Mark VanGessel, Extension Weed Specialist; firstname.lastname@example.org
Some corn fields have to be replanted and killing the existing corn can be challenging. In general, killing corn before it has 2 to 3 collars is difficult because the growing point is below the ground. In a multi-site trial conducted a few years ago, paraquat plus a triazine herbicide (metribuzin or atrazine) was more effective than paraquat by itself. When paraquat plus a triazine was applied to 2 to 3-inch tall corn, control ranged from 67% to 98%. However, when the corn was allowed to reach at least 5 inches tall, control was at least 95% at all six sites. Select Max applied 2 to 3-inch tall corn, averaged 81% control, but at the taller stage, control was not as good as the paraquat treatments. Select Max also requires at least a 6-day period between application and replanting corn.
So, you will need to balance how quickly you want to replant your corn with effectiveness of the herbicide treatments. Applying paraquat plus atrazine (or metribuzin) to 5-inch tall corn was the best option for effective kill.