Document ID: EPA-HQ-OPP-2009-0239-0004
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2009-06-29T04:00Z

S-Metolachlor.  Summary of Analytical Chemistry and Residue Data	DP#s: 
332846, 332847, 332848, 332849 

                                                                        
                                                     350604, 350942,
351174, 351226

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C.  20460

	OFFICE OF PREVENTION, PESTICIDE

	AND TOXIC SUBSTANCES

  SEQ CHAPTER \h \r 1 MEMORANDUM

Date:  Oct 21, 2008

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.

PC Code:  108800	DP Barcodes:	D332846, D332847, D332848, D332849,
D350604, D350942 D351174, D351226

Decision Nos.:	348979, 387719, 387826, 391865	Registration No.:  100-816

Petition No.:  NA	Regulatory Action: Section 3

Risk Assessment Type:  NA	Case No.:  NA

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

MRID No.: 46829501, -02 -03, -04, 47121701, 

                     -02, 47304701, -02.	40 CFR:  180.368 (a-d)(2)

	

	              									

FROM: 	Dennis McNeilly, Chemist

RAB2, Health Effects Division, (7509P)

	

THROUGH:  Douglas Dotson, Ph.D., Chemist

		RAB2, Health Effects Division (7509P)

			and

Michael Doherty, Ph.D., Senior Chemist

		RAB2, Health Effects Division (7509P)	

TO:		Eugene Wilson/Joanne Miller, RM Team 23

Herbicide Branch, Registration Division (7505P)

				and

		Rosanna Louie/Niel Anderson, RM Team 53/Acting RM 53

		Reregistration Branch 3

Special Review and Reregistration Division (7508P) 

  SEQ CHAPTER \h \r 1 This document was originally prepared under
contract by Dynamac Corporation (1910 Sedwick Road, Building 100, Suite
B; Durham, NC 27713).  The document has been reviewed by the Health
Effects Division (HED) and revised to reflect current Office of
Pesticide Programs (OPP) policies. 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 (PPI), pre-emergence, or post-emergence
application, primarily for the control of grass weeds.  S-Metolachlor is
registered to Syngenta Crop Protection, Inc. for use on corn, cotton,
grasses grown for seed, legume vegetables, peanuts, potatoes, safflower,
sorghum, sunflower, and tomatoes.  S-Metolachlor formulations registered
to Syngenta for use on these crops include emulsifiable concentrate
(EC), granular (G), flowable concentrate (FlC) and ready-to-use (RTU)
formulations.  These formulations can be applied using ground or aerial
equipment at rates ranging from 1.0-2.5 lb ai/A, depending on the soil
type, with applications over 2.0 lb ai/A typically being on soils having
high levels of organic matter.  The maximum seasonal use rate allowed on
any crop is 3.7 lb ai/A/season for corn.

For both S-metolachlor and metolachlor the residues of concern are
understood in plants and animals, they include the parent compound (both
R and S-enantiomers) and its metabolites, determined as the derivatives
CGA-37913 and CGA-49751.  Following recommendations made in the revised
Tolerance Reassessment Eligibility Decision (TRED) for Metolachlor and
S-Metolachlor (D292881, S. Kinard, 8/15/03), tolerances for metolachlor
and S-metolachlor have been separated.  Permanent tolerances for
combined S-metolachlor residues have been established in/on plant
commodities ranging from 0.1 ppm in/on a variety of plant commodities to
20 ppm in/on peanut hay [40 CFR §180.368(a)(2)].   Permanent tolerances
for indirect or inadvertent residues of S-metolachlor have also been
established for non-grass animal feeds (Group 18), and the forage, hay,
grain and straw of small cereal grains (barley, buckwheat, oats, rice,
rye and wheat).  Tolerances for rotational crops range from 0.1 ppm
in/on various cereal grains to 1.0 ppm in/on non-grass animal feeds and
hay of barley, oats and wheat [40 CFR §180.368(d)].

Syngenta has submitted new soybean and sorghum field trial data to
support proposed label amendments for the 7.62 lb/gal EC formulation
[EPA Reg. No. 100-816].  For soybeans, Syngenta is proposing to allow
for use of a postemergence application in combination with an early
season soil application.  For sorghum, Syngenta is proposing the
addition of a postemergence application to the label.  Syngenta is also
requesting changes in the labeled rotational crop restrictions based on
recently established tolerances on a variety of crops and crop groups. 
In addition, Syngenta has responded to several deficiencies noted in the
Revised S-Metolachlor TRED (8/15/03, S. Kinard) by providing residue
data on aspirated grain fractions (AGF) for corn, sorghum and soybeans;
legume vegetable (except soybeans) field trials; and extensive
rotational crop field trials on oats and wheat.  No new tolerances have
been proposed with the current submissions.

Adequate methodology is available for enforcing the current tolerances. 
The Pesticide Analytical Manual (PAM, Vol. II) lists a GC/NPD method
(Method I) for determining residues in/on plants and a GC/MSD method
(Method II) for determining residues in livestock commodities.  These
methods determine residues of S-metolachlor and its metabolites as
either CGA-37913 or CGA-49751 following acid hydrolysis.  Residue data
from the current field trials, processing studies, and rotational crop
field trials were obtained using two LC/MS/MS methods, which are derived
from the tolerance enforcement methods.  One of the methods (Method
ENC-5/99) detects and quantifies the hydrolysis products CGA-37913 and
CGA-49751; whereas, the other method (Syngenta Method No. 1848-01)
utilizes a chiral column to separate and detect SYN506357 and SYN508500
(S-enantiomers of CGA-37913 and CGA-49751).  Both methods express
residues in terms of parent equivalents, and both methods were
adequately validated in conjunction with the sample analyses.  The
validated limits of quantitation (LOQ) in each commodity tested were
0.03 ppm for CGA-37913 and 0.05 ppm for CGA-49751, for a combined LOQ of
0.08 ppm.  Although Method 1848-01 does not determine the R-isomers of
the S-metolachlor metabolites (which are included in the tolerance
expression), for the current assessments HED concludes that significant
conversion of the S-isomers to the R-forms in plants is not likely. 
Therefore, since the S:R ratio in the active ingredient is 88:12, this
method will be considered to be adequate to estimate total residues (S +
R) for tolerance determinations (i.e., the method will not significantly
underestimate total residues).  For future tolerance requests, the
petitioner is advised to generate data for both the R and S isomers of
the two analytes.

Adequate data are available on the recovery of metolachlor through
Multi-residue Method Testing Protocols.  The FDA PESTDATA database
indicates that metolachlor is completely recovered through Method 302,
PAM Vol. I (3rd ed., revised 10/97).

  SEQ CHAPTER \h \r 1 Adequate storage stability data are available for
plant commodities to support the sample storage conditions and durations
from the submitted field trials and processing studies.  Data are
available indicating that CGA-37913 and CGA-49751 are stable at
≤-10°C for at least 14 to 37 months in a variety of plant matrices,
including:  asparagus; carrots, cotton seeds and oil; corn grain, 
forage, and oil; green onions;  peanuts; potato tubers, wet peel and
flakes; soybean hulls and meal; and tomatoes.

Although HED is recommending a new tolerance for a livestock feedstuff
(i.e., AGF) and is recommending changes in several existing tolerances
on livestock feedstuffs, these changes do not have a significant impact
on the theoretical dietary burden (TDB) of livestock to S-metolachlor
residues, which were calculated in an earlier petition (D296904, R.
Loranger, 4/17/2006).  Therefore, no changes are required in the current
tolerances for animal commodities.  

The submitted sorghum and soybean field trial data are adequate and will
support the amended uses of S-metolachlor (EC) on these crops, provided
that the recommended label changes are made.  The available sorghum data
support the use of a single postemergence application of S-metolachlor
(EC) to sorghum at up to 1.6 lb ai/A, when plants are up to 5 inches in
height.  These data also support a preharvest interval (PHI) of 75 days
for forage and indicate that residues resulting from the postemergence
application will not exceed the established tolerances on sorghum
forage, grain and stover.  The soybean data support the use of an
early-season PPI, surface or preemergence soil application in
combination with a broadcast foliar application prior to bloom.  The
data support a maximum use rate of 1.3 lb ai/A for the foliar
application, a maximum seasonal use rate of 2.5 lb ai/A, and a minimum
90-day PHI for seed following the foliar application.  The data also
indicate that S-metolachlor residues from the combined applications will
not exceed the established tolerance on soybean seeds.

The submitted legume vegetable field trial data are adequate and support
the use of S-metolachlor (EC) on edible podded peas and beans (subgroup
6A), succulent shelled peas and beans (subgroup 6B), and dried shelled
peas and beans (subgroup 6C), as a single broadcast soil or PPI
application at planting or as a single broadcast foliar application. 
The data support maximum single and seasonal use rates of 1.9 lb ai/A,
and a 50-day PHI for the postemergence application.  The residue
chemistry data support establishing a Crop Group 6 tolerance at 0.3 ppm.
 This would lower the tolerance for subgroup 6A, increase the tolerance
for subgroup 6C and involve establishing a new tolerance for crop
subgroup 6B commodities at 0.3 ppm (to harmonize with metolachlor and
Canada).

The processing studies submitted in conjunction with the new soybean
field trials and the wheat and oat rotational crop field trials are
adequate.  In all three studies, combined S-metolachlor residues in/on
on the raw agricultural commodities (RACs) were <LOQ in/on soybean seeds
(1x and 5x rates), wheat grain (1x rate), and oat grain (0.7x rate). 
Residues were also <LOQ in/on all processed fractions, indicating that
separate tolerances are not required for processed commodities from
these crops.

  

The submitted aspirated grain fraction (AGF) residue data are also
adequate.  S-metolachlor residues did not concentrate in AGF derived
from corn, and concentrated (3.1x) in AGF from sorghum.  However,
residues concentrated by 3.9x in AGF from soybeans.  Based on maximum
residues of <0.17 ppm in/on soybean seeds and the above concentration
factor, HED is recommending that a tolerance be established at 0.7 ppm
for AGF.

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 and its metabolites determined as CGA-37913 and
CGA-49751. 

The submitted wheat and oat rotational crop field trials are adequate
and support reducing the minimum plant-back interval (PBI) for barley,
oats, rye and wheat from 4.5 to 2 months.  The data support the current
rotational crop tolerances for barley grain and straw, buckwheat grain,
oat forage, grain and straw, rice grain, rye forage, grain and straw,
and wheat forage, grain and straw.  The data also indicate that the
current tolerances on barley hay, oat hay and wheat hay can be reduced
to 0.5 ppm.  (Note: The tolerance on rice straw can be revoked, as
tolerances are no longer set on rice straw.)

Provided that the recommended label changes are made, the proposed
revisions to the rotational crop restrictions, allowing a 60-day PBI for
root vegetables (subgroup1B), tuberous and corm vegetables (subgroup
1C), bulb vegetables (group 3), leaf petiole vegetables (subgroup 4B),
head and stem Brassica vegetables (subgroup 5A), fruiting vegetables,
except cucurbits (group 8), and winter squash, are also acceptable.

  SEQ CHAPTER \h \r 1 Regulatory Recommendations and Residue Chemistry
Deficiencies

No major deficiencies were noted in the submitted field trials,
processing studies or rotational crop field trials that would preclude
establishing or reassessing tolerances for S-metolachlor residues in/on
soybeans, sorghum, legume vegetables (except soybean), and rotational
small cereal grains.  However, several minor deficiencies must be
resolved as a condition of registration (see below).  HED recommends
establishing a new permanent tolerance for the combined residues of
S-metolachlor and its metabolites in/on Crop Group 6, Legume Vegetables
(succulent and dried) at 0.3 ppm.  The submitted field trial data
support the existing tolerances for residues on soybean seed (0.2 ppm),
sorghum forage (1.0 ppm), stover (4.0 ppm) and grain (0.3 ppm).

The deficiencies cited in the revised S-Metolachlor TRED pertaining to
residues on corn, sorghum and soybean AGF, and residues in/on rotated
small grains have been resolved.  The available AGF residue data
indicate that a separate tolerance should be established for AGF at 0.7
ppm.  The rotational crop field trial data on wheat and oats support the
existing 0.5 ppm tolerances for barley straw, oat forage and straw, rye
forage and straw, and wheat forage and straw, and the existing 0.1 ppm
tolerances for grain of barley, buckwheat, oats, rice, rye and wheat. 
The data also indicate that the existing 1.0 ppm tolerances for barley
hay, oat hay and wheat hay can be reduced to 0.5 ppm.  In addition, the
existing 0.5 ppm tolerance for rice straw can be revoked as HED no
longer recommends for tolerances on rice straw.  The minor deficiencies
that must be resolved are listed below.  

	•	Label amendments are required for the use directions on soybeans,
sorghum, legume vegetables (except soybeans) and rotational crops (see
conclusions under Directions for Use section).

	•	The reference standards for CGA-37913 and CGA49751 at the National
Pesticide Standards Repository have expired and should be either
recertified or replaced.

	•	Although the Agency has determined that the available confined
rotational crop study is adequate, the previously requested information
from the study remains outstanding.

	•	Based on the legume vegetable field trials, a tolerance must be
proposed for Crop Group 6: Legume Vegetables (succulent and dried),
except soybean, at 0.3 ppm.

	•	Based on the AGF residue data from soybeans, a 0.7 ppm tolerance
should be established for AGF.

	•	Based on the available wheat and oat rotational crop field trials,
rotational crop tolerances for barley hay, oat hay, and wheat hay can
each be reduced to 0.5 ppm.  The tolerance for rice straw can be revoked
as HED no longer recommends for tolerances on this commodity.

A revised human health risk assessment for S-metolachlor is not needed
for the following reasons:  1) Although HED is recommending a new
tolerance for a livestock feedstuff (AGF) and is recommending changes in
several existing tolerances on livestock feedstuffs, these changes do
not have a significant impact on the theoretical dietary burden (TDB) of
livestock to S-metolachlor residues, which were calculated in an earlier
petition (D296904, R. Loranger, 4/17/2006).  No changes are required in
the current tolerance levels (which were used in the dietary assessment)
for animal commodities.  2)  The most recent dietary exposure analysis
conducted for S-metolachlor (D329632, W. Cutchin, 6/28/06) evaluated all
Crop Group 6 commodities at 0.3 ppm, which is the tolerance level being
recommended in this analysis. 3)  The existing drinking water estimate
is based on the crops with the highest seasonal application rate [turf
(s-metolachlor) and corn (racemic and s-metolachlor)] of 4.0 lbs ai/A
and covers the uses discussed in this assessment.  4)  The toxicity
profile for metolachlor and s-metolachlor have remained unchanged since
HED’s July 13, 2006 Risk Assessment for S-metolachlor (D326011, W.
Cutchin).   5)  HED has not been asked to evaluate any additional
residential uses or increased use rates for existing uses; therefore the
aggregate risk for metolachlor and s-metolachlor remain unchanged since
HED’s July 13, 2006 Risk Assessment for S-metolachlor (D326011, W.
Cutchin).   

Background

  SEQ CHAPTER \h \r 1 S-Metolachlor
[S-2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)
acetamide] is a selective, chloroacetanilide herbicide that is applied
to a variety of crops as a preplant, PPI, preemergence, or postemergence
application, primarily for the control of grass weeds.  It is currently
registered to Syngenta Crop Protection, Inc. for use on a wide variety
of crops and is formulated as EC, G, FlC and RTU formulations.  An
extensive review of S-metolachlor uses and tolerances was conducted in
the Revised TRED for metolachlor and S-metolachlor (D292881, S. Kinard,
8/15/03).  S-metolachlor is the isomer-enriched form of metolachlor. 
Additional uses and new tolerances for S-metolachlor were also
considered in a more recent petition from IR-4 (PP#3E6787, D296904, R.
Loranger, 4/17/06).

In response to deficiencies noted in these earlier reviews, Syngenta has
provided the following data:  1) field trial data supporting the use of
S-metolachlor on succulent shelled peas and beans, crop subgroup 6B; 2)
residue data examining the potential for concentration of residues in
AGF from corn, sorghum and soybeans; and 3) extensive rotational crop
field trials on representative small grains (wheat and oats).  In
addition, Syngenta has also provided field trial and processing study
data supporting new use patterns for S-metolachlor on sorghum and
soybeans, and revised label directions for replanting of rotational
crops.

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	

Common name	  SEQ CHAPTER \h \r 1 S-Metolachlor

Company experimental name	CGA-77102

IUPAC name
(S)-2-chloro-N-(2-ethyl-6-methyl-phenyl)-N-(2-methoxy-1-methyl-ethyl)-ac
etamide

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

CAS registry number	87392-12-9

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

Regulated residue  SEQ CHAPTER \h \r 1 	

Common name	None

Company experimental names	CGA-37913

SYN506357 (S-enantiomer of CGA 37913)

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

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

CAS #	61520-53-4

82508-08-5 (S-enantiomer)

Regulated residue  SEQ CHAPTER \h \r 1 	

Common name	None

Company experimental names	CGA-49751

SYN508500 (S-enantiomer of CGA 49751)

IUPAC name	4-(2-ethyl-6-methylphenyl)-2-hydroxy-5-methyl-3-morpholine

CAS name	4-(2-ethyl-6-methylphenyl)-2-hydroxy-5-methyl-3-morpholine

CAS #	61520-54-5

Table 2.	Physicochemical Properties of S-Metolachlor.

Parameter	Value	Reference

  SEQ CHAPTER \h \r 1 Melting point/range	Not applicable, liquid at room
temperature	MRID 47121701

pH	7.8 at 25°C (1% aqueous dispersion)

	Density	1.117 g/cm3 at 20°C

	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, 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°C

	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

Syngenta is proposing amending the use directions for sorghum and
soybeans on the label for the 7.62 lb/gal EC formulation of
S-metolachlor (Dual Magnum®, EPA Reg. No. 100-816).  The current use
directions for sorghum allow for only a single preplant surface, PPI, or
preemergence application at up to 1.0-1.6 lb ai/A, depending on the soil
type and the amount of organic matter in the soil.  Syngenta is
proposing to expand the use directions to allow for a single application
to be made postemergence at up to 1.6 lb ai/A.

For soybeans, S-metolachlor can currently be applied as either a
preplant surface, PPI, preemergence, or postemergence application. 
Syngenta is proposing to amend the use directions to allow for use of
the postemergence application in combination with a preplant surface,
PPI, or preemergence application, provided that the total rate does not
exceed 2.5 lb ai/A/season.  

The proposed use directions for sorghum and soybeans are summarized
below in Table 3.  The current use directions for pod crops (legume
vegetables, except soybean) are also summarized below, for comparison
with the use pattern utilized in the submitted legume vegetable field
trials.

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

Applic. Timing, Type, and Equip.	Formulation

[EPA Reg. No.]	Applic. Rate 

(lb ai/A) 1	Max. No. Applic. per Season	Max. Seasonal Applic. Rate

(lb ai/A)	PHI 2

(days)	Use Directions and Limitations

Legume vegetables, except soybean

Broadcast application in fall to crop stubble after harvest; Ground or
aerial equipment	7.62 lb/gal EC

[100-816]	1.6-1.9	1	1.9	NS	The fall application should not be applied to
frozen ground and is restricted to IA, MN, ND, SD, WI and portions of NE
and IL.

A PHI/PGI of 60 days is specified for forage, and a PHI of 120 days is
specified for cutting of hay.

For English peas, use only a preemergence application and do not use in
northeastern U.S.

Broadcast PPI or  pre-emergence application in spring; Ground or aerial
equipment

1.0-1.9

Sorghum

  SEQ CHAPTER \h \r 1 Single or split preplant surface application to
minimum- or no-till systems in CO, IA, IL, KS, MO, NE, and SD; Ground or
aerial equipment	7.62 lb/gal EC

[100-816]	1.3-1.6	1	1.6	75 3	Use only on sorghum that is seed treated
with Concep.

Do not make more than one application per year, with the exception of
the split preplant surface applications.

Broadcast PPI, preemergence, or postemergence application; Ground or
aerial equipment

1.0-1.6

Soybean

Broadcast application in fall to crop stubble after harvest; Ground or
aerial equipment	7.62 lb/gal EC

[100-816]	1.6-1.9	2	2.5	NS/ 90 4	The fall application should not be
applied to frozen ground and is restricted to IA, MN, ND, SD, WI and
portions of NE and IL. 

 be made as a split (⅔ + ⅓) application on medium or fine soils.

A 30-day PHI/PGI is specified for forage and hay following a preplant,
PPI, or preemergence application.

  SEQ CHAPTER \h \r 1 Do not graze or feed treated forage or hay to
livestock following a postemergence application.

The postemergence application can be use in combination with a preplant,
PPI, or preemergence application, provided the total rate does not
exceed 2.5 lb ai/A/season.

Do not apply more than 1.3 lb ai/A postemergence.

Broadcast preplant surface application to minimum- or no-till systems in
spring; Ground or aerial equipment

 1.3-2.5

Broadcast preplant incorporated or pre-emergence application in spring;
Ground or aerial equipment

1.0-2.5

Broadcast postemergence application from emergence up through the 3rd
trifoliate leaf stage; Ground or aerial equipment

1.0-1.3

1	Label rates are dependent on soil type, with coarse soil requiring the
lower rates and fine soils or soils containing >2.5% organic matter
requiring higher rates.

2	PHI – preharvest interval; PGI – pre-grazing interval.

3	The 75-day PHI for sorghum is for the postemergence application.

4	No PHI is specified for mature soybean seeds following a preplant or
preemergence application; however, a 90-day PHI is specified following a
postemergence application.

NS = not specified.

In addition to the changes being proposed for the sorghum and soybean
use directions, Syngenta is also proposing changes to the rotational
crop restrictions on the label for the 7.62 lb/gal EC.  These changes
are based on the recently established tolerances for various crops and
crop groups (D296904, R. Loranger, 4/17/06).  The following is a summary
of the rotational crop restrictions on the proposed label for the 7.62
lb/gal EC (EPA Reg. No. 100-816):

Following loss of a crop treated with Dual Magnum, any crop on the Dual
Magnum label, or on a supplemental Dual Magnum label may be replanted
immediately, 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.

Unless otherwise indicated below, do not rotate to food or feed crops
for at least 12 months following the last application of Dual Magnum.

Following treatment with Dual Magnum, the minimum PBI is 4 months for
alfalfa, 4 ½ months for barley, oats, rye or wheat, and 9 months for
clover.  Tobacco, buckwheat, and rice may be planted the next spring. 

Depending on the amount of S-metolachlor applied to the previous crop,
the crops and/or crop groups listed below in Table 4 can be planted 60
days following the last application of Dual Magnum to the previous crop.

Table 4.  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 (subgroup1B)	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

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.	

Conclusions.  The current and proposed use directions are adequate to
allow for evaluation of the available legume vegetable (except soybean),
sorghum, and soybean field trial data.  The sorghum, soybean and legume
vegetable field trial data support the current/proposed uses on these
crops.  However, the following label changes are recommended.

	•	The proposed use directions for sorghum should specify that the
postemergence application is made when plants are up to 5 inches in
height.

	•	The use directions for soybeans include a statement that is in
conflict with the proposed combination of a preplant/preemergence
application with a postemergence application.  The directions currently
include the following statement:  “A postemergence application of Dual
Magnum may not be applied if a preplant surface, preplant incorporated,
or preemergence application of S-metolachlor products had already been
applied.”  This statement should be deleted.

	•	Although Syngenta has not indicated that they are seeking a
postemergence use on legume vegetables (except soybean), the available
field trial data support use of a single postemergence application to
legume vegetables at up to 1.9 lb ai/A, with a 50-day PHI.  The field
trial data indicate that residues in/on representative legume vegetables
were similar following either a PPI, preplant surface, or postemergence
application.

With regard to the current rotational crop restrictions, the submitted
rotational wheat and oat field trials support a minimum PBI of 60-days
for barley, oats, rye and wheat, rather than the currently specified
4.5-month PBI.  For fall-planted cereal grains (barley, oats, rye and
wheat), a 2-month PBI would be more typical following a lay-by
application to corn, than the current 4.5-month PBI listed on the label.
 Reducing the PBI does not require increased tolerances for these
rotational crops.

	•	The minimum PBI for barley, oats, rye and wheat can be reduced to 2
months. 

The proposed 60-day PBI is also adequate for root vegetables
(subgroup1B), tuberous and corm vegetables (subgroup 1C), bulb
vegetables (group 3), leaf petiole vegetables (subgroup 4B), head and
stem Brassica vegetables (subgroup 5A), fruiting vegetables, except
cucurbits (group 8), and winter squash, provided that the application to
the previous crop was less than or equal to the maximum approved rates
for these crops/crop groups.  Adequate field trial data reflecting
preplant surface and PPI applications are available on the
representative crops for the various crops/crop groups listed in Table 4
(D296904, R. Loranger, 4/17/06), and the maximum rates listed in Table 4
are consistent with the maximum rates allowed on these crop groups.

	•	Rotational crop directions for the listed crop groups should be
amended to prohibit a second application of S-metolachlor to any of
these crops replanted within 60 days of the original application.

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 (D226780, L. Kutney, 11/12/96) previously
concluded that the residues of concern for S-metolachlor are the same as
for metolachlor.

The Agency has also reviewed (D279110, S. Kinard, 8/15/03) 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.  These data support Syngenta’s
assertion that the metabolism of S-metolachlor in plants is similar to
the racemic mixture.  These data do not appear to address whether there
is any conversion of the S-isomers of metolachlor or its metabolites to
the R-forms; however, HED previously concluded that such conversion of
isomers in plants is not likely to be significant.

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 animal commodities include metolachlor and its metabolites,
determined as the derivatives CGA-37913 and CGA-49751.  The residues of
concern for S-metolachlor in animals are the same as those for
metolachlor.

The Agency has also reviewed (D292881, S. Kinard, 8/15/03) animal
metabolism data on S-metolachlor.  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:    SEQ CHAPTER \h \r 1 Adequate methodology is
available for enforcing the established and recommended tolerances.  The
Pesticide Analytical Manual (PAM) Vol. II, Pesticide Regulation Section
180.368 lists a GC/NPD method (Method I) for determining residues in/on
plants and a GC/MSD method (Method II) for determining residues in
animal commodities.  These methods determine residues of metolachlor and
its metabolites as either CGA-37913 or CGA-49751 following acid
hydrolysis.  

Data-gathering methods:  In the rotational wheat and oat field trials
and processing studies, residues of S-metolachlor in/on forage, hay,
grain, straw, AGF and processed fractions were determined as CGA-37913
and CGA-49751 using a LC/MS/MS method (ENC-5/99).   This method is an
updated version of the tolerance enforcement method (AG-338) and an
earlier data collection method (AG-612).  However, Method ENC-5/99
utilizes LC/MS/MS rather than GC/NPD for detection and quantitation of
the hydrolysis products CGA-37913 and CGA-49751.    SEQ CHAPTER \h \r 1
For this method, residues are acid hydrolyzed to CGA-37913 and CGA-49751
and cleaned up by solvent partitioning.  Residues are then determined by
LC/MS/MS analysis.  Residues are expressed in parent equivalents, and
the LOQs are 0.03 and 0.05 ppm for CGA-37913 and CGA-49751,
respectively, for a combined LOQ of 0.08 ppm.  The method was adequately
validated using fortified control samples analyzed in conjunction with
the treated samples from the rotational crop trials.

In the remaining field trials and processing studies, residues of
S-metolachlor in/on field corn (forage, stover, grain and AGF), legume
vegetables (podded edible, shelled succulent, and dried seed), sorghum
(forage, stover, grain and AGF), and soybeans (seed, AGF, hulls, meal
and refined oil) were determined as SYN506357 and SYN508500
(S-enantiomers of CGA-37913 and CGA-49751) using an LC/MS/MS method
(Syngenta Method No. 1848-01), which is derived from the current
tolerance enforcement method.  This method has been reviewed and deemed
adequate for data collection (D296904, R. Loranger, 4/17/2006).    SEQ
CHAPTER \h \r 1 For this method, residues are acid hydrolyzed to
CGA-37913 and CGA-49751 and cleaned up by using an alumina column. 
Residues are then determined by LC/MS/MS analysis, using a reverse-phase
chiral column to separate out the S-enantiomers.  For each matrix, the
LOQ is 0.03 ppm for SYN506357 and 0.05 ppm for SYN508500, each expressed
in parent equivalents.  The method was adequately validated using
fortified control samples analyzed in conjunction with the treated
samples.

In the Agency’s earlier review of Method 1848-01, HED noted that this
method does not appear to determine the R-isomers (which are included in
the tolerance expression).  However, HED has concluded that significant
conversion of the S-isomers to the R-forms in plants is not likely. 
Therefore, because the S:R ratio in the active ingredient is 88:12, the
method will not significantly underestimate total residues.  Note: The
petitioner should be advised to generate data on both the R and S
isomers of the two analytes for future tolerance requests. 

Conclusions.   Adequate enforcement methods are available for
determining residues in plant and animal commodities, and the LC/MS/MS
methods used for data collection in the submitted field trials and
processing studies were adequately validated in conjunction with the
analysis of treated samples from each of the studies.  For both data
collection methods, the validated LOQ in each plant commodity is 0.03
ppm for CGA-37913 (or it’s S-isomer SYN506357) and 0.05 ppm for
CGA-49751 (or its S-isomer SYN508500), for a combined LOQ of 0.08 ppm. 

860.1360 Multiresidue Methods

  SEQ CHAPTER \h \r 1 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

  SEQ CHAPTER \h \r 1 Adequate storage stability data are available for
plant and animal commodities (DP# D166637, B. Cropp-Kohlligian,
4/16/92).  For plant commodities, the available data indicate that
CGA-37913 is stable at ≤-10°C or at least 24 months 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.  The derivative
CGA-49751 is also stable at ≤-10°C for at least 24 months 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 cottonseeds and cottonseed oil.  In addition, storage
stability studies conducted concurrently with the asparagus, green
onion, and asparagus field trials also indicate that both analytes are
stable at -20°C for at least 14.1 months in asparagus, 24.3 months in
carrots, and 21.7 months in green onions.

The storage durations and conditions of samples from the current crop
field trials, processing studies and rotational crop field trials are
presented in Table 5.  The available storage stability data on corn
(grain, forage and oil), soybean (meal and hulls) and cottonseed (seeds
and oil) support the sample storage conditions and durations from the
submitted field trials and processing studies.

Table 5.	Summary of Storage Conditions and Durations of Samples from
Crop Field Trial, Processing, and Field Rotational Crop Studies.  

MRID	Crop (Matrices)	Storage Temp  (°C)	Actual Storage Duration
(months)	Interval of Demonstrated Storage Stability (months)

46829501	Beans and Peas

(edible podded, succulent shelled, and dried shelled)	<0	4.7-21.4	24 -
in corn grain and forage and soybean meal and hulls

37 – in cottonseed

46829502	Soybean (dried seed and AGF)	-13 to -21	7.4-8.8	24 –in corn
grain and soybean hulls

≤-5	10.1-11.8	37 – cottonseed

	Soybean (hulls, meal, and refined oil)	≤-5	5.1	24 - in soybean meal
and hulls

37 – in cottonseeds and corn oil

Conclusions.  Adequate storage stability data are available to support
the storage durations and conditions for samples from the submitted
field trials, rotational crop field trials and processing studies.

860.1480 Meat, Milk, Poultry, and Eggs

Adequate ruminant and poultry feeding studies are available for
metolachlor, and these data will also support the use of S-metolachlor.

The theoretical dietary burdens (TDB) for livestock to S-metolachlor
residues were recently calculated using the reassessed tolerances from
the revised TRED (D296904, R. Loranger, 4/17/2006).  The TDBs were
calculated to be 26.2 ppm for beef and dairy cattle, 0.51 ppm for
poultry, and 0.43 ppm for swine.  As several changes in tolerances for
livestock feedstuffs are being recommended, the TDBs for livestock were
recalculated using the Agency’s most recent guidance on constructing
reasonably balanced diets for livestock (memo June 2008).  Based on the
established tolerances for S-metolachlor residues in livestock
feedstuffs, the TDBs were calculated to be 26.2 ppm for cattle, 0.51 ppm
for poultry, and 0.44 ppm for swine (Table 6).  

Conclusions.  The proposed changes in use patterns for S-metolachlor
will have no significant impact on the   SEQ CHAPTER \h \r 1 TDB of
livestock.  As a result, no changes are required in the current
tolerances for animal commodities.



Table 6.	Calculation of Dietary Burdens of S-Metolachlor Residues to
Livestock.

Feedstuff	Type1	% Dry Matter2	% Diet2	Tolerance (ppm)	Dietary
Contribution (ppm)3

Beef  and Dairy Cattle

Grass forage	R	25	40	10.0	16.0

Legume forage	R	30 4	20	15.0	10.0

Sorghum grain 	CC	86	30	0.3	0.10

Sunflower meal	PC	92	10	1.0	0.11

TOTAL BURDEN	--	--	100	--	26.21

Poultry

  SEQ CHAPTER \h \r 1 Sorghum grain 	CC	  SEQ CHAPTER \h \r 1 NA	70	0.3
0.21

Sunflower meal	PC	NA	30	1.0	0.30

TOTAL BURDEN	--	--	100	--	0.51

Swine

  SEQ CHAPTER \h \r 1 Sorghum grain	CC	  SEQ CHAPTER \h \r 1 NA	80	0.3
0.24

Sunflower meal	PC	NA	20	1.0	0.20

TOTAL BURDEN	--	--	100	--	0.44

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. 

4	  SEQ CHAPTER \h \r 1 Based on %DM of cowpea forage.

860.1500 Crop Field Trials

46829501.der.doc (Legume vegetables, except soybean)

46829504.der.doc (Field corn, side-by-side test with multiple
formulations)

47304701.der.doc (Sorghum, post-emergence use)

47304702.de1.doc (Soybean, combined pre- and post-emergence uses)

Syngenta has submitted new sorghum and soybean field trials supporting
proposed changes in the use directions for S-metolachlor (EC) on these
crops.  For sorghum, Syngenta is proposing a postemergence use at up to
1.9 lb ai/A.  For soybean, Syngenta is proposing to allow use of the
labeled postemergence application in combination with a preplant
surface, PPI, or preemergence application.

In response to an earlier Agency review (D296904, R. Loranger, 4/17/06),
Syngenta has also submitted new field trials on representative legume
vegetables (except soybean).  To support a general use on legume
vegetables (except soybean), HED required field trial data on succulent,
shelled peas and beans (subgroup 6B) to support the crop subgroup 6B
tolerance and to supplement the existing field trial data on edible
podded peas and beans (subgroup 6A) and dried shelled peas and beans
(subgroup 6C).  Although only data for succulent shelled peas and beans
were required, Syngenta has provided a full set of field trials for all
three crop subgroups (6A, 6B, and 6C) for the use of S-metolachlor (EC)
as either a preplant surface, PPI or postemergence application, each at
1.9 lb ai/A.

Syngenta has also submitted side-by-side field trials on field corn
comparing residues resulting from use of S-metolachlor formulated as
either an EC, which is currently registered for use on corn, or as
lipophilic wax (LW) and capsule suspension (CS) formulations.  These
corn field trials were conducted in conjunction with field trials used
to generate corn AGF, and are reported here only for informational
purposes, as Syngenta has not proposed any uses for the LW or CS
formulations on corn.

 

  SEQ CHAPTER \h \r 1 The results from the field corn, legume vegetable,
sorghum, and soybean field trials are discussed below and the residue
data are summarized in Table 7.

Table 7.	Summary of Residue Data from Crop Field Trials with
S-Metolachlor.

Crop matrix	Use Patterns 1	Total Applic. Rate

(lb ai/A) 2	PHI (days)	Combined Residue Levels (ppm) 3

n	Min.	Max.	HAFT 4	Median	Mean	Std. Dev.

Field Corn (current use = 3.7 lb ai/A total application rate, 30-day
PHI)

Forage	PPI + Directed appl. at Lay-by	LW; 3.69-3.77	28-34	8	0.11	0.86
0.69	0.27	0.34	0.26

CS; 3.68-3.78	28-34	10	0.093	1.2	1.1	0.34	0.50	0.38

EC; 3.68-3.85	28-34	12	<0.082	0.97	0.92	0.25	0.37	0.30

Stover	PPI + Directed appl. at Lay-by	LW; 3.69-3.77	83-116	8	<0.09	1.7
0.91	0.24	0.40	0.54

CS; 3.68-3.78	83-116	10	<0.08	1.0	0.83	0.24	0.33	0.29

EC; 3.68-3.85	83-116	12	<0.08	1.2	0.57	0.39	0.43	0.37

Grain	PPI + Directed appl. at Lay-by	LW; 3.69-3.77	83-116	8	<0.08	<0.08
<0.08	0.08	0.08	NA

CS; 3.68-3.78	83-116	10	<0.08	<0.08	<0.08	0.08	0.08	NA

EC; 3.68-3.85	83-116	12	<0.08	<0.08	<0.08	0.08	0.08	NA

Legume vegetables, subgroups 6A, 6B and 6C 

(proposed use = 1.9 lb ai/A total application rate, 50-day PHI)

Edible-podded beans and peas (6A)	BSS	1.88-2.00	54-130	16	<0.08	0.21
0.175	0.080	0.092	0.035

	PPI	1.91-2.05	54-130	16	<0.08	0.14	0.135	0.080	0.092	0.019

	BFS 5	1.88-2.02	42-106	18	<0.08	0.25	0.205	0.080	0.097	0.044

Succulent shelled beans and peas (6B)	BSS	1.86-2.00	66-153	20	<0.08
<0.08	0.08	0.08	0.08	NA

	PPI	1.86-1.99	66-153	20	<0.08	<0.08	0.08	0.08	0.08	NA

	BFS 5	1.86-1.98	37-127	24	<0.08	<0.14	0.110	0.080	0.083	0.012

Dried shelled beans and peas (6C)	BSS	1.91-2.03	90-128	22	<0.08	<0.08
0.08	0.08	0.08	NA

	PPI	1.84-1.98	77-128	22	<0.08	<0.08	0.08	0.08	0.08	NA

	BFS 5	1.90-1.96	40-92	28	<0.08	0.23	0.21	0.08	0.095	0.035

Sorghum (proposed use = 1.6 lb ai/A total application rate, 75-day PHI)

Forage	PPI	1.63-1.69	84-102	16	<0.08	0.44	0.42	0.18	0.24	0.14

	BSS	1.64-1.71; 

2.28 6	84-97	16	0.14	0.38	0.36	0.19	0.21	0.08

	BFS 5	1.64-1.71	73-77	24	<0.08	0.63	0.58	0.18	0.21	0.13

Stover	PPI	1.63-1.69	120-149	16	0.11	0.54	0.53	0.21	0.27	0.15

	BSS	1.64-1.71; 

2.28 6	120-149	16	0.11	0.49	0.49	0.21	0.25	0.13

	BFS 5	1.64-1.71	95-133	24	<0.08	0.44	0.40	0.22	0.23	0.11

Grain	PPI	1.63-1.69	120-149	16	<0.08	0.11	0.11	0.08	0.08	0.01

	BSS	1.64-1.71; 

2.28 6	120-149	16	<0.08	0.11	0.10	0.08	0.08	0.01

	BFS 5	1.64-1.71	95-133	24	<0.08	0.09	0.09	0.08	0.08	NA

Soybean (proposed use = 2.5 lb ai/A total application rate, 90-day PHI)
7

Dried Seed	BSS	1.97-2.07	113-184	20	<0.08	0.10	0.09	0.08	0.08	0.006

Dried Seed	PPI	1.96-2.03	123-161	16	<0.08	0.09	0.09	0.08	0.08	0.003

Dried Seed	PPI + BFS 5	2.47-2.55	85-103	36	<0.08	0.11	0.11	0.08	0.09
0.008

1	BSS = single broadcast soil surface application at planting; PPI =
single PPI application at planting; BFS = single broadcast foliar
application; PPI+ BFS = combination of PPI application at planting
followed by single broadcast foliar application.

2	S-Metolachlor was applied as an EC formulation in all tests, except
the field corn tests which included side-by-side plots with capsule
suspension (CS) and lipophilic wax (LW) formulations.

3	Residues are expressed in parent equivalents.  The LOQs are 0.03 ppm
for CGA-37913 (or SYN506357), 0.05 ppm for CGA-49751 (or SYN508500), for
a combined LOQ of 0.08 ppm in all commodities.

4	HAFT = Highest Average Field Trial.

5	The new types of applications being requested are for a single BFS
application to legume vegetables (except soybean) and sorghum, and a
combination of a PPI and BFS application to soybeans. 

6	The application to sorghum at one site was inadvertently applied at
134% of the target rate; however, there was not a notable difference in
residues in/on forage, stover or grain from this test.

7	Label directions prohibit the feeding of treated soybean forage or hay
to livestock, following a postemergence application.

Legume Vegetables (Group 6)

Edible-podded beans and peas (Subgroup 6A), Succulent shelled beans and
peas (subgroup 6B) and Dried shelled pea and beans, except soybean
(subgroup 6C).  Thirty-five field trials were conducted in the U.S.
during the 2002 growing season   SEQ CHAPTER \h \r 1 on representative
crops of legume vegetables (excluding soybeans).  Nine field trials were
conducted on edible-podded beans and peas (subgroup 6A) in Zones 1, 2,
3, 5, 6, 10 and 11; twelve field trials were conducted on succulent
shelled beans or peas (subgroup 6B) in Zones 1, 2, 5, 10, 11 and 12; and
fourteen field trials were conducted on dried shelled beans and peas
(subgroup 6C) in Zones 5, 7, 8, 9, 10, and 11.

Three different treatment regimes were used, with each test site
including one control and 2 or 3 treated plots.  In each test,
S-metolachlor (7.64 lb/gal EC) was applied to the representative legume
crops as either a single broadcast soil surface (BSS) application at
planting at 1.86-2.03 lb ai/A (Trt #2; 1x rate), a single PPI
application at planting at 1.84-2.05 lb ai/A (Trt #3; 1x rate), or a
single broadcast foliar (BFS) application approximately 50 days before
harvest at 1.86-2.02 lb ai/A (Trt # 4; 1x rate).  The BFS application
was tested at all 35 field sites, and the BSS and PPI soil applications
were each tested at 29 field sites.  Applications were made using ground
equipment in 14-28 gal/A spray volumes without an adjuvant, with the
exception of three field trials where applications were made in 2 gal/A
to simulate aerial application.

Single control and duplicate samples of mature bean and pea commodities
were harvested at 37-127 days after treatment (DAT) for the BFS
application, with most samples being harvested at 40-59 DAT.  For the
at-planting soil applications, mature samples of bean and pea
commodities were harvested (or cut) at 54-153 DAT.  Additional samples
were collected from three trials (one snap bean, one succulent pea, and
one dried bean) to evaluate residue decline.  For the foliar
application, samples were collected at 7-day intervals from 28-57 DAT
for each type of legume.  For the soil applications, samples were
collected at 7-day intervals from 58-86 DAT for the snap beans, from
71-99 DAT for the succulent shelled peas, and from 76-104 DAT for the
dried peas. Samples were stored frozen for up to 21.4 months prior to
analysis, an interval supported by the available storage stability data.

Residues of S-metolachlor in/on legume vegetables (beans and peas) were
determined as SYN506357 and SYN508500 using an adequate LC/MS/MS method
(Syngenta Method No. 1848-01).  The LOQ is 0.03 ppm for SYN506357 and
0.05 ppm for SYN508500, each expressed in parent equivalents, and the
combined LOQ is 0.08 ppm for total residues.

Following the single soil BSS application at planting at 1.86-2.03 lb
ai/A (1x rate), combined residues of SYN506357 and SYN508500 were
<0.08-0.21 ppm in/on edible podded beans or peas (subgroup 6A) harvested
at 54-130 DAT, with 14 of 16 samples having residues <LOQ.  Combined
residues were also <LOQ (<0.08 ppm) in/on all samples of succulent
shelled beans and peas (subgroup 6B) harvested at 66-153 DAT, and dried
beans and peas (subgroup 6C) harvested at 90-128 DAT.

Following the single PPI application at planting at 1.84-2.05 lb ai/A
(1x rate), combined residues of SYN506357 and SYN508500 were <0.08-0.14
ppm in/on edible podded beans or peas (subgroup 6A) harvested at 54-130
DAT, with 9 of 16 samples having residues <LOQ.  Combined residues were
also <LOQ (<0.08 ppm) in/on all samples of succulent shelled beans and
peas (subgroup 6B) harvested at 66-153 DAT, and dried beans and peas
(subgroup 6C) harvested at 77-128 DAT.

Following the single BFS application at 1.86-2.02 lb ai/A (1x rate),
combined residues were <0.08-0.25 ppm in/on edible podded beans or peas
(subgroup 6A) harvested at 42-106 DAT, with 14 of 18 samples having
residues <LOQ.  Combined residues were <0.08-<0.14 ppm in/on succulent
shelled beans and peas (subgroup 6B) harvested at 37-127 DAT, with 23 of
24 samples having residues <LOQ.  Combined residues were <0.08-0.23 ppm
in/on dried beans and peas (subgroup 6C) harvested at 40-92 DAT, with 21
of 28 samples having residues <LOQ.

The average combined residues for the BSS application were 0.092 ppm
in/on subgroup 6A and 0.08 ppm in/on subgroups 6B and 6C.  Average
combined residues for the PPI application were 0.092 ppm in/on subgroup
6A, and 0.08 ppm in/on subgroups 6B and 6C.  Average combined residues
for the BFS application were 0.097 ppm in/on subgroup 6A, 0.083 ppm
in/on subgroup 6B, and 0.095 ppm in/on subgroup 6C.  

Although residues were slightly higher following the BFS application
than the PPI or BSS applications, these data indicate that the combined
residues of S-metolachlor in/on legume vegetables (except soybean) are
generally similar following either a single broadcast or PPI soil
application at planting or a single BFS application at ca. 50 days prior
to harvest, each at 1.9 lb ai/A (1x rate).

No pattern of decline or increase in residues was apparent from the
residue decline tests conducted on edible podded beans (whole bean) and
dried beans (seed) as residues in/on samples from these tests were <LOQ
at most of the sampling intervals.  However, in the decline tests
conducted on succulent shelled peas, the maximum combined S-metolachlor
residues occurred at the latest sampling interval.  For samples of
succulent shelled peas collected from the BSS application (Trt #2),
average combined residues were <LOQ at 71-92 DAT and increased to <0.10
ppm at 99 DAT.  For samples of succulent shelled peas collected from the
PPI application (Trt #3), average combined residues were below or just
above the LOQ at 71-92 DAT and increased to <0.16 ppm at 99 DAT.  For
samples of succulent shelled peas collected from the BFS application
(Trt #4), average combined residues were <LOQ at 29-43 DAT and increased
to <0.11 and <0.15 ppm at 50 and 57 DAT, respectively.

Soybeans.  In 18 field trials conducted in Zones 2, 4, and 5 during
2002, S-metolachlor (7.64 lb/gal EC) was applied to soybeans using the
following three application regimes:  a single broadcast soil
application at planting at 1.97-2.07 lb ai/A (Trt #2); a single PPI
application at planting at 1.96-2.03 lb ai/A (Trt #3); or a combination
of a PPI application at 1.17-1.22 lb ai/A at planting followed by a
broadcast foliar application at 1.28-1.34 lb ai/A prior to bloom, for a
total of 2.47-2.55 lb ai/A/season (Trt # 4; 1x rate).  The retreatment
interval (RTI) was 23-81 days for the combined applications.  Each field
site included either two or three treated plots, along with a control
plot.  The combination of the PPI and foliar applications was tested at
all 18 field sites, the single broadcast soil application was tested at
10 sites, and the single PPI application was tested at 8 sites.  All
applications were made with ground equipment using 2-26 gal/A and did
not include the use of any adjuvants.

Single control and duplicate treated samples of mature soybean seeds
were harvested at 113-184 DAT from Trt #2, 123-161 DAT from Trt #3,
85-103 DAT for Trt #4.  To assess residue decline, seeds were also
collected at ~7-day intervals from 115-129 DAT for Trt #2 at one site,
from 146-174 DAT for Trt #3 at one site, and from 70-99 DAT for Trt #4
at three sites.  Samples were stored frozen for up to 11.8 months prior
to analysis, an interval that is supported by the available storage
stability data.

Residues of S-metolachlor in/on soybean seeds were determined as
SYN506357 and SYN508500 using an adequate LC/MS/MS method (Syngenta
Method No. 1848-01).  The LOQ is 0.03 ppm for SYN506357 and 0.05 ppm for
SYN508500, each expressed in parent equivalents, and the combined LOQ is
0.08 ppm for total residues.

For the single broadcast soil application at 1.97-2.07 lb ai/A (Trt #2),
the combined residues of SYN506357 and SYN508500 were <0.08-0.10 ppm
in/on seeds harvested at 113-184 DAT.  For the single PPI application at
1.96-2.03 lb ai/A (Trt #3), the combined residues of SYN506357 and
SYN508500 were <0.08-0.09 ppm in/on seeds harvested at 123-161 DAT.  For
the combined PPI and post-emergence foliar applications totaling
2.47-2.55 lb ai/A (Trt #4; 1x rate), the combined residues of SYN506357
and SYN508500 were <0.08-0.11 ppm in/on seeds harvested at 85-103 DAT. 
Average combined residues in/on seeds were 0.08 ppm for Trts #2 and #3
and 0.09 ppm for Trt #4.  These data indicate that the combined residues
of S-metolachlor in/on soybean seeds are similar following either a
single PPI or broadcast soil applications at planting at 2 lb ai/A, or
following combined PPI and foliar applications totaling 2.5 lb ai/A (1x
rate).  

No pattern of decline or increase in residues was apparent from any of
the residue decline tests as seed samples from all of these tests were
below or just above the LOQ at all sampling intervals.

Cereal Grain and Forage, Fodder and Straw of Cereal Grains (Groups 15
and 16)

Field Corn.  In six   SEQ CHAPTER \h \r 1 field corn field trials
conducted during 2002 in Zones 5 and 6, side-by-side plots were
established comparing S-metolachlor residues in/on field corn forage,
stover and grain resulting from use of either an EC formulation, which
is currently registered for use on corn, or lipophilic wax (LW) and
capsule suspension (CS) formulations.  

Each test site consisted of one untreated plot and two or three
side-by-side treated plots.  Each treated plot received a combination of
a PPI application of S-metolachlor at planting at a target rate of 2.38
lb ai/A, followed 40-61 days later, by a single directed application at
lay-by at a target rate of 1.39 lb ai/A, for a total rate of ~3.77 lb
ai/A (1x the maximum label rate).  The applied S-metolachlor was
formulated as either a 6.1 lb/gal LW (Trt #5), a 5.5 lb/gal CS (Trt #6),
or a 7.64 lb/gal EC (Trt #7).  In one field trial, S-metolachlor (7.64
lb/gal EC) was also applied as a PPI application and lay-by application
at exaggerated rates (5x rates; Trt #8) for the generation of AGF. 
Applications were made using ground equipment in 13-27 gal/A spray
volumes without an adjuvant.

For each test, control and duplicate treated samples of forage were
harvested 28-34 DAT, and samples of mature grain and stover were
harvested at normal maturity (83-116 DAT).  Bulk grain samples were also
harvested at 114 DAT from two tests following applications of the EC
formulation at 1x and 5x rates; these bulk grain samples were used to
generate samples of AGF under simulated commercial conditions.  Samples
of the corn commodities were stored frozen for up to 17.6 months, an
interval that is supported by the available storage stability data.

Residues of S-metolachlor in/on corn forage, stover and grain were
determined as SYN506357 and SYN508500 (S-enantiomers of CGA-37913 and
CGA-49751) using an adequate  LC/MS/MS method (Syngenta Method No.
1848-01).  For each matrix, the LOQ is 0.03 ppm for SYN506357 and 0.05
ppm for SYN508500, each expressed in parent equivalents, for a combined
LOQ of 0.08 ppm.

 

For corn treated with the LW formulation (Trt #5) at a total rate of
3.69-3.77 lb ai/A, maximum residues of SYN506357 and SYN508500 were 0.37
and 0.49 ppm, respectively, in/on forage harvested at 28-34 DAT, and the
maximum combined residues were 0.86 ppm.  Maximum residues of SYN506357
and SYN508500 were 0.35 and 1.3 ppm, respectively, in/on stover
harvested at 83-116 DAT, and maximum combined residues were 1.7 ppm. 
Residues in/on grain harvested at 83-116 DAT were <LOQ for both
analytes, for combined residues of <0.08 ppm.

For corn treated with the CS formulation (Trt #6) at a total rate of
3.68-3.78 lb ai/A, maximum residues of SYN506357 and SYN508500 were 0.74
and 0.50 ppm, respectively, in/on forage harvested at 28-34 DAT, and
maximum combined residues were 1.2 ppm.  Maximum residues of SYN506357
and SYN508500 were 0.56 and 0.47 ppm, respectively, in/on stover
harvested at 83-116 DAT, and maximum combined residues were 1.0 ppm. 
Residues in/on grain harvested at 83-116 DAT were <LOQ for both
analytes, for combined residues of <0.08 ppm.

For corn treated with the EC formulation (Trt #7) at a total rate of
3.68-3.85 lb ai/A, maximum residues of SYN506357 and SYN508500 were 0.60
and 0.49 ppm, respectively, in/on forage harvested at 28-34 DAT, and the
maximum combined residues were 0.97 ppm.  Maximum residues of SYN506357
and SYN508500 were 0.46 and 0.79 ppm, respectively, in/on stover
harvested at 83-116 DAT, and the maximum combined residues were 1.2 ppm.
 Residues in/on grain harvested at 83-116 DAT were <LOQ for both
analytes, for combined residues of <0.08 ppm.

The average combined residues from the LW, CS, or EC formulations were
respectively 0.34, 0.50, and 0.37 ppm in/on corn forage and 0.40, 0.33,
and 0.43 ppm in/on corn stover, and average combined residues were 0.08
ppm in/on grain from all three formulations.  These data indicate that
residues of S-metolachlor in/on field corn forage, stover and grain are
similar following applications of the LW, CS, or EC formulations.

Sorghum.  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; 1x rate), a broadcast soil surface
application at planting at 1.64-2.28 lb ai/A (Trt #3; 1-1.4x rates), or
a postemergence foliar application when plants were ~5-inches in height
at 1.64-1.71 lb ai/A (Trt #4; 1x rate).  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.  All applications were made with
ground equipment using 2-30 gal/A, and did not include the use of an
adjuvant.  

Single control and duplicate treated samples of forage, stover and grain
were harvested from each test at the appropriate stage of maturity. 
Forage samples were collected at 84-102 DAT for the soil applications
and at 73-77 DAT for the foliar application.  Grain and stover samples
were collected at 120-149 DAT for the soil applications and at 95-133
DAT for the foliar application.  To assess residue decline, forage
samples were also collected from one site at ca. 7 day intervals from
63-91 DAT for the soil applications and from 52-80 DAT for the foliar
application.  Samples were stored frozen for up to 15.6 months prior to
analysis, an interval that is supported by the available storage
stability data. 

Residues of S-metolachlor in/on sorghum commodities were determined as
SYN506357 and SYN508500 using an adequate LC/MS/MS method (Syngenta
Method No. 1848-01).  The LOQ is 0.03 ppm for SYN506357 and 0.05 ppm for
SYN508500, each expressed in parent equivalents, and the combined LOQ is
0.08 ppm for total residues.

Following a PPI application at 1.63-1.69 lb ai/A (Trt #2; 1x rate),
combined residues were <0.08-0.44 ppm in/on forage harvested at 84-102
DAT and 0.11-0.54 ppm in/on stover and <0.08-0.11 ppm in/on grain
harvested at 120-149 DAT.  Following a soil surface application at
1.64-2.28 lb ai/A (Trt #3; ~1x rate), combined residues were 0.14-0.38
ppm in/on forage harvested at 84-97 DAT and 0.11-0.59 ppm in/on stover
and <0.08-0.11 ppm in/on grain harvested at 120-149 DAT.  Following a
post-emergence application at 1.64-1.71 lb ai/A (Trt #4; 1x rate),
combined residues were <0.08-0.63 ppm in/on forage harvested at 73-77
DAT and <0.08-0.44 ppm in/on stover and <0.08-0.09 ppm in/on grain
harvested at 95-133 DAT.

The average combined residues for Trt #2 were 0.24 ppm in/on forage,
0.27 ppm in/on stover and 0.08 ppm in/on grain.  Average combined
residues for Trt #3 were 0.21 ppm in/on forage, 0.25 ppm in/on stover
and 0.08 ppm in/on grain.  Average combined residues for Trt #4 were
0.21 ppm in/on forage, 0.23 ppm in/on stover and 0.08 ppm in/on grain. 
These data indicate that the S-metolachlor residues resulting from the
three types of applications were similar. 

In the residue decline tests, combined S-metolachlor residues in/on
forage samples generally declined over time for the soil surface
application (Trt #3) and the postemergence application (Trt #4). 
Combined residue levels in/on forage samples from the PPI application
(Trt #4) were erratic, but generally steady from 63-91 DAT.

Conclusions.  The submitted field trial data on sorghum, soybean and
legume vegetables (subgroups 6A, 6B, and 6C) are adequate and indicate
that a crop group tolerance of 0.3 ppm is appropriate.  Adequate numbers
of field trials were conducted for all crops in the appropriate
geographic regions, and the use patterns were consistent with the
current or proposed use directions.  The field trial samples were
analyzed using adequate analytical methods and are supported by the
available storage stability data.

The sorghum field trial data indicate that the combined S-metolachlor
residues in/on each sorghum commodity (forage, stover and grain) are
similar following either a preplant surface, PPI, or postemergence
application.  The available data support the use of S-metolachlor (EC)
on sorghum as a postemergence broadcast application at up to 1.6 lb ai/A
when plants are up to 5 inches in height.  The data support a 75-day PHI
for harvest of forage.  The data also indicate that residues resulting
from the postemergence application will not exceed the established
tolerances on sorghum forage (1.0 ppm), grain (0.3 ppm) and stover (4.0
ppm).

Although only 18 of the required 20 soybean field trials were conducted
for the combined PPI and postemergence applications, the available field
trial data are adequate, as the residue data from the 18 tests were
highly consistent.  Combined S-metolachlor residues in/on soybean seeds
were similar following either a single preplant surface application, a
single PPI application, or the combined PPI and postemergence
applications.  The data support the combination of a PPI or soil surface
application at planting followed by a broadcast foliar application prior
to bloom at up to 1.3 lb ai/A.  The data support a maximum seasonal
application rate of 2.5 lb ai/A for the combined application and a
90-day PHI for the postemergence application.  The data also indicate
that residues from the combined application will not exceed the
established tolerance on soybean seeds (0.2 ppm).

The legume vegetable field trial data indicate that combined
S-metolachlor residues in/on beans and peas resulting from the three
types of applications are similar within each crop subgroup and within
the crop group.  The available data support the use of S-metolachlor
(EC) on edible podded, succulent shelled, and dried shelled peas and
beans as a single broadcast soil or PPI application at planting or as a
single broadcast foliar application.  The data support maximum single
and seasonal use rates of 1.9 lb ai/A, and a 50-day PHI for the
postemergence application.  The residue data indicate that the current
tolerance for subgroup 6C should be increased to 0.3 ppm and that a 0.3
ppm tolerance should be proposed for subgroup 6B.  The data for crop
subgroup 6A indicate that the tolerance for this subgroup could be
lowered to 0.3 ppm (to harmonize with Canada’s tolerance); therefore,
a crop group 6 tolerance of 0.3 ppm would be appropriate.  Although the
field trial data support the use of a postemergence application on
legume vegetables (except soybean), HED notes that Syngenta has not
requested amending the current label to include this use.

The six side-by-side field corn trials are also adequate and indicate
that S-metolachlor residues for each field corn commodity are similar
following combined PPI and lay-by applications of either the EC, LW or
CS formulations, at rates totaling ca. 3.7 lb ai/A.  The data support
PHIs of 30 days for forage and 85 days for grain and stover following
the postemergence application.

860.1520 Processed Food and Feed

46829502.der.doc (Soybean AGF)

46829503.der.doc (Sorghum AGF)

46829504.der.doc (Field corn AGF)

47304702.de2.doc (Soybean)

47121701.de2.doc (Rotational wheat)

47121702.de2.doc (Rotational oats)

In response to data gaps noted in the revised S-metolachlor TRED
(D292881, S. Kinard, 8/15/03), Syngenta submitted residue data depicting
the potential for concentration of residues in AGF derived from
soybeans, sorghum and corn.  Syngenta also submitted new soybean
processing studies in conjunction with field trials supporting the
proposed use pattern, and wheat and oat processing studies conducted in
conjunction with the rotational crop field trials.    SEQ CHAPTER \h \r
1 The results from these AGF and processing studies are discussed below
and the residue data are summarized in Table 8.

  SEQ CHAPTER \h \r 1 Table 8.	Summary of Processing Factors for
S-Metolachlor.

MRID	Crop	Total Rate

(lb ai/A/season)	Commodity	Combined Residues

(ppm)	Processing Factor1

47304702	Soybean	2.5 (1x rate)	Whole seeds (RAC)	<0.08	NA

	Hulls	<0.08	NC

	Meal	<0.08	NC

	Refined oil	<0.08	NC

12.45 (5x rate)	Whole seeds (RAC)	<0.08	NA

	Hulls	<0.08	NC

	Meal	<0.08	NC

	Refined oil	<0.08	NC

46829502	Soybean	2.42 (1x rate)	Whole seed (RAC)	<0.08	NA

	AGF	0.21	5.3x

2.07 (0.8x rate)	Whole seed (RAC)	<0.08	NA

	AGF	<0.10	2.5x

46829503

	Sorghum

	1.67 (1x rate)	Grain (RAC)	<0.08	NA

	AGF	<0.11, <0.14	3.1x

46829504	Field Corn	3.75 (1x rate)	Grain (RAC)	<0.08	NA

	AGF	<0.08	NC

18.77 (5x rate)	Grain (RAC)	<0.08	NA

	AGF	<0.08	NC

47121701	Wheat 

(rotated crop)	3.83 (1x rate)	Grain (RAC)	<0.08	NA

	AGF	<0.08	NC

	Bran	<0.08	NC

	Flour	<0.08	NC

	Middlings	<0.08	NC

	Shorts	<0.08	NC

	Germ	<0.08	NC

47121702	Oats 

(rotated crop)	2.44 (0.7x rate)	Grain (RAC)	<0.08	NA

	Rolled oats	<0.08	NC

	Flour	<0.08	NC

1 - Processing factors calculated by dividing the residue in the
processed fraction by the average residue in the soybean seed (RAC)
providing a conservative estimate.

Soybeans.  In two field trials conducted in IA during 2002
(47304702.de2.doc), S-metolachlor (7.64 lb/gal EC) was applied to
soybeans as a combination of a PPI application at planting followed by a
broadcast foliar application prior to bloom.  The application rates for
the PPI and post-emergence applications were respectively 1.21 and 1.29
lb ai/A in one test, for a total of 2.5 lb ai/A/season (1x rate), and
6.01 and 6.44 lb ai/A in the other test, for a total of 12.45 lb
ai/A/season (5x rate).  The RTI for the two applications was 29 days in
both tests.  All applications were made using ground equipment at
volumes of 13-17 gal/A, and none of the applications included the use of
an adjuvant.

Control and treated subsamples and bulk samples of seeds were harvested
from both tests at normal crop maturity, 94 DAT.  Within ~5 months of
harvest, the frozen bulk seed samples were processed into hulls, meal
and refined oil using simulated commercial procedures.  Prior to
analysis, samples were stored at ≤-5°C for up to 10.3 months for
seeds (RAC) and 5.1 months for processed fractions.  These storage
conditions and durations are supported by the available storage
stability data.

Residues of S-metolachlor in/on soybean seeds, hulls, meal and oil were
determined as SYN506357 and SYN508500 (S-enantiomers of CGA-37913 and
CGA-49751) using an adequate LC/MS/MS method (Syngenta Method No.
1848-01).  The LOQ is 0.03 ppm for SYN506357 and 0.05 ppm for SYN508500,
each expressed in parent equivalents, and the combined LOQ is 0.08 ppm
for total residues.

ere ≤LOQ in/on all samples of seeds, hulls, meal and oil.  As residues
were ≤LOQ in both the RAC and processed fractions, processing factors
were not calculated.  The theoretical concentration factors for soybean
hulls, meal and oil are 11.3x, 2.2x and 12x, respectively.

Soybean (AGF).  In another study examining residues in/on whole seed and
AGF (46829502.der.doc), two field trials were conducted in Zone 5 (IA
and IL) during 2003.  In each test, S-metolachlor (7.64 lb/gal EC) was
applied to soybeans as a combination of a PPI application at planting
followed by a broadcast foliar application at BBCH 61-65, at rates
totaling 2.07 lb ai/A in one test and 2.42 lb ai/A in the other test
(0.8x and 1x rates).  The RTI for the two applications was 56-67 days. 
All applications were made using ground equipment at volumes of 8-17
gal/A, and none of the applications included the use of an adjuvant.

T.  Within ~2-5 months of harvest, the frozen bulk seed samples were
processed into AGF under simulated commercial conditions.  Prior to
analysis, samples were stored at ≤-13°C for up to 7.5 months for
seeds (RAC) and 8.8 months for AGF.  These storage conditions and
durations are supported by the available storage stability data.

Residues of S-metolachlor in/on soybean seed and AGF were determined as
SYN506357 and SYN508500 (S-enantiomers of CGA-37913 and CGA-49751) using
an adequate LC/MS/MS method (Syngenta Method No. 1848-01).  The LOQ is
0.03 ppm for SYN506357 and 0.05 ppm for SYN508500, each expressed in
parent equivalents, and the combined LOQ is 0.08 ppm for total residues.

Residues of SYN508500 and SYN506357 in soybean seed were each below the
method LOQ (<0.05 and <0.03 ppm, respectively), for total residues of
<0.08 ppm.  In the sample of soybean AGF from the IL trial, residues of
SYN508500 and SYN506357 were 0.10 and 0.11 ppm, respectively, for total
residues of 0.21 ppm.  In the sample of soybean AGF from the IA trial,
residues of SYN508500 and SYN506357 were below the LOQ (<0.05 ppm) and
0.05 ppm, respectively, for total residues of <0.10 ppm.

The data indicate that total S-metolachlor residues may concentrate in
soybean AGF, with concentration factors of 2.5x or 5.3x (average 3.9x).

Field corn (AGF).  In conjunction with the side-by-side tests comparing
residues in/on field corn following applications of the EC, CS or LW
formulations of S-metolachlor (46829504.der.doc), two tests were
conducted in IA during 2002 in which S-metolachlor (7.6 lb/gal EC) was
applied to two plots of field corn as a combination of a PPI
application, followed 43 days later by a directed application at lay-by
at total rates of 3.75 or 18.77 lb ai/A (1x and 5x rates).  Applications
were made using ground equipment in 16-20 gal/A spray volumes without an
adjuvant.

Bulk grain samples were harvested at 114 DAT from both tests, and these
bulk grain samples were used to generate samples of AGF under simulated
commercial conditions.  Samples of the corn grain and AGF were stored
frozen for up to 14.7 months, an interval that is supported by the
available storage stability data.

Residues of S-metolachlor in/on corn forage, stover, grain, whole
kernels and AGF were determined as SYN506357 and SYN508500
(S-enantiomers of CGA-37913 and CGA-49751) using an adequate LC/MS/MS
method (Syngenta Method No. 1848-01).  The LOQ is 0.03 ppm for SYN506357
and 0.05 ppm for SYN508500, each expressed in parent equivalents, and
the combined LOQ is 0.08 ppm for total residues.

Residues of SYN506357 and SYN508500 were each <LOQ (<0.03 and <0.05 ppm)
in/on bulk samples of whole grain harvested 114 days after treatment
with the EC formulation at rates totaling 3.75 lb ai/A (1x rate) and
18.77 lb ai/A (5x rate).  Residues of both analytes were also <LOQ in/on
the samples of AGF derived from the 1x- and 5x-treated grain.  

Sorghum (AGF).  In a single field trial conducted in Zone 5 during 2003
(46829503.der.doc), S-metolachlor (7.6 lb/gal EC) was applied to grain
sorghum as a single broadcast foliar application at the V4 growth stage
at a rate of 1.67 lb ai/A (1x rate).  The application was made using
ground equipment in an 11 gal/A spray volume, without use of an
adjuvant. 

Control and treated subsamples and bulk samples of grain were harvested
at normal crop maturity, 100 DAT.  Within ~2-4 months of harvest, the
frozen bulk grain samples were processed into AGF under simulated
commercial conditions.  Prior to analysis, samples were stored at
≤-13°C for up to 8.3 months for grain (RAC) and 9.6 months for AGF. 
These storage conditions and durations are supported by the available
storage stability data.

Residues of S-metolachlor in/on sorghum grain and AGF were determined as
SYN506357 and SYN508500 using an adequate LC/MS/MS method (Syngenta
Method No. 1848-01).  The LOQ is 0.03 ppm for SYN506357 and 0.05 ppm for
SYN508500, each expressed in parent equivalents, for a combined LOQ of
0.08 ppm.

Residues of SYN508500 and SYN506357 in sorghum grain were each below the
method LOQ (<0.05 and <0.03 ppm, respectively), for total residues of
<0.08 ppm.  In two samples of sorghum AGF, residues of SYN508500 were
below the LOQ (<0.05 ppm) and residues of SYN506357 were 0.06 and 0.09
ppm, for total residues of <0.11 and <0.14 ppm.  The data indicate that
total S-metolachlor residues may concentrate slightly in sorghum AGF,
with concentration factors of 2.75-3.5x (average 3.1x).

Wheat (Rotational crop).  In a rotational wheat field trial conducted in
IL during 2005-2006, S-metolachlor (7.6 lb/gal EC) was applied to a
primary crop of corn as a combination of a PPI application at 2.43 lb
ai/A followed 33 days later by a directed application to the base of the
corn plants at lay-by at 1.4 lb ai/A, for a total of 3.83 lb ai/A/season
(1x the maximum seasonal use rate).  Both applications were made using
ground equipment at 12-14 gal/A, and did not include the use of any
adjuvants.  The corn crop was removed, and a rotational crop of winter
wheat was planted 57 days after the lay-by application.

Bulk control and treated samples of wheat grain were harvested at normal
crop maturity, 265 days after planting (DAP), and frozen.  Processing
was initiated within 1 month of harvest.  Samples of wheat AGF were
initially generated using a dust generation room.  The grain was then
also processed into bran, flour, middlings, shorts and germ using
simulated commercial procedures.  Prior to analysis, samples were stored
at -20°C for 4-5 months.  These storage conditions and durations are
supported by the available storage stability data.

Residues of S-metolachlor in/on wheat commodities were determined as
CGA-37913 and CGA-49751 using an adequate LC/MS/MS method (ENC-5/99). 
The method LOQ in each wheat commodity is 0.03 ppm for CGA-37913 and
0.05 ppm for CGA-49751, each expressed in parent equivalents, for a
combined LOQ of 0.08 ppm.

Residues were <LOQ for both CGA-37913 (<0.03 ppm) and CGA-49751 (<0.05
ppm) in/on the treated sample of whole wheat grain.  Residues of both
analytes were also <LOQ in wheat AGF and wheat bran, flour, middlings,
shorts and germ.  As residues were <LOQ in all fractions, processing
factors could not be calculated.  The theoretical concentration factors
for wheat processed fractions are 1.4x-8.3x.

Oats (Rotational crop).  In a rotational oats field trial conducted in
ND during 2005-2006, S-metolachlor (7.6 lb/gal EC) was applied to a
primary crop of corn as a combination of a PPI application at 1.15 lb
ai/A followed 89 days later by a directed application to the base of the
corn plants at lay-by at 1.29 lb ai/A, for a total of 2.44 lb
ai/A/season (0.7x the maximum seasonal use rate).  Both applications
were made using ground equipment at 12-15 gal/A, and did not include the
use of any adjuvants.  The corn crop was harvested at maturity, and a
rotational crop of oats was planted 214 days after the lay-by
application (~7-month PBI).

Bulk control and treated samples of oat grain were harvested at normal
crop maturity, 94 DAP, and frozen.  Processing was initiated ~2 months
after harvest.  The oat grain was processed into rolled oats and oat
flour using simulated commercial procedures.  Prior to analysis, samples
were stored at -20°C for 5-7 months.  These storage conditions and
durations are supported by the available storage stability data.

Residues of S-metolachlor in/on oat commodities were determined as
CGA-37913 and CGA-49751 using an adequate LC/MS/MS method (ENC-5/99).   
SEQ CHAPTER \h \r 1 The method LOQ in each oat commodity is 0.03 ppm for
CGA-37913 and 0.05 ppm for CGA-49751, each expressed in parent
equivalents, for a combined LOQ of 0.08 ppm.

 

Residues were <LOQ for both CGA-37913 (<0.03 ppm) and CGA-49751 (<0.05
ppm) in/on the treated sample of whole oat grain and in rolled oats and
flour.  As residues were <LOQ in all fractions, processing factors could
not be calculated.  The theoretical concentration factors for oat
processed fractions are 1.4x-4.0x.

Conclusions.  The data pertaining to S-metolachlor residues in AGF from
soybean, sorghum and field corn are adequate.  Residues of S-metolachlor
did not concentrate in AGF from field corn following applications at
either 1x or 5x the maximum use rate.  However, residues were shown to
concentrate slightly in AGF derived from soybean seeds (average 3.9x)
and sorghum grain (average 3.1x).  Based on the maximum combined
residues observed in/on soybean seeds (<0.17 ppm, data from TRED) and
sorghum grain (0.09 ppm) following applications of S-metolachlor at 1x
rates, the maximum expected residues would be 0.66 ppm for soybean AGF
and 0.32 ppm for sorghum AGF.  As the tolerances for soybean seeds and
sorghum grain are 0.2 and 0.3 ppm, respectively, a tolerance of 0.7 ppm
should be established for AGF based on the soybean data.

The submitted soybean processing studies, reflecting the combined PPI
and postemergence applications, are adequate.  Following applications at
rates totaling 1x and 5x the maximum labeled rate, combined residues of
S-metolachlor were <LOQ in/on whole seeds and each processed fraction. 
The data indicate that separate tolerances are not required for soybean
hulls, meal and refined oil.

Although the oat grain used for processing was from a field trial
conducted at a 0.7x rate, the processing studies from the rotational
wheat and oat field trials are adequate.  Combined residues were <LOQ
in/on grain from rotational wheat planted 2 months following
applications totaling 3.83 lb ai/A (1x rate) and from rotational oats
planted 7 months following applications totaling 2.44 lb ai/A (0.7x
rate).  Residues were also <LOQ in all processed wheat and oat
fractions.  These data indicate that separate tolerances are not
required for processed fractions derived from small grains (barley,
oats, rye and wheat) rotated with S-metolachlor treated crops.

  SEQ CHAPTER \h \r 1 860.1650 Submittal of Analytical Reference
Standards

Analytical reference standards for metolachlor, CGA-37913 and CGA-49751
are currently available at the EPA National Pesticide Standards
Repository (personal communication with D. Wright, ACB, 6/9/2008). 
However, the standards for CGA-37913 and CGA-49751 have expired
(8/1/2004 and 9/1/2004, respectively).  The registrant must either
recertify the lots in the repository and send in updated certificates of
analysis (COA), or submit new standards (different lot #) if the
previous lots will not be recertified.  If new COAs are being submitted,
they should be faxed to the repository at 410-305-2999.

If new standards are being submitted, they should be sent to the
Analytical Chemistry Lab, which is located at Fort Meade, to the
attention of Theresa Cole at the following address:

	USEPA

	National Pesticide Standards Repository/Analytical Chemistry Branch/OPP

	701 Mapes Road

	Fort George G. Meade, MD  20755-5350

(Note that the mail will be returned if the extended zip code is not
used.)

860.1850 Confined Accumulation in Rotational Crops

Although the available confined rotational crop study was determined to
be adequate (D292881, S. Kinard, 8/15/03), additional information
pertaining to the study remains outstanding.  Information is required on
the percentage of the 14C-residues measured by the current enforcement
method, supporting storage stability data, and sample storage conditions
and intervals.

Although the [14C] S-metolachlor was applied at only 1.45 lb ai/A (0.4x
the maximum seasonal use rate for corn), 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.

860.1900 Field Accumulation in Rotational Crops

47121701.de1.doc (Rotational wheat)

47121702.de1.doc (Rotational oats)

In response to data gaps noted in the revised S-metolachlor TRED
(D292881, S. Kinard, 8/15/03), Syngenta has submitted extensive
rotational crop field trial data for the representative small grains
wheat and oats.  The results from these field trials are discussed below
and the residue data are summarized in Table 9.

Table 9.	Summary of Residue Data from Extensive Rotational Crop Field
Trials with S-Metolachlor.

Crop matrix	Total Applic. Rate

(lb ai/A) 1	PBI 2

(days)	DAP 3 (days)	Combined Residue Levels (ppm) 4

n	Min.	Max.	HAFT 5	Median	Mean	Std. Dev.

Rotational Wheat, 60-day PBI  (Maximum seasonal use rate = 3.7 lb ai/A)

Fall Forage	3.61-3.83	54-86	59-150	22	<0.08	0.47	0.47	0.11	0.15	0.11

Spring Forage

	176-230	22	<0.08	0.14	0.14	0.08	0.09	0.02

Hay

	169-264	28	<0.08	0.26	0.22	0.08	0.10	0.04

Straw

	253-302	28	<0.08	0.28	0.25	0.09	0.12	0.06

Grain

	253-302	28	<0.08	<0.08	<0.08	0.08	0.08	NA

Rotational Oats, 7-month PBI  (Maximum seasonal use rate = 3.7 lb ai/A)

Forage	3.62-3.82 6	201-246	58-62	30	<0.08	0.40	0.30	0.08	0.10	0.061

Hay

	51-114	30	<0.08	0.50	0.48	0.08	0.12	0.101

Straw

	94-147	30	<0.08	0.09	0.09	0.08	0.08	0.003

Grain

	94-147	30	<0.08	<0.08	<0.08	0.08	0.08	NA

1	In each test, S-metolachlor (EC) was applied to the primary corn crop
as a combination of a PPI application at planting and a soil directed
application at lay-by at a seasonal target rate of 3.72lb ai/A (1x
rate).

2	PBI = plant back interval.

3	DAP = days after planting; the interval from planting of the
rotational crop to harvest of the rotational crop commodities.

4	Residues are expressed in parent equivalents.  The LOQs are 0.03 ppm
for CGA-37913, 0.05 ppm for CGA-49751, for a combined LOQ of 0.08 ppm in
all commodities.

5	HAFT = Highest Average Field Trial.

6	Applications were made at ~1x maximum seasonal use rate for the
primary corn crop, except at one field site that had a seasonal rate of
2.44 lb ai/A (0.7x rate).

Wheat.  Fourteen field trials were conducted in Zones 2, 4, 5, 6, 7, 8
and 11 during 2005-2006, examining S-metolachlor residues in/on
rotational winter wheat planted ca. 60 days following the last
application to a primary crop of corn.  In each test, S-metolachlor
(7.64 lb/gal EC) was applied to a primary crop of field corn as a PPI
application at planting at 2.36-2.45 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).  The RTI for
the two applications was 33-92 days, and the lay-by application was
directed to the base of the corn plants, when the plants were ca. 40
inches in height.  All applications were made using ground equipment at
11-27 gal/A, and did not include the use of any adjuvants.  The corn
crop was removed, and a rotational crop of winter wheat was planted at
each site 54-86 days after the last application. 

Single control and duplicate treated samples of fall and spring forage,
hay, grain and straw were collected at the appropriate stages of
maturity.  Fall forage samples were collected from 11 sites at 59-150
DAP, and spring forage samples were collected from 11 sites at 176-230
DAP.  Hay samples were collected from each site at 169-264 DAP, and
grain and straw samples were harvested from each site at 253-302 DAP. 
To assess residue decline, samples of spring forage were collected from
one site at 7-day intervals from 223-237 DAP.  Samples were stored
frozen for up to 12 months prior to analysis, an interval that is
supported by the available storage stability data.

Residues of S-metolachlor in/on wheat commodities were determined as
CGA-37913 and CGA-49751 using an adequate LC/MS/MS method (ENC-5/99). 
The LOQ is 0.03 ppm for CGA-37913 and 0.05 ppm for CGA-49751, each
expressed in parent equivalents, and the combined LOQ is 0.08 ppm for
total residues.

For winter wheat planted ca. 60 days following the last of two
applications of S-metolachlor (EC) to corn at rates totaling 3.61-3.83
lb ai/A (1x maximum seasonal rate), the combined S-metolachlor residues
were <0.08-0.47 ppm in/on fall forage, <0.08-0.14 ppm in/on spring
forage, <0.08-0.26 ppm in/on hay, <0.08-0.28 ppm in/on straw and <0.08
ppm in/on grain.  Average combined residues were 0.15 ppm in/on fall
forage, 0.09 ppm in/on spring forage, 0.10 ppm in/on hay, 0.12 ppm in/on
straw and <0.08 ppm in/on grain.  The residue data for fall and spring
forage indicate that S-metolachlor residues declined at longer harvest
intervals.

Oats.  Fifteen field trials were conducted in Zones 1, 5, 6, 7 and 8
during 2005-2006, examining S-metolachlor residues in/on rotational oats
planted ca. 7 months following the last application to a primary crop of
corn.  In each test, S-metolachlor (7.64 lb/gal EC) was applied to a
primary crop of field corn as a PPI application at planting at 1.15 lb
ai/A (one site) or 2.35-2.49 lb ai/A, followed by a second directed
application at lay-by at 1.25-1.37 lb ai/A, for a total of 2.44-3.82 lb
ai/A/season (ca. 1x the maximum use rate on corn).  The RTI for the two
applications was 38-89 days, and the lay-by application was directed to
the base of the corn plants, when the plants were ca. 40 inches in
height.  All applications were made using ground equipment at 10-25
gal/A, and did not include the use of any adjuvants.  The corn crop was
harvested at maturity, and a rotational crop of oats was planted at each
site 201-246 days after the last application (7 month PBI).

Single control and duplicate treated samples of forage, hay, grain and
straw were collected from each test at the appropriate stage of
maturity.  Forage samples were collected at 58-62 DAP, hay samples were
cut at 51-114 DAP, and grain and straw samples were harvested at
maturity, 94-147 DAP.  To assess residue decline, samples of forage were
also collected from one site at 7-day intervals from 51-65 DAP.  Samples
were stored frozen for up to 10 months prior to analysis, an interval
that is supported by the available storage stability data.

Residues of S-metolachlor in/on oat commodities were determined as
CGA-37913 and CGA-49751 using an adequate LC/MS/MS method (ENC-5/99). 
The LOQ in each commodity is 0.03 ppm for CGA-37913 and 0.05 ppm for
CGA-49751, each expressed in parent equivalents, for a combined LOQ of
0.08 ppm.

 

For oats planted ca. 7 months following the last of two applications of
S-metolachlor (EC) to corn at rates totaling 2.44-3.82 lb ai/A (ca. 1x
maximum seasonal rate), the combined S-metolachlor residues were
<0.08-0.40 ppm in/on forage, <0.08-0.50 ppm in/on hay, <0.08-0.09 ppm
in/on straw and <0.08 ppm in/on grain.  Average combined residues were
0.10 ppm in/on forage, 0.12 ppm in/on hay, and 0.08 ppm in/on straw and
grain.  Although residues in/on forage from the decline test were low,
the data indicated that residues declined over time.

Conclusions.  Although the Agency previously requested rotational crop
field trial data on wheat and oats reflecting a 4.5-month PBI, as
currently specified in the label directions, Syngenta has submitted
rotational field trial data reflecting a 2-month PBI for wheat and a
7-month PBI for oats.  These field trials are 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).

The submitted rotational wheat field trials are adequate.  Although only
14 of the required 20 wheat field trials were conducted, the number and
geographic representation of the field trials is acceptable for winter
wheat, which would be the only type of wheat that would be planted at a
2-month PBI.  The appropriate samples were collected and analyzed using
an adequate method, and the sample storage conditions and intervals are
supported by the available storage stability data.

The submitted rotational oat field trials are also adequate.  Although
only 15 of the required 16 field trials were conducted, the data are
adequate as residues were consistent across all 15 trials, with combined
residues being <LOQ in 67-100% of the samples for each commodity.  The
appropriate samples were collected and analyzed using an adequate
method, and the sample storage conditions and intervals are supported by
the available storage stability data.

Together the wheat and oat data support tolerances of 0.5 ppm for 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 grain of
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 buckwheat grain and rice grain. 
HED no longer recommends for tolerances for rice straw; therefore, this
tolerance can be revoked.

With regard to the proposed 60-day PBI interval for root vegetables
(subgroup1B), tuberous and corm vegetables (subgroup 1C), bulb
vegetables (group 3), leaf petiole vegetables (subgroup 4B), head and
stem Brassica vegetables (subgroup 5A), fruiting vegetables, except
cucurbits (group 8), and winter squash, the available field trial data
(D296904, R. Loranger, 4/17/06) support the proposed 60-day PBI provided
that 1) the application to the previous crop was less than or equal to
the maximum approved rates for the respective crops and crop groups, and
2) the label directions are amended to prohibit application of
S-metolachlor (or metolachlor) to the replanted crops.

860.1550 Proposed Tolerances

The residues of concern in plant and animal commodities include
S-metolachlor and its metabolites, determined as the derivatives
CGA-37913 and CGA-49751.  Tolerances for S-metolachlor are currently
established 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.  

Permanent tolerances for S-metolachlor have been established on numerous
plant commodities ranging from 0.1 ppm in/on various commodities to 20.0
ppm in/on peanut hay [40 CFR §180.368(a)(2)].  Tolerances associated
with regional registrations have also been established for S-metolachlor
residues in/on dry bulb onions and various peppers (chili, Cubanelle,
and tabasco) [40 CFR §180.368(c)(2)].  Tolerances for indirect or
inadvertent residues of S-metolachlor have been established for
non-grass animal feeds (group 18), and the forage, hay, grain and straw
of small cereal grains (barley, buckwheat, oats, rice, rye and wheat). 
Tolerances for rotational crops range from 0.1 ppm in/on various cereal
grains to 1.0 ppm in/on non-grass animal feeds and hay of barley, oats
and wheat.

To assess the adequacy of the existing tolerance on soybean seed (0.2
ppm), a possible tolerance was calculated using the Tolerance/MRL
Harmonization Spreadsheet (January 2008 version) and the residue data
from the submitted soybean field trials, which reflected use of combined
PPI and broadcast foliar applications.  Maximum combined residues from
the current field trials were 0.11 ppm, and the corresponding calculated
tolerance was 0.15 ppm (Appendix I).  These data indicate that the
current 0.2 ppm tolerance for soybean seed is adequate (Table 11).

For the legume vegetable crop subgroups 6A, 6B and 6C, the maximum
observed residues from the trials using the broadcast foliar application
were used to determine recommended tolerances.  75-96% of the residue
values for the representative commodities were <LOQ.  The maximum
combined residues were 0.25 ppm for subgroup 6A, 0.14 ppm for subgroup
6B, and 0.23 ppm for subgroup 6C.  These data indicate that a 0.3 ppm
tolerance for residues on crop group 6 is appropriate.

For sorghum, the adequacy of the existing tolerances on forage and
stover were assessed using the Tolerance/MRL Harmonization Spreadsheet
and the residue data from the submitted field trials, reflecting the
postemergence application to sorghum.  The maximum combined residues
from the postemergence field trials were 0.63 ppm in/on forage and 0.44
ppm in/on stover, and the corresponding calculated tolerances were 0.60
and 0.70 ppm, respectively.  For sorghum grain, maximum combined
residues were 0.09 ppm; the remaining samples had residues <LOQ (<0.08
ppm).  These data indicate that the current tolerances for sorghum
forage (1.0 ppm), stover (4.0 ppm) and grain (0.1 ppm) are adequate.

For AGF, the available corn residue data indicate that residues either
do not concentrate in AGF or would be present at levels below the
tolerances on grain.  However, residues were shown to concentrate by
3.1x in sorghum AGF and 3.9x in soybean AGF.  Based on the maximum
combined residues observed in/on soybean seeds (<0.17 ppm, data from
TRED), the maximum expected residues would be 0.66 ppm for soybean AGF. 
Therefore, a separate tolerance should be established for AGF at 0.7
ppm.

The adequate wheat and oat rotational crop field trial data were used to
reassess the existing tolerances for indirect or inadvertent residues on
rotated small grains (barley, buckwheat, oats, rice, rye, and wheat). 
The maximum observed residues were as follows: 0.47 ppm in/on wheat
forage, 0.40 ppm in/on oat forage, 0.26 ppm in/on wheat hay, 0.50 ppm
in/on oat hay, 0.28 ppm in/on wheat straw, 0.09 ppm in/on oat straw, and
<0.08 ppm in/on wheat and oat grain.  The Tolerance/MRL Harmonization
Spreadsheet was used to calculate possible tolerances only for wheat
forage, hay and straw residue data.  Other commodities has a large
number of samples with residues <LOQ.  The calculated tolerances were
0.5 ppm for wheat forage, 0.25 ppm for wheat hay and 0.40 ppm for wheat
straw.  Considering both the maximum observed residues and the possible
calculated tolerances, the data support the existing 0.5 ppm tolerances
for barley straw, oat forage and straw, rye forage and straw, and wheat
forage and straw, and the existing 0.1 ppm tolerances for grain of
barley, buckwheat, oats, rice, rye and wheat.  The data also indicate
that the existing 1.0 ppm tolerances for barley hay, oat hay and wheat
hay can be reduced to 0.5 ppm, and the existing 0.5 ppm tolerance for
rice straw can be reduced to 0.1 ppm. (Note: as rice can only be
replanted the following spring, the oat straw data (7-month PBI) were
used to set the rice straw tolerance)

Harmonization

No maximum residue limits (MRLs) for metolachlor or S-metolachlor have
been established or proposed by Codex (Steve Funk, email 7/11/08). 
Codex does not set MRLs for Aspirated Grain Fractions (AGF), and there
are no metolachlor/s-metolachlor MRLS for either Mexico or Canada (S.
Funk, 9/27/08).

Canada has the following residue definition: 
2-chloro-N-(2-ethyl-6-methylphenyl)-N-[(1S)-2-methoxy-1-methylethyl)acet
amide and
2-chloro-N-(2-ethyl-6-methylphenyl)-N-[(1R)-2-methoxy-1-methylethyl)acet
amide including the metabolites
2-[(2-ethyl-6-methylphenyl)amino]-1-propanol and
4-(2-ethyl-6-methylphenyl)-2-hydroxy-5-methyl-3-morpholinone.

Mexico has the following residue definition:  S-metolachlor.

Selected MRLs (ppm) germane to this analysis for S-metolachlor are
provided in Table 10 (Note:  It does not include all s-metolachlor
MRLs):

Table 10. 	Selected MRLs for S-Metolachlor.

Commodity	Canada	Mexico

Bean

15

Chick pea

15

Corn, grain	0.1	0.1

Dry bean	0.3

	Lentil

15

Lima bean	0.3

	Pea	0.3

	Snap bean	0.3

	Sorghum, grain

0.3

Soybean, grain	0.2	0.2

Canada currently has a tolerance of 0.3 ppm for S-metolachlor in peas
and snap beans. A higher United States tolerance could result in a trade
irritant for these crops exported from the United States to Canada.  In
addition, Canada has a tolerance of 0.3 ppm for S-metolachlor in dry
beans. A lower United States tolerance could result in a trade irritant
for these crops exported from Canada to the United States.  The residue
data support harmonization of these tolerances at 0.3 ppm tolerance.

Table 11. 	Tolerance Summary for S-Metolachlor.

Commodity	Established/Proposed Tolerance (ppm)	Recommended Tolerance
(ppm)	Comments; Correct Commodity Definition

40 CFR §180.368(a)(3)

Aspirated grain fractions	None	0.7	Based on the average 3.9x
concentration of residues in AGF from soybean and maximum residues in
soybean seed (<0.17 ppm) 1

Vegetable, legume, edible podded, subgroup 6A	0.5	

0.3	Establish Crop Group tolerance for Crop Group 6: Legume Vegetables
(succulent or dried), except soybean.  Harmonizes with Canada.

Pea and bean, succulent  shelled, subgroup 6B	None

Pea and bean, dried shelled, except soybean, subgroup 6C	0.1

Sorghum, grain, forage	1.0	1.0	Grain tolerance harmonizes with Mexico.

Sorghum, grain, stover	4.0	4.0

	Sorghum, grain, grain	0.3	0.3

	Soybean, seed	0.2	0.2	Adequate data are available.  Maximum combined
residues are <0.17 ppm in/on seeds. 

Harmonizes with Canada.

40 CFR §180.368(d)

Barley, grain	0.1	0.1	Recommended tolerances are based on both the
available wheat (2-month PBI) and oat (7-month PBI) field trial data.

Barley, hay	1.0	0.5

	Barley, straw	0.5	0.5

	Buckwheat, grain	0.1	0.1

	Oat, forage	0.5	0.5

	Oat, grain	0.1	0.1

	Oat, hay	1.0	0.5

	Oat, straw	0.5	0.5

	Rice, grain	0.1	0.1	Tolerances are based only on oat field trials
(7-month PBI) as rice would only be replanted the spring following
treatment.

Rice, straw	0.5	0.1

	Rye, forage	0.5	0.5	Recommended tolerances are based on both the
available wheat (2-month PBI) and oat (7-month PBI) field trial data.

Rye, grain	0.1	0.1

	Rye, straw	0.5	0.5

	Wheat, forage	0.5	0.5

	Wheat, grain	0.1	0.1

	Wheat, hay	1.0	0.5

	Wheat, straw	0.5	0.5

	1	The maximum residue value for soybeans was from the revised
S-Metolachlor TRED (D292881, S. Kinard, 8/15/03).

2	The maximum residue value for edible-podded peas and beans was from
the earlier IR-4 petitions (PP# 3E6787, D296904, R. Loranger, 4/17/06).

References

	D226780; Replacement of Metolachlor Technical (Racemic Metolachlor)
with Alpha-Metolachlor (formerly called Chiral Metolachlor) Technical;
Review of Bridging Data; L. Kutney; 11/12/1996.  MRID(s): 
43928901-43928903, 43928939-43928942.	

	D278742/D279110; S-Metolachlor.  Information Supporting the Assertion
That the Metabolism of S-Metolachlor Is Essentially the Same as for the
Racemic Mixture; S. Kinard; 8/15/2003; MRID(s):  45499603, 45499604,
45499605, 45533103	

	D283235; 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; S. Kinard; 8/15/2003;
 MRID:  45672302.  	

	D292881; 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.  R.
Loranger;  8/15/2003;  MRID(s):  44378401, 44908701, 45544701.

D296904; PP# 3E6787.  S-Metolachlor.  Petition for Tolerances on Various
Crops, Crop Groups, and Livestock Commodities.  Summary of Analytical
Chemistry and Residue Data;  R. Loranger; 4/17/2006;  MRID(s): 
45499609, 45499610, and 46046501 through 46046506.

  SEQ CHAPTER \h \r 1 Attachments:  

Appendix I - Tolerance Assessment Calculations

Appendix  I - Tolerance Assessment Calculations

The Agency’s Tolerance/MRL Harmonization Spreadsheet was utilized for
determining possible tolerance levels for soybean seeds, sorghum forage
and stover, and rotational wheat forage, hay and straw, as these were
the only commodities from the current studies for which ≤61% of the
samples had combined residues <LOQ (Guidance for Setting Pesticide
Tolerances Based on Field Trial Data, 5/9/2005).  Maximum likelihood
estimation was used to impute residue values for the samples whose
empirical data were <LOQ (<0.08 ppm) for the above listed commodities. 
Combined S-metolachlor residues were <LOQ in/on >61% of the samples of
sorghum grain, legume vegetables (except soybeans), rotated wheat grain,
and rotated oat forage, hay, grain and straw.  The residue datasets for
the submitted field trials and rotational crop field trials are
presented in Tables I-1 through I-5.

The datasets used to calculate possible tolerances consisted of field
trial data representing applications of a EC formulation at 1x the
maximum proposed use rate.  As specified by the Guidance for Setting
Pesticide Tolerances Based on Field Trial Data SOP, the field trial
application rates were within 25% of the maximum label application rate,
and the PHIs were consistent with the appropriate stage of maturity and
the proposed PHIs.

The datasets for the combined S-metolachlor residues in/on soybeans,
sorghum forage and stover, and wheat forage, hay and straw were entered
into the tolerance spreadsheet.  Visual inspection of the lognormal
probability plot (Figures I-1, -6, -8, -10, -11, -13, -15, -17, and -19)
indicates that the datasets are reasonably lognormal.  With the
exception of wheat forage (Figure I-15), the results from the
approximate Shapiro-Francia tests confirmed this assumption.  The
calculated possible tolerances were 0.15 ppm for soybeans, 0.6 ppm for
sorghum forage, 0.7 ppm for sorghum stover, 0.5 ppm for rotated wheat
forage, 0.25 ppm for rotated wheat hay, and 0.40 ppm for rotated wheat
straw.



Table I-1.	Combined S-Metolachlor Residues in/on Soybean Seeds following
a Combination of PPI and Broadcast Foliar Applications at Rates Totaling
~2.5 lb ai/A/season.

Regulator:	EPA

Chemical:	S-Metolachlor

Crop:	Soybean seed (MLE)

PHI:	85-103 days

App. Rate:	2.47-2.55 lb ai/A

Submitter:	Syngenta

MRID Citation:	MRID 47304702

	Combined Residues

	0.056

	0.059

	0.062

	0.063

	0.065

	0.066

	0.067

	0.068

	0.069

	0.070

	0.071

	0.072

	0.073

	0.074

	0.074

	0.075

	0.076

	0.077

	0.078

	0.078

	0.080

	0.090

	0.090

	0.090

	0.090

	0.090

	0.090

	0.090

	0.090

	0.090

	0.090

	0.100

	0.100

	0.100

	0.100

	0.110

1	Residue values <LOQ are listed in bold.

Figure I-1.	Lognormal Probability Plot of S-Metolachlor Residues in/on
Soybean Seed Following a combined PPI and Broadcast Foliar Application.

Figure I-2.	Data Summary Sheet for Residues of S-Metolachlor in/on
Soybean Seed Following a combined PPI and Broadcast Foliar Application.



Table I-2.	Combined S-Metolachlor Residues in/on Legume Vegetables,
Except Soybeans (Subgroup 6A, 6B and 6C) following a Single Broadcast
Foliar Application at ~1.9 lb ai/A.

Regulator:	EPA

Chemical:	S-Metolachlor

Crop:	Edible Podded Peas and Beans (Subgroup 6A)	Succulent Shelled Peas
and Beans (Subgroup 6B)	Dried Shelled Peas and Beans (Subgroup 6C)

PHI:	42-106 days	37-127 days	40-92 days

App. Rate:	1.88-2.02 lb ai/A	1.86-1.98 lb ai/A	1.90-1.96 lb ai/A

Submitter:	Syngenta

MRID Citation:	MRID 46829501

	Combined Residues

	0.08	0.08	0.08

	0.08	0.08	0.08

	0.08	0.08	0.08

	0.08	0.08	0.08

	0.08	0.08	0.08

	0.08	0.08	0.08

	0.08	0.08	0.08

	0.08	0.08	0.08

	0.08	0.08	0.08

	0.08	0.08	0.08

	0.08	0.08	0.08

	0.08	0.08	0.08

	0.08	0.08	0.08

	0.08	0.08	0.08

	0.09	0.08	0.08

	0.13	0.08	0.08

	0.16	0.08	0.08

	0.25	0.08	0.08

0.08	0.08

0.08	0.08

0.08	0.08

0.08	0.10

0.08	0.10

0.14	0.11

	0.11

	0.13

	0.19

	0.23

1	Residue values <LOQ are listed in bold.

Figure I-3.	Data Summary Sheet for Residues of S-Metolachlor in/on
Subgroup 6A Commodities.

 



Figure I-4.	Data Summary Sheet for Residues of S-Metolachlor in/on
Subgroup 6B Commodities.

Subgroup 6 Commodities With MLE Inputs

Figure I-5.	Data Summary Sheet for Residues of S-Metolachlor in/on
Subgroup 6A Commodities (MLE inputs).

0

Figure I-6.	Lognormal Probability Plot for Residues of S-Metolachlor
in/on Subgroup 6A

                         Commodities (MLE inputs).

Figure I-7.	Data Summary Sheet for Residues of S-Metolachlor in/on
Subgroup 6B

                         Commodities (MLE inputs).

Figure I-8.	Lognormal Probability Plot for Residues of S-Metolachlor
in/on Subgroup 6B Commodities (MLE inputs).

Figure I-9.	Data Summary Sheet for Residues of S-Metolachlor in/on
Subgroup 6C

                         Commodities (MLE inputs).

Figure I-10.	Lognormal Probability Plot for Residues of S-Metolachlor
in/on Subgroup 6C Commodities (MLE inputs).

 

Table I-3.	MLE Inputs for the Combined S-Metolachlor Residues in/on
Legume Vegetables, Except Soybeans (Subgroup 6A, 6B and 6C) following a
Single Broadcast Foliar Application at ~1.9 lb ai/A.

Regulator:	EPA

Chemical:	S-Metolachlor

Crop:	Edible Podded Peas and Beans (Subgroup 6A)	Succulent Shelled Peas
and Beans (Subgroup 6B)	Dried Shelled Peas and Beans (Subgroup 6C)

PHI:	42-106 days	37-127 days	40-92 days

App. Rate:	1.88-2.02 lb ai/A	1.86-1.98 lb ai/A	1.90-1.96 lb ai/A

Submitter:	Syngenta

MRID Citation:	MRID 46829501

	Combined Residues

	0.0085	0.007	0.007

	0.0119	0.009	0.010

	0.0148	0.011	0.012

	0.0177	0.013	0.014

	0.0207	0.015	0.016

	0.0238	0.017	0.018

	0.0271	0.019	0.020

	0.0307	0.021	0.022

	0.0347	0.023	0.024

	0.0392	0.025	0.027

	0.0444	0.027	0.029

	0.0505	0.029	0.031

	0.0579	0.031	0.034

	0.0673	0.034	0.037

	0.09	0.036	0.040

	0.13	0.039	0.044

	0.16	0.042	0.048

	0.25	0.046	0.052

0.050	0.058

0.054	0.064

0.059	0.071

0.065	0.10

0.072	0.10

0.140	0.11

	0.11

	0.13

	0.19

	0.23

1	Residue values <LOQ  and replaced with MLE values are listed in bold.



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ty Plot of S-Metolachlor Residues in/on Sorghum Forage.

Figure I-12.	Data Summary Sheet for Residues of S-Metolachlor in/on
Sorghum Forage.

Figure I-13.	Lognormal Probability Plot of S-Metolachlor Residues in/on
Sorghum Stover.

Figure I-14.	Data Summary Sheet for Residues of S-Metolachlor in/on
Sorghum Stover.

Table I-5.	Combined S-Metolachlor Residues in/on Wheat Commodities from
a 60-day PBI Following Applications Totaling ~3.7 lb ai/A/season.

Regulator:	EPA

Chemical:	S-Metolachlor

Crop:	Wheat fall forage (MLE)	Wheat Hay (MLE)	Wheat straw (MLE)	Wheat
grain

PHI:	60-day PBI

App. Rate:	3.61-3.83 lb ai/A

Submitter:	Syngenta

MRID Citation:	MRID 47121701

	Combined Residues

	0.05	0.04	0.03	0.08

	0.06	0.04	0.04	0.08

	0.07	0.04	0.04	0.08

	0.07	0.05	0.05	0.08

	0.09	0.05	0.05	0.08

	0.09	0.05	0.05	0.08

	0.10	0.05	0.06	0.08

	0.10	0.06	0.06	0.08

	0.10	0.06	0.07	0.08

	0.11	0.06	0.07	0.08

	0.11	0.06	0.08	0.08

	0.11	0.06	0.08	0.08

	0.11	0.08	0.09	0.08

	0.13	0.08	0.09	0.08

	0.13	0.08	0.09	0.08

	0.14	0.08	0.09	0.08

	0.14	0.08	0.10	0.08

	0.15	0.08	0.10	0.08

	0.16	0.08	0.10	0.08

	0.17	0.09	0.11	0.08

	0.46	0.09	0.11	0.08

	0.47	0.09	0.19	0.08

0.11	0.20	0.08

0.11	0.20	0.08

0.13	0.22	0.08

0.15	0.24	0.08

0.17	0.25	0.08

0.26	0.28	0.08

1	Residue values <LOQ are listed in bold.

Figure I-15.	Lognormal Probability Plot of S-Metolachlor Residues in/on
Rotated Wheat Forage from a 60-day PBI.

Figure I-16.	Data Summary Sheet for Residues of S-Metolachlor in/on
Wheat Forage from a 60-day PBI.

Figure I-17.	Lognormal Probability Plot of S-Metolachlor Residues in/on
Rotated Wheat Hay from a 60-day PBI.

Figure I-18.	Data Summary Sheet for Residues of S-Metolachlor in/on
Wheat Hay from a 60-day PBI.

Figure I-19.	Lognormal Probability Plot of S-Metolachlor Residues in/on
Rotated Wheat Straw from a 60-day PBI.

Figure I-20.	Data Summary Sheet for Residues of S-Metolachlor in/on
Wheat Straw from a 60-day PBI.

Table I-6.	Combined S-Metolachlor Residues in/on Oat Commodities from a
7-month PBI Following Applications Totaling ~3.71 lb ai/A/season.

Regulator:	EPA

Chemical:	S-Metolachlor

Crop:	Rotated Oat forage	Rotated Oat hay	Rotated Oat straw	Rotated Oat
grain

PHI:	7.5-month PBI

App. Rate:	3.62-3.82 lb ai/A

Submitter:	Syngenta

MRID Citation:	MRID 47121702

	Combined Residues

	0.08	0.08	0.08	0.08

	0.08	0.08	0.08	0.08

	0.08	0.08	0.08	0.08

	0.08	0.08	0.08	0.08

	0.08	0.08	0.08	0.08

	0.08	0.08	0.08	0.08

	0.08	0.08	0.08	0.08

	0.08	0.08	0.08	0.08

	0.08	0.08	0.08	0.08

	0.08	0.08	0.08	0.08

	0.08	0.08	0.08	0.08

	0.08	0.08	0.08	0.08

	0.08	0.08	0.08	0.08

	0.08	0.08	0.08	0.08

	0.08	0.08	0.08	0.08

	0.08	0.08	0.08	0.08

	0.08	0.08	0.08	0.08

	0.08	0.08	0.08	0.08

	0.08	0.08	0.08	0.08

	0.08	0.08	0.08	0.08

	0.08	0.09	0.08	0.08

	0.08	0.10	0.08	0.08

	0.08	0.10	0.08	0.08

	0.08	0.11	0.08	0.08

	0.08	0.13	0.08	0.08

	0.10	0.14	0.08	0.08

	0.10	0.15	0.08	0.08

	0.10	0.16	0.08	0.08

	0.19	0.46	0.09	0.08

	0.40	0.50	0.09	0.08

1	Residue values <LOQ are listed in bold.

Page   PAGE  1  of   NUMPAGES  55 

S-Metolachlor.  Summary of Analytical Chemistry and Residue Data	DP#s: 
332846, 332847, 332848, 332849 

                                                                        
                                                     350604, 350942,
351174, 351226