Glyphosate-resistant fleabane arrives in Ont.

Researchers from the University of Guelph have confirmed Canada’s second species of glyphosate-resistant weed.

Populations of Canada fleabane that can survive applications of Roundup and other glyphosates already appear in 18 U.S. states and several other countries, but were only found here in southwestern Ontario’s Essex County last fall.

“We have seen the presence of glyphosate-resistant Canada fleabane moving north in the past decade so we are not completely surprised” to see it in fields in Ontario, Francois Tardif of Guelph’s department of plant agriculture said in a release Tuesday from Monsanto, maker of Roundup and breeder of glyphosate-tolerant Roundup Ready crops.

The glyphosate-resistant weeds in question were found from seeds collected in soybeans fields in the region during the fall of 2010. Seed samples were sent to Guelph from growers suspecting resistance to glyphosate.

Of the 12 populations tested, eight — all from fields in Essex County — survived the diagnostic dose of glyphosate in greenhouse tests, the university said.

Glyphosate resistance in Canada fleabane — also known as horseweed, hogweed or mare’s-tail, can be “problematic” as the weed produces many wind-borne seeds and thus spread easily, plant scientist Peter Sikkema of Guelph’s Ridgetown campus said.

Right now, the weed is mainly a problem in no-till soybeans, he added.

That said, “I don’t want people to have the perception that it is across the county — we have confirmed it in eight fields,” he said in a separate Guelph release.

Mark Lawton, Monsanto’s technology development lead in Eastern Canada, said there are “already effective solutions” for impacted farmers, such as herbicides registered for use for pre-plant/pre-emergent burndown in soybeans (Eragon, FirstRate) and corn (Eragon and Banvel II).

Banvel II and FirstRate are also already registered for in-crop control in corn and soybeans respectively, Lawton said in Monsanto’s release.

Guelph graduate students are continuing research on two different fields this spring and summer, trying to see if there are other alternatives, the university said.

“We are looking at generating Ontario-based information to best address the problem,” Sikkema said. “In three to four months we will have better information for Ontario farmers.”

Monsanto said it plans to collaborate with Guelph on research this summer including the assessment of other weed management strategies such as the testing of dicamba-tolerant soybeans.

“The right rate”

“The effective use of Roundup agricultural herbicides and Roundup Ready crops has continued in areas where glyphosate resistance has occurred,” Monsanto’s Lawton noted.

“Glyphosate-resistant weeds have been effectively managed with good agronomic practices such as using tank mixes and/or cultural weed control methods,” he said. “And in all cases, we continue to recommend that farmers use the right rate of glyphosate for the right-sized weed at the right time, as well as additional weed control tools that may be necessary for the weed spectrum on their farm.”

Canada becomes the third country, after the U.S. and Brazil, to see the glyphosate-resistant strain in field crops, Monsanto said. In other countries where it’s appeared, such as China, the Czech Republic and Spain, it’s typically seen along railroad tracks or in orchards.

Glyphosate-resistant giant ragweed was confirmed as Canada’s first such weed in the same region of Ontario in 2008, the company said.

Rigid ryegrass, North America’s first glyphosate-resistant weed, turned up on this continent in 1998, followed by Canada fleabane in 2000.

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