Tent Caterpillars

How to control the devastating tent caterpillar

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Eastern Tent Caterpillar
Eastern tent caterpillar webbing & larvae
Eastern Tent Caterpillar
Eastern tent caterpillar larvae
Eastern Tent Caterpillar
Eastern tent caterpillar moth

Malacosoma spp.

Description
Adults: yellowish tan to brown moths with two narrow, diagonal stripes across wings (1- to 1 1/2-inch wingspan). Larvae: black, hairy, 2- to 21/2 inch caterpillars with a white stripe or rows of dots along the back and irregular, brownish blue or red marks along sides; most spin large "tents" of silk webbing in branch crotches of trees. Eggs: laid on twigs in masses, covered with hardened foamy layer. Eggs resemble a dark, shiny belt encircling a twig. Found throughout North America.

Damage
Larvae feed on leaves of most deciduous trees and shrubs, especially apples, aspens, and wild cherries. Trees may be fully defoliated in years of high caterpillar populations. Trees usually leaf out again later in summer but growth may be stunted for several years. Tent caterpillars spin thick webs in the crotches of trees, while closely related forest tent caterpillars spin mats of silk on tree branches and trunk.

Life Cycle
Moths lay eggs on twigs in midsummer; eggs overwinter and hatch in early spring; caterpillars move to nearest branch crotch and spin a silk tent for protection during rain or at night, and leave it to feed during the day. After feeding 5 to 8 weeks, they pupate in white cocoons attached to tree trunks or leaf litter; adult moths emerge in 10 days. One generation per year.

Control
In early morning or in the evening when most caterpillars are in the nest, prune infested branches and burn or crush the nests or put them deeply inside a hot compost pile. Another way to remove tents filled with caterpillars from branches is by winding them onto a broomstick with nails projecting from it. In winter, remove egg masses from bare branches; attract native parasitic flies and wasps by growing small-flowered herbs, such as catnip, and wildflowers, such as Queen-Anne's lace. Do not destroy wandering caterpillars with white eggs or cocoons attached to their backs; they are hosts for native parasites. Spray BTK weekly while larvae are small.

Photo credits
Webbing & Larvae: Pennsylvania Department of Conservation and Natural Resources - Forestry Archive, Bugwood.org
Larvae: Clemson University - USDA Cooperative Extension Slide Series, Bugwood.org
Moth: Lacy L. Hyche, Auburn University, Bugwood.org

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