Rapid increase in glyphosate resistance and confirmation of dicamba-resistant kochia (Bassia scoparia) in Manitoba

Abstract

Increased adoption of crops with stacked traits conferring glyphosate and dicamba resistance, and recent confirmation of kochia [Bassia scoparia (L.) A.J. Scott] biotypes resistant to these herbicides in Alberta and Saskatchewan, warrant surveillance of herbicide-resistant kochia in Manitoba. A randomized-stratified survey of 315 sites in Manitoba was conducted in the fall of 2018. Overall, 58% of the kochia populations tested were glyphosate-resistant, while 1% were dicamba-resistant. This survey documents rapid increase in glyphosate-resistant kochia over a five-year time frame, and also confirms the first cases of kochia in Manitoba with dicamba resistance alone and in combination with glyphosate resistance.