History & Map of Herbicide-Resistant Weeds In Michigan

In 1980, common lambsquarters was the first weed to be confirmed resistant to the triazine herbicides (Group 5) in Huron County, Michigan by PhD student E. Patrick Fuerst and Professor Donald Penner. Over the years following, a few more weeds were confirmed resistant by MSU weed scientists Donald Penner, Jim Kells, Karen Renner and Bernard Zandstra. In 2000, Steve Gower began a more formalized screening program through MSU Diagnostic Services. In 2010, the screenings were moved to the laboratory of Christy Sprague and in 2015 they returned to Diagnostic Services under the direction of Erin Hill. The current screening process, supported largely by the Michigan Soybean Promotion Committee, involves greenhouse bioassays started from weed seeds harvested from escaped weeds. Each weed is screened against five to six different sites of action in an effort to detect new incidents of resistance and cases of multiple resistance.

To view a summary of our latest findings visit the MSU Extension news article, “2020 Status of herbicide-resistant weeds in Michigan“.

Previous reports can be viewed at the following links:

The shaded counties on the map below are confirmed cases of herbicide-resistant weeds, with the number of resistant species per county is noted. Click on the county of interest (or scroll down the list below the map) to view details. Counties showing no resistance may still have resistant weeds, as samples have not been submitted for all counties. *Map & listing updated April 2020*.