Arts & Culture

How to Prevent Bagworms

  • By Gary L. Pierce

Bagworm eggs hatch near the end of May or the first week in June. Find out how to prevent bagworms from destroying your landscape.


One of the most destructive landscape pests is the bagworm. They are fond of eating Leyland cypresses, arborvitae, and cedars.

Bagworms are caterpillars that make a cocoon shaped like a diamond. They do not make webs like those of spiders and tent caterpillars.

Bagworm eggs hatch near the end of May or the first week in June. Though these little worms are only 1/8 of an inch long, they begin to test the strength of their silk by spinning a thread and hanging around. Spring breezes catch the worms and often blow them into Leyland cypresses, among other trees.

If a bagworm is lucky enough to land on a suitable host plant, then it spins a silk cocoon. This cocoon serves as protection from predators, sunlight, and pesticides. Foliage from the host plant is cleverly incorporated into the silk cocoon as a disguise. Bagworms were the original inventors of the ghillie suit.

As bagworms feed on foliage, they grow and enlarge their silk protection. Homeowners finally begin to spot these pests in August or September. By then, the feeding damage is very obvious and the caterpillars are difficult to kill. Since young caterpillars are easier to eliminate, you should apply an insecticide in late May or early June.

Products containing Bt (Bacillus thuringiensis), like DiPel or Worm Whipper, are not contact insecticides. They have to be eaten by young caterpillars. To apply, simply spray Bt on the foliage and let the baby bagworms nibble. This target specific, non-contact type of pesticide bypasses the protective cocoon and is safe to the applicator and surrounding environment. However, this method does not work well on mature caterpillars.

Contact insecticides like Sevin, Malathion and Orthene, while less safe for the surrounding environment, are also more effective when caterpillars are young. By the end of August or September, bagworms are nearly invincible and your only removal option is handpicking.

Handpicking bagworm cocoons from your trees is an option when the trees are small. However, Leyland cypresses can grow 50 feet tall, which makes this option nearly impossible. Once the cocoons have been picked from the trees, destroy them by burying them underground.

For more information about how to prevent bagworms visit You can also call the North Carolina Extension Office at (919) 893-7533 or email Gary Pierce at

Gary L. Pierce is a Horticulture Extension Agent in Harnett County.

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5 Responses to How to Prevent Bagworms

  1. gale mcdonald says:

    have very few bagworms as I pick the cocoons off by hand. I would just spend a little time every chance I had and put them in a coffee can with lid and leave in the sun. Every year there are fewer and fewer. My question is my trees are starting to get big and picking them won’t always be an option. Hand sprayer won’t reach. Do the systemics work for bag worms? Also, cost is a factor. I have about 50 trees. Is there any options that are reasonably affordable?

  2. Tonya Chatterton says:

    I have a cypress type tree that is still short right now. It’s only about 6 feet tall. I picked all the worms off and threw them in my outside trash. I was finding the suckers getting out of the trash and getting all the way back across the driveway and onto the tree again. So two ways I found to rid yourself of them if your trees are not huge is to pluck them from the tree and either step on them until you see guts or put them in a can and burn them. I put them in a small metal can, poured a little gas on them and burned them,.

  3. JAMIE CANIPE says:

    i need to know how to kill bag worms i got them on some leyland cypresses trees . They seem to be killing out my trees thank you

    • scarlett says:

      I’ve used liquid Seven on mine and I was too late. My trees are turning brown and dying!! Please help…. we need something to kill these suckers!

  4. dan gerber says:

    can i use a granular verses spray insecticide for bagworm and is it better ?
    Where can i purchase this in L.I., N. Y.

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