Author: Eric Day, Virginia Tech
Honey locust and Mimosa
Description of Damage
Larvae feed on the leaf surfaces. The foliage is usually skeletonized. The lower epidermis is usually entirely destroyed. Leaves die and turn dull gray on mimosa; brown, as if fire-scorched on honey locust. Leaves and flowers are webbed together as larvae feed and develop. Usually the entire tree is involved with larvae scattered here and there throughout the foliage. Leaflets from different leaves often are webbed together. Repeated attacks seriously weaken trees, occasionally leading to death of some trees.
Larvae are grayish to dark brown, sometimes tinged with rose or pink and are 1/2" - 1" long. Five white stripes run the length of the body. The larvae are extremely active, wriggle violently, and drop on silk strands when disturbed much like many leaf-rollers. The adult moth may seldom be seen, but has about 1/2" wing span. Wings are gray with silver sheen and black dots.
Moths appear in June and lay eggs on mimosa flowers and foliage. The larvae feed gregariously within a web spun over flowers and leaves. In midsummer larvae descend to the ground on silken threads and spin cocoons in cracks in bark or in ground cover. The webbing is most conspicuous in August from the 2nd brood. Second generation pupae overwinter in crevices on tree trunks or protected by soil cover or litter. There is considerable overlap of generations.
Since many eggs are laid initially and the young larvae begin to feed extensively, trees should be watched for the earliest signs of feeding, in June. Larvae are more difficult to control when larger and webbing is extensive. Adult moths are active over a period of time, so new eggs may be laid after effects of earlier sprays have dissipated.
Sunburst honeylocust is reported to be most susceptible with Moraine, Skyline, and Shademaster less so, although damaged severely. It is helpful to keep leaf and other debris raked up under host trees. Honey locust is more if not as susceptible as mimosa.