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article imageGM crop fails to defeat agri pest

By Tim Sandle     Mar 22, 2014 in Environment
GM crops do not always do what they set out to do. The corn rootworm has become resistant to a genetically modified maize variety that produces an insecticidal toxin.
The western corn rootworm (Diabrotica virgifera virgifera) has evolved to resist insecticide-producing genetically modified (GM) maize varieties, according to a new report.
The maize is called Bt corn and it has been used since 1996 in parts of the U.S. The corn was "made by" the Dow Chemical Company. Genetically modified corn is a genetically modified crop. Specific maize strains have been genetically engineered to express agriculturally-desirable traits, including resistance to pests and to herbicides.
Initially the corn raised yields and drove down populations of corn rootworm and other pests. However, a decade later, populations of rootworms that were resistant to Bt corn cropped up in Iowa, Illinois, Nebraska, South Dakota, and Minnesota. Now these resistant pests are becoming increasingly common.
The Western corn rootworm is one of the most devastating corn rootworm species in North America, especially in the midwestern corn-growing areas such as Iowa. Corn rootworm larvae can destroy significant percentages of corn if left untreated. In the United States, current estimates show that 30 million acres of corn (out of 80 million grown) are infested with corn rootworms and area is expected to grow over the next 20 years.
Iowa State University entomologist Aaron Gassmann has told Wired that "Unless management practices change, it’s only going to get worse. There needs to be a fundamental change in how the technology is used." Outlining what happened, Grassmann continues "Resistance was caused because the farmers did not plant the required refuges and the companies did not enforce the planting of refuges."
It seems that genetically modified crops are not the permanent cure to dealing with crop pests that some of their advocates have heralded.
The findings have been reported in the journal PNAS, in a paper titled "Field-evolved resistance by western corn rootworm to multiple Bacillus thuringiensis toxins in transgenic maize,"
More about Gmo, Genetically modified, Agriculture, corn rootworm
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