UNITED STATES ENVIRONMENTAL PROTECTION AGENCY WASHINGTON, D

.C

. 20460 

## SEP 12 2011

MEMORANDUM
SUBJECT:
FROM:

THRU: BEAD Chemical Profile for Registration Review: Thiobencarb (108401) Sunil Ratnayake, Biologist /\.
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# ~ Biological Analysis Branch

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Jihad Alsadek, Economist 

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# l. Science Information and Analysis Branch

Diann Sims, Chief Science Information and Analysis Branch Timothy Kiely, Chief

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# ~ Economic Analysis Branch Biological and Economic Analysi ivision (7503 TO: Kelly Ballard, Chemical Review Manager Risk Management and Implementation Branch 1 Pesticide Re-evaluation Division (7508P)
Product Review Panel date: June 8, 2011 INTRODUCTION OFFICE OF CHEMICAL SAFETY AND POLLUTION PREVENTION

The purpose ofthis document is to convey usage information and a broad overview ofthe pestmanagement roles ofpesticides that are beginning to undergo registration review. The anticipated audience consists ofthe team ofEPA staffcurrently evaluating the registration status ofthiobencarb, and eventually the general public. 1evaluating the registration status ofThiobencarb, and eventually the general public. This document builds uponthe data already provided in the "Usage and Label Use Data Packages" that are also provided to Registration Review teams by BEAD. The document is based on information and data available to BEAD as ofJune 08, 2011. Thiobencarb belongs to the thiocarbamate herbicide family and it is a systemic herbicide used for control ofmany grasses arid some broadleafweeds inrice production. Thiobencarb is applied as pre-emergence and post-emergence treatments to control weeds inrice producing fields. When applied, thiobencarb is absorbed byroots and shoots and translocated upward to other parts ofthe weed plants. Major weeds inrice production controlled by thiobencarb are: bamyardgrass (Echinochloa spp), sprangletop (Leptochloa spp.), crabgrass (Digitaria spp.), fall panicum (Panicum dichotomiflorum), dayflower (Commelina communis), and eclipta (EcliptaAlba). Thiobencarb is generally tank mixed withpropanil to enhance the post-emergence weed control activity. 

### USE SITES Agricultural Use Sites The only use ofthiobencarb is inrice production as foliar and soil treatments. Non-Agricultural Use Sites There are no non-agricultural uses. COMMON FORMULATIONS AND APPLICATION METHODS Thiobencarb is available in granular and emulsifiable concentrate formulations. Application methods ofthis herbicide are using tractor mounted sprayers and aerial applications. USAGE Agricultural Based on private market pesticide usage data from 1998-2010, the annual total agricultural usage averaged approximately 700,000 pounds active ingredient for 243,000 treated acres for an average**applicatio~** rate of3.0 lbs. a.i. per acre. Thiobencarb is used only onrice (100%). On average, the states with the most agricultural usage in terms ofpounds a.i. applied are California (66%), Arkansas (15%), and Texas (9%) (Proprietary Data, 1998-2010). Non-Agricultural There are no non-agricultural uses ofthiobencarb.

2USE TRENDS Figure 1provides the use ofthiobencarb on rice in terms ofpounds applied. The use ofthiobencarb was highest in 1999 (1.5 million lbs.) and has been declining since then. The precise reason for the decline in usage is not clear, but it coincides with the development ofbarnyardgrass biotypes resistant to thiocarbamates reported in the year 2000 (WSSA, 2011). Figure 1. Thiobencarb Use on Rice

1,600,000 -r----------------------'----

PoundsA.I.


### o 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 Years Proprietary Data, 1998-2010.
BIOLOGICAL ASPECTS RELEVANT TO THIOBENCARB The mode ofaction ofthiocarbamate group ofherbicides is inhibition oflipid synthesis inplant cells and tissues. The major observable biological symptom of this mode ofaction is discoloration and disintegration ofmeristematic tissue at and above the nodes, including nodes ofrhizomes (Publication ofCooperative Extension Service, Indiana Univ., 1996). According to the International Survey ofHerbicide Resistant Weeds, in the United States, wild oat 

### (Avenafatua), barnyardgrass 

### (Echinochloa crus-galli), early watergrass, 

### (Echinochloaphyllopogon), rigid ryegrass 

### (Lolium rigidum), and annual bluegrass 

### (Poa annua) have developed resistance to the mode ofaction ofthe thiocarbamate family ofherbicides (WSSA, 2011). HISTORY OF BEAD ASSESSMENTS FORTIDOBENCARB According to BEAD's Official Records, no assessments onthiobencarb have been conducted. The EPA Section 18 Action Database also indicates that no Section 18 requests have been submitted for the use ofthiobencarb (EPA, 2011).

3INFORMATIONTHAT MAY BE USEFUL FORBEAD'S FUTURE WORK ON THIOBENCARB BEAD specific Registration Review issues, as relevant, including BEAD data gaps needed for future assessments and BEAD work plan. Existing usage data are sufficient for current needs. REFERENCES: Environmental Protection Agency (EPA). 1997. Re-registration Eligibility Decision (RED). http://www.epa.gov/oppsrrdIIREDs/2665red.pdf. Environmental Protection Agency (EPA). 2011. EPA Section 18 Actions Database. Located at: http://cfpubl.epa.gov/oppref/sectionI8/search.cfm. 

### Herbicide Mode ofAction Summary. 1996. Publication ofCooperative Extension Service, Purdue University, West Lafayette, IN. http://www.extension.purdue.edulextmedialWSIWS-23-W.html. International Survey ofHerbicide Resistant Weeds. 2011. Weed Science Society ofAmerica. http://www.weedscience.orglIn.asp
. Proprietary Data, 1998-2010.

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