Supplemental Information for USDA Petition for Nonregulated Status of DAS-68416-6 Soybean Page 1 of 13

Dow AgroSciences LLC

Supplemental Information for Petition for Determination of Nonregulated Status for 

Herbicide Tolerant DAS-68416-4 Soybean

Research Demonstrating Reduction in Potential Off-Target Movement for 2,4-D Choline 

and Colex-D

TM Technology as Part of the EnlistTM Weed Control System

The undersigned submits this information under 7 CFR 340.6 to support the determination that 

the article should not be regulated under 7 CFR 340.

Submitting Company:

Dow AgroSciences LLC

Submitted by:

__________________________________

Mark Krieger, Ph.D.

Regulatory Leader

Regulatory Sciences & Government Affairs

Dow AgroSciences LLC

9330 Zionsville Road

Indianapolis, IN 46268

Telephone: (317) 337- 3458

FAX: (317) 337-4649

mkrieger2@dow.com

September 8, 2011

 

TM Colex-D and Enlist are trademarks of Dow AgroSciences LLC. Components of the Enlist Weed Control System have not yet 

received regulatory approvals; approvals are pending.
Supplemental Information for USDA Petition for Nonregulated Status of DAS-68416-6 Soybean Page 2 of 13

Dow AgroSciences LLC

Summary

Dow AgroSciences (DAS) has submitted a petition to the United States Department of 

Agriculture (USDA)’s Animal and Plant Health Inspection Service (APHIS) for the 

determination of nonregulated status for DAS-68416-4 soybean, which provides tolerance to the 

herbicides 2,4-dichlorophenoxy acetic acid (2,4-D) and glufosinate.

This document is being submitted in response to a request for information from USDA-APHIS 

related to the determination of nonregulated status for DAS-68416-4 soybean and provides 

information pertaining to volatility and spray drift characteristics associated with 2,4-D choline 

and the proprietary formulation comprising Colex-DTM Technology that is part of the EnlistTM 

Weed Control System. 
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Dow AgroSciences LLC

Research Demonstrating Reduction in Potential Off-Target Movement for 

2,4-D Choline and Colex-D

TM Technology as Part of the EnlistTM Weed 

Control System

Summary

Laboratory Studies:

 2,4-D choline demonstrated ultra-low volatilization and significantly less damage to 

sensitive crops placed only inches away when compared to other forms of 2,4-D.

 The Colex-DTM formulation demonstrated a 64% reduction in driftable fines (volume 

percentage of droplets less than 150 μm) vs. conventional 2,4-D/glyphosate tank mix at 

typical use rates.

 Colex-DTM technology showed significantly less spray drift as compared to a commercial 

tank mix in wind tunnel tests using a range of spray nozzle types. For example, using 

the TeeJet AIXR 11002 air induction, Colex-DTM technology reduced driftable fines by 

20-fold as compared to the commercial tank mix.

Field Studies:

 Potted cotton plants placed under domes directly over treated soil showed minimal 

symptoms from 2,4-D volatility when Colex-DTM Technology was utilized (5% visual 

injury in 6 of 20 plants), compared to 13% visual injury in 19 of 20 plants treated with 

2,4-D amine, and 65% visual injury in all 20 plants treated with 2,4-D LV ester.

 Quantification of volatilized 2,4-D from soybean fields showed that calculated loss rates 

of 2,4-D choline were much lower that 2,4-D dimethyl amine and 2,4-D ethylhexyl ester.

The loss rate of 2,4-D ethylhexyl ester was as much as two orders of magnitude greater 

than the 2,4-D dimethyl amine form. Loss rates of 2,4-D choline were about 50X less 

than the 2,4-D dimethyl amine.

 

TM Colex-D and Enlist are trademarks of Dow AgroSciences LLC. Components of the Enlist Weed Control System 

have not yet received regulatory approvals; approvals are pending.
Supplemental Information for USDA Petition for Nonregulated Status of DAS-68416-6 Soybean Page 4 of 13

Dow AgroSciences LLC

Introduction

Dow AgroSciences (DAS) EnlistTM Weed Control System will include a new and innovative 

herbicide featuring Colex-DTM Technology. Colex-DTM Technology includes: 1) the new 2,4-D 

choline, which exhibits ultra-low volatility; and 2) the latest formulation science, which has 

displayed significantly reduced potential for spray droplet drift. The new 2,4-D choline is a 

quaternary ammonium salt,different from traditional ester or amine forms. The combination of 

the ultra-low volatility of 2,4-D choline and the drift reduction properties of the product 

formulation result in significantly lower potential for off-target movement and injury to sensitive 

crops in neighboring fields.

DAS is conducting extensive, state-of-the-art laboratory and field research including work with 

independent, external experts to advance this technology and quantify the improvements 

offered in reduced off-target movement. DAS is also engaged in development of novel modeling 

capabilities to evaluate the behavior of this technology alone and in combination with various 

Best Management Practices. 

This document summarizes research done to-date and underway on potential volatility and drift 

of Colex-DTM Technology, including controlled laboratory observations, field work under realworld conditions and modeling.

Laboratory research

To ensure improvements in potential volatilization and in drift reduction can be examined 

separately and evaluated under controlled conditions, research is being conducted in the 

laboratory and is demonstrating the benefits offered by the Colex-DTM Technology.

Laboratory volatility studies

If 2,4-D volatilization losses and movement from the treated areas occur at high enough 

concentrations for sufficient periods of time, injury to nearby sensitive plants can occur. In the 

laboratory, wheat plants were treated with various forms of 2,4-D, including the ethylhexylester 

(EHE), dimethylamine (DMA), and choline form at rates up to 10X the normal application rates, 

allowed to briefly dry, and then placed in a covered, vented chamber (referred to as a 

humidome, Figure 1). With temperatures at approximately 104o, air was pulled via a fan across 

the wheat to closely-placed tomato (Rutgers) and grape (Carignane) plants that are known to be 

highly susceptible to current commercial 2,4-D forms. Under these optimal conditions for 

volatility and movement, 2,4-D choline demonstrated ultra-low volatilization and significantly less 

damage to sensitive crops placed only inches away when compared to other forms of 2,4-D 

(Figure 1).

Laboratory drift studies

A primary contributor to the magnitude of spray drift is the droplet size distribution of the applied 

spray. Smaller droplets contribute a disproportionally larger degree of off-target spray 

movement. The accepted measure of drift potential is the percentage of „driftable fines‟ (defined 
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Dow AgroSciences LLC

as the volume percentage of the droplets less than 150 μm). The Colex-DTM Technology 

formulation reduces the amount of these fines. A Sympatec laser diffraction particle analyzer 

was used to measure the spray droplet size distribution of commercial 2,4-D/glyphosate tank 

mixes compared to that of the Colex-DTM formulation at typical use rates. Using a typical flat fan 

nozzle (TeeJet XR8002), the percentage of these driftable fines was reduced 64% from about 

50% (by volume) for the conventional formulation to only 18% with the Colex-DTM formulation 

(Figure 2). This represents a significant reduction in the potential for droplet drift to neighboring 

fields. 

This reduction in drift potential was then further confirmed by wind tunnel studies conducted in 

collaboration with Dr. Andrew Hewitt at the University of Queensland Center for Pesticide 

Application. Results comparing a commercial tank mix (Weedar 64 + Round-up PowerMax) to 

the Colex-DTM formulation were obtained in tests using four different nozzles representative of 

the range of current options for farmers (TeeJet XR 11002 flat fan (XR), Turbo TeeJet 11002 

(TT), TeeJet AIXR 11002 air induction (AIXR) and Hypro ULD (Hypro)). Spray drift was 

quantified using nylon strings at 2 and 5 meters downwind from the nozzle to determine the 

percentage of spray that had drifted that distance. For all nozzles, the volume of material drifted 

was much lower for the product containing Colex-DTM Technology (Figure 3). For the XR and 

AIXR nozzles, this reduction with the Colex-DTM Technology compared to the commercial tank 

mix was 50% or greater. Air induction nozzles produce less driftable fines regardless of the 

product being sprayed, and when the best of drift-control nozzle technology (AIXR) was 

combined with the Colex-DTM Technology, the volume at 5 meters dropped from 10% for the 

commercial tank mix formulation with the conventional flat fan XR nozzle to only 0.5% for the 

Colex-DTM Technology product,- a 20-fold reduction in measured drift. 

Field research

Although the many variable factors cannot be as well controlled in the field as in the lab, field 

research allows the opportunity to confirm what has been seen in the lab in larger scale tests 

and under real-world conditions. In the field, DAS has conducted several field volatility studies 

with additional studies underway and is also conducting field drift studies. The results are 

confirming the significant reductions in off-target movement potential offered by Colex-DTM 

Technology. 

Field volatility studies

Georgia

In 2010, a field volatility study in Georgia comparing various forms of 2,4-D, including 2,4-D 

choline, was conducted by a researcher at the University of Georgia in collaboration with DAS.

On a recently harvested and disked corn field, 90 x 90 ft test plots were treated with 2,4-D LV 

ester + Durango (glyphosate) DMA; 2,4-D amine + Durango DMA; or the premix of 2,4-D 
Supplemental Information for USDA Petition for Nonregulated Status of DAS-68416-6 Soybean Page 6 of 13

Dow AgroSciences LLC

choline + glyphosate DMA at the rate of about 2.24 kg ae /ha of 2,4-D and glyphosate (2X the 

typical use rate).

After application, volatility directly over treated ground and outside the boundary of the treated 

plots was measured using cotton plants (5-8 leaves), which are known to be sensitive to 2,4-D:

 Pots were placed at predetermined distances of 5, 10, 20, 40, 80 and 160 ft at the 

cardinal and intercardinal directions around the treated area to evaluate movement from 

the plots.

 Volatility domes (about 3 x 12 ft in size) were put over 20 potted plants placed directly on 

a single application pass within the plots after treatment to evaluate worst-case 

scenarios. Plants were then removed from under the domes after 48 hours. 

Percent visual cotton injury for all cotton plots as well as the number of plants under each dome 

expressing injury symptoms were assessed at multiple time periods after application. 

At 27 days after application, cotton plants out to 160 ft showed injury from volatility of the 2,4-D 

LV ester, while only 8-10% injury from the 2,4-D DMA was observed at 10 ft out, and only 1% or 

less injury at 5 ft with 2,4-D choline. Under the domes directly over treated soil, all 20 plants 

showed symptoms with injury greater than 65% for the 2,4-D LV ester; only 19 of the plants 

showed injury averaging 13% for the 2,4-D amine, and under these conditions which would 

maximize the possibility of injury, the 2,4-D choline showed minimal impact with less than 5% 

injury and only 6 plants showing any symptoms (Figure 4).

Indiana

To quantify actual levels of 2,4-D which volatilized from treated areas, air sampling studies were 

conducted on bare soil and soybean fields at two locations in Indiana in 2010. Separate plots 

were treated with either a commercial 2,4-D ethylhexyl ester, a commercial 2,4-D dimethyl 

amine (DMA), or the new 2,4-D choline at 2,4-D equivalent rates of 1, 2 (double rate) and 5 

(quadruple rate) lbs/acres for the ester, DMA, and choline forms, respectively. Sorbent-filled 

sampling tubes were placed in 8 compass directions at 5 and 10 meters from the field edges 

and samples collected at 4 or 6 and 12 hours after treatment. 

Employing weather data collected on-site and the measured air concentrations, the EPA air 

transport model ISCST was used to back-calculate the rate of 2,4-D loss, or flux, from the plots. 

The resulting calculated loss rates of the ester were as much as two orders of magnitude 

greater than the DMA form, with the choline being about 50X less than the DMA. ISCST was 

further used with the calculated flux profiles to extrapolate concentration multiplied by time

magnitudes (CxT) for a 40-acre treated field more typical of an actual farmer‟s field. The contour 

plots developed from this modeling (Figure 5) indicate the reduction in volatility losses with 

herbicides featuring Colex-DTM Technology would also be very significant over the larger 

treated area. 
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Dow AgroSciences LLC

Modeling of potential pesticide movement

Processes of drift deposition, volatility and air transport are complex and governed by both 

chemistry and physical laws, and numerical modeling of these processes can be used to 

examine potential pesticide transport under the near semi-infinite parameter combinations that 

can exist in the field. To continually expand the understanding of any potential movement of 2,4-

D from herbicides featuring Colex-DTM Technology under future use conditions, DAS has 

invested in the development of a novel, state-of-the-art numerical modeling tool. The model 

input parameters can be determined from data obtained in the laboratory experiments 

discussed earlier in this paper. These modeling simulations are collaborating that the ultra-low 

volatility, low drift and resulting limited transport of 2,4-D choline seen in the lab and field studies 

would also exist in a wide variety of field conditions. In addition to allowing evaluation under 

differing field conditions, these modeling techniques allow DAS to provide guidance on Best

Management Practices for growers to minimize the potential for off-target movement.

Conclusions

Colex-DTM Technology is novel technology that contains 2,4-D choline, which is different than 

other forms of 2,4-D currently available. The differences in the properties of this 2,4-D choline 

combined with advancement in the formulation technology, provide ultra-low volatility and 

reduced spray droplet drift. The reduction in volatilization has been proven in both the laboratory 

and field, and has demonstrated significantly reduced injury to sensitive crops in these studies 

compared to the current forms of 2,4-D. Advancements in formulation technology contained in 

2,4-D products with Colex-DTM Technology are showing a significant reduction in the finer spray 

particles found to be most susceptible to drift compared to current, commercial tank mixes. 

Combining 2,4-D choline with these formulation advances provides significantly reduced offtarget potential, in terms of both volume and distance, to neighboring fields.

DAS is an industry leader and has invested heavily in both development of Colex-DTM 

Technology and research to understand and quantify the benefits of these technology 

advances. DAS recognizes that improvements in technology are only part of the answer to 

prevent off-target movement, and is committed to working with university experts, regulators, 

and growers to develop and encourage proper applications according to Best Management 

Practices. 
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Dow AgroSciences LLC

Figure 1. Humidome showing wheat treated with various forms of 2,4-D placed under an 

enclosed and slightly vented chamber next to sensitive tomato and grape plants (air pulled from 

wheat across sensitive crops from right to left). Graph shows percent visible injury to grapes 

from various forms of 2,4-D tested. There was negligible injury from 2,4-D choline.

 
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Dow AgroSciences LLC

Figure 2. Spray pattern distribution using flat fan nozzle measured with a Sympatec

GmbH, laser diffraction particle analyzer showing a 64% reduction in “driftable fines” 

(those 150 μm and less in size represented by red line in the figure) from about 50% (by 

volume) for the conventional commercial tank mix to only about 18% with the new 

premix formulation containing Colex-DTM Technology (labeled DAS premix). 

. 
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Dow AgroSciences LLC

Figure 3. Percent volume of spray drift of various commercial tank mix formulations 

containing 2,4-D and the new formulation with Colex-DTM (labeled DAS premix) 

measured at 2 and 5 meters downwind from various common spray nozzles in wind 

tunnel tests. For all nozzles, the volume of material drifted was much lower for ColexDTM. Advanced nozzle design, such as AIXR and Hypro add significant drift reduction 

potential.
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Dow AgroSciences LLC

Figure 4: Percent visual injury and number of plants with injury for 20 potted cotton 

plants per treatment placed directly onto the treated field plot in GA with products 

containing various forms of 2,4-D and glyphosate and covered with volatility domes to 

maximize potential volatility injury. Cotton plants on plots treated with 2,4-D choline 

showed significantly fewer plants injured and significantly less injury.

0

10

20

30

40

50

60

70

80

2,4-D LV ester 2,4-D amine 2,4-D choline

% Visual Injury and # Plants from under 

Domes with Injury 27 Days After Application

% Visual Injury (# plants showing symptoms above bar)

19

20

6
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Dow AgroSciences LLC

Figure 5: Actual air sampling data from test sites treated with various commercial forms 

of 2,4-D and the new 2,4-D choline extrapolated using the ISCST model to simulate 

potential volatility losses (ppb/hr) over a larger 40-acre treated field. (Note the ppb/hr 

scale in each figure is logarithmic). 

Ester C x T

distance, m

-400 -200 0 200 400 600 800

distance, m

-400

-200

0

200

400

600

800

0.0001 

0.001 

0.01 

0.1 

1 

10 

100 

Treated Field

DMA, C X T

distance, m

-400 -200 0 200 400 600 800

distance, m

-400

-200

0

200

400

600

800

0.0001 

0.001 

0.01 

0.1 

1 

10 

100 

Treated Field
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Dow AgroSciences LLC

Choline, C x T

distance, m

-400 -200 0 200 400 600 800

distance, m

-400

-200

0

200

400

600

800

0.0001 

0.001 

0.01 

0.1 

1 

10 

100 

Treated Field