Weed treatments applied in the fall following harvest are a great way to gain control over winter annual weeds such as Marestail, Henbit, Dandelion, Shepherdspurse, and Tansymustard. Fall burndown programs - which can be applied from mid-September to early December if weather permits - can achieve the same weed control at a lower cost than herbicides applied in spring.
Many factors can alter weed response. Growing conditions, growth stage of target weeds, temperature, soil type, soil pH, organic matter, and rate of the herbicide used can contribute to the level of weed control achieved. Using the highest labeled rates of herbicides in the fall gives the most reliable weed control. Applying herbicides in the fall reduces the chance of off-target damage as the season’s crops are mature and/or have been harvested.
Despite these benefits, not all farmers take advantage of burndown programs. Here are some of the most common arguments made against fall burndown applications:
Argument 1: “With commodity prices so low, we cannot afford to spend the money to control weeds for the following year.”
Answer: Fall herbicide applications are generally less expensive compared to most herbicide costs in the spring. Without a burndown application in the fall, herbicides applied in the spring may not only cost more but also show lower levels of weed control because the weeds were allowed to grow all winter when environmental conditions allowed.
Argument 2: “My weeds are small and populations seem low so I will wait and treat my weeds in the spring.”
Answer: Small weeds are considerably easier to control than large weeds and the populations of most weed species will normally increase over the winter months. Waiting to spray the weeds in the spring allows the weeds to steal valuable soil moisture and nutrients from the next season's crop.
Argument 3: “I don’t have time to do the herbicide application.”
Answer: It does not take much time to make an application and will pay big dividends next spring. Custom applications also offer a good ROI.
If you had winter annual weeds in your fields last year you can be assured you will have the same winter annual weeds in your fields this year. If you struggle to control winter annual weeds year over year, fall burndown applications might be a good fit for your operation.