Giant Ragweed Strain Could Be Resistant To Herbicide

It could be bad news for allergy sufferers, researchers from Guelph's Ontario Agricultural College have found a giant ragweed biotype that has shown resistance to the herbicide glyphosate, surviving rates that kill normal weeds in tests.

The results are still in the preliminary stage researchers are stressing.

"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.

"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.

So far Canada is in the clear from the herbicide resistant weeds but there are eight species confirmed in the United States. Worldwide there are 15 weed species – including giant ragweed – have been confirmed as resistant to glyphosate. The affected giant ragweed population was discovered in Essex County late last year in a small area of a 580-acre field of Roundup Ready soybeans. The strain was only found in one area scientists stress. The University of Guelph reports:

"This is a very serious situation," Sikkema said. "In other jurisdictions, most glyphosate-resistant weeds biotypes have been effectively managed with other herbicides and cultural practices. We’ll continue our research so we can make recommendations to growers on effective control options."