Wheat can starve insect predators.

• Position: Crops - Hessian fly

A newly identified wheat gene produces proteins that appear to attack the stomach lining of a crop-destroying fly larvae so that the bugs starve to death. The gene's role in creating resistance to Hessian flies was a surprise to researchers at the Department of Agriculture and Purdue University, West Lafayette, Ind., discoverers of the gene and its function. They made the finding as they investigated new, long-term methods to protect wheat from insect damage.

"This is a different kind of defense than what we were expecting," admits Christie Williams, a USDA-Agricultural Research Service scientist and Purdue Department of Entomology adjunct assistant professor. "Usually, we expect the plant to fortify its cell walls or make poisons to use against insects and pathogens."

Instead, the researchers found that a specific protein (HFR-3), one of a group of substances called lectins, is capable of binding with a carbohydrate complex in the Hessian fly larvae. The lectin acts as a key to the carbohydrate structure, known as chitin. When the larvae attack a resistant plant, the plant's lectin production quickly increases by as much as 3,000 times. The larvae then ingest the lectin. This interaction probably damages the larvae's chitin-rich mid-gut lining so that it cannot absorb nutrients from the plant, causing the insects to starve.

The Hessian fly, which German mercenaries apparently introduced into North America during the Revolutionary War, is responsible for catastrophic losses if not controlled by resistant plants. During the 1980s, the state of Georgia suffered $28,000,000 in lost wheat in one year after the fly overcame the plants' resistance gene used in the area at the time. The Hessian fly particularly is insidious because it can control the wheat plant's...