Black Walnut Worms

Types

• The walnut caterpillar is a leaf-defoliating pest that attacks black walnut trees. Colonies of walnut caterpillars are often found congregating on the trunks of trees. This pest is black in color, with yellow stripes running along its sides. Fall webworms are common black walnut pests found throughout the eastern portion of the United States. Full-grown fall webworms are yellow or green with a dark stripe down their backs.

Effects

• Black walnut trees infested with worms or caterpillars have chewed leaves and reduced vigor. The fall webworm is easily recognized by the webs it leaves on tree branches. These pests do not usually cause tree death, but cause the tree to grow more slowly.

Control

• Removing webs and worms by hand is often an effective means of control if worms are found in the early stages of infestation. Chemical control is often necessary for trees that are attacked several years in a row.