Seeds of Biotech Resentment: Part Two

This Business of Farming

The benefits of Bt corn fade as farmers add soil insecticide for 'cheap insurance'

Published on: May 2, 2013

Yesterday I reported here on a debate titled "Understanding and Addressing the anti-GM critique," organized by the Agroecology and Sustainable Agriculture Program at the University of Illinois. Mike Gray, U. of I. entomologist, was among the speaker panel, which included an Illinois farmer, a New York organic farmer, a representative from the Union of Concerned Scientists and a European microbiologist.

Most of the speakers were there to dismiss the benefits of biotechnology, but Gray had another view.  "Over a 14-year period (planting Bt corn) for Illinois, Minnesota and Wisconsin, we found there was a $3.2 billion gain in economic benefits to farmers," he says. "The primary economic impact is 5% greater yields relative to conventional hybrids, with a net economic impact of $10 to $50 per acre. Overall, cumulative economic benefit going back the last 10 years to the American producer is $7.1 billion."

$2.4 billion of that benefit goes to producers who don't even plant Bt corn. Why? Because the technology reduces overall corn borer populations. "When you plant Bt corn there is a halo effect, since it offers area wide suppression of populations," Gray says. "So maybe if you are a producer, the best thing you can do is recommend to your fellow neighbors to plant more Bt corn."

Bt has been a key component of the biotech evolution, but it's effectiveness is now in question, thanks to growing trait failure. Bt corn acres grew from introduction in 1996 until about 2004 and then began to decline. Still, in 2011 47.2 million acres planted in the U.S. had Bt corn rootworm traits. That's 56% of the U.S. corn crop.

Rootworm trait resistance is growing for a number of reasons. When you push continuous corn and forget basic agronomics, something is bound to break. In earlier days there were doubts some farmers were planting the required refuge acres to help slow resistance; now, Refuge-In-Bag insures compliance. But it won't solve the problem.

"This insect can adapt to simple management strategies – even crop rotation," he says. "If you do not integrate tactics or use Integrated Pest Management (IPM), not only this insect but other insects will adapt to that approach.

"One of the problems we make a lot is that we seize on one management strategy, then ride that system into the ground," adds Gray.

Is soil insecticide cheap insurance?

Farmers are going back to soil insecticides across the Corn Belt - even in areas where there are low rootworm populations. In a recent survey of Illinois farmers, Gray asked, do you plan to use a corn rootworm Bt hybrid AND a soil applied insecticide together in 2013? Over 46% of farmers said yes.  In the Moline, Ill., area, where there are heightened concerns over resistance, almost 56% said yes.

Bt seed already costs more than conventional; tack on $20 per acre more for soil insecticide and costs begin to add up. Those surveyed gave several reasons why they were willing to spend more. A growing number said it was to provide cheap insurance against insect problems.

"Instead of IPM, farmers are using soil insecticide as 'Insurance Pest Management,' and it's become the norm in commercial Ag fueled in part by high commodity prices and risk aversion," says Gray. "The problem is, soil applied insecticide doesn't do a great job managing (pest) populations." 

One of the key benefits of Bt hybrids early on was the hope that these products would provoke a large reduction in soil insecticide use. And, despite claims at this debate to the contrary, that certainly did occur for a number of years. Unfortunately today we're seeing a surge in the other direction as more farmers believe they can manage Bt resistance by adding soil insecticides. Long-time studies suggest in some cases the addition of soil insecticides actually showed increases in overall adult rootworm emergence, compared to untreated fields; so it's a mistake to see soil insecticides as population management tools.

"They should protect root systems from excessive feeding and lodging, but it would be incorrect to look at them as a class of compounds that actually manage rootworm populations," concludes Gray.

Tomorrow you'll read why organic farmers hate GM technology.