Lesser Cornstalk Borer
Elasmopalpus lignosellus (Zeller), Pyralidae, LEPIDOPTERA

DESCRIPTION

Adult - The lesser cornstalk borer moth has a wingspan of nearly 26 mm. The male's front wings are brownish yellow and have grayish margins with several dark spots. The female's front wings are nearly black.

Egg - The egg is greenish white and less than 0.5 mm in diameter.

Larva - About 19 mm long, the larva is a slender, bluish- green, brown-striped caterpillar with brown rings around its body. This insect thrashes wildly when disturbed or prodded. Color plate.

Pupa - The pupa is brownish and about 8.5 mm long.

BIOLOGY

Distribution - Although the lesser cornstalk borer is found from Maine to southern California, the bulk of its damage occurs in the more southern states. It is also found in Mexico, Central America, and South America. This insect is a major pest of peanuts in Texas and Oklahoma, Georgia, and Alabama.

Host Plants - The lesser cornstalk borer prefers corn, but it also feeds on bean, cowpea, peanut, pea, crabgrass, Johnson grass, sorghum, and wheat.

Damage - Under moist soil conditions, lesser cornstalk borers tend to be saprophytic. In tilled soils which tend to be drier, the borers often become a problem on crop plants. The larvae feed on and tunnel into lower stems, roots, pods, and pegs. Pegs are severed and developing nuts hollowed out. As a result of such injury, plant growth is retarded and yield is reduced. Feeding by high numbers of lesser cornstalk borers may cause plants to wilt and die.

Life History - Lesser cornstalk borers can hibernate as larvae or pupae. However, they usually overwinter as larvae which develop into pupae before spring. The moths emerge early in the spring and lay their eggs on the leaves or stems of host plants. The eggs hatch in about a week. Feeding first on roots and leaves, the larvae later construct underground silken tubes or burrows near the ground line from which they bore into plants. They become fully grown in 2 to 3 weeks, leave their burrows, and spin silken cocoons under trash on the surface of the ground. In these cocoons, they change to pupae, from which moths emerge in 2 to 3 weeks. Normally, two generations occur each year.

CONTROL

Late fall plowing is of some benefit since it kills overwintering life stages. For specific chemical recommendations, consult the current North Carolina Agricultural Chemicals Manual.