UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C.  20460

	OFFICE OF PREVENTION, PESTICIDE

	AND TOXIC SUBSTANCES

  SEQ CHAPTER \h \r 1 MEMORANDUM

Date:  21-JAN-2010

SUBJECT:	Difenoconazole.  Import Tolerance Request on Mango and Waxapple
(also known as Wax jambu).  Summary of Analytical Chemistry and Residue
Data.

PC Code:  128847	DP Barcode:  D366507

Decision No.:  413927	Registration No.:  NA

Petition No.:  9E7573	Regulatory Action:  None

Risk Assessment Type:  NA	Case No.:  NA

TXR No.:  NA	CAS No.:  19446-68-3

MRID No.:  See MRID Summary Table	40 CFR:  §180.475

	Ver.Apr.08

FROM:	Bonnie Cropp-Kohlligian, Environmental Scientist

		Risk Assessment Branch 4

		Health Effects Division (7509P)  SEQ CHAPTER \h \r 1 		

		

THROUGH:	Susan V. Hummel, Chemist/Senior Scientist

		Risk Assessment Branch 4

		Health Effects Division (7509P)

	

TO:		Rosemary Kearns/Tony Kish (RM 22)

		Fungicide Branch

		Registration Division (7505P)

MRID Summary Table

MRID No.	Study Type	Comments

47760601	860.1500 Waxapple	New DER; 47760601.der.doc

47760602	860.1500 Mango	New DER; 47760602.der.doc



  SEQ CHAPTER \h \r 1 This document was originally prepared under
contract by Dynamac Corporation (1901 Research Boulevard, Suite 220;
Rockville, MD 20850).  

Dynamac QC Reviewer:		Date:  10/28/2009

	Danilo Martinez

	

The document has been reviewed by the Health Effects Division (HED) and
revised to reflect current Office of Pesticide Programs (OPP) policies.

Executive Summary

Difenoconazole is a broad spectrum fungicide belonging to the triazole
group of fungicides (Group 3).  It is currently registered in the U.S.
for use as a seed treatment on cereal grains, canola, and cotton and for
foliar applications on pome fruits, sugar beets, fruiting vegetables,
and tuberous and corm vegetables.  A petition (PP#8F7482) is pending for
foliar uses on bulb vegetables, Brassica leafy vegetables, cucurbit
vegetables, citrus fruits, grapes, pistachios, and tree nuts.  The mode
of action of difenoconazole is as a demethylation inhibitor of sterol
biosynthesis which disrupts membrane synthesis by blocking
demethylation.

Under PP#9E7573, Syngenta Crop Protection, Inc. is proposing the
establishment of import tolerances for residues of difenoconazole
[1-[2-[2-chloro-4-(4-chlorophenoxy)phenyl]-4-methyl-1,3-dioxolan-2-ylmet
hyl]-1H-1,2,4-triazole] in/on the following raw agricultural
commodities:

Mango, fruit	0.09 ppm

Waxapple, fruit	1.5 ppm

The end-use product (EP) for use on mangos grown in Brazil is Score®,
an emulsifiable concentrate (EC) formulation containing 250 g ai/L.  Up
to three foliar spray applications at a target rate of 0.11 lb
ai/A/application (0.125 kg ai/ha/application), with a 14-day retreatment
interval (RTI), may be made to mature mango trees for a total seasonal
rate of 0.33 lb ai/A (0.375 kg ai/ha) using ground equipment in 500 to
1,000 L/ha spray volume (53 to 107 gal/A which is considered a
concentrated spray volume) and a 7-day preharvest interval (PHI).  The
use pattern is supported by adequate residue data from crop field trials
conducted in Brazil.  

The EP for use on waxapples grown in Taiwan is ‘Hao Jia Zan
Azoxystrobin + Difenoconazole’, a soluble concentrate (SC) formulation
containing 12.5% w/v difenoconazole and 20% w/v azoxystrobin.  The
information for waxapple use in Taiwan is incomplete, however, the
submitted field trial data will support up to eight foliar applications
of a 125 g/L SC formulation of difenoconazole to mature waxapple trees
at a target rate of 0.34 lb ai/A/application (0.39 kg
ai/ha/application), with 6- to 8-day RTI, for a total seasonal rate of
2.74 lb ai/A (3.07 kg ai/ha) and a 12-day PHI.  Applications may be made
using ground equipment in a 2,000 L/ha spray volume (214 gal/A which is
considered a dilute spray volume), without an adjuvant.  Consistent with
the submitted field trial data, applications should be restricted to
fruit protected with exclusion net bags or otherwise bagged fruit.  This
review addresses the proposed use of difenoconazole only.

Tolerances for difenoconazole are currently established under 40 CFR
§180.475.  Tolerances for plant commodities are established under
§180.475(a)(1), and are expressed in terms of difenoconazole per se. 
Tolerances are established for raw agricultural and processed
commodities, including barley, sugar beet, canola, corn, pome fruit,
fruiting vegetable, and tuberous and corm vegetable commodities, and
range 0.01-4.5 ppm.  Import tolerances are established for banana,
grape, papaya, and rye grain, and range 0.10-0.30 ppm.  Tolerances for
livestock commodities are 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].
 Livestock tolerances for tissues, milk, and egg range 0.05-0.20 ppm. 
Time-limited tolerances, expressed in terms of difenoconazole per se,
are established under §180.475(b) in support of Section 18 emergency
exemptions for use on almond, cantaloupe, cucumber, and watermelon and
range 0.05-5.0 ppm.

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.

Because difenoconazole is a triazole compound, HED requires that samples
from any metabolism, feeding, field trial, and/or processing studies be
analyzed for the triazole metabolites, triazolylalanine (TA), triazolyl
acetic acid (TAA), and 1,2,4-triazole (1,2,4-T).  These data are needed
for risk assessment only.  HED issued guidance on the residue chemistry
data requirements for the triazole-based metabolites under DP# 327788
(4/25/06, M. Doherty) and has requested submission of these data for all
pending uses on record within the Agency as of September 1, 2005.  The
submitted waxapple field trial study did not include analysis for the
three triazole metabolites; however, these data will not be required to
support this petition since there is no consumption for waxapple in the
current dietary exposure evaluation model.  The submitted mango field
trial study, which was conducted in 2003, did not include analysis for
the three triazole metabolites; however, the study is not considered
upgradable for this purpose.  HED has determined (DP# 371613,
01/21/2010, T. Morton) that the proposed use of difenoconazole on mango
does not result in an increase in dietary exposure estimates for
triazole metabolites in/on mangos which was incorporated into the last
dietary exposure analyses for the triazole metabolites (M. Negussie, 28
Oct. 2009) and which is currently based on existing uses of myclobutanil
and tebuconazole on mangos.  Additional triazole metabolite data for the
proposed use of difenoconazole on mango is not expected to result in
increases to the current dietary exposure estimates for triazole
metabolites; hence, additional triazole metabolite data will not be
required to support the proposed use of difenoconazole on mango. 

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) are 0.01-0.05 ppm.  A confirmatory GC method with
mass-selective detection (MSD) is also available for crop commodities. 
Samples from the submitted the crop field trials were analyzed for
residues of difenoconazole using a high performance liquid
chromatography method with tandem mass spectrometry detection
(LC/MS/MS), Syngenta REM 147.08, or a similar method.  The methods are
adequate for data collection based on acceptable concurrent method
recoveries.  The LOQ was 0.01 ppm for difenoconazole in mango and
waxapple.

Analytical standards for difenoconazole and its metabolite CGA-205375
are currently available in the EPA National Pesticide Standards
Repository.

There are no feedstuffs associated with the foreign uses of
difenoconazole on mango in Brazil and waxapple in Taiwan.  Therefore, no
livestock enforcement methods, storage stability data, or feeding
studies are required to support this petition.

Mangos and waxapple are not typically rotated and rotational crop
restrictions are not relevant for foreign uses.  Therefore, a discussion
pertaining to the need for rotational crop data is not germane to this
petition.

 

Samples of mango and waxapple from the submitted crop field trials were
stored frozen for up to four months prior to analysis for
difenoconazole.  Adequate storage stability data are available for
difenoconazole to conclude that residues are stable in/on all raw
agricultural crop commodities for up to one year.

HED is unable to assess the adequacy of the submitted field trial data
for waxapple because the use directions have not been fully elucidated. 
Syngenta is required to provide label use information as detailed under
‘Directions for Use’ section.  Assuming that the use directions for
waxapple in Taiwan, once fully elucidated, will comport with the
submitted field trial data, HED tentatively recommends for the proposed
import tolerance of 1.5 ppm for waxapple.  No Codex, Canadian, and
Mexican MRLs have been established for residues of difenoconazole in/on
waxapple.   

The submitted field trial data for mango are adequate and reflect the
proposed use of Score® on mango in Brazil.  The residue data from the
trials conducted will support the proposed import tolerance of 0.09 ppm
for mango.  A Codex MRL for residues of difenoconazole per se has been
established at 0.07 ppm for mango.  Canadian and Mexican MRLs have been
established for difenoconazole; however, no MRLs have been established
for mango.  The Codex MRL for residues of difenoconazole per se in/on
mango is based on the same dataset considered herein; however, the
reviewer has been advised (personal communication with S. Funk
OPP/HED/RAB3 via email dated 11/04/2009) that the Joint FAO/WHO Meeting
on Pesticide Residues (JMPR) uses field trial data in the NAFTA
calculator and may interpret the outcomes differently than HED.  JMPR
does not accept the independence of samples from the same location;
hence, JMPR used the following four data points from the four 2003 mango
field trials conducted in Brazil in the NAFTA calculator:  0.025 ppm,
0.025 ppm, 0.035 ppm, and 0.04 ppm .  From these data, the NAFTA
calculator gives 0.06 ppm, which JMPR did not accept.  JMPR typically
goes higher than the NAFTA calculator where there are few samples and so
established the 0.07 ppm MRL for mango.  Harmonization with the
established Codex MRL of 0.07 ppm for residues of difenoconazole in/on
mango is recommended for mango.

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

HED has examined the residue chemistry database for difenoconazole. 
Pending submission of a revised Section B for waxapple (see requirements
under Directions for Use) and a revised Section F (see requirements
under Proposed Tolerances), there are no residue chemistry issues that
would preclude granting import tolerances for residues of difenoconazole
resulting from the uses on mango in Brazil and waxapple in Taiwan:

Mango	0.07 ppm

Waxapple	1.5 ppm

A human health risk assessment is forthcoming.

Notes to PM:

With regards to the use on mangos in Brazil, HED notes that Mexico and
not Brazil is the largest importer of mangos into the U.S.  Since only
data from Brazil were submitted, the registrant should be made aware
that HED makes no ascertain as to the adequacy of the recommended
tolerance to cover residues incurred in other geographical regions of
South America or Mexico from the same or similar use. 

An error was found in MRID 47760601, Section 1.3 Test Item, bottom of
Page 6 of 66.  The stated nominal/actual formulation content in Amistar
Top 325 SC of difenoconazole and azoxystrobin are reversed.  According
to the label, Amistar Top 325 SC contains 125 g/L of difenoconazole and
200 g/L azoxystrobin.  The MRID should be corrected. 

The registrant should be reminded that because difenoconazole is a
triazole compound, HED requires that samples from any metabolism,
feeding, field trial, and/or processing studies be analyzed for the
triazole metabolites triazolylalanine (TA), triazolyl acetic acid (TAA),
and 1,2,4-triazole (1,2,4-T).  Guidance has been issued concerning these
residue chemistry data requirements for the triazole-based metabolites
under DP# 327788 (4/25/06, M. Doherty) and data submitted in support of
future uses of difenoconazole will be accessed accordingly.

The registrant should be reminded that magnitude of the residue data for
papaya, as a representative crop of the tropical fruit crops group, have
been deemed adequate to support the same or substantially similar use on
mango (among other tropical fruits) and the establishment of a separate
mango tolerance.  An import tolerance is currently established under
§180.475(a)(1) for residues of difenoconazole in/on papaya at 0.3 ppm. 
  

860.1200 Directions for Use - Waxapple

Syngenta must submit a complete description of the use of difenoconazole
on waxapple grown in Taiwan (a translated label or complete Section B). 
As required by the NAFTA Guidance Document on Data Requirements for
Tolerances on Imported Commodities in the United States and Canada
(December 2005), it is necessary to submit copies of registered/approved
label(s) translated to English.  The information must include, but is
not limited to, the maximum single application rate, the maximum annual
application rate, application timing (as it relates to plant growth
stage), retreatment interval, application tank-mix preparation, volume
of spray mix per unit area, application equipment, and the preharvest
interval.  The application rates should be expressed in units of pounds
of active ingredient per acre (or kilograms per hectare).

Syngenta must submit a complete description of the use of difenoconazole
on waxapple grown in Taiwan consistent with the use profile of the
submitted field trial data (MRID 47760601).  The submitted field trial
data will support eight foliar applications of a 125 g/L suspension
concentrate (SC) formulation of difenoconazole at a target rate of 0.39
kg ai/ha/application (0.34 lb ai/A/application), with 6- to 8-day
retreatment intervals, for a total rate of 3.07 kg ai/ha (2.74 lb ai/A)
and a 12-day PHI.  Applications may be made using ground equipment in
2,000 L/ha spray volumes (214 gal/A which is considered a dilute spray
volume), without an adjuvant.  

Consistent with the submitted field trial data, applications should be
restricted to fruit protected with exclusion net bags or otherwise
bagged fruit.

860.1550 Proposed Tolerances

The proposed tolerances should be revised to reflect the recommended
tolerance levels and correct commodity definitions as specified in Table
6.  

Background

The chemical structure and nomenclature of difenoconazole and its
regulated livestock metabolite CGA-205375, and the physicochemical
properties of the technical grade of difenoconazole are presented in
Tables 1 and 2.  

Table 1.   Difenoconazole Nomenclature.

Chemical structure	

Common name	  SEQ CHAPTER \h \r 1 Difenoconazole

Company experimental name	CGA-169374

IUPAC name
1-({2-[2-chloro-4-(4-chlorophenoxy)phenyl]-4-methyl-1,3-dioxolan-2-yl}me
thyl)-1H-1,2,4-triazole

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

CAS registry number	119446-68-3

End-use products (EP)	Score® - for mango grown in Brazil.

‘Hao Jia Zan Azoxystrobin + Difenoconazole’ - for waxapple grown in
Taiwan

Chemical structure of CGA-205375 livestock metabolite	



Table 2.	Physicochemical Properties of Difenoconazole.

Parameter	Value	Reference

Melting point	  SEQ CHAPTER \h \r 1 78.6 ºC	  SEQ CHAPTER \h \r 1 DP#s
172067 and 178394, 10/26/92, R. Lascola

pH	  SEQ CHAPTER \h \r 1 6-8 at 20 ºC (saturated solution)

	Density	  SEQ CHAPTER \h \r 1 1.37 g/cm3 at 20 ºC

	Water solubility	  SEQ CHAPTER \h \r 1 3.3 ppm at 20 ºC

	Solvent solubility		  SEQ CHAPTER \h \r 1 g/100 mL at 25 ºC:

n-hexane:	0.5

1-octanol:	35

toluene:	77

acetone:	88

ethanol:	89

	Vapor pressure	  SEQ CHAPTER \h \r 1 2.5 x 10-10 mm Hg at 25 ºC

	Dissociation constant, pKa	  SEQ CHAPTER \h \r 1 Reported as   SEQ
CHAPTER \h \r 1 <0 in MRID 42090003 which was previously reviewed in
DP#s 172067 and 178394; however, questions have arisen concerning this
value.  Re-examination of MRID 42090003 found that the product chemistry
data study to support the reported dissociation constant for the
technical grade of difenoconazole was not included.  New data are
expected.

Octanol/water partition coefficient, Log(KOW)	  SEQ CHAPTER \h \r 1 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)



860.1200 Directions for Use

A list of the end-use products (EPs) relevant to this import tolerance
petition is presented in Table 3a.  A summary of the use directions for
these EPs is presented in Table 3b.

Table 3a.   Summary of Difenoconazole End-Use Products Proposed for Use
on Mango and Waxapple.

Trade Name	Country	a.i. (% of formulation) 	Formulation Type	Proposed 
Crops	Target Pests	Label Date

Score® 	Brazil	25%

 (250 g ai/L)	EC	Mango	Powdery mildew and anthracnose	10/30/02

(Hao Jia Zan) 1

Azoxystrobin + Difenoconazole	Taiwan	12.5%	SC	Waxapple	Anthracnose
undated, Section B

1  The Taiwan end-use product is a soluble concentrate formulation
containing 12.5% w/v difenoconazole and 20% w/v azoxystrobin.

Table 3b.   Summary of Proposed Directions for Use of Difenoconazole.

Applic. Timing, Type, and Equip.	Product

[Formulation]

	Applic. Rate 

(lb ai/A)

[g ai/ha]	Max. No. Applic. per Season	Max. Seasonal Applic. Rate

(lb ai/A)

[g ai/ha]	PHI

(days)	Use Directions and Limitations

Mango

Foliar;

Ground

(500-1,000 L/ha spray volume)	Score®

[250 g  ai/L EC]	0.022-0.11

[25-125]	3	0.33

[375]	7	Applications must start immediately after the engorgement of
floral gems or before flowers bloom, using smallest dose in the first
applications to control powdery mildew and a larger dose to control
anthracnose; 14-day RTI.

Waxapple

Foliar;

equipment not specified (NS)	Hao Jia Zan

[12.5% w/v SC]	3,000x

dilution1	5	NS	30	Only to be applied during fluorescence; 7-day RTI.

1 The application rate could not be determined as the Section B only
reported the concentration to be applied.

Conclusions.  The submitted use direction information for Score®, the
EP for use on mango in Brazil, is adequate to allow evaluation of the
residue data.  The submitted mango field trial data reflect the foreign
use pattern.  However, the use direction information for Hao Jia Zan
Azoxystrobin + Difenoconazole, the EP for use on waxapple in Taiwan is
not adequate to allow evaluation of the residue data.  Specifically, the
use rate on waxapple could not be determined from the Taiwan use pattern
as summarized in Section B; only a concentration (dilution) level was
reported.  A translated label (or complete Section B) which specifies
the use rate (in g ai/ha or lb ai/A) on waxapple in Taiwan must be
submitted before HED can determine if the field trial data support the
proposed import tolerance.  The submitted field trials reflect a maximum
total rate of 3.07 kg ai/ha (2.74 lb ai/A) and a 12-day PHI; the PHI
reported in Section B is 30 days for waxapple.

860.1300 Nature of the Residue - Plants

Residue Chemistry Memo DP# 340379, 8/9/07, W. Wassell and M. Sahafeyan

  SEQ CHAPTER \h \r 1 MARC Decision Memo, 7/22/94, G. Kramer

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.  Based on
the results of available plant metabolism studies, the petitioner has
proposed that difenoconazole is metabolized in plants by the
hydroxylation of the phenyl ring and/or cleavage of the dioxolane ring
followed by cleavage of the carbon-carbon bridge between the phenyl and
triazole rings.  

Previously, when the first foliar uses of difenoconazole on crop
commodities were proposed (DP# 340379), HED re-evaluated the available
plant metabolism data to determine if residues other than difenoconazole
needed to be included in the tolerance expression and/or the risk
assessment and concluded that the residue of concern for both tolerance
enforcement and risk assessment for the crops (fruiting vegetables, pome
fruits, sugar beets, tuberous and corm vegetables, and imported papaya)
in the petition (PP#6F7115) under consideration.  In keeping with the
previous decision, HED concludes that the residue of concern for both
tolerance enforcement and risk assessment for the crops included in this
petition is difenoconazole per se.

860.1300 Nature of the Residue - Livestock

Residue Chemistry Memo DP# 340379, 8/9/07, W. Wassell and M. Sahafeyan

  SEQ CHAPTER \h \r 1 MARC Decision Memo, 7/22/94, G. Kramer

Residue Chemistry Memo DP#s 203644 and 203645, 6/16/94, G. Kramer

Residue Chemistry Memo DP#s 172067 and 178394, 10/26/92, R. Lascola

The nature of the residue in livestock is understood based on acceptable
goat and hen metabolism studies.  The data were originally evaluated in
support of seed treatment uses only, and HED concluded that the residue
of concern in livestock commodities was difenoconazole per se.  When the
first foliar uses of difenoconazole on crop commodities were proposed
(DP# 340379), HED re-evaluated the livestock metabolism data and
concluded that the residues of concern for both tolerance setting and
risk assessment for livestock commodities are difenoconazole and
metabolite CGA-205375.

860.1340 Residue Analytical Methods

Crop Commodities

Residue Chemistry Memo DP# 356135, 9/17/09, B. Cropp-Kohlligian

Residue Chemistry Memo DP# 340379, 8/9/07, W. Wassell and M. Sahafeyan

Enforcement methods:  An adequate enforcement method, GC/NPD method
AG-575B, is available for the determination of residues of
difenoconazole per se in/on plant commodities.  An adequate enforcement
method, GC/MSD method AG-676A, is also available for the determination
of residues of difenoconazole per se in/on canola and barley
commodities.  A confirmatory method, GC/MSD method AG-676, is also
available.  The LOQs are 0.01-0.05 ppm.  

Data collection methods:  Samples of waxapple from the Taiwan field
trials were analyzed for residues of difenoconazole using LC/MS/MS
method, REM 147.08.  This method was previously reviewed and determined
an alternative enforcement method for difenoconazole in plants (DP#
340379).  Briefly, waxapple fruits were extracted with
methanol:concentrated ammonium hydroxide (8:2, v:v) at reflux.  An
aliquot of the extract was diluted with water for cleanup by solid-phase
extraction (SPE; Oasis HLB cartridge).  Residues of difenoconazole were
quantitated by LC/MS/MS analysis.  The validated LOQ was 0.01 ppm for
difenoconazole in waxapple.  The limit of detection was not reported. 

 

Samples of mangos from the Brazil crop field trials were also analyzed
for residues of difenoconazole using an LC/MS/MS method.  This method
varies from Method REM 147.08, in that extraction does not include
ammonium hydroxide and was not conducted at reflux, and a SPE cleanup
step was not performed.  Briefly, mango fruits were
homogenized/extracted with acetone:water (2:1, v:v) and centrifuged.  An
aliquot of the extract was evaporated and redissolved in acetonitrile
(ACN):water (1:1, v:v) for LC/MS/MS analysis.  The validated LOQ was
0.01 ppm for difenoconazole in mango.

Although mango fruits with stones removed were analyzed, consistent with
the food portion of mango fruits to be analyzed according to PAM Vol. I,
Section 102, the residue results were calculated and reported as
difenoconazole in/on whole fruit.  Difenoconazole residues in/on whole
fruits were calculated by dividing the weight of the whole fruit by the
weight of the fruit without the stone and then multiplying by the
residue value found in/on the fruit without the stone.  Only the
calculated whole fruit results were provided in the study submission.

Both methods are adequate for data collection based on acceptable
concurrent recovery data.  The fortification levels used in concurrent
method recovery are adequate to bracket (within an order of magnitude)
expected residues in mango and waxapple.

Conclusions.  An adequate tolerance enforcement method is available for
determination of residues of difenoconazole per se in crop commodities,
and samples from the crop field trial studies were analyzed for residues
of difenoconazole using acceptable methods.

860.1360 Multiresidue Methods

Residue Chemistry Memo DP#s 172067 and 178394, 10/26/92, R. Lascola

Email from C. Stafford (Analytical Chemistry Branch) to B.
Cropp-Kohlligian dated 9/2/09

Multiresidue methods (MRM) testing data (MRID 42090054) were previously
submitted   SEQ CHAPTER \h \r 1 in conjunction with PP#2E4051 (DP#s
172067 and 178394, 10/26/92, R. Lascola).  The study investigated the
recovery of difenoconazole and its metabolites CGA-205374, CGA-205375,
and CGA-189138 through the MRM methods of PAM Vol. I.  Based on the
study results, HED concluded, as did the petitioner, that the MRM
methods were not likely to be appropriate for determining residues of
difenoconazole and its related compounds in plant and livestock tissues.
 The study was forwarded to FDA for further review.  Difenoconazole is
not listed in the most recent PESTDATA (1999).

In contradiction to the MRM study evidence, Analytical Chemistry Branch
(ACB) has noted (Email from C. Stafford (ACB) to B. Cropp-Kohlligian
dated 9/2/09) that (1) FDA routinely monitors for difenoconazole by
GC/MS using their current modified Luke procedures which are not in the
published PAM I manual; (2) difenoconazole has also been tested through
the QuEChERS (Quick, Easy, Cheap, Effective, Rugged, and Safe) method
which is just beginning to be implemented in the FDA field labs using
LC/MS/MS; and (3) the USDA-PDP program labs monitor for difenoconazole;
the California Department of Food and Agriculture (CDFA), a
participating laboratory, uses a multiresidue method with LC/MS
analysis.  Based on these facts, HED accepts that difenoconazole is
recoverable through existing multiresidue methods, although the evidence
is non-guideline and a conclusion concerning whether recovery is
complete (>80%) cannot be reached.  No additional MRM testing data are
required at this time.  

860.1380 Storage Stability

Residue Chemistry Memo DP# 340379, 8/9/07, W. Wassell and M. Sahafeyan

Adequate storage stability data are available indicating that residues
of difenoconazole are stable at -20 (C for at least two years in/on
cotton seed, oil, and meal; potato tuber; tomato; and wheat forage,
grain, and straw.  Data are also available indicating that
difenoconazole residues are stable at -20 (C for at least one year in/on
banana, lettuce, and soybean seed.  HED previously concluded (DP#
340379) that these data represent sufficient diverse crops (a leafy
vegetable, a fruit, a root crop, a non-oily grain, and an oilseed) to
allow translation of storage stability data for difenoconazole to all
raw agricultural crop commodities for a one-year storage interval.  The
available storage stability data for the two-year storage interval are
not sufficient to allow translation to all raw agricultural commodities
because no data are available for a leafy vegetable.  

The storage durations and conditions of samples from the crop field
trials submitted to support this import tolerance petition are presented
in Table 4.  

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

Matrix 	Storage Temperature

 (°C)	Actual Storage Duration	Interval of Demonstrated

≤-18	51-60 days (1.7-2.0 months)	Up to one year.

Waxapple	≤-18	59-113 days (1.9-3.7 months)

	

Conclusions.  The available difenoconazole storage stability data are
adequate to support the storage conditions and durations of samples of
mango and waxapple from the submitted crop field trial studies.  Based
on the submitted data, there are no storage stability issues, and no
corrections need be applied to the crop field trial results.

860.1400 Water, Fish, and Irrigated Crops

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

860.1460 Food Handling

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

860.1480 Meat, Milk, Poultry, and Eggs

There are no livestock feedstuffs associated with foreign uses on mango
or waxapple.  Therefore, data requirements pertaining to meat, milk,
poultry, and eggs are not relevant to this tolerance petition.

860.1500 Crop Field Trials

DER Reference:	47760601.der.doc (waxapple)

		47760602.der.doc (mango)

Table 5.    Summary of Residue Data from Crop Field Trials with
Difenoconazole.

Crop matrix	Total Applic. Rate in lb ai/A

[g ai/ha]	PHI (days)	Residue Levels (ppm)



	N	Min.	Max.	HAFT1	Median	Mean	Std. Dev.

Mango (Brazil use = 375 g ai/ha (0.335 lb ai/A) total application rate,
7-day PHI)

Mango2	0.33

[375 g ai/ha]	7	8	0.01	0.04	0.04	0.03	0.03	0.01

Waxapple (Taiwan use = additional use pattern information is required,
30-day PHI)

Waxapple, paper-bagged fruit3	2.74

[3.07 kg ai/ha]	12	6	0.08	0.16	0.14	0.13	0.12	0.03

Waxapple, net-bagged fruit

	6	0.66	1.27	0.97	0.80	0.85	0.23

1  HAFT = Highest average field trial result.

2  Although mango fruits with stones removed were analyzed, consistent
with the food portion of mango fruits to be analyzed according to PAM
Vol. I, Section 102, the residue results were calculated and reported as
difenoconazole in/on whole fruit.  Difenoconazole residues in/on whole
fruits were calculated by dividing the weight of the whole fruit by the
weight of the fruit without the stone and then multiplying by the
residue value found in/on the fruit without the stone.

3  Fruits were bagged after the second of eight applications.

Mango

Four mango trials were conducted in the northeast region of Brazil
during the 2003 growing season.  At each test location, three foliar
applications of a 250 g/L EC (Score®) formulation of difenoconazole
were made to established and fruit-bearing mango trees at a target rate
of 125 g ai/ha/application (0.11 lb ai/A/application), with a 14-day
retreatment interval, for a total rate of 375 g ai/ha (0.33 lb ai/A). 
The single and total application rates are 1x the label rates. 
Applications were made using ground equipment in 1,000 L/ha (107 gal/A)
spray volumes; the use of an adjuvant was not reported.  Mature mango
fruits were harvested 7 days after the last application (DALA). 
Additional samples were collected from two trials at 0, 3, 5, and 9 DALA
to generate residue decline data. 

Samples of mango fruits with stones removed were analyzed for residues
of difenoconazole using a high performance liquid chromatography method
with tandem mass spectrometry detection (LC/MS/MS Method POPIT
MET.033.Rev03).  The method is adequate for data collection based on
acceptable concurrent method recoveries.  The fortification levels used
in concurrent method validation adequately bracketed the expected
residues in/on treated mango.  The validated LOQ was 0.01 ppm.  The
mango samples were not analyzed for triazole metabolites.

Although mango fruits with stones removed were analyzed, consistent with
the food portion of mango fruits to be analyzed according to PAM Vol. I,
Section 102, the residue results were calculated and reported as
difenoconazole in/on whole fruit.  Difenoconazole residues in/on whole
fruits were calculated by dividing the weight of the whole fruit by the
weight of the fruit without the stone and then multiplying by the
residue value found in/on the fruit without the stone.  Only the
calculated whole fruit results were provided in the study submission. 
This calculation will overestimate the residues of difenoconazole in/on
mango fruits with stones removed; however, based on the single example
calculation provided in the study submission, the reviewer estimates
that mango stones are not likely to exceed 20% by weight of the whole
fruit, and given the low residue levels found, the overestimation is not
considered significant in this case.

 

The collected samples were stored frozen prior to residue analysis;
storage durations are reported in Table 4.  Adequate storage stability
data are available on a wide variety of raw agricultural crop
commodities which support the mango studies.

The results indicate that residues of difenoconazole ranged 0.01-0.04
ppm in/on mango fruits harvested 7 days following the last of three
foliar applications of Score® at a total rate of 375 g ai/ha (0.33 lb
ai/A).  The decline data indicate that residues generally appear to
decline in mango with later sampling intervals; residues were 0.06-0.09
ppm at the 0-day PHI and 0.01-0.04 ppm at the 9-day PHI.

Conclusions.  The submitted field trial studies are adequate and reflect
the use pattern for mango in Brazil.  An acceptable method was used for
the determination of residues of difenoconazole, and the sample storage
conditions and durations for difenoconazole analyses are supported by
adequate storage stability data.  The submitted field trial data will
support the proposed import tolerance of 0.09 ppm for mango; the
tolerance calculation is presented in Appendix I.

The requirements for geographic representation of crop field trials for
import tolerances are specified in the NAFTA Guidance Document on Data
Requirements for Tolerances on Imported Commodities in the United States
and Canada (December 2005).  Using data obtained from Fruit and Tree
Nuts Situation and Outlook Yearbook (USDA, 2008) and averaging data from
the past 5 years (crop seasons 2003-2007), mango imports account for
>75% of the total U.S. consumption.  Imports from Brazil account for
9.4% of all mango imports; Mexico accounts for 62% of all imported
mango.  Because the maximum percent of the diet for mango is <0.05%,
three trials would be required for an import tolerance.  The four field
trials conducted in Brazil are adequate

.  

Waxapple (also known as Wax jambu)

Three waxapple trials were conducted in Taiwan during the 2006-2007
growing season.  Thiamethoxam, azoxystrobin, and difenoconazole were
simultaneously applied in these trials either as co-active ingredients
or as tank mixes.  Although residue data were provided for azoxystrobin
and thiamethoxam, this document only addresses the residue data for
difenoconazole.

At each test location, established and fruit-bearing waxapple trees were
treated with eight foliar applications of a 125 g/L suspension
concentrate (Amistar Top 325 SC) formulation of difenoconazole at a
target rate of 0.39 kg ai/ha/application (0.34 lb ai/A/application),
with 6- to 8-day retreatment intervals, for a total rate of 3.07 kg
ai/ha (2.74 lb ai/A).  Applications were made using ground equipment in
2,000 L/ha (214 gal/A) spray volumes, without an adjuvant.  Waxapple
fruit samples were harvested 12 days after the last (8th) application.  

	

The study was designed to allow collections of “bagged” vs.
“unbagged” fruit samples.  However, “unbagged” waxapple fruit
was covered with a net bag which allowed chemical penetration but
prevented fruit fly damage, and “bagged” fruits were covered with a
paper bag 1-2 days after the second application.  Hence treated samples
were either net-bagged or paper-bagged waxapple fruits.  Note:  The plot
histories noted that the trees were normally treated with imidacloprid
and methomyl for insect control so it is not certain that the use of net
bags to prevent fruit fly damage is a consistent agricultural practice
for waxapple grown in Taiwan.  

The harvested waxapple samples were analyzed for residues of
difenoconazole using a high performance liquid chromatography method
with tandem mass spectrometry detection (LC/MS/MS Method REM 147.08). 
The method was adequate for data collection based on acceptable
concurrent method recoveries.  The fortification levels used in
concurrent method validation adequately bracketed (within an order of
magnitude) the expected residues in/on treated waxapple.  The validated
LOQ was 0.01 ppm.  The waxapple samples were not analyzed for triazole
metabolites.

 

The collected samples were stored frozen prior to residue analysis;
storage durations are reported in Table 4.  Adequate storage stability
data are available on a wide variety of raw agricultural crop
commodities which support the waxapple studies.

The results indicate that residues of difenoconazole ranged 0.66-1.27
ppm in/on net-bagged samples and 0.08-0.16 ppm in/on paper-bagged
samples of waxapples harvested 12 days following the last of eight
foliar applications of Amistar Top 325 SC at a total rate of 2.74 lb
ai/A.  No residue decline data were provided to determine residue levels
that may occur at various preharvest intervals.

Conclusions.  HED is unable to assess the adequacy of the submitted
field trial data for waxapple because the use directions have not been
fully elucidated.  Syngenta is required to provide label use information
as detailed under ‘Directions for Use’ section.  Assuming that the
use directions for waxapple in Taiwan will match the submitted field
trial data, HED tentatively recommends for the proposed import tolerance
of 1.5 ppm for waxapple.  The tolerance calculation using residues in
net-bagged waxapple is presented in Appendix I.

The requirements for geographic representation of crop field trials for
import tolerances on waxapple are not included in the NAFTA Guidance
Document on Data Requirements for Tolerances on Imported Commodities in
the United States and Canada (December 2005).  However, it can be
assumed that >75% of waxapple in the U.S. is imported and that the
maximum percent of the diet for waxapple is likely <0.05%; therefore,
the three trials conducted in Taiwan would be considered acceptable to
support an import tolerance.

860.1520 Processed Food and Feed

HED does not require residue data for any processed commodities
associated with mango or waxapple.  Therefore, data requirements for
processed food and feed are not relevant to this tolerance petition.

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

Analytical standards for difenoconazole (expiration 7/1/2010) and its
metabolite CGA-205375 (expiration 4/30/2010) are currently available in
the EPA National Pesticide Standards Repository (personal communication
with Dallas Wright, ACB, 6/23/09).  

860.1850 and 860.1900 Confined and Field Accumulation in Rotational
Crops

Mango and waxapple are not typically rotated, and rotational crop
restrictions are not relevant for foreign uses, therefore, no data
pertaining to rotational crops are required to support this petition.

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 tolerance
expression proposed by Syngenta is appropriate.  

The tolerances proposed by Syngenta are listed in Table 6, along with
the tolerance levels recommended by HED and corrected commodity
definitions.

The data for waxapple could not be evaluated against the use pattern,
because an insufficient Section B was provided for the Taiwan label. 
However, the available data will support the proposed tolerances for
waxapple at 1.5 ppm.  The tolerance spreadsheet in the Agency’s
Guidance for Setting Pesticide Tolerances Based on Field Trial Data was
utilized for determining appropriate tolerance levels for waxapple (see
Appendix I).  No Codex, Canadian, and Mexican MRLs have been established
for residues of difenoconazole per se in/on waxapple.

Adequate data reflecting the use pattern in Brazil are available for
mango.  These field trial data were entered into the tolerance
spreadsheet in accordance with the Agency’s Guidance for Setting
Pesticide Tolerances Based on Field Trial Data to determine the
appropriate tolerance level for mango (see Appendix I), which supported
the proposed tolerance for mango at 0.09 ppm.  A Codex MRL for residues
of difenoconazole per se has been established at 0.07 ppm for mango;
Canadian and Mexican MRLs have been established for difenoconazole;
however, no MRLs have been established for mango.  The Codex MRL for
residues of difenoconazole per se for mango is based on the same dataset
considered herein; however, the reviewer has been advised (personal
communication with S. Funk OPP/HED/RAB3 via email dated 11/04/2009) that
the Joint FAO/WHO Meeting on Pesticide Residues (JMPR) uses field trial
data in the NAFTA calculator and may interpret the outcomes differently
than HED.  JMPR does not accept the independence of samples from the
same location; hence, JMPR used the following four data points from the
four 2003 mango field trials conducted in Brazil in the NAFTA
calculator:  0.025 ppm, 0.025 ppm, 0.035 ppm, and 0.04 ppm .  From these
data, the NAFTA calculator gives 0.06 ppm, which JMPR did not accept. 
JMPR typically goes higher than the NAFTA calculator where there are few
samples and so established the 0.07 ppm MRL for mango.  Harmonization
with the established Codex MRL of 0.07 ppm is recommended for residues
of difenoconazole in/on mango.

The proposed tolerances should be revised to reflect the recommended
tolerance levels and correct commodity definitions as specified in Table
6.

Table 6.    Tolerance Summary for Difenoconazole.

Commodity	Proposed Tolerance (ppm)	Recommended Tolerance

(ppm)	Comments; 

Correct Commodity Definition

Mango, fruit	0.09	0.07	Mango

Waxapple, fruit	1.5	1.5	Wax  jambu



References

DP#s:	172067 and 178394

Subject:	  SEQ CHAPTER \h \r 1 PP#2E4051.  CGA-169374 (Difenoconazole,
Dividend®) in Imported Wheat, Barley, and Rye Grain.  First Food Use. 
CBTS#s 9029, 9895.

From:	R. Lascola

To:	J. Stone/C. Giles-Parker

Dated:	10/26/92

MRIDs:	42090001-42090004, 42090032-42090059, and 42303901

DP#s:	203644 and 203645

Subject:	PP#2F4107.  Difenoconazole (Dividend) in/on Wheat, and Animal
RACs.  Amendment of 5/18/94.  CBTS# 13771 & 13772.

From:	G. Kramer

To:	C. Giles-Parker/J. Stone and A. Kocialski

Dated:	6/16/94

MRIDs:	43236501-43236503

DP#:	None

Subject:	HED Metabolism Committee Meeting of 7/14/94.  PP#2F4107 &
PP#2E4051.  Difenoconazole (Dividend).

From:	G. Kramer

To:	HED Metabolism Committee

Dated:	7/22/94

MRIDs:	None

DP#:	327788

Subject:	Triazole-Based Metabolites:  Guidance On Residue Chemistry Data
Submissions.

From:	M. Doherty

To:	  SEQ CHAPTER \h \r 1 C. Giles-Parker

Date:	4/25/06

MRIDs:	None

DP#:	340379

Subject:	PP#6F7115; Difenoconazole.  Petition for Establishment of
Tolerances on Fruiting Vegetables, Pome Fruit, Sugar Beets, Tuberous and
Corm Vegetables, and Imported Papaya.  Summary of Analytical Chemistry
and Residue Data.

From:	W. Wassell/M. Sahafeyan

To:	D. Rosenblatt/S. Brothers

Dated:	8/9/07

MRIDs:	46950215-46950237

DP#:	371613

Subject:	Difenoconazole.  Acute and Chronic Aggregate Dietary Exposure
and Risk Assessments for the Section 3 Registration Request for Mango
and Wax Apple.

From:	T. Morton

To:	Yan Donovan and Tony Kish

Dated:	1/21/10

MRIDs:	None

  SEQ CHAPTER \h \r 1 Attachments:  

International Residue Limit Status sheet

Appendix I - Tolerance Assessment Calculations

Template Version September 2005



INTERNATIONAL RESIDUE LIMIT STATUS

Chemical Name:  
1-[2-[2-chloro-4-(4-chlorophenoxy)phenyl]-4-methyl-1,3-dioxolan-2-ylmeth
yl]-1H-1,2,4-triazole	Common Name:  Difenoconazole

	X  Proposed tolerances

□  Reevaluated tolerance

□  Other	Date:  10/14/09

Codex Status (Maximum Residue Limits)	U. S. Tolerances

□ No Codex proposal step 6 or above

□ No Codex proposal step 6 or above for the crops requested	Petition
Number:  PP#9E7573

DP#:  366507

Other Identifier:  Decision No. 413927

Residue definition (step 8/CXL): Difenoconazole	Reviewer/Branch:  B.
Cropp-Kohlligian/RAB4

	Residue definition:  Difenoconazole per se

Crop (s)	MRL (mg/kg)	Crop(s) 	Tolerance (ppm)

Mango		0.07	Mango, fruit	0.09



Waxapple, fruit	1.5





















Limits for Canada	Limits for Mexico

□  No Limits

X No Limits for the crops requested	□ No Limits

X No Limits for the crops requested

Residue definition:  Difenoconazole
[1-[2-[-4-(4-chlorophenoxy)-2-chlorophenyl]-4-methyl-1,3-dioxolan-2-ylme
thyl]-1H-1,2,4-triazole]	Residue definition:  Difenoconazole.  Mexico
defers to Codex MRLs or US tolerances for its export purposes.

Crop(s)	MRL (mg/kg)	Crop(s)	MRL (mg/kg)











Notes/Special Instructions:	 S. Funk, 10/14/2009





Appendix I.  Tolerance Assessment Calculations.

mall (≤15 samples) and reasonably lognormal, the upper bound estimate
of the 95th percentile based on the median residue value was compared to
the minimum of the 95% UCL on the 95th percentile and the point estimate
of the 99th percentile, and the minimum value was selected as the
tolerance value.  The rounding procedures specified in the SOP were also
used.

Mango

The dataset used to establish a tolerance for difenoconazole on mango
consisted of field trial data representing application rates of 0.335 lb
ai/A (3 applications at 0.112 lb ai/A/application) with a 7-day PHI. 
The field trial application rates and PHIs are within 25% of the maximum
label application rate and minimum label PHI, respectively.  The residue
values that were entered into the tolerance spreadsheet are provided in
Table I-1.

All field trial sample results for difenoconazole in/on mango were at or
above the LLMV (LLMV = 0.01 ppm).  The mango dataset was small (8
samples).  Visual inspection of the lognormal probability plot (Figure
I-1) and the results from the approximate Shapiro-Francia test statistic
(Figure I-2) indicated that the mango dataset was reasonably lognormal. 


Using the tolerance spreadsheet, the recommended tolerance is 0.09 ppm
for mango.

Table I-1.	Residue data used to calculate tolerance for residues of
difenoconazole on mango.

Regulator:	EPA

Chemical:	Difenoconazole

Crop:	Mango

PHI:	7 days

App. Rate:	0.335 lb ai/A

Submitter:	Syngenta Crop Protection, Inc.

MRID Citation:	MRID 47760602

	Residues of Difenoconazole (ppm)

	0.02

	0.03

	0.01

	0.02

	0.04

	0.04

	0.03

	0.04



Figure I-1.  Lognormal probability plot of difenoconazole field trial
data for mango.

Figure I-2.  Tolerance spreadsheet summary of difenoconazole field trial
data for mango.

Waxapple

The dataset used to establish a tolerance for difenoconazole on waxapple
consisted of field trial data representing application rates of 2.74 lb
ai/A (8 applications at 0.34 lb ai/A/application) with a 12-day PHI. 
The field trial application rates could not be compared to the maximum
label application (insufficient Section B for the Taiwan label), and the
PHIs were much lower (60%) than the reported minimum label PHI.  The
residue values for net-bagged fruit that were entered into the tolerance
spreadsheet are provided in Table I-2.

All field trial sample results for difenoconazole in/on waxapple were
above the LLMV (LLMV = 0.01 ppm).  The waxapple dataset was small (6
samples).  Visual inspection of the lognormal probability plot (Figure
I-3) and the results from the approximate Shapiro-Francia test statistic
(Figure I-4) indicated that the waxapple dataset was reasonably
lognormal.  

Using the tolerance spreadsheet, the recommended tolerance is 1.5 ppm
for waxapple.

Table I-2.	Residue data used to calculate tolerance for residues of
difenoconazole on waxapple.

Regulator:	EPA

Chemical:	Difenoconazole

Crop:	Waxapple (net-bagged)

PHI:	12 days

App. Rate:	2.74 lb ai/A

Submitter:	Syngenta Crop Protection, Inc.

MRID Citation:	MRID 47760601

	Residues of Difenoconazole (ppm)

	0.75

	0.85

	0.66

	1.27

	0.67

	0.88



Figure I-3.  Lognormal probability plot of difenoconazole field trial
data for waxapple.

 

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Page   PAGE  1  of   NUMPAGES  23 

Difenoconazole	Summary of Analytical Chemistry and Residue Data	DP#: 
366507

Regulator:

EPA

Chemical:

Difenoconazole

Crop:

Waxapple (net-bagged)

PHI:

12 days

App. Rate:

2.74 lb ai/A

Submitter:

Syngenta

n:

6

min:

0.66

max:

1.27

median:

0.80

average:

0.85

95th Percentile

99th Percentile

99.9th Percentile

1.3

1.4

1.6

(1.7)

(2.0)

(--)

1.3

1.5

1.8

(2.5)

(3.0)

(--)

2.0

1.6

7.0

0.8783

p-value > 0.05 : Do not reject lognormality assumption

Approximate 

Shapiro-Francia 

Normality Test 

EU Method I

Normal

UCLMedian95th

95/99 Rule

EU Method II

Distribution-Free

Mean+3SD

Lognormal Probability Plot

99.9

99

98

95

90

80

70

50

30

20

10

5

2

1

0.1

2.0000

1.0000

0.5000

0.5000

0.5000

0.5000

0.5000

0.5000

0.5000

0.5000

0.5000

0.5000

0.5000

0.5000

0.5000

0.5000

y = 0.2478x - 0.1925

R

2

 = 0.8783

Percentiles

Concentrations

EPA Difenoconazole Waxapple (net-bagged) 12 days 2.74 lb ai/A Syngenta

