From the cab of your combine, it is the perfect time to start thinking about next year’s crop. Fall herbicide applications can be a reliable way to help keep fields clean of those winter annual and perennial weeds that will be tough to control the following spring. 

When determining to do a fall herbicide application, consider the history of the field and plan for the following growing season. 

Scouting

When you’re out harvesting this fall, take a good look at the field for small, germinated weeds. Asses the species, health, and size of the weeds present, making sure they are actively growing and have enough leaf surface to actively take the product in. Questions you may want to consider: What were some of the troublesome weeds throughout the season? Are any of those weed species perennial or winter annuals? 

Winter Annuals

Fall germinating winter annuals are controlled effectively in the fall because the plants are small and susceptible to the herbicide. These weeds will continue to grow through the fall frosts and will resume growth in the early spring. Some examples of tough to control winter annuals include Narrow Leafed Hawksbeard, Prickly Lettuce, and Night Flowering Catchfly. 

 Perennials

In the fall, perennials are sending reserves down to the roots to overwinter and will carry the herbicide to the roots. For optimal control, it is important to ensure there is enough regrowth after being cut at harvest for the herbicide to hit its target. Some common examples of tough to control perennial weeds are Dandelions, Canada Thistle, Horsetail (commonly found around sloughs), and Foxtail Barley. 

Spray Conditions

Optimal weather conditions are preferred for an effective fall herbicide application. Ideally warm fall days, temperatures greater than +10 are when the plants are actively growing. Frost and continuous low temperatures will send the weeds into shut down. Making it best to wait a few days after cold temperatures, assess the health of the weeds, and apply an application only after the weeds start growing again. 

Tank Mixing

Tank mixing is another essential consideration when it comes to fall burn-off. Tank mixing allows for herbicide rotation, especially in instances where there is a presence of resistant weed biotypes that limit herbicide group options in-crop. Although a heavy rate of glyphosate may be a straightforward and cost-effective solution, it is important to incorporate a tank mix partner to get multiple modes of action, ensure effective control and mitigate the chance of resistance. Keep in mind any re-cropping restrictions. Heat LQ, Express and 2,4-D are common tank-mix partners to consider. 

A fall weed control application can reduce the spring workload, get your crop off to a weed-free start, and allow you to get into the field earlier. Contact your local Synergy AG agronomist if you need assistance identifying weed species or creating an optimal fall burn-off plan.