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Updated: August 8, 2017
Here are some key distinguishing features of waterhemp and Palmer amaranth. In particular, there is great concern for herbicide resistant Palmer amaranth and waterhemp spreading into our region and on our farms. As seedlings and young plants, they can be difficult to distinguish from our more common redroot and smooth pigweeds. Here are some key distinguishing features:
If you have pigweeds surviving a Post glyphosate herbicide application, that is a tell-tale sign of resistance and you are likely dealing with Palmer amaranth and/or waterhemp. We have a number of newer educational resources available to help manage these problem pigweeds posted on our website.
Palmer amaranth or Amaranthus Palmeri juvenile (Image courtesy of Aaron Hager, Univ of Illinois).
Waterhemp or Amaranthus tuberculatus juvenile. (Image courtesy of Aaron Hager, Univ of Illinois).
Smooth pigweed or Amaranthus hybridus (Image courtesy of Bruce Ackley, Ohio State Universtiy, Bugwood.org)