While dicamba has been around for many years, application changes have led to more regulations. In mid-March, the U.S. EPA approved label amendments to mark June 20 as the cutoff date for 2022 in-season dicamba applications nationwide.

This decision came after numerous dicamba-related incident reports from last year’s growing season in Iowa and beyond, which indicated more than 1 million acres of non-dicamba-tolerant soybean crops were damaged due to drifting. This also affected other crops, plants and trees, according to EPA. The 2021 cutoff date was June 30, a full 10 days later.

Highly regulated

Meghan Anderson, Iowa State University field agronomist, says dicamba is the most highly regulated weed control product. Among the restrictions in place for dicamba are: spraying during a specific growth stage; time of day; wind direction and speed; buffer requirements; adjacent crops; and nozzle requirements.

“If we have a normal growing season this year, I suspect we won’t see much change in dicamba use — as it seems when Iowa farmers follow the other restrictions, they are usually done using it by June 20 anyway,” Anderson says.

The Iowa Department of Agriculture and Land Stewardship says the state-level restriction is to keep the products available to farmers and reduce the risk of drift movement. The affected products include Engenia by BASF, Tavium by Syngenta , and XtendiMax by Bayer.

“Iowa is a national leader in agriculture production, and our farmers need continued access to weed management technology to protect their crops,” says Mike Naig, Iowa Secretary of Agriculture. “I’m glad the EPA has agreed to preserve access to a critical tool farmers need; however, I’m frustrated by the lack of urgency the EPA has shown through the process. Our team will work with stakeholders to ensure Iowans are aware of this change as we quickly approach the growing season.”

Incident review

The 2021 dicamba-related incidents were reviewed and a summary was released by the EPA in December. This review looked at whether dicamba had an effect on nontarget crops and other plants in the proximity of where the spraying occurred.

“The rise in litigation targeting pesticide product registrations and off-target pesticide misuse complaints pose a threat to farmers’ long-term access to dicamba,” Naig says. “While I would have preferred a reasonable, federal solution to this issue, we will implement this approach at the state level to help ensure continued access for Iowa farmers.”

Anderson says the use of dicamba can vary year to year, but she speculates nearly 50% of Iowa farmers are using dicamba-tolerant soybeans, and thus using dicamba to control weeds — especially waterhemp.

“My expectation is that this added regulation will help be more black and white for farmers, as the label already has a lot of information on it,” Anderson says. “The growers will have to be in the field to know what the plant’s growth stage is, and if they can use dicamba for weed control. It might be a little easier to interpret.”