It can be devastating to see your trees being eaten alive.

And what are those ugly looking bags hanging off them?

A natural reaction is to pull them off and stamp on them – but while that might help a little, you’re going to need an insecticide to target the insect inside the bags – the hungry bagworms.

We look a the most effective and ecological ways to get rid of bagworms and here is a line up of our top choices for the best insecticides for bagworm:

Winner
Monterey LG6332 Bacillus Thuringiensis (B.t.) Worm & Caterpillar Killer Insecticide/Pesticide Treatment Concentrate, 16 oz
Heavy Infestation
Ortho Insect Killer Tree & Shrub Concentrate, 16 oz.
Fertilome 40693 Natural Guard Spinosad Bagworm, Tent Caterpillar & Chewing (32 oz. RTS Hose End) Insect Control
FMC Talstar Pro 3/4 Gal-Multi Use Insecticide
Bayer Tempo Insecticide Concentrate
Monterey LG6332 Bacillus Thuringiensis (B.t.) Worm & Caterpillar Killer Insecticide/Pesticide Treatment Concentrate, 16 oz
Ortho Insect Killer Tree & Shrub Concentrate, 16 oz.
Fertilome 40693 Natural Guard Spinosad Bagworm, Tent Caterpillar & Chewing (32 oz. RTS Hose End) Insect Control
FMC Talstar Pro 3/4 Gal-Multi Use Insecticide
Bayer Tempo Insecticide Concentrate
-
$17.97
$48.00
$31.99
$61.49
$16.95
Winner
Monterey LG6332 Bacillus Thuringiensis (B.t.) Worm & Caterpillar Killer Insecticide/Pesticide Treatment Concentrate, 16 oz
Monterey LG6332 Bacillus Thuringiensis (B.t.) Worm & Caterpillar Killer Insecticide/Pesticide Treatment Concentrate, 16 oz
$17.97
Heavy Infestation
Ortho Insect Killer Tree & Shrub Concentrate, 16 oz.
Ortho Insect Killer Tree & Shrub Concentrate, 16 oz.
$48.00
Fertilome 40693 Natural Guard Spinosad Bagworm, Tent Caterpillar & Chewing (32 oz. RTS Hose End) Insect Control
Fertilome 40693 Natural Guard Spinosad Bagworm, Tent Caterpillar & Chewing (32 oz. RTS Hose End) Insect Control
$31.99
FMC Talstar Pro 3/4 Gal-Multi Use Insecticide
FMC Talstar Pro 3/4 Gal-Multi Use Insecticide
-
$61.49
Bayer Tempo Insecticide Concentrate
Bayer Tempo Insecticide Concentrate
$16.95
  • Monterey LG6332 Bacillus Thuringiensis
  • Ortho Insect Killer Tree & Shrub Concentrate
  • Fertilome Spinsosad Bagworm,
  • Talstar 67759 Professional 96oz Insecticide
  • Bayer Tempo Insecticide Concentrate (SC Ultra)

How to tell if your trees are suffering from a bagworm infestation

What to look for 

You may notice the leaves are turning brown or the needles are falling off the evergreen trees. In fact, the trees look in a sorry motheaten state.

If there are many bagworms, they can defoliate and kill evergreen trees over the Summer. Broadleaf trees survive better since the leaves die off in the Autumn, and regrow the following Spring. Bagworms are not particular – almost any tree will do – pine trees, fruit trees, ornamental trees, shrubs, and perennial flowers. 

How to Tell if Your Tree Has Bagworms

More about the bagworms in trees

North America hosts three kinds of bag worms:

The evergreen bagworm, the snailcase bagworm, and the grass bagworm.

You may find both snailcase and grass bagworms hanging from fences and sheds – and the snailcase reproduces pathogenically, without the help of males. But it is most likely the evergreen bagworm that you will see damaging your trees and shrubs.

The bagworm is aptly named since it spends a large portion of its life hanging in a bag, protected from enemies like birds.

Large Bagworm Nest in a Walnut Tree
If bagworms are left long enough, you may spot a nest like this in your tree.

Throughout the winter, the bagworm eggs rest in old spindle-shaped bags. These bags are well camouflaged, made of silken threads with bits of a leaf – you may not notice them unless you are looking very carefully. They may even be mistaken for old pinecones in evergreen trees.

The eggs hatch in early June – and then the damage begins. The larvae emerge from the bag and spin down a strand of silk. Sometimes they may be caught by the wind and blown onto nearby plants. Once they have found a place to stay the larva spins a new bag around its body – and there the female stays for the rest of her life.

At this stage, they are brown caterpillars. They stick out their heads to feed and go on feeding till late August, and they withdraw into their bags when they feel threatened.

In August, the bagworms start to pupate and the males emerge in September, looking like small, furry grey moths. After mating the males die and the female lays her eggs (up to 500 of them) in the bag where she too dies, her body a mummy around her eggs.

You can watch this video from the UNL Extension in Lancaster County – it has some clear pictures.

The plaster bagworm

Plaster bagworms typically can be found near spider webs (which they eat) and in warm houses. The best way to get rid of bagworms in the house is by a thorough vacuuming. Put the vacuum bag into the garbage and take it out of your house – you don’t want a party of well-fed moths living on your vacuum cleaner!

When to spray for bagworms?

You may decide to reduce the population of bagworms by merely removing the bags by hand, then crushing them or drowning them in soapy water. Don’t just throw the bagworms on the ground as they may climb up to their host plant again. Do this in early May as an adjunct to insecticide control.

If you decide to treat by treating the earth around the tree, then treat in May as you want the young bagworm larvae to eat the leaves with the insecticide in before they grow – when they are harder to kill.

It is best to spray for bagworms in late June or early July. If you wait any longer, the caterpillars’ appetite falls off, they eat less, and your sprays are less effective. Spraying trees can be expensive, and to kill bagworms you need to spray the wpact hole tree thoroughly. Once the bags have reached about 2 inches in length, the insecticides are ineffective.

Methods of bagworm control

Picking bagworms off by hand and crushing them or drowning them.

Spray with insecticide in June and July.

The best insecticides for bagworms contain insecticides like spinosad, sevin, or malathion. These should be used while the bagworms are feeding.

Soil application of insecticide around the base of the tree in early May. The insecticide travels up the tree into the leaves, which the bagworm eats – and dies. This is most effective on young bagworms and small trees.

What to look for in an insecticide

  • Safety 

What do you think is most important when looking for a treatment? We put safety first, for you, your children and your pets 

  • Safety for pollinating insects such as bees is an important consideration. Many of the insecticides are very powerful and can be extremely toxic, especially to aquatic life.
  • Effective. Of course, it needs to be a bagworm killer – and how you spray or deliver it has an impact – the time of day and the month of the year affect the potency of the insecticide.
  • Easy to use correctly? How easy is it to use? Getting the right mix is important.
  • How long does the effect last?
  • Do I need protective gear?
  • How ecological is it?
  • Will it damage my trees?
  • When do I apply the bagworm pesticide? – Am I already too late in the season?
  • Is it OMRI listed?

General advice

  • Timing is all-important in killing off the bagworms. Spray in June and July. If you cannot see the caterpillars and they are no longer feeding, and if the bags are no longer moving, you are too late!
  • You can reduce the number or bagworms by picking off the bags by hand in April and drowning the worms in soapy water. 
  • Think about the ecological effects of your chosen insecticide 

Reviews of Insecticide for Bagworms

Monterey LG6332 Bacillus Thuringiensis (B.t.) Worm & Caterpillar Killer Insecticide/Pesticide Treatment Concentrate 

An insecticide specifically designed to kill worm type insects (including bagworms)

Monterey LG6332 Bacillus Thuringiensis (B.t.) Worm & Caterpillar Killer Insecticide/Pesticide Treatment Concentrate, 16 oz

Bacillus Thuringiensis is safe to use on a variety of plants, including edible vegetables. It is also safe for earthworms, ladybirds, and bees, which are beneficial to your garden – provided you follow the instructions for use. 

It is listed by the Organic Materials Resources (OMRI) as approved for organic gardening.

The insecticide comes as an easy to use spray which you can mix with water to get the required strength. It is crucial to spray the tops and undersides of leaves – and a heavy infestation requires repeat sprays.

To be effective, the bagworm caterpillar must eat the insecticide. Once they have eaten, they stop feeding – although you may not see any difference for several days. It’s best to treat them while the bagworms are small because larger worms need larger amounts and are harder to kill. They must be actively feeding, as they grow nearer to pupating their appetite falls off.

You can eat from the plant immediately after the spray, but don’t wash it off the plant as the bagworms only die if they eat it.

Pros

  • Safe
  • Easy to apply

Cons

  • Sunlight sensitive
  • Slow to see the effect
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Ortho Insect Killer Tree & Shrub Concentrate

 Effective bagworm pesticide for heavy infestations of bagworms

Ortho Insect Killer Tree & Shrub Concentrate, 16 oz.

This insecticide is a powerful bagworm killer and controls many other insect pests.

It is recommended for use on ornamental shrubs, and fruit trees. The active ingredient is Spinosad, a fermentation-derived insect killer. It comes as a concentrate that you mix with water and the bagworms start dying off within a few days of application.

The same dilution kills many pests.

Since one dilution rate is effective for all the pests it is easy to work out the required mix. Just one pint is needed for over 2,500 square feet.

The company states it is safe for children and pets provided you follow the instructions on the label.

Pros

  • Controls many insect pests
  • One pint treats over 2,500 square ft
  • For residential use on fruits, nuts, citrus, and ornamentals
  • Only a single dilution rate needed

Cons

  • Effects are not immediately obvious
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Fertilome Spinsosad Bagworm, Tent Caterpillar and Chewing Insect Control, RTS, Quart

 A user-friendly OMRI listed bagworm spray that is effective

Fertilome 40693 Natural Guard Spinosad Bagworm, Tent Caterpillar & Chewing (32 oz. RTS Hose End) Insect Control

This Spinosad bagworms killer is OMRI listed for use on shrubs, ornamental trees, lawns, and flowers. It contains 0.5% Spinosad which is the active ingredient. Fertilome Spinosad is classified as an organic product. 

User Friendly. It comes ready to spray there is no guesswork involved.

It has little effect on beneficial insect life or predatory spiders but does kill the bagworm. As a warning, you may see the bagworm still living on the tree/plants after the spray – but they will no longer be feeding and die off in due course.

The company states that provided you follow the instructions, its is children and pet safe – and even bees will not be affected after 3 hours.

Pros

  • Child and pet safe
  • Bees safe after 3 hours
  • Easy application-ready to spray

Cons

  • Fast results not immediately obvious
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Talstar Pro 96oz Insecticide

Talstar insecticide is effective at low concentrations

FMC Talstar Pro 3/4 Gal-Multi Use Insecticide

This insecticide comes as a concentrate and contains 7.9% Bifenthrin – a powerful bug killer. You can use this spray for bagworms on many plants and shrubs, on your lawns, and even on buildings.

This is an odorless pesticide.

You need to dilute the concentrate with water (according to the label instructions), and to be most effective, you need to spray it when the larvae begin to hatch and are very young.

This insecticide works by interfering with the bagworm’s nervous system which eventually kills it, but it is not instant death. However, the effects last up to three months, so a good spray controls the bagworm population.

Pros

  • Effective
  • Kills many insects
  • Can make a good barrier
  • Lasts up to to 3 months

Cons

  • Ineffective if frozen
  • No immediate effect
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Bayer Tempo Insecticide Concentrate (SC Ultra)

Fast knockdown, lasting up to 4 weeks

Bayer Tempo Insecticide Concentrate

This powerful insecticide kills many other insects – and it kills quickly.

It will kill bagworms up until the time when the bagworm starts to make new bags (once there, insecticides don’t work).

The company states SC Ultra is safe to use around children and pets, once it is completely dry.

But it is a powerful insecticide and caution is needed when you apply it. You can absorb it through your skin, it can irritate your eyes and you must avoid inhaling the spray by using a user-friendly applicator. And after use wash thoroughly with soap and water.

It contains ß- Cyfluthrin 11% this to be for professional only but now is released for general use. It is extremely toxic to aquatic life and should not be allowed to run off. It is not for use in greenhouses or nurseries.

You need a good coverage including the underside of leaves, and is best used at dawn and dusk, when pollinating insects like bees are less likely to be around. You can add a spreader-sticker for hard to cover leaves like evergreen pine needles.

Pros

  • Fast-acting
  • Safe after drying
  • Effective
  • Odorless

Cons

  • Toxic
  • Need precautions
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Conclusion 

For us, the outright winner has to be Monterey LG6332 Bacillus Thuringiensis. The bacillus Thuringiensis is targeted at bagworms, and valuable earthworms and insects such as the pollinating bees are unaffected. An important factor for us due to the declining bee population. 

Sale
Monterey LG6332 Bacillus Thuringiensis (B.t.) Worm & Caterpillar Killer Insecticide/Pesticide Treatment Concentrate, 16 oz
  • Insect Killer - this pest control is designed for use on caterpillars and worm type insects, such as cabbage looper, bagworm, gypsy moth, fall cankerworm, elm spanworm and many more.
  • Foliage protector - this insecticide is designed for use on a variety of plants including broccoli, Celery, cabbage, Turnip greens, mustard greens, Cauliflower, melons, lettuce, tomatoes, shade trees, ornamentals and many more.
  • Safe for earthworms & bees - when used as directed, Monterey b.T. Has no effect on birds, earthworms, or beneficial insects such as honeybees or Ladybugs.
  • Organic gardening - our insecticide is OMRI listed and approved for organic gardening. OMRI, the organic materials Review Institute, determines whether or not a product Qualifies as organic under the USDA's national organic program.
  • Easy to apply - product instantly mixes with water and should be applied using either a trigger spray bottle or pressure tank sprayer. Carefully read and use according to label directions.

If you have a heavy infestation then you may wish to use really powerful bagworm insecticide such as the Ortho Insect Killer Tree & Shrub Concentrate, and provided you carefully follow instructions this should be safe for your children and pets once it is completely dry.

References

https://www.wikihow.com/Get-Rid-of-Bagworms

https://www.rainbowpestexperts.com/labels/TempoSCUltra_spec.pdf

Monterey LG6332 Bacillus Thuringiensis Review
4.6