Canola volunteers with resistance to more than one herbicide are probably more common than you think. If you’ve only grown Liberty Link canola, for example, but your pre-seed glyphosate treatment doesn’t seem to be getting all the volunteers, the volunteers may have resistance to both Liberty and glyphosate.
With so many canola acres, the opportunity for some cross pollination from field to field increases and can lead to stacked volunteers (volunteers with tolerance to more than one herbicide chemistry). Also, while seed purity standards are high, the rules do allow some tolerance for “adventitious presence”, or off-types which may include seed with different herbicide tolerance.
When spraying out volunteers or removing a poorly established canola crop, add a broadleaf chemistry to the tank. CleanStart and Amitrol 240 are registered for use ahead of canola, and provide an alternative to straight glyphosate. Growers have many other options to use ahead of cereals. Volunteer canola management works best when tackled in all crops in the rotation.