WASHINGTON, D.C., U.S. — New requirements governing use of the herbicide dicamba to control weeds in genetically-modified cotton and soybeans in the United States intend to diminish the chance of damaging neighboring crops. The rules, in place for the 2018 growing season, include special training for applicators, classifications, record-keeping, and application limits determined by wind speeds and time of day.

A year after first registering dicamba for over-the-top (use on growing plants) application on cotton and soybeans engineered to resist the herbicide, the Environmental Protection Agency enlisted states, USDA cooperative extension agents and land-grant universities, along with the three companies that sell dicamba for over-the-top use, to root out the underlying causes of recent neighboring-crop damage in the farm belt and southeast.

The three manufacturers, Monsanto, BASF and DuPont, have voluntarily agreed to label changes and to get the revised labels to farmers for the 2018 season. The EPA’s two-year registration of over-the-top dicamba is set to expire following the 2018 growing season. The agency will factor the success of the new rules in deciding whether to allow continued over-the-top use of dicamba.

Dicamba already is registered for use on corn, wheat and other crops. It’s also used to control broadleaf weeds in residences, parks and golf courses. But the over-the-top application, which followed the introduction of dicamba-resistant cotton and soybean varieties in 2015 and 2016, was blamed for injuring nearby crops not designed to resist the herbicide. The damage led the U.S. states of Arkansas and Missouri to suspend use of the application in July, though Missouri later dropped its ban and instituted tighter use restrictions, as did Tennessee.