Page 1 of 52

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C. 20460

OFFICE OF CHEMICAL SAFETY AND

POLLUTION PREVENTON

MEMORANDUM

Date: June 15, 2010 

SUBJECT: S-Metolachlor. Petition for the Establishment of Permanent Tolerances for New 

Uses on Bushberry Subgroup 13-07B; Caneberry Subgroup 13-07A; Carrot; 

Cucumber; Leafy Brassica Greens Subgroup 5B; Melon Subgroup 9A; Okra; Bulb 

Onion Subgroup 3-07A; Green Onion Subgroup 3-07B; Sesame Seed; Sorghum; 

and Turnip Greens. Summary of Analytical Chemistry and Residue Data.

PC Code: 108800 DP Barcode: D369005, D375955

Decision No.: 418569 Registration No.: 100-816 and 100-818

Petition No.: 9E7607 Regulatory Action: Section 3 Registration

Risk Assessment Type: NA Case No.: 0001

TXR No.: NA CAS No.: 87392-12-9

MRID No.: See MRID Summary Table 40 CFR: 180.368 (a)(2)

FROM: Susan V. Hummel, Chemist

Risk Assessment Branch 4, Health Effects Division, 7509P

THROUGH: Ray Kent, Chief

Risk Assessment Branch 4, Health Effects Division, 7509P

TO: Rebecca Daiss, Risk Assessor

Risk Assessment Branch 4, Health Effects Division, 7509P

And

Sidney Jackson, PM#5

Risk Integration, Minor Use & Emergency Response Branch

Registration Division 

MRID Summary Table

MRID No. Study Type Comments

47829401 860.1500 Sesame New DER; 47829401.de1.doc

860.1520 Sesame New DER; 47829401.de2.doc

47829402 860.1500 Cantaloupe New DER; 47829402.der.doc

47829403 860.1500 Caneberry New DER; 47829403.der.doc

47829404 860.1500 Blueberry New DER; 47829404.der.doc

47829405 860.1500 Sweet sorghum New DER; 47829405.de1.doc

860.1520 Sweet sorghum New DER; 47829405.de2.doc

47829406 860.1500 Mustard greens New DER; 47829406.der.doc

47829407 860.1500 Cucumber New DER; 47829407.der.doc

47829408 860.1500 Carrot New DER; 47829408.der.doc

48020601 Addendum to 47829401 thru -08 Included in above DERs
Page 2 of 52

This document was originally prepared under contract by Dynamac Corporation (1901 Research 

Boulevard, Suite 220; Rockville, MD 20850). 

Dynamac QC 

Reviewer:

Date: 01/28/2010

Kelly Luck

Dynamac Program 

Manager:

Date: 01/28/2010

Danilo Martinez

The document has been reviewed by the Health Effects Division (HED) and revised to reflect 

current Office of Pesticide Programs (OPP) policies.
S-Metolachlor Summary of Analytical Chemistry and Residue Data DP#: 369005

Page 3 of 52

Executive Summary

S-Metolachlor (an isomer enriched form of metolachlor) is a selective, chloroacetanilide 

herbicide that is applied to a variety of crops as a preplant, preplant incorporated, preemergence, 

or postemergence application, primarily for the control of grass weeds. S-Metolachlor is 

registered to Syngenta Crop Protection, Inc. for use on a wide variety of crops including: corn, 

cotton, grasses grown for seed, legume vegetables, peanuts, potatoes, safflower, sorghum, 

sunflower, and tomatoes. 

Under PP#9E7607, Interregional Research Project No. 4 (IR-4) is proposing, in Section F of the 

petition, the establishment of tolerances for combined residues of the herbicide S-metolachlor, 

acetamide, 2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)-, (S) and its 

metabolites, determined as the derivatives, 2-(2-ethyl-6-methylphenyl)amino-1-propanol and 4-

(2-ethyl-6-methylphenyl)-2-hydroxy-5-methyl-3-morpholinone, each expressed as the parent 

compound S-metolachlor in/on the following raw agricultural commodities:

Blueberry, lowbush .......................................................1.4 ppm

Bushberry subgroup 13-07B .......................................0.15 ppm

Caneberry, Subgroup 13-07A .....................................0.08 ppm

Carrot ............................................................................0.3 ppm

Cucumber......................................................................0.1 ppm

Leafy Brassica Greens, Subgroup 5-B..........................1.2 ppm

Melon subgroup 9A ....................................................0.08 ppm

Okra...............................................................................0.1 ppm

Onion, Bulb, Subgroup 3-07A......................................0.1 ppm

Onion, Green, Subgroup 3-07B ....................................2.0 ppm

Sesame, seed .................................................................0.1 ppm

Sorghum, sweet.............................................................0.1 ppm

Turnip greens................................................................1.2 ppm

Higher tolerances reflecting total metolachlor residues for the above commodities were proposed 

in an addendum to the MRIDs submitted in support of this petition, but the proposals were not 

submitted as a revised Section F.

Upon establishment of the above tolerances, IR-4 requests the removal of tolerances established 

under 180.368(a)(2) for S-metolachlor and its metabolites in/on bulb onion (0.1 ppm) and green 

onion (2.0 ppm) as the proposed tolerances for the onion subgroups 3-07A and 3-07B will cover 

bulb and green onion, respectively.

The proposed tolerances are requested on behalf of the Agricultural Experiment Station of the 

IR-4 Project and the Agricultural Experiment Stations of:

 OK and TX (sesame requests); 

 MD, MS, TN, AR, NC, SC, GA, CO, TX, DE, FL, NY, NJ, OK, and CA (cantaloupe 

requests);

 MD, MS, TN, and CA (watermelon requests); 

 OR, OK, MN, NY, NJ, MI, MO, AR, NC, VA, and TN (caneberry requests), 
S-Metolachlor Summary of Analytical Chemistry and Residue Data DP#: 369005

Page 4 of 52

 OR, VA, OK, AR, NY, SC, NC, WA, and MO (blueberry requests); 

 NC and TN (sweet sorghum requests); 

 OR, NJ, TX, TN, CO, FL, OK, GA, SC, and MO (mustard greens requests);

 GA, DE, MO, TN, NC, SC, FL, AL, NY, and NJ (cucumber requests); 

 AR and NY (carrot request); 

 NC, FL, and KY (okra requests); 

 CA and OR (dry bulb onion requests); 

 NJ, OH, and MI (green onion requests); 

 AR, OR, TX, TN, CO, MD, and OK (turnip greens requests)

In conjunction with this petition, IR-4 is requesting amended registration of two products, a 7.62 

lb/gal emulsifiable concentrate (EC) formulation of S-metolachlor, Dual Magnum® Herbicide 

(EPA Reg. No. 100-816) and a 7.64 lb/gal EC formulation, Dual II Magnum® (EPA Reg. No. 

100-818), to add uses on the bulb onion subgroup (3-07A), bushberry subgroup (13-07B), the 

caneberry subgroup (13-07A), carrot, cucumber, the green onion subgroup (3-07B), the leafy

Brassica greens subgroup (5B, including turnip greens), the melon subgroup (9A), okra, sesame, 

and sweet sorghum. The products are proposed for postemergence application to the bushberry

subgroup, the caneberry subgroup, okra, the bulb onion subgroup, and the green onion subgroup 

at maximum application rates ranging 1.3-3.8 lb ai/A; preharvest intervals (PHIs) of 21 days for 

the green onion subgroup, 28 days for the bushberry and caneberry subgroup, and 60 days for 

okra and the bulb onion subgroup are proposed. Preemergence, pre-transplant, and/or 

postemergence applications are proposed for carrot, cucumber, leafy Brassica greens, the melon 

subgroup, and sweet sorghum at maximum application rates ranging 1.2-1.9 lb ai/A; PHIs of 64 

days for carrot, 30 days for cucumber and leafy Brassica greens, 60 days for melons, and 90 days 

for sweet sorghum are proposed. In addition, the 7.62 lb/gal EC formulation is proposed for 

preemergence application to sesame at up to 1.9 lb ai/A with a proposed PHI of 100 days. 

The nature of S-metolachlor residues in crops and livestock is understood based on adequate crop 

and livestock metabolism studies with metolachlor and S-metolachlor. For both S-metolachlor 

and metolachlor, the residues of concern in crop and livestock commodities include the parent 

compound (both R and S-enantiomers) and its metabolites, determined as the derivatives CGA37913 and CGA-49751. Following recommendations made in the revised Tolerance 

Reassessment Eligibility Decision (TRED) for Metolachlor and S-Metolachlor (DP# 292881, 

8/15/03, S. Kinard), tolerances for metolachlor and S-metolachlor have been separated. 

Permanent tolerances for combined S-metolachlor residues have been established for crop 

commodities ranging from 0.10 ppm in/on a variety of crop commodities to 20 ppm in/on peanut 

hay [40 CFR §180.368(a)(2)]. Permanent tolerances for indirect or inadvertent residues of Smetolachlor have also been established for non-grass animal feeds (Group 18), and the forage, 

hay, grain and straw of small cereal grains (barley, buckwheat, millet, oats, rice, rye and wheat), 

at levels ranging 0.10 ppm in/on grains to 1.0 ppm in/on non-grass animal feeds [40 CFR 

§180.368(d)(2)].

Adequate methodology is available for enforcing the current tolerances. The Pesticide Analytical 

Manual (PAM), Vol. II, lists a gas chromatography method with nitrogen phosphorus detection 

(GC/NPD) for determining residues in/on crop commodities (Method I) and a GC method with 

mass selective detection (GC/MSD) for determining residues in livestock commodities (Method 
S-Metolachlor Summary of Analytical Chemistry and Residue Data DP#: 369005

Page 5 of 52

II). These methods determine residues of metolachlor and its metabolites as either CGA-37913 

or CGA-49751 following acid hydrolysis. IR-4 and Syngenta have proposed an enantiomerspecific high performance liquid chromatography method with triple quadrupole mass 

spectrometric detection (LC/MS/MS) for the enforcement of the proposed tolerances, Method 

1848-01, which has been previously reviewed by HED (DP# 296904, 4/17/06, R. Loranger). The 

method uses a chiral HPLC column to separate out the S-enantiomers (SYN506357 and 

SYN508500) of the hydrolysis products CGA-37913 and CGA-49751. HED concludes that the 

method is not appropriate for enforcement purposes because it does not determine residues of the 

R-isomers of metolachlor and its metabolites, which are included in the tolerance expression. 

The S:R ratio in the active ingredient is 88:12; therefore, there is potential for residues of the Risomers of metolachlor and its metabolites in crop commodities. The method could be adapted 

for enforcement by measuring both the S- and the R-enantiomers.

Residue data from the current field trial and processing studies were obtained using GC/NPD or 

GC/MS methods derived from the tolerance enforcement method, or using a modified version of 

LC/MS/MS Method No. 1848-01, in which a chiral column was not used for LC analyses. In 

three of the field trial and processing study submissions, the petitioner stated that combined 

residues were reported in parent equivalents; however, the study reviewer could not verify this 

statement. In the remaining submissions, no information was provided indicating whether 

derivative and/or total residues were reported in terms of the analyte or in terms of parent 

metolachlor. In an update to the submitted MRIDs, the petitioner recalculated total metolachlor 

residues, so that the residues are now reported in terms of parent metolachlor equivalents. 

Adequate data are available on the recovery of metolachlor through Multiresidue Method Testing 

Protocols. The FDA PESTDATA database indicates that metolachlor is completely recovered 

through Method 302, PAM Vol. I (3rd ed., revised 10/97).

Adequate concurrent storage stability data were submitted to support the sample storage 

conditions and durations from the submitted field trial and processing studies, other than 

blueberry, and adequate storage stability data are available to support the blueberry field trial 

study. These data indicate that the metolachlor derivatives CGA-49751 and CGA-37913 and/or 

S-metolachlor derivatives SYN506357 and SYN508500 are stable during frozen storage for at 

least 17-49 months in/on caneberry, cantaloupe, carrot root, cucumber, mustard greens, sesame 

seed, sweet sorghum stalks, and tomato; 28 months in sesame meal and oil; and 11 months in 

sweet sorghum syrup. 

Although there is one livestock feedstuff associated with the proposed uses, carrot culls, the 

proposed uses have no impact on the dietary burden of S-metolachlor to livestock. Therefore, no 

changes to the existing tolerances for livestock commodities are needed.

The proposed tolerances are not adequate for bushberry, subgroup 13-07B, caneberry, subgroup 

13-07A; carrot; cucumber; leafy Brassica greens, subgroup 5B; melon subgroup 9A; sesame 

seed; and turnip greens. The tolerance proposals were updated in an addendum to the submitted 

MRIDs, but not formatted as a revised Section F. A revised Section F is needed, expressing the 

tolerance proposals in terms of total metolachlor equivalents. The tolerance for bushberry, 

subgroup 13-07B can only be established at the level needed for the banded, soil directed 
S-Metolachlor Summary of Analytical Chemistry and Residue Data DP#: 369005

Page 6 of 52

application. A tolerance currently exists for residues of S-metolachlor in/on the root vegetable, 

except sugar beet, subgroup, 1B. When the requested tolerance for carrot is established, the 

existing tolerance for subgroup 1B must be revised to “vegetable, root, except carrot and sugar 

beet, subgroup 1B.”

The submitted broadcast foliar data for blueberries are not adequate to support the requested 

tolerances for lowbush blueberry. In addition, the proposed use patterns differ significantly. The 

submitted banded, soil directed application data for highbush blueberry would support a 

tolerance for bushberry, subgroup 13-07B (with use on lowbush blueberry and other low bush 

varieties of berries prohibited on the label), at 0.20 ppm, expressed as total metolachlor 

equivalents. Additional crop field trial data must be submitted before a tolerance may be 

established to cover broadcast foliar use on lowbush blueberry – one additional trial in Region 1, 

one additional trial in Region 5; alternatively, with the additional field trial data reflecting 

broadcast foliar use, the petitioner may wish to submit data and propose a tolerance for the low 

growing berry, except strawberry, subgroup 13-07H. 

The available field trial data for fruiting vegetables may be translated to support the requested 

tolerance for okra; these data support the proposed 0.10 ppm tolerance.

Adequate data have been submitted previously to support the requested tolerances for the bulb 

onion and green onion subgroups; the proposed tolerance levels of 0.10 ppm and 2.0 ppm are 

appropriate. Concomitant with the establishment of tolerances for bulb onion subgroup 3-07A 

and green onion subgroup 3-07B, the established tolerances for S-metolachlor and its metabolites 

in/on bulb garlic, bulb onion, bulb shallot, and green onion under 180.368(a)(2) should be 

removed.

The requested tolerance for sweet sorghum is not needed; the existing tolerance for Smetolachlor residues in/on sorghum grain is adequate to cover residues in/on sweet sorghum 

commodities.

The submitted processing data indicate that no tolerances are needed for S-metolachlor residues 

in the processed commodities of sesame or sweet sorghum.

An adequate confined rotational crop study is available, although additional information 

pertaining to the study remains outstanding. The residues of concern in rotated crops are the 

same as in the primary crops, S-metolachlor, its R-enantiomer, and its metabolites determined as 

CGA-37913 and CGA-49751. Adequate field rotational crop data have been submitted 

previously which support the existing rotational crop restrictions on the labels for EPA Reg. Nos. 

100-816 and 100-818, provided that the label for EPA Reg. No. 100-816 is amended as 

recommended below. 

Regulatory Recommendations and Residue Chemistry Deficiencies

HED has examined the residue chemistry database for S-metolachlor. Pending submission of a 

revised Section B (see requirements under Directions for Use) and revised Section F (see 

requirements under Proposed Tolerances), there are no residue chemistry issues that would 
S-Metolachlor Summary of Analytical Chemistry and Residue Data DP#: 369005

Page 7 of 52

preclude granting a conditional registration for the requested uses of S-metolachlor on Bushberry

subgroup 13-07B, Caneberry, Subgroup 13-07A, Carrot, Cucumber, Leafy Brassica Greens, 

Subgroup 5B, Melon subgroup 9A, Okra, Onion, Bulb, Subgroup 3-07A, Onion, Green, 

Subgroup 3-07B, Sesame, seed, Sorghum, sweet, and Turnip greens, or establishment of 

tolerances for residues of S-metolachlor and its R-enantiomer, including its metabolites and 

degradates, in or on the commodities in the table below. Compliance with the tolerance levels 

specified below is to be determined by measuring only the sum of free and bound S-metolachlor, 

S-2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide, its Renantiomer, and its metabolites, determined as the derivatives, 2-(2-ethyl-6-methylphenyl)amino1-propanol and 4-(2-ethyl-6-methylphenyl)-2-hydroxy-5-methyl-3-morpholinone, calculated as 

the stoichiometric equivalent of S-metolachlor: 

Bushberry, subgroup 13-07B ......................................0.15 ppm

Caneberry, subgroup 13-07A......................................0.10 ppm

Carrot ..........................................................................0.40 ppm

Cucumber....................................................................0.13 ppm

Leafy Brassica Greens, subgroup 5B............................1.8 ppm

Melon subgroup 9B.....................................................0.10 ppm

Okra.............................................................................0.10 ppm

Onion, Bulb, subgroup 3-07A.....................................0.10 ppm

Onion, Green, subgroup 3-07B.....................................2.0 ppm

Sesame, seed ...............................................................0.13 ppm

Sorghum, sweet, stalk ...................................................4.0 ppm

Turnip greens................................................................1.8 ppm

Note to PM: Concomitant with the establishment of tolerances for bulb onion subgroup 3-

07A and green onion subgroup 3-07B, the established tolerances for S-metolachlor and its 

metabolites in/on garlic, bulb (0.10 ppm), onion, bulb (0.10 ppm), shallot, bulb (0.10 ppm), 

and onion, green (2.0 ppm) under 180.368(a)(2) should be removed. Concomitant with the 

establishment of a tolerance for carrot, the existing tolerance for subgroup 1B must be 

revised to “vegetable, root, except carrot and sugar beet, subgroup 1B.”

HED cannot recommend in favor of granting a conditional registration for the requested 

broadcast foliar use of S-metolachlor on lowbush blueberry, due to insufficient residue data (see 

requirements under Directions for Use).

A human health risk assessment is forthcoming.

860.1200 Directions for Use

For EPA Reg. No. 100-816, the following amendments to the proposed uses are needed:

 The proposed use should be amended to specify that postemergence application to sweet 

sorghum may be made to crops up to 5 inches in height. 

 For postemergence applications, the label states that use of an adjuvant may increase risk 

to the crop. Since the field trials were conducted without the use of an adjuvant, the label 

must state that use of adjuvants is prohibited.
S-Metolachlor Summary of Analytical Chemistry and Residue Data DP#: 369005

Page 8 of 52

 Rotational crop directions for crops with a 60-day plantback interval must be amended to 

prohibit a second application of S-metolachlor to any of these crops replanted within 60 

days of the original application.

 Bushberry subgroup 13-07B: The petitioner must revise the proposed use to delete the 

broadcast foliar use on lowbush varieties of berry. Use must be limited to banded, soil 

directed application. The proposed use on highbush blueberry may be expanded to 

include currant, elderberry, gooseberry, and huckleberry. The proposed uses must be 

amended to specify that only one application may be made.

 Carrot: The proposed maximum single and seasonal application rate of 1.9 lb ai/A for 

postemergence application to carrots grown in muck soils must be removed from the 

label; no data have been submitted supporting postemergence application rates >1.27 lb 

ai/A to carrot. Adequate data are available to support the proposed preemergence 

application to carrots grown in muck soils at up to 1.9 lb ai/A.

 Carrot: The proposed use must be amended to specify that postemergence applications 

may be made up to the 5-leaf growth stage. No PHI is needed if postemergence 

application to carrot is defined by crop growth stage.

 Cucumber: The proposed use must be amended to specify that postemergence 

applications may be made up to the 2-leaf growth stage. No PHI is needed if 

postemergence application to cucumber is defined by crop growth stage. 

 Leafy Brassica greens: The proposed use must be amended to specify that postemergence 

applications may be made up to the 2-leaf growth stage. No PHI is needed if 

postemergence application to leafy Brassica greens is defined by crop growth stage.

 Melon: The proposed use on melons not grown in plastic mulch must be amended to 

specify that banded applications are to be made between rows.

For EPA Reg. No. 100-818, the following amendments to the proposed uses are needed:

 The proposed use must be amended to specify that postemergence application to sweet 

sorghum may be made to crops up to 5 inches in height and that postemergence 

application may not be made if preemergence application was made; a maximum of one 

application must be specified. 

 For postemergence applications, the label states that use of an adjuvant may increase risk 

to the crop. Since the field trials were conducted without the use of an adjuvant, the label 

must state that use of adjuvants is prohibited.

 Bushberry subgroup 13-07B: The petitioner must revise the proposed use to delete the 

broadcast foliar use on lowbush varieties of berry. Use must be limited to banded, soil 

directed application. The proposed use on highbush blueberry may be expanded to 

include currant, elderberry, gooseberry, and huckleberry. The proposed uses must be 

amended to specify that only one application may be made.

 Carrot: The proposed use must be amended to specify that only one application may be 

made and that postemergence applications may be made up to the 5-leaf growth stage. 

 Cucumber: The proposed use must be amended to specify that only one application may

be made and that postemergence applications may be made up to the 2-leaf growth stage. 

 Leafy Brassica greens: The proposed use must be amended to specify that only one 

application may be made and that postemergence applications may be made up to the 2-

leaf growth stage.
S-Metolachlor Summary of Analytical Chemistry and Residue Data DP#: 369005

Page 9 of 52

 Melons: The proposed uses must be amended to specify that only one application may be 

made. In addition, the proposed use on melons not grown in plastic mulch must be 

amended to specify that banded applications are to be made between rows.

The following additional data are required to support the requested use on lowbush blueberry.

860.1500 Crop Field Trials

 If the petitioner wishes to support use on lowbush blueberry, two additional field trials 

representing broadcast application would be required, one in Region 1 and one in Region 

5. Alternatively, the petitioner may wish to submit data and propose a tolerance for the 

low growing berry, except strawberry, subgroup, 13-07H. Four additional field trials, 

conducted on lowbush blueberry or cranberry, would be required.

860.1550 Proposed Tolerances

 The tolerances proposed by IR-4 do not include the R-enantiomer. The tolerance 

expression in Section F of the submitted petition should be revised to include the Renantiomer of metolachlor and to conform with current HED guidance, as follows: 

Tolerances are established for residues of S-metolachlor, including its Renantiomer, metabolites and degradates, in or on the commodities in the table 

below. Compliance with the tolerance levels specified below is to be 

determined by measuring only the sum of free and bound S-metolachlor, S-2-

chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide, 

its R-enantiomer, and its metabolites, determined as the derivatives, 2-(2-

ethyl-6-methylphenyl)amino-1-propanol and 4-(2-ethyl-6-methylphenyl)-2-

hydroxy-5-methyl-3-morpholinone, calculated as the stoichiometric equivalent 

of S-metolachlor, in or on the commodity.

 A revised Section F is needed, correcting the proposed tolerance levels, as specified in 

Table 8, to be in terms of total metolachlor, on bushberry subgroup 13-07B; caneberry, 

Subgroup 13-07A; carrot; cucumber; leafy Brassica greens, subgroup 5B; melon 

subgroup 9A; sesame, seed; and turnip greens. 

 HED now considers turnip greens to be a member of the leafy Brassica greens subgroup. 

Pending revision of 40 CFR §180.41, a separate tolerance must be established for turnip 

greens, at the same level as the tolerance for leafy Brassica greens. 

 The proposed tolerance for sweet sorghum is not needed as residues in sweet sorghum 

commodities are covered by the existing tolerance for sorghum grain commodities.

HED recommends that conversion of conditional registration to unconditional registration 

for the requested uses may be considered upon submission of the following outstanding 

residue chemistry data pertaining to confined accumulation in rotational crops.
S-Metolachlor Summary of Analytical Chemistry and Residue Data DP#: 369005

Page 10 of 52

860.1850 Confined Accumulation in Rotational Crops

 To support the confined rotational crop study submitted under MRID 41470601, the 

additional data required by HED (DP# 207842, 10/12/94, S. Hummel) must be submitted; 

additional data were required characterizing the 14C-residues in plants, along with 

information on the percentage of the 14C-residues measured by the current enforcement 

method; sample storage conditions and intervals and supporting storage stability data 

were also required. These data requirements were reiterated in the Metolachlor TRED 

(DP# 292881, 8/15/03, S. Kinard).

Background

The chemical structure and nomenclature of S-metolachlor and its regulated hydrolytic 

derivatives are presented in Table 1, and the physicochemical properties of S-metolachlor are 

presented in Table 2. 

Table 1. Nomenclature of S-Metolachlor and its Regulated Hydrolytic Derivatives.

Parent compound H3C

CH3

N

O

CH3

Cl

H C3

O

Common name 1S-Metolachlor

Company experimental name CGA-77102

IUPAC name (S)-2-chloro-N-(2-ethyl-6-methyl-phenyl)-N-(2-metonym-1-methyl-ethyl)-

acetamide

CAS name 2-chloro-N-(2-ethyl-6-methylphenyl)-N-[(1S)2-methoxy-1-methylethyl]-acetamide

CAS registry number 87392-12-9

End-use product (EP) Dual Magnum® Herbicide (7.62 lb/gal EC; EPA Reg. No. 100-816) and 

Dual II Magnum® Herbicide (7.64 lb/gal EC; EPA Reg. No. 100-818)

Regulated residue

H3C

NH

CH3

HO

CH3

Common name None

Company experimental names CGA-37913

SYN506357 (S-enantiomer of CGA 37913)

Chemical name 2-[(2-ethyl-6-methylphenyl) amino]-1-propanol

CAS registry number 61520-53-4

82508-08-5 (S-enantiomer)
S-Metolachlor Summary of Analytical Chemistry and Residue Data DP#: 369005

Page 11 of 52

Table 1. Nomenclature of S-Metolachlor and its Regulated Hydrolytic Derivatives.

Regulated residue

H3C

CH3

N

O

O

OH

H3C

Common name None

Company experimental names CGA-49751

SYN508500 (S-enantiomer of CGA 49751)

Chemical name 4-(2-ethyl-6-methylphenyl)-2-hydroxy-5-methyl-3-morpholinone

CAS registry number 61520-54-5

Table 2. Physicochemical Properties of S-Metolachlor.

Parameter Value Reference

Melting point/range Not applicable, liquid at room temperature MRID 47121701 

(DP#s 332846, etc., 

10/21/08, D. 

McNeilly)

pH 7.8 at 25 oC (1% aqueous dispersion)

Density 1.117 g/cm3at 20 oC

Water solubility (25°C) 0.48 g/L

Solvent solubility (mg/L at 25°C) Completely miscible with methanol, acetone, toluene, 

n-octanol, n-hexane, ethyl acetate, and dichloromethane.

Vapor pressure at 25°C 2.8 x 10-5 mm Hg

Dissociation constant (pKa) No dissociation constant in pH range 2-12

Octanol/water partition coefficient 

Log(KOW)

3.05 at 25 oC

UV/visible absorption spectrum Neutral: 534 L/mol•cm @ 266.4 nm

443 L/mol•cm @ 274.4 nm

Acidic: 534 L/mol•cm @ 266.4 nm

444 L/mol•cm @ 274.4 nm

Basic: 531 L/mol•cm @ 266.4 nm

411 L/mol•cm @ 274.4 nm

860.1200 Directions for Use

The petitioner provided a text listing of proposed uses in Section B of the petition; these included 

proposed uses for Dual Magnum® (EPA Reg. No. 100-816), a 7.62 lb/gal EC formulation, and 

Dual II Magnum® (EPA Reg. No. 100-818), a 7.64 lb/gal EC formulation. In addition, the 

petitioner submitted two versions of a proposed label for Dual Magnum® Herbicide (EPA Reg. 

No. 100-816): one, dated 9/30/08, included only use directions for the crops proposed in this 

petition (i.e., it did not include any previously registered uses); and the second (which was 

submitted in both highlighted and unhighlighted forms), also dated 9/30/08, included existing 

uses for Dual Magnum Herbicide as well as proposed uses for sweet sorghum. 

The proposed uses are presented below in Table 3. 
S-Metolachlor Summary of Analytical Chemistry and Residue Data DP#: 369005

Page 12 of 52

Table 3. Summary of Proposed Directions for Use of S-Metolachlor.1

Applic. Timing; 

Type; and Equip.

(minimum volume)

Formulation

[EPA Reg. 

No.]

Applic. 

Rate

(lb ai/A)

Max. No. 

Applic. per 

Season

Max. Seasonal 

Applic. Rate

(lb ai/A)

PHI

(days)

Use Directions and 

Limitations

Bulb Onion Subgroup 3-07A 

(Daylily, bulb; fritillaria, bulb; bulb, garlic; great-headed, bulb; garlic, serpent, bulb; lily, bulb; onion, bulb; onion, 

Chinese, bulb; onion, pearl; onion, potato, bulb; shallot, bulb; cultivars, varieties, and/or hybrids of these) 

Postemergence;

Broadcast;

Ground (5 GPA) or 

aerial (2 GPA)

7.62 lb/gal 

EC

[100-816]

0.60-

1.272 2 2.54 60

Application to be made 

to plants at the 2 true 

leaf stage and a second 

application may be made 

21 days later. The 

harvest of green onions 

and the grazing of 

animals on green forage 

or stubble are prohibited. 

Bushberry Subgroup 13-07B and Lowbush Blueberry 

(Bushberries including Aronia berry; blueberry, lowbush; blueberry, highbush; Buffalo currant; Chilean guava; 

currant, red; currant, black; elderberry; European barberry; gooseberry; highbush cranberry; honeysuckle; 

jostaberry; juneberry including Saskatoon berry; lingonberry; native currant; salal; Sea buckthorn)

Postemergence;

Banded;

Ground (10 GPA) 7.62 lb/gal

EC

[100-816]

0.64-1.26 1 1.27 28

Applications to highbush 

blueberry, currant, 

elderberry, gooseberry, 

and huckleberry to be 

made to soil surface on 

each side of the crop 

row.

Postemergence;

Broadcast;

Ground (5 GPA) or 

aerial (2 GPA)

Applications to lowbush 

blueberry to be made as 

a broadcast spray.

Postemergence;

Banded;

Ground (20 GPA) 7.64 lb/gal

EC

[100-818]

0.64-

1.262 NS NS 30 ± 3

Applications to highbush 

blueberry to be made to 

soil surface of both sides 

of the row.

Postemergence;

Broadcast;

Ground (20 GPA)

Applications to lowbush 

blueberry to be made as 

a broadcast spray.

Caneberry Subgroup 13-07A (Caneberries including blackberry; loganberry; red and black raspberry; cultivars 

and/or hybrids of these)

Postemergence;

Banded to the soil 

surface on both 

sides of the cane;

Ground (10 GPA)

7.62 lb/gal

EC

[100-816]

1.90-

3.812 1 3.8 28

Application is to be 

directed to the soil 

surface. 
S-Metolachlor Summary of Analytical Chemistry and Residue Data DP#: 369005

Page 13 of 52

Table 3. Summary of Proposed Directions for Use of S-Metolachlor.1

Applic. Timing; 

Type; and Equip.

(minimum volume)

Formulation

[EPA Reg. 

No.]

Applic. 

Rate

(lb ai/A)

Max. No. 

Applic. per 

Season

Max. Seasonal 

Applic. Rate

(lb ai/A)

PHI

(days)

Use Directions and 

Limitations

Carrot

Preemergence;

Broadcast or 

banded; 

Ground (5 GPA 

broadcast, 10 GPA 

banded) or aerial 

(2 GPA) 7.62 lb/gal

EC

[100-816]

0.64-1.27 

mineral 

soils; 

1.27-1.9 

muck 

soil3

1

1.27 mineral 

soils;

1.9 muck soils

64

Preemergence 

application is to be made 

after planting.

Postemergence;

Broadcast or 

banded; 

Ground (5 GPA 

broadcast, 10 GPA 

banded) or aerial 

(2 GPA)

Postemergence 

application is to be made 

to plants with at least 3-5 

true leaves.

Postemergence;

Broadcast; 

Ground (10 GPA)

7.64 lb/gal

EC

[100-818]

0.63-

1.262 NS NS NS

Foliar application to be 

made after last 

cultivation, to plants at 

3-5 true leaf stage.

Cucumber

Preemergence;

Broadcast; 

Ground (5 GPA) or 

aerial (2 GPA) 7.62 lb/gal

EC

[100-816]

0.64-

1.272 1 1.27 30

Preemergence 

application is to be made 

after planting.

Postemergence;

Broadcast; 

Ground (5 GPA) or 

aerial (2 GPA)

Postemergence 

application is to be made 

to plants with at least 1 

true leaf.

Preemergence;

Broadcast; 

Ground (10 GPA) 7.64 lb/gal 

EC

[100-818]

0.95-

1.272 NS NS NS

Preemergence soil 

application to be made 

after planting. 

Postemergence;

Broadcast; 

Ground (10 GPA)

One postemergence 

foliar application to be 

made to plants at the 1-2 

true leaf stage.

Green Onion Subgroup 3-07B (Chive, fresh leaves; chive, Chinese, fresh leaves; elegans hosta; fritillaria, leaves; 

kurrat; lady’s leek; leek; leek, wild; Onion, Beltsville bunching; onion, fresh; onion, green; onion, macrostem; 

onion, tree, tops; onion, Welsh, tops; shallot, fresh leaves; cultivars, varieties, and/or hybrids of these)

Postemergence;

Broadcast;

Ground (5 GPA) or 

aerial (2 GPA)

7.62 lb/gal 

EC

[100-816]

0.64-

1.272 1 1.27 21

Application to be made 

to plants at the 2 true 

leaf stage. 
S-Metolachlor Summary of Analytical Chemistry and Residue Data DP#: 369005

Page 14 of 52

Table 3. Summary of Proposed Directions for Use of S-Metolachlor.1

Applic. Timing; 

Type; and Equip.

(minimum volume)

Formulation

[EPA Reg. 

No.]

Applic. 

Rate

(lb ai/A)

Max. No. 

Applic. per 

Season

Max. Seasonal 

Applic. Rate

(lb ai/A)

PHI

(days)

Use Directions and 

Limitations

Leafy Brassica Greens Subgroup 5-B (Broccoli raab; cabbage, Chinese (bok choy); collards; kale; mizuna; mustard 

greens; mustard spinach; rape greens; turnip greens)

Preemergence;

Broadcast; 

Ground (5 GPA) or 

aerial (2 GPA) 7.62 lb/gal

[100-816]

0.64-

1.272 1 1.27 30

Preemergence 

application is to be made 

after planting.

Postemergence;

Broadcast; 

Ground (5 GPA) or 

aerial (2 GPA)

Postemergence 

application is to be made 

to plants with at least 1 

true leaf.

Preemergence;

Broadcast; 

Ground (10 GPA) 7.64 lb/gal 

EC

[100-818]

0.63-

1.262 NS NS NS

Preemergence soil 

application to be made 

after planting. 

Postemergence;

Broadcast; 

Ground (10 GPA)

One postemergence 

foliar application to be 

made to plants at the 1-2 

true leaf stage.

Melon Subgroup 9A (Including cantaloupe; citron melon; muskmelon; watermelon)

Preemergence or 

pre-transplant;

Broadcast or 

banded;

Ground (5 GPA 

broadcast, 10 GPA 

banded) or aerial 

(2 GPA)

7.62 lb/gal 

EC

[100-816]

0.64-

1.212 1 1.21 60

For melons grown in 

plastic mulch, broadcast 

application is to be made 

before laying of mulch 

and banded application 

is to be made after laying 

mulch; banded 

application is to be made 

between rows and may 

not be made if broadcast 

application was made 

before laying of mulch. 

For melons not grown in 

plastic mulch, banded 

application is to be 

banded over the crop 

row.

Preemergence or 

pre-transplant;

Broadcast or 

banded;

Ground (20 GPA)

7.64 lb/gal 

EC

[100-818]

0.64-

1.212 NS NS NS

For melons grown in 

plastic mulch, banded 

application is to be made 

between rows. For 

melons not grown in 

plastic mulch, banded 

application is to be 

banded over the crop 

row.
S-Metolachlor Summary of Analytical Chemistry and Residue Data DP#: 369005

Page 15 of 52

Table 3. Summary of Proposed Directions for Use of S-Metolachlor.1

Applic. Timing; 

Type; and Equip.

(minimum volume)

Formulation

[EPA Reg. 

No.]

Applic. 

Rate

(lb ai/A)

Max. No. 

Applic. per 

Season

Max. Seasonal 

Applic. Rate

(lb ai/A)

PHI

(days)

Use Directions and 

Limitations

Okra

Postemergence;

Directed spray;

Ground (10 GPA)

7.62 lb/gal 

EC

[100-816]

0.95-

1.902 1 1.9 60

Application to be made 

to plants at least 4 inches 

tall, directed to the soil 

(or row middle) to 

minimize contact to crop 

foliage.

Sesame

Preemergence;

Broadcast or 

banded;

Ground (5 GPA 

broadcast, 10 GPA 

banded) or aerial 

(2 GPA)

7.62 lb/gal 

EC

[100-816]

0.95-1.921 1.9 100

Application to be made 

to soil surface after 

planting.

Sweet Sorghum

Preplant surface, 

preplant 

incorporated, or 

preemergence;

Broadcast;

Ground (5 GPA)

7.62 lb/gal 

EC

[100-816]

1.0-1.592

1 NS 90

Application may be 

made up to 45 days prior 

to planting. Preplant or 

preemergence 

applications are only to 

be made to seed treated 

with Concep herbicide 

safener.

Postemergence;

Broadcast;

Ground (5 GPA)

0.95-

1.272

Postemergence 

application may not be 

made if preplant or 

preemergence 

application was made.

Preemergence;

Broadcast;

Ground (10 GPA) 7.64 lb/gal 

EC

[100-818]

1.0-1.672

NS NS NS

Application to be made 

to soil surface after 

planting.

Postemergence;

Broadcast;

Ground (10 GPA)

0.64-

1.272

One foliar application to 

be made early 

postemergence.

1

 NS = Not specified. GPA = Gallons per acre.

2

 The lower rates are to be used on soils that are relatively coarse textured and the higher rates are to be used on 

fine-textured soils. 

3

 Muck soils defined as soils with >20% organic matter.

All proposed uses specify that lower rates should be used on relatively coarse textured soils and 

higher rates should be used on fine textured soils. For onions, the proposed uses specify that 

lower rates are to be used on light sandy soils and higher rates are to be used on silt, clay, or 

muck soils or where weed pressure is heavy. For all crops with postemergence uses, it is stated 

that use of an adjuvant may increase risk to the crop.
S-Metolachlor Summary of Analytical Chemistry and Residue Data DP#: 369005

Page 16 of 52

HED notes that for caneberry subgroup 13-07A, okra, and sesame, the use directions provided in 

Section B of the petition differed slightly from those provided on the proposed amended label for 

EPA Reg. No. 100-816. For these crops, the proposed amended label specified a maximum 

seasonal rate and a maximum number of applications; no maximum seasonal rate or maximum 

number of applications were specified for these crops in Section B. In addition, no PHI was 

specified in Section B for application to okra and sesame; the proposed amended label specified a

PHI for both these crops. In all cases, the proposed amended label for EPA Reg. No. 100-816 

was considered to reflect the actual proposed uses. 

The proposed amended label for EPA Reg. No. 100-816 with uses on bulb vegetables, 

bushberries, caneberries, carrot, cucumber, leafy Brassica greens, melon, okra, and sesame did 

not include any information about application equipment, minimum application volume, or 

rotational crop restrictions. The study reviewer has assumed that the general application 

instructions and rotational crop restrictions on the parent label for EPA Reg. No. 100-816 are 

intended to be applied to the proposed uses. 

Plantback restrictions for the proposed uses in Section B refer to the master label. A master label 

was provided in Section A of the petition for Dual Magnum Herbicide (EPA Reg. No. 100-816); 

however, no master label for Dual II Magnum Herbicide (EPA Reg. No. 100-818) was provided. 

The following crop rotation restrictions are specified for EPA Reg. No. 100-816:

 a 0-day plantback interval (PBI) for any crop on the Dual Magnum label, or on a 

supplemental Dual Magnum label, provided that the rate of Dual Magnum applied to the 

previous crop was not greater than the labeled rate for the crop to be replanted;

 a 4-month PBI for alfalfa (provided no more than 1.9 lb ai/A was applied to the previous 

crop);

 a 41⁄2-month PBI for barley, oats, rye, and wheat;

 a 9-month PBI for clover (provided no more than 1.9 lb ai/A was applied to the previous 

crop);

 a 60-day PBI for the crops and/or crop groups listed in the table below, depending on the 

amount of S-metolachlor applied to the previous crop;

 tobacco, buckwheat, and rice may be planted the next spring;

 a 12-month PBI for all other food or feed crops.

Crops/crop groups allowed for rotation 60 days after application of S-metolachlor.

Crop group/subgroup/crop Amount of S-metolachlor previously applied to 

field 1

≤1.3 lb ai/A ≤1.6 lb ai/A ≤1.9 lb ai/A

Root vegetables (subgroup 1B) yes no no

Bulb vegetables (group 3), green plants yes no no

Winter squash, including pumpkins yes no no

Fruiting vegetables, except cucurbits (group 8) yes yes no

Tuberous and corm vegetables (subgroup 1C) yes yes yes

Bulb vegetables (group 3), dry bulbs yes yes yes
S-Metolachlor Summary of Analytical Chemistry and Residue Data DP#: 369005

Page 17 of 52

Crops/crop groups allowed for rotation 60 days after application of S-metolachlor.

Crop group/subgroup/crop Amount of S-metolachlor previously applied to 

field 1

≤1.3 lb ai/A ≤1.6 lb ai/A ≤1.9 lb ai/A

Leaf petiole vegetables (subgroup 4B) yes yes yes

Head and stem Brassica vegetables (subgroup 5A) yes yes yes

1

 If the rate of S-metolachlor applied to the previous crop was greater than the rate listed here, crops from the 

various groups cannot be planted until the following spring.

The following rotational crop restrictions are specified for EPA Reg. No. 100-818 (PPLS label 

accepted 2/19/04):

 a 0-day PBI for any crop on the label [corn, cotton, peanuts, pod crops (garbanzo, great 

northern beans, kidney beans, lima beans, mung beans, navy beans, peas (English, 

southern peas, such as blackeye, pinkeye, crowder, etc.), pinto beans, snap beans (green, 

wax, string), and lupines (sweet, white, white sweet, and grain), potatoes, safflowers, 

grain or forage sorghum, and soybeans];

 a 4-month PBI for alfalfa;

 a 41⁄2-month PBI for barley, oats, rye, and wheat;

 a 6-month PBI for tomato;

 a 9-month PBI for clover;

 any crop on the label, as well as root crops, tobacco, barley, buckwheat, milo, oats, rice, 

rye, wheat, cabbage, and pepper, may be planted in the spring following treatment;

 following a lay-by treatment or multiple treatments applied the previous season, any crop 

on the label, in addition to tobacco, cabbage, peppers, stone fruits, or tree nuts, may be 

planted in the spring.

Conclusions. The proposed use directions are adequate to allow for evaluation of the submitted 

residue data relative to the proposed uses. With the exception of the proposed use on lowbush 

blueberry, the proposed uses are generally supported by the submitted field trial data. Several 

label amendments are required to modify the proposed use to reflect the use patterns of the crop 

field trials.

The proposed broadcast foliar uses on lowbush blueberry are not supported by the available field 

trial data. Adequate field trial data have been submitted to support banded (soil directed) 

application to highbush blueberry.

No data are available to support postemergence applications to carrots at rates >1.3 lb ai/A; 

adequate field trial data have been submitted previously to support preemergence applications to 

carrots grown in muck soils at up to 3.0 lb ai/A.

The proposed uses for the melon subgroup specify that banded applications to melons not grown 

in plastic mulch be made over the crop row. The submitted field trial data only support banded 

applications made between crop rows. 
S-Metolachlor Summary of Analytical Chemistry and Residue Data DP#: 369005

Page 18 of 52

The petitioner proposed PHIs for several crops which are not needed, provided the proposed use 

is amended to specify that applications may only be made up to a certain growth stage, which is 

the growth stage that applications were made at in the submitted field trials. No PHI is needed 

for sesame because applications are to be made prior to crop emergence.

HED notes that application rate was not related to soil type in any of the crop field trials studies 

submitted with this petition. 

For EPA Reg. No. 100-816, the following amendments to the proposed uses are needed:

 The proposed use should be amended to specify that postemergence application to sweet 

sorghum may be made to crops up to 5 inches in height. 

 Rotational crop directions for crops with a 60-day PBI must be amended to prohibit a 

second application of S-metolachlor to any of these crops replanted within 60 days of the 

original application.

 Bushberry subgroup 13-07B: The petitioner must delete the broadcast foliar use on 

lowbush varieties in the bushberry subgroup from the proposed amended label. The 

proposed banded, soil directed uses on highbush blueberry, currant, elderberry, 

gooseberry, and huckleberry are supported by the available data and may remain on the 

proposed amended label. The proposed uses must be amended to specify that only one 

application may be made.

 Carrot: The proposed maximum single and seasonal application rate of 1.9 lb ai/A for 

postemergence application to carrots grown in muck soils must be removed from the 

label; no data have been submitted supporting postemergence application rates >1.27 lb

ai/A to carrot. Adequate data are available to support the proposed preemergence 

application to carrots grown in muck soils at up to 1.9 lb ai/A.

 Carrot: The proposed use must be amended to specify that postemergence applications 

may be made up to the 5-leaf growth stage. No PHI is needed if postemergence 

application to carrot is defined by crop growth stage.

 Cucumber: The proposed use must be amended to specify that postemergence 

applications may be made up to the 2-leaf growth stage. No PHI is needed if 

postemergence application to cucumber is defined by crop growth stage. 

 Leafy Brassica greens: The proposed use must be amended to specify that postemergence 

applications may be made up to the 2-leaf growth stage. No PHI is needed if 

postemergence application to leafy Brassica greens is defined by crop growth stage.

 Melon: The proposed use on melons not grown in plastic mulch must be amended to 

specify that banded applications are to be made between rows.

 Sesame: The proposed use must be amended to specify that application may only be 

made to sesame grown in OK and TX. In addition, because application is to be made 

preemergence, no PHI is needed; the proposed 100-day PHI should be removed. 

For EPA Reg. No. 100-818, the following amendments to the proposed uses are needed:

 The proposed use must be amended to specify that postemergence application to sweet 

sorghum may be made to crops up to 5 inches in height and that postemergence 

application may not be made if preemergence application was made; a maximum of one 

application must be specified. 
S-Metolachlor Summary of Analytical Chemistry and Residue Data DP#: 369005

Page 19 of 52

 Bushberry subgroup 13-07B: The petitioner must delete the broadcast foliar use on 

lowbush varieties in the bushberry subgroup from the proposed amended label. The 

proposed banded, soil directed uses on highbush blueberry, currant, elderberry, 

gooseberry, and huckleberry are supported by the available data and may remain on the 

proposed amended label. The proposed uses must be amended to specify that only one 

application may be made.

 Carrot: The proposed use must be amended to specify that only one application may be 

made and that postemergence applications may be made up to the 5-leaf growth stage. 

 Cucumber: The proposed use must be amended to specify that only one application may

be made and that postemergence applications may be made up to the 2-leaf growth stage. 

 Leafy Brassica greens: The proposed use must be amended to specify that only one 

application may be made and that postemergence applications may be made up to the 2-

leaf growth stage.

 Melons: The proposed uses must be amended to specify that only one application may be 

made. In addition, the proposed use on melons not grown in plastic mulch must be 

amended to specify that banded applications are to be made between rows.

The rotational crop restrictions on the label for EPA Reg. No. 100-816 have been evaluated 

previously (DP#s 332846, etc., 10/21/08, D. McNeilly). It was concluded that the proposed 

restrictions are supported by the available data, provided that that rotational crop directions for 

crops with a 60-day PBI be amended to prohibit a second application of S-metolachlor to any of 

these crops replanted within 60 days of the original application. This label amendment has not 

been made.

The rotational crop restrictions on the label for EPA Reg. No. 100-818 are supported by the 

available field rotational crop data.

860.1300 Nature of the Residue - Plants

The qualitative nature of metolachlor residues in plants is adequately understood based upon the 

adequate corn, potato, and soybean metabolism studies. The metabolism of metolachlor involves 

conjugation with glutathione, breakage of this bond to form the mercaptan, conjugation of the 

mercaptan with glucuronic acid, O-demethylation of the methyl ether, and conjugation of the 

resultant alcohol with a neutral sugar. A minor pathway may involve sugar conjugation of 

metolachlor directly to the corresponding oxo-compounds. Residues of concern in plants include 

metolachlor and its metabolites, determined as the derivatives CGA-37913 and CGA-49751. 

The Agency previously concluded that the residues of concern for S-metolachlor are the same as 

for metolachlor (DP# 226780, 11/15/96, L. Kutney).

The Agency has also reviewed plant metabolism data on S-metolachlor from field tests on 

soybeans and corn, in vitro tests on corn seedlings, and greenhouse tests on seedlings of corn, 

sorghum, soybeans and peanuts (DP#s 278742 and 279110, 8/15/03, S. Kinard). These data 

support Syngenta’s assertion that the metabolism of S-metolachlor in plants is similar to that for 

the racemic mixture. The data did not address whether there is any conversion of the S-isomers 

of metolachlor or its metabolites to the R-isomer forms; however, HED previously concluded 

that such conversion of isomers in plants is not likely to be significant.
S-Metolachlor Summary of Analytical Chemistry and Residue Data DP#: 369005

Page 20 of 52

860.1300 Nature of the Residue - Livestock

Adequate studies are available depicting the metabolism of metolachlor in ruminants and poultry. 

Metolachlor is rapidly metabolized and almost totally eliminated in the urine and feces of

ruminants (goats), non-ruminants (rats), and poultry. Metolachlor per se was not detected in any

of the excreta or tissues. As in plants, metolachlor residues of concern in livestock commodities 

include metolachlor and its metabolites, determined as the derivatives CGA-37913 and CGA49751. The residues of concern for S-metolachlor in livestock are the same as those for 

metolachlor.

The Agency has also reviewed livestock metabolism data on S-metolachlor (DP#s 278742, 

8/15/03, S. Kinard). Data from a goat metabolism study indicated that S-metolachlor was readily

absorbed and extensively metabolized by goats via glutathione conjugation and/or oxidation 

reactions. Oxidized metabolites were also conjugated with glucuronic acid. Data from a poultry

metabolism study indicated that S-metolachlor was also extensively metabolized via O 

demethylation and subsequent glucuronic acid conjugation or oxidation to dihydroxy or 

carboxylic acid metabolites that may also be conjugated with glucuronic acid.

860.1340 Residue Analytical Methods

Enforcement methods: Adequate methodology is available for enforcing the established and 

recommended tolerances. PAM Vol. II, Pesticide Regulation Section 180.368, lists a GC/NPD 

method (Method I) for determining residues in/on crop commodities and a GC/MSD method 

(Method II) for determining residues in livestock commodities. These methods determine 

residues of metolachlor and its metabolites as either CGA-37913 or CGA-49751 following acid 

hydrolysis. 

IR-4 and Syngenta have proposed an LC/MS/MS enantiomer-specific method for the 

enforcement of the proposed tolerances, Method 1848-01. This method has been previously

reviewed by HED (DP# 296904, 4/17/06, R. Loranger). The method as written uses a chiral 

HPLC column to separate out the S-enantiomers (SYN506357 and SYN508500) of the 

hydrolysis products CGA-37913 and CGA-49751. 

Data-gathering methods: Samples of crop commodities from the submitted field trial and 

processing studies were analyzed for residues of metolachlor and its metabolites convertible to 

the derivatives CGA-49751 and CGA-37913 using GC/MS, GC/NPD, or LC/MS/MS methods. 

All methods involved acid hydrolysis in 6 N HCl at reflux for 16 hours to convert residues of 

metolachlor and its metabolites to either CGA-49751 or CGA-37913.

Samples of blueberry were analyzed for metolachlor residues of concern using a GC method with 

either NP or MS detection, developed from Method I in the PAM Vol. II. Briefly, samples were 

subjected to acid hydrolysis in 6 N HCl at reflux for 16 hours and the hydrolysate was isolated by

filtration and diluted to volume with 6 N HCl. For determination of CGA-49751, an aliquot was 

partitioned with dichloromethane (DCM). The DCM phase was subjected to solid-phase 

extraction (SPE) cleanup prior to derivatization with 10% boron trifluoride 2-chloroethanol. The 
S-Metolachlor Summary of Analytical Chemistry and Residue Data DP#: 369005

Page 21 of 52

derivatized product was diluted with 7% aqueous Na2SO4, partitioned into hexane, and the 

hexane phase cleaned up using an alumina column for analysis by GC/MSD. For determination 

of CGA-37913, a second aliquot was basified with 50% NaOH and partitioned into hexane for 

analysis by GC/NPD. The lower limit of method validation (LLMV) was 0.05 ppm for CGA49751 and 0.03 ppm for CGA-37913 in blueberry.

Caneberry samples were analyzed for metolachlor residues of concern using a GC/NPD method 

developed from Method I in PAM Vol. II. Briefly, samples were subjected to acid hydrolysis in 

6 N HCl at reflux for 16 hours and the hydrolysate was isolated by filtration and diluted to 

volume with water. For determination of CGA-49751, an aliquot was partitioned with DCM and 

the DCM phase was evaporated to dryness and then derivatized with 10% boron trifluoride 2-

chloroethanol. The derivatized product was diluted with aqueous 7% Na2SO4 and partitioned

into hexane for analysis. For determination of CGA-37913, a separate aliquot was basified with 

50% NaOH and partitioned into hexane for analysis. Residues of each analyte were quantitated 

by GC/NPD analysis. The LLMV was 0.05 ppm for CGA-49751 and 0.03 ppm for CGA-37913 

in caneberry.

Samples of cantaloupe and sesame commodities (seed, meal, and oil) were analyzed for 

metolachlor residues of concern using an LC/MS/MS method developed from Method I in PAM 

Vol. II. Briefly, samples were subjected to acid hydrolysis in 6 N HCl at reflux for 16 hours and 

the hydrolysate was isolated by filtration and diluted to volume with water; oil hydrolysates were 

first partitioned with hexane. For determination of CGA-49751, an aliquot was partitioned with 

DCM. The DCM phase was filtered and subjected to SPE cleanup (sesame seed and cantaloupe 

only) prior to LC/MS/MS analysis. For determination of CGA-37913, another aliquot was 

basified with 50% NaOH and partitioned with hexane (or DCM for oil). The organic phase was 

filtered and dried over anhydrous sodium sulfate, evaporated to near dryness, and reconstituted in 

methanol or mobile phase for LC/MS/MS analysis. The LLMV was 0.05 ppm for CGA-49751 

and 0.03 ppm for CGA-37913 in cantaloupe, and 0.05 ppm for each analyte in sesame 

commodities.

Samples of carrot, cucumber, mustard greens, and sweet sorghum stalk and syrup were analyzed 

for residues of S-metolachlor and its metabolites convertible to CGA-37913 and CGA 49751 

using a modified version of LC/MS/MS Method No. 1848-01. This method has been previously

reviewed by HED (DP# 296904, 4/17/06, R. Loranger). The method as written uses a chiral 

HPLC column to separate out the S-enantiomers (SYN506357 and SYN508500) of the 

hydrolysis products CGA-37913 and CGA-49751. However, the analytical laboratory did not 

use a chiral HPLC column in the analyses; therefore, the working method determined residues of 

both the R- and S-enantiomers of the hydrolysis products CGA-37913 and CGA 49751. 

In general, samples were subjected to acid hydrolysis in 6 N HCl at reflux for 16 hours; the 

hydrolysate was isolated by filtration and an aliquot was diluted to volume with water and then 

made basic using 25% NaOH and Na2CO3. The hydrolysate was partitioned with DCM and the 

DCM phase was concentrated, and brought to volume with methanol or 5% isopropanol in 

methanol for analysis by LC/MS/MS. The LLMV was 0.05 ppm for each analyte in each 

commodity based on fortifications with SYN508500 and SYN506357.
S-Metolachlor Summary of Analytical Chemistry and Residue Data DP#: 369005

Page 22 of 52

The methods were adequately validated prior to and concurrent with the analysis of field trial 

and/or processing study samples. 

In the sesame, cantaloupe, and caneberry submissions, the petitioner stated that combined 

residues were reported in parent equivalents; however, the study reviewer could not verify this 

statement. In the blueberry, carrot, cucumber, mustard greens, and sorghum submissions, no 

information was provided indicating whether derivative and/or total residues were reported in 

terms of the analyte or in terms of parent metolachlor. The Agency requested corrected 

calculations, which were provided in an MRID addendum to MRIDs 47829401 through 

47829408. This MRID addendum was assigned MRID 48020601. All calculations now are in 

terms of total parent metolachlor equivalents. 

Conclusions. Adequate enforcement methods are available for determining residues in crop and 

livestock commodities. 

The petitioner has proposed the enantiomer-specific LC/MS/MS method, Method No. 1848-01, 

for enforcement purposes. HED concludes that the method is not appropriate for enforcement 

purposes because it does not determine residues of the R-isomers which are included in the 

tolerance expression. The S:R ratio in the active ingredient is 88:12; therefore, there is potential 

for residues of the R-isomers of metolachlor and its metabolites in crop commodities. The 

method could be adapted for enforcement by changing the method to measure both the S- and the 

R-enantiomers.

860.1360 Multiresidue Methods

Adequate data are available on the recovery of metolachlor through Multiresidue Method Testing 

Protocols. The FDA PESTDATA database indicates that metolachlor is completely recovered 

through Method 302, PAM Vol. I (3rd ed., revised 10/97).

860.1380 Storage Stability

Adequate storage stability data are available for crop commodities. Previously submitted data 

(DP# 292881, 8/15/03, S. Kinard) indicate that: CGA-37913 is stable at ≤-10 °C for at least 2 

years in corn (grain and forage), peanut, potato (tubers, wet peel and flakes), soybean (hulls and 

meal) and tomatoes, for at least 29 months in cottonseed oil, and for at least 37 months in 

cottonseed and corn oil; and CGA-49751 is stable at ≤-10°C for at least 2 years in corn (grain, 

forage, and oil), peanuts, potatoes (tubers, wet peel and flakes), soybeans (hulls and meal) and 

tomatoes, and for at least 37 months in cotton seed and cottonseed oil. In addition, storage 

stability studies conducted concurrently with previously submitted asparagus, carrot, and green 

onion field trials indicate that both analytes are stable at -20 oC for at least 14.1 months in 

asparagus, 24.3 months in carrots, and 21.7 months in green onions. 

Concurrent storage stability studies were conducted with the caneberry, cantaloupe, carrot, 

cucumber, mustard greens, sesame, and sorghum field trial and processing studies submitted with 

this petition. These data indicate that the metolachlor derivatives CGA-49751 and CGA-37913 

are stable during frozen storage for up to 48.8 months in/on fortified caneberry; for up to 26.2 
S-Metolachlor Summary of Analytical Chemistry and Residue Data DP#: 369005

Page 23 of 52

months in/on fortified cantaloupe; for up to 30.2 months in/on fortified sesame seed; and for up 

to 28.2 months in fortified sesame meal and oil. In addition, S-metolachlor derivatives 

SYN506357 and SYN508500 were found to be relatively stable during frozen storage for up to 

25.2 months in/on fortified carrots; for up to 18.0 months in/on fortified cucumber; for up to 24.7 

months in/on fortified mustard greens; for up to 17.4 months in/on fortified sorghum stalks; and 

for up to 10.6 months in fortified sorghum syrup. It is noted that zero-day data were not provided 

with any of the concurrent storage stability studies; IR-4 is reminded that storage stability studies 

should always include a zero-day sampling interval to establish the residue levels present at the 

time samples are placed into storage [see OPPTS 860.1380(d)(6)(i)].

The durations and conditions of samples from the current crop field trials and processing studies 

are presented in Table 4.

Table 4. Summary of Storage Conditions and Durations of Samples from Crop Field Trial and 

Processing Studies. 

Matrix Storage Temperature

(°C)

Actual Storage 

Duration

Interval of Demonstrated Storage Stability

Blueberry <-3 364-462 days

(12.0-15.2 months)

CGA-49751 and CGA-37913 are stable for up 

to 2 years in/on various frozen crop 

commodities, including tomato.

Caneberry ≤-16 1447-1491 days

(47.5-49.0 months)

CGA-49751 and CGA-37913 are stable for up 

to 48.8 months in/on frozen caneberry.

Cantaloupe ≤-1 437-718 days

(14.4-23.6 months)

CGA-49751 and CGA-37913 are stable for up 

to 26.2 months in/on frozen cantaloupe.

Carrot root ≤-3 488-756 days

(16.1-24.9 months)

SYN508500 and SYN506357 are relatively 

stable for up to 25.2 months in/on frozen carrot 

root.

Cucumber ≤-4 392-444 days

(12.9-14.6 months)

SYN508500 and SYN506357 are stable for up 

to 18.0 months in/on frozen cucumber.

Mustard greens ≤-2 421-748 days

(13.8-24.6 months)

SYN508500 and SYN506357 are stable for up 

to 24.7 months in/on frozen mustard greens.

Sesame seed ≤-1 856-893 days

(28.2-29.4 months)

CGA-49751 and CGA-37913 are stable for up 

to 30.2 months in/on frozen sesame seed and 

28.2 months in/on frozen meal and oil. Sesame meal 774-807 days 

(25.5-26.5 months)

Sesame oil 824 days 

(27.1 months)

Sweet sorghum, 

stalks

≤-20 469-522 days

(15.4-17.1 months)

SYN508500 and SYN506357 are stable for up 

to 17.4 months in/on frozen sorghum stalks and 

up to 10.6 months in frozen sorghum syrup. Sorghum syrup 314-324 days

(10.3-10.7 months)

Conclusions. Adequate storage stability data are available to support the storage durations and 

conditions for samples from the submitted field trial and processing studies. No corrections for 

potential decline during storage are needed.
S-Metolachlor Summary of Analytical Chemistry and Residue Data DP#: 369005

Page 24 of 52

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

The reregistration requirements for magnitude of the residue in meat, milk, poultry, and eggs are 

fulfilled (DP# 292881, 8/15/03, S. Kinard). Adequate ruminant and poultry feeding studies are 

available for metolachlor, and these data will also support the use of S-metolachlor.

The proposed uses of S-metolachlor in this petition include one livestock feedstuff, carrot culls.

The dietary burdens for livestock to S-metolachlor residues were recently recalculated in 

conjunction with a request to amend use directions for sorghum and soybean (DP#s 332846, etc., 

10/21/08, D. McNeilly). At that time, the dietary burdens were calculated to be 26.2 ppm for 

cattle, 0.51 ppm for poultry, and 0.44 ppm for swine. It was concluded that the established 

tolerances for livestock commodities were adequate to support existing metolachlor uses.

HED has recalculated the reasonable dietary burdens (RDBs) to livestock using the most recent 

guidance (June 2008) and the existing and proposed tolerances for residues of metolachlor in/on 

livestock feedstuffs; see Table 5. The RDBs are 3.11 ppm for beef cattle, 20.2 ppm for dairy

cattle, 0.48 ppm for poultry, and 0.40 ppm for swine. Because these RDBs are less than the 

dietary burdens that were calculated previously, no changes to the established tolerances for 

livestock commodities are needed to support the proposed uses.

Table 5. Calculation of Dietary Burdens of S-Metolachlor Residues to Livestock.

Feedstuff Type1 % Dry 

Matter2 % Diet2 Tolerance (ppm) Dietary Contribution (ppm)

3

Beef Cattle

Corn, field, forage R 40 15 6.0 2.25

Beet, sugar, molasses CC 75 10 2.0 0.27

Potato, processed waste CC 15 30 0.20 0.40

Sorghum, grain CC 86 40 0.30 0.14

Sunflower, meal PC 92 5 1.0 0.054

TOTAL BURDEN -- -- 100 -- 3.11

Dairy Cattle

Grass forage R 25 45 10 18.0

Corn, sweet, cannery waste CC 30 10 6.0 2.0

Sorghum, grain CC 86 35 0.30 0.12

Sunflower, meal PC 92 10 1.0 0.11

TOTAL BURDEN -- -- 100 -- 20.2
S-Metolachlor Summary of Analytical Chemistry and Residue Data DP#: 369005

Page 25 of 52

Table 5. Calculation of Dietary Burdens of S-Metolachlor Residues to Livestock.

Feedstuff Type1 % Dry 

Matter2 % Diet2 Tolerance (ppm) Dietary Contribution (ppm)

3

Poultry

Sorghum, grain CC 2NA 75 0.30 0.23

Sunflower, meal PC NA 25 1.0 0.25

TOTAL BURDEN -- -- 100 -- 0.48

Swine

Corn, field, grain CC NA 5 0.10 0.005

Sorghum, grain CC 3NA 80 0.30 0.24

Sunflower, meal PC NA 15 1.0 0.15

TOTAL BURDEN -- -- 100 -- 0.40

1

 R: Roughage; CC: Carbohydrate concentrate; PC: Protein concentrate.

2

 OPPTS 860.1000 Table 1 Feedstuffs (June 2008). 

3

 Contribution = ([tolerance /% DM] X % diet) for beef and dairy cattle; contribution = ([tolerance] X % diet) for 

poultry and swine.

Conclusions. The proposed uses for S-metolachlor will have no significant impact on the dietary

burden of metolachlor to livestock. As a result, no changes are required in the current tolerances 

for metolachlor residues in livestock commodities.

860.1500 Crop Field Trials

DER References: 47829401.de1.doc (Sesame)

47829402.der.doc (Cantaloupe)

47829403.der.doc (Caneberry)

47829404.der.doc (Blueberry)

47829405.de1.doc (Sweet sorghum)

47829406.der.doc (Mustard greens)

47829407.der.doc (Cucumber)

47829408.der.doc (Carrot)

The petitioner submitted field trial data in support of the proposed uses on bushberry, caneberry, 

carrot, cucumber, leafy Brassica greens, melon, sesame, and sweet sorghum. The results of the 

field trials are summarized in Table 6. The petitioner is relying on existing data to support the 

proposed uses on bulb and green onion, and okra. The submitted and available data for each crop 

are discussed below.

Table 6. Summary of Residue Data from Crop Field Trials with S-Metolachlor.

Crop matrix Total Applic. 

Rate

(lb ai/A)

[kg ai/ha]

PHI 

(days)

Combined Residues of Metolachlor Derivatives (ppm) in Metolachlor 

Equivalents

n Min. Max. HAFT1 Median Mean Std. 

Dev.

BUSHBERRY SUBGROUP 13-07B (proposed use = 1.27 lb ai/A total application rate, 28-day PHI)

Blueberry, 

highbush

1.25-1.38

[1.41-1.54]

27-33 20 <0.10 <0.10 0.10 0.10 0.10 --

2.42-2.76

[2.71-3.09]

27-33 20 <0.10 0.17 0.14 0.10 0.11 0.014
S-Metolachlor Summary of Analytical Chemistry and Residue Data DP#: 369005

Page 26 of 52

Table 6. Summary of Residue Data from Crop Field Trials with S-Metolachlor.

Crop matrix Total Applic. 

Rate

(lb ai/A)

[kg ai/ha]

PHI 

(days)

Combined Residues of Metolachlor Derivatives (ppm) in Metolachlor 

Equivalents

n Min. Max. HAFT1 Median Mean Std. 

Dev.

Blueberry, 

lowbush

1.22

[1.36]

29 2 0.90 1.0 0.96 0.96 0.96 --

2.54

[2.84]

29 2 1.6 1.6 1.6 1.6 1.6 --

CANEBERRY SUBGROUP 13-07A (proposed use = 3.8 lb ai/A total application rate, 28-day PHI)

Caneberry 2.60-2.72

[2.92-3.04]

28-30 10 <0.10 <0.10 0.10 0.10 0.10 --

3.85-4.05

[4.31-4.54]

28-30 10 <0.10 <0.10 0.10 0.10 0.10 --

CARROT (proposed use = 1.27 lb ai/A total application rate for mineral soils and 1.9 lb ai/A total 

application rate for muck soils, 64-day PHI)

Carrot root 0.61-0.71

[0.68-0.79]

26-121 28 <0.13 0.17 0.16 0.13 0.13 0.01

1.23-1.36

[1.38-1.52]

26-121 28 <0.13 0.38 0.37 0.13 0.15 0.06

CUCUMBER (proposed use = 1.27 lb ai/A total application rate, 30-day PHI)

Cucumber 0.89-1.00

[1.00-1.12]

Postemergence

32-52 22 <0.13 <0.13 0.13 0.13 0.13 --

1.22-1.31

[1.36-1.47]

Postemergence

32-52 20 <0.13 <0.13 0.13 0.13 0.13 --

0.92-1.00

[1.03-1.12]

Preemergence

45-76 21 <0.13 <0.13 0.13 0.13 0.13 --

1.22-1.36

[1.36-1.51]

Preemergence

45-76 20 <0.13 <0.13 0.13 0.13 0.13 --

LEAFY BRASSICA GREENS SUBGROUP 5B

(proposed use = 1.27 lb ai/A total application rate, 30-day PHI)

Mustard greens 0.61-0.68

[0.69-0.76]

Postemergence

20-40 24 <0.13 <0.25 0.24 0.16 0.18 0.05

1.24-1.35

[1.39-1.51]

Postemergence

20-40 24 <0.13 0.94 0.89 0.32 0.39 0.23

0.63-0.66

[0.71-0.74]

Preemergence

33-62 24 <0.13 0.23 0.21 0.13 0.15 0.03

1.21-1.38

[1.35-1.54]

Preemergence

33-62 24 <0.13 0.57 0.55 0.17 0.24 0.14
S-Metolachlor Summary of Analytical Chemistry and Residue Data DP#: 369005

Page 27 of 52

Table 6. Summary of Residue Data from Crop Field Trials with S-Metolachlor.

Crop matrix Total Applic. 

Rate

(lb ai/A)

[kg ai/ha]

PHI 

(days)

Combined Residues of Metolachlor Derivatives (ppm) in Metolachlor 

Equivalents

n Min. Max. HAFT1 Median Mean Std. 

Dev.

MELON SUBGROUP 9A (proposed use = 1.21 lb ai/A total application rate, 60-day PHI)

Cantaloupe 1.23-1.46

[1.38-1.64]

Banded

61-112 22 <0.10 <0.10 0.10 0.10 0.10 --

1.26-1.38

[1.42-1.55]

Broadcast

61-112 22 <0.10 <0.10 0.10 0.10 0.10 --

SESAME (proposed use = 1.9 lb ai/A total application rate, 100-day PHI)

Sesame, seed 1.99-2.02

[2.23-2.26]

101-

128

8 <0.13 <0.13 0.13 0.13 0.13 --

SWEET SORGHUM (proposed use = 1.59 lb ai/A total application rate for preemergence application and 

1.27 lb ai/A total application rate for postemergence application, 90-day PHI)

Sweet 

sorghum, stalks

0.64-0.65

[0.72]

Postemergence

87-92 6 <0.13 <0.13 0.13 0.13 0.13 --

1.27-1.29

[1.42-1.45]

Postemergence

87-92 6 <0.13 <0.13 0.13 0.13 0.13 --

1.00-1.02

[1.12-1.15]

Preemergence

92-108 6 <0.13 <0.13 0.13 0.13 0.13 --

1.68-1.72

[1.88-1.93]

Preemergence

92-108 6 <0.13 <0.13 0.13 0.13 0.13 --

1

 HAFT = Highest average field trial result.

Bushberry, subgroup 13-07B

47829404.der.doc

IR-4 has submitted field trial data for S-metolachlor on blueberry as the representative crop of 

bushberry subgroup 13-07B. Eleven blueberry trials were conducted in the U.S. and Canada in 

Zones 1 (ME; 1 trial), 2 (NJ, NC; 3 trials), 5 (MI; 2 trials), 5B (QC; 1 trial), 10 (CA; 1 trial), and 

12 (BC, OR; 3 trials) during the 2004 growing season. The ME trial used a lowbush blueberry

variety; the other trials used highbush blueberry varieties. 

Each trial site consisted of one untreated plot and two treated plots. At each highbush blueberry

trial location, a single banded application of a 7.64 lb/gal EC formulation of S-metolachlor was 

made to the soil surface on both sides of the plant row at 1.25-1.38 lb ai/A (1.41-1.54 kg ai/ha) at 

one of the treated plots or at 2.42-2.76 lb ai/A (2.71-3.09 kg ai/ha) to the other treated plot. At 

the one lowbush blueberry trial location, a single foliar broadcast application of the 7.64 lb/gal 

EC formulation was made to fruiting plants at 1.22 lb ai/A (1.36 kg ai/ha) at one of the treated 

plots or at 2.54 lb ai/A (2.84 kg ai/ha) to the other treated plot. The application rates represent 

~1x and 2x the proposed maximum seasonal rate to bushberries. All applications were made 
S-Metolachlor Summary of Analytical Chemistry and Residue Data DP#: 369005

Page 28 of 52

using ground equipment, in 17-37 gal/A (155-346 L/ha) spray volumes, without an adjuvant. 

Commercially mature berries were collected 27-33 days after application.

Samples of blueberry were analyzed for residues of metolachlor and its metabolites as derivatives 

CGA-49751 and CGA-37913 using an adequate GC/MS method (CGA-49751) or GC/NPD 

method (CGA-37913). The LLMV was 0.05 ppm for CGA-49751 and 0.03 ppm for CGA37913. The combined LLMV was 0.10 ppm total metolachlor residues, expressed as metolachlor 

equivalents. Sample storage conditions and durations are reported in Table 4. Adequate storage 

stability data are available to support the blueberry field trials.

The results of the blueberry field trials are summarized in Table 6. Following a single soil 

banded application of the 7.64 lb/gal EC formulation to highbush blueberries at 1.25-1.38 lb ai/A 

(1.41-1.54 kg ai/ha), residues of CGA-49751 and CGA-37913 were each below the LLMV 

(<0.05 ppm for CGA-49751 and <0.03 ppm for CGA-37913) in/on all samples of highbush 

blueberry harvested 27-33 days following application; total metolachlor residues were below the 

combined LLMVs (<0.10 ppm in metolachlor equivalents). Residues of CGA-49751 were 

nondetectable (<0.023 ppm) in/on all highbush blueberry samples from this treatment rate; 

residues of CGA-37913 residues were nondetectable (<0.009 ppm) in 14 of 20 samples. 

Following treatment at the higher rate of 2.42-2.76 lb ai/A (2.71-3.09 kg ai/ha), residues of CGA49751 and CGA-37913 were <0.05-0.080 and <0.03-0.047 ppm, respectively, in/on highbush 

blueberry; total metolachlor residues were <0.13-0.21 ppm, expressed as metolachlor 

equivalents. In these samples, residues of CGA-49751 were nondetectable in 15 of 20 samples 

and residues of CGA-37913 were nondetectable in 11 of 20 samples.

In the single trial using a lowbush blueberry variety, reflecting a single foliar broadcast 

application of the 7.64 lb/gal EC formulation at a rate of 1.22 lb ai/A (1.36 kg ai/ha), residues of 

CGA-49751 were 0.295 and 0.321 ppm, and residues of CGA-37913 were 0.394 and 0.463 ppm 

in/on lowbush blueberry harvested at a 29-day PHI; total metolachlor residues were 0.90 and 1.0 

ppm. Following treatment at the higher rate of 2.54 lb ai/A (2.84 kg ai/ha), residues of CGA47951 were 0.541 and 0.553 ppm, and residues of CGA-37913 were 0.626 and 0.595 ppm in/on 

lowbush blueberry; total metolachlor residues were 1.6 and 1.4 ppm.

No decline trials were conducted.

Conclusions. The submitted field trial data are not adequate to support the proposed uses on the 

bushberry subgroup because only one field trial reflecting broadcast foliar application on 

lowbush blueberry was conducted. 

The number and locations of field trials are in accordance with OPPTS Guideline 860.1500 for 

blueberry, but are not in accordance with PMRA Directive 98-02, Section 9 for blueberry; three 

additional trials would be needed in Zone 1A. No decline trials will be required to support use 

on highbush blueberry because residues were below the LOQ in/on all samples treated at 1x.

The submitted broadcast foliar data for blueberries are not adequate to support the requested 

tolerances for lowbush blueberry. In addition, the proposed use patterns differ significantly. The 

submitted banded, soil directed application data for highbush blueberry would support a 
S-Metolachlor Summary of Analytical Chemistry and Residue Data DP#: 369005

Page 29 of 52

tolerance for bushberry, subgroup 13-07B (with use on lowbush blueberry and other low bush 

varieties of berries prohibited on the label), at 0.20 ppm, expressed as total metolachlor 

equivalents. 

If the petitioner wishes to support broadcast foliar use on lowbush blueberry, two additional crop 

field trials must be submitted before a tolerance may be established – one additional trial in 

Region 1, one additional trial in Region 5. Alternatively, with the additional field trial data 

reflecting broadcast foliar use, the petitioner may wish to submit data and propose a tolerance for 

the low growing berry, except strawberry, subgroup 13-07H. . Four additional field trials, 

conducted on lowbush blueberry or cranberry would be required.

The tolerance for S-metolachlor residues on the bushberry subgroup can be established, provided 

the use is limited to banded application directed at the soil, and use on low-bush blueberries is 

deleted from the label.

Caneberry, subgroup 13-07A

47829403.der.doc

IR-4 has submitted field trial data for S-metolachlor on blackberry and raspberry, the 

representative crops of the caneberry subgroup 13-07A. Five caneberry trials were conducted in 

the U.S. in Zones 1 (PA; 1 trial), 5 (MI; 1 trial), and 12 (OR; 3 trials) during the 1998 growing 

season. One trial used a blackberry variety; the other trials used raspberry varieties. 

Each trial site consisted of one untreated plot and two treated plots. A single banded application 

of a 7.62 lb/gal EC formulation of S-metolachlor was made to the soil surface on both sides of 

the cane at 2.60-2.72 lb ai/A (2.92-3.04 kg ai/ha) at one of the treated plots or at 3.85-4.05 lb 

ai/A (4.31-4.54 kg ai/ha) at the other treated plot. The application rates represent ~0.8x and 1x 

the proposed maximum seasonal rate to caneberry. Applications were made using ground 

equipment, in 21-42 gal/A (194-395 L/ha) spray volumes, without an adjuvant. Commercially

mature berries were collected 28-30 days after application.

Samples of caneberry were analyzed for residues of metolachlor and its metabolites as 

derivatives CGA-49751 and CGA-37913 using an adequate GC/NPD method. The LLMV was 

0.05 ppm for CGA-49751 and 0.03 ppm for CGA-37913. The combined LLMV was 0.10 ppm 

total metolachlor residues, expressed as metolachlor equivalents. Sample storage conditions and 

durations are reported in Table 4. Adequate storage stability data are available to support the 

caneberry field trials. 

The results of the caneberry field trials are summarized in Table 6. Residues of the metolachlor 

derivatives CGA-49751 and CGA-37913 were each below the respective LLMV (<0.05 or <0.03 

ppm) in/on all samples of caneberry harvested 28-30 days following a single banded application 

of the 7.62 lb/gal EC formulation at 2.60-2.72 lb ai/A (2.92-3.04 kg ai/ha) or 3.85-4.05 lb ai/A 

(4.31-4.54 kg ai/ha). Residues, expressed as total metolachlor equivalents, were below the 

combined LLMVs (<0.10 ppm) in/on all treated caneberry samples. 

No decline trials were conducted; however, decline trials are not required given that all residues 

were nonquantifiable.
S-Metolachlor Summary of Analytical Chemistry and Residue Data DP#: 369005

Page 30 of 52

Conclusions. The submitted field trial data are tentatively adequate to support the proposed uses 

on the caneberry subgroup.

The number and locations of field trials are in accordance with OPPTS Guideline 860.1500 for 

caneberry subgroup 13-07A but not in accordance with PMRA Directive 98-02, Section 9 for 

raspberry; one additional trial would be needed in Zone 5B. The submitted data support a single 

postemergence banded (to the soil) application of S-metolachlor to caneberry at up to 3.8 lb ai/A 

with a 28-day PHI. The submitted data will support a tolerance for S-metolachlor residues in/on 

the caneberry subgroup 13-07A of 0.10 ppm.

Carrot

47829408.der.doc

IR-4 has submitted field trial data for S-metolachlor on carrot. Fourteen trials were conducted in 

the U.S. and Canada in Zones 1A (PE; 1 trial), 2 (GA; 1 trial), 3 (FL; 1 trial), 5 (ON, WI; 3 

trials), 5B (QC; 2 trials), 6 (TX; 1 trial), 10 (CA; 4 trials), and 11 (WA; 1 trial) during the 2004 

growing season. 

Each trial site consisted of one untreated plot and two treated plots. A single foliar broadcast 

application of a 7.64 lb/gal EC formulation of S-metolachlor was made to carrot plants, at 

approximately the 3- to 5-leaf stage, at either 0.61-0.71 lb ai/A (0.68-0.79 kg ai/ha) or 1.23-1.36 

lb ai/A (1.38-1.52 kg ai/ha). The application rates represent ~0.5x and 1x the proposed 

maximum seasonal rate to carrot. Applications were made using ground equipment in ~25-39 

gal/A (238-363 L/ha) spray volumes, without an adjuvant. Mature carrot root was harvested 26-

121 days following application.

Samples of carrot were analyzed for residues of metolachlor and its metabolites as derivatives 

CGA-49751 and CGA-37913 using an adequate LC/MS/MS method, modified Method No. 

1848-01. The LLMV was 0.05 ppm for each analyte based on fortifications with SYN508500 

and SYN506357. The combined LLMV was 0.13 ppm total metolachlor residues, expressed as 

metolachlor equivalents. Sample storage conditions and durations are reported in Table 4. 

Adequate storage stability data are available to support the carrot field trials.

The results of the carrot field trials are summarized in Table 6. Residues of CGA-49751 were 

below the LLMV (<0.05 ppm) and residues of CGA-37913 were <0.05-0.078 ppm in/on carrot

roots harvested 26-121 days following a single foliar broadcast application of the 7.64 lb/gal EC 

formulation at 0.61-0.71 lb ai/A (0.68-0.79 kg ai/ha); total metolachlor residues were <0.13-0.17 

ppm, expressed as metolachlor equivalents. 

Following a single foliar broadcast application of the 7.64 lb/gal EC formulation at the higher 

rate of 1.23-1.36 lb ai/A (1.38-1.52 kg ai/ha), residues of CGA-49751 were <0.05-0.132 ppm and 

residues of CGA-37913 were <0.05-0.169 ppm in/on carrot roots harvested 26-121 days 

following treatment; total metolachlor residues were <0.13-0.38 ppm, expressed as metolachlor 

equivalents.
S-Metolachlor Summary of Analytical Chemistry and Residue Data DP#: 369005

Page 31 of 52

No decline trials were conducted; however, because applications are made early in the growth 

stage, no decline trials are required.

Conclusions. The submitted field trial data are tentatively adequate to support the proposed uses 

on carrot.

The number and locations of field trials are in accordance with OPPTS Guideline 860.1500 and 

PMRA Directive 98-02, Section 9 for carrot.

Crop field trial data for carrot have been submitted previously. Under PP#7E04916 

(DP# 292881, 8/15/03, S. Kinard), adequate carrot data were submitted reflecting a single 

preemergence application of metolachlor (racemic mixture) to carrots grown in muck soils at 2.0-

8.0 lb ai/A, equivalent to 1.25-3.0 lb ai/A S-metolachlor (requested application rate was 2.5 lb 

ai/A S-metolachlor). Combined residues, expressed as parent equivalents, were <0.04-0.115 

ppm in/on carrots harvested 64-91 days following treatment. HED concluded that the data were 

adequate to support a 0.2-ppm tolerance provided application was limited to carrots grown in 

muck soils. Under PP#3E6787 (DP# 296904, 4/17/06, R. Loranger), adequate field trial data for 

carrot and radish were submitted reflecting a single broadcast preplant incorporated or 

preemergence application of S-metolachlor at 1.3 lb ai/A. Samples were analyzed for combined 

S-metolachlor residues SYN506357 and SYN508500 using the LC/MS/MS method, Method No. 

1848-01, which separated the S-enantiomers of the derivatives from the R-enantiomers. 

Combined residues, expressed as S-metolachlor equivalents, were <0.08 ppm in/on radish root 

and <0.08-0.27 ppm in/on carrot root harvested 71-171 days following treatment. HED 

concluded that the data were adequate to support a 0.3 ppm tolerance for the root vegetable, 

except sugar beet, subgroup 1B.

The submitted data support a single postemergence foliar application of S-metolachlor to carrot 

at up to 1.3 lb ai/A, provided that application is only made to carrots up to the 5-leaf growth 

stage. The available data for carrot support the proposed preemergence applications at up to 1.3 

lb ai/A for carrots grown in mineral soils and up to 1.9 lb ai/A for carrots grown in muck soils, 

but do not support postemergence applications to carrots grown in muck soils at rates >1.3 lb 

ai/A. 

The submitted data will support a tolerance for S-metolachlor residues in/on carrot of 0.4 ppm, 

expressed as metolachlor. The existing tolerance for crop subgroup 1B will need to be revised to 

exclude carrot.

Although the previously requested uses were not added to the Section 3 labels for EPA Reg. Nos. 

100-816 or 100-818, 24(c) labels with these uses were issued (based on an OPPIN search). The 

same situation applies to onions (discussed below).

Cucumber

47829407.der.doc

IR-4 has submitted field trial data for S-metolachlor on cucumber. Twelve trials were conducted 

in the U.S. and Canada in Zones 2 (GA, MD, NC; 3 trials), 3 (FL; 1 trial), 4 (TN; 1 trial), 5 (ON; 
S-Metolachlor Summary of Analytical Chemistry and Residue Data DP#: 369005

Page 32 of 52

2 trials), 5B (QC; 2 trials), 6 (TX; 1 trial), 10 (NM; 1 trial), and 12 (BC; 1 trial) during the 2005 

growing season. 

Each trial site consisted of one untreated plot and four treated plots. A single application of a 

7.64 lb/gal EC formulation of S-metolachlor was made to each plot. At two plots, a 

preemergence broadcast application was made to the soil surface 0-4 days after planting at 0.92-

1.00 lb ai/A (1.03-1.12 kg ai/ha) or 1.22-1.36 lb ai/A (1.36-1.51 kg ai/ha). At the other two 

treatment plots, foliar broadcast applications were made early post-emergence (1-2 leaf stage) at 

0.89-1.00 lb ai/A (1.00-1.12 kg ai/ha) or 1.22-1.31 lb ai/A (1.36-1.47 kg ai/ha). The application 

rates represent ~0.8x and 1x the proposed maximum seasonal rate to cucumber. Applications 

were made using ground equipment in ~16-34 gal/A (145-317 L/ha) spray volumes, without an 

adjuvant. Mature cucumbers were harvested 32-52 days after postemergence treatment, and 45-

76 days after preemergence treatment. Low crop yields (due to phytotoxicity) prevented 

collection of samples from a total of 6 plots (one treated preemergence at the low rate, two 

treated preemergence at the high rate, one treated postemergence at the low rate, and two treated 

postemergence at the high rate); in addition, at one plot (treated preemergence at the low rate), 

only one sample could be collected. 

Samples of cucumber were analyzed for residues of metolachlor and its metabolites as 

derivatives CGA-49751 and CGA-37913 using an adequate LC/MS/MS method, modified 

Method No. 1848-01. The LLMV was 0.05 ppm for each analyte based on fortifications with 

SYN508500 and SYN506357. The combined LLMV was 0.13 ppm total metolachlor residues, 

expressed as metolachlor equivalents. Sample storage conditions and durations are reported in 

Table 4. Adequate storage stability data are available to support the cucumber field trials.

The results of the cucumber field trials are summarized in Table 6. Residues of CGA-49751 and 

CGA-37913 were each below the LLMV (<0.05 ppm) in/on all cucumber samples harvested 32-

76 days following a single preemergence soil broadcast application or early postemergence foliar 

broadcast application of the 7.64 lb/gal EC formulation at 0.89-1.00 lb ai/A (1.00-1.12 kg ai/ha) 

or at the higher rate of 1.22-1.36 lb ai/A (1.36-1.51 kg ai/ha). Total metolachlor residues, in 

metolachlor equivalents, were below the combined LLMVs (<0.13 ppm) in/on all treated 

cucumber samples. 

No decline trials were conducted; however, no decline trials are required given that all residues 

were nonquantifiable and applications were made at an early growth stage.

Conclusions. The submitted field trial data are adequate to support the proposed uses on 

cucumber. The number and locations of field trials are in accordance with OPPTS Guideline 

860.1500 and PMRA Directive 98-02, Section 9 for cucumber. 

The submitted data support a single postemergence foliar application of S-metolachlor to 

cucumber at up to 1.3 lb ai/A, provided that application is only made to cucumber up to the 2-

leaf growth stage. The submitted data will support a tolerance for S-metolachlor residues in/on 

cucumber of 0.13 ppm, expressed as metolachlor equivalents.
S-Metolachlor Summary of Analytical Chemistry and Residue Data DP#: 369005

Page 33 of 52

Leafy Brassica greens, subgroup 5B

47829406.der.doc

IR-4 has submitted field trial data for S-metolachlor on mustard greens as the representative crop 

of the Brassica leafy greens, subgroup 5B. Twelve trials were conducted on mustard greens in 

the U.S. and Canada in Zones 2 (NJ, NC; 3 trials), 3 (FL; 1 trial), 4 (TN; 1 trial), 5 (MI, ON; 3 

trials), 6 (TX; 1 trial), 10 (CA; 2 trials), and 12 (BC; 1 trial) during the 2004 growing season. 

Each trial site consisted of one untreated plot and four treated plots. A single application of a 

7.64 lb/gal EC formulation of S-metolachlor was made to each plot. At two plots, a 

preemergence broadcast application was made to the soil surface 0-5 days after planting at 0.63-

0.66 lb ai/A (0.71-0.74 kg ai/ha) or 1.21-1.38 lb ai/A (1.35-1.54 kg ai/ha). At the other two 

treatment plots, foliar broadcast applications were made early postemergence (1-2 leaf stage) at 

0.61-0.68 lb ai/A (0.69-0.76 kg ai/ha) or 1.24-1.35 lb ai/A (1.39-1.51 kg ai/ha). The application 

rates represent ~0.5x and 1x the proposed maximum seasonal rate to leafy greens. Applications 

were made using ground equipment in ~19-42 gal/A (178-389 L/ha) spray volumes, without an 

adjuvant. Mature mustard greens were harvested 20-40 days following postemergence 

application or 33-62 days following preemergence application.

Samples of mustard greens were analyzed for residues of metolachlor and its metabolites as 

derivatives CGA-49751 and CGA-37913 using an adequate LC/MS/MS method, modified 

Method No. 1848-01. The LLMV was 0.05 ppm for each analyte based on fortifications with 

SYN508500 and SYN506357. The combined LLMV was 0.13 ppm total metolachlor residues, 

expressed as metolachlor equivalents. Sample storage conditions and durations are reported in 

Table 4. Adequate storage stability data are available to support the mustard greens field trials.

The results of the mustard greens field trials are summarized in Table 6. Residues of CGA49751 and CGA-37913 were <0.05-0.065 and <0.05-0.107 ppm, respectively, in/on mustard 

greens harvested 33-62 days following a single preemergence soil broadcast application of the 

7.64 lb/gal EC formulation at 0.63-0.66 lb ai/A (0.71-0.74 kg ai/ha); total metolachlor residues 

were <0.13-0.23 ppm, expressed as metolachlor equivalents. Following a preemergence soil 

application at the higher rate of 1.21-1.38 lb ai/A (1.35-1.54 kg ai/ha), residues of CGA-49751 

and CGA-37913 were <0.05-0.188 and <0.05-0.244 ppm, respectively, in/on mustard greens 

harvested 33-62 days after treatment; total metolachlor residues were <0.13-0.57 ppm, expressed 

as metolachlor equivalents.

Residues of CGA-49751 and CGA-37913 were <0.05-0.056 and <0.05-0.134 ppm, respectively, 

in/on mustard greens harvested 20-40 days following a single early postemergence foliar 

broadcast application of the 7.64 lb/gal EC formulation at 0.61-0.68 lb ai/A (0.69-0.76 kg ai/ha); 

total metolachlor residues were <0.13-<0.25 ppm, expressed as metolachlor equivalents. 

Following an early postemergence foliar application at the higher rate of 1.24-1.35 lb ai/A (1.39-

1.51 kg ai/ha), residues of CGA-49751 and CGA-37913 were <0.05-0.172 and <0.05-0.552 ppm, 

respectively, in/on mustard greens harvested 20-40 days after treatment; total metolachlor 

residues were <0.13-0.94 ppm, expressed as metolachlor equivalents.

Residues were generally higher in samples treated early postemergence (foliar application), than 

in those treated preemergence (soil application).
S-Metolachlor Summary of Analytical Chemistry and Residue Data DP#: 369005

Page 34 of 52

No decline trials were conducted however, no decline trials are required because applications 

were made at an early growth stage. In addition, previously submitted residue decline data for 

sorghum forage indicated that combined residues decreased with increasing sampling intervals 

(DP#s 332846, etc., 10/21/08, D. McNeilly).

Conclusions. The submitted field trial data are tentatively adequate to support the proposed uses 

on leafy Brassica greens. 

The number and locations of field trials are in accordance with OPPTS Guideline 860.1500 for 

mustard greens as a representative crop of subgroup 5B; PMRA does not specify any field trial 

requirements for mustard greens. The submitted data support a single postemergence foliar 

application of S-metolachlor to leafy Brassica greens at up to 1.3 lb ai/A, provided that 

application is only made to crops up to the 2-leaf growth stage. The submitted data will support 

a tolerance for S-metolachlor residues in/on leafy Brassica greens at 1.8 ppm. 

HED now considers turnip greens to be a member of the leafy Brassica greens subgroup. 

Pending revision of 40 CFR §180.41, a separate tolerance must be established for turnip greens, 

at the same level as the tolerance for leafy Brassica greens. 

Melon, subgroup 9A

47829402.der.doc

IR-4 has submitted field trial data for S-metolachlor on cantaloupe as the representative crop of 

the melon subgroup 9A. Eleven cantaloupe trials were conducted in the U.S. and Canada in 

Zones 2 (NJ, NC; 2 trials), 5 (MI, ON; 2 trials), 5B (QC; 1 trial), 6 (TX; 2 trials), and 10 (CA, 

NM; 4 trials) during the 2003 growing season. 

Each trial site consisted of one untreated plot and two treated plots. At one of the treated plots, a 

single banded application of a 7.64 lb/gal EC formulation of S-metolachlor was made to the row 

middles 1-4 days after planting (preemergence) or 0-14 days prior to transplanting of cantaloupes 

(cantaloupes were planted at 5 sites and transplanted at 6 sites). At the other treated plot, a single 

broadcast application of the 7.64 lb/gal EC formulation was made to the soil after planting or 

prior to transplanting of cantaloupes. At five trial sites, cantaloupes were grown in plastic 

mulch; at these sites, broadcast applications were made before and banded applications were 

made after the laying of the plastic mulch. Application rates ranged 1.23-1.46 lb ai/A (1.38-1.64 

kg ai/ha; ~1x the proposed maximum seasonal rate to melons), and were made using ground 

equipment in 20-40 gal/A (186-378 L/ha) spray volumes, without an adjuvant. Commercially

mature cantaloupes were collected 61-112 days after application.

Samples of cantaloupe were analyzed for residues of metolachlor and its metabolites as 

derivatives CGA-49751 and CGA-37913 using an adequate LC/MS/MS method. The LLMV 

was 0.05 ppm for CGA-49751 and 0.03 ppm for CGA-37913 in cantaloupe. The combined 

LLMV was 0.10 ppm total metolachlor residues, expressed as metolachlor equivalents. Sample 

storage conditions and durations are reported in Table 4. Adequate storage stability data are 

available to support the cantaloupe field trials.
S-Metolachlor Summary of Analytical Chemistry and Residue Data DP#: 369005

Page 35 of 52

The results of the cantaloupe field trials are summarized in Table 6. Residues of CGA-49751 

and CGA-37913 were each below the LLMV (<0.05 ppm for CGA-49751 and <0.03 ppm for 

CGA-37913) in/on all cantaloupe samples harvested 61-112 days following a single 

preemergence or pre-transplant, banded or soil broadcast application of the 7.64 lb/gal EC 

formulation at 1.23-1.46 lb ai/A (1.38-1.64 kg ai/ha). Total metolachlor residues were below the 

combined LLMVs (<0.10 ppm, expressed as metolachlor equivalents) in/on all treated 

cantaloupe samples. 

No decline trials were conducted; however, decline trials are not required given that all residues 

were nonquantifiable and applications were made early in the growth stage.

Conclusions. The submitted field trial data are adequate to support the proposed uses on melon 

subgroup 9A.

The number and locations of field trials are in accordance with OPPTS Guideline 860.1500 for 

cantaloupe as a representative crop of subgroup 9A, and for PMRA Directive 98-02, Section 9 

for melon. The submitted data support a single preemergence or pre-transplant broadcast or 

banded (to the soil) application of S-metolachlor to melon at up to 1.2 lb ai/A. The submitted 

data will support a tolerance for S-metolachlor residues in/on melon subgroup 9A at 0.10 ppm in 

metolachlor equivalents.

Okra

D296904.mem.doc, PP#3E6787, 4/17/06, R. Loranger

No field trial data were submitted to support the requested use on okra. The petitioner is relying 

on previously submitted residue data for fruiting vegetables to support the proposed use on okra.

Residue data for S-metolachlor on fruiting vegetables were submitted under PP#3E6787 

(DP# 296904, 4/17/06, R. Loranger). In a total of 50 tests conducted at 21 field locations in 

2002, a 7.6 lb/gal EC formulation of S-metolachlor was applied as single application at 1.62-1.79 

lb ai/A to bell peppers (15 tests), hot peppers (8 tests), and tomatoes (27 tests). Three different 

treatment regimes were used with 2 or 3 different types of applications used in side-by-side tests 

at each trial site on each crop. The different applications included either a preplant incorporated 

(PPI) application prior to transplanting, or a broadcast postemergence application at the 8- to 10-

leaf stage (early) or prior to fruit set (late). Duplicate samples of mature tomato, bell pepper, and 

hot pepper samples were collected 73-130 days and 89-149 days following the PPI application, 

39-89 days and 54-103 days following the early postemergence application, and 40-64 days and 

69-80 days following the later postemergence application. Samples were analyzed for combined 

S-metolachlor residues SYN506357 and SYN508500 using the LC/MS/MS method, Method No. 

1848-01, which separated the S-enantiomers of the derivatives from the R-enantiomers. The 

combined residues of SYN506357 and SYN508500, expressed as parent equivalents, were <0.08 

ppm (<LOQ) in/on all bell pepper (n=60), hot pepper (n=32), and tomato (n=106) samples from 

all tests. The established tolerance for S-metolachlor residues in/on the fruiting vegetable group, 

except tabasco pepper, is 0.10 ppm [180.368(a)(2)]; a separate tolerance for tabasco pepper has 

been established because the use pattern on tabasco peppers is substantially different from that 

for the other members of the fruiting vegetable crop group.
S-Metolachlor Summary of Analytical Chemistry and Residue Data DP#: 369005

Page 36 of 52

The proposed use on okra is similar to the supported use on the fruiting vegetables crop group 

(except tabasco pepper): a single postemergence application at the maximum rate of 1.9 lb ai/A 

with a 60-day PHI. HED has approved adding okra to the fruiting vegetable crop group (see 

minutes of the ChemSAC meeting of 10/18/06). Until 40 CFR §180.41 is updated, a separate 

tolerance must be established for okra. The available field trial data for fruiting vegetables may

be translated to okra; these data would support a tolerance of 0.10 ppm for okra. 

Onion, bulb, subgroup 3-07A and onion, green, subgroup 3-07B

D296904.mem.doc, PP#3E6787, 4/17/06, R. Loranger

No field trial data were submitted to support the requested uses on onion subgroups 3-07A and 3-

07B. The petitioner is relying on previously submitted residue data for bulb onion, the 

representative commodity of subgroup 3-07A, and green onion, the representative commodity of 

subgroup 3-07B, to support the proposed uses. 

Residue data for S-metolachlor on onions were submitted under PP#3E6787 (DP# 296904, 

4/17/06, R. Loranger). A total of 11 field trials were conducted on green and dry bulb onions 

during the 2002/2003 growing season. In the 5 green onion tests, a 7.6 lb/gal EC formulation of 

S-metolachlor was applied as a single postemergence application at the 2- to 6-leaf stage at 1.29-

1.33 lb ai/A (1x the maximum proposed rate for subgroup 3-07B), in a volume of 2-26 gal/A. In 

the 6 dry bulb onion tests, a 7.6 lb/gal EC formulation of S-metolachlor was applied as two 

postemergence applications at 1.27-1.34 lb ai/A/application at retreatment intervals of 21-53 

days, for a total of 2.58-2.68 lb ai/A/season (~1x the maximum proposed rate for subgroup 3-

07A), in a volume of 15-29 gal/A. The initial application to bulb onions was made at the 2- to 6-

leaf stage. Duplicate treated samples of green onions were harvested 21-22 days following 

treatment from four tests and 50 days following treatment from one test, and duplicate treated 

samples of dry bulb onions were harvested at 54-62 days following treatment. Samples were

analyzed for combined S-metolachlor residues SYN506357 and SYN508500 using the 

LC/MS/MS method, Method No. 1848-01, which separated the S-enantiomers of the derivatives 

from the R-enantiomers. Residues were reported in S-metolachlor equivalents.

Following a single postemergence application at 1.3 lb ai/A, the combined S-metolachlor 

residues were 0.16-1.76 ppm in/on 8 samples of green onions collected 21-22 days posttreatment 

(proposed PHI) from four of the five tests. In the other green onion test, combined residues were 

0.10 and 0.32 ppm in/on two samples collected 50 days posttreatment. Following the last of two 

postemergence applications totaling ~2.6 lb ai/A, combined S-metolachlor residues were <0.08-

<0.09 ppm in/on 12 samples of bulb onion samples collected at 54-62 days posttreatment. Based 

on these data, tolerances were established for S-metolachlor residues in/on garlic bulb, bulb 

onion, and shallot bulb at 0.10 ppm, and in/on green onion at 2.0 ppm.

The proposed use on bulb onion subgroup 3-07A is identical to the supported use on bulb onion 

and the proposed use on the green onion subgroup 3-07B is identical to the supported use on 

green onion. The available data for bulb onion are adequate to support use on the bulb onion 

subgroup 3-07A and the available data for green onion are adequate to support use on the green 

onion subgroup 3-07B. The proposed tolerances of 0.10 ppm for subgroup 3-07A and 2.0 ppm 

for subgroup 3-07B are appropriate. When these tolerances are established, the existing 
S-Metolachlor Summary of Analytical Chemistry and Residue Data DP#: 369005

Page 37 of 52

tolerances under 180.368(a)(2) for the following commodities should be removed: garlic, bulb; 

onion, bulb; onion, green; and shallot, bulb.

Sesame

47829401.der.doc

IR-4 has submitted field trial data for S-metolachlor on sesame. Four sesame field trials were 

conducted in the U.S. in Zone 6 (TX) during the 2000 growing season. All four trials were 

conducted in the same county; two of the trials were conducted on the same tract of land, and the 

other two trials were conducted nearby, on plots in close proximity to each other. 

Each trial site consisted of one untreated plot and one treated plot. A single broadcast 

application of a 7.62 lb/gal EC formulation of S-metolachlor was made to the soil surface 3-4 

days after planting (preemergence) at 1.99-2.02 lb ai/A (2.23-2.26 kg ai/ha), 1x the proposed 

maximum seasonal rate to sesame. Applications were made using ground equipment, in 20-22 

gal/A (188-208 L/ha) spray volumes, without an adjuvant. Mature sesame seed was harvested 

101-128 days after application.

Samples of sesame seed were analyzed for residues of metolachlor and its metabolites as 

derivatives CGA-49751 and CGA-37913 using an adequate LC/MS/MS method. The LLMV 

was 0.05 ppm for each analyte. The combined LLMV was 0.13 ppm total metolachlor residues, 

expressed as metolachlor equivalents. Sample storage conditions and durations are reported in 

Table 4. Adequate storage stability data are available to support the sesame field trials.

The results of the sesame field trials are summarized in Table 6. Residues of CGA-49751 and 

CGA-37913 were each below the LLMV (<0.05 ppm) in/on sesame seed harvested 101-128 days 

following a single preemergence soil broadcast application of the 7.62 lb/gal EC formulation at 

1.99-2.02 lb ai/A (2.23-2.26 kg ai/ha). Total metolachlor residues were below the combined 

LLMVs (<0.13 ppm, expressed as metolachlor equivalents) in/on all treated sesame seed 

samples.

Conclusions. The submitted field trial data are tentatively adequate to support the proposed uses 

on sesame.

HED concludes that the submitted field trials reflect only two field trial sites; the two trials 

conducted on the same tract of land reflect one site and the other two trials, which were 

conducted in close proximity, reflect a second site. According to “Food and Feed Crops of the 

United States” (G.M. Markle, J.J. Baron, and B.A. Schneider. Second Edition, Meister 

Publishing Co. 1998), sesame is grown in Zones 6, 8, and 10. The petitioner has stated that the 

request for S-metolachlor use on sesame was made on behalf of the Agricultural Experiment 

Stations of OK and TX. The two field trials are adequate to reflect use on sesame.

The submitted data support a single preemergence application of S-metolachlor to sesame at up 

to 1.9 lb ai/A. The submitted data will support a tolerance for S-metolachlor residues in/on 

sesame seed at 0.13 ppm.
S-Metolachlor Summary of Analytical Chemistry and Residue Data DP#: 369005

Page 38 of 52

Sorghum, sweet

47829405.der.doc

D332846.mem.doc, 10/21/08, D. McNeilly

IR-4 has submitted field trial data for S-metolachlor on sweet sorghum. Three trials were 

conducted in the U.S. in Zones 4 (TN; 2 trials) and 6 (TX; 1 trial) during the 2005 growing 

season. The two TN trials were conducted in very close proximity, with the same study director 

and personnel; applications were made one day later in the second TN trial but all TN samples 

were harvested on the same day; therefore, HED concludes that the two TN trials only represent 

one field site. 

Each trial site consisted of one untreated plot and four treated plots. A single application of a 

7.64 lb/gal EC formulation of S-metolachlor was made to each plot. At two plots, a 

preemergence broadcast application was made to the soil surface 0-2 days after planting at 1.00-

1.02 lb ai/A (1.12-1.15 kg ai/ha) or 1.68-1.72 lb ai/A (1.88-1.93 kg ai/ha); the application rates 

represent ~0.6x and 1x the proposed maximum single preemergence application rate to sweet 

sorghum. At the other two treatment plots, a single foliar broadcast application was made early

postemergence (seedling stage) at 0.64-0.65 lb ai/A (0.72 kg ai/ha) or 1.27-1.29 lb ai/A (1.42-

1.44 kg ai/ha); the application rates represent ~0.5x and 1x the proposed maximum single 

postemergence application rate. Applications were made using ground equipment in ~16-20 

gal/A (152-191 L/ha) spray volumes, without an adjuvant. It is noted that sorghum seed was 

treated with Concep II Herbicide Antidote (safener) prior to planting to protect the seed from the 

effects of S-metolachlor. Mature sorghum stalks were harvested 87-92 days following 

postemergence application, or 92-108 days following preemergence application.

Samples of sorghum stalk were analyzed for residues of metolachlor and its metabolites as 

derivatives CGA-49751 and CGA-37913 using an adequate LC/MS/MS method. The LLMV 

was 0.05 ppm for each analyte based on fortifications with SYN508500 and SYN506357. The 

combined LLMV was 0.13 ppm total metolachlor residues, expressed as metolachlor equivalents. 

Sample storage conditions and durations are reported in Table 4. Adequate storage stability data 

are available to support the sweet sorghum field trials.

The results of the sweet sorghum field trials are summarized in Table 6. Residues of CGA49751 and CGA-37913 were each below the LLMV (<0.05 ppm) in/on all sorghum stalk samples 

harvested 87-108 days following a single preemergence soil broadcast application of the 7.64 

lb/gal EC formulation at 1.00-1.02 lb ai/A (1.12-1.15 kg ai/ha) or 1.68-1.72 lb ai/A (1.88-1.93 kg 

ai/ha), or an early postemergence foliar broadcast application of the 7.64 lb/gal EC formulation at 

0.64-0.65 lb ai/A (0.72 kg ai/ha) or 1.27-1.29 lb ai/A (1.42-1.44 kg ai/ha). Total metolachlor 

residues were below the combined LLMVs (<0.13 ppm, expressed as metolachlor equivalents) 

in/on all treated sweet sorghum stalk samples. 

Conclusions. The submitted field trial data are adequate to satisfy data requirements. The 

number of field trials and geographic representation is adequate. 

HED has previously concluded that residues on sweet sorghum commodities will be covered by

sorghum grain and stover tolerances (see Table 1 of OPPTS 860.1000). A tolerance for Smetolachlor residues in/on sorghum grain has been established at 0.3 ppm; and a tolerance for S-
S-Metolachlor Summary of Analytical Chemistry and Residue Data DP#: 369005

Page 39 of 52

metolachlor residues in/on sorghum stover at 4.0 ppm. Field trial data for sorghum were recently

submitted in support of a request to add postemergence use to the label for the 7.62 lb/gal EC 

formulation (EPA Reg. No. 100-816); see DP#s 332846, etc., 10/21/08, D. McNeilly). In 12 

field trials conducted in Zones 2, 4, 5, 6, 7 and 8 during 2002, S-metolachlor (7.64 lb/gal EC) 

was applied to sorghum using three different application regimes, each at a target rate of 1.7 lb 

ai/A. S-Metolachlor was applied as either a PPI application at planting at 1.63-1.69 lb ai/A (Trt 

#2), a broadcast soil surface application at planting at 1.64-2.28 lb ai/A (Trt #3), or a 

postemergence foliar application when plants were ~5-inches in height at 1.64-1.71 lb ai/A (Trt 

#4). The postemergence application was tested at all 12 field sites, and the two soil applications 

were each tested at 8 of the 12 field sites. Forage, grain, and stover samples were collected at all 

sites; only the data for grain are summarized below. Residues of S-metolachlor in/on sorghum 

commodities were determined as SYN506357 and SYN508500 using an adequate LC/MS/MS 

method (Method No. 1848-01); residues were expressed in parent equivalents.

Following a PPI application at 1.63-1.69 lb ai/A (Trt #2), combined residues were <0.08-0.11 

ppm in/on grain harvested 120-149 days after treatment (DAT). Following a soil surface 

application at 1.64-2.28 lb ai/A (Trt #3), combined residues were <0.08-0.11 ppm in/on grain 

harvested 120-149 DAT. Following a post-emergence application at 1.64-1.71 lb ai/A (Trt #4), 

combined residues were <0.08-0.09 ppm in/on grain harvested 95-133 DAT.

The available data for sorghum grain may be translated to support the proposed use on sweet 

sorghum: a single preemergence application at up to 1.67 lb ai/A or a single postemergence 

application at up to 1.3 lb ai/A. The proposed use should be amended to specify that 

postemergence application may be made to crops up to 5 inches in height. A tolerance for sweet 

sorghum grain is not needed. The tolerance for sorghum, grain, stover will be translated to 

sorghum, sweet, stalk, and set at 4.0 ppm.

860.1520 Processed Food and Feed

DER References: 47829401.de2.doc (Sesame)

47829405.de2.doc (Sweet sorghum)

The petitioner submitted processing studies with sesame and sweet sorghum. The results of the 

processing studies are summarized in Table 7. 

Sesame

IR-4 submitted a processing study for S-metolachlor with sesame seed. In a sesame crop field 

trial conducted in TX during the 2000 growing season, a single broadcast application of a 7.62 

lb/gal EC formulation of S-metolachlor was made to the soil surface 4 days after planting 

(preemergence) at 2.02 lb ai/A (2.26 kg ai/ha), ~1x the proposed maximum rate. The study was 

conducted in conjunction with the sesame field trials. Mature sesame seed was harvested 128 

days after application, and processed into meal and oil using procedures simulating commercial 

practices.

Samples of sesame commodities were analyzed for residues of metolachlor and its metabolites as 

derivatives CGA-49751 and CGA-37913 using an adequate LC/MS/MS method. The LLMV 
S-Metolachlor Summary of Analytical Chemistry and Residue Data DP#: 369005

Page 40 of 52

was 0.05 ppm for each analyte in each commodity. The combined LLMV was 0.13 ppm total 

metolachlor residues, expressed as metolachlor equivalents. Sample storage conditions and 

durations are reported in Table 4. Adequate storage stability data are available to support the 

sesame processing study. 

Residues of CGA-49751 and CGA-37913 were each below the LLMV (<0.05 ppm) in/on sesame 

seed harvested 128 days following a single preemergence soil broadcast application of the 7.62 

lb/gal EC formulation at 2.02 lb ai/A (2.26 kg ai/ha); total metolachlor residues were below the 

combined LLMVs (<0.13 ppm). Residues of CGA-49751 and CGA-37913 were also below the 

LLMV in processed sesame meal and oil; therefore, processing factors could not be calculated.

No theoretical processing factors are presented for sesame in 860.1520.

Sweet sorghum

IR-4 submitted a processing study for S-metolachlor with sweet sorghum. In a sorghum crop 

field trial conducted in TX during the 2005 growing season, a single broadcast application of a 

7.64 lb/gal EC formulation of S-metolachlor, was made to the soil surface 2 days after planting 

(preemergence) at 1.72 lb ai/A (1.93 kg ai/ha), ~1x the proposed maximum rate for 

preemergence application. The study was conducted in conjunction with the sorghum field trials. 

Mature sorghum stalks were harvested 92 days following treatment, and processed into syrup 

using procedures simulating commercial practices.

Samples of sorghum stalk and syrup were analyzed for residues of metolachlor and its 

metabolites as derivatives CGA-49751 and CGA-37913 using an adequate LC/MS/MS method. 

The LLMV was 0.05 ppm for each analyte based on fortifications with SYN508500 and 

SYN506357. The combined LLMV was 0.13 ppm total metolachlor residues, expressed as 

metolachlor equivalents. Sample storage conditions and durations are reported in Table 4. 

Adequate storage stability data are available to support the sweet sorghum processing study. 

Residues of CGA-49751 and CGA-37913 were each below the LLMV (<0.05 ppm) in/on 

sorghum stalks harvested 92 days following a single preemergence soil broadcast application of 

the 7.64 lb/gal EC formulation at 1.72 lb ai/A (1.93 kg ai/ha); total metolachlor residues were 

below the combined LLMVs (<0.13 ppm, expressed as metolachlor equivalents). Average 

residues of CGA-49751 and CGA-37913 were 0.088 and 0.059 ppm, respectively, in syrup 

processed from sorghum stalks with nonquantifiable metolachlor residues; total metolachlor 

residues averaged 0.191 ppm in processed sorghum syrup. Based on the results of the sweet 

sorghum processing study, metolachlor residues appear to concentrate in sorghum syrup (>1.5x 

processing factor).

No theoretical processing factors are presented for sweet sorghum in 860.1520.
S-Metolachlor Summary of Analytical Chemistry and Residue Data DP#: 369005

Page 41 of 52

Table 7. Summary of Processing Factors for S-Metolachlor.

RAC Processed Commodity Combined Residues (ppm) Processing Factor

Sesame Seed (RAC) <0.13 Not applicable

Meal <0.13 Not calculated

Oil <0.13 Not calculated

Sweet sorghum Stalk (RAC) <0.13 Not applicable

Syrup 0.191 >1.5x

Conclusions. The submitted processing data are tentatively adequate to support the proposed 

uses on sesame and sorghum. 

Although the sesame processing study was conducted at only 1x with nonquantifiable residues in 

the RAC, it is unlikely that a study conducted at an exaggerated rate will result in quantifiable 

residues in the RAC because applications are made preemergence. The submitted data indicate 

that no tolerances will be needed for sesame processed commodities.

Combined metolachlor residues were found to concentrate in sweet sorghum syrup. However, 

HED concludes that no tolerance will be required because the observed residues in syrup (0.191 

ppm, expressed as metolachlor equivalents) processed from sorghum treated at 1x are less than 

the established tolerance for S-metolachlor residues in/on sorghum stover (4.0 ppm). 

4860.1650 Submittal of Analytical Reference Standards

Analytical standards for the following compounds related to metolachlor are currently available 

in the EPA National Pesticide Standards Repository (personal communication with Dallas 

Wright, ACB, 1/20/10; expiration data in parentheses): metolachlor (11/10/2010); S-metolachlor 

(8/1/2012); metolachlor derivative CGA-37913 (4/30/2010); metolachlor derivative CGA-49751 

(4/30/2011); metolachlor, ethane sulfonic acid sodium salt (CGA-354743, 4/1/2011); and 

metolachlor, oxanilic acid (CGA-51202, 4/1/2011).

860.1850 Confined Accumulation in Rotational Crops

D207842, 10/12/94, S. Hummel

D292881, 8/15/03, S Kinard

The data requirements for confined accumulation in rotational crops are not fulfilled. A confined 

rotational crop study with [14C]metolachlor was reevaluated by HED (DP# 207842, 10/12/94, S. 

Hummel) after review of rotational crop data was transferred to HED. It was concluded that the 

available study was inadequate but potentially upgradable. Additional data were required 

characterizing the 14C-residues in plants, along with information on the percentage of the 14Cresidues measured by the current enforcement method; sample storage conditions and intervals 

and supporting storage stability data were also required. These data requirements, which were 

reiterated in the Metolachlor TRED (DP# 292881, 8/15/03, S. Kinard), remain outstanding.

A confined rotational crop study using S-metolachlor has also been submitted. The study was 

reviewed by HED (DP# 283235, 8/15/03, S. Kinard) and found to be scientifically adequate. 

Although 14C-residue in the representative rotational crops were adequately identified and 
S-Metolachlor Summary of Analytical Chemistry and Residue Data DP#: 369005

Page 42 of 52

characterized, the [14C]-S-metolachlor was applied at only 1.45 lb ai/A, which is ~0.4x the 

maximum seasonal use rate for corn. Based on the available data, HED concluded that the 

metabolism of [14C]S-metolachlor in rotational crops is similar to the metabolism observed in the 

primary crops. Metabolism in rotational crops primarily involves two pathways: (i) conjugation 

of the parent molecule with glutathione by substitution of the chlorine, followed by the 

degradation of the glutathione moiety to form a variety of sulfur containing metabolites; and (ii) 

direct oxidation of parent or secondary metabolites, primarily on the chloroacetyl side chain. 

Complete degradation of secondary metabolites either in the soil and/or plants also resulted in the 

incorporation of molecule fragments into natural plant constituents. The residues of concern for 

both metolachlor and S-metolachlor in rotational crops are the same as for primary crops, 

metolachlor and its metabolites, determined as the derivatives CGA-37913 and CGA-49751. 

860.1900 Field Accumulation in Rotational Crops

D292881, 8/15/03, S Kinard

D332846, 10/21/08, D. McNeilly

D296904, 4/17/06, R. Loranger

Field rotational crop data have been submitted previously which are adequate to support the 

existing rotational crop restrictions on the labels for the 7.62 and 7.64 lb/gal EC formulations 

(EPA Reg. Nos. 100-816 and 100-818), provided that the restrictions on the label for EPA Reg. 

No. 100-816 are amended as specified under 860.1200 Directions for Use. In the TRED it was 

concluded that adequate residue data are available to support a PBI of 4 months for non-grass 

animal feeds and the current 1.0-ppm tolerance for rotated non-grass animal feed (DP# 292881, 

8/15/03, S. Kinard); additional data were required to support cereal grain rotational crop 

restrictions. 

In response, field rotational crop data for oats and wheat were submitted which have been 

reviewed by HED (DP#s 332846, etc., 10/21/08, D. McNeilly). Fourteen field trials were 

conducted with wheat and fifteen trials were conducted with oats. In each test, the 7.64 lb/gal 

EC formulation of S-metolachlor was applied to a primary crop of field corn as a PPI application 

at planting at 2.36-2.49 lb ai/A, followed by a second directed application at lay-by at 1.25-1.4 lb 

ai/A, for a total of 3.61-3.83 lb ai/A/season (1x the maximum use rate on corn). Wheat was 

planted ~60 days and oats were planted ~7 months following the last application. 

These field trials were considered sufficient for assessing rotational crop tolerances for small 

grains rotated with corn, which has the highest labeled use rate. Following a final lay-by

application to corn, the wheat field trials reflect a typical plant-back interval (2 months) for small 

grains that can be planted in the fall (barley, oats, rye and wheat), and the oat field trials reflect 

the typical plant-back interval (7 months) for small grains that can be planted the following 

spring (barley, oats, rice, rye and wheat).

It was concluded that the wheat and oat data support tolerances of 0.5 ppm for rotated barley hay

and straw, oat forage, hay and straw, rye forage and straw, and wheat forage, grain and straw, and 

tolerances of 0.1 ppm for the grain of rotated barley, oats, rye and wheat. For rice and 

buckwheat, which would only be rotated to the following spring (7-month PBI), the oat field trial 

data support tolerances of 0.1 ppm for rotated buckwheat grain and rice grain. 
S-Metolachlor Summary of Analytical Chemistry and Residue Data DP#: 369005

Page 43 of 52

It was also concluded that 60-day PBIs for root vegetables (subgroup 1B), tuberous and corm 

vegetables (subgroup 1C), bulb vegetables (group 3), leaf petiole vegetables (subgroup 4B), head 

and stem Brassica vegetables (subgroup 5A), fruiting vegetables (group 8), and winter squash are 

acceptable based on the available field trial data supporting the tolerances and uses of 

S-metolachlor on these crops (DP# 296904, 4/17/06, R. Loranger) provided that (i) the 

application to the previous crop was less than or equal to the maximum approved rates for the 

respective crops and crop groups, and (ii) the label directions are amended to prohibit application 

of S-metolachlor to the replanted crops. Although the first condition is met on the current label 

for EPA Reg. No. 100-816, the label directions have not yet been amended to prohibit 

application of S-metolachlor to crops planted at a 60-day PBI. 

860.1550 Proposed Tolerances

The residues of concern in plant and animal commodities include S-metolachlor, its Renantiomer, and its metabolites, determined as the derivatives CGA-37913 and CGA-49751. 

Tolerances for S-metolachlor are currently established [40 CFR §180.368(a)(2) and (d)(2)] for 

the combined residues (free and bound) of S-metolachlor, its R-enantiomer, and its metabolites, 

determined as the derivatives, CGA-37913 and CGA-47951, each expressed as parent 

compound. 

The tolerances proposed by IR-4 are listed in Table 8. The tolerance expression proposed by IR4 does not include the R-enantiomer. The tolerance expression in Section F of the submitted 

petition should be revised to include the R-enantiomer of metolachlor and to conform to current 

HED guidance (HED’s Interim Guidance on Tolerance Expressions, 5/27/09, S. Knizner): 

Tolerances are established for residues of S-metolachlor, including its metabolites and 

degradates, in or on the commodities in the table below. Compliance with the tolerance 

levels specified below is to be determined by measuring only the sum of free and bound Smetolachlor, S-2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-

methylethyl)acetamide, its R-enantiomer, and its metabolites, determined as the 

derivatives, 2-(2-ethyl-6-methylphenyl)amino-1-propanol and 4-(2-ethyl-6-methylphenyl)-

2-hydroxy-5-methyl-3-morpholinone, calculated as the stoichiometric equivalent of Smetolachlor, in or on the commodity.

No maximum residue limits (MRLs) for S-metolachlor have been established or proposed by

Codex. MRLs for S-metolachlor have been established in Canada and MRLs for metolachlor 

have been established in Mexico; however, no MRLs have been established in either country for 

the requested crops.

HED notes that a tolerance currently exists for residues of S-metolachlor in/on the root vegetable, 

except sugar beet, subgroup, 1B. When the requested tolerance for carrot is established, the 

existing tolerance for subgroup 1B must be revised to “vegetable, root, except carrot and sugar 

beet, subgroup 1B.”

The submitted broadcast foliar data for blueberries are not adequate to support the requested 

tolerances for lowbush blueberry. In addition, the proposed use patterns for the different berries 

differ significantly. The submitted banded, soil directed application data for highbush blueberry
S-Metolachlor Summary of Analytical Chemistry and Residue Data DP#: 369005

Page 44 of 52

would support a tolerance for bushberry, subgroup 13-07B (with broadcast foliar use deleted and 

use on lowbush blueberry and other low bush varieties of berries prohibited on the label), at 0.20 

ppm, expressed as total metolachlor equivalents. Additional crop field trial data must be 

submitted before a tolerance may be established to cover broadcast foliar use on lowbush 

blueberry – one additional trial in Region 1, one additional trial in Region 5; alternatively, with 

the additional field trial data reflecting broadcast foliar use, the petitioner may wish to submit 

data and propose a tolerance for the low growing berry, except strawberry, subgroup 13-07H. 

The available field trial data for fruiting vegetables may be translated to support the requested 

tolerance for okra; these data support the proposed 0.10 ppm tolerance.

Adequate data have been submitted previously to support the requested tolerances for the bulb 

onion and green onion subgroups; the proposed tolerance levels of 0.10 ppm and 2.0 ppm are 

appropriate. Concomitant with the establishment of tolerances for bulb onion subgroup 3-07A 

and green onion subgroup 3-07B, the established tolerances for S-metolachlor and its metabolites 

in/on bulb garlic (0.10 ppm), bulb onion (0.10 ppm), bulb shallot (0.10 ppm), and green onion 

(2.0 ppm) under 180.368(a)(2) should be removed.

The requested tolerance for sweet sorghum will be based on data for grain sorghum; the existing 

tolerance for S-metolachlor residues in/on sweet sorghum stover of 4.0 ppm is adequate to cover 

residues in/on sweet sorghum commodities.

The submitted processing data indicate that no tolerances are needed for S-metolachlor residues 

in the processed commodities of sesame or sweet sorghum.

HED’s tolerance calculations are different from those done by IR-4 for carrot and mustard greens 

because HED used the full value of the LLMV when calculating combined residues (IR-4 used 

1/2 LLMV for residues <LLMV when calculating combined residues for carrot and mustard 

greens). 

Table 8. Tolerance Summary for Metolachlor.

Commodity Established/

Proposed Tolerance

(ppm)

Recommended

Tolerance

(ppm)

Comments; 

Correct Commodity Definition

Proposed tolerances under §180.368(a)(2)

Blueberry, lowbush 1.4 Remove Additional data needed before tolerance 

may be established.

Bushberry subgroup 13-07B 0.15 0.15 Use must be prohibited on lowbush 

varieties, since inadequate data were 

submitted for lowbush blueberries.

Caneberry, Subgroup 13-07A 0.08 0.10 Caneberry subgroup 13-07A

Carrot 0.3 0.40

Cucumber 0.1 0.13

Leafy Brassica Greens, 

Subgroup 5B

1.2 1.8 Brassica, leafy greens, subgroup 5B

Melon subgroup 9A 0.08 0.10

Okra 0.1 0.10
S-Metolachlor Summary of Analytical Chemistry and Residue Data DP#: 369005

Page 45 of 52

Table 8. Tolerance Summary for Metolachlor.

Commodity Established/

Proposed Tolerance

(ppm)

Recommended

Tolerance

(ppm)

Comments; 

Correct Commodity Definition

Onion, Bulb, Subgroup 3-07A 0.1 0.10 Onion, bulb, subgroup 3-07A

Onion, Green, Subgroup 3-

07B

2.0 2.0 Onion, green, subgroup 3-07B

Sesame, seed 0.1 0.13

Sorghum, sweet 0.1 4.0 Sorghum, sweet, stalk

The existing tolerance for S-metolachlor 

residues in/on sorghum grain of 0.3 ppm and 

sorghum stover of 4.0 ppm is sufficient to 

cover residues in/on sweet sorghum 

commodities. The sorghum stover tolerance 

will be translated to sweet sorghum stalk. 

Turnip greens 1.2 1.7 Turnip, greens

Established tolerances under §180.368(a)(2)

Garlic, bulb 0.10 Remove Garlic will be covered by the tolerance for 

Onion, bulb, subgroup 3-07A

Onion, bulb 0.10 Remove Bulb onion will be covered by the tolerance 

for Onion, bulb, subgroup 3-07A

Onion, green 2.0 Remove Green onion will be covered by the 

tolerance for Onion, green, subgroup 3-07B

Shallot, bulb 0.10 Remove Shallot will be covered by the tolerance for 

Onion, bulb, subgroup 3-07A

Vegetable, root, except 

sugarbeet, subgroup 1B

0.30 0.30 Revise to Vegetable, root, except carrot and 

sugarbeet, subgroup 1B, since a separate, 

higher tolerance is being established on 

carrot.

References

DP#: 207842

Subject: Metolachlor (108801) Addendum to RED, Reregistration Case No. 0001. 

Confined Rotational Crop Data (GLN 165-1). CB No. 14435

From: S. Hummel

To: J. Mitchell/W. Waldrop

Dated: 10/12/94

MRID: 41470601
S-Metolachlor Summary of Analytical Chemistry and Residue Data DP#: 369005

Page 46 of 52

DP#: 226780

Subject: Replacement of Metolachlor Technical (Racemic Metolachlor) with AlphaMetolachlor (formerly called Chiral Metolachlor) Technical; Review of Bridging 

Data.

From: L. Kutney

To: R. Griffin

Dated: 11/15/96

MRIDs: 43928901-43928903, 43928939-43928942

DP#s: 278742 and 279110

Subject: S-Metolachlor. Information Supporting the Assertion That the Metabolism of 

S-Metolachlor Is Essentially the Same as for the Racemic Mixture.

From: S. Kinard

To: S. Kinard

Dated: 8/15/03

MRIDs: 45499603, 45499604, 45499605, 45533103

DP#: 283235

Subject: Sandmeier, P. (2001) Outdoor Confined Accumulation Study on Rotational Crops 

after Bare ground Application of [Phenyl-U-14C] CGA77102: Lab Project 

Number: 99PSA53; 1287-99. Unpublished study prepared by Syngenta Crop 

Protection, Inc. 252 p.

From: S. Kinard

To: N/A (DER)

Dated: 8/15/03

MRID: 45672302

DP#: 292881

Subject: PP#s: 7F04897, 9E06055, 7E04916, 2E06374, 4E04420, 8E05029, and 8E05030. 

Revised Metolachlor and S-metolachlor Residue Chemistry Chapter for the 

Tolerance Reassessment Eligibility Decision (TRED) and Registration for Use on 

Asparagus, Carrots, Cotton, Horseradish, Green Onions, Peppers, Rhubarb, Sugar 

Beet, Sunflower, and Swiss Chard.

From: S. Kinard

To: H. Jamerson

Dated: 8/15/03

MRIDs: 44378401, 44908701, 45544701

DP#: 296904

Subject: PP# 3E6787. S-Metolachlor. Petition for Tolerances on Various Crops, Crop 

Groups, and Livestock Commodities. Summary of Analytical Chemistry and 

Residue Data.

From: R. Loranger

To: B. Madden/S. Jackson

Dated: 4/17/06

MRIDs: 45499609, 45499610, 46046501-46046506
S-Metolachlor Summary of Analytical Chemistry and Residue Data DP#: 369005

Page 47 of 52

DP#s: 332846, 332847, 332848, 332849, 350604, 350942, 351174, 351226

Subject: S-Metolachlor. Amended Use Directions for Sorghum and Soybeans; Revisions 

to Rotational Crop Restrictions; Registrant’s Responses to Deficiencies Noted in 

the Revised S-Metolachlor TRED. Summary of Analytical Chemistry and 

Residue Data.

From: D. McNeilly

To: E. Wilson/J. Miller and R. Louie/N. Anderson

Dated: 10/21/08

MRIDs: 46829501-46829504, 47121701, 47121702, 47304701, 47304702

RDI: RAB4 Chemists (x/x/10)

SHummel: S10827:PY-S:(703)305-7689:7509P:RAB4

Attachments: 

International Residue Limit Status sheet

Tolerance/MRL Spreadsheet

Template Version September 2005
S-Metolachlor Summary of Analytical Chemistry and Residue Data DP#: 369005

Page 48 of 52

INTERNATIONAL RESIDUE LIMIT STATUS

Chemical Name: 2-chloroN-(2-ethyl-6-

methylphenyl)-N-[(1S)2-

methoxy-1-methylethyl]-

acetamide

Common Name: 

S-Metolachlor

X Proposed tolerance

□ Reevaluated tolerance

□ Other

Date: 1/20/10

Codex Status (Maximum Residue Limits) U. S. Tolerances

X No Codex proposal step 6 or above

□ No Codex proposal step 6 or above for the crops 

requested

Petition Number: PP#9E7607

DP#: D369005

Other Identifier: Decision No. 418569

Residue definition (step 8/CXL): N/A Reviewer/Branch: HED/RAB4 S. Hummel

Residue definition: Combined residues (free and bound) 

of S-metolachlor, its R-enantiomer, and its metabolites, 

determined as the derivatives CGA-37913 and CGA49751, calculated as parent equivalents

Crop (s) MRL (mg/kg) Crop(s) Tolerance (ppm)

Bushberry subgroup 13-07B 0.15

Caneberry, Subgroup 13-07A 0.10

Carrot 0.4

Cucumber 0.13

Leafy Brassica Greens, 

Subgroup 5-B

1.8

Melon subgroup 9A 0.10

Okra 0.13

Onion, Bulb, Subgroup 3-07A 0.10

Onion, Green, Subgroup 3-07B 2.0

Sesame, seed 0.13

Sorghum, sweet, stover 4.0

Turnip greens 1.8

Limits for Canada Limits for Mexico

□ No Limits

X No Limits for the crops requested

□ No Limits

X No Limits for the crops requested

Residue definition: 2-chloro-N-(2-ethyl-6-

methylphenyl)-N-[(1S )-2-methoxy-1-

methylethyl)acetamide and 2-chloro-N-(2-ethyl-6-

methylphenyl)-N-[(1R)-2-methoxy-1-

methylethyl)acetamide, including the metabolites 2-[(2-

ethyl-6-methylphenyl)amino]-1-propanol and 4-(2-ethyl6-methylphenyl)-2-hydroxy-5-methyl-3-morpholinone

Residue definition: Only metolachlor is listed (2004), 

and none of the requested crops.

Crop(s) MRL (mg/kg) Crop(s) MRL (mg/kg)

Notes/Special Instructions: S. Funk, 01/25/2010.
S-Metolachlor Summary of Analytical Chemistry and Residue Data DP#: 369005

Page 49 of 52

Appendix II. Tolerance Assessment Calculations.

For each of the crops listed below, the Guidance for Setting Pesticide Tolerances Based on Field 

Trial Data (SOP), along with the tolerance spreadsheet (January 2008 version), was used for 

calculating recommended tolerances. As specified in the SOP, the minimum of the 95% upper 

confidence limit (UCL) on the 95th percentile and the point estimate of the 99th percentile was 

selected as the tolerance value in cases when the dataset was large (greater than 15 samples) and 

reasonably lognormal. For datasets that were small (≤15 samples) and reasonably lognormal, the 

upper bound estimate of the 95th percentile based on the median residue value was compared to 

the minimum of the 95% UCL on the 95th percentile and the point estimate of the 99th 

percentile, and the minimum value was selected as the tolerance value. For datasets that were 

not lognormal, the upper bound on the 89th percentile was selected as the tolerance value 

(distribution-free method). The rounding procedures specified in the SOP were also used.

Mustard Greens

The datasets used to establish a tolerance for S-Metolachlor on mustard greens consisted of field 

trial data with application rates of 1.27 – 1.28 lb ai/A (applied early post-emergence) with a 33 to 

62-day PHI. The field trial application rates and PHIs reflect the maximum label application rate 

and the minimum label PHI, respectively. The residues that were entered into the tolerance 

spreadsheet are provided in Table II-1.

All except 4 field trial sample results (results for 2 field trials) for total S-metolachlor in/on 

mustard greens were above the LLMV (LLMV = 0.05 ppm for each analyte; 0.13 ppm total 

metolachlor equivalents). The field trial sample results for the 4 of 24 field trial sample results 

for garden beet roots which were below LLMV, were entered as 1⁄2 the LLMV. Visual 

inspection of the lognormal probability plot (Figure II-1) and the results from the approximate 

Shapiro-Francia test statistic (Figure II-2) indicated that the dataset was reasonably lognormal. 

Using the tolerance spreadsheet, the recommended tolerance for residues of total metolachlor is 

1.8 ppm for mustard greens.
S-Metolachlor Summary of Analytical Chemistry and Residue Data DP#: 369005

Page 50 of 52

Table II-A1. Field Trial Data Set

Regulator: EPA

Chemical: S-Metolachlor

Crop: Mustard Greens

PHI: early post-E

App. Rate: 1.27-1.28 lb ai/A

Submitter: IR-4

Residues LN(Residues) Z-scores

0.20 -1.61 -0.37

0.19 -1.66 -0.48

0.33 -1.11 0.26

0.40 -0.92 0.37

0.27 -1.31 -0.05

0.17 -1.77 -0.73

0.43 -0.84 0.60

0.52 -0.65 0.88

0.51 -0.67 0.73

0.41 -0.89 0.48

0.83 -0.19 1.50

0.94 -0.06 1.95

0.31 -1.17 0.16

0.30 -1.20 0.05

0.07 -2.73 -1.95

0.07 -2.73 -1.50

0.17 -1.77 -0.60

0.16 -1.83 -0.88

0.78 -0.25 1.24

0.75 -0.29 1.04

0.22 -1.51 -0.16

0.20 -1.61 -0.26

0.07 -2.73 -1.24

0.07 -2.73 -1.04
S-Metolachlor Summary of Analytical Chemistry and Residue Data DP#: 369005

Page 51 of 52

Lognormal Probability Plot

0.1 1 2 5 10 20 30 50 70 80 90 95 98 99 99.9

1.0000

0.5000

0.2500

0.1250

y = 0.5726x - 1.3739

R

2 = 0.9355

Percentiles

Concentrations

EPA S-Metolachlor Mustard Greens early post-E
S-Metolachlor Summary of Analytical Chemistry and Residue Data DP#: 369005

Page 52 of 52

/ Regulator: EPA

Chemical: S-Metolachlor

Crop: Mustard Greens

PHI: early post-E

App. Rate: 1.27-1.28 lb ai/A

Submitter: IR-4

n: 24

min: 0.07

max: 0.94

median: 0.29

average: 0.35

95th Percentile 99th Percentile 99.9th Percentile

0.80 1.0 1.2

(1.0) (1.2) (--)

95/99 Rule 1.1 1.8 3.5

(1.8) (4.0) (--)

1.0

Mean+3SD

1.2

UCLMedian95th

1.6

0.9492

p-value > 0.05 : Do not reject lognormality assumption

Would you like the above values rounded? (Y or N)==> Y

EU Method I

Normal

EU Method II

Distribution-Free

Approximate 

Shapiro-Francia 

Normality Test 

Statistic