Wisconsin Marestail Herbicide Resistance Screening Project

by Rodrigo Werle (UW-Madison Extension Cropping Systems Weed Scientist)

Marestail (aka horseweed) tends to be a troublesome weed species in no-till cropping systems across the Midwest and this year we received several inquiries regarding poor marestail control in parts of Wisconsin. Thus, we would like to invite Wisconsin farmers, crop consultants, educators and industry representatives that are dealing with this weed to collect seeds this fall from their row crop production fields and submit them to UW-Madison for herbicide resistance screenings (please collect marestail seed samples from fields with consistent infestation levels).

We intend to screen samples in the greenhouse for resistance to glyphosate (Group 9), PPO-inhibitor (e.g., Cobra, Flextar, Cadet; Group 14), ALS-inhibitor (e.g., Pursuit, Classic, FirstRate; Group 2), 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.

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

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