The process is designed to identify chemical compounds that could be added to current pesticides to overcome resistance insects have developed to them. In a recent issue of the journal Pesticide Biochemistry & Physiology, the scientists report that the method will be applicable to a variety of insects and chemicals.

"It's becoming more and more difficult to find new, effective pesticides," said Barry Pittendrigh, assistant professor of entomology and senior author of the study. "If we can kill these pesticide-resistant insects in the field, then we have the potential to increase the functional life of the insecticides currently in use."

Crop-damaging insects mutate over time so they are able to overcome the effects of chemicals developed to kill them. A toxin that protected a crop for more than a decade or two eventually may lose its lethality due to resistance in the insect population.

According to the U.S. Department of Agriculture, more than $7.5 billion is spent annually on agricultural pesticides. This is about 30 percent to 50 percent of the variable costs involved in managing harmful insects.

Pittendrigh and his research team studied common research fruit flies, Drosophila melanogaster, in which the molecular mechanism that provides the insect with chemical resistance was known. They applied that knowledge to test known chemicals' toxicity to the resistant insects.

A pesticide's toxic effect occurs when a molecule on an insect's cells, called a receptor, acts as a loading dock for molecules in the pesticide. When a toxic chemical is used, its docking molecule, called a ligand, joins the receptor and kills the bug.

But nature allows pests to challenge control methods by altering their own receptors. These biochemical changes prevent binding of the
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Contact: Susan A. Steeves
ssteeves@purdue.edu
765-496-7481
Purdue University
12-Apr-2004