Our readers keep the lights on and the weekend projects moving. As an Amazon Associate, I earn from qualifying purchases.
Finding an arborvitae stripped bare by bagworms is a sickening sight. These persistent pests weave silk bags loaded with eggs, and by the time you notice the browning, the damage is already deep. You need a spray that hits their specific lifecycle hard, without sacrificing the health of your trees or the safety of your yard.
I’m Rikta — the co-founder and writer behind FitlyFast. I’ve spent countless hours cross-referencing entomology research, active ingredient data, and real-world reviews to identify the most effective treatments for bagworm infestations on arborvitae.
This guide breaks down the best chemical and biological controls available today, so you can stop the damage and keep your evergreens lush. We’re here to help you find the right bagworm spray for arborvitae.
How To Choose The Best Bagworm Spray For Arborvitae
Not all sprays work equally on bagworms. Arborvitae have dense, scale-like foliage that can shield pests, so you need a formula that penetrates deep. The choice comes down to three main active ingredient families, each with a different mode of action and safety profile.
Target the Young Larvae
Sprays are most effective when bagworms are in their early larval stage, typically late spring to early summer. Once they build tough, silken bags, contact sprays may not penetrate. Look for products with long residual activity or systemic properties to catch late-hatching worms.
Choose Between Biological and Synthetic
Bacillus thuringiensis (B.t.) is a naturally occurring bacterium that targets only caterpillars, making it safe for bees and birds. Spinosad, derived from soil bacteria, offers broader pest control while remaining organic-certified. Synthetic pyrethroids like Bifenthrin provide fast knockdown but can impact beneficial insects.
Consider the Application Method
Ready-to-use hose-end sprayers simplify coverage on large arborvitae, while concentrates mixed in a pump sprayer offer more precision. For tall trees, a systemic product applied to the soil may reduce the need for repeated foliar sprays.
Quick Comparison
On smaller screens, swipe sideways to see the full table.
| Model | Category | Best For | Key Spec | Amazon |
|---|---|---|---|---|
| Monterey B.t. | Organic B.t. | Long-term control & organic yards | 32 oz bottle (concentrate) | Amazon |
| BioAdvanced Tree & Shrub | Systemic | Large established arborvitae | 32 oz (ready-to-spray) | Amazon |
| ferti-lome Spinosad | Organic Spinosad | Bagworms & chewing insects | 16 oz concentrate | Amazon |
| Summit Caterpillar Control | B.t. Hose-End | Easy hose-end application | 32 oz concentrate | Amazon |
| Bonide Systemic Insect Control | Systemic | Soil drench for prevention | 16 oz concentrate | Amazon |
| Southern Ag Conserve | Spinosad | Targeted spot treatment | 16 oz pint | Amazon |
| Wisdom Pro Bifenthrin | Synthetic | Severe, large-scale infestation | 1 Quart concentrate | Amazon |
In‑Depth Reviews
1. Monterey B.t. Caterpillar Killer
Monterey B.t. is a premium, targeted biological insecticide using Bacillus thuringiensis var. kurstaki. This bacterium produces proteins that specifically paralyze the digestive system of caterpillars like bagworms, while leaving birds, earthworms, and bees unharmed. It is OMRI Listed for organic gardening, making it the safest option for yards where wildlife and pollinators are a priority.
This makes it a good fit for treating bagworms on arborvitae when applied every 7–10 days during the active hatching period. The concentrate mixes easily with water for use in a standard pump or hose-end sprayer.
This product comes with a measuring spoon for accurate dilution. The only downside noted is the small container size relative to the coverage area. For larger properties, you will likely need to buy multiple bottles to maintain a full-season spraying schedule.
Why it’s great
- OMRI Listed and safe for beneficial insects
- Highly effective on young bagworm larvae
- Includes measuring spoon for precise mixing
Good to know
- Small bottle may not cover large properties in one purchase
- Requires strict 7–10 day reapplication schedule
2. BioAdvanced Tree & Shrub Insect Killer
BioAdvanced delivers a synthetic systemic insecticide that kills by contact and provides residual protection for up to two weeks. Its ready-to-spray formula connects directly to a garden hose, which simplifies treating large arborvitae hedges or tall trees. The active ingredient moves within the plant tissue, offering long-lasting defense against foliar-feeding insects.
The product is marketed for fast knockdown on bagworms, aphids, and whiteflies, with visible results within days per the manufacturer. The rainproof guarantee after one hour means you don’t have to worry about a sudden shower washing away the treatment.
One common concern is the strong chemical odor during application. While it dissipates outdoors, wearing a mask is advisable. Because it is a broad-spectrum synthetic, avoid spraying flowers in bloom to prevent harming bees.
Why it’s great
- Up to 2 weeks of residual pest control
- Rainproof in one hour after application
- Easy hose-end sprayer for large coverage
Good to know
- Strong chemical odor during use
- Not certified for organic gardening
3. ferti-lome Spinosad Insecticide
ferti-lome Spinosad is an OMRI Listed concentrate that uses spinosad, a natural fermentation product from soil bacteria. It targets a wide range of chewing insects, including bagworms, tent caterpillars, and leafminers, with a mode of action that affects the pest’s nervous system. This makes it an excellent mid-range option for users who want an organic label without sacrificing punch against heavy infestations.
Its label lists bagworms among the chewing insects it targets on trees and shrubs. It works well in battery-powered sprayers for broad yard coverage and is gentle enough on ecosystems when used as directed.
The 16-ounce bottle concentrates to make multiple gallons of spray. A few users mention that spinosad degrades more quickly in direct sunlight compared to synthetics, so timing sprays for late afternoon or overcast days improves results. Reapplication every 7-10 days is still needed for heavy populations.
Why it’s great
- OMRI Listed for organic production
- Broad spectrum bagworm and caterpillar control
- Good value per gallon of mixed spray
Good to know
- Breaks down in strong sunlight
- Requires consistent weekly reapplication
4. Summit Caterpillar and Webworm Control
Summit Caterpillar and Webworm Control is a budget-minded B.t. concentrate that delivers the same active bacterium as pricier options. Designed for hose-end application, the 32-ounce bottle treats a significant area of arborvitae, making it a strong entry-level pick for homeowners catching a first-time infestation. It targets insects only, leaving beneficial pollinators safe.
With consistent application every 7-10 days through the critical instar period, B.t. products like this are labeled to reduce bagworm populations over time. It is noted as safe for birds frequenting treated trees.
The primary complaint is the extremely foul smell during mixing and application. Users describe an odor that drives people indoors, so a respirator mask is strongly advised. Despite the smell, the product’s label lists bagworms among its target pests, and it meets the expectations for a mid-range price point.
Why it’s great
- Proven effective against bagworms with regular use
- Safe for birds and beneficial insects
- Generous 32 oz concentrate for large areas
Good to know
- Extremely strong, unpleasant odor
- Needs very consistent weekly application
5. Bonide Systemic Insect Control
Bonide Systemic Insect Control is a systemic formula absorbed by the plant to kill pests that feed on it, including thrips, mealybugs, scale, and spider mites per the product listing. This systemic approach is ideal for pests that are already inside the tree canopy and harder to reach with foliar sprays. The 16-ounce concentrate makes up to 16 gallons, offering solid value for preventative spring treatments. Check the current product label for the exact active ingredient and confirm bagworms are listed before use.
The product listing confirms effective control of thrips, scale, and other listed pests on ornamental plants.
Some users report a strong chemical odor during application. The product label advises against use on edible plants, so it is strictly for ornamentals. The included measuring cup helps simplify dilution, but wearing gloves and a mask is essential during handling.
Why it’s great
- Systemic action protects hard-to-reach foliage
- Makes up to 16 gallons of mixed spray
- Effective against a broad spectrum of tree pests
Good to know
- Very strong, unpleasant odor
- Not for use on edible fruits or vegetables
6. Southern Ag Conserve Naturalyte
Southern Ag Conserve Naturalyte is a spinosad-based insecticide that offers low-toxicity, organic pest control for foliage-feeding worms and caterpillars. Its 16-ounce pint size concentrates to make up to 8 gallons of spray, which is ideal for targeted spot treatments on smaller arborvitae. The product is OMRI listed and notable for having virtually no odor, a major plus for sensitive users.
The product label lists effectiveness on scale insects, spider mites, and leaf-eating caterpillars. The spray is easy to wash off of produce and safe to use in vegetable gardens.
The primary limitation is the small bottle size relative to the price. For large arborvitae hedges, you may find yourself buying multiple units for a full season. Reapplication every 7–10 days is still required for persistent bagworm activity.
Why it’s great
- Virtually no odor during application
- OMRI listed with low mammalian toxicity
- Works on scale, aphids, and mites too
Good to know
- Small bottle requires bulk purchase for large yards
- Needs consistent weekly reapplication
7. Wisdom Pro 7.9% Bifenthrin
Wisdom Pro is a professional-grade synthetic pyrethroid concentrate containing 7.9% bifenthrin. It acts as a sodium channel modulator, causing rapid paralysis and death in bagworms, gypsy moths, tent caterpillars, and many other listed pests. The quart size offers outstanding value for homeowners with large, heavily infested arborvitae stands who need immediate knockdown.
This product is labeled to kill on contact and provide residual activity lasting a couple of weeks, with bagworms and gypsy moth caterpillars listed among its target pests. Mixing rates of 1 to 2 ounces per gallon of water means one quart will last a very long time for most residential properties.
Because bifenthrin is a broad-spectrum synthetic, it can harm beneficial insects and aquatic life. Avoid spraying near ponds, streams, or during bloom when bees are active. The concentrate requires proper mixing and protective gear during handling, making it better suited for confident DIYers than beginners.
Why it’s great
- Fast knockdown of bagworms on contact
- Excellent value per quart for large properties
- Long residual activity for up to two weeks
Good to know
- Harmful to bees and aquatic life if misapplied
- Requires protective gear and precise mixing
FAQ
How often should I spray bagworm insecticide on arborvitae?
Is B.t. or Spinosad safer for birds around my arborvitae?
Can I use a systemic insecticide for bagworms on tall arborvitae?
Final Thoughts: The Verdict
For most users, the bagworm spray for arborvitae winner is the Monterey B.t. because it combines proven efficacy with organic certification and safety for beneficial wildlife. If you want long-lasting systemic protection on large established trees, grab the BioAdvanced Tree & Shrub. And for severe, large-scale infestations that demand fast knockdown, nothing beats the Wisdom Pro Bifenthrin.