Mary Burrows, Montana State University, Bugwood.org
Dense populations of winter annual weeds can compete with wheat and barley in late fall and early spring and slow the rate of crop development potentially reducing yield. If winter annual weeds like common chickweed, henbit, winter annual grasses, and others emerge with the small grain and are left unchecked, the potential impact on yield could be great. In these situations, it may make sense to kill these weeds in the fall rather than early spring. Harmony Extra is the most broad spectrum herbicide for broadleaf control, but resistant populations of common chickweed are becoming evident in parts of the state. In addition, there are several herbicides labeled for grass control in wheat and fall is typically the best time to make an application. Make sure to include the necessary spray adjuvants. Remember that cool (less than 50 F) cloudy days can reduce herbicide activity. Also, if you plan to frost-seed or drill a companion crop such as red clover in early spring it may be best to make a fall herbicide application to avoid certain issues with herbicide residuals affecting their establishment. However, even if products such as PowerFlex HL, Osprey, Glory and others are applied in the fall, their recrop restrictions still prevent seeding next spring. The following table summarizes some fall herbicide options for small grains. Check a current herbicide label for the latest use information.