Adults have siphoning mouths. Host plants include hickory, walnut, oak, willow, honey locust and certain woody shrubs. Young larvae feed only on soft tissue, leaving a skeletonized leaf behind, while older larvae feed on the entire leaf, including the petiole. The last few stages, or instars, do the majority of the feeding damage. Damage may be localized to just a branch to two because they feed together.
Isolated trees are more subject to attack than forest or orchard trees.
They can rapidly defoliate ornamental and orchard trees if not controlled. In some past years, almost all of the native pecan trees in certain areas of the state were defoliated by walnut caterpillars. It also feeds on oak, willow, honey locust and certain woody shrubs. For additional information, contact your local Texas extension service agent, or search for other state extension service offices.