A company that makes dicamba-resistant soybeans and cotton wants to expand use of the controversial weed killer to corn. But critics and experts questioning the logic of the petition.

Bayer, the new parent company of Monsanto, asked the Environmental Protection Agency in March to expand dicamba use to corn with its Xtendimax Herbicide product.

Bayer declined a request for an interview, but said in a statement that it “does not anticipate launching XtendFlex corn until early-to-mid-next decade,” and that the expansion “would add more flexibility to manage weeds through enhanced dicamba tolerance and added crop safety.”

But the problems dicamba has wrought in recent years is a red flag when considering any expansion, according to Iowa State University professor Bob Hartzler.

“It seems like if we can not fix this problem within those five years, how the EPA would even consider any expansion in the use of dicamba would boggle my mind,” said Hartzler, who’s also a weed specialist.

Hartzler said the drift problem needs to be addressed

“By the time these products are registered, hopefully we will have products that will be less likely to move,” Hartzler said. “But there is a concern with increased usage that we will see continued movement from the fields.”

Ultimately, Hartzler said, the EPA should do a thorough scientific review before approving dicamba for corn.

“In my opinion, it seems like the science did not forecast the problems we’ve seen with the use in soybeans, and so I think other things need to be looked at,” Hartzler said.

A lawsuit could play a role in any expanded use, too. More than 1,000 farmers are suing Bayer for damage done to their crops because of dicamba drift. If the suit fails, herbicide and seed companies could say that farmers and their insurance companies are on the hook for any future damage dicamba causes.

“If the insurance companies are held responsible for the off-target movement, then they would no longer be willing to ensure applicators,” Hartzler said. “And I don’t think most applicators would be willing to take the risk if they were going to be held responsible.”

The EPA is taking public comment on Bayer’s petition for corn use through April 17.

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