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Northern Illinois Agriculture

University of Illinois Extension
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Weed resistance in northern Illinois

Posted by Russel Higgins - Weeds

It's never to early to start thinking about weed resistance and strategies to have in place if resistant populations are identified in your fields. While resistant populations of Palmer amaranth and Horseweed (Marestail) have garnered much of the attention in Illinois, another member of the pigweed family deserves attention. As part of a United Soybean Board funded project, growers submitted Waterhemp samples to Dr. Pat Tranel's lab at the University of Illinois. The samples were tested for resistances to glyphosate, PPO inhibitors, and ALS inhibitors using molecular tests. The number of samples submitted was overwhelming, which we consider a good thing. Demonstrating that Illinois growers are cognizant of the weed resistance issue. A 2013 Waterhemp sample submitted from northern Illinois yielded the following response. Dr. Chance Riggins, research assistant professor at the University of Illinois shared that the molecular based tests were negative for PPO-inhibitor resistance (Reflex, Flexstar, Cobra) but positive for glyphosate resistance for the sample.

Be prepared to scout your fields and pay attention to weed size, populations and any irregularities in expected weed control. Especially if your weed control has less than satisfactory in recent growing seasons. Be sure to join us July 10th for the Northern Illinois Agronomy Research Center Field Day and visit our herbicide trials and weed researchers.

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