Picture of Adult Cankerworm
Adult Cankerworm

Picture of Cankworm

Picture of Spring cankerworm
Spring Cankerworm

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Cankerworms and inchworms

Most cankerworm larvae have 5 pairs of prolegs including a pair at the tail end. This reduced number of legs causes larvae to crawl with a looping or inch-worm type movement. When pale stripes are distinguishable along body sides, spring cankerworm has 1 per side and fall cankerworm has 3. The color of both cankerworms is variable.

Many fruit and shade trees are attacked by cankerworms. Leaves are skeletonized by larvae. Silken threads are spun from branch to branch. Generally, most damage occurs when leaves fully develop. Trees may be completely defoliated.

Life cycle:
Fall cankerworms overwinter as eggs that hatch in early spring. Cankerworms feed for 3 to 4 weeks, then either crawl or drop to the ground on silken threads and pupate in the soil. Adults emerge in late fall. Wingless females crawl up tree trunks onto branches, mate with winged males, and then oviposit single-layered masses of flower-pot shaped eggs on limbs and trunks. Spring cankerworms overwinter as pupae and emerge as moths February. Wingless females oviposit oval-shaped eggs in masses under loose tree bark.