Waterhemp continues to be one of the most troublesome weeds in Illinois soybean production, with new cases of resistance making management even more difficult. While past research has helped guide strategies for glyphosate resistance, less is known about how to slow the spread of nontarget-site resistance. By identifying which management practices—such as crop rotation, herbicide mixtures, tillage, or cover crops—are most effective, this project will give farmers science-based recommendations to preserve herbicide effectiveness, protect yields, and keep waterhemp in check.

• Nontarget-site resistance (NTSR) in waterhemp is the greatest challenge to weed control today.
• Unlike target-site resistance, NTSR can evolve in multiple ways and spread quickly, making herbicides less effective.
• Farmers are already seeing more cases of resistance to Group 27 herbicides, due entirely to NTSR.
• Without better understanding, current weed control tools could fail faster.
• This project builds on earlier landmark research in glyphosate resistance but now targets the more unpredictable threat of NTSR.

• This project will study nearly 150 fields in Illinois and analyze 10 years of management records to better understand resistance.
• It will identify which practices—such as crop rotation, herbicide mixtures, tillage, and cover crops—are most effective at slowing nontarget-site resistance.
• Farmers will receive practical, data-driven recommendations they can use to preserve the effectiveness of herbicides.
• The results will help protect soybean yields, reduce costly yield losses, and support long-term, sustainable waterhemp management.

• Dr. Patrick Tranel, Ainsworth Professor & Associate Head, University of Illinois Urbana-Champaign
• Dr. Aaron Hager, Professor & Extension Weed Science Specialist, University of Illinois Urbana-Champaign
• Dr. Adam Davis, Professor and Crop Sciences Department Head, University of Illinois Urbana-Champaign

• East Central Illinois

Dr. Patrick Tranel
Ainsworth Professor & Associate Head
University of Illinois Urbana-Champaign
217-333-1531
tranel@illinois.edu