UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON. D C. 20460 

SEP 0 8 2014 

OFFICE OF CHEMICAL SAFETY lt.Nn Prll I IITinM P~I=\/~P\!T nN 

MEMORANDUM 

SUBJECT: 

FROM: 

THRU: 

BEAD Chemical Profile for Registration Review: Sethoxydim ( 121 001) 

Sunil Ratnayake, Biologist 

Biological Analysis Branch 

Cynthia 

Science Information 

Doucoure, Environmental 

and Analysis Branch 

Protection Specialist (/ ~ 

Economic 

Stephen Smearman, 

Analysis Branch 

Economist 

' 

k,x;,.J,417 ~ 

Biological and Economic Analysis Division (7503P) 

Arnet Jones, Chief 

Biological Analysis Bran 

Diann Sims, Chief 

Science Information and Anal~ysis Branch ~ 

Timothy Kiely, Chief 'M._ 

Economic Analysis Branch · 

Biological and Economic Analy Division (7 ) 

TO: Neil Anderson, Chief 

Tom Moriarty, Team Leader 

Risk Management and Implementation Branch I 

Pesticide Re-evaluation Division (7508P) 

Product Review Panel date: July 30,2014 

Page 1 of10 
SUMMARY 

Sethoxydim was first registered in the U.S. in 1994 as a selective post-emergence herbicide to 

control annual and perennial grass weeds in grains, fruit orchards, tree nuts, vegetable crops, 

herbs, and non-agricultural sites listed under the use sites. 

Overall use of sethoxydim in the U.S. has declined considerably since 1998. However, based 

on the available percent crop treated (PCT) data during the period from 2004 to 2012, 

sethoxydim is reportedly used on over 50 crops and appears to still play a relatively important 

role in control of weeds in dry beans/peas (30% PCT), green beans (1 0% PCT) and 

watermelons (10% PCT). During the period from 2006 to 2012, states with highest 

agricultural usage were North Dakota (45%), California (10%), and Minnesota (7%). 

Available proprietary data also shows a decrease in use of sethoxydim in the non-agricultural 

market. In 2004, approximately 29,000 pounds a.i. were reportedly applied in the 

professional turf and ornamental markets compared to 6,000 pounds a.i. in 2011. Half of this 

amount was applied on turf farms. 

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 a team of EPA staff currently evaluating the registration status of 

sethoxydim, and eventually the general public. This document builds upon the data BEAD 

provides in the Label Use Information System (LUIS) reports and the Screening Level Usage 

Analysis (SLUA) to Registration Review teams. The document is based on information and 

data available to BEAD as of April2014. 

HISTORY OF BEAD ASSESSMENTS FOR SETHOXYDIM 

Sethoxydim was registered in 1994 as a selective post-emergence herbicide to control annual and 

perennial grass weeds in broad-leaved vegetable, fruit, nut, field, and ornamental crops. The 

Reregistration Eligibility Decision (RED) was signed in September 2005. 

BEAD prepared a Screening Level Usage Analysis (SLUA) in May 2014, which showed 

reported usage of sethoxydim on over 50 crops during the 2004-2012 time frame. The crop with 

the highest average percent crop treated (PCT) was dry beans/peas (30%) on which an average of 

100,000 pounds a.i. was applied. Other crops worth noting include green beans and watermelon, 

both with an average of 10% PCT and soybeans, where 30,000 pounds a.i. were applied but with 

an average <1% PCT due to the large number of acres of soybeans in production. 

Benefits Assessments- A search of BEAD's Official Records data base for BEAD benefits 

assessments specifically for sethoxydim did not find any records of prior BEAD assessments in 

the last 1 0 years. 

Page 2 oflO 
Emergency Exemptions- a search of BEAD's Official Records did not fmd any Section 18s 

requests for sethoxydim in the last 8 years. Emergency exemptions may indicate that there is a 

need for a particular chemical that is not registered for use on a particular site. Approval of an 

emergency exemption request may yield information through the emergency exemption process 

about a particular chemical's importance or value that is not found in other EPA records. 

However, a lack of Section 18 assessments by BEAD does not specifically indicate the relative 

importance of the chemical. 

COMMON FORMULATIONS AND APPLICATION METHODS 

Sethoxydim is commonly formulated as an emulsifiable concentrate which is applied using 

handheld sprayers, tractor mounted ground boom sprayers, or using aerial application method. 

USE SITES 

Agricultural Use Sites: 

Sethoxydim is registered for use on grains, fruit, tree nuts, vegetables and herbs. 

Non-Agricultural Use Sites: 

Sethoxydim is registered for use on non-crop areas including ornamentals and flowering plants, 

recreational areas, rights-of-way, along fences, hedgerows, and public and commercial 

buildings/ structures. 

SETHOXYDIM USAGE 

Agricultural Usage Trend 

According to proprietary market research surveys, use of sethoxydim in the U.S. has decreased 

steadily since 1998 as shown in Figure 1. Similar trends were found for the total area treated 

with sethoxydim as shown in Figure 2. During this period, approximately 357,000 pounds a.i. 

were applied on average annually to 2,140,000 acres at an overall application rate of0.2lb a.i. 

per acre. 

Page 3 oflO 
Figure 1. Sethoxydim Usage: Pounds AI Applied, 1998-2012 

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Year 

Source: EPA Proprietary Data, 1998-2012 

Figure 2: Sethoxydim Usage: Total Area Treated (acres), 1998-2012 

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1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 

Year 

Source: EPA Proprietary Data, 1998-2012 

Page 4 oflO 
Agricultural Usage: Top Crops 

Based on available proprietary data, sethoxydim is reported to be used on over 50 crops in the 

U.S. The average annual use ofsethoxydim in terms ofpounds a.i. applied has decreased in 

recent years (2006-2012) by 62%. The top crops treated with sethoxydim has also shifted in 

recent years from a predominant use on soybeans in earlier years to a predominant use on dry 

beans/peas in recent years. The usage on other top crops in recent years include soybeans, 

alfalfa, oranges, and peanuts as shown in Table 1 below. The average a.i. application rate has 

remained consistent for the top crops during the earlier and recent periods except for oranges 

where it is applied at a higher rate (0.4lbs a.i per acre) than other top crops as shown in Table 1. 

Table 1. Sethoxydim: Comparison of Usage on Crops between 1998-2005 and 2006-2012 

Timeframes. 

1998-2005 2006-2012 

Avg Annual Lbs A.l. Applied= 502,000 Avg Annual Lbs A.l. Applied= 190,000 

Crop Proportion of Avg. A.I. Rate Crop Proportion of Avg. A.I. Rate 

Total Lbs A.I. of Application Total Lbs A.I. of Application 

AJmlied (lb a.i./acre) Applied (lb a.i./acre) 

Soybeans 43% 0.2 Dry Beans I 51% 0.1 

Peas 

Dry Beans 12% 0.1 Soybeans 8% 0.2 

/Peas 

Sunflowers 12% 0.2 Alfalfa 5% 0.2 

Alfalfa 9% 0.2 Oranges 4% 0.4 

Sugar 4% 0.1 Peanuts 4% 0.2 

Beets 

Peanuts 3% 0.2 Other* 28% 0.1-0.4 

Other* 17% 0.1-0.4 

*Other crops include nut crops, pome fruit, stone fruit, leafy & stem vegetables, root crop vegetables, 

cucurbits, com, cotton, fallow, citrus, small fruits, seed & pod vegetables, pasture/range, fruiting vegetables, 

tobacco, and wheat. 

Source: Propnetary Data, 1998-2012 

Agricultural Usage: Top States 

Based on available proprietary data, sethoxydim is reported to be used in over 40 states in the 

U.S. The average annual use of sethoxydim in terms of pounds a.i. applied has decreased in 

recent years as described in Table 1. North Dakota has remained the predominant user of 

sethoxydim and has more than do.ubled its usage in recent years (Table 2). Other top states for 

use of sethoxydim in recent years include California, Minnesota, Florida, Georgia, and 

Wisconsin as shown in Table 2 below. The average a.i. rate of application has remained 

consistent for the top states during the earlier and recent periods; however, sethoxydim is applied 

in California and Florida at a higher rate (0.3 lbs a.i per acre) as shown in Table 2. 

Page 5 oflO 
Table 2. Sethoxydii:n: Comparison of Usage in States between 1998-2005 and 2006-2012 

Timeframes. 

1998-2005 2006-2012 

Avg Annual Lbs A.l. Applied= 502,000 Avg Annual Lbs A.l. Applied= 190,000 

State Proportion Avg.A.I. State Proportion Avg.A.I. 

of Total Lbs Rate of of Total Lbs Rate of 

A.I. Applied Application A.I. Applied Application 

(lb a.i./acre) (lb a.i./acre) 

North Dakota 20% 0.1 North Dakota 45% 0.1 

Illinois 10% 0.2 California 10% 0.3 

Minnesota 8% 0.1 Minnesota 7% 0.1 

California 7% 0.3 Florida 6% 0.3 

Iowa 7% 0.2 Georgia 4% 0.2 

South Dakota 7% 0.2 Wisconsin 4% 0.2 

Other 41% 0.1-0.4 

Other states include AL, AZ, AR. CO, CT, DE, FL, Other states include AL, AZ, AR, CO, CT, DE, 

GA, ID, IN, KS, KY, LA, ME, MD, MA, MI, MS, ID, IL, IN, lA, KS, KY, LA, ME, MD, MS, MI, 

MO, MT, NE, NV, NJ, NM, NC, OH, OK, OR. PA MS, MO, MT, NE, NJ, NM, NY, NC, OH, OK, 

SC, TN, TX, UT, VA, WA, WI, & WY OR. PA, SC, SD, TN, TX, VA, WA, & WY 

Source: Propnetary Data, 1998-2012 

Agricultural Use Intensity ofSethoxydim Use in the U.S. 

Another measure of usage is the use intensity. In this analysis, the use intensity is expressed as 

the average annual amount (in pounds) of the active ingredient applied per 1 ,000 acres of crop 

acres grown. This differs from the application rate, which is expressed as the pounds a.i. applied 

per treated area. Figure 3 spatially represents the use intensity for sethoxydim in the U.S. during 

the 2008-2012 timeframe, which appears to be greater in North Dakota due to high usage of 

sethoxydim on dry beans/peas and in California due to relatively high usage on alfalfa, almonds 

and wine grapes. The available data also shows use intensity of sethoxydim in Massachusetts. 

This is due to relatively high percentage of sethoxydim use on low pumpkin and squash acreage. 

For more information about this map, see Appendix A. 

Page 6 oflO 
Figure 3. Annual Average Agricultural Use Intensity of Sethoxydim (2008-2012). 

Pounds Active Ingredient 

per 1,000 Crop Acres Grown 

D No Data 

0 <0.1 

O o.1-0.5 

0.5-2 

- 2-9 

- >9 

-----, 

-----------------------------------_j 

(Source: Proprietary Data, 2008-2012) 

Non-Agricultural Usage 

BEAD reviewed available proprietary data and found reported use on sethoxydim in the turf and 

ornamental market. Non-agricultural use in terms of the pounds a.i. applied has significantly 

declined from 29,000 pounds 2004 to 6,000 pounds in 2011 as shown in Table 3 below. 

T a e bl 3 S e th oxy' di m U sem . T ur f an d 0 mamen tal M ar k t e s 

Sector 2004 2011 

(lbs a.i.) (lbs a.i.) 

Turf Farms 29,000 3,000 

Institutional Turf n/a 1,000 

Nursery I Greenhouse n/a 2,000 

Total 29,000 6,000 

Source: Propnetary Data, 2012 

Page 7 oflO 
BIOLOGICAL ASPECTS RELEVANT TO SETHOXYDIM 

Sethoxydim [2-[1-( ethoxyimino) butyl]-5-[2-( ethylthio) propyl]3-hydroxy-2-cyclohexen-1-one] 

belongs to the cyclohexanedione or cyclohexenone class of herbicides. The mode of action of 

this herbicide is inhibition oflipid biosynthesis. Sethoxydim inhibits the acetyl-CoA 

carboxylase (ACCase) which is a key enzyme in the lipid biosynthesis pathway. This herbicide 

is used for the post-emergence control of certain annual and perennial grass weeds. However, it 

has little or no impact on broadleaf weeds or woody plants. Sethoxydim is rapidly absorbed by 

the foliage and translocated throughout the plant. Soon after the application of sethoxydim, 

growth of susceptible weeds ceases and young and actively growing tissues are affected first and 

leaf chlorosis and necrosis can be observed (Herbicide handbook, 2007). 

ROLE OF SETHOXYDIM IN PEST MANAGEMENT 

Sethoxydim is registered for the post-emergence control of annual and perennial grass weeds in 

grains fruit orchards, tree nuts, vegetable crops, and herbs and non-agricultural sites. Based on 

the available usage information during the period from 2006 to 2012, sethoxydim plays a 

relatively important role in control of weeds in dry beans and peas. According to a publication 

from University oflllinois, on weed control of agricultural crops, post-emergence treatments of 

sethoxydim can be used to control many annual and perennial grass weed species including, 

bamyardgrass (Echinoch/oa crus-galli), crabgrass (Digitaria sanguinalis), giant foxtail (Setaria 

faberi), fall panicum (Panicum dichotomiflorum), sandbur (Cenchrus incertus), shattercane 

(Sorghum bico/or), andjohnsongrass (Sorghum ha/epense) (Illinois Agricultural Pest 

Management Handbook, 2008). However, the use ofsethoxydim in the U.S. has decreased 

steadily since 1998 (Figure 1 ). This could be due to the development of resistant weeds as a 

result of extensive use of herbicides with the mode of action belong to the sethoxydim as well as 

the use of roundup ready soybean varieties in the U.S. soybean production. According to a 

survey on herbicide resistant weeds, 15 weed species have developed resistance to the mode of 

action ofherbicides belongs to sethoxydim. (Heap, Undated). 

INFORMATION THAT MAY BE USEFUL FOR BEAD'S FUTURE WORK ON 

SETHOXYDIM 

The Agency currently does not have important information on sethoxydim. Obtaining the 

following usage information may improve future assessments conducted by the Agency related 

to the use and importance of sethoxydim: 

• Pounds a.i. applied, average application rates, and average number of applications in noncrop uses including recreational areas, rights-of-way, along fences, hedgerows, and 

public and commercial buildings/structures. 

Page 8 oflO 
REFERENCES 

EPA Proprietary Data, 1998-2012. 

EPA, Sethoxydim Screening Level Usage Analysis (SLUA), May 2014. 

Heap, I. (Undated). The International Survey of Herbicide Resistant 

Weeds. Online. Internet. Tuesday, February 11, 2014. Available at: 

http://www.weedscience.org/summary/CountrySummary.aspx. 

Accessed Date. June. 18,2014. 

Herbicide Handbook. 2014. lOth edition. Weed Science Society of America. Sethoxydim. Pp 

413-414. 810 E. lOth Street, Lawrence, KS 66044-8897. 

Illinois Agricultural Pest Management handbook. 2008. Online Publication of University of 

Illinois Urbana Champaign. http://ipm.illinois.edu/pubs/iapmh/02chapter.pdf. 

Accessed on June 17, 2014. 

USEPA. 2005. Registration Eligibility Decision (RED) for Sythoxydim. Online Publication. 

Available at: http://www.epa.gov/oppsrrd1 /REDs/sethoxydim red.pdf. Accessed on June 

16, 2014. 

Page 9 oflO 
APPENDIX A 

The map included herein is primarily for the use of the risk assessors in the Environmental Fate 

and Effects Division. The map provides a very broad geographical view of the average annual 

amount (in pounds) of the active ingredient applied per 1,000 acres of crop acres grown. These 

data are included in the maps because risk assessors are interested in the amount of a pesticide 

used across agricultural land. The calculated values presented in the map are not equivalent to 

an application rate (lb a.i./A). 

The data used to make these maps have several limitations. Any interpretation of the maps 

should consider the underlying data and the associated limitations carefully. 

The numerator (annual average pounds applied) is based on private market surveys of pesticide 

use in agriculture averaged over the last five years (Proprietary Data, 2008-2012). These surveys 

cover about 60 crops and are targeted in states that produce the majority of the crop. Although 

the surveys capture most of the use of a particular active ingredient in agriculture, there are 

several limitations to these surveys. 

• States with minor production of a surveyed crop are not sampled 

• Not all types of pesticides are surveyed in every crop in every year 

• Many specialty crops with very small acreages are not included in the survey 

The result of these limitations is that states that show no usage may actually have a small amount 

of the active ingredient being used. In some cases the displayed use intensity may be distorted 

because the surveyed crops and the reported pesticide usage may not accurately represent the 

actual pesticide usage on the crops produced in the state. 

The denominator (1,000 crop acres grown) was also obtained from the same private market 

survey database. The "Crop Acres Grown" variable represents the total acres grown in a given 

state of all of the surveyed crops. This value is independent of pesticide usage and pesticide 

registration. It is important to note that the surveyed crops (about 60) are sampled from states 

that are major producers of each crop. Therefore, there are cases where the actual crop acreage in 

a state is higher than that reported by crop acres grown in the survey because either that state 

and/or crop was not included in the survey. 

The reader should pay particular attention to the figure legends and realize that a map prepared 

for a particular chemical is not directly comparable to a map prepared for a different chemical as 

the legend bins will likely be different. 

Page 10 oflO