On Crops: Corn, tomatoes, peppers (rarely)
Most of North America, South America and Mexico
The larvae of a nocturnal moth, corn earworms are usually muddy brown caterpillars, although some may be green, yellow, pink, reddish brown or dark gray. The colors of corn earworms tend to be pale when they feed on corn, and darker when they feed on tomatoes.
Corn earworm moths lay eggs on corn silks, and the larvae hatch and burrow into the tops of the corn ears, sometimes this pest can feed into the middle of the ear as well. On tomatoes, corn earworms feed on both the foliage and the fruit, and typically make a round hole, feed, and the exit and move on to damage more fruits.
Many gardeners use eyedroppers or small squirt bottles to apply a few drops of canola or olive oil into the corn ear tips as soon as the silks emerge. Bt (a biological pesticide) can also be used the same way. One of the best ways to prevent corn earworms are to experiment with varieties and planting dates to find the best combination to escape earworm damage all together. Corn varieties with tight ear tips naturally resist corn earworms.
Little can be done once corn is infested beyond popping off the damaged ear tips and composting them. When these pests behave as tomato fruitworms late in the season, Bt can bring them under control.
Vigorous midseason sweet corn varieties with tight husks naturally resist earworm infestation. In small plantings, you can open the end of an immature ear, remove the corn earworms with a tweezers, and secure the husks back in place at the tip with a clothespin.