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Alsophila pometaria, the fall cankerworm, is a lepidopteran pest of hardwood and shade trees, and is native to North America. The larvae (caterpillars) commonly feed on ash, basswood, beech, black cherry, red maple, sugar maple, red oak, and white oak, but will also eat apple, birch, boxelder, dogwood, elm, hickory, and many other hardwoods. The adults are active in the fall, usually emerging from their pupal phase in October to lay orderly clusters of about 100 eggs lined up in neat rows, which overwinter on the small twigs to which they adhered. This lifecycle differentiates the fall cankerworm from the very similar but less common spring cankerworm, Paleacrita vernata, which overwinters as a pupa and is active as an adult to mate and lay eggs in the spring. Both cankerworms feed on the same trees and have overlapping ranges. Population numbers of fall cankerworm naturally fluctuate and reach populations large abundance every 15-20 years. While outbreaks of cankerworms, which last several years, can defoliate trees, healthy trees usually recover without significant damage even when attacked for two years in a row. In outbreaks cankerworms are seen as a nuisance in public areas when in late summer the larvae (small green caterpillars known as loopers or inchworms) drop from trees on silk webs in large numbers on their way to finding spots to pupate, and then again as the adult moths climb buildings to lay their eggs. While adult male moths are grayish-brown with a wingspan of about three centimeters, female moths are wingless, and look more like a spider than a moth.

(Ascerno and Hanh, 2003; Hoover and Haydt, 2010)


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