                                       


                    UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
                               WASHINGTON, D.C.  20460
	
	OFFICE OF CHEMICAL SAFETY AND
	POLLUTION PREVENTON
                                                                               
MEMORANDUM

Date:  August 7, 2013

SUBJECT:	S-Metolachlor, PP#2F8115.  Petition for the Amendment of Permanent Tolerances for Residues of S-Metolachlor on Corn, field, forage; Corn, sweet, forage; and Corn, stover.  Summary of Analytical Chemistry and Residue Data.

PC Code:  108800
DP Barcode:  D407466, D413850
Decision No.:  471357
Registration No.:  100-818
Petition No.:  2F8115
Regulatory Action:  Petition, no amended use
Risk Assessment Type:  NA
Case No.:  0001
TXR No.:  NA
CAS No.:  87392-12-9
MRID No.:  48932501, 49186501
40 CFR:  180.368 (a)(2)
	
FROM:	Susan V. Hummel, Senior Chemist
		Risk Assessment Branch 4, Health Effects Division, 7509P

THROUGH:	Thurston G. Morton, Senior Chemist
		Risk Assessment Branch 4, Health Effects Division, 7509P

TO:		Michael Walsh & Kathryn V. Montague, PM#23
		Fungicides Branch, Registration Division, 7505P


Executive Summary

S-Metolachlor (an isomer enriched form of metolachlor) is a selective, chloroacetanilide herbicide that is applied to a variety of crops as a preplant, preplant incorporated, preemergence, or postemergence application, primarily for the control of grass weeds.  S-Metolachlor is registered to Syngenta Crop Protection, Inc. for use on a wide variety of crops including: corn, cotton, grasses grown for seed, legume vegetables, peanuts, potatoes, safflower, sorghum, sunflower, and tomatoes.  

Pesticide petition #2F8115 was submitted to amend the established tolerances for the herbicide S-metolachlor in or on corn, field, forage; corn, sweet, forage; and corn, stover to 20 ppm; 40 ppm; and 40 ppm, respectively. A tolerance for combined residues (free and bound) of S-metolachlor, its R-enantiomer and its metabolites, determined as the derivatives, 2-[2-ethyl-6-methylphenyl)amino]-1-propanol and 4-(2-ethyl-6-methylphenyl)-2-hydroxy-5-methyl-3-morpholinone is currently established under 40 CFR 180.368 on corn, field, forage; corn, sweet, forage; and corn, stover at 6.0 ppm.  In connection with PP#2F8115, a residue study was submitted with S-metolachlor treated field corn, field corn/simulated sweet corn, sweet corn and popcorn.  A safener was used in the study.  The use pattern used was the currently registered use pattern for Dual II Magnum (EPA Reg. No 100-818).  Residues of S-metolachlor in some samples of forage and stover exceeded the current tolerances.

The nature of S-metolachlor residues in crops and livestock is understood based on adequate crop and livestock metabolism studies with metolachlor and S-metolachlor.  For both S-metolachlor and metolachlor, the residues of concern in crop and livestock commodities include the parent compound (both R and S-enantiomers) and its metabolites, determined as the derivatives CGA-37913 and CGA-49751.  Following recommendations made in the revised Tolerance Reassessment Eligibility Decision (TRED) for Metolachlor and S-Metolachlor (DP# 292881, 8/15/03, S. Kinard), tolerances for metolachlor and S-metolachlor have been separated.  Permanent tolerances for combined S-metolachlor residues have been established for crop commodities ranging from 0.10 ppm in/on a variety of crop commodities to 20 ppm in/on peanut hay [40 CFR §180.368(a)(2)].  Permanent tolerances for indirect or inadvertent residues of 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, millet, oats, rice, rye and wheat), at levels ranging 0.10 ppm in/on grains to 1.0 ppm in/on non-grass animal feeds [40 CFR §180.368(d)(2)].

Adequate methodology is available for enforcing the current tolerances.  The Pesticide Analytical Manual (PAM), Vol. II, lists a gas chromatography method with nitrogen phosphorus detection (GC/NPD) for determining residues in/on crop commodities (Method I) and a GC method with mass selective detection (GC/MSD) for determining residues in livestock commodities (Method II).  These methods determine residues of metolachlor and its metabolites as either CGA-37913 or CGA-49751 following acid hydrolysis.  

Syngenta has proposed an enantiomer-specific high performance liquid chromatography method with triple quadrupole mass spectrometric detection (LC/MS/MS) for the enforcement of the proposed tolerances, Method 1848-01, which has been previously reviewed by HED (DP# 296904, 4/17/06, R. Loranger).  The method uses a chiral HPLC column to separate out the S-enantiomers (SYN506357 and SYN508500) of the hydrolysis products CGA-37913 and CGA-49751, respectively.  HED concluded that the method is not appropriate for enforcement purposes because it does not determine residues of the R-isomers of metolachlor and its metabolites, which are included in the tolerance expression.  The S:R ratio in the active ingredient is 88:12; therefore, there is potential for residues of the R-isomers of metolachlor and its metabolites in crop commodities.  The method could be adapted for enforcement by measuring both the S- and the R-enantiomers and monitoring 2 ion transitions per analyte.  

Residue data from the current field trial studies were obtained using LC/MS/MS Analytical Method No. ENC-5/99, with modifications found in EPL-BAS Study Number 110S50 (MRID 49186501).  A complete description of the method was not included in the submission, nor in MRID 49186501.  Briefly, a subsample of each corn matrix was refluxed for 16 hours in 6N hydrochloric acid.  After cooling and filtering, an aliquot was diluted with water, basified, and partitioned into dichloromethane (DCM).  Partitioning was repeated, and the DCM fractions were combined and concentrated; methanol was added and the sample was again concentrated.  Each sample was then diluted to a final volume with methanol:water (17:83, v:v) for analysis by LC/MS/MS in the positive ionization mode, using a reverse phase column (Luna C18).  MS/MS detection of CGA-37913 and CGA-49751 monitored the ion transitions from m/z 194-->136 and m/z 250-->204, respectively. [The reviewer noted that the incorrect ion transitions were noted in the report; these have been corrected here, and were confirmed via email by the petitioner.]  All residue levels of the metabolites were converted to parent equivalents using molecular weight factors of 1.47 and 1.14 for CGA-37913 and CGA-49751, respectively.  The limits of quantitation (LOQs, based on the LLMVs) were 0.03 and 0.05 ppm for CGA-37913 and CGA-49751, respectively, in all corn matrices. The petitioner used the LLMVs as the limits for reporting residues.  The method was validated prior to and in conjunction with the analysis of field trial samples.

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

Adequate concurrent storage stability data were submitted to support the sample storage conditions and durations from the submitted field trial and processing studies.  These data indicate that the metolachlor derivatives CGA-49751 and CGA-37913 and/or S-metolachlor derivatives SYN506357 and SYN508500 are stable during frozen storage for at least 2 years on corn commodities.

Although there are livestock feedstuffs associated with the current petition, the proposed uses impact the diet for beef cattle, but not dairy cattle.  The tolerance is based on the dietary burden of S-metolachlor to dairy cattle.  Therefore, no changes to the existing tolerances for livestock commodities are needed.

The tolerance proposals are adequate.  Adequate field trial data have been submitted with the current petition to support the requested tolerances.  Geographic representation was adequate.  An adequate analytical method was used for the analysis.  The data were properly supported by storage stability data.

An adequate confined rotational crop study is available, although additional information  pertaining to the study remains outstanding.  The residues of concern in rotated crops are the same as in the primary crops, S-metolachlor, its R-enantiomer, and its metabolites determined as CGA-37913 and CGA-49751.  Adequate field rotational crop data have been submitted previously which support the existing rotational crop restrictions on the labels for EPA Reg. Nos. 100-816 and 100-818.

Regulatory Recommendations and Residue Chemistry Deficiencies

HED has examined the residue chemistry database for S-metolachlor.  Pending submission of analytical standards and a revised Section F, there are no residue chemistry issues that would preclude setting of the recommended tolerances for S-metolachlor on corn forage and stover, as indicated in Table 8.  No change in the current registration for S-metolachlor is requested.

A deficiency remains with regard to the confined rotational crop study.

A human health risk assessment is forthcoming.

860.1850 Confined Accumulation in Rotational Crops

   * To support the confined rotational crop study submitted under MRID 41470601, the additional data required by HED (DP# 207842, 10/12/94, S. Hummel) must be submitted; additional data were required characterizing the [14]C-residues in plants, along with information on the percentage of the [14]C-residues measured by the current enforcement method; sample storage conditions and intervals and supporting storage stability data were also required.  These data requirements were reiterated in the Metolachlor TRED (DP# 292881, 8/15/03, S. Kinard).

Background

The chemical structure and nomenclature of S-metolachlor and its regulated hydrolytic derivatives are presented in Table 1, and the physicochemical properties of S-metolachlor are presented in Table 2.  

Table 1.	Nomenclature of S-Metolachlor and its Regulated Hydrolytic Derivatives.
Parent compound
                                       
Common name
1S-Metolachlor
Company experimental name
CGA-77102
IUPAC name
(S)-2-chloro-N-(2-ethyl-6-methyl-phenyl)-N-(2-metonym-1-methyl-ethyl)-acetamide
CAS name
2-chloro-N-(2-ethyl-6-methylphenyl)-N-[(1S)2-methoxy-1-methylethyl]-acetamide
CAS registry number
87392-12-9
End-use product (EP)
Dual Magnum(R) Herbicide (7.62 lb/gal EC; EPA Reg. No. 100-816) and 
Dual II Magnum(R) Herbicide (7.64 lb/gal EC; EPA Reg. No. 100-818)
Regulated residue
                                       
Common name
None
Company experimental names
CGA-37913
SYN506357 (S-enantiomer of CGA 37913)
Chemical name
2-[(2-ethyl-6-methylphenyl) amino]-1-propanol
CAS registry number
61520-53-4
82508-08-5 (S-enantiomer)
Regulated residue
                                       
Common name
None
Company experimental names
CGA-49751
SYN508500 (S-enantiomer of CGA 49751)
Chemical name
4-(2-ethyl-6-methylphenyl)-2-hydroxy-5-methyl-3-morpholinone
CAS registry number
61520-54-5

Table 2.	Physicochemical Properties of S-Metolachlor.
Parameter
Value
Reference
Melting point/range
Not applicable, liquid at room temperature
MRID 47121701 (DP#s 332846, etc., 10/21/08, D. McNeilly)
pH
7.8 at 25 ºC (1% aqueous dispersion)

Density
1.117 g/cm[3] at 20 ºC

Water solubility (25°C)
0.48 g/L

Solvent solubility (mg/L at 25°C)
Completely miscible with methanol, acetone, toluene, n-octanol, n-hexane, ethyl acetate, and dichloromethane.

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

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

Octanol/water partition coefficient Log(KOW)
3.05 at 25 ºC

UV/visible absorption spectrum
Neutral:	534 L/mol::cm @ 266.4 nm
	443 L/mol::cm @ 274.4 nm
Acidic:	534 L/mol::cm @ 266.4 nm
	444 L/mol::cm @ 274.4 nm
Basic:	531 L/mol::cm @ 266.4 nm
	411 L/mol::cm @ 274.4 nm


860.1200 Directions for Use

The petitioner provided a text listing of proposed uses in Section B of the petition, already registered on the label for Dual II Magnum(R) (EPA Reg. No. 100-818), a 7.64 lb/gal EC formulation.  This use summary is based on Section B of the petition.

Table 3.	Summary of Current Directions for Use of S-Metolachlor.[1]
Applic. Timing; Type; and Equip.
(minimum volume)
                                  Formulation
                                [EPA Reg. No.]
                                 Applic. Rate
                                   (lb ai/A)
                          Max. No. Applic. per Season
                          Max. Seasonal Applic. Rate
                                   (lb ai/A)
                                      PHI
                                    (days)
                                     Corn 
Fall Application for Spring Control/ Early Preplant
Broadcast
                                7.62 lb/gal EC
                                   [100-818]
                                  1.6  -  1.9
                                      NS
                                      3.7
                                      NS
Preplant Incorporated or Preemergence Broadcast
                                       
                                   0.95-1.9
                                      NS
                                      3.7
                                      NS
Postemergence or Layby Broadcast
                                       
                                   Up to 1.9
                                      NS
                                      3.7
                                      NS
Use higher rates on fine or >2,5-3% organic matter soils. Split application may be used. Ground application minimum 5 GPA; aerial application minimum 2 GPA.  Do not use Dual II Magnum on peat or muck soils.  Do not graze or feed forage from treated areas for 30 days following application.  Do not harvest sweet corn ears for 60 days following application.

The proposed uses specify that lower rates should be used on relatively coarse textured soils and higher rates should be used on fine textured soils.  

Conclusions.  The registered use directions are adequate to allow for evaluation of the submitted residue data relative to the current uses.  The registered uses are generally supported by the submitted field trial data.  

The rotational crop restrictions on the label for EPA Reg. No. 100-816 have been evaluated previously (DP#s 332846, etc., 10/21/08, D. McNeilly).  It was concluded that the proposed restrictions are supported by the available data, provided that that rotational crop directions for crops with a 60-day PBI be amended to prohibit a second application of S-metolachlor to any of these crops replanted within 60 days of the original application.  Since the full label was not provided in the current petition, it is unknown if these changes have been made.

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 concen in plants include metolachlor and its metabolites, determined as the derivatives CGA-37913 and CGA-49751.  The Agency previously concluded that the residues of concern for S-metolachlor are the same as for metolachlor (DP# 226780, 11/15/96, L. Kutney).

The Agency has also reviewed plant metabolism data on S-metolachlor from field tests on soybeans and corn, in vitro tests on corn seedlings, and greenhouse tests on seedlings of corn, sorghum, soybeans and peanuts (DP#s 278742 and 279110, 8/15/03, S. Kinard).  These data support Syngenta's assertion that the metabolism of S-metolachlor in plants is similar to that for the racemic mixture.  The data did not address whether there is any conversion of the S-isomers of metolachlor or its metabolites to the R-isomer forms; however, HED previously concluded that such conversion of isomers in plants is not likely to be significant.


860.1300 Nature of the Residue - Livestock

Adequate studies are available depicting the metabolism of metolachlor in ruminants and poultry.  Metolachlor is rapidly metabolized and almost totally eliminated in the urine and feces of ruminants (goats), non-ruminants (rats), and poultry.  Metolachlor per se was not detected in any of the excreta or tissues.  As in plants, metolachlor residues of concern in livestock commodities include metolachlor and its metabolites, determined as the derivatives CGA-37913 and CGA-49751.  The residues of concern for S-metolachlor in livestock are the same as those for metolachlor.

The Agency has also reviewed livestock metabolism data on S-metolachlor (DP#s 278742, 8/15/03, S. Kinard).  Data from a goat metabolism study indicated that S-metolachlor was readily absorbed and extensively metabolized by goats via glutathione conjugation and/or oxidation reactions.  Oxidized metabolites were also conjugated with glucuronic acid.  Data from a poultry metabolism study indicated that S-metolachlor was also extensively metabolized via O demethylation and subsequent glucuronic acid conjugation or oxidation to dihydroxy or carboxylic acid metabolites that may also be conjugated with glucuronic acid.

860.1340 Residue Analytical Methods

Enforcement methods:  Adequate methodology is available for enforcing the established and recommended tolerances.  PAM Vol. II, Pesticide Regulation Section 180.368, lists a GC/NPD method (Method I) for determining residues in/on crop commodities and a GC/MSD method (Method II) for determining residues in livestock commodities.  These methods determine residues of metolachlor and its metabolites as either CGA-37913 or CGA-49751 following acid hydrolysis.

IR-4 and Syngenta have proposed an LC/MS/MS enantiomer-specific method for the enforcement of the proposed tolerances, Method 1848-01.  This method has been previously reviewed by HED (DP# 296904, 4/17/06, R. Loranger).  The method as written uses a chiral HPLC column to separate out the S-enantiomers (SYN506357 and SYN508500) of the hydrolysis products CGA-37913 and CGA-49751.  The method monitors a single ion transition per analyte.

Data-gathering methods:  Samples of crop commodities from the submitted field trial studies were analyzed for residues of metolachlor and its metabolites convertible to the derivatives CGA-49751 and CGA-37913 using high performance liquid chromatography with tandem mass spectrometric detection (LC/MS/MS) according to Analytical Method No. ENC-5/99, with modifications found in EPL-BAS Study Number 110S50 (MRID 49186501).  A complete description of the method was not included in the submission.

Briefly, a subsample of each corn matrix was refluxed for 16 hours in 6N hydrochloric acid.  After cooling and filtering, an aliquot was diluted with water, basified, and partitioned into dichloromethane (DCM).  Partitioning was repeated, and the DCM fractions were combined and concentrated; methanol was added and the sample was again concentrated.  Each sample was then diluted to a final volume with methanol:water (17:83, v:v) for analysis by LC/MS/MS in the positive ionization mode with an APCI interface, using a reverse phase column (Luna C18) and gradient elution with acetonitrile:water.  MS/MS detection of CGA-37913 and CGA-49751 monitored the ion transitions from m/z 194.3 --> 136.3 and m/z 249.9 --> 203.8, respectively.  All residue levels of the metabolites were converted to parent equivalents using molecular weight factors of 1.47 and 1.14 for CGA-37913 and CGA-49751, respectively.  The analytical method description here was corrected for ion transitions monitored by checking MRID 45555901.  The method description in the current submission had the ion transitions reversed and rounded m/z to integers, and was confirmed by email from Syngenta

The limits of quantitation (LOQs, based on the LLMVs) were 0.03 and 0.05 ppm for CGA-37913 and CGA-49751, respectively, in all corn matrices. The petitioner used the LLMVs as the limits for reporting residues.

The method was validated prior to and in conjunction with the analysis of field trial samples.

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

The petitioner has proposed the enantiomer-specific LC/MS/MS method, Method No. 1848-01, for enforcement purposes.  HED concludes that the method is not appropriate for enforcement purposes because it does not determine residues of the R-isomers which are included in the tolerance expression.  The S:R ratio in the active ingredient is 88:12; therefore, there is potential for residues of the R-isomers of metolachlor and its metabolites in crop commodities.  The method could be adapted for enforcement by changing the method to measure both the S- and the R-enantiomers, and upgraded to include two ion transitions per analyte.

860.1360 Multiresidue Methods

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

860.1380 Storage Stability

Adequate storage stability data are available for crop commodities.  Previously submitted data (DP# 292881, 8/15/03, S. Kinard) indicate that:  CGA-37913 is stable at <=-10 °C for at least 2 years in corn (grain and forage), peanut, potato (tubers, wet peel and flakes), soybean (hulls and meal) and tomatoes, for at least 29 months in cottonseed oil, and for at least 37 months in cottonseed and corn oil; and CGA-49751 is stable at <=-10°C for at least 2 years in corn (grain, forage, and oil), peanuts, potatoes (tubers, wet peel and flakes), soybeans (hulls and meal) and tomatoes, and for at least 37 months in cotton seed and cottonseed oil.

The durations and conditions of samples from the current crop field trials and processing studies are presented in Table 4.

Table 4.	Summary of Storage Conditions and Durations of Samples from Crop Field Trial and Processing Studies.  
Matrix 
                              Storage Temperature
                                     (°C)
                            Actual Storage Duration
                  Interval of Demonstrated Storage Stability
Corn commodities (grain, K+CWHR, forage and stover)
                                  -10 -- -20 
                                 116-477 days
CGA-49751 and CGA-37913 are stable for up to 2 years in/on corn grain, forage, and oil


Conclusions.  Adequate storage stability data are available to support the storage durations and conditions for samples from the submitted field trial and processing studies.  No corrections for potential decline during storage are needed.

860.1400 Water, Fish, and Irrigated Crops

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

860.1460 Food Handling

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

860.1480 Meat, Milk, Poultry, and Eggs

The reregistration requirements for magnitude of the residue in meat, milk, poultry, and eggs are fulfilled (DP# 292881, 8/15/03, S. Kinard).  Adequate ruminant and poultry feeding studies are available for metolachlor, and these data will also support the use of S-metolachlor.

The livestock feedstuffs treated with S-metolachlor in this petition include corn forage and stover.

The dietary burdens for livestock to S-metolachlor residues were recently recalculated in conjunction with a request to amend use directions for sorghum and soybean (DP#s 332846, etc., 10/21/08, D. McNeilly).  At that time, the dietary burdens were calculated to be 26.2 ppm for cattle, 0.51 ppm for poultry, and 0.44 ppm for swine.  It was concluded that the established tolerances for livestock commodities were adequate to support existing metolachlor uses.

HED has recalculated the reasonable dietary burdens (RDBs) to livestock using the most recent guidance (June 2008) and the existing and proposed tolerances for residues of metolachlor in/on livestock feedstuffs; see Table 5.  The RDBs are 15.9 ppm for beef cattle, 20.2 ppm for dairy cattle, 0.48 ppm for poultry, and 0.40 ppm for swine.  Because these RDBs are less than the dietary burdens that were calculated previously, no changes to the established tolerances for livestock commodities are needed to support the proposed uses.

Table 5.	Calculation of Dietary Burdens of S-Metolachlor Residues to Livestock.
Feedstuff
                                    Type[1]
                                % Dry Matter[2]
                                   % Diet[2]
                                Tolerance (ppm)
                         Dietary Contribution (ppm)[3]
Beef Cattle
 Corn, field, forage
                                       R
                                      40
                                      15
                                     40.0
                                     15.00
 Beet, sugar, molasses
                                      CC
                                      75
                                      10
                                      2.0
                                     0.27
 Potato, processed waste
                                      CC
                                      15
                                      30
                                     0.20
                                     0.40
 Sorghum, grain
                                      CC
                                      86
                                      40
                                     0.30
                                     0.14
 Sunflower, meal
                                      PC
                                      92
                                       5
                                      1.0
                                     0.054
TOTAL BURDEN
                                      --
                                      --
                                      100
                                      --
                                     15.86
Dairy Cattle
 Grass forage
                                       R
                                      25
                                      45
                                      10
                                     18.0
 Corn, sweet, cannery waste
                                      CC
                                      30
                                      10
                                      6.0
                                      2.0
 Sorghum, grain 
                                      CC
                                      86
                                      35
                                     0.30
                                     0.12
 Sunflower, meal
                                      PC
                                      92
                                      10
                                      1.0
                                     0.11
TOTAL BURDEN
                                      --
                                      --
                                      100
                                      --
                                     20.2
Poultry
 Sorghum, grain 
                                      CC
                                      NA
                                      75
                                     0.30
                                     0.23
 Sunflower, meal
                                      PC
                                      NA
                                      25
                                      1.0
                                     0.25
TOTAL BURDEN
                                      --
                                      --
                                      100
                                      --
                                     0.48
Swine
 Corn, field, grain
                                      CC
                                      NA
                                       5
                                     0.10
                                     0.005
 Sorghum, grain
                                      CC
                                      NA
                                      80
                                     0.30
                                     0.24
 Sunflower, meal
                                      PC
                                      NA
                                      15
                                      1.0
                                     0.15
TOTAL BURDEN
                                      --
                                      --
                                      100
                                      --
                                     0.40
[1]  R:  Roughage; CC:  Carbohydrate concentrate; PC:  Protein concentrate.
[2]  OPPTS 860.1000 Table 1 Feedstuffs (June 2008).  
[3]  Contribution = ([tolerance /% DM] X % diet) for beef and dairy cattle; contribution = ([tolerance] X % diet) for poultry and swine. 

Conclusions.  The proposed uses for S-metolachlor will have no significant impact on the dietary burden of metolachlor to livestock, since corn forage and stover are fed to beef cattle, which had a significantly lower dietary burden than dairy cattle.  As a result, no changes are required in the current tolerances for metolachlor residues in livestock commodities.

860.1500 Crop Field Trials
48932501.der.docx

The petitioner submitted field trial data in support of the registered uses on field corn, sweet corn, and popcorn.  Trials were conducted on simulated sweet corn, field corn, and popcorn.  The  treatments included an early treatment, either preplant incorporated,  pre-emergence, or early post-emergence, plus a layby treatment at either 30" or 40"  The results of the field trials are summarized in Table 6.  

TABLE 6.  Summary of Residue Data from Field Corn, Sweet Corn, and Popcorn Field Trials with 
                       S-Metolachlor.
Corn Matrix
                                  Total Rate
                                   (lb ai/A)
                                       
                               PHI range in days
                              (Mean +- Std. Dev.)
                                    Analyte
                            Residue Levels, ppm[1]
                                       
                                       
                                       
                                       
                                       n
                                  Sample Min.
                                  Sample Max.
                                    LAFT[2]
                                    HAFT[2]
                                    Median
                                     Mean
                                  Std.  Dev.
Treatments 2, 4, 6, and 8: One of Four Types of Soil Surface Treatment + Broadcast OTT[3] Treatment When Corn 
                           Was About 30 Inches Tall
Forage with ears if present
                           3.9159-4.1734 except for
                           2.6539 in trial C01-0745
                                     28-40
                                   (33 +- 3)
CGA-37913
                                      20
                                     0.04
                                      1.8
                                     0.13
                                     1.28
                                     0.79
                                     0.75
                                     0.34

                                       
                                       
CGA-49751
                                      20
                                     0.16
                                      6.3
                                     0.48
                                      5.7
                                     2.58
                                     2.74
                                     1.20

                                       
                                       
Combined Residues
                                      20
                                     0.20
                                      7.5
                                     0.61
                                      7.0
                                     3.42
                                     3.48
                                     1.50
Forage without ears
                                       
                                     28-47
                                   (36 +- 7)
CGA-37913
                                      12
                                     0.10
                                      2.9
                                     0.20
                                      2.5
                                     0.65
                                     0.96
                                     0.74

                                       
                                       
CGA-49751
                                      12
                                     0.43
                                      15
                                     0.55
                                      13
                                     2.70
                                     4.13
                                     3.80

                                       
                                       
Combined Residues
                                      12
                                     0.59
                                      18
                                     0.75
                                      16
                                     3.34
                                     5.09
                                     4.53
K+CWHR
                                       
                                     30-54
                                   (42 +- 8)
CGA-37913
                                      12
                                   <0.03
                                   <0.03
                                   <0.03
                                   <0.03
                                   <0.03
                                   <0.03
                                      NA

                                       
                                       
CGA-49751
                                      12
                                   <0.05
                                   <0.05
                                   <0.05
                                   <0.05
                                   <0.05
                                   <0.05
                                      NA

                                       
                                       
Combined Residues
                                      12
                                   <0.08
                                   <0.08
                                   <0.08
                                   <0.08
                                   <0.08
                                   <0.08
                                      NA
Field corn
grain
                                       
                                    59-111
                                  (95 +- 15)
CGA-37913
                                      20
                                   <0.03
                                   <0.03
                                   <0.03
                                   <0.03
                                   <0.03
                                   <0.03
                                      NA

                                       
                                       
CGA-49751
                                      20
                                   <0.05
                                   <0.05
                                   <0.05
                                   <0.05
                                   <0.05
                                   <0.05
                                      NA

                                       
                                       
Combined Residues
                                      20
                                   <0.08
                                   <0.08
                                   <0.08
                                   <0.08
                                   <0.08
                                   <0.08
                                      NA
Popcorn grain
                                       
                                      77
CGA-37913
                                       1
                                   <0.03
                                   <0.03
                                   <0.03
                                   <0.03
                                   <0.03
                                   <0.03
                                      NA

                                       
                                       
CGA-49751
                                       1
                                   <0.05
<0.05
                                   <0.05
                                   <0.05
                                   <0.05
                                   <0.05
                                      NA

                                       
                                       
Combined Residues
                                       1
                                   <0.08
                                   <0.08
                                   <0.08
                                   <0.08
                                   <0.08
                                   <0.08
                                      NA
Stover of field corn, sweet corn, and popcorn
                                       
                                    47-111
                                  (84 +- 20)
CGA-37913
                                      26
                                   <0.03
                                      2.1
                                   <0.03
                                      1.8
                                     0.55
                                     0.69
                                     0.51

                                       
                                       
CGA-49751
                                      26
                                   <0.05
                                      8.9
                                   <0.05
                                      8.2
                                     2.18
                                     2.64
                                     2.31

                                       
                                       
Combined Residues
                                      26
                                   <0.08
                                      11
                                   <0.08
                                      9.9
                                     2.75
                                     3.32
                                     2.81
Treatments 3, 5, 7, and 9: One of Four Types of Soil Surface Treatment + Broadcast OTT[3] Treatment When Corn 
                           Was About 40 Inches Tall
Forage with ears if present
                                 3.7915-4.1612
                                     28-31
                                   (30 +- 1)
CGA-37913
                                      20
                                     0.09
                                      2.2
                                     0.11
                                      1.9
                                     0.91
                                     0.95
                                     0.55

                                       
                                       
CGA-49751
                                      20
                                     0.21
                                      11
                                     0.26
                                     10.4
                                     2.88
                                     3.67
                                     2.56

                                       
                                       
Combined Residues
                                      20
                                     0.29
                                      13
                                     0.36
                                      12
                                     3.80
                                     4.62
                                     3.06
Forage without ears
                                       
                                     21-42
                                   (32 +- 6)
CGA-37913
                                      12
                                   <0.03
                                      4.7
                                   <0.04
                                      4.3
                                     1.09
                                     1.66
                                     1.34

                                       
                                       
CGA-49751
                                      12
                                   <0.05
                                      24
                                   <0.07
                                      22
                                     4.68
                                     7.28
                                     6.54

                                       
                                       
Combined Residues
                                      12
                                   <0.08
                                      29
                                   <0.10
                                      26
                                     5.75
                                     8.90
                                     7.83
K+CWHR
                                       
                                     21-48
                                   (35 +- 8)
CGA-37913
                                      12
                                   <0.03
                                   <0.03
                                   <0.03
                                   <0.03
                                   <0.03
                                   <0.03
                                      NA

                                       
                                       
CGA-49751
                                      12
                                   <0.05
                                   <0.05
                                   <0.05
                                   <0.05
                                   <0.05
                                   <0.05
                                      NA

                                       
                                       
Combined Residues
                                      12
                                   <0.08
                                   <0.08
                                   <0.08
                                   <0.08
                                   <0.08
                                   <0.08
                                      NA
Field corn
grain
                                       
                                    51-101
                                  (88 +- 16)
CGA-37913
                                      20
                                   <0.03
                                   <0.03
                                   <0.03
                                   <0.03
                                   <0.03
                                   <0.03
                                      NA

                                       
                                       
CGA-49751
                                      20
                                   <0.05
                                   <0.05
                                   <0.05
                                   <0.05
                                   <0.05
                                   <0.05
                                      NA

                                       
                                       
Combined Residues
                                      20
                                   <0.08
                                   <0.08
                                   <0.08
                                   <0.08
                                   <0.08
                                   <0.08
                                      NA
Popcorn grain
                                       
                                      72
CGA-37913
                                       1
                                   <0.03
                                   <0.03
                                   <0.03
                                   <0.03
                                   <0.03
                                   <0.03
                                      NA

                                       
                                       
CGA-49751
                                       1
                                   <0.05
                                   <0.05
                                   <0.05
                                   <0.05
                                   <0.05
                                   <0.05
                                      NA

                                       
                                       
Combined Residues
                                       1
                                   <0.08
                                   <0.08
                                   <0.08
                                   <0.08
                                   <0.08
                                   <0.08
                                      NA
Stover of field corn, sweet corn, and popcorn
                                       
                                    44-101
                                  (77 +- 20)
CGA-37913
                                      26
                                     0.03
                                      5.1
                                     0.04
                                      4.7
                                     0.97
                                     1.38
                                     1.24

                                       
                                       
CGA-49751
                                      26
                                   <0.05
                                      23
                                   <0.05
                                      21
                                     3.63
                                     5.33
                                     5.35

                                       
                                       
Combined Residues
                                      26
                                   <0.08
                                      28
                                   <0.09
                                      26
                                     4.52
                                     6.72
                                     6.61

Syngenta has submitted field trial data for S-metolachlor on field corn, sweet corn, and popcorn.  A total of 20 crop field trials on field corn were conducted in the United States during the 2010 growing season in North American Free Trade Agreement (NAFTA) Growing Zones 1 (NY), 2 (VA), 5 (IA, 4 trials; MN; MO, 2 trials; ND, 3 trials; NE, 2 trials; OH, 2 trials), 5A (WI, 3 trials), and 6 (TX); at 7 of these trials, samples were also collected at the milk stage to simulate sweet corn commodities.   A total of 5 crop field trials on sweet corn were conducted in the United States during the 2010 growing season in NAFTA Growing Zones 1 (PA), 3 (FL), 10 (CA), 11 (OR), and 12 (OR).  One crop field trial on popcorn was conducted in the United States during the 2011 growing season in NAFTA Growing Zone 6.  Examination of the field trial records indicates that individual Field Research Directors (FRDs) supervised two trials each within 23 miles or less of each other in IA (2 instances), MO, ND, NE, and OH; and one FRD supervised 3 trials in one location in WI.  (All other trials within individual states were far apart.)  For purposes of OCSPP 860.1500 data requirements, all of these trials are considered to be separate independent trials because of sufficient differences in residue levels for at least one of the corn commodities and/or differences between trials in some of the sets regarding crop variety, adjuvant class, application spray volume, soil type, and location (distances between the trials).

Each trial consisted of one untreated (control) plot of field corn, sweet corn, or popcorn and plots of the same type of corn that were treated with a 7.64 lb ai/gal emulsifiable concentrate (EC) formulation of S-metolachlor (Dual II MAGNUM[(R)]), which contains 0.375 lb benoxacor/gal as a safener.  Sufficient plots were treated at each site to accommodate two different treatment regimens for each of the commodities to be harvested at that site.  The commodities harvested, which differed depending on the type of corn, were forage with ears if present, forage without ears, kernels plus cob with husk removed (K+CWHR), grain, and stover.  Each treated plot was sprayed twice, once to the soil around the time of planting (using one of four different methods) and once broadcast over-the-top (OTT) of the crop.  At each site, one plot received the OTT spray when it was about 30 inches tall, and another plot received the OTT spray when it was about 40 inches tall.  Because the method of application to the soil was held constant at each site, the only difference at each site for each commodity was the OTT sprayings applied at two different crop heights.  Each pair of applications was assigned either an even or odd treatment ID number depending on whether the OTT application was at 30 or 40 inches, respectively.  In the applications to soil in treatments 2 and 3, spray was incorporated into the top few inches of the soil before planting (pre-plant incorporated, PPI); in treatments 4 and 5, the soil surface was sprayed pre-planting; in treatments 6 and 7, the soil surface was sprayed at the time of planting; and in treatments 8 and 9, the soil surface was sprayed after planting but preemergence.  In the even-numbered treatments, plots received a soil application and a broadcast OTT application of the EC formulation each at rates of 1.89-2.11 lb ai/A/application (2.12-2.36 kg ai/ha/application) for total application rates of 3.92-4.17 lb ai/A (4.39-4.67 kg ai/ha).  At one field corn trial in OH, the soil treatment was made at 0.66 lb ai/A for a total rate of 2.65 lb ai/A.  In the odd-numbered treatments, plots received a soil application and a broadcast OTT application of the EC formulation each at rates of 1.83-2.13 lb ai/A/application (2.05-2.39 kg ai/ha/application) for total application rates of 3.79-4.16 lb ai/A (4.25-4.66 kg ai/ha).  Applications were made in spray volumes of 1.98-2.08 gal/A of water (18.5-19.5 L/ha) at three trials and in spray volumes of 7.88-28.42 gal/A of water (73.7-266 L/ha) in the other 23 trials.  Although no adjuvant was used in most of the soil applications, the OTT application always included a crop oil concentrate (COC), a non-ionic surfactant (NIS), or ammonium sulfate (AMS), singly or in combination, as an adjuvant.  No information was provided as to the types of equipment used for application of the test substance.

In the field corn trials, samples of forage with ears (if present) were collected with a target preharvest interval (PHI) of 30 +- 3 days, and grain and stover samples were collected at standard maturity.  At seven of the field corn trials, samples of forage without ears and K+CWHR were collected at the milk stage to simulate sweet corn commodities.  At the sweet corn trials, samples of forage without ears were collected with a target PHI of 30 +- 3 days, and K+CWHR and stover were collected at standard maturity.  Popcorn grain and stover samples were collected at standard maturity.  Partly because of differences as to when crop maturity was reached, the PHIs for the different commodities varied widely.  The target PHI for forage with ears if present was well achieved for the odd-numbered treatments; however, other forage samples often had PHIs of about 1-2 weeks beyond target.  Residue decline was assessed in two trials each (for one even-numbered treatment and one odd-numbered treatment) in field corn commodities (forage with ears if present, grain, and stover) and in sweet corn commodities (forage without ears, K+CWHR, and stover).  In these trials, additional forage samples were collected at PHIs of 19-21, 25, 35, and 40 days, and additional K+CWHR, grain, and stover samples were collected 14/15 and 7/8 days before mature harvest and 6-8 and 13/15 days after mature harvest.

Samples were analyzed for residues of residues of S-metolachlor as CGA-37913 and CGA-49751 using high performance liquid chromatography with tandem mass spectrometric detection (LC/MS/MS) according to Analytical Method No. ENC-5/99, with modifications found in EPL-BAS Study Number 110S50 (MRID 49186501).  For all matrices, the petitioner used the lowest levels of method validation (LLMVs) of 0.03 and 0.05 ppm as the limit for reporting residues of CGA-37913 and CGA-49751, respectively.  All residue levels were converted to parent equivalents using molecular weight factors of 1.47 and 1.14 for CGA-37913 and CGA-49751, respectively.  The method was adequate for data collection based on acceptable method validation and concurrent recovery data.  The fortification levels used in the concurrent recoveries were adequate to bracket expected residue levels.  Method validation and concurrent recoveries were corrected, if needed, for apparent residues in controls.  No corrections were made for control residue levels in the treated samples.

Samples of corn forage with ears if present, forage without ears, K+CWHR, field corn grain, popcorn grain, and stover were stored frozen (<-10 °C) from collection to extraction for analysis for up to 17.0, 14.7, 14.0, 13.6, 3.8, and 14.6 months, respectively.  Samples were analyzed within 0-60 days of extraction. Adequate storage stability data are available indicating that CGA-37913 is stable at <=-10 °C for at least 2 years in corn (grain and forage), peanut, potato (tubers, wet peel and flakes), soybean (hulls and meal), and tomatoes, and for at least 37 months in corn oil, and CGA-49751 is stable at <=−10 °C for at least 2 years in corn (grain, forage, and oil), peanuts, potatoes (tubers, wet peel and flakes), soybeans (hulls and meal) and tomatoes (DP# 292881, S. Kinard, 8/15/03).  These data are adequate to support the storage conditions and durations of samples from the submitted field trials.  In addition, recovery data for fortified samples analyzed concurrently with treated samples are adequate to support the extended storage of extracts prior to analysis.

Following two approximately equal applications (one sprayed on the soil and one sprayed OTT when the corn was 30 inches tall) of the 7.64 lb ai/gal EC formulation at total rates of 3.92-4.17 lb ai/A, residues (and per trial averages) of CGA-37913, CGA-49751, and both metabolites combined, respectively, were 0.04-1.8 (0.13-1.28), 0.16-6.3 (0.48-5.7), and 0.20-7.5 (0.61-7.0) ppm in/on forage with ears if present harvested with a PHI of 28-40 days; 0.10-2.9 (0.20-2.5), 0.43-15 (0.55-13), and 0.59-18 (0.75-16) in/on forage without ears harvested with a PHI of 28-47 days; and <0.03-2.1 (<0.03-1.8), <0.05-8.9 (<0.05-8.2), and <0.08-11 (<0.08-9.9) ppm in/on stover harvested with a PHI of 47-111 days.  No residues at or above the LLMVs of 0.03 and 0.05 ppm for the two analytes, respectively, were detected in any samples of K+CWHR, field corn grain, or popcorn grain harvested with a PHI of 30-54, 59-111, and 77 days, respectively.  Following two approximately equal applications (one sprayed on the soil and one sprayed OTT when the corn was 40 inches tall) of the 7.64 lb ai/gal EC formulation at total rates of 3.79-4.16 lb ai/A, residues (and per trial averages) of CGA-37913, CGA-49751, and both metabolites combined, respectively, were 0.09-2.2 (0.11-1.9), 0.21-11 (0.26-10.4), and 0.29-13 (0.36-12) ppm in/on forage with ears if present harvested with a PHI of 28-31 days; <0.03-4.7 (<0.04-4.3), <0.05-24 (<0.07-22), and <0.08-29 (<0.10-26) in/on forage without ears harvested with a PHI of 21-42 days; and 0.03-5.1 (0.04-4.7), <0.05-23 (<0.05-21), and <0.08-28 (<0.09-26) ppm in/on stover harvested with a PHI of 44-101 days.  No residues at or above the LLMVs of 0.03 and 0.05 ppm for the two analytes, respectively, were detected in any samples of K+CWHR, field corn grain, or popcorn grain harvested with a PHI of 21-48, 51-101, and 72 days, respectively.

In the residue decline study on field corn, the combined residues of CGA-37913 and CGA-49751 and/or their combined per trial averages in/on forage with ears if present at PHIs of 20, 25, 31, 35, and 40 days (Treatment 2) were 3.6, 2.9, 2.7, 2.7, and 2.7 ppm, respectively, and, at PHIs of 21, 25, 30, 35, and 40 days (Treatment 3), they were 13, 10, 12, 11, and 9.9 ppm, respectively, which demonstrated a slight residue decline with increasing PHIs.  The combined residues and/or their per trial averages at PHIs of 75, 82, 90, 96, and 103 days (Treatment 2) were 3.3, 1.2, 0.91, 0.54, and 0.60 ppm in/on stover, respectively, and at PHIs of 64, 71, 79, 87, and 94 days (Treatment 3), were 16.5, 16.5, 23, 10, and 8.0 ppm in/on stover, respectively, which demonstrated a decline in residues with increasing PHIs.  In the residue decline study on sweet corn, the combined residues and/or their per trial averages in/on forage without ears at PHIs of 20, 25, 29, 35, and 40 days (Treatment 4) were 7.6, 2.7, 3.2, 4.5, and 5.7 ppm, respectively, and, at PHIs of 19, 25, 30, 35, and 40 days (Treatment 5), they were 10, 8.6, 6.6, 7.7, and 7.2 ppm, respectively, which demonstrated a slight decrease in residues with increasing PHIs.  The combined residues and/or their per trial averages at PHIs of 40, 47, 54, 60, and 67 days (Treatment 4) were 5.1, 7.1, 3.8, 7.6, and 10 ppm in/on stover, respectively, and at PHIs of 30, 37, 44, 50, and 57 days (Treatment 5), were 12, 9.2, 11.8, 11, and 15 ppm in/on stover, respectively, which indicated that combined residues remained the same or increased slightly in stover with increasing PHIs.  Residue decline in K+CWHR and grain could not be evaluated because residues of each analyte were below the LLMV at each sampling interval.

Conclusions.  The submitted field trial data are adequate to satisfy data requirements.  The number of field trials and geographic representation is adequate.  An adequate analytical method was used for the analysis.  Adequate storage stability data were available to support the data from this study.  The trials showed tolerance exceeding residues on forage and stover; that is the reason for the submission of the current petition.  Residues were non-quantifiable in samples of field and pop corn grain, and in sweet corn kernals plus cobs with husks removed (K+CWHR), and thus within the currently established tolerances.

860.1520 Processed Food and Feed
MRID 40980705, DEB 4391, R. Quick, 6/14/1989 (Metolachlor Reg. Std. Followup)
D255484, S. Kinard, 8/15/2003 (Res Chem Chapter for TRED)

No processing data for corn commodities were included with the current petition.  Processing data were previously submitted with MRID 40980705.  The data were review in the Metolachlor Registration Standard Followup (R. Quick, 6/14/1989).  Residues of metolachlor do not concentrate in corn or cottonseed processed commodities. This conclusion was extended to S-metolachlor.  (D255484, S. Kinard, 8/15/2003).

860.1650 Submittal of Analytical Reference Standards

Analytical standards for the following compounds related to metolachlor are currently available in the EPA National Pesticide Standards Repository (personal communication with Theresa Cole, 7/23/2013).  The metolachlor metabolite CGA-03713 standard must be replaced or recertified prior to publication of new tolerances for S-metolachlor.

         Table 7.      S-Metolachlor Standards in Pesticide Repository

                                 Chemical Name
                                    Company
                                   Date Recd
                                   Date Exp

metolachlor metab. (CGA-037913)
Syngenta
                                                                       4/1/2003
                                                                      1/31/2013

metolachlor metab. (CGA-49751)
Syngenta
                                                                       9/1/2004
                                                                     12/31/2014

metolachlor, S- (CGA-37913)
Syngenta
                                                                      5/20/2013
                                                                      4/30/2015

metolachlor, S- (CGA-77102)
Syngenta
                                                                       1/3/2011
                                                                      8/31/2015

metolachlor, S- (CGA-77102)
Syngenta
                                                                      8/27/2012
                                                                      8/31/2015

metolachlor, S- ESA (CGA 380168)
Syngenta
                                                                      1/13/2006
                                                                      8/31/2014

metolachlor, S- OA (CGA 351916)
Syngenta
                                                                      1/13/2006
                                                                      8/31/2014


860.1850 Confined Accumulation in Rotational Crops
D207842, 10/12/94, S. Hummel
D292881, 8/15/03, S Kinard

The data requirements for confined accumulation in rotational crops are not fulfilled.  A confined rotational crop study with [[14]C]metolachlor was reevaluated by HED (DP# 207842, 10/12/94, S. Hummel) after review of rotational crop data was transferred to HED.  It was concluded that the available study was inadequate but potentially upgradable.  Additional data were required characterizing the [14]C-residues in plants, along with information on the percentage of the [14]C-residues measured by the current enforcement method; sample storage conditions and intervals and supporting storage stability data were also required.  These data requirements, which were reiterated in the Metolachlor TRED (DP# 292881, 8/15/03, S. Kinard), remain outstanding.

A confined rotational crop study using S-metolachlor has also been submitted.  The study was reviewed by HED (DP# 283235, 8/15/03, S. Kinard) and found to be scientifically adequate.  Although [14]C-residue in the representative rotational crops were adequately identified and characterized, the [[14]C]-S-metolachlor was applied at only 1.45 lb ai/A, which is ~0.4x the maximum seasonal use rate for corn.  Based on the available data, HED concluded that the metabolism of [[14]C]S-metolachlor in rotational crops is similar to the metabolism observed in the primary crops.  Metabolism in rotational crops primarily involves two pathways: (i) conjugation of the parent molecule with glutathione by substitution of the chlorine, followed by the degradation of the glutathione moiety to form a variety of sulfur containing metabolites; and (ii) direct oxidation of parent or secondary metabolites, primarily on the chloroacetyl side chain.  Complete degradation of secondary metabolites either in the soil and/or plants also resulted in the incorporation of molecule fragments into natural plant constituents.  The residues of concern for both metolachlor and S-metolachlor in rotational crops are the same as for primary crops, metolachlor and its metabolites, determined as the derivatives CGA-37913 and CGA-49751.  

The deficiency listed in the RED has not been fulfilled. (DP# 283235, 8/15/03, S. Kinard)  For confined rotational crops, additional information is needed on the percentage of the 14C-residues measured by the current enforcement method, supporting storage stability data, and sample storage conditions and intervals. With regard to field accumulation in rotational crops, "Residue data are required for both metolachlor and S-metolachlor on grain, forage, hay, and straw of representative cereal grains (wheat and oats) supporting the 4.5 month plantback interval."

860.1900 Field Accumulation in Rotational Crops
D292881, 8/15/03, S Kinard
D332846, 10/21/08, D. McNeilly
D296904, 4/17/06, R. Loranger

Field rotational crop data have been submitted previously which are adequate to support the existing rotational crop restrictions on the labels for the 7.62 and 7.64 lb/gal EC formulations (EPA Reg. Nos. 100-816 and 100-818), provided that the restrictions on the label for EPA Reg. No. 100-816 are amended as specified under 860.1200 Directions for Use.  In the TRED it was concluded that adequate residue data are available to support a PBI of 4 months for non-grass animal feeds and the current 1.0-ppm tolerance for rotated non-grass animal feed (DP# 292881, 8/15/03, S. Kinard); additional data were required to support cereal grain rotational crop restrictions. 

In response, field rotational crop data for oats and wheat were submitted which have been reviewed by HED (DP#s 332846, etc., 10/21/08, D. McNeilly).  Fourteen field trials were conducted with wheat and fifteen trials were conducted with oats.  In each test, the 7.64 lb/gal EC formulation of S-metolachlor was applied to a primary crop of field corn as a PPI application at planting at 2.36-2.49 lb ai/A, followed by a second directed application at lay-by at 1.25-1.4 lb ai/A, for a total of 3.61-3.83 lb ai/A/season (1x the maximum use rate on corn).  Wheat was planted ~60 days and oats were planted ~7 months following the last application. 

These field trials were considered sufficient for assessing rotational crop tolerances for small grains rotated with corn, which has the highest labeled use rate.  Following a final lay-by application to corn, the wheat field trials reflect a typical plant-back interval (2 months) for small grains that can be planted in the fall (barley, oats, rye and wheat), and the oat field trials reflect the typical plant-back interval (7 months) for small grains that can be planted the following spring (barley, oats, rice, rye and wheat).

It was concluded that the wheat and oat data support tolerances of 0.5 ppm for rotated barley hay and straw, oat forage, hay and straw, rye forage and straw, and wheat forage, grain and straw, and tolerances of 0.1 ppm for the grain of rotated barley, oats, rye and wheat.  For rice and buckwheat, which would only be rotated to the following spring (7-month PBI), the oat field trial data support tolerances of 0.1 ppm for rotated buckwheat grain and rice grain.  

It was also concluded that 60-day PBIs for root vegetables (subgroup 1B), tuberous and corm vegetables (subgroup 1C), bulb vegetables (group 3), leaf petiole vegetables (subgroup 4B) head and stem Brassica vegetables (subgroup 5A), fruiting vegetables (group 8), and winter squash are acceptable based on the available field trial data supporting the tolerances and uses of S-metolachlor on these crops (DP# 296904, 4/17/06, R. Loranger) provided that (i) the application to the previous crop was less than or equal to the maximum approved rates for the respective crops and crop groups, and (ii) the label directions are amended to prohibit application of S-metolachlor to the replanted crops.  Although the first condition is met on the current label for EPA Reg. No. 100-816, the label directions have not yet been amended to prohibit application of S-metolachlor to crops planted at a 60-day PBI.  

860.1550 Proposed Tolerances

The residues of concern in plant and animal commodities include S-metolachlor, its R-enantiomer, and its metabolites, determined as the derivatives CGA-37913 and CGA-49751.  Tolerances for S-metolachlor are currently established [40 CFR §180.368(a)(2) and (d)(2)] for the combined residues (free and bound) of S-metolachlor, its R-enantiomer, and its metabolites, determined as the derivatives, CGA-37913 and CGA-47951, each expressed as parent compound.  The text of the current tolerance expression is in accordance with our current guidance (S. Knizner, 5/10/2009)

Tolerances are currently established under 40 CFR §180.368 for residues of S-metolachlor, including its metabolites and degradates, in or on the commodity(s), as defined. Compliance with the tolerance levels specified in the following table below is to be determined by  measuring only the sum of free and bound S-metolachlor, S-2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide, its R-enantiomer, and its metabolites, determined as the derivatives, 2-(2-ethyl-6-methylphenyl)amino-1-propanol and 4-(2-ethyl-6-methylphenyl)-2-hydroxy-5-methyl-3-morpholinone, calculated as the stoichiometric equivalent of S-metolachlor, in or on the commodity.

Table 8. 	Tolerance Summary for Metolachlor.
Commodity
                                 Established/
                              Proposed Tolerance
                                     (ppm)
                                  Recommended
                                   Tolerance
                                     (ppm)
Comments; 
Correct Commodity Definition
Proposed tolerances under §180.368(a)(2)
Corn, field, forage 
                                      20
                                      40

Corn, sweet, forage 
                                      40
                                      40

Corn, stover 
                                      40
                                      40
Corn, field, stover
Corn, sweet, stover
Corn, pop, stover

A revised Section F is required.


References

DP#:	207842
Subject:	Metolachlor (108801)  Addendum to RED, Reregistration Case No. 0001. Confined Rotational Crop Data (GLN 165-1). CB No. 14435
From:	S. Hummel
To:	J. Mitchell/W. Waldrop
Dated:	10/12/94
MRID:	41470601

DP#:	226780
Subject:	Replacement of Metolachlor Technical (Racemic Metolachlor) with Alpha-Metolachlor (formerly called Chiral Metolachlor) Technical; Review of Bridging Data.
From:	L. Kutney
To:	R. Griffin
Dated:	11/15/96
MRIDs:	43928901-43928903, 43928939-43928942

DP#s:	278742 and 279110
Subject:	S-Metolachlor.  Information Supporting the Assertion That the Metabolism of S-Metolachlor Is Essentially the Same as for the Racemic Mixture.
From:	S. Kinard
To:	S. Kinard
Dated:	8/15/03
MRIDs:	45499603, 45499604, 45499605, 45533103

DP#:	283235
Subject:	Sandmeier, P. (2001) Outdoor Confined Accumulation Study on Rotational Crops after Bare ground Application of [Phenyl-U-14C] CGA77102: Lab Project Number: 99PSA53; 1287-99.  Unpublished study prepared by Syngenta Crop Protection, Inc.  252 p.
From:	S. Kinard
To:	N/A (DER)
Dated:	8/15/03
MRID:	45672302

DP#:	292881
Subject:	PP#s:  7F04897, 9E06055, 7E04916, 2E06374, 4E04420, 8E05029, and 8E05030. Revised Metolachlor and S-metolachlor Residue Chemistry Chapter for the Tolerance Reassessment Eligibility Decision (TRED) and Registration for Use on Asparagus, Carrots, Cotton, Horseradish, Green Onions, Peppers, Rhubarb, Sugar Beet, Sunflower, and Swiss Chard.
From:	S. Kinard
To:	H. Jamerson
Dated:	8/15/03
MRIDs:	44378401, 44908701, 45544701

DP#:	296904
Subject:	PP# 3E6787.  S-Metolachlor.  Petition for Tolerances on Various Crops, Crop Groups, and Livestock Commodities.  Summary of Analytical Chemistry and Residue Data.
From:	R. Loranger
To:	B. Madden/S. Jackson
Dated:	4/17/06
MRIDs:	45499609, 45499610, 46046501-46046506



RDI: SHummel: 07/25/2013: RAB4 Chemists 07/25/2013

Attachments:  
International Residue Limit Status sheet
OECD Tolerance/MRL Spreadsheet

Appendix I: International Residue Limits 

            S-Metolachlor (PC Code 108800; Date of Request 6/26/13)
Summary of US and International Tolerances and Maximum Residue Limits 
Residue Definition:
US
Canada
Mexico[1]
Codex 
40 CFR: 180.368 sum of
free and bound S-metolachlor,
S-2-chloro-N-(2-ethyl-6-methylphenyl)-N-
(2-methoxy-1-methylethyl)acetamide, its R-enantiomer, and its metabolites, determined as the derivatives, 2-(2-ethyl-6-methylphenyl)amino-1-
propanol and 4-(2-ethyl-6-
methylphenyl)-2-hydroxy-5-
methyl-3-morpholinone
calculated as the
stoichiometric equivalent of
S-metolachlor
2-chloro-N-(2-ethyl-6-
methylphenyl)-N-[(1S)-2-methoxy-1-methylethyl)acetamide
and 2-chloro-N-(2-ethyl-6-methylphenyl)-N-[(1R)-2-methoxy-1-
methylethyl)acetamide, including the metabolites 2-[(2-ethyl-6-methylphenyl)amino]-1-propanol and 4-(2-ethyl-6-methylphenyl)-2-
hydroxy-5-methyl-3-morpholinone

None
Commodity
Tolerance (ppm) /Maximum Residue Limit (mg/kg)

                                      US
Canada
Mexico[1]
Codex 
Corn, field, forage 
40 ppm 



Corn, sweet, forage 
40 ppm 



Corn, stover 
40 ppm



Completed by: M. Negussie; 
1 Mexico adopts US tolerances and/or Codex MRLs for its export purposes.


