The Environmental Protection Agency has verified for the first time that some corn rootworms have developed resistance to genetically modified corn sold by Monsanto. Rootworm resistance is suspected in a number of Midwest states, including Minnesota.
Rootworm is the most damaging corn pest, but Monsanto's product has a built-in pesticide that kills the bugs.
But in the last five years university researchers have found damaged corn and growing evidence of resistance to the pesticide. In 2011, an Iowa State University researcher published study results that he said proved the rootworm has developed resistance.
Now the EPA has affirmed those findings. The agency also says it will look into changing its own criteria for determining resistance to something closer to what the Iowa research used.
Monsanto says it will work with the EPA to revise the regulatory definition of confirmed rootworm resistance.