The eastern tent caterpillar can be a serious pest on cherry, plum, peach, pear, and several other deciduous shade trees. These caterpillars do not feed on evergreens. The preferred host is native black cherry (Prunus seratina), which commonly grows on roadsides and hedgerows. Nests of the eastern tent caterpillar are unsightly and the repeated defoliation they sometimes cause can result in a decline of the host, predisposing it to damage from disease organisms and other insects. A single season's defoliation will seldom kill an otherwise healthy tree, as the feeding occurs early enough in the season for the trees to grow new leaves.

Description:

Larvae vary in size from 10 mm (3/8 inch) upon hatching to 50 mm (2 inches) long when fully grown. The caterpillars are primarily brown and are thinly covered with light brown hairs. A white stripe on the back is bordered with reddish-brown stripes and a row of oval blue spots. The adult moths are brown with a wingspan of about 45 mm (1 3/4 inch). Two narrow, lighter-colored bands may appear on the first pair of wings.

Egg masses of the eastern tent caterpillar may be found on smaller twigs of infested trees. The dark brown, shiny egg masses are about 20 mm (3/4 inch) long and 12 mm (1/2 inch) in diameter, and often encircle a twig. Larvae of the eastern tent caterpillar may be distinguished from those of the forest tent caterpillar, Malacosoma disstria, by the coloration pattern of the back. Forest tent caterpillars have a row of diamond-shaped white spots alternated with small white dots along its back. Forest tent caterpillars, contrary to their name, do not build tents, feeding openly instead, often in large groups or clusters.

Eastern tent caterpillar (left) and forest tent caterpillar (right)	Eastern tent caterpillar eggs on twig

Life Cycle:

Eastern tent caterpillars spend the winter in the egg stage in masses containing several hundred eggs. The eggs hatch in early spring, about the time apple and cherry leaves unfold. After hatching, the young caterpillars, sometimes from several egg masses, gather in a fork in the branches where they construct a web-like tent. The tents are used as shelter by the caterpillars when they are not feeding on the leaves of nearby branches. Eastern tent caterpillars feed from four to six weeks and then disperse to various locations to spin cocoons and pupate. Cocoons may be found on fences, houses, in weeds and ground debris, and on the trunks of infested trees. When the adult moths emerge in mid-summer, egg masses are laid on small twigs, sometimes on the stems of very small trees. Only one generation occurs per year, and these eggs will not hatch until the following spring.

Control:

- Prune out and destroy the egg clusters during winter months.

- Remove nests from trees by hand or with a stick.

- If nest removal is impractical, a spray containing Bt (Bacillus thuringiensis) can be effective.

By David Gadoury, David B. Wallace, and Richard A. Casagrande. Revised 1999.
Photos from the Ohio State University Extension.