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Scientists dusting off ‘old’ chemistry to find new tools for controlling problem weeds

Back in the 1970s, researchers were looking at two new pre-emergence herbicide compounds for cotton. One, a material active on large-seeded broadleaf weeds like cocklebur, went on to become Zorial. The other, which controlled small-seeded weeds like Palmer amaranth, was never pursued in cotton because Palmer amaranth was not a serious problem back then. My how times have changed. Weed specialist Larry Steckel talked about the efforts to develop the second compound, Brake, to help farmers battle glyphosate-resistant pigweed.

Steckel, a speaker at the recent 2013 UT Cotton Tour at the West Tennessee Experiment Station in Jackson, says there are some draw backs to Brake. For openers, it requires more rainfall than other pre-emergence herbicides for activation, up to three-fourths of an inch of rainfall vs. one-fourth to one-half inch for Cotoran or other older residual herbicides.

Expense is also an issue. That’s why Steckel and other University of Tennessee researchers are experimenting with reduced rates for the compound, which is labeled as Sonar for control of aquatic weeds. South Carolina applied for and received a Section 18 emergency use exhibit for Brake for the 2013 use season. The Section 18 rate of two-tenths of a pound active ingredient cost about $50 an acre.

There’s no doubt Brake can provide pre-emergence weed control of Palmer amaranth with little injury to cotton, Steckel says. The issue will be finding a way to apply it economically and effectively. “We’re looking at tank mixing it with a material like Cotoran or Dual with the idea those herbicides will provide a bridge until we get enough rain to activate the Brake.”

Brake is being developed by Sepro. (For more information, go to

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