2

Listed Plant Taxon Potential Direct Effects

Terrestrial and semi-aquatic 

plants – monocots Yes (Grasses) - All uses of clethodim; effects 16 to >997 feet from the edge of the field

Terrestrial and semi-aquatic 

plants – dicots No effects

Aquatic plants No effects

Listed Animal Taxon

Potential Direct Effects

Acute Notes Chronic Notes

Terrestrial invertebrates No effects No effects

Mammals Yes Uses with a total annual app. rate > 

2.0 lb a.i./A (only) 

Yes

(dose-basis)

Uses with total annual app. rate > 1.25 lb a.i./A 

(only); however, no reproductive effects were 

noted in the study.

Birds No effects No effects

Reptiles No effects No effects

Amphibians

(terrestrial-phase) No effects No effects

Fish1 No effects Yes All uses of clethodim

Amphibians (aquatic-phase) No effects Yes All uses of clethodim

Aquatic Invertebrates2 No effects No effects 1 Due to the lack of chronic toxicity data, freshwater fish data was used as a proxy representation to estimate effects to estuarine/marine fish 2 Due to the lack of chronic toxicity data, freshwater invertebrate data was used as a proxy representation to estimate effects to estuarine/marine invertebrates
3

Based on this preliminary assessment, there is the potential of effects to listed and non-listed 

monocot plants, specifically grasses (family Poaceae), from exposure to clethodim residues of 

concern at all application rates. There is also potential of effects to fish (surrogates for aquaticphase amphibians) from chronic exposure to clethodim residues of concern at all application 

rates. There is also the potential of effects to mammals from acute and chronic exposure to 

clethodim residues of concern for a variety of uses. Listed species of terrestrial and aquatic 

plants and animals may also be affected through indirect effects because of the potential for 

direct effects on listed and non-listed monocot plant species, specifically those species that rely 

on grasses. Potential direct effects on mammals, terrestrial monocot plants, and fish (surrogates 

for aquatic-phase amphibians) from the use of clethodim may be associated with modification of 

primary constituent elements of designated critical habitats, where such designations have been 

made. However, at this current stage of the Registration Review process, it is premature to make 

effects determinations for listed species until further refinements are conducted. In order to 

make effects determinations for individual species, useful refinements may include analyses of 

1) more detailed, species-specific ecological and biological data; 2) more detailed and accurate 

information on clethodim use patterns; and 3) sub-county level spatial proximity data for the cooccurrence of potential effects areas and listed species and any designated critical habitat. 

Examples of such refinements are described below.

EFED is currently developing tools that are expected to further refine the assessment and are 

designed to support effects determinations for individual federally listed species and their 

designated critical habitats (where applicable). Scientific information obtained from the U.S. 

Fish & Wildlife Service (USFWS), the National Marine Fisheries Service (NMFS), and other 

reliable sources is being collated by EFED to address all currently listed species. The 

information will be stored in an Office of Pesticide Programs Pesticide Registration Information 

SysteM (PRISM) knowledgebase. The listed species knowledgebase will consist of an 

information repository that houses biological and behavioral information relevant to individual 

species (e.g., habitat, diet, and life history, including specific temporal and spatial associations) 

and a document repository that contains supporting documents (e.g., USFWS recovery plans) 

and electronic information (e.g., GIS data files). For terrestrial taxa, the biological information 

relevant to risk quotient (RQ) calculations (e.g., diet and body weight) will be used to 

parameterize exposure estimates to derive species-specific RQs using a method consistent with 

currently used methods in the T-REX model. 

Refinements may also include more detailed analyses of the registered uses and their use patterns

that result in LOC exceedances for federally listed species in the screening-level assessment. 

The analyses may include more information on where, when, and how clethodim is used on 

crops including: fallow land, golf course turf, non-cropped areas, alfalfa, ornamentals, 

landscaped areas, non-bearing food crops, around buildings, bare soil, mulched areas, grass 

forage/fodder/hay, clover, herbs, turnip greens, mustard, vegetables, radishes, mint, sod farms,

beets, brassica vegetables, carrots, cranberries, cucurbit vegetables, fruiting vegetables, leafy 

vegetables, strawberries, dried beans, Christmas trees, cotton, forest trees, peanuts, potatoes, root 

and tuber vegetables, sainfoin, soybeans, sugar beets, sunflowers, sweet potatoes, tomatoes, 

trefoil, yams, lentils, garlic, onions, tree fruits, tree nuts, asparagus, hops, safflower, sesame, 

sage, shallots, artichokes, bushberries including cranberries, caneberries, peaches, flax, 

meadowfoam, seeds, kenaf, canola, wildlife food plots, succulent beans, legume vegetables, 
4

dried and succulent peas, and corn (field). Actual usage data (when available) and national landcover datasets that indicate potential use sites (e.g., national land cover dataset (NLCD), crop 

data layer (CDL)) may be used to support a more refined analysis of where clethodim is 

reasonably expected to be used. Similarly, refinements for the timing of applications and how 

clethodim is used may be based on the analysis of additional usage data, beyond what were 

available at the time of the screening-level assessment, and a more in-depth exploration of 

agronomic practices. 

A committee of the National Research Council (NRC) has provided advice on ecological risk 

assessment tools and scientific approaches under ESA and FIFRA (Project Identification 

Number DELS-BEST-11-01). Specific recommendations relate to the use of “best available 

data;” methods for evaluating sublethal, indirect, and cumulative effects; the state of the science 

regarding assessment of mixtures and pesticide inert ingredients; the development, application, 

and interpretation of results from predictive models; uncertainty factors; and what constitutes 

authoritative geospatial and temporal information for the assessment of individual species,

habitat effects and probabilistic risk assessment methods. The EPA, NOAA, FWS and USDA 

are currently working to develop a plan on how to address these recommendations.

The refinements based on individual species data; additional, detailed usage information, when 

available; and further recommendations from the NRC report are expected to help to more 

accurately identify potential areas of effect and to better inform effects and habitat 

determinations for listed species and any designated critical habitats. For example, if clethodim

is used when a particular species of concern is not present (e.g., it is migratory) or is not colocated in space, then risk of potential direct effects to the species may often be precluded. If 

LOCs are still exceeded for fish (surrogate for aquatic-phase amphibians), mammals, and 

terrestrial monocot plants after conducting the refined analyses, further analyses of the potential 

spatial and temporal co-occurrence of listed species of concern (and any designated critical 

habitat) may be conducted. The extent of possible refinement in the analyses of spatial/temporal 

co-occurrence will largely depend on the scale and quality of the available sub-county level use 

site (e.g., National Land Cover Dataset, Cropland Data Layer) and species location data.

Mitigations: If registrant-proposed annual application rate limits of 0.5-1.0 lb a.i./A are provided 

on the labels, it may reduce exposure in the environment. For example, when RQ values were 

estimated based on conservative assumptions, (i.e., 7-day interval), there were no RQ values that 

exceeded the LOC (acute or chronic) when the annual application rate was 1.0 lb a.i./A. 

Therefore, this reduction would reduce the potential for effects to listed and non-listed mammals 

based on acute and/or chronic exposure of clethodim. 

Regardless of any changes to the proposed application rates there would not be a reduction in the 

potential for effects to fish (surrogate for aquatic-phase amphibians) on a chronic exposure basis 

or effects to terrestrial monocot plant species, especially grass species sufficient to bring RQs to 

below concern levels. For fish, the only available chronic fish toxicity study did not measure the 

typical sublethal (growth or reproduction) endpoints for fish. The only endpoint that was 

measured was survival; and therefore, the NOAEC could potentially be an underestimation of 

risk to fish, and actual endpoint could potentially be even lower. Effects to terrestrial monocot 

plant species, especially grass species would still be of concern at great distances from the edge 
5

of the field (16 to >997 feet from the edge of the field). However, the distance from the edge of 

the field where effects to listed monocot plants could be decreased with increased spray droplet 

size (medium-coarse to coarse-very coarse) and a decreased boom height (high to low) for aerial 

and ground applications, respectively (e.g., aerial app. rate 0.125 lb a.i./A, medium-coarse to 

coarse-very coarse, distance decreased from >997feet to 955 feet; ground app. rate 0.25 lb a.i./A,

high to low boom hight, distance decreased from 525 feet to 367 feet). 
6

Ecological Risk Assessment for the Registration Review of 

Clethodim

S OH

O

N

O Cl

(5RS)-2-{(1EZ)-1-[(2E)-3-chloroallyloxyimino]propyl}-5-[(2RS)-2-(ethylthio)propyl]-3-

hydroxycyclohex-2-en-1-one

CAS No.: 99129-21-2

PC Code: 121011

Prepared by:

Christina Wendel, Biologist

Greg Orrick, Environmental Scientist

Reviewed by:

R. David Jones, Ph.D., Senior Agronomist

Kristina Garber, M.S. Senior Biologist

Jean Holmes, DVM, MPH, Risk Assessment Process Leader

Approved by:

Brian Anderson, MEM, Branch Chief

Environmental Risk Branch II

Environmental Fate and Effects Division

Office of Pesticide Programs

U.S. Environmental Protection Agency

1200 Pennsylvania Avenue, NW

Washington, D.C. 20460

January 13, 2014
7

Table of Contents

1. EXECUTIVE SUMMARY .................................................................................... 9

1.1. Purpose of Assessment ........................................................................................... 9

1.2. Risk Conclusions .................................................................................................... 9

1.3. Environmental Fate Summary ................................................................................ 9

1.4. Effects Summary..................................................................................................... 9

1.5. Main Uncertainties................................................................................................ 10

2. PROBLEM FORMULATION.............................................................................. 11

2.1. Nature of the Stressor............................................................................................ 11

2.2. Usage Update ........................................................................................................ 12

3. ANALYSIS........................................................................................................... 14

3.1. Use Characterization............................................................................................. 14

3.2. Environmental Fate Characterization ................................................................... 16

3.3. Exposure Characterization.................................................................................... 24

3.3.1. Aquatic Exposure.................................................................................................. 24

3.3.1.1. Bioaccumulation ....................................................................................... 27

3.3.1.2. Monitoring Data........................................................................................ 27

3.3.2. Terrestrial Exposure.............................................................................................. 27

3.3.2.1. Dietary Modeling...................................................................................... 27

3.3.2.2. Inhalation Modeling.................................................................................. 33

3.3.2.3. Drinking Water Modeling......................................................................... 33

3.3.2.4. Plants Modeling ........................................................................................ 33

3.4. Ecological Effects Characterization...................................................................... 34

3.4.1. Aquatic Animals ................................................................................................... 35

3.4.1.1. Fish............................................................................................................ 36

3.4.1.2. Aquatic Invertebrates................................................................................ 37

3.4.2. Aquatic Plants....................................................................................................... 38

3.4.2.1. Non-Vascular Plants ................................................................................. 38

3.4.2.2. Vascular Plants.......................................................................................... 39

3.4.3. Terrestrial Animals ............................................................................................... 39

3.4.3.1. Birds.......................................................................................................... 40

3.4.3.2. Mammals................................................................................................... 40

3.4.3.3. Terrestrial Invertebrates............................................................................ 41

3.4.4. Terrestrial Plants................................................................................................... 41

3.4.4.1. Dicotyledon plants.................................................................................... 42

3.4.4.2. Monocotyledon plants............................................................................... 42

3.4.5. Degradate Toxicity Data ....................................................................................... 42

3.4.6. Endocrine Disruptor Screening Program.............................................................. 42

3.5. Review of Incident Data ....................................................................................... 43

4. RISK ESTIMATION............................................................................................ 44

4.1. Non-target Aquatic Organisms............................................................................. 44

4.2. Non-target Terrestrial Organisms......................................................................... 45

4.2.1. Terrestrial Animals ............................................................................................... 45

4.2.2. Birds...................................................................................................................... 46

4.2.3. Mammals............................................................................................................... 46
8

4.3. Terrestrial Invertebrates........................................................................................ 50

4.4. Non-target Terrestrial and Semi-aquatic Plants.................................................... 50

5. RISK DESCRIPTION .......................................................................................... 51

5.1. Risks to Aquatic Organisms.................................................................................. 51

5.1.1. Fish (surrogates for aquatic-phase amphibians) ................................................... 51

5.1.2. Aquatic Invertebrates............................................................................................ 53

5.1.3. Aquatic Plants....................................................................................................... 53

5.2. Risks to Terrestrial Organisms.............................................................................. 53

5.2.1. Terrestrial Animals ............................................................................................... 53

5.2.2. Terrestrial Plants................................................................................................... 60

5.3. Probit Slope Response Analysis of LOC Values and Acute RQ Values.............. 62

5.4. Re-evaluation of the Risk Hypothesis................................................................... 64

6. REFERENCES ..................................................................................................... 64

6.1. Ecotoxicity Studies ............................................................................................... 65

6.2. Environmental Fate and Product Chemistry Studies............................................ 69

APPENDIX A. Aquatic Model Input/Output Files ..................................................................... 71

APPENDIX B. Sample T-REX, and TerrPlant Inputs/Outputs for Clethodim........................... 72

APPENDIX C. Summary of Toxicity Endpoints and Study Classifications for Clethodim ....... 76

APPENDIX D. Clethodim Incidents ........................................................................................... 82

APPENDIX E. STIR and SIP Inputs and Outputs....................................................................... 85

APPENDIX F. Summary of AgDrift Terrestrial Outputs for Clethodim.................................... 87

APPENDIX G. ECOTOX Summary Tables and Accepted Papers........................................... 103

APPENDIX H. ECOTOX Open Literature That Passed Initial Screen..................................... 114
9

1. EXECUTIVE SUMMARY

1.1. Purpose of Assessment

The purpose of this assessment is to evaluate the potential risks of clethodim’s registered uses on 

non-target organisms, including federally listed endangered and threatened (listed) species. This 

risk assessment incorporates the available exposure and effects data, and most current modeling 

and risk methodologies, some of which were not available at the time previous clethodim risk

assessments were conducted. This assessment is based on the problem formulation document for 

registration review (USEPA, 2008). The problem formulation is cited for information that 

remains current, while information that is new or updated is presented in this assessment.

1.2. Risk Conclusions

There is the potential for chronic direct effects to fish for all uses of clethodim. There are 

potential effects to listed and non-listed monocot plants, specifically grass species (family 

Poaceae), for all uses of clethodim. There is the potential for acute and chronic direct effects to 

mammals for uses of clethodim with a total annual application rate greater than 2.0 lb a.i./A, and 

1.25 lb a.i./A, respectively. 

Risk to other taxonomic groups did not exceed concern levels. 

1.3. Environmental Fate Summary

Clethodim is microbially oxidized to moderately persistent sulfoxide and sulfone degradates 

within days of application. Clethodim is soluble in water up to 29 mg/L and will not appreciably 

volatilize or bioconcentrate in fish. The compound and its sulfoxide and sulfone degradates are 

mobile in soil and may be transported to surface and ground waters. Identified compounds 

containing the cyclohexenone ring and organosulfur side chain are considered the residues of 

concern (ROC) for this assessment because the toxic moiety of the active ingredient appears to 

potentially be intact. Exposure to the residues of concern is estimated using the Total Residue 

(TR) modeling method.

1.4. Effects Summary

Clethodim generally has low acute toxicity, but does cause toxicity on a chronic basis at 

relatively low exposure levels to aquatic organisms, particularly to fish. 

Clethodim is slightly to practically non-toxic to freshwater fish, practically non-toxic to 

estuarine/marine fish, and moderately to slightly toxic to freshwater and estuarine/marine 

invertebrates on an acute exposure basis; practically non-toxic to avian species on an acute oral 

and acute dietary exposure basis; slightly toxic to mammalian species on an acute oral-exposure 

basis; and practically non-toxic to terrestrial invertebrates (contact) on an acute exposure basis. 

Chronic exposure resulted in reduced survival for freshwater fish (fathead minnows), but effects 

on reproduction were not measured, (NOAEC = 0.01 mg a.i./L; LOAEC = 0.31 mg a.i./L);

however, the rainbow trout was more sensitive on an acute exposure basis, and so an acute to 

chronic ratio (ACR) to estimate a NOAEC value for rainbow trout was completed (estimated 
10

NOAEC = 0.002 mg a.i./L for rainbow trout). Chronic exposure resulted in reduced 

reproduction and survival to freshwater invertebrates (Daphnia magna) (NOAEC = 0.93 mg 

a.i./L; LOAEC = 3.0 mg a.i./L). Acute and chronic toxicity data are not available for 

estuarine/marine fish or invertebrates; therefore the estimated freshwater fish and aquatic 

invertebrate NOAEC values for rainbow trout and daphnids were used as a proxy for estimating 

potential toxicity to estuarine/marine fish and invertebrates, respectively. While these values 

could be protective based on comparisons of the toxicity on an acute exposure basis, there are 

also major uncertainties, especially with the chronic fish endpoint, which is detailed below. 

Chronic exposure in birds resulted in no effects under the conditions of the submitted studies

(NOAEC = 833 mg a.i./kg-diet), and chronic exposure in mammals resulted in decreased 

parental weight and food consumption in both generations, but no reproductive effects were 

observed (NOAEC = 500 ppm; 51 mg a.i./kg-bw; LOAEC = 1500 ppm; 263 mg a.i./kg-bw).

No effects were observed for terrestrial dicot plants. Effects to monocot plants were observed in 

corn, ryegrass, and oat; but not onion. The lowest EC25 value was 0.003 lbs a.i./acre. Therefore, 

given the mode of action of clethodim (inhibiting the acetyl-coenzyme A carboxylase (ACCase) 

enzyme of grass species), the target species of clethodim. The results observed in the toxicity 

tests for monocot plant species for clethodim, the risk to terrestrial plants can be refined and 

limited to a narrower portion of monocot plants, grass species. The non-target terrestrial plant 

species of concern from clethodim application are within the grass (Poaceae) family.

1.5. Main Uncertainties

There are uncertainties with the chronic fish endpoint that is used in this risk assessment. First, 

the available fathead minnow toxicity study NOAEC endpoint is based on mortality, and not the 

typical sublethal (growth or reproduction) endpoints that are used for evaluating chronic 

exposures. Therefore, there could be an underestimation of risk to fish on a chronic exposure 

basis. 

There are no ecotoxicity data for any of the degradates of clethodim. Therefore, the toxicities of 

the degradates of concern are uncertain. For the purpose of this assessment, degradates 

containing the cyclohexenone ring and organosulfur side chain (clethodim sulfoxide, clethodim 

sulfone, clethodim oxazole, clethodim oxazole sulfoxide, clethodim oxazole sulfone, clethodim 

imine, clethodim imine sulfoxide, and clethodim trione sulfoxide) are assumed to have the same 

toxicity as the parent compound (USEPA, 2008) because the toxic moiety of the active 

ingredient appears to potentially be intact. However, if the degradates of concern were shown to 

be much less toxic than clethodim, then exposure estimates (for clethodim alone) in this 

assessment would be 4-13x lower. For example, if a study was to show that clethodim sulfoxide 

is much less toxic than clethodim to fish on a chronic exposure basis, then clethodim would have 

no degradates of concern for fish because the sulfoxide is the degradate most structurally similar 

to clethodim and all other degradates could be assumed less toxic than clethodim if the sulfoxide 

is. In the absence of such data or if submitted data confirm the assumption, the degradates of 

concern are assumed no more or less toxic than clethodim.

The total residue (TR) modeling approach involves some uncertainty, since the soil mobility of 

one mobile compound and the product chemistry values of the parent compound are used to 
11

represent all of the residues of concern. Also, the degradation kinetics of the residues of concern 

may not be first-order. The soil mobility of clethodim sulfoxide is used to represent the residues 

of concern because up to 75% of clethodim oxidizes to its sulfoxide (in soil, 3-7 days after 

application), making the sulfoxide the most prominent degradate of concern. Clethodim 

sulfoxide is more mobile in soil than clethodim and its oxazole sulfoxide, but less mobile in soil 

than clethodim sulfone. Therefore, use of its soil mobility to represent the residues of concern in 

modeling may be representative and may be conservative, but is not a worst case assumption.

Conservative assumptions were made for environmental fate inputs for aquatic exposure 

modeling in the absence of data. Without an aerobic aquatic metabolism study, clethodim 

residues of concern in modeled aerobic aquatic systems were assumed to degrade at half the rate 

as that in aerobic soil. The single available anaerobic aquatic metabolism half-life was 

multiplied by three for exposure modeling to account for potential variability. Only two aerobic 

soil metabolism half-lives were available to generate model inputs, both for sandy loam soils 

from Greenville, Mississippi. 

It is uncertain whether maximum use patterns may be implemented due to changing market 

forces or weed pressures. If labeled annual application rates were an order of magnitude lower 

than those assumed in this assessment (e.g., 0.5 versus 4.5 lbs a.i./A), then exposure estimates for 

the lower rates would be an order of magnitude lower as well. In addition, for the terrestrial 

exposure analysis, a 7 day interval between applications was used for modeling the conservative 

assumptions associated with lack of label language. Therefore, based on this assumption for the 

terrestrial exposure analysis new crop cycles would be occurring every two weeks; however, that 

is likely not a realistic representation of field practices. Therefore, if additional information was 

provided for annual application limits, a more refined analysis could be completed, and in some 

cases the RQ values could be reduced to below the LOCs for birds and/or mammals. 

2. PROBLEM FORMULATION

The problem formulation for this assessment, which discusses the stressors, the conceptual 

models used to estimate exposures to non-target organisms, and the tools and methods with 

which EPA will assess potential risk, was provided in the problem formulation document for the 

registration review of clethodim, dated Aug. 13, 2008 (USEPA, 2008).1

 Updated information is 

provided in this assessment.

2.1. Nature of the Stressor

Clethodim (PC code 121011) is a post-emergent selective herbicide used on a variety of crops 

and non-crop areas to control a variety of grasses. As a cyclohexenone, clethodim is structurally 

similar to and regarded as included in the cyclohexanedione family of herbicides that inhibit lipid 

synthesis by inhibiting the acetyl-coenzyme A carboxylase (ACCase) enzyme of grass species

(HRAC, 2012).

Clethodim and its transformation products that contain the cyclohexenone ring and organosulfur 

side chain (i.e., with 5-(2-ethylthiopropyl)-5-hydroxycyclohexene-3-one or 5-(2-

 1 http://www.regulations.gov/#!documentDetail;D=EPA-HQ-OPP-2008-0658-0008
12

ethylthiopropyl)cyclohexene-3-one moieties) are the residues of concern (ROC) for this 

assessment (USEPA, 2008). The products of concern include clethodim sulfoxide, clethodim 

sulfone, clethodim oxazole, clethodim oxazole sulfoxide, clethodim oxazole sulfone, clethodim 

imine, clethodim imine sulfoxide, and clethodim trione sulfoxide. Ecotoxicity data are not 

available for the transformation products of concern. Products of concern are assumed to be of 

similar toxicity to the parent compound in the lack of data and because the toxic moiety of the 

active ingredient appears to potentially be intact.

2.2. Usage Update

The Agency’s Biological and Economic Analysis Division (BEAD) analysis of national-level 

agricultural usage information presented in the 2008 problem formulation (USEPA, 2008) was 

updated on September 6, 2012, as presented in Table 2 (USEPA, 2012). Relatively small 

changes in usage were observed in the 2012 update, which covered the 2003-2010 reporting 

period. More than 400,000 pounds of clethodim are still used annually on agricultural crops,

with the highest annual usage, in terms of pounds of active ingredient (a.i.) applied, on soybeans 

(200,000), sugar beets (50,000), sunflowers (40,000), and alfalfa (40,000). Usage on sugar beets 

and cotton decreased, usage on alfalfa and dry beans/peas increased, while usage on soybeans 

and sunflowers did not change. Maximum percent crop treated (PCT) values increased slightly 

for most of the crops with the highest usage, with the highest PCT value (50%) occurring in

sugar beet usage.

Table 2. Screening Level Estimates of Agricultural Uses of Clethodim (Sep. 6, 2012)A,B,C

Crop lbs. a.i. Percent Crop Treated

Average Maximum

1 Alfalfa 40,000 <2.5 5

2 Almonds <500 <1 <2.5

3 Apricots* <500 N/C N/C

4 Asparagus <500 5 15

5 Barley 1,000 <1 <2.5

6 Beans, Green 1,000 5 10

7 Broccoli 1,000 5 15

8 Brussels Sprouts* <500 N/C N/C

9 Cabbage <500 5 10

10 Caneberries <500 5 10

11 Canola 4,000 5 15

12 Cantaloupes <500 5 10

13 Carrots 2,000 15 40

14 Cauliflower <500 5 10

15 Celery <500 5 10

16 Cherries <500 <1 <2.5

17 Corn 3,000 <1 <2.5

18 Cotton 10,000 <1 <2.5
13

Crop lbs. a.i. Percent Crop Treated

Average Maximum

19 Cucumbers <500 5 10

20 Dry Beans/Peas 10,000 5 15

21 Fallow 3,000 <1 <2.5

22 Garlic <500 5 15

23 Grapes <500 <1 <2.5

24 Lettuce <500 <1 <2.5

25 Nectarines* <500 N/C N/C

26 Onions 5,000 20 35

27 Peaches 1,000 5 10

28 Peanuts 20,000 10 15

29 Peas, Green <500 <2.5 5

30 Peppers 1,000 5 15

31 Pistachios* <500 N/C N/C

32 Plums/Prunes <500 <2.5 <2.5

33 Potatoes 5,000 5 10

34 Pumpkins 1,000 10 25

35 Rice 1,000 <1 <2.5

36 Sorghum <500 <1 <2.5

37 Soybeans 200,000 5 10

38 Spinach <500 <1 <2.5

39 Squash <500 5 10

40 Strawberries <500 <2.5 10

41 Sugar Beets 50,000 30 50

42 Sunflowers 40,000 25 30

43 Tomatoes 2,000 5 10

44 Walnuts <500 <1 <2.5

45 Watermelons 2,000 10 25

46 Wheat <500 <1 <2.5 A All numbers rounded (amounts ≥10,000 lbs a.i. bolded) (percentages ≥25% bolded).

<500 Less than 500 pounds of active ingredient

<2.5 Less than 2.5 percent of crop treated

<1 Less than 1 percent of crop treated

* Based on CA DPR data, only LBS a.i. available. N/C= not calculated B SLUA data sources include (reporting timeframe: 2003-2010):

USDA-NASS (United States Department of Agriculture's National Agricultural Statistics Service) 

Private Pesticide Market Research

California DPR (Department of Pesticide Regulation) C These results reflect amalgamated data developed by the Agency and are releasable to the public.
14

3. ANALYSIS

3.1. Use Characterization

Clethodim is applied with aerial, ground, hand-held, and irrigation equipment to a variety of 

agricultural and non-agricultural use sites. Approximately 67 uses and use groups (i.e., use sites) 

are listed on dozens of end-use labels registered by 21 registrants. These uses and use groups are 

organized into the following 26 maximum use patterns (i.e., conservative use patterns that result 

in maximum exposure following labeled directions) listed in Table 3 that are ranked by annual

application rate. The use sites are not grouped by similarity and are not meant to be used as 

surrogates for other use sites that share the same use pattern.

Many use sites have application rate limits on a seasonal or crop basis, not on an annual basis. 

Annual application rates were assumed for use sites with multiple seasons per year, when not 

specified on labels, based on estimates in USEPA, 2007 for California agriculture. These 

estimates are more applicable to the lower latitudes of the United States and their applicability is 

complicated by the common practice of crop rotation. Specifically, for uses on alfalfa, fallow 

land, and non-cropped areas, the annual application rate was assumed to be 4.5 lbs a.i./A, which 

represents nine cuttings of alfalfa per year, with 0.5 lbs a.i./A applied per cutting, or eighteen 

applications per year on the other use sites. For grass for forage, fodder, or hay, eighteen 

applications per year were also assumed. Other assumptions included five crops per year for 

radishes, four crops per year for turnip greens and mustard greens, and two crops per year for 

sod, beets, and most brassica and leafy vegetables (USEPA, 2007).

A reapplication interval of 14 days is labeled for a variety of uses. In the absence of label 

directions, a reapplication interval of 7 days is assumed. This is the minimum interval assumed 

to be practical for control of re-emerged weeds following an earlier treatment.

Table 3. Maximum Use Patterns for Current Uses of Clethodim A

Use Site(s)

Single 

App. Rate

(lbs a.i./A)

Reapp. 

Interval B

(days)

Max. No. 

of App. 

per Crop

App. Rate 

per Crop 

(lbs a.i./A)

Annual 

App. Rate C

(lbs a.i./A)

App. 

Method D

Geographic

Applicability

Fallow land, golf course turf, noncropped areas E 0.25 NS F NS NS 4.5 G Aerial United States

Alfalfa I 0.25 NS NS 0.50 4.5 J Aerial United States

Ornamentals, landscaped areas, nonbearing food crops H, around 

buildings, bare soil, mulched areas

0.25 14 NS NS 4.5 G Ground United States

Grass forage/fodder/hay 0.19 NS NS NS 3.4 G Sprayer MO only

Clover 0.25 NS NS 0.25 2.25 J Aerial United States

Herbs, turnip greens 0.125 14 NS 0.50 2.0 N Aerial United States

Mustard, vegetables 0.12 14 NS 0.485 1.9 N Aerial

ID only (and 

OR & WA for 

mustard)

Radishes 0.125 14 NS 0.25 1.25 M Aerial United States

Mint 0.25 14 NS 0.50 1.0 K Aerial United States

Sod farms 0.25 NS NS 0.50 1.0 L Aerial AL, FL, GA, 

NC, SC only
15

Use Site(s)

Single 

App. Rate

(lbs a.i./A)

Reapp. 

Interval B

(days)

Max. No. 

of App. 

per Crop

App. Rate 

per Crop 

(lbs a.i./A)

Annual 

App. Rate C

(lbs a.i./A)

App. 

Method D

Geographic

Applicability

Beets, brassica vegetables, carrots, 

cranberries, cucurbit vegetables, 

fruiting vegetables, leafy vegetables, 

strawberries

0.125 14 NS 0.50 1.0 L Aerial United States

Dried beans, Christmas trees, cotton, 

forest trees, peanuts, potatoes, root & 

tuber vegetables, sainfoin, soybeans, 

sugar beets, sunflowers, sweet 

potatoes, tomatoes, trefoil, yams

0.25 NS NS 0.50 0.50 Aerial United States

Lentils 0.25 14 NS 0.50 0.50 Aerial United States

Garlic, onions 0.25 NS 2 0.50 0.50 Chemigation

Except ID, 

MT, OR, WA

Tree fruits, tree nuts, asparagus, hops, 

safflower, sesame 0.125 NS NS 0.50 0.50 Aerial United States

Sage 0.24 NS NS 0.485 0.485 Ground NC only

Shallots 0.24 14 NS 0.485 0.485 Aerial United States

Artichokes, bushberries including 

cranberries, caneberries, peaches 0.12 14 NS 0.485 0.485 Aerial United States

Flax 0.125 NS NS 0.25 0.25 Aerial Except CA

Meadowfoam 0.125 NS NS 0.25 0.25 Aerial OR only

Seeds 0.125 NS NS 0.25 0.25 Aerial MN, ND only

Kenaf 0.125 NS NS 0.25 0.25 Ground NC only

Canola 0.10 NS NS 0.25 0.25 Aerial United States

Wildlife food plots 0.24 14 NS NA F 0.24 Not stated United States

Succulent beans, legume vegetables, 

dried & succulent peas 0.125 NA 1 0.125 O 0.125 Aerial United States

Corn (field) 0.045 NA 1 0.045 0.045 Aerial United States

A Listed use patterns represent those of the maximum use pattern and do not represent all labeled use patterns for 

that use.

B Reapplication intervals of 14 days were labeled for a variety of uses. In the absence of label directions, a 

reapplication interval of 7 days is assumed for control of emerged weeds.

C The annual application rate accounts for how many crops may occur per year. For perennial crops (e.g., alfalfa), 

the number of cuttings per year was used. Source: USEPA, 2007.

D Aerial application is assessed unless it is not allowed for the use.

E Non-cropped areas include fallow agricultural land, rights-of-way, around airports, electric utilities, commercial 

buildings, manufacturing plants, storage yards, rail yards, fence lines, parkways, golf courses, uncultivated 

areas, and beneath greenhouse benches.

F NS means “not stated.” NA means “not applicable.”

G For non-cropped areas, fallow land, golf course turf, and hay, eighteen applications were assumed in the absence 

of a labeled annual application limit.

H Non-bearing crops include apples, berries including strawberries, citrus fruits, grapes, olives, pears, stone fruits, 

and tree nuts.

I Alfalfa use pattern includes an alfalfa plus clover mixture.

J For alfalfa, nine cuttings may occur per year in California. Nine cuttings were assumed for clover as well 

(USEPA, 2007).

K Annual application rate is 1.04 lbs a.i./A for spearmint and 0.52 lbs a.i./A for peppermint.

L Two crops of sod, beets, and most brassica and leafy vegetables may be grown per year (USEPA, 2007).

M Radishes may have 5 crops per year (USEPA, 2007).

N Turnip greens and mustard greens may have 4 crops per year (USEPA, 2007).
16

O The seasonal application rate limit is stated as 0.50 lbs a.i./A; however, no more than one application of 0.125 lbs 

a.i./A may be applied per season. Therefore, the practical seasonal rate limit is 0.125 lbs a.i./A.

3.2. Environmental Fate Characterization

Clethodim is microbially oxidized to moderately persistent degradates within days of application. 

Clethodim is soluble in water up to 29 mg/L and will not appreciably volatilize or bioconcentrate 

in fish. The compound and its degradates are mobile in soil and may be transported to surface 

waters and the degradates may be transported to ground waters. The available environmental 

fate data for clethodim are listed in Table 4. The information in this section is provided to 

expand the brief characterization provided in the 2008 problem formulation for registration 

review (USEPA, 2008).

Table 4. Chemical Properties and Environmental Fate Parameters of Clethodim

Parameter Value Source

Selected Physical/Chemical Parameters

Molecular mass (molecular formula) 359.92 g/mol (C12H10ClN3O) (Calculated)

Vapor pressure (25 °C) <1 x 10-7 torr MRID 48881401

Aqueous solubility (20°C) 29 mg/L MRID 48881405

Henry’s Law Constant (25 °C) <2 x10-9 atm-m3/mol (Calculated)

Log octanol-to-water partition coefficient

(log KOW)

4.81 MRID 48881405

Dissociation constant (pKa) 4.62 MRID 48881405

Persistence in Water

Hydrolysis half-life (25°C) A pH 5: 28 days

pH 7: 289 days

pH 9: 305 days

MRID 40974520

Aqueous photolysis half-life (25°C) pH 5: 1.5-1.7 days

pH 7: 2.5-6.8 days

pH 9: 6.0-9.6 days

MRID 41030133,

41030134

Anaerobic aquatic metabolism half-life 

(25°C)

233 days MRID 41652301

Persistence in Soil

Aerobic soil metabolism half-life (25°C) 1.2 days MRID 41376801

2.5 days MRID 40974522

Photolysis half-life in soil (13-23°C) 7 days MRID 41030135

Mobility

Freundlich soil-water partition 

coefficients (KF); Freundlich organic 

carbon-normalized coefficients (KFOC)

0.08, 0.15, 0.46, 0.51, 1.57 L/kg;

4.9, 65, 68, 132, 271 L/kgOC

MRID 40974523
17

Parameter Value Source

Field Dissipation

Terrestrial field dissipation half-life Half-lives and leaching depths could not 

be calculated due to high LOQs (20 ppb) 

relative to dose rates (MS cotton; CA 

cotton; NC soybean; and IA soybean 

sites)

MRID 41030207

MRID 41030208

(MRID 41030209) B

(MRID 41030210) B

Fish Bioconcentration

Fish bioconcentration factors (steadystate, total residues); depuration rate0.7-2.1 (edible), 3.0-4.0 (inedible),

2.3-3.6 (whole fish);

>70% depuration in 3-14 days

MRID 40974524/ 

40974531

A Technically, clethodim underwent non-hydrolytic, abiotic, thermal degradation in the presence of aqueous buffers. 

Half-life values only represent the propyl-labeled studies because allyl-labeled clethodim was not studied at pH 9 

and was studied at an elevated concentration at pH 5 and 7. B Studies with MRIDs in parentheses are provisional until reviewed.

Clethodim and many of its degradates have multiple types of isomerization. The compound is an 

equilibrium mixture of four tautomers, which are predominantly two keto-enol tautomers at the 

cyclohexene ring (MRID 41376801). The other two tautomers, which are cyclohexane diones 

with tautomerization at the oxime, may be intermediates. Clethodim also has two chiral centers 

along the thiopropyl side chain and two double bonds that can form cis-trans isomers. 

Clethodim and its degradates include only the E-isomer of the chloropropenyl group. Clethodim 

is a racemic mixture, however, of the sixteen combinations of the other two cis-trans isomers, 

four enantiomers, and two predominant tautomers. MRID 41376801 Appendix D provides a 

more complete discussion of the complex isomerism in clethodim and its degradates. Isomerism

complexity often complicates study results because multiple observed chromatograph peaks may 

represent isomers or tautomers of the same compound. When this occurs, the concentrations of 

isomers or tautomers are summed together to represent a total concentration for the compound.

In the fish bioconcentration (BCF) studies, clethodim and its sulfoxide were identified and 

quantified in the tank water and identified in the fish. Residue concentrations were too low to 

quantify clethodim or its sulfoxide in fish or to identify any other metabolites in fish that may 

have been present at lower concentrations than the sulfoxide. Total-residue fish BCF values for 

whole fish were 2.3-3.6x. Allyl-labeled residues depurated from fish by 72% in 14 days. 

Cyclohexenone-labeled residues depurated from fish faster, by >70% in 3 days. Due to the low 

bioconcentration of clethodim residues and their relatively rapid depuration, bioaccumulation of 

clethodim residues of concern in aquatic organisms is not expected.

Degradates of clethodim and their amounts formed in submitted studies are listed in Table 6. 

Clethodim sulfoxide is the main degradate of clethodim, formed in soil at up to 75% of the 

applied compound three days after application. Clethodim sulfone forms up to 16% of the 

applied 30 days after application. These degradates are more persistent than the parent 

compound, but not expected to generally persist, with 0.4-0.9% of the applied remaining 380 

days after application. Clethodim oxazole sulfone does persist, with up to 10% of the applied at 

study termination, 380 days after application. Nine additional major photolysis degradates are 
18

formed in shallow, clear, well-lit water bodies; however, most of the applied clethodim is likely 

to biodegrade prior to reaching a water body, prior to photolyzing, or both.

Clethodim’s sulfoxide and sulfone are more mobile than clethodim in soil. However, 

clethodim’s oxazole sulfoxide is less mobile in soil than the parent compound. Table 5 lists the 

available environmental fate information for degradates of clethodim, which is only focused on 

soil mobility.

Table 5. Environmental Fate Parameters of Clethodim Degradates

Parameter Degradate Value Source

Freundlich organic 

carbon-normalized 

coefficients (KFOC)

Clethodim sulfoxide 12, 27, 38, 57, 86 L/kgOC

Clethodim sulfone 6, 13, 19, 29, 43 L/kgOC MRID 40974523

Clethodim oxazole sulfoxide 50, 135, 429, 460, 771 L/kgOC
19

Table 6. Chemical Names and Structures of Clethodim and Its Environmental Degradates A

Code Name/ 

Synonym

Chemical Name Chemical Structure Study Type Ref. B

(MRID)

Maximum 

%AR (day)

Final %AR 

(study length)

PARENT

Clethodim

RE-45601

(Z-isomer is 

RE-46116)

(5RS)-2-{(1EZ)-1-[(2E)-3-

chloroallyloxyimino]propyl}-5-[(2RS)-2-

(ethylthio)propyl]-3-hydroxycyclohex-2-

en-1-one

CAS No.: 99129-21-2

Formula: C17H26ClNO3S

MW: 359.92 g/mol

SMILES:C1C(CC(=C(C1=O)\C(CC)=N

\OCC=CCl)O)CC(C)SCC

S OH

O

N

O Cl

TRANSFORMATION PRODUCTS

Clethodim 

sulfoxide

RE-45924

CLSO

SOX

(5RS)-2-{(1EZ)-1-[(2E)-3-

chloroallyloxyimino]propyl}-5-[(2RS)-2-

(ethylsulfinyl)propyl]-3-

hydroxycyclohex-2-en-1-one

Formula: C17H26ClNO4S

MW: 375.92 g/mol

SMILES:C1C(CC(=C(C1=O)\C(CC)=N

\OCC=CCl)O)CC(C)[S](CC)=O

S OH

O

N

O Cl

O

Hydrolysis –pH 5

Hydrolysis –pH 7

Hydrolysis –pH 9

40974520

2.6% (0 d)

3.0% (14 d)

5.3% (14 d)

1.7% (32 d)

2.0% (32 d)

4.5% (32 d)

Aq. photo.– dark

Aq. photo.– light 41030133 5.2% (3 d)14% (3 d)

1.4% (10 d)

nd (30 d)

Aq. photo.– dark

Aq. photo.– light 41030134 3.6% (3 d)14% (30 d)

2.7% (10 d)

14% (30 d)

Aq. photo.– dark

Aq. photo.– light 44066701 4.6% (25 d)7.6% (1 d)

4.4% (30 d)

nd (30 d)

Soil photo.– dark

Soil photo.– light 41030135 64% (7 d)74% (4 d)

64% (7 d)

71% (7 d)

Aerobic soil 40974522 65% (7 d) nd (380 d)

Aerobic soil 41376801 75% (3 d) 0.9% (121 d)

Anaerobic aquatic 41652301 23-38%B (181 d) 23-38%B (181 d)

Clethodim 

sulfone

RE-47253

ONE

(5RS)-2-{(1EZ)-1-[(2E)-3-

chloroallyloxyimino]propyl}-5-[(2RS)-2-

(ethylsulfonyl)propyl]-3-

hydroxycyclohex-2-en-1-one

Formula: C17H26ClNO5S

MW: 391.92 g/mol

SMILES:C1C(CC(=C(C1=O)\C(CC)=N

\OCC=CCl)O)CC(C)[S](CC)(=O)=O

S OH

O

N

O Cl

O

O

Aerobic soil 40974522 12% (62 d) 0.4% (380 d)

Aerobic soil 41376801 16% (30 d) 5.6% (121 d)

Anaerobic aquatic 41652301 0.6% (42 d) nd (181 d)
20

Code Name/ 

Synonym

Chemical Name Chemical Structure Study Type Ref. B

(MRID)

Maximum 

%AR (day)

Final %AR 

(study length)

Clethodim 

oxazole

RE-47365

CLOX

OX

(±)-6,7-dihydro-2-ethyl-6-[2-

(ethylthio)propyl]-4(5H)-benzoxazolone

Formula: C14H21NO2S

MW: 267.39 g/mol

SMILES:C12=C(OC(=N1)CC)CC(CC2

=O)CC(C)SCC O

N

S

O

Hydrolysis –pH 5

Hydrolysis –pH 7

Hydrolysis –pH 9

40974520

54% (32 d)

7.3% (32 d)

5.1% (32 d)

54% (32 d)

7.3% (32 d)

5.1% (32 d)

Aq. photo.– dark

Aq. photo.– light 41030134 14% (2.5 d)5.5% (3 d)

14% (2.5 d)

0.5% (14 d)

Aq. photo.– dark

Aq. photo.– light 44066701 34% (30 d)12% (1.5 d)

34% (30 d)

nd (30 d)

Aerobic soil 40974522 2.1% (3 d) nd (380 d)

Anaerobic aquatic 41652301 1.2% (181 d) 1.2% (181 d)

Clethodim 

oxazole 

sulfoxide

RE-47796

OXSO

OXSOX

(±)-6,7-dihydro-2-ethyl-6-[2-

(ethylsulfinyl)propyl]-4(5H)-

benzoxazolone

Formula: C14H21NO3S

MW: 283.39 g/mol

SMILES:C12=C(OC(=N1)CC)CC(CC2

=O)CC(C)[S](CC)=O

O

N

S

O

O

Aq. photo.– dark

Aq. photo.– light 41030134 1.2% (2.5 d)5.9% (10 d)

1.0% (14 d)

nd (30 d)

Aq. photo.– dark

Aq. photo.– light 44066701 1.9% (30 d)8.9% (6 d)

1.9% (30 d)

2.2% (30 d)

Aerobic soil 40974522 6.1% (90 d) 3.0% (380 d)

Aerobic soil 41376801 5.3% (30 d) 4.9% (121 d)

Anaerobic aquatic 41652301 10% (70 d) 7.7% (181 d)

Clethodim 

oxazole 

sulfone

RE-47797

OXONE

(±)-6,7-dihydro-2-ethyl-6-[2-

(ethylsulfonyl)propyl]-4(5H)-

benzoxazolone

Formula: C14H21NO4S

MW: 299.39 g/mol

SMILES:C12=C(OC(=N1)CC)CC(CC2

=O)CC(C)[S](CC)(=O)=O

O

N

S

O

O

O

Aerobic soil 40974522 10% (380 d) 10% (380 d)

Aerobic soil 41376801 8.6% (121 d) 8.6% (121 d)

Anaerobic aquatic 41652301 5.1% (181 d) 5.1% (181 d)

Clethodim 

imine

RE-47686

CLIM

IMINE

(±)-5-[2-(ethylthio)propyl]-3-hydroxy-2-

(1-iminopropyl)cyclohex-2-enone

Formula: C14H23NO2S

MW: 269.41 g/mol

SMILES:C1C(CC(=C(C1=O)C(CC)=N)

O)CC(C)SCC S OH

O

NH

Aq. photo.– light 41030134 18% (2.5 d) 18% (2.5 d)

Aq. photo.– dark

Aq. photo.– light 44066701 1.4% (25-30 d)28% (2 d)

1.4% (30 d)

nd (30 d)

Anaerobic aquatic 41652301 1.3-17%B

(181 d) 1.3-17%B (181 d)
21

Code Name/ 

Synonym

Chemical Name Chemical Structure Study Type Ref. B

(MRID)

Maximum 

%AR (day)

Final %AR 

(study length)

Clethodim 

imine 

sulfoxide

RE-47718

IMSO

IMSOX

(±)-5-[2-(ethylsulfinyl)propyl]-3-

hydroxy-2-(1-iminopropyl)cyclohex-2-

enone

Formula: C14H23NO3S

MW: 285.41 g/mol

SMILES:C1C(CC(=C(C1=O)C(CC)=N)

O)CC(C)[S](CC)=O

S OH

O

NH

O

Aq. photo.– light 41030134 23% (21 d) 20% (30 d)

Aq. photo.– dark

Aq. photo.– light 44066701 0.5% (25 d)30% (10 d)

0.4% (30 d)

11% (30 d)

Aerobic soil 40974522 1.1% (14-30 d) nd (380 d)

Aerobic soil 41376801 2.1% (3 d) 2.0% (121 d)

Anaerobic aquatic 41652301 1.6% (181 d) 1.6% (181 d)

Clethodim 

imine ketone

IMK

(±)-5-[propyl-2-one]-3-hydroxy-2-(1-

iminopropyl)cyclohex-2-enone

Formula: C12H17NO3

MW: 223.27 g/mol

SMILES:C1C(CC(=C(C1=O)C(CC)=N)

O)CC(=O)C

O

OH

O

NH

Aq. photo.– light 41030134 12% (15, 25 d) 9.5% (30 d)

Aq. photo.– light 44066701 15% (2-4 d) 5.8% (30 d)

Clethodim 

trione

TRIONE

(±)-5-[2-(ethylthio)propyl]-3-hydroxy-2-

(1-oxopropyl)cyclohex-2-enone

Formula: C14H22O3S

MW: 270.39 g/mol

SMILES:C1C(CC(=C(C1=O)C(CC)=O)

O)CC(C)SCC S OH

O

O Aq. photo.– light 44066701 2.9% (7 d) nd (30 d)

Clethodim 

trione 

sulfoxide

RE-47386

TRISO

(±)-5-[2-(ethylsulfinyl)propyl]-3-

hydroxy-2-(1-oxopropyl)cyclohex-2-

enone

Formula: C14H22O4S

MW: 286.39 g/mol

SMILES:C1C(CC(=C(C1=O)C(CC)=O)

O)CC(C)[S](CC)=O

S OH

O

O

O

Aq. photo.– light 41030134 4.4% (0.5 d) 2.7% (2.5 d)

Aq. photo.– light 44066701 18% (20-30 d) 18% (30 d)

Clethodim 

trione 

ketone

(±)-5-[propyl-2-one]-3-hydroxy-2-(1-

oxopropyl)cyclohex-2-enone

Formula: C12H16O4

MW: 224.26 g/mol

SMILES:C1C(CC(=C(C1=O)C(CC)=O)

O)CC(=O)C

O

OH

O

O Aq. photo.– light 41030134 5.3% (20 d) 4.8% (30 d)
22

Code Name/ 

Synonym

Chemical Name Chemical Structure Study Type Ref. B

(MRID)

Maximum 

%AR (day)

Final %AR 

(study length)

Clethodim 

imine ketone

IMK

(±)-5-[propyl-2-one]-3-hydroxy-2-(1-

iminopropyl)cyclohex-2-enone

Formula: C12H17NO3

MW: 223.27 g/mol

SMILES:C1C(CC(=C(C1=O)C(CC)=N)

O)CC(=O)C

O

OH

O

NH

Aq. photo.– light 41030134 12% (15, 25 d) 9.5% (30 d)

Aq. photo.– light 44066701 15% (2-4 d) 5.8% (30 d)

DME 

sulfoxide

RE-52453

DMESO

(±)-3-[2-

(ethylsulfinyl)propyl]pentanedioic acid

Formula: C10H18O5S

MW: 250.32 g/mol

SMILES:C(C(CC(=O)O)CC(C)[S](CC)

=O)C(=O)O

S

O

O

O

OH

OH

Aq. photo.– light 41030134 49% (30 d) 49% (30 d)

Aq. photo.– light 44066701 11% (20-30 d) 11% (30 d)

DME sulfone

DMESO2

(±)-3-[2-

(ethylsulfonyl)propyl]pentanedioic acid

Formula: C10H18O6S

MW: 266.32 g/mol

SMILES:C(C(CC(=O)O)CC(C)[S](CC)(

=O)=O)C(=O)O

S

O

O

O

OH

O OH Aq. photo.– light 41030134 7.4% (30 d) 7.4% (30 d)

Unknown-2 (±)-3-[propyl-2-one]pentanedioic acid

(proposed chemical name)

O

O

O

OH

OH

(proposed chemical structure)

Aq. photo.– light 41030134 7.4% (30 d) 7.4% (30 d)

3-chloroprop

enal

(E)-3-chloropropenal

Formula: C3H3ClO

MW: 90.51 g/mol

SMILES:O=CC=CCl

O Cl Aq. photo.– light 41030133 31% (2.5 d) 31% (2.5 d)

Chloroallyl 

alcohol

RE-46261

(E)-3-chloroallyl alcohol

Formula: C3H5ClO

MW: 92.53 g/mol

SMILES:OCC=CCl

HO Cl

Hydrolysis –pH 5

Hydrolysis –pH 7 40974520 35% (30 d)

5.3% (30 d)

35% (30 d)

5.3% (30 d)

Aq. photo.– dark

Aq. photo.– light 41030133 11% (2.5 d)31% (15 d)

11% (2.5 d)

29% (30 d)
23

Code Name/ 

Synonym

Chemical Name Chemical Structure Study Type Ref. B

(MRID)

Maximum 

%AR (day)

Final %AR 

(study length)

Unextracted 

residues

(not applicable)

(not applicable)

Soil photo.– dark

Soil photo.– light 41030135 5.5% (7 d)6.2% (7 d)

5.5% (7 d)

6.2% (7 d)

Aerobic soil 40974522 23% (183 d) 18% (380 d)

Aerobic soil 41376801 29% (125 d) 29% (125 d)

Anaerobic aquatic 41652301 11% (181 d) 11% (181 d)

Carbon 

dioxide

Carbon dioxide

Formula: CO2

MW: 44.01 g/mol

SMILES:O=C=O

O O

Aq. photo.– light 41030133 12% (30 d) 12% (30 d)

Soil photo.– dark

Soil photo.– light 41030135 3.7% (7 d)4.2% (7 d)

3.7% (7 d)

4.2% (7 d)

Aerobic soil 40974522 54% (380 d) 54% (380 d)

Aerobic soil 41376801 57% (121 d) 57% (121 d)

Anaerobic aquatic 41652301 0.1% (181 d) 0.1% (181 d) A nd means “not detected”. AR means “applied radioactivity”. MW means “molecular weight”. Bolded values are laboratory study values >10%AR. B These values have a range because portions of the sulfoxide and imine degradates co-eluted and the proportions of the mixture are unclear, i.e., whether the residue was one 

degradate, the other, or both.
24

3.3. Exposure Characterization

The available physical/chemical and environmental fate properties of clethodim and its 

degradates of concern were used to calculate exposure model input parameters to estimate 

potential environmental concentrations. The compounds of concern include those with 5-(2-

ethylthiopropyl)-5-hydroxycyclohexene-3-one or 5-(2-ethylthiopropyl)cyclohexene-3-one 

moieties. Half-lives calculated for the residues of concern (ROC) are listed in Table 7. Also 

listed is the soil mobility of the most prominent residue of concern, clethodim sulfoxide, which is 

used to represent the residues of concern.

Table 7. Environmental Fate Parameters of Clethodim Residues of Concern (ROC)

Parameter Value Source

Persistence in Water

Hydrolysis half-life (25°C) pH 5: 414 days

pH 7: 3,660 days

pH 9: 45,000 days

MRID 40974520

Aqueous photolysis half-life (25°C) pH 5: 2.1-8.0 days

pH 7: 4.1-24 days

pH 9: 7.5-27 days

MRID 41030133,

41030134

Anaerobic aquatic metabolism half-life 

(25°C)

1217 days MRID 41652301

Persistence in Soil

Aerobic soil metabolism half-life (25°C) 44 days MRID 41376801

87 days MRID 40974522

Photolysis half-life in soil (13-23°C) No observable degradation MRID 41030135

Mobility

Freundlich organic carbon-normalized 

coefficients (KFOC)

12, 27, 38, 57, 86 L/kgOC MRID 40974523

3.3.1. Aquatic Exposure

The Total Residue (TR) modeling approach was used to estimate aquatic exposure with the ROC 

half-lives (from Table 7), the soil mobility of clethodim sulfoxide (from Table 7), and the 

physical/chemical properties of clethodim (from Table 4). The TR approach is appropriate 

because there are multiple degradates of concern, for none of which a full environmental fate 

data profile is available, and the toxic moiety of the active ingredient appears to potentially be 

intact. Because up to 75% of clethodim oxidizes to its sulfoxide in soil, the sulfoxide is the most 

prominent degradate of concern. With a mean KOC value of 44 L/kg, clethodim sulfoxide is 

more mobile in soil than clethodim and its oxazole sulfoxide, but less mobile in soil than 

clethodim sulfone; therefore, use of its KOC value in modeling may be representative and may be 

conservative, but is not a worst case assumption. PE chemical inputs for the ROC are listed in 

Table 8.
25

Table 8. PE Chemical Input Parameters for Clethodim Residues of Concern

Input Parameter Value Justification Source

Molecular Mass (g/mol) 359.9 Product chemistry data (Calculated)

Henry’s Law Constant

(atm m3

/mol) 2.0 × 10-9 Ratio of vapor pressure to water 

solubility

(Calculated from 

MRIDs 48881401 

and 48881405)

Solubility in Water (mg/L) 29 Study value for clethodim MRID 48881405

Organic Carbon Partition 

Coefficient (KOC) (L/kgOC) 44 Mean value for clethodim sulfoxide, the most prominent degradate of concern MRID 40974523

Aerobic Soil Metabolism 

Half-life (days) 132 90th percentile confidence bound on the mean total residue value for two soils

MRIDs 40974523 

and 41376801

Aerobic Aquatic Metabolism 

Half-life (days) 264 Aerobic soil metabolism input value times two

MRIDs 40974523 

and 41376801

Anaerobic Aquatic 

Metabolism Half-life (days) 3650 Single available anaerobic aquatic metabolism value times three MRID 41652301

Hydrolysis Half-life at pH 7 

(days) 3660 Study value for clethodim residues of concern

MRID 40974520

Aqueous Photolysis

Half-life (days) 24 Maximum study value for clethodim residues of concern MRID 41030134

PRZM use pattern inputs are listed in Table 9. Modeled PRZM scenarios were those applicable 

to the use sites that resulted in the highest exposure, resulted in exposure bracketing 

toxicological levels of concern, or were otherwise modeled for characterization. In the interest 

of concision and resource savings, not all labeled uses of clethodim were modeled. This is 

because the pesticide is labeled for use on approximately 67 uses and use groups and risk 

conclusions are similar for many of them. Modeled use sites are not surrogates for other use 

sites not modeled. Exposure estimates from modeled use sites are used to bracket toxicological 

levels of concern, which allows for the characterization of the risks for all use sites. In this 

assessment, risk conclusions were the same for all 67 use sites. It only takes two crops (the crop 

of highest exposure and the crop of lowest exposure) to bracket the rest and show that risk 

conclusions are the same for all crops. To identify these two crops, use sites expected to produce 

high exposure, such as alfalfa, and use sites expected to produce low exposure, such as corn, 

were modeled for risk estimation.

Modeled application rates and numbers of applications per year include the maximum allowed 

on a label. Dates of initial application were selected within the scenario crop season (if allowed 

by the number of applications per year) and characterized by vulnerability to runoff. Runoff 

vulnerability was explored by modeling a range of initial application dates falling on the 1st or 

15th of months within the crop season and selecting the date for which exposure estimates were 

highest. This was expected to produce high-end exposure estimates that are conservative but that 

may not represent the highest possible exposure.
26

Table 9. PRZM Scenarios and Input Parameters Describing Maximum Patterns of 

Clethodim Use on Representative Use Sites A

Use Site PRZM 

Scenario

Date of 

Initial 

App.

App. Rate in 

lbs a.i./A

(kg a.i./ha)

App. 

per 

Year

App. 

Interval 

(days)

CAM 

Input

IPSCND 

Input

Application 

Efficiency/ 

Spray Drift

Alfalfa NC alfalfa May 150.25 (0.28)

18

7 B 2 3 0.95/0.05

Jun. 1 1

Hay MO melon C Apr. 1 0.19 (0.21)

18

7 B 2 2 0.99/0.01

3

Fallow/noncropped areas FL turf

Jun. 1

0.25 (0.28)

18

7 B Mar. 15 6 2 3 0.95/0.05

Apr. 1 1

Ornamentals CA nursery Mar. 15 0.25 (0.28) 18 14 2 3 0.99/0.01

Cotton MS cotton Sep. 1 0.25 (0.28)

2

7 B 2 3 0.95/0.05

1

Peanuts NC peanut Sep. 15 0.25 (0.28) 2 7 B 2 1 0.95/0.05

Asparagus MI asparagus Sep. 1 0.125 (0.14) 2 7 B 2 2 0.95/0.05

Hops OR hops Jun. 1 0.125 (0.14) 2 7 B 2 2 0.95/0.05

Legumes MS soybean Sep. 15 0.125 (0.14) 1 N/A 2 1 0.95/0.05

Corn KS corn Aug. 1 0.045 (0.050) 1 N/A 2 2 0.95/0.05 A Multiple numbers of applications per year were modeled for some use sites to explore risk conclusions. Where 

multiple dates of initial application are listed for a use site, they correspond to the number of applications per year in 

the table row.

B A 7-day interval for control of emerged weeds was assumed in the absence of label directions. C The Missouri melon scenario was used for hay because the hay use pattern is limited to the State of Missouri.

Surface water exposure estimates per use site for clethodim residues of concern are listed in 

Table 10. Model input and output files are attached in Appendix A. The maximum use pattern 

on alfalfa results in the highest environmental exposure concentrations (EEC).

Table 10. Aquatic Exposure Estimates from Clethodim Use Sites A

Use Site PRZM Scenario 1-in-10-year Peak 

(μg/L)

1-in-10-year 21-

day Mean (μg/L)

1-in-10-year 60-

day Mean (μg/L)

Alfalfa NC alfalfa 113 110 108

Hay MO melon 42 41 39

Fallow/non-cropped areas FL turf 29 29 28

Ornamentals CA nursery 36 36 34

Cotton MS cotton 26 25 24

Peanuts NC peanut 16 16 16

Asparagus MI asparagus 3.9 3.9 3.8

Hops OR hops 2.6 2.6 2.5

Legumes MS soybean 6.3 6.1 5.8

Corn KS corn 6.2 6.1 5.8 A Maximum values are in bold.
27

For characterization, surface water exposure was also estimated for clethodim, without the 

degradates of concern. Model inputs for clethodim alone were the same as for the total residues 

of concern model run for use on alfalfa, with the following clethodim-specific differences: a KOC

of 108 L/kg, an aerobic soil metabolism half-life of 3.8 days, an aerobic aquatic metabolism halflife of 7.5 days, an anaerobic aquatic metabolism half-life of 699 days, a hydrolysis half-life of 

289 days, and an aqueous photolysis half-life of 6.8 days. The resulting 1-in-10-year clethodimonly EECs were 29 μg/L (peak), 15 μg/L (21-day mean), and 8.6 μg/L (60-day mean).

3.3.1.1. Bioaccumulation

Clethodim residues of concern are not expected to appreciably bioaccumulate in aquatic or 

terrestrial organisms. With a log KOW of 4.81, clethodim meets the criteria for chemicals that are 

modeled with KABAM for bioaccumulation in birds and mammals. Bioaccumulation modeling 

was not conducted, however, because of the following considerations:

• The submitted fish BCF study indicates that clethodim residues do not appreciably 

bioconcentrate, with whole-fish BCF values of 2-4x. Depuration from fish was relatively 

quick (>70% depuration in 3-14 days).

• Clethodim is rapidly biodegraded in aerobic conditions (half-lives of 1-7 days), typically 

to more polar degradates that are expected to be easier to metabolize and to have lower 

KOW values than clethodim.

• Clethodim is of low toxicity to birds and mammals on acute and chronic exposure basis, 

with respective NOAECs of 833 and 500 mg/kg-diet (ppm). No reproductive effects 

were observed in either the avian or mammalian reproduction toxicity tests.

3.3.1.2. Monitoring Data

Clethodim is not an analyte in the following water monitoring programs: the California 

Department of Pesticide Regulation (CDPR) surface water database 

(http://www.cdpr.ca.gov/docs/emon/surfwtr/surfcont.htm, the USGS NAWQA surface and 

ground water database (http://infotrek.er.usgs.gov/apex/f?p=136:1:0::NO:::), the USEPA 

STORET Data Warehouse (http://www.epa.gov/storet/), and the USDA Pesticide Data Program 

drinking water monitoring analyses 

(http://www.ams.usda.gov/AMSv1.0/ams.fetchTemplateData.do?template=TemplateG&navID=

&rightNav1=&topNav=&leftNav=ScienceandLaboratories&page=PDPDownloadData/Reports&

resultType=&acct=pestcddataprg).

3.3.2. Terrestrial Exposure

3.3.2.1. Dietary Modeling

Terrestrial exposure estimates for avian and mammalian risk assessments were derived using the 

T-REX model (version 1.5.1, 05/22/2013). In this model, the assumption is that the bird or 

mammal receives 100% of their diet for one day from on-field items. The exposure estimates for 

birds are considered to be surrogates for exposures to terrestrial-phase amphibians and reptiles.
28

Crop Uses

For clethodim application to crops, a foliar application in T-REX was used. Potential dietary 

exposure for terrestrial wildlife in this assessment is based on consumption of clethodim residues 

on food items following spray applications. The input parameters are presented in Table 11. An 

evaluation into a potential foliar dissipation half-life rate was conducted; however, none of the 

available information could be used to refine the foliar dissipation half-life. Therefore, when data 

are absent, as in this case, EFED uses the default foliar dissipation rate of 35 days based on the 

work of Willis and McDowell (1987). Reapplication intervals of 14 days were labeled for a 

variety of uses; however, in the absence of label directions, a reapplication interval of 7 days is 

assumed for control of emerged weeds. Also, the annual application rate accounts for how many 

crops may occur per year. For perennial crops (e.g., alfalfa), the number of cuttings per year was 

used (USEPA, 2007). 

For the preliminary assessment, terrestrial dietary and dose-based EECs of clethodim residues on 

food items were derived using the range of application rates for clethodim (Table 12 through 

Table 14). The acute avian toxicity studies were all non-definitive endpoints, and only the most 

sensitive size class, small (20g) birds, was modeled for dose-based EECs (Table 13). For acute 

mammalian toxicity, the two most sensitive size class, small (15g) and medium (35g) mammals 

were modeled for dose-based EECs (Table 14). All use patterns (with aerial, ground, or 

chemigation application methods) with total annual application rates less than 0.5 lb a.i./A were 

not modeled, as it was determined, based on the modeled values of representative crops, these 

uses do not pose risk to birds and/or mammals on an acute or chronic basis (see Table 3 for a list 

of applicable uses; and Section 5 - Risk Description, for additional discussion). Example 

input/outputs from T-REX for clethodim can be found in Appendix B. 

Table 11. Input Parameters for T-REX Modeling for the Scenarios

Use(s) 

Single 

App. Rate 

(lbs a.i./A)

Maximum 

Annual App. Rate 

(lbs a.i./A)

Maximum 

No. of 

App.

Minimum 

Reapplication 

Interval (days)

Fallow land, golf course turf, 

& non-cropped areas 0.25 4.5A 18A 7-dB

Ornamentals, landscaped areas, 

non-bearing food crops, around 

buildings, bare soil, & mulched 

areas 0.25 4.5A 18A 14-dB

Alfalfa 0.25 4.5C 18C 7-dB

Dried beans, Christmas trees, 

cotton, forest trees, peanuts, 

potatoes, sainfoin, soybeans, 

sugar beets, sunflowers, sweet 

potatoes, tomatoes, trefoil, 

yams, & lentils 0.25 0.5 2 7-dB

Mint 

(spearmint, peppermint) 0.25

1.0E (spearmint) 4E (spearmint) 14-d (spearmint)

0.5E (peppermint) 2E (peppermint) 14-d (peppermint)

Clover 0.25 2.25D 9D 7-dB

Sod Farms 0.25 1.0F 4F 7-dB

Grass forage/fodder/hay 0.19 4.5A 18A 7-dB
29

Use(s) 

Single 

App. Rate 

(lbs a.i./A)

Maximum 

Annual App. Rate 

(lbs a.i./A)

Maximum 

No. of 

App.

Minimum 

Reapplication 

Interval (days)

Radishes 0.125 1.25G 10G 14-d

Beets, Brassica vegetables, 

& leafy vegetables 0.125 1.0F 8F 14-d

Turnip & mustard greens 0.125 2.0H 16H 14-d

Abbreviations: App. Application(s)

A For non-cropped areas, fallow land, ornamentals, golf course turf, and hay, 18 applications were assumed in the 

absence of a labeled annual application limit.

B The labels do not specify minimum reapplication intervals for a large number of uses. When the reapplication 

interval is not specified, an assumed reapplication interval of 7 days may be used in the assessment

C For alfalfa there are 2 applications per crop, and alfalfa and clover may have 9 cuttings per year in California; 

therefore for one (1) year of application a total of 18 applications were used for modeling the alfalfa use. D For clover there is 1 application per crop, and alfalfa and clover may have 9 cuttings per year; therefore for one (1) 

year of application a total of 9 applications were used for modeling the clover use. E Annual application rate is 1.0 lbs a.i./A for spearmint and 0.50 lbs a.i./A for peppermint F For sod, beets, and brassica and leafy vegetables there are four applications per crop, and sod, beets, and most 

brassica and leafy vegetables may be grown twice per year; therefore for one (1) year of application a total of 8 

applications were used for modeling sod, beets, and brassica and leafy vegetables uses. G For radishes there are 2 applications per crop, and radishes may have 5 crops per year; therefore for one (1) year of 

application a total of 10 applications were used for modeling the radishes use. H For turnip greens and mustard greens there are 4 applications per crop, and turnip greens and mustard greens may 

have 4 crops per year; therefore for one (1) year of application a total of 16 applications were used for modeling the 

turnip greens and mustard greens use.

Table 12. Dietary-Based Clethodim EEC Values for Various Crops

Application Rate (crop)

Dietary-Based EECs (mg/kg-diet)

Dietary Item

Short 

Grass

Tall 

Grass

Broadleaf 

plants

Fruits/pods/

seeds Arthropods

0.25 lb a.i./A @18 apps/7-d interval 

(annual app. 4.5 lb a.i./A) (fallow land, golf 

course turf, non-cropped areas; alfalfa)

425 195 239 27 167

0.25 lb a.i./A @ 9 apps/7-d interval 

(annual app. 2.25 lb a.i./A) (clover) 330 151 186 21 129

0.19 lb a.i./A @ 18 apps/7-d interval (annual 

app. 3.4 lb a.i./A) (grass forage/ fodder/hay) 323 148 182 20 127

0.25 lb a.i./A @ 18 apps/14-d interval 

(annual app. 4.5 lb a.i./A) (ornamentals, 

landscaped areas, non-bearing food crops, 

around buildings, bare soil, mulched areas)

246 113 138 15 96

0.25 lb a.i./A @ 4 apps/7-d interval

(annual app. 1.0 lb a.i./A) (sod farms-only in 

AL, FL, GA, NC, SC)

197 90 111 12 77

0.25 lb a.i./A @ 4 apps/14-d interval

(annual app. 1.0 lb a.i./A) (spearmint) 166 76 93 10 65

0.125 lb a.i./A @ 16 apps/14-d interval (annual 

app. 2.0 lb a.i./A) (i.e.,turnip & mustard greens) 122 56 69 7.7 48

0.125 lb a.i./A @ 10 apps/14-d interval

(annual app. 1.25 lb a.i./A) (radishes) 116 53 65 7.3 45
30

Application Rate (crop)

Dietary-Based EECs (mg/kg-diet)

Dietary Item

Short 

Grass

Tall 

Grass

Broadleaf 

plants

Fruits/pods/

seeds Arthropods

0.25 lb a.i./A @ 2 apps/7-d interval

(annual app. 0.5 lb a.i./A) (i.e., dried beans, 

Christmas trees, cotton, forest trees, peanuts, 

potatoes, sainfoin, soybeans, sugar beets, 

sunflowers, sweet potatoes, tomatoes, trefoil, 

yams, lentils)

112 51 63 7.0 44

0.125 lb a.i./A @ 8 apps/14-d interval

(annual app. 1.0 lb a.i./A) (beets, brassica 

vegetables, leafy vegetables)

110 51 62 6.9 43

0.25 lb a.i./A @ 2 apps/14-d interval 

(annual app. 0.5 lb a.i./A) (peppermint) 105 48 59 6.6 41

Table 13. Avian Dose-Based Clethodim Upper Bound EEC Values for Various Crops

Application Rate

(crop)

Size 

Class 

(g)1

Avian Dose-Based EECs (mg/kg-bw)

Dietary Item

Short 

Grass

Tall 

Grass

Broadleaf 

plants

Fruits/ 

pods Arthropods Seeds

0.25 lb a.i./A @18 apps/7-d 

interval (annual app. 4.5 lb 

a.i./A) (fallow land, golf course 

turf, non-cropped areas; alfalfa) 20 484 222 272 30 190 6.7

0.25 lb a.i./A @ 9 apps/7-d 

interval (annual app. 2.25 lb 

a.i./A) (clover) 20 376 172 212 24 147 5.2

0.19 lb a.i./A @ 18 apps/7-d 

interval (annual app. 3.4 lb 

a.i./A) (grass forage/ fodder/hay) 20 368 169 207 23 144 5.1

0.25 lb a.i./A @ 18 apps/14-d 

interval (annual app. 4.5 lb 

a.i./A) (ornamentals, landscaped 

areas, non-bearing food crops, 

around buildings, bare soil, 

mulched areas) 20 280 128 158 18 110 3.9

0.25 lb a.i./A @ 4 apps/7-d 

interval (annual app. 1.0 lb 

a.i./A) (sod farms - only in AL, 

FL, GA, NC, SC) 20 225 103 127 14 88 3.1

0.25 lb a.i./A @ 4 apps/14-d 

interval (annual app. 1.0 lb 

a.i./A) (spearmint) 20 189 87 106 12 74 2.6
31

Application Rate

(crop)

Size 

Class 

(g)1

Avian Dose-Based EECs (mg/kg-bw)

Dietary Item

Short 

Grass

Tall 

Grass

Broadleaf 

plants

Fruits/ 

pods Arthropods Seeds

0.125 lb a.i./A @ 16 apps/14-d 

interval (annual app. 2.0 lb 

a.i./A) (i.e.,turnip & mustard 

greens) 20 139 64 78 8.7 55 1.9

0.125 lb a.i./A @ 10 apps/14-d 

interval (annual app. 1.25 lb 

a.i./A) (radishes) 20 132 61 74 8.3 52 1.8

0.25 lb a.i./A @ 2 apps/7-d 

interval (annual app. 0.5 lb 

a.i./A) (i.e., dried beans, 

Christmas trees, cotton, forest 

trees, peanuts, potatoes, sainfoin, 

soybeans, sugar beets, 

sunflowers, sweet potatoes, 

tomatoes, trefoil, yams, lentils) 20 128 59 72 8.0 50 1.8

0.125 lb a.i./A @ 8 apps/14-d 

interval (annual app. 1.0 lb 

a.i./A) (beets, brassica 

vegetables, leafy vegetables) 20 126 58 71 7.9 49 1.7

0.25 lb a.i./A @ 2 apps/14-d 

interval (annual app. 0.5 lb 

a.i./A) (peppermint) 20 120 55 68 7.5 47 1.7

1 Adjusted LD50 values (mg/kg-bw): 20 g – 1441; 100 g – 1834; 1000 g– 2591

Table 14. Mammalian Dose-Based Clethodim Upper Bound EEC Values for Various Crops

Application Rate 

(crop)

Size 

Class 

(g)1

Mammalian Dose-Based EECs (mg/kg-bw)

Dietary Item

Short 

Grass

Tall 

Grass

Broadleaf 

plants

Fruits/ 

pods Arthropods Seeds

0.25 lb a.i./A @18 apps/7-d 

interval (annual app. 4.5 lb a.i./A) 

(fallow land, golf course turf, noncropped areas; alfalfa)

15 405 186 228 25 159 5.6

35 280 128 158 18 110 3.9

0.25 lb a.i./A @ 9 apps/7-d 

interval (annual app. 2.25 lb 

a.i./A) (clover) 

15 315 144 177 20 123 4.4

35 218 100 122 14 85 3.0

0.19 lb a.i./A @ 18 apps/7-d 15 308 141 173 19 121 4.3
32

interval (annual app. 3.4 lb a.i./A) 

(grass forage/ fodder/hay) 35 213 98 120 13 83 3.0

0.25 lb a.i./A @ 18 apps/14-d 

interval (annual app. 4.5 lb a.i./A) 

(ornamentals, landscaped areas,

non-bearing food crops, around 

buildings, bare soil, mulched 

areas)

15 235 108 132 15 92 3.3

35 162 74 91 10 64 2.3

0.25 lb a.i./A @ 4 apps/7-d 

interval (annual app. 1.0 lb a.i./A) 

(sod farms - only in AL, FL, GA, 

NC, SC)

15 188 86 106 12 74 2.6

35 130 60 73 8 51 1.8

0.25 lb a.i./A @ 4 apps/14-d 

interval (annual app. 1.0 lb a.i./A) 

(spearmint)

15 158 73 89 10 62 2.2

35 109 50 62 7 43 1.5

0.125 lb a.i./A @ 16 apps/14-d 

interval (annual app. 2.0 lb a.i./A) 

(i.e.,turnip & mustard greens)

15 117 53 66 7 46 1.6

35 81 37 45 5 32 1.1

0.125 lb a.i./A @ 10 apps/14-d 

interval (annual app. 1.25 lb 

a.i./A) (radishes)

15 111 51 62 7 43 1.5

35 77 35 43 5 30 1.1

0.25 lb a.i./A @ 2 apps/7-d 

interval (annual app. 0.5 lb a.i./A) 

(i.e., dried beans, Christmas trees, 

cotton, forest trees, peanuts, 

potatoes, sainfoin, soybeans, sugar 

beets, sunflowers, sweet potatoes, 

tomatoes, trefoil, yams, lentils)

15 107 49 60 7 42 1.5

35 74 34 42 5 29 1.0

0.125 lb a.i./A @ 8 apps/14-d 

interval (annual app. 1.0 lb a.i./A) 

(beets, brassica vegetables, leafy 

vegetables)

15 105 48 59 7 41 1.5

35 73 33 41 5 28 1.0

0.25 lb a.i./A @ 2 apps/14-d 

interval (annual app. 0.5 lb a.i./A) 

(peppermint)

15 101 46 57 6 39 1.4

35 69 32 39 4 27 0.97

1 Adjusted LD50 values (mg/kg-bw): 15 g – 2989; 35 g – 2418; 1000 g – 1046

2 Adjusted NOAEL values (mg/kg-bw): 15 g – 112.9; 35 g – 90.7; 1000 g –39.2
33

3.3.2.2. Inhalation Modeling

Inhalation exposure of clethodim to birds and mammals from foliar application of clethodim is 

not a potential route of exposure. STIR (v. 1.0) was used to calculate an upper bound estimate of 

exposure using clethodim’s vapor pressure and molecular weight for vapor phase exposure as 

well as the maximum application rate and method of application for spray drift. STIR 

incorporates results from several toxicity studies including acute oral and inhalation rat toxicity 

endpoints [rat (R. norvegicus) LD50 (oral) and LD50 (inhalation; 4-hr exposure) of 1360 mg 

a.i./kg-bw (MRID 40974507) and >3.9 mg a.i./L (MRID 40974512), [bobwhite quail (C. 

virginianus) LD50 of >2,000 mg a.i./kg-bw (MRID 40974525)]. Based on the results of the STIR 

model, inhalation exposure alone was determined not to be a potential pathway of concern for 

avian or mammalian species on an acute basis. Refer to Appendix E for additional details on the 

inhalation modeling for clethodim.

3.3.2.3. Drinking Water Modeling

Drinking water alone is not a potential route of exposure of clethodim to birds and mammals. 

SIP (v. 1.0) was used to calculate an upper bound estimate of exposure using daily water intake 

rates (Fluxwater) for birds (20g bird = 0.162 L) and mammals (1000 g mammal = 0.172 L), and 

the solubility in water at 25°C. SIP incorporates the results from several toxicity studies include 

acute and chronic avian and mammalian endpoints [bobwhite quail (C. virginianus) LD50 of 

>2,000 mg a.i./kg-bw (MRID 40974525); rat (R. norvegicus) LD50 (oral) 1360 mg a.i./kg-bw 

(MRID 40974507); mallard duck (A. platyrhynchos) NOAEC of 833 mg a.i./kg-diet (MRID 

41030205); rat NOAEL = 51 mg a.i./kg-bw (MRID 41030120)]. Based on the results of the SIP 

model, drinking water exposure alone was determined not to be a potential pathway of concern 

for avian or mammalian species on an acute and/or chronic basis. Refer to Appendix E for 

additional details on the drinking water exposure modeling for clethodim. 

3.3.2.4. Plants Modeling

Terrestrial Plants

Terrestrial exposure estimates for plant risk assessment was derived using the TerrPlant model 

(version 1.2.2, 05/28/2013). TerrPlant provides estimates of exposure to terrestrial plants from a 

single pesticide application, and pesticide EECs in runoff and drift are estimated. This model 

does not consider exposures to plants from multiple pesticide applications. Exposure 

calculations are based on a pesticide’s water solubility and the amount of pesticide present on the 

surface soil within the first inch of depth. For dry areas, the loading of pesticide active 

ingredient from runoff to an adjacent non-target area is assumed to occur from one acre of 

treatment to one acre of non-target area; for semi-aquatic (wetland) areas, runoff is considered to 

occur from a larger source area with active ingredient loading originating from 10 acres of 

treated area to a single area of non-target wetland. Default spray drift assumptions are 1% for 

ground applications, and 5% for aerial, airblast, forced air, and chemigation applications. The 

input parameters and EECs for terrestrial and semi-aquatic plants exposed to a single application 

of clethodim at labeled rates are presented in Table 15. Example input/outputs from TerrPlant 

for clethodim can be found in Appendix B.
34

Table 15. TerrPlant Inputs and Resulting EECs for Plants Inhabiting Dry and Semiaquatic Areas Exposed to Clethodim via Runoff and Drift1

Use

App.

rate

(lbs 

a.i./A)

Application 

method

Drift 

Value 

(%)

Spray drift 

EEC 

(lbs a.i./A)

Dry area 

EEC 

(lbs a.i./A)

Semi-aquatic 

area EEC

(lbs a.i./A)

Maximum single app. rate (aerial) -

fallow land, golf course turf, noncropped areas, alfalfa, clover, dried 

beans, Christmas trees, cotton, 

forest trees, peanuts, potatoes, 

sainfoin, soybeans, sugar beets, 

sunflowers, sweet potatoes, 

tomatoes, trefoil, yams, mint, 

lentils, sod farms; (chemigation) -

garlic and onions 

0.25

Foliar –

Aerial and 

chemigation

5 0.0125 0.0175 0.0625

Maximum single app. rate (ground) 

- Ornamentals, landscaped areas, 

non-bearing food crops, around 

buildings, bare soil, mulched areas 

0.25 Foliar –

ground 1 0.003 0.008 0.053

Mid app. rate - turnip greens, 

mustard greens, herbs, beets, 

brassica vegetables, carrots, 

cranberries, cucurbit vegetables, 

fruiting vegetables, leafy 

vegetables, strawberries, radishes, 

tree fruits, tree nuts, asparagus, 

hops, safflower, sesame, artichokes, 

bushberries including cranberries, 

caneberries, peaches, flax, 

meadowfarm, seeds, succulent 

beans, legume vegetables, dried and 

succulent peas

0.125 Foliar -

Aerial 5 0.006 0.009 0.031

Mid app. rate - sage, kenaf 0.125

Foliar -

Ground 1 0.001 0.004 0.026

Second lowest app. rate - canola 0.10

Foliar –

Aerial 5 0.005 0.007 0.025

Lowest app. rate - corn (field) 0.045

Foliar –

Aerial 5 0.002 0.003 0.011 1 The TerrPlant model considers only exposures to plants from single pesticide applications. 

3.4. Ecological Effects Characterization

The ecological effects characterization for clethodim is based upon registrant-submitted toxicity 

data for the TGAI and specified formulations of the parent clethodim. There is no available 

ecotoxicity data for the degradates of clethodim, and due to the similarity of the structures of 

clethodim (parent) and the degradates, are assumed to be of equal toxicity to the parent. A

summary of the available ecological toxicity data (including review classifications and 

associated deficiencies) for clethodim is in Appendix C. The data is summarized briefly in 
35

Sections 3.4.1 to 3.4.6. The bobwhite quail avian reproduction study previously identified as 

supplemental was recently downgraded to unacceptable/invalid due to a high rate of control 

mortality and general concern for the health of the test organisms. Numerous studies including 

estuarine/marine acute and chronic studies have been received since the Problem Formulation 

was issued; the results of these studies are described briefly in the following sections. In 

addition, clethodim was identified among the second list of chemicals identified in the endocrine 

disruptor screening program, and is discussed further in Section 3.4.6.

The results of the review of the Ecological Incident Information System (EIIS) are described in 

Section 3.5. A search of the ECOTOXicology database in July 2012 yielded two non-vascular 

aquatic plant toxicity studies with more sensitive toxicity endpoints than the registrant-submitted 

guideline studies described below (Section 3.4.4.1).

3.4.1. Aquatic Animals

A summary of the most sensitive aquatic animal toxicity data for clethodim, based on Agency 

review of all submitted data, is provided in Table 16, and discussed further in Sections 3.4.1.1

through 3.4.1.2. The full summary of the aquatic toxicity data for clethodim is found in 

Appendix C. Studies conducted with technical grade clethodim were submitted for the 

following aquatic animals: five fish [rainbow trout (Oncorhynchus mykiss), bluegill sunfish 

(Lepomis macrochirus), zebra fish (Danio rerio), and fathead minnow (Pimephales promelas), 

(sheepshead minnow, Cyprinodon variegates)]; one estuarine/marine mollusk (Eastern oyster, 

Crassostrea virginica); and, one estuarine/marine invertebrate - mysid shrimp (Americamysis 

bahia). For the freshwater invertebrate (Daphnia magna) the available acute toxicity study was 

conducted with a clethodim end use product (Select 2EC); as the study conducted with the

technical grade material was an unacceptable study. The available toxicity data indicate that 

clethodim TGAI ranges from slightly to practically non-toxic to freshwater and estuarine/marine 

fish and invertebrates, and moderately toxic to estuarine/marine mollusks, on an acute exposure 

basis. Formulated clethodim is slightly toxic to freshwater invertebrates, on an acute exposure 

basis. Chronic toxicity data is available for only freshwater aquatic organisms, and therefore, in 

the absence of data will be used as a conservative estimate of risks to estuarine/marine aquatic 

organisms resulting from chronic exposure to clethodim.

Table 16. Summary of the Most Sensitive Acute and Chronic Toxicity Data for Aquatic 

Animals Exposed to Clethodim

Species Test 

Material

Acute Toxicity Chronic Toxicity1s

LC50/EC50

(mg a.i./L) 

(Toxicity 

Classification)

MRID

(Study 

Classification)

NOAEC/

LOAEC

(mg a.i./L) 

(Endpoints)

MRID

(Study 

Classification)

Rainbow trout 

(O. mykiss)

TGAI 

(83.3%)

24.4

(slightly toxic)

40974528

(Acceptable) 0.002* ACR derived NOAEC*

Fathead 

minnow 

(P. promelas)

TGAI 

(95.4%)

110

(practically 

non-toxic)

48417002

(Acceptable)

0.010/0.031

(reduced survival; 

effects on reproduction 

were not measured)

48104303

(Supplemental)
36

Species Test 

Material

Acute Toxicity Chronic Toxicity1s

LC50/EC50

(mg a.i./L) 

(Toxicity 

Classification)

MRID

(Study 

Classification)

NOAEC/

LOAEC

(mg a.i./L) 

(Endpoints)

MRID

(Study 

Classification)

Waterflea

(D. magna)

Acute: 

EP (25.6%)

Chronic: 

TGAI 

(95.7%)

20.2 

(slightly toxic)

41685101

(Acceptable)

0.94/3.0

(Reduction in 

reproduction 

(offspring per female) 

& total length of 

surviving daphnids)

48104305 

(Supplemental)

Eastern oyster

(C. virginica)

TGAI 

(95.4%)

5.3

(moderately 

toxic)

48563001

(Supplemental) -- --

ND = No data; -- = Not applicable

*Rainbow trout was the most sensitive acute fish value; therefore a NOAEC was derived using an ACR of available 

acute and chronic toxicity data for the fathead minnow = [(Fathead LC50/ NOAEC) = ACR; (RT LC50/ACR) = 

0.002 mg a.i./L]

1 No acceptable estuarine/marine fish or invertebrate chronic toxicity data are available for clethodim; therefore the 

estimated freshwater fish and aquatic invertebrate NOAEC values for rainbow trout and daphnids were used as a 

conservative estimates of potential toxicity to estuarine/marine fish and invertebrates (NOAEC = 0.002 mg a.i./L 

and 0.94), respectively.

3.4.1.1. Fish

A total of six fish toxicity studies are available to evaluate the acute effects of clethodim

exposure. Observed sublethal effects included lethargy, surfacing, lying on the bottom, a 

swollen abdomen, loss of equilibrium, gulping air, and quiescence. The reported 96-hr LC50

values fall in the range of 24.4-133 mg a.i./L; therefore clethodim technical ranges from slightly 

to practically non-toxic to fish on an acute exposure basis (Appendix C). Although an 

estuarine/marine fish toxicity study is available for the sheepshead minnow, the acute toxicity 

value for rainbow trout (LC50 = 24.4 mg a.i./L; MRID 40974528) will be used as a proxy to 

estimate acute risk to fish in this risk assessment. This endpoint is protective for all species of 

fish (both freshwater and estuarine/marine). 

There is only one study available for assessing the effects of chronic exposure to fish, a fathead 

minnow with clethodim technical (TGAI; 95.7%; MRID 48104303). In absence of 

estuarine/marine chronic toxicity data, as in the case with the acute toxicity to fish, the 

freshwater fish data will be used to estimate the potential toxicity to estuarine/marine fish on a 

chronic exposure basis. The fathead minnow study was classified as supplemental and does not 

fulfill guideline requirements due to numerous deviations (i.e., no reproductive endpoints (time 

to hatch, hatchling success, and post-hatch survival) were measured; the dilution water was 

dechlorinated tap water and chlorine was not measured; and the actual concentrations were not 

measured). The NOAEC and LOAEC, based on mortality, were determined to be 0.01 mg/L and 

0.031 mg/L, respectively. Rainbow trout is the most sensitive fish based on acute exposure to 

clethodim, and therefore, perhaps rainbow trout may also be more sensitive to clethodim on a 

chronic basis. Therefore, in order to account for the potential difference in toxicity to other fish 

species on a chronic exposure basis, an acute to chronic ratio (ACR) was used to estimate a 

NOAEC value relative to an increase in sensitivity on an acute exposure basis. Using the acute 
37

and chronic toxicity endpoints for fathead minnow, the derived ACR was calculated to be 11000 

[FH LC50 (110 mg a.i./L) / FH NOAEC (0.01 mg/L)]. The estimated NOAEC value was derived 

using the acute toxicity endpoint for rainbow trout and the fathead minnow (FH) ACR [RT LC50

(24.4 mg a.i./L) / FH ACR (11000)] = 0.002 mg a.i./L. The estimated chronic toxicity value for 

rainbow trout (ACR derived NOAEC = 0.002 mg a.i./L) will be used to estimate chronic risk to 

fish in this risk assessment. 

It should be noted that there are major uncertainties associated with the chronic fish endpoint that 

is used in this risk assessment. First, the available fathead minnow toxicity study NOAEC 

endpoint is based on mortality, and not the typical sublethal (growth or reproduction) endpoints 

that are used for chronic exposures, and could be an underestimation of risk to fish. Second, the 

chronic toxicity value that is being used is based on an ACR which relies on an extrapolation 

among species. However, this is the best available information to evaluate chronic risk to fish in 

this risk assessment.

3.4.1.2. Aquatic Invertebrates

The acute toxicity studies for clethodim and aquatic invertebrates resulted in the following: 

freshwater invertebrate (water flea) EC50 value of 20.2 mg a.i./L (EP, 25.6% a.i.; MRID 

41685101) and estuarine/marine invertebrate (mollusk, Eastern oyster) EC50 (shell deposition) 

value of 5.3 mg a.i./L (TGAI, 95.4 % a.i.; MRID 48563001); and estuarine-marine invertebrate 

(shrimp, mysid) EC50 value 33 mg a.i./L (TGAI 95.4% a.i.; MRID 48417001). Therefore, 

clethodim is classified as moderately to slightly toxic to freshwater and estuarine/marine 

invertebrates on an acute exposure basis. The daphnid and mysid studies were classified as 

acceptable and the oyster study was classified as supplemental. Sublethal effects were only 

observed in the estuarine/marine invertebrate (mysid) acute toxicity test and included lethargy, 

surfacing, and lying on the bottom of the chamber. The acute toxicity value for daphnids (EC50

= 20.2 mg a.i./L) and the acute toxicity value for oysters (EC50 = 5.3 mg a.i./L) will be used to 

estimate acute risk to freshwater and estuarine/marine invertebrates in this risk assessment, 

respectively. 

A chronic study was available for clethodim and freshwater invertebrates (D. magna) that 

resulted in NOAEC and LOAEC values of 0.93 mg a.i./L and 3.0 mg a.i./L, respectively, based 

on reduction in reproduction (offspring per female) and total length of surviving daphnids 

(MRID 48104305). Survival was also significantly decreased; however it was not the most 

sensitive endpoint. In addition, based on visual observations of the data, there also appears to be 

a significant delay in time to first brood release. There are currently no acceptable 

estuarine/marine chronic invertebrate toxicity data available for clethodim; therefore, the 

freshwater aquatic invertebrate NOAEC value for daphnids will be used as a conservative 

estimate of potential toxicity to estuarine/marine invertebrates, this endpoint is protective of 

aquatic invertebrates (both freshwater and estuarine/marine). 

For sediment-dwelling organisms, there is some uncertainty with the lack of toxicity data. 

Although a whole sediment toxicity study could potentially be triggered (log Kow ≥3, the 

anaerobic aquatic metabolism half-life of clethodim is 233 days), clethodim is rapidly 

biodegraded in aerobic conditions (half-lives of 1-7 days) typically to more polar degradates that 
38

are expected to be easier to metabolize and to have lower KOW values than clethodim. However, 

based on the variation of degradation between the anaerobic and aerobic environments and the 

lack of aerobic aquatic metabolism data, there is some uncertainty with toxicity to sedimentdwelling organisms. Additional data would decrease the uncertainty of risk to sedimentdwelling aquatic organisms. 

3.4.2. Aquatic Plants

A summary of the most sensitive aquatic plant toxicity data for clethodim, based on Agency 

review of all submitted data (registrant-submitted and open literature), is provided in Table 17, 

and discussed further in Sections 3.4.2.1 through 3.4.2.2. The full summary of the aquatic plant 

toxicity data for clethodim is found in Appendix C. The mode of action of clethodim is very 

specific to terrestrial grass species, and aquatic plants are not as sensitive as terrestrial grass 

species.

Table 17. Summary of the Most Sensitive Toxicity Data for Aquatic Plants Exposed to 

Clethodim

Species Test 

Material

Endpoint

(mg a.i./L)

Effect 

(MRID; Study Classification)

Marine Diatom

(Skeletonema costatum)

EP

(25.6%)

120 hr EC50 = 8.6

120 hr NOAEC = 5.4

Inhibition of growth rate based on cell 

counts after 5 days (120 hours). 

(42029704; Acceptable)

Green algae 

(Raphidocelis subcapitata)

EP

(12%) 96 hr EC50 = 2.7

Inhibition in growth rate based on cell 

counts after 96 hours.

(E083543; Ma et al., 2006; Qualitative)

Duckweed

(Lemna gibba)

TGAI 

(82.4%)

14-d EC50 = 1.34

14-d NOAEC = 0.37

Percent inhibition based on mean frond 

counts on day 14.

(42029701; Acceptable)

3.4.2.1. Non-Vascular Plants

Five studies were submitted for aquatic non-vascular plants; two studies were submitted for

green algae (S. capricornutum) using both clethodim technical (MRID 41685106) and an end use 

product (MRID 42029703), and one study each using a clethodim end-use product (Select 2.0 

EC; 25.6% a.i.) for blue-green algae (A. flos-aquae; MRID 42029705), a freshwater diatom (N.

pelliculosa; MRID 42029706) and a marine diatom (S.costatum; MRID 42029704). The 120 hr 

EC50 for non-vascular aquatic plants using a clethodim end-use product ranged from 8.6 mg 

a.i./L to 19.5 mg a.i./L, with NOAEC values ranging from 5.4 mg a.i./L to 11.4 mg a.i./L. The 

most sensitive registrant submitted non-vascular aquatic plant was the marine diatom with EC50

and NOAEC values of 8.6 mg a.i./L and 5.4 mg a.i./L, respectively, based on inhibition of 

growth rate. 

In addition to the available registrant submitted studies for non-vascular aquatic plants, there 

were two open literature studies that were identified in the ECOTOXicology database. These 

two studies were reviewed as it was indicated that there were more sensitive endpoints for nonvascular aquatic plants (the green algae C. vulgaris and R. subcapitata; E065938; Ma et al., 2002

and E083543; Ma et al., 2006, respectively) with 96 hr EC50 values of 4.6 mg a.i./L and 2.7 mg 
39

a.i./L, respectively. Based on the review of the available data, both of these studies were 

classified to be used qualitatively within the risk assessment. Therefore, the results for the open 

literature studies, although more sensitive, will not be used to calculate RQ values, but they will 

be incorporated into the risk characterization of the risks to non-vascular aquatic plants. 

3.4.2.2. Vascular Plants

Two vascular aquatic plant toxicity studies are available for clethodim on duckweed (Lemna 

gibba), one was conducted with technical grade material (82.4% a.i.; MRID 42029701) and the 

second used a clethodim end-use product (Select 2.0 EC; 25.6% a.i.; MRID 42029702). The 14-

day EC50 and NOAEC values were 1.34 mg a.i./L and 0.37 mg a.i./L, respectively using 

technical grade material, based on mean frond counts, which was more sensitive than the 

endpoint obtained from the end-use product toxicity study. 

3.4.3. Terrestrial Animals

A summary of the most sensitive terrestrial animal toxicity data for clethodim, based on Agency 

review of all submitted data, is provided in Table 18, and discussed further in Sections 3.4.3.1

through 3.4.3.3. The full summary of the terrestrial animal toxicity data for clethodim is found 

in Appendix C. Studies conducted with technical grade clethodim were submitted for the 

following terrestrial animals: two birds [(Northern Bobwhite Quail, Colinus virginianus), and 

(Mallard Duck, Anas platyrhynchos)]; one mammal (laboratory rat; (Rattus norvegicus). The 

honey bee, (Apis mellifera) acute toxicity study was conducted with a clethodim end use product. 

The available toxicity data indicate that clethodim TGAI ranges from slightly to practically nontoxic to mammals and birds, on an acute exposure basis. Formulated clethodim is practically 

non-toxic to honey bees (terrestrial invertebrates), on an acute exposure basis. The available 

avian and mammalian reproduction studies for clethodim do not show any reproductive effects 

resulting from chronic exposure to clethodim. 

Table 18. Summary of the Most Sensitive Acute and Chronic Toxicity Data for Terrestrial 

Animals Exposed to Clethodim

Species Test 

Material

Acute Toxicity Chronic Toxicity

LD50

(mg a.i./kg bw) 

(Toxicity 

Classification)

LC50

(mg a.i./kg 

diet (ppm))

(Toxicity 

Classification)

MRID

(Study 

Classification)

NOAEC/

LOAEC

(mg a.i./kg diet 

(ppm)) 

(Endpoints)

MRID

(Study 

Classification)

Bobwhite 

Quail

(C. 

virginianus)

TGAI 

(82%)

> 2000

(practically 

non-toxic)

> 4270

(practically 

non-toxic)

40974525 

(Acceptable)

&

40974526

(Acceptable)

NA1 NA

Mallard Duck

(A.

platyrhynchos)

TGAI 

(Acute: 82%)

(Chronic: 

83.3%)

ND

> 3978 

(practically 

non-toxic)

40974527 

(Acceptable)

833/ >833

(No effects)

41030205

(Acceptable)
40

Species Test 

Material

Acute Toxicity Chronic Toxicity

LD50

(mg a.i./kg bw) 

(Toxicity 

Classification)

LC50

(mg a.i./kg 

diet (ppm))

(Toxicity 

Classification)

MRID

(Study 

Classification)

NOAEC/

LOAEC

(mg a.i./kg diet 

(ppm)) 

(Endpoints)

MRID

(Study 

Classification)

Laboratory rat

(R.norvegicus) 

TGAI 

(Acute:

83.3%)

(Chronic: 

82.3%)

1360

(slightly 

toxic)

-- 40974507

(Acceptable)

500/2500 

(51/263 mg 

a.i./kg-bw/day)

(decreased body 

weight & food 

consumption in 

parental 

organisms, NO

reproductive 

effects)

41030120

(Acceptable)

Honey Bee

(A.

mellifera)

EP

(26% a.i.)

>100 μg 

a.i./bee

(practically 

non-toxic)

2

-- 41685107

(Acceptable) -- --

ND = No Data; NA = Not Available; -- = Not applicable 1 A high rate of adult mortality in both control and test subjects were not adequately explained. This study 

was recently downgraded to unacceptable/invalid. 2 Based on classification in paper by Atkins, E.L. Division of Agricultural Sciences, University of California. MRID 

44038201. A LD50 of >11 μg/bee was classified as practically non-toxic.

3.4.3.1. Birds

Based on the 14-day non-definitive LD50 value for the northern bobwhite quail (C. virginianus) 

of >2000 mg a.i./kg-bw clethodim is classified as practically non-toxic to avian species on an 

acute oral-exposure basis (MRID 40974525). However, overt signs of toxicity (i.e., lethargy, 

wing droop and ruffled appearance) and a reduction of body weight gain were observed in the 

1650 mg a.i./kg-bw concentration, but not at any lower test levels (i.e., ≤ 1250 mg a.i./kg-bw). 

Based on the 8-day non-definitive LC50 value for bobwhite quail of >4,270 mg a.i./kg diet 

(MRID 40974526), and mallard ducks of >3,978 mg a.i./kg diet (MRID 40974527), clethodim is 

classified as slightly to practically non-toxic to avian species on a subacute dietary exposure 

basis. There is only one acceptable avian reproduction study available for clethodim: a study 

using mallard duck (A. platyrhynchos; MRID 41030205); the bobwhite quail study was 

downgraded. For the mallard duck study, there were no observed effects (mortality or 

reproductive), and the NOAEC and LOAEC values for the mallard duck study were 833 and 

>833 mg a.i./kg diet, respectively. The chronic toxicity value for mallard duck (833 mg a.i./kg 

diet) will be used to estimate chronic risk to birds in this assessment. 

3.4.3.2. Mammals

Based on the acute oral LD50 value of 1,360 mg a.i./kg-bw for the laboratory rat (R. norvegicus),

clethodim is characterized as slightly toxic to mammalian species on an acute oral-exposure 

basis (MRID 40974507). A 2-generation study was performed with clethodim technical in rats. 

The NOAEC and LOAEC values were 500 and 2500 ppm (51 and 263 mg/kg-bw/day), 
41

respectively, based on a decrease in body weight and food consumption in parents in both 

generations (MRID 41030120). There were no reproductive effects reported in the mammalian 

reproductive toxicity study. The acute oral toxicity value (LD50 = 1,360 mg a.i./kg-bw) and 

chronic toxicity value (NOAEC = 500 ppm (51 mg/kg/day)) for rats will be used to estimate 

acute and chronic risk to mammals in this assessment.

3.4.3.3. Terrestrial Invertebrates

There is one acute honey bee contact study available for clethodim. The young adult honey bee 

(A. mellifera) acute contact study reported a LD50 of >100 μg a.i./bee (MRID 41685107) using 

an end-use product of clethodim (26% a.i.); there were no mortalities or sublethal effects at this 

dose. Based on the acute contact honeybee study, clethodim is classified as practically nontoxic. 

3.4.4. Terrestrial Plants

A summary of the most sensitive aquatic plant toxicity data for clethodim, based on Agency 

review of all submitted data (registrant-submitted and open literature), is provided in Table 19, 

and discussed further in Sections 3.4.4.1 through 3.4.4.2. The full summary of the terrestrial 

plant toxicity data for clethodim is found in Appendix C. The mode of action of clethodim is 

very specific to grasses (inhibiting the acetyl-coenzyme A carboxylase (ACCase) enzyme of 

grass species), and the monocot plants, specifically, the members of the Poaceae family were the 

most sensitive terrestrial plant species to clethodim exposure. No effects were observed in dicot 

plant species when tested at the highest single application rate (0.25 lbs a.i./A).

Table 19. Summary of the Most Sensitive Toxicity Data for Terrestrial Plants Exposed to 

Clethodim

Species/

Test material

EC25

(lb a.i./acre)

NOAEC

(lb a.i./acre)

Most Sensitive 

Endpoint

MRID

(Study 

Classification)

Seedling Emergence

All Dicots tested

EP (82.4%) > 0.25 ≥ 0.25 No effects at max. app. rate

41685102 

(Acceptable)

Monocots

Oat (Aveana sativa)

EP (82.4%) 0.0076 0.0004*(EC05) Plant height 41685104(Acceptable)

Onion (Allium cepa)

EP (82.4%) > 0.25 ≥ 0.25 No effects 41685104(Acceptable)

Vegetative Vigor

All Dicots tested

EP (82.4%) > 0.25 ≥ 0.25 No effects at max. app. rate

41685103

(Acceptable)

Monocots

Rye grass (Lolium perenne)

EP (82.4%) 0.003 0.002*(EC05) Dry weight 41685105(Acceptable)

Onion (A. cepa)

EP (82.4%) > 0.25 ≥ 0.25 No effects 41685105(Acceptable)

ND = No Data; NA = Not Available; -- = Not applicable

* EC05 is used when a NOAEC could not be calculated or NOAEC is higher than the EC25
42

3.4.4.1. Dicotyledon plants

Based on the results of the submitted Tier I seedling emergence and vegetative vigor toxicity 

tests for clethodim using an end-use product (SELECT; 82.4% a.i.; MRID 41685102 and 

41685103, respectively), it was determined that all dicot species that were tested demonstrated 

no significant effects resulting from clethodim application at the maximum single application 

rate. 

3.4.4.2. Monocotyledon plants

For monocot plants effects were observed in both the seedling emergence and vegetative vigor 

toxicity tests for clethodim using an end-use product (SELECT; 82.4% a.i.; MRID 41685104 and 

41685105, respectively) for all monocot species tested, except for onion. No significant effects 

were observed for onions exposed to clethodim in either the seedling emergence or vegetative 

vigor toxicity tests. One note is that the three of the four monocot plant species that showed 

effects (corn, perennial ryegrass, and oats) all belong to family Poaceae, the grass family (which 

is the same family as the target species of clethodim), whereas onion (which showed no effects) 

is in a different monocot family, family Liliaceae. However, there are numerous other monocot 

families that are not represented, but there is evidence to suggest based on the mode of action of 

clethodim, and the mechanism of selectivity within grass species for the ACCase enzyme site of 

action, suggests that there are differential sensitivity between grass species, and species (Hess, 

1997). For seedling emergence the most sensitive parameter was plant height and the most 

sensitive monocot species was oats (A.sativa, MRID 41685104). Oat had an EC25 value of 

0.0076 lbs a.i./A and NOAEC (EC05) value of 0.0004 lbs a.i./A (MRID 41685104). For 

vegetative vigor the most sensitive parameter was dry weight and the most sensitive monocot 

species was perennial ryegrass (L. perenne, MRID 41685105). Ryegrass had an EC25 value of 

0.003 lbs a.i./A and NOAEC (EC05) value of 0.0023 lbs a.i./A (MRID 41685105). The EC25

was lower than the NOAEC; therefore, the EC05 was calculated and used in place of a NOAEC 

value for monocot plants exposed to clethodim. These endpoints for oats and perennial ryegrass 

for seedling emergence and vegetative vigor, respectively, will be used to assess risk to monocot 

plants in this assessment. 

3.4.5. Degradate Toxicity Data

There is no ecotoxicity data for any of the degradates of clethodim, specifically for the clethodim 

sulfone and clethodim sulfoxide degradates. For the purpose of this assessment, the degradates 

(clethodim sulfoxide and clethodim sulfone) containing the hexenone moiety are assumed to 

have the same toxicity as the parent compound (USEPA, 2008) because the toxic moiety of the 

active ingredient appears to potentially be intact. 

3.4.6. Endocrine Disruptor Screening Program

As required by FIFRA and FFDCA, EPA reviews numerous studies to assess potential adverse 

outcomes from exposure to chemicals. Collectively, these studies include acute, subchronic and 

chronic toxicity, including assessments of carcinogenicity, neurotoxicity, developmental, 

reproductive, and general or systemic toxicity. These studies include endpoints which may be 
43

susceptible to endocrine influence, including effects on endocrine target organ histopathology, 

organ weights, estrus cyclicity, sexual maturation, fertility, pregnancy rates, reproductive loss, 

and sex ratios in offspring. For ecological hazard assessments, EPA evaluates acute tests and 

chronic studies that assess growth, developmental and reproductive effects in different 

taxonomic groups. As part of the Preliminary Problem Formulation for Registration Review (DP 

Barcode 349758), EPA reviewed these data and selected the most sensitive endpoints for 

relevant risk assessment scenarios from the existing hazard database. However, as required by 

FFDCA section 408(p), clethodim is subject to the endocrine screening part of the Endocrine 

Disruptor Screening Program (EDSP). 

EPA has developed the EDSP to determine whether certain substances (including pesticide 

active and other ingredients) may have an effect in humans or wildlife similar to an effect 

produced by a “naturally occurring estrogen, or other such endocrine effects as the Administrator 

may designate.” The EDSP employs a two-tiered approach to making the statutorily required 

determinations. Tier 1 consists of a battery of 11 screening assays to identify the potential of a 

chemical substance to interact with the estrogen, androgen, or thyroid (E, A, or T) hormonal 

systems. Chemicals that go through Tier 1 screening and are found to have the potential to 

interact with E, A, or T hormonal systems will proceed to the next stage of the EDSP where EPA 

will determine which, if any, of the Tier 2 tests are necessary based on the available data. Tier 2 

testing is designed to identify any adverse endocrine-related effects caused by the substance, and 

establish a dose-response relationship between the dose and the E, A, or T effect. 

Under FFDCA section 408(p), the Agency must screen all pesticide chemicals. Between 

October 2009 and February 2010, EPA issued test orders/data call-ins for the first group of 67 

chemicals, which contains 58 pesticide active ingredients and 9 inert ingredients. A second list 

of chemicals identified for EDSP screening was published on June 14, 20132 and includes some 

pesticides scheduled for registration review and chemicals found in water. Neither of these lists 

should be construed as a list of known or likely endocrine disruptors. 

Clethodim is on List 2. List 2 represents the next set of chemicals for which EPA intends to issue 

test orders/data call-ins in the near future. For further information on the status of the EDSP, the 

policies and procedures, the lists of chemicals, future lists, the test guidelines and the Tier 1 

screening battery, please visit our website.3

3.5. Review of Incident Data

Reviews of the Ecological Incident Information System (EIIS, version 2.1), the Avian Incident 

Monitoring System (AIMS)4, and the EPA Incident Data System (IDS) were conducted on June 

6, 2013. There are two incidents involving clethodim and terrestrial plants that were reported in 

the EIIS database (I002969-058 and I022217-034). Both of these incidents were of 

undetermined legality and clethodim was listed as a possible cause of the alleged damage to the 

respective crops; cotton after the use of Select 2EC (the active ingredient is clethodim) (I002969-

 2 See http://www.regulations.gov/#!documentDetail;D=EPA-HQ-OPPT-2009-0477-0074 for the final second list of 

chemicals. 3 http://www.epa.gov/endo/

4 http://www.abcbirds.org/abcprograms/policy/pesticides/aims/aims/index.cfm
44

058), and soybean after the product Ignite 280 SL (a.i. glufosinate-ammonium) and Select (a.i. 

clethodim) were applied (I022217-034). Cotton and soybeans are dicots, and based on the 

available toxicity data for clethodim, these species would not be expected to be sensitive to 

clethodim as it is an herbicide that targets monocot species. Although very little information is 

available for I002969-058, potential cotton crop injury, tissue testing was completed to 

determine that Select (clethodim a.i.) was not likely the cause of the injury. It is unclear what, or 

if another pesticide was involved at all. For I022217-034, the damage to the soybean crop was 

likely the result of tank contamination; however, it is not clear which chemical the tank 

contaminated with. The number of reported incidences may only reflect a small proportion of 

actual incidents that occurred, uncertainties and animal behavior may influence the number of 

observed deaths associated with pesticide usage. There are no reported incidents for clethodim 

in the AIMS database. There are 2 reported minor plant incidents in IDS database reported in 

2000 and 2006 (010131-3 and 018521-3, respectively) for the Select 2EC formulation of 

clethodim. The lack of reported incidences should not be construed as the absence of incidents. 

Incident reports for non-target organisms typically provide information only on mortality events 

and plant damage. Sublethal effects in organisms such as abnormal behavior, reduced growth 

and /or impaired reproduction are rarely reported, except for phytotoxic effects in terrestrial 

plants. 

4. RISK ESTIMATION

For this preliminary assessment of clethodim, the deterministic risk quotient (RQ) method was 

used to provide a metric of potential risks. The RQ is a comparison of exposure estimates to 

toxicity endpoints. The resulting RQs are compared to the Agency’s risk levels of concern 

(LOC), which are the Agency’s interpretive policy such that when risk LOCs for listed and/or 

non-listed species, are exceeded, the need for regulatory action may be considered. These 

criteria are used to indicate when the use of a pesticide, as directed on the label, has the potential 

to cause adverse effects to non-target organisms.

4.1. Non-target Aquatic Organisms

Clethodim is classified as slightly to practically non-toxic to fish and aquatic invertebrates on an 

acute exposure basis. In the absence of chronic estuarine/marine fish and invertebrate toxicity 

data, the freshwater fish and aquatic invertebrate toxicity data will be used to evaluate the 

chronic risk to fish and aquatic invertebrates from exposure to clethodim. The RQ values for the 

use site with highest EECs (alfalfa) and using the most sensitive acute and chronic toxicity 

values for fish and aquatic invertebrates are presented in Table 20, and aquatic plant values are 

presented in Table 21. 

RQs exceeded the chronic risk LOC for listed and non-listed fish, only (RQ≥1.0). There were no 

other risk LOC exceedances for aquatic organisms, i.e., no chronic listed or non-listed species 

LOC exceedances for aquatic invertebrates (freshwater or estuarine/marine) (RQ<1.0), no acute 

listed species LOC exceedances for aquatic invertebrates and/or fish (RQ<0.05), and no risk 

LOC exceedances for aquatic plants (RQ<1.0) (Table 20 and Table 21).
45

RQ values for use sites other than alfalfa are also presented in Table 20 to explore chronic risk 

LOC exceedances. The chronic risk LOC for fish is exceeded by all modeled uses of clethodim, 

including those expected to produce the lowest exposure estimates (e.g., hops and corn). Based 

on these results, all use sites of clethodim that are currently registered (i.e., all 67 uses and use 

groups in Table 3) result in chronic listed and non-listed species LOC exceedances to fish. Risk 

to fish, aquatic invertebrates, and aquatic plants are discussed further in the Risk Description 

section. 

Table 20. Maximum Clethodim RQ Values for Aquatic Animals A

Use Site Taxa

EECs (μg a.i./L) RQ

Peak Chronic

(21-d/60-d) AcuteB

ChronicC

(60-d for fish/21-d for 

invertebrates)

Aquatic Invertebrates

Alfalfa Aquatic

invertebrates 113 21-day = 110 0.02 0.120.07

Fish

Alfalfa Fish 113 60-day = 108 <0.01 54

Hay Fish 42 60-day = 39 <0.01 20

Fallow/non-cropped areas Fish 29 60-day = 28 <0.01 14

Ornamentals Fish 36 60-day = 34 <0.01 17

Cotton Fish 26 60-day = 24 <0.01 12

Peanuts Fish 16 60-day = 16 <0.01 8.0

Asparagus Fish 3.9 60-day = 3.8 <0.01 1.9

Hops Fish 2.6 60-day = 2.5 <0.01 1.3

Legumes Fish 6.3 60-day = 5.8 <0.01 2.9

Corn Fish 6.2 60-day = 5.8 <<0.01 2.9 A Bold values exceed the chronic risk LOC of 1.0. Alfalfa is the use site with highest EECs. B RQ = EEC (ppb a.i.)/LC or EC50 (ppb a.i.); EEC is Peak EEC; Fish LC50 = 24,400 ppb a.i.; Aquatic Invertebrate 

EC50 = 5,300 ppb a.i. C RQ = EEC (ppb a.i.)/NOAEC (ppb a.i.); 21-d EEC for invertebrates and 60-d EEC for fish; Fish NOAEC = 2.0 

ppb a.i.; Aquatic Invertebrate NOAEC = 930 ppb a.i.

Table 21. Maximum Clethodim RQ Values for Aquatic Plants A

Use Site Taxa Peak EEC

(μg a.i./L)

Listed 

RQB

Non-listed 

RQB

Alfalfa Vascular aquatic plants

Non-vascular aquatic plants 113 0.310.02

0.08

0.01 A Bold values exceed the plant LOC 1.0. Alfalfa is the use site with highest EECs. B RQ = EEC/EC50 for non-listed species; EEC/NOAEC for listed species; Duckweed (vascular) EC50 = 1,340 ppb 

a.i.; NOAEC = 370 ppb a.i.; Marine Diatom (non-vascular) EC50 = 8,600 ppb a.i.; NOAEC = 5,400 ppb a.i.

4.2. Non-target Terrestrial Organisms

4.2.1. Terrestrial Animals

The RQ values for birds and mammals are presented in Table 22 through Table 25. Risk to 

birds and mammals are discussed further in the Risk Description section.
46

4.2.2. Birds

Clethodim is classified as practically non-toxic to birds on an acute oral and sub-acute dietary 

exposure basis. Since the endpoints from the acute oral and sub-acute avian toxicity studies are 

non-definitive (i.e., they are ‘greater than’ values), they will not be used to calculate RQs. Acute 

toxicity data for passerines are not available, and as such there is uncertainty about the effects to 

these species. This uncertainty will be discussed in the Risk Description section. 

The RQs calculated for chronic exposure to birds do not result in RQ values that exceed the 

chronic LOC (1.0). RQ values range from 0.03 - 0.51, refer to Table 22 for a summary of the 

chronic avian dietary RQ values. Risk to birds is discussed further in the Risk Description 

section.

Table 22. Avian Chronic Dietary RQ values from Application of Clethodim.

Application Rate (Crop) Dietary Item Chronic RQ 1

0.25 lb a.i./A @ 18 apps/7-d interval 

(fallow land, golf course turf, noncropped areas; alfalfa)

Short Grass 0.51

Tall Grass 0.23

Broadleaf plants 0.29

Fruits/pods/seeds 0.03

Arthropods 0.20

Bold values exceed the chronic LOC of 1.0 1 Chronic RQ = (EEC, mg/kg-diet) / chronic NOAEC, mg/kg-diet; where the chronic NOAEC is 250 mg/kg-diet

4.2.3. Mammals

Clethodim is classified as slightly toxic to mammals on an acute exposure basis. RQ values for 

the following use rates exceed the acute listed species LOC (RQ≥0.1) for small (15g) mammals 

consuming short grass for all uses with a total annual application rate greater than 2.0 lb a.i./A 

(Table 23). Also, only the highest use pattern on fallow land, golf course turf, non-cropped 

areas, and alfalfa results in acute listed species LOC exceedance for medium (35g) mammals 

consuming short grass. For all of the remaining use patterns with total annual application rates of 

equal to or less than 2.0 lb a.i./A, none of the acute RQs for mammals exceed the Agency’s acute 

listed species LOC (RQ≤0.08). However, there is one exception to this when the total annual 

application rate is greater than 2.0 lb a.i./A, if there is a 14-day interval for the single application 

rate of 0.25 lb a.i./A at 18 applications (Ornamentals, landscaped areas, non-bearing food crops, 

around buildings, bare soil, mulched areas) there no mammalian acute RQ values exceed the 

listed species LOC (RQ ≤0.08 ) (Table 23). Acute risks to mammals are discussed further in the 

Risk Description section.
47

Table 23. Mammalian Acute RQ Values for Application of Clethodim

Application Rate

(Crop)

Functional Feeding Group 

Dietary Item

15 g 

mammals

35 g 

mammals

1000 g 

mammals

Acute1 Acute1 Acute1

0.25 lb a.i./A @18 apps/7-d 

interval (annual app. 4.5 lb 

a.i./A) (fallow land, golf course 

turf, non-cropped areas; 

alfalfa)

Herbivores/Insectivores

 Short Grass 0.14 0.12 0.06

 Tall Grass 0.06 0.05 0.03

 Broadleaf plants 0.08 0.07 0.03

 Fruits/pods 0.01 0.01 <0.01

 Arthropods 0.05 0.05 0.02

 Seeds <0.01 <0.01 <0.01

0.25 lb a.i./A @ 9 apps/7-d 

interval (annual app. 2.25 lb 

a.i./A) (clover)

Herbivores/Insectivores

 Short Grass 0.11 0.09 0.05

 Tall Grass 0.05 0.04 0.02

 Broadleaf plants 0.06 0.05 0.03

 Fruits/pods 0.01 0.01 <0.01

 Arthropods 0.04 0.04 0.02

 Seeds <0.01 <0.01 <0.01

0.19 lb a.i./A @ 18 apps/7-d 

interval (annual app. 3.4 lb 

a.i./A) (grass forage/ 

fodder/hay)

Herbivores/Insectivores

 Short Grass 0.10 0.09 0.05

 Tall Grass 0.05 0.04 0.02

 Broadleaf plants 0.06 0.05 0.03

 Fruits/pods 0.01 0.01 <0.01

 Arthropods 0.04 0.03 0.02

 Seeds <0.01 <0.01 <0.01

0.25 lb a.i./A @ 18 apps/14-d 

interval (annual app. 4.5 lb 

a.i./A) ornamentals, landscaped 

areas, non-bearing food crops,

around buildings, bare soil, 

mulched areas)

Herbivores/Insectivores

 Short Grass 0.08 0.07 0.04

 Tall Grass 0.04 0.03 0.02

 Broadleaf plants 0.04 0.04 0.02

 Fruits/pods <0.01 <0.01 <0.01

 Arthropods 0.03 0.03 0.01

 Seeds <0.01 <0.01 <0.01 1 Acute RQ = (upper bound dose-based EEC, mg/kg-bw) / (LD50; mg/kg-bw).

The dose-based chronic RQ for mammals exceeded the chronic listed and non-listed LOC 

(RQ≥1.0) for multiple size and dietary classes for all foliar uses with a total annual application 

rate greater than 0.5 lbs a.i./A (Table 24). However, there is one exception to this when the 

single application rate is 0.125 lb a.i./A, and the total annual application rate is 1.0 or 1.25 lb 

a.i./A, there are no mammalian chronic risk LOC exceedances. RQ values range overall from 

1.0 - 3.6; refer to Table 24 for a summary of the chronic mammalian dose-based RQ values. On 

a chronic dietary-basis, the RQ values for all uses did not exceed the chronic LOC (Table 25). 

Table 24 and Table 25 summarize the mammalian chronic dose- and dietary-based RQs, 

respectively, based on foliar applications of clethodim. Chronic risks to mammals are discussed 

further in the Risk Description section.
48

Table 24. Mammalian Chronic Dose-based RQ values for Application of Clethodim

Application Rate

(Crop)

Functional Feeding Group

Dietary Item

15 g 

mammals

35 g 

mammals

1000 g 

mammals

Chronic1 Chronic1 Chronic1

0.25 lb a.i./A @18 apps/7-d 

interval (annual app. 4.5 lb 

a.i./A) (fallow land, golf course 

turf, non-cropped areas; alfalfa)

Herbivores/Insectivores

 Short Grass 3.6 3.1 1.7

 Tall Grass 1.7 1.4 0.76

 Broadleaf plants 2.0 1.7 0.93

 Fruits/pods 0.23 0.19 0.10

 Arthropods 1.4 1.2 0.65

 Seeds 0.05 0.04 0.02

0.25 lb a.i./A @ 9 apps/7-d 

interval (annual app. 2.25 lb 

a.i./A) (clover)

Herbivores/Insectivores

 Short Grass 2.8 2.4 1.3

 Tall Grass 1.3 1.1 0.59

 Broadleaf plants 1.6 1.4 0.72

 Fruits/pods 0.18 0.15 0.08

 Arthropods 1.1 0.94 0.50

 Seeds 0.04 0.03 0.02

0.19 lb a.i./A @ 18 apps/7-d 

interval (annual app. 3.4 lb 

a.i./A) (grass forage/ fodder/hay)

Herbivores/Insectivores

 Short Grass 2.8 2.4 1.3

 Tall Grass 1.3 1.1 0.58

 Broadleaf plants 1.6 1.3 0.71

 Fruits/pods 0.17 0.15 0.08

 Arthropods 1.1 0.92 0.49

 Seeds 0.04 0.03 0.02

0.25 lb a.i./A @ 18 apps/14-d 

interval (annual app. 4.5 lb 

a.i./A) (ornamentals, landscaped 

areas, non-bearing food crops, 

around buildings, bare soil, 

mulched areas)

Herbivores/Insectivores

 Short Grass 2.1 1.8 0.96

 Tall Grass 0.96 0.82 0.44

 Broadleaf plants 1.2 1.0 0.54

 Fruits/pods 0.13 0.11 0.06

 Arthropods 0.82 0.70 0.38

 Seeds 0.03 0.02 0.01

0.25 lb a.i./A @ 4 apps/7-d

interval (annual app. 1.0 lb a.i./A) 

(sod farms - only in AL, FL, GA, 

NC, SC)

Herbivores/Insectivores

 Short Grass 1.7 1.4 0.77

 Tall Grass 0.77 0.66 0.35

 Broadleaf plants 0.94 0.81 0.43

 Fruits/pods 0.10 0.09 0.05

 Arthropods 0.66 0.56 0.30

 Seeds 0.02 0.02 0.01
49

Application Rate

(Crop)

Functional Feeding Group

Dietary Item

15 g 

mammals

35 g 

mammals

1000 g 

mammals

Chronic1 Chronic1 Chronic1

0.25 lb a.i./A @ 4 apps/14-d 

interval (annual app. 1.0 lb a.i./A) 

(spearmint)

Herbivores/Insectivores

 Short Grass 1.4 1.2 0.65

 Tall Grass 0.65 0.55 0.30

 Broadleaf plants 0.79 0.68 0.36

 Fruits/pods 0.09 0.08 0.04

 Arthropods 0.55 0.47 0.25

 Seeds 0.02 0.02 0.01

0.125 lb a.i./A @ 16 apps/14-d 

interval (annual app. 2.0 lb 

a.i./A) (i.e.,turnip & mustard 

greens) 

Herbivores/Insectivores

 Short Grass 1.0 0.89 0.48

 Tall Grass 0.48 0.41 0.22

 Broadleaf plants 0.59 0.50 0.27

 Fruits/pods 0.07 0.06 0.03

 Arthropods 0.41 0.35 0.19

 Seeds 0.01 0.01 0.01

0.125 lb a.i./A @ 10 apps/14-d 

interval (annual app. 1.25 lb 

a.i./A) (radishes)

Herbivores/Insectivores

 Short Grass 0.99 0.84 0.45

 Tall Grass 0.45 0.39 0.21

 Broadleaf plants 0.56 0.47 0.25

 Fruits/pods 0.06 0.05 0.03

 Arthropods 0.39 0.33 0.18

 Seeds 0.01 0.01 0.01

0.25 lb a.i./A @ 2 apps/7-d 

interval (annual app. 0.5 lb a.i./A) 

(i.e., dried beans, Christmas trees, 

cotton, forest trees, peanuts, 

potatoes, sainfoin, soybeans, sugar 

beets, sunflowers, sweet potatoes, 

tomatoes, trefoil, yams, lentils)

Herbivores/Insectivores

 Short Grass 0.95 0.82 0.44

 Tall Grass 0.44 0.37 0.20

 Broadleaf plants 0.54 0.46 0.25

 Fruits/pods 0.06 0.05 0.03

 Arthropods 0.37 0.32 0.17

 Seeds 0.01 0.01 0.01

Bold values exceed the chronic LOC of 1.0 1 Chronic RQ = (upper bound dose-based EEC, mg/kg-bw) / (NOAEC; mg/kg-bw).

Table 25. Mammalian Chronic Dietary-based RQ values for Application of Clethodim

Application Rate (Crop) Dietary Item Chronic RQ 1

0.25 lb a.i./A @18 apps/7-d interval

(annual app. 4.5 lb a.i./A) (fallow land, golf 

course turf, non-cropped areas; alfalfa)

Short Grass 0.85

Tall Grass 0.39

Broadleaf plants 0.48

Fruits/pods/seeds 0.05

Arthropods 0.33 1 Chronic RQ = (EEC, mg/kg-diet) / chronic NOAEC, mg/kg-diet; where the chronic NOAEC is 500 mg/kg-diet 
50

4.3. Terrestrial Invertebrates

Clethodim is classified as practically non-toxic to non-target terrestrial invertebrates on an acute 

contact exposure basis (LD50 >100 μg a.i./bee). RQ values could not be calculated because no 

definitive toxicity endpoints were available for honeybees. Risk to terrestrial invertebrates is 

discussed further in the Risk Description section.

4.4. Non-target Terrestrial and Semi-aquatic Plants

Clethodim is a post-emergence selective herbicide used on a variety of crops and non-crop areas 

to control a variety of grasses (monocotyledon plant species in the Poaceae family). Definitive 

toxicity values are available only for monocot plant species for clethodim; therefore, RQ values 

were not determined for dicot plants. All uses result in LOC exceedances to both listed and nonlisted terrestrial monocot plants from runoff in semi-aquatic environments, and listed monocot 

plants from drift and runoff to dry environments. Uses with application rates greater than 0.10 lb 

a.i./A also resulted in risk to non-listed monocot plants from drift, and uses greater than 0.125 lb 

a.i./A resulted in risk to listed and non-listed monocot plants from runoff and drift to all 

environments. For foliar aerial and chemigation uses of clethodim RQ values range from 0.41 to 

156.25 and for foliar ground uses of clethodim RQ values ranged from 0.42 to 131.25 (Table 

26). Again, three of the four monocot plant species that showed effects (corn, ryegrass, and oat) 

all belong to family Poaceae, the grass family (which is the same family as the target species of 

clethodim), whereas onion (which showed no effects) is in a different monocot family, family 

Liliaceae. Additional refinements and a spray drift analysis were completed and risk to terrestrial 

plants is discussed further in the Risk Description section. 

Table 26. Terrestrial Monocot Plants Inhabiting Dry and Semi-aquatic Areas Exposed to 

Clethodim via Runoff and Drift

Application Rate

(Crop)

Spray drift Dry area Semi-aquatic area

Listed 

Species 

RQ1

Non-listed 

Species

RQ2

Listed 

Species 

RQ1

Non-listed 

Species

RQ2

Listed 

Species 

RQ1

Non-listed 

Species

RQ2

Foliar Aerial and Chemigation Applications

0.25 lb a.i./A (Aerial - fallow land, 

golf course turf, non-cropped areas, 

alfalfa, clover, dried beans, 

Christmas trees, cotton, forest trees, 

peanuts, potatoes, sainfoin, 

soybeans, sugar beets, sunflowers, 

sweet potatoes, tomatoes, trefoil, 

yams, mint, lentils, sod farms); 

(Chemigation - garlic and onions)

5.25 4.17 43.75 2.30 156.25 8.22
51

Application Rate

(Crop)

Spray drift Dry area Semi-aquatic area

Listed 

Species 

RQ1

Non-listed 

Species

RQ2

Listed 

Species 

RQ1

Non-listed 

Species

RQ2

Listed 

Species 

RQ1

Non-listed 

Species

RQ2

0.125 lb a.i./A (Aerial - turnip greens, 

mustard greens, herbs, beets, brassica 

vegetables, carrots, cranberries, 

cucurbit vegetables, fruiting 

vegetables, leafy vegetables,

strawberries, radishes, tree fruits, tree 

nuts, asparagus, hops, safflower, 

sesame, artichokes, bushberries 

including cranberries, caneberries, 

peaches, flax, meadowfarm, seeds,

succulent beans, legume vegetables, 

dried and succulent peas)

2.72 2.08 21.88 1.15 78.13 4.11

0.10 lb a.i./A (Aerial - canola) 2.17 1.67 17.50 0.92 62.50 3.29

0.045 lb a.i./A (Aerial - corn - field) 0.98 0.75 7.88 0.41 28.13 1.48

Foliar Ground Applications

0.25 lb a.i./A (ornamentals, 

landscaped areas, non-bearing food 

crops, around buildings, bare soil, 

mulched areas)

1.09 0.83 18.75 0.99 131.25 6.91

0.125 lb a.i./A (sage, kenaf) 0.54 0.42 9.38 0.49 65.63 3.45

Bold values exceed the terrestrial plant LOC of 1.0 1 Listed Plant species RQ = (EEC) / EC25 2 Non-listed Plant species RQ = (EEC) / NOAEC (EC05)

5. RISK DESCRIPTION

5.1. Risks to Aquatic Organisms

5.1.1. Fish (surrogates for aquatic-phase amphibians)

Exposures to clethodim residues of concern resulted in RQ values that exceeded the chronic risk 

LOC (1.0) for fish (surrogates for aquatic-phase amphibians) for all 67 labeled uses and use 

groups of clethodim (Table 20). There was no acute risk (listed or non-listed) LOC exceedances 

for fish (Table 20).

Using the highest exposure estimates for alfalfa, the chronic LOC (RQ>1.0) is continuously 

exceeded (RQ>2) from the first year until the end of the model simulation (Figure 1).
52

Figure 1. Exposure estimates from the maximum use pattern on alfalfa

Although the chronic level of concern was exceeded for all uses of clethodim, there are 

numerous uncertainties associated with this risk call. First, the only available chronic fish 

toxicity study using fathead minnow did not measure the typical sublethal (growth or 

reproduction) endpoints for fish, the only endpoint that was measured was survival; and 

therefore, the NOAEC could potentially be an underestimation of risk to fish, and actual 

endpoint could potentially be even lower. Second, the most sensitive acute fish toxicity value 

was for a different species (rainbow trout), and the chronic toxicity value that was used in the 

risk assessment is an ACR derived NOAEC that relies on an extrapolation among species 

(fathead minnow); to try and account for the potential difference in sensitivity among species on 

an acute and chronic basis.

Third, there is a lack of aerobic aquatic metabolism data resulting in a conservative assumption 

for aquatic exposure modeling. Fourth, there is a lack of toxicity data for the residues of concern 

resulting in the assumption that they are no more or less toxic than the parent compound because 

its toxic moiety appears to potentially be intact (USEPA, 2008). If the degradates of concern 

were shown to be much less toxic than clethodim, then exposure estimates and the resulting RQ 

values for clethodim alone in this assessment would be 4-13x lower. When clethodim is 

modeled alone, the risk to listed and non-listed fish on a chronic exposure basis for use on alfalfa 

is decreased by 13x (8.6 μg/L versus 108 μg/L). However, this change in aquatic exposure 

modeling does not decrease the RQ value below the chronic risk LOC for fish (surrogates for 

aquatic-phase amphibians), which is also the case for any use of clethodim with multiple 

applications allowed per year. If both 1) the degradates of concern were shown to be much less 

toxic than clethodim and 2) uses were limited to one application per year, then RQ values for 

clethodim alone in this assessment would decrease to a value below the chronic risk LOC for 

fish.

In summary, concern levels were exceeded for chronic exposures to fish and aquatic phase 

amphibians. In addition, fish may be indirectly impacted by potential impacts to monocot plants 

(risks to monocot plants are discussed below). 

0

20

40

60

80

100

120

140

1/1/1965 6/24/1970 12/15/1975 6/6/1981 11/27/1986

Concentration (μg/L)

Date
53

5.1.2. Aquatic Invertebrates

Exposures to clethodim residues of concern did not result in RQ values that exceeded the acute

listed species or chronic listed or non-listed species LOCs (0.05 and 1.0, respectively) for aquatic

invertebrates. However, based on the adverse direct effects to fish (surrogates for aquatic-phase 

amphibians) (on a chronic exposure basis), and terrestrial monocot plants, as discussed below, 

there is still the potential for indirect effects to aquatic invertebrates resulting from changes in 

the aquatic ecosystem. 

5.1.3. Aquatic Plants

There were no LOC exceedances for aquatic plants exposed to clethodim residues of concern. 

Aquatic vascular plants were the most sensitive aquatic plant species to clethodim (EC25 = 1.34 

mg a.i./L; NOAEC = 0.94 mg a.i./L), and they did not result in risk to listed or non-listed aquatic 

plants. Although there is open literature data for aquatic non-vascular plants that show a more 

sensitive EC25 value than registrant submitted data, the toxicity value is still less toxic than the

aquatic vascular plant toxicity data, which did not show risks of concern from exposure to 

clethodim. However, based on the adverse effects to fish (surrogates for aquatic-phase 

amphibians) (on a chronic exposure basis), and terrestrial monocot plants, as discussed below, 

there is still the potential for indirect effects to aquatic plants resulting from changes in the 

aquatic ecosystem.

5.2. Risks to Terrestrial Organisms

5.2.1. Terrestrial Animals

5.2.1.1. Birds (surrogates for reptiles and terrestrial-phase amphibians)

There were no avian mortalities observed in the acute oral or sub-acute dietary toxicity studies at 

the highest treatment levels that were tested (i.e., LC50 endpoints are ‘greater than’ values); 

therefore, these endpoints were not used to calculate RQ values. However, in the acute oral 

bobwhite quail study overt signs of toxicity (i.e., lethargy, wing droop and ruffled appearance) 

and a reduction of body weight gain was observed in the 1650 mg a.i./kg-bw concentration, and 

no effects (lethal or sublethal) were observed in the 1250 mg a.i./kg-bw concentration. A 

comparison of the dose-based EEC values to the no mortality level and the concentrations at 

which sublethal effects were observed is presented in Figure 2. There were no effects observed 

in the sub-acute dietary toxicity study, and a comparison of the dietary-based EEC values to the 

no effect level (representing mortality and sublethal effects) is presented in Figure 3.
54

Figure 2. Comparison of the acute dose-based EEC values for small (20g) birds consuming 

short grass to levels where sublethal effects were observed.

Figure 3. Comparison of the dietary-based EEC values for small (20g) birds consuming 

short grass to no effect levels from the sub-acute dietary toxicity study.

For small birds (20g) consuming short grass the maximum dose-based EEC value that was 

calculated (484 mg a.i./kg-bw) was for the maximum annual application rate (4.5 lb a.i./A) that 

was modeled. The maximum application rates that were modeled were all based on conservative 

0

200

400

600

800

1000

1200

1400

1600

1800

2000

18 9 6 3 2

Avian Acute Dose-based EEC Values for Short 

Grass (mg a.i./kg-bw)

# of applications per year

Fallow land Clover Ornamentals Alfalfa Hay

Sublethal effects were observed = 1650 mg a.i./kg-bw

Highest test concentration; no mortality, sublethal effects were observed; LD50 > 2000 mg a.i./kg-bw

No sublethal effects observed = 1250 mg a.i./kg-bw

No sublethal effects observed = 875 mg a.i./kg-bw

No sublethal effects observed = 500 mg a.i./kg-bw

0

300

600

900

1200

1500

1800

2100

2400

2700

3000

3300

3600

3900

18 9 6 3 2

Avian Sub-acute Dietary-based EEC Values for 

Short Grass (ppm) 

# of applications per year

Fallow land Clover Ornamentals Alfalfa Hay

No effects were observed at 2750 mg/kg-diet 

Highest concentration; no mortality & no sublethal effects were observed LC50 > 3978 mg a.i./kg-diet

No effects were observed at 1290 mg/kg-diet 

No effects were observed at 600 mg/kg-diet 
55

assumptions. The maximum dose-based EEC value (484 mg a.i./kg-bw) is three (3) times less 

than the lowest test level at which sublethal effects were observed. The maximum dietary-based 

EEC value (425 mg a.i./kg-diet) is nine (9) times less than the highest test concentration (3978 

mg a.i./kg-diet), where no effects (lethal or sublethal) were observed. 

There were no chronic listed and non-listed LOC exceedances for birds (Table 20). However, 

there is only one avian reproduction study available for clethodim and no effects on survival, 

behavior, growth or reproduction were observed in mallard ducks. Therefore, there is some 

uncertainty if the northern bobwhite quail would have similar sensitivity to chronic clethodim 

exposure. Therefore, to further characterize the potential risk to birds on a chronic basis, avian 

reproduction data for chemicals of the same cyclohexene oxime herbicide family class were 

reviewed; tralkoxydim (PC 121000), sethoxydim (PC 121001), and tepraloxydim (PC 121005). 

Sethoxydim (PC 121001) and tepraloxydim (PC 121005) both have at least one avian 

reproduction toxicity study with observed definitive endpoints; there were issues with the control 

birds in the tralkoxydim avian reproduction studies, and therefore the data could not be used for 

comparison. 

Sethoxydim is the only chemical with both mallard and bobwhite quail avian reproductive 

toxicity data, and based on the results of these studies, the mallard duck was the more sensitive 

bird species (NOAEC = 512 ppm and LOAEC = 1047 ppm (expressed as clethodim a.i.), based 

on reduction in hatchability; MRID 48000901). No effects were observed in the sethoxydim 

bobwhite quail reproductive toxicity test (MRID 44003401). For tepraloxydim, the bobwhite 

quail is the only reproductive toxicity data available (NOAEC = 382 ppm and LOAEC = 1093 

ppm (expressed as clethodim a.i.), based on reduction in hatchability, reduction in percent 

normal hatchlings of eggs laid, reduction in normal hatchlings of eggs set, and reduction of 14-

day old survivors of eggs set; MRID 44467123). For both of these other chemicals the 

concentration where the lowest effects where observed were both greater than the maximum test 

concentration of clethodim, in which no effects were observed. A comparison of the dietarybased EEC values to the no effect level is presented in Figure 4. 
56

Figure 4. Comparison of the dietary-based EEC values for small (20g) birds consuming 

short grass to NOAEC levels in the chronic dietary toxicity studies available for 

cyclohexene oxime herbicide family class of chemicals.

The maximum dietary-based EEC value (425 mg a.i./kg-diet) is two (2) times less than the 

highest test concentration (833 mg a.i./kg-diet), where no effects (lethal or sublethal) were 

observed. Based on the results of the chronic toxicity clethodim does appear to be less toxic on a 

chronic exposure basis than the other two cyclohexene oxime herbicide family chemicals 

(sethoxydim and tepraloxydim). 

For both acute and chronic exposure measurements, it is important to note a major uncertainty;

the EECs used in the RQ calculations for birds were based on the single maximum application 

rate using the minimum application interval between successive applications. It is important to 

note that the estimated EEC values are based on conservative assumptions that were made 

regarding the application methodology of clethodim. In the absence of label directions for the 

maximum annual application, the potential total number of crop cycles were used to conduct a 

screening-level risk assessment. The modeled input parameters, used very conservative 

assumptions that new crop cycles would be occurring every two weeks; however, that may not 

be realistic representation of field practices. Therefore, if additional information was provided 

for annual application limits and crop cycle duration, a more refined analysis could be 

completed, and under more realistic conditions the EEC values would likely decrease. However, 

there are no LOC exceedances for listed and non-listed birds on a chronic basis. 

In combination with the lack of reproductive effects to mammals when exposed to clethodim (as 

discussed below), available chronic toxicity data for two cyclohexene oxime herbicide family 

chemicals, and the potential decreased dose-based and dietary-based EEC values based on field

practices, potential direct effects to listed and non-listed birds on an acute and/or chronic 

exposure basis is below concern levels. However, based on the adverse effects to terrestrial 

monocot plants, as discussed below, there is still the potential for indirect effects to birds 

0

125

250

375

500

625

750

875

1000

18 9 6 3 2

AvianChronic Dietary-based EEC Values for 

Short Grass (ppm)

# of applications per year

Fallow land Clover Alfalfa Hay

Highest test concentration; no effects: NOAEC = 833 ppm clethodim a.i.

Sethoxydim; reduced hatchability; Mallard: NOAEC = 512 ppm (as clethodim a.i.)

Tepralkoxydim; reduced hatchability; Bobwhite: NOAEC = 382 ppm (as clethodim a.i.)

Sethoxydim; Mallard: LOAEC = 1047 ppm (as clethodim a.i.)

Tepralkoxydim; Bobwhite: LOAEC = 1093 ppm (as clethodim a.i.)
57

(surrogates for terrestrial-phase amphibians) resulting from changes in the diet and habitat of 

listed birds (surrogates for terrestrial-phase amphibians). 

5.2.1.2. Mammals

For the all uses of clethodim, there were no LOC exceedances for non-listed mammals on an 

acute exposure basis (dose-based). On an acute exposure basis there were LOC exceedances for 

listed small (15g) mammals consuming short grass for all uses with a total annual application 

rate greater than 2.0 lb a.i./A (Table 21, RQs = 0.10-0.14), and medium (35g) mammals 

consuming short grass at the highest use pattern on fallow land, golf course turf, non-cropped 

areas, and alfalfa (Table 21, RQ = 0.12) . A comparison of the dose-based EEC values for small 

and medium sized mammals to the no mortality level and the concentrations at which sublethal 

effects were observed is presented in Figure 5 and Figure 6, respectively. For all of the 

remaining use patterns of clethodim with total annual application rates of equal to or less than 

2.0 lb a.i./A (Table 3), or if there is a 14-day interval for the maximum single application rate of 

0.25 lb a.i./A (i.e., ornamentals, landscaped areas, non-bearing food crops, around buildings, bare 

soil, mulched areas), there were no acute listed species LOC exceedances (Table 21, RQ≤0.08). 

Figure 5. Comparison of the dose-based EEC values for small (15g) mammals consuming 

short grass to concentrations where mortality and sublethal effect were observed in the 

acute oral toxicity study.

0

250

500

750

1000

1250

1500

1750

2000

2250

2500

18 9 6

Acute Mammalian dose-based EECs (small 15g) 

mammals consuming short grass (mg a.i./kg-bw)

# of applications per year

Fallow land Clover Ornamentals Alfalfa Hay

Highest test concentration; mortality and sublethal effects were observed = 2500 mg/kg-bw (M)

Highest test concentration; mortality and sublethal effects were observed = 2000 mg/kg-bw (F)

LD50 = 1360 mg/kg-bw (F)

Sublethal effects were observed = 800 mg/kg-bw

Sublethal effects were observed = 1450 mg/kg-bw

Sublethal effects were observed = 1860 mg/kg-bw

LD50 = 1630 mg/kg-bw (M)
58

Figure 6. Comparison of the dose-based EEC values for medium (35g) mammals 

consuming short grass to concentrations where mortality and sublethal effect were 

observed in the acute oral toxicity study.

For mammals, although the chronic LOC was exceeded for multiple size classes and dietary 

items, no reproductive effects were observed in the mammalian two-generation reproduction 

study. All uses with an annual application rate of less than 1.25 lb a.i./A, based on conservative 

assumptions do not result in chronic risk to mammals (Table 22). Chronic dose-based RQ 

values for uses with application rates greater than 1.25 lb a.i./A ranged from 1.04 - 3.62 (Table 

22). Dietary-based RQs did not exceed the chronic LOC for any use of clethodim (Table 23). 

The NOAEC (500 ppm; 51 mg/kg-bw/day) from the two-generation mammalian reproduction 

toxicity study was based on decreased body weight and food consumption in parental organisms 

at the 2500 ppm test concentration (approx. 263 mg/kg-bw/day). There were no adverse effects 

on reproductive performance or survival of either generation during the two-generation toxicity 

study. Comparisons of the dose-based EEC values to the levels where effects to adults were and 

were not observed are presented in Figure 7. The maximum dose-based EEC value (405) is 8 

times greater than the highest test concentration (51 mg/kg-bw/day), where no effects were 

observed. 

0

250

500

750

1000

1250

1500

1750

2000

2250

2500

18 9 6

Acute Mammalian dose-based EECs (medium 35g) 

mammals consuming short grass (mg a.i./kg-bw)

# of applications per year

Fallow land Clover Ornamentals Alfalfa Hay

LD50 = 1630 mg/kg-bw (M)

LD50 = 1360 mg/kg-bw (F)

Highest test concentration; mortality and sublethal effects were observed = 2500 mg/kg-bw (M)

Highest test concentration; mortality and sublethal effects were observed = 2000 mg/kg-bw (F)

Subethal effects were observed = 1860 mg/kg-bw

LD50 = 1630 mg/kg-bw (M)

Sublethal effects were observed = 1450 mg/kg-bw

LD50 = 1360 mg/kg-bw (F)

Sublethal effects were observed = 800 mg/kg-bw
59

Figure 7. Comparison of the dose-based EEC values for small (20g) mammals consuming 

short grass to NOAEL/LOAEL levels in the chronic toxicity study for mammals.

However, it should be noted that a majority of these acute and chronic LOC exceedances for 

multiple dietary items, and size classes of mammals are for use patterns that do not have detailed 

annual application rates, and often have multiple crop cycles per year (i.e., fallow land, golf 

course turf, non-cropped areas; alfalfa; clover; and grass forage/fodder/hay). The EECs used in 

the RQ calculations for mammals were based on the single maximum application rate using the 

minimum application interval between successive applications. It is important to note that the 

estimated EEC values are based on conservative assumptions that were made regarding the 

application methodology of clethodim. In the absence of label directions for the maximum 

annual application, the potential total number of crop cycles were used to conduct a screeninglevel risk assessment. Also, the modeled input parameters, used very conservative assumptions 

that new crop cycles would be occurring every two weeks; however, that may not be realistic 

representation of field practices. Therefore, if additional information was provided for annual 

application limits and crop cycle duration, a more refined analysis could be completed, and under 

more realistic conditions the EEC values would likely decrease, which in turn could reduce RQ 

values to below the LOCs. 

In combination with the lack of reproductive effects to mammals when exposed to clethodim, 

and the likelihood of decreased dose-based and dietary-based EEC values with additional 

information, direct effects to listed and non-listed mammals on an acute and chronic exposure 

basis is unlikely. However, based on the adverse effects to terrestrial monocot plants, as 

discussed below, there is still the potential for indirect effects to mammals resulting from 

changes in the diet and habitat of listed mammals. 

0

50

100

150

200

250

300

350

400

450

500

18 9 6 3 2 1

Mammalian chronic dose-based EECs small (15g) 

mammals (mg a.i./kg-bw)

# applications per year

Fallow land Clover Ornamentals Alfalfa Hay

LOAEL = 263 mg/kg-bw/day (2500 ppm); reduced body weight & food consumption

NOAEL = 51 mg/kg-bw/day (500 ppm); No effects
60

5.2.1.3. Terrestrial Invertebrates

Based on the acute contact honeybee study, clethodim is classified as practically non-toxic. In 

the acute contact study with the Select 2EC formulation, although 22% mortality was observed 

in the 100 μg a.i./bee dose group, the 48-hour LD50 was >100 μg a.i./bee. No signs of toxicity 

were observed in dose groups less than 100 μg a.i./bee, the resulting no-effect dose level was 60 

μg a.i./bee. Although there is no toxicity data for other life stages of honey bee, which could 

result in differences not captured by adult acute toxicity studies, there appears to be a low 

likelihood of potential direct effects to terrestrial invertebrates from clethodim use. 

5.2.2. Terrestrial Plants

Clethodim is a post-emergence selective herbicide used on a variety of crops and non-crop areas 

to control a variety of grasses (monocotyledon plant species in the poaceae family). TerrPlant 

(version 1.2.2, 05/28/2013) was used to calculate EECs from runoff and drift resulting from a 

single pesticide application, and are presented in Table 24. There were no adverse effects 

observed for dicot plants, and therefore RQ values were not determined for dicot plant species. 

All uses of clethodim result in LOC exceedances to both listed and non-listed terrestrial monocot 

plants from runoff in semi-aquatic environments, and listed monocot plants from drift and runoff 

to dry environments. Uses of clethodim with a single application greater than 0.125 lb a.i./A 

resulted in risk to listed and non-listed monocot plants from runoff and drift to all environments. 

Of the four monocot plant species that were tested, three, (corn, ryegrass, and oat) showed 

adverse effects to clethodim application, whereas onion did not show any adverse effects to 

clethodim application. The three species (corn, perennial ryegrass, and oats) all belong to family 

Poaceae, the grass family (which is the same family as the target species of clethodim), whereas 

onion (which showed no effects) is in a different monocot family, family Liliaceae. However, 

there are numerous other monocot families that are not represented, but there is evidence to 

suggest based on the mode of action of clethodim, and the mechanism of selectivity within grass 

species for the ACCase enzyme site of action, suggests that there are differential sensitivity 

between grass species, and species (Hess, 1997). 

Although there were two reported incidents in the EIIS database involving clethodim and 

terrestrial dicot plants (I002969-058 and I022217-034), both of these incidents were of 

undetermined legality and clethodim was listed as a “possible” cause of the alleged damage to

cotton and soybean. Cotton and soybeans are dicots, and based on the available toxicity data for 

clethodim, these species would not be expected to be sensitive to clethodim as it is an herbicide 

that targets monocot grass species. Although very little information is available for I002969-

058, the cotton crop injury that was observed after the use of Select 2EC (the active ingredient is 

clethodim), tissue testing was completed to determine that Select (clethodim a.i.) was not likely 

the cause of the injury. However, it is unclear if another pesticide was involved in this incident. 

For I022217-034, the damage to the soybean crop after the product Ignite 280 SL (a.i. 

glufosinate-ammonium) and Select (a.i. clethodim) were applied was likely the result of tank 

contamination; however, it is not clear which chemical the tank contaminated wit (clethodim or 

glufosinate-ammonium). However, it should be noted that glufosinate-ammonium does have 
61

definitive toxicity data available and effects observed on dicot and monocot plants (USEPA, 

2013). 

To evaluate exposure from spray drift, AgDrift (v2.1.1) was used. Due to plant LOC 

exceedances for all application rates, AgDrift was used to estimate the distances from the edge of 

the field for which risks to non-listed and listed monocot plant species extend to for aerial and 

ground spray applications. For aerial applications AgDrift was run using large (medium to 

coarse and coarse to very coarse) droplet size distribution, and application rates of 0.045 to 0.25 

lbs a.i./A; and for ground applications AgDrift was run using high and low boom ground spray, 

fine to medium/coarse droplet size distributions, and application rates of 0.25 and 0.125 lbs 

a.i./A (Table 27 and Table 28, non-listed and listed monocots, respectively). Example 

input/outputs from AgDrift for clethodim can be found in Appendix F.

Table 27. Distances from the edge of the field for which risks extend for non-listed monocot

plant species exposed to clethodim.

Application 

method Droplet size distribution

Application 

rate 

(lb a.i./A)

Distance (ft) for 

vegetative vigor 

endpoint1

Distance (ft) for 

seedling emergence 

endpoint2

Aerial

medium-coarse 0.25 358 171

coarse-very coarse 233 118

medium-coarse 0.125 203 95

coarse-very coarse 137 69

medium-coarse 0.10 174 79

coarse-very coarse 118 49

medium-coarse 0.045 85 26

coarse-very coarse 62 23

Ground

fine to medium/coarse; high boom height 0.25 52 16

fine to medium/coarse; low boom height 26 10

fine to medium/coarse; high boom height 0.125 23 10

fine to medium/coarse; low boom height 13 7 1

Most sensitive vegetative vigor EC25 = 0.003 lb a.i./A (ryegrass), most sensitive parameter was dry weight. 2 Most sensitive seedling emergence EC25 = 0.0076 lb a.i./A (oat), most sensitive parameter was plant height.

Table 28. Distances from the edge of the field for which risks extend for listed monocot

plant species exposed to clethodim.

Application 

method Droplet size distribution

Application 

rate 

(lb a.i./A)

Distance (ft) for 

vegetative vigor 

endpoint1

Distance (ft) for 

seedling emergence 

endpoint2

Aerial

medium-coarse 0.25 463 >997

coarse-very coarse 289 >997

medium-coarse 0.125 253 >997

coarse-very coarse 171 955

medium-coarse 0.10 213 >997

coarse-very coarse 144 682

medium-coarse 0.045 112 479

coarse-very coarse 75 299

Ground fine to medium/coarse; high boom height 0.25 72 525

fine to medium/coarse; low boom height 39 367
62

fine to medium/coarse; high boom height 0.125 30 259

fine to medium/coarse; low boom height 16 157

* EC05 is used when a NOAEC could not be calculated or NOAEC is higher than the EC25 1

Most sensitive vegetative vigor NOAEC* = 0.0023 lb a.i./A (ryegrass), most sensitive parameter was dry weight. 2 Most sensitive seedling emergence NOAEC* = 0.0004 lb a.i./A (oat), most sensitive parameter was plant height.

Based on the AgDrift spray drift analysis, and the refinements made for aerial applications, all 

aerial uses of clethodim result in risk to listed terrestrial monocot plants, at distances of 75 to 

>997 feet from the edge of the field; and risks to non-listed terrestrial monocot plants extend 7 to 

358 feet from the edge of the field. For ground applications, based on the refinement of boom 

height risks to listed terrestrial monocot plants, at distances of 16 to 367 feet from the edge of 

the field; and risks to non-listed terrestrial monocot plants extend 7 to 26 feet from the edge of 

the field.

The direct risk to listed and non-listed terrestrial dicot plants from clethodim use is anticipated to 

be very low. However, based on the information above, and the anticipated off-field effect area, 

risk to listed and non-listed monocot plants, specifically those in the Poaceae (grass) family,

from clethodim use is anticipated to be very high. 

5.3. Probit Slope Response Analysis of LOC Values and Acute RQ Values

As part of the risk estimation, the odds of an individual effect (mortality) from exposure to 

clethodim were estimated. The probability of mortality calculations are based on the probit slope 

dose-response relationship from acute studies. The probability of mortality for an exposed 

individual are calculated using an Excel spreadsheet tool IECV1.1 (Individual Effect Chance 

Model Version 1.1) developed by EFED of the U.S. EPA, OPP, Environmental Fate and Effects 

Division (June 22, 2004).

The acute toxicity results consisted of limit dose type tests (e.g., avian acute oral toxicity), and 

other acute studies which did not provide data which can be used to calculate a probit doseresponse slope. In these cases (for acute fish and avian acute oral), the odds of mortality were 

only calculated for the listed acute LOC using the default slope of 4.5 (95% CL 2, 9). A probit 

slope was available for the following studies: acute mammal, and aquatic invertebrate toxicity. 

The probit slope for the acute oral toxicity study with the rat was 1.39; 95% CL of 0.84 and 2.30, 

the probit slope for the acute toxicity study with the daphnid was 4.57; 95% CL of 2.62, and 

6.53, and the probit slope for the shell deposition toxicity study with the oyster was 2.04; 95% 

CL of 1.78, and 2.30. The odds of mortality for an individual at the RQ value or endangered 

species LOC for terrestrial and aquatic animals based on the slopes discussed in the previous 

paragraph are provided in Table 29. 
63

Table 29. Probit Slope and Odds of Mortality for an Individual at the RQ/LOC for Uses of 

Clethodim

Listed 

Species Birds1 Mammals Fish2

Aquatic Invertebrates

Freshwater 

(Daphnids)

Estuarine/

Marine 

(Oyster)

RQ/LOC 0.1 (LOC)

RQ (15 g & 35 g mammals) = 

0.14 & 0.12 (fallow land, golf 

course turf, non-cropped areas; 

alfalfa); 

RQ (15 g mammals) = 0.11 

(clover); 

RQ (15 g mammals) = 0.10 (grass 

forage/ fodder/hay)

0.05 (LOC) RQ = 0.006 RQ = 0.02

Slope 4.51 1.39 4.52 4.57 2.04

Slope 

95% CL 2, 91 0.84, 2.30 2, 92 2.62, 6.53 1.78, 2.30

Odds of 

individual 

effect

1 in 2.94 x 105

1 in 8.5 & 1 in 10 (15 g & 35 g 

mammals) (fallow land, golf 

course turf, non-cropped areas; 

alfalfa); 

1 in 11 (15 g mammals) (clover); 

1 in 12.2 (15 g mammals) (grass 

forage/ fodder/hay)

1 in 4.18 x 108 1 in 4580 1 in 48.4

95% CL 1 in 44, 

1 in 8.86 x1018

1 in 4.23,1 in 40.4 & 1 in 4.55, 1 

in 58.5 (15 g & 35 g mammals) 

(fallow land, golf course turf, 

non-cropped areas; alfalfa); 

1 in 4.8, 1 in 72.8 (15 g 

mammals) (clover); 

1 in 5, 1 in 93.2 (15 g mammals) 

(grass forage/fodder/hay)

1 in 216, 

1 in 1.75 x 1031

1 in 45.7, 

1 in 3.98 x 106

1 in 26.6, 

1 in 93.2

1

As the study resulted in a non-definitive value (LC50 > highest concentration tested), and the use of a probit model 

was not appropriate; therefore, default mean slope value (4.5) and 95% CL (2, 9) is used. 2 For the freshwater fish toxicity study no mortalities were observed in the study, and the use of a probit model was 

not appropriate; therefore, default mean slope value (4.5) and 95% CL (2, 9) is used. The estuarine/marine fish 

toxicity study resulted in a non-definitive value (LC50 > highest concentration tested), and the use of a probit model 

was not appropriate; therefore, default mean slope value (4.5) and 95% CL (2, 9) is used.

Based on the calculated odds of mortality for an individual effect using conservative assumptions 

for the highest application rate, the odds for an individual effect for terrestrial organisms are as 

follows: birds range from <0.01 to 2%; and for mammals range from 2 to 23% (for small, 15g, 

mammals) and 2 to 22% (for medium, 35g, mammals). Although there are no LOC exceedances 

for aquatic organisms (RQ<0.05), the odds for an individual effect range from <0.01 to 0.5% for 

fish; <0.01 to 2% for freshwater invertebrates; and 1 to 4% for estuarine/marine invertebrates. 
64

5.4. Re-evaluation of the Risk Hypothesis

The results of this preliminary risk assessment indicate that the uses of clethodim have the 

potential for direct adverse effects to listed and non-listed non-target monocot plants, chronic 

risk to birds (and, thus, reptiles and terrestrial-phase amphibians), and mammals, acute effects to 

mammals, and potential acute effects to birds (and, thus, reptiles and terrestrial-phase 

amphibians), and chronic effects to freshwater and estuarine/marine fish. Therefore, the risk 

hypotheses based on the risk assessment [Clethodim, when used in accordance with the label, 

results in potential adverse effects upon survival, growth, and reproduction of non-target 

monocot plants, especially within family Poaceae, exposed to runoff and drift from areas >1000 

feet from the edge of fields treated with clethodim. Use of clethodim also results in potential 

adverse effects to fish when exposed on a chronic basis to drift and runoff from areas treated 

with clethodim. Although clethodim is fairly non-persistent, it is mobile and is expected to occur 

in adjacent aquatic ecosystems on a continuous or recurrent basis. Also, the major toxic 

degradates of concern (clethodim sulfoxide and clethodim sulfone) are much more mobile and 

persistent than the parent. Thus, there is a possibility for exposure to the residues of concern 

(parent plus degradates) to non-target organisms from use of clethodim], was not disproven. 

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2010). http://www.hracglobal.com/Publications/WorldofHerbicidesMap.aspx

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

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F. Korte, eds., Environmental Quality and Safety: Chemistry, Toxicology, and 

Technology, Georg Thieme Publ., Stuttgart, West Germany, pp. 9-28.

U.S. Environmental Protection Agency (USEPA). 1993. Wildlife Exposure Handbook, United 

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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. 

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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.
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USEPA. 2006. User’s Guide TerrPlant version 1.2.2. United States Environmental Protection 

Agency, Office of Pesticide Programs, Environmental Fate and Effects Division.

December 2006.

USEPA. 2007. Kaul, M. Maximum Number of Crop Cycles per Year in California for Methomyl 

Use Sites. U.S. Environmental Protection Agency, Office of Prevention, Pesticides, and 

Toxic Substances, Biological and Economic Analysis Division. Memorandum to the 

Environmental Fate and Effects Division. Feb. 28, 2007.

USEPA. 2008. Dean, R. and J. Angier. Registration Review – Preliminary Problem Formulation 

for the Ecological Risk Assessment of Clethodim. DP barcode 349758. U.S. 

Environmental Protection Agency, Office of Pesticide Programs, Environmental Fate and 

Effects Division. Memorandum to the Special Review and Reregistration Division. Aug. 

13, 2008.

USEPA. 2009. Guidance for Selecting Input Parameters in Modeling the Environmental Fate and 

Transport of Pesticides. Version 2.1. U.S. Environmental Protection Agency, Office of 

Pesticide Programs, Environmental Fate and Effects Division. Oct. 22, 2009.

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

USEPA. 2012. Clethodim (121011): Screening Level Usage Analysis (SLUA). U.S. 

Environmental Protection Agency, Office of Pesticide Programs, Biological and 

Economic Analysis Division. Sep. 6, 2012.

6.1. Ecotoxicity Studies

71-1 Avian Single Dose Oral Toxicity

MRID Citation Reference

40974525 Hinken, C.; Grimes, J. (1986) RE-45601 Technical (SX-1688): An Acute Oral Toxicity Study 

with the Bobwhite: Project ID: S-2830. Unpublished study prepared by Wildlife International 

Ltd. 63 p.

71-2 Avian Dietary Toxicity

MRID Citation Reference

40974526 Hinken, C.; Grimes, J. (1986) RE-45601 Technical (SX-1688): A Diet- ary LC50 Study with the 

Bobwhite: Project ID: S-2832. Unpublished study prepared by Wildlife International Ltd. 48 p. 

40974527 Hinken, C.; Grimes, J.; Jaber, M. (1986) RE-45601 Technical (SX-1688): A Dietary LC50 

Study with the Mallard: Project ID: S-2831. Unpublished study prepared by Wildlife 

International Ltd. 54 p. 

71-4 Avian Reproduction

MRID Citation Reference

41030205 Beavers, J. (1988) RE-45601 Technical: A One-generation Reproduction Study with the Mallard 

(Anas platyrhynchos): Project ID S-28- 37. Unpublished study prepared by Wildlife 
66

International, Ltd. 155 p. 

72-1 Acute Toxicity to Freshwater Fish

MRID Citation Reference

40974528 Swigert, J. (1986) Acute Toxicity of Chevron RE-45601 Technical to Rainbow Trout in a Static 

Test System: Project ID: S-2838. Un- published study prepared by ABC Laboratories, Inc. 50 p. 

40974529 Swigert, J. (1986) Acute Toxicity of Chevron RE-45601 Technical to Bluegill Sunfish in a Static 

Test System: Project ID: S-2839. Unpublished study prepared by ABC Laboratories, Inc. 50 p. 

850.1075 Fish acute toxicity test, freshwater and marine

MRID Citation Reference

48104304 Bidinotto, P. (2003) Acute Toxicity of Clethodim Agan Technical to Fish Danio rerio: Final 

Report. Project Number: 90005085, RF/0409/208/099/02. Unpublished study prepared by 

BIOAGRI Laboratorios, Ltda. 59 p.

48417002 Palmer, S.; Kendall, T.; Krueger, H. (2011) Clethodim: A 96-Hour Static Renewal Acute 

Toxicity Test wtih the Fathead Minnow (Pimephales promelas). Project Number: 201100054, 

263A/121, VP/37738. Unpublished study prepared by Wildlife International, Ltd. 57 p.

48417003 Palmer, S.; Kendall, T.; Krueger, H. (2011) Clethodim: A 96-Hour Static-Renewal Acute 

Toxicity Test with the Rainbow Trout (Oncorhynchus mykiss). Project Number: 201100055, 

263A/122, VP/37733. Unpublished study prepared by Wildlife International, Ltd. 55 p.

48417004 Palmer, S.; Kendall, T.; Krueger, H. (2011) Clethodim: A 96-Hour Static-Renewal Acute 

Toxicity Test with the Sheepshead Minnow (Cyprinodon variegatus). Project Number: 

201100057, 263A/124, VP/37743. Unpublished study prepared by Wildlife International, Ltd. 

53 p.

72-2 Acute Toxicity to Freshwater Invertebrates

MRID Citation Reference

40974530 Forbis, A. (1986) Acute Toxicity of Chevron RE-45601 Technical to Daphnia magna in a Static 

System: Project ID: S-2835. Unpublished study prepared by ABC Laboratories, Inc. 49 p. 

41685101 Burgess, D.; Blasberg, J.; Stuerman, L. (1990) Acute Toxicity of Select 2EC to Daphnia magna: 

Lab Project Number: 38601: 89-437: 6065. Unpublished study prepared by Analytical Biochemistry Laboratories, Inc. 53 p. 

850.1035 Mysid acute toxicity test

MRID Citation Reference

48417001 Palmer, S.; Kendall, T.; Krueger, H. (2011) Clethodim: A 96-Hour Static-Renewal Acute 

Toxicity Test with the Saltwater Mysid (Americamysis bahia). Project Number: 201100056, 

263A/123, VP/37741. Unpublished study prepared by Wildlife International, Ltd. 55 p.

72-3 Shellfish Acute

MRID Citation Reference

48563001 Palmer, S.; Kendall, T.; Gallagher, S. (2011) Clethodim: A 96-Hour Shell Deposition Test with 

the Eastern Oyster (Crassostrea virginica). Project Number: 263A/125 VP/37748. Unpublished 

study prepared by Wildlife International, Ltd. 60p.
67

72-4 now 850.1400 Fish Early Life Stage/Aquatic Invertebrate Life Cycle Study

MRID Citation Reference

48104303 Bidinotto, P. (2003) Chronic Toxicity of Clethodim Agan Technical to Fish, Early-Life Stage: 

Final Report. Project Number: RF/0409/217/002/02, 90005087. Unpublished study prepared by 

BIOAGRI Laboratorios, Ltda. 68 p.

72-4 now 850.1300 Daphnid chronic toxicity test

MRID Citation Reference

48104305 Muniz, T. (2002) Chronic Toxicity of Clethodim Agan Technical to Daphnia magna: Final 

Report. Project Number: 90005084, RF/0409/207/032/02. Unpublished study prepared by 

BIOAGRI Laboratorios, Ltda. 73 p.

72-4 Mysid chronic reproduction test

MRID Citation Reference

No acceptable data

81-1 Acute oral toxicity in rats

MRID Citation Reference

40974507 Easter, M. (1986) The Acute Oral Toxicity of RE-45601 Technical (SX-1688) in Adult Male and 

Female Rats: Project ID: S-2764. Unpublished study prepared by Chevron Environmental Health 

Center, Inc. 71 p. 

81-3 Acute inhalation toxicity in rats

MRID Citation Reference

40974512 Bruce, E. (1986) The Acute Inhalation Toxicity of RE-45601 Technical (SX-1688) in Rats: 

Project ID: S-2783. Unpublished study prepared by Chevron Environmental Health Center, Inc. 

46 p. 

83-4 2-generation repro.-rat

MRID Citation Reference

41030119 MacKenzie, K. (1986) Final Report: Pilot Rat Reproduction Study with Chevron RE-45601 

Technical: Project ID S-2758. Unpublished study prepared by Hazleton Laboratories America, 

Inc. 235 p. 

41030120 Tellone, C. (1987) Two Generation (One Litter) Reproduction Study in Rats with RE-45601 

Technical: Project ID S-2778. Unpublished study prepared by Chevron Environmental Health 

Center, Inc. 2218 p. 

122-1 Seed Germination/Seedling Emergence and Vegetative Vigor

MRID Citation Reference

41685102 Maggio, R. (1990) Tier I Seed Germination/Seedling Emergence Non- target Phytotoxicity 

Study Using Select (Clethodim): Lab Project Number: LR 89-54B. Unpublished study prepared 
68

by Pan-Agricul- ture Laboratories, Inc. 126 p. 

41685103 Maggio, R. (1990) Tier I Vegetative Vigor Nontarget Phytotoxicity Study Using Select 

(Clethodim): Lab Project Number: LR 89-54A. Unpublished study prepared by PanAgricultural Laboratories, Inc. 102 p. 

ACC 9011861 Rose, A.F. 1990. Nontarget Vegetative Vigor Study with SELECT 2EC Herbicide

123-1 Seed germination/seedling emergence and vegetative vigor

MRID Citation Reference

41685104 Chetram, R. (1990) Tier 2 Seed Germination/Seedling Emergence Non- target Phytotoxicity 

Study Using Select (Clethodim): Lab Project Number: LR 89-55B. Unpublished study prepared 

by Pan-Agricul- tural Laboratories, Inc. 149 p. 

41685105 Chetram, R. (1990) Tier 2 Vegetative Vigor Nontarget Phytotoxicity Study Using Select 

(Clethodim): Lab Project Number: LR 89-55A. Unpublished study prepared by PanAgricultural Laboratories, Inc. 121 p. 

123-2 Aquatic plant growth

MRID Citation Reference

41685106 Forbis, A.; Blasberg, J. (1990) Acute Toxicity of RE-45601 Technical to the Freshwater Algae 

(Selenastrum capricornutum) Printz: Lab Project Number: 38373: 89-404. Unpublished study 

prepared by Analytical Bio-chemistry Laboratories, Inc. 60 p. 

42029701 Rhodes, J.; Hughes, J. (1991) The Phytotoxicity of RE-45601 Technical with Duckweed 

(Lemna gibba G3) in a Static System: Lab Project Number: B765-01-1: 38621. Unpublished 

study prepared by Malcolm Pirnie, Inc. and ABC Labs, Inc. 77 p. 

42029702 Thopmpson, S.; Holmes, C.; Peters, G. (1991) Select 2.0 EC: A 14- Day Toxicity Test with 

Duckweed (Lemna gibba G3): Lab Project Number: 162A-117. Unpublished study prepared by 

Wildlife Inter- national, Inc. 51 p. 

42029703 Grimstead, S.; Holmes, C.; Peters, G. (1991) Select 2 EC: A 5-Day Toxicity Test with the 

Freshwater Alga (Selenastrum capricornutum): Lab Project Number: 162A-121. Unpublished 

study pre- pared by Wildlife International, Ltd. 48 p. 

42029704 Grimes, J.; Thompson, S.; Holmes, C. (1991) Select 2.0 EC: A 5-Day Toxicity Test with the 

Marine Diatom (Skeletonema costatum): Lab Project Number: 162A-120. Unpublished study 

prepared by Wildlife International Ltd. 51 p. 

42029705 Thompson, S.; Holmes, C.; Peters, G. (1991) Select 2.0 EC: A 5-Day Toxicity Test with the 

Freshwater Alga (Anabaena flos-aquae): Lab Project Number: 162A-119A. Unpublished study 

prepared by Wildlife International Ltd. 53 p. 

42029706 Thompson, S.; Holmes, C.; Peters, G. (1991) Select 2.0 EC: A 5-Day Toxicity Test with the 

Freshwater Diatom (Navicula pelliculosa): Lab Project Number: 162A-118. Unpublished study 

prepared by Wildlife International Ltd. 52 p. 

E065938 Ma J., L. Xu, S. Wang, R. Zheng, S. Jin, S. Huang, Y. Huang. 2002. Toxicity of 40 Herbicides 

to the Green Alga Chlorella vulgaris. Ecotoxicology and Environmental Safety 51: 128-132.

E083543 Ma J., S. Wang, P. Wang, L. Ma, X. Chen, and R. Xu. 2006. Toxicity Assessment of 40 

Herbicides to the Green Alga Raphidocelis subcapitata. Ecotoxicology and Environmental 

Safety 63: 456-462.
69

141-1 Honey bee acute contact

MRID Citation Reference

40974532 Atkins, E. (1986) Bee Adult Toxicity Dusting Test(BATDT) Evaluating the Comparative Acute 

Contact Toxicity of RE-45601; 9433-16, 87.9% Technical (Select) to Honey Bee Worker 

Adults: Project ID: Test 439. Unpublished study prepared by University of California, Riverside. 

53 p. 

41685107 Hoxter, K.; Smith, G. (1990) Select 2. 0 EC: An Acute Contact Toxicity Study with the Honey 

Bee: Lab Project Number: 263-120. Un- published study prepared by Wildlife International Ltd. 

66 p. 

165-4 Bioaccumulation in fish

MRID Citation Reference

40974524 Rose, A.; Suzuki, J. (1988) Characterization of |carbon 14| Residues in Bluegill Sunfish Treated 

with (Allyl-2-|Carbon 14|- Clethodim or (Cyclohexene-1-One-4,6-?carbon 14|)-Clethodim: Project ID: MEF-0020. Unpublished study prepared by Chevron Chemi- cal Co. 109 p. 

40974531 Forbis, A. (1987) Uptake, Depuration and Bioconcentration of Allyl-2 |carbon| and 

Cyclohexene-1-One-4,6|carbon| RE-45601 to Bluegill Sunfish (Lepomis macrochirus): Project 

ID: S-2827. Un- published study prepared by ABC Laboratories, Inc. 87 p. 

6.2. Environmental Fate and Product Chemistry Studies

MRID Citation Reference

40974520 Pack, D. (1988) Hydrolysis Study on RE-45601: Project ID: MEF-0013/ 8703899. Unpublished 

study prepared by Chevron Chemical Co. 52 p. 

40974522 Pack, D. (1988) The Aerobic Soil Metabolism of ?Propyl-1-?carbon 14|Clethodium: Project ID: 

MEF/0014/8721028. Unpublished study prepared by Chevron Chemical Co. 54 p. 

40974523 Pack, D. (1988) Freundlich Soil Adsorption/Desorption Coefficients of Clethodim and Three 

Metabolites: Project ID: MEF-0102/ 8829844. Unpublished study prepared by Chevron Chemical 

Co. 122 p. 

40974524 Rose, A.; Suzuki, J. (1988) Characterization of |carbon 14| Residues in Bluegill Sunfish Treated 

with (Allyl-2-|Carbon 14|- Clethodim or (Cyclohexene-1-One-4,6-?carbon 14|)-Clethodim: Project ID: MEF-0020. Unpublished study prepared by Chevron Chemi- cal Co. 109 p. 

40974531 Forbis, A. (1987) Uptake, Depuration and Bioconcentration of Allyl-2 |carbon| and Cyclohexene1-One-4,6|carbon| RE-45601 to Bluegill Sunfish (Lepomis macrochirus): Project ID: S-2827. Unpublished study prepared by ABC Laboratories, Inc. 87 p. 

41030133 Chen, Y. (1988) Allyl-2-Carbon 14|-Clethodim Photodegradation in Water: Project ID MEF0025. Unpublished study prepared by Chev- ron Chemical Co. 93 p. 

41030134 Chen, Y. (1988) 4,6-Ring-Carbon 14|-Clethodim Photodegradation in Water: Project ID MEF0024. Unpublished study prepared by Chev- ron Chemical Co. 97 p. 

41030135 Chen, Y. (1988) Clethodim Photodegradation on Soil: Project ID MEF- 0022. Unpublished study 

prepared by Chevron Chemical Co. 44 p. 

41030207 Ho, B. (1989) Field Dissipation Study with Clethodim on Cotton in Mississippi--T7227: Project 
70

MRID Citation Reference

ID 1641-88-7227. Unpublished study prepared by Chevron Chemical Co. 512 p. 

41030208 Ho, B. (1989) Field Dissipation Study with Clethodim on Cotton in California--T7226: Project ID 

1641-88-7226. Unpublished study prepared by Chevron Chemical Co. 427 p. 

41030209 Ho, B. (1989) Field Dissipation Study with Clethodim on Soybean in North Carolina--T7229: 

Project ID 1641-88-7229. Unpublished study prepared by Chevron Chemical Co. 501 p. 

41030210 Ho, B. (1989) Field Dissipation Study with Clethodim on Soybean in Iowa--T7228: Project ID 

1641-88-7228. Unpublished study prepared by Chevron Chemical Co. 536 p. 

41376801 Pack, D. (1990) The Aerobic Soil Metabolism of Clethodim Using ?Ring-4,6-(Carbon 14)|- and 

?Allyl-2-(Carbon 14)|-Clethodim Revised January 5, 1990: Lab Project ID: MEF0015/0016/8914823. Unpublished study prepared by Chevron Chemical Co. 161 p. 

41652301 Tucker, B. (1990) The Anaerobic Aquatic Metabolism of Ring-4,6- ?carbon 14||Clethodim: Lab 

Project Number: MEF-0141/9004983. Unpublished study prepared by Chevron Chemical Co. 85 

p. 

45591605 Hiscock, A., R. Warren, and B. Patterson. A Small-Scale Prospective Groundwater Monitoring 

Study for Oxamyl. DuPont Report No. AMR 4318-97. Unpublished study conducted by Stone 

Environmental, Inc., Ecologic, Inc., Agricultural Systems Associates, AGVISE Laboratories, 

Centre Analytical Laboratories, Inc., and E.I. du Pont de Nemours and Company; submitted by 

E.I. du Pont de Nemours and Company, Wilmington, DE. Jan. 14, 2002.

48881401 Gregory, A. (2012) Clethodim TGAI: Summary of Product Properties Test Guidelines. Project 

Number: ALB12/14. Unpublished study prepared by Albaugh, Inc. 8p.

48881405 Li, H. (2012) Chemical and Physical Characterization of Clethodim TGAI: Color, Physical State, 

Odor, Stability, pH, Oxidation/Reduction, UV-Vis, Boiling Point, Density, Viscosity, 

Dissociation Constant, Partition Coefficient and Solubility: Final Report. Project Number: 

NC/2011/083. Unpublished study prepared by Nutrichem Laboratory Co., Ltd. 87p.
71

APPENDIX A. Aquatic Model Input/Output Files
72

APPENDIX B. Sample T-REX, and TerrPlant Inputs/Outputs for Clethodim

T-REX

Acute and Chronic RQs are based on the Upper Bound 

Kenaga Residues.

Chemical Name: The maximum single day residue estimation is used for 

 Use both the acute and reproduction RQs.

 Formulation

Application Rate 0.25 lbs a.i./acre RQs reported as "0.00" in the RQ tables below should be noted as

Half-life 35 days <0.01 in your assessment. This is due to rounding and significant

Application Interval 7 days figure issues in Excel.

Maximum # Apps./Year 18

Length of Simulation 1 year

Variable application rates? no

Bobwhite quail LD50 (mg/kg-bw) 2000.00

Mallard duck) LC50 (mg/kg-diet) 3978.00

Mallard duck NOAEL(mg/kg-bw) 0.00

Mallard duck NOAEC (mg/kg-diet) 833.00

1360.00

0.00

51.00

500.00

Kenaga

Values

Short Grass 425.28

Tall Grass 194.92

Broadleaf plants 239.22

Fruits/pods/seeds 26.58

Arthropods 166.57

Endpoints

 Upper Bound Kenaga Residues For RQ Calculation

Dietary-based EECs (ppm)

NOAEL (mg/kg-bw)

NOAEC (mg/kg-diet)

Mammals LD50 (mg/kg-bw)

LC50 (mg/kg-diet)

clethodim

fallow land, golf course turf, non-cropped 

areas; alfalfa (2 apps with 9 cuttings/yr = 

18 apps/yr)

0

Avian

Questions? 

Comments? 

Click here

Avian Results

Avian Body Ingestion (Fdry) Ingestion (Fwet) % body wgt FI

Class Weight (g) (g bw/day) (g/day) consumed (kg-diet/day)

Small 20 5 23 114 2.28E-02

Mid 100 13 65 65 6.49E-02

Large 1000 58 291 29 2.91E-01

20 5 5 25 5.06E-03

Granivores 100 13 14 14 1.44E-02

1000 58 65 6 6.46E-02

Avian Body Adjusted LD50

Weight (g) (mg/kg-bw)

20 1440.86

100 1834.29

1000 2591.00

small mid large

20 100 1000

Short Grass 484.35 276.20 123.66

Tall Grass 221.99 126.59 56.68

Broadleaf plants 272.45 155.36 69.56

Fruits/pods 30.27 17.26 7.73

Arthropods 189.70 108.18 48.43

Seeds 6.73 3.84 1.72

20 100 1000

Short Grass 0.34 0.15 0.05

Tall Grass 0.15 0.07 0.02

Broadleaf plants 0.19 0.08 0.03

Fruits/pods 0.02 0.01 0.00

Arthropods 0.13 0.06 0.02

Seeds 0.00 0.00 0.00

Dietary-based RQs 

Acute Chronic

Short Grass 0.11 0.51

Tall Grass 0.05 0.23

Broadleaf plants 0.06 0.29

Fruits/pods/seeds 0.01 0.03

Arthropods 0.04 0.20

Note: To provide risk management with the maximum possible information,

it is recommended that both the dose-based and concentration-based 

RQs be calculated when data are available

Dose-based EECs 

(mg/kg-bw) 

Avian Classes and Body Weights (grams)

Dose-based RQs 

(Dose-based EEC/adjusted LD50)

RQs

Avian Acute RQs

Size Class (grams)
73

clethodim fallow land, golf course turf, non-cropped areas; alfalfa (2 ap Upper bound Kenaga Residues

Mammalian Results

Mammalian Body Ingestion (Fdry) Ingestion (Fwet) % body wgt FI

Class Weight (g bwt/day) (g/day) consumed (kg-diet/day)

15 3 14 95 1.43E-02

Herbivores/ 35 5 23 66 2.31E-02

insectivores 1000 31 153 15 1.53E-01

15 3 3 21 3.18E-03

Grainvores 35 5 5 15 5.13E-03

1000 31 34 3 3.40E-02

Mammalian Body Adjusted Adjusted

Class Weight LD50 NOAEL

15 2989.05 112.09

Herbivores/ 35 2418.46 90.69

insectivores 1000 1046.06 39.23

15 2989.05 112.09

Granivores 35 2418.46 90.69

1000 1046.06 39.23

15 35 1000

Short Grass 405.47 280.23 64.97

Tall Grass 185.84 128.44 29.78

Broadleaf plants 228.08 157.63 36.55

Fruits/pods 25.34 17.51 4.06

Arthropods 158.81 109.76 25.45

Seeds 5.63 3.89 0.90

15 grams 35 grams 1000 grams

Acute Chronic Acute Chronic Acute Chronic

Short Grass 0.14 3.62 0.12 3.09 0.06 1.66

Tall Grass 0.06 1.66 0.05 1.42 0.03 0.76

Broadleaf plants 0.08 2.03 0.07 1.74 0.03 0.93

Fruits/pods 0.01 0.23 0.01 0.19 0.00 0.10

Arthropods 0.05 1.42 0.05 1.21 0.02 0.65

Seeds 0.00 0.05 0.00 0.04 0.00 0.02

Acute Chronic

Short Grass #DIV/0! 0.85

Tall Grass #DIV/0! 0.39

Broadleaf plants #DIV/0! 0.48

Fruits/pods/seeds #DIV/0! 0.05

Arthropods #DIV/0! 0.33

Note: To provide risk management with the maximum possible information,

it is recommended that both the dose-based and concentration-based 

RQs be calculated when data are available

Dose-Based EECs 

(mg/kg-bw)

(grams)

Mammalian Classes and Body weight

Dietary-based RQs 

(Dietary-based EEC/LC50 or 

NOAEC)

Mammal RQs

Medium mammal Large mammal Dose-based RQs 

(Dose-based EEC/LD50 or 

NOAEL)

Small mammal
74

TerrPlant

TerrPlant v. 1.2.2

Green values signify user inputs (Tables 1, 2 and 4). 

Input and output guidance is in popups indicated by red arrows.

Chemical Name

PC code

Use

Application Method

Application Form 

Solubility in Water (ppm)

Input Parameter Symbol Value Units

Application Rate A 0.25 lbs ai/A

Incorporation I 1 none

Runoff Fraction R 0.02 none

Drift Fraction D 0.05 none

Equation EEC

(A/I)*R 0.005

(A/I)*R*10 0.05

A*D 0.0125

((A/I)*R)+(A*D) 0.0175

((A/I)*R*10)+(A*D) 0.0625

Plant type EC25 NOAEC EC25 NOAEC 

Monocot 0.0076 0.0004 0.003 0.0023

Dicot 0.25 0.25 0.25 0.25

Plant Type Listed Status Dry Semi-Aquatic Spray Drift

Monocot non-listed 2.30 8.22 4.17

Monocot listed 43.75 156.25 5.43

Dicot non-listed <0.1 0.25 <0.1

Dicot listed <0.1 0.25 <0.1

Description

Total for semi-aquatic areas

Table 1. Chemical Identity.

Clethodim

Max. Single app. (fallow land, golf course turf, noncroped areas, etc)

Table 2. Input parameters used to derive EECs.

Aerial

Liquid

29

121011

Table 3. EECs for Clethodim. Units in lbs ai/A.

Runoff to dry areas

Runoff to semi-aquatic areas

Spray drift

Total for dry areas

*If RQ > 1.0, the LOC is exceeded, resulting in potential for risk to that plant group.

Seedling Emergence Vegetative Vigor

Table 5. RQ values for plants in dry and semi-aquatic areas exposed to Clethodim through runoff 

and/or spray drift.*

Table 4. Plant survival and growth data used for RQ derivation. Units are in lbs ai/A.
75

TerrPlant v. 1.2.2

Green values signify user inputs (Tables 1, 2 and 4). 

Input and output guidance is in popups indicated by red arrows.

Chemical Name

PC code

Use

Application Method

Application Form 

Solubility in Water (ppm)

Input Parameter Symbol Value Units

Application Rate A 0.045 lbs ai/A

Incorporation I 1 none

Runoff Fraction R 0.02 none

Drift Fraction D 0.05 none

Equation EEC

(A/I)*R 0.0009

(A/I)*R*10 0.009

A*D 0.00225

((A/I)*R)+(A*D) 0.00315

((A/I)*R*10)+(A*D) 0.01125

Plant type EC25 NOAEC EC25 NOAEC 

Monocot 0.0076 0.0004 0.003 0.0023

Dicot 0.25 0.25 0.25 0.25

Plant Type Listed Status Dry Semi-Aquatic Spray Drift

Monocot non-listed 0.41 1.48 0.75

Monocot listed 7.88 28.13 0.98

Dicot non-listed <0.1 <0.1 <0.1

Dicot listed <0.1 <0.1 <0.1

Table 3. EECs for Clethodim. Units in lbs ai/A.

Runoff to dry areas

Runoff to semi-aquatic areas

Spray drift

Total for dry areas

*If RQ > 1.0, the LOC is exceeded, resulting in potential for risk to that plant group.

Seedling Emergence Vegetative Vigor

Table 5. RQ values for plants in dry and semi-aquatic areas exposed to Clethodim through runoff 

and/or spray drift.*

Table 4. Plant survival and growth data used for RQ derivation. Units are in lbs ai/A.

Description

Total for semi-aquatic areas

Table 1. Chemical Identity.

Clethodim

Lowest app. Rate (field corn)

Table 2. Input parameters used to derive EECs.

Aerial

Liquid

29

121011
76

APPENDIX C. Summary of Toxicity Endpoints and Study Classifications for Clethodim

TAXON ENDPOINT FORMULATION MRID

STUDY 

CLASSIFICATIONCOMMENTS

FRESHWATER FISH

Acute

Rainbow trout 

(Oncorhynchus 

mykiss)

96-hr LC50 =

24.4 mg a.i./L

(slightly toxic)

TGAI (83.3%) 40974528 Acceptable

Sublethal effects observed 

were surfacing, loss of 

equilibrium, dark 

discoloration, fish on the 

bottom of the test chamber 

and/or quiescence at 32, 56, 

and 100 mg/L (nominal) the 

only test levels measured were 

levels 1 (10 mg/L = 7.8 mg 

a.i./L), level 3 (32 mg/L = 18 

mg a.i./L), and level 5 (100 

mg/L = 33 mg a.i./L), 

representing nominal and the 

mean-measured concentrations 

of that test level, respectively.

Rainbow trout 

(Oncorhynchus 

mykiss)

96-hr LC50 > 110

mg a.i./L

(practically nontoxic)

TGAI (95.4%) 48417003 Acceptable

Sublethal effects observed 

were lethargy, lying on the 

bottom, and loss of 

equilibrium.

Bluegill 

sunfish

(Lepomis 

macrochirus)

96-hr LC50 > 33 

mg a.i./L

(slightly toxic)

TGAI (83.3%) 40974529 Acceptable

Sublethal effects (surfacing 

and/or gulping air) were 

observed at in one chamber of 

the 100 mg/L (33 mg a.i./L -

mean-measured) test level at 

96 hours. Only test levels 

measured were levels 1 (10 

mg/L = 8.8 mg a.i./L), level 3 

(32 mg/L = 20 mg a.i./L), and 

level 5 (100 mg/L = 33 mg 

a.i./L), representing nominal 

and the mean-measured 

concentrations of that test 

level, respectively.

Fathead 

minnow 

(Pimephales 

promelas)

96-hr LC50 = 110 

mg a.i./L 

(practically nontoxic)

TGAI (95.4%) 48417002 Acceptable

Sublethal effects observed 

were lethargy, surfacing, lying 

on the bottom, and swollen 

abdomen at 55 and 115 mg 

a.i./L. 

Zebrafish

(Danio rerio)

96-hr LC50 = 133

mg a.i./L

(practically nontoxic)

TGAI (95.7%) 48104304 Supplemental Mortality only, sublethal 

effects were not reported.
77

TAXON ENDPOINT FORMULATION MRID

STUDY 

CLASSIFICATIONCOMMENTS

Chronic

Fathead 

minnow 

(Pimephales 

promelas)

NOAEC = 0.010 

mg a.i./L

LOAEC = 0.031 

mg a.i./L

TGAI (95.7%) 48104303 Supplemental

LOAEC based on reduced 

survival. Test concentrations 

were not measured; therefore 

the results were adjusted for 

purity of the technical grade 

material (95.7%). Time to 

hatch, hatching success, and 

post-hatch survival were not 

evaluated; effects on 

reproduction were not 

measured in this study. 

Rainbow trout 

(Oncorhynchus 

mykiss)

ACR derived 

NOAEC = 0.002 

mg a.i./L

NA NA NA

Rainbow trout acute toxicity 

endpoint was the most 

sensitive, the fathead minnow 

acute and chronic toxicity data 

were used to estimate a 

NOAEC for the rainbow trout. 

[(Fathead LC50/ NOAEC) = 

ACR; (RT LC50/ACR) = 

0.002 mg a.i./L]

ESTUARINE/MARINE FISH

Acute

Sheepshead 

Minnow

(Cyprinodon 

variegates)

96-hr LC50 > 124 

mg a.i./L

(practically nontoxic)

TGAI (95.4%) 48417004 Acceptable No Mortality or sublethal 

effects were observed.

Chronic

No acceptable estuarine/marine fish chronic toxicity data is available for clethodim; therefore the estimated freshwater fish 

NOAEC value for rainbow trout was used as a conservative estimate of potential toxicity to estuarine/marine fish (NOAEC = 

0.002 mg a.i./L).

FRESHWATER INVERTEBRATES

Acute

Water flea 

(Daphnia 

magna)

48-hr EC50 = 20.2 

mg a.i./L

(slightly toxic)

EP (25.6%) 41685101 Acceptable No Mortality or sublethal 

effects were observed.

Chronic

Water flea 

(Daphnia 

magna)

NOAEC = 0.94 

mg a.i./L 

LOAEC = 3.0 mg 

a.i./L

TGAI (95.7%) 48104305 Supplemental

Based on offspring production

per female and total length of 

surviving adults. Survival and 

treatment-related delay in time 

to first brood released was 

observed at the 9.3 mg a.i./L 

treatment level.

ESTUARINE/MARINE INVERTEBRATES

Acute

Eastern oyster 

(Crassostrea 

virginica)

96-hr EC50 = 5.3

mg a.i./L1

(moderately toxic)

TGAI (95.4%) 48563001 Supplemental

Reductions in shell deposition 

at all treatment levels relative 

to the negative control.
78

TAXON ENDPOINT FORMULATION MRID

STUDY 

CLASSIFICATIONCOMMENTS

Mysid Shrimp

(Americamysis 

bahia)

96-hr EC50 = 33

mg a.i./L

(slightly toxic)

TGAI (95.4%) 48417001 Acceptable

Mortality and sublethal effects 

were observed. Sublethal 

effects included lethargy, 

surfacing, lying on the bottom 

of the test and chamber at 28, 

56, and 166 mg a.i./L.

Chronic

No acceptable estuarine/marine invertebrate chronic toxicity data is available for clethodim; therefore the freshwater 

invertebrate NOAEC value for daphnid was used as a conservative estimate of potential toxicity to estuarine/marine 

invertebrate (NOAEC = 0.94 mg a.i./L).

AQUATIC PLANTS

Non-Vascular

Marine Diatom

(Skeletonema 

costatum)

120 hr EC50 = 8.6 

mg a.i./L

NOAEC = 5.4 mg 

a.i./L

EP (25.6%) 42029704 Acceptable

Inhibition of growth rate 

based on cell counts after 5 

days (120 hours).

Green algae

(Selenastrum 

capricornutum)

120 hr EC50 > 11.4 

mg a.i./L

NOAEC = 11.4 

mg a.i./L

TGAI (83.3%) 41685106 Acceptable No effects

Green algae

(Selenastrum 

capricornutum)

5d EC50 = 19.5 mg 

a.i./L

NOAEC = 11.1 

mg a.i./L

EP (25.6%) 42029703 Acceptable

Inhibition of growth rate 

based on cell counts after 5 

days (120 hours).

Blue-green 

algae 

(Anabeana flosaquae)

5d EC50 = 16.7 mg 

a.i./L

NOAEC = 5.6 mg 

a.i./L

EP (25.6%) 42029705 Acceptable

Inhibition of growth rate 

based on cell counts after 5 

days (120 hours).

Freshwater 

diatom 

(Navicula 

pelliculosa)

120 hr EC50 = 11.0 

mg a.i./L

NOAEC = 3.1 mg 

a.i./L

EP (25.6%) 42029706 Acceptable

Inhibition of growth rate 

based on cell counts after 5 

days (120 hours).

Green algae

(Chlorella 

vulgaris)

96 hr EC50 = 4.6 

mg a.i./L EP (12%)

E065938; 

Ma et al., 

2002

Qualitative 

(Open 

Literature)

Inhibition in growth rate 

based on cell counts after 

96 hours.

Green algae 

(Raphidocelis 

subcapitata)

96 hr EC50 = 2.7 

mg a.i./L EP (12%)

E083543; 

Ma et al., 

2006

Qualitative 

(Open 

Literature)

Inhibition in growth rate 

based on cell counts after 

96 hours.

Vascular

Duckweed

(Lemna gibba)

14-day EC50 = 1.34 

mg a.i./L

NOAEC = 0.37 

mg a.i./L

TGAI (82.4%) 42029701 Acceptable Percent inhibition based on 

mean frond counts on day 14.

Duckweed

(Lemna gibba)

14d EC50 = 42.5 

mg a.i./L

NOAEC = 1.1 mg 

a.i./L

EP (25.6%) 42029702 Supplemental Percent inhibition based on 

mean frond counts on day 14.
79

TAXON ENDPOINT FORMULATION MRID

STUDY 

CLASSIFICATIONCOMMENTS

BIRDS

Acute Oral

Bobwhite quail 

(Colinus 

virginianus)

14-day > 2000 mg 

a.i./kg-bw

(practically nontoxic)

TGAI (82%) 40974525 Acceptable

NOAEL = 1250 mg a.i./kg-bw 

based on overt signs (lethargy, 

wing droop and ruffled 

appearance) of toxicity and a 

reduction in weight gain at 

1650 mg a.i./kg-bw.

Sub-Acute Dietary

Bobwhite quail 

(Colinus 

virginianus)

8-day LC50 > 4270 

mg a.i./kg-diet

(practically nontoxic)

TGAI (82%) 40974526 Acceptable No mortality or signs of 

toxicity were observed.

Mallard duck 

(Anas 

platyrhynchos)

8-day LC50 > 3978 

mg a.i./kg-diet

(practically nontoxic)

TGAI (82%) 40974527 Acceptable No mortality or signs of 

toxicity were observed.

Chronic

Bobwhite quail 

(Colinus 

virginianus)

No Valid Data

Available TGAI (83.3%) 41030206 Unacceptable/ 

Invalid

A high rate of adult mortality 

in both control and test 

subjects were not adequately 

explained, it is not clear if the 

deaths were due to the test 

chemical, poor husbandry, 

random error, or a 

combination of these factors. 

This study was downgraded to 

unacceptable/invalid. 

Mallard duck 

(Anas 

platyrhynchos)

19-wk NOAEC = 

833 mg a.i./kg-diet 

LOAEC > 833 mg 

a.i./kg-diet

TGAI (83.3%) 41030205 Acceptable

No effects on mortality, 

behavior, growth or 

reproduction.

MAMMALS

Acute 

Rat

(Rattus 

norvegicus)

LD50 = 1360 

mg/kg-bw

(slightly toxic)

TGAI (83.3%) 40974507 Acceptable

Acute oral; Signs of toxicity 

that were observed included 

salivation, motor activity, 

unsteady gait, hyperreactivity, 

lacrimation, diarrhea, red nasal 

discharge, red or clear ocular 

discharge, clonic convulsions, 

and/or collapse on the day of 

dosing. Reduced food 

consumption and yellow 

anogenital stains were 

observed in the surviving rats 

in all treated groups.
80

TAXON ENDPOINT FORMULATION MRID

STUDY 

CLASSIFICATIONCOMMENTS

Rat 

(Rattus 

norvegicus)

LC50 > 3.9 mg/L TGAI (83.3%) 40974512 Supplemental

Acute inhalation; 4-hr 

exposure; there were no 

deaths. Clinical signs of 

toxicity included squinted or 

closed eyes, colorless eye 

discharge, salivation, red nasal 

discharge, abnormal 

respiratory sounds, decreased 

feces, unkempt appearance, 

and a yellow/red anogenital 

discharge.

Chronic

Rat 

(Rattus 

norvegicus)

NOAEC = 500 

mg/kg-diet (51 

mg/kg-bw/day) 

LOAEC = 2500 

mg/kg-diet (263 

mg/kg-bw/day) 

TGAI (82.3%) 41030120 Acceptable

Decreased body weight and

food consumption in parental 

organisms, NO reproductive 

effects at up to 2500 ppm

(approx. 263 mg/kg-bw/day).

TERRESTRIAL INVERTEBRATES

Honey Bee

(Apis mellifera)

LD50 >100 μg 

a.i./bee

(practically nontoxic)

(EP 26% a.i.) 41685107 Acceptable

22% mortality in the 100 μg 

a.i./bee dose group; signs of 

toxicity were not observed in 

dose groups less than 100 μg 

a.i./bee; the no-effect dose was

60 μg a.i./bee.

TERRESTRIAL PLANTS

DICOTS

All Dicots 

tested

Seedling 

emergence EC25

>0.25 lb a.i./A

EP (82.4%) 41685102 Acceptable All dicot species tested 

demonstrated no significant 

effects due to clethodim 

application at the maximum 

application rate

Vegetative Vigor 

EC25 >0.25 lb 

a.i./A

EP (82.4%) 41685103 Acceptable

MONOCOTS

Seedling Emergence

Oat

(Aveana sativa)

EC25 = 0.0076 lb 

a.i./A 

NOAEC2 = 0.0004 

lb a.i./A

EP (82.4%) 41685104 Acceptable Plant height

Rye grass 

(Lolium 

perenne)

EC25 = 0.0561 lb 

a.i./A 

NOAEC = 0.031

lb a.i./A

EP (82.4%) 41685104 Acceptable Plant height

Corn

(Zea mays)

EC25 = 0.0125 lb 

a.i./A 

NOAEC = 0.0063 

lb a.i./A

EP (82.4%) 41685104 Acceptable Plant height

Onion

(Allium cepa)

EC25 > 0.25 lb a.i./A 

NOAEC ≥ 0.25 lb 

a.i./A

EP (82.4%) 41685104 Acceptable

No significant effects were 

observed for onions exposed 

to clethodim.
81

TAXON ENDPOINT FORMULATION MRID

STUDY 

CLASSIFICATIONCOMMENTS

Vegetative Vigor

Rye grass 

(Lolium 

perenne)

EC25 = 0.003 lb 

a.i./A

NOAEC2 = 0.0023 

lb a.i./A

EP (82.4%) 41685105 Acceptable Dry weight

Oat

(Aveana sativa)

EC25 = 0.016 lb 

a.i./A 

NOAEC = 0.013

lb a.i./A

EP (82.4%) 41685105 Acceptable Dry weight

Corn

(Zea mays)

EC25 = 0.005 lb 

a.i./A 

NOAEC = 0.006 

lb a.i./A

EP (82.4%) 41685105 Acceptable Dry weight

Onion

(Allium cepa)

EC25 > 0.25 lb 

a.i./A 

NOAEC ≥ 0.25 lb 

a.i./A

EP (82.4%) 41685105 Acceptable

No significant effects were 

observed for onions exposed 

to clethodim.

1 Time-weighted average (TWA) 2 EC05 is used when a NOAEC could not be calculated or NOAEC is higher than the EC25
82

APPENDIX D. Clethodim Incidents

A search for ecological incidents related to thiacloprid use, conducted on June 5, 2013, yielded two incidents involving terrestrial 

plants which are summarized below.

Table X-1. Clethodim Incidents, as Reported in the EIIS Database

Incident ID # State, County Magnitude Year Description Legality Certainty

I002969-058 Florida Unknown 1995 Use of Select 2EC (a.i. Clethodim) allegedly caused damage to 

cotton. Clethodim was directly treated on the field. Undetermined Possible

I022217-034 Illinois, Logan 100% of 75 

acres

2010

On July 12, 2010 in Logan County, IL 100% of 75 acres of 

soybean experienced leaf burn after the product Ignite 280 SL 

(a.i. glufosinate-ammonium) and Select (a.i. clethodim) were 

applied. Alleged phytotoxic reaction to product following 

application to soybean crop. The Registrant suggested the 

probable cause for the leaf burn was tank contamination.

Undetermined Possible

Uncertainties Related to the Use of Incident Information from the Ecological Incident Information System 

Incident data are used in risk assessments to provide evidence that the risk predictions from the screening level assessment are 

supported by actual effects in the field. Incident reports submitted to EPA since approximately 1994 have been tracked by assignment 

of incident numbers in an Incident Data System (IDS), microfiched, and then entered to a second database, the Ecological Incident 

Information System (EIIS). Additionally, there is an on-going effort to enter information to EIIS on incident reports received prior to 

establishment of current databases. Incident reports are not received in a consistent format (e.g., states and various labs usually have 

their own formats), may involve multiple incidents involving multiple chemicals in one report, and may report on only part of a given 

incident investigation (e.g., residues). 

Incidents entered into EIIS are categorized into one of several certainty levels regarding the likelihood that a particular pesticide is 

associated with the incident: highly probable, probable, possible, unlikely, or unrelated. In brief, “highly probable” incidents usually 

require carcass residues and/or clear circumstances regarding the exposure. “Probable” incidents include those where residues were 

not available and/or circumstances were less clear than for “highly probable.” “Possible” incidents include those where multiple 

chemicals may have been involved and it is not clear what the contribution was of a given chemical. The “unlikely” category is used, 

for example, where a given chemical is practically nontoxic to the category of organism killed and/or the chemical was tested for but 

not detected in samples. “Unrelated” incidents are those that have been confirmed to be not pesticide-related.
83

Incidents entered into the EIIS are also categorized as to use/misuse. Unless specifically confirmed by a state or federal agency to be 

misuse, or there was very clear misuse such as intentional baiting to kill wildlife, incidents are not typically considered misuse. 

The number of documented kills in EIIS is believed to be a small fraction of total mortality caused by pesticides. Mortality incidents 

must be seen, reported, investigated, and have investigation reports submitted to EPA to have the potential for entry into the database. 

Incidents often are not seen, due to scavenger removal of carcasses, decay in the field, or simply because carcasses may be hard to see 

on many sites and/or few people are systematically looking. Poisoned animals may also move off-site to less conspicuous areas 

before dying. Incidents may not get reported to appropriate authorities capable of investigating the incident for a variety of reasons 

including the finder may not know of the importance of reporting incidents, may not know who to call, may not feel they have the 

time or desire to call, or may hesitate to call because of their own involvement in the kill. Incidents reported may not get investigated 

if resources are limited or may not get investigated thoroughly, with residue analyses, for example. Also, if kills are not reported and 

investigated promptly, there will be little chance of documenting the cause, since tissues and residues may deteriorate quickly. 

Reports of investigated incidents often do not get submitted to EPA, since reporting by states is voluntary. 

Furthermore, the database relies heavily on registrant-submitted incident reports, and registrants are currently only required to submit 

detailed information on ‘major’ ecological incidents, while ‘minor’ incidents are reported aggregately. 

Based on the 40 CFR (§159.184 Toxic or adverse effect incident reports), an ecological incident is considered ‘major’ if any of the 

following criteria are met:

Fish or wildlife:

(A) Involves any incident caused by a pesticide currently in Formal Review for ecological concerns. 

(B) Fish: Affected 1,000 or more individuals of a schooling species or 50 or more individuals of a non-schooling species. 

(C) Birds: Affected 200 or more individuals of a flocking species, or 50 or more individuals of a songbird species, or 5 or more 

individuals of a predatory species. 

(D) Mammals, reptiles, amphibians: Affected 50 or more individuals of a relatively common or herding species or 5 or more 

individuals of a rare or solitary species. 

(E) Involves effects to, or illegal pesticide treatment (misuse) of a substantial tract of habitat (greater than or equal to 10 acres, 

terrestrial or aquatic). 
84

Plants: 

(A) The effect is alleged to have occurred on more than 45 percent of the acreage exposed to the pesticide.

All other ecological incidents are considered ‘minor’ and only need to be aggregately reported. ‘Minor’ incidents reported by the 

registrants are not included in the EIIS database. Therefore, for example, an incident could affect 900 fish, 150 birds, 45 mammals, 

and 40% of an exposed crop and not be included in the EIIS database [unless is it reported by a non-registrant (e.g., an incident 

submitted by a state agency – which are not systematically collected)]. Therefore, because the number of documented kills in EIIS is 

believed to be a small fraction of total mortality caused by pesticides, absence of reports does not necessarily provide evidence of an 

absence of incidents. 
85

APPENDIX E. STIR and SIP Inputs and Outputs

STIR

Input

Application and Chemical Information

Enter Chemical Name clethodim

Enter Chemical Use herbicide

Is the Application a Spray? (enter y or n) y

If Spray What Type (enter ground or air) ground

Enter Chemical Molecular Weight (g/mole) 359.92

Enter Chemical Vapor Pressure (mmHg) 1.00E-07

Enter Application Rate (lb a.i./acre) 0.26

Toxicity Properties

Bird

Enter Lowest Bird Oral LD50 (mg/kg bw) 2000

Enter Mineau Scaling Factor 1.15

Enter Tested Bird Weight (kg) 0.178

Mammal

Enter Lowest Rat Oral LD50 (mg/kg bw) 1360

Enter Lowest Rat Inhalation LC50 (mg/L) 3.9

Duration of Rat Inhalation Study (hrs) 4

Enter Rat Weight (kg) 0.35

Output

Results Avian (0.020 kg )

Maximum Vapor Concentration in Air at Saturation (mg/m3

) 1.94E-03

Maximum 1-hour Vapor Inhalation Dose (mg/kg) 2.43E-04

Adjusted Inhalation LD50 3.20E+01

Ratio of Vapor Dose to Adjusted Inhalation LD50 7.61E-06 Exposure not Likely Significant

Maximum Post-treatment Spray Inhalation Dose (mg/kg) 2.75E-02

Ratio of Droplet Inhalation Dose to Adjusted Inhalation LD50 8.59E-04 Exposure not Likely Significant

Results Mammalian (0.015 kg )

Maximum Vapor Concentration in Air at Saturation (mg/m3

) 1.94E-03

Maximum 1-hour Vapor Inhalation Dose (mg/kg) 3.06E-04

Adjusted Inhalation LD50 2.32E+02

Ratio of Vapor Dose to Adjusted Inhalation LD50 1.32E-06 Exposure not Likely Significant

Maximum Post-treatment Spray Inhalation Dose (mg/kg) 3.45E-02

Ratio of Droplet Inhalation Dose to Adjusted Inhalation LD50 1.49E-04 Exposure not Likely Significant

**NOTE**: When entering values, press the "Enter" key 

in order to update linked cells.
86

SIP

Table 1. Inputs

Parameter Value

Chemical name Clethodim

Solubility (in water at 25o

C; mg/L) 29

Mammalian LD50 (mg/kg-bw) 1360

Mammalian test species laboratory rat

Body weight (g) of "other" mammalian species

Mammalian NOAEL (mg/kg-bw) 51

Mammalian test species laboratory rat

Body weight (g) of "other" mammalian species

Avian LD50 (mg/kg-bw) 2000

Avian test species northern bobwhite quail

Body weight (g) of "other" avian species

Mineau scaling factor 1.15

Mallard NOAEC (mg/kg-diet) 833

Bobwhite quail NOAEC (mg/kg-diet) 250

NOAEC (mg/kg-diet) for other bird species 0

Body weight (g) of other avian species

NOAEC (mg/kg-diet) for 2nd other bird species 0

Body weight (g) of 2nd other avian species

Table 2. Mammalian Results

Parameter Acute Chronic

Upper bound exposure (mg/kg-bw) 4.9880 4.9880

Adjusted toxicity value (mg/kg-bw) 1046.0584 39.2272

Ratio of exposure to toxicity 0.0048 0.1272

Conclusion*

Drinking water exposure 

alone is NOT a potential 

concern for mammals

Drinking water exposure 

alone is NOT a potential 

concern for mammals

Table 3. Avian Results

Parameter Acute Chronic

Upper bound exposure (mg/kg-bw) 23.4900 23.4900

Adjusted toxicity value (mg/kg-bw) 1440.8590 26.5746

Ratio of exposure to acute toxicity 0.0163 0.8839

Conclusion*

Drinking water exposure 

alone is NOT a potential 

concern for birds

Drinking water exposure 

alone is NOT a potential 

concern for birds

*Conclusion is for drinking water exposure alone. This does not combine all routes of exposure. Therefore, 

when aggregated with other routes (i.e., diet, inhalation, dermal), pesticide exposure through drinking water 

may contribute to a total exposure that has potential for effects to non-target animals.
87

APPENDIX F. Summary of AgDrift Terrestrial Outputs for Clethodim

VV (Non-Listed) - Aerial 
88
89

VV (Non-Listed) - Ground
90
91

SE (Non-Listed) - Aerial
92
93

SE (Non-Listed) - Ground
94
95

VV (Listed) - Aerial
96
97

VV (Listed) - Ground
98
99

SE (Listed) - Aerial
100
101

SE (Listed) - Ground
102
103

APPENDIX G. ECOTOX Summary Tables and Accepted Papers

Clethodim 2008 Acceptable 

Reference List

1. Carey III, V. F.; Smith, R. J. Jr., and Talbert, R. E. Reduced and Standard Herbicide Rates for Grass Control in 

Rice (Oryza sativa). POP,GROWATER,AQUA; 1992; 6, (2): 409-414. 

Notes: EcoReference No.: 101451

Chemical of Concern: HFP,FNP,CLT,SXD

2. De Nardo, E. A. B. and Grewal, P. S. Compatibility of Steinernema feltiae (Nematoda: Steinernematidae) with 

Pesticides and Plant Growth Regulators Used in Glasshouse Plant Production. 

MOR,BEHENV,AQUA; 2003; 13, (4): 441-448. 

Notes: EcoReference No.: 71382

Chemical of Concern: SS,PCNB,MFX,FTL,FX,AZX,TPM,IPD,DFZ,CLT,ACP,ACM,PBZ

3. Ma, J. and Liang, W. Acute Toxicity of 12 Herbicides to the Green Algae Chlorella pyrenoidosa and 

Scenedesmus obliquus. POPWATER,AQUA; 2001; 67, (3): 347-351. 

Notes: EcoReference No.: 61984

Chemical of Concern: GFS,CZE,ACO,TFN,FTS,CRME,BSFM,CLT,MTL,BMN

4. Ma, J.; Lin, F.; Wang, S., and Xu, L. Acute Toxicity Assessment of 20 Herbicides to the Green Alga 

Scenedesmus quadricauda (Turp.) Breb. POPWATER,AQUA; 2004; 72, (6): 1164-1171. 

Notes: EcoReference No.: 101396

Chemical of Concern: 

TFN,PDM,ANL,BP,FTS,EMSF,DZP,QZF,HFP,FZFP,CLT,NSF,MTSM,TN,BSFM,CRME

5. Ma, J.; Wang, S.; Wang, P.; Ma, L.; Chen, X., and Xu, R. Toxicity Assessment of 40 Herbicides to the Green 

Alga Raphidocelis subcapitata. POPWATER,AQUA; 2006; 63, (3): 456-462. 

Notes: EcoReference No.: 83543

Chemical of Concern: 

CLT,DFP,FNP,FZF,HFP,QZF,BSFM,BP,CRME,EMSF,FTS,MTSM,NSF,ACO,BTC,MTL,AMTR,A

TZ,BMN,DU,PAQT,PMT,FXP,MCPA,QNC,PDM,TFN,GFS,GYP,SZ

6. Ma, J.; Xu, L.; Wang, S.; Zheng, R.; Jin, S.; Huang, S., and Huang, Y. Toxicity of 40 Herbicides to the Green 

Alga Chlorella vulgaris. POPWATER,AQUA; 2002; 51, (2): 128-132. 

Notes: EcoReference No.: 65938

Chemical of Concern: 

DFP,QZF,HFP,FNP,FZF,CLT,NSF,TN,EMSF,BSFM,CRME,FTS,BP,ANL,TFN,PDM,BTC,MTL,M

LT,ACO,ATZ,SZ,CZE,DU,PAQT,BMN,FXP,QNC,OXF,GYP,GFSNH

7. Perschbacher, P. W.; Stone, N.; Ludwig, G. M., and Guy, C. B. Jr. Evaluation of Effects of Common AeriallyApplied Soybean Herbicides and Propanil on the Plankton Communities of Aquaculture Ponds. 

POP,PHYWATER,AQUA; 1997; 157, (1/2): 117-122. 

Notes: EcoReference No.: 53095

Chemical of Concern: CRM,FSF,PPN,ACF,GYP,BT,IMQ,FZF,CLT

8. Schrader, K. K.; De Regt, M. Q.; Tidwell, P. D.; Tucker, C. S., and Duke, S. O. Compounds with Selective 

Toxicity Towards the Off-Flavor Metabolite-Producing Cyanobacterium Oscillatoria cf. chalybea. 

POPWATER,AQUA; 1998; 163, (1/2): 85-99. 

Notes: EcoReference No.: 69879

Chemical of Concern: 

PAQT,ACF,ATZ,DU,FMU,NFZ,IMQ,DFP,HFP,CLT,BMN,DBN,DFQ,EDT,FDE,GYP,Cu,SMU,IXB

,SXD
104

9. Wyss, G. S.; Charudattan, R.; Rosskopf, E. N., and Littell, R. C. Effects of Selected Pesticides and Adjuvants 

on Germination and Vegetative Growth of Phomopsis amaranthicola, a Biocontrol Agent for 

Amaranthus spp. MOR,REPENV; 2004; 44, (6): 469-482. 

Notes: EcoReference No.: 96666

Chemical of Concern: 

PEB,DCF,EPTC,OXF,PAQT,CLT,TFN,NPM,PDM,AMTR,PRM,NPP,MBZ,IZT,IPD,VCZ,BMY,DM

T,MLN,CYR,LNR,DU,BS,GYPI,MTL,SXD,DCPA,IZP,SZ,ATZ,Maneb,MZB,CuOH,CTN,FSTL

Clethodim 2012 Refresh - Acceptable 

Reference List

1. Aigner, P. A. and Woerly, R. J. Herbicides and Mowing to Control Barb Goatgrass (Aegilops triuncialis) and 

Restore Native Plants in Serpentine Grasslands. POPSOIL,ENV; 2011; 4, (4): 448-457. 

Notes: EcoReference No.: 156883

Chemical of Concern: CLT,GYPI

2. Arregui, M. C.; Sanchez, D., and Scotta, R. Weed Control in Established Alfalfa (Medicago sativa) with 

Postemergence Herbicides. PHY,POPSOIL,ENV,MIXTURE; 2001; 15, (3): 424-428. 

Notes: EcoReference No.: 67066

Chemical of Concern: 24DB,CLT,CRM,FTS,GYP

3. Askew, S. D.; Shaw, D. R., and Street, J. E. Graminicide Application Timing Influences Red Rice (Oryza 

sativa) Control and Seedhead Reduction in Soybean (Glycine max). POPSOIL,ENV; 2000; 14, 

176-181. 

Notes: EcoReference No.: 59315

Chemical of Concern: CLT,FZFP,SXD

4. Askew, S. D.; Street, J. E., and Shaw, D. R. Herbicide Programs for Red Rice (Oryza sativa) Control in 

Soybean (Glycine max). PHY,POP. S.D. Askew, Dept. of Plant and Soil Sciences, Mississippi State 

University, Mississippi State, MS 39762////: SOIL,ENV,MIXTURE; 1998; 12, (1): 103-107. 

Notes: EcoReference No.: 63442

Chemical of Concern: ACR,CLT,CMZ,IAZ,IZT,MTL,PDM,TFN

5. Bailly, G. C.; Dale, R. P.; Archer, S. A.; Wright, D. J., and Kaundun, S. S. Role of Residual Herbicides for 

the Management of Multiple Herbicide Resistance to ACCase and ALS Inhibitors in a Black-Grass 

Population. MOR,POPSOIL,ENV,MIXTURE; 2012; 34, (0): 96-103. 

Notes: EcoReference No.: 157123

Chemical of Concern: CLFP,CLT,DFC,IZPI,PDM,SMM,SS

6. Ball, D. A.; Frost, S. M., and Bennett, L. H. ACCase-Inhibitor Herbicide Resistance in Downy Brome 

(Bromus tectorum) in Oregon. GRO,MORSOIL,ENV; 2007; 55, (2): 91-94. 

Notes: EcoReference No.: 157092

Chemical of Concern: ALSV,CLT,FZFB,MOIL,QZFPE

7. Barnes, J. W. and Oliver, L. R. Cloransulam Antagonizes Annual Grass Control with 

Aryloxyphenoxypropionate Graminicides but not Cyclohexanediones. ACC,GRO,POP. Univ 

Arkansas, Dept Crop & Soil Environm Sci, Fayetteville, AR 72701 USA//: SOIL,ENV,MIXTURE; 

2004; 18, (3): 763-772. 

Notes: EcoReference No.: 156884

Chemical of Concern: CLNS,CLT,FNP,FZFP,GYP,SXD

8. Barnes, T. G. Using Herbicides to Rehabilitate Native Grasslands. POPSOIL,ENV; 2007; 27, (1): 56-65. 

Notes: EcoReference No.: 156982

Chemical of Concern: CLT,IAZ,SFS
105

9. Bedmar, F. Bermudagrass (Cynodon dactylon) Control in Sunflower (Helianthus annuus), Soybean (Glycine 

max), and Potato (Solanum tuberosum) with Postemergence Graminicides. POP. Prof. F. Bedmar, 

Departamento de Produccion Vegetal, Faculdad de Ciencias Agrarias-UNMDP, C.C. 276, 7620 

Balcarce, Argentina//: SOIL,ENV; 1997; 11, (4): 683-688. 

Notes: EcoReference No.: 152009

Chemical of Concern: CLT,FNPE,FNPPE,FZFP

10. ---. Evaluation on Postemergence Grass Herbicides Against Cynodon dactylon in Sunflower. 

POPSOIL,ENV; 1992; 13, 58-59. 

Notes: EcoReference No.: 156977

Chemical of Concern: CLT,FNPPE

11. Blackshaw, R. E.; Derksen, D. A., and Muendel, H. H. Herbicides for Weed Control in Safflower (Carthamus 

tinctorius). PHY,POPSOIL,ENV,MIXTURE; 1990; 70, (1): 237-245. 

Notes: EcoReference No.: 120455

Chemical of Concern: 

ALSV,CLT,DDP,DFPM,DFQ,EFL,EMSFM,MOIL,PHMD,SXD,TFN,THF,TNM

12. Blackshaw, R. E.; Semach, G., and Entz, T. Postemergence Control of Foxtail Barley (Hordeum jubatum) 

Seedlings in Spring Wheat (Triticum aestivum) and Flax (Linum usitatissimum). POP. 

blackshaw@em.agr.ca//R.E. Blackshaw, Research Centre, Agriculture and Agri-Food Canada, P.O. 

Box 3000, Lethbridge, Alta. T1J 4B1, Canada//: SOIL,ENV,MIXTURE; 1998; 12, (4): 610-616. 

Notes: EcoReference No.: 63023

Chemical of Concern: CLT,FZFP,MBZ,SXD,TKY

13. Bohannan, D. R. and Jordan, T. N. Effects of Ultra-Low Volume Application on Herbicide Efficacy Using 

Oil Diluents as Carriers. GRO,POP. Dep. Botany Plant Pathol., Purdue Univ., West Lafayette, IN 

47907, USA.//: SOIL,ENV; 1995; 9, (4): 682-688. 

Notes: EcoReference No.: 156984

Chemical of Concern: ALSV,BT,CLT,FZFP,GYP,IZT,MBZ,MTL,SOYBN,SXD

14. Bradley, K. W. and Hagood, E. S. Jr. Identification of a Johnsongrass (Sorghum halepense) Biotype Resistant 

to Aryloxyphenoxypropionate and Cyclohexanedione Herbicides in Virginia. GRO,POPSOIL,ENV;

2001; 15, (4): 623-627. 

Notes: EcoReference No.: 66802

Chemical of Concern: CLT,FZFP,SXD

15. Braverman, M. P. Control of Mannagrass (Glyceria declinata) and Southern Watergrass (Luziola fluitans) in 

Water-Seeded Rice (Oryza sativa). PHY,POPSOIL,ENV; 1996; 10, (1): 68-71. 

Notes: EcoReference No.: 96386

Chemical of Concern: CLT,FNP,FZF,GFS,GYP,GYPT,PAQT,SXD

16. Brighenti, A.; Voll, E., and Gazziero, D. L. P. Chloris polydactyla (L.) Sw., a Perennial Poaceae Weed: 

Emergence, Seed Production, and Its Management in Brazil. GRO,POPSOIL,ENV; 2007; 7, (2): 

84-88. 

Notes: EcoReference No.: 156939

Chemical of Concern: ACO,ACR,CLFP,CLT,GYP,HFPM,MTC,SXD,TFN

17. Bruce, B.; Kallenbach, R. L.; Bradley, K., and Fuqua, B. Preplant Herbicides Don't Increase Forage

Production of Cereal Rye Interseeded into Bermudagrass. BCM,POPSOIL,ENV; 2009; 101, (5): 

1175-1181. 

Notes: EcoReference No.: 156888

Chemical of Concern: CLT,PQT

18. Burke, I. C.; Holland, J. B.; Burton, J. D.; York, A. C., and Wilcut, J. W. Johnsongrass (Sorghum halepense) 
106

Pollen Expresses ACCase Target-Site Resistance. GRO,REPENV; 2007; 21, (2): 384-388. 

Notes: EcoReference No.: 156994

Chemical of Concern: CLT

19. Burke, I. C.; Thomas, W. E.; Burton, J. D.; Spears, J. F., and Wilcut, J. W. A Seedling Assay to Screen 

Aryloxyphenoxypropionic Acid and Cyclohexanedione Resistance in Johnsongrass (Sorghum 

halepense). GROSOIL,ENV; 2006; 20, (4): 950-955. 

Notes: EcoReference No.: 156992

Chemical of Concern: CLT,FZFP

20. Burke, I. C.; Wilcut, J. W., and Cranmer, J. Cross-Resistance of a Johnsongrass (Sorghum halepense) Biotype 

to Aryloxyphenoxypropionate and Cyclohexanedione Herbicides. GROSOIL,ENV; 2006; 20, (3): 

571-575. 

Notes: EcoReference No.: 156993

Chemical of Concern: CLT,SXD

21. Campbell, M. H.; Burbidge, D. W., and Nicol, H. I. Control of Carex appressa R.Br. Using Herbicides and 

Surface Sown Pasture Species. POP. NSW Agric., Agric. Res. and Vet. Centre, Forest Road, 

Orange, NSW 2800, Australia.//: SOIL,ENV; 1997; 12, (3): 120-124. 

Notes: EcoReference No.: 157039

Chemical of Concern: CLT,FZF,GYP,IZP,PMR,SXD

22. Capell, B.; Reeleder, R. D.; Grohs, R., and Zilkey, B. Evaluation of Herbicides for Management of Weeds in 

Cultivation of Panax quinquefolius L. POPSOIL,ENV,MIXTURE; 1999; 23, (3): 135-147. 

Notes: EcoReference No.: 120528

Chemical of Concern: CLT,DMDP,DQTBr,EFL,GYP,MCPANa,OYZ

23. Cox, K. G. and Harrington, K. C. Selective Herbicide Strategies for Use in Australian Desmanthus Seed 

Crops. GRO,POPSOIL,ENV,MIXTURE; 2005; 39, (3): 171-181. 

Notes: EcoReference No.: 157094

Chemical of Concern: 

24DB,ACF,ACFNa,ACO,ACR,ASM,ATZ,BMN,BT,CLT,CPP,CRM,CRME,CSF,CZE,DCPA,DM

DP,DQTBr,DU,EFS,EPTC,FTS,GYPI,HXZ,IMQ,IZT,LNR,MBZ,MCPA,MCPB,MTL,MTZ,NFZ,O

DZ,OXF,OYZ,PDM,PQT,PYD,PYZ,PZM,SZ,TFN,TRB

24. Crooks, H. L.; York, A. C.; Culpepper, A. S., and Brownie, C. CGA-362622 Antagonizes Annual Grass 

Control by Graminicides in Cotton (Gossypium hirsutum). POP. N Carolina State Univ, Dept Crop 

Sci, Raleigh, NC 27695 USA Univ Georgia, Dept Crop & Soil Sci, Tifton, GA 31793 USA N 

Carolina State Univ, Dept Stat, Raleigh, NC 27695 USA//: SOIL,ENV,MIXTURE; 2003; 17, (2): 

373-380. 

Notes: EcoReference No.: 156893

Chemical of Concern: ALSV,BMN,CLT,FSF,FZFP,MOIL,MSMA,PMT,PTB,SXD

25. Czarnota, M. A. and Derr, J. Controlling Bamboo (Phyllostachys spp.) with Herbicides. 

GRO,PHY,POPSOIL,ENV; 2007; 21, (1): 80-83. 

Notes: EcoReference No.: 154909

Chemical of Concern: CLT,DBN,DTP,FNP,FZF,GFS,GYP,IZP,MSMA,QNC,SXD

26. Dastgheib, F.; Plew, J. N., and Hill, G. D. Chemical Weed Control in Chickpeas. 

POPSOIL,ENV,MIXTURE; 1995; 0, 186-188. 

Notes: EcoReference No.: 120308

Chemical of Concern: BT,CLT,CZE,MBZ,MCPB,TBZ

27. Dear, B. S.; Sandral, G. A., and Wilson, B. C. D. Tolerance of Perennial Pasture Grass Seedlings to Pre- and 

Post-Emergent Grass Herbicides. GRO,PHYSOIL,ENV; 2006; 46, (5): 637-644. 
107

Notes: EcoReference No.: 86670

Chemical of Concern: 

ATZ,CLT,CSF,CZE,DFPM,FNPPE,FZFB,MBZ,PDM,PZM,QZFE,SXD,SZ,TFN,TKY,TRL,TSF

28. Derr, J. F. Common Reed (Phragmites australis) Response to Mowing and Herbicide Application. 

GRO,POPSOIL,ENV; 2008; 1, (1): 12-16. 

Notes: EcoReference No.: 103875

Chemical of Concern: CLT,DTP,FNP,FZF,GFS,GYPI,MSMA,QNC,SXD

29. Ferrell, J. A.; Earl, H. J., and Vencill, W. K. The Effect of Selected Herbicides on CO2 Assimilation, 

Chlorophyll Fluorescence, and Stomatal Conductance in Johnsongrass (Sorghum halepense L). 

CEL,PHYSOIL,ENV; 2003; 51, (1): 28-31. 

Notes: EcoReference No.: 157102

Chemical of Concern: CLT,GYP,IAZ,NSF

30. Foy, C. L. and Witt, H. L. Annual Grass Control in Alfalfa (Medicago sativa) with Postemergence 

Graminicides. POPSOIL,ENV,MIXTURE; 1992; 6, (4): 938-948. 

Notes: EcoReference No.: 120431

Chemical of Concern: CLT,FNP,FZF,FZFP,PAQT,PQT,SXD,THF,TRB

31. Frans, R.; McClelland, M.; Jordan, D., and Johnson, B. Herbicide Trials on Field Crops, 1989. 

PHY,POPSOIL,ENV,MIXTURE; 1990: 110 p. 

Notes: EcoReference No.: 157119

Chemical of Concern: 

24DB,ACF,ACFNa,ACR,ATZ,BFL,BMN,BT,CLT,CMZ,CRME,CZE,DMB,DMDP,DU,FMU,FNP,

FSF,IMQ,IZT,LCF,LNR,MBZ,MSMA,MTL,MTZ,NFZ,NSF,OXF,PDM,PMT,PQT,QZFE,SXD,TF

N

32. Frans, R.; McClelland, M.; Smith, C., and Jordan, D. Herbicide Trials on Field Crops, 1992. 

PHY,POPSOIL,ENV,MIXTURE; 1993; 427, 63 p. 

Notes: EcoReference No.: 73962

Chemical of Concern: 

24BF,24D,24DB,24DXY,ACFNa,ACR,ATZ,BMN,BT,CLT,CMZ,CRM,CZE,DMB,DU,FMU,FNP

PE,FSF,FTS,FZFP,IAZ,IMQ,IZT,LCF,LNR,MBZ,MSMA,MTL,MTZ,NFZ,NSF,OXF,PDM,PMT,P

QT,PTBNa,PYD,SXD,SYD,TFN,TPZ

33. Grichar, W. J. Comparison of Postemergence Herbicides for Common Bermudagrass (Cynodon dactylon) 

Control in Peanut (Arachis hypogaea). POP. Res. Sci., Texas Agric. Exp. St., Box 755, Yoakum, 

TX 77995////: SOIL,ENV,MIXTURE; 1995; 9, (4): 825-828. 

Notes: EcoReference No.: 157103

Chemical of Concern: CLT,FNP,FNPE,FZFP,PDM,SXD

34. ---. Control of Texas Panicum (Panicum texanum) and Southern Crabgrass (Digitaria ciliaris) in Peanuts 

(Arachis hypogaea) with Postemergence Herbicides. POP. Tex. Agric. Exp. Stn., Yoakum, Tex. 

77995////: SOIL,ENV; 1991; 18, (1): 6-8. 

Notes: EcoReference No.: 156970

Chemical of Concern: CLT,FNP,FZFP

35. Grichar, W. J. and Boswell, T. E. Bermudagrass (Cynodon dactylon) Control with Postemergence Herbicides 

in Peanut (Arachis hypogaea). POPSOIL,ENV; 1989; 3, (2): 267-271. 

Notes: EcoReference No.: 157020

Chemical of Concern: CLT,FNP,FZF,FZFP,MTL,SXD,TFN

36. Grichar, W. J. and Ocumpaugh, W. R. Response of Three Annual Medic Species to Postemergence 

Herbicides. GRO,POPSOIL,ENV; 2009; 23, (3): 412-415. 
108

Notes: EcoReference No.: 156904

Chemical of Concern: 24DB,CLT,FTS,IZT,IZX

37. Griffin, J. L.; Miller, D. K., and Salassi, M. E. Johnsongrass (Sorghum halepense) Control and Economics of 

Using Glyphosate-Resistant Soybean in Fallowed Sugarcane Fields. POPSOIL,ENV; 2006; 20, (4): 

980-985. 

Notes: EcoReference No.: 155807

Chemical of Concern: CLT,FZF,GYP

38. Han, J.; Liu, H.; Guo, P., and Hao, C. Weed Control in Summer-Sown Soybeans with Flumioxazin plus 

Acetochlor and Flumiclorac-Pentyl plus Clethodim. POP. College of Agronomy, Shanxi 

Agricultural University, Taigu, eo . Re . China////: SOIL,ENV,MIXTURE; 2002; 2, (2): 120-122. 

Notes: EcoReference No.: 157118

Chemical of Concern: ACO,CLT,FMCP,FMX

39. Harker, K. N. Ammonium Sulfate Effects on the Activity of Herbicides for Selective Grass Control. 

GRO,POP. Res. Sci., Agric. Canada Res. Stn., Bag Serv. 5000, Lacombe, AB T0C 1S0, Canada////: 

SOIL,ENV,MIXTURE; 1995; 9, (2): 260-266. 

Notes: EcoReference No.: 157105

Chemical of Concern: CLT,FNP,FZF,NHSO4

40. Harrington, K. C. and Rahman, A. Tolerance to Herbicides of Ground Cover Species for New Zealand 

Orchards. PHYSOIL,ENV,MIXTURE; 1998; 13, (3): 111-115. 

Notes: EcoReference No.: 70295

Chemical of Concern: 

AMTL,ASM,CLT,CPR,CSF,DBN,DMB,DMDP,DQTBr,DU,EFS,FZF,GFS,GYP,LNR,MCPA,MC

PP2,NFZ,ODZ,OXF,OYZ,PAQT,PDM,PQT,SXD,SZ,TBNU,TPR

41. Harrington, K. C.; Southward, R. C.; Kitchen, K. L., and He, X. Z. Investigation of Herbicides Tolerated by 

Stevia rebaudiana Crops. GRO,PHY,POP. [Harrington, KC//: SOIL,ENV; 2011; 39, (1): 21-33. 

Notes: EcoReference No.: 157121

Chemical of Concern: 

ASM,BT,CLT,EFS,FTS,FXPM,LNR,MBZ,OYZ,PDM,PMT,PYZ,TFN,THFM,TRB

42. Hennigh, D. S.; Al-Khatib, K.; Stahlman, P. W., and Shoup, D. E. Prairie Cupgrass (Eriochloa contract) and 

Windmillgrass (Chloris verticillata) Response to Glyphosate and Acetyl-CoA CarboxylaseInhibiting Herbicides. ACC,GRO,REPSOIL,ENV,MIXTURE; 2005; 53, (3): 315-322. 

Notes: EcoReference No.: 157106

Chemical of Concern: ACO,ACR,ATZ,CLT,DMM,FFC,GYPI,IXF,MTC,PDM,RIM,SXD

43. Hochberg, O.; Sibony, M., and Rubin, B. The Response of ACCase-Resistant Phalaris paradoxa Populations 

Involves Two Different Target Site Mutations. GRO,POPSOIL,ENV,MIXTURE; 2009; 49, (1): 37-

46. 

Notes: EcoReference No.: 156947

Chemical of Concern: CLFP,CLT,DFPM,FFC,PNX,PZM,QZFPE,TKY

44. Ivany, J. A. and Sanderson, J. B. Quackgrass (Elytrigia repens) Control in Potatoes (Solanum tuberosum) 

with Clethodim. GRO,POP. IvanyJ@agr.gc.ca//: SOIL,ENV,MIXTURE; 2003; 84, (1): 27-35. 

Notes: EcoReference No.: 82407

Chemical of Concern: ALSV,CLT,MBZ,NHSO4,SXD

45. Johnson III, W. C.; Prostko, E. P., and Grey, T. L. Annoying Trends in Strip-Tillage Weed Control in Peanut: 

What are Our Options? POP. BOOK 

http://www.ag.auburn.edu/auxiliary/nsdl/scasc/Proceedings/2002/JohnsonWC.pdf//: SOIL,ENV; 

2002: 165-170. 
109

Notes: EcoReference No.: 156906

Chemical of Concern: ACR,CLT,DMM,EFL,MTL,PDM,SXD

46. Johnson III, W. C.; Prostko, E. P., and Mullinix, B. G. Jr. Texas Panicum (Panicum texanum) Control in 

Strip-Tillage Peanut (Arachis hypogaea) Production. PHY,POPSOIL,ENV,MIXTURE; 2002; 29, 

(2): 141-145. 

Notes: EcoReference No.: 120386

Chemical of Concern: ACR,CLT,DMM,EFL,MTL,PDM,SXD

47. Kurtz, M. E. and Neill, S. W. Tolerance of Kenaf to Selected Postemergence Herbicides. GRO,PHY. Delta 

Branch, Mississippi Agric. For. Ex . Stn., Stoneville, MS//: SOIL,ENV; 1992; 6, (1): 125-128. 

Notes: EcoReference No.: 157110

Chemical of Concern: ACF,BT,CLT,CRM,FSF,FZFP,IAZ,IMQ,IZT,LCF,MSMA,MTS,SMU,SXD

48. Leys, A. R.; Plater, B., and Cullis, B. Response of Six Temperate Annual Grass Weeds to Six Selective 

Herbicides. POPSOIL,ENV; 1988; 3, (4): 163-168. 

Notes: EcoReference No.: 157040

Chemical of Concern: CLT,FNPE,FZFP,QZFE,SXD

49. Marshall, G.; Kirkwood, R. C., and Leach, G. E. Comparative Studies on Graminicide-Resistant and 

Susceptible Biotypes of Eleusine indica. POP,REP. Dep. Plant Sci., Scottish Agric. Coll., 

Auchincruive, Ayr KA6 5HW, UK.////: SOIL,ENV; 1994; 34, (3): 177-185. 

Notes: EcoReference No.: 156975

Chemical of Concern: CLT,DFP,FNP,FZF,SXD,TKY

50. Matthews, N.; Powles, S. B., and Preston, C. Mechanisms of Resistance to Acetyl-Coenzyme A CarboxylaseInhibiting Herbicides in a Hordeum leporinum Population. ACC,BCM,MORSOIL,ENV; 2000; 56, 

441-447. 

Notes: EcoReference No.: 63953

Chemical of Concern: CLT,DFP,FZFB,QZFPE,SXD,TKY

51. McCullough, P. E.; Hart, S. E.; Askew, S.; Dernoeden, P. H.; Reicher, Z., and Weisenberger, D. Kentucky 

Bluegrass Control with Postemergence Herbicides. POPSOIL,ENV; 2006; 41, (1): 255-258. 

Notes: EcoReference No.: 87931

Chemical of Concern: CLT,GFSNH,GYPI,RIM,SXD

52. McWhorter, C. G.; Barrentine, W. L., and Hanks, J. E. Postemergence Grass Control with Herbicides Applied 

at ULV in Paraffinic Oil. POP. Plant Physiol., Applic. Tech. Res. Unit, Agric Res. Serv., U.S. Dep. 

Agric., Stoneville, Miss. 38776.//: SOIL,ENV; 1992; 6, (2): 262-268. 

Notes: EcoReference No.: 157069

Chemical of Concern: ALSV,CLT,COTSD,FZFP,KER,MOIL,SOYBN,SXD

53. Minton, B. W.; Kurtz, M. E., and Shaw, D. R. Barnyardgrass (Echinochloa crus-galli) Control with Grass and 

Broadleaf Weed Herbicide Combinations. POP. Dep. Plant Pathol. Weed Sci., Mississippi State 

Univ., Mississippi State, MS//: SOIL,ENV,MIXTURE; 1989; 37, (2): 223-227. 

Notes: EcoReference No.: 157113

Chemical of Concern: 24DB,ACF,ALSV,BT,CLT,CRM,FNP,FSF,FZFP,IMQ,LCF,MOIL,SXD

54. Moyer, J. R. and Schaalje, G. B. Quackgrass (Elytrigia repens) Interference and Control in Seed Alfalfa 

(Medicago sativa). POP. Agric. Can. Res. Stn., Lethbridge, AB, Can. T1J 4B1.//: 

SOIL,ENV,MIXTURE; 1993; 7, (1): 58-64. 

Notes: EcoReference No.: 157070

Chemical of Concern: CLT,FZFP,NHSO4,SXD

55. Nastasi, P. and Smith, R. J. Jr. Red Rice (Oryza sativa) Control in Soybeans (Glycine max). 
110

POPSOIL,ENV,MIXTURE; 1989; 3, (2): 389-392. 

Notes: EcoReference No.: 73747

Chemical of Concern: ACR,CLT,FZFP,FZP,IMQ,IZT,MTL,PDM

56. Ndou, A. Interaction of Weed Emergence, Weed Density, and Herbicide Rate in Soybean. 

MOR,POPSOIL,ENV,MIXTURE; 2009: 102 p. (UMI# 3380407). 

Notes: EcoReference No.: 152884

Chemical of Concern: CLT,GYP,LCF,MBZ,MTC,SFZ

57. Nelson, K. A. and Renner, K. A. Postemergence Weed Control with CGA-277476 and Cloransulam-Methyl 

in Soybean (Glycine max). GRO,PHY,POP. Prof. K.A. Renner, Department of Crop and Soil 

Sciences, Michigan State University, East Lansing, MI 48824-1325, United States//: 

SOIL,ENV,MIXTURE; 1998; 12, (2): 293-299. 

Notes: EcoReference No.: 64012

Chemical of Concern: ACF,CLNSM,CLT,CRM,THF

58. Novo, R. J.; Darre, C. A., and Zumelzu, G. Weed Control in Aloysia polystachya with Pre and Post 

Emergence Herbicides. PHY,POPSOIL,ENV; 1998; 20, (3): 679-682. 

Notes: EcoReference No.: 70779

Chemical of Concern: BMN,BT,CLT,FSF,FZFB,IZT,PAQT,PDM,PMT,PQT,SZ,TFN,TRB

59. Palmer, E. W.; Shaw, D. R., and Holloway, J. C. Jr. Influence of CGA-277476 on Efficacy of Postemergence 

Graminicides. POPSOIL,ENV,MIXTURE; 1999; 13, (1): 48-53. 

Notes: EcoReference No.: 157073

Chemical of Concern: CLT,FZFP

60. Park, K. W. and Mallory-Smith, C. A. Multiple Herbicide Resistance in Downy Brome (Bromus tectorum) 

and Its Impact on Fitness. GRO,PHYSOIL,ENV; 2005; 53, (6): 780-786. 

Notes: EcoReference No.: 154031

Chemical of Concern: ATZ,CLT,CMZ,DU,EFS,FZF,GFS,GYP,MBZ,NFZ,PAQT,TFN,TRB

61. Perschbacher, P. W.; Stone, N.; Ludwig, G. M., and Guy, C. B. Jr. Evaluation of Effects of Common 

Aerially-Applied Soybean Herbicides and Propanil on the Plankton Communities of Aquaculture 

Ponds. POPAQUA; 1997; 157, (1-2): 117-122. 

Notes: EcoReference No.: 53095

Chemical of Concern: ACF,ACFNa,BT,CLT,CRM,CRME,FSF,FZF,FZFB,GYP,GYPI,IMQ,PPN

62. Petersen, J.; Neser, J. M., and Dresbach-Runkel, M. Resistant Factors of Target-Site and Metabolic Resistant 

Black-Grass (Alopecurus myosuroides Huds.) Biotypes Against Different ACC-ase-Inhibitors. 

GRO. pryrtdrn@fh-bingen.de//: SOIL,ENV; 2008; Sp. Iss. 21, 23-28. 

Notes: EcoReference No.: 156760

Chemical of Concern: CLT

63. Prokop, M. and Veverka, K. Influence of Droplet Spectra on the Efficiency of Contact and Systemic 

Herbicides. POP. State Phytosanitary Admin, Div Plant Protect Equip, Brno, Czech Republic 

Mendel Univ Agr & Forestry Brno, Brno, Czech Republic//: SOIL,ENV,MIXTURE; 2003; 49, (2): 

75-80. 

Notes: EcoReference No.: 156921

Chemical of Concern: BT,CLT

64. Prostko, E. P.; Johnson III, W. C., and Mullinix, B. G. Jr. Annual Grass Control with Preplant Incorporated 

and Preemergence Applications of Ethalfluralin and Pendimethalin in Peanut (Arachis hypogaea). 

PHY,POPSOIL,ENV,MIXTURE; 2001; 15, (1): 36-41. 

Notes: EcoReference No.: 67060

Chemical of Concern: 24DB,BT,CLT,EFL,PDM,PYD,SXD
111

65. Reynolds, J. H.; Krueger, W. A., and Walker, C. L. Effects of Clethodim on Seedhead Density, Forage Yield, 

and Quality of Tall Fescue (Festuca arundinacea). BCM,POP,REP. Plant and Soil Sci. Dep., Univ. 

Tennessee, Knoxville, TN 37901-1071, USA.//: SOIL,ENV; 1993; 7, (3): 751-755. 

Notes: EcoReference No.: 157075

Chemical of Concern: ALSV,CLT,MOIL

66. Rosales-Robles, E.; Chandler, J. M.; Senseman, S. A., and Prostko, E. P. Integrated Johnsongrass 

Management in Cotton with Reduced Rates of Clethodim and Cultivation. POPSOIL,ENV; 1999; 3, 

27-34. 

Notes: EcoReference No.: 63480

Chemical of Concern: CLT

67. Ruffner, M. E. and Barnes, T. G. Natural Grassland Response to Herbicides and Application Timing for 

Selective Control of Tall Fescue, an Invasive Cool-Season Grass. POPSOIL,ENV; 2010; 3, (3): 

219-228. 

Notes: EcoReference No.: 156927

Chemical of Concern: ALSV,CLT,MOIL

68. Schuh, J. F. and Harvey, R. G. Woolly Cupgrass (Eriochloa villosa (Thunb.) Kunth) Control in Corn (Zea 

mays L.) and Soybean (Glycine max (L.) Merr.) and the Influence of Moisture on Imazethapyr 

Diffusion. PHY,POPSOIL,ENV,MIXTURE; 1990: 334 p. (UMI#9100162). 

Notes: EcoReference No.: 116575

Chemical of Concern: 

24D,24DXY,ACF,ACO,ACR,AMTR,ATZ,BT,BTY,CLT,CMZ,CYC,CZE,DFPM,EPTC,FNP,FZFP

,GYP,IZT,LNR,MBZ,MTL,NSF,PAQT,PDM,SXD,SZ,TFN

69. Smeda, R. J.; Snipes, C. E., and Barrentine, W. L. Identification of Graminicide-Resistant Johnsongrass 

(Sorghum halepense). PHY,POPSOIL,ENV; 1997; 45, (1): 132-137. 

Notes: EcoReference No.: 155808

Chemical of Concern: CLT,FNPE,FZFP,GFS,GYP,GYPT,IZT,LNR,MSMA,NSF,PAQT,PQT,SXD

70. Snipes, C. E. and Allen, R. L. Interaction of Graminicides Applied in Combination with Pyrithiobac. POP. 

Mississippi Agric. For. Exp. Stn., Delta Branch, Stoneville, MS 38776, USA.//: 

SOIL,ENV,MIXTURE; 1996; 10, (4): 889-892. 

Notes: EcoReference No.: 157076

Chemical of Concern: CLT,FZFP,NFZ,PTB,SXD

71. Stanton, R. A.; Pratley, J. E.; Hudson, D., and Dill, G. M. Herbicide Tolerant Canola Systems and Their 

Impact on Winter Crop Rotations. POPSOIL,ENV,MIXTURE; 2010; 117, (1): 161-166. 

Notes: EcoReference No.: 150459

Chemical of Concern: ATZ,CLT,CSF,DFPM,DQT,GYP,PQT,SZ,TFN,TSF

72. Stoltenberg, D. E. and Wiederholt, R. J. Giant Foxtail (Setaria faberi) Resistance to 

Aryloxyphenoxypropionate and Cyclohexanedione Herbicides. GRO,MOR,POP. Dep. Agron., 

Univ. Wisconsin, Madison, WI 53706, USA.//: SOIL,ENV; 1995; 43, (4): 527-535. 

Notes: EcoReference No.: 157078

Chemical of Concern: CLT,DFPM,FNPE,IZT,LNR,NSF,OXF,SXD

73. Talbert, R. E.; Wichert, R. A.; Carey III, V. F.; Johnson, D. H.; Ruff, D. F., and Kendig, J. A. Field 

Evaluation of Herbicides on Small Fruit, Vegetable and Ornamental Crops 1991. 

PHY,POPSOIL,ENV,MIXTURE; 1992; 417, 58 p. 

Notes: EcoReference No.: 70759

Chemical of Concern: 

ACFNa,ATZ,BS,BT,CLT,CMZ,CRM,DCPA,DTP,DU,EFL,EPTC,FSF,FZFP,GFSNH,GYPI,IMQ,I

XB,IZT,MBZ,MTL,NPM,NPP,OXF,OYZ,PDM,PQT,PYD,SXD,SZ,TFN,TPZ,TRB
112

74. Talbert, R. E.; Wichert, R. A.; McCarty, J. T.; Johnson, D. H.; Ruff, D. F.; Kendig, J. A., and Carey, V. F. 

Field Evaluation of Herbicides on Small Fruit, Vegetable and Ornamental Crops 1990. 

PHY,POPSOIL,ENV,MIXTURE; 1991; 412, 56 p. 

Notes: EcoReference No.: 155813

Chemical of Concern: 

ACF,ACFNa,ACR,ATZ,BS,BT,CLT,CMZ,CPR,CRME,CYC,DCPA,DEE,DTP,DU,EFL,EPTC,FSF

,GFSNH,GYPI,IAZ,IMQ,IXB,IZT,LCF,MB,MTL,MTZ,NPM,NPP,NSF,OXF,OYZ,PDM,PHMD,P

QT,PRM,SXD,TFN,TRB

75. Taverner, J.; Beasley, J. S.; Strahan, R. E.; Griffin, J. L., and Borst, S. M. Selective Postemergence Herbicide 

Control of Torpedograss in Centipedegrass. PHY,POPSOIL,ENV; 2011; 25, (2): 212-216. 

Notes: EcoReference No.: 154969

Chemical of Concern: CLT,QNC,SXD

76. Teuton, T. C. Management of Hybrid Bluegrass (Poa arachnifera Torr. x Poa pratensis L.) in the Transition 

Zone. BCM,GRO,PHY,POPSOIL,ENV; 2006: 159 p. (UMI#3214429). 

Notes: EcoReference No.: 154952

Chemical of Concern: 

BP,CLT,CSF,DFPM,DTP,EPH,HSF,IAZ,IMQ,MTSM,ODZ,OYZ,PBZ,PCZ,PDM,PRM,QNC,RIM,

SFS,SXD,TFN,TXE

77. Tredaway, J. A.; Patterson, M. G., and Wehtje, G. R. Interaction of Clethodim with Pyrithiobac and 

Bromoxynil Applied in Low Volume. POP. Dep. Plant Soil Sci., Univ. Tenn., Knoxville, TN 

37901-1071, USA.//: SOIL,ENV,MIXTURE; 1998; 12, (1): 185-189. 

Notes: EcoReference No.: 157082

Chemical of Concern: BMN,CLT,PTB

78. Wall, D. A. and Smith, M. A. H. Quackgrass (Elytrigia repens) Management in Flax (Linum usitatissimum). 

POP. Agr & Agri Food Canada, Brandon Res Ctr, Brandon, MB R7A 5Y3, Canada Agr & Agri 

Food Canada, Cereal Res Ctr, Winnipeg, MB R3T 2M9, Canada//: SOIL,ENV,MIXTURE; 2000; 

80, (2): 411-417. 

Notes: EcoReference No.: 156933

Chemical of Concern: BMN,CLT,DFPM,FZFP,GYP,SXD

79. Webber III, C. L. Kenaf (Hibiscus cannabinus L.) Response to Four Grass Control Herbicides Broadcast 

Postemergence. GRO,POPSOIL,ENV; 1994; 8, (3): 457-460. 

Notes: EcoReference No.: 156934

Chemical of Concern: CLT,FZF,SXD

80. Webster, T. M.; Bednarz, C. W., and Hanna, W. W. Sensitivity of Triploid Hybrid Bermudagrass Cultivars 

and Common Bermudagrass to Postemergence Herbicides. GRO,POP. USDA ARS, Coastal Plain 

Expt Stn, Crop Protect & Management Res Unit, Tifton, GA 31794 USA Univ Georgia, Dept Crop 

& Soil Sci, Coastal Plain Expt Stn, Tifton, GA 31794 USA//: SOIL,ENV,MIXTURE; 2003; 17, (3): 

509-515. 

Notes: EcoReference No.: 156935

Chemical of Concern: CLT,FZFP,GFS,GYP

81. Webster, T. M.; Hanna, W. W., and Mullinix, B. G. Jr. Bermudagrass (Cynodon spp.) Dose-Response 

Relationships with Clethodim, Glufosinate and Glyphosate. GRO,PHYSOIL,ENV; 2004; 60, (12): 

1237-1244. 

Notes: EcoReference No.: 155802

Chemical of Concern: CLT,GFS,GYP

82. Wiederholt, R. J. and Stoltenberg, D. E. Cross-Resistance of a Large Crabgrass (Digitaria sanguinalis) 

Accession to Aryloxyphenoxypropionate and Cyclohexanedione Herbicides. GROSOIL,ENV; 

1995; 9, (3): 518-524. 
113

Notes: EcoReference No.: 156936

Chemical of Concern: ALSV,CLT,DFP,FNP,FZFP,IZT,LNR,MOIL,SXD

83. Wilcut, J. W. Efficacy and Economics of Common Bermudagrass (Cynodon dactylon) Control in Peanut 

(Arachis hypogaea). POP. Dep. Agron., Box 748, Coastal Plain Exp. Stn., Univ. Ga., Tifton, Ga. 

31793-0748.//: SOIL,ENV,MIXTURE; 1991; 18, (2): 106-109. 

Notes: EcoReference No.: 156971

Chemical of Concern: CLT,FZFP,SXD

84. Wright, S. D.; Vargas, R. N.; Martin-Duvall, T., and Jimenez, M. R. Jr. Pyrithiobac, Grass Herbicide 

Antagonism Study in Cotton. POPSOIL,ENV,MIXTURE; 1998; 51, 17-18.

Notes: EcoReference No.: 156937

Chemical of Concern: CLT,FZF,PTB,SXD

85. Yu, Q.; Collavo, A.; Zheng, M. Q.; Owen, M.; Sattin, M., and Powles, S. B. Diversity of Acetyl-Coenzyme A 

Carboxylase Mutations in Resistant Lolium Populations: Evaluation Using Clethodim. 

MORSOIL,ENV; 2007; 145, (2): 547-558. 

Notes: EcoReference No.: 111509

Chemical of Concern: CLT,DFP,FZF,PNX,SXD,TKY
114

APPENDIX H. ECOTOX Open Literature That Passed Initial Screen

Accepted ECOTOX DATA Table – Clethodim

The code list for ECOTOX can be found at: http://cfpub.epa.gov/ecotox/blackbox/help/codelist.pdf

May 2008

Chemical 

Name Genus Species Common Name

Effect 

Group Effect Meas Endpt1 Endpt2

Dur 

Preferred 

Mean

Dur Unit 

Preferred

Conc #1 

Purity 

Adjusted in 

Preferred 

Unit Mean

Conc 

Units 

Preferred

% 

Purity Ref #

Clethodim Chlorella vulgaris Green Algae POP POP PGRT EC50 4 d 4.644564 mg/L 12 65938

Clethodim Chlorella pyrenoidosa Green Algae POP POP PGRT EC50 4 d 10.842084 mg/L 12 61984

Clethodim Scenedesmus acutus var. 

acutus Green Algae POP POP PGRT EC50 4 d 6.816684 mg/L 12 61984

Clethodim Scenedesmus quadricauda Green Algae POP POP PGRT EC50 4 d 9.228 mg/L 12 101396

Clethodim Oscillatoria chalybea Blue-Green 

Algae POP POP ABND LOEC 5 d 1000 uM 99 69879

Clethodim Pseudokirchneriella subcapitata Green Algae POP POP ABND LOEC 5 d 1000 uM 99 69879

Clethodim Pseudokirchneriella subcapitata Green Algae POP POP ABND EC100 5 d 1000 uM 99 69879

Clethodim Oscillatoria chalybea Blue-Green 

Algae POP POP ABND EC100 5 d 1000 uM 99 69879

Clethodim Plankton sp. Plankton POP POP PSYN NOAEL 2 d 0.07 AI kg/ha 100 53095

Clethodim Echinochloa crus-galli Barnyard 

Grass POP POP ABND LOAEL ea 0.03 kg/ha 100 101451

Clethodim Echinochloa crus-galli Barnyard 

Grass POP POP ABND LOAEL ea 0.03 kg/ha 100 101451

Clethodim Leptochloa fusca Malabar 

Sprangletop POP POP ABND LOAEL ea 0.03 kg/ha 100 101451

Clethodim Leptochloa fusca Malabar 

Sprangletop POP POP ABND LOAEL ea 0.03 kg/ha 100 101451

Clethodim Oryza sativa Rice PHY INJ DAMG LOAEL 14 d 0.03 kg/ha 100 101451

Clethodim Oryza sativa Rice PHY INJ DAMG NOAEL 14 d 0.06 kg/ha 100 101451

Clethodim Oryza sativa Rice POP POP BMAS NOAEL hv 0.06 kg/ha 100 101451

Clethodim Echinochloa crus-galli Barnyard 

Grass POP POP ABND LOAEL ea 0.03 kg/ha 100 101451

Clethodim Echinochloa crus-galli Barnyard 

Grass POP POP ABND LOAEL ea 0.03 kg/ha 100 101451

Clethodim Leptochloa fusca Malabar 

Sprangletop POP POP ABND LOAEL ea 0.03 kg/ha 100 101451

Clethodim Leptochloa fusca Malabar 

Sprangletop POP POP ABND LOAEL ea 0.03 kg/ha 100 101451
115

Chemical 

Name Genus Species Common Name

Effect 

Group Effect Meas Endpt1 Endpt2

Dur 

Preferred 

Mean

Dur Unit 

Preferred

Conc #1 

Purity 

Adjusted in 

Preferred 

Unit Mean

Conc 

Units 

Preferred

% 

Purity Ref #

Clethodim Oryza sativa Rice PHY INJ DAMG LOAEL 21 d 0.03 kg/ha 100 101451

Clethodim Oryza sativa Rice PHY INJ DAMG LOAEL 21 d 0.03 kg/ha 100 101451

Clethodim Oryza sativa Rice POP POP BMAS NOAEL hv 0.03 kg/ha 100 101451

Clethodim Pseudokirchneriella subcapitata Green Algae POP POP ABND EC50 4 d 2.744112 mg/L 12 83543

Clethodim Steinernema feltiae Nematode BEH BEH GBHV NOAEL 9 d 1.26 ml/L 12.6 71382

Clethodim Steinernema feltiae Nematode MOR MOR SURV NOAEL 3 d 1.26 ml/L 12.6 71382

Clethodim Phomopsis amaranthicola Fungus MOR MOR MORT LD50 1.0125 d 0.48 L/ha 100 96666

Clethodim Phomopsis amaranthicola Fungus MOR MOR MORT LD50 1.0125 d 0.48 L/ha 100 96666

July 2012 - Refresh

Chemical 

Name Genus Species Common Name Effect Group Effect Meas Endpt1 Endpt2

Dur 

Preferred 

Mean

Dur Unit 

Preferred

Conc #1 

Purity 

Adjusted in 

Preferred 

Unit Mean

Conc Units 

Preferred

% 

Purity Ref #

Clethodim Setaria faberi Mutton 

Bluegrass GRO GRO BMAS ED50 21 d 8.90E-05 lb/acre 100 157078

Clethodim Setaria faberi Mutton 

Bluegrass GRO GRO BMAS ED50 21 d 0.000712 lb/acre 100 157078

Clethodim Digitaria sanguinalis Purple Crabgrass GRO GRO BMAS ED50 21 d 0.00178 lb/acre 100 156936

Clethodim Sorghum bicolor Broomcorn POP POP DBMS EC50 28 d 0.00224784 lb/acre 100 152884

Clethodim Sorghum bicolor Broomcorn POP POP DBMS EC50 28 d 0.00224784 lb/acre 100 152884

Clethodim Sorghum bicolor Broomcorn POP POP DBMS EC50 28 d 0.00224784 lb/acre 100 152884

Clethodim Sorghum bicolor Broomcorn POP POP DBMS EC50 28 d 0.0024976 lb/acre 100 152884

Clethodim Sorghum bicolor Broomcorn POP POP DBMS EC50 28 d 0.00274736 lb/acre 100 152884

Clethodim Sorghum bicolor Broomcorn POP POP DBMS EC80 28 d 0.00349664 lb/acre 100 152884

Clethodim Sorghum bicolor Broomcorn POP POP DBMS EC50 28 d 0.00349664 lb/acre 100 152884

Clethodim Sorghum bicolor Broomcorn POP POP DBMS EC80 28 d 0.00349664 lb/acre 100 152884

Clethodim Sorghum bicolor Broomcorn POP POP DBMS EC80 28 d 0.0037464 lb/acre 100 152884

Clethodim Sorghum arundinaceum Shattercane POP POP DBMS EC50 28 d 0.0037464 lb/acre 100 152884

Clethodim Sorghum bicolor Broomcorn POP POP DBMS EC80 28 d 0.0037464 lb/acre 100 152884

Clethodim Lolium rigidum Wimmera 

Ryegrass MOR MOR MORT LD50 21 d 0.003916 lb/acre 100 111509

Clethodim Digitaria sanguinalis Purple Crabgrass POP POP DBMS EC50 28 d 0.00449568 lb/acre 100 152884

Clethodim Sorghum arundinaceum Shattercane POP POP DBMS EC50 28 d 0.00449568 lb/acre 100 152884

Clethodim Sorghum bicolor Broomcorn POP POP DBMS EC50 28 d 0.00449568 lb/acre 100 152884

Clethodim Sorghum bicolor Broomcorn POP POP DBMS EC80 28 d 0.00449568 lb/acre 100 152884

Clethodim Sorghum bicolor Broomcorn POP POP DBMS EC50 28 d 0.00474544 lb/acre 100 152884

Clethodim Schedonorus arundinaceus Tall Fescue POP POP BMAS NOAEL LOAEL 57 d 0.004984 lb/acre 100 157075

Clethodim Schedonorus arundinaceus Tall Fescue BCM BCM PRCO NOAEL LOAEL 57 d 0.004984 lb/acre 100 157075
116

Chemical 

Name Genus Species Common Name Effect Group Effect Meas Endpt1 Endpt2

Dur 

Preferred 

Mean

Dur Unit 

Preferred

Conc #1 

Purity 

Adjusted in 

Preferred 

Unit Mean

Conc Units 

Preferred

% 

Purity Ref #

Clethodim Schedonorus arundinaceus Tall Fescue POP POP BMAS LOAEL 26 d 0.004984 lb/acre 100 157075

Clethodim Schedonorus arundinaceus Tall Fescue REP REP SEED LOAEL 26 d 0.004984 lb/acre 100 157075

Clethodim Schedonorus arundinaceus Tall Fescue BCM BCM FIBR LOAEL 26 d 0.004984 lb/acre 100 157075

Clethodim Schedonorus arundinaceus Tall Fescue POP POP BMAS NOAEL LOAEL 194 d 0.004984 lb/acre 100 157075

Clethodim Schedonorus arundinaceus Tall Fescue REP REP SEED NOAEL LOAEL 194 d 0.004984 lb/acre 100 157075

Clethodim Schedonorus arundinaceus Tall Fescue POP POP BMAS LOAEL 58 d 0.004984 lb/acre 100 157075

Clethodim Schedonorus arundinaceus Tall Fescue REP REP SEED LOAEL 58 d 0.004984 lb/acre 100 157075

Clethodim Schedonorus arundinaceus Tall Fescue BCM BCM PRCO LOAEL 58 d 0.004984 lb/acre 100 157075

Clethodim Schedonorus arundinaceus Tall Fescue REP REP SEED NOAEL LOAEL 187 d 0.004984 lb/acre 100 157075

Clethodim Schedonorus arundinaceus Tall Fescue POP POP BMAS LOAEL 58 d 0.004984 lb/acre 100 157075

Clethodim Schedonorus arundinaceus Tall Fescue REP REP SEED LOAEL 58 d 0.004984 lb/acre 100 157075

Clethodim Schedonorus arundinaceus Tall Fescue POP POP BMAS NOAEL LOAEL 56 d 0.004984 lb/acre 100 157075

Clethodim Schedonorus arundinaceus Tall Fescue REP REP SEED NOAEL LOAEL 56 d 0.004984 lb/acre 100 157075

Clethodim Schedonorus arundinaceus Tall Fescue POP POP BMAS NOAEL LOAEL 34 d 0.004984 lb/acre 100 157075

Clethodim Schedonorus arundinaceus Tall Fescue REP REP SEED NOAEL LOAEL 34 d 0.004984 lb/acre 100 157075

Clethodim Digitaria sanguinalis Purple Crabgrass POP POP DBMS EC50 28 d 0.0049952 lb/acre 100 152884

Clethodim Sorghum bicolor Broomcorn POP POP DBMS EC50 28 d 0.0049952 lb/acre 100 152884

Clethodim Sorghum bicolor Broomcorn POP POP DBMS EC80 28 d 0.00549472 lb/acre 100 152884

Clethodim Digitaria sanguinalis Purple Crabgrass POP POP DBMS EC50 28 d 0.00574448 lb/acre 100 152884

Clethodim Setaria faberi Mutton 

Bluegrass GRO GRO BMAS ED50 21 d 0.00623 lb/acre 100 157078

Clethodim Phalaris paradoxa Hood 

Canarygrass GRO GRO WGHT ED50 21 d 0.006408 lb/acre 100 156947

Clethodim Sorghum arundinaceum Shattercane POP POP DBMS EC50 28 d 0.00649376 lb/acre 100 152884

Clethodim Digitaria sanguinalis Purple Crabgrass POP POP DBMS EC50 28 d 0.00674352 lb/acre 100 152884

Clethodim Digitaria sanguinalis Purple Crabgrass POP POP DBMS EC80 28 d 0.00699328 lb/acre 100 152884

Clethodim Sorghum bicolor Broomcorn POP POP DBMS EC80 28 d 0.00724304 lb/acre 100 152884

Clethodim Sorghum bicolor Broomcorn POP POP DBMS EC80 28 d 0.00774256 lb/acre 100 152884

Clethodim Sorghum bicolor Broomcorn POP POP DBMS EC80 28 d 0.00799232 lb/acre 100 152884

Clethodim Sorghum arundinaceum Shattercane POP POP DBMS EC50 28 d 0.00824208 lb/acre 100 152884

Clethodim Digitaria sanguinalis Purple Crabgrass POP POP DBMS EC80 28 d 0.00824208 lb/acre 100 152884

Clethodim Alopecurus myosuroides Blackgrass MOR MOR MORT LD50 21 d 0.0084194 lb/acre 100 157123

Clethodim Sorghum arundinaceum Shattercane POP POP DBMS EC50 28 d 0.00849184 lb/acre 100 152884

Clethodim Digitaria sanguinalis Purple Crabgrass POP POP DBMS EC50 28 d 0.0087416 lb/acre 100 152884

Clethodim Sorghum halepense Johnson Grass GRO GRO WGHT EC50 21 d 0.0089 lb/acre 100 156993

Clethodim Sorghum arundinaceum Shattercane POP POP DBMS EC50 28 d 0.00899136 lb/acre 100 152884

Clethodim Digitaria sanguinalis Purple Crabgrass POP POP DBMS EC80 28 d 0.00924112 lb/acre 100 152884

Clethodim Sorghum arundinaceum Shattercane POP POP DBMS EC50 28 d 0.00924112 lb/acre 100 152884

Clethodim Digitaria sanguinalis Purple Crabgrass POP POP DBMS EC50 28 d 0.00949088 lb/acre 100 152884

Clethodim Digitaria sanguinalis Purple Crabgrass POP POP DBMS EC50 28 d 0.00974064 lb/acre 100 152884
117

Chemical 

Name Genus Species Common Name Effect Group Effect Meas Endpt1 Endpt2

Dur 

Preferred 

Mean

Dur Unit 

Preferred

Conc #1 

Purity 

Adjusted in 

Preferred 

Unit Mean

Conc Units 

Preferred

% 

Purity Ref #

Clethodim Digitaria sanguinalis Purple Crabgrass POP POP DBMS EC50 28 d 0.00974064 lb/acre 100 152884

Clethodim Schedonorus arundinaceus Tall Fescue POP POP BMAS NOAEL LOAEL 188 d 0.009968 lb/acre 100 157075

Clethodim Schedonorus arundinaceus Tall Fescue REP REP SEED NOAEL LOAEL 188 d 0.009968 lb/acre 100 157075

Clethodim Schedonorus arundinaceus Tall Fescue POP POP BMAS NOAEL LOAEL 188 d 0.009968 lb/acre 100 157075

Clethodim Schedonorus arundinaceus Tall Fescue REP REP SEED NOAEL LOAEL 57 d 0.009968 lb/acre 100 157075

Clethodim Schedonorus arundinaceus Tall Fescue BCM BCM PRCO NOAEL LOAEL 57 d 0.009968 lb/acre 100 157075

Clethodim Schedonorus arundinaceus Tall Fescue BCM BCM FIBR NOAEL LOAEL 26 d 0.009968 lb/acre 100 157075

Clethodim Schedonorus arundinaceus Tall Fescue BCM BCM FIBR NOAEL LOAEL 194 d 0.009968 lb/acre 100 157075

Clethodim Schedonorus arundinaceus Tall Fescue POP POP BMAS NOAEL LOAEL 187 d 0.009968 lb/acre 100 157075

Clethodim Schedonorus arundinaceus Tall Fescue BCM BCM PRCO NOAEL LOAEL 58 d 0.009968 lb/acre 100 157075

Clethodim Schedonorus arundinaceus Tall Fescue POP POP BMAS NOAEL LOAEL 187 d 0.009968 lb/acre 100 157075

Clethodim Schedonorus arundinaceus Tall Fescue BCM BCM PRCO NOAEL LOAEL 56 d 0.009968 lb/acre 100 157075

Clethodim Schedonorus arundinaceus Tall Fescue BCM BCM PRCO NOAEL LOAEL 34 d 0.009968 lb/acre 100 157075

Clethodim Schedonorus arundinaceus Tall Fescue REP REP SEED NOAEL LOAEL 34 d 0.009968 lb/acre 100 157075

Clethodim Alopecurus myosuroides Blackgrass GRO GRO WGHT ED50 20 d 0.01 L/ha 100 156760

Clethodim Alopecurus myosuroides Blackgrass GRO GRO WGHT ED50 20 d 0.01 L/ha 100 156760

Clethodim Alopecurus myosuroides Blackgrass GRO GRO WGHT ED50 20 d 0.01 L/ha 100 156760

Clethodim Digitaria sanguinalis Purple Crabgrass GRO GRO BMAS ED50 21 d 0.01068 lb/acre 100 156936

Clethodim Digitaria sanguinalis Purple Crabgrass POP POP DBMS EC50 28 d 0.01073968 lb/acre 100 152884

Clethodim Digitaria sanguinalis Purple Crabgrass POP POP DBMS EC80 28 d 0.01073968 lb/acre 100 152884

Clethodim Digitaria sanguinalis Purple Crabgrass POP POP DBMS EC50 28 d 0.0112392 lb/acre 100 152884

Clethodim Digitaria sanguinalis Purple Crabgrass POP POP DBMS EC50 28 d 0.01148896 lb/acre 100 152884

Clethodim Digitaria sanguinalis Purple Crabgrass POP POP DBMS EC50 28 d 0.01148896 lb/acre 100 152884

Clethodim Sorghum arundinaceum Shattercane POP POP DBMS EC50 28 d 0.01173872 lb/acre 100 152884

Clethodim Sorghum arundinaceum Shattercane POP POP DBMS EC50 28 d 0.01273776 lb/acre 100 152884

Clethodim Digitaria sanguinalis Purple Crabgrass POP POP DBMS EC80 28 d 0.01398656 lb/acre 100 152884

Clethodim Digitaria sanguinalis Purple Crabgrass POP POP DBMS EC50 28 d 0.01648416 lb/acre 100 152884

Clethodim Digitaria sanguinalis Purple Crabgrass POP POP DBMS EC50 28 d 0.01673392 lb/acre 100 152884

Clethodim Digitaria sanguinalis Purple Crabgrass POP POP DBMS EC50 28 d 0.0174832 lb/acre 100 152884

Clethodim Digitaria sanguinalis Purple Crabgrass POP POP DBMS EC50 28 d 0.01773296 lb/acre 100 152884

Clethodim Setaria faberi Mutton 

Bluegrass GRO GRO BMAS ED50 21 d 0.018067 lb/acre 100 157078

Clethodim Digitaria sanguinalis Purple Crabgrass POP POP DBMS EC50 28 d 0.01948128 lb/acre 100 152884

Clethodim Lolium rigidum Wimmera 

Ryegrass POP POP BMAS ED50 42 d 0.019758 lb/acre 100 157040

Clethodim Schedonorus arundinaceus Tall Fescue BCM BCM PRCO NOAEL 188 d 0.019936 lb/acre 100 157075

Clethodim Schedonorus arundinaceus Tall Fescue REP REP SEED NOAEL 188 d 0.019936 lb/acre 100 157075

Clethodim Schedonorus arundinaceus Tall Fescue BCM BCM PRCO NOAEL 188 d 0.019936 lb/acre 100 157075

Clethodim Schedonorus arundinaceus Tall Fescue POP POP BMAS NOAEL 57 d 0.019936 lb/acre 100 157075

Clethodim Schedonorus arundinaceus Tall Fescue REP REP SEED NOAEL 57 d 0.019936 lb/acre 100 157075
118

Chemical 

Name Genus Species Common Name Effect Group Effect Meas Endpt1 Endpt2

Dur 

Preferred 

Mean

Dur Unit 

Preferred

Conc #1 

Purity 

Adjusted in 

Preferred 

Unit Mean

Conc Units 

Preferred

% 

Purity Ref #

Clethodim Schedonorus arundinaceus Tall Fescue POP POP BMAS NOAEL 26 d 0.019936 lb/acre 100 157075

Clethodim Schedonorus arundinaceus Tall Fescue REP REP SEED NOAEL 26 d 0.019936 lb/acre 100 157075

Clethodim Schedonorus arundinaceus Tall Fescue REP REP SEED NOAEL 194 d 0.019936 lb/acre 100 157075

Clethodim Schedonorus arundinaceus Tall Fescue BCM BCM FIBR NOAEL 194 d 0.019936 lb/acre 100 157075

Clethodim Schedonorus arundinaceus Tall Fescue POP POP BMAS NOAEL 194 d 0.019936 lb/acre 100 157075

Clethodim Schedonorus arundinaceus Tall Fescue BCM BCM PRCO NOAEL 187 d 0.019936 lb/acre 100 157075

Clethodim Schedonorus arundinaceus Tall Fescue REP REP SEED NOAEL 187 d 0.019936 lb/acre 100 157075

Clethodim Schedonorus arundinaceus Tall Fescue BCM BCM PRCO NOAEL 187 d 0.019936 lb/acre 100 157075

Clethodim Schedonorus arundinaceus Tall Fescue POP POP BMAS NOAEL 56 d 0.019936 lb/acre 100 157075

Clethodim Schedonorus arundinaceus Tall Fescue REP REP SEED NOAEL 56 d 0.019936 lb/acre 100 157075

Clethodim Schedonorus arundinaceus Tall Fescue BCM BCM PRCO NOAEL 56 d 0.019936 lb/acre 100 157075

Clethodim Schedonorus arundinaceus Tall Fescue POP POP BMAS NOAEL 34 d 0.019936 lb/acre 100 157075

Clethodim Schedonorus arundinaceus Tall Fescue BCM BCM PRCO NOAEL 34 d 0.019936 lb/acre 100 157075

Clethodim Hordeum murinum ssp. 

leporinum

Leporinum 

Barley MOR MOR MORT LD50 35 d 0.02047 lb/acre 100 63953

Clethodim Digitaria sanguinalis Purple Crabgrass POP POP DBMS EC50 28 d 0.02097984 lb/acre 100 152884

Clethodim Hordeum vulgare Barley GRO GRO WGHT LOAEL 28 d 0.02225 lb/acre 100 157105

Clethodim Hordeum vulgare Barley GRO GRO WGHT LOAEL 28 d 0.02225 lb/acre 100 157105

Clethodim NR Poaceae Grass Family POP POP CNTL LOAEL 14 d 0.02314 lb/acre 100 156984

Clethodim NR Poaceae Grass Family POP POP CNTL LOAEL 14 d 0.02314 lb/acre 100 156984

Clethodim NR Poaceae Grass Family POP POP CNTL LOAEL 14 d 0.02314 lb/acre 100 156984

Clethodim Sorghum halepense Johnson Grass GRO MPH LGTH ED50 5 d 0.0248 ppm 100 156992

Clethodim Echinochloa crus-galli Barnyard Grass POP POP CNTL LOAEL 21 d 0.02492 lb/acre 100 157069

Clethodim Echinochloa crus-galli Barnyard Grass POP POP CNTL LOAEL 21 d 0.02492 lb/acre 100 157069

Clethodim Echinochloa crus-galli Barnyard Grass POP POP CNTL LOAEL 70 d 0.02492 lb/acre 100 157069

Clethodim Sorghum halepense Johnson Grass POP POP CNTL LOAEL 21 d 0.02492 lb/acre 100 157069

Clethodim Echinochloa crus-galli Barnyard Grass POP POP CNTL LOAEL 70 d 0.02492 lb/acre 100 157069

Clethodim Sorghum halepense Johnson Grass POP POP CNTL LOAEL 21 d 0.02492 lb/acre 100 157069

Clethodim Sorghum halepense Johnson Grass POP POP CNTL LOAEL 21 d 0.02492 lb/acre 100 157069

Clethodim Sorghum halepense Johnson Grass POP POP CNTL LOAEL 21 d 0.02492 lb/acre 100 157069

Clethodim Echinochloa crus-galli Barnyard Grass POP POP CNTL LOAEL 21 d 0.02492 lb/acre 100 157069

Clethodim Echinochloa crus-galli Barnyard Grass POP POP CNTL LOAEL 21 d 0.02492 lb/acre 100 157069

Clethodim Sorghum halepense Johnson Grass POP POP CNTL LOAEL 21 d 0.02492 lb/acre 100 157069

Clethodim Sorghum halepense Johnson Grass POP POP CNTL LOAEL 21 d 0.02492 lb/acre 100 157069

Clethodim Sorghum halepense Johnson Grass POP POP CNTL LOAEL 21 d 0.02492 lb/acre 100 157069

Clethodim Echinochloa crus-galli Barnyard Grass POP POP CNTL LOAEL 70 d 0.02492 lb/acre 100 157069

Clethodim Echinochloa crus-galli Barnyard Grass POP POP CNTL LOAEL 21 d 0.02492 lb/acre 100 157069

Clethodim Echinochloa crus-galli Barnyard Grass POP POP CNTL LOAEL 21 d 0.02492 lb/acre 100 157069

Clethodim Sorghum halepense Johnson Grass POP POP CNTL LOAEL 21 d 0.02492 lb/acre 100 157069

Clethodim Sorghum halepense Johnson Grass POP POP CNTL LOAEL 21 d 0.02492 lb/acre 100 157069
119

Chemical 

Name Genus Species Common Name Effect Group Effect Meas Endpt1 Endpt2

Dur 

Preferred 

Mean

Dur Unit 

Preferred

Conc #1 

Purity 

Adjusted in 

Preferred 

Unit Mean

Conc Units 

Preferred

% 

Purity Ref #

Clethodim Sorghum halepense Johnson Grass POP POP CNTL LOAEL 21d 0.02492 lb/acre 100 157069

Clethodim Sorghum halepense Johnson Grass POP POP CNTL LOAEL 21d 0.02492 lb/acre 100 157069

Clethodim Echinochloa crus-galli Barnyard Grass POP POP CNTL LOAEL 70d 0.02492 lb/acre 100 157069

Clethodim Echinochloa crus-galli Barnyard Grass POP POP CNTL LOAEL 70d 0.02492 lb/acre 100 157069

Clethodim Echinochloa crus-galli Barnyard Grass POP POP CNTL LOAEL 70d 0.02492 lb/acre 100 157069

Clethodim Sorghum halepense Johnson Grass POP POP CNTL LOAEL 21d 0.02492 lb/acre 100 157069

Clethodim Sorghum halepense Johnson Grass POP POP CNTL LOAEL 21d 0.02492 lb/acre 100 157069

Clethodim Sorghum halepense Johnson Grass POP POP CNTL LOAEL 21d 0.02492 lb/acre 100 157069

Clethodim Echinochloa crus-galli Barnyard Grass POP POP CNTL LOAEL 21d 0.02492 lb/acre 100 157069

Clethodim Echinochloa crus-galli Barnyard Grass POP POP CNTL LOAEL 21d 0.02492 lb/acre 100 157069

Clethodim Echinochloa crus-galli Barnyard Grass POP POP CNTL LOAEL 21d 0.02492 lb/acre 100 157069

Clethodim Sorghum halepense Johnson Grass POP POP CNTL LOAEL 21d 0.02492 lb/acre 100 157069

Clethodim Sorghum halepense Johnson Grass POP POP CNTL LOAEL 21d 0.02492 lb/acre 100 157069

Clethodim Sorghum halepense Johnson Grass POP POP CNTL LOAEL 21d 0.02492 lb/acre 100 157069

Clethodim Echinochloa crus-galli Barnyard Grass POP POP CNTL LOAEL 21d 0.02492 lb/acre 100 157069

Clethodim Echinochloa crus-galli Barnyard Grass POP POP CNTL LOAEL 21d 0.02492 lb/acre 100 157069

Clethodim Echinochloa crus-galli Barnyard Grass POP POP CNTL LOAEL 21d 0.02492 lb/acre 100 157069

Clethodim Sorghum halepense Johnson Grass POP POP CNTL LOAEL 21d 0.02492 lb/acre 100 157069

Clethodim Sorghum halepense Johnson Grass POP POP CNTL LOAEL 21d 0.02492 lb/acre 100 157069

Clethodim Sorghum halepense Johnson Grass POP POP CNTL LOAEL 21d 0.02492 lb/acre 100 157069

Clethodim Sorghum halepense Johnson Grass POP POP CNTL LOAEL 21d 0.02492 lb/acre 100 157069

Clethodim Sorghum halepense Johnson Grass POP POP CNTL LOAEL 21d 0.02492 lb/acre 100 157069

Clethodim Sorghum halepense Johnson Grass POP POP CNTL LOAEL 21d 0.02492 lb/acre 100 157069

Clethodim Echinochloa crus-galli Barnyard Grass POP POP CNTL LOAEL 21d 0.02492 lb/acre 100 157069

Clethodim Echinochloa crus-galli Barnyard Grass POP POP CNTL LOAEL 21d 0.02492 lb/acre 100 157069

Clethodim Echinochloa crus-galli Barnyard Grass POP POP CNTL LOAEL 21d 0.02492 lb/acre 100 157069

Clethodim Echinochloa crus-galli Barnyard Grass POP POP CNTL LOAEL 21d 0.02492 lb/acre 100 157069

Clethodim Echinochloa crus-galli Barnyard Grass POP POP CNTL LOAEL 21d 0.02492 lb/acre 100 157069

Clethodim Echinochloa crus-galli Barnyard Grass POP POP CNTL LOAEL 21d 0.02492 lb/acre 100 157069

Clethodim Sorghum halepense Johnson Grass POP POP CNTL LOAEL 21d 0.02492 lb/acre 100 157069

Clethodim Sorghum halepense Johnson Grass POP POP CNTL LOAEL 21d 0.02492 lb/acre 100 157069

Clethodim Sorghum halepense Johnson Grass POP POP CNTL LOAEL 21d 0.02492 lb/acre 100 157069

Clethodim Sorghum halepense Johnson Grass POP POP CNTL LOAEL 21d 0.02492 lb/acre 100 157069

Clethodim Echinochloa crus-galli Barnyard Grass POP POP CNTL LOAEL 70d 0.02492 lb/acre 100 157069

Clethodim Echinochloa crus-galli Barnyard Grass POP POP CNTL LOAEL 70d 0.02492 lb/acre 100 157069

Clethodim Echinochloa crus-galli Barnyard Grass POP POP CNTL LOAEL 70d 0.02492 lb/acre 100 157069

Clethodim Digitaria sanguinalis Purple Crabgrass POP POP CNTL LOAEL9d 0.024976 lb/acre 100 157082

Clethodim Digitaria sanguinalis Purple Crabgrass POP POP DBMS EC80 28d 0.02647456 lb/acre 100 152884

Clethodim Digitaria sanguinalis Purple Crabgrass POP POP DBMS EC80 28d 0.02847264 lb/acre 100 152884

Clethodim Bromus tectorum Downy Brome GRO GRO WGHT ED50 21d 0.02848 lb/acre 100 154031
120

Chemical 

Name Genus Species Common Name Effect Group Effect Meas Endpt1 Endpt2

Dur 

Preferred 

Mean

Dur Unit 

Preferred

Conc #1 

Purity 

Adjusted in 

Preferred 

Unit Mean

Conc Units 

Preferred

% 

Purity Ref #

Clethodim Alopecurus myosuroides Blackgrass MOR MOR MORT LD50 21d 0.02937 lb/acre 100 157123

Clethodim Digitaria sanguinalis Purple Crabgrass POP POP DBMS EC80 28d 0.03122 lb/acre 100 152884

Clethodim Digitaria sanguinalis Purple Crabgrass POP POP DBMS EC80 28d 0.03346784 lb/acre 100 152884

Clethodim Phalaris paradoxa Hood 

Canarygrass POP POP BMAS ED50 42

d 0.034532 lb/acre 100 157040

Clethodim Sorghum halepense Johnson Grass GRO GRO WGHT EC50 21d 0.03471 lb/acre 100 156993

Clethodim Cynodon sp. Bermudagrass GRO GRO VGOR IC50 31d 0.03568 lb/acre 100 155802

Clethodim Cynodon sp. Bermudagrass GRO GRO VGOR IC50 31d 0.03568 lb/acre 100 155802

Clethodim Cynodon sp. Bermudagrass GRO GRO VGOR IC50 31d 0.03568 lb/acre 100 155802

Clethodim Digitaria sanguinalis Purple Crabgrass POP POP CNTL IC80 21d 0.03738 lb/acre 100 156893

Clethodim Hordeum jubatum Foxtail Barley POP POP BMAS LOAEL1 gs 0.04005 lb/acre 100 63023

Clethodim Hordeum jubatum Foxtail Barley POP POP BMAS LOAEL1 gs 0.04005 lb/acre 100 63023

Clethodim Linum usitatissimum Flax POP POP BMAS NOAEL hv 0.04005 lb/acre 100 63023

Clethodim Hordeum jubatum Foxtail Barley POP POP BMAS LOAEL1 gs 0.04005 lb/acre 100 63023

Clethodim Hordeum jubatum Foxtail Barley POP POP BMAS LOAEL1 gs 0.04005 lb/acre 100 63023

Clethodim Hordeum jubatum Foxtail Barley POP POP BMAS LOAEL1 gs 0.04005 lb/acre 100 63023

Clethodim Hordeum jubatum Foxtail Barley POP POP BMAS LOAEL1 gs 0.04005 lb/acre 100 63023

Clethodim Linum usitatissimum Flax POP POP BMAS LOAEL hv 0.04005 lb/acre 100 63023

Clethodim Linum usitatissimum Flax POP POP BMAS NOAEL hv 0.04005 lb/acre 100 63023

Clethodim Linum usitatissimum Flax POP POP BMAS NOAEL hv 0.04005 lb/acre 100 63023

Clethodim Elymus repens Quackgrass POP POP BMAS LOAEL 45.66d 0.04005 lb/acre 100 156933

Clethodim Elymus repens Quackgrass POP POP BMAS LOAEL 45.66d 0.04005 lb/acre 100 156933

Clethodim Elymus repens Quackgrass POP POP BMAS LOAEL 45.66d 0.04005 lb/acre 100 156933

Clethodim Elymus repens Quackgrass POP POP BMAS LOAEL 45.66d 0.04005 lb/acre 100 156933

Clethodim Elymus repens Quackgrass POP POP BMAS LOAEL 45.66d 0.04005 lb/acre 100 156933

Clethodim Linum usitatissimum Flax POP POP BMAS LOAEL 85d 0.04005 lb/acre 100 156933

Clethodim Phalaris paradoxa Hood 

Canarygrass GRO GRO WGHT ED50 21

d 0.04094 lb/acre 100 156947

Clethodim NR Magnoliopsida Dicot Class POP POP ABND NOAEL 42d 0.04272 lb/acre 100 150459

Clethodim Lolium rigidum Wimmera 

Ryegrass POP POP ABND LOAEL 42

d 0.04272 lb/acre 100 150459

Clethodim NR Poaceae Grass Family POP POP ABND NOAEL 42d 0.04272 lb/acre 100 150459

Clethodim Sorghum halepense Johnson Grass GRO GRO WGHT EC50 28d 0.044322 lb/acre 100 66802

Clethodim Eleusine indica Goosegrass POP POP BMAS LOAEL 21d 0.0445 lb/acre 100 156975

Clethodim Eleusine indica Goosegrass POP POP BMAS LOAEL 21d 0.0445 lb/acre 100 156975

Clethodim Avena fatua Red Oats POP POP WGHT NOAEL LOAEL hv 0.0445 lb/acre 100 157105

Clethodim Hordeum vulgare Barley POP POP WGHT NOAEL LOAEL hv 0.0445 lb/acre 100 157105

Clethodim Hordeum vulgare Barley POP POP WGHT NOAEL LOAEL hv 0.0445 lb/acre 100 157105

Clethodim Cynodon sp. Bermudagrass PHY INJ DAMG IC50 17d 0.0446 lb/acre 100 155802

Clethodim Cynodon sp. Bermudagrass GRO GRO VGOR IC50 17d 0.0446 lb/acre 100 155802
121

Chemical 

Name Genus Species Common Name Effect Group Effect Meas Endpt1 Endpt2

Dur 

Preferred 

Mean

Dur Unit 

Preferred

Conc #1 

Purity 

Adjusted in 

Preferred 

Unit Mean

Conc Units 

Preferred

% 

Purity Ref #

Clethodim Setaria faberi Mutton 

Bluegrass MOR MOR SURV LOAEL 21

d 0.046725 lb/acre 100 157078

Clethodim NR Poaceae Grass Family POP POP CNTL LOAEL 14d 0.04717 lb/acre 100 156984

Clethodim NR Poaceae Grass Family POP POP CNTL LOAEL 14d 0.04717 lb/acre 100 156984

Clethodim NR Poaceae Grass Family POP POP CNTL LOAEL 14d 0.04717 lb/acre 100 156984

Clethodim Glycine max Soybean POP POP BMAS NOAEL hv 0.04717 lb/acre 100 156984

Clethodim Glycine max Soybean POP POP BMAS NOAEL hv 0.04717 lb/acre 100 156984

Clethodim Glycine max Soybean POP POP BMAS NOAEL hv 0.04717 lb/acre 100 156984

Clethodim Glycine max Soybean POP POP BMAS NOAEL hv 0.04717 lb/acre 100 156984

Clethodim Glycine max Soybean POP POP BMAS NOAEL hv 0.04984 lb/acre 100 157069

Clethodim Glycine max Soybean POP POP BMAS NOAEL hv 0.04984 lb/acre 100 157069

Clethodim Glycine max Soybean POP POP BMAS NOAEL hv 0.04984 lb/acre 100 157069

Clethodim Glycine max Soybean POP POP BMAS NOAEL hv 0.04984 lb/acre 100 157069

Clethodim Glycine max Soybean POP POP BMAS NOAEL hv 0.04984 lb/acre 100 157069

Clethodim Glycine max Soybean POP POP BMAS NOAEL hv 0.04984 lb/acre 100 157069

Clethodim Glycine max Soybean POP POP BMAS NOAEL hv 0.04984 lb/acre 100 157069

Clethodim Glycine max Soybean POP POP BMAS NOAEL hv 0.04984 lb/acre 100 157069

Clethodim Glycine max Soybean POP POP BMAS NOAEL hv 0.04984 lb/acre 100 157069

Clethodim Glycine max Soybean POP POP BMAS NOAEL hv 0.04984 lb/acre 100 157069

Clethodim Glycine max Soybean POP POP BMAS NOAEL hv 0.04984 lb/acre 100 157069

Clethodim Glycine max Soybean POP POP BMAS NOAEL hv 0.04984 lb/acre 100 157069

Clethodim Glycine max Soybean POP POP BMAS NOAEL hv 0.04984 lb/acre 100 157069

Clethodim Glycine max Soybean POP POP BMAS NOAEL hv 0.04984 lb/acre 100 157069

Clethodim Glycine max Soybean POP POP BMAS NOAEL hv 0.04984 lb/acre 100 157069

Clethodim Glycine max Soybean POP POP BMAS NOAEL hv 0.04984 lb/acre 100 157069

Clethodim Glycine max Soybean POP POP BMAS NOAEL hv 0.04984 lb/acre 100 157069

Clethodim Glycine max Soybean POP POP BMAS NOAEL hv 0.04984 lb/acre 100 157069

Clethodim Glycine max Soybean POP POP BMAS NOAEL hv 0.04984 lb/acre 100 157069

Clethodim Glycine max Soybean POP POP BMAS NOAEL hv 0.04984 lb/acre 100 157069

Clethodim Glycine max Soybean POP POP BMAS NOAEL hv 0.04984 lb/acre 100 157069

Clethodim Glycine max Soybean POP POP BMAS NOAEL hv 0.04984 lb/acre 100 157069

Clethodim Glycine max Soybean POP POP BMAS NOAEL hv 0.04984 lb/acre 100 157069

Clethodim Cynodon dactylon Bermudagrass GRO GRO VGOR IC50 31d 0.05352 lb/acre 100 155802

Clethodim Phalaris paradoxa Hood 

Canarygrass GRO GRO WGHT ED50 21

d 0.056515 lb/acre 100 156947

Clethodim Hordeum murinum ssp. 

leporinum

Leporinum 

Barley POP POP BMAS ED50 42

d 0.057939 lb/acre 100 157040

Clethodim Sorghum halepense Johnson Grass POP POP CNTL LOAEL 14d 0.05874 lb/acre 100 157076

Clethodim Sorghum halepense Johnson Grass POP POP CNTL LOAEL 14d 0.05874 lb/acre 100 157076

Clethodim Sorghum halepense Johnson Grass POP POP CNTL LOAEL 14d 0.05874 lb/acre 100 157076
122

Chemical 

Name Genus Species Common Name Effect Group Effect Meas Endpt1 Endpt2

Dur 

Preferred 

Mean

Dur Unit 

Preferred

Conc #1 

Purity 

Adjusted in 

Preferred 

Unit Mean

Conc Units 

Preferred

% 

Purity Ref #

Clethodim Gossypium hirsutum Cotton POP POP BMAS NOAEL hv 0.05874 lb/acre 100 157076

Clethodim Bromus diandrus Ripgut Brome POP POP BMAS ED50 42 d 0.059007 lb/acre 100 157040

Clethodim Avena fatua Red Oats POP POP BMAS ED50 42 d 0.060164 lb/acre 100 157040

Clethodim Sorghum halepense Johnson Grass GRO GRO WGHT EC50 28 d 0.061499 lb/acre 100 66802

Clethodim Sorghum halepense Johnson Grass POP POP BMAS LOAEL 1 gs 0.0623 lb/acre 100 63480

Clethodim Sorghum halepense Johnson Grass POP POP BMAS LOAEL 1 gs 0.0623 lb/acre 100 63480

Clethodim Sorghum halepense Johnson Grass POP POP BMAS LOAEL 1 gs 0.0623 lb/acre 100 63480

Clethodim Sorghum halepense Johnson Grass POP POP ABND LOAEL 1 gs 0.0623 lb/acre 100 63480

Clethodim Sorghum halepense Johnson Grass POP POP ABND LOAEL 1 gs 0.0623 lb/acre 100 63480

Clethodim Sorghum halepense Johnson Grass POP POP ABND NOAEL LOAEL 1 gs 0.0623 lb/acre 100 63480

Clethodim Sorghum halepense Johnson Grass POP POP ABND LOAEL 1 gs 0.0623 lb/acre 100 63480

Clethodim Sorghum halepense Johnson Grass POP POP ABND LOAEL 1 gs 0.0623 lb/acre 100 63480

Clethodim Oryza sativa Rice POP POP BMAS NOAEL d 0.0623 lb/acre 100 59315

Clethodim Oryza sativa Rice POP POP BMAS NOAEL d 0.0623 lb/acre 100 59315

Clethodim Oryza sativa Rice POP POP BMAS LOAEL d 0.0623 lb/acre 100 59315

Clethodim Oryza sativa Rice POP POP BMAS LOAEL d 0.0623 lb/acre 100 59315

Clethodim Oryza sativa Rice POP POP BMAS LOAEL d 0.0623 lb/acre 100 59315

Clethodim Oryza sativa Rice POP POP BMAS LOAEL d 0.0623 lb/acre 100 59315

Clethodim Oryza sativa Rice POP POP BMAS NOAEL d 0.0623 lb/acre 100 59315

Clethodim Oryza sativa Rice POP POP BMAS NOAEL d 0.0623 lb/acre 100 59315

Clethodim Oryza sativa Rice POP POP BMAS LOAEL d 0.0623 lb/acre 100 59315

Clethodim Oryza sativa Rice POP POP BMAS LOAEL d 0.0623 lb/acre 100 59315

Clethodim Oryza sativa Rice POP POP BMAS LOAEL d 0.0623 lb/acre 100 59315

Clethodim Eriochloa villosa Hairy Cupgrass POP POP CNTL LOAEL 16 d 0.06244 lb/acre 100 116575

Clethodim Cynodon sp. Bermudagrass GRO GRO VGOR IC50 31 d 0.06244 lb/acre 100 155802

Clethodim Cynodon sp. Bermudagrass GRO GRO VGOR IC50 31 d 0.06244 lb/acre 100 155802

Clethodim Cynodon sp. Bermudagrass GRO GRO VGOR IC50 31 d 0.06244 lb/acre 100 155802

Clethodim Cynodon sp. Bermudagrass GRO GRO VGOR IC50 31 d 0.06244 lb/acre 100 155802

Clethodim Echinochloa crus-galli Barnyard Grass POP POP BMAS LOAEL 28 d 0.06244 lb/acre 100 157113

Clethodim Bromus tectorum Downy Brome MOR MOR MORT NRLETH 47 d 0.06244 lb/acre 100 157092

Clethodim Bromus tectorum Downy Brome GRO GRO BMAS EC50 47 d 0.06244 lb/acre 100 157092

Clethodim Urochloa texana Texas Signalgrass POP POP CNTL LOAEL 88 d 0.06244 lb/acre 100 156970

Clethodim Urochloa texana Texas Signalgrass POP POP CNTL LOAEL 75 d 0.06244 lb/acre 100 156970

Clethodim Urochloa texana Texas Signalgrass POP POP CNTL LOAEL 74 d 0.06244 lb/acre 100 156970

Clethodim Urochloa texana Texas Signalgrass POP POP CNTL LOAEL 53 d 0.06244 lb/acre 100 156970

Clethodim Setaria faberi Mutton 

Bluegrass POP POP BMAS LOAEL 21 d 0.06319 lb/acre 100 64012

Clethodim NR Magnoliopsida Dicot Class POP POP ABND LOAEL 21 d 0.06408 lb/acre 25 157118

Clethodim NR Poaceae Grass Family POP POP BMAS LOAEL 21 d 0.06408 lb/acre 25 157118
123

Chemical 

Name Genus Species Common Name Effect Group Effect Meas Endpt1 Endpt2

Dur 

Preferred 

Mean

Dur Unit 

Preferred

Conc #1 

Purity 

Adjusted in 

Preferred 

Unit Mean

Conc Units 

Preferred

% 

Purity Ref #

Clethodim NR Plantae Plant Kingdom POP POP ABND LOAEL 21 d 0.06408 lb/acre 25 157118

Clethodim Glycine max Soybean POP POP BMAS NOAEL 21 d 0.06408 lb/acre 25 157118

Clethodim Bromus tectorum Downy Brome GRO GRO WGHT ED50 21 d 0.06586 lb/acre 100 154031

Clethodim Elymus repens Quackgrass POP POP CNTL LOAEL 1 gs 0.0669 lb/acre 100 82407

Clethodim Elymus repens Quackgrass POP POP CNTL LOAEL 1 gs 0.0669 lb/acre 100 82407

Clethodim NR Poaceae Grass Family POP POP CNTL LOAEL 7 d 0.07136 lb/acre 100 120431

Clethodim Echinochloa crus-galli Barnyard Grass POP POP CNTL LOAEL 19 d 0.07136 lb/acre 100 120431

Clethodim Echinochloa crus-galli Barnyard Grass POP POP CNTL LOAEL 19 d 0.07136 lb/acre 100 120431

Clethodim Echinochloa crus-galli Barnyard Grass POP POP CNTL LOAEL 18 d 0.07136 lb/acre 100 120431

Clethodim Echinochloa crus-galli Barnyard Grass POP POP BMAS LOAEL 50 d 0.07136 lb/acre 100 120431

Clethodim Echinochloa crus-galli Barnyard Grass POP POP CNTL LOAEL 19 d 0.07136 lb/acre 100 120431

Clethodim Echinochloa crus-galli Barnyard Grass POP POP CNTL LOAEL 18 d 0.07136 lb/acre 100 120431

Clethodim Agrostis castellana Bentgrass PHY INJ DAMG LOAEL 49 d 0.07136 lb/acre 100 70295

Clethodim Cynodon sp. Bermudagrass PHY INJ DAMG IC50 17 d 0.07136 lb/acre 100 155802

Clethodim Cynodon sp. Bermudagrass GRO GRO VGOR IC50 31 d 0.07136 lb/acre 100 155802

Clethodim Cynodon sp. Bermudagrass PHY INJ DAMG IC50 17 d 0.07136 lb/acre 100 155802

Clethodim Hordeum murinum ssp. 

leporinum

Leporinum 

Barley MOR MOR MORT LD50 35 d 0.07832 lb/acre 100 63953

Clethodim Linum usitatissimum Flax POP POP BMAS NOAEL 81 d 0.0801 lb/acre 100 156933

Clethodim Linum usitatissimum Flax POP POP BMAS NOAEL 89 d 0.0801 lb/acre 100 156933

Clethodim Linum usitatissimum Flax POP POP BMAS NOAEL 78 d 0.0801 lb/acre 100 156933

Clethodim Linum usitatissimum Flax POP POP BMAS NOAEL 90 d 0.0801 lb/acre 100 156933

Clethodim Cynodon sp. Bermudagrass PHY INJ DAMG IC50 17 d 0.08028 lb/acre 100 155802

Clethodim Cynodon sp. Bermudagrass GRO GRO VGOR IC50 31 d 0.08028 lb/acre 100 155802

Clethodim Cynodon dactylon Bermudagrass PHY INJ DAMG IC50 17 d 0.08028 lb/acre 100 155802

Clethodim Sorghum halepense Johnson Grass POP POP CNTL LOAEL 13 d 0.08028 lb/acre 100 73962

Clethodim Sorghum halepense Johnson Grass POP POP CNTL LOAEL 17 d 0.08028 lb/acre 100 73962

Clethodim Lolium rigidum Wimmera 

Ryegrass MOR MOR MORT LD50 21 d 0.08722 lb/acre 100 111509

Clethodim Urochloa texana Texas Signalgrass POP POP CNTL LOAEL 62 d 0.0892 lb/acre 100 67060

Clethodim Urochloa texana Texas Signalgrass POP POP CNTL LOAEL 62 d 0.0892 lb/acre 100 67060

Clethodim Dactyloctenium aegyptium Crowfoot Grass POP POP CNTL LOAEL 62 d 0.0892 lb/acre 100 67060

Clethodim Arachis hypogaea Peanut POP POP BMAS NOAEL hv 0.0892 lb/acre 100 67060

Clethodim Arachis hypogaea Peanut POP POP BMAS NOAEL hv 0.0892 lb/acre 100 67060

Clethodim Digitaria ciliaris Smooth 

Crabgrass POP POP CNTL LOAEL 62 d 0.0892 lb/acre 100 67060

Clethodim Digitaria ciliaris Smooth 

Crabgrass POP POP CNTL LOAEL 62 d 0.0892 lb/acre 100 67060

Clethodim Urochloa texana Texas Signalgrass POP POP CNTL LOAEL 62 d 0.0892 lb/acre 100 67060

Clethodim Digitaria ciliaris Smooth POP POP CNTL LOAEL 62 d 0.0892 lb/acre 100 67060
124

Chemical 

Name Genus Species Common Name Effect Group Effect Meas Endpt1 Endpt2

Dur 

Preferred 

Mean

Dur Unit 

Preferred

Conc #1 

Purity 

Adjusted in 

Preferred 

Unit Mean

Conc Units 

Preferred

% 

Purity Ref #

Crabgrass

Clethodim Dactyloctenium aegyptium Crowfoot Grass POP POP CNTL LOAEL 62 d 0.0892 lb/acre 100 67060

Clethodim Dactyloctenium aegyptium Crowfoot Grass POP POP CNTL LOAEL 62 d 0.0892 lb/acre 100 67060

Clethodim Arachis hypogaea Peanut POP POP BMAS NOAEL hv 0.0892 lb/acre 100 67060

Clethodim Arachis hypogaea Peanut POP POP BMAS NOAEL hv 0.0892 lb/acre 100 67060

Clethodim Oryza sativa Rice POP POP CNTL LOAEL ea 0.0892 lb/acre 100 73747

Clethodim Glycine max Soybean POP POP BMAS NOAEL hv 0.0892 lb/acre 100 73747

Clethodim Glycine max Soybean POP POP BMAS NOAEL hv 0.0892 lb/acre 100 73747

Clethodim Setaria viridis Green Foxtail POP POP BMAS LOAEL 21 d 0.0892 lb/acre 100 120455

Clethodim Setaria viridis Green Foxtail POP POP BMAS LOAEL 21 d 0.0892 lb/acre 100 120455

Clethodim Avena fatua Red Oats POP POP BMAS LOAEL 21 d 0.0892 lb/acre 100 120455

Clethodim Avena fatua Red Oats POP POP BMAS LOAEL 21 d 0.0892 lb/acre 100 120455

Clethodim Avena fatua Red Oats POP POP BMAS LOAEL 1 gs 0.0892 lb/acre 100 120455

Clethodim Avena fatua Red Oats POP POP BMAS LOAEL 1 gs 0.0892 lb/acre 100 120455

Clethodim Carthamus tinctorius Safflower POP POP BMAS NOAEL hv 0.0892 lb/acre 100 120455

Clethodim Carthamus tinctorius Safflower POP POP BMAS NOAEL hv 0.0892 lb/acre 100 120455

Clethodim Carthamus tinctorius Safflower POP POP BMAS NOAEL hv 0.0892 lb/acre 100 120455

Clethodim Carthamus tinctorius Safflower POP POP BMAS NOAEL hv 0.0892 lb/acre 100 120455

Clethodim Carthamus tinctorius Safflower PHY INJ DAMG NOAEL 21 d 0.0892 lb/acre 100 120455

Clethodim Sorghum halepense Johnson Grass PHY INJ DAMG LOAEL 21 d 0.0892 lb/acre 100 155808

Clethodim Sorghum halepense Johnson Grass PHY INJ DAMG LOAEL 21 d 0.0892 lb/acre 100 155808

Clethodim Arachis hypogaea Peanut POP POP BMAS NOAEL hv 0.0892 lb/acre 100 120386

Clethodim Cynodon sp. Bermudagrass GRO GRO VGOR IC50 31 d 0.0892 lb/acre 100 155802

Clethodim Urochloa texana Texas Signalgrass POP POP CNTL LOAEL 90 d 0.09 AI lb/acre 100 156906

Clethodim Glycine max Soybean POP POP BMAS NOAEL hv 0.09345 lb/acre 100 156984

Clethodim Glycine max Soybean POP POP BMAS NOAEL hv 0.09345 lb/acre 100 156984

Clethodim Lolium rigidum Wimmera 

Ryegrass MOR MOR MORT LD50 21 d 0.09345 lb/acre 100 111509

Clethodim Setaria faberi Mutton 

Bluegrass MOR MOR MORT NRLETH 21 d 0.09345 lb/acre 100 157078

Clethodim Urochloa platyphylla Broadleaf 

Signalgrass POP POP CNTL LOAEL 14 d 0.09345 lb/acre 100 157073

Clethodim Sorghum halepense Johnson Grass POP POP CNTL LOAEL 14 d 0.09345 lb/acre 100 157073

Clethodim Echinochloa crus-galli Barnyard Grass POP POP CNTL LOAEL 14 d 0.09345 lb/acre 100 157073

Clethodim Sorghum halepense Johnson Grass POP POP CNTL LOAEL 14 d 0.09345 lb/acre 100 157073

Clethodim Echinochloa crus-galli Barnyard Grass POP POP CNTL LOAEL 14 d 0.09345 lb/acre 100 157073

Clethodim Sorghum halepense Johnson Grass POP POP CNTL LOAEL 14 d 0.09345 lb/acre 100 157073

Clethodim Urochloa platyphylla Broadleaf 

Signalgrass POP POP CNTL LOAEL 14 d 0.09345 lb/acre 100 157073

Clethodim Urochloa platyphylla Broadleaf POP POP CNTL LOAEL 14 d 0.09434 lb/acre 100 156884
125

Chemical 

Name Genus Species Common Name Effect Group Effect Meas Endpt1 Endpt2

Dur 

Preferred 

Mean

Dur Unit 

Preferred

Conc #1 

Purity 

Adjusted in 

Preferred 

Unit Mean

Conc Units 

Preferred

% 

Purity Ref #

Signalgrass

Clethodim Echinochloa crus-galli Barnyard Grass POP POP CNTL LOAEL 14d 0.09434 lb/acre 100 156884

Clethodim Glycine max Soybean POP POP BMAS NOAEL hv 0.09434 lb/acre 100 156884

Clethodim Glycine max Soybean PHY INJ GINJ NOAEL 27d 0.094552 lb/acre 100 73962

Clethodim Glycine max Soybean POP POP BMAS NOAEL 121d 0.094552 lb/acre 100 73962

Clethodim Glycine max Soybean PHY INJ GINJ NOAEL 87d 0.094552 lb/acre 100 73962

Clethodim Oryza sativa Rice POP POP BMAS LOAELd 0.0979 lb/acre 100 59315

Clethodim Oryza sativa Rice POP POP BMAS LOAELd 0.0979 lb/acre 100 59315

Clethodim Oryza sativa Rice POP POP BMAS LOAELd 0.0979 lb/acre 100 59315

Clethodim Oryza sativa Rice POP POP BMAS NOAELd 0.0979 lb/acre 100 59315

Clethodim Oryza sativa Rice POP POP BMAS LOAELd 0.0979 lb/acre 100 59315

Clethodim Oryza sativa Rice POP POP CNTL LOAEL 28d 0.0979 lb/acre 100 63442

Clethodim Oryza sativa Rice POP POP CNTL LOAEL 28d 0.0979 lb/acre 100 63442

Clethodim Oryza sativa Rice POP POP CNTL LOAEL 28d 0.0979 lb/acre 100 63442

Clethodim Sorghum halepense Johnson Grass GRO GRO WGHT EC50 21d 0.0979 lb/acre 100 156993

Clethodim Hibiscus cannabinus Deccan Hemp GRO GRO HGHT NOAEL 26d 0.0979 lb/acre 100 157110

Clethodim Hibiscus cannabinus Deccan Hemp PHY INJ GINJ NOAEL 10d 0.0979 lb/acre 100 157110

Clethodim Hibiscus cannabinus Deccan Hemp PHY INJ GINJ NOAEL 10d 0.0979 lb/acre 100 157110

Clethodim Hibiscus cannabinus Deccan Hemp GRO GRO HGHT NOAEL 26d 0.0979 lb/acre 100 157110

Clethodim Urochloa texana Texas Signalgrass POP POP CNTL LOAEL 79d 0.09812 lb/acre 100 156970

Clethodim Digitaria ciliaris Smooth 

Crabgrass POP POP CNTL LOAEL 79

d 0.09812 lb/acre 100 156970

Clethodim Digitaria ciliaris Smooth 

Crabgrass POP POP CNTL LOAEL 74

d 0.09812 lb/acre 100 156970

Clethodim Xanthium strumarium Common 

Cocklebur POP POP CNTL NOAEL 28

d 0.09812 lb/acre 100 157119

Clethodim Glycine max Soybean PHY INJ GINJ NOAEL 28d 0.09812 lb/acre 100 157119

Clethodim Glycine max Soybean POP POP BMAS NOAEL 138d 0.09812 lb/acre 100 157119

Clethodim Digitaria sanguinalis Purple Crabgrass POP POP CNTL LOAEL 10d 0.09812 lb/acre 100 157119

Clethodim Amaranthus hybridus Green Amaranth POP POP CNTL NOAEL 28d 0.09812 lb/acre 100 157119

Clethodim Ipomoea lacunosa White 

Morninglory POP POP CNTL NOAEL 28

d 0.09812 lb/acre 100 157119

Clethodim Ipomoea hederacea Ivyleaf Morning

-

Glory POP POP CNTL NOAEL 28

d 0.09812 lb/acre 100 157119

Clethodim Sesbania herbacea Colorado

-River-

Hemp POP POP CNTL NOAEL 28

d 0.09812 lb/acre 100 157119

Clethodim Sida spinosa Prickly Mallow POP POP CNTL NOAEL 28d 0.09812 lb/acre 100 157119

Clethodim Xanthium strumarium Common 

Cocklebur POP POP CNTL NOAEL 28

d 0.09812 lb/acre 100 157119

Clethodim Glycine max Soybean PHY INJ GINJ NOAEL 28d 0.09812 lb/acre 100 157119

Clethodim Glycine max Soybean POP POP BMAS NOAEL 145d 0.09812 lb/acre 100 157119
126

Chemical 

Name Genus Species Common Name Effect Group Effect Meas Endpt1 Endpt2

Dur 

Preferred 

Mean

Dur Unit 

Preferred

Conc #1 

Purity 

Adjusted in 

Preferred 

Unit Mean

Conc Units 

Preferred

% 

Purity Ref #

Clethodim Amaranthus hybridus Green Amaranth POP POP CNTL NOAEL 28d 0.09812 lb/acre 100 157119

Clethodim Digitaria sanguinalis Purple Crabgrass POP POP CNTL LOAEL 10d 0.09812 lb/acre 100 157119

Clethodim Ipomoea lacunosa White 

Morninglory POP POP CNTL NOAEL 28

d 0.09812 lb/acre 100 157119

Clethodim Ipomoea hederacea Ivyleaf Morning

-

Glory POP POP CNTL NOAEL 28

d 0.09812 lb/acre 100 157119

Clethodim Sesbania herbacea Colorado

-River-

Hemp POP POP CNTL NOAEL 28

d 0.09812 lb/acre 100 157119

Clethodim Sida spinosa Prickly Mallow POP POP CNTL NOAEL 28d 0.09812 lb/acre 100 157119

Clethodim Digitaria sanguinalis Purple Crabgrass POP POP CNTL LOAEL 14d 0.09812 lb/acre 100 157119

Clethodim Amaranthus hybridus Green Amaranth POP POP CNTL NOAEL 32d 0.09812 lb/acre 100 157119

Clethodim Sesbania herbacea Colorado

-River-

Hemp POP POP CNTL NOAEL 32

d 0.09812 lb/acre 100 157119

Clethodim Sida spinosa Prickly Mallow POP POP CNTL NOAEL 32d 0.09812 lb/acre 100 157119

Clethodim Amaranthus hybridus Green Amaranth POP POP CNTL NOAEL 28d 0.09812 lb/acre 100 157119

Clethodim Ipomoea lacunosa White 

Morninglory POP POP CNTL NOAEL 28

d 0.09812 lb/acre 100 157119

Clethodim Ipomoea hederacea Ivyleaf Morning

-

Glory POP POP CNTL NOAEL 28

d 0.09812 lb/acre 100 157119

Clethodim Sesbania herbacea Colorado

-River-

Hemp POP POP CNTL NOAEL 28

d 0.09812 lb/acre 100 157119

Clethodim Sida spinosa Prickly Mallow POP POP CNTL NOAEL 28d 0.09812 lb/acre 100 157119

Clethodim Glycine max Soybean PHY INJ GINJ NOAEL 28d 0.09812 lb/acre 100 157119

Clethodim Glycine max Soybean POP POP BMAS NOAEL 153d 0.09812 lb/acre 100 157119

Clethodim Digitaria sanguinalis Purple Crabgrass POP POP CNTL LOAEL 10d 0.09812 lb/acre 100 157119

Clethodim Ipomoea lacunosa White 

Morninglory POP POP CNTL NOAEL 28

d 0.09812 lb/acre 100 157119

Clethodim Ipomoea hederacea Ivyleaf Morning

-

Glory POP POP CNTL NOAEL 28

d 0.09812 lb/acre 100 157119

Clethodim Sesbania herbacea Colorado

-River-

Hemp POP POP CNTL NOAEL 28

d 0.09812 lb/acre 100 157119

Clethodim Sida spinosa Prickly Mallow POP POP CNTL NOAEL 28d 0.09812 lb/acre 100 157119

Clethodim Abutilon theophrasti Butter Print POP POP CNTL NOAEL 28d 0.09812 lb/acre 100 157119

Clethodim Xanthium strumarium Common 

Cocklebur POP POP CNTL NOAEL 28

d 0.09812 lb/acre 100 157119

Clethodim Glycine max Soybean PHY INJ GINJ NOAEL 28d 0.09812 lb/acre 100 157119

Clethodim Glycine max Soybean POP POP BMAS NOAEL 150d 0.09812 lb/acre 100 157119

Clethodim Abutilon theophrasti Butter Print POP POP CNTL NOAEL 28d 0.09812 lb/acre 100 157119

Clethodim Xanthium strumarium Common 

Cocklebur POP POP CNTL NOAEL 28

d 0.09812 lb/acre 100 157119

Clethodim Ipomoea lacunosa White POP POP CNTL NOAEL 32d 0.09812 lb/acre 100 157119
127

Chemical 

Name Genus Species Common Name Effect Group Effect Meas Endpt1 Endpt2

Dur 

Preferred 

Mean

Dur Unit 

Preferred

Conc #1 

Purity 

Adjusted in 

Preferred 

Unit Mean

Conc Units 

Preferred

% 

Purity Ref #

Morninglory

Clethodim Ipomoea hederacea Ivyleaf Morning

-

Glory POP POP CNTL NOAEL 32

d 0.09812 lb/acre 100 157119

Clethodim Glycine max Soybean PHY INJ GINJ NOAEL 32d 0.09812 lb/acre 100 157119

Clethodim Glycine max Soybean POP POP BMAS NOAEL 138d 0.09812 lb/acre 100 157119

Clethodim Digitaria sanguinalis Purple Crabgrass POP POP CNTL LOAEL 10d 0.09812 lb/acre 100 157119

Clethodim Abutilon theophrasti Butter Print POP POP CNTL NOAEL 28d 0.09812 lb/acre 100 157119

Clethodim Xanthium strumarium Common 

Cocklebur POP POP CNTL NOAEL 28

d 0.09812 lb/acre 100 157119

Clethodim Amaranthus hybridus Green Amaranth POP POP CNTL NOAEL 28d 0.09812 lb/acre 100 157119

Clethodim Digitaria sanguinalis Purple Crabgrass POP POP CNTL LOAEL 10d 0.09812 lb/acre 100 157119

Clethodim Amaranthus hybridus Green Amaranth POP POP CNTL NOAEL 28d 0.09812 lb/acre 100 157119

Clethodim Ipomoea lacunosa White 

Morninglory POP POP CNTL NOAEL 28

d 0.09812 lb/acre 100 157119

Clethodim Ipomoea hederacea Ivyleaf Morning

-

Glory POP POP CNTL NOAEL 28

d 0.09812 lb/acre 100 157119

Clethodim Sesbania herbacea Colorado

-River-

Hemp POP POP CNTL NOAEL 28

d 0.09812 lb/acre 100 157119

Clethodim Sida spinosa Prickly Mallow POP POP CNTL NOAEL 28d 0.09812 lb/acre 100 157119

Clethodim Glycine max Soybean PHY INJ GINJ NOAEL 28d 0.09812 lb/acre 100 157119

Clethodim Glycine max Soybean POP POP BMAS NOAEL 154d 0.09812 lb/acre 100 157119

Clethodim Xanthium strumarium Common 

Cocklebur POP POP CNTL NOAEL 32

d 0.09812 lb/acre 100 157119

Clethodim Glycine max Soybean POP POP BMAS NOAEL hv 0.09968 lb/acre 100 157069

Clethodim Glycine max Soybean POP POP BMAS NOAEL hv 0.09968 lb/acre 100 157069

Clethodim Glycine max Soybean POP POP BMAS NOAEL hv 0.09968 lb/acre 100 157069

Clethodim Glycine max Soybean POP POP BMAS NOAEL hv 0.09968 lb/acre 100 157069

Clethodim Digitaria sanguinalis Purple Crabgrass POP POP CNTL LOAEL 21d 0.099904 lb/acre 100 157082

Clethodim Digitaria sanguinalis Purple Crabgrass POP POP CNTL LOAEL 21d 0.099904 lb/acre 100 157082

Clethodim Digitaria sanguinalis Purple Crabgrass POP POP CNTL LOAEL9d 0.099904 lb/acre 100 157082

Clethodim Lolium rigidum Wimmera 

Ryegrass MOR MOR MORT LD50 21

d 0.10235 lb/acre 100 111509

Clethodim Vulpia myuros Foxtail Fescue POP POP BMAS ED50 42d 0.10413 lb/acre 100 157040

Clethodim Chloris elata Tall Windmill 

Grass POP POP BMAS LOAEL 16

d 0.1068 lb/acre 100 156939

Clethodim Elymus repens Quackgrass POP POP CNTL LOAEL1 gs 0.10704 lb/acre 100 82407

Clethodim Cynodon sp. Bermudagrass PHY INJ DAMG IC50 17d 0.10704 lb/acre 100 155802

Clethodim Cynodon sp. Bermudagrass PHY INJ DAMG IC50 17d 0.10704 lb/acre 100 155802

Clethodim Desmanthus virgatus Wild Tantan POP POP WGHT NOAEL 35d 0.10704 lb/acre 100 157094

Clethodim Cicer arietinum Chick Pea POP POP DBMS NOAEL 107d 0.10704 lb/acre 100 120308

Clethodim Cicer arietinum Chick Pea POP POP DBMS NOAEL 107d 0.10704 lb/acre 100 120308
128

Chemical 

Name Genus Species Common Name Effect Group Effect Meas Endpt1 Endpt2

Dur 

Preferred 

Mean

Dur Unit 

Preferred

Conc #1 

Purity 

Adjusted in 

Preferred 

Unit Mean

Conc Units 

Preferred

% 

Purity Ref #

Clethodim Cicer arietinum Chick Pea POP POP DBMS NOAEL 22d 0.10704 lb/acre 100 120308

Clethodim NR Plantae Plant Kingdom POP POP DBMS NOAEL 22d 0.10704 lb/acre 100 120308

Clethodim Phragmites australis Grass POP POP CNTL LOAEL 35d 0.11596 lb/acre 100 103875

Clethodim Phragmites australis Grass GRO MPH WGHT NOAEL 70d 0.11596 lb/acre 100 103875

Clethodim Phyllostachys aurea Golden Bamboo PHY INJ DAMG NOAEL 28d 0.11596 lb/acre 100 154909

Clethodim Phyllostachys aurea Golden Bamboo GRO GRO WGHT NOAEL 42d 0.11596 lb/acre 100 154909

Clethodim Cynodon sp. Bermudagrass PHY INJ DAMG IC50 17d 0.11596 lb/acre 100 155802

Clethodim Gossypium hirsutum Cotton POP POP BMAS NOAEL1 gs 0.1246 lb/acre 100 63480

Clethodim Gossypium hirsutum Cotton POP POP BMAS NOAEL1 gs 0.1246 lb/acre 100 63480

Clethodim Gossypium hirsutum Cotton POP POP BMAS NOAEL1 gs 0.1246 lb/acre 100 63480

Clethodim Gossypium hirsutum Cotton POP POP BMAS NOAEL1 gs 0.1246 lb/acre 100 63480

Clethodim Gossypium hirsutum Cotton POP POP BMAS NOAEL1 gs 0.1246 lb/acre 100 63480

Clethodim Gossypium hirsutum Cotton POP POP BMAS NOAEL1 gs 0.1246 lb/acre 100 63480

Clethodim Gossypium hirsutum Cotton POP POP BMAS NOAEL1 gs 0.1246 lb/acre 100 63480

Clethodim Gossypium hirsutum Cotton POP POP BMAS NOAEL1 gs 0.1246 lb/acre 100 63480

Clethodim Gossypium hirsutum Cotton POP POP BMAS NOAEL1 gs 0.1246 lb/acre 100 63480

Clethodim Poa sp. Bluegrass PHY INJ DAMG LOAEL 14d 0.1246 lb/acre 100 154952

Clethodim Poa sp. Bluegrass GRO GRO VGOR LOAEL 14d 0.1246 lb/acre 100 154952

Clethodim Poa sp. Bluegrass BCM BCM CHLO LOAEL 14d 0.1246 lb/acre 100 154952

Clethodim Zea mays Corn GRO GRO HGHT LOAEL 14d 0.1246 lb/acre 100 64012

Clethodim Zea mays Corn GRO GRO WGHT LOAEL 14d 0.1246 lb/acre 100 64012

Clethodim Cynodon dactylon Bermudagrass POP POP CNTL LOAEL 77d 0.1246 lb/acre 100 157103

Clethodim Cynodon dactylon Bermudagrass POP POP CNTL LOAEL 72d 0.1246 lb/acre 100 157103

Clethodim Cynodon dactylon Bermudagrass POP POP CNTL LOAEL 77d 0.1246 lb/acre 100 157103

Clethodim Cynodon dactylon Bermudagrass POP POP CNTL LOAEL 102d 0.1246 lb/acre 100 157103

Clethodim Cynodon dactylon Bermudagrass POP POP CNTL LOAEL 72d 0.1246 lb/acre 100 157103

Clethodim Sorghum bicolor ssp. 

bicolor Grain Sorghum GRO GRO HGHT LOAEL 21

d 0.1246 lb/acre 100 64012

Clethodim Sorghum bicolor ssp. 

bicolor Grain Sorghum GRO GRO WGHT LOAEL 21

d 0.1246 lb/acre 100 64012

Clethodim Digitaria sanguinalis Purple Crabgrass GRO GRO HGHT LOAEL 21d 0.1246 lb/acre 100 64012

Clethodim Digitaria sanguinalis Purple Crabgrass GRO GRO WGHT LOAEL 21d 0.1246 lb/acre 100 64012

Clethodim Sorghum halepense Johnson Grass PHY PHY STOC ET50 6.1d 0.1246 lb/acre 100 157102

Clethodim Sorghum halepense Johnson Grass PHY PHY CASS ET50 6.5d 0.1246 lb/acre 100 157102

Clethodim Glycine max Soybean PHY INJ GINJ NOAEL 16d 0.12488 lb/acre 100 116575

Clethodim Glyceria declinata Waxy 

Mannagrass POP POP CNTL LOAEL

7d 0.12488 lb/acre 100 96386

Clethodim Luziola fluitans Southern 

Watergrass POP POP CNTL LOAEL 35

d 0.12488 lb/acre 100 96386

Clethodim Cynodon dactylon Bermudagrass POP POP CNTL LOAEL 91.32d 0.12488 lb/acre 100 156971
129

Chemical 

Name Genus Species Common Name Effect Group Effect Meas Endpt1 Endpt2

Dur 

Preferred 

Mean

Dur Unit 

Preferred

Conc #1 

Purity 

Adjusted in 

Preferred 

Unit Mean

Conc Units 

Preferred

% 

Purity Ref #

Clethodim Urochloa texana Texas Signalgrass POP POP CNTL LOAEL 60 d 0.12488 lb/acre 100 156970

Clethodim Digitaria ciliaris Smooth 

Crabgrass POP POP CNTL LOAEL 53 d 0.12488 lb/acre 100 156970

Clethodim Digitaria ciliaris Smooth 

Crabgrass POP POP CNTL LOAEL 60 d 0.12488 lb/acre 100 156970

Clethodim Arachis hypogaea Peanut POP POP BMAS NOAEL 116 d 0.12488 lb/acre 100 156970

Clethodim Arachis hypogaea Peanut POP POP BMAS NOAEL 103 d 0.12488 lb/acre 100 156970

Clethodim Arachis hypogaea Peanut POP POP CNTL NOAEL 102 d 0.12488 lb/acre 100 156970

Clethodim Arachis hypogaea Peanut POP POP BMAS NOAEL 81 d 0.12488 lb/acre 100 156970

Clethodim Arachis hypogaea Peanut POP POP BMAS NOAEL 107 d 0.12488 lb/acre 100 156970

Clethodim Arachis hypogaea Peanut POP POP BMAS NOAEL 88 d 0.12488 lb/acre 100 156970

Clethodim Cynodon dactylon Bermudagrass POP POP CNTL LOAEL d 0.12488 lb/acre 100 157020

Clethodim Cynodon sp. Bermudagrass PHY INJ DAMG IC50 17 d 0.12488 lb/acre 100 155802

Clethodim Bromus tectorum Downy Brome MOR MOR MORT NOAEL 47 d 0.12488 lb/acre 100 157092

Clethodim Bromus tectorum Downy Brome MOR MOR MORT NRZERO 47 d 0.12488 lb/acre 100 157092

Clethodim Geranium sp. Geranium PHY INJ DAMG NOAEL 49 d 0.12488 lb/acre 100 155813

Clethodim Ageratum sp. Whiteweed PHY INJ DAMG NOAEL 49 d 0.12488 lb/acre 100 155813

Clethodim Alyssum sp. Alyssum PHY INJ DAMG NOAEL 49 d 0.12488 lb/acre 100 155813

Clethodim Aster sp. Aster PHY INJ DAMG NOAEL 49 d 0.12488 lb/acre 100 155813

Clethodim Celosia sp. Cock's Comb PHY INJ DAMG NOAEL 49 d 0.12488 lb/acre 100 155813

Clethodim Dahlia sp. Dahlia PHY INJ DAMG NOAEL 49 d 0.12488 lb/acre 100 155813

Clethodim Dianthus sp. Pink PHY INJ DAMG NOAEL 49 d 0.12488 lb/acre 100 155813

Clethodim Hibiscus sp. Hibiscus PHY INJ DAMG NOAEL 49 d 0.12488 lb/acre 100 155813

Clethodim Impatiens sp. Touchmenot PHY INJ DAMG NOAEL 49 d 0.12488 lb/acre 100 155813

Clethodim Tagetes sp. Marigold PHY INJ DAMG NOAEL 49 d 0.12488 lb/acre 100 155813

Clethodim Tagetes sp. Marigold PHY INJ DAMG NOAEL 49 d 0.12488 lb/acre 100 155813

Clethodim Nicotiana sp. Tobacco PHY INJ DAMG NOAEL 49 d 0.12488 lb/acre 100 155813

Clethodim Capsicum sp. Pepper PHY INJ DAMG NOAEL 49 d 0.12488 lb/acre 100 155813

Clethodim Petunia sp. Petunia PHY INJ DAMG NOAEL 49 d 0.12488 lb/acre 100 155813

Clethodim Petunia sp. Petunia PHY INJ DAMG NOAEL 49 d 0.12488 lb/acre 100 155813

Clethodim Salvia sp. Salvia PHY INJ DAMG NOAEL 49 d 0.12488 lb/acre 100 155813

Clethodim Salvia sp. Salvia PHY INJ DAMG NOAEL 49 d 0.12488 lb/acre 100 155813

Clethodim Antirrhinum sp. Snapdragon PHY INJ DAMG NOAEL 49 d 0.12488 lb/acre 100 155813

Clethodim Vinca sp. Periwinkle PHY INJ DAMG NOAEL 49 d 0.12488 lb/acre 100 155813

Clethodim Zinnia sp. Zinnia PHY INJ DAMG NOAEL 49 d 0.12488 lb/acre 100 155813

Clethodim Ageratum houstonianum Ageratum PHY INJ DAMG NOAEL 56 d 0.12488 lb/acre 100 70759

Clethodim Lobularia maritima Sweet Alyssum PHY INJ DAMG NOAEL 56 d 0.12488 lb/acre 100 70759

Clethodim Callistephus chinensis China Aster PHY INJ DAMG NOAEL 56 d 0.12488 lb/acre 100 70759

Clethodim Celosia cristata Crested Cock's PHY INJ DAMG NOAEL 56 d 0.12488 lb/acre 100 70759
130

Chemical 

Name Genus Species Common Name Effect Group Effect Meas Endpt1 Endpt2

Dur 

Preferred 

Mean

Dur Unit 

Preferred

Conc #1 

Purity 

Adjusted in 

Preferred 

Unit Mean

Conc Units 

Preferred

% 

Purity Ref #

Comb

Clethodim Coreopsis lanceolata Lanceleaf 

Tickseed PHY INJ DAMG NOAEL 56 d 0.12488 lb/acre 100 70759

Clethodim Dahlia sp. Dahlia PHY INJ DAMG NOAEL 56 d 0.12488 lb/acre 100 70759

Clethodim Dianthus barbatus Sweet-William PHY INJ DAMG NOAEL 56 d 0.12488 lb/acre 100 70759

Clethodim Pelargonium x hortorum Zonal Geranium PHY INJ DAMG NOAEL 56 d 0.12488 lb/acre 100 70759

Clethodim Hibiscus moscheutos Crimsoneyed 

Rosemallow PHY INJ DAMG NOAEL 56 d 0.12488 lb/acre 100 70759

Clethodim Impatiens walleriana Busy Lizzy PHY INJ DAMG NOAEL 56 d 0.12488 lb/acre 100 70759

Clethodim Tagetes patula French Marigold PHY INJ DAMG NOAEL 56 d 0.12488 lb/acre 100 70759

Clethodim Tagetes patula French Marigold PHY INJ DAMG NOAEL 56 d 0.12488 lb/acre 100 70759

Clethodim Nicotiana alata Jasmine Tobacco PHY INJ DAMG NOAEL 56 d 0.12488 lb/acre 100 70759

Clethodim Capsicum annuum Bell Pepper PHY INJ DAMG NOAEL 56 d 0.12488 lb/acre 100 70759

Clethodim Petunia x hybrida Petunia PHY INJ DAMG NOAEL 56 d 0.12488 lb/acre 100 70759

Clethodim Petunia x hybrida Petunia PHY INJ DAMG NOAEL 56 d 0.12488 lb/acre 100 70759

Clethodim Salvia farinacea Mealycup Sage PHY INJ DAMG NOAEL 56 d 0.12488 lb/acre 100 70759

Clethodim Salvia splendens Scarlet Sage PHY INJ DAMG NOAEL 56 d 0.12488 lb/acre 100 70759

Clethodim Antirrhinum majus Snapdragon PHY INJ DAMG NOAEL 56 d 0.12488 lb/acre 100 70759

Clethodim Catharanthus roseus Bright-Eyes PHY INJ DAMG NOAEL 56 d 0.12488 lb/acre 100 70759

Clethodim Zinnia violacea Zinnia PHY INJ DAMG NOAEL 56 d 0.12488 lb/acre 100 70759

Clethodim Digitaria sanguinalis Purple Crabgrass POP POP CNTL LOAEL 14 d 0.12488 lb/acre 100 70759

Clethodim Amaranthus sp. Amaranth POP POP CNTL NOAEL 56 d 0.12488 lb/acre 100 70759

Clethodim Cynodon dactylon Bermudagrass POP POP CNTL LOAEL 14 d 0.12488 lb/acre 100 157119

Clethodim Sorghum halepense Johnson Grass POP POP CNTL LOAEL 7 d 0.125 lb/acre 100 156937

Clethodim Sorghum halepense Johnson Grass POP POP CNTL LOAEL 7 d 0.125 lb/acre 100 156937

Clethodim Medicago sativa Alfalfa POP POP BMAS NOAEL 70 d 0.12816 lb/acre 100 67066

Clethodim NR Plantae Plant Kingdom POP POP BMAS LOAEL 20 d 0.12816 lb/acre 100 67066

Clethodim Medicago sativa Alfalfa POP POP BMAS NOAEL 20 d 0.12816 lb/acre 100 67066

Clethodim NR Plantae Plant Kingdom POP POP BMAS LOAEL 20 d 0.12816 lb/acre 100 67066

Clethodim Medicago sativa Alfalfa POP POP BMAS NOAEL 170 d 0.12816 lb/acre 100 67066

Clethodim NR Plantae Plant Kingdom POP POP BMAS LOAEL 170 d 0.12816 lb/acre 100 67066

Clethodim Medicago sativa Alfalfa POP POP BMAS NOAEL 70 d 0.12816 lb/acre 100 67066

Clethodim NR Plantae Plant Kingdom POP POP BMAS LOAEL 70 d 0.12816 lb/acre 100 67066

Clethodim Medicago sativa Alfalfa POP POP BMAS NOAEL 70 d 0.12816 lb/acre 100 67066

Clethodim NR Plantae Plant Kingdom POP POP BMAS LOAEL 70 d 0.12816 lb/acre 100 67066

Clethodim Elymus repens Quackgrass POP POP CNTL LOAEL 1 gs 0.1338 lb/acre 100 82407

Clethodim Cynodon sp. Bermudagrass POP POP CNTL LOAEL 133 d 0.1338 lb/acre 100 156935

Clethodim Cynodon dactylon Bermudagrass POP POP CNTL LOAEL 133 d 0.1338 lb/acre 100 156935

Clethodim Cynodon dactylon Bermudagrass POP POP CNTL LOAEL 133 d 0.1338 lb/acre 100 156935

Clethodim Cynodon dactylon Bermudagrass POP POP CNTL NOAEL LOAEL 133 d 0.1338 lb/acre 100 156935
131

Chemical 

Name Genus Species Common Name Effect Group Effect Meas Endpt1 Endpt2

Dur 

Preferred 

Mean

Dur Unit 

Preferred

Conc #1 

Purity 

Adjusted in 

Preferred 

Unit Mean

Conc Units 

Preferred

% 

Purity Ref #

Clethodim Glycine max Soybean POP POP BMAS NOAEL hv 0.13884 lb/acre 100 157073

Clethodim Glycine max Soybean POP POP BMAS NOAEL hv 0.13884 lb/acre 100 157073

Clethodim Glycine max Soybean POP POP BMAS NOAEL hv 0.13884 lb/acre 100 157073

Clethodim Lolium rigidum Wimmera 

Ryegrass PHY INJ DAMG LOAEL 15 d 0.15 L/ha 100 86670

Clethodim Lolium rigidum Wimmera 

Ryegrass GRO GRO NLEF LOAEL 30 d 0.15 L/ha 100 86670

Clethodim Avena sativa Common Oat GRO GRO NLEF LOAEL 30 d 0.15 L/ha 100 86670

Clethodim Avena sativa Common Oat PHY INJ DAMG LOAEL 15 d 0.15 L/ha 100 86670

Clethodim Dactylis glomerata Orchardgrass GRO GRO NLEF LOAEL 30 d 0.15 L/ha 100 86670

Clethodim Dactylis glomerata Orchardgrass PHY INJ DAMG LOAEL 15 d 0.15 L/ha 100 86670

Clethodim Schedonorus arundinaceus Tall Fescue PHY INJ DAMG LOAEL 15 d 0.15 L/ha 100 86670

Clethodim Schedonorus arundinaceus Tall Fescue GRO GRO NLEF LOAEL 30 d 0.15 L/ha 100 86670

Clethodim Lolium perenne

Perennial 

Ryegrass PHY INJ DAMG LOAEL 15 d 0.15 L/ha 100 86670

Clethodim Lolium perenne

Perennial 

Ryegrass GRO GRO NLEF LOAEL 30 d 0.15 L/ha 100 86670

Clethodim Triticum aestivum Bread Wheat PHY INJ DAMG LOAEL 15 d 0.15 L/ha 100 86670

Clethodim Triticum aestivum Bread Wheat GRO GRO WGHT LOAEL 30 d 0.15 L/ha 100 86670

Clethodim Phalaris aquatica Kolea Grass GRO GRO NLEF LOAEL 30 d 0.15 L/ha 100 86670

Clethodim Phalaris aquatica Kolea Grass PHY INJ DAMG LOAEL 15 d 0.15 L/ha 100 86670

Clethodim Trifolium subterraneum Subterranean 

Clover PHY INJ DAMG NOAEL 30 d 0.15 L/ha 100 86670

Clethodim Trifolium subterraneum Subterranean 

Clover GRO GRO NLEF NOAEL 30 d 0.15 L/ha 100 86670

Clethodim Rytidosperma richardsonii Wallaby Grass GRO GRO NLEF LOAEL 30 d 0.15 L/ha 100 86670

Clethodim Rytidosperma richardsonii Wallaby Grass PHY INJ DAMG LOAEL 15 d 0.15 L/ha 100 86670

Clethodim Festuca rubra Ravine Fescue PHY INJ DAMG NOAEL 49 d 0.15164 lb/acre 100 70295

Clethodim Festuca trachyphylla Hard Fescue PHY INJ DAMG NOAEL 49 d 0.15164 lb/acre 100 70295

Clethodim Cynodon sp. Bermudagrass PHY INJ DAMG IC50 17 d 0.15164 lb/acre 100 155802

Clethodim Bromus tectorum Downy Brome GRO GRO BMAS EC50 47 d 0.15164 lb/acre 100 157092

Clethodim Medicago sativa Alfalfa POP POP BMAS NOAEL 730 d 0.16056 lb/acre 100 157070

Clethodim Medicago sativa Alfalfa POP POP BMAS NOAEL 730 d 0.16056 lb/acre 100 157070

Clethodim Elymus repens Quackgrass POP POP BMAS LOAEL 365 d 0.16056 lb/acre 100 157070

Clethodim Elymus repens Quackgrass POP POP BMAS LOAEL 730 d 0.16056 lb/acre 100 157070

Clethodim Elymus repens Quackgrass POP POP BMAS NOAEL 1095 d 0.16056 lb/acre 100 157070

Clethodim Cynodon sp. Bermudagrass PHY INJ DAMG IC50 17 d 0.16056 lb/acre 100 155802

Clethodim Cynodon sp. Bermudagrass PHY INJ DAMG IC50 17 d 0.16948 lb/acre 100 155802

Clethodim Eriochloa contracta Prairie cupgrass REP REP VEGR LOAEL 28 d 0.1869 lb/acre 100 157106
132

Chemical 

Name Genus Species Common Name Effect Group Effect Meas Endpt1 Endpt2

Dur 

Preferred 

Mean

Dur Unit 

Preferred

Conc #1 

Purity 

Adjusted in 

Preferred 

Unit Mean

Conc Units 

Preferred

% 

Purity Ref #

Clethodim Chloris verticillata Tumble windmill 

grass

REP REP VEGR LOAEL 28d 0.1869 lb/acre 100 157106

Clethodim Eriochloa contracta Prairie cupgrass REP REP VEGR LOAEL 28d 0.1869 lb/acre 100 157106

Clethodim Chloris verticillata Tumble windmill 

grass

REP REP VEGR LOAEL 28d 0.1869 lb/acre 100 157106

Clethodim Eriochloa contracta Prairie cupgrass REP REP VEGR LOAEL 28d 0.1869 lb/acre 100 157106

Clethodim Chloris verticillata Tumble windmill 

grass

REP REP VEGR LOAEL 28d 0.1869 lb/acre 100 157106

Clethodim NR Plantae Plant Kingdom POP POP COVR LOAEL1 gs 0.18732 lb/acre 100 156982

Clethodim NR Plantae Plant Kingdom POP POP DVRS NOAEL1 gs 0.18732 lb/acre 100 156982

Clethodim NR Plantae Plant Kingdom POP POP COVR NOAEL2 gs 0.18732 lb/acre 100 156982

Clethodim Schedonorus arundinaceus Tall Fescue POP POP ABND LOAEL1 gs 0.18732 lb/acre 100 156982

Clethodim Schedonorus arundinaceus Tall Fescue POP POP ABND LOAEL2 gs 0.18732 lb/acre 100 156982

Clethodim NR Poaceae Grass Family POP POP ABND NOAEL1 gs 0.18732 lb/acre 100 156982

Clethodim NR Poaceae Grass Family POP POP ABND LOAEL2 gs 0.18732 lb/acre 100 156982

Clethodim Medicago sativa Alfalfa POP POP BMAS NOAEL 90d 0.19624 lb/acre 100 120431

Clethodim Schedonorus arundinaceus Tall Fescue POP POP COVR LOAEL 90d 0.20516 lb/acre 100 156927

Clethodim Schedonorus arundinaceus Tall Fescue POP POP COVR LOAEL 74d 0.20516 lb/acre 100 156927

Clethodim NR Poaceae Grass Family POP POP COVR NOAEL 517.48d 0.20516 lb/acre 100 156927

Clethodim NR Poaceae Grass Family POP POP COVR NOAEL 517.48d 0.20516 lb/acre 100 156927

Clethodim NR Plantae Plant Kingdom POP POP COVR NOAEL 517.48d 0.20516 lb/acre 100 156927

Clethodim NR Plantae Plant Kingdom POP POP COVR NOAEL 517.48d 0.20516 lb/acre 100 156927

Clethodim Stevia rebaudiana Candyleaf GRO MPH HGHT NOAEL 28d 0.2136 lb/acre 100 157121

Clethodim Stevia rebaudiana Candyleaf PHY INJ DAMG NOAEL 56d 0.2136 lb/acre 100 157121

Clethodim Stevia rebaudiana Candyleaf POP POP BMAS NOAEL 70d 0.2136 lb/acre 100 157121

Clethodim NR Plantae Plant Kingdom POP POP ABND NOAEL 28d 0.2136 lb/acre 100 157121

Clethodim NR Poaceae Grass Family POP POP ABND LOAEL 28d 0.2136 lb/acre 100 157121

Clethodim NR Poaceae Grass Family PHY INJ DAMG NOAEL 49d 0.2136 lb/acre 100 157121

Clethodim Solanum nigrum Black Nightshade PHY INJ DAMG NOAEL 49d 0.2136 lb/acre 100 157121

Clethodim NR Plantae Plant Kingdom POP POP BMAS NOAEL 70d 0.2136 lb/acre 100 157121

Clethodim Stevia rebaudiana Candyleaf GRO MPH HGHT NOAEL 28d 0.2136 lb/acre 100 157121

Clethodim Stevia rebaudiana Candyleaf PHY INJ DAMG NOAEL 56d 0.2136 lb/acre 100 157121

Clethodim Stevia rebaudiana Candyleaf POP POP BMAS NOAEL 70d 0.2136 lb/acre 100 157121

Clethodim NR Poaceae Grass Family POP POP BMAS NOAEL 1460d 0.21408 lb/acre 100 120528

Clethodim NR Poaceae Grass Family POP POP BMAS LOAEL 1460d 0.21408 lb/acre 100 120528

Clethodim NR Poaceae Grass Family POP POP BMAS LOAEL 1460d 0.21408 lb/acre 100 120528

Clethodim Panax quinquefolius American 

Ginseng POP POP BMAS NOAEL 1460

d 0.21408 lb/acre 100 120528

Clethodim Panax quinquefolius American 

Ginseng POP POP BMAS NOAEL 1460

d 0.21408 lb/acre 100 120528
133

Chemical 

Name Genus Species Common Name Effect Group Effect Meas Endpt1 Endpt2

Dur 

Preferred 

Mean

Dur Unit 

Preferred

Conc #1 

Purity 

Adjusted in 

Preferred 

Unit Mean

Conc Units 

Preferred

% 

Purity Ref #

Clethodim Panax quinquefolius American 

Ginseng POP POP BMAS NOAEL 1460

d 0.21408 lb/acre 100 120528

Clethodim Solanum tuberosum Potato POP POP BMAS NOAEL hv 0.21408 lb/acre 100 82407

Clethodim Solanum tuberosum Potato POP POP BMAS NOAEL hv 0.21408 lb/acre 100 82407

Clethodim Alopecurus myosuroides Blackgrass GRO GRO WGHT ED50 20d 0.23 L/ha 100 156760

Clethodim Sorghum halepense Johnson Grass POP POP CNTL LOAEL7d 0.2492 lb/acre 100 155807

Clethodim Glycine max Soybean POP POP BMAS NOAEL hv 0.2492 lb/acre 100 155807

Clethodim Sorghum halepense Johnson Grass POP POP CNTL LOAEL7d 0.2492 lb/acre 100 155807

Clethodim Cynodon dactylon Bermudagrass POP POP CNTL LOAEL 102d 0.2492 lb/acre 100 157103

Clethodim Arachis hypogaea Peanut POP POP BMAS NOAEL hv 0.2492 lb/acre 100 157103

Clethodim Arachis hypogaea Peanut POP POP BMAS NOAEL hv 0.2492 lb/acre 100 157103

Clethodim Arachis hypogaea Peanut POP POP BMAS NOAEL hv 0.2492 lb/acre 100 157103

Clethodim Arachis hypogaea Peanut POP POP BMAS NOAEL hv 0.2492 lb/acre 100 157103

Clethodim Medicago sativa Alfalfa POP POP BMAS NOAEL 50d 0.24976 lb/acre 100 120431

Clethodim Medicago sativa Alfalfa POP POP BMAS NOAEL 45d 0.24976 lb/acre 100 120431

Clethodim Medicago sativa Alfalfa POP POP BMAS NOAEL 40d 0.24976 lb/acre 100 120431

Clethodim Medicago sativa Alfalfa POP POP BMAS NOAEL 50d 0.24976 lb/acre 100 120431

Clethodim Medicago sativa Alfalfa POP POP BMAS NOAEL 45d 0.24976 lb/acre 100 120431

Clethodim Medicago sativa Alfalfa POP POP BMAS NOAEL 40d 0.24976 lb/acre 100 120431

Clethodim Digitaria sanguinalis Purple Crabgrass MOR MOR MORT NR

-

LETH 28

d 0.24976 lb/acre 100 152884

Clethodim Sorghum arundinaceum Shattercane MOR MOR MORT NR

-

LETH 28

d 0.24976 lb/acre 100 152884

Clethodim Digitaria sanguinalis Purple Crabgrass MOR MOR MORT NR

-

LETH 28

d 0.24976 lb/acre 100 152884

Clethodim Sorghum arundinaceum Shattercane MOR MOR MORT NR

-

LETH 28

d 0.24976 lb/acre 100 152884

Clethodim Digitaria sanguinalis Purple Crabgrass MOR MOR MORT NR

-

LETH 28

d 0.24976 lb/acre 100 152884

Clethodim Sorghum arundinaceum Shattercane MOR MOR MORT NR

-

LETH 28

d 0.24976 lb/acre 100 152884

Clethodim Digitaria sanguinalis Purple Crabgrass MOR MOR MORT NR

-

LETH 28

d 0.24976 lb/acre 100 152884

Clethodim Sorghum arundinaceum Shattercane MOR MOR MORT NR

-

LETH 28

d 0.24976 lb/acre 100 152884

Clethodim Digitaria sanguinalis Purple Crabgrass MOR MOR MORT NR

-

LETH 28

d 0.24976 lb/acre 100 152884

Clethodim Sorghum arundinaceum Shattercane MOR MOR MORT NR

-

LETH 28

d 0.24976 lb/acre 100 152884

Clethodim Digitaria sanguinalis Purple Crabgrass MOR MOR MORT NR- 28d 0.24976 lb/acre 100 152884
134

Chemical 

Name Genus Species Common Name Effect Group Effect Meas Endpt1 Endpt2

Dur 

Preferred 

Mean

Dur Unit 

Preferred

Conc #1 

Purity 

Adjusted in 

Preferred 

Unit Mean

Conc Units 

Preferred

% 

Purity Ref #

LETH

Clethodim Sorghum arundinaceum Shattercane MOR MOR MORT NR

-

LETH 28

d 0.24976 lb/acre 100 152884

Clethodim Digitaria sanguinalis Purple Crabgrass MOR MOR MORT NR

-

LETH 28

d 0.24976 lb/acre 100 152884

Clethodim Sorghum arundinaceum Shattercane MOR MOR MORT NR

-

LETH 28

d 0.24976 lb/acre 100 152884

Clethodim Digitaria sanguinalis Purple Crabgrass MOR MOR MORT NR

-

LETH 28

d 0.24976 lb/acre 100 152884

Clethodim Sorghum arundinaceum Shattercane MOR MOR MORT NR

-

LETH 28

d 0.24976 lb/acre 100 152884

Clethodim Digitaria sanguinalis Purple Crabgrass MOR MOR MORT NR

-

LETH 28

d 0.24976 lb/acre 100 152884

Clethodim Sorghum arundinaceum Shattercane MOR MOR MORT NR

-

LETH 28

d 0.24976 lb/acre 100 152884

Clethodim Glyceria declinata Waxy 

Mannagrass POP POP CNTL NOAEL

7d 0.24976 lb/acre 100 96386

Clethodim Medicago polymorpha Burclover POP POP BMAS NOEL 80d 0.24976 lb/acre 100 156904

Clethodim Medicago lupulina Black Medic POP POP BMAS NOEL 80d 0.24976 lb/acre 100 156904

Clethodim Medicago truncatula Barrelclover POP POP BMAS NOEL 80d 0.24976 lb/acre 100 156904

Clethodim Medicago polymorpha Burclover POP POP BMAS NOEL 79d 0.24976 lb/acre 100 156904

Clethodim Medicago lupulina Black Medic POP POP BMAS NOEL 79d 0.24976 lb/acre 100 156904

Clethodim Medicago truncatula Barrelclover POP POP BMAS NOEL 79d 0.24976 lb/acre 100 156904

Clethodim Lamium amplexicaule Common Henbit POP POP ABND NOEL 79d 0.24976 lb/acre 100 156904

Clethodim Medicago sp. Burclover POP POP ABND NOEL 79d 0.24976 lb/acre 100 156904

Clethodim Cynodon dactylon Bermudagrass POP POP CNTL LOAEL 91.32d 0.24976 lb/acre 100 156971

Clethodim Arachis hypogaea Peanut POP POP BMAS NOAEL hv 0.24976 lb/acre 100 156971

Clethodim Arachis hypogaea Peanut POP POP BMAS NOAEL hv 0.24976 lb/acre 100 156971

Clethodim Cynodon dactylon Bermudagrass POP POP CNTL LOAELd 0.24976 lb/acre 100 157020

Clethodim Gossypium hirsutum Cotton PHY INJ GINJ NOAEL 53d 0.24976 lb/acre 100 157119

Clethodim Poa pratensis Kentucky 

Bluegrass POP POP ABND NOAEL 56

d 0.24976 lb/acre 100 87931

Clethodim Poa pratensis Kentucky 

Bluegrass POP POP ABND LOAEL 28

d 0.24976 lb/acre 100 87931

Clethodim Poa pratensis Kentucky 

Bluegrass POP POP ABND LOAEL 28

d 0.24976 lb/acre 100 87931

Clethodim Poa pratensis Kentucky 

Bluegrass POP POP ABND LOAEL 28

d 0.24976 lb/acre 100 87931

Clethodim Poa pratensis Kentucky POP POP ABND LOAEL 28d 0.24976 lb/acre 100 87931
135

Chemical 

Name Genus Species Common Name Effect Group Effect Meas Endpt1 Endpt2

Dur 

Preferred 

Mean

Dur Unit 

Preferred

Conc #1 

Purity 

Adjusted in 

Preferred 

Unit Mean

Conc Units 

Preferred

% 

Purity Ref #

Bluegrass

Clethodim Poa pratensis Kentucky 

Bluegrass POP POP ABND LOAEL 28

d 0.24976 lb/acre 100 87931

Clethodim Poa pratensis Kentucky 

Bluegrass POP POP ABND LOAEL 28

d 0.24976 lb/acre 100 87931

Clethodim Poa pratensis Kentucky 

Bluegrass POP POP ABND LOAEL 56

d 0.24976 lb/acre 100 87931

Clethodim Bromus tectorum Downy Brome MOR MOR MORT LOAEL 47d 0.24976 lb/acre 100 157092

Clethodim Cynodon dactylon Bermudagrass POP POP CNTL LOAEL 60d 0.25632 lb/acre 100 152009

Clethodim Cynodon dactylon Bermudagrass POP POP CNTL LOAEL 60d 0.25632 lb/acre 100 152009

Clethodim Cynodon dactylon Bermudagrass POP POP CNTL LOAEL 60d 0.25632 lb/acre 100 152009

Clethodim Cynodon dactylon Bermudagrass POP POP CNTL LOAEL 60d 0.25632 lb/acre 100 152009

Clethodim Cynodon dactylon Bermudagrass POP POP CNTL LOAEL 60d 0.25632 lb/acre 100 152009

Clethodim Cynodon dactylon Bermudagrass POP POP CNTL LOAEL 60d 0.25632 lb/acre 100 152009

Clethodim Cynodon dactylon Bermudagrass POP POP BMAS NOAEL LOAEL1 gs 0.25632 lb/acre 24 156977

Clethodim Cynodon dactylon Bermudagrass POP POP BMAS LOAEL1 gs 0.25632 lb/acre 24 156977

Clethodim Eremochloa ophiuroides Centipede Grass PHY INJ DAMG LOAEL 42d 0.2676 lb/acre 100 154969

Clethodim Eremochloa ophiuroides Centipede Grass PHY INJ DAMG LOAEL 42d 0.2676 lb/acre 100 154969

Clethodim Cynodon sp. Bermudagrass POP POP CNTL LOAEL 133d 0.2676 lb/acre 100 156935

Clethodim Cynodon dactylon Bermudagrass POP POP CNTL LOAEL 133d 0.2676 lb/acre 100 156935

Clethodim Cynodon dactylon Bermudagrass POP POP CNTL LOAEL 133d 0.2676 lb/acre 100 156935

Clethodim Cynodon dactylon Bermudagrass POP POP CNTL NOAEL 133d 0.2676 lb/acre 100 156935

Clethodim Cynodon sp. Bermudagrass POP POP CNTL NOAEL1 gs 0.2676 lb/acre 100 156935

Clethodim Cynodon dactylon Bermudagrass POP POP CNTL NOAEL1 gs 0.2676 lb/acre 100 156935

Clethodim Cynodon dactylon Bermudagrass POP POP CNTL LOAEL1 gs 0.2676 lb/acre 100 156935

Clethodim Cynodon dactylon Bermudagrass POP POP CNTL LOAEL1 gs 0.2676 lb/acre 100 156935

Clethodim Helianthus annuus Common Annual 

Sunflower POP POP CNTL NOAEL hv 0.29904 lb/acre 100 152009

Clethodim Helianthus annuus Common Annual 

Sunflower POP POP BMAS NOAEL hv 0.29904 lb/acre 100 152009

Clethodim Helianthus annuus Common Annual 

Sunflower POP POP BMAS NOAEL hv 0.29904 lb/acre 100 152009

Clethodim Glycine max Soybean POP POP BMAS NOAEL hv 0.29904 lb/acre 100 152009

Clethodim Glycine max Soybean POP POP BMAS NOAEL hv 0.29904 lb/acre 100 152009

Clethodim Helianthus annuus Common Annual 

Sunflower POP POP BMAS NOAEL hv 0.29904 lb/acre 100 152009

Clethodim Helianthus sp. Sunflower POP POP BMAS NOAEL hv 0.29904 lb/acre 24 156977

Clethodim Helianthus sp. Sunflower POP POP BMAS NOAEL hv 0.29904 lb/acre 24 156977

Clethodim Alopecurus myosuroides Blackgrass GRO GRO WGHT ED50 20d 0.3 L/ha 100 156760

Clethodim Sorghum halepense Johnson Grass POP POP CNTL LOAEL 14d 0.3115 lb/acre 100 66802
136

Chemical 

Name Genus Species Common Name Effect Group Effect Meas Endpt1 Endpt2

Dur 

Preferred 

Mean

Dur Unit 

Preferred

Conc #1 

Purity 

Adjusted in 

Preferred 

Unit Mean

Conc Units 

Preferred

% 

Purity Ref #

Clethodim Sorghum halepense Johnson Grass POP POP CNTL LOAEL 42d 0.3115 lb/acre 100 66802

Clethodim Sorghum halepense Johnson Grass POP POP CNTL LOAEL 70d 0.3115 lb/acre 100 66802

Clethodim Hibiscus cannabinus Deccan Hemp POP POP BMAS NOAELd 0.3738 lb/acre 100 156934

Clethodim Hibiscus cannabinus Deccan Hemp GRO GRO HGHT NOAELd 0.3738 lb/acre 100 156934

Clethodim Solanum tuberosum Potato POP POP BMAS NOAEL hv 0.4014 lb/acre 100 82407

Clethodim Plankton sp. Plankton POP POP PSYN NOAEL1d 0.43 AI kg/ha 100 53095

Clethodim Carex appressa Tall Sedge POP POP COVR NOAEL 329d 0.446 lb/acre 100 157039

Clethodim Sorghum halepense Johnson Grass GRO MPH LGTH ED505d 0.4625 ppm 100 156992

Clethodim Cynodon dactylon Bermudagrass BCM BCM PRCO NOAEL 365d 0.49952 lb/acre 100 156888

Clethodim Cynodon dactylon Bermudagrass POP POP BMAS LOAEL 365d 0.49952 lb/acre 100 156888

Clethodim Cynodon dactylon Bermudagrass POP POP BMAS LOAEL 365d 0.49952 lb/acre 100 156888

Clethodim Cynodon dactylon Bermudagrass BCM BCM PRCO LOAEL 365d 0.49952 lb/acre 100 156888

Clethodim Eremochloa ophiuroides Centipede Grass PHY INJ DAMG NOAEL 84d 0.5352 lb/acre 100 154969

Clethodim Sorghum halepense Johnson Grass GRO GRO WGHT EC50 21d 0.54201 lb/acre 100 156993

Clethodim Aegilops triuncialis Barbed 

Goatgrass POP POP ABND LOAEL

d 0.55304 lb/acre 100 156883

Clethodim NR Magnoliophyta Angiosperm 

Division POP POP ABND LOAEL

d 0.55304 lb/acre 100 156883

Clethodim Holocarpha virgata Yellowflower 

Tarweed POP POP COVR LOAEL

d 0.55304 lb/acre 100 156883

Clethodim Navarretia jepsonii Jepson's 

Pincushionplant POP POP COVR NOAEL

d 0.55304 lb/acre 100 156883

Clethodim Poa secunda Sandberg'S 

Bluegrass POP POP COVR NOAEL

d 0.55304 lb/acre 100 156883

Clethodim Bromus hordeaceus Soft Chessgrass POP POP COVR NOAELd 0.55304 lb/acre 100 156883

Clethodim Sorghum halepense Johnson Grass POP POP CNTL LOAEL 30d 0.7359 lb/acre 100 70779

Clethodim Cynodon dactylon Bermudagrass POP POP CNTL LOAEL 30d 0.7359 lb/acre 100 70779

Clethodim Aloysia polystachya Te de Burro 

Shrub PHY INJ GINJ NOAEL 30

d 0.7359 lb/acre 100 70779

Clethodim Aloysia polystachya Te de Burro 

Shrub POP POP BMAS NOAEL hv 0.7359 lb/acre 100 70779

Clethodim Amelichloa brachychaeta Puna Needle 

Grass POP POP CNTL LOAEL 30

d 0.7359 lb/acre 100 70779

Clethodim Bromus tectorum Downy Brome MOR MOR MORT NR

-

LETH 47

d 0.99904 lb/acre 100 157092

Clethodim Sorghum halepense Johnson Grass GRO GRO GGRO EC50 0.25d 16.4 uM 100 156994

Clethodim Sorghum halepense Johnson Grass REP REP GERM EC50 0.125d 25.8 uM 100 156994

Clethodim Elymus repens Quackgrass POP POP WGHT LOAEL1 gs 240000 ppm 100 156921

Clethodim Elymus repens Quackgrass POP POP WGHT LOAEL1 gs 240000 ppm 100 156921

Clethodim Elymus repens Quackgrass POP POP WGHT LOAEL1 gs 240000 ppm 100 156921
137

Chemical 

Name Genus Species Common Name Effect Group Effect Meas Endpt1 Endpt2

Dur 

Preferred 

Mean

Dur Unit 

Preferred

Conc #1 

Purity 

Adjusted in 

Preferred 

Unit Mean

Conc Units 

Preferred

% 

Purity Ref #

Clethodim Elymus repens Quackgrass POP POP WGHT LOAEL 1 gs 240000 ppm 100 156921

Clethodim Elymus repens Quackgrass POP POP WGHT LOAEL 1 gs 240000 ppm 100 156921

Clethodim Elymus repens Quackgrass POP POP WGHT LOAEL 1 gs 240000 ppm 100 156921

Clethodim Elymus repens Quackgrass POP POP WGHT LOAEL 1 gs 240000 ppm 100 156921

Clethodim Elymus repens Quackgrass POP POP WGHT LOAEL 1 gs 240000 ppm 100 156921

Clethodim Elymus repens Quackgrass POP POP WGHT LOAEL 1 gs 240000 ppm 100 156921

Clethodim Elymus repens Quackgrass POP POP WGHT LOAEL 1 gs 240000 ppm 100 156921

Clethodim Elymus repens Quackgrass POP POP WGHT LOAEL 1 gs 240000 ppm 100 156921

Clethodim Elymus repens Quackgrass POP POP WGHT LOAEL 1 gs 240000 ppm 100 156921

Clethodim Panicum repens Torpedo Grass POP POP COVR LOAEL 42 d lb/acre 100 154969

Clethodim Panicum repens Torpedo Grass POP POP COVR LOAEL 42 d lb/acre 100 154969

Clethodim Panicum repens Torpedo Grass POP POP COVR LOAEL 42 d lb/acre 100 154969

Clethodim Cynodon dactylon Bermudagrass POP POP CNTL LOAEL 91.32 d lb/acre 100 156971

Clethodim Arachis hypogaea Peanut POP POP BMAS NOAEL hv lb/acre 100 156971

Clethodim Cynodon dactylon Bermudagrass POP POP CNTL LOAEL d lb/acre 100 157020

Clethodim Cynodon dactylon Bermudagrass POP POP CNTL LOAEL d lb/acre 100 157020