Daniel Stephenson, Copes, Josh | 6/28/2017 7:23:03 PM
Palmer amaranth and common waterhemp are extremely troublesome weeds in corn, cotton and soybean. They have the potential to substantially reduce crop yield and harvesting efficiency. Glyphosate-resistant Palmer amaranth and common waterhemp were documented in Louisiana in 2010 and 2015, respectively. Currently, Palmer amaranth has spread to essentially all crop-producing parishes in Louisiana, while glyphosate-resistant common waterhemp has only been documented in two parishes. Utilization of herbicides with differing modes of action (how they kill) for soil residual activity is vital for management of these two pigweed species. In addition, these herbicides typically need to be applied multiple times during the growing season. It is very important to control glyphosate-resistant Palmer amaranth and common waterhemp at germination or before they reach 3 inches in height. Timely applications are crucial because control with many herbicides is poor if they are applied after glyphosate-resistant Palmer amaranth height is taller than 3 inches.
The LSU AgCenter and the LSU College of Agriculture