Identification of Palmer amaranth in Illinois

Palmer amaranth continued to expand its presence in Illinois during 2014. Palmer amaranth populations have been confirmed in counties colored orange or blue in Figure 1; orange designates glyphosate-resistant populations are present in these counties. It should be neither construed nor assumed that Palmer amaranth populations occur only in the counties colored on this map. It is altogether likely that Palmer amaranth populations are present in many other counties. Emerged Palmer amaranth plants were observed on May 7 at our field research location west of Kankakee.

Palmer amaranth distribution May 2015

Once again, we will assist Illinois weed management practitioners in accurately identifying Palmer amaranth. We will accept tissue samples from suspected Palmer amaranth plants and use tools of molecular biology to identify whether the sample is Palmer amaranth or another species of Amaranthus. Information on how to collect and submit tissue samples from suspected Palmer amaranth plants can be found in the “Palmer Amaranth Identification” form that accompanies this article. Please download this form, provide as much information as possible, and submit it along with the tissue samples to the address listed at the top of the form.

Also, please note that screening for herbicide resistance in waterhemp is now a service offered by the University of Illinois Plant Clinic and requires a different sample submission form.  More details about sample submission for herbicide resistance screening is available at:

Palmer Amaranth Identification