Growers should scout corn and soybean fields for Palmer amaranth. This weed is making its way to Northwest Missouri and may be found in the Missouri River bottom. An Extension agronomist recently found Palmer amaranth in Andrew County near Amazonia on the Missouri River bottom.
Palmer amaranth has both male and female plants which causes outcrossing. This gives the weed the ability to quickly spread.
Correct identification and aggressive management of this weed species, once identified, is important. The leaf shape is wide to ovate compared to long, linear leaves of water-hemp. Secondly, the petiole is the stem like structure that connects the leaf to the main stem. Older leaves of Palmer amaranth will be as long or longer than the leaf itself. Take a leaf and petiole off the plant and bend the petiole back over the leaf to compare the petiole and leaf lengths. This is the most consistent method of identification of this weed species.
Once Palmer has been identified, develop a plan to reduce the completion with crops then prevent all plants from going to seed. Avoid spreading seed to other fields and areas.
For more information, contact Wayne Flanary at 660-446-3724 or Kurt Nagel at 816-776-6961, Extension Agronomists, University of Missouri Extension.