Supplemental Information for Petition for Determination of Nonregulated Status for Herbicide Tolerant DAS

- 40278

- 9 Corn



### Estimate of Herbicide Volume and Impact on Environmental Load of Herbicides with the Introduction of Enlist corn (DAS

‐ 40278

‐ 9)

The undersigned submits this information under 7 CFR 340.6 to support the determination that the article should not be regulated under 7 CFR 340.

S ubmitting Company:

Dow AgroSciences LLC

Submitted by:

__________________________________

T. Craig Blewett Regulatory Leader

Regulatory Sciences & Government Affairs Dow AgroSciences LLC

9330 Zionsville Road Indianapolis, IN 46268 Telephone: (317) 337

- 4421 FAX: (317) 337

- 4649

tcblewett @dow.com

July 2, 2012Supplemental Information for USDA Petition for Nonregulated Status of DAS

- 40278

- 9 Corn Page 2 of 1 6 Dow AgroSciences LLC

Summary

Dow AgroSciences (DAS) has submitted a petition to the United States Department of Agriculture (USDA)’s Animal and Plant Health Inspection Service (APHIS) for the determination of nonregulated status for DAS

- 40278

- 9 corn, which provides tolerance to the herbicides 2,4

- dichlorophenoxy acetic acid (2,4

- D) and quizalofop.

Th e deregulation of DAS

- 40278

- 9 corn will usher in a new era of weed control by improving existing weed control p ractices and introducing new modes of action in corn production. Various scenarios based on different input assumptions have been constructed to estimate potential volumes of 2,4

- D, glyphosate and quizalofop on commercial corn hybrids that contain DAS

- 402 78

- 9 and other herbicide tolerant traits. The projected environmental loading of herbicide use in response to the growing emergence of glyphosate resistant weeds as previously discussed is reviewed. Additionally, the ecological assessment of pesticides i n light of new projected volumes is addressed from a regulatory perspective.

### Estimate of Herbicide Volume and Impact on Environmental Load of
Herbicides with the Introduction of Enlist corn (DAS

‐ 40278

‐ 9)

Executive Summary

The introduction of DAS-40278-9 corn (Enlist TM corn) and Enlist Duo TM herbicide will bring a
much needed new herbicide tolerant trait and vastly improved herbicide technology into American agriculture. The new crop trait offers increased tolerance to 2,4-D as well as tolerance to the ‘fop’ family of herbicides, combining prov en broadleaf weed control with a new mode of action for control of grassy weed s in corn. The new trait will be stacked with existing glyphosate
tolerance traits to enable the continued use of the extremely popular and beneficial glyphosatetolerant technology and help pr event further emergence of gl yphosate tolerant weeds.

To accompany this new crop trait technology a ne w herbicide offering, featuring the novel 2,4-D choline salt, in a premix with glyphosate has be en developed. Combining the features of the 2,4-D choline salt with new developments in pr oprietary formulation an d manufacturing science has resulted in a 2,4-D herbicid e product with significantly reduced potential for drift and volatility as well as decreased odor and better handling properties.

To first look at the herbicide rates used on a si ngle acre, a recent study modeled several farms in the corn belt. (1) The study found that when th e average Enlist Duo he rbicide use rates were compared to the average use rates of all of the top alternate, currently available herbicides popular for controlling glyphosate-resistant weeds, the use of Enlist Duo on DAS-40278-9 corn would reduce the per acre environm ental load of herbicides comp ared to these top, currently available, alternative programs.

To realistically estimate the total 2,4-D volume increase across the country that may occur with Enlist and Enlist Duo, the followi ng scenarios were developed ba sed on realistic, yet very conservative (bias towards ove r-predicting) assumptions.

Scenario 1 assumes growers will only apply Enlist Duo to DAS-40278-9 corn where growers are facing or actively trying to prevent the establis hment of glyphosate-resistant weeds. Additionally this also assumes that all farmers with corn acres that have glyphosate resistant weeds will plant DAS- 40278-9 corn and will use Enlist Duo herbicide. The projections indicate an approxi mate six-fold increase in 2,4-D use in 2020 compared to the volume of 2,4-D curre ntly used on conventional corn.

Scenario 2 assumes that all acres of DAS-40278-9 corn would receive applications of Enlist Duo, regardless of weed control need, a nd thus relies on estimat es of the projected market share of DAS-40278-9 corn. These pr ojections estimate an approximately 8X increase in 2,4-D use compared to what is currently used on conventional corn.Scenario 3 assumes that all current glyphosate-tolerant corn ac res would be planted to hybrids that also contain th e DAS-40278-9 trait. This is an unrealistically high estimation but provides an upper confidence level on 2,4-D volume. Even with this extreme assumption, the estimated 2,4-D volum e is only a 17-fold increase in 2,4-D use on corn compared to the current use of 2,4-D on conventional corn

Some projections in the comment s and press have suggested incr eases in volume of 100’s to even 1000 fold. When actual use patterns and market dynamics are taken into consideration, more reasonable projections are only a 6-8 fo ld increase, with an extremely conservative estimate of only17-fold.

Introduction of New Technology

A new herbicide product, to be commercialized as Enlist Duo, is curr ently under regulatory
review at the Environmental Protec tion Agency (EPA or the Agency) 1 . This product, when approved, will be marketed for use on DAS 40278-9 co rn. Enlist Duo is a proprietary pre-mix of 2,4-D choline and glyphosate DMA and contains Colex-D TM Technology. Prominent attributes of this technology are a greatly reduced volatility and drift pr ofile, very low odor and better handling characteristics (MRID 48862902 and 48844001). Enlist Duo is formulated as an approximate 1:1 ratio of 2,4-D choline:glyphosate DMA. Use directions for Enlist Duo have
been well described in the draft Environmental Assessment for DAS 40278-9 corn and documents previously submitted by DAS to EPA and USDA.

The new use directions under consideration by EPA will allow a pre-emergent (burn down) application of 0.5-1 lb acid e quivalents/acre (ae/ac) of 2,4- D (and glyphosate) and up to two applications (0.5-1 lb 2,4-D ae/ ac each, and glyphosate) post-emergent through the V8 stage or
48” tall corn. Total seasonal use is limited to a total of 3 lbs 2,4-D ae/ac /season, identical to the current seasonal maximum use of 2,4-D on conven tional (non-Enlist) co rn. DAS-40278-9 corn will also tolerate applications of the herbicide quizalofop.

__________________________

1 EPA published a Notice of Receipt on May 23, 2012, opening up a comment period that ends on June 22, 2012. See 77 Fed. Reg. 30524, 30526 (May 23, 2012) (“Active ingredient: 2,4-D choline salt.) Proposed
Classification/Use: Enlist AAD–1 Corn (Trait Code: DAS–40278–9)”).Current 2,4-D Use on Corn

The current EPA-approved use directions for 2,4- D on corn allows a single pre-emergent (burn down) application of 0.5-1 lb acid equivalents/acre (ae/ac) of 2,4-D, a single post-emergent application of 0.5 lbs ae/ac, and a single preharvest application of up to 1.5 lbs ae/ac. Seasonal
maximum use is 3 lbs ae/ac/season.

Estimates of US corn acreage from private and public sources ranges from 92MM acres to approximately 96 MM acres. Current corn acreage is estimated by USDA at approximately 96 million acres ( http://www.nass.usda.gov/Newsroom/2012/03_30_2012.asp ). 2,4-D is currently used on approximately 8% of the corn acres with a recent historical range from 8%-14% of corn acreage according to USDA estimates (Plant Pest Risk Assessment; www.aphis.usda.gov/brs/ aphisdocs/09_23301p_dpra.pdf ). When 2,4-D is utilized in a burn down or pre-plant treatment, it is almost always co mbined in a tank mix with glyphosate or other non-selective herbicide and, when tank-mixed, 2,4- D is generally recommended at the lower end of the rate range ~ 0.5 lbs ae/ac ( http://www3.ag.purdue.edu/btny/weedscience/Documents/BurndownMadness.pdf ) . 2,4-D is currently labeled for a single post- emergent application at 0.5 lbs ae/ac. While current estimates of 2,4-D volume used on corn are not readily availa ble in a public format, third party proprietary data (data not submitted) estimated in 2011that 5.5 million pounds of 2,4-D were applied to 9.5 million acres for an average of 0.57 lbs ae/treated acre. This is up rather sharply from 2009 when 4 million pounds were used on 7.3 million acres. This increase in 2,4-D use may be driven by farmers seeking non-glyphosate weed control opti ons to control glyphos ate-resistant and/or
hard to control weeds.

Current Glyphosate Use on Corn

Current glyphosate use directi ons approved by EPA for use on gl yphosate-tolerant corn allow:

A maximum pre-emergence application am ount of 3.7 lbs glyphosate ae/ac, and two post-emergent applications each at 1.125 lbs glyphosate ae/ac (total 2.25 lbs ae/ac). An additional pre-harvest applica tion of 0.77 lbs ae/ac can be ma de. Total seasonal use rate is 6 lbs glyphosate ae/ac.

Third party proprietary market re search data indicate that the pe rcentage of glyphosate-tolerant corn acres has grown over the last four years (Table 1). Total pounds of glyphosate applied to corn have also increased during this time (along with 2,4-D use, as mentioned above). There is a slight but increasing trend in both the rate of glyphosate applie d per acre as well as the total number of applications made per acre. Thes e increases reflect the fact that farmers are continuing to adopt glyphosate-tolerant corn for its many cultural, agronomic and economic benefits even with the growing presence of gl yphosate resistant and hard to control weeds.Table 1. Glyphosate Use on Glyphosate Tolerant Corn

Year Total Acres Gly-Tol Acres Gly-Tol as % of Total Acres Total Pounds Gly Lbs Gly/Acre Total Applications/ Acre 2008 86,705,017 66,854,236 77 67,760,400 1.06 1.29 2009 86,409,977 71,071,345 82 68,621,113 1.05 1.28 2010 87,230,005 75,958,684 87 75,582,434 1.11 1.31 2011 91,620,001 82,163,813 90 85,671,957 1.17 1.33 From third party proprietary data

Changes in 2,4-D and Glyphosate Use Directions for Enlist Duo Herbicide

Enlist Duo TM Herbicide was designed to fit with the existing EPA-approved glyphosate use pattern which has resulted in ma ny benefits including reduced er osion and runoff. Glyphosate is expected to remain a core post-emergent herbic ide due to these benefits, as well as its broad spectrum of weed control. Use di rections for Enlist Duo were deve loped to directly overlap with the glyphosate use pattern on corn, so that fa rmers who currently us e glyphosate will find it extremely easy to use Enlist Duo on DAS-40278-9 corn.

As described above, Enlist Duo herbicide is an approximate 1:1 premix of 2,4-D choline and glyphosate DMA, based on acid equivalents. By using Enlist Duo herbicide on DAS_40278-9 corn, glyphosate use would be:

 A single 1.0 lb glyphosate ae/ac app lication made pre-emergence;

 Up to two post-emergent applications each at 1.0 lbs glyphosate ae/ac.

While DAS-40278-9 corn growers could make a dditional glyphosate applications, up to the seasonal maximum allowed on glyphosate labels, Dow AgroSciences (DAS) anticipates that additional glyphosate applications would be unlikel y due to Enlist Duo’s improved weed control, the growing use of foundationa l herbicide (preplant) progra ms, and the adoption of other products with additional modes of action.

The EPA-approved label directions for use of 2,4- D on corn currently allo ws a single pre-plant application of up to 1.0 lbs ae/ac. A single pos t-emergent application of 0.5 lbs ae/ac can be applied. This application can be broadcast if the corn is less than 8” tall. Drop nozzles should be used if the corn is greater than 8” to avoi d injury to the corn cr op. A single pre-harvest application of 1.5 lbs ae/ac can be made after co rn is physiologically mature (denting).

With the Enlist Weed Control System and use of Enlist Duo herbicide, 2,4-D choline use on
DAS-40278-9 corn would be:

 A single 1.0 lb 2,4-D ae/ac applicat ion made pre-emergence; Up to two post-emergent applications each at 1.0 lbs 2.4-D ae/ac.

Thus, use of Enlist Duo herbicide would provide fo r a total seasonal use of up to 3 lbs ae/ac of 2,4-D choline (or 6 lbs ae/ac of both 2, 4-D and glyphosate actives) on DAS 40278-9 corn (Figure 1).

Quizalofop Use on Corn

Quizalofop is an aryloxyphenoxypropiona te (Fop) grass selec tive herbicide that is used to control a broad list of grassy weeds, sedges and some br oadleaf weeds. Corn is a member of the grass family and as such is extremely sensitive to quizalofop with minute quantities causing severe injury or death to conventional corn plants. DAS 40278-9 corn is tolerant to quizalofop at current commercial application rates used for broadleaf crops.

E.I. DuPont Company (DuPont) has submitted a label amendment (Assure II, EPA Reg. No. 352-541, active ingredient quizalofop) to provide new directions fo r quizalofop use as a selection agent in growing seed corn and as a grass herbic ide for use in corn. DAS anticipates that the primary use of quizalofop initially wi ll be as a selection agent, to re move (kill) any corn plants in the seed propagation nursery that do not contain the DAS 40278-9 tra it. This helps to ensure a high degree of purity in corn bred to contain the trait as all corn plants not containing the trait
would be eliminated.Tolerance to quizalofop also brings a new mode of action for the control of grassy weeds in corn. Glyphosate is a strong grass herbicid e but reports in the science lite rature indicate that six grass species have developed resistan ce to glyphosate in the US (Jungl e rice, Goose grass, Italian Ryegrass, Rigid Ryegrass, Annual Ryegrass and J ohnson grass). The amount of acres infested with these glyphosate-resistant gr asses has been publis hed (~31000 ac) but th ere is uncertainty about the estimation accuracy ( http://www.weedsc ience.org/In.asp ). With the exception of Italian Ryegrass and Rigid Ryegra ss the acreage thought to be invol ved is small and located in the southern US and California. Quizalofop o ffers a new mode of action to control these glyphosate resistant grasses.

Changes in Quizalofop Use Directions with Enlist Weed Control System

Upon EPA approval of the herbicide registra tion amendment, a quiza lofop herbicide (e.g., Assure II ) would be available for use on DAS-40278- 9 corn. The primary anticipated use at this time would be as a selection agent in corn nurseries to select out (kill) those plants that do not contain the AAD-1 gene. EPA’s approval of th e registration amendment would also allow quizalofop to be used as a post emergent grass herbicide on DAS-40278-9 corn.

Whether used as a selection agent or as a herbic ide, the proposed use dire ctions would essentially be the same. The proposed directions for us e of quizalofop on DAS-40278-9 corn would allow up to two post emergent applications from the V2 to V6 growth stage. Application rates are
0.034 – 0.082 lbs ai/ac. The total amount that could be applied in a season is 0.082 lbs ai/ac. The maximum seasonal rate for quizalofop on DAS-40278-9 corn would be less than or equal to the
maximum seasonal rate on the label for all ot her crops. Soybeans cu rrently represent a significant post-emergent use of quizalofop. It is important to note th at soybeans are often grown rotationally with corn so the introduction of quizalofop use on corn would not represent a significant new geography for quizalofop use.2,4-D Choline and Glyphosate proposed Use on DAS 40278-9 Corn

Third-party proprietary market research dem onstrates that approxima tely 90% of glyphosatetolerant corn acres r eceive at least one glyphosate applic ation. Interestingly, significant populations of farmers (~10%) that purchase glyphosate tolerant co rn elect not to make a postemergent glyphosate application. The market res earch also indicates th at only 22% of planted corn acres currently receive a burn-down (pre-plant or pre-emergence) herb icide application.

Utilizing the historically consistent data from the current and broad use of glyphosate on corn, DAS has estimated that farmers who grow DAS -40278-9 corn will use an average of 0.875 lbs 2,4-D ae/ac/application with an average of 1.33 applications 1 per season. The application rate (0.875 lbs 2,4-D ae/ac) is the midpoi nt between the medium and high rates allowed on the Enlist Duo label and is consistent with the gl yphosate rate needed for weed control.

Estimating total acres of DAS-40278-9 corn plante d and the use of Enlist Duo herbicide on that corn has many inherent accuracy limitations, and it is difficult, if not impossible, to make any such predictions with certainty. Nevertheless, DAS has derived three scenarios to estimate the potential use of 2,4-D in DAS-40278-9 corn after deregulation and commercialization:2,4-D: Scenario One. The first scenario assumes that gr owers will only apply Enlist Duo to DAS-40278-9 corn where growers are facing or activ ely trying to prevent the establishment of glyphosate-resistant weeds. Additionally this also assumes that all farmers with corn acres that have glyphosate resistant weeds will plant DAS -40278-9 corn and will us e Enlist Duo herbicide (a very aggressive assumption due to other weed control options available). Using third party market data, DAS has estimated that 5% of US corn acreage had glyphosate resistant weeds in 2010, and that the percentage would grow to 10% of corn acreage by 2015 and to 30% by 2020 (Figure 2). This is consistent with but less aggressive than pred ictions made by other others, (see Foresman, Figure 2).

Figure 2. Projected corn and soybean acres infested with glyphosate resistant weeds.

Sources:

 Foresman, C. 2009. Syngenta Resistance Fighter TM Message Board. http://blog.syngenta

‐ us.com/blogs/ask_the_exp ert/archive/2009/04.aspx Accessed January 16, 2011.

 Dow AgroSciences LLC. 0 5 10 15 20 25 30 35 40Millions of Aces

Syngenta DowAssuming that minimal additional acreage would be treated to prevent glyphosate resistant weeds from becoming established, and using the a ssumptions set forth above regarding total corn acres, application rates and app lications per season, the following formula was used to calculate total lbs of 2,4-D ae that might be used on DAS 40278-9 corn:

92MM acres x 30% resistant weeds (in 2020) x .875 lbs ae/ac/application x 1.33 applications/season = 31MM lbs 2,4-D ae per year . This represents an approximate sixfold increase in 2,4-D use in 2020 compared to the volume of 2,4-D currently used on
conventional corn.

2,4-D: Scenario Two. The second scenario assumes, for purposes of this discussion, that all acres of DAS-40278-9 corn would receive applications of Enlist Duo, regardless of weed control need, and thus relies on estimates of what the projected market share of DAS-40278-9 corn will
be:

DAS sells corn seed through its subsidiary seed companies, i.e., Mycogen Seeds, Renze Seeds, Dairyland Seed, Pfister Seeds, Brodbeck Seeds, Triumph Seed, Prairie Brand Seed and Hyland Seeds. Through these subsidiaries, DAS currently has <5% of the market share for field corn and silage corn, markets for which DAS-40278-9 corn could be introgressed. At this time, DAS is not planning to breed DAS-40278-9 corn into all of its corn hybrids, so DAS-40278-9 corn would occupy considerably less than DAS’s current < 5% of the market. However, for purposes of this estimate, 5% will be used as a minimum potential DAS-40278-9 corn acreage.

DAS is interested in and is pur suing licensing agreements with additional corn seed companies to breed DAS-40278-9 corn into a licensee’s corn ge rmplasm. To date, no licensing agreement has been made. Through natural growth and licensing arrangements it is reas onably possible that, at maturity, approximately 45% of the corn germplasm could have the Enlist trait. For the purposes of this estimation, licensing cont racts will be assumed with seed companies having 40% of the market. Together with DAS’s market share, for purposes of this estimate, we therefore assume DAS-40278-9 corn could ultimately be bred into corn hybrids planted on up to 45% of the total

corn acreage.

Due to the technical aspects of corn seed breeding, rapid improvement of germplasm and stacking with other traits, this level of adoption of DAS-40278-9 corn is estimated to take 5-10 years to reach maturity (maturity in 2018-2023), which is consistent with other current herbicide tolerant traits. Application ra tes of 2,4-D are as described above: an average of 0.875 lbs ae/ac/application with 1.33 a pplications per year.Utilizing the data and assumptions stated in this scenario, the estimated range of acreage and 2,4-
D volume can be estimated as follows:

Low: 92MM acres x 5% market share x 90% estimated 2 DAS-40278-9 corn acres treated x 0.875 lbs ae/ac/app lication x 1.33 applications pe r DAS-40278-9 corn acre = 4,709,250 lbs 2,4-D ae per year. This represents a slight decrease to essentially no change in 2,4-D volume compared to current use on corn.

High: 92MM acres x 45% market share x 90% DAS-4027 8-9 corn acres treated x 0.875 lbs ae/ac/application x 1.33 estimated applications per DAS-4078-9 corn acre = 43,361,325 lbs 2,4-D ae per year. This represents approximately an 8X increase in 2,4-D use compared to what is curre ntly used on conventional corn.

2,4-D: Scenario Three : The third scenario assumes that all current glyphosate-tolerant corn acres would be planted to hybrids that also c ontain the DAS-40278-9 corn trait. This is an unrealistically high estimation but provides an upper confidence level on 2,4-D volume. DAS40278-9 corn will be stacked with a glyphosate tolerant trait but it is impractical to assume that all glyphosate tolerant traits will be stacked wi th DAS-40278-9 corn due to competing offerings by other seed companies and the likelihood of other herbicide-tolera nt corn options. Nevertheless, from Table 1, 82MM acres of the 92 MM total corn acres ar e planted to glyphosate tolerant corn. Using the same application information and other assumptions used in the previous two scenarios, the 2,4-D vo lume can be estimated as follows:

82MM glyphosate tolerant acres x 90% DAS-40278-9 corn acres treated x 0.875 lbs ae/ac/application x 1.33 estim ated applications per DAS-4078-9 corn acre = 85,884,750 lbs 2,4-D per year. This repres ents a 17-fold increase in 2,4 -D use on corn compared to the current use of 2,4-D on conventional corn.

Quizalofop Proposed Use on DAS 40278-9 Corn

There are two major considerations in predic ting the use of quizalofop on DAS 40278-9 corn: Use as a selection agent in producing hybrid s eed corn, and use as a herbicide to control glyphosate resistant grasses.

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2 Estimates based on current glyphosate application information. The Enlist Duo TM application window with DAS

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‐ 9 corn is consistent with the current glyphosate application window.Seed Corn Production : The production of hybrid seed corn requires approximately 1 acre of nursery to produce sufficient hybrid seed to pl ant 125 acres the following season. An additional
refinement is that not all rows would be trea ted depending upon whether the trait is carried on the male or female parent. The range would be 20%-80% of the nursery field would be treated with quizalofop. For the purposes of this exer cise we will use 80%. Two scenarios will be presented, both using the same assumptions as described above for 2,4-D use on DAS 40278-9

corn.

Quizalofop Use in Seed Corn: Scenario 1 : This scenario uses DAS’ current 5% market share for field and silage corn.

92MM acres /125 acres nursery/a cre of field corn x 5% market share x 80% estimated DAS-40278-9 corn nursery acres treated x 0.082 lbs ai/ac/application x 1 application = 2,415 lbs quizalofop.

Quizalofop Use in Corn Seed Production: Scenario two : The second quizalofop scenario
assumes a total of 45% of the market share contains the trait.

92MM acres /125 acres nursery/a cre of field corn x 45% mark et share x 80% estimated DAS-40278-9 corn nursery acres treated x 0.082 lbs ai/ac/application x 1 application = 21,730 lbs quizalofop.

Control of glyphosate-resistant grasses : As indicated above six species of grasses have developed resistance to glyphosate. Only Italia n Ryegrass and Rigid Ryegrass have what could be considered substantially infe sted acreage: 10,000 acres of It alian Ryegrass in Arkansas and Mississippi each and 10,000 acres of Rigid Ryegrass in California. All other species infest <100 acres per species, mostly in the Southern US or California. None of the grasses appear in significant corn growing regions but for the purpose s of this exercise we will assume that all 31000 acres are in corn growing acres and those growers will use quizalofop to control these
weeds:

Quizalofop Use in Field Corn: Scenario three : This scenario assumes that quizalofop will be used on all 31,000 acres of gl yphosate resistant grasses.

31M acres x 0.082 lbs ai/ac = 2,542 lbs quizalofop.Environmental Loading of Herbicides Used on Corn

DAS has conducted an analysis to determine the anticipated impact on envi ronmental loading of herbicides resulting from the use of 2,4-D chol ine on herbicide tolerant DAS-40278-9 corn and DAS-68416-4 soybeans. Specifically, this anal ysis looked at the environmental load of herbicides applied on glyphosate tolerant corn and soybeans to control glyphosate resistant and hard-to-control weed biotypes (1). The top cu rrently available herbicide programs (excluding just increasing the rate of gl yphosate alone) that are currently being recommended to control glyphosate resistant weeds in corn under scenario s representative of different key corn-growing regions were compared to projected use of Enlis t. While the range of rates of these currently available alternate programs and the ones for Enlist programs overlapped, when the average of the Enlist program rates were comp ared to the average of all of these top alte rnates, the analysis indicated that the use of 2,4-D on herbicide tolerant DAS-40278-9 corn would reduce the per acre environmental load of herbicides compared to these top, currently available, non-glyphosate alternative programs. Reductions on corn rang ed by 0.15 to 0.74 lb ai/ac, within the individual scenarios, with an overall averag e reduction of 0.49 lb ai/ac across a ll scenarios. As discussed in the draft EA, no evidence supports any increase in total corn acreage pl anted as a result of deregulation of DAS-40278-9 corn.

Ecological Assessment of Herbicide Use on Corn

The EPA is the regulatory agen cy responsible for the review and approval or denial of all pesticide registrations. It is a violation of federal law for pestic ides to be sold or distributed without an EPA registration. The Agency uses a risk assessment process in its registration decisions, evaluating risk based on exposure and hazard, for both humans and ecological organisms. EPA cannot register th e use of a pesticide, or amend an existing registration to add a new use, unless the use of the pesticide meets the statutory “no unreasonable adverse effects” standard, i.e., EPA can only register new pesticides or pesticide uses if the us e of that pesticide in accordance with the EPA-approved label will cau se no unreasonable adverse effects on human
health or the environment.

In order to make its registra tion decisions, the Agency develops exposure assessments that characterize the potential environmental exposures th at may result from the use of a pesticide.
EPA uses the results of environmental fate st udies, in combination with modeling work and pesticide use information to characterize the envir onmental fate of the pes ticide in question.

The Agency also uses modeling work to cons ervatively predict potential impacts on surface and ground water. This modeling work is used not on ly for environmental risk evaluations but is also an input parameter into di etary risk evaluations for humans (providing the drinking water component for dietary assessments).

The results of the environmental fate work enab le EPA to determine where a pesticide and its metabolites and degradates will go in the enviro nment (air, water, soil), how long they willpersist, and in what quantities. Based on st udy, model, and use information, the Agency then develops estimated environmental concentrations (EECs), which are compared to the toxicity endpoints of ecotoxicology studies for risk asse ssment purposes. EEC values are based on the maximum allowable application rate(s) for a pes ticide even though typical application rates are
lower than the maximum.

As in the case of risk assessments for humans, EPA scientists use the most sensitive toxicity endpoints for ecotoxicology studies for risk assessment purposes. Using EECs based on maximum application rates and the most sensit ive toxicity endpoints ensures that EPA risk
assessments for wildlife are conservative a nd protective.

EPA uses risk quotients (RQ’s) and levels of concern (LOC) for acute and chronic risk to wildlife to quantify and ch aracterize risk assessments for plants and animals. RQ’s are ratios of EEC values over toxicity endpoints. The Agency uses different LOCs for non-endangered and endangered species. If planned use rates and use techniques re sult in RQ values that exceed LOCs, EPA may conduct a more refined risk assessm ent to better characteri ze risk. The Agency also considers how to mitigate potential risks, which may require changes in application rates and techniques, or may otherwise limit the use of the pesticide.

EPA assessments of potential impacts on wildlif e and the environment are designed to be conservative and protective. The Agency wants to be cautious in its assessments and would
rather overstate than understate risk concerns. Each intended use pattern (e.g., corn, soybeans, consumer use) is evaluated. Agency environm ental and ecological asse ssments are designed to cover each particular use of a pesticide (e.g., co rn) regardless of whethe r all corn acreage is treated or only a portion of the acreage is treated (much more t ypical). Thus, even if the percent crop treated increases, the EPA assessments are still valid.

2,4-D has an extensive history of safe and effectiv e use. It has been thoroughly reviewed and reregistered by all major regulatory agencies in the world within the last ten years. Recently (April 2012), the EPA denied a petition to cancel the tolerances and registrations for 2,4-D based on toxicological hazard. The Agency issued a re sounding denial of that petition, affirming that 2,4-D posed no unreasonable risk when used as directed (2).

Summary

The introduction of the Enlist Weed Control Sy stem and Enlist Duo herbicide will provide a
much needed additional weed control tool to co rn farmers in American agriculture. The Enlist Weed Control System offers a novel mechanism to offer, at the same time, multiple modes of action which has been cited by th e National Academy of Sciences and the Weed Science Society of America as key components to an effec tive resistant weed management plan. The introduction of herbicide tolerant crops has helped enable the grow ing practice of no-till agriculture which has re sulted in dramatic reductions in so il loss through erosion, made farmingmuch more efficient, reduced trips across the fiel d with resultant fuel and equipment savings, and enabled farmers to proficiently farm more acres (1).

This exercise depicts the curre nt use of 2,4-D in conventional corn and the expanded use of 2,4-
D choline introduced in Enlist Duo herbicide wi th the adoption of Enlist corn and the Enlist Weed Control System. Additi onally, estimates on the use of quizalofop in DAS-40278-9 corn are portrayed. While growers will get improved w eed control performance they will also benefit
from the additional attributes of Enlist Duo herbic ide, particularly the reduction in off-target movement potential via drift or volatility. These improvements help keep the herbicide on the treated field, further reducing risk to the environment and ecological organisms.

1. Public Interest Document Supporting th e Registration of 2,4-D and Quizalofop on
Herbicide Tolerant DAS-40278-9 Corn a nd 2,4-D on Herbicide Tolerant DAS-68416-4 Soybeans to Improve the Performance of Current Weed Control Systems, Provide Increased Weed Resistance Management Opti ons, and Help Sustain the Widely Adopted Glyphosate Tolerant Cropping System that Help s Make Farming Easier, More Affordable and More Environmentally Beneficial. MRID 48535501.

2. EPA Denies Petition on 2,4-D Pesticide http://www.epa.gov/oppfead1/cb/csb _page/updates/2012/2-4d-petition.html

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