With row crop harvest well underway, it is time to start planning fall herbicide applications.
Herbicide applications in late October through November can improve control of difficult winter annual weeds. Fall weed control is associated with warmer soils and easier planting in the spring, however, it is important to remember that fall-applied herbicides may limit your crop options in the spring. Also remember that herbicides should not be applied to frozen ground.
Some of the key herbicides to consider for fall herbicide applications include chlorimuron (Classic, others), flumioxazin (Valor, others), suflentrazone (Spartan, others), and Autumn Super, for residual activity. One thing to keep in mind about residual activity from fall herbicide applications is that weather conditions will influence the length of residual control and the weed emergence patterns. So, even though they provide some residual activity, additional spring application pre-emergence herbicides will likely be needed for season-long weed control.
For burndown activity, glyphosate, 2,4-D or dicamba are good options to consider. Alternatives for grass control include Group 1 herbicides like clethodim (Select, others) or quizalofop (Assure II, others). Alternatives for controlling broadleaf weeds include paraquat (Gramoxone, others) or saflufenacil (Sharpen).
Some key weeds to target with fall herbicide applications are marestail, henbit, dandelion, prickly lettuce, pepperweed, field pansy, and recently-emerged cool-season grasses. When higher rates of herbicides are used in the fall some suppression of early spring-germinating summer annual broadleaf weeds such as kochia, common lambsquarters, wild buckwheat, and Pennsylvania smartweed can be achieved, according to recent research in Kansas.
Marestail is a problem that merits special attention. This weed is classified as a winter annual, but it germinates well into spring and summer, making it even more difficult to manage. Marestail is much easier to control in fall or early spring while it is still in the rosette growth stage.
The use of trade names is for clarity to readers and does not imply endorsement of a particular product, nor does exclusion imply non-approval.
Always consult the herbicide label for the most current use requirements.
For more information on weed control refer to the 2023 Chemical Weed Control for Field Crops, Pastures, Rangeland, and Noncropland. You can find it by typing into your internet browser “Chemical Weed Control Guide, KSU.” Or stop by your local county or district extension office for a paper copy.
Stacy Campbell is a Crop Production Extension agent in the Cottonwood District (which includes Barton and Ellis counties) for K-State Research and Extension. You can contact him by e-mail at [email protected] or by calling 785-628-9430.