By James Bush, M.Sc., AAg, Manager, Crop Protection Laboratory, Regina
December 2024
Unmanaged weed populations have significant impacts on crop production. Weedy species may outcompete the crop for resources, produce allelopathic substances that inhibit crop growth or their seeds can result in dockage fees when grain is sold. Weeds can also act as a disease reservoir within a crop or they may act as a host for problematic insect pests. Regardless of potential impacts or outcomes, weed management has become increasingly difficult with time. Pest control product registrations are dynamic and resistance to some herbicides is becoming prevalent, making some weed populations problematic to manage or control.
The best way to tell if a herbicide will be effective against a population of weeds is to test for resistance to that herbicide. It is likely producers with problematic weed patches have applied herbicides to them, but the weeds have survived. Submitting a sample for testing is the only way to know if this is due to herbicide resistance.
herbicide resistance testing.
Weed seeds need to be collected at maturity before a desiccant is applied to the crop. For most species, hand collection is the best method. However, for some wind-dispersed seeds, a sweep net or small vacuum may be best for collecting seeds. The Crop Protection Lab needs 2,000 seeds per herbicide group tested. However, for some populations this number is not realistic, so it is asked that you collect as many seeds as possible.
Seeds must be submitted completely dry, which can be accomplished by allowing them to air dry on a piece of paper for a few weeks. This ensures proper evaluation at the lab. Samples can either be dropped off in person at 1610 Park Street, Regina or sent by mail. When mailing, place the weed seeds in a dry paper bag with a completed herbicide resistance form attached. All herbicide resistance tests must be submitted to the laboratory by January 15, 2025. Due to the current Canada Post mail strike, it is recommended to use a company other than Canada Post to ship your seeds, as Canada Post deliveries may not be in time for the submission deadline.
Informed management decisions can lead to the most cost-effective solutions to crop production problems. The impacts of weeds can be significant; however, if controlled appropriately the impact can be minimized.