Auburn weed scientists outline 2026 dicamba requirements

In 2025, row crop producers faced regulatory changes regarding the widely used herbicide dicamba, which was effectively removed from legal use for over-the-top applications that season. On Feb. 6, the Environmental Protection Agency (EPA) once again allowed the registration of three new dicamba products, this time with new stipulations. Auburn University researchers and Alabama Extension specialists continue to guide growers through the new labels and requirements.

With reinstatement underway, it’s important to understand how dicamba works. Dicamba is a systemic herbicide that interferes with a plant’s growth process. As a result, it is effective at controlling aggressive broadleaf weeds, like pigweed, in cotton and soybeans.

David Russell, associate professor and specialist with Alabama Extension at Auburn University, encouraged farmers to participate in trainings and use available information. These resources can help farmers make the best use of the new products.

“We always encourage our growers to follow the labels and contact us if they need help interpreting the new product regulations,” Russell said. “Even without dicamba over-the-top applications last year, using practical weed-science practices, like sound management and well-timed residuals, goes a long way.”

Steve Li, associate professor in the Department of Crop, Soil & Environmental Sciences and Alabama Extension specialist, advised growers to account for weather before applying.

“Herbicide efficacy generally decreases in hot, dry conditions. That means spraying small weeds — ideally under 5–6 inches — will be critical for good control,” Li said. “If growers plan to mix Roundup with dicamba for weedy grasses, they should be aware of how dicamba can reduce glyphosate efficacy.”

The new labels have been approved by the Alabama Department of Agriculture and Industries and are available for 2026 through 2027. These updated labels allow growers to utilize dicamba products designed to reduce herbicide drift and volatility, thereby shielding more vulnerable crops and plants.

The new products, Engenia (BASF), Stryax (Bayer) and Tavium (Syngenta), were created for over-the-top applications on dicamba-tolerant cotton and soybeans and are all labeled as restricted use. To meet the requirements, growers can obtain a commercial or private applicator license through the Alabama Department of Agriculture and Industries.

There have been key changes made to these new products. Under the new label restrictions, lower limits of overall use are required. In addition, there are updated rules regarding conservation practices as well as temperature restrictions to help minimize drift movement.

“The limit is now one pound of dicamba per season, with no more than two over-the-top applications within that total,” Russell said. “These changes are meant to narrow the application window and protect nearby sensitive plants, and the new system uses temperature-based cutoffs rather than fixed dates. New labels only allow applications to half of untreated acres when temperatures are 85 to 95 degrees and no applications are allowed when temperatures exceed 95 degrees.”

To see what seasons without dicamba could look like for Alabama producers, Russell performed research trials through the Alabama Agricultural Experiment Station.

Over the last few years, Russell conducted trials at outlying units including E.V. Smith Research and Extension Center in Shorter, Gulf Coast Research and Extension Center in Fairhope and Tennessee Valley Research and Extension Center in Belle Mina.

With uncertainty about dicamba’s future past 2027, Russell and a team of researchers tested field studies to explore alternatives. They evaluated Liberty and  the newly released Liberty Ultra — the first glufosinate product to meet all the updated label requirements. Russel said the team looked closely at different rates of Liberty. The goal was to determine whether the products could match dicamba’s performance.

“For soybeans, we walked growers through what combinations would give them the strongest control — whether that was a single active ingredient, two-way mixes or three-way mixes,” Russell said. “The goal was to show how layering actives can extend the level of control and help them build a more reliable weed management program.”

Many growers utilize dicamba products to control pigweed, but it may require more than one application. For this reason, growers may commonly use dicamba for early application and then follow-up with a glufosinate product to finish off tough broadleaf weeds. It’s a one–two punch.

For best results, Russell recommended growers focus on weed science basics like utilizing residuals and mixing active ingredients when planning out their growing season. He encouraged them to have sound plans ready, no matter what pesticides they are using.

“We want our growers to know that dicamba is not the sole solution to control broadleaf weeds,” Russell said. “With late summer rains becoming less reliable, establishing a healthy early season canopy remains one of the most effective ways to limit how much dicamba they need.”

As Auburn researchers continue to analyze products and management practices, they strive to help Alabama row crop producers find solutions to manage their toughest weeds.

“Looking forward, we’re watching for new products and technologies, but stewardship is a main priority,” Russell said. “Helping our growers use the tools they have responsibly is what will allow us to keep the technologies we rely on.”

Auburn University research and Alabama Extension outreach provide guidance so growers can navigate in-field decisions with precision and clarity.