Seed samples from a dozen Canada fleabane infestations in the area were sent to the University of Guelph from growers suspecting resistance to glyphosate (i.e. Roundup). Testing showed farmers were right; most samples were glyphosate resistant.
Professors Peter Sikkema and Francois Tardif, who made the discovery, say glyphosate-resistant Canada fleabane has wind-blown seeds and can spread relatively easily. Currently, they say, it's primarily a focus in no-till crop production systems. Resistant populations have been found in North America since 2000, and are now confirmed in 18 states in the United States, as well as in Brazil, China, Czech Republic and Spain.
"We have seen the presence of glyphosate-resistant Canada fleabane moving north in the past decade so we are not completely surprised that we found this glyphosate-resistant weed in fields in Ontario," Tardif says.
Efforts are underway to develop and communicate management strategies for controlling glyphosate-resistant Canada fleabane.
"If fleabane is a problem, it makes sense to add another effective mode of action to ensure good control," Mike Cowbrough, weed management specialist with the Ontario Ministry of Agriculture, Food and Rural Affair, noted on Twitter earlier this week.
Mark Lawton, Monsanto's technology development lead in Eastern Canada, says glyphosate-resistant weeds have been effectively managed with good agronomic practices such as tank mixes and cultural weed control methods.
He says glyphosate-resistant weed management may include products registered for use for pre-plant/pre-emergent burndown in soybeans (Eragon, FirstRate) and corn (Eragon and Banvel II). Lawton says registered options exist for in-crop control in corn (Banvel II) and soybeans (FirstRate), as well.
Monsanto plans ongoing research with the University of Guelph this summer, which will include a review of other weed management strategies such as Dicamba-tolerant soybeans. However, says Lawton, don't give up on Roundup.
"The effective use of Roundup agricultural herbicides and Roundup Ready crops has continued in areas where glyphosate resistance has occurred," Lawton says. "And in all cases, we continue to recommend that farmers use the right rate of glyphosate for the right sized weed at the right time, as well as additional weed control tools that may be necessary for the weed spectrum on their farm."
