How Does a Corn Ear Worm Infestation Occur?

Identification

The eggs of corn earworms are white, with a dark ring that forms on the top just before erupting as larvae. As the egg darkens, the corn earworm larvae emerges just days later. The larvae of the corn earworm, also known as the tomato fruit worm, are about 1.5 inches long with distinctive light and dark stripes on their tannish-brown, pink or green body. This particular type of earworm larvae has three pairs of legs on the thorax or chest area and four pairs of mini legs on the abdomen. The corn earworm eggs are usually in the silk entry area of the corncob and larvae typically work their way into the sweet kernel area of the corn.

Crop Infestation

Corn earworms are naturally occurring pests found in many kinds of vegetable crops: sweet corn, tomatoes, squash, cabbage and eggplants. An early corn earworm infestation causes plants to lose their leaves, may affect the overall plants, results in tassel damage or harm to the corn silk and kernels. As the larvae mature, they continue to feed on the corncob and work their way down the ear. As the corn itself matures, a second-generation infestation of corn earworm occurs as the larvae travel down the silk vein into the maturing cob where more significant crop damage occurs. The corn earworms even eat one another, normally leaving one corn earworm per cob until it eats its way out by eating a hole through the husk.

Control and Prevention

Various forms of corn earworm treatment are available for a farmer or gardener to use. Prevent a significant infestation by examining crops at least once a week and thinning or heading any produce with signs of corn earworms. When the presence of corn earworms is more than one larva per two plants, it is time to treat the crop using alternative means. For biological control of corn earworms, use minute pirate bugs, lady beetles or green lacewing larvae as an effective weapon. After the first frost of the year, till or plow the fields to destroy any corn earworm pupae that live in the ground and could cause reinfestation in the spring. Use pheromone traps or black-light traps to capture egg-laying corn earworm moths and prevent them from producing and to determine a spray schedule for the eggs.