corn borer or European corn borer, common name for the larva of a moth of the family Pyralidae, introduced from S Europe into the Boston area in 1917. The corn borer, Ostrinia nubilalis, has steadily spread southward into the Gulf States and northward and westward across the continent to the Rocky Mts. It also still occurs in most of Europe and parts of Asia. The full-grown larva is about 1 in. (2.5 cm) long, with a dark brown head and pinkish body. It is a major pest of all types of corn, its host preference, but also attacks many other cultivated crops (e.g., sorghum, soybeans, and potatoes) and flower plants (e.g., dahlias, asters, and gladioli). The newly hatched yellowish larvae cause damage by feeding on the leaves of the host plant; older larvae bore into the stalk thereby severely weakening the plant and causing ear damage, which results in a loss in yield and reduction of quality. The full-grown larvae overwinter in cornstalks, corncobs, and debris on the ground. Adults emerge in the spring and are brownish with zigzag streaks across the tips of the forewings. There are sometimes more than one generation per year depending on an increased length of the host's growing season. Control of these pests is complicated by the fact that the larvae also infest common weeds and wild grasses growing near the cornfields. For insecticidal control, see bulletins of the U.S. Dept. of Agriculture. Corn borers are classified in the phylum Arthropoda, class Insecta, order Lepidoptera, family Pyralidae.

borer, name applied to various animals that are injurious because of their ability to penetrate plant or animal tissues. Among insects, some borers are beetles, e.g., the flatheaded apple-tree borer, a serious pest of many shade and fruit trees; the roundheaded apple-tree borer; and the bronze birch, locust, elm, shot-hole, and poplar borers. Other boring insects are moths that are harmful in the larval stage, e.g., the peach, currant, squash, lilac, and southern cornstalk borers and the European corn borer. Marine borers include the boring sponges, certain marine worms, and some bivalve mollusks, e.g., the rock borer, the shipworm, and the piddock, which are thought to secrete acids that dissolve rock and other substances. The hagfish, or borer, is a marine pest that burrows into the bodies of other fish.

European corn borer: see corn borer.