The fall webworm is not considered an important forest pest. However, ugly webs can seriously detract from aesthetic values. The preferred hosts in the South are persimmon, pecan, and sourwood, but it is also found on black walnut, hickory, cherry, sycamore, crab apple, and sweetgum. The insects range throughout North America.
Fall webworm larva.
The adult is a pure white moth about 1¼ inches long. The forewing is sometimes marked with blackish dots. The larva is about one inch long when full grown, generally pale yellow or greenish with a broad dark longitudinal stripe on the back and a yellowish stripe extending from black and orange warts. The insect has one generation per year in the northern part of its range, and two in the southern part. Moths of the first generation emerge from May to July and those of the second in July and August. Adult females lay 400-500 eggs in white cottony patches on the underside of the leaves of host plants. The eggs hatch in about a week, and the larvae form a web and begin to skeletonize the leaves by feeding in rows. As the larvae grow they expand the web to cover the colony. When the larvae are ready to pupate, they crawl or drop to the ground and form a brownish cocoon in the duff around the tree where they overwinter.
Fall webworm infestation.
Natural enemies usually keep this insect under control. Webs can be pruned from high-value trees in scenic or recreation areas.
OAK LEAF TIER, Croesia albicomana (Clem.)
This oak leaf tier has been associated with the decline and mortality of several species of oak in the northeastern United States and southern Appalachians. An outbreak population in the mountains of West Virginia and Virginia in 1966-68 resulted in the loss of several thousand acres of scarlet oak. Usually such outbreaks coincide with periods of drought which increase the impact of defoliation on the host. Its hosts include northern red oak, black oak, scarlet oak, and pin oak. The latter two species seem to be hit hardest by this insect.
