UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, D.C. 20460 

SEP 12 2011 

MEMORANDUM 

SUBJECT: 

FROM: 

THRU: 

BEAD Chemical Profile for Registration Review: Thiobencarb 

(108401) 

Biological 

Sunil Ratnayake, 

Analysis 

Biologist 

Branch ~ 

/\. 

'I"4J\ 

. t-L ~ 

Jihad Alsadek, Economist .r ~ It < If-: l. 

Science Information and Analysis Branch 

Diann Sims, Chief 

Science Information and Analysis Branch 

Timothy 

Economic Kiely, Analysis 

Chief 

Branch ~ M ~ 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 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 of thiobencarb, and eventually the general public. 

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evaluating the registration status of Thiobencarb, and eventually the general public. 

This document builds upon the 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 of June 08, 2011. 

Thiobencarb belongs to the thiocarbamate herbicide family and it is a systemic 

herbicide used for control of many grasses arid some broadleafweeds in rice 

production. Thiobencarb is applied as pre-emergence and post-emergence 

treatments to control weeds in rice producing fields. When applied, thiobencarb is 

absorbed by roots and shoots and translocated upward to other parts of the weed 

plants. Major weeds in rice production controlled by thiobencarb are: bamyardgrass 

(Echinochloa spp), sprangletop (Leptochloa spp.), crabgrass (Digitaria spp.), fall 

panicum (Panicum dichotomiflorum), dayflower (Commelina communis), and 

eclipta (Eclipta Alba). Thiobencarb is generally tank mixed with propanil to enhance 

the post-emergence weed control activity. 

USE SITES 

Agricultural Use Sites 

The only use of thiobencarb is in rice 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 of this 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 on rice (100%). 

On average, the states with the most agricultural usage in terms of pounds a.i. 

applied are California (66%), Arkansas (15%), and Texas (9%) 

(Proprietary Data, 1998-2010). 

Non-Agricultural 

There are no non-agricultural uses ofthiobencarb. 

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USE TRENDS 

Figure 1 provides the use ofthiobencarb on rice in terms of pounds 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 of barnyard grass 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 of action of thiocarbamate group of herbicides is inhibition of lipid 

synthesis in plant cells and tissues. The major observable biological symptom of 

this mode of action is discoloration and disintegration of meristematic tissue at and 

above the nodes, including nodes of rhizomes (Publication of Cooperative Extension 

Service, Indiana Univ., 1996). According to the International Survey of Herbicide 

Resistant Weeds, in the United States, wild oat (Avenafatua), barnyardgrass 

(Echinochloa crus-galli), early watergrass, (Echinochloa phyllopogon), rigid 

ryegrass (Lolium rigidum), and annual bluegrass (Poa annua) have developed 

resistance to the mode of action of the thiocarbamate family of herbicides (WSSA, 

2011). 

HISTORY OF BEAD ASSESSMENTS FOR TIDOBENCARB 

According to BEAD's Official Records, no assessments on thiobencarb have been 

conducted. The EPA Section 18 Action Database also indicates that no Section 18 

requests have been submitted for the use of thiobencarb (EPA, 2011). 

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INFORMATION THAT MAY BE USEFUL FOR BEAD'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://cfpub l.epa.gov/oppref/sectionI8/search.cfm. 

Herbicide Mode of Action Summary. 1996. Publication of Cooperative 

Extension Service, Purdue University, West Lafayette, IN. 

http://www .extension.purdue.edulextmedialWSIWS-23-W.html. 

International Survey of Herbicide Resistant Weeds. 20 11. Weed Science 

Society of America. http://www.weedscience.orglIn.asp. 

Proprietary Data, 1998-2010. 

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