Baseline survey of herbicide resistance in Russian thistle (Salsola tragus L.) finds no resistance in Manitoba
Geddes, C.M., Gulden, R.H., Jones, T., Leeson, J.Y., Pittman, M.M., Sharpe, S.M., Shirriff, S.W., Beckie, H.J. (2022). Baseline survey of herbicide resistance in Russian thistle (Salsola tragus L.) finds no resistance in Manitoba. Canadian Journal of Plant Science, [online] 102(1), 246-249. http://dx.doi.org/10.1139/cjps-2020-0260
Plain language summary
Russian thistle is a tumbleweed that is problematic in the semi-arid regions of the Northern Great Plains. Russian thistle with resistance to group 2 herbicides has been found in Saskatchewan and Alberta, while glyphosate (group 9)-resistant biotypes have been found in western United States bordering Canada. Herbicide-resistant Russian thistle can evade herbicide control and result in significant crop yield losses. A Manitoba survey of Russian thistle populations collected in 2018 found that the Russian thistle collected from Manitoba did not exhibit resistance to herbicide groups 2, 4 or 9. This research suggests that kochia populations in Manitoba remain herbicide-susceptible. This is good news for Manitoba farmers because the herbicides used to manage Russian thistle remain effective in this province.
Recent confirmations of glyphosate-resistant Russian thistle (Salsola tragus L.) in Montana, Washington, and Oregon, warrant greater surveillance of herbicide-resistant Russian thistle in western Canada. A randomized-stratified survey of 315 sites in Manitoba was conducted in 2018 to determine the incidence of herbicide resistance in Russian thistle and other weeds sampled post-harvest. Russian thistle populations were collected from 14 of the 315 sites surveyed. None of these populations exhibited resistance to acetolactate synthase inhibitors (tribenuron/thifensulfuron), synthetic auxins (2,4-D ester or fluroxypyr), or glyphosate. This Manitoba survey of herbicide-resistant Russian thistle serves as a baseline for future surveillance efforts.