UNITED STATES ENVIRONMENTAL PROTECTION AGENCY WASHINGTON , D.C

. 20460 

### NOV 

## 062014

OFFICE OF CHEMICAL SAFETY AND POLLUTION PREVENTION MEMORANDUM SUBJECT: 

### BEAD Chemical Profile (BCP) for Registration Review: Metolachlor Case [Smetolachlor (108800) and Metolachlor (108801)] FROM: 

### Leonard Yourman, Ph.D., Plant Pathologist 

## {J Biological Analysis Branch

## ~**~** Jihad Alsadek, Ph

.D., Economist

# V~**A;~** Science Information and Analysis Branch Elizabeth Hill, Economist Economic Analysis Branch Biological and Economic Analysis Division (7 THRU: 

### Arnet Jones, Chief /)

- -

## !JA) Biological Analysis

# Bran},**~** v { 

# ' j,J J;n1,_- Diann Sims, Chief

### ./d1~7-**~.** 

# . Science Information and Analysis Branch Timothy Kiely, Chief 

# £1**\M.,~** Economic Analysis Branch Biological and Economic Analysi ivision (750 TO: 

### Kaitlin Keller, Chemical Review Manager Risk Management and Implementation Branch 3 Pesticide Re-evaluation Division (7508P)

Peer Review Panel date: 

### June 11, 2014

1

### INTRODUCTION The Biological and Economic Analysis Division (BEAD) chemical profile (BCP) provides an overview ofthe pest management roles and quantitative usage information for metolachlor and S-metolachlor. The BCP includes summaries ofprevious BEA_D products and available public and/orprivate use and usage data for these chemicals to describe their roles in pest management
. Additional information on use is available in the S-metolachlor and metolachlor LUIS Label Data Reports. Information provided in the BCP may be used by stakeholders (e.g., users and registrants), OPP risk and benefit assessors, OPP risk managers, and the general public during the Registration Review process ofthese herbicides. Metolachlor and S-metolachlor are chloroacetamide herbicides, used to control grasses and some broadleafweeds prior to weed emergence. Metolachlor was first registered in the U.S. in 1976. S-metolachlor was developed by the original registrant as a replacement for metolachlor and was introduced in 1997 (O'Connell et al., 1998). A Registration Eligibility Decision (RED) was issued for metolachlor in 1995 (EPA, 1995). Metolachlor and S-metolachlor are herbicides used to control grass weeds and some broadleaf weeds, primarily for production ofcom, soybean, sorghum, and cotton, and in terms ofpercent crop treated, they are widely used for production oftomato, green beans, and sweet com. They may be used preplant orpost-plant on some crops to inhibitpre· -emerged grasses. An advantage ofthese herbicides is that for many crops seeds can be planted immediately after herbicide treatment (e.g., Nielsen et al., 2008). Another advantage for cotton production, for example, is their use later inthe season as layby herbicides, which can provide effective control ofpreemerged weeds, especially in combination with a post-emergence herbicide. Based onprivate market usage data from 1998-2012, usage for S-metolachlor averaged approximately 28 million pounds active ingredient (a.i.) applied annually on approximately 24 million acres treated. The average a.i. rate overthis time period for S-metolachlor was 1.2 pounds a.i./acre. Reported usage ofS-metolachlor for nursery and floriculture was 6,800 lbs in 2006 (USDA, 2006). Based on usage data for the same time period, usage for metolachlor averaged approximately 9 million pounds active ingredient (a.i.) applied annually on approximately 6 million acres treated

. The average a.i

. rate over this time period was 1.5 pounds a.i./acre. There were 127,000 lbs. a.i. reported usage data for turfand ornamentals in 2011 (Proprietary data, 2012).



### USE SITES Agricultural Use Sites S-metolachlorregistered agricultural use sites include: blueberries, citrus fruits, tree nuts, stone fruits, root and tuber vegetables, bulb vegetables, fruiting vegetables, legume vegetables, stem vegetables, seeds and sugar beets.



### 2Metolachlor registered agricultural use sites include: blueberries, citrus, stone fruits, figs, cilantro, ginger, melons, leafy vegetables, cole crops, bulb crops, root crops, pod crops, seed crops, grain crops, cotton, Christmas trees, and fruit trees. Non-agricultural Use Sites S-metolachlor registered non-agricultural use sites include: grasses, ornamentals, airports, recreation areas, athletic fields and roadsides. Metolachlor registered non-agricultural use sites include: airports, grasses, nurseries, ornamentals, turf, recreation areas and roadsides.

FORMULATIONS AND APPLICATION METHODS S-metolachlor is formulated as granular, emulsifiable/flowable/soluble concentrate, solutionready to use and as pressurized liquid. S-metolachlor is applied both onthe ground and aerially through fixed wing and rotary aircrafts. Metolachlor is formulated as granular, emulsifiable/flowable/soluble concentrate, solution-ready to use and as pressurized liquid. Metolachlor is applied aerially (fixed wing and rotary aircraft) and low volume application through water spray.

HISTORY OF BEAD PRODUCTS 

### for S-METOLACHLOR & METOLACHLOR Recent Screening Level Usage Analyses (SLUA) for metolachlor (BEAD, 2014a) and Smetolachlor (BEAD, 2014b) provide national level poundage applied by active ingredient (a.i.) and percent crop treated (PCT) data for crops for which usage data were available. Data for these analyses are from 2004 to 2012. For S-metolachlor, the agricultural sites with the greatest number ofpounds used were for com (20% crop treated), soybeans (5% crop treated), sorghum (25% crop treated), and cotton (10% crop treated). Highest percent crop treated are found in tomatoes (55% crop treated), followed by green beans (50% crop treated) and sweet com (40% crop treated). The high percent crop treated on these crops may indicate high benefits for these crops, or atthe very least, a high reliance on S-metolachlor to control weeds in these crops. The use ofs-metolachlor on onions is 5% crop treated and onpotatoes 20% crop treated. Formetolachlor, the agricultural sites with the greatest number ofpounds applied were for com, followed by sorghum, soybeans and cotton. In terms ofthe percent crop treated, green beans with 10 percent crop treated, followed by sorghum and tomatoes with 5 percent crop treated for each. The remaining crops in the SLUA crop list are less than 2.5 percent crop treated. The percent crop treated was lower for metolachlor than for S-metolachlor possibly reflecting a user's choice ofthe more active form ofthe chemical.

3

### A search ofthe BEAD database for previous BEAD products for S-metolachlor and metolachlor indicates that since 1997, 12 emergency exemption assessments have been conducted by BEAD-six for S-metolachlor and six for metolachlor. These exemptions were for a wide range ofcrops, including tomatoes, spinach, pumpkin, red beets, sweet potato, leafy greens, lettuce, and sesame. Although S-metolachlor and metolachlor were both requested for a variety of broadleafweeds, metolachlor was most often requested for the control ofnutsedges, while smetolachlor was requested for nightshade control. Both were primarily requested given a lack of available alternatives when targeting these particular types ofweeds. In

### most cases EPA OPP supported this need and approved dozens ofSection 18s requests/crises for the use of metolachlor (beets, grasses, spinach, and tomatoes) and S-metolachlor (beets, leafy greens, pumpkins, sesame, spinach, sweet potato, and tomato). All ofthese use sites are currently registered inthe U.S. An 

### exclusive use request for S-metolachlor for use on tomatoes and certain grasses grown for seed was submitted in 2007. This request claimed that this chemical served a role inresistance management given a lack ofefficacious alternatives. BEAD's assessment supported an exclusive use for tomatoes, but not for grasses grown for seed as there was a lack of sufficient evidence to support the resistance management claim.



### USAGE Agricultural Usage S-metolachlor · Based onprivate market usage data from 1998-2012, S-metolachlor usage averaged approximately 28 million pounds active ingredient (a.i.) applied annually on approximately 24 million acres treated. The average a.i. rate over this time period was 1.2 pounds a.i./acre. Figure 1presents S-metolachlor usage in pounds a.i. over the 1998-2012 timeframe

. Figure 2 presents total area treated in acres over the same time period (Proprietary Data, 1998-2012). The use ofsmetolachlor increases, both in terms ofpounds a.i. applied and total area treated, during the 1998-2012 time frame. 

### FIGURE 1. S-Metolachlor Usage in Pounds Active IngredientApplied (1998-2012) 45,000,000



### 0 A'b**A~ ~~** **~'\. ~'It** **~'? ~~** **~" ~b** **~ ~'b** **~~ ~~** **~'\. ~'It** **~ ~** **'It~ 'It~** **'It~ 'It~** **'It~ 'It~** **'It~ 'It~** **~ ~** **~ ~** **'It~** 

### Years
Source: Proprietary Data, 1998-2012 4

### FIGURE 2. S-Metolachlor Total Area Treated in Acres (1998-2012)

"0**~** 

# = Q,)

### ~ 

# = e <


# - = 

# -**~** 40,000,000

0

### ~'b**~"' ~~** **~'\. ~ry** **~" ~** **~~ ~b** **~~ ~'b** **~"' ~~** **~'\. ~ry** **~ ~** **~ ry~** **~ ry~** **ry~ ry~** **ry~ ry~** **~ ry~** **ry~ ry~** **~** 

### Years
Source: Proprietary Data, 1998-2012



### Table 1. 

### Comparison ofCrops with Highest Use ofS-metolachlor- Percent ofTotalLbs. Applied (2003-2007 and 2008-2012) 2003-2007 2008-2012 Average Annual Usage= 31,000,000 Average Annual Usage= 33,000,000 lbs/yr lbs/yr 

### Crop %Lbs Crop %Lbs Com 82,000,000 Com 70 Sorghum 7,000,000 Soybean 13 Soybean 3,000,000 Sorghum (Milo) 5

Cotton 2,000,000 Cotton 5 Other 6,000,000 Other 7 Source: Propnetary Data, 2003-2012. 

### Table 2. Comparison ofStates with Highest Use ofS-metolachlor- Percent ofTotal Lbs. Applied (2003-2007 and 2008-2012) 2003-2007 2008-2012 Average Annual Usage= 31,000,000 lbs/)'!"_ Average Annual Usage= 33,000,000 lbs/yr 

### State Lbs State %Lbs Illinois 17,000,000 Illinois 12

Iowa 12,000,000 Nebraska 11 Nebraska 10,000,000 Kansas 

### 9

Kansas 8,000,000 Iowa 8 Indiana 8,000,000 Indiana 6 Source: Propnetary Data, 2003-2012 The amount ofS-metolachlor used on com decreased between the 2003-2007 and 2008-2012 time periods and increased on sorghum, soybeans and cotton (Table 1 ). The percent ofthe total use ofS-metolachlor decreased similarly in the com belt states ofIllinois, Iowa, and Indiana, with increases in the Plains states ofNebraska and Kansas (Table 2).
5

### The average a.i. rate for S-metolachlor on the top crops interms ofpounds a.i. applied was the highest for com at 1.1 lbs. a.i. /acre and the lowest for cotton/sorghum/soybeans at 1.0 lbs. a.i. /acre for each, as shown 

### in Table 3. The application rates for S-metolachlor, for the 2008-2012 timeframe, are 1.11 lbs. a.i. for asparagus, 0.95 lbs. a.i. for cabbage, 0.54 lbs. a.i. for spinach and 0.91 lbs. a.i. for squash.

S-Metolachlor Application Rates 

### T bl 3 S

a e 

# . I 

### hi U -meto ac or se on T C op rops: A

### verage AIR 

# .. ate, 2008 2012 

# - Average Annual Average Annual Avg. Annual A.I. Crop Pounds A.I. Total Acres Rate (lbs Applied Treated* a.i./acres) Com 23,000,000 21,000,000 1.1 Cotton 2,000,000 2,000,000 1.0 Sorghum 2,000,000 2,000,000 1.0 Soybean 4,000,000 4,000,000 1.0 *Total Acres Treated sums all acres treated for a crop, mcludmg those acres thatreceive multiple treatments. Source: Proprietary Data, 2008 -2012



### Metolachlor Based onprivate market usage data from 1998-2012, usage for metolachlor averaged approximately 9 million pounds active ingredient (a.i.) applied annually on approximately 6 million acres treated. The average a.i. rate over this time period was 1.50 pounds a.i. /acre. Figure 3 presents metolachlor usage in pounds a.i. over the 1998-2012 timeframe. Figure 4 presents total area treated in acres over the same time period (Proprietary Data, 1998-2012). This time period begins when the S-metolochlor product was first available and marketed by the registrant as a replacement for their metolachlor product.



### 6

### FIGURE 3. Metolachlor Usage in Total Pounds A.I. Applied (1998-2012)
'1:1 

### 60,000,000 Q) 

# ·- 

# l

........ 

# < Cll 

# § 0**~** 

### ]**~** 0**~% ~0,** **~~ ~'\.** **~'\; ~....,** **~'>< ~"** **~b ~f\.** **~% ~0,** **~~ ~'\.** **~I), ~** **~ '\;~** **'\;~ ~** **'\;~ '\;~** **'\;~ '\;~** **'\;~ '\;~** **'\;~ '\;~** **'\;~ '\;~**  

### Years
Source: Proprietary Data, 1998-2012

.


### FIGURE 4. Metolachlor TotalArea Treated in Acres (1998-2012)

Cll 

### 35,000,000

# ~ = 

# ·-

0**~% ~0,** **~~ ~'\.** **~'\; ~""** **~'>< ~"** **~b ~f\.** **~% ~0,** **~~ ~'\.** **~'\; ~** **~ '\;~** **'\;~ '\;~** **~ '\;~** **'\;~ '\;~** **'\;~ ~** **'\;~ '\;~** **~ '\;~**  

### Years
Source: Proprietary Data, 1998-2012.



### 7Table 4. Comparison ofCrops with Highest Use ofMetolachlor- Percent ofTotal Lbs. A.I. Applied (2003-2007 and 2008-2012) 2003-2007 2008-2012 Average Annual Usage= 720,000 Lbs/Yr. Average Annual Usage= 3,670,000 Lbs/Yr. Crop %Lbs Crop %Lbs Com 71 Com 55 Soybean 10 Sorghum (Milo) 16 Sorghum (Milo) 8 Soybean 16 Cotton 7 Cotton 8 Other 4 Other 5 Source: Propnetary Data, 1998 -2012. Table 5. Comparison ofStates with Highest Use ofMetolachlor- Percent ofTotal Lbs. A.I. Applied (2003-2007 and 2008-2012) 2003-2007 2008-2012 Average Annual Usage= 720,000 Lbs/Yr. Average Annual Usage= 3,670,000 Lbs/Yr. State 0 /o Lbs State %Lbs Illinois 18 Illinois 13 Kansas 11 Kansas 13 Indiana 10 Wisconsin 7 Missouri '9 Nebraska 7

Iowa 9 Texas 7 Source: Proprietary Data, 1998 -2012

. The percent oftotal pounds used ofmetolachlor decreased between the 2003-2007 and 2008- 2012 time periods on com, with an increase inpercent oftotal pounds for the 2008-2012 time frame for othertop crops (Table 4). The percent ofthe total use ofmetolachlor decreased in the states withthe highest usage, possibly due to the availability ofS-metolachlor designed as a metolachlorreplacement product (Table 5). The overall increase inuse (lb per year) as shown in Tables 4 and 5 should be noted. BEAD does not have information as to why there is a nearly · five-fold increase in use, althoughresistance to otherherbicides or weather conditions that may increase weed pressure are possible (but unsubstantiated) explanations. The average a.i. rate for the top crops interms ofpounds a.i. applied was the highest for soybeans at 1.40 lbs. a.i. /acre and the lowest for cotton at 0.99 lbs. a.i. /acre as shown in Table 6. Application rates for metolachlor, for the same time period, on asparagus isl.46lbs. No use was found for cabbage, spinach and squash.



### 8

### Metolachlor Application Rates 

### T bl 6 M 

### t I 

### hi U

a e . eo ac or se on 

### T C op rops: A

### verage An IAI R nua 

# .. ate, 2008 2012 

# - Average Annual Average Annual Avg. Annual A.I. Crop Pounds A.I. Total Acres Rate (Lbs. A.I. Applied Treated* /Acre) Corn 2,021,000 1,667,000 1.21 Soybean 577,000 421,000 1.40 Sorghum (Milo) 577,000 487,000 1.20 Cotton 286,000 290,000 0.99 *Total Acres .Treated sums all acres treated for a crop, mcludmg those acres that recetve multtple treatments. Source: Proprietary Data, 2008 -2012


### Geographic Distribution ofMetolachlor and S-Metolachlor Use
Figure 5 provides a very broad geographical view ofthe average annual amount (in pounds) of metolachlor applied per 1,000 acres ofcrop acres grown. Figure 6 provides a broad geographical view ofthe average annual amount (inpounds) ofS-metolachlor applied per 1,000 acres ofcrop acres grown. The calculated values presented in the maps are not equivalentto an application rate (lb ail 

### A), therefore, the maps may show areas ofhigh use intensity that do not necessarily correspond to the states listed in Tables 2 and 5 since those are the states with the highest use of metolachlor and S-metolachlor based onpounds active ingredient applied. Table 5 shows New Mexico, Louisiana, and Wisconsin as having the greatest intensity ofuse ofmetolachlor. Table 6 indicates thatthe greatest intensity ofuse for S-metolachlor is for Maryland, Delaware, and Massachusetts. Please note that the scale for the two maps are quite different. Please see Appendix A for a more detailed explanation ofthe information presented on the map.

9PoundsActive Ingredient per 1,000 Crop Acres Grown CJ No Data CJ <3 CJ 3-5 5-10

- 10-25

- >25 

### Figure 5. Annual average agricultural use intensity ofmetalochlor (2008-2012).

10PoundsActive Ingredient per 1,000 Crop Acres Grown 0NoData 0 <10 

## D 1o-5o 50-100

- 100-210

- >210 

### Figure 6. Annual average agricultural use intensity ofS-metalochlor (2008-2012).
Non-Agricultural Usage S-metolachlor There were 6,800 lbs. S-metolachlor reported for nursery and floriculture in 2006 (USDA, 2006). Metolachlor There were 127,000 lbs. metolachlor reported for turf

### and ornamentals in 2011 (Proprietary Data, 2012).



### S-METOLACHLOR & 

### METOLACHLORAND USE CHARACTERISTICS Metolachlor and S-metolachlor are chloroacetamide herbicides. Other chloroacetamide herbicides include acetochlor, alachlor, and dimethenamid. Metolachlor was first registered in the U.S. in 1976. S-metolachlor was developed bythe original registrant as a replacement for
11metolachlor and was introduced in 1997 (O'Connell et al., 1998). Metolachlor consists offour stereoisomers ofwhichthe most active components are twoS-isomers (S-metolachlor) (Xie et al., 2010; Hartzler, 2000). Generally metolachlor will provide less residUal activity than S-metolachlor (e.g., Ferrell, 2012). S-metolachlor contains approximately 88% ofS-isomers whereas metolachlor contains approximately halfS-isomers and halfR-isomers (less active forms). It is unlikely that there would be observable efficacy differences at labeled rates for products containing either formulation, although the overall amount used would be greater for metolachlor (e.g., Hartzler, 2004; Ohio, 2007). The reduction intotal areatreated for metolachlor (Fig. 4, above) compared to S-metolachlor (Fig. 2, above) reflects the preference for the more concentrated active component ofS-isomers in S-metolachlor. The reduction inuse may be due to increased use of alternative herbicides or other factors currently unknown to BEAD. A "safener" (an antidote such as fluxofenim) is commonly applied as a seed treatment or formulated in the herbicide product to protect some crops (e.g., sorghum and com) from herbicide damage (e.g., Ferrell, 2012).



### ROLE OF S-METOLACHLORAND METOLACHLOR IN PEST MANAGEMENT Metolachlor and S-metolachlor are herbicides used to control grass weeds and some broadleaf weeds, primarily for production ofcom, soybean, sorghum, and cotton. They may be used preplant or post-plant on some crops to inhibitpre-emerged grasses. These herbicides affect seedling germination and thus control weeds prior to weed emergence but do not control after weeds emerge. · An advantage ofthese herbicides is that for some crops, such as com, soybean, and sorghum, seeds can be planted immediately after herbicide treatment (e.g., Nielsen et al., 2008). Another advantage for cotton production, for example, is their use later in the season as layby herbicides, which can provide effective control ofpre-emerged weeds, especially in combination with a post-emergence herbicide. These layby applications complement earlier weed control strategies and offer residual activity until the canopy closes shading outmany emerging weeds (e.g., McCloskey, 2001; Laws, 2006; UC, 2013). S-metolachlor and metolachlor are used as fall treatments in some locations (e.g., some areas in Illinois) in soybean and com fields in an attempt to reduce emergence ofweeds inthe spring (Illinois, 2007). Higher rates are needed for this strategy andherbicide dissipation by spring may reduce efficacy. There are variable rates indicated on labels depending on soil texture (Kendig et al., 2007). S-metolachlor and metolachlor maybe incorporated in the soil prior to planting or applied onthe soil surface. Preplant incorporated applications are most effective when there is little rain; preemergence applications provide more effective weed control when rain is present (e.g., Gunsolus, 2005). In com and sorghum production in addition to grass weed control, nutsedge, redroot pigweed, and nightshade may be acceptably controlled. The herbicides are sometimes

12

### combined with other herbicides, such as atrazine, to broaden the spectrum oftargeted weeds (e.g., Bennett, 2007; Marshall, 2013). Similarly, for no-till soybean (e.g., Young and Young, 2005) or cotton (Dodds, 2011) production, metolachlor herbicides can be mixed with glyphosate to broaden the spectrum oftargeted weeds and provide residual activity. However, damage to plants has been observed. In cottonproduction, metolachlor herbicides have been used in combination with glyphosate in an attempt to manage pigweed amaranth (Bauer, 2013). However, costs ofpigweed control due to glyphosate-resistance were said to have risen from $23 to $80-100 per acre (Thompson, 2013). S-metolachlor is one ofthe herbicides recommended for use in tomato production pre- and posttransplant (e.g., Dittmar and Stall, 2012a). Similarly, for sweet com S-metolachlor is among the herbicides recommended for treatment pre- and post- com emergence (e.g

., Dittmar and Stall, 2012b). For green bean production, S-metolachlor may be used as a treatment prior to bean emergence (e.g., Term, 2003). The high percent crop treated with S-metolachlor ontomatoes, green beans and sweet com may indicate high benefits for these crops, or at the very least, a high reliance on S-metolachlor to control weeds in these crops. For non-agriculture crops, metolachlor was used substantially more than S-metolachlor. This is possibly due to metolachlor use on extensive areas ofturfin comparisonto nursery and floriculture uses.

DATA NEEDS S-Metolachlor Obtaining usage information on crops where S-metolachlor is registered but not surveyed such as lentils and triticale and non-agricultural use sites such as grasses may improve future assessments conducted by the Agency related to the use and importance ofS-metolachlor. Metolachlor Obtaining usage information on crops where metolachlor is registered but not surveyed such as figs and non-agricultural use sites such as grasses may improve future assessments conducted by the Agency related to the use and importance ofmetolachlor.

REFERENCES Bauer, M. 2013. Palmer amaranth control a challenge in cotton (Part 

### 1). University ofFlorida Extension. http:/ /flacrops.com/20 13/06/11/palmer-amaranth-control-a-challenge-in-cotton-part

## lL BEAD. 2014a. Metolachlor Screening Level Usage Analysis. Biological and Economic Analysis Division, Office ofPesticide Programs, US Environmental Protection Agency. April21, 2014.
13

### BEAD. 2014b. S-Metolachlor Screening Level Usage Analysis. Biological and Economic Analysis Division, Office ofPesticide Programs, US Environmental Protection Agency. April 24,2014. Bennett, D. 2007. Options for weed control in corn. Delta Farm Press, Feb. 26, 2007. http://deltafarmpress.com/options-weed-control-com Dittmar, P. 

### J. and Stall, W. M. 2012a. Weed management in tomato. University ofFlorida Publ. HS200. http:/ /edis.ifas.ufl

.edu/pdffiles/WG/WG04000.pdf Dittmar, P. J. and Stall, W. M. 2012b. Weed management in sweet corn. University ofFlorida Publ. HS197. http:/ /edis.ifas.ufl.edu/pdffiles/WG/WG03800.pdf Dodds, D. 2011. Cotton damage from POST applied residual herbicides. Mississippi State University Extension. http:/ /www.mississippi-crops.com/20 11/06/17/cotton-damage-from-postapplied-residual-herbicides/ EPA. 1995. Registration Eligibility Decision-Metolachlor. http://www.epa.govI

### oppOOOO 1I

### chem search/reg actions/reregistration/fs PC-10880 1 1-Apr95.pdf Ferrell, 

### J. A., MacDonald, G. E., and Brecke, B. 

### J. 2012. Weed management in sorghum. University ofFlorida Extension Publ. SS-AGR-06. http://edis.ifas.ufl.edu/wg002 Gunsolus, J. L. 2005. Weed control in corn. University ofMinnesota Extension. http:/ /appliedweeds.cfans.umn.edu/weedbull/Com.pdf Hartzler, B. 2004. Are all metolachlor products equal? Version 2.0. Iowa State University, Department ofAgronomy, Weed Science. http://www.weeds.iastate.edu/mgmt/2004/stalwart2.shtml Hartzler, B. 2000. Resolved isomers explained. Iowa State University, Department of Agronomy, Weed Science. http://www.weeds.iastate.edu/mgmt/gtr00-1/isomers.htm Illinois. 2007. Weed control for corn, soybeans, and sorghum. University ofIllinois Extension. http://ipm.illinois.edu/pubs/iapmh/02chapter.pdf Kendig, J. A., Nichols, 

### R. L., and Ohmes, G. A. 2007. Tolerance ofcotton (Gossypium hirsutum) seedlings to preemergence and postemergence herbicides with four modes ofaction. Plant ManagementNetwork. Plant Health Progress Nov. 8, 2007. http://www.plantmanagementnetwork.org/pub/php/research/2007

### I cotton! Laws, F. 2006. For layby herbicides: Growers get new options. Delta Farm Press, July 14, 2006. http:/I

### deltafarmpress.com/layby-herbicides-growers-get-new-options

14Marshall, M. 2013. Weed control in grain sorghum. South Carolina Pest Management Handbook for Field Crops. Clemson University Extension. http:/ /www.clemson.edu/extensionlrowcrops/pest/files/2013pestmanagementfiles/weedcontrolins orghumPMH2013.pdf McCloskey, W. B. 2001. Using layby herbicides for weed control in cotton. University of Arizona Extension. http://ag.arizona.edu/crops/cottonlweeds/laybyherbicides.html Nielsen, R. L., Johnson, B., andNice, G. 2008. Grain sorghum considerations for late planting in southern Indiana. Purdue University Extension. http://www.agry.purdue.edu/Ext/ cornlnews/timeless/LatePlantGrainSorghum.html O'Connell, P. J., Harms, C. T., and Allen, J. R. F. 1998. Metolachlor; S-metolachlor and their role within sustainable weed-management. Crop Protection 17(3):207-212. http://www.sciencedirect.com/science/article/pii/S0261219498800112; http://ac.elscdn

.com/S0261219498800112/1-s2.0-S0261219498800112-main.pdf? tid=3cf54d2e-el18-11e3- 9671-00000aabOfDl&acdnat=l400698177 327df47715b474f66176fea5d967669a ). Ohio. 2007. Weed control principles. Ohio Department ofAgriculture. Pp 38. http://www.agri.ohio.gov/Public Docs/Pest Study Material/2c%20Weed% 20Control%20Guide. 

### pM Proprietary Data. 2012. Proprietary Data, 1998-2012. Tenn. 2003. Crop Profile for Beans (Snap) 

### in Tennessee. http://www.ipmcenters.org/cropprofiles/docs/TNSnapbean.pdf Thompson, C. 2013. Georgia cotton: Battling Palmer amaranth a costly fight. AgFax, June 6, 2013. http://agfax.com/2013/06/06/georgia-cotton-battling-palmer-amaranth-a-costly-fight/ UC

. 2013. Herbicide TreatmentTable-Cotton

. University ofCalifornia Pest Management Guidelines. http://www.ipm.ucdavis.edu/PMG/rl147003ll

.html#LAYBY USDA. 2006. NASS Crop Reporting Districts (shape file ofCRDs). Available at: http://www.ers.usda.gov/briefing/arms/resourceregions/resourceregions.htm#nass; http://www.nass.usda.gov/Data and Statistics/County Data Files/Frequently Asked Questions /county list.txt Young, B. G. and Young, J. M. 2005. Glyphosate & s-metolachlor in no-till soybean. North Central Weed Science Society Research Report V. 62, pp 199. http://www.ncwss.org/proceed/2005/ResRep05/199.pdf

15Xie, F. Liu, H. J., and Cai, W. D. 2010. Enantioselectivity ofracemic metolachlor and Smetolachlor in maize seedlings. Journal ofEnvironmental Science and Health Part B 45:774-782. http://www.tandfonline.com/doi/pdf / 1 0.1080/03601234.2010.515173

16APPENDIX A 

### The map included herein primarily for the use ofthe risk assessors in the Environmental Fate and Effects Division. The map provides a very broad geographical view ofthe amount (inpounds) ofthe active ingredient applied per 1,000 acres of"land in farms". These data are included in the maps because risk assessors are interested in the 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 to an application rate (lbs a.i. I A). 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 on the 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 inthe 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 on private market surveys ofpesticide 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 ofthe crop. Although the surveys capture most ofthe use ofa particular active ingredient in agriculture, there are several limitations to these surveys.

• States with minor production 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 in the survey The result ofthese limitations is that CRDs that show no usage may actually have a small amount ofthe active ingredient being 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

17areas treated with pesticides. The category "Land in Farms" is defined by the Census of Agriculture as being made up offour components: • Total cropland • Permanent pasture • Total woodland • Land in farmsteads, buildings, livestock facilities, ponds, roads, wasteland, etc. This category includes land in the various USDA conservation programs. 

### It should be noted that the Census ofAgriculture does not include grazing land rented (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 attention to the figure legends and realize that a map prepared for a particular metolachlor is not directly comparable to a map prepared for a different metolachlor. Scale and units ofmeasurement do matter and may be different between maps.

18