UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D,C, 20460

DEC 02 20 10

OFfiCE OF CHE MICAL SAFETY

AND POLLUTIO N PREVENTION

MEMORANDUM

SUBJECT:

FROM:

THRU:

TO:

BEAD Chemical Profile for Registration Review: Chlorimuron-ethyl (128901)

Sunil Ratnayake, Biologist /\ t 0

Biological Analysis Branch l __ (\~~

Katherine Stebbins, Biologist ~~ \

Science Inform ation and Analysis Branch

John Faulkner, Economist (L~M c--r _..f h A/I /1/\

Economic Analysis Branch "~I ::JTAJ.AA'(/YW,

Biological and Economic Analysis Divisio n (7503P)

Bi

Arnet

ological An

Jones, C

alysis

hief

BranchL~

1~. U rTimothy Kiely, Chief 9l V

Economic Analysis Branch \;,--

Biological and Economic Analyst Division.50 P)

1 J . Diann Sims, Chief

Science Information and Analysis Branch

Wilhelmena Livingston, Chemical Review Manager

Pesticide Reevaluation Division (7508P)

Peer Review Panel date: May 19,2010

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 for this paper consists ofthe team of EPA staff currently evaluating the

registration status of Chlorimuron-ethyl and eventually the general public. This document build s

upon the data already provided in the "Usage and Label Use Data Packages" that are also

provided to Registration Review teams by BEAD.
Chlorimuron-ethyl belongs to the sulfonylurea cla ss of herbicide that inhibits the enzyme

acetolactate synthase (ALS). It is registered for use on soybeans, field com, peanuts and noncrop areas such as fencerows and road sides. Chlorimuron-ethy l controls grasses and broadleaf

weed s. In general, for a season-long control of grasses and broadleaf weed s, 1-3 oz/acre planned

sequential application is needed. For agricultural usage, soybean is the predominant use site.

Chlorimuron-ethyl may be appli ed to soybean crop at pre-plant, pre -emergence, post-emergence,

or postharvest stages as a band treatment, broadcast, ground spray, low volume spray, or soil

incorporated treatment. The pre-harvest intervals are 60 days for soybeans and 45 days for

peanuts. Chlorimuron-ethyl may also be appli ed to non-crop land at the foliar stage as a

broadcast treatment.

USE SITES

Agri cultural Use Sites

Chlorimuron-ethyl is labe led for use on soybeans, peanuts, and field corn. There is also a special

local needs (SLN) registration for cranberries (WA).

No n-Agricultural Use Sites

Chlorimuron-ethy l may be applied to non-crop areas such as: fencerows, roadside s, equipment

storage areas, and other similar areas.

COMMON FORMULATIONS AND APPLICATION METHODS'

The only labeled formulation is dry flowable.

According to the labels, this AI may be applied with aerial or ground equipment. The type of

appli cations include: broadcast, band, soil incorporated, low volume, burn-down, and

conservation tillage treatments. The type of equipment that may be used includes: ground,

aircraft, sprayer (including boom and band sprayers), low pressure/low volume sprayers, and soil

incorporation equipment.

IThis is a summaryof the application methods. Please refer to the PRDAppendix A: Food/Feed & Non-Food/Non-Feed Uses Considered in

Registration Review WorkPlanning fOT a comprehensive list

USAGE

Agricultural Usage

Based on pri vate market research data from 1998-2008, the annual agricultural usage averaged

approximately 90,000 pounds for nearly 6 million acres (GfK Kynetec, 1998-2008). The

predominant market is for soybeans, which accounts for 99% ofthe total pounds appli ed (GfK

Kynetec, 1998-2008). (Figure 1)

Figure 1. Chlorimuron-ethyl Usage on Agricultural Sites

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Pounds AI Ap pli9d

• Soybeans

• l'eanlJls

Cc>""

Source: OfK Kynetec, 1998-2008

The states with the most agricultural usage in tenus of pounds AI applied are Illinois, Ohio,

Indiana, Missouri, and Iowa. (Figure 2) These states were also the top in tenus of the total acres

treated.

Figure 2. Top States for Chlorimuron-ethyl Usage on Agricultural Sites

Pounds AI Applied

"'''''''' ,,.

Source: GfK Kynetec, 1998-2008

Non-Agricultural Usage

Usage data is not available for the non-crop sites.

BIOLOGICAL ASPECTS RELEVANT TO CHLORIMURON-ETHYL

The mode of action ofthis herbicide is inhibition ofthe enzyme acetolactase synthase (ALS).

Since the introduction of sulfonylureas in 1980s, ALS inhibitors such as chlorimuron-ethyl were

widely used in crop production (Patzoldt et al, 2001). Low rate, low mammalian toxicity,

flexible application timing, and broad spectrum of weed control were the advantages of using

these herbicides. However, wide use ofALS inhibitors contributed to the development of

resistance bio-types to these herbicides group. Resistant weed species include: common

ragweeds Ambrosia artemisiifolia, giant ragweeds (Ambrosia trifida), prickly lettuce (/ectuca

serriola), kochia (Kochia scoparia), smooth pigweed (Amaranthus hybridus), Livid amaranth

(Amaranthus lividus), Redstem (Ammania auriculata) (Herbicide Resistant Weeds, 2010).

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USE TRENDS

Figure 4. Chlorimuron Usage on Soybeans

Soybeans

] 200,000

"-c

;;

£

o

1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008

Year

Source: GfK Kynetec, 1998-2008

The development of resistant weed biotypes, the introduction of Roundup Ready soybeans, and

the cost effectiveness of Roundup Ready technology may have contributed to the decrease in

chlorimuron-ethyl usage since 1998 (Carpenter & Gianessi, 1999). However, the trend data

(Figure 4) has not been fully analyzed so there may be other factors contributing to the patterns

In usage.

HISTORY OF BEAD ASSESSMENTS FOR CHLORIMURON·ETHYL

There were no past BEAD assessments of this chemical in the BEAD Official Records

DATA NEEDS RELEVANT TO BEAD'S FUTURE WORK ON CHLORIMURONETHYL

• Usage data (such as the amount c f a.i. used and the acres treated) for the non-crop areas

such as fencerows and road sides.

• Usage data is needed for cranberries.

REFERENCES

Carpenter J. & Gianess i L. (1999). Herbicide tolerant soybeans: Why growers are adopting

Roundup Ready varieties. AgBioForum, 2(2), 65-72. http ://wv...'W.agbioforum.org/v2n2/v2n2a02-

carpenter.htm

GfK Kynetec. (1998- 2008). Proprietary data.

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Patzoldt, W. L., Tranel, P. J., Alexander, P L., and P. R.Schmitzer . 2001. A common ragweed

population resistant to cloransulam-methyl. Weed Sci. Vo1.49, No.4, pp. 485-490.

Herbicide Resistant Weeds. 2010. http: //www.weedscience .orgisummarv/MOASummary.asp

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