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.
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.
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.
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.
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.
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.
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.
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:
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 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.
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.
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.
Over the years, our website, whatsthatbug.com has received hundreds of letters and some interesting images asking us about these insects. Scroll down to have a look at some of them.
Letter 1 – Large Bagworm or Saunder's Case Moth from Australia
Stick-shelled beetlepillar Location: Australia (Sydney Basin) April 2, 2011 10:50 pm My daughter found this wandering around my backyard. I’ve seen these before but always assumed they were a cocoon, rather than a sort of shell. This one has been around the backyard for at least a month as I have seen it hanging from trees, then mysteriously vanishing. I also have video of it checking out the camera Signature: Carey Hi Carey, This is a Bagworm in the family Psychidae, and we quickly identified it as a Large Bagworm or Saunder’s Case Moth, Metura elongatus, on the Brisbane Insect Website. The caterpillar forms a silken case containing plant material from its food plant that it remains in, eventually pupating inside of the case. The adult female is wingless and she never leaves her case, using pheromones to attract a mate. The Butterfly House website has images of the entire life cycle. Thanks for that, my daughter was fascinated (so was I) to see photographs of the adult moth. Cheers Carey
Letter 2 – Bagworm Moth lays eggs in Australia
unusual bug Location: eastern suburbs Sydney April 9, 2011 2:27 am I came across this bug in my backyard 9/4/11. It’s about 8mm in body length. Second image the next day after being kept under a glass. What looks like thousend of eggs! Signature: Heinz57 Dear Heinz57, This is a Moth, though we haven’t been able to come up with a conclusive identification. We also don’t know if her wings failed to expand after metamorphosis, or if this is a flightless species with vestigial wings. Many female Tussock Moths are flightless, and the markings on your specimen match those of Oligeria hemicalla pictured on the ButterflyHouse website, but we are unable to locate an image of a female moth. The Painted Apple Moth is an example of a Tussock Moth in the family Lymantriidae that has a wingless female. The photos on Wikipedia indicate that it is not your species, though the eggs look quite similar. Perhaps one of our readers will be able to supply an identification. Karl provides an identification Unknown flightless moth lays eggs in Australia Hi Daniel and Heinz57: The looks like a female Australian Bagmoth, Cebysa leucotelus (Psychidae). It is native to southern Australia and has recently shown up in New Zealand. Apparently the larvae feed on lichens growing on tree trunks, rocks, etc. and the lichen fragments get incorporated into the larval cases, or ‘bags’. Only the females are flightless. Regards. Karl
Letter 3 – Bug of the Month: September 2007 – Bagworm
a little caterpillar with a traveling cocoon Hi, I’m hoping you can identify this little fellow. He’s been hanging around (literally) ,and under my blue ceramic bird bath. At first I thought he was building a cocoon, but he keeps crawling all over the place with it . Let me know, please, if you can identify him. His cocoon seems to be about 3″ long. I live in Parma, Ohio (a suburb of Cleveland). Thank you. Mary Griffin Hi Mary, This caterpillar is a Bagworm. Bagworms are Moths in the family Psychidae. According to BugGuide: “Larvae (bagworms) construct spindle-shaped bags covered with pieces of twigs, leaves, etc., and remain in them, enlarging them as they grow, till they pupate (also in the bag). Adult females remain in the bag, emitting pheromones which attract adult males to mate with them.”
Letter 4 – Male Evergreen Bagworm Moth
Wow, you nailed it!
I saw this weird moth on my garage so I captured it: Went to your site and found it without even looking: Large Tolype I scanned down a bit and found this one too: Chickweed Moth
But I wouldn’t even know where to start with this one:
We are happy to hear you find our site user friendly and helpful. No matter how hard you tried, you would not have located your Male Evergreen Bagworm, Thyridopteryx ephemeraeformis, on our site since your photo is the first adult photo we have received. We have a Bagworm page since we get so many requests to identify the caterpillars and cocoons. Only male Bagworm moths are winged. Females never leave the cocoon and mating occurs when the winged male locates a female ready to mate. She then lays her eggs in the bag and dies. Thanks for your wonderful addition to our archives.
Letter 5 – Tiger Beetle and Bagworm from Japan
Hi I am an American in Japan and thought you’d be interested in seeing what the tiger beetles here look like. They’re called hanmyou here. I also included photos of a bagworm called a minomushi which means “straw raincoat”. They are a favorite of children here. Melody McFarland Yokosuka, Japan Hi Melody, Thank you for sending us your wonderful images as well as the language lesson. The jaws on that Hanmyou Tiger Beetle are quite formidable.
Letter 6 – Oiketicus Bagworm
I found this cocoon on my rose bush in west central Florida on Sept. 17, 2005. I’d never seen one like it before, and being a 4th grade teacher, took it in for my class to see. No one at school seems to know what it is, nor have they ever seen one before. I keep putting fresh rose leaves in the container with a bit of water and the catepillar ventures out occasionally to feed. Attaching a photo. Any idea what it is?
We were pretty sure this was a Bagworm, but didn’t recognize it. Now we believe it is in the genus Oiketicus. Thank you for the great photo.
Letter 7 – Mystery: Bagworm (we think) from Oman
What bug had made this? May 23, 2010 I clicked this picture thinking it was a screw.. Then someone corrected me saying that its probably an insect which makes a cocoon out of twigs. Can you tell what it really is… ‘coz its definitely not a screw that I shot! brinda Muscat, Oman Hi Brinda, The only conclusion we can draw is that this must be some species of Bagworm, a group of moths in the family Psychidae. Many North American species are represented on BugGuide. We decided to search online in an effort to be more specific with your individual. The closest we found is a Bagworm from Singapore with a bag construction similar to your example, but with an interesting twist. Some photos are on a Blog about Singapore (scroll about 3/4 way down) and one of the photos is also posted on Flickr. Bagworms begin constructing a bag when they are young caterpillars, adding to the bag as they grow. The bag acts as a means of shelter and protection and the caterpillar does not leave the bag, eventually pupating inside. The bag is constructed from silk and plant material, generally from the plant upon which the caterpillar feeds. Many female Bagworms are wingless and legless, and they never leave the shelter of the bag. The male seeks the female out when she is sexually mature and mates either inside the bag or in the entrance to the bag. Perhaps one of our readers will have better luck identifying the species for us. Hey, Thanks a bunch.. I did a bit of research myself on bagworms..but still a bit lost on which type is this one. Most of them are on leaves or branches, but this one was on a concrete block on the side of a road. I’m going to try and dig a bit more on bagworms in Oman. Thanks again! Regards brinda
Letter 8 – Evergreen Bagworm
unidentified bug Location: Midwest North America August 2, 2011 2:53 pm Hi, I am from Bradley, IL. It is the beginning of August and we have these little ”pods” or ”pine cone” looking sacks all over our pine tree in the back yard. They have a small ”worm like” animal inside and attach themselves to anything that is stationary. The outside of the ”pod” is camouflaged to match the berries on the tree. Signature: Thanks, Anna Hi Anna, We absolutely love that you have documented an Evergreen Bagworm, Thyridopteryx ephemeraeformis (see BugGuide), that has incorporated berries into its bag. Bagworms are moth caterpillars that use leaves and twigs from the plants that they feed upon to construct a bag that protects them from predators and the elements. The Bagworm will eventually attach the bag to a stem, fence or wall, seal the bag and pupate inside. Only male Bagworm Moths have wings. Females are legless and wingless and they do not leave the bag. The male mates with an immobile female who then lays eggs in the bag as well.