UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, D.C. 20460 

NO 'I 2 8 Z01Z 

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 

Economic 

Kiely, 

Analysis 

Chief 

Branch 

(J_ 

\.J ) 

vU_, ~ 

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 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 

ofMesosulfuron-methyl, 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 October 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 of wild oat (Avena 

fatua )and wild mustard (Synapis arvensis) in triticale and wheat (winter, spring), including durum. 

Similar to other sulfonylurea herbicides the mode of action of this herbicide is inhibition of 

acetolactate synthase (ALS) enzyme which is needed for the production of branch chained amino 

acids required for the growth and development of plant cells. 

COMMON FORMULATIONS AND APPLICATION METHODS 

Mesosulfuron-methyl is formulated as dispersible granules and emulsifiable concentrate. It is 

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

Agricultural Uses 

Mesosulfuron-methyl is registered for use on durum wheat, common wheat (winter, spring), and 

triticale. There are no registered non-agricultural uses for this chemical. 

Agricultural use Sites 

From 2007-2011, the annual total agricultural usage averaged approximately 8,000 pounds active 

ingredient (a.i.) for 1 million treated acres with an overall application rate of0.01 lbs. a.i. per 

acre. 

During this time frame, the crops with the most use in terms of total pounds of active ingredient 

applied are winter wheat (88%) and spring wheat (12%). The crops with most total area treated 

(TAT) are winter wheat (69%) spring wheat (30%), and fallow (1 %). On average, the states with 

the most agricultural usage in terms of pounds a.i. applied are North Carolina (25%) and 

Washington (20%), (Proprietary Data, 2007-2011). 

Figure 1 shows the trend in terms of total pounds used. The year of initial registration for this 

chemical was in 2004. Overall use trend of mesosulfuron-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 thereby justified the use of additional production inputs such as use of mesosulfuron-methyl. 

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Figure 1. Agricultural Usage Data for Mesosulfuron-methyl in Pounds A.I. on all Crops 

(2003-2011) 

Source: 

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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 of wheat 

production in terms of acres grown for winter wheat reported in the year 2008 (NASS, 2012). 

The use ofmesosulfuron-methyl on spring wheat was relatively constant over the years 2007-

2011as the number of acres in production has been relatively constant. 

Figure 2. Agricultural Usage Data for Mesosulfuron-methyl Top Crops (2007-2011) 

16,000 

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0 I' 00 0 0 0 0 N N 

Source: 

Proprietary Data, 2007-2011 

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Page 3 

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Wheat, Spring 

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_._Other 
Agricultural Usage by Crop Reporting District 

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

the pounds a.i. applied per acre of land in farms. This differs from the application rate, which is 

expressed as the pounds a.i. applied per treated area. Figure 3 spatially represents 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. 2006-20 1 0 

USDA, 2006-2010. NASS Crop Reporting Districts. 

http://www.ers.usda.gov/briefing/anns/resourceregions/resourceregions.htm#nass. 

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

This is a map of agricultural 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 of counties (USDA, 2010). Pesticide usage is displayed as average pounds (for the years 2006-

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2010) 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 of agricultural 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 of a 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 of the cooperative group that used 

the land. In many instances, an entire American Indian reservation was reported 

as one farm (2007 Census of Agriculture, USDA). 

Usage is based on private market surveys of pesticide 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 of pesticide 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 of farmland) 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 of the 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) of a crop or crops with a high application rate and frequency of application. 

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 may be 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-leaf weeds. 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 of amino acids required for plant growth. More 

than 120 weed species resistant to ALS inhibitors have been reported in the United States 

(WeedScience.org, 2012). The control ofweed species resistant to mesosulfuron-methyl can be 

achieved by tank mixing a compatible registered herbicide with a different mode of action to 

mesosulfon-methyl. The presence of Italian ryegrass (Lolium multiflorum) biotypes with cross 

resistance to mesosulfuron-methyl and other ALS inhibitors such as chlorsulfuron, sulfometuron, 

and imazamox has been reported in the Southern United States (Kuk & Bugos, 2007). A 

significant increase on use of mesosulfuron-methyl in wheat production was observed in 2008 

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and this is likely due to an increase in winter wheat production acreage reported in the same year. 

(NASS, 2012). 

HISTORY OF BEAD ASSESSMENTS FOR MESOSULFURON-METHYL 

A search of the BEAD document data base found two Section 18 requests for mesosulfuronmethyl. 

In 2002 Georgia and Arkansas requested the use of mesosulfuron-methyl to control rye grass 

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 

increasing resistance and growers were likely to experience significant economic loss without the 

use of an 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 in North 

Carolina Wheat" (03-NC-07, DP Barcode D293980). BEAD determined that the situation was 

urgent and non-routine due to increasing resistance and growers were likely to experience a 

significant economic loss without the use of an effective herbicide. 

These requests indicate that at the time, growers in Arkansas, 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 on the mesosulfuron-methyl and it may be required as 

part of the registration review of this pesticide. For triticale and other crops, this may include 

application rates, total number of pounds applied nationally by crop, the percent of the crop 

treated with the names and number of compatible products that mesosulfuron-methyl can be 

mixed. This type of information will be beneficial on assessing the use patterns and benefits of 

mesosulfuron-methyl. 

REFERENCES: 

Kuk, Y, and N. R. Bugos. 2007. Cross -resistance profile ofmesosulfuron-methyl-resistant 

Italian ryegrass in the southern United 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 of Agriculture. Online: 

http://www.agcensus.usda.gov/Publications/2007/index.asp. Accessed on Oct. 10, 2012. 

USDA, NAAS. 2012. Census of Agriculture. Online: Quick Stats. 

http://quickstats.nass.usda.gov/results/2F30BlOC-OBC8-34F2-BlB2-B6F7D92342A3. Accessed 

on Oct. 15, 2012. 

WeedScience.org. 2012. International Survey of Herbicide Resistant Weeds. 

http://www.weedscience.org/In.asp . Accessed on Oct. 18, 2012. 

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