Bagworms are most common on cedar, juniper, arborvitae, pine and spruce trees and shrubs. These brown bags contain eggs which will be hatching in late May and early June.
After hatching, the larvae or worm stage emerge from a hole at the base of the old brown bags and spin down a strand of silk. The tiny insect is often ballooned by the wind to nearby branches or plants.
Once a suitable host is found these little worms immediately begin to form a new bag over its body. Controlling bagworms is best accomplished when the worms are small and have not formed large bags.
Insecticides to control bagworms should be applied in late June. This will allow most of the eggs to have been hatched and should result in greater control of the new worms. Labeled insecticides are Bacillus thuringiensis, BT, which is available at nurseries and garden centers as Dipel or Thuricide. Other insecticides currently labeled are acephate (Orthene), carbaryl (Sevin), malathion and permethrin. For best results, thoroughly cover the plants with insecticide so that it is ingested by the insects as they feed.
Bagworms are common in Eastern Nebraska. Evergreen trees and shrubs may be killed if completely defoliated and less severe attacks can slow growth. Bagworms also feed on shade, orchard, and forest trees of nearly every kind, as well as many ornamental shrubs and perennials, however, severe attacks are unusual.
