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Dow AgroSciences LLC dowagro.com

9330 Zionsville Road, Indianapolis, IN 46268-1054

308/2E

January 22, 2013

Dr. Neil Hoffman

Science Advisor

USDA/APHIS/BRS

4700 River Road, Unit 98

Riverdale, MD 20737

Diane Sinkowski

Senior Environmental Protection Specialist

USDA/APHIS/BRS

4700 River Road, Unit 147

Riverdale, MD 20737

DAS-68416-4 Soybean and DAS-40278-9 Corn

Dow AgroSciences Petition Numbers 09-349-01p and 09-233-01p

SUPPLEMENTARY DOCUMENTATION IN SUPPORT OF ENVIRONMENTAL ASSESSMENTS

Dear Dr. Hoffman and Ms. Sinkowski:

This letter and attached information is in response to your email of Dec.10, 2012 which included a request for 

information from Dow AgroSciences (DAS) to support your efforts in developing the final Environmental 

Assessment and Response to Comments for DAS-402780-9 corn and DAS-68416-4 soybean. 

The attached information addresses Questions 8,9, 10 and 11 from Section C. Herbicide Drift Issues.

Herewith, Dow AgroSciences (DAS) is submitting our response to these questions on the enclosed CD.

If you should have any questions or require further information, please contact me at 317-337-3692.

Sincerely,

Gregory L. Orr, Ph.D.

Global Regulatory Leader 

317-337-3692

317-337-4649 (fax)

glorr@dow.com
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DISTRIBUTION PAGE

DED Code: D1C / B1C

bcc: Laura Tagliani, 308/2E

Greg Orr, 308/2E

Heidi Reistad, 308/2E

Federal Action Files, 308/2E unstapled
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Table of Contents

Section C. Herbicide drift issues. 

Question 8. Where in the US is 2, 4-D use restricted? .................................... 4 

Question 9. Describe the incidents/history/political process that led to the restrictions in 

2, 4-D use. ...........................................................................................7 

Question 10. How many offsite incidents from pesticide use are reported each year in 

the US? 

Question 11. What is the breakdown with regards to where (what state or region) the 

incidents occurred, the active ingredient alleged to have caused the damage, the total 

number of applications of that active ingredient, types of crop affected, amount of 

damages sustained, amount of compensation paid? ........................................12

2,4-D Off-Target Exposure and Sensitive Crops.............................................59
4 of 68

DOW AGROSCIENCES RESPONSE TO USDA-APHIS 

QUESTIONS RECEIVED DECEMBER 10, 2012 REGARDING 

DAS-40278-9 CORN AND DAS-68416-4 SOY.

C. Herbicide drift issues. 

8. Where in the US is 2, 4-D use restricted? 

US Restrictions on the use of 2,4-D

Summary

The USEPA's registration for 2,4-D under section 3 of FIFRA includes certain restrictions on 

use that appear on the product's label, but USEPA has not classified 2,4-D as a “restricted use 

pesticide” (RUP). 2,4-D, first registered in 1946, is one of the most widely used herbicides 

in the world and over 60 years later, it still is a viable product for weed control in multiple 

uses. The most frequently means by which EPA addresses potential adverse effects is 

through warnings, prohibitions, restrictions and directions for use on the product label (40 

CFR Part 156). When registering a product, the US EPA also has the ability to classify a 

pesticide as a RUP should it deem that the product needs additional restrictions to decrease 

the risk of adverse affects (40 CFR Subpart I, 152.160). RUPs can only be applied by or 

under the direct supervision of an applicator certified by the state or EPA. After a pesticide is 

registered by US EPA, states can register pesticides under specific state pesticide registration 

laws. State lead agencies have primary authority for pesticides used within the state. In 

some cases, states may enact additional restrictions for use of a product to meet the uses and 

needs of their state. Currently, there are 18 states with some type of restriction on the use of 

2,4-D. Types of use 

restrictions on registered 

products include general 

RUP regulations, 

formulation- specific 

restrictions, time-specific 

restrictions and/or locationspecific restrictions. 
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US State 2,4-D Restrictions*

TYPE OF RESTRICTION STATE

State RUP designation, but with no spray/use 

restrictions (e.g. licensed applicators, permitting, 

record keeping, etc.)

MA, NJ, NM, VT

State RUP designation and spray/use restrictions CA, LA, TX, WA

No state RUP designation but spray/use 

restrictions AR, FL, ID, IA, MI, MS, NY, OH, OK, OR

Total number of states 18

*State regulations subject to change. It is the applicator’s responsibility to be aware of and comply with 

all current state regulations.

Types of state restrictions

Four states have designated 2,4-D products as a RUP – Massachusetts, New Jersey, New Mexico 

and Vermont. The RUP designation means that applicators must be certified to use the RUP 

product or have a licensed applicator within the vicinity of the person making the application. 

The applicator must also keep spray records. 

Four state have designated 2,4-D products as a RUP along with spray use restrictions –

California, Louisiana, Texas and Washington. The types of additional spray use restrictions vary 

by state. In these states, applications are restricted or prohibited during certain times of the year 

(e.g. April through September) in designated counties. For the remaining counties in the states 

of Louisiana and Texas, buffers from sensitive or susceptible crops are established. 

Ten states have no RUP designation for 2,4-D but do have specific spray use restrictions –

Arkansas, Idaho, Iowa, Florida, Michigan, Mississippi, New York, Ohio, Oklahoma and Oregon. 

The restrictions range from buffers to aerial versus ground applications to the type of 2,4-D 

formulations. For example, New York has spray use restrictions in only three counties. No 2,4-

D can be applied within 100 feet of any grape vineyard and there is a 2 mile buffer for all ester 

formulations. In Mississippi, 2,4-D is limited to ground applications only from April 1 to 

September 30. In Iowa, ester formulations only are prohibited in five counties.

STATE RUP RESTRICTIONS

Arkansas No

All 2,4-D are in Class F with use restrictions. Apr. 15 - Sept. 15: no 

use in Clay, Greene, Craighead, Poinsett, Cross, Crittenden, St. 

Francis, Lee, Phillips, and Mississippi Counties. Permits may be 

obtained to allow exemption with key requirements recording 

application details. Buffer zone/wind speed requirements. Buffer 

zones set: e.g. 4 mile aerial; 1 mile ground. AR Regulations on 

Pesticide Classification - Final Rule (Rev. 06/07): 
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California Yes

RUP for products 1 gal or greater containing over 15% active 

ingredient. Areas: Central Valley...specifically defined areas of: 

Sacramento, Madera, Fresno, Kings, Tulare, Kern, San Joaquin 

Counties. Authorized permits needed. Restrictions based on dates, 

formulation type, wind speed, set-back from commercial vineyard or 

cotton planting. 2,4-D use restrictions to protect CRLF (buffer zones 

in 33 counties); 2,4-D salts and esters designated as toxic air 

contaminants. Title 3, CCR 3, Sec. 6400

Florida No

(1)(2)Sale and use of highly volatile1 forms of organo-auxin

herbicides...is prohibited except for those products labeled as PGR 

on citrus. (3) Minimum set-back distances from susceptible crops 

are specified based on wind speed. Max wind speed = 10 mph. (6) 

Applicator record keeping requirement. (7) Aerial application by 

fixed-wing aircraft prohibited Jan 1 until May 1 in Hendry, Palm 

Beach, Glades, Martin counties.

Florida Administrative Code Chapter 5E-2.033 (Effective 7-29-04) 

Idaho No

2,4-D ester restrictions for counties: Latah, Nez Perce, Clearwater 

Counties. Restrictions based on aerial or ground, formulation type, 

set-back from susceptible crop, wind speed. Buffers from hazard 

areas for 2,4-D amines and acids2

, MCPA, MCPB, and dicamba. 

IDAPA 02.03.03 Sec. 550

Iowa No

The use of high volatile esters formulations of 2,4-D and 2,4,5-T, the 

alcohol fraction of which contains five or fewer carbons, shall be 

prohibited in the counties of Harrison, Mills, Lee, Muscatine and that 

part of Pottawattamie county west of Range 41 West of the 5th P.M. 

to become effective upon filing. 21—45.27(206)

Louisiana Yes

RUP for ag uses of 2,4-D. Restrictions for commercial and private 

applicators based on timing, location, wind speed. Complex 2008 

waiver process specifically for 2,4-D in place impacting aerial and 

ground applications based on timing and location. 32 parishes with 

restrictions. LA Title 7, Part XXIII, § 1103

Massachusetts Yes If product contains >20% 2,4-D it is State RUP -- application made 

by certified applicators and reporting requirements. 333 CMR 1.00

Michigan No

No use of volatile ester forms of 2,4-D and MCPA within specified 

regions from May 1 to Oct. 1 in parts of Berrien, Cass, Kalamazoo 

and Van Buren counties. Sprayer specifications for amine forms. 

MDA Reg 285.637

Mississippi No

Hormone-type herbicide3 restrictions for aerial application. By date, 

fixed-wing or helicopter, No ester formulations, 1/2 mile set-back 

from cotton and susceptible crops. Wind speed < 5 mph. Recording 

of application data. Applicator requirements and licensing. Miss. 

Code Ann. § 69-21-109 (Part 3-Ch 10-Sub 01)

New Jersey Yes 2,4-D (concentrations >20%) purchased and used only by certified 

applicators N.J.A.C. 7:30-2.10

New Mexico Yes

All 2,4-D Ag-use products are state-restricted use. Spray 

restrictions in Curry, Roosevelt counties based on timing, application 

method, < 10 mph. Certified applicators. Need permits for 

applications of low volatile. No permits issued for esters in these 2 

counties. No aerial application in these 2 counties Apr.15 to Oct. 1. 

21.17.56 NMAC
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New York No

2,4-D, 2,4-5T, MCP spray restrictions and set-backs of 100 ft from 

grape vineyards in portions of Chautauqua, Erie, Niagara counties. 

NY ECL Art. 33 § 321-324

Ohio No Restriction from use of ester formulation in Madison township of 

Lake County. ORC Title IX, Ch. 921

Oklahoma No

Spray restrictions in 5 counties: (a) Applications of products 

containing 2,4-D esters or dicamba to agricultural lands shall not be 

made in Greer, Harmon, and Kiowa counties May 1-October 15; (b) 

Applications of products containing 2,4-D, dicamba, picloram, 

triclopyr, or clopyralid shall not be made in Jackson and Tillman 

counties May 1 - October. Notification and reporting procedures 

defined to allow applications. 2 O.S. § 3-84 (35:30-17-24.1)

Oregon No

Restrictions on high volatile esters of 2,4-D in areas of Morrow and 

Umatilla counties: no use Apr 1 - Sept 1 except by permit. 

OAR 603-057-0301 to 0320

Texas Yes

Regulated: 2,4-D, MCPA, dicamba, quinclorac. 53 "Pesticide 

Regulated Herbicide Counties". General restrictions: highly volatile 

prohibited within 4 miles of susceptible crop. No applications in wind 

>10 mph. Additional provisions set county-by-county for 53 

counties. Processes for spray permits when required. Process for 

counties to become regulated. TAC 4-1-7-E §7.50, 53

Vermont Yes Class A restricted use. Application and reporting requirements like 

Federal RUP. 6 V.S.A. Ch 87

Washington Yes 

All phenoxy hormone-type herbicides restrictioned throughout 

eastern Washington with additional restrictions in 14 counties: 

Adams, Benton, Columbia, Douglas/Chelan, Franklin, Garfield, 

Grant, Kittitas, Klickitat, Lincoln, Okanogan, Spokane, Walla Walla, 

Whitman, Yakima. Specific restrictions set in specific rules by 

county: boundaries defined; formulation type, application 

parameters, dates, aerial or ground, set-backs. Applications by 

permit process. 16 WAC 16-228,232

1

Note: High volatility esters of 2,4-D are those that have five or fewer carbons on the alcohol side chain. 

Currently there are no high volatility esters registered for use in the United States.

2 Note: the 2,4-D choline in Enlist Duo is a quaternary ammonium salt. Not an amine or an ester.

3

Hormone-type herbicides include 2,4-D, 2,4-DB, aminopyralid, clopyralid, dicamba, dichlorprop, 

fluroxypyr, MCPA, MCPB, mecoprop, picloram, quinclorac and triclopyr.
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DOW AGROSCIENCES RESPONSE TO USDA-APHIS 

QUESTIONS RECEIVED DECEMBER 10, 2012 REGARDING 

DAS-40278-9 CORN AND DAS-68416-4 SOY.

C. Herbicide drift issues. 

9. Describe the incidents/history/political process that led to the restrictions in 2, 4-D 

use. 

History of 2,4-D regulations in Arkansas

From Arkansas State Plant Board Annual Report (2011-2012)i

All pesticides registered for sale in Arkansas are assigned to a Class. Each Class carries with

it one or more restrictions that must be complied with by the user, applicator, or dealer. The

classification system ranges from Class A which presumably all pesticides are registered as

initially, until a problem develops. The only use-restrictions assigned to Class A products are

those on the product label. If problems develop with a product, the Plant Board, after a public 

hearing, can move a product from the Class A designation to another designation (B, C, D, E or 

F) which has more restrictions. Each classification carries with it all the restriction(s) that are 

specified for that class plus all that came before it. That is, if a product is classified as Class D it 

will be bound to the restriction(s) specified for Class D and those specified for Classes A, B and 

C.

This allows the Plant Board to a have a systematic approach to placing use-restrictions on

products when needed as opposed to creating a unique set of restrictions for each product as

needed. This has also cut down on the confusion that existed as to what regulations apply to

what products.

2,4-D containing products are assigned to Class F. This designation was enacted by the 

Arkansas State Plant Board (ASPB) in 2007 after an unusual number of off-target incidences 

were reported in the 2006 crop season. More than 100 complaints about 2,4-D drift were 

made to the ASPB Pesticide Division. It is the Board’s responsibility to investigate each 

complaint they receive. With the record number of complaints received that year, not all 

requests could be attributed to a definitive cause. However, the ASPB Pesticide Division 

Director said that based on the information from university extension and ASPB field 

inspectors the widespread occurrences of off-target movement of 2,4-D occurred “probably 

not due to a specific application as much as it is volatilization...It’s almost assuredly 

something that was applied in a temperature inversion.”ii The 2006 crop season in northeast 

Arkansasiii had a very wet spring which resulted in many applications being conducted 

aerially and done in a short period of time. A similar spike in incidences occurred in 2003 

when the crop season was unusually wetiv. [NOTE: The proposed label for Enlist Duo 

prohibits aerial application and also provides specific instructions on avoiding applications 

during temperature inversions.]
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The ASPB created a 2,4-D task force and a glyphosate task force in 2006 charged with the

mission of developing proposed regulations for the board to consider. v The task forces, led 

by the director of ASPB Pesticide Division, included representatives from University of 

Arkansas Extension and researchers, and crop consultant Ford Baldwin.vi After conducting 

public meetings and taking testimony from representatives from various agriculture sectors, 

the task forces submitted recommendations to the ASPB at the end of 2006. The final rule, 

adopted in February 2007vii, called for ban on most aerial and ground applications of 2,4-D in 

ten northeastern counties (area known as Crowley’s Ridge) between April 15 and September 

15 and buffers of 2,4-D applications from susceptible crops in the remaining counties. 

Applications of glyphosate were limited to wind speeds no higher than 10 mph or 15 mph if 

using a commercially available hooded sprayer. University of Arkansas Cooperative 

Extension also held over 340 applicator education classes, well above their target 90.viii

In the ASPB Annual report for 2011-2012, the Pesticide Division reported 195 requests for 

investigations made in 2011. Of these 195 investigations, only 5 were attributed to 2,4-D.ix 

(See appendix A). On average over the past four years, the ASPB conducted about 170 

investigations each year. 

i

 Arkansas State Plant Board annual report (2011-2012), page 43. 

http://plantboard.arkansas.gov/Pages/default.aspx

ii

Bennett, David. “2,4-D damages Arkansas cotton”, Delta Farm Press; Aug. 15, 2006. iii National Weather Service, Little Rock, AR Yearly Climate Summary (2006). 

http://www.srh.noaa.gov/lzk/?n=2006.htm

iv

National Weather Service, Little Rock, AR “Severe Storms Flash Flooding (May 2003), 

http://www.srh.noaa.gov/lzk/?n=events2003.htm

v Bennett, David. “Proposed regulations target Arkansas 2,4-D and glyphosate drift”, Delta Farm Press; Jan. 25, 

2007. 

vi Bennett, David. “In Arkansas: Task force tackles drift problems”, Delta Farm Press; Aug. 11, 2006. vii Arkansas Regulations on Pesticide Classification, Agency # 209.02, (Rev. 06/07). Viii University of Arkansas Combined Research and Extension Annual Report (2007), pg. 152. ix

Arkansas State Plant Board annual report (2011-2012), page 41-42.
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APPENDIX A

Arkansas State Plant Board Annual Report (2011-2012)
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 2005 281

 2004 249

 2003 256

2002 215
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DOW AGROSCIENCES RESPONSE TO USDA-APHIS 

QUESTIONS RECEIVED DECEMBER 10, 2012 REGARDING 

DAS-40278-9 CORN AND DAS-68416-4 SOY.

C. Herbicide drift issues. 

10. How many offsite incidents from pesticide use are reported each year in the US? 

11. What is the breakdown with regards to where (what state or region) the incidents 

occurred, the active ingredient alleged to have caused the damage, the total number 

of applications of that active ingredient, types of crop affected, amount of damages 

sustained, amount of compensation paid? 

Dow AgroSciences is not aware of a comprehensive, national database of offsite incidents 

from pesticide use1

. Incidents involving alleged pesticide spray drift may be reported by 

various sources to the grower, applicator, retailer, state or federal agency and/or the product 

manufacturer. Information associated with the alleged incidents and investigations is 

managed by each respective party or entity. 

Pesticide product registrants are required under FIFRA Section 6(a)(2) to submit certain 

types of factual information to the U.S. Environmental Protection Agency (EPA) regarding 

adverse effects on human health or the environment from the use of their registered products. 

EPA maintains this information in its Aggregate Incident Reports database. Registrants are 

only required to submit information that has been provided to them or that they otherwise 

have knowledge of, and no investigation or follow-up is required. Out of an abundance of 

caution, registrants routinely submit reports on alleged incidents that have not been 

independently verified. Thus, due to the nature of incidents and how they are typically 

reported through the FIFRA 6(a)(2) process, the authenticity, validity, and/or accuracy of 

information contained in the reports cannot be guaranteed by the registrants and may not 

accurately reflect actual incidents and products involved. In many cases there is not enough 

information to determine if the alleged adverse effects noted were in fact the result of 

pesticide spray drift and not another contributing factor. Thus, spray drift allegations may be 

reported as plant damage which may, in fact, have been caused by diseases, insects, nutrient 

deficiencies, herbicide residue (carryover) and growing conditions.

 1 US EPA Office of Pesticide Programs’. (2007). Report on Incident Information: The Baseline. 

Retrieved from http://www.epa.gov/pesticides/ppdc/2007/oct2007/session10-finalrpt.pdf.
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For its part, EPA does not require reporting of adverse effects to non-target plants at the use 

site when the pesticide label provides adequate notice. As a result, some incidents may not 

be reported because EPA is already aware of the potential for those effects to occur under 

certain conditions. Adverse effects and incident data are not shared across registrants and 

duplicative reporting is possible. Therefore, to obtain adverse effects data for all products 

across registrants requires submitting a request to the EPA pursuant to the Freedom of 

Information Act (FOIA). Dow AgroSciences is not aware of the extent to which EPA can 

search its Aggregate Incident Reports database for specific types of adverse effects 

information, such as damage to non-target plants.

EPA’s Office of Pesticide Program's also maintains the Ecological Incident Information 

System database (EIIS), which includes information on ecological incidents reported to EPA 

prior to 1998 by pesticide registrants and all of the "major" incidents reported by pesticide 

registrants since 1998. EIIS also includes information on incident reports submitted through 

other sources, such as the States, regardless if they are "major" incidents or not. Incidents of 

adverse effects on lawns and other ornamentals caused by direct application of pesticide 

products are not entered into EIIS. When available, EIIS includes date and location of 

incident, type and magnitude of effects observed in various species, use(s) of pesticides 

known or suspected of contributing to the incident. However, the database contains a limited 

number of reported incidents and is not readily available to the public.

While accurate, comprehensive, and reliable national data on offsite incidents from pesticide 

use is not readily available, EPA’s Office of Pesticide Programs may publish incident data as 

part its periodic review of all pesticides to ensure that their registrations continue to meet 

current scientific standards. Recently, EPA published a scoping document for 2,4-D acid, 

salts, and esters to support registration review that includes the results of a search of the EIIS 

and the Aggregate Incident Reports databases for ecological incidents involving 2,4-D acid 

and its forms2

. 

A summary of the incident data is provided in Section 3.3 of the scoping document. (See

Appendix 1). The EIIS database returned both residential and agricultural incidents 

involving 2,4-D reported from 1949 to the present, as summarized in Table 9. A listing of 

each of the individual incidents from the search of the EIIS database is provided in Table C.1 

Ecological Information from the EIIS Database (See Appendix 2). Many of the plant 

incidents appeared to result from over-application of 2,4-D products to lawns or application 

of 2,4-D products to types of grass that are sensitive to 2,4-D. Other plant incidents were the 

result of spray drift in agricultural settings. As noted in the report, these incidents need to be 

carefully reviewed to determine the role that 2,4-D products may have played as many 

incidents also involved the application of other pesticides.

Table 10 of the EPA Report provides a summary of incidents reported in the Aggregate 

Incident Reports database from 1996 to the present for 2,4-D acid and its forms. However, 

 2 US EPA Environmental Fate and Effects Division. (2012). EFED Registration Review Problem 

Formulation for 2,4-D. Retrieved from http://www.regulations.gov/#!documentDetail;D=EPA-HQOPP-2012-0330-0003
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specific information was not available for these incidents (e.g., species involved, other 

chemicals, etc.). In many cases there is not enough information to determine if the alleged 

effects noted were in fact the result of pesticide spray drift and not another contributing 

factor. Thus, spray drift allegations may be reported as plant damage which may, in fact, 

have been caused by diseases, insects, nutrient deficiencies, herbicide residue (carryover) and 

growing conditions.

It is also important to note that the incident data summarized in the EPA report is for 2,4-D 

acid, salts, and esters. The herbicide solution for DAS-40278-9 corn is centered on the 

innovative choline salt of 2,4-D. This proprietary salt provides significant advantages over 

2,4-D amine salts and esters, including exceptionally low volatility. Dow AgroSciences has 

developed innovative formulations for use with DAS-40278-9 corn that will combine the 2,4-

D choline salt with glyphosate in a premix. These new formulation technologies significantly 

reduce the potential for off-target movement via spray droplet drift. New premix 

formulations of 2,4-D choline plus glyphosate also will provide greater spray tank stability 

and compatibility than current tank mixes of 2,4-D plus glyphosate. The novel attributes and 

technologies offered in the premix of 2,4-D choline plus glyphosate have been shown to 

significantly reduce the amount of driftable spray droplets (droplets below 150 μm) 

compared with tank mixtures of commercial glyphosate and 2,4-D formulations. The premix 

formulation will combine excellent efficacy and stability in the spray solution with low 

potential for off-target movement via particle or vapor drift. 

In addition to the technology innovations, the herbicide product label and product use guide 

do not allow applications into areas where temperature inversions are present, do not allow 

applications when winds exceed 15 mph, do not allow aerial applications, and require use of 

only spray nozzles that produce a coarse or coarser spray droplet size. Such stewardship and 

responsible use requirements will help to further minimize the potential for off-target 

herbicide movement.

Use of the innovative choline salt of 2,4-D, the new formulation technologies, and Dow 

AgroSciences’ Stewardship Program will help reduce the potential for off-target impacts on 

sensitive crops and non-crop plants/organisms.
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Appendix 1 – Report Excerpt Section 3.3 Ecological Incidents
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Appendix 2 – Table C.1 Ecological Information from the EIIS Database

Incident Information from the EIIS Database
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2,4-D Off-Target Exposure and Sensitive Crops

Federal and state regulation of off-target pesticide movement

EPA is the federal agency vested with the authority and responsibility for regulating the sale, 

distribution and use of pesticides, including herbicides such as 2,4-D. EPA registers or approves 

a pesticide for one or more uses only after determining that the product will not cause 

unreasonable adverse effects on the environment – the statutory test for registration under 

FIFRA. When EPA approves the registration of a pesticide, it approves a particular product for a 

particular use or uses under specified conditions (including composition, application methods, 

usage rates, and protective measures) and specifies the language that must appear on the label of 

the pesticide product that sets forth those conditions and limitations. If a pesticide product is 

used in a manner that is inconsistent with its labeling, the user is subject to federal and state 

enforcement action. When making its registration decision, EPA specifies the data and 

information it needs to support that registration. Among the data EPA requires are those relating 

to off-target pesticide movement including, e.g., spray drift and volatilization (40 C.F.R. Part 

158, Subparts L and N). 

Federal law requires EPA to periodically review existing pesticide registrations to ensure that 

they meet the FIFRA standard for registration (the "no unreasonable adverse effects" criteria of 

FIFRA) under current scientific standards. EPA specifically addressed issues regarding off-site 

pesticide movement of 2,4-D in EPA’s 2005 Reregistration Eligibility Decision (RED) for 2,4-D, 

which incorporated major label revisions to products containing 2,4-D. These revisions included: 

• lower limits for spray droplet size; 

• prohibitions on spraying at wind speeds greater than 15 mph, spraying with a wind 

direction that is not favorable to on-target deposition, or spraying with sensitive nontarget crops within 250 feet downwind; 

• a prohibition on spraying at wind speeds of less than 3 mph if there are temperature 

inversion conditions, or stable atmospheric conditions at or below nozzle height; 

• a prohibition on spraying where sensitive crops might otherwise be susceptible to drift; 

• restrictions on boom length and spray release height for aerial applications, and nozzle 

height for ground boom applications; 

• lower limits on application rates and total applications per year for specific crops; and

• compliance with any state and local laws that are more stringent (e.g., California, areas of 

which have seasonal limitations on use of 2,4-D)(EPA, 2005a). 

EPA determined the use of the then-existing formulations of 2,4-D to be eligible for 

reregistration with those label restrictions.

As mentioned above, states also regulate the use of pesticides, including herbicides. A number 

of states have passed laws to specifically address spray drift(Feitshans, 1999). These laws may 

include penalties and/or restrict application methods, require prior notification, impose buffer 

zones, etc., as each state has deemed appropriate. 
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Additional EPA actions to address spray drift and volatility

In addition to registering individual pesticides, EPA also regularly assesses the safety of 

pesticide use more broadly, and has repeatedly addressed issues associated with off-target 

pesticide movement. Some of these efforts include:

• In 2009, EPA developed and issued for public comment a draft guidance document (PR 

Notice) on Pesticide Drift Labeling to provide guidance to pesticide manufacturers on 

labeling statements concerning pesticide drift, and to inform the public of EPA’s policies 

with regard to pesticide drift. EPA continues to work with stakeholders to finalize this 

guidance.

• For many years EPA has contributed funding to support education and training programs 

on drift management. EPA provides annual funds to states to support pesticide applicator 

training programs, many of which include educational material on drift management, and

EPA has contributed to other educational programs, such as the National Coalition on 

Drift Minimization educational video and CD-Rom, the National Pesticide Applicator 

Certification Core Manual, and the National Agricultural Aviation Association’s 

Professional Aerial Applicator Support System (PAASS) to support their training and 

education programs to reduce drift incidents.

• EPA encourages pesticide applicators to use all feasible means available to them to 

minimize off-target drift. To support this goal, EPA has stated its intent to work with 

applicators, agricultural extension agents, registrants, environmental groups, and other 

interested stakeholders to collect and develop information on best management practices 

(BMPs) to reduce off-target drift for specific application methods and crop sector 

combinations. These guidance documents will be consolidated by EPA and made 

available online. 

• OPP and the 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. 

• EPA has also taken action to address issues around pesticide volatility. In December 

2009, EPA convened the FIFRA Scientific Advisory Panel (SAP) to examine scientific 

issues associated with field volatilization of conventional pesticides, focusing on 

methodologies by which bystander inhalation could be measured. 

Additional information relating to EPA’s actions to address spray drift may be found at its 

website at http://www.epa.gov/pesticides/factsheets/spraydrift.htm. 
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Existing precautions against off-target exposure 

Despite federal and state controls and the best efforts of applicators, off-target pesticide 

movement occasionally damages neighboring crops. Crops may be exposed to pesticide 

volatility or drift from a variety of sources, including public right of way uses for road 

maintenance and utilities, and agricultural uses(Moses, 2009). Crops that have the potential for 

damage due to exposure to a particular pesticide are considered sensitive crops. Sensitive crop 

growers use a number of approaches to protect their crops from off-target exposure. Location of 

where the crop is grown is a key consideration; sensitive crop growers may choose to plant in 

fields that are sheltered or protected from potential exposure, and are not immediately adjacent to 

conventional crops3

. Buffer zones and vegetative barriers are often used as a no spray zone 

between a sensitive area and a crop being sprayed. A buffer zone may be a vegetative barrier 

consisting of groves, hedge rows, wind breaks, pastures, or even the grower’s own conventional 

crops. Vegetation planted in strategic lines can reduce the extent of spray drift of agricultural 

chemicals by filtering out spray droplets in air passing through their foliage(DPI, 2009). In some 

cases, growers are able to select a sensitive crop variety that is less sensitive to pesticides that are 

commonly applied to neighboring areas. Modified cultural practices, including timing of 

operations, are another approach that can be used to protect against off-target exposure(Maynard

et al., 2012). 

Sensitive crop growers may avoid exposure in right of way areas by posting signs and making 

arrangements with government road crews or utility companies to do their own maintenance of 

easements and road ways near their sensitive crops. Similarly, neighboring farms can be notified 

of the presence of sensitive crops that require protection from herbicide spray drift and volatility. 

Since applications of herbicides are increasingly being made by custom applicators, signage 

placed near field entrances alerting operators to the presence of sensitive crops and that no sprays 

are allowed, are also used. Alternatively, sensitive crop growers may notify the local coops and 

applicators directly. There are also tools available on the internet for growers to register 

sensitive crop fields so that pesticide applicators can easily locate registered sites before they 

spray using a Google MapsTM interface(Driftwatch, 2012).

If crop damage occurs, affected growers can seek compensation by a variety of mechanisms. 

The pesticide applicator may have insurance to cover such losses. State pesticide enforcement 

bureaus are notified to view and document the damage. In some states, the applicator may be 

subject to fines or other penalties(Feitshans, 1999). The crop damage may also give rise to 

claims for legal damages in private lawsuits. 

Potential off-target pesticide impacts on organic crops

Growers of organic crops may also face economic damages from off-target pesticide movement, 

even if their crops are not damaged. If a certifying agent tests a crop grown under organic 

production and the test reveals the presence of residues from a pesticide not approved for use 

 3 U of IL Extension. Reducing Pesticide Drift. University of Illinois Extension and Illinois Department of 

Agriculture
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under the National Organic Program (NOP), the crop may not be sold as organic if the residue is 

present at a level greater than five percent of the EPA tolerance for the detected prohibited 

residue (7 CFR 205.671). A grower whose organic crops were subject to off-target pesticide 

movement that resulted in residue levels greater than five percent of the EPA tolerance could 

then lose the organic premium he may otherwise have obtained for his crop. While some 

certifying agents have refused to allow organic production on fields that have been the objects of 

spray drift, a recent court decision found this three year ban on organic production following 

spray drift to be inconsistent with the NOP (Johnson v. Paynesville Farmers Union Cooperative 

Oil Co., 2012 WL 3101667 (Minn.) at 16).

In finalizing the NOP, USDA described the following in regards to grower’s responsibilities to 

protect against chemical drift (65 FR 80556):

Drift has been a difficult issue for organic producers from the beginning. Organic operations 

have always had to worry about the potential for drift from neighboring operations, particularly 

drift of synthetic chemical pesticides. As the number of organic farms increases, so does the 

potential for conflict between organic and nonorganic operations. 

It has always been the responsibility of organic operations to manage potential contact of 

organic products with other substances not approved for use in organic production systems, 

whether from the nonorganic portion of a split operation or from neighboring farms. The organic 

system plan must outline steps that an organic operation will take to avoid this kind of 

unintentional contact. 

When we are considering drift issues, it is particularly important to remember that organic 

standards are process based. Certifying agents attest to the ability of organic operations to follow 

a set of production standards and practices that meet the requirements of the Act and the 

regulations. 

All of the preventions discussed above are available to organic growers and many are required 

by the NOP as part of their organic production plan. Similarly, insurance and legal recourse may 

be available to organic growers who lose premiums as a result of spray drift.

2,4-D and off-target movement

One of the herbicides that DAS-40278-9 corn and DAS 68416-4 soybean have been engineered 

to tolerate is commonly known as 2,4-D. 2,4-D is a synthetic plant growth regulator (auxin) that 

has been registered for use in the US as a broadleaf weed herbicide since 1948.(EPA, 2005b) 

2,4-D is absorbed through the leaves and is translocated to the meristems of the plant. 

Uncontrolled, unsustainable growth ensues, causing stem curl-over, leaf withering, and eventual 

plant death. Thus, any inadvertent contact to an adjacent broadleaf crop plant, through drift or 

volatility, has the potential to produce very noticeable physiological symptomology. 

As of 2005, EPA had registered over 600 end-use products containing 2,4-D.(EPA, 2005b) 

Throughout the period 2001-2007, 2,4-D remained the #1-ranked herbicide for industrial, 

commercial, governmental, home and garden use, with a total annual usage for these applications 

in the range 24-33 million pounds.(EPA, 2011) Although from 2001 to 2007 its ranking as a 
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herbicide for agricultural use fell from #4 to #5, annual usage was in a similar range: 28-33 

million pounds in 2001 and 25-29 million pounds in 2007.

Since it was introduced in 1948, there have been reports of 2,4-D adversely affecting non-target 

broadleaf food and feed crops, such as cotton, grapes and tomatoes, growing in the vicinity of 

target crops.(Schultz et al., 1956) Such incidents have been linked to drift of spray droplets 

(especially through aerial spraying) or drift of vapors formed by volatilization of the 2,4-D 

itself.(Dexter, 1993) 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. 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. 

Increased control of drift and volatilization across pesticides has been achieved with proper 

equipment setup and attention paid to climatic conditions at the time of application. University 

extension agencies have been especially prominent in developing and disseminating “Good 

Application Practices” to minimize drift. Additionally, pesticide label restrictions, state pesticide 

regulations, nozzle technology and manufacturer stewardship programs have helped to develop 

and establish application practices that minimize the potential for off-target exposure. 

2,4-D is currently formulated as an ester or amine salt. Attributions of volatility to 2,4-D have 

largely been associated with the esters, particularly short chain esters. Early forms of 2,4-D 

included short chain esters that were favored due to rapid herbicidal activity, but these were 

relatively volatile(Nice et al., 2004). A desire to reduce risk of off-target injury to sensitive 

crops, such as cotton, tomatoes or grapes, led to the development of longer chain esters that were 

notably less volatile, and to development of various amine salts that are considered much less 

volatile than ester formulations ((International Programme on Chemical Safety, 1989) (NPIC)). 

The volatility of the salt forms approaches two orders of magnitude reduction compared to the 

short chain esters (Dow AgroSciences, 2011). In the last two decades, longer chain esters have 

replaced the shorter chain esters and as a result, volatility issues have largely abated. 

New technologies for controlling drift and volatility 

DAS conducted an extensive evaluation of various salts under conditions inducing high volatility 

to identify candidates that had significantly reduced volatility and thus lowered potential for 

injury to susceptible plants. The results led to the development of 2,4-D choline salt. This novel 

form of 2,4-D has been tested in the laboratory and subsequently in field studies. Quantification 

of volatilized 2,4-D from soybean and bare soil fields demonstrated: 2,4-D ethylhexylester was 

the most volatile, with calculated loss rates of the 2,4-D ethylhexylester as much as two orders of 

magnitude greater than the 2,4-D dimethylamine (DMA) form, which is considered to be much 

less volatile than ester formulations ((NPIC; International Programme on Chemical Safety, 
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1989)). As detailed in materials submitted to APHIS by DAS(Dow AgroSciences, 2011), the 

choline form of 2,4-D measured as much as 50X less volatility than the DMA form and had 

dramatically less injury to a variety of crops known to be sensitive to auxin herbicides under 

confined conditions as compared to ester and amine forms of 2,4-D. 

DAS’s new product containing 2,4-D choline and glyphosate DMA (Enlist Duo herbicide) will 

make the herbicide spray droplets larger and more uniform in size compared to a standard 2,4-D 

and glyphosate tank mix application. DAS has measured a 3X improvement (reduction) in 

driftable fines (<150 μ) for both 2,4-D choline and glyphosate under field conditions using 

commercial application equipment. This validates observations made under controlled laboratory 

and wind tunnel conditions. Coupled with using the latest in drift reduction nozzles, as much as a 

10X reduction in drift was achieved compared to a standard tank mix application of the same 

active ingredients using conventional nozzles. 

Pending registration by EPA, DAS intends to market Enlist Duo Herbicide with Colex-D 

Technology, a pre-mix of the new 2,4-D choline salt and glyphosate dimethylamine with reduced 

drift and volatility characteristics, for use with DAS-40278-9 corn and DAS-68416-4 soybeans. 

Via a Technology Use Agreement, DAS will require growers of DAS-40278-9 corn and DAS68416-4 soybean who choose to use 2,4-D in post-plant applications to “use only EPA accepted 

and DAS authorized 2,4-D formulations containing Colex-D Technology, such as EnlistTM Duo, 

for in-crop application” to provide this added protection against off-target exposure. A 

combination of EPA-required label restrictions, contractual obligations and grower education 

and outreach will further minimize any off-target effects to neighboring crops caused by 

application of Enlist Duo to DAS-40278-9 corn and DAS-68416-4 soybeans.

Proposed herbicide label language for Enlist Duo 

DAS has submitted to EPA for approval a proposed label for its Enlist Duo Herbicide with 

Colex-D Technology, a pre-mix of the new 2,4-D choline salt and glyphosate DMA. The first 

submission to EPA is for use on Enlist corn, DAS-40278-9, and once approved then DAS will 

submit a label amendment for the use of Enlist Duo on DAS-68416-4 soybean. DAS’s proposed 

label contains the instructions for use directly addressing the potential for spray drift and 

volatility. The same label instructions will be submitted for use on Enlist soybean, DAS-68416-

4. Of course, during its label approval process, EPA may impose additional use restrictions or 

other protective measures for corn and/or soybean.

DAS has submitted for EPA approval the following Enlist Duo label language specifically 

addressing spray drift management: 
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Spray Drift Management 

Avoid drift. Use extreme care when applying this product to prevent injury to 

desirable plants and crops. 

Do not allow GF-2726 to mist, drip, drift or splash onto desirable vegetation since minute 

quantities of this product can cause severe damage or destruction to the crop, plants or 

other areas on which treatment was not intended. The likelihood of injury occurring from 

the use of this product increases when winds are gusty, as wind velocity increases, when 

wind direction is constantly changing or when there are other meteorological conditions 

that favor spray drift. When spraying, avoid combinations of pressure and nozzle type 

that will result in fine particles (mist) which are likely to drift. 

Do not apply at excessive speed or pressure. 

Use of this product in any manner not consistent with this label may result in injury to 

persons, animals or crops, or other unintended consequences. 

Avoiding spray drift at the application site is the responsibility of the applicator. The 

interaction of many equipment- and-weather-related factors determines the potential for 

spray drift. The applicator and the grower are responsible for considering all these factors 

when making decisions. 

Do not aerially apply this product. 

Droplet Size 

Apply as a coarse or very coarse spray (ASABE S-572 Standard). Use drift reducing 

nozzle tips in accordance with manufacturer directions that produce a droplet 

classification of coarse or very coarse to significantly reduce the potential for drift.

Groundboom Application 

Use the minimum boom height based upon the nozzle manufacturer’s directions. Spray 

drift potential increases as boom height increases. Spray drift can be minimized if nozzle 

height is not greater than the maximum height specified by the nozzle manufacturer for 

the nozzle selected. 

Wind

Drift potential is lowest at wind speeds of 10 mph or less. However, many factors, 

including droplet size and equipment type, determine drift potential at any given speed. 

Do not apply at wind speeds greater than 15 mph. Note: Local terrain can influence wind 

patterns. The applicator should be familiar with local wind patterns and how they affect 

drift. 

Temperature and Humidity 

When making applications in low relative humidity, set up equipment to produce larger 

droplets to compensate for evaporation. Droplet evaporation is most severe when 

conditions are both hot and dry. 
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Temperature Inversions 

If applying at wind speeds less than 3 mph, the applicator must determine if: a) 

conditions of temperature inversion exist, or b) stable atmospheric conditions exist at or 

below nozzle height. Do not make applications during a temperature inversion or stable 

atmospheric conditions. Temperature inversions restrict vertical air mixing, which causes 

small suspended droplets to remain in a concentrated cloud. This cloud can move in 

unpredictable directions due to the light variable winds common during inversions. 

Temperature inversions are characterized by increasing temperatures with altitude and are 

common on nights with limited cloud cover and light to no wind. They begin to form as 

the sun sets and often continue into the morning. Their presence can be indicated by 

ground fog; however, if fog is not present, the presence of an inversion can also be 

identified by the movement of smoke from a ground source. Smoke that layers and 

moves laterally in a connected cloud (under low wind conditions) indicates an inversion, 

while smoke that moves upwards and rapidly dissipates indicates good vertical air 

mixing. 

Drift Setbacks from Sensitive Areas 

Allow setbacks (buffer zones) upwind of sensitive area (e.g., residential areas, bodies of 

water, known habitat for threatened or endangered species, sensitive non-target crops 

other than those listed above) according to the following table. 

If a coarse or very coarse droplet classification cannot be maintained, an upwind setback 

of 250 feet from sensitive areas must be observed. 

Susceptible Plants 

Do not apply under circumstances where spray drift may occur to food, forage, or 

other plantings that might be damaged or crops thereof rendered unfit for sale, use 

or consumption. Avoid contact of herbicide with foliage, green stems, exposed 

non-woody roots of crops, desirable plants and trees because severe injury or 

destruction may result. Small amounts of spray drift that may not be visible may 

injure susceptible broadleaf plants. Before making an application, please refer to 

your state’s sensitive crop registry (if available) to identify any commercial 

specialty or certified organic crops that may be located nearby.

Commercially grown tomatoes and other fruiting vegetables (EPA crop group 8), 

cucurbits (EPA crop group 9), and grapes are particularly sensitive to drift from this 

product. Do not apply when wind direction favors off-target movement onto these crops.

State and Local Requirements 

Applicators must follow all state and local pesticide drift requirements regarding 

application of 2,4-D herbicides. Where states have more stringent regulations, they must 

be observed. 

The submitted Enlist Duo label language also requires additional measures to avoid offtarget movement and crop injury, including detailed instructions for clean-out of sprayer 

equipment, use of drift control additives, and boom and nozzle height instructions. 
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Additional DAS measures to address spray drift and volatility 

As noted above, DAS will contractually require growers of DAS-40278-9 corn and DAS-68416-

4 soy who wish to use 2,4-D as an in-crop herbicide to use only EPA accepted and DAS 

authorized 2,4-D formulations (all of which will contain Colex-D Technology), such as EnlistTM 

Duo, for in-crop application. This new 2,4-D technology will provide substantially lower 

volatility than any other form of 2,4-D, as well as improved drift control, low odor, and 

improved handling characteristics. 

Through its Technology Use Agreement, DAS will impose a legal and contractual obligation that 

will require all growers of DAS-40278-9 corn and DAS-68416-4 soybean to: 

• Use only EPA accepted and DAS authorized 2,4-D formulations containing Colex-D 

Technology, such as Enlist Duo, for in-crop applications to DAS-40278-9 corn and DAS68416-4 soybean. 

• Read and follow FIFRA Pesticide Product Label directions. 

• Read and follow the Enlist Weed Control System Product Use Guide. 

• Use properly maintained and calibrated ground application equipment for Enlist Duo 

with Colex-D Technology with minimum boom heights. 

• Use nozzles that reduce the potential for physical drift of Enlist Duo with Colex-D 

Technology. 

• Follow instructions for equipment clean-out after product use. 

DAS will provide comprehensive training on its technology and portfolio of products to growers, 

dealers and distributors through a variety of formats. Education and training, reinforced through 

product profiles, technical bulletins, sales literature, direct mailing and websites will also be 

presented in multiple formats to enhance learning and mastery of core concepts related to 

stewardship to be employed around DAS-40278-9 corn and DAS-68416-4 soybean. A variety of 

educational formats will be used to promote concept learning. This training will include 

education on spray technology and herbicide application, including spray quality basics, as well 

as spray quality of Enlist Duo, as well as how to minimize the potential for off-target movement 

of Enlist Duo.

References

Dexter, A.G., 1993. Herbicide spray drift. North Dakota State University.

Dow AgroSciences, 2011. Research demonstrating reduction in potential off-target movement 

for 2,4-d choline and colex-dTM technology as part of the enlistTM weed control system. 

Dow AgroSciences LLC. Indianapolis IN.

DPI, V., 2009. Using buffer zones and vegetative barriers to reduce spray drift. 

http://www.dpi.vic.gov.au/agriculture/farming-management/chemical-use/agriculturalchemical-use/spraying-spray-drift-and-off-target-damage/ag0860-using-buffer-zonesand-vegetative-barriers-to-reduce-spray-drift.

Driftwatch, 2012. Driftwatch registry of pesticide sensitive crops. 
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EPA, 2005a. Gis-based risk assessment of pesticide drift case study: Fresno county, california. . 

EPA/600/R-05/029. 

EPA, 2005b. Reregistration eligibility decision for 2,4-d. EPA 738-R-05-002. 

www.epa.gov/oppsrrd1/REDs/24d_red.pdf.

EPA, 2011. Pesticides industry sales and usage 2006 and 2007 market estimates. EPA 733-R-11-

001 U.S Environmental Protection Agency. Washington DC.

Feitshans, T.A., 1999. An analysis of state pesticide drift laws,. San Joaquin Agriculture Law 

Review 37.

International Programme on Chemical Safety, 1989. Environmental health criteria, 2,4-d 

environmental aspects. http://www.inchem.org/documents/ehc/ehc/ehc84.htm

Maynard, E., Overstreet, B., Riddle, J., 2012. Pesticide drift and organic production. 

https://mdc.itap.purdue.edu/item.asp?itemID=20611.

Moses, 2009. Protecting your organic land from unwanted chemical sprays. 

http://www.mosesorganic.org/attachments/productioninfo/fsnospray.html.

Nice, G.R.W., Johnson, B., Bauman, T.T., 2004. Amine or ester, which is better? Purdue 

Extension Weed Science.

NPIC, State pesticide regulatory agencies. http://npic.orst.edu/state1.htm.

Schultz, H.B., Akesson, N.B., Yates, W.E., Ingebretson, K.H., 1956. Drift of 2,4-d applied by 

plane. California agriculture, . California Agriculture.

 i

 Arkansas State Plant Board annual report (2011-2012), page 43. 

http://plantboard.arkansas.gov/Pages/default.aspx

ii Bennett, David. “2,4-D damages Arkansas cotton”, Delta Farm Press; Aug. 15, 2006. iii National Weather Service, Little Rock, AR Yearly Climate Summary (2006). 

<http://www.srh.noaa.gov/lzk/?n=2006.htm> iv National Weather Service, Little Rock, AR “Severe Storms Flash Flooding (May 2003), 

http://www.srh.noaa.gov/lzk/?n=events2003.htm v Bennett, David. “Proposed regulations target Arkansas 2,4-D and glyphosate drift”, Delta Farm Press; Jan. 25, 

2007. 

vi

 Bennett, David. “In Arkansas: Task force tackles drift problems”, Delta Farm Press; Aug. 11, 2006. vii Arkansas Regulations on Pesticide Classification, Agency # 209.02, (Rev. 06/07). viii University of Arkansas Combined Research and Extension Annual Report (2007), pg. 152. ix Arkansas State Plant Board annual report (2011-2012), page 41-42.