Enlisting Some Aid For Weed Resistance

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Pigweed, glyphosate resistance

Drive along any stretch of the nation’s highways in 2011, and you are likely to notice them. Interspersed among healthy-looking rows of corn or fields of soybeans are all kinds of weeds. Pigweed, giant ragweed and velvetleaf of all shapes and sizes are present — not because the growers that own these fields didn’t apply herbicides during the spring, but because these weeds have developed resistance to the various crop protection products being used. Based upon available research, approximately 20 million acres of U.S. farmland contain resistant weeds, which will cost growers $1.9 billion in lost income by the end of this year.

“In 2010, there were 24 states in the country that had weeds with confirmed resistance,” says Damon Palmer, U.S. commercial leader Enlist weed control system for Dow AgroSciences. “And based upon a recent study, 80% of growers feel that, without some kind of enhancement, the nation’s current weed control system will be ineffective within 10 years.”

Of course, for most growers, the current weed control system centers heavily on a single active ingredient — glyphosate. Unlike previous crop protection products, glyphosate offered broad-based weed control when it was first introduced back in the 1990s, which allowed it to quickly catch on as the herbicide of choice for growers when coupled with Roundup Ready crops. “When Roundup was first launched, it was like a miracle to us,” says Bob Scott, a weed scientist at the University of Arkansas. “At that time, agriculture was in desperate need of that molecule for weed control.”

Trouble Shows Up

However, in the early 2000s, the first signs that some weeds were developing resistance to glyphosate application began to appear on the East Coast in Delaware. Within a few years, many of these problem weeds had spread west to cover large portions of the Midwest. Today, says Scott, the problem is increasingly showing up south of the Mason-Dixon line as well.

“I see the resistant weed problem today in Arkansas like it was four or five years ago in the Midwest,” he says. “Now, it’s getting to the point where glyphosate application is almost not effective anymore at weed control in our state.”

Malcolm Haigwood, a grower in Newport, AR, agrees with Scott’s assessment. Many of the fields in his area had very tall weeds growing in them during 2011 in spite of regular glyphosate work being done on them. But, adds Haigwood, some of his fellow growers insist the problem is “bad chemical” and not weed resistance. “That’s just denial,” he says. “I’ve sprayed hundreds of thousands of acres since the 1960s and I’ve never had a bad chemical. The weeds are resistant, plain and simple.”

Because of these resistant weeds, Haigwood says his application rates have increased significantly in recent years. “It used to cost me around $12 to $15 per acre for weed control,” he says. “But in 2010, because of extra application work and the need for other chemistries, my cost was up to around $80 per acre. Looking forward, I’m betting the average for the next few years will be $65 per acre.”

Tripp Maddux, a sales representative for Triangle Chemical Co., Mason, GA, has noted the same kinds of per acre increases in his area as well. “Our customers are probably spending between $60 and $100 per acre to achieve the same level of weed control in their cotton fields today,” says Maddux. “That’s probably double what it was a few years ago.”

The Need For New Modes Of Action

To fight back against this literally growing problem, Dow AgroSciences is planning to introduce a new crop production weapon in the next few years called the Enlist Weed Control System. This will consist of a herbicide named Enlist Duo which features Colex-D technology. The Enlist system will be a single postemergence product, combining glyphosate with a new 2,4-D choline (instead of an amine or an ester as in traditional 2,4-D formulations), offering users multiple modes of action for their weed control. This will be coupled with herbicide-tolerant traits in elite germplasm (including glufosinate tolerance in soybeans).

“This will offer growers an important tool to prevent and manage tough weeds,” says Dow AgroSciences’ Palmer. “It is technology tailored for the grower, and represents another way we’re building on the glyphosate system so growers can continue farming the way they prefer.”

In addition to offering better weed control, Palmer says that the use of the Enlist system could aid in soil conservation as well. According to a study commissioned by Dow AgroSciences and conducted by IHS Global Insight and James E. Nelson Consulting, some growers looking for better weed control might be forced to switch from no-till farming methods. The study predicts this could result in 25 million tons of soil loss and increased carbon emissions.

“This research underscores the importance of preserving glyphosate-tolerant technology to help growers sustain the benefits from current herbicide-tolerant systems,” says Palmer. “Pending expected regulatory approvals, the Enlist Weed Control System should be available in corn for the 2013 crop year, 2015 for soybeans and 2016 for cotton.”

Sfiligoj is the Editor for both CropLife and CropLife IRON magazines. He travels regularly to cover industry events and has been dedicated to the ag retail industry since he joined the staff in 2000.
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