Canada fleabane glyphosate resistance confirmed

Monday, May 2, 2011

by BETTER FARMING STAFF

First came glyphosate resistant giant ragweed. Now Ontario’s farmers will have to prepare for the reality of dealing with glyphosate resistant Canada fleabane.

On Tuesday, Monsanto announced that the weed with the small white and yellow flowers, also known as marestail or horseweed, is the second weed in Ontario to develop resistance to the popular herbicide.

“I hope I don’t have any,” says Henry Denotter, who farms more than 1,500 acres of corn, soybeans and wheat in rotation near Kingsville in Essex County.

Denotter says the announcement doesn’t come as a surprise – the possibility had been discussed throughout the winter at local farm group meetings. And he doubts the weed will pose too much of a problem on his farm because it’s not prevalent in his area. “Giant ragweed is more of a concern,” he says.

Brian Taylor, vice-president and owner of Essex-based Setterington’s farm services, says he hasn’t seen a lot of fleabane in the area his business serves. But anything that has become resistant to glyphosate is a concern in the county. “We’re moving more and more towards Roundup Ready crops as we speak.”

Mark Lawton, Monsanto's Technology Development Lead in Eastern Canada, says the glyphosate resistant form of the weed was found in eight different locations, mostly in the southern portion of the county near Lake Erie.

He says its appearance in the province comes as no surprise but is “a little disappointing, especially for the producers involved.”

He says researchers have been monitoring the resistant weed’s spread in the United States. Because Canada fleabane’s seeds are windborne, the resistant variety will eventually have a broader distribution in Canada “than giant ragweed would have, for example,” Lawton says.

He notes there are chemical products available that will help to control it and crop product companies are working on other solutions and are promoting best management practices. These include using tillage or a burn down herbicide to control weeds early; introducing different modes of herbicide action and ensuring they are applied at the right rate and right time; maintaining a diverse crop rotation; and controlling weeds throughout the season.

In 2010 the company also published a website (www.weedtool.com) to help growers assess the risk of glyphosate resistance occurring on their farm. BF