2015 Status of herbicide resistant weeds in Michigan

Glyphosate and other herbicide-resistant weeds continue to spread across Michigan.

Horseweed or marestail. Photo credit: Steve Gower

Horseweed or marestail. Photo credit: Steve Gower

Each fall we receive several weed seed samples from around the state to test for resistance to various herbicides. All testing is conducted by the weed science group within the Department of Plant, Soil, and Microbial Sciences at Michigan State University and is sponsored by the Michigan Soybean Promotion Committee. In 2014, we received samples of redroot pigweed (1), Palmer amaranth (2), common waterhemp (5), common ragweed (7), common lambsquarters (2), and horseweed/marestail (15). Each sample received is tested for resistance to five or six herbicide Sites of Action.

We will again be conducting free herbicide resistance testing in the fall of 2015. Please view “How to submit a sample to MSU Diagnostic Services” in the back of the 2015 Weed Control Guide for Field Crops (E0434) for more information on submitting a sample. Submission of several mature seedheads/plants by early November will ensure enough time for our team to break seed dormancy and conduct the screenings. If you have any questions regarding weed seed collection, please contact Christy Sprague (.(JavaScript must be enabled to view this email address)) for more information. Below is the update published by Michigan State University Extension.

New county locations and/or incidents of resistance confirmed from 2014

Redroot pigweed

  • ALS-resistant: Shiawassee Co.

Palmer amaranth

  • ALS-resistant: Shiawassee Co. [multiple (glyphosate/ALS)-resistant was reported in 2011]

Common waterhemp

  • ALS-resistant: Shiawassee Co.
  • Multiple-resistant (glyphosate/ALS): Berrien, Saginaw, Shiawassee, St. Joseph Co.

Common ragweed

  • ALS-resistant: Branch, Montcalm Co.
  • Multiple-resistant (glyphosate/ALS): Isabella, Shiawassee Co.

Common lambsquarters

  • ALS-resistant: Branch Co.

Horseweed/marestail

  • ALS-resistant: Isabella Co.
  • Multiple-resistant (glyphosate/ALS): Berrien, Cass, Gratiot, Montcalm Co.

View maps of Michigan counties with these resistant weeds.

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