UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

 

MEMORANDUM

Date: 27-OCT-2011

SUBJECT: Difenoconazole. 

Add Seed Treatment 

Oat Commodities, Rye Commodities, and Wheat Hay

Analytical Chemistry and Residue Data.

PC Code: 128847

Decision Nos.: 440121

Petition Nos.: 0F7785

Risk Assessment Type: Not Applicable

TXR No.: Not Applicable

MRID No.: None

 

FROM: Bonnie Cropp-Kohlligian, Environmental Scientist

Risk Assessment Branch 4

Health Effects Division (7509P)

THROUGH: Susan V. Hummel, Chemist/Senior Scientist

Risk Assessment Branch

Health Effects Division (7509P)

TO: Rosemary Kearns

Fungicide Branch

Registration Division (7505P)

Difenoconazole is a broad spectrum fungicide belonging to the triazole group of 

(Group 3) that acts by inhibiting sterol demethylation

use as a seed treatment on barley

currently registered in the U.S. for foliar appl

Page 1 of 23

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C. 20460 

OFFICE OF CHEMICAL SAFETY

 AND POLLUTION PREVENTION

. Amended Section 3 Registration (Dividend®

Seed Treatment Uses on Oats and Rye and Establish Tolerances in/on 

Oat Commodities, Rye Commodities, and Wheat Hay. Summary of 

Analytical Chemistry and Residue Data.

DP Barcodes: 384073

Registration No.: 100-740

Regulatory Action: Amended Section 3 Registration

ot Applicable Case No.: 7014

CAS No.: 119446-68-3 

40 CFR: 180.475

Kohlligian, Environmental Scientist

Risk Assessment Branch 4

Health Effects Division (7509P)

Susan V. Hummel, Chemist/Senior Scientist

Risk Assessment Branch 4

Health Effects Division (7509P)

Rosemary Kearns/Tony Kish (RM 22)

Fungicide Branch

Registration Division (7505P)

Difenoconazole is a broad spectrum fungicide belonging to the triazole group of 

that acts by inhibiting sterol demethylation. It is currently registered in the U.S. for 

barley, canola, cotton, sweet corn, wheat, and triticale. It is also 

for foliar applications on numerous crops, but not cereal grains

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

CHEMICAL SAFETY

POLLUTION PREVENTION

® Fungicide) to 

and Establish Tolerances in/on 

Summary of 

Section 3 Registration

Difenoconazole is a broad spectrum fungicide belonging to the triazole group of fungicides 

. It is currently registered in the U.S. for 

, sweet corn, wheat, and triticale. It is also 

, but not cereal grains. 
Difenoconazole Summary of Analytical Chemistry and Residue Data DP#: 384073 

Page 2 of 23

Tolerances for difenoconazole in/on plant commodities are currently established under 

§180.475(a)(1) and are expressed in terms of difenoconazole per se. Tolerances are established 

for numerous raw agricultural and processed commodities ranging from 0.01 ppm to 35 ppm; 

including tolerances for barley grain (0.1 ppm), barley hay (0.05 ppm), barley straw (0.05 ppm), 

wheat grain (0.1 ppm), wheat forage (0.1 ppm), and wheat straw (0.1 ppm). Import tolerances 

are also established for a number of raw agricultural commodities (RACs), including rye grain 

(0.1 ppm). [Note: In accordance with 40 CFR 180.1(g), tolerances established in/on wheat 

RACs apply to triticale RACs.] 

Tolerances for difenoconazole on livestock commodities are currently established under 

§180.475(a)(2) and are expressed in terms of difenoconazole and its metabolite, CGA-205375 

[1-[2-chloro-4-(4-chloro-phenoxy)phenyl]-2-[1,2,4]triazol-1-yl-ethanol]. Tolerances are 

established for tissue, milk, and egg ranging from 0.01ppm to 0.20 ppm.

Under PP# 0F7785, Amended Section F submitted to T. Kish (via email from R. Rezaaiyan 

dated 4/27/11), Syngenta Crop Protection, Inc. (hereafter referred to as Syngenta) is proposing 

the establishment of tolerances for residues of difenoconazole [1-[2-[2-chloro-4-(4-

chlorophenoxy)phenyl]-4-methyl-1,3-dioxolan-2-ylmethyl]-1H-1,2,4-triazole] in/on the 

following raw agricultural commodities:

Oats, grain............................................................................0.1 ppm

Oats, forage ..........................................................................0.1 ppm

Oats, hay ..............................................................................0.1 ppm

Oats, straw............................................................................0.1 ppm

Rye, grain1............................................................................0.1 ppm

Rye, forage...........................................................................0.1 ppm

Rye, straw ............................................................................0.1 ppm

Wheat, hay ...........................................................................0.1 ppm

1Note that although difenoconazole is not currently registered in the U.S. for use on rye, an import 

tolerance is currently established under 40 CFR §180.475(a)(1) for residues of difenoconazole 

in/on rye grain at 0.1 ppm. 

In conjunction with PP#0F7785, Syngenta is requesting an amended Section 3 registration for a 

3.1 lb/gal flowable concentrate for seed treatment (FS) formulation (Dividend® Fungicide; EPA 

Reg. No. 100-740) to add seed treatment uses on oats and rye at a maximum use rate of 11 g 

ai/100 lb seed; the same use currently registered in the U.S. on other cereal grain seed, including 

barley, wheat, and triticale. There is a proposed restriction for the grazing of green oat and rye 

forages until 55 days after planting on the submitted proposed label but not on Section B of the 

petition; this same restriction is currently registered for the grazing of green wheat and triticale 

forages. 

No new residue chemistry data were submitted with the current petition. Instead the petitioner 

has requested the translation of available wheat and barley magnitude of the residue data 

reflecting seed treatment uses of difenoconazole to support the proposed seed treatment uses of 
Difenoconazole Summary of Analytical Chemistry and Residue Data DP#: 384073 

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difenoconazole on oats and rye. These data have been re-evaluated herein primarily for the 

purposes of harmonization and secondarily for the purposes of setting tolerances in accordance 

with current guidance. [Note: Since no new residue chemistry data were submitted, only the 

subject wheat and barley field trial data have been discussed in depth under Detailed 

Consideration.]

Because difenoconazole is a triazole compound, HED requires that samples from any

metabolism, field trial, and/or processing study be analyzed for the triazole metabolites 

triazolylalanine (TA), triazolyl acetic acid (TAA), and 1,2,4-triazole (1,2,4-T). HED issued 

guidance on the residue chemistry data requirements for the triazole-based metabolites under 

DP# 327788 (4/25/06, M. Doherty). The supporting barley and wheat magnitude of the residue 

data consider herein were submitted prior to the HED issued guidance, and do not include any

triazole metabolite data. This issue will not be discussed further.

It is important to note that the first food use of difenoconazole, which was reviewed under a 

previous petition, PP#2E4051 (DP#s 172067 and 178394, 10/26/92, R. Lascola), was for the 

establishment of import tolerances in/on barley, rye, and wheat resulting from seed treatment 

uses of difenoconazole on rye and wheat at 27.2 g ai/100 lb seed and on barley at 10.2 g ai/100 lb 

seed. Hence, taking into account the proposed maximum seed treatment use rates of 

difenoconazole on oats and rye and the existing maximum seed treatment use rates on barley, 

rye, wheat, and triticale (both domestic (Dividend® Fungicide (EPA Reg. No. 100-740)) and 

non-domestic (use information previously provided under PP#2E4051 (DP#s 172067 and 

178394, 10/26/92, R. Lascola)), HED has evaluated the available data for the following 

maximum seed treatment use rates: 27.2 g ai/100 lb seed for the rye, wheat, and triticale and 11 

g ai/100 lb seed for barley and oats. 

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

reflecting foliar applications in canola, grape, potato, tomato, and wheat, and seed treatment in 

wheat. HED concludes that the residue of concern for both tolerance enforcement and risk 

assessment for crops included in this petition is difenoconazole per se. The nature of the residue 

in livestock is understood based on acceptable goat and hen metabolism studies. The residues of 

concern for both tolerance setting and risk assessment for livestock commodities are 

difenoconazole per se and its metabolite CGA-205375.

An adequate tolerance enforcement method, Method AG-575B, is available for crop 

commodities. The method determines residues of difenoconazole per se in/on crop commodities 

by gas chromatography with nitrogen-phosphorus detection (GC/NPD). The method limits of 

quantitation (LOQs) range from 0.01-0.05 ppm. A confirmatory GC method with mass-selective 

detection (MSD) is also available for crop commodities.

An adequate tolerance enforcement method, Method REM 147.07b, is available for livestock 

commodities. The method determines residues of difenoconazole and CGA-205375 in livestock 

commodities by liquid chromatography with tandem mass spectrometry detection (LC/MS/MS). 

The method LOQs are 0.01 ppm (for each analyte) for livestock tissues and 0.005 ppm (for each 
Difenoconazole Summary of Analytical Chemistry and Residue Data DP#: 384073 

Page 4 of 23

analyte) for milk. Adequate confirmatory methods, Method AG-544A and Method REM 147.06, 

are available for the determination of residues of difenoconazole and CGA-205375, respectively, 

in livestock commodities.

Adequate cattle and poultry feeding studies are available for difenoconazole, and tolerances for 

difenoconazole residues of concern in livestock commodities were recently re-evaluated in 

conjunction with a petition for tolerances in/on carrots, chickpeas, soybeans, stone fruits, 

strawberries, and turnip greens (PP# 9F7676; DP# 378829, 2/23/11, B. Cropp-Kohlligian). 

Using the Agency’s most recent guidance on constructing reasonably balanced livestock diets 

(ChemSAC memo, 6/30/08), the maximum dietary burdens (MDB) of livestock for 

difenoconazole residues were calculated to be 6.0 ppm for beef cattle, 1.6 ppm for dairy cattle, 

0.09 ppm for swine, and 0.11 ppm for poultry. These diets included barley and wheat livestock 

feedstuffs. Although there are several livestock feedstuffs associated with the proposed uses on 

oats and rye, the reviewer has determined that they will not increase the dietary exposure of 

livestock to difenoconazole residues and that reassessment of livestock tolerances is not required 

for this petition. 

No oats and rye field trial data were submitted with the current petition (PP#0F7785). Instead 

the petitioner has requested the translation of previously submitted wheat and barley field trial 

data reflecting seed treatment uses of difenoconazole to support the proposed seed treatment uses 

of difenoconazole on oats and rye. Given the deliberations by ChemSAC (meetings of 11/25/09 

and 9/1/10) on this subject, the requested translations are deemed appropriate since the seed 

treatment uses under consideration are substantially similar to those reflected in the available 

wheat and barley field trial data and the resulting residues were either nondetectable (grain and 

hay), negligible (straw), or very low (forage) in/on the raw agricultural commodities (RACs) of 

wheat and barley. Hence, barley grain data may be translated to oat grain since barley and oat 

grains are kernels (caryopsis) plus hulls (lemma and palea); wheat grain data may be translated 

to rye grain since rye and wheat grains are kernels with hulls removed. Wheat forage data may

be translated to oat and rye forage. Wheat straw data may be translated to oat and rye straw. 

Wheat hay may be translated to oat hay.

For grains, no detectable residues of difenoconazole were found in/on any of the wheat and 

barley grain samples collected from the supporting field trials. Most of these data were collected 

with the current enforcement method, Method AG-575B (GC/NPD), or a substantially similar 

precursor (Method AG-575), having a LOQ of 0.01 ppm in/on grain. However, a limited 

number of the older wheat grain data submitted with the first food use of difenoconazole 

(PP#2E4051; DP#s 172067 and 178394, 10/26/92, R. Lascola) from trials conducted in Europe 

(France (5 trials) and Germany (4 trials)) were generated with other, less sensitive data collection 

methods, precipitating the earlier recommendation to establish tolerances for residues of 

difenoconazole in/on barley grain, rye grain, and wheat grain at the higher current levels, 0.1 

ppm. These established tolerance levels are based primarily on wheat grain samples from trials 

conducted in France at the maximum seed treatment use rate for wheat (27.2 g ai/100 lb seed) in 

which residues in/on grain samples were reported as nondetectable, <0.02 ppm; below the 

reported “limit of sensitivity” of the data collection method (0.02 ppm in/on grain). The original 
Difenoconazole Summary of Analytical Chemistry and Residue Data DP#: 384073 

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HED reviewer of these data (PP#2E4051; DP#s 172067 and 178394, 10/26/92, R. Lascola) 

determined that the demonstrated limit of detection, 0.08 ppm in/on grain, was higher than the 

reported “limit of sensitivity” (0.02 ppm in/on grain) based on the recovery data; hence, a 

tolerance level of 0.1 ppm was established. Having re-evaluation the chromatograms for the 

grain samples collected from the trials conducted in France and Germany, the reviewer finds that 

residues of difenoconazole in/on the treated grain samples were not greater than those in/on the 

associated untreated grain samples. Hence, taking into account all of the available evidence, the 

reviewer finds that no detectable residues of difenoconazole (i.e., no residues above the LOQ of 

the current enforcement method, 0.01 ppm in/on grain), are expected in/on the grains of barley, 

oats, rye, and wheat from the proposed and/or existing maximum seed treatment use rates of 

difenoconazole on these grains. Therefore, the tolerances proposed by the petitioner for oat grain 

(0.1 ppm) and rye grain (0.1 ppm) are too high; tolerances of 0.01 ppm are appropriate. 

For hay and straw, having re-evaluated the previously submitted wheat hay and straw data, the 

reviewer finds that residues of difenoconazole are not expected to exceed 0.05 ppm (the LOQ of 

the current enforcement method for hay and straw) in/on barley hay, barley straw, oat hay, oat 

straw, rye straw, wheat hay, and wheat straw from the proposed and/or existing maximum seed 

treatment use rates of difenoconazole on these grains. Therefore, the tolerances proposed by the 

petitioner for oat hay (0.1 ppm), oat straw (0.1 ppm), rye straw (0.1 ppm), and wheat hay (0.1 

ppm) are too high; tolerances of 0.05 ppm are appropriate.

For forage, having re-evaluated the previously submitted wheat forage data, and using the OECD 

MRL calculator, the reviewer finds that the available data will support a tolerance of 0.15 ppm 

in/on oat, rye, and wheat forages. Residues of difenoconazole are not expected to exceed 0.15 

ppm in/on oat, rye, and wheat forages from the proposed and/or existing maximum seed 

treatment use rates of difenoconazole on these grains. Therefore, the tolerances proposed by the 

petitioner for oat forage (0.1 ppm) and rye forage (0.1 ppm) are too low; tolerances of 0.15 ppm 

are appropriate. Pregrazing and/or preharvest intervals are not needed for barley forage which is 

not considered a raw agricultural commodity (RAC) of barley. Pregrazing and/or preharvest 

intervals are not needed for oat, rye, and wheat forages given that the use pattern is limited to 

seed treatment and the supporting wheat forage data collected at 34- to 61-days after planting, 

which were used to set tolerances in/on oat, rye, and wheat forages, reasonably reflect the 

shortest period possible between planting and grazing/harvesting these forages.

No oat and rye processing data were submitted with the current petition and none are available. 

A wheat processing study (MRID 42090055) was previously submitted and reviewed by HED 

(PP#2E4051; DP#s 172067 and 178394, 10/26/92, R. Lascola). Spring wheat seed was treated at 

23.2 g ai/100 lb seed and planted. Later the wheat was also treated twice foliarly with an 

emulsifiable concentrate (EC) formulation of difenoconazole at 100 g ai/A to attempt to achieve 

detectable residue in/on grain. [Note: Difenoconazole is not registered in the U.S. for foliar uses 

on cereal grains.] Wheat grain was harvested 28 days after the last foliar treatment and 

processing into bran, middlings, shorts and germ, and patent flour. No residues of 

difenoconazole (<0.01 ppm) were detected in the grain and processed commodities. These data 

may be translated to the processed commodities of barley, oats, and rye given the nature of the 
Difenoconazole Summary of Analytical Chemistry and Residue Data DP#: 384073 

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subject wheat processing study which was conducted at an exaggerated rate resulting in 

nondetectable residues in both the RAC and processed commodities and given the use pattern for 

these cereal grains. Hence, based on the available wheat processing data, tolerances in the 

processed commodities of barley, oats, rye, wheat, and triticale are not needed for the seed 

treatment uses under consideration. 

Previously submitted confined rotational crop data are adequate to support the proposed seed 

treatment uses of difenoconazole on oats and rye. A 30-day plantback interval is appropriate for 

the proposed uses on these crops. [Note: Additional confined rotational crop data have been 

required to support foliar uses of difenoconazole but are not required to support the proposed 

seed treatment uses. These data have been submitted (MRID 48203402) and are under review in 

HED (D382946).]

Codex maximum residue limits (MRLs) for residues of difenoconazole have been established. 

However, since no Codex MRLs have been established for residues of difenoconazole in/on oat

commodities, rye commodities, and wheat hay, harmonization with Codex is not an issue. 

Canadian MRLs for residues of difenoconazole have been established at 0.01 ppm for oat grain

and 0.01 ppm for rye grain and harmonization with these established Canadian MRLs is 

recommended. Mexican MRLs for residues of difenoconazole have been established; however, 

no Mexican MRLs have been established for any of the cereal grain commodities. 

I. CONCLUSIONS

HED has examined the residue chemistry database for difenoconazole and pending submission 

of a revised Section F (see requirements under Proposed Tolerances), there are no residue 

chemistry issues that would preclude granting a registration for the requested seed treatment uses 

of difenoconazole on oats and rye or establishment of tolerances for residues of difenoconazole 

only in/on the raw agricultural commodities listed below. Furthermore, pregrazing restrictions 

on forages are not needed for the requested seed treatment uses (see Directions for Use).

Oat, grain..............................................................................0.01 ppm

Oat, forage............................................................................0.15 ppm

Oat, hay................................................................................0.05 ppm

Oat, straw .............................................................................0.05 ppm

Rye, grain.............................................................................0.01 ppm

Rye, forage...........................................................................0.15 ppm

Rye, straw ............................................................................0.05 ppm

Wheat, hay ...........................................................................0.05 ppm

Notes to the PM: 

(1) The recommended tolerance for rye grain (0.01 ppm) should replace the existing import 

tolerance for rye grain (0.1 ppm).
Difenoconazole Summary of Analytical Chemistry and Residue Data DP#: 384073 

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(2) Having re-evaluated the available barley and wheat magnitude of the residue data 

which were translated to support the proposed seed treatment uses of difenoconazole on 

oats and rye, HED finds that, with regards to the maximum seed treatment uses of 

difenoconazole on barley, wheat, and triticale: (i) the existing permanent tolerances for 

residues of difenoconazole in/on barley hay (0.05 ppm) and barley straw (0.05 ppm) are 

appropriate; (ii) the existing permanent tolerance for residues of difenoconazole in/on 

barley grain may be decreased from 0.1 ppm to 0.01 ppm to harmonize with the existing 

Canadian MRL (iii) the existing permanent tolerance for residues of difenoconazole in/on 

wheat grain may be decreased from 0.1 ppm to 0.02 ppm to harmonize with the existing 

Codex MRL; (iv) the existing permanent tolerance for residues of difenoconazole in/on 

wheat straw may be decreased from 0.1 ppm to 0.05 ppm consistent with the tolerances 

recommended for oat and rye straw; and (v) the existing permanent tolerance for residues 

of difenoconazole in/on wheat forage should be increased from 0.1 ppm to 0.15 ppm 

consistent with the tolerances recommended for oat and rye forages. 

860.1200 Directions for Use

 Pregrazing restrictions are not needed for barley, oat, rye, and wheat forages and should 

be removed from the proposed and currently registered Dividend® Fungicide (EPA Reg. 

No. 100-740) labels. [Note: Pregrazing restrictions were not included in Section B of 

petition PP#0F7785.]

860.1550 Proposed Tolerances

 The proposed tolerances should be revised to reflect the recommended tolerance levels 

and correct commodity definitions as specified in Table 3. 
Difenoconazole Summary of Analytical Chemistry and Residue Data DP#: 384073 

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II. DETAILED CONSIDERATIONS

Background

Difenoconazole is a broad spectrum fungicide belonging to the triazole group of fungicides 

(Group 3) that acts by inhibiting sterol demethylation. 

The chemical structures and nomenclature of difenoconazole are presented in Table 1 and the 

physicochemical properties of the technical grade of difenoconazole are presented in Table 2. 

Table 1. Structures and Nomenclature. 

Chemical structure of 

difenoconazole

Common name Difenoconazole

Company experimental name CGA-169374

IUPAC name 1-({2-[2-chloro-4-(4-chlorophenoxy)phenyl]-4-methyl-1,3-dioxolan-2-

yl}methyl)-1H-1,2,4-triazole

CAS name 1-[[2-[2-chloro-4-(4-chlorophenoxy)phenyl]-4-methyl-1,3-dioxolan-2-yl]methyl]-

1H-1,2,4-triazole

CAS registry number 119446-68-3

End-use products (EP) Dividend® Fungicide, 3.1 lb/gal FS (EPA Reg. No. 100-740).

O O

O

N N Cl

N

CH3

Cl
Difenoconazole Summary of Analytical Chemistry and Residue Data DP#: 384073 

Page 9 of 23

Table 2. Physicochemical Properties of Difenoconazole.

Parameter Value Reference

Melting point 78.6 oC DP#s 172067 and 178394, 10/26/92, 

R. Lascola pH 6-8 at 20 oC (saturated solution)

Density 1.37 g/cm3at 20 oC

Water solubility 3.3 ppm at 20 oC

Solvent solubility g/100 mL at 25 oC:

n-hexane: 0.5

1-octanol: 35

toluene: 77

acetone: 88

ethanol: 89

Vapor pressure 2.5 x 10-10 mm Hg at 25 oC

Dissociation constant, pKa 1.1 for pure grade (99.3% ± 0.3%) 

difenoconazole in water (with 4% 

methanol) at 20oC 

DP# 375159, 5/26/10, B. CroppKohlligian

Octanol/water partition 

coefficient, Log(KOW)

4.2 at 25 oC DP#s 172067 and 178394, 10/26/92, 

R. Lascola

UV/visible absorption spectrum max at about 200 and 238 nm 

(in methanol at 26 oC)

PMRA Proposed Regulatory Decision 

Document on Difenoconazole, 4/14/99 

(PRDD99-01)
Difenoconazole Summary of Analytical Chemistry and Residue Data DP#: 384073 

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860.1200 Directions for Use

Residue Chemistry Memo: PP#2E4051; DP#s 172067 and 178394, 10/26/92, R. Lascola

Dividend® Fungicide (EPA Reg. No. 100-740; EPA accepted 10/22/10) is a systemic seed 

dressing, formulated as a flowable concentrate for seed treatment (FS) containing 3.1 lb/gal 

(32.8%) of difenoconazole, which controls or suppresses certain seed-borne, soil-borne, and 

early season foliar diseases of wheat, barley, and triticale, and certain seed and seedling diseases 

of canola, sweet corn, and cotton. Applications are made as water-based slurry though standard 

slurry or mist-type seed treatment equipment. Tank mixed with other seed treatment products is 

permitted. The use of an EPA-approved dye or colorant that imparts an unnatural color to seed is 

required. Also bags containing treated seed are to be labeled with the following restrictive 

language: (1) Do not use for feed, food, or oil purposes; (2) Store away from feeds and 

foodstuffs; (3) Green wheat or triticale forage may not be grazed until 55 days after planting; (4) 

Green barley forage may not be grazed until 30 days after planting; and (5) Do not plant any crop 

other than those on this label within 30 days to fields in which treated seeds were planted. 

In conjunction with the current petition (PP#0F7785) Syngenta is requesting an amended 

registration for Dividend® Fungicide (EPA Reg. No. 100-740) to add use as a seed treatment on 

oats and rye at 11 g ai/100 lb seed, the same maximum use rate it is currently registered on 

barley, wheat, and triticale. The petitioner has submitted a Section B reflecting proposed use 

rates for the 3.1 lb/gal FS formulation (Dividend® Fungicide; EPA Reg. No. 100-740) on oats 

and rye without any additional restrictive language; supporting draft labeling (dated 9/20/10) was 

also submitted. Consistent with the currently registered grazing restrictions for green wheat and 

triticale forage, the proposed label restricts the grazing of green oats and rye forage until 55 days 

after planting.

 

It is important to note that non-domestic seed treatment uses of difenoconazole on barley, rye, 

and wheat have been previously considered by the Agency and are different from the 

registered/proposed domestic use rates. The first food use of difenoconazole, which was 

reviewed under a previous petition (PP#2E4051; DP#s 172067 and 178394, 10/26/92, R. 

Lascola), was for the establishment of import tolerances in/on barley, rye, and wheat resulting 

from seed treatment uses of difenoconazole on barley reported to the Agency at 10.2 g ai/100 lb 

seed, and on rye and wheat at 27.2 g ai/100 lb seed. While the reported non-domestic maximum 

seed treatment use rate on barley is slightly less than the currently registered domestic maximum 

use rate, the reported non-domestic maximum seed treatment use rates on rye and wheat are 

roughly 2.5x higher than the proposed domestic maximum use rate on rye and the currently

registered domestic maximum use rate on wheat.

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

relative to the proposed uses of difenoconazole on oats and rye. No oats and rye field trial data 

were submitted with the current petition (PP#0F7785). Instead the petitioner has requested the 

translation of previously submitted wheat and barley field trial data reflecting seed treatment 

uses of difenoconazole to support the proposed seed treatment uses of difenoconazole on oats 

and rye. 
Difenoconazole Summary of Analytical Chemistry and Residue Data DP#: 384073 

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The maximum proposed seed treatment use rate for oats and rye is 11 g ai/100 lb seed, the same 

maximum use rate currently registered for barley, wheat, and triticale. Based on the use of an 

EPA-approved dye or colorant to impart an unnatural color to the treated seed and the equipment 

used for application, the use appears limited to commercial facilities although this is not 

specified on the proposed Dividend® Fungicide (EPA Reg. No. 100-740) label.

It is important to note that non-domestic seed treatment uses of difenoconazole on barley, rye, 

and wheat have been previously considered by the Agency and are different from the 

registered/proposed domestic use rates. The first food use of difenoconazole, which was 

reviewed under a previous petition (PP#2E4051; DP#s 172067 and 178394, 10/26/92, R. 

Lascola), was for the establishment of import tolerances in/on barley, rye, and wheat resulting 

from seed treatment uses of difenoconazole on barley reported to the Agency at 10.2 g ai/100 lb 

seed and on rye and wheat at 27.2 g ai/100 lb seed.

Taking into account the proposed maximum seed treatment use rates of difenoconazole on oats 

and rye and the existing maximum seed treatment use rates on barley, rye, wheat, and triticale 

(both domestic (Dividend® Fungicide (EPA Reg. No. 100-740) and non-domestic (use 

information previously provided under PP#2E4051 (DP#s 172067 and 178394, 10/26/92, R. 

Lascola)), HED will evaluate available data for the following maximum seed treatment use rates: 

27.2 g ai/100 lb seed for the rye, wheat, and triticale and 11 g ai/100 lb seed for barley and oats.

Based on the available data, pregrazing restrictions are not needed for barley, oat, rye, and wheat 

forages and should be removed from the proposed and currently registered Dividend® Fungicide 

(EPA Reg. No. 100-740) labels.
Difenoconazole Summary of Analytical Chemistry and Residue Data DP#: 384073 

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860.1500 Crop Field Trials

Residue Chemistry Memos:

PP#2E4051; DP#s 172067 and 178394, 10/26/92, R. Lascola (MRIDs 42090055 and 42090056)

PP#2F4107; DP#s 248285 and 248419, 10/28/98, S. Chun (MRID 44602001)

PP#6F4748; DP# 228403, 9/23/96, G. Kramer (MRID 44056001)

No oats and rye field trial data were submitted with the current petition (PP#0F7785). Instead 

the petitioner has requested the translation of available acceptable wheat and barley field trial 

data reflecting seed treatment uses of difenoconazole to support the proposed seed treatment uses 

of difenoconazole on oats and rye. The available wheat and barley field trial data reflecting seed 

treatment use of difenoconazole have been re-evaluated and are discussed below. 

Wheat field trial data (MRIDs 4209055 and 4209056) conducted in the U.S. and Europe were 

submitted for the first food use of difenoconazole and reviewed under a previous petition, 

PP#2E4051 (DP#s 172067 and 178394, 10/26/92, R. Lascola). Later, a new and substantially

complete set of wheat field trial data (MRID 44602001) were submitted under another petition, 

PP#2F4107 (DP#s 248285 and 248419, 10/28/98, S. Chun). Barley field trial data (MRID 

44056001) were submitted under yet another petition, PP#6F4748 (DP# 228403, 9/23/96, G. 

Kramer). Related data deficiencies were addressed over a period of several years under a 

number of HED reviews.

Wheat Field Trials

MRID 42090055 – Data previously submitted and reviewed by HED under PP#2E4051 

(DP#s 172067 and 178394, 10/26/92, R. Lascola)

Spring wheat seed was treated with difenoconazole at either 11 or 23.2 g ai/100 lb seed and 

planted at 3 sites (ND (1), WA (1), and MT (1)) Spring wheat seed was treated with 

difenoconazole at 11 g ai/100 lb seed and planted at 3 sites (MN (1), SD (1), and IL (1)). Plants 

were grown to maturity; forage samples were collected 54-92 days after planting, and grain and 

straw samples were collected 81-119 days after planting. Samples were analyzed with an 

acceptable data collection method (Method AG-575 (GC/NPD)); based on recovery data the 

demonstrated LOQ was 0.01 ppm for grain, forage, and straw. No detectable residues (<0.01 

ppm) of difenoconazole were found in/on any of the grain or straw samples. No detectable 

residues (<0.01 ppm) were found in/on forage in 5 of the 6 trials; only the SD trial, conducted at 

11 g ai/100 lb seed, showed any detectable residues (0.02 ppm).

Winter wheat seed was treated with difenoconazole at either 9.5 or 21.2 g ai/100 lb seed and 

planted at 5 sites (NY (1), AR (1), TX (1), OK (1), and WA (1)). Winter wheat seed was treated 

with difenoconazole at 9.5 g ai/100 lb seed and planted at 1 site (KS (1)). Spring wheat seed was 

treated with difenoconazole at 9.5 or 21.2 g ai/100 lb seed and planted at 2 sites (AZ (1) and CA

(1)). This corresponds to 7 trials in the following regions: Region 1 (1 trial), Region 4 (1 trial), 

Region 6 (2 trials), Region 8 (1 trial), Region 10 (2 trials), and Region 11 (1 trial). Forage 

samples were collected 56-67 days after planting, and grain and straw samples were collected 
Difenoconazole Summary of Analytical Chemistry and Residue Data DP#: 384073 

Page 13 of 23

149-328 days after planting. Forage samples from CA, OK, and WA were not viable for various 

reasons. Samples were analyzed with an acceptable data collection method (Method AG-575

(GC/NPD)); based on recovery data the demonstrated LOQ was 0.01 ppm for grain, forage, and 

straw. No detectable residues (<0.01 ppm) of difenoconazole were found in/on any of the 

samples with the following exceptions: (1) for forage, detectable residues (≤0.02 ppm) were 

found at the NY and AR trials and (2) for straw, detectable residues (≤0.03 ppm) were found at 

the AR, TX, and AZ trials.

MRID 42090056 – Data previously submitted and reviewed by HED under PP#2E4051

(DP#s 172067 and 178394, 10/26/92, R. Lascola)

European Trials. Residues trials were conducted in France (5 trials) and Germany (4 trials) 

using wheat, barley, or rye seed treated with difenoconazole. In France, wheat seeds were 

treated at 8.2 g ai/100 lb seed (1 trial), 16.4 g ai/100 lb seed (1 trial), or 27.3 g ai/100 lb seed (3 

trials) and grain samples were collected. In Germany, wheat seed (1 trial), barley seed (2 trials), 

and rye seed (1 trial) were treated at 27.3 g ai/100 lb seed and grain, forage, and straw samples 

were collected. No detectable residues of difenoconazole were reportedly found in/on any of the 

grain and straw samples; detectable residues of difenoconazole were reportedly found in/on the 

rye forage sample and one of the two barley forage samples from the trials conducted in 

Germany (reported as 0.02 ppm and 0.03 ppm, respectively). 

Grain samples from the trials in France were analyzed with Method REM 07/86 (GC/ECD) with 

a reported “limit of sensitivity” of 0.02 ppm in/on grain; the original HED reviewer determined 

that the demonstrated limit of detection was 0.08 ppm in/on grain based an evaluation of the 

recovery data. Grain samples from the trials in Germany were analyzed with a modified version 

of Method AG-537 (GC/ECD) or a modified version of Method AG-514, which is essentially

identical to Method AG-537, with a reported “limit of sensitivity” of 0.02 or 0.03 ppm in/on 

grain; the original HED reviewer determined that the demonstrated LOQ was 0.05 ppm in/on 

grain.

MRID 44602001 – Data previously submitted and reviewed by HED under PP#2F4107

(DP#s 248285 and 248419, 10/28/98, S. Chun)

Wheat seed was treated with difenoconazole at 10.9 g ai/100 lb seed and planted at 15 sites (OK 

(2), TX (1), NC (1), MT (1), KS (2), CO (1), ND (1), SD (1), AR (1), ID (1), MO (1), MN (1), 

and NE (1)). Wheat seed was treated with difenoconazole at 21.8 g ai/100 lb seed and planted at 

3 sites (OK (1), KS (1), and (ND (1)). Forage samples were collected 34-112 days after planting, 

additional forage samples were collected 164-241 days after planting (11 out of 15 trials), hay

samples were collected 48-281 days after planting, and grain and straw samples were collected 

83-322 days after planting. Samples were analyzed with an acceptable data collection method 

(Method AG-575B (CG/NPD)); based on recovery data the demonstrated LOQ was 0.01 ppm for 

grain and 0.05 ppm for forage, hay, and straw. No detectable residues of difenoconazole were 

found in/on any of the grain (<0.01 ppm), straw (<0.05 ppm), and hay (<0.05 ppm) samples. 

Residues of difenoconazole were detectable in/on 4 of the 52 forage samples collected from the 
Difenoconazole Summary of Analytical Chemistry and Residue Data DP#: 384073 

Page 14 of 23

trials conducted at 10.9 g ai/100 lb seed; they ranged from <0.05 to 0.077 ppm. No detectable 

residues of difenoconazole were found in/on the forage samples from the 3 trials conducted at 

21.8 g ai/100 lb seed. [Note: The trials which found detectable residues of difenoconazole in/on 

forage were only conducted at the lower, 10.9 g ai/100 lb seed, treatment rate.]

Barley Field Trials

MRID 44056001 – Data previously submitted and reviewed by HED under PP#6F4748

(DP# 228403, 9/23/96, G. Kramer)

Barley seed was treated with difenoconazole at 10.9 g ai/100 lb seed and planted at 9 sites (ID 

(1), ND (1), MN (1), MT (1), ND (1), SD (1), VA (1), CO (1), and CA (1)). Barley seed was 

treated with difenoconazole at 21.8 g ai/100 lb seed and planted at 1 site (ND). Forage samples 

were collected 32-152 days after planting; hay samples were collected 54-191 days after 

planting; and grain and straw samples were collected 89-224 days after planting. Samples were 

analyzed with an acceptable data collection method (Method AG-575B (CG/NPD)); based on 

recovery data the demonstrated LOQ was 0.01 ppm for grain and 0.05 ppm for forage, hay, and 

straw. No detectable residues of difenoconazole were found in/on any of the grain (<0.01 ppm), 

forage (<0.05 ppm), straw (<0.05 ppm), and hay (<0.05 ppm) samples.

Conclusions: No oats and rye field trial data were submitted with the current petition 

(PP#0F7785). Instead the petitioner has requested the translation of previously submitted wheat 

and barley field trial data reflecting seed treatment uses of difenoconazole to support the 

proposed seed treatment uses of difenoconazole on oats and rye. Given the deliberations by

ChemSAC (meetings of 11/25/09 and 9/1/10) on this subject, the requested translations are 

deemed appropriate since the seed treatment uses under consideration are substantially similar to 

those reflected in the available wheat and barley field trial data and the resulting residues were

either nondetectable (grain and hay), negligible (a few detectable residues in/on some straw

samples below the LOQ of the current enforcement method for straw), or very low (a few 

detectable residues in/on some forage samples) in/on the raw agricultural commodities (RACs) 

of wheat and barley. Hence, barley grain data may be translated to oat grain since barley and oat 

grains are kernels (caryopsis) plus hulls (lemma and palea); wheat grain data may be translated 

to rye grain since rye and wheat grains are kernels with hulls removed. Wheat forage data may

be translated to oat and rye forage. Wheat straw data may be translated to oat and rye straw. 

Wheat hay data may be translated to oat hay.

Taking into account the proposed maximum seed treatment use rates of difenoconazole on oats 

and rye and the existing maximum seed treatment use rates on barley, rye, and wheat (both 

domestic (Dividend® Fungicide (EPA Reg. No. 100-740) and non-domestic (use information 

previously provided under PP#2E4051 (DP#s 172067 and 178394, 10/26/92, R. Lascola)), HED 

will need to evaluate the available data for the following maximum seed treatment use rates: 

27.2 g ai/100 lb seed for the rye and wheat and 11 g ai/100 lb seed for barley and oats. 
Difenoconazole Summary of Analytical Chemistry and Residue Data DP#: 384073 

Page 15 of 23

Grains. No detectable residues of difenoconazole were found in/on any of the wheat and barley

grain samples collected from the supporting field trials. Most of these data were collected with 

the current enforcement method, Method AG-575B (GC/NPD), or a substantially similar 

precursor (Method AG-575), having a LOQ of 0.01 ppm in/on grain. However, a limited 

number of the older wheat grain data submitted with the first food use of difenoconazole 

(PP#2E4051; DP#s 172067 and 178394, 10/26/92, R. Lascola) from trials conducted in Europe 

(France (5 trials) and Germany (4 trials)) were generated with other, less sensitive data collection 

methods, precipitating the earlier recommendation to establish tolerances for residues of 

difenoconazole in/on barley grain, rye grain, and wheat grain at the higher current levels, 0.1 

ppm. These established tolerance levels are based primarily on wheat grain samples from trials 

conducted in France at the maximum seed treatment use rate for wheat (27.2 g ai/100 lb seed) in 

which residues in/on grain samples were reported as nondetectable, <0.02 ppm; below the 

reported “limit of sensitivity” of the data collection method (0.02 ppm in/on grain). The original 

HED reviewer of these data (PP#2E4051; DP#s 172067 and 178394, 10/26/92, R. Lascola) 

determined that the demonstrated limit of detection, 0.08 ppm in/on grain, was higher than the 

reported “limit of sensitivity” (0.02 ppm in/on grain) based on the recovery data; hence, a 

tolerance level of 0.1 ppm was established. Having re-evaluation the chromatograms for the 

grain samples collected from the trials conducted in France and Germany, the reviewer finds that 

residues of difenoconazole in/on the treated grain samples were not greater than those in/on the 

associated untreated grain samples. Hence, taking into account all of the available evidence, the 

reviewer finds that no detectable residues of difenoconazole (i.e., no residues above the LOQ of 

the current enforcement method, 0.01 ppm in/on grain), are expected in/on the grains of barley, 

oats, rye, and wheat from the proposed and/or existing maximum seed treatment use rates of 

difenoconazole on these grains. 

Hay and Straw. Available wheat straw data were translated to oat and rye straw. Available

wheat hay data were translated to oat hay. Available barley hay and straw data are considered 

supporting data.

Having re-evaluated the previously submitted wheat hay and straw data, the reviewer finds that 

residues of difenoconazole are not expected to exceed 0.05 ppm (the LOQ of the current 

enforcement method for hay and straw) in/on barley hay, barley straw, oat hay, oat straw, rye 

straw, wheat hay, and wheat straw from the proposed and/or existing maximum seed treatment 

use rates of difenoconazole on these grains.

Forage. Available wheat forage data were translated to oat and rye forage. Available barley

forage data are considered supporting data.

Having re-evaluated the previously submitted wheat forage data, and using the OECD MRL 

calculator, the reviewer finds that the available data will support a tolerance of 0.15 ppm in/on 

rye, oat, and wheat forages. The tolerance calculation is presented in Appendix I. The wheat 

forage field trial data selected for inclusion in the OECD MRL calculation was a large dataset 

(24 field trials) reflecting the maximum proposed seed treatment use rate for oats and rye (11 g 

ai/100 lb seed), the same maximum use rate currently registered in the U.S. for barley, wheat, 
Difenoconazole Summary of Analytical Chemistry and Residue Data DP#: 384073 

Page 16 of 23

and triticale, and reflecting foraging/harvesting 34- to 61-days after planting treated seed. Taken 

as a whole, the available wheat forage data indicate that residues of difenoconazole are not 

expected to exceed 0.15 ppm in/on rye, oat, and wheat forages from the proposed and/or existing 

maximum seed treatment use rates of difenoconazole on these grains. 

Pregrazing and/or preharvest intervals are not needed for barley forage which is not considered a 

raw agricultural commodity (RAC) of barley.

Pregrazing and/or preharvest intervals are not needed for oat, rye, and wheat forages given that 

the use pattern is limited to seed treatment and the supporting wheat forage data collected at 34-

to 61-days after planting, which were used to set tolerances in/on oat, rye, and wheat forages, 

reasonably reflect the shortest period possible between planting and grazing/harvesting these 

forages. [Note: Agricultural practices information provided via personal communication with B. 

Schneider of HED. Reference: http://northerngraingrowers.org/wp-content/uploads/managingsmall-grains-for-forage.pdf] Furthermore, according to the Agency’s most recent guidance on 

constructing reasonably balanced livestock diets (ChemSAC memo, 6/30/08), oat, rye, and wheat 

forages are fed to high-production dairy cattle only and the most recently constructed dairy cattle 

diet (PP# 9F7676; DP# 378829, 2/23/11, B. Cropp-Kohlligian) included wheat forage which 

contributed little (0.04 ppm) to the 1.6 ppm maximum dietary burden (MDB) for dairy cattle 

which was dominated by the contribution of wet apple pomace (1.13 ppm). Hence, even a 

relatively significant increase in residues of difenoconazole in/on oat, rye, and wheat forages is 

expected to have no significant impact on the MDB for dairy cattle.
Difenoconazole Summary of Analytical Chemistry and Residue Data DP#: 384073 

Page 17 of 23

860.1550 Proposed Tolerances

Tolerances for plant commodities are established under §180.475(a)(1), and are expressed in 

terms of difenoconazole per se. The tolerances proposed by Syngenta are also expressed in 

terms of difenoconazole per se and are listed in Table 3 along with the tolerance levels 

recommended by HED and corrected commodity definitions.

No new residue chemistry data were submitted with the current petition. Instead available barley

and wheat magnitude of the residue data were translated to support the proposed uses on oats and 

rye. These data were re-evaluated primarily for the purposes of harmonization and secondarily

for the purposes of setting tolerances in accordance with current guidance. See Table 3 for 

details. Based on the available wheat processing data, tolerances in the processed commodities 

of barley, oats, rye, wheat, and triticale are not needed for the seed treatment uses under 

consideration. 

Codex maximum residue limits (MRLs) for residues of difenoconazole have been established. 

Codex MRLs for residues of difenoconazole per se have been established at 0.02 ppm (absent at 

the limit of quantitation) for wheat grain and 3 ppm for wheat straw and fodder, dry; these levels 

are based on a foliar use of difenoconazole which is not registered in the U.S. Since no Codex 

MRLs have been established for residues of difenoconazole in/on oat commodities, rye 

commodities, and wheat hay, harmonization with Codex is not an issue. Canadian MRLs for 

residues of difenoconazole per se have been established at 0.01 ppm for barley grain; 0.01 ppm 

for oat grain; 0.01 ppm for rye grain; and 0.1 ppm for wheat grain. Harmonization with the 

established Canadian MRLs of 0.01 ppm for residues of difenoconazole in/on oat grain and rye 

grain is recommended. Mexican MRLs have been established for difenoconazole; however, no 

Mexican MRLs have been established for any cereal grains. 

Table 3. Tolerance Summary for Difenoconazole.

Commodity Proposed 

Tolerance 

(ppm)

Recommended 

Tolerance

(ppm)

Correct Commodity Definition;

Comments

Oats, grain 0.1 0.01 Oat, grain. The proposed tolerance is too high. Based on 

the translation and re-evaluation of available barley grain 

data, no detectable residues of difenoconazole per se are 

expected in/on oat grain from the maximum seed treatment 

use under consideration. Therefore, the tolerance should 

be established at the limit of quantitation (LOQ) of the 

current enforcement method, 0.01 ppm in/on grain; a level 

consistent with the established Canadian MRL in/on the 

same commodity. 

Oats, forage 0.1 0.15 Oat, forage. Based on the translation and re-evaluation of 

available wheat forage data, and using the OECD MRL 

calculator, a tolerance of 0.15 ppm is appropriate for the 

maximum seed treatment use under consideration. 
Difenoconazole Summary of Analytical Chemistry and Residue Data DP#: 384073 

Page 18 of 23

Table 3. Tolerance Summary for Difenoconazole.

Commodity Proposed 

Tolerance 

(ppm)

Recommended 

Tolerance

(ppm)

Correct Commodity Definition;

Comments

Oats, hay 0.1 0.05 Oat, hay. Based on the translation and re-evaluation of 

available wheat hay data, residues of difenoconazole are 

not expected to exceed the LOQ of the current 

enforcement method, 0.05 ppm in/on hay, for the 

maximum seed treatment use under consideration.

Oats, straw 0.1 0.05 Oat, straw. Based on the translation and re-evaluation of 

available wheat straw data, residues of difenoconazole are 

not expected to exceed the LOQ of the current 

enforcement method, 0.05 ppm in/on straw, for the 

maximum seed treatment use under consideration.

Rye, grain 0.1 0.01 Based on the translation and re-evaluation of available 

wheat grain data, no detectable residues of difenoconazole 

per se are expected in/on oat grain from the maximum 

seed treatment use under consideration. Therefore, the 

tolerance should be established at the limit of quantitation 

(LOQ) of the current enforcement method, 0.01 ppm in/on 

grain; consistent with the established Canadian MRL in/on 

the same commodity. Note: The recommended 

tolerance for rye grain (0.01 ppm) should replace the 

existing import tolerance for rye grain (0.1 ppm).

Rye, forage 0.1 0.15 See comments above under Oat, forage.

Rye, straw 0.1 0.05 See comments above under Oat, straw.

Wheat, hay 0.1 0.05 Based on the re-evaluation of available wheat hay data, 

residues of difenoconazole are not expected to exceed the 

LOQ of the current enforcement method, 0.05 ppm in/on 

hay, for the maximum seed treatment use under 

consideration.

References

DP#s: 172067 and 178394

Subject: PP#2E4051. CGA-169374 (Difenoconazole, Dividend®) in Imported Wheat, 

Barley, and Rye Grain. First Food Use. CBTS# 9029, 9895.

From: R. Lascola

To: J. Stone/C. Giles-Parker

Dated: 10/22/92

MRIDs: 42090001-42090004, 42090032-42090059, and 42303901
Difenoconazole Summary of Analytical Chemistry and Residue Data DP#: 384073 

Page 19 of 23

DP#: 228403

Subject: PP#6F4748. Difenoconazole (Dividend) in or on Barley, Oats, and Triticale. 

Evaluation of Residue Data and Analytical Methods. Case 287954. Chemical 

128847. CBTS# 17407.

From: G. Kramer

To: C. Eiden/D. McCall

Dated: 9/23/96

MRIDs: 44056001

DP#s: 248285 and 248419

Subject: PP#2F4107. Difenoconazole (Dividend) in/on Wheat and Animal RACs. 

Amendments of 7/8/98 and 7/30/98. Chemical 128847.

From: S. Chun

To: C. Giles-Parker/J. Bazuin

Dated: 10/28/98

MRIDs: 44602001-44602001 and 44619401

DP#: 375159

Subject: Difenoconazole. Dissociation Constant in Water Data to Satisfy OPPTS 

830.7370 Guideline Requirements.

From: B. Cropp-Kohlligian

To: Rosemary Kearns/Tony Kish

Dated: 5/26/10

MRID: 47957001

DP#: 378829

Subject: Difenoconazole. Application for Amended Section 3 Registration to Add Uses on 

Carrots, Chickpeas, Soybeans, Stone Fruits (Group 12), Strawberries, and Turnip 

Greens. Summary of Analytical Chemistry and Residue Data.

From: B. Cropp-Kohlligian

To: Rosemary Kearns/Tony Kish

Dated: 2/23/11

MRIDs: 47929801-47929805

F. DOCUMENT TRACKING

Petition Number: 0F7785 (oat commodities, rye commodities, and wheat hay)

DP Barcode(s): 384073

PC Code: 128847

Template Version September 2003
Difenoconazole Summary of Analytical Chemistry and Residue Data DP#: 384073 

Page 20 of 23

International Residue Limits 

Difenoconazole (128847; 3/21/11)

Summary of US and International Tolerances and Maximum Residue Limits 

Residue Definition:

US Canada Mexico2 Codex3

40 CFR 180.475:

Plant: difenoconazole, 1-[2-[2-chloro4-(4-chlorophenoxy)phenyl]-4-

methyl-1,3-dioxolan-2-ylmethyl]-1H1,2,4-triazole

Livestock: difenoconazole, 1-[2-[2-

chloro-4-(4-chlorophenoxy)phenyl]-4-

methyl-1,3-dioxolan-2-ylmethyl]-1H1,2,4-triazole, and its metabolite, 

CGA-205375, 1-[2-chloro-4-(4-

chloro-phenoxy)phenyl]-2-

[1,2,4]triazol-1-yl-ethanol

1-[2-[4-(4-

chlorophenoxy)-2-

chlorophenyl]-4-

methyl-1,3-

dioxolan-2-

ylmethyl]-1 H1,2,4-triazole

Plant commodities: 

difenoconazole

Animal commodities:

sum of difenoconazole 

and 1-[2-chloro-4-(4-

chloro-phenoxy)-phenyl]-

2-(1,2,4-triazol)-1-ylethano), expressed as 

difenoconazole. The 

residue is fat soluble.

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

US Canada Mexico2 Codex

Oat, grain30.01 0.01

Oat, forage 0.15

Oat, hay 0.05

Oat, straw 0.05

Rye, grain30.01 0.01

Rye, forage 0.15

Rye, hay 0.05

Rye, straw 0.05

Wheat, hay 0.05

Completed: M. Negussie; 03/28/2011

Subsequently Edited by B. Cropp-Kohlligian to Provide More Information With Additional Footnote 3

1

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

not those proposed by the applicant.

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

3 Having re-evaluated the available barley and wheat field trial data which were translated to support the proposed 

seed treatment uses of difenoconazole on oats and rye, the reviewer finds that no detectable residues of 

difenoconazole (i.e., no residues above the LOQ of the current enforcement method, 0.01 ppm in/on grain), are 

expected in/on the grains of barley, oats, rye, and wheat from the proposed and/or existing maximum seed treatment 

use rates of difenoconazole on these grains. Although difenoconazole is not currently registered in the U.S. for use 

on rye, an import tolerance is currently established under 40 CFR §180.475(a)(1) for residues of difenoconazole 

in/on rye grain at 0.1 ppm. 
Difenoconazole Summary of Analytical Chemistry and Residue Data DP#: 384073 

Page 21 of 23

Appendix I. Tolerance Assessment Calculations.

For each of the crops listed below, the OECD MRL Calculator User Guide (SOP), along with the 

tolerance spreadsheet, was used for calculating recommended tolerances. As specified in the 

SOP, the tolerance calculation is in the region of the 95th percentile of the underlying residue 

distribution, and is more likely to overestimate rather than underestimate the 95th percentile. The 

rounding procedures specified in the SOP were also used. The OECD tolerance spreadsheet 

does not require the use of maximum-likelihood estimation (MLE) procedures for values <LOQ. 

Wheat forage

The dataset used was large (24 samples) and consisted of field trial data representing seed 

treatment at a maximum seasonal application rate of 9.5-11 g ai/100 lb seed (consistent with the 

proposed domestic use rate) and reflecting 35-61 day PHIs. Seventy-five percent of the data 

were censored. Data reflecting longer PHIs were excluded from the calculation; they were all 

censored data. [Note: Exclusion of data reflecting longer PHIs had no effect on the tolerance 

estimate.] The residue values that were entered into the OECD tolerance spreadsheet are 

provided in Table I-1. Using the OECD spreadsheet (Figure I-1) the appropriate tolerance is 

0.15 ppm in/on wheat forage and, by translation, oat and rye forages.

Table I-1. Residue data used to calculate tolerance for difenoconazole in/on wheat forage.

Trial No. Trial Site

Trial ID

Region

PHI

(days)

Residues Found

(ppm)

Average Residues 

Used in OECD MRL 

Calculations

(ppm)

MRID 42090055; Data previously reviewed by HED under PP#2E4051 (DP#s 172067 and 178394, 10/26/92, 

R. Lascola).

1

ND

MW-FR-504-89

Region 5

60 <0.01, <0.01 <0.01

2

MT

MW-FR-503-89

Region 7

60 <0.01, <0.01 <0.01

3

MN

MW-FR-703-89

Region 5

61 <0.01, <0.01 <0.01

4

SD

MW-FR-603-89

Region 5

60 0.02, 0.02 0.02

5

IL

04-FR-001-89

Region 5

54 <0.01, <0.01 <0.01

6

NY

05-FR-004-89

Region 1

60 0.02, <0.01 0.015

7

AR

0S-FR-208-89

Region 4

61 <0.01, 0.02 0.015
Difenoconazole Summary of Analytical Chemistry and Residue Data DP#: 384073 

Page 22 of 23

Table I-1. Residue data used to calculate tolerance for difenoconazole in/on wheat forage.

Trial No. Trial Site

Trial ID

Region

PHI

(days)

Residues Found

(ppm)

Average Residues 

Used in OECD MRL 

Calculations

(ppm)

8

TX

OS-FR-208-89

Region 6

59 <0.01, <0.01 <0.01

9

AZ

OW-FR-504-89

Region 10

56 <0.01, <0.01 <0.01

10

KS

MW-FR-304-89

Region 5

61 <0.01, <0.01 <0.01

MRID 44602001; Data previously reviewed by HED under PP#2F4107 (DP#s 248285 and 248419, 10/28/98, 

S. Chun).

11

Caddo County, OK

OS-FR-101-95

Region 8

45 <0.05, <0.05 <0.05

12

Wayne County, NC

OS-FR-601-95

Region 9

42 <0.05, <0.05 <0.05

13

Yellowstone County, MT

OW-FR-201-95

Region 9

52 <0.05, <0.05 <0.05

14

Pawnee County, KS

MW-FR-301-95

Region 8

40 <0.05, <0.05 <0.05

15

Edwards County, KS

MW-FR-302-95

Region 8

42 <0.05, <0.05 <0.05

16

Weld County, CO

MW-FR-303-95

Region 8

42 0.074, 0.062 0.068

17

Ward County, ND

MW-FR-501-95

Region 7

35 <0.05, <0.05 <0.05

18

Corson County, SD

MW-FR-502-95

Region 7

34 <0.05, <0.05 <0.05

19

Jackson County, AR

OS-FR-101-96

Region 4

42 <0.05, 0.077 0.064

20

Caddo County, OK

OS-FR-750-96

Region 8

42 <0.05, <0.05 <0.05

21

Latah County, ID

OW-FR-601-96

Region 9

42 <0.05, <0.05 <0.05

22

Jackson County, MO

MW-FR-210-96

Region 5

42 <0.05, 0.061 0.056
Difenoconazole Summary of Analytical Chemistry and Residue Data DP#: 384073 

Page 23 of 23

Table I-1. Residue data used to calculate tolerance for difenoconazole in/on wheat forage.

Trial No. Trial Site

Trial ID

Region

PHI

(days)

Residues Found

(ppm)

Average Residues 

Used in OECD MRL 

Calculations

(ppm)

23

Traverse County, MN

MW-FR-503-96

Region 5

36 <0.05, <0.05 <0.05

24

York County, NE

MW-FR-610-96

Region 5

42 <0.05, <0.05 <0.05

Figure I-1. OECD tolerance spreadsheet summary of difenoconazole field trial data for wheat 

forage.

Difenoconazole

Wheat Forage

Use Rate: 9.5-11 g ai/100 lb seed

PHI: 35-61 days

Total number of data (n) 24

Percentage of censored data 75%

Number of non-censored data 6

Lowest residue 0.010

Highest residue 0.068

Median residue 0.050

Mean 0.036

Standard deviation (SD) 0.021

Correction factor for censoring (CF) 0.500

Proposed MRL estimate

- Highest residue 0.068

- Mean + 4 SD 0.120

- CF x 3 Mean 0.054

Unrounded MRL 0.120

Rounded MRL 0.15

High uncertainty of MRL estimate.

[High level of censoring]