Herbicide resistant weeds in Michigan

History & map of herbicide-resistant weed species in MI

map2019 — The latest on herbicide-resistant weeds in MI by county

Learn what weeds have been confirmed as herbicide-resistant in specific counties
Visit the map at this link to learn more
Updated: April 2019

Glyphosate-resistant common waterhemp in Michigan

Submitting your weed seed sample for testing

Tips for collecting weed seeds: Ensure your resistance sample gets tested
Submission form – Screening for herbicide resistance at MSU Plant & Pest Diagnostics
Testing includes multiple sites of action, based on seed quantity and quality – $90.00
MI Soybean growers qualify for free testing of the following species courtesy of the
Michigan Soybean Promotion Committee:
- Palmer amaranth
- Waterhemp
- Horseweed/marestail
- Common lambsquarters
- Common ragweed
- Giant ragweed
Testing of other species in other cropping systems may be possible in consultation with the Weed Diagnostician, Erin Hill (hiller12@msu.edu)

Weed seed is required to conduct a whole plant bioassay in the greenhouse to screen for herbicide resistance. Mature, high-quality seed or seedheads should be collected from suspicious plants in the late summer or fall; ideally pooled samples with seed/seedheads from 5 or more plants will ensure adequate seed quantity. For species-specific seed collection and submittal information please refer to the top link above. Screens will be designed by herbicide site of action (e.g. EPSP synthase inhibitor, ALS inhibitors, Photosynthesis inhibitors, etc.) and are generally available 2-3 months after submission to allow for seed cleaning, dormancy breaking measures, greenhouse growth, herbicide application, and evaluation.