by National Gardening Association Editors
Corn earworms can grow to 1-1/2" long.
This pest is common throughout North America. The adult is an inch-long tan moth that lays yellow eggs on leaf undersides in the spring. The caterpillar larva has alternating light and dark stripes that may be green, pink, or brown. This first generation of caterpillars feeds on the leaves. Eggs of later generations are laid on corn silk; the emerging caterpillars feed on the silk and the kernels at the tip of the ear just inside the husk. In some cases this same caterpillar feeds on a variety of plants and hence has many common names: tomato fruitworm, cotton bollworm, geranium budworm. It also is know to feed on beans, peas, peppers, potatoes, and squash.
Squirt half a medicine dropper of mineral oil into the tip of each ear of corn after the silks have wilted and have begun turn brown (applying oil earlier may interfere with pollination). Plow the garden in fall to kill overwintering pupae. Apply Bacillus thuringiensis (Bt) before caterpillars enter ears or fruits. Cultivate the soil between crops to destroy pupae.
Photography by Jack Dykinga, USDA Agricultural Research Service, Bugwood.org