Methods to Control Volunteer Roundup Ready or Glyphosate-Tolerant Corn in a Corn Replant Situation
Although we don’t have near the issues with replanting this year like we have had the past two years (yet……), we have had a few calls on corn replant decision in fields that were planted initially to Roundup Ready corn. There are four legal options to kill an existing stand of Roundup Ready or GT corn in a replant situation – tillage, Select Max, Gramoxone + Sencor, or Ignite.
Our experience has been that tillage is a reliable method for killing the existing stand, and would not have the waiting interval associated with Select Max, but is not desirable for those in a long-term no-till situation. Select Max is labeled for volunteer corn control in a corn replant situation, and is very effective on volunteer corn that is tolerant to glyphosate (Roundup Ready) or glufosinate (Liberty Link) as well. But you cannot plant until 6 days after the field is treated with Select Max. The directions on the label indicate that up to 6 fl oz/A can be applied and NIS at 0.25% and AMS at 2.5 to 4 lb/A should be used as the spray additives. Apply to corn that is 12 inches or less. Avoid overlapping the boom for overlaps may result in rates that can cause excessive crop injury. Another option for controlling corn that is both Roundup Ready and Liberty Link is to use Gramoxone (2-3 pt/A) + Sencor (4-6 oz/A). Application of Gramoxone alone, without the addition of Sencor, is likely to be less effective. Corn that has advanced past the V3 growth stage will generally be more difficult to control.
Another option for controlling volunteer corn that is just tolerant to glyphosate (Roundup Ready), and not tolerant to Ignite (Liberty Link) would to plant Liberty Link corn and use Ignite herbicide. Use the full labeled rate of Ignite (22 oz/A) on volunteer corn 6 to 12 inches tall. Apply with 1.5 to 3 lbs/A of AMS. Ignite can provide somewhat variable control of volunteer corn, but it has the potential to suppress it to the point of reducing it’s competiveness. In addition, sequential treatments can be used if needed.