Friday, December 06, 2002

An article in PNAS shows that cotton bollworm feeds on corn in the offseason -- which means that Bt resistance is going to happen a lot faster than people thought. From the NSU story:
Gould's finding that the same moths feed on corn in America's Midwest and cotton further south hints that the refuge strategy alone might not hold back the spread of resistance.

For the time being, the discovery is actually good news. Today, only about 25% of Midwestern corn contains Bt - current varieties are not as effective against insects as is modified cotton.

So the remaining 75% is helping to keep earworms susceptible to Bt cotton. "Corn is serving as a great refuge," says entomologist Bruce Tabashnik at the University of Arizona in Tucson, who describes the new results as "very exciting".

But if the percentage of Bt corn increases - which, with new varieties in development, could happen soon - then moths feeding on Bt corn all summer may rapidly come resistant.

Flying south to feed on cotton later in the year, their offspring could well be immune to the effects of Bt cotton as well. "If 90% of corn in the Midwest becomes Bt then we could be in real trouble," says Gould.

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