Now what?

With dicamba-tolerant soybeans in the ground, what do farmers do next?

Talk about a curveball thrown to soybean producers. 

On Wednesday, the U.S. Ninth Circuit of Appeals Court vacated the Environmental Protection Agency’s conditional registration of three dicamba herbicides for use in dicamba-tolerant crops. 

In plain language, that means effective immediately, farmers in many states may not legally apply:

  • XtendiMax, from Bayer CropScience
  • FeXapan, from Corteva
  • Engenia, from BASF

“This comes at a bad time for farmers,” says Bob Hartzler, weed scientist at Iowa State University. 

Some farmers are hoping the court decision will be overturned. Hope, however, is not a good strategy, Hartzler says. “Next week would probably be the peak timing for Iowa farmers to make postapplications of dicamba herbicide on their soybeans.”

Hartzler points out that Tavium plus VaporGrip, a dicamba plus S-metolachlor herbicide premix from Syngenta, may still be applied, as it was not registered until later. 

“While we are not aware of the supply of Tavium, we suspect Syngenta only has enough product for a fraction of Xtend acres. Most growers will probably be unable to get product for all their fields,” Hartzler wrote in a blog post on the Iowa State University website. 

The weed specialist says growers need to learn what products are available and scout fields to prioritize which fields need treated earliest. 

“In over half the acres in Iowa, waterhemp is resistant to all the alternatives on dicamba soybeans, including Group 2 (ALS inhibitors), 9 (glyphosate), and 14 (PPO-inhibitors),” Hartzler told Successful Farming.  

Hartzler estimates the percentage of fields with waterhemp resistant to these herbicide are: Group 2: >95%; Group 9: >75%; Group 14: >50%. 

“Thus, the repeal of the dicamba label leaves many farmers no effective postemergence herbicides for multiple-resistant waterhemp in Xtend soybean fields,” he writes.

Hartzler says the best chance of controlling waterhemp is likely a Group 14 herbicide (acifluorfen, fomesafen, lactofen), which should be applied as soon as waterhemp is found in a field, and a Group 15 herbicide (acetochlor, dimethenamid, pyroxasulfone, S-metolachlor) should be included to provide residual control after the postapplication. Glyphosate or other appropriate tank mix partners should be included in the mix to broaden the spectrum of weeds controlled.

Preemergence herbicides appear to be providing effective control in most soybean fields at this time, but timeliness of application of the Group 14 herbicide will be critical. Spraying waterhemp between 0.5 and 1.5 inches in height is ideal. Follow all recommendations on the Group 14 label to maximize effectiveness, including carrier volume, nozzle type, spray pressure, spray additives, and sprayer speed.

Mechanical weed control is not a desirable option for most, but farmers with Xtend planted in 30-inch rows should consider the feasibility of interrow cultivation. Large farms probably can’t cover all their acres with a cultivator, but fields could be prioritized based on weediness.

All good in Kansas

Regulators in Kansas have decided that the “purchase and application of the products in Kansas is not yet prohibited,” the Kansas Agribusiness Retailers Association said in a news release June 5. “Seasonal application can continue until instructed otherwise.” The KARA is the trade association for that state’s ag retailers. 

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