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Bayer again seeks approval for dicamba herbicide

In response to court ruling, company proposes label changes to reduce drift

by Britt E. Erickson
May 15, 2024 | A version of this story appeared in Volume 102, Issue 15


Close-up of soybean seedlings emerging from the soil.
Credit: Shutterstock
Under a proposal by Bayer Crop Science, growers would be allowed to spray dicamba herbicide on soybeans until seedlings emerge.

Bayer Crop Science is trying again to get the drift-prone herbicide dicamba back on the US market for use on soybeans and cotton crops that are genetically modified to tolerate it.

Chemical structure of dicamba herbicide.

In response to a Feb. 6 court ruling that vacated the US Environmental Protection Agency’s approval of dicamba for such uses, Bayer has proposed slight changes to how and when farmers can apply the herbicide. The proposal would allow growers to spray dicamba on soybeans until seedlings emerge but no later than June 12 each year and to spray it over the top of cotton until July 30.

Dicamba is problematic in summer heat because it is volatile in high temperatures and in temperature inversions, which occur when cool air near the ground is trapped beneath warm air. Once in the air, the herbicide can drift with the wind and damage or kill unintended plants in its way.

The EPA allowed farmers to use dicamba on genetically modified soybeans and cotton beginning with the 2017 growing season. Ever since, states have received thousands of complaints about herbicide drift damaging nontargeted plants, including conventional soybeans that have not been modified to tolerate dicamba.

In 2020, a federal appeals court overturned the EPA’s approval in response to a lawsuit by environmental groups, but a few months later the agency allowed the product back on the market. Environmental groups sued the agency again, which led to the Feb. 6 ruling.

Those groups claim that Bayer’s proposal will do little to reduce drift. “Virtually nothing in this application addresses the concerns the public and the courts have about this destructive pesticide,” Nathan Donley, environmental health science director at the Center for Biological Diversity, says in a statement. “The EPA should stop this once and for all with a quick, decisive denial.”

The EPA is letting farmers use existing stocks of dicamba on soybeans and cotton for the 2024 growing season. Cutoff dates are in June and July depending on the state and use. But it’s not clear if the agency will approve Bayer’s revised dicamba label in time for next year’s growing season.

“The next steps in this registration process are up to the EPA,” Bayer says in an update on its website. “We hope the EPA will continue to move swiftly so growers have access to the technology in time for the 2025 season.”

The EPA is seeking comments on Bayer’s proposal until June 3.



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