UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, D.C. 20460 

NOV ro 20" 

OFFICE OF CHEMICAL SAFETY 

AND POLLUTION PREVENTION 

MEMORANDUM 

SUBJECT: 

FROM: 

THRU: 

TO: 

BEAD Chemical Profile for Registration Review: Diflufenzopyr (005108) and 

Diflufenzopyr-sodium (005107) 

Bill 

Biological 

Phillips, 

Analysis 

II, PhD, 

Branch 

AgrOnOmi~ ~ f / 

Sepehr Haddad, Environmental Protection Specialist h./;w-u Science Information and Analysis Branch 7 

Derek Berwald, Economist .G r 4 VI\: ~ Economic Analysis Branch ~ J. Biological and Economic Analysis Divlsion (7503P 

Arnet Jones, Chief 

Biological Analysis Branc 

Diann 

Science 

Sims, 

Information 

Chief ~ and Analysis Branch 

Timothy 

Economic 

Kiely, 

Analysis 

Chief 

Branch 95~ J . Biological and Economic AnalYSlS Division (7503P) 

Julia Stokes, Chemical Review Manager 

Risk Management and Implementation Branch ~ 

Pesticide Reevaluation Division (7508P) 

Product Review Panel date: October 26, 2010 

INTRODUCTION 

The purpose of this document is to convey usage information and a broad overview of the pest 

management roles of pesticides that are beginning to undergo registration review. The 

anticipated audience consists of the team of EPA staff currently evaluating the registration status 

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of diflufenzopyr and diflufenzopyr-sodium, and eventually the general public. This document 

builds upon the data already provided in the "V sage and Label V se Data Packages" that are also 

provided to Registration Review teams by BEAD. The document is based on infonnation and 

data available to BEAD as of October 2011. 

Diflufenzopyr-sodium is applied as a postemergence herbicide that controls annual and perennial 

broadleaf weeds as well as some grass species in agricultural and non-agricultural sites. 

The herbicide diflufenzopyr-sodium is a semicarbazone with the mechanism of action of 

inhibiting the transportation of the synthetic (e.g. herbicides and growth regulators) and the 

miturally occurring plant honnone auxin (e.g. indoleacetic acid). Weed control is achieved by 

causing the buildup of auxins at the growing points (shoots and roots) of plants. This chemical is 

classified as a group B herbicide by the Weed Science Society of America. 

Currently in the V.S. there have been no reports of resistant weed biotypes of any plant species. 

At this time there is no known mechanism in plants known to convey resistance to this herbicide. 

USE SITES 

Agricultural Vse Sites 

Diflufenzopyr-sodium is labeled for use on com (field, pop and sweet), wheat, cotton, soybeans, 

forage grasses, hay, rangeland, and non-crop areas. The only registration for diflufenzopyr is a 

technical registration. 

Non-Agricultural Vse Sites 

Diflufenzopyr-sodium is labeled for the following non-agricultural use sites: airports, rights-ofway, tank farms and fence rows. 

COMMON FORMULATIONS AND APPLICATION METHODS 

Diflufenzopyr-sodium is fonnulated as water dispensable granules or emulsifiable concentrate. 

It is applied as foliar, soil and seed treatment. . 

Application methods are broadcast (spray and banded) and aerial. 

USAGE 

Agricultural V sage 

Based on private market usage data from 2001-2010, usage averaged approximately 120,000 

pounds active ingredient (a.i.) for 3.2 million acres treated. Figure 1 presents diflufenzopyrsodium usage over this time period. The average a.i. rate was approxim~tely 0.04 pounds per 

acre during 2001-2006, and decreased to about 0.03 pounds per acre from 2007-2010. ~e crop 

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with the major use in terms of pounds a.i. applied and total area treated is com with close to 

100% of the total use; however, very minor use was reported on soybeans, cotton and sweet com 

during 2001-2010 (Proprietary Data, 2001-2010). 

FIGURE 1. Diflufenzo yr-sodium Usa e on Corn 

180,000 ,---------------------

o 

2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 

Source: Proprietary Data, 2001-2010 

KANSAS 

4% 

WISCONSIN 

4% 

OHIO 

4% 

5% 

7% 

Source: Proprietary Data, 2001-2010 

Years 

7% 

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As shown in Figure 1, the use on com peaked in 2002. From 2001 - 2010, an average of3.1 

million com acres were treated with diflufenzopyr-sodium; the amount applied on com over the 

same period averaged about 100,000 lbs. a.i. Although applied to a large acreage, that acreage is 

well under 5% of the com crop. It appears that use has been trending down, with a temporary 

reversal when com prices and acreage increased in 2007. 

Figure 2 presents the states with the most agricultural usage in terms of pounds a.i. applied. 

These are: Minnesota (15%), Illinois (14%), Iowa (12%) followed by North Dakota, Nebraska, 

and Indiana each at (7%), and South Dakota, Ohio, Wisconsin, and Kansas at 5% or less. The 

"other" category of states which comprise 21 % of the usage include Texas, Colorado, Michigan, 

Kentucky, and Missouri among other states. 

Non-Agricultural Usage 

U sage data are not available for the labeled non-agricultural use sites for diflufenzopyr-sodium. 

BIOLOGICAL ASPECTS RELEVANT TO DIFLUFENZOPYR-SODIUM 

Diflufenzopyr-sodium is usually sold in product mixtures with dicamba. This is due to the 

unique way that the two herbicides interact to result in the control of broad leaf and grass weed 

species. Because diflufenzopyr-sodium inhibits the transport of the naturally occurring plant 

hormone indoleacetic acid and the synthetic auxin-like plant hormone dicamba, these plant 

hormones become concentrated in plant shoots and roots. Weed control is achieved through this 

buildup of both natural and synthetic auxins at the plant's growing points (shoots and roots). As 

a result of this action, reduced rates of dicamba can be used to obtain the same weed control 

efficacy as the full rate. 

Currently in the U.S. there have been no reports of weed biotypes resistant to diflufenzopyrsodium. This is postulated to be because there is no known mechanism for resistance to this 

group of herbicides in plants. 

BEAD ASSESSMENTS FOR DIFLUFENZOPYR-SODIUM 

Although there have not been any BEAD assessments of diflufenzopyr-sodium in recent years, it 

appears that diflufenzopyr-sodium does not have particularly high benefits. It is applied to a 

relatively small share of the total com acreage, and use appears to have been trending down over 

time. 

INFORMATION THAT MAY BE USEFUL FOR BEAD'S FUTURE WORK 

BEAD will appreciate any information on uses where diflufenzopyr-sodium is particularly 

important or has few alternatives, or situations where the standard alternatives are unavailable. 

This data will assist analysts in characterizing any use of this herbicide that may be vital to a 

specific production system. 

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REFERENCES 

Proprietary Data, 2001-2010. 

Senseman, S.A. Herbicide Handbook, Ninth Edition. 2007. Weed Sci. Soc. Of America. 

Lawrence, Kansas 66044-8897 

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