UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, D.C. 20460 

OFFICE OF CHEMICAL SAFETY AND 

POLLUTION PREVENTION 

MEMORANDUM 

Date: 

Subject: 

December 18, 2014 

Sethoxydim. Section 3 Registration for Grass Grown for Seed; Request for an 

Amended Use on Blueberry; Crop Group Conversions: Group 3 to Group 3-07, 

Group 8 to Group 8-10, Group 10 to Group 10-10, Group 11 to Group 11-1 0; and 

Crop Subgroup Conversions: Caneberry to Subgroup 13-07 A, Blueberry to 

Subgroup 13-07B, Grape to Subgroup 13-07F Except Fuzzy Kiwifruit, 

Strawberry to Subgroup 13-07G Except Cranberry, Cranberry to Subgroup 13-

07H, Canola Seed to Subgroup 20A, Sunflower Seed to Subgroup 20B Except 

Safflower, and Cotton Undelinted Seed to Subgroup 20C. Summary of Analytical 

Chemistry and Residue Data. 

PC Code: 12 1001 DP Barcode: 0422744 

Decision No.: 487076 Registration No.: 7969-56 & 7969-58 

Petition No.: 4E8239 Re2ulatory Action: Section 3 Registration 

Risk Assessment Type: NA Case No.: 2600 

TXRNo.: NA CAS No.: 74051-80-2 

MRID Nos.: 49257701 & 49257702 40 CFR: §180.412 

FROM: 

THROUGH: 

TO: 

Peter 

Risk Assessment 

Savoia, Chemist 

Branch 

r:;}_ 

(RAB) 

ft 

V 

£-

/ 

~ ~ 

Health Effects Division (7509P) 

William H. Donovan, Ph.D., Chemitt~ ~ MichaelS. Metzger, Branch Chief 

RAB V/VII 

Health Effects Division (7509P) 

Sidney Jackson/Barbara Madden, RM OS 

Minor Use and Emergency Response Branch 

Registration Division (7505P) 

And 

Ronnie J. Bever, Risk Assessor 

Risk Assessment Branch (RAB) VII 

Health Effects Division (7509P) 

Page 1 of23 
Sethoxydim Summary of Analytical Chemistry and Residue Data D422744

Page 2 of 23

1.0 Executive Summary

The Interregional Research Project Number 4 (IR-4) has submitted a petition for establishing 

tolerances for sethoxydim in or on grass grown for seed and a request for an amended use on 

blueberry. In addition IR-4 is also requesting to convert the established tolerances for bulb 

vegetable crop group 3 to bulb vegetable crop group 3-07, fruiting vegetable crop group 8 to 

fruiting vegetable crop group 8-10, citrus fruit crop group 10 to citrus fruit crop group 10-10, 

pome fruit crop group 11 to pome fruit crop group 11-10, caneberry to crop subgroup 13-07A, 

blueberry to crop subgroup 13-07B, grape to crop subgroup 13-07F, except fuzzy kiwifruit, 

strawberry to crop subgroup 13-07G, cranberry to crop subgroup 13-07H, except strawberry, 

canola seed to rapeseed crop subgroup 20A, sunflower seed to sunflower crop subgroup 20B,

except safflower, and cotton undelinted seed to cottonseed crop subgroup 20C. 

Adequate residue chemistry data have been provided to support the new use requests for 

sethoxydim. The nature of the residue in plants is adequately understood for the purposes of this 

petition based on previously reviewed plant metabolism studies. Field trials are of adequate 

number and geographic representation. Crop field trial data analyses employed validated 

analytical methods that determine the residue of concern via common moiety, and are supported 

by adequate storage stability data. An adequate analytical enforcement method is available to 

enforce sethoxydim tolerances. Tolerance recommendations were based on use of the 

Organization for Economic Cooperation and Development (OECD) Maximum Residue Limit 

(MRL) calculation procedures, international harmonization considerations, and data translation 

where appropriate. No processing studies were required to support the proposed uses. 

Previously reviewed field rotational crop studies support the rotational crop restrictions specified 

on the main label. 

2.0 Regulatory Recommendations

Pending submission of a revised Section F as detailed in Section 2.2.2 and a revised Section B as 

indicated in Section 2.3, there are no residue chemistry considerations that would preclude 

establishment of the recommended tolerances. 

2.1 Data Deficiencies/Data Needs

There are no residue chemistry deficiencies identified for this petition. 

The residue chemistry database is complete for sethoxydim and no outstanding data are required. 

The additional safflower field trial and storage stability data required by the 2005 Reregistration 

Eligibility Decision (RED) has been adequately fulfilled (D312563, D. Soderberg, 04/12/2012). 

2.2 Tolerance Considerations

2.2.1 Enforcement Analytical Method

An adequate gas chromatography/flame photometric detection GC/FPD method is available 

(Method I in PAM Vol. II) for determining the combined residues of sethoxydim and its 

metabolites containing the 3-alkyl substituted pentanedioic acid moiety in plant and livestock 
Sethoxydim Summary of Analytical Chemistry and Residue Data D422744

Page 3 of 23

commodities (D312567, W. H. Donovan, 04/22/2005). This common moiety method involves

solvent extraction followed by alkaline precipitation, acidification, and partitioning to convert 

sethoxydim and its metabolites into the 3-alkyl substituted pentanedioic acid moiety. The acid 

moiety is methylated to dimethyl 3-[2-(ethylsulfonyl)propyl]pentanedioate (DME) and dimethyl 

3-[2-(ethylsulfonyl)propyl]3-hydroxy pentanedioate (DME-OH). These derivatives are then 

partitioned into methylene chloride and cleaned up by silica gel chromatography. Analysis is 

performed by GC/FPD which provides a 0.05 ppm limit of quantitation (LOQ). 

2.2.2 Recommended Tolerances

Table 2.2.2 summarizes the sethoxydim tolerances resulting from the current petition. 

Table 2.2.2. Tolerance Summary for Sethoxydim1.

Commodity Proposed 

Tolerance (ppm)

Recommended 

Tolerance (ppm)

Comments; Correct Commodity 

Definition

Fruit, citrus, group 10-10 0.5 0.5

Fruit, pome, group 11-10 0.2 0.2

Fruit, caneberry, subgroup13-07A 5.0 5.0 Caneberry subgroup 13-07A

Fruit, bushberry, subgroup13-07B 5.0 4.0 Bushberry subgroup 13-07B

Fruit, small, vine climbing, except 

fuzzy kiwifruit, subgroup 13-07F 1.0 1.0

Fruit, small, vine climbing, 

subgroup 13-07F, except fuzzy 

kiwifruit

Fruit, low growing berry, except 

cranberry, subgroup 13-07G 10.0 10.0 Berry, low growing, subgroup 13-07G, except cranberry

Fruit, low growing berry, subgroup 

13-07H 2.5 2.5 Berry, low growing, subgroup 13-07H, except strawberry

Rapeseed, subgroup 20A 35.0 35.0

Sunflower, except safflower, 

subgroup 20B 7.0 7.0 Sunflower subgroup 20B, except safflower

Cottonseed, subgroup 20C 5.0 5.0

Vegetable, bulb, group 3-07 1.0 1.0

Vegetable, fruiting, group 8-10 4.0 4.0

Grass, forage, fodder and hay, 

group 17, forage 6.0 7.02

Grass, forage, fodder and hay, 

group 17, hay 4.0 4.02

1 These tolerances should be established under 40 CFR §180.412(a).

2 These tolerances should be established under 40 CFR §180.412(c).

Note to RD: Upon establishment of the recommended tolerances listed above, tolerance listings 

for the following individual crops should be revoked since they will be included in the new crop 

group and crop subgroups listings: blueberry, borage meal, borage seed, canola seed, cotton 

undelinted seed, crambe seed, cupea seed, echium seed, flax seed, gold of pleasure seed, grape, 

hare’s ear mustard seed, juneberry, lesquerella seed, lingonberry, lunaria seed, meadowfoam 

seed, milkweed seed, mustard seed, oil radish seed, poppy seed, rapeseed seed, salal, sesame 

seed, strawberry, sunflower seed, and sweet rocket seed. The crop group and subgroup listings 

for caneberry subgroup 13A, citrus fruit group 10, pome fruit group 11, bulb vegetable group 3, 

and fruiting vegetable group 8 are also to be removed and replaced by the current crop group 

definitions. In addition, the established tolerance for sugar beet tops should be revoked since this 

commodity is no longer a significant livestock feed or a recognized human food item. The 
Sethoxydim Summary of Analytical Chemistry and Residue Data D422744

Page 4 of 23

tolerance with regional registration listed for rhubarb should also be revoked, since this 

commodity is included in crop group 4 which has an already established tolerance. 

The tolerance expression for sethoxydim has been reviewed and should be updated as follows 

based on HED’s Interim Guidance on Tolerance Expressions (S. Knizner, 05/27/2009).

Tolerances are established for the herbicide sethoxydim, including its metabolites and 

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

levels specified below is to be determined by measuring only the sum of DME (dimethyl 

3-[2-(ethylsulfonyl)propyl]pentanedioate) and DME-OH (dimethyl 3-[2-

(ethylsulfonyl)propyl]3-hydroxy pentanedioate), calculated as the stoichiometric 

equivalent of the parent compound, in or on the commodity. 

2.2.3 Revisions to Petitioned-For Tolerances

The crop group conversion requested for the low growing berry subgroup 13-07G based on 

strawberry was not specified in Section F of the petition. The tolerance for the bushberry 

subgroup 13-07B is recommended to follow the residue data acquired for the blueberry 

representative crop at 4.0 ppm and not the previously established tolerances for juneberry,

lingonberry, and salal at 5.0 ppm. The juneberry, lingonberry, and salal tolerances are based on 

the translation of caneberry data which is no longer relevant to these crops following updated 

crop grouping realignment. In addition, the OECD MRL calculation procedures determine the 

recommended tolerance of 7.0 ppm for grass forage and not 6.0 ppm as proposed by the 

petitioner. This difference stems from the conclusion that only 4 independent grass trials were 

conducted instead of 5 (as assumed by IR-4). Therefore, the petitioner must submit a revised 

Section F in which the proposed tolerances are the same as those recommended by HED.

2.2.4 International Harmonization

There are no Codex or Mexican maximum residue limits (MRLs) established for the residues of 

sethoxydim in/on raw agricultural or processed commodities. However, there are established 

MRLs for sethoxydim in Canada which have harmonized tolerance definitions with the U.S. All 

Canadian MRLs are harmonized with U.S. tolerances to the greatest extent possible. In regard to 

the grass forage and hay tolerances requested in this petition, Canada does not establish MRLs

on livestock feed items so harmonization is not a consideration for these uses. The data provided 

in support of the requested amended use on blueberry is consistent with the established 4.0 ppm

U.S. tolerance on this commodity. For the requested crop group conversions, these tolerances 

are supported by extension of the representative crop(s) already established for use. As such, the 

establishment of subgroup 13-07B for bushberry will follow the representative crop of blueberry 

and the set tolerance of 4.0 ppm. Although the bushberries of juneberry, lingonberry, and salal 

have established U.S. tolerances of 5.0 ppm, these limits were set on translation from caneberry 

data which is no longer a crop in this subgroup. Therefore, in following the blueberry 

representative crop, the bushberry subgroup will harmonize with the already established 

Canadian MRL of 4.0 ppm for this crop grouping. For the other conversions, the Canadian 

MRLs on rapeseed (canola), grapes, cranberry, and bulb vegetables are significantly less than 

those needed to cover the residues in the U.S. Thus, tolerance harmonization for these crop

groupings are not possible. 
Sethoxydim Summary of Analytical Chemistry and Residue Data D422744

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2.3 Label Recommendations

The supplemental label for fine fescue grown for turfgrass seed should indicate the use is 

restricted to the Pacific Northwest region of the United States.

3.0 Introduction

3.1 Chemical Identity

Table 3.1. Sethoxydim and Metabolite Nomenclature.

Chemical structure

Common name Sethoxydim

Company experimental name BAS 9052 H or BAS 562 05H

IUPAC name (±)-(EZ)-2-(1-ethoxyiminobutyl)-5-[2-(ethylthio)propyl]-3-hydroxycyclohex-2-

enone

CAS name (±)-2-[1-(ethoxyimino)butyl]-5-[2-(ethylthio)propyl]-3-hydroxy-2-cyclohexen-1-

one

CAS registry number 74051-80-2

End-use product (EP) 1.5 lb/gal EC formulation (Poast® Herbicide; EPA Reg. No. 7969-58)

Chemical structure of 2-

cyclohexen-1-one metabolites

Derivatized residues 

determined by the analytical 

method

Common and chemical names DME; 3-[2-(ethylsulfonyl)propyl]-

pentanedioic acid dimethyl ester

DME-OH; 3-[2-ethylsulfonyl)propyl]-3-

hydroxypentanedioic acid dimethyl ester

Metabolites used for sample 

fortification 1

Common and chemical names MSO; 2-[1-(ethoxyimino)butyl]-5-[2-

(ethylsulfinyl)propyl]-3-hydroxy-2-

cyclohexen-1-one

5-OH-MSO2; 2-[1-(ethoxyimino)butyl]-

5-[2-(ethylsulfonyl)propyl]-3,5-

dihydroxy-2-cyclohexen-1-one

1 Sethoxydim is readily oxidized to MSO and 5-OH-MSO2 in air; therefore, these metabolites are used for sample 

fortification.

OH

CH3

O

N

O CH3

S

CH3

H3C

R

OH

R

O

S

CH3

H3C

O

O

COOCH3

COOCH3

S

CH3

H3C

O

O

COOCH3

COOCH3

OH

OH

CH3

O

N

O CH3

S

CH3

H3C

O

OH

CH3

O

N

O CH3

S

CH3

H3C

O

O

OH
Sethoxydim Summary of Analytical Chemistry and Residue Data D422744

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3.2 Physical/Chemical Characteristics

Physiochemical properties for sethoxydim are shown in Table 3.2.

Table 3.2. Physicochemical Properties of Sethoxydim. 

Parameter Value Reference

Color Brown MRID No. 41607203

Physical State Viscous Liquid

Odor Garlic-Like

Boiling Point >130°C at 6 x 10-1 mm Hg

Density, Bulk Density, or Specific Gravity 1.058 specific gravity at 20°C

Solubility Water at 25°C: 2.57 x 102 ppm at pH 5, 4.39 

x 103 ppm at pH 7;

Organic solvents (methanol, n-octanol, ethyl 

acetate, n-hexane, toluene, xylene, and olive 

oil) at 20°C: freely soluble (>103 g/100mL).

MRID Nos. 41475201 and 

41510601

Vapor Pressure 1.6 x 10-7 mm Hg at 25°C MRID No. 00047647

Dissociation Constant pKa is 4.6 at pH 4.5 and 25 °C MRID No. 00047650

Octanol/Water Partition Coefficient KOW is 3.26 x 103at pH 5; 45.1 at pH 7; 0.93 

at pH 9

MRID No. 41475202

pH 3.95 at 20°C MRID No. 41607203

Stability Stable at normal temperatures (24°C) and in 

the presence of metals (zinc and iron powder) 

, unstable at elevated temperatures (54°C) 

and in the presence of sunlight. 

3.3 Pesticide Use Pattern/Directions for Use (860.1200)

A summary of the use directions for the requested new uses on blueberry and fine fescue grasses 

is provided below in Table 3.3.

Table 3.3. Summary of Directions for Proposed Uses of Sethoxydim.

Applic. Timing;

Type; and

Equip.

Formulation

[EPA Reg. 

No.]

Applic. 

Rate 

(lb ai/A)

Max. No. 

Applic. per 

Season

Max. Seasonal 

Applic. Rate

(lb ai/A)

PHI

(days) Use Directions and Limitations

Blueberry, highbush

Broadcast foliar;

Apply as a selective 

control for grass 

weeds;

Ground or aerial 

equipment

PoastTM 1.5

lb/gal 

Emulsifiable 

Concentrate 

(EC)

[7969-58]

0.5 2 1.0 1 For the control of perennial and 

annual weeds.

Make up to 2 applications, 

each at 2.5 pints per acre, at a 

14-day minimum interval with 

the last application 1-day prior 

to harvest. 

Fine Fescue Grasses

Broadcast foliar;

Apply when fine 

fescue is semidormant;

Ground and Aerial

equipment

PoastTM 1.5

lb/gal 

Emulsifiable 

Concentrate 

(EC)

[7969-58]

0.5 2 1.0 14 For the control of perennial and 

annual weeds.

Make up to 2 applications, 

each at 2.5 pints per acre, at a 

30-day interval with the last 

application 14-days prior to 

foraging or collection of hay. 

Apply when fine fescue is 

semi-dormant (generally Nov. 

1 through March 15). 
Sethoxydim Summary of Analytical Chemistry and Residue Data D422744

Page 7 of 23

The use directions are adequate to allow evaluation of the residue data relative to the proposed 

uses. The proposed maximum application rates, re-treatment intervals, and pre-harvest intervals 

are supported by the submitted field trial data. The fine fescue grass supplemental label should 

indicate that use is limited to the Pacific Northwest region of the United States.

4.0 Metabolite/Degradate Residue Profile

4.1 Nature of the Residue

4.1.1 Summary of Plant Metabolism (860.1300)

The nature of the residue in plants is adequately understood for purposes of the crops that are the 

subject of this petition. The qualitative nature of the residue in plants is adequately understood 

based on soybean, tomato, and sugar beet metabolism studies. Sethoxydim is rapidly 

metabolized in plants to a multitude of cyclohexenone derivatives including the corresponding 

parent sulfoxide, parent sulfone, their hydroxylated and desethoxylated analogs, and oxazole 

compounds; very little (≤0.5%) sethoxydim is left un-metabolized. The residues of concern for 

tolerance expression and risk assessment in plants are the combined residues of sethoxydim and 

its metabolites containing the 2-cyclohexen-1-one moiety (calculated as sethoxydim).

4.1.2 Summary of Livestock Metabolism (860.1300)

The nature of the residue in livestock is understood based on acceptable metabolism studies in 

ruminants (goat) and poultry (hens). The residues of concern for tolerance expression and risk 

assessment in livestock commodities are the combined residues of sethoxydim and its 

metabolites containing the 2-cyclohexen-1-one moiety (calculated as sethoxydim).

4.2 Residues of Concern Summary and Rationale

The metabolism of sethoxydim in plants and livestock is adequately understood. Residues of 

concern for both tolerance expression and risk assessment are the combined residues of 

sethoxydim and its metabolites containing the 2-cyclohexen-1-one moiety, calculated as 

sethoxydim (Phase V Review of soybeans, tomatoes, Goats, and poultry Metabolism Studies, 

CBRS17851, L. Cheng, 04/04/97). The Metabolism Assessment Review Committee (MARC) 

has also met and discussed the residues of sethoxydim which are found in water (D246356, R. 

Loranger, 05/27/1998). The predominant degradates in soil are the sulfoxide and sulfone 

derivates of parent (MSO and MSO2). Those degradates are expected to be found in water along 

with M1S (loss of ethoxy group on imino nitrogen) and M2S (formation of oxazole ring). In the 

absence of available toxicity data, the MARC considers the degradates of sethoxydim as having 

comparable toxicity to that of the parent compound. Therefore, the MARC concluded that for 

risk assessment purposes the residues in water are the “total sethoxydim residues” in water 

(parent plus degradates). 
Sethoxydim Summary of Analytical Chemistry and Residue Data D422744

Page 8 of 23

Table 4.2 Summary of Metabolites and Degradates to be included in the Risk 

Assessment and Tolerance Expression

Matrix Residues included in Risk Assessment Residues included in Tolerance Expression

Plants (Primary and 

Rotational Crops)

Sethoxydim and all metabolites containing 

the 2-cyclohexen-1-one moiety

Sethoxydim and all metabolites containing 

the 2-cyclohexen-1-one moiety

Livestock Sethoxydim and all metabolites containing 

the 2-cyclohexen-1-one moiety

Sethoxydim and all metabolites containing 

the 2-cyclohexen-1-one moiety

Drinking Water Total sethoxydim residues (parent plus 

degradates) Not Applicable

5.0 Residue Profile

5.1 Residue Analytical Methods (860.1340)

5.1.1 Data Collection Methods

Samples from the current grass and blueberry field trial studies were analyzed for the combined 

residues of sethoxydim and its metabolites convertible to the 3-alkyl substituted pentanedioic 

acid moiety using GC/FPD methodology. The GC/FPD methods used for these analyses are 

derived from the current tolerance enforcement method, BASF Wyandotte Corporation Method 

No. 30, included in Method I PAM II. These methods are determined to be adequate for data 

collection based upon acceptable concurrent recovery provided with each study. 

Briefly, residues are extracted with methanol, evaporated, reconstituted, and precipitated with 

calcium hydroxide. After filtration, the extract was acidified and then partitioned four times with 

dichloromethane (DCM). Sethoxydim and its metabolites were oxidized with hydrogen peroxide 

at reflux, and then esterified with acidic methanol to DME and DME-OH. The derivatives were 

partitioned into DCM, evaporated to dryness, re-dissolved in acetone, and determined by 

GC/FPD in the sulfur mode. Residues are expressed as sethoxydim using molecular weight 

conversion factors of 1.11x for DME and 1.05x for DME-OH.

5.1.2 Multi-Residue Methods (860.1360)

Sethoxydim is not recovered through the PAM I multi-residue methods.

5.1.3 Tolerance Enforcement Methods

An adequate enforcement methodology using GC/FPD analysis is available for determining the 

residues of sethoxydim. BASF Wyandotte Corporation Method No. 30, "Determination of BAS 

9052H and its Metabolites in Soybean Seed, Soybean Seed Process Fractions, Chicken Tissues, 

Beef Tissues, Milk and Eggs", is designed to determine residues of sethoxydim and its 

metabolites, including the parent sulfoxide (MSO), the parent sulfone (MSO2) and hydroxylated 

derivatives (e.g. 5-OH-MSO2). Residues are determined as 3-[2-(ethylsulfonyl)-propyl] 

pentanedioic acid dimethyl ester (DME) and its 3-hydroxy derivative: 3-[2-(ethoxysulfonyl) 
Sethoxydim Summary of Analytical Chemistry and Residue Data D422744

Page 9 of 23

propyl]-3-hydroxypentanedioic acid dimethyl ester (DME-OH), respectively. The limit of 

quantitation for each analyte is reported to be 0.05 ppm sethoxydim equivalents. Method 30 is 

included as Sethoxydim Method I in PAM II, and is therefore approved as an enforcement 

method. 

5.1.4 Submittal of Analytical Reference Standards (860.1650)

Analytical standards for sethoxydim (CAS # 74051-80-2) and its regulated metabolites are 

available at the EPA National Pesticide Standards Repository [personal communication from T. 

Cole of ACB/BEAD to K. King, 09/29/2014] with the following receipt and expiration dates:

Inventory

Chemical Name Company Date Exp

sethoxydim 5-hydroxy sulfone (see sethoxydim , 5-

OH- MSO2) 

sethoxydim sulfone (183612) BASF 6/1/2016

sethoxydim sulfoxide Nisso 

Chem

9/29/2008

sethoxydim sulfoxide (0183611) BASF 6/1/2016

sethoxydim sulfoxide (0183611) BASF 2/1/2015

sethoxydim, use li-sethoxydim see folder BASF

sethoxydim, 5-OH-MSO2 248657 BASF 3/1/2015

sethoxydim, 5-OH-Sulfoxide 248657 BASF 3/1/2015

sethoxydim, DME metabolite 229159 BASF 4/1/2024

sethoxydim, DME-OH metabolite BASF 4/1/2020

sethoxydim, li (reg 282305) BASF 2/1/2016

Prior to the listed expiration dates, fresh standards should be re-submitted to the Repository. The 

reference standard(s) 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

The full 9 digit zip code is mandatory or the mail will be returned.

5.2 Storage Stability (860.1380)

Adequate storage stability data are available depicting the stability of sethoxydim residues held 

under frozen storage conditions at durations incurred for the studies supporting this petition. For 

the field trial studies carried out for grass, forage and hay samples were stored frozen (-21 ± 7 
Sethoxydim Summary of Analytical Chemistry and Residue Data D422744

Page 10 of 23

°C) from collection to extraction for 108-123 days (3.6-4.0 months) and 172-272 days (5.7-8.9 

months), respectively. All samples were analyzed within 2-4 days of extraction. Storage 

stability data were generated concurrently with the field trial study to demonstrate that residues 

of sethoxydim, determined as DME and DME-OH are stable in grass commodities when stored 

frozen for these durations. For the blueberry field trials, the maximum sample storage interval 

between harvest and analysis was 848 days (28.2 months). Residues of sethoxydim have been 

shown to be stable in strawberries stored frozen for up to 31 months (D219970, L. Cheng, 

04/09/1996). As a result, adequate data are available to support the storage conditions and 

intervals for the blueberry samples comprising the current trials.

5.3 Residue Data

5.3.1 Crop Field Trials (860.1500)

49257701.der (Blueberry Trials)

49257702.der (Grass Grown for Seed Trials)

Blueberry Trials

The Interregional Research Project No. 4 (IR-4) submitted magnitude of the residue data for 

sethoxydim on blueberry grown in both the United States and Canada. Eleven (11) field trials 

for sethoxydim on blueberries in all were conducted in the North American Free Trade 

Agreement (NAFTA) Growing Regions 1A (3 trials in NS), 1 (1 trial in ME), 2 (3 trials in NC), 

5A (3 trials in MI) and 12 (1 trial in OR) during the 2008 growing season. Of these 11 field 

trials, 4 were conducted on lowbush blueberries and 7 were conducted on highbush blueberries.

The trials reflect the use of two post-emergent foliar applications of sethoxydim formulated as

the 1.5 lb. ai/gal POAST® emulsifiable concentrate (EC) herbicide. Treatments were made at a 

rate of 0.476-0.523 lbs ai/A (534-586 g ai/ha) for a total seasonal rate of 0.961-1.019 lbs ai/A 

(1078-1142 g ai/ha). A re-treatment interval (RTI) of 13-16 days and a 1-day pre-harvest 

interval (PHI) was followed. An adjuvant or crop oil concentrate was added to the spray mixture 

for all applications.

 

All samples were maintained frozen at the testing facility, during shipping to the laboratory, and 

were stored frozen until analysis. The maximum storage interval for samples between harvest 

and analysis was 848 days (28.2 months). Residues of sethoxydim have been shown to be stable 

in strawberries for up to 31 months under frozen conditions (D219970, L. Cheng, 04/09/1996). 

Translating the strawberry storage stability data to blueberry, adequate storage stability data are 

available to support the storage conditions and intervals for samples in the current trials.

The blueberry samples in this study were analyzed using Method Version #36, a GC/FPD 

method to determine residues of sethoxydim derived from the Method I PAM II enforcement 

method. Acceptable method validation and concurrent recoveries were reported for blueberry 

samples at fortification levels of 0.05 ppm, 0.50 ppm, 5.0 ppm and/or 15.0 ppm with the 

exception of one concurrent recovery at 67%, thus validating the method. The limit of 

quantitation (LOQ) was determined to be 0.05 ppm for each analyte (i.e. MSO and 5-OH-MSO2) 

in blueberries which corresponds to a LOQ of 0.047 ppm for DME and 0.044 ppm for DME-OH 

(expressed as sethoxydim equivalents).

 
Sethoxydim Summary of Analytical Chemistry and Residue Data D422744

Page 11 of 23

Individual sample (and per-trial average) residues in lowbush blueberries ranged from 0.164 ppm 

to 8.92 ppm (3.34 ppm to 8.72 ppm) when treated at a total rate of 0.961-1.019 lbs ai/ha (1078-

1142 g ai/ha) and sampled 1 day after treatment. Individual sample (and per-trial average) 

residues in highbush blueberries ranged from <0.091 ppm to 0.204 ppm (<0.091 ppm to 0.184 

ppm) when treated at a total rate of 0.978-1.078 lbs ai/ha (1096-1208 g ai/ha) and sampled 1 day 

after treatment. The results from these studies are summarized in Table 5.3.1.1.

Table 5.3.1.1. Summary of Residues from Blueberry Field Trials with Sethoxydim

Crop Matrix

Total Application 

Rate 

(lbs ai/A) 

[g ai/ha]

PHI 

(days) n

Residues1(ppm)

Min.2 Max.2 LAFT3 HAFT3 Median3 Mean3 SD3

LOWBUSH BLUEBERRIES 

Lowbush 

blueberries

0.961-1.019

[1078-1142]

1 4 0.164 8.92 3.34 8.72 7.72 6.88 2.41

HIGHBUSH BLUEBERRIES

Highbush 

blueberries

0.978-1.078

[1096-1208]

1 7 0.091 0.204 0.091 0.184 0.091 0.106 0.035

1 Combined residues of DME and DME-OH expressed as sethoxydim equivalents.

2 Values based on total number of samples.

3 Values based on per-trial averages. LAFT = lowest average field trial, HAFT = highest average field trial, SD = standard 

deviation. For computation of the LAFT, HAFT, median, mean, and standard deviation, values < LOQ are assumed to be at the 

LOQ (xx ppm).

n = number of field trials.

Conclusions: The current petition requests only to amend the use of sethoxydim on highbush 

blueberries to a reduced 1-day PHI. All other bushberry varieties, including lowbush 

blueberries, will retain the established labeled rate which follows a 30-day PHI. As a result, the 

lowbush blueberry data acquired at the 1-day PHI contained in this study are not used for 

tolerance setting purposes since they do not reflect a proposed or registered use pattern. 

Although eight (8) highbush blueberry trials are recommended for tolerance determination, the 

seven (7) provided are considered adequate due to the consistently low residues observed. All 

highbush blueberry samples acquired for study were analyzed using an adequate analytical 

method with the incurred storage intervals appropriately supported by available stability data. 

The current tolerance set on blueberries is 4.0 ppm and this limit remains adequate given that all 

of the highbush blueberry data acquired at the 1-day PHI are well below this level. 

 

Grass Grown for Seed Trials

IR-4 submitted field trial data for sethoxydim on fine fescue grass grown for seed. Five (5) grass 

field trials were conducted in the United States in NAFTA Zones 11 (WA; 2 trials) and 12 (OR; 

3 trials) during the 2007 growing season. Careful examination of the field trial records indicates 

that the two WA trials were conducted at the same locations with very few differences in study 

design; for this reason HED has determined these trials constitute a single trial with replicate 

samples for purposes of 860.1500 data requirements. The three OR trials were also conducted at 

the same location; however, HED has concluded that these may be considered independent due 

differences in the grass variety used.

The trials reflect the use two foliar broadcast applications of sethoxydim formulated as the 1.5 lb. 

ai/gal POAST® emulsifiable concentrate (EC) herbicide. Treatments were made at 0.465-0.498 

lb ai/A/application for a total seasonal rate of 0.936-0.973 lb ai/A. Applications were made at 

30- to 44-day retreatment intervals (RTIs) using ground equipment in spray volumes of 14.9-
Sethoxydim Summary of Analytical Chemistry and Residue Data D422744

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20.3 gal/A. A crop oil concentrate (COC) was added to each spray mixture. Following the 

second application, samples were harvested from all trials at preharvest intervals (PHIs) of 13-14 

days for grass forage and 21-28 days for grass hay. Hay samples were allowed to dry in an 

enclosed area for 3-7 days prior to collection. 

Samples of grass forage and hay were stored frozen (-21 ± 7 °C) from collection to extraction for 

108-123 days (3.6-4.0 months) and 172-272 days (5.7-8.9 months), respectively. All samples 

were analyzed within 2-4 days of extraction. Storage stability data generated concurrently with 

the field trial study to demonstrate that residues of sethoxydim, determined as DME and DMEOH, are stable on grass samples for these durations. 

The grass forage and hay samples in this study were analyzed using Method Version #35 and 

35A, a GC/FPD method to determine residues of sethoxydim derived from the Method I PAM II 

enforcement method. The method is adequate for data collection based on acceptable concurrent 

recovery data. The calculated LOD and LOQ for DME and DME-OH in fine fescue grass forage 

were determined to be 0.007, 0.021, 0.005, and 0.014 ppm, respectively. The calculated LOD 

and LOQ for DME and DME-OH in fine fescue grass hay were determined to be 0.013, 0.038, 

0.004, and 0.011 ppm.

Following two foliar broadcast applications of the 1.5 lb ai/gal EC formulation of sethoxydim at 

a total rate of 0.936-0.973 lb ai/A, residues (and per trial averages) of sethoxydim equivalents, 

(determined as DME, DME-OH, and combined residues; respectively, were: 1.0-2.8 (1.4-2.7), 

0.21-0.42 (0.22-0.34), and 1.24-3.16 (1.65-3.04) ppm, in/on fine fescue grass forage harvested at 

a 13- to 14-day PHI; and 0.48-1.3 (0.65-1.1), 0.14-0.40 (0.15-0.35), and 0.75-1.45 (0.98-1.26)

ppm, in/on fine fescue grass hay harvested at a 21- to 28-day PHI. Residue decline data were not 

submitted. The results from these studies are summarized in Table 5.3.1.2.

Table 5.3.1.2. Summary of Residue Data from Grass Crop Field Trials with Sethoxydim.

Commodity Analyte Total App. 

Rate 

(lb ai/A)

PHI

(days)

Residue Levels (ppm)1

n Sample 

Min.

Sample 

Max.

LAFT2 HAFT2 Median Mean Std. 

Dev.

Grass

forage

DME3 0.936-0.973 13-14 4 1.0 2.8 1.4 2.7 1.5 1.8 0.63

DME-OH3 4 0.21 0.42 0.22 0.34 0.29 0.29 0.07

Combined 4 1.24 3.16 1.65 3.04 1.74 2.04 0.67

Grass

hay

DME3 21-28 4 0.48 1.3 0.65 1.1 0.84 0.86 0.19

DME-OH3 4 0.14 0.40 0.15 0.35 0.30 0.27 0.09

Combined 4 0.75 1.45 0.98 1.26 1.16 1.14 0.14

1

 Except for sample min/max, values reflect per trial averages; n = no. of field trials. For calculation of median, mean, and 

standard deviation, the LOQ (0.042 ppm for all analytes) was used for any results reported as <LOQ.

2

 LAFT = lowest average field trial; HAFT = highest average field trial.

3

 Residues of DME and DME-OH are reported in sethoxydim parent equivalents as calculated by the petitioner.

Conclusions: The submitted residue data made for the grass forage and hay commodities are 

adequate to support a regional registration limiting use to the Pacific Northwest region of the 

United States. The number and location of field trials are sufficient having been made in line 

with the guidance document, “Grasses Grown for Seed”, an Agency memorandum dated 

09/30/2000. This memorandum requires the collection of forage and hay data for this 

commodity since it is considered to be a subgroup of grass pasture and rangeland. Further, it 
Sethoxydim Summary of Analytical Chemistry and Residue Data D422744

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specifies that for a national registration, a total of 8 trials are recommended (5 in the Pacific 

Northwest plus 3 in Region 5). HED notes that although according to current policy only 4 

independent grass trials were submitted, the trials were conducted prior to when the criteria for 

distinguishing independent trials became available. In addition, the consistency observed in the 

data set makes it unlikely that requiring an additional trial would lead to different conclusions 

that what can be determined from the results now available. Thus, applying OECD MRL 

calculation procedures to the 4 independent trials gives recommended tolerances of 7.0 ppm for 

grass forage and 4.0 ppm for grass hay (see Appendix B).

Tolerance Conversions to Crop Groups/Subgroups

 Citrus Fruit Group 10 to Citrus Fruit Group 10-10

IR-4 proposed that the established tolerances of 0.5 ppm for citrus fruit crop group 10 be 

converted to the updated citrus fruit crop group 10-10 listing at the same limit. This request is 

supported by the following observations: 1) adequate residue data for the orange, lemon, and 

grapefruit representative crops were previously submitted and evaluated to establish a citrus fruit 

crop group tolerance at 0.5 ppm, and 2) proposed revisions to the POAST® EC herbicide label 

submitted as part of Section B of the petition, are consistent with the requested conversion. 

 Pome Fruit Group 11 to Pome Fruit Group 11-10

IR-4 proposed that the established tolerances of 0.2 ppm for pome fruit group 11-10 be converted 

to the updated pome fruit group 11-10 listing at the same limit. This request is supported by the 

following observations: 1) adequate residue data for the apple and pear representative crops 

were previously submitted and evaluated to establish a pome fruit crop group tolerance at 0.2 

ppm, and 2) proposed revisions to the POAST® EC herbicide label submitted as part of Section 

B of the petition, are consistent with the requested conversion.

 Caneberry Subgroup 13A to Caneberry Subgroup 13-07A

IR-4 proposed that the established tolerances of 5.0 ppm for caneberry subgroup 13A be 

converted to the updated caneberry subgroup 13-07A listing at the same limit. This request is 

supported by the following observations: 1) adequate residue data for the raspberry 

representative crop were previously submitted and evaluated to establish a caneberry subgroup 

tolerance at 5.0 ppm, and 2) proposed revisions to the POAST® EC herbicide label submitted as 

part of Section B of the petition, are consistent with the requested conversion. 

 Blueberry to Bushberry Subgroup 13-07B

IR-4 proposed that the established tolerances of 4.0 ppm for blueberry and 5.0 ppm for 

juneberry, lingonberry, and salal be converted to the updated bushberry subgroup 13-07B listing 

at 5.0 ppm. This request is supported but at the recommended tolerance of 4.0 ppm and not the 

proposed limit of 5.0 ppm based on the following observations: 1) adequate residue data for the 

blueberry representative commodity were previously submitted and evaluated to establish a 

tolerance of 4.0 ppm on this crop, 2) the juneberry, lingonberry, and salal tolerances are based on 

the translation of caneberry data which is no longer relevant to these crops following updated 

crop group realignment, and 3) proposed revisions to the POAST® EC herbicide label submitted 

as part of Section B of the petition, are consistent with the requested conversion. 
Sethoxydim Summary of Analytical Chemistry and Residue Data D422744

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 Grape to Crop Subgroup 13-07F [Fruit, small vine climbing, except fuzzy kiwifruit, 

subgroup 13-07F]

IR-4 proposed that the established tolerance of 1.0 ppm for grape be converted to crop subgroup 

13-07F, also at 1.0 ppm. This request is supported by extension of the grape use pattern to 

include crop subgroup 13-07F, as indicated in the proposed revisions to the POAST® EC 

herbicide label, submitted as part of Section B of the petition. Grape is the representative 

commodity for crop subgroup 13-07F. 

 Strawberry to Crop Subgroup 13-07G, Except Cranberry [Berry, low growing, subgroup 

13-07F, except cranberry]

IR-4 proposed that the established tolerance of 10.0 ppm for strawberry be converted to crop 

subgroup 13-07G, except cranberry, also at 10.0 ppm. This request is supported by extension of 

the strawberry use pattern to include crop subgroup 13-07G, except cranberry, as indicated in the 

proposed revisions to the POAST® EC herbicide label, submitted as part of Section B of the 

petition. Strawberry is the representative commodity for crop subgroup 13-07G. 

 Cranberry to Crop Subgroup 13-07H

IR-4 proposed that the established tolerance of 2.5 ppm for cranberry be converted to crop 

subgroup 13-07H, also at 2.5 ppm. This request is supported by extension of the cranberry use 

pattern to include crop subgroup 13-07H, as indicated in the proposed revisions to the POAST® 

EC herbicide label, submitted as part of Section B of the petition. Cranberry is the representative 

commodity for crop subgroup 13-07H. 

 Canola Seed to Rapeseed Crop Subgroup 20A

IR-4 proposed that the established tolerance of 35.0 ppm for canola seed be converted to crop 

subgroup 20A, also at 35.0 ppm. This request is supported by extension of the canola use pattern 

to include rapeseed crop subgroup 20A, as indicated in the proposed revisions to the POAST® 

EC herbicide label, submitted as part of Section B of the petition. Canola is the representative 

commodity for rapeseed crop subgroup 20A. 

 Sunflower Seed to Sunflower Crop Subgroup 20B, Except Safflower

IR-4 proposed that the established tolerance of 7.0 ppm for sunflower seed be converted to crop 

subgroup 20B, also at 7.0 ppm. This request is supported by extension of the sunflower use 

pattern to include sunflower crop subgroup 20B, except safflower, as indicated in the proposed 

revisions to the POAST® EC herbicide label, submitted as part of Section B of the petition. 

Sunflower is the representative commodity for rapeseed crop subgroup 20A. 

 Cotton Undelinted Seed to Cottonseed Crop Subgroup 20C

IR-4 proposed that the established tolerance of 5.0 ppm for cotton undelinted seed be converted 

to crop subgroup 20C, also at 5.0 ppm. This request is supported by extension of the cotton use 

pattern to include cottonseed crop subgroup 20C, as indicated in the proposed revisions to the 

POAST® EC herbicide label, submitted as part of Section B of the petition. Cotton is the 

representative commodity for rapeseed crop subgroup 20C. 

 Bulb Vegetable Group 3 to Bulb Vegetable Group 3-07

IR-4 proposed that the established tolerances of 1.0 ppm for bulb vegetable crop group 3 be 

converted to the updated bulb vegetable crop group 3-07 listing at the same limit. This request is 
Sethoxydim Summary of Analytical Chemistry and Residue Data D422744

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supported by the following observations: 1) adequate residue data for the green onion and bulb 

onion representative crops were previously submitted and evaluated to establish a bulb vegetable 

crop group tolerance at 1.0 ppm, and 2) proposed revisions to the POAST® EC herbicide label 

submitted as part of Section B of the petition, are consistent with the requested conversion. 

 Fruiting Vegetable Group 8 to Fruiting Vegetable Group 8-10

IR-4 proposed that the established tolerances of 4.0 ppm for fruiting vegetable crop group 8 be 

converted to the updated fruiting vegetable crop group 8-10 listing at the same limit. This 

request is supported by the following observations: 1) adequate residue data for the tomato and 

pepper representative crops were previously submitted and evaluated to establish a fruiting 

vegetable crop group tolerance at 4.0 ppm, and 2) proposed revisions to the POAST® EC 

herbicide label submitted as part of Section B of the petition, are consistent with the requested 

conversion. 

Conclusions: HED concludes that the tolerance conversions proposed by IR-4 are acceptable. 

Upon establishment of the requested crop group/subgroup tolerances, the individual crop 

tolerances for blueberry, borage meal, borage seed, canola seed, cotton undelinted seed, crambe 

seed, cupea seed, echium seed, flax seed, gold of pleasure seed, grape, hare’s ear mustard seed, 

juneberry, lesquerella seed, lingonberry, lunaria seed, meadowfoam seed, milkweed seed, 

mustard seed, oil radish seed, poppy seed, rapeseed seed, salal, sesame seed, strawberry, 

sunflower seed, and sweet rocket seed should be revoked as they will be included in the 

group/subgroup tolerance listings. In addition, the crop group and subgroup listings for 

caneberry subgroup 13A, citrus fruit group 10, pome fruit group 11, bulb vegetable group 3, and 

fruiting vegetable group 8 are also to be removed and replaced by the current crop group 

definitions.

 

5.3.2 Field Rotational Crops (860.1900)

D312567, W.H. Donovan, 04/22/2005

An adequate limited field study using soybeans and cotton treated with 14C-ring-labeled 

sethoxydim was submitted by the registrant. Following treatment and harvest, selected rotational 

crops of leafy vegetable, root crop, and small grain groups were sown at intervals to simulate 

emergency replant, fall crop rotations, and annual crop rotations. Total radioactive residues 

(TRRs) were <0.005-0.01 ppm with some exceptions: 0.05 ppm in sorghum forage at a plantback interval (PBI) of 30 days (0.5 lb ai/A application rate); 0.02 ppm in winter wheat forage and 

0.05 ppm in winter wheat straw at a PBI of 134 days (1 lb ai/A application rate); and 0.024 ppm 

in spring wheat grain and 0.06 ppm in spring wheat straw at a PBI of 283 days (0.5 lb ai/A 

application rate). HED noted that even though the application rate in cotton was below the 

maximum for this crop, it was similar to that of many other crops. The chance that using the 

highest possible application rate could lead to rotational crop residues in excess of the LOQ is 

judged unlikely. Given that the sethoxydim residues appear to be below the LOQ in all 

rotational crops at all PBIs and tolerances have been established for representative crops of the 

leafy vegetable and root crop groups, HED concluded that no tolerances on rotational crop are 

required for plant-back times greater than 30 days. In addition, HED noted that the label 

prohibits planting crops not registered for the product for 120 days after application (D189273, 

G. Kramer, 08/03/1993).
Sethoxydim Summary of Analytical Chemistry and Residue Data D422744

Page 16 of 23

5.3.3 Processed Food and Feed (860.1520)

There are no processed commodities associated with grass grown for seed or blueberry. 

Therefore, data requirements for processed food and feed are not relevant to this tolerance 

petition.

5.3.4 Meat, Milk, Poultry and Eggs (860.1480)

Chemistry Chapter of the Reregistration Eligibility Decision, D312567, W. H. Donovan, 04/22/2005

For this action, the recommended tolerances for grass forage and hay are 7.0 ppm and 4.0 ppm, 

respectively. The sethoxydim maximum theoretical dietary burdens to livestock were previously 

calculated in the residue chemistry summary for the 2005 RED. Grass forage and hay are both 

classified as roughages. A tolerance of 40.0 ppm on alfalfa forage, another livestock roughage 

feed item, was included in the maximum theoretical dietary burden calculation in 2005; 

therefore, the addition of these new tolerances will not increase the previously calculated dietary 

burden. If HED were to recalculate the MRBD burden for sethoxydim at this time, grass forage 

and hay be superseded by alfalfa forage, and the use of STMR and HR values would 

substantially reduce the dietary burden compared to the 2005 value. Current sethoxydim 

tolerances in livestock commodities are based on the conservative 2005 RED dietary burden; 

therefore, current livestock tolerances are adequate to support the new uses proposed for 

sethoxydim. 

5.4 Food Residue Profile

Adequate residue chemistry data have been provided to support the registration of sethoxydim on 

on grass grown for seed and its amended use on blueberry. Field trials are of adequate number 

and geographic representation. Data analyses employed validated analytical methods and are 

supported by adequate storage stability data. No processing studies were submitted because 

sethoxydim use in grass grown for seed and blueberry are not expected to be processed for 

economic reasons. For the requested new use on grass grown for seed, the establishment of 

tolerances on grass forage and hay will not increase livestock dietary burden; therefore, no new 

revised tolerances on livestock commodities are required.

The nature of the residue in plants and livestock is adequately understood. The residues of 

concern in plants and livestock are the combined residues of sethoxydim and its metabolites 

containing the 2-cyclohexen-1-one moiety (calculated as sethoxydim). For risk assessment 

purposes, the residues in water are parent plus degradates. The degradates which are expected to 

be found in water are the sulfoxide and sulfone derivatives of the parent (MSO and MSO2) along

with M1S (loss of ethoxy group on imino nitrogen) and M2S (formation of oxazole ring).

No tolerances have been established for inadvertent or indirect residues of sethoxydim in or on 

rotational crops and none are needed at this time.

6.0 Tolerance Derivations

The recommended tolerances for sethoxydim were derived by 1) use of the OECD MRL 

calculation procedures for grass forage and hay, and 2) direct translation of the established 
Sethoxydim Summary of Analytical Chemistry and Residue Data D422744

Page 17 of 23

representative crops for the crop group conversions that were requested. The calculated 

tolerances for grass forage is 7.0 ppm and 4.0 ppm for grass hay. For these calculations, 

examination of the field trial records showed that the two WA trials were conducted at the same 

locations with very few differences in study design; for this reason HED has determined these 

trials constitute a single trial with replicate samples. Consequently, the four replicate residue 

values from the WA trial were averaged prior to use in the OECD calculator as a single value. 

Listings of the OECD MRL calculator input and output for grass forage and hay are provided in 

Appendix B. 

List of Appendices

A. International Residue Limits Table.

B. Tolerance Calculations.

C. 49257701.der.docx [blueberry trials]

D. 49257702.der.docx [grass grown for seed trials]
Sethoxydim Summary of Analytical Chemistry and Residue Data D422744

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References

DP No.: D312563

Subject: Sethoxydim: Submission of a Study of Residues on Safflower in Response to a 

RED Data Gap Requirement

From: D. Soderberg

To: J. Parker

Dated: 04/12/2012

MRID No.: 48514501

DP No.: D312567

Subject: Sethoxydim. HED Chemistry Chapter of the Reregistration Eligibility Decision 

(RED). Summary of Analytical Chemistry and Residue Data. Case No. 2600.

From: W. H. Donovan

To: A. Johnson

Dated: 04/22/2005

MRID No.: None

DP No.: None

Subject: Sethoxydim. Case 2600. Phase V Review of Soybeans, Tomatoes, Goats, and 

Poultry Metabolism Studies. CBRS 17851. DP Barcode: None.

From: L. Cheng

To: K. Whitby

Dated: 04/04/1997

MRID No.: None

DP No.: D246356

Subject: Sethoxydim. Conclusions of the 05/14/98 Meeting of the Metabolism 

Assessment Review Committee.

From: R. Loranger

To: G. Kramer

Dated: 05/27/1998

MRID No.: None

DP No.: D219970

Subject: Sethoxydim. Case 2600. Craven Replacement Data: Freezer Storage in Fruit and 

Vegetable Crops; Residue in Tomatoes, Broccoli, Mustard Greens, and Cabbage.

From: L. Cheng

To: B. Adler

Dated: 04/09/1996

MRID No.: 43801401-43801405
Sethoxydim Summary of Analytical Chemistry and Residue Data D422744

Page 19 of 23

DP No.: D189273

Subject: ID# 121001-007969. Review of Rotational Crop Studies of Sethoxydim (Poast 

Herbicide, EPA Reg. No. 7969-58). MRID Nos. 42825 and 415106-12. Barcode 

D189273. Case 816519. CBTS# 11575.

From: G. F. Kramer

To: K. Davis

Dated: 08/03/1993

MRID No.: 42825 and 415106-12
Sethoxydim Summary of Analytical Chemistry and Residue Data D422744

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Appendix A. International Residue Limits Table

Table B1. Summary of US and International Tolerances and Maximum Residue Limits for 

Sethoxydim (121001)

Residue Definition:

US Canada Mexico2 Codex

40 CFR 180.412:

Plant: sethoxydim: 2-[1-

ethoxyimino)butyl]-5-[2-(ethylthio)propyl]-

3-hydroxy-2-cyclohexen-1-one

(±)-2-[1-(ethoxyimino)butyl]-5-[2-

(ethylthio)propyl]-

3-hydroxy-2-cyclohexen-1-one, including 

metabolites

containing the cyclohexen-2-one moiety, 

expressed

as sethoxydim

None

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

US Canada Mexico2 Codex

Fruit, citrus, group 10-10 0.5

Fruit, pome, group 11-10 0.2

Fruit, caneberry, subgroup 13-07A 5.0 5 raspberries 

Fruit, bushberry, subgroup 13-07B 4.0 4 aronia berries, buffalo currants, Chilean 

guavas, currants, elderberries, European 

barberries, gooseberries, highbush 

(blueberries, cranberries), honeysuckle, 

huckleberries, jostaberries, Juneberries 

(Saskatoon berries), lingonberries, 

lowbush blueberries, native currants, salal 

berries, sea buckthorn

Fruit, small vine climbing, except 

fuzzy kiwifruit, subgroup 13-07F

1.0 0.2 amur river grapes, , grapes, hardy 

kiwifruit, maypop, schisandra berries

4 gooseberries

0.6 raisins

Fruit, low growing berry, except 

cranberry, subgroup 13-07G

10.0 2 cranberries

4 lowbush blueberries, lingonberries

10 strawberry

Fruit, low growing berry, except 

strawberry, subgroup 13-07H

2.5 2 cranberries

4 lowbush blueberries, lingonberries

Rapeseed, subgroup 20A 35.0 2.5 borage seeds

0.2 flax seeds

25 rapeseeds (canola) 

Sunflower, except safflower, 

subgroup 20B

7.0 7 sunflower seeds

Cottonseed, subgroup 20C 5.0

Vegetable, bulb, group 3-07 1.0 0.2 onions

Vegetable, fruiting, group 8-10 4.0 2 eggplants

0.5 peppers

4 tomatoes

15 tomato paste
Sethoxydim Summary of Analytical Chemistry and Residue Data D422744

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Table B1. Summary of US and International Tolerances and Maximum Residue Limits for 

Sethoxydim (121001)

Residue Definition:

US Canada Mexico2 Codex

Grass, forage, fodder and hay, group 

17, forage

6.0

Grass, forage, fodder and hay, group 

17, hay

4.0

Completed: M. Negussie; 11/13/14 

1

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

not those proposed by the applicant.

2 Mexico adopts US tolerances and/or Codex MRLs for its export purposes.
Page 22 of 23

Appendix B. Results of OECD Tolerance Calculations

Sethoxydim

Grass, Crop Group 17, Forage

US

PHI @ 14-days (EC)

Total number of data (n) 4

Percentage of censored data 0%

Number of non-censored data 4

Lowest residue 1.650

Highest residue 3.040

Median residue 1.745

Mean 2.045

Standard deviation (SD) 0.665

Correction factor for censoring (CF) 1.000

Proposed MRL estimate

- Highest residue 3.040

- Mean + 4 SD 4.706

- CF x 3 Mean 6.135

Unrounded MRL 6.135

Rounded MRL 7

High uncertainty of MRL estimate.

[Small dataset]

Residues (mg/kg) n

1.65 1

1.72 1

1.77 1

3.04 1
Sethoxydim Summary of Analytical Chemistry and Residue Data D422744

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Sethoxydim

Grass, Crop Group 17, Hay

US

PHI @ 21-28-days (EC)

Total number of data (n) 4

Percentage of censored data 0%

Number of non-censored data 4

Lowest residue 0.980

Highest residue 1.260

Median residue 1.155

Mean 1.138

Standard deviation (SD) 0.140

Correction factor for censoring (CF) 1.000

Proposed MRL estimate

- Highest residue 1.260

- Mean + 4 SD 1.696

- CF x 3 Mean 3.413

Unrounded MRL 3.413

Rounded MRL 4

High uncertainty of MRL estimate.

[Small dataset]

Residues (mg/kg) n

0.98 1

1.06 1

1.25 1

1.26 1
Sethoxydim (SOD)/BASF Canada Inc. (BAZ)

EPA MRID #: 49257701/DP No. D422744

PMRA # of document: 2432176

Page 1 of 8

B.7.6 Residues Resulting from Supervised Trials

(Annex IIA 6.3; Annex IIIA 8.3)

B.7.6.1 Residues in Target Crops

B.7.6.1.1 Blueberries (highbush and lowbush)

Document ID: MRID No. 49257701

PMRA No. 2387982

Report: Barney, W. P., Lennon, G. (2011) “Sethoxydim: Magnitude of the Residue 

on Blueberry”, IR-4 PR No. 09933, Analytical Laboratory Identification 

Number 09933.08-NYR02. Unpublished study prepared by IR-4 Project 

Headquarters, Rutgers, The State University of NJ, Princeton, NJ, 304 

pages.

Guidelines: EPA OCSPP Harmonized Test Guideline 860.1500 Crop Field Trials 

(August 1996)

PMRA Regulatory Directive DIR98-02 – Residue Chemistry Guidelines, 

Section 9 – Crop Field Trials 

PMRA Regulatory Directive DIR2010-05 – Revisions to the Residue 

Chemistry Crop Field Trial Requirements

OECD Guideline 509 Crop Field Trial (September 2009)

GLP Compliance: No deviations from regulatory requirements were reported which would 

have an impact on the validity of the study. 

Acceptability: The study is considered scientifically acceptable. 

Evaluator: Natalie Gaudreau (PMRA Canada)

EXECUTIVE SUMMARY

Eleven field trials for sethoxydim on blueberries were conducted in Canada and the United States 

encompassing North American Free Trade Agreement (NAFTA) Growing Regions 1A (3 trials 

in NS), 1 (1 trial in ME), 2 (3 trials in NC), 5A (3 trials in MI) and 12 (1 trial in OR) during the 

2008 growing season. Of these 11 field trials, 4 were conducted on lowbush blueberries and 7 

were conducted on highbush blueberries. For the highbush blueberry trials, 2 were conducted at 

the same location using the same spray mixture (i.e. Trial No. NC06 and NC07), therefore, these 

are not distinct trials.

At each lowbush blueberry trial location, sethoxydim formulated as POAST® Herbicide 

(emulsifiable concentrate containing 18% ai) was applied twice as a post-emergent foliar 

treatment at a rate of 0.476-0.523 lbs ai/A (534-586 g ai/ha) for a total seasonal rate of 0.961-

1.019 lbs ai/A (1078-1142 g ai/ha). At each highbush blueberry trial location, sethoxydim 

formulated as POAST® Herbicide (emulsifiable concentrate containing 18% ai) was applied 

twice as a broadcast application to the ground on each side of the blueberry row at a rate of 

0.479-0.548 lbs ai/A (537-614 g ai/ha) for a total seasonal rate of 0.978-1.078 lbs ai/A (1096-

1208 g ai/ha). An adjuvant or crop oil concentrate was added to the spray mixture for all 

applications. Blueberries were harvested at a preharvest interval (PHI) of 1 day. In one lowbush 
Sethoxydim (SOD)/BASF Canada Inc. (BAZ)

EPA MRID #: 49257701/DP No. D422744

PMRA # of document: 2432176

Page 2 of 8

blueberry trial, samples were collected at different time intervals (PHIs of 0, 3, 7 and 10 days) to 

monitor residue decline.

All samples were maintained frozen at the testing facility, during shipping to the laboratory, and 

were stored frozen until analysis. The maximum storage interval for samples between harvest 

and analysis was 848 days (28.2 months). Residues of sethoxydim have been shown to be stable 

in strawberries for up to 31 months under frozen conditions. Adequate storage stability data are 

therefore available to support the storage conditions and intervals for samples in the current 

trials.

Samples in the current study were analyzed using Method Version #36, a GC/FPD method to 

determine residues of sethoxydim. In this method, sethoxydim and its sulfide and sulfoxide 

metabolites are oxidized to sulfones, and the cyclohexene-1-one ring is cleaved to two common 

moieties: 3-alkyl and 3-alkyl-3-hydroxy substituted pentanedioic acid. The acids are methylated 

to dimethyl 3-[2-(ethylsulfonyl)propyl]pentanedioate (DME) and dimethyl 3-[2-

(ethylsulfonyl)propyl]3-hydroxy pentanedioate (DME-OH), which are the conversion products 

of the sethoxydim metabolites sethoxydim sulfoxide (MSO) and 5-hydroxy sethoxydim sulfone 

(5-OH-MSO2), respectively. Acceptable method validation and concurrent recoveries were 

reported for blueberry samples at fortification levels of 0.05 ppm, 0.50 ppm, 5.0 ppm and/or 15.0 

ppm with the exception of one concurrent recovery at 67%, thus validating the method. The 

limit of quantitation (LOQ) was determined to be 0.05 ppm for each analyte (i.e. MSO and 5-

OH-MSO2) in blueberries which corresponds to a LOQ of 0.047 ppm for DME and 0.044 ppm 

for DME-OH (expressed as sethoxydim equivalents).

Individual sample (and per-trial average) residues in lowbush blueberries ranged from 0.164 ppm 

to 8.92 ppm (3.34 ppm to 8.72 ppm) when treated at a total rate of 0.961-1.019 lbs ai/ha (1078-

1142 g ai/ha) and sampled 1 day after treatment. Residue decline data show that residues of 

sethoxydim increased in lowbush blueberries from a 0 to 7-day PHI and decreased from a 7 to 

10-day PHI.

Individual sample (and per-trial average) residues in highbush blueberries ranged from <0.091 

ppm to 0.204 ppm (<0.091 ppm to 0.184 ppm) when treated at a total rate of 0.978-1.078 lbs 

ai/ha (1096-1208 g ai/ha) and sampled 1 day after treatment.

I. MATERIALS AND METHODS

A. MATERIALS

Table B.7.6.1.1-1. Nomenclature for Sethoxydim and Metabolites of Interest.

Common name Sethoxydim

CAS Name (±)-2-[1-(ethoxyimino)butyl]-5-[2-(ethylthio)propyl]-3-hydroxy-2-

cyclohexen-1-one CAS no. 74051-80-2

Company experimental name BAS 562 05H

Other synonyms (if applicable) None

Metabolites Metabolites containing the cyclohexen-2-one moiety (i.e. MSO and 5-OH 

MSO2; expressed as sethoxydim equivalents)
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EPA MRID #: 49257701/DP No. D422744

PMRA # of document: 2432176

Page 3 of 8

B. Study Design

1. Test Procedure

A total of 4 residue trials in/on lowbush blueberries and 7 residue trials in/on highbush 

blueberries were conducted with an emulsifiable concentrate (Poast Herbicide, EPA Reg. No. 

7969-58) during the 2008 growing season (Table B.7.6.1.1-2).

Table B.7.6.1.1-2. Trial Numbers and Geographical Locations.

Crop

Region

Total

1 2 3 4 5 6 7 8 9 10 11 12 13 14

Lowbush 

blueberries 4 - - - - - - - - - - - - - 4

Highbush 

blueberries - 3 - - 3 - - - - - - 1 - - 7

Locations and detailed use patterns for the trials are provided in Table B.7.6.1.1-3. 

Table B.7.6.1.1-3. Study Use Pattern.

Location: City, 

State/Province; 

Year 

(Trial ID)*

End-use 

Product/ 

Formulation 

(% ai)

Method of Application/ 

Timing of Application

Volume

(gal/A)

[L/ha]

Rate per 

Application

(lbs ai/A)

[g ai/ha]

Retreatment 

Interval 

(days)

Total Rate

(lbs ai/A)

[g ai/ha]

Surfactant/ 

Adjuvant

LOWBUSH BLUEBERRIES

Trial No. NS01

Kentville, NS/ 

2008

POAST®

Herbicide 

emulsifiable 

concentrate

(18%)

1.Foliar Broadcast/

Berries Formed

32.09

[300]

0.501

[562]

- 1.006

[1128]

Merge 

Adjuvant

2.Foliar Broadcast/ 1% (v/v)

70% of ripe blueberries

32.35

[303]

0.505

[566]

12

Trial No. NS02

Rawdon, NS/ 2008

POAST®

Herbicide 

emulsifiable 

concentrate

(18%)

1. Foliar Broadcast/

Berries turning blue

31.7

[297]

0.495

[555]

- 0.989

[1109]

Merge 

Adjuvant

2. Foliar Broadcast/ 1% (v/v)

Berries blue

31.64

[296]

0.494

[554]

14

Trial No. NS03

Debert, NS/ 2008

POAST®

Herbicide 

emulsifiable 

concentrate

(18%)

1. Foliar Broadcast/

Berries blue in color

31.73

[297]

0.496

[556]

- 1.019

[1142]

Merge 

Adjuvant

2. Foliar Broadcast/ 1% (v/v)

Berries blue in color

33.47

[313]

0.523

[586]

14

Trial No. ME03

Jonesboro, ME/ 

2008

POAST®

Herbicide 

emulsifiable 

concentrate

(18%)

1. Foliar Broadcast/

Fruiting

19.5

[182]

0.485

[544]

- 0.961

[1078]

Crop oil 

concentrate

2. Foliar Broadcast/ 1.25% (v/v)

Fruiting

19.1

[179]

0.476

[534]

14

HIGHBUSH BLUEBERRIES

Trial No. MI30

Holt, MI/ 2008

POAST®

Herbicide 

emulsifiable 

concentrate

(18%)

1. Broadcast to the ground/

Fruiting

20

[187]

0.499

[559]

- 0.978

[1096]

Crop oil 

concentrate

2. Broadcast to the ground/ 0.55% (v/v)

Fruiting

19.2

[180]

0.479

[537]

16

Trial No. MI31

Fennville, MI/ 

2008

POAST®

Herbicide 

emulsifiable 

concentrate

(18%)

1. Broadcast to the ground/

Fruiting

20.2

[189]

0.505

[566]

- 1.009

[1131]

Crop oil 

concentrate

2. Broadcast to the ground/ 0.58% (v/v)

Fruiting

20.2

[189]

0.504

[565]

14
Sethoxydim (SOD)/BASF Canada Inc. (BAZ)

EPA MRID #: 49257701/DP No. D422744

PMRA # of document: 2432176

Page 4 of 8

Table B.7.6.1.1-3. Study Use Pattern.

Location: City, 

State/Province; 

Year 

(Trial ID)*

End-use 

Product/ 

Formulation 

(% ai)

Method of Application/ 

Timing of Application

Volume

(gal/A)

[L/ha]

Rate per 

Application

(lbs ai/A)

[g ai/ha]

Retreatment 

Interval 

(days)

Total Rate

(lbs ai/A)

[g ai/ha]

Surfactant/ 

Adjuvant

Trial No. MI32

Benton Harbor, MI/ 

2008

POAST®

Herbicide 

emulsifiable 

concentrate

(18%)

1. Broadcast to the ground/

Fruiting

19.7

[184]

0.492

[551]

- 1.016

[1138]

Crop oil 

concentrate

2. Broadcast to the ground/ 0.61% (v/v)

Fruiting

21.0

[196]

0.524

[587]

13

Trial No. NC06

Castle Hayne, NC/ 

2008**

POAST®

Herbicide 

emulsifiable 

concentrate

(18%)

1. Broadcast to the ground/

Fruiting

33.1

[310]

0.495

[555]

- 0.991

[1111]

Crop oil 

concentrate

2. Broadcast to the ground/ 0.75% (v/v)

Fruiting

33.2

[311]

0.496

[556]

15

Trial No. NC07

Castle Hayne, NC/ 

2008**

POAST®

Herbicide 

emulsifiable 

concentrate

(18%)

1. Broadcast to the ground/

Fruiting

33.0

[309]

0.494

[554]

- 0.986

[1105]

Crop oil 

concentrate

2. Broadcast to the ground/ 0.75% (v/v)

Fruiting

32.9

[308]

0.492

[551]

15

Trial No. NC29

Castle Hayne, NC/ 

2008

POAST®

Herbicide 

emulsifiable 

concentrate

(18%)

1. Broadcast to the ground/

Fruiting

31.5

[295]

0.496

[556]

- 0.993

[1113]

Crop oil 

concentrate

2. Broadcast to the ground/ 0.79% (v/v)

Fruiting

31.6

[296]

0.497

[557]

15

Trial No. OR19

Aurora, OR/ 2008

POAST®

Herbicide 

emulsifiable 

concentrate

(18%)

1. Broadcast to the ground/

Some blue fruit; mostly 

green

31.8

[297]

0.530

[594]

- 1.078

[1208]

Crop oil 

concentrate

0.84% (v/v)

2. Broadcast to the ground/

Blue ripe berries present

32.9

[308]

0.548

[614]

13

* All trial Nos. have the prefix “09933.08-“.

** These trials were conducted at the same location using the same spray mixture. Therefore these are not distinct trials.

Lowbush blueberries and highbush blueberries were grown and maintained according to typical 

agricultural practices. Irrigation was used at trial No. NC06, NC07, NC29 and OR19. No 

unusual weather conditions were reported during the study.

Sample Handling and Preparation

At each trial site, duplicate samples of blueberries were collected from the control plot and the 

treated plot one day after the last application. Samples were collected from at least 12 separate 

areas of each plot. In the highbush blueberry plots, the blueberries were collected by hand from 

all areas of the blueberry bush (high, low, exposed and sheltered by the foliage). In the lowbush 

blueberry plots, the berries were collected by raking the blueberries from a diagonal swath across 

the plot (the collected berries were exposed and sheltered by the foliage). Samples weighed 

approximately 2 lbs (0.9 kg). Collected samples were stored frozen (≤ 32°F / ≤ 0°C) within 7 

hours and 10 minutes of harvest. All samples were shipped frozen via ACDS freezer truck, 

except for trial No. ME03 which was shipped through Federal Express, to the NYSAES in 

Geneva, NY for extraction and analysis.

The samples were received frozen and in good condition at the analytical laboratory and held 

frozen (-21 ± 7oC) until ground. The blueberry samples were removed from the freezer for 

grinding and returned to frozen storage until used for fortification and/or analysis.
Sethoxydim (SOD)/BASF Canada Inc. (BAZ)

EPA MRID #: 49257701/DP No. D422744

PMRA # of document: 2432176

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2. Description of Analytical Procedures

Samples of highbush and lowbush blueberries were analyzed for residues of sethoxydim using 

the working Analytical Method version #36 entitled “Residue Analysis of BAS 9052H and its 

Metabolites on blueberry by GC/FPD”. This method is based on the reference Analytical 

Method No. 30 and addendums 30B, 30G or 30H, BASF Wyandotte Corporation, 1982-1985 

entitled “Determination of BAS 9052H and its Metabolite Residues in Soybean Seed, Soybean 

Seed Process Fractions, Chicken Tissues, Beef Tissues, Milk and Eggs”. BASF Method 30, also 

known as BASF Method No. 181 (PMRA #1150979), was previously reviewed by the PMRA 

and deemed adequate as a data gathering method (Review of September 17, 1987). The limit of 

quantitation (LOQ) was 0.047 ppm for DME and 0.044 ppm for DME-OH, each expressed as 

parent equivalents.

In this method, sethoxydim and its sulfide and sulfoxide metabolites are oxidized to sulfones, and 

the cyclohexene-1-one ring is cleaved to two common moieties: 3-alkyl and 3-alkyl-3-hydroxy 

substituted pentanedioic acid. The acids are methylated to dimethyl 3-[2-

(ethylsulfonyl)propyl]pentanedioate (DME) and dimethyl 3-[2-(ethylsulfonyl)propyl]3-hydroxy 

pentanedioate (DME-OH), which are the conversion products of the sethoxydim metabolites 

sethoxydim sulfoxide (MSO) and 5-hydroxy sethoxydim sulfone (5-OH-MSO2), respectively. 

Residues were presented in the laboratory analytical data sheets as DME and DME-OH. The values 

obtained for DME and DME-OH were converted to sethoxydim equivalents by multiplying by 

1.11 and 1.05, respectively. 

Briefly, samples were blended with methanol for 5 minutes, evaporated, reconstituted in methanol 

and water (1:2, v:v) and precipitated with calcium hydroxide. After filtration, the filtrate was 

acidified with concentrated HCl and partitioned with methylene chloride three times. After 

evaporation of the solvent, the extract was oxidized with hydrogen peroxide. Excess hydrogen 

peroxide was removed with Catalase suspension, and evaporated to dryness. The extract was 

methylated (esterified) with acidic methanol and again partitioned with methylene chloride. After 

evaporation to dryness, the extract was dissolved in acetone and analysed for DME and DME-OH 

by GC/FPD operated in sulfur mode. The limit of quantitation (LOQ) was determined to be 0.05 

ppm for each analyte (i.e. MSO and 5-OH-MSO2) which corresponds to a LOQ of 0.047 ppm for 

DME and 0.044 ppm for DME-OH (expressed as sethoxydim equivalents).

II. RESULTS AND DISCUSSION

Method performance was evaluated during method validation and by use of concurrent recovery 

samples by fortifying blueberries at 0.05 ppm, 5.0 ppm and 15.0 ppm. Twelve samples of 

blueberries were fortified with MSO at 0.05 ppm and individual recoveries ranged from 88% to 

120% with a standard deviation of 10%. Six samples of blueberries were fortified with MSO at 

5.0 ppm and individual recoveries ranged from 72% to 86% with a standard deviation of 6%. 

Three samples of blueberries were fortified with MSO at 15.0 ppm and individual recoveries 

ranged from 67% to 73% with a standard deviation of 3%. Twelve samples of blueberries were 

fortified with 5-OH-MSO2 at 0.05 ppm and individual recoveries ranged from 88% to 112% with 

a standard deviation of 9%. Six samples of blueberries were fortified with 5-OH-MSO2 at 5.0
Sethoxydim (SOD)/BASF Canada Inc. (BAZ)

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PMRA # of document: 2432176

Page 6 of 8

ppm and individual recoveries ranged from 74% to 92% with a standard deviation of 7%. Three 

samples of blueberries were fortified with 5-OH-MSO2 at 15.0 ppm and individual recoveries 

ranged from 73% to 80% with a standard deviation of 4%. With the exception of one concurrent 

recovery at 67%, all recoveries were within the acceptable range of 70% to 120%; therefore, the 

method was considered valid for the analysis of sethoxydim residues in blueberries matrices. 

The fortification levels did bracket the measured residues.

The detector response was linear (coefficient of determination, r2 ≥ 0.98812 for DME and r2 ≥ 

0.98440 for DME-OH) within the range of 0.1 – 1.0 μg/mL. Representative chromatograms of 

control samples, fortified samples and treated samples were provided. The control 

chromatograms generally had no peaks of interest above the chromatographic background. The 

fortified sample chromatograms contained only the analyte of interest, and peaks were 

symmetrical and well defined. Metabolites were expressed in parent equivalents.

The field residue samples were stored frozen a maximum of 848 days (28.2 months) from 

harvest to analysis (Table B.7.6.1.1-5). A concurrent freezer storage stability study was not 

conducted. However, freezer storage stability data are on file for strawberries, a crop within the 

Berry and Small Fruit Crop Group 13-07 which indicate that residues of sethoxydim are stable 

for up to 31 months (PMRA # 2387981; Previously reviewed under review of February 11, 

1993).

Table B.7.6.1.1-5. Summary of Storage Conditions

Matrix

(RAC or Extract)

Storage Temperature 

(oF / °C)

Actual Storage Duration

(months)

Interval of Demonstrated Storage Stability

(months)

Blueberries ≤ 32 / ≤ 0 28.2 Data are on file for strawberries, a crop within 

the Berry and Small Fruit Crop Group 13-07 

indicating that residues of sethoxydim are stable 

for up to 31 months of frozen storage (PMRA 

#2387981; Review of February 11, 1993).

The results from these trials showed that when harvested 1 day after the last of 2 applications at a 

seasonal rate of 0.961-1.078 lbs ai/A (1078-1208 g ai/ha), total combined residues of sethoxydim 

equivalents in lowbush blueberries ranged from <0.164 ppm to 8.92 ppm and residues in 

highbush blueberries ranged from <0.091 ppm to 0.204 ppm (Tables B.7.6.1.1-6 and B.7.6.1.1-

7).

In the residue decline trials, mean residue level increased from 7.89 ppm to 10.48 ppm in 

lowbush blueberries between PHIs of 0 and 7 days and decreased to 9.25 ppm at a PHI of 10 

days.
Sethoxydim (SOD)/BASF Canada Inc. (BAZ)

EPA MRID #: 49257701/DP No. D422744

PMRA # of document: 2432176

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Table B.7.6.1.1-6. Residue Data from Blueberry Field Trials with Sethoxydim

Location: City, 

State/Province; 

Year 

(Trial ID)*

Region Crop

Variety Matrix End-Use Product

Rate

(lbs ai/A)

[kg ai/ha]

PHI

(days)

Residues1(ppm)

DME DME-OH

Total2

(per-trial 

average)

LOWBUSH BLUEBERRIES

Trial No. NS01

Kentville, NS/ 

2008

1A Wild 

Clones Berries POAST®Herbicide

1.006

[1128]

0 7.8, 7.3 0.32, 0.36 8.12, 7.66

(7.89)

1 7.4, 7.6 0.42, 0.40 7.82, 8.0

(7.91)

3 9.1, 10 0.46, 0.46 9.56, 10.46

(10.01)

7 10, 9.5 0.76, 0.70 10.76, 10.2

(10.48)

10 8.6, 8.4 0.67, 0.82 9.27, 9.22

(9.25)

Trial No. NS02

Rawdon, NS/ 

2008

1A Wild 

Clones

Berries POAST®

Herbicide

0.989

[1109] 1 6.9, 7.4 0.35, 0.40 7.25, 7.8(7.53)

Trial No. NS03

Debert, NS/ 2008 1A Wild Clones

Berries POAST®

Herbicide

1.019

[1142] 1 8.5, 8.1 0.42, 0.42 8.92, 8.52(8.72)

Trial No. ME03

Jonesboro, ME/ 

2008

1

VariesWild 

Plants

Berries POAST®

Herbicide

0.961

[1078] 1 6.3, 0.12 0.21, <0.044 6.51, <0.164(3.34)

HIGHBUSH BLUEBERRIES

Trial No. MI30

Holt, MI/ 2008 5A Jersey

Berries POAST®

Herbicide

0.978

[1096] 1

<0.047, 

<0.047

<0.044, 

<0.044

<0.091, 

<0.091

(<0.091)

Trial No. MI31

Fennville, MI/ 

2008

5A Rubel

Berries POAST®

Herbicide

1.009

[1131] 1 0.048, 0.069 <0.044, <0.044

0.092, 0.113

(0.103)

Trial No. MI32

Benton Harbor, 

MI/ 2008

5A Blue 

Crop

Berries POAST®

Herbicide

1.016

[1138] 1

<0.047, 

<0.047

<0.044, 

<0.044

<0.091, 

<0.091

(<0.091)

Trial No. NC06

Castle Hayne, 

NC/ 2008**

2 Croatan

Berries POAST® 

Herbicide

0.991

[1111] 1 <0.047, 

<0.047

<0.047, 

<0.047

<0.044, 

<0.044

<0.044, 

<0.044

<0.091, 

<0.091

<0.091, 

<0.091

(<0.091)

Trial No. NC07

Castle Hayne, 

NC/ 2008**

2 Duplin

Berries POAST® 

Herbicide

0.986

[1105] 1

Trial No. NC29

Castle Hayne, 

NC/ 2008

2 Summit

Berries POAST®

Herbicide

0.993

[1113] 1 0.16, 0.12 <0.044, <0.044

0.204, 0.164

(0.184)

Trial No. OR19

Aurora, OR/ 2008 12 Blue 

Crop

Berries POAST®

Herbicide

1.078

[1208] 1

<0.047, 

<0.047

<0.044, 

<0.044

<0.091, 

<0.091

(<0.091)

1 Expressed as parent equivalents.

2 Total = DME + DME-OH (expressed as sethoxydim equivalents)

* All trial Nos. have the prefix “09933.08-“.

** These trials were conducted at the same location using the same spray mixture. Therefore these are not distinct trials.
Sethoxydim (SOD)/BASF Canada Inc. (BAZ)

EPA MRID #: 49257701/DP No. D422744

PMRA # of document: 2432176

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Table B.7.6.1.1-7. Summary of Residues from Blueberry Field Trials with Sethoxydim

Crop Matrix

Total Application 

Rate 

(lbs ai/A) 

[g ai/ha]

PHI 

(days) n

Residues1(ppm)

Min.2 Max.2 LAFT3 HAFT3 Median3 Mean3 SD3

LOWBUSH BLUEBERRIES

Lowbush

blueberries

0.961-1.019

[1078-1142]

1 4 0.164 8.92 3.34 8.72 7.72 6.88 2.41

HIGHBUSH BLUEBERRIES

Highbush 

blueberries

0.978-1.078

[1096-1208]

1 7 0.091 0.204 0.091 0.184 0.091 0.106 0.035

1 Combined residues of DME and DME-OH expressed as sethoxydim equivalents.

2 Values based on total number of samples.

3 Values based on per-trial averages. LAFT = lowest average field trial, HAFT = highest average field trial, SD = standard 

deviation. For computation of the LAFT, HAFT, median, mean, and standard deviation, values < LOQ are assumed to be at the 

the LOQ (0.091 ppm; combined LOQs of DME and DME-OH expressed as parent equivalents).

n = number of field trials.

III. CONCLUSIONS

The blueberry field trials are considered scientifically acceptable. The results of the study 

showed that following a total application rate of 0.961-1.019 lbs ai/A (1078-1142 g ai/ha) in 

lowbush blueberry samples collected at a PHI of 1 day, total combined residues of sethoxydim 

equivalents ranged from 0.164 ppm to 8.92 ppm. A decline study indicates that the level of 

combined residues of sethoxydim equivalents in lowbush blueberries increase up to a PHI of 7 

days and decrease by a PHI of 10 days. 

Following a total application rate of 0.978-1.078 lbs ai/A (1096-1208 g ai/ha) in highbush 

blueberry samples collected at a PHI of 1 day, total combined residues of sethoxydim 

equivalents ranged from <0.091 ppm to 0.204 ppm. The residue decline behaviour was not 

assessed in the highbush blueberry trials.

An acceptable method was used for residue quantitation and adequate storage stability data are 

available to support sample storage durations and conditions. 

REFERENCES

PMRA # 1150979. Beutel, P. (1981) “BAS 9052H: GC Determination, Total method including 

MU type compounds determination”, Method No. 181. Unpublished study prepared by BASF 

Aktiengesellschaft, 136 pages.

PMRA #2387981. Zehr, R. D. (1987) “Magnitude of the Residue of Sethoxydim and Metabolites 

in Blueberries” Registration Document #BASF: 87/5084. Unpublished study prepared by BASF 

Corporation Chemicals Division, Parsippany, NJ, 94 pages. (NOTE: This study includes the 

freezer storage stability data for sethoxydim in/on strawberries)
Sethoxydim/PC Code 121 00 1/lnterregional Research Project No. 4 

DACO 7.4.117.4.2/0CSPP 860.1500/0ECD IIA 6.3.1 , 6.3.2, 6.3.3 and lilA 8.3.1, 8.3.2, 8.3.3 

Crop Field Trial - Fine Fescue Grass (grown for seed) 

Primary· Evaluator Date: 06/05/20 14 

Versar, Inc. 

_;.-...,. ~ 

Approved by ( _/ -;t-, l A ~ Date: 11119/2014 

Peter Savoia, Chemist, OCSPP-HED-RAB V 

Note: This Data Evaluation Record (DER) was originally prepared under contract by Versar, Inc. (6850 Versar 

Center, Springfield, VA 22151; submitted 6/5/14). The DER has been reviewed by HED and revised to reflect 

current Office of Pesticide Programs (OPP) policies. 

STUDY REPORT: 

49257702 Barney, W.; Homa, K. (2009) Sethoxydim: Magnitude of the Residue on Fine Fescue 

Grasses. Project Numbers: A4873 and A4873.07-NYR05. Unpublished study prepared by 

Interregional Research Project No. 4 and Cornell University. 355 p. 

EXECUTIVE SUMMARY: 

The Interregional Research Project No.4 (IR-4) has submitted field trial data for sethoxydim on 

fine fescue grass. Five grass field trials were conducted in the United States during the 2007 

growing season in the North American Free Trade Agreement (NAFTA) Zones 11 (WA; 2 trials) 

and 12 (OR; 3 trials). Careful examination ofthe field trial records indicates that the two WA 

trials were conducted at the same locations with very few differences in study design; for this 

reason HED has determined these trials constitute a single trial with replicate samples for 

purposes of 860.1500 data requirements. The three OR trials were also conducted at the same 

location; however, HED has concluded that these may be considered independent due 

differences in the grass variety used. 

Each trial consisted of one untreated plot and one treated plot. At each trial location, the treated 

plot received two foliar broadcast applications of a 1.5 lb ail gal emulsifiable concentrate (EC) 

formulation of sethoxydim (POAST® 1.5 EC) at 0.465-0.498 lb ail A/application for a total 

seasonal rate of0.936-0.973 lb ai/A. Applications were made at 30- to 44-day retreatment 

intervals (RTis) using ground equipment in spray volumes of 14.9-20.3 gal/A. A crop oil 

concentrate (COC) was added to each spray mixture. Following the second application, samples 

were harvested from all trials at preharvest intervals (PHis) of 13-14 days for grass forage and 

21-28 days for grass hay. Hay samples were allowed to dry in an enclosed area for 3-7 days 

prior to collection. 

Samples of grass forage and hay were analyzed for residues of sethoxydim and its metabolites 

using a gas chromatography method with flame photometric detection in the sulfur mode 

(GC/FPD) adapted from the accepted enforcement analytical method. With this method, 

sethoxydim and its metabolites are determined as 3-(2 (ethylsulfonyl)propyl]-pentanedioic acid 

DP# 422744/MRID No. 49257702 Page I of 12 
Sethoxydim/PC Code 121001/Interregional Research Project No. 4

DACO 7.4.1/7.4.2/OCSPP 860.1500/OECD IIA 6.3.1, 6.3.2, 6.3.3 and IIIA 8.3.1, 8.3.2, 8.3.3

Crop Field Trial – Fine Fescue Grass (grown for seed)

DP# 422744/MRID No. 49257702 Page 2 of 12

dimethyl ester (DME) and 3-[2-(ethylsulfonyl)propyl]-3-hydroxypentanedioic acid dimethyl 

ester (DME-OH) following oxidation and derivatization, and residues are reported in terms of 

sethoxydim equivalents using conversion factors. The limit of quantitation (LOQ), determined 

as the lowest level of method validation, (LLMV) was 0.042 ppm for all analytes and sample 

matrices. The method is adequate for data collection based on acceptable concurrent recovery 

data. Because sethoxydim contains a labile thioether, it readily oxidizes to 2-[1-

(ethoxyimino)butyl]-5-[2-(ethylsulfinyl)propyl]-3-hydroxy-2-cyclohexen-1-one (MSO) and to 2-

[1-(ethoxyimino)butyl]-5-[2-(ethylsulfonyl)propyl] -3,5-dihydroxy-2-cyclohexen-1-one (5-OHMSO2), so these sulfoxy analytes were used for sample fortification. The fortification levels 

used in the concurrent method recoveries were adequate to bracket expected residue levels.

Samples of grass forage and hay were stored frozen (-21 ± 7 °C) from collection to extraction for

108-123 days (3.6-4.0 months) and 172-272 days (5.7-8.9 months), respectively. All samples 

were analyzed within 2-4 days of extraction. Storage stability data generated concurrently with 

the field trial study demonstrate that residues of sethoxydim, determined as DME and DME-OH,

were stable in/on samples of grass forage and hay (fortified with MSO and 5-OH-MSO2) stored 

frozen for up to 174-193 and 277-281 days, respectively. These data are acceptable to support 

the storage conditions and durations of samples from the submitted grass field trials; however,

storage stability studies should always include a 0-day sampling interval to establish the residue 

levels present at the time samples are placed into storage [see OCSPP 860.1380(d)(6)(i)].

Following two foliar broadcast applications of the 1.5 lb ai/gal EC formulation of sethoxydim at 

a total rate of 0.936-0.973 lb ai/A, residues (and per trial averages) of sethoxydim equivalents, 

(determined as DME, DME-OH, and combined residues; respectively, were: 1.0-2.8 (1.4-2.7), 

0.21-0.42 (0.22-0.34), and 1.24-3.16 (1.65-3.04) ppm, in/on fine fescue grass forage harvested at 

a 13- to 14-day PHI; and 0.48-1.3 (0.65-1.1), 0.14-0.40 (0.15-0.35), and 0.75-1.45 (0.98-1.26), 

in/on fine fescue grass hay harvested at a 21- to 28-day PHI.

Residue decline data were not submitted.

STUDY/WAIVER ACCEPTABILITY/DEFICIENCIES/CLARIFICATIONS:

Under the conditions and parameters used in the study, the field trial residue data are classified 

as scientifically acceptable. The acceptability of this study for regulatory purposes is addressed 

in the forthcoming U.S. EPA Residue Chemistry Summary Document [DP No. 422744].

COMPLIANCE:

Signed and dated Good Laboratory Practice (GLP), Quality Assurance, and Data Confidentiality 

statements were provided. No deviations from regulatory requirements were reported which 

would have an impact on the validity of the study.
Sethoxydim/PC Code 121001/Interregional Research Project No. 4

DACO 7.4.1/7.4.2/OCSPP 860.1500/OECD IIA 6.3.1, 6.3.2, 6.3.3 and IIIA 8.3.1, 8.3.2, 8.3.3

Crop Field Trial – Fine Fescue Grass (grown for seed)

DP# 422744/MRID No. 49257702 Page 3 of 12

A. BACKGROUND INFORMATION

Sethoxydim is a selective, systemic, postemergence herbicide used for the control of annual and 

perennial grass weeds in broadleaf crops. Sethoxydim is a member of the cyclohexanedione 

class of pesticides. Other members of this class include cycloxydim, clethodim, and 

tralkoxydim. The sethoxydim nomenclature is summarized in Table A.1 and the 

physicochemical properties are summarized in Table A.2.

TABLE A.1. Sethoxydim Nomenclature.

Chemical structure

Common name Sethoxydim

Company experimental name BAS 9052 H or BAS 562 05H

IUPAC name (5RS)-2-[(EZ)-1-(ethoxyimino)butyl]-5-[(2RS)-2-(ethylthio)propyl]-3-hydroxycyclohex-2-

en-1-one

CAS name 2-[1-(ethoxyimino)butyl]-5-[2-(ethylthio)propyl]-3-hydroxy-2-cyclohexen-1-one

CAS registry number 74051-80-2

End-use product (EP) 1.5 lb ai/gal EC formulation (Poast® Herbicide; EPA Reg. No. 7969-58)

Chemical structure of 2-

cyclohexen-1-one metabolites

Derivatized residues determined 

by the analytical method

Common and chemical names DME; 3-[2-(ethylsulfonyl)propyl]-

pentanedioic acid dimethyl ester

DME-OH; 3-[2-(ethylsulfonyl)propyl]-3-

hydroxypentanedioic acid dimethyl ester

Metabolites used for sample 

fortification 1

Common and chemical names MSO; 2-[1-(ethoxyimino)butyl]-5-[2-

(ethylsulfinyl)propyl]-3-hydroxy-2-

cyclohexen-1-one

5-OH-MSO2; 2-[1-(ethoxyimino)butyl]-5-

[2-(ethylsulfonyl)propyl]-3,5-dihydroxy-2-

cyclohexen-1-one

OH

CH3

O

N

O CH3

S

CH3

H3C

R

OH

R

O

S

CH3

H3C

O

O

COOCH3

COOCH3 S

CH3

H3C

O

O

COOCH3

COOCH3

OH

OH

CH3

O

N

O CH3

S

CH3

H3C

O

OH

CH3

O

N

O CH3

S

CH3

H3C

O

O

OH
Sethoxydim/PC Code 121001/Interregional Research Project No. 4

DACO 7.4.1/7.4.2/OCSPP 860.1500/OECD IIA 6.3.1, 6.3.2, 6.3.3 and IIIA 8.3.1, 8.3.2, 8.3.3

Crop Field Trial – Fine Fescue Grass (grown for seed)

DP# 422744/MRID No. 49257702 Page 4 of 12

1

 Sethoxydim is readily oxidized to MSO and 5-OH-MSO2 in air; therefore, these metabolites are used for sample fortification.

TABLE A.2. Physicochemical Properties of Sethoxydim

Parameter Value Reference

Boiling point/range >130 °C at 6 x 10-1 mm Hg HED Chemistry Chapter of the 

Sethoxydim RED, 6/22/05, W. 

Donovan

pH 3.95 at 20 °C

Density 1.058 g/cm3at 20 °C (specific gravity)

Water solubility 257 ppm at pH 5, 4390 ppm at pH 7 (25 °C)

Solvent solubility Freely soluble (>103 g/100 mL) in organic solvents 

(methanol, n-octanol, ethyl acetate, n-hexane, 

toluene, and xylene) at 20 °C

Vapor pressure 1.6 x 10-7 mm Hg at 25 °C

Dissociation constant, pKa 4.6 at pH 4.5 and 25 °C

Octanol/water partition 

coefficient, Log(KOW)

KOW = 3.26 x 103at pH 5; 45.1 at pH 7; and 0.93 at 

pH 9

UV/visible absorption spectrum Not available

B. EXPERIMENTAL DESIGN

B.1. Study Site Information

Five grass field trials were conducted in the United States during the 2007 growing season in the 

NAFTA Zones 11 (WA; 2 trials) and 12 (OR; 3 trials). As detailed below, HED has determined 

that the two WA trials are replicates and therefore constitute a single trial with replicate samples 

for purposes of 860.1500 data requirements. HED has further concluded that the OR trials may 

be considered independent due differences in the grass variety. The replicate trial determination 

for the study is summarized in the table below.

Independent Trial Determination1

Trial Nos. Differences Decision

-WA24 and -WA25 

(fine fescue grass, forage and hay)

PHI: 13 days for forage; 28 and 22 days for hay

RTI: 31 and 30 days

Harvest Timing: forage was harvested pre-boot 

stage (6 to 8 inches tall) for trial –WA24 and the 

vegetative, pre-boot stage (8 to 10 inches tall) for 

trial –WA25; hay samples, were harvested at the 

early seed head for both trials.

Residues: comparable

No other differences were found. 

Replicates

-OR18, -OR 19, and –OR20 Variety: Hard fescue (Predator) vs. Creeping red 

fescue (Razor) vs. Chewing Fine Fescue (Shadow 

II)

Residues: ~2x higher in Trial –OR19 than in Trials 

–OR18 and –OR20

Independent due to variety

1

 All assessments are based on the replicate trial guidance presented in draft memo 568_Criteria for Independence of Trials 

04/23/2013 (EPA and PMRA).
Sethoxydim/PC Code 121001/Interregional Research Project No. 4

DACO 7.4.1/7.4.2/OCSPP 860.1500/OECD IIA 6.3.1, 6.3.2, 6.3.3 and IIIA 8.3.1, 8.3.2, 8.3.3

Crop Field Trial – Fine Fescue Grass (grown for seed)

DP# 422744/MRID No. 49257702 Page 5 of 12

Each trial consisted of one untreated plot and one treated plot. At each trial location, the treated 

plot received a two foliar broadcast applications of a 1.5 lb ai/gal EC formulation of sethoxydim 

(POAST® 1.5 EC) at 0.465-0.498 lb ai/A/application for a total seasonal rate of 0.936-0.973 lb 

ai/A. Applications were made at 30- 44-day RTIs using ground equipment in spray volumes of 

14.9-20.3 gal/A. A COC was added to the foliar spray mixture for each trial. Samples of grass 

forage and hay were harvested from all trials at preharvest intervals (PHIs) of 13-28 days 

following the second application. Hay samples were allowed to dry for 3-7 days prior to 

collection

The petitioner stated that agronomic practices typical of the trial locations were used for growing 

crops. Maintenance pesticides and fertilizers were used as needed to produce a commercial 

quality crop. Minimum and maximum temperatures and total monthly precipitation were 

provided, as well as the historical averages. Irrigation was used to supplement rainfall as needed.

Weather conditions at all field locations were generally considered normal. However, at the OR 

trials, there was an unusually cold and wet spring that delayed crop maturity until later in the 

year. The petitioner indicated that prior to harvest, the crops had matured as normal.

Trial conditions are presented in Table B.1.1. The study use pattern is presented in Table B.1.2, 

and the crop varieties grown are identified in Table C.3.

TABLE B.1.1. Trial Site Conditions.

Trial Identification:

City, State; Year (Trial No.)

Soil characteristics1

Type %OM pH CEC

(meq/100 g)

Prosser, WA; 2007 (-WA24) Silt loam 1.25 7.4 12.7

Prosser, WA; 2007 (-WA25) Silt loam 1.25 7.4 12.7

Silverton, OR; 2007 (-OR18) Silty clay loam 3.0-6.0 4.5-6.5 10-25

Silverton, OR; 2007 (-OR19) Silty clay loam 2.0-6.0 5.6-6.5 15-30

Silverton, OR; 2007 (-OR20) Silty clay loam 3.0-8.0 5.1-6.0 15-25

1 OM = organic matter; CEC = cation-exchange capacity

TABLE B.1.2. Study Use Pattern.

Location

(City, State; Year) 

Trial ID1

EP

2 Application Information Tank Mix/ 

Adjuvants4 Method; Timing Volume 

(gal/A)

Rate

(lb ai/A)

RTI3

(days)

Total Rate

(lb ai/A)

Prosser, WA; 2007 

(-WA24)

1.5 lb 

ai/gal EC

1. Foliar broadcast; semi-dormant 19.6 0.467 - 0.939 COC

2. Foliar broadcast; vegetative 19.6 0.472 31

Prosser, WA; 2007 

(-WA25)

1.5 lb 

ai/gal EC

1. Foliar broadcast; semi-dormant 14.9 0.471 - 0.936 COC

2. Foliar broadcast; vegetative 20.3 0.465 30

Silverton, OR; 2007 

(-OR18)

1.5 lb 

ai/gal EC

1. Foliar broadcast; semi-dormant 15.1 0.475 - 0.973 COC

2. Foliar broadcast; semi-dormant 15.8 0.498 44
Sethoxydim/PC Code 121001/Interregional Research Project No. 4

DACO 7.4.1/7.4.2/OCSPP 860.1500/OECD IIA 6.3.1, 6.3.2, 6.3.3 and IIIA 8.3.1, 8.3.2, 8.3.3

Crop Field Trial – Fine Fescue Grass (grown for seed)

DP# 422744/MRID No. 49257702 Page 6 of 12

TABLE B.1.2. Study Use Pattern.

Location

(City, State; Year) 

Trial ID1

EP

2 Application Information Tank Mix/ 

Adjuvants4 Method; Timing Volume 

(gal/A)

Rate

(lb ai/A)

RTI3

(days)

Total Rate

(lb ai/A)

Silverton, OR; 2007 

(-OR19)

1.5 lb 

ai/gal EC

1. Foliar broadcast; semi-dormant 15.6 0.487 - 0.954 COC

2. Foliar broadcast; semi-dormant 14.9 0.467 44

Silverton, OR; 2007 

(-OR20)

1.5 lb 

ai/gal EC

1. Foliar broadcast; semi-dormant 17.1 0.475 - 0.946 COC

2. Foliar broadcast; semi-dormant 16.9 0.471 44

1 HED has concluded that Trials -WA24 and -WA25 constitute a single trial with replicate samples for purposes of 860.1500 data 

requirements.

2

 EP = End-use Product; a 1.5 lb ai/gal emulsifiable concentrate (EC) formulation (POAST® 1.5 EC).

3

 RTI = Retreatment Interval.

4

 COC = Crop oil concentrate.

TABLE B.1.3. Trial Numbers and Geographical Locations.

NAFTA Growing Zones Grass (grown for seed)

Submitted Requested1

Canada U.S.

1 -- -- --

1A -- -- --

2 -- -- --

3 -- -- --

4 -- -- --

5 -- -- --

5A -- -- --

5B -- -- --

6 -- -- --

7 -- -- --

7A -- -- --

8 -- -- --

9 -- -- --

10 -- -- --

11 1

2

-- --

12 3 -- --

13 -- -- --

14 -- -- --

15 -- -- --

16 -- -- --

17 -- -- --

18 -- -- --

19 -- -- --

20 -- -- --

21 -- -- --
Sethoxydim/PC Code 121001/Interregional Research Project No. 4

DACO 7.4.1/7.4.2/OCSPP 860.1500/OECD IIA 6.3.1, 6.3.2, 6.3.3 and IIIA 8.3.1, 8.3.2, 8.3.3

Crop Field Trial – Fine Fescue Grass (grown for seed)

DP# 422744/MRID No. 49257702 Page 7 of 12

TABLE B.1.3. Trial Numbers and Geographical Locations.

NAFTA Growing Zones Grass (grown for seed)

Submitted Requested1

Canada U.S.

Total 4 5/8

1

In accordance with OCSPP 860.1000 and 860.1500, the following crop field trials are recommended for grasses grown for seed: 

for use in the Pacific Northwest - five trials on representative varieties conducted on grass forage and hay, with two trials in Zone 

11 and three trials in Zone 12; or for use in the U.S. - eight trials on representative varieties conducted on grass forage and hay, 

with two trials in Zone 11, three trials in Zone 12, and three trials in Zone 5 (refer to Draft Memo, dated 9/30/00, Additional 

Guidance on the Crop – ‘Grasses Grown for Seed’, Grasses Grown for Seed Policy Team, P. Errico, et al).

2

 HED has concluded that two trials conducted in WA (Zone 11) are replicate trials for purposes of 860.1500 data requirements.

B.2. Sample Handling and Preparation

Duplicate control and duplicate treated samples were harvested from all trials following the 

second application at PHIs of 13-14 days for forage and 21-28 days for hay. A minimum of two

pounds of fine fescue forage was collected per sample. Forage was harvested in the 6-10 inch to 

boot stage, pre-boot stage (6-8 inches tall), or vegetative, pre-boot stage (8-10 inches tall). Hay 

was harvested at early seed head. Hay samples were allowed to dry for 3-7 days in an enclosed 

area prior to collection of a minimum of one pound per sample. Samples of grass forage and hay 

were placed in frozen storage at the field sites within ~4 hours of collection. 

All samples were shipped by ACDS freezer truck within 4-57 days of collection to the analytical 

laboratory, New York State Agricultural Experiment Station (NYSAES; Geneva, NY) for 

residue analysis. Samples were maintained frozen (-21 ± 7 °C) at the analytical laboratory prior 

to homogenization and analysis. In preparation for analysis, samples were homogenized in the 

presence of dry ice. 

B.3. Analytical Methodology

Grass forage and hay samples were analyzed for residues of sethoxydim using the Cornell 

Analytical Laboratory Method titled “Residue Analysis of BAS 9052H (Sethoxydim) and Its 

Metabolites on Fine Fescue Grasses (forage and hay) by GC/FPD Detection in Sulfur Mode. 

Version #35 and 35A.”

 

Briefly, residues were extracted with methanol, evaporated, reconstituted, and precipitated with 

calcium hydroxide. After filtration, the extract was acidified and then partitioned four times with 

dichloromethane (DCM). Sethoxydim and its metabolites were oxidized with hydrogen peroxide 

at reflux, and then esterified with acidic methanol to DME and DME-OH. The derivatives were

partitioned into DCM, evaporated to dryness, redissolved in acetone, and determined by GC/FPD 

in the sulfur mode. Residues are expressed as sethoxydim using molecular weight conversion 

factors of 1.11x for DME and 1.05x for DME-OH.
Sethoxydim/PC Code 121001/Interregional Research Project No. 4

DACO 7.4.1/7.4.2/OCSPP 860.1500/OECD IIA 6.3.1, 6.3.2, 6.3.3 and IIIA 8.3.1, 8.3.2, 8.3.3

Crop Field Trial – Fine Fescue Grass (grown for seed)

DP# 422744/MRID No. 49257702 Page 8 of 12

Because sethoxydim is very readily oxidized to MSO and 5-OH-MSO2, samples of untreated 

grass forage and hay were fortified with MSO and 5-OH-MSO2 to generate concurrent recovery 

and storage stability data. Recoveries are expressed as DME and DME-OH using molecular 

weight conversion factors of 0.85x and 0.83x. The LOQ (determined as the LLMV) was 0.042 

ppm each for MSO and 5-OH-MSO2. We note that the petitioner also presented calculated

values for the LOD and LOQ based on the recoveries obtained at the 0.042-ppm fortification 

level. The calculated LOD and LOQ for DME and DME-OH in fine fescue grass forage were

calculated to be 0.007, 0.021, 0.005, and 0.014 ppm, respectively. The calculated LOD and LOQ 

for DME and DME-OH in fine fescue grass hay were calculated to be 0.013, 0.038, 0.004, and

0.011 ppm.

 

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

C. RESULTS AND DISCUSSION

Sample storage conditions and durations are summarized in Table C.2.1. Samples of grass 

forage and hay were stored frozen (-21 ± 7 °C) from collection to extraction for 108-123 days 

(3.6-4.0 months) and 172-272 days (5.7-8.9 months), respectively. Hay samples were allowed to 

dry in an enclosed area for 3-7 days prior to collection. All samples were analyzed within 2-4

days of extraction. To support the sample storage intervals, a concurrent storage stability study 

was conducted with the field trial study; the results are presented in Table C.2.2. The data 

demonstrate that residues of sethoxydim, determined as DME and DME-OH were stable in/on 

samples of grass forage and hay (fortified with MSO and 5-OH-MSO2) stored frozen for up to 

174-193 and 277-281 days; no 0-day data were provided. These data are acceptable to support 

the storage conditions and durations of samples from the submitted field trials; however, storage 

stability studies should always include a 0-day sampling interval to establish the residue levels 

present at the time samples are placed into storage [see OCSPP 860.1380(d)(6)(i)].

Concurrent method recovery data for the GC/FPD method are presented in Table C.1. Grass 

forage and hay samples were fortified at 0.042-4.2 ppm with MSO and 5-OH-MSO2. The 

method was adequate for data collection based on acceptable concurrent recovery data. 

Recoveries were generally within the acceptable range of 70-120%. The method is considered 

adequate based on concurrent recovery data. The fortification levels used in concurrent method 

recovery were adequate to bracket expected residue levels. Apparent residues of DME and 

DME-OH were below the LOQ in/on all samples of untreated grass forage and hay.

Residue data from the grass field trials are reported in Table C.3, and a summary of residue data 

is presented in Table C.4. Following two foliar broadcast applications of the 1.5 lb ai/gal EC 

formulation of sethoxydim at a total rate of 0.936-0.973 lb ai/A, residues (and per trial averages) 

of sethoxydim equivalents, (determined as DME, DME-OH, and combined residues; 

respectively, were: 1.0-2.8 (1.4-2.7), 0.21-0.42 (0.22-0.34), and 1.24-3.16 (1.65-3.04) ppm, in/on 

fine fescue grass forage harvested at a 13- to 14-day PHI; and 0.48-1.3 (0.65-1.1), 0.14-0.40
Sethoxydim/PC Code 121001/Interregional Research Project No. 4

DACO 7.4.1/7.4.2/OCSPP 860.1500/OECD IIA 6.3.1, 6.3.2, 6.3.3 and IIIA 8.3.1, 8.3.2, 8.3.3

Crop Field Trial – Fine Fescue Grass (grown for seed)

DP# 422744/MRID No. 49257702 Page 9 of 12

(0.15-0.35), and 0.75-1.45 (0.98-1.26), in/on fine fescue grass hay harvested at a 21- to 28-day 

PHI.

Residue decline data were not submitted.

TABLE C.1. Summary of Method Validation and Concurrent Recoveries of Sethoxydim Metabolites 

from Fine Fescue Grass.1 

Matrix Analyte Spike 

Level

(ppm)

Sample 

Size

(n)

Recoveries

(%)

Mean ± Std. Dev.

(%)2

Method Validation

Grass, 

forage

DME 0.042 4 90, 95, 95, 100 95 ± 4.1

0.42 4 81, 81, 86, 105 88 ± 11.4

4.2 4 76, 88, 90, 93 87 ± 7.5

DME-OH 0.042 4 95, 95, 100, 100 98 ± 2.9

0.42 4 69, 71, 76, 88 76 ± 8.5

4.2 4 71, 88, 90, 90 85 ± 9.2

Grass, hay DME 0.042 9 76, 76, 78, 81, 81, 93, 95, 95, 105 87 ± 10.5

0.42 3 95, 95, 98 96 ± 1.7

4.2 3 81, 81, 86 83 ± 2.9

DME-OH 0.042 9 71, 74, 76, 76, 76, 78, 78, 81, 81 77 ± 3.2

0.42 3 95, 95, 98 96 ± 1.7

4.2 3 71, 71, 76 73 ± 2.9

Concurrent Recovery

Grass, 

forage

DME 0.042 3 100, 105, 105 103 ± 2.9

0.42 1 100 100

4.2 1 86 86

DME-OH 0.042 3 90, 95, 100 95 ± 5.0

0.42 1 90 90

4.2 1 81 81

Grass, hay DME 0.42 3 98, 105, 107 103 ± 4.7

4.2 2 76, 83 80

DME-OH 0.42 3 81, 88, 95 88 ± 7.0

4.2 2 69, 74 72

1

 Samples were fortified with MSO and 5-OH-MSO2; recoveries are expressed as DME and DME-OH using molecular weight 

conversion factors of 0.85x and 0.83x.

2

 Standard deviation is not calculated for sample sizes <3
Sethoxydim/PC Code 121001/Interregional Research Project No. 4

DACO 7.4.1/7.4.2/OCSPP 860.1500/OECD IIA 6.3.1, 6.3.2, 6.3.3 and IIIA 8.3.1, 8.3.2, 8.3.3

Crop Field Trial – Fine Fescue Grass (grown for seed)

DP# 422744/MRID No. 49257702 Page 10 of 12

TABLE C.2.1. Summary of Storage Conditions.

Matrix Analyte Storage 

Temperature (°C)

Actual Storage Duration1 Limit of Demonstrated Storage Stability2

Grass,

forage

DME -21 ± 7 108-123 days

(3.6-4.0 months)

174-193 days

DME (5.7-6.3 months)-OH

Grass,

hay

DME 172-272 days

(5.7-8.9 months)

277-281 days

DME (9.1-9.2 months)-OH

1

 Interval from harvest to extraction. Samples were analyzed within 2-4 days of extraction.

2

 Based on concurrent storage stability study. See Table C.2.2.

TABLE C.2.2. Stability of Sethoxydim Metabolites in Frozen Fine Fescue Grass.

1

Analyte Spike

Level

(ppm)

Storage 

interval2

(days)

Fresh Fortification 

Recoveries (%) 

[Average]

Recovered 

Residues (ppm)

Mean 

Recovered 

Residues

(ppm)

Mean 

Recovery 

(%)

Corrected % 

recovery3

Grass forage

DME 0.42 174-193 100, 71, 81 [84] 0.36, 0.34, 0.32 0.34 81 96

DME-OH 0.42 174-193 90, 71, 76 [79] 0.32, 0.30, 0.32 0.31 74 94

Grass hay

DME 0.42 277-281 95, 93, 100 [96] 0.38, 0.39, 0.34 0.37 88 92

DME-OH 0.42 277-281 86, 90, 100 [92] 0.36, 0.39, 0.35 0.37 88 96

1

 Samples were fortified with MSO and 5-OH-MSO2; recoveries are expressed as DME and DME-OH using molecular weight 

conversion factors of 0.85x and 0.83x.

2

 Interval from fortification to extraction. Samples were analyzed 2-4 days after extraction.

3

 Corrected for mean recovery of freshly fortified samples
Sethoxydim/PC Code 121001/Interregional Research Project No. 4

DACO 7.4.1/7.4.2/OCSPP 860.1500/OECD IIA 6.3.1, 6.3.2, 6.3.3 and IIIA 8.3.1, 8.3.2, 8.3.3

Crop Field Trial – Fine Fescue Grass (grown for seed)

DP# 422744/MRID No. 49257702 Page 11 of 12

TABLE C.3. Residue Data from Grass Field Trials with Sethoxydim.

Trial ID (City, 

State; Year)1

Zone Grass Variety Commodity Total Rate

(lb ai/A)

PHI

(days)2

Residues (ppm)

3

[Average]

DME4 DME-OH4 Combined

Prosser, WA; 

2007 (-WA24 and 

-WA25)

11 Fine fescue; 

Festuca ovina

Forage 0.936-

0.939

13 1.2, 1.0, 1.6,

1.7,

[1.4]

0.31, 0.24, 

0.40, 0.42

[0.34]

1.51, 1.24,

2.00, 2.12

[1.72]

Hay 22-28

(4)

0.48, 0.64, 

0.84, 0.64

[0.65]

0.27, 0.36,

0.38, 0.29

[0.33]

0.75, 1.00,

1.22, 0.93

[0.98]

Silverton, OR; 

2007 (-OR18)

12 Hard fescue;

Predator

Forage 0.973 14 1.6, 1.2

[1.4]

0.26, 0.23

[0.25]

1.86, 1.43

[1.65]

Hay 28

(3)

0.81, 0.76

[0.79]

0.27, 0.28

[0.28]

1.08, 1.04

[1.06]

Silverton, OR; 

2007 (-OR19)

12 Creeping red 

fescue;

Razor

Forage 0.954 14 2.8, 2.6

[2.7]

0.36, 0.32

[0.34]

3.16, 2.92

[3.04]

Hay 21

(7)

1.3, 0.92

[1.1]

0.15, 0.14

[0.15]

1.45, 1.06

[1.26]

Silverton, OR; 

2007 (-OR20)

12 Chewing fine 

fescue;

Shadow II

Forage 0.946 14 1.5, 1.6

[1.6]

0.21, 0.22

[0.22]

1.71, 1.82

[1.77]

Hay 28

(3)

0.80, 1.0

[0.90]

0.30, 0.40

[0.35]

1.10, 1.40

[1.25]

1 HED has concluded that Trials -WA24 and -WA25 constitute a single trial with replicate samples for purposes of 860.1500 data 

requirements.

2 The number of days grass was allowed to dry in the field prior to collection is reported in parenthesis.

3 For all analytes and all matrices: LOQ = 0.042 ppm; the calculated LOD for DME and DME-OH was 0.007 and 0.005 ppm in 

forage and 0.013 and 0.004 ppm in hay, respectively. Each value represents the average of duplicate analyses of a single sample.

4 Reported as Sethoxydim equivalents by the petitioner based on the quantified residues of DME x 1.11 and DME-OH x 1.05.

TABLE C.4. Summary of Residue Data from Grass Crop Field Trials with Sethoxydim.

Commodity Analyte Total App. 

Rate

(lb ai/A)

PHI

(days)

Residue Levels (ppm)1

n Sample 

Min.

Sample 

Max.

LAFT2 HAFT2 Median Mean Std. 

Dev.

Grass

forage

DME3 0.936-0.973 13-14 4 1.0 2.8 1.4 2.7 1.5 1.8 0.63

DME-OH3 4 0.21 0.42 0.22 0.34 0.29 0.29 0.07

Combined 4 1.24 3.16 1.65 3.04 1.74 2.04 0.67

Grass

hay

DME3 21-28 4 0.48 1.3 0.65 1.1 0.84 0.86 0.19

DME-OH3 4 0.14 0.40 0.15 0.35 0.30 0.27 0.09

Combined 4 0.75 1.45 0.98 1.26 1.16 1.14 0.14

1

 Except for sample min/max, values reflect per trial averages; n = no. of field trials. For calculation of median, mean, and 

standard deviation, the LOQ (0.042 ppm for all analytes) was used for any results reported as <LOQ in Table C.3.

2

 LAFT = lowest average field trial; HAFT = highest average field trial.

3

 Residues of DME and DME-OH are reported in sethoxydim parent equivalents as calculated by the petitioner.
Sethoxydim/PC Code 121001/Interregional Research Project No. 4

DACO 7.4.1/7.4.2/OCSPP 860.1500/OECD IIA 6.3.1, 6.3.2, 6.3.3 and IIIA 8.3.1, 8.3.2, 8.3.3

Crop Field Trial – Fine Fescue Grass (grown for seed)

DP# 422744/MRID No. 49257702 Page 12 of 12

D. CONCLUSION

The submitted fine fescue grass field trial data are acceptable. Following two foliar broadcast 

applications of the 1.5 lb ai/gal EC formulation of sethoxydim at a total rate of 0.936-0.973 lb 

ai/A, residues (and per trial averages) of sethoxydim equivalents, (determined as DME, DMEOH, and combined residues; respectively, were: 1.0-2.8 (1.4-2.7), 0.21-0.42 (0.22-0.34), and 

1.24-3.16 (1.65-3.04) ppm, in/on fine fescue grass forage harvested at a 13- to 14-day PHI; and 

0.48-1.3 (0.65-1.1), 0.14-0.40 (0.15-0.35), and 0.75-1.45 (0.98-1.26), in/on fine fescue grass hay 

harvested at a 21- to 28-day PHI.

 

An acceptable method was used for residues quantitation, and the study is supported by adequate 

storage stability data.

E. REFERENCES

Draft Memo, dated 9/30/00, Additional Guidance on the Crop – ‘Grasses Grown for Seed’, 

Grasses Grown for Seed Policy Team (P. Errico, J. Fleuchaus, B. Hazel, H. Jamerson, J. 

Kempter, R. Loranger, J. Smith, and J. Tompkins)

F. DOCUMENT TRACKING

RDI: P. Savoia 11/19/2014

Petition Number(s): 4E8239

DP Barcode(s): D422744

PC Code: 121001

Template Version June 2005.