The webs produced by the fall webworm, Hyphantria cunea (Drury), are familiar to everyone. Leaves are eaten by the larvae which live in loosely woven, dirty white webs, [Figure 19].
The adult is a white moth which may have black or brown spots on the forewing. Its wings have a span of about 1 inch.
The larvae are pale yellow spotted with black. They attain a length of 1 inch when full grown and are covered with long black and white hairs.
The insect overwinters as a pupa in lightly woven cocoons in debris on the soil or under the bark. In the spring the adults emerge and lay masses of greenish white eggs on the leaves. The caterpillars which hatch from the eggs feed on the leaves in colonies under webs which they construct. After feeding for a month to 6 weeks, the larvae crawl down the tree and pupate in loose cocoons in debris, under bark, or in loose soil. Adults appear during the summer and deposit eggs for the second generation. The larvae of this generation feed extensively until fall, crawl down the tree and pupate for the winter.
Control.—Light infestations on a few trees can be eliminated by pruning out the affected branches and burning them. If this method of control is not practicable, the trees should be sprayed with 2 pounds of 50 percent DDT wettable powder; 1 pound of 25 percent parathion wettable powder; or 3 pounds of lead arsenate per 100 gallons of water[9].
Figure 19. Web of the fall webworm on a pecan limb.
WALNUT CATERPILLAR
During the spring and summer, the walnut caterpillars, Datana integerrima G. & R. and others, may strip the leaves from branches or entire small trees. The adult is a moth with a wingspan of 1½ to 2 inches. The forewings are light brown with darker wavy lines. The hindwings are lighter in color without lines.
The immature larva is reddish brown with narrow yellowish lines that extend the length of the body. The full-grown larva is almost black with two grayish lines on the back and two on the sides. Many long, soft gray hairs are distributed over the body.