Jay Sjerven

American farmers have proved time and again they’re willing, even eager, to embrace new technologies and production aids to ensure they remain competitive with their neighbors and producers across the world. This enthusiasm was sorely tested, though, this season by what by any measure was a troubled debut of “over-the-top” application of dicamba-based herbicides on soybeans and cotton engineered to tolerate the pesticide. The problem was while dicamba-tolerant soybean and cotton varieties fared very well after the dicamba applications, many adjacent fields planted to crops not engineered to tolerate the herbicide were damaged, in instances, seriously so.

Dicamba is an herbicide developed several years ago but because of its strength had limited uses in agriculture. But in recent years, three agrichemical manufacturers — Monsanto, BASF and DuPont — were able to develop dicamba-based formulations for foliar application on soybeans and cotton and engineered soybean and cotton seeds that tolerate the dicamba products.

The dicamba-based products were seen as the next generation herbicide for suppressing weeds, which over the years were developing resistance to other herbicides, such as Roundup, which was introduced in the mid-1970s by Monsanto.

Dicamba on soybean field
Many adjacent fields planted to crops not engineered to tolerate the herbicide were damaged.

Last year, the Environmental Protection Agency approved the new dicamba-based herbicides for “over-the-top” application in 2017, i.e. for application to growing plants. Soon into the growing season, complaints about drifting of the dicamba to neighboring fields planted to crops not tolerant of the herbicide soon emerged in large numbers.

In addition to the problems emanating from actual physical drift of windborne drops of the herbicide during application, it was the chemical’s volatility that also was a great concern. In this instance, volatility means that during hot and humid weather, the herbicide may evaporate from treated plants and the resulting gas drift over and alight on untreated plants that may be quite distant from the point of application.

Plants not engineered to tolerate dicamba respond to the chemical as they would to any other novel broad leaf herbicide. In the case of soybeans, plant leaves wilt and curl.

About 22 million acres of dicamba-tolerant soybeans were seeded this year and about 3 million acres of dicamba-tolerant cotton. That equated to about 24% of all acres planted to soybeans.

At a Nov. 1 stakeholders meeting convened by the E.P.A., agency representatives indicated dicamba may have damaged more than 3.6 million acres of soybeans. Reuben Baris, acting chief of the herbicides branch of the E.P.A., told meeting participants that through mid-October, 2,708 complaints had been lodged with state departments of agriculture about crop damage from dicamba. A third of those complaints, 986, were lodged in Arkansas, which announced a 120-day ban on the herbicide’s use this past summer in response.

Mr. Baris suggested there also is likely to be damage that was yet to be reported.

“It is an extremely high profile and significant situation,” Mr. Baris said.

When the E.P.A. approved “over-the-top” dicamba applications, it notified the herbicide manufacturers they would have to win new approval for the products after two years. Mr. Baris indicated that approval may not be renewed if measures agreed between the E.P.A. and the herbicide manufacturers in October don’t result in a dramatic reduction in the drift problem in 2018.

Mr. Baris was referring to an Oct. 13 agreement reached by the E.P.A. with Monsanto, BASF and DuPont on measures to further minimize the potential for drift to damage neighboring crops. The E.P.A. said new requirements for the use of dicamba “over the top” will allow farmers to make informed choices for seed purchases for the 2018 growing season. The E.P.A. said manufacturers have agreed to label changes that impose additional requirements for “over-the-top” use of the dicamba products in 2018.

Manufacturers have agreed to a process to get the revised labels into the hands of farmers in time for the 2018 use season. The E.P.A. said it will monitor the success of these changes to help inform its decision whether to allow the continued “over-the-top” use of dicamba beyond the 2018 growing season.