Herbicide resistance falls into six herbicide groups for this aggressive weed species (Shyam et al. 2021). The best course of action is to assume that Palmer amaranth is resistant to at least one class of herbicide and diversify your weed management strategies accordingly.
If you have concerns regarding herbicide resistance in Palmer amaranth, please contact the University of Minnesota Extension Crop Production Specialist in your region or discuss with your crop consultant. You can also contact the Minnesota Department of Agriculture Noxious Weed Program. More information is available on the University of Minnesota Extension Herbicide Resistance Management Web Site.
Testing Laboratories
Two labs offer testing to determine if Palmer amaranth plants are glyphosate or PPO resistant: University of Illinois Plant Clinic and National Agricultural Genotyping Center. Contact either lab to learn more about the services they provide and how to properly collect and ship samples. A grow out would be required to test for all the different mechanisms of resistance.
