Federal scientists have confirmed the first case of a so-called 'super weed' in Western Canada.

Agriculture and Agri-Food Canada scientists in August found kochia in three fields in southern Alberta. The weeds were resistant to glyphosate, the active chemical in the world's top-selling herbicide, Roundup, which is made by Monsanto.

Monsanto Canada announced the confirmation on its website Wednesday.

Glyphosate resistant weeds mean higher weed control costs and lower crop yields for farmers.

Other super weeds found in Ontario

Kochia populations resistant to glyphosate have previously been confirmed in Kansas, Colorado and Nebraska.

There are also suspected cases being investigated in North Dakota, South Dakota and Montana.

Two other resistant weed species had previously been found in Canada, both in southwestern Ontario. Giant ragweed was confirmed in 2009 and Canada fleabane was confirmed in 2011.

This is the first time resistant weeds have been confirmed in Canada's most important grain and canola growing region.

What makes the Alberta case different is that the kochia does not appear to have developed in a field where producers regularly grew crops that had been genetically modified to tolerate Roundup.

Canada is the biggest exporter of spring wheat, canola, durum and malting barley in the world.