Clopyralid Summary of Analytical Chemistry and Residue Data DP Number D391747

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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C. 20460

OFFICE OF CHEMICAL SAFETY

 AND POLLUTION PREVENTION

MEMORANDUM

Date: 6/6/2012

Subject: Clopyralid. Petition for the Section 3 Registration and the Establishment of 

Tolerances on Apples, Brassica Leafy Greens (Subgroup 5-B), Teff, and Rapeseed 

(Subgroup 20-A) Except Gold of Pleasure. Summary of Analytical Chemistry and 

Residue Data

PC Code: 117403 (acid)

117401 (alkanolamine salts)

DP Barcode: D391747

Decision No.: 450262 Registration Nos.: 62719-73, 62719-80, 62719-81, 

and 62719-84 

Petition: 1E7882 Regulatory Action: Section 3 Registration

Risk Assessment Type: NA Case No.: 7053

TXR No.: NA CAS No.: 1702-17-6 (acid)

57754-85-5 (monoethanolamine salt)

MRID No.: 48504801 40 CFR: 180.431

From: Douglas A. Dotson, Ph.D., Chemist

RABII 

Health Effects Division (7509P) 

Through: Michael Doherty, Ph.D., Senior Chemist

RABII

Health Effects Division (7509P)

To: Laura Nollen/Barbara Madden, RM Team 5

RIMUERB

Registration Division (7505P)
Clopyralid Summary of Analytical Chemistry and Residue Data DP Number D391747

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Executive Summary

Clopyralid (3,6-dichloro-2-pyridinecarboxylic acid) is a pyridine herbicide registered for use on 

a variety of food and feed crops in the U.S. for the postemergence control of broadleaf weeds, 

particularly thistles and clover. Tolerances are established for residues of clopyralid in/on a wide 

variety of plant commodities at levels ranging from 0.5 ppm in/on stone fruits and bushberries 

(Crop subgroup 13-07B)to 500 ppm in/on grass forage and hay (40 CFR §180.431(a)). 

Tolerances are also established for residues of clopyralid in livestock commodities at levels 

ranging from 0.1 ppm in eggs to 36 ppm in meat byproducts, except liver, of cattle, goats, horses 

and sheep. Currently there are no tolerances for inadvertent or indirect residues of clopyralid.

The Interregional Research Project Number 4 (IR-4) submitted a tolerance petition proposing the 

use of clopyralid on apples. As part of the same tolerance petition, IR-4 proposed to amend the 

Stinger® Herbicide label (EPA Reg. No. 62719-73) to expand the mustard greens use to the 

entire Brassica leafy greens subgroup (5-B), and to expand the use on canola, crambe, and 

rapeseed to the entire Rapeseed subgroup (20-A), except gold of pleasure. In addition, IR-4 

submitted a separate tolerance petition for the use of clopyralid on teff.

The only study that IR-4 submitted in support of the current petition was a combined field 

trial/processing study for apples. For the other commodities, IR-4 is proposing that currently 

established tolerances be extended to the proposed commodities. A tolerance of 5.0 ppm is 

established for mustard greens. IR-4 is proposing that this tolerance be extended to the Brassica 

leafy greens subgroup. A tolerance of 3.0 ppm is established for canola seed. IR-4 is proposing 

that this tolerance be extended to rapeseed (Subgroup 20-A) except gold of pleasure. The 

following tolerances are established for wheat and barley commodities: 3.0 ppm for grain, 9.0 

ppm for straw, 9.0 ppm for forage (wheat only), and 9.0 ppm for hay (barley only). IR-4 is 

proposing that these tolerances be extended to teff commodities. 

The end-use product that IR-4 proposed for use on these commodities is Stinger® Herbicide, 

which is a 3 lb acid equivalent (ae)/gal emulsifiable concentrate (EC) formulation of the 

monoethanolamine salt of clopyralid.

Based on the available cabbage, grass, wheat, and barley metabolism studies, the nature of 

clopyralid residues in plants is adequately understood for purposes of this petition. The residue 

of concern in plants for both risk assessment and tolerance enforcement is parent clopyralid.

Although teff commodities and wet apple pomace are animal feedstuffs, the maximum 

reasonably balanced diet (MRBD) previously determined by HED will not increase as a result of 

the addition of these commodities to the currently permitted uses for clopyralid. Clopyralid is 

already registered for use on cereal grain commodities, grass forage and hay (both with 

tolerances of 500 ppm), as well as other more esoteric feedstuffs (such as sugar beet molasses at 

10 ppm). As a result, issues pertaining to residues in livestock commodities do not need to be 

addressed in the current petition.
Clopyralid Summary of Analytical Chemistry and Residue Data DP Number D391747

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An adequate gas chromatograph/electron-capture detection (GC/ECD) method (Method ACR 

75.6) is available for enforcing tolerances for clopyralid in/on plant commodities. In the 

submitted apple field trials, residues of clopyralid in apple fruit, juice, and wet pomace were 

determined using a slightly modified version of the current enforcement method. The method 

was adequately validated in conjunction with the analysis of field trial samples. The lowest level 

of method validation (LLMV) was 0.05 ppm for apple fruit, juice, and wet pomace. 

The submitted apple field trial data are adequate and support the proposed use. IR-4 performed 

an adequate number of trials and they were performed in the recommended EPA growing zones. 

The application rate was 1x the maximum proposed rate, and the samples were collected at the 

proposed PHI. Residues of clopyralid in/on each commodity were determined using an adequate 

GC/ECD method, and the duration and conditions of sample storage are supported by the 

available storage stability data. The available field trial data support an LOQ tolerance of 0.05 

ppm for apple fruit. For the other commodities in this tolerance petition, the tolerances are being 

translated from other commodities with established tolerances.

In the apple processing study, no detectable residues were found in the samples of apple fruit, 

apple juice, or wet apple pomace. Because of phytotoxicity concerns, IR-4 did not perform an 

exaggerated rate study. No residues were found in the processed commodities; which indicates 

that if concentration did occur, it was not to a considerable extent.

The existing confined rotational crop study adequately supports the rotational crop restrictions 

specified on the current label.

MRL Harmonization

There are no Codex or Mexican maximum residue limits (MRLs) for residues of clopyralid in/on 

the proposed commodities (Attachment I). However, there is a Canadian MRL for residues of 

clopyralid in or on flax at 0.2 ppm. This MRL does not harmonize with the existing U.S. 

tolerance of 3.0 ppm for flax seed (or the proposed tolerance of 3.0 ppm for the rapeseed 

subgroup). Based on the differing use patterns and the available residue data, the recommended 

tolerance for the flaxseed subgroup cannot be harmonized with the Canadian MRL on flax.

Regulatory Recommendations and Residue Chemistry Deficiencies

There are no residue chemistry data deficiencies that would preclude granting the requested 

registrations and establishing tolerances for residues of clopyralid on the proposed commodities. 

The proposed tolerances, the recommended tolerances, and the correct commodity definitions are 

given in Table 7.

Background

Clopyralid is a selective, postemergence pyridine herbicide that is used for the control of 

broadleaf weeds, particularly thistles and clover, in a variety of crops. 
Clopyralid Summary of Analytical Chemistry and Residue Data DP Number D391747

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IR-4 submitted a tolerance petition proposing the use of clopyralid on apples. As part of the 

same tolerance petition, IR-4 proposed to amend the Stinger® Herbicide label (EPA Reg. No. 

62719-73) to expand the mustard greens use to the entire Brassica leafy greens subgroup (5-B), 

and to expand the use on canola, crambe, and rapeseed to the entire Rapeseed subgroup (20-A), 

except gold of pleasure. In addition, IR-4 submitted a separate tolerance petition for the use of 

clopyralid on teff.

The only study that IR-4 submitted in support of the petition was a combined field 

trial/processing study for apples. For the other commodities, IR-4 is proposing that currently 

established tolerances be extended to the proposed commodities. A tolerance of 5.0 ppm is 

established for mustard greens. IR-4 is proposing that this tolerance be extended to the Brassica 

leafy greens subgroup. A tolerance of 3.0 ppm is established for canola seed. IR-4 is proposing 

that this tolerance be extended to rapeseed (Subgroup 20-A) except gold of pleasure. The 

following tolerances are established for wheat and barley commodities: 3.0 ppm for grain, 9.0 

ppm for straw, 9.0 ppm for forage (wheat only), and 9.0 ppm for hay (barley only). IR-4 is 

proposing that these tolerances be extended to teff commodities. 

The chemical structure and nomenclature of the monoethanolamine salt of clopyralid is 

summarized in Table 1, and the physicochemical properties of clopyralid are summarized in 

Table 2. 

Table 1. Clopyralid Nomenclature

Compound

Common name Clopyralid, monoethanolamine salt

Company experimental 

name

Dowco 290

IUPAC name 3,6-dichloropyridine-2-carboxylic acid, monoethanolamine salt

CAS name 3,6-dichloro-2-pyridinecarboxylic acid, monoethanolamine salt

CAS registry number 1702-17-6 (acid)

57754-85-5 (monoethanolamine salt)

End-use products (EUP) Stinger® Herbicide (EPA Reg. No. 62719-73)

Lontrel®35A Herbicidal Concentrate (EPA Reg. No. 62719-84)

Table 2. Physicochemical Properties of the Technical Grade Clopyralid

Parameter Value References

Physical State Solid A world Compendium, 

The Pesticide Manual, 

14th Edition. C.D. S 

Tomlin (Editor), 2006.

Color Colorless

Melting Point/Range 151-152°C

Dissociation Constant (pKa) 2

N

Cl

Cl

O

O

OH

NH3

+
Clopyralid Summary of Analytical Chemistry and Residue Data DP Number D391747

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Table 2. Physicochemical Properties of the Technical Grade Clopyralid

Parameter Value References

Density at 20°C 1.57 g/cm3 

Vapor Pressure at 25°C 1.0 x 10-5 mm Hg (1.33 mPa)

Water Solubility at 20°C 7.85 g/L

Solvent solubility (g/L) at 20°C Acetone: 250

Ethyl acetate: 102

Xylene: 4.6

Hexane: 6.0

Octanol/water partition coefficient, 

Log (KOW)

-1.81 (pH 5) 

-2.63 (pH 7) 

-2.55 (pH 9)

860.1200 Directions for Use

Stinger® Herbicide is currently registered to Dow AgroSciences for use on a wide variety of 

crops for the postemergence control of weeds. The label includes use directions for the 

following crops: (1) mustard greens, (2) canola (rapeseed) and crambe, and (3) barley, oats, and 

wheat. IR-4 submitted supplemental labels for the Brassica leafy greens subgroup and the 

rapeseed subgroup. The use directions on those supplemental labels are consistent with the use 

directions for the commodities from which the tolerances are being extended. IR-4 also 

submitted a supplemental label for apples. The use directions for teff are the same as those on 

the Stinger®label for barley, oats, and wheat. The proposed use directions are summarized 

below in Table 3.

Table 3. Summary of Directions for Use of Clopyralid

Applic. Timing, Type, and 

Equip. 1

Formulation

[EPA Reg. 

No.]

Applic. 

Rate 

(lb ae/A)

Max. No. 

Applic. 

per 

Season

Max. 

Seasonal 

Applic. Rate

(lb ae/A)

PHI Use Directions and 

Limitations 2

Apple

Apply to non-bearing (wellestablished, 1 year or older) 

and bearing trees. Apply to 

actively growing weeds. 

Apply with ground 

equipment only.

Stinger, 3.0 

lb ae/gal EC 

[62719-73]

0.094-

0.25 1 0.25 30days

Apply in a minimum of 

10 gal/A. Do not use in 

Florida or in Nassau or 

Suffolk Counties, New 

York. Do not apply by 

aircraft.

Leafy Brassica Greens Subgroup, 5-B

3

Apply to actively growing 

weeds. Apply with ground 

equipment only.

Stinger, 3.0 

lb ae/gal EC 

[62719-73]

0.06-0.25 2 0.5 30

days

Apply in a minimum of 

10 gal/A, with a 

minimum RTI of 14 

days. Do not apply by 

aircraft.
Clopyralid Summary of Analytical Chemistry and Residue Data DP Number D391747

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Table 3. Summary of Directions for Use of Clopyralid

Applic. Timing, Type, and 

Equip. 1

Formulation

[EPA Reg. 

No.]

Applic. 

Rate 

(lb ae/A)

Max. No. 

Applic. 

per 

Season

Max. 

Seasonal 

Applic. Rate

(lb ae/A)

PHI Use Directions and 

Limitations 2

Rapeseed Subgroup 20-A, Except Gold of Pleasure

Apply in the 2- to 6-leaf stage 

of crop growth. Apply to 

actively growing weeds. 

Apply with ground and aerial 

equipment only.

Stinger, 3.0 

lb ae/gal EC 

[62719-73]

0.113-

0.25 1 0.25 7days

Use in the State of 

Oregon only. Apply in 

a minimum of 20 gal/A. 

Do not use with a 

surfactant. Apply with 

ground and aerial 

equipment only.

Teff (Use Directions for Barley, Oats, and Wheat)

Apply when crop is from 3-

leaf stage up to early boot 

stage of growth.

Stinger, 3.0 

lb ae/gal EC 

[62719-73]

0.094-

0.125 1 0.125

Not 

Specified

Do not harvest hay from 

treated grain fields4.

1 Do not apply through any type of irrigation system.

2 The label for the 3 lb ae/gal EC contains the following rotational crop restrictions: barley, canola, cole crops, flax, garden 

beets, grasses, corn (field, pop and sweet), oats, spinach, sugar beets, turnips and wheat may be planted at anytime following a

treated crop. Depending on the amount of soil organic matter, rainfall and location (state), the plant-back intervals for all other 

crops range from 10.5 to 18 months.

3

For use and distribution only in the states of AZ, AR, CA, CO, DE, FL, GA, MD, MI, MO, NJ, NM, NY, NC, OH, OK, PA, 

SC, TX, VA and WI. Not for sale or distribution in Nassau and Suffolk Counties in New York State.

4 Do not permit lactating dairy animals or meat animals being finished for slaughter to forage or graze treated grain fields within 

one week after treatment.

Conclusions. The supplemental label for apples is adequate to allow evaluation of the residue 

data relative to the proposed use. The available field trial data support the proposed use 

directions. The supplemental labels for Brassica leafy greens and rapeseed as well as the SLN 

label for teff are adequate. The use directions and restrictions are adequate to ensure that overtolerance residues will not result in any plant or animal commodities. 

860.1300 Nature of the Residue - Plants

DP# 270507, 8/6/2002, D. Dotson

The nature of the residue in plants is adequately understood for purposes of this petition based on

the acceptable cabbage, grass, barley, and wheat metabolism studies. In each of these studies, 

the major 14C-residue was determined to be only parent compound. Although data are available 

for only two dissimilar crops (leafy vegetables and cereal grains), HED has concluded that the 

residue of concern in plants for purposes of this petition is clopyralid. However, the Agency

reserves the right to require additional metabolism studies in the future should the petitioner 

request the establishment of clopyralid tolerances for additional crops. 

860.1300 Nature of the Residue - Livestock

Goat and poultry metabolism studies were previously reviewed. The nature of the residue in 

livestock commodities is understood. The only major residue is parent clopyralid. Although teff 
Clopyralid Summary of Analytical Chemistry and Residue Data DP Number D391747

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commodities and wet apple pomace are animal feedstuffs, the maximum reasonably balanced 

diet (MRBD) previously determined by HED will not increase as a result of the addition of these 

commodities to the currently permitted uses for clopyralid. Clopyralid is already registered for 

use on cereal grain commodities, grass forage and hay (both with tolerances of 500 ppm), as well 

as other more esoteric feedstuffs (such as sugar beet molasses at 10 ppm). As a result, issues 

pertaining to residues in livestock commodities do not need to be addressed in the current 

petition.

860.1340 Residue Analytical Methods

Enforcement method. The Pesticide Analytical Manual (PAM) Vol. II lists a GC/ECD method 

for determining clopyralid residues in/on plant commodities (Method I or Method ACR 75.6).

For this method, residues are extracted with dilute NaOH (0.25% or 0.1%) and filtered. The 

extract is then acidified and salinized, and residues are partitioned into ethyl ether. Residues are 

then methylated using diazomethane and cleaned up on an activated alumina column. Residues 

are then determined by GC/ECD using external standards. The reported LOQs are 0.5 ppm for 

grains and 2.0 ppm for green forage.

Data Collection Method. In the submitted field trials, residues of clopyralid in/on samples of 

apples and apple processed commodities were determined using a slightly modified version of 

the current tolerance enforcement method. The method that was used was the Cornell Analytical 

Laboratory Method titled: “Residue Analysis of 3, 6-Dichloropicolinic Acid (Clopyralid) 

Residues by GC/Electron Capture Detector, Version #19.” Ten grams of sample are extracted 

with 0.5% NaOH. A portion is then extracted with ether and methylated with freshly prepared 

diazomethane. After evaporation of the ether, the residue is re-dissolved in toluene and cleaned 

up on an activated alumina A column and eluted with toluene. The sample is then analyzed for 

clopyralid methyl ester by GC/ECD.

The residue analytical method for clopyralid residues in/on apple and apple processing samples 

was adequately validated in conjunction with field sample analyses and is acceptable as a datagathering method. The calculated limits of quantitation (LOQ) were 0.05 ppm for apple fruit, 

0.04 ppm for apple juice, and 0.07 ppm for apple pomace. The lowest level of method validation 

(LLMV) was 0.05 ppm in/on all three matrices (fruit, juice, and pomace). The calculated limits

of detection (LOD) were 0.02 ppm for apple fruit, 0.01 ppm for apple juice, and 0.02 ppm for 

apple pomace.

Conclusions. An adequate GC/ECD method (Method ACR 75.6) is available for enforcing the 

proposed tolerances on apples, Brassica leafy vegetables, rapeseed, and teff. The data collection 

method used for analysis of apples and processed apple commodities is also adequate.

860.1360 Multiresidue Methods

The FDA Pestrak Database (PAM Vol. I, Appendix dated 11/6/90) indicates that the existing 

FDA multiresidue methods are not likely to recover clopyralid. Clopyralid does appear to be 

adequately recovered by the “QuEChERS” multiresidue method (http://www.quechers.com).
Clopyralid Summary of Analytical Chemistry and Residue Data DP Number D391747

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860.1380 Storage Stability

DP# 270507, 8/6/2002, D. Dotson

Under frozen storage conditions, clopyralid has been shown to be stable in plant commodities for 

the following durations: 50 months in safflower seeds, soybeans, sugar beet roots and tops, and 

oat forage, grain and straw; 30 months in strawberries; 26 months in dried hops cones; 16 

months in cherries and plums; 15 months in canola meal; 10 months in canola seed and oil; 9 

months in cabbage and spinach; 5 months in mustard greens; and 3 months in peaches.

Samples collected from the submitted field trials were stored frozen within 3 hours of harvest, 

shipped frozen to the analytical laboratory 2-40 days later, and stored at -21°C at the analytical 

laboratory until analysis. The maximum frozen storage intervals, from harvest to analysis of 

samples, are listed in Table 4.

Table 4. Summary of Storage Conditions

Matrix 

(RAC or 

Extract)

Analyte Storage 

Temperature 

(C)

Recoveries

(%)

Actual Storage 

Duration

(days)

Interval of 

Demonstrated 

Storage Stability 

(days)

Apple Fruit Clopyralid -21 ± 7 C 108-120 76-279 267

Apple Juice Clopyralid -21 ± 7 C 106-108 104 175

Apple Pomace Clopyralid -21 ± 7 C 92–96* 113 179

*After subtracting apparent residues of 0.058 ppm observed in the untreated control apple pomace sample

Conclusions. Adequate storage stability data are available to support the sample storage 

conditions and durations in the submitted apple field trials and processing studies.

860.1400 Water, Fish, and Irrigated Crops

There are no proposed uses that are relevant to this guideline topic.

860.1460 Food Handling

There are no proposed uses that are relevant to this guideline topic.

860.1480 Meat, Milk, Poultry, and Eggs

Although teff commodities and wet apple pomace are animal feedstuffs, the maximum 

reasonably balanced diet (MRBD) previously determined by HED will not increase as a result of 

the addition of these commodities to the currently permitted uses for clopyralid. Clopyralid is 

already registered for use on cereal grain commodities, grass forage and hay (both with 

tolerances of 500 ppm), as well as other more esoteric feedstuffs (such as sugar beet molasses at 

10 ppm). As a result, issues pertaining to residues in livestock commodities are not being 

addressed in the current petition.
Clopyralid Summary of Analytical Chemistry and Residue Data DP Number D391747

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860.1500 Crop Field Trials

The only study that IR-4 submitted in support of the current tolerance petition was a combined 

field trial/processing study for apples. For the other commodities, IR-4 is proposing that 

currently established tolerances be extended to the proposed commodities. As a result, no new 

field trial data were submitted for the Brassica leafy greens subgroup, the rapeseed subgroup, or 

for teff. 

48504801.der (Apples)

As stated above, IR-4 submitted a field trial study to support the proposed uses of clopyralid (3 

lb ae/gal EC) on apples. Apples have two associated regulated processed commodities, apple 

juice and wet apple pomace. The study that IR-4 submitted was a combined field 

trial/processing study. The results of the field trial study are discussed below, and the residue 

data are summarized in Table 5.

Table 5. Summary of Residue Data from Crop Field Trials with Clopyralid

Crop Matrix Total Applic. 

Rate1

(lb ae/A)

PHI

(days) 

Residue Levels (ppm)

n Mean Std. 

Dev.

HAFT2 Min Max

Apple Fruit 0.244–0.275 28-30 24 <0.05 NA3< 0.05 < 0.05 < 0.05

1 One foliar application of Stinger Herbicide at approximately 0.25 lb ae/A was made

2 HAFT = Highest Average Field Trial.

3NA = Not applicable

Apples. IR-4 conducted twelve field trials in the 2007 and 2008 growing seasons. Three trials 

were conducted in New York (EPA Growing Region 1), one in North Carolina (Region 2), two

in Michigan (Region 5), one in Colorado (Region 9), one in California (Region 10) and four in 

Washington State (Region 11). The total number of field trials was in accordance with OPPTS 

Guideline 860.1500. 

At each trial, treatment was via a single broadcast application to the orchard floor at the 

approximate rate of 0.25 lb acid equivalent per acre (ae/A). Spray adjuvants were not used in 

any of the field trials. Samples were harvested 28 to 30 days after the application and placed into 

frozen storage shortly after harvest. At the NY27 trial, an additional apple sample was taken 

from each plot for processing into apple juice and apple pomace.

The maximum storage duration was 279 days for field-treated fresh apple samples. This

duration is supported by appropriate storage stability data.

In all 24 samples of apple fruit, residues were below the LOQ of 0.05 ppm. Although no 

quantifiable residues were found in the samples of apple fruit, the registrant did not perform an 

exaggerated rate study. 
Clopyralid Summary of Analytical Chemistry and Residue Data DP Number D391747

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Conclusions. The magnitude of the residue study of clopyralid on apple is acceptable. The 

number and location of the field trials satisfy OPPTS Guideline 860.1500. The residue data are 

adequate to support the establishment of a tolerance of 0.05 ppm for apple fruit.

860.1520 Processed Food and Feed

Apples

At one of the apple field trial sites (the NY27 trial), an apple sample was taken from each plot for 

processing into apple juice and apple pomace. The trial was performed at a 1x application rate 

(0.246 lb ae/A) and samples were taken at a PHI of 30 days. Because of phytotoxicity concerns, 

IR-4 did not perform an exaggerated rate study. 

 

The samples were processed at the processing facility on the day of harvest. A grab sample was 

taken from each of the processing apple samples prior to processing into juice and wet pomace. 

The processed and grab samples were stored frozen until being shipped. A typical commercial 

process was used for processing. Small lots of fresh apples (1-2 bushels) were ground in a 

Hammer-mill. Wet mash was collected in a container and loaded into one or more cloth stacks 

(cheeses) on the hydraulic press. When the stack was complete (up to 5 cloths depending on 

sample size), the hydraulic pump was activated and the sample was pressed to 2200-3000 psi for 

a minimum of 5 minutes to achieve efficient juice yield. The juice was collected in 1⁄2 to 1 gallon 

plastic bottles for storage. After the pressing cycle, the cloths were opened up and the wet 

pomace cake was broken up to obtain the wet pomace sample.

The maximum storage duration was 279 days for field-treated fresh apple samples, 104 days for

apple juice, and 113 days for pomace. These durations are supported by appropriate storage 

stability data.

Clopyralid residues were below the LOQ of 0.05 ppm in the apple fruit samples (both treated and 

untreated). No quantifiable residues were found in apple juice. A residue of 0.056 ppm was 

found in the treated apple pomace sample; however, the corresponding untreated control sample 

had an apparent residue of 0.042 ppm. After subtraction of the residue detected in the control 

from the residue in the treated pomace sample, the resulting residue would be 0.014 ppm, which 

is considerably below the reported LOQ.

 

Table 6. Residue Data from Apple Processing Study with Fluazinam

Location

(City, State; Year)

Total Rate

(lb ae/A)

PHI 

(days)

Commodity Fluazinam Residues

(ppm)

Fluazinam 

Processing 

Factor

North Rose, NY; 

1993

0.246 30 Fruit (RAC) <0.05, <0.05 NA

Juice <0.05 NA

Wet Pomace <0.051 NA

1After subtracting apparent residue (0.042 ppm) detected in the untreated control sample from the residue in the wet 

pomace sample (0.056), the residue level was < 0.05 ppm.
Clopyralid Summary of Analytical Chemistry and Residue Data DP Number D391747

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Conclusions. The apple processing study is acceptable. It can be concluded that if concentration 

occurred in juice and pomace, it was to a very limited extent.

860.1650 Submittal of Analytical Reference Standards

An analytical reference standard for clopyralid monoethanolamine salt is currently available in 

the EPA National Pesticide Standards Repository. The expiration date is 2-26-2015 (electronic

communication, Theresa Cole, ACB, 2/27/2012).

860.1850/1900 Confined and Field Accumulation in Rotational Crops

DP# 193219, 8/4/93, G. Kramer

An acceptable confined rotational crop study is available for clopyralid. In this study, the total 

radioactive residues in/on representative rotational crop commodities (lettuce, turnips, green 

beans, and wheat) were below 0.01 ppm at plant back intervals of 49-98 days following 

application of [14C]clopyralid to the soil at 0.29 lb ae/A (1.17x the maximum seasonal rate for 

crops which can be rotated).

 

The current label for the 3 lb ae/gal EC of clopyralid allows for the replanting of the following 

crops at any time: barley, canola, cole crops, flax, garden beets, grasses, corn (field, pop and 

sweet), oats, spinach, sugar beets, turnips, and wheat. The plant-back interval for all other crops 

is 10.5 to 18 months, depending on the amount of soil organic matter, rainfall, and location.

The established rotational crop restrictions are adequate. Limited field rotational crop studies are 

not required, and no tolerances are required for inadvertent or indirect residues in rotational 

crops.

860.1550 Proposed Tolerances

The submitted apple field trial and processing studies are adequate to support the proposed 

tolerance of 0.05 ppm for apple, fruit. The trials were performed at a 1x application rate and 

samples were taken at the proposed PHI. Geographic representation of the field trials was 

adequate. Separate tolerances are not needed for apple juice or wet apple pomace. HED uses the 

OECD tolerance calculator to determine recommended tolerances. However, in cases where all 

field trial samples are below the LOQ of the analytical method, HED recommends that the 

tolerance be set at the LOQ. As a result, the recommended tolerance for apple is 0.05 ppm.

For the other commodities in this tolerance petition, IR-4 is proposing that currently-established 

tolerances be extended to the proposed commodities. A tolerance of 5.0 ppm is established for 

mustard greens. IR-4 is proposing that this tolerance be extended to the Brassica leafy greens 

subgroup. A tolerance of 3.0 ppm is established for canola seed. IR-4 is proposing that this 

tolerance be extended to rapeseed (Subgroup 20-A) except gold of pleasure. The following 

tolerances are established for wheat and barley commodities: 3.0 ppm for grain, 9.0 ppm for 

straw, 9.0 ppm for forage (wheat only), and 9.0 ppm for hay (barley only). IR-4 is proposing 

that these tolerances be extended to teff commodities. There are no residue chemistry issues that 

would preclude the extension of these tolerances. 
Clopyralid Summary of Analytical Chemistry and Residue Data DP Number D391747

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There are no Codex or Mexican maximum residue limits (MRLs) for residues of clopyralid in/on 

the proposed commodities (Attachment I). However, there is a Canadian MRL for residues of 

clopyralid in or on flax at 0.2 ppm. This MRL does not harmonize with the existing U.S. 

tolerance of 3.0 ppm for flax seed (or the proposed tolerance of 3.0 ppm for the rapeseed 

subgroup). Based on the differing use patterns and the available residue data, the recommended 

tolerance for the flaxseed subgroup cannot be harmonized with the Canadian MRL on flax.

Table 7 provides a summary of the recommended tolerances for the proposed commodities.

Table 7. Tolerance Summary for Clopyralid

Commodity as Proposed by Registrant

Proposed 

Tolerance 

(ppm)

Recommended 

Tolerance 

(ppm)

Comments

(correct commodity definition)

40 CFR §180.431(a)

Apple 0.05 0.05 Adequate field trial data are available.

Leafy Brassica greens subgroup 5B 5.0 5.0 The proposed and recommended tolerance is 

based on the existing tolerance for mustard 

greens, the representative commodity of the 

Leafy Brassica greens subgroup

(Brassica, leafy greens, subgroup 5B)

Rapeseed subgroup 20A, except Gold of 

pleasure, seed

3.0 3.0 The proposed and recommended tolerance is 

based on the existing tolerance of 3.0 ppm 

for rapeseed, canola, and flax seed

(Rapeseed, subgroup 20A, except gold of 

pleasure)

Rapeseed subgroup 20A, except Gold of 

pleasure, meal

6.0 6.0 The proposed and recommended tolerance is 

based on the existing tolerance of 6.0 ppm 

for canola meal and flax meal

(Rapeseed, meal)

Rapeseed subgroup 20A, except Gold of 

pleasure, forage

3.0 None Tolerance is not needed because rapeseed 

forage is not a significant livestock feed 

item.

Teff, forage 9.0 9.0 Based on wheat forage (9.0 ppm)

Teff, grain 3.0 3.0 Based on wheat and barley grain (3.0 ppm)

Teff, hay 9.0 9.0 Based on barley hay (9.0 ppm)

Teff, straw 9.0 9.0 Based on wheat and barley straw (9.0 ppm)
Clopyralid Summary of Analytical Chemistry and Residue Data DP Number D391747

Page 13 of 14

References

MRID No. 48504801. J. Corley, (2010). Clopyralid: Magnitude of the Residue on Apple. 

Project Number: 03623. Unpublished study prepared by The Center for Minor Crop Pest 

Management Technology Center of New Jersey Rutgers, The State University of New Jersey

D361787, M. Doherty, Clopyralid – Petition for Tolerances on Swiss chard, Bushberry Subgroup 

13-07B, and Strawberry (Regional Restriction). Summary of Analytical Chemistry and Residue 

Data, 10/27/2009

D361316, M. Doherty, et al., Clopyralid – Human Health Risk Assessment to Evaluate New 

Uses on Swiss Chard, Bushberry Subgroup (13-07B), and Strawberry (Regional Restriction), 

12/3/2009

D270507, D. Dotson, Clopyralid. Review of Residue Chemistry Data in Support of Permanent 

or Time-Limited Tolerances Proposed for Canola...Summary of Analytical Chemistry and 

Residue Data, 8/6/2002

D193219, G. Kramer, ID# 062719-00073. Review of confined rotational study of clopyralid, 

MRID# 428150-01, 8/4/93
Clopyralid Summary of Analytical Chemistry and Residue Data DP Number D391747

Page 14 of 14

Attachment I. International Residue Limit Status Sheet

Clopyralid (117403; 2-22-2012)

Summary of US and International Tolerances and Maximum Residue Limits 

Residue Definition: 

US Canada Mexico2 Codex3

40 CFR 180.431:

Plants/Livestock: clopyralid, 3,6-dichloro2-pyridinecarboxylic acid

3,6-dichloro-2-

pyridinecarboxylic acid

None

Commodity1 Tolerance (ppm) /Maximum Residue Limit (mg/kg)

US Canada Mexico2 Codex3

Apple 0.05

Leafy brassica greens, subgroup 

5-B

5.0

Teff, grain 3.0

Teff, hay 9.0

Teff, forage 9.0

Teff, straw 9.0

Rapeseed, subgroup 20-A, 

except gold of pleasure, seed 3.0 0.2 flax

Rapeseed, subgroup 20-A, 

except gold of pleasure, meal 6.0

Rapeseed, subgroup 20-A, 

except gold of pleasure, forage 3.0

Completed: M. Negussie; 02/24/2012

1

Includes only commodities of interest for this action. Tolerance values should be the HED recommendations and 

not those proposed by the applicant.

2 Mexico adopts US tolerances and/or Codex MRLs for its export purposes.

3 * = absent at the limit of quantitation; Po = postharvest treatment, such as treatment of stored grains. PoP = 

processed postharvest treated commodity, such as processing of treated stored wheat. (fat) = to be measured on the 

fat portion of the sample. MRLs indicated as proposed have not been finalized by the CCPR and the CAC.