Are Bagworms Harmful to Humans? Unraveling the Truth

Bagworms are caterpillars known for the spindle-shaped bags they create to protect themselves from predators. These insects often go unnoticed until they inflict significant damage to trees and plants on which they feed.

Many wonder if they are harmful to humans and if there’s any danger in coming in contact with them. This is exactly what we are going to discuss in this article.

Are Bagworms Harmful?

While bagworms primarily inflict harm on plants, they do not directly cause harm to humans even on direct skin contact.

However, they can have an indirect impact on human life as they can damage plants and trees in gardens, landscaping, and agriculture which may affect the overall aesthetics or crop yields.

Are Bagworms Harmful to Humans
Bagworm

The good news is that bagworms are generally not a threat to human health and there are various methods available to manage and control their population.

It is important to stay informed about bagworms, their impact on our environment, and the available control measures to protect and preserve our plants and trees from damage.

Though not a direct danger, understanding their life cycle and habits can help us minimize their negative effects on plants and trees.

What Are Bagworms?

Bagworms are a type of caterpillar pests whose larvae live inside protective silk bags, camouflaged by bits of foliage and debris.

Their life cycle begins when the female moth lays eggs inside her cocoon-like bag. Upon hatching, the larvae emerge and create their silk bags.

As they go through multiple development stages called instars, they often feed on leaves and foliage, causing damage to plants and trees.

Physical Appearance

The physical appearance of bagworms varies depending on their stage in the life cycle.

Larvae have a caterpillar-like form and live inside their camouflaged bags.

Adult bagworm moths look different depending on their gender. Males have wings and resemble bees, while females are wingless and spend their entire life inside the bag.

  • Larvae: Caterpillar-like, live in silk bags
  • Male Moth: Bee-like, clear wings
  • Female Moth: Wingless, lives in the bag

Species and Genera

Bagworms belong to the family Psychidae, with numerous species and genera. There are 1,324 bagworm species across 236 genera worldwide. A common species encountered is Thyridopteryx ephemeraeformis.

Bagworm

Effects on Plants and Trees

Types of Trees Affected

Bagworms, specifically Thyridopteryx ephemeraeformis, are harmful to a variety of trees and plants. Some common host plants include:

  • Evergreen trees: Spruce, Pine, Arborvitae, Juniper, Cedar, and Fir
  • Deciduous trees: Maple, Oak, Black Locust, and Willow

Infestation and Damage

Bagworms start as eggs laid on multiple host plants. The eggs hatch and caterpillars emerge, feeding on leaves and foliage. Notable damage can be seen as:

  • Holes in leaves
  • Browning or yellowing of foliage
  • Depletion of host plant’s health

Infested trees can suffer from reduced growth and weakened branches.

Defoliation and Long-Term Impact

When an infestation becomes severe, bagworms may defoliate entire host plants. Various consequences include:

  • Loss of habitat: Birds and other animals relying on affected trees for shelter may lose their homes
  • Reduced soil quality: Leaves no longer drop and enrich soil, causing other plants in the landscape to suffer
  • Increased disease: Weakened plants become more susceptible to other pests and diseases

Defoliated trees can eventually die over time if left untreated.

Are Bagworms Harmful to Humans?

Bagworms are primarily a concern for trees and shrubs, as they feed on their foliage.

While the larvae can defoliate and cause damage to plants, they do not pose a direct threat to humans. In fact, they are more of a nuisance to our gardens and landscapes rather than a health hazard.

Since bagworms are the larval or caterpillar stages of moths, they are not known to carry diseases or parasites that could harm humans.

Most of their impact is felt by trees and shrubs as they feed and construct their spindle-shaped bags from silken threads and foliage.

To summarize,

  • Harmful: No direct harm to humans
  • Primary concern: Damage to trees and shrubs
  • Stage: Larval/caterpillar stage of moths
  • Impact: Feeding and construction of bags

In comparison, other worms, such as zoonotic hookworms, can cause health issues for humans. When these larvae penetrate human skin, they can result in a red, itchy reaction, which is called cutaneous larva migrans.

Table comparing bagworms and zoonotic hookworms

 BagwormsZoonotic Hookworms
Harmful to humans?No direct harmYes, skin infections
Primary concernDamage to trees and shrubsHuman and animal health
StageLarval/caterpillar stage of mothsLarvae stage of roundworms
ImpactFeeding and construction of bagsPenetrating human skin, causing health issues

While bagworms can be a nuisance to the ecosystem, they are not harmful to humans. However, it is essential to properly maintain our gardens and landscapes to prevent their possible infestation and damage to plant life.

Natural and Chemical Control Methods

Handpicking and Manual Removal

Handpicking and manual removal are effective methods to control bagworms in small infestations. It involves physically removing the cocoons from the affected trees. For example:

  • Check for bagworm shelters on trees like apple, elm, and honey locust
  • Dip removed cocoons in soapy water to kill larvae

Using Natural Predators

Natural predators can help keep bagworm populations in check. Some examples include:

  • Ichneumonid wasp: Preys on tent caterpillars and evergreen bagworms
  • Birds (e.g., woodpeckers): Peck off bagworm shelters and feed on larvae

Biological Control

Biological control methods involve utilizing organisms or bacteria to target bagworms. These methods are safe, environmentally friendly, and often more effective during the larval stage. Common biological control agents:

  • Bacteria: Bacillus thuringiensis (Bt) targets larvae without harming other organisms
  • Neem oil: A botanical insecticide that disrupts larval feeding

Chemical Insecticides

Chemical insecticides can be effective in controlling bagworms, but their use should be limited to severe infestations. Common insecticides include:

  • Spinosad: A low-toxicity insecticide that targets larvae
  • Carbaryl, acephate or permethrin: Stronger chemicals, but may harm beneficial insects

Comparison Table: Natural vs. Chemical Control

Control MethodProsCons
Handpicking– Environmentally friendly
– Low-cost
– Labor intensive
– Less suitable for large infestations
Natural Predators– Sustainable
– Reduced reliance on chemicals
– Takes time for predators to be effective
– Predators may not completely control bagworm populations
Biological Control– Target-specific
– Safe for other organisms
– Less effective on adult bagworms
– May require multiple applications
Chemical Insecticides– Rapid results
– Effective for large infestations
– Can harm beneficial insects
– Potential environmental impact

Prevention and Management

The first step in dealing with bagworms is to prevent their appearance in your garden. One strategy is to attract birds like titmice, chickadees, and nuthatches, which feed on bagworms. Install birdhouses or bird feeders to attract them.

To prevent bagworms from spreading, regularly inspect trees and shrubs for their presence. Remove any bagworms you find to stop them from multiplying. You can do this by hand, simply cutting off the silk bags that the larvae reside in.

Although bagworms usually prefer coniferous trees like red cedar, they can also be found on persimmon, sweetgum, sycamore, poplar, and pine trees. Regularly inspect any of these trees around your property.

When it comes to management of established bagworm infestations, manual removal is effective for small-scale infestations. Remove bags containing adult females before they can lay eggs. Note that adult males will have feathery antennae and can fly.

Common prevention methods

PreventionManagement
Attract birdsManual removal
Regularly inspect treesRemove bags containing adult females
Remove bagwormsApply appropriate insecticides

If you have a large infestation, consider using insecticides containing acephate or cyfluthrin. However, it’s important to apply them before the bags become too large and thick, as they can protect the larvae from the insecticides.

In summary:

  • Attract birds to help prevent bagworm infestations
  • Regularly inspect trees and shrubs, and remove any bagworms found
  • For management, remove bags containing adult females and use appropriate insecticides for larger infestations

Remember, always follow label instructions when using insecticides and consult with a local expert if unsure about the best course of action for your specific situation.

Conclusion

While bagworms are not directly harmful to humans, they can cause significant damage to plants and trees, affecting the aesthetics of gardens and landscapes.

Understanding their life cycle and habits can help minimize their negative impact. Effective control methods include handpicking, attracting natural predators, using biological agents, and, in severe cases, employing chemical insecticides.

Regular inspection and prevention strategies are crucial in managing bagworm infestations and preserving our plant life. By staying informed and taking appropriate measures, we can protect and maintain the health of our environment.

Reader Emails

Over the years, our website, whatsthatbug.com has received hundreds of letters and some interesting images asking us about bagworms. Scroll down to have a look at some of them.

Letter 1 – Bagworm

What is in this cocoon?
I’m in Silver Spring, Maryland and took this cocoon off a tree. Can you tell me what it might be?
Thanks,
Walt

Hi Walt,
Sorry for the delay. This is a Bagworm, a type of moth.

Letter 2 – Bagworm

Dear Bug man,
Hello my name is Justin Holohan. I teach 2nd grade at West Amwell School. One of my students brought in this cocoon thing as asked me what it is. I TEACH MATH AND READING NOT INSECTS!!! So hopefully you can help!

They found it on their house and it looks as if something has nested inside the branch. (It looks like a juniper branch) I also saw something very similar in central Jersey.

But they were attached to a pine tree. We live in the wooded area outside of the city of Lambertville. Which is just 20 minutes north of Trenton NJ. Thanks for any help you can provide!!
Justin Holohan
West Amwell School
Lambertville NJ

Hi Justin,
In the interest of education, we are pleased to help. This is a Bagworm, Thyridopteryx ephemeraeformis. This is a moth. The caterpillars form the bags as a camoflauge and protection and never leave the bags, dragging them along as they eat. They are fond of juniper, arborvitae, other conifers and some deciduous trees.

The caterpillars also pupate in the bags. You have a pupa. The bags are sometimes found in such numbers they appear on branches all over the trees. The pupa are often found on the siding of homes. The female moth is flightless, wingless and legless but manages to leave the bag when she emerges.

Males will mate with her and she crawls back into the bag to lay her eggs. We have an entire page devoted to this insect and you can show your student the response by visiting our site where it is prominently featured on the homepage.

Letter 3 – Bagworm

Hello –
Came upon your web site trying to locate some information on a cocoon we have hanging in one of our trees. I am sending this picture showing this odd looking form with the hopes you may have some kind of an answer for us.

We are hoping that some sort of nice butterfly will emerge, and not some sort of destructive bug. We are located in North Carolina, where we have an array of strange things. Don’t know if this would help, but it is located in a Maple Tree. Any help you could give us would be appreciated.
Thank you for your assistance.
Gerri Francisco

Hi Gerri
You have Bagworms, Thyridopteryx ephemeraeformis, an unnattractive moth that forms the cocoon you pictured while still a caterpillar. It drags around this protective housing while feeding, eventually pupating inside. The males are winged and females winglessand legless. The appendageless female never lays her eggs inside the bag after mating. They are pests.

 

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.

2 thoughts on “Are Bagworms Harmful to Humans? Unraveling the Truth”

  1. I am seeing bagworms in North Corrales on young crimson spire oaks and on a young willow. The willow is planted about 60 feet from the oaks. What is the best approach to control or eliminate them? Thanks in advance.

    Reply

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