Updated date:

How to Get Rid of Bagworms Safely

Jill likes cooking, writing, painting, & stewardship, and studies gardening through MD Master Gardener & Master Naturalist programs.

No, it's not a rustic Christmas tree ornament—it's a bagworm nest! And it can damage your conifers if left unchecked.

No, it's not a rustic Christmas tree ornament—it's a bagworm nest! And it can damage your conifers if left unchecked.

Got the Bagworm Blues?

If you live in the eastern U.S., you've probably seen your share of bagworms (Thyridopteryx ephemeraeformis). It's not uncommon for large infestations to plague forestland along neglected roadways or, if you're unlucky, within your own landscape.

Bagworms spin cobweb-like "bags" in trees and shrubs. They particularly like to infest conifers such as pine, cedar, arborvitae, Leyland cypress, and juniper. Sometimes, they're so prolific that they kill their host tree. Because the bags are shaped like pine cones, they often pass unnoticed in conifers—until it's too late.

Bagworms may also spin cocoon-like nests in deciduous trees, such as locust, maple, linden, sycamore, and boxelder. Although these trees may suffer damage, they're rarely killed by bagworms. Nevertheless, few homeowners want even one bagworm nest in their yard.

Where Do Bagworms Come From?

Bagworms are actually moths in their larval (caterpillar) stage of development. After hatching, moth caterpillars spin cocoon-like bags. These bags have pieces of leaves from the plants they're feeding upon attached to them.

At first, the bags are very small—only about 1/8 inch long. The young bagworms move about freely as they feed, carrying their bags with them, enlarging them as they themselves grow bigger.

It's at this point—when moth caterpillars are young—that they're easiest to destroy through the application of a bacteria commonly called BT.

How to Get Rid of Bagworms

Bagworm-killing bacteria

Bacillus thuringiensis (BT) is a bacteria that kills certain insects, including bagworms, but doesn't adversely affect humans or other animals.

BT works extremely well against young moth caterpillars. So if you're going to use BT, be sure to apply it early. Common brand names of products that contain BT include Dipel, Caterpillar Killer, and Thuricide.

Pesticides

These insecticides are also labelled for bagworm management: Bifenthrin Pro Multi-Insecticide, Onyx Insecticide, Talstar F, Talstar Lawn & Tree Flowable, Talstar GC Flowable, TalstarOne Multi-Insecticide, and Dursban 50W.

Like BT, they should be applied shortly after the moth eggs hatch.

Handpicking

Removing bagworm bags from trees by hand isn't as gross as it sounds. Remove the bags in winter or early spring (before the moth eggs hatch) and destroy them.

How NOT to Get Rid of Bagworms

You may have heard of gardeners pouring gasoline on bagworm bags and then setting them on fire. It's a dangerous practice that could cause serious damage to you, your tree, and your property. Don't try it!

Stick with handpicking the bags when the eggs are dormant. Or, if your infestation is severe, opt for BT or some other non-petroleum chemical solution. Those are the best ways to beat the bagworm blues.

This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.

Questions & Answers

Question: What should you do with bag worms that are emerging from a pod? I tied them in a bag and open garbage can, but some escaped. I had even tied the bag shut.

Answer: At least you removed some. That will definitely mitigate the damage they could have done.

Question: I just realized that I have these things in a spruce. I don't see them in any of my other trees. Can I just cut this tree down and burn it? Will that get rid of them?

Answer: That would work for that spruce, but it would be like killing the patient to get rid of the disease. And chances are a few bagworms are on other trees, too. While weeding the other day, I found one hanging from a solar light! I prefer handpicking them, but you may want to use two methods if you just can't tolerate any bagworms at all on your trees. You could also do some judicious pruning.

Comments

Jill Spencer (author) from United States on July 27, 2019:

Thanks for commenting, Renee. Unlike you, I have not seen tree death from bag worms "many times." Trees can recover from a stripping for a season, although multiple repeated onslaughts or bag worms combined with other issues over time may kill them. This was confirmed by MG coordinators at a pest seminar I attended recently. If you have seen trees or shrubs infested by bag worms die, I think it likely that other problems were in play as well. Thanks again for reading and commenting. All the best, Jill

Renee Mikan on July 25, 2019:

Jill, I disagree with your commet that the bag worms won't kill the host. I have seen many times there being a big infestation and has killed the tree and shrub.

I have also heard this statement about Japanese Beetles that they don't hurt the tree after they have eaten every leaf on the tree. I wonder how the tree not having any leaves in the middle of summer doesn't stress out the tree and how then does the tree make food for itself.

Jill Spencer (author) from United States on June 24, 2019:

As noted above, you could apply BT. You could also simply ignore the problem, as bagworms, although unsightly, are unlikely to kill your evergreen unless some other problem is in play.

Wendy Fisher on June 24, 2019:

What to use now that evergreen had bagworms

Jill Spencer (author) from United States on February 23, 2013:

Thanks so much, Stellar Phoenix! A good review is an awesome thing. (: Take, Jill

Stellar Phoenix on February 22, 2013:

This content is incredible! You certainly know how to keep a reader entertained. Between your wit and your videos, I was almost moved to start my own blog (well, almost..aha) Fantastic job. I really loved what you had to say, and more than that, how you presented it. Too cool! Stellar Phoenix Review

Jill Spencer (author) from United States on September 13, 2012:

@ lrc7815 -- How horrible. Bagworms can really cause some serious damage. Hope the info helps you keep the rest of your trees safe. Take care, Jill

Jill Spencer (author) from United States on September 13, 2012:

@ lrc7815 -- How horrible. Bagworms can really cause some serious damage. Hope the info helps you keep the rest of your trees safe. Take care, Jill

Linda Crist from Central Virginia on September 13, 2012:

Great hub. Wish I had had this information a few y ears ago when I lost two 30 year old junipers to bag worms. Thanks for sharing this great information.

tebo from New Zealand on August 11, 2011:

I have never heard of bagworms and am unsure whether we have them here in NZ, but I do have some conifers so I will check them. Thanks for the heads up.

NMLady from New Mexico & Arizona on August 08, 2011:

Re bag worms don't vacation in NM....Yep, I am very glad!

Jill Spencer (author) from United States on August 08, 2011:

No, I haven't tried it--although I know someone who uses it in his fruit orchard. Thanks for your comment! Aren't you glad bagworms don't vacation in NM?

NMLady from New Mexico & Arizona on August 07, 2011:

Have you ever tried diatomaceous earth? (ground up coral) It is a pretty good bug killer w/o being poisonous to warm-blooded animals like us and our pets.

I DO remember these and they are yucky.

Jill Spencer (author) from United States on August 07, 2011:

Thanks, Esmeowl12. Hope you have time to pick off the dormant bags once the weather gets colder. Although bagworms spread slowly, they do spread! Happy gardening, DF

Cindy A Johnson from Sevierville, TN on August 07, 2011:

Wow. I never knew that's what these are. I have a few, thankfully not many. I appreciate the info. Voted up and useful.