- The best time to spray is any time between the end of harvest and Thanksgiving. Mark Loux, Ph.D., from Ohio State University, says he has even applied into late December and still had good weed control. Once hard freezes start to occur, there is usually a substantial change in certain weeds, such as dandelion and thistle, that renders them less sensitive to herbicides.
- Regardless of even heavy residue left on the fields, herbicides still seem to work. However, it doesn’t hurt to wait a while after harvest to let the residue settle down and the weeds to poke through.
- Don’t overthink fall weed control or spend a ton of money. Keep in mind the primary goal is control of already-emerged weeds. This is hard to accomplish with a single herbicide, but there are a number of relatively low-cost, two-way mixtures that easily achieve this goal.
- There is no advantage to using residual herbicides because almost all of them deteriorate over the winter and fail to provide any control of spring-emerging weeds. Research has repeatedly shown that applying residual herbicides in the fall to get control in spring is a waste of money.
- It doesn’t take a lot of herbicides to control weeds in fall, just the right ones. Consider that fall treatments should comprise no more than about 25 percent of your total herbicide budget, and it can often be accomplished for even less than that.
Courtesy Ohio Soybean Council