Keep dreaded palmer amaranth at bay

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By David Harrison

Palmer amaranth (Amaranthus palmeri) is another weed that LaRue County farmers will likely encounter before too long as it continues to march across Kentucky. Initially this weed was present primarily in the west end of the state, but has been reported (at least in a single field) in counties that border, or are near, LaRue County.

These sightings would indicate that Palmer amaranth is a growing threat to grain crop production in LaRue County.

How this weed specifically arrived on the farms in other counties is yet to be determined. However, it is known that the seed of Palmer amaranth can be introduced when cotton hulls are fed to livestock and the subsequent manure spread on crop fields. Other possible routes for introduction can be from transport of farm equipment and trucks hauling supplies from the south where Palmer amaranth is widespread.

Palmer amaranth is a species of pigweed. Young palmer amaranth plants can look similar to other pigweed species. As it grows, more differences occur. Palmer amaranth has smooth stems and leaves, no hairs on the plant, and longer leaf petioles than other types of pigweeds, for example. There are also male and female plants. If farmers notice a new pigweed type weed that has this general appearance you may need to confirm its identification.

After Palmer amaranth becomes established it can be very competitive and very difficult to control. Many populations of this plant are known to be resistant to glyphosate.

Crop producers need to be on the lookout for this weed in both soybean and corn fields. If palmer amaranth is found, efforts need to be made to prevent its spread. Contact the extension office for assistance or to report its occurrence. Catching the presence of this weed before large populations become established in crop fields can help minimize a larger economic impact in the future.