Resistant Weeds Prove Menacing Recently
Glyphosate weed resistance is flooding the U.S this summer. Kansas recently confirmed four weeds resistant to glyphosate herbicides, making it the first state to have four confirmed resistant species. Mississippi and California also have each added an additional species to their lists of resistance weeds – Italian ryegrass and hairy fleabane, respectively. In addition, reports of glyphosate-resistant waterhemp are believed to be spread across Illinois, and extension agents continue to try to determine the occurrence and extent of resistant waterhemp.
This issue of The Bulletin by Integrated Crop Management discusses why Illinois extension scientists are saying waterhemp presents significant challenges for corn and soybean growers across the state.
Illinois has seen several reports of giant ragweed and common lambsquarters populations this growing season that have not been controlled by glyphosate, even after multiple applications. Although it is not confirmed, tests are being conducted to determine whether or not these populations are also experiencing glyphosate resistance.
Whether or not glyphosate resistance is the culprit in each situation, it seems that weeds across the Midwest are becoming harder to control. Weeds that require more applications and higher doses of glyphosate are one indication that resistance may be on its way.
So, what can be done? This bulletin outlines the Syngenta recommendations for resistance management, and the following Web sites are also helpful: