Researchers have made significant strides in screening Illinois waterhemp populations for resistance to Group 15 herbicides. Over the summer, Travis Wilke, a graduate research assistant at the University of Illinois studying under Dr. Aaron Hager, reported that 50 waterhemp samples have been tested using an updated discriminating dose. “This drastic change in efficiency bodes well for completing the remaining screenings in 2025,” said Wilke. 

Since the last update, seeds from 49 females—each from a different population collected last fall—were planted, sprayed, and evaluated against non-treated controls. The team’s greenhouse efficiency increased dramatically, allowing for 36 samples to be tested in just three weeks. However, due to decreasing day lengths and inadequate UV levels, screenings will pause until 2025. Before the greenhouse season ends, the team plans to conduct dose-response experiments to further characterize suspected resistance. 

This summer’s focus on replication and refined techniques led to the best seed germination and consistency to date. Despite some weather-related delays in August due to heat stress, the team’s ability to execute large-scale screenings in a short time marks a significant leap forward for the project. These methods pave the way for highly replicable residual herbicide research in the future. 

The team will analyze data and consider initial results for winter presentations and outreach. 

Learn more about this project and stay tuned for more updates from the 2024 growing season: https://fieldadvisor.org/documenting-group-15-herbicide-resis-in-il-waterhemp/