Harmful Insects

Cankerworms

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The cankerworm is the most common shade tree defoliator in areas of Minnesota where elm is the predominate tree. The slender green or brown caterpillars prefer to feed on the leaves of elm, basswood, and apple. They will also feed on hackberry, oak, boxelder, maple and ash as well as shrubs below infested trees. There are two species of cankerworm, the fall cankerworm and the spring cankerworm. They are similar in the type of damage they do and times of year they feed. Many people are not as concerned about the health of their tree as they are about the nuisance that mature cankerworms cause when they spin to the ground on silken threads, crawling or falling on sidewalks, driveways, picnic tables, doors or house siding. Large numbers can make being outside extremely unpleasant.

To learn more see the attached information sheet by clicking the PDF icon below.