'Pigweed on steroids' heading north to Ontario


Palmer amaranth could be the next glyphosate resistance weed problem for Ontario farmers.

University of Arkansas weed scientist Jason Norsworthy calls it “pigweed on steroids.” Norsworthy, who first saw glyphosate-resistant palmer amaranth in Arkansas in 2006, says the weed can grow two to three inches a day after it reaches four inches tall. “You can quickly lose control of the weed and once you lose control of it you are quickly going to lose the crop.”

Norsworthy says the weed is on the march and has been found as far north as central Michigan. “People said it won’t move forward in this climate, but that’s not the case. It thrives very well on these rich, fertile soils.

Read more: Common herbicide pitfalls when trying to control glyphosate resistant weeds

Speaking at Bayer CropScience’s Dead Weeds Tour earlier this month, Norsworthy offered tips on how growers can do a better job of managing resistance and keeping weeds like glyphosate-resistant palmer amaranth at bay.

Norsworthy is a big fan of glyphosate and says diversity, including strong herbicide rotations, is the best strategy for preserving the technology and controlling resistance. He also warns that there are no new silver bullets coming through the product pipeline and urges farmers to be proactive in preserving current weed control technologies. He believes growers should be relying more on pre-emerge herbicides; ensure they use full herbicide rates when spraying; do a better job of timing their post-emerge herbicide applications; and be more diligent in managing the weed seedbank.

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