Bt corn is a kind of corn that has been modified with genes from the bacterium Bacillus thuringiensis to produce its own insecticide, protecting the plant from all kind of pests. Released in 1996, Bt corn is now grown as three-quarters of the American corn crop. Still, nature finds a way: through natural selection, corn rootworms have developed a resistance to the insecticide.
By the turn of the millennium, however, scientists who study the evolution of insecticide resistance were warning of imminent problems. Any rootworm that could survive Bt exposures would have a wide-open field in which to reproduce; unless the crop was carefully managed, resistance would quickly emerge.
Key to effective management, said the scientists, were refuges set aside and planted with non-Bt corn. Within these fields, rootworms would remain susceptible to the Bt toxin. By mating with any Bt-resistant worms that chanced to evolve in neighboring fields, they’d prevent resistance from building up in the gene pool.
But the scientists’ own recommendations — an advisory panel convened in 2002 by the EPA suggested that a full 50 percent of each corn farmer’s fields be devoted to these non-Bt refuges — were resisted by seed companies and eventually the EPA itself, which set voluntary refuge guidelines at between 5 and 20 percent. Many farmers didn’t even follow those recommendations.
It's the classic story of too much of a good thing. Bt corn still kills off other kinds of insects, but for how long? Read the full story at Wired. -via Boing Boing
(Image credit: Flickr user Sarah Zukoff)
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