Trees, Shrubs, and Vines: Bagworm

Problem
Leaves are chewed; branches or the entire tree may be defoliated. Carrot-shaped cases or "bags," from 1 to 3 inches long, hang from the branches. The bags are constructed from interwoven bits of dead foliage, twigs, and silk. When a bag is cut open, a tan or blackish caterpillar or a yellowish grublike insect may be found inside. A heavy attack by bagworms may stunt deciduous trees or kill evergreens.

Analysis
(Thyridopteryx ephemeraeformis)

Bagworms eat the leaves of many trees and shrubs. The larvae hatch in late May or early June and immediately begin feeding. Each larva constructs a bag that covers its entire body, and to which it adds as it develops. The worm partially emerges from its bag to feed. When all the leaves are eaten off the branch, the bagworm moves to the next branch, dragging its bag along. By late August the larva spins silken bands around a twig, attaches a bag permanently, and pupates. In the fall, the winged male moth emerges from his case, flies to a bag containing a female, mates, and dies. The female bagworm spends her entire life inside her bag. After mating, she lays 500 to 1,000 eggs and dies. The eggs spend the winter in the mother's bag.

Solution
Spray with an insecticide containing acephate, carbaryl, or diazinon between late May and mid-July. Older bagworms are more difficult to control. Repeat the spray after 10 days if leaf damage is still occurring. Handpick and destroy bags in winter to reduce the number of eggs.