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How to Collect and Test Herbicide Resistant Weeds

By Royce Moellenbeck, AAg, Crops Extension Intern, Humboldt

Are you noticing your herbicide is not working as good as it has in the past? In Saskatchewan, common weeds that have developed herbicide resistance include wild oats, green foxtail, kochia, wild mustard and shepherd’s purse. It is important to know which herbicide group these weeds have developed a resistance to so you can plan an alternative weed management strategy, such as selecting a different herbicide group or adjusting your crop rotation. The population of herbicide resistant weeds will continue to increase when herbicide management does not change.

Close-up of wild oat seed heads growing on slender stems with pale golden husks against a softly blurred grassland background.

The Crop Protection Lab, located in Regina, can test these weed seeds for herbicide resistance. Weed seeds need to be collected at maturity before a desiccant is applied to the crop, before the suspected area is harvested or before it is sprayed with herbicides post-harvest. Selection of the seeds is crucial. You must avoid green or diseased seeds as they will not germinate properly and may hinder the diagnosis or make testing impossible. Make sure these seeds are only from suspected plants that have appeared to survive the herbicide application.

Wild Oats