Manitoba has its first official glyphosate-resistant weed, and as expected, it is kochia.
But out of 283 fields surveyed last fall, only two were found with glyphosate-resistant kochia. Both are in the Red River Valley.
“I was surprised about where it was found,” Bruce Brolley, Manitoba Agriculture, Food and Rural Development’s (MAFRD) crops knowledge centre manager said in an interview Monday.
Agronomists had predicted the first cases would be discovered in Western Manitoba because glyphosate-resistant kochia was confirmed in Saskatchewan and Alberta in 2012. But officials suspect this seeds of this infestation came from North Dakota.
However, Brolley said the small presence is good news.
MAFRD is not revealing the exact location of the glyphosate-resistant kochia. Staff will closely monitor the fields and work with the affected farmers and those nearby to contain its spread.
“This is a shot across the bow,” said Gary Martens, an agronomy instructor at the University of Manitoba. “I am afraid there’s so much noise out there farmers won’t pay attention to this. But they need to because there is more (herbicide resistance) to come.”
It’s assumed almost all kochia in Manitoba is already resistant to Group 2 herbicides, making glyphosate-resistant kochia more complicated to control.
Controlling it in Roundup Ready soybeans, for example, will be a challenge. Basagran might control young kochia in soybeans, but the weed is not on the label, Martens said.
“It is a wake-up call for changing weed management,” Brolley said. “And because we appear to have detected it early, we can make farmers aware of it and prevent its spread.”
It will be more critical than ever for farmers to employ an integrated weed management program, he said.
Weed scientists recommend farmers rotate herbicide groups to switch up the “mode of action” or the way the herbicide kills a weed. Better still is a combination of different modes applied as a tank mix or during the same growing season in separate applications.
That’s especially important when applying glyphosate before seeding to “burn down” weeds. Failing to do that led to the development of glyphosate-resistant kochia, Hugh Beckie, an Agriculture and Agri-Food Canada research scientist based in Saskatoon who specializes in herbicide-resistant weeds, said in an earlier interview.
“Farmers were just using glyphosate alone at high rates and that quickly selected for resistance,” he said. “They should be tank mixing another mode of action whenever possible with glyphosate and to only spray glyphosate when it’s really needed…”
Crop rotation, including perennials, can also help to delay the onset of herbicide-tolerant weeds.
“Since it’s so widespread in Saskatchewan and Alberta now, why wouldn’t it be in Manitoba, especially in the southwest where kochia is such a prevalent weed?” Beckie said last year.
In an online survey last year 281 Manitoba farmers said they believed there was glyphosate-resistant kochia on 23,000 acres in Manitoba.
Beckie oversaw last fall’s survey with funding from the Western Grains Research Foundation and assistance from MAFRD and the University of Manitoba.
Manitoba is no stranger to herbicide-resistant weeds, with Group 3 resistant green foxtail first identified in 1988. However, glyphosate-resistant weeds are relatively new to Canada. The first documented case was giant ragweed in Ontario in 2009 followed by Canada fleabane in 2011, also in Ontario.