First-generation larvae feed in the whorl until they are large enough to tunnel into the stalk. Larvae feed in the leaf sheath and husk leaves before tunneling into the stalk. Depending on geography and season, these larvae will either overwinter in the base of the corn plant or pupate in the stalk to begin a third generation. Corn leaf showing shothole feeding and midrib tunneling. First-brood larvae migrate to the whorl of the corn plant after hatching.
Larger borers tunnel into the midribs of leaves and eventually into the stalk.
When attacked, these very small corn plants may be severely damaged. Severed corn stalk from internal girdling of stalk and subsequent breakage. After about two weeks, the larvae migrate down the plant and tunnel into the stalk. Overwintering larvae display a peculiar feeding behavior that can magnify field losses. Larvae migrate down the plant, tunnel into the stalk near the base and begin construction of a hibernation tunnel.