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By Dan Gunderson, Minnesota Public Radio News

The U.S. Environmental Protection Agency says farmers can use “existing stocks” of the chemical dicamba this year, despite a federal court ruling that vacated the chemical registration (meaning the EPA’s approval for dicamba use is no longer valid).

Farmers plant crops that are genetically modified to be resistant to the herbicide, allowing them to spray the chemical on weeds without damaging the crop.

But dicamba often drifts from fields where it is applied, damaging crops in neighboring fields and causing significant financial loss for farmers.

This is not the first court battle over dicamba. The herbicide was registered for use on genetically modified crops in 2016.

A federal court vacated the registration in June 2020 on the basis that “EPA substantially understated risks that it acknowledged and failed entirely to acknowledge other risks.”

The EPA registered dicamba again in 2020.

Environmental groups sued, challenging the EPA process for approving the chemical. A federal judge early this month ruled the agency violated procedures requiring public input when it registered the chemical in 2020.

The EPA announced this week it invoke a rule that allows existing stocks of a chemical to be used.

The agency says “millions of gallons” of dicamba had already entered the market.

The ruling allows use of dicamba that is “outside the control of pesticide companies.”

“It’s a big deal. I think that dicamba is an important tool and it’s an effective tool for many farmers,” said Minnesota Commissioner of Agriculture Thom Petersen.

“Being able to use the existing stock that’s out there is important because farmers have already made their planning decisions for this year, they’ve already purchased the product,” said Petersen.

In response to the damage caused by dicamba drifting onto neighboring fields, Minnesota imposed rules on when the chemical can be applied. The rules are designed to minimize chemical drift.

Petersen said those rules will remain in effect this year, and the agency will continue to monitor and study the issue.