How to get rid of bagworms on pine trees

The bagworm (Thyridopteryx ephemeraeformis) is a common pest of many coniferous and deciduous trees in the eastern U.S. This moth’s larvae spin unsightly baglike shelters in tree canopies and can cause serious damage through defoliation. Typical control methods include mechanical removal of the bagworm shelters (when feasible) and the application of pesticides. However, the bagworm has a number of natural enemies—in particular, parasitoid insects, such as ichneumonid wasps—and research at the University of Illinois at Urbana-Champaign has shown that bagworm control by these insects can be enhanced by planting certain flowering plants near trees and shrubs that are susceptible to bagworm infestations. The flowering plants used in the UIUC research were all members of the Asteraceae, or aster family, which includes many species with daisylike blossoms known to attract parasitoids. Among them were a shasta daisy cultivar (Leucanthemum × superbum ‘Alaska’), a cultivar of the Newfoundland aster (Aster novi-belgii ‘Professor Anton Kippenburg’), and the treasure flower (Gazania rigens), a South African native. The bagworm host plant was an arborvitae cultivar (Thuja occidentalis ‘Woodwardii’). In one trial, surrounding host plants with flowers led to a 70 percent increase in the parasitism of bagworms. In another trial, attacks on bagworms by parasitoid insects increased by a factor of three when host plants were surrounded by a high density of daisy flowers. Many plants in the Asteraceae are native to North America.

Contents

Bagworms: Are They Harmful and How Can I Get Rid of Them?

Seeing a butterfly emerge from its cocoon is magical. As it spreads its wings, you look in awe at the array of fluttering colors before you!

But, that sense of wonder doesn’t translate when a black, fuzzy moth emerges from its bag! Those moths, likely bagworms, were busy eating your evergreen or tree before making their debut.

Jodie H. saw them on her tree and asked, “My mimosa tree has bagworms. How do I get rid of them?”

Learn what bagworms look like, the damage they do to your trees and how you can control them below.

Bagworm Damage and Control

What do bagworms look like?

You probably won’t see the bagworms themselves, but instead, the 2” homes bagworms make in your trees. In the fall, the insects use their silk and pieces of the tree to create a camouflaged, cocoon-looking bag, which they fill with up to 1,000 eggs!

The eggs hatch in late spring or early summer, when super tiny, black larvae emerge. At 2 mm, they’re barely larger than a pinhead, which makes them light as a feather. The caterpillars use their silk thread as a parachute to travel to nearby trees and begin building a new home (or bag) there.

The pests hang out in their bags until late summer or early fall when the adult males emerge to mate. About the size of a quarter, male bagworms are ashy-black moths with transparent wings.

Where do bagworms come from?

They’re actually native to North America. But they’re mainly in the Eastern United States, dispersed all along the East Coast and in much of the Southeast.

What damage do bagworms do?

Bagworms will attack more than 120 different types of trees. Though, they prefer evergreens, like juniper, arborvitae, cedar and spruce.

Once they’ve found a tree to call home, bagworms start munching.

On evergreens, they’ll eat lots of the buds and foliage, causing branch tips to turn brown and then die. But if they eat more than 80 percent of the tree, the entire evergreen may die.

On deciduous trees (those that lose their leaves in winter), bagworms chew small holes in the leaves and can cause defoliation. Generally, these trees will bounce back if you get rid of the bagworms.

Bagworms also wrap silk around the twigs they build their bags on, which could kill the tree twigs a few years from now.

How can I get rid of bagworms on arborvitae, evergreens and other trees?

You aren’t going to like this, but the easiest way to remove bagworms is to cut off the bags by hand and destroy them. Be sure to cut off all their silk, too, because that could strangle (and kill) twigs later.

If that’s too gross or there are too many bagworms for you to remove, we can help! A certified arborist can apply a treatment to the tree when the larvae emerge in late spring or early summer.

How Do You Get Rid of Bag Worms on Pine Trees?

The best way to remove bag worms from pine trees is to remove the bags by hand or to kill the bag worms using an insecticide. Controlling bag worm population is important as they can spread from tree to tree.

The bags of bag worms can be removed from the tree by hand, sealed in a plastic bag and thrown away. This is best done before hatching begins in late May. After eggs hatch, the bag worms can be killed by spraying the tree with an insecticide aimed at lepidopteran insects. After late May or early June, destroying the bag does not kill all the bag worms since the worms are mobile and not fully contained to the bag. Bag worms on pine trees are camouflaged as small pine cones.

After spraying the tree with pesticide, locate any remaining sacks, and remove them from the tree manually. The sacks can be placed in a bucket of soapy water to ensure the live worms in the sack are eliminated.

To determine the best way to deal with bag worms, understand their life cycle. Bag worms overwinter in their bags. When the larvae begin to hatch from May to early June, they eat the foliage of the pine tree. In August, the bag worms begin to build their bags for mating and laying eggs. The bags suffocate the tree and cause the areas they cover to brown and die.

Bag worms are actually caterpillars that grow to be an inch in length. They are a dull grey with darker markings close to their heads. Bag worm males eventually mature into small, black, fur-covered moths with clear wings, but the females remain in a larvae-like state and do not come out of the bag.

When Is It Too Late To Treat For Bagworms?

For many areas in southern Iowa (“bagworm territory”), it is now too late to treat for bagworms. If the caterpillars are no longer visible and feeding, if the bags are no longer moving, then it is too late to treat. When the caterpillars have tied the bag to the twig, sealed it shut they are pupating inside and no further feeding will occur. The photos below from Madison County Extension and Jeromoy Baumbach show the difference of what bagworm bags look like when the caterpillars are active, and what they look like after the caterpillars are done feeding and growing for the summer. Note the sealed end and the silken strap that connected the bag to the twig in the lower photo.

When the caterpillars are no longer feeding, the tree will not experience additional damage beyond what has already occurred, and most importantly, spraying after that point is a complete and counterproductive waste of time and money. Even if caterpillars are still visible, spraying this late in the season may not be effective. Trees should be protected from bagworm defoliation by spraying in late-June to mid-July.

Bagworm with caterpillar exposed. Photo by Jeromy Baumbach.

Bagworm bags after caterpillars are finished feeding. Photo by Molly Allen.

How To: Get Rid of Bagworms

Photo: flickr.com via NY State IPM Program at Cornell University

Notice an inexplicable mass destruction, yellowing, or defoliation in your evergreens? A close and careful look through the branches might reveal the culprit in clever camouflage: bagworms.

These destructive insects attack many species of tree or bush but are most often found on conifers like juniper, pine, arborvitae, cyprus, cedar, and spruce. They’re called “bagworms” because after the larvae feed on plants and trees, they encase themselves in cocoon-like “bags” constructed from twigs, leaves, and self-spun silk.

Once in its bag, a female bagworm can lay 500 to 1,000 eggs, escalating your bagworm problem to a serious infestation fast. Each egg will hatch into another bagworm primed to defoliate whatever it’s near. The worst part? Your problem may go unnoticed until too late because these bags assume the appearance of conifer cones.

Should you find yourself with a bad case of bagworms, follow this thorough guide to get rid of them.

Photo: fotosearch.com

HANDPICKING

If you find just a few bagworms, you may have caught the infestation early enough that you can effectively control the situation by handpicking the bags off the plants and submerging them in a bucket of soapy water to suffocate the larvae.

This will work, however, only if the larvae haven’t yet left the bags to go out to feed. Hatching generally happens in late May to early June, so do your handpicking of bagworms from late fall to early spring.

BIOLOGICAL CONTROL

Sometimes it’s not feasible to handpick bagworms, particularly when you’re dealing with tall trees. But if you can harness the power of creatures that feed on bagworms, you may still be able to control your bagworm population.

  • Bacteria: Bt, the bacteria Bacillus thuringiensis, is effective at controlling bagworms if it’s applied as soon as the eggs hatch in the spring. Don’t wait too long—this bacteria won’t be as effective when the larvae have grown large. Follow the application instructions on the product you buy, and apply it with a garden sprayer. Follow up and reapply every 7 to 10 days until the bagworms are gone.
  • Birds: Sparrows are predators of bagworms, so you may be able to keep the bagworm population down by attracting sparrows to your yard. To make your property more appealing for the birds, provide water at ground level (a low birdbath) as well as materials and places for nesting (thickets and trees). Sparrows also appreciate shelter to flit between, so brush piles and shrubbery can be assets, as can dusty areas for dust-bathing.

CHEMICAL CONTROL

An insecticide with malathion, diazinon, or carbaryl (such as Ortho Tree & Shrub Insect Killer, available on Amazon) can rid you of a bagworm problem if applied to bushes and trees when the worms are still young larvae. So, aim to spray in late spring, just after the bagworms have hatched and begun to feed, and always follow the insecticide manufacturer’s instructions.

No matter where or what time of year you find bagworms, don’t wait to start formulating a plan to eradicate them. Left unchecked, they can completely defoliate and kill your yard’s trees, bushes, or hedges.

Photo: flickr.com via Dick Culbert

Bagworm Control

by Mary Jane Frogge, Extension Associate

Printable Resource (.pdf)

Bagworms have become an increasing problem in Lancaster County, Nebraska and surrounding areas. Last year, Lancaster County Horticulture Extension staff and Lancaster County Master Gardeners received hundreds of calls on bagworms. They can severely defoliate and kill evergreens, such as spruce and junipers. Bagworms may also feed on shade and ornamental trees, fruit trees, ornamental shrubs and perennial flowers. Since deciduous plants grow new leaves each year, the defoliation caused by the feeding usually does not kill them.

Please take the time to inspect your landscape for bagworms. Mature bagworms are small, one to two inch long, brown bags covered with dead plant material and tightly attached to twigs.

The overwintering bags contain as many as 300 to 1000 eggs each. Removing the bags before the end of May can help reduce their summer populations. Crush the bags or place them in the trash in a sealed trash bag. If bags containing larvae are discarded on the ground, the larvae may return to host plants after hatching.

Once the eggs hatch in early June, large bagworm populations can completely defoliate and kill evergreens during summer. Light infestations slow the growth of evergreens and lower their windbreak value and aesthetic appearance.

Lifecycle

Bagworm eggs hatch in late May and early June. Young bagworms are as small as one-eighth inch long and can be difficult to see. After hatching, the larvae emerge from a hole at the base of the bag and spin down a strand of silk. The tiny insect is often caught by the wind and ballooned to nearby plants.

Once a host is found, larvae begin to form a new bag around their body. The larva is a brown or tan caterpillar with black markings. Larvae remain in their protective bag, sticking their head out to feed.

Bagworm larvae feed up until late August. The mature larvae then attach their bag to a branch with a strong band of silk and begin to pupate. Adult males emerge in September. They are small, furry gray moths with clear wings. The adult female does not have wings and never leaves the bag. After mating, the male moth dies. The female dies in the bag, mummified around the egg mass that overwinters until the following June.

Insecticide control needs to be aimed at young larvae in mid to late June to be effective. Spraying trees is expensive. To get the best control for windbreaks or large stands of trees, late June to early July is the best time to apply insecticides for bagworm control.

Feeding by mature caterpillars slows in August before pupation into adults, so chemical control in late summer and fall is not effective.

Bacillus thuringiensis is available at nurseries and garden centers as Dipel or Thuricide. Other insecticides currently labeled for bagworm control include acephate, carbaryl, cyfluthrin, malathion and permethrin. Affected plants must be thoroughly covered with the insecticide in June so the insects ingest it as they are feeding. Be sure to read and follow all label directions.

The information on this Web site is valid for residents of southeastern Nebraska. It may or may not apply in your area. If you live outside southeastern Nebraska, visit your local Extension office

(Last Updated On: September 17, 2015)

The brown, spindle shaped bags in this image are the cases of bagworms, a caterpillar that can be a pest in dozens of different trees.

You’ve been watching your arborvitae all summer and noticing brown, spindle-shaped sacs hanging from the branches. Someone points out to you that these are bagworms, a case-making caterpillar that feeds on leaves and can be highly damaging, especially to evergreen trees and shrubs like arborvitae and cedar.

Now it’s late September, what do you do?

Before I answer that question, it’s worth pointing out that bagworms are interesting insects with a decidedly non-traditional life cycle. Bagworms are not really worms, but caterpillars, the immature stages of a nondescript moth. They are called bagworms because, shortly after they are born, they begin spinning a silken case or sac around themselves, using silk from glands associated with their mouth. The case is added to continually as the caterpillar grows. The caterpillar feeds on the host plant by sticking its head and legs out of the top of the bag and chewing on nearby leaves. Its legs grasp the branch of the host plant, and propel the caterpillar like a kid cruising the monkeybars.

A now-empty case of a male bagworm is marked by the pupal “skin” left dangling from the bottom of the sac. The presence of these empty cases signals the end of a generation of bagworm feeding.

Bagworms have one generation each year in Texas (some species possibly two). Once the larvae are fully grown they stop feeding. Males pupate and emerge as adults, usually a little before the female. Adult male moths exit the bag through the bottom, and fly off in search of a mate. Females also pupate, but the adult female that emerges is eyeless, wingless and legless. She remains in her bag, emitting a pheromone to alert males to her presence. Male moths locate the female bags and mate. Once mated the female gestates her eggs and dies, leaving a bag full of eggs that will hatch the following spring.

Once both male and female bagworms enter this last phase of life, feeding is over and so is any chance for effective control with insecticides. Bagworm bags are made of tightly woven silk and bits of leaves from their food plant. For this reason, the caterpillars, pupae and eggs inside are well protected from insecticides. Only when actively feeding are bagworms vulnerable to insecticide sprays.

So it’s late summer. Is it too late to spray for bagworms? That’s a good question, and will require some close observation on your part. If you have a bagworm-infested tree, pull off as many bags as you can for a quick inspection. Do you see red-brown pupal skins sticking out from the bottoms of many of the cases? If so, this is an indication that pupation and mating by at least some of the bagworms has begun. Are the cases easy to pull off the tree, or are they tightly bound with thick silk? Cases with thick bands of silk attaching them to the branch are an indication that the caterpillar has started the process of pupation, mating or egg laying. Open up some cases with a pointed knife or scissors. Do you find caterpillars still in the cases? If so, a spray may be worthwhile. If most cases are empty, or have only pupal skins or eggs inside, you’ve missed your chance this year to treat.

Bagworms are slow to spread. Notice that the infestation damaging the middle tree has not yet spread to adjacent trees.

If you’ve missed your chance to spray this summer, that’s OK. Your bagworms will do no further damage this year. You have two options: wait until next spring to treat, or consider handpicking bags from trees during the winter or early spring.

Because female bagworms do not have wings, and there is only one generation a year, bagworm infestations are usually slow to spread. This means that on smaller trees, or trees that are deciduous (making the bags easy to spot), handpicking can sometimes eliminate or greatly reduce an infestation. Trees picked clean of bags are unlikely to become re-infested the following year.

Your other treatment option is to wait until spring when bagworms hatch (usually May to early June) to treat the tree. A relatively easy way to know the best time to treat emerging bagworms is to remove a number of bags from a tree and place outdoors in a screened jar in a shady spot. When the eggs hatch and young caterpillars are seen inside the jar, chances are that eggs are also hatching on your trees. Sprays such as Bacillus thuringiensis, spinosad and any of the pyrethroid insecticides are effective on bagworms, especially early in the season. Late season infestations, when bagworm caterpillars are larger and more difficult to kill, are best treated with pyrethroid sprays.

For more information on bagworms, including photos of many of the life stages, see the excellent publication by the University of Florida.

Hi,

I first noticed bagworms on my blue spruce and pine trees last fall. There were a limited number and I was able to pick off most of the sacks. Now it is spring and I feel I should take some precaution against them because I know there are more I either can’t reach or have missed. My concern is that three trees are tall. One tree is about 20 feet tall. What kind of sprayer do you recommend for tall trees? Do I need a professional to do these trees? If so, what do I ask for? In other words, should I go with one treatment and wait to see if I get more infestation before I have them sprayer again? Of course, I am looking at the least expensive way to treat. Right now there is one bagworm out of my reach from last year and it is driving me crazy. Any suggestions? I know I can treat the small shrubs myself but the tall one concern me.

This is an easy one. Once any tree has bagworms, the best control method is to spray it down in the fall and following spray with some BIFEN. If you treat early spring, the residual should get the larvae as they emerge. Bifen will remain active for 3-4 weeks no problem. To be sure you get them all, treating twice is advised.

To reach high up, get the TROMBONE SPRAYER. This will easily spray 20+ feet and when you’re standing and spraying, there is no problem reaching 25 feet high.

Here are direct links to the information and products listed above:

Bifen IT: https://www.bugspraycart.com/insecticide/liquid/bifen

Trombone: https://www.bugspraycart.com/equipment/sprayers/trombone-sprayer

Bagworm Control: https://bugspray.com/article/bagworm.html

Parts of my juniper tree are turning brown. When I look closely I see there are many small cocoons hanging from underneath the branches. What’s damaging my tree?

Walk through your landscape this month, and you may spot small, tan, oval-shaped, cocoon-like structures hanging down from your plant’s branches. A closer inspection of the plant might also show that some of the leaves have been eaten away. What are these things, and what’s damaging your plant? The answer is bagworms.

The bagworm is an insect native to the United States and is common in eastern Nebraska. Bagworms feed on many species of trees and shrubs, but are most common on evergreen trees and shrubs. Juniper, arborvitae, pine, and spruce may be killed if completely defoliated and less severe attacks can slow growth. Bagworms also feed on shade, orchard, and forest trees of nearly every kind, as well as many ornamental shrubs and perennials, however, severe attacks are unusual. Since deciduous plants regrow new leaves each year, the defoliation caused by bagworm feeding is usually not serious. The growth of small or newly planted trees, however, could be slowed by leaf feeding.

The adult male bagworm is a small, furry gray moth with clear wings; the adult female does not have wings and never leaves the bag she constructs during feeding. The larva is a brown or tan caterpillar with black markings. Bagworms overwinter in the egg stage inside the female bags, which are fastened to twigs. There may be as many as 300-1000 eggs in a single bag. Since the female bagworm cannot fly, local populations can build up to damaging levels as succeeding generations of insects emerge. Eggs hatch in late May and early June, and larvae feed until late August or early September. There is one generation per year.

After hatching, the larvae emerge from a hole at the base of the mother’s bag and spin down a strand of silk. The tiny insect is often ballooned by the wind to nearby branches or plants.

Once a suitable host is found the new insect immediately begins to form a new bag over its body. Initially the young insect’s bag is about 1/8 inch long, but at maturity will grow up to 2 inches long. By mid-August the mature larvae attach their bag to a branch with a strong band of silk and begin to pupate. Adult males emerge in September.

How can bagworms be controlled? Hand-picking is the best way to control light infestations on small plants during the dormant season. Be sure to remove the bags before eggs begin to hatch next May. Destroy bags by burning, immersing in kerosene or by crushing. If bags containing larvae are discarded on the ground, the larvae may return to the host plants.

Plan to apply insecticides to control next year’s small larvae in late June. Bacillus thuringiensis, BT, is available at nurseries and garden centers as Dipel, or Thuricide. Other insecticides currently labeled for bagworm control include acephate, carbaryl, cyfluthrin, malathion and permethrin. Affected plants must be thoroughly covered with the insecticide so that it is ingested by the insects as they feed.

Feeding by mature caterpillars slows in August before pupation into the adults, so chemical control in late summer and fall may not be effective.

Bagworms – Trees and Shrubs

Back to Insect/Mites-Shrubs

Key Points

  • Appearance and Habits
  • Life cycle (important to know for control purposes)
  • Damage
  • Control

Bagworm (Thyridopteryx ephemeraeformis (Haworth), is a serious insect pest of many ornamental shrubs and trees in the eastern half of the United States. Conifers, especially arborvitae, cedar, juniper, and pine are the most frequently damaged host plants.

Deciduous trees such as sycamore,maple, locust, boxelder, and linden are also attacked but they are not seriously damaged. This pest is sometimes confused with Eastern tent caterpillar.

Appearance and Habits

  • Bagworms are actually the larval or caterpillar stages of moths.
  • After hatching they immediately spin a small 1/8 inclh long cocoon-like bag to which are attached pieces of leaves from the plants they feed upon. If you look closely, you will see them moving around as they feed on the plant.
  • Bagworms move about freely to feed, and they carry their bags with them. The bags gradually enlarge as they feed during the summer to house the growing caterpillar.
  • They spread from tree to tree by ballooning (they spin a fine web and use wind currents to infest nearby trees).


Closeup of bagworm caterpillar

Young bagworm feeding


Male bagworm moth

Life Cycle

  • In central Maryland, the eggs hatch about the first week in June.
  • Bagworms complete their growth in August or early September. At this time, the 1-2 inch long bags are permanently attached to plant twigs by means of tough silken threads.
  • In late summer, they pupate inside the bags and then transform into moths, but only the males have wings.
  • The males emerge from their bags in late summer and fly to the bags containing females. The males mate with the wingless females which remain in their bags.
  • Then each female lays 200 to 1,000 eggs in its bag and dies. The eggs remain in the bags until hatching occurs the following spring.


Bagworm infestation on a pine tree

Damage


Bagworm damage

  • When populations are high, bagworms are serious defoliators of plants. They cause permanent damage on evergreens.
  • Shrubs and trees that become heavily infested, particularly conifers, may be killed.
  • Injury is not conspicuous early in the season because the caterpillars and their bags are small. The bags are not easily seen at this time unless large numbers are present. Bagworms often are not detected by the untrained observer until August after severe damage has been done.

Control

Mechanical Control

  • On landscape shrubs and small trees, a simple method of control is to pick off the bags during the fall, winter, and spring.
  • Do not throw them on the ground near the trees but destroy them and throw them in the trash.
  • Remove the bags in any season but do it before the new generation hatches out in late May or early June.
  • When too many plants are involved, to make hand picking practical, sprays are in order.

Biological Control

  • Bacillus thuringiensis, often called Bt, is a type of bacteria that only kills certain insects and does not affect humans or animals.
  • Bt must be applied between mid-June and mid-July because it works well only on young bagworms.
  • Bt is commercially available under the following common brand names: Dipel, Thuricide, and others. Many of these brands are sold in local hardware stores and garden centers.
  • Use according to label directions. Multiple sprays may be necessary.

Chemical Control

  • If chemical control is absolutely necessary, a registered insecticide should provide control if applied thoroughly to all infested plant foliage after July 15.
  • Check the label on the pesticide to be sure bagworm and the type of plant you wish to spray are listed. CAREFULLY FOLLOW ALL LABEL DIRECTIONS WHEN MIXING AND APPLYING THE SPRAY.

common name: bagworm
scientific name:Thyridopteryx ephemeraeformis Haworth (Insecta: Lepidoptera: Psychidae)

Introduction – Distribution – Description – Biology – Host Plants – Economic Importance – Damage – Management – Selected References

Introduction (Back to Top)

Approximately 1,000 species make up the family Psychidae, in which all species’ larvae are enclosed in a bag and most species have flightless adult females. Bagworms can feed on many different plants, and Thyridopteryx ephemeraeformis (also called the evergreen bagworm, eastern bagworm, common bagworm, common basket worm, or North American bagworm) can feed on over 50 families of deciduous and evergreen trees and shrubs (Rhainds et al. 2009). Severe infestations can damage the aesthetics and health of host plants, especially juniper (Juniperus) and arborvitae (Thuja) species, which are commonly grown in temperate climates (Ellis et al. 2005, Rhainds and Sadof 2008). Several species of bagworms can be found in Florida, Thyridopteryx ephemeraeformis is not found here in Florida with great frequency.

Figure 1. Bagworms and their damage on Indian hawthorn, Raphiolepis indica. Photograph by Brooke L. Moffis, University of Florida.

Figure 2. Defoliated Indian hawthorn, Raphiolepis indica, as a result of bagworm infestation. Photograph by Brooke L. Moffis, University of Florida.

Distribution (Back to Top)

The family Psychidae is distributed widely in North, South, and Central America between Banff, Canada to the southern tip of Argentina (Davis 1964). In North America, the bagworm is distributed throughout the eastern United States to Nebraska and as far north as southern Michigan in the Midwest U.S. (Rhainds and Fagan 2010).

Description (Back to Top)

Adults: Adult bagworms will often go unnoticed in the landscape, especially the female, because she is enclosed in her bag and inside of her pupal casing throughout her life. In many species of bagworms, the adult female’s wings and appendages are greatly reduced to vestigial mouthparts and legs, small eyes, and no antennae or wings. The female remains in a caterpillar-like state, mates, and then becomes essentially an egg-filled sac. The male bagworm emerges as a freely flying moth that is hairy and charcoal black. His membranous wings measure 25 mm in length (FDACS 1983). Neither the male nor the female adult feeds. The female lives a couple of weeks, while the male lives only one to two days (Rhainds et al. 2009).

Figure 3. Adult male bagworm, Thyridopteryx ephemeraeformis. Photograph by Curtis Young, Ohio State University.

Figure 4. Adult female bagworm, Thyridopteryx ephemeraeformis. Photograph by Curtis Young, Ohio State University.

Eggs: Shortly after mating, the female lays a large egg clutch (500-1,000 eggs) inside of her pupal case enclosed within her bag. The eggs are smooth and cylindrical in shape and laid in a mass that is covered in a waxy, tuft-like layer (Peterson 1969). Bagworm eggs will overwinter.

Figure 5. Bagworm eggs. Photograph by David J. Shetlar, Ohio State University.

Larvae: Hatching larvae are small (approximately 2 mm long) and often disperse to surrounding plants by spinning a silken thread and ‘ballooning’ on the wind. Once a suitable host is found, the caterpillar begins feeding and incorporating material into its bag, which it constructs with pieces of twigs, leaves, and silk (Peterson 1969). Only the head and the thorax emerge from the anterior end of the bag, so that the caterpillar can feed and move along plant material. If the bag were to be dissected, the posterior end of the caterpillar would appear medium to dark brown in color with the dorsal portion of the first three segments being white to yellow with a dark brown pattern. The common bagworm caterpillar develops through seven instars before it transforms into a pupae (Rhainds and Sadof 2008). The fully grown larva is approximately 25 mm (1 inch) long and takes up to four months to develop, depending on temperature.

Figure 6. Bagworm larva removed from its bag. The bag is attached to Ligustrum. Photograph by Luis Aristizabal, University of Florida.

Figure 7. Bagworm larva feeding on Ligustrum. Photograph by Brooke L. Moffis, University of Florida.

Pupae: The mature larva attaches its bag to a branch with a strong band of silk. The pupa remains inside the bag and is dark brown to black in color. The pupal stage generally lasts for 7-10 days.

Figure 8. Silk strand produced by a bagworm larva. Photograph by Steven P. Arthurs, University of Florida.

Figure 9. Common bagworm pupa. Photograph by Pennsylvania Department of Conservation and Natural Resources – Forestry Archive, Bugwood.org.

Figure 10. Bagworm pupae on Mexican fan palm. Photograph by Steven P. Arthurs, University of Florida.

Biology (Back to Top)

Throughout the U.S., the common bagworm has one generation per year and overwinters in the egg stage inside the female’s pupal case. Other bagworm species may spend the winter as partially developed caterpillars. Common bagworm larvae hatch in late spring and early summer and may disperse with the wind via silken threads; if there is sufficient food, others may remain on the same host plant as their mother (Rhainds and Sadof 2008). Throughout the larval instars, the caterpillar increases the size of its bag as it grows and can survive long periods without food, especially during the later stages of development (Rhainds et al. 2009). Once the larva has consumed enough food during the last instar, it attaches its bag securely with a thick silken strand to its host plant or disperses to another structure. Prior to molting and pupation, the bagworm will seal the anterior portion of the bag (Leonhardt et al. 1983).

Adult males emerge in the fall while females release a pheromone that attracts the male moths. During mating, the male climbs onto the female’s bag, hangs upside down, and extends and inserts his abdomen about 4 cm into the bag (Leonhardt et al. 1983). Once mated, the female ceases production of pheromone and is no longer attractive to males (Rhainds et al. 2009). After oviposition, the female may die inside the bag, mummifying around her eggs, or may fall to the ground just before death (Peterson 1969, Rhainds et al. 2009).

Figure 11. Male (top) and female bagworm. Photograph by Curtis Young, Ohio State University.

Host Plants (Back to Top)

Economic Importance (Back to Top)

The common bagworm is considered an occasional pest in Florida as many of the preferred host plants do not grow well below the USDA hardiness zone 8A. Due to its wide host range, high female fecundity, and method of dispersal, bagworm can still be problematic in the Florida landscape. In the northeastern and southern U.S., the common bagworm is one of the most damaging pests of urban trees. Less than 10% damage on woody plants is tolerated by consumers (Lemke et al. 2005), and during the summer months, as few as four bagworm larvae can cause a four-foot arborvitae to be unmarketable for sale (Sadof and Raupp 1987).

Damage (Back to Top)

Initial feeding damage on evergreen trees causes branch tips to appear brown and unhealthy (Baxendale and Kalisch 2009). As the larvae become larger, their feeding damage becomes more apparent. During the summer, larvae can cause severe defoliation and even death, especially on evergreen species because their leaves are not replenished as readily as those of deciduous trees.

Bagworms can develop into localized infestations as larvae can move only a few meters from their mother’s host plant resulting in high populations on some plants while others nearby may experience very few bagworms. This method of dispersal can also lead to the same host plant experiencing bagworm populations year after year.

Management (Back to Top)

Cultural control: Handpicking bagworms and placing them in a bucket with soapy water or a sealed bag is an effective control method when populations are low and individuals can be reached easily (Lemke et al. 2005). Handpicking is most effective from late fall to early spring before adults reproduce and new bagworm larvae disperse.

Chemical control: When handpicking is not feasible, insecticide control should be aimed at young larvae. Penetration with insecticides can be challenging due to the protective bag. When feeding slows later in the season, control with insecticides may not be effective.

Biological insecticides: Entomopathogenic bacteria (esp. Bacillus thuringiensis var. kurstaki) offer an effective means of control when applied to early instar larvae (Gill and Raupp 1994). Under certain weather conditions, entomopathogenic nematodes (esp. Steinernema carpocapsae) have been shown to provide control of bagworm larvae.

Natural controls: The common bagworm is attacked by at least 11 species of parasitic wasps (Balduf 1937). Ellis et al. (2005) found that the addition of flowering species to a mock landscape increased parasitism by the ichneumonid parasitoid wasps Pimpla disparis, Itoplectis conquisitor, and Gambrus ultimus. Predators of bagworms include white footed mice and sparrows (Ellis et al. 2005).

Selected References (Back to Top)

  • Balduf WV. 1937. Bionomic notes on the common bagworm, Thyridopteryx ephemeraeformis Haw., (Lepid., Psychidae) and its insect enemies (Hym., Lepid.). Proceedings of the Entomological Society of Washington 39: 169-184.
  • Baxendale F, Kalisch JA. 2009. Bagworms. University of Nebraska Lincoln, NebGuide. G1951.
  • Davis DR. 1964. Bagworm moths of the Western Hemisphere. Bulletin U.S. National Museum, No. 244. 233 p., Washington D.C.
  • Ellis JA, Walter AD, Tooker JF, Ginzel MD, Reagel F, Lacey ES, Bennett AB,
    Grossman EM, Hanks LM. 2005. Conservation biological control in urban landscapes: manipulating parasitoids of bagworm (Lepidoptera: Psychidae) with flowering forbs. Biological Control 34: 99-107.
  • FDACS. 1983. Insects of hardwood foliage bagworm. Bull. 196-A.
  • Gill SA, Raupp MJ. 1994. Using entomopathogenic nematodes and conventional and biorational pesticides for controlling bagworm. Journal of Arboriculture 20: 318-322.
  • Lemke HD, Raupp MJ, Shrewsbury PM. 2005. Efficacy and costs associated with the manual removal of bagworms, Thyridopteryx ephemeraeformis, from leyland cypress. Journal of Environmental Horticulture 23:123-126.
  • Leonhardt BA, Neal JW, Klun JA, Schwarz M, Plimmer JR. 1983. An unusual lepidopteran sex pheromone system in the bagworm moth. Science 219: 314-316.
  • Peterson A. 1969. Bagworm photographs: eggs, larvae, pupae, and adults of Thyridopteryx ephemeraeformis (Psychidae: Lepidoptera). The Florida Entomologist 52: 61-72.
  • Rhainds M, Fagan WF. 2010. Broad-scale latitudinal variation in female reproductive success contributes to the maintenance of a geographic range boundary in bagworms (Lepidoptera: Psychidae). PLoS One 5(11):e14166.
  • Rhainds M, Davis DR, Price PW. 2009. Bionomics of bagworms (Lepidoptera: Psychidae). Annual Review of Entomology 54: 209-226.
  • Rhainds M, Sadof CS. 2008. Elements of population dynamics (Lepidoptera: Psychidae) on hedge rows of white pine. Annals of the Entomological Society of America 101: 872-880.
  • Sadof CS, Raupp MJ. 1987. Consumer attitudes toward the defoliation of American arborvitae, Thuja occidentalis, by bagworm, Thyridopteryx ephemeraeformis. Journal of Environmental Horticulture 5: 164-166.
  • Shetlar DJ. 2010. Bagworm and its control. The Ohio State University Extension Article HGY-2149-10.

Bagworms

What is a Bagworm?

It is a perennial moth like insect that is wingless and resides on a number of evergreen as well as junipers. It causes extensive damage to plants and trees.

Bagworms Scientific Classification

Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Lepidoptera
Family: Psychidae
Genus: Thyridopteryx
Scientific Name: Thyridopteryx ephemeraeformis

Scientific Classification

Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Lepidoptera
Family: Psychidae
Genus: Thyridopteryx
Scientific Name: Thyridopteryx ephemeraeformis

Other names for this pest are Common Bagworm and Evergreen Bagworm.

What is a Bagworm like?

Adult males of this species of moths are dark and hairy in appearance with a wingspan of approximately 1 inch. Female bagworms look like maggots and are yellow in color. An average insect of this type appears similar to a tiny caterpillar.

Picture 1 – Bagworms
Source – hortipm.tamu.edu

These pests are about 1-2 inch in size.

Family Name

This pest is a member of the family Psychidae and belongs to order Lepidoptera.

What does a Bagworm eat?

Bagworm food comprises of leaves of plants. They are parasitic in nature and reside in plants, feeding on them. Bagworm larvae feed on leaves and needles of evergreen plants. Young insects of this species eat the upper epidermis of hosts, which leaves tiny holes on the foliage of these plants.

Habitat

The pest generally resides and feeds on Willow, Sycamore, Spruce, Maple, Bald Cypress, Boxelder, Oaks, Rose Plants, Black Locusts, Pines and other deciduous trees. It also attacks fruit trees, ornamental trees, perennial flowers and decorative shrubs.

Life Cycle

Bagworms life cycle are differentiated into separate stages, much like any other organism. Here is a glimpse into the various Bagworm life stages –

  • The eggs of Bagworm moths hatch in end of May and beginning of June. Once the eggs hatch, the larva spins a silk strand that hangs down it. The larva is also transported to nearby plants by wind.
  • Once the larva finds a host, it starts to make a new protective bag around itself. It remains inside this bag sticking only its head out to eat from the host.
  • The larva continues feeding until it matures by the end of August. It then attaches the bag they are in to a branch with a strand of silk and starts developing into a pupa.
  • Adult male worms appear in September. These are tiny, grayish moth-like insects with fur on their body and transparent wings. Adult Bagworm females are wingless. They never leave the protective bag.
  • When fully mature, these pests mate and die immediately afterwards.

Reproduction

Mature male and female worms mate with each other to produce offspring. Strikingly, these pests die after mating. Male moths die outside the bag after copulation. Females die inside the bag and get mummified around the mass of several hundred eggs that they produce. The eggs hatch in end-May or beginning of June.

Only one generation of Bagworm eggs are produced every year.

Control

These pests cause excessive damage to plants. Only deciduous plants can withstand the onslaught of these plants. In Deciduous plants new leaves arise every year. This is why the defoliation (loss of foliage) caused by the parasitic feeding of this insect does not kill these plants. All other plants are incapable of surviving Bagworm attacks. The worm is controlled with insecticides because of this reason.

For control of Bagworms insecticides should be sprayed on young larvae during late- June or early-July. This is the best time to apply insecticides for Bagworm control as feeding by these moths slow down by August. Naturally, chemical control during this time is not as effective.

Common insecticides used for controlling this pest include Carbaryl, Acephate, Cyfluthrin, Permethrin and Malathion. Affected plants must be thoroughly sprayed with any of these pesticides in June for Bagworm killing as soon as they start feeding on plants.

Moth Bag


Photo 2 – Bagworm’s Bag Image
Source – lifeandlawns.com

Protective bags of these insects hang from slender stems of plants and trees and are generally hidden by foliage. These Bagworm nests are usually brow or gray in color and look like small pine cones. Once spotted, these should be immediately cut away with garden shears, scissors or knife. Simply pulling away these bags will leave a silk strand behind that will encircle the twig while it is growing.

Organic Control

An organic pesticide that contains the bacteria Bacillus Thuringiensis is often used on plants in early spring for controlling these moths. The chemical is safe to use in plants in areas where pets and children roam about. There are many other chemical sprays available to control these pests.

Management

The insect can be managed by both chemical and non-chemical means. Chemical process of getting rid of Bagworms involves spraying insecticides and organic pesticides on the habitats of the pests. Non-chemical way of Bagworm removal includes cutting away the bags formed by these worms from plants they have infested. Bag removal should be carried out in early spring, late autumn or winter season before the eggs hatch. Proper disposal of these bags will help avoid return of these insects.

Are Bagworms Poisonous?

Bagworms are often mistaken to be poisonous creatures as they cause the death of plants. This is however, a non-poisonous bug that causes plant death due to feeding on their foliage. Insecticides used for Bagworm prevention often produce toxic effects when used in large quantities. Safety precautions and usage directions on labels of pesticides should be strictly followed to avoid damage to valuable plants. When used in excess, these can not only damage plants but also contaminate ponds or streams located nearby.

Predators

Ichneumonid wasps and parasitoid insects are two organisms that are natural enemies of this pest.

Natural Control

These pests can be naturally removed in two ways. Manually removing the nests of these bugs is one such option. It can also be controlled by planting daisy plants near plants where the pest is found to nest on. Research conducted by the University of Illinois has shown that flowering plants such as daisies that are members of the Asteraceae family can attract parasitoid insects to them. Naturally, Bagworms nesting on such plants have a high chance of being destroyed by parasitoids.

Pictures


Picture 3 – Bagworm Picture
Source – woodypests.cas.psu.edu

Want to get an idea about the appearance of this insect? Here are some Bagworm photos that you will find useful. Take a peek at these Bagworm images and know about the appearance of these pests.

The life cycle of the bagworm caterpillar is broken down into 4 stages; the egg, larvae, pupal, and adult. The most damage is done during the larva stage, while the caterpillars are actively feeding on needles and plant material from your Newnan, Georgia trees. During this stage, the bagworm also begins to construct a protective bag around his hind parts to hide in when disturbed. The protective bags are often mistaken for parts of the host plant. During the early fall, the bags reach approximately 2 inches and the bagworms then permanently attach its bag to twigs to prepare for the pupate stage. This “resting stage” lasts about 4 weeks before the adult males emerge ready for flight. Only the adult male will emerge from its bag as a moth. The females remain in their bags, releasing a pheromone that attracts males to mate. Once the female has been fertilized and has laid several hundred eggs, she drops from the bag and dies. The eggs overwinter and remain in the protective bag until the next summer and this process begins again! Have a problem with bagworms this summer? It’s not too late! Call Nature’s Turf today for your free Plant Health Care estimate!

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