Risks of Myclobutanil Use to Federally
Threatened California Red-legged Frog
(Rana aurora draytonii)
Pesticide Effects Determination
Environmental Fate and Effects Division
Office of Pesticide Programs
Washington, D.C. 20460
June 17,2009
-------
Primary Authors:
James K. Wolf, Ph.D., Environmental Scientist
Michael Lowit, Ph.D., Ecologist
Rebecca Daiss, M.S., Biologist
Secondary Review:
Pamela M. Hurley, Ph.D., Toxicologist
James Hetrick, Ph.D., Senior Science Advisor
Branch Chief, Environmental Risk Assessment Branch 3:
Dana Spatz
-------
Table of Contents
1 Executive Summary 10
2 Problem Formulation 17
2.1 Purpose 17
2.2 Scope 19
2.3 Previous Assessments 20
2.4 Stressor Source and Distribution 21
2.4.1 Physical and Chemical Properties 21
2.4.2 Environmental Fate Assessment 22
2.4.3 Environmental Transport Assessment 25
2.4.4 Mechanism of Action 25
2.4.5 Use Characterization 26
2.5 Assessed Species 30
2.5.1 Distribution 30
2.5.2 Reproduction 33
2.5.3 Diet 34
2.5.4 Habitat 34
2.6 Designated Critical Habitat 35
2.7 Action Area 37
2.8 Assessment Endpoints and Measures of Ecological Effect 40
2.8.1 Assessment Endpoints for the CRLF 40
2.8.2 Assessment Endpoints for Designated Critical Habitat 42
2.9 Conceptual Model 44
2.9.1 Risk Hypotheses 44
2.9.2 Diagram 44
2.10 Analysis Plan 46
2.10.1 Measures to Evaluate the Risk Hypothesis and Conceptual Model 47
3 Exposure Assessment 51
3.1 Label Application Rates and Intervals 51
3.2 Aquatic Exposure Assessment 52
3.2.1 Modeling Approach 52
3.2.2 PRZM Scenarios 53
3.2.3 Model Inputs 56
3.2.4 Available Monitoring Data 58
3.2.5 Modeling Results 60
3.3 Terrestrial Animal Exposure Assessment 64
3.4 Terrestrial Plant Exposure Assessment 67
4 Effects Assessment 68
4.1 Evaluation of Aquatic Ecotoxicity Studies 71
4.1.1 Toxicity to Freshwater Fish 72
4.1.2 Toxicity to Freshwater Invertebrates 73
4.1.3 Toxicity to Aquatic Plants 76
4.2 Toxicity of Myclobutanil to Terrestrial Organisms 77
4.2.1 Toxicity to Birds 78
4.2.2 Toxicity to Mammals 81
-------
4.2.3 Toxicity to Terrestrial Invertebrates 87
4.2.4 Toxicity to Terrestrial Plants 87
4.3 Use of Probit Slope Response Relationship to Provide Information on the
Endangered Species Levels of Concern 89
4.4 Incident Database Review 90
4.4.1 Terrestrial Incidents 90
4.4.2 Aquatic Incidents 91
Risk Characterization 91
5.1 Risk Estimation 91
5.1.1 Exposures in the Aquatic Habitat 91
5.1.2 Exposures in the Terrestrial Habitat 94
5.1.3 Primary Constituent Elements of Designated Critical Habitat 99
5.2 Risk Description 101
5.2.1 Direct Effects 105
5.2.2 Indirect Effects (via Reductions in Prey Base) 108
5.2.3 Indirect Effects (via Habitat Effects) 112
5.2.4 Effects to Designated Critical Habitat 114
5.2.5 Spatial Extent of Potential Effects 117
Uncertainties 121
6.1 Exposure Assessment Uncertainties 121
6.1.1 Maximum Use Scenario 121
6.1.2 Aquatic Exposure Modeling of Myclobutanil 121
6.1.3 Usage Uncertainties 123
6.1.4 Terrestrial Exposure Modeling of My clobutanil 123
6.1.5 Spray Drift Modeling 124
6.2 Effects Assessment Uncertainties 125
6.2.1 Age Class and Sensitivity of Effects Thresholds 125
6.2.2 Use of Surrogate Species Effects Data 125
6.2.3 Sublethal Effects 125
6.2.4 Location of Wildlife Species 126
6.2.5 Use of Surrogate Chemical Effects Data 126
Risk Conclusions 126
References 132
-------
List of Tables
Table 1.1 Effects Determination Summary for Myclobutanil Use and the CRLF 13
Table 1.2 Effects Determination Summary for Myclobutanil Use and CRLF Critical
Habitat Impact Analysis 14
Table 1.3 Myclobutanil Use-specific Direct Effects Determinations1 for the CRLF 15
Table 1.4 Myclobutanil Use-specific Indirect Effects Determinations1 Based on Effects to
Prey 16
Table 2.1 Summary of Myclobutanil and 1,2,4-triazole Physical and Environmental Fate
Properties 23
Table 2.2 Myclobutanil Uses Assessed for the CRLF 26
Table 2.3 Summary of California Department of Pesticide Registration (CDPR) Pesticide
Use Reporting (PUR) Data from 1999 to 2006 for Currently Registered
Myclobutanil Uses 29
Table 2.4 Assessment Endpoints and Measures of Ecological Effects 41
Table 2.5 Summary of Assessment Endpoints and Measures of Ecological Effect for
Primary Constituent Elements of Designated Critical Habitata 43
Table 3.1 Summary of PRZM and EXAMS Environmental Fate Data Used for Aquatic
Exposure Inputs for Myclobutanil and Myclobutanil plus 1,2,4-triazole for
Endangered Species Assessment for the CRLF l 57
Table 3.2 Myclobutanil results from the summary of analysis of moderate-use pesticides
and degradates in water samples from water supply intakes and finished-
supply taps in Reservoir Pilot Monitoring Program. (USGS, 2001) 58
Table 3.3 Distribution of Myclobutanil Concentrations (|ig/L) in USGS NAWQA Surface
Water Monitoring Data Monitoring Data (1998-2007) 59
Table 3.4 Myclobutanil concentrations in Rain in California Agricultural Watershed
(Vogel et al., 2008) 59
Table 3.5 Aquatic EECs (|ig/L) for Myclobutanil Uses in California 60
Table 3.6 EECs California Red legged frog - myclobutanil + 1,2,4-triazole 61
Table 3.7 Time (years) for myclobutanil and myclobutanil plus 1,2,4-triazole to reach
plateau concentration in standard farm pond (USEPA, 2007) 64
Table 3.8 Input Parameters for Foliar Applications Used to Derive Terrestrial EECs for
myclobutanil with T-REX 65
Table 3.9 Upper-bound Kenega Nomogram EECs for Dietary- and Dose-based
Exposures of the CRLF and its Prey to Myclobutanil 66
-------
Table 3.10 EECs (ppm) for Indirect Effects to the Terrestrial-Phase CRLF via Effects to
Terrestrial Invertebrate Prey Items 67
Table 3.11 TerrPlant Inputs and Resulting EECs for Plants Inhabiting Dry and Semi-
aquatic Areas Exposed to Myclobutanil via Runoff and Drift 68
Table 4.1 Freshwater Aquatic Toxicity Profile for Myclobutanil 71
Table 4.2 Categories of Acute Toxicity for Fish and Aquatic Invertebrates 72
Table 4.3 Conazole (DMI triazole) Fungicide Chronic Toxicity to Aquatic Invertebrates
75
Table 4.4 Conazole (DMI Triazole) Fungicide Toxicity to Aquatic Vascular Plants 76
Table 4.5 Terrestrial Toxicity Profile for Myclobutanil 77
Table 4.6 Categories of Acute Toxicity for Avian and Mammalian Studies 78
Table 4.7 Avian Acute Toxicity Data 79
Table 4.8 Avian Chronic Toxicity Data 81
Table 4.9 Mammalian Acute Toxicity Data 82
Table 4.10 Acute Rat Toxicity Comparison of Myclobutanil Formulations 83
Table 4.11 Mammalian Chronic Toxicity Data 85
Table 4.12 Terrestrial Plant Toxicity Data for 5 Other DMI Fungicides 88
Table 5.1 Summary of Acute and Chronic Direct Effect RQs for the Aquatic-phase CRLF
92
Table 5.2 Summary of Acute and Chronic RQs Used to Estimate Indirect Effects to the
CRLF via Direct Effects on Aquatic Invertebrates as Dietary Food Items (prey
of CRLF juveniles and adults in aquatic habitats) 94
Table 5.3 Summary of Acute RQs Used to Estimate Direct Effects to the Terrestrial-
phase CRLF (non-granular application) 95
Table 5.4 Summary of Acute RQs Used to Estimate Direct Effects to the Terrestrial-
phase CRLF (granular application) 96
Table 5.5 Summary of Chronic RQs Used to Estimate Direct Effects to the Terrestrial-
phase CRLF (non-granular application) 96
Table 5.6 Summary of Acute and Chronic RQs Used to Estimate Indirect Effects to the
Terrestrial-phase CRLF via Direct Effects on Small Mammals as Dietary
Food Items (non-granular application) 98
Table 5.7 Summary of Acute RQs Used to Estimate Indirect Effects to the Terrestrial-
phase CRLF via Direct Effects on Small Mammals as Dietary Food Items
(granular application) 98
Table 5.8 Risk Estimation Summary for Myclobutanil - Direct and Indirect Effects to
CRLF 102
-------
Table 5.9 Risk Estimation Summary for Myclobutanil - PCEs of Designated Critical
Habitat for the CRLF 103
Table 5.10 Thirty Seven Gram Amphibian T-HERPS RQs for Consumption of Small
Herbivorous Mammals 106
Table 5.11 Myclobutanil Application Rates Combined with Endpoints from 5 Triazole
DMI Fungicides Exceeding the Terrestrial Plant LOG for Listed and Non-
Listed Dicots in Semi-Aquatic Areas 114
Table 5.12 Input Parameters for Simulation of Myclobutanil in Spray Drift Using AgDrift
(v. 2.01) 118
Table 5.13 Summary of Maximum Predicted Distances for Potential Spray Drift Effects
118
Table 7.1 Effects Determination Summary for Myclobutanil Use and the CRLF 128
Table 7.2 Effects Determination Summary for Myclobutanil Use and CRLF Critical
Habitat Impact Analysis 129
-------
List of Figures
Figure 2.1 Myclobutanil Degradates 24
Figure 2.2 Myclobutanil Terrestrial Plant Metabolite 24
Figure 2.3 Map of Estimated Annual Agricultural Use of Myclobutanil in 2002 28
Figure 2.4 Recovery Unit, Core Area, Critical Habitat and Occurrence Designations for
CRLF 32
Figure 2.5 CRLF Reproductive Events by Month 33
Figure 2.6 Initial Area of Concern of "footprint" of potential use for myclobutanil 39
Figure 2.7 Conceptual Model for Myclobutanil Effects on Terrestrial Phase of the CRLF
45
Figure 2.8 Conceptual Model for Myclobutanil Effects on Aquatic Phase of the CRLF 46
Figure 3.1 Summary of Applications (pounds versus date) of Myclobutanil to Grapes in
2001 from CDPR PUR Data 53
Figure 3.2 Accumulation of PRZM/EXAMS Annual Peak Concentrations of
Myclobutanil and Myclobutanil plus 1,2,4-triazole in the California Tomato
Scenario (surrogate for CA Okra aerial spray use) 63
Figure 5.1 Overlap Map: CRLF Habitat and Myclobutanil Initial Area of Concern .... 120
-------
Appendices
Appendix A
Appendix B
Appendix C
Appendix D
Appendix E
Appendix F
Appendix G
Appendix H
Appendix I
Appendix J
Appendix K
Appendix L
Appendix M
Appendix N
Appendix O
Attachment 1.
Attachment 2.
Multi-ai Product Analysis
Aquatic Exposure Modeling
Environmental Fate Data
BEAD Analysis of CDPR PUR Database
CRLF - Spatial Summary
The Risk Quotient Method and Levels of Concern
T-REX Example Output
Bibliography of ECOTOX Open Literature
Accepted ECOTOX Data Table
HED Effects Table
Ecotoxicity Data
Incident Data
T-HERPS Example Output
Terrplant Example Output
Ecotoxicity and Environmental Fate Bibliography
Status and Life History of the California Red-legged Frog
Baseline Status and Cumulative Effects for the California Red-legged Frog
-------
1 Executive Summary
The purpose of this assessment is to evaluate potential direct and indirect effects on the
California red-legged frog (Rana aurora draytonii) (CRLF) arising from FIFRA
regulatory actions regarding use of myclobutanil on agricultural and non-agricultural
sites. In addition, this assessment evaluates whether these actions can be expected to
result in effects to the species' designated critical habitat. This assessment was
completed in accordance with the U.S. Fish and Wildlife Service (USFWS) and National
Marine Fisheries Service (NMFS) Endangered Species Consultation Handbook
(USFWS/NMFS, 1998 and procedures outlined in the Agency's Overview Document
(U.S. EPA, 2004).
The CRLF was listed as a threatened species by USFWS in 1996. The species is endemic
to California and Baja California (Mexico) and inhabits both coastal and interior
mountain ranges. A total of 243 streams or drainages are believed to be currently
occupied by the species, with the greatest numbers in Monterey, San Luis Obispo, and
Santa Barbara counties (USFWS, 1996) in California.
Myclobutanil is a systemic fungicide. Current labeled uses of myclobutanil include the
following food uses: almond, apple, apricot, artichoke, asparagus, beans (succulent),
blackberry, boysenberry, canistel, cherry, chrysanthemum garland, cotton, cucurbits
(pumpkin, squash, watermelon), currant, dewberry, eggplant, gooseberry, grapes, hops,
lettuce (head, leaf), loganberry, mamey (mamme apple), mango, mayhaw (Hawthorn),
melons, nectarines, okra, olallie berries, papaya, peach, pepper, peppermint, pimento,
plum, prune, raspberry (black, red), sapodilla, sapote white, spearmint, star apple,
strawberry, tomato, and youngberry. Non-food/non-feed uses include bluegrass,
commercial/industrial lawns, cotton (seed), Douglas Fir (seed orchard, shelter belt), golf
course turf, grasses grown for seed, hybrid cottonwood/poplar plantations, loblolly pine
(forest), ornamental and shade trees, ornamentals (ground cover, herbaceous plants,
lawns and turf, non-flowering plants, sod farm (turf), woody shrubs and vines),
residential lawns and slash pine forest. Grapes, apples, almonds, and cherries together
make up 80% of all labeled uses of myclobutanil in California.
Myclobutanil is stable to both hydrolysis and photolysis. Myclobutanil degradation is
controlled by microbial-mediated transformations. Myclobutanil is moderately persistent
to persistent (DT50> 70 days) in aerobic soils and persistent in anaerobic soils. The major
degradation products observed in the aerobic soil metabolism (ASM) studies are 1,2,4-
triazole (maximum 18%), CC>2, a polar degradate (p-4-chlorophenyl-p-cyano-y-(lH-
l,2,4-triazole)-butyric acid and unextractable residues. At the conclusion of the 367 day
aerobic soil metabolism study, 29 to 33 percent of the applied radioactivity remained as
parent myclobutanil and 13 percent was identified as 1,2,4-triazole. Once the maximum
level of 1,2,4-triazole is reached, its decline pattern parallels myclobutanil. Terrestrial
field dissipation half-life values range from 92 to 292 days. Because the myclobutanil
residues are fairly persistent, the potential to remain in soil is possible, especially when
10
-------
there are multiple applications. Fate studies for 1,2,4-triazole suggest aerobic soil
metabolism half-lives ranging from 22 to 375 days.
In addition to 1,2,4-triazole, plant and animal metabolism studies have identified a
number of metabolites not identified in the environmental fate studies (soil and water).
These metabolites include triazole alanine (TA), triazole acetic acid (TAA) and RH-9090.
Myclobutanil is mobile as indicated by the Freundlich Kads values (from 1.46 to 9.77
mL/g). The degradate (1,2,4-triazole) has lower Freundlich Kads values (0.234 to 0.833
mL/g), suggesting it would be more mobile than the parent compound.
Due to its persistence and mobility, the primary routes of dissipation are thought to be
through leaching, runoff, and spray drift. The limited monitoring data for myclobutanil
shows detected myclobutanil residues in surface water in California, but not in ground
water. Myclobutanil was also found in rainwater in a California watershed, suggesting the
occurrence of atmospheric transport.
Since CRLFs exist within aquatic and terrestrial habitats, exposure of the CRLF, its prey
and its habitats to myclobutanil are assessed separately for the two habitats. Tier-II
aquatic exposure models are used to estimate high-end exposures of myclobutanil in
aquatic habitats resulting from runoff and spray drift from different uses. The aquatic
assessment quantitatively considers exposure from parent myclobutanil as well as
exposure from myclobutanil and the degradation product 1,2,4-triazole. 1,2,4-triazole is a
major degradation product that is slowly formed from biodegradation under aerobic and
anaerobic conditions in soil. The 1,2,4-triazole's persistence appears to be equal to or
less than that of the parent myclobutanil, and it is more mobile. Peak model-estimated
environmental concentrations in surface water resulting from different myclobutanil uses
range from 2.1 to 61.4 |ig/L. These estimates are supplemented with analysis of available
California surface water monitoring data from U. S. Geological Survey's National Water
Quality Assessment (NAWQA) program and the California Department of Pesticide
Regulation. The maximum concentration of parent myclobutanil reported by NAWQA
for California surface waters with agricultural watersheds is 0.51 |ig/L. This value is
approximately 120 times less than the maximum model-estimated environmental
concentration. There were no detections of myclobutanil reported in the California
Department of Pesticide Regulation surface water database.
To estimate myclobutanil exposures to the terrestrial-phase CRLF, and its potential prey
resulting from uses involving myclobutanil applications, the T-REX model is used for
foliar, granular and cotton seed treatment uses. The AgDRIFT model is also used to
estimate deposition of myclobutanil on terrestrial and aquatic habitats from spray drift.
Due to lack of terrestrial plant data for myclobutanil, the TerrPlant model is used for risk
description purposes using plant effects data from similar fungicides to estimate
myclobutanil exposures to terrestrial-phase CRLF habitat, including plants inhabiting
semi-aquatic and dry areas, resulting from uses involving foliar myclobutanil
applications. The T-HERPS model is used to allow for further refinement of oral
exposures of terrestrial-phase CRLFs (the model allows for an estimation of food intake
11
-------
for poikilotherms using the same basic procedure as T-REX to estimate avian food
intake).
The effects determination assessment endpoints for the CRLF include direct toxic effects
on the survival, reproduction, and growth of the CRLF itself, as well as indirect effects,
such as reduction of the prey base or potential effects to its critical habitat. Direct effects
to the CRLF in the aquatic habitat are based on toxicity information for freshwater fish,
which are generally used as a surrogate for aquatic-phase amphibians. In the terrestrial
habitat, direct effects are based on toxicity information for birds, which are used as a
surrogate for terrestrial-phase amphibians. Given that the CRLF's prey items and
designated critical habitat requirements in the aquatic habitat are dependant on the
availability of freshwater aquatic invertebrates and aquatic plants, toxicity information
for these taxonomic groups is also discussed. In the terrestrial habitat, indirect effects
due to depletion of prey are assessed by considering effects to terrestrial insects, small
terrestrial mammals, and frogs. Indirect effects due to effects to the terrestrial habitat are
characterized by available data for terrestrial monocots and dicots.
One of the myclobutanil degradation products observed in environmental fate studies is
1,2,4-triazole. The Office of Pesticide Program's Health Effects Division (HED) has
conducted aggregate human health risk assessments for 1,2,4-triazole and triazole
conjugates (triazole alanine and triazole acetic acid) derived from conazole fungicides
(USEPA. 2006a, 2006b). 1,2,4-triazole and its conjugates are common metabolites to the
class of compounds known as the triazoles (a.k.a. triazole-derivative fungicides, T-D
fungicides, conazoles). These compounds all have a triazole ring with nitrogen atoms at
the 1, 2, and 4 positions.
For the terrestrial exposure assessment, a conservative default foliar dissipation half-life
of 35 days is used for all uses of myclobutanil to account for terrestrial exposure to the
parent, the primary plant metabolite RH-9090, the 1,2,4-triazole degradate and the
triazole conjugates (triazole alanine and triazole acetic acid). Mammalian toxicity data
on the degradates and/or a structure-activity analysis on degradates with no toxicity data
indicate that they are either equivalent to or less toxic than the parent.
Risk quotients (RQs) are derived as quantitative estimates of potential high-end risk.
Acute and chronic RQs are compared to the Agency's levels of concern (LOCs) to
identify instances where myclobutanil use within the action area has the potential to
adversely affect the CRLF and its designated critical habitat via direct toxicity or
indirectly based on direct effects to its food supply (i.e., freshwater invertebrates, algae,
fish, frogs, terrestrial invertebrates, and mammals) or habitat (i.e., aquatic plants and
terrestrial upland and riparian vegetation). When RQs for each particular type of effect
are below LOCs, the pesticide is determined to have "no effect" on the CRLF. Where
RQs exceed LOCs, a potential to cause adverse effects is identified, leading to a
conclusion of "may affect." If a determination is made that use of myclobutanil use
within the action area "may affect" the CRLF or its designated critical habitat, additional
information is considered to refine the potential for exposure and effects, and the best
available information is used to distinguish those actions that "may affect, but are not
12
-------
likely to adversely affect" (NLAA) from those actions that are "likely to adversely affect"
(LAA) the CRLF.
Based on the best available information, the Agency makes a "Likely to Adversely
Affect" determination for the CRLF from the use of myclobutanil. Additionally, the
Agency has determined that there is the potential for effects to CRLF designated critical
habitat from the use of the chemical. The CRLF and/or its critical habitat may be affected
for all crops, cotton and turf uses. The terrestrial-phase CRLF may be at risk following
consumption of small herbivorous mammals (acute exposure: most crop uses, cotton and
turf) and small insects (chronic exposure: cotton and turf uses). Direct effects on the
aquatic-phase CRLF are not expected. Indirect effects to the terrestrial-phase CRLF,
based on reduction in prey base may occur with terrestrial phase amphibians following
acute exposure (most crops, cotton and turf) and chronic exposure (turf and cotton) and
with mammals following acute exposure (apple, apricot, cherry, nectarine, peach, hops
and turf uses) and chronic exposure (all uses). Indirect effects to the aquatic-phase
CRLF, based on reduction in prey base are not expected. Indirect effects to both the
aquatic- and terrestrial-phase CRLF based on aquatic and riparian habitat, cover and/or
primary productivity may occur due to potential effects on the riparian terrestrial plant
community, particularly dicots in semi-aquatic areas (all uses). Direct effects on aquatic
plant habitat are not expected. Based on potential effects to the avian/terrestrial-phase
amphibians, mammals and terrestrial plants, there is a potential for terrestrial and aquatic
habitat effects. A summary of the risk conclusions and effects determinations for the
CRLF and its critical habitat is presented in Table 1.1 and 1.2. Further information on
the results of the effects determination is included as part of the Risk Description in
Section 5.2. Given the LAA determination for the CRLF and potential effects to
designated critical habitat, a description of the baseline status and cumulative effects for
the CRLF is provided in Attachment 2.
Table 1.1 Effects Determination Summary for Myclobutanil Use and the CRLF
Assessment
Endpoint
Effects
Determination 1
Basis for Determination
Survival, growth,
and/or reproduction
of CRLF
individuals
LAA1
Potential for Direct Effects
Aquatic-phase (Eggs, Larvae, and Adults):
Acute and chronic freshwater fish RQs are below the respective level of concern
(LOG) for all uses of myclobutanil.
Terrestrial-phase (Juveniles and Adults):
The acute avian LOG is exceeded at application rates of 0.12 Ib a.i./A and above
(most crops, cotton and turf). The highest probabilities of an individual effect
range from 1 in ~ 3.88E+02 to 1 in ~ 1. The chronic avian LOG is exceeded
following uses on cotton (0.06 Ib a.i./cwt) and turf at 1.3 Ibs a.i./A. Myclobutanil
uses overlap CRLF habitat.
Potential for Indirect Effects
Aquatic prey items, aquatic habitat, cover and/or primary productivity
Acute and chronic freshwater fish RQs are below the respective LOG for all uses
13
-------
Assessment
Eiulpoint
Effects
Determination 1
Basis for Determination
of myclobutanil.
Acute freshwater invertebrate RQs are below the LOG for all uses of
myclobutanil. No chronic freshwater invertebrate studies are available for
myclobutanil. Weight of the evidence from RQs based on myclobutanil EECs
and toxicity data from 9 other conazole fungicides indicates that minimal impact
is expected from chronic exposure to freshwater invertebrates as prey items.
Acute RQs for aquatic non-vascular plants for all uses of myclobutanil are below
the LOG. No aquatic vascular plant studies are available. Weight of the
evidence from RQs based on myclobutanil EECs and toxicity data from 7 other
conazole fungicides indicates minimal impact to the CRLF aquatic habitat, cover
and/or primary productivity.
Terrestrial prey items, riparian habitat
See description above for direct effects on birds as surrogate for terrestrial phase
amphibians. LOCs for listed mammals exceeded following acute exposure at
application rates of 0.25 Ib a.i./A and above and chronic exposure at application
rates of 0.0625 Ibs a.i./A and above. Percent effect on mammalian population is
estimated to range from 4 - 42% for the myclobutanil uses. Myclobutanil uses
overlap CRLF habitat.
For terrestrial invertebrates, the honeybee acute contact data show no mortalities
at concentration levels up to and including 2836 ppm (highest level tested),
which is higher than highest dietary-based EEC for small insects with the use on
turf; however, there is some uncertainty for potential mortality. For large
invertebrates, there is no concern. Based on the results of the honey bee study
and weight of the evidence from open literature studies, indirect impact to the
CRLF via effects of myclobutanil on terrestrial invertebrate food items is
expected to be minimal.
No acceptable terrestrial plant studies are available. RQs based on EECs and
toxicity data from 5 other conazole fungicides indicate that most uses may affect
terrestrial plants, particularly dicots in semi-aquatic areas. Weight of the
evidence from these data, the open literature and incident reports indicates that
these effects may have an impact on riparian habitat.
1 No effect (NE); May affect, but not likely to adversely affect (NLAA); May affect, likely to adversely
affect (LAA)
Table 1.2 Effects Determination Summary for Myclobutanil Use and CRLF Critical
Habitat Impact Analysis
Assessment
Endpoint
Effects
Determination
Basis for Determination
Modification of
aquatic-phase PCE
Habitat Effects
Acute RQs for aquatic non-vascular plants for all uses of myclobutanil are below
the LOC.
No aquatic vascular plant studies are available. Weight of the evidence from
RQs based on myclobutanil EECs and toxicity data from 7 other conazole
fungicides indicates minimal impact to the CRLF aquatic habitat.
No acceptable terrestrial plant studies are available. RQs based on EECs and
toxicity data from 5 other conazole fungicides indicate that most uses may affect
14
-------
Assessment
Eiulpoint
Effects
Determination
Basis for Determination
Modification of
terrestrial-phase
PCE
terrestrial plants, particularly dicots in semi-aquatic areas. Weight of the
evidence from these data, the open literature and incident reports indicates that
these effects may have an impact on riparian habitat.
Acute and chronic freshwater fish RQs are below the respective levels of concern
(LOG) for all uses of myclobutanil.
Indirect effects to the CRLF through effects to its prey in the aquatic habitat
(freshwater invertebrates) are expected to be minimal (see table 1.1).
No acceptable terrestrial plant studies are available. RQs based on EECs and
toxicity data from 5 other conazole fungicides indicate that most uses may affect
terrestrial plants, particularly dicots in semi-aquatic areas. Weight of the
evidence from these data, the open literature and incident reports indicates that
these effects may have an impact on riparian habitat.
The acute avian LOG is exceeded at application rates of 0.12 Ib a.i./A and above
(most crops, cotton and turf). The chronic avian LOG is exceeded following uses
on cotton (0.06 Ib a.i./cwt) and turf at 1.3 Ibs a.i./A.
LOCs for endangered species exceeded following acute exposure on a dose-basis
for many crops and chronic exposure on a dose-basis for all uses and on a
dietary-basis for many crops.
For terrestrial invertebrates, the weight of the evidence indicates that minimal
potential indirect impact to the CRLF via effects on terrestrial invertebrate food
items is expected.
Table 1.3 Myclobutanil Use-specific Direct Effects Determinations1 for the CRLF
Use(s)
All uses
All uses except artichoke, boysenberry, dewberry,
youngberry, grape and tomato
Artichoke, boysenberry, dewberry, youngberry, grape
and tomato
Cotton and turf
All uses except cotton and turf
Aquatic Habitat
Acute
NE
-
-
-
-
Chronic
NE
-
-
-
-
Terrestrial Habitat
Acute
-
LAA
NE
-
-
Chronic
-
-
-
LAA
NE
1 NE = No effect; NLAA = May affect, but not likely to adversely affect; LAA = Likely to adversely affect
15
-------
Table 1.4 Myclobutanil Use-specific Indirect Effects Determinations1 Based on
Effects to Prey
Use(s)
All uses
Footnote 2
Cotton, turf
Footnote 3
Algae
NE
-
-
-
Aquatic
Invertebrates
Acute
NE
-
-
-
Chronic
NLAA
-
-
-
Terrestrial
Invertebrates
(Acute)
NLAA
-
-
-
Aquatic-phase
frogs and fish
Acute
NE
-
-
-
Chronic
NE
-
-
-
Terrestrial-
phase frogs
Acute
-
LAA
-
-
Chronic
-
-
LAA
-
Small Mammals
Acute
-
-
-
LAA
Chronic
LAA
-
-
-
1 NE = No effect; NLAA = May affect, not likely to adversely affect; LAA = Likely to adversely affect
2 All uses except artichoke, boysenberry, dewberry, youngberry, grape and tomato
3 Apple, apricot, cherry, nectarine, peach, hops and turf uses
Based on the conclusions of this assessment, a formal consultation with the U. S. Fish
and Wildlife Service under Section 7 of the Endangered Species Act should be initiated.
When evaluating the significance of this risk assessment's direct/indirect and habitat
effects determinations, it is important to note that pesticide exposures and predicted risks
to the species and its resources (i.e., food and habitat) are not expected to be uniform
across the action area. In fact, given the assumptions of drift and downstream transport
(i.e., attenuation with distance), pesticide exposure and associated risks to the species and
its resources are expected to decrease with increasing distance away from the treated field
or site of application. Evaluation of the implication of this non-uniform distribution of
risk to the species would require information and assessment techniques that are not
currently available. Examples of such information and methodology required for this
type of analysis would include the following:
• Enhanced information on the density and distribution of CRLF life stages
within specific recovery units and/or designated critical habitat within the
action area. This information would allow for quantitative extrapolation
of the present risk assessment's predictions of individual effects to the
proportion of the population extant within geographical areas where those
effects are predicted. Furthermore, such population information would
allow for a more comprehensive evaluation of the significance of potential
resource impairment to individuals of the species.
• Quantitative information on prey base requirements for individual aquatic-
and terrestrial-phase frogs. While existing information provides a
preliminary picture of the types of food sources utilized by the frog, it
does not establish minimal requirements to sustain healthy individuals at
varying life stages. Such information could be used to establish
biologically relevant thresholds of effects on the prey base, and ultimately
establish geographical limits to those effects. This information could be
used together with the density data discussed above to characterize the
likelihood of adverse effects to individuals.
• Information on population responses of prey base organisms to the
pesticide. Currently, methodologies are limited to predicting exposures
16
-------
and likely levels of direct mortality, growth or reproductive impairment
immediately following exposure to the pesticide. The degree to which
repeated exposure events and the inherent demographic characteristics of
the prey population play into the extent to which prey resources may
recover is not predictable. An enhanced understanding of long-term prey
responses to pesticide exposure would allow for a more refined
determination of the magnitude and duration of resource impairment, and
together with the information described above, a more complete prediction
of effects to individual frogs and potential effects to critical habitat.
2 Problem Formulation
Problem formulation provides a strategic framework for the risk assessment. By
identifying the important components of the problem, it focuses the assessment on the
most relevant life history stages, habitat components, chemical properties, exposure
routes, and endpoints. The structure of this risk assessment is based on guidance
contained in U.S. EPA's Guidance for Ecological Risk Assessment (U.S. EPA 1998), the
Services' Endangered Species Consultation Handbook (USFWS/NMFS 1998) and is
consistent with procedures and methodology outlined in the Overview Document (U.S.
EPA 2004) and reviewed by the U.S. Fish and Wildlife Service and National Marine
Fisheries Service (USFWS/NMFS 2004).
2.1 Purpose
The purpose of this endangered species assessment is to evaluate potential direct and
indirect effects on individuals of the federally threatened California red-legged frog
(Rana aurora draytonii) (CRLF) arising from FIFRA regulatory actions regarding use of
myclobutanil on almond, asparagus, canistel, cotton, grapes, hops, mamey (mamme
apple), okra, peppermint, sapodilla, sapote white, spearmint, star apple, strawberry, and
selected crops from the following crop groups: root and tuber; leafy, legume and fruiting
vegetables; cucurbits; pome, stone and tropical fruits and berries. Non-food/non-feed
uses include bluegrass and grasses grown for seed, various lawn and turf uses, cotton
(seed), Douglas Fir (seed orchard, shelter belt), hybrid cottonwood/poplar plantations,
loblolly and slash pine forest, ornamental and shade trees, ornamentals, woody shrubs
and vines. In addition, this assessment evaluates whether use on these crops is expected
to result in effects to the species' designated critical habitat. This ecological risk
assessment has been prepared consistent with a settlement agreement in the case Center
for Biological Diversity (CBD) vs. EPA et al. (Case No. 02-1580-JSW(JL)) entered in
Federal District Court for the Northern District of California on October 20, 2006.
In this assessment, direct and indirect effects to the CRLF and potential effects to its
designated critical habitat are evaluated in accordance with the methods described in the
Agency's Overview Document (U.S. EPA 2004). Screening level methods include use of
standard models such as PRZM-EXAMS, T-REX, Terrplant and AgDRIFT, all of which
are described at length in the Overview Document. Additional refinements include an
analysis of the usage data, a spatial analysis and the use of the T-HERPS model. Use of
17
-------
such information is consistent with the methodology described in the Overview
Document (U.S. EPA 2004), which specifies that "the assessment process may, on a
case-by-case basis, incorporate additional methods, models, and lines of evidence that
EPA finds technically appropriate for risk management objectives" (Section V, page 31
of U.S. EPA 2004).
In accordance with the Overview Document, provisions of the ESA, and the Services'
Endangered Species Consultation Handbook, the assessment of effects associated with
registrations of myclobutanil is based on an action area. The action area is the area
directly or indirectly affected by the federal action. It is acknowledged that the action
area for a national-level FIFRA regulatory decision associated with a use of myclobutanil
may potentially involve numerous areas throughout the United States and its Territories.
However, for the purposes of this assessment, attention will be focused on relevant
sections of the action area including those geographic areas associated with locations of
the CRLF and its designated critical habitat within the state of California. As part of the
"effects determination," one of the following three conclusions will be reached regarding
the potential use of myclobutanil in accordance with current labels:
• "No effect";
• "May affect, but not likely to adversely affect"; or
• "May affect and likely to adversely affect".
Designated critical habitat identifies specific areas that have the physical and biological
features, (known as primary constituent elements or PCEs) essential to the conservation
of the listed species. The PCEs for CRLFs are aquatic and upland areas where suitable
breeding and non-breeding aquatic habitat is located, interspersed with upland foraging
and dispersal habitat.
If the results of initial screening-level assessment methods show no direct or indirect
effects (no LOG exceedances) upon individual CRLFs or upon the PCEs of the species'
designated critical habitat, a "no effect" determination is made for use of myclobutanil as
it relates to this species and its designated critical habitat. If, however, potential direct or
indirect effects to individual CRLFs are anticipated or effects may impact the PCEs of the
CRLF's designated critical habitat, a preliminary "may affect" determination is made for
the FIFRA regulatory action regarding myclobutanil.
If a determination is made that use of myclobutanil within the action area(s) associated
with the CRLF "may affect" this species or its designated critical habitat, additional
information is considered to refine the potential for exposure and for effects to the CRLF
and other taxonomic groups upon which these species depend (e.g., aquatic and terrestrial
vertebrates and invertebrates, aquatic plants, riparian vegetation, etc.). Additional
information, including spatial analysis (to determine the geographical proximity of CRLF
habitat and myclobutanil use sites) and further evaluation of the potential impact of
myclobutanil on the PCEs is also used to determine whether effects to designated critical
habitat may occur. Based on the refined information, the Agency uses the best available
information to distinguish those actions that "may affect, but are not likely to adversely
18
-------
affect" from those actions that "may affect and are likely to adversely affect" the CRLF.
This information is presented as part of the Risk Characterization in Section 5 of this
document.
The Agency believes that the analysis of direct and indirect effects to listed species
provides the basis for an analysis of potential effects on the designated critical habitat.
Because myclobutanil is expected to directly impact living organisms within the action
area (defined in Section 2.7), critical habitat analysis for myclobutanil is limited in a
practical sense to those PCEs of critical habitat that are biological or that can be
reasonably linked to biologically mediated processes (i.e., the biological resource
requirements for the listed species associated with the critical habitat or important
physical aspects of the habitat that may be reasonably influenced through biological
processes). Activities that may affect critical habitat are those that alter the PCEs and
appreciably diminish the value of the habitat. Evaluation of actions related to use of
myclobutanil that may alter the PCEs of the CRLF's critical habitat form the basis of the
critical habitat impact analysis. Actions that may affect the CRLF's designated critical
habitat have been identified by the Services and are discussed further in Section 2.6.
2.2 Scope
The fungicide, myclobutanil is currently registered for both agricultural and non-
agricultural uses in the State of California.
The end result of the EPA pesticide registration process (i.e., the FIFRA regulatory
action) is an approved product label. The label is a legal document that stipulates how
and where a given pesticide may be used. Product labels (also known as end-use labels)
describe the formulation type (e.g.., liquid or granular), acceptable methods of application,
approved use sites, and any restrictions on how applications may be conducted. Thus, the
use or potential use of myclobutanil in accordance with the approved product labels for
California is "the action" relevant to this ecological risk assessment.
Although current registrations of myclobutanil allow for use nationwide, this ecological
risk assessment and effects determination addresses currently registered uses of
myclobutanil in portions of the action area that are reasonably assumed to be biologically
relevant to the CRLF and its designated critical habitat. Further discussion of the action
area for the CRLF and its critical habitat is provided in Section 2.7.
1,2,4-triazole and its conjugates are common metabolites to the triazole class of
compounds, including myclobutanil. Only the 1,2,4-triazole degradate was identified in
soil and water metabolism studies. The percentage of 1,2,4-triazole reached a high of
18% in the aerobic soil metabolism study with 13 % remaining at the termination of a
367 day study. Because only a limited amount of environmental fate data for 1,2,4-
triazole are available, its concentration can not be estimated. For the aquatic exposure
assessment, concentrations of parent myclobutanil and the total residues (myclobutanil
plus 1,2,4-triazole) are estimated. The total residues for aquatic exposure is conservative
if the toxicity of the 1,2,4-triazole is less than or equal to the toxicity of myclobutanil.
19
-------
For the terrestrial exposure assessment, a conservative default foliar dissipation half-life
of 35 days is used to account for terrestrial exposure to the parent, the primary plant
metabolite RH-9090, the 1,2,4-triazole degradate and the triazole conjugates (triazole
alanine and triazole acetic acid). Crop-specific residue decline data on combined residues
of myclobutanil and the primary metabolite RH-9090, provide a range of half-lives from
14 to 26 days. Since no decline data are available for the 1,2,4-triazole and triazole
conjugates, toxicity data on the degradates indicate that they are either equivalent to or
less toxic than the parent and structure-activity analyses indicate that RH-9090 is likely to
be of equivalent toxicity to the parent, the default 35 day half-life is selected for use in
estimating terrestrial exposure.
The Agency does not routinely include in its risk assessments an evaluation of mixtures
of active ingredients, either those mixtures of multiple active ingredients in product
formulations or those in the applicator's tank. In the case of the product formulations of
active ingredients (that is, a registered product containing more than one active
ingredient), each active ingredient is subject to an individual risk assessment for
regulatory decision regarding the active ingredient on a particular use site. If effects data
are available for a formulated product containing more than one active ingredient, they
may be used qualitatively or quantitatively in accordance with the Agency's Overview
Document and the Services' Evaluation Memorandum (U.S., EPA 2004; USFWS/NMFS
2004).
Myclobutanil has registered products that contain multiple active ingredients. Analysis
of the available open literature and acute oral mammalian LD50 data for multiple active
ingredient products relative to the single active ingredient is provided in Appendix A.
The results of this analysis show that an assessment based on the toxicity of the single
active ingredient of myclobutanil is appropriate. All products with available acute
toxicity data had oral LD50 values of greater than 5000 mg/kg. Because the active
ingredients are not expected to have similar mechanisms of action, metabolites, or
toxicokinetic behavior, it is reasonable to conclude that an assumption of dose-addition
would be inappropriate. Consequently, an assessment based on the toxicity of
myclobutanil is the only reasonable approach that employs the available data to address
the potential acute risks of the formulated products.
2.3 Previous Assessments
Myclobutanil was registered in the U.S. after 1984 and has not been through the
reregi strati on process. Myclobutanil has been assessed a number of times for new uses
including Section 18 assessments. Based on the various past assessments, in general, risk
tended to be greatest for freshwater fish (acute), marine/estuarine invertebrates (acute),
birds (acute and chronic), and mammals (acute and chronic) depending on the use
patterns and application rates. To date, no data on toxicity of myclobutanil to terrestrial
plants, aquatic vascular plants, and chronic exposure to invertebrates (freshwater and
marine/estuarine) or marine/estuarine fish have been submitted to the Agency for review
and so risk has not been assessed quantitatively. Furthermore, certain toxicity data were
not available (e.g. chronic exposure to birds and acute exposure to marine/estuarine
organisms (fish and invertebrates) and aquatic non-vascular plants) at the time when
20
-------
some uses were assessed; however, that data have been subsequently obtained and used
in risk assessments of other uses.
2.4 Stressor Source and Distribution
2.4.1 Physical and Chemical Properties
Selected physical and chemical properties of myclobutanil are summarized below.
Common name:
Chemical name:
Myclobutanil
(CAS):
alpha-butyl-alpha (4-chlorophenyl)- 1H-1,2-triazole-1 -propane-nitrile
(IUPAC):
(RS)-2-(4-chlorophenyl)-2-( 1H-1,2,4-triazol-1 -ylmethyl)hexanentrile
Chemical structure:
H,C
Molecular formula
Molecular weight
Physical state:
Melting point:
Solubility:
Vapor pressure
Henry's Law constant
Log Octanol/Water partition
coefficient:
Dissociation Constant,
(pKa)
Ci5Hi7ClN4
288.8 g/mol
White crystalline solid
63 to 68 °C
142 mg/L water @ 25 °C and pH 7
124 mg/L @ 20 °C
1.49x 10-°6mmHgat25°C
3.25 x 10'06 atm m3/mole @ 25 °C
1.75xlO'07unitless @ 20 °C
2.89 @ pH 7 and 20 °C
2.3 (S 25 °C
21
-------
2.4.2 Environmental Fate Assessment
Available environmental fate parameters of myclobutanil and 1,2,4-triazole degradate are
listed in Table 2.1. These data are based on studies that were conducted prior to 1986
before Good Laboratory Practice (GLP) standards (40 CFR 160) and data requirements
for registration were promulgated in the Code of Federal Regulations (40 CFR 158). The
previously submitted studies have not been re-reviewed, although rate of degradation
(i.e., half-life) of myclobutanil in the aerobic soil metabolism study was re-estimated.
Due to its persistence and mobility, the primary routes of dissipation are through
leaching, runoff, and spray drift. Myclobutanil has been detected in rain in several
agricultural watersheds in California (Vogel et al., 2008); thus, there is also a potential
for atmospheric transport. Myclobutanil is stable to hydrolysis and to photolysis.
Myclobutanil degradation is controlled by microbial-mediated transformations.
Myclobutanil was moderately persistent to persistent (DT50 > 70 days) in aerobic soils
and persistent in anaerobic soils. The major degradation products observed in the aerobic
soil metabolism (ASM) studies were 1,2,4-triazole (maximum 18%), CC>2, a polar
degradate (p-4-chlorophenyl-p-cyano-y-(lH-l,2,4-triazole)-butyric acid; (maximum 9
%), and unextractable residues. At the conclusion of the 367 day ASM study, 29 to 33
percent of the applied radioactivity remained as parent myclobutanil and 13 percent was
identified as 1,2,4-triazole.
Myclobutanil degradation in the aerobic soil metabolism (ASM) studies does not appear
to follow first-order kinetics based upon visual inspection, but follows a "hockey stick"
degradation pattern (a rapid initial decline followed by a slower decline), thus the first-
order half-life does not accurately describe the decline of myclobutanil residues. The
observed (visible inspection) aerobic metabolism DT50 value for myclobutanil ranged
between 75 and 90 days. The DT90 for myclobutanil was not reached during the course
of the study (367 days). Once the maximum level of 1,2,4-triazole is reached, its decline
pattern parallels myclobutanil. The decline of the combined residues also followed the
hockey stick pattern. Myclobutanil photo-degrades with a half-life of approximately 143
days on soil. Thus, myclobutanil residues are fairly persistent. Terrestrial field dissipation
half-life values ranged from 92 to 292 days. Generally, half-lives estimated in terrestrial
field dissipation studies are less than aerobic soil metabolism studies because they
include other dissipation pathways in addition to metabolism. The study with the 292 day
terrestrial field dissipation half-life was conducted in California. Leaching was not a
significant dissipation pathway. The potential for accumulation in soil and sediment is
possible due to the persistence, especially when there are multiple applications. Further
discussion is provided in Section 3.2.5, Aquatic Exposure Modeling and Appendix B. In
an aerobic soil metabolism study the half-life of 1,2,4-triazole was estimated as 315 days.
Because log Kows for parent and degradation products are low (log Kow= 2.94), the
myclobutanil residues are not expected to bioaccumulate (MRID # 00162541).
Table 2.1 lists the selected physical and environmental fate properties of myclobutanil,
along with the major and minor degradate products detected in the submitted
22
-------
environmental fate and transport studies. The submitted study citations can be found in
Appendix O.
Table 2.1 Summary of Myclobutanil and 1,2,4-triazole Physical and Environmental
Fate Properties
Study
Molecular Weight
Vapor Pressure
Henry's Law
Constant
Laboratory
Volatility
Log Kow
Hydrolysis
Direct Aqueous
Photolysis
Photolysis on soil
Photodegradation
in air
Aerobic Soil
Metabolism
Anaerobic Soil
Metabolism
Anaerobic Aquatic
Metabolism
Aerobic Aquatic
Metabolism
Mobility
Terrestrial Field
Dissipation
Value (units)
288.8 g/mol
1.49xlO-°6mmHgat25°C
1.6xl(r06mmHg
3.25 x 10'09 atm nrVmole @ 25 °C
No data
log Kow= 2.94
Stable at pH 5, 7, and 9
Stable
143 days
No data
198, 2441 days
Assumed stable, No appreciable
degradation in 62 days.
No data
No data
Myclobutanil
Freundlich Kads -
1.46, 2.39, 4.44, 7.08, 9.77 mL/g
(l/n-0.89to 1.02)
Koc2
92 to 292 days
Major Degradates
Minor Degradates
-
-
-
-
-
-
-
1,2,4-triazole
-
1,2,4-triazole, CO2 and
fS-4-chlorophenyl-fS-cyano-
j (lH-l,2,4—triazole)-
butyric acid
1,2,4-triazole
-
-
1,2,4-triazole
Freundlich Kads -
0.19to3.35mL/g
(1/n- 0.65 to 0.85)
Koc2
MRID#
or Data
Source
D190680
calculated
-
00162541
001416-79
40641501
40319801
40528801
00164988
-
00164561
NoMRID
-
-
141602
40891501
164563
Study Status
-
-
No study
submitted
Acceptable
Acceptable
Acceptable
No study
submitted
Acceptable
Acceptable
No study
submitted
No study
submitted
Acceptable
Acceptable
1 Half-lives were recalculated (Appendix C) by EFED (D336254).
""' Koc not valid, sorption does not appear to be correlated with soil organic carbon (D336254).
23
-------
The metabolite/degradate 1,2,4-triazole has been detected in plant and animal metabolism
studies. However, a number of other degradates or metabolites not identified in soil and
water studies have been identified in plant and animal metabolism. These include
triazole-analine (TA) and triazole acetic acid (TTA).
The following figures provide the structures of the degradates/metabolites discussed in
this assessment.
-NH
\
.OH
1,2,4-Triazole
(a.k.a. 1,2,4-T; free triazole)
1-H-1,2,4-triazole
Triazole Alanine Triazole Acetic Acid
(a.k.a. TA) (a.k.a. TAA)
a-Amino- 1H-1,2,4-triazole- 1H-1,2,4-Triazole-1 -acetic
1-propanoicacid acid
Chemical structures for 1,2,4-triazole, triazole alanine, and triazole acetic acid
Figure 2.1 Myclobutanil Degradates
HO
N:
Figure 2.2 Myclobutanil Terrestrial Plant Metabolite
RH-9090 (a-(3-hydroxybutyl)-a-(4-chlorophenyl)-l/7-l,2,4-triazole-l-propanenitrile)
24
-------
2.4.3 Environmental Transport Assessment
Potential transport mechanisms include pesticide surface water runoff, spray drift, and
secondary drift of volatilized or soil-bound residues leading to deposition onto nearby or
more distant ecosystems. Surface water runoff and spray drift are expected to be the
major routes of exposure for myclobutanil. The USGS NAWQA Program has detected
myclobutanil residues in surface water samples collected in California (USGS, 2009).
Myclobutanil has been detected in rain in an agricultural watersheds sampled in
California (Vogel et al., 2008). Thus, there appears to a potential for atmospheric
transport of myclobutanil.
Myclobutanil is mobile as indicated by the Freundlich Kads values (from 1.46 to 9.77
mL/g) (Table 2.1). The lowest non-sand value is 2.39 mL/g. Desorption coefficients
were generally less than the sorption coefficients. The degradate (1,2,4-triaziole) has
lower Freundlich Kads values (0.234 to 0.833 mL/g), suggesting it would be more mobile
than the parent compound (Table 2.1). The sorption is not strongly correlated to soil
organic carbon (matter), thus Koc is not a good measure of mobility for modeling.
A number of studies have documented atmospheric transport and re-deposition of
pesticides from the Central Valley to the Sierra Nevada Mountains (Fellers et al., 2004,
Sparling et al., 2001, LeNoir et al., 1999, and McConnell et al., 1998). Myclobutanil was
detected in rain water in a study partially conducted in California (Vogel et al., 2008).
Prevailing winds blow across the Central Valley eastward to the Sierra Nevada
Mountains, transporting airborne industrial and agricultural pollutants into the Sierra
Nevada ecosystems (Fellers et al., 2004, LeNoir etal, 1999, and McConnell et al., 1998).
Several sections of critical habitat for the CLRF are located east of the Central Valley.
The magnitude of transport via secondary drift depends on the ability of myclobutanil to
be mobilized into air and its eventual removal through wet and dry deposition of
gases/particles and photochemical reactions in the atmosphere. Therefore,
physicochemical properties of myclobutanil that describe its potential to enter the air
from water or soil (e.g., Henry's Law constant and vapor pressure), pesticide use data,
modeled estimated concentrations in water and air, and available air monitoring data
from the Central Valley and the Sierra Nevadas are considered in evaluating the potential
for atmospheric transport of myclobutanil to locations where it could impact the CRLF.
In general, deposition of drifting or volatilized pesticides is expected to be greatest close
to the site of application. Computer models of spray drift (AgDRIFT) are used to
determine potential exposures to terrestrial organisms via spray drift. The distance of
potential impact away from the use sites is determined by the distance required to fall
below the chronic LOG for mammals.
2.4.4 Mechanism of Action
Myclobutanil is a triazole fungicide in the conazole class of fungicides which is a
systemic fungicide used to control powdery mildew on a number of crops. Myclobutanil
25
-------
appears to be a specific inhibitor of sterol 14-demethylase, which disrupts the ergosterol
biosynthesis pathway which is vital to fungal cell wall formation. It is classified as a
demethylation inhibitor (DMI) fungicide.
2.4.5 Use Characterization
Analysis of labeled use information is the critical first step in evaluating the federal
action. The current label for myclobutanil represents the FIFRA regulatory action;
therefore, labeled use and application rates specified on the label form the basis of this
assessment. The assessment of use information is critical to the development of the
action area and selection of appropriate modeling scenarios and inputs.
Myclobutanil is a triazole fungicide in the conazole class of fungicides. It is a systemic
fungicide used to control powdery mildew. It is registered for use on variety of terrestrial
food and feed crops and terrestrial non-food crops. Myclobutanil is formulated as a
wettable powder (2-40% a.i.) or as an emulsifiable concentrate (1-25% a.i.), granular
(<1% a.i.), dust (5% a.i.), dry flowable (60% a.i.), and ready to use (<1% a.i.).
Application rates range from 0.04 to 5.0 Ibs a.i./acre. Myclobutanil is applied at multiple
growth stages (e.g., seed treatment, pre-bloom, bloom, foliar, post-bloom etc.).
Application equipment includes hand held devices for both liquids and solids (e.g.,
trigger spray bottle, aerosol can, shaker jar, high and low volume sprayers),
chemigation/irrigation (e.g., sprinkler, solid state), spreader, groundboom, and aircraft.
Myclobutanil is also used to treat cotton seed. The formulation for this use is a 25% ai
EC. The application rate for cotton is 0.06 Ib ai per hundred weight (cwt). Planting
depth for cotton seeds varies depending on soil moisture and soil texture. Most labels
include the following restrictions/prohibitions: do not apply directly to water or to areas
where surface water is present or to intertidal areas below the mean high water mark; do
not apply directly to water; do not apply when drift is likely to occur; do not apply where
runoff is likely to occur. Table 2.2 presents the uses and corresponding application rates
and methods of application considered in this assessment.
Table 2.2 Myclobutanil Uses Assessed for the CRLF
Use
Max Single
Application
Rate (Ib ai/A)
Max Number
of
Applications
Number of
Crop Cycles
Per Year ab
Max Seasonal/Yearly
Application Rate
(Ib ai/A)
Minimum
Application
Interval
Non-Food/Non-Feed Uses
Turf
Commercial
Residential Lawn
Golf Course
Grass grown for
seed
Cotton (seed)
Forest
Douglas Fir
Loblolly Pine
Cottonwood/
1.3
(0.031b/lKft2)
0.19
0.06 Ib cwt
0.25
0.15
4
NS
NS
NS
NS
1
1
NS
1
1
NS
NS
NS
0.6
0.6
5
14
NS
14
10
26
-------
Use
Poplar Plantation
Ornamentals
Shade Trees
Groundcover
Herbaceous Plant
Woody Scrubs/vines
Ornamental Sod
Farm
Slash Pine
Max Single
Application
Rate (Ib ai/A)
0.26
0.6
(0.0141b/lKft2)
0.003 Ib ai/gal
Max Number
of
Applications
NS
NS
Number of
Crop Cycles
Per Year ab
1
1
1
Max Seasonal/Yearly
Application Rate
(Ib ai/A)
2.0
NS
Minimum
Application
Interval
10
14
Food/Feed Uses
Almond
Apple
Apricot
Artichokes
Asparagus
Beans, Green
Blackberry
Boysenberry
Canistel
Carrot
Cherry
Cucurbit Vegetables
Balsam Pear
Cantaloupe
Casaba
Honeydew Melon
Watermelon
Cucumber
Pumpkin
Squash
Currant
Dewberry
Eggplant
Gooseberry
Grapes
Hops
Lettuce
Mango
Mayhaw
Nectarine
Okra
Papaya
Peach
Pepper
Plum
Prune
Raspberry
Sapodilla
Strawberry
Sugar Beet
Tomato
0.2
0.5
0.5
0.1
0.125
0.125
0.125
0.1
0.25
0.2
0.5
0.125
0.125
0.0625
0.125
0.125
0.13
0.25
0.125
0.25
0.25
0.5
0.125
0.25
0.5
0.125
0.16
0.15
0.125
0.25
0.125
0.19
0.1
3/cc 3/yr
10/cc
7/cc
6/cc
6/cc
4/cc
4/cc 4/yr
NS
8/cc
NS
7/cc 7/yr
Melon 7/cc
7/yr
Other 5 cc
8/cc
NS
4/cc
8/cc
6/cc
4/cc
4/cc
8/cc
10/cc
7/yr
4/cc
8/cc
7/cc 7/yr
NS
7/cc 7/yr
7/cc 7/yr
4/cc
8/cc
6/cc
NS
4/cc
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
2
1
1
1
1
1
1
1
1
1
1
1
1
1
1
0.6
2.0
1.0
0.6
0.75
0.5
0.5
0.25
2.0
0.375
1.3
0.6
1.0
0.25
0.5
1.0
0.6
1.0
0.5
2.0
2.0
1.3
0.5
2.0
1.3
0.5
1.1
1.1
0.25
2.0
0.75
NS
0.5
7
7
7
14
14
7
10
10
14
14
7
7
7
10
10
10
7
7
14
14
7
7
10
14
7
10
7
7
10
14
14
NS
21
27
-------
Use
Youngberry
Max Single
Application
Rate (Ib ai/A)
0.0625
Max Number
of
Applications
NS
Number of
Crop Cycles
Per Year ab
1
Max Seasonal/Yearly
Application Rate
(Ib ai/A)
0.25
Minimum
Application
Interval
10
a Number of crop cycles per year for all crops except lettuce as assumed by EFED.
Number of crop cycles for lettuce USEPA 2007 - Memo from Anisha Kaul (BEAD) to Melissa Panger (EFED). Maximum Number
of Crop Cycles Per Year in California for Methomyl Use Sites 2/28
NS = Not specified
U.S. Geological Survey (USGS) National Water Quality Assessment Program
(NAWQA) data indicate that in 2002, myclobutanil was used on agricultural crops
predominantly in California, and Washington, with high usage also in Wisconsin,
Michigan and a number northern and mid Atlantic states (Figure 2.3). At that time, the
use of myclobutanil on grapes, apples and almonds represented more than 80% of the
national use. Based on national usage data compiled by the Biological and Economic
Analysis Division (BEAD) primarily from 2001 to 2006, on average, roughly 159,000
pounds of myclobutanil are applied annually to agricultural crops. These data show that
usage is highest on grapes, almonds and apples with annual average applications 50,000,
40,000, and 20,000 Ibs. a.i. respectively. The crop with the highest average percent crop
treated with myclobutanil is artichokes (65%).
MYCLOBUTANIL - fungicide
2002 estimated annual agricultural use
Average annual use of
active ingredient
(pounds per square mile of agricultural
land in county)
EH no estimated use
D 0.001 to 0.002
D 0.003 to 0.005
D 0.006 to 0.014
D 0.015 to 0.05
• >= 0.051
Crops
grapes
apples
almonds
cherries
hops
strawberries
peaches
pumpkins
chile peppers
bell peppers
Total
pounds applied
53377
45729
16793
10488
6838
5892
3774
2942
1535
1308
Percent
national use
34.20
29.30
10.76
6.72
4.38
3.7B
2.42
1.89
0.98
0.84
Figure 2.3 Map of Estimated Annual Agricultural Use of Myclobutanil in 2002
http://water.usgs.gov/nawqa/pnsp/usage/maps/show_map.php?year=02&map=m5036
28
-------
Use data specific to California are available from the California Department of Pesticide
Regulation's (CDPR) Pesticide Use Reporting (PUR) database, which includes every
pesticide application made by professional applicators. BEAD summarized these data,
from 1999 to 2006, to the county level by site, pesticide, and unit treated. Based on this
analysis, California accounts for approximately 50% of national usage. An average of
81,868 Ibs of myclobutanil was applied in California to an average of 763,456 acres per
year. Use in California was at a maximum of 95,411 Ibs in 2000 and at a minimum of
70,735 Ibs in 2006. Usage ranged from 70,000 to 84,000 Ibs between 2003 and 2006.
From 1999-2006, myclobutanil was used in a total of 54 counties involving 41 different
uses. Five counties accounted for 50% of the total Ibs applied on average per county
[Fresno (14%), Kern (16%), Monterey (11%), San Joaquin (6.5%) and Tulare (10%)].
Each of the other counties used <5% of the total Ibs applied. Grapes (table and wine)
accounted for approximately 60% of the total Ibs applied per year in CA on average.
Other major crops include almonds (10%) and strawberries (6%). All other crops
accounted for <5% of the total usage on a per crop basis. This analysis may not be
entirely representative of current use patterns because labeled uses may have changed
since these data were collected, and because it may also include misreporting. A
summary of myclobutanil usage for all California use sites is provided below in Table
2.3. Complete data from the BEAD analysis of the CDPR PUR database are presented in
Appendix D.
Table 2.3 Summary of California Department of Pesticide
Pesticide Use Reporting (PUR) Data from 1999 to 2006 for
Myclobutanil Uses
Registration (CDPR)
Currently Registered
Site Name
Almond
Apple
Apricot
Artichoke
Asparagus
Beans, Green
Cantaloupe
Cherry
Cucumber
Grape
Melon
Nectarine
Peach
Pepper
Plum
Prune
Pumpkin
Raspberry
Squash
Strawberry
Tomato
Average Pounds
All Uses
426
44
15
103
46
2
0.4
40
4
644
17
40
34
48
42
12
8
7
o
J
193
38
Avg App Rate
All Uses
Ibs a.i./A
0.16
0.12
0.11
0.09
0.12
0.12
0.09
0.10
0.10
0.10
0.10
0.13
0.12
0.16
0.11
0.12
0.12
0.07
0.11
0.10
0.10
Avg 95th%
App Rate
Ibs a.i./A
0.24
0.21
0.16
0.10
0.13
0.14
0.11
0.14
0.11
0.14
0.11
0.18
0.21
0.19
0.14
0.14
0.23
0.09
0.12
0.14
0.11
Avg 99th %
App Rate
Ibs a.i./A
0.41
0.28
0.19
0.13
0.13
0.14
0.12
0.19
0.13
0.19
0.20
0.21
0.28
0.21
0.39
0.14
0.29
0.17
0.12
0.21
0.21
Avg Max App
Rate
Ibs a.i./A
0.80
0.40
0.28
0.29
0.40
0.14
0.12
0.40
0.13
0.41
0.20
0.35
0.47
0.23
0.58
0.21
0.29
0.28
0.12
0.40
0.23
29
-------
Site Name
Watermelon
Greenhouse
Landscaping
Rights of Way
Turf/Sod
Average Pounds
All Uses
29
6
33
0.5
5
Avg App Rate
All Uses
Ibs a.i./A
0.10
0.11
0.46
0.07
1.15
Avg 95th%
App Rate
Ibs a.i./A
0.12
0.22
0.47
0.09
1.36
Avg 99th%
App Rate
Ibs a.i./A
0.12
0.40
0.47
0.09
1.41
Avg Max App
Rate
Ibs a.i./A
0.13
0.55
0.47
0.09
1.41
2.5 Assessed Species
The CRLF was federally listed as a threatened species by USFWS effective June 24,
1996 (USFWS 1996). It is one of two subspecies of the red-legged frog and is the largest
native frog in the western United States (USFWS 2002). A brief summary of information
regarding CRLF distribution, reproduction, diet, and habitat requirements is provided in
Sections 2.5.1 through 2.5.4, respectively. Further information on the status, distribution,
and life history of and specific threats to the CRLF is provided in Attachment I.
Final critical habitat for the CRLF was designated by USFWS on April 13, 2006
(USFWS 2006; 71 FR 19244-19346). Further information on designated critical habitat
for the CRLF is provided in Section 2.6.
2.5.1
Distribution
The CRLF is endemic to California and Baja California (Mexico) and historically
inhabited 46 counties in California including the Central Valley and both coastal and
interior mountain ranges (USFWS 1996). Its range has been reduced by about 70%, and
the species currently resides in 22 counties in California (USFWS 1996). The species has
an elevational range of near sea level to 1,500 meters (5,200 feet) (Jennings and Hayes
1994); however, nearly all of the known CRLF populations have been documented below
1,050 meters (3,500 feet) (USFWS 2002).
Populations currently exist along the northern California coast, northern Transverse
Ranges (USFWS 2002), foothills of the Sierra Nevada (5-6 populations), and in southern
California south of Santa Barbara (two populations) (Fellers 2005a). Relatively larger
numbers of CRLFs are located between Marin and Santa Barbara Counties (Jennings and
Hayes 1994). A total of 243 streams or drainages are believed to be currently occupied
by the species, with the greatest numbers in Monterey, San Luis Obispo, and Santa
Barbara counties (USFWS 1996). Occupied drainages or watersheds include all bodies
of water that support CRLFs (i.e., streams, creeks, tributaries, associated natural and
artificial ponds, and adjacent drainages), and habitats through which CRLFs can move
(i.e., riparian vegetation, uplands) (USFWS 2002).
The distribution of CRLFs within California is addressed in this assessment using four
categories of location including recovery units, core areas, designated critical habitat, and
known occurrences of the CRLF reported in the California Natural Diversity Database
30
-------
(CNDDB) that are not included within core areas and/or designated critical habitat (see
(see Figure 2.4 Recovery Unit, Core Area, Critical Habitat and Occurrence Designations
for CRLF). Recovery units, core areas, and other known occurrences of the CRLF from
the CNDDB are described in further detail in Attachment I, and designated critical habitat
is addressed in Section 2.6. Recovery units are large areas defined at the watershed level
that have similar conservation needs and management strategies. The recovery unit is
primarily an administrative designation, and land area within the recovery unit boundary
is not exclusively CRLF habitat. Core areas are smaller areas within the recovery units
that comprise portions of the species' historic and current range and have been
determined by USFWS to be important in the preservation of the species. Designated
critical habitat is generally contained within the core areas, although a number of critical
habitat units are outside the boundaries of core areas, but within the boundaries of the
recovery units. Additional information on CRLF occurrences from the CNDDB is used
to cover the current range of the species not included in core areas and/or designated
critical habitat, but within the recovery units.
-------
Recovery Units
1. Sierra Nevada Foothills and Central Valley
2. North Coast Range Foothills and Western
Sacramento River Valley
3. North Coast and North San Francisco Bay
4. South and East San Francisco Bay
5. Central Coast
6. Diablo Range and Salinas Valley
7. Northern Transverse Ranges and Tehachapi
Mountains
8. Southern Transverse and Peninsular Ranges
Legend
] Recovery Unit Boundaries
Tj Currently Occupied Core Areas
HI Critical Habitat
HI CNDDB Occurence Sections
County Boundaries n.
45
Core Areas
1. Feather River
Yuba River- S. Fork Feather River
Traverse Creek/ Middle Fork/ American R. Rubicon
Cosumnes River
South Fork Calaveras River*
Tuolumne River*
Piney Creek*
Cottonwood Creek
Putah Creek - Cache Creek*
10. Lake Berryessa Tributaries
11. Upper Sonoma Creek
12. Petaluma Creek - Sonoma Creek
13. R. Reyes Peninsula
14. Belvedere Lagoon
15. Jameson Canyon - Lower Napa River
16. East San Francisco Bay
17. Santa Clara Valley
18. South San Francisco Bay
* Core areas that were historically occupied by the California red-legged frog are not included in the map
19.
20.
21.
22.
23.
24.
25.
26.
27.
28.
29.
30.
31.
32.
34.
35.
Watsonville Slough-Elkhorn Slough
Carmel River — Santa Lucia
Gablan Range
Estero Bay
Arroyo Grange River
Santa Maria River - Santa Ynez River
Sisquoc River
Ventura River - Santa Clara River
Santa Monica Bay — Venura Coastal Streams
Estrella River
San Gabriel Mountain*
Forks of the Mojave*
Santa Ana Mountain*
Santa Rosa Plateau
San Luis Ray*
Sweetwater*
Laguna Mountain*
Figure 2.4 Recovery Unit, Core Area, Critical Habitat and Occurrence Designations
for CRLF
32
-------
Other Known Occurrences from the CNDBB
The CNDDB provides location and natural history information on species found in
California. The CNDDB serves as a repository for historical and current species location
sightings. Information regarding known occurrences of CRLFs outside of the currently
occupied core areas and designated critical habitat is considered in defining the current
range of the CRLF. See: http://www.dfg.ca.gov/bdb/html/cnddb_info.html for additional
information on the CNDDB.
2.5.2 Reproduction
CRLFs breed primarily in ponds; however, they may also breed in quiescent streams,
marshes, and lagoons (Fellers 2005a). According to the Recovery Plan (USFWS 2002),
CRLFs breed from November through late April. Peaks in spawning activity vary
geographically; Fellers (2005b) reports peak spawning as early as January in parts of
coastal central California. Eggs are fertilized as they are being laid. Egg masses are
typically attached to emergent vegetation, such as bulrushes (Scirpus spp.) and cattails
(Typha spp.) or roots and twigs, and float on or near the surface of the water (Hayes and
Miyamoto 1984). Egg masses contain approximately 2000 to 6000 eggs ranging in size
between 2 and 2.8 mm (Jennings and Hayes 1994). Embryos hatch 10 to 14 days after
fertilization (Fellers 2005a) depending on water temperature. Egg predation is reported
to be infrequent and most mortality is associated with the larval stage (particularly
through predation by fish); however, predation on eggs by newts has also been reported
(Rathburn 1998). Tadpoles require 11 to 28 weeks to metamorphose into juveniles
(terrestrial-phase), typically between May and September (Jennings and Hayes 1994,
USFWS 2002); tadpoles have been observed to over-winter (delay metamorphosis until
the following year) (Fellers 2005b, USFWS 2002). Males reach sexual maturity at 2
years, and females reach sexual maturity at 3 years of age; adults have been reported to
live 8 to 10 years (USFWS 2002).
J
F
M
A
M
J
J
A
S
o
N
D
Light Blue = Breeding/Egg Masses
Green = Tadpoles (except those that over- winter)
Orange =
Adults and juveniles can be present all year
Figure 2.5 CRLF Reproductive Events by Month
33
-------
2.5.3 Diet
Although the diet of CRLF aquatic-phase larvae (tadpoles) has not been studied
specifically, it is assumed that their diet is similar to that of other frog species, with the
aquatic phase feeding exclusively in water and consuming diatoms, algae, and detritus
(USFWS 2002). Tadpoles filter and entrap suspended algae (Seale and Beckvar, 1980)
via mouthparts designed for effective grazing of periphyton (Wassersug, 1984,
Kupferberg et al.; 1994; Kupferberg, 1997; Altig and McDiarmid, 1999).
Juvenile and adult CRLFs forage in aquatic and terrestrial habitats, and their diet differs
greatly from that of larvae. The main food source for juvenile aquatic- and terrestrial-
phase CRLFs is thought to be aquatic and terrestrial invertebrates found along the
shoreline and on the water surface. Hayes and Tennant (1985) report, based on a study
examining the gut content of 35 juvenile and adult CRLFs, that the species feeds on as
many as 42 different invertebrate taxa, including Arachnida, Amphipoda, Isopoda,
Insecta, and Mollusca. The most commonly observed prey species were larval alderflies
(Stalls cf californicd)., pillbugs (Armadilliadrium vulgare), and water striders (Gerris sp).
The preferred prey species, however, was the sowbug (Hayes and Tennant, 1985). This
study suggests that CRLFs forage primarily above water, although the authors note other
data reporting that adults also feed under water, are cannibalistic, and consume fish. For
larger CRLFs, over 50% of the prey mass may consists of vertebrates such as mice, frogs,
and fish, although aquatic and terrestrial invertebrates were the most numerous food
items (Hayes and Tennant 1985). For adults, feeding activity takes place primarily at
night; for juveniles feeding occurs during the day and at night (Hayes and Tennant 1985).
2.5.4 Habitat
CRLFs require aquatic habitat for breeding, but also use other habitat types including
riparian and upland areas throughout their life cycle. CRLF use of their environment
varies; they may complete their entire life cycle in a particular habitat or they may utilize
multiple habitat types. Overall, populations are most likely to exist where multiple
breeding areas are embedded within varying habitats used for dispersal (USFWS 2002).
Generally, CRLFs utilize habitat with perennial or near-perennial water (Jennings et al.
1997). Dense vegetation close to water, shading, and water of moderate depth are habitat
features that appear especially important for CRLF (Hayes and Jennings 1988).
Breeding sites include streams, deep pools, backwaters within streams and creeks, ponds,
marshes, sag ponds (land depressions between fault zones that have filled with water),
dune ponds, and lagoons. Breeding adults have been found near deep (0.7 m) still or slow
moving water surrounded by dense vegetation (USFWS 2002); however, the largest
number of tadpoles have been found in shallower pools (0.26 - 0.5 m) (Reis, 1999). Data
indicate that CRLFs do not frequently inhabit vernal pools, as conditions in these habitats
generally are not suitable (Hayes and Jennings 1988).
CRLFs also frequently breed in artificial impoundments such as stock ponds, although
additional research is needed to identify habitat requirements within artificial ponds
34
-------
(USFWS 2002). Adult CRLFs use dense, shrubby, or emergent vegetation closely
associated with deep-water pools bordered with cattails and dense stands of overhanging
vegetation (http://www.fws.gov/endangered/features/rl_frog/rlfrog.html#where).
In general, dispersal and habitat use depends on climatic conditions, habitat suitability,
and life stage. Adults rely on riparian vegetation for resting, feeding, and dispersal. The
foraging quality of the riparian habitat depends on moisture, composition of the plant
community, and presence of pools and backwater aquatic areas for breeding. CRLFs can
be found living within streams at distances up to 3 km (2 miles) from their breeding site
and have been found up to 30 m (100 feet) from water in dense riparian vegetation for up
to 77 days (USFWS 2002).
During dry periods, the CRLF is rarely found far from water, although it will sometimes
disperse from its breeding habitat to forage and seek other suitable habitat under downed
trees or logs, industrial debris, and agricultural features (UWFWS 2002). According to
Jennings and Hayes (1994), CRLFs also use small mammal burrows and moist leaf litter
as habitat. In addition, CRLFs may also use large cracks in the bottom of dried ponds as
refugia; these cracks may provide moisture for individuals avoiding predation and solar
exposure (Alvarez 2000).
2.6 Designated Critical Habitat
In a final rule published on April 13, 2006, 34 separate units of critical habitat were
designated for the CRLF by USFWS (USFWS 2006; FR 51 19244-19346). A summary
of the 34 critical habitat units relative to USFWS-designated recovery units and core
areas (previously discussed in Section 2.5.1) is provided in Attachment I.
'Critical habitat' is defined in the ESA as the geographic area occupied by the species at
the time of the listing where the physical and biological features necessary for the
conservation of the species exist, and there is a need for special management to protect
the listed species. It may also include areas outside the occupied area at the time of
listing if such areas are 'essential to the conservation of the species.' All designated
critical habitat for the CRLF was occupied at the time of listing. Critical habitat receives
protection under Section 7 of the ESA (Section 7) through prohibition against destruction
or adverse modification with regard to actions carried out, funded, or authorized by a
federal Agency. Section 7 requires consultation on federal actions that are likely to result
in the destruction or adverse modification of critical habitat.
To be included in a critical habitat designation, the habitat must be 'essential to the
conservation of the species.' Critical habitat designations identify, to the extent known
using the best scientific and commercial data available, habitat areas that provide
essential life cycle needs of the species or areas that contain certain primary constituent
elements (PCEs) (as defined in 50 CFR 414.12(b)). PCEs include, but are not limited to,
space for individual and population growth and for normal behavior; food, water, air,
light, minerals, or other nutritional or physiological requirements; cover or shelter; sites
for breeding, reproduction, rearing (or development) of offspring; and habitats that are
35
-------
protected from disturbance or are representative of the historic geographical and
ecological distributions of a species. The designated critical habitat areas for the CRLF
are considered to have the following PCEs that justify critical habitat designation:
• Breeding aquatic habitat;
• Non-breeding aquatic habitat;
• Upland habitat; and
• Dispersal habitat.
Further description of these habitat types is provided in Attachment I.
Occupied habitat may be included in the critical habitat only if essential features within
the habitat may require special management or protection. Therefore, USFWS does not
include areas where existing management is sufficient to conserve the species. Critical
habitat is designated outside the geographic area presently occupied by the species only
when a designation limited to its present range would be inadequate to ensure the
conservation of the species. For the CRLF, all designated critical habitat units contain all
four of the PCEs, and were occupied by the CRLF at the time of FR listing notice in
April 2006. The FR notice designating critical habitat for the CRLF includes a special
rule exempting routine ranching activities associated with livestock ranching from
incidental take prohibitions. The purpose of this exemption is to promote the
conservation of rangelands, which could be beneficial to the CRLF, and to reduce the rate
of conversion to other land uses that are incompatible with CRLF conservation. Please
see Attachment I for a full explanation on this special rule.
USFWS has established adverse modification standards for designated critical habitat
(USFWS 2006). Activities that may destroy or adversely modify critical habitat are those
that alter the PCEs and jeopardize the continued existence of the species. Evaluation of
actions related to use of myclobutanil that may alter the PCEs of the CRLF's critical
habitat form the basis of the critical habitat impact analysis. According to USFWS
(2006), activities that may affect critical habitat and therefore result in adverse effects to
the CRLF include, but are not limited to the following:
(1) Significant alteration of water chemistry or temperature to levels beyond the
tolerances of the CRLF that result in direct or cumulative adverse effects to
individuals and their life-cycles.
(2) Alteration of chemical characteristics necessary for normal growth and viability
of juvenile and adult CRLFs.
(3) Significant increase in sediment deposition within the stream channel or pond or
disturbance of upland foraging and dispersal habitat that could result in
elimination or reduction of habitat necessary for the growth and reproduction of
the CRLF by increasing the sediment deposition to levels that would adversely
affect their ability to complete their life cycles.
(4) Significant alteration of channel/pond morphology or geometry that may lead to
changes to the hydrologic functioning of the stream or pond and alter the timing,
duration, water flows, and levels that would degrade or eliminate the CRLF
36
-------
and/or its habitat. Such an effect could also lead to increased sedimentation and
degradation in water quality to levels that are beyond the CRLF's tolerances.
(5) Elimination of upland foraging and/or aestivating habitat or dispersal habitat.
(6) Introduction, spread, or augmentation of non-native aquatic species in stream
segments or ponds used by the CRLF.
(7) Alteration or elimination of the CRLF's food sources or prey base (also
evaluated as indirect effects to the CRLF).
As previously noted in Section 2.1, the Agency believes that the analysis of direct and
indirect effects to listed species provides the basis for an analysis of potential effects on
the designated critical habitat. Because myclobutanil is expected to directly impact living
organisms within the action area, critical habitat analysis for myclobutanil is limited in a
practical sense to those PCEs of critical habitat that are biological or that can be
reasonably linked to biologically mediated processes.
2.7 Action Area
For listed species assessment purposes, the action area is considered to be the area
affected directly or indirectly by the federal action and not merely the immediate area
involved in the action (50 CFR 402.02). It is recognized that the overall action area for
the national registration of myclobutanil is likely to encompass considerable portions of
the United States based on the large array of agricultural uses. However, the scope of this
assessment limits consideration of the overall action area to those portions that may be
applicable to the protection of the CRLF and its designated critical habitat within the state
of California. The Agency's approach to defining the action area under the provisions of
the Overview Document (U.S. EPA 2004) considers the results of the risk assessment
process to establish boundaries for that action area with the understanding that exposures
below the Agency's defined Levels of Concern (LOCs) constitute a no-effect threshold.
For the purposes of this assessment, attention will be focused on the footprint of the
action (i.e., the area where pesticide application occurs), plus all areas where offsite
transport (i.e., spray drift, downstream dilution, etc.) may result in potential exposure
within the state of California that exceeds the Agency's LOCs.
Deriving the geographical extent of this portion of the action area is based on
consideration of the types of effects that myclobutanil may be expected to have on the
environment, the exposure levels to myclobutanil that are associated with those effects,
and the best available information concerning the use of myclobutanil and its fate and
transport within the state of California. Specific measures of ecological effect that define
the action area include any direct and indirect toxic effect and any potential effects to
critical habitat, including reduction in survival, growth, and fecundity as well as the full
suite of sublethal effects available in the effects literature. Therefore, the action area
extends to a point where environmental exposures are below any measured lethal or
sublethal effect threshold for any biological entity at the whole organism, organ, tissue,
and cellular level of organization. In situations where it is not possible to determine the
threshold for an observed effect, the action area is not spatially limited and is assumed to
be the entire state of California.
37
-------
The definition of action area requires a stepwise approach that begins with an
understanding of the federal action. The federal action is defined by the currently labeled
uses for myclobutanil. An analysis of labeled uses and review of available product labels
was completed. Several of the currently labeled uses are special local needs (SLN) uses
or are restricted to specific states and are excluded from this assessment. In addition, a
distinction has been made between food use crops and those that are non-food/non-
agricultural uses. For those uses relevant to the CRLF, the analysis indicates that, for
myclobutanil, the following agricultural uses are considered as part of the federal action
evaluated in this assessment:
• almond, apple, apricot, artichoke, asparagus, blackberry, boysenberry, canistel,
carrot, cherry, cucurbit vegetables (e.g. melons, squash), currant, dewberry,
eggplant, gooseberry, green beans, grapes, hops, lettuce, mango, mayhaw,
nectarine, okra, papaya, peach, pepper, plum, prune, raspberry, sapodilla,
strawberry, sugar beet, tomato, and youngberry.
In addition, the following non-food and non-agricultural uses are considered:
• commercial, residential and golf course turf, ornamental and herbaceous plants,
grass grown for seed, cotton seed, ornamental sod farms, Douglas fir and loblolly
pine and slash pine forests, and hybrid cotton wood/poplar plantations.
Following a determination of the assessed uses, an evaluation of the potential "footprint"
of myclobutanil use patterns (i.e., the area where pesticide application occurs) is
determined. This "footprint" represents the initial area of concern, based on an analysis of
available land cover data for the state of California. The initial area of concern is defined
as all land cover types and the stream reaches within the land cover areas that represent
the labeled uses described above. A map representing all the land cover types that make
up the initial area of concern for myclobutanil is presented in Figure 2.6.
The following land cover types were used for myclobutanil cultivated crops, forest,
orchards and vineyards and turf. More information regarding which specific uses are
represented for each land cover types can be found in Appendix E.
38
-------
Myclobutanil Use - Initial Area of Concern
Forest use
Turf use
Orchard vineyard use
Cultivated crop use
County boundaries
• Kilometers
0 2040 80 120 160
Compiled from California County boundaries (ESRI, 2002),
USDA Gap Analysis Program Orchard/ Vineyard Landcover (GAP)
National Land Cover Database (NLCD) (MRLC, 2001)
Map created by US Environmental Protection Agency, Office
of Pesticides Programs, Environmental Fate and Effects Division.
Projection: Alters Equal Area Conic USDS, Noith American
Datum of 1983 (NAD 1983).
Figure 2.6 Initial Area of Concern of "footprint" of potential use for myclobutanil
39
-------
As previously discussed, the action area is defined by the most sensitive measure of
direct and indirect ecological toxic effects including reduction in survival, growth,
reproduction, and the entire suite of sublethal effects from valid, peer-reviewed studies.
Due to the lack of a defined dose at which there were no effects and the presence of
sublethal effects (lethargy and anorexia) and mortalities at all dose levels in an avian
acute oral toxicity study (MRID 00144286), the spatial extent of the action area (i.e., the
boundary where exposures and potential effects are less than the Agency's LOG) for
myclobutanil cannot be determined. Therefore, it is assumed that the action area
encompasses the entire state of California, regardless of the spatial extent (i.e., initial area
of concern or footprint) of the pesticide use(s).
2.8 Assessment Endpoints and Measures of Ecological Effect
Assessment endpoints are defined as "explicit expressions of the actual environmental
value that is to be protected."1 Selection of the assessment endpoints is based on valued
entities (e.g., CRLF, organisms important in the life cycle of the CRLF, and the PCEs of
its designated critical habitat), the ecosystems potentially at risk (e.g., waterbodies,
riparian vegetation, and upland and dispersal habitats), the migration pathways of
myclobutanil (e.g., runoff, spray drift, etc.), and the routes by which ecological receptors
are exposed to myclobutanil (e.g., direct contact, etc.).
2.8.1 Assessment Endpoints for the CRLF
Assessment endpoints for the CRLF include direct toxic effects on the survival,
reproduction, and growth of the CRLF, as well as indirect effects, such as reduction of
the prey base or effects to its habitat. In addition, potential effects to critical habitat are
assessed by evaluating potential effects to PCEs, which are components of the habitat
areas that provide essential life cycle needs of the CRLF. Each assessment endpoint
requires one or more "measures of ecological effect," defined as changes in the attributes
of an assessment endpoint or changes in a surrogate entity or attribute in response to
exposure to a pesticide. Specific measures of ecological effect are generally evaluated
based on acute and chronic toxicity information from registrant-submitted guideline tests
that are performed on a limited number of organisms. Additional ecological effects data
from the open literature are also considered. It should be noted that assessment endpoints
are limited to direct and indirect effects associated with survival, growth, and fecundity,
and do not include the full suite of sublethal effects used to define the action area.
According the Overview Document (USEPA 2004), the Agency relies on acute and
chronic effects endpoints that are either direct measures of impairment of survival,
growth, or fecundity or endpoints for which there is a scientifically robust, peer reviewed
relationship that can quantify the impact of the measured effect endpoint on the
assessment endpoints of survival, growth, and fecundity.
A complete discussion of all the toxicity data available for this risk assessment, including
resulting measures of ecological effect selected for each taxonomic group of concern, is
U.S. EPA (1992). Framework for Ecological Risk Assessment. EPA/630/R-92/001.
40
-------
included in Section 4.0 of this document. A summary of the assessment endpoints and
measures of ecological effect selected to characterize potential assessed direct and
indirect CRLF risks associated with exposure to myclobutanil is provided in Table 2.4.
Table 2.4 Assessment Endpoints and Measures of Ecological Effects
Assessment Endpoint
Measures of Ecological Effects2
Aquatic-Phase CRLF
(Eggs, larvae, juveniles, and adults)*
Direct Effects
1. Survival, growth, and reproduction of CRLF
la. Bluegill sunfish acute LC50
Ib. Fathead minnow chronic NOAEC
Indirect Effects and Critical Habitat Effects
1. Survival, growth, and reproduction of CRLF
individuals via indirect effects on aquatic prey food
supply (i.e., fish, freshwater invertebrates, non-
vascular plants)
3. Survival, growth, and reproduction of CRLF
individuals via indirect effects on habitat, cover,
food supply, and/or primary productivity (i.e.,
aquatic plant community)
4. Survival, growth, and reproduction of CRLF
individuals via effects to riparian vegetation
2a. Bluegill sunfish acute LC50, water flea acute
LC50, green algae EC50.
2b. Fathead minnow chronic NOAEC; no
freshwater invertebrate chronic study available;
daphnia chronic NOAEC from 9 similar conazole
fungicides.
3a. No vascular plant study available; duckweed
EC50 data from 7 similar conazole fungicides.
3b. Green algae EC50.
4a. No seedling emergence or vegetative vigor
studies available; terrestrial plant EC25 and NOAEC
data from 5 similar conazole fungicides
4b. No seedling emergence or vegetative vigor
studies available; terrestrial plant EC25 and NOAEC
data from 5 similar conazole fungicides
Terrestrial-Phase CRLF
(Juveniles and adults)
Direct Effects
5. Survival, growth, and reproduction of CRLF
individuals via direct effects on terrestrial phase
adults and juveniles
5a. Bobwhite quail LD50 and Mallard duck LC50b
5b. Bobwhite quail chronic NOAEC
Indirect Effects and Critical Habitat Effects
6. Survival, growth, and reproduction of CRLF
individuals via effects on terrestrial prey
(i.e., terrestrial invertebrates, small mammals , and
frogs)
7. Survival, growth, and reproduction of CRLF
individuals via indirect effects on habitat (i.e.,
riparian and upland vegetation)
6a. Honey bee acute EC50 and mouse acute LD50
6b. Rat chronic NOAEC (no chronic invertebrate
study available)
7a. No seedling emergence or vegetative vigor
studies available; terrestrial plant EC25 and NOAEC
data from 5 similar conazole fungicides
7b. No seedling emergence or vegetative vigor
studies available; terrestrial plant EC25 and NOAEC
data from 5 similar conazole fungicides
a Adult frogs are no longer in the "aquatic phase" of the amphibian life cycle; however, submerged adult
frogs are considered "aquatic" for the purposes of this assessment because exposure pathways in the water
are considerably different that exposure pathways on land.
b Birds are used as surrogates for terrestrial phase amphibians.
2 All registrant-submitted and open literature toxicity data reviewed for this assessment are included in
Appendix A.
41
-------
2.8.2 Assessment Endpoints for Designated Critical Habitat
As previously discussed, designated critical habitat is assessed to evaluate actions related
to the use of myclobutanil that may alter the PCEs of the CRLF's critical habitat. PCEs
for the CRLF were previously described in Section 2.6. Actions that may modify critical
habitat are those that alter the PCEs and jeopardize the continued existence of the CRLF.
Therefore, these actions are identified as assessment endpoints. It should be noted that
evaluation of PCEs as assessment endpoints is limited to those of a biological nature (i.e.,
the biological resource requirements for the listed species associated with the critical
habitat) and those for which myclobutanil effects data are available. Effects to the
critical habitat of the CRLF include, but are not limited to those listed in Section 2.6.
Measures of such possible effects by labeled use of myclobutanil on critical habitat of the
CRLF are described in Table 2.5. Some components of these PCEs are associated with
physical abiotic features (e.g., presence and/or depth of a water body, or distance between
two sites), which are not expected to be measurably altered by use of pesticides.
Assessment endpoints used for the analysis of designated critical habitat are based on the
adverse modification standard established by USFWS (2006).
42
-------
Table 2.5 Summary of Assessment Endpoints and Measures of Ecological Effect for
Primary Constituent Elements of Designated Critical Habitat3
Assessment Endpoint
Measures of Ecological Effect
Aquatic-Phase CRLFPCEs
(Aquatic Breeding Habitat and Aquatic Non-Breeding Habitat)
Alteration of channel/pond morphology or geometry
and/or increase in sediment deposition within the
stream channel or pond: aquatic habitat (including
riparian vegetation) provides for shelter, foraging,
predator avoidance, and aquatic dispersal for juvenile
and adult CRLFs.
Alteration in water chemistry /quality including
temperature, turbidity, and oxygen content necessary
for normal growth and viability of juvenile and adult
CRLFs and their food source.
Alteration of other chemical characteristics necessary
for normal growth and viability of CRLFs and their
food source.
Reduction and/or modification of aquatic-based food
sources for pre-metamorphs (e.g., algae)
a. Green algae EC50. No vascular plant study available;
duckweed EC50 data from 7 similar conazole fungicides.
b. No seedling emergence or vegetative vigor studies
available; terrestrial plant EC25 and NOAEC data from 5
similar conazole fungicides
c. No seedling emergence or vegetative vigor studies
available; terrestrial plant EC25 and NOAEC data from 5
similar conazole fungicides
a. Green algae EC50. No vascular plant study available;
duckweed EC50 data from 7 similar conazole fungicides.
b. No seedling emergence or vegetative vigor studies
available; terrestrial plant EC25 and NOAEC data from 5
similar conazole fungicides
c. No seedling emergence or vegetative vigor studies
available; terrestrial plant EC25 and NOAEC data from 5
similar conazole fungicides
a. Bluegill sunfish acute LC50 and water flea acute LC50.
b. Fathead minnow chronic NOAEC. No freshwater
invertebrate chronic study available; daphnia chronic
NOAEC from 9 similar conazole fungicides.
a. Green algae EC50. No vascular plant study available;
duckweed EC50 data from 7 similar conazole fungicides.
Terrestrial-Phase CRLFPCEs
(Upland Habitat and Dispersal Habitat)
Elimination and/or disturbance of upland habitat;
ability of habitat to support food source of CRLFs:
Upland areas within 200 ft of the edge of the riparian
vegetation or dripline surrounding aquatic and riparian
habitat that are comprised of grasslands, woodlands,
and/or wetland/riparian plant species that provides the
CRLF shelter, forage, and predator avoidance
Elimination and/or disturbance of dispersal habitat:
Upland or riparian dispersal habitat within designated
units and between occupied locations within 0.7 mi of
each other that allow for movement between sites
including both natural and altered sites which do not
contain barriers to dispersal
Reduction and/or modification of food sources for
terrestrial phase juveniles and adults
Alteration of chemical characteristics necessary for
normal growth and viability of juvenile and adult
CRLFs and their food source.
a. No seedling emergence or vegetative vigor studies
available; terrestrial plant EC25 and NOAEC data from 5
similar conazole fungicides.
b. No seedling emergence or vegetative vigor studies
available; terrestrial plant EC25 and NOAEC data from 5
similar conazole fungicides.
c. Bobwhite quail LD50, mallard duck LC50, bobwhite quail
chronic NOAEC, honey bee acute EC50, mouse acute LD50,
rat chronic NOAEC (no chronic invertebrate study
available), bluegill sunfish acute LC50 and fathead minnow
chronic NOAEC.
a Physico-chemical water quality parameters such as salinity, pH, and hardness are not evaluated because these processes are not
biologically mediated and, therefore, are not relevant to the endpoints included in this assessment.
43
-------
2.9 Conceptual Model
2.9.1 Risk Hypotheses
Risk hypotheses are specific assumptions about potential adverse effects (i.e., changes in
assessment endpoints) and may be based on theory and logic, empirical data,
mathematical models, or probability models (U.S. EPA, 1998). For this assessment, the
risk is stressor-linked, where the stressor is the release of myclobutanil to the
environment. The following risk hypotheses are presumed for this endangered species
assessment:
The labeled use of myclobutanil within the action area may:
• directly affect the CRLF by causing mortality or by adversely affecting growth or
fecundity;
• indirectly affect the CRLF by reducing or changing the composition of food
supply;
• indirectly affect the CRLF or affect designated critical habitat by reducing or
changing the composition of the aquatic plant community in the ponds and
streams comprising the species' current range and designated critical habitat, thus
affecting primary productivity and/or cover;
• indirectly affect the CRLF or affect designated critical habitat by reducing or
changing the composition of the terrestrial plant community (i.e., riparian habitat)
required to maintain acceptable water quality and habitat in the ponds and streams
comprising the species' current range and designated critical habitat;
• affect the designated critical habitat of the CRLF by reducing or changing
breeding and non-breeding aquatic habitat (via modification of water quality
parameters, habitat morphology, and/or sedimentation);
• affect the designated critical habitat of the CRLF by reducing the food supply
required for normal growth and viability of juvenile and adult CRLFs;
• affect the designated critical habitat of the CRLF by reducing or changing upland
habitat within 200 ft of the edge of the riparian vegetation necessary for shelter,
foraging, and predator avoidance;
• affect the designated critical habitat of the CRLF by reducing or changing
dispersal habitat within designated units and between occupied locations within
0.7 mi of each other that allow for movement between sites including both natural
and altered sites which do not contain barriers to dispersal;
• affect the designated critical habitat of the CRLF by altering chemical
characteristics necessary for normal growth and viability of juvenile and adult
CRLFs.
2.9.2 Diagram
The conceptual model is a graphic representation of the structure of the risk assessment.
It specifies the stressor (myclobutanil) release mechanisms, biological receptor types, and
44
-------
effects endpoints of potential concern. The conceptual models for terrestrial and aquatic
exposures are shown in Figure 2.7 and Figure 2.8, respectively, which include the
conceptual models for the aquatic and terrestrial PCE components of critical habitat.
Exposure routes shown in dashed lines are not quantitatively considered because the
contribution of those potential exposure routes to potential effects on the CRLF and
designated critical habitat is expected to be negligible.
Stressor
Source
Exposure
Media
Myclobutanil applied to use site
Dermal uptake/lnaestiorr*—
.T.
Long range
atmospheric
transport
Ingestion
I
Terrestrial-phase
amphibians
Terrestrial/riparian plants
grasses/forbs, fruit, seeds
(trees, shrubs)
Root uptake^!
Wet/drv deposition^1
Ingestion
Receptors
Birds/terrestrial-
phase amphibians/
reptiles/mammals
Attribute
Change
Individual
organisms
Reduced survival
Reduced growth
Reduced reproduction
Ingestion
1
Food chain
Reduction in prey
Modification of PCEs
related to prey availability
Habitat integrity
Reduction in primary productivity
Reduced cover
Community change
Modification of PCEs related to
habitat
Figure 2.7 Conceptual Model for Myclobutanil Effects on Terrestrial Phase of the
CRLF
45
-------
Stressor
Myclobutanil applied to use site
Source | Spray drift] | Runoff |
Exposure
Media
*• Groundwater:
Surface water/
Sediment
T
.T.
Long range
atmospheric
transport
.Wet/dry deposition .
Receptors
Uptake/gills
or integument
1
Uptake/gills
or integument
Aquatic Animals
Invertebrates
Vertebrates
Fish/aquatic-phase
amphibians
"Piscivorous mammals
and birds
Inqe^tion
Attribute Individual
Change
organisms
Reduced survival
Reduced growth
Reduced reproduction
Uptake/cell,
roots^ leaves
Aquatic Plants
\lon-vascular
Vascular
t
Inqestion
Food chain
Reduction in algae
Reduction in prey
Modification of PCEs
related to prey availability
1
Habitat integrity
Reduction in primary
productivity
Reduced cover
ommunity change
Modification of PCEs related to
habitat
** Route of exposure includes only ingestion of aquatic fish and invertebrates
Figure 2.8 Conceptual Model for Myclobutanil Effects on Aquatic Phase of the
CRLF
2.10 Analysis Plan
In order to address the risk hypothesis, the potential for direct and indirect effects to the
CRLF, its prey, and its habitat is estimated. In the following sections, the use,
environmental fate, and ecological effects of myclobutanil are characterized and
integrated to assess the risks. This is accomplished using a risk quotient (ratio of
exposure concentration to effects concentration) approach. Although risk is often defined
as the likelihood and magnitude of adverse ecological effects, the risk quotient-based
approach does not provide a quantitative estimate of likelihood and/or magnitude of an
adverse effect. However, as outlined in the Overview Document (U.S. EPA, 2004), the
likelihood of effects to individual organisms from particular uses of myclobutanil is
estimated using the probit dose-response slope and either the level of concern (discussed
below) or actual calculated risk quotient value.
46
-------
2.10.1 Measures to Evaluate the Risk Hypothesis and Conceptual Model
2.10.1.1 Measures of Exposure
The environmental fate properties of myclobutanil and the degradation product 1,2,4-
triazole along with available monitoring data indicate that for myclobutanil runoff and
spray drift are the principle potential transport mechanisms and for 1,2,4-triazole runoff
and erosion are the principle potential transport mechanisms to the aquatic and terrestrial
habitats of the CRLF. Monitoring data have also detected myclobutanil in rain water,
thus secondary deposition is also a potential route of exposure but is expected to be
minor. In this assessment, transport of myclobutanil and myclobutanil plus 1,2,4-triazole
through runoff and spray drift is considered in deriving quantitative estimates of
myclobutanil exposure to CRLF, its prey and its habitats.
Measures of exposure are based on aquatic and terrestrial models that predict estimated
environmental concentrations (EECs) of myclobutanil using maximum labeled
application rates and methods of application. The models used to predict aquatic EECs
are the Pesticide Root Zone Model coupled with the Exposure Analysis Model System
(PRZM/EXAMS). The model used to predict terrestrial EECs on food items is T-REX.
The model used to derive EECs relevant to terrestrial and wetland plants is TerrPlant.
These models are parameterized using relevant reviewed registrant-submitted
environmental fate data.
PRZM (V3.12.2, May 2005) and EXAMS (v2.98.4.6, April 2005) are screening
simulation models coupled with the input shell pe5.pl (Aug 2007) to generate daily
exposures and l-in-10 year EECs of myclobutanil and myclobutanil plus 1,2,4-triazole
that may occur in surface water bodies adjacent to application sites receiving
myclobutanil through runoff and spray drift. PRZM simulates pesticide application,
movement and transformation on an agricultural field and the resultant pesticide loadings
to a receiving water body via runoff, erosion and spray drift. EXAMS simulates the fate
of the pesticide and resulting concentrations in the water body. The standard scenario
used for ecological pesticide assessments assumes application to a 10-hectare agricultural
field that drains into an adjacent 1-hectare water body, 2-meters deep (20,000 m3 volume)
with no outlet. PRZM/EXAMS was used to estimate screening-level exposure of aquatic
organisms to myclobutanil and myclobutanil plus 1,2,4-triazole. The measure of
exposure for aquatic species is the l-in-10 year return peak or rolling mean concentration.
The l-in-10 year peak is used for estimating acute exposures of direct effects to the
CRLF, as well as indirect effects to the CRLF through effects to potential prey items,
including: algae, aquatic invertebrates, fish and frogs. The l-in-10-year 60-day mean is
used for assessing chronic exposure to the CRLF and fish and frogs serving as prey
items; the l-in-10-year 21-day mean is used for assessing chronic exposure for aquatic
invertebrates, which are also potential prey items.
Exposure estimates for the terrestrial-phase CRLF and terrestrial invertebrates and
mammals (serving as potential prey) assumed to be in the target area or in an area
exposed to spray drift are derived using the T-REX model (version 1.4.1, 10/09/2008).
47
-------
This model incorporates the Kenega nomograph, as modified by Fletcher et al. (1994),
which is based on a large set of actual field residue data. The upper limit values from the
nomograph represented the 95th percentile of residue values from actual field
measurements (Hoerger and Kenega, 1972). For modeling purposes, direct exposures of
the CRLF to myclobutanil through contaminated food are estimated using the EECs for
the small bird (20 g) which consumes small insects. Dietary-based and dose-based
exposures of potential prey (small mammals) are assessed using the small mammal (15 g)
which consumes short grass. The small bird (20g) consuming small insects and the small
mammal (15g) consuming short grass are used because these categories represent the
largest RQs of the size and dietary categories in T-REX that are appropriate surrogates
for the CRLF and one of its prey items. Estimated exposures of terrestrial insects to
myclobutanil are bound by using the dietary based EECs for small insects and large
insects. For granular applications, an LD50 per square foot is estimated based on
application rate and toxicity.
Birds are currently used as surrogates for terrestrial-phase CRLF. However, amphibians
are poikilotherms (body temperature varies with environmental temperature) while birds
are homeotherms (temperature is regulated, constant, and largely independent of
environmental temperatures). Therefore, amphibians tend to have much lower metabolic
rates and lower caloric intake requirements than birds or mammals. As a consequence,
birds are likely to consume more food than amphibians on a daily dietary intake basis,
assuming similar caloric content of the food items. Therefore, the use of avian food
intake allometric equation as a surrogate to amphibians is likely to result in an over-
estimation of exposure and risk for reptiles and terrestrial-phase amphibians. Therefore,
T-REX (version 1.4.1) has been refined to the T-HERPS model (v. 1.0), which allows for
an estimation of food intake for poikilotherms using the same basic procedure as T-REX
to estimate avian food intake.
EECs for terrestrial plants inhabiting dry and wetland areas are derived using TerrPlant
(version 1.2.2, 12/26/2006). This model uses estimates of pesticides in runoff and in
spray drift to calculate EECs. EECs are based upon solubility, application rate and
minimum incorporation depth.
The spray drift model, AgDRIFT is used to assess exposures of terrestrial phase CRLF
and its prey to myclobutanil deposited on terrestrial habitats by spray drift. In addition to
the buffered area from the spray drift analysis, the downstream extent of myclobutanil
that exceeds the LOG for the effects determination is also considered.
2.10.1.2 Measures of Effect
Data identified in Section 2.8 are used as measures of effect for direct and indirect effects
to the CRLF. Data were obtained from registrant submitted studies or from literature
studies identified by ECOTOX. The ECOTOXicology database (ECOTOX) was searched
in order to provide more ecological effects data and in an attempt to bridge existing data
gaps. ECOTOX is a source for locating single chemical toxicity data for aquatic life,
48
-------
terrestrial plants, and wildlife. ECOTOX was created and is maintained by the USEPA,
Office of Research and Development, and the National Health and Environmental Effects
Research Laboratory's Mid-Continent Ecology Division.
The assessment of risk for direct effects to the terrestrial-phase CRLF makes the
assumption that toxicity of myclobutanil to birds is similar to or less than the toxicity to
the terrestrial-phase CRLF. The same assumption is made for fish and aquatic-phase
CRLF. Algae, aquatic invertebrates, fish, and amphibians represent potential prey of the
CRLF in the aquatic habitat. Terrestrial invertebrates, small mammals, and terrestrial-
phase amphibians represent potential prey of the CRLF in the terrestrial habitat. Aquatic,
semi-aquatic, and terrestrial plants represent habitat of CRLF.
The ecotoxicity database for myclobutanil is not complete. Acceptable data are not
available, either submitted or in the open literature for chronic toxicity to aquatic
freshwater invertebrates, aquatic vascular plants and terrestrial plants. For the purpose of
risk description in this assessment, toxicity data from other triazole sterol 14a-
demethylase-inhibitors (DMIs) for these particular studies were utilized.
The acute measures of effect used for animals in this screening level assessment are the
LD50, LC50 and EC50. LD stands for "Lethal Dose", and LD50 is the amount of a material,
given all at once, that is estimated to cause the death of 50% of the test organisms. LC
stands for "Lethal Concentration" and LCso is the concentration of a chemical that is
estimated to kill 50% of the test organisms. EC stands for "Effective Concentration" and
the EC50 is the concentration of a chemical that is estimated to produce a specific effect in
50% of the test organisms. Endpoints for chronic measures of exposure for listed and
non-listed animals are the NOAEL/NOAEC and NOEC. NOAEL stands for "No
Ob served-Adverse-Effect-Level" and refers to the highest tested dose of a substance that
has been reported to have no harmful (adverse) effects on test organisms. The NOAEC
(i.e.., "No-Observed-Adverse-Effect-Concentration") is the highest test concentration at
which none of the observed effects were statistically different from the control. The
NOEC is the No-Observed-Effects-Concentration. For non-listed plants, only acute
exposures are assessed (i.e.., EC25 for terrestrial plants and ECso for aquatic plants).
It is important to note that the measures of effect for direct and indirect effects to the
CRLF and its designated critical habitat are associated with impacts to survival, growth,
and fecundity, and do not include the full suite of sublethal effects used to define the
action area. According the Overview Document (USEPA 2004), the Agency relies on
effects endpoints that are either direct measures of impairment of survival, growth, or
fecundity or endpoints for which there is a scientifically robust, peer reviewed
relationship that can quantify the impact of the measured effect endpoint on the
assessment endpoints of survival, growth, and fecundity.
49
-------
2.10.1.3 Integration of Exposure and Effects
Risk characterization is the integration of exposure and ecological effects characterization
to determine the potential ecological risk from agricultural and non-agricultural uses of
myclobutanil, and the likelihood of direct and indirect effects to CRLF in aquatic and
terrestrial habitats. The exposure and toxicity effects data are integrated in order to
evaluate the risks of adverse ecological effects on non-target species. For the assessment
of myclobutanil risks, the risk quotient (RQ) method is used to compare exposure and
measured toxicity values. EECs are divided by acute and chronic toxicity values. The
resulting RQs are then compared to the Agency's levels of concern (LOCs) (USEPA,
2004) (see Appendix F).
For this endangered species assessment, listed species LOCs are used for comparing RQ
values for acute and chronic exposures of myclobutanil directly to the CRLF. If
estimated exposures directly to the CRLF of myclobutanil resulting from a particular use
are sufficient to exceed the listed species LOG, then the effects determination for that use
is "may affect". When considering indirect effects to the CRLF due to effects to animal
prey (aquatic and terrestrial invertebrates, fish, frogs, and mice), the listed species LOCs
are also used. If estimated exposures to CRLF prey of myclobutanil resulting from a
particular use are sufficient to exceed the listed species LOG, then the effects
determination for that use is a "may affect." If the RQ being considered also exceeds the
non-listed species acute risk LOG, then the effects determination is a LAA. If the acute
RQ is between the listed species LOG and the non-listed acute risk species LOG, then
further lines of evidence (i.e. probability of individual effects, species sensitivity
distributions) are considered in distinguishing between a determination of NLAA and a
LAA. When considering indirect effects to the CRLF due to effects to algae as dietary
items or plants as habitat, the non-listed species LOG for plants is used because the CRLF
does not have an obligate relationship with any particular aquatic and/or terrestrial plant.
If the RQ being considered for a particular use exceeds the non-listed species LOG for
plants, the effects determination is "may affect". Further information on LOCs is
provided in Appendix F.
2.10.1.4 Data Gaps
Fate
Data characterizing the environmental fate of myclobutanil and its degradation products
is limited. The data was inadequate to determine the rate of formation and decline of the
1,2,4-triazole degradation product. Models currently used by EFED assume that the
degradation follow first order kinetics, and therefore require an estimate of the half-life.
Myclobutanil degradation, however, is best described using a hockey stick degradation
pattern. This type of degradation pattern cannot be modeled using first-order kinetics.
The previously reported half-lives for myclobutanil range between 61 and 71 days, which
described the decline reasonably well for the first 90 days of the study, but grossly
overestimates the remaining decline. The method used to estimate these half-lives was
50
-------
not stated, but it appears that only the first 90 (or less) days of a 367 day study were used.
EFED re-evaluated the data and re-estimated the decline rate constants utilizing all the
data for myclobutanil (see discussion in Appendix C, Tables 2 and 3).
The linear regression of the log-normal transformed myclobutanil radioactivity provided
the best estimate of the measured residues (as percent of applied radioactivity) versus
time (e.g., 29 to 33% myclobutanil) remaining at 367 days. The study was not conducted
long enough to observe a DT75 or DT90. The 90-percent upper bound of the mean (n=2)
aerobic soil metabolism half-life for myclobutanil was estimated to be 251 days.
Analysis of the Freundlich Kads indicates sorption is not significantly correlated with
organic matter (carbon). Therefore, lowest non-sand Freundlich Kads was used to
estimate the EDWCs for myclobutanil (USEPA, 2002).
Because there are no aerobic aquatic metabolism data, half-life was assumed to be twice
that of the aerobic soil metabolism half-life estimated as a model input (USEPA, 2002).
The anaerobic metabolism was assumed to be stable.
Ecotoxicity
No toxicity data are available for freshwater invertebrates (chronic exposure), aquatic
vascular plants, and terrestrial plants. Qualitative assessments were conducted with data
from similar DMI triazole fungicides, information from the open literature, and incident
data.
3 Exposure Assessment
Myclobutanil is formulated as a dust, emulsifiable concentrate, granular, liquid, water
dispersible granules (dry flowable), pressurized liquid, ready to use liquid, and wettable
powder. Application equipment includes ground application, aerial application,
chemigation, high and low volume spray, hand held, pressurized and pump up sprayers,
moveable and solid set irrigation, and broadcast spreaders for granular applications.
Risks from ground boom and aerial applications are expected to result in the highest off-
target levels of myclobutanil due to generally higher spray drift levels. Ground boom and
aerial modes of application tend to use lower volumes of application applied in finer
sprays than applications coincident with sprayers and spreaders and thus have a higher
potential for off-target movement via spray drift.
3.1 Label Application Rates and Intervals
Myclobutanil labels may be categorized into two types: labels for manufacturing uses
(including technical grade myclobutanil and its formulated products) and end-use
products. While technical products, which contain myclobutanil of high purity, are not
used directly in the environment, they are used to make formulated products, which can
be applied in specific areas to control brown patch, black spot, rust, powdery mildew,
blights, scab, mold, and leaf spot. The formulated product labels legally limit
myclobutanil's potential use to only those sites that are specified on the labels.
51
-------
Currently registered agricultural and non-agricultural uses of myclobutanil within
California included in this assessment are shown in Table 2.2.
3.2 Aquatic Exposure Assessment
3.2.1 Modeling Approach
Aquatic exposures are quantitatively estimated for all of assessed uses using scenarios
that represent high exposure sites for myclobutanil use. Each of these sites represents a
10 hectare field that drains into a 1-hectare pond that is 2 meters deep and has no outlet.
Exposure estimates generated using the standard pond are intended to represent a wide
variety of vulnerable water bodies that occur at the top of watersheds including prairie
pot holes, playa lakes, wetlands, vernal pools, man-made and natural ponds, and
intermittent and first-order streams. As a group, there are factors that make these water
bodies more or less vulnerable than the standard surrogate pond. Static water bodies that
have larger ratios of drainage area to water body volume would be expected to have
higher peak EECs than the standard pond. These water bodies will be either shallower or
have large drainage areas (or both). Shallow water bodies tend to have limited additional
storage capacity, and thus, tend to overflow and carry pesticide in the discharge whereas
the standard pond has no discharge. As watershed size increases beyond 10 hectares, at
some point, it becomes unlikely that the entire watershed is planted to a single crop,
which is all treated with the pesticide. Headwater streams can also have peak
concentrations higher than the standard pond, but they tend to persist for only short
periods of time and are then carried downstream.
Crop-specific management practices for all of the assessed uses of myclobutanil were
used for modeling, including application rates, number of applications per year,
application intervals, and the first application date for each crop. The date of first
application was developed based on several sources of information including data
provided by BEAD, a summary of individual applications from the CDPR PUR data, and
Crop Profiles maintained by the USDA. For example, the first applications of
myclobutanil reported in the CDPR PUR database occurred in late February or early
March and continued through mid-August, during the years 2001 to 2005. For grapes,
the heaviest period of application began in April. Precipitation also tends to be greater in
late winter and early spring then in the summer. Based upon the dates selected for crop
emergence and harvest in the standard PRZM CA Grape scenario and the CDPR PUR
data, the date selected for first application of myclobutanil for modeling was April 1 in
(Figure 3.1).
52
-------
350
300
1!
//
Date of Application
Figure 3.1 Summary of Applications (pounds versus date) of Myclobutanil to
Grapes in 2001 from CDPR PUR Data.
More detail on the crop profiles and the previous assessments may be found at:
http://pestdata.ncsu.edu/cropprofiles/cropprofiles.cfm
3.2.2
PRZM Scenarios
PRZM scenarios used to model aquatic exposures resulting from applications of specific
uses are identified in Tables 3.5 and 3.6. In cases where a scenario does not exist for a
specific use, it is necessary to assign a surrogate scenario. Those surrogates are assigned
to be most representative of the use being considered. Factors considered in the selection
of scenarios include the similarity of crop growth and morphology, soils, product use and
cropping area. Particular attention is given to the areas where the crops are grown
because rainfall is understood to be a driving variable in PRZM modeling. Justifications
for assignments of surrogates are defined below. All scenarios were parameterized for
irrigation.
Almond scenario (CA Almond STD)
This scenario is intended to represent almond and walnut production in CA and is
therefore, directly relevant to this use. The only crop using this scenario in this
assessment was almonds.
53
-------
Citrus scenario (CA Citrus STD)
This scenario is intended to represent applications of pesticides to oranges, grapefruit,
kumquats, lemons, limes, tangelos, and tangerines in CA and is therefore, directly
relevant to this use. The crops modeled with this scenario were mangoes, papaya,
sapodilla, and white sapote.
Cotton scenario (CA Cotton STD)
This scenario is intended to represent applications of pesticides to cotton in CA and is
therefore, directly relevant to this use. This scenario was used for cotton seed.
Forestry Scenario (CA Forestry)
This scenario is intended to represent forestlands in northern California. The area of
interest (AOI) includes Trinity, Shasta, Modoc, and Humboldt counties since they are
predominantly forested and comprise the largest amount of pesticide application to forest
lands in California. Based on typical forest composition and common pest species, this
scenario is intended to represent coniferous evergreen forests. This scenario was used to
represent Douglas Fir (seed orchard, forest, and shelter belt), loblolly pine forests, and
hybrid cottonwood and poplar plantations, slash pine (forest), and ornamental and/or
shade trees.
Fruit scenario (CA Fruit STD)
The CA fruit scenario represents an orchard in Fresno County, which is located in the
Central Valley. This scenario is intended to represent non-citrus fruit, including apples,
crabapples, pears, quince, apricots, sweet and sour cherries, nectarines, peaches, plums,
and prunes. Crops modeled using this scenario were apples, apricot, canistel, cherry,
mamey (mamme apple), and mayhaw (hawthorn), nectarines, peaches, plums, and
prunes.
Grape Scenario (CA Grapes with Irrigation STD)
The CA grape scenario represents a vineyard located in Southern San Joaquin Valley.
According to the 1997 Census of Agriculture, California is the major producer of table,
wine, and raisin grapes with 85 percent of California's production in the San Joaquin
Valley and the bulk of the remainder in the Coachella Valley. This scenario was used to
model grapes.
Wine grapes scenario (CA Wine Grapes)
This scenario is intended to represent applications of pesticides to grapes used for wine
production in CA and is therefore, directly relevant to this use. Crops considered with this
54
-------
scenario included blackberry, boysenberry, currant, dewberry, gooseberry, raspberry, and
youngberry.
Hops Scenario (OR Hop STD)
This scenario, developed based on a hops vineyard in the Pacific Northwest, represents a
vineyard located north of the area where hops are grown in CA Since the locations
where hops are grown in CA are mostly in the northern part of the state, this scenario was
deemed appropriate for modeling hops grown in CA. This scenario was used to represent
hops.
Lettuce Scenario (CA Lettuce STD)
A major leaf lettuce production area is the Coastal Valley of California. Since lettuce
(Lectuca saliva) is predominantly grown on the West Coast, this scenario is used to
represent lettuce production nationally. It is thus also suitable for representing lettuce
culture in California and would be expected to be more vulnerable than most places in the
state that grow lettuce and could impact the habitat of the red-legged frog. This scenario
was used for both head and leaf lettuce.
Melon scenario (CA Melon)
This scenario is intended to represent applications of pesticides to cantaloupes,
cucumbers, melons, pumpkins, watermelons, winter and summer squash in CA and is
therefore, directly relevant to this use. This scenario was used to represent cantaloupes,
casaba, cucumber, cucurbit vegetables, melons, squash, and watermelons.
Mint Scenario (OR Mint STD)
According to NASS data, mint (grown for oil) has been grown in Lassen, Shasta and
Siskiyou Counties. These counties are located in northern CA, bordering OR. Although
this scenario represents a field located north of the area where mint is grown in CA, it
was developed based on a mint field in the Pacific Northwest. Since the locations where
mint is grown in CA are in the northern part of the state, this scenario was deemed
appropriate for modeling mint grown in CA. This scenario was used to represent
spearmint and peppermint crops.
Nursery scenario (CA Nursery STD)
This scenario is intended to represent applications of pesticides in outdoor nurseries in
CA and is therefore, directly relevant to this use. Uses considered with this scenario
included garland, chrysanthemum, ornamental ground cover, ornamental herbaceous
plants, ornamental and non-flowering plants, ornamental woody shrubs and vines.
55
-------
Row crop scenario (CA Row Crop)
This scenario is intended to represent production of carrots, beans, peppers and other
crops in CA, and is therefore, directly relevant to these uses. Crops considered with this
scenario included artichokes, asparagus, beans, carrots, pepper, and pimento.
Strawberry scenario (CA Strawberry no plastic)
This scenario is intended to represent applications of pesticides to strawberries, non-
tarped, in CA. While the majority of strawberry growers use tarps, this scenario is
considered a conservative approach and is therefore, is used for strawberries.
Sugar beet scenario (CA Sugar beet OP)
This scenario was intend to represent applications of pesticides to sugar beets in CA, and
is therefore, relevant to this use. This scenario was used to represent sugar beets.
Tomato scenario (CA Tomato STD)
This scenario is intended to represent applications of pesticides to tomatoes in CA and is
therefore, directly relevant to this use. This scenario was used to represent eggplant,
okra, and tomato crops.
Turf scenario (CA Turf)
This scenario is intended to represent applications of pesticides to sod farms, parks,
recreational fields, grass for seed, and golf courses in CA and is therefore, directly
relevant to this use. This scenario was used to represent Bluegrass, commercial and
industrial lawns, golf-course turf, grasses grown for seed, ornamental lawns, residential
lawns, sod farms, and turf.
3.2.3 Model Inputs
Myclobutanil is a fungicide used on a wide variety of food and non-food crops.
Myclobutanil and selected myclobutanil plus 1,2,4-triazole environmental fate data used
for generating model parameters is listed in Table 2.1. The input parameters used for
PRZM and EXAMS models to estimate myclobutanil and myclobutanil plus 1,2,4-
triazole are summarized in Table 3.1. Residues in surface water were estimated for
myclobutanil (parent) and for myclobutanil plus 1,2,4-triazole. The number of
applications and the reapplication intervals for each crop modeled are listed in Tables 3.5
and 3.6 and Appendix B (Tables 2 and 3).
56
-------
Table 3.1 Summary of PRZM and EXAMS Environmental Fate Data Used for
Aquatic Exposure Inputs for Myclobutanil and Myclobutanil plus 1,2,4-triazole for
Endangered Species Assessment for the CRLF l
Parameter
Molecular Weight
Solubility
Aquatic Photolysis (t1/2)
Soil Partition
Coefficient, Freundlich
Kads
Solubility in water (pH
7, 25°C)
Vapor Pressure
Henry's Law Constant
Hydrolysis
Aerobic Soil
Metabolism (ti/2)
Aerobic Aquatic
Metabolism (ti/2)
Application Efficiency
(APPEFF)
Drift (DRFT)
Aerial Spray
Chemical Application
Method (CAM)
Input Value and Unit
288.8 g/ mola'b
142 ppm @ 25 "C^
0 days (Stable)
Myclobutanil: 2.39 mg/L3
1,2,4-triazole: 0.719 mg/Lb
1420 mg/L (142 mg/L * lO)^
1.49xlO-°6mmHgat25°Ca
3.25 x 10'09 atm nrVmole @ 25 °C
0 days (Stable)
Myclobutanil: 25 1 days3
Myclobutanil + 1,2,4-triazol: 315 daysb
Myclobutanil
Estimated as 502 days3
Myclobutanil + 1,2,4-triazole
Estimated as 630 daysb
0.95 aerial spray
0.99 ground spray
1.00 granular
Aerial (0.05 Drift)
Ground (O.OlDrift)
Granular (0.00)
2 - foliar
1 - granular
5 - cotton seed (incorporation depth 3
cm)
Rational
No Data
Lowest non-sand value
Lowest non-sand value
EFED, Guidance
USEPA, 2002
Upper 90th bound on
mean
Only 1 value
2xASM
2 x ASM per USEPA,
2002
EFED Guidance
USEPA, 2002
EFED Guidance
USEPA, 2002
Label
1 - Inputs determined in accordance with EFED "Guidance for Chemistry and Management Practice Input
Parameters for Use in Modeling the Environmental Fate and Transport of Pesticides" dated February 28,
2002
3- Value used to estimate myclobutanil EECs.
b - Value used to estimate myclobutanil plus 1,2,4-triazole EECs
The myclobutanil plus 1,2,4-triazole EECs were estimated by using the half-life
estimated from the decline of the sum of myclobutanil and 1,2,4-triazole with time using
assuming first-order kinetics (Appendix C. Environmental Fate Data) and assuming the
greater mobility (Freundlich Kads) of the 1,2,4-triazole (Table 3.1).
The myclobutanil was assumed to be applied by ground and aerial spray methods as a
foliar, and broadcast as a granular. The other methods of application include chemigation,
57
-------
sprinkler irrigation, and hand sprayers. The application rates were obtained from the
labels. The maximum number of applications, the maximum single application rate, and
maximum total application rate per crop cycle or year, and minimum reapplication
interval were used when possible. When the number of applications times the maximum
single rate exceeded the labels total maximum rate per crop cycle (cc) or yearly rate, the
last application was reduced so as not to exceed the total amount. Several uses (i.e.,
nectarines) did not have enough applications (0.15 Ib ai/A/application x 7 applications =
1.05 Ib ai/A/cc with a maximum per cc of 1.305 Ib ai/A) to obtain the total maximum
crop cycle or year rate. Eight applications at 0.15 Ib ai/A/application + 1 application of
0.105 Ib ai/A would be required.
3.2.4 Available Monitoring Data
3.2.4.1 Aquatic Exposure Monitoring and Field Data
Monitoring studies which included myclobutanil as an analyte were the USGS NAWQA
(USGS, 1991) and the Reservoir Pilot Monitoring Program (USGS, 2001). Myclobutanil
is not included in the CDPR monitoring program. These monitoring studies, which are
discussed in further detail below, were not specifically targeted to myclobutanil use areas.
The 1,2,4-triazole degradate was not included in the analysis.
Reservoir Pilot Monitoring Program (USGS, 2001)
Myclobutanil was included in a study that monitored a number of water supply reservoirs
and finished water (USGS, 2001). Residues were detected at low concentrations in about
1 percent of 317 samples of raw water, with no detections in the finished water (Table
3.2). The degradation products were not included.
Table 3.2 Myclobutanil results from the summary of analysis of moderate-use
pesticides and degradates in water samples from water supply intakes and finished-
supply taps in Reservoir Pilot Monitoring Program. (USGS, 2001)
Raw Water
Finished Water
No. of
Samples
317
221
No. of Detections
(Quantifiable No.
of Detections)
3(2)
0
Frequency of
Detection
(%)
0.9
0
Maximum
Detection
(Hg/L)
0.015
0
Method
Reporting
Level
(Hg/L)
0.008
0.008
USGS NAWQA (National Water Quality Assessment Program)
The USGS NAWQA data was downed load on 05/13/09
(http://infotrek.er.usgs.gov/traverse/f?p=NAWQA:HOME:3748645897450568)
and "contained data through water year 2007".
58
-------
Surface Water Analysis
Myclobutanil was detected in ambient surface water (Table 3.3) at a detection frequency
of 37.8 % (166 of 439 samples) collected in five counties in California. The maximum
daily myclobutanil concentration was 0.507 ug/L for a sampling site located near
Montpelier California in Merced County California (USGS Sampling Station
373112120382901). The minimum reporting limit (MRL) varies from 0.0022 to 0.25
Ug/L, with a median MRL of 0.008 ug/L.
Table 3.3 Distribution of Myclobutanil Concentrations (ug/L) in USGS NAWQA
Surface Water Monitoring Data Monitoring Data (1998-2007)
River Basin
Santa Ana
San Joaquin-Tulare
Sacramento
County
Riverside
Merced
San Joaquin
Stanislaus
Sacramento
Total
No. samples
55
149
87
30
118
439
No. Detections
2
89
25
15
35
166 (37.8%)
Min
0.0118
0.0091
0.0045
0.0082
0.0094
0.0045
Max
0.033
0.507
0.021
0.380
0.288
0.507
Ground Water Analysis
Myclobutanil was not detected in ground water in California samples collected in
California (300 samples). Wells were located in Butte, Colusa, Fresno, Glenn, Madera,
Merced, Placer, Sacramento, San Bernardino, San Joaquin, Stanislaus, Sutler, Tulare, and
Yuba Counties. The minimum reporting limit (MRL) varies from 0.0022 to 0.033 ug/L
with a median MRL of 0.008
Rain data
Rainfall samples were collected during the growing seasons of 2003 and 2004 at four
agriculture locations across the United States (Vogel et al., 2008). One of the watersheds
was located in Western California where the cropland is comprised of almonds and
vineyards with some corn and dairy. Myclobutanil (Table 3.4) was detected in 74% of
rain samples (n=23), between February and April corresponding to use after almond trees
bud. The myclobutanil residues were not detected in the local watershed.
Table 3.4 Myclobutanil concentrations in Rain in California Agricultural
Watershed (Vogel et al., 2008)
Number of samples
23
Percent of
Detections
57 %> 0.01 ug/L
4%>0.1 ug/L
Median
0.014 ug/L
Maximum
0.113 ug/L
59
-------
3.2.5 Modeling Results
The estimated environmental concentrations (EECs) for myclobutanil varied by scenario,
crop, and by rate and date (i.e., date of first application and reapplication interval), and
method of application. The dates of the first application of myclobutanil ranged from
early February to earlier September. The myclobutanil peak concentrations ranged from
2.11 |ig/L to 54.56 |ig/L, for cotton seed treatment to the granular application to turf,
respectively. The 21-day and 60-day rolling averages were 2.1 and 2.08 |ig/L, for cotton
seed treatment and 54.29 to 53.84 jig/L for granular turf, respectively. The selected
aquatic EECs for myclobutanil for other crops and scenarios and application practice
(aerial spray, granular, and seed treatment) are listed in Table 3.5. All crops simulated
(ground and aerial spray) are summarized in Appendix B, Table 1.
Table 3.5 Aquatic EECs (ug/L) for Myclobutanil Uses in California
CA Scenario
Almond
Citrus
Cotton
Forestry
Forestry
Fruit
Fruit
Fruit
Fruit
Fruit
Fruit
Fruit
Grapes
Grapes
Lettuce
Melons
Nursery
Row Crop
Row Crop
Row Crop
Row Crop
Strawberry
Turf
Turf
Method
Date of First
Application
as
as
Seed trt.
as
as
as
as
as
as
as
as
as
as
as
as
as
as
as
as
as
as
as
Granular
as
2-10
8-01
4-15
8-05
8-05
3-10
3-10
4-10
4-10
4-10
3-10
3-10
4-01
4-01
9-02
6-15
7-01
2-15
7-15
2-20
9-14
3-01
2-01
2-01
Representative
Crop
Almond
Mango
Cotton
Douglas fir
Douglas fir
Apple
Apple
Cherry
Cherry
Fruit2
Peach
Peach
Grapes
Grapes
Lettuce3
Melon
Ornamental
Artichoke
Asparagus
Beans
Pepper, pimento
Strawberry
Turf
Turf
#@rate/total/Interval
Rate
3@0.2/0.6/7
8@0.25/2.0/14
0.891
2@0.25 + 1@0. 1/0.6/14
4@0. 15/0.6/10
4@0.5/2.0/7
8@0.25/2.0/7
2@0/0.47+l@0.11/1.31/7
8@0.15 + l@0.11/1.31/7
8@0.25/2.0/14
2@0.47 + l@0.37/1.31/7
8@0. 15 + 1@0. 123/1.3 1/7
4@0.13 + l@0.08/0.60/7
6@0. 10/0.60/7
4@0. 125/0.50/14
4@0. 12 + 1@0. 10/0.60/7
0.26/ns4/2.05/7
6@0. 10/0.60/7
6@0. 125/0.76/14
4@0. 125/0.50/7
4@0. 125/0.50/10
6@0. 125/0.75/14
6@1.34/
4@0. 19/0.75/14
EEC 1-year in 10-year
Peak
11.93
21.75
2.11
21.76
21.74
29.79
30.13
21.25
21.35
31.35
19.45
19.88
8.99
9.07
41.02
16.32
45.25
15.92
22.29
13.62
17.70
34.19
54.56
20.69
21day
11.86
21.58
2.10
21.61
21.58
29.45
29.81
21.72
21.09
30.31
19.24
19.69
8.88
8.98
40.58
15.74
44.93
15.79
22.16
13.52
17.52
34.03
54.29
20.53
60 day
11.77
21.30
2.08
21.46
21.44
28.94
29.49
20.59
20.52
30.17
18.85
19.39
8.73
8.83
38.61
15.61
44.21
15.55
21.95
13.35
17.34
33.83
53.84
20.34
60
-------
CA Scenario
Hops6
Hops
Method
Date of First
Application
as
as
9-01
4-01
Representative
Crop
Hops
Hops
#@rate/total/Interval
Rate
4@0.25/1.0/7
4@0.25/1.0/7
EEC 1-year in 10-year
Peak
28.83
17.96
21day
28.65
17.82
60 day
28.38
17.56
1 Cotton rate is 0.0625 Ib a.i./lOO Ib seed; [4200 seed/lb; 60,000 seed/acre = 14.29 Ib seed/acre]
2 Fruit - Mamey, Mayhaw, Star Apple; canistel
Lettuce and Brussels Sprouts
4
ns is not specified on label.
5 Ornamentals - maximum rate = 0.26 Ib ai/A/application; season total = 2.0 Ib ai/A/year or cc. Number of
applications is not specified. Maximum seasonal rate is achieved by assuming 7 applications at 0.26 Ib ai/A
and an 8th application at 0.18 to obtain 2.0 Ib ai/A per year. Reapplication interval is 7 days.
6 Hops STD Scenario are located in Oregon rather than California
The estimated environmental concentrations (EECs) for myclobutanil plus 1,2,4-triazole
varied by scenario, crop, and by rate, date (i.e., date of first application and reapplication
interval), and method of application. The dates of the first application of myclobutanil
ranged from early February to earlier September. The myclobutanil peak concentrations
ranged from 2.84 |ig/L to 61.41 |ig/L, for cotton seed treatment to the granular
application to turf, respectively. The 21-day and 60-day rolling averages were 2.82 and
2.77 |ig/L, for cotton seed treatment and 61.15 to 60.71 |ig/L for granular turf,
respectively. The selected aquatic EECs for myclobutanil for other crops and scenarios
and application practice (aerial spray, granular, and seed treatment) are listed in Table
3.6. All the crops simulated (ground and aerial spray) are summarized in Appendix B.
Table 2.
Table 3.6 EECs California Red legged frog - myclobutanil + 1,2,4-triazole
CA Scenario
Almond
Citrus
Forestry
Forestry
Fruit
Fruit
Fruit
Fruit
Fruit
Fruit
Fruit
Grapes
Method
as
as
as
as
as
as
as
as
as
as
as
as
Date of First
Application
app
2-10
8-01
8-05
8-05
3-10
3-10
4-10
4-10
4-10
3-10
3-10
4-01
Represent-
ative
Crop
Almond
Mango
Douglas fir
Douglas fir
Apple
Apple
Cherry
Cherry
Fruit1
Peach
Peach
Grapes
# @ rate/total
# @lb ai/A/lb ai/A/days
Rate
3@0.2/0.6/7
8@0.25/2.0/14
2@0.25 + 1@0. 1/0.6/14
4@0. 15/0.6/10
4@0.5/2.0/7
8@0.25/2.0/7
2@0/0.47 + l@0.37/1.31/7
8@0.15 + l@0.11/1.31/7
8@0.25/2.0/14
2@0.47 + l@0.37/7
8@0.15 + l@0.123/1.31/7
4@0.13 + l@0.08/0.60/7
EEC 1-year in 10-year
peak
14.17
27.90
22.37
22.40
37.75
37.94
25.87
24.01
36.33
24.55
24.70
11.18
21day
14.10
27.78
22.28
22.29
37.36
37.63
25.61
24.51
35.18
24.29
24.51
11.06
60 day
13.99
27.37
22.10
22.11
36.64
37.16
25.04
24.22
35.03
23.88
24.22
10.82
61
-------
CA Scenario
Grapes
Lettuce
Melons
Nursery
Row Crop
Row Crop
Row Crop
Row Crop
Strawberry
Strawberry
Turf
Turf
Hops 5
Hops
Method
as
as
as
as
as
as
as
as
as
as
Granular
as
as
as
Date of First
Application
app
4-01
9-02
6-15
7-01
2-15
7-15
2-20
9-14
3-01
3-01
2-01
2-01
9-01
4-01
Represent-
ative
Crop
Grape
Lettuce2
Melon
Ornamental
Artichoke
Asparagus
Beans
pepper, pimento
Strawberry
Berries
Turf
Turf
Hops
Hops
# @ rate/total
# @lb ai/A/lb ai/A/days
Rate
6@0. 10/0.60/7
4@0. 125/0.50/14
4@0. 12 + 1@0. 10/0.50/7
0.26/ns3/2.04/7
6@0. 10/0.60/7
6@0. 125/0.75/14
4@0. 125/0.50/7
4@0. 125/0.50/10
6@0. 125/0.75/14
4@0.063/0.25/10
6@1.34/
4@0. 19/0.75/14
4@0.25/1.0/7
4@0.25/1.0/7
EEC 1-year in 10-year
peak
11.11
41.94
18.61
51.96
17.57
21.09
15.56
16.97
40.84
14.62
61.41
24.06
28.81
20.52
21day
11.02
41.79
18.41
51.71
17.46
20.99
15.48
16.91
40.69
14.55
61.15
23.93
28.65
20.39
60 day
10.85
41.22
18.21
51.22
17.27
20.68
15.35
16.82
40.41
14.43
60.71
23.78
28.38
20.18
1 Fruit - Mamey, Mayhaw, Star Apple; canistel
2 Lettuce and Brussels sprouts.
3 ns is not specified on label.
4 Ornamentals - maximum rate = 0.26 Ib ai/A/application; season total = 2.0 Ib ai/A/year or cc. Number of
applications is not specified. Maximum seasonal rate is achieved by assuming 7 applications at 0.26 Ib ai/A
and an 8th application at 0.18 to obtain 2.0 Ib ai/A per year. Reapplication interval is 7 days.
5 Hops STD and Mint STD Scenarios are located in Oregon rather than California
In a previous assessment (USEPA, 2007), it was observed that the Tier II EECs indicated
year-to-year accumulation of myclobutanil in the standard pond (Figure 3.2). This
accumulation is not unexpected due to the persistence of myclobutanil and myclobutanil
plus 1,2,4-triazole in soil and water environments, and the lack of inflow and outflow in
the standard pond that precludes decreases in concentrations of residues due to dilution.
62
-------
19 -,
O) 10 -
c
o
« 8
4=
0)
c 6
O
« 4 _
0) H
0.
3
Co _
n -
19
• •
**« * • *
* * ** *»*» »
»* *
f
1
»
60 1970 1980 1990
Years
• Myclobutanil
• Myclobutanil + 1,2,4-triazole
Figure 3.2 Accumulation of PRZM/EXAMS Annual Peak Concentrations of
Myclobutanil and Myclobutanil plus 1,2,4-triazole in the California Tomato
Scenario (surrogate for CA Okra aerial spray use)
This apparent accumulation limits any probabilistic interpretation of the return frequency
of concentrations because of the accumulation over approximately 27 years simulated in
the standard farm pond. Therefore, the l-in-10 year concentrations reported in the farm
pond in the standard EFED ecological risk assessments are conservative compared to
flowing systems. Modeling of accumulation curves was conducted to allow for estimation
of concentrations during a 30 year time period. The modeling was conducted on annual
peak concentrations from PRZM/EXAMS using Sigmaplot Regression Wizard. The
model used was the exponential rise to maximum model (y = a(l-e("b*x)) where y =
annual peak concentration (ug/L), x = time (years), a= plateau concentration of
accumulation, and b= annual rate of rise (year"1). Table 3.7 shows the model parameters
for several PRZM/EXAMS simulations.
63
-------
Table 3.7 Time (years) for myclobutanil and myclobutanil plus 1,2,4-triazole to
reach plateau concentration in standard farm pond (USEPA, 2007)
Scenario
CA Okra
C A Lettuce
CA Artichoke
CA Tropical Fruit
Application
Method
Air
Ground
Air
Ground
Air
Ground
Air
Ground
Model Predicted Constants
a1
6.1507
2.7613
92.26
81.23
17.40
11.45
21.22
7.66
b2
0.3930
0.4002
0.24
0.24
0.23
0.24
0.50
0.76
R2
0.87
0.55
0.76
0.69
0.94
0.87
0.72
0.15
Years to reach plateau concentration in standard farm pond.
Annual rate of rise (year"1).
3.3 Terrestrial Animal Exposure Assessment
T-REX (Version 1.4.1) is used to calculate dietary and dose-based EECs of myclobutanil
for the CRLF and its potential prey (e.g. small mammals and terrestrial insects)
inhabiting terrestrial areas. EECs used to represent the CRLF are also used to represent
exposure values for frogs serving as potential prey of CRLF adults. T-REX simulates a 1-
year time period. For this assessment, spray and granular applications of myclobutanil
are considered, as discussed below. In addition, the exposure estimation for use on
cotton seeds assumes that the seeds are 100% available based on shallow planting
conditions and an associated planting depth of 1A inch.
Terrestrial EECs for foliar formulations of myclobutanil were derived for the uses
summarized in Table 3.8. Crop-specific decline data for combined residues of
myclobutanil and the primary metabolite RH-9090 from submitted crop field trial studies
are available for several commodities. Based on available data, foliar dissipation half-
lives can be derived for pome fruit and stone fruit (19 days), caneberries (14 days),
bushberries (25 days) hops (15 days), and peppers (26 days). However, no dissipation
data are available for the 1,2,4-triazole and triazole conjugates (triazole alanine and
triazole acetic acid) which are common degradates of myclobutanil. Using conservative
assumptions that the mode of action of the parent and degradates are similar and that the
compounds are of equivalent toxicity, a conservative default foliar dissipation half-life of
35 days based on the work of Willis and McDowell (1987) is used for all uses of
myclobutanil. Use specific input values, including number of applications, application
rate and application interval are provided in Table 3.8. An example output from T-REX
is available in Appendix G.
64
-------
Table 3.8 Input Parameters for Foliar Applications Used to Derive Terrestrial
EECs for myclobutanil with T-REX
Use1
Almond
Apple (pressure spray /hose-end spray)
Apricot (irrigation)
Artichoke
Asparagus
Beans
Blackberry/EggPlant/Okra/Pepper/Raspberry
Boysenberry /Dewberry /Youngberry
Carrot
Canistel/Mango/Papaya/Sapodilla
Cherry /Nectarine/Peach (pressure
spray/chemigation)
Cotton
Cucurbit Vegetables
Currant
Gooseberry
Grapes
Hops
Lettuce
Plum/Prune
Tomato
Turf (ground)
Turf (granule - broadcast spreader)
Application rate
(Ibs ai/A)
0.2
0.5
0.5
0.125
0.125
0.125
0.125
0.0625
0.1875
0.25
0.5
0.06 Ib ai/cwt
0.12
0.125
0.125
0.1
0.25
0.125
0.16
0.1
1.3
1.35
Number of
Applications
3
4
2
6
6
4
4
4
2
8
3
NS
5
8
8
6
4
4
7
4
4
6
Application
Interval (days)
7
7
7
14
14
7
10
10
14
14
7
NS
7
7
10
7
7
14
7
21
5
14
Aerial Application unless otherwise specified
T-REX is also used to calculate EECs for terrestrial insects exposed to myclobutanil.
Dietary-based EECs calculated by T-REX for small and large insects (units of a.i./g) are
used to bound an estimate of exposure to terrestrial insects. Available acute contact
toxicity data for bees exposed to myclobutanil (in units of jig a.i./bee), are converted to
jig a.i./g (of bee) by multiplying by 1 bee/0.128 g. The EECs are later compared to the
adjusted acute contact toxicity data for bees in order to derive RQs.
For modeling purposes, exposures of the CRLF to myclobutanil through contaminated
food are estimated using the EECs for the small bird (20 g) which consumes small
insects. Dietary-based and dose-based exposures of potential prey are assessed using the
small mammal (15 g) which consumes short grass. Upper-bound Kenega nomogram
values reported by T-REX for these two organism types are used for derivation of EECs
for the CRLF and its potential prey (Table 3.9). Dietary-based EECs for small and large
insects reported by T-REX as well as the resulting adjusted EECs are available in Table
3.10. An example output from T-REX v. 1.3.1 is available in Appendix G.
65
-------
Table 3.9 Upper-bound Kenega Nomogram EECs for Dietary- and Dose-based
Exposures of the CRLF and its Prey to Myclobutanil
Use
Almond
Apple
Apricot
Artichoke
Asparagus
Beans
Blackberry/EggPlant/Okra/Pepper/Raspberry
Boysenberry /Dewberry /Youngberry
Carrot
Canistel/Mango/Papaya/Sapodilla
Cherry /Nectarine/Peach
Cucurbit Vegetables
Currant
Gooseberry
Grapes
Hops
Lettuce
Plum/Prune
Tomato
Turf
EECs for CRLF
Dietary-
based EEC
(ppm)
71
222
126
45
56
55
52
26
45
124
177
63
59
75
77
111
47
103
37
609
Dose-based
EEC
(mg/kg-bw)
81
253
143
51
64
63
59
29
51
141
202
71
67
85
87
126
53
118
32
693
EECs for Prey
(small mammals)
Dietary-
based
EEC
(ppm)
126
395
225
80
100
99
91
46
79
221
315
111
104
133
136
197
83
175
57
1082
Dose-based
EEC
(mg/kg-bw)
120
376
214
77
96
94
87
44
75
211
301
106
99
127
100
188
79
184
55
1031
66
-------
Table 3.10 EECs (ppm) for Indirect Effects to the Terrestrial-Phase CRLF via
Effects to Terrestrial Invertebrate Prey Items
Use
Almond
Apple
Apricot
Artichoke
Asparagus
Beans
Blackberry/EggPlant/Okra/Pepper/Raspberry
Boysenberry /Dewberry /Youngberry
Carrot
Canistel/Mango/Papaya/Sapodilla
Cherry /Nectarine/Peach
Cotton
Cucurbit Vegetables
Currant
Gooseberry
Grapes
Hops
Lettuce
Plum/Prune
Tomato
Turf
Turf (granular)
Small Insect
71
221
126
45
56
55
51
26
45
124
177
NA
63
59
75
77
111
47
104
32
609
504
Large Insect
8
25
14
5
6
6
6
o
J
5
14
20
NA
7
7
8
9
12
5
12
4
68
56
Myclobutanil is applied as a 0.62% ai granular formulation to non-residential and
residential turf grass at a rate of 1.35 Ib ai per acre. Therefore a quantitative analysis of
terrestrial exposure to granular formulations was conducted. For granular applications,
an LDso per square foot is estimated based on application rate and toxicity.
3.4 Terrestrial Plant Exposure Assessment
TerrPlant (Version 1.1.2) is used to calculate EECs for non-target plant species inhabiting
dry and semi-aquatic areas. Due to the lack of terrestrial plant data with myclobutanil,
toxicity data on other conazole fungicides were used with TerrPlant and discussed in the
risk description (Section 5.2.3.2). Parameter values for application rate, drift assumption
and incorporation depth are based upon the use and related application method (Tables
2.2 and 3.5). As classified by Terrplant, a runoff value of 0.05 (5%) is utilized based on
the solubility of myclobutanil (142 ppm). For aerial and ground application methods,
drift is assumed to be 5% and 1%, respectively. EECs relevant to terrestrial plants
consider pesticide concentrations in drift and in runoff. These EECs are listed by use in
Table 3.11. An example output from TerrPlant v. 1.2.2 is available in Appendix N.
67
-------
Table 3.11 TerrPlant Inputs and Resulting EECs for Plants Inhabiting Dry and
Semi-aquatic Areas Exposed to Myclobutanil via Runoff and Drift
Use
Boysenberry /Dewberry /Youngberry
Boysenberry /Dewberry /Youngberry
Grapes, tomato
Grapes, tomato
Cucurbit Vegetables
Cucurbit Vegetables
Artichoke, Asparagus, Beans,
Blackberry/EggPlant/Okra/Pepper/
Raspberry, Currant, Gooseberry,
Lettuce
Artichoke, Asparagus, Beans,
Blackberry/EggPlant/Okra/Pepper/
Raspberry, Currant, Gooseberry,
Lettuce
Plum/Prune
Plum/Prune
Carrot, Hops
Carrot, Hops
Almond
Almond
Canistel/Mango/Papaya/Sapodilla
Canistel/Mango/Papaya/Sapodilla
Apple, Apricot,
Cherry /Nectarine/Peach
Apple, Apricot,
Cherry /Nectarine/Peach
Turf
Turf
Application
rate
(Ibs a.i./A)
0.0625
0.0625
0.1
0.1
0.12
0.12
0.125
0.125
0.16
0.16
0.1875
0.1875
0.2
0.2
0.25
0.25
0.5
0.5
1.3
1.35
Application
method
Foliar - aerial
Foliar - ground
Foliar - aerial
Foliar - ground
Foliar - aerial
Foliar - ground
Foliar - aerial
Foliar - ground
Foliar - aerial
Foliar - ground
Foliar - aerial
Foliar - ground
Foliar - aerial
Foliar - ground
Foliar - aerial
Foliar - ground
Foliar - aerial
Foliar - ground
Foliar - ground
Granule
broadcast spreader
Drift
Value
(%)
0.05
0.01
0.05
0.01
0.05
0.01
0.05
0.01
0.05
0.01
0.05
0.01
0.05
0.01
0.05
0.01
0.05
0.01
0.01
0.00
Spray
drift
EEC
(Ibs
a.i./A)
0.003
0.0006
0.005
0.001
0.006
0.001
0.006
0.001
0.008
0.002
0.009
0.002
0.010
0.002
0.013
0.003
0.025
0.005
0.013
0.00
Dry
area
EEC
(Ibs
a.i./A)
0.006
0.004
0.010
0.006
0.012
0.007
0.013
0.008
0.016
0.010
0.019
0.011
0.020
0.012
0.025
0.015
0.050
0.030
0.078
0.068
Semi-
aquatic
area
EEC
(Ibs
a.i./A)
0.034
0.032
0.055
0.051
0.066
0.061
0.069
0.064
0.088
0.082
0.103
0.096
0.110
0.102
0.138
0.128
0.175
0.255
0.663
0.675
4 Effects Assessment
This assessment evaluates the potential for myclobutanil to directly or indirectly affect
the CRLF or affect its designated critical habitat. As discussed in Section 2.8, assessment
endpoints for the CRLF effects determination include direct toxic effects on the survival,
reproduction, and growth of CRLF, as well as indirect effects, such as reduction of the
prey base or effects to its habitat. In addition, potential effects to critical habitat are
assessed by evaluating effects to the PCEs, which are components of the critical habitat
areas that provide essential life cycle needs of the CRLF. Direct effects to the aquatic-
phase of the CRLF are based on toxicity information for freshwater fish, while terrestrial-
phase effects are based on avian toxicity data, given that birds are generally used as a
68
-------
surrogate for terrestrial-phase amphibians. Because the frog's prey items and habitat
requirements are dependent on the availability of freshwater fish and invertebrates, small
mammals, terrestrial invertebrates, and aquatic and terrestrial plants, toxicity information
for these taxa are also discussed. Acute (short-term) and chronic (long-term) toxicity
information is characterized based on registrant-submitted studies and a comprehensive
review of the open literature on myclobutanil.
As described in the Agency's Overview Document (U.S. EPA, 2004), the most sensitive
endpoint for each taxon is used for risk estimation. For this assessment, evaluated taxa
include freshwater fish (surrogate for aquatic-phase amphibians), freshwater
invertebrates, aquatic plants, birds (surrogate for terrestrial-phase amphibians), mammals,
and terrestrial invertebrates. No acceptable data were available for aquatic or terrestrial
phase amphibians and terrestrial plants.
Toxicity endpoints are established based on data generated from guideline studies
submitted by the registrant, and from open literature studies that meet the criteria for
inclusion into the ECOTOX database maintained by EPA/Office of Research and
Development (ORD) (U.S. EPA, 2004). Open literature data presented in this assessment
were obtained from ECOTOX information obtained on October 31, 2008. In order to be
included in the ECOTOX database, papers must meet the following minimum criteria:
(1) the toxic effects are related to single chemical exposure;
(2) the toxic effects are on an aquatic or terrestrial plant or animal species;
(3) there is a biological effect on live, whole organisms;
(4) a concurrent environmental chemical concentration/dose or application
rate is reported; and
(5) there is an explicit duration of exposure.
Data that pass the ECOTOX screen are evaluated along with the registrant-submitted
data, and may be incorporated qualitatively or quantitatively into this endangered species
assessment. In general, effects data in the open literature that are more conservative than
the registrant-submitted data are considered. The degree to which open literature data are
quantitatively or qualitatively characterized for the effects determination is dependent on
whether the information is relevant to the assessment endpoints (i.e., maintenance of
CRLF survival, reproduction, and growth) identified in Section 2.8. For example,
endpoints such as behavior modifications are likely to be qualitatively evaluated, because
quantitative relationships between modifications and reduction in species survival,
reproduction, and/or growth are not available. Although the effects determination relies
on endpoints that are relevant to the assessment endpoints of survival, growth, or
reproduction, it is important to note that the full suite of sublethal endpoints potentially
available in the effects literature (regardless of their significance to the assessment
endpoints) are considered to define the action area for myclobutanil.
Citations of all open literature not considered as part of this assessment because they
were either rejected by the ECOTOX screen or accepted by ECOTOX but not used (e.g.,
the endpoint is less sensitive) are included in Appendix H. Appendix H also includes a
69
-------
rationale for rejection of those studies that did not pass the ECOTOX screen and those
that were not evaluated as part of this endangered species risk assessment. A detailed
spreadsheet of the available ECOTOX open literature data, including the full suite of
lethal and sublethal endpoints is presented in Appendix I. Appendix J contains a
summary of the human health effects data for myclobutanil.
In addition to registrant-submitted and open literature toxicity information, other sources
of information, including use of the acute probit dose response relationship to establish
the probability of an individual effect and reviews of the Ecological Incident Information
System (EIIS), are conducted to further refine the characterization of potential ecological
effects associated with exposure to myclobutanil. A summary of the available aquatic
and terrestrial ecotoxicity information, use of the probit dose response relationship, and
the incident information for myclobutanil are provided in Sections 4.1 through 4.4,
respectively.
There are three registrant-submitted studies on the toxicity of the 1,2,4-triazole degradate
to aquatic organisms, but they are pending review. From these studies, it is provisionally
concluded that 1,2,4-triazole has no greater toxicity to aquatic organisms than the parent
compound, myclobutanil. There are currently no open literature studies reported in the
ECOTOX database for 1,2,4-triazole. Each of the registrant submitted studies is briefly
summarized below.
A rainbow trout (Salma gairdnerf) acute toxicity study (MRTD 45284017) was
submitted for 1,2,4-triazole. Mortality was observed only in the highest test level
(1000 mg/L). The calculated LCso was 760 mg/L. For myclobutanil, the rainbow
trout showed a 96-hour LC50 of 4.2 (3.2 to 5.6, 95% C.I.) mg a.i./L (MRID
00141677). The most sensitive endpoint for myclobutanil was the bluegill sunfish
96-hour LC50 of 2.4 (1.5 to 4.7, 95% C.I.) mg a.i/L (MRID 00144285).
Therefore, 1,2,4-triazole shows significantly less toxicity than myclobutanil.
A water flea (Daphnia magnet) acute toxicity study was submitted for 1,2,4-
triazole (MRID 00133381). The calculated LC50 was 900 (730 to 2200, 95% C.I.)
mg/L. The myclobutanil Daphnia magna 48-hour LCso was 11 (9.5 to 13, 95%
C.I.) mg a.i./L (MRID 00141678). Therefore, 1,2,4-triazole shows significantly
less toxicity than myclobutanil.
A non-vascular aquatic plant study for a green algae (Scenedesmus subspicatus)
was submitted for 1,2,4-triazole (MRID 00133382). The calculated EC50 was 6.3
(5.5 to 7.1, 95% C.I.) mg/L. For myclobutanil, the freshwater green algae
Selenastrum capricornutum showed a 120-hour ECso of 0.83 (0.56 to 1.1, 95%
C.I.) mg a.i./L based on cell density (MRID 419848-01). It is not certain which of
these species is more or less sensitive, therefore it is provisionally concluded that
1,2,4-triazole shows less toxicity than myclobutanil.
Available acute and reproduction studies on the degradate 1,2,4-triazole indicate that for
mammals, the degradate is either less or equally toxic as the parent. For birds, a report
70
-------
was submitted which indicates that 1,2,4-triazole does not have a determinate acute
toxicity value with coturnix quail under the conditions of the study but is possibly less
toxic than the parent, myclobutanil. This report also indicated that a single oral dose of
the triazole degradate to male birds does not indicate any reproductive effects; however,
the protocol of this study is not comparable to the typical avian reproduction study.
Acute mammalian toxicity data on myclobutanil formulations, including those mixed
with other pesticides indicate that with one exception (the 60% formulation) the
formulations are not more acutely toxic than the technical grade compound. The rat LD50
for the technical product is 1600 mg/kg bw, the rat LD50 for the 60% formulation is 980
mg/kg bw. Therefore, EEC's were derived separately for the 60% formulation using the
rat LD50 and actual use parameters (i.e., label specified use and application rate) to
determine the toxicity of the formulation relative to the technical product and/or other
formulations in the field. A detailed summary of the available ecotoxicity information
for 1,2,4-triazole and all myclobutanil formulated products is presented in Appendix K.
The submitted study citations can be found in Appendix O.
4.1 Evaluation of Aquatic Ecotoxicity Studies
Table 4.1 summarizes the most sensitive aquatic toxicity endpoints for the CRLF, based
on an evaluation of both the submitted studies and the open literature, as previously
discussed. A brief summary of submitted and open literature data considered relevant to
this ecological risk assessment for the CRLF is presented below.
Table 4.1 Freshwater Aquatic Toxicity Profile for Myclobutanil
Assessment Endpoint
Acute Direct Toxicity to
Aquatic-Phase CRLF
Chronic Direct Toxicity
to Aquatic-Phase CRLF
Indirect Toxicity to
Aquatic -Phase CRLF via
Acute Toxicity to
Freshwater Invertebrates
(i.e. prey items)
Indirect Toxicity to
Aquatic -Phase CRLF via
Chronic Toxicity to
Freshwater Invertebrates
(i.e. prey items)
Species
Bluegill sunfish
(Lepomis
macrochirus)
Fathead minnow
(Pimephales
prom el as)
Water flea
(Daphnia
magna)
Toxicity Value Used in
Risk Assessment
LC50=2.4mg/L
NOAEC = 0.98 mg/L
LOAEC = 2.2 mg/L
LC50= 11 mg/L
MRID
00144285
00164986
40409201
40480401
00141678
Study
Classification
Acceptable
Acceptable
Acceptable
No data available for myclobutanil
71
-------
Assessment Endpoint
Indirect Toxicity to
Aquatic -Phase CRLF via
Toxicity to Non-vascular
Aquatic Plants
Indirect Toxicity to
Aquatic -Phase CRLF via
Toxicity to Vascular
Aquatic Plants
Species
Freshwater green
algae
(Selenastrum
capricornutum)
Toxicity Value Used in
Risk Assessment
EC50 = 0.83 mg/L
MRID
419848-01
Study
Classification
Acceptable
Tier II growth
and
reproduction
No data available for myclobutanil
Toxicity to aquatic fish and invertebrates is categorized using the system shown in Table
4.2 (U.S. EPA, 2004). Toxicity categories for aquatic plants have not been defined.
Table 4.2 Categories of Acute Toxicity for Fish and Aquatic Invertebrates
LC50 (ppm)
<0.1
>0.1-1
>1-10
> 10 - 100
>100
Toxicity Category
Very highly toxic
Highly toxic
Moderately toxic
Slightly toxic
Practically nontoxic
4.1.1 Toxicity to Freshwater Fish
Given that no acceptable myclobutanil toxicity data are available for aquatic-phase
amphibians, freshwater fish data were used as a surrogate to estimate direct acute and
chronic risks to the CRLF. Freshwater fish toxicity data were also used to assess
potential indirect effects of myclobutanil to the CRLF. Effects to freshwater fish
resulting from exposure to myclobutanil may indirectly affect the CRLF via reduction in
available food. As discussed in Section 2.5.3, over 50% of the prey mass of the CRLF
may consist of vertebrates such as mice, frogs, and fish (Hayes and Tennant, 1985).
A summary of acute and chronic freshwater fish data is provided below in Sections
4.1.1.1 through 4.1.1.3.
4.1.1.1 Freshwater Fish: Acute Exposure (Mortality) Studies
Available data indicate that myclobutanil is moderately toxic on an acute basis to two
surrogate freshwater fish species (Appendix K). The most sensitive endpoint, the bluegill
sunfish 96-hour LC50 of 2.4 (1.5-4.7, 95% C.I.) mg a.i./L (MRID 00144285) will be used
to calculate RQs for direct effects to the aquatic-phase CRLF. The probit dose-response
slope used for this study is the default of 4.5 (2-9) because there were less than two
concentrations at which the percent dead was between 0 and 100, thus a statistically
sound calculation of the slope cannot be made from the experimental data. The acute
72
-------
study available for rainbow trout reported a 96-hour LCso of 4.2 (3.2-5.6, 95% C.I.) mg
a.i./L (MRID 00141677).
4.1.1.2 Freshwater Fish: Chronic Exposure (Early Life Stage and
Reproduction) Studies
There is one submitted early life stage study for chronic freshwater fish toxicity to
myclobutanil (MRID 00164986, 40409201, 40480401). Total length of juvenile fish at
the end of the 35-day exposure was the most sensitive endpoint for the fathead minnow
(Pimephalespromelas); the reported NOAEC and LOAEC were 0.98 mg/L and 2.2
mg/L, respectively. At the LOAEC (2.2 mg/L) there was a 9.7% reduction in mean total
length compared to the control. The LOAEC for growth as determined by wet weight
was reported as 4 mg/L. The 8-day egg survival showed no significant differences
between the control and any of the tested concentrations. After 35 days of exposure,
100% mortality occurred at 8.5 mg/L, the highest concentration tested.
4.1.1.3 Freshwater Fish: Sublethal Effects and Additional Open
Literature Information
In the bluegill sunfish acute toxicity study (MRID 00144285) used to calculate RQs, it
was reported that the test organisms exhibited quiescence and loss of equilibrium prior to
death at 2.7 mg/L (LOAEC). The NOAEC for this study was 1.5 mg/L. The rainbow
trout acute toxicity study (MRID 00141677) reported toxic symptoms at 3.2 mg/L
(LOAEC) - the fish exhibited loss of equilibrium, surfacing, and dark coloration.
Mortality was observed at 5.6 mg/L and above. The NOAEC was 1.8 mg/L
In the chronic fish early life stage study for myclobutanil (MRID 00164986, 40409201,
40480401), the raw data indicates no differences in behavior on any groups analyzed.
Total length was the most sensitive endpoint. The reported NOAEC and LOAEC for
total length were 0.98 mg/L and 2.2 mg/L, respectively.
There were no studies on myclobutanil toxicity to freshwater fish identified in the open
literature.
4.1.1.4 Aquatic-phase Amphibian: Acute and Chronic Studies
There were no acceptable studies available for myclobutanil on toxicity to aquatic-phase
amphibians.
4.1.2 Toxicity to Freshwater Invertebrates
Freshwater invertebrate toxicity data were used to assess potential indirect effects of
myclobutanil to the CRLF. Effects to freshwater invertebrates resulting from exposure to
73
-------
myclobutanil could indirectly affect the CRLF via reduction in available food items. As
discussed in Section 2.5.3, the main food source for juvenile aquatic- and terrestrial-
phase CRLFs is thought to be aquatic invertebrates found along the shoreline and on the
water surface, including aquatic sowbugs, larval alderflies and water striders.
A summary of acute and chronic freshwater invertebrate data is provided below in
Sections 4.1.2.1 through 4.1.2.3.
4.1.2.1 Freshwater Invertebrates: Acute Exposure (Mortality) Studies
Available data indicate that myclobutanil is slightly toxic on an acute basis to Daphnia
magna. The available study (MRID 00141678) reported the 48-hour LC50 for
myclobutanil was 11 (9.5-13, 95% C.I.) mg a.i./L. The probit dose-response slope for
this study is 6.8 (4.1-9.6, 95% C.I.)-
4.1.2.2 Freshwater Invertebrates: Chronic Exposure (Reproduction)
Studies
There are currently no submitted chronic freshwater invertebrate studies available for
myclobutanil. It was not possible to estimate a chronic toxicity value for freshwater
invertebrates using an acute to chronic ratio with estuarine/marine invertebrate data
because no chronic studies are available for myclobutanil. In lieu of any myclobutanil
data, toxicity data from other conazole (DMI triazole) fungicides were used to
characterize risk to freshwater invertebrates, assuming that myclobutanil toxicity is
similar to other conazoles due to similar mode of action. Toxicity data were obtained
from the EFED database (registrant-submitted studies) for the chemicals categorized as
conazole fungicides (DMI triazoles) by the Fungicide Resistance Action Committee
(FRAC)3. Acute to chronic ratios were calculated only for conazoles with acute and
chronic water flea (Daphnia magna) studies (the species for which acute data are
available for myclobutanil). Furthermore, the only studies considered were those
categorized as acceptable or supplemental, tested the technical product, and resulted in a
definitive endpoint. Table 4.3 summarizes the toxicity endpoints for the nine conazole
fungicides that met these data standards.
In addition to studies on the water flea (Daphnia magna}, four of the conazoles had
studies submitted for other aquatic invertebrate taxa (Fenbuconazole: MRID 46553601,
Prothioconazole: MRID 46246131, Tetraconazole: MRID 46614304, and Triadimefon:
MRID 00149324). For these four conazoles, Daphnia magna is the most sensitive
aquatic invertebrate species tested.
3 http://www.frac.info/frac/index. htm
74
-------
Table 4.3 Conazole (DMI triazole) Fungicide Chronic Toxicity to Aquatic
Invertebrates
Conazole1
Cyproconazole
Difenoconazole
Fenbuconazole
Hexaconazole
Prothioconazole
Tebuconazole
Tetraconazole
Triadimefon
Triadimenol
48-hr
ECgo/LCgo
(mg/L)
26
0.77
2.3
2.9
1.2
4
3.07
2.63
7.16
2.5
MRID/
Study
Classification
4060773 5/
Acceptable
42245 1107
Acceptable
41073507/
Acceptable
00160502/
Acceptable
46246009/
Acceptable
40700913/
Acceptable
45823201/
Acceptable
44367018/
Supplemental
43257001/
Acceptable
00126282/
Acceptable
NOAEC
(mg/L)
0.019
0.29
0.0056
0.078
0.226
0.51
0.120
0.19
0.51
0.052
0.087
0.199
Most sensitive
parameter
Reproduction (# live
offspring)
Reproduction (# live
offspring)
Number of young per
adult per reproductive
day and adult length
Reproduction and
length
Total young and young
per female reproductive
day and length
Number of offspring
per parent per
reproduction day and
terminal length
Adult length and
survival and young per
adult per reproduction
day
Time to first brood
release and
reproduction
(neonates/adult)
Survival and
reproduction
Adult length
Reproduction
Reproduction (# young
produced)
MRID/
Study
Classification
4703620 11
Supplemental
43187701/
Acceptable
42245 114/
Supplemental
41875007/
Supplemental
42147301/
Acceptable
46246028/
Acceptable
407009 15/
Acceptable
45823207/
Acceptable
44367019/
Supplemental
41922102/
Supplemental
00094679/
Supplemental
00094680/
Acceptable
ACR2
1368a
89.6a
137.5
29.5
12.8
2.4
33.3
13.8bto
16.2C
5.2bto6.0c
137.7d
82.3d
12.6
1 Based on toxicity to Daphnia magna
2 Acute-to chronic ratio
a Based on acute toxicity of 26 mg/L
b Based on acute toxicity of 2.63 mg/L
0 Based on acute toxicity of 3.07 mg/L
d Based on acute toxicity of 7.16 mg/L
75
-------
4.1.2.3 Freshwater Invertebrates: Sublethal Effects and Open
Literature Data
In the Daphnia magna acute toxicity study (MRID 00141678) used to calculate RQs, it
was reported that the test organisms settled to the bottom of the test vessel at 5.6 mg/L
(LOAEC) and above. The NOAEC for this study was 3.2 mg/L.
There were no studies on toxicity to freshwater invertebrates identified in the open
literature.
4.1.3 Toxicity to Aquatic Plants
Aquatic plant toxicity studies were used as one of the measures of effect to evaluate
whether myclobutanil may affect primary production and the availability of aquatic
plants as food for CRLF tadpoles. Primary productivity is essential for indirectly
supporting the growth and abundance of the CRLF.
Laboratory studies were considered for determining whether myclobutanil may cause
direct effects to aquatic plants. A summary of the laboratory data and freshwater field
studies for aquatic plants is provided in Sections 4.1.3.1 and 4.1.3.2. There were no
studies on toxicity to aquatic plants identified in the open literature.
4.1.3.1 Aquatic Plants: Laboratory Data
The available study for non-vascular aquatic plants (MRID 419848-01) examined the
freshwater green algae Selenastrum capricornutum. This study reported a 120-hour ECso
for myclobutanil of 0.83 (0.56-1.1, 95% C.I.) mg a.i./L based on cell density. The
NOAEC for this study was 0.56 mg/L (mean measured concentration).
There are currently no submitted studies for vascular aquatic plants available for
myclobutanil. In lieu of any myclobutanil data, toxicity data from other conazole (DMI
triazole) fungicides were used to characterize risk to aquatic vascular plants, assuming
that myclobutanil toxicity is similar to other conazoles due to similar mode of action.
Conazole toxicity data were obtained from the EFED database as described in section
4.1.2.2. Table 4.4 summarizes the toxicity endpoints for the seven conazoles with studies
categorized as acceptable or supplemental that tested the technical product and resulted in
a definitive endpoint.
Table 4.4 Conazole (DMI Triazole) Fungicide Toxicity to Aquatic Vascular Plants
Conazole
Bromuconazole
Difenoconazole
Metconazole
ECgoCmg/L)1
0.16
1.9
0.022
Most sensitive
parameter
Frond production
Frond number
Frond number
MRID
42937141
46950204
46808428
Study Classification
Acceptable
Supplemental
Acceptable
76
-------
Conazole
Propiconazole
Prothioconazole
Tetraconazole
Triticonazole
ECsoCmg/L)1
9.02
0.073
0.31
1.4
Most sensitive
parameter
Frond production
Frond number
Frond number
Frond number
MRID
00133363
46246101
45842201
44802119
Study Classification
Supplemental
Acceptable
Acceptable
Acceptable
1 Based on toxicity to duckweed (Lemna gibba)
4.1.3.2 Freshwater Field Studies
There are currently no submitted freshwater aquatic plant field studies available for
myclobutanil.
4.2 Toxicity of Myclobutanil to Terrestrial Organisms
Table 4.5 summarizes the most sensitive terrestrial toxicity endpoints for the CRLF,
based on an evaluation of both the submitted studies and the open literature. In addition
to the parent myclobutanil, toxicity data on metabolites and degradates are also
considered when available. RH-9090 [a-(3-hydroxybutyl)-a-(4-chlorophenyl)-l//-l,2,4-
triazole-1-propanenitrile] 6-chloro-3-pyridinyl)methyl]-7V-nitro-2-imidazolidinimine]
(free and bound) is a major metabolite of myclobutanil in plants i.e., > 10%. RH-9090 is
considered to be of equivalent toxicity to the parent based on structural activity
relationship (SAR). In addition, 1,2,4-triazole and triazole conjugates (triazole alanine
and triazole acetic acid) are common degradates of triazole compounds, including
myclobutanil. A brief summary of submitted and open literature data considered relevant
to this ecological risk assessment for the CRLF is presented below.
Table 4.5 Terrestrial Toxicity Profile for Myclobutanil
Assessment Endpoint
Acute Dose-based Direct
Toxicity to Terrestrial-
Phase CRLF
Acute Dietary -based Direct
Toxicity to Terrestrial-
Phase CRLF
Chronic Direct Toxicity to
Terrestrial-Phase CRLF
Indirect Toxicity to
Terrestrial-Phase CRLF
(via acute toxicity to
mammalian prey items)
Indirect Toxicity to
Terrestrial-Phase CRLF
Species
Bobwhite Quail
(Colinus
virginianus)
Mallard Duck
(Anas
platyrhynchos)
Bobwhite Quail
(Colinus
virginianus)
Mouse
Rat
Toxicity Value Used in
Risk Assessment 1
LD50 = 498 mg/kg bw
LC50 = >4090 ppm
NOAEC = 256 ppm
LOAEC >256 ppm:
LD50= 1360 mg/kg
NOAEC = 200 ppm
LOAEC = 1000 ppm
Citation/
MRID#
00144286
00144288
43087901
00165239
00141662
00149581
00143766
Study
Classification
Acceptable
Acceptable
Supplemental
Acceptable
Acceptable
77
-------
Assessment Endpoint
(via chronic toxicity to
mammalian prey items)
Indirect Toxicity to
Terrestrial-Phase CRLF
(via acute toxicity to
terrestrial invertebrate prey
items)
Indirect Toxicity to
Terrestrial- and Aquatic-
Phase CRLF (via toxicity
to terrestrial plants)
Species
Honey bee
Seedling
Emergence
Monocots
Seedling
Emergence
Dicots
Vegetative Vigor
Monocots
Vegetative Vigor
Dicots
Toxicity Value Used in
Risk Assessment 1
NOAEL = 16 mg/kg
bw/day
LOAEL = 80 mg/kg
bw/day
LD50 = > 100 ug a.i.
bee (dust)
Citation/
MRID#
00144289
Study
Classification
Acceptable
No Data Available
1 All studies were conducted with the technical material (approximately 96% pure) and the toxicity values are
adjusted for %a.i.
Acute toxicity to terrestrial animals is categorized using the classification system shown
in Table 4.6 (U.S. EPA 2004). Toxicity categories for terrestrial plants have not been
defined.
Table 4.6 Categories of Acute Toxicity for Avian and Mammalian Studies
Toxicity Category
Very highly toxic
Highly toxic
Moderately toxic
Slightly toxic
Practically non-toxic
Oral LD50
< 10 mg/kg
10 - 50 mg/kg
51 -500 mg/kg
501 -2000 mg/kg
> 2000 mg/kg
Dietary LCSO
< 50 ppm
50 - 500 ppm
501 - 1000 ppm
1001 -5000 ppm
> 5000 ppm
4.2.1 Toxicity to Birds
As specified in the Overview Document, the Agency uses birds as a surrogate for
terrestrial-phase amphibians when amphibian toxicity data are not available (U.S. EPA,
2004). No terrestrial-phase amphibian data are available for myclobutanil; therefore,
acute and chronic avian toxicity data are used to assess the potential direct effects of
myclobutanil to terrestrial-phase CRLFs.
4.2.1.1 Birds: Acute Exposure (Mortality) Studies
Based on the submitted acute oral toxicity study for theBobwhite Quail (MRID
00144286), myclobutanil is categorized as moderately toxic to birds on a dose basis with
an acute LD50 of 498 (408-598, 95% C.I.) mg/kg bw.
78
-------
Based on avian subacute dietary studies for two bird species, myclobutanil is categorized
as slightly toxic on a dietary basis with subacute dietary LCso's of >4090 ppm for mallard
duck (MRID 00144288) and > 4530 ppm for bobwhite quail (MRID 00144287).
Although no definitive subacute dietary LC50s could be determined from these studies,
there were mortalities in both studies. There was one mortality at 4090 ppm, the highest
concentration tested in the mallard duck study and mortalities at 3000 ppm and 4530
ppm, the highest concentration tested in the bobwhite quail study.
Table 4.7 Avian Acute Toxicity Data
Common
Name
Bobwhite
Quail
Colinus
virginianus
Bobwhite
Quail
Colinus
virginianus
%AI
84.5
84.5
Study parameters
Acute oral study
10 birds/dose level
21 day observation
period
0 (vehicle), 316,
464, 681, 1000,
1470 mg/kg tested
Subacute dietary
study
10
birds/concentration
level
5 days on
treatment, 3 days
observation
0 (vehicle), 246,
641, 1150,3000,
4530 ppm tested
(measured
concentrations)
LDso/LCso NOAEC/
LOAEC
LD50498 (408-598)
mg/kg bw1
Slope = 7.03 (3.5-10.5)
NOAEL not
determined
LOAEL316mg/kg
(lethargy and anorexia).
Mortalities at all dose
levels (1, 4, 8, 10 and
10, respectively).
Good dose response;
NOAEL not critical in
this case.
LC50 >4530 ppm
NOAEC: 1150 ppm
LOAEC: 3000 ppm
Mortality: 2 at 3000
ppm and 1 at 4530
nnvn
ppm.
Anorexia and lethargy
at 3000 and 4530 ppm
MRID
00144286
00144287
Classification/
Category
Acceptable
Moderately
toxic
Acceptable
Slightly toxic
79
-------
Common
Name
Mallard
Duck
Anas
platyrhync
hos
%AI
84.5
Study parameters
Subacute dietary
study
10
birds/concentration
level
5 days on
treatment, 3 days
observation
0 (vehicle), 270,
620, 1250, 2220,
4090 ppm tested
(measured
concentrations)
LDso/LCso NOAEC/
LOAEC
LC50 >4090 ppm
NOAEC: 1250 ppm
LOAEC: 2220 ppm
(anorexia and lethargy).
One bird died at 4090
ppm.
MRID
00144288
Classification/
Category
Acceptable
Slightly toxic
1 Bold value is the value that will be used to calculate risk quotients
4.2.1.2 Birds: Chronic Exposure (Growth, Reproduction) Studies
Two avian chronic toxicity studies are available for myclobutanil. One-generation
reproductive toxicity studies were conducted on both the mallard duck and bobwhite
quail (MRID numbers 43087901 and 43087902). The studies were conducted
simultaneously using the same dosing regimen. In both studies, no adverse effects were
seen at the maximum level tested. Therefore, the NOAEC for both studies is 256 ppm
and the LOAEC is > 256 ppm. The studies are classified as supplemental since no
LOAEC was established and the concentrations tested are expected to be relatively low
when compared to terrestrial EECs . The NOAEC of 256 ppm is used for risk estimation.
RH-9090 [a-(3-hydroxybutyl)-a-(4-chlorophenyl)-l//-l,2,4-triazole-l-propanenitrile] 6-
chloro-3-pyridinyl)methyl]-7V-nitro-2-imidazolidinimine] (free and bound) is a major
metabolite of myclobutanil in plants i.e., > 10%. RH-9090 is considered to be of
equivalent toxicity to the parent based on structural activity relationship (SAR). In
addition, 1,2,4-triazole and triazole conjugates (triazole alanine and triazole acetic acid)
are common degradates of triazole compounds, including myclobutanil. A submitted
report is available which indicates that the acute LD50 of the 1,2,4-triazole degradate in
coturnix quail is >316 mg triazole/kg bird (MRID 45284015). This report also contains a
reproduction study in which male birds were treated to a single oral dose of 316 mg
triazole/kg bird. No mortality was observed and there was no indication of reproductive
effects. This report has not yet been reviewed. In addition, this protocol is not
comparable to the standard submitted avian reproduction study.
80
-------
Table 4.8 Avian Chronic Toxicity Data
Common
Name
Bobwhite
Quail
Colinus
virginianus
Mallard Duck
Anas
platyrhynchos
%AI
94.2
94.2
Study Parameters
Reproduction study
Mean measured
concentrations: 0
(vehicle), 72.5, 124.2,
181.8, 255.8 ppm for 22
consecutive weeks to 18
week old quail.
16 pairs per
concentration level
Reproduction study
Mean measured
concentrations: 0
(vehicle), 72.5, 124.2,
181.8, 255. 8 ppm for 22
consecutive weeks to 17
week old ducks.
16 pairs per
concentration level
NOAEC/LOAEC
NOAEC = 256 ppm1
LOAEC >256 ppm
No treatment-related
effects at any level.
Not tested at
sufficiently high
concentration levels
NOAEC = 256 ppm
LOAEC >256 ppm
No treatment-related
effects at any level.
Not tested at
sufficiently high
concentration levels
MRID
43087901
43087902
Classification/
Category
Supplemental
Supplemental
1 Bold value is the value that will be used to calculate risk quotients
4.2.1.3 Birds: Sublethal Effects and Additional Open Literature
In the acute oral toxicity study for the bobwhite quail (MRID 00144286), it was reported
that the test organisms exhibited lethargy and anorexia at all dose levels. The LOAEL for
this study was 316 mg/kg (lowest dose tested). The NOAEL was not determined for
sublethal effects. In the mallard duck subacute dietary study used for risk estimation
(MRID 00144288), anorexia and lethargy were observed in birds at and above 2500 ppm
starting at day two and ending on day 4. After day four all birds appeared normal. The
NOAEC was 1250 ppm. The subacute dietary study with bobwhite quail also exhibited
anorexia and lethargy at 3000 and 4530 ppm. There were no avian studies available in
the ECOTOX open literature for myclobutanil.
4.2.2 Toxicity to Mammals
Mammalian toxicity data are used to assess potential indirect effects of myclobutanil to
the terrestrial-phase CRLF. Effects to small mammals resulting from exposure to
myclobutanil could indirectly affect the CRLF via reduction in available food. As
discussed in Section 2.5.3, over 50% of the prey mass of the CRLF may consist of
vertebrates such as mice, frogs, and fish (Hayes and Tennant 1985).
81
-------
4.2.2.1 Mammals: Acute Exposure (Mortality) Studies
Available acute toxicity data for the TGAI and several formulations with the mouse and
rat are available for myclobutanil. The available data suggest that myclobutanil is
slightly toxic to small mammals on an acute oral basis (Appendices J and K). The most
sensitive endpoint for the TGAI, the mouse LDso of 1360 mg/kg, will be used to estimate
risk to the CRLF via indirect effects to mammals. The probit dose-response slope for this
study is 1.19 with no confidence interval provided.
Acute toxicity data with the mouse on the 1,2,4-triazole degradate indicates that it is not
more acutely toxic than the parent. The acute LD50 is 3650 mg/kg bw (MRTD 45284001).
With the exception of the 60 DF formulation, the myclobutanil formulations, including
those mixed with other pesticides are not more acutely toxic to mammals than the
technical material. The 60 DF formulation has a rat LDso of 980 mg formulation/kg bw
and may therefore be more toxic than the technical material but still falls within the
category of slightly toxic. Risk estimations are conducted for the 60 DF formulation with
the rat to ensure that the assessment is protective of acute mammalian exposure to the DF
formulation.
Table 4.9 Mammalian Acute Toxicity Data
Common
Name
Laboratory
mouse
Mus
musculus
Laboratory
mouse
Mus
musculus
%AI
91.9
1,2,4-
triazole
Study parameters
Acute oral study
0, 1.3,2.0,3.2,5.0
g/kg bw tested
10/dose level
14-day observation
period
Acute oral study
LD50 /NOAEL
Acute oral LD50=1360
mg/kg bw in female mice
(most sensitive species
(original DER mistakenly
stated that it was in the
rat)). Mortality at all
dose levels tested.
Multiple clinical signs,
including ataxia, tremors,
loss of righting and others
- not dose-related;
however, early deaths
may have affected
reporting.
Probit slope: 1.19.
LD50 = 3650 mg/kg
MRID
00165239
00141662
45284001
Classification/
Category
Acceptable
Slightly toxic1
Practically
nontoxic
1 Based onLD50 (mg/kg) <10 very highly toxic; 10-50 highly toxic; 51-500 moderately toxic; 501-2000
slightly toxic; >2000 practically nontoxic
2 Bold value is the value that will be used to calculate risk quotients
82
-------
Table 4.10 Acute Rat Toxicity Comparison of Myclobutanil Formulations
Formulation (%)
Technical Product
1.5% with 2.5% permethrin
2.25% with 60% mancozeb
60% formulation with inerts
Fludioxonil, 1.45%; Mefenoxam, 3.61%;
Azoxystrobin, 8.55%; and Myclobutanil, 9.75%
Up-and-Down Method: 0.9% Myclobutanil (granules)
1% formulation
21% formulation
6.0% formulation
1% formulation
LD50 (mg/kg bw)
1600 (M)
2290 (F)
> 5050 (M & F)
> 5000 (M)
980 (M)
1235 (F)
5979 (F)
> 5000 (F)
> 5000 (M & F)
3749 (F)
>5000 (M)
LD50 between 500 &
5,000 (M & F)
> 5,000 (M & F)
MRID
00141662
44155803
40149003
00164467, 00164468
47092603
46886701
45381001
45218401
45056903
44265201
4.2.2.2 Mammals: Chronic Exposure (Growth, Reproduction) Studies
In a two-generation reproduction study in rats on myclobutanil (MRIDs 00149581 and
00143766), the NOAEC/NOAEL used in the assessment is 200 ppm/16 mg/kg bw/day
with a LOAEC/LOAEL of 1000 ppm/80 mg/kg bw/day based on a decrease in pup body
weight gain during lactation, an increased incidence in the number of stillborns and
atrophy of the testes and prostate (offspring systemic and reproductive endpoints). These
endpoints were used in the risk assessment because the parental systemic toxicity
endpoints are not considered to be relevant to either growth or reproductive effects
(MRID 00149581).
As previously noted, RH-9090 is a major metabolite of myclobutanil. It is considered to
be of equivalent toxicity to the parent based on S AR and tolerances for myclobutanil
residues in food are established for the combined residues of myclobutanil and RH-9090
on registered commodities.
In addition, 1,2,4-triazole and triazole conjugates (triazole alanine and triazole acetic
acid) are common degradates of triazole compounds, including myclobutanil. The 1,2,4-
triazole degradate was tested in a two-generation reproduction study (MRID 46467304).
The parental NOAEL/LOAEL is <15 mg/kg bw/day/15 mg/kg bw/day based on a
decrease in bodyweight and bodyweight gain and decrease in spleen weight. The
offspring NOAEL/LOAEL is <19 mg/kg bw/day/19 mg/kg bw/day based on decrease in
bodyweight and bodyweight gain and brain and spleen weight. The reproductive
NOAEL/LOAEL is 15/31 mg/kg bw/day based on abnormal sperm and a decrease in the
number of corpora lutea. At 218 mg/kg bw/day, there was reproductive failure (no viable
offspring) and an increase in corpora lutea in F0 parental females. A comparison of the
endpoints between the parent and the degradate, indicates that the degradate may have a
greater effect on bodyweight and bodyweight gain for both parents and pups; however,
83
-------
the endpoint values for reproductive effects for the parent are equivalent to the degradate.
There is an uncertainty due to dose spacing; however, the results indicate that the
degradate is at least as toxic as the parent.
Toxicity data are also available for the degradate triazole alanine. Other triazole
conjugates are considered to be lexicologically equivalent to triazole alanine.
A two-generation rat reproduction study conducted on triazole alanine (MRID 00164112)
indicates that the triazole conjugates exhibit less toxicity than the parent.
Maternal/parental toxicity was not seen in the rat reproduction study at the highest dose
tested (929/988 M/F mg/kg bw/day). Reproductive toxicity was also not seen at the
highest dose tested. The offspring NOAEL/LOAEL is 192/929 mg/kg bw/day based on
reduced mean litter weights in both generations.
Since 1,2,4-triazole and triazole conjugates are common degradates of triazole
compounds and the mechanism of toxicity of these compounds is considered to be
fundamentally different than the toxicity for the parent triazoles (e.g., myclobutanil),
separate human health risk assessments have been conducted for 1,2,4-triazole and
triazole conjugates. (February 7, 2006, 1,2,4-Triazole, Triazole Alanine, Triazole Acetic
Acid: Human Health Aggregate Risk Assessment in Support of Reregi strati on and
Registration Actions for Triazole-derivative Fungicide Compounds DP322215).
4.2.2.3 Mammals: Open Literature
A review of mammalian studies available in the ECOTOX open literature for
myclobutanil indicates that no additional toxicity data relevant to the myclobutanil CRLF
assessment were provided in the open literature i.e., none of the available mammalian
studies identified a more sensitive endpoint. Therefore, only toxicity data provided in
submitted studies were used to assess mammalian effects.
84
-------
Table 4.11 Mammalian Chronic Toxicity Data
Common
Name
Laboratory
rat
Rattus
norvegicus
o/oAI
84.5
Study Parameters
2-Generation
reproduction study
25 rats/sex/group
0, 50, 200 or 1000
ppm
4, 16 or 80 mg/kg
bw/day based on
overall mean
concentration of
active ingredient in
dietary analyses.
NOAEC/
LOAEC
Parental
NOAEC/NOAEL: 50
ppm/4 mg/kg bw/day
Parental
LOAEC/LOAEL: 200
ppm/ 16 mg/kg bw/day
based on hepatocellular
hypertrophy and increases
in liver weights.
Offspring/Reproductive
NOAEC/NOAEL: 200
ppm/16 mg/kg/day
Offspring/Reproductive
LOAEC/LOAEL: 1000
ppm/80 mg/kg/day based
on testicular, epididymal
and prostatic atrophy in
P2 males; slight increase
in stillborns, decrease in
body weight gain in pups
during lactation in FI and
F2 generations.
MRID
00149581
00143766
Classification/
Category
Acceptable
85
-------
Common
Name
Laboratory
rat
Rnttii 9
i \iillltt5
norvegicus
Laboratory
rat
Rattus
norvegicus
%AI
1,2,4-
triazole
Triazole
Alanine
Study Parameters
Reproduction and
fertility effects
0, 250, 500, 3000
ppm
M: 15, 31, 189mkd
F: 18, 36, 218 mkd
Reproduction and
fertility effects
0, 200, 2000, 10000
ppm
M: (FO/F1) 0,
50/47,213/192,
1098/929
mg/kg/day
F: 0,51/49,
223/199, 1109/988
mg/kg/day
NOAEC/
LOAEC
Parental
NOAEC/NOAEL: <250
ppm/ 15 mg/kg/day
Parental
LOAEC/LOAEL: 250
ppm/ 15 mg/kg/day based
on decrease in
bodyweight, bodyweight
gain and spleen weight.
Offspring
NOAEC/NOAEL: <250
ppm/ 19 mg/kg/day
Offspring
LOAEC/LOAEL: 250
ppm/ 19 mg/kg/day based
on decrease in
bodyweight, bodyweight
gain, brain and spleen
weights Repro
NOAEC/NOAEL: 250
ppm/ 15 mg/kg/day
Repro LOAEC/LOAEL:
500 ppm/3 1 mg/kg/day
based on abnormal sperm
and^ofCLinFj
females
At3000ppm/218
mg/kg/day, reproductive
failure (no viable
offspring), tCL in F0
parental females
Parental
NOAEC/NOAEL: 10000
ppm/929 mg/kg/day
Parental
LOAEC/LOAEL: >10000
ppm/929mg/kg/day
Offspring
NOAEC/NOAEL: <250
ppm/19 mg/kg/day
Offspring
LOAEC/LOAEL:
2000ppm/192 mg/kg/day
based on reduced mean
litter weights in both
generations
Repro LOAEC/LOAEL:
>10000
ppm/929mg/kg/day
MRID
46467304
00164112
Classification/
Category
Acceptable
Acceptable
1 Bold value is the value that will be used to calculate risk quotients
86
-------
4.2.3 Toxicity to Terrestrial Invertebrates
Terrestrial invertebrate toxicity data are used to assess potential indirect effects of
myclobutanil to the terrestrial-phase CRLF. Effects to terrestrial invertebrates resulting
from exposure to myclobutanil could indirectly affect the CRLF via reduction in
available food.
4.2.3.1 Terrestrial Invertebrates: Acute Exposure (Mortality) Studies
Myclobutanil is classified as non-toxic to bees with an acute contact LD50 of >362
jig/bee (MRID 00144289). The bees were exposed to a finished dust containing 27.58%
a.i. in a bell jar vacuum duster at dosages of approximately 120, 240 or 362 jig technical
material per bee. Observations for clinical signs of toxicity were made daily for at 24
hour intervals from 24 to 96 hours. Mortality in the treated bees did not differ from the
untreated controls.
4.2.3.2 Terrestrial Invertebrates: Open Literature Studies
There are several terrestrial invertebrate toxicity studies available in the open literature
(Appendices H and I). Five acceptable literature studies were reviewed for this
assessment; one study on beneficial arthropods, three studies on predacious mites and one
study on mirids, a predacious insect (EcoReference Nos.: 104765, 96453, 64063, 63621,
63599). These studies were used qualitatively as part of a weight of the evidence
analysis/determination. The arthropods study showed myclobutanil to be harmless to all
of the five arthropods tested including, parasitic wasps, lady-birds, hoverfly, rove beetle,
and carabid beetle. The three mite studies showed no adverse effects on the four species
evaluated. In the study on the mired, myclobutanil showed moderate toxicity (LD50 =
150 jig ai/L) to adult mirid at the manufacturer's label rate of 440 jig ai/L but no toxicity
to nymphs.
Although one of the available open literature studies identified a more sensitive endpoint
than the submitted honey bee toxicity study that determined a dust LDso of > 100 jig/bee,
the weight of the evidence indicates that myclobutanil is non-toxic to terrestrial
invertebrates. Four of the five studies clearly showed that myclobutanil was not toxic to
terrestrial invertebrates at label rates. Only one of the five available acceptable studies
provided an LDso. That study indicated moderate toxicity to adult mirids only with no
toxicity to the nymphs. Myclobutanil toxicity to adults was unexpected because
myclobutanil was seen to be innocuous to all stages of mites in three literature studies
and mites are usually more easily intoxicated than insects (mirids). Therefore, based on
the totality of the available data, the honey bee study represents the most appropriate
study for endpoint selection.
4.2.4 Toxicity to Terrestrial Plants
Terrestrial plant toxicity data are used to evaluate the potential for myclobutanil to affect
riparian zone and upland vegetation within the action area for the CRLF. Impacts to
87
-------
riparian and upland (i.e., grassland, woodland) vegetation could result in indirect effects
to both aquatic- and terrestrial-phase CRLFs, as well as effects to designated critical
habitat PCEs via increased sedimentation, alteration in water quality, and reduction of
upland and riparian habitat that provides shelter, foraging, predator avoidance and
dispersal for juvenile and adult CRLFs.
There are currently no registrant-submitted terrestrial plant toxicity data for myclobutanil
with which to assess the potential for indirect effects to the aquatic- and terrestrial-phase
CRLF via effects to riparian vegetation or effects to the primary constituent elements
(PCEs) relevant to the aquatic- and terrestrial-phase CRLF. However, there is some
evidence in the open literature that myclobutanil has the potential to elicit phytotoxic
effects. Three terrestrial plant studies were reviewed for this assessment. No adverse
effects were observed in two of the three studies (EcoReference Nos.: 104715, 104728,
76524). In a cucumber study, myclobutanil sprayed onto seedlings at the first true leaf
(application rate not provided) did not affect fruit quality. In a seed treatment study,
infected spring wheat treated with myclobutanil at a rate of 0.12 g/ ai./kg seed performed
similarly to untreated seed. In the third study, myclobutanil was applied at two rates (6.1
g ai/100 m2 (0.54 Ibs/A) and 12.19 g/ai 100 m2 (1.09 lbs/A)) to "Tifgreen" Bermuda grass
to determine if it would produce a plant growth regulation effect on healthy Bermuda
grass. After three applications at 28 to 30 day intervals, compared to the control, the high
rate of myclobutanil significantly decreased turf grass quality on at least one evaluation
date in each year of the study.
In order to characterize potential effects to terrestrial plants following exposure to
myclobutanil in the risk description, terrestrial plant data from 5 other triazole DMI
fungicides were obtained and used as inputs values in the TerrPlant (v. 1.2.2) model for
terrestrial plants. Table 4.12 summarizes the toxicity values and endpoints for the 5
triazole fungicides.
Table 4.12 Terrestrial Plant Toxicity Data for 5 Other DMI Fungicides
Fungicide
Metconazole
Monocot
Dicot
Prothioconazole
Monocot
Dicot
EC25 (Ibs a.i./A)
Seedling
Emergence
0.78
0.15
>0.272
>0.272
Vegetative
Vigor
>0.6
0.44
>0.272
>0.272
NOAEC/ECos (Ibs
a.i./A)
Seedling
Emergence
0.3
0.075
0.272
0.03
Vegetative
Vigor
0.6
0.0036
(EC05)
0.272
O.272
Effect/MRID
Seedling
Emergence
Ryegrass:
reduced
plant height
46805103
Radish:
reduced
plant height
46805103
46246049
Cucumber:
shoot height
and dry
Vegetative
Vigor
46805104
Radish:
reduced dry
weight
46805104
46246049
46246049
88
-------
Fungicide
Cyproconazole
Monocot
Dicot
Propiconazole
Monocot
Dicot
Triticonazole
Monocot
Dicot
EC25 (Ibs a.i./A)
Seedling
Emergence
>0.64
0.091
>1.5
0.18
>4.25
0.015
Vegetative
Vigor
>0.62
0.50
0.315
0.039
>4.2
1.3
NOAEC/ECos (Ibs
a.i./A)
Seedling
Emergence
0.64
0.066
1.5
0.056
1.3
0.004
Vegetative
Vigor
0.62
0.09
0.0815
0.056
4.2
1.0
Effect/MRID
Seedling
Emergence
weight
46246049
46218512
Cabbage:
fresh weight
46218512
41673201
Cabbage:
dry weight
41673201
Rye grass:
shoot length
44802116
Lettuce:
shoot length
44802116
Vegetative
Vigor
46218511
Cabbage: dry
weight
46218511
Rye grass:
plant height
41673203
Cabbage: dry
weight
41673203
44802116
Turnip: dry
weight
44802116
4.3 Use of Probit Slope Response Relationship to Provide Information on the
Endangered Species Levels of Concern
The Agency uses the probit dose response relationship as a tool for providing additional
information on the potential for acute direct effects to individual listed species and
aquatic animals that may indirectly affect the listed species of concern (U.S. EPA, 2004).
As part of the risk characterization, an interpretation of acute RQ for listed species is
discussed. This interpretation is presented in terms of the chance of an individual event
(i.e., mortality or immobilization) should exposure at the EEC actually occur for a species
with sensitivity to myclobutanil on par with the acute toxicity endpoint selected for RQ
calculation. To accomplish this interpretation, the Agency uses the slope of the dose
response relationship available from the toxicity study used to establish the acute toxicity
measures of effect for each taxonomic group that is relevant to this assessment. The
individual effects probability associated with the acute RQ is based on the mean estimate
of the slope and an assumption of a probit dose response relationship. In addition to a
single effects probability estimate based on the mean, upper and lower estimates of the
effects probability are also provided to account for variance in the slope, if available.
Individual effect probabilities are calculated based on an Excel spreadsheet tool IECV1.1
(Individual Effect Chance Model Version 1.1) developed by the U.S. EPA, OPP,
Environmental Fate and Effects Division (June 22, 2004). The model allows for such
calculations by entering the mean slope estimate (and the 95% confidence bounds of that
89
-------
estimate) as the slope parameter for the spreadsheet. In addition, the acute RQ is entered
as the desired threshold.
4.4 Incident Database Review
A review of the EIIS database for ecological incidents involving myclobutanil was
completed on May 26, 2009. Three incident reports were filed for myclobutanil between
1994 and 2003, all with effects on terrestrial plants (two incidents with grapes and one
with roses). The two incidents with grapes occurred in California and the one with roses
was reported in Maryland. The certainty index for the damage in all 3 incidents was
rated as possibly related to exposure to myclobutanil. The two incidents with grapes
involved application of other pesticides as well as the myclobutanil. Therefore, it is
unclear whether the effects were due to exposure to myclobutanil in these two incidents.
Myclobutanil was the only pesticide applied to the rose bushes in the third reported
incident. A brief description of each of the reported incidents is provided below.
It should be noted that these reported incidents may only represent a fraction of actual
incidents. Actual incidents may not have been reported due to various factors such as
lack of reporting, or a lack of witness to effects. Therefore, the lack of an incident report
does not necessarily indicate a lack of an incident.
Complete incident tables are provided in Appendix L.
4.4.1 Terrestrial Incidents
Between 5/30/1994 and 6/3/1994, Rally 40W (myclobutanil), Pro Gibb (gibberellic acid),
Dimethogan 25 WP, Pro Kil Cryolite 96 (sodium fluoaluminate), Britz binder, and
Booster 42 Foliar Spray (polymeric polyhydroxy acids) were applied by ground spray to
grape vines. Shortly after the last application, scarring of the berries, stunted vine
growth, lack of berry size increase, dieback of fruit from total bunches, and limited cone
growth with straggly branches were observed. No residue analysis was conducted. The
California Commissioner's report indicated that mixtures of Pro-Gibb 4% and Pro-Kil
Cryolite 96 may cause some compatibility problems. The certainty index for this incident
(1002621-006) is possible.
It was reported that Rally 40W (myclobutanil) damaged 6 acres of Red Globe and
Thompson's grapes to the point that they could not be sold. Burns and necrosis on
bunches (Red Globe) and leaf burn (Thompson's) was observed. AGRI-MEK
(abamectin) and Ad-Wet were also applied, using a ground spray on the vineyard. The
certainty index for this incident (1013563-014) is possible.
Systhane (myclobutanil) was applied via a broadcast ground spray to rose bushes grown
in greenhouses by local residents in Maryland. The total magnitude was 200 houses.
Foliar necrosis and some defoliation were observed after exposure to Systhane. Damage
varied from house to house and by rose variety. The certainty index for this incident
(1014702-074) is possible.
90
-------
No incidents involving terrestrial animals were reported.
4.4.2 Aquatic Incidents
No incidents involving aquatic plants or animals were reported.
5 Risk Characterization
Risk characterization is the integration of the exposure and effects characterizations.
Risk characterization is used to determine the potential for direct and/or indirect effects to
the CRLF or to its designated critical habitat from the use of myclobutanil in CA. The
risk characterization provides an estimation (Section 5.1) and a description (Section 5.2)
of the likelihood of adverse effects; articulates risk assessment assumptions, limitations,
and uncertainties; and synthesizes an overall conclusion regarding the likelihood of
adverse effects to the CRLF or its designated critical habitat (i.e., "no effect," "likely to
adversely affect," or "may affect, but not likely to adversely affect").
5.1 Risk Estimation
Risk is estimated by calculating the ratio of exposure to toxicity. This ratio is the risk
quotient (RQ), which is then compared to pre-established acute and chronic levels of
concern (LOCs) for each category evaluated (Appendix F). For acute exposures to the
CRLF and its animal prey in aquatic habitats, as well as terrestrial invertebrates, the LOG
is 0.05. For acute exposures to the CRLF and mammals, the LOG is 0.1. The LOG for
chronic exposures to CRLF and its prey, as well as acute exposures to plants is 1.0.
Risk to the aquatic-phase CRLF is estimated by calculating the ratio of exposure to
toxicity using l-in-10 year EECs based on the label-recommended myclobutanil usage
scenarios summarized in Tables 3.5 and 3.6 and the appropriate aquatic toxicity endpoint
from Table 4.1. Risks to the terrestrial-phase CRLF and its prey (e.g. terrestrial insects,
small mammals and terrestrial-phase frogs) are estimated based on exposures resulting
from applications of myclobutanil (Tables 3.9 - 3.10) and the appropriate toxicity
endpoint from Table 4.5. Due to lack of toxicity data for myclobutanil, exposures are not
estimated for freshwater invertebrates (chronic exposure), aquatic vascular plants, and
terrestrial plants.
5.1.1 Exposures in the Aquatic Habitat
Estimated risk for the aquatic habitat is based on a total toxicity approach, that is, EECs
for myclobutanil plus 1,2,4-triazole (parent plus degradate) which are higher than the
EECs for myclobutanil. There are no aquatic toxicity data available for the primary
degradate of myclobutanil (1,2,4-triazole); however, available mammalian studies
indicate that it is either less than or equally toxic as the parent. Use of the total toxicity
91
-------
approach for estimating risk was based on two conservative assumptions. First, that the
mode of action is the same for 1,2,4-triazole and the parent (myclobutanil) and second
that the two compounds are of equivalent toxicity to aquatic organisms.
5.1.1.1 Direct Effects to Aquatic-Phase CRLF
Direct acute effects to the aquatic-phase CRLF are based on peak EECs from the
PRZM/EXAMS models and the lowest acute 96-hour LCso toxicity value for freshwater
fish. The highest modeled peak EEC is 61.41 ppb (myclobutanil plus 1,2,4 triazole) for
the turf scenario (representing turf use). The acute RQ for this scenario is 0.025 which is
lower than the acute endangered species LOG of 0.05.
In order to assess direct chronic risks to the CRLF, 60-day EECs from the
PRZM/EXAMS models and the lowest chronic toxicity value (NOAEC) for freshwater
fish are used. The highest modeled 60-day EEC is 60.71 ppb (myclobutanil plus 1,2,4
triazole) for the turf scenario. The chronic RQ for this scenario is 0.061 which is much
lower than the chronic LOG of 1 for fish.
Acute and chronic RQs for all modeled scenarios for myclobutanil and myclobutanil plus
1,2,4 triazole were lower than the related LOG (a summary of the highest RQs is
provided in Table 5.1). Based on these results, the effects determination for myclobutanil
is "no effect" for direct effects on the aquatic-phase of the CRLF.
Table 5.1 Summary of Acute and Chronic Direct Effect RQs for the Aquatic-phase
CRLF
Direct Effects
to CRLF
Acute Direct
Toxicity a
Chronic Direct
Toxicity b
Scenario
Turf
Turf
EECOig/LT
Peak: 61.41
60-day: 60.71
RQ
0.025'
0.061g
Probability of
Individual Effect
at
ESLOCd'e
~lin4.18E+8
(~1 in 2 16 to
~linl.75E+31)
Probability of
Individual Effect
atRQd
~lin3.56E+12
(~1 in 1.48E+3 to
~lin5.06E+46)
Not calculated for chronic endpoints
a Based on bluegill sunfish (Lepomis macrochirus) acute 96-hour LC50 = 2.4 mg/L.
b Based on fathead minnow (Pimephales promelas) chronic NOAEC = 0.98 mg/L.
0 From scenario with the highest EECs: granular use on turf (myclobutanil plus 1,2,4-triazole) (see Table 3.6).
d The probit dose-response slope value for the bluegill sunfish acute toxicity study is not available; therefore,
the effect probability was calculated based on a default slope assumption of 4.5 with upper and lower 95%
confidence intervals of 2 and 9 (Urban and Cook, 1986).
e Endangered species LOG of 0.05.
f RQ < acute endangered species LOG of 0.05.
8 RQ < chronic LOC of 1 .
92
-------
5.1.1.2 Indirect Effects to Aquatic-Phase CRLF via Reduction in Prey
(non-vascular aquatic plants, aquatic invertebrates, fish, and
frogs)
a) Non-vascular Aquatic Plants
Indirect effects of myclobutanil to the aquatic-phase CRLF (tadpoles) via reduction in
non-vascular aquatic plants in its diet are based on peak EECs from the PRZM/EXAMS
models and the lowest toxicity value (ECso) for aquatic non-vascular plants. The most
sensitive non-vascular plant 120-hour ECso is 0.83 mg/L (freshwater green algae). The
highest modeled peak EEC is 61.41 ppb (myclobutanil plus 1,2,4 triazole) for the turf
scenario (representing turf use). The acute RQ for this scenario is 0.074 (61.41 ppb / 830
ppb) which is much lower than the LOG of 1 for aquatic plants.
RQs for all modeled scenarios for myclobutanil and myclobutanil plus 1,2,4 triazole were
lower than the aquatic plant LOG. Based on these results, the effects determination for
myclobutanil is "no effect" for indirect effects on the CRLF via reduction in non-vascular
plants.
b) Aquatic Invertebrates
Indirect acute effects to the aquatic-phase CRLF via effects to prey (invertebrates) in
aquatic habitats are based on peak EECs from the PRZM/EXAMS models and the lowest
acute toxicity value (LCso) for freshwater invertebrates. The highest modeled peak EEC
is 61.41 ppb (myclobutanil plus 1,2,4 triazole) for the turf scenario (representing turf
use). The acute RQ for this scenario is 0.005 which is much lower than the acute
endangered species LOG of 0.05.
Indirect chronic effects to the aquatic-phase CRLF via effects to prey (invertebrates)
cannot be quantitatively estimated because there is currently no chronic invertebrate
toxicity data available for myclobutanil.
Acute RQs for all modeled scenarios for myclobutanil and myclobutanil plus 1,2,4
triazole were lower than the endangered species LOG of 0.05 (a summary of the highest
RQ is provided in Table 5.2). Based on these results, on an acute basis the effects
determination for myclobutanil is "no effect" for indirect effects on the CRLF via
reduction in freshwater invertebrates prey items.
93
-------
Table 5.2 Summary of Acute and Chronic RQs Used to Estimate Indirect Effects to
the CRLF via Direct Effects on Aquatic Invertebrates as Dietary Food Items (prey
of CRLF juveniles and adults in aquatic habitats)
Direct Effects
to Aquatic
Invertebrate
Prey of
CRLF
Acute Direct
Toxicity a
Chronic Direct
Toxicity
Scenario
Turf
EEC(u,g/L)b
Peak: 61.41
RQ
0.005d
% Expected Effect on Prey Population
atRQc
0.00 1(0.00 1-0.001)
Not calculated (no toxicity data available)
a Based on water flea (Daphnia magna) acute 48-hour LC50 =11 mg/L.
b From scenario with the highest EECs: granular use on turf (myclobutanil plus 1,2,4-triazole) (see Table 3.6)
0 The % expected effect on prey population was calculated based on a probit dose-response slope of 6.8 (4. 1-
9.6) for the water flea acute toxicity study.
d RQ < acute endangered species LOG of 0.05.
c) Fish and Frogs
Fish and frogs also represent potential prey items of adult aquatic-phase CRLFs. RQs
associated with acute and chronic direct toxicity to the CRLF (Table 5.1) are used to
assess potential indirect effects to the CRLF based on a reduction in freshwater fish and
frogs as food items. Based on the conclusions about direct effects to freshwater fish (see
section 5.1.1.1), the effects determination for myclobutanil is "no effect" for indirect
effects on the CRLF via reduction in freshwater fish and frogs as food items.
5.1.1.3 Indirect Effects to CRLF via Reduction in Habitat and/or
Primary Productivity (Freshwater Aquatic Plants)
Indirect effects to the CRLF via direct toxicity to aquatic plants are estimated using the
most sensitive non-vascular and vascular plant toxicity endpoints. The effects
determination for myclobutanil is "no effect" for indirect effects on the CRLF via
reduction in non-vascular plants (see section 5.1.1.2 for details). Effects to aquatic
vascular plants cannot be quantitatively estimated because there is currently no toxicity
data available for myclobutanil.
5.1.2 Exposures in the Terrestrial Habitat
5.1.2.1 Direct Effects to Terrestrial-phase CRLF
As previously discussed in Section 3.3, potential direct effects to terrestrial-phase CRLFs
are based on foliar and granular applications of myclobutanil. In addition, the RQ
94
-------
calculation for use on cotton seeds assumes that the seeds are 100% available based on
shallow planting conditions and an associated planting depth of /^ inch.
Potential direct acute effects to the terrestrial-phase CRLF are derived by considering
dose- and dietary-based EECs modeled in T-REX for a small bird (20 g) consuming
small invertebrates and acute oral and subacute dietary toxicity endpoints for avian
species. Definitive subacute dietary-based RQ values cannot be derived because a
statistically meaningful LC50 could not be determined as no dose levels resulted in 50%
or greater mortality (i.e., mallard duck LCso is > 4090 ppm). Although definitive LCso's
were not derived in the subacute dietary studies, there were mortalities in both studies.
The concentration levels at which mortalities were observed will be compared to the
terrestrial EECs in the Risk Description section.
Results of the dose-based EEC analysis of direct effects to terrestrial-phase CRLF
indicate acute LOG exceedances (RQ > 0.1) for all uses of myclobutanil except
Boysenberry/Dewberry/Youngberry (Tables 5.3 and 5.4).
Table 5.3 Summary of Acute RQs Used to Estimate Direct Effects to the
Terrestrial-phase CRLF (non-granular application)
Use
Almond
Apple
Apricot
Artichoke
Asparagus
Beans
Blackberry/EggPlant/Okra/Pepper/Raspberry
Boysenberry /Dewberry /Youngberry
Carrot
Canistel/Mango/Papaya/Sapodilla
Cherry /Nectarine/Peach
Cotton
Cucurbit Vegetables
Currant
Gooseberry
Grapes
Hops
Lettuce
Plum/Prune
Tomato
Turf
Application Rate
(Ib ai/A)
0.2
0.5
0.5
0.1
0.125
0.125
0.125
0.0625
0.1875
0.25
0.5
0.06 Ib ai/cwt
0.12
0.125
0.125
0.13
0.25
0.125
0.16
0.1
1.3
Dose-based
Acute RQ*1
0.23
0.70
0.40
0.14
0.18
0.18
0.16
0.08
0.14
0.39
0.56
0.42
0.20
0.19
0.24
0.24
0.35
0.15
0.33
0.10
1.93
Probability of Individual
Effect at RQ2
lin~2.77E+05
in~7.24E+00
in~3.88E+02
in~1.03E+09
in~1.21E+07
in~1.21E+07
in~9.04E+07
in~1.54E+14
in~1.03E+09
in~4.95E+02
in~2.61E+01
in~2.47E+02
in~2.24E+06
in~1.21E+07
in~1.52E+05
in~5.03E+06
in~1.97E+04
in~2.87E+08
in~2.81E+03
lin~9.62E+ll
lin~l
* = LOG exceedances (acute RQ > 0.1) are bolded and shaded.
1 Based on bobwhite quail acute oral LD50 of 498 mg/kg .
The effect probability was calculated based on a calculated slope of 7.03 with upper and lower 95% confidence intervals of
3.5 and 10.5
95
-------
Table 5.4 Summary of Acute RQs Used to Estimate Direct Effects to the Terrestrial-
phase CRLF (granular application)
Use
Turf
Application Rate
(Ib ai/A)
1.35
Dose-based Acute
RQ*1
1.96
Probability of Individual
Effect at RQ
lin~l
* = LOG exceedances (acute RQ > 0.1) are bolded and shaded.
1 Based on bobwhite quail acute oral LD50 of 498 mg/kg and a calculated LD50/sq. ft
Potential direct chronic effects of myclobutanil to the terrestrial-phase CRLF are derived
by considering dietary-based exposures modeled in T-REX for a small bird (20g)
consuming small invertebrates. Chronic effects are estimated using the lowest available
toxicity data for birds. EECs are divided by toxicity values to estimate chronic dietary-
based RQs. Results of the analysis of direct effects to terrestrial-phase CRLF indicate a
chronic LOG exceedance (RQ>1) for turf and cotton use only.
Based on the exceedance of the LOG for the majority of uses after acute exposure and
two uses after chronic exposure, myclobutanil may affect directly, the terrestrial-phase of
the CRLF.
Table 5.5 Summary of Chronic RQs Used to Estimate Direct Effects to the
Terrestrial-phase CRLF (non-granular application)
Use
Almond
Apple
Apricot
Artichoke
Asparagus
Beans
Blackberry /EggPlant/Okra/Pepper/Raspberry
Boysenberry /Dewberry /Youngberry
Carrot
Canistel/Mango/Papaya/Sapodilla
Cherry /Nectarine/Peach
Cotton
Cucurbit Vegetables
Currant
Gooseberry
Grapes
Hops
Lettuce
Plum/Prune
Tomato
Turf
Application Rate (Ib ai/A)
0.2
0.5
0.5
0.1
0.125
0.125
0.125
0.0625
0.1875
0.25
0.5
0.06 Ib ai/cwt
0.12
0.125
0.125
0.13
0.25
0.125
0.16
0.1
1.3
Dietary-based Chronic RQ*1
0.28
0.87
0.49
0.18
0.22
0.22
0.20
0.10
0.17
0.49
0.69
2.342
0.24
0.23
0.23
0.30
0.43
0.18
0.40
0.13
2.38
* = LOG exceedances (chronic RQ > 1 ) are bolded and shaded.
1 Based on bobwhite quail NO AEG of 256 ppm.
Planting depth for cotton seeds varies depending on soil moisture and soil texture. The RQ calculation assumes that cotton
seeds are 100% available based on shallow planting conditions and an associated planting depth of 1A inch
96
-------
5.1.2.2 Indirect Effects to Terrestrial-Phase CRLF via Reduction in
Prey (terrestrial invertebrates, mammals, and frogs)
5.1.2.2.1 Terrestrial Invertebrates
In order to assess the risks of myclobutanil to terrestrial invertebrates, which are
considered prey of CRLF in terrestrial habitats, the honey bee is used as a surrogate for
terrestrial invertebrates. The toxicity value for terrestrial invertebrates is calculated by
multiplying the lowest available acute contact (dust) LDso of > 363 jig a.i./bee by 1
bee/0.128g, which is based on the weight of an adult honey bee. This is estimated to be
>2836 jig a.i./g bw. Because the acute contact effects data shows an LD50 of greater than
the highest test concentration of 363 jig a.i./bee, definitive acute RQ values cannot be
derived. Therefore, a quantitative assessment of risk to terrestrial invertebrates was not
conducted. Mortality in the treated bees did not differ from the untreated controls. Given
that the honey bee data shows low toxicity, minimal potential indirect impact to the
CRLF via effects of myclobutanil on freshwater invertebrate food items is expected.
Risk to terrestrial invertebrates will be discussed further in the risk description section.
5.1.2.2.2 Mammals
Risks associated with ingestion of small mammals by large terrestrial-phase CRLFs are
derived for dietary-based and dose-based exposures modeled in T-REX for a small
mammal (15g) consuming short grass. Acute and chronic effects are estimated using the
most sensitive mammalian toxicity data. EECs are divided by the toxicity value to
estimate acute and chronic dose-based RQs as well as chronic dietary-based RQs. For
granular applications the RQ is based on an estimated LD50 per square foot calculated
based on application rate and toxicity. For non-granular applications, the acute listed
species LOG of 0.1 is exceeded for apple, apricot, cherry/nectarine/peach,
canistel/mango/papaya/sapodilla, hops, plum/prune, and turf uses. The chronic LOG of 1
on a dose basis is exceeded for all uses and the chronic LOG on a dietary basis is
exceeded for apples, apricots, canistel/mango/papaya/sapodilla, cherry/nectarine/peach,
cotton, and turf. For granular uses, the acute listed species LOG is exceeded for turf.
Based on both acute and chronic LOG exceedances for many uses, myclobutanil may
affect indirectly, the terrestrial-phase CRLF via reduction in small mammal prey items.
97
-------
Table 5.6 Summary of Acute and Chronic RQs Used to Estimate Indirect Effects to
the Terrestrial-phase CRLF via Direct Effects on Small Mammals as Dietary Food
Items (non-granular application)
Use (Application Rate Ib ai/acre)
Almond (0.2)
Apple (0.5)
Apricot (0.5)
Artichoke (0.1)
Asparagus (0.125)
Beans (0.125)
Blackberry /EggPlant/Okra/Pepper/Raspberry (
0.125)
Boysenberry/Dewberry/Youngberry (0.0625)
Carrot (0.1875)
Canistel/Mango/Papaya/Sapodilla(0.25)
Cherry /Nectarine/Peach (0.5)
Cotton
Cucurbit Vegetables (0. 12)
Currant (0.125)
Gooseberry (0.125)
Grapes (0.13)
Hops (0.25)
Lettuce (0.125)
Plum/Prune (0.1 6)
Tomato (0.1)
Turf (1.3)
Dose-based
Chronic
RQ*1
3.42
10.7
6.09
2.18
2.72
2.67
2.48
1.24
2.14
5.99
8.55
NA
3.02
2.82
3.60
3.69
5.35
2.25
5.00
1.55
29.35
Dietary-
based
Chronic
RQ*2
0.63
1.97
1.12
0.40
0.50
0.49
0.46
0.23
0.40
1.10
1.58
3.00
0.56
0.49
0.66
0.68
0.99
0.42
0.92
0.29
5.41
Dose-
based
Acute
RQ*3
0.08
0.25
0.14
0.05
0.06
0.06
0.06
0.03
0.05
0.14
0.20
NA
0.07
0.06
0.08
0.09
0.12
0.05
0.12
0.04
0.68
% Expected
Effect on Prey
Population at
RQ4
9.6
23.7
15.5
6.1
7.3
7.3
7.3
3.5
6.1
15.5
20.3
NA
8.5
7.3
9.6
10.7
13.7
6.1
13.7
4.8
42.1
* = LOG exceedances (acute RQ > 0.1; chronic RQ > 1) are bolded and shaded
1 Based on dose-based EEC and myclobutanil rat NOAEL =16 mg/kg-bw.
Based on dietary-based EEC and myclobutanil rat NOAEC = 200 mg/kg-diet.
3 Based on dose-based EEC and myclobutanil mouse acute oral LD50 = 1360 mg/kg-bw.
4 % expected effect on prey population at RQ is calculated using the acute mouse toxicity study probit dose-response slope of
1.19. No confidence interval was provided.
Table 5.7 Summary of Acute RQs Used to Estimate Indirect Effects to the
Terrestrial-phase CRLF via Direct Effects on Small Mammals as Dietary Food
Items (granular application)
Use
Turf
Application Rate (Ib ai/A)
1.35
Dose-based Acute RQ*1
0.63
% Expected Effect on Prey
Population at RQ
40.2
* = LOG exceedances (acute RQ > 0.1) are bolded and shaded.
1 Based and adjusted LD50 of 1380 mg/kg and a calculated LD50/sq. ft
5.1.2.2.3 Frogs
An additional prey item of the adult terrestrial-phase CRLF is other species of frogs. In
order to assess risks to these organisms, dietary-based and dose-based exposures modeled
in T-REX for a small bird (20g) consuming small invertebrates are used. See Section
5.1.2.1 and associated tables for results. The acute LOC for listed species is exceeded for
98
-------
the majority of myclobutanil uses. The chronic LOG is exceeded for cotton and turf.
Therefore, following both acute and chronic exposure myclobutanil may affect indirectly,
the CRLF via reduction in frogs as prey items.
5.1.2.3 Indirect Effects to CRLF via Reduction in Terrestrial Plant
Community (Riparian and Upland Habitat)
Indirect effects to the CRLF via reduction in terrestrial plant community cannot be
quantitatively estimated because there are no vegetative vigor or seedling emergence
plant toxicity data available for myclobutanil. For a qualitative risk description, see
Section 5.2.3.2.
5.1.3 Primary Constituent Elements of Designated Critical Habitat
For myclobutanil use, the assessment endpoints for designated critical habitat PCEs
involve a reduction and/or modification of food sources necessary for normal growth and
viability of aquatic-phase CRLFs, and/or a reduction and/or modification of food sources
for terrestrial-phase juveniles and adults. Because these endpoints are also being
assessed relative to the potential for indirect effects to aquatic- and terrestrial-phase
CRLF, the effects determinations for indirect effects from the potential loss of food items
are used as the basis of the effects determination for potential effects to designated
critical habitat.
5.1.3.1 Aquatic-Phase (Aquatic Breeding Habitat and Aquatic Non-
Breeding Habitat)
Three of the four assessment endpoints for the aquatic-phase primary constituent
elements (PCEs) of designated critical habitat for the CRLF are related to potential
effects to aquatic and/or terrestrial plants:
• Alteration of channel/pond morphology or geometry and/or increase in sediment
deposition within the stream channel or pond: aquatic habitat (including riparian
vegetation) provides for shelter, foraging, predator avoidance, and aquatic
dispersal for juvenile and adult CRLFs.
• Alteration in water chemistry/quality including temperature, turbidity, and
oxygen content necessary for normal growth and viability of juvenile and adult
CRLFs and their food source.
• Reduction and/or modification of aquatic-based food sources for pre-metamorphs
(e.g., algae).
Based on the risk estimation for potential effects to aquatic non-vascular plants provided
in Section 5.1.1.2, myclobutanil is expected to have no effect on aquatic-phase PCEs of
99
-------
designated habitat related to effects on aquatic non-vascular plants. The highest modeled
peak EEC for turf use (61.41 ppb) and the most sensitive non-vascular plant endpoint
(830 ppb) provide an aquatic non-vascular plant RQ of 0.074, which is much lower than
the LOG of 1 for aquatic plants. Therefore, the RQs for all scenarios will be less than the
LOG for aquatic plants.
Risk estimations for potential effects to aquatic vascular plants and terrestrial plants were
not conducted because no toxicity data are available for myclobutanil. Therefore, it
cannot be estimated whether or not myclobutanil is likely to affect aquatic-phase PCEs of
designated habitat related to effects on aquatic vascular plants and terrestrial plants. Risks
to aquatic vascular plants and terrestrial plants will be discussed qualitatively in Section
5.2.3.
The remaining aquatic-phase PCE is "alteration of other chemical characteristics
necessary for normal growth and viability of CRLFs and their food source." To assess
the impact of myclobutanil on this PCE (i.e.., alteration of food sources), acute and
chronic freshwater fish and invertebrate toxicity endpoints, as well endpoints for aquatic
non-vascular plants, are used as measures of effects. RQs for these endpoints were
calculated in Sections 5.1.1.1 and 5.1.1.2. Based on acute RQs for freshwater fish and
invertebrates and for non-vascular plants that are less than the LOCs for all uses,
myclobutanil is expected to have no effect on aquatic-phase PCEs of designated habitat
related to effects of alteration of other chemical characteristics necessary for normal
growth and viability of CRLFs and their food source. Following chronic exposure, data
are only available for freshwater fish. For all uses, the chronic RQs for freshwater fish
are less than the LOG. Therefore, following chronic exposure, it can only be partially
estimated whether or not myclobutanil is likely to affect aquatic-phase PCEs of
designated habitat related to effects of alteration of other chemical characteristics
necessary for normal growth and viability of CRLFs and their food source. Based on
chronic effects to freshwater fish, myclobutanil is expected to have no effect on this PCE.
Chronic risk to freshwater invertebrates will be discussed qualitatively in section 5.2.2.2.
5.1.3.2 Terrestrial-Phase (Upland Habitat and Dispersal Habitat)
The first two assessment endpoints for the terrestrial-phase PCEs of designated critical
habitat for the CRLF are related to potential effects to terrestrial plants:
• Elimination and/or disturbance of upland habitat; ability of habitat to support food
source of CRLFs: Upland areas within 200 ft of the edge of the riparian
vegetation or dripline surrounding aquatic and riparian habitat that are comprised
of grasslands, woodlands, and/or wetland/riparian plant species that provides the
CRLF shelter, forage, and predator avoidance
• Elimination and/or disturbance of dispersal habitat: Upland or riparian dispersal
habitat within designated units and between occupied locations within 0.7 mi of
each other that allow for movement between sites including both natural and
altered sites which do not contain barriers to dispersal
100
-------
The risk estimation for terrestrial-phase PCEs of designated habitat related to potential
effects on terrestrial plants cannot be quantitatively addressed because there are no
vegetative vigor or seedling emergence plant toxicity data available for myclobutanil.
The risk will be discussed qualitatively in Section 5.2.3.2.
The third terrestrial-phase PCE is "reduction and/or modification of food sources for
terrestrial phase juveniles and adults." To assess the impact of myclobutanil on this PCE,
acute and chronic toxicity endpoints for birds, mammals, and terrestrial invertebrates are
used as measures of effects. RQs for these endpoints were calculated in Sections 5.1.2.1
and 5.1.2.2. For terrestrial-phase amphibians, using birds as a surrogate, there are acute
LOG listed species exceedances for multiple uses. The chronic avian LOG is exceeded
for turf and cotton uses. RQs for terrestrial invertebrates were not estimated because a
definitive LD50 was not available. For mammals, the acute LOG for listed species is
exceeded for multiple crops and the acute LOG for non-listed species is exceeded for turf.
The chronic LOG is exceeded for multiple crops. Therefore, myclobutanil may affect the
third terrestrial-phase PCE.
The fourth terrestrial-phase PCE is based on alteration of chemical characteristics
necessary for normal growth and viability of juvenile and adult CRLFs and their food
source. Direct acute and chronic RQs for terrestrial-phase CRLFs are presented in
Section 5.1.2.1. Again, the acute LOG is exceeded for multiple uses and the chronic
LOG for cotton and turf uses. The same acute and chronic RQ estimates are used for
indirect effects based on terrestrial-phase amphibians as a food source. For other prey
species, RQs for terrestrial invertebrates were not estimated because a definitive LD50
was not available. For mammals, the acute LOG for listed species is exceeded for
multiple crops and the acute LOG for non-listed species is exceeded for turf. The chronic
LOG is exceeded for multiple crops. Therefore, myclobutanil may affect the fourth
terrestrial-phase PCE.
5.2 Risk Description
The risk description synthesizes an overall conclusion regarding the likelihood of adverse
impacts leading to an effects determination (i.e., "no effect," "may affect, but not likely
to adversely affect," or "likely to adversely affect") for the CRLF and its designated
critical habitat.
Based on the RQs presented in the Risk Estimation (Section 5.1) a preliminary effects
determination is may affect for the CRLF and critical habitat.
Direct/indirect effect LOCs are exceeded and myclobutanil use may affect the PCEs of
the CRLF's critical habitat. Therefore, the Agency concludes a preliminary "may
affect" determination for the FIFRA regulatory action regarding myclobutanil. A
summary of the risk estimation results are provided in Table 5.8 for direct and indirect
effects to the CRLF and in Table 5.9 for the PCEs of designated critical habitat for the
CRLF.
101
-------
Table 5.8 Risk Estimation Summary for Myclobutanil - Direct and Indirect Effects
toCRLF
Assessment Endpoint
LOC
Exceedances
(Y/N)
Description of Results of Risk Estimation
Aquatic Phase
(eggs, larvae, tadpoles, juveniles, and adults)
Direct Effects
Survival, growth, and reproduction
of CRLF individuals via direct
effects on aquatic phases
N
There are no LOC exceedences for listed species following
both acute and chronic exposure using freshwater fish as the
surrogate for aquatic-phase amphibians.
Indirect Effects
Survival, growth, and reproduction
of CRLF individuals via effects to
food supply (i.e., freshwater
invertebrates, non-vascular plants)
Unknown
There are no LOC exceedences for listed species following
acute exposure to freshwater invertebrates. No chronic
exposure data are available. A qualitative discussion of risk is
provided. There are no LOC exceedences for aquatic non-
vascular plants.
Indirect Effects
Survival, growth, and reproduction
of CRLF individuals via effects on
habitat, cover, and/or primary
productivity (i.e., aquatic plant
community)
Unknown
There are no LOC exceedences for aquatic non-vascular plants.
No aquatic vascular plant data are available. A qualitative
discussion of risk is provided.
Indirect Effects
Survival, growth, and reproduction
of CRLF individuals via effects to
riparian vegetation, required to
maintain acceptable water quality
and habitat in ponds and streams
comprising the species' current
range.
Unknown
No vegetative vigor or seedling emergence plant toxicity data
are available. A qualitative discussion of risk is provided.
Terrestrial Phase
(Juveniles and adults)
Direct Effects
Survival, growth, and reproduction
of CRLF individuals via direct
effects on terrestrial phase adults and
juveniles
Y
For the terrestrial-phase CRLF, birds are used as a surrogate.
There are dose-based acute LOC exceedances (RQ > 0.1) for all
uses except Boysenberry/Dewberry/Youngberry. The chronic
avian LOC is exceeded for turf and cotton uses.
Y
Indirect Effects
Survival, growth, and reproduction
of CRLF individuals via effects on
prey (i.e., terrestrial invertebrates,
small terrestrial mammals and
terrestrial phase amphibians)
For mammals following non-granular applications, the acute
listed species LOC is exceeded for apple, apricot, cherry,
nectarine, peach, hops and turf uses. The chronic LOC on a dose
basis is exceeded for all uses and the chronic LOC on a dietary
basis is exceeded for apples, apricots, cherries, nectarines,
peaches, cotton and turf. For granular uses, the acute listed
species LOC is exceeded for turf. For terrestrial invertebrates,
the acute contact LD50 is greater than the highest dose tested. In
addition, there were no mortalities. Risk the terrestrial
invertebrates will be discussed qualitatively in the risk
description. For terrestrial-phase amphibians, birds are used as a
surrogate. For birds, There are dose-based acute LOC
exceedances (RQ > 0.1) for all uses except
Boysenberry/Dewberry/Youngberry. The chronic avian LOC is
102
-------
Assessment Endpoint
Indirect Effects
Survival, growth, and reproduction
of CRLF individuals via effects on
habitat (i.e., riparian vegetation)
LOC
Exceedances
(Y/N)
Unknown
Description of Results of Risk Estimation
exceeded for turf and cotton uses.
No vegetative vigor or seedling emergence plant toxicity data
are available. A qualitative discussion of risk is provided.
Table 5.9 Risk Estimation Summary for Myclobutanil - PCEs of Designated
Critical Habitat for the CRLF
Assessment Endpoint
Habitat Effects
(Y/N)
Description of Results of Risk Estimation
Aquatic Phase PCEs
(Aquatic Breeding Habitat and Aquatic Non-Breeding Habitat)
Alteration of channel/pond morphology or
geometry and/or increase in sediment
deposition within the stream channel or
pond: aquatic habitat (including riparian
vegetation) provides for shelter, foraging,
predator avoidance, and aquatic dispersal
for juvenile and adult CRLFs.
Alteration in water chemistry /quality
including temperature, turbidity, and oxygen
content necessary for normal growth and
viability of juvenile and adult CRLFs and
their food source.
Alteration of other chemical characteristics
necessary for normal growth and viability of
CRLFs and their food source.
Reduction and/or modification of aquatic-
based food sources for pre-metamorphs
(e.g., algae)
Unknown
Unknown
Unknown
N
There are no LOC exceedences for aquatic non-
vascular plants. No aquatic vascular or terrestrial
plant data are available. A qualitative discussion of
risk is provided.
There are no LOC exceedences for aquatic non-
vascular plants. No aquatic vascular or terrestrial
plant data are available. A qualitative discussion of
risk is provided.
There are no LOC exceedences for listed species
following acute and chronic exposure to freshwater
fish or acute exposure to freshwater invertebrates.
There are no LOC exceedences for aquatic non-
vascular plants. No data are available for freshwater
invertebrates (chronic exposure) or aquatic vascular
plants. A qualitative discussion of risk is provided.
There are no LOC exceedences for aquatic non-
vascular plants.
Terrestrial Phase PCEs
(Upland Habitat and Dispersal Habitat)
Elimination and/or disturbance of upland
habitat; ability of habitat to support food
source of CRLFs: Upland areas within 200
ft of the edge of the riparian vegetation or
dripline surrounding aquatic and riparian
habitat that are comprised of grasslands,
woodlands, and/or wetland/riparian plant
species that provides the CRLF shelter,
forage, and predator avoidance
Elimination and/or disturbance of dispersal
habitat: Upland or riparian dispersal habitat
Unknown
Unknown
No vegetative vigor or seedling emergence plant
toxicity data are available. A qualitative discussion
of risk is provided.
No vegetative vigor or seedling emergence plant
toxicity data are available. A qualitative discussion
103
-------
Assessment Endpoint
Habitat Effects
(Y/N)
Description of Results of Risk Estimation
within designated units and between
occupied locations within 0.7 mi of each
other that allow for movement between sites
including both natural and altered sites
which do not contain barriers to dispersal
of risk is provided.
Reduction and/or modification of food
sources for terrestrial phase juveniles and
adults
Y
For mammals, the acute and chronic LOCs are
exceeded for multiple crops. For terrestrial
invertebrates, the acute contact LD50 is greater than
the highest dose tested with no mortalities. Risk the
terrestrial invertebrates will be discussed
qualitatively in the risk description. For terrestrial-
phase amphibians, birds are used as a surrogate.
Acute and chronic LOCs are exceeded for multiple
crops.
Alteration of chemical characteristics
necessary for normal growth and viability of
juvenile and adult CRLFs and their food
source.
Y
See above box.
Following a "may affect" determination, additional information is considered to refine
the potential for exposure at the predicted levels based on the life history characteristics
(i.e., habitat range, feeding preferences, etc.) of the CRLF. Based on the best available
information, the Agency uses the refined evaluation to distinguish those actions that
"may affect, but are not likely to adversely affect" from those actions that are "likely to
adversely affect" the CRLF and its designated critical habitat.
The criteria used to make determinations that the effects of an action are "not likely to
adversely affect" the CRLF and its designated critical habitat include the following:
• Significance of Effect: Insignificant effects are those that cannot be meaningfully
measured, detected, or evaluated in the context of a level of effect where "take"
occurs for even a single individual. "Take" in this context means to harass or
harm, defined as the following:
• Harm includes significant habitat effects or degradation that results in
death or injury to listed species by significantly impairing behavioral
patterns such as breeding, feeding, or sheltering.
• Harass is defined as actions that create the likelihood of injury to listed
species to such an extent as to significantly disrupt normal behavior
patterns which include, but are not limited to, breeding, feeding, or
sheltering.
• Likelihood of the Effect Occurring: Discountable effects are those that are
extremely unlikely to occur.
• Adverse Nature of Effect: Effects that are wholly beneficial without any adverse
effects are not considered adverse.
104
-------
A description of the risk and effects determination for each of the established assessment
endpoints for the CRLF and its designated critical habitat is provided in Sections 5.2.1
through 5.2.3
5.2.1 Direct Effects
5.2.1.1 Aquatic-Phase CRLF
The aquatic-phase considers life stages of the frog that are obligatory aquatic organisms,
including eggs and larvae. It also considers submerged terrestrial-phase juveniles and
adults, which spend a portion of their time in water bodies that may receive runoff and
spray drift containing myclobutanil.
Acute and chronic RQs for all modeled scenarios for myclobutanil and myclobutanil plus
1,2,4 triazole were lower than the related LOG. The highest acute RQ was 0.025 and the
highest chronic RQ was 0.061, both RQs based on the turf scenario. The probability of
an individual effect at the highest RQ (turf scenario) is estimated to be 1 in 3.56 x 1012 (1
in 1.48 x 103 to 1 in 5.06 x 1046, 95% C.I.) based on a default slope assumption of 4.5 (2
to 9, 95% C.I.)
Water monitoring and rainfall data support the risk conclusions based on RQs calculated
with modeled EECs. The available non-targeted monitoring data show myclobutanil
concentrations that are much lower than the modeled concentrations. The highest
concentrations of myclobutanil were detected in surface water. Myclobutanil was
detected in ambient surface water (Table 3.3) at a detection frequency of 37.8 % (166 of
439 samples) collected in five counties in California. The maximum daily myclobutanil
concentration was 0.507 ug/L for a sampling site (USGS Sampling Station
373112120382901) located near Montpelier California in Merced County California. In
comparison to surface water monitoring data which did not include 1,2,4-triazole, the
lowest modeled concentrations of myclobutanil (plus 1,2,4 triazole) were 2.84 ug/L
(peak), 2.82 ug/L (21-day), and 2.77 ug/L (60-day).
There are no relevant data in the open literature and no incident data for fish.
The effects determination is no effect on aquatic-phase CRLF from direct exposures to
myclobutanil.
5.2.1.2 Terrestrial-Phase CRLF
As stated in the Risk Estimation section (Section 5.1.2.1), the acute avian dose-based
RQs exceed the acute LOG for listed species (0.1) for all uses of myclobutanil except
boysenberry/dewberry/youngberry at an application rate of 0.0625 Ibs. a.i./A. In an effort
to refine the acute dose-based risk estimates, the T-REX model was modified to account
for the lower metabolic rate and lower caloric requirement of amphibians (compared to
birds). Acute dose-based RQs were recalculated using the T-HERPS (Version 1.0) model
105
-------
for small (1 g), medium (37 g), and large (238 g) frogs. An example output from T-
HERPS is in Appendix M. Using this refinement, the acute dose-based RQ exceeds the
acute listed species LOG of 0.1 for 238 gram amphibians eating small herbivorous
mammals following application to turf. The dose-based RQs for 37 gram amphibians
eating small herbivorous mammals exceed the acute LOG for listed species following
application to all crops except boysenberry/dewberry/youngberry at an application rate of
0.0625 Ibs a.i./A and tomatoes at 0.1 Ibs a.i./A (see Table 5.10).
Table 5.10 Thirty Seven Gram Amphibian T-HERPS RQs for Consumption of
Small Herbivorous Mammals
USE
Almond
Apple
Apricot
Artichoke
Asparagus
Beans
Blackberry/EggPlant/Okra/Pepper/Raspberry
Boysenberry /Dewberry /Youngberry
Carrot
Canistel/Mango/Papaya/Sapodilla
Cherry /Nectarine/Peach
Cucurbit Vegetables
Currant
Gooseberry
Grapes
Hops
Lettuce
Plum/Prune
Tomato
Turf
RQ
0.16
0.49
0.28
0.10
0.13
0.12
0.11
0.06
0.10
0.28
0.39
0.14
0.13
0.17
0.13
0.25
0.10
0.23
0.07
1.41
Bold indicates that the RQ exceeds the listed species LOG of 0.1
2 T-HERPS turf use RQ for 238 gram amphibians consuming small herbivorous mammals = 0.22, which
exceeds the acute listed species LOG of 0.1
In the acute oral study with Bobwhite quail (MRID 00144286), lethargy and anorexia
were observed in all birds at all dose levels. The lowest dose level tested was 316 mg/kg
bw. These symptoms lasted until death in the two highest test doses (1000 and 1470
mg/kg bw), seven days at 681 mg/kg bw, three days at 464 mg/kg bw, and two days at
the lowest dose. All birds except for one each in the 1000 and 681 mg/kg bw groups
showed distention of the crop containing either test material or air, and food. Five birds
(two from the 464 mg/kg group and one each from the 681, 1000 and 1470 mg/kg
groups) showed microscopic findings in liver and intestinal tissues. Three of the
surviving birds showed microscopic findings in liver and intestinal tissues. Since all
birds were affected in this study, no NOAEL could be established. The lowest dose
tested (316 mg/kg bw) corresponds to an adjusted dose of 228 mg/kg bw for a 20 gram
bird. For the turf use, the dose-based EEC for small insects is 693 mg/kg bw, which is
106
-------
higher than the lowest dose tested adjusted for a 20 gram bird. The dose-based EEC for
small insects is also greater than the lowest adjusted dose tested. None of the other uses
generated dose-based EECs for small insects that were greater than the lowest adjusted
dose tested. The dose-based EECs ranged from 29 for
Boysenberry/Dewberry/Youngberry to 693 for turf (see Table 3.9 in Section 3.3). Since
there were effects at the lowest dose, there is an uncertainty associated with potential
sublethal effects in birds on a dose-basis for all the uses.
The probability of an individual effect on a dose-basis ranges from 1 in ~ 1.54E+14 for
uses on boysenberry/dewberry/youngberry to 1 in ~ 1 for use on turf. The highest
probabilities are for uses on turf, apples (1 in ~ 7.24E+00), cherries/nectarines/peaches (1
in ~ 2.61E+01), canistel/mango/papaya/sapodilla (1 in ~ 4.95E+02) and apricots (1 in ~
3.88E+02).
RQs on an acute dietary basis were not estimated because the LCso value exceeds the
maximum limit concentration tested. As stated in the effects section, myclobutanil is
categorized as slightly toxic on a dietary basis with subacute dietary LCso's of >4090 ppm
for mallard ducks (MRID 00144288) and > 4530 ppm for bobwhite quail (MRID
00144287). Although no definitive subacute dietary LCso's could be determined from
these studies, there were mortalities in both studies. There was one mortality at 4090
ppm, the highest concentration tested in mallard ducks and mortalities at 3000 ppm and
4530 ppm, the highest concentrations tested in bobwhite quail. The estimated dietary-
based EEC for small insects following use on turf is 609 ppm, which is roughly 4.9 times
lower than 3000 ppm, the lowest concentration where mortality was observed (e.g., the
upper bound subacute dietary based RQ would be 0.2). This value is greater than the
avian acute risk to listed species LOG of 0.1. Therefore, there is an uncertainty
associated with potential mortality to listed species following turf uses. For apples,
which have the next highest terrestrial exposure on a dietary basis the EEC is 222 ppm
for small insects, which is 13.5 times less than the lowest concentration where mortality
was observed (e.g., the upper bound subacute dietary based RQ would be 0.07). This is
less than the acute avian LOG for listed species.
As stated in the Risk Estimation section, the chronic avian LOG is exceeded following
use on turf and cotton (assuming 100% of seed available). None of the other uses
generated chronic RQs that exceeded the chronic LOG.
There were no avian or amphibian studies available in the ECOTOX open literature for
myclobutanil. Similarly, no myclobutanil incidents have been reported involving birds or
terrestrial-phase amphibians.
The Agency concludes that there is a potential direct impact to the terrestrial-phase
CRLF. The effects determination is likely to adversely affect based on the weight of the
evidence as follows:
107
-------
Acute dose-based RQs estimated from T-HERPS exceed the acute LOG of 0.1 for
listed species for both 37 and 238 gram amphibians eating small herbivorous
mammals following application to turf. The dose-based RQs for 37 gram
amphibians eating small herbivorous mammals exceed the acute LOG for listed
species following application to all crops except
boysenberry/dewberry/youngberry and tomatoes.
On an acute dose-basis, there is an uncertainty associated with potential sublethal
effects for all uses.
Based on the lowest dietary concentration where mortality was observed in the
subacute dietary studies (both studies had LC50's greater than the highest
concentration tested), there is an uncertainty associated with potential mortality to
listed species following turf uses.
The highest probabilities of an individual effect on a dose-basis are for uses on
turf (1 in ~ 1), apples (1 in ~ 7.24E+00), cherries/nectarines/peaches (1 in ~
2.61E+01), canistel/mango/papaya/sapodilla(l in ~ 4.95E+02) and apricots (1 in
-3.88E+02).
The chronic avian LOG is exceeded following use on turf and cotton (assuming
100% of seed available).
5.2.2 Indirect Effects (via Reductions in Prey Base)
5.2.2.1 Algae (non-vascular plants)
As discussed in Section 2.5.3, the diet of CRLF tadpoles is composed primarily of
unicellular aquatic plants (i.e., algae and diatoms) and detritus. Acute RQs for aquatic
non-vascular plants did not exceed the LOG of 1 for any of the assessed uses. The
highest acute RQ (0.074) was for the turf scenario. As previously discussed, available
monitoring data show myclobutanil concentrations that are much lower than the modeled
concentrations. There are no relevant data in the open literature and no incident data for
aquatic plants. The effects determination is no effect on indirect impact to the CRLF via
effects of myclobutanil on algal food items.
5.2.2.2 Aquatic Invertebrates
The potential for myclobutanil to elicit indirect effects to the CRLF via effects on
freshwater invertebrate food items is dependent on several factors including: (1) the
potential magnitude of effect on freshwater invertebrate individuals and populations; and
(2) the number of prey species potentially affected relative to the expected number of
species needed to maintain the dietary needs of the CRLF. Together, these data provide a
basis to evaluate whether the number of individuals within a prey species is likely to be
reduced such that it may indirectly affect the CRLF.
No acute RQs exceeded the endangered species LOG of 0.05. The highest acute RQ for
aquatic invertebrates was 0.005 (turf scenario). At this RQ, the percent effect to the
108
-------
aquatic invertebrate prey base is < 0.001% (i.e. the percentage of the aquatic invertebrate
population that may be affected following exposure to myclobutanil).
No chronic freshwater invertebrate toxicity data are available for myclobutanil. It was
not possible to estimate a chronic toxicity value for freshwater invertebrates using an
acute to chronic ratio with estuarine/marine invertebrate data because no chronic studies
are available for myclobutanil. Therefore, a quantitative assessment of risk following
chronic exposure to myclobutanil was not possible using these methods. However, the
risk may be considered using other approaches.
Using the modeled EECs, freshwater invertebrate chronic toxicity values that would
trigger an exceedence of the LOG can be calculated for myclobutanil. The highest 21-
day EEC modeled is 61.15 ug/L (turf scenario). Based on that value, for myclobutanil a
chronic toxicity value of < 0.061 mg/L would exceed the LOG of 1. In the context of the
acute toxicity of myclobutanil to aquatic invertebrates (11 mg/L), a chronic toxicity value
< 0.061 mg/L would yield an acute to chronic ratio of >180.
As previously described, acute and chronic toxicity data from other conazole (DMI
triazole) fungicides were available for aquatic invertebrates. For risk description
purposes, these endpoints were used to calculate acute to chronic ratios, assuming that
myclobutanil toxicity is similar to other conazoles due to similar mode of action. Data
were available for nine conazole to calculate acute to chronic ratios from water flea
(Daphnia magnet) studies (the species which acute data is available for myclobutanil).
As applied to myclobutanil, only one of the conazole acute-to-chronic ratios (high-end
estimate for cyproconazole = 1368) is higher that the ratio of >180 that would trigger
chronic LOG exceedences for freshwater invertebrates based on myclobutanil modeled
EECs. Assuming an acute-to-chronic ratio of 1368, chronic toxicity of myclobutanil to
freshwater invertebrates is estimated to be 8.04 |ig/L. Based on this high-end estimate
for cyproconazole, RQs based on the 21-day EEC of myclobutanil plus 1,2,4 triazole
range from 0.35 to 7.61. Nearly all uses exceed the chronic LOG of 1; only those with
21-day EECs less than 8.04 jig/L do not exceed (see Table 3.6). It is important to note
that there were two available chronic toxicity studies for cyproconazole. The
NOAEC/LOAECs for these two studies are: 0.019/0.073 and 0.29/0.57 mg/L,
respectively. Both studies are acceptable for assessment of risk, but the one with the
lower endpoints was graded as supplemental and was a static study. The other study with
the higher endpoints was graded acceptable and was a flow-through study. The low end
cyproconazole acute-to-chronic ratio estimate (89.6) is less than the ratio of >180 that
would trigger LOG exceedences for myclobutanil. Thus, as applied to myclobutanil there
are no exceedences of the LOG based on the lower end acute-to-chronic estimate for
cyproconazole. Cyproconazole toxicity data suggests the possibility of effects from
myclobutanil on freshwater invertebrates that may exceed the LOG. However, there is
considerable uncertainty associated with extrapolating toxicity from other conazoles to
myclobutanil including the high variability among conazole acute-to-chronic ratios
(range from 2.4 to 1368). Thus, the effects of myclobutanil cannot be quantified without
data on myclobutanil toxicity to aquatic invertebrates.
109
-------
In addition to studies on the water flea (Daphnia magnet), four of the conazoles had
studies submitted for other aquatic invertebrate taxa. For these four conazoles, Daphnia
magna was the most sensitive aquatic invertebrate species tested.
As previously discussed, available monitoring data show myclobutanil concentrations
that are much lower than the modeled concentrations. It was observed that the Tier II
EECs indicated year-to-year accumulation of myclobutanil in the standard pond model.
However, this accumulation is not unexpected due to the persistence of myclobutanil and
myclobutanil plus 1,2,4-triazole in soil and water environments, and the lack of inflow
and outflow in the standard pond model that precludes decreases in concentrations of
residues due to dilution. Therefore, the accumulation is conservative (an overestimate)
compared to flowing systems. Furthermore, the Koc is probably not high enough for
accumulation in the sediment to be much of an issue.
There are no acceptable open literature data available or reported aquatic invertebrate
incidents attributed myclobutanil.
Based on the weight of evidence, there is minimal potential indirect impact to the CRLF
via effects of myclobutanil on freshwater invertebrate food items. The effects
determination is no effect on an acute basis and may effect, not likely to adversely affect
on a chronic basis.
5.2.2.3 Fish and Aquatic-phase Frogs
Myclobutanil is moderately toxic on an acute basis to freshwater fish, the surrogate for
the aquatic-phase CRLF. The acute and chronic RQs for all modeled scenarios for
myclobutanil and myclobutanil plus 1,2,4 triazole were lower than the related LOG. The
probability of an individual effect at the highest RQ (turf scenario) is estimated to be 1 in
3.56 x 1012 (1 in 1.48 x 103 to 1 in 5.06 x 1046, 95% C.I.) based on a default slope
assumption of 4.5 (2 to 9, 95% C.I.). Water monitoring and rainfall data support the risk
conclusions based on RQs calculated with modeled EECs. Available monitoring data
show myclobutanil concentrations that are much lower than the modeled concentrations.
There are no relevant data in the open literature and no incident data for fish. The effects
determination is myclobutanil has "no effect" on indirectly impacting the aquatic-phase
CRLF based on the endpoints generated from the freshwater fish data.
5.2.2.4 Terrestrial Invertebrates
When the terrestrial-phase CRLF reaches juvenile and adult stages, its diet is mainly
composed of terrestrial invertebrates. As stated in the risk estimation section (Section
5.1.2), the acute RQs for terrestrial invertebrates were not estimated because no definitive
LCso can be estimated from the available data. The data indicate no mortalities at
concentration levels up to and including 2836 jig a.i./g bw or 2836 ppm (highest level
110
-------
tested) in the acute contact study with honey bees. The estimated dietary-based EEC for
small insects with the use on turf is 608.82 ppm, which is 4.7 times lower than 2836 ppm
(e.g., the upper bound acute RQ would be 0.21). This value is higher than the acute LOG
of 0.05 for listed terrestrial invertebrate species. Upper bound RQs for small insects
would also slightly exceed the acute LOG for apple (RQ = 0.08) and cherry, nectarine
and peach uses (RQ = 0.06). Estimated upper bound small insect RQs for all other uses
are below the LOG. Based on the above estimates for small insects, there is an
uncertainty associated with potential mortality for listed terrestrial invertebrates. The
estimated dietary-based EEC for large insects with the use on turf is 67.65 ppm. This is
41 times lower than 2836 ppm (upper bound RQ of 0.02). This value is lower than the
acute LOG of 0.05 for listed terrestrial invertebrate species and thus, there is no concern
for listed large invertebrates for any of the myclobutanil uses.
As noted in Section 4.2 on toxicity to terrestrial organisms, one of the five available
literature studies on terrestrial invertebrates provided an LD50. Three mite studies and
one arthropod study showed no adverse effects on the species evaluated. A single study
on mirids provided an LD50 of 150 jig ai/L to adult mirids. The study did not show
toxicity to nymphs. A quantitative analysis of potential risk to terrestrial invertebrates
based on the LD50 for mirids cannot be conducted, however, because insufficient data are
available to calculate ppm exposures (i.e., data on the weight of the organism are not
available). However, based on the results of the honey bee study, the absence of adverse
effects in four of the five available literature studies, and the fact that the mirid study
showed no toxicity to nymphs, minimal potential indirect impact to the CRLF via effects
of myclobutanil on freshwater invertebrate food items is expected. The effects
determination is may affect, not likely to adversely affect.
5.2.2.5 Mammals
Life history data for terrestrial-phase CRLFs indicate that large adult frogs consume
terrestrial vertebrates, including mice. The dose-based chronic RQs exceed the listed
species chronic LOG for all uses and the dietary-based chronic RQs for a number of
myclobutanil uses. The dose-based acute RQs also exceed the listed species acute RQs
for a number of uses. The chronic dietary-based RQ exceedances range from 1.1 for uses
of myclobutanil on canistel, mango, papaya and sapodilla to 5.4 for uses on turf. Chronic
dose-based RQs range from 1.24 (caneberries) to 29.35 (turf). Acute dose-based RQ
exceedances range from 0.12 (plums and hops) to 0.68 (turf). At the lowest acute RQ
exceedance of 0.12 for hops and plums, the expected effect on the prey population is
13.7% based on a default slope factor of 1.19. The highest acute RQ exceedance for turf
of 0.68 corresponds with an expected effect on the prey population of 42%. As noted in
Section 4.2, the 60 DF myclobutanil formulation was identified as potentially more toxic
than the technical material based on a rat LD50 of 980 mg formulation/kg bw for the 60
DF product. The 60 DF formulation is used only on apple and grape crops. Therefore,
RQs were derived using the rat LDsofor the 60 DF formulation for apples (RQ = 0.21)
and grapes (RQ = 0.05). These results indicate that based on actual use parameters, the
60 DF formulation does not present higher toxicity in the field than other formulations
111
-------
when applied at label prescribed rates. Based on the weight-of-evidence, uses for
myclobutanil may indirectly impact the CRLF through effects to the mammalian prey
base. The effects determination is likely to adversely affect.
5.2.2.6 Terrestrial-phase Amphibians
Terrestrial-phase adult CRLFs also consume frogs. RQ values representing direct
exposures of myclobutanil to terrestrial-phase CRLFs are used to represent exposures of
myclobutanil to frogs in terrestrial habitats. Based on the assessment of risk to the
terrestrial-phase CRLF (direct effects), the Agency concludes that myclobutanil may
indirectly impact the CRLF through effects to the terrestrial-phase amphibian prey base.
The effects determination is likely to adversely affect (see Section 5.2.1.2 for more
details).
5.2.3 Indirect Effects (via Habitat Effects)
5.2.3.1 Aquatic Plants (Vascular and Non-vascular)
Aquatic plants serve several important functions in aquatic ecosystems. Non-vascular
aquatic plants are primary producers and provide the autochthonous energy base for
aquatic ecosystems. Vascular plants provide structure as attachment sites and refugia for
many aquatic invertebrates, fish, and juvenile organisms, such as fish and frogs. In
addition, vascular plants also provide primary productivity and oxygen to the aquatic
ecosystem. Rooted plants help reduce sediment loading and provide stability to
nearshore areas and lower streambanks. In addition, vascular aquatic plants are important
as attachment sites for egg masses of CRLFs.
Potential indirect effects to the CRLF based on impacts to habitat and/or primary
production were assessed using RQs for aquatic freshwater non-vascular plants based on
myclobutanil toxicity data. There is no freshwater vascular plant data for myclobutanil
so risk is assessed qualitatively.
As previously discussed, acute RQs for aquatic non-vascular plants did not exceed the
LOG of 1 for any of the assessed uses.
No aquatic vascular plant toxicity data are available for myclobutanil. As previously
described, toxicity data from other conazoles were used to assess risk from myclobutanil.
For the seven conazole fungicides evaluated, the range of 7/14-day ECsos was 0.02 to
9.02 mg a.i./L and the mean was 1.84 mg a.i./L. Assuming that myclobutanil toxicity to
aquatic vascular plants is similar to other conazoles, there were no exceedences of the
LOG using the ECso data from 6 of the 7 conazoles and the conazole mean ECso.
However, using the most sensitive endpoint (metconazole = 0.02 mg a.i./L), resulted in
exceedences of the LOG of 1 for about one third of the myclobutanil use scenarios (RQs
based on myclobutanil plus 1,2,4 triazole EECs ranged from 0.13 to 2.79). Metaconazole
112
-------
toxicity data suggests the possibility of effects from myclobutanil on aquatic vascular
plants that may exceed the LOG. However, there is considerable uncertainty associated
with extrapolating toxicity from other conazoles to myclobutanil, thus the effects of
myclobutanil cannot be quantified without data on myclobutanil toxicity to aquatic
vascular plants.
As previously discussed, available monitoring data show myclobutanil concentrations
that are much lower than the modeled concentrations. There are no acceptable open
literature data available or reported aquatic plant incidents attributed myclobutanil.
Based on the weight of evidence, there is minimal potential indirect impact to the CRLF
(habitat effects) based on effects of myclobutanil on aquatic plants (vascular and non-
vascular). The effects determination is may effect, not likely to adversely affect.
5.2.3.2 Terrestrial Plants
There are no registrant-submitted terrestrial plant toxicity data for myclobutanil for
assessment of the potential for indirect effects to the aquatic- and terrestrial-phase CRLF
via effects to riparian vegetation or effects to the primary constituent elements (PCEs)
relevant to the aquatic- and terrestrial-phase CRLF. As stated previously, limited
evidence in the open literature indicates that myclobutanil has the potential to elicit
phototoxic effects. At 1.07 Ibs a.i./A applied at 28-30 day intervals, there was evidence
of decreased quality of "Tifgreen" Bermuda grass (ECOTOX ref. no. 76524). One
incident report (1014702-074) indicated foliar necrosis and some defoliation with roses
after exposure to myclobutanil. Damage varied from house to house and by rose variety.
The certainty index for this incident (1014702-074) was possible. The application rate(s)
were not reported for this incident.
Also stated previously, myclobutanil is a member of the class of triazole sterol 14a-
demethylase-inhibitors (DMIs). To date, no other DMI triazole fungicides have been
assessed for risk to the CRLF. However, terrestrial plant studies are available on 5 other
DMI triazole fungicides that have at least one endpoint that may be used in the TerrPlant
(v. 1.2.2) model for terrestrial plants. For risk description purposes, these endpoints were
used in the model as surrogates for myclobutanil, using the solubility of myclobutanil for
the potential runoff fraction. In general, using the endpoints from the other triazole DMI
fungicides with the myclobutanil application rates, dicots living in semi-aquatic areas
would be the most sensitive terrestrial plant species. The TerrPlant model was used to
determine the myclobutanil application rates that would exceed the LOG for listed dicots
and non-listed dicots inhabiting semi-aquatic areas for both aerial and ground
applications. Table 5.11 summarizes these application rates.
113
-------
Table 5.11 Myclobutanil Application Rates Combined with Endpoints from 5
Triazole DMI Fungicides Exceeding the Terrestrial Plant LOC for Listed and Non-
Listed Dicots in Semi-Aquatic Areas
Triazole Fungicide
Cyproconazole
Metconazole
Propiconazole
Prothioconazole
Triticonazole
Application Rate (Ibs a.i./A)
Non-listed dicots
Aerial, Airblast,
Spray
Chemigation
0.16
0.28
0.33
Not available1
0.03
Ground
0.17
0.30
0.36
Not available1
0.03
Listed dicots
Aerial, Airblast,
Spray
Chemigation
0.12
0.14
0.10
0.05
0.007
Ground
0.13
0.15
0.11
0.06
0.008
1 No EC25 available
It is noted that the labeled uses of myclobutanil include direct application to a variety of
terrestrial plants (agricultural and ornamental) at multiple growth stages (e.g., seed
treatment, pre-bloom, bloom, foliar, post-bloom etc.). Considering the fact that the labels
provide for exposure to terrestrial plants throughout the growth stage, it is probable that
the damage to the crops is not so extensive to inhibit the use of this pesticide by
applicators.
Nevertheless, due to the lack of terrestrial plant data and weight of the evidence from
information provided in the open literature, incident data and the fact that surrogate data
from similar fungicides would exceed the terrestrial plant LOC for many of the
myclobutanil uses, it is determined that there is a potential of indirect impacts to the
CRLF (habitat effects) based on effects of myclobutanil on terrestrial plants. The effects
determination is likely to adversely affect.
5.2.4 Effects to Designated Critical Habitat
Risk conclusions for the designated critical habitat are the same as those for indirect
effects.
5.2.4.1 Aquatic-Phase PCEs
Three of the four assessment endpoints for the aquatic-phase primary constituent
elements (PCEs) of designated critical habitat for the CRLF are related to potential
effects to aquatic and/or terrestrial plants:
• Alteration of channel/pond morphology or geometry and/or increase in sediment
deposition within the stream channel or pond: aquatic habitat (including riparian
vegetation) provides for shelter, foraging, predator avoidance, and aquatic
dispersal for juvenile and adult CRLFs.
114
-------
• Alteration in water chemistry /quality including temperature, turbidity, and
oxygen content necessary for normal growth and viability of juvenile and adult
CRLFs and their food source.
• Reduction and/or modification of aquatic-based food sources for pre-metamorphs
(e.g., algae).
Conclusions for potential indirect effects to the CRLF via direct effects to aquatic and
terrestrial plants are used to determine whether effects to critical habitat may occur. There
were no LOG exceedences for aquatic non-vascular plants (section 5.2.2.1). As stated
previously, toxicity data from other conazole (triazole) fungicides were used to
characterize risk to aquatic vascular plants, assuming that myclobutanil toxicity is similar
to other conazoles due to similar mode of action (section 5.2.3.1). There were no
exceedences of the LOG using the ECso data from 6 of the 7 conazoles and the conazole
mean ECso. However, using the most sensitive endpoint resulted in exceedences of the
LOG for about one third of the myclobutanil use scenarios. There are no registrant-
submitted terrestrial plant toxicity data for myclobutanil. When the results of terrestrial
plant studies conducted with five other triazole DMI fungicides are used with the
application rates for myclobutanil in the Terrplant model, dicots living in semi-aquatic
areas appear to be the most sensitive terrestrial plants, with potential exceedance of the
terrestrial plant LOG for a variety of uses (section 5.2.3.2). Overall, there is a potential
for effects to habitat via impacts to terrestrial plants.
The remaining aquatic-phase PCE is "alteration of other chemical characteristics
necessary for normal growth and viability of CRLFs and their food source." This PCE is
assessed by considering impacts to algae as food items for tadpoles and direct and
indirect effects to the aquatic-phase CRLF via acute and chronic freshwater fish and
invertebrate toxicity endpoints as measures of effects. There were no LOG exceedences
for aquatic non-vascular plants, freshwater fish, or freshwater invertebrates (acute
effects). No chronic freshwater invertebrate studies are available for myclobutanil.
There are no exceedences of the freshwater invertebrate chronic LOG using toxicity data
from 8 of 9 conazoles with similar mechanisms of toxicity. For the 9th conazole, 2
chronic toxicity studies are available, one of which indicates LOG exceedances and the
other does not. Overall, effects to habitat are not expected via alteration of other
chemical characteristics necessary for normal growth and viability of CRLFs and their
food source.
5.2.4.2 Terrestrial-Phase PCEs
Two of the four assessment endpoints for the terrestrial-phase PCEs of designated critical
habitat for the CRLF are related to potential effects to terrestrial plants:
• Elimination and/or disturbance of upland habitat; ability of habitat to support food
source of CRLFs: Upland areas within 200 ft of the edge of the riparian
vegetation or drip line surrounding aquatic and riparian habitat that are comprised
of grasslands, woodlands, and/or wetland/riparian plant species that provides the
CRLF shelter, forage, and predator avoidance.
115
-------
• Elimination and/or disturbance of dispersal habitat: Upland or riparian dispersal
habitat within designated units and between occupied locations within 0.7 mi of
each other that allow for movement between sites including both natural and
altered sites which do not contain barriers to dispersal.
There are no registrant-submitted terrestrial plant toxicity data for myclobutanil for
assessment of effects to the primary constituent elements (PCEs) relevant to the aquatic-
and terrestrial-phase CRLF. As stated above, there is limited evidence in the open
literature that myclobutanil has the potential to elicit phototoxic effects and one incident
was reported in which myclobutanil may have caused some foliar necrosis and
defoliation in roses. In addition, when the results of terrestrial plant studies conducted
with five other triazole DMI fungicides are used with the application rates for
myclobutanil in the TerrPlant model, dicots living in semi-aquatic areas appear to be the
most sensitive terrestrial plants, with potential exceedance of the terrestrial plant LOG for
a variety of uses. Therefore, there is a potential for effects to habitat via effects to
terrestrial plants (Section 5.2.3.2).
The third terrestrial-phase PCE is "reduction and/or modification of food sources for
terrestrial phase juveniles and adults." To assess the impact of myclobutanil on this PCE,
acute and chronic toxicity endpoints for terrestrial invertebrates, mammals, and
terrestrial-phase frogs are used as measures of effects. For terrestrial invertebrates,
although there is an uncertainty associated with potential mortality for listed small
terrestrial invertebrates following acute exposure, based on the lack of mortality in the
honey bee study, the absence of adverse effects in four of the five available literature
studies, and the fact that the mirid study showed no toxicity to nymphs, it was determined
that although there may be an effect, it is not likely to adversely affect the terrestrial
invertebrate prey base for the CRLF. For mammals, the acute listed species LOG and the
chronic LOG are exceeded for multiple uses. For terrestrial-phase amphibians, using
birds as a surrogate, there are acute LOG listed species exceedances for multiple uses.
The chronic avian LOG is exceeded for turf and cotton uses. Therefore, there is a
potential for effects to habitat via indirect effects to terrestrial-phase CRLFs via reduction
in prey base (Sections 5.2.2.5 for mammals, and 5.2.2.6 for frogs).
The fourth terrestrial-phase PCE is based on alteration of chemical characteristics
necessary for normal growth and viability of juvenile and adult CRLFs and their food
source. Again, for terrestrial invertebrates, although there is an uncertainty associated
with potential mortality for listed small terrestrial invertebrates following acute exposure,
based on the lack of mortality in the honey bee study, the absence of adverse effects in
four of the five available literature studies, and the fact that the mirid study showed no
toxicity to nymphs, it was determined that although there may be an effect, it is not likely
to adversely affect the terrestrial invertebrate prey base for the CRLF. For mammals, the
acute listed species LOG and the chronic LOG are exceeded for multiple uses. For
terrestrial-phase amphibians, using birds as a surrogate, there are acute LOG listed
species exceedances for multiple uses. The chronic avian LOG is exceeded for turf and
116
-------
cotton uses. Therefore, there is a potential for effects to habitat via indirect effects
(Sections 5.2.2.5 for mammals and 5.2.2.6 for frogs) to terrestrial-phase CRLFs.
5.2.5 Spatial Extent of Potential Effects
An LAA effects determination applies to those areas where it is expected that the
pesticide's use will directly or indirectly affect the CRLF or its designated critical habitat.
To determine this area, the footprint of myclobutanil's use pattern is identified, using
land cover data that correspond to myclobutanil's use pattern. The spatial extent of the
effects determination also includes areas beyond the initial area of concern that may be
impacted by runoff and/or spray drift. The identified direct/indirect effects and/or effects
to critical habitat are anticipated to occur only for those currently occupied core habitat
areas, CNDDB occurrence sections, and designated critical habitat for the CRLF that
overlap with the initial area of concern plus greater than 158 feet from its boundary. It is
assumed that non-flowing waterbodies (or potential CRLF habitat) are included within
this area.
In addition to the spray drift buffer, a downstream dilution extent analysis would
normally be conducted that would result in a specified distance which would represent
the maximum continuous distance of downstream dilution from the edge of the initial
area of concern. This was not conducted for myclobutanil because all aquatic RQs with
all modeled scenarios with myclobutanil and myclobutanil plus 1,2,4 triazole were lower
that the related LOCs.
The determination of the buffer distance for spatial extent of the effects determination is
described below.
5.2.5.1 Spray Drift
In order to determine terrestrial and aquatic habitats of concern due to myclobutanil
exposures through spray drift, it is necessary to estimate the distance that spray
applications can drift from the treated area and still be present at concentrations that
exceed levels of concern. An analysis of spray drift distances was completed using
AgDrift(v. 2.01).
Spatial analysis of spray drift effects is limited to consideration of a single application
because, due to variable wind conditions, multiple applications are not likely to impact
the same location each time. Spray drift distances depend on both application rate and
method. The range of possible impacts was assessed by modeling uses with the highest
and lowest single maximum application rate for each method of application that resulted
in LOG exceedances. A turf grass use was modeled as the highest application rate for
ground equipment. Mango and hops commodities were modeled as the highest rate for
aerial application. A use on caneberries (e.g., boysenberry) was modeled for lowest
single maximum application rate for both ground and aerial methods to represent a lower
bound for potential impact.
117
-------
Myclobutanil labels do not have specific application requirements for reducing potential
spray drift, that is, restrictions on wind speed, release height and droplet size. Therefore,
conservative Tier I AgDrift default values are used for these inputs (Table 5.12).
Table 5.12 Input Parameters for Simulation of Myclobutanil in Spray Drift Using
AgDrift (v. 2.01)
Parameter Description
Application Method
Application Rate
Droplet Size Distribution
Release Height
Turf Grass
Ground
1.3
Mango
Aerial
0.25
Caneberry
Ground
0.0625
Caneberry
Aerial
0.0625
Very Fine to Fine - 90th Percentile
High Boom
NA
High Boom
NA
Table 5.13 includes uses with the maximum single application rates for each application
method and presents a summary of the buffer distances at which spray drift deposition
from these uses drop below levels of concern (e.g., RQs will be below LOCs). The
estimated buffer distance identifies those locations where terrestrial landscapes can be
impacted by spray drift deposition alone (no runoff considered). These distances
represent the maximum extent where effects are possible using the most sensitive
terrestrial data and, in the case of myclobutanil, the chronic LOG of 1. The terrestrial
analysis is based on the rat reproduction study NOAEL of 16 mg/kg bw/day, the most
sensitive terrestrial endpoint. Using this endpoint and the highest rates for both aerial and
ground applications, the estimated maximum distance at which any LOG for terrestrial
species may be exceeded is 158 feet from the treated area for aerial applications and 76
feet for ground applications. An analysis of potential risk to the aquatic-phase CRLF
from spray drift was not conducted because no myclobutanil uses resulted in LOG
exceedances for freshwater aquatic species.
Table 5.13 Summary of Maximum Predicted Distances for Potential Spray Drift
Effects
Application Method
Aerial
Ground
Application Rate
(Ib/ai Acre)
0.5
0.0625
1.3
0.0625
Uses
Mango
Caneberries
Turf Grass
Caneberries
Terrestrial LD50
Distance (ft)
158
0
76
0
5.2.5.2 Downstream Dilution Analysis
Downstream dilution analysis is an approach used to estimate the downstream extent of
exposure in streams and rivers where the EEC may be above levels that would exceed
LOCs. As stated earlier, all aquatic RQs from all modeled scenarios with myclobutanil
and myclobutanil plus 1,2,4 triazole were lower that the related LOCs. Therefore, given
that no LOCs were exceeded, a downstream dilution analysis was not performed.
118
-------
5.2.5.3 Overlap between CRLF habitat and Spatial Extent of Potential
Effects
An LAA effects determination is made to those areas where it is expected that the
pesticide's use will directly or indirectly affect the CRLF or its designated critical habitat
and the area overlaps with the core areas, critical habitat and available occurrence data
for CRLF.
For myclobutanil, the use pattern in the following land cover classes (cultivated crops,
developed land (low, medium and high intensity and open space), forest, open water,
orchards and vineyards, pasture/hay, wetlands, turf and rights-of-way) also includes areas
beyond the initial area of concern that may be impacted by runoff and/or spray drift
overlaps with CRLF habitat. When the footprint of the initial area of concern (which
represents potential myclobutanil use sites) is compared to CRLF habitat, there are
several areas of overlap (Figure 5.1). Appendix E provides maps of the initial area of
concern, along with CRLF habitat areas, including currently occupied core areas,
CNDDB occurrence sections, and designated critical habitat. It is expected that any
additional areas of CRLF habitat that are located 158 ft (to account for offsite migration
via spray drift) outside the initial area of concern may also be impacted and are part of
the full spatial extent of the LAA/effects to critical habitat effects determination.
119
-------
Myclobutanil Use & CRLF Habitat Overalp
I Myciobutani! use &CRLF habitat overlap
CNDDB occurrence sections
| Critical habitat
Core areas
County boundaries
i Kilometers
0 2040 80 120 160
Compiled from California County boundaries (ESRI, 2002),
USDA Gap Analysis Program Orchard/ Vineyard Landcover (GAP)
National Land Coyer Database (NLCD) (M RLC, 2001)
Map created by US Environmental ProtectionAgency, Office
of PesUcides Programs, Environmental Fate and Effects Division.
Projection: AlbersEqualArea Conic USGS, NortriAmerican
Datum of 1993 (NAD 1983).
3COC009
Figure 5.1 Overlap Map: CRLF Habitat and Myclobutanil Initial Area of Concern
120
-------
6 Uncertainties
6.1 Exposure Assessment Uncertainties
6.1.1 Maximum Use Scenario
The screening-level risk assessment focuses on characterizing potential ecological risks
resulting from a maximum use scenario, which is determined from labeled statements of
maximum application rate and number of applications with the shortest time interval
between applications. The frequency at which actual uses approach this maximum use
scenario may be dependant on pest resistance, timing of applications, cultural practices,
and market forces.
6.1.2 Aquatic Exposure Modeling of Myclobutanil
The standard ecological water body scenario (EXAMS pond) used to calculate potential
aquatic exposure to pesticides is intended to represent conservative estimates, and to
avoid underestimations of the actual exposure. The standard scenario consists of
application to a 10-hectare field bordering a 1-hectare, 2-meter deep (20,000 m3) pond
with no outlet. Exposure estimates generated using the EXAMS pond are intended to
represent a wide variety of vulnerable water bodies that occur at the top of watersheds
including prairie pot holes, playa lakes, wetlands, vernal pools, man-made and natural
ponds, and intermittent and lower order streams. As a group, there are factors that make
these water bodies more or less vulnerable than the EXAMS pond. Static water bodies
that have larger ratios of pesticide-treated drainage area to water body volume would be
expected to have higher peak EECs than the EXAMS pond. These water bodies will be
either smaller in size or have larger drainage areas. Smaller water bodies have limited
storage capacity and thus may overflow and carry pesticide in the discharge, whereas the
EXAMS pond has no discharge. As watershed size increases beyond 10-hectares, it
becomes increasingly unlikely that the entire watershed is planted with a single crop that
is all treated simultaneously with the pesticide. Headwater streams can also have peak
concentrations higher than the EXAMS pond, but they likely persist for only short
periods of time and are then carried and dissipated downstream.
The Agency acknowledges that there are some unique aquatic habitats that are not
accurately captured by this modeling scenario and modeling results may, therefore,
under- or over-estimate exposure, depending on a number of variables. For example,
aquatic-phase CRLFs may inhabit water bodies of different size and depth and/or are
located adjacent to larger or smaller drainage areas than the EXAMS pond. The Agency
does not currently have sufficient information regarding the hydrology of these aquatic
habitats to develop a specific alternate scenario for the CRLF. CRLFs prefer habitat with
perennial (present year-round) or near-perennial water and do not frequently inhabit
vernal (temporary) pools because conditions in these habitats are generally not suitable
(Hayes and Jennings 1988). Therefore, the EXAMS pond is assumed to be representative
121
-------
of exposure to aquatic-phase CRLFs. In addition, the Services agree that the existing
EXAMS pond represents the best currently available approach for estimating aquatic
exposure to pesticides (USFWS/NMFS 2004).
In general, the linked PRZM/EXAMS model produces estimated aquatic concentrations
that are expected to be exceeded once within a ten-year period. The Pesticide Root Zone
Model is a process or "simulation" model that calculates what happens to a pesticide in
an agricultural field on a day-to-day basis. It considers factors such as rainfall and plant
transpiration of water, as well as how and when the pesticide is applied. It has two major
components: hydrology and chemical transport. Water movement is simulated by the use
of generalized soil parameters, including field capacity, wilting point, and saturation
water content. The chemical transport component can simulate pesticide application on
the soil or on the plant foliage. Dissolved, adsorbed, and vapor-phase concentrations in
the soil are estimated by simultaneously considering the processes of pesticide uptake by
plants, surface runoff, erosion, decay, volatilization, foliar wash-off, advection,
dispersion, and retardation.
Uncertainties associated with each of these individual components add to the overall
uncertainty of the modeled concentrations. Additionally, model inputs from the
environmental fate degradation studies are chosen to represent the upper confidence
bound on the mean values that are not expected to be exceeded in the environment
approximately 90 percent of the time. Mobility input values are chosen to be
representative of conditions in the environment. The natural variation in soils adds to the
uncertainty of modeled values. Factors such as application date, crop emergence date,
and canopy cover can also affect estimated concentrations, adding to the uncertainty of
modeled values. Factors within the ambient environment such as soil temperatures,
sunlight intensity, antecedent soil moisture, and surface water temperatures can cause
actual aquatic concentrations to differ for the modeled values.
Unlike spray drift, tools are currently not available to evaluate the effectiveness of a
vegetative setback on runoff and loadings. The effectiveness of vegetative setbacks is
highly dependent on the condition of the vegetative strip. For example, a well-
established, healthy vegetative setback can be a very effective means of reducing runoff
and erosion from agricultural fields. Alternatively, a setback of poor vegetative quality
or a setback that is channelized can be ineffective at reducing loadings. Until such time
as a quantitative method to estimate the effect of vegetative setbacks on various
conditions on pesticide loadings becomes available, the aquatic exposure predictions are
likely to overestimate exposure where healthy vegetative setbacks exist and
underestimate exposure where poorly developed, channelized, or bare setbacks exist.
In order to account for uncertainties associated with modeling, available monitoring data
were compared to PRZM/EXAMS estimates of peak EECs for the different uses. As
discussed above, several data values were available from NAWQA for myclobutanil, but
not the 1,2,4-triazole degradate, concentrations measured in surface waters receiving
runoff from agricultural areas. The specific use patterns (e.g. application rates and timing,
crops) associated with the agricultural areas are unknown, however, they are assumed to
122
-------
be representative of potential myclobutanil use areas. The l-in-10 year peak, and 21 and
60-day running mean concentrations (EECs) for myclobutanil and myclobutanil plus
1,2,4-triazole estimated by PRZM/EXAMS were all higher than the highest myclobutanil
concentration observed in the USGS NAWQA (0.51 |ig/L) monitoring data. The peak
myclobutanil plus 1,2, 4-triazole concentrations ranged between 5.1 and 61.4 |ig/L; the
21-day means ranged from 15.1 to 61.2 |ig/L and the 60-day mean ranged from 5.08 to
60.7 |ig/L, respectively. There are no detections of myclobutanil report in ground water
in the NAQWA studies.
Based upon the vapor pressure and Henry's Law Constant, the transport of myclobutanil
in the atmosphere vapor phase would not be expected. However, myclobutanil residues
have been detected in rain water. The study by Vogel et al., 2008 attributed the
myclobutanil to almonds. It is assumed that the reason for the detections are because
fungicides are typically applied to almonds trees my air blast or aerial spray (Mosz, 2002)
or that the myclobutanil is sorbed to wind blow soil particles.
6.1.3 Usage Uncertainties
County-level usage data were obtained from California's Department of Pesticide
Regulation Pesticide Use Reporting (CDPR PUR) database. Four years of data (2002 -
2005) were included in this analysis because statistical methodology for identifying
outliers, in terms of area treated and pounds applied, was provided by CDPR for these
years only. No methodology for removing outliers was provided by CDPR for 2001 and
earlier pesticide data; therefore, this information was not included in the analysis because
it may misrepresent actual usage patterns. CDPR PUR documentation indicates that
errors in the data may include the following: a misplaced decimal; incorrect measures,
area treated, or units; and reports of diluted pesticide concentrations. In addition, it is
possible that the data may contain reports for pesticide uses that have been cancelled.
The CPDR PUR data does not include home owner applied pesticides; therefore,
residential uses are not likely to be reported. As with all pesticide usage data, there may
be instances of misuse and misreporting. The Agency made use of the most current,
verifiable information; in cases where there were discrepancies, the most conservative
information was used.
6.1.4 Terrestrial Exposure Modeling of Myclobutanil
The Agency relies on the work of Fletcher et al. (1994) for setting the assumed pesticide
residues in wildlife dietary items. These residue assumptions are believed to reflect a
realistic upper-bound residue estimate, although the degree to which this assumption
reflects a specific percentile estimate is difficult to quantify. It is important to note that
the field measurement efforts used to develop the Fletcher estimates of exposure involve
highly varied sampling techniques. It is entirely possible that much of these data reflect
residues averaged over entire above ground plants in the case of grass and forage
sampling.
123
-------
It was assumed that ingestion of food items in the field occurs at rates commensurate
with those in the laboratory. Although the screening assessment process adjusts dry-
weight estimates of food intake to reflect the increased mass in fresh-weight wildlife food
intake estimates, it does not allow for gross energy differences. Direct comparison of a
laboratory dietary concentration- based effects threshold to a fresh-weight pesticide
residue estimate would result in an underestimation of field exposure by food
consumption by a factor of 1.25 - 2.5 for most food items.
Differences in assimilative efficiency between laboratory and wild diets suggest that
current screening assessment methods do not account for a potentially important aspect of
food requirements. Depending upon species and dietary matrix, bird assimilation of wild
diet energy ranges from 23 - 80%, and mammal's assimilation ranges from 41 - 85%
(U.S. Environmental Protection Agency, 1993). If it is assumed that laboratory chow is
formulated to maximize assimilative efficiency (e.g., a value of 85%), a potential for
underestimation of exposure may exist by assuming that consumption of food in the wild
is comparable with consumption during laboratory testing. In the screening process,
exposure may be underestimated because metabolic rates are not related to food
consumption.
For the terrestrial exposure analysis of this risk assessment, a generic bird or mammal
was assumed to occupy either the treated field or adjacent areas receiving a treatment rate
on the field. Actual habitat requirements of any particular terrestrial species were not
considered, and it was assumed that species occupy, exclusively and permanently, the
modeled treatment area. Spray drift model predictions suggest that this assumption leads
to an overestimation of exposure to species that do not occupy the treated field
exclusively and permanently.
6.1.5 Spray Drift Modeling
Although there may be multiple myclobutanil applications at a single site, it is unlikely
that the same organism would be exposed to the maximum amount of spray drift from
every application made. In order for an organism to receive the maximum concentration
of myclobutanil from multiple applications, each application of myclobutanil would have
to occur under identical atmospheric conditions (e.g., same wind speed and - for plants -
same wind direction) and (if it is an animal) the animal being exposed would have to be
present directly downwind at the same distance after each application. Although there
may be sites where the dominant wind direction is fairly consistent (at least during the
relatively quiescent conditions that are most favorable for aerial spray applications), it is
nevertheless highly unlikely that plants in any specific area would receive the maximum
amount of spray drift repeatedly. It appears that in most areas (based upon available
meteorological data) wind direction is temporally very changeable, even within the same
day. Additionally, other factors, including variations in topography, cover, and
meteorological conditions over the transport distance are not accounted for by the
AgDRIFT model (i.e., it models spray drift from aerial and ground applications in a flat
124
-------
area with little to no ground cover and a steady, constant wind speed and direction).
Therefore, in most cases, the drift estimates from AgDRIFT may overestimate exposure
even from single applications, especially as the distance increases from the site of
application, since the model does not account for potential obstructions (e.g., large hills,
berms, buildings, trees, etc.). Furthermore, conservative assumptions are often made
regarding the droplet size distributions being modeled (e.g.: 'ASAE Very Fine to Fine'
for all uses), the application method (e.g., aerial), release heights and wind speeds.
Alterations in any of these inputs would change the area of potential effect.
6.2 Effects Assessment Uncertainties
6.2.1 Age Class and Sensitivity of Effects Thresholds
It is generally recognized that test organism age may have a significant impact on the
observed sensitivity to a toxicant. The acute toxicity data for fish are collected on
juvenile fish between 0.1 and 5 grams. Aquatic invertebrate acute testing is performed on
recommended immature age classes (e.g., first instar for daphnids, second instar for
amphipods, stoneflies, mayflies, and third instar for midges).
Testing of juveniles may overestimate toxicity at older age classes for pesticide active
ingredients that act directly without metabolic transformation because younger age
classes may not have the enzymatic systems associated with detoxifying xenobiotics. In
so far as the available toxicity data may provide ranges of sensitivity information with
respect to age class, this assessment uses the most sensitive life-stage information as
measures of effect for surrogate aquatic animals, and is therefore, considered as
protective of the CRLF.
6.2.2 Use of Surrogate Species Effects Data
Guideline toxicity tests and open literature data on myclobutanil are not available for
frogs or any other aquatic-phase amphibian; therefore, freshwater fish are used as
surrogate species for aquatic-phase amphibians. Endpoints based on freshwater fish
ecotoxicity data are assumed to be protective of potential direct effects to aquatic-phase
amphibians including the CRLF, and extrapolation of the risk conclusions from the most
sensitive tested species to the aquatic-phase CRLF is likely to overestimate the potential
risks to those species. Efforts are made to select the organisms most likely to be affected
by the type of compound and usage pattern; however, there is an inherent uncertainty in
extrapolating across phyla. In addition, the Agency's LOCs are intentionally set very
low, and conservative estimates are made in the screening level risk assessment to
account for these uncertainties.
6.2.3 Sublethal Effects
When assessing acute risk, the screening risk assessment relies on the acute mortality
endpoint as well as a suite of sublethal responses to the pesticide, as determined by the
125
-------
testing of species response to chronic exposure conditions and subsequent chronic risk
assessment. Consideration of additional sublethal data in the effects determination t is
exercised on a case-by-case basis and only after careful consideration of the nature of the
sublethal effect measured and the extent and quality of available data to support
establishing a plausible relationship between the measure of effect (sublethal endpoint)
and the assessment endpoints. However, the full suite of sublethal effects from valid
open literature studies is considered for the purposes of defining the action area.
No sublethal effects related to this assessment were available in the open literature. To
the extent to which sublethal effects are not considered in this assessment, the potential
direct and indirect effects of myclobutanil on CRLF may be underestimated.
6.2.4 Location of Wildlife Species
For the terrestrial exposure analysis of this risk assessment, a generic bird or mammal
was assumed to occupy either the treated field or adjacent areas receiving a treatment rate
on the field. Actual habitat requirements of any particular terrestrial species were not
considered, and it was assumed that species occupy, exclusively and permanently, the
modeled treatment area. Spray drift model predictions suggest that this assumption leads
to an overestimation of exposure to species that do not occupy the treated field
exclusively and permanently.
6.2.5 Use of Surrogate Chemical Effects Data
Guideline toxicity tests and open literature data on myclobutanil were not available for
aquatic invertebrate (chronic exposure), aquatic vascular plants, or terrestrial plants. In
lieu of any myclobutanil data, toxicity data from other conazole (DMI triazole)
fungicides were used to characterize risk, assuming that myclobutanil toxicity is similar
to other conazoles due to similar mode of action. In so far as data from other conazoles
provides a range of sensitivity for conazole fungicides, there is considerable uncertainty
associated with extrapolating toxicity from other conazoles to myclobutanil. Thus, the
effects of myclobutanil cannot be quantified without data on myclobutanil toxicity to
aquatic invertebrates, aquatic vascular plants, and terrestrial plants.
7 Risk Conclusions
In fulfilling its obligations under Section 7(a)(2) of the Endangered Species Act, the
information presented in this endangered species risk assessment represents the best data
currently available to assess the potential risks of myclobutanil to the CRLF and its
designated critical habitat.
Based on the best available information, the Agency makes a "Likely to Adversely
Affect" determination for the CRLF from the use of myclobutanil. The Agency has also
determined that there is the potential for effects to CRLF designated critical habitat from
the use of the chemical. The CRLF and/or its critical habitat may be affected for all uses.
126
-------
This assessment indicates that direct effects to the terrestrial-phase CRLF eating small
herbivorous mammals on a dose-basis may be at risk following acute exposure to
myclobutanil at application rates of 0.12 Ib a.i./A and above (most crops and turf; cotton
seed treatment). In addition, the terrestrial-phase CRLF eating small invertebrates on a
dietary basis may be at risk for direct effects following chronic exposure to myclobutanil
applied to cotton (0.06 Ib a.i./cwt) and turf at 1.3 Ibs a.i./A. Direct effects on the aquatic-
phase CRLF are not expected.
Indirect effects to the terrestrial-phase CRLF, based on reduction in prey base may occur
with terrestrial phase amphibians on a dose-basis following acute exposure at application
rates of 0.12 Ib a.i./A and above (most crops, cotton and turf) and on a dietary-basis
following chronic exposure at an application rate of 1.3 Ibs a.i./A (turf) and when applied
to cotton (0.06 Ib a.i./cwt). Indirect effects (reduction in prey base) may also occur with
mammals following acute exposure on a dose-basis at application rates of 0.25 Ib a.i./A
and above (apple, apricot, cherry, nectarine, peach, hops and turf uses) and chronic
exposure on a dose-basis at application rates of 0.0625 Ibs a.i./A and above (e.g., all uses)
and on a dietary-basis of 0.25 Ibs a.i./A and above (apples, apricots, cherries, nectarines,
peaches, cotton and turf). Indirect effects to the aquatic-phase CRLF, based on reduction
in prey base are not expected. Minimal potential indirect impact to the CRLF via effects
of myclobutanil on terrestrial invertebrate food items is expected. No effects were
observed with aquatic non-vascular plants and with aquatic invertebrates following acute
exposure. No chronic data are available for aquatic invertebrates. The weight of the
evidence, including chronic data from similar conazole pesticides indicates that although
myclobutanil may affect the aquatic invertebrate population following chronic exposure,
it is not expected to adversely affect the population.
Indirect effects to both the aquatic- and terrestrial-phase CRLF based on aquatic and
riparian habitat, cover and/or primary productivity (e.g., effects on aquatic and terrestrial
plants) may occur due to potential effects on the riparian terrestrial plant community. As
stated previously, no effects were observed with aquatic non-vascular plants. No data are
available for either aquatic vascular or terrestrial plants. For aquatic vascular plants, the
weight of the evidence, including plant data from similar conazole pesticides indicates
that although there may be effects with some of the registered myclobutanil uses, adverse
affects are not expected. For terrestrial plants, weight of the evidence from information
provided in the open literature, incident data and the fact that surrogate data from similar
fungicides would exceed the terrestrial plant LOG for many of the myclobutanil uses, it is
determined that effects to terrestrial plants may affect the CRLF via habitat effects. Based
on potential effects to the avian/terrestrial-phase amphibian, mammalian and terrestrial
plant populations, there is a potential for habitat effects associated with all 4 of the
terrestrial-phase PCE's: elimination and/or disturbance of upland habitat and ability of
habitat to support food source of CRLFs, elimination and/or disturbance of dispersal
habitat, reduction and/or modification of food sources for terrestrial phase juveniles and
adults and alteration of chemical characteristics necessary for normal growth and
viability of juvenile and adult CRLFs and their food source.
127
-------
Given the LAA determination for the CRLF and potential effects to designated critical
habitat, a description of the baseline status and cumulative effects for the CRLF is
provided in Attachment 2.
The LAA effects determination applies to those areas where it is expected that the
pesticide's use will directly or indirectly affect the CRLF or its designated critical habitat.
To determine this area, the footprint of myclobutanil's use pattern is identified, using
corresponding land cover data. The spatial extent of the LAA effects determination also
includes areas beyond the initial area of concern that may be impacted by runoff and/or
spray drift. The identified direct and indirect effects and/or effects to critical habitat are
anticipated to occur only for those currently occupied core habitat areas, CNDDB
occurrence sections, and designated critical habitat for the CRLF that overlap with the
initial area of concern plus 158 feet from its boundary (see Section 5.1.4 for further
analysis). It is assumed that non-flowing waterbodies (or potential CRLF habitat) are
included within this area.
Appendix E provides maps of the initial area of concern, along with CRLF habitat areas,
including currently occupied core areas, CNDDB occurrence sections, and designated
critical habitat. It is expected that any additional areas of CRLF habitat that are located
158 ft (to account for offsite migration via spray drift) outside the initial area of concern
may also be impacted and are part of the full spatial extent of the LAA/effects to critical
habitat determination.
A summary of the risk conclusions and effects determinations for the CRLF and its
critical habitat, given the uncertainties discussed in Section 6, is presented in Table 7.1
and Table 7.2.
Table 7.1 Effects Determination Summary for Myclobutanil Use and the CRLF
Assessment
Endpoint
Effects
Determination 1
Basis for Determination
Survival, growth,
and/or reproduction
of CRLF
individuals
LAA1
Potential for Direct Effects
Aquatic-phase (Eggs, Larvae, and Adults):
Acute and chronic freshwater fish RQs are below the respective level of concern
(LOG) for all uses of myclobutanil.
Terrestrial-phase (Juveniles and Adults):
The acute avian LOG is exceeded at application rates of 0.12 Ib a.i./A and above
(most crops, cotton and turf). The highest probabilities of an individual effect
range from 1 in ~ 3.88E+02 to 1 in ~ 1. The chronic avian LOG is exceeded
following uses on cotton (0.06 Ib a.i./cwt) and turf at 1.3 Ibs a.i./A. Myclobutanil
uses overlap CRLF habitat.
Potential for Indirect Effects
Aquatic prey items, aquatic habitat, cover and/or primary productivity
Acute and chronic freshwater fish RQs are below the respective LOG for all uses
of myclobutanil.
128
-------
Assessment
Eiulpoint
Effects
Determination 1
Basis for Determination
Acute freshwater invertebrate RQs are below the LOG for all uses of
myclobutanil. No chronic freshwater invertebrate studies are available for
myclobutanil. Weight of the evidence from RQs based on myclobutanil EECs
and toxicity data from 9 other conazole fungicides indicates that minimal impact
is expected from chronic exposure to freshwater invertebrates as prey items.
Acute RQs for aquatic non-vascular plants for all uses of myclobutanil are below
the LOG. No aquatic vascular plant studies are available. Weight of the
evidence from RQs based on myclobutanil EECs and toxicity data from 7 other
conazole fungicides indicates minimal impact to the CRLF aquatic habitat, cover
and/or primary productivity.
Terrestrial prey items, riparian habitat
See description above for direct effects on birds as surrogate for terrestrial phase
amphibians. LOCs for listed mammals exceeded following acute exposure at
application rates of 0.25 Ib a.i./A and above and chronic exposure on at
application rates of 0.0625 Ibs a.i./A and above. Percent effect on mammalian
population is estimated to range from 4 - 42% for the myclobutanil uses.
Myclobutanil uses overlap CRLF habitat.
For terrestrial invertebrates, the honeybee acute contact data show no mortalities
at concentration levels up to and including 2836 ppm (highest level tested),
which is higher than highest dietary-based EEC for small insects with the use on
turf; however, there is some uncertainty for potential mortality. For large
invertebrates, there is no concern. Based on the results of the honey bee study
and weight of the evidence from open literature studies, indirect impact to the
CRLF via effects of myclobutanil on terrestrial invertebrate food items is
expected to be minimal.
No acceptable terrestrial plant studies are available. RQs based on EECs and
toxicity data from 5 other conazole fungicides indicate that most uses may affect
terrestrial plants, particularly dicots in semi-aquatic areas. Weight of the
evidence from these data, the open literature and incident reports indicates that
these effects may have an impact on riparian habitat.
1 No effect (NE); May affect, but not likely to adversely affect (NLAA); May affect, likely to adversely
affect (LAA)
Table 7.2 Effects Determination Summary for Myclobutanil Use and CRLF Critical
Habitat Impact Analysis
Assessment
Eiulpoint
Effects
Determination
Basis for Determination
Modification of
aquatic-phase PCE
Habitat Effects
Acute RQs for aquatic non-vascular plants for all uses of myclobutanil are below
the LOC.
No aquatic vascular plant studies are available. Weight of the evidence from
RQs based on myclobutanil EECs and toxicity data from 7 other conazole
fungicides indicates minimal impact to the CRLF aquatic habitat.
No acceptable terrestrial plant studies are available. RQs based on EECs and
toxicity data from 5 other conazole fungicides indicate that most uses may affect
129
-------
Assessment
Eiulpoint
Effects
Determination
Basis for Determination
terrestrial plants, particularly dicots in semi-aquatic areas. Weight of the
evidence from these data, the open literature and incident reports indicates that
these effects may have an impact on riparian habitat.
Acute and chronic freshwater fish RQs are below the respective level of concern
(LOG) for all uses of myclobutanil.
Indirect effects to the CRLF through effects to its prey in the aquatic habitat
(freshwater invertebrates) are expected to be minimal (see table 1.1).
Modification of
terrestrial-phase
PCE
No acceptable terrestrial plant studies are available. RQs based on EECs and
toxicity data from 5 other conazole fungicides indicate that most uses may affect
terrestrial plants, particularly dicots in semi-aquatic areas. Weight of the
evidence from these data, the open literature and incident reports indicates that
these effects may have an impact on riparian habitat.
The acute avian LOG is exceeded at application rates of 0.12 Ib a.i./A and above
(most crops, cotton and turf). The chronic avian LOG is exceeded following uses
on cotton (0.06 Ib a.i./cwt) and turf at 1.3 Ibs a.i./A.
LOCs for listed mammals exceeded following acute exposure on a dose-basis for
many crops and chronic exposure on a dose-basis for all uses and on a dietary-
basis for many crops.
For terrestrial invertebrates, the weight of the evidence indicates that minimal
potential indirect impact to the CRLF via effects on terrestrial invertebrate food
items is expected.
Based on the conclusions of this assessment, a formal consultation with the U. S. Fish
and Wildlife Service under Section 7 of the Endangered Species Act should be initiated.
When evaluating the significance of this risk assessment's direct/indirect and habitat
effects determinations, it is important to note that pesticide exposures and predicted risks
to the species and its resources (i.e., food and habitat) are not expected to be uniform
across the action area. In fact, given the assumptions of drift and downstream transport
(i.e., attenuation with distance), pesticide exposure and associated risks to the species and
its resources are expected to decrease with increasing distance away from the treated field
or site of application. Evaluation of the implication of this non-uniform distribution of
risk to the species would require information and assessment techniques that are not
currently available. Examples of such information and methodology required for this
type of analysis would include the following:
• Enhanced information on the density and distribution of CRLF life stages within
specific recovery units and/or designated critical habitat within the action area.
This information would allow for quantitative extrapolation of the present risk
assessment's predictions of individual effects to the proportion of the population
extant within geographical areas where those effects are predicted. Furthermore,
such population information would allow for a more comprehensive evaluation of
the significance of potential resource impairment to individuals of the species.
130
-------
• Quantitative information on prey base requirements for individual aquatic- and
terrestrial-phase frogs. While existing information provides a preliminary picture
of the types of food sources utilized by the frog, it does not establish minimal
requirements to sustain healthy individuals at varying life stages. Such
information could be used to establish biologically relevant thresholds of effects
on the prey base, and ultimately establish geographical limits to those effects.
This information could be used together with the density data discussed above to
characterize the likelihood of adverse effects to individuals.
• Information on population responses of prey base organisms to the pesticide.
Currently, methodologies are limited to predicting exposures and likely levels of
direct mortality, growth or reproductive impairment immediately following
exposure to the pesticide. The degree to which repeated exposure events and the
inherent demographic characteristics of the prey population play into the extent to
which prey resources may recover is not predictable. An enhanced understanding
of long-term prey responses to pesticide exposure would allow for a more refined
determination of the magnitude and duration of resource impairment, and together
with the information described above, a more complete prediction of effects to
individual frogs and potential effects to critical habitat.
131
-------
8 References
Alvarez, J. 2000. Letter to the U.S. Fish and Wildlife Service providing comments on
the Draft California Red-legged Frog Recovery Plan.
Altig, R. and R.W. McDiarmid. 1999. Body Plan: Development and Morphology. In
R.W. McDiarmid and R. Altig (Eds.), Tadpoles: The Biology of Anuran Larvae.
University of Chicago Press, Chicago, pp. 24-51.
Fellers, G.M, L.L. McConnell, D. Pratt, S. Datta. 2004. Pesticides in Mountain Yellow-
Legged Frogs (Rana Mucosa) from the Sierra Nevada Mountains of California,
USA. Environmental Toxicology & Chemistry 23 (9):2170-2177.
Fellers, Gary M. 2005a. Rana draytonii Baird and Girard 1852. California Red-legged
Frog. Pages 552-554. In: M. Lannoo (ed.) Amphibian Declines: The Conservation
Status of United States Species, Vol. 2: Species Accounts. University of
California Press, Berkeley, California, xxi+1094 pp.
(http://www.werc.usgs.gov/pt-reyes/pdfs/Rana%20draytonii.PDF)
Fellers, Gary M. 2005b. California red-legged frog, Rana draytonii Baird and Girard.
Pages 198-201. In: L.L.C. Jones, et al (eds.) Amphibians of the Pacific Northwest.
xxi+227.
Fletcher, J.S., I.E. Nellesson, and T. G. Pfleeger. 1994. Literature review and evaluation
of the EPA food-chain (Kenaga) nomogram, an instrument for estimating
pesticide residues on plants. Environ. Tox. and Chem. 13(9):1383-1391.
Hayes, M. P. and M. R. Jennings. 1988. Habitat correlates of distribution of the
California redlegged frog (Rana aurora draytonii) and the foothill yellow-legged
frog (Rana boylii): Implications for management. Pages 144-158 In: R. Sarzo, K.
E. Severson, and D. R. Patton (technical coordinators). Proceedings of the
Symposium on the Management of Amphibians, Reptiles, and small mammals in
North America. U.S.D.A. Forest Service General Technical Report RM-166.
Hayes, M.P. and M.M. Miyamoto. 1984. Biochemical, behavioral and body size
differences between Rana aurora aurora and R. a. draytonii. Copeia 1984(4):
1018-22.
Hayes and Tennant. 1985. Diet and feeding behavior of the California red-legged frog.
The Southwestern Naturalist 30(4): 601-605.
Hoerger, F. and E.E. Kenaga. 1972. Pesticide residues on plants: correlation of
representative data as a basis for estimation of their magnitude in the
environment. IN: F. Coulston and F. Corte, eds., Environmental Quality and
Safety: Chemistry, Toxicology and Technology. Vol 1. George Theime
Publishers, Stuttgart, Germany, pp. 9-28.
132
-------
Jennings, M.R. and M.P. Hayes. 1985. Pre-1900 overharvest of California red-legged
frogs (Rana aurora draytonii): The inducement for bullfrog (Rana catesbeiana)
introduction. Herpetological Review 31(1): 94-103.
Jennings, M.R. and M.P. Hayes. 1994. Amphibian and reptile species of special concern
in California. Report prepared for the California Department of Fish and Game,
Inland Fisheries Division, Rancho Cordova, California. 255 pp.
Jennings, M.R., S. Townsend; R.R. Duke. 1997. Santa Clara Valley Water District
California red-legged frog distribution and status - 1997. Final Report prepared
by H.T. Harvey & Associates, Alviso, California. 22 pp.
Kupferberg, S. 1997. Facilitation of periphyton production by tadpole grazing: Functional
differences between species. Freshwater Biology 37:427-439.
Kupferberg, S.J., J.C. Marks and M.E. Power. 1994. Effects of variation in natural algal
and detrital diets on larval anuran (Hyla regilla) life-history traits. Copeia 1994:
446-457.
LeNoir, J.S., L.L. McConnell, G.M. Fellers, T.M. Cahill, J.N. Seiber. 1999.
Summertime Transport of Current-use pesticides from California's Central Valley
to the Sierra Nevada Mountain Range,USA. Environmental Toxicology &
Chemistry 18(12): 2715-2722.
McConnell, L.L., J.S. LeNoir, S. Datta, J.N. Seiber. 1998. Wet deposition of current-use
pesticides in the Sierra Nevada mountain range, California, USA. Environmental
Toxicology & Chemistry 17(10):1908-1916.
Mosz, N. 2002. Almond Timeline. Biological and Economic Assessment Branch. Office
of Pesticide Programs. United States Environmental Protection Agency.
Rathburn, G.B. 1998. Rana aurora draytonii egg predation. Herpetological Review,
29(3): 165.
Reis, D.K. 1999. Habitat characteristics of California red-legged frogs (Rana aurora
draytonii): Ecological differences between eggs, tadpoles, and adults in a coastal
brackish and freshwater system. M.S. Thesis. San Jose State University. 58 pp.
Sparling, D.W., G.M. Fellers, and L.L. McConnell. 2001. Pesticides and amphibian
population declines in California, USA. Environmental Toxicology & Chemistry
20(7): 1591-1595.
Seale, D. B., and N. Beckvar. 1980. The comparative ability of anuran larvae (genera:
Hyla, Bufo, and Rana) to ingest suspended blue-green algae. Copeia 1980: 495-
503
133
-------
Urban, DJ. and NJ. Cook. 1986. Hazard Evaluation Division Standard Evaluation
Procedure Ecological Risk Assessment. EPA 540/9-85-001. U.S. Environmental
Protection Agency, Office of Pesticide Programs, Washington, DC.
U.S. EPA. 1998. Guidance for Ecological Risk Assessment. Risk Assessment Forum.
EPA/630/R-95/002F, April 1998.
U.S. EPA. 2002. Guidance for Selecting Input Parameters in Modeling the
Environmental Fate and Transport of Pesticides. Version II February 28, 2002.
http://www.epa.gov/oppefedl/models/water/input guidance2 28 02.htm. U.S.
Environmental Protection Agency, Office of Pesticide Programs, Environmental
Fate and Effects Division. Arlington, VA.
U.S. EPA. 2004. Overview of the Ecological Risk Assessment Process in the Office of
Pesticide Programs. Office of Prevention, Pesticides, and Toxic Substances.
Office of Pesticide Programs. Washington, D.C. January 23, 2004.
U.S. EPA. 2006a. Memorandum: 1,2,4-Triazole, Triazole Alaline, Triazole Acetic Acid:
Human Health Aggregate Risk Assessment in Support of Reregi strati on and
Registration Actions for Triazole-derivative Fungicide Compounds. Date:
02/07/06. DP Barcode 322215. U.S. Environmental Protection Agency, Office of
Pesticide Programs, Environmental Fate and Effects Division and Health Effects
Division. Arlington, VA.
U.S. EPA. 2006b. Memorandum: 1,2,4-Triazole, Triazole Alaline, Triazole Acetic Acid:
Drinking Water Assessment in Support of Reregi strati on and Registration Actions
for Triazole-derivative Fungicide Compounds. Date: 02/28/06. DP Barcode
320682. U.S. Environmental Protection Agency, Office of Pesticide Programs,
Environmental Fate and Effects Division and Health Effects Division. Arlington,
VA.
U.S. EPA. 2007. Mycobutanil. Ecological Risk Assessment on New Uses for Tropical
Fruit, Fruiting Vegetables and Artichokes [D336613] (10/12/07). U.S.
Environmental Protection Agency, Office of Pesticide Programs, Environmental
Fate and Effects Division and Health Effects Division. Arlington, VA.
U.S. Fish and Wildlife Service (USFWS). 1996. Endangered and threatened wildlife and
plants: determination of threatened status for the California red-legged frog.
Federal Register 61(101):25813-25833.
USFWS. 2002. Recovery Plan for the California Red-legged Frog (Rana aurora
draytonif). Region 1, USFWS, Portland, Oregon.
(http://ecos.fws.gov/doc/recovery_plans/2002/020528.pdf)
134
-------
USFWS. 2006. Endangered and threatened wildlife and plants: determination of critical
habitat for the California red-legged frog. 71 FR 19244-19346.
USFWS. Website accessed: 30 December 2006.
http://www.fws.gov/endangered/features/rl_frog/rlfrog.html #where
U.S. Fish and Wildlife Service (USFWS) and National Marine Fisheries Service
(NMFS). 1998. Endangered Species Consultation Handbook: Procedures for
Conducting Consultation and Conference Activities Under Section 7 of the
Endangered Species Act. Final Draft. March 1998.
USFWS/NMFS. 2004. 50 CFR Part 402. Joint Counterpart Endangered Species Act
Section 7 Consultation Regulations; Final Rule. FR 47732-47762.
USGS. 2001. J. Bloomquist, J. Denis, J. Cowles, J. Hetrick, R. Jones, andN. Birchfield.
Pesticides in Selected Water-Supply Reservoirs and Finished Drinking Water,
1999-2000: Summary of Results from a Pilot Monitoring Program. Open File
Report 01-456.
USGS/NAWQA. 1999. The Quality of Our Nation's Waters. Nutrients and Pesticides.
Circular 1225.
USGS/NAWQA Monitoring Data. 2009. NAWQA Data Warehouse.
http://infotrek.er.usgs.gov/traverse/f?p=NAWQA:HOME:2314757460620449
Vogel, J.R., M.S. Majewski, and P.O. Capel., 2008. Pesticides in Rain in Four
Agricultural Watersheds in the United States. J. Env. Qual. 37:1101-1115.
Wassersug, R. 1984. Why tadpoles love fast food. Natural History 4/84.
135
------- |