With many areas across the Corn Belt looking at the possibility of an early harvest, bare fields could be breeding grounds for fall weeds. Before combines hit the dirt and time runs thin, plan your method of attack against problem weeds. “The practice of applying herbicides after crop harvest has increased in Illinois over the past few seasons,” said Aaron Hager, University of Illinois Extension weed scientist in a recent news release. “Herbicides applied in the fall often can provide improved control of many winter annual weed species compared with similar applications made in the spring.” Before you create a herbicide mix, make sure you know what weeds are common in your area. For Channel Seedsman Kyle Allen, of Hawkpoint, Mo., marestail is the biggest problem.
“Our main goal in the fall is to control marestail,” Allen says. “We know we can control it best with a fall spray application because that’s when it germinates. I suggest farmers use as many effective modes of action as possible—at the right cost.” In his area 2,4-D, Roundup and Sencor are effective. In Illinois, Hager says to use higher application rates of products such as 2,4-D. “[Applications] in the fall almost always results in better control at planting compared with targeting overwintered and often larger plants with lower rates of 2,4-D in the spring,” Hager said. It’s also important to consider whether to use a soil-residual herbicide. “Delaying the herbicide application until later in the fall [say, mid-November] often diminishes the necessity of a soil-residual herbicide since most of the winter annual weeds have emerged and can be controlled with non-residual herbicides,” Hager explained. If you’re concerned about the size weeds might reach by November, consult with herbicide labels or your chemical retailer to make sure they’re still effective. When using a residual herbicide, check plant-back restrictions, Allen says. In some cases, certain herbicides could damage future crops. “Work alongside your local chem retailer or agronomist to line up the best possible residual on the crop you’ll be planning in 2019.”