American farmers have planted 20 million acres of genetically modified corn, engineered to repel predatory insects without using noxious chemicals. If farmers are not careful, a new report warns, the scheme could backfire and breed even more troublesome strains of pests.
The modified crops pump out Bt toxin, a natural insecticide created by bacteria. Some insects, in turn, carry genes that protect them from the toxin. To check the spread of those genes, the U.S. Environmental Protection Agency requires that farmers intersperse fields of genetically modified crops with islands of non-modified plants. The idea is that insects in the refuges would remain vulnerable to Bt toxin, and the bugs would interbreed to keep the whole population susceptible.
For the first time, scientists have proof the tactic works. Entomologist Anthony Shelton of Cornell University and his colleagues sowed fields of altered broccoli and then unleashed broccoli-eating diamondback moths. In fields containing ...
