Cankerworms

    Cankerworms

    Alsophila pometaria (Fall Cankerworm); Paleacrita vernata (Spring Cankerworm)

    fall cankerworm adult

    Fall cankerworm adult (William M. Ciesla, Forest Health Management International, Bugwood.org)

    fall cankerworm

    Fall cankerworm larva (Joseph Berger, Bugwood.org)

    spring cankerworm adult

    Spring cankerworm adult (Nolie Schneider, Bugwood.org)

    spring cankerworm

    Spring cankerworm larva (James B. Hanson, USDA Forest Service, Bugwood.org)

    Pest Description

    • adult males: 1 1⁄8 inches long; dull gray brown
    • adult females: 5/16 inch long; dull gray brown; wingless
    • larvae: ~ 1 inch long; green to light brown to black; inchworms that crawl by arching their backs
    • fall cankerworm larvae: three pairs of prolegs and three white stripes on either side of the abdomen
    • spring cankerworm larvae: two pairs of prolegs and one larger white stripe down each side of the abdomen
    • eggs: barrel shaped, shiny gray with a light brown ring around a dark brown spot; laid in clusters

    Host Plants, Diet & Damage

    • feed on leaves of apple, ash, red and white oak, maple (including boxelder), elm, cherry, linden and honeylocust
    • tattered skeletonizing (leaving veins) or total defoliation
    • can stress trees or kill trees over years of defoliation

    Biology, Life Cycle & Damaging Life Stage

    • overwinter as eggs on host (fall cankerworm) or pupae in soil (spring cankerworm)
    • eggs hatch in early spring around budbreak
    • fall cankerworm and spring cankerworm larvae feed at the same time
    • fall cankerworm adults emerge after a hard freeze in fall; spring cankerworm adults emerge in early spring
    • wingless females climb trees to mate with winged males
    • larvae can be blown from tree to tree on silken threads
    • one generation per year
    • larvae are the damaging stage

    IPM Recommendations

    • Manage trees to maintain overall health.
    • Monitor trees in early spring for egg masses and larvae.
    • If populations are low, allow minor feeding on trees.
    • Apply an insecticide (Bacillus thuringiensis; carbamate; pyrethroid) to target larvae when they are smaller than 1/2 inch (~10 days after egg hatch).

    For more information, see our Cankerworms fact sheet.