UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, D.C. 20460 

SEP 26 2011 

OFFICE OF CHEMICAL SAFETY 

AND POLLUTION PREVENTION 

MEMORANDUM 

SUBJECT: 

FROM: 

THRU: 

TO: 

BEAD Chemical Profile for Registration Review: Tralkoxydim (121000) 

Sunil Ratnayake, Biologist ~.. L . 0 

Biological Analysis Branch l I"-w \ ~ 

Jihad Alsadek, Economist ,z::2:s~ 

Science Information and Analysis Branch ~ 

Andrew Lee, Economist ~ Ct\- \Iv\... 

Economic Analysis Branch \j J 

Biological and Economic Analysis Division (7503P) 

Arnet Jones, Chief ~ 1 Biological Analysis Branch ~' "I 

Diann Sims, Chief $0' LA.>'Scf~Yt Science Information and Analysis Branch 

Timothy 

Economic 

Kiely, 

Analysis 

Chief 

Branchr\.. ~) LM.. ~ 

Biological and Economic Analysis Division 503P) 

Katherine St. Clair, Chemical Review Manager 

Risk Management and Implementation Branch 2 

Pesticide Re-evaluation Division (7508P) 

Peer Review Panel date: Sep. 7, 2011 

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 

of Tralkoxydim (121000), 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 09-06-2011. 

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Tralkoxydim is a member of the cyclohexanedione group of herbicides. The mode of action of 

this herbicide is inhibition of acetyl-coA carboxylase. Tralkoxydim is recommended for the 

control of annual grass weeds in wheat, barley, and triticale. It is a systemic, foliar applied postemergence herbicide recommended for selective control of major grassy weeds such as wild oat 

(Avenafatura L.), green foxtail (Setaria viridis), yellow foxtail (Setaria lutescens), Italian 

ryegrass (Lolium multiflorum), and Persian darnel (Lolium persicum). To increase the weed 

control spectrum, tralkoxydim can be tank mixed with compatible broadleaf herbicides. 

USE SITES 

Agricultural Use Sites 

Wheat, barley, and triticale 

Non-Agricultural Use Sites 

There are no non-agricultural uses. 

COMMON FORMULATIONS AND APPLICATION METHODS 

Tralkoxydim is formulated as water dispersible granules and soluble concentrate only. It is 

applied by ground and aerial methods. 

USAGE 

Figure 1 provides usage trends, in terms of pounds applied, for the largest agricultural markets 

for tralkoxydim. The use of tralkoxydim on spring wheat, barley and other crops fluctuated 

during the period 1998-2010. There was a significant increase in use on spring wheat in 2000. 

There was also a sharp increase in use oftralkoxydim on barley in 2002 -2003 and a sharp 

decrease in 2005 on this crop. 

From 2006-2010, the most recent available usage data, annual total agricultural usage averaged 

approximately 34,000 pounds active ingredient for 190,000 treated acres for an average 

application rate of 0.2 lbs. a.i. per acre. During this period, the crops with the most use in terms 

of total pounds of active ingredient applied are spring wheat (58%) and barley (30%). 

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

Montana (57%), Idaho (19%), and North Dakota (14%). (Proprietary Data, 2006-2010). 

USE TRENDS 

As shown in Figure 2, Tralkoxydim Agricultural Usage Data, from 2006 -2008, use on barley 

declined by 64%, while the use oftralkoxydim on spring wheat and other crops fluctuated with 

no clear trend. Use on spring wheat increased dramatically in 2010. 

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Figure 1. Tralkoxydim Agricultural Usage Data (1998-2010) 

Pounds A.I. 

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

° @)CQ @)o, ~c::, ~'" ~'" ~", ~~ ~" do &- ~CQ ~o, ~c::, 

~ ~ "'~ ~ "'~ "'~ "'~ "'~ "'~ ~ "'~ ~ ~ 

Years 

"Other crops" includes winter wheat (12% of total usage). 

Source: Proprietary Data, 1998-2010 

Figure 2. Tralkoxydim Agricultural Usage Data (2006-2010) 

50,000 '1-------------------

• Wheat, Spring 

• Barley 

• Other 

PoundsA.I. . Wheat, Spring 

• Barley 

o 

• Other 

2006 2007 2008 2009 2010 

Years 

"Other crops" include winter wheat (12%). 

Source: Proprietary Data, 2006-2010 

BIOLOGICAL ASPECTS RELEVANT TO TRALKOXYDIM 

The mode of action of tralkoxydim herbicide is inhibition of acetyl-coA carboxylase enzyme 

(ACCase) which is involved in the synthesis oflong chain fatty acids. Tralkoxydim is a member 

of the cyclohexanedione group of herbicides and belongs to the Group A herbicides according to 

the classification of the Herbicide Resistance Action Committee (HRAC). Weeds such as wild 

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oat (A vena fatua) , downy brome (Bromus tectorum), smooth crabgrass (Digitaria ischaemum), 

large crabgrass (Digitaria ischaemum), barnyard grass (Echinochloa crus-galli), late watergrass 

(Echinochloa phyUopogon), Amazon sprangletop (Leptochloa panicoides),Italian ryegrass 

(Lolium multiflorum),Persian darnel (Lolium persicum), little seed canary grass (Phalaris 

minor)Itchgrass (Rottboellia exalta), giant foxtail (Setariafaberi), Johnsongrass (Sorghum 

hale pense) are some of the weeds which have developed resistance to Group A herbicides in the 

United States (Heap, 1997). The development of resistance in many weed species may have 

contributed to some extent to the reduction in tralkoxydim usage. 

HISTORY OF BEAD ASSESSMENTS FOR TRALKOXYDIM 

There have been no BEAD assessments since 2000. 

DATA NEEDS RELEVANT TO BEAD'S FUTURE WORK ON TRALKOXYDIM 

There are no known data gaps at this time. 

REFERENCES 

Acetyl coenzyme A carboxylase. (2011). In Encyclopa!dia Britannica. Retrieved from 

http://www.britannica.comlEBcheckeditopic/3307/acetyl-coenzyme-A-carboxylase. 

Heap, 1. M. 1999. Occurrence of Herbicide Resistant Weeds, Worldwide. 

http://www.weedscience.com/paper/resist97.htm 

Proprietary Data, 1998-2010. 

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