The U.S. Environmental Protection Agency is criticizing Monsanto for its handling of cases of damage to corn crops by rootworm.
The pest is a significant threat to corn crops, and the damage occurred in crops that Monsanto genetically modified to protect against rootworm.
A growing number of reports of rootworm damage from farmers in Minnnesota and other midwestern states have raised concerns that rootworms are developing resistance to the Monsanto's genetically modified corn.
The EPA says Monsanto's mandatory resistance monitoring program is 'ineffective' and 'inadequate'.
The plant contains a gene which is supposed to make the corn fatal to rootworms. The EPA says Monsanto, the nation's leading seller of seed corn, must do more testing of insects from problem fields to find out if they can survive feeding on the genetically modified corn.
The EPA says Monsanto also must instruct farmers in rootworm problem areas to use conventional insecticides to kill the adult insects. The EPA stopped short though of saying that scientists have confirmed that rootworms have developed resistance to the Monsanto corn. Instead the EPA says it "suspects" resistance.
The EPA report notes that scientists have demonstrated that rootworms are showing a greater ability to survive feeding on the Monsanto corn, but that there may be flaws in some of their tests.
Monsanto's Mimi Ricketts said so far the EPA has not proven that resistant rootworms have developed.
"Monsanto takes reports on performance of its corn rootworm products seriously," Ricketts said. "And we're committed to working with farmers to encourage an adoption of integrated pest management practices when they manage high corn rootworm populations on the farm."