Corn earworms are a bane to both home gardeners and commercial farmers alike. In fact, they cause more damage to corn crops than any other insect and are found throughout the continental U.S. In addition to corn, corn earworms eat at least 16 other cultivated crops and over 100 wild plants. It is also known as the tomato fruitworm, cotton bollworm, soybean podworm and vetchworm, depending on its preferred food source.
Corn Earworm Identification
Corn earworms are the larvae of the corn earworm moth, a creamy yellow moth found throughout the U.S. Corn earworm eggs are white to cream, and dome-shaped. They are found along the stems and leaves of the host plant. Young larvae are creamy, but older larva may be pale green, rose or brown, with light stripes and black spines. Corn earworm larvae feed for two to four weeks, before burrowing into the ground to pupate. They emerge as moths 10 to 25 days later.
Corn Earworm Damage
Early in the season, corn earworms feed on the leaves of the plants, leaving ragged edges. They also excrete brown droppings that leave corn ears dingy and unappetizing. Later in the season, corn earworms may feed on the tips of the ears of corn, as well as the leaves. Corn plants that have been ravaged by corn earworms are more susceptible to secondary infections from fungal diseases.
Corn Earworm Prevention
Outwit corn earworms by planting corn in a different location each year. Choose high-quality seed, adapted to your region and plant as soon as possible in early summer. Handpick any corn earworms that you find and drop them in a bucket of soapy water to dispatch them. Dab a bit of vegetable oil on the silks of each corn ear to discourage corn earworms from crawling inside. Cut and destroy all corn stalks in the fall to prevent the insects from overwintering in them.
Controls for Corn Earworms
Spray corn stalks with Bacillus thuringiensis, or Bt, which controls corn earworms by paralyzing their digestive system. Bt is preferable to other pesticides because it does not pollute ground water and causes no harm to birds, mammals or beneficial insects, such as ladybugs and honey bees. Rotenone is another organic pesticide that is effective against corn earworms. Follow all package directions carefully and spray it in the leaf axils to reach the insects.