Postemergence Options for Palmer Amaranth Control in Corn

Mark VanGessel, Extension Weed Specialist;

The recent rains in many areas will have moved many of the soil-applied herbicides out of the top one to two inches of soil. As a result, there may be a number of fields requiring postemergence treatments.

Postemergence control of Palmer amaranth requires an effective herbicide to be applied to small (3-inches or shorter) Palmer amaranth plants and often requires a herbicide that provides residual control. Emerged Palmer amaranth control in corn can be achieved with a Group 27 herbicide plus atrazine. These herbicides include mesotrione (active ingredient in Callisto and Halex GT), topramezone (Impact or Armezon), and tembotrione (Laudis, Capreno, DiFlexx Duo). All of the Group 27 herbicides should include atrazine, so these applications need to be applied before the corn is 12 inches tall. All of the Group 27 herbicides can provide 2 to 4 weeks of residual control, depending on rates and soil texture.

Liberty is an option with Liberty Link corn. Dicamba will control small Palmer amaranth in areas where it is appropriate to use it, this includes Status and Diflexx. Liberty and dicamba do not provide residual control and should be tankmixed with atrazine or a product like Dual or Harness, or Zidua provide residual control. Be sure to check the label for maximum corn size with any herbicide applied postemergence.