Page 1-1

Appendix 1.

USDA Notifications and States Approved for

Environmental Releases of MON 88701 Dicamba- and 

Glufosinate-Resistant Cotton and MON 87708 

Dicamba-Resistant Soybean
Page 1-2

Table 1-1. USDA Notifications, Permits and States

Approved for MON 88701 Cotton

USDA No. Date State/Territory-Number of Releases

07-241-107n 9/28/2007 PR-2

08-042-109n 3/12/2008 TX-2, TN-1, NC-2, MS-3, GA-4

08-056-112n

08-056-117n

3/26/2008

3/26/2008

NM-2

TX-3, SC-2, NC-2, MS-2, LA-1, GA-4,

AR-1

08-266-130n 10/19/2008 PR-3

09-058-104n 3/29/2009 CA-1

09-065-111n 4/5/2009 AZ-5, GA-1, MS-3, SC-2, TX-4

09-068-108n 4/8/2009 AL-1, AR-2, AZ-1, GA-1, IL-1, LA-1,

MS-1, NC-4, NM-2, TX-1

09-072-103n 4/8/2009 AR-1, MS-2, SC-5, TN-2, TX-5

09-224-101n 9/21/2009 PR-2

10-054-134n 3/20/2010 TX-4

10-059-109n 3/28/2010 GA-2, NC-9, SC-3

10-061-102n 7/10/2010 MS-1, PR-7

10-064-101n 4/3/2010 CA-2, GA-1, LA-1, MO-1, OK-3, SC-1,

AR-1

10-067-104n 4/7/2010 AZ-5, IL-1, MS-4, NM-2, PR-2, TX-10

10-071-101n 4/9/2010 AR-4, AZ-2, GA-2, KS-1, LA-1, NC-2,

NM-1, SC-1, TX-2

10-071-102n 4/10/2010

AR-1, GA-1, LA-1, MS-1, NC-1, SC-1,

TN-1, TX-2

10-242-102n 9/29/2010 PR-2

10-285-105n 11/11/2010 AR-1, GA-1, LA-1, NM-1

11-045-101n 3/16/2011 MS-1, PR-2

11-052-105n 3/23/2011 AL-1, FL-2, GA-9, MS-1, NC-6, SC-4

11-053-105n 3/25/2011 AR-3, LA-2, MO-2, MS-8, TN-5, TX-4

11-075-107n 4/15/2011 AL-1, AR-1, AZ-4, IL-1, LA-1, MO-1,

MS-4, NC-1, SC-1, TX-9

11-068-103n 4/8/2011

AL-2, AR-2, AZ-1, CA-2. GA-2, LA-1,

NC-1, NM-1, SC-1, TX-5

11-083-104n 4/23/2011 AL-1, MS-1

11-084-107n 4/24/2011 NC-1

11-091-102n 5/1/2011 TX-1
Page 1-3

Table 1-1 (Continued). USDA Notifications, Permits and

States Approved for MON 88701 Cotton

USDA No. Date State/Territory-Number of Releases 

11-094-101n 5/4/2011 RRReleases AZ-1Release

11-111-104n 5/21/2011 FL-1

11-133-103n 6/12/2011 IL-1

11-153-101n 7/2/2011 MS-1, PR-2

11-152-101n 7/1/2011 GA-1

11-199-102n 8/17/2011 PR-1

11-290-101n 11/16/2011 MS-1, PR-3

12-018-101n 2/17/2012 AL-1, TX-2

12-053-110n 3/23/2012 AR-3, CA-1, GA-2, LA-2, MS-11, NC- 1,

TN-1, TX-2

12-046-104n 3/16/2012

AL-1, AR-4, FL-1, GA-2, LA-1, NC-3,

SC-1, TN-4, TX-2

12-051-106n 3/21/2012

AL-3, AR-3, FL-1, GA-3, MS-7, SC-1,

TN-1, TX-5

12-051-105n 3/21/2012 GA-5, MS-4, NC-6, SC-2, TN-1, TX-5

12-046-109n 3/16/2012 AR-1, MO-5, TN-13,TX-2

12-055-101n 3/25/2012 AR-1, CA-1, SC-1, TX-1

12-068-101n 4/7/2012 CA-4

12-053-109n 3/23/2012 AL-1, NC-1, SC-1, TX-4

12-069-101n 4/8/2012 GA-9, TX-2

12-075-102n 4/14/2012 AL-1, AR-2, MS-1, NC-1, SC-1, TX-4

12-074-107n 4/13/2012 TX-1

12-081-101n 4/20/2012 AL-1, TX-2

Abbreviations:

AL = Alabama; AR = Arkansas; AZ = Arizona; CA = California; FL = Florida; GA = Georgia; 

LA = Louisiana; IL = Illinois; MO = Missouri; MS = Mississippi; NC = North Carolina; PR = 

Puerto Rico; SC = South Carolina; TN = Tennessee; TX = Texas
Page 1-4

Table 1-2. USDA Notifications, Permits and States

Approved for MON 87708 Soybean

USDA No. Date State/Territory-Number of Releases

05-269-02n 11/16/2005 PR-1

06-045-15n 5/18/2006 HI-5

06-045-17n 5/18/2006 PR-3

06-052-01n 3/20/2006 IL-7, KS-5

06-052-02n 4/24/2006 IA-7, IL-5, IN-2

06-052-09n 4/24/2006 IA-2, IL-6, IN-2

06-067-05n 4/24/2006 IL-2

06-090-03n 5/5/2006 IL-2

06-275-102n 11/14/2006 PR-1

06-345-101n 1/10/2007 PR-3

07-018-103n 2/17/2007 IL-10, IN-3, MO-1, PR-1

07-018-106n 2/17/2007 IA-7, KS-6

07-018-109n 2/17/2007 IA-1, IL-10, IN-3, MO-1

07-024-101n 3/18/2007 IA-7, KS-6

07-039-101n 3/18/2007 IA-4, IL-5, IN-3, KS-3

07-043-102n 4/10/2007 IA-1, IL-2, KS-1

MD-1, WI-1

07-050-107n 4/9/2007 IA-1, IL-2, IN-1, KS-1

KY-1, MN-1, NE-1, SD-1

07-057-109n 4/6/2007 AL-1, IA-3, IL-1

IN-1, LA-1, MN-1

07-094-104n 5/4/2007 MO-2, MS-1, NE-1

 SD-1, TN, IA-1

07-094-116n 5/4/2007 MN-1

07-113-103n 6/4/2007 PR-2

07-241-103n 9/28/2007 PR-1

07-250-102n 10/7/2007 PR-2

07-261-101n 10/18/2007 PR-2

07-271-101n 10/28/2007 PR-2

07-312-101n 12/5/2007 PR-1
Page 1-5

Table 1-2 (Continued). USDA Notifications, Permits and

States for MON 87708 Soybean

USDA No. Date State/Territory-Number of Releases

07-352-101rm 3/26/2008 IA-8, IL-16, IN-4, KS-7, MO-1

08-030-103n 2/29/2008 PR-2

08-031-105n 3/13/2008 IA-5, IL-4, KS-5

08-031-106n 3/1/2008 IA-2, IL-5, IN-3

08-039-107n 3/9/2008 IA-5, IL-1, IN-3, KS-5, MO-1

08-043-107n 3/13/2008 IA-3, IL-10, IN-1, OH-1

08-049-101n 3/19/2008 IL-1, MD-1, WI-1

08-058-101n 3/28/2008 IA-3, IL-2, IN-1, MO-1,

PA-1, WI-2

08-059-109n 3/29/2008 IA-1

08-059-110n 3/29/2008 IL-1

08-059-112n 3/29/2008 IN-1

08-060-103n 4/2/2008 MN-1

08-063-112n 4/2/2008 IA-4, IL-2, IN-1, MI-1

MO-1, NE-2

08-063-113n 4/4/2008 MN-2, ND-1, SD-5, WI-5

08-065-101n 4/4/2008 IL-2, IN-1

08-064-102n 4/3/2008 PA-1

08-064-103n 4/3/2008 IL-1

08-064-104n 4/3/2008 AR-1, GA-1, KS-5

LA-1, MO-1 SC-1

08-064-105n 4/3/2008 AR-1, IL-2, IN-1, KS-3, MD-1

MN-3, NC-1, SD-1, WI-1, ND-1

08-072-110n 4/25/2008 AR-1, IA-1, IN-3

KS-1, MI-1, MO-2

08-079-101n 4/17/2008 NE-1, IA-3

08-084-102n 4/24/2008 IA-1, NE-1

08-182-101n 8/1/2008 PR-2

08-219-101n 9/5/2008 PR-1

08-263-101n 10/19/2008 AR-1, IA-1, IL-1, MO-1

08-266-105n 10/22/2008 PR-1

08-323-101n 12/18/2008 PR-1

08-352-108n 1/26/2009 PR-1

08-357-101rm 3/17/2009 IA-8, IL-7, IN-3, KS-5, NE-1
Page 1-6

Table 1-2 (Continued). USDA Notifications, Permits and

States for MON 87708 Soybean

USDA No. Date State-Number of Releases

09-007-106n 2/25/2009 PR-1

09-036-103n 3/7/2009 IA-2, IL-2, IN-1, NE-1

09-042-103n 3/19/2009 MS-1

09-049-110n 3/20/2009 IA-1

09-050-136n 4/3/2009 IA-2, IL-2, IN-2,MD-1, MN-1,

OH-1, PR-1

09-061-108n 4/1/2009 AR-1, IA-1, IL-3, KS-1, SD-1

09-061-117n 4/1/2009 IL-1, MO-2

09-068-111n 4/8/2009 IL-2, IN-2, MS-1

NE-2, OH-1

09-071-102n 4/11/2009 NE-1, SD-1, TN-2

09-082-103n 4/22/2009 IN-1

09-091-103n 5/1/2009 AR-1

09-093-120n 5/3/2009 AR-1

09-124-102n 6/3/2009 PR-1

09-124-105n 5/13/2009 IA-1

09-135-104n 6/14/2009 IL-1

09-162-105n 7/11/2009 PR-1

09-162-106n 7/11/2009 PR-1

09-222-101n 9/9/2009 PR-2

09-237-104n 9/24/2009 PR-1

09-247-101rm 11/17/2009 PR-1

Abbreviations:

AR = Arkansas; GA = Georgia; HI = Hawai’i; KS = Kansas; KY = 

Kentucky; LA = Louisiana; IA = Iowa; IL = Illinois; IN = Indiana; MD = 

Maryland; MI = Michigan; MN = Minnesota; MO = Missouri; MS = 

Mississippi; NC = North Carolina; ND = North Dakota; NE = Nebraska; OH 

= Ohio; PA = Pennsylvania; PR = Puerto Rico; SC = South Carolina; SD = 

South Dakota; TN = Tennessee; WI =Wisconsin 
Appendix 2. Summary of Public Comments

Page 2-1
Public Scoping Comments

Members of the public were invited to participate in the scoping process for this draft EIS through 

an announcement of a notice of intent (NOI) to prepare an environmental impact statement (EIS) in 

connection with making a determination on the status of Monsanto petitions 10-188-01p

(designated as event MON 87708 soybean) and 12-185-01p (designated as event MON 88701 

cotton). APHIS published an NOI to prepare an EIS for the two petitions and requested public 

comments for scoping the EIS in the Federal Register on May 16, 2013. The 60-day public 

comment period closed on July 17, 2013. The docket file was published 

at http://www.regulations.gov/#!docketDetail;D=APHIS-2013-0043.

In this NOI, APHIS asked for comments, data, and information regarding 18 broad, overlapping 

issues. APHIS also requested the public to provide suggestions for other issues to be discussed or 

alternatives to be analyzed in the draft EIS. During this comment period, APHIS received 64

comments (see summary in Table 2-1) with an additional 16 comments from the virtual public 

meetings (see summary in Table 2-2). Comments were made by interest groups, industry

representatives, industry trade organizations, growers, private individuals, scientists, agronomists 

and crop specialists, and a Federal agency. Full text of the comments received during the open 

comment period is available online at www.regulations.gov.

In addition to posting written comments directly to the docket, members of the public were given 

opportunities to provide their comments directly to APHIS during public meetings held on June 26 

and 27, 2013. Transcripts of the public meetings are available as follows:

For the June 26, 2013, virtual meeting:

http://www.aphis.usda.gov/biotechnology/downloads/VPM/062613/VPM_062613_transcript.pdf

For June 27, 2013, virtual meeting:

http://www.aphis.usda.gov/biotechnology/downloads/VPM/062713/VPM_062713_transcript.pdf

In all, a total of 80 public comments were received with 64 public comments submitted to the

docket folder on the NOI for the preparation of an EIS on dicamba-resistant soybean and cotton 

and an additional 16 comments were given on the NOI during the virtual meetings. 

APHIS used the public comments to identify issues to be considered in development of the Draft 

EIS. A number of commenters indicated they object to APHIS Notice of Intention to prepare an 

EIS, finding the level of analysis performed in the EAs scientifically sufficient. These commenters 

felt preparing an EIS unnecessarily keeps valuable traits and tools currently needed by growers 

battling herbicide-resistant weeds. 

Commenters who were opposed to the deregulation of MON 87708 soybean and MON 88701 

cotton generally were concerned about the potential increased use of dicamba by growers with 

adoption of the deregulated events. While APHIS recognizes these concerns, APHIS does not 

regulate pesticide use. EPA is reviewing and analyzing the information Monsanto has submitted in 

support of the registration of their dicamba formulation. This includes assessing the physical and 

chemical properties of, fate and transport of, and impacts to the environment and human health 

Page 2-2
from the new formulation. APHIS has no input into the decision of permitting the use of the new 

dicamba uses; therefore, those issues are not analyzed in this EIS. 

Page 2-3
Table 2-1. EIS Public Scoping Comments Submitted Online

Comment # Comment ID Commenter Comment Excerpt

1 APHIS-2013-

0043-0002

Anna Fox • Opposed to Monsanto receiving unregulated status for herbicide resistant 

soybeans and cotton.

• These crops may be resistant to the herbicides glufosinate but what about all 

the other organisms in the ecosystem? 

2 APHIS-2013-

0043-0003

Darryl Figueroa • We need to stop using pesticides that are banned in Europe and killing our 

bees.

• Stop using genetically engineered food without long term study RE the 

impact on our health. GE crops and seeds are creating super weeds and 

changing the bacteria in our stomachs and changing how we digest food.

• We want and need labelling of all genetically engineered food and products 

using GE seeds and crops.

3 APHIS-2013-

0043-0004

Arthur Tesla • Opposed to Monsanto receiving unregulated status for herbicide resistant 

soybeans and cotton.

• Spraying these crops with dangerous herbicides makes these crops plant 

pests!.

4 APHIS-2013-

0043-0006

Caitlyn Batche • Opposed to Monsanto receiving unregulated status for herbicide resistant 

soybeans and cotton.

• Monsanto’s “Roundup Ready” crops require about 4 times more water, and 

the application of several pesticides. Clean water is a diminishing resource 

because of exploitation and pollution. In Environmental Protection 

Agency’s Numeric Nutrient Criteria, pesticides were a major problem in 

water systems.

• GMO products should be labelled.

5 APHIS-2013-

0043-0005

Philip Nelson, Illinois 

Farm Bureau (IFB)

• These traits have already gone through USDA's rigorous regulatory review 

protocol and there have been no scientific, findings to warrant additional 

EIS. On behalf of nearly 83,000 Illinois farmers, I write today to requestthat, APHIS move expeditiously when completing this seemingly 

superfluous regulatory review.

• Biotechnology has produced vast improvements in farm production 

practices, permitting farmers to do more with less. Herbicide-tolerant seeds 

are simply another tool for our producers to utilize towards helping feed the 

world's ever increasing population. These technologies will have a positive 

impact on farming and the food that we produce.

6 APHIS-2013-

0043-0008

U.S. Department of 

Interior, National Park 

Service – Elaine Leslie

• The National Park Service supports the objective identified or development 

of science that addresses the Environmental Issues for Consideration 

identified on pages 28799 [of the Federal Register notice]. The NPS is 

Page 2-4
Comment # Comment ID Commenter Comment Excerpt

concerned about the indirect effects on the soil and water quality in NPS 

areas as a result of increased herbicide use. We believe the indirect effects 

on soil and water quality as a result of increased herbicide use of the 

products proposed to be de-regulated, be evaluated.

7 APHIS-2013-

0043-0009

Jean Public • Opposed to Monsanto receiving unregulated status for herbicide resistant 

soybeans and cotton.

• I do not believe the tests on these products are adequate. This is new stuff. It 

has not had rigorous long term testing.

8 APHIS-2013-

0043-0010

None None • No content

9 APHIS-2013-

0043-0011

Sergio Benitez • Wants labeling of GMOs

10 APHIS-2013-

0043-0012

Kelli Lord • Opposed to Monsanto receiving unregulated status for herbicide resistant 

soybeans and cotton.

11 APHIS-2013-

0043-0013

Omar Flores • Two documents, one in English and the other in Spanish (by European 

Union and Greenpeace Mexico), show the negative health, economical and 

ecological consequences of having allowed Monsanto's GMO soybean 

RoundUp(tm) resistant in the Yucatan Peninsula and in Argentina.

• An economical study by the Autonomous University of Yucatan shows that 

the economical costs of using GMO soybean, not even counting the 

environmental costs is 55 higher than the total benefit.

12 APHIS-2013-

0043-0016

Carl Bausch • Opposed to preparation on an EIS.

• The statement of purpose and need is missing from the notices. To what 

need and for what purposes are petitioners responding in developing and 

commercializing their products? The answer to this question largely 

determines the range of reasonable alternatives the agency must consider in 

the NEPA process.

• Granting (with or without conditions) or denying petitions does not 

constitute “alternatives” to be considered in NEPA’s environmental impact 

statement process; rather, they are decision options for the agency (see my 

earlier comment for explanation). Alternatives that must be considered 

under NEPA relate directly to the purposes of and need for proposed 

actions.

• APHIS NEPA documents are not written in plain language, as required by 

the NEPA implementing procedures (40 C.F.R. § 1502.8). 

• Monitoring, which is an essential component of the NEPA process (40 

C.F.R. § 1505.3), should be employed in biotechnology permitting to 

confirm assumptions made in NEPA documents and respond to many 

Page 2-5
Comment # Comment ID Commenter Comment Excerpt

unanswered, but oft-repeated questions.

• APHIS has often claimed that, although individual farmers may be affected 

by releasing genetically engineered organisms in the area, when examined 

in total, none of the potential business losses is expected to be so severe as 

to amount to a significant impact. This determination fails to recognize that 

environmental “significance” exists at all levels―“society as a whole 

(human, national), the affected region, the affected interests, and the 

locality.” 40 C.F.R. § 1508.27(a).

• APHIS tends to rely on the United States Environmental Protection 

Agency’s (EPA) consideration of environmental effects in the context of the 

Federal Insecticide, Fungicide and Rodenticide Act (FIFRA) registration 

process, as well as FDA’s determinations under its enabling legislation. 

The regulatory and review processes of EPA and FDA cannot be relied 

upon to relieve APHIS from considering in the context of the National 

Environmental Policy Act (NEPA) process any and all effects associated 

with release into the environmental of petitioners’ products. 

• In the past, APHIS appears to have placed a great deal of reliance on 

petitioners in complying with NEPA. Agencies have a responsibility under 

NEPA to independently investigate and assess the environmental impacts of 

proposals under consideration (40 C.F.R. § 1506.5(a) and (b)). 

• There is considerable uncertainty regarding potential environmental effects 

of releasing genetically engineered organisms. Although an agency is not 

precluded from approving a particular proposal involving substantial 

uncertainty, it must disclose all areas of uncertainty. Save Our Ecosystems 

v. Clark, 747 F.2d 1240, 1246 (9th Cir. 1984).

• The taxpayer and the agricultural biotechnology industry would be better 

served if APHIS announced it would no longer “regulate” agricultural 

biotechnology because there has not been a proven plant-pest risk 

associated with the technology in decades, perhaps ever.

13 APHIS-2013-

0043-0014

Sally Smith-Weymouth • Opposed to Monsanto receiving unregulated status for herbicide resistant 

soybeans and cotton.

• Please do not grant Monsanto's request for nonregulated status of herbicide 

resistant soybeans and cotton. Such herbicides are already wreaking havoc 

all over the world causing crop failures and super weeds, soil depletion, and 

a plethora of ailments afflicting humans the world over.

• Wants labeling of GMOs

14 APHIS-2013-

0043-0015

Sarah Stolar • The raise in acceptable levels of glyphosphate on our foods are ridiculous 

and criminal. Round up is toxic to the environment, soil organisms, and 

Page 2-6
Comment # Comment ID Commenter Comment Excerpt

people.

15 APHIS-2013-

0043-0017

Jessica Padgett • Opposed to Monsanto receiving unregulated status for herbicide resistant 

soybeans and cotton.

• One theory for the cause of the decrease in the bee population is because of the 

bacterial toxin, Bacill Thuringiensis (Bt), which was created by Monsanto for 

the GM corn seeds. According to the Health Wyze Report, “Bbacterial toxin 

Bacill Thuringiensis is known to provoke an immune response in humans and 

bees. An immune response in a bee prevents proper memory formation, and 

causes confusion. One of the symptoms of Colony Collapse Disorder is bees' 

decreased navigational ability [1].” The bees are unable to go back to their 

hives and end up dying.

• According to the American Academy of Environmental Medicine (AAEM), 

“Several animal studies indicate serious health risks associated with GM food, 

including infertility, immune problems, accelerated aging, faulty insulin 

regulation, and changes in major organs and the gastrointestinal system [2].”

• According to the Institute for Responsible Technology, “the only published 

human feeding experiment revealed that the genetic material inserted into GM 

soy transfers into bacteria living inside our intestines and continues to function. 

This means that long after we stop eating GM foods, we may still have their 

GM proteins produced continuously inside us [5].”

16 APHIS-2013-

0043-0018 Gregg Langer

• This technology will be very valuable to our growers as a herbicide option of 

choice. It will broaden and increase our control options while limiting impact 

on environment. It will be an essential technology to prevent and control 

resistance in weed control.

17 APHIS-2013-

0043-0019

Reid J. Smeda, Professor 

of Weed Science, 

University of Missouri

• Development of dicamba-tolerant soybean represents a novel solution to the 

postemergence control of glyphosate-resistant weeds. I would urge you to 

not limit a potentially significant management tool (dicamba) because of 

fears that past mistakes will be repeated. The path forward should be an 

integrated approach to weed management in soybean. 

• I believe that adoption of dicamba-tolerant soybean technology will be 

different than adoptive practices of glyphosate-resistant soybean, and the 

potential for selection for dicamba-resistant weeds will be lower than for 

glyphosate. 

Below are my reasons to support the previous statement:

1) In-crop, growers know that weed size is important for using dicamba. I believe 

this same mentality can be transferred to postemergence use of dicamba on 

tolerant soybean.

Page 2-7
Comment # Comment ID Commenter Comment Excerpt

2) I believe that the current mind-set of soybean growers, especially in Missouri, 

is to apply labeled rates of residual herbicides in soybean, and clean up escape 

weeds with a timely postemergence herbicide. This is the pattern that was 

practiced before glyphosate-resistant soybeans were introduced, and I believe 

sets the stage for proper use of the dicamba-tolerant technology.

3) Current options for postemergence control of glyphosate-resistant weeds in 

soybean are limited. We have observed a dramatic increase in the use of PPO 

herbicides (lactofen, fomesafen, etc.). However, prior to the introduction of 

glyphosate-resistant soybean, a number of biotypes of waterhemp were found 

resistant to lactofen and fomesafen. Re-release of Liberty Link® soybean has 

resulted in effective control of glyphosate-resistant weeds in soybean. 

However, growers have few other options and my fear is that glufosinateresistant weeds in soybean will occur. Now is the time to adopt the use of 

dicamba-tolerant soybean to preclude selection for weed resistance to 

glufosinate.

4) Dicamba use will be limited in amount (total applied per cropping year) and to 

specific weed sizes, which should reduce selection pressure for resistance. 

5) I believe increased grower knowledge about Amaranthus species will improve 

decision-making with dicamba-tolerant soybean, which will lower the risk for 

selection of resistant Amaranthus species.

6) In my field trials, we have shown over time that dicamba can provide from 3-7 

days of residual weed control. This can provide some short-term benefit to 

growers, but is not a substitute for adoption of preemergence herbicides. 

Therefore, dicamba is not a stand alone product.

7) Although reduction of production costs remains important, the higher 

commodity price for soybean has resulted in openness of the grower to adopt 

use of residual herbicides to protect soybean yield. Use of residual herbicides 

will be important for protecting the integrity of the dicamba-tolerant crop 

technology.

8) ....herbicide use cannot be reversed or abandoned for the majority of our 

soybean acres. Continued education on proper herbicide use is, in my opinion, 

the only path forward. Dicamba-tolerant soybeans provide crop producers with 

a highly effective tool, and integration of dicamba should be in the context of 

proper use of residual herbicides. 

18 APHIS-2013-

0043-0020

J. Christopher Hall, 

Professor, University of 

Guelp

Emphasize the following points in regards to de-regulation of dicamba-tolerant 

crops; specifically in terms of evolution of resistance to auxinic herbicides (e.g., 

dicamba and others) in weed species:

• ...the risk of evolution of week resistance to herbicides can be 

Page 2-8
Comment # Comment ID Commenter Comment Excerpt

Mithila Jugulam, 

Assistant Professor, 

Kansas State University

significantly mitigated through implementation of diversified weed 

management programs by farmers, that include: use of multiple 

herbicides with overlapping activity on target weeds and/or the inclusion 

of mechanical and/or cultural weed control practices.

• Compared with other herbicides families, the incidence of resistance to 

auxinic herbicides is relatively low...

• Information about fitness cost associated with auxin herbicides has been 

documented in a few species indicating that resistant plants are less fit in 

the absence of herbicide application. This could be a major reason for 

the limited occurrence of auxinic herbicide-resistant weeds. 

Additionally, this could explain why farmers continue to use and derive 

benefits from these products after resistant populations have been 

identified.

• The recessive trait spreads much slower in a population than a dominant 

trait. Since the resistance to auxinic herbicides in some weeds is 

determined by recessive genes..., this may be one of the reasons for low 

occurrence of auxinic herbicide resistant weeds.

• In many cases the use and, thus, selection pressure of these auxinic 

herbicides has exceeded that of other herbicides groups to which 

resistance is more common.

• Definitive mechanisms of resistance to auxinic herbicides have yet to be 

defined....This suggests a relatively low probability for cross resistance 

to other herbicide groups and classes that could occur because of 

common metabolic resistance pathways.

• The low probability in combination with stringent implementation with 

integrated weed management practices should reduce risks of evolution 

of resistance to there herbicides.

Overall, the key is, educating the farmer of the negative consequences of 

continuous use of herbicides with the same mode of action and the positive 

consequences of implementing efficient weed-management practices such as 

herbicide rotations, use of multiple herbicides in mixtures and sequences, 

inclusion of tillage where necessary and other non-chemical-based weed 

management practices, which will help reduce the chances of evolution of 

herbicide-resistant weed populations.

See attached review article:

Mithila, J., J.C. Hall, W.G. Johnson, K.B. Kelley, and D.E. Riechers. 2011. 

Evolution of resistance to auxinic herbicides: Historical perspectives, 

Page 2-9
Comment # Comment ID Commenter Comment Excerpt

mechanisms of resistance, and implications for broadleaf weed management in 

agronomic crops. Weed Sci. 59: 445-457.

19 APHIS-2013-

0043-0020

Fred Yoder, grower, 

Ohio Corn and Wheat 

Growers Association, 

and former president of 

the National Corn 

Growers Association

• Farmers should have the choice to use safe and valuable new agricultural 

technologies to help manage weeds, using multiple modes of action.

• It is important to ensure the USDA regulatory review of new biotech traits 

does not fall further behind those of other major crop producing countries 

such as Brazil or Argentina, who are rapidly gaining a larger share of the 

global market.

• Farmers have many years of experience using products like dicamba, and 

are very capable of preventing off-site movement through proper 

stewardship including application techniques, equipment settings, nozzle 

selection, and consideration of environmental conditions during application, 

such as wind speed.

20 APHIS-2013-

0043-0032

Charles Hall, North 

Carolina Soybean 

Producers Association

• I support the full deregulation of event MON 87708 - dicamba-tolerant 

soybeans- so that soybean farmers will have full access to this technology 

which, combined with other currently available technologies, will expand 

options for weed management practices on the farm. Timely access to a safe, 

sustainable new technology will increase farmer options for cost-effective 

weed management. The beneficiaries will be the downstream users of soybean 

products, including human and livestock nutrition products. As demand 

increases worldwide for human and livestock nutrition, effective weed 

management will be vital to sustaining the soybean yield increases that will be 

demanded of U.S. soybean farmers.

• The dicamba- tolerant soybeans and the same tolerance being developed in 

cotton expands the dicamba weed control window from the current preplant 

burndown use to allow in-crop applications of dicamba herbicide for the 

control of broadleaf weeds pre-emergence and post-emergence. When 

combined with Roundup Ready, it will allow a new mode of action for 

improved weed control and weed resistance management. Use of dicamba at 

planting in this system eliminates having to wait the three weeks required in 

non-dicamba tolerant crops. This translates into a three week gain on weed 

control. Additionally, dicamba provides potential residual benefit, depending 

on soil type and rainfall.

• The dicamba product has a decades-long record of safety and effectiveness, 

and is highly effective at combating the major weed pests of soybeans. North 

Carolina soybean farmers have the knowledge and training to incorporate 

Page 2-10
Comment # Comment ID Commenter Comment Excerpt

dicamba-tolerant soybeans into on-farm stewardship practices.

• I oppose USDA’s proposal to conduct an Environmental Impact Statement 

(EIS), which is not necessary and would only serve to delay farmers’ access 

and ability to use this new tool.

21 APHIS-2013-

0043-0023

Steve Austin • Wishes to join the concerns expressed by the Save Our Crops Coalition in its 

comment to this docket.

• Non-target plant damage associated with herbicide spray drift and 

volatilization is a major concern for specialty crop growers and processors. 

Credible estimates project significant increases in the amount of dicamba that 

will be applied upon the introduction of dicamba tolerant crops. Dicamba, 

because of its potential to drift and volatilize, has proven to be one of 

America’s most dangerous herbicides for non-target plant damage. 

• We do not oppose advances in plant technology, however, we will not accept a 

range of alternatives that includes only wholesale deregulation or wholesale 

prohibition of these crops. We request that USDA expand the scope of its 

inquiry to consider uses of its authority to address a range of issues our 

membership faces. 

• We request that USDA strictly analyze changes to agronomic practices, 

including herbicide use, that will result from deregulation of these crops, and 

consider where USDA and EPA may be able to jointly develop effective 

measures to protect against the threat of non-target plant damage these crops 

pose.

22 APHIS-2013-

0043-0024

Victor Miller • Herbicide use, possible selection for and the spread of weeds resistant to the 

herbicide and drift from applications of dicamba onto dicamba intolerant 

crops and other areas, seems to be the responsibility of EPA not USDA. All 

of these questions are under review at EPA, which is responsible for issues 

related to herbicides and their use.

• This is a safe, widely used herbicide. Over the past 10 years it has been used 

very successfully on over 250 million acres, including corn, wheat, pasture 

and range land, as well as other crop land.

• The equipment, the knowledge, and the desire to use the products in a 

responsible manner by the Agricultural Community already exists!

• Glyphosate tolerant weeds are becoming a problem and we as producers 

need more modes of action to limit this problem. Dicamba is one of those 

additional modes of action and it becomes criminal to deny that tool to us as 

we then have less produce to serve to a hungry world.

23 APHIS-2013- Kenneth Martin, • We are a medium sized food processor and our business was built and 

Page 2-11
Comment # Comment ID Commenter Comment Excerpt

0043-0025 Director Ag Operations, 

Furmano Foods, Inc.

continues on specialty crops who are highly suspectable to Dicamba drift. 

Non-target plant damage associated with herbicide spray drift and 

volatilization is a major concern for specialty crop growers and processors 

like us. Credible estimates project significant increases in the amount of 

dicamba that will be applied upon the introduction of dicamba tolerant 

crops. Dicamba, because of its potential to drift and volatilize, has proven to 

be one of America’s most dangerous herbicides for non-target plant 

damage. Because of these drift issues a large portion of row crop growers 

have discontinued the use of this product.

• I do not oppose advances in plant technology, however, the answer is not 

in accepting a range of alternatives that includes only wholesale 

deregulation or wholesale prohibition of these crops. I think that USDA 

should expand the scope of its inquiry to consider uses of its authority to 

help look for better ways to combat the resistant weed issue from the over 

use of certain chemicals.

• Approving Dicamba tolerant crops seems very short sighted given the 

potential of drift damage that we know has happened in the past. There has 

to be better alternatives to work at this problem, lets find them.

24 APHIS-2013-

0043-0026

Mark Jackson, 

president Iowa Soybean 

Association

• I write to reaffirm our strong support for full deregulation of dicamba-tolerant 

soybeans and cotton. Full deregulation of dicamba-tolerant soybeans will help 

Iowa growers increase yields in an environmentally-friendly manner and is 

consistent with the ISA’s mission. 

• ISA understands USDA APHIS’ reasons for conducting an Environmental 

Impact Statement (EIS) on dicamba-tolerant technologies, and how they 

appear to relate to potential impacts associated with herbicide use and 

resistance. However, matters relating to herbicide use are regulated under the 

authority of the Environmental Protection Agency (EPA).

• growers need access to weed management technologies with proven efficacy 

over a broad spectrum of weeds - like dicamba tolerant soybeans 

(MON87708) and dicamba tolerant cotton (MON88701). As herbicide 

resistance becomes more prevalent, the arsenal of tools at our disposal to 

effectively control and manage resistance is limited. Weed scientists tell us 

that the best way to address herbicide resistance is to implement diversity in 

weed management practices, including the use of multiple herbicide modes of 

action. The dicamba-tolerant system will provide an additional mode of 

action, while expanding the dicamba weed control window, eliminating 

planting restrictions and permitting in-crop applications.

• Access to a broad range of technologies will help us maintain healthy 

yields and ensure a stable supply of quality soybeans to the food and 

Page 2-12
Comment # Comment ID Commenter Comment Excerpt

feed processing industries. USDA’s decision on dicamba-tolerant 

technologies will have broad implications for the entire soybean 

value chain in the U.S. and globally.

• we believe that dicamba-tolerant technologies will enable growers to 

continue to be good stewards of the land. Compared to some weed 

control programs, this system may result in fewer herbicide 

applications. Glyphosate-tolerant crops enabled widespread adoption 

of conservation tillage practices. This has been a tremendous advance 

in sustainable farming practices thanks to the preservation of the 

topsoil, reduced fuel emissions and better water conservation. The 

use of dicamba as part of the Roundup Ready Xtend Crop system will 

help us preserve the value of existing pre- and post-emergent 

herbicides, which continue to bring significant value.

• With regard to concerns about dicamba off-site movement, growers 

have experience with various cropping systems and are experienced 

and capable of applying dicamba in a manner that will minimize drift. 

With the use of an appropriate formulation, following label 

directions, training and communicating with neighbors, we are 

confident these concerns will be addressed. Newer dicamba 

formulations, along with best management practices make it possible 

for all types of growers to co-exist and prosper.

25 APHIS-2013-

0043-0027 Wayne Keeling, 

Professor, Texas A&M 

University

Darrin Dodds, Associate 

Extension Professor, 

Mississippi State 

University

Dr. Stanley Culpepper, 

Professor, University of 

Georgia

• We believe that the ability to selectively use dicamba in cotton will 

provide a much needed tool for management of broadleaf weeds and in 

particular Amaranthus spp., currently the most troublesome weed species 

in cotton. In particular additional postemergence options in cotton are 

needed for control of broadleaf weeds and dicamba will be such an option. 

However with the launch of any new herbicide in a cropping system we 

must understand how to use it in a sustainable way so to minimize the risk 

of resistance.

• It is widely recognized that the way to mitigate resistance to herbicides is

to use herbicides in diversified weed management systems. The WSSA 

has define this as using more than one herbicide mode of action that is 

effective on the targeted specie(s) in mixtures, sequences or in rotation 

and/or using herbicides in combination mechanical and/or cultural 

practices. Weed management is ultimately the responsibility of farmers 

and requires that the weed science community, including industry, 

academics, crop commodity groups and others reach out to farmers and 

communicate information on practices to best manage resistance as well as 

the benefits of implementing these practices. By so doing resistance to our 

Page 2-13
Comment # Comment ID Commenter Comment Excerpt

existing herbicide resources, as well as new options such as dicamba, will 

be minimized.

• We believe that farmers will integrate dicamba into diversified 

management programs because they will see better overall weed control. 

• The risk of resistance for an herbicide is a function of the probability for 

resistance based upon genetic and biological factors and the probability 

that farmers will implement recommended best management practices. In 

the case of dicamba’s use in dicamba and glufosinate tolerant cotton we 

believe that the risk of evolution of resistance is relatively low. If one 

balances risk of resistance with benefits of use, the benefits greatly 

outweigh the risk in this case. 

26 APHIS-2013-

0043-0028

Dale Moore Executive 

Director

Public Policy, American 

Farm Bureau Federation

• Farm Bureau respectfully asks APHIS to abide by the Ninth Circuit’s 

interpretation of its legal obligations under the PPA and NEPA and 

reconsider its decision to prepare EISs for the herbicide tolerant crops 

identified in the Notices. Farm Bureau asks APHIS to act expeditiously 

to finalize the deregulation process for these crops in keeping with the 

Ninth Circuit’s recent RRA decision and the APHIS regulations 

governing deregulation petitions.

27 APHIS-2013-

0043-0029

Dennis M. Dixon, 

Hartung Brothers, 

Incorporated

• Non-target plant damage associated with herbicide spray drift and 

volatilization is a major concern for specialty crop growers and processors. 

Credible estimates project significant increases in the amount of dicamba 

that will be applied upon the introduction of dicamba tolerant crops. 

Dicamba, because of its potential to drift and volatilize, has proven to be 

one of America’s most dangerous herbicides for non-target plant damage. 

• We do not oppose advances in plant technology, however, we will not 

accept a range of alternatives that includes only wholesale deregulation or 

wholesale prohibition of these crops. We request that USDA expand the 

scope of its inquiry to consider uses of its authority to address a range of 

issues our membership faces. 

• We request that USDA strictly analyze changes to agronomic practices, 

including herbicide use, that will result from deregulation of these crops, 

and consider where USDA and EPA may be able to jointly develop 

effective measures to protect against the threat of non-target plant damage 

these crops pose.

28 APHIS-2013-

0043-0030

Kimberly Iott, Iott 

Ranch & Orchard

• Iott Ranch & Orchard, Inc wishes to join the concerns expressed by the 

Save Our Crops Coalition in its comment to this docket.

• Non-target plant damage associated with herbicide spray drift and 

volatilization is a major concern for specialty crop growers and processors. 

Page 2-14
Comment # Comment ID Commenter Comment Excerpt

Credible estimates project significant increases in the amount of dicamba 

that will be applied upon the introduction of dicamba tolerant crops. 

Dicamba, because of its potential to drift and volatilize, has proven to be 

one of America’s most dangerous herbicides for non-target plant damage. 

• We do not oppose advances in plant technology, however, we will not 

accept a range of alternatives that includes only wholesale deregulation or 

wholesale prohibition of these crops. We request that USDA expand the 

scope of its inquiry to consider uses of its authority to address a range of 

issues our membership faces. 

• We request that USDA strictly analyze changes to agronomic practices, 

including herbicide use, that will result from deregulation of these crops, 

and consider where USDA and EPA may be able to jointly develop 

effective measures to protect against the threat of non-target plant damage 

these crops pose.

29 APHIS-2013-

0043-0031

Kevin Wilson • I'm a tomato grower from Indiana,and also a corn and soybean producer 

as well. What I am asking for is a reasonable ruling that will let me 

protect my crop as well as use these products as well. The agreement 

that was worked between DOW agriscience and the SOCC accomplishes 

this. Monsanto has chosen to ignore the SOCC's request to work out an 

agreement similar to DOW. The current label that Monsanto is trying to 

get approval does not address several issues that I feel have potential 

events that can cause losses of my crops.

30 APHIS-2013-

0043-0032

Thomas Parker, H & T 

Parker Farms

• H & T Parker Farms wishes to join the concerns expressed by the Save Our 

Crops Coalition in its comment to this docket.

• Non-target plant damage associated with herbicide spray drift and 

volatilization is a major concern for specialty crop growers and processors. 

Credible estimates project significant increases in the amount of dicamba 

that will be applied upon the introduction of dicamba tolerant crops. 

Dicamba, because of its potential to drift and volatilize, has proven to be 

one of America’s most dangerous herbicides for non-target plant damage. 

• We do not oppose advances in plant technology, however, we will not 

accept a range of alternatives that includes only wholesale deregulation or 

wholesale prohibition of these crops. We request that USDA expand the 

scope of its inquiry to consider uses of its authority to address a range of 

issues our membership faces. 

• We request that USDA strictly analyze changes to agronomic practices, 

including herbicide use, that will result from deregulation of these crops, 

and consider where USDA and EPA may be able to jointly develop 

effective measures to protect against the threat of non-target plant 

Page 2-15
Comment # Comment ID Commenter Comment Excerpt

damage these crops pose.

31 APHIS-2013-

0043-0033

A. Stanley Culpepper -

University of Georgia, 

Weed Scientist, and 

grower

• Cotton weed management programs in Georgia have undergone, and are 

continuing to undergo, significant changes. Currently recommended 

programs are complex, costly, and challenging to implement in a timely 

fashion. Growers are desperately in need of new technologies to improve 

control of Palmer amaranth, reduce the potential for further herbicide 

resistance development to currently used tools, and to reduce the economic 

burden that Palmer amaranth is placing on the agricultural industry. 

• We admire and respect the desire of USDA and EPA to be certain that 

no agriculture technology will negatively impact the consumer, the user, 

or the environment in which we and our children live. Our request is 

simple, if deemed safe please assist in the movement of all new 

technologies to our growers as rapidly as feasible.

• Herbicide-resistance has significantly changed agriculture forever in the 

Southeast; especially for cotton growers. To combat this pest, growers 

have relied heavily on herbicides, tillage, and hand weeding. Herbicide 

use in cotton has increased sharply with 2.5-times more herbicide active 

ingredient applied to cotton following the confirmation of glyphosate 

resistance in Palmer amaranth as compared to before documented 

resistance. Although grower herbicide input costs have more than 

doubled following the evolution and spread of glyphosate resistance, 

Palmer amaranth control is still not adequate. Thus, 92% of Georgia 

cotton growers hand-weed 52% of the crop with an average cost of $23 

per hand-weeded acre, which is an increase of at least 475% as 

compared to hand weeding costs prior to resistance. In addition to 

increased herbicide use and hand weeding, growers in Georgia have 

indicated that they are using mechanical, in-crop cultivation (44% of 

acres), tillage for the incorporation of preplant herbicides (20% of the 

acres), and deep turning (19% of the acres every three years) to aid in 

Palmer amaranth control. Current weed management systems are 

extremely diverse, complex, less environmentally friendly, and costly 

when compared to those systems employed only a decade ago. Growers 

are in desperate need of new technologies that will aid in the 

management of glyphosate-resistant Palmer amaranth, and other 

problematic weeds, for long term sustainability.

31 APHIS-2013-

0043-0033

A. Stanley Culpepper -

University of Georgia, 

Weed Scientist, and 

grower

Benefits of 2,4-D or Dicamba Technologies For the Georgia Cotton Grower: 

1. Improved Weed Control: Neither dicamba nor 2,4-D are consistently 

effective in controlling Palmer amaranth larger than 4 inches when applied 

alone (Culpepper et al. 2010; Culpepper et al. 2011; Merchant et al. 2011); 

Page 2-16
Comment # Comment ID Commenter Comment Excerpt

however, weed management systems including these herbicides are more 

consistently effective than current standards (Braxton et al. 2010; Beckie 

2011; Merchant et al. 2013; Richburg et al. 2012; Shaw and Arnold 2012). 

Weed management programs including 2,4-D or dicamba would improve a 

grower’s ability to manage this problematic weed in the following ways: 1) 

improved consistency in weed control especially on dryland production 

acres where residual herbicides often are not activated with rainfall at 

planting time, 2) more flexibility with herbicide application timings because 

glufosinate plus dicamba or 2,4-D will consistently control Palmer 

amaranth up to 6 inches in height (at least 2 inches larger than todays 

standards), 3) less herbicide carryover to subsequent crops because growers 

would be less dependent on long lasting residual herbicides, and 4) less 

yield loss from Palmer amaranth crop competition for light, nutrients, and 

water (Coetzer et al. 2002; Culpepper et al. 2010; Merchant et. al 2013; 

MacRae et al. 2013). 

2. Prevention of Additional Herbicide Resistance Development: USDA has 

voiced concerns that growers may adopt 2,4-D or dicamba technologies and 

rely too heavily on these herbicides thereby developing an even greater 

weed resistance scenario. Science has clearly shown that there is risk of 

resistance development to all herbicides; dicamba and 2,4-D are no 

exception. In fact, weeds have developed resistance to nearly all forms of 

weed management including herbicides, tillage, mowing and even hand 

weeding. Our data and surveys contrast the assumption that rapid 

development of resistance to 2,4-D or dicamba would occur in Georgia 

cotton. First, our data notes that since these auxin herbicides control only 

very small Palmer amaranth then they must be applied in tank mixtures 

with other herbicides such as glufosinate. Second, even mixtures of 

glufosinate plus 2,4-D or dicamba will only control Palmer amaranth less 

than six inches in height and since Palmer amaranth can grow as much as 

two inches per day selective residual herbicides must be used throughout 

the season. Simply put, data throughout the belt supports the fact that overuse and/or over-dependence of 2,4-D or dicamba in cotton would equal 

poor weed control and eventual crop failure which is a practice no grower 

would follow. Dicamba and 2,4-D would be an additional tool to include in 

the weed management program.

The greatest risk for developing herbicide resistance is actually occurring at 

this moment with the PPO herbicides and glufosinate. These products are 

being over used as growers have no other effective herbicidal options. New 

technologies such as dicamba or 2,4-D could be used to delay resistance 

Page 2-17
Comment # Comment ID Commenter Comment Excerpt

development to the PPO herbicides and glufosinate and, in turn, systems 

could be developed using the PPO herbicides, glufosinate, 2,4-D, and 

dicamba extending the life of each of these chemistries. 

It is also critical to stress that, at least in Georgia, no weed management 

program relies exclusively on herbicides. The University of Georgia Weed 

Science Extension Team stresses to growers at more than 50 meetings each 

year that herbicides are only one part of the weed management program. 

Sustainability is only possible with the adoption and implementation of 

diverse management programs and Georgia growers have accepted this 

message as fact (Sosnoskie and Culpepper 2013). Growers are using 

programs that are complex and diverse integrating herbicides, hand 

weeding, and tillage or cover crops. Neither dicamba nor 2,4-D would 

change this approach but would simply be an additional tool to add into 

these management systems.

3. Reduction in Herbicide Use: Glyphosate-resistant Palmer amaranth has 

increased herbicide pounds of active ingredient applied in Georgia cotton 

by a factor of 2.5 when compared to herbicide use prior to resistance 

(Sonoskie and Culpepper 2013). Programs developed by the University of 

Georgia for 2,4-D or dicamba technologies suggest the pounds of herbicide 

active ingredient may be able to be reduced by at least 30% while actually 

providing better weed control; similar results are also noted in other areas 

across the cotton belt (Edwards et al. 2013; Merchant et al. 2013; Smith and 

Hagood 2013; Steckel et al. 2013). 

4. Reduction in Tillage, Wind Erosion, and Soil Erosion: As the spread of 

glyphosate-resistant Palmer amaranth occurred, the adoption of tillage 

including deep turning of the land with moldboard plows has become 

common (Sosnoskie and Culpepper 2013). The return of conventional 

tillage has led to increased wind and water erosion. Neither 2,4-D nor 

dicamba technologies would eliminate tillage, but they would greatly 

reduce the need for deep tillage allowing many growers to return to more 

reduced tillage production systems. This opportunity to return to reduced 

tillage systems would be in response to a more consistently effective 

management program.

31 APHIS-2013-

0043-0033

A. Stanley Culpepper -

University of Georgia, 

Weed Scientist, and 

grower

Concerns With 2,4-D- or Dicamba-Resistant Technologies: 

1. Off-Target Movement: Off target movement of 2,4-D and dicamba pose the 

greatest limitation to the adoption of either auxin technology. Although it is 

currently unknown what restrictions will be in place to minimize off-target 

movement by herbicide labels, an enormous amount of research by the registrants 

Page 2-18
Comment # Comment ID Commenter Comment Excerpt

and other scientists across the world is being conducted to develop methods to 

minimize the potential for off-target movement. These efforts include 1) 

improving herbicide formulations, thereby reducing volatility and/or drift, 2) 

improving application equipment techniques and application methods, thereby 

reducing drift, and 3) developing educational materials to assist growers in 

reducing off target movement when making pesticide applications (Bagley 2013, 

Huff et al. 2013; Kendig et al. 2013; Magidow et al. 2013; Newsom et al. 2013; 

Reynolds et al. 2013, Sandbrink et al. 2013). Benefits from these efforts will be 

monumental in minimizing off-target movement of ALL pesticides, not just 2,4-

D and dicamba, and will greatly improve the ability of a grower to apply 

pesticides that stay in the targeted area. In Georgia, the University of Georgia and 

the Georgia Department of Agriculture are currently developing additional 

methods to further minimize off-target movement of auxin herbicides and other 

pesticides. Also, a cooperative effort between The University of Georgia, Georgia 

Department of Ag, Agronomic Industry leaders, and Horticultural Industry 

leaders is underway to further define methods to minimize off-target movement.

32 APHIS-2013-

0043-0034

Richard Minor, Past 

President and current 

Board Member of The 

Georgia Fruit and 

Vegetable Growers 

Association.

• I support full and timely deregulation of dicamba- and glufosinate- tolerant 

cotton and dicamba tolerant soybeans, an essential weed management tool 

that is badly needed by growers. Over the past several years, the pressure 

from glyphosate resistant weeds has become stronger and harder to manage, 

despite diligent stewardship. Our growers need multiple-mode-of-action 

options at their disposal to manage and prevent weed resistance. Farmers in 

this part of the country have no choice but to manage multiple chemistries 

to fight and control weeds. The dicamba tolerant traits will provide farmers 

with a cotton and soybean product that have increased yield opportunity and 

tolerance to multiple herbicides with different modes of action for weed 

control making dicamba tolerant cotton and soybeans an important weed 

management tool.

• I believe Monsanto has convinced a majority of these growers that proper 

training and support will be available to combat any problems which might 

have concerned our growers concerning off target applications. In addition, 

Monsanto has demonstrated new spray technology which has further 

convinced our specialty crop growers that we will be able to adapt these 

new technologies.

We recognize the complexity that can exist from off-site movement of 

certain herbicides and impact on vegetable crops. We would point out, 

however, that through proper application requirements and stewardship, 

much of the off-site movement and, thus, potential damage may be 

managed and allow fruit and vegetable crops to be grown in proximity to 

Page 2-19
Comment # Comment ID Commenter Comment Excerpt

traditional row crops. This crop diversity is well know to Georgia growers 

and on behalf of my members, wanted to express our organization’s view 

that dicamba applications can and have successfully been made, provided 

care is taken in the type of equipment that is used, applications are not made 

in strong winds toward a sensitive crop and tank clean out is properly 

addressed. 

• Dicamba has been a safe and reliable resource in modern agriculture, used 

by growers in over 25 countries including the USA and Canada. In the 

U.S., dicamba has been used on more than 237 million acres over the past 

10 years. Growers have experience and a long track record of using 

dicamba according to label specifications.

• Dicamba has the potential to protect and may also increase the current acres 

under conservation tillage. Once approved, dicamba tolerance will allow 

growers to use dicamba in burn down without plant-back restrictions while 

providing effective control of hard to control and glyphosate resistant 

weeds including pigweed and marestail. More complete burn down has the 

ability to further enhance conservation tillage. 

• This system may lead to fewer herbicide applications, which may result is 

better soil and water conservation and a reduction in greenhouse gas 

emissions because of fewer trips across the field. Maintaining reduced 

tillage practices will enable our growers to preserve the value of their land.

• In addition to helping growers maintain productivity thanks to improved 

weed management, dicamba tolerant traits will offer efficiencies and 

convenience to growers and improve their quality of life. 

33 APHIS-2013-

0043-0035

Mike Schulte • As a vegetable farmer, I am quite concerned about the drift possibility of 

dicamba. Please reconsider the regulations on these types of chemicals 

as they could well cause hundreds of thousands of dollars of damage to a 

vegetable crop.

34 APHIS-2013-

0043-0036

Scott 

Bretthauer, Extension 

Specialist in Pesticide 

Application Technology, 

University of Illinois

• I have conducted research investigating the use of drift reduction 

technologies for making applications of glyphosate and dicamba. These 

technologies have included drift reduction nozzles, drift reduction 

adjuvants, and combinations of the two. The results of this research, and 

research I’ve seen conducted by colleagues, indicates that applications 

of dicamba can be made both effectively and safely.

• Applications of dicamba can be made safely by understanding two key 

components of drift reduction: droplet size and weather.

• I believe the major drift risk for dicamba applications is particle drift, 

not vapor drift. This is positive because it means that application 

technology and understanding weather impacts can be used to reduce the 

Page 2-20
Comment # Comment ID Commenter Comment Excerpt

risk of drift.... research on the new formulation of dicamba, which 

shows volatility is virtually a non-issue...many off-target incidents 

blamed on volatility and vapor drift were in fact caused by particle drift 

of very small spray droplets that moved off target during an 

inversion....I have seen many reports from insurance companies, and in 

many cases the cause of drift was because applications were made 

during an inversion. Symptoms can be similar to vapor drift because the 

exposure is very minimal, damage will not show up for sometime after 

the application, and the pattern does not look like normal particle drift.

• The label for a Monsanto registered pre-mix of glyphosate and dicamba has 

specific requirements that extend beyond current requirements for dicamba 

applications and will help ensure the risk of particle drift is minimized. 

Proper selection of nozzles and adjuvants has shown that the driftable 

fraction of the spray volume can be reduced to less than 1 percent in many 

cases, and one combination of nozzle and adjuvant completely eliminated 

all droplets of the size considered to be at risk of drift.

• I believe that applicators can safely and effectively apply dicamba 

through the use of a combination of drift reduction technologies, 

including nozzles and adjuvants, operating those correctly through the 

use of other technologies such as pulse width modulation and auto boom 

height controllers, and making applications in suitable weather 

conditions with appropriate downwind buffers zones.

• it is important to consider successful applications are both possible and 

being made today. U.S. farmers need access to new technologies to help 

control weeds and provide options in their operations. Spray applications 

can and will be managed to maximize both efficacy and safety.

35 APHIS-2013-

0043-0037

Jerry Bambauer, Ohio 

Soybean Association

• OSA urges USDA to reconsider the need for the EIS since USDA’s basis 

for conducting the EIS all relate to herbicide uses. The dicamba uses in 

question are currently being reviewed by the EPA, and as such EPA will 

review and mandate the conditions in which it may be used. Conducting a 

time-consuming analysis already within the responsibilities of other federal 

agencies will cause a significant delay in bringing needed technologies to 

growers.

• Soybean farmers need new technologies such as dicamba-tolerant 

soybeans to increase yields, manage weed resistance and keep their 

farming operations profitable.

• Soybean farmers need new technologies such as dicamba-tolerant soybeans 

to increase yields, manage weed resistance and keep their farming 

operations profitable. In light of the recent ruling by the Ninth Circuit Court 

Page 2-21
Comment # Comment ID Commenter Comment Excerpt

of Appeals on the Roundup Ready alfalfa case -- which confirmed that 

issues relating to the use of herbicides are the responsibility of the 

Environmental Protection Agency (EPA), not USDA – OSA urges USDA 

to reconsider the need for the EIS since USDA’s basis for conducting the 

EIS all relate to herbicide uses. The dicamba uses in question are currently 

being reviewed by the EPA, and as such EPA will review and mandate the 

conditions in which it may be used. Conducting a time-consuming analysis 

already within the responsibilities of other federal agencies will cause a 

significant delay in bringing needed technologies to growers.

• U.S. growers should have the choice to use safe and valuable new agricultural 

technologies to increase yields and keep their farms profitable. Farmers today 

need multiple mode-of-action weed management tools. Dicamba tolerance 

would be a valuable addition to the existing soybean weed control options to 

maximize yield potential. Dicamba has been used in crops for many decades 

in the U.S. and continues to be effective on major broad leaf weeds. Farmers 

have proven they are able to use different application techniques and 

equipment for different types of pesticides to ensure proper performance of 

the product as well as on-target application. OSA understands that newer 

dicamba formulations have been developed to substantially reduce volatility 

compared to first-generation dicamba products. The petitioner has also 

addressed the potential for off-site movement by prohibiting aerial 

applications and implementing specific environmental and equipment 

application requirements on the dicamba label, including a wind-directional 

buffer when sensitive areas are present, and use of low volatility dicamba 

formulations.

• The U.S. soybean processing and feed industries, along with the growing 

U.S. soybean export markets, are very healthy segments of our economy. 

The availability of these new effective soybean production tools is vital to 

maintaining that health. Weed resistance pressures underscore the need for 

timely regulatory approval of multiple mode-of-action technologies that can 

help manage resistant weeds and keep U.S. agriculture productive, 

sustainable and globally competitive. It is important that USDA follow 

through on its commitment to U.S. farmers by expediting the science-based 

regulatory review process and put a stop analyses that are duplicative and 

outside the scope of its authority. 

36 APHIS-2013-

0043-0038

Bill Wykes, Chair, 

Illinois Soybean 

Association

• ISA requests USDA to not conduct an EIS on dicamba tolerant soybean and 

cotton and move quickly to approve these new weed fighting tools so our 

farmers may have access to them and incorporate them as they see a fit in 

Page 2-22
Comment # Comment ID Commenter Comment Excerpt

their operations and remain able to control weeds for the future.

• The proposed EIS is seen as an inherent conflict. Given that the proposed 

subject of the EIS is to assess impacts on weed resistance and off-site 

movement of dicamba which can be attributed to the herbicide application, 

the subject of the EIS would appear to fall under the EPA jurisdiction and 

not that of USDA. 

• We urge the USDA to move quickly to approve new weed management 

tools, such as dicamba tolerant soybeans and dicamba tolerant cotton, 

referred to as MON87708 and MON88701, respectively. When both the 

trait and chemistry are used together, farmers will be able to realize several 

benefits from utilizing the proposed dicamba weed management systems. 

These benefits include: 

– Effective and sustainable management of glyphosate-resistant weed species 

including Palmer amaranth, waterhemp, giant ragweed, and marestail

– Provides an additional mode of action and reduces the dependence on ALS 

and PPO herbicides helping to preserve these herbicide tools

– Improved and more consistent control of hard-to-control broadleaf weed 

species

– Crop safety to dicamba and glyphosate herbicides to maximize yield 

potential

– Application flexibility in the event of challenging weather conditions 

especially in the spring

– Proactive program for weed resistance management

– Preservation of conservation tillage benefits

• U.S. farmers are capable and experienced at making herbicide 

applications and effectively managing off-site movement. Just as with 

other herbicides, off-site movement of dicamba can be prevented 

through proper stewardship including application techniques, equipment 

settings, nozzle selection, and consideration of environmental conditions 

during application. Equipment and hand held applications facilitate 

access to weather data, field plot maps and other on board information. 

The technology and capability exists and is at work on the farm fields 

across America today. Additionally, newer dicamba formulations have 

been developed to substantially reduce volatility compared to firstgeneration dicamba products to which much of the folklore is attributed.

37 APHIS-2013-

0043-0039

Andrew LaVigne -

American Seed Trade 

Association

The Notices of Intent published on May 16 identify two issues that led APHIS to 

conclude that EISs were required by NEPA – the development of herbicide-resistant 

weeds (i.e., weed resistance) and increased herbicide use. Both of these issues relate 

Page 2-23
Comment # Comment ID Commenter Comment Excerpt

solely to the herbicides, such as 2,4-D and Dicamba, that would be available for use 

in conjunction with the crops modified to tolerate their application. As such, these 

issues are subject to the exclusive jurisdiction of the U.S. Environmental Protection 

Agency (“EPA”) under the Federal Insecticide, Fungicide, and Rodenticide Act 

(“FIFRA”) and are decidedly not subject to APHIS’s jurisdiction under the Plant 

Protection Act (“PPA”).

38 APHIS-2013-

0043-0040

Steve Verett, Executive 

Vice President, Plains 

Cotton Growers, Inc.

• Urge APHIS to make a recommendation to fully deregulate dicamba-tolerant 

technologies for cotton and soybeans.

• An EIS on dicamba and glufosinate-tolerant cotton is not warranted from a 

legal standpoint.

• The competitiveness of the U.S. cotton industry depends on the ability of 

growers to access new, cost-effective and sustainable technologies to manage 

production pressures, such as weed control. Weeds reduce cotton yields by an 

average of 30 percent. Herbicide resistant weeds are becoming a persistent 

problem that could affect the productivity of cotton production across the 

cotton belt. Texas growers currently experience fewer issues with resistant 

weeds, but they recognize the need to proactively manage weeds with multiple 

modes-of-action to prevent or delay future resistance issues. The dicamba and 

glufosinate-tolerant trait will be stacked with the Genuity® Roundup Ready 

Flex providing farmers with a cotton product that has increased yield 

opportunity and tolerance to three herbicides with three different modes-ofaction for weed control, making dicamba and glufosinate-tolerant cotton an 

important weed management tool. The impact of dicamba and glufosinatetolerant cotton is that it will provide growers with two additional herbicide 

modes-of-action for the control of broadleaf weeds in cotton, including hardto-control and herbicide-resistant broadleaf weeds. Weed resistance pressures 

underscore the need for timely regulatory approval of multiple mode of-action 

technologies that can help manage resistant weeds.

39

APHIS-2013-

0043-0041

Josh Carey, Carey Farms The widespread use of the dicamba chemistry will endanger many non-resistant 

crops through the volatility of the chemical. Specialty crop growers like myself 

will have significant crop damage and loss due the use of this chemical.

40 APHIS-2013-

0043-0042

Michael Forche, M 

Forche Farms Inc.

• Michael A. Forche wishes to join the concerns expressed by the Save Our 

Crops Coalition in its comment to this docket.

• Non-target plant damage associated with herbicide spray drift and 

volatilization is a major concern for specialty crop growers and processors. 

Credible estimates project significant increases in the amount of dicamba that 

will be applied upon the introduction of dicamba tolerant crops. Dicamba, 

because of its potential to drift and volatilize, has proven to be one of 

America’s most dangerous herbicides for non-target plant damage. 

Page 2-24
Comment # Comment ID Commenter Comment Excerpt

• We do not oppose advances in plant technology, however, we will not accept a 

range of alternatives that includes only wholesale deregulation or wholesale 

prohibition of these crops. We request that USDA expand the scope of its 

inquiry to consider uses of its authority to address a range of issues our 

membership faces. 

• We request that USDA strictly analyze changes to agronomic practices, 

including herbicide use, that will result from deregulation of these crops, 

and consider where USDA and EPA may be able to jointly develop 

effective measures to protect against the threat of non-target plant damage 

these crops pose.

41 APHIS-2013-

0043-0043

Robert Wolf, Wolf 

Consulting & Research 

LLC, Retired Professor 

Emeritus and Extension 

Specialist in Application 

Technology in the 

Biological and 

Agricultural Engineering 

Department, Kansas 

State University

• Particle drift is controllable through equipment selection and conditions of use, 

such as formulation, spray tips and other technologies, wind speed and direction 

at application, sprayer speed and boom height. In some of my most recent 

research, selecting the proper nozzle type alone can be shown to reduce spray 

drift from 13.5% down to 0.5% and in some cases the inclusion of drift control 

additives can reduce that drift amount even more. 

• Newer dicamba formulations have been developed to substantially 

reduce volatility compared to first-generation dicamba products. The 

research is supporting this and through further research, education and 

training this point will be stressed.

• Tank contamination will be of concern when switching between tolerant and 

non-tolerant crops. This will be addressed through proper tank clean out 

procedures that adequately clean out herbicide residues from the lining of the 

tank, boom and inner workings of the sprayer, including all hoses and filters,

crevices and drain lines. Newer spray systems are being engineered to improve 

cleanout. 

• Monsanto has addressed one concern of the potential for offsite movement by 

prohibiting aerial applications and other concerns by implementing specific 

environmental and equipment application requirements on the draft dicamba 

label, including a wind-directional buffer when sensitive areas are present, and 

the use of low volatility dicamba formulations.

• It is my opinion that US farmers and commercial applicators are capable and 

experienced at preventing off-site movement. Like any other herbicides, off-site 

movement of dicamba can be prevented through proper stewardship including 

application techniques, equipment settings, nozzle selection, and consideration 

of environmental conditions during application.

• Equipment and hand held tools such as smart phone apps that support 

applications to facilitate access to weather data, field plot maps, nozzle details, 

and other on board information now exists. This technology and capability is at 

Page 2-25
Comment # Comment ID Commenter Comment Excerpt

work on the farm fields across America today.

• When recommended label practices are followed, growers of various crops can 

co-exist and prosper. I believe that in combination with approved best 

management practices, including the use of the proper nozzle type(s), 

applications using dicamba will have potential to reduce the amount of offtarget drift.

42 APHIS-2013-

0043-0044

Bruce 

Rohwer, President, Iowa 

Corn Growers 

Association

• New technologies are needed to ensure agricultural productivity meets growing 

demand for food. We believe US farmers should have the choice to use safe 

and valuable agricultural technologies, such as herbicide tolerant soybeans, to 

help manage weeds. With the growing glyphosate resistance threat to soil 

conservation and the limited postemergence options for control of Palmer 

pigweed, waterhemp, and marestail, farmers need new technology solutions. 

Without effective weed management practices, herbicide resistance can 

decrease farm productivity and increase the complexity of crop production. 

Tillage may increase in order to control weeds, which increases the risk of 

erosion.

• Farmers need new tools to manage weed resistance in order to preserve the 

value of their land. Dicamba tolerant technology is a sustainable solution that 

gives farmers additional choice and helps them to be good stewards of the land. 

Compared to some weed control programs, this system can equate to fewer 

herbicide applications, resulting in fewer trips across the field, reduced 

greenhouse gas emissions, reduced soil erosion, reduced soil compaction and 

enhanced water conservation.

• The deregulation of MON 87708 helps sustain the long-term agronomic, 

environmental, and economic benefits of glyphosate as a weed control tool in 

soybeans. Growers should be able to access new agricultural technologies to 

keep agricultural productivity on pace to meet demands for food. In order for 

farmers to remain competitive, it is critical that the USDA regulatory review of 

new biotech traits does not fall further behind those of other major crop 

producing countries such as Brazil or Argentina.

43 APHIS-2013-

0043-0045

Steve Smith, Save Our 

Crops Coalition

• Requests APHIS consider a range of possible alternatives beyond out-right 

denial or approval of these crops, and requests that APHIS specifically address 

the problem of non-target drift damage caused by the increased use of dicamba 

on dicamba tolerant crops. 

• SOCC requests that APHIS expand the scope of its EIS inquiry to address nontarget drift damage impacts cause by the use of dicamba on dicamba tolerant 

crops, especially in sensitive areas. Dicamba tolerant crops heighten the drift 

and volatilization concerns associated with dicamba. The introduction of 

Page 2-26
Comment # Comment ID Commenter Comment Excerpt

dicamba tolerant crops is anticipated to increase the use of dicamba in cotton‐

producing regions. These regions also produce substantial acreages of 

broadleaf crops that are sensitive to dicamba. Thus, any drift or volatilization 

from dicamba could be expected to have significant impacts on non-target 

crops grown in proximity.

• If APHIS considers spray drift and volatilization impacts but determines on 

balance that the environmental effect is positive, and therefore does not 

anticipate adverse effects within its conclusion, this level of consideration is 

insufficient. If spray drift and volatility impacts are significant effects, the 

regulations require APHIS consider and explain them within an EIS. Upon 

consideration of the “context” factor, APHIS would find the proposed action to 

be “significant” in multiple contexts. Upon consideration of the “intensity” 

factor, APHIS would find the proposed action to have “severe” impacts. Thus, 

upon consideration of the “context” and “intensity” factors, APHIS would find 

the proposed action raises substantial questions about whether it may have a 

significant effect on the environment. Therefore, APHIS should prepare an EIS 

addressing dicamba spray drift and volatilization impacts associated with 

Dicamba Tolerant Soybeans and Cotton.

• The use of dicamba has declined precipitously from its peak 1994 level. 

Monsanto’s petitions do not indicate the rate of change in dicamba use from 

current use levels. This omission was particularly glaring given the intensity of 

the rate of change. The latest figures place the amount of dicamba applied at 

about 2.7 million pounds annually. Monsanto’s projected use pattern would 

represent an approximately 925% increase in pounds applied over current 

levels, an almost 250% increase in the total acreage treated, and a 5660% 

increase in soybean acreage treated. Such an increase would represent a 

dramatic shift in the utilization of an herbicide both in terms of total pounds 

applied and areas in which the herbicide would be used. Even the increase in 

the use of glyphosate upon the introduction glyphosate tolerant crops, an 

increase of almost 600% in pounds applied, would be eclipsed by this shift in 

use.

• Dicamba has substantial harmful effects on unmodified broadleaf crops even at 

very low applications rates, and because dicamba tolerant crops will be grown 

in such close proximity to unmodified broadleaf crops like soybeans and 

tomatoes, the potential for non‐target plant damage caused by drift and 

volatilization is great.

• We suggest that APHIS and EPA work together to find solutions that protect 

against non- target drift damage caused by the increased use of dicamba on 

dicamba tolerant crops. Because SOCC cannot be certain that EPA will 

Page 2-27
Comment # Comment ID Commenter Comment Excerpt

adequately evaluate the potential for environmental harms, at this time, SOCC 

requests that APHIS withhold a grant of the petition until such time as effective 

measures are in place to protect against non-target plant damage, whether 

imposed by it, or in conjunction with other agencies.

44 APHIS-2013-

0043-0046

Wenonah Hauter – Food 

& Water Watch

Food & Water Watch urges the USDA to consider the following risks in its 

upcoming Environmental Impact Statement for dicamba-tolerant soybeans and 

cotton:

• Dicamba‐resistant cotton and soybeans will lead to an increase in dicamba 

use, which will spur the evolution of dicamba resistant weeds and the 

abandonment of conservation tillage practices;

• Higher volumes of dicamba will lead to pollution of surface water, which 

will impact non‐target plants and animals, including endangered species; 

• The volatility of dicamba will result in more occurrences of pesticide drift 

into neighboring fields, affecting plant health and the livelihoods of nearby 

farmers;

• Dicamba‐tolerant crops will cost farmers more through higher seed prices, 

the loss of export markets due to contamination of non‐genetically 

engineered (GE) or organic seed and through the presence of dicamba--‐

resistant weeds; and

• Dicamba is dangerous to human health and its continued use will endanger 

agricultural workers and the general public.

The USDA’s Environmental Impact Statement must include, at a minimum:

• An analysis on how dicamba-tolerant soybeans and cotton will facilitate increased 

use of dicamba, leading to the evolution of dicamba‐resistant weeds and the 

abandonment of conservation tillage practices;

• Data on the potential carcinogenicity and long‐term risks to human health that 

dicamba would pose at new application levels and the cumulative effects of its 

interaction with other herbicides on human health and the environment;

• Studies on the effects of increased application of dicamba on surface water quality 

and impacts on non‐target plants and animals, including endangered species;

• A detailed evaluation of the volatility of dicamba, including a map of potentially 

affected specialty crop growing regions that would be in the proximity of dicambatolerant cotton and soybean growing areas. The USDA must look at the impacts of 

pesticide drift onto neighboring conventional specialty crop and organic fields, 

including its effects on plant health and farmer costs;

• Research on how the ingestion of foods manufactured from this crop would affect 

human health and how the continued use of the herbicide in agriculture could

Page 2-28
Comment # Comment ID Commenter Comment Excerpt

endanger agricultural workers and the public; and

• A detailed examination of the cumulative effects of stacking dicamba-tolerant corn 

with other herbicide tolerances, including the costs of contamination to non‐GE 

farmers and the costs that dicamba and glyphosate resistant weeds would impose on 

these growers.

45 APHIS-2013-

0043-0047

Cory Rosenbaum,

Rosenbaum Farms

• Rosenbaum Farms wishes to join the concerns expressed by the Save Our 

Crops Coalition in its comment to this docket. 

• Non-target plant damage associated with herbicide and volatilization is a 

major concern for specialty crop growers and processors. Credible estimates 

project significant increases in the amount of dicamba that will be applied 

upon the introduction of dicamba tolerant crops. Dicamba, because of its 

potential to drift and volatilize, has proven to be one of America's most 

dangerous herbicides for non-target plant damage

• We do not oppose advances in plant technology, however, we will not 

accept a range of alternatives that includes only wholesale deregulation or 

wholesale prohibition of these crops. We request the USDA expand the 

scope of its inquiry to consider uses of its authority to address a range of 

issues our membership faces. 

• We request that USDA strictly analyze changes to agronomic practices, 

including herbicide use, that will result from deregulation of these crops, 

and consider where USDA and EPA may be able to jointly develop 

effective measures to protect against the threat of non-target plant damage 

these crops pose.

46 APHIS-2013-

0043-0048

Curt Utterback, 

Secretary, Utterback 

Farms, Inc.

Utterback Farms, Inc. wishes to join the concerns expressed by the Save Our Crops 

Coalition in its comment to this docket.

• Non-target plant damage associated with herbicide spray drift and 

volatilization is a major concern for specialty crop growers and processors. 

Credible estimates project significant increases in the amount of dicamba that 

will be applied upon the introduction of dicamba tolerant crops. Dicamba, 

because of its potential to drift and volatilize, has proven to be one of 

America’s most dangerous herbicides for non-target plant damage. 

• We do not oppose advances in plant technology, however, we will not accept a 

range of alternatives that includes only wholesale deregulation or wholesale 

prohibition of these crops. We request that USDA expand the scope of its 

inquiry to consider uses of its authority to address a range of issues our 

membership faces.

• We request that USDA strictly analyze changes to agronomic practices,

including herbicide use, that will result from deregulation of these crops, and 

consider where USDA and EPA may be able to jointly develop effective 

Page 2-29
Comment # Comment ID Commenter Comment Excerpt

measures to protect against the threat of non-target plant damage these crops 

pose.

47 APHIS-2013-

0043-0049

E. Keith Menchey,

Manager, Science & 

Environmental 

Issues, National Cotton 

Council

• With regard to the proposed EIS on dicamba-tolerant cotton, the NCC 

believes this activity is not warranted from a legal standpoint and will 

unnecessarily delay a needed technology for cotton farmers.

• The competitiveness of the U.S. cotton industry depends on the ability of 

growers to access new, cost-effective, and sustainable technologies to 

manage production pressures such as weed control.

• The availability of dicamba- and glufosinate-tolerant cotton will help the 

sustainability of related industries (including gins, cottonseed processors, 

livestock operations, food processors, and textile mills) who could 

potentially face higher input costs if cotton supplies decrease due to weed 

resistance pressures. The loss of cotton acreage could result in the inability 

to reach “critical mass” of production to support gins and other related 

infrastructure.

• The use of dicamba- and glufosinate-tolerant cotton provides a new weed 

control system that should provide for fewer herbicide applications resulting 

in less trips across the field, reduced greenhouse gas emissions, reduced soil 

erosion, reduced soil compaction, and enhanced water conservation. In fact, 

the use of dicamba- and glufosinate-tolerant cotton has the potential to 

protect and may also increase the current acres under conservation tillage. 

Once approved, dicamba tolerance will allow growers to use dicamba in 

burn down without planting restrictions, while providing effective control of 

herbicide resistant weeds. More complete burn down should further enhance 

conservation tillage. Most importantly, dicamba and glufosinate tolerance 

will offer a robust weed management program, incorporating multiple 

herbicide modes of action, to combat weed resistance.

• Cotton farmers are good stewards of the land and have extensive experience 

in preventing off-site movement. Like any other herbicides, off-site 

movement of dicamba can be prevented through proper stewardship 

including application techniques, equipment settings, nozzle selection, and 

consideration of environmental conditions during application, such as wind 

speed. Moreover, newer dicamba formulations have been developed to 

substantially reduce volatility compared to first-generation dicamba 

products. Today, growers of different crops have access to information, 

resources, equipment, and best management and application practices 

necessary to enable responsible usage of dicamba, with benefits to all 

parties.

48 APHIS-2013- Adam Hartley, grower Dicambia has a long history of volitization after it has been sprayed. You can 

Page 2-30
Comment # Comment ID Commenter Comment Excerpt

0043-0050 spray this active ingredient on days when the wind is calm and then a few days 

later it will get up and move onto adjacent crops that are not resistant to it. This 

will cause a huge liability on row crop producers that have speciality crops raised 

in the same area. Just this year I have had an issue where the railroad sprayed the 

track and the product got up and moved onto my soybeans on both sides of the 

railroad. This was caused by volitization and not drift since it was on both sides 

of the track. Please consider requiring similar limitations and restrictions on the 

use of dicamba similar to what Dow Agro Sciences supported with their 

agreement with the SOCC. Those were reasonable and proper and recognizes the 

need for weed control alternatives but works to protect sensitive crops.

49 APHIS-2013-

0043-0051

Leon Corzine, LPC 

Farms, former President 

of Illinois Corn Growers 

Association and the 

National Corn

Growers Association

• Opposes preparation of an EIS.

• Supports full deregulation of dicamba-tolerant soybeans and dicamba- and 

glufosinate-tolerant cotton. 

• Technologies like these give farmers choices so we can continue to improve 

our farms and remain competitive in the global marketplace, pass on 

reasonable prices to processors and, ultimately, end consumers who buy highprotein soybean-containing products in the form of food and feed.

• Soybeans resistant to both glyphosate and dicamba will add a new mode of 

action to the system, allowing for better weed control and harvested soybeans 

with less foreign material from weed seeds, a valuable characteristic for 

processors.

• Dicamba-tolerant soy and cotton are not only likely to help us manage weed 

resistance, but will enable us to continue to be good stewards of

• the land. Compared to some weed control programs, this system may result in 

fewer herbicide applications, less tillage, reduced greenhouse gas emissions, 

and soil conservation. Dicamba tolerance will allow growers to use dicamba in 

burn down without plant-back restrictions while providing effective control of 

hard to control and resistant weeds, further enhancing conservation tillage.

• Growers follow label instructions closely, go through training and and invest 

heavily in equipment that prevents and minimizes drift. In addition, the new 

formulations of dicamba have lower volatility than previous generations of the 

product. Today, growers of different crops have access to information, 

resources, tools and best management and application practices necessary to 

enable responsible usage of dicamba, with benefits to all parties.

50 APHIS-2013-

0043-0052

TJ Idlewin, grower I am concerned and do not want to be held liable due to volatilization and drift 

from dicamba herbicide spray. I not only have specialty crops neighboring my 

commercial grain crops but will also have some neighbor’s crops that are not 

dicamba tolerant. I have great concern with drift and volatilization when spraying 

next to homeowner’s properties and grandmas backyard gardens.

Page 2-31
Comment # Comment ID Commenter Comment Excerpt

51 APHIS-2013-

0043-0053

Pam Johnson - National 

Corn Growers 

Association

• Opposed to preparation of an EIS. USDA should immediately convey 

nonregulated status on these traits and make them available to U.S. growers.

• Growers need new tools for weed management. Growers need new tools for 

weed management. With additional modes of action, growers will be able to 

more effectively manage glyphosate-resistant and conventional weeds. 

52 APHIS-2013-

0043-0054

Dallas Peterson,

Professor and Extension 

Weed Specialist,

Kansas State University

• Support the deregulation of dicamba tolerant soybeans, which could provide 

benefits for control of problematic weeds and provide a needed management 

tool for herbicide resistance management. New technologies such as dicamba 

tolerant soybeans would provide an additional tool that could be incorporated 

into an integrated weed management program to improve overall weed 

management, including glyphosate resistant weeds.

• The introduction of dicamba tolerant soybean would likely increase the 

potential for developing dicamba resistant weeds, but I feel the potential 

benefits of helping to control existing herbicide resistant weeds far outweighs 

the risk of developing dicamba resistant weeds. I also believe the risk of 

developing dicamba resistant weeds if this technology is introduced is much 

lower than what has occurred with glyphosate in recent years.

• Many problematic weeds, especially waterhemp and Palmer amaranth 

germinate over an extended period of time, so later flushes of weeds will not be 

controlled by short residual herbicides like glyphosate and dicamba. 

Consequently, weed management will be much more successful if glyphosate 

plus dicamba is used in conjunction with preemergence residual herbicides that 

can provide extended control. The use of preemergence herbicides as part of an 

integrated approach has increased in recent years due to the difficulties of 

controlling glyphosate resistant weeds and because of the improved commodity 

prices. Although growers were successful with multiple postemergence 

applications of glyphosate before the development of glyphosate resistant 

weeds, I think farmers now realize the many benefits of using a preemergence 

herbicide in conjunction with a postemergence treatment. This approach helps 

minimize potential for early season weed competition and provides more 

flexibility and better efficacy with the postemergence treatment. The other 

huge benefit is that by utilizing multiple herbicide modes of action, the risk of 

developing herbicide resistant weeds is greatly diminished. 

• Finally, I think farmers and crop advisers now realize that relying simply on a 

single technology such as glyphosate in Roundup Ready crops is not a 

sustainable practice and will eventually lead to the development of herbicide 

resistant weeds and the loss of an effective tool for weed management. 

53 APHIS-2013-

0043-0055

Cathleen Enright -

Biotechnology Industry 

• Opposes the preparation of an EIS. 

• BIO and its members are also concerned that the decision to prepare EISs for 

Page 2-32
Comment # Comment ID Commenter Comment Excerpt

Organization (BIO) the crops identified by APHIS will unnecessarily delay Issuance of 

determinations of nonregulated status, causing significant harm to American 

farmers and the developers of the crops without any additional environmental 

benefit. 

• The delay that will result from preparation of the EISs will deny American 

farmers the new tools they need to prevent and combat herbicide-resistant 

weeds and maximize yields. BIO members have submitted applications to EPA 

that would authorize use of their herbicides on the associated herbicide tolerant 

crops identified In the APHIS Notices. These herbicides have differing modes 

of action, enhancing the ability of growers to address weed problems and 

supporting the continued use of environmentally sustainable practices such as 

no-till farming.

• Delays inherent in the EIS process will also put U.S. corn, soybean and 

cotton growers at a particular disadvantage in relation to their counterparts 

in other nations that are now completing their review processes for GE 

crops on a far more timely basis than the United States. In addition, the 

developers of these crops will suffer further delay in commercializing and 

offering valuable new products for sale and other developers of Innovative 

products may reconsider whether to invest in the U.S. market. Because the 

APHIS Notices failed to provide a satisfactory legal or scientific 

justification for opting to prepare an EIS for the subject products, 

developers of future products also lack predictability as to whether APHIS 

will opt to prepare an EA or an EIS, which significantly affects the 

deregulation timeline and product development decisions.

54 APHIS-2013-

0043-0056

Rachel Lattimore, Senior 

Vice President, General 

Counsel, Secretary -

CropLife America

• Opposed the preparation of an EIS.

• We strongly urge you to reconsider the need for EISs for these technologies. 

The proposed EISs would introduce unnecessary regulatory redundancy and 

potential regulatory confusion by analyzing the proposed use of herbicides 

that are under active review by EPA and outside the jurisdictional purview 

of APHIS.

55 APHIS-2013-

0043-0057

- Agricultural 

Retailers 

Association 

- American Farm 

Bureau Federation 

- American Seed 

Trade Association 

- American Soybean 

Association 

• Oppose the preparation of an EIS.

• Our members, who produce the vast majority of commodity crops in 

America, must be able to utilize the very best available methods to combat 

weed resistance problems. Weed resistance is a well understood scientific 

phenomenon that is not unique to biotechnology or any other form of 

agriculture. Different herbicides attack weeds by different methods or 

“modes of action.” 

• The delay that will result from preparation of the EISs as proposed by 

APHIS will deny growers the tools they need to prevent and combat weed 

Page 2-33
Comment # Comment ID Commenter Comment Excerpt

- American 

Sugarbeet Growers 

Association 

- Biotechnology 

Industry 

Organization 

- National 

Association of 

Wheat Growers 

- National Corn 

Growers 

Association 

- National Cotton 

Council

resistance and maximize yields through the use of herbicides that have been 

shown to operate with differing modes of action. The proposed use of these 

herbicides in conjunction with the associated herbicide tolerant plants also 

supports the continued use of environmentally sustainable practices such as 

no-till and low-till farming.

• The delays inherent in the EIS process proposed by APHIS will put 

American growers at a further disadvantage to corn, soybean and cotton 

growers in other nations that are now completing their review processes for 

biotechnology-derived crops on a far more timely basis than the United 

States.

56 APHIS-2013-

0043-0058

Michael Owen, 

Extension Weed 

Scientist, Iowa State 

University

• I support the deregulation of the new technologies as they will be helpful in 

managing weeds with evolved resistance to glyphosate and other herbicides 

and giving farmers a choice to use tools to maximize yield potential and meet 

growing global demand for their product.

• I believe that if growers use these technologies in compliance with the 

stewardship programs developed by the companies, the potential issues will be 

minimal. 

57 APHIS-2013-

0043-0059

David Cleavinger, 

grower, past president of 

the National Association 

of Wheat Growers

• American farmers count on USDA to be timely and scientific in the review of 

beneficial new biotech crop technologies. Growing delays in this process have 

a real cost to farmers who need these tools. In the case of dicamba-tolerant 

crops, we are in dire need of new weed management tools that allow us to 

diversify weed management and thereby address weeds developing resistance 

to other herbicides. Several already have, and more will if USDA continues to 

delay such an important technology.

• USDA’s delays have already resulted in the US falling behind other countries 

that have more reliable, science-based regulatory processes. Canada, for 

example has already approved the dicamba-tolerant soybean trait and South 

American governments are poised to approve it.

58 APHIS-2013-

0043-0060

Robert Savage, Director 

of Risk Management, 

Red Gold, Inc.

Wishes to join the concerns expressed by the Save Our Crops Coalition in its 

comment to this docket.

• Non-target plant damage associated with herbicide spray drift and 

volatilization is a major concern for specialty crop growers and processors. 

Credible estimates project significant increases in the amount of dicamba that 

Page 2-34
Comment # Comment ID Commenter Comment Excerpt

will be applied upon the introduction of dicamba tolerant crops. Dicamba, 

because of its potential to drift and volatilize, has proven to be one of 

America’s most dangerous herbicides for non-target plant damage. 

• We do not oppose advances in plant technology, however, we will not accept a 

range of alternatives that includes only wholesale deregulation or wholesale 

prohibition of these crops. We request that USDA expand the scope of its 

inquiry to consider uses of its authority to address a range of issues our 

membership faces.

• We request that USDA strictly analyze changes to agronomic practices, 

including herbicide use, that will result from deregulation of these crops, and 

consider where USDA and EPA may be able to jointly develop effective 

measures to protect against the threat of non-target plant damage these crops 

pose.

59 APHIS-2013-

0043-0061

Phillip Miller, Vice 

President, Global 

Regulatory Sciences & 

Affairs,

Monsanto Company

• Opposed to the preparation of an EIS.

• Because EPA, not USDA, regulates herbicides under FIFRA and according to 

the Coordinated Framework, and because herbicide resistance is not a proper 

factor for USDA to consider in making its plant pest risk determination under 

the PPA, herbicide resistance alone (or any other alleged herbicide impacts) 

cannot justify the preparation of a full EIS in this instance.

• The vitality of the agricultural economy in the United States depends upon the 

development of new technologies like those GE crops under review. These 

products will provide important benefits to farmers, and growers should not be 

required to wait for USDA to perform duplicative and time consuming 

analyses already within the regulatory responsibilities of another federal 

agency. As numerous growers, grower groups and agronomy professors have 

previously commented in 2012 for DT soybean and 2013 for DT cotton, such 

products are needed now and should be approved promptly.

60 APHIS-2013-

0043-0062

Danny Murphy -

American Soybean 

Association

• Soybean farmers need new technologies such as dicamba-tolerant soybeans to 

increase yields, manage weed resistance and maintain profitability. As stated in 

ASA’s comment on MON87708, we strongly support biotechnology and

believe the development of biotechnology-enhanced soybean varieties and 

products can benefit farmers, consumers, and the environment.

• ASA strongly urges USDA to reconsider the need for the EIS. The delay that 

will result from preparation of the EISs as proposed by APHIS will deny 

growers the tools they need to prevent and combat weed resistance and 

maximize yields through the use of herbicides that have been shown to operate 

with differing modes of action.

• The proposed use of these herbicides in conjunction with the associated 

Page 2-35
Comment # Comment ID Commenter Comment Excerpt

herbicide tolerant plants also supports the continued use of environmentally 

sustainable practices such as no-till and low-till farming. 

• The introduction of soybeans tolerant to both glyphosate and dicamba will 

allow an additional mode of action to be used in the system, allowing for better 

weed control and harvested soybeans with less foreign material from weed 

seeds, a valuable characteristic for processors.

• To meet growing global demand and maintain the United States as the largest 

producer of soybeans globally, growers need access to new and effective 

technologies such as MON 87708 to increase yield potential and keep soybean 

prices stable. U.S. soybeans rely on exports and the EIS would need to take 

into consideration any implications for international trade.

• While ASA appreciates concerns about off-target movement of dicamba, we 

are confident that farmers have a long history of successfully using proper 

equipment and application procedures to avoid and minimize off-target 

movement of herbicides. Similarly to other herbicide products, off-site 

movement of dicamba can be prevented through proper stewardship, 

application techniques, equipment settings and consideration of environmental 

conditions during application, such as wind speed. ASA is pleased that newer 

dicamba formulations have been developed to substantially reduce volatility 

compared to first-generation dicamba products. We are also pleased that the 

petitioner has addressed the potential for off-site movement by prohibiting 

aerial applications and implementing specific environmental and equipment 

application requirements on the dicamba label, including a wind-directional 

buffer when sensitive areas are present, and the use of low volatility dicamba 

formulations. ASA believes that when recommended label practices are 

followed, farmers of various crops can co-exist and prosper.

61 APHIS-2013-

0043-0063

Joyce Dillard We request that more thorough studies occur on bees and colony collapse, birds and 

the watershed ecosystems as well as viruses that spread through migration related to 

watershed ecosystem connectivity.

Water contamination is a problem in a watershed not necessarily in the vicinity of 

the crops, so all avenues need to be studied.

The liabilities of the Clean Water Act should not be placed on other watershed 

systems.

62 APHIS-2013-

0043-0064

Lee Van Wychen, 

Director Science Policy - 

WSSA

Science has clearly shown that there is a risk of resistance development to all 

herbicides, and 2,4-D and dicamba are no exception. In fact weeds have evolved 

resistance to nearly all forms of weed control including herbicides, tillage, mowing 

and hand weeding. Some of our members have voiced concerns that growers may 

adopt 2,4-D and dicamba technologies and rely too heavily on these herbicides 

thereby developing an even greater weed resistance situation. However, the majority 

Page 2-36
Comment # Comment ID Commenter Comment Excerpt

of our member scientists view 2,4-D and dicamba resistant crops as an additional 

weed management tool to include in an integrated weed management program. The 

greatest risk for developing herbicide resistance is actually occurring right now with 

the PPO herbicides and glufosinate. These products are being over-used in certain 

cropping systems as farmers have no other effective herbicide options. The 2,4-D 

and dicamba resistant crops could be used to delay resistance development to the 

PPO herbicides and glufosinate and, in turn, weed management systems could be 

developed using the PPO herbicides, glufosinate, 2,4-D and dicamba, extending the 

life of each of these chemistries.

Weed management is ultimately the responsibility of farmers and farm advisors. 

However, the weed science community, including industry, academics, crop 

commodity groups and others who reach out to farmers, must recommend robust and 

effective stewardship programs espousing the basic principles of good weed 

management and encourage adoption of these practices. By doing so, evolution of 

resistance to our herbicide resources and new options such as 2,4-D and dicamba 

resistant crops will be minimized.

Research indicates that 2,4-D and dicamba will fit best in a fully diversified program 

and such a program is particularly important when glyphosate resistant palmer 

pigweed and waterhemp are the targets.

Resistance to 2,4-D and dicamba represents no more a threat to agricultural 

production than resistance to other critical herbicides and the likelihood that it will 

be used in a manner consistent with best management practices is good. 

Stacking 2,4-D and dicamba tolerance with that of glyphosate, glufosinate, and other 

herbicide tolerant traits will further facilitate the use of these herbicides in a 

diversified program. Stacking herbicide traits does not in itself promote the evolution 

of resistance to more than one herbicide since, just as for individual herbicides, the 

evolution of resistance is a function of how the herbicides are used rather than a 

function of the selectivity of the crop to multiple herbicides.

The ability of farmers to use 2,4-D and dicamba in diversified weed management 

programs in soybeans, corn, and cotton is not expected to significantly change 

current farming practices. These herbicide tolerant crops will, however, provide 

valuable new postemergence options that will allow farmers to most effectively 

manage their weeds when practicing conservation tillage even in the presence of 

glyphosate resistant populations. Farmers have clearly shown a preference for 

postemergence weed control in conservation tillage systems and 2,4-D and dicamba 

can be an important part of this system. 

As the spread of glyphosate-resistant weeds occurred, the adoption of tillage, 

including deep tillage with a moldboard plow has once again become more common. 

Page 2-37
Comment # Comment ID Commenter Comment Excerpt

The return of conventional tillage has led to increased wind and water erosion. 

Neither 2,4-D nor dicamba technologies would eliminate tillage, but they would 

greatly reduce the need for deep tillage allowing many farmers to return to more 

reduced tillage production systems.

New and expanded uses of existing herbicides are needed for integrated weed 

management programs in order to mitigate weed resistance and meet our current and 

future crop production needs.

Off target movement of 2,4-D and dicamba pose the greatest limitation to the 

adoption of either auxin technology. An enormous amount of research by the 

registrants and other weed scientists around the world has been conducted to develop 

methods to minimize the potential for off-target movement. These efforts include 1) 

improving herbicide formulations, thereby reducing volatility and/or drift, 2) 

improving application equipment techniques and application methods, thereby 

reducing drift, and 3) developing educational materials to assist growers in reducing 

off target movement when making pesticide applications. There is no question these 

research efforts will greatly minimize off-target movement of all pesticides, not just 

2,4-D and dicamba, and will greatly improve the ability of a grower to apply 

pesticides that stay in the targeted area.

63 APHIS-2013-

0043-0065

Center for Food Safety 2,4-D-resistant crops must be viewed as weed control systems 

APHIS must assess dicamba-resistant soybeans and cotton as crop systems 

comprising the herbicide-resistant crop itself and associated use of dicamba. 

Monsanto describes its Roundup Ready (RR) crops as RR crop systems, and will 

also treat its dicamba-resistant crops in the same manner.

Impacts of dicamba-resistant crop systems on herbicide use

APHIS must assess the shift in dicamba use patterns to be expected in various DR 

crop adoption scenarios. APHIS should assess both the change in amount applied, 

per acre per crop, and the shift in use pattern (i.e. amount used pre-emergence vs. 

post-emergence). APHIS should also assess the impact of DR crops on overall 

herbicide use, keeping in mind that dicamba would likely displace little if any 

glyphosate, which has a broader spectrum of activity, including (unlike 2,4-D) 

activity on grass family weeds. We refer APHIS to our comments, where CFS makes 

such projections.

Features of HR crop systems that promote HR weeds 

As discussed in our comments, HR crop systems promote not only (near-) exclusive 

reliance on the associated herbicide(s), but also more frequent use over a broader 

application window that extends much further into the crop season than would 

otherwise be possible. Resistant weeds with Roundup Ready crops are too often 

treated superficially as simply the result of excessive glyphosate use, but as Paul 

Neve has pointed out, the post-emergence use pattern of glyphosate with RR crops is 

Page 2-38
Comment # Comment ID Commenter Comment Excerpt

another, independent factor promoting weed resistance, beyond exclusivity and 

frequency of glyphosate use. In other words, the timing as well as the exclusivity 

and frequency of herbicide use is a factor in promoting weed resistance. In practice, 

applications are often made late post-emergence to larger weeds, increasing 

resistance risks still more. Additional evidence comes from weed resistance to ALS 

inhibitor herbicides, many of which were and are used post-emergence. ALS 

inhibitor-resistant weeds arose in 1987 just five years after the first ALS inhibitor 

herbicide was introduced, and became extremely prevalent in less than a decade; in 

fact, by undermining the efficacy of widely used ALS inhibitors (especially in 

soybeans), resistant weeds provided much of the impetus for adoption of RR crops 

(as a means to kill ALS inhibitor-resistant weeds), just as glyphosate-resistant weeds 

have become the rationale for 2,4-D-resistant crop systems. We emphasize that 

while a post-emergence herbicide use pattern is certainly not a necessary condition 

for weed resistance to evolve (e.g. atrazine used primarily pre-emergence and early 

post-emergence in corn led to substantial weed resistance), it does appear to be a 

facilitating factor where present. APHIS must assess the post-emergence weed 

control paradigm that is a central feature of HR crop systems for its resistancepromoting potential in the case of 2,4-D-resistant crops and weeds, in addition to the 

more obvious factors of exclusivity and frequency of use.

Socioeconomic factors associated with HR crops and HR weeds

As discussed in our comments, pricing strategies influence farmer weed 

management decisions in such a way as to contribute to evolution of weed 

resistance. Companies charge fees for HR traits that are substantial enough to create 

a strong incentive for the farmer to make full use of the trait(s) through total reliance 

on the associated herbicide(s). APHIS should find or develop studies that explore the 

extent to which pricing strategies for HR crop systems (e.g. high-priced seed, lowcost herbicide) reinforce herbicide use patterns that foster resistance in the case of 

2,4-D-resistant corn and soybeans. 

RR crops’ major and closely intertwined “benefits” are reduced labor needs for weed 

management (at least until resistant weeds emerge) and the simplicity of glyphosateonly weed control. In addition, glyphosate’s superior ability to control large weeds 

relative to other herbicides broadens the application window for acceptable weed 

control. These factors together facilitate increased farm size, since more land can be 

managed for weeds with the same labor, and labor needs for weed control are a 

major limiting factor on farm size. One can expect 2,4-D- resistant crops to have 

similar impacts. APHIS should assess the socioeconomic consequences of 2,4-Dresistant corn and soybeans, in terms of increased land and rental prices from 

increased competition for land, increased average size of farms, and accelerated exit 

of small- to medium-size farmers from agriculture.

Page 2-39
Comment # Comment ID Commenter Comment Excerpt

HR crops and drift damage

HR crop systems entail a pronounced shift in herbicide use to much later in the 

season when neighboring crops have leafed out and are more vulnerable to drift 

damage (from early season herbicide use when drift poses much less risk). 

Glyphosate has become a leading cause of drift damage in the era of Roundup Ready 

crops, despite the fact that it is not a volatile or drift-prone herbicide. This is not 

merely because its use has increased so dramatically, but also because its use has 

shifted heavily to later in the season. 2,4-D is much more volatile than glyphosate, 

and is particularly prone to vapor drift. APHIS must comprehensively assess the 

increased drift damage that would occur with various 2,4-D-resistant corn and 

soybean adoption scenarios, both in terms of lost yield and income, broken down by 

major crop (e.g. soybeans, cotton) or crop category (e.g. vegetables). APHIS should 

further assess the extent to which 2,4-D-resistant crop adoption would reduce 

plantings of susceptible crops (e.g. vegetables, grapes) and/or shift acreage to 2,4-Dtolerant crops that could withstand drift level doses (e.g. corn). In conducting this 

assessment, APHIS must account for the inevitable use of more drift-prone 2,4-D 

formulations (e.g. because likely to be cheaper than the choline salt), and not 

presume an ideal world scenario where only potentially less drift-prone formulations 

are used. 

Crop volunteers resistant to 2,4-D, ACCase inhibitors, glyphosate, glufosinate, 

etc. as weeds

RR crop volunteers have been repeatedly noted as problematic weeds, particularly 

corn, but also cotton and soybeans; and particularly where RR crops are rotated (see 

comments). SmartStax corn is even more problematic, since glufosinate as well as 

glyphosate are eliminated as control options. APHIS must assess the increased 

weediness of volunteers of corn and soybeans resistant to 2,4-D, ACCase inhibitors, 

glyphosate, and/or glufosinate. Further, since cross-pollination with other 

prospective herbicide-resistant cultivars will be possible (e.g. dicamba-resistant 

corn), APHIS should consider scenarios with volunteers that have stacked resistance. 

The assessment should include increased costs of control, increased use of 

herbicides, increased weed resistance risks from a narrowing of herbicidal control 

options and increased reliance on those (few) herbicides still effective.

Interplay between HR traits and Bt resistant pests 

2,4-D-resistant corn will be offered mainly in stacks with Bt traits. Research 

described in the 2,4-D comments shows that HR corn volunteers produce lower 

levels of Bt toxin and thereby promote Bt resistance in corn rootworm; the more HR 

traits in the corn volunteers, the less likely they will be managed adequately, and 

hence the more likely they will contribute to Bt resistance. See discussion in 2,4-Dcomments.

Page 2-40
Comment # Comment ID Commenter Comment Excerpt

Cross-resistance between 2,4-D, dicamba and other synthetic auxin herbicides

In our comments, we discuss evidence that certain weeds resistant to 2,4-D (e.g. 

waterhemp) also exhibit increased tolerance to dicamba; and that dicamba-resistant 

crops have increased tolerance to chlorophenoxy herbicides like 2,4-D. In view of 

their common mechanism of action, these findings strongly suggest the potential for 

evolution of cross-resistance in weeds to dicamba and phenoxy herbicides. Most 

weed biotypes resistant to either dicamba or 2,4-D have not been tested for 

resistance to the other. APHIS must assess the potential for 2,4-D crop systems to 

foster resistance, not only to 2,4-D, but also to dicamba, and the impacts such crossresistant weeds (against a background of resistance to glyphosate, ALS inhibitors 

and/or other herbicides), would have on weed control in soybeans, corn and other 

crops. Known weed biotypes with resistance to either 2,4-D or dicamba should be 

tested for tolerance to the other, to help establish the potential for such crossresistance.

Non-target effects of 2,4-D-resistant crops

Roundup Ready crop systems have dramatically increased use of one of the most 

effective plant-killing compounds ever developed. Glyphosate is particularly noted 

for its efficacy against perennial weeds, which most other herbicides have difficulty 

controlling. Glyphosate use with Roundup Ready crops is a major factor in the 

dramatic decline in Monarch butterfly populations over the past two decades (see 

2,4-D-resistant soybean comments to USDA). Glyphosate has decimated milkweed 

populations in Midwest corn and soybean fields; and milkweed in such fields is the 

major breeding ground for migratory Monarchs that overwinter in Mexico. APHIS 

must project the impact of 2,4-D-resistant corn and soybean systems (with additional 

resistance to glyphosate and/or glufosinate) in further reducing populations of 

milkweed in agricultural fields and thus exacerbating the decline in Monarch 

populations. 

Many glyphosate formulations are extremely toxic to various species of frogs. 

Massive glyphosate use accompanying Roundup Ready crops has been posited as a 

likely factor in the global decline of amphibian populations. APHIS must assess the 

impacts of 2,4-D-resistant corn and soybean systems (with additional resistance to 

glyphosate and/or glufosinate) on amphibian populations.

Impact of HR crop systems on sustainable weed control

Please assess the impact that Roundup Ready crop systems have had on efforts to 

advance adoption of sustainable weed management techniques (e.g. crop rotation, 

cover crops); and based on this analysis, similarly project the impacts that 2,4-Dresistant crops (with additional resistance to ACCase inhibitors, glyphosate and/or 

glufosinate) would have on the same.

Health impacts of increased 2,4-D use with 2,4-D-resistant crop systems

Page 2-41
Comment # Comment ID Commenter Comment Excerpt

Medical scientists have found 2,4-D use associated with increased risk of nonHodgkin’s lymphoma and other adverse human health impacts (for discussion see 

human health section of 2,4-D comments to EPA). Dioxins continue to contaminate 

2,4-D, and EPA has failed to collect comprehensive, independent data on the dioxin 

content of the many 2,4-D formulation used by farmers. CFS projects a many-fold 

increase in use of 2,4-D with introduction of either or both 2,4-D crop systems, and 

thus a further increase in exposure to and disease from this toxic herbicide. APHIS 

and EPA must assess the increased incidence of disease to be expected with the 

substantial increase in 2,4-D use accompanying introduction of these crop systems.

2,4-D-resistant crops and tillage

Roundup Ready crops have not, as popularly imagined, fostered increased use of 

conservation tillage. The major gains in conservation tillage adoption came in the 

1980s and early 1990s, in consequence of 1985 and 1990 Farm Bill provisions that 

tied subsidies to use of soil-conserving practices. In fact, adoption of conservation 

tillage actually stagnated in the decade of Roundup Ready crop adoption. Instead, 

the glyphosate-resistant weeds generated by RR crop systems have led to increased 

tillage for weed control and hence greater soil erosion. CFS has presented a detailed 

analysis to support these conclusions in the 2,4-D-resistant soybean comments. 

APHIS must assess the potential for 2,4-D crop systems to further increase soil 

erosion through increased use of tillage to control the 2,4-D-resistant weeds that will 

be generated by these crop systems. 

APHIS should also require the applicants to supply information necessary for 

meaningful risk assessments that is not in their petitions, or better yet undertake 

appropriate research to fill in the gaps. For example, the following information 

should be available for review by APHIS and the public:

• Proposed herbicide application regime: how much herbicide, how often, 

window of application. 

• Degree of resistance conferred by the transgene in different plant parts and 

stages of development.

• Expression of the transgene in pollen, nectar; levels of herbicide residues 

and metabolites in pollen, nectar. 

• Herbicide residues and metabolites in plant tissues from the time of 

application through post-harvest.

APHIS needs to analyze the following areas: 

• Agricultural production impacts, including and not limited to burden on 

organic and non-transgenic agricultural production and potential harms to 

non--‐target crops from the adoption of the HR crop system.

• Environmental impacts, including but not limited to:

- Herbicide use and changes in herbicide use patterns;

Page 2-42
Comment # Comment ID Commenter Comment Excerpt

- Gene flow from 2,4-D-resistant corn and soybeans to compatible varieties 

and the resulting increased weediness;

- Agricultural practices, including herbicide use, effects on tillage; and

- Weed resistance and volunteers.

• Socioeconomic impacts, such as:

- Transgenic contamination and their effects on both domestic and export 

markets, as well as, consumers and farmers’ right of choice 

- Changes in seed industry market concentration and their impacts, 

- Effects on the methods and costs of weed control

• Human health impacts, such as:

- Herbicide use, including impacts on farm workers; and

- Safety of food products 

• Livestock health, such as: 

- Herbicide use; and

- Safety of animal feed.

• Threatened and endangered species, such as:

- Herbicide use; and

- Quality of crop tissues as food sources.

• Disease and pest impacts stemming from 2,4-D-resistant soybeans and corn 

and the associated herbicide use.

63 APHIS-2013-

0043-0065

Center for Food Safety Comments to USDA APHIS on Environmental Assessment for the Determination of 

Nonregulated Status of Herbicide‐Tolerant DAS‐40278-9 Corn, Zea mays, Event 

DAS‐40278‐9 - Center for Food Safety, Science Comments II

See Comment Summary for DEA for DAS-40278-9 Corn

64 APHIS-2013-

0043-0066

Center for Food Safety Comments to USDA APHIS on Draft Environmental Assessment and Draft Plant 

Pest Risk Assessment for Dupont-Pioneer’s Petition (11-244-01p) for Determination 

of Nonregulated Status of Insect-Resistant and Herbicide-Resistant Pioneer 4414 

Maize: Event DP-004114-3

Page 2-43
Table 2-2. Public Scoping Comments Submitted During Virtual Public Meeting

Commenter Affiliation Concern/Issue

June 26, 2013

Victor Miller grower and past 

chairman U.S. 

Grains Council

As USDA surveys the topics to be considered in the development 

of the draft EIS, I would first offer that USDA should take a hard 

look at the question is an EIS even warranted. USDA's and 

APHIS' reasons for conducting the EIS all appear to relate to 

potential impacts associated with herbicide use, possible selection 

for, and spread of weed resistance to herbicides...from 

applications of dicamba on the dicamba intolerant crop and other 

areas.

Use of dicamba is nothing new. According to industry estimates, 

dicamba has been used successfully on more than 250 million 

acres over the past 10 years. In 2012, it was the fifth most widely 

used herbicide in the U.S. in terms of acres treated, used on over 

32 million acres of farmland across the range of crops, including 

12 million acres of corn, 6 million acres of wheat, 4 million acres 

of other crops, and 10 million acres of fallow for (indiscernible). 

Additionally, any homeowner who has gone to their local WeedB-Gon herbicide product has used dicamba without certification or 

licensing.

The equipment, the know-how, and the ability to successfully 

apply dicamba as part of the new dicamba tolerant soybean and 

cotton weed control system under review exists today. I have 

purchased upgrades through my current system to accommodate 

the new requirements, and I'm confident that I and other producers 

will do this successfully.

The ability to choose dicamba within my soybean acres will allow 

me to have a badly needed additional mode of action to control 

weeds such as waterhemp and lambsquarters that are a problem on 

my farm. Without it, I am left with few viable alternatives to 

control weeds in my field, resulting in poor yields, which means I 

produce less on these acres. This means I get paid less for my 

crop, I deliver fewer beans to my local elevator, and this cascade 

of impact carries on down the line, as the elevator adds 

(indiscernible) fewer beans and more weed seed to foreign 

material that end up at the local crushing plants. The crush plant 

profitability is hurt, and so is bean quality that is made into animal 

feed, soybean oil, biodiesel, food ingredients, and ultimately either 

used domestically in many applications or sold to foreign buyers 

Page 2-44
Commenter Affiliation Concern/Issue

for their use in international markets. Now, not only has my 

income been impacted, but very possibly, hungry people in foreign 

markets have less to eat.

Looking on the bright side, incorporating dicamba tolerant 

soybeans into my weed management program allows me to reduce 

dependence on ALS and PPO herbicides and would offer a 

proactive program for weed resistance management and preserve 

the value of glyphosate, an herbicide that still controls most of the 

weeds on my farm.

Lastly, I adopted no till, also called conservation tillage, because 

of the great environmental benefits that it creates: reduced soil 

erosion, increased moisture and benefit to top soil. Here, I use 

Roundup to remove the weeds in my field before I plant instead of 

tilling them under. With dicamba tolerant soybeans, I have another 

tool to assist me in my conservation tillage efforts and potentially 

help me and other farmers to expand this practice. Without 

dicamba tolerant beans, I may be forced to till my fields if and 

when weed pressure dictates, which could lead to soil erosion, 

impaction, and unsatisfactory weed control. 

In closing, restricting the use or denying access to these new 

technologies would have a negative effect on U.S. farmers' 

operations, reduced weed control capability, increasing costs, 

reducing farm returns, and impacting the producer's ability to meet 

foreign market demand. And also, it stands a very great chance of 

reducing conservation tillage options. Ultimately, this has a very 

negative impact on the food supply of not only the U.S. but the 

world as well. I urge you to complete your report and remove 

promptly so that other farmers may have access to this knowledge. 

Ray Gaesser grower and First 

Vice President of the 

American Soybean 

Association

Those traits (indiscernible) are much needed. They will allow us, 

on our farm at least, to continue to no till. If we don't have those 

products, we may have to go back to tillage to deal with some of 

the weeds that we have. So I would really urge you to move 

forward with the approval of both the dicamba and the 2,4-D for 

our soybeans and our corn...

We use them [2,4-D and dicamba] on our farms. I've been farming 

25 years now, and I've had experience using both of those 

products in a different formulation for all that time. And, really, 

I've never had any problems with it, (static - call interference) 

response to our own crop or our neighbor's. As the previous 

Page 2-45
Commenter Affiliation Concern/Issue

speaker said, we are tested in Iowa. As is required of all of our 

applicators that come from the co-ops and from the industry, are 

tested, and understand the need and the right way to apply 

herbicides.

We used to use a lot of those products, and now with glyphosate, 

we use less in order to address the issues of weed resistance in 

particular, and the real need for multiple modes of actions. All of 

our universities are saying that we need multiple modes 

(indiscernible) of action to avoid weed resistance. So I would 

urge you to move forward with both of these applications.

David Shaw Past President, 

Weed Science 

Society of America 

(WSSA)

Biotechnology has allowed us to maximize yields in economics, to 

be able to mitigate the potential development of herbicide 

resistance, and to be able to effectively gain tremendously with the 

development of conservation tillage practices in the United States. 

Herbicide resistance has developed substantially over the last few 

years, but is not a new phenomenon. In fact, it has been recorded 

and noted for over 40 years now.

One of the primary practices that we scientists recommend in 

managing proactively herbicide resistance is the ability to use a 

wide diversity of mechanisms of actions with different herbicides 

that affect plants in different ways. We need more herbicide 

options to be able to manage these and to be able to preserve the 

utility of those that we already have. The ability to effectively use 

dicamba and 2,4-D in soybean and cotton will help fill this critical 

need.

We have seen the development of herbicide resistant plants most 

notably in the last few years with glyphosate resistance in 

(indiscernible) crops. This problem has become widespread, in 

several of our major commodities. And dicamba and 2,4-D, also 

the ability to use a different mechanism of action than what is 

currently available in these crops to be able to more effectively 

and proactively mitigate and delay the evolution of herbicide 

resistance.

There are a number of factors that come into play in the evolution 

of herbicide resistant weeds and crops. However, we scientists 

understand that this is a function of managing the practices and the 

herbicides that are available for weed management. It is as such 

not a plant biotechnology issue. It is a use of the technology and 

Page 2-46
Commenter Affiliation Concern/Issue

the rotation and a development of an overall plan using various 

management practices that have been identified.

Weed management is ultimately the responsibility of farmers and 

farm advisors that requires the entire community of weed 

scientists, industry, academia, crop commodity, and others to be 

able to effectively steward herbicide resistance management. By 

using the development of resisted crops that have the tolerance to 

dicamba and 2,4-D, this represents no greater threat than the 

development of any herbicide technology that has hurt in the past.

Dicamba best fits in a fully diversified program that utilizes many 

different mechanisms of action of herbicides, and is therefore a 

tool that can be used either in stacked (indiscernible) or as stand 

alone to be able to offer the growers options that

16 they currently do not have. It is also noted that one of the major 

challenges that we have with the development of herbicide 

resistance is the losses that we are now experiencing in 

conservation tillage acres. Dicamba and 2,4-D tolerance will 

certainly allow us to help preserve these valuable gains and the 

preservation of our soils in the United States.

We urge the USDA to expedite the necessary review process that 

will lead to final approval of dicamba and 2,4-D tolerant crops, 

and we appreciate the opportunity to provide this comment.

Victor Miller grower and past 

chairman U.S. 

Grains Council

I would like to make an additional comment on the fact or the idea 

that we as private applicators applying herbicides to our crops, the 

amount of time that we spend in reading and understanding and 

following the label is of paramount importance to us. And as we 

look at this, there are many reasons for doing it, but the two that 

stick out the most are the fact that if we do not follow those label 

requirements, we risk unsatisfactory control. And worse yet, we 

risk crop injury, which is at the ultimate end a reduction in our 

incomes. And so, I think it's very important for USDA to 

understand that we spend a great deal of time doing exactly what 

is on that label.

Ray Gaesser grower and First 

Vice President of the 

American Soybean 

Association

I'd like to talk from my heart, and I really don't understand the fear 

of these products, because on our farms -- and I have 25 years in 

this experience -- we've been using these products for all that time, 

for a decade now, and we haven't had a problem. And they've been 

used all over the world for a decade. And you have all the data and 

Page 2-47
Commenter Affiliation Concern/Issue

the experience that I would think you need. I can't understand why 

there is a need for an environmental impact assessment. I just 

really struggle with that. It's going to delay my ability and my 

fellow farmers here in the United States to use these products in a 

new way that allows us to (indiscernible) of this issue; that let's us 

use multiple modes of action to avoid these resistances in the first 

place and let's us farm the way we really need to run our land so 

that we can continue, and not have to use facilities to incorporate 

some of the other herbicides that can work okay, but it's not very 

good for my part of the country where we're having 

(indiscernible). So I would really encourage you to move forward 

to deregulate these products, to not do the EIS. You have all the 

data in the world. You have all the data you need to move forward 

with these two products, and I would encourage you to do that.

Michael McCarty grower We've been fighting this [resistant weeds] for probably the last 

five or six years. We have glyphosate tolerant cotton, soybeans, all 

that was great. We followed the stewardship requirements, 

followed everything that was presented to us, all that by the book. 

And now we've come upon a resistant, amaranth, pigweed. And it 

is totally destroying the infrastructure on our cotton industry. 

We've gone from a 2800-acre cotton farm down to 1500 acres. 

And trying to maintain, it's a battle we just can't fight. We don't 

have enough tools in our arsenal. There aren't enough -- it's 

enough technology for us to overcome this problem, so we're just 

totally out of the cotton industry now. We have zero acres of 

cotton. And I've got a $600,000 cotton picker that's sitting under 

the shed -- it's decreased in value, probably now cut in half 

because there's nobody interested in buying it so they can plant 

cotton. 

My problem is, I know that there's technology out there, and why 

haven't we been able to use it? It's out there for us. I've been to two 

fields, test spots, looked at different things, read different articles 

about it. And my main concern is we're getting ready to totally 

lose it. And I'm just voicing a concern from the field standpoint. I 

read all these -- these people in Austin and California and all these 

different places that are trying to tell us what we need to be doing 

and how we need to do it. I'm telling you from the field level, we 

need the technology, and we need it quick. These other countries 

Page 2-48
Commenter Affiliation Concern/Issue

are already using it, and we're at a disadvantage to them.

I know some of the problems are worried about drift management, 

whether or not we can control it. We've got the John Deere, the 

green release, all technologies, everything in our arsenal to keep 

drift down, (indiscernible), GPS equipment, stuff that doesn't have 

any overlap. We've got sprayers that will cut off to keep from 

overlapping. It's an amazing amount of technology that's out there 

to keep out drift control down. I know that was one of the 

problems that I read about. It was a concern. 

Farmers are some of the most responsible people because we get 

back from the earth whatever we put in it. If we destroy our 

ground, we overlay chemicals, then we don't get anything back. 

That's how we make a living. We're not going to do that. We're not 

going to abuse anything, nothing like that. No farmer that's still in 

business has ever abused a chemical because simply there's EPA 

regulations; there's everything that can toss us out. And it's just not 

going to happen. 

My deal is -- my main concern is let's get this technology. You've 

been going over this for three years, and steady having meetings, 

talking about them. Come back with another set of meetings. You 

can only meet so long. You can only have so many (indiscernible) 

to do this for, so let's open it up. Let's give us the technology we 

need so we can start using them.

June 27, 2013

Genna Reed Food and Water 

Watch

Our previously submitted comments outline issues that must be 

considered carefully in (indiscernible). Environmental Impact 

Statement. The Food and Water Watch analysis of USDA data 

revealed that for every 1 million acres of dicamba tolerant soybean 

plant, there could be an additional 2 millions of dicamba applied 

to crop. Even if just a million dicamba tolerant soybean acres are 

planted, that would be 17 times the current dicamba volume used 

on soybeans.

If 2,4-D corn were adopted as quickly a Roundup Ready corn, 

about 1 million acres a year between 1997 and 2001, 2,4-D 

application on corn is easily increased by nearly three 

Page 2-49
Commenter Affiliation Concern/Issue

(indiscernible), from 3.5 million pounds to 5.5 million pounds in 

two years

21 of 2,4-D tolerant corn introduction.

USDA must look at the economic cost to development of 2,4-D 

and dicamba tolerant weeds could have on (indiscernible). 

Farmers face significant costs from (indiscernible).and increased 

production costs. These costs can range from $12 to $50 an acre, 

or as much as $12,000 for an average bag of corn or soybean farm, 

or $28,000 for an average cotton farm. 

Since U.S. farmers have found herbicide-resistant weeds in their 

fields, they've changed farming methods to control them, resulting 

in higher weed control costs and even tillage and hand tilling. 

Additionally, USDA must also look at the impacts that these 

resistant and multiple herbicides could have on farmers and 

agriculture. Second, increased applications of 2,4-D and dicamba 

will lead to elevated surface water pollution, which will not only 

affect the quality of water near agriculture, but will impact plants 

and animals, including endangered species.

USDA must consider the biological opinion of the National 

Marine Fishery Service regarding 2,4-D registration and specific 

(indiscernible), and look carefully at the individual and synergistic 

effects of increased volumes that of these chemicals on non-target 

organisms, threatened and endangered species. 

Robert Wolf retired professor 

emeritus, application

technology in the 

biological and 

agricultural 

engineering 

department, and 

extension specialist, 

Kansas State 

University

My main responsibility while at Kansas State was to conduct an 

extension and research program in our chemical pesticide 

application with a particular emphasis on novel technology. My 

research focus was and continues to evaluating novel types for 

improved pest control efficacy while minimizing the straight drift. 

In retirement, I have formed a consulting company, Wolf 

Consulting and Research and continued working with the 

application industry as a researcher and a trainer. 

As a part of my consulting work, I have had the opportunity to 

work with Monsanto's dicamba tolerant soybean train team and 

trained Monsanto employees and others on the topic of spray 

technology basics, including the focus on selecting and using 

Page 2-50
Commenter Affiliation Concern/Issue

proper novels for the application with dicamba as a part of a 

prescribed weed control system as it relates to the introduction of 

these dicamba tolerant crops. 

For the past four years, the focus of this reach has involved 

conducting commercial size sprayer oriented research trials 

involving spray nozzles and drip- producing (indiscernible) to 

support this training, with the most recent efforts used in resistant 

weed plots (ph). As the USDA considers areas of study for the 

plant environmental impact statement, I would like to offer some 

thoughts and consideration, as well as my perspective on the new 

weed control tool. Current spray technologies for residual off-site 

movement and the application practices available to make 

herbicide applications accessible. 

Some forces of concern include off-site movement caused by 

particle drift, volatility, contamination due to improper clean out 

and making applications in unfavorable environmental conditions.

Here are some of my key points.

Particle drift is controllable through equipment selection and 

conditions of use, such as

formulation, spray tips, and other technologies, wind speed and 

direction of application considerations and sprayers feed and 

(indiscernible). In some of my most recent research, selecting a 

proper nozzle type alone was shown to reduce (indiscernible) as 

much as 13 and a half percent, down to as low as half a percent. 

And in some cases, with the inclusion of drip control additives 

reducing drip even more.

Newer dicamba formulations have been developed to substantially 

reduce volatility compared to earlier generations of dicamba 

products. The research is supporting this and to further research, 

education and training at this point will be stress, and 

contamination will be a major concern when switching between 

tolerant and non-tolerant crops. This will be addressed through 

proper cleanout procedures that adequately clean out herbicide 

residues from the lining tank and inner workings of the sprayer, 

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Commenter Affiliation Concern/Issue

including all (indiscernible) 45 builders, crevices, drain lines, et 

cetera. Newer spray systems are being engineered to improve this 

cleanout process.

Monsanto has addressed one concern of the potential for off-site 

movement by prohibiting aerial applications and other concerns by 

implementing specific environmental and equipment applications 

comments on the draft dicamba label, including wind directional 

buffer when sensitive areas are present and the use of low 

volatility dicamba formulations.

In my opinion, the U.S. farmers and applicators are capable and 

experienced after many on-site movement. Like any other 

herbicides off-site movement of dicamba can be prevented 

through proper stewardship, including application techniques, 

equipment settings, nozzle selection, and consideration of the 

environmental conditions during the application.

Equipment and other hand-held tools, such as Smartphone apps 

that support applications to facilitate access to weather data, field 

crop mass, nozzle details

and other information now exist in this technology, and its 

capabilities are being used in fields across America today. Correct 

label practices are followed and growers of various crops will coexist and prosper. I believe that in combination with approved best 

management practices, including the use of proper novel type, or

types, applications using dicamba will have the potential to reduce 

the amount of off-target drift.

In closing, the use of dicamba does not (indiscernible) at 2012 

pictures indicating its use in over 32 million acres of farmland in 

the U.S. The equipment know-how and ability to successfully 

apply dicamba as a part of the new dicamba tolerant soybean and 

cotton weed control systems exist today. Putting these application 

details on a label is an effective means of communicating and 

requiring these strategies to be followed. Restricting the use or 

denying access to these new technologies, based on concerns for 

off-site movement because it may not be controlled or labeled 

formulations may not be successfully applied (indiscernible) 

Page 2-52
Commenter Affiliation Concern/Issue

exaggeration are a huge disservice to the farmers who I understand 

the USDA is representing. 

Jim Broten Grower and past 

chairman, U.S. 

Grains Council

I just want to comment that in spite of the, problems with weeds 

(indiscernible), including (indiscernible). These weeds compete 

with our crops for (indiscernible), water, and (indiscernible), and 

they hurt our fields. If left without effective control, these weeds 

can decrease our (indiscernible).

Bill Bridgeforth Grower and 

chairman, National 

Black

Growers Council

...we produce cotton and soybeans on our farm. And the pigweed 

problem has become a very serious issue for us. This year, 

pigweed threatens our profitability. It could take the whole farm, 

just that one weed alone. We do have -- each year, we'll have some 

areas of our farm where the technologies that we're using now and 

the chemicals we're using, they just do not work. And we'll have to 

abandon those crops. It's not a large percentage of the acres, but 

we do have it. It does happen. 

Without another mode of action on the pigweed, we're going to 

see more and more of this -- we're just going to have to start --

we're going to start seeing more acres that will have to be 

amended because the pigweed is just taking over.

And so I believe that the dicamba technology in cotton and 

soybeans on our farm is going to be very important. We're already 

using all the technology and

precision. All the tools out there that can help us be better farmers, 

we're using them. And we just think that the approval of dicamba 

cotton and soybeans will keep us on track to being good farmers 

with a high level of productivity.

Michael Owen extension weed 

scientist and 

professor (weed 

management), Iowa 

State University

I would like to suggest a couple of things. First of all, that as the 

previous speaker indicated, growers not just in the south or the 

Delta, or in the Midwest, need as many tools to manage weeds as 

possible. Weeds represent the most important, most prolific and 

most consistent pest complex that causes reductions in yields and 

profitability throughout the world. And having new tools to help 

manage those pests are incredibly important. 

A comment was made earlier that the de-registration or 

deregulation of these traits -- and I am speaking both to Docket 42 

and to Docket 43. The statement was made that there will be an 

Page 2-53
Commenter Affiliation Concern/Issue

increased use of these two herbicides, dicamba and 2,4-D. I would 

look back not that far in history where 2,4-D/dicamba was the 

most prevalent herbicide treatment used in corn production across 

the United States. And thus, I do not see that this change in the 

technology is going to dramatically change how over the history 

these two herbicides have been used.

Importantly, I would also point out that the concern for the EIS 

reflects the concern for evolved resistance to these herbicides. The 

fact is that these herbicides represent no more greater risk than any 

other herbicide in whether or not they will select for herbicide 

resistant weed biotype. It is the decision on how those herbicides 

are used and the management practices that dictate the level of 

selection pressure and the likelihood of herbicide resistant weeds.

The truth is that there are already some leaves that evolve 

resistance to dicamba and some leaves that evolve resistant to 

2,4D. The manner by which the companies are prescribing the use 

of these new technologies and the concomitant use of these 

herbicides to such that selection pressure by their rules will be 

reduced significantly; and thus in my opinion, reduce the 

probability that new leaves will indeed be selected and have the 

training for resistance to either 2,4-D or dicamba.

The other point is that we talk about these concerns about 

volatilization. And again, the new formulations of the 2,4-D and of 

the dicamba are such that volatization potential is minimized. It's 

not eliminated but if you significantly minimize – and once again, 

it is the decision as to how these herbicides are applied, as Dr. 

Wolf explained, will determine the risk of all target movement, 

based on the stewardship programs that the companies are placing 

in effect in anticipation of deregulation. My sense is that the 

potential for off- target movement of these herbicides has been 

managed very effectively.

he other comment that was made is that if these trades were 

deregulated, that we will lose opportunities for conservation 

tillage. The fact remains that these products specifically do 

support the success of conservation tillage in all row crops that 

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Commenter Affiliation Concern/Issue

form the soybean and the cotton, where these new geneticallyengineered traits will be sold and these herbicides will be used.

The final point that I want to make is that it was suggested that. 

But the final point that I want to make is that it was suggested that

herbicides are now a major problem with regard to how widely 

they are used and how other alternative strategies have been 

compromised as a result of the ubiquitous use of herbicides. This 

is not new. This has been an agricultural fact over 40 years. And 

so, I do not see where the deregulation of the corn, cotton and 

soybeans, with traits for either 2,4-D or dicamba is dramatically 

going to change. The amount of herbicides or the acres of 

herbicides treated crops, will occur.

I think that in fact, the industry has learned from their historical 

efforts with developing products and having them cause selection 

pressure resulting in herbicide resistance. There's historical 

knowledge, and they're putting this into practice with the 

stewardship programs that they now are beginning to up into 

place. I think this will change grower behavior. And by changing 

grower behavior the potential negative consequences of these new 

genetically engineered crops or the use of either 2,4-D or dicamba 

will be minimized.

Kip Tom grower, Tom Farms This is nothing new to us. We've experienced a lot of -- in 

Argentina as well, so we're not surprised we're seeing some of it 

here. And when I say that, I'm talking about the (indiscernible). 

Well, I've got to tell you that on May 10th of this year, USDA 

took an action-oriented step by delaying the regulatory approval of 

the dicamba tolerant

technologies for corn and soybeans and the 2,4-D tolerant 

technologies for soybeans and corn from Dow, requiring an 

environmental impact statement.

This move threaten, though, severe delays to the Farmers Act, 

that's multiple weed control technology across three major U.S. 

crops: corn, cotton, and soybeans. These technologies have been 

under USDA for approximately three years, a timeline that is 

already much longer than expected. And now the USDA is 

initiating a process that's taken as long as four years, when I think 

Page 2-55
Commenter Affiliation Concern/Issue

about Roundup Ready alfalfa in the past. Unacceptable. 

USDA's stated purposes for the EIS revolves around stewardship 

of chemistry herbicide-resistant weed and (indiscernible), which is 

EPA's goal as

determined by Congress decades ago and upheld in federal courts 

as recent as last month, the Ninth Circuit Court of Appeals ruling 

on Roundup Ready alfalfa. USDA has no legal authority to 

regulate these matters, and it's hurting farmers with delays, while 

it

takes this overreaching step.

These traits already have been approved by the Canadian 

government for the Canadian soybean farmer. This is bad enough, 

but further delays may result in Argentina and South American 

governments also close to approving these technologies. If it 

delays another three years, it's going to put the U.S. way behind 

most other countries and access to these technologies to address an 

issue that we have today.

Continued delays and lack of predictability in USDA's process 

hinders innovation and creates insurmountable barriers to entry for 

a variety of new tools and competitive product choices that would 

benefit all of us in U.S. agriculture and our consumers globally. 

The impact of U.S. delays are potentially not deregulating these 

technologies on our farm and our communities, and the U.S. 

farmer's ability to compete for supplies and growing global 

markets. We all know the numbers. Today we're feeding 7 billion 

people, and we're on the pathway to feed 9 billion people by the 

year 2050, a big job to do, especially when we have to face some 

of the challenges we do in these regulatory processes.

This technology is critical to allow successful over-the-top control 

broadleaf weeds, crops and soybeans, cotton and corn. Several 

broadleaf weed species, such as palmer amaranth, waterhemp, and 

(indiscernible) must be controlled with a limited set of tools, 

including tillage and other less effective chemistries that also face 

the same resistant issues, and (indiscernible), and farmers are 

forced to (indiscernible).

Page 2-56
Commenter Affiliation Concern/Issue

The weeds are only on USA (indiscernible), but will continue to 

get worse as a great cost to farmers and consumers who benefit 

from the productivity. Failure to deploy multiple tools for the sake 

of diversifying management by farmers result in the development 

of resistance to one herbicides at a time, which can lead to 

multiple herbicide resistance evolving. When a new tool finally 

gets approved, all the pressure's on it.

If major global competitors have access to this technology and 

U.S. farmers do not, it will hurt global competitors, exports, and 

economic value. This is very important in all American agriculture 

to see if this gets moved forward. If U.S. gives up leadership in 

these important technologies, it will be a major setback in reaching 

the critical goal of growing production to meet the demand of a 

growing and hungry population on planet earth. 

U.S. farmers already manage these tools and many others 

responsibly. Although it is EPA's job to regulate matters related to 

chemistry, USDA should know that farmers use herbicides 

responsibly and understand the risk of careless misuse. Farmers 

and applicators who use these tools are highly sophisticated. These 

have to be in order to stay in business. Awareness and compliance 

with labels is higher than ever as the applicator training and 

experience. The sophistication of application equipment, safety 

features, and GIS systems is far beyond what most of the public, 

including regulators, ever experienced in their vehicles, offices, or 

Smartphone apps. As it relates to herbicide resistance, farmers 

have rapidly adopted diverse weed management programs that put 

more weight on multiple herbicides, tillage and cultural practices 

and one herbicide. This has been the (indiscernible) neglect of safe 

resistance.

These new tools are critical of broadleaf control that do not 

provide the full strength and control of (indiscernible) or even the 

same timing flexibility, not effective in all tall weeds. It is 

impossible for a farmer to rely exclusively on them the way 

glyphosate (indiscernible) was often used for many years, which 

leads to resistant weeds. After decades of use on hundreds of 

Page 2-57
Commenter Affiliation Concern/Issue

millions of acres over time, there are very few weed resistance to 

these chemistries.

As it relates to drip and off-site movement, these chemistries are 

very familiar to farmers who have used them over the last several 

decades. In 2012, over 30 million acres of U.S. crop 

(indiscernible) was treated with dicamba. A large crop market was 

done.

Farmers and applicators are eager to use the new formulation and 

technologies to reduce any drip on off-site movement. This is 

motivated by a good neighbor stewardship, inherent to agriculture 

as well as financial motives that (indiscernible) costly damage. 

In conclusion, many farmers who grow sensitive crops and 

specialty crops also grow row crops, and benefit from the use of 

herbicide tolerant technologies. This is more mutual need to 

understanding and stewardship than (indiscernible) between 

different

crop types, as most farmers produce a variety of crops for 

economic and agronomic reasons. This is not about a soybean 

farmer and a vegetable farmer, or a cotton farmer and a soybean 

farmer. It's about farmers and farmers.

I hope that my comments paint a clear picture for our needs here 

in rural agriculture. But we need this technology today because the 

problem is becoming more evident each and every year we wait.

Danny Murphy Current president, 

American Soybean 

Association

As I've traveled around the country speaking to the soybean 

farmers this year, I continually hear the story of farmers having to 

deal with resistance to mainly palmer amaranth, and their 

frustration and desire for these new chemicals to be able to help 

combat that resistance. Many of those farmers have adopted no-till 

practices. They're comfortable with those, but their only 

alternative at this point is for many years to go back to tillage, 

which results in soil erosion and more expensive reduction costs.

So it was really disappointing to see the additional delay in both 

the dicamba and 2,4-D products. I really feel like the farmers 

really need these tools to be able to combat this resistance. I think 

it's critical for us -- for USDA and APHIS to move these products 

Page 2-58
Commenter Affiliation Concern/Issue

alone and give farmers the opportunity to use them. Both of these 

products have been used, probably 2,4-D over 50 years and 

dicamba over 40 years, that they've used. So farmers are familiar 

with those products, and I think they understand how to use them. 

They understand the labels that we operate under today, and 

they're used to dealing with off-target movement and drift and 

understand what they need to do to correct that.

I also would like to respond as a farmer in Mississippi that grows 

cotton and corn and soybeans. I'm fortunate in this area that I do 

not have resistant palmer amaranth today. My field's more 

isolated, but I'm really concerned that the next time I spray, that it 

may show up. So these tools, both dicamba and 2,4-D, would 

really provide me an alternative to an alternate chemistry to make 

sure that I don't develop resistant palmer, or glyphosate resistant 

palmer. And it would really be a great benefit to me if I was able 

to insert one of those products in my application and be able to 

make sure that I don't develop that resistance in the future.

I've begun to adopt no-till (indiscernible) farming just as those 

farmers across the nation have, and super savings in soil erosion 

and reduced reduction cost, reduced inputs for diesel and labor and 

equipment. We really need to be able to continue to use these 

practices. I can say that we really need the availability of the best 

technology. And to delay the vote for 2,4-D and the dicamba --

and there are a number of products that are coming down the line 

as that will also be available and help to combat this resistance.

So I think it's critical for U.S. agriculture and U.S. farmers that we 

have these products available.

Barron Brown Grower This technology is really made for the (indiscernible). I am 

fortunate enough that I was in the -- been a part of the Roundup 

Ready (indiscernible). And I had several acres of the dicamba 

resistant soybeans.

(Comments are indiscernible.)

Soybeans are not always important. From my logic, they're also 

important to crop in the United States. They're found on over more 

than 55 million acres. We've got to have this technology. That's 

Page 2-59
Commenter Affiliation Concern/Issue

basically all I really have to say.

Bryan Young Professor of wheat 

science, Southern 

Illinois University

Ultimately, the responsibility that I have with the university is to 

develop solid recommendations for growers to implement in their 

field, primary corn and soybeans, as well as some wheat, to be 

successful and profitable in managing weeds and productivity. 

So in terms of experience with herbicide-resistant crops, 

obviously, I've been involved with the use of herbicide-resistant 

crops with both corn and soybean to date, and I have been 

involved with testing both the dicamba tolerant soybean system, as 

well as the 2,4-D tolerant soybean system, the Roundup Ready, 

and then corn and beans (indiscernible).

I think I first want to comment on what brought you to this point. 

So there's a need for the technology because we have seen a rapid 

decline in recent years in the robust weed control that we can 

achieve with glyphosate in some geographies because of 

resistance. But it's not just resistance to glyphosate, it's resistance 

to the other herbicides that we have used in the past, such as the 

inhibiting herbicides, the triazine herbicides, the PTO-inhibiting 

herbicides.

And so, it's been a culmination that's been building for years were 

you selected for herbicides as to weed biotypes that have been 

extremely problematic, and now it's represented within the 

(indiscernible) complex, as well as amaranth and pigweed family, 

both waterhemp and palmer amaranth. And so, there's a definite 

need.

I'll just share that on Friday, I had a phone call from somebody 

who is involved with the industry giving recommendations to 

growers. And they wanted me to provide them, what criteria do I 

give to the grower to determine if they just dig up the entire 

soybean field and try again because they applied all available 

herbicides to date this year, and they still have waterhemp that 

they were not able to control. And so they obviously need 

additional tools.

So we've gotten to this point where the previous herbicides that 

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Commenter Affiliation Concern/Issue

we've utilized are not working out, (indiscernible) herbicides 

resistance, and we need additional tools, and in some cases more 

herbicides, which sounds like more fuel on the fire, but I would 

contend that is probably the best solution we have to date until 

another alternative presents itself. But none have as of yet.

So we've gotten to this point in some ways because of our efforts 

to be more sustainable in crop productivity and crop production. I 

was part of an analysis looking at the sustainability of U.S. 

soybean production. That was a publication by CAS (ph),

Council for Cultural Science and Technology (ph), and I was the 

author for the part of weed management side. And that publication 

spoke towards the greatest component, at least towards 

sustainability, of soybean production in the U.S., its conservation 

tillage practices. And because we are reducing the amount of 

tillage that we use pre-plant or in the fall, or even row cultivation, 

that means we rely more heavily on herbicides today that we ever 

have. And so, it would be logical to expect that an outcome of that 

would be greater selection pressure for herbicide-resistant weeds. 

So it's not a surprise that in our efforts to be more sustainable in 

soil conservation practices, that we have greater challenges in how 

we utilize our herbicides.

Now, how do these two technologies fit, the 2,4-D and dicamba 

technology? Well, actually we've used these herbicides for 

decades. That has been mentioned by some of the growers as well 

as Mike Owen and Bob Wolf, who participated thus far. So we're 

really expanding their use window, so it allows greater flexibility 

utilizing the herbicides to provide a greater benefit in overall weed 

management, and I would say the sustainability or stability, if you 

will, of our weed management practices.

So I think they're a key component, and right now they're the only 

component that we have available because the discovery of new 

herbicides active ingredients, like that have come in the past 50 

years, that pipeline of new active ingredients has dried up

temporarily possibly. But we don't have any alternatives, so we're 

going back to the older herbicides that growers have decided that 

didn't provide as much benefit. And so these two technologies, 

Page 2-61
Commenter Affiliation Concern/Issue

2,4-D and dicamba, provide another -- some other options that I 

would suggest might be favored than some of the other 

alternatives that we might be considering, especially when it 

comes to conservation practices and some of the deep tillage that 

might be occurring in some areas because of these resisting weeds.

So the other thing I want to comment about is I have tested both 

the technologies that have been listed on ready to extend, and in 

the program, if you will, the herbicide program concept. Now, 

how we achieve weed control with these technologies in the

future, as stated before, it's not just a 2,4-D or a dicamba, and 

that's all you need like we did with squat (indiscernible), and soon 

won't develop resistance.

I think in most cases I've seen residual herbicides, which represent 

different herbicide modes of action that are utilized prior to 

planting and then after planting. And then other herbicides, that all 

provide solar (ph) activity. It might be glufosinate or glyphosates, 

around the liberty involved in the mixtures as well.

So what I have tested in my research on glyphosate-resistant 

waterhemp (indiscernible) and glyphosate-resistant marestail, with 

these technologies has been multiple herbicide modes of action to 

develop a more sustainable weed management program. So it's

not just based on a single herbicide active ingredient. It's more 

robust, so I think that it is a more sustainable approach to 

achieving a well-rounded IPM approach for how we manage our 

weeds. And those are the things I think are important because, as 

stated

before, 2,4-D or dicamba will not control all of our weeds. It's 

going to be required to involve other herbicides. And I think that is 

the part that's different than where we went through with the 

Roundup Ready system back in 1996 when it was released.

So moving forward over the next ten years, obviously weed 

management is going to get a lot more difficult because if we don't 

have other alternatives to glyphosate that are viable or another 

older herbicide like the PPO-inhibiting herbicides, we're going to 

continue to use those herbicides, and we're going to continue to 

Page 2-62
Commenter Affiliation Concern/Issue

get more resistance to those herbicides and create an even larger 

problems than what we have today.

So it's going to be a challenge to manage these until we get these 

tools that tell us as scientists be more -- that are able to develop 

these solutions. And as growers or crop consultants to devise a 

program on a field-by-field basis to be sustainable as much as 

possible, as well as being effective and profitable in wheat 

management and crop production.

Jim Broten Grower and past 

chairman, U.S. 

Grains Council

As you can see, the farmers across the nation all emphasize the 

importance of our needed to use both 2,4-D and dicamba. And to 

use it with glyphosate tolerance would just be fantastic. We are in 

a world market. We need it to feed the world, but we also need to 

be competitive. And we need all the advantages that we can have, 

and we need to encourage USDA to pass this quickly as they can.

Page 2-63
Appendix 3. Weed Management and Herbicide Use

Page 3-1
Weed Management and Herbicide Use

Weed control programs are important aspects of soybean and cotton production intended to 

prevent the establishment of plants other than the intended crop. In crop production systems, 

these plants, identified as weeds, are controlled using a number of tactics to maximize the 

production of food, fiber, and fuel (Green and Martin, 1996). The goal of weed management is to 

reduce weed populations, allowing for more efficient use of herbicides and other cultural 

practices to control weeds.

Each field has a finite amount of resources, i.e., light, nutrients, and moisture, available for the 

growth and development of crops. Weeds allowed to compete with crops can ultimately result in 

crop yield loss. Once the critical period of weed control (CPWC) has been reached, if weed 

control is delayed, the yield loss can increase fairly rapidly. Knezevic concluded that delaying 

the time of weed removal after the starting point of CPWC will cost soybean producers an 

average of 2% in yield loss per every leaf stage of delay (Knezevic et al., 2003). According to 

Iowa State University research, uncontrolled weeds of 3-4 inches in corn at the V-3 to V-4 

growth stage have been shown to decrease yields by about 3 bushels per acre per day 

(Rosenberg, 2013). For cotton, if weed control is implemented later than 30 days after crop 

emergence, it will result in a crop loss yield of greater than 1 % (Schutte et al., 2010).

Weeds species present varying degrees of competitiveness. Table 3-1 shows the potential yield 

losses associated with specific weed species present at two different densities. The impacts to 

yield are based on normal weather conditions and adequate soil moisture and assume that the 

weeds emerged with the crop. Crops under drought conditions or other stresses may have higher 

yield losses. According to the data, at higher densities annual broadleaf weeds impact yields 

more than annual grasses (Ontario Ministry of Agriculture and Food, 2009).

The degree of yield loss for a crop can be related to:

• Environmental conditions (e.g., temperature, moisture, etc.),

• The distribution of weed species within a given field;

• Weed density; and 

• The timing of weed emergence (i.e., weed height) relative to the crop growth stage

(Knezevic, 2007). 

Therefore, weed management programs should not only focus on minimizing weed density and 

yield reductions, they should also include approaches to minimize weed seed banks. Eliminating 

weeds before seed production diminishes contributions to the weed seed bank and provides the 

best assurance for improving future weed management.

Weed control programs vary by crop, weed problem, geography, and cropping system (e.g., notill, conventional-till, etc.). Many growers use a combination of weed control techniques,

including cultural, mechanical, and chemical. Practices that establish a dense, vigorous crop 

canopy quickly (e.g., higher seeding rates, optimum soil fertility, proper seedbed preparation, 

seeding depth) provide competition to smother weeds. 

The keys components to successful weed management are:

Page 3-2
• Knowing the exact identity of all weeds in the field; 

• Treating (if necessary) while the weeds are small; 

• Tailoring control measures to the type of weed and its size (Linker et al.). 

Although weed control typically involves an integrated approach that includes herbicide use, 

crop rotation, weed surveillance, and weed monitoring (Farnham, 2001; IPM, 2004; 2007; 

Hartzler, 2008; University of California, 2009), currently, herbicides are the most common and 

efficient tactic to manage weeds within agroecosystems (Gianessi and Reigner, 2007). Various 

strategies utilized for weed management are discussed in the following sections.

Chemical Control - Herbicides

Herbicides are chemicals that move into a plant and disrupt vital biological process. Herbicides 

have been the primary tactic used to manage weed communities in cotton and soybean since the 

mid-1960s and will continue to be an important feature of row crop weed management for the 

foreseeable future. One study, which examined aggregated data on crop yield losses and 

herbicide use, estimated that even if additional tillage and hand weeding labor replaced the use of 

herbicides, U.S. crop production would decline by 20 percent with a $16 billion loss in value if 

herbicides were not used (Gianessi and Reigner, 2007). Herbicide use is not regulated by APHIS 

but rather by EPA under FIFRA and its amendments.

Before selecting a herbicide program, growers should know what weeds are present or expected 

to appear, the soil texture and organic matter content, capabilities and limitations of the various 

herbicides, and how to best apply the herbicides (York and Culpepper, 2000). Additionally, 

when selecting an herbicide, a grower must consider, among other factors, whether an herbicide 

can be used on the crop (herbicides are registered by EPA for specific uses and crops), potential 

adverse effects on the crop, residual effects that can limit crops that can be grown in rotation, 

effectiveness on expected weeds, and cost.

To be effective, herbicides must (1) adequately contact plants, (2) be absorbed by plants, (3) 

move within the plants to the site of action without being deactivated, and (4) reach toxic levels 

at the site of action (Penn State Extention, 2013).

Herbicides are classified according to their effects on plants as either selective or nonselective.

Selective herbicides will kill weeds without significant damage to desirable plants. Nonselective 

herbicides kill or injure all when applied at an adequate rate (Penn State Extention, 2013).

Herbicide action is either contact or systemic. Contact herbicides kill only plant tissue contacted 

by the chemical. Systemic herbicides are absorbed from the point of application, either the roots 

or foliage, and move within the plant to other plant parts. Systemic herbicides may be effective 

against both annual and perennial weeds, but are particularly effective for control of established 

perennial weeds. However, systemic movement of an herbicide in perennial weeds can vary 

seasonally (NC State University, 1998).

Applications of herbicides to a crop or weed are described according to when they are applied:

• Pre-plant (i.e., burndown): applied to soil before the crop is planted. In burndown 

situations, there is no crop present requiring post-emergence selectivity if soil-residual 

Page 3-3
herbicide is a component of the burndown application. Burndown applications in both

cotton and soybean often incorporate glyphosate, dicamba, and 2,4-D and may include 

paraquat or glufosinate to control weeds prior to planting the crop.

• Pre-plant incorporated (PPI): for PPI, herbicides are applied to soil and mechanically 

incorporated into the top 2 to 3 inches of soil before the crop is planted.

• Pre-emergence: applied after the crop is planted, but prior to emergence of the crop. Preemergent herbicides are generally not effective after weeds have established.

• Post-emergence: applied after the weeds and crop emerges. Early post emergence 

application occurs when the crop has just emerged and the weeds are small. Postemergent herbicides selectively target weeds relative to the crop. The post materials have 

activity when applied to leaves and can be used over the top of crops if the crop is 

resistant to the active ingredient.

Most herbicides used as pre-plant and pre-emergent applications are residuals, herbicides that 

remain active for several weeks and theoretically work continuously after application. These 

types of herbicides are finding increasing use in the management of glyphosate-resistant weeds. 

(See Appendix 4, Herbicide Use Trends, for more details). Examples include acetochlor, 

trifluralin, metolachlor, metolachlor-S, pendimethalin, atrazine and alachlor. These herbicides 

work by controlling weeds before they germinate or emerge. Usually residual herbicides need to 

be activated by water (Hager and McGlamery, 1997). In rainfed crops, residual herbicides may 

fail to become activated during drought. The foliar product controls emerged weeds while the 

residual material controls weeds prior to germination or emergence.

When herbicides are applied, biochemical pathways that control the growth and development of 

plants are interrupted and plant death and injury occurs (Sosnoskie and Hanson). These 

biochemical pathways control the growth and development of plants; when herbicides are 

applied, these processes are constrained and plant injury and death will occur. Most herbicides 

bind to, and thereby block the action of, a specific enzyme. Herbicides are classified according to 

their mode of action, which is the overall manner in which the herbicide affects a plant at the 

tissue or cellular level. The Weed Science Society of America (WSSA) has classified herbicides 

by group number, based on their mode of action. Brief descriptions of these groups are provided 

(Sosnoskie and Hanson) :

Group 1: herbicides inhibit the action of acetyl CoA carboxylase (ACCase) needed for 

the synthesis of lipids. Grasses, but not broadleaf weeds, are affected.

Group 2: herbicides inhibit the action of acetolactate synthase (ALS) needed for the 

synthesis of three amino acids (isoleucine, leucine, and valine).

Group 3: herbicides inhibit cell division (mitosis inhibitors).

Group 4: herbicides are growth regulators. At low concentrations, they mimic the plant 

growth hormone auxin and are referred to as synthetic auxins. At high 

concentration they produce distinctive symptoms on broadleaf weeds; twisted 

and curled stems, malformed flowers, thickened or stunted roots, and cupped, 

strapped or otherwise deformed leaves. Grasses are usually resistant.

Page 3-4
Group 5, 6, and 7: herbicides inhibit photosynthesis leading to a buildup of highly 

reactive free radicals that damage chlorophyll and cell membranes.

Group 8: herbicides inhibit fatty acid and lipid biosynthesis but not ACCase (

Group 1).

Group 9: herbicides inhibit the action of the enzyme enolpyruvyl shikimate-3-phosphate 

synthase (EPSPS) needed for the synthesis of three aromatic amino acids 

(tryptophan, phenylalanine, and tyrosine) that are produced through the 

shikimate pathway.

Group 10: herbicides inhibit glutamine synthetase. These herbicides stop the conversion 

of glutamate and ammonia to glutamine which causes ammonia to accumulate 

in the plant, inhibiting photosynthesis and destroying plant cells.

Group 12: herbicides inhibit carotenoid biosynthesis. Lack of carotenoids results in 

destruction of chlorophyll, which is needed for plant photosynthesis.

Group 14: herbicides inhibit protopophyrinogen oxidase (PPO). PPO inhibitors block 

the production of chlorophyll and cause reactive molecules to form in the cell, 

resulting in the destruction of existing chlorophyll molecules, carotenoids and 

cell membranes.

Group 15: herbicides block mitosis by inhibiting the synthesis of very long chain fatty 

acids.

Group 20, 21, 29: herbicides inhibit the synthesis of cellulose needed for the synthesis 

of cell walls.

Group 22: herbicides inhibit photosystem I (PSI) forming reactive molecules that 

destroy lipids, eventually breaking down plant cell membranes.

Group 27: herbicides inhibit 4-hydroxyphenyl-pyruvate-dioxygenase needed for the 

synthesis of carotenoids.

Herbicides with a common chemistry are grouped into “families.” Also, two or more families 

may have the same site of action, and thus can be grouped into “classes.” Table 3-1 provides 

WSSA herbicide groups with information on modes of action, chemical families, and example 

active ingredients and herbicides.

Table 3-1. Herbicide Groups with Example Active Ingredients and Herbicides.

Site of 

Action 

Group 

(WSSA 

Group) Site of Action

Number of 

Resistant 

Weed 

Species in 

U.S. Chemical Family Active Ingredient Herbicide

Lipid 

Synthesis 

Inhibitors

1 ACCase 

Inhibitors 

(acetyl CoA 

carboxylase) 

15 Aryloxyphenoxy

propionate 

(“FOPs”)

fenoxaprop Puma

diclofop Hoelon

fluazifop Fusilade

quizalofop Assure II

Page 3-5
Site of 

Action 

Group 

(WSSA 

Group) Site of Action

Number of 

Resistant 

Weed 

Species in 

U.S. Chemical Family Active Ingredient Herbicide

Cyclohexanedione

(“DIMs”)

clethodim Select

sethoxydim Poast

Phenylpyrazoline

(“DENs”)

pinoxaden Axial XL

Amino Acid 

Synthesis 

Inhibitors

2 ALS Inhibitors 

(acetolactate 

synthase)

44 Sulfonylurea

(“SUs”)

chlorimuron Classic

foramsulfuron Option

halosulfuron Permit

iodosulfuron Autumn

nicosulfuron Accent

primisulfuron Beacon

prosulfuron Peak

rimsulfuron Resolve

thifensulfuron Harmony

tribenuron Express

metsulfuron Ally

triasulfuron Amber

chlorsulfuron Glean

sulfofsulfuron Maverick

mesosulfuron Osprey

Imidazolinone

(“IMIs”)

imazamox Beyond

imazaquin Scepter

imazapic Cadre

imazethapyr Pursuit

Triazoloyrmidine flumetsulam Python

chloransulammethylFirstRate

pyroxysulfam PowerFlex

diclosulam Strongarm

Triazolinones thiencarbazone Component 

of Caperno

Pyrimidinyl(thio)

benzoate

pyrithiobac Staple

Sulfonylaminocar

bonyltriazilonones

flucarbazone Everest

propoxycarbazone Olympus

9 EPSP 

Synthase 

Inhibitor

13 glyphosate RoundUp

Growth 

Regulators 

(Synthetic 

Auxins)

4

19

Specific Site 

Unknown

10 Phenoxy 2,4-D

2,4-DB Butyrac

MCPA

Benzoic acid dicamba Banvel

Carboxylic acid chlopyralid Stinger

fluroxypr Starane

picloram Tordon

Auxin 

Transport

0 Semicarbazone diflufenzopyr Component 

of Status

Photosynthesis 5 Photosynthesis 24 Triazine prometryn Caparol

Page 3-6
Site of 

Action 

Group 

(WSSA 

Group) Site of Action

Number of 

Resistant 

Weed 

Species in 

U.S. Chemical Family Active Ingredient Herbicide

Inhibitors

6

7

II Inhibitors 

(binding sites 

other than 6 

and 7)

atrazine Aatrex

simazine Princep

Triazinone hexazinone Velpar

metribuzin Sencor

Photosynthesis

II Inhibitors 

(binding sites 

other than 5 

and 7)

1 Nitrile bromoxynil Buctril

Benzodiazole bentazon Basagran

Photosynthesis 

II Inhibitors 

(binding sites 

other than 5 

and 6)

7 Ureas Lorox

Nitrogen 

Metabolism

10 Glutamine 

Synthesis 

Inhibitor

Phosphonic Acid glufosinate Liberty

Pigment 

Inhibitors

13

27

Diterpene 

Synthesis 

Inhibitors

1 Isoxazolidinone clomazone Command

HPPD 

Inhibitors

1 Isoxazole isoxaflutole Balance

Pyrazolone topramezone Impact

Triketone mesotrione Callisto

tembotrione Laudis

Cell 

Membrane 

Disruptors

14

27

PPO Inhibitors 2 Diphenylether acifluoron Blazer

fomasefen Reflex

lactofen Cobra

oxyfluorfen Goal

NPhenylphthalamid

e

flumiclorac Resource

flumioxazin Valor

Aryl triazinone sulfentrazone Spartan

carfentrazone Aim

fluthiacet-ethyl Cadet

Photosystem I 

Electron 

Diverter

5 Bipyridium paraquat Gramoxone 

Inteon

diquat Reglone

Seedling Root 

Growth 

Inhibitors

3 Microtubule 

Inhibitors

6 Dinitroaniline ethalfluralin Sonalan

pendamethalin Prowl

trifluralin Treflan

Seedling Shoot 

Growth 

8 Lipid 

Synthesis 

8 Thiocarbamate butylate Sutan +

EPTC Eradicane

Page 3-7
Site of 

Action 

Group 

(WSSA 

Group) Site of Action

Number of 

Resistant 

Weed 

Species in 

U.S. Chemical Family Active Ingredient Herbicide

Inhibitors

15

Inhibitors

Long-chain 

Fatty Acid 

Inhibitors

1 Chloroacetamide acetochlor Harness

alachlor Intrro

metalochlor Dual

dimethanamid Outlook

Oxyacetamide flufanacet Define

Pyrazole pyroxasulfone Zidua

Sources: (Armstrong, 2009; Glyphosate Stewardship Working Group, 2012).

Mechanical Weed Control – Tillage

Prior to planting, the soil must be stripped of weeds that would otherwise compete with the crop 

for space, water, and nutrients. Tillage is used to prepare a seedbed, address soil compaction, 

incorporate fertilizers and herbicides, manage water movement both within and out of a 

production field, and control weeds (Heatherly et al., 2009). Soil cultivation or tillage can be 

very valuable in many situations and should be considered as an alternate weed control practice 

where appropriate:

• Tillage serves as another way to control weeds and break certain weed patterns

• Tillage reduces complete reliance on herbicides

• Periodic tillage is a reliable cultural practice that also provides the benefits of removing 

trash build-up on the soil surface and levels ruts or rough spots in fields. 

Some form of conservation tillage is utilized by the majority of cotton and soybean growers.

Tillage can supplement chemical control (i.e., herbicides) and, in the case of light weed 

infestations, could provide sufficient control if used alone. Cultivation should be shallow to 

reduce crop root damage and to avoid breaking through any residual herbicide layer and bringing 

up untreated soil and weed seed. Use of tillage is optimized when weeds are small and should not 

be practiced for a week prior or after post-emergence herbicide application (York and Culpepper, 

2000).

Tillage can be a useful weed control method in some situations but may not be appropriate for all 

producers or areas. For example, tillage is not a good practice where soils are susceptible to 

erosion. Also, no-till soybean production is less successful in heavier, cooler soils more typical 

of northern latitudes (Kok et al., 1997; NRC, 2010).

Although tillage may control weeds, fuel costs and machine maintenance may represent 

substantial farm expenditures (NRC, 2010). This fact and the availability of herbicide technology 

have driven producers to increasingly adopt chemical management strategies. For example, in 

2012, 98 percent of soybean acreage was treated with synthetic herbicides (USDA-NASS, 2013).

Page 3-8
Cultural Weed Control

The successive planting of different crops on the same land is known as crop rotation. In 

contrast, the planting of the same crop on the same field in successive years is known as 

continuous crop production. Crop rotations are used to optimize soil nutrition and fertility, 

reduce pathogen loads, control volunteers (carry over in successive years), and limit the potential 

for weeds to develop resistance to herbicides (IPM, 2004; 2007; USDA-ERS, 2010).

Crop rotation is also a key element of successful weed control as it often reduces the populations 

of weeds that closely mimic the appearance of the young crop or are tolerant to herbicides often 

used in these crops. Crop rotation should be an integral component of a weed management 

program. Crop rotation generally leads to healthier crops that are more competitive with weeds. 

Moreover, certain weeds are more easily or more economically managed in one crop than in 

another. Additionally, crop rotation allows use of different herbicide chemistries on the same 

field in different years. This can prevent weed population shifts (changes in the species 

composition), avoid selection of herbicide resistant weeds, and help to keep the overall weed 

population at lower levels. 

Weed control in cotton is essential to maximize both yield and quality of cotton fiber. The slow 

early growth of cotton does not permit the crop to aggressively compete against weed species 

that often grow more rapidly and utilize the available water, nutrients, light, and other resources 

for growth (Smith and Cothren, 1999). Cotton yields can be reduced substantially if weeds are 

uncontrolled. Palmer amaranth has been reported to cause yield losses as high as 54 percent

(Morgan et al., 2001) and johnsongrass and barnyardgrass have been reported to reduce yields by 

90 percent and 98 percent, respectively (Vargas et al., 1996). Based on 2005 data, not using 

herbicides in cotton would result in an increased production cost of approximately $2.3 billion 

annually and an estimated yield loss of 27 percent (Gianessi and Reigner, 2006).

Weed-crop competition studies have demonstrated that the control of weeds during the first four 

to eight weeks after cotton planting is critical as weeds compete against the crop for water, 

nutrients, light and other resources necessary for growth (Smith and Cothren, 1999). The primary 

weed competition factors affecting yield loss potential are the weed species, weed density, and 

the timing/duration of weed competition. Cotton emergence and above ground growth is 

relatively slow during the first few weeks after planting, and does not permit the crop to 

aggressively compete against often more rapidly developing weed species (Smith and Cothren, 

1999). In addition, cotton is primarily planted using wide row spacing which delays crop canopy 

closure until layby stage of cotton and extends the window of weed-crop competition.

Crop rotation is a common practice on U.S. soybean fields, with approximately 95 percent of the 

soybean acreage planted in some form of a crop rotation system since 1991 (USDA-ERS, 2013).

A variety of crops may be rotated with soybean. In terms of acreage however, corn is the most 

commonly rotated crop. In a survey of major corn/soybean production states, corn and soybean 

were alternated on 72 to 80 percent of acreage, other rotations were grown on 16 to 20 percent of 

acreage, and soybean was grown continuously on 5 to 12 percent of acreage between 1996-2002 

(Sandretto and Payne, 2006). Other crops that may be rotated with soybean include wheat, 

cotton, rice, sorghum, barley, oats, and dry beans.

Page 3-9
The mitigation of pest cycles on an agricultural field is one of the primary benefits of crop 

rotation. The rotation of other crops following soybean production may disrupt pest life cycles 

that are more adapted to soybean field cultivation than other crops (Poole, 2004) through the 

creation of a relatively unstable agroecosystem (Weller et al., 2010). For example, crop rotation 

may encourage the use of alternative herbicides to further control broadleaf weeds in the same 

field in successive years that would not otherwise be used if continuous soybean was grown 

(Gunsolus, 2012).

Planting high-quality, weed-free crop seed is another cultural practice that keeps weed infestations 

low and easier to manage. One of the most effective means of reducing weed competition is to 

establish a highly competitive crop. This is best accomplished by planting good quality seed into 

a well-prepared seedbed with good fertility and soil moisture. Higher seeding rates can help 

establish a competitive crop and for some weed species delaying planting will allow for 

destruction of early flushes of weeds via tillage or non-selective herbicide application.

Integrated Weed Management

To reduce or mitigate against the selective pressures associated with the use of a single weed 

management practice, agronomists have recommended that growers adopt a diverse weed 

management strategy, also known as integrated weed management (IWM) (Norsworthy, 2012; 

HRAC, 2013). Effective IWM in crops usually involves a combination of cultural, mechanical, 

and chemical methods. Thus, IWM does not exclude any one management technique. IWM 

integrates practices such as crop rotation, cover crops, competitive crop cultivars, the judicious 

use of tillage, and targeted herbicide application to reduce weed populations and selection 

pressures toward the development of herbicide resistant weeds (Mortensen et al., 2012).

Resistance management begins with good agronomic practices, including the implementation of 

IWM to incorporate diverse weed control practices to reduce the frequency of herbicide 

applications and decrease selection pressure for herbicide resistant weed populations 

(Norsworthy, 2012). IWM programs that use herbicides from different groups, vary cropping 

systems, rotate crops, and use mechanical as well as chemical weed control methods will prevent 

the selection of herbicide-resistant weed populations (Powles, 2008; Green and Owen, 2011; 

Sellers et al., 2011; Gunsolus, 2012; HRAC, 2013).

The Herbicide Resistance Action Committee, an industry-based group, has developed the 

following general principles of weed resistance management:

• Apply integrated weed management practices. Use multiple herbicide sites-of-action 

with overlapping weed spectrums in rotation, sequences, or mixtures;

• Use the full recommended herbicide rate and proper application timing for the hardest 

to control weed species present in the field;

• Scout fields after herbicide application to ensure control has been achieved. Avoid 

allowing weeds to reproduce by seed or to proliferate vegetatively; and 

• Monitor site and clean equipment between sites.

Page 3-10
For annual cropping situations, the following recommendations of the Herbicide Resistance 

Action Committee (HRAC, 2013) are provided:

• Start with a clean field and control weeds early by using a burndown treatment or 

tillage in combination with a pre-emergence residual herbicide as appropriate;

• Use cultural practices such as cultivation and crop rotation, where appropriate; and

• Use good agronomic principles that enhance crop competitiveness.

References

Armstrong, J. "Herbicide How-to: Understanding Herbicide Mode of Action." Oklahoma 

Cooperative Extension Service, 2009. Vol. PSS2778. http://pods.dasnr.okstate.edu/docushare/dsweb/Get/Version11370/Pss2778web.pdf.

Farnham, D (2001) "Corn Planting." Cooperative Extension Service, Iowa State University of 

Science and Technology. Last Accessed: April 6, 

2011 http://www.extension.iastate.edu/publications/pm1885.pdf.

Gianessi, L and Reigner, N (2007) "The value of herbicides in U.S. crop production." Weed 

Technology. (21): p 559-66. 

Gianessi, LP and Reigner, NP (2006) "The Value of Herbicides in U.S. Crop Production 2005 

Update." CropLife America. http://croplifefoundation.files.wordpress.com/2012/07/2005-

update-report-and-data.pdf.

Glyphosate Stewardship Working Group. "GWC-3, Corn and Soybean Herbicide Chart." 

Glyphosate, Weeds, and Crop 

Series2012. http://www.glyphosateweedscrops.org/Info/MOA_060807.pdf.

Green, DJ and Martin, RJ (1996) "Dealing with Perennial Broadleaf Weeds in Conservation 

Tillage Systems." 

Green, JM and Owen, MD (2011) "Herbicide-resistant crops: Utilities and limitations for 

herbicide-resistant weed management." Journal of Agricultural and Food Chemistry. 59 

p 5819-29. 

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Page 3-13
Appendix 4. Herbicide Use Trends and Predicted XtendTM Use on 

Dicamba-Resistant Soybean and Cotton

Page 4-1
Herbicide Use Trends

The following information was presented in Monsanto’s Petitioner’s Environmental Report for 

Dicamba-Tolerant Soybean MON 87708 and Dicamba- and Glufosinate-Tolerant Cotton 

MON 88701 (ER) (citation). Additional information can be obtained in the ER, which will be 

posted by USDA as supplementary information to the Federal Register docket for this EIS:

http://www.regulations.gov/#!docketDetail;D=APHIS-2013-0043

Herbicide Use – Soybean

The use of herbicides has become an important part of managing weeds in soybean. 

Approximately 98 percent of the soybean acreage received an herbicide application in 2012 

(USDA-NASS, 2012b). The availability of herbicide-tolerant soybean products is an important 

aspect of weed management in U.S. soybean production. Herbicide-tolerant soybean was 

introduced to provide growers with additional options by improving crop safety (no herbicide 

damage to the crop) and improving weed control. In 2013, 93% of the U.S. soybean crop was 

herbicide-tolerant (USDA-ERS, 2013); almost all is glyphosate-tolerant. As a result and as 

shown by the 2012 use data shown in Table 4-1 (ER Appendix A, Table A-8 (Monsanto, 2013)), 

glyphosate is the most widely used herbicide, being applied on 98 percent of the soybean acreage 

in 2012, including for pre-plant burndown and post-emergence in crop applications (USDANASS, 2012b). In 2012, dicamba-treated acres in soybean accounted for only 87 thousand acres, 

or 0.07% of the total pre-emergent treated acres (USDA-NASS, 2012b). This is primarily 

because dicamba is phytotoxic to current soybean varieties and is therefore currently only 

labeled for application at timings that avoid contact with the growing plant, such as pre-plant 

treatments prior to planting, depending on rate and rainfall.

Over 35 different herbicide active ingredients are registered and available for use by soybean 

growers to control weeds. The ten most widely used alternative herbicides in soybean are listed 

in Table 4-2 (ER Table II.B-6 (Monsanto, 2013)). Alternative soybean herbicide use has almost 

doubled between 2009 and 2012. Integration of DT soybean into the glyphosate-tolerant soybean 

system and the subsequent use of dicamba will result in the displacement of some currently used, 

or foreseeable future use, non-glyphosate herbicides. Some non-glyphosate alternative herbicides

have less benign human health and environmental characteristics as compared to dicamba, and 

reduced agronomic flexibility due to soybean planting restrictions, rotational crop planting 

restrictions, the need for adequate soil moisture for activation, or the need to apply prior to 

planting to minimize crop injury.1

 The properties of these alternative herbicides are summarized 

in Appendices A and C (see ER (Monsanto, 2013)) to provide a baseline for comparison to 

dicamba use on DT soybean. 

Herbicide weed control programs in conventional soybean consist of pre-emergence herbicides 

used alone or in mixtures. Mixtures of two pre-emergence herbicides are used to broaden the 

1 In order to approve a new use of a herbicide EPA must conclude that the herbicide, when used according to the label, does 

not pose an unreasonable adverse effect to humans or the environment, and, in order to establish a tolerance for the use of a 

herbicide on a food or feed crop, find there is a reasonable certainty of no harm to human health from non-occupational 

(food, water and residential/recreational) exposures to the herbicide. Therefore, all alternative herbicides used in soybean 

production can be used safely, and do not pose an unreasonable risk to humans or the environment. 

Page 4-2

 
Table 4-1. Herbicide Applications Registered for Use in Soybean in 20121

Herbicide Chemical Family

Mode-of-Action 

(MOA)

PercentTreated

Acres

Total Area 

Applied

(Percent/MOA)

Quantity 

Applied

(1000 lb)

Total Quantity 

Applied

(1000 lb/MOA)

Glyphosate glycine EPSPS inhibitor 98 100 109,336 110,589 Sulfosate glycine 3 1,253

Pendimethalin dinitroanaline Tubulin inhibitor 2 4 1,559 2,865 Trifluralin dinitroanaline 2 1,306

Metribuzin triazinone PSII inhibitor 3 11 675 1,753 Sulfentrazone triazolinone 8 1,078

Chlorimuron-ethyl sulfonylurea

ALS inhibitor

11

26

187

590

Cloransulam-methyl triazolopyrimidine 4 83

Flumetsulam triazolopyrimidine * 14

Imazamox imidazolinone * 6

Imazaquin imidazolinone * 34

Imazethapyr imidazolinone 5 221

Rimsulfuron Imidazolinone * 4

Thifensulfuron sulfonylurea 5 31

Tribenuron-methyl sulfonylurea 1 10

Acetochlor chloroacetamide Cell division

inhibitor

1

9

635

Metolachlor chloroacetamide 7 5,683 6,553

Dimethenamid chloroacetamide 1 235

Paraquat bipyridilium PSI disruption 3 3 813 813

Page 4-3
Table 4-1 (continued). Herbicide Use in Soybean in the U.S. in 20121

Herbicide Chemical Family

Mode-of-Action 

(MOA)

PercentTreated 

Acres

Total Area 

Applied

(Percent/MOA)

Quantity 

Applied

(1000 lb)

Total Quantity 

Applied

(1000 lb/MOA)

Clethodim cyclohexenone

ACCase inhibitor

9

14

524

907

Fenoxaprop aryloxyphenoxy

propionate

* 7

Fluazifop-P-butyl aryloxyphenoxy 

propionate 3 195

Quizalofop-P-ethyl aryloxyphenoxy 

propionate 2 118

Sethoxydim cyclohexenone * 63

Acifluorfen diphenylether

PPO inhibitor

1

29

210

2,477

Carfentrazone-ethyl triazolinones * 1

Fluthiacet thiadiazole 2 10

Flumiclorac-pentyl N-phenylphthalimide 1 35

Flumioxazin N-phenylphthalimide 11 602

Fomesafen diphenylether 8 1,347

Lactofen diphenylether 2 192

Saflufenacil pyrimidinedione 4 80

2,4-D phenoxy Synthetic auxin 15 15 6,021 6,108 Dicamba benzoic acid * 87

Total 132,979

* Area receiving application is less than 0.5 percent.

1 Data derived from (USDA-NASS, 2013). Planted acreage for the nineteen primary soybean production states was 72.9 million acres, which 

represented 96.5% of total planted acres.

Source: Appendix A, Table A-8 (Monsanto, 2013),

Page 4-4
spectrum of control to both grasses and broadleaf weed species. Preemergence herbicides 

are followed by postemergence applications to control weeds that emerge later in the crop. 

Total postemergence weed control programs were seldom used in conventional soybean 

prior to 1995 when glyphosate-tolerant soybean was first introduced. Prior to glyphosatetolerant soybean, soybean planted in a no-till system would receive a preplant burndown

herbicide application for broad-spectrum control of existing weeds at time of planting, 

followed by different soil residual herbicides at planting and possibly still other herbicides 

applied postemergence to the crop and the weeds. In conventional soybeans, the typical 

herbicide program consisted of multiple soil residual herbicides applied preemergence to the 

crop and weeds and, possibly, other herbicides applied postemergence to the crop and 

weeds. Therefore, multiple herbicides and/or multiple applications were generally used in 

conventional and no-till non-glyphosate-tolerant soybean. The average number of herbicide 

applications per acre in soybean rose from 1.5 in 1990 to 1.7 applications in 1995, reflecting 

the use of at-plant and postemergence applications or two postemergence applications 

(Gianessi et al., 2002).

Table 4-2. Ten Most Widely Used Alternative Herbicides in U.S. Soybean Production 

in 2012

Herbicide Treated Acres 

(millions)1 Pounds Applied

(millions)1

2,4-D (acid, salts, and esters, 11.58 6.02

Flumioxazin 8.49 1.56

Imazethapyr 3.86 1.35

cloransulam-methyl 3.09 0.60

chlorimuron-ethyl 8.49 0.52

Fomesafen 6.18 0.22

Clethodim 6.95 0.19

pendimethalin 1.54 0.08

Tribenuron 0.77 0.04

flumiclorac-pentyl 0.77 0.01 1 (USDA-NASS, 2012b)

Source: Table II.B-6 (Monsanto, 2013)

Selective herbicides are designed to kill specific types of plants, usually grasses or broadleaf 

weeds, and have proven effective to reduce in-crop tillage or cultivation to control weeds in 

soybean production. The development of selective herbicides has progressed since the 

introduction of the first herbicide (2,4-D) for weed control in corn in early 1940s. Although 

the primary purpose of tillage is for seedbed preparation, tillage still is used to supplement 

weed control with selective herbicides in soybean production. Refer to Appendix A (see

(Monsanto, 2013)) for details on alternative herbicides used in soybean production.

In glyphosate-tolerant soybean, a total of 53 different non-glyphosate herbicides had been 

used in the preemergence (PRE) timing, while 37 different non-glyphosate herbicides had 

been used in the postemergence (POST) timing Table 4-3 (ER Table A-9 (Monsanto, 

2013)). 

Page 4-5
Table 4-3. Non-Glyphosate Herbicides Used in Glyphosate-Tolerant Soybeans from 

2002 to 2011a

Preemergence (PRE) Active 

Ingredients

Postemergence (POST) Active 

Ingredients

2,4-D

2,4-DB

Acifluorfen

Alachlor

Bentazone

Carfentrazone-ethyl

Chlorimuron 

Chlorsulfuron 

Clethodim

Clomazone

Cloransulam-methyl 

Dicamba

Diflufenzopyr 

Dimethenamid 

Dimethenamid-P

Ethalfluralin

Fenoxaprop

Fluazifop

Flufenacet

Flumetsulam

Flumiclorac 

Flumioxazin

Fluthiacet-methyl

Fomesafen

Glufosinate

Imazamox

Imazaquin

Imazethapyr

Iodosulfuron

Lactofen

Linuron

MCPA

Metolachlor

Metolachlor-S

Metribuzin

Metsulfuron

MSMA

Nicosulfuron

Norflurazon 

Paraquat

Pelargonic acid

Pendimethalin

Pyraflufen ethyl 

Quizalofop

Rimsulfuron 

Saflufenacil 

Sethoxydim

Simazine

Sulfentrazone 

Sulfosate

Thifensulfuron 

Tribenuron methyl 

Trifluralin

2,4-D

2,4-DB

Acetochlor

Acifluorfen

Alachlor

Bentazone

Carfentrazone-ethyl

Chlorimuron 

Clethodim

Cloransulam-methyl 

Dicamba

Dimethenamid 

Dimethenamid-P

Fenoxaprop

Fluazifop

Flumetsulam

Flumiclorac 

Flumioxazin

Fluthiacet-methyl

Fomesafen

Imazamox

Imazaquin

Imazethapyr

Lactofen

Linuron

Metolachlor

Metolachlor-S

Naptalam

Paraquat

Pelargonic acid

Pendimethalin

Pyraflufen ethyl 

Quizalofop

Sethoxydim

Sulfosate

Thifensulfuron 

Tribenuron methyl

a Unpublished market research data (Monsanto, 2012b)

Source: Table A-9 (Monsanto, 2013).

Herbicide Use – Cotton

Herbicides are used on essentially all (>99%) cotton acres, and in 2011 approximately 39 

million pounds of herbicides were applied pre- or postemergence in cotton production 

(Brookes and Barfoot, 2012; Monsanto, 2012b). According to 2010 market data2

, there were 

approximately 46.3 million herbicide-treated cotton acres. Herbicides were applied to 21.8 

million acres prior to the planting or emergence of cotton (preemergent) and to 24.5 million 

acres after the emergence of cotton (postemergent). For clarification, the market survey data 

counts one treated acre as the application of one active ingredient (a.i.) one time to an acre. 

If the same a.i. is applied a second time to that same acre or if two a.i.s are applied, it counts 

as two treated acres. USDA reports that 11.0 million acres of cotton were planted in 2010,3

so that the 46.3 million herbicide-treated cotton acres means that on average each planted 

2 Monsanto Company. 2011. Farmer Survey Data. St. Louis, MO.

3 USDA Statistics for crops and geographic regions are available at http://www.nass.usda.gov/index.asp.

Page 4-6

 
acre received at least 4 herbicide treatments. Cotton acres also received on average four 

treatments with herbicides during the 2011 growing season (USDA-ERS, 2012).

Herbicide-tolerant cotton is planted on the majority of U.S. cotton acres (73% in 2011), 

which allows for the postemergence in-crop use of glyphosate for control a broad spectrum 

of weeds. Glyphosate is the most widely-used herbicide in cotton, applied on 91% of cotton 

acres with an average of 2.4 applications per growing season (Monsanto, 2012b). In 2010, 

between 49 and 76% of the growers who plant glyphosate-tolerant (GT) cotton applied nonglyphosate herbicides prior to planting, at planting, or postemergence. Percentages varied 

among cropping systems, with 76% of GT cotton in a rotation system with GT soybean 

receiving non-glyphosate herbicide applications, whereas non-glyphosate herbicides were 

only applied 49% of the time in continuous cotton cropping systems (Prince et al., 2011a). 

Over 30 different herbicide active ingredients are registered and available for use by cotton 

growers to control weeds. Table 4-4 (ER Table A-33 (Monsanto, 2013)) provides a 

summary of the herbicide applications registered for use in cotton in 2011, demonstrating 

that herbicides are used on essentially all (>99%) cotton acres in the U.S (Brookes and 

Barfoot, 2012; Monsanto, 2012b). Approximately 39 million pounds of herbicide active 

ingredient were applied to cotton in 2011. 

Of these treatments, 50% (23.3 million acres) were made with glyphosate herbicides, and 

the remaining 50% of treatments were made with more than 25 other active ingredients. The 

number of glyphosate applications on an average cotton acre was between 2 and 3 

applications per year at an average rate of 2.0 pounds acid equivalent (a.e.) of glyphosate 

active ingredient per acre per crop year. 

Approximately 53% to 64% of growers used a non-glyphosate herbicide in addition to 

glyphosate in the glyphosate-tolerant cotton systems in 2005 (Givens et al., 2009a). In 2007,

approximately 39% of the growers often or always used herbicides with different modes-ofaction in the glyphosate-tolerant cotton systems (Frisvold et al., 2009). 

Non-glyphosate herbicides with different modes-of-action are also frequently used to 

provide residual weed control, improve control on certain weed species, and extend weed 

control or control resistant weed species (Prince et al., 2011a). The non-glyphosate

herbicides applied on cotton in 2011, included ALS inhibitors (trifloxysulfuron, 

pyrithiobac), longchain fatty acid inhibitors (acetochlor, metolachlor), microtubule 

inhibitors (pendimethalin, trifluralin), PSII inhibitors (prometryn, fluometuron, diuron), PPO 

inhibitors (flumioxazin, fomesafen), synthetic auxins (2,4-D, dicamba), glufosinate, MSMA 

and paraquat (Monsanto, 2012b).

. 

Page 4-7
Table 4-4. Herbicide Applications Registered for Use in Cotton in 20111

Herbicide Herbicide Family

Mode-ofAction 

(MOA)

Cotton 

Acres 

Treated 

(%)

Cotton 

Acres 

Treated 

per 

MOA 

Quantity 

Applied 

(1000 lb 

a.i. 2)

Total Quantity 

Applied/MOA 

(1000 lb a.i.2)

Glyphosate Glycine EPSPS 

inhibitor 73 73 20,015 20,015

Pendimethalin Dinitroanaline Microtubule 

inhibitor

16

40

1,964

5,043

Trifluralin Dinitroanaline 24 3,079

Diuron Urea

PSII 

inhibitor

15

34

1,727

3,737

Prometyrn Triazine 10 1,102

Fluometuron Urea 8 870

Linuron Urea <1 38

Acifluorfen Diphenylether <1 1

Carfentrazone Triazolinone

PPO 

inhibitor

<1

38

<1

856

Flumiclorac Nphenylphthalimide <1 <1

Flumioxazin Nphenylphthalimide 19 192

Fomesafen Diphenylether 17 626

Oxyfluorfen Diphenylether 1 36

Pyraflufen Phenylpyrazole <1 <1

2,4-D Phenoxy Synthetic 

Auxin

17

27

1,659

2,023

Dicamba Benzoic acid 10 364

Pyrithiobac Benzoate ALS 

inhibitor 14 21 113 120

Page 4-8
Table 4-4. (continued). Herbicide Applications Registered for Use in Cotton in 20111

Herbicide

Herbicide 

Family

Mode-ofAction 

(MOA)

Cotton 

Acres 

Treated 

(%)

Cotton 

Acres 

Treated 

per 

MOA 

(%)

Quantity 

Applied 

(1000 lb 

a.i. 2)

Total 

Quantity 

Applied/MOA 

(1000 lb a.i.2)

Thifensulfuron Sulfonylurea <1 <1

Thibenuron Sulfonylurea <1 <1

Trifloxysulfuron Sulfonylurea 6 6

Acetochlor Chloroacetamide Long-chain 

fatty acid 

inhibitor

8

25

1,502

4,587

Metolachlor Chloroacetamide 17 3,085

Norflurazon Pyridazinone Inhibition of 

carotenoid <1 <1 2 2

Paraquat Bipyridylium PhotosystemI-electron 10 10 735 735

Glufosinateammonium Phosphinic acid Glutamine 

synthesis 10 10 800 800

MSMA Organoarsenical Cell 

membrane 6 6 1,066 1,066

Clethodim Cyclohexanedione ACCase 

inhibitor

<1

<1

3

3

Fluazifop Aryloxphenoxy 

propionate <1 <1

Diflufenzopyr Semicarbazone Auxin 

transport <1 <1 3 3

Clomazone Isoxazolidinone Diterpene

synthesis <1 <1 <1 <1

Total 99.4 38,992

1 Updated version of Table VIII-9 of petition 12-185-01p_a1 (Monsanto, 2012a) with 2011 data (Monsanto, 

2012b). 2

lb a.i.= pounds active ingredient.

Source: Table A-33 (Monsanto, 2013).

Page 4-9
Dicamba is currently labeled for use in cotton although its use is limited to preplant 

applications due to cotton’s susceptibility to dicamba. Consequently, the average application 

rate preplant in cotton is 0.26 pounds of dicamba per acre with one application per season. 

Dicamba preplant use in cotton has been on the rise in recent years, increasing from 140,000 

acres in 2004, to 590,000 acres in 2008, and 1.4 million acres, or 9.6% of U.S. cotton acres, 

in 2011 (Monsanto, 2012b). This is primarily because it is a leading recommended herbicide 

for control of glyphosate-resistant marestail and Palmer amaranth in the Southeast and 

Midsouth region (McClelland et al., 2006; AgWatch, 2011; University of Georgia, 2012)

The ten most widely used alternative herbicides in cotton in 2010 are listed in Table 4-5 (ER 

Table B-18 (Monsanto, 2013)), compared to 2007 use. 

Table 4-5. Ten Most Widely Used Alternative Herbicides in U.S. Cotton Production

Herbicide 2007 Applications

(million lb)1

2010 Applications 

(million lb)1

Trifluralin 2.8 3.1

Diuron 1.3 1.3

Pendimenthalin 1.3 1.2

S-metolachlor 0.6 1.1

Prometryn 0.6 0.4

2,4-D, dimethylamine salt 0.3 0.4

Fluormeturon 0.3 0.4

MSMA 0.4 0.3

Fomesafen 0.05 0.2

2,4-D, ethylhexyl ester 0.1 0.1

1 (USDA-NASS, 2014)

Source: Table B-18 (Monsanto, 2013)

Soil residual herbicides play an important role in cotton weed management by providing 

control of a number of weeds species that continuously germinate in cotton prior to canopy 

closure (Wilcut et al., 2003). Soil residual herbicides, such as pendimethalin, trifluralin, 

diuron, fluometuron, acetochlor, and metolachlor, are applied to more than 40% of the 

current cotton acres (Monsanto, 2012b). In addition, many of the soil residual herbicides are 

limited by application restrictions, plant-back restrictions, the need for adequate soil 

moisture for activation, and the need to apply prior to planting or with hooded sprayers incrop to minimize crop injury. Approximately 20% of growers applied a fall residual 

herbicide to control weeds prior to planting the following spring, and 60% (continuous 

cotton system) to 75% (GR cotton/GR soybean rotation) applied a mixture of glyphosate 

and a synthetic auxin herbicide (2,4-D or dicamba) as a spring burndown application (Prince

et al., 2011a). Post emergent residual herbicides, such as metolachlor and acetochlor, were 

applied on over 25% of cotton acres in 2010 (Monsanto, 2012b). 

In glyphosate-tolerant cotton, a total of 38 different non-glyphosate herbicides had been 

used in the PRE timing while 40 non-glyphosate herbicides had been used at the POST 

timing (Table 4-6) (ER Table A-34 (Monsanto, 2013)).

Page 4-10
Table 4-6. Non-Glyphosate Herbicides Used in Cotton from 2002-2011

Preplant/preemergence Active Ingredients Postemergence Active Ingredients

2,4-D 2,4-D

2,4-DB Acetochlor

Alachlor Acifluorfen

Bromoxynil Alachlor

Carfentrazone-Ethyl Bromoxynil

Clethodim Carfentrazone-Ethyl

Clomazone Clethodim

Cyanazine Cyanazine

Dicamba Dicamba

Diflufenzopyr Dimethipin

Diuron Diuron

Fluazifop DSMA

Flumiclorac Fenoxaprop

Flumioxazin Fluazifop

Fluometuron Flumiclorac

Fomesafen Flumioxazin

Glufosinate Fluometuron

Lactofen Fomesafen

Linuron Glufosinate

Metolachlor Hexazinone

Metolachlor-S Lactofen

MSMA Linuron

Norflurazon Metolachlor

Oxyfluorfen Metolachlor-S

Paraquat Metsulfuron

Pendimethalin MSMA

Prometryn Oxyfluorfen

Pyraflufen Ethyl Paraquat

Pyrithiobac-Sodium Pelargonic Acid

Quizalofop Pendimethalin

Rimsulfuron Prometryn

Saflufenacil Pyraflufen Ethyl

Sethoxydim Pyrithiobac-Sodium

Sulfosate Quizalofop

Thifensulfuron Rimsulfuron

Tribenuron Methyl Sethoxydim

Trifloxysulfuron Sulfosate

Trifluralin Trifloxysulfuron

Trifluralin

Total 38 40

Source: Table A-34 (Monsanto, 2013).

Page 4-11
Further details on the use of non-glyphosate herbicides in cotton producing states can be 

found in Prince et al. (2011a; 2011b), where it is reported that approximately 50% of 

surveyed growers who did not have glyphosate-resistant weeds on their farm used a nonglyphosate residual and/or postemergence herbicide in the 2009 growing season. For 

growers who have on-farm herbicide-resistant weed populations, the percentage of growers 

was higher, with 72% to 75% reporting the use of non-glyphosate herbicides. Older studies 

report that approximately 40 to 50% of the growers utilizing glyphosate-tolerant crops 

indicate that applying herbicides with different modes-of-action in sequence, rotating 

herbicides with different modes-of-action across the season, or tank mixing glyphosate with 

other herbicide modes-of-action are effective management practices to minimize the 

evolution and/or development of glyphosate resistance (Powles et al., 1996; Diggle et al., 

2003; Beckie, 2006; Beckie and Reboud, 2009). The use of non-glyphosate herbicides in 

cotton production is expected to continue to increase as more growers adopt more 

diversified weed management strategies. Refer to Appendix A (see ER (Monsanto, 2013))

for details on alternative herbicides used in cotton production.

Volume Projections for Proposed New Uses of Dicamba

The following sections of Appendix 4 present Monsanto’s projections of the increases in 

dicamba usage volumes based on the proposed new dicamba application rates for DT 

soybean and cotton. Monsanto has submitted an application to EPA to amend current 

registrations of DGA salt formulation for new uses of dicamba on dicamba-resistant 

soybean and cotton. The application is currently being evaluated by the U.S. Environmental 

Protection Agency (EPA).

Details on and supporting information for Monsanto’s calculations can be found in the 

Environmental Report prepared by Monsanto (Monsanto, 2013) and posted by USDA as 

supplementary information to the Federal Register docket for this EIS:

http://www.regulations.gov/#!docketDetail;D=APHIS-2013-0043

Impact of DT Soybean Deregulation on Dicamba Usage 

Use of Low-Volatility DGA Salt of Dicamba – Proposed Changes in Dicamba 

Registration: Monsanto has submitted to EPA an application to amend EPA Reg. No. 524-

582 to register a new use pattern for dicamba on DT soybean. The current and proposed uses 

are summarized in Table 4-7 (ER Table IV.A-1 (Monsanto, 2013)).

Page 4-12
Table 4-7. Summary of Dicamba Uses on Soybean

Current Approved Uses Proposed Uses on DT soybean 

Application 

Timing

Maximum Single 

Application Rate

(lb a.e./acre)

Maximum 

Annual 

Application 

Rate

(lb a.e./acre)

Maximum 

Single 

Application 

Rate

(lb a.e./acre)

Maximum 

Annual 

Application 

Rate

(lb a.e./acre)

Pre-emergence 0.501

2.0

1.02

2.0

Post-emergence Not labeled

0.50 (V3) 

+ 

0.50 (R1/R2)3

Pre-harvest 

(7 days prior to 

harvest)

1.0 Not labeled

1

 14-28 day planting interval based on product application rate 2

 No planting interval 3

 In-crop application through V3 with a sequential application through R1/R2 growth stage as needed. Total of 

all in-crop applications from emergence up to R1/R2 is 1.0 lb a.e./acre.

Source: Table IV.A-1 (Monsanto, 2013).

In the pending application to EPA, Monsanto requested approval only for the low volatility 

DGA salt formulation of dicamba (U.S. EPA Reg. No. 524-582) for use on DT soybean, and 

has proposed that dicamba applications be limited to ground applications only (i.e., no aerial 

spraying), as well as proposing additional enforceable directions for use. Monsanto has also

requested the establishment of a tolerance for soybean forage and hay; no other revisions to 

the dicamba residue tolerances are necessary, including animal products such as meat and 

milk. 

Combination with Glyphosate-Tolerant Soybean. DT soybean is intended to be combined 

with glyphosate-tolerant soybean utilizing traditional breeding techniques. Soybean 

containing both DT soybean and glyphosate tolerance will allow the use of glyphosate and 

dicamba herbicides in a diversified weed management program, which includes the use of 

residual herbicides or other cultural practices, to control a broad spectrum of grasses and 

broadleaf weed species, and to sustain and complement the benefits and value of the 

glyphosate use in the glyphosate-tolerant systems. The combined system will support longterm sustainability of weed management in soybean and, in turn, support sustained, 

economic soybean production.

Inclusion of Potential Impacts from Herbicide Use: As discussed above, it is EPA’s 

regulatory authority under FIFRA to register pesticide products for their intended uses. EPA 

has sole authority to regulate the use of any herbicide. Nonetheless, for the reasons 

discussed above, this environmental report evaluates potential impacts of dicamba use 

associated with DT soybean on the human environment. 

Page 4-13
Anticipated Weed Management Recommendations for DT Soybean: Monsanto’s weed 

management system recommendations are shown in Table 4-8 (ER Table IV.A-2

(Monsanto, 2013)). The recommended use patterns for dicamba on DT soybean will vary 

across U.S. soybean growing regions based on differences in growth habits and 

competitiveness of certain glyphosate-resistant weed species. Option 1 would be 

recommended for more aggressive glyphosate-resistant weed species, such as Palmer 

amaranth (Amaranthus palmeri) and waterhemp (Amaranthus rudis). These weed species 

are very fast growing, highly competitive with crops, high seed producers, very densely 

populated, and germinate and emerge throughout the growing season (Keeley et al., 1987; 

Nordby et al., 2007; Fast et al., 2009; Sprague, 2012). Two sequential postemergence 

applications will generally be required to control late-season emergence of these weed 

species. However, low rainfall conditions and/or early crop canopy closure that can be 

associated with narrow row spacing of soybean can reduce late-season weed emergence and 

potentially reduce the number of dicamba postemergence applications. Option 2 would be 

used for less aggressive glyphosate resistant weed species, such as horseweed (Conyza 

canadensis), common ragweed (Ambrosia artemisiifolia) and giant ragweed (Ambrosia

trifida). 

These weed management system recommendations represent a high-end proposal for 

dicamba use associated with DT soybean when combined with glyphosate-tolerant soybean. 

The actual number of applications and timing of applications of dicamba or glyphosate that

the grower will make will vary depending on the specific weed spectrum, weed infestation 

levels, and the agronomic situation of the individual soybean field. Applying a residual 

herbicide preemergence in sequence with glyphosate plus dicamba postemergence, or tank 

mixing a residual herbicide with glyphosate plus dicamba postemergence could be 

considered as an alternative to two postemergence applications of glyphosate plus dicamba 

for season long weed control.

Table 4-8. Proposed Weed Management System Recommendations for DT Soybean 

Combined with Glyphosate-Tolerant Soybean. 

Application 

Timing

Conventional Tillage1 Conservation Tillage

(No-till or reduced till) 1

No GR 

Weeds

GR Weeds or Suspected 

GR Weeds2 No GR 

Weeds

GR Weeds or Suspected

GR Weeds2

Option 14 Option 25 Option 14 Option 25

Pre-emergence/

Pre-plant 

Burndown3 

Residual Residual Residual

Residual

plus

Glyphosate

plus

Dicamba

Residual

plus

Glyphosate

plus

Dicamba

Residual

plus

Glyphosate

plus

Dicamba

Post-emergence 1 

(V1-V3)

Glyphosate

plus

Dicamba

Glyphosate

plus

Dicamba

Glyphosate

plus

Dicamba

Glyphosate

plus

Dicamba

Glyphosate

plus

Dicamba

Glyphosate

plus

Dicamba

Post-emergence 2 

(V4-R1) ---

Glyphosate

plus

Dicamba

--- ---

Glyphosate

plus

Dicamba

---

Page 4-14
1 Anticipated average rate for dicamba is 0.38 pound a.e. per acre except for fields with glyphosate resistant 

(GR) species where a 0.5 pound a.e. per acre postemergence application rate will be recommended in most 

situations. See Appendix A (Monsanto ER (Monsanto, 2013)). 2 GR indicates glyphosate-resistant

3 Monsanto and academics recommend the use of soil residuals as part of a comprehensive weed resistance 

management program to ensure that at least two effective herbicide modes-of-action are used in soybean and to 

provide protection against additional resistance development to existing herbicides used in soybean 

production. When a residual plus glyphosate plus dicamba is recommended the residual may be applied 

separately or in tank mixture with glyphosate plus dicamba.

4 Option 1 would be used for more aggressive glyphosate resistant weed species, such as Amaranthus spp. 5 Option 2 would be used for less aggressive glyphosate resistant weed species, such as horseweed.

Source: Table IV.A-2 (Monsanto, 2013).

Potential Additional Dicamba Use. It is impossible to determine the exact amount of 

acreage on which DT soybean may be grown if deregulated. Projections on the annual 

application of dicamba used on DT soybean are based on market adoption rates and the 

dicamba use pattern on DT soybean. The maximum possible annual application of dicamba 

on DT soybean, based on 100% adoption of across all U.S. soybean acreage (75 million 

acres) and applications of dicamba at the maximum labeled rates (proposed at 2.0 lbs a.e. 

per acre per year), would be 150 million pounds dicamba (as acid equivalent or a.e.). 

However, as discussed below, the actual total anticipated application will be much lower.

For the purposes of this assessment, it is assumed that DT soybean will occupy 40% of the 

U.S. soybean acreage at peak penetration. This estimate is based on a number of factors: 1) 

the percentage of non-glyphosate herbicides currently used in glyphosate-tolerant soybean, 

2) current and historical use of dicamba in corn, 3) the development of glyphosate-resistant 

weeds in soybean cultivation areas, 4) the effectiveness of other non-glyphosate herbicides 

used in glyphosate-tolerant soybean, s; and 5) the foreseeable future introduction of new 

competitive biotechnology-derived traits in soybean.

Similarly the anticipated use patterns for dicamba on DT soybean will vary across U.S. 

soybean growing regions. This variability is dictated by growth habits and competitiveness 

of certain glyphosate-resistant weed species. As discussed above in Anticipated Weed 

Management Recommendations for DT Soybean, weed management recommendations will 

vary based on cultivation practices (i.e., tillage) and spectrum of glyphosate-resistant weeds 

present in the field. Based on weed management trials conducted across regions and weed 

spectrum a single early season in-crop application per year of dicamba at 0.38 lb a.e. per 

acre is expected on the majority of DT soybean acres. However, in no-till or conservation 

tillage soybean systems, an additional preplant application at 0.50 lb a.e. per acre could also 

be common practice, and in areas where glyphosate resistant weeds, especially Ambrosia 

and Amaranthus species, are present two in-crop applications at 0.5 lb a.e. each may be 

needed in some situations. See Appendix A (of Monsanto’s ER: (Monsanto, 2013)) for 

additional information supporting these anticipated use patterns.

Based on the anticipate dicamba application and use rate analysis summarized above, use of 

DT soybean on 40% of U.S. soybean acres would result in approximately 20.5 million lbs 

a.e. of dicamba applied to DT soybean annually (including preplant, preemergence and incrop applications), see Table 4-9 (ER Table IV.A-3 (Monsanto, 2013)). Currently 233,000 

lbs a.e. of dicamba are applied preplant to commercially available soybean (Monsanto, 

2012b).

Page 4-15
The potential increase in dicamba usage associated with DT soybean production is expected 

to displace, in part, some of the current herbicides used in soybean today. Dicamba offers a 

relative reduction of risk potential in comparison to some of the alternative non-glyphosate 

herbicides currently available to soybean growers (see Appendices E and F (Monsanto, 

2013)). Dicamba could be expected to conservatively replace approximately 21% of the 

projected total acres treated (TAT)4 for all non-glyphosate herbicides used in 

preplant/preemergence application timing and 56% of the projected TAT for all nonglyphosate herbicides used in postemergence application timing at peak dicamba use based 

on a projection that 40% of total planted soybean acres may be treated with dicamba 

following the introduction of DT soybean. At projected peak penetration of dicamba use in 

DT soybean, an increase in both total soybean acres treated and total pounds of nonglyphosate herbicides applied to soybean is projected, however estimated increases are 12% 

or less of the total herbicide use projections if DT soybean is not commercialized. 

4 The use of TAT provides a way to look at herbicide use that is independent of the various use rates of herbicides. If a 

herbicide is used more than once on an acre the TAT will reflect this multiple use, and consequently the TAT may exceed 

the number of crop acres planted. This provides a more complete view of herbicide use.

Page 4-16

 
Table 4-9. Projected Dicamba Use on DT Soybean 

Use Scenario

Dicamba 

Treated DT 

Soybean 

Acres 

(x1,000,000)

# PRE 

applications

PRE 

application 

rate 

(lb/acre 

a.e.)

# POST 

applications 

(V3 or V3 

& R1)

POST 

application 

rate 

(lb/acre 

a.e.)

Total lb 

of Dicamba

(000,000)a

Total 

Annual lb 

of Dicamba 

Maximum labeled use pattern, 100% adoption

75 1 1.0 2 0.50 150 150

Anticipated use pattern, 100% adoption

no-till acres b 30 1 0.5 1 0.38 26.4

conventional tillage acresc 45 1 0.38 17.1

Total 44

Anticipated use pattern, anticipated peak adoption of dicamba-treated DT soybean acres

no-till acres b 12d 1 0.5 1 0.38 10.6

conventional tillage acresc 18d 1 0.38 6.8

Resistant Amaranthus spp. acres e 5 2 0.31f 3.1

Total 20.5g

a Total lbs dicamba is calculated combining the lbs of dicamba PRE and POST, where the lbs dicamba used either PRE or POST is calculated by multiplying the 

number of applications by the application rate for the respective application timing. 

b No-tillage is practiced on 40% of the U.S. soybean acres (CTIC, 2007). c Conventional tillage acres also includes acres where reduced or minimum tillage is practiced and where it is assumed that a preemergent application of dicamba will 

be needed for weed control.

d Monsanto projects dicamba to be used on 40% of U.S. soybean acres (i.e., 30 million acres). e These acres are a subset of the no-till and conventional tillage acres. f

Monsanto anticipates that two POST applications at 0.5 lb/acre a.e. each will be needed on acres resistant with Amaranthus spp. Since these acres are a subset of the 

no-till and conventional tillage acres where a single POST application at 0.38 lb/acre dicamba a.e. has already been accounted for, the POST application rate is 

adjusted to avoid double counting of dicamba use on this subset of acres (i.e., adjusted POST application rate = 0.5 lb/acre – (0.38÷2) lb/acre).

Page 4-17
g This figure is slightly less than the estimate of 22 million pounds described in Section VIII.H of the petition because it subtracts out the single 0.38 lb/acre a.e. 

application already accounted for in the no-till and conventional tillage calculations.

Page 4-18
Impact of DGT Cotton Deregulation on Dicamba Usage 

The deregulation and commercialization of DGT cotton will expand dicamba use to in-crop 

postemergence applications to address hard-to-control and herbicide-resistant broadleaf weeds 

found in U.S. cotton production. The impact that DGT cotton will have on overall dicamba use 

will depend on the level of DGT cotton adoption by growers. Therefore, the extent of DGT cotton 

acreage following the deregulation of DGT cotton is difficult to forecast. Monsanto estimates that 

dicamba-treated acres could ultimately reach 50% of the total U.S. cotton acres. This estimate is 

based on a number of factors, including: (1) the percentage of non-glyphosate herbicides currently 

used in glyphosate-tolerant cotton; (2) the development of glyphosate-resistant weeds; (3) the 

effectiveness of other non-glyphosate herbicides used in the glyphosate-tolerant cotton weed 

control systems; (4) the perceived risk of offsite movement onto dicamba-sensitive crops; and (5) 

the foreseeable future introduction of new competitive GE-derived traits in cotton.

Approximately 53% to 64% of growers used a non-glyphosate herbicide in addition to glyphosate 

in the glyphosate-tolerant cotton systems in 2005 (Givens et al., 2009a). In 2007, approximately 

39% of the growers often or always used herbicides with different modes-of-action in the 

glyphosate-tolerant cotton systems (Frisvold et al., 2009). Regardless of the availability of DGT 

cotton, the future use of non-glyphosate herbicides is expected to increase in order to support the 

management of glyphosate-resistant weeds. Additionally, grower educational programs on weed 

resistance management conducted by industry and universities encourage the use of nonglyphosate herbicides with alternative modes-of-action in glyphosate-tolerant cropping systems as 

a proactive measure to minimize the potential for development of glyphosate-resistant weeds 

(Powles, 2008; Beckie et al., 2011). These programs will likely drive a further increase in nonglyphosate herbicides applied in cotton production. 

A second factor impacting dicamba-treated cotton acreage is the current and future need for 

control of glyphosate-resistant weeds. Glyphosate-resistant weeds have been identified in multiple 

states (Heap, 2014). When a glyphosate-resistant weed biotype has been confirmed to be present in 

a geographical area, growers in that area are advised proactively to implement glyphosate-resistant 

weed management programs to ensure effective control of the resistant weed biotype regardless of 

whether the weed species has been confirmed to be resistant on a grower’s farm. Therefore, the 

acreage in an area where responsive weed resistance management practices are implemented is 

potentially greater than the actual acres known to be impacted by glyphosate-resistant weeds. 

University weed scientists recommend that growers implement best management practices, 

including a non-glyphosate herbicide with a second mode-of-action, in their cropping systems to 

minimize the development and potential spread of glyphosate-resistant weeds in the future (Hurley

et al., 2009; Owen et al., 2011; Norsworthy, 2012; University of Georgia, 2012; Culpepper et al., 

2013).

It is anticipated that even in locations where glyphosate-resistant weeds are present, glyphosate 

will continue to be the base herbicide applied to DGT cotton as a combined trait product with 

glyphosate-tolerant cotton. Table 4-4 (ER Table A-33 (Monsanto, 2013)) provides a summary of 

the herbicide applications registered for use in cotton in 2011, demonstrating that herbicides are 

used on essentially all (>99%) cotton acres in the U.S (Brookes and Barfoot, 2012; Monsanto, 

2012b). Approximately 39 million pounds of herbicide active ingredient were applied to cotton in 

2011. These alternative herbicides will compete with dicamba and are expected to reduce the 

Page 4-19
potential dicamba use on DGT cotton integrated into the glyphosate-tolerant cotton systems and in 

future combined trait products containing DGT cotton. 

Another factor influencing the number of dicamba-treated cotton acres in the future will be the 

introduction of competing herbicide-tolerant traits in cotton. Currently, there are numerous 

herbicide-tolerant cotton products that are under regulatory review or have recently been 

authorized. This includes several products that have tolerance to multiple herbicides with different 

modes-of-action. These new GE-derived herbicide-tolerant cotton products are anticipated to be 

introduced in future years and will compete with Monsanto’s DGT cotton and glyphosate-tolerant 

cotton products, thereby further reducing the potential dicamba use in cotton.

Taking into consideration the above assessment, the potential acreage of DGT cotton treated with 

dicamba is estimated to be 50% of the U.S. cotton acres, and would result in approximately 5.2 

million pounds a.e. of dicamba applied to DGT cotton annually (including preplant, preemergence, 

and in-crop applications). Currently, 364,000 pounds of dicamba are applied preplant to 

commercially available cotton (see Table 4-4) (ER Table A-33 (Monsanto, 2013)). It is anticipated 

that dicamba applications will continue for all other currently labeled crops at the current annual 

level of approximately 3.8 million pounds (see Table 4-4) (ER Table A-33 (Monsanto, 2013)). 

Therefore, the addition of the estimated 5.2 million pounds of dicamba that would be applied to 

DGT cotton would result in a total U.S. dicamba use of approximately 9 million pounds annually.

Use of Low-Volatility DGA Salt of Dicamba – Proposed Changes in Dicamba Registration:

Monsanto has requested a registration from U.S. EPA for the expanded use of a low volatility 

diglycolamine (DGA) salt of dicamba on DGT cotton, limited dicamba application to ground 

application equipment, as well as proposing additional stewardship measures. Monsanto plans to 

further address the use of dicamba on DGT cotton with U.S. EPA to evaluate whether any 

additional measures may be appropriate to further address potential drift and offsite movement. 

Monsanto has also requested an increase in the dicamba residue tolerance for cottonseed, the 

establishment of a tolerance for cotton gin by-products, and the inclusion of DCSA in the residue 

definitions for both cottonseed and gin by-products. 

Monsanto submitted an application to EPA to amend Registration number 524-582, a lowvolatility DGA salt formulation, to remove all existing preemergence planting restrictions 

(application intervals, rainfall, and geographic) and to allow in-crop postemergence dicamba 

applications to DGT cotton containing varieties5

. Before any application of dicamba can be made 

onto commercially cultivated DGT cotton, the EPA must first approve a label describing the 

conditions of use of the herbicide on DGT cotton – including the appropriate application rates and 

timing, and other measures necessary to address potential impacts of dicamba drift and offsite 

movement. Dicamba can currently be applied to cotton in the U.S. as a preplant application, at 

least 21 days prior to planting. Following EPA approval of the dicamba label amendment, growers 

would be authorized to apply dicamba alone or in mixtures with glyphosate, glufosinate, or other 

registered herbicides for preplant or postemergence in-crop applications on DGT cotton. If the 

proposed label is approved by EPA, dicamba would be authorized to be applied up to 1.0 lb a.e. 

5 The current dicamba label approved by EPA prohibits dicamba preplant application on cotton west of the Rockies due to the 

potential for direct crop injury caused by dicamba in conjuction with the environmental conditions in this area. This restriction will 

not be included on the amended label for application of dicamba on DGT cotton since DGT cotton is tolerant to dicamba.

Page 4-20

 
per acre any time prior to cotton emergence, and postemergence in-crop up to 0.5 lbs a.e. per acre 

per application up through seven days prior to harvest. Maximum application amounts for dicamba 

would be 1.0 lb a.e. per acre for preplant/preemergence applications and 0.5 lb a.e. per acre per incrop application with the combined total not to exceed 2.0 lbs a.e. dicamba per year for all 

applications. The proposed application rates on DGT cotton would be less than or equivalent to 

rates for dicamba established for other uses in the dicamba RED including the 2.0 lbs a.e. dicamba 

per year for all applications (U.S. EPA, 2009). Based on Monsanto’s proposed dicamba label, 

aerial applications of dicamba will not be allowed on DGT cotton, thereby reducing spray drift 

potential (BASF, 2008). Monsanto has requested a registration from U.S. EPA for the expanded 

use of dicamba on DGT cotton, an increase in the dicamba residue tolerance from 0.2 ppm to 3 

ppm for cottonseed, the establishment of a tolerance of 70 ppm for cotton gin by-products, and the 

inclusion of DCSA in the residue definitions for cottonseed and gin by-products. No other 

revisions to the dicamba residue tolerances are necessary, including animal products such as meat 

and milk. Furthermore, the use of dicamba on DGT cotton does not present any new 

environmental exposure scenarios not previously evaluated in the RED and deemed acceptable by 

EPA. 

Use of Glufosinate – No Changes in Registration: The PAT(bar) protein acetylates the free 

amino group of glufosinate to produce non-herbicidal N-acetyl glufosinate, a known metabolite in 

glufosinate-tolerant plants (OECD, 2002). The use pattern and rate of glufosinate application on 

DGT cotton will follow the existing glufosinate-tolerant cotton uses outlined on the existing 

glufosinate herbicide label (Bayer Crop Science, 2007) and Monsanto has confirmed that 

glufosinate residues on DGT cotton treated with commercial glufosinate rates are below the 

established pesticide residue tolerances established by U.S. EPA for both cottonseed and gin byproducts (40 CFR 180.473). Consequently, Monsanto has not and will not pursue any changes in 

the glufosinate label or the established tolerances for its use on DGT cotton. Because there will be 

no changes in the use pattern and rate of glufosinate on DGT cotton from the current baseline, 

these aspects related to the associated use of glufosinate on DGT cotton are not discussed in detail 

in this analysis.

Combination with Glyphosate-Tolerant Cotton. DGT cotton is intended to be combined with 

glyphosate-tolerant cotton utilizing traditional breeding techniques. Cotton containing both DGT 

cotton and glyphosate tolerance will allow the use of glyphosate, dicamba, and glufosinate 

herbicides in a diversified weed management program, which includes the use of residual 

herbicides or other cultural practices, to control a broad spectrum of grasses and broadleaf weed 

species, and to sustain and complement the benefits and value of the glyphosate use in the 

glyphosate-tolerant systems. The combined system will support long term sustainability of weed 

management in cotton and, in turn, support sustained, economic cotton production.

Use of Multiple Herbicide-Tolerant Traits. In recent years, the development, in certain areas of 

the U.S., of glyphosate-resistant weeds, as well as shifts in broadleaf weed populations to species 

that are inherently more tolerant to glyphosate, have increased the use of non-glyphosate 

herbicides that work through different modes-of-action to achieve an acceptable level of weed 

control. As a result, multiple herbicide-tolerant traits are and have been developed to provide 

cotton growers with additional weed control options that will compete with DGT cotton. These 

herbicides and traits will be available at the time DGT cotton is introduced to the marketplace; 

thus, DGT cotton will compete for market share with approved herbicide tolerance traits, including 

Page 4-21
LibertyLink®, GlyTol®, and TwinLink combined-trait products, and new herbicide-tolerance 

traits that will be available in the foreseeable future. Growers will ultimately select weed control 

systems that fit the needs for their individual farming operation, such that some proportion of 

growers will choose to use DGT cotton-containing varieties integrated into glyphosate-tolerant 

cotton systems.

Anticipated Weed Management Recommendations for DGT Cotton: The expected use 

patterns for dicamba and glufosinate on DGT cotton will vary across U.S. cotton growing regions. 

This variability is dictated by the environment and weed spectrum variations across these regions. 

Monsanto’s recommendations for the Midsouth and Southeast regions are shown in Table 4-10 

(ER Table IV.A-4 (Monsanto, 2013)). In these regions, conventional tillage planted acres are 

expected to receive a single in-crop application per season of dicamba at 0.5 lbs a.e. per acre and 

conservation tillage or no-tillage acres are expected to receive two applications (one preplant 

application at 0.375 lbs a.e. per acre and one in-crop application at 0.50 lbs a.e. per acre). All acres 

in this region where glyphosate-resistant weeds are present, regardless of tillage, are expected to 

receive a single in-crop application of glufosinate as 0.53 lbs a.i. per acre. For the remaining acres 

where glyphosate-resistant weeds are not present, glyphosate will likely be used for control of lateemerging weeds. Dicamba and glufosinate use in eastern Texas and California is expected to be 

similar to that described for the Midsouth and Southeast regions.

In western Texas, New Mexico, Kansas, Oklahoma, and Arizona, dicamba is expected to be 

utilized more extensively than glufosinate for management of hard-to-control and/or glyphosateresistant weeds in DGT cotton. Glufosinate is considered less effective on the weed spectrum 

under the high temperature and low humidity environmental conditions in these regions (Bayer 

CropScience, 2011). The recommendations for these cotton growing areas are shown in Table 4-11

(ER Table IV.A-5 (Monsanto, 2013)). All acres are expected to receive one preplant application of 

dicamba (0.375 lbs a.e. per acre). Areas with glyphosate-resistant weeds are also expected to 

receive two in-crop applications of dicamba (0.50 lbs a.e./acre) per season, whereas areas without 

glyphosate-resistant weeds will only receive one in-crop application of dicamba (0.50 lbs 

a.e./acre). 

 LibertyLink, GlyTol, and TwinLink are registered trademarks of Bayer CropSciences.

Page 4-22

 
Table 4-10. Anticipated Weed Management Recommendations for DGT Cotton Combined 

with Glyphosate-Tolerant Cotton Systems for MO, AR, TN, AL, FL, GA, NC, SC, VA, LA, 

MS, eastern TX and CA.1,2

Application Timing Conventional Tillage Conservation Tillage 

(No-till or reduced till)

Preplant burndown 

and/or Preemergence Residual Dicamba + Glyphosate + Residual

Postemergence 1 Dicamba + Glyphosate + 

Residual3

Dicamba + Glyphosate + 

Residual

Postemergence 2 Glyphosate OR 

Glufosinate4,5

Glyphosate OR Glufosinate + 

Residual5,6

1 Recommendations modified from those presented in Petition 12-185-01p_a1. 2 Monsanto and academics recommend the use of soil residuals as part of a comprehensive weed resistance 

management program to ensure that two effective herbicide modes-of-action are used in cotton and to provide 

protections against additional resistance development to existing herbicides used in cotton production. 3 Residual recommended if GR weeds present.

4 Glyphosate recommended if no GR weeds present, glufosinate recommended in the presence of GR weeds. 5 Tank mixes of glyphosate and glufosinate will not be recommended, because reduced weed control has been 

observed with the glyphosate and glufosinate tank mix as compared to each individual herbicide (Dotray et al., 2011; 

Reed et al., 2011; Reed et al., 2012). 6 Glyphosate only if no GR weeds present, glufosinate and residual recommended in the presence of GR weeds.

Source: Table IV.A-4 (Monsanto, 2013).

Table 4-11. Anticipated Weed Management Recommendations for DGT Cotton 

Combined with Glyphosate-Tolerant Cotton Systems for Western TX, NM, KS, OK, 

and AZ 1,2

Application Timing Conventional Tillage Conservation Tillage 

(No-till or reduced till)

Pre-plant burndown 

and/or Pre-emergence

Dicamba + Glyphosate + 

Residual

Dicamba + Glyphosate + 

Residual

Post-emergence 1 Dicamba + Glyphosate Dicamba + Glyphosate

Post-emergence 2 Glyphosate ± Dicamba3 Glyphosate ± Dicamba3

1 Recommendations modified from those presented in Petition 12-185-01p_a1. 2 Monsanto and academics recommend the use of soil residuals as part of a comprehensive weed 

resistance management program to ensure that two effective herbicide modes-of-action are used in cotton 

and to provide protections against additional resistance development to existing herbicides used in cotton 

production.

3 Dicamba recommended when GR weeds present.

Source: Table IV.A-5 (Monsanto, 2013).

Page 4-23
Inclusion of Potential Impacts from Herbicide Use: As discussed above, it is EPA’s regulatory 

authority under FIFRA to register pesticide products for their intended uses. EPA has sole 

authority to regulate the use of any herbicide. Nonetheless, for the reasons discussed above, this 

environmental report evaluates potential impacts of dicamba use associated with DGT cotton on 

the human environment. Glufosinate will not be discussed in detail because glufosinate use on 

DGT cotton is equivalent to currently deregulated glufosinate-tolerant cotton and will be 

considered baseline. 

Potential Additional Dicamba Use: The maximum possible annual application of dicamba on 

cotton, with 100% adoption of DGT cotton across all U.S. upland cotton acreage (14.8 million 

acres)6 and applications of dicamba at the maximum labeled rates (proposed at 2.0 lbs a.e. per acre 

per year), would be 29.6 million pounds a.e. However, as discussed below, the actual total 

anticipated application will be much lower and will not likely be additive with the current 

application of herbicides currently used on cotton, as dicamba will displace some of the current 

herbicide usage in cotton.

As discussed above, in the Midsouth, and Southeast regions, conventional tillage-planted acres are 

expected to receive a single in-crop application per season of dicamba at 0.5 lbs a.e. per acre and 

conservation tillage or no-tillage acres are expected to receive two applications (one preplant 

application at 0.375 lbs a.e. per acre and one in-crop application at 0.50 lbs a.e. per acre). Dicamba 

use in East Texas and California is expected to be similar to that described for the Midsouth and 

Southeast regions. In West Texas, Kansas, Oklahoma, New Mexico, and Arizona dicamba is 

expected to be utilized more extensively than glufosinate for management of troublesome and/or 

glyphosate-resistant weeds. Glufosinate is considered less effective on the weed spectrum under 

the high temperature and low humidity environmental conditions in these regions (Bayer 

CropScience, 2011). In West Texas, Kansas, Oklahoma, New Mexico, and Arizona conventional 

tillage acres are expected to receive two in-crop applications of dicamba per season at 0.50 lbs a.e. 

per acre. No-till or conservation tillage cotton acres will realistically receive three applications per 

season (one preplant application at 0.375 lbs a.e. per acre and two in-crop applications at 0.50 lbs 

a.e. per acre. Assuming these anticipated applications and use rates of dicamba, and using the 

assumption that DGT cotton has 100% adoption across all U.S. cotton acres and conservation 

tillage systems are used on approximately 21% of the U.S. cotton acres (CTIC, 2008), dicamba use 

on DGT cotton would total approximately 10.5 million pounds. 

It is impossible to determine the exact amount of acreage on which DGT cotton may be grown if 

deregulated. A 100% adoption rate of DGT cotton among cotton growers is unrealistic. Monsanto 

estimates dicamba-treated acres could eventually reach 50% of the total U.S. cotton acres. Growers 

will ultimately select weed control systems that fit the needs for their individual farming 

operations such that some proportion of growers will choose to use DGT cotton integrated into the 

glyphosate-tolerant cotton systems. As discussed in ER Section II.B.2.d (See ER (Monsanto, 

2013)), growers produced herbicide-tolerant cotton on approximately 73% of U.S. cotton acres in 

2011, with almost all of this cotton being glyphosate-tolerant and approximately 3% being 

glufosinate tolerant. Growers currently producing herbicide-tolerant cotton are the growers most 

likely to adopt DGT cotton. Some of these growers may continue to grow the currently-available 

6 Based on approximately 14.8 million acres planted to cotton in 2011, see ER Table II.B-12 Monsanto (2013).

Page 4-24

 
types of herbicide-tolerant cotton, and use other herbicides for hard-to-control weeds. For 

example, approximately 53 to 64% of growers of glyphosate-tolerant cotton used a non-glyphosate 

herbicide in addition to glyphosate in their cotton crops in 2005 (Givens et al., 2009b). An 

additional factor influencing the number of dicamba-treated cotton acres in the future will be the 

introduction of competing herbicide-tolerant traits in cotton. 

Based on the dicamba application and use rate analysis summarized above, use of DGT cotton on 

50% of U.S. cotton acres would result in approximately 5.2 million lbs a.e. of dicamba applied to 

DGT cotton annually (including preplant, preemergence and in-crop applications). Currently 

364,000 lbs a.e. of dicamba are applied preplant to commercially available cotton (Monsanto, 

2012b).

It is anticipated that dicamba applications will continue for all other currently labeled crops at the 

current annual level of approximately 3.8 million pounds (Monsanto, 2012b). Therefore, the 

addition of the estimated 5.2 million pounds of dicamba that would be applied to DGT cotton 

would result in a total estimated U.S. dicamba use of approximately 9.0 million pounds annually. 

This does not include the additional amount from DT soybean (ER Section IV.A.1 (Monsanto, 

2013)).

The potential increase in dicamba usage associated with DGT cotton production is expected to 

displace a number of the current herbicides used in cotton today, particularly applications of 

fluometuron, fomesafen, MSMA, and paraquat. Dicamba offers a relative reduction of risk 

potential in comparison to some of the alternative non-glyphosate herbicides currently available to 

cotton growers (see Appendices E and F. Dicamba could be expected to conservatively replace 

approximately 34% of the projected total acres treated (TAT)7 for all non-glyphosate herbicides 

used in preplant/preemergence application timing and 37% of the projected TAT for all nonglyphosate herbicides used in postemergence application timing at peak dicamba use based on a 

projection that 50% of total planted cotton acres may be treated with dicamba following the 

introduction of DGT cotton. At projected peak penetration of dicamba use in DGT cotton an 

increase in both total cotton acres treated and total pounds of non-glyphosate herbicide active 

ingredient applied to cotton is projected, however estimated increases are 16% or less of the total 

herbicide use projections (16% for TAT and 12% of total pounds of active ingredient) if DGT 

cotton is not commercialized. 

Projected Dicamba Use (Total Pounds) on DGT Cotton: Based upon anticipated use patterns 

for dicamba on DGT cotton, projections on the number of dicamba TAT and total pounds of 

dicamba used on DGT cotton were determined for the combined PRE and POST application 

timing. The anticipated use projections represent a high-end estimate of the incremental dicamba 

use. Projected dicamba use at peak penetration is 10.8 million TAT (see ER Table A-40) and 5.2 

million pounds active ingredient Table 4-12 (Table A-41) (Monsanto, 2013). 

7 The use of TAT provides a way to look at herbicide use that is independent of the various use rates of herbicides. If a herbicide is 

used more than once on an acre the TAT will reflect this multiple use, and consequently the TAT may exceed the number of crop

acres planted. This provides a more complete view of herbicide use.

Page 4-25

 
Table 4-12. Estimated Dicamba Total lbs a.i. at Peak Dicamba Use on DGT Cotton

Cotton 

Growing 

Region

Tillage 

system

2011 

planted 

acres 

(000) 

available 

for 

dicamba 

use1

Planted 

acres at 

Peak (i.e.

15% 

reduction)

Planted 

conventional 

till acres 

(000) at Peak

Planted 

no till 

acres 

(000) at 

Peak

Conventional 

Tillage: # 

dicamba incrop 

applications

Conservation 

tillage: # 

dicamba apps 

in crop2

Conservation 

Tillage: # 

dicamba 

application 

preplant

Conventional 

Tillage: 

Dicamba 

rate in-crop

Conservation 

tillage: 

Dicamba 

Rate 

Preplant

Total lbs 

dicamba ai 

(000)

SE, Delta, 

E.TX

Conventional 2,310 1 0.5 1,155

Conservation 614 1 1 0.5 0.375 537

Total 3,441 2,924 1,693

CA

Conventional 214 1 0.5 107

Conservation 57 1 1 0.5 0.375 50

Total 319 271 157

W.TX, 

AZ, OK, 

NM, KS

Conventional 2,472 2 0.5 2,472

Conservation 657 2 1 0.5 0.375 904

Total 3,682 3,129 3,376

US Total 5,225

1 Acres from (USDA-NASS, 2012a). Note: Total planted acres for 2011 varies between USDA-NASS and the grower survey data used in previous tables. 

USDA-NASS was used to calculate dicamba TAT in the different cotton growing areas because only USDA-NASS planted acres is broken out by state. 2 Based on 21% of cotton acres being no till.

Source: ER Table A-41(Monsanto, 2013). 

Page 4-26
References:

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Bayer Crop Science. "Liberty® herbicide label." Bayer CropScience. Research Triangle Park, North 

Carolina: Bayer Crop Science, 2007.

Bayer CropScience. "Liberty Herbicide label." Research Triangle Park, North Carolina: Bayer 

CropScience LP, 2011.

Beckie, HJ (2006) "Herbicide-resistant weeds: Management tactics and practices." Weed Technology. 20 p 

793-814. 

Beckie, HJ; Harker, KN; Hall, LM; Holm, FA; and Gulden, RH (2011) "Risk assessment of glyphosate 

resistance in Western Canada." Weed Technology. 25 p 159-64. 

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Technology. 23 (3): p 363-70. 

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GM Crops and Food: Biotechnology in Agriculture and the Food Chain. 3 (2): p 129-

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Technology Information Center. Last Accessed: June, 14, 

2010 http://www.conservationinformation.org/pdf/National_Summary_2007_Amendment.pdf.

CTIC. "2008 amendment to the national crop residue management survey summary." West Lafayette, 

Indiana: Conservation Technology Information Center, 2008.

Culpepper, AS; Kichler, J; and York, AC (2013) "University of Georgia programs for controlling Palmer 

amaranth in 2013 cotton." University of Georgia Cooperative Extension. 

Page 4-27
Diggle, AJ; Neve, PB; and Smith, FP (2003) "Herbicides used in combination can reduce the probability of 

herbicide resistance in finite weed populations." Weed Research. 43 (5): p 371-82. 

Dotray, P; Keeling, W; and Johnson, J. "Synergistic/antagonistic effects of glyphosate and glufosinate in 

tank mixture in GlytolTM plus LibertyLink® cotton." College Station, Texas: Texas A&M 

University, AgriLIFE Research, 2011.

Fast, BJ; Murdock, SW; Farris, RL; Willis, JB; and Murray, DS (2009) "Critical timing of Palmer 

amaranth (Amaranthus palmeri) removal in second-generation glyphosate-resistant cotton." 

Journal of Cotton Science. 13 p 32-36. 

Frisvold, GB; Hurley, TM; and Mitchell, PD (2009) "Adoption of best management practices to control 

weed resistance by corn, cotton, and soybean growers." AgBioForum. 12 p 370-81. 

Gianessi, LP; Silvers, CS; Sankula, S; and Carpenter, JE (2002) Plant biotechnology: Current and 

potential impact for improving pest management in U.S. agriculture. An analysis of 40 case 

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(2009a) "A grower survey of herbicide use patterns in glyphosate-resistant cropping systems." 

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Givens, WA; Shaw, DR; Johnson, WG; Weller, SC; Young, BG; Wilson, RG; Owen, MDK; and Jordan, D 

(2009b) "A grower survey of herbicide use patterns in glyphosate-resistant cropping systems." 

Weed Technology. 23 p 156-61. 

Heap, I "The International Survey of Herbicide Resistant Weeds." www.weedscience.com.

Hurley, TM; Mitchell, PD; and Frisvold, GB (2009) "Weed management costs, weed best management 

practices, and the Roundup Ready weed management program." AgBioForum. 12 p 281-90. 

Keeley, PE; Carter, CH; and Thullen, RJ (1987) "Influence of planting date on growth of Palmer amaranth 

(Amaranthus palmeri)." Weed Science. 35 p 199-204. 

McClelland, MR; Smith, KL; and Norsworthy, JK. "Managing glyphosate-resistant horseweed in 

conservation-tillage cotton production: Final summary and recommendations." Fayetteville, 

Arkansas: University of Arkansas Agricultural Experiment Station, 2006. Vol. AAES Research 

Series 552.

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Monsanto (2012a) "Petition for the Determination of Nonregulated Status for Dicamba and GlufosinateTolerant Cotton MON 88701." Submitted by Marianne Malven, Registration Manager. Monsanto 

Company. St. Louis, MO. http://www.aphis.usda.gov/brs/aphisdocs/12_18501p.pdf.

Monsanto. "Unpublished grower survey data performed by a contracting agency." St. Louis, Missouri: 

Monsanto Company, 2012b.

Monsanto (2013) "Petitioner's Environmental Report for Dicamba-Tolerant Soybean MON 87708 and 

Dicamba and Glufosinate Tolerant Cotton MON 88701." 

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Lafayette, Indiana: Purdue Extension, Purdue University, 2007.

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management in GlytolTM + LibertyLink® cotton." San Juan, Puerto Rico. 

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glyphosate/glufosinate-tolerant cotton." Charleston, South Carolina. 

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Page 4-30
Appendix 5. Common Weeds in Cotton and Soybean

Page 5-1
Common Weeds in Cotton and Soybean

Weeds are simply plants growing in areas where their presence is undesired by humans (Baucom 

and Holt, 2009). Plants that colonize frequently disturbed environments have evolved with 

characteristics or mechanisms that allow them to survive conditions in agricultural environments. 

Weedy plants typically exhibit early germination and rapid growth from seedling to sexual 

maturity, have the ability to reproduce sexually and asexually, and therefore are well adapted to 

agricultural fields (Baucom and Holt, 2009).

The presence of weeds in cotton and soybean fields is a primary detriment to productivity.

Weeds are the most important pest complex in agriculture, impacting yields by competing with 

crops for light, nutrients, and moisture. In addition to taking valuable resources from crops, 

weeds can introduce weed seed or plant material to a crop, thereby reducing the market grade of 

the crop.

Additionally, weeds can harbor insects and diseases; weeds also can interfere with harvest, 

clogging and causing extra wear on harvest equipment (Loux et al., 2008). For example, some 

winter annuals have been found to serve as alternative hosts for the soybean cyst nematode, a 

pest that affects soybean yields in the U.S.

Effective weed management involves an understanding of weed biology and of weed 

management strategies. This section provides an overview of weed types, the weed seed bank, 

and the timing and occurrence of weeds. Also described are the types of weeds that occur in corn 

and soybean. Weed management is discussed in Appendix 3.

Weed Classification

Weeds are classified according to their life cycle, as annuals, biennials or perennials. Weeds are 

also classified as broadleaf (dicots) or grass (monocots). Weeds can reproduce by seed, rhizome 

(underground creeping stems), or other underground part (e.g., buds, bulbs).

An annual is a plant that completes its lifecycle in one year or season and reproduces only by 

seed. Annuals can be further differentiated into summer or winter annuals. Summer annuals 

appear in the spring or early summer and die prior to or by the first frost, producing seeds within 

the same growing season. These weeds grow rapidly, strongly competing with crops for 

resources, and can outgrow and shade slower-growing crops.

Summer annuals can be further categorized into three groups: small-seeded summer annual 

broadleaf weeds, large-seeded summer annual broadleaf weeds, and summer annual grass weeds 

(Schonbeck, 2010). Some small-seeded summer annual broadleaf weeds include pigweeds, 

common lambsquarters, common purslane, galinsoga, and smartweeds. Commonly found largeseeded summer annual broadleaf weeds include velvetleaf, common cocklebur, and 

morningglory. Summer annual grass weeds have small to medium sized seeds and include 

foxtail, crabgrass, and goosegrass.

Winter annuals typically emerge in late summer or early fall, but can also germinate as late as 

early spring. Usually these weeds over-winter as small seedlings and set seed in the spring. 

These weeds have little effect on warm season crops. Common winter annuals include purple 

Page 5-2
deadnettle, henbit, field pennycress, shepherd’s-purse, and chickweed (Schonbeck, 2010; Mock

et al., 2011).

Biennials have a life cycle of two years or seasons. After persisting as low-growing vegetation 

during their first season, biennial weeds overwinter, then flower and produce seeds in their 

second growing season. Examples of biennial weeds are burdock, bull thistle, poison hemlock, 

and wild carrot.

Perennials are plants that live for more than two years and are typically categorized as simple or 

creeping or invasive perennials. Canada thistle, bermudagrass, common milkweed, common 

pokeweed, dandelion, Johnsongrass are examples of perennial weeds (Penn State University, 

2009; Mock et al., 2011).

Weed Seed Bank

An important concept in weed control is the seed bank which is the reservoir of seeds that are on 

the soil surface and scattered at different depths in the soil. The soil weed seedbank determines

the size and species composition of the weed community within a growing season (Norsworthy, 

2012). Under favorable conditions, these seeds have the potential to germinate and emerge, 

creating weed pressure (i.e., competition) in crops. The weed seed bank contains recently 

dropped seeds, older seeds mixed into the soil, tubers, bulbs, rhizomes, and other vegetative 

structures. Climate, soil characteristics, shifts in agricultural management practices, such as 

tillage, crop selection, and weed management practices, affect the density and species 

composition of the seed bank within a given field (Davis et al., 2005; May and Wilson, 2006; 

Buhler et al., 2008).

The majority of seeds in the weed seed bank come from the weeds that have grown and set seed 

in the field. Wind, water, animals, and birds can carry seeds, adding to the weed seeds already 

present. Also, manure or other material (e.g., mulch, feed, soil) transported by humans or farm 

equipment from other locations can be indirect sources of weed seed (Renner, 2000).

Agricultural soils can contain thousands of weed seeds and a dozen or more vegetative weed 

propagules per square foot (Menalled and Schonbeck, 2013). Annual weeds produce large 

numbers of seeds. For example, a pigweed plant can shed at least 100,000 mature seeds and one 

lambsquarters plant can produce more than 50,000 seeds (Renner, 2000). If left untended and 

without crop competition, giant ragweed can produce approximately 10,000 seeds, common 

waterhemp 70,000 seeds, and waterhemp 100,000 seeds, or more, per plant. Larger-seeded 

broadleaf weeds are not as prolific in comparison to small-seeded summer broadleaf weeds, but 

seed production is still high, with a few hundred to a few thousand per plant (Schonbeck, 2010).

It has been observed that weeds in agricultural fields produce less seeds as a result of 

competition from the crop, damage from herbicides, and other factors, although these weed still 

produce high numbers of seeds that can affect production (Buhler et al., 1997). Effective weed 

control is required to limit the number of weed seeds entering the soil seed bank that will 

contribute to sustained competition with the crops into subsequent growing seasons.

Although seedbanks are made up of numerous weed species, generally only a few species will 

comprise 70 to 90 percent of the total seed bank (Wilson, 1988; Buhler et al., 1997; Renner, 

Page 5-3
2000). For example, common lambsquarters (Chenopodium album) is the dominant weed seed in 

many field soils in the north central region of the U.S. (Michigan) (Renner, 2000). A second 

smaller group of weed species may represent 10 to 20 percent of the seed bank (Buhler et al., 

1997).

Additionally, only a fraction of the seeds in a weed seed bank germinate and grow each year. 

Birds, rodents, insects, and other animals typically will consume available weed seeds found on 

the soil surface. Some seeds may decay or become unviable in the soil; other seeds may 

germinate but will die. Some seeds can remain dormant in the soil for long periods of time.

When changes in the cropping system change, creating conditions that are suitable for 

germination and development of a particular weed species, that species can respond rapidly, 

becoming non-dormant and establish itself in the cropping system (Renner, 2000; Durgan and 

Gunsolus, 2003; May and Wilson, 2006; Steckel et al., 2007). It is estimated that less than 10% 

of the weed seeds in the soil are non-dormant and able to germinate within a season. The 

remaining dormant seeds thereby serve to extend the longevity of the seed bank (Renner, 2000; 

PhysicalWeeding, 2009). For example, summer annuals can remain viable for years, even if 

buried deeper in the soil, while the larger broadleaf seeds can remain viable for decades 

(Schonbeck, 2010).

The majority of weeds grow from seeds in the top two inches of soil with the most significant 

numbers emerging from only the top one inch of soil (PhysicalWeeding, 2009). In general, most 

small-seeded weeds (e.g., foxtail, pigweed) germinate and emerge within the upper half inch of 

the soil surface. The large-seeded summer annual broadleaf weeds are usually found in soils 

below the surface layer (about 0.5 to 2 inches below the surface) and can germinate from soil 

depths of 1.5 inches or more. Summer annual grass weeds germinate predominantly from the top 

inch of soil. Generally, tillage brings these seeds to the surface, where they rapidly grow in 

response to light. The effects of different forms of tillage on the prevalence of weed species are 

discussed further, below.

Weed populations change in response to agricultural management decisions. Collectively, 

management decisions will impart selection pressures1 on the present weed community, resulting 

in weed shifts on a local level (i.e., field level). These weed shifts occur regardless of what the 

selection pressure may be and may result in changes in weed density or weed diversity (Reddy 

and Norsworthy, 2010; Weller et al., 2010). Weed shifts are generally most dramatic when a 

single or small group of weeds increases in abundance at the expense of other weed populations, 

potentially dictating the primary management efforts of the grower.

The vertical distribution of weed seeds in the soil is primarily influenced by the tillage system 

used.2 These resulting changes in the distribution of the weed seeds in the weed seedbank will 

1 Selection pressure may be defined as any event or activity that reduces the reproductive likelihood of an individual 

in proportion to the rest of the population of that one individual. In agriculture, selection pressure may be imparted 

by any facet of management in the production of a crop, including the type of crop cultivated, strategy of pest 

management, or when and how a crop is planted or harvested.

2

Tillage represents a mechanical means of weed control and is generally characterized by the amount of remaining 

in-field residue and may be classified as conservation (>30 percent), reduced (15-30 percent), or intensive (0-15 

percent) CTIC (2008)

Page 5-4

 
impact weed emergence and the resulting weed population in farm fields (Renner, 2000). As 

shown in Figure 5-1, the practice of no-till results in a majority of the weed seeds remaining at or 

near the soil surface where they have been deposited (Renner, 2000; Shrestha et al., 2006; 

Menalled and Schonbeck, 2013). In no-till fields with more seeds at the surface, a greater 

diversity of annual and perennial weeds species may occur (Baucom and Holt, 2009). Winter 

annuals thrive in soil that is undisturbed from late summer or fall through early summer the 

following year which is best provided by no-till systems. Similarly, biennial weeds are prevalent

in fields that have been no-till for several years, as they need undisturbed soil for two 

consecutive growing seasons.

Under reduced tillage systems (such as chisel plowing), approximately 80 to 90 percent of the 

weed seeds are distributed in the top four inches, with the majority found at depths ranging from 

two to four inches. Summer annual grass weeds germinate predominantly from the top inch of 

soil with prevalence in shallow and reduced tilled fields (Curran et al., 2009). With recent 

increased rates of conservation tillage, there has been an observed decrease in large-seeded 

broadleaf weeds and an increase in perennial, biennial, and shallow-emerging annual grasses, 

small-seeded broadleaves, and winter annual weed species in those fields (Green and Martin, 

1996; Durgan and Gunsolus, 2003; Norsworthy, 2012). The growth and spread of some perennial 

species that reproduce by spread of underground structures (e.g., rhizomes) may be encouraged 

by no-till or conservation tillage system which allows these structures to remain undisturbed 

(Buhler et al., 2008; Baucom and Holt, 2009; Curran et al., 2009).

Source: (Shrestha et al., 2006)

Figure 5-1. Vertical Distribution of Weed Seeds in the Soil Profile at Depths of 0 to 2 

inches, 2 to 4 inches, and 4 to 6 inches Affected by Different Tillage Regimes

90%

27%

12%

9%

66%

25%

1% 7%

63%

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

No-till Chisel Plow Moldboard Plow

Percent Seeds (%)

Tillage System

4-6

2-4

0-2

Soil 

Depth 

(in)

Page 5-5
Weed seeds become buried approximately four to six inches below the surface as a result of 

increasing tillage (Menalled and Schonbeck, 2013). As fewer weeds can germinate when buried,

weed diversity tends to decline and annual large-seeded broadleaves are more prominent 

(Norsworthy, 2012).

These shifts in weed species necessitate changes in weed management strategies. Tillage 

practices must be regularly changed, in a manner similar to that of other agricultural production 

practices, to prevent buildup of any particular species or group of weeds in the soil seedbank.

Weed Emergence/Timing

In addition to weed density, the timing of weed emergence affects how they compete with the 

cotton or soybean crop and influences the level of crop yield loss. The critical period of weed 

control (CPWC) is the time during which weeds must be controlled to prevent yields losses. The 

key components defining CPWC are 1) knowing when weeds need to be removed and 2) when 

the crop becomes dominant (Boerboom, 2000). Weeds emerging before the CPWC may not 

impact crop yields if those weeds are controlled by the start of the CPWC. Weed competition 

occurring after the end of the CPWC will not affect yield (Boerboom, 2000; Knezevic, 2007). In 

particular, early in the growing season, the critical period of weed competition is most affected 

by: 1) how competitive the different weed species are, 2) the density of weeds, and 3) the relative 

time of weed emergence (Boerboom, 2000).

In contrast to other crops, including corn and soybean, cotton emergence and above ground 

growth is relatively slow during the first few weeks after planting. The slow early growth of 

cotton does not permit the crop to aggressively compete against weed species that often grow 

more rapidly (Smith and Cothren, 1999). Weeds in cotton are controlled through the diversified

use of various cultural, mechanical, and chemical methods (Hake et al., 1996). Historically, 

mechanical tillage and hand-weeding were the most important tools in cotton weed control due 

to the limited application window afforded to most chemical applications. Today with the advent 

of GE cotton, approximately 38% of the total cotton acres are post-plant cultivated. In fields 

classified as employing conventional tillage systems, over 50% cotton acres are cultivated for 

weed control (USDA-ERS, 2012).

Due to the biology and planting practices of cotton, in the U.S., whereby complete crop canopy 

closure is at times never achieved, herbicides are used at multiple intervals throughout the entire 

growing season on essentially all (>99%) the cotton acres in the U.S. (Brookes and Barfoot, 

2012; Monsanto, 2012).

In soybean, the later that weeds emerge, the less impact they will have on yield, although weeds 

emerging later can have a negative influence on seed quality and harvest efficiency (Prostko, 

2013). Soybean plants withstand early season weed competition longer than corn because the 

soybean canopy closes earlier (Boerboom, 2000). The extent of canopy closure restricts the light 

available for weeds and other plants growing below the soybean. In addition, canopy closure 

occurs more quickly when soybean is drilled or planted in narrow rows (Boerboom, 2000; 

Bradley, 2006); however, in some studies it has also been observed that, depending on factors 

such as weed species, environmental conditions (i.e., rainfall amounts) and soybean cultivar, 

soybeans are able to compete with weeds with no resulting yield reduction (Krausz et al., 2001). 

Page 5-6
Place et al. have determined that larger soybean seeds produce a larger canopy more quickly and 

are, therefore, more successful at outcompeting weeds (Place et al., 2011). Full-season soybean 

planting is preferable during the drier late spring conditions; however, summer annual weed 

emergence often occurs at this same time, resulting in a high level of weed interference with 

soybean emergence and establishment (DeVore et al., 2013).

Common Weeds in Cotton and Soybean

Weed species emerge in a particular order throughout the year with each species having one or 

more periods of high emergence. The initial emergence date can vary from year to year, but the 

order stays relatively constant. Figure 5-2 shows the relative emergence of common weed 

species found in summer annual crops such as soybean and cotton. Weed emergence timing can 

dictate which weeds will be the most problematic for or be more easily controlled by a specific 

crop production or weed management practice (Buhler et al., 2008). Weed management is 

discussed in Appendix 3.

Page 5-7
Table 5-1. Summary of Problem Weeds Affecting Cotton and Soybean

Source: (Monsanto, 2013)

Notes:

Green: Weeds managed in both corn and soybean 

Yellow: Weeds primarily managed in corn 

Blue: Weeds primarily managed in soybean

Broadleaf Weeds Grass Weeds

Cotton + 

Soybean Cotton Soybean

Cotton + 

Soybean Cotton Soybean

Browntop millet Bindweed Wild buckwheat Barnyard grass Bermuda grass Fall Panicum

Cutleaf primrose Black 

nightshade Burcucumber Crabgrass Crowfoot grass Quackgrass

Florida 

beggerweed

Common 

cocklebur Canada thistle Cupgrass Large crabgrass

Florida pusley Common 

lambsquarter Chickweed Johnsongrass

Foxtail Common 

purslane Cockeburr Goose grass

Ground Cherry Common 

ragweed Copperleaf hophorn Broadleaf signal grass

Hemp sesbania Devil’s claw Dandelion

Henbit Hairy 

Nightshade

Honeyvine 

milkweed

Horseweed Junglerice Eastern black 

nightshade

Jimson weed Palmer 

amaranth Hairy nightshade

Kochia Red 

Sprangletop Wild oats

Lambsquarter Russian thistle Common pokeweed

Morning Glory Shepardspurse Wild proso millet

Mustard Smellmelon Common ragweed

Nutsedge Sprangletop Giant ragweed

Palmer pigweed Spurred anoda Field sandbur

Prickly sida Texas 

blueweed Shattercane

Pigweed Volunteer 

peanut

Venice mallow

Sicklepod Volunteer 

corn Volunteer cereal

Smart weed Field 

bindweed Waterhemp

Spurge Horse 

purslane Tropic croton

Sunflower Woolyleaf 

bursage

Texas millet Silverleaf 

nightshade

Velvet leaf

Volunteer Corn

Page 5-8
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evolutionary ecology and crop and weed science." New Phytologist. (184): p 741-43. 

Boerboom, C (2000) "Timing Postemergence Herbicides in Corn and 

Soybeans." http://www.soils.wisc.edu/extension/wcmc/proceedings/3B.boerboom.pdf.

Bradley, KW (2006) "A Review of the Effects of Row Spacing on Weed Management in Corn 

and Soybean." http://www.plantmanagementnetwork.org/pub/cm/review/2006/weed/.

Brookes, G and Barfoot, P (2012) "Global impact of biotech crops: Environmental effects, 1996–

2010." GM Crops and Food: Biotechnology in Agriculture and the Food Chain. 3 (2): p 

129-37. http://www.landesbioscience.com/journals/gmcrops/article/20061/.

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Weed Management." Weed Science. 45 (3): p 329-

36. http://www.jstor.org/stable/4046027.

Buhler, DD; Hartzler, RG; Forcella, F; and Gunsolus, JL (2008) "Relative emergence sequence 

for weeds of corn and 

soybeans." http://www.extension.iastate.edu/Publications/SA11.pdf.

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Conservation Technology Information 

Center. http://www.ctic.purdue.edu/media/pdf/National%20Summary%202008%20(Ame

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Curran, WS; Lingenfelter, DD; and Garling, L (2009) "An Introduction to Weed Management 

for Conservation Tillage Systems - Conservation Tillage Series Number 

Two." http://pubs.cas.psu.edu/freepubs/pdfs/uc126.pdf.

Davis, AS; Renner, KA; and Gross, KL (2005) "Weed seedbank and community shifts in a longterm cropping systems experiment." Weed Science. 53 (3): p 296-306. Last Accessed: 

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DeVore, JD; Norsworthy, JK; and Brye, KR (2013) "Influence of Deep Tillage, a Rye Cover 

Crop, and Various Soybean Production Systems on Palmer Amaranth Emergence in 

Soybean." Weed Technology. 27 (2): p 263-70. Last Accessed: 

2013/12/04 http://dx.doi.org/10.1614/WT-D-12-00125.1.

Durgan, BR and Gunsolus, JL (2003) "Developing Weed Management Strategies that Address 

Weed Species Shifts and Herbicide Resistant 

Weeds." http://appliedweeds.cfans.umn.edu/pubs/03pub01.pdf.

Green, JD and Martin, JR (1996) "Dealing with Perennial Broadleaf Weeds in Conservation 

Tillage 

Systems." http://www.ag.auburn.edu/auxiliary/nsdl/scasc/Proceedings/1996/Green.pdf.

Hake, SJ; Kerby, TA; and Hake, KD (1996) "Preparation for the new crop season - Fall/winter." 

Cotton Production Manual. Davis, California: University of California Division of 

Agriculture and Natural Resources. p 6-14. 

Knezevic, S (2007) "Timing Weed Control in Corn to Get the Most 

Effect." http://cropwatch.unl.edu/archive/-

/asset_publisher/VHeSpfv0Agju/content/891332.

Krausz, RF; Young, BG; Kapusta, G; and Matthews, JL (2001) "Influence of weed competition 

and herbicides on glyphosate-resistant soybean (Glycine max)." Weed Technology. 15 p 

530-34. http://www.bioone.org/doi/abs/10.1614/0890-

037X(2001)015%5B0530:IOWCAH%5D2.0.CO%3B2.

Loux, M; Stachler, J; Johnson, W; Nice, G; and Bauman, T (2008) "Weed Control Guide for 

Ohio Field Crops " Ohio State University 

Extension. http://ohioline.osu.edu/b789/index.html.

May, M and Wilson, R. "Chapter 14: Weeds and Weed Control. Pgs. 359–386." Sugar Beet. Ed. 

Draycott, A.P. Oxford, United Kingdom: Blackwell Publishing Ltd., 2006. 474 pgs. Vol. 

World Agricultural Series.

Menalled, F and Schonbeck, M (2013) "Manage the Weed Seed Bank—Minimize "Deposits" 

and Maximize "Withdrawals"." http://www.extension.org/pages/18527/manage-theweed-seed-bankminimize-deposits-and-maximize-withdrawals.

Mock, VA; Creech, EJ; Johnson, B; Faghihi, J; Ferris, VR; Westphal, A; and Bradley, K (2011) 

"Winter Annual Weeds and Soybean Cyst Nematode Management With a Guide for 

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Identifying Known Weed Hosts." http://www.extension.purdue.edu/extmedia/WS/WS36.pdf.

Monsanto. "Unpublished grower survey data performed by a contracting agency." St. Louis, 

Missouri: Monsanto Company, 2012.

Monsanto (2013) "Petitioner's Environmental Report for Dicamba-Tolerant Soybean MON 

87708 and Dicamba and Glufosinate Tolerant Cotton MON 88701." 

Norsworthy, JK, Ward, S. M., Shaw, D. R., Llewellyn, R. S., Nichols, R. L., Webster, T. M., 

Bradley, K. W., Frisvold, G., Powles, S. B., Burgos, N. R., Witt, W. W., and Barrett, M. 

(2012) "Reducing the Risks of Herbicide Resistance: Best Management Practices and 

Recommendations." Weed Science. (Special issue): p 31-

62. http://www.bioone.org/doi/abs/10.1614/WS-D-11-00155.1.

Penn State University (2009) "An Introduction to Weed Management for Conservation Tillage 

Systems." http://pubs.cas.psu.edu/freepubs/pdfs/uc126.pdf.

PhysicalWeeding (2009) "Information: Integrated Weed 

Management." http://physicalweeding.com/information/index.html.

Place, GT; Reberg-Horton, SC; Carter, TE; and Smith, AN (2011) "Effects of soybean seed size 

on weed competition." Agronomy Journal. 103 p 175-

81. http://www.ars.usda.gov/research/publications/publications.htm?SEQ_NO_115=2581

70&pf.

Prostko, E (2013) "Soybeans Weed Control 

" http://www.caes.uga.edu/commodities/fieldcrops/soybeans/documents/2013GeorgiaSoy

beanProductionGuide.pdf.

Reddy, K and Norsworthy, J (2010) "Glyphosate-Resistant Crop Production Systems: Impact on 

Weed Species Shifts." Glyphosate Resistance in Crops and Weeds. Hoboken, NJ: John 

Wiley & Sons, Inc. p 213-33. 

Renner, KA (2000) "Weed Seedbank 

Dynamics." http://www.msuweeds.com/assets/ExtensionPubs/E2717.pdf.

Schonbeck, M. "Know the Weeds." eXtension.com, 

2010. http://www.extension.org/pages/18540/know-the-weeds.

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Shrestha, A; Lanini, T; Wright, S; Mitchell, J; and Vargas, R "Conservation Tillage and Weed 

Management." 

Smith, CW and Cothren, JT (1999) Cotton: Origin, history, technology, and production. New 

York, New York: John Wiley and Sons, Inc. 

Steckel, LE; Sprague, CL; Stoller, EW; Wax, LM; and Simmons, FW (2007) "Tillage, Cropping

System, and Soil Depth Effects on Common Waterhemp (Amaranthus rudis) Seed-Bank 

Persistence." Weed Science. 55 (3): p 235-39. Last Accessed: 

2013/12/04 http://wssajournals.org/doi/abs/10.1614/WS-06-198.

USDA-ERS (2012) "Crop production practices for cotton: National." 

Weller, S; Owen, M; and Johnson, W (2010) "Managing Glyphosate-resistant Weeds and 

Populations Shifts in Midwestern U.S. Cropping Systems." Glyphosate Resistance in 

Crops and Weeds. Hoboken, NJ: John Wiley & Sons, Inc. p 213-33. 

Wilson, R. (1988). ed.^eds. Biology of weed seeds in the soil. Boca Raton, FL: CRC Press. Print.

Page 5-12
Appendix 6. Herbicide Resistance

Page 6-1
Herbicide Resistance

Not unlike other agronomic practices, herbicide use may impart selection pressures on weed 

communities, resulting in shifts in the weed community that favor those weeds that do not 

respond to the herbicide used (Owen, 2008). Herbicide resistance is described by the Weed 

Science Society of America as the “inherited ability of a plant to survive and reproduce 

following exposure to a dose of herbicide normally lethal to the wild type” (WSSA, 2011b). The 

shift to herbicide resistance in plants is largely a function of the natural selection of herbicideresistant traits and is strongly related to the repeated use of one or a limited number of herbicides 

(Durgan and Gunsolus, 2003; Duke, 2005).

Individual plants within a species can exhibit different responses to the same herbicide rate. 

Initially, herbicide rates are set to work effectively on the majority of the weed population under 

normal growing conditions. Genetic variability, including herbicide resistance, is exhibited 

naturally in normal weed populations, although at very low frequencies. When only one 

herbicide is used year after year as the primary means of weed control, the number of weeds 

resistant to that herbicide compared to those susceptible to the herbicide may change as the 

surviving resistant weeds reproduce. With no change in weed control strategies, in time, the 

weed population may be composed of more and more resistant weeds.

Both the increased selection pressure from the extensive use of glyphosate associated with 

glyphosate-tolerant crops along with the subsequent reduction in the use of other herbicides and 

changes in weed management practices (i.e., conservation tillage or no-till) have resulted in weed 

population shifts and increasing glyphosate resistance among some weed populations (Owen, 

2008; Duke and Powles, 2009). Glyphosate-resistant crops themselves do not influence weeds 

any more than non-transgenic crops. It is the weed control tactics chosen by growers that create 

selection pressure that ultimately over time changes these weed communities and may result in 

the selection of herbicide-resistant weeds (Owen, 2008).

History of Weed Resistance to Herbicides and its Development

One of the earliest selective chemical herbicides to be used in agriculture was 2,4-D, a synthetic 

auxin, whose commercial use began in 1945 (Burnisde, 1996). Use of 2,4-D in corn was 

successful in controlling broadleaf weeds such that in the mid-1950s 2,4-D was applied to nearly 

one-half of all U.S. corn acres (Knake, 1996). Within 12 years, the first herbicide resistance to 

2,4-D was reported in spreading dayflower in a Hawaiian sugarcane field (Commelina diffusa) in 

1957 (see report in (Sellers et al., 2011; Isaac et al., 2013)).

Simazine was the first triazine to be used commercially in 1956. In 1958, the herbicide atrazine 

was first registered for weed control in corn in the U.S. Similar to what had occurred with 2,4-D, 

triazines were used extensively in the 1960s and common groundsel resistant to triazine 

herbicides was discovered in Washington in 1970 (Buhler, unknown). Regardless of the

occurrence of resistant weeds, atrazine was, and still is, an extremely effective herbicide due to 

its broad spectrum, low cost, and flexible timing of applications (CropLife International, 2012).

ALS inhibitors or Group 2 herbicides were introduced in the mid-1980s and became extensively 

used in soybeans. With its broad-spectrum weed control, residual activity, and flexibility in 

Page 6-2
application timing, the Group 2 herbicides became popular in the late 1980s and early 1990s. For 

example, by the early-1990s, PursuitTM, containing the ALS herbicide imazethapyr, was used on 

more than 75 percent of the soybeans in Iowa (Tranel and Wright, 2002). The widespread use of 

Group 2 herbicides resulted in the rapid selection of ALS-resistant waterhemp. By the mid1990s, Group 2 resistant waterhemp was so widespread that the industry essentially stopped 

recommending Group 2 herbicides for this weed (Hartzler, 2013).

Sales of glyphosate began in 1974 and it became one of the most commercially successful and 

dominant herbicides in the U.S. (Duke and Powles, 2008). There are several reasons for the 

success of glyphosate in the market and the corresponding market sector penetration of 

glyphosate-tolerant crops since their introduction in the mid-late 1990s. Glyphosate: 1) works 

non-selectively on a wide range of plant species; 2) is a relatively low-cost herbicide; 3) 

enhances no-till farming practices; and 4) has minimal animal toxicological and environmental 

impact (Duke and Powles, 2008; Owen, 2008; Duke and Powles, 2009).

The widespread adoption of glyphosate-tolerant soybean, in combination with an increased 

reliance on glyphosate, has been related to the adoption of no-till cultivation which depends on 

controlling weeds without tillage. Glyphosate tolerant soybean also led to a simplification in 

weed control compared to past practices, reduced input and labor costs associated with the 

cultivar and glyphosate use, and increased flexibility in herbicide application timing (Lorenz et 

al., 2006).

Most instructive are the events leading to the development of glyphosate resistance in weeds in 

the U.S. The previous history of glyphosate use for 20 years did not result the selection of 

herbicide-resistant weeds. As a result, industry promoted the view that widespread glyphosate 

use was unlikely to result in the selection of glyphosate resistant weeds (Bradshaw et al., 1997),

despite the fact that resistance to other herbicides, such as 2,4-D were being reported (see history 

in (Mithila et al., 2011)). The first case reported, glyphosate resistant rigid ryegrass, was 

documented and confirmed in Australia in 1996 (Powles et al., 1998), over twenty years after 

glyphosate first began to be used in agriculture.

Herbicide-resistant crops were introduced in 1996 with glyphosate-resistant soybean rapidly 

adopted by growers. As glyphosate went off patent in 2000, increased usage of glyphosateresistant crops was facilitated by the low price of the herbicide. Tank mixes for separate activity 

against grasses and broad-leaf weeds were not needed when glyphosate could be used for weed 

control. In the mid-1990s, 51% of growers were using three, four or more herbicides for soybean 

weed control (cited in Gianessi et al. (2008)) or about three overall in 1995 (USDA-ERS, 1997). 

With the availability of glyphosate and glyphosate-resistant crops, herbicide applications could 

be reduced in many situations. 

The efficacy of post-applications of glyphosate became clear, with weed control often not 

requiring a pre-application for good control (Reddy, 2001). If a grower needed additional weed 

control for effectiveness or flexibility, a pre-application of glyphosate and a post-glyphosate 

application were as effective and cost less than a pre-application with a non-glyphosate residual 

herbicide followed by post-application of glyphosate (Reddy, 2001). Increasing glyphosate 

applications resulted in a decline of the sales and use of most other herbicides. The earliest U.S.

glyphosate resistance in a GE crop was found in horseweed, Conyza canadensis, in Delaware 

Page 6-3
soybean in 2000 (Heap, 2013). Increasing exposure of weeds to glyphosate in other herbicide 

resistant crops such as corn and cotton soon began to expand the numbers and populations of 

resistant weeds in the U.S. 

The intense use of glyphosate compared to sparing use of other herbicides on field crops is 

apparent in overall herbicide use trends over the last decade, and surveys of grower usage, such 

as that of Prince et al. (2012), provide specific details. These surveys give evidence of the 

prevalent practices employed by growers in which glyphosate was nearly the only herbicide used 

with the subsequent overexposure of crops and weeds to glyphosate.

It was reported by Young (Young, 2006) that there was a dramatic increase in the use of 

glyphosate in soybean and cotton production. In 2005, surveyed growers in multiple states 

rotating soybean and cotton indicated they chose glyphosate 51 % of the time for spring 

burndown, versus 21% for other herbicides (Table 6-1). For continuous soybean, growers chose 

glyphosate 46% of the time and 22% another herbicide (Table 6-1) (Prince et al., 2012). Overall, 

74% of the continuous soybean growers used glyphosate two or more times during a growing 

season (Table 6-2). When growers used non-glyphosate herbicides, continuous soybean growers 

used these herbicides in post-emergence applications 67% of the time, and cotton/soybean 

growers applied the herbicides on soybean post-emergence 76 % of the time (Table 6-2). 

Growers of GR cotton more frequently resorted applying glyphosate three or more times unless 

the GR cotton was rotated with GR corn (Prince et al., 2012).

Table 6-1. Frequency of Spring Pre-plant Application of Glyphosate Among Surveyed 

Growers (2005)

Herbicide Application

Crop Glyphosate Non-glyphosate

Continuous soybean 46% 22%

Soybean in soybean/cotton 

rotation 51% 21%

Source: (Prince et al., 2012) 

Table 6-2. Frequency of Glyphosate Application to Crop by Surveyed Growers (2005).

Herbicide Application

Glyphosate Non-glyphosate

Frequency 1X 2X 3X 1X 2X 3X

Crop

Continuous soybean 23 62 12 27 7 67

Soybean in soybean/cotton rotation 26 53 13 24 --- 76

Source: (Prince et al., 2012)

It is clear that when herbicides are applied, selection for those weeds with adaptive mechanisms 

to escape elimination will survive. If the herbicide is repetitively used in crop production, the 

surviving weeds will be further selected, and dominant genes as well as multi-component 

resistance mechanisms will be selected. While many practices can be used to manage weeds, the 

Page 6-4
recent history of glyphosate use shows that when the collective knowledge of resistance 

development is either neglected or practices not sufficiently integrated with mechanical and 

cultural controls, or with more robust herbicidal strategies, resistant weeds will arise. As noted 

earlier, it is not so much herbicide resistant crops that are a cause of herbicide resistant weeds, 

but from the failure to apply best management practices in the production of herbicide resistant 

crops.

Mechanisms of Herbicide Resistance in Weeds and Relationship to Selective Pressure

Two types of weed resistance may arise following inadvertent weed selection and both confer 

complex management concerns for growers. The first is target site-specific resistance (TSR), and 

the second, non-target site-specific resistance (NTSR). The first results in an alteration of the 

target site of the herbicide so the target is no longer inhibited. The second type of resistance is 

more general and may confer resistance to a wide range of chemistries. For example, NTSR 

resistance may provide protection by reduced penetration of the herbicide, altered translocation, 

overproduction of targets, target mutation, or neutralization of cytoplasmic toxins (Délye et al., 

2013). TSR confers resistance usually to a single herbicide, and NTSR may confer resistance to 

as many as nine different modes of action (e.g., Lolium rigidum) and 16 herbicides (Beckie, 

2011). In the case of NTSR, the use of herbicides on weeds with unknown NTSRs may provide a 

substantial risk for development of weed resistance (Délye et al., 2013).

The target site alterations leading to TSR are often produced by dominant or semidominant 

nuclear mutations and can be found in herbicide Groups 1, 2, 3, 23, 14, and 9, while triazine 

herbicides (Group 5) result from dominant cytoplasmic mutations (Délye et al., 2013). This 

resistance arises following a single mutation, which because of its beneficial nature promotes 

immediate survival and is positively and rapidly selected within the agricultural environment. 

Glyphosate resistance that is TSR is a consequence of one amino acid change at position 106 of 

the chloroplast EPSPS protein. Worldwide, 14 of these populations have been identified (Beckie, 

2011).

Natural Tolerance

Natural tolerance to certain herbicides may be apparent when weeds are first exposed to a

herbicide, or with selection, existing genes may be selected and then accumulated to produce 

varying levels of tolerance (likely by NTSR). Field morning glory (Convolvulus arvensis L.) has 

such tolerance to glyphosate and has been assessed in detail (Westwood and Weller, 1997). 

Glyphosate tolerance in Convolvulus was also found in historical populations which predated 

glyphosate resistant crop introductions (Baucon and Mauricio, 2010). The pre exposure NTSR to 

glyphosate was at about the same level as that which is currently observed. Morning glory can 

also be shown to have pre-existing resistance (that is, by TSR) but which is not as high as that 

expressed by plants now collected (Baucon and Mauricio, 2010). Both types of resistance can 

exist in the species, but independently, with resource allocation costs apparent for the plant’s 

tolerance mechanisms for the herbicide (Baucon and Mauricio, 2008). At least some populations 

of 16 species have been alleged as not controllable by recommended field rates of glyphosate, 

presumably by natural tolerance mechanisms (Duke and Powles, 2008).

Page 6-5
Weeds Resistant to Multiple Herbicides

Direct resistance of a weed species to an herbicide is an unwelcome consequence of weed 

selection, but cross resistance to other herbicides in the same class or to other classes of 

herbicides provides an even greater consequence to those who manage weeds, since a grower’s 

choice of herbicide site of action (SOA) will be restricted in the present season’s crop and 

potentially also in the rotation crop. When resistance is based on non-target site mechanisms, 

which may include increased metabolism and reduced translocation to target sites, the weed may 

be capable of resistance to multiple herbicide modes of action (Beckie and Tardif, 2012). NTSR 

appears to arise from a weed’s accretion of variants of several genes which may originally have 

been subsets of stress-tolerance genes (see review in Délye (2013)). Délye (2013) attributes 

much of the recently discovered weed resistance to this mechanism, and it is particularly 

important in Groups 9 (glyphosate) and 1 (acetyl-CoA carboxylase inhibitors), as well as grasses 

and probably broadleaf weeds (Group 2: acetohydroxyacid synthase inhibitors). In the case of 

glyphosate, Beckie (2011) lists 15 instances worldwide of glyphosate NTSR.

Weed Selection for Resistance to Herbicides by Overuse

The intense use of glyphosate on field crops compared to decreased use of other herbicides is a 

trend within the last decade, but how growers use glyphosate in field situations makes the 

situation clearer in grower surveys such as that of Prince (2012). These surveys give evidence of 

the prevalent practices employed by growers in which glyphosate is sometimes the only 

herbicide used, allowing the overexposure of crops and weeds to glyphosate. Growers were 

choosing glyphosate frequently for pre-plant burndown, but also post-planting with high 

frequency, so that repeated exposure of weeds to glyphosate during crop production was 

common within the same season. Because the most common rotation crop for corn is soybean, 

exposure of weeds to selecting doses of glyphosate occurs in consecutive seasons as well.

Because conservation tillage systems are inherently more dependent upon weed management 

using herbicides, selective pressure on weeds is greater than that on fields using conventional 

tillage with its greater options for pre-plant primary tillage and post plant secondary tillage 

(Vencill et al., 2012). In a survey conducted in 2007, growers that planted 87% of their crops to 

glyphosate resistant corn, soy or cotton varied the SOA used on their crops ‘always’ or ‘mostly’ 

just 39% of the time, with the remaining 61% affirming they did so ‘seldom’ or ‘never’ (Frisvold

et al., 2009). Thus, when conservation tillage and HR crops define the production system, 

growers are likely to use the same herbicide (i.e., glyphosate) frequently. Some other options 

also may be foreclosed by conservation till (especially no-till), such as soil incorporation of 

residual herbicides, although some residuals can also be soil applied (Penn State Extention, 

2013). 

Considering the recommendations for success in reducing resistant weed development (Vencill

et al., 2012), unsuccessful herbicide strategies that have encouraged resistant weeds can include:

1. Herbicide use of mostly one or a few modes of action (Norsworthy, 2012) and infrequent 

use of herbicide tank mixes, sequences and diversity across seasons (WSSA, 2011a);

2. Incorrect timing of herbicide application (Norsworthy, 2012);

Page 6-6
3. Failure to consider the likelihood that a weed already has non-target site resistance 

mechanisms (Délye et al., 2013) against specific herbicides (including metabolic 

potential, ability to prevent translocation, or ability to sequester the herbicide);

4. Applying low doses of herbicide thereby allowing weeds to be exposed to low rates 

herbicide which encourages sequential escapes and accumulating resistance genes

(WSSA, 2011b);

5. Not establishing fields devoid of active weeds at planting or good weed control at canopy 

closure (for soybean) because not all available tools and herbicides were used (Monsanto, 

2013); resulting in poorer crop establishment and more weed initiation.

Weed Resistance from Undervaluing a Balance of Residual and Contact Herbicides

The decrease in use of soil applied residual herbicides and a focus instead on mainly foliarapplied contact herbicides may be another basic and strategic misapplication of technology by 

field crop producers and these resulted in resistant weed development. In the era before 

introduction of HR soybean and cotton, and afterwards, production changes by growers were 

noted in the use of herbicides in the transition to greater HR crop acreage. For soybeans, in 1996, 

70% of growers used pre-emergent herbicides, but by 2002 they did so less than 20% of the time 

(Livingston and Osteen, 2012). Likewise, Prince (2012) concluded that soybean growers were 

less likely than corn or cotton growers to use a residual herbicide (often pre-emergent) in their 

multistate survey of herbicide use in 2005 and 2010. Growers thus lost value from an herbicide 

by not deploying a residual (soil applied residual in no-till production) herbicide that has a 

different SOA than glyphosate, and relying on post-emergence control using glyphosate or 

another foliar active herbicide. Perhaps as a consequence of awareness of weed herbicide 

resistance or in an effort to combat glyphosate resistant crops, use of residual herbicides has 

increased modestly between 2005 and 2009 from 15% to 27% of soybean acreage (Owen et al., 

2011). 

Related to the issue of reductions in residual pesticide use is that of reductions in total numbers 

of herbicides used in soybean and cotton. An USDA Agricultural Resources and Environmental 

Indicators (AREI) survey showed that soybean growers reached a high point of rotating

pesticides to slow resistance evolution in1998, but this declined steadily to low single digits in 

2010 (USDA-ERS, 2010). 

Herbicide-Resistant Weeds in Soybean and Cotton

It is important to distinguish herbicide resistance from herbicide tolerance. A herbicide-resistant 

weed is one in which there is an inherited ability of a plant to survive and reproduce following 

exposure to a dose of herbicide normally lethal to the wild type (WSSA, 2012). A herbicidetolerant weed species is one that is naturally tolerant to a herbicide; for example, a grass species 

is not killed by the application of a broadleaf herbicide (WSSA, 2012). Furthermore, certain 

weed species, while neither resistant nor tolerant, are inherently difficult to control with a 

particular herbicide, requiring more careful herbicide use and weed management practices 

(Monsanto, 2013).

Page 6-7
As of April 2014, 429 herbicide-resistant weed biotypes have been reported to be resistant to 22

different herbicide modes-of-action worldwide (Heap, 2014b). Glyphosate-resistant weeds, 

which occur in certain areas of the United States, account for approximately 7% of the herbicideresistant biotypes while weeds resistant to herbicides that inhibit acetolactate synthase (ALS) 

account for 34% of the herbicide-resistant biotypes. Synthetic auxin-resistant and glufosinateresistant weeds account for 7% and 0.5% of resistant biotypes, respectively (Heap, 2014b; Heap, 

2014a).

There are currently 429 unique cases of herbicide-resistant weeds globally, with 234 species (138 

dicots and 96 monocots). Weeds have evolved resistance to 22 of the 25 known herbicide sites of

action (Heap, 2014b). The first herbicide-resistant biotypes were described in the 1950s, but the 

number of weeds resistant to herbicides increased dramatically in the 1980s and 1990s, and 

resistance to 22 of the 25 known herbicide sites of action has been identified throughout the 

world (Heap, 2014b) and to 154 different herbicides. Herbicide-resistant weeds have been 

reported in 81 crops in 65 countries (Heap, 2014b).

While there are hundreds of cases of herbicide-resistant weeds, most of these weeds are not 

actively managed in cotton and soybean.

Herbicide-resistant Weeds in Soybean Production

Glyphosate-resistant weed biotypes that can be found in soybean fields include Palmer amaranth 

(Amaranthus palmeri), spiny amaranth (Amaranthus spinosus), tall waterhemp (Amaranthus 

tuberculatus), common ragweed (Ambrosia artemisiifolia), giant ragweed (Ambrosia trifida), 

horseweed (Conyza canadensis), kochia (Kochia scoparia), goosegrass (Eleusine indica), Italian 

ryegrass (Lolium multifloru), and Johnsongrass (Sorghum halepe) (Heap, 2014c).

In certain areas of the United States, resistance to the ALS group of herbicides is present in most 

of the major broadleaf weed species commonly found in soybeans. For common ragweed and 

waterhemp, there is known resistance to at least one member for several of the major soybean 

herbicide chemistry classes. While there are effective options for managing common ragweed, 

waterhemp, Palmer amaranth and other key broadleaf weeds, the availability of additional 

herbicide modes-of-action will help combat future resistance in soybeans and manage existing 

herbicide-resistant weed populations in areas of the United States where such populations exist. 

Similarly, there has been an increase in the detection of weed populations with multiple 

resistance (i.e., resistance to multiple herbicide modes-of-action) in some weed species, for 

example, Amaranthus spp. (Tranel et al., 2010). The emergence of these resistant biotypes in 

certain areas of the U.S. and continued need to utilize diversified weed management practices 

supports the need for additional herbicide modes-of-action in major crops such as soybean.

The relative occurrence of herbicide-resistant weeds varies between the different sub-groups of 

auxinic herbicides. Considering that auxin herbicides have been widely used in agriculture for 

more than 60 years, weed resistance to this class is relatively low (31 species, to date, 

worldwide) and its development has been slow, especially when compared to the speed of 

appearance of resistance to ALS inhibitors (144 species) or triazine-resistant populations (72

species) (Heap, 2014a). The relatively low incidence of auxinic herbicide resistance is believed 

Page 6-8
to be attributable to the fact that there are multiple target sites for these herbicides (Gressel and 

Segel, 1982; Morrison and Devine, 1993; Monsanto, 2012).

Herbicide-resistant Weeds in Cotton Production

Glyphosate-resistant weed biotypes found in cotton fields in certain areas of the United States 

may include Palmer amaranth (Amaranthus palmeri), spiny amaranth (Amaranthus spinosus), 

tall waterhemp (Amaranthus tuberculatus), common ragweed (Ambrosia artemisiifolia), giant 

ragweed (Ambrosia trifida), horseweed (Conyza canadensis), junglerice (Echinochloa colona),

kochia (Kochia scoparia), goosegrass (Eleusine indica), and Italian ryegrass (Lolium multifloru)

(Heap, 2014c). The emergence and growth of herbicide-resistant weeds (including glyphosateresistant weed biotypes) in certain areas of the United States over the past decade, has required 

growers to adapt and implement improved weed management strategies.

The occurrence of weed-resistant biotypes varies across the cotton-growing regions, with more 

resistance issues observed in certain areas of the Southeast and Midsouth cotton-growing 

regions. Amaranthus spp., in particular Palmer amaranth, are problematic weeds in the mid-south 

and southeastern U.S. Palmer amaranth is considered to be one of the most competitive and 

aggressive of the Amaranthus spp. because of its rapid growth and prolific seed production. In 

addition, it has developed resistance to multiple herbicide classes (glycines, ALS, and 

dinitroanilines) (Culpepper et al., 2011; Heap, 2014b). Managing herbicide-resistant Palmer 

amaranth has proven to be challenging due to the biology of this particular weed, including its 

dioecious nature (the male and female flowers occur on separate plants), which leads to greater 

genetic diversity in the plant population and increases the potential for spreading herbicide 

resistance (Sosnoskie et al., 2011).

Resistance to the ALS group of herbicides is present in most of the major broadleaf weed species 

commonly found in cotton. For Amaranthus spp. and Ambrosia spp., there is known resistance to 

at least one member for several of the major herbicide chemistry classes. In an effort to manage 

glyphosate-resistant Palmer amaranth in certain areas of the U.S., certain non-glyphosate cotton 

herbicides are being used in conditions and practices that can result in increased selection of 

resistant biotypes to those herbicides, and as a result some key agricultural herbicides in some 

major herbicide classes, such as glufosinate and PPO inhibitors, are at further risk (Nichols et al., 

2010; Prostko, 2011b; Prostko, 2011a). While there are effective options for managing Ambrosia

spp., and Amaranthus spp., including Palmer amaranth and other key broadleaf weeds, the 

availability of additional herbicide modes-of-action will help combat potential future resistance 

of the key herbicides needed for weed management in cotton. In addition, there has been an 

increase in the detection of weed populations with multiple resistances (i.e., resistance to 

multiple herbicide modes-of-action) in some weed species, for example, Amaranthus spp.

(Tranel et al., 2010). The emergence of these resistant biotypes in certain areas of the U.S. 

highlights the continuing need to utilize diversified weed management practices and the ongoing 

need for additional herbicide modes-of-action that are effective in major crops. 

Page 6-9
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Page 6-14
Appendix 7. Off-Target Pesticide Movement

Page 7-1
Off-Target Pesticide Movement

Once applied, pesticides (which include herbicides) remaining on the application site that are not 

taken up by targeted plants that have been harvested will persist, degrade, or move in the 

environment. The potential environmental fate of an herbicide is shown in Figure 7-1. 

Degradation occurs by hydrolysis, photolysis, or microbial dissipation resulting in the herbicide 

being broken down and eventually losing its herbicidal activity. Herbicides can be transported 

from their original application site by spray drift, runoff, leaching, volatility, wind erosion, or 

crop removal. Off-site movement of herbicides have the potential to impact non-target plant and 

animal communities living in proximity to fields in which herbicides are used, as well as human 

populations.

Figure 7-1. Environmental fate of herbicides in the environment.

Source: (Wright et al., 1996).

The length of persistence of herbicides in the environment depends on the concentration and rate 

of degradation by biotic and abiotic processes (Carpenter et al., 2002). Persistence is measured 

by the half-life or dissipation time (DT50), which equates to the length of time needed for the 

herbicide to degrade to half of its original concentration.

Use of herbicides for field crop production may introduce these chemicals to water through spray 

drift, cleaning of pesticide application equipment, soil erosion, or filtration through soil to 

groundwater. Irrigation and rainfall occurring the first few days after herbicide application can 

influence herbicide loss through leaching and runoff. However, it has been estimated that even 

after heavy rains, herbicide losses to runoff generally do not exceed 5 to 10 percent of the total 

applied (USDA-NRCS, 2000; Tu et al., 2001). Planted vegetation, such as grass buffer strips, or 

crop residues can effectively reduce runoff (Fishel, 1997; USDA-NRCS, 2000). 

Pesticides applied to crops may volatilize, thereby introducing chemicals to the air. Volatilization 

typically occurs during application, but herbicide deposited on plants or soil can also volatilize. 

Page 7-2
Volatilization occurs when pesticide surface residues change from a solid or liquid to a gas or 

vapor after application. Volatilization refers to the transformation of a liquid or solid pesticide 

into a gas. The extent of volatilization is dependent on properties of the chemical and herbicide 

formulation, and environmental factors such as air temperature, wind speed, and relative 

humidity. Volatilized pesticides can be carried by air currents potentially leading to off-target 

exposure. Once airborne, volatilized pesticides may be carried long distances from the treatment 

location by air currents. The higher the vapor pressure of a chemical, the more volatility it 

exhibits. In addition, other physical and chemical pesticide properties, agricultural practices, 

meteorological conditions, persistence of a pesticide on plant surfaces, and soil properties 

influence the extent of volatilization (University of Missouri, 1997; US-EPA, 2012). It is also 

important to note that once volatilized, pesticides may undergo transformation in the atmosphere 

or physical removal in precipitation. Most of the herbicides considered highly volatile are no 

longer used (Tu et al., 2001).

Drift is the physical movement of spray droplets moving off-site as a chemical application is 

made. Under certain conditions, the potential for physical drift from an application site to 

adjacent non-target environments is possible for all types of pesticide spray applications. This is 

an application-related phenomenon independent of the chemical pesticide, which may be

influenced by the formulation ingredients and spray mix additives. Spray drift is a concern for 

non-target susceptible plants growing adjacent to fields when herbicides are used in the 

production of any crop. This potential impact relates to exposure of non-target susceptible plants 

to the off-target herbicide drift (Jordan et al., 2009). Damage from spray drift typically occurs at 

field edges or at shelterbelts (i.e., windbreaks), but highly volatile herbicides may drift further 

into a field. The risk of off-target herbicide drift is recognized by EPA, which has incorporated 

both equipment and management restrictions to address drift on EPA-approved herbicide labels. 

These EPA label restrictions include requirements that the grower manage droplet size, control 

spray boom height above the crop canopy, restrict applications under certain wind speeds and 

environmental conditions, and use drift control agents (Jordan et al., 2009). 

The amount of drift varies widely and is influenced by a range of factors, including weather 

conditions, topography, the crop or area being sprayed, application equipment and methods, and 

practices followed by the applicator (US-EPA, 2000). EPA’s Office of Pesticide Programs 

(OPP), which regulates the use of pesticides and herbicides in the U.S., encourages pesticide 

applicators to use all feasible means available to minimize off-target drift. EPA-OPP has 

introduced several initiatives to help address and prevent the problems associated with drift. 

EPA-OPP is evaluating new guidance for pesticide drift labeling and the identification of BMPs

to control such drift (US-EPA, 2009a) as well as identifying scientific issues surrounding field 

volatility of conventional pesticides (US-EPA, 2010). Additionally, EPA-OPP and its Office of 

Research and Development are developing a new voluntary program, the Drift Reduction 

Technology (DRT) Program, which encourages the development, marketing, and use of 

application technologies verified to significantly reduce spray drift (US-EPA, 2009a).

EPA’s core pesticide risk assessment and regulatory processes ensure that protections are in 

place for all populations of non-target species potentially exposed to pesticides, including 

humans. These assessments provide EPA with information needed to develop label use 

restrictions for the pesticide. Growers are required to use pesticides, such as dicamba and 

glyphosate, consistent with the application instructions provided on the EPA-approved pesticide 

Page 7-3
label. Labels can include restrictions related to minimizing drift or exclusion distances from 

bodies of water when necessary. These label restrictions carry the weight of law and are enforced 

by EPA and the states (FIFRA 7 USC 136j (a)(2)(G) Unlawful Acts). 

Pesticide Regulation & Registration (Monsanto, 2013)

APHIS does not have any statutory authority to regulate herbicide uses in agriculture. Instead the 

use of a pesticide is regulated by the U.S. Environmental Protection Agency (EPA) under the 

Federal Insecticide Fungicide and Rodenticide Act (FIFRA).1

EPA considers possible effects from offsite movement as part of the pesticide registration 

process under FIFRA. Additionally, pesticide registrants must report drift incidents to EPA as an 

adverse effect in order to ensure the pesticide continues to meet FIFRA requirements for 

registration. 40 C.F.R. § 159.195(a)(2). Before any registered herbicide can be applied to any 

new use site (including any deregulated GE-derived crop), EPA must approve a label amendment 

setting out the use pattern and specific application requirements for that new use site. 

Specifically, in order to approve a new use of a pesticide, EPA must conclude that no 

unreasonable adverse effects on the environment will result from the new use when applied 

according to label directions, which includes potential offsite movement. Offsite impacts are 

diminished when herbicides are applied in accordance with label instructions. Registered 

herbicides, including dicamba and glufosinate, are assessed by EPA for potential risks to nontarget plants. A detailed discussion of the use of dicamba and glufosinate in the U.S. can be 

found in Appendix 4.

Use of Dicamba on DT soybean and DGT Cotton (Monsanto, 2013)

Dicamba (3,6-dichloro-2-methoxybenzoic acid) is a broad-spectrum, selective, post-emergence 

systemic herbicide with activity on a wide range of annual and perennial broadleaf plants. It was 

first registered in the United States in 1967 and is widely used in agricultural, industrial and 

residential settings. Dicamba controls annual, biennial and perennial broadleaf weeds in 

monocotyledonous crops and grasslands, and it is used to control brush and bracken in pastures. 

Because of the sensitivity of broadleaf plants to dicamba, the uses of dicamba in broadleaf crops 

until now have been limited to early pre-emergence and pre-harvest applications. DT soybean 

and DGT cotton have been developed to exhibit tolerance to dicamba herbicide applications by 

the insertion of a demethylase gene from Stenotrophomonas maltophilia. As a result DT soybean 

and DGT cotton express the dicamba mono-oxygenase (DMO) protein that rapidly demethylates 

dicamba to form the herbicidally inactive metabolite DCSA. 

The use of dicamba is projected to increase if DT soybean and DGT cotton are deregulated. 

Please see Appendix A to this Environmental Report for a detailed discussion of the projections 

for increased use of dicamba in this scenario. 

Offsite movement of herbicide to sensitive crops and plants during application is a concern 

during the growing season (Jordan et al., 2009). The potential for effects to off-target crops from 

offsite movement due to spray drift is generally greatest with a postemergence application 

1 7 U.S.C. §136 et seq.

Page 7-4

 
because the treatment is made directly to the crop and requires the spray equipment to be higher 

above the ground, which results in more spray drift potential. In addition, postemergence 

herbicides typically have foliar activity, thereby increasing the potential of foliar effects or visual 

symptoms on desirable plants. The presence of dicamba can cause visible morphological effects 

to trees and certain sensitive crops, particularly beans (e.g., dry and snap beans), cotton, flowers, 

fruit trees, grapes, ornamentals, peas, potatoes, soybean, sunflower, tobacco, tomatoes, and other 

broadleaf plants when contacting their roots, stems or foliage (BASF, 2008; Jordan et al., 2009). 

These plants are most sensitive to dicamba during their development or growing stage (BASF, 

2008).

Spray Drift (Monsanto, 2013)

Spray drift of herbicides is a familiar and well-studied phenomenon, notably by the Spray Drift 

Task Force, of which Monsanto is a member. EPA defines drift as “the movement of pesticide 

through air at the time of application or soon thereafter, to any site other than that intended for 

application” (US-EPA, 2000). Factors affecting the occurrence of spray drift include application 

equipment and method, weather conditions, topography, and the type of crop being sprayed (USEPA, 2000). Aerial application is associated with an increased drift potential compared to ground 

spray application because the herbicide is released at a greater distance above the crop canopy. In 

addition to the method of application, spray drift potential is also impacted by equipment type 

(e.g., nozzle types and ratings), settings (e.g., spray pressure, application speed, and application 

volume), equipment maintenance, environmental conditions (wind speed, temperature inversion), 

applicator behavior and distance from the edge of the application area (SDTF, 1997; Felsot et al., 

2010).

Prevention of Spray Drift (Monsanto, 2013)

Growers and commercial herbicide applicators have been applying dicamba to agricultural row 

crops for over 40 years. This experience has provided valuable knowledge and learning on the 

proper application of dicamba for effective weed control and also for minimizing offsite 

movement to sensitive crops. Spray drift can be reduced during application by using industry 

standard procedures for minimizing spray drift. Depending upon the herbicide being used, 

factors for managing the potential for spray drift include the selectivity and sensitivity of the 

herbicide, local weather conditions at the time of application (wind, temperature, humidity, 

inversion potential), droplet size distribution, application volume, boom height (height of the 

application equipment above the crop canopy), sprayer speed, and distance from the edge of the 

application area (SDTF, 1997; Felsot et al., 2010). The minimization of droplets less than 150 

microns is important in reducing any potential for spray drift. Droplet size can be increased by 

requiring the use of certain nozzle types, reducing spray pressure, increasing volume per minute 

spray rates, and by specifying an application volume per acre rate of at least 10 gallons (SDTF, 

1997; TeeJet Technologies, 2011). Arvidsson et al. (Arvidsson et al., 2011) investigated 

meteorological and technical factors affecting total spray drift and determined that boom height 

and wind speed were the primary factors affecting the potential for spray drift among those 

tested, followed by air temperature, driving speed and vapor pressure deficit. Arvidsson et al. 

(Arvidsson et al., 2011) demonstrated that drift increased with driving speed. This increase was 

attributed to either air flows associated with the forward movement of the sprayer or to increased 

vertical boom movement. 

Page 7-5
EPA’s Office of Pesticide Programs (OPP), which regulates the use of pesticides in the U.S., 

encourages pesticide applicators to use all feasible means available to them to minimize offtarget drift. The Agency has introduced several initiatives to help address and prevent issues 

associated with drift. EPA is evaluating new regulations for pesticide drift labeling and the 

identification of best management practices to control such drift (US-EPA, 2009a), as well as 

identifying scientific issues surrounding field volatility of conventional pesticides (US-EPA, 

2010). Additionally, OPP and EPA’s Office of Research and Development are developing a new 

voluntary program, the Drift Reduction Technology (DRT) Program, which encourages the 

development, marketing and use of application technologies verified to significantly reduce 

spray drift (US-EPA, 2009a).

When herbicides are applied according to the FIFRA label application instructions, offsite 

impacts can be avoided. EPA concluded in the dicamba Registration Eligibility Decision (RED) 

(US-EPA, 2006; 2009b) that existing label language to mitigate offsite movement was sufficient 

to reduce the potential risk of damage to adjacent vegetation. Because the proposed application 

rates for dicamba on DT soybean and DGT cotton are less than or equivalent to rates for dicamba 

established for other uses in the dicamba RED, and because these uses were evaluated by EPA as 

part of the RED and the proposed label contains the offsite movement mitigation language, it is 

reasonable to conclude that the use of dicamba on DT soybean and DGT cotton also meets the 

FIFRA no unreasonable adverse effects on the environment standard for drift and offsite 

movement (US-EPA, 2006; 2009b).

Growers and commercial applicators follow label directions and restrictions, and are educated by 

university specialists and industry representatives on the proper application equipment, 

equipment setup, and climatic conditions to maximize herbicide performance and minimize 

offsite movement of herbicides. Equipment manufacturers have developed spray nozzles that 

provide uniform coverage for effective weed control while applying larger spray droplets to 

reduce the potential for particle drift. 

Monsanto’s Proposed Label Instructions (Monsanto, 2013)

Monsanto is proposing a multi-faceted approach to address potential for off-site movement of 

dicamba used on DT soybean and DGT cotton. Monsanto has proposed a range of application 

restrictions on its dicamba label. Collectively, these restrictions (which are currently pending 

before EPA) would go far beyond any other currently applicable limitations on dicamba 

application—indeed go beyond any label restrictions ever imposed on dicamba in the nearly half 

century that dicamba has been on the market.2 Monsanto proposes to EPA that the supplemental 

labels for M1691 Herbicide use on DT soybean and DGT cotton contain application 

requirements that would minimize dicamba offsite movement, summarized as follows:

• No aerial application of M1691 Herbicide. 

2 For example, Monsanto’s proposed limits are far more restrictive than those for Dicamba Max 4, which allows 

aerial applications and does not require the use of drift-reducing additives. See Dicamba Max 4 Label, 

http://www.kellysolutions.com/erenewals/documentsubmit/KellyData/ND/pesticide/Product%20Label/83222/83222-

14/83222-14_DICAMBA_MAX_4_3_10_2009_6_06_42_PM.pdf. 

Page 7-6

 
• Use only spray nozzles that produce extremely coarse to ultra-coarse spray droplets and 

minimal amounts of fine spray droplets as defined by the American Society of 

Agricultural and Biological Engineers (ASABE S-572.1) and follow nozzle 

manufacturer’s recommendations to deliver desired droplet size.

• Apply using a minimum of 10 gallons of spray solution per acre.

• Select a ground speed under 15 mph that will deliver the desired spray volume while 

maintaining the desired spray pressure.

• Spray at the appropriate boom height based on nozzle selection and nozzle spacing (not 

more than 24 inches above target pest or crop canopy). Set boom to lowest effective 

height over the target pest or crop canopy based on equipment manufacturer’s directions.

• When making applications in low relative humidity, set up equipment to produce larger 

droplets to compensate for evaporation.

• Do not apply during a temperature inversion.

• Survey the application site for neighboring sensitive areas prior to application. A 

potential way of locating sensitive areas is through the use of sensitive crop registries.3

• Do not apply when the wind is blowing in the direction of a sensitive area at a wind speed 

greater than 10 mph. Sensitive areas include known habitat for threatened or endangered 

species, non-target sensitive crops, residential areas, and greenhouses.

• Implement a spray buffer (to be determined by EPA) between the last treated row and the 

closest downwind edge of any sensitive area when the wind is blowing in the direction of 

a sensitive area at a speed of 10 mph or less.

• Do not apply if wind speed is greater than 15 mph.

• Do not use crop oil concentrate or methylated seed oil as adjuvants when applied with 

glyphosate-based agricultural products. Do not add acidifying buffering agents.

• Clean equipment immediately after using this product using the procedures outlined in 

the label.

These proposed label instructions and/ or any measures imposed by EPA will limit the offsite 

movement of dicamba via spray drift and inadvertent spray application for the reasons described 

in more detail in the following paragraphs.

3 For example, www.driftwatch.org

Page 7-7

 
Reduction of Small Droplets (Monsanto, 2013)

Monsanto has taken a variety of measures to reduce offsite spray drift, including proposing label 

requirements to minimize the factors that result in small droplet generation, suspension, and 

movement into non-target areas. The factors that affect spray drift and associated impacts to 

adjacent areas can be divided into three main categories: a) droplet size and number, b) droplet 

transport, and c) the physical location of the spray. Droplet size and number is controlled by the 

nozzle type, application volume, spray pressure, and additives in the tank. Droplet transport is 

affected by wind speed, boom height, air temperature, vapor pressure deficit4

, and application 

speed. The third factor includes the proximity to sensitive non-target species which can be 

controlled through a mandate that applicators be aware of sensitive areas - including areas where 

threatened or endangered species may be present - that could be impacted from a dicamba 

application and implement a no-spray buffer as specified on the label.

Droplet Size and Number (Monsanto, 2013)

The minimization of droplets less than 150 microns is important in reducing any potential for 

spray drift. Nozzles used for application of agricultural products do not produce droplets of one 

uniform size, but rather produce a spectrum of droplet sizes (TeeJet Technologies, 2011). 

Nozzles are generally classified as very fine, fine, medium, coarse, very coarse, extremely 

coarse, or ultra-coarse by comparison of a nozzle’s droplet size distribution when spraying water 

to that of a set of standard nozzles. ASABE has established a nozzle classification system in its 

published standard, ASABE S-572.1 (ASABE, 2009; Wilson, 2011b), which is the U.S. industry 

standard for agricultural spray drop size classification. Nozzles classified as Extremely Coarse to 

Ultra Coarse have a small percentage of the spray volume in droplets with diameters less than 

150 microns.

Nozzle orifice size and operating pressure also affect the droplet size spectrum for a given nozzle 

type (SDTF, 1997). The relationship between orifice size, operating pressure, spray volume 

delivered, and droplet size classification can be found in the nozzle manufacturers’ catalogs. The 

use of a larger orifice size allows the application to be made at a higher volume per minute rate 

without increasing the operating pressure, and consequently reducing the droplet size 

classification (TeeJet Technologies, 2011). Additionally, a higher volume per minute rate allows 

the spray volume per acre to be higher at a given operating speed. Specifying an application 

volume per acre of at least 10 gallons may result in the use of larger orifice nozzles for some 

equipment to reduce the percentage of small droplets with the higher potential to drift.

The proposed label instructions direct the applicator to employ all of the relevant practices –

including nozzle type, operating pressure, and application volume – to ensure that the droplet 

size distribution can be classified as extremely coarse to ultra-coarse – which limits the 

percentage of spray droplets in the size category that has the potential to move offsite.

4 Vapor pressure deficit is the difference between the amount of water vapor in the air and the amount of water 

vapor in the air at saturation. Evaporation reduces droplet size, and the greater the vapor pressure deficit the more 

rapid the evaporation and the greater the potential for drift.

Page 7-8

 
Reduction of the Transport of Small Droplets (Monsanto, 2013)

Arvidsson et al. (Arvidsson et al., 2011) investigated meteorological and technical factors 

affecting total spray drift and determined that boom height and wind speed were the primary 

factors affecting the potential for spray drift among those tested, followed by air temperature, 

driving speed and vapor pressure deficit. Establishing a maximum wind speed (15 mph, or 10 

mph if sensitive areas are downwind) limits the distance that fine droplets will travel before 

settling. A temperature inversion5 can result when wind speeds are less than 3 mph, and can 

cause the suspension of the small spray droplets for extended periods of time. Prohibiting 

application during inversion conditions avoids the potential for suspension and farther transport 

of fine spray droplets (Wilson, 2011a). 

Boom height is also restricted in the proposed application use instructions for dicamba to the 

minimum height required to get a uniform spray pattern in order to minimize the amount of time 

that spray droplets are suspended before settling to the ground (Wilson, 2011b). As shown in the 

Spray Drift Task Force information booklet on Ground Applications (SDTF, 1997), a difference 

in boom height between 20 and 50 inches can impact the extent to which spray volume may 

move offsite by allowing additional time for the droplets to be blown offsite before settling. 

Prohibiting aerial application and limiting the boom height for ground applications to 24 inches 

above the target pest or crop canopy will minimize the amount of time that spray droplets are 

suspended and available to move offsite.

Arvidsson et al. (Arvidsson et al., 2011) demonstrated that drift increased with driving speed. 

This increase was attributed to either air flows associated with the forward movement of the 

sprayer or to increased vertical boom movement. Limiting driving speed to 15 mph or less will 

minimize this potential contributing factor.

Physical Location of the Spray and Use of Wind Buffers (Monsanto, 2013)

Awareness of the presence of sensitive areas and whether the wind direction at the time of 

application may move any suspended spray droplets toward a sensitive area are important 

considerations at the time of application. Since the implementation of the 

DriftWatchTM 6program in Indiana, drift incidents onto sensitive crops have been significantly 

reduced (Hahn et al., 2011). This program has now been expanded to several states across the 

major Midwest soybean growing area and to some Great Plains states as well (IL, IN, MI, MN, 

MO, WI, CO, MT, and NE). Under some circumstances, a buffer may be needed to provide 

further protection to a sensitive area. This method is highly effective when used. 

5 A temperature inversion occurs when the air at the soil surface is cooler than the air above. Since cool air sinks, the 

surface air layer does not mix with upper layers of air. Under this condition, spray droplets are trapped near the 

surface and may stay suspended for increased periods of time.

6 Driftwatch is a voluntary program that allows growers to reports locations of fields in which sensitive crops are 

being grown (and also identified other types of sensitive areas such as organic fields). The sensitive crop 

information is presented on a website in a map format which can then be utilized by pesticide applicators prior to 

application.

Page 7-9

 
For these reasons, the proposed FIFRA product labels state that applicators should consult with 

available sensitive crop registries prior to making dicamba applications to DT soybean or DGT 

cotton. Many state lead agriculture agencies (IA, IL, IN, KS, MI, MN, MO, NE, OK, WI) have 

developed tools and resources to assist the applicator in the location of sensitive areas, such as 

vegetable or organic production fields, in an effort to minimize commercial impacts associated 

with pesticide offsite movement. Furthermore, prior to commercialization of DT soybeans and 

DGT cotton, Monsanto will implement an endangered species mitigation system for dicamba. 

The implemented system will either be an EPA-specific system and/or a web-based system, 

similar to that currently available for glyphosate at PreServe.org. This will facilitate applicator 

and grower implementation of use restrictions for protection of threatened and endangered nonmonocotyledonous terrestrial plant species.

Determination of Proper Buffer Distances (Monsanto, 2013)

Monsanto has submitted information to the EPA that summarizes studies conducted at eight field 

locations to assess the buffer distance required to be protective of survival, growth, and 

reproduction of plant species that are very sensitive to dicamba (Orr et al., 2012). These studies 

utilized nozzles that fit the droplet size classification requirements, the minimum application 

volume and the maximum boom height requirements specified above. 

Justification for use of soybean plant height as the endpoint for risk assessment

Soybean was selected as the test species since it has been shown to be a highly sensitive 

indicator species for post-emergence dicamba effects. In the vegetative vigor study conducted in 

a greenhouse with the DGA salt of dicamba, soybean had the lowest endpoint of the ten species 

tested (Porch et al., 2009). Comparable sensitivity for soybean to that observed in the greenhouse 

has also been displayed in field studies (Wax et al., 1969; Auch and Arnold, 1978; Weidenhamer

et al., 1989; Al-Khatib and Peterson, 1999; Kelley et al., 2005). See Table 7-1 for a summary of 

endpoints from these studies.

Higher Dicamba rates are needed to cause effects on soybean yield than are needed to 

cause effects on soybean plant height at early growth stages

Effects of dicamba on plant growth have been evaluated by considering effects on plant height at 

very sensitive early growth stages. Effects of dicamba on plant reproduction can be evaluated by 

assessing the effect of dicamba on plant species seed or fruit yields. A number of the field studies 

(Wax et al., 1969; Auch and Arnold, 1978; Weidenhamer et al., 1989; Al-Khatib and Peterson, 

1999; Kelley et al., 2005; Wright, 2012) indicate that soybean yield is no more sensitive, and is 

generally less sensitive, to dicamba treatment than is soybean plant height at the early growth 

stages at which studies to estimate buffer distances have been conducted. Additionally, results of 

these studies demonstrate that significant morphological effects in soybeans such as plant height 

reduction do not always result in yield reduction, but yield reduction in soybeans occurs at rates 

greater than that affecting soybean plant height at the early vegetative stages which were used in 

studies for buffer distance estimation. See Table 7-2 for a summary of the results of these 

studies. 

Page 7-10
Dicamba effects on yields of other crops occur at rates greater than or equal to rates 

affecting soybean plant height

The effects of dicamba on crop yield have been reported by a number of investigators in at least 

eleven other crops besides soybean. Monsanto has submitted field data on soybean to EPA and 

conducted an extensive review of relevant literature for use by EPA in establishing an 

appropriate buffer distance from potentially sensitive plant communities. The field data was 

generated across multiple growing seasons with diverse geographic and climatic conditions. The 

literature review included results from studies testing 12 possible sensitive crops, with many 

crops tested across multiple growing seasons and/or geographies and/or growth stages. The 

potential sensitive crops included in these studies were soybean, tomato, cantaloupe, cotton, pea, 

peanut, pepper, potato, sugarbeet, sunflower, tobacco, and watermelon. 

These studies also indicate that the dicamba no effect rate for soybean plant height at vegetative 

growth stages is a lower value (approximately 0.3 g a.e./ha) than the dicamba no effect rates for 

plant yield in these other species that have been tested. See Table 7-3 for a summary of endpoints 

from these studies.

Because soybean plant height measured at vegetative growth stages is a more sensitive endpoint 

for dicamba effects than soybean yield or yield of eleven other plant species in five additional 

plant families, the use of the soybean plant height endpoint is appropriate to assess potential 

dicamba effects on survival, growth, and reproduction of sensitive species. 

Monsanto’s application management practices, including buffer distances that have been 

determined to not result in soybean plant height reduction after dicamba applications, can 

therefore be considered effective measures for mitigation of potential effects of dicamba on nontarget plants.

Page 7-11
Table 7-1. Soybean Field Studies with Dicamba

Growth Stage 

& Other 

Treatment 

Information

Dicamba Salt a Time of 

Measurement

Plant Height

No Effect 

Rate 

(g a.e./ha)b

Reference

2-3 trifoliate 

1997 Not Specified 60 DAT <5.6 (Al-Khatib and Peterson, 1999)

2-3 trifoliate 

1998 Not Specified 60 DAT 5.6 (Al-Khatib and Peterson, 1999)

1-2 trifoliate -

1974 DMA At maturity 56 (Auch and Arnold, 1978)

3-4 trifoliate -

1974 DMA At maturity 1 (Auch and Arnold, 1978)

6-7 trifoliate -

1974 DMA At maturity 1 (Auch and Arnold, 1978)

V3 DMA At maturity < 1.1 (Wax et al., 1969)

Williams -

prebloom 1980 

(41 DAP)

DMA At maturity 0.32c (Weidenhamer et al., 

1989)

Elf - prebloom 

1980 (41 DAP) DMA At maturity 1.3c (Weidenhamer et al., 1989)

V3 DGA

Full height 

before leaf 

senescence

< 0.56 (Kelley et al., 2005)

V7 DGA

Full height 

before leaf 

senescence

< 0.56 (Kelley et al., 2005)

a DMA – dimethylamine; DGA – diglycolamine bFor conversion of g a.e./ha to lb a.e./A divide the g a.e./ha value by 1120. Application rates expressed as oz/A were 

assumed to be of a 4 lb a.e./gal formulation and were converted to g a.e./ha

c Highest rate at which less than 10% effect on height was observed based on Table 2 of the publication

Page 7-12
Table 7-2. Comparison of No Effect Rates for Plant Height and Yield from Dicamba 

Application to Soybeans

Growth Stage & 

Other Treatment 

Information

No Effect Rate (g a.e./ha)a

Reference Plant Height Yield

Williams - prebloom 

1980 0.32b,c 20b (Weidenhamer et al., 1989)

Elf - prebloom 1980 1.3b,c 10b (Weidenhamer et al., 1989)

8-12 inches, 3 WAEd, 

RM1 2009 -- 11 (Johnson et al., 2012)

8-12 inches, 3 WAE, 

RM2 2009 -- 41 (Johnson et al., 2012)

8-12 inches, 3 WAE, 

RM1 2010 -- 3 (Johnson et al., 2012)

8-12 inches, 3 WAE, 

RM2 2010 -- 3 (Johnson et al., 2012)

2-3 trifoliate 1997 5.6e 17 (Al-Khatib and Peterson, 1999)

2-3 trifoliate 1998 <5.6e 17 (Al-Khatib and Peterson, 1999)

V3f - SE Farm -- < 5.6 (Andersen et al., 2004)

V3 - Brookings Farm -- < 5.6 (Andersen et al., 2004)

V3 < 1c 1 (Wax et al., 1969)

V3 < 0.56c < 0.56g (Kelley et al., 2005)

1-2 trifoliate - 1974 56c 56 (Auch and Arnold, 1978)

3-4 trifoliate - 1974 1c 56 (Auch and Arnold, 1978)

6-7 trifoliate - 1974 1c 56 (Auch and Arnold, 1978)

V7h < 0.56c 0.56 (Kelley et al., 2005)

Early bloom - 1974 1c 11 (Auch and Arnold, 1978)

Early bloom - 1975 1c,i 1 (Auch and Arnold, 1978)

Early bloom - 1976 < 11c < 11 (Auch and Arnold, 1978)

R2j NAk < 1 (Wax et al., 1969)

R2 NA 0.56 (Kelley et al., 2005)

Elf - midbloom 1980 NA 40b (Weidenhamer et al., 1989)

Mid-bloom - 1976 NA 28 (Auch and Arnold, 1978)

Williams - midbloom 

1980 NA 10b (Weidenhamer et al., 1989)

Williams - midbloom 

1981 NA 7.4b (Weidenhamer et al., 1989)

Early-pod - 1975 NA 11 (Auch and Arnold, 1978)

Early pod - 1976 NA 11 (Auch and Arnold, 1978)

Late pod - 1976 NA 28 (Auch and Arnold, 1978)

a For conversion of g a.e./ha to lb a.e./A divide the g a.e./ha value by 1120. Application rates expressed as oz/A were 

assumed to be of a 4 lb a.e./gal formulation and were converted to g a.e./ha

b Highest rate at which less than 10% and 20% effect on height and yield, respectively, were observed based on 

Table 2 & Table 3 of the publication c Height at maturity

Page 7-13
d WAE – weeks after emergence e

Assessed at 60 days after treatment

f At V3 growth stage the third trifoliate leaf is unfolded 

(http://extension.agron.iastate.edu/soybean/production_growthstages.html) g

Yield reduction was statistically significant but not considered biologically significant at rates of 0.56 and 5.6 g 

a.e./ha because a ten-fold increase in rate did not cause an increase in the yield reduction, and the percent reduction 

is small compared to the untreated control (i.e., less than 10% yield reduction). hAt V7 growth stage the seventh trifoliate leaf is unfolded.

i

A height reduction of 18% was observed at rates above 1 g a.e./ha, but this reduction was not statistically 

significant

j

R2 growth stage is when there is an open flower at one of the two uppermost nodes 

(http://extension.agron.iastate.edu/soybean/production_growthstages.html) k Rates at which no effect on plant height are provided in the literature references, but are not provided here since 

yield values are being compared to rates causing plant height effects at earlier time points.

Page 7-14
Table 7-3. Effect of Dicamba on Yield in Plant Species Other than Soybean

Crop

Growth Stage & 

Other 

Treatment 

Information

Effect

No Effect 

Rate 

(g a.e./ha)a

Reference

Soybean pre-bloom Plant Height 0.32b (Weidenhamer et al., 1989)

Cantaloupe 3 Weeks after 

transplanting Total Harvest 560 (Hynes and Weller, 2010)

Cantaloupe 3 Weeks after 

transplanting Total Harvest 11.2 (Hynes et al., 2011)

Cotton Cot – 2 Leaf Lint Yield 140 (Everitt and Keeling, 2009)

Cotton

4-5 Leaf

Pinhead Square

First Bloom

Lint Yield 14 (Everitt and Keeling, 2009)

Cotton

20-30 cm tall

RM 2009

LW 2009

LW 2010

Yield 140 (Johnson et al., 2012)

Cotton 20-30 cm tall

RM 2010 Yield 11 (Johnson et al., 2012)

Cotton 6-8 Leaf Lint Yield 2.8 (Marple et al., 2007)

Cotton

3-4 Leaf

8-node

14-node

18-node

Lint Yield 2.8 (Marple et al., 2007)

Pea Flower buds 

formed Yield 6.25 c (Al-Khatib and Tamhane, 1999)

Pea Vegetative & 

Flowering

Seed dry 

weight 5.63 (Olszyk et al., 2009)

Peanut 15-20 cm width

RM 2010 Yield 140 (Johnson et al., 2012)

Peanut

15-20 cm width

RM 2009

LW 2010

Yield 41 (Johnson et al., 2012)

Peanut

15-20 cm width

LW 2009 Yield 11 (Johnson et al., 2012)

Pepper 3 Weeks after 

transplanting Total harvest 11.2 (Hynes and Weller, 2010)

Pepper 3 Weeks after 

transplanting Total harvest 560 (Hynes and Weller, 2010)

Pepper 3 Weeks after 

transplanting Total harvest 560 (Hynes et al., 2011)

Potato 11-15 Days after 

emergence

Tuber fresh 

weight 5.58 (Olszyk et al., 2010)

Page 7-15
Crop

Growth Stage & 

Other 

Treatment 

Information

Effect

No Effect 

Rate 

(g a.e./ha)a

Reference

Potato 15% flowering Tuber Yield 11.2 (Leino and Haderlie, 1985)

Sugarbeet 10-15 leaf Extractable 

sucrose

70 (Schroeder et al., 1983)

Sugarbeet 10-15 leaf Root yield >140 (Schroeder et al., 1983)

Sunflower 2-4 leaf Yield 1.6 (Derksen, 1989)

Tomato Full bloom -

1972 Total Yield 1 (Jordan and Romanowski, 1974)

Tomato Green fruit stage 

1971 Total Yield 20 (Jordan and Romanowski, 1974)

Tomato Green fruit stage 

1972 Total Yield 100 (Jordan and Romanowski, 1974)

Tomato 3 Weeks after 

transplanting

Total Yield

Fruit weight

11.2

5.6 (Hynes and Weller, 2010)

Tomato 3 Weeks after 

transplanting Total Yield 560 (Hynes et al., 2011)

Tomato 15 cm tall

Early vegetative

Marketable 

Fruit 0.9d (Kruger et al., 2012)

Tomato 25 cm tall

Early bloom

Marketable 

Fruit 0.5d (Kruger et al., 2012)

Watermelon 3 Weeks after 

transplanting

Total Harvest 11.2 (Hynes and Weller, 2010)

Watermelon 3 Weeks after 

transplanting

Total Harvest 560 (Hynes et al., 2011)

a For conversion of g a.e./ha to lb a.e./A divide the g a.e./ha value by 1120. Application rates expressed as oz/A were assumed to be of a 4 lb 

a.e./gal formulation and were converted to g a.e./ha

b Lowest rate from 

c Next rate below rate with greater than a 25% effect on yield (lowest such rate of 5 sites). 25% effect on yield was chosen due to high 

variability.

d Value from dose response curve estimated to result in 1% fruit loss

Applicator Education and Awareness (Monsanto, 2013)

As mentioned above, growers and commercial applicators are aware of the sensitivity of certain 

crops to dicamba and the extra precautions that should be taken in making dicamba applications 

when these crops are nearby. In addition, growers and commercial applicators follow label 

directions and restrictions, and growers are educated by university specialists and industry 

representatives on the proper application equipment, equipment setup, and climatic conditions to 

maximize herbicide performance and minimize offsite movement of herbicides. To provide 

growers with specific information for dicamba applications to dicamba-tolerant crops, Monsanto 

is implementing a robust stewardship program that will include a strong emphasis on grower and 

Page 7-16
applicator training. In addition, U.S. EPA and state agencies have enforcement authority over the 

use of any registered pesticide in a manner inconsistent with its labeling. 

Equipment manufacturers developed spray nozzles that provide uniform coverage for effective 

weed control while applying larger spray droplets to reduce the potential for particle drift. 

Similarly, offsite movement of dicamba has been managed with the knowledge of the proper 

spray equipment and equipment setup, climatic conditions for accurate, on-target applications, 

and based on the requirements for applying dicamba at an appropriate distance from sensitive 

crops and plants (Jordan et al., 2009).

Volatilization (Monsanto, 2013)

Volatilization of fertilizers and pesticides from soil and plant surfaces also introduces certain 

chemicals to the air and can cause offsite movement. A substance is volatile if it is likely to 

vaporize at atmospheric pressure. The USDA Agricultural Research Service (ARS) is conducting 

a long-term study to identify factors that affect pesticide levels in the Chesapeake Bay region 

airshed (USDA-ARS, 2011). This study has determined that volatilization is highly dependent 

upon exposure of disturbed unconsolidated soils, and that variability in measured compound 

levels is correlated with temperature and wind conditions. Another ARS study of volatilization of 

certain herbicides after application to fields has found moisture in dew and soils in higher 

temperature regimes significantly increases volatilization rates (USDA-ARS, 2011).

Physicochemical characteristics of the individual chemical have been shown to have little impact 

on spray drift. However, unlike spray drift, the potential for post-application volatilization is 

primarily a function of the physicochemical properties of the chemical, (e.g., vapor pressure, 

Henry’s Law constant, etc.), method of application (e.g., soil-incorporated or not), and the local 

environmental conditions (e.g., temperature, humidity, wind speed). Due to this complexity, the 

potential for post-application vapor loss is often measured experimentally.

In EFED’s Chapter in the Dicamba RED, laboratory volatility data have been summarized for 

potassium and dimethylamine (DMA) salts of dicamba from a moist soil. Monsanto has also 

submitted information to the EPA that summarizes a field study that was conducted to measure 

the volatilization rate of a dicamba DGA salt formulation from foliage.

DGA Salts Reduce Volatilization (Monsanto, 2013)

Monsanto seeks to minimize volatile loss from treated soybean and cotton fields by labeling 

optimal formulations and salt forms of dicamba. The DGA salt formulation of dicamba, which is 

proposed for use on DT soybean and DGT cotton, has low volatility. Side-by-side field 

experiments have indicated that a formulation of the diglycolamine (DGA) salt of dicamba 

dramatically reduced volatilization of dicamba compared to a similar formulation of the DMA 

salt form and that volatility is not a significant component of offsite movement for the DGA salt 

of dicamba (Egan and Mortensen, 2012). The use of formulations of, or similar to, the DGA salt 

of dicamba will help to limit non-target plant risk due to post-application vapor loss. In the 

publication, the authors state, “Our data demonstrate that the diglycolamine formulation has a 

dramatic effect on reducing dicamba vapor drift. Estimates of total gram acid equivalent vapor 

drift outside of the treated area were reduced 94% relative to the dimethylamine formulation, and 

the dose-distance curves indicate that predicted mean exposures drop close to zero only short 

Page 7-17
distances away from the treated area.” Additionally, measured air concentrations when using the 

DGA salt were at least 70-fold lower than those in the potassium and DMA salt laboratory 

studies EFED evaluated, even though the application rate was twice that of DMA (Mueller et al., 

2013).

Monsanto has requested the use of dicamba on DT soybean and DGT cotton only for lowvolatility salts, including the DGA salt formulation (U.S. EPA Reg. No. 524-582). Specific 

application requirements on the proposed FIFRA product label (currently pending before EPA), 

and/or any other measures imposed, by EPA will minimize dicamba offsite movement. 

Monsanto plans to continue to invest in research and development of new dicamba formulations 

for use with DT soybean and DGT cotton. Monsanto and BASF have submitted separate 

applications to EPA seeking the approval of novel dicamba formulations (EPA File Symbols 

7969-GUL, 524-ANO and 524-ARN). EPA will review relevant data and information as a part of 

its registration process and confirm that the product when used according to the approved label 

directions meets the FIFRA standard before granting a registration including the use on DT 

soybean or DGT cotton. Furthermore, Monsanto has indicated that it does not plan to allow 

growers to use dimethylamine salt (DMA) of dicamba and/or dicamba acid on DT soybean or 

DGT cotton.

Page 7-18
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Page 7-21
Page 7-22
Appendix 8. EPA Assessment of Herbicides Used on MON 

87708 Soybean and MON 88701 Cotton

Page 8-1
EPA Regulation of Pesticides

The use of pesticides is regulated by EPA under the Federal Insecticide, Fungicide, and 

Rodenticide Act (FIFRA). The purpose of the Agency’s review is to ensure that the pesticide, 

“when used in accordance with widespread and commonly recognized practice,” will not cause 

“unreasonable adverse effects on the environment” FIFRA 3(c)(5)(D). 

If the pesticide may be used on food or feed crops, EPA ensures the safety of the food supply by 

establishing the amount of each pesticide that may safely remain in or on foods. These maximum 

pesticide residue levels (called “tolerances”) limit the amount of the pesticide residue that can 

legally remain in or on foods. EPA undertakes this analysis under the authority of the Federal 

Food, Drug, and Cosmetic Act (FFDCA), as amended by the Food Quality Protection Act of 

1996 (FQPA), and must conclude that such tolerances will be safe, meaning that there is a 

reasonable certainty that no harm will result from aggregate (food, water and non-occupational 

residential/recreational) exposure to the pesticide residues (US-EPA, 2013b). In addition, when 

multiple pesticides affect the same target organs through the same toxicological mode- of-action, 

EPA considers the cumulative effect of those pesticides. In addition, the FDA and the USDA 

monitor foods for pesticide residues and work with the EPA to enforce these tolerances (USDAAMS, 2013).

The use of registered pesticides is further governed by labels, which are legally enforceable and 

define maximum application rates, total annual application limits, methods of application, and 

other use restrictions. 

To register a new pesticide product, EPA evaluates potential risks to humans and the 

environment, and typically requires applicants to submit more than 100 different scientific 

studies conducted according to EPA’s harmonized test guidelines. The data required by EPA are 

used to evaluate whether a pesticide has the potential to cause adverse effects on humans 

(including acute, chronic, reproductive, and carcinogenic risk), wildlife, fish, and plants 

(including endangered species and other non-target organisms, i.e., organisms against which the 

pesticide is not intended to act). FIFRA was amended in 1988 to require the reregistration of 

products with active ingredients registered prior to November 1, 1984. In 1996, FIFRA was 

amended by the FQPA to require reevaluation of all pesticide active ingredient at fifteen year (or 

shorter) intervals thereafter (a process called Registration Review). The amendments called for 

the development and submission of data to support the continued registration of the active 

ingredient, as well as a review of all data submitted to the EPA. During the reregistration and 

registration review processes, EPA thoroughly reviews the scientific database since a pesticide’s 

original registration.

EPA has responsibility to regulate the use of pesticides (including herbicides) that may be used 

on feed crops, and must establish pesticide tolerances (maximum pesticide residue levels) for the 

amount of pesticide residue that can legally remain in or on the feed crop. EPA undertakes this 

analysis under the authority of the FFDCA, and must conclude that such tolerances will be safe, 

meaning that there is a “reasonable certainty that no harm” to human health will result from the 

use of the pesticide. This finding of reasonable certainty of no harm is obligated under the 

FFDCA, as amended by the FQPA of 1996. Similar to the establishment of pesticide tolerances 

for food, the EPA will consider the toxicity of the pesticide and its break-down products, 

pesticide use rate and frequency of application; and how much of the pesticide (i.e., the residue) 

Page 8-2
remains in or on food by the time is it marketed and prepared in its establishment of tolerance for 

animal feed (US-EPA, 2013b).

MON 87708 Soybean and MON 88701 Cotton

Two petitions were submitted by Monsanto to APHIS seeking determinations of nonregulated 

status for GE soybean and cotton cultivars engineered for resistance to herbicides. 

APHIS Petition 10-188-01p is for GE soybean (Glycine max), designated as event MON 87708 

soybean. It contains a demethylase gene from Stenotrophomonas maltophilia that expresses a 

dicamba mono-oxygenase (DMO) protein to confer resistance to the broadleaf herbicide 

dicamba. DMO protein rapidly demethylates dicamba to the inactive metabolite 3,6-

dichlorosalicylic acid (DCSA), a known metabolite of dicamba in non-GE cotton, soybean, 

livestock and soil.

APHIS Petition 12-185-01p is for GE cotton (Gossypium spp.), designated as event MON 88701 

cotton, that is also resistant to dicamba as a result of the expression of the DMO protein. MON 

88701 cotton also contains a bialaphos resistance (bar) gene from Streptomyces hygroscopicus

that expresses the phosphinothricin N-acetyltransferase [PAT (bar)] protein to confer tolerance 

to the herbicide glufosinate. The PAT (bar) protein acetylates the free amino group of 

glufosinate to produce non-herbicidal N-acetyl glufosinate, a known metabolite in glufosinatetolerant plants (OECD, 2002). 

As with any other GE crop deregulated by APHIS, deregulated status of these two events would 

include dicamba-resistant soybean, dicamba- and glufosinate-resistant cotton, any progeny 

derived from crosses between MON 87708 soybean and conventional or other previously 

deregulated GE soybean varieties, and any progeny derived from crosses between MON 88701 

cotton and conventional or other previously deregulated GE cotton varieties. Monsanto has 

indicated that both MON 87708 soybean and MON 88701 cotton will be combined with 

glyphosate-resistance traits utilizing traditional breeding techniques.

Monsanto has submitted pesticide registration petitions to EPA requesting Section 3 registration 

for the use of dicamba on dicamba-resistant soybean and cotton. For these petitions, Monsanto 

is requesting to establish new tolerances for dicamba-resistant soybean forage at 45 ppm and for 

dicamba tolerant soybean hay at 70 ppm. Monsanto is also requesting to amend the cotton undelinted seed tolerance from 0.2 ppm to 3.0 ppm and establish a new tolerance for cotton gin 

byproducts at 70.0 ppm. 

A brief overview of the three herbicides (dicamba, glufosinate, and glyphosate) that are intended 

to be used on the two Monsanto events are presented in the following sections. Additionally, the 

proposed uses of these herbicides on MON 87708 soybean and MON 88701 cotton and any EPA 

assessments performed assessing the potential effects from the new uses are summarized.

Dicamba

Background and Current Uses

Dicamba (benzoic acid, 3,6-dichloro-2-methoxy-, aka 3,6-dichloro-o-anisic acid) is a selective 

systemic herbicide belonging to the benzoic acid chemical family. Dicamba is a broadleaf 

selective herbicide that was approved by the EPA for agricultural application uses in 1967 (USPage 8-3
EPA, 2006; 2009c). Dicamba is registered for use on agricultural crops and for use as spot and 

broadcast treatments on turf, in addition to residential uses. Dicamba is currently labeled for 

weed control in corn, soybean, cotton, sorghum, wheat, barley, oats, millet, pasture, rangeland, 

asparagus, sugarcane, turf, grass grown for seed, conservation reserve programs, and fallow 

croplands. The herbicide is currently registered for use on both soybeans and cotton as pre-plant 

applications and not as post emergence applications because crop injury could occur if dicamba

were to come in contact with roots, stems, or foliage. 

Dicamba belongs to the auxin class of herbicides, which is the oldest class of known synthetic 

herbicides. This class includes 2,4-D, 2,4-DB, mecoprop, MCPA, clopyralid, and several other 

active ingredients, and is WSSA Herbicide Group Number 4 (HRAC, 2009).

1 On the basis of 

their structural and chemical properties, auxinic herbicides have been classified into several subgroups, viz., phenoxyalkanoic acids (e.g., 2,4-D, MCPA), benzoic acids (e.g., dicamba, 

chloramben), pyridines (e.g., picloram, clopyralid), and quinolinecarboxylic acids (e.g., 

quinclorac, quinmerac). Generally, auxinic herbicides are effective against broadleaf 

(dicotyledonous) plant species, allowing them to often be used in production of narrow leaf 

(monocotyledonous) crops.

Various salt formulations of dicamba are formulated as standalone herbicide products and 

marketed by several companies under various trade names such as Banvel®, Clarity®, Diablo®, 

Rifle®, Sterling®, and Vision®. These dicamba products can also be tank-mixed with one or 

more active ingredients depending on the crop to be treated. For example, Clarity® can be tank 

mixed with over 75 herbicide products in labeled crops. Additionally, dicamba is currently 

formulated as a premix product with one or more other herbicide active ingredients, including 

glyphosate, 2,4-D, diflufenzopyr, atrazine, nicosulfuron, metsulfuron, primsulfuron, triazulfuron, 

rimsulfuron, and halosulfuron.

Dicamba-treated acreage has ranged from 17.4 to 36.3 million acres between 1990 and 2011. 

Usage of dicamba peaked during the period of 1994 through 1997, where 1994 was the peak year 

when 36 million crop acres were treated with 9.4 million pounds of dicamba. The use of dicamba 

steadily declined to 17.4 million treated acres with 2.7 million pounds applied in 2006. The 

reduction in dicamba use has been attributed to the competitive market introductions of 

sulfonylurea herbicides (chlorsulfuron, metsulfuron-methyl, and thifensulfuron-methyl) in wheat, 

new broadleaf herbicide active ingredients in corn, and introduction of glyphosate-tolerant corn. 

More recently, however, dicamba-treated acres have been on the rise and have increased by as 

much as 7.9 million acres between 2006 to 2011. Most of this increase has occurred in fallow, 

pastureland, sorghum, and cotton (pre-plant) (Monsanto, 2012). Dicamba-treated acres have 

increased in cotton, in particular, because it is a common pre-plant herbicide recommendation for 

glyphosate-resistant marestail (horseweed) and Palmer amaranth in the Midsouth region

(McClelland et al., 2006). Figure 8-1 shows the changes in dicamba use by year and crop from 

1992 through 2011.

1 There are several systems of herbicide mode-of action classification. Among the most widely used are 

those of the Herbicide Resistance Action Committee (HRAC) and the Weed Science Society of America. 

Page 8-4

 
Approximately 25.3 million acres of crops were treated with dicamba in 2011 (see Table 8-1 for 

a summary of the dicamba-treated acres by crop in 2011). Figure 8-2 shows a map reflecting the 

estimated agricultural use for dicamba in 2011. Heavy dicamba usage occurred in the Mid-West 

and states along the Mississippi River. Dicamba is currently labeled for use in conventional or 

glyphosate-resistant soybean, although dicamba use is extremely limited because applications are 

restricted to very early preplant and/or preharvest applications due to soybean (crop) injury 

concerns. The dicamba-treated acreage in 2011 soybean production was approximately 872,000 

acres, representing 1.2 % of the total soybean acreage (Table 8-1) (Monsanto, 2012). Dicamba 

can currently be applied to cotton in the U.S. as a pre-plant application, at least 21 days prior to 

planting. 

Figure 8-1. Dicamba Use by Year and Crop, 1992-2011.

Source: (USGS, 2013a)

Page 8-5
Figure 8-2. Estimated Agricultural Use for Dicamba, 2011.

Source: (USGS, 2013a).

Table 8-1. Dicamba-Treated Acres and Amounts Applied for Labeled Crops, 2011

Crop

Total Crop

Acres 

(x1,000)

DicambaTreated 

Acres 

(000)

% U.S. 

DicambaTreated 

Acres2

% Crop 

Acres 

Treated 

with 

Dicamba3

Dicamba 

(a.e.)

(x1,000 lb)

Asparagus 29 2 0.01 NA <1

Barley 2,460 80 0.3 3.2 6

Corn 92,146 10,880 43.0 10.3 1,531

Cotton 14,533 1,416 5.6 9.6 364

Fallow 14,899 3,966 15.7 18.7 597

Pastureland 95,532 2,009 7.9 2.0 438

Sorghum 5,315 1,316 5.2 18.1 206

Soybean 74,835 872 3.4 1.2 233

Sugarcane 825 163 0.6 15.6 36

Wheat, all 53,223 4,532 17.9 7.4 418

All other uses NA 65 0.3 NA 9

Total 25,301 100.0 3,837

Page 8-6
Definitions: a.e. = acid equivalent; lbs = pounds; NA = not applicable. 1 Source: (Monsanto, 2012; 2013). 2 The percentage of the total dicamba-treated acres for all labeled crops and uses. 3 Percentages calculated from crop acres treated with dicamba (data not shown).

Based on USDA-NASS ((USDA-NASS, 2005; 2007; 2010; 2011; 2012)) statistics, dicamba 

application rates ranged from 0.07 to 0.24 pounds per acre with the average number of 

applications ranging from 1 to 1.9 applications per cropping season. Dicamba rates are lowest in 

barley, wheat and oats, where typically more than one application is made in these crops per 

cropping season (see Table 8-2) (Monsanto, 2012).

Table 8-2. Dicamba Applications – Average Number and Rates to Labeled Crops1

Crop

# of Dicamba 

Applications

Rate of Dicamba 

per Application

Rate of Dicamba 

per Crop Year

Corn 1.2 0.209 0.249

Cotton 1.0 0.244 0.244

Sorghum 1.9 0.159 0.298

Soybean 1.0 0.223 0.223

Barley 1.0 0.112 0.112

Wheat, spring - 0.110 0.113

Wheat, winter 1.7 0.149 0.247

Oats 1.00 0.066 0.066 1

Source:(USDA-NASS, 2005)(oats), (USDA-NASS, 2007)(cotton), (USDA-NASS, 2010)(corn), (USDA-NASS, 2011)(barley & 

sorghum), (USDA-NASS, 2012)(soybean & wheat); (Monsanto, 2013).

EPA has evaluated dicamba and has concluded that it has a complete and comprehensive 

regulatory database (toxicity, environmental fate, and ecological toxicity). EPA completed the 

reregistration process for dicamba and a Registration Eligibility Decision (RED) was issued in 

2006 and subsequently amended in 2008 and 2009 (US-EPA, 2006; 2009c). EPA concluded 

there is a reasonable certainty that no harm will result to the general population, or to infants and 

children, as a result of aggregate (combined) exposure to dicamba residues; and that the available 

data submitted for dicamba are complete and adequate to support the continued registration of 

dicamba products and uses including current uses on commercial cotton and soybean. Part of 

EPA’s risk assessment included exposure to drinking water using a conservative modeled 

scenario that assumed that essentially all (87%) crop acres within the watershed were treated 

with dicamba (US-EPA, 2006; 2009c; 2011).

EPA reassessed all dicamba pesticide food and feed tolerances as part of the dicamba RED, 

including the 10 ppm soybean seed tolerance supporting the existing use in conventional soybean 

(US-EPA, 2006; 2009c). A complete listing of dicamba feed tolerances can be found at 40 CFR 

§ 180.227. Permanent tolerances are established under 40 CFR §180.227(a)(1) for dicamba and 

its 3,6-dichloro-5-hydroxybenzoic acid (5-hydroxydicamba) metabolite. Additional tolerances 

are established under 40 CFR §180.227(a)(2) for dicamba and its 3,6-dichloro-2-hydroxybenzoic 

acid (aka 3,6-diclorosalicyclic acid or DCSA) metabolite, as well as under 40 CFR 

§180.227(a)(3) for dicamba, 5-hydroxydicamba, and the DCSA metabolite. Table 8-3 lists the 

current tolerances established for commodities of cotton and soybean.

Page 8-7
Table 8-3. Tolerances for Residues of Dicamba

Commodity Tolerance

(parts per million)

Cotton, undelinted seed 0.2

Soybean, hulls1 30.0

Soybean, seed1 10.0

Source: 40 CFR §180.227 Dicamba; tolerances for residues.

1 Tolerance established for residues of the herbicide dicamba, 3,6-dichloro-o-anisic acid, including its metabolites and degradates, 

in or on the commodities. Compliance with the tolerance levels is to be determined by measuring only the residues of dicamba, 

3,6-dichloro-o-anisic acid, and its metabolites, 3,6-dichloro-5-hydroxy-o-anisic acid, and 3,6-dichloro-2-hydroxybenzoic acid, 

calculated as the stoichiometric equivalent of dicamba.

EPA Assessments of Proposed Section 3 New Uses on Dicamba-resistant Soybean and

Cotton

Before any application of dicamba can be made onto commercially cultivated dicamba-resistant 

soybean or cotton, the EPA must first approve a label describing the conditions of use of the 

herbicide in connection with dicamba-resistant soybean and cotton – including the appropriate 

application rates and timing, and other measures necessary to address potential impacts of 

dicamba offsite movement. 

The dicamba product used for treating dicamba-tolerant soybean and cotton proposed for 

registration is the M1691 Herbicide (EPA Reg. No. 524-582) which is a soluble (flowable) 

concentrate formulation. This end–use product contains 56.8% active ingredient in the form of 

the diglycolamine salt (DGA) of dicamba (equivalent to 4.0 lb ae/gal). A summary of the 

proposed directions for use taken directly from the supplemental M1691 herbicide label provided 

by the registrant are presented below in Table 8-4.

Monsanto has submitted an application to U.S. EPA to amend Registration Number 524-582, a 

low volatility DGA salt formulation, to remove all preemergence planting restrictions (intervals 

and rainfall) and to allow in-crop postemergence dicamba applications to MON 87708 soybean 

through the R1/R2 growth stage. Once approved, growers would be authorized to apply dicamba 

alone or in mixtures with glyphosate or other herbicides for preplant or in-crop postemergence 

applications on MON 87708 soybean. Dicamba would be authorized to be applied preemergence 

up to crop emergence as a single application or split applications up to a total of 1.0 lb a.e. per 

acre, and up to two postemergence applications up to 0.5 lb a.e. per acre each through the R1/R2 

growth stage of soybean. The maximum annual application rate of dicamba on MON 87708 

soybean is 2.0 lb dicamba a.e. per acre. The proposed dicamba use on soybean is summarized in 

Table 8-4.

If the proposed label is approved by EPA, dicamba would be authorized to be applied up to 1.0 

lb a.e. per acre any time prior to cotton emergence, and postemergence in-crop up to 0.5 lbs a.e. 

per acre per application up through seven days prior to harvest. Maximum application amounts 

for dicamba would be 1.0 lb a.e. per acre for preplant/preemergence applications and 0.5 lb a.e. 

per acre per in-crop application with the combined total not to exceed 2.0 lbs a.e. dicamba per 

Page 8-8
year for all applications. The proposed application rates on MON 88701 cotton would be less 

than or equivalent to rates for dicamba established for other uses in the dicamba RED including 

the 2.0 lbs a.e. dicamba per year for all applications (US-EPA, 2006; 2009c). The proposed 

dicamba use on soybean is summarized in Table 8-4.

Following EPA approval of the dicamba label amendment, growers would be authorized to apply 

dicamba alone or in mixtures with glyphosate, glufosinate, or other registered herbicides for preplant or post-emergence in-crop applications on MON 87708 soybean and MON 88701 cotton. 

Dicamba residue levels in soybean seed harvested from dicamba tolerant (DT) soybean treated 

with dicamba at more than twice the anticipated commercial in-crop application rate were less 

than 0.1 ppm, which is well below the established 10 ppm pesticide residue tolerance supporting 

dicamba use on commercial soybean. Soybean forage and hay, which can be feed to livestock, 

have no established tolerance, for that reason Monsanto is also petitioning (Pesticide Petition # 

0F7725) the agency for the establishment of new tolerances on forage (45 ppm) and hay (70 

ppm). 

Monsanto has requested a registration of an expanded use of a low-volatility DGA dicamba 

formulation on DT soybean, and petitioned (Pesticide Petition # 0F7725) the EPA to establish

new feed tolerances on soybean forage (45 ppm) and soybean hay (70 ppm). Tolerances for 

soybean forage and hay for current dicamba uses in conventional soybean were not previously 

established because the current preharvest application is made past the stage where the crop 

would be useful as forage or hay. No other revisions to dicamba pesticide residue tolerances are 

needed including animal products such as meat or milk. 

Monsanto has petitioned (Pesticide Petition # 0F7725) EPA to establish new feed tolerances on 

soybean forage (45 ppm) and soybean hay (70 ppm). Tolerances for soybean forage and hay for 

current dicamba uses in conventional soybean were not previously established because the 

current preharvest application is made past the stage where the crop would be useful as forage or 

hay. No other revisions to dicamba pesticide residue tolerances are needed including animal 

products such as meat or milk. 

Dicamba residue levels in cottonseed harvested from dicamba-glufosinate tolerant (DGT) cotton 

treated with dicamba at the anticipated commercial in-crop application rate, and were 0.54 ppm, 

which is greater than the established 0.2 ppm pesticide residue tolerance supporting dicamba use 

on commercial cotton (40 CFR § 180.227) which is for the combined residues of parent dicamba 

and its metabolite 5-hydroxy dicamba. Cotton gin by-products, which serve as a ruminant feed 

supplement, have no established dicamba tolerance PP 2F8067 for the expanded use of dicamba 

on MON 88701, an increase in the dicamba residue tolerance from 0.2 ppm to 3 ppm for 

cottonseed, the establishment of a tolerance of 70 ppm for cotton gin by-products, and the 

inclusion of DCSA in the residue definitions for cottonseed and gin by-products.

Based on the studies submitted on the DGA salt formulation of dicamba by Monsanto, EPA has 

conducted draft assessments on the potential environmental fate, ecological effects, and human 

health effects of the proposed new uses of dicamba DGA salt. The conclusions from those 

assessments are summarized in this section. EPA will be publishing these complete draft 

analyses in the Federal Register for public comment.

Page 8-9
Table 8-4. Summary of Directions for Proposed Uses of Dicamba on MON 87708 Soybean 

and MON 88701 Cotton

Formulation 

[EPA Reg. 

No.]

Applic. 

Timing, 

Type, and 

Equip.

Max. 

Applic. 

Rate

(lb ae/A)

Max. No. 

Application

per Season

Max. 

Seasonal 

Application 

Rate

(lb ae/A)

Combined 

Max. 

Seasonal 

Application

Rate

(lb ae/A)

RTI1

(days)

PHI2

(days)

Use Directions 

and Limitations3

MON 87708 Soybean

M1691

4.0 lb ae/gal 

SL

[524-582]

Preemergence

Broadcast 

(20 gal/A)

1.0 NS4 1.0 2.0 7 7 The maximum 

rate for any 

single, in-crop 

(post-emergence) 

application must 

not exceed 0.5 lb 

dicamba a.e. per 

acre.

A second postemergence 

application may 

follow up to the 

R1 reproductive 

stage

Postemergence, 

Broadcast

(20 gal/A)

0.5 NS 2.0

MON 88701 Cotton

M1691

4.0 lb ae/gal 

SL

[524-582]

Preemergence

Broadcast 

(20 gal/A)

1.0 NS4 1.0 2.0 7 7 Use of a COC or 

MSO is not 

recommended 

with Roundup 

branded 

herbicides. These 

adjuvants are only 

used when other 

products require 

them. For best 

results apply at 

min spray rate of 

10 GPA.

Postemergence, 

Broadcast

(20 gal/A)

0.5 NS 2.0

1

 RTI = Re-Treatment Interval 2

 PHI = Pre-Harvest Interval 3

 COC = Crop Oil Concentrate; MSO = Methylated Seed Oil. 4

 NS = Not Specified

Page 8-10
Human Health Risk Assessment

The EPA Health Effects Division (HED) of the Office of Pesticide Programs (OPP) is charged 

with estimating the risk to human health from exposure to pesticides. HED evaluated hazard and 

exposure data and conducted dietary, residential (non-occupational), aggregate, and occupational 

exposure assessments to estimate the risk to human health that will result from the proposed new 

use of the DGA salt formulation of dicamba on dicamba-resistant soybean and cotton. Based on 

information contained in Monsanto’s pesticide petition and the label conditions HED has 

concluded that the request for a registration for the use of the DGA salt formulation of dicamba 

on dicamba-resistant soybean and cotton would pose a reasonable certainty of no harm to 

humans. A summary of the results of the assessment are provided, below. The draft assessment 

will be published by EPA in the Federal Register for public review and comment.

“Monsanto has submitted new metabolism studies for dicamba-tolerant soybean and 

cotton, which show that dicamba generally follows the same metabolic pathway to other 

plants. Dicamba applied to dicamba-tolerant soybean and cotton is converted to the nonherbicide metabolite 3,6-dichlorosalicylic acid (DCSA) and its glycosidic conjugates, 

which are the main metabolites formed. In a minor metabolic pathway, DCSA is 

hydroxylated at the 5-position, to form 2,5-dichloro-3,6-dihydroxybenzoic acid (DCGA) 

and its glycosidic conjugates, which are found in amounts less than 10% of the total 

radioactive residue (TRR). The dicamba metabolite 5-hydroxydicamba was not identified 

in the TRR of dicamba-tolerant soybean and cotton. 

The nature of residues for dicamba-tolerant soybean and cotton is understood. The 

residues of concern (ROC) for monitoring the tolerance under 40 CFR §180.227(a)(3) for 

soybean includes parent dicamba, and the metabolites 5-hydroxydicamba, and DCSA 

remains appropriate. Data from the newly submitted metabolism and field trial studies 

support including residues of DCSA to the tolerance expression for cotton to fall under 

40 CFR §180.227(a)(3). These data also necessitate including DCGA to the ROCs for 

the risk assessment of soybean which include the residues established for tolerance 

expression (parent, 5-hydroxydicamba, and DCSA).

The nature of dicamba residues in animals and in rotational crops were previously 

determined based on acceptable studies. The establishment of a tolerance on soybean 

forage and hay, as well as on cotton gin byproducts will not increase livestock dietary 

burden; therefore, no new revised tolerances on livestock commodities are required to 

support this petition. 

The residue values obtained from the field trial studies were evaluated using the 

Organization for Economic Cooperation and Development (OECD) calculation 

procedures for estimating tolerances/Maximum Residue Limits (MRLs). Using the 

OECD calculation procedures, and inputting the total residue, which includes the sum of 

the parent compound, and its metabolites 5-OH dicamba, and DCSA, expressed as parent 

equivalents, tolerances of 60 ppm for soybean forage and 100 ppm for soybean hay are 

recommended. The current tolerances of 10 ppm in soybean seed and 30 ppm in soybean 

hull are adequate. For cotton, the OECD calculation procedures determined that the 

recommended tolerances of 3.0 ppm for cotton undelinted seed and 70.0 ppm for cotton 

Page 8-11
gin byproducts are appropriate. The US EPA and PMRA (Canada) established a 

harmonized tolerance (MRL) for soybean on seed at 10 ppm. 

There are currently no Mexican, Canadian or Codex MRLs established for soybean 

forage and hay as well as in cotton gin byproducts. There are MRLs of 0.2 ppm in 

Mexico and 0.04 ppm established by Codex on cotton seed currently established. Since 

the registrant has requested a late season use of dicamba on dicamba-tolerant cotton, the 

currently established international tolerances are inadequate to cover residues likely from 

the newly proposed use in the U.S. In addition, the dicamba residues of concern for 

dicamba-tolerant cotton also include the DCSA metabolite which is not found nor 

regulated in the other common varieties of cotton. Therefore, harmonization is not 

possible at this time for cotton seed. Since there are no international tolerances on cotton 

gin byproducts, there is no issue of international harmonization relevant to that tolerance. 

There are no proposed residential uses at this time; however, there are existing residential 

uses that have been reassessed in this document to reflect updates to HED’s 2012 

Residential Standard Operating Procedures (SOPs). The residential handler and postapplication risk estimates are not of concern for dicamba for all scenarios and all routes 

of exposure.

The label-required personal protective equipment (PPE) include that mixers, loaders, 

applicators and other handlers wear a long-sleeved shirt and long pants, socks, shoes, and 

chemical-resistant gloves (except for applicators using ground boom equipment, pilots or 

flaggers). The restricted entry interval (REI) on the proposed label is 24 hours. The 

occupational handler and post-application risk estimates are not of concern for dicamba 

for all scenarios and all routes of exposure for the use on herbicide-tolerant cotton and 

soybean.”

Environmental Fate and Ecological Risks

The Environmental Fate and Effects Division (EFED) has completed a review of the new use 

request for the herbicide dicamba [M1691 Herbicide, EPA Reg. No. 524-582 diglycolamine salt 

of dicamba (DGA); PC code 128931)] for use on dicamba-tolerant soybeans (MON 87708). 

Dicamba is currently registered for use on soybeans at applications rates similar to those 

proposed for the new use. The use of dicamba on soybeans was assessed by the Environmental 

Fate and Effects Division (EFED) in 2005 (USEPA, 2005, D317696). The primary difference 

between the proposed new use on soybeans and the previous soybean use assessed is the timing 

of the applications. The current registration for dicamba use on soybeans is limited to preemergence applications; however, for the proposed new use on dicamba-tolerant soybeans, 

dicamba could be applied pre-emergence and/or post-emergence. Therefore, an abbreviated 

ecological risk assessment is provided.

The draft assessment will be published by EPA in the Federal Register for public review and 

comment. The results are summarized as follows:

“Based on the proposed maximum application rates, there is a potential for direct adverse 

effects to listed and non-listed birds (acute exposure), listed and non-listed mammals 

Page 8-12
(chronic exposure), listed vascular aquatic plants, and listed and non-listed terrestrial dicots 

from the proposed new use. This assessment uses new submitted information on the toxicity 

of diglycolamine salt of dicamba (DGA) to terrestrial plants. Although for monocots toxicity 

of the DGA salt formuation is decreased compared to TGAI dicamba acid, the vegetative 

vigor data indicate that toxicity in the DGA salt formulation is enhanced for dicots. It is 

unclear if the enhanced toxicity to dicots is due to synergistic effects with surfactants and 

adjuvants in the formulation used (Clarity Herbicide, EPA Reg No. 7969-137, 56.8% DGA 

salt) or due to the DGA salt itself. The study with TGAI dicamba acid did not use surfactants 

or adjuvants. Although levels of concern were not exceeded for listed and non-listed species 

of monocots, exceedances for monocots would occur if toxicity data for dicamba acid was 

used in place of the data for the DGA salt. Risks to aquatic animals from chronic exposure to 

dicamba could not be assessed at this time because of a lack of data; therefore, since risk to 

these taxa cannot be precluded, it is assumed.

At this time, no federally-listed taxa can be excluded from the potential for direct and/or 

indirect effects from the proposed new use of dicamba, since there is a potential for indirect 

effects to taxa that might rely on plants, birds, aquatic animals, and/or mammals for some 

stage of their life-cycle. A complete co-occurrence analysis could not be completed for listed 

species at this time, since the specific use site associated with the proposed new use of 

dicamba ( dicambatolerant soybeans) is not available for analysis in LOCATES. Therefore, 

without further refinement, no species currently listed as federally threatened or endangered 

can be excluded from the potential for adverse effects from the proposed new use of dicamba.

Although the risks, based on standard risk assessment methods used by the Environmental 

Fate and Effects Division (EFED), are not expected to differ from the previous assessment 

done for dicamba use on soybeans (because the rates are similar to those already assessed), 

there is potential for other ecological concerns that would not normally be captured using our 

standard risk assessment methods. These concerns are related to a potential increase in usage 

of dicamba products and the proposed changes in the timing of applications. In general, there 

is also a potential for increased susceptibility of late season plants to direct impact from offsite transport. Thus, unlike previous assessments of dicamba the risk conclusions in this 

assessment have increased uncertainty.”

Glufosinate Ammonium

Glufosinate is a nonselective herbicide that is registered for preplant and post-emergent 

applications to control broadleaf weeds in a variety of crop and non-crop areas. Additionally, it is 

also used as a defoliant and as a means of conducting chemical burndown. 

Since it is a nonselective herbicide it injures or kills crop plants that it contacts. Glufosinate is a 

contact herbicide which is taken up by the plant primarily through the leaves. There is no uptake 

from the soil through the roots, presumably because of the rapid degradation of glufosinate by 

soil microorganisms. There is limited translocation of glufosinate within the plant.

Glufosinate herbicides contain the active ingredient phosphinothricin and are in the phosphinic 

acid family of herbicides. The herbicide acts by blocking the plant enzyme glutamine 

synthetase, which is responsible for nitrogen metabolism and for detoxifying ammonia, a byproduct of plant metabolism. The exposed plant dies by the over-accumulation of ammonia 

(US-EPA, 2008).

Page 8-13
First registered with EPA in 1993, initial glufosinate end-use products were designed for home 

owners; light industrial, non-food users; and farmstead, weed-control users (OSTP, 2001). 

Glufosinate is registered for use on apples, berries, canola, citrus, corn, cotton, currants, grapes, 

grass grown for seed, olives, pome fruit, potatoes, rice, soybeans, stone fruit, sugar beets, and 

tree nuts. Registrations for noncrop areas include golf course turf, residential lawns, 

ornamentals, and a variety of industrial and public areas. 

Application rates of glufosinate range significantly by use pattern, with the highest rate allowed 

for broadcast (ground) spray applications, at 1.5 lb a.i./A, on orchard nuts and fruits, grapes, 

grasses grown for seed, and golf course turf. On the low end of application rates, labeled uses of 

glufosinate on turf and patio are at 0.03 lb a.i./A. Multiple applications are allowed by most 

labels, although the interval is not generally specified (US-EPA, 2008).

Based on its proprietary data for the period from 2007–2011, EPA estimated that the highest 

annual agricultural uses of glufosinate are in corn (1.3 million lb), almonds (200,000 lb), cotton 

(200,000 lb), grapes (200,000 lb), canola (100,000 lb) and soybeans (100,000 lb) (Table 8-5) 

(US-EPA, 2012a). Almonds, cotton, and grapes are also appreciable uses reported in the BEAD 

analysis. Uses which have not been calculated do not imply zero use, though they are likely low 

in comparison to those uses that are quantified in Table 8-5. Stone fruits, such as peaches, 

cherries, and plums/prunes, are new uses which were approved in 2012. Registered nonagricultural uses, such as fallow fields, lawns and gardens, conifer tree areas, and non-crop areas 

(e.g., farmstead building foundations, shelter belts, along fences, etc.) are not captured in the 

above data. These data do not include non-agricultural uses (US-EPA, 2013a). 

The map in Figure 8-3 shows the use of glufosinate from 2011, with most use of glufosinate 

concentrated in the Midwest (USGS, 2013b). Figure 8-4 shows the increasing use of glufosinate 

in crops (USGS, 2013b).

Page 8-14
Table 8-5. Estimates of Agricultural Usage of Glufosinate, 2007-2011.

Source: (US-EPA, 2012a; 2013a).

Page 8-15
Figure 8-3. Estimated Annual Agricultural Use of Glufosinate in the U.S. Source: (USGS, 2013b).

Figure 8-4. Glufosinate Use by Year and Crop, 1992 to 2011

Source: (USGS, 2013b).

Both aerial and ground spray is allowed for most uses, although some applications are limited to 

methods using hand wands and backpack sprayers. As glufosinate is designed primarily to 

control broadleaf weeds, applications are normally ground applications, to prevent damage to 

crops. Aerial application is considered a viable option for genetically modified crops (e.g., 

Page 8-16
canola, corn, cotton, rice, sugarbeets, and soybeans) that are resistant to glufosinate’s herbicidal 

properties, and for burndown applications.

Several crop plants have been modified by inserting a gene that produces an enzyme which 

detoxifies glufosinate by converting the herbicide into a non-active form. The PAT (bar) protein 

acetylates the free amino group of glufosinate to produce non-herbicidal N-acetyl glufosinate, a 

known metabolite in glufosinate-tolerant plants (OECD, 2002). Bayer Crop Science has 

registered glufosinate for use on glufosinate-resistant crops, including corn, soybean, and cotton. 

Ignite 280 SL Herbicide (EPA Reg. No. 264-829) is a commercially available glufosinate

containing herbicide with directions for use on glufosinate-resistant crops. Glufosinate is 

currently labeled for in-crop application with glufosinate-tolerant cotton from emergence through 

early bloom growth stage (Bayer CropScience, 2011) (Table 8-6).

Table 8-6. Current Labeled Application Rates for Glufosinate-resistant Cotton.

Use Pattern 1st Application 

(Burndown)

2nd

Application

3rd

Application

Season 

Maximum

Cotton Use 

Pattern 1 22-29 fl oz/A 22-29 fl oz/A 22-29 fl oz/A 87 fl oz/A

Cotton Use 

Pattern 2 30-43 fl oz/A 22-29 fl oz/A None 72 fl oz/A

Source: (Bayer CropScience, 2011).

Due to its nonselective activity, glufosinate has a weed management spectrum similar to 

glyphosate and its use has grown, particularly in areas with glyphosate-resistant weeds 

(Southeast Farm Press, 2012). In the southeast in 2011, glufosinate was the ninth most 

frequently used herbicide on soybean. Glufosinate use is likely to continue to follow the recent 

trend of increased use associated with the adoption of glufosinate-resistant crops.

Although glufosinate provides an additional means of weed control, it is not as versatile as 

glyphosate. For example, glufosinate needs to be applied to smaller weeds with finer droplet sizes 

and larger carrier volumes to achieve adequate control. This is in part because, unlike glyphosate 

which translocates readily throughout the plant, glufosinate has limited mobility and thus requires

better coverage for control (hence the larger carrier volumes and smaller droplet sizes)

(Monsanto, 2013).

Products include Derringer® (Reg. No.432-1228), Derringer® F Herbicide (Reg. No. 432-960), 

Finale® Super Concentrate (Reg. No.432-954), Finale® Ready-to-Use (Reg. No. 432-955), 

Finale® Concentrate (Reg. No. 432-956), Finale® Herbicide (Reg. No. 432-1229), Glufosinate 

280 (Reg. No. 88685-2), Liberty® (Reg. No. 264-660), Liberty® ATZ (Reg. No. 264-668), 

Liberty 280® (Reg. No. 264-829), Rely® (Reg. No. 264-652), and Remove® (Reg. No. 264-663).

The EPA-established glufosinate residue tolerances are 4.0 ppm and 15.0 ppm for cottonseed and 

gin by-products, respectively (40 CFR 180.473). Both of these tolerances include the combined 

residues of parent glufosinate and its metabolites N-acetyl glufosinate and 3-methylphosphinicopropionic acid.

Page 8-17
Currently glufosinate is undergoing Registration Review at EPA with a decision expected by the 

end of 2013 (US-EPA, 2008). It is expected that EPA will affirm the safety and efficacy of 

glufosinate and approve its continued use in the marketplace upon completion of the registration 

process.

Glufosinate Use on MON 88701 Cotton

Glufosinate use on MON 88701 cotton will be equivalent to currently deregulated glufosinateresistant cotton. The use pattern and rate of glufosinate application on MON 88701 cotton will 

follow the existing glufosinate-resistant cotton uses outlined on the existing glufosinate herbicide

label (Bayer Crop Science, 2007). Like commercially available glufosinate-resistant cotton, 

MON 88701 cotton enables application of up to 0.53 lb a.i. per acre per application of 

glufosinate from emergence through early bloom growth stage. Monsanto has confirmed that 

glufosinate residues on MON 88701 cotton treated with commercial glufosinate rates are below 

the established pesticide residue tolerances established by EPA for both cottonseed and gin byproducts (40 CFR 180.473). Consequently, Monsanto is not pursuing any changes in the 

glufosinate label or the established tolerances for its use on MON 88701 cotton (Monsanto, 

2013).

Glyphosate

Glyphosate acid is a broad spectrum, nonselective systemic herbicide widely used to control most 

annual and perennial grass and broadleaf weeds in agricultural crops and non-agricultural sites. The 

herbicide is registered for pre- and post-emergence application on a variety of fruit, vegetable, and 

field crops, as well as for aquatic and terrestrial uses. Labeled uses of glyphosate include over 100

terrestrial food crops as well as other non-food sites including forestry, greenhouse, non-crop, and 

residential. Glyphosate can also be used as a plant growth regulator and accelerate fruit ripening. 

Additionally, glyphosate is registered for use on GE glyphosate-resistant crops, including canola, 

corn, cotton, soybeans, alfalfa, and sugar beets. Glyphosate is the most widely used herbicide on 

U.S. corn, soybean, and cotton. 

Glyphosate was first introduced under the trade name of RoundupTM by Monsanto in 1974. 

Glyphosate salts serve as the source of the active ingredient (a.i.) N-(phosphonomethyl) glycine 

and improve handling, performance, and concentration of the glyphosate acid. Glyphosate is 

distributed in several forms, including technical grade glyphosate, isoproplyamine salt, 

monoammonium salt, diammonium salt, N-methylmethanamine salt , trimethylsulfonium salt, or 

potassium salt (US-EPA, 2009b). Isopropylamine salt is the most typically used form in 

formulated products (Henderson, 2010).

Glyphosate acid is a nonselective Group 9 herbicide and kills plants by inhibiting the 5-

enolpyruvylshikimate-3-phosphate synthase (ESPS) enzyme. This enzyme is essential for the 

biosynthesis of aromatic amino acids (e.g., tyrosine, tryptophan, and phenylalanine) and other 

aromatic compounds in algae, higher plants, bacteria and fungi. By creating a deficiency in 

EPSP enzyme and aromatic amino acids production, glyphosate affects protein synthesis and 

plant growth (US-EPA, 2009b). Glyphosate is absorbed across the leaves and stems of plants 

and moves throughout the plant, concentrating in the meristem tissue (Henderson, 2010).

Glyphosate use is concentrated heavily in the Midwest, along the Mississippi River, the 

Southeast seaboard, and the Central Valley of California, as depicted in Figure 8-5. 

Page 8-18
Figure 8-5. Estimated Agricultural Use for Glyphosate, 2011

Source: (USGS, 2013c).

Based on pesticide usage data from USDA-NASS, private pesticide market research, and 

California Department of Pesticide Regulation (DPR), EPA estimated glyphosate usage from 

2004 through 2011. The crops with the highest glyphosate uses (based on average treated 

fraction of acreage) were: almond (85%), apples (55%), apricots (55%), asparagus (55%), 

avocados (45%), barley (20%), blueberries (20%), canola (65%), cherries (65%), corn (60%), 

cotton (85%), cucumbers (20%), dates (20%), dry beans/peas (25%), fallow (55%), figs (40%), 

grapefruit (80%), grapes (70%), hazelnuts (70%), kiwifruit (30%), lemons (70%), nectarines 

(45%), olives (45%), onions (30%), oranges (90%), peaches (55%), peanuts (20%), pears (65%), 

pecans (35%), peppers (20%), plums (65%), pumpkins (20%), rice (25%), sorghum (40%), 

soybeans (95%), squash (20%), sugar beets (50%), sugarcane (45%), sunflowers (55%), tangelos 

(55%), tangerines (65%), tomatoes (35%), walnuts (75%), and wheat (25%). All other treated 

crops averaged 15% or less of the total acreage grown (US-EPA, 2012b). Figure 8-6 shows the 

glyphosate use on crops from 1992 to 2011.

The current approved maximum pre-emergence application of glyphosate on glyphosate-resistant 

corn or soybeans is 3.7 lb a.e./acre. A glyphosate post-emergence application from 0.75 to 1.5 lb 

a.e./acre (total 2.25 lb/acre/season post-emergence) and an additional pre-harvest application of 

0.77 lb a.e./acre are permitted. The current maximum total seasonal use rate for glyphosate on 

glyphosate-resistant corn and soybean is 6 lb a.e./acre.

Page 8-19
Figure 8-6. Glyphosate Use by Year and Crop, 1992 to 2011.

Source: (USGS, 2013c).

Pesticide residue tolerances for glyphosate are listed in 40 CFR Part 180.364, representing

combined residues of glyphosate, N-(phosphonomethyl)glycine and its metabolite N-acetylglyphosate (expressed as glyphosate) (US-EPA, 2010). Table 8-7 shows the current tolerances 

for residues of glyphosate established for corn and soybean commodities.

Table 8-7. Glyphosate Tolerances for Corn and Soybean Commodities

Commodity Residue (parts per million)

Cotton, gin byproducts 210

Soybean, forage 100

Soybean, hay 200

Soybean, hulls 120

Soybean, seed 20

Source: 40 CFR 180.364

EPA is currently conducting a registration review of glyphosate which was begun in 2009 and is 

currently scheduled to be completed in 2015 (US-EPA, 2009a). According to EPA, as part of 

their review, “the Agency plans to require a number of ecological fate and effects studies, an acute 

and subchronic neurotoxicity study, and an immunotoxicity study through a data call-in, which is 

expected to be issued in 2010. The new information will be used to conduct a comprehensive 

ecological risk assessment, including an endangered species assessment, as well as a revised 

occupational human health risk assessment, for all glyphosate pesticidal uses (US-EPA, 2009a).”

All documents related to the glyphosate registration review can be viewed at the registration

review docket:

http://www.regulations.gov/#!docketDetail;D=EPA-HQ-OPP-2009-0361

Page 8-20
MON 87708 soybean and MON 88701 cotton are intended to be combined with glyphosateresistant varieties utilizing traditional breeding techniques. The combined system will support 

long term sustainability of weed management in soybean and cotton and, in turn, support 

sustained, economic cotton production.

References:

Bayer Crop Science. "Liberty® herbicide label." Bayer CropScience. Research Triangle Park, 

North Carolina: Bayer Crop Science, 2007.

Bayer CropScience (2011) "Ingite 280 SL Herbicide Label 5a " Bayer 

CropScience. http://fs1.agrian.com/pdfs/Ignite_280_SL_Herbicide_Label5a.pdf.

Henderson, AMG, J. A.; Luukinen, B.; Buhl, K.; Stone, D. "Glyphosate Technical Fact Sheet." 

Ed. National Pesticide Information Center, Oregon State University Extension 

Services.2010. 14. http://npic.orst.edu/factsheets/glyphotech.pdf.

HRAC (2009) "Classification of herbicides according to mode of action." Herbicide Resistance 

Action 

Committee. http://www.hracglobal.com/Publications/ClassificationofHerbicideModeofA

ction/tabid/222/Default.aspx.

McClelland, MR; Smith, KL; and Norsworthy, JK (2006) "Managing Glyphosate-Resistant 

Horseweed in Conservation-Tillage Cotton Production: Final Summary and 

Recommendations." AAES Research Series. p 108-11. 

Monsanto. "Unpublished grower survey data performed by a contracting agency." St. Louis, 

Missouri: Monsanto Company, 2012.

Monsanto. "Petitioner’s environmental report for dicamba-tolerant soybean MON 87708 and 

dicamba- and glufosinate-tolerant cotton MON 88701." St. Louis, Missouri: Monsanto 

Company, 2013. Vol. November 22, 2013.

OECD (2002) "Module II: Herbicide biochemistry, herbicide metabolism and the residues in 

glufosinate-ammonium (Phosphinothricin)-tolentant transgenic plants." 

OSTP (2001) "Case Studies of Environmental Regulation for Biotechnology: Herbicide-Tolerant 

Soybean." The White House Office of Science and Technology 

Policy. http://www.whitehouse.gov/files/documents/ostp/Issues/ceq_ostp_study4.pdf.

Southeast Farm Press (2012) "Glufosinate herbicide shortage sparks 

controversy." http://southeastfarmpress.com/cotton/glufosinate-herbicide-shortagesparks-controversy.

US-EPA (2006) "Reregistration Eligibility Decision for Dicamba and Associated Salts." 

Environmental Protection Agency. http://www.epa.gov/oppsrrd1/REDs/dicamba_red.pdf.

US-EPA (2008) "Glufosinate final work plan registration review: August 2008." 

US-EPA (2009a) "Glyphosate Final Work Plan (FWP) - Registration Review Case Number 

0178." Office of Prevention, Pesticides, and Toxic 

Substances,. http://www.regulations.gov/#!documentDetail;D=EPA-HQ-OPP-2009-

0361-0042.

US-EPA (2009b) "Registration Review- Preliminary Problem Formulation for the Ecological 

Risk and Drinking Water Exposure Assessments for Glyphosate and Its Salts (PC Code 

417300, 103601, 103604, 103607, 103608, 103613, 103603, 103605, 

Page 8-21
128501)." http://www.regulations.gov/#!documentDetail;D=EPA-HQ-OPP-2009-0361-

0007.

US-EPA (2009c) "Sodium and Potassium Dimethyldithiocarbamate Salts Amendment to the 

Ferbam (PC Code 034801) and Ziram (PC Code 034805) Reregistration Eligibility 

Decisions." Environmental Protection 

Agency. http://www.epa.gov/opp00001/reregistration/REDs/ddcsalts-red-amended.pdf.

US-EPA (2010) "40 CFR §180.364 - Glyphosate; tolerances for residues. ." U.S. Environmental 

Protection Agency. http://cfr.vlex.com/vid/180-364-glyphosate-tolerances-residues19814904.

US-EPA (2011) "2011 edition of the drinking water standards and health advisories." 

US-EPA (2012a) "Glufosinate (128850) Screening Level Usage Analysis (SLUA)." Office of 

Chemical Safety and Pollution 

Prevention. http://www.regulations.gov/#!documentDetail;D=EPA-HQ-OPP-2008-0190-

0029.

US-EPA (2012b) "Updated Screening Level Usage Analysis (SLUA) Report in Support of 

Registration Review of Glyphosate." Office of Chemical Safety and Pollution 

Prevention. http://www.regulations.gov/#!documentDetail;D=EPA-HQ-OPP-2009-0361-

0045.

US-EPA (2013a) "Preliminary Ecological Risk Assessment for the Registration Review of the 

Herbicide, Glufosinate-ammonium." 

US-EPA (2013b) "Setting tolerances for pesticide residues in foods." Last Accessed: November 

5, 2013 http://www.epa.gov/opp00001/factsheets/stprf.htm.

USDA-AMS (2013) "Pesticide data program annual summary, calendar year 

2011." http://www.ams.usda.gov/AMSv1.0/getfile?dDocName=stelprdc5102692.

USDA-NASS (2005) "Agricultural Statistics 2005." USDA- National agricultural Statistics 

Service. 

USDA-NASS (2007) "Census of Agriculture: Summary and State Data Volume 1 • Geographic 

Area Series • Part 51." USDA-National Agricultural Statistics Service. 

USDA-NASS (2010) "Agricultural Statistics 2010." USDA-National Agricultural Statistics 

Service. 

USDA-NASS (2011) "Agricultural Statistics 2011." UDSA-National Agricultural Statistics 

Service. 

USDA-NASS (2012) "Census of Agricultrue-Preliminary Report." USDA-National Agricultural 

Statistics Service. 

USGS. "Pesticide Use Maps - Dicamba." Pesticide National Synthesis Project 

2013a. http://water.usgs.gov/nawqa/pnsp/usage/maps/show_map.php?year=2011&map=

DICAMBA&hilo=L&disp=Dicamba.

USGS. "Pesticide Use Maps - Glufosinate." Pesticide National Synthesis Project 

2013b. http://water.usgs.gov/nawqa/pnsp/usage/maps/show_map.php?year=2011&map=

GLUFOSINATE&hilo=H&disp=Glufosinate.

USGS. "Pesticide Use Maps - Glyphosate." Pesticide National Synthesis Project 

2013c. http://water.usgs.gov/nawqa/pnsp/usage/maps/show_map.php?year=2011&map=

GLYPHOSATE&hilo=H&disp=Glyphosate.

Page 8-22
Appendix 9. Monsanto Tillage Report

Page 9-1
[This document has been submitted by Monsanto Company for use by USDA APHIS in support 

of a request for nonregulated status for Xtend soybean and cotton crops. USDA APHIS has 

chosen to include this section in its entirety because it is the most recent and comprehensive 

regional analysis of agricultural tillage.]

Introduction

Recently there have been speculation and in some cases, reports, that the growth of conservation 

tillage acres and, in particular, no-till acres has slowed or is reversing in some parts of the 

country. Accordingly, Monsanto undertook an analysis of grower market research information

from an independent market research company and follow up consultation with leading 

conservation tillage experts to understand more precisely current tillage trends and reasons for 

these trends in key soybean, corn and cotton growing areas.

Multiple factors could influence conservation tillage practices. Growth in the spread of 

glyphosate-resistant weed populations has been speculated or reported to be one such factor, 

because of the need for some farmers to incorporate more tillage into their farming operations in 

order to control some difficult to control weed species, such as Palmer amaranth. For example, 

where populations of glyphosate-resistant Palmer amaranth have grown large in areas such as 

Georgia, western Tennessee, and Arkansas, weed control experts recommend deep pre-plant 

tillage as one way to reduce the population before other weed control measures are applied 

(Culpepper, et al. 2013; Culpepper, et al. 2011; Price, et al. 2011). However, growers and 

leading conservation experts themselves report a range of factors other than weed management 

that can and do influence farmer practices relative to conservation tillage practices.

Materials and Methods

This analysis used market research data from an unpublished national grower survey conducted 

by a third party market research company. The data retrieved from this database included the 

number of crop acres planted conventionally, in a no-till system, or in a reduced tillage system. 

No-till acres are defined as those in which the farmer does not till the ground after the harvest of 

the last crop and before planting a new crop. Reduced tillage (reduced-till) is defined as 

situations where the farmer practices various types of reduced tillage after harvest of the last crop 

and before planting the new crop where significant crop residues (~15%-30%) are left on the soil 

surface. Examples of reduced tillage practices include ridge-till (planting row crops on 

permanent ridges), strip-till (planting crops directly in narrow strips that had been tilled), and 

mulch-till (any reduced tillage system that leaves at least 1/3 of soil surface covered with crop 

residue). Conventional tillage (conventional) is defined as situations where the farmer conducts 

several tillage operations such that the new crop is planted into soil with little to no surface 

residue.

The farmer market research data was sorted by crop (soybeans, cotton, and corn) and state. 

Selected states were combined into growing regions (East, Midwest, Southeast, Mid-South, and 

West, as indicated in Table 1). Data was retrieved for the period from 1998 through 2013 for 

soybeans and corn, and through 2012 for cotton (Note: 2013 cotton data from the market 

Page 9-2
research company is not currently available). The estimated acreage of each tillage type for each 

crop and growing region was converted to percent of total crop planted acreage and submitted 

for statistical regression analysis over the designated time period. The data was analyzed to fit a 

linear or quadratic regression model at the 5% level of significance. Details of the statistical 

analysis are provided in the statistical report found in Appendix A [of the Environmental Report 

(ER)].

To understand possible reasons for some of the changes observed in this data set, Monsanto 

worked with CTIC (Conservation Tillage Information Center, www.ctic.org) to conduct a survey 

of leading conservation tillage experts in select Midwest, Southeastern and Mid-South. (Note: 

experts from these areas were surveyed because they represent the major regions for the 

production of soybean, corn and cotton, and because they represent the areas with the highest 

levels of herbicide resistant weeds). In this survey, the experts were asked to indicate the level 

of importance of 11 different factors to farmers as they make decisions as to which tillage system 

and in general how much tillage they will use on their farm(s). Examples of factors included 

“manage excess crop residue,” “manage existing weeds,” “manage disease,” “economics,” and 

“prevent weed resistance.” To rank the factors, a number from 1 to 4 was assigned to each

response category, with 1 assigned to “not important or not mentioned” and 4 assigned to 

“extremely important”. The experts were not limited in the number of factors to which they 

could assign an individual ranking. (i.e., the experts could rank all – or none – of the 11 factors 

as “extremely important”). The assigned number was multiplied by the number of responses 

from the experts and then added together for each factor. The factors with the 5 highest 

numerical sums are listed in Table 3 for each crop and region. The detailed results of this survey 

for corn, soybeans and cotton can be found in Appendix B [of the ER] .

Table 1. States in each Geographic Region

Region Crop Focus States

East Corn, soybean Connecticut, Delaware, Maine, Maryland, Massachusetts, 

New Hampshire, New Jersey, New York, Pennsylvania, 

Rhode Island, Vermont, West Virginia

Southeast Corn, cotton, 

soybean

Alabama, Georgia, S. Carolina, N. Carolina, Virginia, 

Florida

Mid-South Corn, cotton, 

soybean

Mississippi, Louisiana, Arkansas, Tennessee

Midwest Corn, cotton, 

soybean

Ohio, Michigan, Indiana, Illinois, Wisconsin, Missouri, 

Minnesota, Iowa, Kentucky, Kansas, Nebraska, N. Dakota, 

S. Dakota

West Corn, cotton, 

soybean

Arizona, California, New Mexico, Oklahoma, Texas, 

Colorado, Idaho, Montana, Nevada, Utah, Washington, 

Wyoming 

Page 9-3
Results and Discussion

A summary of the results of the grower market research data analysis on tillage trends can be 

found in Table 2. Key points are as follows:

• From 1998 to 2007, the conventional tillage acreage decreased and no-till acres increased 

across all crops and geographic areas. Likewise, reduced tillage acres generally increased 

during this time period, although for some areas and crops, no significant relationship 

between the tillage practice and time could be detected. The growth in no-till and 

reduced tillage acres coincides with, and was facilitated by, the growth in glyphosatetolerant corn, soybean and cotton acres (Givens, et al. 2009a; Givens, et al. 2009b; 

McClelland, et al. 2000; Osteen and Fernandez-Cornejo 2013; Sankula 2006; Towery and 

Werblow 2010). 

• Since 2007, however, some crops in some geographic areas have continued to see growth 

in no-till acreage, while other crops in other geographic areas have seen decreases in notill acreage, accompanied by an increase in conventional and/or reduced tillage acreage. 

A more detailed, crop-by-crop discussion is presented below.

• Corn: From 1998 to 2007, the conventional tillage acreage decreased and no-till acres 

increased across all geographic areas. From 2007 through 2013, the trends varied across 

regions:

o In the West and East, conventional tilled corn acres continued to decrease, and 

no-till acreage continued to increase. Reduced tillage acres also increased in the 

West, but there was no clear trend in the East.

o In the Midwest, conventional tilled corn acres continued to decrease but there 

appeared to be a shift from strict no-till practices to reduced tillage acres where 

some tillage is practiced but significant (15% -30%) crop residues remain on the 

surface at planting. 

o In the Southeast, conventional tillage acres planted to corn tended to level off or 

increase while no-till acres tended to decrease.

o In the Mid-South, there were no significant trends in conventional or no-till 

acreage, but reduced till acres increased throughout the time period.

• Soybean: From 1998 to 2007, the conventional tillage acreage decreased and no-till 

acres increased across all geographic areas. From 2007-2013, the trends varied across 

region:

o In the West, conventional tilled soybean acres continued to decrease, and no-till 

acreage continued to increase. There was no significant trend for reduced tillage 

acres.

o In the East, Midwest, Southeast and Mid-South regions, conventional tilled 

soybean acres were flat or increasing, while no-till acres were flat or decreasing.

Reduced tillage acres in the Midwest increased during the same time period, but 

there was no clear relationship between time and reduced tillage plantings in the 

Page 9-4
East, Southeast or Mid-South regions (not significant at the 95% confidence 

interval). Thus, in the Midwest, the reduction in no-till acres appears in large part 

to be offset by an increase in reduced tillage acres, but similar offsetting does not 

appear to be occurring in other regions.

• Cotton: From 1998 to 2007, the conventional tillage acreage decreased and no-till acres 

increased across all geographic areas. From 2007-2012, the trends varied across regions:

o In the West, conventional tilled soybean acres continued to decrease, and no-till 

acreage continued to increase. Reduced tillage acres also continued to increase.

o In the Midwest, Southeast and Mid-South, conventionally-tilled cotton acres 

tended to be flat or increase, while a clear increase was found in the Mid-South

region. Reduced tillage acres increased in the Midwest and Southeast during this 

period, but both no-till and reduced tillage acreages decreased in the Mid-South 

region. Thus, in the Midwest and Southeast, the reduction in no-till acres appears 

in large part to be offset by an increase in reduced tillage acres, but similar 

offsetting does not appear to be occurring in the Mid-South.

Overall, changes in tillage practices from 2007 to 2012 (cotton)/2013 (soybean and corn) varied 

by crop and region relative to changes seen in the earlier period from 1998 to 2006 where

consistent trends were observed across all the regions (i.e., increase in no-till and reduced tillage 

with a decrease in conventional tillage systems).

In order to understand the reasons growers adopt specific tillage practices, a survey was 

conducted of top conservation tillage experts across the Midwest (for corn and soybeans), 

Southeast and Mid-South regions (combined, for corn, soybeans, and cotton). In Table 3, the top 

5 factors, according to conservation tillage experts, governing farmer decisions relative to which 

tillage practice they adopt for their farm are provided by crop and region of the country. Key 

findings included:

• Economics (i.e., the importance of cost of production and/or commodity prices), and 

managing soil moisture (i.e., less tillage conserves soil moisture) were top-5 factors 

across all the crops and regions. 

• Seed bed preparation was a top-5 factor in 4 out of 5 crop x region segments.

• Managing excessive crop residue (i.e., excessive prior crop residue may require more 

tillage) and managing weeds (existing weeds or preventing weed resistance) were 

important factors in 3 out of 5 crop x region segments. 

• Managing weeds was an important factor across all soybean and cotton regional 

segments, but was not a top 5 factor for corn in either regional segment. The difference 

between corn and the other crops is likely because growers have a broad range of 

herbicide options (including atrazine, dicamba and 2,4-D) that are effective against 

species that are difficult to control in soybeans and cotton, i.e., glyphosate resistant 

Palmer amaranth and waterhemp.

This survey of conservation tillage experts highlights that farmers consider multiple factors when 

making decisions as to what type tillage system to employ.

Page 9-5
Conclusions 

From 1998-2007, no-till acreage increased steadily across all crops and all regions, with an 

accompanying decrease in conventional tillage. A more complicated picture emerged after 2007, 

with some crops and regions continuing to experience increases in no-till and decreases in 

conventional tillage, while other crops and regions experienced decreases in no-till acreage, 

either accompanied by increases in reduced tillage acreage and/or in conventional tillage. 

Based upon information provided by conservation tillage experts regarding the most important 

factors governing farmer’s decisions with respect to tillage practices, no one factor is driving 

these changes. Managing existing herbicide resistance and/or mitigating the potential for 

resistance to develop is a factor is some regions. For example, academics have been 

recommending more pre-plant tillage in parts of the Southeast and Mid-South (AR, western TN, 

and MS) in order to better manage glyphosate-resistant Palmer amaranth. But weed resistance 

management/mitigation does not appear to be a driver for other crops and regions. Indeed, the 

survey results indicate that higher corn and soybean grain prices, along with more focus on seed 

bed preparation, is likely to be a reason for some of switch to conventional tillage since a better 

stand (and thus higher potential yields) can usually be achieved in conventional tillage systems. 

Moreover, newer corn varieties can produce excessive crop residue, which may also be causing a 

move to more tillage and may be needed to optimize crop stands in this period of high grain 

prices. 

Based upon the tillage trends seen over the last 5-6 years and with the information on the factors 

most influencing farmers’ decision on tillage practices, more study, appropriately directed 

research, education, and new technology from a weed management and crop production 

standpoint are needed to maintain and further grow conservation tillage practices. In some areas 

and for some crops, managing existing herbicide resistance and/or mitigating the potential for 

resistance to develop has been reported as an important factor in influencing farmer tillage 

decisions. DT soybean and DGT cotton are two new herbicide technologies that have the 

characteristics that can significantly assist in reversing stagnated and downward trends and 

promote new growth in conservation tillage acres. Weed management has always been a 

limiting factor for many farmers in determining whether to adopt no-till production practices 

because farmers had to rely primarily on soil residual herbicides. Glyphosate, in 

glyphosate-tolerant crops, with its broad spectrum post-emergence control provided a way to 

achieve consistent weed control in these situations and facilitated an increase in adoption of notill and, in general, conservation tillage practices (Fawcett and Towry, 2002). The effectiveness 

of dicamba to provide post-emergent control of broadleaf weeds, suggests that it too will 

promote adoption of no-till and conservation tillage practices. Additionally, dicamba’s ability to 

control glyphosate resistant broadleaf weeds and its compatibility with glyphosate are 

characteristics that will facilitate the promotion of conservation tillage practices. 

Page 9-6
Table 2. Trends in Tillage Practices in Soybean, Corn and Cotton 

Crop Geography Tillage system Trend

1998-

2007

2007-

2012/13

Corn West Conventional Dec Dec

No-till Inc Inc

Reduced-till Inc Inc

Midwest Conventional Dec Dec

No-till Inc Flat/Dec1

Reduced-till Dec Inc

Southeast Conventional Dec Flat/Inc1

No-till Inc Dec

Reduced-till NS NS

Mid-South Conventional NS NS

No-till NS NS

Reduced-till Inc Inc

East Conventional Dec Dec

No-till Inc Inc

Reduced-till NS NS

Soybeans West Conventional Dec Dec

No-till Inc Inc

Reduced-till NS NS

Midwest Conventional Dec Flat/Inc1

No-till Inc Dec

Reduced-till Dec Inc

Southeast Conventional Dec Flat

No-till Inc Flat

Reduced-till NS NS

Mid-South Conventional Dec Inc

No-till Inc Dec

Reduced-till NS NS

East Conventional Dec Flat/Inc1

No-till Inc Flat/Dec1

Reduced-till NS NS

Page 9-7
Table 2 (continued). Trends in Tillage Practices in Soybean, Corn and Cotton 

Crop Geography Tillage system Trend

1998-

2007

2007-

2012/13

Cotton West Conventional Dec Dec

No-till Inc Inc

Reduced-till Inc Inc

Southeast Conventional Dec Flat/Inc1

No-till Inc Dec

Reduced-till Inc Inc

Midwest Conventional Dec Flat/Inc1

No-till Inc Dec

Reduced-till Inc Inc

Mid-South Conventional Dec Inc

No-till Inc Dec

Reduced-till Inc Dec

NS=no significant trend at 5% Confidence Interval Inc= Increase 

Dec=decrease Flat=no change

Source of data is propriety grower market research data (Monsanto, 2013).

1

Where the trend is indicated as two phases (i.e. Flat/Dec), this means 

that statistically the trend is for no change over the designated time 

period but the slope over the last two years of the time period tended to 

be either reflective of an increase or a decrease. 

Table 3. Top 5 Factors Governing Farmer’s Tillage Practice Decisions

Factor

Midwest

Corn

(14 Experts)

Midwest

Soybeans

(13 Experts)

South Corn

(6 Experts)

South 

Soybeans

(6 Experts)

South Cotton

(6 Experts)

1 Managing soil 

moisture

Excessive 

crop residue Economics Economics Economics

2 Seed bed 

preparation

Seed bed 

preparation

Seed bed 

preparation

Managing 

existing 

weeds

Managing 

existing 

weeds

3 Economics Economics Excessive 

crop residue

Seed bed 

preparation

Availability 

of Labor

4 Excessive 

crop residue

Managing 

existing 

weeds

Improving 

water 

penetration

Managing soil 

moisture

Managing soil 

moisture

5 Managing soil 

temperature

Managing soil 

moisture

Managing soil 

moisture

Preventing 

weed 

resistance

Use of strip 

till / vertical 

tillage tools

Page 9-8
References:

Culpepper, A.S., J. Kichler and A.C. York. 2013. University of Georgia programs for controlling 

Palmer amaranth in 2013 cotton. University of Georgia Cooperative Extension, Athens, Georgia.

Culpepper, A.S., A.C. York and L.E. Steckel. 2011. Glyphosate-resistant Palmer amaranth 

management in cotton. 2011 Proceedings, Southern Weed Science Society, San Juan, Puerto 

Rico.

Fawcett, R. and D. Towery. 2002. Conservation tillage and plant biotechnology: How new 

technologies can improve the environment by reducing the need to plow. Conservation 

Technology Information Center, Purdue, Indiana.

Givens, W.A., D.R. Shaw, W.G. Johnson, S.C. Weller, B.G. Young, R.G. Wilson, M.D.K. Owen 

and D. Jordan. 2009a. A grower survey of herbicide use patterns in glyphosate-resistant cropping 

systems. Weed Technology 23:156-161.

Givens, W.A., D.R. Shaw, G.R. Kruger, W.G. Johnson, S.C. Weller, B.G. Young, R.G. Wilson, 

M.D.K. Owen and D. Jordan. 2009b. Survey of tillage trends following the adoption of 

glyphosate-resistant crops. Weed Technology 23:150-155.

McClelland, M.R., J.L. Barrentine, K.J. Bryant and E.P. Webster. 2000. Roundup Ready cotton 

programs in conservation tillage. Pages 197-201 in Proceedings of the 2000 Cotton Research 

Meeting, Fayetteville, Arkansas.

Osteen, C.D. and J. Fernandez-Cornejo. 2013. Economic and policy issues of U.S. agricultural 

pesticide use trends. Pest Management Science 69:1001-1025.

Price, A.J., K.S. Balkcom, S.A. Culpepper, J.A. Kelton, R.L. Nichols and H. Schomberg. 2011. 

Glyphosate-resistant Palmer amaranth: A threat to conservation tillage. Journal of Soil and Water 

Conservation 66:265-275.

Sankula, S. 2006. Quantification of the impacts on US agriculture of biotechnology-derived 

crops planted in 2005. National Center for Food and Agricultural Policy, Washington, D.C.

Towery, D. and S. Werblow. 2010. Facilitating conservation farming practices and enhancing 

environmental sustainability with agricultural biotechnology: Exective summary. Conservation 

Technology Information Center, West Lafayette, Indiana.

Page 9-9
Appendix A: Statistical Analysis of Tillage Market Research Data

Summary of Statistical Analysis of Tillage Data

Purpose 

Assess if tillage practices have significantly changed between 1998 and 2007, and between 2007 

and 2013 (or 2012, for cotton). 

Data Description

For the analysis PROC MEANS in SAS was used to calculate the acres that utilized each tillage 

type and total acres for each crop, region and year. The percent of total acres was calculated by 

dividing acres that utilized each tillage type by total acres.

Statistical Methods and Results

A quadratic regression model of the following form was fit for each crop, region and tillage type 

combination:

Percent of total acres = β0 + β1*Year + β2*Year* Year + ε (1)

in which β0 is the intercept, β1 is the linear slope, β2 is the quadratic slope and ε is the residual 

error. PROC MIXED in SAS was used to fit model (1) separately for each crop, region and 

tillage type combination. Tests were performed to determine if the quadratic slopes of the 

regression lines were significantly different from zero. These tests are displayed in Table 1. 

Twenty of the 42 tests observed quadratic slopes that were significantly different from zero at the 

5% level of significance. 

In the 20 cases where the quadratic slopes were significant, a quadratic regression model was 

deemed appropriate. For the 22 cases where the quadratic slopes were not significant, a linear 

regression model of the following form was fit for each crop, region and tillage type 

combination:

Percent of total acres = β0 + β1*Year + ε (2)

in which β0 is the intercept, β1 is the linear slope and ε is the residual error. PROC MIXED in 

SAS was used to fit model (2) separately for each crop, region and tillage type combination. 

Tests were performed to determine if the linear slopes of the regression lines were significantly 

different from zero. These tests are displayed in Table 2. Fourteen of the 22 tests observed 

linear slopes that were significantly different from zero at the 5% level of significance. 

In the 14 cases where the linear slopes were significant, a linear regression model was deemed 

appropriate. For the 8 cases where the linear slopes were not significant, there was no significant 

change in tillage practices over time.

Page 9-10
Conclusions

In 8 of the 42 crop, region and tillage type combinations there was no significant change over 

time. 

In 14 of the 42 crop, region and tillage type combinations the change over time can be described 

using a linear regression model. 

In 20 of the 42 crop, region and tillage type combinations the change over time can be described 

using a quadratic regression model. 

The regression parameter estimates for the crop and region combinations with a significant the 

change over time, are displayed in Table 3.

Plots of the percent total acres data and model fit are displayed in the Appendix.

Page 9-11
Table A-1. Tests to Determine if the Quadratic Slopes of the Regression Lines Were Significantly 

Different From Zero 

Crop Region Tillage_Type P-value

Corn East Conservation 0.1381

Corn East Conventional 0.6663

Corn East No-Till 0.1161

Corn MidSouth Conservation 0.5547

Corn MidSouth Conventional 0.1925

Corn MidSouth No-Till 0.0582

Corn MidWest Conservation 0.0218 *

Corn MidWest Conventional 0.5444

Corn MidWest No-Till 0.0015 *

Corn Southeast Conservation 0.1322

Corn Southeast Conventional 0.0038 *

Corn Southeast No-Till 0.0018 *

Corn West Conservation 0.9108

Corn West Conventional 0.2174

Corn West No-Till 0.1183

Cotton MidSouth Conservation 0.0018 *

Cotton MidSouth Conventional <.0001 *

Cotton MidSouth No-Till <.0001 *

Cotton MidWest Conservation 0.2096

Cotton MidWest Conventional 0.0017 *

Cotton MidWest No-Till <.0001 *

Cotton Southeast Conservation 0.7367

Cotton Southeast Conventional 0.0002 *

Cotton Southeast No-Till <.0001 *

Cotton West Conservation 0.0539

Cotton West Conventional 0.0582

Cotton West No-Till 0.8615

Soybeans East Conservation 0.4610

Soybeans East Conventional 0.0051 *

Page 9-12
Table A-1 (continued). Tests to Determine if the Quadratic Slopes of the Regression Lines 

Were Significantly Different From Zero 

Crop Region Tillage_Type P-value

Soybeans East No-Till 0.0017 *

Soybeans MidSouth Conservation 0.5038

Soybeans MidSouth Conventional 0.0003 *

Soybeans MidSouth No-Till 0.0013 *

Soybeans MidWest Conservation 0.0006 *

Soybeans MidWest Conventional 0.0056 *

Soybeans MidWest No-Till 0.0002 *

Soybeans Southeast Conservation 0.3208

Soybeans Southeast Conventional 0.0495 *

Soybeans Southeast No-Till 0.0447 *

Soybeans West Conservation 0.1184

Soybeans West Conventional 0.0921

Soybeans West No-Till 0.7472

Note: Twenty of the 42 tests observed quadratic slopes that were significantly different from zero at the 

5% level of significance. The tests that were significant at the 5% level are marked with an ‘*’. 

Page 9-13
Table A-2. Tests to Determine if the Linear Slopes of the Regression Lines Were 

Significantly Different From Zero

Crop Region Tillage_Type P-value

Corn East Conservation 0.2078

Corn East Conventional <.0001 *

Corn East No-Till <.0001 *

Corn MidSouth Conservation 0.0195 *

Corn MidSouth Conventional 0.4904

Corn MidSouth No-Till 0.3690

Corn MidWest Conventional 0.0011 *

Corn Southeast Conservation 0.0835

Corn West Conservation 0.0011 *

Corn West Conventional <.0001 *

Corn West No-Till 0.0114 *

Cotton MidWest Conservation 0.0210 *

Cotton Southeast Conservation <.0001 *

Cotton West Conservation <.0001 *

Cotton West Conventional <.0001 *

Cotton West No-Till 0.0001 *

Soybeans East Conservation 0.1917

Soybeans MidSouth Conservation 0.1896

Soybeans Southeast Conservation 0.6675

Soybeans West Conservation 0.1233

Soybeans West Conventional 0.0067 *

Soybeans West No-Till 0.0002 *

Note: Fourteen of the 22 tests observed linear slopes that were significantly different from zero at the 5% 

level of significance. The tests that were significant at the 5% level are marked with an ‘*’. 

Page 9-14
Table A-3. Regression Parameter Estimates for the Crop and Region Combinations with a 

Significant the Change in Tillage Over Time 

Crop Region Tillage Type Intercept Year Year*Year

Corn East Conventional 3466.72 -1.7079 .

Corn East No-Till -3039.87 1.5340 .

Corn MidSouth Conservation -1769.03 0.8933 .

Corn MidWest Conservation 300587 -299.62 0.07467

Corn MidWest Conventional 1114.90 -0.5355 .

Corn MidWest No-Till -383597 381.93 -0.09506

Corn Southeast Conventional 766604 -763.20 0.1900

Corn Southeast No-Till -1202619 1198.66 -0.2987

Corn West Conservation -2375.58 1.1991 .

Corn West Conventional 3782.79 -1.8592 .

Corn West No-Till -1307.20 0.6601 .

Cotton MidSouth Conservation -1044452 1041.04 -0.2594

Cotton MidSouth Conventional 2648507 -2639.72 0.6577

Cotton MidSouth No-Till -1603955 1598.68 -0.3983

Cotton MidWest Conservation -2277.83 1.1529 .

Cotton MidWest Conventional 1707629 -1701.22 0.4237

Cotton MidWest No-Till -2295716 2289.07 -0.5706

Cotton Southeast Conservation -3534.42 1.7786 .

Cotton Southeast Conventional 1405216 -1399.58 0.3485

Cotton Southeast No-Till -1304016 1300.48 -0.3242

Cotton West Conservation -2656.63 1.3372 .

Cotton West Conventional 4244.03 -2.0828 .

Cotton West No-Till -1487.40 0.7456 .

Soybeans East Conventional 902937 -899.02 0.2238

Soybeans East No-Till -1061879 1057.33 -0.2632

Soybeans MidSouth Conventional 1373279 -1368.84 0.3411

Soybeans MidSouth No-Till -1208347 1204.77 -0.3003

Soybeans MidWest Conservation 387479 -386.03 0.09615

Soybeans MidWest Conventional 311116 -309.83 0.07714

Page 9-15
Table A-3 (continued). Regression Parameter Estimates for the Crop and Region 

Combinations with a Significant the Change in Tillage Over Time 

Crop Region Tillage Type Intercept Year Year*Year

Soybeans MidWest No-Till -698495 695.85 -0.1733

Soybeans Southeast Conventional 600500 -597.28 0.1485

Soybeans Southeast No-Till -768636 765.12 -0.1904

Soybeans West Conventional 3901.95 -1.9250 .

Soybeans West No-Till -6423.22 3.2204 .

Page 9-16
Appendix A Figures

Figures

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Appendix B: CTIC Survey Results of Leading Conservation Tillage Experts 

The following pages summarize the results of the CTIC (Conservation Tillage Information 

Center) survey of 21 total (14 in Midwest and 7 in South) leading conservation tillage experts 

across the key agronomic regions of the U.S. for soybean, corn and cotton production. These 

experts were asked to rate the importance of 11 factors that could influence tillage practices of 

growers in their region. Responses the the question below are summarized on the following 

pages.

Question: In general, how important are the following factors to the majority of the farmers in 

your region as they determine the total amount of tillage done to produce corn, regardless of 

whether the tillage is done prior to planting or done during the growing season? Choose the 

rating below that best reflects the importance of each factor in determining the amount of tillage 

being used.

Page 9-59
Table B-1. Midwest Corn (14 total Experts)

Number of Experts Responding

Manage 

excess 

crop 

residue

Manage 

existing 

weeds

Manage 

disease

Manage 

soil 

moisture

Manage soil 

temperature

Prevent 

weed 

resistance

Seed bed 

preparation

Use of 

strip till / 

vertical 

tillage 

tools

Economics Availability 

of labor

Water 

penetration

Not 

important / 

Not 

mentioned

4 6 4 4 4 8 4 6 6 8 6

Sometimes 

important 4 3 5 3 3 2 2 3 1 2 4

Quite 

important 2 2 4 5 5 2 3 2 3 2

Extremely 

important 4 3 1 2 2 2 5 3 7 1 2

Ranking 

Sum1 34 30 30 33 33 26 37 30 36 25 28

1

Ranking Sum was calculated as follows, a number from 1 to 4 was assigned to each response category, with 1 assigned to ‘not important or not 

mentioned’ and 4 assigned to ‘extremely important’. The assigned number was multiplied by the number of responses from the experts and then 

added together for each factor. 

Page 9-60
Table B-2. Midwest Soybean (13 total Experts)

Number of Experts Responding

Manage 

excess 

crop 

residue

Manage 

existing 

weeds

Manage 

disease

Manage 

soil 

moisture

Manage soil 

temperature

Prevent 

weed 

resistance

Seed bed 

preparation

Use of 

strip till 

/ 

vertical 

tillage 

tools

Economics Availability 

of labor

Water 

penetration

Not 

important / 

Not 

mentioned

6 4 7 3 5 6 4 10 4 2 4

Sometimes 

important 0 4 2 6 4 3 2 1 3 6 5

Quite 

important 1 2 2 2 1 2 3 0 2 3 2

Extremely 

important 6 3 2 2 3 2 4 2 4 1 1

Ranking 

Sum1 33 30 25 29 28 26 33 20 32 27 24

1

Ranking Sum was calculated as follows, a number from 1 to 4 was assigned to each response category, with 1 assigned to ‘not important or not 

mentioned’ and 4 assigned to ‘extremely important’. The assigned number was multiplied by the number of responses from the experts and then 

added together for each factor. 

Page 9-61
Table B-3. South Corn (6 total Experts)

Number of Experts Responding

Manage 

excess 

crop 

residue

Manage 

existing 

weeds

Manage 

disease

Manage 

soil 

moisture

Manage soil 

temperature

Prevent 

weed 

resistance

Seed bed 

preparation

Use of 

strip till 

/ 

vertical 

tillage 

tools

Economics Availability 

of labor

Water 

penetration

Not 

important / 

Not 

mentioned

2 2 3 1 2 2 1 2

Sometimes 

important 1 1 2 4 5 2 1 2 1 3 1

Quite 

important 3 1 1 2 1 4 2 2 1 1

Extremely 

important 1 1 1 3 1 2

Ranking 

Sum1 13 11 10 14 11 13 18 12 20 14 15

1

Ranking Sum was calculated as follows, a number from 1 to 4 was assigned to each response category, with 1 assigned to ‘not important or not 

mentioned’ and 4 assigned to ‘extremely important’. The assigned number was multiplied by the number of responses from the experts and then 

added together for each factor.

Page 9-62
Table B-4. South- Soybean (6 total Experts)

Number of Experts Responding

Manage 

excess 

crop 

residue

Manage 

existing 

weeds

Manage 

disease

Manage 

soil 

moisture

Manage soil 

temperature

Prevent 

weed 

resistance

Seed bed 

preparation

Use of 

strip till 

/ 

vertical 

tillage 

tools

Economics Availability 

of labor

Water 

penetration

Not 

important / 

Not 

mentioned

3 4 2 1 1 1

Sometimes 

important 2 2 1 3 4 1 2 3 1 2 3

Quite 

important 1 3 1 2 4 3 2 3 1 1

Extremely 

important 1 1 1 1 2 1 1

Ranking 

Sum1 10 17 9 16 10 18 17 13 19 12 14

1

Ranking Sum was calculated as follows, a number from 1 to 4 was assigned to each response category, with 1 assigned to ‘not important or not 

mentioned’ and 4 assigned to ‘extremely important’. The assigned number was multiplied by the number of responses from the experts and then 

added together for each factor.

Page 9-63
Table B-5. South- Cotton (6 total Experts)

Number of Experts Responding

Manage 

excess 

crop 

residue

Manage 

existing 

weeds

Manage 

disease

Manage 

soil 

moisture

Manage soil 

temperature

Prevent 

weed 

resistance

Seed bed 

preparation

Use of 

strip till 

/ 

vertical 

tillage 

tools

Economics Availability 

of labor

Water 

penetration

Not 

important / 

Not 

mentioned

3 2 1 2

Sometimes 

important 4 3 2 2 3 4 1 3 2 1

Quite 

important 1 1 1 3 1 1 3 2 4 3 2

Extremely 

important 1 2 1 1 1 1 2 1 1

Ranking 

Sum1 15 17 10 17 11 18 16 16 20 17 14

1

Ranking Sum was calculated as follows, a number from 1 to 4 was assigned to each response category, with 1 assigned to ‘not important or not 

mentioned’ and 4 assigned to ‘extremely important’. The assigned number was multiplied by the number of responses from the experts and then 

added together for each factor.

Page 9-64
Appendix 10. EPA Resistance Management Requirements for 

Registration of Dow Agrosciences Enlist DuoTM

Page 10-1
The following text in this appendix contains excerpts regarding the weed resistance management 

requirements specified in the U.S. EPA’s Proposed Registration of Enlist DuoTM Herbicide. 

EPA may require similar requirements be added to the proposed registration of Monsanto’s 

dicamba formulation, ExtendiMax.

IV. Resistance Management

The emergence of herbicide resistant weeds is an increasing problem that has become a 

significant economic issue to growers. This has led to a concern that the use of 2,4-D on GE 

crops may result in more resistant weeds. In an effort to address this issue going forward, EPA is 

requiring that DAS develop a stewardship program that will aggressively promote resistance 

management efforts.

The overall goal of the stewardship plan is to assist and support responsible use of the product. 

With regard to weed resistance management, the plan mandates that DAS must immediately 

investigate any claims of non-performance. The initial mechanism users can use for 

communicating directly with DAS is a toll-free number to get advice on how to resolve any 

uncontrolled weeds.

Academia, growers, USDA, and other leaders involved with pest management acknowledge the 

importance of field scouting. For this reason, the Enlist DuoTM label includes a requirement to 

scout treated fields. Field scouting before application will be essential to determining the weed 

species present as well as their stage of growth. Scouting 7-21 days after herbicide application 

will be used to assess the performance of weed control. In the event that a user encounters a nonperformance issue, the toll-free number could be used to initiate an intervention against that 

weed population.

The DAS response to reports of non-performance must be immediate and must ensure that 

possible incidents of resistance are promptly investigated and resolved. EPA proposes that when 

a non-performance issue is identified , DAS or its representative will conduct a site visit and 

evaluate the issue using decision criteria identified by leading weed science experts (Norsworthy, 

et al.), in order to determine if “likely herbicide resistance” is present. This is distinct from, and 

more broad than, the term “likely herbicide resistance,” as explained below. For purposes of this 

decision, a report of non-performance to DAS will be the trigger for a site visit.

Non-performance refers to any cause that results in inadequate weed control after an herbicide 

application. “Lack of herbicide efficacy” refers to inadequate weed control with various possible 

causes, including but not limited to: application rate, stage of growth, environmental conditions, 

herbicide resistance, plugged nozzle, boom shut off, tank dilution, post-application weed flush, 

unexpected rainfall event, weed misidentification, etc. EPA recognizes that it can be challenging 

to determine emerging weed resistance at an early stage. Therefore, EPA is selecting criteria that 

it feels will be helpful to DAS and to users in identifying when instances of “lack of herbicide 

efficacy” in fact constitute “likely herbicide resistance.” These “likely herbicide resistance” 

criteria are: (1) failure to control a weed species normally controlled by the herbicide at the dose 

applied, especially if control is achieved on adjacent weeds; (2) a spreading patch of 

Page 10-2
uncontrolled plants of a particular weed species; and (3) surviving plants mixed with controlled 

individuals of the same species (Norsworthy, et al., 2012).

When DAS or its representative applies the Norsworthy, et al., criteria cited above and likely 

herbicide resistance is identified, then DAS must take immediate action to eradicate likely 

resistant weeds in the infested area. This may be accomplished by re-treating with an herbicide 

or using mechanical control methods. If herbicide re-treatment is used to eliminate the likely 

resistant weed(s), follow-up scouting will be required to confirm that the lack of herbicide 

efficacy has been resolved. DAS must also notify EPA that likely herbicide resistance has been 

identified and report this on a monthly basis. In addition, samples of the likely herbicide resistant 

weeds and/or seeds must be taken, and prior to the next growing season laboratory or greenhouse 

testing must be initiated in order to determine whether resistance is the reason for the lack of 

herbicide efficacy. DAS must also work to develop a laboratory diagnostic test to quickly 

identify herbicide resistance, and report to EPA its progress toward developing such a diagnostic 

test.

In addition to reporting incidents of likely resistance, on or before October 15 of each year, DAS 

will submit annual summary reports to EPA. These reports must include a summary of the 

number of instances of likely and confirmed resistance to Enlist DuoTM by weed species, crop, 

county and state. They will also summarize the status of laboratory or greenhouse testing for 

resistance, as well as the status of the development of a laboratory test. The annual reports will 

also address the disposition of incidents of likely or confirmed resistance reported in previous 

years.

Users and other stakeholders must be informed of reports of likely and confirmed herbicide 

resistance to Enlist DuoTM, if any. The information will include details of weed species and crop. 

To accomplish this, EPA expects that DAS will establish a website to facilitate delivery of 

resistance information.

Several management practices that are designed to help users avoid initial occurrences of weed 

resistance will appear on the product labeling under the Resistance Management heading of the 

label. These practices are discussed in Section VII.B.3 of this document.

Refer to Section VII.C below for EPA’s delineation of necessary terms of registration to address 

the issue of weed resistance.

VII. Proposed Registration Decision

B. Labeling Requirements

3. Resistance Management

a. Herbicide Selection:

• Apply full rates of GF-2726 for the most difficult to control weed in the field at the 

specified time (correct weed size) to minimize weed escapes.

• Rotate the use of this product with non-Group 4 and non-Group 9 herbicides.

Page 10-3
• Utilize sequential applications of herbicides with alternative modes of action.

• Avoid using more than two applications of GF-2726 and any other Group 4 or Group 9 

herbicide within a single growing season unless mixed with another mode of action 

herbicide with overlapping weed spectrum.

• Use a broad spectrum soil applied herbicide with other modes of action as a foundation in 

a weed control program.

b. Crop Selection and Cultural Practices:

• Incorporate additional weed control practices whenever possible, such as mechanical 

cultivation, crop rotation, and weed-free crop seeds, as part of an integrated weed control 

program.

• Do not allow weed escapes to produce seeds, roots or tubers.

• Thoroughly clean plant residues from equipment before leaving fields suspected to 

contain resistant weeds.

• Scout fields before application to ensure herbicides and rates will be appropriate for the 

weed species and weed sizes present.

• Scout fields between 7 and 21 days after application to detect weed escapes or shifts in 

weed species.

• If resistance is suspected, treat weed escapes with an alternate mode of action or use 

nonchemical methods to remove escapes.

• User report any incidence of non-performance of this product against a particular weed 

species to the DAS representative.

C. Registration Terms

EPA has determined that certain registration terms are needed to ensure that likely weed

resistance as discussed in section IV can be adequately addressed. EPA believes that it is

important to address likely weed resistance and not wait until confirmation of resistance has been

found. EPA is basing the registration terms on a list of criteria, presented in the peer-reviewed

publication, Norsworthy, et al., “Reducing the Risks of Herbicide Resistance: Best Management

Practices and Recommendations,” Weed Science 2012 Special Issue: 31–62 (Norsworthy

criteria).

1. Stewardship Program

EPA has determined that the registration must contain a term that requires DAS to have a

stewardship program for Enlist DuoTM. DAS has begun developing its program which it states is 

focused on educating and training retailers, farmers and applicators on the appropriate use of the 

EnlistTM technology. EPA has determined that the stewardship program must include the

following measures (also to be included as terms on the registration) that would minimize the

potential for off-target movement and avoid the development of weed resistance.

Page 10-4
a. Investigation

EPA has determined that the registration must contain a term that requires DAS or its

representative to investigate reports of non-performance as reported by users following required 

“scouting” (in accordance with labeling requirements). When investigating these reports, DAS or 

its representative would be required to conduct site visits.

b. Reporting of the Incidence of Likely Herbicide Resistance

EPA has determined that the registration must contain a term that requires DAS to use the

Norsworthy criteria for determining likely herbicide resistance and inform EPA if likely

resistance has been identified. This information must be submitted to the Agency on a monthly 

basis.

c. Remediation

EPA has determined that the registration must contain a term that requires DAS to take

immediate action to eradicate likely resistant weeds in the infested area as well as requiring DAS 

to collect material for further testing.

d. Annual Reporting of Herbicide Resistance to EPA

EPA has determined that the registration must contain a term that requires DAS to submit annual 

summary reports to EPA that include a summary of the number of instances of likely and 

confirmed weed resistance by weed species, crop, county and state. The annual reports must 

include summaries of the status of laboratory or greenhouse testing for resistance. The annual 

reports would also address the disposition of incidents of likely or confirmed resistance reported 

in previous years. These reports would not replace or supplement adverse effects reporting 

required under FIFRA 6(a)(2).

e. Reporting of Likely Resistance to other Interested Parties

EPA has determined that the registration must contain a term that requires DAS to inform

growers and other stakeholders of likely and confirmed resistance to Enlist DuoTM. The

information will include details of weed species and crop. EPA understands that DAS already

plans to provide this information though a devoted website.

f. Reporting on the development of diagnostic tests

EPA has determined that the registration must contain a term that requires that DAS would

inform EPA of DAS’s progress toward diagnostic testing for evaluating resistant weed species.

Page 10-5
g. Monitoring the use of Enlist DuoTM on EnlistTM Seed

EPA believes it is important to require DAS to monitor whether Enlist DuoTM is being used on 

the EnlistTM seed purchased from DAS. EPA has determined that the registration must contain a 

term that requires DAS to provide EPA with a protocol to survey whether Enlist DuoTM is being 

used on EnlistTM seed purchased from DAS and not the non-choline 2,4-D products that are not 

registered for these application windows. EPA expects that a protocol would be agreed upon 

quickly so that monitoring the use of Enlist DuoTM can begin shortly thereafter.

h. Training and Education

EPA has determined that the registration must contain a term that requires DAS to provide

training on the use of Enlist DuoTM when it provides training on the EnlistTM Seed technology.

The training would focus on proper use of the technology to avoid off-target movement as well 

as avoid weed resistance.

2. EPA’s Continued Control over the Registration

Because the issue of weed resistance is an extremely important issue to keep under control and

can be very fast moving, EPA has determined that the registration must contain terms that ensure 

that EPA retains control to easily and quickly modify or cancel the registration if necessary.

References:

Jason K. Norsworthy, Sarah M. Ward, David R. Shaw, Rick S. Llewellyn, Robert L. Nichols, 

Theodore M. Webster, Kevin W. Bradley, George Frisvold, Stephen B. Powles, Nilda R. Burgos, 

William W. Witt, and Michael Barrett, Reducing the Risks of Herbicide Resistance: Best 

Management Practices and Recommendations, Weed Science 2012 60 (sp1), 31-62.

Page 10-6