Tree Care: Attack of the Bagworms - Complete Landsculpture

Tree Care: Attack of the Bagworms

Have you ever looked up in your tree and thought, “what are those weird little things in my tree?” Those weird little things in your tree that look like natural Christmas tree ornaments that someone hung there out of season are bagworm bags. Those little bagworm cases turn into big bad bagworms, which then turn into big bad problems.

Bagworm infestations are common here in Texas. Some years the bagworms are more abundant than others, but once a tree or plant is infested, the problem will persist unless controlled.

Although each species has different life cycles and habits, infestations by bagworms can defoliate trees and shrubs and kill plants if left unchecked.

Unfortunately, these infestations may not be noticed at first, which is why it’s crucial to have an expert regularly take a look at your trees and shrubs.

The Life of a Bagworm

Bagworms begin their lives as eggs contained in a 2″ cocoon-looking bag that is attached to a tree or shrub twig. These starter bags can be filled with as many as 1,000 eggs! In the late spring or early summer, the eggs hatch into tiny 2mm black larvae.


The larvae excrete silk thread that they use to travel to nearby trees where they will build a new home. Their new home is made of silk with layers of leaves, bark fragments, and twigs arranged crosswise like shingles around it. This strengthens the silken bag as well as provides camouflage.

As the worms grow, the bag becomes elongated. The top of the bag is wider than the lower part. The wider opening is used as a doorway when the worm needs to crawl out for food or repair its home. The narrow opening at the bottom is used as a sewage drain pipe where the larva expels refuse.


The bagworms hang out in their bags and molt and pupate until late summer or early fall. At this point, the male leaves its bag through the lower end. Its pupal skin gets snagged on the bag, which leaves the caterpillar, now moth, free to open its wings.

Now an ashy-black moth the size of a quarter, the male searches for a mate. Adult females do not turn into moths. They emerge with no eyes, legs, or antenna.

They are wingless and look like a maggot with a soft, yellowish body. Females appear only halfway out of their bags and wait to mate with the males. After mating, a female deposits 400 to 1,000 eggs in the empty pupal case, drops to the ground and dies.

The Devastation Caused by Bagworms

Although bagworms are just going about their natural life cycle, they can cause significant damage to trees and shrubs. Bagworms are voracious eaters.

Though they prefer evergreens like juniper, cedar and spruce trees, they also attack deciduous varieties like:

  • Apple
  • Black locust
  • Boxelder
  • Honey locust
  • Elm
  • Maple
  • Indian hawthorn
  • Various oaks
  • Sumac
  • Persimmon
  • Sycamore
  • Wild cherry
  • Willow trees

On deciduous trees, bagworms cause defoliation by chewing small holes in the leaves. On evergreens, bagworms chow down on buds and foliage, which will cause branch tips to turn brown and die.

Bagworms have been known to kill whole trees by eating more than 80% of the tree. But bagworms don’t just damage trees by eating them, tree twigs that bagworms wrap in silk can die over time.

Getting Bagworms Under Control

Generally, trees will bounce back if you get the bagworms under control. When it comes to bagworms, birds, insect predators, and insect parasites are your best friends.

They are a bagworm’s natural enemies and can keep bagworm outbreaks brief. But sometimes, natural enemies aren’t enough to manage an infestation. At this point, you have two options:

1. Handpick bagworms off of the plants.

This is the cheapest way to control them, particularly during the winter months. Thoroughly pick off all of the bags from your plants. Then make sure to destroy or discard, or the eggs will hatch in the spring and develop into larvae that could reinfest the plants.

2. Use an insecticide spray.

As soon as the eggs have hatched, or even while the larvae are still small, spray them with insecticide. Collecting a few bags from your trees in the late winter and keeping them in a container away from the sun can help you determine when the right time is to treat the worms.

After you see the caterpillars hatch from the bags in the container, apply the insecticide to your plants. If you spray while the bags are closed for molting or pupation, the spray will not be as effective.

Make sure to use spray equipment that gives complete coverage of all foliage. If you don’t have the proper equipment, hire a professional to apply insecticides.

Bagworms Are Hatching Right Now!

Don’t want to deal with them yourself? We’ve got solutions. Call us for a consultation, and we’ll mobilize our bagworm eradication team.

We’ll send one of our experienced Arborists out to evaluate how big the problem is, come up with a treatment plan, and get those bagworms under control!

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