Problem Formulation for the Environmental Fate, 

Ecological Risk, Endangered Species, and Drinking 

Water Exposure Assessments in Support of the 

Registration Review of Methiocarb 

 

CAS Registry Number: 2032-65-7 

PC Code: 100501 

Prepared by:

Melissa Panger, Ph.D., Biologist 

Cheryl Sutton, Ph.D., Environmental Scientist 

Reviewed by: 

Thomas M. Steeger, Ph.D., Senior Biologist

Marietta Echeverria, Risk Assessment Process Leader 

Elizabeth Behl, Branch Chief

U. S. Environmental Protection Agency 

Office of Pesticide Programs 

Environmental Fate and Effects Division 

Environmental Risk Branch IV 

1200 Pennsylvania Ave., NW 

Mail Code 7507P 

Washington, DC 20460

April 6, 2010 

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Table of Contents 

1. Purpose....................................................................................................................................... 4 

2. Problem Formulation ................................................................................................................. 4 

2.1. Nature of Regulatory Action............................................................................................... 4 

2.2. Previous Assessments ......................................................................................................... 5 

2.2.1. Ecological Risk Assessments....................................................................................... 5 

2.2.2. Drinking Water Exposure Assessments....................................................................... 6 

3. Stressor Source and Distribution ............................................................................................... 6 

3.1. Mechanism of Action.......................................................................................................... 8 

3.2. Overview of Pesticide Use and Usage................................................................................ 8 

3.3. Environmental Fate and Transport.................................................................................... 11 

3.3.1. Mobility...................................................................................................................... 13 

3.3.2. Degradation........................................................................................................... 14

3.3.3. Field Dissipation ........................................................................................................ 14 

3.4. Water Quality................................................................................................................ 15 

4. Receptors.................................................................................................................................. 16 

4.1. Effects to Aquatic Organisms ........................................................................................... 16

4.2. Effects to Terrestrial Organisms ....................................................................................... 18

4.3. Incident Databases Review............................................................................................... 19 

4.4. Ecosystems Potentially at Risk ......................................................................................... 20

5. Assessment Endpoints ............................................................................................................. 20 

6. Conceptual Model.................................................................................................................... 20 

6.1. Risk Hypothesis ................................................................................................................ 21 

6.2. Conceptual Diagram ......................................................................................................... 21 

7. Analysis Plan ........................................................................................................................... 23 

7.1. Stressors of Concern ......................................................................................................... 24 

7.2. Measures of Exposure....................................................................................................... 24 

7.3. Measures of Effect ............................................................................................................ 26 

7.4. Integration of Exposure and Effects ................................................................................. 27 

7.5. Deterministic and Probabilistic Assessment Methods...................................................... 27 

7.6. Endangered Species Assessments..................................................................................... 28 

7.8. Preliminary Identification of Data Gaps........................................................................... 29 

7.8.1. Fate............................................................................................................................. 29 

7.8.2. Effects Data for Methiocarb....................................................................................... 30 

8. References................................................................................................................................ 35 

APPENDIX A. Label Restrictions for Mesurol® 75% Wettable Powder Aversive Conditioning 

Egg Treatment............................................................................................................................... 44 

APPENDIX B. Toxicity Data for Methiocarb:............................................................................ 45 

APPENDIX C. Chemical Names and Stuctures for Methiocarb and its Environmental 

Degradates..................................................................................................................................... 56 

APPENDIX D: Data Call-In Tables. ........................................................................................... 59 

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1. Purpose 

The purpose of this problem formulation is to provide an understanding of what is known about 

the environmental fate and ecological effects of methiocarb, considering its currently registered 

uses. Methiocarb is an N-methyl carbamate registered for use as a molluscicide, avian repellent, 

insecticide, and acaricide. The compound is registered for use around home and flower gardens, 

ornamentals (including non-bearing fruit and nut trees), and to reduce predation on the eggs of 

federally-listed species of birds. All of the methiocarb products, except for the homeowner 

products, are classified as Restricted Use Pesticides (RUP) “due to toxicity to fish, birds and 

aquatic organisms” (as stated on the RUP labels). 

This document will provide a plan for analyzing data relevant to methiocarb and for conducting 

environmental fate, ecological risk, endangered species, and drinking water exposure 

assessments for the registered uses of methiocarb. Additionally, this problem formulation is 

intended to identify data gaps, uncertainties, and potential assumptions used to address those 

uncertainties relative to characterizing the ecological risk associated with the registered uses of 

methiocarb. 

2. Problem Formulation 

2.1. Nature of Regulatory Action 

Under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA), all pesticides distributed 

or sold in the United States generally must be registered by the Environmental Protection 

Agency (EPA). In determining whether a pesticide can be registered in the U.S., the Agency 

evaluates its safety to non-target species based on a wide range of environmental and health 

effects studies. In 1996, FIFRA was amended by the Food Quality Protection Act, and the 

Agency was mandated to implement a new program for the periodic review of pesticides, i.e., 

Registration Review (http://www.epa.gov/oppsrrd1/registration_review/). The Registration 

Review program is intended to ensure that, as the ability to assess risk evolves and as policies 

and practices change, all registered pesticides continue to meet the statutory standard of no 

unreasonable adverse effects to human health and the environment. Changes in science, public 

policy, and pesticide use practices will occur over time. Through the new Registration Review 

program, the Agency periodically reevaluates pesticides to make sure that as change occurs, 

products in the marketplace can be used safely. 

As part of the implementation of the new Registration Review program pursuant to Section 3(g) 

of the Federal Insecticide, Fungicide and Rodenticide Act (FIFRA), the Agency is beginning its 

evaluation of methiocarb to determine whether it continues to meet the FIFRA standard for 

registration. This problem formulation for the environmental fate, ecological risk, endangered 

species, and drinking water assessment chapter in support of the Registration Review will be 

posted in the initial docket which will open the public phase of the review process. 

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2.2. Previous Assessments 

2.2.1. Ecological Risk Assessments 

Methiocarb was first registered as a pesticide in the United States in 1972. There were several 

assessments conducted as part of Emergency Exemption (Section 18) actions during the 1980’s 

for the use of methiocarb on artichokes (CA), golf courses (CT), blueberries (OR and WA), and 

rice (TX and LA). 

A Registration Standard for methiocarb was issued in March 1987 [the ecological topical 

summary was completed in 1986 (USEPA, 1986)]. The Registration Standard summarized 

available data supporting the registration of products containing methiocarb used as a bird 

repellent in corn fields and fruit orchards and for slug, snail, and insect control on ornamentals, 

lawns, turf, and ginseng. Additionally, the Registration Standard required all outdoor and nonresidential uses of methiocarb be classified as Restricted Use Pesticide due to risks to birds and 

aquatic organisms, requiring that methiocarb only be applied by trained applicators. In 1989 the 

technical producer of methiocarb at the time (Miles Inc.) cancelled all terrestrial food uses of 

methiocarb. The registration standard also states that the technical producer dropped its support 

of all commercial turf and field-grown ornamental uses. 

The last ecological risk assessment conducted by the Agency for methiocarb was done as part of 

the Reregistration Eligibility Decision (RED) for methiocarb in 1994 (USEPA, 1994). The RED 

addressed the use on ornamentals, ginseng, lawn, turf, and household/domestic outdoor premises. 

The ecological effects risk assessment for methiocarb indicated that the acute and chronic risk 

levels of concern (LOC) were exceeded for birds (and for reptiles and terrestrial-phase 

amphibians for which birds serve as surrogates), the acute risk LOCs were exceeded for 

mammals and aquatic invertebrates, and the chronic risk LOC was exceeded for fish (as well as 

aquatic-phase amphibians for which fish serve as surrogates) for all outdoor use sites and 

formulations. 

The following studies were requested at the time of the RED: 

 161-1 Hydrolysis 

 163-1 Adsorption-Desorption/Leaching 

164-1 Terrestrial Field Dissipation 

72-3 (a) Acute Estuarine/marine Fish Toxicity 

72-3 (b) Acute Estuarine/marine Mollusk Toxicity 

72-3 (c) Acute Estuarine/marine Invertebrate Toxicity 

72-4 (a) Fish Early Life Stage 

72-4 (b) Aquatic Invertebrate Life-Cycle 

72-5 Fish Life-Cycle 

A fish accumulation study (165-4) was waived because methiocarb and its degradates in aquatic 

systems were assumed to kill fish before residues could accumulate to levels of concern in fish 

tissue. This waiver will be revoked as part of the Registration Review process based on current 

guideline requirements. 

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2.2.2. Drinking Water Exposure Assessments 

A separate drinking water exposure assessment has not been conducted for methiocarb, nor was 

a qualitative assessment done as part of the RED process. Methiocarb was included in the NMethyl Carbamate Cumulative Risk Assessment (EPA; revised 9/07). The assessment 

conducted for Registration Review will consider both groundwater and surface water exposure. 

3. Stressor Source and Distribution

Methiocarb is currently registered for use around home and flower gardens, on ornamentals, and 

to reduce predation on the eggs of federally-listed species. The parent compound degrades in the 

environment to the major degradates methiocarb phenol (MP), methiocarb sulfoxide (MSO), and 

methiocarb sulfoxide phenol (MSOP); and to the minor degradates methiocarb sulfone (MSO2) 

and methiocarb sulfone phenol (MSO2P). Parent methiocarb, MSO and MSO2 are all 

acetylcholinesterase inhibitors (http://pesticideinfo.org). Methiocarb is registered for outdoor 

uses, creating a potential for exposure to both aquatic and terrestrial non-target organisms. 

For the ecological risk assessment conducted as part of the Registration Review process, all of 

the degradates listed above will be considered and the degradates of concern will be identified. 

Modeled exposure estimates resulting from methiocarb usage will reflect the predicted 

environmental fate of either methiocarb and individual degradates separately or together as total 

toxic residues (in methiocarb equivalents), depending on the toxicity differential of the 

compounds for assessed organisms. For the drinking water assessment, parent methiocarb, 

MSO, MSO2 , and MP will likely be assessed in addition to any other degradates identified as 

degradates of concern. The final determination of which degradates will included in the 

assessment will be made following consultation with the OPP Residues of Concern 

Knowledgebase Subcommittee (ROCKS). 

Toxicity data for the methiocarb degradates have not been submitted to the Agency. Toxicity 

values for aquatic organisms and MSO2and MSO were estimated using ECOSAR (version 1.00) 

(see Table 3.1). The structure-activity relationships (SARs) in ECOSAR are used to predict the 

aquatic toxicity of chemicals based on their similarity of structure to chemicals for which the 

aquatic toxicity data have been previously measured. The estimated toxicity values for 

methiocarb sulfone and methiocarb sulfoxide suggest that they are either equitoxic or less toxic 

than the parent to the aquatic organisms included in the analyses. Some toxicity data for MSO2, 

MSO, MSO2P, and MSOP are available through the European Union’s Pesticide Properties 

Database (PPDB) (http://sitem.herts.ac.uk/aeru/footprint/en/index.htm). The studies from which 

these endpoints are derived were not available for review at this time. Taken at face value, 

however, the data suggest that the degradates are not more toxic than the parent for the taxa 

considered, with the exception of the acute toxicity values for earthworms (see Table 3.1). 

The residues of concern for exposure and risk assessment will be reconsidered prior to analysis. 

In the absence of confirmatory data indicating low toxicity concerns for the major degradates of 

methiocarb (i.e., MP, MSO, MSOP, MSO2, and MSO2P), they will be assumed of equal toxicity 

as the parent. 
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Table 3.1. Toxicity Data for Methiocarb Degradates (no registrant-submitted toxicity data are available o

SOURCE METHIOCARB METHIOCARB SULFONE (MSO2) METHIOCARB SULFOXIDE (MSO) METHIOC

SULFON

PHENOL (M

ECOSARAcute Fish (LC50; mg/L) -- 157.8 182.6 -- Acute Fish (SW) (LC50; mg/L) -- 0.395 0.373 -- Acute Daphnid (EC50; mg/L) -- 3.5 3.4 -- 96-hr Green algae (EC50; mg/L) -- > solubility limit > solubility limit -- Chronic Fish (SW) (mg/L) -- 2.2 2.5 -- Chronic Daphnid (mg/L) -- 0.22 0.23 -- Chronic Green algae (mg/L) -- > solubility limit 5262 -- Chronic Fish (SW) (mg/L) -- 0.033 0.032 -- PPDB (EU) WEBSITE1Acute oral Rat (LD50; mg/kg-bw) 19 -- -- -- Acute oral Avian (LD50; mg/kg-bw) 5 -- -- -- Acute Fish (LC50; mg/L) 0.65 -- 6.6 68.7 Chronic Fish (NOAEC; mg/L) 0.05 -- -- -- Acute FW Invertebrate (EC50; mg/L) 0.008 -- 0.056 54 Chronic FW Invertebrate (NOAEC) 0.0001 -- -- -- NV Aquatic Plant (EC50; mg/L) 2.2 -- 2.75 120 Acute Honeybees (LD50; μg/bee) 0.23 -- -- -- Acute Earthworms (LC50; mg/kg) 1322 -- 78 >1000 

1 Pesticide Properties Database (PPDB) (http://sitem.herts.ac.uk/aeru/footprint/en/index.htm) 
3.1. Mechanism of Action 

Methiocarb is an N-methyl carbamate molluscicide/avian repellent/insecticide/acaricide. 

Carbamate pesticides act by inhibiting acetylcholinesterase and reducing the degradation of the 

neurotransmitter acetylcholine. As a result, intersynaptic concentrations of acetylcholine 

increase leading to increased firing of the postsynaptic neurons. This may ultimately lead to 

convulsions, paralysis, and death of an organism exposed to the chemical. 

3.2. Overview of Pesticide Use and Usage 

Methiocarb was first registered in the U.S. in 1972. Methiocarb is currently registered for use on 

ornamentals (including non-bearing fruit and nut trees), around home and flower gardens, and to 

reduce predation on the eggs of Federally-listed species of birds. The 1987 registration standard 

for methiocarb states that the technical producer dropped its support of all commercial turf and 

field-grown ornamental uses. There are no turf uses on the current labels. The term ‘field-grown 

ornamentals’ does not appear on current labels; however, the use of methiocarb products on 

field-grown ornamentals cannot be precluded based on current labels. Therefore, we assume that 

the use of methiocarb on ornamentals could include field-grown ornamentals. 

There are currently five methiocarb end-use products registered in the U.S. (see Table 3.2). All 

of the products contain only one active ingredient (methiocarb). All of the products, except for 

the homeowner product (Mesurol® 2% Bait), are classified as Restricted Use Pesticides (RUP). 

TABLE 3.2. Summary of Methiocarb Products Registered in the U.S. 

Product Name (EPA Reg. No.) Registrant RUP?1

Percent 

Active 

Ingredient

Use 

Mesurol® 2% Bait (10163-232) Gowan No 2% 

Around the home (including around 

building foundations) and flower 

gardens 

Mesurol® 75 WDG (10163-252) Gowan Yes 75% 

Mesurol® 75-W (10163-231) Gowan Yes 75% 

Mesurol Pro® (10163-228) Gowan Yes 2% 

Ornamentals 

Mesurol® 75% Wettable Powder 

Aversive Conditioning Egg 

Treatment (56228-33) 

USDA Yes 75% Reduce predation on the eggs of listed 

bird species 

1

 RUP = Restricted Use Pesticide 

Methiocarb products include flowable (wettable powder, water-dispersible granule) and granular 

(bait) formulations. According to the labels, methiocarb can be applied as a flowable liquid [via 

ground equipment (including chemigation systems)]. Aerial applications are not precluded on the 

labels; however, based on the use patterns aerial applications are not likely, and, thus, will not be 

modeled if the registrant indicates that they will be precluded on the labels. Methiocarb is also 

used as a scatter bait on ornamentals and flower gardens and as an injection into bird eggs. 

According the the Mesurol 75% Wettable Powder Aversive Conditioning Egg treatment label, 

injected [poisoned] eggs are used to condition common ravens (Corvus corax), white-necked 

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raves (C. cryptoleucas), or the common crow (C. brachyrhnchos), collectively referred to as 

corvid egg predators, not to prey upon eggs of Federally listed threatened or endangered species 

or eggs of other species designated to be in need of special protection Methiocarb can be used 

nationally (i.e., there are no geographic restrictions on where it can be used). The maximum 

single application rates specified on the labels per use range from 0.002 lb a.i./acre (treated eggs, 

based on calculations from the label) to 0.87 lb a.i./acre (ornamentals, around the home, and 

flower gardens) (see Table 3.3). 

The maximum application rates per year specified on the labels range from 0.004 lb a.i./acre 

(treated eggs) to 1.74 lb a.i./acre (ornamentals, around the home, and flower gardens). The 

maximum number of applications allowed per year is two. The minimum re-application interval, 

where specified on the label, is 10 days. The maximum single or seasonal application rate is not 

specified on the Mesurol® 75 WDG or Mesurol® 75-W labels. The minimum application 

interval is not specified on the Mesurol® 2% Bait, Mesurol Pro®, or Mesurol® 75% Wettable 

Powder Aversive Conditioning Egg Treatment labels. Conservative assumptions will be made in 

the absence of labeled directions. Specifically, a maximum single application rate of 1.5 lb 

a.i./acre (seasonal maximum of 3 lb a.i./acre) will be assumed for Mesurol® 75 WDG or 

Mesurol® 75-W based on an estimate for the amount of liquid required to drench soil without 

causing runoff (i.e., 200 gallons/acre, based on a sampling of insecticide labels on which soil 

drench rates are stipulated). Furthermore, a 3-day minimum application interval will be assumed 

if it is not stipulated on the label. 

In the assessment, EFED will consider additional use factors, such as whether the pesticide is 

used mainly for nursery and greenhouse plants, or for established plantings; how much is used 

for insect control and how much for slug/snail control; and whether there are geographic areas 

where use is high and/or important. 

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TABLE 3.3. Summary of Methiocarb Application Methods and Rates. 

PRODUCT FORMULATION APPLICATION 

METHOD USE 

MAX 

SINGLE 

APPL RATE 

(lb a.i./acre)

MAX 

NUMBER 

OF APPL/ 

YEAR 

MAX APPL 

RATE/ 

YEAR 

(lb a.i./acre)

MIN APPL 

INTERVAL

Flowable 

Mesurol® 75 

WDG 

Mesurol® 75-

W 

Water soluble bag 

(wettable powder) 

Foliar 

Drench 

Chemigation 

Ground 

Aerial3

Ornamentals 

(including 

non-bearing 

fruit and nut 

trees) 

Not specified 

(0.75 lb 

a.i./100 

gallon; 1.5 lb 

a.i./acre 

assumed – see 

text) 

2 

Not specified 

(3 lb a.i./acre 

assumed – see 

text) 

10 days 

Bait 

Mesurol® 2% 

Bait 

Around the 

home; flower 

garden (not for 

use on lawns 

or turf) 

Mesurol Pro® 

Granule Scatter bait Ornamentals 

(including 

non-bearing 

fruit and nut 

trees) 

1 lb of 

product/1000 

ft2

 

(0.02 lb 

a.i./1000 ft2

 = 

0.87 lb 

a.i./acre) 

2 1.74 lb 

a.i./acre 

Not specified 

(3 days 

assumed) 

Treated Eggs 

Mesurol 75% 

Wettable 

Powder 

Aversive 

Conditioning 

Egg 

Treatment1, 2

Wettable powder Treated raw eggs 

Reduce corvid 

egg predation 

on listed bird 

species 

0.002 lb 

a.i./acre4 2 0.004 lb 

a.i./acre 

Not specified 

(3 days 

assumed) 

1 Before using, consult with local, state, and Federal wildlife authorities to ensure that the use of the product 

does not present a hazard to threatened or endangered species. Do not apply in areas where eggs treated 

with the product may be consumed by threatened or endangered species. 

2 Only to be used in efforts to condition common ravens (Corvus corax), white-necked ravens (C. 

cryptoleucas), or common crows (C. brachyrhynchos), collectively referred to as corvid egg predators, not 

to prey on the eggs of listed species. 

3 Aerial applications are not precluded on the current labels, however, based on the use patterns (i.e., 

nursery-grown ornamentals) aerial applications are not likely, and, thus, will not be modeled 

4 0.75 g a.i./60 ml = 0.0125 g a.i./ml; 3 ml = 0.0375 g a.i./egg; 20 eggs/acre = 0.75 g a.i./acre = 0.002 lb 

a.i./acre 

For Mesurol® 75% Wettable Powder Aversive Conditioning Egg Treatment which is used as a 

poison for birds that scavenge nests, there are several precautions stipulated on the label that 

could reduce non-target mortality. Please see APPENDIX A for a list of the precautions. 

National-level usage data are not available for methiocarb, however, usage data are available for 

the state of California [California Department of Pesticide Regulation (CADPR)]. Based on 

CADPR data for the three most recent years for which data are available (2005 – 2007), an 

average of 2005 lb of methiocarb (including non-residential uses only) were applied each year in 

California (see Table 3.4). The largest use was on nursery/outdoor container for field grown 

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plants representing 71.8% of total pounds applied in 2005, but declining to 57.5 and 59.9% of 

total use in 2006 and 2007, respectively. 

Table 3.4. Methiocarb Usage Data (Non-Residential Uses Only) for California Based on 

California Department of Pesticide Regulation (CADPR) Data. 

Use1

2005 

Pounds 

Applied 

2006 

Pounds 

Applied 

2007 

Pounds 

Applied 

Avocados (All or unspecified) -- -- 6.00 

Grapes -- 22.50 -- 

Landscape Maintenance 8.22 17.28 8.96 

Lemons 1.50 17.65 4.5 

Nursery/Greenhouse Grown Cut Flowers or greens 251.70 262.78 185.30 

Nursery/Geenhouse Grown Plants in Containers 417.30 261.32 350.22 

Nursery/Greenhouse grown transplanted Propagative Material 2.76 73.20 1.88 

Nursery/Outdoor Container/Field Grown Plants 1,742.08 1,028.37 1,056.82 

Nursery/Outdoor Grown Transplant/Propagative Material 12.00 17.80 18.19 

Oranges (All or Unspecified) 24.76 85.99 133.28 

Totals 2,460.32 1,787.89 1,765.89 

Prepared: August 26, 2009 

Cal DPR Data: http://www.cdpr.ca.gov/docs/pur/purmain.htm 

-- indicates no available data. 

1

 Methiocarb is currently registered for use on ornamentals (including non-bearing fruit and nut trees), around home 

and flower gardens, and to reduce predation on the eggs of Federally-listed species of birds. 

3.3. Environmental Fate and Transport 

Registrant-submitted data defining the physical, chemical, fate and transport characteristics 

associated with methiocarb are summarized in Table 3.5. Environmental degradates from the 

laboratory studies are listed in Table 3.6 along with their maximum concentration and associated 

sampling intervals. 

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TABLE 3.5. General Chemical and Environmental Fate Parameters of Methiocarb. 

Parameter Value Reference/Comments

Selected Physical-Chemical Parameters

Molecular mass 225.3 Product Chemistry 

Vapor pressure (Torr) 2.85 x 10-7 (20°C) 

6.6 x 10-7 (25°C) Product Chemistry 

Water solubility (25°C) 27 mg/L Product Chemistry 

Henry’s law constant (20°C; atmm3

/mole) 1.18 x 10-9

The Pesticide Manual - 

World Compendium, 

11th ed., British Crop 

Protection Council (1997)

Octanol-air partition coefficient (Koa) No data. 

Octanol-water partition coefficient (Kow; 

20°C) 2200 Product Chemistry 

Bioconcentration 

Fish Bioconcentration Factor 

No data. 

Data to be called in based 

on 40CFR data 

requirements. 

Mobility

Soil partition coefficient (Kd; Freundlich) No data. Data gap. 

Organic carbon-normalized adsorption 

coefficients (Koc) No data. Data gap. 

Persistence

Hydrolysis half-life (25°C) 763 (pH 5) 

28.1 (pH7) 

<1 (pH 9) 

MRID 40624502 

Aqueous photolysis half-life (25°C; 

days) 

128 (reported as equivalent to 66 days in a 

typical summer growing season in 

Lexington, KY, 38 N latitude) 

MRID 40624501 

Natural light; pH 5. 

Soil photolysis half-life (25°C; days) 

53 (reported as equivalent to 21 days in a 

typical summer growing season in 

Lexington, KY, 38 N latitude) 

MRID 40622301 

Natural light. 

Supplemental study (light 

and moisture conditions 

cited as issues). Soil pH 

6.6 

Aerobic soil metabolism half-life (25°C; 

days) 17.7 (sandy loam) 

MRID 41194601 

Bi-phasic degradation. 

Data gap; studies on 

additional soils are 

necessary. 

Anaerobic soil metabolism half-life 

(25°C; days) 64 (sandy loam) MRID 41194601 

Aerobic aquatic metabolism half-life 

(25°C) No data. Data gap. 

Anaerobic aquatic metabolism half-life 

(25°C) No data. Data gap. 

Field Dissipation

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Parameter Value Reference/Comments

Terrestrial field dissipation half-life; 

maximum leaching depth No data. 

No data. None of the 

submitted studies were 

classified acceptable or 

supplemental based on 

current guidelines. 

Table 3.6. Summary of major degradate formation from degradation of methiocarb in 

laboratory environmental fate studies. 

MAJOR DEGRADATE and MAXIMUM CONCENTRATION (as 

% of applied; days post-treatment) 

STUDY TYPE methiocarb phenol 

(MP) methiocarb sulfoxide 

(MSO) 

methiocarb 

sulfoxide phenol 

(MSOP) 

methiocarb 

sulfone 

(MSO2) 

methiocarb 

sulfone 

phenol 

(MSO2P) 

SOURCE 

Hydrolysis 46% (day 30; pH 7) 

82% (day 3; pH 9) 

6% (day 7; pH 5) 

10% (0.04 days; pH 7)

4% (0.04 days; pH 9) 

4% (day 14; pH 7)

11% (day 1; pH 9) -- -- MRID 40624502 

Aqueous 

Photolysis -- 10.1% 2.7% -- -- MRID 

40624501 

Soil Photolysis -- 23.8 (day 20) 3.7 (day 30) -- -- MRID 

40622301 

Aerobic Soil 

Metabolism 2% (time 0) 30% (29 days) 18% (64 days) 1% (29-91 

days) 

9% (91 

days) 

MRID 

41194601 

Anaerobic Soil 

Metabolism 47% (64 days) 

24% (time 0; formed 

during aerobic degrade. 

phase) 

8% (time 0; formed 

during aerobic 

degrade. phase) 

<1% (day 

64) 

<1% (days 

15-64) 

MRID 

41194601 

Aerobic Aquatic 

Metabolism -- -- -- -- -- No Data. 

Anaerobic 

Aquatic 

Metabolism -- -- -- -- -- No Data. 

3.3.1. Mobility 

Methiocarb is not expected to volatilize from soil or water based on its vapor pressure and 

Henry’s Law Constant (Table 3.5). In contrast to the conclusions stated in the Reregistration 

Evaluation Decision (RED) document for methiocarb, parent methiocarb and three major 

degradates (MSO, MSOP, MP) are presumed to be mobile in soil based on their presence in the 

leachate samples of an aged soil column leaching study (MRID 40342201). A data gap exists for 

the adsorption/desorption data on parent methiocarb and the major degradates MSO, MSOP, and 

MP. These three degradates were detected, along with parent methiocarb, in the leachate of the 

aged leaching column study conducted on sand, sandy loam and silty loam soils (MRID 

40342201). A previously acceptable adsorption/desorption (batch equilibrium) study of the 

parent compound a single loam soil (Accession No. 00145802) was reclassified as unacceptable 

because it was conducted in an aqueous phosphate buffer solution (pH 6) rather than in 0.01 N

calcium ion solution as currently required for guideline studies. Several submitted 

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adsorption/desorption or leaching studies (Accession #’s 00036494, 00109232, 00144666) were 

determined to be not scientifically valid, and would be classified as unacceptable based on 

current guidelines. An additional adsorption/desorption study (MRID 43617301) submitted in 

response to data requested in the RED was classified as unacceptable due to inadequate 

experimental methods. 

3.3.2. Degradation 

Methiocarb hydrolyzes rapidly at alkaline pHs (pH 9 t1/2 of <1 day), but is stable to hydrolysis at 

pH 5 (t1/2 of 763 days) and only hydrolyzes slowly at pH 7 (t1/2 of 28 days). The major 

hydrolytic degradate is MP (46% and 82% of the applied at pH 7 and 9, respectively), with some 

hydrolysis to MSO (4-10%) and MSOP (4-11%). Methiocarb photolyzes slowly in water and on 

soil (t1/2 of 128 and 53 days, respectively), and is not expected to be a significant degradation 

pathway in the environment. The degradates detected in irradiated samples, MSO and MSOP, 

were also detected in dark controls. Methiocarb is not expected to be persistent in aerobic or 

anaerobic soils in the environment, based on respective half-lives of 17.7 days and 64 days in a 

single sandy loam soil. In aerobic soil, methiocarb degrades mainly to MSO (30%) and MSOP 

(18%), with some degradation (1-9%) to MP, MSO2 and MSO2P. In anaerobic soil, the major 

degradates are MP (47%) and MSO (24%), with some degradation to MSOP (8%); both MSO2

and MSO2P were detected at <1% in anaerobic soil. There are no data available for either 

aerobic or anaerobic aquatic metabolism. 

The degradation of methiocarb in soil is not well defined, as only a single aerobic soil was 

utilized in the one acceptable study. Additional submitted studies (Accession #’s 00127159, 

00147797, 00145790) were not adequate for use in the risk assessment and would not be 

classified as acceptable or supplemental based on current guidelines. Based on guideline 

requirements, data from at least three additional aerobic soils are needed to more adequately 

demonstrate the rate of transformation of methiocarb in soils that are representative of the 

environmental conditions where use will occur. 

Based on current label uses, data are also needed for aerobic and anaerobic aquatic metabolism 

to more fully understand the fate of methiocarb and its degradates in the environment. Note that 

if all labels were amended to preclude field-grown ornamentals, there would be no need for these 

data. The term ‘field-grown ornamentals’ does not appear on current labels; however, the use of 

methiocarb products on field-grown ornamentals cannot be precluded based on current labels. 

Therefore, we assume that the use of methiocarb on ornamentals could include field-grown 

ornamentals, and the Data Call-In will include the recommendation for these studies as part of 

the Registration Review process.

3.3.3. Field Dissipation 

The environmental fate of methiocarb and its degradates in the field is uncertain. Although 

numerous terrestrial field dissipation studies have been submitted, none of them are classified as 

acceptable based on current guidelines. In general, the studies were deficient due to inadequate 

analytical methods (e.g., analytical method nonspecific for individual compounds); the formation 

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and decline patterns of the degradates were not addressed; and/or the experimental method was 

insufficient (e.g., field data were incomplete and the soil was not sampled deep enough to define 

the extent of leaching). The request for additional field dissipation data in the RED was based on 

uses (turf, lawn) that are no longer on the label. Data requirements under 40CFR Section 

158.1300 (Subpart N) include a terrestrial field dissipation study for pesticides with terrestrial 

and/or residential outdoor uses. Although the previously submitted terrestrial field dissipation 

studies are not acceptable and do not provide useful data, the EFED believes that additional 

studies would provide only limited information for this kind of use pattern. Thus, while the 

terrestrial field dissipation study is a data gap, it will not be recommended for inclusion in the 

Data Call-In as part of the Registration Review process. 

3.3.4. Bioaccumulation 

The Fish Accumulation data requirement was previously waived. As stated in the RED, 

“...methiocarb and its degradates in aquatic systems are likely to kill fish before the residues 

could accumulate to levels of concern in fish tissues.” However, based on 40 CFR data 

requirements, the lack of a fish bioconcentration study is considered a data gap, as methiocarb 

has a Kow of >1000 and does not hydrolyze rapidly at pH 5 or 7. Thus, the data will be called in 

as part of the Registration Review process. 

3.4. Water Quality 

No surface water or groundwater monitoring data for methiocarb could be located. Although 

included as part of the N-Methyl Carbamate Cumulative Risk Assessment (EPA; revised 9/07), 

there were no monitoring data included for methiocarb. Any available data will be considered at 

the time the assessment is conducted. 

Methiocarb is not identified as a cause of impairment for any water bodies under section 303(d) 

of the Clean Water Act (based on information provided at 

http://iaspub.epa.gov/tmdl_waters10/attains_nation_cy.cause_detail_303d?p_cause_group_id=88

5, accessed Jan. 26, 2010). In addition, no Total Maximum Daily Loads (TMDL) have been 

developed for methiocarb (based on information provided at 

http://iaspub.epa.gov/tmdl_waters10/attains_nation.tmdl_pollutant_detail?p_pollutant_group_id

=885&p_pollutant_group_name=PESTICIDES, accessed Jan. 26, 2010) and there are no aquatic 

life criteria for methiocarb (based on information provided at 

http://www.epa.gov/waterscience/criteria/aqlife/index.html). More information on impaired 

water bodies and TMDLs can be found at http://www.epa.gov/owow/tmdl/. 

The Agency invites submission of water quality data for this pesticide. To the extent possible, 

data should conform to the quality standards in Appendix A of the OPP Standard Operating 

Procedure: Inclusion of Impaired Water Body and Other Water Quality Data in OPP’s 

Registration Review Risk Assessment and Management Process (see: 

http://www.epa.gov/oppfead1/cb/ppdc/2006/november06/session1-sop.pdf), in order to ensure 

they can be used quantitatively or qualitatively in pesticide risk assessments. 

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4. Receptors 

Consistent with the process described in the Overview Document (USEPA 2004), the risk 

assessment for methiocarb relies on a surrogate species approach. Toxicity data generated from 

surrogate test species, which are intended to be representative of broad taxonomic groups, are 

used to extrapolate the potential effects on a variety of species (receptors) included under these 

taxonomic groupings. The most sensitive endpoints from the available toxicity data for 

methiocarb will be used to quantify risk. 

Acute and chronic toxicity data from studies submitted by pesticide registrants along with the 

available open literature are used to evaluate the potential direct and indirect effects of 

methiocarb to aquatic and terrestrial receptors. This includes toxicity data on the technical grade 

active ingredient, degradates, and when available, formulated products (e.g., “Six-Pack” studies). 

The open literature studies are identified through EPA’s ECOTOXicology (ECOTOX) database, 

which employs a literature search engine for locating chemical toxicity data for aquatic life, 

terrestrial plants, and wildlife. The evaluation of both sources of data may also provide insight 

into the direct and indirect effects of methiocarb and its degradates on biotic communities from 

loss of species that are sensitive to the chemical and from changes in structure and functional 

characteristics of the affected communities. A review of the data from ECOTOX will be 

conducted for evaluation for possible quantitative and/or qualitative inclusion in this risk 

assessment. 

Toxicity data for the methiocarb degradates have not been submitted to the Agency. Toxicity 

values for aquatic organisms and MSO2and MSO were estimated using ECOSAR (version 1.00) 

(see Table 3.1). The structure-activity relationships (SARs) in ECOSAR are used to predict the 

aquatic toxicity of chemicals based on their similarity of structure to chemicals for which the 

aquatic toxicity data have been previously measured. The estimated toxicity values for 

methiocarb sulfone and methiocarb sulfoxide suggest that they are either equitoxic or less toxic 

than the parent to the aquatic organisms included in the analyses. 

A summary of the most sensitive endpoints representing non-target organisms exposed to 

methiocarb in aquatic and terrestrial habitats is provided in Sections 4.1 and 4.2, respectively. A 

summary of ecological incidents associated with methiocarb and a description of ecosystems 

potentially at risk are provided in Sections 4.3 and 4.4, respectively. 

4.1. Effects to Aquatic Organisms 

A summary of the most sensitive aquatic toxicity data for methiocarb from registrant-submitted 

studies is provided in Table 4.1. A summary of all submitted ecotoxicity data for methiocarb is 

provided in Appendix A. Methiocarb is classified as very highly toxic to freshwater fish and 

freshwater invertebrates on an acute exposure basis; since freshwater fish serve as a surrogate for 

aquatic-phase amphibians, methiocarb is considered very highly toxic to aquatic-phase 

amphibians as well. There are currently no methiocarb toxicity data available for 

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estuarine/marine fish, estuarine/marine invertebrates, or aquatic plants (vascular and nonvascular). 

Regarding chronic effects, the only data currently available for methiocarb and aquatic 

organisms are for freshwater fish (i.e., there are currently no chronic data available for 

estuarine/marine fish, estuarine/marine invertebrates, or freshwater invertebrates). For 

freshwater fish, the only available NOAEC is 0.05 mg a.i./L for the rainbow trout 

(Oncorhynchus mykiss) based on clinical signs of intoxication (behavior) (MRID 00155967). 

Because bluegill sunfish (Lepomis macrochirus), and not rainbow trout, are the most sensitive 

freshwater fish based on acute exposure, an acute-to-chronic (ACR) is used to estimate a chronic 

NOAEC for the bluegill sunfish. This results in a NOAEC of 0.02 mg a.i./L for bluegill sunfish 

[rainbow trout acute = 0.436 mg a.i./L; rainbow trout chronic = 0.05 mg a.i./L; ACR = 

0.436/0.05 = 8.72; bluegill sunfish acute = 0.18 mg a.i./L; 0.18/8.72 = 0.02 mg a.i./L). In the 

rainbow trout study there was increased mortality and weight reduction at concentrations ≥0.20 

mg a.i./L. There are currently no chronic data available for freshwater invertebrates. 

TABLE 4.1. Summary of the Most Sensitive Endpoints from Submitted Aquatic Toxicity 

Studies for Methiocarb. 

Species Taxa Represented Toxicity Value MRID # Classification Comment 

Bluegill sunfish 

(Lepomis 

macrochirus) 

96-hr LC50 = 0.18 

mg a.i./L 

400980011

Supplemental Slope = 4.4 (95% CI 

= 1.9, 6.9) 

Bluegill sunfish 

(Lepomis 

macrochirus) 

Freshwater fish and 

aquatic-phase 

amphibians NOAEC = 0.02 

mg a.i./L N/A N/A 

Based on an acute-tochronic ratio using 

acute and chronic 

data from rainbow 

trout and acute data 

from bluegill sunfish; 

based on clinical 

signs of intoxication 

(behavior); 

significant mortality 

and weight reduction 

≥0.20 mg a.i./L in the 

rainbow trout study 

(MRID 00155967). 

96-hr EC50 = 

0.0055 mg a.i./L 400980011 Supplemental A slope could not be 

calculated Stonefly 

(Pteronarcys 

californica) 

Freshwater 

invertebrates No chronic data 

available N/A N/A N/A 

Estuarine/marine fish No data available N/A N/A N/A 

Estuarine/marine invertebrates No data available N/A N/A N/A 

Non-vascular aquatic plants No data available N/A N/A N/A 

Vascular aquatic plants No data available N/A N/A N/A 1

 Per EFED policy, the raw data from this study (Mayer and Ellersieck, 1986; MRID 40098001) were reviewed and 

were found to be supplemental. 

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4.2. Effects to Terrestrial Organisms 

Table 4.2 summarizes the most sensitive terrestrial toxicity endpoints for methiocarb based on 

an evaluation of submitted studies. There are currently no acceptable acute oral avian studies 

available for methiocarb. However, there are several supplemental studies that provide acute 

toxicity data on a variety of bird species (see APPENDIX A). Methiocarb is classified as very 

highly toxic to birds and highly toxic to mammals and honey bees on an acute exposure basis. 

Since birds serve as a surrogate for both terrestrial-phase amphibians and reptiles, methiocarb is 

considered very highly toxic to terrestrial-phase amphibians and reptiles as well. In addition to 

the acute studies available for birds and mammals (and sub-acute dietary studies for birds), there 

are several field studies and aversion studies available for birds and mammals (see APPENDIX 

A). There are currently no methiocarb toxicity data available for terrestrial plants. 

For chronic exposure, previous methiocarb assessments have reported no reproductive effects in 

mallard ducks (Anas platyrhynchos) tested up to 100 mg a.i./kg-diet or bobwhite quail (Colinus 

virginianus) tested up to 50 mg a.i./kg-diet. However, a re-evaluation of the bobwhite quail data 

(MRID 00128119) found reproductive effects (i.e., reduced percent of 14-day survivors and 

reduced egg-shell thickness) at 2 mg a.i./kg-diet, the lowest concentration tested. Therefore, the 

resulting NOAEC is non-definitive (i.e., <2 mg a.i./kg-diet). For mammals, a reproduction study 

is not available, however, there are data for chronic dietary toxicity (2-year study)(MRIDs 

00115226 and 00128723) for the laboratory rat (Ratus norvegicus). The chronic endpoint for 

mammals is a NOAEC of 200 mg/kg-diet (10 mg/kg/day) based on decreased body weight at the 

600 mg a.i./kg-diet level There was also increased cholinesterase inhibition in laboratory rats at 

200 mg a.i./kg-diet. 

TABLE 4.2. Summary of the Most Sensitive Endpoints from Submitted Terrestrial 

Toxicity Studies for Methiocarb. 

Species Taxa 

Represented Toxicity Value MRID # Classification Comment 

House finch 

(Carpodacus 

mexicanus) 

LD50 = 2.37 mg/kg-bw 40560001 Supplemental 

Procedures varied 

from test to test but 

which procedure 

used for each test 

was not provided; 

no raw data 

provided; 

procedures were 

not in accordance 

with Agency 

guidelines. 

Mallard duck 

(Anas 

platyrhynchos) 

LC50 = 929 mg/kg-diet 00022923 Acceptable None 

Bobwhite quail 

(Colinus 

virginianus)

Birds, reptiles, 

and terrestrialphase 

amphibians 

NOAEC = <2 mg 

a.i./kg-diet 43313004 Acceptable 

LOAEC = 2 mg 

a.i./kg-diet; based 

on reduced 14-day 

survival and 

reduced egg-shell 

thickness.

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Species Taxa 

Represented Toxicity Value Classification MRID # Comment 

Laboratory rat 

(Rattus norvegicus) 

LD50 = 14 mg a.i./kgbw (males) 00083437 Acceptable None 

Laboratory rat 

(R. norvegicus) 

Mammals 

NOAEC = 200 mg 

a.i./kg-diet (10 mg 

a.i./kg-bw) (based on 

decreased body weight) 

00115226 

and 

00128723 

Acceptable 

Based on a chronic 

dietary study; 

decreased body 

weight at 600 mg 

a.i./kg-diet; there 

was also 

cholinesterase 

inhibition at 200 

mg a.i./kg-diet; a 

reproduction study 

is not available 

Honey bee 

(Apis mellifera)

Terrestrial 

invertebrates 

LD50 = 0.375 μg 

a.i./bee 00036935 Acceptable Acute contact 

Terrestrial Plants No data available N/A N/A N/A 

4.3. Incident Databases Review 

Preliminary reviews of the Ecological Incident Information System (EIIS, version 2.1) and the 

Avian Incident Monitoring System (AIMS)1 were conducted on December 30, 2009. There are 

currently no reported wildlife or plant incidents involving methiocarb listed in the EIIS. 

However, the Agency has recently received a report (yet to be entered into the EIIS) from the 

National Wildlife Health Center for an incident involving the death of 30 little brown bats 

(Myotis lucifugus) in July 2009 in Valley County, ID. Some of the bats tested positive for 

carbofuran (N-methyl carbamate insecticide) and methiocarb, each at 0.5 micrograms/g. 

Information on how the bats might have been exposed to these chemicals is not available. 

The AIMS database contains one bird incident involving methiocarb (event no. 2012). This 

incident, which occurred in 1995 in St. Charles County, MO, involved both carbofuran and 

methiocarb and was the result of intentional misuse. The incident resulted in the death of three 

bald eagles (Haliaeetus leucocephalus), six chickens (Gallus gallus domesticus), one great 

horned owl (Bubo virginianus), and four red-tailed hawks (Buteo jamaicensis). Methiocarb and 

carbofuran were both classified as having been ‘highly likely’ the cause of the incident. 

In addition to the incidents recorded in EIIS and AIMS, additional incidents are reported to the 

Agency in aggregated incident reports. Pesticide registrants report certain types of incidents to 

the Agency as aggregate counts of incidents occurring per product per quarter. Ecological 

 

1

 http://www.abcbirds.org/abcprograms/policy/pesticides/aims/aims/index.cfm 

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incidents reported in aggregate reports include those categorized as ‘minor fish and wildlife’ (WB), ‘minor plant’ (P-B), and ‘other non-target’ (ONT) incidents. ‘Other non-target’ incidents 

include reports of adverse effects to insects and other terrestrial invertebrates. No aggregate 

incident reports have been submitted to the Agency for methiocarb. 

Although relatively few incidents involving methiocarb have formally been reported to the 

Agency, the absence of incident reports cannot be construed as the absence of incidents. 

4.4. Ecosystems Potentially at Risk 

The ecosystems potentially at risk are often extensive in scope; therefore, it may not be possible 

to identify specific ecosystems during the development of a nation-wide ecological risk 

assessment. However, in general terms, terrestrial ecosystems potentially at risk could include 

the treated site and immediately adjacent areas that may receive drift or runoff. Areas adjacent 

to the treated site could include cultivated fields, fencerows and hedgerows, meadows, fallow 

fields or grasslands, woodlands, riparian habitats and other uncultivated areas. 

Aquatic ecosystems potentially at risk include water bodies adjacent to, or down stream from, the 

treated site and could include impounded bodies such as ponds, lakes and reservoirs; or flowing 

waterways such as streams or rivers; or groundwater. For uses in coastal areas, aquatic habitat 

also includes marine ecosystems, including estuaries. 

5. Assessment Endpoints 

Assessment endpoints represent the actual environmental value that is to be protected, defined by 

an ecological entity (species, community, or other entity) and its attribute or characteristics 

(USEPA 1998). For methiocarb, the ecological entities may include the following: birds, 

mammals, terrestrial-phase amphibians, reptiles, freshwater fish and invertebrates, aquatic-phase 

amphibians, estuarine/marine fish and invertebrates, terrestrial plants, terrestrial invertebrates, 

and aquatic plants. The attributes for each of these entities include growth, reproduction, and 

survival. 

6. Conceptual Model 

For a pesticide to pose an ecological risk, it must reach ecological receptors in biologically 

significant concentrations. An exposure pathway is the means by which a pesticide moves in the 

environment from a source to an ecological receptor. For an ecological pathway to be complete, 

it must have a source, a release mechanism, an environmental transport medium, a point of 

exposure for ecological receptors, and a feasible route of exposure. 

The conceptual model for methiocarb provides a written description and visual representation of 

the predicted relationships between methiocarb, potential routes of exposure, and the predicted 

effects for the assessment endpoint. A conceptual model consists of two major components: risk 

hypothesis and a conceptual diagram (USEPA 1998). 

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Based on the submitted environmental fate data, methiocarb is not expected to volatilize from 

aerobic soils or alkaline water bodies, but may persist in some soils and potentially leach to 

groundwater and move to surface water through runoff and spray drift. However, lack of 

sufficient data add to the uncertainty of the potential for persistence of the parent in aerobic soil. 

The three major degradates, MSO, MSOP, and MP, may also potentially leach to groundwater or 

move to surface water through runoff and baseflow. Additional data are still necessary to 

determine the potential for mobility of these degradates in soil. However, they were detected in 

the leachates of several soils in an aged leaching column study. Methiocarb is degraded by 

microbially-mediated metabolism in aerobic and anaerobic soils, and by hydrolysis in neutral to 

alkaline waters. Photolysis of methiocarb may occur in water or on soil, but so slowly that it is 

not expected to be a significant environmental fate process. It is not clear whether methiocarb 

will bioaccumulate in aquatic or terrestrial food chains due to a lack of data. 

Based on previous ecological risk assessments for methiocarb, there is the potential for acute 

and/or chronic risk from the exposure of birds, mammals, fish, and aquatic invertebrates to 

methiocarb. Because of the potential risk for direct effects to taxa (both listed and non-listed) 

described above, listed species in all taxa may potentially be affected indirectly due to alterations 

in their habitat and prey items (e.g., food sources, shelter, and areas to reproduce). These 

preliminary conclusions are used to derive the risk hypothesis and conceptual diagram discussed 

below. 

6.1. Risk Hypothesis 

A risk hypothesis describes the predicted relationship among the stressor, exposure, and 

assessment endpoint response along with the rationale for their selection. For methiocarb and its 

degradates, the following ecological risk hypothesis is being employed for this ecological risk 

assessment: 

Based on the application methods, mode of action, fate and transport, and the sensitivity 

of non-target aquatic and terrestrial species, methiocarb and its degradtes have the 

potential to reduce survival, reproduction, and/or growth in non-target terrestrial and 

aquatic organisms when used in accordance with the current labels. These non-target 

organisms include federally-listed threatened and endangered species as well as nonlisted species. 

6.2. Conceptual Diagram 

The environmental fate properties of methiocarb indicate that runoff, leaching, spray drift and 

direct spray represent potential transport mechanisms of the parent compound and its degradates 

[methiocarb phenol (MP), methiocarb sulfoxide (MSO), methiocarb sulfoxide phenol (MSOP), 

methiocarb sulfone MSO2) and methiocarb sulfone phenol (MSO2P)] to aquatic and terrestrial 

habitats where non-target organisms may be exposed. These transport mechanisms (i.e., sources) 

are depicted in the conceptual models below (Figures 6.1 and 6.2) along with the receptors of 

concern and the potential attribute changes in the receptors due to exposures to methiocarb and 

its degradates of potential concern (to be identified when data are available). 

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Methiocarb applied to use site 

Stressor 

Source 

Receptors 

Attribute 

Change 

Fish/aquatic-phase 

amphibians 

Eggs 

Larvae 

Juveniles / Adults 

Individual organisms 

Reduced survival 

Reduced growth 

Reduced reproduction 

Food chain 

Reduction in algae 

Reduction in prey 

Habitat integrity 

Reduction in primary productivity

Reduced cover 

Community change 

Surface water/ 

Sediment 

Runoff 

Aquatic Animals 

Invertebrates 

Vertebrates 

Exposure 

Media 

Uptake/gills 

or integument 

Ingestion Ingestion

Long-range 

atmospheric 

transport 

Wet/dry deposition 

Soil Groundwater 

Uptake/gills 

Spray drift 

(flowable 

only) 

or integument 

Aquatic Plants 

Non-vascular 

Vascular 

Uptake/cell, 

roots, leaves Riparian plant

terrestrial 

exposure 

pathways see 

Figure 6.2 

FIGURE 6.1. Conceptual Model for Methiocarb Effects on Aquatic Organisms. Dotted 

Lines Indicate Exposure Pathways that Have a Low Likelihood of Contributing to 

Ecological Risk. 

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Methiocarb applied to use site 

Stressor 

Source

Receptors 

Attribute 

Change 

Direct 

application 

Birds / Terrestrialphase amphibians 

/ reptiles / 

mammals 

Terrestrial 

invertebrate

Individual organisms 

Reduced survival 

Reduced growth 

Reduced reproduction 

Food chain 

Reduction in prey 

Habitat integrity 

Reduction in primary productivity

Reduced cover 

Terrestrial/riparian plants 

grasses/forbs, fruit, seeds 

(trees, shrubs) 

Runoff 

Mammals

Exposure 

Media 

Soil 

Ingestion 

Ingestion

Ingestion

Ingestion

Dermal uptake/Ingestion 

Long-range 

atmospheric 

transport 

Root uptake 

Wet/dry deposition 

Birds / 

Amphibians 

Ingestion 

Spray drift 

(flowable only) 

Community change 

FIGURE 6.2. Conceptual Model for Methiocarb Effects on Terrestrial Organisms. 

7. Analysis Plan 

In order to address the risk hypothesis, the potential for adverse effects on the environment will 

be estimated. The use, environmental fate, and ecological effects of methiocarb and its 

degradates [methiocarb phenol (MP), methiocarb sulfoxide (MSO), methiocarb sulfoxide phenol 

(MSOP), methiocarb sulfone (MSO2) and methiocarb sulfone phenol (MSO2P)] will be 

characterized and integrated to assess the risks. Exposure to methiocarb residues will reflect the 

predicted environmental fate of each compound separately or together as total toxic residues (in 

methiocarb equivalents), depending on the toxicity differential for each of the compounds to the 

assessed organisms. Risk quotients (RQs) will be derived for methiocarb by dividing estimated 

environmental concentrations (EEC) by the most sensitive endpoint from the relevant, available 

toxicity data for methiocarb. 

This analysis plan will be revisited and may be revised depending upon a full review of the data 

available in the open literature and the information submitted by the public in response to the 

opening of the Registration Review docket. 

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7.1. Stressors of Concern 

The parent compound degrades in the environment mainly to the major degradates methiocarb 

phenol (MP), methiocarb sulfoxide (MSO), and methiocarb sulfoxide phenol (MSOP), with 

some additional degradation to the minor degradates methiocarb sulfone MSO2) and methiocarb 

sulfone phenol (MSO2P). Parent methiocarb, MSO and MSO2 are all acetocholinesterase 

inhibitors and will likely be assessed in the drinking water assessment along with the major 

degradate MP. For the ecological risk assessment all of the degradates listed above will be 

considered. Modeled exposure estimates resulting from methiocarb usage will reflect the 

predicted environmental fate of methiocarb and individual degradates separately or together as 

total toxic residues (in methiocarb equivalents), depending on the toxicity differential for each of 

the compounds for assessed organisms. 

The identification of which degradates constitute residues of concern for exposure and risk 

assessment will be reconsidered prior to analysis. In the absence of data indicating low toxicity 

concerns for the degradates of methiocarb, they will be assumed of equal toxicity to that of the 

parent for the ecological risk assessment. 

In its ecological risk assessments, the Agency does not routinely include an evaluation of 

mixtures of active ingredients, either those mixtures of multiple active ingredients in product 

formulations or those in the applicator’s tank. In the case of the product formulations of active 

ingredients (that is, a registered product containing more than one active ingredient), each active 

ingredient is subject to an individual risk assessment for regulatory decision regarding the active 

ingredient on a particular use site. If effects data are available for a formulated product 

containing more than one active ingredient, the data may be used qualitatively or quantitatively 

in accordance with the Agency’s Overview Document and the Services’ Evaluation 

Memorandum (USEPA 2004; USFWS/NMFS 2004). 

Available toxicity data for environmental mixtures of methiocarb with other pesticides will be 

presented as part of the ecological risk assessment. It is expected that the toxic effect of 

methiocarb, in combination with other pesticides used in the environment, is likely to be a 

function of many factors including but not necessarily limited to: (1) the exposed species, (2) the 

co-contaminants in the mixture, (3) the ratio of methiocarb and co-contaminant concentrations, 

(4) differences in the pattern and duration of exposure among contaminants, and (5) the 

differential effects of other physical/chemical characteristics of the receiving waters (e.g. organic 

matter present in sediment and suspended water). Quantitatively predicting the combined effects 

of all these variables on mixture toxicity to any given taxa with confidence is beyond the 

capabilities of the available data and methodologies. However, a qualitative discussion of 

implications of the available pesticide mixture effects data on the confidence of risk assessment 

conclusions will be addressed as part of the uncertainty analysis. 

7.2. Measures of Exposure 

In order to estimate risks of methiocarb exposures in aquatic and terrestrial environments, all 

exposure modeling and resulting risk conclusions will be made based on maximum application 

rates for the currently registered uses (i.e., around homes and gardens, ornamentals, and bird 

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repellent) as discussed in Section 5. Measures of exposure for the home owner and ornamental 

uses are based on aquatic and terrestrial models that predict estimated environmental 

concentrations (EEC) of methiocarb using maximum labeled application rates and application 

methods that have the greatest potential for off-site transport of the chemical. The models used 

to predict aquatic EECs in surface water are the Pesticide Root Zone Model coupled with the 

EXposure Analysis Model System (PRZM/EXAMS). The models used to predict aquatic EECs 

in groundwater is Screening Concentration in Ground Water (SCI-GROW). The model used to 

predict terrestrial EECs on food items is T-REX. The model used to derive EECs relevant to 

terrestrial and wetland plants is TerrPlant. These models are parameterized using relevant 

reviewed registrant-submitted environmental fate data. 

PRZM (v3.12.2, May 2005) and EXAMS (v2.98.4.6, April 2005) are screening simulation 

models coupled with the graphical user interface, PE (v5.0, November 2006) to generate daily 

exposures and 1-in-10-year EECs of methiocarb residues that may occur in surface water bodies 

adjacent to application sites receiving methiocarb through runoff and spray drift. PRZM 

simulates pesticide application, movement and transformation on an agricultural field and the 

resultant pesticide loadings to a receiving water body via runoff, erosion, and spray drift. 

EXAMS simulates the fate of the pesticide and resulting concentrations in the water body. The 

standard watershed geometry used for ecological pesticide assessments assumes application to a 

10-hectare agricultural field that drains into an adjacent 1-hectare water body that is 2 meters 

deep (20,000 m3

 volume) with no outlet. The composite model PRZM/EXAMS is used to 

estimate screening-level exposure of aquatic organisms to methiocarb. The measure of exposure 

for aquatic species is the 1-in-10-year peak or rolling mean concentration. The 1-in-10-year 

peak is used for estimating acute exposures of direct effects to aquatic organisms. The 1-in-10-

year 60-day mean is used for assessing chronic exposure to fish and aquatic-phase amphibians. 

The 1-in-10-year 21-day mean is used for assessing aquatic invertebrate chronic exposure. 

SCIGROW (Screening Concentration in Ground Water) is a regression model used as a 

screening tool to estimate pesticide concentrations found in ground water used as drinking water. 

SCIGROW was developed by fitting a linear model to groundwater concentrations with the 

Relative Index of Leaching Potential (RILP) as the independent variable. Groundwater 

concentrations were taken from 90-day average high concentrations from Prospective Ground 

Water studies; the RILP is a function of aerobic soil metabolism and the soil-water partition 

coefficient. The output of SCIGROW represents the concentrations that might be expected in 

shallow unconfined aquifers under sandy soils, which is representative of the ground water most 

vulnerable to pesticide contamination likely to serve as a drinking water source. 

To estimate potential exposure to aquatic organisms from the egg treatment it will be assumed 

that all 20 eggs placed in an acre are somehow washed into a standard 20,000,000-liter farm 

pond. This is a conservative assumption because it is assumed that all of the pesticide is 

available for dissolution. This results in a concentration of 0.045 μg/L (0.002 lb a.i./20,000,000 

L). 

Exposure estimates for terrestrial animals that are assumed to be in the target area or in an area 

exposed to spray drift from the home owner and ornamental uses are derived using the T-REX 

model (version 1.4.1, 10/08/2008). This model incorporates the Kenaga nomograph, as modified 

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by Fletcher et al. (1994), which is based on a large set of actual field residue data. The upper 

limit values from the nomograph represent the 95th percentile of residue values from actual field 

measurements (Hoerger and Kenaga, 1972). The Fletcher et al. (1994) modifications to the 

Kenaga nomograph are based on measured field residues from 249 published research papers, 

including information on 118 species of plants, 121 pesticides, and 17 chemical classes. For 

granular applications, estimated loadings of pesticide per unit area are calculated. This approach, 

which is intended to represent exposure via multiple routes and not just direct ingestion, 

considers observed effects in field studies and relates them to the pesticide applied to surface 

area. In the absence of data, EFED will assume a foliar dissipation half-life of 35 days. The 

amount of pesticide per square foot (relative to the application rate) is calculated using the 

following assumption: broadcast treatment without incorporation assumes 100% of granules are 

unincorporated. 

To estimate potential exposure to non-target terrestrial animals from the egg treatment the 

assessment will assume that non-target birds and mammals of the medium and large size classes 

from T-REX eat two treated eggs (since they are cached in sets of one or two eggs). This would 

result in the ingestion of 0.0002 lb a.i./animal or 90.7 mg a.i./animal. For example, for a 100 g 

bird, this would result in a dose-based EEC of 90.7 mg a.i./0.1 kg-bw = 907 mg a.i./kg-bw. 

If terrestrial plant toxicity data are available, EECs for terrestrial plants inhabiting dry and 

wetland areas are derived for the home owner and ornamental uses using TerrPlant (version 

1.2.2, 12/26/2006). This model uses estimates of pesticides in runoff and in spray drift to 

calculate EECs. EECs are based upon solubility, application rate and minimum incorporation 

depth. The AgDRIFT spray drift model (v2.01; May 2001) is used to assess exposures of 

organisms to methiocarb deposited on terrestrial habitats by spray drift. 

7.3. Measures of Effect 

 

Ecological effects data are used as measures of direct and indirect effects to biological receptors. 

Data are obtained from registrant-submitted studies or from literature studies identified by 

ECOTOX. The ECOTOX database provides more ecological effects data in an attempt to bridge 

existing data gaps. ECOTOX is a source for locating single chemical toxicity data and potential 

chemical mixture toxicity data for aquatic life, terrestrial plants, and wildlife. ECOTOX was 

created and is maintained by the USEPA, Office of Research and Development, and the National 

Health and Environmental Effects Research Laboratory's Mid-Continent Ecology Division. 

Information on the potential effects of methiocarb on non-target animals is also collected from 

the Ecological Incident Information System (EIIS). The EIIS is a database containing adverse 

effect (typically mortality) reports on non-target organisms where such effects have been 

associated with the use of pesticides. Incidents reported in the aggregate incident reports and the 

Avian Incident Monitoring System (AIMS) will also be searched. AIMS is a database 

administered by the American Bird Conservancy (it was partially funded by the EPA). It 

contains publicly available data on reported avian incidents involving pesticides 

(http://www.abcbirds.org/abcprograms/policy/pesticides/aims/aims/index.cfm). 

Where available, sub-lethal effects observed in both registrant-submitted and open literature 

studies will be evaluated qualitatively. Such effects may include behavioral changes (e.g., 

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lethargy and changes in coloration). Quantitative assessments of risks, though, are limited to 

those endpoints that can be directly linked to the Agency’s assessment endpoints of impaired 

survival, growth and reproduction. 

The assessment of risk for direct effects to non-target organisms makes the assumption that 

toxicity of methiocarb to birds is similar to terrestrial-phase amphibians and reptiles. The same 

assumption is made for fish and aquatic-phase amphibians. 

The acute measures of effect used for animals in this assessment are the LD50, LC50 and EC50. 

LD stands for "Lethal Dose", and LD50 is the amount of a material, given all at once, that is 

estimated to cause the death of 50% of the test organisms. LC stands for “Lethal Concentration” 

and LC50 is the concentration of a chemical that is estimated to kill 50% of the test organisms. 

EC stands for “Effective Concentration” and the EC50 is the concentration of a chemical that is 

estimated to produce a specific effect in 50% of the test organisms. Endpoints for chronic 

measures of exposure for listed and non-listed animals are the NOAEL/NOAEC and NOEC. 

NOAEL stands for “No Observed-Adverse-Effect-Level” and refers to the highest tested dose of 

a substance that has been reported to have no harmful (adverse) effects on test organisms. The 

NOAEC (i.e., “No-Observed-Adverse-Effect-Concentration”) is the highest test concentration at 

which none of the observed effects were statistically different from the control. The NOEC is 

the No-Observed-Effects-Concentration. For non-listed plants, only acute exposures are 

assessed (i.e., EC25 for terrestrial plants and EC50 for aquatic plants); for listed plants either the 

NOAEC or EC05 is used. 

7.4. Integration of Exposure and Effects 

Risk characterization is the integration of exposure and ecological effects characterization to 

determine the potential ecological risk from the use of methiocarb and the likelihood of direct 

and indirect effects to non-target organisms in aquatic and terrestrial habitats. The exposure and 

toxicity effects data are integrated in order to evaluate the risks of adverse ecological effects on 

non-target species. For the assessment of methiocarb risks, the risk quotient (RQ) method is 

used to compare exposure and measured toxicity values. EECs are divided by acute and chronic 

toxicity values. The resulting RQs are then compared to the Agency’s Levels of Concern (LOC) 

(USEPA 2004). These criteria are used to indicate when methiocarb’s use, as directed on the 

labels, has the potential to cause adverse direct or indirect effects to non-target organisms. In 

addition, incident data from EIIS, aggregate incident reports, and AIMS will be considered as 

part of the risk characterization. 

7.5. Deterministic and Probabilistic Assessment Methods 

The quantitative assessment of risk will primarily depend on the deterministic point-estimate 

based approach described in the risk assessment. Depending on the risk manager’s need for 

additional information regarding risk, an effort will be made to further qualitatively describe risk 

using probabilistic tools that the Agency has developed. These tools have been reviewed by 

FIFRA Scientific Advisory Panels (http://www.epa.gov/scipoly/sap/index.htm) and have been 

deemed as appropriate means of refining assessments where deterministic approaches have 

identified risks. 

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7.6. Endangered Species Assessments 

Consistent with the Agency’s responsibility under the Endangered Species Act (ESA), the 

Agency will evaluate risks to federally-listed threatened and/or endangered (listed) species from 

registered uses of methiocarb. This assessment will be conducted in accordance with the 

Overview Document (USEPA 2004), provisions of the ESA, and the Services’ Endangered 

Species Consultation Handbook (USFWS/NMFS 1998). 

The assessment of effects associated with the registration of methiocarb is based on an action 

area. The action area is considered to be the area directly or indirectly affected by the federal 

action, as indicated by the exceedance of Agency Levels of Concern (LOCs) used to evaluate 

direct or indirect effects. In the case of a nationwide risk assessment conducted under 

Registration Review, the action area will encompass the entire U.S. and its territories. The 

purpose of defining the action area as the entire U.S. and its territories is to ensure that the initial 

area of consideration encompasses all areas where the pesticide may be used now and in the 

future, including the potential for off-site transport via spray drift and downstream dilution. 

Additionally, the concept of a nationwide action area takes into account the potential for direct 

and indirect effects and any potential modification to critical habitat based on ecological effect 

measures associated with reduction in survival, growth, and reproduction, as well as the full suite 

of sublethal effects available in the effects literature. 

It is important to note that the nationwide action area does not imply that direct and/or indirect 

effects and/or critical habitat modification are expected to or are likely to occur over the full 

extent of the action area, but rather to identify all listed species and critical habitat that may 

potentially be affected by the action. The Agency will use more rigorous analysis including 

consideration of available land cover data, toxicity data, and exposure information to determine 

areas where individual listed species and designated critical habitat may be affected or modified 

via endpoints associated with reduced survival, growth, or reproduction. 

7.7. Drinking Water Assessment 

Methiocarb is currently registered on non-food commodities only. The Drinking Water 

Exposure Assessment (DWA) will potentially include methiocarb and the degradates methiocarb 

sulfoxide (MSO), methiocarb sulfoxide phenol (MSOP), methiocarb sulfone (MSO2) and 

methiocarb phenol (MP). These degradates may be mobile, and MSO and MSO2 are 

cholinesterase inhibitors as is the parent compound. The final determination of which degradates 

will included in the assessment will be made following consultation with the OPP Residues of 

Concern Knowledgebase Subcommittee (ROCKS). 

 

The drinking water assessment will incorporate model estimates of methiocarb residues of 

concern in both surface water and groundwater. Concentrations of methiocarb residues of 

concern in surface water will be estimated using PRZM/EXAMS (see description in Section 

7.2). Groundwater exposure estimates for methiocarb residues of concern will be estimated 

using the Screening Concentration in Ground Water (SCI-GROW) model (v.2.3, July 2003) 

followed by a higher tier model if necessary. The drinking water assessment will also include a 

summary of available surface water and groundwater monitoring data. Because methiocarb is 

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included in the Common Assessment Group for the N-methyl carbamate cumulative, potential 

exposure to methiocarb in drinking water will be considered in that assessment. 

7.8. Preliminary Identification of Data Gaps 

 7.8.1. Fate 

The studies submitted to fulfill environmental fate data requirements for methiocarb are not 

sufficient for exposure assessment. There is only a single aerobic soil metabolism half-life, 

whereas OPPTS guidelines require that data from at least three soil types be submitted in 

addition to the initial soil from which kinetic data and degradate data are obtained. No aquatic 

metabolism studies have been submitted. Adsorption/desorption data are necessary for the 

parent compound and the degradates MP, MSO, and MSOP. Submission of environmental 

chemistry methods in water and soil, and an associated independent laboratory validation is also 

requested in order to support enforcement and monitoring purposes at the Federal, state, and 

local levels. A fish bioconcentration study, which was previously waived, will be required as 

part of Registration Review based on the Kow (2200) and hydrolysis half-lives of >5 days at pH 5 

and 7. Draft Data Call-In (DCI) tables for these data are provided in APPENDIX C. 

Although the previously submitted terrestrial field dissipation studies are not acceptable and do 

not provide useful data, the EFED believes that additional studies would provide only limited 

information for this kind of use pattern. Thus, while the terrestrial field dissipation study is a data 

gap, it will not be recommended for inclusion in the Data Call-In as part of the Registration 

Review process. 

The requirement for the aquatic metabolism data is based on 40CFR Section 158.1300 (Subpart 

N) data requirements for pesticides with terrestrial uses. Note that if all labels were amended to 

preclude field-grown ornamentals, there would be no need for these data, as strictly 

residential/outdoor uses do not require aquatic metabolism data. The term ‘field-grown 

ornamentals’ does not appear on current labels; however, the use of methiocarb products on 

field-grown ornamentals cannot be precluded based on current labels. Therefore, we assume that 

the use of methiocarb on ornamentals could include field-grown ornamentals, which is a 

terrestrial use. 

Table 7.1 identifies studies by MRID that offer data for each guideline requirement, as well as 

study classifications and whether or not additional data are needed in order to support the 

Registration Review risk assessment (i.e., whether there is a data gap). 

TABLE 7.1. Environmental Fate Data Requirement Table for Methiocarb.

OPPTS 

Guideline Data Requirement 

Submitted 

Studies 

(MRID) 

Classification Data 

Gap? Comments 

835.2120 Hydrolysis 

MRID 

40624502 Acceptable No 

835.2240 Aqueous photolysis MRID 

40624501 Acceptable No Natural light; pH 5. 

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OPPTS 

Guideline Data Requirement 

Submitted Data Studies Classification Comments Gap? (MRID) 

835.2410 Soil photolysis 

MRID 

40622301 Supplemental No 

Natural light. Supplemental study (light 

and moisture conditions cited as issues). 

Soil pH 6.6. 

835.4100 Aerobic soil 

metabolism 

MRID 

41194601 Acceptable Yes 

Data from at least three additional soils, 

representative of intended use areas, are 

required. 

835.4200 Anaerobic soil 

metabolism 

MRID 

41194601 Acceptable No 

835.4300 Aerobic aquatic 

metabolism No data Yes 

Study required for pesticides with 

terrestrial uses. Study would not be 

required if label precludes use on fieldgrown ornamentals. 

835.4400 Anaerobic aquatic 

metabolism No data Yes 

Study required for pesticides with 

terrestrial uses. Study would not be 

required if label precludes use on fieldgrown ornamentals. 

00145802 Not acceptable 835.1230 

835.1240 

Adsorption/ 

desorption and 

leaching 40342201 Not acceptable 

Yes 

Analytical methods were inadequate. 

Studies are needed for the parent, MP, 

MSO and MSOP. 

835.1410 Laboratory 

volatility No data No Not required. 

Terrestrial field 

dissipation 40994801 Not Acceptable No 

None of the ten field studies are adequate 

based on current data requirements. 

However, additional studies would 

provide only limited information for this 

kind of use pattern. 

835.6100 

Analytical method 

in soil 

No data Yes Required study. 

835.6200 Analytical method 

in water 

No data Yes Required study. 

850.1730 Fish 

bioconcentration 

No data. 

Yes 

Data are required for this compound 

based on the Kow (2200) and hydrolysis 

half-lives of >5 days at pH 5 and 7. 

7.8.2. Effects Data for Methiocarb 

Although many submissions have been made to provide data on the effects of methiocarb to 

aquatic and terrestrial organisms, data gaps still exist (Tables 7.2-7.4). Data gaps include the 

following: avian acute oral toxicity, avian reproduction, early-life stage estuarine/marine fish 

toxicity, estuarine/marine fish acute toxicity, estuarine/marine invertebrate acute toxicity, 

estuarine/marine invertebrate (mollusk) acute toxicity, freshwater fish early life stage, 

estuarine/marine early life stage, freshwater invertebrate life-cycle, estuarine/marine invertebrate 

life-cycle, terrestrial plant, and aquatic plant toxicity studies. These data gaps are discussed 

below. 

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TABLE 7.2. Available Ecological Effects Data for Terrestrial Animals Exposed to 

Methiocarb and Remaining Data Gaps.

Guideline Description MRID/ 

Accession Classification Data Gap? Comments 

Avian oral toxicity 

(passerine) 40560001 Supplemental Yes1

850.2100 

Avian oral toxicity 

(upland game species) 00036482 Supplemental Yes1

Avian dietary toxicity 

(waterfowl) 00022923 Acceptable No 

850.2200 

Avian dietary toxicity 

(upland game species) 00022923 Acceptable No 

1

 Acute oral toxicity data are 

required for a passerine and a 

waterfowl or upland game 

species under 40 CFR Part 

158. Acceptable avian acute 

oral toxicity data are not 

available for any bird species. 

Therefore, this is identified as 

a data gap. However, since 

supplemental data are 

available for a variety of 

species, EFED does not 

recommend requesting these 

data at this time. 

. 

Avian reproduction 

(waterfowl) 128120 Acceptable No 

850.2300 

Avian reproduction 

(upland game species) 128119 Supplemental Yes2

2

 Avian reproduction data are 

required for a waterfowl and 

an upland game species under 

40 CFR Part 158. A definitive 

NOAEC has not been 

established for birds, because 

the lowest dose tested resulted 

in effects. Therefore, the 

specific risk to birds from 

chronic exposure to 

methiocarb is unknown and 

EFED recommends requesting 

these data (for an upland game 

species). 

850.3020 Honeybee acute 

contact toxicity 00036935 Acceptable No 

850.3030 Honey bee toxicity of 

residues on foliage None Not applicable Yes3

3 Data on honey bee toxicity 

of residues on foliage are 

required when the acute honey 

bee contact LD50 <11 μg/bee 

and the use pattern(s) 

indicate(s) that honey bees 

may be exposed to the 

pesticide 

-31 of 69-
TABLE 7.3. Available Ecological Effects Data for Aquatic Animals Exposed to Methiocarb 

and Remaining Data Gaps.

Guideline Description MRID/ 

Accession Classification Data Gap? comments 

Freshwater fish – 

Acute toxicity 

(coldwater species) 

150628 Acceptable No 850.1075 

Freshwater fish – 

Acute toxicity 

(warmwater species) 

150628 Acceptable No 

850.1075 Saltwater fish – 

Acute toxicity None Not applicable Yes1

850.1010 

Freshwater 

invertebrates – 

Acute toxicity 

127638 Acceptable No 

850.1025 

Saltwater invertebrates 

– 

Acute toxicity (oyster 

shell deposition) 

None Not applicable Yes1

1

 Acute toxicity data on a 

saltwater fish, mollusk, and a 

saltwater invertebrate are 

required under 40 CFR Part 

158. Since these data are not 

currently available, EFED 

recommends requesting these 

data at this time. 

850.1035, 

850.1045, 

or 

850.1055 

Saltwater invertebrates 

– 

Acute toxicity (mysid, 

penaeid, or bivalve) 

None Not applicable Yes1

850.1300 

Freshwater 

invertebrate – 

 life cycle test 

None Not applicable Yes2

850.1350 

Saltwater invertebrates 

– 

life cycle test 

None Not applicable Yes2

850.1400 

Freshwater fish – 

early life stage test 

(freshwater) 

00155967 Supplemental Yes3

850.1400 

Fish – 

early life stage test 

(saltwater) 

None Not applicable Yes2

2

 Since the LC50 values for the 

most sensitive fish and 

invertebrate species tested are 

< 1 mg/L, an estuarine/marine 

invertebrate life cycle test and 

an estuarine/marine fish early 

life stage test are required 

under the new 40 CFR Part 

158. Therefore, these are 

identified as a data gaps and 

EFED recommends requesting 

these data. 

3

 Chronic toxicity data from 

the most acutely sensitive 

species (i.e., bluegill sunfish) 

is currently not available. 

Therefore, this is identified as 

a data gap. 

-32 of 69-
TABLE 7.4. Available Ecological Effects Data for Plants Exposed to Methiocarb and 

Remaining Data Gaps.

Guideline Description MRID Classification Data 

Gap? comments 

850.4100 

Terrestrial Plant 

toxicity: Tier I seedling 

emergence 

None Not applicable Yes1

850.4225 

Terrestrial Plant 

toxicity: Tier II seedling 

emergence 

None Not applicable No2

850.4150 

Terrestrial Plant 

toxicity: Tier I 

vegetative vigor 

None Not applicable Yes1

850.4250 

Terrestrial Plant 

toxicity: Tier II 

vegetative vigor 

None Not applicable No2

850.5400 Aquatic Plant Growth: 

algae None Not applicable Yes1

850.4400 Aquatic Plant Growth: 

vascular plants None Not applicable Yes1

1

 Tier I vegetative vigor and 

seedling emergence studies 

and aquatic plant studies (both 

vascular and non-vascular) are 

required under 40 CFR Part 

158. These data are not 

currently available; therefore, 

EFED recommends requesting 

these data. 

2

 Tier II studies may be 

required depending on the 

results of the Tier I plant 

studies. 

Avian Acute Oral Toxicity 

Acute oral toxicity data (850.2100) are required for a passerine and a waterfowl or upland game 

species under 40 CFR Part 158. Acceptable guideline avian acute oral toxicity data are not 

available for any bird species for methiocarb. Therefore, this is identified as a data gap. 

However, since supplemental nonguideline data are available for a variety of species (including 

passerines, upland game species, and waterfowl – see APPENDIX C), EFED does not 

recommend requesting these data at this time. 

Avian Reproduction Toxicity 

Under the 40 CFR Part 158 (July 1, 2009) avian reproduction data are required on waterfowl and 

upland game species (OPPTS 850.2300). Currently acceptable data for methiocarb are only 

available for waterfowl. The chronic toxicity data available for birds indicate that bobwhite 

quail (NOAEC <2 mg a.i./kg-diet based on reduced survival of 14-day old birds and reduced 

eggshell thickness) (MRID 128119) are more sensitive to methiocarb than mallard duck 

(NOAEC = 100 mg a.i./kg-diet, the highest concentration tested) (MRID 128120). Since a 

definitive NOAEC for bobwhite quails is not available (the lowest dose tested resulted in 

effects), the specific risk to birds from chronic exposure to methiocarb is unknown. Therefore, 

in order to complete the risk assessment, additional data are needed. In the absence of such data, 

risks to both listed and non-listed bird species will be presumed in the risk assessment conducted 

for Registration Review. 

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Honey Bee Toxicity of Residues on Foliage 

Under the 40 CFR Part 158 (July 1, 2009) data on honey bee toxicity of residues on foliage are 

required (OPPTS 850.3030) when the acute honey bee contact LD50 <11 μg/bee and the use 

pattern(s) indicate(s) that honey bees may be exposed to the pesticide. The acute contact LD50

for methiocarb is 0.375 μg a.i./bee (MRID 00036935). Furthermore, the use of foliar methiocarb 

on ornamentals (some of which may be flowering) represents a route of potential exposure to 

honey bees. Therefore, in order to complete the risk assessment, additional data are needed. In 

the absence of such data, risks to honey bees will be presumed in the risk assessment conducted 

for Registration Review. 

Acute Estuarine/marine Fish and Invertebrate Toxicity 

Acute toxicity data on a saltwater fish (850.1075), mollusk (850.1025), and a saltwater 

invertebrate (850.1035, 850.1045, or 850.1055) are required under 40 CFR Part 158. Since these 

data are not currently available, EFED recommends requesting these data at this time. In the 

absence of such data, risks to both listed and non-listed estuarine/marine species will be 

presumed in the risk assessment conducted for Registration Review. 

Chronic Toxicity Studies with Aquatic Animals 

Acceptable chronic toxicity data for methiocarb are not available for estuarine/marine fish 

(850.1400), freshwater invertebrates (850.1300) or estuarine/marine invertebrates (850.1350). 

Furthermore, a supplemental study is available for freshwater fish, but not for the most acutely 

sensitive species (i.e., bluegill sunfish). Since the LC50 values for the most sensitive fish and 

invertebrate species tested are < 1 mg/L, estuarine/marine and freshwater invertebrate life cycle 

studies and estuarine/marine and freshwater fish early life stage studies are required under the 

current 40 CFR Part 158. Therefore, these are identified as a data gaps. In the absence of 

chronic methiocarb toxicity data for fish, an acute-to-chronic ratio (ACR) using rainbow trout 

data will be used to extrapolate a chronic endpoint for bluegill sunfish and estuarine/marine fish. 

In the absence of chronic toxicity data for estuarine/marine invertebrates, an ACR using 

freshwater invertebrate data (once available) will be used extrapolate a chronic endpoint for 

estuarine/marine invertebrates. If chronic toxicity for aquatic invertebrates is not available, the 

Agency will presume risks to aquatic invertebrates from the use of methiocarb. 

Terrestrial Plant Studies 

Terrestrial plant toxicity studies [both seedling emergence (850.4100) and vegetative vigor 

(850.4150)] and associated risk analysis of plants are required for registration of pesticides with 

outdoor uses (40 CFR Part 158). Tier II studies (850.4225 and 850.4250) may be required 

depending on the results of the Tier I plant studies. If toxicity data for terrestrial plants are not 

submitted for methiocarb, EFED will presume risk for terrestrial plants. 

 

Vascular and Non-vascular Aquatic Plant Studies

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Aquatic plant toxicity studies and associated risk analysis of plants are required for registration 

of pesticides with outdoor uses (40 CFR Part 158). Toxicity data for both vascular and nonvascular aquatic plants (Tier I, OPPTS Guidelines 850.4400 and 850.5400) are required but are 

not available for methiocarb. Therefore, EFED recommends requesting toxicity data on vascular 

and non-vascular aquatic plants for methiocarb. If toxicity data for aquatic plants are not 

submitted for methiocarb, EFED will presume risk for aquatic plants. 

8. References 

Fletcher, J.S., J.E. Nellessen, and T.G. Pfleeger. 1994. Literature review and evaluation of the EPA food-chain 

(Kenaga) nomogram, an instrument for estimating pesticide residues on plants. Environ. Tox. Chem. 

13:1383-1391. 

Hoerger, F. and E. E. Kenaga. 1972. Pesticide Residues on Plants: Correlation of Representative Data as a Basis 

for Estimation of their Magnitude in the Environment. In F. Coulston and F. Korte, eds., Environmental 

Quality and Safety: Chemistry, Toxicology, and Technology, Georg Thieme Publ., Stuttgart, West 

Germany, pp. 9-28. 

USEPA, 1986. Methiocarb Registration Standard; Environmental Effects Topical; Summary. U.S. Environmental 

Protection Agency, Office of Pesticide Programs, Washington, DC. December 1, 1986. 

USEPA, 1994. Reregistration Eligibility Decision Document. U.S. Environmental Protection Agency, Office of 

Pesticide Programs, Washington, DC. March 30, 1994. 

http://www.epa.gov/oppsrrd1/REDs/old_reds/methiocarb.pdf 

USEPA. 1998. Guidelines for Ecological Risk Assessment. Risk Assessment Forum, Office of Research and 

Development, Washington, D.C. EPA/630/R-95/002F. April 1998. 

http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=30759 

USEPA. 2002. Guidance for Selecting Input Parameters in Modeling the Environmental Fate and Transport of 

Pesticides, Version II. US Environmental Protection Agency, Washington DC. Online at: 

http://www.epa.gov/oppefed1/models water/input_guidance2_28_02.htm. 

USEPA. 2004. Overview of the Ecological Risk Assessment Process in the Office of Pesticide Programs. U.S. 

Environmental Protection Agency, Office of Prevention, Pesticides and Toxic Substances, Office of 

Pesticide Programs, Washington DC. January 23, 2004. 

USEPA. 2009. 40 CFR Part 158. Pesticides; Data Requirements for Conventional Chemicals: Final Rule. 72 FR 

60934. July 1, 2009. 

USEPA. 2007. ECOTOXicology Database. Office of Research and Development National Health and 

Environmental Effects Research Laboratory’s (NHEERL’s) Mid-Continent Ecology Division (MED). 

http://cfpub.epa.gov/ecotox/. 

U.S. Fish and Wildlife Service (USFWS) and National Marine Fisheries Service (NMFS). 1998. Endangered 

Species Consultation Handbook: Procedures for Conducting Consultation and Conference Activities Under 

Section 7 of the Endangered Species Act. Final Draft. March 1998. 

SUBMITTED ENVIRONMENTAL FATE STUDIES:

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Abdel-Wahab, A.; Kuhr, R.; Casida, J. (1966) Fate of C14-carbonyl- labeled aryl 

methylcarbamate insecticide chemicals in and on bean plants. J. Agr. Food Chem. 14(3):290-

297. (Submitter 18274; also In unpublished submission received Jul 15, 1976 under 3125-EX135; submitted by Mobay Chemical Corp., Kansas City, MO; CDL:227756-E) 

Atwell, S.H.; Gronberg, R.R. (1975) Photodecomposition of Bay NTN 9306-Ring-UL-14C: 

Report No. 44844. (Unpublished study received Nov 1, 1975 under 3125-EX-132; submitted by 

Mobay Chemical Corp., Kansas City, Mo.; CDL:095559-H) 

Atwell, S.; Murphy, J. (1978) Soil Absorption and Desorption of [Carbon 14] Mesurol: Mobay 

report No. 66145. Unpublished study prepared by Mobay Chemical Corp. 14 p. 

Becker, B.D.; Schiller, L.K. (1981) ?Residue of ^(R)IMesurol in Soil|: Report No. 69230. 

(Unpublished study received May 29, 1981 under 3125-288; prepared in cooperation with 

Everglades Laboratories, Inc., submitted by Mobay Chemical Corp., Kansas City, Mo.; 

CDL:070111-E) 

Becker, B.D.; Schiller, L.K. (1981) ?^(R)IMesurol Residue in Soil|: Report No. 69231. 

(Unpublished study received May 29, 1981 un- der 3125-288; prepared in cooperation with 

Everglades Laborato- ries, Inc., submitted by Mobay Chemical Corp., Kansas City, Mo.; 

CDL:070111-F) 

Becker, B.D.; Schiller, L.K. (1981) ?^(R)IMesurol Residue in Soil|: Report No. 69239. 

(Unpublished study received May 29, 1981 un- der 3125-288; prepared in cooperation with 

Everglades Laborato- ries, Inc., submitted by Mobay Chemical Corp., Kansas City, Mo.; 

CDL:070111-J) 

Borderland Products Inc. (1986) Residue Data on Methiocarb in Paddy Canal and Receiving 

Waters. Unpublished study prepared in cooperation with Craven Laboratories, Inc. and Morse 

Laborato- ries, Inc. 71 p. 

Borderland Products Inc. (1986) Aquatic Field Dissipation in Water. Unpublished compilation 

prepared in cooperation with Craven Lab- oratories Inc. and Morse Laboratories Inc. 74 p. 

Borderland Products Inc. (1986) Aquatic Field Dissipation in Soil. Unpublished compilation 

prepared in cooperation with Morse Lab- oratories, Inc. 33 p. 

Chemagro Corporation (1973) Chemagro Corporation Soil Persistence Study: Report No. 26880. 

(Unpublished study including report nos. 26881 and 26883, received Mar 26, 1975 under 3125-

EX-119; submitted by Mobay Chemical Corp., Kansas City, Mo.; CDL: 094390-BC) 

Chemagro Corporation (1973) Chemagro Division of Baychem Corpora- tion Soil Persistance 

Study: ?^(R)IMesurol|: Report No. 38948. (Unpublished study including report nos. 38949 and 

38950, re- ceived Mar 26, 1975 under 5F1607; prepared in cooperation with Agricultural 

Consultants, Inc., submitted by Mobay Chemical Corp., Kansas City, Mo.; CDL:094391-AF) 

-36 of 69-
Chemagro Corp. (1970) Chemagro Corporation Soil Persistence Study: Report No. 26880. 

(Unpublished study received Sep 8, 1971 under 3125-234; CDL:119895-C) 

Church, D.D. (1970) Bay 37344--Runoff, Leaching, and Water Stabili- ty: Report No. 26894. 

(Unpublished study received Jul 2, 1975 under 6F1652; submitted by Chemagro Corp., Kansas 

City, Mo.; CDL:094636-D) 

Church, D.D.; Flint, D.R. (1971) The Fate of (R)Mesurol (4-(Meth- ylthic)-3,5-xylyl 

methylcarbamate) in Soil: Report No. 29591. (Unpublished study received Mar 26, 1975 under 

5F1607; prepared in cooperation with Agricultural Consultants Laboratory, sub- mitted by 

Mobay Chemical Corp., Kansas City, Mo.; CDL:094391-K) 

Church, D.D.; Flint, D.R. (1971) The Fate of ^(R)IMesurol ?4-(Meth- ylthio)-3,5-xylyl 

methylcarbamate| in Soil: Report No. 29591. (Unpublished study received Jul 2, 1975 under 

6F1652; submitted by Chemagro Corp., Kansas City, Mo.; CDL:094636-I) 

Crosby, D.; Leitis, E.; Winterlin, W. (1964) The Photodecomposition of Carbamate Insecticides: 

?Submitter| 16458. (Presented at the 148th National Meeting of the American Chemical Society; 

Aug 31, 1964, Chicago, IL; unpublished study received Jun 2, 1975 under 2F1244; prepared by 

Univ. of California--Davis, Agri- cultural Toxicology and Residue Research Laboratory, 

submitted by Mobay Chemical Corp., Kansas City, MO; CDL:094546-C) 

Crosby, D.; Leitis, E.; Winterlin, W. (1965) Photodecomposition of carbamate insecticides. 

Agricultural and Food Chemistry 13 (3):204-207. (Also In unpublished submission received Apr 

12, 1968 under 464-EX-30; submitted by Dow Chemical U.S.A., MIdland, MI; CDL:123614-A) 

Flint, D.R.; Shaw, H.R., II (1974) The Mobility of ^(R)IMesurol Residues in Soil Runoff Water 

and the Degradation of Mesurol-14C in Pond Water: Report No. 39258. (Unpublished study 

received Mar 26, 1975 under 5F1607; prepared in cooperation with Agri- cultural Consultants, 

Inc., submitted by Mobay Chemical Corp., Kansas City, Mo.; CDL:094391-AH) 

Houseworth, L.D.; Tweedy, B.G. (1974) Photodecomposition of ^(R)IMesurol-ring-1-14C: 

Report No. 39895. (Unpublished study received Mar 26, 1975 under 5F1607; prepared in 

cooperation with Univ. of Missouri, Dept. of Plant Pathology, submitted by Mobay Chemical 

Corp., Kansas City, Mo.; CDL:094391-AL) 

Houseworth, L.D.; Tweedy, B.G. (1974) Photodecomposition of ^(R)IMesurol-ring-1-14C: 

Report No. 39895. (Unpublished study received Mar 26, 1975 under 5F1607; prepared in 

cooperation with Univ. of Missouri, Dept. of Plant Pathology, submitted by Mobay Chemical 

Corp., Kansas City, Mo.; CDL:094391-AL) 

Houseworth, L.D.; Tweedy, B.G. (1974) Parent Leaching Studies for ^(R)IMesurol: Report No. 

39937. (Unpublished study received Mar 26, 1975 under 5F1607; prepared in cooperation with 

Univ. of Missouri, Dept. of Plant Pathology, submitted by Mobay Chemical Corp., Kansas City, 

Mo.; CDL:094391-AM) 

-37 of 69-
Jackson, S.; Kesterson, A.; Lawrence, L. (1988) Soil Surface Photo- lysis of ?Carbon 14|Mesurol 

in Natural Sunlight: Report No. 1148: Project No. 220. Unpublished study prepared by 

Pharmaco- logy and Toxicology Research Laboratory. 71 p. 

Kazano, H.; Kearney, P.; Kaufman, D. (1972) Metabolism of methyl- carbamate insecticides in 

soils. J. Agr. Food Chem. 20(5):975- 979. 

Kesterson, A.; Marsh, J.; Lawrence, B.; et al. (1988) Photochemical Degradation of ?Carbon 

14|Mesurol in Aqueous Solutions: Project No. 214; Report No. 1147. Unpublished study 

prepared by Pharma- cology and Toxicology Research Laboratory. 78 p. 

Lamb, D.W. (1974) Accumulation and Persistence of Residues in Blue- gill Fish Exposed to 

^(R)IMesurol-14C: Report No. 40096. (Un- published study received Mar 26, 1975 under 

5F1607; submitted by Mobay Chemical Corp., Kansas City, Mo.; CDL:094391-AN) 

Minor, R.; Atwell, S. (1979) Metabolic Fate of Mesurol in Aerobic and Anaerobic Aquatic 

Environments:Mobay Report No. 66775. Un- published study prepared by Mobay Chemical 

Corp. 22 p. 

Minor, R.; Freeseman, P. (1989) Fate of Methiocarb under Aerobic and Anaerobic Soil 

Conditions: Project ID 99206. Unpublished study prepared by Mobay Corp. 71 p. 

Mobay Chemical Corporation (1970) Persistence of Mesurol (Bay 37344) in Soil. (Compilation; 

unpublished study, including re- port nos. 26883 and 26880, received May 20, 1971 under 3125-

257; CDL:050509-B) 

Mobay Chemical Corp. (1970) Mesurol (Bay 37344): Metabolic, Analyt- ical, Residue, and 

Flavor Information (Apples and Pears). (Com- pilation; unpublished study received Sep 9, 1971 

under 1G1030; CDL:091909-A; 091907) 

Mobay Chemical Corp. (1971) ?Mesurol: Analytical and Residue In- formation for Seed 

Treatment of Corn|. (Compilation; unpub- lished study received Feb 14, 1973 under unknown 

admin. no.; CDL:126889-A) 

Mobay Chemical Corp. (1974) Metabolism of [Carbon-14]-Labeled Me- thiocarb (4-

Methylthio)-3,5-xylyl Methylcarbamate) in Soil and Water: 38747. Unpublished study. 20 p. 

Mobay Chemical Corp. (1979) Mesurol: The Effects on the Environ- ment--Environmental 

Chemistry: Document No. AS79-995. (Com- pilation; unpublished study received May 16, 1979 

under 7F1879; CDL:098341-A; 098342) 

Mobay Chemical Corp. (1979) Mesurol: The Effects on the Environ- ment--Environmental 

Chemistry: Document No. AS79-995. (Com- pilation; unpublished study received May 16, 1979 

under 7F1879; CDL:098341-A; 098342) 

-38 of 69-
Mobay Chemical Corp. (1979) Mesurol: The Effects on the Environ- ment--Environmental 

Chemistry: Document No. AS79-995. (Com- pilation; unpublished study received May 16, 1979 

under 7F1879; CDL:098341-A; 098342) 

Mobay Chemical Corporation (1979) ?Residue of ^(R)IMesurol in Soil|: Report No. 66928. 

(Compilation; unpublished study, in- cluding report no. 67052, received May 29, 1981 under 

3125-288; CDL:070111-D) 

Mobay Chemical Corporation (1981) [Product Chemistry Data for Mes- urol]. Unpublished 

compilation. 44 p. 

Mobay Chemical Corporation (1981) ?Residue of ^(R)IMesurol--Various Crops|: Report No. 

45379. (Compilation; unpublished study, including report nos. 45850, 46257, 46436..., received 

May 29, 1981 under 3125-288; CDL:070112-B) 

Mobay Chemical Corp. (1982) Mesurol Addition No. 4 to the Brochure Entitled: Mesurol, the 

Effects on the Environment--Environmental Chemistry: Document No. AS 82-1813. 

(Compilation; unpublished study received Jul 16, 1982 under 3125-288; CDL:247869-A) 

Murphy, J. (1989) Field Dissipation of Mesurol in Sand and Sandy Loam: Proj. ID ME092101. 

Unpublished Mobay report no. 98512 prepared in cooperation with Wilbur-Ellis Co., and EPL 

Bio- Analytical Services, Inc. 300 p. 

Ridlen, R. (1987) Soil Leaching of Aged Residues of Mesurol. Unpublished Mobay Report 

94872 prepared by Mobay Corp., Stanley Research Center. 40 p. 

Ridlen, R.; Pfankuche, L. (1987) Adsorption and Desorption of (carbon 14) Mesurol by Soil: Lab 

Project Number: 95032: MS 719. Unpublished study prepared by Mobay Corp. Stanley Research 

Center. 63 p. 

Saakvitne, J.; Gustafson, D.; Wilkes, L.; et al. (1981) Mesurol Hydrolysis in Sterile Buffers: 

Proj. No. 443. Unpublished Mobay study 69272 prepared by Analytical Development Corp. 32 

p. 

Saakvitne, J.A.; Gustafson, D.E.; Wilkes; L.C.; et al. (1981) ^(R)IMesurol Hydrolysis in Sterile 

Buffers: ADC Project #443; Report No. 69272. (Unpublished study received May 29, 1981 

under 3125-288; prepared by Analytical Development Corp., sub- mitted by Mobay Chemical 

Corp., Kansas City, Mo.; CDL:070111-B) 

Schiller, L.K. (1981) ?^(R)IMesurol Residue in Soil|: Report No. 69233. (Unpublished study 

received May 29, 1981 under 3125- 288; prepared in cooperation with Chemonics Industries, 

submit- ted by Mobay Chemical Corp., Kansas City, Mo.; CDL:070111-G) 

Schiller, L.K. (1981) ?^(R)IMesurol Residue in Soil|: Report No. 69234. (Unpublished study 

received May 29, 1981 under 3125- 288; prepared in cooperation with Chemonics Industries, 

submit- ted by Mobay Chemical Corp., Kansas City, Mo.; CDL:070111-H) 

-39 of 69-
Schiller, L.K. (1981) ?^(R)IMesurol Residue in Soil|: Report No. 69236. (Unpublished study 

received May 29, 1981 under 3125- 288; prepared in cooperation with Everglades Laboratories, 

Inc., submitted by Mobay Chemical Corp., Kansas City, Mo.; CDL: 070111-I) 

Spare, W. (1987) Determination of Adsorption/Desorption Constants of (Inert Ingred.): Lab. 

Study No. 1278. Unpublished study prepared by Agricsearch, Inc. 129 p. 

Stanley, C.W.; Parker, G.D. (1981) Octanol/Water Partition Co- efficient and Water Solubility of 

^(R)IMesurol: Report No. 69271. (Unpublished study received May 29, 1981 under 3125-288; 

submitted by Mobay Chemical Corp., Kansas City, Mo.; CDL:070112-C) 

Starr, R.I.; Cunningham, D.J. (1973) Metabolism of 14C-labeled Methiocarb ?(4-methylthio)-

3,5-xylyl methyl carbamate| in Soil and Water: Report No. 38747. (U.S. Fish and Wildlife 

Service, Denver Wildlife Research Center, unpublished study; CDL: 094391-AE) 

Thornton, J.S.; Hurley, J.B.; Obrist, J.J. (1976) Soil Thin-Layer Mobility of Twenty Four 

Pesticides (sic) Chemicals: Report No. 51016. (Unpublished study received Jan. 28, 1980 under 

5F1547; submitted by Mobay Chemical Corp., Pittsburgh, Pa.; CDL: 099216-I) 

Tweedy, B.G.; Houseworth, L.D. (1974) Leaching of Aged Residues of ^(R)IMesurol-ring-1-

14C in Sandy Loam Soil: Report No. 40568. (Unpublished study received Mar 26, 1975 under 

5F1607; submit- ted by Mobay Chemical Corp., Kansas City, Mo.; CDL:094391-AP) 

Winkler, V. (2000) Methiocarb Soil Dissipation Testing on a Range of Representative Soils: Lab 

Project Number: 112700: 98512: ME092101. Unpublished study prepared by Mobay Chemical 

Corp. and Bayer PLC. 271 p. {OPPTS 835.6100} 

SUBMITTED EFFECTS STUDIES:

MRID:

22923 Hill, E.F.; Heath, R.G.; Spann, J.W.; et al. (1975) Lethal Dietary Toxicities of Environmental 

Pollutants to Birds: Special Scientific Report--Wildlife No. 191. (U.S. Dept. of the Interior, 

Fish and Wildlife Service, Patuxent Wildlife Research Center; unpublished report) 

36466 Eddy, B.P. (1969) To Assess the Effects of Methiocarb Pellets on Soil Fauna: Technical 

Report No. 600; Report No. 28287. (Un- published study received Mar 26, 1975 under 

5F1607; prepared by Baywood Chemicals, Ltd., submitted by Mobay Chemical Corp., 

Kansas City, Mo.; CDL:094391-D) 

36481 Lamb, D.W.; Jones, R.E. (1973) Toxicity of (R)Mesurol 75% Wettable Powder to English 

Sparrows, Bobwhite Quail and New Zealand Rabbits under Simulated Field Conditions: 

Report No. 35970. (Unpublished study received Mar 26, 1975 under 5F1607; submitted by 

Mobay Chemical Corp., Kansas City, Mo.; CDL:094391-Y) 

36482 Schafer, E.W., Jr.; Brunton, ? (1973) Toxicity and Repellancy Tests of 9 Materials from 

Bayer and Chemagro: Report No. S-225; Re- port No. 36054. (Unpublished study including 

report nos. S-223 and 36055, received Mar 26, 1975 under 5F1607; prepared in co- operation 

with U.S. Fish and Wildlife Service, Denver Wildlife Research Center, submitted by Mobay 

Chemical Corp., Kansas City, Mo.; CDL:094391-Z) 

-40 of 69-
36483 Colburn, R.; Asquith, D. (19??) Tolerance of Stethorus punctum adults and larvae to various 

pesticides. Journal of Economic Entomology 66(4):961-962. (Submitter report no. 36414; 

also In unpublished submission received Mar 26, 1975 under 5F1607; submitted by Mobay 

Chemical Corp., Kansas City, Mo.; CDL: 094391-AA) 

36484 Lamb, D.W.; Roney, D.J. (1973) Acute Toxicity of ^(R)IMesurol 75% Wettable Powder to 

Bluegill and Rainbow Trout: Report No. 36612. (Unpublished study received Mar 26, 1975 

under 5F1607; submitted by Mobay Chemical Corp., Kansas City, Mo.; CDL:094391-AB) 

36485 Colburn, R.B. (1972) Laboratory Evaluation of Mesurol on~Stethorus~ ?~punctum~Adults: 

Report No. 37606. (Pennsylvania, Dept. of Ag- riculture, Fruit Research Laboratory, 

unpublished study; CDL: 094391-AC) 

36491 Schafer, E.W., Jr.; Brunton, R.B.; Lockyer, N.F.; et al. (1973) The Chronic Toxicity of 

Methiocarb to Grackles, Doves, and Quail and Reproductive Effects in Quail: Report No. 

39615. (U.S. Fish and Wildlife Service, Denver Wildlife Research Center, unpublished study; 

CDL:094391-AJ) 

36492 Hermann, ? (1973) Earthworm Toxicity: Report No. RgE 11; Report No. 39766. 

(Unpublished study received Mar 26, 1975 under 5F1607; prepared by Bayer, AG, submitted 

by Mobay Chemical Corp., Kansas City, Mo.; CDL:094391-AK) 

36935 Atkins, E.L.; Greywood, E.A.; Macdonald, R.L. (1975) Toxicity of Pesticides and Other 

Agricultural Chemicals to Honey Bees: Labo- ratory Studies. By University of California, 

Dept. of Entomolo- gy. ?: UC, Cooperative Extension. (Leaflet 2287; published study.) 

37798 Atkins, E.L., Jr.; Anderson, L.D.; Todd, F.E.; et al. (1961) ?Ef- ficacy of Pesticides on Honey 

Bees|: Report No. 8576. (Unpub- lished study received Mar 26, 1975 under 3125-EX-119; 

prepared by Univ. of California--Riverside, Dept. of Entomology, sub- mitted by Mobay 

Chemical Corp., Kansas City, Mo.; CDL:094390-H) 

37799 Johansen, C. (1961) Bee Poisoning Investigations, 1961: Report No. 8577. (Unpublished 

study received Mar 26, 1975 under 3125- EX-119; prepared by Washington State Univ., 

submitted by Mobay Chemical Corp., Kansas City, Mo.; CDL:094390-I) 

37821 Martin, T.J. (1968) A Cage Test To Study the Palatability and Possible Toxicity of 5622b 

(Blue) Pellets (4% Methiocarb) to Semi-Domesticated Pheasants (?~Phasianus colchicus~?): 

Technical Report No. T.F. 423; Report No. 23192. (Unpublished study re- ceived Mar 26, 

1975 under 3125-EX-119; prepared by Baywood Chemicals, Ltd., submitted by Mobay 

Chemical Corp., Kansas City, Mo.; CDL:094390-AO) 

37822 Cunningham, D.; Schafer, E.W., Jr. (1968) ?Toxicity Studies on Birds|: Report No. 23196. 

(U.S. Fish and Wildlife Service, Denver Wildlife Research Center, unpublished study; CDL: 

094390-AP) 

37823 Boddington, D.G.; Martin, T.J. (1968) A Field Study To Discover Any Evidence of Acute 

Toxicity to Birds of 5622b Pellets Used as a Molluscicide, and Observations on the Nonacceptability of 5622b Pellets to a Population of House Sparrows: Technical Report No. T.F. 

422; Report No. 23622. (Unpublished study received Mar 26, 1975 under 3125-EX-119; 

prepared by Baywood Chemicals, Ltd., submitted by Mobay Chemical Corp., Kansas City, 

Mo.; CDL:094390-AQ) 

37826 Walker, J.O. (1968) A Trial to Access the Consequences of Feeding Chickens with 

Methiocarb Poisoned Slugs and Methiocarb Pellets: Technical Report No. TR 541; Report 

No. 24546. (Unpublished study received Mar 26, 1975 under 3125-EX-119; prepared by 

-41 of 69-
Baywood Chemicals, Ltd., submitted by Mobay Chemical Corp., Kansas City, Mo.; 

CDL:094390-AT) 

37828 Myram, C. (1968) Observations on Wildlife Effects following the Application of Methiocarb 

Pellets: Toxicological Report No. 167; Report No. 24775. (Unpublished study received Mar 

26, 1975 under 3125-EX-119; submitted by Mobay Chemical Corp., Kansas City, Mo.; 

CDL:094390-AV) 

37845 University of California, Agricultural Extension (19??) Toxicity of Pesticides and Other 

Agricultural Chemicals to Honey Bees. ?: UC, AES. (Submitter report no. 29844; also In 

unpublished submission received Apr 25, 1975 under 5F1607; submitted by Mobay Chemical 

Corp., Kansas City, Mo.; CDL:094391-AS) 

60625 Johansen, C.; Hutt, R. (1962) Bee Poisoning Investigations, 1962: Report No. 10617. 

(Unpublished study received Mar 27, 1974 un- der 4F1485; prepared by Washington State 

Univ., submitted by Chemagro Corp., Kansas City, Mo.; CDL:092011-E) 

81142 Mobay Chemical Corporation (1964) Toxicity and Repellency Studies with Bayer 37344 on 

Wild Birds and Rodents: Report No. 9567B. (Compilation; unpublished study received Mar 

23, 1970 under 3125-234; CDL:007173-AD) 

094390 Shafer, E.W. (1965) Secondary Hazard to Hawks. 1 p. Study conducted by Denver Wildlife 

Research Center. Submitted by Chemagro; reg # 3125-234/288; Acc. # 094390 (report 16190 

– in part). 

094391 Toxicological Evaluation of Three Chemagro Chemicals with Fish (1970) Gulf South 

Research Institute, Chemagrol 5F1607. 

127638 Nelson, D.; Roney, D. (1979) Acute Toxicity of Mesurol Technical to Daphnia magna: 

Report No. 67264. (Unpublished study re- ceived Sep 14, 1979 under 3125-288; submitted 

by Mobay Chemical Corp., Kansas City, MO; CDL:098965-D) 

128119 Lamb, D.; Carsel, M.; Mallicoat, D.; et al. (1982) Methiocarb Re- production Study with 

Bobwhite Quail: 82400. (Unpublished study received Feb 10, 1983 under 3125-234; 

submitted by Mobay Chemi- cal Corp., Kansas City, MO; CDL:071396-A) 

128120 Lamb, D.; Carsel, M.; Mallicoat, D.; et al. (1982) Methiocarb Re- production Study with 

Mallard Duck: 82398. (Unpublished study received Feb 10, 1983 under 3125-234; submitted 

by Mobay Chemi- cal Corp., Kansas City, MO; CDL:071396-B) 

128121 Carlisle, J.; Carsel, M.; Lamb, D.; et al. (1982) A Laboratory Study Exposing Bobwhite 

Quail to Mesurol 2% Bait: 82399. (Un- published study received Feb 10, 1983 under 3125-

234; submitted by Mobay Chemical Corp., Kansas City, MO; CDL:071396-C) 

128122 Carlisle, J.; Toll, P.; Lamb, D.; et al. (1982) Small Pen Field Study of Mesurol 2% Bait 

Toxicity To Bobwhite Quail: 82674. (Unpublished study received Feb 10, 1983 under 3125-

234; submit- ted by Mobay Chemical Corp., Kansas City, MO; CDL:071396-D) 

150383 Marking, L.; Chandler, J. (1981) Toxicity of six bird control chem- icals to aquatic 

organisms. Bull. Environm. Contam. Toxicol. (26):705-716. 

150628 Lamb, D. (1981) Acute Toxicity of Technical Methiocarb (Mesurol) to Bluegill and Rainbow 

Trout: Study Nos. 81-066-03 and 80-066-12: Mobay Report No. 69407. Unpublished study 

prepared by Mobay Chemical Co. 9 p. 

155049 Hermann (1983) Bird Toxicity, Oral: Japanese Quail (Coturnix cotur- nix Japonica): [Test 

-42 of 69-
Compound Mesurol]: Report No. VW-76. Un- published study prepared by Bayer AG. 2 p. 

155967 Carlisle, J. (1985) Toxicity of Methiocarb (Mesurol) Technical to Early Life Stages of 

Rainbow Trout: Study No. 85-666-02: 90579. Unpublished study prepared by Mobay 

Chemical Corp. 19 p. 

2046935 Bayer A.G., Pflanzenshutz Anwendungstechnik, Biological Research, Report No. FF-105. 

40098001 Mayer, F.; Ellersieck, M. (1986) Manual of Acute Toxicity: Inter- pretation and Data Base 

for 410 Chemicals and 66 Species of Freshwater Animals. US Fish & Wildlife Service, 

Resource Pub- lication 160. 579 p. 

40560001 Dolbeer, R.; Avery, M.; Tobin, M. (1988) Assessment of Field Hazards to Birds and 

Mammals from Methiocarb Applications to Fruit Crops: Report No. 87266. Unpublished 

compilation. 1198 p . 

40615001 Greig-Smith, P.; Hardy, A.; Brown, P. et al. (1981) Assessment of the Hazard to Wildlife 

from the Use of Methiocarb To Protect Ripening Cherries: Project No. C/88/0127. 

Unpublished study prepared by ADAS Tolworth Laboratory. 214 p. 

43459801 Kuhn, J. (1994) Acute Oral Toxicity Study in Rats: Metaldehyde-Methiocarb 2-1: Final 

Report: Lab Project Number: 1380-94. Unpublished study prepared by Stillmeadow, Inc. 24 

p. 

45743001 Eiben, R.; Bach, U.; Popp, A. (2002) H 321 (Methiocarb): Two-Generation Study in Wistar 

Rats: Lab Project Number: PH 31760: T4069306: H 321. Unpublished study prepared by 

Bayer Ag. 937 p. {OPPTS 870.3800} 

-43 of 69-
APPENDIX A. Label Restrictions for Mesurol® 75% Wettable Powder Aversive 

Conditioning Egg Treatment 

For Mesurol® 75% Wettable Powder Aversive Conditioning Egg Treatment which is used as a 

poison for birds that scavenge nests, there are several precautions stipulated on the label that 

could reduce non-target mortality: 

- For retail sale to and use by APHIS (U.S. Department of Agriculture’s Animal 

and Plant Health Inspection Service) Certified Applicators or persons under their 

direct supervision and only for those uses covered by the Certified Applicator’s 

certification. 

- Before using, consult with local, state, and Federal wildlife authorities to ensure 

that the use of the product does not present a hazard to threatened or endangered 

species. 

- Do not place eggs treated with the product in areas where there is a danger that 

Threatened or Endangered Species will consume them, unless special precautions 

are taken to limit exposure. 

i. Such special precautions may include constant observation while treated 

eggs are in the field and the use of hazing tactics to frighten away nontarget species that might feed upon the treated eggs. 

ii. If birds of the species to be protected feed upon or peck at treated eggs, 

remove all treated eggs from the field. 

- When controlling a protected bird species, it is usually necessary to obtain a 

permit from the U.S. Fish and Wildlife Service (USFWS) and/or applicable State 

Wildlife Agency. 

- Prior to utilizing this control method, an endangered species consultation should 

be conducted with the USFWS to determine if endangered or threatened species 

that could or would consume treated eggs may be present during the treatment 

period. 

- Treated areas must be observed, at least periodically, to monitor the responses of 

target birds, nesting birds, and other nontarget species. Video equipment may be 

used to supplement direct observations. 

- Place treated eggs in sets of 1 or 2 eggs (apply no more than 20 treated eggs per 

acre). 

- Check egg sets at intervals of 24-hrs or less. Replace eggs that are damaged or 

removed with fresh treated eggs. 

- Unless treatments and monitoring can be continued without adverse effects on the 

species to be protected, remove all treated eggs when these birds begin laying 

eggs. 

- Carcasses of dead or dying animals should be collected. 

-44 of 69-
APPENDIX B. Toxicity Data for Methiocarb: 

TABLE 1. Submitted Toxicity Data for Methiocarb (Excluding Invalid Studies): 

TAXON ENDPOINT FORMULATION MRID 

STUDY 

CLASSIFICATION 

COMMENTS 

BIRDS 

Birds (Acute) (see additional table below) 

Various bird 

species No endpoint Not reported 40560001 Supplemental 

Repellency study; nonguideline; no raw data 

provided; appears to have 

been a preliminary screening 

of many chemicals to see 

which warranted further 

investigation as a bird 

repellent. 

Ring-necked 

pheasant 

(Phasianus 

colchicis) 

LD50 = 13.3 mg 

a.i./kg-bw Not reported 40560001 Supplemental 

Procedures varied from test to 

test but which procedure used 

for each test was not provided; 

no raw data provided; 

procedures were not in 

accordance with Agency 

guidelines. 

Horned lark 

(Eremophilia 

alpestris) 

LD50 = 4.22 mg 

a.i./kg-bw Not reported 40560001 Supplemental 

Procedures varied from test to 

test but which procedure used 

for each test was not provided; 

no raw data provided; 

procedures were not in 

accordance with Agency 

guidelines. 

Japanese quail 

(Coturnix 

coturnix) 

LD50 = 10 mg 

a.i./kg-bw 

(males) 

LD50 = 5-10 mg 

a.i./kg-bw 

(females) 

TGAI (98% a.i.) 00155049 Supplemental 

No information on bird age or 

weight change provided; 7-day 

observation period. 

Japanese quail 

(Coturnix 

coturnix) 

LD50 = 8.84 mg 

a.i./kg-bw Not reported 40560001 Supplemental 

Procedures varied from test to 

test but which procedure used 

for each test was not provided; 

no raw data provided; 

procedures were not in 

accordance with Agency 

guidelines. 

Starling 

(Sturnus vulgaris) 

LD50 = 12 - 15 

mg a.i./kg-bw TGAI 81142 Supplemental Only summary data provided and too few birds used. 

Starling 

(Sturnus vulgaris) 

LD50 = 11.3 mg 

a.i./kg-bw Not reported 40560001 Supplemental 

Procedures varied from test to 

test but which procedure used 

for each test was not provided; 

no raw data provided; 

procedures were not in 

accordance with Agency 

guidelines. 

Starling 

(Sturnus vulgaris) 

LD50 = 24.2 mg 

a.i./kg-bw TGAI 00036482 Supplemental Only summary data provided and too few birds used; cannot 

-45 of 69-
TAXON ENDPOINT FORMULATION 

STUDY 

MRID CLASS- COMMENTS 

IFICATION 

be used to fulfill guideline 

requirements. 

Starling 

(Sturnus vulgaris) No endpoint 75% WP (75% a.i.) 40560001 Supplemental 

Non-guideline aversion study 

using grapes; no raw data 

provided. 

Red-winged 

blackbird 

(Agelaius 

phoeniceus) 

LD50 = 11 - 20 

mg a.i./kg-bw TGAI 81142 Supplemental Only summary data provided and too few birds used. 

Red-winged 

blackbird 

(Agelaius 

phoeniceus) 

LD50 = 4.67 mg 

a.i./kg-bw Not reported 40560001 Supplemental 

Procedures varied from test to 

test but which procedure used 

for each test was not provided; 

no raw data provided; 

procedures were not in 

accordance with Agency 

guidelines. 

Pigeon 

(Columbia livia) 

LD50 = 50 mg 

a.i./kg-bw TGAI 81142 Supplemental Only summary data provided and too few birds used. 

Eared dove 

(Zebauda 

auriculata) 

LD50 = 3.16 mg 

a.i./kg-bw Not reported 40560001 Supplemental 

Procedures varied from test to 

test but which procedure used 

for each test was not provided; 

no raw data provided; 

procedures were not in 

accordance with Agency 

guidelines. 

Ring-billed gull 

(Larus 

delauarensis) 

LD50 = 5 - 10 

mg a.i./kg-bw TGAI 81142 Supplemental Only summary data provided and too few birds used. 

Budgerigar 

(Melopsittacus 

undulates) 

LD50 = 1.33 mg 

a.i./kg-bw Not reported 40560001 Supplemental 

Procedures varied from test to 

test but which procedure used 

for each test was not provided; 

no raw data provided; 

procedures were not in 

accordance with Agency 

guidelines. 

Cedar waxwing 

(Bombycilla 

cedrorum) 

LD50 = 5.62 mg 

a.i./kg-bw Not reported 40560001 Supplemental 

Procedures varied from test to 

test but which procedure used 

for each test was not provided; 

no raw data provided; 

procedures were not in 

accordance with Agency 

guidelines. 

Red-billed quelea 

(Quelea quelea) 

LD50 = 4.22 mg 

a.i./kg-bw Not reported 40560001 Supplemental 

Procedures varied from test to 

test but which procedure used 

for each test was not provided; 

no raw data provided; 

procedures were not in 

accordance with Agency 

guidelines. 

House finch 

(Carpodacus 

mexicanus) 

LD50 = 2.42 mg 

a.i./kg-bw TGAI 00036482 Supplemental Only summary data provided and too few birds used. 

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IFICATION 

House finch 

(Carpodacus 

mexicanus) 

LD50 = 2.37 mg 

a.i./kg-bw Not reported 40560001 Supplemental 

Procedures varied from test to 

test but which procedure used 

for each test was not provided; 

no raw data provided; 

procedures were not in 

accordance with Agency 

guidelines. 

House finch 

(Carpodacus 

mexicanus) 

No endpoint 75% WP (75% a.i.) 40560001 Supplemental 

Non-guideline aversion study 

using grapes; no raw data 

provided. 

Sandhill crane 

(Grus 

Canadensis) 

LD50 = 23.7 mg 

a.i./kg-bw Not reported 40560001 Supplemental 

Procedures varied from test to 

test but which procedure used 

for each test was not provided; 

no raw data provided; 

procedures were not in 

accordance with Agency 

guidelines. 

Golden crowned 

sparrow 

(Zonotrichia 

atricapilla) 

LD50 = 3.16 mg 

a.i./kg-bw TGAI 00036482 Supplemental Only summary data provided and too few birds used. 

Golden crowned 

sparrow 

(Zonotrichia 

atricapilla) 

LD50 = 3.16 mg 

a.i./kg-bw Not reported 40560001 Supplemental 

Procedures varied from test to 

test but which procedure used 

for each test was not provided; 

no raw data provided; 

procedures were not in 

accordance with Agency 

guidelines. 

White crowned 

sparrow 

(Zonotrichia 

leucophrys) 

LD50 = 4.21 mg 

a.i./kg-bw TGAI 00036482 Supplemental Only summary data provided and too few birds used. 

Yellow-headed 

blackbird 

(Xanthocephalus 

xanthocephalus) 

LD50 = 3.2 mg 

a.i./kg-bw TGAI 37822 Supplemental Only summary data provided and too few birds used. 

Grackle 

(Quiscalus 

quiscula) 

LD50 = 10 mg 

a.i./kg-bw TGAI 37822 Supplemental Only summary data provided and too few birds used. 

Brown-headed 

cowbird 

(Molothrus ater) 

LD50 = 7.5 mg 

a.i./kg-bw TGAI 37822 Supplemental Only summary data provided and too few birds used. 

Bobwhite quail 

(Colinus 

virginianus) 

LD50 = 2.42 mg 

a.i./kg-bw TGAI 00036482 Supplemental Only summary data provided and too few birds used. 

Bobwhite quail 

(Colinus 

virginianus) 

LD50 = 19.6 mg 

a.i./kg-bw Not reported 40560001 Supplemental 

Procedures varied from test to 

test but which procedure used 

for each test was not provided; 

no raw data provided; 

procedures were not in 

accordance with Agency 

guidelines. 

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TAXON ENDPOINT FORMULATION 

STUDY 

MRID CLASS- COMMENTS 

IFICATION 

Birds (Acute/Sub-Acute)

Japanese quail 

(Coturnix 

coturnix) 

LC50 = 1199 mg 

a.i./kg-diet Mesurol (50% a.i.) 00022923 Supplemental Lack of detail regarding methodology. 

Japanese quail 

(Coturnix 

coturnix) 

LC50 = 1427 mg 

a.i./kg-diet TGAI (97% a.i.) 00022923 Supplemental Lack of detail regarding methodology. 

Ring-necked 

pheasant 

(Phasianus 

colchicis) 

LC50 = 3849 mg 

a.i./kg-diet Mesurol (50% a.i.) 00022923 Acceptable Lack of detail regarding methodology. 

Ring-necked 

pheasant 

(Phasianus 

colchicis) 

LC50 = >5000 

mg a.i./kg-diet TGAI (97% a.i.) 

00022923 

Acceptable Lack of detail regarding 

methodology. 

Ring-necked 

pheasant 

(Phasianus 

colchicis) 

No endpoint 4% Methiocarb 

Pellets (4% a.i.) 37821 Supplemental Non-guideline (repellency study). 

Mallard duck 

(Anas 

platyrhynchos) 

LC50 = 2082 mg 

a.i./kg-diet Mesurol (50% a.i.) 

00022923 

Acceptable Lack of detail regarding 

methodology. 

Mallard duck 

(Anas 

platyrhynchos) 

LC50 = 929 mg 

a.i./kg-diet Mesurol (50% a.i.) 00022923 Acceptable Lack of detail regarding methodology. 

Mallard duck 

(Anas 

platyrhynchos) 

LC50 = 4113 mg 

a.i./kg-diet TGAI (97% a.i.) 00022923 Acceptable Lack of detail regarding methodology. 

Mallard duck 

(Anas 

platyrhynchos) 

LC50 = 1071 mg 

a.i./kg-diet TGAI (97% a.i.) 00022923 Acceptable Lack of detail regarding methodology. 

Mallard duck 

(Anas 

platyrhynchos) 

LC50 = >5,000 

mg a.i./kg-diet TGAI (97.7% a.i.) 00022923 Acceptable 

There was 42% mortality at 

the 5000 ppm concentration. 

There was avoidance of 

treated food at all treatment 

levels (lowest 265 ppm). 

Grackle 

(Quiscalus 

quiscala) 

28- to 30-day 

LC50 = >100 mg 

a.i./kg-diet 

Not reported 36491 Supplemental 

Too few birds and 

concentrations tested to 

provide statistically significant 

results; one of four birds in 

100 mg a.i./kg-diet treatment 

level died. 

Mourning dove 

(Zenaidura 

macroura) 

28- to 30-day 

LC50 = 630 mg 

a.i./kg-diet 

Not reported 36491 Supplemental 

Too few birds and 

concentrations tested to 

provide statistically significant 

results. 

Japanese quail 

(Coturnix 

coturnix) 

28- to 30-day 

LC50 = >1000 

mg a.i./kg-diet 

Not reported 36491 Supplemental 

Too few birds and 

concentrations tested to 

provide statistically significant 

results; three of six females 

and one of six males at the 

1000 mg a.i./kg-diet level 

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TAXON ENDPOINT FORMULATION 

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MRID CLASS- COMMENTS 

IFICATION 

died. 

Bobwhite quail 

(Colinus 

virginianus) 

NOAEC = 1 lb 

a.i./acre 

2% Methiocarb 

Pellets (2% a.i.) 00128122 Supplemental 

Non-guideline study (small 

pen field study); no effects 

seen at the rate tested (1 lb 

a.i./acre). 

Bobwhite quail 

(Colinus 

virginianus) 

No endpoint Mesurol 2% Bait 

(2% a.i.) 128121 Supplemental 

Non-guideline study; birds 

were fed various combinations 

of bait and control feed ad 

libitum; birds were able to 

pick out food and avoid bait 

(some repellency); no 

mortality in 7-day study; 

weight loss (~20% compared 

to controls) occurred in birds 

that had no control feed 

available 

Bobwhite quail 

(Colinus 

virginianus) 

No endpoint 

Mesurol 75% 

wettable powder 

(75% a.i.) 

00036481 Supplemental 

Non-guideline study; 

simulated field (5 week) 

study; no treatment-related 

effects with 4 applications of 9 

lb a.i./acre/application. 

Sharp-shinned 

hawk 

(Accipiter 

striatus) 

No endpoint unknown 094390 Supplemental 

Non-guideline study; hawk fed 

for 116 days on red-winged 

blackbirds fed methiocarb – 

the hawk was ‘unaffected’. 

Sparrow hawk 

(Accipiter nisus) No endpoint unknown 094390 Supplemental 

Non-guideline study; hawk fed 

for 120 days on red-winged 

blackbirds fed methiocarb – 

the hawk was ‘unaffected’. 

Red-winged 

blackbirds 

(Turdus merula) 

No endpoint Not reported 40560001 Supplemental 

Non-guideline aversion study; 

it is not clear the exact 

concentration tested; the study 

demonstrated visuallyacquired aversion to a 

repellent (methiocarb). 

Chicken 

(Gallus gallus 

domesticus) 

No endpoint 4% Methiocarb 

Pellets (4% a.i.) 00037826 Supplemental 

Non-guideline; only three 

birds per treatment level; birds 

fed poisoned slugs; no adverse 

effects to birds noted; birds 

‘quickly learned to resist 

consumption of poisoned 

slugs’. 

English sparrow 

(Passer 

domesticus) 

No endpoint 

Mesurol 75% 

wettable powder 

(75% a.i.) 

00036481 Supplemental 

Non-guideline study; 

simulated field (5 week) 

study; no treatment-related 

effects with 4 applications of 9 

lb a.i./acre/application. 

House finch 

(Carpodacus 

mexicanus) 

No endpoint 75% wettable 

powder (75% a.i.) 40560001 Supplemental 

Non-guideline study; efficacy 

study; the concentration of 

methiocarb on the hulled oats 

is not known; does provide 

evidence for repellency in 

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TAXON ENDPOINT FORMULATION 

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IFICATION 

birds. 

House finch 

(Carpodacus 

mexicanus) 

No endpoint 75% wettable 

powder (75% a.i.) 40560001 Supplemental 

Non-guideline efficacy study; 

the concentration of 

methiocarb on the hulled oats 

is not known; author states 

that finches do not avoid 

methiocarb-treated food based 

on taste; reduction in food 

intake could be due to 

methiocarb-induced illness. 

Field study 0.28 lb a.i./acre 4% Methiocarb 

Pellets (4% a.i.) 0037823 Supplemental 

Non-guideline study; 0.28 lb 

a.i./acre applied to barley 

field; bird census only 

extended 3 days postapplication. No sick or dead 

birds observed (dead and 

dying earthworms common). 

Field study 

1.9 lb a.i./acre 

applied to 

highbush 

blueberries 

Mesurol 75 WP 

(75% a.i.) 40560001 Supplemental 

Searches for carcasses did not 

include off-site areas; carcass 

searches only conducted 3 

days post-treatment; malathion 

was used concurrently; 5 

incapacitated Baltimore 

orioles (2 adults and 3 

juveniles) were observed. 

Field study 

0.95 or 1.9 lb 

a.i./acre applied 

to blueberries 

(depending on 

the field) 

Mesurol 75 WP 

(75% a.i.) 40560001 Supplemental 

Description of how and when 

carcass searches were 

conducted was not provided; 

malathion was used 

concurrently; 7 incapacitated 

birds (5 robins and 2 

Baltimore orioles) were 

observed. 

Field study 

2 applications 

of 2 lb a.i./acre 

applied twice to 

cherries 

Mesurol 75 WP 

(75% a.i.) 40560001 Supplemental 

Insufficient description of 

carcass search effort; carcass 

search only conducted on day6 post-treatment; 3 dead birds 

(one Brewer blackbird and 

two grackles) and partially 

paralyzed starling found. 

Field study 

2 or 3 

applications to 

grapes 

(depending on 

field); 

application rate 

not provided on 

DER 

Mesurol 75 WP 

(75% a.i.) 40560001 Supplemental 

Carcass searches not 

conducted daily after 

treatments; carcass efficiency 

and predator removal trials 

were not conducted; carcass 

searching not done off-field; 

10 incapacitated birds (7 

robins, 1 housefinch, and 2 

Western bluebirds) found (all 

recovered within 4 hrs). 

Field study 2 or 3 

applications to 

Mesurol 75 WP 

(75% a.i.) 40560001 Supplemental Carcass searches only conducted once within first 24 

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TAXON ENDPOINT FORMULATION 

STUDY 

MRID CLASS- COMMENTS 

IFICATION 

grapes 

(depending on 

the field) at 2.8 

lb a.i./acre 

hrs after treatment; carcass 

efficiency and predator 

removal trials were not 

conducted; no dead or 

incapacitated birds found. 

Field study 

3 applications at 

1.9 lb a.i./acre 

(14-day 

application 

interval) to 

cherries 

50% WP (50% a.i.) 40615001 Acceptable 

16 dead or incapacitated birds 

found [greenfinch (3), 

blackbird (3), blue tit (2), 

starling (2), house sparrow (3), 

linnet (1), chaffinch (1), tree 

sparrow (1)]; authors attribute 

6-12 due to methiocarb; 

estimated 25% carcass 

efficiency = 24 – 48 dead 

birds from methiocarb. 

Birds (Chronic) 

Bobwhite quail 

(Colinus 

virginianus) 

NOAEC = <2 

mg a.i./kg-diet TGAI (97% a.i.) 128119 Supplemental 

Reproductive effects seen at 

the lowest concentration tested 

(2 ppm). 

Mallard duck 

(Anas 

platyrhynchos) 

Reproductive 

effects: 

NOAEC = 100 

mg a.i./kg-diet 

LOAEC - >100 

mg a.i./kg-diet 

Cholinesterase 

activity: 

NOAEC = 50 

mg a.i./kg-diet 

LOAEC - 100 

mg a.i./kg-diet 

TGAI (97% a.i.) 128120 Acceptable 

No reproductive effects seen 

at the highest concentration 

tested (100 ppm). 

Coturnix quail 

(Coturnix 

coturnix) 

NOAEC = 100 

mg a.i./kg-diet 

LOAEC = 316 

mg a.i./kg-diet 

Not reported 36491 Supplemental 

Based on reduced egg 

production and live-chick 

production; appropriate 

reproductive parameters were 

not measured, raw data were 

not provided, and the 

experimental procedure not 

completely described. 

MAMMALS 

Mammals (Acute) 

Laboratory rat 

(Rattus 

norvegicus) 

LD50 = 14 mg 

a.i./kg-bw 

(males) 

TGAI 00083437 Acceptable None 

Black-tailed 

prairie dog 

(Cynomys 

ludovicianus) 

No endpoint TGAI (dust) 40560001 Supplemental 

Non-guideline field study 

(aversion); grains were dusted 

and fed to the prairie dogs; 

study demonstrates repellency; 

adults learned to avoid the 

grain with the methiocarb (and 

continued grain aversion after 

treatment ended). 

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TAXON ENDPOINT FORMULATION 

STUDY 

MRID CLASS- COMMENTS 

IFICATION 

Fox squirrel 

(Sciurus niger 

rufiventer) 

No endpoint 

Mesurol Hopper 

Box Treater (50% 

a.i.) 

40560001 Supplemental 

Non-guideline aversion study; 

it is not possible to estimate 

concentrations tested; raw data 

not provided; animals avoided 

treated food. 

Ground squirrel 

(Spermophilus 

tridecemlineatus) 

No endpoint 

Mesurol Hopper 

Box Treater (50% 

a.i.) 

40560001 Supplemental 

Non-guideline aversion study; 

raw data not provided; animals 

avoided treated food. 

Mammals (Chronic) 

Laboratory rat 

(Rattus 

norvegicus) 

NOAEC = 67 

mg a.i./kg-diet 

(3.35 mg 

a.i./kg-bw) 

(based on 

cholinesterase 

inhibition)

TGAI 

00115226 

and 

00128723 

Acceptable 

Based on a chronic dietary 

study; decreased body weight 

at 600 mg a.i./kg-diet; 

LOAEC = 200 mg a.i./kg-diet 

based on cholinesterase 

inhibition; a reproduction 

study is not available 

TERRESTRIAL INVERTEBRATES 

Honey bee 

(Apis mellifera) 

LD50 < 1.25 lb 

product/100 

gallon (resulted 

in 100% 

mortality) 

50% WP (50% a.i.) 00060625 Acceptable 

Only one concentration tested 

(tested both with direct 

application and exposed to dry 

residues). 

Honey bee 

(Apis mellifera) 

LD50 < 1 lb 

product/100 

gallon (resulted 

in 100% 

mortality) 

Mesurol (% a.i. not 

provided) 0037799 Supplemental 

Only one concentration tested 

(tested either with direct 

application or exposed to dry 

residues) – based on DER 

(1978). Direct application 

resulted in complete mortality 

within 3 hr; 92-100% 

mortality resulted from 

residues after 4 days posttreatment. 

Honey bee 

(Apis mellifera) 

LD50 <0.25% 

>0.125% 

Mesurol (% a.i. not 

provided) 0037798 Supplemental 

Applied as a dust (0.125, 0.25, 

0.5, 1, 2, 4, and 8% 

concentrations). After 48 hr, 

100% mortality at 4 and 8%; 

1.0, 0.5, 0.25, and 0.125% 

resulted in the following 

mortalities: 93%, 81%, 58% 

and 5%, respectively. 

Honey bee 

(Apis mellifera) 

LD50 = 0.375 

μg 

formulation/bee 

Mesurol (% a.i. not 

reported) 00037845 Supplemental None 

Honey bee 

(Apis mellifera) 

LD50 = 0.375 

μg a.i./bee Mesurol 00036935 Acceptable None 

Earthworm 

(Lumbricus 

terrestris 

Allobophora 

rubellus) 

LC50 > 0.8 lb 

a.i. 

Draza pellets (4% 

a.i.) 00036466 Supplemental 

Non-guideline study. 

Earthworm populations were 

reduced by 1.25, 2.25, and 5% 

(as compared to controls) for 

0.2, 0.4, and 0.8 lb a.i., 

respectively. 

Erthworm 35-day LC50 TGAI (99.2% a.i.) 00036492 Supplemental Non-guideline study. No 

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TAXON ENDPOINT FORMULATION 

STUDY 

MRID CLASS- COMMENTS 

IFICATION 

(Eisenia foetida) >200 ppm effects noted at 2.5 or 10 

ppm); severe damage and 

some mortality occurred at 50 

and 200 ppm; worms were 

exposed for 10 days. 

Ladybird beetle 

(Stethorus 

punctum) 

LD50 < 0.094 lb 

a.i./100 gallon 

water 

Mesurol 75% WP 

(75% a.i.) 00036483 Supplemental 

Non-guideline study; adult 

beetles were dipped in 

solution; after 48-hr, there was 

complete mortality. 

Ladybird beetle 

(Stethorus 

punctum) 

LD50 < 0.375 lb 

a.i./100 gallon 

water (0.5 

formulation/100 

gallon water) 

Mesurol 75% WP 

(75% a.i.) 00036485 Supplemental 

Non-guideline study; adult 

beetles were dipped in 

solution; complete mortality 

after 4 hr in the 0.5 lb 

formulation/100 gallon; 

complete mortality within 1 hr 

at 1 and 2 lb rates. 

Field study 0.28 lb a.i./acre 4% Methiocarb 

Pellets (4% a.i.) 0037823 Supplemental 

Non-guideline study; 0.28 lb 

a.i./acre applied to barley 

field; bird census only 

extended 3 days postapplication. No sick or dead 

birds observed (dead and 

dying earthworms common). 

Field study 

0.20 lb a.i. 

applied to 

brussell sprouts 

and cauliflower 

fields. ‘High’ 

rate applied to 

garden. 

4% Methiocarb 

Pellets (4% a.i.) 0037828 

Supplemental 

(invertebrate 

portion) 

Non-guideline study; only 

minimal avifauna 

investigation. No sick or dead 

birds observed (dead 

earthworms, carabid beetles, 

slugs, and one dead field 

mouse). 

FRESHWATER FISH 

Freshwater Fish (Acute) 

Rainbow trout 

(Oncorhynchus 

mykiss) 

LC50 = 4.7 mg 

a.i./L TGAI ((8.4% a.i.) ACC No. 2046935 Supplemental 

Tanks were aerated during the 

study and concentrations were 

not measured. 

Rainbow trout 

(Oncorhynchus 

mykiss) 

LC50 = 1.4 mg 

a.i./L 

(1.05 mg a.i./L) 

Mesurol 75% WP 

(75% a.i.) 36484 Acceptable 

The results do not appear to 

have been corrected for a.i. 

(the reviewer converted the 

results for a.i.). 

Rainbow trout 

(Oncorhynchus 

mykiss) 

LC50 = 0.436 

mg a.i./L TGAI (98% a.i.) 150628 Acceptable None 

Rainbow trout 

(Oncorhynchus 

mykiss) 

LC50 = 0.9 mg 

a.i./L TGAI (% a.i. not 

reported) 094391 Supplemental No method of statistical analysis provided. 

Rainbow trout 

(Oncorhynchus 

mykiss) 

LC50 = 0.672 

mg a.i./L TGAI (99% a.i.) 40098001 Supplemental Insufficient study details; no 

slope could be calculated. 

Bluegill sunfish 

(Lepomis 

macrochirus) 

LC50 = 0.182 

mg a.i./L TGAI (99% a.i.) 40098001 Supplemental 

Insufficient study details; 

slope = 4.4 (95% CI = 1.9, 

6.9). 

Bluegill sunfish LC50 = 1.9 mg Mesurol 75% WP 36484 Acceptable The results do not appear to 

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MRID CLASS- COMMENTS 

IFICATION 

(Lepomis 

macrochirus) 

a.i./L 

(1.4 mg a.i./L) 

(75% a.i.) have been corrected for a.i. 

(the reviewer converted the 

results for a.i.). 

Bluegill sunfish 

(Lepomis 

macrochirus) 

LC50 = 0.754 

mg a.i./L TGAI (98% a.i.) 150628 Acceptable None 

Catfish 

LC50 = 4.6 mg 

a.i./L TGAI (% a.i. not 

reported) 094391 Supplemental No method of statistical analysis provided. 

Goldfish 

(Carassius 

auratus auratus) 

LC50 = 5.1 mg 

a.i./L TGAI (% a.i. not 

reported) 094391 Supplemental No method of statistical analysis provided. 

Freshwater Fish (Chronic) 

Rainbow trout 

(Oncorhynchus 

mykiss) 

NOAEC = 

0.050 mg a.i./L 

LOAEC = 0.10 

mg a.i./L 

TGAI (97% a.i.) 00155967 Supplemental 

Lack of raw environmental 

data; based on clinical signs of 

intoxication (behavior); 

significant mortality, weight 

reduction and effect on larval 

swimup ≥0.20 mg a.i./L. 

Amphibian (Acute) 

Frog larvae 

(aquatic-phase) 

(Rana 

spheocephala) 

96-hr LC50 = 

8.7 mg a.i./L TGAI 150383 Supplemental 

Lack of raw data and adequate 

information describing 

materials and methods. 

ESTUARINE/MARINE FISH 

Estuarine/Marine Fish (Acute) 

No data 

FRESHWATER INVERTEBRATES 

Freshwater Invertebrates (Acute) 

Daphnid 

(Daphnia magna) 

EC50 = 0.019 

mg a.i./L TGAI 127638 Acceptable None 

Glass shrimp 

(Palaemonetes 

kadiakensis) 

96-hr LC50 = 

0.11 mg a.i./L TGAI 150383 Supplemental 

Lack of raw data and adequate 

information describing 

materials and methods. 

Crayfish 

(Procambarus 

acutus acutus) 

96-hr LC50 = 

1.3 mg a.i./L TGAI 150383 Supplemental 

Lack of raw data and adequate 

information describing 

materials and methods. 

Mayfly 

(Isonychia sp.) 

96-hr LC50 = 

0.007 mg a.i./L TGAI 150383 Supplemental 

Lack of raw data and adequate 

information describing 

materials and methods. 

Caddisfly larvae 

(Hydropsyche sp.)

96-hr LC50 = 

0.014 mg a.i./L TGAI 150383 Supplemental 

Lack of raw data and adequate 

information describing 

materials and methods. 

River horn snail 

(Oxytrema 

catenaria) 

96-hr LC50 = 

0.10 mg a.i./L TGAI 150383 Supplemental 

Lack of raw data and adequate 

information describing 

materials and methods. 

Asiatic clam 

(Corbicula 

menilensis) 

96-hr LC50 = 

8.8 mg a.i./L TGAI 150383 Supplemental 

Lack of raw data and adequate 

information describing 

materials and methods. 

Stonefly 

(Pteronarcys 

californica) 

96-hr LC50 = 

0.0055 mg 

a.i./L 

TGAI (99% a.i.) 40098001 Supplemental Insufficient study details; no 

slope could be calculated 

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-55 of 69-

TAXON ENDPOINT FORMULATION MRID 

STUDY 

CLASSIFICATION 

COMMENTS 

Freshwater Invertebrates (Chronic) 

No data 

ESTUARINE/MARINE INVERTEBRATES 

Estuarine/Marine Invertebrate (Acute) 

No data 

AQUATIC PLANTS 

Aquatic Plants (Non-Vascular) 

No data 

BIOACCUMULATION 

No data 
APPENDIX C. Chemical Names and Stuctures for Methiocarb and its Environmental Degradates 

methiocarb [3,5-dimethyl-4-)methylthio)phenol methylcarbamate] 

methiocarb phenol (MP) [3,5-dimethyl-4-(methythio)=phenol]

 R1 = -OH 

 R2 = -SCH3

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methiocarb sulfoxide (MSO) [3,5-dimethyl-4-(methylsul=phenyl)phenyl methylcarbamate] 

 O 

 "  R1 = -O-C-NH-CH3 O  ‘'  R2 = -SCH3methiocarb sulfoxide phenol (MSOP) [3,5-dimethyl-4-(methylsul=phinyl)phenol] R1 = -OH  O  ‘'  R2 = -SCH3

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methiocarb sulfone (MSO2) [3,5-dimethyl-4-(methylsul=phonyl)phenyl methylcarbamate]

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 O 

 "  R1 = -O-C-NH-CH3

 O  ‘'  R2 = -SCH3  “  O methiocarb sulfone phenol (MSO2P) [3,5-dimethyl-4-(methylsul=phonyl)phenol]

 R1 = -OH 

 O  ‘'  R2 = -SCH3  “  O 
APPENDIX D: Data Call-In Tables. 

The Environmental Fate and Effects Division (EFED) has completed a Data Call-In (DCI) table 

for the methiocarb environmental fate and effects data gaps identified in Registration Review. 

The attached DCI tables, which include the guideline number and study title for required data, 

also provide a rationale for requiring the data, an explanation of how the data will be used, and a 

brief description of how the data could impact the Agency’s future decision-making. 

Environmental Fate Data:

Guideline Number: 835.4100 

Study Title: Aerobic Soil Metabolism 

Compound: Methiocarb 

Rationale for Requiring the Data 

Acceptable data on the aerobic soil metabolism of methiocarb are required under 40 CFR Part 158, 

Subpart N (revised July 1, 2009) for labeling that includes terrestrial and/or residential outdoor 

uses. The Agency has a limited understanding of the environmental fate of methiocarb in the 

environment. Aerobic soil metabolism data for at least three additional soils, representative of 

intended use areas, must be submitted to the Agency. 

Practical Utility of the Data 

How will the data be used? 

Currently there are limited aerobic soil metabolism data that provide information on the fate of 

methiocarb and its degradates in soil. The submitted data will be used to help characterize and 

quantify the environmental fate of methiocarb and its degradates in the environment. For 

quantitative exposure estimation, these data will be used in modeling estimated environmental 

concentrations (EECs) of methiocarb for the aquatic exposure assessment. 

How could the data change the Agency’s decision or impact the Agency’s future decisionmaking? 

In the absence of the requested data, a single study will be used to represent microbial metabolism 

in all soils. This assumption will contribute to uncertainty in the risk assessment. 

Guideline Number: 835.4300 

Study Title: Aerobic Aquatic Metabolism 

Active Ingredient: Methiocarb 

Rationale for Requiring the Data 

Acceptable data on the aerobic aquatic metabolism of methiocarb are required under 40 CFR Part 

158, Subpart N (revised July 1, 2009) for labeling that includes terrestrial uses. Because the 

current labels do not specifically exclude use on field-grown ornamentals, data requirements for 

terrestrial uses apply. The Agency has a limited understanding of the environmental fate of 

methiocarb in the environment. Data on the aerobic aquatic metabolism of methiocarb have not 

been submitted to the Agency. 

Practical Utility of the Data 

How will the data be used? 

The Agency has a limited understanding of the fate of methiocarb and its degradates in aquatic 

environments. The submitted data will be used to characterize and quantify the environmental 

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fate of methiocarb and its degradates in aquatic environments. For quantitative exposure 

estimation, these data are used to model estimated environmental concentrations (EECs) of 

methiocarb for the aquatic exposure assessment. 

How could the data change the Agency’s decision or impact the Agency’s future decisionmaking? 

In the absence of the requested data and consistent with EFED model input parameter guidance, 

the aerobic aquatic metabolism half-life used to model EECs for methiocarb will be 

conservatively assumed to be equal to two times the modeling input value for the aerobic soil 

metabolism half-life, which will be based on total toxic residues rather than on parent alone. 

Implicit in this assumption is that all of the aerobic soil degradates are assumed to also be present 

in aquatic environments. This may not be the case. This assumption could overestimate risk in 

aquatic environments. 

Guideline Number: 835.4400 

Study Title: Anaerobic Aquatic Metabolism 

Active Ingredient: Methiocarb 

Rationale for Requiring the Data 

Acceptable data on the anaerobic aquatic metabolism of methiocarb are required under 40 CFR 

Part 158, Subpart N (revised July 1, 2009) for labeling that includes terrestrial uses. Because the 

current labels do not specifically exclude use on field-grown ornamentals, data requirements for 

terrestrial uses apply. The Agency has a limited understanding of the environmental fate of 

methiocarb in the environment. Data on the anaerobic aquatic metabolism of methiocarb have 

not been submitted to the Agency. 

Practical Utility of the Data 

How will the data be used? 

The Agency has a limited understanding of the fate of methiocarb and its degradates in aquatic 

environments. The submitted data will be used to characterize and quantify the environmental 

fate of methiocarb and its degradates in aquatic environments. For quantitative exposure 

estimation, these data will be used to model estimated environmental concentrations (EECs) of 

methiocarb for the aquatic exposure assessment instead of using a default value to represent the 

anaerobic aquatic metabolism half-life of the compound. 

How could the data change the Agency’s decision or impact the Agency’s future decisionmaking? 

In the absence of the requested data and consistent with EFED model input parameter guidance, 

the anaerobic aquatic metabolism half-life used to model EECs for methiocarb will be 

conservatively assumed to be equal to two times the modeling input value for the anaerobic soil 

metabolism half-life, which will be based on total toxic residues rather than on parent alone. 

Implicit in this assumption is that all of the anaerobic soil degradates are assumed to also be 

present in aquatic environments. This may not be the case. This assumption could overestimate 

risk in aquatic environments. 

Guideline Number: 835.1230 and 835.1240 

Study Title: Leaching and adsorption/desorption 

Compound: Methiocarb 

Rationale for Requiring the Data 

Acceptable data on the leaching and adsorption/desorption of methiocarb are required under 40 

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CFR Part 158, Subpart N (revised July 1, 2009) for labeling that includes terrestrial and/or 

residential outdoor uses. The Agency has a limited understanding of the environmental fate of 

methiocarb, particularly with respect to potential leaching. Acceptable adsorption/desorption data 

have not been submitted to the Agency. 

Practical Utility of the Data 

How will the data be used? 

Currently there are no acceptable leaching and adsorption/desorption studies that provide 

information on the potential leaching behavior of methiocarb in soil. The submitted data will be 

used to help characterize and the environmental fate of methiocarb in the environment. For 

quantitative exposure estimation, these data will be used in modeling estimated environmental 

concentrations (EECs) of methiocarb for the aquatic exposure assessment. Adsorption/ desorption 

data using the batch equilibrium method are preferred. If the compound is not stable during a batch 

equilibrium study, then soil column leaching methods (aged and unaged) may be more appropriate. 

How could the data change the Agency’s decision or impact the Agency’s future decisionmaking? 

In the absence of the requested data, the potential leaching behavior of methiocarb will be 

unknown, and will contribute to the uncertainty in the risk assessment. The potential for leaching 

to groundwater will not be able to be precluded in the assessment.

Guideline Number: 835.1230 and 835.1240 

Study Title: Leaching and adsorption/desorption 

Compound: Methiocarb phenol (MP) 

Rationale for Requiring the Data 

Acceptable data on the leaching and adsorption/desorption of methiocarb phenol (MP), a degradate 

of methiocarb, are required under 40 CFR Part 158, Subpart N (revised July 1, 2009) for labeling 

that includes terrestrial and/or residential outdoor uses. The Agency has a limited understanding of 

the environmental fate of MP, particularly with respect to potential leaching. Acceptable 

adsorption/desorption data have not been submitted to the Agency. 

Practical Utility of the Data 

How will the data be used? 

Currently there are no acceptable leaching and adsorption/desorption studies that provide 

information on the potential leaching behavior of MP in soil. The submitted data will be used to 

help characterize and the environmental fate of MP in the environment. For quantitative exposure 

estimation, these data will be used in modeling estimated environmental concentrations (EECs) of 

MP for the aquatic exposure assessment. Adsorption/ desorption data using the batch equilibrium 

method are preferred. If the compound is not stable during a batch equilibrium study, then soil 

column leaching methods (aged and unaged) may be more appropriate. 

How could the data change the Agency’s decision or impact the Agency’s future decisionmaking? 

In the absence of the requested data, the potential leaching behavior of MP will be an unknown, 

and will contribute to uncertainty in the risk assessment. The potential for leaching to groundwater 

will not be able to be precluded in the assessment.

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Guideline Number: 835.1230 and 835.1240 

Study Title: Leaching and adsorption/desorption 

Compound: Methiocarb sulfoxide (MSO) 

Rationale for Requiring the Data 

Acceptable data on the leaching and adsorption/desorption of methiocarb sulfoxide (MSO), a 

degradate of methiocarb, are required under 40 CFR Part 158, Subpart N (revised July 1, 2009) for 

labeling that includes terrestrial and/or residential outdoor uses. The Agency has a limited 

understanding of the environmental fate of MSO, particularly with respect to potential leaching. 

Acceptable adsorption/desorption data have not been submitted to the Agency. 

Practical Utility of the Data 

How will the data be used? 

Currently there are no acceptable leaching and adsorption/desorption studies that provide 

information on the potential leaching behavior of MSO in soil. The submitted data will be used to 

help characterize and the environmental fate of MSO in the environment. For quantitative 

exposure estimation, these data will be used in modeling estimated environmental concentrations 

(EECs) of MSO for the aquatic exposure assessment. Adsorption/ desorption data using the batch 

equilibrium method are preferred. If the compound is not stable during a batch equilibrium study, 

then soil column leaching methods (aged and unaged) may be more appropriate. 

How could the data change the Agency’s decision or impact the Agency’s future decisionmaking? 

In the absence of the requested data, the potential leaching behavior of MSO will be an unknown, 

and will contribute to uncertainty in the risk assessment. The potential for leaching to groundwater 

will not be able to be precluded in the assessment. 

Guideline Number: 835.1230 and 835.1240 

Study Title: Leaching and adsorption/desorption 

Compound: Methiocarb sulfoxide phenol (MSOP) 

Rationale for Requiring the Data 

Acceptable data on the leaching and adsorption/desorption of methiocarb sulfoxide phenol 

(MSOP), a degradate of methiocarb, are required under 40 CFR Part 158, Subpart N (revised July 

1, 2009) for labeling that includes terrestrial and/or residential outdoor uses. The Agency has a 

limited understanding of the environmental fate of MSOP, particularly with respect to potential 

leaching. Acceptable adsorption/desorption data have not been submitted to the Agency. 

Practical Utility of the Data 

How will the data be used? 

Currently there are no acceptable leaching and adsorption/desorption studies that provide 

information on the potential leaching behavior of MSOP in soil. The submitted data will be used to 

help characterize and the environmental fate of MSOP in the environment. For quantitative 

exposure estimation, these data will be used in modeling estimated environmental concentrations 

(EECs) of MSOP for the aquatic exposure assessment. Adsorption/ desorption data using the batch 

equilibrium method are preferred. If the compound is not stable during a batch equilibrium study, 

then soil column leaching methods (aged and unaged) may be more appropriate. 

How could the data change the Agency’s decision or impact the Agency’s future decisionmaking? 

In the absence of the requested data, the potential leaching behavior of MSOP will be an unknown, 

and will contribute to uncertainty in the risk assessment. The potential for leaching to groundwater 

will not be able to be precluded in the assessment.

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Guideline Number: 835.6100 

Study Title: Analytical Method (and Associated Independent Laboratory Validations) in Soil 

Compound: Methiocarb 

Rationale for Requiring the Data 

Acceptable data on the analytical method in soil (and the associated independent laboratory 

validations) of methiocarb are required under 40 CFR Part 158, Subpart N (revised July 1, 2009). 

Independently validated analytical methods for residues in soil, water, sediment, and plant material 

(environmental chemistry methods) submitted by the registrant are used to evaluate analyses 

described in submitted environmental fate and ecological effects studies. Submitted analytical 

methods are also used by various Federal, State, Tribal, and local agencies to detect and monitor 

residues that are or are suspected to be in environmental compartments due to outdoor uses and 

accidental releases. Independent laboratory validations for submitted analytical methods are 

necessary to confirm that the methods are functional and to confirm the levels of detection and 

quantitation reported in registrant-prepared validations. 

Use of methiocarb may impact surface water quality due to runoff of rainwater and drift of 

residues. This is especially true for poorly draining soils, erodible soils, and soils with shallow 

ground water. Therefore, outside agencies may request analytical methods with which to monitor 

for methiocarb residues in water and in soil. 

Practical Utility of the Data 

How will the data be used? 

In the absence of independently validated environmental chemistry methods, submitted 

environmental fate and ecological effects data may not be reviewable and entities outside the 

Agency may lack chemical-specific methods for analyses in environmental compartments. 

Independently validated environmental chemistry methods will be used to evaluate newly 

submitted environmental fate and ecological effects data and will be made available for 

enforcement and monitoring purposes at the federal, state, and local levels. 

How could the data change the Agency’s decision or impact the Agency’s future decisionmaking? 

Risk assessment conclusions could be altered if they are not supported by either study data or 

environmental monitoring detections that are based on independently validated environmental 

chemistry methods. Furthermore, while not directly related to Agency decision-making, 

independently validated environmental chemistry methods are necessary to ensure the safety of 

those in proximity to releases of methiocarb residues in the environment.

Guideline Number: 835.6200 

Study Title: Analytical Method in Water 

Compound: Methiocarb 

Rationale for Requiring the Data 

Acceptable data on the analytical method in soil (and the associated independent laboratory 

validations) of methiocarb are required under 40 CFR Part 158, Subpart N (revised July 1, 2009). 

Independently validated analytical methods for residues in soil, water, sediment, and plant material 

(environmental chemistry methods) submitted by the registrant are used to evaluate analyses 

described in submitted environmental fate and ecological effects studies. Submitted analytical 

methods are also used by various Federal, State, Tribal, and local agencies to detect and monitor 

residues that are or are suspected to be in environmental compartments due to outdoor uses and 

accidental releases. Independent laboratory validations for submitted analytical methods are 

necessary to confirm that the methods are functional and to confirm the levels of detection and 

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quantitation reported in registrant-prepared validations. 

Use of methiocarb may impact surface water quality due to runoff of rainwater and drift of 

residues. This is especially true for poorly draining soils, erodible soils, and soils with shallow 

ground water. Therefore, outside agencies may request analytical methods with which to monitor 

for methiocarb residues in water and in soil. 

Practical Utility of the Data 

How will the data be used? 

In the absence of independently validated environmental chemistry methods, submitted 

environmental fate and ecological effects data may not be reviewable and entities outside the 

Agency may lack chemical-specific methods for analyses in environmental compartments. 

Independently validated environmental chemistry methods will be used to evaluate newly 

submitted environmental fate and ecological effects data and will be made available for 

enforcement and monitoring purposes at the federal, state, and local levels. 

How could the data change the Agency’s decision or impact the Agency’s future decisionmaking? 

Risk assessment conclusions could be altered if they are not supported by either study data or 

environmental monitoring detections that are based on independently validated environmental 

chemistry methods. Furthermore, while not directly related to Agency decision-making, 

independently validated environmental chemistry methods are necessary to ensure the safety of 

those in proximity to releases of methiocarb residues in the environment. 

Guideline Numbers: 850.1730 

Study Title: Fish Bioconcentration Study 

Rationale for Requiring the Data 

Bioconcentration data are not available for methiocarb and fish. A fish bioconcentration study is required 

under 40 CFR Part 158 when the octanol/water partition coefficient of the chemical is >1,000; there are 

potential exposures to fish and other non-target aquatic animals; and the hydrolysis half-life is >5 days at 

pH 5, 7, and/or 9. All of these criteria are met with methiocarb. Therefore, since these data are not 

currently available, EFED recommends requesting these data at this time. In the absence of such data, it 

will be assumed that methiocarb bioconcentrates in food, and, therefore, risks to both listed and nonlisted aquatic species (and those that eat aquatic species) will be presumed in the risk assessment 

conducted for Registration Review. 

Practical Utility of the Data 

How will the data be used? 

Fish bioconcentration data will be used to refine the screening-level assessment by determining whether 

there are potential risks to animals inhabiting aquatic environments and those that eat aquatic animals 

from the use of methiocarb. If bioconcentration data are not submitted for fish, risk will be presumed for 

animals in aquatic environments and those that eat aquatic animals potentially exposed to methiocarb. 

How could the data impact the Agency’s future decision-making? 

If future endangered species risk assessments are performed without these data, the Agency would have 

to presume that methiocarb “may affect” listed aquatic animal species directly (and listed species from 

other taxa indirectly), and use of methiocarb and its formulated products may need to be restricted in 

areas where listed species could be exposed. The lack of these data will limit the flexibility the Agency 

and registrants have in coming into compliance with the Endangered Species Act and could result in use 

restrictions for methiocarb use that are unnecessarily severe. 

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Ecological Effects Data:

Guideline Number: 850.2300 

Study Title: Avian Reproduction Test (Bobwhite Quail) 

Rationale for Requiring the Data 

Under the 40 CFR Part 158 (July 1, 2009) avian reproduction data are required on waterfowl and upland 

game species (OPPTS 850.2300). Currently acceptable data for methiocarb are only available for 

waterfowl. The chronic toxicity data available for birds indicate that bobwhite quail (NOAEC <2 mg 

a.i./kg-diet based on reduced survival of 14-day old birds and reduced eggshell thickness) (MRID 

128119) are more sensitive to methiocarb than mallard duck (NOAEC = 100 mg a.i./kg-diet, the highest 

concentration tested) (MRID 128120). Since a definitive NOAEC for bobwhite quails is not available 

(the lowest dose tested resulted in effects), the specific risk to birds from chronic exposure to methiocarb 

is unknown. Therefore, in order to complete the risk assessment, additional data are needed. In the 

absence of such data, risks to both listed and non-listed bird species will be presumed in the risk 

assessment conducted for Registration Review. 

Practical Utility of the Data 

How will the data be used? 

Reproduction data for bobwhite quail will be used to reduce uncertainties associated with using a nondefinitive endpoint for assessing chronic risks to birds from methiocarb exposure. If reproduction data 

are not submitted for bobwhite quail, risks to birds from chronic exposure will be presumed. 

How could the data impact the Agency’s future decision-making? 

If future endangered species risk assessments are performed without these data, the Agency would have 

to assume that methiocarb “may affect” listed birds directly (and listed species from other taxa 

indirectly), and use of methiocarb and its formulated products may need to be restricted in areas where 

listed species could be exposed. The lack of these data will limit the flexibility the Agency and registrants 

have in coming into compliance with the Endangered Species Act and could result in use restrictions for 

methiocarb use that are unnecessarily severe. 

Guideline Number: 850.3030 

Study Title: Honey Bee Toxicity of Residues on Foliage

Rationale for Requiring the Data 

Under the 40 CFR Part 158 (July 1, 2009) data on honey bee toxicity of residues on foliage are required 

(OPPTS 850.3030) when the acute honey bee contact LD50 <11 μg/bee and the use pattern(s) indicate(s) 

that honey bees may be exposed to the pesticide. The acute contact LD50 for methiocarb is 0.375 μg 

a.i./bee (MRID 00036935). Furthermore, the use of foliar methiocarb on ornamentals (some of which 

may be flowering) represents a route of potential exposure to honey bees. Therefore, in order to 

complete the risk assessment, additional data are needed. In the absence of such data, risks to honey bees 

will be presumed in the risk assessment conducted for Registration Review. 

Practical Utility of the Data 

How will the data be used? 

Honey bee toxicity of residues on foliage data will be used to reduce uncertainties associated with 

assessing risks to honey bees from methiocarb exposure. In the absence of such data, risks to honey bees 

will be presumed in the risk assessment conducted for Registration Review. 

How could the data impact the Agency’s future decision-making? 

If future endangered species risk assessments are performed without these data, the Agency would have 

to presume that methiocarb “may affect” listed terrestrial invertebrates directly (and listed species from 

other taxa indirectly), and use of methiocarb and its formulated products may need to be restricted in 

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areas where listed species could be exposed. The lack of these data will limit the flexibility the Agency 

and registrants have in coming into compliance with the Endangered Species Act and could result in use 

restrictions for methiocarb use that are unnecessarily severe. 

Guideline Numbers: 850.1075, 850.1025, and 850.1035, 850.1045, or 850.1055 

Study Title: Estuarine/Marine Fish and Invertebrate Acute Toxicity Tests 

Rationale for Requiring the Data 

Acute toxicity data for methiocarb are not available for estuarine/marine fish or invertebrates. Acute 

toxicity data on a saltwater fish (850.1075), saltwater mollusk (850.1025), and a saltwater invertebrate 

(850.1035, 850.1045, or 850.1055) are required under 40 CFR Part 158. Since these data are not 

currently available, EFED recommends requesting these data at this time. In the absence of such data, 

risks to both listed and non-listed estuarine/marine species will be presumed in the risk assessment 

conducted for Registration Review. 

Practical Utility of the Data 

How will the data be used? 

Acute toxicity data for estuarine/marine species will be used to refine the screening-level assessment by 

determining whether there are potential risks to animals inhabiting estuarine/marine environments from 

the use of methiocarb. If acute toxicity data are not submitted for estuarine/marine fish and invertebrates, 

risk will be presumed for animals in estuarine/marine environments potentially exposed to methiocarb. 

How could the data impact the Agency’s future decision-making? 

If future endangered species risk assessments are performed without these data, the Agency would have 

to presume that methiocarb “may affect” listed estuarine/marine fish and invertebrate species directly 

(and listed species from other taxa indirectly), and use of methiocarb and its formulated products may 

need to be restricted in areas where listed species could be exposed. The lack of these data will limit the 

flexibility the Agency and registrants have in coming into compliance with the Endangered Species Act 

and could result in use restrictions for methiocarb use that are unnecessarily severe. 

Guideline Number: 850.1300 and 850.1350 

Study Title: Invertebrate Life Cycle Toxicity Test (Freshwater and Estuarine/Marine) 

Rationale for Requiring the Data 

Acceptable chronic toxicity data for methiocarb are not available for freshwater invertebrates (850.1300) 

or estuarine/marine invertebrates (850.1350). Since the LC50 values for the most sensitive invertebrate 

species tested is < 1 mg/L, estuarine/marine and freshwater invertebrate life cycle studies are required 

under the new 40 CFR Part 158. Therefore, an estuarine/marine invertebrate life cycle toxicity test 

(OPPTS Guideline 850.1350) and a freshwater invertebrate life cycle toxicity test (OPPTS Guideline 

850.1300) are required. In the absence of chronic methiocarb toxicity data for aquatic invertebrates, the 

Agency will presume risks to aquatic invertebrates from the use of methiocarb. 

Practical Utility of the Data 

How will the data be used? 

Chronic toxicity data for estuarine/marine and freshwater invertebrate species will be used to refine the 

screening-level assessment by determining whether there are potential risks to invertebrates inhabiting 

estuarine/marine and/or freshwater environments from the use of methiocarb. If chronic toxicity data are 

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not submitted for estuarine/marine and freshwater invertebrates, risk will be presumed for all aquatic 

invertebrates potentially exposed to methiocarb. 

How could the data impact the Agency’s future decision-making? 

If future endangered species risk assessments are performed without these data, the Agency would have 

to presume that methiocarb “may affect” listed aquatic invertebrate species directly (and listed species 

from other taxa indirectly), and use of methiocarb and its formulated products may need to be restricted 

in areas where listed species could be exposed. The lack of these data will limit the flexibility the 

Agency and registrants have in coming into compliance with the Endangered Species Act and could 

result in use restrictions for methiocarb use that are unnecessarily severe. 

Guideline Number: 850.1400 

Study Title: Fish Early Life Stage Toxicity Test (Freshwater and Estuarine/Marine) 

Rationale for Requiring the Data 

Acceptable chronic toxicity data for methiocarb are not available for estuarine/marine fish (850.1400) or 

the most acutely sensitive freshwater fish (i.e., bluegill sunfish)(850.1400). A supplemental study is 

available for freshwater fish, but not for the most acutely sensitive species (i.e., bluegill sunfish). Since 

the LC50 values for the most sensitive fish species tested is < 1 mg/L, estuarine/marine and freshwater 

fish early life stage studies are required under the new 40 CFR Part 158. Therefore, a fish early life stage 

toxicity test (OPPTS Guideline 850.1400) is required for both freshwater and estuarine/marine fish. In 

the absence of chronic methiocarb toxicity data for fish, an acute-to-chronic ratio (ACR) using rainbow 

trout data will be used to extrapolate a chronic endpoint for bluegill sunfish and estuarine/marine fish. 

Practical Utility of the Data 

How will the data be used? 

Chronic toxicity data for estuarine/marine and freshwater fish species will be used to refine the 

screening-level assessment by determining whether there are potential risks to fish inhabiting 

estuarine/marine and/or freshwater environments from the use of methiocarb. If chronic toxicity data are 

not submitted for estuarine/marine or freshwater fish, risk will be presumed for all fish potentially 

exposed to methiocarb. 

How could the data impact the Agency’s future decision-making? 

If future endangered species risk assessments are performed without these data, the Agency would have 

to presume that methiocarb “may affect” listed fish species directly (and listed species from other taxa 

indirectly), and use of methiocarb and its formulated products may need to be restricted in areas where 

listed species could be exposed. The lack of these data will limit the flexibility the Agency and 

registrants have in coming into compliance with the Endangered Species Act and could result in use 

restrictions for methiocarb use that are unnecessarily severe. 

Guideline Numbers: 850.4100 and 850.4150 

Study Title: Terrestrial Plant Toxicity Tests (Tier I) 

Rationale for Requiring the Data 

Terrestrial plant toxicity studies [both seedling emergence (850.4100) and vegetative vigor (850.4150)] 

and associated risk analysis of plants are required for registration of pesticides with outdoor uses (CFR 

Part 158). Tier I seedling emergence and vegetative vigor studies (OPPTS Guidelines 850.4100 and 

850.4150) are, therefore, required. In the absence of such data, risks to terrestrial plants from the use of 

methiocarb will be presumed in the risk assessment. Tier II studies (850.4225 and 850.4250) may be 

required depending on the results of the Tier I plant studies. 

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Practical Utility of the Data 

How will the data be used? 

Tier I vegetative vigor and seedling emergence data for terrestrial plants will be used to determine the 

potential for methiocarb to affect non-target plant species in the terrestrial environment. In the absence 

of data specific for these plants, risk to terrestrial plants will be presumed. 

How could the data impact the Agency’s future decision-making? 

If future endangered species risk assessments are performed without these data, the Agency would have 

to presume risk to non-target terrestrial plants from use of methiocarb. Therefore, use of methiocarb and 

its formulated products may need to be restricted in areas where listed species could be exposed. The 

lack of these data will limit the flexibility the Agency and registrants have in coming into compliance 

with the Endangered Species Act and could result in use restrictions for methiocarb that are unnecessarily 

severe. 

Guideline Number: 850.4400 

Aquatic Plant Growth Tier I Study (Vascular Aquatic Plant) 

Rationale for Requiring the Data 

Aquatic (both vascular and non-vascular species) toxicity studies and associated risk analysis of plants are 

required for registration of pesticides with outdoor uses (CFR Part 158). There are currently no data 

available to determine the levels of methiocarb that could result in effects to aquatic vascular plants. 

Therefore, effects on non-target aquatic plants cannot be discounted, and the level of risk is unknown. 

Therefore, an aquatic vascular plant study is required as specified in 40 CFR Part 158 (OPPTS Guideline 

850.4400). 

Practical Utility of the Data 

How will the data be used? 

Data from Tier I aquatic plant toxicity studies will be used to estimate potential risks to aquatic plants 

associated with uses of methiocarb. The data will reduce uncertainties associated with the current risk 

assessment for plants and will improve our understanding of the potential effects of methiocarb on aquatic 

plants. Because plants form the basis of most habitats and significantly contribute to overall 

environmental quality, a solid understanding of the potential risks to aquatic plants is essential for sound 

environmental management. The data will also be used in determining whether a “may affect” to 

Federally-listed threatened and endangered species is likely under the Endangered Species Act. 

Additionally, the need for labeling language to mitigate effects on non-target aquatic plant species is 

unknown. Results of this study would be used to determine if surface water exposure concentrations, due 

to run-off, are below levels of concern at the current label rates and to identify what, if any, label language 

is needed to mitigate identified risks. 

How could the data impact the Agency’s future decision-making? 

Without aquatic plant growth data for methiocarb, the Agency cannot determine the levels of methiocarb 

that result in effects to vascular aquatic plants. Until these data are available, the registration decision will 

be based on the information listed on the label. The lack of these data will limit the flexibility the Agency 

and registrants have in coming into compliance with the Endangered Species Act, and could result in use 

restrictions for methiocarb which may otherwise be avoided, or which are unnecessarily severe.

 

Guideline Number: 850.5400 

Aquatic Plant Growth Tier I Study (Non-vascular Aquatic Plant) 

Rationale for Requiring the Data 

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Aquatic (both vascular and non-vascular species) toxicity studies and associated risk analysis of plants are 

required for registration of pesticides with outdoor uses (40 CFR Part 158). There are currently no data 

available to determine the levels of methiocarb that could result in effects to aquatic non-vascular plants. 

Therefore, effects on non-target aquatic plants cannot be discounted, and the level of risk is unknown. 

Therefore, an aquatic non-vascular plant study is required as specified in 40 CFR Part 158 (OPPTS 

Guideline 850.5400). 

Practical Utility of the Data 

How will the data be used? 

Data from Tier I aquatic plant toxicity studies will be used to estimate potential risks to aquatic plants from 

methiocarb exposure. The data will reduce uncertainties associated with the current risk assessment for 

plants and will improve our understanding of the potential effects of methiocarb use on aquatic plants. 

Because plants form the basis of most habitats and significantly contribute to overall environmental 

quality, a solid understanding of the potential risks to aquatic plants is essential for sound environmental 

management. The data will also be used in determining whether a “may affect” to Federally-listed 

threatened and endangered species is likely under the Endangered Species Act. 

Additionally, the need for labeling language to mitigate effects on non-target aquatic plant species is 

unknown. Results of this study would be used to determine if surface water exposure concentrations, due 

to run-off, are below levels of concern at the current label rates and to identify what, if any, label language 

is needed to mitigate identified risks. 

How could the data impact the Agency’s future decision-making? 

Without aquatic plant growth data for methiocarb, the Agency cannot determine the levels of methiocarb 

that result in effects to non-vascular aquatic plants. Until these data are available, the registration decision 

will be based on the information listed on the label. The lack of these data will limit the flexibility the 

Agency and registrants have in coming into compliance with the Endangered Species Act, and could result 

in use restrictions for methiocarb which may otherwise be avoided, or which are unnecessarily severe.

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