Many experts recommend in-season overlapping herbicide residuals for season-long control of waterhemp. However, this concept has not been explored by breaking out the residuals to fall-applied, followed by the second residual at soybean planting. This research will bridge that gap and provide information on the effectiveness of fall-applied residuals on waterhemp at planting, and determine the in-season benefit of layered fall applications followed by spring residuals compared to fall or spring applications alone. The research will determine effectiveness of this use pattern on later-emerging weeds to determine the benefit from the practice already in use by some farmers for early emerging weeds.
The objective of this project is to determine the effectiveness of flumioxazin (Valor) and pyroxasulfone (Zidua) on waterhemp when applied only in the fall, only in the spring, or as a layered fall followed by spring application. This research could determine how these use patterns will control waterhemp across the North Central region. Research will be conducted in four northern states, where the practice of fall herbicide applications for residual control in the spring is already being used; and three southern states, along the Interstate 70 corridor, that typically experience warmer winters and have a higher risk of residual degradation prior to spring soybean planting.
With pyroxasulfone coming off patent, it will become more affordable to use. Farmers will have increased interest in fall-applied herbicides to control spring weeds. This research will help to determine if applying additional residual in the spring provides an added benefit over residual herbicides applied in either the fall or spring. This use pattern could help reduce early spring weed emergence, when sprayers are unable to enter fields, and could be a method for residual herbicides on early planted soybeans.