After mating, the female lays 500-1,000 eggs in her bag and dies. Removal of the egg-containing bags during winter and early spring is a very effective method for preventing problems before the next growing season. Once removed, the bags should be destroyed or placed in a deep container, which allows beneficial parasites that may also be present in the bags to escape while retaining the bagworm larvae. If the infestation is severe or the bags are out of reach, spray with the bacterial insecticide, Dipel. This insecticide contains spores of the bacterium, Bacillus thuringiensis , which when eaten kill the caterpillar.
Young larvae are much more susceptible to the treatment than are older larvae.
As such, apply this pesticide in the spring as soon as bagworms are seen. Control is most effective when spraying is done in late afternoon or early evening. This insecticide is very safe to use. As with any pesticide, read and follow all label directions and precautions before using. Mites are not insects but are more closely related to spiders.