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The Resistance Movement

January 28, 2012
p36 The Resistance Movement

It’s time to steward agriculture technology

There’s a resistance movement going on in America’s crop fields. Weeds, insects and diseases that were once no match for modern chemistry are fighting back, and winning.

Farm Journal Field Agronomist Ken Ferrie hopes that farmers are paying attention to the resistance scoreboard. "This isn’t the 1970s and 1980s when we had new products coming through the pipelines on a yearly basis," Ferrie says.

The good news is that there are paths to stave off resistance through management and stewardship.

During the next few months, a Farm Journal series of articles will explore how resistance is evolving and what you can do about it.

Resistance is not new, nor unique to the U.S. The first report of insect resistance came in 1908. Plant pathogens started fighting back against fungicides in 1940, and the first reports of weed resistance were confirmed in the late 1950s. The difference today is that the products at risk, such as glyphosate, Bt and strobilurin, are widely used across the agricultural landscape.

USDA’s National Agricultural Statistics Service says insect-tolerant crops containing Bt traits were planted on 73% of cotton acres and 65% of corn acres the past year. While multiple Bt proteins and a non-Bt protein are being employed in insect-tolerant trait strategies, the most recent Bt resistance case involves Cry3Bb1, a critical component of some current pyramided products.

Less than a decade ago, fungicides were mostly a way to protect fruits and vegetables. In 2011, more than 20 million acres of corn and soybean received at least one application of fungicide, with strobilurin-based products among the most popular yield protectors.

Of all these challenges, nothing has galvanized the industry quite like weeds that no longer succumb to glyphosate. In 2011, U.S. farmers planted 94% of their soybean acres, 75% of their cotton acres and 72% of their corn acres with herbicide-resistant varieties. The majority of these acres are glyphosate-resistant and many received multiple applications. Since 2000, there have been 21 weed species confirmed resistant to glyphosate.

Ferrie says reversing the trend will require changing a mindset. "Growers look at weed control as a cost," he says. "As a result, they attempt to kill weeds in the cheapest, easiest way. If an herbicide program is working, there hasn’t been a lot of incentive for them to change the system. Unfortunately, it’s usually the guy in trouble that’s typically looking for options," he says.

By comparison, insect and disease control tend to be viewed more as a way to improve profits and tack on extra yield. "Our pest thresholds haven’t changed, but crop prices have, and that triggers treatment at lower infestation levels. Growth of insecticide and fungicide use is a result of growers willing to throw more money at the crop to protect or boost yield," Ferrie says.

The result is the same: Constantly using more of the same product with more frequency is a recipe that leads to resistance. In general, pests develop a resistance to a chemical through natural selection. The most resistant weeds, pests and diseases survive and pass on their genetic ability to survive to their offspring.

Pat Tranel, a University of Illinois molecular weed scientist working to unravel the secrets of waterhemp, believes agriculture might still be in a dangerous state of denial.

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FEATURED IN: Farm Journal - February 2012

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