Moths of the eastern tent caterpillar, Malacosoma americanum, are brown to reddish-brown with two pale diagonal lines on the forewing. Eggs are laid in masses around twigs and covered with a foamy secretion that dries into a firm, brown covering. The larvae hatch but do not emerge from the egg mass until the following spring. Eastern tent caterpillars are somewhat hairy and black with gold, white, and blue markings. There is a white stripe down the back. The caterpillars grow to almost 2 inches long. The cocoon is about 1 inch long and is spun of white or yellowish-white silk.

Eastern tent caterpillar egg masses are fastened to host twigs.

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Eastern tent caterpillar egg masses are fastened to host twigs.

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Eastern tent caterpillars crawl about looking for a place to pupate.

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Eastern tent caterpillars crawl about looking for a place to pupate.

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Note the absence of leaves on this infested apple.

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Note the absence of leaves on this infested apple.

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Eastern tent caterpillars on small apple tree.

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Eastern tent caterpillars on small apple tree.

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Black cherry trees infested in early spring.

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Black cherry trees infested in early spring.

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Eastern tent caterpillar cocoons are found in dry, sheltered places.

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Eastern tent caterpillar cocoons are found in dry, sheltered places.

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Eastern tent caterpillar moths are brown with pale stripes on each fore wing.

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Eastern tent caterpillar moths are brown with pale stripes on each fore wing.

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Eastern tent caterpillars emerge from the egg mass just as the buds are breaking on wild cherry, crabapples and other ornamental plants. There is only one generation per year (the caterpillar that builds nests in trees later in the summer is the fall webworm). Eastern tent caterpillars build their silk nests in the crotches of wild cherry, crabapple, apple and other host plants. Soon the caterpillars crawl down from the trees to search for a place to spin their cocoons and pupate. Sometime in late spring, a new generation of moths emerges to mate and lay eggs for the following year's generation.

Black cherry, crabapple and apple are the usual hosts of the eastern tent caterpillar, but many other kinds of trees are occasionally infested. Because the tiny caterpillars emerge from the egg masses just as the host plant buds break in spring, they may give their host plants the appearance of never sprouting. The leaves are completely eaten away just as they emerge from the buds. Pregnant mares that ingest eastern tent caterpillars may abort, a phenomenon called mare reproductive loss syndrome.

Because eastern tent caterpillars spend the winter inside the egg masses, one effective method of controlling the caterpillars is to remove and destroy the egg masses before the caterpillars hatch. If the caterpillars have already hatched, the tents can be pulled down with a stick and the caterpillars crushed or otherwise destroyed. {Never use fire to destroy eastern tent caterpillars as fire is extremely dangerous. Fire may damage the tree and fire endangers the operator and nearby property.} Sevin and other pesticides are labeled for caterpillar control in the landscape. Because eastern tent caterpillars also infest woodland trees that are never sprayed, this pest has not developed resistance to pesticides.

• Eastern Tent Caterpillar. Anonymous. 2022. Missouri Botanical Garden.
• Eastern Tent Caterpillar. Bessin, R. 2003 (revised). University of Kentucky Cooperative Estension Service ENTFACT-423.
• The mare reproductive loss syndrome and the eastern tent caterpillar: a toxicokinetic/statistical analysis with clinical, epidemiologic, and mechanistic implications. Sebastian, M. et al. 2003. Veterinary Therapeutics 4 (4): 324-39.
• NC State Extension Plant Pathology Publications and Factsheets
• NC State Horticultural Science Publications
• North Carolina Agricultural Chemicals Manual

For assistance with a specific problem, contact your local N.C. Cooperative Extension center.