Ace Landscaping Services Inc.

Tree and Shrub Problems - Bag Worm

Bagworms feed on many species of trees and shrubs, but are most common on junipers. Newly hatched larvae begin to spin a silken bag around themselves shortly after hatching. The first evidence of infestation is the presence of 1/4 inch bags which are carried almost on end by the young caterpillars inside. As larvae grow, leaf fragments are added to the bag, which may reach a length of two inches by the end of summer.

Bagworms overwinter in the egg stage inside female bags fastened to twigs. Eggs hatch in late May and early June, and larvae feed until late August or early September. Males emerge in September and mate with females through the bag entrance.

Control infestations on small trees and shrubs by removing bags during the winter and spring before the eggs begin to hatch in late May. Destroy bags by burning, immersing in kerosene or by crushing. If bags containing larvae are discarded on the ground the larvae can return to host plants.

Chemical control are effective if applied during early stages of bagworm development. For most effective insecticidal control and prevention of damage, apply sprays from mid to late June. Treatment later is often ineffective since the bag will provide protection from the insecticide. Some of the insecticides registered for control of bagworms on ornamentals include Bacillus thurnigiensis (Dipel), Sevin, diazinon, malathion and others.