WEST LAFAYETTE, Ind. For years, farmers and agribusinesses have talked about being on the "pesticide treadmill": A few years after a pesticide is introduced, insects develop resistance to it. So another chemical is used at least until the bugs overwhelm that one.

Then another chemical is used. Then another. Then another.

But Barry Pittendrigh, assistant professor of entomology at Purdue University, says it's possible to stop the treadmill, or at least slow it to a crawl.

Pittendrigh and Patrick Gaffney, of the University of Wisconsin-Madison, have developed a method to use pesticides so that genetic resistance doesn't arise.

The technique is called negative cross-resistance, and it involves using multiple pesticides in a precise way to stop the pests.

With the technique, scientists would identify a second biocide pesticide, antibiotic, herbicide or fungicide that specifically kills the resistant pest. Then the two biocides would be used together, either concurrently or alternated, to prevent resistance.

Previous attempts to find compounds that would have a negative cross-resistance effect haven't worked because they focused on fewer than several dozen compounds, Pittendrigh says.

However, Pittendrigh says it is necessary to screen upwards of 100,000 compounds to develop a negative cross-resistance system. Pittendrigh and Gaffney have invented a method to conduct these screens.

"Specifically, in our paper, we outline how companies or individuals can search for and develop NCR compounds to a commercially applicable level," Pittendrigh says. "This paper provides part of the theoretical framework for research currently in progress here at Purdue for the development of negative cross-resistant toxins and their use in field applications."

The researchers say their model shows that using negative cross-resistant biocides could delay resistance for decades, or even more than 100 years in some
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Contact: Steve Tally
tally@aes.purdue.edu
765-494-9809
Purdue University
21-Aug-2001