Malacosoma americanum

Symptoms

• Eastern tent caterpillars feed on the leaves of apple, crabapple, chokecherry and cherry trees.
• Caterpillars hatch at the time leaves are breaking bud in the spring and will continue feeding for six to eight weeks.
• The larvae then spin cocoons and the adult moths appear in late June to early July.
• Feeding damage is conspicuous because caterpillars will consume entire leaves.
• At night and during cool, rainy weather, caterpillars will congregate in a webbed tent spun at branch junctions in trees.
• These hairy caterpillars are blue and black and have a creamy-white stripe down the middle of their backs. The stripe is bordered by orange stripes on either side.

Caterpillars have prominent white and orange stripes. (David Cappaert, Bugwood.org)

Silken tents appear in the crotches of tree branches. (Steven Katovich, U.S. Department of Agriculture Forest Service, Bugwood.org)

Management and other important facts

• Mature trees can handle tent caterpillar defoliation better than younger trees.
• A simple organic control method is to use a stick to remove the webbing and caterpillars when they congregate in the silken tents during cool weather. Dispose of this mass to prevent further feeding and caterpillar maturation.
• If chemical control is to be used, pesticide applications should take place when larvae are outside the tent and feeding on leaves.
• If the tree is in flower, apply Bacillus thuringiensis (Bt) to the foliage near the tent. Bt is a biorational pesticide that will poison the caterpillars feeding on the treated leaves without hurting the bees or other pollinators.
• Other biorational pesticides include spinosad and insecticidal soap.
• If larvae are larger, conventional pesticides that include carbaryl or malathion may be more effective. Do not apply carbaryl within 30 days of petal fall to avoid apple drop.

Author: Esther McGinnis