What Eats Bagworms? Tips and Tricks To Manage These Pests

Bagworms, scientifically known as Thyridopteryx ephemeraeformis, are a common pest that many North American gardeners are unfortunately familiar with. 

These unique insects are easily identified by their spindle-shaped cocoons, which they meticulously craft using silk and materials from their host plants, such as leaves or needles. 

These cocoons not only serve as a protective shield but also camouflage the bagworms, allowing them to blend seamlessly into their environment.

The significance of bagworms extends beyond their intriguing appearance.

In North American gardens, particularly in the eastern regions, they pose a considerable threat to a variety of trees and shrubs.

What Eats Bagworms
bagworm

While they might seem harmless at first glance, bagworms are voracious eaters. 

They feed on the foliage of over 100 different species, including many that are commonly found in gardens and landscapes, such as arborvitae, juniper, and pine. 

When left unchecked, these pests can defoliate and severely weaken plants, leading to long-term damage or even the death of the host plant. 

Given their potential for destruction, understanding and managing bagworm populations is crucial for maintaining healthy and vibrant gardens.

In this article, we will look at one of the most ecologically friendly ways of managing bagworms – by introducing natural predators of these pests. We will also look at other ways of doing this.

Life Cycle and Identification of Bagworms

Bagworms have a fascinating and distinct life cycle that sets them apart from many other garden pests.

Lifecycle Stages: From Egg to Adult

  • Egg: The lifecycle of a bagworm begins inside the protective bag, where the female lays between 500 to 1000 eggs. These eggs overwinter inside the bag, awaiting the warmth of spring to hatch.
  • Larva: As spring arrives, usually around May and June, the eggs hatch, releasing tiny caterpillars. These larvae immediately begin constructing their own protective bags using materials from their host plants. As they feed and grow, they drag these bags along, enlargening them to accommodate their increasing size.
  • Pupa: By mid-August, having reached about an inch in length, the bagworm enters the pupal stage. The larva attaches its bag to a branch, seals itself inside, and begins its transformation.
  • Adult: By mid-September, the transformation is complete. Male bagworms emerge as black, furry moths with transparent wings that span about an inch. Their primary purpose is to find a female and mate. Interestingly, the female bagworms undergo a different transformation. They evolve into a maggot-like, soft-bodied worm that remains inside the bag, awaiting a male to mate with her through an opening in the bag.
Bagworm Moth

Physical Appearance: Cocoon Bags, Camouflage Techniques, and Adult Forms

Cocoon Bags: The most distinguishing feature of bagworms is their cocoon-like bags. 

These bags, often mistaken for pine cones or other tree debris, are constructed from silk and pieces of the host plant. 

This not only provides protection but also acts as a brilliant camouflage against predators.

Bagworms can be found inside the house as well.

Camouflage Techniques: The art of camouflage is vital for the bagworm’s survival. 

By using materials from their immediate environment, they blend seamlessly, making them hard to spot. 

This is especially true for the younger larvae, whose bags are smaller and even more inconspicuous.

Adult Forms: While the bags of the larvae are often the most noticed, the adult forms are less commonly seen. 

The male moths, with their black furry bodies and transparent wings, are the more mobile of the two sexes, flying in search of females. 

In contrast, the female remains stationary, never leaving the bag she constructed during her larval stage.

Preferred Habitats 

Bagworms are not particularly picky when it comes to their habitat, but they do have preferences. 

Evergreen trees are especially susceptible to bagworm infestations. 

Arborvitae, junipers, and cedars often bear the brunt of their appetite. However, they are also known to infest deciduous trees, expanding their potential habitats and food sources. 

The choice of host plant plays a significant role in the materials the bagworms use for their bags, influencing their appearance and camouflage techniques.

Damage Caused by Bagworms

While they are not directly harmful to humans, bagworms can be a significant menace to various trees and plants. 

Their insatiable appetite, if left unchecked, can lead to severe consequences for the affected vegetation.

Types of Trees and Plants Affected

Bagworms are not particularly selective eaters, but they do have their favorites. They are known to feed on the foliage of over 100 different species. Some of their preferred hosts include:

  • Evergreen trees such as arborvitae, juniper, cedar, and pine.
  • Deciduous trees like maple, oak, sycamore, and poplar.
  • Other plants including spruce, fir, sweetgum, black locust, honey locust, and more.

Detecting an Infestation

Detecting a bagworm infestation early can be the key to managing and mitigating the damage. Some signs to look out for include:

  • Bag-like Cocoons: One of the most evident signs of a bagworm infestation is the presence of their distinctive bags. These can often be seen hanging from the branches of trees and shrubs, resembling small pine cones or other tree debris.
  • Defoliation: As bagworms feed, they strip trees and plants of their foliage. An affected tree might display patchy, uneven defoliation or entirely bare branches.
  • Brown or Dying Branch Tips: Especially in evergreen trees, the tips of branches may turn brown and eventually die due to the feeding activity of bagworms.

Long-term Impact on Trees and Shrubs

The damage caused by bagworms can range from mild to severe, depending on the extent of the infestation.

  • Weakening of Plants: Continuous feeding can weaken trees and shrubs, making them more susceptible to diseases and other pests.
  • Death of Trees: In severe cases, especially with evergreen trees, bagworms can consume so much of the foliage that the tree cannot recover. If they eat more than 70% of an evergreen tree, it can lead to the tree’s death.
  • Aesthetic Damage: Even if the tree or shrub survives, the aesthetic damage can be long-lasting. Trees can appear patchy, and their growth can be stunted.
  • Impact on Deciduous Trees: While deciduous trees can also be affected, they often have a better chance of recovery. Even if defoliated, they can produce new leaves in the following growth season.
Bagworm

What Eats Bagworms? Natural Predators of Bagworms

Nature has its own checks and balances, and when it comes to bagworms, several natural predators play a crucial role in controlling their population. 

These predators not only help in reducing the number of bagworms but also provide an eco-friendly alternative to chemical control methods.

Birds

Several bird species are known to feed on bagworms, playing a significant role in keeping their numbers in check.

  • Sparrows: These common birds are known to be effective predators of bagworms. Making landscapes bird-friendly, especially for sparrows, can help in reducing bagworm populations.
  • Finches: Recognizable by their yellow breasts, finches consume various insects, including bagworms, especially during specific periods of the year.
  • Chickadees: These birds have a varied diet that includes berries, seeds, and insects. They are particularly fond of bagworms and can help control their population.
  • Nuthatches: During winter, nuthatches feed on insect eggs, including those of bagworms. They can be particularly effective in reducing the next generation of bagworms.
  • Titmice: These birds are natural predators of various insects, including bagworms. They feed on insects primarily during the summer months, helping control bagworm populations.

Insects

Certain insects are natural enemies of bagworms and can be effective in controlling their population.

Predatory Wasps: These tiny insects, such as Chirotic thyridopteryx and Itoplectis conquisitor, belong to a group of insects known as predatory wasps. 

They do not sting humans and are known to parasitize other insects, including bagworms. 

Planting members of the aster family can attract these wasps, which lay their eggs inside bagworms, effectively controlling their population.

Assassin Bugs: These bugs have a unique ability to attack bagworms. 

Their long, pointy mouthpart, known as the rostrum, allows them to pierce the protective cocoon of the bagworm and feed on the larva inside.

Bagworm Cocoon

Planting Strategies to Attract Predators

To encourage the presence of these natural predators, certain planting strategies can be adopted.

  • Nectar-producing Plants: Planting a strip of long-blooming, nectar-rich perennials, such as Agastache or Pycnanthemum, can attract beneficial predatory wasps.
  • Mixed Buffers: Incorporating a mix of deciduous trees and broadleaf evergreens in your landscape can provide food and shelter for birds, especially those that nest in June. This encourages predation of bagworm larvae when they are most vulnerable.
  • Bird-friendly Landscapes: Ensuring that your landscape is bird-friendly by providing nesting materials, bird baths, and feeders can attract birds that feed on bagworms.

Alternative Control and Management Methods

While natural predators play a significant role in controlling bagworm populations, there are times when additional intervention may be necessary. 

Here’s a look at some alternative methods for managing and controlling bagworm infestations:

Manual Removal

One of the most straightforward and organic methods to control bagworms is manual removal.

Especially effective for smaller trees and shrubs, this method involves physically removing the bagworm’s bags from the tree and destroying them. 

This approach is most effective from late fall to spring when the bags contain eggs, ensuring the removal of future generations.

Chemical Controls

Chemical interventions can be effective but should be used judiciously to minimize harm to the environment and beneficial insects.

Bt (Bacillus thuringiensis): Bt is a naturally occurring soil bacterium that specifically targets bagworm caterpillars. 

When ingested, it causes the caterpillars to become sick, cease feeding, and eventually die. 

The best time to apply Bt is during the hatching period of young worms, typically in late May or early June. 

Bagworms

Synthetic Pesticides: Chemicals such as acephate (Orthene), cyfluthrin, sevin, and spinosad can be used to control bagworms. 

While they can be effective, they also come with environmental considerations. These chemicals are toxic to bees and other beneficial insects. 

If using synthetic pesticides, it’s essential to apply them on calm, dry days to minimize drift and ensure rapid drying.

Strategies for Prevention

Prevention is always better than cure. Adopting certain strategies can help prevent or reduce bagworm infestations.

Planting Less Susceptible Trees and Shrubs: While bagworms can feed on a wide variety of trees, certain species are less prone to infestation. 

Broadleaf evergreens and deciduous trees, for instance, show much less damage compared to needle evergreens.

Encouraging Bird Activity: Birds are natural predators of bagworms. 

By setting up birdfeeders and creating bird-friendly landscapes, you can attract birds like chickadees, nuthatches, and titmice, which feed on bagworms.

Importance of Monitoring

Regular monitoring is crucial for early detection and effective management of bagworm infestations.

IPM (Integrated Pest Management): IPM is a holistic approach to pest control that combines various strategies and practices to manage pests effectively and in an environmentally friendly manner. 

It emphasizes understanding the life cycle of the pest and its interaction with the environment.

PHC (Plant Health Care) Program: PHC is a proactive approach that focuses on maintaining and improving the health of plants, making them less susceptible to pests and diseases. 

Regular monitoring, proper fertilization, and appropriate watering are some of the components of a PHC program.

In conclusion, while bagworms can be a challenge, a combination of natural predators, manual removal, chemical controls, and preventive strategies can effectively manage and control their populations. 

Regular monitoring and a proactive approach are key to ensuring the health and beauty of your landscape.

Conclusion

Bagworms, while small, can pose a significant threat to the health and aesthetics of our landscapes. 

However, nature itself offers some of the most effective solutions to this challenge. 

Natural predators, such as specific bird species and insects, play a pivotal role in keeping bagworm populations in check. 

Their presence not only reduces the need for chemical interventions but also contributes to a balanced and thriving ecosystem.

Early detection and timely intervention are crucial in managing bagworm infestations. 

By regularly monitoring our plants and being observant of the early signs of infestation, we can take proactive measures before the situation escalates. 

This not only saves our plants but also reduces the need for aggressive control methods.

It’s also important to prioritize environmentally-friendly control methods. 

Whether it’s manual removal, using targeted organic treatments, or fostering habitats for natural predators, these methods ensure that we address the problem without causing undue harm to the environment.

The battle against bagworms is not just about protecting our plants but also about preserving the delicate balance of our ecosystem. 

By leaning on nature’s own mechanisms and adopting sustainable practices, we can ensure a green, healthy, and harmonious landscape for generations to come.

Authors

    by
  • Bugman

    Bugman aka Daniel Marlos has been identifying bugs since 1999. whatsthatbug.com is his passion project and it has helped millions of readers identify the bug that has been bugging them for over two decades. You can reach out to him through our Contact Page.

  • Piyushi Dhir

    Piyushi is a nature lover, blogger and traveler at heart. She lives in beautiful Canada with her family. Piyushi is an animal lover and loves to write about all creatures.

11 thoughts on “What Eats Bagworms? Tips and Tricks To Manage These Pests”

  1. Hi Brinda,
    This neat little bug is a bagworm moth, Amicta quadrangularis. It is a desert species, also found in Southern Israel. It is unusual in that it creates a bag with the twigs perpendicular to the opening and arranged in a square like a log cabin, and not aligned with it like other bagworms.
    Very cool!
    Ben,
    Israel

    Reply
  2. We want to know how to look after our ones properly can you tell us how?
    We have 3 Saunders case moth caterpillars (large bag worm ) ones really small ones medium sized and the other is quite big really big!!!!!! That one is really really brave/tame.

    Reply
  3. We want to know how to look after our ones properly can you tell us how?
    We have 3 Saunders case moth caterpillars (large bag worm ) ones really small ones medium sized and the other is quite big really big!!!!!! That one is really really brave/tame.

    Reply
  4. The bag is quadrate (four sides). This is characteristic to the bagworm Amicta quadrangularis (Lepidoptera: Psychidae). It is common in arid and semiarid ecosystems; also in Middle East e.g. Egypt and Israel. Adult male winged, dark gray nearly black in color. Female wingless does not leave its shelter bag; its bag is ca 3 cm long and 1 cm wide. Male bag ca 2 cm long and 0.5 cm wide. Female bag hosts the male during mating with the female. Moths do not feed like silkworms; their mouthparts are vestigial.

    Reply
    • Thanks so much for providing information on the life cycle of this Middle Eastern Bagworm, a species that shares many characteristics with other Bagworms.

      Reply
  5. My Paracantha is loaded with bag worms . How do I get rid of them . I’ve been killing them one by one . I’d rather do it all at once.
    Elaine Davis

    Reply
  6. My Paracantha is loaded with bag worms . How do I get rid of them . I’ve been killing them one by one . I’d rather do it all at once.
    Elaine Davis

    Reply
  7. i live in sydney nsw and have been wondering what these caterpillars were it would seem they are saunders case moth which may explain the wasps that we get here look the same

    Reply
  8. we have a very large bagmoth on our hedge, it is orange and brown in colour and retreats when disturbed. How long does it take to mutate into a moth and how big will it be when it comes out. Are the small ones the female bagworm if so will she die once she leaves her cocoon.

    Reply

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