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Problem: Bagworms - Thyridopteryx ephemeraeformis
Hosts: Numerous trees and shrubs but especially junipers and arbovitae.
Description: Young bagworms normally hatch in May in Kansas and start out about 1/25 of an inch long. The young larvae begin to spin silken bags around themselves which they carry as they feed. Larvae usually feed on the original plant or those nearby but very young larvae may be transported to other hosts via a long silken thread that can be carried by the wind. As the larvae grow, leaf fragments are added to the bag providing a natural camouflage. Often the bags are not noticed until the larvae are nearing maturation and the bags approach 1 to 2 inches in length. Mature bags hang off the tree or shrub like Christmas ornaments. Bagworms reach maturity in August. The now mature larvae attach their bags to branches or other objects and change into adults. The adult male is a small, gray, clear-winged moth that resembles a wasp.
The female is wingless and legless and never leaves the bag. Males emerge in September and mate with the female through the bag entrance. The female then produces her eggs and dies. Eggs overwinter inside the bag and the cycle repeats the following year.
Recommendations: Small infestations can be picked off by hand once the larvae are large enough to see easily. However, any insecticide spray will be more effective if used on young larvae that are actively feeding. In Kansas, start looking for the new hatch about the middle of May. Wait a week after seeing the first larvae emerge to allow those still in the bag to make their appearance.
Insecticides commonly used for controlling bagworms include Orthene,
cyfluthrin, permethrin, malathion
and Sevin. Also, products containing Bacillus thuringiensis are effective
when used against bagworm larvae while they are still small. THOROUGH SPRAY COVERAGE
TO FOLIAGE IS ESSENTIAL FOR CONTROLLING BAGWORM! Controls applied in August
are often a waste of time and expense because the larvae are large, tough and may have
stopped feeding.
References:
1. Life Histories of Common Insects, Mites and nematodes Infesting Ornamental Plants in Missouri, Missouri Department of Agriculture, Plant Industries Division, pg F-1
2. Insects that Feed on Trees and Shrubs, Cornell University Press, pg 150
3. Bagworms, Nebraska Extension Nebguide G73-4-A
4. Bagworms, Purdue University Extension publication E-27
5. Bagworms, K-State Research and Extension, Entomology Publication 403
Last Update: 03/28/2003
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