
The radioactivity in the water was monitored throughout the experimental
period. In both the ring- and carbonyl-labeled experiments, radioactivity in
the water reached a peak on the seventh day. However, radioactivity in the
tanks containing the ring-labeled carbofuran peaked at about 0.3 ppm, compared
to less than 0.05 ppm in the tanks containing the carbonyl-labeled carbofuran.
This indicated the rapid hydrolysis of carbofuran to carbofuran phenol and n-
methyl-carbamic acid. The latter is then further degraded to C02 and other
metabolites. To verify this conclusion, carbonyl-labeled carbofuran was placed
in a closed aquatic system fitted with a C02 trap which contained NaOH. The
radioactivity in the water decreased rapidly, while radioactivity in the C02
trap steadily increased. However, the radioactivity collected in the C02 trap
was only about 25% of the total 14c put into the system. The radioactivity
remaining in the water was less than 10% of the introduced radioactivity. The
authors explain this discrepancy in the ^C balance by the inefficiency of the
C02 trap.
129
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As reported above, no parent carbofuran was found in any of the living or-
ganisms analyzed. However, large amounts of carbofuran were found in 2 crabs
found dead the second day after applying carbonyl-labeled carbofuran to the
tanks, and in 1 of the 2 crabs which became moribund after being introduced in-
to the same tank 20 days after application. A second crab stocked in this tank
at the same time did not die, and no intact carbofuran was found in this living
crab at the end of the experiment on the thirtieth day. Apparently, the crabs
did not metabolize carbofuran extensively as 61 to 92% of the radioactivity was
extractable by acetone from the whole body. In other organisms, only about 20%
of the radioactivity was acetone-extractable.
Insoluble residues remaining after acetone extraction from the water and
organisms were not analyzed further and, therefore, their chemical nature is
not known. The authors presume that they are conjugated with glucose or other
large molecules because they are very polar.
In summarizing their findings, Yu et al. (1974) stated that carbofuran was
rapidly hydrolyzed in water. Hydroxylation of the benzofuranyl moiety consti-
tuted the major degradation pathway.
Wong and Fisher (1975) determined the residues of carbofuran and its meta-
bolites, 3-hydroxycarbofuran and 3-ketocarbofuran, in animal tissue by gas-liq-
uid chromatography with electron capture detection as N-trifluroacetyl deriva-
tives. The procedure has a minimum sensitivity of approximately 0.5 ppm carbo-
furan, 0.07 ppm 3-ketocarbofuran, and 0.05 ppm 3-hydroxycarbofuran for the test
animals which were oyster, shrimp, mullet, menhaden, skate, and red-winged black-
bird. After being fortified with 2.5 to 25.7 ppm carbofuran, 0.12 to 8.2 ppm
3-hydroxycarbofuran, and 0.23 to 0.82 ppm 3-ketocarbofuran, the resulting resi-
dues averaged 84.2, 83.8 and 72.8%, respectively.
Data on the rate of uptake and excretion of carbofuran by the common dew
worm, Lumbricus terrestris, and a manure worm, Eisenia foetida, is reported in
the subsection on Interactions with Lower Terrestrial Organisms, p. 109.
Other studies related to storage patterns of carbofuran and its metabolites
in plants and animals can be found in the section on Metabolism and Metabolism
in Mammals.
Environmental Transport Mechanisms
Lateral Movement - Bowling (1970) studied the lateral movement, sites of uptake,
and retention of carbofuran applied in different ways to rice plants. Rice was
planted in rows 20 cm long and 7.5 cm apart in metal trays kept under green-
house conditions. The trays were fertilized 18 days after planting, then flood-
ed to a water depth of 1 in. Twenty-one days after planting, the trays were
moved to a growth chamber programmed to a 19 to 36°C daily temperature cycle
and 14 hr daily illumination coinciding with the warmer period.
When the trays were placed in the growth chamber, carbofuran 3% sand-core
granules were applied to the first 7.5 cm at one end of the tray at the rate of
130
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1 Ib Al/acre. Field-collected adult leafhoppers, Draeculacephala portola, were
caged on each of the four rows of rice plants, and numbers of surviving leaf-
hoppers were recorded at 6, 22, 24, and 48 hr after application of the carbo-
furan. The rate of survival of leafhoppers on the rice plants in relation to
the distances of the plants from the center of the area where the carbofuran
granules had been applied indicated that the insecticide moved laterally 22.5
cm in 22 hr in quantities toxic to the leafhoppers. Both carbofuran and its
metabolites were absorbed and translocated by the plants, especially when car-
bofuran was placed near the roots prior to flooding, or when carbofuran wettable
powder was placed on the leaf sheafs. The authors concluded that optimum utili-
zation of carbofuran would be obtained by placement in dry soil, near the root
system, followed by flood water.
Leaching Studies - FMC Corporation (1972a) studied the leaching properties of
carbofuran in 7 different soil types in the laboratory, following the methods
developed by Harris (1969a). In a segmented column consisting of aluminum tub-
ing, soil was packed in 1-in segments to a height of 7 in, and 1^C-carbonyl-
labeled carbofuran mixed with soil was placed in the second segment 1-in from
the bottom. The column was then placed in a container in which water was kept
at a constant level. Water moved upward in the column by capillary action to
the soil surface when it was allowed to evaporate. After 3 days, each column
segment was analyzed for radioactivity. The results showed that carbofuran
moved more slowly in columns high in clay or organic matter. In soils of equal
clay content, carbofuran moved further in soils with lower exchange capacity.
In this test, another pesticide' was used as a standard, and its upward
movement through comparable soil columns was monitored by bioassay. The rate
of movement of carbofuran was slightly greater than that of the other pesti-
cide, which Harris (1969a) classified as being "intermediate" in relative soil
mobility.
Field leaching studies in 3 different soil types using lysimeters were con-
ducted in Illinois. Carbofuran 10% granules were applied broadcast at the rate
of 4 Ib Al/acre over the top of lysimeters packed with Plainfield sand (little
or no organic matter), Blount silt loam (light forest soil), and Elliot (an
agricultural soil, highest among the 3 soils in organic matter). The lysime-
ters were embedded in a field exposed to normal year-round weather conditions.
Initial residues were 0.08 to 0.32 ppm in the runoff water and 0.005 to
0.009 ppm in the sediment. Some carbofuran residues percolated through the
lysimeter containing the sandy soil. After 1 yr, negligible carbofuran residues
were found in the top 1.5 ft of the 2 heavier soils; they were equally distri-
buted throughout 3 ft in the sand. The lysimeters were new and had not fully
settled at the start of the experiment. Therefore, the significance of the
results is questionable.
The leaching behavior of carbofuran under field conditions was studied by
analysis of soil samples from 2 corn fields in Iowa and Nebraska (treated with
carbofuran 10% granules, at the rate of 1 Ib Al/acre banded) and from 3 fallow
fields in New York (treated with carbofuran 50% wettable powder at an exagger-
ated rate of 10 Ib Al/acre broadcast). Maximum initial carbofuran residues in
131
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the corn field soils were 1.1 ppm. Residues below 6 in did not exceed 0.2 ppm
during the entire growing season. In the samples from the fallow fields, ini-
tial residues of carbofuran were as high &s 10 ppm in the upper 3 in soil layer.
Residues of less than 0.1 ppm were found below 6 in over the year of sampling
following treatment except for the muck soil. In all soil samples, essentially
all carbofuran residues dissipated during the 1-yr sampling period.
In another study, a Nebraska fallow field and a Georgia tobacco field were
treated broadcast with carbofuran 10% granules at the rate of 10 Ib Al/acre.
Samples from 0 to 6 in and 6 to 12 in depths were an /zed for carbofuran resi-
dues. The results were as follows:
Days after Nebraska fallow field Georgia tobacco field
treatment 0-6 in 6-12 in 0-6 in 6-12 in
0 11.0 0.1 10.0 5.0
124 - - 0.5 0.2
136 0.3 Nondetect-
able
The data shows that most of the carbofuran residue remained in the upper 6
in of the soil in both locations, and that the total residue decreased to less
than 3% of the initial concentration in the Nebraska soil within 136 days and
to 5% of the initial concentration in the Georgia soil within 24 days.
Runoff Studies - In the carbofuran dissipation studies discussed above (see sub-
section on Field and Combined Field/Laboratory Studies p. 120), Caro et al. (1973)
investigated losses of carbofuran in the runoff water from both of the watersheds
treated in 1971 and from the watershed that was retreated in 1972. The runoff-
producing rainfalls and carbofuran losses in the runoff water are shown in Table
26. In 1971, the carbofuran losses occurred almost entirely in 2 heavy rains
that fell within 48 hr after the application. In both watersheds, the carbofuran
concentration in the runoff water was much higher in the second rainfall than in
the first, indicating a greatly increased rate of release of carbofuran active
ingredient from the applied granules by the second day.
In 1972, rainfall was more evenly distributed over the season, with measur-
able runoff occurring on the treated watershed on 13 occasions. Once again, the
major carbofuran losses occurred in the early rainfall events. The first runoff-
producing rainfall did not occur until almost 1 month after the carbofuran appli-
cation. Therefore, the carbofuran concentrations in the runoff water never
reached the high levels of 1971. The sudden increase in the carbofuran concen-
tration that appeared 168, 173, and 179 days after treatment resulted from the
disturbance of the soil surface at corn harvest which took place 154 days after
application.
Some rainfalls were sufficiently intense to produce measurable quantities
of carbofuran-bearing sediment in the runoff. Fine solids suspended in the
water and coarser sediment deposited on the floor of the flume collecting the
runoff were analyzed for carbofuran content. Residues on the suspended solids
ranged from 0.46 to 1.64 mg/kg, and on the flume floor deposit from 0.98 to 1.11
ppm.
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Table 26. Runoff-Producing Rainfalls and Carbofuran Losses in
Runoff Water from Carbofuran-Treated Watersheds
Days after
pesticide
application
1
2
39
65
82
239
Total
1
2
239
Total
Amount of runoff
(I)
Average carbofuran
concentration
(ug/£)
Watershed No. 113 (broacast application). 1971
31,900
7,170
1,480
120
300
3,760
473
1,394
537
33
15
5
44,730
Watershed No. 118 (band application), 1971
40,640
3,470
9.190
272
1,002
19
53,300
Watershed No. 113 (band application), 1972
Carbofuran in
runoff water
(tng)
15,089
9.995
795
4
5
19
25,907
11,054
3,477
175
14,706
26
28
53
76
82
91 (a.m.)
91 (p.m.)
119
123
147
168
173
179
Total
35,840
61,320
30,710
630
3,190
12,430
9,170
1,130
6,160
2,710
11,400
33,970
34,020
242,680
191
223
58
8.8
6.9
4.4
2.9
2.8
1.8
2.6
14.2
16.9
19.9
6,845
13,674
1,781
6
22
55
27
3
11
7
162
574
677
23,934
Source: Adapted from Caro et al. (1973)
In the 1972 runoff study, the concentration of 3-ketocarbofuran in the run-
off water was also determined. About 5% of the parent compound was 3-ketocar-
bofuran. However, peak 3-ketocarbofuran concentrations were reached earlier in
the runoff water than in the soil.
Overall, from 0.5 to 2.0% of the carbofuran applied was lost in runoff, most
of it in water rather than in sediments.
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Several additional carbofuran runoff studies have been reported by FMC Cor-
poration (1972b). In Illinois, a 4-acre watershed close to a pond was planted
with corn and treated with carbofuran 10% granules broadcast at the rate of 4
Ib Al/acre. Soil, pond mud, and pond water samples were analyzed periodically.
The initial half-life of carbofuran in the soil was 1 to 2 weeks on the average
of 7 sampling stations, varying somewhat in relation to soil pH. Initial soil
residues of about 1 ppm reached levels of less than 0.1 ppn by the fall and were
nondetectable the following spring. Residues of about 1 ppm occurred in the pond
water following a heavy rainfall 4 days after treatment. This residue declined
to "negligible" by the next sampling date (16 days from application and 12 days
from first sampling), and was not detectable thereafter. Highest residues of
0.2 ppm were found in the pond mud during the first few weeks after the runoff,
but they disappeared thereafter. There was no fish mortality in the pond.
In another runoff study, carbofuran 10% granules were applied broadcast at
the rate of 6 Ib Al/acre to the top 4 ft strip of 24 ft x 24 ft plot having a
4% slope. Soil cores of 6 in were taken at 1 ft intervals in 3 replicates down-
slope, starting in the treated zone, down to 3 water-catch basins at the base.
Soil samples were taken periodically throughout the growing season, and water
samples were taken from the catch basins after each significant rainfall. In
the treated zone, carbofuran residues declined to 10% of the initial concen-
tration within 64 days. Residues were found in the first foot below the treated
zone, but none further downslope. No detectable residues (0.01 to 0.02 ppm de-
tectability) were found at any time in runoff water collected in the catch ba-
sins 25 ft downslope.
In western Iowa, 4 watersheds (2 to 4 acres in size with slopes of 15 to
20%, containing alluvial silt with about 2% organic matter content) were treated
with carbofuran 10% granules banded on corn at planting time at the rate of 1
Ib Al/acre. Runoff water and sediment were collected through flumes and water-
wheels. Three major rainfall events created measurable runoff on one or more
of the watersheds 37, 60, and 70 days after planting. Analysis of the runoff
showed carbofuran residues of 0.15 ppm or less in the water and 0.7 ppm or less
in the sediment. There were no significant differences in carbofuran residue
content between the watersheds. There was less runoff of water and sediment
from ridge-planted than contour-planted watersheds.
In California, an 8.5 acre tomato field (sandy loam, average pH 8.2) was
sprayed by air with a concentration of carbofuran 4 Ib Al/gal (flowable formu-
lation) applied at the rate of 1 Ib Al/acre. At the time of treatment the to-
mato plants provided a canopy that protected from one-third to two-thirds of
the soil surface from the direct spray. The treated field was furrow-irrigated
weekly for 4 weeks. Soil samples were taken at weekly intervals from 3 points:
(a) along the plant beds not covered by the plant canopy (exposed bed); (b)
along the plant rows in the area protected from the spray by the foliage (pro-
tected row); and (c) in the irrigated furrows that were also exposed to the
direct spray. Soil samples were taken to a 6 in depth, with 25 cores diago-
nally across the field comprising one sample. Duplicate samples were taken
along the other diagonal.
134
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Carbofuran residues in the exposed bed (a) declined from a maximum of 0.3
ppm 4 days after application to below 0.05 ppm after 32 days. Residues in the
protected row (b) slowly increased to a maximum of 0.09 ppm within 25 days,
then declined to 0.01 ppm at 32 days. Residues in the exposed irrigation furrow
°'3 PPI" ** the *&J °f treatment to below °-05 PPm 24 days after
treatment
Samples of the irrigation water (pH 8 to 9) were taken several times during
A i qnnJ* al°n8 the ta±1 ditch drainin8 the field at distances of 0, 750,
TVh H * * 8 thS ditch' Maximum carbofuran residues of 0.1 ppm were found
at tne head of the ditch 1 day after spraying. Residues decreased with distance
along the ditch and declined to undetectable levels (less than 0.0023 ppm)
throughout the entire length of the ditch within 28 days after treatment.
135
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References
Anderson, L. D., E. L. Atkins, Jr., H. Nakakihara, and E. A. Greywood, Toxicity
of Pesticides and Other Agricultural Chemicals to Honey Bees, Field Study.
University of California Agricultural Extension Bulletin AXT-251, Revised
(June, 1971).
Atkins, E.L., Jr., L. D. Anderson, and E. A. Greywood, "Research on the
Effect of Pesticides on Honey Bees 1968 to 1969, Part II," Am. Bee J..
110(11):426-429 (1970).
Atkins, E. L., E. A. Greywood, and R. L. Macdonald, Toxicity of Pesticides
and Other Agricultural Chemicals to Honey Bees, University of California,
Agricultural Extension, Report M-16 (1973).
Bailey, J. B., and J. E. Swift, "Honey Bee and Other Pollinating Insect Losses,"
Contained in: University of California Division of Agricultural Sciences,
Pesticide Information and Safety Manual, pp. 7-10 (1968).
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137
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138
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L39
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140
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PART II. INITIAL SCIENTIFIC REVIEW
SUBPART D. PRODUCTION AND USE
CONTENTS
Page
Registered Uses of Carbofuran 143
Production and Domestic Supply 143
Volume of Production 143
Imports 143
Exports 143
Domestic Supply 144
Formulations 144
Use Patterns of Carbofuran in the United States 144
General 144
Carbofuran Uses in 1971 145
Carbofuran Uses in 1972 145
Carbofuran Uses in 1974 146
Carbofuran Uses in California 146
References 160
142
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This section contains data on registration and on production and
uses of carbofuran. The section summarizes rather than interprets
scientific data reviewed.
Registered Uses of Carbofuran
Federally Registered Uses - Carbofuran is a broad spectrum insecticide-
nematicide registered as a contact insecticide on crops and as a systemic
soil treatment. The chemical was introduced for commercial use in
agriculture in the United States about 1970. Carbofuran has been
highly effective against corn rootworms and alfalfa weevils. Dosages,
tolerances and limitations for currently registered uses are summarized
in Table 27.
Production and Domestic Supply
Volume of Production - Carbofuran is produced in the United States by a
single manufacturer, the Agricultural Chemical Division of FMC Corporation,
Middleport, New York.
The United States Tariff Commission (1973b, 1974) does not report
the production and sales volumes of carbofuran individually. Carbofuran
is included in the category "All Other Cyclic Insecticides and Rodenticides."
In comparison to all other pesticides in this category, the production
and sales volumes of carbofuran are so small that Tariff Commission data
is not significant in estimating carbofuran volumes. However, carbofuran
was one of 25 selected pesticides whose production, distribution, use,
and environmental impact potential was studied by von Rumker et al.
(1974). Estimates for 1972 placed domestic production of carbofuran at
6.0 million Ib.
Imports - A report by the U.S. Tariff Commission (1973a) shows an
absence of carbofuran imports. The probability that there were no
imports of carbofuran into the United States in 1972 is further supported
by the fact that the product is the subject of a patent held by the only
U.S. producer, FMC Corporation.
Exports - Carbofuran is not listed in the U.S. Bureau of the Census commodity
descriptions on pesticide exports for 1970 (U.S. Bureau of the Census, 1971).
This may be due to the fact that, at least in some statistics, carbofuran is
classified as a nematicide. The reports do not contain a separate breakdown
of nematicides.
However, von Rumker et al. (1974) estimated that, in 1972, approximately
1.0 million Ib of carbofuran Al were exported from the United States.
143
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There are indications that the export volume of carbofuran is increasing.
Carbofuran is an effective, versatile insecticide and nematicide that is
in demand in other parts of the world. According to von Rumker et al. (1974),
recent increases in carbofuran production capacity have eased supply
problems that limited carbofuran export (as well as domestic) sales in
the early 1970's. It is considered likely that not only domestic (see
below) but also export sales of carbofuran have increased since 1972.
Domestic Supply - As estimated by von Rumker et al. (1974), approximately
5.0 million Ib of carbofuran Al were used in the United States.
Formulations - Carbofuran is not available domestically as technical
active ingredient. The only formulations available are those from the
basic producer, the Agricultural Chemical Division of FMC Corporation.
FMC currently offers 4 different carbofuran granular formulations containing,
respectively, 10, 5, 3, and 2% Al. In addition, a flowable formulation
containing 4 Ib i ^available. These formulations are marketed under the
trade name FuradarPP. Furadan®2, 3, and 10% granules, and 4 Ib/gal
flowable formulation produced by FMC are also marketed by the Chemagro
Division of Mobay Chemical Corporation, Kansas City, Missouri. Most or
all of the carbofuran granular formulations are dense, freeflowing,
uniform sand-core granules. Accurate calibration of application equipment
is essential to distribution of carbofuran at the intended dosage rate.
Use Patterns of Carbofuran in the United States
General - Carbofuran is an insecticide-nematicide with a broad spectrum
of biological activity. It can be used either as a contact insecticide-
applied to the foliage of target crops, or as a soil-applied systemic
insecticide-nematicide. Applied to the soil, carbofuran controls certain
soil-inhabiting pests. In addition, it is systemically absorbed by the
roots and translocated by treated plants to provide control of a number
of foliar pests. It is the most effective insecticide currently available
against corn rootworms and especially against some strains that are re-
sistant to other insecticides.
Carbofuran is registered, recommended and used in the United States
primarily on certain agricultural crops, as outlined in greater detail
in the preceding section. There are only a few nonagricultural uses,
namely, application as a soil treatment to cottonwoods and Siberian
elms, and as a clay slurry for the treatment of pine seedlings. These
nonagricultural uses account for only very small quantities of carbofuran
active ingredient. The product is not registered or used for any other
industrial, commercial, or institutional pest control purposes, nor for
use on ornamentals, in home gardens or indoors. Thus, most of the
quantities of carbofuran currently used in the United States are
agricultural.
144
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Carbofuran was introduced in the U.S. for commercial agricultural use in
about 1970. Its use increased rapidly, mainly due to its superior effectiveness
against corn rootworms and alfalfa weevils. These insects were major economic
problems, becoming resistant to certain other insecticides when carbofuran be-
came available and placing it in great demand.
Carbofuran Uses in 1971 - Carbofuran is reported individually in the U.S. De-
partment of Agriculture's survey of the quantities of pesticides used by farmers
in 1971 (U.S. Department of Agriculture, 1974). Table 28 summarizes the uses
of carbofuran in the United States. Uses are shown both by quantities of carbo-
furan AI and by numbers of acres treated. According to the U.S. Department of
Agriculture's survey, 93.9% of the total quantity of carbofuran used by farmers
in 1971 was used on corn, followed by rice (5.7%). Other field crops, vege-
tables and fruit and nut crops accounted for the balance (0.4%). The U.S. De-
partment of Agriculture's data indicates that carbofuran was used at an average
rate of 0.73 Ib Al/acre on corn whereas the average use rate on rice was 2.1 Ib
Al/acre. The latter rate is questionable, however, since it exceeds recommended
rates. As indicated in the section on Carbofuran Uses in California, there is
approximately a 12-fold discrepancy between the USDA and California data on
usage for rice.
Table 29 summarizes the use of carbofuran in the U.S. in 1971 by regions,
by quantity used, and by acreage treated. This data indicates that about 90%
of the total quantities of carbofuran used in 1971 were used on corn in the
corn belt, lake and northern plains states. In the Pacific and delta states,
carbofuran was used primarily on rice. The remaining quantities of carbofuran
used by farmers in 1971, according to the USDA survey, were used primarily on
corn in the northeastern, mountain, and Appalachian states.
Carbofuran Uses in 1972 - In. 1973 and early 1974, von Rumker et al. (1974) con-
ducted a comprehensive study on the production, distribution, use and environ-
mental impact potential of 25 selected pesticides, including carbofuran. They
estimated that,in 1972, 5.0 million Ib of carbofuran AI were used on agricul-
tural crops in the United States. Of this total, an estimated 4.4 million Ib
were used in the north central states, 200,000 Ib each in the south central
and'western states, and 100,000 Ib each in the northeastern and southeastern
states. The authors' surveys further indicated that,in 1972, uses of carbo-
furan for industrial, commercial, institutional, governmental, or home garden
pest control purposes were negligible, if used at all.
Figure 8 presents the materials flow diagram for carbofuran for 1972 from
the report by von Rumker et al. (1974). This figure shows the flow of raw
materials (open arrows) to FMC's plant in Baltimore, Maryland, where 2,3-dihy-
dro-2,2-dimethyl-7-benzofuranol, the final intermediate in the production of
carbofuran, was produced in 1972. This intermediate was then transported to
145
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another FMC plant in Middleport, New York, where the final reaction step
and the formulation of the technical active ingredient were carried out.
Shaded arrows, graduated in proportion to the quantities represented,
indicate the flow of carbofuran products to the major use areas. Where
substantial quantities of carbofuran were used in 1972, the geographic
distribution is broken down by states or small groups of states (boundaries
indicated by light shading of the state lines). Smaller uses in larger
geographic areas are broken down to the level of the regions whose
boundaries are indentified by dark shading of the state lines concerned.
Carbofuran Uses in 1974 - Von Rumker et al. (1975) studied the use of
soil insecticides on corn in 1974 in 8 midwestern states (Iowa, Illinois,
Indiana, Ohio, Missouri, Minnesota, South Dakota, and Nebraska). These
8 states accounted for 75% of the total acreage of corn grown for grain
in the United States in 1974. It was concluded from a survey of extension
entomologists and of pesticide trade sources in these states that, in
1974, approximately 5.3 million Ib of carbofuran active ingredient were
used on corn in the 8 states surveyed. Taking into account this information
and the state use patterns of carbofuran as reported by the U.S. Department
of Agriculture (1974) for 1971, it is estimated that, in 1974, approximately
6.8 million Ib of carbofuran active ingredient were used on corn in the
U.S. (6.3 million Ib in the corn belt, lake and northern plains
states, 500,000 Ib in the remaining corn growing states).
Carbofuran Uses in California - The California Department of Food and
Agriculture keeps detailed records of pesticide uses by crops and other
uses; the data is published quarterly and summarized annually. Table 30
summarizes the uses of carbofuran in California by major crops for the
1970 - 1974 period. According to the California reports, the annual
volume of carbofuran used in the state increased from 9,500 Ib AI in
1970 and 1971 to 10,600 Ib in 1972, 106,000 Ib in 1973, and 146,000 Ib
in 1974.
During the 5-year period covered by Table 30, the quantities of
carbofuran used on rice in California ranged from a low of 7,800 Ib in
1972 to a high of 11,300 Ib in 1973. The use of carbofuran on alfalfa
increased rapidly, from 100 Ib AI in 1971 to 2,700 Ib in 1972, 94,000 Ib
in 1973, and 135,700 Ib in 1974. There were no significant uses of
carbofuran on other crops during this period, according to the Department
of Food and Agriculture's reports. It should be noted there is a large
unexplained discrepancy between the quantities of carbofuran used on
rice in California in 1971 according to the California Department of
Food and Agriculture—8,700 Ib, and that reported by the U.S. Department
of Agriculture (1974)--103,000 Ib.
Table 31 presents the carbofuran uses in California by crops and
other uses, number of applications, pounds of active ingredient, and
number of acres treated for 1972, 1973, and 1974, the 3 most recent
years for which such data are available.
146
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Table 32 summarizes the estimated uses of carbofuran in the United
States by regions in 1971, 1972, and 1974, based on reports, estimates
and information sources discussed in the preceding subsections of this
chapter. It is emphasized that the estimates for 1971 are those reported
by the USDA (1974), whereas those for 1972 and 1974 were obtained by RvR
Consultants. The RvR data estimates for these 2 yr are not directly
comparable to those for 1971 from USDA since sources and methods are
different. RvR's 1972 and 1974 surveys as well as pesticide use reports
from several of the north central states suggest that USDA's reported
total use of carbofuran in 1971, 2,860,000 Ib, may be low. It is believed
that the use of carbofuran in the United States did not actually increase
by about 75% (from 2.86 to 5.0 million Ib) from 1971 to 1972, but that
the actual use volume in 1971 was somewhat higher than estimated by USDA
and that, accordingly, the rate of growth from 1971 to 1972 was not
quite as steep.
It is estimated that in 1974 7.2 million Ib of carbofuran active
iJ^Zoi?* Were U86d ** the United States. Of this total, 6.3 million
Ib (88%) were used in the north central states, primarily on corn. An
estimated 400,000 Ib were used in the western states primarily on alfalfa
and rice. About 250,000 Ib were used in the south central states,
mainly on rice. The remaining 250,000 Ib were used in the northeastern
and southeastern states, mainly on corn.
147
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00
Ccrbofurcyi
i«72 estimated:
Source: von Rumker et al. (1974).
Figure 8. Materials Flow Diagram for Carbofuran (1972)
-------
Table 27. Currently Registered Uaee of Carbofuran
Site and peat
Agricultural crops
Alfalfa
Dosage
(Ib actual)'
Alfalfa blotch leaf mirer
Alfalfa snout beet'e
Alfalfa weevil (larvae)
Alfalfa weevil (adults)
Egyptian alfalfa weevil
' (larvae)
Grasshoppers
Lygus bugs
Pea aphid
Potato leafhopper
Bananas
Banana root borer
Corn (field)
1.0/acre (flow)
0.25-1.0/acre (flow)
0.25-1.0/acre (WP, flow)
0.5-1.0/acre (flow)
0.25-1.0/acre (UP. flow)
• 0.125-0.25/acre (flow)
1.0/acre (flow)
0.2S-1.0 acre (flow)
1.0/acre (flow)
1.25-1.5 g/cepa (G)
2.0 g/cepa (C)
2.0-2.5 g/cepo (G)
Tolerance, use, limitation* .
10 ppm' (fresh alfalfa) (not more than 5 ppm carbanates).
'40 ppm (alfalfa hay) (not more than 20 ppm carbamatea).
7-Day preharvcst interval through 0.25 Ib/acre.
Foliage application.
14-Day preharvest Interval ubove 0.25 through 0.5 Ib/acre.
Foliage application.
28-Day preharvest Interval from above 0.5
through 1.0 Ib/acre. Foliage application.
Do not apply more than once per season.
Apply only to pure stands of alfalfa.
Do not move bees into alfalfa fields within
7 days of application.
Northeastern states. Apply when Insects appear.
Dse restricted to New York state. Foliage application.
Apply when insects appear or feeding is first noticed.
Foliage application. Apply when larval feeding is first
ooticed.
{ullage application. Apply when adults appear.
Foliage application. Apply when larval feeding is first
noticed.
Use when grasshopper feeding is noticed.
Foliage application. Apply prior to bloom.
Foliage application. Apply when Insects appear.
Apply when Insects appear.
0.1 ppm.
No preharvest Interval through 3.0 Ib/acre or
5.5 g/unlt of production (cepa).
For export to Central and South America.
At planting time treatment. Apply 0.8-1.0 g to
planting hole and 0.45-0.5 g to the soil s.urface
after the hole has been filled in.
-plus-
Soil treatment. Apply 4 months and again 8 months
after planting.
Soil treatment to established plantings. Apply
twice per year. For the first treatment apply 0.4-0.5 g
around the base of the mother, daughter and grand-
daughter plants. For the second treatment apply
1.6-2.0 g over an area of 50 cm around the producing
unit Including the anther, dunghtcr and granddaughter plants.
0.2 ppm (grain) (not more than 0.1 ppm cnrbamatce).
25 ppm (fodder and forage) (not more'than 5 ppm
carbamates).
Multiple applications allowed if l.Olb or less was
used at planting.
Source: U.S. Environmental Protection Agency, EPA Compendium of Rcp.tHtorod
Poatlclilnd. Vol. Ill (1974).
149
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Table 27. (Continued)
Site and peat
Corn (continued)
Armyworm
Armyvorm, fill
Dosage
(Ib actual)
Tolerance, use, limitations
0.75-1.0/acre (with 40-ln. (1) Direct granules into planter shoe with iced
row spacing) or (2) place applicator Into furrow and mix
or with the covering soil or (3) apply granules
0.75-1.0/13,000 linear In 7-In. band behind planter shoe and incorpo-
feet of row (C) rate Into top Inch of soil. Will control army-
worn and fall arm/worm for approximately 4-6
weeks.
Corn borer, European
Second and third
generations
First generation
0.75-l.O/acre (with 40-
In. row spacing)
or
0.75-1.0/13,000 linear
feet of row (G)
1.0/acre (G)
2.0-3.0/13,000 linear
feet of row (with 40-
in. row spacing) (G)
Corn borer, southwestern 1.0/acre (G)
Fl«a beetles
Nematodes (dag'ger, lance,
lesion, root-knot,
spiral, sting, stubby
root, stunt)
Rootvonas, corn
1.5-3.0/acre (with 40-
in. row spacing)
or
1.5-3.0/13,000 linear
feet of row (C)
0.75-1.0/acre (with 40-
in. row spacing)
or
0.75-1.0/13,000 linear
feet of row (G)
1.5-2.0/13,000 linear
feet of row
Soil treatment at time of planting. Apply In •
7-in. band over the covered seed row. In-
corporate Into top Inch of soil. Claims are
limited to aid in the control of first genera-
tion European corn borers.
Foliage application. Broadcast by air or direct
granules into whorls with ground equipment.
Apply when eggs begin to hatch. Do not make
over two foliage applications per season.
For control of first generation larvae. (1)
Direct granules into planter shoe with seed
or (2) place applicator Into furrow and mix
with the covering soil or (3) apply granules
In 7-ln. band behind planter shoe and in-
corporate into top Inch of soil.
Foliage application. Broadcast by air or direct
granules Into whorls with ground equipment.
Apply when eggs begin to hatch. Claims limited
to control of second and third generation
larvae. Do not make foliage application if
more than 1.0 Ib actual carbofuran was applied
at planting. Do not make over two foliage ap-
plication* per season.
Apply in the seed furrow at time of planting.
(1) Direct granules into planter shoe with seed
or (2) place applicator Into furrow and mix
with the covering soil or (3) apply granules
In 7-ln. band behind planter shoe and incorpo-
rate into top Inch of soil.
Apply at planting time in a 7-15 in. band and
Incorporate into the top 3 in. of soil.
0.75-1.0/acr* (with 40-
in. row spacing)
or
0.75-1.0/13.000 llnMr
f««C of rev (flow, G)
susp. in a 7-ln. band over the row, or
inject It on each sldo of the row. Susp. may
be mixed with liquid fertilizer. Be certain
mixture is physically compatible. Do not mix
until ready to use. Apply G Into the seed
furrow at time of planting.
150
-------
Table 27. (Continued)-
Site and peit
Corn (field) (Continued)
Dotage
(Ib actual)
Rootworm, northern corn 0.75-1.0/acre (with 40-
In. row (pacing)
or
Rootvorm, southern com 0.73-1.0/13,000 linear
feet of row (G)
Rootwonn, weitern com
Stalk rot
0.75-1.0/acre (with 40-
in. row apaclng)
or
0.75-1.0/13,000 linear
feet of row (G)
0.75-1.0/13,000 linear
feet of row (G)
Wlreworms
Peanut*
2.0-3.0/acre (with 40-
In. row spacing)
or
2.0-3.0/13,000 linear
feet of row (G)
Thrlp* 2.0-4.0/acre (with 36-
in. row spacing)
or
0.133-0.275/1,000 linear
feet of row (G)
3.0-5.0/acre (with 36-
In. row spacing)
or
0.2-0.35/1,000 linear
feet of row (G)
Nenatodes (lesion, ring, 2.0-4.0/14,520 linear
root-knot, sting, stunt) feet of row
Potatoe leaf hopper
Rootworm, southern corn
Thrlps
Peppers
0.033-0.066/1,000 linear
feet of row
0.5-1.0/acre (with 36-in.
row spacing)
or
0.033-0.066/1,000 linear
feet of row (C)
Tolerance, use, limitations
Soil treatment at tine of planting. Apply In
a 7-in. band over the covered seed row. In-
corporate into the top Inch of soil.
Postplant soil treatment. Apply by banding over
the row and Incorporate it Into the soil, or
by side-dressing on both sides of the row.
Soil treatment at time ot planting. Apply in
a 7-in. band over the covered seed row. In-
corporate Into the top inch of soil.
Apply a 7-in. band and Incorporate into the
top 1-in. of aoll. This treatment reduces
losses due to stalk rot by reducing the
Incidence of insect wounds which permit
entry of the stalk rot fungus.
Soil treatment at time of planting. Apply in
a covered band or in the seed furrow.
0.2 ppm (not more than 0.1 ppra carbamates)
(peanuts).
S ppm (not more than I ppm carbamates)
(peanut hulls).
Do not feed treated forage to dairy animals or
animals being finished for slaughter.
Use restricted to Southeastern states. Apply
In 12-In. band over the row prior to plant-
Ing. Incorporate into top 3-6 in. of soil.
Use restricted to Southeastern states. Apply
In 18-in. band over the row prior to plant-
ing. Incorporate Into top 3-6 in. of soil.
Use restricted to Oklahoma, Texas and south-
eastern states. Apply as a 12-In. band over
the row and Incorporate into the top 3-6 in.
'prior to planting.
Use restricted to southeastern states. Apply
In seed furrow at tine of planting.
Use restricted to southeastern states. Apply
in the seed furrow at planting. This treat-
ment will also aid In controlling southern
corn rootworms.
1.0 ppa (not more than O.I ppm carbamates).
21-Day preharveat Interval through 3.0 Ib/acre.
Slde-dreas soil application.
151
-------
Table 27. (Continued)
Site «nd peat
Peppers (continued)
European corn borer
Green peach aphid
Potatoes
Aphlds
Colorado potato beetle
European corn borer
Potato flea beetle
Potato leafhopper
Potato tuberworm
Wirewonns
Colorado potato uetle
Potato flea beetle
Potato leafhopper
.Rice
Dark field
Mosquito (larvae)
Rice water weevil
Dosage
(Ib actual)
2.0 and 3.0/ocre iwith
38-ln. row spacing)
or
0.075 and 0.1/500 linear
feet of row (G)
2.0 and 3.0/acre (with
38-ln. row spacing)
or
0.075 and 0.1/500 linear
feet of row (G)
2.0-3.0/acre (with 38-
ln. row spacing)
or
0.143-0.218/1,000 linear
feet of row (G)
0.5.-1.0/acre (flow)
0.45-0.6/acre (C)
0.5/acre (C)
0.45-0.6/acre (C)
Shorghun Crecnbug
0.75-1.0/acre (C)
Toleranid. Use, llnltatlona
Side-dress soil treatment to one or both
sides of the row. If application is
- made to both sides, use half the speci-
fied row dosage per side. Hake two appli-
cations. Apply low dosage 2-4 weeks after
transplanting and hl&h dosage 4-6 week*
later. Incorporate Into soil.
Use restricted to the Delmarva Pennlnsula
and southern Now Jersey. Side-dress
soil treatment to one or both sides of
row. Make first application 2-4 weiks
after transplanting. Make second appli-
cation 4-6 weeks later.
2.0 ppm of which no more than 0.1 ppm is
carbamates.
Use restricted to New York state. Apply
directly Into the bottom of the seed
furrow at planting.
Mortheast, North Central and Colorado only.
Apply when insects appear. Do not make more
than 8 applications/season. Do not apply more
than 3 qt. to foliage If Furadan 10G were used
at planting. T)o not apply more than 1 qt./
application. Do not apply within 10 days of
harvest. Use ground equipment only;
1.0 ppm (rice and rice straw) (not more than
0.2 ppm carbamates). Do not apply more than
once per season.
Use restricted to Arkansas, Louisiana, Missi-
ssippi, and Texas. Apply from 1 day before
to within 2 days after permanent flooding.
For dark rlcefield mosquito, application
must be made within 2-4 days after flooding.
Occasional tip burn may occur if propanil
la also used. Do not make more than one
application per season. Apply by air or
ground equipment.
Use restricted to California. Preplant soil
treatment. Apply to soil aurface prior to
flooding. Subsequent use of propanil may
result in crop injury. Do not make more
than one application per season. Apply by
air or ground equipment.
Use restricted to Arkansas, Louisiana, Missi-
ssippi, and Texas. Apply from 1 day before
to within 21 days after permanent {loading.
Occasional tip burn may occur if propanil
'is alao used. Do not make more than one
application per season. Apply by air or
ground equipment.
Use only on grain sorghum grown for forage.
Apply in seed furrow or In a 7-inch band
over the row.
Strawberry
Root weevils
Sugarcane
1.0-2.0/acre (flow)
152
Washington and Oregon, apply as 10 to 12
Inch bond over the row after lost harvest
but before Oct. 1. Do not make more than
one application per season.
0.1 ppm.
17-nny prchnrvont Intcrvnl through 0.75 lh/
aero. HromlrnHt application.
Do not use In llnwnlt.
4.0 lb/B,500 ft pi-r Hcnwon.
-------
Table 27. (Cci.tlnuad)
Pest aM site
Sugarcane (continued)
Meoatodes (root-knot,
•tunt) . .
Sugarcane borer
Wirovor
Sugar beet
Root oaggot
Tobacco (flue cured)
Flea beetles
Hornvorms
Dosage
(Ib actual)
2.0-4,0/8, 500 linear
feet of row (0)
0.5-0.75/acre (WP, flow G)
Nematodea (root-knot,
atunt)
2.0-4.0/acre (with 60-in.
row apaclng)
or
0.2i-2.5/1,000 linear
feet of row (G)
20/acre (G)
6.0/acre .(G)
4.0/acre (G)
6.0/acre (G)
Tobacco budworm
Wireworms
Tobacco (Hurley)
Flea beetlei
. 6.0/acre (G)
3.0-4.0/scre (G)
Toleronee. me. limitations
Apply at planting tine In a 15-ln. band directly
over planted cane juat before covering with
•oil. For atubble cane apply in a 15-ln. band
over the atubble row within 1-2 weeke following
harveat then cover with 1-2 in. of toil
Broadcaat application. Check field weekly from
early June through Auguat. Hake firat application
only after visible joints form and 5Z or more of
the plants are Infested with young larvae feeding
In or under the leaf aheath and which have not
bored Into stalks. Repeat whenever field checks
indicate the infeatation rate exceeds St.
At planting soil application. Apply in a 15-ln.
band directly over planted cane and cover with
soil. Do not use In Hawaii.
Stubble treatment. Apply in a 15-ln. band over
the stubble row. Apply anytime after harvest
until regrowth reaches 18 in. Cover with a
1-2 in. layer of soil. Covering with more than
2 in. of soil may reduce stand. For use
in Florida only.
Apply in a 6- to 7-ln. band and Incorporate
into top one in. of soil.
07
Broadcast soil application before forming beds.
Incorporate into top 4-6 In. of soil. Form
beds and plant as usual.
or
Band application after forming beds. Apply In a
14-18 in. band over bed. Incorporate Into top
4-6 In. of soil and reform bed. Plant as usual.
This gives full season control of flea beetles
and controls homworms for approximately 60 days.
Before forming beds, apply granules broadcast over
soil surface and Incorporate 4-6 in. deep. Form
beds and plant.
or
After forming beds, apply granules In a 14-18 In.
band over the bed and Incorporate to a depth
of 4-6 in. Reform bed and plant. For flue-cured
tobacco only.
Broadcast soil application before forming beds.
Incorporate Into top 4-6 In. of aoil. Form
beds and plant as usual. Claims are limited
to aids In the control of the tobacco budworm.
Broadcast granules over the soil surface prior
to transplanting and Incorporate with a suitable
device.
153
-------
Table 27. (Continued)
Site «nd post
Ornamentals
(Woody (hrubs, trees *nd vines)
Cottonwood
Dosage
(Ib actual)
Cottonwood tvlg borer
Cottonwood leaf beetle
Clearwlng borer
Siberian elm
Elm leaf beetle
0.275-0.55/1,000 linear
feet of row 12-ln. row
spacing - 1.0-2.0/acre
(C)
0.3/1,000 linear feet of
row - 40 In. row spac-
ing - 4.0/acre (G)
0.003 Ib 01 0.049 oz/ln
of girth at 3-4 ft
height/tree (soluble
packet)
Forest, nonagricultural and wastelands
Pine seedlings
Pales weevil
Pitch-eating weevil
0.05/half gallon water
(flow)
1 teaspoon 10% (G)/
seedling
or
1.0 g/seedling (C)
Tolerance, use, limitations
For use in commercial planting!. Apply during
June or July to the root tone of the cutting
by the use of a subsoil applicator as a side-
dress 10-12 in. from the trees In a continuous
band on both sides of the trees.
For use in nursery plantings. Apply In Hay or
June to the root zone of the cutting by the
use of a subsoil applicator as a aldedress
10-12 in. from the trees in a continuous band
on both sides of the trees.
Use limited to Arizona, Colorado, Kansas,
Nebraska, New Mexico, Utah and Wyoming. Soil
treatment. Measure circumference (girth) at
3-4 ft height and place holes in ground (us-
ing probing tool) evenly spaced around treei
Locate holes away
If girth is; from trunk;
1-10 in. 1 ft
16-20 in. 3 ft
24-40 in. 6 and 12 ft (alternating)
44-80 in. 10 and 12 ft (alternating)
80 in. and larger 12 and 20 ft (alternating)
Thoroughly soak area under trees. Determine
proper location for holes and insert plugging
tool in soil with a slight twisting motion.
If soil is properly soaked, tool will enter
soil easily. Push tool in soil to depth of
black mark on stem of tool. Leave foil plug
in stem as the next plug will force the pre-
ceding one out. Place soil plug by each hole.
Drop one packet in each hole unopened. PUce
small amount of water on top of each packet.
Replace soil plug Iranediately and compress
with foot. Keep treated areas soaked with
water for 14 days.
Prctransplant root treatment. For use In pine
plantations. Prepare and apply a 11 (w/w)
actual slurry of clay to roots of pine
seedlings. Treat roots by dipping or other
suitable method which allows for a thorough
coating. Keep roots moist until seedlings
are transplanted. This amount treats 150-200
seedlings. Adequate ventilation Is required
lor indoor treatment.
Apply at transplanting. Distribute granules
on soil in a 6-in. radius around each seed-
ling. Cover granules with soil.
154
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Table 28. Use of Carbofuran in the U.S. by Crops, 1971
Quantity used
Crop
Corn
Rice£/
Other field crops
Vegetables
Fruits and nuts
Total
1,000 Lb
active ingredient
2,681
164
4
2
3
2,854
Percent
93.9
5.7
0.2
0.1
0.1
100.0
Acreage treated
1,000
Acres
3,677
78
7
8
2
3,772
Percent
97.5
2.1
0.2
0.2
Negl.
100.0
aj The quantity of the compound may be upward biased or the rice acreage
treated may be downward biased since the recommended application rate
is only 0.5 Ib/acre.
Source: U.S. Department of Agriculture (1974).
155
-------
Table 29. Use of Carbofuran in the U.S. by Regions, 1971
Farm production
region
Northeast-/
Appalachian^/
Southeast—'
Delta States!/
Corn Belt!/
Lake States!/
North Plains^/
South Plains]!/
Mountain!.'
Pacific!/
Total
Quantity used
1,000 Lb
active ingredient Percent
59 2.1
22 0.8
4 0.1
62 2.2
1,140 39.9
791 27.7
635 22.3
38
103
2,854 100.0
Acreage treated
1,000
Acres Percent
2.1
0.8
0.2
1.0
38.
34,
79
30
7
36
1,443
1,302
779
54
42
3,772 100.0
20.7
&l Maine, New Hampshire, Massachusetts, Vermont, Connecticut, Rhode
Island, New York, Delaware, Pennsylvania, Maryland, New Jersey.
b/ Kentucky, Tennessee, West Virginia, Virginia, North Carolina.
£/ Alabama, Georgia, South Carolina, Florida".
jd/ Arkansas, Louisiana, Mississippi.
£/ Iowa, Missouri, Illinois, Indiana, Ohio.
f/ Minnesota, Wisconsin, Michigan.
£/ North Dakota, South Dakota, Nebraska, Kansas.
h_/ Texas, Oklahoma.
_i/ Montana, Idaho, Wyoming, Nevada, Utah, Colorado, Arizona, New Mexico,
j/ Washington, Oregon, California.
Source: U.S. Department of Agriculture (1974).
acre added by RvR Consultants.)
(Application rates per
156
-------
Table 30. Use of Carbofuran in California by Major
Crons and Other Uses, 1970-1974
-•• rr
1 "^""-^ ->_ Year 1970 197
brop/use ' — 1,000 1
Alfalfa!/ - 0.1
Rice 8.8 8.7
1 1972 1973 1974
b of active ingredient
2.7 94.0 135.7
7.8 11.3 10.4
Cotton^' - 0.4 - 1.1
All other crops
and uses 0.7 0.3 0.1 0.2 ^_
Total 9.5 9.5 10.6 106.6 146.1
a/ Including alfalfa for hay and for seed.
b_/ Carbofuran is not registered for use on cotton.
Source: California Department of Agriculture (1973, 1974 and 1975).
157
-------
Table 31. Use of Carbofuran in California in 1972, 1973 and 1974
by Crops and Other Uses, Applications, Quantities,
and Acres Treated
Commodity
1972
Alfalfa
Alfalfa for seed
Rice
Tomato
University of California
Total
1973
Alfalfa
Alfalfa for seed
Almond
Apple
Apricot
Beans , dry edible
Cotton
Fallow (open ground)
Nonagricultural areas
Peach
Potato
Rice
Soil (fumigation only) '
University of California
Water areas
Total
1974
Alfalfa
Rice
Rice
Total
Applications
187
1
343
1
532
2,744
5
2
1
1
5
1
1
1
1
8
224
1
2
2,997
2,841
241
1
3,082
Pound
active ingredient
2,719.29
21.02
7,849.20
1.87
0.11
10,591.49
93,720.02
229.50
16.19
17.87
15.32
51.66
1,114.27
45.00
0.03
1.75
31.52
11,309.73
5.00
0.28
15.76
106,573.90
135,670.12
10,437.11
0.20
146,107.43
Acres
18,687.50
24.00
15,748.90
50.00
34,510.40
268,279.50
304.00
37.00
51.00
35.00
76.00
53.00
90.00
12.00
8.00
36.00
18,150.70
10.00
18.00
287,160.20
267,605.63
21,075.30
40.00
288,680.93
Source: California Department of Agriculture (1971 to 1975)
158
-------
Table 32. Estimated Uses of Carbofuran in the U.S.
by Regions in 1971, 1972 and 1974
"" ~~~~ — -—— ____J[ear
Region ' • • _
a/
Northeast-'
Southeast—'
1971 I 1972 1 1974
1,000 Lb of active ingredient
60 100 125
30 100 125
c/
North central- 2,570 4,400 6,300
South central—
West^
••
60 200 250
140 200 400
Total 2,860 5,000 7,200
a/ New England States, New York, New Jersey, Pennsylvania.
b/ Maryland, Delaware, Virginia, West Virginia, North Carolina, South
Carolina, Georgia, Florida.
c/ Ohio, Indiana, Illinois, Minnesota, Wisconsin, Michigan, Iowa,
Missouri, North Dakota, South Dakota, Nebraska, Kansas.
d/ Kentucky, Tennessee, Arkansas, Louisiana, Mississippi, Alabama,
Oklahoma, Texas.
el rtontana, Idaho, Wyoming, Colorado, Utah, Washington, Oregon, Alaska,
New Mexico, Nevada, Arizona, California, Hawaii.
Sources: 1971 - U.S. Department of Agriculture (1974).
1972 - von Rumker et al. (1974).
1974 - RvR estimates; see text.
Note: The estimates for 1971 and those for 1972 and 1974 originate from
different sources and were obtained by different methods and are
therefore not directly comparable; see text.
159
-------
References
California Department of Agriculture, Pesticide Use Report; 1970. Sacramento,
Calif. (1971).
California Department of Agriculture, Pesticide Use Report: 1971, Sacramento,
Calif. (1972).
California Department of Agriculture, Pesticide Use Report; 1972. Sacramento,
Calif. (1973).
California Department of Agriculture, Pesticide Use Report: 1973. Sacramento,
Calif. (1974).
California Department of Agriculture, Pesticide Use Report; 1974. Sacramento,
Calif. (1975).
U.S. Bureau of the Census, U.S. Foreign Trade Statistical Classification of
Domestic and Foreign Commodities Exported from the United States, Schedule
B, Section 5, Chemicals (1971).
U.S. Department of Agriculture, Farmers' Use of Pesticides in 1971...Quantities/
Agricultural Economic Report No. 252, Economic Research Service (1974).
U.S. Environmental Protection Agency, EPA Compendium of Registered Pesticides.
Vol. Ill, Washington, D.C. (1974).
U.S. Tariff Commission, Imports of Benzenoid Chemicals and Products 1972, TC
Publication 601 (1973a).
U.S. Tariff Commission, United States Production and Sales of Pesticides and
Related Products. 1972 Preliminary (1973b).
U.S. Tariff Commission, United States Production and Sales of Pesticides and
Related Products. 1973 Preliminary (1974).
Von Rumker, R., E. W. Lawless, and A. F. Meiners, Production, Distribution.
Use, and Environmental Impact Potential of Selected Pesticides, Contract No.
EQC-311, Report for the Environmental Protection Agency and Council on
Environmental Quality, EPA 540/1-74-001 (1974).
Von Rumker, R., E. S. Raun, and F. Horay, Substitutes for Aldrin, Dieldrin.
Chlordane and Heptachlor for Insect Control on Corn and Apples, U.S.
Environmental Protection Agency, Contract No. 68-01-2448 (1975).
160
-------
PART III. MINIECONOMIC REVIEW
CONTENTS
Page
Introduction 163
Efficacy of Pest Control on Alfalfa 164
Cost Effectiveness of Pest Control—Alfalfa 165
Efficacy of Pest Control on Field Corn 165
Cost Effectiveness of Pest Control—Field Corn 167
Efficacy of Pest Control on Peanuts 168
Cost Effectiveness of Pest Control—Peanuts 169
Efficacy of Pest Control on Peppers 169
Cost Effectiveness of Pest Control—Peppers 170
Efficacy of Pest Control on Potatoes 170
Cost Effectiveness of Pest Control—Potatoes 171
Efficacy of Pest Control on Rice 171
Cost Effectiveness of Pest Control—Rice 172
Efficacy of Pest Control on Sugarcane 172
Cost Effectiveness of Pest Control—Sugarcane 173
Efficacy of Pest Control on Tobacco 173
Cost Effectiveness of Pest Control—Tobacco 174
References 181
162
-------
This section contains a general assessment of the efficacy and cost
effectiveness of carbofuran. Data on the production of carbofuran in the
United States, as well as an analysis of its use patterns at the regional
level, were developed as part of the Scientific Review (Part II) of this
report. The section summarizes rather than interprets data reviewed.
Introduction
The efficacy and cost effectiveness of a specific pesticide applied
to cropland should be measurable in terms_of the value of increased yield
or improved quality or in terms of reduced ^osts associated with the
pesticide's use. Therefore, one should be able to select a test plot of
a given crop, treat it with a pesticide, and compare its yield with a similar
untreated plot. The difference in yield should be the increase related to
the use of the pesticide. The increased income (i.e., the yield increase
multiplied by the selling price of the commodity) less the additional cost
(i.e., the pesticide, its application, and the harvesting of the increased
yield) is the net economic benefit related to the use of the pesticide.
Unfortunately, this method has many limitations. The data derived is
incomplete and should be looked on with caution. Review of the literature
and EPA registration files revealed pesticide-treated versus nontreated
crop experiments are conducted by many of the state agricultural experimental
stations. Only a few tests, however, have attempted to measure increased
yield and most of the yield information is found with a few crops such as
cotton, corn, potatoes, sorghum, and selected vegetables. Most crop experi-
ments measure the reduction in pest populations which cannot be directly
related to yield.
Even yield data from the test plots is only marginally reliable, since
these tests are conducted under field conditions that may never be duplicated
again or may not be representative of actual field practices. Each experi-
ment is somewhat unique since yield is affected by rainfall, fertilizer use,
severe weather conditions, soil type, region of the country, pest infestation
levels, and the rate, frequency and method of pesticide application.
Because of the above factors, yield tests at different locations and
in different years will show wide variations ranging from declines to
significant increases. For example, in a year of heavy pest infestation,
pesticide use can result in a high yield increase because of extensive
damage in the untreated test plot. Conversely, in a year of light infestation,
the yield increase will be slight.
The use of market price to estimate the value received by the producer
also has limitations. If the use of a pesticide causes an increase in the
national production, then the market price should decline. According to
Headley and Lewis (1967), a 1% increase in quantity marketed has at times
resulted in a greater than 1% decrease in price. Thus, the marginal revenue
from the increased yield would be a better measure of the value received.
163
-------
A third limitation to the quantification of the economic costs and
benefits is the limited data on the pesticide quantities used by crop
or pest, the number of acres treated, and the number of applications.
In most cases the amount of carbofuran used on different crops is not
available.
As a result of these limitations, an overall economic benefit for
a crop-pest combination cannot be determined. Where applicable, a range
of the potential economic benefits derived from *"he use of the pesti-
cide for control of a specific pest on a crop is ieveloped. This eco-
nomic benefit or loss is measured in dollars per acre for the highest
and lowest yield found in reviewed experimental tests. The highest
and lowest yield increases are multiplied by the price of the crop and
reduced by the cost of the pesticide and its application to give a range
of net economic benefits.
Carbofuran is a broad spectrum insecticide and nematicide available
as a flowable or granular formulation. The chemical may be applied at
planting time or as a foliar treatment (post-planting) depending on the
crop and target pest. It is registered for use on alfalfa, corn, peanuts,
peppers, potatoes, rice, sugarcane, and tobacco. Target pests of carbofuran
include armyworms, corn borers, nematodes, rootworms, wireworms, weevils,
aphids, lygus bugs, beetles, leafhoppers, tuberworms, grasshoppers, horn
worms, and tobacco budworms. The degree of control varies with the method,
rate and timing of application, the specific pest, and the crop. The use
of carbofuran has been shown to give excellent control of several pests
and to increase yields significantly.
Carbofuran prices are estimated at $4.55/lb AI for granular formulations
and $6.86/lb AI for 4F formulations (Shmerler, 1975).
For the purpose of this analysis, carbofuran application costs are
neglected when carbofuran is applied with the seed at the time of planting;
the incremental costs would be insignificant. Cost for incorporation into
the soil is estimated to be $2.50/acre and the estimated cost for foliar
application is $1.50/acre. All application rates are reported in pounds
of active ingredient.
Efficacy of Pest Control on Alfalfa
Carbofuran is recommended for control of the alfalfa snout beetle,
alfalfa weevil, Egyptian alfalfa weevil larvae, lygus bugs, and the pea
aphid.
Depew (1969) evaluated several insecticides for control of the weevil
in tests at Garden City, Kansas, during 1967 and 1968. Carbofuran EC at
0.25 Ib/acre provided 98% control after 14 days. In a second test, carbo-
furan EC at 0.5 Ib/acre gave 100% control after 7 days and 94% control after
28 days.
164
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Summers et al. (1971) found in alfalfa weevil tests at Ithaca,
New York, that carbofuran at 1.0 Ib/acre sprayed on alfalfa was su-
perior to other insecticides used in the test and that effects of the
insecticide were evident 4 weeks after application. The carbofuran-
treated plots looked excellent and rated 1 on a scale of 1 (no visible
damage) to 10 (crop destroyed). Carbofuran also gave 95% control of
aphids. Similar results were achieved in a second experiment conducted
later in the season.
The Egyptian alfalfa weevil is a serious pest of alfalfa in
California. Losses from this weevil in 1970 exceeded $6 million
(Summers and Cothran, 1972). Several insecticides for control of the
weevil at Strathmore, California, were evaluated during 1971. Carbo-
furan sprayed on a plot at a rate of 1 Ib/acre as early as 80 days
prior to cutting gave effective control-. The mean damage rating on a
scale of 1 (no damage) to 10 (crop destroyed) was 2.0 for carbofuran
and 7.3 for the untreated plot.
Johansen and Eves (1972) evaluated the effect of aerial applications
at 1.0 Ib/acre of prebloom sprays on lygus bugs and aphids in alfalfa fields
at Zillah, Washington. Carbofuran was quite effective against lygus bugs
which increased to only 4.4 nymphs per sweep at the end of 33 days. However,
aphid counts gradually increased (to 232.0/sweep) after 33 days. At this
population level, the field needed retreatment for both pests.
Cost Effectiveness of Pest Control
The yield effects related to the use of carbofuran on alfalfa ranged
from a decline of .08 to an increase of 1.18 tons/acre. At a 1971 to 1973
average hay price of $33.33/ton (U.S. Department of Agriculture, 1974), the
net economic benefits associated with the use of carbofuran on alfalfa
ranged from a loss of $11.03 to a gain of $34.97/acre. These results are
summarized in Table 33.
Efficacy of Pest Control on Field Corn
Carbofuran formulations are registered for control of several pests
that attack field corn. These include the armyworm and fall armyworm;
European and southwestern corn borers; flea beetles; the dagger, lance,
lesion, root-knot, spiral, sting, stunt and stubby root-knot nematodes;
corn rootworms (northern, southern, and western) and wireworms.
The western corn rootworm is a serious pest in the midwestern corn belt.
Hills and Peters (1972) evaluated several insecticides and application methods
at Newell, Iowa, in 1969. Carbofuran was applied at a rate of 1.0 Ib/acre in
liquid and granular formulations to De Kalb XL306 seed corn. With an assumed
acceptable adjusted root damage rating equal to or less than 2.5, carbofuran
performed favorably with damage ratings ranging from 1.62 to 2.23.
165
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Musick and Fairchild (1968) concluded that carbofuran, at rates varying
from 0.25 to 1.0 Ib/acre, would be.recommended for control of the western
corn rootworm larvae in Missouri. Carbofuran was applied with the seed at
planting and was rated for control of root damage. All tests were signifi-
cantly better than an untreated check at the 5% probability level.
Apple et al. (1969) found that 0.84 kg/ha (0.77 Ib/acre) of carbofuran
provided outstanding protection from the northern corn rootworm in tests
during 1968. The average number of larvae were reduced 99.6% compared to
an untreated check.
Petty and Kuhlman (1972) reported on corn rootworm control tests in
Illinois from 1968 to 1971. For the 1971 tests, carbofuran 10% granules
banded at 0.8 Ib/acre gave the highest control (77.7%) of all materials
evaluated and resulted an 11.4% yield enhancement. The summary of tests
over the 4-yr period showed that carbofuran averaged 84.6% control and
resulted in a yield enhancement of 12.3%. Kuhlman and Petty (1973) reported
on 1972 tests in Illinois which demonstrated that carbofuran 10G banded at
1.0 Ib/acre gave an average of 92% larvae control and increased yields by
5.8%.
The southwestern corn borer is a major pest in certain states. In pest
control tests, Henderson and Davis (1970) studied 4 insecticides at State
College and Holly Springs, Mississippi, from 1966 to 1968. The results
showed that 4 applications of 3% carbofuran granules applied to the foliage
at 0.5 Ib/acre reduced borer infestation by 48 to 84% and stalk girdling
by 70 to 95%. Yield changes compared to untreated plots ranged from a loss
of 2.0 bu/acre to a gain of 18.0 bu/acre. In 1968 tests with 4 applications
of 1.0 and 0.5 Ib/acre/application reduced borer infestation from 58 to 95%.
Yield changes ranged from a 1.0 bu/acre reduction to a 10.0 bu/acre increase
over the untreated plot. Some of the use rates in this test were above the
quantities registered for use.
Keaster (1972) found that carbofuran 10G applied at rates of 1.44 to
2.0 Ib/acre to the foliage of corn at Portageville, Missouri, in 1968 reduced
the amount of borer girdling by 49 to 90%. Yield effects varied from a loss
of 6.6 bu/acre to a gain of 21.8 bu/acre.
The European corn borer has been effectively controlled with carbofuran.
Harding et al. (1968) found that 0.25 Ib/acre provided 91% control of the first-
generation borer and 78% control of the second-generation borer in field tests
in 1966. Berry et al. (1972) conducted similar tests and reported 75 to 81%
control of first-generation borers with a 3% granular formulation at rates of
0.25, 0.50, and 1.0 Ib/acre. Control of second-generation borers was not as
good, ranging from 21% with an application of 0.25 Ib/acre granules to 78%
with 1.0 Ib/acre of 3% granules.
166
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Wedderburn et al. (1973) observed that carbofuran granules applied
at 0.75 Ib/acre to the whorls reduced first-generation corn borers by 77%
in tests at Mead, Nebraska, in 1971. In a second test, carbofuran 10%
granules at 2.0 Ib/acre applied either to the furrow or band reduced the
number of tunnels by 42 to 71%.
Kuhlman and Petty (1972) found that carbofuran at 1.0 Ib/acre applied
at planting with corn in Illinois did not control the first-generation
borer. However, 90% control was achieved at rates of 2.0 Ib/acre and 100%
control occurred at 3.0 Ib/acre.
Musick and Suttle (1973) evaluated carbofuran for control of the
annyworm. Carbofuran 10G was applied at rates of 1.2, 2.4, and 4.8 oz
AI/1,000 linear feet of row at planting. They found that the effectiveness
varied with the date of treatment and rate of application. An application
rate of 2.4 oz/1,000 linear feet of row was required at planting for maximum
suppression of the armyworm.
Kuhlman (1974) found that carbofuran applied with no-till corn at
1.0 Ib/acre achieved 100% control. These tests were conducted in Illinois
in 1973 when armyworm infestation was light.
Kuhlman and Petty (1972) found that wireworm control was poor with
carbofuran. Tests in Illinois in 1971 at 1.0 Ib/acre applied with corn at
planting showed an average control of 13.3%. These results were confirmed
by Sechriest and Sherrod (1973) who found that 1.3 Ib/acre of carbofuran
banded on corn for wireworm control was not significantly different at the
5% level from an untreated plot. The application rates were lower than the
2.0 to 4.0 Ib/acre recommended rate.
Nematode control was evaluated by Dickson and Johnson (1972). Although
control of sting and lesion nematodes with 10G carbofuran at a rate from
1.0 to 2.0 Ib/acre was slightly better than the untreated plots it was not
significantly different at the 5% probability level. Yield, however, in-
creased from 13 to 22 bu/acre. Arnett (1973) found similar results with
carbofuran 10G at the 2 Ib/acre rate. Yields increased from 26.5 to 27.2
bu/acre, but stubby rootknot and spiral nematodes were not controlled.
Cost Effectiveness of Pest Control
The range of yield changes due to the use of carbofuran varied from a
loss of 6.6 to a gain of 49.4 bu/acre as a result of several tests on corn.
With a 1971 to 1973 average corn price of $2.01/bu (U.S. Department of
Agriculture, 1974), the net economic benefits associated with the use of
carbofuran on corn after subtracting pesticide and application costs ranged
from a loss of $22.44/acre to a gain of $48.09/acre. Reduction in yields
only occurred in 2 of the tests. These results are summarized in Table 34.
167
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Efficacy of Pest Control on Peanuts
Carbofuran is registered for control of thrips, nematodes (lesion,
ring, root-knot, sting, and stunt), the potato leafhopper, and the
southern corn rootworm on peanuts. Several references on the efficacy
and yield changes associated with carbofuran applications on peanuts
were available from tests conducted by the agricultural experiment
stations at Tifton, Georgia; Virginia Polytechnic Institute at Blacks-
burg and Holland, Virginia; and Oklahoma State University at Stillwater,
Oklahoma. Data was available on all of the above pests with the exception
of the potato leafhopper. Most tests measured carbofuran efficacy against
several pests so that yield changes could not be identified with control
of any single pest.
Osborne (1970) conducted several tests at various locations in Vir-
ginia comparing carbofuran to other pesticides for control of root-knot,
sting, stunt, and ring nematodes as well as control of thrips on peanuts.
Application rates varied from 2 to 5 Ib/acre. They were applied in an
18 in wide band and incorporated 6 to 8 in deep. Control of sting nema-
todes at the 2.0 Ib/acre rate ranged from 72 to 92%, and only slight
damage from thrips was noticed. Thrips damage was rated 15 on a scale
of 10 (no damage) to 30 (severe damage). Yield increases ranged from
300 to 1,028 Ib/acre.
Smith (1972) conducted tests at Courtland, Virginia, and Cyprus Chapel,
Virginia, in 1971 comparing insecticides for control of thrips and ring
nematodes on peanuts. Carbofuran was applied in 14-in bands at a depth of
8 in. At Courtland, carbofuran 10G was applied at planting at 1.0 and
4.0 Ib/acre. Although thrips control increased 63% at both rates, ring
nematodes were not controlled at the 1.0 Ib/acre rate. Yields were also
lower by 357 and 412 Ib/acre. Results were similar at Cyprus Chapel,
although yield effects were not reported.
Smith (1971) also evaluated several insecticides for the control of
southern corn rootworm on peanuts grown in Virginia from 1965 to 1967.
Carbofuran applied at planting at rates from 1.0 to 4.0 Ib/acre (the latter
rate being higher than the current recommended rate). The 1.0 Ib rate pro-
vided control ranging from 1.8 to 9.3% damaged fruit. The damage to the
comparable test plots was 7.1 and 29.8%, respectively. Yield increase at
1.0 Ib/acre was 7.0%.
Several tests were conducted in Georgia to evaluate the ability of
carbofuran to control ring, root lesion, and root-knot nematodes, thrips,
and leafhoppers. Minton et al. (1969) found that the number of ring
nematodes in a peanut plot treated with 3.0 Ib/acre of carbofuran had
more nematodes than an untreated test plot. Minton and Morgan (1970)
reported more effective control of ring nematodes with carbofuran 10G
applied at planting of 5.0 Ib/acre than at 3.0 Ib/acre. Control increased
34% at the 5.0 Ib rate. (A 4.0 Ib/acre rate is currently recommended.)
168
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Carbofuran effectively controlled the lesion nematodes as measured
by a pod lesion index. On a scale of 1 to 3 (3 = severely discolored) ,
carbofuran-treated peanuts were significantly better than the untreated
check at the 5% level of significance. The rating index ranged from
1.0 to 1.8 at rates of 3.0 to 5.0 Ib/acre. Yields increased from 114
to 232 Ib/acre (Minton et al., 1970).
Morgan and Minton (1970) concluded that high yields of peanuts were
directly related to control of root-knot nematodes. This was supported
by Minton and Morgan (1971). Carbofuran applied at a rate of 5.0 Ib/acre
(which is higher than registered use rates) in this test resulted in a
peanut yield of 2,806 Ib/acre compared to a rototilled check plot yield
of 1,469 Ib/acre. Galling of roots was measured by an index of 1 to 5
with 1 representing the least galled and the 5 the most severely galled.
The index for the carbofuran plot was 2.9, compared to 4.7 for the check.
Carbofuran controlled thrips in most tests, but little relation was
found between thrips control and yields (Minton et al. , 1969).
Sturgeon and Shackelford (1972) reported that carbofuran at 2.0
and 4.0 Ib/acre applied with the seed effectively reduced nematode popu-
lations and increased yields from 423 to 485 Ib/acre over an untreated
plot.
Cost Effectiveness of Pest Control
The range of yield changes associated with the use of carbofuran
varied from a loss of 412 Ib/acre to a gain of 1,137 Ib/acre. At-an
average 1971 to 1973 price of 14.7
-------
Burbutis et al. (1972) tested carbofuran for control of the green
peach aphid in several tests in Delaware between 1969 to 1971. Single
and double applications of carbofuran granules side-dressed in a band at
rates varying from 1 to 4 Ib/acre reduced aphid populations by 56 to 95%.
Burbutis and Lesiewicz (1974), in 1971 tests at Bridgeville, Delaware,
found that 2 Ib/acre of carbofuran 10G, followed by a 3 Ib/acre application,
reduced European corn borer infestation later to 1% (compared to 30% for
the check) and increased yields by 3.6 tons/acre. Hale and Shorey (1971)
conducted tests at Santa Maria, California, from 1965 to 1969. They found
that carbofuran foliar sprays at 0.5 and 1.0 Ib/acre reduced aphids by
87 to 100% 14 days after treatment and up to 99% 28 days after treatment.
Cost Effectiveness of Pest Control
Pepper yield changes, due to the use of carbofuran, varied from a
gain of 22 cwt to 82 cwt/acre when compared to untreated test plots. At
a 1971 to 1973 average price of $12.97/cwt for peppers (U.S. Department
of Agriculture, 1974) and a cost of $4.55/lb AI for carbofuran, and an
application cost of $12.50/acre, the net economic benefits ranged from
a gain of $269.19 to $l,035.79/acre.
Efficacy of Pest Control on Potatoes
Carbofuran is registered for control of aphids, the Colorado potato
beetle, European corn borer, potato flea beetle, potato leafhoppers,
potato tuberworm and wireworms on potatoes.
Onsager (1969) tested several insecticides at Quincy, Washington,
in 1966 and George, Washington, in 1967. Carbofuran at rates of 2.2 lb/
acre provided wireworm control and reduced the degree of injury to tubers
by 71%. However, there were no significant differences in yields. Onsager
and Foiles (1970) found that carbofuran applied by band application at 2.3
Ib/acre was 27 to 64% more effective against wireworms than broadcast
application at 4.0 to 8.0 Ib/acre. (These latter rates are greater than
registered uses.) No significant difference in yields was observed.
Day (1970) found that 5.0 Ib/acre (3.0 Ib/acre is the recommended rate)
carbofuran granules broadcast on the soil gave 94% initial control of the
southern potato wireworm. Control, however, declined to 45% by the end of
53 days. Day and Crosby (1972) found that carbofuran at 2.0 Ib/acre pro-
duced erratic results in several experiments between 1965 and 1969 in South
Carolina. ' Control varied from 24 to 100%.
170
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Hofmaster and Waterfield (1972) evaluated insecticides for control
of the Colorado potato beetle in several tests in Virginia. At Painter,
Virginia, in 1967, 2.0 Ib/acre of carbofuran were banded on each side of
the row and effectively controlled the beetle for 120 days. Only 11
larvae/10 hills remained, whereas the plants that were not treated were
defoliated. Tests during 1968 to 1971 showed similar reductions in
larvae. In 1970, heavy infestations of the beetle destroyed the check
plot resulting in significantly increased yields in the treated plots.
Chapman (1971) tested 2 formulations of carbofuran (4F and 10G) at
3 different rates of application (.5 Ib/acre, 1.0 Ib/acre and 3.0 Ib/acre)
to control flea beetles. Yield increases ranged from 25 cwt/acre for 3.0
Ib/acre of a 10G formulation applied in-furrow to 78 cwt/acre^ for^ ._5
Ib/acre of a 4F formulation that was applied as a spray. Carbofuran
10G applied at 3.0 Ib/acre gave complete control of the flea beetles
and provided commercial control of aphids for 71 days after treatment.
FMC (1971) tested a 10G formulation of carbofuran for control of
the green peach aphid and the Colorado potato beetle. A banded application
of 1.18 Ib/acre enhanced the potato yield by 72 cwt/acre when the green
peach aphid was the target pest. With an application rate of 3.0 Ib/acre
directed at the Colorado potato beetle, the yield per acre was increased
by 85 cwt.
Cost Effectiveness of Pest Control
The range of potato yield increases related to the use of carbofuran
varied from 25 to 213 cwt/acre when compared to untreated potato test plots.
At a 1971 to 1973 average price of $2.99/cwt for potatoes (Agricultural
Statistics, 1974), net economic benefits after subtracting pesticide and
application costs ranged from $61.10 to $625.27/acre. Results are summarized
in Table 36.
Efficacy of Pest Control on Rice
Carbofuran is recommended for control of tihe rice water-weevil and
mosquito larvae.
Donoso-Lopez and Grigarick (1969) demonstrated that preplant treat-
ment of rice fields with carbofuran at 1.0 Ib/acre AI effectively controlled
adult weevils (78% mortality) on rice seedlings up to 4 weeks following the
applications. After 6 weeks mortality still occurred, but was reduced to
43%. At rates of 0.25 and 0.50 Ib AI, mortality was less but not signifi-
cantly so.
Gifford et al. (1975) evaluated carbofuran in several Louisiana
parishes between 1970 and 1972. They concluded that a single broadcast
application of 3% carbofuran granules at a rate of 0.5 Ib/acre AI applied
171
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as much as 5 weeks after the rice seedlings are flooded will reduce infesta-
tions of the rice water weevil larvae established in the root systems. Yield
increases per acre of rough rice ranged from 86 to 614 Ib.
The dark rice field mosquito breeds exclusively in the rice-producing
areas of Louisiana. Craven and Steelman (1968) evaluated several insecti-
cides for control of the mosquito at Crowley, Louisiana, in 1967. Propanil
at 3.0 Ib/acre was also applied with all treatments. The mixture with car-
bofuran EC at 0.1 Ib/acre applied 26 days after planting was phytotoxic
to the plants; the control was only 26.4% which was less than in the check
plot. Carbofuran at 0.05 Ib/acre gave 47.0% control and phytotoxicity was
not evident.
Lancaster and Tugwell (1969) found that carbofuran 10% granules applied
to the soil prior to the first watering of rice fields completely eliminated
the larvae of the southern house mosquito in tests at Stuttgart, Arkansas,
in 1967. Similar results were also obtained in 1968 tests.
Cost Effectiveness of Pest Control
Several tests were conducted to determine yield effects of carbofuran
for rice water weevil control. The results of these tests showed that yield
effects ranged from a loss of 199 Ib/acre to a gain of 1,614 Ib/acre.
With a 1971 to 1973 average price of $8.72/cwt for rice (U.S. Department
of Agriculture, 1974), economic benefits after subtracting pesticide and appli-
cation costs ranged from a loss of $20.88/acre to a gain of $50.01/acre. Most
of the tests showed positive yield changes. These results are summarized in
Table 37.
Efficacy of Pest Control on Sugarcane
Carbofuran is recommended for control of the sugarcane borer, wireworms,
and root-knot and stunt nematodes on sugarcane. Only one study was found
which evaluated insecticides for control of the sugarcane borer. Fuchs et al.
(1973) found that carbofuran at 0.75 Ib/acre applied as an aerial spray was
significantly more effective at the 5% level of probability than no treatment.
Control of the borer, as measured by the percent of bored internodes, was
52% better than the untreated check.
Tests at the Everglades Experimental Station in Belle Glade, Florida, in
1966 showed that carbofuran for nematode control gave a 36.5% yield increase
at an 8.0 Ib/acre rate and 37.8% yield increase at a 16.0 Ib/acre rate
(Applewhite, 1969a).
Tests at Canal Point, Florida, from 1966 to 1967 showed that a 3.8 lb/-
acre carbofuran in a banded application at planting gave better than 90% cont-
rol of wireworms, and it increased yields by 34,1 tons/acre (Applewhite, 1969b).
172
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In a 1971 Belle Glade, Florida, experiment (Metz, 1973a), 2 granular
formulations (5G and 10G) of carbofuran were applied at rates of 2.0 and
4.0 Ib/acre to control wireworms in stubble crop sugarcane grown in a muck
soil. The 4 Ib/acre rate was more efficacious than the 2 Ib/acre rate, with
wireworm control ranging from 52.2% to 82.6% 40 days after treatment. In-
creases in millable stalks/acre for all formulations ranged from 38.5% to
51.9%.
In a 1971/1972 Lantana, Florida, test (Metz, 1973a), 1 flowable and 2
granular formulations (4F, 10G, and 5G) of carbofuran were applied in-furrow
at rates of 2.0 and 4.0 Ib/acre to control wireworms in sugarcane. All for-
mulations and application rates completely controlled the wireworms, but the
largest yields resulted from the 4F formulations. Applied at 2 and 4 Ib/acre,
the 4F formulations increased the millable stalks/acre by 109.6% and 105.9%,
respectively.
Cost Effectiveness of Pest Control
Yield increases related to the use of carbofuran on sugarcane ranged
from 2.9 to 15.0 tons/acre. At a 1971 to 1973 average sugarcane price of
$12.53/ton (U.S. Department of Agriculture, 1974), a carbofuran cost of
$4.55/lb AI and an application cost of $2.50/acre, net economic benefits
ranged from $38.37 to $172.48/acre. These results are summarized in Table
38.
Efficacy of Pest Control on Tobacco
Mistric and Smith (1972) found that foliar damage to newly set flue-
cured tobacco plants by overwintered flea beetles was reduced by 97% with
4.1 Ib/acre of carbofuran. Mistric and Smith (1973) also achieved 76% flea
beetle control up to 16 weeks with 4.2 Ib/acre of carbofuran applied prior
to transplanting. The authors concluded that carbofuran was effective
against all major insects attacking flue-cured tobacco. These insects in-
clude the tobacco wireworm, southern potato wireworm, tobacco flea beetle,
tobacco budworm, and tobacco hornworm.
Dominick (1968) compared several insecticides for the control of the
hornworm on tobacco. Carbofuran applied as a foliar spray at 1.0 Ib/acre
produced tobacco that remained free from hornworms during the 21-day test
period. Mistric and Smith (1973) found in tests in Clayton, North Carolina,
during 1965-1967 that a pretransplant treatment of 4.2 Ib/acre (4.0 Ib rate
as recommended) carbofuran gave 96% control 31 days after transplanting, but
its effectiveness decreased rapidly by the eleventh week.
Girardeau (1971) evaluated carbofuran for control of the tobacco bud-
worm in experiments at Tifton, Georgia, in 1968 and 1969. The results of
these tests showed that plots treated with carbofuran at 6 Ib/acre had the
lowest number of damaged plants on each observation date throu"^ut the
173
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season. Treatments at 3.0 Ib or less per acre apparently became ineffective
after the seventh and eighth week after application. They concluded that
rates of 4 to 6 Ib/acre of carbofuran 10G would provide good season-long pro-
tection as measured by percent of leaves lost to the budworm. This loss
ranged from 2.6 to 4.2%. Mistric and Smith (1973) applied carbofuran prior
to transplanting at rates of 4.0 to 4.5 Ib/acre and obtained 38 to 52% bud-
worm control for 5 weeks in 2 out of 3 tests when the carbofuran was applied
prior to transplanting. Carbofuran control of the budworm in one of the 2
post-transplant experiments was 70%.
Cost Effectiveness of Pest Control
The yield increases related to the use of carbofuran on tobacco ranged
from 102 to 578 dried Ib/acre. At a 1971 to 1973 average tobacco price of
$.839/lb (U.S. Department of Agriculture, 1974), a carbofuran cost of $4.55/-
Ib AI, and an application cost of $2.50/acre, net economic benefits ranged
from $55.78 to $455.14/acre. These results are summarized in Table 39.
174
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Table 33. Sunmary of Carbofuran Testa on Alfalfa.
Ul
.
Applications
Feet
Alfalfa veevil
Alfalfa weevil.
Alfalfa veevil
Alfalfa weevil
Alfalfa veevil
Alfalfa weevil
Alfalfa weevil
Alfalfa weevil
Alfalfa weevil
Alfalfa veevil
Foraulation
4F .
4?
4F
4F
4?
4F
4F
. 4F
4F
4F
. Hethodi/
A
A
FS
FS
A
FS
FS
FS
FS
FS
Rate
(Ib/acre)
.5
.5
.5
.5
1.0
1.0
1/0
1.0
1.0
1.0
No.
1
1
1
1
1
1
1
1
1
1
Yield
Increase
(dried
ton»/'acre)b/-
.6
.11
.15
-
.79
1.3
1.18
.3
-
(.08)
Additional
Zncooa at
$33.33/ton
($/acre)
20.00
3.71
5.00
-
26.39
43.33
39.33
10.00
-
(2.67)
Carbofuran
CostaS/
($/acre)
3.43
3.43
3.43
3.43
6/86
6.86
6.86
6.86
6.86
6.86
Application
Coed/
(S/acra)
1.00
1.00
1.50
1.50
1.00
1.50
1.50
. 1.50
1.50
1.50
Economic
Benefit
($/ecre)
15.57
( .72)S/
.07
(4.93)«/
18.53
34.97
30.97
1.64
(8.36)fi/
(11.03)"
Source
Brant aad
Broadus. 1973
Broadua, 1973b
Broadua, 1973a
Keeude and
Broadua. 1973
Broadus, 1973b
Fienkoveki. 1974
Flenkowski, 1974
Broadus, 1973a
Kesuda and
Broadus. 1973
Fienkowski. 1974
£/ A • Aerially applied.
FS - Foliar spray.
£/ Yield is expressed as a dried weight, which la approxlaataly 25Z of the wet weight.
e/ 4F formulation - $6.86/lb (Shnerler. 1975).
i/ Aerial application - $1.007acre; Spray application - S1.50/acre.
e/ Data In parentheaea Indicates decreeses in yield. Incone, and economic benefit.
-------
Table 34. Sunoary of Carbofu-an Tests on Corn.
Applications
Pest
Xecatodes
Nematodes
Nexatodes
Xesatodes
Nesatodes
Nematodes
Ncoatodes
£exatodes
Neaatodes
Nematodes
Kematodes
Neca Codes
Xecatodee
Southwestern com borer
Southwestern corn borer
Southwestern corn borer
Southwestern corn borer
^~! Southwestern corn borer
CT\ Southwestern corn borer
Southwestern corn borer
Southwestern corn borer
Southwestern corn borer
Southwestern corn borer
Southwestern corn borer
Southwestern corn borer
Southwestern corn borer
Southwestern corn borer
Southwestern corn borer
Southwestern corn borer
Southwestern corn borer
Rootwora
Root worn
Forculatlon
10G
IOC
10G
10G
10G
IOC
4F
IOC
10G
10G
10G
10G
IOC
10G
IOC
IOC
10G
10G
10G
10G
10G
IOC
IOC
10G
10G
3G
3G
3G
3G
3G
IOC
IOC
Methods/
B
B
B
B
B
B
B
B
B
B
B
B
B
F
P .
P
t
P
P
F
P
PC
PC
PC
PC
PC
PC
PC
PC
PC
B
B
Rate
(ib/acre)
1.0
2.0
1.0
1.0
2.0
2.0
2.0
2.0
1.0
2.0
2.0
2.0
2.0
3.0
2.0
3.0
2.0
3.0
2.0
3.0
2.0
1
1
0.72
0.72
0.5
0.5
0.5
O.S
O.S
0.92
0.9
No.
1
1
1
1
1
1
1
1
1
1
1 '
1
1
1
1
1
1
1
1
1
1
2
2
2
2
4
4
4
4
4
1
1
Yltld
Increase]*/
(bu/r.cre)
13
22
22
14
27.2
26.5
37
32
21 '
10
32
20
21
21.9
25.2
15.5
23.0
18.2
19.9
36.6
49.4
21.8
14.7
(t,6)
6.9
9.0
15.0
(2.0)
18.0
16.0
13.8
13.3
Additional
Inconujk/
at $1.67/bu
(S/acre).
21.71
36.74
36.7.'
23.38
45.24
44.26
61.79
53.44
35.07
16.70
53.44
33.40
35.07
36.57
42.08
. 25.88
38.41
30.39
33.23
61.12
82.50
36.41
24.55
(11.02)
11.52
15.03
25.05
(3.34)
30.06
26.72
23.05
22.21
Carbofuran
CostsS./
($/acre)
4.55
9.10
4.55
4.55
9.10
9.10
13.72
9.10
4.55
9.10
9.10
9.10
9.10
13.65
9.10
13.65
9.10
13.65
9.10
13.65
9.10
13.65
9.10
6.55
6.55
9.10
9.10
9.10
9.10
9.10
4.19
4.10
Application
Cosed/
($/acre)
2.50
2.50
-
-
2.50
2.50
_
-
-
-
_
2.50
-
_
-
-
_
_
-
_
-
5.00
5.00
5.00
5.00
10.00
10.00
10.00
10.00
10.00
-
Economic
Benefit^/
($/aere)
14.66
25.14
32.19
18.83
33.64
32.66
48.07
44.34
30.52
7.60
44.34
21.80
25.97
22.92
32.98
12.23
29.31
16.74
24.13
47.47
73.40
17.76
10.45
(22.57)
(.03)
(4.07)
5.95
(22.44)
10.96
7.62
18.86
18.11
Source
Dickaon and Johnson (1972)
Dickson and Johnson (1972)
Dickson and Johnson (1972)
Dickson and Johnson (1972)
Arnett (1973)
Arnect (1973)
Dickson and Johnson (1973)
Dickson and Johnson (1973)
Dickson and Johnson (1973)
Dickson and .Johnson (1973)
Johnson et al. (1973)
Johnson et al. (1973)
Dickson et al. (1973)
Keaster and Fairchild (1968)
Keaster and Fairchild (1968)
Keaster and Fairchild (1968)
Keaster and Fairchild (1968)
Keaster and Fairchild (1968)
Keaster and F&irchild (1968)
Keaster and Fairchild (1968)
Keaster and Fairchild (1968)
Keaster (1.972)
Keaster (1972)
Keaster (1972)
Keaster (1972)
Henderson and Davis (1970)
Henderson and Davis (1970)
Henderson and Davis (1970)
Henderson and Davis (1970)
Henderson and Davis (1970)
Petty and Kuhlnan (1972)
Kuhlman and Petty (197.3)
•/ FS • Foliar granule*
~ B - Banded
F • Furrow
b/ Data la parenthases Indicate decreases to yield. IncoM, and economic benefit.
c/ Craaules - *4.55/lb; 4 F femulation - $6.86/lb (Shaerler. 197S).
d/ Foliar application - $1.50/acre; granular applications not applied at planting • $2.50/acr«.
-------
Table 35. Suauty of Carbofurao Teats on Peanuts
Peat
Neaatodea
Se=atodes
Xeaatodes
Xeaatodes
Thrips
Kesacodes
Seaatodes
Senatodes
Kesatodes
Seca codes
XezACodes
Senatodes
Neaatodea
Necatades
Seaatodea
Keaatodes
Xenatader
Xerutodes
Nasa^ades
.'^enatodes
Ke=atodes
XezaCodes
and
and
and
aad
and
and
and
and
and
aad
and
chrips
thrips
chrips
thrips
thrips
thrips
chrips
thrips
Chrips
thrips
thrips
Formulation
IOC
10G
10G
10G
IOC
IOC
IOC
10G
10G
IOC
IOC
10G
IOC
IOC
IOC
IOC
IOC
10G
10G
ICG
IOC
Application
Rate
(Ib/acre)
4.0
3.0
3.0
3.0
• 3.0
3.0 + 2.0
3.0
5.0
3.0 •(• 2.0
5.0
3.0
5.0
3.0
3.0 + 2.0
5.0
3.0
2.0
2.0
4.0
3.0
5.0
Method*/
B
B
B
B
B
B
B
B
B
B
B
B
B
B
B
B
B
B
B
B
B
. thrips, and
1— > leafhoppers
—J Xeaatodcs.
10G
5.0
B
Yield
Iiicreaaek/
(Ib/a^.-e)
1.290
105
568
266
764
812
131
62
232
147
114
931
810
692
370
300
1,028
5/2
362
731
1,337
620
. chrips, and
*"J leafhoppers
Sezatcdcs and
Ne=atodes
Se=«todes
S«c*todes
Xezitcdes
Xecatodes
Neeatodea
Seca codes
Xesatoucs
Thrips
Thrips
Thrips
and
and
and.
thrips
thrips
chrips
thrips
.
IOC
IOC
10G
IOC
4F
IOC
IOC
IOC
IOC
IOC
IOC
IOC
IOC
3.0
3.0
5.0
5.0
5.0
4.0
2.0
1.0 + 2.0
2.C + 2.0
2.0
4.0
1.0
1.0
B
B
B
B
S
FU
ru
FD + B
B
B
B
B
B
(11)
392
327
465
443
485
423
105
1.110
261
(357)
(412)
(35)
Additional'
IncOBeb./ at
Carbofuran
Costac/
14.7c/lb (S/acre) .(S/acre)
189.63
15.44
83.50
39.10
112.31
119.36
19.26
9.10
34.10
21.61
16.76
136.86
119.07
101.72
54.39
44.10
151.12
76.73
53.21
107.46
196.54
91.14
(1.62)
57.62
48.07
68.36
65.12
71.30
62.18
15.44
163.17
38.37
(52.48)
(60.56)
(5.14)
18.20
13.65
13.65
13.65
13.65
22.75
13.65
22.75
22.75
22.75
13.65
22.75
13.65
22.75
22.75
13.65
9.10
9.10
18.20
13.65
22.75
22.75
13.65
13.65
22.75
22.75
34.30
18.20
9.10
13.65
18.20
9.10
18.20
4.55
4.55
Application Economic
Cost!/ Benefitb/
(S/acre)
2.50
2.50
2.50
2.50
2.50
2.50
-
-
-
2.50
2.50
2.50
2.50
2.50
••
2.50
2.50
2.50
2.50
2.50
2.50
2.50
1.50
-
2.50
2.50
2.50
($/acre) Source
168.93 Osborne 09681
1.79
67.35
22.95
96.16
94.11
5.61
(13.64)
8.85
(1.14)
3.11
14.11
105.42
76.47
29.14
27.95
139.52
65.13
35.01
91.31
171.29
65.89
(17.77)
41.47
22.82
43.11
29.32
53.10
53.08
(0.71)
142.47
27.27
(70.68)
(65.11)
(12-19)
Laughlin et al. (1969)
Mlnton et al. (1969)
Morgan and Mir ton (1969)
Morgan and Minton (1969)
Mlnton and Morgan (1970)
Minton and Morgan (1970)
Mlnton and Morgan (1970)
Mincon et al. (1970)
Minton et al. (1970)
Minton et al. (1970)
Morgan and Minton (1970)
Morgan and Minton (1970)
Morgan and Minton (1970)
Osborne (1970)
Osborne (1970)
Osborne (1970)
Osborne (1970)
deletion et al. (197i)
Kinloch (1971)
Mlnton and Morgan (1971)
Morgan and Mlnton (1971)
Mor^n and Xlntcn (1971)
Morgan et al. (1571)
Morgan et al. (1971)
Mincer, and Morgan (1972)
Mlnton and Morgan (1972)
Scurgon and Shackdlt'ord
(1972)
Sturgeon and Shackeltbrd
(1972)
Sturgeon and Shaciteiford
(1472)
Sturgeon «t al. (1973)
Sturgton «t al. (1973)
S=ith (1972)
SalLh (1972)
Morgan et al. (1970)
_. S • Spray
~ FV • Furrov application.
b • Banded application.
b/ Data in parentheses indicates decreases In yield. Income acd ecocovlc benefit.
£/ Crandl«a - J4.55/lb Al; 4F fonaulatlon - $6.86/lb Al (ShawrUr. 1975).
4/ Spray application - $1.50/acra; granular application not applied at planting - $2.50/acre.
-------
Table ')6. Summary of Carbofuran Tests on Potatoes.
Pest Fonaulation
Colorado potato beetle
Colorado potato beetle
Colorado potato beetle
Colorado potato beetle
Colorado potato beetle
Colorado potato beetle
Colorado potato beetle
Colorado potato beetle
Colorado potato beetle
Fles beetles
Flea beetles
Flea beetles
Flea beetles
Potato leafhopper
Potato aphlds
Green peach aphid
Colorado potato beetle
Colorado potato beetle
^j Colorado potato beetle
00 Colorado potato beetle
European corn borer
Green peach aphidt
Green peach aphids
IOC
10G
10G
10G
4F
4F
10G
10G
10G
4F
4F
10G
10G
10G
10G
10G
10G
10G
10G
10G "
10G
10G
4F
Method8./
B
B
B
B
B
B
B -
B
B
S
S
FU
FU
B
B
B
B
SD
FU
SD
B
B
S
Rates
(Ib/acre)
2.0
2.0
2.0
J.O
2.0
2.0
2.0
2.0
2.0
0.5
1.0
1.0
3.0
2.0
3.0
1.18
3.0
3.0
3.0
3.0
2.0
2.0
0.5
Yield
"ncreaseA/
(cwt/acre)
187
191
213
209
142
140
171
134
150
78
53
57
25
85
87
72
85
128.4
128.1
194.6
181
174
148
Additional
Income]!/ at
$2.99/cut
($/acre)
559.13
571.09
636.87
624.91
424.58
418.60
511.29
4C0.6o
448.50
233.22
158.47
170.43
74.75
254.15
2f0.14
215.28
254.15
383.92
383.02
581.85
541.19
520.26
442.52
Carbofuran
Cost£/
($/acreL
9.10
9.10
9.10
13.65
13.72
13.72
9.10
9.10
9.10
3.43
6.86
4.55
13.65
9.10
13.65
5.37
13.65
13.65
13.65
13.65
9.10
9.10
3.43
Application Economic
O^sd/ Benefit^/
(S/acre) (S/acre)
2.
2.
2.
2.
1.
1.
2.
2.
2.
1.
1.
-
-
-
—
-
—
2.
-
2.
_
-
1.
50
50
50 "
50
50
50
50
50
50
50
50
50
50
50
547.53
559.49
625.27
608.76
409.36
403.38
499.69
389.06
436.90
228.29
150.11
165.88
61.10
245.05
246.48
209.91
240.50
367.77
369.37
565.70
532.09
511.16
437.59
Source
Hofnaster and Wacerfield
Hotmaster and Waterfield
Hofmaster and Waterfield
Hofmaster and Waterfield
Hofmaster and Waterfield
Hofmaster and Waterfield
Hofmaster and Waterfield
Hofmaster and Waterfield
Hofmaster and Waterfield
Chapcan (1971)
Chapman (1971)
Chapman (1971)
Chapman (1971)
Wells (1971)
Wells (1971)
FMC (1971)
FMC (1971)
Semel and Wilde (1969)
Semel and Wilde (1969)
Semel and Wilde (1969)
Hoi master and Waterfield
Hofmaster and Waterfield
Ho roaster and Waterfield
(1972)
(1972)
(1972)
(1972)
(1972)
(1972)
(1972)
(1972)
(1972)
(1969)
(1S69)
(1969)
a/ B • Banded application.
FU - Furrow application.
S - Spray application.
SD " Side-dressed.
b/ Data in parentheses Indicate decreases in yield. Income, and economic benefit.
c/ G.-anules - $4.55/lb AI 4F - $6.86/lb AI (Shmerler. 1975).
d/ Spray application - $1.50/acre; granular application, applied at planting - $2.50/acre.
-------
Table 37. Summary of C*rbofuran Tests on Rice.
. Applications
Pest
Rice water weevil
Rice vater weevil
?.ice vater veevil
Rice vater veevil
Rice vater veevil
Rice vater weevil
Rice vater weevil
Rice water veevil
Rice vater veevil
Rice water weevil
Rice water weevil
Rice water veevil
Rice vater weevil
Rice water weevil
Rice vater weevil
a/ £R • Broadcast.
Foraulation
30
30
30
30
30
30
30
30
30
'30
30
30
30
30
30
Method!/
BR
BR
BR
BR
BR '
BR
BR
BR
ER
BR
BR
BR
BR
BR
BR
It Data in parentheses indicate decrease! in
7/ Sorter (1975)
.
d"/ Broadcast applications - $1.
25/acre.
Rates
(Ib/acrc)
0.5
0.5
- 0.5
0.5 •>
0.5
0.5
0.5
0.5
0.5
0.5
0.25
0.50
0.25
0.50
0.50
Additional Carboturan
Yield Income^/ at Cost— at Application Economic
Increase^/ $8.72/cwt $4.55/lb Cost! Benefit^/
(Ib/ncre)
86
275
246
412
123
400
560
349
235
614
270-
(199)
13
(16)
326
-
yield*, income, and economic
Table
38. Suranary of
(S/acre) (S/acre)
7.50
23.98
21.45
27.21
10.73
34.88
48.83
30.43
20.49
53.54
23.54
(17.35)
1.13
(1.40)
28.43
benefit.
Carbofuran Tests
2.
2.
2.
2.
2.
2.
2.
2.
2.
2.
1.
2.
1.
2.
2.
28
'•3
28
28
23
28
28
28
28
28
14
28
14
28
28
($/acre) (S/acreJ
1.25
• 1.25
1.25
1.25
1.25
1.25
1.25
1.25
1.25
1.25
1.25
1.25
1.25
1.25
1.25
3.97
20.45
17.92.
32.40
7.20
31.35
45.30
26.90
16.96
50.01
2.15
(20.88)
(1.26)
' (4.93)
24.90
I Source
Clfford
Clffcrd
Cifford
Cifford
Clfford
Cifford
Cifford
Cifford
Clfford
Clfford
Clfford
Cifford
Cifford
Cifford
Cifford
et al. (1975)
ct.al. (1975)
et al. (1975)
et al. (1975)
et al. (1975)
et al. (1975)
et al. (1975)
et al. (1975)
et al. (1975)
et al. (1975)
and Trahan (19£9)
and Trahan (15i»)
and Trahas (1569)
acd Trahaa (1969)
and Trahaa (1969)
on Sugarcane.
Additional
Applications
Pest
Soil insects
Soil infects
Soil Insects
Soil Insects
Soil insects
Soil insects
Formulation
• ice
100
100
100
ICO
100
Methodi/
B
S
B
B
B
B
Rate
(Ib/.icre)
2.85
3.0
3.0
3.0
3.14
3.63
Yield
Increase
Income at
$12.53/ton
No. (tons/acre) • (S/ncre)
1 • 15.0
1 4.7
1 5.0
1 2.9
1 14.7
1 4.58
187.95
58.39
62.65
36.34
184.19
57.39
Carbofuran
(S/acre)
12.97
13.65
13.65
13.65
14.29
16.52
Application
Cost£/
($/acre)
2.50
2.50
2.50
2.50
2.50
2.50
Scntfit
172.48
42.74
46.50
20.19
167.40
38.37
Valdes. 1972a
Eroadus, 1973d
Eroadus, 1973c
Broadus, 1973*
Valdes, 1972a
Valdes. 1972b
-------
Table 39.
ary of Carbofuran Teat* on Tobacco.
Pest
Root-knot
Root-knot
Root-knot
Root-'-not
Root-knot
nematode
nematode
nematode
nematode
nematode
Application*
Rate
Formulation Mvthodi/ (Ib/acre)
IOC
IOC
IOC
IOC
IOC
6.0
6.0
6.0
6.0
6.0
lo.
1
1
1
1
1
Yield
Increaae
(cured
Ib/acre)
578
304
278
138
102
Additional
Income at
$.839/lb
($/acre)
484.94
255.06
233.24
115.78
85.58
Carbofuran
CostsW
(S/acre)
27.30
27.30
27.30
27.30
27.30
Application
Cost c/
(S/acre)
2.50
2.50
2.50
2.50
2.50
Economic
Benefit
.(S/acre)
455.14
225.26
.203.44
85.98
55.78
Source
Nance,
Ketz,
Nance,
Nance,
• Nance,
1972
1973c
1972
1972
1972
Tobacco flea beetle,
tobacco thrip, and
green peach aphid
IOC
4.0
456
382.58
18.20
2.50
366.88
Moore, 1971
Not identified
Not identified
IOC
IOC
B
B
5.0
5.0
1
1
161
152
135.08
127.53
22.75
22.75
2.50
2.50
109.83
102.28
Pleaa et al.,
Pleaa at al..
1971
1971
*f B • Banded application.
b/ Cranulea - $4.55/lb Al (Schmerlcr. 1973).
£/ Banded application! - $2.50/acra.
00
O
Table 40.
of Carbofuran Tests on Peppers.
Application*
PfSt
European corn
European corn
European corn
European corn
European corn
European corn
European corn
European corn
borer
borer
borer
borer
borer
borer
borer
borer
#
Formulation
10G'
IOC
IGi.
IOC
IOC
IOC
IOC
IOC
Method*!/
SD
SD
SD
SD
SD
SD
SD
SD
Ratea
(Ib/acre)
3.0
2.0 -I- 3.0
2.0 + 3.0
2.0 + 3.0
3.0
4.0
2.0 •»• 2.0
2.0 + 3.0
Yield
Increaae
(cvt/acre)
58
72
82
32
22
78
55.7
54.8
Additional
income at
$12.97/cwt
($/acre)
752.26
933.84
1,063.54
415.04
285.34
1,011.66
722.43
710.76
Carbofuran
coses at Application
$4.55/lb>./
($/acre)
13.65
.'22.75
22.75
18.20
13.65
18.20
18.20
22.75
costc/
($/acre)
2.50
5.00
5.00
5.00
7.50
2.50
5.00
5.00
Economic
benefit
(S/acre)
736.11
906.09
1,035.79
391.84
269.19
990.96
699.23
683.01
Source
Ryder etal.(1969)
Burbutls & Uslevicz (1974)
Burbutis & Kelscy
Burbutls & Kelsey
Burbutis & Kelaey
Burbutla 4 Kelsey
Uofmaater (1971)
Kofmaster (1971)
(1971)
(1971)
(1971)
(1971)
•
a/ SD • Stdc-dreused.
b/ Shaerler (1975).
c/ Slda-dreaaed application* - $2.50/acre/appllcation
-------
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«U.S. GOVERNMENT PRINTING OFFICE: 1976 210-810/156
187
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