Latin name: Operophtera brumata, O. bruceata
Reason for Concern:
1) Winter Moth and Blueberry Spanworm are major early season pests. Larvae bore into and feed on developing buds.
2) Destruction of the flower buds leads to greatly diminished harvest on fruit crops.
3) They chew on new growth, tie leaves with silken threads, and feed on mature flowers and fruit.
4) Severe infestations, if not controlled, can cause total defoliation.
Eggs, light green at first, later changing to bright orange, are laid in bark crevices. Prior to hatching in early spring, they become very dark. After hatch, larvae initially feed by mining developing buds, leaving holes in leaves, which become conspicuous as the leaves expand. After leaf buds open, the small caterpillars can be found within the tight clusters of new leaves during the day. Larvae of both species are stout-bodied, hairless loopers, with 3 pairs of legs behind the head and 2 pairs of prolegs in the rear. They arch their body when moving along a branch. The larvae are about 1/8-inch long when young and ¾-inch long when fully grown. Young Blueberry Spanworm larvae are dark in color, having blackish heads and dark gray bodies with 3 whitish bands along each side. Fully grown larvae are yellowish-orange with rows of black spots that look like continuous black strips running the length of the body. Spanworm larvae often appear on plants in large numbers at night. During the day, shelter in the litter at the base of the plants. Winter moth larvae have a green body, a narrow, dark green mid-dorsal line, and 3 creamy yellow stripes along each side. Adults are drab gray or gray-brown moths and the 2 species are almost identical in appearance and habits. Females (rarely seen) are 0.6 to 0.8 cm long and have only vestigial wings. Males are light brown, slender-bodied moths with bluish gray wings with brownish markings most noticeable on the veins, and a wingspan of 2.5 to 3.0 cm. All 4 wings are fringed with small elongate scales that give the hind margins a hairy or fringed appearance. Adults are evident from late October to the end of January, often in weedy areas or windbreaks.
Winter Moth females lay overwintering eggs in early winter in bark crevices, while Spanworms tend to lay eggs in litter at the base of the plant. Eggs are deposited singly or in clusters. After mating and egg laying, adult moths die. Egg hatch occurs just at or right before bud break. Some of the newly hatched larvae crawl up tree trunks and produce a strand of silk, which makes them air buoyant. They may also use the silken strand to drop to the ground to hide in leaf litter during the day. At night they crawl back up the plant to feed on buds, foliage, flowers and fruit. In June or July, when larvae are full-grown, they stop feeding and drop to the ground to pupate in the soil. Adult moths begin to emerge about 2 weeks later. There is 1 generation per year.