This past summer, a diligent agronomist in southern Alberta was suspicious of downy brome that was not being controlled by glyphosate.

The population in question was widespread in a glyphosate-tolerant canola field in Taber County, Alberta, and was not controlled following multiple applications of glyphosate, says Charles Geddes, weed scientist at Agriculture and Agri-Food Canada, Lethbridge.

After sending in seeds for testing, Geddes, and research technician Mattea Pittman confirmed glyphosate resistance in the downy brome population.

“Further analyses showed that the population exhibits between 7- and 12-fold resistance to glyphosate depending on the parameter of interest,” Geddes says. “We currently do not know whether the problem exists beyond a single farm, but we urge any farmer or agronomist to contact us if they suspect that they are dealing with a similar situation.”

The confirmation marks the first population of a grassy weed species to be resistant to the herbicide in Canada, says Geddes.

“The story here certainly isn’t to use more glyphosate, it’s that other management practices will need to be used,” notes Geddes on the subject during a presentation at Alberta Agronomy Update on Jan 12.

During the question period, Geddes said that cleaning equipment will be critical when it comes to limiting the spread of glyphosate-resistant downy brome.

“Seed dispersal of this weed is not as efficient as kochia,” said Geddes. ” Similarly, downy brome is predominantly self-pollinated. This means that spread of resistance traits by pollen will not be as efficient as kochia. Instead, the biggest risk, I think, is that downy brome seeds can easily be caught in equipment, and in animal feed sources. This physical transport of seeds is the biggest risk, I think.”

Initial confirmations of herbicide resistance usually begin with farmers or agronomists observing something out of the ordinary and contact a lab or scientist to confirm resistance.

“Without these valuable farmer/agronomist/researcher partnerships, we would not be able to catch new cases or weed resistance before they spread beyond the initial field/farm,” he adds.

If you suspect glyphosate-resistant downy brome in your fields, contact Geddes directly at [email protected]

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