Waterhemp continued to be one of the most problematic weeds for Illinois farmers in 2020. WinField United agronomist Jason Haegele says the weed has been especially troublesome for soybean growers.

Haegele notes that two major factors contributed to waterhemp challenges this year. The first was herbicide resistance, which Illinois waterhemp populations have developed over time. Additional in-season dicamba restrictions also made it difficult to achieve timely control of waterhemp with postemergence herbicide applications in 2020. Many farmers struggled to find effective waterhemp control options in soybeans due to the temporary cessation of dicamba applications in June.

Haegele says that farmers who relied heavily on postemergence herbicides for weed control may not have gotten the results they were hoping for. Building a solid preemergence weed control plan that includes layering residual herbicides will be key to managing waterhemp in 2021.

Dicamba regulations will also continue to impact weed control in 2021. The dicamba application cutoff date in Illinois was June 20 in 2020, and the new federal label’s 2021 cutoff date is June 30. Coupled with other label requirements that specify allowable wind speeds, buffer distances and application timing relative to expected rainfall, the window of opportunity for making postemergence dicamba applications will be limited. Being prepared with a contingency plan for postemergence weed control on dicamba-tolerant soybean acres will be critical.