Corn Earworm

Corn earworms and tomato fruitworms damage sweet corn, tomatoes, peppers, and beans.

Caterpillars are up to 1 inch long and can vary in color from yellow, green, brown, or reddish. Caterpillars usually have two broad, dark strips on the sides of their bodies near the top, and a light-yellow stripe on their sides near the bottom of their bodies. Caterpillars will often also have two narrow dark stripes on the tops of their bodies.

The adult moths are also variable in color. The front pair of wings are usually yellowish-brown with a small dark spot in the middle. The front wings may also have a dark band near the wingtip. The hind wings are creamy-white near the body and black towards the tips. The wings span is around 1 1/2 inch.


Damage Caused by Corn Earworms and Tomato Fruitworms

Caterpillars attack sweet corn, tomato, peppers, beans, and other vegetables.

  • Sweet corn: Eggs are laid singly on green corn silk. Caterpillars move into the ear and will feed on the kernels, silk, and corncob from the tip downwards, leaving a mass of brown fecal matter
  • Tomatoes and peppers: Eggs are laid singly on the younger leaves and around the developing fruit. Caterpillars bore into and feed on fruit near the cap eventually exiting through a hole 1/4 inch in diameter.
  • Beans: They will feed on the leaves and burrow into the pods as well.


Life Cycle of the Corn Earworm

There are several generations per year. In some portions of the state, the insect overwinters as a pupa in the soil. They do not overwinter in northern Illinois. The adults migrate from the southern parts of the state in early spring. Adults also migrate into Illinois from the south on summer storm fronts. Yellowish eggs are laid singly on green corn silks and tomato leaves.


Management of Corn Earworms

Gardeners: Corn plants can be sprayed with an insecticide once ears begin to silk every 2-5 days (depending on product being used) until silks are brown. In Northern Illinois, corn harvested by the end of July usually does not have damage.

Fruitworms usually damage less than 5% of the tomato crop, so treatment may not be justified. Pesticides can be applied to late-maturing tomatoes at 4-10 day intervals (depending on product being used) from the small fruit stage onwards.


Commercial: Use pheromone-baited cone traps to monitor for the presence of moths.

For fresh-market sweet corn, if traps are capturing corn earworm moths, treat at 2- to 5-day intervals, from first silk until 90% or more of the silks are brown. For processing corn, if pheromone traps are catching more than ten moths per trap per night, treat at three- to six-day intervals, from first silk until 90% of the silks are brown.

Treat to control tomato fruitworm when tomatoes are fruiting and pheromone traps capture twenty or more moths per night. Treatment may be delayed if no eggs are present on the leaves. Moths deposit few eggs in tomatoes if nearby corn is silking.

Beans should be watched from bud stage until about one week before harvest.

Contact your county Extension office for current pesticide controls.