Increasing frequency of multiple herbicide-resistant kochia (Bassia scoparia) in Alberta

Multiple herbicide-resistant kochia [Bassia scoparia (L.) A.J. Scott] is a growing weed management concern for farmers in the Canadian prairies. A randomized-stratified survey of 319 sites in Alberta was conducted in 2021 to determine the frequency and incidence of glyphosate, fluroxypyr, and dicamba resistance in kochia samples four and nine years after the previous rounds of surveys. Kochia samples exhibiting resistance to glyphosate, fluroxypyr, and dicamba were found at 78%, 44%, and 28% of the sites, respectively. Triple herbicide-resistant kochia samples, resistant to acetolactate synthase inhibitors, glyphosate, and at least one synthetic auxin, were found at 45% of the sites.