The adult stage of the western corn rootworm searches for pollen on corn silk.WIKIMEDIA, USDA - TOM HLAVATYScientists had been warning agrichemical companies and US corn farmers for years that the western corn rootworm (Diabrotica virgifera virgifera) would evolve resistance to insecticide-producing genetically modified (GM) maize varieties if the modified trait wasn’t deployed more thoughtfully. Now, a PNAS paper published this week (March 17) details just how problematic that rising resistance has become in corn fields across the nation. “Unless management practices change, it’s only going to get worse,” Iowa State University entomologist Aaron Gassmann, who led the study, told Wired. “There needs to be a fundamental change in how the technology is used.”
First grown on a wide scale in 1996, the GM maize—called Bt corn for the bacterial toxin gene it incorporated from Bacillus thuringiensis—raised yields and drove down populations of corn rootworm and other pests. But little more than a decade later, populations of rootworms that were resistant to Bt corn cropped up in Iowa, Illinois, Nebraska, South Dakota, and Minnesota.
The problem was that farmers were growing too much Bt corn without planting sufficiently large refuges of non-Bt corn so that the insects there would remain susceptible to the toxin and that susceptibility could be kept alive through the pests’ mating with rootworms from populations feeding on Bt corn. Even though independent researchers warned that resistance would evolve, farmers and the companies that created and ...
