Insect Pests

When a corn earworm attacks a tomato, it’s called a tomato fruitworm. - Clemson University USDA Cooperative Extension Slide Series, www.insectimages.org

This young corn earworm is enjoying bites of a green bean. The caterpillars often feed in one spot, leave a hole, and move on to another pod. - Clemson University USDA Cooperative Extension Slide Series, www.insectimages.org

Corn earworms secretly eat away inside corn only to be discovered when you shuck the ear. - Clemson University USDA Cooperative Extension Slide Series, www.insectimages.org

If you’ve ever shucked an ear of corn, you’ve probably met a corn earworm, eating its way through an ear and often ruining all or part of it. Earworms are the larvae of moths that appear in the spring. They lay eggs on corn; if corn is not available, they will find tomatoes, beans, and other crops.

When the caterpillars hatch from the eggs, they begin feeding on the leaves of young corn, and later on the silks and in the ears. When corn is not available, they attack tomatoes, boring through the fruit. They also bore into beans, broccoli, cabbage, lettuce, okra, peas, peppers, squash, and pumpkin.

Newly hatched caterpillars are very small with a dark brown to black head but grow quickly into caterpillars that may be yellow, green, or brown, with characteristic longitudinal stripes that are often but not always white. The corn earworm can be hard to identify because it has so many looks.

Once the caterpillars are inside the ears or fruit, they are impossible to control, so you must kill them before they enter. Fortunately, the damage to tomatoes, beans, and other crops is usually not so bad that you can’t just live with it, sacrificing a few fruit or pods to the pests. You can protect corn ears with pyrethrin or Bt spray or dust applied regularly just before the silks appear and continuing until the silks dry. Timing is very important. Check with your local Extension agent for the exact time so that you can be ready.