1 of 33 Dow AgroSciences LLC dowagro.com 9330 Zionsville Road Indianapolis, IN 46268 USA

308/2E February 14, 2013

Dr. Neil Hoffman Science Advisor USDA/APHIS/BRS 4700 River Road, Unit 98 Riverdale, MD 20737

Diane Sinkowski Senior Environmental Protection Specialist USDA/APHIS/BRS 4700 River Road, Unit 147 Riverdale, MD 20737

DAS

- 68416

- 4 Soybean and DAS

- 40278

- 9 Corn Dow AgroSciences Petition Numbers 09

- 349

- 01p and 09

- 233

- 01p SUPPLEMENTARY DOCUMENTATION IN SUPPORT OF ENVIRONMENTAL ASSESSMENTS

Dear Dr. Hoffman and Ms. Sinkowski:

This letter and attached information is in r esponse to your email of Dec.10, 2012 which included a request for information from Dow AgroSciences (DAS) to support your efforts in developing the final Environmental Assessment and Response to Comments for DAS

- 402780

- 9 corn and DAS

- 68416

- 4 soybean.

Th e attached information addresses Questions 1, 2 and 3 from Section A. H erbicide Use Issues.

Herewith, DAS is submitting our response to these questions on the enclosed CD. We are also including a Word version of this document. This Word version is inten ded only for internal use by USDA

- APHIS staff and not for release.

If you should have any questions or require further information, please contact me at 317

- 337

- 3692.

Sincerely,

Gregory L. Orr, Ph.D. Global Regulatory Leader 317

- 337

- 3692 317

- 337

- 4649 (fax) glorr@dow.com2 of 33 

### DISTRIBUTION PAGE

DED Code: D1C / B1C

bcc: Laura Tagliani, 308/2E Greg Orr, 308/2E Heidi Reistad, 308/2E Federal Action Files, 308/2E unstapled3 of 33 

## Table of Contents

Section A. Herbicide Use Issues

Questions 1 2, 3

Herbicide Use Trends in US Soybeans and Corn ....................................................4

Soybean Herbicide Use Trends........................................................................

.. 6

Corn Herbicide Use Trends............................................................................

. 1 7

Timing of 2,4

- D Application in Key Crops......................................................... 24

Total Herbicide Use Trends of the Major Active Ingredients Used in Corn and Soybeans..

. . 2 7

Timing of Use of the Different Active Ingredients in Corn and Soybean Crops ...............314 of 33 

## DOW AGROSCIENCES RESPONSE TO USDA

- APHIS QUESTIONS RECEIVED
DECEMBER 10, 2012 REGARDING DAS

- 40278

- 9 CORN AND DAS

- 68416

- 4 SOY.

A. Herbicide use issues

1. What herbicide active ingredients have been used on corn and soybean since 1990. If this information is available on a state basis, it would be useful to send it to us state b y state because we need to do a regional analysis in the cumulative impacts as well as a national analysis.
2. For each active ingredient, list the total pounds used in each season data is available for

a. Corn
b. Soybean

c. all agricultural use
d. all non agricultural use. 3. If data is available, list the amounts used as either

a. preplant burndown/pre emergent use
b. post

- emergent use



### Herbicide Use Trends in US Soybeans and Corn

This section focuses on the top 10 herbicides by pounds of active ingredients and the trends in use for the crops of interest. A discussion of general herbicide use and practices is provided in our response to Section B on 2,4

- D use (submitted to USDA v ia email on Jan.. 24, 2013 and Feb. 1, 2013) . The data in this section have been obtained from public sources (as indicated in the document) and any additional data was obtained from third party proprietary sources as survey
response data.

Growers in the U S have been quick and significant adopters of genetically introduced traits (Figure 1). Adoption of herbicide tolerant crops has been rapid and almost universal, particularly for soybean and cotton. Adoption of herbicide tolerant varieties in corn has al so been strong but somewhat slower, likely due to an emphasis growers place on elite yielding hybrids, greater number of herbicide options and slower emergence of glyphosate resistant weeds in the greater corn belt.

The acres in the Conservation Reserve Pr ogram (CRP) have declined approximately 10 million acres over the past ten years, as the government has scaled back the program. This has helped fuel an increase in planted corn acreage which has trended upward in response to the attractive profit opportun ity for the US farmer to supply the strong demand for feed, fuel and exports5 of 33 

### (Figure 2). Soybeans have also gained acreage while wheat has declined in area planted in the US.

Figure 1. Adoption of genetically engineered crops in the United States 1997

- 2012

http://www.ers.usda.gov/data

- products/adoption

- of

- genetically

- engineered

- crops

- in

- the

- us.aspx6 of 33 

### Figure 2. Acreage planted to corn, soy and wheat in the US.

http://www.fas.usda.gov/psdonline/psdhome.aspx



### Herbicides are used at different times in the various market segments depending on the properties of the active ingredient (a.i.), the susceptibility of the crop and the nature of the weed problems. The terms “pre” or “preemergence” and “post” or “post emergence” refer to the stage of the crop’s emergence from the soil.

Residual herbicides work by controlling weeds before they germinate or emerge. These compounds are applied prior to planting or prior to crop emergence in most cases. When weather complicates the timing of herbicide applications with planting, gr owers may plant and apply the residual herbicide in a mix with a foliar applied product. The foliar product controls emerged weeds while the residual material controls weeds prior to germination or emergence.

Soybean Herbicide Use Trends

The trend in soybean herbicide use changed dramatically with the introduction of Roundup Ready ® 

### (RR) soybeans. As shown in Figure 1, RR soybeans had the most rapid adoption curve of the transgenic crops and by 2003 were planted on 80% of the US soybean acres. The adopt ion of RR soybeans allowed post emergent application of a systemic herbicide (glyphosate) that controlled most grasses and broadleaves. This required much less time and was simpler to implement than using incorporated pre

- plant herbicides which require dif ferent rates for different soil types and pH. The speed of adoption was enhanced by the fact that the use of glyphosate on7 of 33 

### post emergent RR soybeans cost less than many farmers had been spending on weed control in soybeans as well as delivering better weed control.

Prior to the introduction of RR soybeans, farmers used many different active ingredients, both residual and post emergent herbicides, to control the varied weed problems that existed in corn and soybeans . Growers used these different products s equentially or in combination. For example, trifluralin or metolachlor was used to target grass weeds and some broadleaf weeds. Other products, such as metribuzen, targeted broadleaf weeds. The ability to use glyphosate over the top of soybeans allowed f armers to target both grass and broadleaves with one product that only required an average of 1.5 applications. This had the added benefits of using a single rate across soil types or pH and did not require either mechanical incorporation into the soil or rainfall for activation. This proved an attractive option for farmers that allowed a simpler solution and also gave a better weed control result in many cases. The use of glyphosate post emergent on RR soybeans worked very well because soybeans are usually planted in narrow rows which provide rapid canopy closure thereby preventing most weeds from germinating. The benefit of total post emergent weed control also supported adoption of no till practices, saving time and money for the grower while reducing soi l erosion.

Top 10 Soybean Herbicides (total pounds applied)

As stated above, t he data utilized in this section have been obtained from third party proprietary sources. Glyphosate accounted for 81% of all herbicide active ingredient pounds used in US soybe ans during 2011 and accounted for 113 million treatment acres (Figure 3.). The top 10 herbicides (by pounds used), account for 97% of total herbicide pounds used in US soybeans in 2011. As the figure below shows, the pounds of glyphosate active ingredient grew to over 100 million pounds per year in soybeans and replaced much of the other herbicides that had been used. The sharp increase in 2008 was due to the large increase in soybean acres that year.8 of 33 

### Figure 3. Top 10 Soybean Herbicides 1990

- 2011

Top 10 Soybean Herbicides (treated acres)

Evaluating treated acres within crop by the different actives (Figure 4) provides a better comparison of the relative use of the herbicides than focusing on pounds applied due to differences in use rate between actives and trends in use rate over time.9 of 33 

### Figure 4. Top 10 Soybean Herbicides 1990

- 2011

Removing glyphosate from the analysis provides a clearer picture of the other soybean herbicides used over time (Figure 5), indicating that chlorimuron and flumioxazin we re the second and third most common herbicide treatments in soybeans in the US in 2011. From 2008 a clear trend towards including additional herbicides in soybean weed control programs can be seen. This is related to the increasing emergence of hard to co ntrol weeds and glyphosate resistant weeds, with additional herbicides being used to control them plus prevent the emergence of additional resistant weeds.10 of 33 

### Figure 5. Top 9 Soybean Herbicides 1990

- 2011

Regional Use of Herbicides in Soybean by US Cropping Region

The U.S. states can be divided into agricultural regions as shown in the map below (Figure 6). Overall, the herbicides used to control weeds in soybean are similar across regions (Figures 7

- 16). Glyphosate provides the principal basis for weed control in each of the regions with other actives being used to control weeds that are not controlled satisfactorily by glyphosate alone.

The Heartland Region accounts for half of all soybean herbicide treatments (data not shown). Some of the increa se in herbicide use has been tied to an increase in soybean acreage. This is especially true in the Northern Great Plains Region which has seen acres of corn and soybeans increase greatly in the past 5 years (data not shown).

The trends have been similar a cross the regions with the use of other products starting to trend upward again as weed control has slipped in recent years with some weeds developing increased tolerance or resistance to glyphosate and ALS compounds (ex., chlorimuron, thifensulfuron). Soy bean growers are responding by using other products either in combination or sequentially with glyphosate. In the Heartland region, 2,4

- D use in burndown applications started increasing in 2008 (Figures 7 and 8). In the southern regions, a number of produ cts have increased in use led by metolachlor

- S and 2,4

- D (Figures 15 and 16). The SouthEast region has seen weed resistance to glyphosate develop the most rapidly and this is likely causing the more rapid change in herbicide use patterns compared to the ot her regions. The use of fomesafen,11 of 33 

### flumioxazin, chlorinuron, Metolachlor

- S and 2,4

- D have all increased rapidly since 2008 as farmers strive to get control of weeds that are not being controlled adequately by glyphosate treatments (Figure 16).

Figure 6. U .S. States Grouped Into Regions



## States Grouped into Regions12 of 33 

### Figure 7: Top 10 Soybean Herbicides (total lbs applied) in the Heartland Region

Figure 8: Top 10 Soybean Herbicides (treatment acres) in Heartland13 of 33 

### Figure 9: Top 10 Soybean Herbicides (total lbs applied) in the Northern Crescent

Figure 10: Top 10 Soybean Herbicides (treatment acres) in the Northern Crescent14 of 33 

### Figure 11: Top 10 Soybean Herbicides (total lbs applied) in the Northern Great Plains

Figure 12: Top 10 Soybean Herbicides (treatment acres) in the Northern Great Plains15 of 33 

### Figure 13: Top 10 Soybean Herbicides (total lbs applied) in the Prairie Gateway Region

Figure 14: Top 10 Soybean Herbicides (treatment acres) in the Prairie Gateway16 of 33 

### Figure 15: Top Soybean Herbicides (total lbs applied) in the SouthEast

Figure 16: Top Soybean Herbicides (treatment acres) in the SouthEast17 of 33 

### Corn Herbicide Use Trends

Corn yields are more negatively impacted by early season weed competition than soybeans. Corn is also planted in wider rows than soybeans and the resulting penetration of light allows weed germination over a longer period of time than soybeans. As a resul t, most corn growers have continued to use residual herbicides followed by application of post emergent herbicides as needed to provide good weed control and maximize yield potential. Some growers have reduced rates of residual herbicides since they have good post emergent options to clean up later germinating weeds.

Top 10 Corn Herbicides

Glyphosate is the top herbicide active ingredient used in corn, accounting for roughly 40% of the pounds of active used (Figure 17). The top 10 actives account for over 97% of all of the pounds a.i. used in corn in the US in 2011. However, glyphosate did not replace the other actives in corn to the extent it did in soybeans. Rather, it was used in combination to improve weed control. Note that one of the larger products in the early 90’s was alachlor, which does not show in this chart (Figure 18). Alachlor was displaced by acetochlor which has the same mode of action but can be used at a lower rate

.

Figure 17. Top 10 US Corn Herbicides (total lbs applied)

0 10,000,000 20,000,000 30,000,000 40,000,000 50,000,000 60,000,000 70,000,000 80,000,000 90,000,000Total lbs AI 

## Top Herbicides in US Corn 2011

GLYPHOSATE ATRAZINE ACETOCHLOR METOLACHLOR

- S

2,4

- D METOLACHLOR SIMAZINE MESOTRIONE

DICAMBA DIMETHENAMID

- P ss18 of 33 

### Figure 18. Top 10 US Corn Herbicides (treatment acres)

The trends in corn herbicide use reflect the adoption of Roundup Ready ® 

### corn (launched in 1998) and the resulting increase in the use of glyphosate. The use of other actives declined somewhat until about 200 8 and then began to increase again. This was in response to the increased value of the crop due to the high price of corn and the appearance of hard to control and glyphosate resistant weeds. The trends are similar across the regions (Figure 6), but all

r egions (Figures 19

- 28) show an increase in more modes of action being employed (photosystem II, ALS, mitotic, and carotenoid biosynthesis inhibitors). The increases are primarily in the broadleaf and cross spectrum products, with mesotrione, 2,4

- D and dica mba increasing as well as metolachlor and acetochlor.19 of 33 

### Regional Use of Herbicides in US Corn

Figure 19. Top 10 US Corn Herbicides (total lbs applied) in the Heartland Region

Figure 20. Top 10 US Corn Herbicides (treatment acres) in the Heartland Region 0 5,000,000 10,000,000 15,000,000 20,000,000 25,000,000 30,000,000 35,000,000 40,000,000 45,000,000Total lbs AI 

## Corn Herbicide Trends

- Heartland Region

GLYPHOSATE ATRAZINE ACETOCHLOR METOLACHLOR

- S

2,4

- D SIMAZINE MESOTRIONE METOLACHLOR

DIMETHENAMID DIMETHENAMID

- P ss20 of 33 

### Figure 21. Top 10 US Corn Herbicides (total lbs applied) in the Northern Crescent

Figure 22. Top 10 US Corn Herbicides (treatment acres) in the Northern Crescent21 of 33 

### Figure 23. Top 10 US Corn Herbicides (total lbs applied) in the Northern Great Plains

Figure 24. Top 10 US Corn Herbicides (treatment acres) in the Northern Great Plains22 of 33 

### Figure 25. Top 10 US Corn Herbicides (total lbs applied) in the Prairie Gateway

Figu re 26. Top 10 US Corn Herbicides (treatment acres) in the Prairie Gateway23 of 33 

### Figure 27. Top 10 US Corn Herbicides (total lbs applied) in the SouthEast

Figure 28. Top 10 US Corn Herbicides (treatment acres) in the SouthEast 0 1,000,000 2,000,000 3,000,000 4,000,000 5,000,000 6,000,000 7,000,000 8,000,000Total lbs AI 

## Corn Herbicide Trends in Pounds

- SouthEast

GLYPHOSATE ATRAZINE METOLACHLOR

- S 2,4

- D SIMAZINE

PARAQUAT DICAMBA MESOTRIONE ALACHLOR METOLACHLOR ss24 of 33 

### Timing of 2,4

- D Application in Key Crops

Late fall and the period prior to planting account for all of the 2,4

- D applications to soybeans (otherwise it would kill the soybeans) and the vast majority of 2,4

- D treatments to corn (Figures 27, 28).

Much of the 2,4

- D herbicide use in corn and soybeans is focused on controlling difficult to control weeds or preventing resistance development. The use in burndown applications prior to planting helps establish a clean seedbed and reduce early season competition without a tillage

op eration. Some applications are also done the previous fall to clean up weed escapes (including any potentially resistant weeds) in the prior crop and/or to control winter annuals.

Figure 29. 2,4

- D Application Timing: Soybean25 of 33 

### Figure 30. 2,4

- D Application Timing: Corn

Corn often follows soybeans in rotation , which are generally harvested earlier in the fall, allowing more time for weed growth prior to winter. Usually corn planting begins earlier in the spring than soybean planting. Thus, there is less opportunity for weed emergence prior to planting corn which decreases the weeds that can be controlled with a spray application prior to planting. Both of the factors drive growers to make a fall application(s) to control weeds before planting corn the next season.

In winter wheat, roughly 20% of 2,4

- D is applied in the fall or at plant to provide early weed control (Figure 31). However, the vast majority is applied the following spri ng after the wheat and the new crop of weeds are actively growing.

Winter wheat, being planted in the fall of the year, provides the crop with a large advantage over many of the weeds that germinate in the spring. In crop seasons with favorable conditions, the wheat establishes a dense stand and tillers to form a canopy that prevents light penetration, thus preventing many weeds from germinating. This is one of the major factors that allow almost half of winter wheat in the US to be successfully grown witho ut a single herbicide application.

In Spring Wheat, roughly 20% of 2,4

- D applications occur prior to or at planting with the remaining treatments usually more than 3 weeks after crop emergence (Figure 32). This allows the wheat to get established and for m a canopy. Weeds germinate and begin to establish during this early part of the season and are most vulnerable to a herbicide application at this time. Late post is defined as more then 3 weeks after emergence26 of 33 

### Figure 31. 2,4

- D Application Timing: Winter Wheat

Figure 32. 2,4

- D Application Timing: Spring W heat27 of 33 

### Total Herbicide Use Trends of the Major Active Ingredients Used in Corn and Soybeans

Historical use of major agricultural herbicides for corn and soybean is shown in Figure 33. Glyphosate has developed into the predominant herbicide in both crops i n the last 10 years. For historical sake, alachlor is included even though it is not currently used.

Glyphosate is by far the most utilized herbicide in US agriculture. Many of the active ingredients do not have large enough usage to show up on the chart and several of the ones that did, have declined dramatically over time including alachlor, metolachlor, trifluralin and pendimethalin. The introduction of metolachlor

- S and acetochlor caused much of the reduction in alachlor and metolachlor use. All of the se actives are residual herbicides that provide control for an extended period of time by preventing weeds from emerging.

Figure 33. Major Corn and Soybean Actives Total Use in Agriculture

Herbicide Use in the Different Market Segments

Of the active ingredients shown in Figure 33, only a few have a significant portion of their use in

non

- crop markets. These actives are 2,4

- D, glyphosate, clopyralid, dicamba, and pendimethalin (Figures 34

- 38). There are three major market segments of 2,4

- D use : agricultural crop use, range and pasture use, and non

- crop use. The use of 2,4

- D (and all other herbicides in Fig. 33) varies from year to year depending on the respective area planted to different crops and the weather conditions that occur during the year which will influence crop and weed development. 0 50 100 150 200 250 300Million Pounds ai 

### Total Agricultural Use of Major Corn and Soybean Herbicides

1990

1995

2000

2005

2011 

## d

r28 of 33 

### The non

- crop segment use also depends on weather conditions, with use decli ning during drought years when lawns and rights

- of

- way dry up. The range of use of 2,4

- D across all segments varies from 58

- 68 million pounds with an average of 64 million pounds ai based on information from several proprietary sources and internal company expertise.

The agricultural segment is made up of the crop use segment and the range and pasture segment. Within the crop segment these uses are very diverse ranging from burndown application prior to planting soybeans, to use underneath tree crops and u se on wheat. The range and pasture segment consists of control of annual weeds as well as control of perennial weeds, woody and invasive species.

The non

- crop segment includes use on rights of ways for roadways, utilities and railroads, nurseries, forestry , lawns, cemeteries, and other uses to control undesirable plants.

Figure 34. 2,4

- D Use by Market Segment



### 2011 Use of 2,4

- D by Pounds Active

Crops
Range & Pasture

Non

- Crop29 of 33 

### Figure 35. Glyphosate Use by Segment 2011

Figure 36. Clopyralid Use by Segment 2011 

### Glyphosate Use by Segment 2011

Crop Use
Range & Pasture
Non Ag



### Clopyralid Use by Segment

Crop Use
Range & Pasture
Non Ag30 of 33 

### Figure 37. Pendimethalin Use by Segment 2011

Fig ure 38. Dicamba Use by Segment 2011 

## Pendimethalin Use by Segment 2011

Crop Use
Range & Pasture

Non Ag



## Dicamba Use by Segment 2011

Crop Use
Range & Pasture

Non Ag31 of 33 

### Timing of Use of the Different Active Ingredients in Corn and Soybean Crops

Herbicides are used at different times in the various market segments depending on the properties of the active ingredient , the susceptibility of the crop and the nature of the weed problems (Figures 39

- 42). The terms “pre” or “preemergence” and “post” or “post emergence” refer to the stage of the crop’s emergence from the soil. Non

- applicable (NA) refers to perennial

crops, examples are tree crops, pasture, sugarcane and hay crops or fallow where there is no

crop.

Residual herbicides such as acetochlor, trifluralin, metolachlor, metolachlor

- S, pendimethalin, acetochlor, atrazine and alachlor work by controlling weeds before they germinate or emerge. These compounds are applied prior to planting or prior to crop emergence in most cases. When weather complicates the timing of herbicide applications with planting, growers may plant and apply the residual herbicide in a mix with a foliar applied product, such as acetochlor combined with glyphosate applied to corn. The foliar product (glyphosate in this example) controls emerged weeds while the residual material (acetochlor) controls weeds prior to germination or

emergence.
The po st materials have activity when foliar applied to plants and can be used over the top of crops if the crop is selective for that active or has been modified to be tolerant (ex., RR corn and RR soybeans). If the crop is not tolerant the active may still pr ovide useful weed control by using the herbicide prior to the crop emerging (pre

- emergence application). Burndown applications in both crops often incorporate glyphosate, diacamba,and 2,4

- D and may include paraquat or glufosinate to control weeds prior to crop emergence. Most of the actives will have some use in both corn and soybeans, but a few are used in only corn or soybeans. Atrazine, mesotrione and simazine are not used on soybeans and imazethapyr, fomesafen, chlorimuron, flumioxazin and trifluralin a re predominantly used on soybeans.32 of 33 

### Figure 39. Timing of Use for 2,4

- D, Acetochlor, Atrazine, and Dicamba

Figure 40. Timing of Use for flumetsulam, fomesafen, glufosinate, glyphosate and imazethapyr 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

NA POST PRE NA POST PRE NA POST PRE NA POST PRE

2,4

- D Acetachlor Atrazine Dicamba 

### Timing of Active Use

1990

1995

2000

2005

2011

0 0.2 0.4 0.6 0.8

1 1.2NAPOSTPRENAPOSTPRENAPOSTPRENAPOSTPRENAPOSTPRE

Flumetsulam Fomesafen Glufosinate Glyphosate Imazethapyr 

### Timing of Active Use

1990

1995

2000

2005

201133 of 33 

### Figure 41. Timing of Use for Isoxaflutole, Mesotrione, Metalachlor and Metolachlor

- S

Figure 42. Timing of Use for Pendimethalin, Thifensulfuron, Trifluralin and Paraquat 0 0.2 0.4 0.6 0.8

1 1.2

NA POST PRE NA POST PRE NA POST PRE NA POST PRE

Isoxaflutole Mesotrione Metolachlor Metolachlor

- S 

### Timing of Active Use

1990

1995

2000

2005

2011

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

NA POST PRE NA POST PRE NA POST PRE NA POST PRE

Pendimethalin Thifensulfuron Trifluralin Paraquat 

### Timing of Active Use

1990

1995

2000

2005

2011