Armyworm
 Pseudaletia unipuncta (Haworth), Noctuidae, LEPIDOPTERA

DESCRIPTION

Adult - The true armyworm moth has grayish-brown forewings, each with a white spot near the center, and grayish-white hind wings. The wingspan averages 38.5 mm.

Egg - The minute, greenish-white egg is globular in shape.

Larva - The young armyworm is pale green. The mature larva is basically yellowish- or brownish-green with a tan or greenish- brown head mottled with dark brown. The smooth, practically hairless body is marked with three longitudinal dark stripes, one along each side and one down the back. A full grown armyworm is 30 to 35 mm long. Color plate.

Pupa - The reddish-brown, 13-mm long pupa darkens gradually until it is almost black.

BIOLOGY

Distribution - True armyworms occur throughout the United States east of the Rocky Mountains. In North Carolina, they are particularly abundant in the Piedmont and Coastal Plain regions. During daylight hours, larvae prefer to remain under litter on the ground.

Host Plants - Although true armyworms strongly prefer grasses and cereals, they have occasionally been reported to infest various vegetables, fruits, legumes, and weeds, especially when they are on the march. Most commonly, however, they are pests of corn, sorghum, timothy, small grains, flax, millet, and some wild grasses.

Damage - Preferring to feed at night, armyworms devour succulent foliage. By feeding on leaves and occasionally stems, they can severely damage seedling stands. In corn, armyworms characteristically feed on the lower leaves and progress toward the top of the plant. Leaves of seedlings are completely eaten, but the midribs are left on mature plants. Because they feed at night, the worms may inflict much injury before they are detected. Once having exhausted their food supply, the worms migrate as an "army" to new host plants. Fields adjacent to or harboring lush grass are most commonly attacked, particularly no-till corn planted into a small grain cover crop.

Life History - True armyworms overwinter as partly grown larvae. Early in the spring, larvae resume feeding at night, usually on grasses and small grains. First generation adults appear in May or June depending upon climatic conditions. Moths mate soon after emergence and feed on nectar for 7 to 10 days. Females then deposit up to 2000 eggs in small clusters or rows on the leaf sheaths of grasses. About 6 to 10 days later, larvae emerge. After feeding for 3 or 4 weeks, they drop to the ground and pupate in earthen cells 5 to 7.5 cm deep within the soil. Moths emerge about 2 to 4 weeks later. True armyworms complete five or more generations per year in North Carolina.

CONTROL

Parasites, various diseases, insect predators, and birds usually keep armyworms under control except after cold, wet springs. When practical, cultural methods, such as disking large areas, can help reduce future armyworm populations by exposing the pupae to natural enemies and host weather. However, since armyworm moths are strong fliers, most areas will be subject to constant reinfestation.

Because armyworms feed exposed, are active during their larval stages, and are susceptible to several insecticides, they are easily controlled when buildup occurs. Controls are warranted when defoliation by armyworms averages 20 percent. For specific control information, consult the current North Carolina Agricultural Chemicals Manual.