At the 2010 North Central Weed Science Society Annual Meeting and the 2011 Southern Weed Science Society Annual Meeting, scientists and researchers from Dow AgroSciences presented scientific, equipment, and application methods papers on new technology on the horizon to address weed control challenges. Many topics at the meetings related to weed resistance and hard-to-control weeds that are threatening the productivity of agriculture, and Dow AgroSciences’ information provided an overview of components of the EnlistTM Weed Control System, which is currently undergoing regulatory review for approval.

“Dow AgroSciences has invested substantial resources into developing game-changing technology that will provide farmers new options for exceptional weed control and management,” said Mark Peterson, global biology team leader at Dow AgroSciences. “During the weed science society meetings, we had the opportunity to present to the weed science and academic communities and explain the cutting-edge research and development findings behind our innovative trait and herbicide technologies.”

Research and development presentations for the Enlist Weed Control System focused on volatility, drift, crop tolerance, and overall efficacy and stewardship programs.

Ultra Low Volatility To evaluate the volatility potential of 2,4-D choline, a component of the Colex-DTM Technology, scientists from Dow AgroSciences used a variety of methods, including complex laboratory evaluations and field-level analytical studies. Volatilization describes vapor loss and migration of previously applied active ingredient molecules—in other words—movement of herbicide to unintended locations after application because the molecules change from a solid or liquid to

a gas or vapor. 1 

# Weed Science Society Recap: Key Components of New Technology to Address Weed Control Challenges Shared with Scientific Community“To determine the relative volatility of different 2,4-D products, including 2,4-D choline among others, laboratory test methods such as humidome and volatility chamber tests were utilized,” explained Dave Ouse, a scientist at Dow AgroSciences. “Humidome testing served as a
worst case scenario and as a reliable method to evaluate herbicide volatility in a contained, laboratory environment.”

During the humidome tests, 2,4-D tolerant crops were sprayed with a high dose of 2,4-D, exposing neighboring sensitive broadleaf plants to any vapors generated from the treated plants. Humidome tests occurred during a 24-hour period at 40° C, and then the sensitive plants were moved to a greenhouse and their growth was monitored for an additional six days. As another research method, volatility chambers were used to quantify vapor evolution from 2,4-D formulations at different levels of humidity and temperature over 24, 48, 72, and 96 hours.

To validate laboratory results, field studies were conducted on large-scale, small-scale, and micro-scale plots to generate qualitative and quantitative data to measure the volatility of 2,4-D choline. Multiple sized plots were used to obtain the most comprehensive set of test data and to generate meaningful quantification of movement.

“Compared to other 2,4-D products, 2,4-D choline consistently demonstrated significantly lower volatility in the humidome and volatility chamber tests,” said Ouse. “Additionally, multiple studies on all plots—large, small, and micro—demonstrate 2,4-D choline has ultra low volatility, reducing the frequency and severity of injury to non-target plants due to volatility.”

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### What is the EnlistTM Weed Control System?

The EnlistTM Weed Control System is a herbicide-tolerant trait technology that will provide farmers new solutions for managing the increasing prevalence of glyphosate-resistant
and other hard-to-control weeds in corn, soybeans, and cotton. Enlist will sustain the flexibility, convenience, and value gained from herbicide-tolerant crops by partnering with and improving the current glyphosate-tolerant cropping system.

Colex-DTM Technology will be
featured in the Enlist herbicide
solution. This new herbicide technology will utilize 2,4-D choline, a unique quaternary
ammonium salt that is different
from traditional ester or amine 2,4-D products, as well as
feature the latest formulation science and a proprietary manufacturing process.

Colex-D Technology will provide new features while retaining the same weed control efficacy and favorable environmental profile of traditional 2,4-D products. These new features will provide farmers and applicators a
herbicide solution with ultra low volatility, minimized potential for physical drift, decreased odor, and improved handling characteristics, improving non-target crop and environmental safety.Minimized Potential for Drift In addition to volatilization, the other potential contributor to off-target movement that needs to be addressed in weed management is spray drift. Different from volatilization, drift is the physical movement of spray droplets immediately following application and is a function of spray droplet size.

“Nozzle type and application parameters, such as pressure and speed, have major effects on drift,” said Steve Wilson, Ph.D., a scientist at Dow AgroSciences. “Tank mix composition and formulation properties are also significant since they affect particle size distribution and the amount of very small spray droplets that are the primary contributors to drift.”

To demonstrate the effectiveness of the new anti-drift technology in Colex-D Technology, cutting-edge wind tunnel research was conducted at the University of Queensland Center for Pesticide Application and Safety in Australia. The research compared traditional tank mixes of glyphosate and 2,4-D to Dow AgroSciences’ new Colex-D Technology which will be featured in the herbicide solution for the Enlist Weed Control System.

“Our new technology was found to be quite effective at reducing drift for a variety of nozzles that were tested,” said Wilson. “Even with low drift nozzle designs, such as induction nozzles, significant additional drift reduction was found with our formulation.”

Improved Tolerance and Efficacy Tolerance was assessed on the basis of overall crop injury, including growth inhibition, leaning and several other factors, as explained by Eric Scherder, a scientist at Dow AgroSciences.

“Crop tolerance studies conclude the new traits will exhibit robust tolerance to 2,4-D choline alone or in combination with glyphosate, providing exceptional crop tolerance and safety,”
said Scherder.

Efficacy was assessed on the basis of percentage of visual weed control, as tested on weeds which were generally four-to-six inches tall.

“Weed efficacy studies conclude that the new herbicide products in development by Dow AgroSciences will provide an exceptional level of weed control equal to the current amine formation used today,” said Scherder.

Stewardship Dow AgroSciences is developing a comprehensive stewardship program to promote responsible use and sustain long-term future performance of trait and herbicide technologies.

“Dow AgroSciences is committed to stewardship of its new weed control system,” said Kirk

Dietz, global product leader, agrochemicals, at Dow AgroSciences. “The stewardship program was developed to promote integrated trait and herbicide solutions.” 3The stewardship program in development will be comprised of comprehensive product use guidelines, grower agreements, education and training, and compliance monitoring to ensure the technology is used responsibly and is in compliance with state and federal regulatory requirements.

Dow AgroSciences is encouraging continued dialogue between the company and key stakeholders regarding latest research, innovations, and best management practices. The company is committed to providing distributors, retailers, growers, and applicators with comprehensive stewardship guidance for deploying the Enlist Weed Control System when it is approved for use.

“Patents for the new technologies have been submitted in major crop growing countries around the world,” added Dietz. “Regulatory submissions for the trait and herbicide technologies have also been made to relevant government authorities.”

Farmers are becoming overwhelmed by weeds. The list of resistant and hard-to-control weeds has grown substantially during the past decade — resulting in an evolving landscape of increasingly challenging weeds. Dow AgroSciences is developing the Enlist Weed Control System to help farmers manage resistant and hard-to-control weeds. Enlist will introduce a more effective combination of herbicides, traits in elite genetics, and comprehensive stewardship programs. This system will give farmers the clean fields that are necessary to deliver top yields, while maintaining industry-preferred farming practices.

Presenters and co-authors included the following scientists and researchers from Dow AgroSciences in Indianapolis, Indiana: A.A. Ahmed; N.M. Carranza; K. Dietz; S.C. Ditmarsen; B. Downer; A.T. Ellis; J.M. Ellis; S.M. Ferguson; C.A. Gallup; J.M. Gifford; R.L. Hamm; P.L. Havens; D.E Hillger; B.W. Hopkins; J.A. Huff; C.J. Jennings; T. Jones-Jefferson; B.D. Olson; D.G. Ouse; K. Qin; J.S. Richburg; D.C. Ruen; E.F. Scherder; M.E. Schultz; D.M. Simpson; N.A. Spomer; J. Stautz; G.R. Tofoli; and S.L. Wilson.

Enlist Weed Control System was announced as the global brand name for Dow AgroSciences herbicide tolerant trait technology on March 2, 2011.

TMEnlist is a trademark of Dow AgroSciences LLC. Components of the Enlist Weed Control System have not yet received regulatory approvals; approvals are pending. The information provided here is not an offer for sale. ©2011 Dow AgroSciences LLC

M26401003 (06/11) FH010-42296

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