Late-stage European corn borer larvae occasionally tunnel through the softer central tissues of the corn cob. The center of the corn cob may be used by the larva as an overwintering site.
Fourth and fifth-stage larvae commonly tunnel into corn stalks. The tunneling can disrupt the flow of water and nutrients to from the roots to the growing parts of the plant.
This late-stage larva died inside a corn stalk from an infection of Beauveria bassiana, a fungal pathogen. This naturally-occurring disease helps to reduce populations of this insect in corn.
European corn borers develop through five larval stages. A distinguishing feature is that the larva in each stage has a dark head, often black or reddish brown in color. The prothoracic shield (neck) may or may not be dark.
Larvae tunneling into a corn stalk often expel frass (sawdust-like fecal material) from their tunnels. The frass may accumulate on the leaf below the tunnel entrance.
