Northern farmers have weed resistance, too
Mike Jones, Bayer technical service representative in eastern Iowa, concurs with Stachler’s observations. “In the 20 counties in which I work, I’ve seen glyphosate resistance issues in each of them.”
Jones has watched as weed resistance has become obvious because of overuse of glyphosate. “Any herbicide that is overused will encourage weed resistance. You could say the weeds will adapt,” he said.
“Bayer is trying to point out the need for herbicide diversity as well as trait and crop diversity,” Jones said. “Respect the Rotation field days and materials are tools we have been using for the last three years to tell the message about weed resistance. We have also been working with universities—in my area it is Iowa State University—supporting their messages.”
Confirmation of weed resistance usually comes late in the cycle of resistance buildup in a field, noted Stachler. Although not officially confirmed in all cases, it appears there is probably glyphosate resistance to giant ragweed, common ragweed, waterhemp, marestail and kochia in his northern climate area. In other words, weed resistance isn’t being contained to the southern U.S. It has spread from border to border.