Bagworms In Trees And Shrubs: How to Get Rid of

Bagworms are the caterpillar stage of the bagworm moth that lives inside the cocoons, They feed on trees and shrubs, especially evergreens, such as pine, bald cypress, maple, box elder, sycamore, oaks, and roses, but are partial to eastern red cedar, junipers, and arborvitae. Apart from feeding on these plants, the worms use plant materials and their bodies’ silk to form long, thin, brown sacks.

At first, bagworm cocoons are easy to miss because they look like conifer cones. However, you will realize something is amiss when these “cones” grow and move as the larvae inside continue to feed on foliage. At the end of the larval stage, the bagworms attach their bag to a host plant and enter the pupal stage.

After metamorphosizing, adult male moths fly off to find females that remain in the bag in grub-like form. The female lays between 500 and 1,000 eggs after mating and dies shortly thereafter while her eggs mature. These eggs overwinter within the bags and hatch in the late spring or early summer. Once hatched, they feed on the green branches. 

Here’s how to identify bagworms in each stage. 

• Bag — The 1-2 inches long brown cocoon bags are spindle-shaped, fashioned from silk and pieces of foliage, twigs, and bark of the host plant. They are conical at first and diamond-shaped later. These bags are filled with eggs eventually.
• Larvae — In the initial stage, the larvae look like nothing but black dots the size of a pinhead and are featherlight. Once full-grown, they are an inch long with a dark brown abdomen and white head and thorax dotted with black. It is in this stage that bagworms are most destructive. They feed on buds, needles, and other plant material while creating their bags, causing branch tips to turn brown and die. 
• Adults — The adults are moths with transparent 1-inch wings and a black, hairy body. Male bagworms are ashy-black. The adult female’s body is soft, yellowish-white, and practically naked except for a circle of woolly hairs at the posterior end of the abdomen. They are wingless and have no functional legs, eyes, or antennae.

It is crucial to confirm that bagworms are your problem before starting treatments. Here are some key things to look for:

• Missing needles from a tree's new growth
• Dead or dying leaves and branches
• Brown spots on tree or shrub foliage
• Unhealthy leaves and excessive, unseasonable leaf drop
• Small 2-inch long brown bags dangling from branches throughout the tree that are most visible in winter
• Only the largest veins of leaves are left behind
• Weakened trees may contain emerald ash borer, a small, metallic green beetle

When bagworms infest a deciduous tree, they may chew small holes in the leaves, causing defoliation, but on evergreen trees, they may consume 80% of the trees, turning branch tips brown on evergreens. There is nothing you can do to save your evergreen tree if it reaches this stage. They will eventually die and you need to remove them from your garden. 

You know the damage bagworms cause, so avoid leaving anything up to chance. If you have verified that the pests infesting your garden are bagworms, eliminate them.  Any of the methods mentioned below can be used, but the choice should be based on the extent of infestation.

1. Handpick the Bagworms Off

Handpicking the bagworm cocoons is effective when only a few are on your plants because you caught the infestation early. With fewer numbers, physically removing them is feasible and not arduous. Once you’ve picked the bags, burn or crush them or drop them in a bucket with hot, soapy water to kill off any grubs or eggs inside. Not destroying or disposing of the bags containing the eggs can result in re-infestation. 

However, this method is effective only if the eggs have not yet hatched into a larvae. Hatching usually occurs in late May to early June, so handpicking the pests from late fall to early spring. Ensure you check all of your trees and shrubs while doing so. 

2. Cut Off Dead and Infested Branches

Pruning branches infested with bagworms can prevent further infestation. These insects attach their bags to a branch, which means removing them will eliminate the larvae and eggs. Focus on cutting off branches with visible bags, especially those at the center of the infestation, to reduce the pest population significantly. 

Late fall through winter is ideal for pruning because the eggs within the bags are still dormant. Remember to burn or place the cut branches in a plastic bag and throw them in the trash. Do not leave them in your garden, as the bagworms may reattach themselves to another tree or shrub.

3. Attract Bagworm Predators

Sometimes, it’s not feasible to handpick all the bagworms or remove all infected branches, especially when dealing with tall trees. In these situations, you can rely on creatures that prey on bagworms to control their population. One such creature is a bird.

Different species of birds are prey bagworms. Attracting birds will play a significant role in controlling the bagworm population in your yard. Provide food, water, and shelter to lure them into your property. For food, scatter seeds and suet in your yard or install birdfeeders. Fresh water is essential, so add a birdbath, fountain, or shallow dish, and always keep it clean and filled. As for shelter, include trees and dense bushes where they can build nests.

4. Attract Bagworm Predators

Sometimes, it’s not feasible to handpick all the bagworms or remove all infected branches, especially when dealing with tall trees. In these situations, you can rely on creatures that prey on bagworms to control their population. One such creature is a bird.

Different species of birds are prey bagworms. Attracting birds will play a significant role in controlling the bagworm population in your yard. Provide food, water, and shelter to lure them into your property. For food, scatter seeds and suet in your yard or install birdfeeders. Fresh water is essential, so add a birdbath, fountain, or shallow dish, and always keep it clean and filled. As for shelter, include trees and dense bushes where they can build nests.

5. Spraying BT

Bacillus thuringiensis (Bt) is another organism that feeds on bagworms. It contains a crystal protein that causes the infected insect to stop feeding and die from starvation or a ruptured stomach. The bacteria has to be applied as soon as the eggs hatch in the spring for it to work. 

If you wait till the larvae get too big, the bacteria will not be as effective, so act quickly with this one! Follow the application instructions on the product and apply it with a garden sprayer. You’ll likely need multiple applications, about seven to ten days apart until the bagworms are gone.

6. Plant Moth-Repelling Plants

Add plant-repelling moths that naturally deter the bagworms to keep the females from laying their eggs in or around your yard. Various plants may effectively repel these moths, but aromatic herbs such as sage, tarragon, lavender, borage, and rosemary are particularly effective since the worms are sensitive to the herbs’ strong scents.

Planting these herbs around vulnerable trees and shrubs can create a protective barrier, making them less likely to settle in those areas. This reduces the risk of bagworm infestations while supporting beneficial insects and enhancing outdoor space.

7. Release Parasitic Wasps

Destroying bagworms and controlling other pests while at it could be as simple as using Trichogramma wasps. When released to an infested site, the female wasps release and deposit their eggs into bagworms' cocoons. After taking over the cocoons, the wasp larvae develop further by feeding on the unborn bagworms. This feeding habit affects the life cycle of the bagworms, preventing the next generation from emerging.

If you want to increase the wasp larva population to decrease the bagworm population, you need to attract the adults into your garden, where they will lay eggs. Adult wasps are attracted to areas with plentiful food sources such as carrot flowers, asters, brassicas, verbenas, and legumes.

8. Introduce Neem Oil

Neem oil (like horticultural oil) contains hydrophobic extracts and other insecticidal properties that kill various insects by suffocation. However, it is only effective during the pupating or hatching stage of a bagworm's life cycle. You can drop the handpicked worms in a bucket of diluted neem oil water to die before disposing of them. Alternatively, you can spray the affected trees with the neem oil-water mixture because this doesn't harm plants. 

Purely diluted neem oil, which is neither facial nor pesticide neem oil, is harmless to you and your pets unless accidentally ingested. It will likely lead to gastrointestinal tract-related problems. Therefore, remember to suit up before spraying to protect yourself.

9. Spray Chemical Pesticide

A serious bagworm infestation is fatal for your evergreens, but a mild one benefits your garden ecosystem. However, if you cannot stand them anymore and wonder how to kill bagworms, your answer is chemical pesticides. It is best for a severe infestation and may be more practical than handpicking.

For maximum effectiveness, you should focus on the timing of application instead of trying to find the best insecticides for bagworms. The insecticide should be applied right when the young caterpillars first hatch from eggs in the bag and start feeding, which is from early to mid-June. Ensure you follow all label directions and check before use that the insecticide is appropriate for the treated plant. Some insecticides are harmful to certain plants.

10. Turn Off Outdoor Lights

The fewer moths in your yard, the fewer bagworms you have to deal with. Like other moth species, the bagworm moth is attracted to light at night. Moths navigate using natural light sources like the moon. Artificial lights confuse them, and they fly right into them.

Leaving patio or outdoor lights on unnecessarily creates an inviting environment for these moths to gather and lay eggs, which eventually hatch into destructive bagworms. Therefore, to keep the bagworm moths away by making your yard less attractive, turn off your patio lights or put them on a motion sensor to automatically go out.

Treatments alone may not guarantee the bagworms won't reappear on your trees and shrubs. That doesn't mean you should stop caring for them, among other things. There are other ways you may keep your plants from dying.

Inspect Your Plants Regularly

Watch over your yard after successful treatments for bagworms to prevent re-infestation. Bagworms may return, so regular checks will be essential, especially during the late spring to summer period when they are active. Examine trees, shrubs, and hedges for small, cone-shaped bags that camouflage with the foliage. If you find evidence of their return, act immediately, as early intervention can save your plants.

Bagworms consume excessively, and when left untreated, they can defoliate your trees and bushes, exposing them to stress or even death. It is strategically wise to formulate a plan as soon as you detect them, such as handpicking the bags or targeted treatments, to be one step ahead. Even outside peak periods, routine monitoring would help catch any remaining bagworms and maintain the health of your yard year-round.

Create a Healthy Garden

A healthy garden or yard is necessary for nurturing strong, pest-resistant trees and shrubs. Plants stressed from poor soil conditions, lack of proper nutrition, and inadequate care become weaker and more likely to become victims of pests like bagworms. Therefore, maintaining your garden will help keep potential pests from damaging your plants.

Native flowering plants that serve as natural pest controllers could be used to draw pollinators, birds, and other beneficial insects. Soil should be replenished of its nutrients to nourish plants for better resilience against stress. Furthermore, there should be a routine clean-up of excess leaves, twigs, pine cones, and plant debris. Cleaning up would reduce potential hiding areas for bagworms where they can attach their protective cocoons, thus making it less attractive for infestation. 

Call a Professional

When the infestation is extensive or keeps returning despite trying every method, or it is on taller trees or conifers, the best option may be to enlist the services of a certified arborist. Arborists have the expertise to identify the scale of the infestation and equipment to implement targeted treatments.

These treatments are more effective than DIY solutions. They apply specialized insecticides at the right time to disrupt the bagworm lifecycle. Moreover, they can advise on preventative measures to stop future infestations, ensuring your plants recover and stay healthy.