Cankerworm is the larva (caterpillar) of a moth. It is a measuring worm and crawls by humping its back and bringing its hind feet up to its forefeet to make a loop of its body (see Measuring worm). Two kinds of cankerworms damage orchards and shade trees. They are the spring cankerworm and the fall cankerworm. The adult females of both these insects have no wings. They climb trees to lay their eggs. The spring cankerworm hatches about the time elm leaves grow, and eats the leaves. The fall cankerworm usually comes from eggs laid by adults that have appeared from their cocoons the autumn before. It hatches in early spring as the leaves unfold.
These caterpillars can strip an orchard or a grove of shade trees in a few days. When they are disturbed, they drop from the leaves and hang in the air by silken threads. Bands of cloth or paper that have been smeared with a sticky substance and wrapped around bases of the tree trunks will keep the females from laying eggs in the trees. Spraying the trees with carbaryl kills the caterpillars.
