Insects & Pests
Bagworms
Bagworms are destructive caterpillar pests that build protective spindle-shaped bags from foliage and plant debris as they feed. They are most often associated with evergreens, but they can also attack some deciduous plants. Because bagworms can blend in with the plant, homeowners may not notice them until feeding damage becomes more obvious. Early detection matters, especially on valuable privacy screens and ornamental evergreens.
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On this page
What is it?
Signs & symptoms
What causes it
Trees affected
When to act
How we help
Prevention tips
FAQs
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Overview
What Are Bagworms?
Bagworms are the larval stage of a moth. As they grow, they create hanging protective bags that can look like small pinecones or bits of foliage attached to branches. Inside those bags, the larvae feed on the host plant. Heavy infestations can remove significant foliage and create permanent thinning, especially on arborvitae and other evergreens that do not push new growth from old wood as readily.
When you'll see it in Michigan
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Overview
Common signs & symptoms
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Root Cause
What Causes Bagworm Problems?
Bagworm problems begin when larvae hatch and begin feeding on susceptible host plants. Because the insects are well-camouflaged, infestations may go unnoticed until populations grow. In established landscapes, leftover bags from previous seasons can contribute to recurring pressure. Plants that are already stressed may also have a harder time recovering once feeding damage begins.
Plants at Risk
Trees commonly affected
Bagworms are especially concerned with arborvitae, juniper, cedar, and other evergreen plants commonly used for screening and ornamental value. They may also feed on certain deciduous trees and shrubs, but evergreen damage is often the most visible and lasting.
Red Flags
When Should You Act?
Bagworms should be addressed sooner rather than later. Once feeding is advanced, visible damage can be significant, and evergreens may not fill back in quickly. It is a good idea to act promptly if you notice hanging bags, thinning foliage, or repeated seasonal damage on arborvitae or other valuable plants. Early-season identification generally creates more treatment options and better overall results.
Moderate/Severe
Our Approach
How My Arborist helps
My Arborist begins by confirming whether bagworms are present and evaluating how much feeding damage has already occurred. Our ISA Certified Arborists can recommend the most appropriate response based on plant type, infestation level, and seasonal timing. Depending on the situation, solutions may include targeted insect control, removal recommendations where practical, tree and shrub health evaluation, and follow-up monitoring to help reduce recurring pressure.
01
Disease evaluation
Confirm the diagnosis before treating
02
Targeted disease control
Timed fungicide applications when warranted
03
Monitoring
Reduce recurring pressure
Stay Ahead
Prevention tips
Inspect evergreens regularly during the growing season
Look for hanging bags before damage becomes severe
Do not ignore thinning or browning on privacy screens
Address infestations early before larvae mature
Support plant health so evergreens can better handle seasonal stress
Common Questions
Frequently asked questions
What do bagworms look like?
Bagworms create small hanging bags made from plant material and silk. They often look like little cones or debris attached to branches, which makes them easy to overlook.
Are bagworms harmful to arborvitae?
Yes. Bagworms can cause significant thinning and browning on arborvitae, especially when populations are heavy or the infestation is left untreated.
Can a plant recover from bagworm damage?
Recovery depends on the plant type and how much foliage was lost. Some evergreens recover slowly, while severe damage can leave lasting thin spots.
When should bagworms be treated?
Earlier is generally better. Once larvae are larger and damage is widespread, management becomes more difficult and the plant may already have visible decline.
Do I need an arborist for bagworms?
If you are seeing bags, thinning, or browning on valuable landscape plants, an ISA Certified Arborist can help confirm the issue and recommend the right treatment timing.
Keep Exploring
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Small, soft-bodied insects
Emerald Ash Borer
Wood-boring insect
Spider Mites
Tiny pests that cause noticeable damage
CONSULTATION
Seeing hanging bags or thinning evergreens?
If your arborvitae or other evergreens are showing signs of bagworm damage, My Arborist can evaluate the issue and recommend the right next step.
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