With a spring like this, we are starting to get questions about poor corn emergence and replanting issues. There are times when corn (previously planted or volunteer) must be removed from a field with the intention of replanting a corn crop. Tillage is one effective method, but it is not appropriate in no-tillage situations. The use of glyphosate is highly effective for non–Roundup Ready corn.
But the challenge is in removing Roundup Ready hybrids. There are limited herbicides to consistently kill small corn plants. Gramoxone SL, Liberty, and Select are three products that have shown the most activity. Research conducted in this region with Gramoxone and Select demonstrated that Select was the most effective for corn 2 to 3 inches tall. For taller corn (4 to 6 inches tall), Gramoxone in combination with a photosystem II–inhibiting herbicide (metribuzin, Lorox, or atrazine) was the most effective. Liberty is a third option, but it will not control LibertyLink hybrids. So here is what we suggest:
- Select Max: up to 6 oz of Select Max with a non-ionic surfactant at 0.25% v/v plus AMS at 2.5 to 4 lb/A. Do not use a COC or MSO. Wait a minimum of 6 days from time of application until planting corn due to the risk of crop injury. (Select Max will also control corn hybrids containing Roundup Ready and LibertyLink stacked traits.)
- Gramoxone SL 2.0: 3 to 4.5 pt/A (2 to 2.7 pints of 3.0 SL formulation) in combination with metribuzin (4 to 6 oz/A), Lorox (1 pt/A), or atrazine (1 lb/A). These photosystem II inhibitors are not added to control the corn but used to slow down the Gramoxone activity, which helps provide more consistent control.
- Liberty 280: 22 to 29 fl oz/A Liberty has not been as consistent for control of corn as Gramoxone and will not control varieties with LibertyLink traits. However, higher rates of Liberty (32 to 43 fl oz) should provide more consistent control.