Fall Cankerworm Control

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The fall cankerworm, also known as the inchworm, is an insect native to our area. During the first cold temperatures in late fall (late November), the adult moth stage of the cankerworm leaves its cocoon in the soil. The female moth crawls up the trunks of trees looking for a high point or branch to lay her eggs. During early spring, the tiny caterpillars hatching from the fall cankerworms emerge to feed as leaves begin to open (around late February), destroying the tree’s young leaves and buds. While this does not generally kill the tree, repeated feasting from the worms causes the tree to use its stored energy sources, and over repeated seasons, this can weaken the tree. After they have finished feeding, they string down from the tree on a silken thread and bury into the soil making a new cocoon in the ground.

Cankerworm infestation can be controlled through either chemical sprays done in the spring when the caterpillars are feeding or through tree banding in the fall. Sprays containing Bacillus thuringiensis (B.t.), which cause the caterpillars to stop eating and die a few days later, can be sprayed on foliage of small trees. Large trees require professional spray equipment and extensive cost. Other foliage sprays include Liquid Sevin (carbaryl), which requires reapplication several times every 5 days, is harmful to beneficial insects, and may result in a worse situation in upcoming seasons, as well as insecticidal soap, which kills only soft-bodied insects who come in contact with the spray and requires 3 sprays per week. Additional products containing spinosad, bifenthrin, permethrin, or chlorantraniliprole may be used. Large area infestation may require spraying by air from a plane or helicopter.

Tree banding blocks the wingless females from crawling up the trees to lay eggs and should be in place from mid-November through the end of January. Tanglefoot™ or another sticky agent can be applied to the band around the tree and may need to be “refreshed” periodically.

Fall female moth stage                               Spring inchworm

Fall cankerworm female moth