Failure of another 'pyramid' scheme.

• Position: Pet Management - Insecticide resistance - Brief article

The popular new "pyramid strategy" of planting genetically engineered crops that make two or more toxins to fend off insect pests rests on some assumptions that do not always apply, researchers at the University of Arizona, Tucson, have discovered. Their study helps explain why one major pest is evolving resistance much faster than predicted and offers ideas for more sustainable pest control.

Corn and cotton have been modified genetically to produce pest-killing proteins from the bacterium Bacillus thuringiensis, or Bt for short. Compared with typical insecticide sprays, the Bt toxins produced by genetically engineered crops are much safer for people and the environment, explains study leader Yves Carriere, professor of entomology.

Although Bt crops have helped to reduce insecticide sprays, boost crop yields, and increase farmer profits, their benefits will be short-lived if pests adapt rapidly, indicates Bruce Tabashnik, coauthor of the study and head of the Department of Entomology.

"Our goal is to understand how insects...