Description
    The walnut caterpillar is a common pest of black walnut trees throughout eastern United States. The larvae are gregarious, often found in masses on the trunks of trees or feeding on the foliage.

    Very young caterpillars are red with grayishwhite hairs covering the body. Full-grown caterpillars are as long as 2 inches and have a black body with longitudinal yellow stripes along their sides. The entire body is covered with long white hairs.

    The adult moth is brownish gray and has a wingspread of nearly 2 inches. The front wings are marked by curving transverse dark lines.

Injury
    Young caterpillars eat only the outer layer of cells on the lower leaf surface; older larvae consume the entire leaf. Walnut caterpillars are gregarious and feed in colonies. One colony can defoliate an entire young tree in a short time. Often they seem to move down a line of walnut trees, stripping each of its leaves in turn.

Control
    Hand removal of young caterpillars is most effective in preventing further defoliation. If this is impractical, consult your service forester or county extension agent for recommended chemical control.