The Auxin Wait is Over

From Cotton Grower Magazine – January 2017

It’s official. The age of auxin herbicide applications for weed control in cotton is here.

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EPA ushered in the long-anticipated era with its label approval of Monsanto’s XtendiMax with Vapor Grip technology on November 9 – a lower volatility formulation of dicamba specifically developed for use on Bollgard II XtendFlex cotton varieties and Roundup Ready 2 Xtend soybeans. The federal label for Engenia, a low volatility dicamba product from BASF, followed in late December.

EPA approval of the label expansion for Enlist Duo – Dow AgroScience’s low volatility 2,4-D product – for use in Enlist cotton varieties was received January 13.

State reactions to the XtendiMax registration came quickly.

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The Arkansas State Plant Board, which regulates use of pesticides in Arkansas, held a public hearing about the new dicamba formulation on November 21, on the heels of a growing season that saw thousands of acres of crops damaged by illegal use of dicamba in the state and other areas of the Mid-South. Tragically, a dispute over off-label applications resulted in the shooting death of a northeast Arkansas grower.

The Plant Board, on the recommendations of its Pesticide Committee, sent new state regulations regarding dicamba use to the Governor – and ultimately the State Legislature – for review and approval. Those regulations, if approved, would place tighter use restrictions on all dicamba formulations within the state and require applicator training and state certification.

In Mississippi, task forces for both the state Department of Agriculture and the Delta Council have been actively working on ways to best integrate the new auxin herbicides into the state’s row crop agriculture. Mississippi State University was commissioned to develop a training program for applicator certification, which will required under the state label for the products.

“We have developed six training modules,” said Dan Reynolds, professor of weed science at Mississippi State. “They will all be available online, and participants can register via a link through the continuing education component of Extension. Each module has a 10-question exam at the end. If participants don’t pass, they get to take the test again, but are likely to see different questions.”

The training modules include an introduction to herbicide resistance in weeds; how auxin herbicides work; off-target deposition through drift, volatility and equipment; and details on the Enlist Duo and XtendiMax labels.

The state of Arkansas will also utilize the Mississippi State training modules for applicator training and certification. Additional states and organizations have expressed interest in the program and are likely to adopt it, as well.

North Carolina also recently announced a mandatory training requirement for growers and applicators planning to use the new auxin formulations.

According to Reynolds, the training is critical to help prevent – or at least reduce – application issues that are likely to occur with the auxin formulations.

“Bottom line, even though the dicamba and 2,4-D products are both auxins, they are not cross resistant,” he said. “Dicamba on Enlist cotton will look just like dicamba on regular or Roundup Ready cotton. Enlist on Xtend cotton will look just like 2,4-D on regular cotton.”

Details on the XtendiMax label – including information on required buffers, tank mix restrictions, specific nozzle recommendations and updates on additional state registrations and training requirements – are available at RoundupReadyXtend.com. Growers are urged to consult the website prior to any XtendiMax application.

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