Racing against resistance — managing multiple herbicide-resistant Canada fleabane

Glyphosate-resistant Canada fleabane was first confirmed in Ontario in 2010. Fast-forward thirteen years and the weed now has developed resistance to multiple herbicide groups and can be found in Essex County, bordering Michigan, all the way east to Glengarry County, adjacent to the Quebec border.

University of Guelph weed scientist Dr. Peter Sikkema has been tracking the resistant weed’s movements since it started its march across the province. At the Ontario Agricultural Conference earlier this year, RealAgriculture’s Bernard Tobin asked Sikkema to share his top herbicide control recommendations and best management practices to help farmers control the invading resistant weed.

In this video, Sikkema outlines his recommendations for multiple herbicide resistant Canada fleabane in corn, soybeans and wheat based on his research. In terms of the pre-plant herbicide options for corn, the two herbicides that consistently give the best control are Integrity or Acuron, both providing greater than 95 per cent control of fleabane. (Story continues after the video.)

If growers don’t control the weed before emergence they’ll have to look for in-crop control. “There are really three groups of herbicides that you can use post-emergence in corn,” says  Sikkema. These include a number of Group 5, 6 and 27 herbicides. “That’s really a benefit to Ontario farmers, because you have different herbicides from different herbicide groups that all provide greater than 90 per cent control. And that allows growers to change their herbicide choice and change the herbicide groups so they don’t use the same herbicides with the same mode of action repeatedly.”

When it comes to soybeans, Sikkema says choosing the most effective herbicide really depends on whether growers are planting identity preserved (IP) soybeans or Roundup Ready soybeans. When it comes to IP, growers have to rely on a one-pass, pre-plant program. “In the research that we’ve done, the best way to manage multiple herbicide resistant Canada fleabane and soybean is with a pre-plant burndown of Roundup plus Eragon plus metribuzin.” That three-way mix will deliver 95 per cent or better pre-plant control.

There are also good options for growers who use other programs. Dicamba-based herbicides deliver strong results in Xtend soybeans and Enlist herbicides are effective in E3 soybeans.

For winter wheat, Sikkema says growers have an expanding number of herbicide options. For many years, Infinity was his first recommendation but in 2023 there are more options, including Infinity FX, Pixxaro + MCPA and Lontrel.

In the video, Sikkema discusses how aggressive tillage and cover crops can also play a key role in helping growers manage multiple herbicide-resistant Canada fleabane.

Wake up with RealAgriculture

Subscribe to our daily newsletters to keep you up-to-date with our latest coverage every morning.

Wake up with RealAgriculture