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 darker brown. The smooth, practically hairless body is marked with three dark longitudinal stripes, one along each side and one down the back. A full-grown armyworm is 30 to 35 mm long.

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


BIOLOGY

Distribution - True armyworm occurs throughout the U.S. 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. Some of their vegetable host plants include bean, beet, cabbage, carrot, cauliflower, corn, cucumber, lettuce, onion, pea, pepper, radish, and sweet potato.

Damage - Preferring to feed at night, armyworms devour succulent foliage. By feeding on leaves and occasionally stems, they can severely damage seedling stands. Because they feed at night, armyworms may inflict much injury before they are detected. Having exhausted a current food supply, the worms migrate as an "army" to new host plants. Fields adjacent to or harboring lush grass are most commonly attacked.

Life History - True armyworms overwinter as partly grown larvae. Early in 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 2,000 eggs in small clusters or rows on the leaf sheaths of grasses. About 6 to 20 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 hot 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 chemically when buildup occurs. For specific control information, consult the current North Carolina Agricultural Chemicals Manual.

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