Armyworm
Pseudaletia unipuncta (Haworth), Noctuidae, LEPIDOPTERA


DESCRIPTION

Adult - The adult moth is pale brown to grayish brown with a wingspan of about 38.5 mm. In the center of each forewing is a characteristic white spot.

Egg - The minute egg is greenish-white and globular.

Larva - The young larva is pale green. The full-grown larva is basically yellow to brownish-green with 3 longitudinal, dark stripes. A mature armyworm may be 30 to 35 mm long.

Pupa - The pupa, reddish-brown at first, gradually darkens until it is almost black.


BIOLOGY

Distribution - Widely distributed, the armyworm inhabits most regions of the world. In North Carolina, it is particularly abundant in the Piedmont and Coastal Plain regions. During bright daylight hours, larvae prefer to remain under litter on the ground.

Host Plants - The armyworm infests weedy grasses, such as crabgrass and fall panicum, as well as most grass crops, especially corn, millet, bluegrass, and small grains. Under stress of hunger, however, it will eat broad-leaved plants, such as alfalfa, clover, bean, and pea, as well as a number of fruit, vegetable, and weedy plants.

Damage - Armyworms, apparently native to North America, vary greatly in abundance and destructiveness from year to year. They are particularly attracted to lush new growth of grass crops. After consuming all the tender, young foliage, they may devour the remainder of the host plant or move on to more succulent hosts.

Life History - In North Carolina, armyworms overwinter as partly grown larvae. Early in the spring they resume feeding on lush stands of grass and small grains. The larval stages prefer to hide during the day and feed at night. Migration of many larvae ("armies") from infested areas to nearby, more succulent grasses in an increasing threat as small grain matures (see Small Grain Armyworm Note).

First generation adults appear in May or June and mate. After feeding primarily on nectar for 7 to 10 days, the females lay eggs at night on succulent grasses and grain crops. An individual female may deposit as many as 2,000 eggs (in clusters of 25 to 134). Six to 10 days later, second generation larvae emerge and feed for about 3 weeks. They then pupate in earthen cells 5 to 7.5 cm deep in the soil. Moths emerge about 4 weeks later. There are five or more generations per year in North Carolina. However, generations which develop after early July are usually kept below economic threshold by natural controls.

CONTROL

Parasites, various diseases, insect predators, and birds often keep the armyworm under control. The effectiveness of these natural control agents, however, is reduced during cool, wet springs and during growing seasons that follow years of drought.

The presence of five medium to large armyworms per 929 cm2 (1 ft2) is recognized as a threshold in North Carolina. For specific chemical control information, consult the current North Carolina Agricultural Chemicals Manual.