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Walnut caterpillar

 Image of Walnut caterpillar

The walnut caterpillar is a relatively common insect in hardwood forests of eastern North America. It  is a serious threat to pecan, hickory and walnut trees. It also endangers oak, willow, honey locust and certain woody shrubs.

The adult moth has a 2-inch wing span, is brown and tan with a dark region on the body behind the head and has wavy, dark lines across the front wings. Caterpillars are reddish brown to black with white markings and long white hairs. Large larvae are conspicuously fuzzy and may grow up to 2 inches (50 mm) long.

Adult walnut caterpillars are found throughout the spring and summer. The females deposit eggs in masses on the undersides of the leaves. Upon hatching, the larvae feed in colonies but do not construct tents or webs. As they grow, the caterpillars molt several times. Often, they are found in masses on the trunk and larger limbs where they congregate to molt. Later, they return to the foliage to continue their feeding. Upon completion of feeding, larvae crawl from the tree and pupate in the soil.


Clipping foliage to destroy egg masses and larvae, removing clustered larvae as they gather to molt, and destroying pupae by shallowly disking the soil after larvae have pupated.