Glyphosate-resistant kochia in Manitoba

Find out what you need to know about new reports of glyphostate resistance across the Prairies

Kochia is not the first glyphosate-resistant weed in Canada but it is the first in the West. Giant ragweed was the first weed confirmed with glyphosate resistance in Canada. It was discovered in 2008 near Windsor, Ontario. Giant ragweed is an extremely competitive weed — if herbicide control options for giant ragweed are diminished, it can cause significant yield losses.

The second glyphosate-resistant weed discovered in Canada was also in Ontario — Canada fleabane.

Now the first glyphosate-resistant weed has been discovered in the West. Glyphosate-resistant kochia was discovered in 2011 in Alberta, 2013 in Saskatchewan and, to no weed expert’s surprise, in 2014 in Manitoba.

Manitoba resistance

“The only odd thing about finding glyphosate-resistant kochia in Manitoba was where we found it,” says Nasir Shaikh, provincial weed specialist with Manitoba Agriculture, Food and Rural Development. “We expected to find it in the western part of the province where kochia populations are more plentiful, but we found it close to the U.S. border in the Red River Valley where it is not as common.” In the Alberta and Saskatchewan situations, the glyphosate-resistant kochia was found in chemical fallow fields. In Manitoba it was found in fields under annual crops, one in corn and one in soybeans in 2013.

“In the case of the soybean field, the grower sprayed glyphosate on his Roundup Ready soybeans and shortly afterwards noticed kochia was not controlled,” says Shaikh. “He then contacted his local Manitoba Ag rep and he was advised to remove the remaining weeds by hand, which he did.” Shaikh will be working extensively this season to work with and educate growers about glyphosate resistance, glyphosate-resistant kochia and strategies farmers can use now to reduce the likelihood of the problem spreading. He will also be monitoring for spread of the resistant weed with surveys in 2014.

“Farmers will have to increase their attention to utilizing integrated weed management strategies,” says Shaikh. “This means increased attention to herbicide tank mixing, tillage operations, crop and herbicide rotations and field scouting for escapes or uncontrolled patches after spraying.”

Identifying resistance

How will farmers know if glyphosate-resistant kochia is present? “Glyphosate-resistant kochia will present with a range of symptoms,” says Shaikh. “There will be some stunted or roasted plants, some will be curled up, but not dying off and some will just yellow. None will die completely and if seeds are set, they will be glyphosate resistant.” It is therefore very important that farmers scout fields diligently to find patches of kochia that might survive and then get rid of those plants before seed is set.

“Farmers could try another herbicide application with a different herbicide group, but that is dependent on the stage of the crop and the weed,” says Shaikh. “The best and surest bet is to use a tillage operation or hand weed the surviving plants.”

There is a good chance that this is a problem that will spread given the nature of kochia. “I can’t emphasise enough the importance of vigilance,” says Shaikh. “If farmers lose glyphosate as an herbicide option, weed control options are diminished greatly.”

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