Fall Armyworm
Spodoptera frugiperda (Smith), Noctuidae, LEPIDOPTERA


DESCRIPTION

Adult - The adult moth has a wingspan of about 38.5 mm. The hind wings are grayish-white; the front wings are dark gray mottled with lighter and darker splotches. Each forewing has a noticeable whitish spot near the extreme tip.

Egg - Minute, light gray eggs are laid in clusters and covered with grayish fuzzy scales from the body of the female moth. Each egg becomes very dark just before hatching.

Larva - About 30 to 40 mm long, the fully grown larva varies in color from light tan or green to nearly black. Along each side of its body is a longitudinal black stripe. Down the middle of its back is a wider yellowish-gray stripe with four black dots on each segment. The head of the fall armyworm often is marked with a pale but distinct inverted "Y."

Pupa - The pupa, approximately 13 mm long, is originally reddish-brown and darkens to black as it matures.


BIOLOGY

Distribution - The fall armyworm is a continuous resident of the Gulf states, the tropics of North, Central, and South America, and some of the West Indies. Each year it migrates as far northward as Montana, Michigan, and New Hampshire.

Host Plants - Field corn, sweet corn, sorghum, and grasses are preferred foods. However, the fall armyworm may also infest alfalfa, bean, peanut, potato, soybean, sweet potato, turnip, spinach, tomato, cabbage, cucumber, cotton, tobacco, all grain crops, and clover.

Damage - The fall armyworm is the second most important pest of sweet corn. It most frequently causes damage to the whorl of late pretassel corn. Larvae feed throughout the tightly coiled blades causing what is known as "shatterworm" injury. When the blades unfurl, the new leaves are riddled with numerous ragged holes. As with the corn earworm, wet tan excrement lodges in the remaining blades and blade axils.

In addition to defoliation, damage to corn may be three-fold. First, larvae feed on the undeveloped tassels of young plants. Secondly, immature ears are attacked near the shank. Lastly, large larvae may bore into maturing ears and stalks.

Life History - Fall armyworms overwinter in Florida and along the Gulf Coast in several life stages, but usually as pupae. Egg-laying moths appear in North Carolina about the middle of July. Each female lays about 1000 eggs in masses of 50 to several hundred. Two to 10 days later, the small larvae emerge, feed gregariously on the remains of the egg mass, and then scatter in search of food. They usually are unnoticed until they are about 25.5 to 38.5 mm long, by which time, if abundant, they have consumed so much foliage that they create alarm. Larvae are most active early in the morning or late in the evening. When abundant, these caterpillars eat all the food at hand and then crawl in great armies to adjoining fields. After feeding for 2 or 3 weeks, the larvae dig about 20 mm into the ground to pupate. Within 2 weeks, a new swarm of moths emerges, usually flying several miles before laying eggs. Several generations may occur each year.


CONTROL

During favorable seasons, a number of parasitic enemies keep fall armyworm larvae down to moderate numbers. Cold, wet springs seem to reduce the effectiveness of these parasites and a population explosion often results.

Early planting is the most effective cultural control method in our state. For recommended chemical controls, consult the current North Carolina Agricultural Chemicals Manual.

Return to AG-295 Table of Contents