UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON D.C , 20460

MEMORANDUM

MAY 1 4 2010 OFFICE OF

CHEMICAL SAFETY AND

POLLUTION PREVENTION

SUBJECT:

FROM :

TIIRU:

TO:

Response to a Comment Regarding "Usc and Usage lnfonnation for

Azoxystrobin", a Part of Azoxystrobin Registration Review (Docket No. EPAHQ-OPP-2009-0835) (DP365674)

r.: Leonard Younnan, Plant Pathologist (I

Biological Anal ysis Branch

Arnet Jones, Chief

Biological Analysis Branch

Biological and Economic Analysis Division

Kelly Ballard, Chemical Review Manager

Pesticide Reevaluation Division (7508P)

Product Review Panel: May 5, 2010

As part ofthe azoxystrobin registration review (Docket No. EPA-HQ-OPP-2009-0835) BEAD

provided "Use and Usage Information for Azoxystrobin" (Ste bbins and Younnan, 2009) to the

Pesticide Reevaluation Division. The memorandum included information concerning the

fungicide azoxystrobin such as usage data, use sites, target diseases, formulations, application

methods, and a discussion of "plant health" issues related to azoxystrobin. The plant health issue

refers to uses for improving yields and certain plant health characteristics in the absence of

fungal disease. Dr. Ulrich Gisi, a professor at the Unive rsity of Basel and a consultant for

Syngenta Corp. submitted a comment regarding the "Plant Health Properties" section of the "Use

and Usage" memorandum.

BACKGROUND

Syngenta's azoxystrobin product labels do not have plant health claims. Another registrant,

BASF, obtained a supplemental label for a related fungicide Headline<g:·(pyraclostrobin), which

states that the fungic ide can be used for " improved plant health ." in addition to trad itional plant

disease management. The label lists several characteristics that the fungicide can provide
includ ing improved straw strength in wheat and com, increased fruit size in citrus, improved

tolerance to frost in mint and sugar beet, and improved quality in potato and soybean.

After the approval ofthe supplemental label for Headline" , 46 state extension plant pathologists

wrote a letter to the Agency (EPA, 2009a). The letter voiced concerns that the approval of a

label making plant health claims was unwise since it would encourage the use of a fungicide for

purposes separate from plant disease managem ent uses, for which it was originally registered.

There was a concern that products with similar active ingredients (including azoxystrobin) would

also be given supplemental labels and this use would interfere with IPM pest management

strategies.

The plant pathologists stated that "the use of a fungicide for growth regulating properties is a

serious blow to lPM principles and almost guarantees earlier selection for resistance in certain

pathogen populations to a valuable class of fungicides." They also stated that data to support

claims that fungicides can enhance such characteristics as seed quality in soybean has not been

properly substantiated.

In addition to the resistance issues the plant pathologists stated that "there are also non-target

effects of fungicides (including strobilurins [e.g., pyraclostrobin , azoxystrobinJ) to consider such

as suppression of beneficial fungi in many cropping systems."

COMMENT

In his comme nt, Dr. Gisi noted that the letter by the plant pathologists referred to Headline®, but

could apply generally to all Qol (quinine outside inhibitor) fungicides (also called strobilurin

fungicides), including azoxystrobin. Dr. Gisi commented on the situation for com and potential

resistance to azoxystrobin by comm on com pathogens and concluded that:

"Ifthe number ofazoxystrobin applications is strictly limited to one to maximum 2 per

season and the treatments are made before a potential outbreak of epidemics occurs, the

use of QoIs as growth regulating compounds in com can be recommended without

running into unacceptable resistance risks. If additional QoI applications would be

needed for disease control in com, a new [resistance] risk assessment should be made. In

addition, sensitivity monitoring programm es for important com pathogens may be

implemented in area of intensive Qo I usage to follow any chan ges in sensitivity of

pathogen populations.

As to the plant pathologists concern of non-target effects, Dr. Gisi stated that "There are no data

available on QoI activity against ' beneficial fungi' ; therefore, no fungicide resistance risk

assessment can be made."

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AGENCY RESPONSE

Dr. Gisi believes that the incidence of resistance by com pathogens to azoxy strobi n would be

low due to the nature ofthe major com pathogens and the typical one or two fungicide

applications on com. While some pathogens and crop systems might have a reduced incidence

of developing resistance to azoxystrobin, overall this and other Qo I fungicides are considered

"high risk" for deve lopment of resistance by some pathogens (FRAC, 2009). The Agency agrees

with Dr. Gisi that high rates ofresistance might be expected (and have been observed) with some

pathogens or "crops such as grapes and potatoes with up to four and eight treatments,

respectively," It is not only the number of applications that might affect the incidence of

resistance, but the combination ofrepeated exposure to the pesticide and genetic makeup of a

pathogen population. As described in the "Use and Usage" memorandum (Stebbins and

Yourman. 2009), resistance to azox ystrobi n and other QoI fungicides has developed by least 32

pathogen species that are important on several crops (FRAC, 2008). The resistance issue speaks

to the concerns of the state plant pathol ogists and the reason that the Agency is currently looking

into the issue ofthe use of fungicides for non-disease mana gement purposes.

Dr. Gisi stated that for com if more than one or two applications were necessary , an assessment

could be conducted to determine the likelihood ofresistance development and pathogen

sensitivity programs could be implemented. However, it is unclear who would conduct the

assessments and what would be the implications for subsequent pesticide use on a crop if a high

probability of resistance were identified.

There is evolving interest in the issue of the use of pesticides for non-pest management purposes.

Issues such as pesticide effects on benefi cial organisms require field data that currently are

lacking. The Agency is also interested in the impl ications of possible increases in pesticide use

for purposes other than pest management. As the "Use and Usage" memorandum noted, EPA's

Office of Pesticide Programs has recentl y formed an internal resistance management workgroup

to review this issue and to develop a strategic work plan to address emerging areas of concern

(EPA, 2009b). This workgroup will examine field data supplied by various sources, including

the registrant and plant pathologists who signed the 2009 letter (EPA, 2009a). The Agency

appreciates comments on this matter, which will be considered in its regulatory decisions.

CITATIONS

EPA. 2009a. Letter from Universities Regarding the Strobilurin, Pyraclostrobin {Headline)

Supplemental Label. February 13, 2009 (Addendum February 20, 2009).

http://www.epa.gov/pesticides/regulatinglhead line-Ietter.pdf

EPA. 2009b . EPA Response to Letter from Universities Regarding the Strobilurin,

Pyraclostrobin (Headline) Supplemental Label. June 4, 2009 .

http://\\,,",,w .epa.gov/pesticides/regulatinglheadline-response.pdf

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FRAC (Fungicide Resistance Action Committee). 2008 . List of pathogens with field resistance

towards QoI fungicides. (updated 02/12/08). Fungicide Resistance Action Committee.

http://Yiww,[rac.info/frac/meeting/2008IPathogens with field resistance toward s 2008 .pdf

FRAC (Fungicide Resistance Action Committee). 2009 . Qol Working Grou p-2009 Minutes.

December 3. 2009 . http ://\\'ww.frac.info/fraclworkIFRAC 0 01 Minut es2009Final.pdf

Stebbins. K. and Younnan, L. 2009 . Use and Usage Information for Azoxystrobin. BEAD

document, October 8, 2009 . Docket No. EPA-HQ-OPP -2009-0835 .

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