Some winter annual weeds are easier to manage in the fall rather than waiting for spring, say researchers from Penn State University Extension.
With small grain sowing happening in earnest this time of year, populations of winter annual weeds will be emerging and can potentially compete with wheat and barley in late fall and early spring potentially reducing yield. If winter annual weeds like common chickweed, henbit, Italian ryegrass, Bromus species, 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 (thifensulfuron + tribenuron) or a similar product is the most broad-spectrum herbicide for broadleaf control, but resistant populations of common chickweed are becoming evident. 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 and others are applied in the fall, recrop restrictions may still prevent seeding next spring, so check a current herbicide label for additional guidelines.