# 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., E nvironmental Scientist Michael Lowit, Ph.D., Ecologist Rebecca Daiss, M.S., Biologist

Secondary Review: Pamela M. Hurley, Ph.D., Toxicologist James Hetrick, Ph.D., Se nior Science Advisor

Branch Chief, Environmental Risk Assessment Branch 3: Dana Spatz

2Table 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

34.2.3 Toxicity to Terrestrial Invertebrates ............................................................. 87 4.2.4 Toxicity to Terrestrial Plants ........................................................................ 87 4.3 Use of Probit Slope Response Relation ship 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 5 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 Re ductions 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
6 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 Myclobutanil ........................................ 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 7 Risk Conclusions ............................................................................................ 126 8 References ....................................................................................................... 132

4List 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 Determinations 1 for the CRLF ....... 15
Table 1.4 Myclobutanil Use-specific I ndirect Effects Determinations 1 Based on Effects to Prey ................................................................................................................. 16
Table 2.1 Summary of Myclobutanil and 1,2,4-tr iazole 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 Habitat a ...................... 43
Table 3.1 Summary of PRZM and EXAMS Environmental Fate Data Used for Aquatic Exposure Inputs for Myclobut anil and Myclobutanil pl us 1,2,4-triazole for Endangered Species Assessment for the CRLF 1 ........................................... 57
Table 3.2 Myclobutanil results from the summar y of analysis of moderate-use pesticides and degradates in water samples fromwater supply intakes and finishedsupply taps in Reservoir Pilo t Monitoring Progr am. (USGS, 2001) .............. 58
Table 3.3 Distribution of Myclobutanil Concen trations (μg/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 (μg/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 st andard farm pond (USEPA, 2007) ........................ 64
Table 3.8 Input Parameters for Foliar Applica tions 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

5Table 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 EEC s for Plants Inhabiting Dry and Semiaquatic Areas Exposed to Myclobutanil via Runoff and Drift ....................... 68
Table 4.1 Freshwater Aquatic To xicity Profile for Myclobutanil .................................... 71
Table 4.2 Categories of Acute Toxicity for Fish and Aquatic Invertebrates .................... 72
Table 4.3 Conazole (DMI triazo le) Fungicide Chronic Toxicity to Aquatic Invertebrates ......................................................................................................................... 75
Table 4.4 Conazole (DMI Triazole) Fungici de Toxicity to Aquatic Vascular Plants ..... 76
Table 4.5 Terrestrial Toxicity Profile for Myclobutanil ................................................... 77
Table 4.6 Categories of Acute Toxic ity 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 Compar ison 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 Dire ct Effect RQs for the Aquatic-phase CRLF ......................................................................................................................... 92
Table 5.2 Summary of Acute and Chronic RQs Us ed to Estimate Indirect Effects to the CRLF via Direct Effects on Aquatic Inve rtebrates as Dietary Food Items (prey of CRLF juveniles and adu lts in aquatic habitats) .......................................... 94
Table 5.3 Summary of Acute RQs Used to Es timate Direct Effect s to the Terrestrialphase CRLF (non-granular application) ......................................................... 95
Table 5.4 Summary of Acute RQs Used to Esti mate Direct Effects to the Terrestrialphase CRLF (granular application) ................................................................. 96
Table 5.5 Summary of Chroni c RQs Used to Estimate Direct Effects to the Terrestrialphase 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 E ffects on Small Mammals as Dietary Food Items (non-granular application) ........................................................... 98
Table 5.7 Summary of Acute RQs Used to Esti mate Indirect Effects to the Terrestrialphase CRLF via Direct Effects on Sm all Mammals as Dietary Food Items (granular application) ...................................................................................... 98
Table 5.8 Risk Estimation Summary for Myclobu tanil - Direct and Indirect Effects to CRLF ............................................................................................................. 102

6Table 5.9 Risk Estimation Summary for Mycl obutanil – 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 Co mbined with Endpoints from 5 Triazole DMI Fungicides Exceeding the Terrestr ial Plant LOC for Listed and NonListed 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 Dist ances for Potential Spray Drift Effects ....................................................................................................................... 118

Table 7.1 Effects Determination Summa ry for Myclobutanil Use and the CRLF ........ 128
Table 7.2 Effects Determination Summary for Myclobutanil Use and CRLF Critical Habitat Impact Analysis ................................................................................ 129

7List of Figures

Figure 2.1 Myclobutanil Degradates ................................................................................. 24
Figure 2.2 Myclobutanil Terr estrial Plant Metabolite ...................................................... 24
Figure 2.3 Map of Estimated Annual Ag ricultural Use of Myclobutanil in 2002 ............ 28
Figure 2.4 Recovery Unit, Core Area, Critical Habitat and Occurre nce Designations for CRLF ............................................................................................................... 32
Figure 2.5 CRLF Reproductive Events by Month ............................................................ 33
Figure 2.6 Initial Area of Concern of “foot print” 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 Myclobutan il Effects on Aquatic Phase of the CRLF 46
Figure 3.1 Summary of Applicat ions (pounds versus date) of Myclobutanil to Grapes in 2001 from CDPR PUR Data. .......................................................................... 53
Figure 3.2 Accumulation of PRZM/EXAM S 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 a nd Myclobutanil Initial Area of Concern .... 120

8Appendices

Appendix A Multi-ai Product Analysis Appendix B Aquatic Exposure Modeling Appendix C Environmental Fate Data Appendix D BEAD Analysis of CDPR PUR Database Appendix E CRLF – Spatial Summary Appendix F The Risk Quotient Method and Levels of Concern Appendix G T-REX Example Output Appendix H Bibliography of ECOTOX Open Literature Appendix I Accepted ECOTOX Data Table Appendix J HED Effects Table Appendix K Ecotoxicity Data Appendix L Incident Data Appendix M T-HERPS Example Output Appendix N Terrplant Example Output Appendix O Ecotoxicity and Envi ronmental Fate Bibliography Attachment 1. Status and Life History of the California Red-legged Frog Attachment 2. Baseline Status and Cumulativ e Effects for the California Red-legged Frog

9

### 1 Executive Summary

The purpose of this assessment is to evaluate potential direct and i ndirect 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 evaluate s 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 co astal 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, de wberry, 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 youngbe rry. Non-food/non-feed us es include bluegrass, commercial/industrial lawns, cotton (seed), Doug las Fir (seed orchard, shelter belt), golf course turf, grasses grown for seed, hybrid cottonwood/poplar plantations, loblolly pine (forest), ornamental and shade trees, orna mentals (ground cover, herbaceous plants, lawns and turf, non-flowering plants, sod farm (turf), woody shrubs and vines), residential lawns and slash pine forest. Grap es, apples, almonds, a nd cherries together make up 80% of all labeled uses of myclobutanil in California.

Myclobutanil is stable to both hydrolysis and photolysis. Myclobut anil degradation is controlled by microbial-mediated transformatio ns. Myclobutanil is moderately persistent to persistent (DT 50 > 70 days) in aerobic soils and persis tent in anaerobic soils. The major degradation products observed in the aerobi c soil metabolism (ASM) studies are 1,2,4- triazole (maximum 18%), CO 2 , a polar degradate ( β -4-chlorophenyl- β -cyano- γ -(1H1,2,4-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 iden tified as 1,2,4-triazole. Once the maximum level of 1,2,4-triazole is reached, its declin e pattern parallels myclobutanil. Terrestrial field dissipation half-life va lues range from 92 to 292 days. Because the myclobutanil residues are fairly persistent, the potential to remain in soil is possible, especially when

10there are multiple applications. Fate studi es for 1,2,4-triazole suggest aerobic soil metabolism half-lives ra nging from 22 to 375 days.

In addition to 1,2,4-triazole, plant and anim al 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 K ads values (from 1.46 to 9.77 mL/g). The degradate (1,2,4-tri azole) has lower Freundlich K ads 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 primar y routes of dissipat ion are thought to be through leaching, runoff, and spray drift. Th e limited monitoring data for myclobutanil shows detected myclobutanil residues in surf ace water in California, but not in ground water. Myclobutanil was also found in rainwate r in a California watershed, suggesting the occurrence of atmospheric transport.

Since CRLFs exist within aquatic and terrestria l habitats, exposure of the CRLF, its prey and its habitats to myclobutanil are assesse d separately for the two habitats. Tier-II aquatic exposure models are used to estim ate high-end exposures of myclobutanil in aquatic habitats resulting from runoff and spray drift from different uses. The aquatic assessment quantitatively considers exposur e from parent myclobutanil as well as exposure from myclobutanil and the degradati on product 1,2,4-triazole. 1,2,4-triazole is a major degradation product that is slowly fo rmed from biodegradat ion under aerobic and anaerobic conditions in soil. The 1,2,4-triazole’s pe rsistence appears to be equal to or less than that of the parent myclobutanil, a nd it is more mobile. Peak model-estimated environmental concentrations in surface wate r resulting from different myclobutanil uses range from 2.1 to 61.4 μg/L. These estimates ar e 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 μg/L. This value is approximately 120 times less than the ma ximum model-estimated environmental concentration. There were no detections of myclobutanil reported in the California Department of Pesticide Regula tion surface water database.

To estimate myclobutanil exposures to the terre strial-phase CRLF, and its potential prey resulting from uses involving myclobutanil a pplications, the T-REX model is used for foliar, granular and cotton seed treatment us es. The AgDRIFT model is also used to estimate deposition of myclobutanil on terrestria l and aquatic habitats from spray drift. Due to lack of terrestrial plant data for mycl obutanil, the TerrPlant model is used for risk description purposes using pl ant 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

11for poikilotherms using the same basic pr ocedure 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 th e CRLF itself, as well as indirect effects, such as reduction of the prey base or potential effects to its critical ha bitat. 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 a quatic-phase amphibians. In the terrestrial habitat, direct effects are ba sed 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 invertebra tes 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 consid ering 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 ob served in environmental fate studies is 1,2,4-triazole. The Office of Pesticide Progr am’s Health Effects Division (HED) has conducted aggregate human health risk a ssessments for 1,2,4-triazole and triazole conjugates (triazole alanine and triazole ace tic 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 th e triazoles (a.k.a. triazole-derivative fungicides, T-D fungicides, conazoles). These compounds all ha ve 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 al anine and triazole acetic acid). Mammalian toxicity data on the degradates and/or a structure-activity an alysis on degradates with no toxicity data indicate that they are either equivale nt to or less toxic than the parent.

Risk quotients (RQs) are derived as quantita tive 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 wi thin the action area ha s the potential to adversely affect the CRLF and its designated critical habitat via direct toxicity or indirectly based on direct eff ects to its food supply (i.e., freshwater invertebrates, algae, fish, frogs, terrestrial inverteb rates, and mammals) or hab itat (i.e., aquatic plants and terrestrial upland and riparian vegetation). Wh en 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 adve rse effects is identified, leading to a conclusion of “may affect.” If a determin ation 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 poten tial for exposure and e ffects, and the best available information is used to distinguish those actions that “may affect, but are not

12likely to adversely affect” (NLAA) from those actions that are “likely to adversely affect” (LAA) the CRLF.

Based on the best available information, th e 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 poten tial for effects to CRL F 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 terr estrial-phase CRLF may be at risk following consumption of small herbivorous mammals ( acute exposure: most crop uses, cotton and turf) and small insects (chroni c exposure: cotton and turf uses). Direct effects on the aquatic-phase CRLF are not expected. Indirect effects to the terre strial-phase CRLF, based on reduction in prey base may occur with terrestrial phase amphibians following acute exposure (most crops, co tton and turf) and chronic expo sure (turf and cotton) and with mammals following acute exposure (app le, apricot, cherry, nectarine, peach, hops and turf uses) and chronic e xposure (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 aq uatic and riparian ha bitat, cover and/or primary productivity may occur due to potential effect s on the riparian terrestrial plant community, particularly dicots in semi-aquatic areas (all uses). Direct effects on aquatic plant habitat are not expecte d. Based on potential effects to the avian/terrestrial-phase amphibians, mammals and terrestrial plants, ther e 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 stat us 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

Potential for Direct Effects Aquatic-phase (Eggs, Larvae, and Adults) :

Acute and chronic freshwater fish RQs are below the respective level of concern (LOC) for all uses of myclobutanil.

Terrestrial-phase (Juveniles and Adults) :

The acute avian LOC is exceeded at applic ation rates of 0.12 lb 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 LOC is exceeded following uses on cotton (0.06 lb a.i./cwt) and turf at 1.3 lbs a.i./A. Myclobutanil uses overlap CRLF habitat.

Potential for Indirect Effects Survival, growth, and/or reproduction of CRLF individuals LAA 1

Aquatic prey items, aquatic habitat, cover and/or primary productivity

Acute and chronic freshwater fish RQs ar e below the respective LOC for all uses

13Assessment Endpoint Effects Basis for Determination Determination 1 of myclobutanil.

Acute freshwater invertebrate RQs are below the LOC 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 LOC. No aquatic vascular plant st udies 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 lb a.i./A and above and chronic exposure at application rates of 0.0625 lbs 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-base d 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 terr estrial invertebrate food items is expected to be minimal.

No acceptable terrestrial plant studies ar e 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 av ailable. 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 ar e available. RQs based on EECs and toxicity data from 5 other conazole fungicides indicate that most uses may affect

14Assessment Endpoint Effects Basis for Determination 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 ar e below the respective levels of concern (LOC) for all uses of myclobutanil.

Indirect effects to the CRLF through eff ects 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 ar e 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 LOC is exceeded at applic ation rates of 0.12 lb a.i./A and above (most crops, cotton and turf). The chroni c avian LOC is exceeded following uses on cotton (0.06 lb a.i./cwt) and turf at 1.3 lbs a.i./A.

LOCs for endangered species exceeded follo wing 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 Determinations 1 for the CRLF

Aquatic Habitat Terrestrial Habitat Use(s) Acute Chronic Acute Chronic All uses NE NE - - All uses except artichoke, boysenberry, dewberry, youngberry, grape and tomato - - LAA - Artichoke, boysenberry, dewberry, youngberry, grape and tomato - - NE -

Cotton and turf

- - - LAA All uses except cotton and turf

- - - NE

1 NE = No effect; NLAA = May affect, but not likely to adversely affect; LAA = Likely to adversely affect

15Table 1.4 Myclobutanil Use-specific Indirect Effects Determinations 1 Based on Effects to Prey

Aquatic Invertebrates Aquatic-phase frogs and fish Terrestrialphase frogs Small Mammals Use(s) Algae
Acute Chronic Terrestrial Invertebrates (Acute) Acute Chronic Acute Chronic Acute Chronic

All uses NE NE NLAA NLAA NE NE - - - LAA
Footnote 2

- - - - - - LAA - - - Cotton, turf

- - - - - - - LAA - - Footnote 3

- - - - - - - - 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 Secti on 7 of the Endangered Species Act should be initiated.

When evaluating the significance of this ri sk assessment’s direct/indirect and habitat effects determinations, it is important to not e that pesticide exposur es 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 a ssumptions of drift and downstream transport (i.e., attenuation with distance), pesticide e xposure and associated ri sks to the species and its resources are expected to decrease with in creasing 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 informa tion and assessment techniques that are not currently available. Examples of such in formation 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 pred ictions of individual effects to the proportion of the population extant with in geographical areas where those effects are predicted. Furthermore, such population information would allow for a more comprehensive eval uation of the significance of potential resource impairment to individuals of the species.

• Quantitative information on prey base requirements for individual aquaticand terrestrial-phase frogs. Wh ile existing information provides a preliminary picture of the types of food sources util ized by the frog, it does not establish minimal requirements to sustain healthy individuals at varying life stages. Such informa tion could be used to establish biologically relevant thresholds of ef fects 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

16and likely levels of direct mortalit y, 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 ex tent to which prey resources may recover is not predictable. An e nhanced 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 descri bed 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 st ages, 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 Ecol ogical Risk Assessment (U.S. EPA 1998), the Services’ Endangered Species Consul tation 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 assessme nt is to evaluate potential direct and indirect effects on individuals of the fede rally threatened California red-legged frog ( Rana aurora draytonii ) (CRLF) arising from FIFRA regul atory actions regarding use of myclobutanil on almond, asparagus, canistel, cotton, grapes, hops, mamey (mamme apple), okra, peppermint, sapodilla, sapote whit e, spearmint, star apple, strawberry, and selected crops from the following crop groups: root and tuber; leaf y, legume and fruiting vegetables; cucurbits; pome, stone and tropi cal fruits and berries. Non-food/non-feed uses include bluegrass and grasses grown fo r seed, various lawn and turf uses, cotton (seed), Douglas Fir (seed orchard, shelter belt), hybrid cottonwood/ poplar plantations, loblolly and slash pine fore st, ornamental and shade tree s, ornamentals, woody shrubs and vines. In addition, this assessment eval uates whether use on these crops is expected to result in effects to the species’ designate d 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 Calif ornia on October 20, 2006.

In this assessment, direct a nd indirect effects to the CRLF and potential effects to its designated critical habitat ar e 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-RE X, 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

17such information is consistent with the methodology described in the Overview Document (U.S. EPA 2004), wh ich specifies that “the a ssessment process may, on a case-by-case basis, incorporat e 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 a ssessment of effects associated with registrations of myclobutanil is based on an action area. The acti on area is the area directly or indirectly affect ed by the federal action. It is acknowledged that the action area for a national-level FIFRA regulatory deci sion associated with a use of myclobutanil may potentially involve numerous areas throughout the United St ates and its Territories. However, for the purposes of this assessment, attention will be focused on relevant sections of the action area including those ge ographic areas associated with locations of the CRLF and its designated critical habitat with in 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 phys ical and biological features, (known as primary constituent elem ents or PCEs) essential to the conservation of the listed species. The PCEs for CRLFs ar e aquatic and upland areas where suitable breeding and non-breeding aquatic habitat is located, interspe rsed with upland foraging and dispersal habitat.

If the results of initial scr eening-level assessment methods show no direct or indirect effects (no LOC exceedances) upon individual CRL Fs 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 crit ical habitat. If, howev er, potential direct or indirect effects to individual CRLFs are anticip ated or effects may impact the PCEs of the CRLF’s designated critical habita t, a preliminary “may affect” determination is made for the FIFRA regulatory acti on regarding myclobutanil.

If a determination is made that use of my clobutanil within the acti on area(s) associated with the CRLF “may affect” this species or its designated critical habitat, additional information is considered to refine the poten tial for exposure and fo r effects to the CRLF and other taxonomic groups upon which these sp ecies depend (e.g., aquatic and terrestrial vertebrates and invertebrates, aquatic plan ts, riparian vegetation, etc.). Additional information, including spatial analysis (to de termine the geographical proximity of CRLF habitat and myclobutanil use sites) and furt her 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 info rmation, the Agency uses the best available information to distinguish those actions that “may affect, but are not likely to adversely

18affect” from those actions that “may affect and are likely to adversely affect” the CRLF. This information is presented as part of th e Risk Characterization in Section 5 of this document.

The Agency believes that the analysis of di rect and indirect eff ects to listed species provides the basis for an analys is 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 fo r 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 bi ological 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 ma y affect critical habitat are t hose 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 CRL F’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 discus sed further in Section 2.6.

2.2 Scope

The fungicide, myclobutanil is currently registered for both agricultural and nonagricultural 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 la bel 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), accepta ble methods of application, approved use sites, and any rest rictions 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 ecol ogical 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 de signated critical habitat. Fu rther discussion of the action area for the CRLF and its critical ha bitat is provided in Section 2.7.

1,2,4-triazole and its conjugate s are common metabolites to the triazole class of compounds, including myclobutanil. Only the 1,2,4-triazole degradat e was identified in soil and water metabolism studies. The percen tage of 1,2,4-triazole reached a high of 18% in the aerobic soil metabo lism study with 13 % remaini ng 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 mycl obutanil 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-triazo le is less than or equal to the toxicity of myclobutanil.

19For the terrestrial exposure assessment, a conservative default foliar dissipation half-life of 35 days is used to account for terrestri al exposure to the pare nt, the primary plant metabolite RH-9090, the 1,2,4-triazole degradate and the triazole conjugates (triazole alanine and triazole acetic acid). Crop-speci fic 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 av ailable 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 indi cate 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 ev aluation of mixtures of active ingredients, either those mixtur es of multiple active ingredients in product formulations or those in the applicator’s ta nk. In the case of the product formulations of active ingredients (that is, a registered product containing mo re than one active ingredient), each active ingredient is subj ect 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 contai ning 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 cont ain multiple active ingredients. Analysis of the available open literature and acute oral mammalian LD 50 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 myclobut anil is appropriate. All pr oducts with available acute toxicity data had oral LD 50 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 assu mption of dose-addition would be inappropriate. Consequently, an assessment based on the toxicity of myclobutanil is the only reasonable approach th at 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 reregistration process. Myclobutanil has b een 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 (acu te), marine/estuarine invertebrates (acute), birds (acute and chronic), and mammals (a cute and chronic) depending on the use patterns and application rates. To date, no data on toxicity of myclobutanil to terrestrial plants, aquatic vascular plan ts, and chronic exposure to i nvertebrates (freshwater and marine/estuarine) or marine/estuarine fish have been submitted to the Agency for review and so risk has not been assessed quantitativel y. Furthermore, certain toxicity data were not available (e.g. chronic exposure to birds and acute exposure to marine/estuarine organisms (fish and invertebrates) and aqua tic non-vascular plants) at the time when

20some 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 propertie s of myclobutanil are summarized below.

Common name: Myclobutanil

Chemical name: (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: Cl

N

N N

CH

3 CN

Molecular formula C 15 H 17 ClN 4 Molecular weight 288.8 g/mol
Physical state: White crystalline solid
Melting point: 63 to 68 oC

Solubility: 142 mg/L water @ 25 oC and pH 7 124 mg/L @ 20 oC
Vapor pressure 1.49 x 10 -06 mm Hg at 25 oC

Henry’s Law constant 3.25 x 10 -06 atm m 3 /mole @ 25 oC

1.75 x 10 -07 unitless @ 20 oC
Log Octanol/Water partition coefficient: 2.89 @ pH 7 and 20 oC

Dissociation Constant, (pKa) 2.3 @ 25 oC

212.4.2 Environmental Fate Assessment
Available environmental fate parameters of myclobutanil and 1,2,4-tr iazole degradate are listed in Table 2.1. These data are based on studies that were conducted prior to 1986 before Good Laboratory Practice (GLP) sta ndards (40 CFR 160) and data requirements for registration were promulgated in the C ode of Federal Regulations (40 CFR 158). The previously submitted studies have not been re-reviewed, although rate of degradation (i.e., half-life) of myclobutan il in the aerobic soil meta bolism study was re-estimated.

Due to its persistence and mobility, the pr imary routes of dissipation are through leaching, runoff, and spray drift. Myclobutanil has been detected in rain in several agricultural watersheds in Calif ornia (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 (DT 50 > 70 days) in aerobic soils and persistent in anaerobic soils. The majo r degradation products observed in the aerobic soil metabolism (ASM) studies were 1,2,4-triazole (maximum 18%), CO 2 , a polar degradate ( β -4-chlorophenyl- β -cyano- γ -(1H-1,2,4-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 in itial decline followed by a slow er decline), thus the firstorder half-life does not accura tely describe the decline of myclobutanil residues. The observed (visible inspecti on) aerobic metabolism DT 50 value for myclobutanil ranged between 75 and 90 days. The DT 90 for myclobutanil was not reached during the course of the study (367 days). Once the maximum leve l of 1,2,4-triazole is reached, its decline pattern parallels myclobutanil. The decline of the combined residues also followed the hockey stick pattern. Myclobutan il photo-degrades with a half-life of approximately 143 days on soil. Thus, myclobutanil residues are fa irly persistent. Terrest rial field dissipation half-life values ranged from 92 to 292 days. Ge nerally, half-lives estimated in terrestrial field dissipation studies are less than aer obic soil metabolism studies because they include other dissipation pathways in additi on 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 S ection 3.2.5, Aquatic Exposure Mo deling and Appendix B. In an aerobic soil metabolism study the half-life of 1,2,4-triazole was estimated as 315 days.

Because log K ow s for parent and degradation products are low (log K ow = 2.94), the myclobutanil residues are not expect ed to bioaccumulate (MRID # 00162541).

Table 2.1 lists the selected physical and envi ronmental fate properties of myclobutanil, along with the major and minor degradat e products detected in the submitted

22environmental 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 Value (units) Major Degradates Minor Degradates MRID # or Data Source Study Status

Molecular Weight 288.8 g/mol -
Vapor Pressure 1.49 x 10 -06 mm Hg at 25 oC

1.6 x 10 -06 mm Hg - D190680 -

Henry’s Law Constant 3.25 x 10 -09 atm m 3 /mole @ 25 oC - calculated - Laboratory Volatility No data - - No study submitted Log K ow log K ow = 2.94 - 00162541 Hydrolysis Stable at pH 5, 7, and 9 - 001416-79 Acceptable

Direct Aqueous Photolysis Stable - 40641501

40319801

40528801 Acceptable

Photolysis on soil 143 days 1, 2,4-triazole 00164988 Acceptable Photodegradation in air No data - - No study submitted

Aerobic Soil Metabolism 198, 244 1 days 1,2,4-triazole, CO 2 and β -4-chlorophenyl- β -cyanoγ (1H-1,2,4—triazole)- butyric acid 00164561 Acceptable

Anaerobic Soil Metabolism Assumed stable, No appreciable degradation in 62 days. 1,2,4-triazole No MRID Acceptable

Anaerobic Aquatic Metabolism No data

- - No study submitted

Aerobic Aquatic Metabolism No data

- - No study submitted

Mobility Myclobutanil

Freundlich K ads - 1.46, 2.39, 4.44, 7.08, 9.77 mL/g (1/n – 0.89 to 1.02)

Koc 2 1,2,4-triazole

Freundlich K ads - 0.19 to 3.35 mL/g (1/n – 0.65 to 0.85)

Koc 2 141602

40891501 Acceptable

Terrestrial Field Dissipation 92 to 292 days 164563 Acceptable

1 Half-lives were recalculated (A ppendix C) by EFED (D336254).

2 Koc not valid, sorption does not appear to be correlated with soil organic carbon (D336254).

23The 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 pl ant and animal metabolism. These include triazole-analine (TA) and tr iazole acetic acid (TTA).
The following figures provide the structures of the degradates/metabolites discussed in this assessment.

NH

N N

1,2,4-Triazole (a.k.a. 1,2,4-T; free triazole)

1-H-1,2,4-triazole N N N

N H 2 O O H

Triazole Alanine
(a.k.a. TA)

α -Amino-1H-1,2,4-triazole1-propanoic acid N N

N O

OH

Triazole Acetic Acid
(a.k.a. TAA)

1H-1,2,4-Triazole-1-acetic acid

Chemical structures for 1,2,4-triazole, triazole alanine, and triazole acetic acid
Figure 2.1 Myclobutanil Degradates

C l C N H O

C H 3

N H

N

N

Figure 2.2 Myclobutanil Terres trial Plant Metabolite RH-9090 ( α -(3-hydroxybutyl)- α -(4-chlorophenyl)-1 H -1,2,4-triazole-1-propanenitrile)

242.4.3 Environmental Transport Assessment

Potential transport mechanisms include pest icide 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 samp les 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 K ads values (from 1.46 to 9.77 mL/g) (Table 2.1). The lowest non-sand valu e is 2.39 mL/g. Desorption coefficients were generally less than the sorption coefficients. The de gradate (1,2,4-triaziole) has lower Freundlich K ads values (0.234 to 0.833 mL/g), sugge sting it would be more mobile than the parent compound (Table 2.1). The so rption is not strongly correlated to soil organic carbon (matter), thus Koc is not a good measure of m obility for modeling.

A number of studies have documented at mospheric 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 Californi a (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 et al., 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 dr ift depends on the abil ity of myclobutanil to be mobilized into air and its eventual removal through wet and dry deposition of gases/particles and photochemical reacti ons in the atmosphere. Therefore, physicochemical properties of myclobutanil that describe its potenti al 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 Nevada s 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 m odels 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 LOC for mammals.

2.4.4 Mechanism of Action

Myclobutanil is a triazole fungicide in th e conazole class of fungicides which is a systemic fungicide used to control powder y mildew on a number of crops. Myclobutanil

25appears to be a specific inhi bitor 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 cr itical first step in evaluating the federal action. The current label for myclobutanil represents the FIFRA regulatory action; therefore, labeled use and app lication rates specified on the label form the basis of this assessment. The assessment of use informa tion is critical to the development of the action area and selection of appropriate modeling scenarios and inputs.

Myclobutanil is a triazole fungicide in the con azole 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 terr estrial non-food crops. Mycl obutanil is formulated as a wettable powder (2-40% a.i.) or as an emulsi fiable 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 lbs 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., sp rinkler, solid state), spread er, groundboom, and aircraft. Myclobutanil is also used to treat cotton see d. The formulation for this use is a 25% ai EC. The application rate for cotton is 0.06 lb ai per hundred wei ght (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 (lb ai/A) Max Number of Applications Number of Crop Cycles Per Year a b Max Seasonal/Yearly Application Rate (lb ai/A) Minimum Application

Interval Non-Food/Non-Feed Uses Turf Commercial Residential Lawn Golf Course 1.3 (0.03lb/1Kft 2 ) 4 1 NS 5

Grass grown for seed 0.19 NS 1 NS 14

Cotton (seed) 0.06 lb cwt NS NS NS NS
Forest Douglas Fir Loblolly Pine 0.25 NS 1 0.6 14

Cottonwood/ 0.15 NS 1 0.6 10

26Use Max Single Application Rate (lb ai/A) Max Number of Applications Number of Crop Cycles Per Year a b Max Seasonal/Yearly Minimum Application Rate Application (lb ai/A) Interval Poplar Plantation Ornamentals Shade Trees Groundcover Herbaceous Plant Woody Scrubs/vines 0.26 NS 1 2.0 10

Ornamental Sod
Farm 0.6 (0.014lb/1Kft 2 ) 1 NS

Slash Pine 0.003 lb ai/gal NS 1 14 Food/Feed Uses Almond 0.2 3/cc 3/yr 1 0.6 7 Apple 0.5 10/cc 1 2.0 7 Apricot 0.5 7/cc 1 1.0 7 Artichokes 0.1 6/cc 1 0.6 14 Asparagus 0.125 6/cc 1 0.75 14 Beans, Green 0.125 4/cc 1 0.5 7 Blackberry 0.125 4/cc 4/yr 1 0.5 10 Boysenberry 0.1 NS 1 0.25 10 Canistel 0.25 8/cc 1 2.0 14
Carrot 0.2 NS 1 0.375 14 Cherry 0.5 7/cc 7/yr 1 1.3 7 Cucurbit Vegetables Balsam Pear Cantaloupe Casaba Honeydew Melon Watermelon Cucumber Pumpkin Squash 0.125 Melon 7/cc 7/yr Other 5 cc 1 0.6 7

Currant 0.125 8/cc 1 1.0 7 Dewberry 0.0625 NS 1 0.25 10 Eggplant 0.125 4/cc 1 0.5 10 Gooseberry 0.125 8/cc 1 1.0 10 Grapes 0.13 6/cc 1 0.6 7 Hops 0.25 4/cc 1 1.0 7
Lettuce 0.125 4/cc 2 0.5 14 Mango 0.25 8/cc 1 2.0 14 Mayhaw 0.25 10/cc 1 2.0 7 Nectarine 0.5 7/yr 1 1.3 7 Okra 0.125 4/cc 1 0.5 10 Papaya 0.25 8/cc 1 2.0 14 Peach 0.5 7/cc 7/yr 1 1.3 7 Pepper 0.125 NS 1 0.5 10 Plum 0.16 7/cc 7/yr 1 1.1 7
Prune 0.15 7/cc 7/yr 1 1.1 7 Raspberry 0.125 4/cc 1 0.25 10 Sapodilla 0.25 8/cc 1 2.0 14 Strawberry 0.125 6/cc 1 0.75 14 Sugar Beet 0.19 NS 1 NS NS
Tomato 0.1 4/cc 1 0.5 21

27Use Max Single Application Rate (lb ai/A) Max Number of Applications Number of Crop Cycles Per Year a b Max Seasonal/Yearly Minimum Application Rate Application (lb ai/A) Interval Youngberry 0.0625 NS 1 0.25 10

a Number of crop cycles per year for all crops except lettuce as assumed by EFED.
b 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 th at in 2002, myclobutanil was used on agricultural crops predominantly in California, and Washi ngton, with high usage also in Wisconsin, Michigan and a number northern and mid Atlantic states (Fig ure 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 appl es with annual averag e applications 50,000, 40,000, and 20,000 lbs. a.i. respectively. The crop with the highest average percent crop treated with myclobutanil is artichokes (65%).

Figure 2.3 Map of Estimated Annual Agri cultural Use of Myclobutanil in 2002 http://water.usgs.gov/nawqa/pnsp/usage/ maps/show_map.php?year=02&map=m5036

28Use data specific to California are available from the California Department of Pesticide Regulation’s (CDPR) Pesticide Use Reporti ng (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, pe sticide, and unit trea ted. Based on this analysis, California accounts for approximate ly 50% of national usage. An average of 81,868 lbs of myclobutanil was applied in Calif ornia to an average of 763,456 acres per year. Use in California was at a maximu m of 95,411 lbs in 2000 and at a minimum of 70,735 lbs in 2006. Usage ranged from 70,000 to 84,000 lbs between 2003 and 2006. From 1999-2006, myclobutanil was used in a to tal of 54 counties involving 41 different uses. Five counties accounted for 50% of the total lbs 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 lbs applied. Grapes (table and wine) accounted for approximately 60% of the total lbs 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 cu rrent use patterns because labeled uses may have changed since these data were collected, and becau se it may also include misreporting. A summary of myclobutanil usage for all Califo rnia 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 Departme nt of Pesticide Registration (CDPR) Pesticide Use Reporting (PUR) Data from 1999 to 2006 for Currently Registered Myclobutanil Uses

Site Name Average Pounds All Uses Avg App Rate All Uses lbs a.i./A Avg 95th% App Rate lbs a.i./A Avg 99th% App Rate lbs a.i./A Avg Max App Rate lbs a.i./A
Almond 426 0.16 0.24 0.41 0.80 Apple 44 0.12 0.21 0.28 0.40 Apricot 15 0.11 0.16 0.19 0.28
Artichoke 103 0.09 0.10 0.13 0.29 Asparagus 46 0.12 0.13 0.13 0.40 Beans, Green 2 0.12 0.14 0.14 0.14 Cantaloupe 0.4 0.09 0.11 0.12 0.12 Cherry 40 0.10 0.14 0.19 0.40
Cucumber 4 0.10 0.11 0.13 0.13 Grape 644 0.10 0.14 0.19 0.41
Melon 17 0.10 0.11 0.20 0.20
Nectarine 40 0.13 0.18 0.21 0.35
Peach 34 0.12 0.21 0.28 0.47 Pepper 48 0.16 0.19 0.21 0.23
Plum 42 0.11 0.14 0.39 0.58
Prune 12 0.12 0.14 0.14 0.21 Pumpkin 8 0.12 0.23 0.29 0.29 Raspberry 7 0.07 0.09 0.17 0.28 Squash 3 0.11 0.12 0.12 0.12 Strawberry 193 0.10 0.14 0.21 0.40
Tomato 38 0.10 0.11 0.21 0.23

29Site Name Average Pounds All Uses Avg App Rate All Uses lbs a.i./A Avg 95th% App Rate lbs a.i./A Avg 99th% Avg Max App App Rate Rate lbs a.i./A lbs a.i./A
Watermelon 29 0.10 0.12 0.12 0.13
Greenhouse 6 0.11 0.22 0.40 0.55 Landscaping 33 0.46 0.47 0.47 0.47 Rights of Way 0.5 0.07 0.09 0.09 0.09
Turf/Sod 5 1.15 1.36 1.41 1.41

2.5 Assessed Species

The CRLF was federally listed as a threaten ed 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 (U SFWS 2002). A brief summary of information regarding CRLF distribution, repr oduction, diet, and habitat re quirements is provided in Sections 2.5.1 through 2.5.4, respectively. Furt her 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 Ca lifornia including the Central Valley and both coastal and interior mountain ranges (USF WS 1996). Its range has b een 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 Ne vada (5-6 populations), and in southern California south of Santa Barbara (two populat ions) (Fellers 2005a). Relatively larger numbers of CRLFs are located between Mari n and Santa Barbara Counties (Jennings and Hayes 1994). A total of 243 streams or draina ges 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 drai nages or watersheds include all bodies of water that support CRLFs (i.e., streams, cr eeks, 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 with in California is addressed in this assessment using four categories of location including r ecovery units, core areas, desi gnated critical habitat, and known occurrences of the CRLF reported in the California Natural Diversity Database

30(CNDDB) that are not included within core ar eas and/or designated critical habitat (see (see Figure 2.4 Recovery Unit, Core Area, Cr itical Habitat and Occurrence Designations for CRLF). Recovery units, co re areas, and other known oc currences of the CRLF from the CNDDB are described in further detail in Attachment I, and desi gnated critical habitat is addressed in Section 2.6. Recovery units are large areas defined at the watershed level that have similar conservation needs and mana gement 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’ hi storic and current range and have been determined by USFWS to be important in th e preservation of the species. Designated critical habitat is generally contained within the core ar eas, although a number of critical habitat units are outside the boundaries of core areas, but within the bound aries 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.

31Recovery 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

Core Areas

1. Feather River 2. Yuba River- S. Fork Feather River
3. Traverse Creek/ Middle Fork/ American R. Rubicon 4. Cosumnes River 5. South Fork Calaveras River* 6. Tuolumne River* 7. Piney Creek*
8. Cottonwood Creek 9. Putah Creek – Cache Creek* 10. Lake Berryessa Tributaries 11. Upper Sonoma Creek
12. Petaluma Creek – Sonoma Creek 13. Pt. 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 19. Watsonville Slough-Elkhorn Slough
20. Carmel River – Santa Lucia 21. Gablan Range 22. Estero Bay 23. Arroyo Grange River
24. Santa Maria River – Santa Ynez River 25. Sisquoc River 26. Ventura River – Santa Clara River 27. Santa Monica Bay – Venura Coastal Streams 28. Estrella River 29. San Gabriel Mountain* 30. Forks of the Mojave* 31. Santa Ana Mountain* 32. Santa Rosa Plateau 33. San Luis Ray*
34. Sweetwater* 35. Laguna Mountain*

* Core areas that were historically occupied by the California red-legged frog are not included in the map 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

Core Areas

1. Feather River 2. Yuba River- S. Fork Feather River
3. Traverse Creek/ Middle Fork/ American R. Rubicon 4. Cosumnes River 5. South Fork Calaveras River* 6. Tuolumne River* 7. Piney Creek*
8. Cottonwood Creek 9. Putah Creek – Cache Creek* 10. Lake Berryessa Tributaries 11. Upper Sonoma Creek
12. Petaluma Creek – Sonoma Creek 13. Pt. 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 19. Watsonville Slough-Elkhorn Slough
20. Carmel River – Santa Lucia 21. Gablan Range 22. Estero Bay 23. Arroyo Grange River
24. Santa Maria River – Santa Ynez River 25. Sisquoc River 26. Ventura River – Santa Clara River 27. Santa Monica Bay – Venura Coastal Streams 28. Estrella River 29. San Gabriel Mountain* 30. Forks of the Mojave* 31. Santa Ana Mountain* 32. Santa Rosa Plateau 33. San Luis Ray*
34. Sweetwater* 35. Laguna Mountain*

* Core areas that were historically occupied by the California red-legged frog are not included in the map
Figure 2.4 Recovery Unit, Core Area, Critic al Habitat and Occurrence Designations for CRLF

32Other Known Occurrences from the CNDBB

The CNDDB provides location and natural history information on species found in California. The CNDDB serves as a repositor y for historical and current species location sightings. Information regarding known occurrences of CRLFs outside of the currently occupied core areas and designated critical ha bitat 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). Accord ing to the Recovery Plan (USFWS 2002), CRLFs breed from November through late April. Peaks in spawning activity vary geographically; Fellers (2005b) re ports peak spawning as early as January in parts of coastal central California. Eggs are fertili zed as they are being laid. Egg masses are typically attached to emergent vegetation, su ch 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 appr oximately 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 re quire 11 to 28 weeks to me tamorphose into juveniles (terrestrial-phase), typica lly between May and Septem ber (Jennings and Hayes 1994, USFWS 2002); tadpoles have been observed to over-winter (delay metamorphosis until the following year) (Fellers 2005b, USFWS 200 2). 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).

D N O S A J J M A M F J

Light Blue = Breeding/Egg Masses
Green = Tadpoles (except those that over-winter) Orange = Young Juveniles Adults and juveniles can be present all year D N O S A J J M A J F M

Light Blue = Breeding/Egg Masses
Green = Orange = Young Juveniles Adults and juveniles can be present all year Tadpoles (except those that over-winter)

Figure 2.5 CRLF Reproductive Events by Month

332.5.3 Diet

Although the diet of CRLF aquatic-phase la rvae (tadpoles) has not been studied specifically, it is assumed that their diet is si milar to that of other frog species, with the aquatic phase feeding exclusiv ely in water and consuming diatoms, algae, and detritus (USFWS 2002). Tadpoles filter and entrap suspended algae (Seale and Beckvar, 1980) via mouthparts designed for effectiv e grazing of periphyton (Wassersug, 1984, Kupferberg et al

. ; 1994; Kupferberg, 1997; A ltig and McDiarmid, 1999).

Juvenile and adult CRLFs forage in aquatic a nd terrestrial habitats, and their diet differs greatly from that of larvae. The main food source for juvenile aquatic- and terrestrialphase CRLFs is thought to be aquatic a nd terrestrial invert ebrates found along the shoreline and on the water surface. Hayes a nd Tennant (1985) report, based on a study examining the gut content of 35 juvenile a nd adult CRLFs, that the species feeds on as many as 42 different invertebrate taxa , including Arachnida, Amphipoda, Isopoda, Insecta, and Mollusca. The most commonly obs erved prey species were larval alderflies ( Sialis cf. californica ), 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 c onsists of vertebrates such as mice, frogs, and fish, although aquatic and terrestrial inve rtebrates were the most numerous food items (Hayes and Tennant 1985). For adults, feeding activity takes place primarily at night; for juveniles feeding o ccurs during the day and at ni ght (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 lif e cycle. CRLF use of their environment varies; they may complete their entire life cycl e 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 ha bitats used for dispersal (USFWS 2002). Generally, CRLFs utilize habitat with perennial or near-perennial water (Jennings et al. 1997). Dense vegetation close to water, shadin g, and water of modera te depth are habitat features that appear especially impor tant for CRLF (Hayes and Jennings 1988). Breeding sites include streams, deep pools, b ackwaters 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 be en found near deep (0.7 m) still or slow moving water surrounded by dense vegetati on (USFWS 2002); however, the largest number of tadpoles have been found in sha llower pools (0.26 – 0.5 m) (Reis, 1999). Data indicate that CRLFs do not fre quently 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, sh rubby, or emergent vegetation closely associated with deep-water pools bordered w ith cattails and dense stands of overhanging vegetation ( http://www.fws.gov/endangered/f eatures/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 resti ng, feeding, and dispersal. The foraging quality of the riparian habitat depends on moisture, composition of the plant community, and presence of pools and backwa ter 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 hab itat to forage and seek othe r suitable habitat under downed trees or logs, industrial debr is, and agricultural features (UWFWS 2002). According to Jennings and Hayes (1994), CRLFs also use sm all mammal burrows and moist leaf litter as habitat. In addition, CRLFs may also use larg e cracks in the bottom of dried ponds as refugia; these cracks may provide moisture for individuals avoidi ng predation and solar exposure (Alvarez 2000).

2.6 Designated Critical Habitat

In a final rule published on April 13, 2006, 34 se parate units of critical habitat were designated for the CRLF by USFWS (USF WS 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 th e geographic area occupi ed by the species at the time of the listing where the physical and biological features necessary for the conservation of the species exis t, and there is a need for special management to protect the listed species. It may also include ar eas outside the occupied area at the time of listing if such areas are ‘essential to the c onservation of the species.’ All designated critical habitat for the CRLF was occupied at the time of listing. Cr itical habitat receives protection under Section 7 of the ESA (Section 7) through prohibition against destruction or adverse modification with regard to actions carried ou t, 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 desi gnation, the habitat must be ‘essential to the conservation of the species.’ Critical hab itat designations identify, to the extent known using the best scientific a nd commercial data available, habitat areas that provide essential life cycle needs of the species or areas that contai n 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 a nd for normal behavior; food, water, air, light, minerals, or other nutritional or physiolo gical requirements; cove r or shelter; sites for breeding, reproduction, rearing (or developmen t) of offspring; a nd habitats that are

35protected from disturbance or are represen tative of the histor ic geographical and ecological distributions of a species. The de signated 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 thes e habitat types is provided in Attachment I.

Occupied habitat may be include d in the critical habitat only if essential features within the habitat may require special management or protection. Theref ore, USFWS does not include areas where existing management is su fficient 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 ra nge would be inadequa te to ensure the conservation of the species. For the CRLF, all designated critical habi tat units contain all four of the PCEs, and were occupied by th e CRLF at the time of FR listing notice in April 2006. The FR notice designating critic al habitat for the CRLF includes a special rule exempting routine ranchi ng activities associated with livestock ranching from incidental take prohibitions. The purpose of this exemption is to promote the conservation of rangelands, which could be bene ficial 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 designate d critical habitat (USFWS 2006). Activities that may destroy or adversely modify critic al habitat are those that alter the PCEs and jeopardize the continue d 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 hab itat 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 chemistr y or temperature to levels beyond the tolerances of the CRLF that result in di rect or cumulative adverse effects to individuals and their life-cycles. (2) Alteration of chemical characteristics n ecessary 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 fora ging 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 deposit ion to levels that would adversely affect their ability to co mplete their life cycles. (4) Significant alteration of ch annel/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

36and/or its habitat. Such an effect coul d 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 aes tivating 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 myclobut anil 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 biological ly mediated processes.

2.7 Action Area

For listed species assessment purposes, the action area is considered to be the area affected directly or indirec tly by the federal action and not merely the immediate area involved in the action (50 CFR 402.02). It is recognized th at the overall action area for the national registration of myclobutanil is like ly to encompass considerable portions of the United States based on the large array of ag ricultural uses. However, the scope of this assessment limits considerati on of the overall action area to those portions that may be applicable to the protection of the CRLF and its designated critical ha bitat within the state of California. The Agency’s approach to defining the action area unde r the provisions of the Overview Document (U.S. EPA 2004) cons iders 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, attenti on will be focused on the footprint of the action (i.e., the area where pesticide applica tion occurs), plus all areas where offsite transport (i.e., spray drift, downstream dilu tion, etc.) may result in potential exposure within the state of California th at 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 asso ciated with those effects, and the best available information concerni ng the use of myclobutan il and its fate and transport within the state of California. Speci fic 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 surviv al, growth, and fecundity as well as the full suite of sublethal effects avai lable in the effects literature. Therefore, the action area extends to a point where environmental expos ures are below any m easured lethal or sublethal effect threshold for any biological entity at the whole organism, organ, tissue, and cellular level of or ganization. In situations where it is not possible to determine the threshold for an observed effect, the action ar ea is not spatially limite d and is assumed to be the entire state of California.

37The definition of action area requires a stepwise approach that begins with an understanding of the federal act ion. The federal action is de fined by the currently labeled uses for myclobutanil. An analysis of labele d 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 th is assessment. In addition, a distinction has been made between food use crops and those that are non-food/nonagricultural uses. For those uses relevant to the CRLF, the analysis indicates that, for myclobutanil, the following agricultural uses ar e considered as part of the federal action evaluated in this assessment:

• almond, apple, apricot, artichoke, as paragus, 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, pepp er, 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, ornament al 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 ini tial area of concern, based on an analysis of available land cover data for the state of Califor nia. 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 repr esenting all the land c over types that make up the initial area of co ncern for myclobutanil is presented in Figure 2.6.

The following land cover types were used for myclobutanil cultivated crops, forest, orchards and vineyards and tu rf. More information regarding which specific uses are represented for each land cover types can be found in Appendix E.

38Figure 2.6 Initial Area of Concern of “foot print” of potential use for myclobutanil

39As previously discussed, the action area is defined by the most sensitive measure of direct and indirect ecological toxic effects including re duction 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 (M RID 00144286), the spatial extent of the action area (i.e., the boundary where exposures and potential effect s are less than the Agency’s LOC) for myclobutanil cannot be determined. Therefor e, it is assumed that the action area encompasses the entire state of California, rega rdless 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 ac tual environmental value that is to be protected.” 1 Selection of the assessment endpoints is based on valued entities (e.g., CRLF, organisms im portant in the life cycle of the CRLF, and the PCEs of its designated critical habita t), the ecosystems potentially at risk (e.g., waterbodies, riparian vegetation, and upla nd 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 effect s to critical habitat are assessed by evaluating potential effects to PCEs, which are compone nts of the habitat areas that provide essential life cycle n eeds of the CRLF. Each assessment endpoint requires one or more “measures of ecological e ffect,” 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 ar e 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 indi rect 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 endpoint s for which there is a scientif ically 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 ecologica l effect selected for each ta xonomic group of concern, is

1 U.S. EPA (1992). Framework for Ecological Risk Assessment. EPA/630/R-92/001.

40included in Section 4.0 of this document. A summary of the assessment endpoints and measures of ecological effect selected to characterize po tential assessed direct and indirect CRLF risks associated with exposur e to myclobutanil is pr ovided in Table 2.4.

Table 2.4 Assessment Endpoints and Measures of Ecological Effects

Assessment Endpoint Measures of Ecological Effects 2 Aquatic-Phase CRLF (Eggs, larvae, juveniles, and adults) a Direct Effects
1. Survival, growth, and reproduction of CRLF 1a. Bluegill sunfish acute LC 50 1b. Fathead minnow chronic NOAEC Indirect Effects and Critical Habitat Effects

2. Survival, growth, and reproduction of CRLF individuals via indirect effects on aquatic prey food supply ( i.e., fish, freshwater invertebrates, nonvascular plants) 2a. Bluegill sunfish acute LC 50 , water flea acute LC 50 , green algae EC 50 . 2b. Fathead minnow chronic NOAEC; no freshwater invertebrate chronic study available; daphnia chronic NOAEC from 9 similar conazole fungicides. 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) 3a. No vascular plant study available; duckweed EC 50 data from 7 similar conazole fungicides. 3b. Green algae EC 50 .

4. Survival, growth, and reproduction of CRLF individuals via effects to riparian vegetation 4a. No seedling emergence or vegetative vigor studies available; terrestrial plant EC 25 and NOAEC data from 5 similar conazole fungicides 4b. No seedling emergence or vegetative vigor studies available; terrestrial plant EC 25 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 LD 50 and Mallard duck LC 50 b 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) 6a. Honey bee acute EC 50 and mouse acute LD 50 6b. Rat chronic NOAEC (no chronic invertebrate study available)

7. Survival, growth, and reproduction of CRLF individuals via indirect effects on habitat ( i.e., riparian and upland vegetation) 7a. No seedling emergence or vegetative vigor studies available; terrestrial plant EC 25 and NOAEC data from 5 similar conazole fungicides 7b. No seedling emergence or vegetative vigor studies available; terrestrial plant EC 25 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 th is 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 da ta reviewed for this assessment are included in Appendix A.

412.8.2 Assessment Endpoints for Desi gnated Critical Habitat

As previously discussed, designa ted critical habitat is assessed to evaluate actions related to the use of myclobutan il that may alter the PCEs of the CRLF’s critical habitat. PCEs for the CRLF were previously described in S ection 2.6. Actions that may modify critical habitat are those that alter the PCEs and jeopa rdize the continued existence of the CRLF. Therefore, these actions are id entified as assessment endpoints. It should be noted that evaluation of PCEs as assessment endpoints is lim ited to those of a biological nature (i.e., the biological resource requirements for the list ed species associated with the critical habitat) and those for which myclobutanil eff ects 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 cri tical habitat of the CRLF are described in Table 2.5. Some compon ents 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 exp ected to be measurably alte red by use of pesticides. Assessment endpoints used for the analysis of designated critical ha bitat are based on the adverse modification standard established by USFWS (2006).

42Table 2.5 Summary of Assessment Endpoints and Measures of Ecological Effect for Primary Constituent Elements of Designated Critical Habitat a

Assessment Endpoint Measures of Ecological Effect

Aquatic-Phase CRLF 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. a. Green algae EC 50 . No vascular plant study available; duckweed EC 50 data from 7 similar conazole fungicides. b. No seedling emergence or vegetative vigor studies available; terrestrial plant EC 25 and NOAEC data from 5 similar conazole fungicides c. No seedling emergence or vegetative vigor studies available; terrestrial plant EC 25 and NOAEC data from 5 similar conazole fungicides

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. a. Green algae EC 50 . No vascular plant study available; duckweed EC 50 data from 7 similar conazole fungicides. b. No seedling emergence or vegetative vigor studies available; terrestrial plant EC 25 and NOAEC data from 5 similar conazole fungicides c. No seedling emergence or vegetative vigor studies available; terrestrial plant EC 25 and NOAEC data from 5 similar conazole fungicides

Alteration of other chemical characteristics necessary for normal growth and viability of CRLFs and their food source. a. Bluegill sunfish acute LC 50 and water flea acute LC 50 . b. Fathead minnow chroni c NOAEC. No freshwater invertebrate chronic study available; daphnia chronic NOAEC from 9 similar conazole fungicides. Reduction and/or modification of aquatic-based food sources for pre-metamorphs ( e.g., algae) a. Green algae EC 50 . No vascular plant study available; duckweed EC 50 data from 7 similar conazole fungicides.

Terrestrial-Phase CRLF 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 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 ch aracteristics 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 EC 25 and NOAEC data from 5 similar conazole fungicides. b. No seedling emergence or vegetative vigor studies available; terrestrial plant EC 25 and NOAEC data from 5 similar conazole fungicides. c. Bobwhite quail LD 50 , mallard duck LC 50 , bobwhite quail chronic NOAEC, honey bee acute EC 50 , mouse acute LD 50 , rat chronic NOAEC (no chronic invertebrate study available), bluegill sunfish acute LC 50 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 releva nt to the endpoints included in this assessment.

432.9 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, wh ere 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 mortal ity or by adversely a ffecting growth or fecundity;

• indirectly affect the CRLF by reducing or changing the composition of food supply;

• indirectly affect the CRLF or affect designated critical ha bitat by reducing or changing the composition of the aquatic plant community in the ponds and streams comprising the species’ current rang e and designated critic al habitat, thus affecting primary productivity and/or cover;

• indirectly affect the CRLF or affect designated critical ha bitat by reducing or changing the composition of the terrestrial plant community (i.e., riparian habitat) required to maintain acceptable water qual ity and habitat in the ponds and streams comprising the species’ current range and designated critical habitat;

• affect the designated critical habita t of the CRLF by reducing or changing breeding and non-breeding aqua tic habitat (via modifi cation of water quality parameters, habitat morphology, and/or sedimentation);

• affect the designated critical habita t of the CRLF by reducing the food supply required for normal growth and viabili ty 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 habita t 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 moveme nt between sites including both natural and altered sites which do not contain barriers to dispersal;

• affect the designated critical habi tat 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 stresso r (myclobutanil) release mechanisms , biological recept or types, and

44effects endpoints of potential concern. The conc eptual models for terrestrial and aquatic exposures are shown in Figure 2.7 and Fi gure 2.8, respectively, which include the conceptual models for the aquatic and terrestr ial PCE components of critical habitat. Exposure routes shown in dashed lines are not quantitatively considered because the contribution of those potential exposure rout es to potential effects on the CRLF and designated critical habitat is expected to be negligible.

Stressor

Source

Receptors

Attribute Change Myclobutanil applied to use site

Direct application Spra y drift

Birds/terrestrialphase amphibians/ reptiles/mammals

Terrestrial

insects

Individual organisms Reduced survival Reduced growth Reduced reproduction 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 Terrestrial/riparian plants grasses/forbs, fruit, seeds (trees, shrubs) Runoff

Mammals/ birds Exposure Media Soil

Ingestion In g estion

Ingestion In g estion Dermal u p take/In g estion Long range atmospheric

transport

Root uptake

Wet/dr y de p osition

Terrestrial-phase amphibians Ingestion

Figure 2.7 Conceptual Model for Myclobut anil Effects on Terres trial Phase of the CRLF

45Myclobutanil applied to use site Stre ssor

Source

Receptors

Attribute Change

** Route of exposure includes only inges tion of aquatic fish and invertebrates Spra y drift

Fish/aquatic-phase amphibians Exposure Media

**Piscivorous mammals and birds

Individual organisms Reduced survival Reduced growth Reduced reproduction Food chain Reduction in algae 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 Surface water/ Sediment Runoff

Aquatic Animals Invertebrates Vertebrates Uptake/gills or integument

In g estion In g estion Uptake/gills or integument

A quatic Plants Non-vascular Vascula r Uptake/cell,
roots

, leaves Riparian plants terrestrial
exposure pathways see

Figure 2.7 Long range atmospheric

transport

Wet/dry deposition

Groundwate r Soil

Figure 2.8 Conceptual Model for Myclobut anil Effects on Aquatic Phase of the CRLF

2.10 Analysis Plan

In order to address the risk hypot hesis, the potential for direct and indirect effects to the CRLF, its prey, and its habitat is estimat ed. In the following sections, the use, environmental fate, and ecological effect s of myclobutanil are characterized and integrated to assess the risks. This is accomplished using a risk quotient (ratio of exposure concentration to effect s concentration) approach. Although risk is often defined as the likelihood and magnitude of adverse ecological effect s, the risk quotient-based approach does not provide a quantitative estim ate 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 indivi dual 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.

462.10.1 Measures to Evaluate the Risk Hypothesis and Conceptual Model

2.10.1.1 Measures of Exposure

The environmental fate properties of myclobutanil and the de gradation product 1,2,4- triazole along with available monitoring da ta indicate that for myclobutanil runoff and spray drift are the principle potential transp ort 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 al so a potential route of expos ure but is expected to be minor. In this assessment, transport of my clobutanil and myclobutanil plus 1,2,4-triazole through runoff and spray drift is considered in deriving quant itative 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 te rrestrial 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 1-in-10 year EECs of myclobut anil and myclobutanil plus 1,2,4-triazole that may occur in surface water bodies ad jacent 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. Th e 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 m 3 volume) with no outlet. PRZM/EXAMS was used to esti mate screening-level exposure of aquatic organisms to myclobutanil and myclobutanil plus 1,2,4-triazole. The measure of exposure for aquatic species is the 1-in-10 year return peak or rolling mean concentration. The 1-in-10 year peak is used for estimati ng 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 inve rtebrates, fish and frogs. The 1-in-10-year 60-day mean is used for assessing chronic exposure to the CRLF and fish and frogs serving as prey items; the 1-in-10-year 21-day mean is us ed for assessing chronic exposure for aquatic invertebrates, which are al so potential prey items.

Exposure estimates for the terrestrial-phase CRLF and terrestria l invertebrates and mammals (serving as potential prey) assumed to be in the target area or in an area exposed to spray drift are derived usi ng the T-REX model (version 1.4.1, 10/09/2008).

47This model incorporates the Kenega no mograph, 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 95t h percentile of residue values from actual field measurements (Hoerger and Ke nega, 1972). For modeling pur poses, direct exposures of the CRLF to myclobutanil thr ough 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 categ ories represent the largest RQs of the size and dietary categorie s in T-REX that are appropriate surrogates for the CRLF and one of its prey items. Es timated exposures of terrestrial insects to myclobutanil are bound by using the dietary based EECs for small insects and large insects. For granular applications, an LD 50 per square foot is estimated based on application rate and toxicity.

Birds are currently used as surrogates for te rrestrial-phase CRLF. However, amphibians are poikilotherms (body temperat ure varies with environmenta l temperature) while birds are homeotherms (temperature is regulate d, constant, and largely independent of environmental temperatures). Therefore, am phibians 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 f ood items. Therefore, the use of avian food intake allometric equation as a surrogate to amphibians is likely to result in an overestimation of exposure and risk for reptiles a nd terrestrial-phase amphibians. Therefore, T-REX (version 1.4.1) has been refined to th e 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 a nd wetland areas are derived using TerrPlant (version 1.2.2, 12/26/2006). This model uses es timates 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 terrestria l habitats by spray drift. In addition to the buffered area from the spray drift analys is, the downstream extent of myclobutanil that exceeds the LOC for the effects de termination is also considered.

2.10.1.2 Measures of Effect

Data identified in Section 2.8 are used as measur es of effect for direct and indirect effects to the CRLF. Data were obtained from regi strant 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,

48terrestrial plants, and wildlife. ECOTOX wa s created and is maintained by the USEPA, Office of Research and Devel opment, and the National Health and Environmental Effects Research Laboratory's Mid- Continent Ecology Division.

The assessment of risk for direct effect s to the terrestrial-phase CRLF makes the assumption that toxicity of mycl obutanil to birds is similar to or less than the toxicity to the terrestrial-phase CRLF. The same assu mption is made for fish and aquatic-phase CRLF. Algae, aquatic invertebrates, fish, and amphibians represent potential prey of theCRLF in the aquatic habitat. Terrestrial invertebrates, small mammals, and terrestrialphase amphibians represent potential prey of th e 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 plan ts and terrestrial plants . For the purpose of risk description in this assessment, toxi city data from other triazole sterol 14 α

demethylase-inhibitors (DMIs) for these particular studies were utilized.

The acute measures of effect used for animal s in this screening level assessment are the
LD 50 , LC 50 and EC 50 . LD stands for "Lethal Dose", and LD 50 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 LC 50 is the concentration of a chemical that is estimated to kill 50% of the test organisms. EC stands for “Effective Concentration” and the EC 50 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 an d NOEC. NOAEL stands for “No Observed-Adverse-Effect-Level” and refers to the highest tested dose of a substance that has been reported to have no harmful (adve rse) 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 statis tically different from the control. The NOEC is the No-Observed-Effects-Concentra tion. For non-listed plants, only acute exposures are assessed ( i.e. , EC 25 for terrestrial plants and EC 50 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 as sociated 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 Docu ment (USEPA 2004), the Agency relies on effects endpoints that are either direct measures of impairme nt 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.

492.10.1.3 Integration of Exposure and Effects

Risk characterization is the integration of exposure and ecological e ffects characterization to determine the potential ecolo gical risk from agricultural and non-agricultural uses of myclobutanil, and the likelihood of direct and indirect eff ects to CRLF in aquatic and terrestrial habitats. The expos ure 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 Ag ency’s levels of c oncern (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 LOC, 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 th e listed species LOC, then the effects determination for that use is a “may affect.” If the RQ being considered also exceeds the non-listed species acute risk LOC, then the eff ects determination is a LAA. If the acute RQ is between the listed species LOC and th e non-listed acute risk species LOC, 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 indir ect effects to the CRLF due to effects to algae as dietary items or plants as habitat, the non-listed sp ecies LOC for plants is used because the CRLF does not have an obligate relationship with any pa rticular aquatic and/or terrestrial plant. If the RQ being considered for a particul ar use exceeds the non-listed species LOC 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 envir onmental fate of myclobutanil and its degradation products is limited. The data was inadequate to determin e the rate of formation and decline of the 1,2,4-triazole degradation produc t. Models currently used by EFED assume that the degradation follow first order ki netics, and therefore require an estimate of the half-life. Myclobutanil degradation, however, is best described using a hocke y stick degradation pattern. This type of degradation pattern cannot be modeled using first-order kinetics.
The previously reported half-lives for my clobutanil range between 61 and 71 days, which described the decline reasonably well for th e first 90 days of the study, but grossly overestimates the remaining decline. The met hod used to estimate these half-lives was

50not 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 tran sformed myclobutanil radioactivity provided the best estimate of the measured residues (a s 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 DT 75 or DT 90 . The 90-percent upper bound of the mean (n=2) aerobic soil metabolism half-life for myclobut anil was estimated to be 251 days.
Analysis of the Freundlich K ads indicates sorption is not si gnificantly correlated with organic matter (carbon). Theref ore, lowest non-sand Freundlich K ads was used to estimate the EDWCs for mycl obutanil (USEPA, 2002).
Because there are no aerobic aquatic metabolism data, half-life was assumed to be twice that of the aerobic soil meta bolism half-life estimated as a model input (USEPA, 2002). The anaerobic metabolism was assumed to be stable.

Ecotoxicity
No toxicity data are available for freshwat er 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, emulsi fiable concentrate, granular, liquid, water dispersible granules (dry flow able), pressurized liquid, rea dy 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 broad cast spreaders for granular applications. Risks from ground boom and aerial applications are expected to resu lt in the highest offtarget levels of myclobutanil due to generally higher spray drift levels. Ground boom and aerial modes of application tend to use lowe r volumes of applica tion applied in finer sprays than applications coincident with sp rayers 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 a nd its formulated products) and end-use products. While technical products, which co ntain 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 br own 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 si tes that are specified on the labels.

51Currently registered agricu ltural and non-agricultural uses of myclobutanil within California included in this asse ssment 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 myclobutan il use. Each of thes e 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 sta ndard pond are intended to represent a wide variety of vulnerable water bodi es 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 standa rd surrogate pond. Stat ic 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 te nd to have limited additional storage capacity, and thus, tend to overflow a nd carry pesticide in the discharge whereas the standard pond has no discharge. As wa tershed size increases beyond 10 hectares, at some point, it becomes unlikely that the enti re 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 ra tes, number of applications per year, application intervals, and the first applica tion 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 fr om the CDPR PUR data, and Crop Profiles maintained by the USDA. Fo r example, the first applications of myclobutanil reported in the CD PR PUR database occurred in late February or early March and continued through mid-August, dur ing the years 2001 to 2005. For grapes, the heaviest period of ap plication began in April. Precipitation also te nds to be greater in late winter and early spring th en in the summer. Based upon the dates selected for crop emergence and harvest in the standard PR ZM CA Grape scenario and the CDPR PUR data, the date selected for first applicati on of myclobutanil for modeling was April 1 in (Figure 3.1).

.

520 50 100 150 200 250 300 350

3/1/01 3/8/01 3/15/01 3/22/01 3/29/01 4/5/01 4/12/0 1 4/19/01 4/26/01 5/3/01 5/

10/01 5/17/01 5/24/01 5/

31/01 6/7/01 6/14/01 6/21/01 6/28/01 7/5/01 7/12/01 7/19/01 7/26/01

Date of ApplicationPounds Myclobutanil Applied

Figure 3.1 Summary of Applications (po unds 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/c ropprofiles/cropprofiles.cfm

3.2.2 PRZM Scenarios

PRZM scenarios used to mode l 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 surr ogate scenario. Those surrogates are assigned to be most representative of the use being c onsidered. Factors considered in the selection of scenarios include the similarity of cr op growth and morphology, soils, product use and cropping area. Particular atte ntion 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 belo w. All scenarios were parameterized for irrigation.

Almond scenario (CA Almond STD)

This scenario is intended to represent al mond and walnut production in CA and is therefore, directly relevant to this use. The only crop us ing this scenario in this assessment was almonds.

53Citrus scenario (CA Citrus STD)

This scenario is intended to represent applica tions of pesticides to oranges, grapefruit, kumquats, lemons, limes, tangelos, and tangeri nes 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 fore stlands in northern Calif ornia. The area of interest (AOI) includes Trinity, Shasta, M odoc, and Humboldt counties since they are predominantly forested and comprise the larges t amount of pesticide application to forest lands in California. Based on typical fore st composition and comm on pest species, this scenario is intended to represent coniferous ev ergreen forests. This scenario was used to represent Douglas Fir (seed orch ard, 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 orchar d 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 a nd sour cherries, nectarines, peaches, plums, and prunes. Crops modeled using this scenar io were apples, apricot, canistel, cherry, mamey (mamme apple), and mayhaw (hawthor n), 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 producti on in the San Joaquin Valley and the bulk of the rema inder 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

54scenario included blackberry, boysenberry, cu rrant, 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 no rthern 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 sativa ) is predominantly grown on the West Coast, this scenario is used to represent lettuce production nati onally. It is thus also su itable 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 repres ent 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 loca ted 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 Pa cific Northwest. Since the locations where mint is grown in CA are in the northern pa rt of the state, this scenario was deemed appropriate for modeling mint grown in CA. This scenar io was used to represent spearmint and peppermint crops.

Nursery scenario (CA Nursery STD)

This scenario is intended to represent applic ations of pesticides in outdoor nurseries in CA and is therefore, directly relevant to this use. Uses considered with this scenario included garland, chrysanthemum, ornament al ground cover, ornamental herbaceous plants, ornamental and non-flowering plan ts, ornamental woody shrubs and vines.

55Row crop scenario (CA Row Crop)

This scenario is intended to represent pr oduction 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 applic ations of pesticides to strawberries, nontarped, in CA. While the majority of strawb erry 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 applica tions of pesticides to sugar beets in CA, and is therefore, relevant to this use. This scenario was used to re present 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 applic ations 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 us ed to represent Bluegrass, commercial and industrial lawns, golf-course tu rf, grasses grown for seed, or namental lawns, residential lawns, sod farms, and turf.

3.2.3 Model Inputs

Myclobutanil is a fungicide used on a wi de variety of food and non-food crops. Myclobutanil and selected myclobutanil plus 1,2, 4-triazole environmen tal fate data used for generating model paramete rs 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 myclobutan il plus 1,2,4-triazole. The number of applications and the reapplica tion intervals for each crop mode led are listed in Tables 3.5 and 3.6 and Appendix B (Tables 2 and 3).

56Table 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 1

Parameter Input Value and Unit Rational
Molecular Weight 288.8 g/ mol a,b

Solubility 142 ppm @ 25 oC a,b

Aquatic Photolysis (t 1/2 ) 0 days (Stable) No Data

Soil Partition Coefficient, Freundlich
K ads Myclobutanil: 2.39 mg/L a 1,2,4-triazole: 0.719 mg/L b Lowest non-sand value

Lowest non-sand value

Solubility in water (pH 7, 25 o C) 1420 mg/L (142 mg/L * 10) a,b EFED, Guidance
USEPA, 2002
Vapor Pressure 1.49 x 10 -06 mm Hg at 25 oC a
Henry’s Law Constant 3.25 x 10 -09 atm m 3 /mole @ 25 oC
Hydrolysis 0 days (Stable)

Aerobic Soil Metabolism (t 1/2 ) Myclobutanil: 251 days a Myclobutanil + 1,2,4-triazol: 315 days b Upper 90 th bound on

mean 0nly 1 value
Aerobic Aquatic Metabolism (t 1/2 ) Myclobutanil

Estimated as 502 days a Myclobutanil + 1,2,4-triazole

Estimated as 630 days b 2 x ASM 2 x ASM per USEPA, 2002

Application Efficiency (APPEFF) 0.95 aerial spray 0.99 ground spray 1.00 granular EFED Guidance
USEPA, 2002

Drift (DRFT) Aerial Spray Aerial (0.05 Drift) Ground (0.01Drift) Granular (0.00) EFED Guidance
USEPA, 2002

Chemical Application Method (CAM) 2 - foliar 1 – granular 5 – cotton seed (incorporation depth 3 cm) Label

1 – Inputs determined in accordance with EFED “G uidance for Chemistry and Management Practice Input Parameters for Use in Modeling the Environmental Fate and Transport of Pesticides” dated February 28, 2002

a – 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 my clobutanil and 1,2,4-tri azole with time using assuming first-order kinetics (Appendix C. E nvironmental Fate Data) and assuming the greater mobility (Freundlich K ads ) of the 1,2,4-triazole (Table 3.1).

The myclobutanil was assumed to be appl ied by ground and aerial spray methods as a foliar, and broadcast as a granular. The othe r methods of application include chemigation,

57sprinkler 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 cy cle 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 ra te 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 lb ai/A/a pplication x 7 applications = 1.05 lb ai/A/cc with a maximum per cc of 1.305 lb ai/A) to obtai n the total maximum crop cycle or year rate. Eight applications at 0.15 lb ai/A /application + 1 application of 0.105 lb 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 we re the USGS NAWQA (USGS, 1991) and the Reservoir Pilot Mon itoring Program (USGS, 2001). Myclobutanil is not included in the CD PR monitoring program. These monitoring studies, which are discussed in further detail belo w, were not specifically target ed 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 m onitored 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 fi nished water (Table 3.2). The degradation produc ts were not included.

Table 3.2 Myclobutanil results from the summary of analysis of moderate-use pesticides and degradates in water sample s from water supply intakes and finishedsupply taps in Reservoir Pilot Monitoring Program. (USGS, 2001)

No. of Samples No. of Detections
(Quantifiable No.

of Detections) Frequency of Detection
(%) Maximum Detection

(μg/L) Method Reporting

Level
(μg/L)

Raw Water 317 3 (2) 0.9 0.015 0.008

Finished Water 221 0 0 0 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”.

58Surface Water Analysis

Myclobutanil was detected in ambient surface wa ter (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 μ g/L for a sampling site located near Montpelier California in Merced Co unty California (USGS Sampling Station 373112120382901). The minimum reporting limit (M RL) varies from 0.0022 to 0.25

μ g/L, with a median MRL of 0.008 μ g/L.

Table 3.3 Distribution of Myclobutanil Co ncentrations (μg/L) in USGS NAWQA Surface Water Monitoring Data Monitoring Data (1998-2007)

River Basin County No. samples No. Detections Min Max

Santa Ana Riverside 55 2 0.0118 0.033 San Joaquin-Tulare Merced 149 89 0.0091 0.507 San Joaquin 87 25 0.0045 0.021

Stanislaus 30 15 0.0082 0.380

Sacramento Sacramento 118 35 0.0094 0.288

Total 439 166 (37.8%) 0.0045 0.507

Ground Water Analysis

Myclobutanil was not detected in ground wa ter in California samples collected in California (300 samples). Wells were loca ted in Butte, Colusa, Fresno, Glenn, Madera, Merced, Placer, Sacramento, San Bernardino, Sa n Joaquin, Stanislaus, Sutter, Tulare, and Yuba Counties. The minimum reporting limit (MRL) varies from 0.0022 to 0.033 μ g/L with a median MRL of 0.008 μ g/L.

Rain data

Rainfall samples were collected during th e 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 th e cropland is comprised of almonds and vineyards with some corn and dairy. Mycl obutanil (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 Percent of Detections Median Maximum

23 57 % > 0.01 μg/L 0.014 μg/L 0.113 μg/L 4 % > 0.1 μg/L

593.2.5 Modeling Results

The estimated environmental concentrations (EECs) for myclobutanil varied by scenario, crop, and by rate and date (i.e ., date of first application a nd reapplication interval), and method of application. The dates of the fi rst application of my clobutanil ranged from early February to earlier September. The my clobutanil peak concentrations ranged from 2.11 μg/L to 54.56 μg/L, for cotton seed treatment to the granular ap plication to turf, respectively. The 21-day and 60-day rolling averages were 2.1 and 2.08 μg/L, for cotton seed treatment and 54.29 to 53.84 μg/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 summ arized in Appendix B, Table 1.

Table 3.5 Aquatic EECs (μg/L) for Myclobutanil Uses in California

Method Date of First Representative Crop #@rate/total/Interval EEC 1-year in 10-year

CA Scenario Application Rate Peak 21day 60 day

Almond as 2-10 Almond 3@0.2/0.6/7 11.93 11.86 11.77

Citrus as 8-01 Mango 8@0.25/2.0/14 21.75 21.58 21.30

Cotton Seed trt. 4-15 Cotton 0.89 1 2.11 2.10 2.08
Forestry as 8-05 Douglas fir 2@0.25 + 1@0.1/0.6/14 21.76 21.61 21.46
Forestry as 8-05 Douglas fir 4@0.15/0.6/10 21.74 21.58 21.44

Fruit as 3-10 Apple 4@0.5/2.0/7 29.79 29.45 28.94

Fruit as 3-10 Apple 8@0.25/2.0/7 30.13 29.81 29.49

Fruit as 4-10 Cherry 2@0/0.47 + 1@0.11/1.31/7 21.25 21.72 20.59

Fruit as 4-10 Cherry 8@0.15 + 1@0.11/1.31/7 21.35 21.09 20.52

Fruit as 4-10 Fruit 2 8@0.25/2.0/14 31.35 30.31 30.17

Fruit as 3-10 Peach 2@0.47 + 1@0.37/1.31/7 19.45 19.24 18.85

Fruit as 3-10 Peach 8@0.15 + 1@0.123/1.31/7 19 .88 19.69 19.39

Grapes as 4-01 Grapes 4@0.13 + 1@0.08/0.60/7 8.99 8.88 8.73

Grapes as 4-01 Grapes 6@0.10/0.60/7 9.07 8.98 8.83

Lettuce as 9-02 Lettuce 3 4@0.125/0.50/14 41.02 40.58 38.61

Melons as 6-15 Melon 4@0.12 + 1@0.10/0.60/7 16.32 15.74 15.61
Nursery as 7-01 Ornamental 0.26/ns 4/ 2.0 5 /7 45.25 44.93 44.21
Row Crop as 2-15 Artichoke 6@0.10/0.60/7 15.92 15.79 15.55
Row Crop as 7-15 Asparagus 6@0.125/0.76/14 22.29 22.16 21.95
Row Crop as 2-20 Beans 4@0.125/0.50/7 13.62 13.52 13.35
Row Crop as 9-14 Pepper, pimento 4@0.125/0.50/10 17.70 17.52 17.34
Strawberry as 3-01 Strawberry 6@0.125/0.75/14 34.19 34.03 33.83

Turf Granular 2-01 Turf 6@1.34/ 54.56 54.29 53.84

Turf as 2-01 Turf 4@0.19/0.75/14 20.69 20.53 20.34

60Representative Method Date of First #@rate/total/Interval EEC 1-year in 10-year Crop

CA Scenario Application Rate Peak 21day 60 day
Hops 6 as 9-01 Hops 4@0.25/1.0/7 28.83 28.65 28.38
Hops as 4-01 Hops 4@0.25/1.0/7 17.96 17.82 17.56

1 Cotton rate is 0.0625 lb a.i./100 lb seed; [4 200 seed/lb; 60,000 seed/acr e = 14.29 lb seed/acre]

2 Fruit – Mamey, Mayhaw, Star Apple; canistel 3 Lettuce and Brussels Sprouts
4 ns is not specified on label.

5 Ornamentals – maximum rate = 0.26 lb ai/A/application; season total = 2.0 lb ai/A/year or cc. Number of applications is not specified. Maximum seasonal rate is achieved by assuming 7 applications at 0.26 lb ai/A and an 8 th application at 0.18 to obtain 2.0 lb 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 firs t application and reapplication interval), and method of app lication. The dates of the firs t application of myclobutanil ranged from early February to earlier Septem ber. The myclobutanil peak concentrations ranged from 2.84 μg/L to 61.41 μg/L, for cotton seed treatment to the granular application to turf, respectively. The 21-da y and 60-day rolling averages were 2.82 and 2.77 μg/L, for cotton seed treatment a nd 61.15 to 60.71 μg/L for granular turf, respectively. The selected aquatic EECs fo r 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 aeria l spray) are summarized in Appendix B. Table 2.

Table 3.6 EECs California Red legged frog – myclobutanil + 1,2,4-triazole

Date of First Application Representative Crop # @ rate/total # @lb ai/A/lb ai/A/days EEC 1-year in 10-year

CA Scenario Method app Rate peak 21day 60 day

Almond as 2-10 Almond 3@0.2/0.6/7 14.17 14.10 13.99

Citrus as 8-01 Mango 8@0.25/2.0/14 27.90 27.78 27.37
Forestry as 8-05 Douglas fir 2@0.25 + 1@0.1/0.6/14 22.37 22.28 22.10
Forestry as 8-05 Douglas fir 4@0.15/0.6/10 22.40 22.29 22.11

Fruit as 3-10 Apple 4@0.5/2.0/7 37.75 37.36 36.64

Fruit as 3-10 Apple 8@0.25/2.0/7 37.94 37.63 37.16

Fruit as 4-10 Cherry 2@0/0.47 + 1@0.37/1.31/7 25.87 25.61 25.04

Fruit as 4-10 Cherry 8@0.15 + 1@0.11/1.31/7 24.01 24.51 24.22

Fruit as 4-10 Fruit 1 8@0.25/2.0/14 36.33 35.18 35.03

Fruit as 3-10 Peach 2@0.47 + 1@0.37/7 24.5 5 24.29 23.88

Fruit as 3-10 Peach 8@0.15 + 1@0.123/1.31/7 24 .70 24.51 24.22

Grapes as 4-01 Grapes 4@0.13 + 1@0.08/0.60/7 11.18 11.06 10.82

61Represent- # @ rate/total Date of First ative EEC 1-year in 10-year Application # @lb ai/A/lb ai/A/days Crop

CA Scenario Method app Rate peak 21day 60 day

Grapes as 4-01 Grape 6@0.10/0.60/7 11.11 11.02 10.85

Lettuce as 9-02 Lettuce 2 4@0.125/0.50/14 41.94 41.79 41.22

Melons as 6-15 Melon 4@0.12 + 1@0.10/0.50/7 18.61 18.41 18.21
Nursery as 7-01 Ornamental 0.26/ns 3 /2.0 4 /7 51.96 51.71 51.22
Row Crop as 2-15 Artichoke 6@0.10/0.60/7 17.57 17.46 17.27
Row Crop as 7-15 Asparagus 6@0.125/0.75/14 21.09 20.99 20.68
Row Crop as 2-20 Beans 4@0.125/0.50/7 15.56 15.48 15.35
Row Crop as 9-14 pepper, pimento 4@0.125/0.50/10 16.97 16.91 16.82
Strawberry as 3-01 Strawberry 6@0.125/0.75/14 40.84 40.69 40.41
Strawberry as 3-01 Berries 4@0.063/0.25/10 14.62 14.55 14.43

Turf Granular 2-01 Turf 6@1.34/ 61.41 61.15 60.71

Turf as 2-01 Turf 4@0.19/0.75/14 24.06 23.93 23.78
Hops 5 as 9-01 Hops 4@0.25/1.0/7 28.81 28.65 28.38
Hops as 4-01 Hops 4@0.25/1.0/7 20.52 20.39 20.18

1 Fruit – Mamey, Mayhaw, Star Apple; canistel

2 Lettuce and Brussels sprouts.

3 ns is n ot s pecified on label.

4 Ornamentals – maximum rate = 0.26 lb ai/A/application; season total = 2.0 lb ai/A/year or cc. Number of applications is not specified. Maximum seasonal rate is achieved by assuming 7 applications at 0.26 lb ai/A and an 8 th application at 0.18 to obtain 2.0 lb 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 wa s observed that the Ti er 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 environmen ts, and the lack of inflow and outflow in the standard pond that precludes decreases in concentrations of re sidues due to dilution.

620 2 4 6 8 10 12

1960 1970 1980 1990

YearsAnnual Peak Concentration (ug/L)

Myclobutanil
Myclobutanil + 1,2,4-triazole

Figure 3.2 Accumulation of PRZM/EXAM S 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 probabili stic interpretation of the return frequency of concentrations because of the accumulati on over approximately 27 years simulated in the standard farm pond. Therefore, the 1-in-10 year concentrations reported in the farm pond in the standard EFED ecological risk a ssessments are conservative compared to flowing systems. Modeling of accumulation curv es 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 ri se to maximum model (y = a(1-e (-b*x )) where y = annual peak concentration ( μ g/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.

63Table 3.7 Time (years) for myclobutanil and myclobutanil plus 1,2,4-triazole to reach plateau concentration in standard farm pond (USEPA, 2007)

Model Predicted Constants Scenario Application Method a 1 b 2 R 2

Air 6.1507 0.3930 0.87 CA Okra Ground 2.7613 0.4002 0.55
Air 92.26 0.24 0.76 CA Lettuce Ground 81.23 0.24 0.69
Air 17.40 0.23 0.94 CA Artichoke Ground 11.45 0.24 0.87
Air 21.22 0.50 0.72 CA Tropical Fruit Ground 7.66 0.76 0.15

1 Years to reach plateau concen tration in standard farm pond.

2 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 re present the CRLF are also used to represent exposure values for frogs serving as potentia l prey of CRLF adults. T-REX simulates a 1- year time period. For this assessment, spra y and granular applic ations 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 1⁄2 inch.

Terrestrial EECs for foliar formulations of myclobutanil were derived for the uses summarized in Table 3.8. Crop-specific d ecline data for combined residues of myclobutanil and the primary metabolite RH- 9090 from submitted crop field trial studiesare available for several commodities. Based on available data, foliar dissipation halflives can be derived for pome fruit and stone fruit (19 da ys), caneberries (14 days), bushberries (25 days) hops (15 days), and pe ppers (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 degrad ates of myclobutanil. Using conservative assumptions that the mode of action of the pa rent and degradates are similar and that the compounds are of equivalent toxicity, a conser vative default foliar dissipation half-life of 35 days based on the work of Willis and Mc Dowell (1987) is used for all uses of myclobutanil. Use specific input values, incl uding 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.

64Table 3.8 Input Parameters for Foliar A pplications Used to Derive Terrestrial EECs for myclobutanil with T-REX

Use 1 Application rate (lbs ai/A) Number of Applications Application Interval (days)

Almond 0.2 3 7 Apple (pressure spray/hose-end spray) 0.5 4 7 Apricot (irrigation) 0.5 2 7

Artichoke 0.125 6 14 Asparagus 0.125 6 14

Beans 0.125 4 7 Blackberry/EggPlant/Okra/Pepper/Raspberry 0.125 4 10 Boysenberry/Dewberry/Youngberry 0.0625 4 10

Carrot 0.1875 2 14 Canistel/Mango/Papaya/Sapodilla 0.25 8 14 Cherry/Nectarine/Peach (pressure spray/chemigation) 0.5 3 7

Cotton 0.06 lb ai/cwt NS NS Cucurbit Vegetables 0.12 5 7

Currant 0.125 8 7 Gooseberry 0.125 8 10 Grapes 0.1 6 7 Hops 0.25 4 7

Lettuce 0.125 4 14

Plum/Prune 0.16 7 7

Tomato 0.1 4 21 Turf (ground) 1.3 4 5 Turf (granule – broadcast spreader) 1.35 6 14

1 Aerial Application unl ess otherwise specified

T-REX is also used to calculate EECs for terrestrial insects exposed to myclobutanil. Dietary-based EECs calculated by T-REX for sma ll and large insects (units of a.i./g) are used to bound an estimate of exposure to te rrestrial insects. Av ailable acute contact toxicity data for bees exposed to myclobutanil (in units of μg a.i./bee), are converted to μg 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 fo r 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 exposur es 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 organi sm 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.

65Table 3.9 Upper-bound Kenega Nomogram EE Cs for Dietary- and Dose-based Exposures of the CRLF and its Prey to Myclobutanil

EECs for CRLF EECs for Prey (small mammals)

Use Dietarybased EEC (ppm) Dose-based EEC (mg/kg-bw) Dietarybased EEC (ppm) Dose-based EEC (mg/kg-bw)

Almond 71 81 126 120 Apple 222 253 395 376 Apricot 126 143 225 214
Artichoke 45 51 80 77 Asparagus 56 64 100 96

Beans 55 63 99 94 Blackberry/EggPlant/Okra/Pepper/Raspberry 52 59 91 87 Boysenberry/Dewberry/Youngberry 26 29 46 44
Carrot 45 51 79 75 Canistel/Mango/Papaya/Sapodilla 124 141 221 211 Cherry/Nectarine/Peach 177 202 315 301 Cucurbit Vegetables 63 71 111 106
Currant 59 67 104 99 Gooseberry 75 85 133 127 Grapes 77 87 136 100 Hops 111 126 197 188

Lettuce 47 53 83 79
Plum/Prune 103 118 175 184

Tomato 37 32 57 55
Turf 609 693 1082 1031

66Table 3.10 EECs (ppm) for Indirect Effe cts to the Terrestrial-Phase CRLF via Effects to Terrestrial Invertebrate Prey Items

Use Small Insect Large Insect

Almond 71 8 Apple 221 25 Apricot 126 14
Artichoke 45 5 Asparagus 56 6
Beans 55 6 Blackberry/EggPlant/Okra/Pepper/Raspberry 51 6 Boysenberry/Dewberry/Youngberry 26 3
Carrot 45 5 Canistel/Mango/Papaya/Sapodilla 124 14 Cherry/Nectarine/Peach 177 20
Cotton NA NA Cucurbit Vegetables 63 7
Currant 59 7 Gooseberry 75 8 Grapes 77 9 Hops 111 12

Lettuce 47 5
Plum/Prune 104 12

Tomato 32 4
Turf 609 68 Turf (granular) 504 56

Myclobutanil is applied as a 0.62% ai gra nular formulation to non-residential and residential turf grass at a rate of 1.35 lb ai per acre. Therefore a qua ntitative analysis of terrestrial exposure to granular formulations was conducted. For gr anular applications,
an LD 50 per square foot is estimated base d on application rate and toxicity.

3.4 Terrestrial Plant Ex posure 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 da ta with myclobutanil, toxicity data on other conazole fungicides were used with Te rrPlant and discussed in the risk description (Section 5.2.3.2). Parameter va lues for application rate, drift assumption and incorporation depth are based upon the use and related applic ation method (Tables 2.2 and 3.5). As classified by Terrplant, a r unoff 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%, respectiv ely. EECs relevant to terrestrial plants consider pesticide concentrations in drift a nd in runoff. These EECs are listed by use in Table 3.11. An example output from TerrPla nt v.1.2.2 is available in Appendix N.

67Table 3.11 TerrPlant Inputs and Resultin g EECs for Plants Inhabiting Dry and Semi-aquatic Areas Exposed to Myclobutanil via Runoff and Drift

Use Application
rate (lbs a.i./A) Application method Drift Value

(%) Spray drift EEC (lbs a.i./A) Dry

area EEC (lbs a.i./A) Semiaquatic

area EEC (lbs a.i./A) Boysenberry/Dewberry/Youngberry 0.0625 Foliar – aerial 0.05 0.003 0.006 0.034 Boysenberry/Dewberry/Youngberry 0.0625 Foliar - ground 0.01 0.0006 0.004 0.032 Grapes, tomato 0.1 Foliar – aerial 0.05 0.005 0.010 0.055 Grapes, tomato 0.1 Foliar - ground 0.01 0.001 0.006 0.051 Cucurbit Vegetables 0.12 Foliar – aerial 0.05 0.006 0.012 0.066 Cucurbit Vegetables 0.12 Foliar - ground 0.01 0.001 0.007 0.061 Artichoke, Asparagus, Beans, Blackberry/EggPlant/Okra/Pepper/ Raspberry, Currant, Gooseberry,
Lettuce 0.125 Foliar – aerial 0.05 0.006 0.013 0.069

Artichoke, Asparagus, Beans, Blackberry/EggPlant/Okra/Pepper/ Raspberry, Currant, Gooseberry,
Lettuce 0.125 Foliar - ground 0.01 0.001 0.008 0.064

Plum/Prune 0.16 Foliar – aerial 0.05 0.008 0.016 0.088

Plum/Prune 0.16 Foliar - ground 0.01 0.002 0.010 0.082 Carrot, Hops 0.1875 Foliar – aerial 0.05 0.009 0.019 0.103 Carrot, Hops 0.1875 Foliar - ground 0.01 0.002 0.011 0.096

Almond 0.2 Foliar - aerial 0.05 0.010 0.020 0.110

Almond 0.2 Foliar - ground 0.01 0.002 0.012 0.102 Canistel/Mango/Papaya/Sapodilla 0.25 Foliar – aerial 0.05 0.013 0.025 0.138 Canistel/Mango/Papaya/Sapodilla 0.25 Foliar - ground 0.01 0.003 0.015 0.128 Apple, Apricot, Cherry/Nectarine/Peach 0.5 Foliar - aerial 0.05 0.025 0.050 0.175
Apple, Apricot, Cherry/Nectarine/Peach 0.5 Foliar - ground 0.01 0.005 0.030 0.255

Turf 1.3 Foliar - ground 0.01 0.013 0.078 0.663

Turf 1.35 Granule broadcast spreader 0.00 0.00 0.068 0.675



### 4 Effects Assessment

This assessment evaluates the potential for mycl obutanil to directly or indirectly affect the CRLF or affect its designated critical habi tat. As discussed in Section 2.8, assessment endpoints for the CRLF effects determination in clude direct toxic effects on the survival, reproduction, and growth of CRLF, as well as in direct effects, such as reduction of the prey base or effects to its habitat. In a ddition, potential effects to critical habitat are assessed by evaluating effects to the PCEs, which are component s of the critical habitat areas that provide essential life cycle needs ofthe CRLF. Direct effects to the aquaticphase of the CRLF are based on toxicity inform ation for freshwater fi sh, while terrestrialphase effects are based on avian toxicity data , given that birds are generally used as a

68surrogate 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 invertebrate s, 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 fo r aquatic-phase amphibians), freshwater invertebrates, aquatic plants, birds (surrogate for terrestrial-phase amphibians), mammals, and terrestrial invertebrates. No acceptable da ta were available for aquatic or terrestrial phase amphibians and terrestrial plants.

Toxicity endpoints are esta blished based on data gene rated 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 l iterature data presented in this assessment were obtained from ECOTOX information obtai ned 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 ev aluated 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 mo re 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 releva nt 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 qualitativ ely evaluated, because quantitative relationships between modificat ions and reduction in species survival, reproduction, and/or growth ar e not available. Although the effects determination relies on endpoints that are relevant to the asse ssment endpoints of survival, growth, or reproduction, it is important to note that the full suite of subletha l endpoints potentially available in the effects literature (regardle ss 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

69rationale for rejection of t hose studies that did not pass the ECOTOX screen and those that were not evaluated as part of this e ndangered species risk assessment. A detailed spreadsheet of the available ECOTOX open literature data, including the full suite of lethal and sublethal endpoints is presente d in Appendix I. Appendix J contains a summary of the human health effects data for myclobutanil.

In addition to registrant-submitted and open lite rature toxicity information, other sources of information, including use of the acute pr obit dose response rela tionship to establish the probability of an individual effect and re views of the Ecological Incident Information System (EIIS), are conducted to further refi ne the characterization of potential ecological effects associated with exposure to myclobut anil. A summary of the available aquatic and terrestrial ecotoxicity information, use of the probit dose res ponse relationship, and the incident information for myclobut anil 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 revi ew. From these studies, it is provisionally concluded that 1,2,4-triazole has no greater toxicity to aquati c organisms than the parent compound, myclobutanil. There are currently no open literature stud ies reported in the ECOTOX database for 1,2,4-triazole. Each of the registrant submitted studies is briefly summarized below.

A rainbow trout ( Salma gairdneri ) acute toxicity study (MRID 45284017) was submitted for 1,2,4-triazole. Mortality was obs erved only in the highest test level (1000 mg/L). The calculated LC 50 was 760 mg/L. For myclobutanil, the rainbow trout showed a 96-hour LC 50 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 LC 50 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 toxi city than myclobutanil.

A water flea ( Daphnia magna ) acute toxicity study was submitted for 1,2,4- triazole (MRID 00133381). The calculated LC 50 was 900 (730 to 2200, 95% C.I.) mg/L. The myclobutanil Daphnia magna 48-hour LC 50 was 11 (9.5 to 13, 95% C.I.) mg a.i./L (MRID 00141678). Therefor e, 1,2,4-triazole s hows 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 EC 50 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 EC 50 of 0.83 (0.56 to 1.1, 95% C.I.) mg a.i./L based on cell density (MRI D 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 t oxicity 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

70was submitted which indicates that 1,2,4-tri azole 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 repor t also indicated that a single oral dose of the triazole degradate to ma le birds does not indicate any reproductive effects; however, the protocol of this study is not compar able to the typical avian reproduction study.

Acute mammalian toxicity data on myclobutan il formulations, including those mixed with other pesticides indicate that with one exception (the 60% formulation) the formulations are not more acutely toxic th an the technical grade compound. The rat LD 50 for the technical product is 1600 mg/kg bw, the rat LD 50 for the 60% formulation is 980 mg/kg bw. Therefore, EEC’s were derived se parately for the 60% formulation using the
rat LD 50 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 avai lable ecotoxicity information for 1,2,4-triazole and all myclobutanil formulat ed products is presen ted in Appendix K.

The submitted study citations can be found in Appendix O.

4.1 Evaluation of Aquati c 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 Species Toxicity Value Used in Risk Assessment MRID Study Classification Acute Direct Toxicity to Aquatic-Phase CRLF Bluegill sunfish ( Lepomis macrochirus ) LC 50 = 2.4 mg/L 00144285 Acceptable

Chronic Direct Toxicity to Aquatic-Phase CRLF Fathead minnow ( Pimephales promelas ) NOAEC = 0.98 mg/L LOAEC = 2.2 mg/L 00164986 40409201 40480401 Acceptable

Indirect Toxicity to Aquatic-Phase CRLF via Acute Toxicity to Freshwater Invertebrates (i.e. prey items) Water flea ( Daphnia magna) LC 50 = 11 mg/L 00141678 Acceptable

Indirect Toxicity to Aquatic-Phase CRLF via Chronic Toxicity to Freshwater Invertebrates (i.e. prey items) No data available for myclobutanil

71Assessment Endpoint Species Toxicity Value Used in Risk Assessment MRID Study Classification Indirect Toxicity to Aquatic-Phase CRLF via Toxicity to Non-vascular Aquatic Plants Freshwater green algae ( Selenastrum capricornutum ) EC 50 = 0.83 mg/L 4 19848-01 Acceptable

Tier II growth and reproduction Indirect Toxicity to Aquatic-Phase CRLF via Toxicity to Vascular Aquatic Plants No data available for myclobutanil

Toxicity to aquatic fish a nd invertebrates is categorized using the system shown in Table 4.2 (U.S. EPA, 2004). Toxicity categories fo r aquatic plants have not been defined.

Table 4.2 Categories of Acute Toxicity for Fish and Aquatic Invertebrates

LC 50 (ppm) Toxicity Category
< 0.1 Very highly toxic
> 0.1 - 1 Highly toxic
> 1 - 10 Moderately toxic
> 10 - 100 Slightly toxic
> 100 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 i ndirectly 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, fr ogs, and fish (Hayes and Tennant, 1985).

A summary of acute and chroni c freshwater fish data is provided below in Sections 4.1.1.1 through 4.1.1.3.

4.1.1.1 Freshwater Fish: Acute Ex posure (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 LC 50 of 2.4 (1.5-4.7, 95% C.I.) mg a.i./L (MRID 00144285) will be used to calculate RQs for direct e ffects to the aquatic-phase CRL F. 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

72study available for rainbow tr out reported a 96-hour LC 50 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). Tota l length of juvenile fish at the end of the 35-day exposure was the most sensitive endpoint for the fathead minnow ( Pimephales promelas ); 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% reduc tion in mean total length compared to the control. The LOAE C for growth as determined by wet weight was reported as 4 mg/L. The 8-day egg su rvival 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 E ffects and Additional Open Literature Information

In the bluegill sunfish acute toxicity st udy (MRID 00144285) used to calculate RQs, it was reported that the test orga nisms 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 stud y (MRID 00141677) reported toxi c symptoms at 3.2 mg/L (LOAEC) - the fish exhibited loss of equi librium, 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 st age 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 endpoi nt. 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 fo r myclobutanil on toxicity to aquatic-phase amphibians.

4.1.2 Toxicity to Freshwater Invertebrates

Freshwater invertebrate toxici ty data were used to assess potential indire ct effects of myclobutanil to the CRLF. Effects to freshw ater invertebrates resulting from exposure to

73myclobutanil could indirectly affect the CRLF via reduction in available food items. As discussed in Section 2.5.3, the main food s ource for juvenile aquatic- and terrestrialphase CRLFs is thought to be aquatic inve rtebrates found along the shoreline and on the water surface, including aquatic sowbugs, larval alderf lies and water striders.

A summary of acute and chroni c freshwater invertebrate data is provided below in Sections 4.1.2.1 through 4.1.2.3.

4.1.2.1 Freshwater Invertebrates: Acut e 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 LC 50 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 estimat e a chronic toxicity value for freshwater invertebrates using an acute to chronic ratio with estuarin e/marine invertebrate data because no chronic studies are available fo r myclobutanil. In lieu of any myclobutanil data, toxicity data from other conazole (DMI triazole) fungicides were used to characterize risk to freshwater invertebra tes, assuming that my clobutanil toxicity is similar to other conazoles due to similar m ode 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 studi es considered were those categorized as acceptable or supplemental, test ed 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 inve rtebrate 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

74Table 4.3 Conazole (DMI triazole) Fung icide Chronic Toxicity to Aquatic Invertebrates

Conazole 1 48-hr EC 50 /LC 50

(mg/L) MRID/ Study Classification NOAEC (mg/L) Most sensitive parameter MRID/ Study Classification ACR 2

26 40607735/ Acceptable 0.019 Reproduction (# live offspring) 47036201/ Supplemental 1368 a Cyproconazole

0.29 Reproduction (# live offspring) 43187701/ Acceptable 89.6 a

Difenoconazole 0.77 42245110/ Acceptable 0.0056 Number of young per adult per reproductive day and adult length 42245114/ Supplemental 137.5

Fenbuconazole 2.3 41073507/ Acceptable 0.078 Reproduction and length 41875007/ Supplemental 29.5

Hexaconazole 2.9 00160502/ Acceptable 0.226 Total young and young

p er female reproductive day and length 42147301/ Acceptable 12.8

Prothioconazole 1.2 46246009/ Acceptable 0.51 Number of offspring per parent per reproduction day and terminal length 46246028/ Acceptable 2.4

Tebuconazole 4 40700913/ Acceptable 0.120 Adult length and survival and young per adult per reproduction day 40700915/ Acceptable 33.3

3.07 45823201/ Acceptable 0.19 Time to first brood release and reproduction (neonates/adult) 45823207/ Acceptable 13.8 b to 16.2 c Tetraconazole

2.63 44367018/ Supplemental 0.51 Survival and reproduction 44367019/ Supplemental 5.2 b to 6.0 c

7.16 43257001/ Acceptable 0.052 Adult length 41922102/ Supplemental 137.7 d Triadimefon

0.087 Reproduction 00094679/ Supplemental 82.3 d

Triadimenol 2.5 00126282/ Acceptable 0.199 Reproduction (# young produced) 00094680/ Acceptable 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

c Based on acute toxicity of 3.07 mg/L

d Based on acute toxicity of 7.16 mg/L

754.1.2.3 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 toxi city to freshwater inverteb rates 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 pr oduction and the availability of aquatic plants as food for CRLF tadpoles. Primary productivity is essen tial 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 aqua tic plants (MRID 419848-01) examined the freshwater green algae Selenastrum capricornutum . This study reported a 120-hour EC 50 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 da ta, toxicity data from other conazole (DMI triazole) fungicides were used to characterize risk to aqua tic vascular plants, assuming that myclobutanil toxicity is similar to othe r 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 endpoin ts 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) Fungicid e Toxicity to Aquatic Vascular Plants

Conazole EC 50 (mg/L) 1 Most sensitive parameter MRID Study Classification

Bromuconazole 0.16 Frond pr oduction 42937141 Acceptable

Difenoconazole 1.9 Frond number 46950204 Supplemental

Metconazole 0.022 Frond number 46808428 Acceptable

76Conazole Most sensitive EC 50 (mg/L) 1 Study Classification MRID parameter
Propiconazole 9.02 Frond production 00133363 Supplemental

Prothioconazole 0.073 Frond number 46246101 Acceptable

Tetraconazole 0.31 Frond number 45842201 Acceptable

Triticonazole 1.4 Frond number 44802119 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 terrestr ial toxicity endpoints for the CRLF, based on an evaluation of both the submitted stud ies and the open literature. In addition to the parent myclobutanil, toxicity data on metabolites and degradates are also considered when available. RH-9090 [ α -(3-hydroxybutyl)- α -(4-chlorophenyl)-1 H -1,2,4- triazole-1-propanenitrile] 6-chloro-3-pyridinyl)methyl]- N -nitro-2-imidazolidinimine] (free and bound) is a major metabolite of myclob utanil in plants i.e., > 10%. RH-9090 is considered to be of equivalent toxicity to the parent based on structural activity relationship (SAR). In add ition, 1,2,4-triazole an d triazole conjugate s (triazole alanine and triazole acetic acid) are common de gradates 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 Species Toxicity Value Used in Risk Assessment 1 Citation/ MRID # Study Classification Acute Dose-based DirectToxicity to TerrestrialPhase CRLF Bobwhite Quail ( Colinus virginianus ) LD50 = 498 mg/kg bw 00144286 Acceptable

Acute Dietary-based DirectToxicity to TerrestrialPhase CRLF Mallard Duck ( Anas platyrhynchos ) LC50 = >4090 ppm 00144288 Acceptable

Chronic Direct Toxicity to Terrestrial-Phase CRLF Bobwhite Quail ( Colinus virginianus ) NOAEC = 256 ppm LOAEC >256 ppm: 43087901 Supplemental

Indirect Toxicity to Terrestrial-Phase CRLF (via acute toxicity to mammalian prey items) Mouse LD50 =1360 mg/kg 00165239

00141662 Acceptable

Indirect Toxicity to Terrestrial-Phase CRLF Rat NOAEC = 200 ppm LOAEC = 1000 ppm 00149581

00143766 Acceptable

77Assessment Endpoint Species Toxicity Value Used in Risk Assessment 1 Citation/ Study MRID # Classification (via chronic toxicity to mammalian prey items) NOAEL = 16 mg/kg bw/day LOAEL = 80 mg/kg bw/day Indirect Toxicity to Terrestrial-Phase CRLF (via acute toxicity to terrestrial invertebrate prey items) Honey bee LD50 = > 100 μg a.i. bee (dust) 00144289 Acceptable

Seedling Emergence Monocots Seedling Emergence Dicots Vegetative Vigor
Monocots Indirect Toxicity toTerrestrial- and AquaticPhase CRLF (via toxicity to terrestrial plants)

Vegetative Vigor Dicots No Data Available

1 All studies were conducted with the technical material (approximately 96% pure) and the t oxicity values are adjusted for %a.i.

Acute toxicity to terrestrial animals is categ orized using the classi fication system shown in Table 4.6 (U.S. EPA 2004). Toxicity categor ies for terrestrial plants have not been defined.
Table 4.6 Categories of Acute Toxicity for Avian and Mammalian Studies

Toxicity Category Oral LD 50 Dietary LC 50 Very highly toxic < 10 mg/kg < 50 ppm Highly toxic 10 - 50 mg/kg 50 - 500 ppm Moderately toxic 51 - 500 mg/kg 501 - 1000 ppm

Slightly toxic 501 - 2000 mg/kg 1001 - 5000 ppm Practically non-toxic > 2000 mg/kg > 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 to xicity 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 asse ss the potential dire ct 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 the Bobwhite Quail (MRID 00144286), myclobutanil is categorized as modera tely toxic to birds on a dose basis with
an acute LD 50 of 498 (408-598, 95% C.I.) mg/kg bw.

78Based on avian subacute dietary studies for tw o bird species, myclobut anil is categorized as slightly toxic on a dietary basis with subacute dietary LC 50 ’s of >4090 ppm for mallard duck (MRID 00144288) and > 4530 ppm fo r bobwhite quail (MRID 00144287). Although no definitive subacute dietary LC 50 s could be determined from these studies, there were mortalities in both studies. Th ere was one mortality at 4090 ppm, the highest concentration tested in the mallard duc k study and mortalities at 3000 ppm and 4530 ppm, the highest concentration te sted in the bobwhite quail study.

Table 4.7 Avian Acute Toxicity Data

Common Name %AI Study parameters LD 50 /LC 50 NOAEC/

LOAEC MRID Classification/ Category

Bobwhite Quail Colinus virginianus 84.5 Acute oral study

10 birds/dose level 21 day observation period 0 (vehicle), 316, 464, 681, 1000, 1470 mg/kg tested LD 50 498 (408 – 598) mg/kg bw 1
Slope = 7.03 (3.5-10.5)

NOAEL not determined LOAEL 316 mg/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. 00144286 Acceptable Moderately toxic

Bobwhite Quail

Colinus virginianus 84.5 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) LC 50 > 4530 ppm NOAEC: 1150 ppm LOAEC: 3000 ppm Mortality: 2 at 3000 ppm and 1 at 4530

ppm. Anorexia and lethargy at 3000 and 4530 ppm 00144287 Acceptable Slightly toxic

79Common %AI Study parameters LD 50 /LC 50 NOAEC/ MRID Classification/ Name Category LOAEC

Mallard Duck

Anas platyrhync hos 84.5 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) LC 50 > 4090 ppm NOAEC: 1250 ppm LOAEC: 2220 ppm (anorexia and lethargy). One bird died at 4090

ppm. 00144288 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 av ailable for myclobutanil. One-generation reproductive toxicity studies were conduc ted 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. Ther efore, 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 NOAE C of 256 ppm is used for risk estimation.

RH-9090 [ α -(3-hydroxybutyl)- α -(4-chlorophenyl)-1 H -1,2,4-triazole-1-pr opanenitrile] 6- chloro-3-pyridinyl)methyl]- N -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 rela tionship (SAR). In addition, 1,2,4-triazole and tri azole conjugates (triazole alan ine and triazole acetic acid) are common degradates of triazole co mpounds, including myclobutanil. A submitted report is available which indicates that the acute LD 50 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 observ ed and there was no i ndication of reproductive effects. This report has not yet been reviewed. In a ddition, this protocol is not comparable to the standard submitted avian reproduction study.

80Table 4.8 Avian Chronic Toxicity Data

Common Name %AI Study Parameters NOAEC/LOAEC MRID Classification/ Category

Bobwhite Quail

Colinus virginianus 94.2 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 NOAEC = 256 ppm 1
LOAEC >256 ppm

No treatment-related effects at any level. Not tested at sufficiently high concentration levels 43087901 Supplemental

Mallard Duck

Anas platyrhynchos 94.2 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 = 256 ppm LOAEC >256 ppm

No treatment-related effects at any level. Not tested at sufficiently high concentration levels 43087902 Supplemental

1 Bold value is the value that will be used to calculate risk quotients

4.2.1.3 Birds: Sublethal Effects and A dditional Open Literature

In the acute oral toxicity study for the bobwhite quail (MRID 00144286), it was reported that the test organisms exhibi ted lethargy and anorexia at a ll 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 sub acute dietary study used for risk estimation (MRID 00144288), anorexia and lethargy were ob served 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. Th ere 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 eff ects 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 th e prey mass of the CRLF may consist of vertebrates such as mice, frogs, a nd fish (Hayes and Tennant 1985).

814.2.2.1 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 avai lable 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 LD 50 of 1360 mg/kg, will be used to estimate risk to the CRLF via indirect effects to ma mmals. 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 indi cates that it is not more acutely toxic than the parent. The acute LD 50 is 3650 mg/kg bw (MRID 45284001).

With the exception of the 60 DF formulati on, 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 LD 50 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 pr otective of acute mammalian exposure to the DF formulation.

Table 4.9 Mammalian Acute Toxicity Data

Common Name %AI Study parameters LD 50 /NOAEL MRID Classification/ Category

Laboratory

mouse
Mus musculus 91.9 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 LD 50 = 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. 00165239

00141662 Acceptable Slightly toxic 1

Laboratory

mouse
Mus musculus 1,2,4- triazole Acute oral study LD 50 = 3650 mg/kg 45284001 Practically nontoxic

1 Based on LD 50 (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

82Table 4.10 Acute Rat Toxicity Comparison of Myclobutanil Formulations
Formulation (%) LD 50 (mg/kg bw) MRID Technical Product 1600 (M) 2290 (F) 00141662

1.5% with 2.5% permethrin > 5050 (M & F) 44155803 2.25% with 60% mancozeb > 5000 (M) 40149003 60% formulation with inerts 980 (M) 1235 (F) 00164467, 00164468

Fludioxonil, 1.45%; Mefenoxam, 3.61%; Azoxystrobin, 8.55%; and Myclobutanil, 9.75% 5979 (F) 47092603

Up-and-Down Method: 0.9% Myclobutanil (granules) > 5000 (F) 46886701 1% formulation > 5000 (M & F) 45381001 21% formulation 3749 (F) >5000 (M) 45218401

6.0% formulation LD 50 between 500 & 5,000 (M & F) 45056903

1% formulation > 5,000 (M & F) 44265201

4.2.2.2 Mammals: Chronic Exposure (Growth, Reproduction) Studies

In a two-generation reproduction study in rats on myclobutan il (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 (offspri ng 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 gr owth or reproductive effects (MRID 00149581).

As previously noted, RH-9090 is a major metabol ite of myclobutanil. It is considered to be of equivalent toxicity to the parent based on SAR a nd tolerances for myclobutanil residues in food are establis hed for the combined residue s of myclobutanil and RH-9090 on registered commodities.

In addition, 1,2,4-triazole and tr iazole conjugates (triazole al anine and triazole acetic acid) are common degradates of triazole compounds, including myclobutanil. The 1,2,4- triazole degradate was tested in a tw o-generation reproductio n 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 an d 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 re productive failure (no viable offspring) and an increase in corpora lutea in F 0 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,

83the endpoint values for reproductive effects for th e 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 de gradate triazole alanine. Other triazole conjugates are considered to be toxicologica lly equivalent to triazole alanine. A two-generation rat reproduction study c onducted on triazole alanine (MRID 00164112) indicates that the triazole conjugates e xhibit less toxicity than the parent. Maternal/parental toxicity was not seen in the rat reproduction st udy at the highest dose tested (929/988 M/F mg/kg bw/day). Reproducti ve toxicity was also not seen at the highest dose tested. The o ffspring NOAEL/LOAEL is 192/ 929 mg/kg bw/day based on reduced mean litter weight s in both generations.

Since 1,2,4-triazole and tri azole 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 triazo les (e.g., myclobutanil), separate human health risk assessments have been conducted for 1,2,4-triazole and triazole conjugates. (Februar y 7, 2006, 1,2,4-Triazole, Triazole Alanine, Triazole Acetic Acid: Human Health Aggregate Risk Asse ssment in Support of Reregistration and Registration Actions for Triazole-d erivative 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 toxici ty data relevant to the myclobutanil CRLF assessment were provided in the open litera ture i.e., none of the available mammalian studies identified a more sensitive endpoint. Therefore, only toxic ity data provided in submitted studies were used to assess mammalian effects.

84Table 4.11 Mammalian Chronic Toxicity Data

Common Name %AI Study Parameters NOAEC/

LOAEC MRID Classification/ Category

Laboratory

rat

Rattus norvegicus 84.5 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. 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
P 2 males; slight increase in stillborns, decrease in body weight gain in pups during lactation in F 1 and
F 2 generations. 00149581

00143766 Acceptable

85Common %AI Study Parameters NOAEC/ MRID Classification/ Name Category LOAEC

Laboratory

rat

Rattus norvegicus 1,2,4- triazole Reproduction and fertility effects 0, 250, 500, 3000

ppm M: 15, 31, 189 mkd F: 18, 36, 218 mkd 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/31 mg/kg/day based on abnormal sperm
and ↓ # of CL in F 1 females At 3000 ppm/218 mg/kg/day, reproductive failure (no viable offspring), ↑ CL in F 0 parental females 46467304 Acceptable

Laboratory

rat

Rattus norvegicus Triazole Alanine Reproduction and fertility effects 0, 200, 2000, 10000

ppm M: (F0/F1) 0, 50/47, 213/192, 1098/929 mg/kg/day F: 0, 51/49, 223/199, 1109/988 mg/kg/day 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 00164112 Acceptable

1 Bold value is the value that will be used to calculate risk quotients

864.2.3 Toxicity to Terrestrial Invertebrates

Terrestrial invertebrate toxici ty data are used to assess pot ential indirect effects of myclobutanil to the terrestrial- phase CRLF. Effects to terres trial invertebra tes resulting from exposure to myclobutanil could indi rectly affect the CRLF via reduction in available food.

4.2.3.1 Terrestrial Invertebrates: Acut e Exposure (Mortality) Studies

Myclobutanil is classified as non-toxic to bees with an acute contact LD50 of >362 μg/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 μg 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 toxici ty studies available in the open literature (Appendices H and I). Five acceptable lite rature studies were reviewed for this assessment; one study on beneficial arthropods, three studies on pred acious mites and one study on mirids, a predacious insect (EcoReference Nos.: 104765, 96453, 64063, 63621, 63599). These studies were used qualitativel y as part of a weight of the evidence analysis/determination. The ar thropods 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, mycl obutanil showed moderate toxicity (LD 50 = 150 μg ai/L) to adult mirid at the manufacturer’s label rate of 440 μg 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 LD 50 of > 100 μg/bee, the weight of the evidence indicates that myclobutanil is non-toxic to terrestrial invertebrates. Four of the five studies cl early showed that mycl obutanil was not toxic to terrestrial invertebrates at label rates. Only one of the five available acceptable studies provided an LD 50 . That study indicated moderate toxi city to adult mirids only with no toxicity to the nymphs. Myclobutanil toxi city to adults was unexpected because myclobutanil was seen to be innocuous to all stages of mites in th ree literature studies and mites are usually more easily intoxicated than insects (mirids). Therefore, based on the totality of the available data, the hone y 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

87riparian and upland (i.e., gra ssland, woodland) vegetation coul d result in indirect effects to both aquatic- and terrestrial -phase CRLFs, as well as effe cts to designated critical habitat PCEs via increased sedimentation, a lteration in water quali ty, 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 terr estrial 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 e ffects to the primary constituent elements (PCEs) relevant to the aquatic- and terrestri al-phase CRLF. However, there is some evidence in the open literature that myclobut anil has the po tential to elicit phytotoxic effects. Three terrestrial plant studies were reviewed for this assessment. No adverse effects were observed in two of the th ree studies (EcoReference Nos.: 104715, 104728, 76524). In a cucumber study, myclobutanil spraye d onto seedlings at the first true leaf (application rate not pr ovided) did not affect fruit quali ty. In a seed treatment study, infected spring wheat treated w ith myclobutanil at a rate of 0.12 g/ ai./kg seed performed similarly to untreated seed. In the third study, myclobutanil was app lied at two rates (6.1 g ai/100 m 2 (0.54 lbs/A) and 12.19 g/ai 100 m 2 (1.09 lbs/A)) to “Tifgreen” Bermuda grass to determine if it would pr oduce a plant growth regulati on effect on healthy Bermuda grass. After three applications at 28 to 30 day intervals, comp ared 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 desc ription, terrestrial plant data from 5 other triazole DMI fungicides were obtained and us ed as inputs values in the TerrPlant (v. 1.2.2) model for terrestrial plants. Table 4.12 summarizes the toxicity va lues and endpoints for the 5 triazole fungicides.

Table 4.12 Terrestrial Plant Toxicity Data for 5 Other DMI Fungicides Fungicide EC 25 (lbs a.i./A) NOAEC/EC 05 (lbs a.i./A) Effect/MRID

Seedling Emergence Vegetative Vigor Seedling Emergence Vegetative Vigor Seedling Emergence Vegetative Vigor Metconazole
Monocot 0.78 >0.6 0.3 0.6 Ryegrass: reduced plant height 46805103 46805104

Dicot 0.15 0.44 0.075 0.0036 (EC 05 ) Radish: reduced plant height 46805103 Radish: reduced dry weight 46805104 Prothioconazole
Monocot >0.272 >0.272 0.272 0.272 46246049 46246049
Dicot >0.272 >0.272 0.03 <0 .272 Cucumber: shoot height and dry 46246049

88Fungicide EC 25 (lbs a.i./A) NOAEC/EC 05 (lbs Effect/MRID a.i./A) Seedling Emergence Vegetative Vigor Seedling Emergence Vegetative Vigor Seedling Emergence Vegetative Vigor weight 46246049 Cyproconazole
Monocot >0.64 >0.62 0.64 0.62 46218512 46218511
Dicot 0.091 0.50 0.066 0.09 Cabbage: fresh weight 46218512 Cabbage: dry weight 46218511 Propiconazole
Monocot > 1.5 0.315 1.5 0.0815 41673201 Rye grass: plant height 41673203 Dicot 0.18 0.039 0.056 0.056 Cabbage: dry weight 41673201 Cabbage: dry weight 41673203 Triticonazole
Monocot >4.25 >4.2 1.3 4.2 Rye grass: shoot length 44802116 44802116

Dicot 0.015 1.3 0.004 1.0 Lettuce: shoot length 44802116 Turnip: dry weight 44802116

4.3 Use of Probit Slope Response Relation ship to Provide Information on the Endangered Species Levels of Concern

The Agency uses the probit dose response rela tionship 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 inte rpretation 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 expos ure 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 interpretati on, 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 relationshi p. In addition to a single effects probability es timate based on the mean, upper and lower estimates of the effects probability are also pr ovided to account for variance in the slope, if available.

Individual effect probabilitie s are calculated based on an Ex cel spreadsheet tool IECV1.1 (Individual Effect Chance Model Version 1.1) developed by the U.S. EPA, OPP, Environmental Fate and Effects Division (J une 22, 2004). The model allows for such calculations by entering the mean slope estimate (and the 95% confidence bounds of that

89estimate) as the slope parameter for the spread sheet. In addition, the acute RQ is entered as the desired threshold.

4.4 Incident Database Review

A review of the EIIS database for ecol ogical incidents involving myclobutanil was completed on May 26, 2009. Three incident repo rts were filed for myclobutanil between 1994 and 2003, all with effects on terrestrial plan ts (two incidents with grapes and one with roses). The two incidents with grapes oc curred in California and the one with roses was reported in Maryland. The certainty inde x for the damage in all 3 incidents was rated as possibly related to exposure to my clobutanil. The two incidents with grapes involved application of other pesticides as well as the my clobutanil. Therefore, it is unclear whether the effects were due to expos ure 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 th e reported incidents is provided below.

It should be noted that thes e reported incidents may only represent a fraction of actual incidents. Actual incident s may not have been reported du e to various factors such as lack of reporting, or a lack of w itness to effects. Therefore, th e lack of an incident report does not necessarily indicate a lack of an incident.

Complete incident tables ar e provided in Appendix L.

4.4.1 Terrestrial Incidents

Between 5/30/1994 and 6/3/1994, Rally 40W (mycl obutanil), Pro Gibb (g ibberellic acid), Dimethogan 25 WP, Pro Kil Cryolite 96 (sodi um 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 bunc hes, and limited cone growth with straggly branches were observe d. No residue analysis was conducted. The California Commissioner’s report indicated th at mixtures of Pro- Gibb 4% and Pro-Kil Cryolite 96 may cause some compatibility problem s. The certainty index for this incident (I002621-006) is possible.

It was reported that Rally 40W (myclobut anil) 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 (T hompson’s) was observed. AGRI-MEK (abamectin) and Ad-Wet were also applie d, using a ground spray on the vineyard. The certainty index for this incide nt (I013563-014) is possible.

Systhane (myclobutanil) was applied via a broadcast ground spray to rose bushes grown in greenhouses by local residents in Mary land. The total magnitude was 200 houses. Foliar necrosis and some defoliation were obser ved after exposure to Systhane. Damage varied from house to house and by rose variet y. The certainty index for this incident (I014702-074) is possible.

90No incidents involving terrest rial animals were reported.

4.4.2 Aquatic Incidents

No incidents involving aquatic pl ants 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 habita t from the use of myclobutanil in CA. The risk characterization provides an estimation (Section 5.1) and a desc ription (Section 5.2) of the likelihood of adverse e ffects; articulates risk assessment assumptions, limitations, and uncertainties; and synthesizes an overall conclusion regarding the likelihood of adverse effects to the CRLF or its designated cr itical habitat (i.e., “ no effect,” “likely to adversely affect,” or “may affect, but not likely to a dversely affect”).

5.1 Risk Estimation

Risk is estimated by calculating the ratio of e xposure to toxicity. Th is ratio is the risk quotient (RQ), which is then compared to pr e-established acute a nd chronic levels of concern (LOCs) for each category evaluated (A ppendix F). For acute exposures to the CRLF and its animal prey in aquatic habitats, as well as terrestrial invertebrates, the LOC is 0.05. For acute exposures to the CRLF and mammals, the LOC is 0.1. The LOC 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 1-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 toxi city data for myclobutanil, exposures are not estimated for freshwater invertebrates (chron ic exposure), aquatic vascular plants, and terrestrial plants.

5.1.1 Exposures in the Aquatic Habitat

Estimated risk for the aquatic habitat is base d on a total toxicity approach, that is, EECs for myclobutanil plus 1,2,4-tri azole (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, av ailable mammalian studies indicate that it is either less than or equally toxic as the parent. Us e of the total toxicity

91approach 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 equivale nt toxicity to a quatic organisms.

5.1.1.1 Direct Effects to Aquatic-Phase CRLF

Direct acute effects to the aquatic-ph ase CRLF are based on peak EECs from the PRZM/EXAMS models and th e lowest acute 96-hour LC 50 toxicity value for freshwater fish. The highest modeled peak EEC is 61.41 ppb (myclobutanil plus 1,2,4 triazole) for the turf scenario (repre senting turf use). The acute RQ for this scenario is 0.025 which is lower than the acute endangered species LOC of 0.05.

In order to assess direct chronic ri sks to the CRLF, 60-day EECs from the PRZM/EXAMS models and the lowest chroni c 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 tu rf scenario. The chronic RQ for this scenario is 0.061 which is much lower than the chronic LOC of 1 for fish.

Acute and chronic RQs for all modeled scen arios for myclobutanil and myclobutanil plus 1,2,4 triazole were lower than the related LOC (a summary of the highest RQs is provided in Table 5.1). Based on these results, the effects de termination for myclobutanil is “no effect” for direct effects on the aquatic-phase of the CRLF.

Table 5.1 Summary of Acute and Chronic Di rect Effect RQs for the Aquatic-phase CRLF

Direct Effects to CRLF Scenario EEC ( μ g/L) c RQ Probability of Individual Effect
at ES LOC d, e Probability of Individual Effect at RQ d

Acute Direct Toxicity a Turf Peak: 61.41 0.025 f ~1 in 4.18E+8 (~1 in 216 to ~1 in 1.75E+31) ~1 in 3.56E+12 (~1 in 1.48E+3 to ~1 in 5.06E+46) Chronic Direct Toxicity b Turf 60-day: 60.71 0.061 g Not calculated for chronic endpoints

a Based on bluegill sunfish ( Lepomis macrochirus ) acute 96-hour LC 50 = 2.4 mg/L.

b Based on fathead minnow ( Pimephales promelas ) chronic NOAEC = 0.98 mg/L.

c 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 sunfis h 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 LOC of 0.05.

f RQ < acute endangered species LOC of 0.05.

g RQ < chronic LOC of 1.

925.1.1.2 Indirect Effects to Aquatic-Phas e CRLF via Reduction in Prey (non-vascular aquatic plants, a quatic 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 ar e based on peak EECs from the PRZM/EXAMS models and the lowest toxicity value (EC 50 ) for aquatic non-vascula r plants. The most sensitive non-vascul ar plant 120-hour EC 50 is 0.83 mg/L (freshwa ter 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 acu te RQ for this scenario is 0.074 (61.41 ppb / 830 ppb) which is much lower than th e LOC 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 LOC. Based on these results, the effects determination for myclobutanil is “no effect” for indirect eff ects 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/EXA MS models and the lowest acute toxicity value (LC 50 ) for freshwater invertebrates. The highest modeled peak EEC is 61.41 ppb (myclobutanil plus 1, 2,4 triazole) for th e turf scenario (representing turf use). The acute RQ for this scenario is 0.005 which is much lower than the acute endangered species LOC of 0.05.

Indirect chronic effects to the aquatic-phase CRLF via effects to prey (invertebrates) cannot be quantitatively estimated because th ere is currently no chronic invertebrate toxicity data available for myclobutanil.

Acute RQs for all modeled scenarios fo r myclobutanil and myclobutanil plus 1,2,4 triazole were lower than th e endangered species LOC of 0.05 (a summary of the highest RQ is provided in Table 5.2). Based on th ese results, on an acute basis the effects determination for myclobutanil is “no eff ect” for indirect effects on the CRLF via reduction in freshwater i nvertebrates prey items.

93Table 5.2 Summary of Acute and Chronic RQs Used to Estimate Indirect Effects to the CRLF via Direct Effects on Aquatic Inve rtebrates as Dietary Food Items (prey of CRLF juveniles and adul ts in aquatic habitats)

Direct Effects to Aquatic Invertebrate Prey of CRLF Scenario EEC ( μ g/L) b RQ % Expected Effect on Prey Population at RQ c

Acute Direct Toxicity a Turf Peak: 61.41 0.005 d <0.001 (<0.001 - <0.001)

Chronic Direct Toxicity Not calculated (no toxicity data available)

a Based on water flea ( Daphnia magna) acute 48-hour LC 50 = 11 mg/L.

b From scenario with the highest EECs: granular use on turf (myclobutanil plus 1,2,4-triazole) (see Table 3.6)

c The % expected effect on prey p opulation 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 LOC 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 to xicity 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 a bout direct effects to freshwater fish (see section 5.1.1.1), the effects determination fo r myclobutanil is “no effect” for indirect effects on the CRLF via reduction in freshw ater 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 vi a direct toxicity to aquatic plants are estimated using the most sensitive non-vascular and vascular plant toxicity endpoi nts. The effects determination for myclobutanil is “no eff ect” for indirect effects on the CRLF via reduction in non-vascular plants (see secti on 5.1.1.2 for details). Effects to aquatic vascular plants cannot be quantitatively estim ated 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, potenti al direct effects to terrestrial-phase CRLFs are based on foliar and granular applicatio ns of myclobutanil. In addition, the RQ

94calculation for use on cotton se eds assumes that the seeds are 100% available based on shallow planting conditions and an associated planting depth of 1⁄2 inch.

Potential direct acute effect s to the terrestrial-phase CRL F 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 sub acute dietary toxicity endpoints for avian species. Definitive subacute dietary-base d RQ values cannot be derived because a statistically meaningful LC 50 could not be determined as no dose levels resulted in 50% or greater mortality (i.e., mallard duck LC 50 is > 4090 ppm). Although definitive LC 50 ’s were not derived in the subacute dietary stud ies, there were morta lities in both studies. The concentration levels at which mortalit ies 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 LOC exceedances (RQ > 0.1) for all uses of myclobutanil except Boysenberry/Dewberry/Youngbe rry (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 Application Rate (lb ai/A) Dose-based Acute RQ* 1 Probability of Individual Effect at RQ 2

Almond 0.2 0.23 1 in ~ 2.77E+05 Apple 0.5 0.70 1 in ~ 7.24E+00 Apricot 0.5 0.40 1 in ~ 3.88E+02

Artichoke 0.1 0.14 1 in ~ 1.03E+09 Asparagus 0.125 0.18 1 in ~ 1.21E+07

Beans 0.125 0.18 1 in ~ 1.21E+07 Blackberry/EggPlant/Okra/Pepper/Raspberry 0.125 0.16 1 in ~ 9.04E+07 Boysenberry/Dewberry/Youngberry 0.0625 0.08 1 in ~ 1.54E+14

Carrot 0.1875 0.14 1 in ~ 1.03E+09 Canistel/Mango/Papaya/Sapodilla 0.25 0.39 1 in ~ 4.95E+02 Cherry/Nectarine/Peach 0.5 0.56 1 in ~ 2.61E+01

Cotton 0.06 lb ai/cwt 0.42 1 in ~ 2.47E+02 Cucurbit Vegetables 0.12 0.20 1 in ~ 2.24E+06

Currant 0.125 0.19 1 in ~ 1.21E+07 Gooseberry 0.125 0.24 1 in ~ 1.52E+05 Grapes 0.13 0.24 1 in ~ 5.03E+06 Hops 0.25 0.35 1 in ~ 1.97E+04

Lettuce 0.125 0.15 1 in ~ 2.87E+08

Plum/Prune 0.16 0.33 1 in ~ 2.81E+03

Tomato 0.1 0.10 1 in ~9.62E+11

Turf 1.3 1.93 1 in ~ 1 * = LOC exceedances (acute RQ > 0.1) are bolded and shaded.

1 Based on bobwhite quail acute oral LD50 of 498 mg/kg .
2 The effect probability was calculated based on a calculated sl ope of 7.03 with upper and lower 95% confidence intervals of

3.5 and 10.5

95Table 5.4 Summary of Acute RQs Used to Es timate Direct Effect s to the Terrestrialphase CRLF (granular application)

Use Application Rate (lb ai/A) Dose-based Acute RQ* 1 Probability of Individual Effect at RQ

Turf 1.35 1.96 1 in ~ 1 * = LOC 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 eff ects of myclobutanil to the terrestrial-phase CRLF are derived by considering dietary-based exposures m odeled in T-REX for a small bird (20g) consuming small invertebrates. Chronic eff ects are estimated using the lowest available toxicity data for birds. EECs are divided by toxicity values to estimate chronic dietarybased RQs. Results of the analysis of direct effects to terrestrial-phase CRLF indicate a chronic LOC exceedance (RQ>1) for turf and cotton use only.

Based on the exceedance of the LOC for the ma jority of uses after acute exposure and two uses after chronic exposure, myclobutanil ma y affect directly, the terrestrial-phase of the CRLF.

Table 5.5 Summary of Chronic RQs Us ed to Estimate Di rect Effects to the Terrestrial-phase CRLF (non-granular application)

Use Application Rate (lb ai/A) Dietary-based Chronic RQ* 1

Almond 0.2 0.28 Apple 0.5 0.87 Apricot 0.5 0.49
Artichoke 0.1 0.18 Asparagus 0.125 0.22

Beans 0.125 0.22 Blackberry/EggPlant/Okra/Pepper/Raspberry 0.125 0.20 Boysenberry/Dewberry/Youngberry 0.0625 0.10
Carrot 0.1875 0.17 Canistel/Mango/Papaya/Sapodilla 0.25 0.49 Cherry/Nectarine/Peach 0.5 0.69
Cotton 0.06 lb ai/cwt 2.34 2 Cucurbit Vegetables 0.12 0.24
Currant 0.125 0.23 Gooseberry 0.125 0.23 Grapes 0.13 0.30 Hops 0.25 0.43

Lettuce 0.125 0.18
Plum/Prune 0.16 0.40

Tomato 0.1 0.13
Turf 1.3 2.38 * = LOC exceedances (chronic RQ > 1) are bolded and shaded.

1 Based on bobwhite quail NOAEC of 256 ppm.

2 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 1⁄2 inch

965.1.2.2 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 terrestria l invertebrates, which are considered prey of CRLF in terrestrial habita ts, 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) LD 50 of > 363 μg a.i./bee by 1 bee/0.128g, which is based on the weight of an ad ult honey bee. This is estimated to be >2836 μg a.i./g bw. Because the acute contact effects data shows an LD 50 of greater than the highest test concentrati on of 363 μg a.i./bee, definitiv e acute RQ values cannot be derived. Therefore, a quantita tive assessment of risk to terrestrial invertebrates was not conducted. Mortality in the treat ed bees did not differ from the untreated controls. Given that the honey bee data shows low toxicit y, minimal potential indirect impact to the CRLF via effects of myclobutan il on freshwater invertebrate food items is expected. Risk to terrestrial invertebrates will be discus sed 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 a nd dose-based exposures modeled in T-REX for a small mammal (15g) consuming short grass. Acute and chronic effects ar e 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 LD 50 per square foot calculated based on application rate and toxicity. Fo r non-granular applica tions, the acute listed species LOC of 0.1 is exceeded for apple, apricot, cherry/nectarine/peach, canistel/mango/papaya/sapodilla, hops, plum/pr une, and turf uses. The chronic LOC of 1 on a dose basis is exceeded for all uses a nd the chronic LOC on a dietary basis is exceeded for apples, apricots, canistel/mango/ papaya/sapodilla, cherry/nectarine/peach, cotton, and turf. For granular uses, the acu te listed species LOC is exceeded for turf.

Based on both acute and chronic LOC exceed ances for many uses, myclobutanil may affect indirectly, the terrestrial-phase CRLF via reduction in small mammal prey items.

97Table 5.6 Summary of Acute and Chronic RQ s Used to Estimate Indirect Effects to the Terrestrial-phase CRLF via Direct Effect s on Small Mammals as Dietary Food Items (non-granular application)

Use (Application Rate lb ai/acre) Dose-based Chronic

RQ* 1 Dietarybased Chronic

RQ* 2 Dosebased Acute RQ* 3 % Expected Effect on Prey Population at RQ 4 Almond (0.2) 3.42 0.63 0.08 9.6 Apple (0.5) 10.7 1.97 0.25 23.7 Apricot (0.5) 6.09 1.12 0.14 15.5 Artichoke (0.1) 2.18 0.40 0.05 6.1 Asparagus (0.125) 2.72 0.50 0.06 7.3 Beans (0.125) 2.67 0.49 0.06 7.3 Blackberry/EggPlant/Okra/Pepper/Raspberry ( 0.125) 2.48 0.46 0.06 7.3

Boysenberry/Dewberry/Youngberry (0.0625) 1.24 0.23 0.03 3.5 Carrot (0.1875) 2.14 0.40 0.05 6.1 Canistel/Mango/Papaya/Sapodilla (0.25) 5.99 1.10 0.14 15.5 Cherry/Nectarine/Peach (0.5) 8.55 1.58 0.20 20.3
Cotton NA 3.00 NA NA Cucurbit Vegetables (0.12) 3.02 0.56 0.07 8.5 Currant (0.125) 2.82 0.49 0.06 7.3 Gooseberry (0.125) 3.60 0.66 0.08 9.6 Grapes (0.13) 3.69 0.68 0.09 10.7 Hops (0.25) 5.35 0.99 0.12 13.7 Lettuce (0.125) 2.25 0.42 0.05 6.1 Plum/Prune (0.16) 5.00 0.92 0.12 13.7 Tomato (0.1) 1.55 0.29 0.04 4.8 Turf (1.3) 29.35 5.41 0.68 42.1 * = LOC exceedances (acute RQ > 0.1; chronic RQ > 1) are bolded and shaded

1 Based on dose-based EEC and mycl obutanil rat NOAEL = 16 mg/kg-bw.

2 Based on dietary-based EEC and my clobutanil rat NOAEC = 200 mg/kg-diet.

3 Based on dose-based EEC and my clobutanil mouse acute oral LD 50 = 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 Application Rate (lb ai/A) Dose-based Acute RQ* 1 % Expected Effect on Prey Population at RQ
Turf 1.35 0.63 40.2 * = LOC exceedances (acute RQ > 0.1) are bolded and shaded.

1 Based and adjusted LD 50 of 1380 mg/kg and a calculated LD 50 /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, di etary-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 ac ute LOC for listed speci es is exceeded for

98the majority of myclobutanil uses. The ch ronic LOC is exceeded for cotton and turf. Therefore, following both acute and chronic ex posure 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 reducti on in terrestrial plan t community cannot be quantitatively estimated because there are no vegetative vigor or seedling emergence plant toxicity data available for myclobutan il. For a qualitative ri sk description, see Section 5.2.3.2.

5.1.3 Primary Constituent Elements of Designated Critical Habitat

For myclobutanil use, the assessment endpoi nts for designated critical habitat PCEs involve a reduction and/or modi fication of food sources neces sary 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 determ ination for potential effects to designated critical habitat.

5.1.3.1 Aquatic-Phase (Aquatic Breeding Habitat and Aquatic NonBreeding Habitat)

Three of the four assessment endpoints for the aquatic-phase primary constituent elements (PCEs) of designated critical ha bitat for the CRLF are related to potential effects to aquatic and/or terrestrial plants:

• Alteration of channel/pond morphology or ge ometry and/or increase in sediment deposition within the stream channel or pond: aquatic ha bitat (including riparian vegetation) provides for shelter, fora ging, 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-b ased food sources for pre-metamorphs ( e.g., algae).

Based on the risk estimation for potential effect s to aquatic non-vasc ular plants provided in Section 5.1.1.2, myclobutanil is expected to have no effect on aquatic-phase PCEs of

99designated habitat related to effects on aquatic non-vascular plants. The highest modeled peak EEC for turf use (61.41 ppb) and the mo st sensitive non-vascular plant endpoint (830 ppb) provide an aquatic non-vascular plan t RQ of 0.074, which is much lower than the LOC of 1 for aquatic plants. Therefore, the RQs for all scenarios will be less than the LOC for aquatic plants.

Risk estimations for potential effects to aquatic vascular plants and te rrestrial 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 e ffects on aquatic vascular plants and terrestrial plants. Risks to aquatic vascular plants and terrestrial plan ts will be discussed qualitatively in Section 5.2.3.

The remaining aquatic-phase PCE is “altera tion 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 i nvertebrate toxicity endpoints, as well endpoints for aquatic non-vascular plants, are used as measures of effects. RQs for these endpoints were calculated in Secti ons 5.1.1.1 and 5.1.1.2. Based on acute RQs for freshwater fish and invertebrates and for non-vascular plants th at 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 altera tion of other chemical charac teristics necessary for normal growth and viability of CRLFs and their food source. Following chronic exposure, data are only available for freshwater fish. For a ll uses, the chronic RQs for freshwater fish are less than the LOC. Therefore, followi ng chronic exposure, it can only be partially estimated whether or not myclobutanil is lik ely to affect aquatic-phase PCEs of designated habitat related to effects of alteration of othe r chemical characteristics necessary for normal growth and viability of CRLFs and their food source. Based on chronic effects to freshwater fi sh, myclobutanil is expected to have no effect on this PCE. Chronic risk to freshwater i nvertebrates will be discussed qualitatively in section 5.2.2.2.

5.1.3.2 Terrestrial-Phase (Upland Ha bitat and Dispersal Habitat)

The first two assessment endpoints for the terr estrial-phase PCEs of designated critical habitat for the CRLF are related to poten tial effects to terrestrial plants:

• Elimination and/or disturbance of upland ha bitat; ability of hab itat to support food source of CRLFs: Upland areas within 200 ft of the edge of the riparian vegetation or dripline surroundi ng aquatic and riparian ha bitat that are comprised of grasslands, woodlands, and/or wetland/r iparian plant species that provides the CRLF shelter, forage, and predator avoidance

• Elimination and/or disturbance of dispersa l habitat: Upland or riparian dispersal habitat within designated un its and between occupied locations within 0.7 mi of each other that allow for movement be tween sites including both natural and altered sites which do not cont ain barriers to dispersal

100The risk estimation for terrestrial-phase PCEs of designated habitat related to potential effects on terrestrial plants cannot be qua ntitatively 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 “reducti on and/or modification of food sources for terrestrial phase juven iles and adults.” To assess the im pact of myclobutanil on this PCE, acute and chronic toxicity e ndpoints for birds, mammals, and terrestrial invertebrates are used as measures of effects. RQs for thes e endpoints were calculated in Sections 5.1.2.1 and 5.1.2.2. For terrestrial-phase amphibians, us ing birds as a surrogate, there are acute LOC listed species exceedances for multiple uses. The chronic avian LOC is exceeded for turf and cotton uses. RQs for terrestrial invertebrates were not estimated because a definitive LD 50 was not available. For mammals, the acute LOC for listed species is exceeded for multiple crops and the acute LOC fo r non-listed species is exceeded for turf. The chronic LOC 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 LOC is exceeded for multiple uses and the chronic LOC 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 we re not estimated because a definitive LD 50 was not available. For mammals, the acute LOC for listed species is exceeded for multiple crops and the acute LOC for non-listed species is exceeded for turf. The chronic LOC is exceeded for multiple crops. Theref ore, myclobutanil may affect the fourth terrestrial-phase PCE.

5.2 Risk Description

The risk description synthesizes an overall conclusion regarding th e likelihood of adverse impacts leading to an effects determination ( i.e ., “no effect,” “may affect, but not likely to adversely affect,” or “likely to advers ely affect”) for the CRLF and its designated critical habitat.

Based on the RQs presented in the Risk Es timation (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 regul atory action regarding myclobutanil. A summary of the risk estimation results are pr ovided 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.

101Table 5.8 Risk Estimation Summary for Myclobutanil - Direct and Indirect Effects to CRLF

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 exceeden ces 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 LO C exceedences for aquatic nonvascular 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, bi rds 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.

Indirect Effects Survival, growth, and reproduction of CRLF individuals via effects on prey ( i.e., terrestrial invertebrates, small terrestrial mammals and terrestrial phase amphibians) Y 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, ap ricots, cherries, nectarines, peaches, cotton and turf. For granular uses, the acute listed species LOC is exceeded for turf. For terrestrial invertebrates, the acute contact LD 50 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, Ther e are dose-based acute LOC exceedances (RQ > 0.1) for all uses except Boysenberry/Dewberry/Youngberry. The chronic avian LOC is

102LOC Assessment Endpoint Exceedances Description of Results of Risk Estimation (Y/N)

exceeded for turf and cotton uses.
Indirect Effects Survival, growth, and reproduction of CRLF individuals via effects on habitat ( i.e., riparian vegetation) Unknown No vegetative vigor or seedling emergence plant toxicity data are available. A qualitative discussion of risk is provided.

Table 5.9 Risk Estimation Summary fo r 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. Unknown There are no LOC exceed ences for aquatic nonvascular plants. No aquatic vascular or terrestrial plant data are available. A qualitative discussion of risk is provided.

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. Unknown There are no LOC exceed ences for aquatic nonvascular plants. No aquatic vascular or terrestrial plant data are available. A qualitative discussion of risk is provided.

Alteration of other chemical characteristics necessary for normal growth and viability of CRLFs and their food source. Unknown There are no LOC ex ceedences for listed species following acute and chronic exposure to freshwater fish or acute exposure to freshwater invertebrates. There are no LOC exceed ences for aquatic nonvascular plants. No data are available for freshwater invertebrates (chronic exposure) or aquatic vascular plants. A qualitative discussion of risk is provided.Reduction and/or modification of aquaticbased food sources for pre-metamorphs (e.g., algae) N There are no LOC exceed ences for aquatic nonvascular 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 Unknown No vegetative vigor or seedling emergence plant toxicity data are available. A qualitative discussion of risk is provided.

Elimination and/or disturbance of dispersal habitat: Upland or riparian dispersal habitat Unknown No vegetative vigor or seedling emergence plant toxicity data are available. A qualitative discussion

103Habitat Effects Assessment Endpoint Description of Results of Risk Estimation (Y/N)

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 cr ops. For terrestrial invertebrates, the acute contact LD 50 is greater than the highest dose tested with no mortalities. Risk the terrestrial invertebrates will be discussedqualitatively in the risk description. For terrestrialphase 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, additio nal information is considered to refine the potential for exposure at th e predicted levels based on th e life history characteristics ( i.e. , habitat range, feedi ng preferences, etc.) of the CRLF. Based on the best available information, the Agency uses the refined ev aluation to distinguish those actions that “may affect, but are not likely to adversely a ffect” 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 acti on 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 c ontext of a level of effect where “take” occurs for even a single individual. “T ake” in this context means to harass or harm, defined as the following:

 Harm includes significant habitat effect s 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 crea te the likelihood of injury to listed species to such an extent as to significantly disrupt normal behavior patterns which include, but are no t limited to, breeding, feeding, or sheltering.

• Likelihood of the Effect Occurring : Discountable effect s are those that are extremely unlikely to occur.

• Adverse Nature of Effect : Effects that are wholly be neficial without any adverse effects are not considered adverse.

104A description of the risk and effects determ ination for each of the established assessment endpoints for the CRLF and its designated crit ical 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 th e frog that are obligatory aquatic organisms, including eggs and larvae. It also considers submerged te rrestrial-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 scen arios for myclobutanil and myclobutanil plus 1,2,4 triazole were lower than the related LO C. 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 (tur f scenario) is estimated to be 1 in 3.56 x 10 12 (1 in 1.48 x 10 3 to 1 in 5.06 x 10 46 , 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-ta rgeted monitoring da ta show myclobutanil concentrations that are much lower than the modeled concentrations. The highest concentrations of myclobutanil were dete cted in surface water. Myclobutanil was detected in ambient surface water (Table 3.3) at a detection fre quency of 37.8 % (166 of 439 samples) collected in five counties in California. The maximum daily myclobutanil concentration was 0.507 μ g/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 my clobutanil (plus 1,2,4 tr iazole) were 2.84 μ g/L (peak), 2.82 μ g/L (21-day), and 2.77 μ g/L (60-day).

There are no relevant data in the open lit erature and no incident data for fish.

The effects determination is no effect on a quatic-phase CRLF from direct exposures to myclobutanil.

5.2.1.2 Terrestrial-Phase CRLF

As stated in the Risk Es timation section (Section 5.1.2.1), the acute avian dose-based RQs exceed the acute LOC for listed species (0.1) for all uses of myclobutanil except boysenberry/dewberry/youngberry at an application rate of 0.0625 lbs. a.i./A. In an effort to refine the acute dose-based risk estimate s, the T-REX model was modified to account for the lower metabolic rate and lower calor ic requirement of amphibians (compared to birds). Acute dose-based RQs were recalcul ated using the T-HERPS (Version 1.0) model

105for small (1 g), medium (37 g), and large (238 g) frogs. An example output from THERPS is in Appendix M. Using this refinement, the acute dose-based RQ exceeds the acute listed species LOC of 0.1 for 238 gr am amphibians eating small herbivorous mammals following application to turf. The dose-based RQs for 37 gram amphibians eating small herbivorous mammals exceed th e acute LOC for listed species following application to all crops except boysenberry/dew berry/youngberry at an application rate of 0.0625 lbs a.i./A and tomatoes at 0.1 lbs a.i./A (see Table 5.10).

Table 5.10 Thirty Seven Gram Amphibi an T-HERPS RQs for Consumption of Small Herbivorous Mammals

USE RQ
Almond 0.16 Apple 0.49 Apricot 0.28
Artichoke 0.10 Asparagus 0.13

Beans 0.12 Blackberry/EggPlant/Okra/Pepper/Raspberry 0.11 Boysenberry/Dewberry/Youngberry 0.06
Carrot 0.10 Canistel/Mango/Papaya/Sapodilla 0.28 Cherry/Nectarine/Peach 0.39 Cucurbit Vegetables 0.14
Currant 0.13 Gooseberry 0.17 Grapes 0.13 Hops 0.25

Lettuce 0.10
Plum/Prune 0.23

Tomato 0.07
Turf 1.41
1 Bold indicates that the RQ exceeds the listed species LOC 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 LOC 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 te st doses (1000 and 1470 mg/kg bw), seven days at 681 mg/kg bw, thr ee 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 fi ndings in liver an d 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 ad justed 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

106higher 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. N one of the other uses generated dose-based EECs for small insects th at 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 we re not estimated because the LC 50 value exceeds the maximum limit concentration tested. As stat ed in the effects section, myclobutanil is categorized as slightly toxic on a di etary basis with subacute dietary LC 50 ’s of >4090 ppm for mallard ducks (MRID 00144288) and > 4530 ppm for bobwhite quail (MRID 00144287). Although no definitive subacute dietary LC 50 ’s could be determined from these studies, there were mortalities in bot h 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 dietarybased EEC for small insects following use on turf is 609 ppm, which is roughly 4.9 times lower than 3000 ppm, the lowest concen tration 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 LOC of 0.1. Therefore, ther e is an uncertainty associated with potential mortality to liste d species following turf uses. For apples, which have the next highest terrestrial e xposure 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 diet ary based RQ would be 0.07). This is less than the acute avian LOC for listed species.

As stated in the Risk Estim ation section, the chronic avian LOC is exceeded following use on turf and cotton (assumi ng 100% of seed available). None of the other uses generated chronic RQs that exceeded the chronic LOC.

There were no avian or amphibi an studies available in the ECOTOX open literature for myclobutanil. Similarly, no myclobutanil incident s have been reported involving birds or terrestrial-phase amphibians.

The Agency concludes that there is a potenti al 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 LOC 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 ma mmals exceed the acute LOC for listed species following applica tion to all crops except boysenberry/dewberry/youngbe rry and tomatoes.

• On an acute dose-basis, there is an uncerta inty associated with potential sublethal effects for all uses.

• Based on the lowest dietary concentrati on where mortality was observed in the subacute dietary studies (both studies had LC 50 ’s greater than the highest concentration tested), there is an uncertain ty 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 ( 1 in ~ 4.95E+02) and apricots (1 in ~ 3.88E+02).

• The chronic avian LOC 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 diat oms) and detritus. Acute RQs for aquatic non-vascular plants did not exceed the LOC of 1 for any of the assessed uses. The highest acute RQ (0.074) was for the turf scen ario. As previously discussed, available monitoring data show myclobutan il concentrations that are mu ch lower than the modeled concentrations. There are no re levant data in the open litera ture and no incident data for aquatic plants. The effects de termination 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 in direct effects to the CRLF via effects on freshwater invertebrate food items is depende nt on several factor s 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 indivi duals within a prey species is likely to be reduced such that it may indirectly affect the CRLF.

No acute RQs exceeded the endangered specie s LOC of 0.05. The highest acute RQ for aquatic invertebrates was 0.005 (turf scenario). At this RQ, the percent effect to the

108aquatic invertebrate prey base is < 0.001% (i.e . the percentage of th e aquatic invertebrate population that may be affected following exposure to myclobutanil).

No chronic freshwater inverteb rate toxicity data are availa ble for myclobutanil. It was not possible to estimate a chronic toxicity value for freshwater invertebrates using an acute to chronic ratio with es tuarine/marine invertebrate da ta because no chronic studies are available for myclobutanil. Therefore, a quantitative assessment of risk following chronic exposure to myclobutanil was not pos sible using these methods. However, the risk may be considered using other approaches.

Using the modeled EECs, freshwater inverteb rate chronic toxicity values that would trigger an exceedence of the LOC 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 LOC 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 acu te to chronic ratio of ≥ 180.

As previously described, acute and chronic toxicity data from other conazole (DMI triazole) fungicides were avai lable for aquatic invertebrates. For risk description purposes, these endpoints were used to calcula te acute to chronic ratios, assuming that myclobutanil toxicity is similar to other con azoles due to similar m ode of action. Data were available for nine conazole to calculat e acute to chronic ratios from water flea ( Daphnia magna ) studies (the species which acute da ta is available for myclobutanil).

As applied to myclobutanil, only one of the conazole acute-to-chr onic ratios (high-end estimate for cyproconazole = 1368) is higher that the ratio of ≥ 180 that would trigger chronic LOC exceedences for freshwater in vertebrates based on myclobutanil modeled EECs. Assuming an acute-to-chronic ratio of 1368, chronic toxicity of myclobutanil to freshwater invertebrates is es timated to be 8.04 μg/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 exce ed the chronic LOC of 1; only those with 21-day EECs less than 8.04 μg/L do not exceed (see Table 3.6). It is important to note that there were two available chronic t oxicity studies for cyproconazole. The NOAEC/LOAECs for these two studie s are: 0.019/0.073 and 0.29/0.57 mg/L, respectively. Both studies are acceptable fo r 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 estim ate (89.6) is less than the ratio of ≥ 180 that would trigger LOC exceedences for myclobutanil . Thus, as applied to myclobutanil there are no exceedences of the LOC based on th e lower end acute-to-chronic estimate for cyproconazole. Cyproconazole toxicity data suggests the possibility of effects from myclobutanil on freshwater inve rtebrates that may exceed the LOC. However, there is considerable uncertainty associated with extr apolating 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.

109In addition to studies on the water flea ( Daphnia magna ), 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 monito ring data show myclobut anil concentrations that are much lower than the modeled concentr ations. 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 accumu lation is conservative (an overestimate) compared to flowing systems. Furthermore, the K oc 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 mi nimal 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 a nd 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 fi sh, the surrogate for the aquatic-phase CRLF. The acute and ch ronic RQs for all modeled scenarios for myclobutanil and myclobutanil pl us 1,2,4 triazole were lower th an the related LOC. The probability of an individual effect at the highest RQ (turf scenario) is estimated to be 1 in 3.56 x 10 12 (1 in 1.48 x 10 3 to 1 in 5.06 x 10 46 , 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 m odeled EECs. Available monitoring data show myclobutanil concentrati ons that are much lower than the modeled concentrations. There are no relevant data in the open literat ure 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 juveni le 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 invertebrate s were not estimated because no definitive LC 50 can be estimated from the available data . The data indicate no mortalities at concentration levels up to and including 2836 μg a.i./g bw or 2836 ppm (highest level

110tested) 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 LOC of 0.05 for listed terrestrial invertebrate species. Upper bound RQs for small insects would also slightly exceed the acute LOC 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 LOC. Based on the above estimates for small insects, there is an uncertainty associated with potential mortalit y 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 LOC of 0.05 for listed terrestrial inverteb rate 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 terres trial organisms, one of the five available literature studies on terrestria l invertebrates provided an LD 50 . Three mite studies and one arthropod study showed no adverse effects on the species evaluated. A single study on mirids provided an LD 50 of 150 μg 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 LD 50 for mirids cannot be conducted, howev er, because insufficient data are available to calculate ppm expos ures (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 av ailable literature st udies, and the fact that the mirid study showed no toxicity to nymphs, minimal potentia l 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 terres trial-phase CRLFs indicate that large adult frogs consume terrestrial vertebrates, including mice. The dose-based chronic RQs exceed the listed species chronic LOC for all uses and the dietary-based chronic RQs for a number of myclobutanil uses. The dose-based acute RQ s 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 e xpected 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 wa s identified as potentially more toxic than the technical material based on a rat LD 50 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 LD 50 for the 60 DF formulation for apples (RQ = 0.21) and grapes (RQ = 0.05). These results indi cate that based on actual use parameters, the 60 DF formulation does not pres ent higher toxicity in the fi eld than other formulations

111when applied at label prescribed rates. Based on the weight-of-evidence, uses for myclobutanil may indirectly impact the CRL F 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 terr estrial habitats. Based on th e assessment of risk to the terrestrial-phase CRLF (direct effects), th e 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 functi ons in aquatic ecosystems. Non-vascular aquatic plants are primary producers and pr ovide the autochthonous energy base for aquatic ecosystems. Vascular plants provide structure as at tachment sites and refugia for many aquatic invertebrates, fish, and juvenile organisms, such as fish and frogs. In addition, vascular plants al so provide primary productivity and oxygen to the aquatic ecosystem. Rooted plants help reduce se diment loading and provide stability to nearshore areas and lower streambanks. In a ddition, vascular aquatic plants are important as attachment sites for egg masses of CRLFs.

Potential indirect effects to the CRLF ba sed on impacts to habitat and/or primary production were assessed using RQs for aquatic freshwater non-vasc ular plants based on myclobutanil toxicity data. Th ere is no freshwater vascular plant data for myclobutanil so risk is assessed qualitatively.

As previously discussed, acute RQs for aqua tic non-vascular plants did not exceed the LOC of 1 for any of the assessed uses.

No aquatic vascular plant toxicity data ar e available for myclobutanil. As previously described, toxicity data from other conazoles we re used to assess risk from myclobutanil. For the seven conazole fungicides ev aluated, the range of 7/14-day EC 50 s 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 othe r conazoles, there were no exceedences of the LOC using the EC 50 data from 6 of the 7 conazoles and the conazole mean EC 50

. However, using the most sensitive endpoint (m etconazole = 0.02 mg a.i./L), resulted in exceedences of the LOC of 1 for about one thir d of the myclobutanil use scenarios (RQs based on myclobutanil plus 1,2,4 triazole EECs ranged from 0.13 to 2.79). Metaconazole

112toxicity data suggests the po ssibility of effects from my clobutanil on aquatic vascular plants that may exceed the LOC. However, th ere is considerable uncertainty associated with extrapolating toxicity from other con azoles to myclobutanil, thus the effects of myclobutanil cannot be quantif ied without data on myclobutanil toxicity to aquatic vascular plants.

As previously discussed, available monito ring data show myclobut anil 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 mi nimal potential indirect impact to the CRLF (habitat effects) based on effects of mycl obutanil on aquatic plants (vascular and nonvascular). The effects determination is ma y effect, not likely to adversely affect.

5.2.3.2 Terrestrial Plants

There are no registrant-submitted terrestria l plant toxicity data for myclobutanil for assessment of the potential for indirect eff ects to the aquatic- and terrestrial-phase CRLF via effects to riparian vegetation or effect s to the primary constituent elements (PCEs) relevant to the aquatic- a nd terrestrial-phase CRLF. As stated previously, limited evidence in the open literature indicates th at myclobutanil has the potential to elicit phototoxic effects. At 1.07 lbs a.i./A applied at 28-30 day intervals, there was evidence of decreased quality of “Tifgreen” Be rmuda grass (ECOTOX ref. no. 76524). One incident report (I014702-074) indicated foliar necrosis and some defoliation with roses after exposure to myclobutanil. Damage vari ed from house to house and by rose variety. The certainty index for this incident (I014702-07 4) was possible. The application rate(s) were not reported for this incident.

Also stated previously, mycl obutanil is a member of the class of triazole sterol 14 α

demethylase-inhibitors (DMIs). To date, no other DMI triazole fungicides have been assessed for risk to the CRLF. However, terre strial plant studies ar e available on 5 other DMI triazole fungicides that ha ve at least one endpoint that may be used in the TerrPlant (v. 1.2.2) model for terrestrial plants. For ri sk description purposes , these endpoints were used in the model as surrogates for myclobutan il, using the solubility of myclobutanil for the potential runoff fraction. In general, us ing the endpoints from th e 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 applic ation rates that would exceed the LOC for listed dicots and non-listed dicots inhabiting semi-a quatic areas for both aerial and ground applications. Table 5.11 summari zes these application rates.

113Table 5.11 Myclobutanil Application Rates Combined with Endpoints from 5Triazole DMI Fungicides Exceeding the Terrestrial Plant LOC for Listed and NonListed Dicots in Semi-Aquatic Areas Application Rate (lbs a.i./A)
Non-listed dicots Listed dicots Triazole Fungicide Aerial, Airblast, Spray Chemigation Ground Aerial, Airblast, Spray Chemigation Ground

Cyproconazole 0.16 0.17 0.12 0.13

Metconazole 0.28 0.30 0.14 0.15 Propiconazole 0.33 0.36 0.10 0.11 Prothioconazole Not available 1 Not available 1 0.05 0.06

Triticonazole 0.03 0.03 0.007 0.008

1 No EC 25 available

It is noted that the la beled uses of myclobutan il include direct applic ation to a variety of terrestrial plants (agricultural and orname ntal) at multiple growth stages (e.g., seed treatment, pre-bloom, bloom, foliar, post-bloom et c.). Considering the fact that the labels provide for exposure to terrestr ial plants throughout the growth stage, it is probable that the damage to the crops is not so extensiv e 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, inci dent 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 ther e 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 ha bitat for the CRLF are related to potential effects to aquatic and/or terrestrial plants:

• Alteration of channel/pond morphology or ge ometry and/or increase in sediment deposition within the stream channel or pond: aquatic ha bitat (including riparian vegetation) provides for shelter, fora ging, 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-b ased food sources for pre-metamorphs ( e.g., algae).

Conclusions for potential indire ct effects to the CRLF via di rect effects to aquatic and terrestrial plants are used to determine whethe r effects to critical habitat may occur. There were no LOC exceedences for aquatic non-vascular plants (section 5.2.2.1). As stated previously, toxicity data from other con azole (triazole) fungi cides were used to characterize risk to aquatic va scular plants, assuming that my clobutanil toxicity is similar to other conazoles due to similar mode of action (section 5.2.3.1). There were no exceedences of the LOC using the EC 50 data from 6 of the 7 conazoles and the conazole mean EC 50 . However, using the most sensitive endpoint resulted in exceedences of theLOC for about one third of the myclobutanil use scenarios. There are no registrantsubmitted terrestrial plant toxicity data for my clobutanil. When the results of terrestrial plant studies conducted with five other tr iazole DMI fungicides are used with the application rates for myclobutanil in the Terrp lant model, dicots living in semi-aquatic areas appear to be the most se nsitive terrestrial plants, with potential exceedance of the terrestrial plant LOC for a variety of uses (section 5.2.3.2). Overall, there is a potential for effects to habitat via imp acts to terrestrial plants.

The remaining aquatic-phase PCE is “altera tion 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 LOC exceedences for aquatic non-vascular plants, freshwater fish, or freshwater invertebrates (acute effects). No chronic freshwater invertebra te studies are available for myclobutanil. There are no exceedences of the freshwater in vertebrate chronic LOC using toxicity data from 8 of 9 conazoles with similar mechanisms of toxicity. For the 9 th conazole, 2 chronic toxicity studies are available, one of which indicates LOC exceedances and the other does not. Overall, effects to habita t are not expected via alteration of other chemical characteristics necessary for norma l growth and viability of CRLFs and their food source.

5.2.4.2 Terrestrial-Phase PCEs

Two of the four assessment endpoints for the te rrestrial-phase PCEs of designated critical habitat for the CRLF are related to poten tial effects to terrestrial plants:

• Elimination and/or disturbance of upland ha bitat; ability of hab itat to support food source of CRLFs: Upland areas within 200 ft of the edge of the riparian vegetation or drip line surr ounding aquatic and riparian ha bitat that are comprised of grasslands, woodlands, and/or wetland/r iparian plant species that provides the CRLF shelter, forage, and predator avoidance.

115• Elimination and/or disturbance of dispersa l habitat: Upland or riparian dispersal habitat within designated un its and between occupied locations within 0.7 mi of each other that allow for movement be tween sites including both natural and altered sites which do not cont ain barriers to dispersal.

There are no registrant-submitted terrestria l plant toxicity data for myclobutanil for assessment of effects to the pr imary constituent elements (PCE s) relevant to the aquaticand 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 ap plication rates for myclobutanil in the TerrPlant model, dicots liv ing in semi-aquatic areas appear to be the most sensitive terrestrial plants, with potenti al exceedance of the terre strial plant LOC for a variety of uses. Therefore, there is a pot ential for effects to habitat via effects to terrestrial plan ts (Section 5.2.3.2).

The third terrestrial-phase PCE is “reducti on and/or modification of food sources for terrestrial phase juven iles and adults.” To assess the im pact of myclobutanil on this PCE, acute and chronic toxicity endpoints for terrestrial i nvertebrates, 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 exposur e, 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 no t likely to adversely affect the terrestrial invertebrate prey base for the CRLF. For mammals, the acute listed species LOC and the chronic LOC are exceeded for multiple uses. For terrestrial-phase amphibians, using birds as a surrogate, there are acute LOC lis ted species exceedances for multiple uses. The chronic avian LOC is exceeded for turf and cotton uses. Therefore, there is a potential for effects to habitat via indirect effects to terrest rial-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 un certainty associated with potential mortality for listed small terr estrial 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 th e mirid study showed no toxicity to nymphs, it was determined that alt hough there may be an effect, it is not likely to adversely affect the terres trial invertebrate prey base for the CRLF. For mammals, the acute listed species LOC and the chronic LO C are exceeded for multiple uses. For terrestrial-phase amphibians, using birds as a surrogate, there are acute LOC listed species exceedances for multiple uses. The chronic avian LOC is exceeded for turf and

116cotton 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 t hose 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 f ootprint 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 iden tified direct/indirect effects and/or effects to critical habitat are anticipat ed to occur only for those curr ently occupied core habitat areas, CNDDB occurrence sections, and designa ted 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 downstrea m 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 tr iazole were lower that the related LOCs.

The determination of the buffer distance for spa tial extent of the effects determination is described below.

5.2.5.1 Spray Drift

In order to determine terrestrial and aqua tic habitats of concern due to myclobutanil exposures through spray drift, it is necessary to estimat e 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 lim ited 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 fo r each method of application that resulted in LOC exceedances. A turf grass use was m odeled 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 me thods to represent a lower bound for potential impact.

117Myclobutanil labels do not have specific appl ication requirements for reducing potential spray drift, that is, restrictions on wind speed, release height and dropl et 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 Turf Grass Mango Caneberry Caneberry Application Method Ground Aerial Ground Aerial Application Rate 1.3 0.25 0.0625 0.0625 Droplet Size Distribution Very Fine to Fine - 90 th Percentile Release Height High Boom NA High Boom NA

Table 5.13 includes uses with the maximum single a pplication 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 con cern (e.g., RQs will be below LOCs). The estimated buffer distance identifies those lo cations where terrestrial landscapes can be impacted by spray drift deposition alone ( no runoff considered). These distances represent the maximum extent where effect s are possible using the most sensitive terrestrial data and, in the case of myclobutanil, the chroni c LOC 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 hi ghest rates for both aerial and ground applications, the estimated maximum di stance at which any LOC 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 becau se no myclobutanil uses resulted in LOC exceedances for freshwater aquatic species.

Table 5.13 Summary of Maximum Predicted Distances for Potential Spray Drift Effects

Application Method Application Rate (lb/ai Acre) Uses Terrestrial LD 50 Distance (ft)
0.5 Mango 158 Aerial 0.0625 Caneberries 0
1.3 Turf Grass 76 Ground 0.0625 Caneberries 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, a ll aquatic RQs from all modele d scenarios with myclobutanil and myclobutanil plus 1,2,4 tri azole were lower that the rela ted LOCs. Therefore, given that no LOCs were exceeded, a downstream dilution analysis was not performed.

1185.2.5.3 Overlap between CRLF habitat a nd Spatial Extent of Potential Effects

An LAA effects determination is made to t hose 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, crit ical habitat and available occurrence data for CRLF.

For myclobutanil, the use pattern in the fo llowing land cover cla sses (cultivated crops, developed land (low, medium and high inte nsity and open space), forest, open water, orchards and vineyards, pastur e/hay, wetlands, turf and right s-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 footprin t of the initial area of concern (which represents potential myclobutanil use sites) is compared to CRLF habitat, there are several areas of overlap (Figur e 5.1). Appendix E provides ma ps of the initial area of concern, along with CRLF habitat areas, in cluding currently occupied core areas, CNDDB occurrence sections, and designated critical habitat. It is expected that any additional areas of CRLF habita t that are located 158 ft (t o account for offsite migration via spray drift) outside the ini tial area of concern may also be impacted and are part of the full spatial extent of the LAA/effects to critical habitat effects determination.

119Figure 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 poten tial ecological risks resulting from a maximum use scenario, which is determined from labeled statements of maximum application rate and number of appli cations with the shortest time interval between applications. The frequency at whic h 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 border ing a 1-hectare, 2-meter deep (20,000 m 3 ) pond with no outlet. Exposure estimates genera ted 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-treate d 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. Sm aller water bodies have limited storage capacity and thus may overflow and carry pesticide in the discharge, whereas the EXAMS pond has no discharge. As waters hed size increases beyond 10-hectares, it becomes increasingly unlikely that the entire watershed is planted w ith a single crop that is all treated simultaneously with the pesticid e. 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 car ried and dissipated downstream.

The Agency acknowledges that there are so me unique aquatic habitats that are not accurately captured by this modeling scenar io 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 a nd depth and/or are located adjacent to larger orsmaller drainage areas than the EXAMS pond. The Agency does not currently have sufficient informa tion regarding the hydrology of these aquatic habitats to develop a specific alternate scenar io 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

121of exposure to aquatic-phase CRLFs. In addi tion, the Services agree that the existing EXAMS pond represents the best currently available approach for estimating aquatic exposure to pesticid es (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 fi eld capacity, wilting point, and saturation water content. The chemical transport com ponent 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 cons idering the processes of pesticide uptake by plants, surface runoff, erosion, decay, volatilization, foliar wash-off, advection, dispersion, and retardation.

Uncertainties associated with each of thes e individual components add to the overall uncertainty of the modeled concentrations . Additionally, model inputs from the environmental fate degradation studies ar e chosen to represen t the upper confidence bound on the mean values that are not expected to be exceeded in the environment approximately 90 percent of the time. M obility input values are chosen to be representative of conditions in the environment. The natural va riation in soils adds to the uncertainty of modeled values. Factors such as application date, crop emergence date, and canopy cover can also affect estimated c oncentrations, adding to the uncertainty of modeled values. Factors within the ambien t environment such as soil temperatures, sunlight intensity, antecedent soil moistu re, and surface water temperatures can cause actual aquatic concentrations to differ for the modeled values.

Unlike spray drift, tools are currently not av ailable to evaluate th e effectiveness of a vegetative setback on runoff and loadings. Th e effectiveness of vegetative setbacks is highly dependent on the condition of the vegetative strip. For example, a wellestablished, healthy vegetative setback can be a very eff ective means of reducing runoff and erosion from agricultural fields. Alternatively, a setbac k of poor vegetative quality or a setback that is channelized can be ine ffective 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 aqua tic exposure predictions are likely to overestimate exposure where h ealthy vegetative setbacks exist and underestimate exposure where poorly developed, channelized, or bare setbacks exist.

In order to account for uncertainties associ ated 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, concentrati ons measured in surface waters receiving runoff from agricultural areas. The specific use patterns (e.g. application rates and timing, crops) associated with the ag ricultural areas are unknown, however, they are assumed to

122be representative of potential myclobutanil us e areas. The 1-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 NAW QA (0.51 μg/L) monitoring data. The peak myclobutanil plus 1,2, 4-triazole concentr ations ranged between 5.1 and 61.4 μg/L; the 21-day means ranged from 15.1 to 61.2 μg/L a nd the 60-day mean ranged from 5.08 to 60.7 μg/L, respectively. There are no detec tions of myclobutanil report in ground water in the NAQWA studies.

Based upon the vapor pressure and Henry’s La w Constant, the transport of myclobutanil in the atmosphere vapor phase would not be expected. However, myclobutanil residues have been detected in rain water. Th e 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 aeria l spray (Mosz, 2002) or that the myclobutanil is sorb ed 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 Reporti ng (CDPR PUR) database. F our years of data (2002 – 2005) were included in this analysis b ecause 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 out liers was provided by CDPR for 2001 and earlier pesticide data; therefore, this inform ation 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 c oncentrations. 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 pesticid e usage data, there may be instances of misuse and misreporting. The Agency made use of the most current, verifiable information; in cases where ther e 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 it ems. These residue assumptions are believed to reflect a realistic upper-bound residue estimate, alt hough 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 devel op 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 pl ants in the case of grass and forage sampling.

123It was assumed that ingestion of food items in the field occurs at rates commensurate with those in the laborato ry. Although the screening a ssessment process adjusts dryweight 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 concentrati on- 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 betw een laboratory and wild diets suggest that current screening assessment me thods 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 mamm al’s assimilation ranges from 41 – 85% (U.S. Environmental Protection Agency, 1993). If it is assumed that laboratory chow is formulated to maximize assimilative efficien cy (e.g., a value of 85%), a potential for underestimation of exposure may exist by assu ming that consumption of food in the wild is comparable with consumption during labora tory testing. In th e screening process, exposure may be underestimated because me tabolic 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 sugges t 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 applic ations 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 or ganism to receive the maximum concentration of myclobutanil from multiple applications, eac h 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 directi on is fairly consistent (at least during the relatively quiescent conditions that are most fa vorable for aerial spra y applications), it is nevertheless highly unlikely that plants in any specific area would receive the maximum amount of spray drift re peatedly. It appears that in most areas (based upon available meteorological data) wind direction is temporal ly very changeable, even within the same day. Additionally, other factors, includi ng variations in topography, cover, and meteorological conditions over the trans port distance are not accounted for by the AgDRIFT model ( i.e ., it models spray drift from aeria l and ground applications in a flat

124area with little to no ground cover and a st eady, constant wind speed and direction). Therefore, in most cases, th e drift estimates from AgDR IFT 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 di stributions being modeled (e.g.: ‘ASAE Very Fine to Fine’ for all uses), the application method ( e .g., aerial), release height s 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 orga nism 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. Aqua tic 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 overe stimate toxicity at older age classes for pesticide active ingredients that act directly without me tabolic transformation because younger age classes may not have the enzymatic systems a ssociated 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 th e most sensitive life-stage information as measures of effect for surrogate aquatic an imals, 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 amphibi ans. Endpoints based on freshwater fish ecotoxicity data are assumed to be protective of potential direct e ffects to aquatic-phase amphibians including the CRLF, and extrapolati on 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 se lect the organisms most likely to be affected by the type of compound and usage pattern; howev er, 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 respon ses to the pesticide, as determined by the

125testing of species response to chronic expos ure conditions and subsequent chronic risk assessment. Consideration of additional sublet hal 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 fu ll 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 mycl obutanil 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 sugges t 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 mycl obutanil were not available for aquatic invertebrate (chronic e xposure), aquatic vascular plants , or terrestrial plants. In lieu of any myclobutanil data, toxicity da ta from other conazole (DMI triazole) fungicides were used to charac terize risk, assuming that mycl obutanil 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 f ungicides, 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 vascul ar plants, and te rrestrial plants.



### 7 Risk Conclusions

In fulfilling its obligations under Section 7(a)(2) of the Endangered Species Act, the information presented in this endangered specie s risk assessment represents the best data currently available to asse ss the potential risks of myclobutanil to the CRLF and its designated critical habitat.

Based on the best available information, th e 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 e ffects to CRLF designated critical habitat from the use of the chemical. The CRLF and/or its crit ical habitat may be affected for all uses.

126This assessment indicates that direct effect s 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 lb a.i./A and above (most crops and turf; cotton seed treatment). In addition, the terrestr ial-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 lb a.i./cwt ) and turf at 1.3 lbs a.i./A. Direct effects on the aquaticphase CRLF are not expected.

Indirect effects to the terres trial-phase CRLF, based on reduction in prey base may occur with terrestrial phase amphibians on a dose-ba sis following acute expos ure at application rates of 0.12 lb a.i./A and above (most cr ops, cotton and turf) and on a dietary-basis following chronic exposure at an application rate of 1.3 lbs a.i. /A (turf) and when applied to cotton (0.06 lb a.i./cwt). Indirect effects (reduction in pr ey base) may also occur with mammals following acute exposure on a dose-basi s at application rate s of 0.25 lb a.i./A and above (apple, apricot, cherry, nectarin e, peach, hops and turf uses) and chronic exposure on a dose-basis at application rates of 0.0625 lbs a.i./A a nd above (e.g., all uses) and on a dietary-basis of 0.25 lbs a.i./A and a bove (apples, apricots, cherries, nectarines, peaches, cotton and turf). Indirect effects to the aquatic-phase CRLF, based on reduction in prey base are not expecte d. Minimal potential indirect im pact to the CRLF via effects of myclobutanil on terrestrial invert ebrate food items is expected. No effects were observed with aquatic non-vasc ular 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 pestic ides indicates that although myclobutanil may affect the aquatic invert ebrate population following chronic exposure, it is not expected to adve rsely affect the population.

Indirect effects to both the aquatic- a nd terrestrial-phase CRLF based on aquatic and riparian habitat, cover and/or primary produc tivity (e.g., effects on aquatic and terrestrial plants) may occur due to potenti al effects on the riparian terre strial plant community. As stated previously, no effects were observed w ith aquatic non-vascular plants. No data are available for either aquatic vascular or terres trial plants. For aquati c 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 plan ts, weight of the evidence from information provided in the open literature, in cident data and the fact that surrogate data from similar fungicides would exceed the terre strial plant LOC 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 av ian/terrestrial-phase amphibi an, mammalian and terrestrial plant populations, there is a pot ential for habitat e ffects 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 modi fication of food sources for terrestrial phase juveniles and adults and alteration of chemical charact eristics necessary for normal growth and viability of juvenile and a dult CRLFs and their food source.

127Given the LAA determination for the CRLF and potential effects to designated critical habitat, a description of the baseline st atus and cumulative effects for the CRLF is provided in Attachment 2.

The LAA effects determination applies to t hose 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 f ootprint 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 dire ct and indirect effects and/or effects to critical habitat are anticipated to occur only for those current ly 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 fr om its boundary (see Section 5.1.4 for further analysis). It is assumed that non-flowi ng waterbodies (or poten tial 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 spra y drift) outside the in itial area of concern may also be impacted and are part of the full spatial extent of the L AA/effects to critical habitat determination.

A summary of the risk conclusions and e ffects determinations for the CRLF and its critical habitat, given the un certainties discussed in Secti on 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

Potential for Direct Effects Aquatic-phase (Eggs, Larvae, and Adults) :

Acute and chronic freshwater fish RQs are below the respective level of concern (LOC) for all uses of myclobutanil.

Terrestrial-phase (Juveniles and Adults) :

The acute avian LOC is exceeded at applic ation rates of 0.12 lb 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 LOC is exceeded following uses on cotton (0.06 lb a.i./cwt) and turf at 1.3 lbs a.i./A. Myclobutanil uses overlap CRLF habitat.

Potential for Indirect Effects Survival, growth, and/or reproduction of CRLF individuals LAA 1

Aquatic prey items, aquatic habitat, cover and/or primary productivity

Acute and chronic freshwater fish RQs ar e below the respective LOC for all uses of myclobutanil.

128Assessment Endpoint Effects Basis for Determination Determination 1

Acute freshwater invertebrate RQs are below the LOC 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 LOC. No aquatic vascular plant st udies 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 lb a.i./A and above and chronic exposure on at application rates of 0.0625 lbs 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-base d 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 terr estrial invertebrate food items is expected to be minimal.

No acceptable terrestrial plant studies ar e 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

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 av ailable. 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 ar e available. RQs based on EECs and toxicity data from 5 other conazole fungicides indicate that most uses may affect

129Assessment Endpoint Effects Basis for Determination 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 (LOC) for all uses of myclobutanil.

Indirect effects to the CRLF through eff ects 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 ar e 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 LOC is exceeded at applic ation rates of 0.12 lb a.i./A and above (most crops, cotton and turf). The chroni c avian LOC is exceeded following uses on cotton (0.06 lb a.i./cwt) and turf at 1.3 lbs a.i./A.

LOCs for listed mammals exceeded following acute exposure on a dose-basis formany crops and chronic exposure on a dose-basis for all uses and on a dietarybasis 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 Sect ion 7 of the Endangered Specie s Act should be initiated.

When evaluating the significance of this ri sk assessment’s direct/indirect and habitat effects determinations, it is important to not e that pesticide exposur es 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 a ssumptions of drift and downstream transport (i.e., attenuation with distance), pesticide e xposure and associated ri sks to the species and its resources are expected to decrease with in creasing 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 informa tion and assessment techniques that are not currently available. Examples of such in formation 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 quantitat ive extrapolation of the present risk assessment’s predictions of individual effects to the proportion of the population extant within geographical areas where t hose effects are predicted. Furthermore, such population information would allow fo r a more comprehensive evaluation of the significance of potential resource impa irment to individuals of the species.

130• Quantitative information on prey base requirements for individual aquatic- and terrestrial-phase frogs. While existing in formation provides a preliminary picture of the types of food sources utilized by the frog, it does not establish minimal requirements to sustain healthy individua ls at varying life stages. Such information could be used to establish bi ologically relevant thresholds of effects on the prey base, and ultimately establis h geographical limits to those effects. This information could be used together with the density data discussed above to characterize the likelihood of a dverse effects to individuals.

• Information on population responses of prey base organisms to the pesticide. Currently, methodologies are limited to pr edicting exposures and likely levels of direct mortality, growth or reproduct ive impairment immediately following exposure to the pesticide. The degree to which repeated exposure events and the inherent demographic characte ristics 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 pesticid e exposure would allow for a more refined determination of the magnitude and durati on 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.

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