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News Archive - Summer 2009

U of G Researchers Find Suspected Glyphosate Resistant Weed

F. TardifMay 07, 2009 - News Release

Researchers at the University of Guelph's Ontario Agricultural College have found a giant ragweed biotype that is showing resistance to the popular herbicide glyphosate. The plants are able to survive glyphosate use rates that kill normal susceptible weeds.

"We've seen a difference in control of this giant ragweed biotype than what is normally expected when sprayed with glyphosate," said Prof. François Tardif of the Department of Plant Agriculture. The plants were still able to grow after an application of the herbicide at recommended levels, whereas susceptible ragweed did not survive.

"Glyphosate has become a tool of choice for the control for many weeds, so the appearance of a glyphosate resistant population can complicate management for growers," added Peter Sikkema, a plant agriculture professor at the University's Ridgetown Campus, who conducted the research with Tardif.

Currently, no weeds in Canada have been confirmed as resistant to glyphosate, the most often used herbicide globally. But in other countries around the world, 15 weed species – including giant ragweed – have been confirmed as resistant to glyphosate. Eight of those species are in the United States.

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