UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, D.C. 20460 

NOV 0 6 2014 

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, 

Science Information 

Ph.D., 

and 

Economist 

Analysis Branch 

V~ A;~ 

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 of the pest management roles and quantitative usage information for metolachlor and 

S-metolachlor. The BCP includes summaries of previous BEA_D products and available public 

and/or private 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 of these 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 of com, soybean, sorghum, and cotton, and in terms of percent 

crop treated, they are widely used for production of tomato, green beans, and sweet com. They 

may be used preplant or post-plant on some crops to inhibit pre·-emerged grasses. An advantage 

of these 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 in the season as layby herbicides, which can provide effective control of preemerged weeds, especially in combination with a post-emergence herbicide. 

Based on private 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 over this time period for S-metolachlor was 1.2 

pounds a.i./acre. Reported usage of S-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 turf and ornamentals in 2011 

(Proprietary data, 2012). 

USE SITES 

Agricultural Use Sites 

S-metolachlor registered 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. 

2 
Metolachlor 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 on the 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 of pounds 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 at the very least, a high 

reliance on S-metolachlor to control weeds in these crops. The use of s-metolachlor on onions is 

5% crop treated and on potatoes 20% crop treated. 

For metolachlor, the agricultural sites with the greatest number of pounds applied were for com, 

followed by sorghum, soybeans and cotton. In terms of the 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 of the more active form of the chemical. 

3 
A search of the 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 

of crops, 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 

broadleaf weeds, metolachlor was most often requested for the control of nutsedges, while smetolachlor was requested for nightshade control. Both were primarily requested given a lack of 

available alternatives when targeting these particular types of weeds. In most cases EPA OPP 

supported this need and approved dozens of Section 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 in the 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 in resistance management given a lack of efficacious 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 on private 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 

1 presents 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 of smetolachlor increases, both in terms of pounds a.i. applied and total area treated, during the 

1998-2012 time frame. 

FIGURE 1. S-Metolachlor Usage in Pounds Active Ingredient Applied (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) 

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40,000,000 

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~'b ~"' ~~ ~'\. ~ry ~" ~ ~~ ~b ~~ ~'b ~"' ~~ ~'\. ~ry ~ ~ ~ ry~ ~ ry~ ry~ ry~ ry~ ry~ ~ ry~ ry~ ry~ ~ 

Years 

Source: Proprietary Data, 1998-2012 

Table 1. Comparison of Crops with Highest Use of S-metolachlor- Percent of Total Lbs. 

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 of States with Highest Use of S-metolachlor- Percent of Total 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 of the total 

use of S-metolachlor decreased similarly in the com belt states of Illinois, Iowa, and Indiana, with 

increases in the Plains states of Nebraska and Kansas (Table 2). 

5 
The average a.i. rate for S-metolachlor on the top crops in terms of pounds 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 a e bl 3 . S -meto I ac hi or U 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 that receive multiple treatments. 

Source: Proprietary Data, 2008 -2012 

Metolachlor 

Based on private 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) 

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

Years 

Source: Proprietary Data, 1998-2012. 

FIGURE 4. Metolachlor Total Area Treated in Acres (1998-2012) 

Cll 35,000,000 

~ = ·-

0 

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

Years 

Source: Proprietary Data, 1998-2012. 

7 
Table 4. Comparison of Crops with Highest Use of Metolachlor- Percent of Total 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 of States with Highest Use of Metolachlor- Percent of Total 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 of total pounds used of metolachlor decreased between the 2003-2007 and 2008-

2012 time periods on com, with an increase in percent of total pounds for the 2008-2012 time 

frame for other top crops (Table 4). The percent of the total use ofmetolachlor decreased in the 

states with the highest usage, possibly due to the availability of S-metolachlor designed as a 

metolachlor replacement product (Table 5). The overall increase in use (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, although resistance to other herbicides or weather conditions that may 

increase weed pressure are possible (but unsubstantiated) explanations. 

The average a.i. rate for the top crops in terms of pounds 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 a e . bl 6 M eo t I ac hi or U se on T C op rops: A verage An nua IAI .. R 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 of the average annual amount (in pounds) of 

metolachlor applied per 1,000 acres of crop acres grown. Figure 6 provides a broad geographical 

view of the average annual amount (in pounds) of S-metolachlor applied per 1,000 acres of crop 

acres grown. The calculated values presented in the maps are not equivalent to an application 

rate (lb ail A), therefore, the maps may show areas of high 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 on pounds active ingredient applied. Table 5 shows New 

Mexico, Louisiana, and Wisconsin as having the greatest intensity of use ofmetolachlor. Table 6 

indicates that the greatest intensity of use 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 of the information presented on the map. 

9 
Pounds Active 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 of metalochlor (2008-2012). 

10 
Pounds Active 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 of S-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 & METOLACHLOR AND 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 by the original registrant as a replacement for 

11 
metolachlor and was introduced in 1997 (O'Connell et al., 1998). Metolachlor consists of four 

stereoisomers of which the 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% of S-isomers whereas metolachlor contains 

approximately half S-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 in total area treated for metolachlor (Fig. 4, above) compared 

to S-metolachlor (Fig. 2, above) reflects the preference for the more concentrated active 

component of S-isomers in S-metolachlor. The reduction in use 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-METOLACHLOR AND METOLACHLOR IN PEST MANAGEMENT 

Metolachlor and S-metolachlor are herbicides used to control grass weeds and some broadleaf 

weeds, primarily for production of com, soybean, sorghum, and cotton. They may be used 

preplant or post-plant on some crops to inhibit pre-emerged grasses. These herbicides affect 

seedling germination and thus control weeds prior to weed emergence but do not control after 

weeds emerge. · 

An advantage of these 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 of pre-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 out many 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 of weeds in the spring 

(Illinois, 2007). Higher rates are needed for this strategy and herbicide 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 may be incorporated in the soil prior to planting or applied on the 

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 of targeted 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 of targeted weeds and provide residual activity. However, damage to 

plants has been observed. In cotton production, metolachlor herbicides have been used in 

combination with glyphosate in an attempt to manage pigweed amaranth (Bauer, 2013). 

However, costs of pigweed control due to glyphosate-resistance were said to have risen from $23 

to $80-100 per acre (Thompson, 2013). 

S-metolachlor is one of the 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 on tomatoes, 

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 of turf in comparison to 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 of S-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 of Florida 

Extension. http:/ /flacrops.com/20 13/06/11 /palmer-amaranth-control-a-challenge-in-cotton-partlL 

BEAD. 2014a. Metolachlor Screening Level Usage Analysis. Biological and Economic Analysis 

Division, Office of Pesticide Programs, US Environmental Protection Agency. April21, 2014. 

13 
BEAD. 2014b. S-Metolachlor Screening Level Usage Analysis. Biological and Economic 

Analysis Division, Office of Pesticide 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 of Florida Publ. 

HS200. http:/ /edis.ifas. ufl.edu/pdffiles/W G/W G04000. pdf 

Dittmar, P. J. and Stall, W. M. 2012b. Weed management in sweet corn. University of Florida 

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. gov I oppOOOO 1 I chem search/reg actions/reregistration/fs PC-1 0880 1 1-Apr95.pdf 

Ferrell, J. A., MacDonald, G. E., and Brecke, B. J. 2012. Weed management in sorghum. 

University of Florida Extension Publ. SS-AGR-06. http://edis.ifas.ufl.edu/wg002 

Gunsolus, J. L. 2005. Weed control in corn. University of Minnesota Extension. 

http:/ /appliedweeds.cfans. umn.edu/weedbull/Com. pdf 

Hartzler, B. 2004. Are all metolachlor products equal? Version 2.0. Iowa State University, 

Department of Agronomy, 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 of Illinois Extension. 

http://ipm.illinois.edu/pubs/iapmh/02chapter.pdf 

Kendig, J. A., Nichols, R. L., and Ohmes, G. A. 2007. Tolerance of cotton (Gossypium hirsutum) 

seedlings to preemergence and postemergence herbicides with four modes of action. Plant 

Management Network. 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 

14 
Marshall, 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., and Nice, 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/S0261219498800 112; 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 of Agriculture. Pp 38. 

http://www .agri.ohio. gov /Public Docs/Pest Study Material/2c%20 Weed%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/20 13/06/06/georgia-cotton-battling-palmer-amaranth-a-costly-fight/ 

UC. 2013. Herbicide Treatment Table-Cotton. University of California Pest Management 

Guidelines. http://www.ipm.ucdavis.edu/PMG/rl147003ll .html#LA YBY 

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 

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Xie, F. Liu, H. J., and Cai, W. D. 2010. Enantioselectivity of racemic metolachlor and Smetolachlor in maize seedlings. Journal of Environmental Science and Health Part B 45:774-782. 

http://www.tandfonline.com/doi/pdf/ 1 0.1080/03601234.2010.515173 

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APPENDIX A 

The map included herein primarily for the use of the risk assessors in the Environmental Fate and 

Effects Division. The map provides a very broad geographical view of the 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 in the amount of a pesticide used across farmland. 

Because ofthe definition of Land 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 of the 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 of multiple 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 of CRDs 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 of pesticide 

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 of the crop. Although 

the surveys capture most of the use of a particular active ingredient in agriculture, there are 

several limitations to these surveys. 

• States with minor production of a surveyed crop are not sampled 

• Not all types of pesticides are surveyed in every crop in every year 

• Many specialty crops with very small acreages are not included in the survey 

The result of these limitations is that CRDs that show no usage may actually have a small 

amount of the active ingredient being used. 

The denominator (1,000 Acres of land in farms) was selected from the Census of Agriculture 

(USDA, 2007) to represent agricultural acreage that is actively managed and includes most of the 

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areas treated with pesticides. The category "Land in Farms" is defined by the Census of 

Agriculture as being made up of four 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 of Agriculture does not include grazing land rented (on a per-animal basis) from the 

Bureau of Land Management or Forest 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 of measurement do matter and may be different between maps. 

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