Submit Seeds for Herbicide Resistance Testing

By Haylee Hachkewich, Lab Administrative Summer Student, and James Bush, M.Sc., AAg, Manager, Crop Protection Laboratory, Crops & Irrigation Branch, Regina

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 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 as pest control product registrations are dynamic and resistance to some herbicides is becoming prevalent making some weed populations particularly problematic to manage or control.

The first documented case of herbicide resistance in Canada was reported in wild carrots in 1957. Today, herbicide resistance is a wide-spread issue impacting most of the crop producing region in Saskatchewan, with over 15 million acres of weed patches resistant to groups 1 and 2 herbicides. Based on scientific understanding of herbicide resistance and modelling, it is predicted that every field in Saskatchewan will have at least one herbicide resistant weed species by 2027. While Integrated weed management strategies have the most promise for long-term weed control, short-term solutions are needed. There is no more powerful short-term solution than an effective herbicide to control the weeds.

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 that most producers with problematic weed patches have already applied herbicides to them, but the weeds have survived. The only way to know if this is due to herbicide resistance is to submit a sample for testing.

Below is information for collecting the weed seeds, filling out the submission forms, packaging, mailing, how the lab completes testing and interpreting test results.

Collection: 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, but for some wind-dispersed seeds a sweep net or small vacuum may be best for collecting seeds. The Crop Protection Lab needs 2000 seeds per herbicide group tested. However, for some populations this number is not realistic, so it is asked that as many seeds be collected as possible.

Filling out the submission form: The submission form can be found online, or at the Herbicide Resistance Submission Form. Please be sure to fill out all the information on the form as it is required for testing.

Packaging and mailing seeds: Seeds must be submitted completely dry; this 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.

Testing: Weed seeds are germinated and grown in a controlled environment facility to the appropriate growth-stage. Then, the herbicide is applied to the populations. The plants are returned to a separate facility until they are analyzed and scored.

Invoicing and Payment: The cost per test is $125 (+ GST) for Saskatchewan residents and $200 (+GST) for non-Saskatchewan residents. The Crop Protection Lab will invoice clients once test results are completed with full instructions on how to pay. Please do not make a payment before you receive an invoice. The results of the tests will be communicated to the submitter after payment is made.

Interpreting results: Each population is given a resistance rating based on the proportion of plants surviving the herbicide application. The rating classes are susceptible, low resistance, medium resistance and high resistance. It is important to remember that if any resistance is found in the population, then the repeated use of the same herbicide will quickly make the issue worse. If the results indicate the population is susceptible when resistance was expected, there may be other issues causing the weeds to survive, including staging of the plants at the time of spraying, quality of water used, or potential misses with the sprayer itself.

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.