Wheat School: Cultural practices as effective as a new mode of action

What’s old is new again, or at least as relevant as ever when it comes to managing herbicide resistant weeds.

Research led by Charles Geddes, weed scientist with Agriculture and Agri-Food Canada at Lethbridge, shows cultural practices — tighter row spacing, higher seeding rates, and longer crop rotations — can be just as effective as a new mode of action when it comes to managing kochia that’s resistant to multiple herbicides in Western Canada.

“This project has been ongoing for the last five years, and there are multiple different components to it, but really the theme is, ‘how can we manage multiple herbicide resistant kochia?’ And what we’re finding is that many of these cultural tools are quite effective,” he explains, in this new Wheat School video.

By switching from 18 to 9 inch row spacing, and doubling recommended seeding rates, kochia biomass has been reduced by more than 80 per cent across all the site years in the study, he says. (more below the video)

“To put that into perspective, that 80 per cent is similar to the threshold that herbicide regulators use to register a herbicide for control of a specific species. So we’re seeing control levels similar to a new herbicide mode of action. That’s pretty impressive,” says Geddes.

On the crop rotation side, he says they’re seeing excellent efficacy in rotations that include winter wheat.

“The idea there being winter wheat, for example, is already established in the spring when kochia is just emerging, giving it a competitive advantage. But then also, winter wheat tends to be harvested before kochia produces viable seed, at least where we’ve been researching it across western Canada. So if you can harvest that crop before the kochia produces seed, that decapitates the plants, and is helping to prevent seed returned to the soil seed bank,” explains Geddes.

As the five-year research project reaches its conclusion, he says they’re going also be compiling yield and economic results comparing the impact of different cultural kochia management practices.

The research was funded by Agriculture and Agri-Food Canada, Western Grains Research Foundation, Manitoba Pulse and Soybean Growers, Manitoba Wheat and Barley Growers Association through the Integrated Crops Agronomy Cluster under the Canadian Agricultural Partnership, which ended in March 2023.

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