The EPA commented in response to questions about a scientific study last month that found western corn rootworms on two Illinois farms had developed resistance to insecticide produced by Monsanto’s corn. Rootworms affect corn’s ability to draw water and nutrients from the soil and were responsible for about $1 billiona year in damages and pesticide bills until seeds with built-in insecticide were developed a decade ago.
The agency’s latest statement on rootworm resistance comes a year after the problem was first documented and just as U.S. corn yields are forecast to be the lowest in 17 years amid drought in the Corn Belt. Corn is St. Louis-based Monsanto’s biggest business line, accounting for $4.81 billion of sales, or 41 percent of total revenue, in its 2011 fiscal year.
“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.
The studies of rootworms in Illinois and Iowa don’t confirm resistance in the field, Kelly J. Clauss, a spokeswoman for St. Louis-based Monsanto, said in an e-mail. More data is needed to prove resistance and the company is working with the EPA to investigate and respond to fields where rootworms cause “greater-than-expected damage,” Clauss said.