GLYPHOSATE RESISTANT KOCHIA IS PREVELANT IN WESTERN KANSAS. Phillip W. Stahlman*, Patrick W. Geier; Kansas State University, Hays, KS (166)


The presence of glyphosate resistance in four populations of kochia in western Kansas was confirmed in 2007.  The populations were dispersed more than 100 km apart and were considered to have developed resistance independent of each other.  A few additional reports of lack-of-control of kochia with glyphosate in other regions were received in 2008 and 2009 and the number of such reports escalated dramatically in 2010. An extensive driving tour and unscientific field survey in the fall of 2010 confirmed the presence of uncontrolled kochia in many corn, soybean, and fallow fields throughout the western one-third of Kansas that had been sprayed with glyphosate alone or in mixture with other postemergence herbicides.  Seed was collected from 17 kochia populations dispersed throughout the region that had survived spraying operations.  Glyphosate dose-response trials are being conducted to determine if the sampled populations are indeed resistant to glyphosate as suspected.   If resistance is confirmed, then glyphosate-resistant kochia is prevalent throughout western Kansas.