The University of Wisconsin Agronomy Department recommends using Crossbow, Glyphosate, Miletone or Weedmaster to control biennial and Canada thistles. Using cultural practices such as controlled grazing, weed-free manures and crop rotation also will help eliminate these weeds.
About this Author
Aileen Clarkson has been an award-winning editor and reporter for more than 20 years, earning three awards from the Society of Professional Journalists. She has worked for several newspapers, including "The Washington Post" and "The Charlotte Observer." Clarkson earned a Bachelor of Arts in journalism from the University of Florida.