The Environmental Protection Agency (EPA) expressed its concern recently about what it calls “mounting evidence” that Monsanto’s corn modified to control western corn rootworms (WCR)is losing its effectiveness.

EPA shared its concern after a scientific study was released in August that found western corn rootworms on two Illinois farms had developed resistance to insecticide produced by Monsanto’s corn. EPA’s latest comments come one year after researchers first discovered and documented that rootworm resistance was developing.

“There is mounting evidence raising concerns that insect resistance is developing in parts of the Corn Belt,” the EPA said Aug. 31 in an e-mail, according to Bloomberg.

Monsanto responded to EPA’s statement by saying that the studies of rootworms in Illinois and Iowa do not confirm resistance in the field, according to Kelly J. Clauss, a spokeswoman for Monsanto. The company stresses that more data is needed to prove resistance and the company is working with EPA to investigate fields that show greater than expected damage, Clauss said.

EPA is expected to receive data on the performance of Monsanto’s YieldGard corn within two months. Analysis is expected to be completed by the end of the year.

“EPA is concerned about the reported resistance to Cry3Bb1 in corn rootworm populations in some parts of the country, as are others in the agricultural community,” EPA said in a statement, according to Bloomberg.

The EPA could implement new strategies to reduce the spread of resistance to CryBb1, but gave no details as to what those strategies may be.

Read Monsanto's comments here.