Integrated Pest Management for Evergreen Bagworms on Conifers in South Carolina

Evergreen Bagworm Management at a Glance

Affected Plants: Arborvitae (Thuja spp.), cedar (Cedrus spp.), juniper (Juniperus spp.), Leyland cypress (× Hesperotropsis leylandii), and pines (Pinus spp.)

Primary Insect Pest: Evergreen bagworm (Thyridopteryx ephemeraeformis)

Factors that Increase Infestations: Overwintering egg populations, delayed detection, stressed landscape plants, and unmanaged infestations

Most Important Prevention Strategy: Inspect susceptible conifers regularly and remove bagworm bags before eggs hatch in spring

Best Time to Remove Bags: Fall, winter, or early spring, before eggs hatch

Biological Control: Bacillus thuringiensis subsp. kurstaki (Bt) and naturally occurring parasitic wasps

Chemical Control: Spinosad, pyrethrins, pyrethroids, malathion, acephate, horticultural oils, neem oil, insecticidal soaps, and azadirachtin products when necessary

Evergreen bagworm (Thyridopteryx ephemeraeformis) is a destructive caterpillar pest of arborvitae, cedar, juniper, Leyland cypress, and pine in South Carolina landscapes.

Bagworms often go unnoticed until significant feeding damage occurs because they live inside protective bags made from host plant foliage. Early scouting and timely management are essential for preventing severe infestations.

Infestations are most common on stressed plants and can rapidly increase when populations are not managed.

Bagworms feed on many landscape plants, but are especially damaging to:

• Leyland cypress
• Arborvitae
• Cedar
• Juniper
• Pines

Effective integrated pest management (IPM) begins with accurate identification, regular monitoring, and timely intervention. Understanding the bagworm life cycle and recognizing early signs of infestation can help prevent severe damage to susceptible conifers.

For more information about bagworm damage to Leyland cypress and juniper (cedar) trees, visit Leyland Cypress Diseases and Insect Pests in South Carolina (HGIC 2004) and Juniper Diseases & Insect Pests (HGIC 2056).

How to Identify Evergreen Bagworms

Correct identification is an effective component of an integrated pest management (IPM) program. The most recognizable sign is the protective bag attached to branches and foliage.

Evergreen Bagworm Bags and Pupal Cases

Bagworms construct distinctive bags from needles, leaves, and silk. These bags serve as protection for developing larvae and later become overwintering sites for eggs.

Symptoms

• Cone-shaped bags attached to branches
• Bags range from ¼ inch to over 2 inches long
• Bags composed of host plant foliage and silk
• Female pupal cases are wider than males to accommodate the eggs

Adult Male Evergreen Bagworms

Adult males are small, brown moths with dark wings. After emerging from the bag, males fly in search of females to mate with.

These eggs will hatch in late spring to early summer. Newly hatched caterpillars are 1/8 inch long and grow to 2 inches long. The rate of foliage consumption increases dramatically with caterpillar size.

Adult Female Evergreen Bagworms

Adult female bagworms remain inside the bag throughout their lives. Females are wingless, legless, and grub-like in appearance. After mating, females lay approximately 500 to 1,000 eggs within the bag before dying.

Bagworm feeding damage increases as caterpillars grow. Large larvae consume substantially more foliage than newly hatched caterpillars and can cause severe injury to susceptible conifers.

Signs of Evergreen Bagworm Damage

• Missing needles or foliage
• Thinning canopy
• Brown branches
• Declining plant vigor
• Heavy defoliation during severe infestations

For more information about bagworms, visit the Clemson Extension publication Bagworms.

Integrated Pest Management for Evergreen Bagworms

Integrated pest management (IPM) combines monitoring, prevention, biological controls, and targeted pesticide use to manage evergreen bagworms while minimizing impacts on pollinators and beneficial insects. Successful management depends on early detection and on selecting the least disruptive control option that effectively reduces populations.

Step 1: Scout and Monitor Evergreen Bagworms

Regular scouting allows homeowners to detect bagworms before populations become difficult to manage. Because bagworms often resemble cones or plant debris, infestations can go unnoticed until substantial feeding damage occurs.

What to Look For

Inspect:

• Arborvitae
• Cedar
• Juniper
• Leyland cypress
• Pine

Pay particular attention to:

• Lower branches
• Interior foliage
• Previously infested plants
• Stressed plants

Look for:

• Small developing bags
• Mature bags attached to branches
• Needle loss
• Browning foliage
• Thinning canopy

Monitoring Recommendations

• Inspect susceptible plants several times during the growing season.
• Monitor plants closely during late spring when eggs begin hatching.
• Record areas with previous infestations for future inspections.
• Prioritize monitoring stressed or declining plants.

When to Look for Evergreen Bagworms

Understanding the evergreen bagworm life cycle helps improve scouting and treatment timing. The following seasonal guide outlines when bagworms are active and the most effective management actions.

Season	Bagworm Activity	Recommended Action
Fall	Adult females lay 500 to 1,000 eggs inside the bag before dying. Eggs remain protected inside the bag.	Remove and destroy bags by hand to reduce next year’s population.
Winter	Eggs overwinter inside bags attached to branches.	Continue hand-picking and destroying bags before egg hatch.
Early Spring	Eggs remain dormant inside bags.	Inspect susceptible conifers for overwintering bags and remove them when found.
Late Spring	Eggs begin hatching. Newly emerged caterpillars start feeding on foliage.	Begin scouting regularly and consider applications of Bacillus thuringiensis subsp. kurstaki (Bt) when larvae are small.
Early Summer	Caterpillars continue feeding and constructing larger bags.	Continue monitoring populations and apply management measures when necessary.
Mid to Late Summer	Larger caterpillars consume increasing amounts of foliage and can cause significant plant damage.	Use biological, mechanical, or chemical controls as needed based on infestation levels.
Fall	Adult males emerge and mate with females. Females remain inside bags and lay eggs.	Remove bags before eggs overwinter and begin the cycle again.

Bagworm management is most effective when bags are removed during fall, winter, or early spring and when Bt applications target newly hatched larvae in late spring.

Step 2: Remove Bagworm Bags by Hand

Mechanical removal is one of the most effective management practices for small infestations. Since eggs remain inside the bags during fall and winter, removing bags directly reduces future populations.

Hand Removal Procedures

• Remove bags during fall, winter, or early spring prior to the eggs hatching
• Remove as many bags as possible to significantly reduce the population in one step
• Place removed bags in sealed trash bags or destroy them

 

Advantages of Hand Removal

• Immediate reduction of bagworm populations
• No pesticide exposure
• No impact on pollinators
• No impact on natural enemies
• Effective for light infestations

Even when trees are too large for complete removal, partial bag removal can substantially reduce future populations.

Step 3: Use Biological Control for Evergreen Bagworms

Biological controls can help suppress evergreen bagworm populations while minimizing impacts on pollinators and other beneficial insects.

Bacillus thuringiensis subsp. kurstaki (Bt)

Bt is a naturally occurring bacterium that targets caterpillars. After ingestion, Bt produces toxins in the insect gut, leading to death within several days.

The main biological control for caterpillars is Bacillus thuringiensis, subsp. kurstaki, also known as Bt. This bacterial spore suspension is sprayed onto landscape plants, and the insect then ingests the spores as it feeds on conifer needles. The bacterium releases a toxin inside the insect’s gut, killing it within a few days.

Many gardeners are looking for a safe preventive treatment, and Bt is one of the most effective options when applied every 7 to 14 days during late spring, when eggs are hatching.

Parasitic Wasps

Small parasitic wasps provide another effective biological control. Trichogramma wasps are endoparasitoids that live and reproduce inside another animal, ultimately killing it.

They parasitize the eggs of more than 200 species of moths and butterflies and are among the most widely released biological control agents in North America.

These wasps can be purchased, but it is often more economical and practical to reduce the use of broad-spectrum insecticides, so naturally occurring populations are not harmed.

Cultural Practices that Support Beneficial Insects

• Plant a variety of flowering plants.
• Provide nectar sources throughout the growing season.
• Provide pollen sources throughout the growing season.
• Limit unnecessary use of broad-spectrum insecticides.
• Preserve habitat for beneficial insects.

These practices help maintain naturally occurring predators and parasitoids in the landscape.

Step 4: Use Chemical Controls Only When Necessary

Chemical insecticides may be needed when biological, cultural, and mechanical control measures have failed to keep bagworm populations under control. The goal with insecticide use is to choose a product that has minimal impact on pollinators and natural enemies while still providing effective control of the target pest.

Bagworm egg casings are notoriously impervious to sprays, and even the strongest insecticides have difficulty penetrating the lining. For effective control, insecticide applications should be made before bags become firmly attached to landscape plants and while larvae are actively feeding.

Before purchasing and using an insecticide:

• Read and follow ALL label directions.
• Verify the active ingredient listed on the product label.
• Confirm the product is labeled for the intended use site.
• Follow all labeled application rates and restrictions.
• Spray late in the day for best results and to help protect beneficial insects.

Spinosad

Products containing the active ingredient spinosad are among the safer chemical control options for bagworms. Spinosad is derived from the actinomycete bacterium, Saccharopolyspora spinosa. This insecticide provides good control and is generally less hazardous to pollinators and other beneficial insects than many broad-spectrum alternatives, though it is not completely harmless.

Spinosad takes about 3 to 7 days from treatment to kill the caterpillar, and repeat applications may be necessary.

Pyrethrins

Pyrethrins are botanically derived, natural compounds that can provide a relatively quick knockdown of caterpillars. These products may harm pollinators and natural enemies that are directly exposed during application, and the residues on foliage may temporarily repel beneficial insects.

However, these effects are generally short-lived, lasting only a few hours. As a result, pyrethrins can be useful for reducing large bagworm populations while causing less long-term disruption to biological controls.

Pyrethroids

Bifenthrin, permethrin, and gamma-cyhalothrin are pyrethroid insecticides, which are synthetic versions of pyrethrins. These products provide quick knockdown and persist on plants for longer periods under varying weather conditions, providing effective control of both larvae and adults.

Avoid repeated use to help reduce the risk of insect resistance. Because pyrethroids are broad-spectrum insecticides that can affect pollinators and beneficial insects, they should be used sparingly and applied during the early evening whenever possible.

Malathion and Acephate

Traditional chemical controls containing malathion or acephate are also available for bagworm management. These insecticides have been used for many years, are available in liquid formulations, and can persist on foliage for extended periods.

When using these pesticides, limit application to infested plants. Because these insecticides are broad-spectrum and hazardous to pollinators, they are best reserved for heavy infestations when other management options have not provided adequate control.

Recommended Insecticides for Evergreen Bagworms

The following biological and chemical insecticides may be used as part of an integrated pest management program for evergreen bagworms when monitoring, hand removal, and biological controls do not provide adequate suppression.

Product names are provided as examples only and are not intended as endorsements. Always read and follow all label directions before purchasing or applying any pesticide.

Biological Insecticides for Evergreen Bagworms (Table 1)

Active Ingredient	Example Product Names	Notes
Bt (Bacillus thuringiensis subsp. kurstaki)	Bonide Thuricide Bacillus thuringiensis (Bt) Garden Safe Brand Bt Worm & Caterpillar Killer Monterey Bt Natural Guard by ferti-lome Caterpillar Killer Spray with Bt Natural Guard by ferti-lome Caterpillar Killer Spray with Bt Ready to Use Safer Brand Caterpillar Killer For Trees, Shrubs, & Vegetables Concentrate II Southern Ag Thuricide Bt Caterpillar Control Ferti-lome Dipel Dust Biological Insecticide SA-50 Southern Ag Dipel Dust	pollinator friendly

Insecticides for Evergreen Bagworms

Active Ingredient	Example Product Names	Notes
Azadiractin	Aza-Direct Botanical Insecticide AzaGuard Botanical Based Insecticide/Nematicide AzaMax Botanical Insecticide, Miticide, and Nematicide AzaSol Non-oil Based, Water Soluble Powder Azatin O Biological Insecticide Azera Gardening (with Pyrethrins)	pollinator friendly
Horticultural Oil	Bonide All Seasons Horticulture Spray Oil Ready-to-Use Bonide All Seasons Horticulture & Dormant Spray Oil Ready-to-Spray ferti-lome Horticultural Oil Spray Monterey Horticultural Oil Concentrate Monterey Horticultural Oil RTU Safer Brand Horticultural & Dormant Spray Oil Concentrate Southern Ag Parafine Horticultural Oil Summit Year-Round Spray Oil	pollinator friendly
Insecticidal Soap	Bonide Insecticidal Soap Multi-purpose Insect Control Ready to Use Garden Safe Brand Insecticidal Soap Insect Killer Miracle-Gro Nature’s Care Insecticidal Soap Natria Insecticidal Soap Ready-to-Use Natural Guard by ferti-lome Insecticidal Soap Concentrate Safer Brand Insect Killing Soap Concentrate II Whitney Farms Insecticidal Soap 1	pollinator friendly
Malathion	Bonide Malathion 50% Insect Control Gordon’s Malathion 50% Spray Hi-Yield 55% Malathion Insect Spray Martin’s Malathion 57% Ortho Max Malathion Insect Spray Concentrate Southern Ag Malathion 50% EC Spectracide Malathion Insect Spray Concentrate Tiger Brand 50% Malathion	harmful to pollinators
Neem Oil	Bonide Captain Jack’s Neem Oil Concentrate Bonide Captain Jack’s Neem Oil Ready to Use Bonide Rose Rx 3-in-1 Concentrate Bonide Rose Rx 3-in-1 Ready to Use Garden Safe Fungicide 3 Garden Safe Fungicide 3 Concentrate Garden Safe Neem Oil Extract Concentrate Monterey 70% Neem Oil Fungicide/Insecticide/Miticide Natria Neem Oil Concentrate Natria Neem Oil Ready-to-Use Natural Guard Brand by ferti-lome Neem Safer Brand Neem Oil Concentrate Fungicide/Miticide/Insecticide Safer Brand Neem Oil RTU Fungicide/Miticide/Insecticide Southern Ag Triple Action Neem Oil	pollinator friendly
Spinosad	Bonide Captain Jack’s Deadbug Brew Concentrate Bonide Captain Jack’s Deadbug Brew Ready to Spray Bonide Captain Jack’s Deadbug Brew Ready to Use Bonide Colorado Potato Beetle Beater Concentrate Conserve SC Turf & Ornamental Monterey Garden Insect Spray Monterey Garden Insect Spray RTU Natural Guard by ferti-lome Spinosad Bagworm, Tent Caterpillar & Chewing Insect Control Natural Guard by ferti-lome Spinosad Soap Ortho Insect Killer Tree & Shrub Concentrate Southern Ag Conserve Naturalyte Insect Control	can be harmful to pollinators

Abbreviations

• RTU = Ready-to-Use
• RTS = Ready-to-Spray

Best Management Practices for Evergreen Bagworms

• Scout susceptible conifers regularly.
• Remove bags before eggs hatch.
• Preserve beneficial insects.
• Apply Bt to young larvae.
• Reserve broad-spectrum insecticides for severe infestations.

Pesticides are updated annually. The last updates were made on 6/26 by N. Jordan Franklin.

Originally published 02/19