Postemergence herbicide applications impact Canada thistle control and spring wheat yields

Canada thistle (Cirsium arvense L.) growing in spring wheat (Triticum aestivum) is difficult to control for several reasons. First, it is a perennial weed that has an extensive root system. Second, the cash-crop wheat prevents the use of many chemicals, and third, Canada thistle is becoming resistant to many single action herbicides. The objective of this study was to evaluate the effect of postemergence herbicide applications on Canada thistle control growing in a spring wheat field. Replicated studies conducted in Russia between 2015 and 2017 evaluated the impact of different herbicide mixtures on Canada thistle control. The formulated mixtures of (iodosulfuron/mesosulfuron/antidote mefenpyr-diethyl) mixed with triasulfuron and metsulfuron and triasulfuron + metsulfuron increased wheat yields 48 to 60% and provided the greatest (>85%) Canada thistle suppression in all experiments. Generally, (aminopyralid/florasulam), triasulfuron and (2,4-D/florasulam) provided little control. It can be concluded that in all treatments, the herbicide mixtures did not provide 100% control, and therefore care must be used to prevent the creation of herbicide resistant Canada thistle. © 2019 The author(s).