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


DESCRIPTION

Adult - The moth has a wingspan of nearly 25.5 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 1 mm in diameter.

Larva - The larva is a slender, bluish-green, brown-striped caterpillar about 19 mm long.

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


BIOLOGY

Distribution - Though the lesser cornstalk borer is found from Maine to southern California, the bulk of its damage occurs in the southern states, particularly Alabama, Georgia, and South Carolina. It is also found in Mexico, Central America, and South America.

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

Damage - Larvae of this small moth have been sporadically injurious to seedlings of many plant species and seem to be on the increase in the South. Injury is caused when a larva bores into the stalk of a host plant, thereby disrupting the growing point. Damage can be slight, or it can kill the plant. Damage is most prevalent in crops grown on sandy soils during dry conditions.

Life History - Lesser cornstalk borers hibernate as larvae or pupae. In North Carolina, they usually overwinter as larvae which develop into pupae before spring. Moths emerge early in spring and lay eggs on or near the host's leaves or stems. Eggs hatch in 2 to 7 days. Larvae feed first on leaves or roots of peanuts. On peas, the larvae tunnel up the main stems causing them to wilt. They can seldom penetrate older stems, however. Later they construct underground silken tubes or burrows from which they bore into plants near the ground line. They become full 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. Two generations are known to occur in the mid-Atlantic States; three generations occur in South Carolina; and four generations occur in south Georgia and Florida.


CONTROL

Cultural practices, such as clean cultivation and weed destruction along fence rows, have long been recommended for lesser cornstalk borer control. Recent research findings in Georgia, however, indicate that cultivation promotes, not retards, injury by this insect on corn. The fact that damage by lesser cornstalk borer is rare under no-tillage cropping systems has been attributed to higher soil moisture and to the fact that larvae feed on old crop residue. Under conventional cropping systems, the cultural practice of late fall plowing may still be of some benefit since it kills overwintering life stages. For up-to-date chemical control recommendations, consult the current North Carolina Agricultural Chemicals Manual.

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