Kochia confirmed glyphosate-resistant in Kansas

Published on: 17:12PM Apr 09, 2010
Chuck Foresman
Recently Dr. Phil Stahlman, a Kansas State University weed scientist at the research center in Hays, confirmed that there are kochia populations resistant to glyphosate in Kansas. Both greenhouse and in-field studies showed that glyphosate-resistant kochia is a reality.
Kochia has been a tough – and important – weed to control in the western Corn Belt for years. Now, growers concerned that they may have glyphosate-resistant kochia will need to plan ahead to manage it. Stahlman and his colleagues recommend a two-pass weed control program that includes a pre-emergence residual herbicide that controls kochia. They also recommend using full herbicide rates. He noted that areas that first saw glyphosate-resistant kochia are areas where reduced glyphosate rates are often used. 
My colleagues in Kansas have both a pre-emergence and a post-emergence recommendation for glyphosate-resistant kochia in corn.  
In corn, just one uncontrolled kochia per square yard (about the area of a hula-hoop) can cut yield nearly 10%. In soybean, that same weed can cost 33% of your yield, according to www.WeedSOFT.org.
Are you dealing with glyphosate-resistant kochia?