Herbicide resistent weeds challenge growers

“Start by 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,” Moellenbeck said.

The Crop Protection Lab, located in Regina, Sask., can test these weed seeds for herbicide resistance. Farmers can collect weed seeds at maturity before a desiccant is applied to the crop, and 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,” he said. “Make sure these seeds are only from suspected plants that have appeared to survive the herbicide application.”

For most weeds, hand collection is the best method. For wind dispersed seeds, a sweep net or small vacuum may be best for collecting seeds. The seed sample can’t contain any stems and as little foreign material as possible.

The lab requires a minimum of 2,000 seeds for each herbicide group tested, and the number of seeds will also need to increase with more herbicide groups being tested. For certain species, it can be a challenge to reach the minimum seed threshold, so collect as many seeds as possible.

For wild oats, collect about one large coffee can of seeds. For smaller-seeded weeds such as wild mustard, one small hot chocolate can is enough.

Moellenbeck said after the seeds are collected, they must be completely dry before being submitted. Mouldy samples will not be tested.

“The recommended method is to air-dry the seeds on a piece of paper for a few weeks. Place the dry seeds in a labelled paper bag for shipment to the lab and ensure the Herbicide Resistance Testing Form is completed and submitted along with the sample,” he said.

Also, plastic bags should not be used as they do not allow the seeds to breathe, and mould may grow.

The annual submission deadline for weed seeds harvested during the prior year is Jan.15. Processing times may vary, and results are not guaranteed prior to seeding, as ample time is needed for testing.

Questions about how to submit a sample can be answered by calling the Crop Protection Lab at 306-787-8130 or by email at cpl@gov.sk.ca.

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alice.mcfarlane@pattisonmedia.com

by Alice McFarlane

Herbicide resistent weeds challenge growers

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