Scientists Pursue Genetic Fly Swatter : Chromosomes: If genes can be mapped for pest resistance, researchers may tackle more complex traits. Some could increase crop yields with less chemical reliance.

After raising millions of insects to feast on corn plants in test fields this summer, researchers are surveying the damage for genetic clues to fight the $400-million pests.

Using the same techniques that enable law enforcement agencies to identify the “genetic fingerprints” of criminals, they are trying to pinpoint pest-resistant genes on corn chromosomes.

The aim is not only to breed corn that resists infestation by the European corn borer, but also to use the findings to protect corn and other crops from a wide range of pests and diseases, says Michael Lee, an assistant professor of agronomy at Iowa State University.

“You end up with an agricultural system less dependent on chemical control of insects,” Lee says, “a more stable agricultural system.”

If scientists can map the location of genes for such traits as pest resistance, they can tackle more complex genetic traits, such as those that could increase crop yields with less reliance on chemical fertilizers, he says.

Lee is working in cooperation with academic and government scientists at the Corn Insects Research Unit of the Department of Agriculture at Ankeny, a community between Des Moines and Ames, home of Iowa State.

He has a $160,000 grant for a four-year genetic study. The USDA contributed about $10,000 of its $477,000 budget from the corn research unit this year to produce the insects, place them on tens of thousands of plants and record data, according to the Agricultural Research Service.

At laboratories in the midst of corn fields, about 3 million egg masses of 25 corn borer eggs each were produced this year and kept in Mason jars. The larvae were raised in a mixture of ground corn grits and later placed in plastic dispensers that released them in batches of 60.

Typically, 240 larvae are placed on a corn plant, but in some cases up to 900 pests are let loose on one plant. There are six to 10 plants in each of the more than 14,000 test plots in Ankeny and Ames.

“Nothing escapes infestation,” says Bud Guthrie, research leader at the Ankeny corn insects research unit.

Adult moths do not damage corn but lay eggs in fields that hatch and can decimate crops.

The corn borer causes damage when the first generation of larvae eats corn leaves and the second generation eats the protective sheath around the stalk at the time of pollination, burrowing into the plant. The damage weakens the plants and causes them to topple before harvest.

First found in this country in 1917, the European corn borer was a seemingly unbeatable scourge. In the 1930s, entire fields were laid waste.

Guthrie, estimates that in Iowa fields this past summer, where corn is typically sown 25,000 plants to an acre, there was one borer for every other plant. That is down from an average of eight a plant 40 years ago, when fields were not so thick with corn.

Development of hybrid corn strains and spraying has helped reduce the devastation, but it still costs U.S. farmers $400 million a year in losses and control efforts, the USDA says. In Iowa, the leading corn producing state, the corn borer costs farmers about $100 million a year.

This summer, in test plots near the laboratory, corn with brittle stalks and leaves that looked like they’d been raked by shotgun fire stood beside plants that would have been at home in any healthy field.

Even the highly susceptible plants look good compared with pictures of the crop devastation of the 1930s.

“Compared with the old times, the entire acreage is resistant,” Guthie says.