UNITED STATES ENVIRONMENTAL PROTECTION AGENCY WASHINGTON, D

.C

. 20460 

## NO'I 

## 28Z01Z

MEMORANDUM OFFICE OF CHEMICAL SAFETY AND POLLUTION PREVENTION

SUBJECT: 

### BEAD Chemical Profile for Registration Review: Mesosulfuron-methyl (122009) FROM:

THRU:

TO: 

### Sunil Ratnayake, Biologist Biological Analysis Branch Jihad Alsadek, Economist Science Information and Analysis Branch Stephen Smearman, Economist

Diann Sims, Chief Science Information and Analysis Branch

....... 

### Timothy Kiely, Chief 

# (J_ vU_,

# ~ Economic Analysis Branch 

### \.J) Biological and Economic Analysis Division (7503P) Jolene Trujillo, Chemical Review Manager Risk Management and Implementation Branch 5 Pesticide Reevaluation Division (7508P)

Product Review Panel date: November 7, 2012 INTRODUCTION 

### The purpose ofthis document is to convey usage information and a broad overview ofthe pest management roles ofpesticides that are beginning to undergo registration review. The anticipated audience consists ofthe team ofEPA staffcurrently evaluating the registration status ofMesosulfuron-methyl, and eventuallythe general public. This documentbuilds uponthe data already provided 

### inthe "Usage and Label Use DataPackages" that are also provided toRegistration Reviewteams byBEAD. The document is based on information anddata available to BEAD as ofOctober 24,2011. Mesosulfuron-methyl was originally registered as a pesticide in the United States in March 2004. This herbicide belongs to the sulfonylurea herbicide family and it is applied as a post-emergence treatment to control annal grasses and broadleafweeds, especially for the control ofwild oat (Avena fatua )and wild mustard (Synapis arvensis) in triticale and wheat (winter, spring), including durum. Similarto other sulfonylurea herbicides the mode ofaction ofthis herbicide is inhibition of acetolactate synthase (ALS) enzyme which is needed for the production ofbranch chained amino acids required for the growth and development ofplant cells. 

### COMMONFORMULATIONS AND APPLICATION METHODS Mesosulfuron-methyl is formulated as dispersible granules and emulsifiable concentrate. 

### Itis applied as a post-emergence treatment using ground or aerial equipment. 

### AgriculturalUses Mesosulfuron-methyl is registered for use on durum wheat, commonwheat (winter, spring), and triticale. There are no registered non-agricultural uses for this chemical. 

### Agriculturaluse Sites From 2007-2011, the annual total agricultural usage averaged approximately 8,000 pounds active ingredient (a.i.) for 1milliontreated acres with an overall applicationrate of0.01 lbs. a.i. per acre. During this time frame, the crops withthe most use interms oftotal pounds ofactive ingredient applied are winter wheat (88%) and spring wheat (12%). The crops withmosttotal areatreated (TAT) are winter wheat (69%) spring wheat (30%), and fallow (1%). On average, the states with the most agricultural usage interms ofpounds a.i. applied are North Carolina (25%) and Washington (20%), (Proprietary Data, 2007-2011). Figure 1 shows the trend interms oftotal poundsused. The year ofinitial registration for this chemical was in 2004. Overall use trend ofmesosulfuron-methyl is, it is increasing from 2003 to 2011. There have been significant fluctuations between 2004 and 2010 probably due to market forces on agricultural commodities that resulted in increased prices for commodities like wheat and therebyjustifiedthe use ofadditional production inputs such as use ofmesosulfuron-methyl.

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### Figure 1. 

### Agricultural Usage Datafor Mesosulfuron-methyl in Pounds A.I. on all Crops (2003-2011)

Source: m 0 0 N

Proprietary Data, 2003 -2011**~** 0 N Ill 0 0 N <J:) 0 0 N I' 0 0 N Years 00 0 0 N 0'1 0 0 N 0 .-I 0 N .-I .-I 0 N



### Figure 2 provides usage data for 2007-2011. The use ofmesosulfuron-methyl on winter wheat increased significantly in 2008. This spike may be due to the significant increase ofwheat production in terms ofacres grown for winter wheatreported inthe year 2008 (NASS, 2012). The use ofmesosulfuron-methyl on spring wheat was relatively constant over the years 2007- 2011as the number ofacres inproductionhas been relatively constant. 

### Figure 2. AgriculturalUsage Data for Mesosulfuron-methyl Top Crops (2007-2011)
16,000

.t( VI -a c ::::11 0 a.

0 I' 00 0 0 0 0 N N

Source: Proprietary Data, 2007-2011 0'1 0 0 N Years



### Page 3 0 .-I 0 N .-I .-I 0 N**Wheat,** Spring

- Wheat, Winter

_._Other

### Agricultural Usage by Crop Reporting District Another measure ofusage is the use intensity. In this analysis, the use intensity is expressed as the pounds a.i. applied per acre ofland in farms. This differs from the application rate, which is expressed as the pounds a.i. applied per treated area. Figure 3 spatiallyrepresents mesosulfuronmethyl's use intensity in the U.S. 

### Figure 3. Mesosulfuron-methyl Usage by Crop Reporting District (2006-2010)

Sources: Average Pounds Per 1.000 Acres of Farmland

. 0.00-0

.01

- 0.02-0

.05 

### D o.o6-o

.1o 0.11-0

.35 0.36- 0

.68

Proprietary Data. 2006-201 0 USDA, 2006-2010. NASS Crop Reporting Districts. http://www.ers.usda.gov/briefing/anns/resourceregions/resourceregions.htm#nass

. USDA, 2007. Census ofAgriculture. http://www.agcensus.usda.gov/Publications/2007/index.asp

. This is a map ofagricultural pesticide usage at the Crop Reporting District (CRD) level prepared by BEAD for use in the Environmental Fate and Effects Division documents. These maps are used to help visualize where the pesticide being considered is most likely to be used and can be helpful in scenario selection and placing the exposure assessment in context. CRDs are boundaries created by USDA NASS which are aggregates ofcounties (USDA, 2010). Pesticide usage is displayed as average pounds (for the years 2006-


### Page42010) per 1,000 acres of farmland in a CRD to normalize for the variation in farmland between CRDs. Farmland acreage was obtained from USDA (2007). Farmland or "land in farms" is defined as follows: The acreage designated as "land in farms" consists primarily ofagricultural land used for crops, pasture, or grazing. It also includes woodland and wasteland not actually under cultivation or used for pasture or grazing, provided it was part of the farm operator's total operation. Large acreages of woodland or wasteland held for nonagricultural purposes were deleted from individual reports during the edit process. Land in farms includes CRP, WRP, FWP, and CREP acres. Land in farms is an operating unit concept and includes land owned and operated as well as land rented from others. Land used rent free was reported as land rented from others. All grazing land, except land used under government permits on a per-head basis, was included as "land in farms" provided it was part of a farm or ranch. Land under the exclusive use ofa grazing association was reported by the grazing association and included as land in farms. All land in American Indian reservations used for growing crops, grazing livestock, or the potential of grazing livestock was included as land in farms. Land in reservations not reported by reservation, individual American Indians or nonNative Americans was reported in the name ofthe cooperative group that used the land. In many instances, an entire American Indian reservation was reported as one farm (2007 Census ofAgriculture, USDA). Usage is based on private market surveys ofpesticide use in agriculture (Proprietary Data, 2006-2010). The survey data are limited to the states that represent the top 80-90% of acreage for the individual crops; therefore, use may be occurring in regions outside the scope of the survey. CRDs showing no usage of pesticides may be due to either the lack ofpesticide use in the region or non-participation in the agricultural surveys. In addition, across the years, there may be variations in the specific crops included in the CRD survey. This may result in a lower annual average for the CRD. This map displays ratio data (i.e., average pounds per 1,000 acres offarmland) summarized at a very highlevel. Readers are strongly cautioned against trying to over interpret the map without examination of the underlying data. The underlying data may explain some ofthe many reasons that a Crop Reporting District may have a high value for a particular active ingredient such as significant acreage (compared with the CRD as a whole) ofa crop or crops with a high application rate and frequency ofapplication. 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. Scale and units of measurement do matter and maybe different between maps.


### BIOLOGICAL ASPECTS RELEVANT TO MESOSULFURON-METHYL Mesosulfuron-methyl belongs to the sulfonylurea herbicide family and it is applied for the control of annual grasses and broad-leafweeds. It is significantly effective in controlling wild oats 

### (Avena fatua) and wild mustard 

### (Synapis arvensis) species. This herbicide inhibits the enzyme acetolactate

synthase (ALS) and interferes with the production ofamino acids required for plant growth. More than 120 weed species resistant to ALS inhibitors have beenreported 

### inthe United States (WeedScience.org, 2012). The control ofweed species resistant to mesosulfuron-methyl can be achieved bytankmixing a compatible registered herbicide with a different mode ofactionto mesosulfon-methyl. The presence ofItalian ryegrass 

### (Lolium multiflorum) biotypes with cross resistance to mesosulfuron-methyl and otherALS inhibitors such as chlorsulfuron, sulfometuron, and imazamox has been reported 

### inthe Southern United States (Kuk 

### & Bugos, 2007). A significant increase onuse ofmesosulfuron-methyl inwheatproduction was observed in 2008 Page 5

### and this is likely due to an increase inwinter wheatproduction acreage reported inthe same year. (NASS, 2012). HISTORY OF BEAD ASSESSMENTS FORMESOSULFURON-METHYL A search ofthe BEAD document data base found two Section 18 requests for mesosulfuronmethyl. In 2002 Georgia and Arkansas requested the use ofmesosulfuron-methyl to control ryegrass resistant to diclofop-methyl herbicide in Georgia and Arkansas wheat (02-GA-09, DP Barcodes D285471, D285634). BEAD determined that the situation was urgent and non-routine due to increasingresistance and growers were likely to experience significant economic loss without the use ofan effective herbicide. In 2003, BEAD conducted a review entitled "Request for the Emergency Exemption for Use of Mesosulfuron-methyl to Control Ryegrass Resistant to Diclofop-methyl Herbicide inNorth Carolina Wheat" (03-NC-07, DP Barcode D293980). BEAD determined thatthe situation was urgent and non-routine due to increasingresistance and growers were likely to experience a significant economic loss without the use ofan effective herbicide. These requests indicate that atthe time, growers inArkansas, Georgia and North Caroline had a need for mesosulfuron-methyl. DATA NEEDS RELEVANT TO BEAD'S FUTURE WORK ON MESOSULFURONMETHYL Obtaining additional information for mesosulfuron-methyl use on all wheat varieties and triticale would improve future BEAD assessments onthe mesosulfuron-methyl and it may be required as part ofthe registration review ofthis pesticide. Fortriticale and other crops, this may include application rates, total number ofpounds applied nationally by crop, the percent ofthe crop treated withthe names and number ofcompatible products that mesosulfuron-methyl canbe mixed. This type ofinformation will be beneficial on assessing the use patterns andbenefits of mesosulfuron-methyl. REFERENCES: Kuk, Y, and N. R. Bugos. 2007. Cross -resistanceprofile ofmesosulfuron-methyl-resistant Italian ryegrass inthe southernUnited States. Pest Manage. Scie. 63(4):349-357. http://www.ncbi.nlm.nih.gov/pubmed/17315272

. Accessed on Oct. 12, 2012. Proprietary Data, 2000-2010.

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### USDA, 2006-2010. NASS Crop Reporting Districts. Online: http://www.ers.usda.gov/briefing/arms/resourceregions/resourceregions.htm#nass

. Accessed on Oct. 4, 2012. USDA, 2007. Census ofAgriculture. Online: http://www.agcensus.usda.gov/Publications/2007/index.asp

. Accessed on Oct. 10, 2012. USDA, NAAS. 2012. Census ofAgriculture. Online: Quick Stats. http://quickstats.nass.usda.gov/results/2F30BlOC-OBC8-34F2-BlB2-B6F7D92342A3

. Accessed on Oct. 15, 2012. WeedScience.org. 2012. International Survey ofHerbicide Resistant Weeds. http://www.weedscience.org/In.asp

. Accessed on Oct. 18, 2012.

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