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Post-harvest treatment can slow resistant Palmer Amaranth spread

Post-harvest treatment can slow resistant Palmer Amaranth spread

Study shows that stopping Palmer amaranth before seeding helps stop spread of resistant plants

A study featured in the most recent issue of the journal Weed Technology shows that post-harvest treatment of glyphosate-resistant Palmer amaranth can significantly reduce seed production and help to control the spread of the weed’s resistant traits.

A research team from the University of Tennessee treated two test fields after corn crops were harvested. Fourteen days after treatment, they found that the herbicide paraquat used alone or in a mix with S-metolachlor controlled 91 percent of glyphosate-resistant Palmer amaranth in the fields.  Even better results were achieved, though, when paraquat was tank-mixed with residual herbicides to control subsequent regrowth of the weed.

Post-harvest treatments were found to prevent approximately 12 million Palmer amaranth seeds per hectare – significantly reducing the weed seedbank.

Researchers also discovered that the residual herbicides used in post-harvest treatments of Palmer amaranth had no impact on the yields achieved from a winter wheat crop subsequently planted in the same fields.

Lawrence Steckel, Ph.D., one of the authors of the Weed Technology article, says the prevalence of glyphosate-resistant Palmer amaranth has led scientists to recommend a zero tolerance policy toward the weed, with year-round management programs that incorporate multiple control methods and multiple herbicide mechanisms of action.

“We now know that herbicides applied post-harvest can play an important role in a sustainable Palmer amaranth weed management program by reducing the number of seeds left in the field by herbicide-resistant plants,” he said.  

Full text of the article, “Evaluation of POST-Harvest Herbicide Applications for Seed Prevention of Glyphosate-Resistant Palmer amaranth (Amaranthus palmeri),” is now available in Weed Technology Vol. 29, Issue 3, July-September 2015.

Weed Technology is a journal of the Weed Science Society of America, a nonprofit scientific society focused on weeds and their impact on the environment. The publication presents original research and special articles about weeds, crops and new technologies used for more effective weed management. To learn more, visit

TAGS: Wheat
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