Registration of the New Active 

 Ingredient Aminocyclopyrachlor for 

 Use on Non-Crop Areas, Sod Farms, 

 Turf, and Residential Lawns

August 24, 2010 

U.S. Environmental Protection Agency 

Office of Pesticide Programs 

Registration Division 

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TABLE OF CONTENTS 

1. REGULATORY RATIONALE........................................................................................... 4

1.1. CHEMICAL INFORMATION ............................................................................................. 4

1.1.1. Chemical Name: Aminocyclopyrachlor (parent acid) .........................................................................5

1.1.2. Chemical Name: Aminocyclopyrachlor-methyl (methyl ester)...........................................................5

1.1.3. Chemical Name: Aminocyclopyrachlor potassium salt.......................................................................6

1.2. HUMAN HEALTH RISK ................................................................................................... 6

1.2.1. Toxicological Summary and Considerations.........................................................................................6

1.2.1.1. Degradate of Concern .................................................................................................................................. 7

1.2.2. Toxicological End Points and Doses .....................................................................................................7

1.2.2.1. Acute Dietary............................................................................................................................................... 7

1.2.2.2. Chronic Dietary............................................................................................................................................ 8

1.2.2.3. Short- and Intermediate-Term Incidental Oral and Inhalation ..................................................................... 8

1.2.2.4. Short- and Intermediate-Term Dermal......................................................................................................... 8

1.2.2.5. Cancer.......................................................................................................................................................... 8

1.2.3. Consideration of Toxicity to Children ...................................................................................................9

1.2.4. Dietary Risk...........................................................................................................................................9

1.2.5. Residential Risk...................................................................................................................................10

1.2.5.1. Residential Handler Risk ........................................................................................................................... 10

1.2.5.2. Residential Post-Application Risk ............................................................................................................. 10

1.2.6. Aggregate Risk ....................................................................................................................................11

1.2.7. Occupational Risk................................................................................................................................11

1.2.7.1. Occupational Handler Risk ........................................................................................................................ 11

1.2.7.2. Occupational Post-Application Risk .......................................................................................................... 12

1.3. ENVIRONMENTAL RISK................................................................................................ 13

1.3.1. Environmental Summary and Considerations......................................................................................13

1.3.1.1. Degradates of Concern............................................................................................................................... 13

1.3.2. Environmental Fate..............................................................................................................................13

1.3.3. Ecological Risk....................................................................................................................................14

1.3.3.1. Aquatic Risk .............................................................................................................................................. 14

1.3.3.1.1. Fish Risk............................................................................................................................................... 14

1.3.3.1.2. Aquatic Invertebrate Risk ..................................................................................................................... 15

1.3.3.1.3. Aquatic Plant Risk ................................................................................................................................ 15

1.3.3.2. Terrestrial Risk .......................................................................................................................................... 15

1.3.3.2.1. Avian Risk............................................................................................................................................ 15

1.3.3.2.2. Mammalian Risk................................................................................................................................... 16

1.3.3.2.3. Terrestrial Invertebrate Risk ................................................................................................................. 16

1.3.3.2.4. Terrestrial Plant Risk ............................................................................................................................ 16

1.4. PUBLIC INTEREST......................................................................................................... 16

2. REGULATORY DECISION............................................................................................. 17

2.1. DATA REQUIREMENTS ................................................................................................. 17

2.1.1. Human Health Data Requirements ......................................................................................................17

2.1.2. Environmental Data Requirements......................................................................................................18

2.2. LABEL REQUIREMENTS................................................................................................ 18

2.2.1. Environmental Hazards........................................................................................................................18

2.2.1.1. Surface Water Advisory............................................................................................................................. 19

2.2.1.2. Ground Water Advisory............................................................................................................................. 19

2.2.2. Plant Residue .......................................................................................................................................20

2.2.3. Livestock .............................................................................................................................................21

2.2.4. Spray Drift ...........................................................................................................................................21

2.2.5. Restricted-Entry Interval (REI)............................................................................................................23

2.3. REGISTRATION DECISION ............................................................................................ 23

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Registration of the New Active Ingredient Aminocyclopyrachlor for 

Use on Non-Crop Areas, Sod Farms, Turf, and Residential Lawns 

1. REGULATORY RATIONALE 

The Agency is granting conditional registration of the new active ingredient 

aminocyclopyrachlor, formulated as 2 technical products, 3 manufacturing-use products, and 15 

end-use products. It is a selective herbicide providing pre- and post-emergent control of 

broadleaf weeds, woody species, vines, and grasses in non-crop areas [private, public, and 

military lands: uncultivated non-agricultural areas (such as airports, highway, railroad and utility 

rights-of-way, sewage disposal areas), uncultivated non-crop agricultural areas (such as 

farmyards, fuel storage areas, fence rows, non-irrigation ditchbanks, barrier strips), outdoor 

industrial sites (such as lumberyards, pipeline, and tank farms), natural areas (such as wildlife 

management areas, wildlife openings, wildlife habitats, recreation areas, campgrounds, 

trailheads, and trails)], turf/lawns (residential, industrial, and institutional), golf courses, parks, 

cemeteries, athletic fields, and sod farms. 

Three forms of aminocyclopyrachlor are being registered: the parent acid (aminocyclopyrachlor), 

the methyl ester (aminocyclopyrachlor-methyl), and the potassium salt (aminocyclopyrachlor 

potassium salt). The parent acid, aminocyclopyrachlor, is considered the active ingredient. 

Aminocyclopyrachlor may be applied in three different formulations: granular, water dispersible 

granular (dry flowable), and soluble liquid. Occupational application scenarios include: aerial 

(fixed wing or helicopter), ground boom, right-of-way sprayer, push-type spreader, push cyclone 

spreader, tractor drawn broadcast spreader, and lawn care operator (LOC) handgun. Broadcast 

applications may be performed by using either a single ground boom, a tractor type broadcast, or 

as a banded application for pre-plant, pre-emergence, or early post-emergence. Pre-plant 

applications can be made as either a single or split application that is either surface applied or 

incorporated. Residential application scenarios include low pressure hand wand, hose-end 

sprayer, and hand-held spreader (i.e. belly grinder). Maximum annual application rates range 

from 0.05 – 0.324 lb acid equivalent (ae)/acre/year. 

1.1. Chemical Information 

Aminocyclopyrachlor is a systemic herbicide in the pyrimidine carboxylic acids class within the 

family of synthetic auxins, which disrupts gene expression resulting in undifferentiated cell 

division and elongation. It is biologically active in soil and is rapidly absorbed by roots and 

leaves. Effects to target weeds include downward bending of leaves, severe necrosis, stem 

thickening, growth stunting, leaf crinkling and cupping, calloused stems and leaf veins, and 

enlarged roots. Symptoms may begin from a few hours to a few days after application, and plant 

death may take weeks to several months. 

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1.1.1. Chemical Name: Aminocyclopyrachlor (parent acid)

 6-amino-5-chloro-2-cyclopropyl-4-pyrimidinecarboxylic acid 

 EPA PC Code: 288008 

 CAS Number: 858956-08-8 

 Mode of Action: Synthetic auxin-type herbicide causing disorganized plant growth 

 (pyrimidine carboxylic acid) 

Registrant: E.I. du Pont de Nemours and Company (EPA Company No.: 352) 

 Products: 

EPA Reg. No. Product Name % a.i. 

352-TIE (782) DPX-MAT28 Technical Herbicide 89.3 

352-TOA (796) DPX-MAT28 10% Manufacturing Concentrate 10.0 

352-TIT (787) DPX-MAT28 50SG Herbicide 50.0 

352-TOU (794) DPX-MAT28 50SG Turf Herbicide 50.0 

352-IRG (813) DPX-MAT28 0.05G Turf Herbicide + Fertilizer 0.05 

352-IRU (814) DPX-MAT28 0.03G Turf Herbicide + Fertilizer 0.03 

352-IRL (815) DPX-MAT28 0.068G Lawn Herbicide + Fertilizer 0.068 

1.1.2. Chemical Name: Aminocyclopyrachlor-methyl (methyl ester) 

 methyl 6-amino-5-chloro-2-cyclopropyl-4-pyrimidinecarboxylate 

 EPA PC Code: 288009 

 CAS Number: 858954-83-3 

 Mode of Action: Synthetic auxin-type herbicide causing disorganized plant growth 

 (pyrimidine carboxylic acid) 

 Registrant: E.I. du Pont de Nemours and Company (EPA Company No.: 352) 

 Products: 

EPA Reg. No. Product Name % a.i. 

352-TIG (783) DPX-KJM44 Technical Herbicide 95.6 

352-TIU (784) DPX-KJM44 80 MUP Herbicide 80.0 

352-TOL (795) DPX-KJM44 10% Manufacturing Concentrate 10.0 

352-TIL (785) DPX-KJM44 80XP Herbicide 80.0 

352-TOE (792) DPX-KJM44 80XP Turf Herbicide 80.0 

352-TOT (797) DPX-KJM44 0.064G Turf Herbicide + Fertilizer 0.064 

352-INN (800) DPX-KJM44 0.073G Lawn Herbicide + Fertilizer 0.073 

352-ING (803) DPX-KJM44 0.053G Lawn Herbicide + Fertilizer 0.053 

352-INU (804) DPX-KJM44 0.049G Lawn Herbicide + Fertilizer 0.049 

352-INT (807) DPX-KJM44 0.033G Lawn Herbicide + Fertilizer 0.033 

352-IRR (811) DPX-KJM44 0.02G Lawn Herbicide + Fertilizer 0.02 

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1.1.3. Chemical Name: Aminocyclopyrachlor potassium salt

 potassium 6-amino-5-chloro-2-cyclopropyl-4- 

 pyrimidinecarboxylate 

 EPA PC Code: 288010 

 CAS Number: 858956-35-1 

 Mode of Action: Synthetic auxin-type herbicide causing disorganized plant growth 

 (pyrimidine carboxylic acid) 

Registrant: E.I. du Pont de Nemours and Company (EPA Company No.: 352) 

 Products: 

EPA Reg. No. Product Name % a.i. 

352-TIA (786) DPX-MAT28 240SL Herbicide 25.0 

352-TOG (793) DPX-MAT28 240SL Turf Herbicide 25.0 

1.2. Human Health Risk 

A summary of the human health effects and risk of aminocyclopyrachlor as assessed in the 

Agency document titled “Aminocyclopyrachlor: Human Health Risk Assessment for Proposed 

Uses as an Herbicide” is provided below. 

1.2.1. Toxicological Summary and Considerations 

Pharmacokinetic oral studies indicate that both aminocyclopyrachlor and aminocyclopyrachlormethyl are rapidly absorbed, with rapid metabolic conversion of aminocyclopyrachlor-methyl to 

aminocyclopyrachlor. Elimination is almost complete within 24 hours. Similar acute toxicities, 

subchronic dietary, reproductive toxicity, and gene mutation studies results for both chemicals, 

along with evidence from metabolism studies form a scientific justification for considering 

aminocyclopyrachlor and aminocyclopyrachlor-methyl toxicologically equivalent, thus allowing 

bridging of the toxicity database for aminocyclopyrachlor-methyl with studies using 

aminocyclopyrachlor. 

The toxicology database for aminocyclopyrachlor is adequate for risk assessment for the new use 

patterns. Aminocyclopyrachlor has low acute toxicity by oral, dermal, and inhalation routes of 

exposure, and does not cause skin sensitization or irritation. However, it can cause mild eye 

irritation. Aminocyclopyrachlor and aminocyclopyrachlor-methyl have low subchronic toxicity 

via the oral route. The most sensitive species is the rat, with decreased body weight at the limit 

dose in subchronic dietary studies as the most sensitive endpoint of toxicity. The major effect 

observed across species for aminocyclopyrachlor was decreased body weight at the limit dose. 

No toxicity was observed in subchronic dietary studies in dogs at the highest dose of 

aminocyclopyrachlor tested, which was half the limit dose, but still higher than the dose at which 

no adverse effects occurred in the rat. No target organ of toxicity was identified. No sex 

differences in toxicity were observed for either aminocyclopyrachlor or aminocyclopyrachlormethyl. 

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Aminocyclopyrachlor was not neurotoxic when administered acutely or subchronically via the 

oral route. Aminocyclopyrachlor-methyl showed no evidence of neurotoxicity or reproductive 

toxicity in an extended one generation reproductive toxicity study in rats. Aminocyclopyrachlor 

did not cause developmental toxicity in rats or rabbits. Therefore, there is low concern for 

reproductive, developmental, or neurotoxicity for aminocyclopyrachlor and 

aminocyclopyrachlor-methyl. 

Aminocyclopyrachlor and aminocyclopyrachlor-methyl are considered to have low potential to 

cause chronic toxicity or carcinogenicity. No evidence of genotoxic effects was observed in 

mutagenicity studies in vitro for aminocyclopyrachlor and aminocyclopyrachlor-methyl or in 

vivo for aminocyclopyrachlor. No evidence of target organ toxicity was observed in oral 

subchronic studies for aminocyclopyrachlor and aminocyclopyrachlor-methyl at doses exceeding 

the limit dose. 

Immunotoxicity was investigated via the oral route in two species (rats and mice) for 

aminocyclopyrachlor. There was no evidence of immunotoxicity. 

1.2.1.1. Degradate of Concern

An environmental photodegradate of aminocyclopyrachlor present only in surface water was of 

possible concern for drinking water exposures. This photodegradate, cyclopropane carboxylic 

acid (IN-V0977), has a different mode of toxic action than aminocyclopyrachlor. Oral 

administration of cyclopropane carboxylic acid causes severe impairment of mitochondrial 

function by inhibiting the beta oxidation of fatty acids, resulting in microvesicular steatosis 

(accumulation of small fat droplets in cells). The liver is the most sensitive organ, and 

hepatocellular microvesicular steatosis is often accompanied by liver necrosis and inflammation, 

decreased hepatic glycogen, and decreased blood glucose levels. These effects have been 

observed with acute (one to three days) and longer (up to 14 days) exposure. The most sensitive 

species is the rabbit. Hepatic microvesicular steatosis in the rabbit follows a different doseresponse than body weight decreases observed with aminocyclopyrachlor and 

aminocyclopyrachlor-methyl in rats, with a lowest observed adverse effect level (LOAEL) that is 

100-fold lower. However, based on the new use pattern, the dietary exposure to IN-V0977 from 

drinking water is below the Agency’s level of concern (LOC) (see Section 1.2.4). 

1.2.2. Toxicological End Points and Doses 

1.2.2.1. Acute Dietary 

For aminocyclopyrachlor, no acute reference dose (aRfD) or acute population adjusted dose 

(aPAD) was established because no toxicity was observed at the limit dose in the acute oral 

toxicity studies. 

For the degradate IN-V0977, the Agency has established an aRfD of 0.0026 mg/kg (body 

wt)/day, based on the LOAEL of 2.55 mg/kg/day from a rabbit study in which hepatic steatosis 

was observed and an uncertainty factor of 1000X. The 1000X uncertainty factor takes into 

account interspecies and intraspecies variability (10X for each) as well as the uncertainty 

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associated with extrapolation of a no observed adverse effect level (NOAEL) from a LOAEL 

(10X). 

1.2.2.2. Chronic Dietary 

For aminocyclopyrachlor, the Agency has established a chronic reference dose (cRfD) and a 

chronic population adjusted dose (cPAD) of 0.35 mg/kg/day, based on the NOAEL of 350 

mg/kg/day from the 90-day oral toxicity study in rats and an uncertainty factor of 1000X. In this 

study, decreased body weights, body weight gains, food consumption, and food efficiency in 

both sexes were observed at the LOAEL of 1044.6/1424.9 mg/kg/day. The 1000X uncertainty 

factor takes into account interspecies and intraspecies variability (10X for each) as well as the 

uncertainty associated with using an endpoint from a subchronic study to assess chronic 

exposure (10X). 

For the degradate IN-V0977, the Agency has established a cRfD of 0.00087 mg/kg/day, based on 

the LOAEL of 2.55 mg/kg/day from a rabbit study in which hepatic steatosis was observed and 

an uncertainty factor of 3000X. The 3000X uncertainty factor takes into account interspecies 

and intraspecies variability (10X for each), uncertainty associated with extrapolation of a 

NOAEL from a LOAEL (10X), and uncertainty arising from using a short-term study to assess 

long-term risk (3X). 

1.2.2.3. Short- and Intermediate-Term Incidental Oral and Inhalation 

The Agency has established a LOC of 3.5 mg/kg/day for the margin of exposure (MOE) of 100, 

based on the NOAEL of 350 mg/kg/day from the chronic 90-day oral toxicity study in rats and 

an uncertainty factor of 100X (10X interspecies x 10X intraspecies). In this study, decreased 

body weights, body weight gains, food consumption, and food efficiency in both sexes were 

observed at the limit dose LOAEL of 1044.6/1424.9 mg/kg/day. Long-term incidental oral 

exposures are not anticipated based on the new use pattern. 

1.2.2.4. Short- and Intermediate-Term Dermal 

No dermal endpoint was established because no toxicity was observed at the limit dose in the 28-

day dermal toxicity study. The 90-day dermal toxicity study was waived because the 28-day 

dermal toxicity study is considered suitable for long-term exposures and all endpoints of concern 

were assessed. 

1.2.2.5. Cancer 

The Agency has classified aminocyclopyrachlor as “Not likely to be Carcinogenic to Humans” 

based on the lack of evidence of genotoxic effects in the in vitro and in vivo mutagenicity 

studies. Aminocyclopyrachlor is considered to have low potential to cause chronic toxicity or 

carcinogenicity. No evidence of target organ toxicity was observed in oral subchronic studies at 

doses exceeding the limit dose. Therefore, cancer risk was not assessed. 

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1.2.3. Consideration of Toxicity to Children 

Food Quality Protection Act (FQPA) considerations do not apply to aminocyclopyrachlor for the 

non-food use patterns described in this risk assessment. However, the Agency has reviewed the 

toxicity database and has determined that the young will not be particularly sensitive to the 

effects of aminocyclopyrachlor when used in residential settings based on the following: 

• The toxicity database is considered complete and includes acceptable developmental 

toxicity studies in rats and rabbits, a two-generation reproductive toxicity study in rats, 

and an extended one-generation reproductive toxicity study in rats that included a 

modified functional observational battery. 

• No evidence of neurotoxicity was observed in the acute or subchronic neurotoxicity 

studies in rodents at the limit dose after exposure to aminocyclopyrachlor. Also, no 

evidence of neurotoxicity was observed in an extended one-generation reproduction study 

in rats with aminocyclopyrachlor-methyl that included a modified functional 

observational battery. 

• No evidence of developmental toxicity was observed when aminocyclopyrachlor was 

administered in the diet of rats or orally by gavage to rabbits at the limit dose. 

• No evidence of adverse effects of aminocyclopyrachlor or aminocyclopyrachlor-methyl 

on reproduction or fertility parameters was observed in dietary studies with rats. 

• No evidence of prenatal toxicity was observed following maternal exposure to 

aminocyclopyrachlor. There is no evidence of increased susceptibility following in utero 

exposure to aminocyclopyrachlor in rats or rabbits in developmental toxicity studies, 

which showed no adverse effects in offspring at the limit dose. An increase in abortions 

in maternal rabbits was observed at the limit dose, but this was considered secondary to 

decreases in body weight. There was also no evidence of increased susceptibility of 

offspring to aminocyclopyrachlor in reproduction and fertility studies in rats, for which 

adverse effects were limited to decreased body weights in both maternal animals and 

offspring at the limit dose. Therefore, the young are not considered more susceptible 

than adults to adverse effects from aminocyclopyrachlor or aminocyclopyrachlor-methyl. 

• There are no residual uncertainties identified in the exposure databases. EPA made 

conservative (protective) assumptions in the ground and surface water modeling used to 

assess exposure to aminocyclopyrachlor in drinking water. EPA used similarly 

conservative assumptions to assess post-application exposure of children including 

incidental oral exposure of toddlers. These assessments will not underestimate the 

exposure and risks posed by aminocyclopyrachlor. 

1.2.4. Dietary Risk 

Dietary risk assessment addresses exposure that individuals receive through food consumption 

and drinking water. Since there are no new food uses for aminocyclopyrachlor, only dietary 

exposure to aminocyclopyrachlor and its environmental degradates from drinking water were 

considered. 

 

For aminocyclopyrachlor, no acute dietary risk assessment was performed since no acute toxicity 

endpoint was identified. Cancer risks from dietary exposure to aminocyclopyrachlor and the 

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degradate IN-V0977 in drinking water were not assessed since no cancer dietary endpoint was 

identified. Risks for chronic dietary exposures to aminocyclopyrachlor from drinking water 

were considered, and the risk estimates for the general U.S. population and all other regulated 

population subgroups are below the Agency’s LOC of greater than 100% of the cRfD. Chronic 

exposure to aminocyclopyrachlor from drinking water will occupy <1% of the cRfD for infants 

less than 1 year old, the population subgroup with the highest estimated exposure. 

The major route of environmental degradation of aminocyclopyrachlor is aqueous photolysis, 

which produces five degradates. Of these, one environmental degradate, IN-V0977 

(cyclopropane carboxylic acid), was of concern. Dietary assessments of acute and chronic 

dietary exposures of cyclopropane carboxylic acid from drinking water were performed, and are 

below the Agency’s LOC of greater than 100% of the aRfD/cRfD. Acute exposure to the 

degradate IN-V0977 from drinking water will occupy 13% of the aRfD and 9.9% of the cRfD for 

infants less than 1 year old, the population subgroup with the highest estimated exposure. 

1.2.5. Residential Risk 

Residential risk assessment addresses exposures that individuals receive through their use of 

consumer products and exposures that individuals receive from frequenting areas that have been 

previously treated with aminocyclopyrachlor. 

1.2.5.1. Residential Handler Risk

Residential handler exposure to aminocyclopyrachlor may occur dermally and by inhalation. No 

dermal risk was assessed because no toxicity was observed at the limit dose in the subchronic 

dermal toxicity study. Inhalation risk was assessed by analysis of short-term and intermediateterm exposures using the lawn/turf products with the highest application rates (0.07 - 0.10 lb 

ae/A) and hazards identified in subchronic oral toxicity studies. 

The Agency has identified the following residential exposure scenarios from applications to 

lawns/turf: 

Mixing/Loading/Applying 

• Low Pressure Handwand (dry flowable and soluble liquid) 

• Hose-End Sprayer (dry flowable and soluble liquid) 

• Hand-Held Spreader/Belly Grinder (granular) 

The margins of exposure (MOEs) for the three inhalation exposure scenarios range from 

7,300,000 to 41,200,000. Since the Agency’s LOC is for MOEs less than 100, residential 

handler exposures are not of concern. 

1.2.5.2. Residential Post-Application Risk

Residential post-application exposure to aminocyclopyrachlor may occur dermally and orally for 

a variety of populations. No dermal risk was assessed because no toxicity was observed at the 

limit dose in the subchronic dermal toxicity study. Oral risk in toddlers was assessed by analysis 

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of short-term and intermediate-term post-application exposures using the lawn/turf product with 

the highest application rate (0.10 lb ae/A). 

The Agency has identified the following residential post-application exposure scenarios from 

applications to lawns/turf: 

Toddlers 

• Hand-to-Mouth Activity on Lawn/Turf 

• Object-to-Mouth Activity on Lawn/Turf 

• Soil Ingestion 

The single and combined MOEs for short-term and intermediate-term oral exposures range from 

234,000 to 70,000,000. Since the Agency’s LOC is for MOEs less than 100, residential postapplication exposures are not of concern for any population, including toddlers. 

1.2.6. Aggregate Risk 

Aggregate risk assessment addresses combined exposures that individuals receive from dietary 

and residential exposures to aminocyclopyrachlor. Quantitative, aggregate exposure and risk 

assessments for aminocyclopyrachlor are not required for the new non-food use patterns because 

Food Quality Protection Act (FQPA) considerations do not apply. However, the potential for 

significant aggregate exposures to aminocyclopyrachlor from dietary (drinking water) and 

residential uses relative to non-aggregate exposures was considered. The highest estimated 

residential exposure (0.000048 mg/kg/day via inhalation during mixing, loading, and applying a 

granular formulation with a belly grinder) was combined with the highest estimated dietary 

exposure (0.002778 mg/kg/day for all infants < 1 year old). This combined value of 0.003 

mg/kg/day was over 1000- fold lower than the point of departure of 3.5 mg/kg/day, based on the 

most conservative LOC for MOE (350 mg/kg/day with MOE =100). This estimate indicates that 

aggregate exposures to aminocyclopyrachlor will not result in significantly increased risk 

relative to non-aggregate exposure. 

1.2.7. Occupational Risk 

Occupational risk assessment addresses risks to individuals who are exposed to 

aminocyclopyrachlor as part of their employment, via contact while using commercial products 

(handler) or by being in areas that have been previously treated (post-application). 

1.2.7.1. Occupational Handler Risk 

Occupational handler exposure to aminocyclopyrachlor may occur dermally and by inhalation. 

No dermal risk was assessed because no toxicity was observed at the limit dose in the subchronic 

dermal toxicity study. Inhalation risk was assessed by analysis of short-term and intermediateterm exposures using the products with the highest application rates (0.07 - 0.28 lb ae/A) and 

hazards identified in subchronic oral toxicity studies. 

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The Agency has identified the following occupational exposure scenarios from applications to 

private, public and military lands including un-cultivated non-agricultural (non-crop) areas such 

as airports, highways, railroads, golf courses, lumber yards, wild life habitats, multi family 

residential complexes, recreation areas, sod farms, utility rights of way, and residential lawns: 

Mixing/Loading 

• Groundboom (dry flowable and soluble liquid) to non-crop areas, golf courses, sod 

farms, and lawn/turf 

• Aerial (fixed and non-fixed wing) (dry flowable) to non-crop areas 

• LCO handgun (dry flowable and soluble liquid) to non-crop areas, golf courses, sod 

farms, and lawn/turf 

• Right-of-way sprayer (dry flowable and soluble liquid) to non-crop areas, golf 

courses, sod farms, and lawn/turf 

• Push-type spreader (granular) to golf courses, sod farms, and lawn/turf 

• Tractor drawn broadcast spreader (granular) to golf courses, sod farms, and lawn/turf 

• Push cyclone spreader (granular) to golf courses, sod farms, and lawn/turf 

Applying 

• Groundboom (dry flowable and soluble liquid) to non-crop areas, golf courses, sod 

farms, and lawn/turf 

• Aerial (fixed and non-fixed wing) (dry flowable) to non-crop areas 

• LCO handgun (dry flowable and soluble liquid) to non-crop areas, golf courses, sod 

farms, and lawn/turf 

• Right-of-way sprayer (dry flowable and soluble liquid) to non-crop areas, golf 

courses, sod farms, and lawn/turf 

• Tractor drawn broadcast spreader (granular) to golf courses, sod farms, and lawn/turf 

Flagging 

• Aerial (fixed and non-fixed wing) (dry flowable) to non-crop areas 

The MOEs for the identified inhalation exposure scenarios range from 190,000 to 50,000,000. 

Since the Agency’s LOC is for MOEs less than 100, occupational handler exposures are not of 

concern. 

1.2.7.2. Occupational Post-Application Risk

Occupational post-application exposure to aminocyclopyrachlor may occur dermally and by 

inhalation. No dermal risk was assessed because no toxicity was observed at the limit dose in the 

subchronic dermal toxicity study. A quantitative post-application inhalation risk assessment was 

not deemed necessary, based on the high occupational handler MOE values. Post-application 

exposures would be lower than those for handlers due to aminocyclopyrachlor’s low vapor 

pressure and dilution in outdoor air. Therefore, occupational post-application exposures are not 

of concern. 

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1.3. Environmental Risk 

A summary of the environmental fate and ecological effects and risks of aminocyclopyrachlor as 

assessed in the Agency document titled “Ecological Risk Assessment for the Section 3 New 

Chemical Registration of Aminocyclopyrachlor on Non-crop Areas and Turf” is provided below. 

1.3.1. Environmental Summary and Considerations 

A dissociation constant study indicated that the potassium salt form of aminocyclopyrachlor 

rapidly dissociates to the acid when it is mixed with water prior to application. This similarity in 

behavior once the potassium salt is dissociated in water allows bridging of the environmental fate 

and toxicity database for aminocyclopyrachlor potassium salt with studies using 

aminocyclopyrachlor. 

Laboratory and field dissipation studies indicated that aminocyclopyrachlor-methyl rapidly 

hydrolyzes to aminocyclopyrachlor in alkaline aquatic environments, moist soils, and soil/water 

slurries. Degradation under environmentally-relevant pH conditions is primarily microbe 

mediated. Therefore, aminocyclopyrachlor-methyl applications may result in short-term 

exposures to the methyl ester form prior to hydrolysis to the acid. Aquatic studies on freshwater 

fish and invertebrates for aminocyclopyrachlor-methyl showed higher toxicity than 

aminocyclopyrachlor. As a result, with the exception of acute aquatic toxicity data, 

acute/chronic terrestrial and chronic aquatic toxicity data may be bridged for 

aminocyclopyrachlor-methyl with studies using aminocyclopyrachlor. 

1.3.1.1. Degradates of Concern

Model estimates suggest that degradates IN-LXT69 and IN-YY905 may be more toxic than 

aminocyclopyrachlor to daphnids on a chronic basis. Based on human health effects evaluation 

of degradates (see Sections 1.2.1.1 and 1.2.4), the degradate IN-V0977 may be more toxic than 

aminocyclopyrachlor to birds and mammals. However, by comparing the concentrations 

expected in the environment to the effects thresholds, IN-V0977 would have to be more than two 

orders of magnitude more toxic than aminocyclopyrachlor to exceed the Agency’s LOC. Also, 

since aqueous photolysis is the only significant rapid degradation pathway of 

aminocyclopyrachlor, aquatic exposure to the three degradates of concern would not result in any 

additional risks over those presented from exposure to aminocyclopyrachlor unless the 

degradates were considerably more toxic. 

1.3.2. Environmental Fate 

Aminocyclopyrachlor is non-volatile, highly soluble in water, and highly mobile to mobile in 

soils. Dissipation in the environment is expected to occur predominantly via aqueous photolysis, 

runoff, and leaching. Terrestrial field dissipation occurred with half-lives ranging from 22 to 126 

days. Aminocyclopyrachlor was detected at soil depths of 70 – 90 cm at 365 days, indicating 

that leaching of residues into groundwater may occur. 

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Aminocyclopyrachlor is environmentally persistent in diverse environments. It persists in 

aerobic aquatic environments with a dissipation time of greater than 100 days and in aerobic 

terrestrial environments with a half-life of 373 days. It is also stable in anaerobic aquatic 

environments with a half life of 1733 days and in anaerobic terrestrial environments with a halflife of 6932 days. It has a low tendency for bioaccumulation. 

The major route of degradation of aminocyclopyrachlor is abiotic via aqueous photolysis with a 

half-life of l.2 days in shallow, clear, and well-lit natural (pH 6.2) water bodies and 7.8 days in 

pH 4 buffer solution. However, it is slowly photolyzed on soil, with a half-life of 129 days. 

Aminocyclopyrachlor is stable to hydrolysis at pH 4, 7, and 9. 

To address concerns with the potential leaching of aminocyclopyrachlor that may result from the 

persistence and mobility described above, end-use product labels will be required to include 

surface and ground water advisories that stress the potential of runoff after treatment and 

descriptions of conditions that may promote leaching to groundwater (see Section 2.2.1). 

1.3.3. Ecological Risk 

Ecological risk assessment addresses exposures that non-target aquatic and terrestrial organisms 

and plants receive through the use of aminocyclopyrachlor. 

A screening-level risk assessment based on the new uses suggests that aminocyclopyrachlor 

presents potential risk to terrestrial and semi-aquatic plants and to organisms that depend on the 

plants for habitat and forage. 

To better characterize and confirm chronic risks to birds and freshwater invertebrates, additional 

data will be required as a condition of registration (see Section 2.1.2). To mitigate potential risk 

to non-target terrestrial and semi-aquatic plants, end-use product labels will be required to 

include language that is intended to keep the pesticide on the treatment area (see Section 2.2.4). 

1.3.3.1. Aquatic Risk

The highest surface water estimated environmental concentration (EEC) values resulted from the 

new aerial non-crop applications at 0.284 lb ae/A. This conservative approach of using an EEC 

of 0.284 lb ae/A will also cover turf applications, which resulted in lower EECs. EECs were 

compared to toxicity endpoints to derive risk quotients (RQs), which is then compared to the 

Agency’s LOC. 

 

1.3.3.1.1. Fish Risk

Aminocyclopyrachlor is practically non-toxic to freshwater and estuarine/marine fish on an acute 

basis. Acute risk was not quantified since no toxicity was observed at the highest concentration 

tested; therefore, RQs are not expected to exceed LOCs. Aminocyclopyrachlor-methyl is 

slightly toxic to freshwater fish on an acute basis; however, the RQ of <0.01 does not exceed the 

LOC. Chronic risk to freshwater fish resulted in a RQ of <0.01 and does not exceed the LOC. 

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1.3.3.1.2. Aquatic Invertebrate Risk

Aminocyclopyrachlor and aminocyclopyrachlor-methyl are slightly toxic to freshwater 

invertebrates on an acute basis; however, RQs of <0.01 do not exceed LOCs. 

Aminocyclopyrachlor is practically non-toxic to estuarine/marine invertebrates on an acute basis; 

where the RQ <0.01 does not exceed the LOC. 

In the chronic freshwater invertebrate (daphnid) study, non dose-response mortalities were 

observed at the three lowest treatment levels. Therefore, the resulting toxicity values could not 

be used quantitatively to assess chronic risk to aquatic invertebrates. Despite the lack of valid 

data, chronic risk to freshwater invertebrates is not expected to exceed the Agency’s LOC. 

Environmental concentrations of aminocyclopyrachlor in surface waters from applications at the 

maximum rates are expected to be in the parts per billion (ppb) range; whereas all aquatic 

toxicity studies were conducted at concentrations in the parts per million (ppm) range. Based on 

the results of chronic studies in freshwater fish, where the no observed adverse effect 

concentration (NOAEC) is 11 ppm, EPA also expects the freshwater invertebrate NOAEC to be 

in the ppm range, well above the expected environmental concentrations. A repeated Freshwater 

Invertebrate Life Cycle Toxicity Test (Guideline 850.1300) is expected to be confirmatory and 

will be required as a condition of registration (see Section 2.1.2). 

1.3.3.1.3. Aquatic Plant Risk

Risks to aquatic vascular and non-vascular plants resulted in RQs <0.01, which do not exceed the 

Agency’s LOC. 

1.3.3.2. Terrestrial Risk

Terrestrial wildlife EECs are estimated emphasizing a dietary exposure route for uptake of 

pesticide residues on vegetative matter and insects. Birds are used as surrogates for terrestrialphase amphibians and reptiles. Honey bee is used as a surrogate for terrestrial invertebrates. 

1.3.3.2.1. Avian Risk

Aminocyclopyrachlor and aminocyclopyrachlor-methyl are practically non-toxic to birds (also 

terrestrial-phase amphibians and reptiles) on an acute basis. Acute risk was not quantified since 

no toxicity was observed; therefore, RQs are not expected to exceed LOCs. 

The submitted avian reproduction studies were invalid due to improper husbandry practices 

(small cage sizes) that may have caused incidental mortalities in quails and reduced egg 

production in mallards. Despite the improper husbandry conditions, there was no evidence in 

either study of adverse treatment-related effects, including overt toxicity, mortality, effects on 

feed consumption and body weight, macroscopic findings, or reproductive effects. A repeated 

Avian Reproduction Toxicity Test (Guideline 850.2300) is expected to be confirmatory and will 

be required as a condition of registration (see Section 2.1.2). 

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1.3.3.2.2. Mammalian Risk

Aminocyclopyrachlor and aminocyclopyrachlor-methyl are practically non-toxic to mammals on 

an acute basis. Acute risk was not quantified since no toxicity was observed; therefore, RQs are 

not expected to exceed LOCs. Chronic risks to mammals resulted in RQs of <0.1 and do not 

exceed the LOC. 

1.3.3.2.3. Terrestrial Invertebrate Risk

Aminocyclopyrachlor is practically non-toxic to terrestrial invertebrates, due to lack of mortality 

and sublethal effects in the honey bee study for aminocyclopyrachlor. An acute earthworm 

toxicity study for aminocyclopyrachlor-methyl also showed no mortalities or behavioral 

abnormalities, but the study is classified as supplemental since the Agency does not currently 

have an OPPTS guideline for earthworms. The Agency does not routinely quantify risks to 

terrestrial invertebrates. 

1.3.3.2.4. Terrestrial Plant Risk

As expected for herbicides, terrestrial and semi-aquatic plants are sensitive to 

aminocyclopyrachlor, where RQs exceeded the LOC. Non-target terrestrial and semi-aquatic 

plants may be exposed to aminocyclopyrachlor via runoff and spray drift, with dicots being more 

susceptible than monocots. To mitigate potential risk to non-target terrestrial and semi-aquatic 

plants, end-use product labels will be required to include language that is intended to keep the 

pesticide on the treatment area (see Section 2.2.4). 

1.4. Public Interest 

Aminocyclopyrachlor poses very low risk to humans, including workers and the general 

population, due to its low toxicity and low volatility. Similarly, because of its low toxicity to 

terrestrial and aquatic non-target organisms other than plants, aminocyclopyrachlor poses low 

environmental risks. 

The benefits afforded by registration of aminocyclopyrachlor may be substantial. Along with 

other herbicides in the same chemical family, this herbicide will be an important component in 

integrated pest management programs for both non-crop and turf areas. Aminocyclopyrachlor 

controls a broad spectrum of weeds, including difficult to manage invasive and noxious brush 

and herbicide-resistant species. In particular, aminocyclopyrachlor demonstrates very good 

long-term control of Leafy Spurge, considered one of the most difficult to control invasive weeds 

in the western United States. Leafy Spurge is listed as a noxious weed in 22 states, making 

control mandatory by legal statute in those areas. Very few alternative chemicals provide 

effective long-term control of Leafy Spurge, which reproduces aggressively, actively destroying 

native biodiversity and rendering pastures and rangelands unfit for cattle and horses grazing due 

to its unpalatability and toxicity. A single application of aminocyclopyrachlor will provide longlasting control, obviating the need for multiple applications of the current alternatives and 

thereby reducing the pesticide load in the environment. Aminocyclopyrachlor will also provide 

- 16 - 
the commercial turf industry with an important tool. Because of its low volatility, it can be used 

in turf applications around valuable ornamental plants with less risk of damage than the current 

staples of the industry, 2,4-D and dicamba. 

Based on these considerations, the Agency believes that the registration of aminocyclopyrachlor 

is in the public’s interest. 

2. REGULATORY DECISION 

The Agency is granting conditional registration of the new active ingredient 

aminocyclopyrachlor, formulated as 2 technical products, 3 manufacturing-use products, and 15 

end-use products. It is a selective herbicide providing pre-emergence and post-emergence 

control of broadleaf weeds, woody species, vines, and grasses in non-crop areas [private, public, 

and military lands: uncultivated non-agricultural areas (airports, highway, railroad and utility 

rights-of-way, sewage disposal areas), uncultivated non-crop agricultural areas (farmyards, fuel 

storage areas, fence rows, non-irrigation ditchbanks, barrier strips), outdoor industrial sites 

(lumberyards, pipeline, and tank farms), natural areas (wildlife management areas, wildlife 

openings, wildlife habitats, recreation areas, campgrounds, trailheads, and trails)], turf/lawns 

(residential, industrial, and institutional), golf courses, parks, cemeteries, athletic fields, and sod 

farms. 

In the Federal Register of January 27, 2010 (75 FR 4384), EPA issued a notice pursuant to 

section 3(c)(4) of FIFRA entitled “Pesticide Products; Registration Applications” announcing 

receipt of applications to register pesticide products containing the new active ingredient, 

aminocyclopyrachlor, by E.I. du Pont de Nemours and Company. There were no comments 

received in response to the notice of receipt. 

On June 17, 2010, the Agency posted the proposed decision document for aminocyclopyrachlor 

entitled “Proposed Registration of Aminocyclopyrachlor on Non-Crop Areas, Sod Farms, Turf, 

and Residential Lawns”, the associated risk assessments, and the proposed labels in the docket 

EPA-HQ-OPP-2009-0789. The registrant provided a response to the Agency on July 16, 2010 

entitled “DuPont Response to the EPA’s “Proposed Registration of Aminocyclopyrachlor on 

Non-Crop Areas, Sod Farms, Turf, and Residential Lawns”. No other comments were received. 

2.1. Data Requirements 

The Agency has determined that additional data are required in order to better characterize risk. 

The studies identified below are required as a condition of the registration of 

aminocyclopyrachlor. 

2.1.1. Human Health Data Requirements

The human health risk assessment concluded that the following study is required in support of 

the new uses: 

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• A repeated-dose study in a sensitive species is required to address the hazard of 

subchronic/chronic exposure to the environmental degradate cyclopropane 

carboxylic acid (IN-V0977): To account for the lack of this study, EPA applied an 

additional 3X uncertainty factor (UF) to the point of departure (POD) used in the chronic 

exposure assessment for drinking water. Even with the additional UF and the 

conservative assumptions of the drinking water models used to estimate concentrations of 

aminocyclopyrachlor in drinking water, estimated chronic risk is well below the LOC 

(<10% of the cPAD for all population groups).

2.1.2. Environmental Data Requirements

The ecological risk assessment concluded that the following studies are required in support of the 

new uses: 

• Avian Reproduction Toxicity Test (850.2300): 

Data are required for both an upland game and waterfowl species for the new use 

patterns. The submitted studies were invalid due to improper husbandry practices that 

may have caused incidental mortalities in quails and reduced egg production in mallards. 

Despite the improper husbandry conditions, there was no evidence in either study of 

adverse treatment-related effects, including overt toxicity, mortality, effects on feed 

consumption and body weight, macroscopic findings, or reproductive effects. Therefore, 

submission of a repeat-study performed under proper husbandry conditions is expected to 

be confirmatory and will better characterize chronic risk to birds. 

• Freshwater Invertebrate Life-Cycle Toxicity Test (850.1300): 

Non dose-response mortalities were observed in the three lowest treatment levels for the 

submitted freshwater daphnid study. Therefore, the resulting toxicity values could not be 

used quantitatively to assess chronic risk to aquatic invertebrates. Despite the lack of 

valid data, chronic risk to freshwater invertebrates is not expected to exceed the Agency’s 

LOC. Environmental concentrations of aminocyclopyrachlor in surface waters from 

applications at the maximum rates are expected to be in the parts per billion (ppb) range; 

whereas all aquatic toxicity studies were conducted at concentrations in the parts per 

million (ppm) range. Based on the results of chronic studies in freshwater fish, where the 

NOAEC is 11 ppm, EPA also expects the freshwater invertebrate NOAEC to be in the 

ppm range, well above the expected environmental concentrations. Therefore, 

submission of a repeat-study is expected to be confirmatory and will better characterize 

chronic risk to freshwater invertebrates. 

 

2.2. Label Requirements

2.2.1. Environmental Hazards 

Based on potential leaching and runoff that may result from the persistence and mobility of 

aminocyclopyrachlor, surface and ground water advisories must be placed on the following 

aminocyclopyrachlor end-use product labels. 

- 18 - 
2.2.1.1. Surface Water Advisory

The surface water advisory was revised from the language stated in the proposed decision 

document by removing the phrase “spray drift and” and the reference to the USDA manual so 

that it is consistent with the EPA’s standardized language. Also, the proposed surface water 

advisory for products primarily intended for consumer use on residential lawns has been 

replaced with the environmental hazard statements recommended in the Pesticide Registration 

(PR) Notice 2008-1 for outdoor residential use products. These statements present instructions 

similar to those of the commercial-use surface water advisory, but in terms suitable for 

consumers. 

Products Primarily Intended for Commercial Use on Non-Crop Areas, Sod Farms, and 

Turf/Lawns 

“This Product may impact surface water quality due to runoff of rain water. This is especially 

true for poorly draining soils and soils with shallow ground water. This product is classified as 

having high potential for reaching surface water via runoff for several months after application. 

A level, well-maintained vegetative buffer strip between areas to which this product is applied 

and surface water features such as ponds, streams, and springs will reduce the potential loading 

of aminocyclopyrachlor from runoff water and sediment. Runoff of this product will be reduced 

by avoiding applications when rainfall is forecasted to occur within 48 hours.” 

Products Primarily Intended for Consumer Use on Residential Lawns (Broadcast Granular 

Applications) 

“To protect the environment, do not allow pesticide to enter or run off into storm drains, drainage 

ditches, gutters, or surface waters. Applying this product in calm weather when rain is not 

predicted for the next 24 hours will help to ensure that wind or rain does not blow or wash 

pesticide off the treatment areas. Sweeping any product that lands on a driveway, sidewalk, or 

street back onto the treated area of the lawn or garden will help to prevent runoff to water bodies 

or drainage systems.” 

2.2.1.2. Ground Water Advisory

The label requirement for the ground water advisory was revised so that it is required for 

products primarily intended for commercial use instead of all end-use products. The ground 

water advisory for products primarily intended for consumer use on residential lawns has been 

replaced with the environmental hazard statements in the PR Notice 2008-1. 

Products Primarily Intended for Commercial Use on Non-Crop Areas, Sod Farms, and 

Turf/Lawns 

“This chemical has properties and characteristics associated with chemicals detected in ground 

water. This chemical may leach into ground water if used in areas where soils are permeable, 

particularly where the water table is shallow.” 

- 19 - 
Products Primarily Intended for Consumer Use on Residential Lawns (Broadcast Granular 

Applications) 

“To protect the environment, do not allow pesticide to enter or run off into storm drains, drainage 

ditches, gutters, or surface waters. Applying this product in calm weather when rain is not 

predicted for the next 24 hours will help to ensure that wind or rain does not blow or wash 

pesticide off the treatment areas. Sweeping any product that lands on a driveway, sidewalk, or 

street back onto the treated area of the lawn or garden will help to prevent runoff to water bodies 

or drainage systems.”

2.2.2. Plant Residue 

Although no incidents have been reported for aminocyclopyrachlor, a pyrimidine carboxylic 

acid, because it is a new chemical; several incidents have been reported for a similar class of 

chemicals, the pyridine carboxylic acids, which includes herbicides such as aminopyralid, 

clopyralid, and picloram. Incidents were reported where treated plant residues or manure from 

animals which were fed treated residues were used in compost, which caused desirable crop or 

lawn damage. Some states as well as the United Kingdom were prompted to take regulatory 

action due to these incidents. Since aminocyclopyrachlor also shares the persistent and systemic 

nature in soil and the high seedling emergence toxicity with these similar chemicals, similar 

incidents could occur following application of aminocyclopyrachlor. Therefore, the Agency is 

requiring that the following language be placed on all aminocyclopyrachlor end-use product 

labels. 

The restriction for products primarily intended for commercial use on sod farms and turf/lawns 

was revised for clarity and to be more protective.

 

Plant Residue Restrictions

Products Primarily Intended for Commercial Use on Non-Crop Areas 

“Do not use plant material treated with this product for mulch or compost.” 

Products Primarily Intended for Commercial Use on Sod Farms and Turf/Lawns 

“Do not use grass clippings from treated areas for mulch or compost, or allow for collection to 

composting facilities. Grass clippings must either be left on the treated area, or if allowed by 

local yard waste regulations, disposed of in the trash. Applicators must give verbal or written 

notice to property owner/property manager/residents to not use grass clipping from treated turf 

for mulch or compost.” 

Products Primarily Intended for Consumer Use on Residential Lawns 

“Do not use grass clippings from treated areas for mulch or compost. Grass clippings must 

either be left on the treated lawn or if allowed by local yard waste regulations, disposed of in the 

trash.” 

- 20 - 
2.2.3. Livestock 

 

Aminocyclopyrachlor can be applied in uncultivated agricultural areas and other areas with 

potential exposure to livestock via feeding or grazing. Since aminocyclopyrachlor is being 

registered for non-food use and no tolerances have been established on livestock commodities, 

the following restriction is required on all applicable end-use labels to protect feeding exposure 

to livestock. 

Livestock Restriction

Products Primarily Intended for Commercial Use on Non-Crop Areas 

“Do not graze or feed forage, hay, or straw from treated areas to livestock.” 

2.2.4. Spray Drift 

As expected for an herbicide, aminocyclopyrachlor presents potential risk to terrestrial plants, 

particularly through spray drift (see Section 1.3.3.2.4). In order to mitigate risk to non-target 

plants and keep the pesticide on the intended treatment area, spray drift language must be placed 

on aminocyclopyrachlor end-use product labels that are applied as liquids. 

Spray Drift Management

The phrase “(>150 – 200 microns)” must be removed from the current spray drift management 

statement so that it reads “The most effective way to reduce spray drift potential is to apply large 

droplets. The best drift management strategy is to apply the largest droplets that provide 

sufficient coverage and control.” 

Products Primarily Intended for Commercial Use on Non-Crop Areas

The application restrictions for products primarily intended for commercial use on non-crop 

areas were revised from those specified in the proposed decision document by removing the 

buffer restrictions and including additional restrictions to further mitigate spray drift. The 

aminocyclopyrachlor products labeled for “non-crop areas” are intended for vegetative 

management (VM) use in areas such as utility rights-of-way, roadsides, and railroads. In such 

situations, the treatment area is typically narrow and linear, requiring single-swath applications. 

By contrast, agricultural applications cover a wider area with multiple swaths. While buffers 

may be practical for agricultural applications, they would overly restrict or, in some cases, 

preclude use in many non-crop areas. In addition, the narrow, linear treatment area in VM 

applications may reduce the potential for runoff and drift compared to agricultural applications, 

thereby obviating the need for buffers. 

As described in the registrant’s response to the proposed decision, herbicides are important 

tools in VM/IVM programs for controlling invasive/noxious species and ensuring human safety. 

The ability to apply herbicides up to the edge of target areas will avoid or minimize the need for 

mechanical mowing, which is an ineffective method of eradicating invasive/noxious weeds. Also, 

systemic herbicides such as aminocyclopyrachlor will provide long-term control of weeds and 

- 21 - 
reduce proliferation, as compared to herbicides used for chemical mowing such as glyphosate. 

Furthermore, the ability to use systemic herbicides up to the edge of target areas will reduce the 

need for applicators to make spot treatments using backpack sprayers. Complete control of 

weeds in rights-of-way also ensures public and worker safety by providing a clear line-of-sight, 

reducing fire and electrical hazards, and reducing obstructions. EPA notes that Canada’s Pest 

Management Regulatory Authority (PMRA) routinely exempts VM herbicides from buffer 

requirements provided that spray drift concerns can be addressed in other ways. With advances 

in application technology, spray drift to non-target areas can be reduced without the need for 

buffers through the use of specialized spray equipment, nozzles, and drift control agents. 

Therefore, to address and mitigate spray drift in the absence of buffer requirements, additional 

restrictions will be placed on VM labels to ensure that applications will be protective of nontarget areas. 

Use Restrictions 

“Do not make applications when circumstances favor movement from treatment site.” 

“Do not apply or otherwise permit this product or sprays containing this product to come into 

contact with any non-target crop or desirable broadleaf plants.” 

“Do not contaminate water intended for irrigation. To avoid injury to crops and other desirable 

plants, do not treat or allow spray drift or runoff to fall onto banks or bottoms of irrigation 

ditches, either dry or containing water, or other channels that carry water that may be used for 

irrigation purposes. Do not apply to snow covered or frozen ground.” 

Aerial Application Restrictions 

“When applying by air, apply only using nozzles which will deliver coarse or greater (VMD 

>350 microns) droplets as defined by ASABE S572 standard. Do not release spray at a height 

greater than 10 feet above the ground or canopy unless a greater height is required for aircraft 

safety. Do not apply when wind speed is greater than 10 mph. Do not apply during a 

temperature inversion.” 

“For aerial applications near susceptible crops or other desirable plants, use a drift control 

additive as recommended by the manufacturer, or apply through a Micro-Foil or Thru-Valve 

boom, or use an equivalent drift control system. Thickened sprays prepared by using high 

viscosity invert systems or other drift control systems may be utilized if drift control is 

comparable to that obtained with drift control additives or the Thru-Valve boom. If a spray 

thickening agent is used, follow all recommendations and precautions on the product label. Do 

not use a thickening agent with the Micro-Foil boom or other systems that cannot accommodate 

thick sprays.” 

Ground Application Restrictions 

“When applying by ground, apply only using nozzles which will deliver coarse or greater (VMD 

>350 microns) droplets as defined by ASABE S572 standard. Do not apply with a nozzle height 

- 22 - 
- 23 - 

greater than 4 feet above the ground or canopy unless necessitated by the application equipment. 

Apply with the spray boom or nozzle height as low as possible. Do not apply when wind speed 

is greater than 10 mph. Do not apply during a temperature inversion.” 

“For ground applications, keep the spray boom as low as possible; apply 10 gallons or more of 

spray per acre; use spray pressures no greater than are required to obtain adequate plant 

coverage; use large-droplet producing nozzle tips; use drift control additives; use shieldedsprayers or other drift control systems; and/or spray when wind velocity is low.” 

Products Primarily Intended for Commercial Use on Sod Farms and Non-Residential, NonInstitutional, or Non-Industrial Turf (Golf Courses, Parks, Cemeteries, and Athletic Fields)

The requirement for the ground application restrictions was revised to clarify that it is required 

for products primarily intended for commercial use on sod farms and turf (non-residential, noninstitutional, non-industrial). The ground application restrictions for commercial use on sod 

farms and turf were revised by changing the volume mean diameter to “>250 microns” to 

correspond to the ASABE S572 standard for coarse droplets of “250 – 375 microns”. There are 

no aerial application restrictions since no products are being registered for aerial applications 

to sod farms and turf/lawns.

Ground Application Restrictions 

“Maintain a 25-foot buffer around non-target aquatic areas and between the point of direct 

application and the closest downwind edge of non-target terrestrial areas. Apply only using 

nozzles which will deliver coarse or greater (VMD >250 microns) droplets as defined by 

ASABE S572 standard. Do not apply with a nozzle height greater than 4 feet above the ground 

or crop canopy. Do not apply when wind speed is greater than 10 mph. Do not apply during a 

temperature inversion.” 

2.2.5. Restricted-Entry Interval (REI) 

The REI must be changed to 12 hours from the proposed REI of 4 hours. The minimum standard 

REI for agricultural pesticides is 12 hours. EPA allows a reduced REI of 4 hours for certain 

minimum-risk pesticides that meet low-toxicity standards and that have not been reported to 

cause illness or injury due to post-application exposure. Since aminocyclopyrachlor is a new 

pesticide with no history of actual use, incident information (illness or injury reports) is not 

available for this chemical. Therefore, EPA believes the minimum standard REI of 12 hours is 

appropriate for aminocyclopyrachlor. 

2.3. Registration Decision

In accordance with FIFRA Section 3(c)(7)(C), the Agency believes that the conditional 

registration of aminocyclopyrachlor will not cause any unreasonable adverse effects to human 

health or to the environment and that the use of the pesticide is in the public’s interest; and is 

therefore granting the conditional registration.