WASHINGTON -- Corn beetles have been consuming plants that were genetically modified to be resistant to that very beetle, raising fears that a new superbug could develop or that farmers could be forced to increase the use of pesticides.
In a study published late last month, Iowa State University entomologist Aaron Gassmann found that western corn rootworms (WCR) in four Iowa fields have developed resistance to an insect-killing protein derived from Bacillus thuringiensis, also known as Bt, the natural insecticide in Monsanto's genetically modified corn plant.
While there's still no evidence that any significant number of the pests have become resistant to the genetically modified seeds sold by agribusiness giant Monsanto, the findings may have farmers looking for alternatives.
Laboratory testing confirmed beetles were able to pass on Bt-resistance to their offspring.
"These results suggest that improvements in resistance management and a more integrated approach to the use of Bt crops may be necessary," Gassmann wrote in his study.
But Monsanto, which first released the genetically modified seeds in 2003, said the vast majority of customers are still getting good returns from the technology.
"These products continue to perform very well for growers in 2011, providing the expected level of WCR control on more than 99% of the acres planted with this technology," Monsanto wrote in a statement on its website.
AFP reported that Michael Gray, a crop scientist at the University of Illinois, is investigating whether pests that devoured genetically modified corn in Illinois earlier this year have also developed resistance to the plant's toxins.
To curb the development of resistance, Monsanto is recommending that farmers rotate crops, using non-Bt corn and SmartStax seeds introduced in 2010 to kill the pests in a new way.
The four fields in which the pests were found had been planted with the genetically modified seeds for at least three consecutive years.