Research Objective
To conduct a baseline survey of PPO inhibitor-resistant kochia in Western Canada.
Objective 4To work toward determining the mechanisms of auxinic herbicide resistance in kochia in Western Canada.
To conduct a baseline survey of PPO inhibitor-resistant kochia in Western Canada; to assess kochia populations for cross-resistance to other synthetic auxin herbicides, herbicide mixtures, and usage windows; to assess the efficacy of a potential “new” (old) herbicide, dichlorprop, for management of auxinic herbicide-resistant kochia; to work toward determining the mechanisms of auxinic herbicide resistance in kochia in Western Canada; to determine whether dicamba or fluroxypyr resistance traits in kochia confer fitness penalties.
The 2021/22 fiscal year was the first year of this 4-year project that aims to further our understanding of synthetic auxin resistance in Canadian kochia populations, and to proactively assess kochia populations for other types of resistance at risk of selection. In the 2021/22 fiscal year, the majority of research focused on a proactive survey of Manitoba assessing the potential for group 14 resistance in kochia and studies assessing cross-resistance to dicamba and fluroxypyr in Alberta kochia populations.
The 2022/23 fiscal year was the second year of this four-year project that aims to further our understanding of synthetic auxin resistance in Canadian kochia populations, and to proactively assess kochia populations for other types of resistance at risk of selection. In 2022/23 we discovered what is likely the first case of PPO inhibitor-resistant kochia globally in a grower-submitted sample from Saskatchewan. However, this type of resistance is not widespread because it was not present in 772 survey samples screened from the Canadian prairies to-date. Among 314 kochia samples collected from Alberta in 2021, we found that 14% were resistant to dicamba but not fluroxypyr, 30% were resistant to fluroxypyr but not dicamba, and 14% were resistant to both auxinic herbicides. It is therefore more likely that a kochia population in Alberta is resistant to one of these active ingredients and not the other than it is to be resistant to both. Isobole analyses discovered that mixing dicamba and fluroxypyr together resulted in synergistic management of kochia populations that were resistant to one or both of these herbicides when used alone. Therefore, opportunity remains to manage auxinic herbicide resistant kochia using a mixture of dicamba and fluroxypyr. Other research focused on using vegetative cloning to segregate kochia populations into resistant and susceptible lines that will eventually be used to assess fitness penalties after increasing over three generations. Overall, the project remains in good health and continues to provide new information that improves our understanding of auxinic herbicide-resistant kochia and its management.