Hyphantria cunea (Drury)
Author: Elizabeth McCarty, Forest Health Specialist, University of Georgia.
Description
Fall webworm has two color forms – red- and black-headed, referring to color of the head capsule. Red-headed webworm adult moths are white with brown spots and are most often found in the southern U.S. Caterpillar color varies, but in general, red-headed larvae are yellowish-tan with long white hairs, orange bumps, and a dark stripe along their back.
Biology
Fall webworm can have up to 5 generations a year in the south, resulting in inactive webs on the same trees as fresh webs. In the spring females lay egg masses on lower surface of leaves. Larvae hatch and feed on leaves and construct silken webs that enclose branch ends and foliage, preferring new leaves exposed to sunlight. Webbing increases in size as caterpillars develop. Mature caterpillars leave the nest at dusk to feed on foliage, returning to the nest before
daybreak. Mature caterpillars leave the nest to spin cocoons in crevices in tree bark, under stones, or in soil. Adults emerge, and the cycle begins again up to four more times a year.
Damage
Native to North America, fall webworms feed on over 400 tree species in forests, yards, and fruit and nut orchards including pecan, hickory, walnut, persimmon, maple, sweet gum, river birch, etc. Though not a serious pest in forests, they can be problematic in nutand fruit-bearing tree orchards. Webworms are a nuisance in ornamental settings as defoliation can be unsightly. Smaller trees are more susceptible to serious damage. Healthy deciduous trees tolerate defoliation later in the year and resprout new foliage in the spring.
Management
Populations are naturally controlled by native predators and parasites. Since healthy trees recover from defoliation, the best approach is to leave webworms alone in non-commercial settings. The best time to attempt control is when insects are young and more susceptible. Pruning out webs is a possibility, but the tree will be left with unsightly gaps in the canopy. Nests can be removed with a stick to destroy caterpillars and disrupting the web leaves younger caterpillars more vulnerable to enemies. This method may not be possible for larger trees. Insecticides can be used when caterpillars are young. Control is less effective as nest size increases. Current pesticide recommendations are available from your county Extension office and the Georgia Pest Management Handbook. Be sure to carefully read the entire pesticide label before applying any pesticide.