Bagworms: Identification and Control

Common east of the Rocky Mountains, bagworms aren't worms at all—they're moth larvae. These pests strip foliage from trees and shrubs, starting at the top and working downward. As they feed, they construct dangling silken bags. Later, they retreat into these bags to pupate and emerge as adult moths. Females remain in their bags to lay eggs; caterpillars hatch in spring and often disperse to new trees on silk threads.

Control Methods

Biological: Bacillus thuringiensis (Bt) is the preferred treatment. Apply when caterpillars are newly emerged and feeding heavily.

Mechanical: For light infestations, cut off and burn affected stems and branches.

Chemical: Options include acephate, carbaryl, diazinon, and malathion—apply when infestation is visible.