UNITED STATES ENVIRONMENTAL PROTECTION AGENCY WASHINGTON, D

.C

. 20460



## MAY 31 2012

MEMORANDUM OFFICE OF CHEMICAL SAFETY AND POLLUTION PREVENTION

SUBJECT: BEAD Chemical Profile for Registration Review: Methanearsonic acid, salts (MSMA) (013803) Bill Phillips, II, PhD

# AgrOfJ(Jmist~~--- FROM:

THRU: 

# :::::Y;:v:::w Protection Speciwist / 

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# ~ Science Information and Analysis Branch John Faulkner,

# Economist~ Economic Analysis Branch Biological and Economic ysis Division (7503P) Arnet Jones, Chief Biological Analysis Branch Diann Sims, Chief

# ~~**' l...A-~~'V"""'­**  Science Information and Analy

. Timothy Kiely, Chief Economic Analysis Branch Biological and Economic Analysis TO: Tom Myers, Chemical Review Manager Risk Management and Implementation Branch 2 Pesticide Re-evaluation Division (7508P)

Product Review Panel date: May 16, 2012 INTRODUCTION The purpose ofthis document is to conveyusage information and a broad overview ofthepest managementroles ofpesticides that are beginning to undergo registration review. The anticipated audience consists ofthe team ofEPA (Agency) staffcurrently evaluating the 1registration status ofmethanearsonic acid, salts (MSMA), and eventually the general public. This documentbuilds uponthe data already provided inthe "Usage and Label Use DataPackages" that are also provided to Registration Reviewteams by BEAD. The document is based on information and data available to BEAD as ofMay 4, 2012. MSMA is an organic arsenical (OA) herbicide that is a broad-spectrum herbicide used to selectively control grasses andbroadleafweeds in cotton and turfgrass. Applications are made postemergence and post-directed to the weed and crop in cotton and are applied in turf postemergence to the target weed. This herbicide is classified by the Weed Science Society of Americainthe mechanism ofaction group 17; which is a class ofpotential nucleic acid inhibitors ornon-descript mechanism ofactionherbicides. The mechanism ofaction by which MSMA controls weeds is unknown; however itis currently thoughtto be via cell membrane disruption and subsequent destruction. Currently there is registration follow up and evaluation work being conducted bythe Agency on the MSMAregistrations. Part ofthis work stems from the 2006 reregistration eligibility decision (RED) which found that none ofthe OA herbicides (CAMA, cacodylic acid, DSMA and MSMA)I were eligible for reregistration. In addition to the 2006 work, a post-RED (2009) follow up with the registrants resulted in an "agreementinprinciple" where CAMA, cacodylic acid, DSMA were voluntarily canceled and most ofthe uses ofMSMA were either voluntarily cancelled or scheduled for voluntary phased out.2 

### Itwas determined thatthe use in cotton was one use with such highbenefits that this single use ofMSMA was determined to be eligible for reregistration. 3 In addition, there were several turfgrass uses that remain labeled but are currently part ofthe phase-outprogram. Those uses whichremain have had significant restrictions placed upon them (e.g., buffers, number ofapplications, spot treatments, etc.). The uses that are scheduled to be phased out, as a part ofthe agreement inprinciple, were divided into two phases. Phase one included the following uses that were removed in 2009, forestry, all fruit and nut crops, drainage ditch banks, grass seedproduction, non-crop areas, and residential lawns. Phase two uses were golfcourse, highway rights-of-way, and sodfarms which are scheduled to be removed as ofDecember 31, 2013, but as a condition ofthe continued use of MSMA in these sites, restrictions were placed onthese uses to cover the periodbetween 2009 thru 2013 (e.g., buffers, spottreatments, etc.). As a part ofphase two the Agency agreed to review any benefits information that would be submitted before December 31, 2011. Ifafter the Agency's review ofthis information it is determined that the benefits are considered significant, with respect to human and environmental risks, these use sites would not be phased out; however, additional restrictions maybe placed on the continued use.

1 monosodium methanearsonate (MSMA), disodium methanearsonate (DSMA), calcium acid methanearsonate (CAMA), and cacodylic acid and its sodium salt. 2 http://www.epagov/oppsrrdl/reregistration!organic_arsenicalsJs

.html#msma 3 PhiHips, B., D. Berwald, and E

. Rim, 2006

. Alternatives Assessment ofthe Organic Arsenical Herbicides Used in Residential and GolfCourse Turfgrass, and Cotton (DP Barcode: 309117), Biological and Economic Analysis Division, U.S. EPA, April 12, 2006, 27pp. 2

### USE SITES Prior to the 2006 RED cancelations and the subsequent 2009 agreement inprinciple, the agricultural use sites for MSMA included citrus fruits, nut crops, pome fruits, stone fruits, cotton vineyards, and non-bearing fruit trees. 

### In addition, there were non-agricultural use sites registered that included forest lands, omamentallawns and 

### turf, athletic fields, parks, golf courses and storage yards. All ofthese uses still remain onmany older labels as the existing stocks were allowed to be used. Current labeled uses include cotton and non-agricultural uses, golfcourse, highway rights-ofway, and sod farms. The non-agricultural uses are scheduled for cancellation in 2013.


### COMMON FORMULATIONS AND APPLICATION METHODS Methanearsonic acid, salts (MSMA) is formulated as emulsifiable concentrate, flowable concentrate, granular, and ready to use and canbe applied as a foliar treatment, soil treatment and by aerial application

.


### USAGE Agricultural Usage Based onprivate market usage data from 2000-2010, usage averaged approximately one million pounds active ingredient (lbs a.i.) for 850,000 acres treated. The average a.i. rate during this time period was approximately 1.14 pounds per acre. Between 2000 and 2005, the crops with the major use interms ofpounds a.i. applied were cotton (97%) and pasture (approximately 3%). The other crops that comprised less than one percent ofusage included citrus (oranges and lemons), nuts (pistachios, walnuts and pecans) and apples. Between 2006-2010, cotton (89%) and pastureland (10%) still accounted for the major use in terms ofpounds a.i. applied, while the remaining onepercent ofusage included citrus, nuts (pecans and almonds), wine grapes, and apples. Figure 1 presents usage ofMSMA on cotton 

### inpounds a.i. applied and total areatreated, over the 2000-2010 time period. Because there has notbeen sufficienttime betweenthe 2009 agreement inprinciple and present cropping years, plus the continued use ofexisting stocks ofthe herbicide, there are insufficient datato quantitatively evaluate the use ofMSMA since this time. However, a cursory view ofthe data in Figure 1, demonstrates that there does not appear to 

### be a dramatic change inthe total area treated (TAT) and lbs a.i. ofMSMA between 2009 and 2010. As stated above, other thanthe cottonuse datathere does not appear to be a sizeable use in this herbicide. However, looking at the period between 2007 

### thru 2010 the TAT use overthis periodhas increased in both cotton and the consolidated data but the actual amount ofthe a.i. applied for the same time periodhas begun to level offfor the consolidated data (post 2009) and remains increasing for the cotton data



### 3

## r'

FIGURE 1. MSMA Use on Cotton in Pounds A.I. Applied and TotalArea Treated in Acres (2000-2010 2500000 ,...-----------



### o 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 Years 

### Source: ProprietaryData, 2000-2010 TAT

-a- lbsAI

While the Agency was compiling infonnationregarding the use ofMSMA 4, researchers inthe state ofGeorgia, in 2005, confinned that there was a case ofglyphosate resistant Palmer amaranth 

### (Amaranthuspalmeri) (GrAMAPA5) established in a few counties in the state. 6 Since that time, the occurrence ofthis resistant weed biotype has dramatically increased and spread; the results ofwhich has lead some farmers to destroy entire crop stands in order to 

### try to contain and eventually stop the spread ofthis problem. Quickly following the confirmation ofresistance, weed control research provided evidence that the primaryherbicide that controls the GrAMAPA was MSMA. Given the few herbicides, compared to other crops and the fact that this is a broadleafweed in a broadleafcrop makes the choices that farmers have very limited.

4 Phillips, B., D. Berwald, and E. Rim, 2006. Alternatives Assessment ofthe Organic Arsenical Herbicides Used in Residential and GolfCourse Turfgrass, and Cotton (DP Barcode: 309117), Biological and Economic Analysis Division, U.S. EPA, April 12, 2006, 27 pp. 5 AMAPA is the official WSSA computer code forAmaranthuspalmeri. "Gr" is the prefix to the WSSA code that is used only in this documentto denote the glyphosate resistant biotype ofthis particular genus and species. 6 A. Stanley Culpepper, Timothy L. Grey, William K. Vencill, Jeremy M. Kichler, Theodore M. Webster, Steve M. Brown, Alan C. York, Jerry W. Davis, and Wayne W. Hanna. 2006. Glyphosate-resistant Palmer amaranth (Amaranthuspalmeri) confinned in Georgia. Weed Science 54(4):620-626. Weed Sci. Soc. ofAmerica 4

# r'

This lack oftools and the increase inthe amount ofthe a.i. applied between 2007 and 2010 coincides with the 2005 discovery and subsequent spread ofthe glyphosate resistant biotype of GrAMAPA, as well as the subsequent research that demonstrated the high efficacy ofMSMA on GrAMAPA. This is indicative ofthe need to increase the application rate ofan he:r:bicide given control problems with difficult-to-control weed species. Table 1 demonstrates the high use of MSMA in the state ofGeorgia for the period of2006 to 2010. From this very limited use data it would seem thatthe use ofMSMA will at least remain consistent, ifnot increase, inthe near future. Overthe years MSMA use in cottonhas declined dramatically and was on its way to being relegated to the occasional use. Due to the establishment ofthis pernicious weed biotype in Georgia, and now in other cottonproducing states (e.g., North Carolina), coupled with the early research conducted at the University ofGeorgia, MSMA has again been adopted as what may soon be a commonly used herbicide throughout the cotton growing region (Figure 2). However, even with the potential increase in the use ofMSMA, itis doubtful that the lbs a.i. and the TAT ofthis herbicide will returnto the level ofuse of2000. Table 1 compares the states with the most agricultural usage betweenthe years of2000 and 2005 and the years between 2006 and 2010. The state with

.the mostpounds a.i. applied inboth timeframes was Georgia (21% oftotallbs applied in 2000-2005, and 59% oftotallbs applied in 2006-2010), where bothpounds applied and acres treated increased inthe state during the 2006- 2010 timeframe. This timeframe coincides with the establishment ofGrAMAPA. The "other" states accounting for approximately 13% ofusage in the 2000-2005 timeframe included South Carolina, California, Tennessee, Missouri, Virginia, and Florida. In the 2006-2010 timeframe, the "other states" accounting for approximately 9% ofusage included California, Arkansas, Louisiana, Arizona, Oklahoma, and South Dakota. While use in other cottonproducing states have not increased, and in some cases have decreased, the current trend ofincreasing confIrmation ofcases ofGrAMAPA inmany ofthese states where cotton is produced will lead to an increase inuse given that some ofthese states have cropping systems where MSMA will be a good fit.

5

### TABLE 1. 

### Comparison ofStates with Highest Use ofMSMA- Percent ofTotalLbs. Applied Between the2000-2005 and the2006-2010 Timeframes 2000-2005 Average = 1.27 million lbs/year 

### State %Lbs Georgia 21 Mississippi 18 N.Carolina 

### 13

Arkansas 12 Louisiana 10 Alabama 7

Texas 6 Other 

### 13 Source: Proprietary Data, 2000-2010

Non-Agricultural Usage 

### 2006-2010 Average = 621,000 lbs/year 

### State %Lbs Georgia 59 N. Carolina 12 Mississippi 7

Alabama 6 S. Carolina 4 Texas 3 Other 9

Intenns ofnon-agricultural usage, data are available only for use priorto the restrictions and cancellations imposed as a result ofthe 2009 RED and the 2006 AGREEMENT IN PRINCIPLE. Some ofthe historic data is available for sites that are no longer on the MSMA label (e.g., nursery/greenhouse) (Table 2). Site such as lawn care operators (LCO's) and golfcourses, landscape, nursery/greenhouse, and turffanns will continue to be available for at least until 2013. The data suggest that prior to the 2009 label changes the lbs a.i. for non-agricultural usage surpassedthe agricultural use. Data for sites where MSMA has been cancelled will continue to show use while existing stocks are exhausted.


### Table 2. MSMA Select Non-AgriculturalUsage (Pounds A.I.) (2002-2006) Site 2002 2004 2006 GolfCourses 482,284 206,203 311,537 Institutional Turf 67,691 299,950 211,700 Landscape 15,123 37,461 306,069 Lawn Care Operators 299,875 104,862 94,420 TurfFanns 375,690 186,636 182,348 Nursery/Greenhouse N/A 43,104 N/A 

### TOTAL Reported (lbs. a.i.) 1,240,633 878,216 1,106,074 N/A=not avruJable Source: Kline & Co., 2002, 2004, and 2006



### 6

### REFERENCES

Kline 

### & Co., 2002, 2004, and 2006 Proprietary Data, 2000-2010 Senseman, S.A. Herbicide Handbook, Ninth Edition. 2007. Weed Sci. Soc

. OfAmerica. Lawrence, Kansas 66044-8897 USDA, 2006-2010. NASS Crop Reporting Districts. Online: http://www.ers.usda.govibriefing/arms/resourceregions/resourceregions.htm#nass

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

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### Appendix Provided for the Environmental Fate and Effect Division RiskAssessment: MSMA Usage by 

### Crop Reporting District (2006-2010) Another measure ofusage is the use intensity. Inthis 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 acre. Figure 2 spatially represents MSMA use intensity over the period of2006 thru 

### 2010 inthe US with use in Georgia showing the highest intensity compared to other states where MSMA is used. Again, this information supports the current use and increases in the amount ofMSMA, with respect to lbs a.i. applied, in Georgia where the GrAMAPA issues have arisen.


### FIGURE 2. MSMA Usage by 

### Crop Reporting District (2006-2010)

Average Pounds Per 1,000 Acres of Farmland

. 0-3 4-10 D 11-24 25- 55 58

- lOB



### 8I



### Sources: Proprietary Data. 2006-2010 USDA, 2006-2010. NASS Crop Reporting Districts. USDA, 2007. Census ofAgriculture. This is a map of agricultural pesticide usage at the Crop Reporting District (CRD) level. CRDs are boundaries created by USDA NASS which are aggregates of counties (USDA, 2010). Pesticide usage is displayed as average pounds (for the years 2006-2010) per 1,000 acres offarmland in a CRD to normalize for the variation in farmland between CRDs. Farmland acreage was obtained from USDA (2007)

. Usage is based on private market surveys ofpesticide use in agriculture (Proprietary Data, 2006-2010).**Th~** 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.

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