UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, D.C. 20460 

MAY 212015 

MEMORANDUM 

OFFICE OF CHEMICAL SAFETY 

AND POLLUTION PREVENTION 

SUBJECT: BEAD Response to Public Comments in Support of Registration Review (EPA Docket ID 

No.: EPA-HQ-OPP-2014-0772}-Metolachlor Case [S-metolachlor (108800) and 

Metolachlor (108801)] 

FROM: Leonard Yourman, Ph.D., Plant Pathologist 

THRU: 

Biological Analysis Branch . . 

Jihad Alsadek, Ph.D., Economist ..;r~ A- --A~ Science Information and Analysis Branch 

Elizabeth Hill, Economist 

Economic Analysis Branch 

Biological and Economic Analysis Division (7503P) ) 

Arnet Jones, Chief 

Biological Analysis Bran 

Diann Sims, Chief 

I 

Science Information and Analysis Branch 

Timothy Kiely, Chief 

Economic Analysis Branch 

Biological and Economic Analysi 

TO: Steven Snyderman, Chemical Review Manager 

Risk Management and Implementation Division Branch 3 

Pesticide Re-Evaluation Division (7508P) 

Product Review Panel date: May 13, 2015 

1 
INTRODUCTION 

This memorandum presents BEAD's response to comments submitted by Syngenta concerning 

the BEAD Chemical Profile (BCP) document included in the initial Registration Review for 

Metolachlor Case (Yourman et. al., 2014). 

EPA Statement Page 2, 4th paragraph 

"Based on usage data for the same time period usage [1998-2012] for metolachlor averaged 

approximately 9 million pounds active ingredient (a.i.) applied annually on approximately 6 

million acres treated." 

Syngenta Comment: These numbers are correct but present an incomplete picture of the 

variation among years. From 1998 - 2000 Syngenta was deregistering metolachlor following the 

registration of S-metolachlor and, as shown in BEAD's Figure 3, usage dropped from 

approximately 50 million pounds to around 20 million pounds. Use continued to decline as 

stocks were eliminated and by 2004 less than 500,000 pounds were applied. At this time 

metolachlor was re-introduced to the market by other registrants. Since then metolachlor usage 

has increased, so that over the 2008-2012 period use has averaged roughly 3.5 million pounds 

per year. The 9 million average pounds applied does not reflect the current use pattern over the 

last five years. The same rationale applies to the acres treated. Based on proprietary data, the 

current.five year average is around 3 million acres for metolachlor. 

BEAD Response: BEAD acknowledges and appreciates the clarifications offered by Syngenta and 

will take it into consideration as appropriate as registration review progresses. 

EPA Statement (Page 2, 4th paragraph) 

"(Regarding metolachlor): The average a.i. use rate over this time period was 1.5 pounds 

a.i./acre." 

Syngenta Comment: For the 1998-2002 period, the average rate per base acre for Syngenta's 

metolachlor was 1.74 lbs a.i. /A. This can be compared to the current metolachlor average use 

rate of 1.26 lbs a.i. I A. This reflects the reduction of labelled use rates required by the Agency on 

metolachlor products to coincide with the introduction of S-metolachlor. Therefore, the blending 

of these two time periods for the average 1.5 lbs a.i. I A is not representative of actual use rates. 

BEAD Response: BEAD acknowledges and appreciates the clarifications offered by Syngenta and 

will take it into consideration as appropriate as registration review progresses. 

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EPA Statement (Page 4, 2nd paragraph; Page 4 Figure 1; Page 5 Figure 2) 

"The use of S-metolachlor increases, both in terms of pounds a.i. applied and total area treated, 

during the 1998-2012 time frame." 

Syngenta Comment: S-metolachlor was registered as a reduced risk replacement for 

metolachlor and its use increased rapidly during its introduction and conversion from 

metolachlor during the years of 1998-2002. This is better described as a replacement of 

metolachlor usage, rather than an increase in overall pounds applied. This was followed by a 

period of relatively constant use through 2009. Use has increased in the latter years partly due to 

an increase in planted acres, and partly due to an overall increase in the use of pre-emergence 

herbicides as weed resistance to contact herbicides has developed. 

BEAD Response: BEAD acknowledges and appreciates the clarifications offered by Syngenta 

and will take it into consideration as appropriate as registration review progresses. 

EPA Statement (Page 5, Table 1 2003-2007) 

"Average Annual Usage: 31,000,000 lbs/yr.% Lbs: Com 82,000,000; Sorghum 7,000,000; 

Soybean 3,000,000; Cotton 2,000,000; Other 6,000,000." 

Syngenta Comment: The presented values do not fit the column heading. 

BEAD Response: BEAD acknowledges the error; values should have been percentages, not 

millions of pounds: 82 percent for com, 7 percent for sorghum, 3 percent for soybeans, 2 percent 

for cotton and 6 percent for other crops. The corrected table is shown below. 

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

Aoolied (2003-2007 and 2008-2012) 

2003-2007 2008-2012 

Average Annual Usage = 31,000,000 lbs/yr Average Annual Usage= 33,000,000 lbs/yr 

Crop %Lbs Crop %Lbs 

Com 82 Com 70 

Sonmum 7 Soybean 13 

Soybean 3 Sorghum (Milo) 5 

Cotton 2 Cotton 5 

Other 6 Other 7 

Source: Proprietary Data, 2003-2012. 

EPA Statement (Page 5, Table 2) 

2003-2007 Average Annual Usage = 31,000,000 lbs/yr. Reported values by state: IL 

17,000,000; IA 12,000,000; NE 10,000,000; KS 8,000,000; IN 8,000,000. 

Syngenta Comment: These values exceed the annual total of 31,000,000 pounds in the line 

above. It is possible that the values represent the total pounds across the 5 year period and each 

value should be divided by 5 to get the annual average use. Then instead of reporting the average 

pounds per state, a calculation can be made to determine the percentage of pounds per state to 

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match the columns in Table 1 to allow the comparison of percent lbs to the 2008-2012 time 

interval. 

BEAD Response: BEAD acknowledges the error; values should have been percentages, not 

millions of pounds: 17 percent for Illinois, 12 percent for Iowa, 10 percent for Nebraska and 8 

percent each for Kansas and Indiana. Table 2 shows corrected values, below. 

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/yr Average Annual Usage = 33,000,000 lbs/yr 

State %Lbs State %Lbs 

Illinois 17 Illinois 12 

Iowa 12 Nebraska 11 

Nebraska 10 Kansas 9 

Kansas 8 Iowa 8 

Indiana 8 Indiana 6 

Source: Proprietary Data, 2003-2012 

EPA Statement (Page 5, last paragraph) 

"The percent of the total use of S-metolachlor decreased similarly in the com belt states of IL, 

IA, and IN, with increases in the Plains states of NE and KS." 

Syngenta Comment: This conclusion cannot be determined without the percent of pounds for 

the 2003-2007 interval being known. 

BEAD Response: BEAD acknowledges and appreciates the information provided. Table 2 has 

been corrected to capture the percent of pounds used in each state relative to the S-metolachlor 

total pounds a.i. used. 

EPA Statement (Page 6, last paragraph) 

"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. 

Syngenta Comment: This paragraph presents a blend of Syngenta' s metolachlor usage at high 

volumes and high use rates during the phase-out period of 1998 thorough 2002 with the lower 

usage of metolachlor at reduced use rates following 2002, which marks the introduction of the 

reduced use rate replacement product S-metolachlor. The average use rate of 1.5 lbs/a does 

not accurately reflect either usage scenario." 

BEAD Response: BEAD acknowledges and appreciates the information and clarification 

provided pertaining to last paragraph on page 6 of the BCP document. 

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EPA Statement (Page 8, 1st paragraph) 

"BEAD does not have information as to why there is a nearly fivefold increase in use, although 

resistance to other herbicides or weather conditions that may increase weed pressure are possible 

(but unsubstantiated) explanations." 

Syngenta Comment: Syngenta began cancelling its metolachlor end-use product registrations in 

July 2001 and cancelled its metolachlor technical registration in August 2002. The first nonSyngenta metolachlor registrations occurred in the 2002-2004 timeframe. Thus, the metolachlor 

sales of less than 100,000 pounds reported in 2003 reflect the re-initiation of metolachlor to the 

market. Since corn is the main crop treated, the majority of sales and usage during the earlier reintroduction of metolachlor (2003-2007) would be expected to occur in corn. As overall sales 

increased other crop uses expanded, resulting in a reduction in the percentage of usage devoted 

to corn. The expansion of use in crops other than corn also explains the reduced percentage of 

sales in major com-growing states. 

BEAD Response: BEAD appreciates the information provided by Syngenta and will take it into 

consideration as appropriate as registration review progresses. 

EPA Statement (Page 12, 2nd paragraph) 

"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)." 

Syngenta Comment: This statement is inaccurate, mainly because metolachlor is currently 

labeled at the same use rates as S-metolachlor. A 35% rate increase in metolachlor is required to 

provide equivalent control to S-metolachlor. Therefore, "the amount used would be greater for 

metolachlor" is not an option to match the upper label rates ofS-metolachlor. A bulletin 

published by the University of Illinois (Hager 2007) explains the difference in S-metolachlor and 

metolachlor use rates and equivalency and notes, "while applying the same product rate of an Smetolachlor-containing product and a metolachlor-containing product can provide similar 

amounts of total active ingredient, the amount of the active isomer applied can vary 

considerably." 

Likewise, researchers at Colorado State University (Shaner 2006) conducted a comparison study 

that concluded, in part, "formulations based primarily on the S-metolachlor isomer are more 

active on a gram for gram metolachlor basis than formulations based on a racemic mixture of 

metolachlor containing a 50:50 ratio of the Rand S isomers." Of note, while showing a 

difference in herbicidal activity, this study also demonstrated similar soil binding behavior and 

rate of soil solution dilution between S-metolachlor and racemic metolachlor. The BEADreferenced Hartzler 2004 Iowa State University document states, in part, "The Stalwart C label 

recommends the same product use rate as those for Dual II Magnum, but the product contains the 

less active unresolved form of metolachlor. This results in Stalwart providing less 'weed-killing 

power' than Dual II Magnum when applied at equal rates. [ ... ] 

However, the reduced activity of the unresolved isomer will result in reduced performance in 

many situations (i.e. heavy weed pressure, difficult to kill weeds, dry weather, late-season weeds, 

etc.)." Page 49-50 of the BEAD-referenced Ohio State University 2007 publication (Corn: Soil 

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Applied Herbicides - Preplant or Preemergence) includes comparisons of labeled Bicep II 

Magnum/Cinch ATZ and Stalwart Xtra use rates, as well as Dual II Magnum/Cinch and Stalwart 

C/Parallel use rates. The labeled application rates are shown with the following comment: 

"Stalwart Xtra has undergone limited testing in OSU and Purdue University field research. 

Bicep II Magnum includes primarily the S isomer of metolachlor, which allows the use of lower 

rates of active ingredient compared to a mix of S and R isomers. The mix of S and R metolachlor 

isomers in Stalwart Xtra is similar to Bicep/Bicep II, which should result in similar use rates. 

Stalwart Xtra use rates are similar to Bicep II Magnum, however, and are lower than use rates of 

Bicep/Bicep II." 

A similar statement occurs under the Dual II Magnum/Cinch Use Rates and the Stalwart 

C/Parallel Use Rates: "Dual II Magnum includes primarily the S isomer of metolachlor, which 

allows the use of lower rates of active ingredient compared to a mix of S and R isomers. The mix 

of S and R metolachlor isomers in Stalwart and Parallel is similar to Dual/Dual II, which should 

result in similar use rates. Stalwart and Parallel use rates are similar to Dual II Magnum, 

however, and are lower than use rates of Dual/Dual." 

These statements show that users recognize that current metolachlor labelled use rates do not 

provide equivalent efficacy to that which is delivered by the S-metolachlor products at 

equivalent rates. The Table 5 Weed Response to Herbicides in Com in the Ohio State University 

report shows the same weed control ratings for metolaclilor and S-metolachlor with the footnote, 

"Metolachlor and S-metolachlor, and premixes of these with atrazine, are available from a 

number of manufacturers - see com herbicide descriptions for more information. Metolachlor 

products have undergone limited testing at their labeled rates in OSU and Purdue University 

research." 

While some University Extension Services may combine S-metolachlor and metolachlor 

products into a single category when presenting information, this does not imply equivalency. 

This is demonstrated in the Ohio State University publication referenced above, and in the 2014 

Georgia Com Production Guide published by the University of Georgia. The University of 

Georgia guide presents S-metolachlor and metolachlor product information together but notes, 

"The generic formulations of metolachlor (Parallel, Stalwart, Me-Too-Lachlor) have not 

provided the same length of residual control of certain weeds at similar rates of Dual Magnum 

formulations in some UGA field trials." 

Syngenta refer~nces: 

• Hager A. 4/13/2007. Isomers Resolved. The Bulletin: Pest Management and Crop 

Development Information for Illinois, No. 3 Article 4. 

• Shaner DL, Brunk G, Belles D, Westra P, and Nissen P. 2006. Soil Dissipation and 

Biological Activity of Metolachlor and S-metolachlor in Five Soils. Pesticide 

Management Science 62: 617-623. 

• Lee D. 2014. A Guide to Com Product in Georgia in 2014. The University of Georgia, 

College of Agriculture and Environmental Sciences, Cooperative Extension, Crop and 

Soil Sciences. 

6 
BEAD Response: BEAD hoped to clearly point out (Yourman et. al., 2014) that S-metolachlor had a 

greater proportion of active isomer than metolachlor. BEAD appreciates the correction regarding 

labeled use rates being the same for products containing either active ingredient. 

EPA Statement (Page 12, 2nd paragraph) 

"The reduction in use [of metolachlor] may be due to increased use of alternative herbicides or 

other factors currently unknown to BEAD." 

Syngenta Comment: Syngenta proposes that the reduction [in pounds of metolachlor] is due to 

S-metolachlor being registered at approximately 35% lower use rates than those originally 

labeled for metolachlor. After S-metolachlor registration, metolachlor labels were registered 

with the same 35% reduction in use rates. This results in an overall reduction ofroughly 35% of 

total pounds applied, even if the number of acres treated remains unchanged. 

BEAD Response: BEAD appreciates the insight addressing the possible reason for a reduction 

in pounds of product. BEAD pointed out (Figure 1, below) that the total acres treated decreased 

from a high of approximately 30 million acres in 1998, to 4.7 million acres in 2012. 

FIGURE 1. Metolachlor Total Area Treated in Acres (1998-2012) 

00 35,000,000 

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Years 

Source: Proprietary Data, 1998-2012. Originally shown in Yourman et al. 2014 (Figure 4, page 7). 

REFERENCE 

Yourman, L., Alsadek, J. and Hill, E. 2014. BEAD Chemical Profile (BCP) for Registration 

Review: Metolachlor Case [S-metolachlor (108800) and Metolachlor (108801)], Nov. 6, 2014. 

[Registration Review EPA Docket ID No.: EPA-HQ-OPP-2014- 0772-0005]. 

7