Black Cutworm
Agrotis ipsilon (Hufnagel), Noctuidae, LEPIDOPTERA


DESCRIPTION

Adult - The moth is characterized by long, narrow, usually dark forewings which are pale near the tips. There are three black dashes on each forewing. Hind wings are white with dark veins and broad, dark, indefinite margins. The wingspan varies from 38 to 51 mm.

Egg - The egg is white, round, and about 0.5 mm in diameter.

Larva - There are six instars ranging from 4 to 46 mm in length. Above the spiracles, the larva is basically one color, varying from light gray to nearly black. The spiracles are distinctly black. When disturbed, the larva curls up. Color plate.

Pupa - The brown pupa is about 17 to 22 mm long, with distinct mouthparts and antennae.


BIOLOGY

Distribution - The black cutworm is a widespread species which can be found from southern Canada throughout the United States, Mexico, and South America. Each year in North Carolina, infested fields occur from the coast to the Tennessee state line. The threat of an infestation appears to be greatest in no-till or weedy corn fields, especially in poorly drained areas.

Host Plants - The black cutworm feeds on a wide range of field and garden crops. Corn and tobacco are two of its preferred crops. Other known hosts include asparagus, bean, beet, cabbage, castor bean, cotton, grape, lettuce, peanut, pepper, potato, radish, spinach, squash, strawberry and tomato.

Damage - Black cutworms are among the most destructive of all cutworms. The larvae sever plants from roots near the soil line; usually no other feeding damage is present. Many larvae move from plant to plant on successive nights, while some stay to feed on the roots and underground stems of cut plants.

Life History - Little is known about the biology of this pest in North Carolina, but in Tennessee there are four broods annually. Moths of the first or overwintering brood emerge between the middle of March and the first of May. They mature about the middle of May. Second brood moths emerge from the latter part of May to the middle of July. Third brood moths emerge between the middle of July and the last of August. Fourth brood moths make their appearance near the first of September and continue to emerge into December; they produce the overwintering generation. A similar seasonal history probably occurs in North Carolina, where the majority of this pest population overwinters as pupae, though a few overwinter as larvae.

Between 5 and 11 days after emergence, each female begins to deposit about 1300 eggs in clusters of 1 to 30. Most eggs are laid on low, densely growing plants like chickweed, curly dock, and mustard; corn and soybeans are among the least attractive oviposition hosts. The egg stage lasts 3 to 16 days, depending upon the temperature. These cutworms prefer moist soil where they are usually found in tunnels 8 to 10 cm beneath the surface. The destructive larval stage varies in duration from 3 weeks (or slightly more) in July to over 4 weeks in September. The July-to- August pupal stage lasts about 2 weeks for early pupae; later ones require as much as 8 or 9 weeks.


CONTROL

Damage from these cutworms often can be avoided by not planting corn on newly broken sod or on land which was grassy or weedy the previous summer. Other important components in cutworm control are rapid seedling growth, scouting, and properly applied insecticides. Treatment should begin when 5 percent or more of the optimum stand of seedlings has been cut. All fields should be examined before the corn is 8 cm (3 inches) tall. For specific control information, consult the current North Carolina Agricultural Chemicals Manual.