Canada thistle an issue for alfalfa

Herbicide trials underway for Canada thistle

Planting on clean field is still the best way to avoid having weeds invade a perennial seed crop. Photos: Shannon VanRaes

The Manitoba Forage Seed Association (MFSA) is running herbicide trials with the hopes of providing producers more options for weed control.

“Perennial weeds are typically the biggest issue with alfalfa, the one that we seem to have the most trouble with is Canada thistle,” said Kevin Gulay, research manager for the organization. “It’s tough to control that weed in alfalfa, but it’s also tough of course to deal with dandelions, and narrow-leaved hawk’s beard — night-flowering catchfly can also be difficult to control.”

Although the results are far from complete, producers toured the plots during MFSA’s summer tour in mid-July to get a look at early results.

Gulay hopes the end result of the trials is a greater number of registered herbicides to deal with perennial weeds, Canada thistle in particular.

“There’s the common products on the market, like Pursuit, Odyssey, Partner, but it’s definitely limited compared to your grain crops. A lot of the companies just don’t do the research and development in alfalfa seed as they would do in some of the major crops,” he said. “Farmers have to do a lot of work themselves.”

The products MFSA are testing aren’t yet registered, but Gulay is optimistic some will make it to market in the near future.

What the researcher is looking at more closely this summer, is how well alfalfa tolerates these newer herbicides. Although some products can cause burn-down, most damage can be avoided if applied when the crop is dormant, he said.

The trials are also looking at how soil type affects the effectiveness of different products and the amount of residue left behind.

But Gulay adds the best defence against Canada thistle and other weeds is to get off to a good start when establishing a field.

“Of course the best option is always to start with a clean field,” he said.

About the author


Shannon VanRaes is a journalist and photojournalist at the Manitoba Co-operator. She also writes a weekly urban affairs column for Metro Winnipeg, and has previously reported for the Winnipeg Sun, Outwords Magazine and the Portage Daily Graphic.



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