Waterhemp populations from soybean fields across Illinois are being collected and screened to better understand the level of resistance to Group 15 herbicides. Results will be used to provide farmers with recommendations on how best to incorporate these herbicides into integrated weed management programs. Resistant populations will be used in subsequent research to identify the gene(s) conferring the metabolism-based resistance.

• Waterhemp populations in Illinois have evolved resistance to herbicides from more site-of-action-groups than any other weed species.
• Noticing potential resistance to this group of chemistry is more difficult because they are residual herbicides, and resistance results in shorter length of control rather than lack of control common with other classes of chemistry.
• In addition, fields can contain waterhemp populations resistant to herbicides from multiple herbicide groups, with individual plants carrying genes for resistance to multiple herbicides.

• Understanding the frequency of Group 15-resistant waterhemp will give farmers, their advisors and Illinois Extension the ability to refine integrated weed management recommendations to help slow resistance development in more waterhemp populations.
• Researchers also intend to conduct a genome-wide association study to identify the gene(s) responsible for Group 15 resistance. This data could lead to rapid molecular testing tools for future resistance diagnosis.

• Dr. Aaron Hager, Professor & Weed Science Extension Specialist, UIUC
• Dr. Patrick Tranel, Professor, UIUC
• Travis Wilke, Master’s Student, UIUC

• Waterhemp seeds will be collected from at least 100 locations across the state

Dr. Aaron Hager
Professor & Weed Science Extension Specialist
University of Illinois Urbana-Champaign (UIUC)
217-333-9646
hager@illinois.edu