Send in Waterhemp Seeds for Free Herbicide Resistance Screening

Wisconsin Waterhemp Herbicide Resistance Project

by Rodrigo Werle, UW-Madison Extension Cropping Systems Weed Scientist

According to our recent SURVEY, waterhemp has become the most concerning weed in row crop production in Wisconsin. Thus, we invite Wisconsin farmers and agronomists to collect waterhemp seeds this fall from their row crop production fields and submit them to UW-Madison for herbicide resistance screenings (we ask farmers to collect samples from only one of their fields; preferably the one with the most troublesome infestation level).

Common waterhemp

We intend to screen samples in the greenhouse for resistance to glyphosate (Group 9) and also to PPO-inhibitor (e.g., Cobra, Flextar, Cadet; Group 14), ALS-inhibitor (e.g., Pursuit, Classic, FirstRate; Group 2), HPPD-Inhibitor (e.g., Callisto; Group 27), PSII-inhibitor (e.g., Atrazine; Group 5) and Growth Regulator (e.g., dicamba, 2,4-D; Group 4) herbicides. Results will be made available to those who submit the samples after the greenhouse screenings are completed.

There is no cost associated to the herbicide resistance screening. The only cost will be your time to collect the seed samples and mailing them to: Rodrigo Werle, 1575 Linden Drive, Madison, WI 53706.

Please download and print the SEED COLLECTION FORM (PDF file) for information on how to collect the seeds and fill out the information necessary for the project. Please submit the form with the seed sample. Samples will only be included in the herbicide resistance screening if the information requested herein is provided by the farmer/agronomist.

For questions, contact Dr. Rodrigo Werle via e-mail: or phone: 608-262-7130.

We thank the Wisconsin Soybean Marketing Board for providing partial funding to support this project and also those submitting samples.

Here is a short ID video which includes waterhemp.