North Carolina Corn: Don’t Neglect Post-Harvest Pigweed Control

    Palmer Pigweed, Amaranth. Photo: Missouri State University

    Hopefully, by now all cotton fields have been hand-weeded before viable seed were produced.  Hand-weeding is the first step and a big step in weed management for the following season.

    However, there is one more important step that growers can take to further reduce the seedbank of Palmer amaranth.  Neglecting this important step can undo prior efforts to holistically reign in, control, or reduce the seedbank of Palmer amaranth.

    Corn harvest is just around the corner.  Once corn harvest is complete, it is easy to forget about those fields for a while, as harvest of other crops will soon begin following corn harvest.  As corn is generally harvested rather early in the fall (August – September), small plants that were present in the corn can flourish after harvest.  And, new weeds can emerge.

    Harvested corn fields provide no shading of the soil surface (light is necessary for pigweed germination) and there is plenty of time and heat units before a killing frost to allow for seed production of Palmer amaranth.  The photos below illustrate how Palmer amaranth can easily become established after corn harvest, and how well that Palmer amaranth can be controlled with a post-harvest herbicide application.

    The good news is that Palmer amaranth can be controlled well and relatively economically.  A well-timed application of paraquat at 0.75 lb ai/A (3 pt/A of Gramoxone, 2 pt /A of generics) applied prior to seedhead development can effectively control these weeds while significantly reducing the seedbank for the following year.



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