From Aquatic Weeds To Cotton Weeds

A 2011 tour of Mid-South cotton fields was organized by the Weed Science Society of America (WSSA) to acquaint federal agencies with the emerging problem of glyphosate-resistant Palmer amaranth.

One tour participant thought fluridone (trade name Brake), originally discovered nearly 35 years ago, should be reevaluated. As an experimental compound, it showed excellent promise as a pre-emergence cotton herbicide but wasn’t commercialized for the U.S. market. Fluridone was eventually registered as the aquatic herbicide Sonar and is currently marketed by SePRO Corporation.

“We had to find out how Brake would fit into today’s cropping system,” says Dr. Bob Nichols, Senior Director, Cotton Incorporated.

The spread of glyphosate resistance has increased producer interest in residual herbicides.

“Brake fits in pre-emergence/post emergence weed management programs very well,” says Nichols.

Section 18 Granted

In 2012, Brake was granted Section 18 emergency exemptions in Arkansas and South Carolina for the control of glyphosate-resistant Palmer amaranth. That year, Arkansas experienced lingering drought, and the performance of the product was greatly compromised – like that of many other residual herbicides.

In contrast, good early season rainfall in the Southeast provided adequate activation and Brake, in some instances, provided more than eight weeks of control. These experiences made the product development staff at SePRO start thinking.

“We asked ourselves what we could add to fluridone to increase its effectiveness under more diverse conditions,” says Dr. Tyler Koschnick, Vice President, Research and Regulatory for SePRO.

The answer came in the form of Brake F2 where a second active ingredient, fomesafen, was added to fluridone. Fomesafen is registered for use as a residual herbicide but can be damaging to cotton.

“We’ve been able to reduce the use rates of Brake F2 and still get excellent early season Palmer pigweed control that provides a foundation for a season-long cotton weed management program,” says Koschnick.

“You get the early activation with fomesafen and staying power with flouridone, while maintaining exceptional crop safety.”

Encouraging Performance

A Section 18 was granted for Brake F2 in South Carolina for 2013. Even under heavy rainfall, cotton tolerance and residual control were very good while unacceptable levels of crop injury occurred in adjacent fields using other herbicides. Based on the encouraging performance of Brake F2, it is anticipated that Section 18s will again be applied for in South Carolina, Tennessee, Georgia and possibly North Carolina for 2014.

“During the current period, when we lack effective soil-applied materials for thrips control, it is especially important that we have herbicides that do not retard early season cotton growth,” says Nichols.

Meanwhile, Koschnick gives high praise to Cotton Incorporated for its assistance in this project, knowing that Brake F2 will help farmers in their weed control.

“A multi-state field evaluation program of this magnitude would not have happened without the assistance of Cotton Incorporated and university cooperators,”says Koschnick.

“They have shown an interest in the potential of Brake F2, and we have come a long way in a short period of time understanding the advantages of Brake F2 in today’s cropping system – thanks in no small part to Cotton Incorporated.”

The Cotton Board, which administers Cotton Incorporated’s Research and Promotion Program, contributed information for this article.

 

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