First-stage larvae are so small that they often don’t chew completely through a leaf. Their injury consists of small scrapings on the leaf surface that results in a translucent "window-pane".

Small holes called "shot holes" in newly developing leaves indicate that early-stage European corn borer larvae may be present inside the whorl causing additional injury.

A repeating pattern of small holes in a leaf indicates that early-stage larvae feed on the young developing leaf when it was still rolled up inside the corn whorl.

When larvae reach the third stage, they become large enough to start tunneling. Backlit from the sun, this larva can be seen tunneling into the leaf midrib. Shot holes from earlier injury are to the right of the midrib.

Transgenic corn does not have broken tassels from second generation larvae.

A field with significant tunneling by second generation larvae can have widespread breakage of corn tassels.

Broken tassels, or whole stalks, is an indication of extensive injury from second generation European corn borer larvae.

Broken tassels, or whole stalks, is an indication of extensive injury from second generation European corn borer larvae.

Injury by European corn borer larvae to the tip of a corn ear allows molds to invade the ear and reduce the quality of the grain.

Transgenic corn (right) protects against stalk tunneling by European corn borer larvae. Nontransgenic corn (left and center) can be heavily injured by larvae tunneling into the stalk.