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Bagworms are aptly named for the bag the larva make of silk and bits of twigs or leaves interwoven to disguise and strengthen the case.The insect begins its life as an egg laid by a female moth that never leaves her bag.Females produce 500-1000 eggs in a single mass. The female dies shortly after depositing the egg mass. The egg is the overwintering stage. Larvae hatch in late spring immediately beginning to feed and construct their protective bag. The bag enlarges as the caterpillar increases in size.As the caterpillar moves it takes its bag with it. The caterpillar pupates in the bag that then serves as a cocoon. We find bagworms predominately on junipers, cedar and Leyland cypress trees.
Severe infestations of the caterpillars can defoliate trees and shrubs causing death. Parasitic wasps can reduce the numbers of bagworms. Hand picking and destroying the bags can be affective when there are low numbers. A foliage spray with an insecticide in early June applied in the late afternoon when the bags are small can be effective. Bacillus thuringiensis, (a biological), Orthene TTO, Malathion and Carbaryl are some recommended insecticides. Always check the front of the label to make sure you are purchasing the correct active ingredient. Read the product label for mixing instructions and handling precautions.
For additional information on insects contact your local Extension Office or go online to the LSU AgCenter web page.
The LSU AgCenter and the LSU College of Agriculture