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Do higher corn prices mean less adherence to ecological principles?

August 22, 2007

Expectations of higher corn prices are leading some farmers to neglect or ignore integrated pest management strategies, and their behavior could undermine the very technologies that sustain them, University of Illinois researchers report today at the American Chemical Society meeting in Boston.

Integrated pest management (IPM) is a set of principles developed to minimize the ecological impacts of pesticides, transgenic crops and other pest management technologies. A primary goal is to slow the emergence of "resistant" insects that have adapted or evolved to evade management strategies that work. Traditional approaches for slowing the development of insect resistance include crop rotation and scouting for pests to determine whether and when to use chemicals to limit damage. Newer strategies include planting non-transgenic corn "refuges" alongside crops of transgenic corn.

(Transgenic corn hybrids, such as Bt corn, are engineered to produce toxins that target specific insect pests. Planting refuges of non-Bt corn near Bt crops slows the development of Bt-resistance in insects.)

The use of corn for biofuels production has pushed corn prices higher this year than they have been for a long time, said Kevin Steffey, a U. of I. Extension specialist in entomology and professor of crop sciences. Steffey is one of three researchers at Illinois to present at the ACS meeting.

The higher return on the corn crop is encouraging some growers to use multiple pest management techniques on their crops - without first determining whether they are needed, Steffey said.

"Some people are using chemical inputs when they're not necessary," he said. "If
transgenic corn kills a percentage of corn rootworms, then some growers will put an insecticide with it to push the percentage higher."

"They're willing to spend money without challenging why they're spending money, simply because they can afford it," he said.

Other important strategies are also being neglected or abandoned. Because non-Bt corn hybrids sometimes yield less than Bt hybrids, some farmers are doing away with refuges altogether - a violation of federal law. These practices will increase the rate at which target insects become resistant, Steffey said.

"Some corn growers are looking at short-term gains and ignoring long-term consequences. This is a mistake repeating itself from the 1960s," he said.

Steffey emphasized that most corn growers do follow IPM practices to control insect pests. But a few are abandoning these practices to boost profits, he said.

He noted that many growers are too young to remember the crop losses that occurred after insects became resistant to the powerful, and environmentally damaging, chlorinated hydrocarbons used in the mid-20th century. Some growers take the new technologies, such as transgenic corn, for granted, believing that the problems of resistance will not arise with these new products.

But resistance is a normal, ecological adaptation to any selective stress, Steffey said.

"We have an insect, the western corn rootworm, that became resistant to crop rotation," Steffey said. "That made us aware of what we're dealing with: This insect is plastic, genetically, and can adapt to a lot of things."

Implementing IPM strategies is never a simple task. For example, the most productive hybrid corn varieties on the market include Bt genes that are effective against two different insects. Growers want higher yields and so will buy these "double-stack" varieties even though one of the insects the corn is designed to kill may not be a problem in their region, Steffey said. And since non-Bt corn hybrids often yield less corn than the Bt hybrids, the growers must be prepared for lower yields from their refuge corn.

Other factors add to the complexity of the task. In some instances, a Bt corn that kills one pest can be used as a refuge plant for a Bt corn that kills another pest. However, the use of "triple stack" hybrids (which contain traits for control of corn rootworms and corn borers plus herbicide resistance) complicates the planning of refuges.

Despite these difficulties, Steffey said, the potential rewards for corn growers are higher now than ever. And the consequences of ignoring the hard lessons learned over decades of trial and error could be dire, he said.

This work was funded in part by the U.S. Department of Agriculture, Smith-Lever and Hatch Funds. The research is also supported by the U. of I. and by several companies that develop and market agricultural products.

University of Illinois at Urbana-Champaign