Bollworm beats the odds against Bt.

• Position: Insecticide - Brief article

A pest insect known as bollworm is the first to evolve resistance in the field to plants modified to produce an insecticide called Bt, according to a research report from the University of Arizona, Tucson. Bt-resistant populations of the bollworm Helicoverpa zea were found in more than a dozen crop fields in Mississippi and Arkansas over the last few years.

"What we're seeing is evolution in action," lead researcher Bruce Tabashnik indicates. 'This is the first documented case of field-evolved resistance to a Bt crop."

Bt crops are so named because they have been genetically altered to produce Bt toxins, which kill some insects. The toxins are produced in nature by the widespread bacterium Bacillus thuringiensis, hence the abbreviation Bt. The bollworm resistance to Bt cotton was discovered when a team of University of Arizona entomologists analyzed published data from monitoring studies of six major...