2016 status of herbicide-resistant weeds in Michigan
Last year saw a record number of submissions for herbicide resistance screening of weeds; be aware of new confirmed cases in your area.
In the fall of 2015, the herbicide resistance screening returned to Michigan State University Diagnostic Services after spending many successful years under the direction of MSU weeds specialist Christy Sprague. The 2015 season saw a surge in submissions, with a total of 46 samples, a 40 percent increase over 2014. The samples included three Palmer amaranth, three Powell amaranth, 10 common waterhemp, nine common ragweed, three common lambsquarters and 18 horseweed/marestail. Each sample received was tested for resistance to five or six herbicide Sites of Action, with all testing being sponsored by the Michigan Soybean Promotion Committee. Please view the listing below for the new incidents and locations of resistance that were confirmed. A cumulative listing of confirmed herbicide resistant weeds by county is currently being compiled and will be made available through the MSU Diagnostic Services website soon.
New county locations and incidents of resistance confirmed from 2014
*G# refers to the herbicide site of action group.
- Powell amaranth
- ALS-resistant (acetolactate synthase inhibitor, G2): Saginaw, Sanilac, Newago counties
- Multiple-resistant (ALS-G2/atrazine-G5): Allegan County
- Multiple-resistant (glyphosate-G9/ALS-G2): Isabella, Sanilac, Wayne counties
- Multiple-resistant (ALS-G2/atrazine-G5): Saginaw, St. Clair counties
- ALS-resistant (G2): Clinton County
- Multiple-resistant (glyphosate-G9/ALS-G2): Sanilac County
- ALS-resistant (G2): Allegan, Arenac, Saginaw counties
- ALS-resistant (G2): Saginaw, Sanilac counties
- Multiple-resistant (glyphosate-G9/ALS-G2): Branch, Hillsdale, Macomb, Monroe, Oakland, Saginaw, Shiawassee, St. Clair counties