UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON D.C., 20460 

FEB 0 6 ~ '.l 

MEMORANDUM 

OFFICE OF 

CHEMICAL SAFETY AND 

POLLUTION PREVENTION 

SUBJECT: Response to Public Comments from the Center for Food Safety and Bayer Crop 

Science on the Glufosinate Draft Risk Assessments, Docket No. EPA-HQ-OPP2008-0190 

FROM: 

THRU: 

William Chism, Senior Biologist 

Biological Analysis Branch 

Cynthia Doucoure, Environmental Protection Specialist 

Science Information and Analysis Branch (SlAB) 

Derek Berwald, Economist k { r'l"\- (M_~ Economic Analysis Branch ' J v '-.1 ) 

Biological and Economic Analysis Division (7503P) 

Biological 

Amet "Skee" 

Analysis 

Jones, 

Branch 

Chief ~~ . / u , ) 

Diann 

Science 

Sims, 

Information 

Chief a~ and Analysis Branch 

Economic 

Timothy Kiely, 

Analysis 

Chief 

Branch QJ. \ \M..... 

.. ~ 

Biological and Economic Analysis ranch (7 P 

TO: Shirley Keel, Acting Team Leader 

Risk Management and Implementation Branch V 

Pesticide Re-evaluation Division (7508P) 

Product Review Panel Date: September 25, 2013 

Through this memo, BEAD is providing responses to comments on glufosinate usage data 

submitted by the Center for Food Safety (CPS) and Bayer Crop Science (BCS) in their May 6, 

Page l of 7 
2013 submissions to OPP in response to the Glufosinate Draft Risk Assessment, Docket No. 

EPA-HQ-OPP-2008-0190. The CFS and BCS comments below are verbatim as received in the 

submissions. 

Center for Food Safety (CSF) Comments 

IV. EPA's ASSESSMENT OF GLUFOSINATE USAGE 

CFS Comment 

BEAD shows a total of 2.24 million lbs. of glufosinate applied to 21 crops in addition to fallow 

land in its updated Screening Level Usage Estimate (SLUA, p. 2). This estimate is based on data 

from various sources dated 2003 to 2010, which are thus from 3-10 years old (SLUA, p. 1). 

The majority of crops listed by BEAD are orchard crops, fruit and nut trees. This reflects 

glufosinate's historical use pattern: small-acreage specialty crops concentrated in states like 

California and Oregon where orchards are prevalent. While glufosinate will likely continue to be 

used in these settings, these specialty crops represent only 24% of overall glufosinate use, or 0.54 

million lbs. 

In contrast, just four large-acreage field crops (canol a, com, cotton and soybeans) claim 76% of 

overall glufosinate use (1.7 million lbs.). All or nearly all of this 1.7 million lbs. is attributable to 

glufosinate-resistant varieties. This is true despite the fact that glufosinate-resistant crop 

adoption is extremely low (just a few percent) for com and soybeans, and 5-10% for cotton. The 

extremely large acreage planted to these crops means that the glufosinate applied to even the tiny 

proportion that is glufosinate-resistant predominates over that used on much smaller acreage 

orchard crops. 

Glufosinate use is surging due to several well-documented developments. First, glyphosateresistant (GR) weeds are continuing to infest ever more cropland, and use of glufosinate with 

glufosinate-resistant varieties is one of the major recommendations being made by pesticide-seed 

firms and extension agents as a response to the epidemic. Second, there is rapidly increasing 

availability and adoption of glufosinate-resistant field crops, driven primarily by GR weeds. 

These factors ensure a continuation of the ongoing and dramatic rise in glufosinate use to a level 

that is several to many times that estimated by BEAD in just the next few years, perhaps even 

before the registration review is complete. Below, we explain these developments, and then 

provide a realistic assessment of glufosinate use informed by these developments. 

According to a three-year survey of glyphosate-resistant weeds in 31 states by the agri-marketing 

firm Stratus, 49% of farmers surveyed in 2012 had glyphosate-resistant weeds on their farm, up 

from 34% of farmers in 20 11~ 61.2 million acres of cropland are now infested by GR weeds; GR 

weeds are rapidly expanding in the Midwest; and ever more farmers report two or more resistant 

species on their farms (Stratus 2013). The weed science community has reported on this 

development many times, and it is indisputable that GR weeds continue to infest more and more 

cropland. Dow likewise reports 60 million acres of cropland infested by GR weeds (Bomgardner 

2012), while Ian Heap, who manages the International Survey ofHerbicide:-Resistant Weeds, 

estimates somewhat less, 30-40 million acres (Heap 2012). 

Page 2 of 7 
BEAD Response 

We agree that the small acreage specialty crops account for ~ 24% and the large acreage field 

crops claim ~ 7 6% of the overall glufosinate use. We also agree that usage of glufosinate in the 

U.S. is increasing and is likely to continue to increase in the future. The Screening Level Usage 

Analysis (SLUA) provides average usage estimates of a specific chemical on registered crops 

over several years. This information is often used to characterize use of the chemical. 

However, BEAD also produces analyses that take into account trends in chemical use. Our 

available market data for glufosinate supports the surge in glufosinate as described above. The 

additional information you provided that document reasons for the surge is greatly appreciated. 

CFSComment 

Thus far, GR weeds have caused the most economic and agronomic damage in cotton. 

Glufosinate-resistant cotton adoption has increased sharply as GR Palmer amaranth and 

horseweed and other GR weeds undermine the effectiveness of a glyphosate-based weed control 

program. The latest data from USDA's Agricultural Marketing Service suggests that roughly 

24% of the nation's cotton acres were planted to varieties resistant to glufosinate herbicide 

(USDA AMS 2012). Only 6% of cotton planted represents LibertyLink varieties from Bayer 

CropScience, which are marketed as resistant to glufosinate; the other 18% are Phytogen 

Widestrike cotton varieties, which incorporate glufosinate-resistance in the form of a resistance 

marker gene. Though not advertised as glufosinate-resistant, cotton growers have learned that it 

is and often apply glufosinate to these crops to kill glyphosate-resistant weeds (Golden 2010). 

The latest figures from USDA NASS's Agricultural Chemical Usage survey show that 333,000 

lbs. of glufosinate were applied to Program State cotton acres in 2010/5 which represent 84.5% 

oftotal cotton acres planted in the US; correction for the unsurveyed 15.5% yields just under 

400,000 lbs. of glufosinate applied to cotton (333,000/0.845). 

BEAD Response 

BEAD agrees that the 2010 estimates of pounds of glufosinate applied to cotton provided by 

CFS exceed the amount provided on the SLUA. However, as a reminder, BEAD did not just 

look at one year of data but averages available usage data over 7 to 8 years. The average pounds 

of glufosinate applied to cotton during the 2003 to 2010 period was 200,000 lbs a.i. and the 

average PCT was 5%. 

CFS Comment 

GR weeds have also become a huge problem for many soybean growers. Glufosinate-resistant 

soybeans were first made available to farmers in 2009, despite deregulation in 1996. Dow reports 

proprietary data on glufosinate-resistant soybean adoption and associated glufosinate use that is 

summarized in the table below. 

Page 3 of 7 
Year Glufosinate- Total Glufosinate- Pounds Pounds 

Resistant Soy Soybean Resistant Glufosinate Glufosinate per 

as 9'0 Total Soy Acres Soybean Acres Applied (a.i.) Acre (a.i.) 

Acres (thousands) lthousands) 

2009 < 19'0 77,451 71,718 

2010 1.19'0 77,404 851 460,026 0.54 

2011 1.39'0 75,208 978 556,775 0.57 

Source: Dow (20 11 ). "Supplementary documentallon tn support of draft enVlronmental assessment: Glufosmate use 

on soybeans," Dow AgroSciences, Nov. 115, 2011; USDA NASS for soybean acreage figures. 

Glufosinate use on soybeans jumped nearly eight-fold in just the two years from 2009 to 2011, 

tracking the rapid increase in glufosinate-resistant soybean acreage. Though applied to just 1.3% 

of soybean acres, soybeans represent the second-highest use of the herbicide (over 500,000 lbs.), 

second only to com. 

BEAD Response 

BEAD agrees that use of glufosinate on soybeans has jumped nearly eight-fold in just the three 

years from 2009 to 2011. 

CFS Comment 

Glyphosate-resistant weeds have not yet become as problematic or extensive in com as in 

soybeans or cotton, though reports have been on the rise since 2005. Accordingly, glufosinateresistant com has not been widely adopted, and glufosinate has only been employed to a limited 

extent on com resistant to it. EPA reports glufosinate applied to an average of 5% of com acres 

and a maximum of 10%, which would also reflect glufosinate-resistant com acreage since 

glufosinate can only be used post-emergence with glufosinate-resistant varieties, and glufosinate 

is used little if at all pre-emergence since there are better and cheaper pre-emergence herbicide 

options in com. 

Assuming deregulation by USDA, DuPont-Pioneer will be introducing com hybrids based on 

4114 maize, which will incorporate both glufosinate- and glyphosate-resistance as well as 

resistance to lepidopteran pests and com rootworm (Appendix, p. 27). DuPont-Pioneer expects to 

more efficiently develop glufosinate-resistant com varieties based on 4114 maize, which should 

mean more rapid development of multiple highly-stacked com varieties that contain this trait and 

retirement of more affordable varieties with few or no biotech traits (Appendix, p. 46). 

This increased availability coupled with rapid emergence of glyphosate-resistant weed biotypes 

in com since 2005 ensures a trend of sharply increasing glufosinate use in com as well. 

Increasing use driven primarily by glufosinate-resistant crops has led to "all-time high" in 

demand for glufosinate (trade name: Liberty), as explained by a Bayer spokesman below: 

"Bayer Spokesman AI Luke says, 'Due to the increased pressure of glyphosate resistant weeds 

and the use of Liberty herbicide in both Liberty Link and non-LibertyLink crops, demand for 

Liberty herbicide has reached an all-time high. Although Bayer CropScience has dramatically 

.fage 4 of 7 
increased production quantities of Liberty for the 2012 crop season, some local areas may face 

challenges in locating supply."' (Roberson 2012) 

In light of this analysis, it is clear that EPA has underestimated current glufosinate use associated 

with glufosinate-resistant crops, and made no allowance for clear trends that are driving 

increased use. For instance, EPA reports 100,000 lbs. of glufosinate applied to soybeans 

(SLUA), in contrast to the more than 500,000 lbs. reported by Dow (2011). BEAD's estimate of 

200,000 lbs. of glufosinate on cotton (SLUA) is only half the 2010 usage of 400,000 lbs., and 

glufosinate use on cotton has surely increased since then. 

However, current use does not capture well-delineated trends that EPA should account for. In the 

table below, CFS provides a projection of glufosinate use under various scenarios. 

ProJection ofGlufoslnate Use on Glufosinate-Reslstant Crops 

Crop Rate' Total Crop Annual Use rn Four Different Scenarfos: 

(a.l./acre/year) Acru + current use, 10%, 25%, SO% Crop Acres 

(millions) Treated 

{million lbs. a.l.) 

Current 10% 2S% SO% 

Use"' 

Corn 0.51b. 100 2.5 5.0 12.5 25.0 

Cotton 0.61b. 12 0.5 0.7 1.8 3.6 

Soybeans 0.61b. 75 0.6 4.5 11.3 22.5 

TOTAL 3.6 10.2 25.6 51.1 

# Slightly higher than current usage rates m each ca$e, to account for creepmg glufosmate reSistance, although any 

signi fi.cant emergence of gl ufo sin ate-resistant weeds would increase use rates more than indicated here. 

+ Based on extrapolation of current acreage trends 

• So/o com (BEAD); 7% cotton (USDA NASS 2010), I 3% soybeans (Dow estimate for 2011) 

In light ofthe above discussion, the scenario projecting 10% total com, cotton and soybean acres 

treated with glufosinate is a conservative projection of current trends just a few years into the 

future. In this scenario, 10.2 million lbs. glufosinate would be applied to these three crops and 

10.7 million lbs. total, assuming the other, primarily orchard crop uses remain at 0.5 million lbs. 

This conservative scenario would represent nearly a five-fold increase in glufosinate use over the 

2.24 million lbs. estimated by BEAD. Glufosinate treatment of 50% of cotton acres and 25% of 

soybean acres is certainly conceivable in the near future in light of glyphosate-resistant weed 

pressure in these crops, which would mean annual use of approximately 20 million lbs. 

glufosinate. Practically all of this vastly increased use would be post-emergence applications to 

field crops in areas (e.g. Midwest, Northern Plains, mid-South) where glufosinate is used 

sparingly at present. 

BEAD Response 

BEAD agrees that use of glufosinate on cotton and soybeans has increased, especially over the 

most recent three years and that increased use is likely to continue. As for com, BEAD finds 

that, based on the available data, there was a sharp increase in glufosinate usage from 2005 to 

2007; however, after 2007, there was a sharp decline in usage in terms of pounds of glufosinate 

Page 5 of 7 
applied and total area treated. 

V. GLUFOSINATE-RESISTANT CROPS, WEEDS. AND VOLUNTEER WEEDS 

CFSComment 

CFS provides a documented discussion of the problem of glufosinate- and multiple herbicideresistant weeds as they relate to glufosinate-resistant crops in the Appendix (pp. 14-28). A 

documented discussion of why herbicide-resistant crop systems foster more rapid evolution of 

resistant weeds is found in the Appendix, pp. 17-20, while the high potential for glufosinateresistant weeds is addressed on pages 20-25. One important issue here is the discovery of a weed 

biotype that had evolved resistance to glyphosate through continual glyphosate use, but which 

has also been found to be resistant to glufosinate, an "alarming weed management issue" that 

casts great doubt on the strategy of using POST glufosinate to kill glyphosate-resistant weeds on 

crops resistant to both herbicides, and more generally on the "multiple modes of action" dogma 

as the chief recommendation to forestall or manage herbicide-resistant weeds. The high potential 

for already multiple herbicide-resistant weeds (e.g. waterhemp) to rapidly evolve resistance to 

glyphosate is also discussed. EPA should be interested in how glufosinate- and multiple 

herbicide-resistant crop volunteers can accelerate evolution of resistance in pests such as the com 

rootworm, when those HR crops also express Bt insecticidal toxins (Appendix, pp. 27-28). 

BEAD Response 

The use of any pesticide can lead to increased selection pressure for resistant pests. Historically 

glufosinate, which was registered in 1993 in the U.S., has not had a severe problem with 

resistant weeds and there is only one weed species Italian ryegrass found in the United States that 

is resistant to glufosinate (Heap, I. The International Survey of Herbicide Resistant Weeds. 

Online. Internet. Wednesday, October 30,2013. Available www.weedscience.org). The EPA, 

Office of Pesticide Program (OPP) is concerned about pesticide resistance and is actively 

working on a wide range of resistance issues. OPP- has a voluntary program (the Food and Drug 

Administration also has voluntary programs for antibiotics and anthelmintics) for resistance 

management that is described in our Pesticide Registration Notice 97-2. The program is 

updating that PR Notice on resistance management. It is developing a webpage of definitions 

and frequently asked questions. And it is working with registrants to put the mode of action and 

resistance management language on their pesticide labels. OPP has been working with the 

Fungicide, Herbicide and Insecticide Resistance Action Committees (FRAC, HRAC, and IRAC) 

as well has a professional societies (Agronomy, Entomology, Plant Pathology, Weed), and crop 

consultants (National Assoc Ind. Crop Consultants & Certified Crop Consultants). HRAC and 

the Weed Science Society of America have provided a list of Best Management Practices for 

resistance management which could be used as a template for farmers to develop their own 

herbicide resistance plan. The best management practices take a very holistic approach (e.g. 

crop rotation, mechanical weed control, scouting and identification of weeds, etc.) and only a 

few of the elements can be directly addressed by pesticide regulations. 

Page 6 of 7 
Bayer Crop Science Comments 

- Glufosinate Typical Use Data, DP #405082, Document EPA-OPP-2008-0190-0030, dated 

September 17, 2012 

Bayer Comment 

EPA indicates there is no active registration for peaches, plums or prunes. Glufosinate use on 

these crops was registered Sept 27, 2012. Please refer to Appendices 1 and 2 for the maximum 

application rates and number of applications for all listed crops. 

Please refer to Table 1 for the total area (in acres) treated and maximum application rate (lb 

a.i./acre) for the years 2010- 2012 for the crops listed. 

BEAD Response 

We appreciate the update on the registration of peaches and plums/prunes and for the data. 

Bayer Comment 

Information presented in Appendices 1 and 2 provides the currently registered use scenarios by 

crop as per the label directions on the current labels for Liberty® 280 SL Herbicide (EPA Reg. 

No. 264-829), Liberty® 200 SL Herbicide (EPA Reg. No. 264-660) and Finale® Herbicide 

(EPA Reg. No. 432-1229), Derringer Herbicide (432-1228) and Derringer F Herbicide (432-960) 

for non-crop weed control and weed control in conifer and hardwood tree plantings. 

BEAD Response 

Thanks for the data provided for currently registered uses of the above mentioned products. 

Page 7 of 7