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2,4-D Herbicide- Tolerant crops, soon

The cavalry may be on the way, so to speak, to help farmers struggling with glyphosate resistance.

November 17, 2011  By Donna Fleury

The cavalry may be on the way, so to speak, to help farmers struggling with glyphosate resistance. Using 2,4-D as part of the Enlist Weed Control System, corn, soybean and cotton growers will be better able to manage and prevent glyphosate resistance.

Plant breeding technology has enabled the development of 2,4-D-tolerant crops.
Photos courtesy of Dow AgroSciences.


Herbicide-tolerant cropping systems have been readily adopted by growers during the past decade. In the US today, herbicide-tolerant crops have been adopted on 85 to 95 percent of corn, soy and cotton acres, with similar rates in Canada on corn, soy and canola acres. “Many growers have adopted conservation tillage and Roundup technology, with about 85 to 95 percent of growers dependent on Roundup, or glyphosate, for weed control,” explains Tony Klemm, global business leader for Dow AgroSciences. “However, the results of widespread and consistent use of glyphosate have contributed to hard-to-control and glyphosate-resistant weeds, with the first resistance initially confirmed in the eastern US and now a pronounced problem in the southern US. This resistance is now spreading into the upper Midwest, and similar resistance problems are developing in Canada and Latin America.”


The number of resistant species in North America has increased from zero in 1995 to 19 in 2010. Recent studies show that up to one-third of all corn and soybean growers and two-thirds of all growers in the southern US have problems with weed resistance. Experts estimate one resistant weed species costs farmers an extra $25 to $100 per acre in manual labour to achieve weed control. “In key row crop markets, weeds are adapting, becoming more difficult to control, resulting in a decline of glyphosate herbicide performance and increased resistance,” says Klemm. “New weed management tools and technologies are critical to sustaining the long-term effectiveness of the current production systems. By partnering with and improving on the current glyphosate-tolerant cropping system, the Enlist Weed Control System being developed by Dow AgroSciences will address growers’ needs while enabling exceptional weed control.”

2,4-D to the rescue
The Enlist Weed Control System will include a herbicide solution featuring Colex-D technology made up of a new 2,4-D product: 2,4-D choline. The Enlist system is currently undergoing regulatory review. “The Enlist Weed Control system being developed in corn, soybean and cotton crops will be a new evolution in weed control based on sustaining the glyphosate system,” explains Klemm. “There are three key elements of the new technology, including a new trait, called Enlist, in elite seed genetics, a new herbicide solution in the 2,4-D product with the new Colex-D technology, and product stewardship offering a tremendous opportunity to meet the needs of today’s farmers globally and for the environment. Enlist has ultra-low volatility, minimized potential for physical drift, decreased odour, plus improved handling and tank-mixing characteristics.”

 The Enlist system will help manage glyphosate resistance in corn, soybeans and cotton.

Photos courtesy of Dow AgroSciences.


The new 2,4-D technology will provide another mode of action in combination with glyphosate in a pre-mix formulation. The Enlist Weed Control System will allow for application in both early and mid-stages of crop development (pre-emergence and post-emergence). “By integrating another mode of action with glyphosate, growers can continue to rely on conservation tillage while gaining new crop tolerance and application flexibility,” says Klemm. “Currently, if growers use 2,4-D as a burndown application in soybeans, they have to wait seven days before planting. However, this new product allows growers to plant immediately. This offers flexibility and a wider window of application, particularly in wet years or seasons where timing is tight.”

This new technology will be a broadly applicable solution to some of the challenges facing growers. By introducing multiple modes of action, Enlist will increase the effectiveness of the herbicides used while decreasing the potential for weeds to develop resistance to any one herbicide. Enlist will significantly improve control of glyphosate-resistant or hard-to-control weeds, including morning glory, amaranthus species, lamb’s-quarters, giant and common ragweeds, horseweed, velvetleaf and others.

Billions of dollars at stake
“A recent research report released by Global Insight in co-operation with Dr. James E. Nelson assessed the impact of weed resistance on US agriculture with the potential impact Enlist could provide in the future for managing resistant and hard-to-control weeds,” says Klemm.

The study showed that if a product such as Enlist is not available as the glyphosate-resistant weed problem continues to expand, the use of the alternative herbicide and tillage programs is projected to reduce net farm income by $1.9 billion in 2011, up to $2.5 billion as early as 2017, and then continue at that level every year through the rest of the simulation to 2020. During those next 10 years, the study projected that products such as Enlist will cut farm losses by 18 percent, with savings that translate into $4 billion for US farmers and $563 million dollars in consumer welfare.

The Enlist Weed Control System is anticipated to be commercially available in the US in corn for the 2013 crop year, with limited introduction in Canada. Enlist will be available in elite genetics combined with SmartStax Technology, which adds insect control for below- and aboveground pests in corn. Commercial launch in soybeans is expected to follow in 2015 and in cotton in 2016. 


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