Whitemarked Tussock Moth, Orgyia leucostigma (J. E. Smith)

Leininger, T.D; Solomon, J.D.; Wilson, A. Dan; Schiff, N.M. 1999. A Guide to Major Insects, Diseases, Air Pollution Injury, and Chemical Injury of Sycamore. Gen. Tech. Rep. SRS-28. Asheville, NC: USDA Forest Service, Southern Research Station. 44 p.

Importance.-This tussock moth defoliates a wide variety of trees, but the sycamore is among its preferred hosts. It occurs throughout the Eastern United States and Southern Canada. Heavy defoliation causes growth loss and dieback but rarely kills trees.

Identifying the Insect (fig. 2a, b).- The yellowish, hairy larva (30 mm long) has a coral-red head and thoracic shield with a black dorsal stripe. Four yellowish, brushlike hair tufts occur dorsally. A pair of black hair pencils arises anteriorly, and a single hair pencil arises posteriorly. Male moths are gray with dark wavy bands on the forewings. Females have no wings. Eggs are deposited in flattened clusters covered with whitish, frothy material.

Figure 2a. - Wingless female whitemarked tussock moth laying a mass of eggs. Photo by John L. Foltz, University of Florida

Identifying the Injury (fig. 2c).- Young larvae skeletonize the undersides of leaves. Older larvae disperse and consume leaf patches, eventually consuming all but the leaf’s midrib and main veins. Late-summer defoliation by large populations may cause a skeletonlike appearance to entire trees as well as entire stands.

Biology. - Overwintering eggs hatch from April to June. Newly hatched larvae feed close together but often are dispersed on silken threads by wind. Larvae mature in 5 to 7 weeks and spin grayish, hairy cocoons on the underside of branches and in bark crevices. The pupal stage lasts 2 weeks. Females deposit 50 to 300 eggs in masses usually on or near the old cocoons. There are one to three generations per year. Egg masses overwinter on host plants.

Figure 2b. - Larva and feeding injury Photo by James Solomon, USDA Forest Service

Figure 1c. - Young trees defoliated

Control.-Populations on small trees can be controlled by destroying the conspicuous, whitish egg masses. Insecticides may be needed.