Soybean response to simulated dicamba/diflufenzopyr drift followed by postemergence herbicides

Five field experiments were conducted in 2007 to determine the effect of simulated dicamba/diflufenzopyr drift followed by postemergence applications of chlorimuron-ethyl, imazethapyr or bentazon on soybean (Glycine max Merr.) crop injury, dry weight, height and yield. In the absence of a postemergence herbicide, as the dose of simulated dicamba/diflufenzopyr increased there was an increase in soybean injury and a decrease in dry weight, height and yield. The application of registered postemergence herbicides following simulated dicamba/diflufenzopyr drift resulted in a synergistic increase in crop injury in some environments. There was no synergistic response in respect to dry weight and height when simulated drift was followed by postemergence herbicides. A synergistic yield response was observed with yield being decreased 4–7% more than expected due to simulated dicamba/diflufenzopyr drift followed by the application of chlorimuron-ethyl. No synergistic yield response was observed for dicamba/diflufenzopyr drift followed by either imazethapyr or bentazon.