Colorado State Researcher Uses Natural Chemicals To Battle Major Corn Pest

July 25, 1997

FORT COLLINS--Louis Bjostad has whipped up a recipe of death for the Colorado corn industry's No. 1 pest using an inexpensive food processor and ingredients available at most grocery stores.

Bjostad, entomology professor at Colorado State, is testing several non-toxic materials that target Western corn rootworm, a pest that causes $1 billion in crop losses in the United States each year.

After tests in the laboratory and field over the past six months, Bjostad is confident his materials can tackle rootworm just as effectively as insecticides, which are more toxic and expensive.

Bjostad, who has studied the pesky bugs for more than a decade, recently made a breakthrough that showed why rootworm larvae only eat corn plant roots. The professor, with colleagues Elisa Bernklau and Erich Fromm, discovered that carbon dioxide given off by corn roots is responsible for luring larvae to their meal.

To steer rootworms off course, Bjostad and his team of researchers made non-toxic granules and pellets that also release carbon dioxide. The experimental treatments, placed near the corn seed at planting time, mix the signal that larvae rely on to find their only source of food.

"These larvae must find the corn roots within 24 hours after hatching or they die," Bjostad said. "We are essentially sending them away from the plant so by the time they realize their mistake we've dealt a lethal blow."

Main ingredients in Bjostad's treatments include baker's yeast and a nutrient mixture, or sodium bicarbonate (the main ingredient in baking soda), citric and other acids, combinations of which produce carbon dioxide naturally.

In addition, the professor is on the verge of identifying key chemicals responsible for stimulating rootworm larvae to feed on corn roots. Once identified, Bjostad hopes to add these chemicals to his formulas so larvae are not only attracted to the pellets but also are tricked into feeding on the pellet itself. The idea is to keep larvae away from corn roots as long as possible so the plant has time to mature. Corn plants with established root systems are less vulnerable to larvae.

Bjostad has taken his research--already being eyed by major chemical manufacturers for future development into biological products--several steps further. The professor's studies also unexpectedly found that corn roots produce small amounts of natural chemicals that, when produced in large amounts, repel larvae. Because these repellants aren't in high enough doses in commercial varieties of corn to thwart rootworm, Bjostad is studying ways to isolate the natural repellants and manufacture them in large amounts. These concentrated, natural repellents also would be formulated into granules or pellets and applied near the corn seed at planting time.

While biological insecticides are more ideal than toxic chemicals available, Bjostad says the best alternative would be to genetically engineer corn plants that produced higher concentrations of these natural repellents so no man-made chemicals would have to be used.

The next step, Bjostad says, is to refine these natural insecticides so they do the best job possible for the least cost to the farmer. Bjostad plans to conduct two more years of field tests before deciding which compounds should be developed further.

"The health and public safety issue is really driving this research," Bjostad said. "The whole idea is to develop a biological control that isn't toxic, costs less and is safer for workers to handle."
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Colorado State University

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