Recognizing corn earworms

Several people have inquired about the caterpillars now feeding inside corn whorls. The likely candidates are stalk borers, European corn borers, or corn earworms. Armyworms feed on the outside of the whorl and fall armyworms have not yet arrived. Specimens that have been sent to me, however, have all been corn earworms. Correct identification of any insect is necessary before a wise pest management decision can be made.

Young corn earworm.

Corn earworms are probably the most difficult of corn caterpillars to correctly identify. They come in a multitude of colors, including red, brown, green, yellow, and pink with white stripes. The characters that I use in the field are

  1. four pairs of prolegs on the abdomen;
  2. cone-shaped tubercles (warts) with dark hairs; and
  3. head freckled, often with orange but occasionally green or a darker color.

Corn earworms feed in the whorl but do not tunnel into the stalk like European corn borers or stalk borers. They are seldom an economic pest in field corn.

See also the Simple pictorial key for identifying some common late-instar caterpillars found on corn.

This article originally appeared on page 153 of the IC-486(19) -- July 23, 2001 issue.

Updated 07/22/2001 - 1:00pm