Q: Which formulation of 2,4-D should be used for fall herbicide applications?
A: The ester formulation is relatively more effective biologically and likely to provide better weed control in the fall, but it's also more volatile. The amine (salt) formulation would be preferred for spring burndown application, particularly if sensitive crops are in the vicinity.
Q: Which herbicides can be tank-mixed with 2,4-D for fall weed control?
A: Some commonly used tank-mix partners are dicamba (Clarity/Banvel), Sharpen, Gramoxone, and Valor.
Tank-mixing them will improve the weed control spectrum of 2,4-D. If grass weeds are present, growers can tank-mix glyphosate; however, if grass weeds are not present, I don’t recommend using glyphosate. It's widely used during the crop season and we already have six weeds in Nebraska resistant to glyphosate. Applying glyphosate in the fall would only add more selection pressure.
Q: Will fall herbicide application provide effective control of summer annual weeds?
A: No. It is highly unlikely that you will get control of summer annual weeds such as pigweeds (common waterhemp, palmer amaranth) with fall herbicide application simply because they start emerging in May and June. If your field has lot of pigweeds, applying an effective pre-emergence herbicides at crop planting will provide better control.