corn borer

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.

Corn Borer

 

(Ostrinia, or Pyrausta, nubilalis), a moth of the family Pyralidae, a polyphagous plant pest. The body length is 13–15 mm, and the wingspread is 27–32 mm. The females are larger than the males. The fore wings of the females vary in color from pale yellow to light cinnamon brown and have two dark zigzag lines at right angles to each other; the hind wings are lighter in coloration and have a light middle band. The wings of the male are darker than those of the female. The caterpillars, which measure about 25 mm long, are light gray or, sometimes, cinnamon brown with a dark stripe across the back.

The corn borer occurs in Europe, Asia, and the Americas. In the USSR it is found in the steppe and forest-steppe zones of the European USSR, in southern Siberia, in the Far East, and in Middle Asia. The caterpillars are injurious to about 230 plant species, mostly such large-stemmed species as corn, hemp, millet, sorghum, and hops. Less often, the caterpillars infest potato, sunflower, ambary, and Chinese bellflower.

Female corn borers lay eggs on the underside of leaves. Caterpillars penetrate the sheaths, leafstalks, inflorescences, and stems. They continue to feed and develop inside the stems and, in the case of corn, inside the cobs. The feeding conditions of the plants deteriorate, the plants break in two, and the stems and inflorescences dry up. There is a sharp decrease in total plant weight, number of seeds, and, in the case of bast plants, amount of fiber.

Control measures include the implementation of sanitary farming practices and the use of resistant varieties. Also effective is the release of the egg parasite Trichogramma (70,000–100,000 per hectare) twice, once at the beginning of intensive egg laying and again ten days later. Chemical methods are difficult to use because of the caterpillar’s concealed mode of life.

REFERENCES

Khomiakova, V. O. Kukuruznyi motylek. Leningrad-Moscow, 1962.
Pospelov, S. M., M. V. Arsent’eva, and T. S. Gruzdev. Zashchitarastenii. Leningrad, 1973.