How to get rid of bagworms in trees

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 eliminate the tree twigs a few years from now.

If the caterpillars are no longer visible and feeding, if the bags are no longer moving, then it is too late to treat. 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.

Another natural insecticide homeowners can use for bagworm control is spinosad, which is sold under brand names like Captain Jack’s deceased Bug Brew and Green Light Lawn & Garden Spray Spinosad Concentrate. Neem oil is an additional natural insecticide that will control bagworms, as well as a wide range of insect pests.

How Did I Get Bagworms? Bagworm moths make their homes in many types of trees, especially cedar trees. Larvae crawl to nearby plants and their bags can be seen hanging on trees that they feed on. Some may spin a silk thread that catches the wind and carries them off to new trees.

Life cycle of bagworms

The adult female moth does not leave the bag the caterpillar created. She remains inside while the winged, male moth does emerge to fly about the infested tree to locate the waiting female. After mating the female lays 500 to 1000 eggs within her bag and then she dies.

If only a few small trees or shrubs are infested, handpicking and destroying attached bags may provide satisfactory control. This must be done effective during fall, winter or early spring before the eggs hatch. When many small bagworms are present and feeding, an insecticide may be needed to prevent serious damage.

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.

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 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.

The small, silk weaving that resembles a Christmas tree ornament on your favorite tree or shrub is not decoration. These bags protect the caterpillars, or larvae, pupae, female adults and eggs of bagworms (Order Lepidoptera Family Psychidae, Fig. 1).

There are also three common birdfeeder birds that are known to scavenge bagworm eggs from twigs and branches during the winter months: chickadees, nuthatches, and titmice.

Encourage Natural Predators

Sparrows are another well-known predator of bagworms. You can encourage this kind of predation by making your landscape bird-friendly and limiting your use of pesticides that eliminate helpful insects.

In the spring, the bagworm eggs hatch and each larva leaves the bag by releasing a thin silk thread and floating down out of the bag. The wind will then carry it to another host plant, where it will attach and start creating its own bag. Larvae will pupate in September.

Since bagworms add plant materials to the top of the bag, the freshest and greenest material is on the top of the bag. When you see a bag that is entirely brown, the insect inside has stopped feeding or is dead.

The Damage They Do

Bagworms can attack a variety of hardwood and evergreen plants, but prefer Leyland Cypress, Arborvitae, Cedars and all juniper plants. Bagworms reach maturity during the summer and can quickly defoliate infested trees. Infested and susceptible plants need to be treated for control to prevent damage.

Signs/Damage: Sudden, dramatic changes in evergreens signal bagworm damage. Trees become sickly, pale and dying in a matter of weeks over summer months. Trees and shrubs turn brown and leaves or needles drop, as though deprived of water, but irrigation and fertilization won’t help.

Bagworm, like all moths, undergoes complete metamorphosis with four stages. Egg: In late summer and fall, the female lays up to 1,000 eggs in her case. She then leaves her bag and drops to the ground; the eggs overwinter. Larva: In late spring, larvae hatch and disperse on silken threads.

The Psychidae (bagworm moths, also simply bagworms or bagmoths) are a family of the Lepidoptera (butterflies and moths). This means that the bagworms and case-bearers are only as closely related to each other as either is to butterflies (Rhopalocera).

To be honest, I have never known of anything to eat nandina’s or arborvitaes (except bagworms for the latter). Squirrels, deer, raccoons, are among the possible culprits.

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.