Late-season weeds in wheat continue to be a problem in many parts of Kansas as a result of the thin wheat crop and continued wet weather. No one wants to spend extra money on a below-average crop, but these weeds can make harvest very difficult. However, there continues to be a lot of questions about which herbicides are approved and the use guidelines and restrictions for preharvest treatments in wheat.
One herbicide that is sometimes mentioned as a preharvest treatment is paraquat. Paraquat is not labeled for preharvest treatment in wheat. Application of paraquat to wheat is an illegal treatment and can result in a quarantine and destruction of the harvested grain, along with severe fines.
Below are the various herbicide options producers can use as pre-harvest aids in wheat. There are differences in how quickly they act to control the weeds, the interval requirement between application and grain harvest, and the level or length of control achieved. All of them will require good thorough spray coverage to be most effective.