UNITED STATES ENVIRONMENTAL PROTECTION AGENCY WASHINGTON, D.C. 20460 

## APR J 9 2014

MEMORANDUM OFFICE OF CHEMICAL SAFETY AND POUliTION PREVENTION


### SUBJECT: BEAD Chemical Profile (BCP) for Registration Review: Diclofop-methyl (110902) FROM: Bill Phillips, Ph.D.,

## Agronomis~ Biological Analysis Branch

### ~ . /

THRU:



### TO: Jihad Alsadek, Ph.D., Economist 

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# ~~ Science Information and Analysis Branch Michelle Ranville, Economist { 

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# rrYJ Economic Analysis Branch 

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## "--'t......AJ Biological and Economic Analysis Division (7503P) Arnet Jones, Chief Biological Analysis Branch Diann Sims, Chief

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# r**/}.~,...,.J/** Science Information and An9)alys1s Branch:Q Timothy Kiely, Chief 

# \}AL Economic Analysis Branch \ Biological and Economic An y s Division (7 3P) Steven Snyderman, Chemical Review Manager Risk Management and Implementation Branch 3 Pesticide Re-evaluation Division (7508P)


### PeerReview Panel date: Apri116, 2014 SUMMARY Diclofop-methyl was first registered as anherbicide inthe U.S. in 1982 (USEPA, 2000) to control annual grasses in wheat and barley as well as inturfgrass. This herbicide is in the Weed Science Society ofAmerica group one, a member ofthe aryloxyphenoxy propionate herbicide family, and is applied both preemergence and postemergence. During the period covering 2008to 2012, 91% ofthe total pounds ofdiclofop-methyl was applied inwinter wheat. However, based on current weed resistance issues as well as the decline in overall usage, BEAD is unable to determine whether diclofop-methyl plays an importantrole inpest management for winter wheatproduction. Based onprivate market usage data from 1998-2012, usage averaged approximately 144,000 pounds active ingredient (a.i.) applied annually on approximately 236,000 acres treated. The average a.i. rate overthis time period was 0.610 pounds a.i. /acre. Available non-agricultural usage data fordiclofop-methyl is limited and dated.


### INTRODUCTION The Biological and Economic Analysis Division (BEAD) Chemical Profile (BCP) provides an overview ofthe pest management roles and quantitative usage information for diclofop-methyl. The BCP includes summaries ofprevious BEAD products and available public and/or private use and usage datafor diclofop-methyl to describe the role ofthis chemical inpest management. Information provided inthis BCPmay be used by stakeholders (e.g., users and registrants), OPP risk assessors, OPP risk manag_ers, and the general public during the Registration Reviewprocess ofthis chemical.


### USE SITES Agricultural Use Sites Diclofop-methyl registered agricultural use sites are barley and wheat. Non-agricultural Use Sites Diclofop-methyl registered non-agricultural use sites are golfcourses and roadsides.


### FORMULATIONS AND APPLICATION METHODS Diclofop-methyl formulations include emulsifiable concentrate and liquid. Diclofop-methyl is applied by commercial sprayer spottreatment and viabroadcast application withhose end sprayer.


### HISTORY OFDICLOFOP-METHYL and BEAD PRODUCTS Diclofop-methyl is anherbicide registered for use inthe U.S. since 1982. A Screening Level Usage Analysis (SLUA) was prepared by BEAD for this chemical in 2014 that provides national level poundage applied by active ingredient (a.i.) andpercent crop treated (PCT) data for barley and wheat. Both crops have less than one percent crop treated (PCT) with diclofop-methyl

2(EPA, 2014). The relatively low PCT on barley and wheat indicate a low level ofreliance on diclofop-methyl to control weeds inthese crops. A search ofthe BEAD database for previous BEAD products for diclofop-methyl indicates that there have not been any benefits assessments or Section 18 analyses prepared for this chemical. A search ofthe OPP Section 18 database indicates there have been no requests for emergency exemptions to use diclofop-methyl. The absence ofthese assessments and requests, however, does not indicate that the chemical has no benefits to users.
USAGE Agricultural Usage Based onprivate market usage data from 1998-2012, usage averaged approximately144, 000 pounds active ingredient (a.i.) applied annually on approximately 236,000 acres treated. The average a.i. rate over this time period was 0.610 pounds a.i. /acre. Figure 1presents diclofopmethyl usage in pounds a.i. over the 1998-2012 time frame. Figure 2 presents total area treated in acres over the same time frame (Proprietary Data, 1998-2012).

800,000

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FIGURE 1. Diclofop-methyl Usage in Pounds Active Ingredient, 1998-2012 Source: Proprietary Data, 1998-2012 N

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### 31,300,000

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### .... N m -t 11'1 1.0 r-- 00 0'1 0'1 0 0 0 0 0 0 0 0 0 0'1 0'1 0 0 0 0 0 0 0 0 0


### .... .... N N N N N N N N N Year 

### FIGURE 2. Diclofop-methyl Total Area Treated in Acres, 1998-2012 Source: Proprietary Data, 1998-2012 0'1 0 

### .... N 0 

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### .... 0 0 0 0 N N N N

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### Table 1. 

### Crops with Highest :Use ofDiclofop-methyl in Two Time Periods, Percent ofTotal Lbs. Applied{2003-2007 and 2008-2012) 2003-2007 2008-2012 Average Annual = 236,000 lbs/yr Average Annual= 27,000 lbs/yr 

### Crop %Lbs Crop %Lbs Winter Wheat 93% Winter Wheat 91% Spring Wheat 4% Spring Wheat 7% Barley 3% Barley 2% Source: ProprietaryData, 1998 -2012.


### Table 2. States with Highest Use ofDiclofop-methyl in Two Time Periods, Percent ofTotal Lbs. Applied (2003-2007 and 2008-2012) 2003-2007 2008-2012 Average Annual= 236,000 lbs/yr Average Annual= 27,000 lbs/yr 

### State %Lbs State %Lbs North Carolina 31% North Carolina 61% Arkansas 14% Arkansas 20% Tennessee 13% North Dakota 7%

Oregon 11 Tennessee 5% Source: ProprietaryData, 1998 -2012 The major agricultural use ofdiclofop-methyl inboththe 2003-2007 and 2008-2012 time frames was on winter wheat (93% oftotal pounds applied in 2003-2007 and 91% oftotal pounds applied in 2008-2012) followed by spring wheat (4%) and barley (3%) in 2003-2007, and (7% for spring

4wheat and 2% for barley) during the 2008-2012 time frame. Usage has decreased on winter wheat and barley and increased on spring wheat inthe mostrecent 2008-2012 time frame. Application Rates The average a.i. rate for the top crops interms ofpounds a.i. applied was the highest for spring wheat at 0.566lbs a.i./acre and the lowest for winter wheat at 0.499lbs a.i./acre as shown in Table 3. 

### T bl 3 

# n· I fi hI U

a e 

# . IC o op-met tyl se on T C op rops: Average A I Ra 2008 2012 

# . . te, 

# - Crop Average Annual Average Annual A vg. Annual A.I. Pounds Applied Total Acres Treated* Rate Obs a.iJacres) Winter Wheat 73,925 147,972 0.499 Spring Wheat 5,524 9,757 0.566 Barley 1,434 2,550 0.562 *TotalAcres Treated sums all acres treated for a crop, mcludmg those acres thatreceive multiple treatments. Source: Proprietary Data, 2008 -2012 Non-Agricultural Usage There was minimal use ofdiclofop-methyl onturfand ornamentals in the most recent year that data was available, less than tenpounds active ingredient (Proprietary Data, 2012). Geographic Distribution ofDiclofop-methyl Use Figure 3 displays the average usage intensity ofdiclofop-methyl for the years 2008-2012. The highest usage intensity occurred inNorth Carolina and Arkansas followed by Virginia and North Carolina.

5PoundsActive Ingredient per 1,000 Crop Acres Grown c:::JNoOata c:::J <OD9 o o.09-0.17

. 0.18-0.33

- >0.33 

### FIGURE 3. Diclofop-methyl Usage Intensity by State, 2008-2012 Source: Proprietary Data, 2008-2012


### BIOLOGICAL ASPECTS RELEVANT TO DICLOFOP-METHYL Diclofop-methyl is an herbicide inthe Weed Science Society ofAmerica group one and is a member ofthe aryloxyphenoxy propionate herbicide family. This herbicide has the mechanism ofaction ofinhibiting the acetyl CoA carboxylase (ACCase) enzyme. Diclofop-methyl is used bothpreemergence and postemergence to control annual grasses in agronomic crops such as barley and wheat. In addition, this herbicide canbeused to control some grass weeds in turf grass. 

### ROLE OFDICLOFOP-METHYL IN PEST MANAGEMENT Overall, the use ofdiclofop-methyl has been decreasing since 1998. Based onthe total amount ofthe herbicide that was applied betweenthe years of2008 and 2012, nearly all ofthe diclofop applied was in winter wheat (91%), withmost ofthe herbicide applied inArkansas (20%) and North Carolina (61 %). When applied in winter wheat, diclofop-methyl is used primarily to control ryegrass weed species. Research focused on the efficacy ofdiclofop-methyl inNorth Carolinafound that this herbicide provides excellent control ofryegrass (NCSCE, 2013). However, ryegrass populations resistant to diclofop are becoming more widespread. The increase inthe resistant ryegrass


### 6population over the years, may explain some ofthe decrease in diclofop-methyl use. Based on the resistance issue and the decline in usage, BEAD is unable to determine whether diclofopmethyl plays an importantrole inpestmanagement for winter wheatproduction.

DATA NEEDS The Agency currently does not have important information on diclofop-methyl. Obtaining the following information may improve future assessments conducted by the Agency related to the use and importance ofdiclofop-methyl: Usage information (e.g., acres treated, lbs applied, applicationrates, target pests) for nonagricultural uses Informationregarding the importance ofdiclofop-methyl for pestmanagement in any of the registered uses.
REFERENCES EPA. 2000. Reregistration Eligibility Decision (RED) Diclofop-methyl. Available at: http://www.epa

.gov/oppOOOOl/chem search/reg actions/reregistration/red PC110902 1-Sep-OO.pdf · EPA. 2014. Diclofop-methyl (110902) Screening Level Usage Analysis (SLUA). Biological and Economic Analysis Division. March 24,2014. Proprietary Data. 1998-2012. North Carolina State Cooperative Extension (NCSCE). 2013. Herbicide Efficacy onMost Common Weeds inNorth Carolina Winter Wheat. Available at: http:/ /www.ces.ncsu.edu/wp-content/uploads/2013/12/Herbicide-Efficacy-.pdf. Accessed April2014. USDA, 2006-2010. NASS Crop Reporting Districts (shape file ofCRDs). Available at: http://www.ers.usda.gov/briefing/arms/resourceregions/resourceregions.htm#nass

. USDA, 2006-2010. NASS Crop Reporting Districts. Online: http://www.nass.usda.gov/Data and Statistics/County Data Files/Frequently Asked Q uestions/county list.txt USDA, 2007. Census ofAgriculture. Online: http://www.agcensus.usda.gov/Publications/2007/index.asp

.

7APPENDIX A The map included herein primarily for the use ofthe risk assessors inthe Environmental Fate and · Effects Division. The map provides a very broad geographical view ofthe amount (in pounds) ofthe active ingredient applied per 1,000 acres of"land in farms." These data are included in the maps because risk assessors are interested inthe amount ofa pesticide used across farmland. Because ofthe definition ofLand in Farms, as discussed below, the calculated values presented in the map are 

### not equivalent**t~** an application rate (lbs a.i. 

### IA). The data used to make these maps have many limitations. Any interpretation ofthe maps should consider the underlying data and the associated limitations carefully. The smallest areas shown onthe maps within each state are Crop Reporting Districts (CRD). CRDs are defined by USDA and each consists ofmultiple counties that have similar soils, growing conditions, and farming practices. The CRDs within many states have roughly the same area. Because it is not feasible

- to conduct an agricultural survey that samples every county in the United States, the use ofCRDs allow for a sample to be collected that represent a much larger area with relatively homogeneous agricultural characteristics. The numerator (annual average pounds applied) is based onprivate market surveys ofpesticide use in agriculture averaged overthe last five years (Proprietary Data, 2008-2012). These surveys cover about 60 crops and are targeted in states that produce the majority ofthe crop. Although the surveys capture most ofthe use ofa particular active ingredient in agriculture, there are several limitations to these su.rVeys.

• States with minorproduction ofa surveyed crop are not sampled • Not all types ofpesticides are surveyed in every crop in every year • Many specialty crops with very small acreages are not included inthe survey The result ofthese limitations is that CRDs that show no usage may actually have a small amount ofthe active ingredientbeing used. The denominator (1,000 Acres ofland in farms) was selected from the Census ofAgriculture (USDA, 2007) to represent agricultural acreage that is actively managed and includes most ofthe



### 8areas treated withpesticides. The category "Land inFanns" is defined bythe Census of Agriculture as being made up offour components:

• Total cropland • Permanentpasture • Total woodland • Land in fannsteads, buildings, livestock facilities, ponds, roads, wasteland, etc. This category includes land inthe various USDA conservationprograms. It should be noted that the Census ofAgriculture does not include grazing landrented (on a per-animal basis) from the Bureau ofLand Management orForest Service, thus it is an underestimate ofthe land being managed for agricultural purposes. The reader should pay particular attentionto the figure legends andrealize that a map prepared for a particular chemical is not directly comparable to a map prepared for a different chemical. Scale andunits ofmeasurement do matter and may be different betweenmaps.



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