The best way to control horseweed is to kill it with your burndown herbicide application. Typically, either dicamba or 2,4-D is tank mixed with glyphosate during the burndown application. These products will severely injure or kill cotton if not applied properly. When using dicamba, a minimum of 1 inch of rainfall and a 21-day waiting period per 8 ounces used is required before cotton can be planted. A 30-day waiting period between application and cotton planting is required for 2,4-D.
The application of a preemergence herbicide at planting will provide residual control of horseweed by preventing later emerging seedlings from becoming established.
