Palmer Amaranth Control in Soybeans

Mark VanGessel, Extension Weed Specialist;

In my opinion, successful management of Palmer amaranth is more about when you treat it, rather than what you use. Timing is important, and plants visible above the soybean canopy will not be controlled. Sure you can burn those plants with herbicides, even burn off all the leaves; but that is not controlling them. Controlling Palmer amaranth means the plant is killed, not just injured. Consistently killing plants over 3 inches tall is difficult; killing those plants above the soybean canopy means you got lucky. So does that mean you shouldn’t spray fields with large Palmer amaranth plants? No, because if there are large plants, it usually means there are smaller plants that may be effectively controlled. But those fields with large Palmer amaranth plants need to be walked to pull and remove the surviving plants from the field.