Matt A. Bahm
Canada thistle (Cirsium arvense) is a perennial weed found in agronomic, as well as natural systems. Herbicides are the most common management prescription for thistle invasions. During the spring of 2006, we implemented a study to test the efficacy of 4 herbicides commonly used for Canada thistle control. Aminopyralid, picloram, clopyralid + triclopyr, and triclopyr + 2,4- D were applied to thistle invaded areas in Kentucky, Indiana, and South Dakota. Control plots ranged from 30 stems/m2 in Kentucky to 58 stems/m2 in South Dakota. All treatments significantly reduced Canada thistle as compared to control plots, while causing little harm to grass species. Aminopyralid was the most effective treatment 1 year after treatment, reducing thistle to <2 stems/m2 at all sites.
Keywords: CANADA THISTLE, CIRSIUM ARVENSE, CONTROL, HERBICIDE
