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Thyidopteryx ephemeraeformis

Common bagworm inside bag. (Photo: Tawny Simisky)
Scientific Name: 
Thyidopteryx ephemeraeformis
Common Name: 
Growing Degree Days (GDD's): 
600–900 GDD's, Base 50F, March 1st Start Date (Approx. Mid-June.) (Source: Cornell Cooperative Extension.)
Host Plant(s) Common Name (Scientific Name): 
Arborvitae (Thuja spp.)
Black locust (Robinia spp.)
Boxelder (Acer negundo)
Buckeye (Aesculus spp.)
Eastern white pine (Pinus strobus)
Elm (Ulmus spp.)
Juniper (Juniperus spp.)
Ligustrum (Ligustrum japonica)
Linden (Tilia spp.)
Live oak (Quercus virginiana)
London planetree (Platanus x acerifolia)
Pine (Pinus spp.)
Maple (Acer spp.)
Red cedar (Juniperus virginiana)
Sycamore (Platanus spp.) 
Viburnum (Viburnum spp.)
Willow (Salix spp.)
Insect Description: 

This species of bagworm is native to North America and has a large geographic range in the eastern and parts of central US. It is one of many species of native bagworm, although few cause measurable damage. Adult female bagworms do not look like moths, but rather soft, yellow-white caterpillar-like organisms that are devoid of: hairs, eyes, wings, legs, antennae, and functional mouthparts. Adult females never leave the protective case/bag that they create as a larva. Adult males, however, emerge as moths with wings spanning 1 inch and antennae and are covered in dark hairs. The male has a very short lifespan, measured in days, during which time he must find the female to mate. Neither adult feeds. Females can produce 500-1,000 eggs which overwinter in the bag. The bag is made of silk, twigs, and leaves. Young larvae feed on the upper side of the host plant leaves. Older larvae feed on the lower leaf surface and may consume everything except the larger leaf veins. As the larva grows, the bag is enlarged. A full grown larva may have a bag measuring 1.18-2 inches in length. Pupation occurs inside the bag which serves the same function as a cocoon.

Damage to Host: 

Brown spots form on leaves from the feeding of young larvae. On broad-leaved hosts, older larvae feed from the leaf underside and will consume everything except for the midvein. Because female dispersal is limited, a single host may suffer great damage in a season. Spindle-shaped bags may remain on the plant even after management has been successful (if the management technique did not involve bag removal). Extended warm autumns enhance its survival in New England.


Look for browning of leaves from young larval feeding, along with the twig and leaf-covered bags produced by this insect. (Bagworm bags might look slightly different depending on the host plant the insect is found on, since they incorporate material from the specific host to create the bag.)

Cultural Management: 

In small populations, bags may be handpicked from the host and destroyed: placed in a plastic bag, or submerged in soapy water.

Natural Enemies & Biological Control: 

At least 11 species of parasitic wasps attack these insects, including ichneumonids. Some examples of parasitic wasps attacking bagworms include: Pimpla disparis, Itoplectis conquisitor, and Gambrus ultimus. Schaffner (1959) also lists the following natural enemies of bagworm that were collected from samples in Massachusetts, New York, New Jersey, Pennsylvania, Maryland, Delaware, and Missouri: Anachaetopsis spp., Phorocera claripennis, and Zenillia blanda (Diptera), as well as Brachymeria ovata ovata, Habrocytus thyridopterigis, Itoplectis conquisitor, and Phobetes thyridopteryx (Hymenoptera). Adding flowering plants to the landscape may increase the presence of certain parasitic wasps and the percentage of bagworm parasitism. Predators include white footed mice and certain birds.

Chemical Management: 

Acephate (NL)

Azadirachtin (NL)

Bacillus thuringiensis subsp. kurstaki (NL)

Bifenthrin (NL)

Carbaryl (L)

Chlorantraniliprole (NL)

Chlorpyrifos (N)

Chromobacterium subtsugae (NL)

Cyfluthrin (NL)

Deltamethrin (L)

Emamectin benzoate (L)

Gamma-cyhalothrin (L)

Indoxacarb (L)

Lambda-cyhalothrin (larva only) (L)

Malathion (L)

Permethrin (L)

Spinetoram+sulfoxaflor (N)

Spinosad (larva only) (NL)

Tau-fluvalinate (NL)

Tebufenozide (NL)


Active ingredients that may be applied systemically include: acephate (injection), azadirachtin (injection, soil drench), chlorantraniliprole (soil drench), and emamectin benzoate (injection).

When used in nurseries, chlorpyrifos is for quarantine use only.

The common bagworm has over 128 host plant species, all of which are not included in this guide.

Contact sprays should target young caterpillars before they create their protective covering as the bag creates a barrier for adequate coverage. All chemical management options are most effective when directed against bagworms that are still small in size. Thorough coverage of foliage is required.

Reduced risk insecticides such as Bacillus thuringiensis Kurstaki can be used to effectively manage young bagworm caterpillars as they feed.

Chlorantraniliprole was shown in a study to be as effective at managing bagworms as bifenthrin and spinosad (Rhainds and Sadof, 2009).

Soil application of dinotefuran was also tested and determined to be effective at managing young bagworms, particularly on small evergreen shrubs (Rhainds and Sadof, 2009).

Make insecticide applications after bloom to protect pollinators. Applications at times of the day and temperatures when pollinators are less likely to be active can also reduce the risk of impacting their populations.

Note: Beginning July 1, 2022 neonicotinoid insecticides are classified as state restricted use for use on tree and shrub insect pests in Massachusetts. For more information, visit the MA Department of Agricultural Resources Pesticide Program. 

Read and follow all label instructions for safety and proper use. If this guide contradicts language on the label, follow the most up-to-date instructions on the product label. Always confirm that the site you wish to treat and the pest you wish to manage are on the label before using any pesticide. Read the full disclaimer. Active ingredients labeled "L" indicate some products containing the active ingredient are labeled for landscape uses on trees or shrubs. Active ingredients labeled "N" indicate some products containing the active ingredient are labeled for use in nurseries. Always confirm allowable uses on product labels. This active ingredient list is based on what was registered for use in Massachusetts at the time of publication. This information changes rapidly and may not be up to date. If you are viewing this information from another state, check with your local Extension Service and State Pesticide Program for local uses and regulations. Active ingredient lists were last updated: January 2024. To check current product registrations in Massachusetts, please visit: .