Updates on Dicamba Products (Engenia, Tavium and XtendiMax) Applied in Dicamba-Tolerant Soybean in Nebraska

By Chabella Guzman

Soybean growers in Nebraska and across the U.S. have recently been navigating the complexities of weed management in dicamba-tolerant soybeans as a federal court in Arizona vacated registration of XtendiMax, Engenia and Tavium on Feb. 6, 2024. The U.S. EPA notice, dated Feb. 14, 2024, addresses the existing stocks of preciously listed dicamba products following a court order vacating their registrations. It clarifies that, as of Feb. 6, 2024, selling or distributing XtendiMax, Engenia and Tavium is unlawful under FIFRA, except under U.S. EPA-authorized conditions. The order allows for the limited sale and distribution of existing stocks by persons other than the registrants, under specific conditions, until certain dates for proper disposal, lawful export, or return to the manufacturer. Additionally, the use of existing stocks must adhere to previously approved labeling, with specified cut-off dates for usage, to ensure environmental protection and compliance. More information is available here.

Depending on inventory and when purchases have been made, some growers may still benefit from the products they have purchased. This provision introduces flexibility, ensuring that not all growers will meet the same level of impact and may still utilize dicamba for broadleaf weed management.

The ruling will put some growers of soybeans, Nebraska's second-largest crop, at a management challenge, recognizing that not all acres of dicamba-tolerant soybeans will be equally affected. This nuanced situation reflects the U.S. EPA's provision allowing the use of existing dicamba stocks under specific conditions, meaning that the impact of the ruling will vary depending on a grower's current inventory and the timing of purchases.

For Nebraska, the specific regulations regarding the sale, distribution and use of dicamba products such as XtendiMax, Engenia and Tavium are clearly outlined with Friday, May 31 as the deadline for sale or distribution, and Sunday, June 30 as the deadline for their field use in 2024. It is important to note that these dates apply specifically to Nebraska, and regulations may vary by state. For comprehensive information on the regulations in other states, refer to the U.S. EPA website or the document titled "Existing Stocks Order for Dicamba Products Previously Registered for Over-the-Top Use on Dicamba-Tolerant Cotton and Soybean" is recommended.

What implications does this hold for soybean producers in Nebraska? The EPA answer provided some certainty for the 2024 growing season.

• Making big changes this late in the game represents significant challenges. Affected growers can try to find other soybean seeds, but available quantities may be limited. For affected growers, depending on a grower's current inventory and the timing of purchases, it will put pressure on limited alternative post-emergence herbicide options.
• One viable option is implementing a pre-emergence herbicide program with extended residual activity multiple modes of action. Such a program would effectively decrease weed pressure, facilitating suitable terrain for a follow-up post-emergence herbicide application.
• Certain residual herbicides are labeled in soybean that can be applied after soybean emergence in all type of soybean traits. Most of them do not have a foliar activity; however, they provide overlapping residual activity. If weeds are present at the time of application, mixing with a post-emergence, foliar active herbicide is required. Consider soybean growth stage when using residual herbicides applied post-emergence.
• When considering follow-up applications, it is crucial to ensure timely and precise execution, targeting small weeds (two to three inches) and utilizing increased spray volume (at least 20 gallons per acre), especially if glufosinate-based herbicides are used (e.g., Liberty/Interline/Cheetah). Reliance for affected growers may shift towards contact-type products based on glufosinate (essential to ensure the presence of the glufosinate-trait [LibertyLink] listed on the seed bag) or one of the PPO-inhibiting herbicides (acifluorfen, fomesafen, lactofen or others classified under WSSA Group 14) for broadleaf weed control.

If a grower is unsure of a program selection, they can refer to the 2024 Guide for Weed, Disease, and Insect Management in Nebraska (EC-130). Growers are also encouraged to contact their local University of Nebraska research and extension specialist for options and help in building alternative weed management plans.