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Bagworms hang in silk bags from arborvitae, junipers, and other evergreens, and the spray you choose matters less than when you use it. Bagworm sprays only kill the young caterpillars, so timing decides whether a treatment works. We looked for products labeled for bagworms on trees and shrubs, with clear mixing rates and a listing you can actually buy.
Our top pick is the Fertilome Caterpillar Killer with Bt in the 16 oz size. Bt is the active ingredient named most often across the expert reviews and reader lists we checked, and the maker says it is not toxic to humans and pets. The ready-to-spray spinosad and the larger Monterey Bt suit other jobs.
1 Fertilome Caterpillar Killer Spray with Bt, 16 oz | 2 Fertilome Spinosad Bagworm, Tent Caterpillar and Chewing Insect Control, Ready to Spray, Quart | 3 Monterey B.t. Bacillus Thuringiensis, 32 oz with Spoon | |
|---|---|---|---|
| Best for | Best overall | Best spinosad option | Best for big jobs |
| Active ingredient | Bacillus thuringiensis (Bt) | Spinosad | Bacillus thuringiensis (Bt) |
| Size | 16 oz | Quart (32 oz) | 32 oz, with measuring spoon |
| Certification | OMRI listed for organic gardening | Not listed | OMRI listed for organic gardening |
| Listed targets | Bagworms, tent caterpillar, gypsy moth, cabbage looper, tomato hornworm | Bagworms, tent caterpillars, loopers, armyworms, leafminers | Cabbage looper, bagworm, gypsy moth, fall cankerworm, elm spanworm |
| Check price at Amazon | Check price at Amazon | Check price at Amazon |
Fertilome Caterpillar Killer Spray with Bt, 16 ozBest overallMost recommended by reviewers
Check price at Amazon
Fertilome Spinosad Bagworm, Tent Caterpillar and Chewing Insect Control, Ready to Spray, QuartBest spinosad option
Monterey B.t. Bacillus Thuringiensis, 32 oz with SpoonBest for big jobs
A ready-to-use Bt spray for young bagworms on trees, shrubs, and vegetables, with mixing rates printed on the listing.
Most recommended by reviewers
Check price at AmazonPrices and availability on Amazon change often.
One catchBt only works on small bags, under about an inch long, so it has to go on early in the season.
Bt is the option most often recommended across the expert reviews and reader lists we checked, and this 16 oz bottle gives the most backing for the money. The listing names bagworms and tent caterpillars among its targets and gives separate mix rates for trees and vegetables, which makes it easy to match to a yard with both.
It is the right choice for someone who wants an organic-listed spray for young caterpillars on evergreens and shade trees. Expect to spray again if the bags are already large, since Bt is most effective on small larvae.
A spinosad spray in a ready-to-use bottle for trees and shrubs, for people who want a different active ingredient from Bt.
Prices and availability on Amazon change often.
If you want a different active ingredient from Bt, spinosad is the main alternative in the expert guidance. This quart comes ready to spray, so you can treat a few shrubs without measuring. The listing names bagworms and tent caterpillars and covers a wide range of trees, shrubs, and garden plants.
It fits a homeowner with a mix of ornamentals and vegetables who wants one bottle for several pests. Spray when the larvae are small, as with any caterpillar product.
A larger Bt concentrate that mixes with water for a pump or pressure tank sprayer, sized for many trees or a larger yard.
Prices and availability on Amazon change often.
If you are treating a long row of arborvitae or several large shade trees, the 32 oz size saves refills. the maker says it mixes instantly with water and works with either a trigger bottle or a pressure tank sprayer, which is useful when you are covering a lot of foliage.
It is a good fit for a larger yard or a gardener who already owns a pump sprayer. The same timing rule applies: spray when the bags are young and the larvae are small.
Bagworm eggs usually hatch from late May to mid-June, and every expert source we used says the best time to spray is while the larvae are small. Extension guidance says insecticides applied in April, May, and June are effective in most areas, but they lose effect as the larvae grow. One extension guide recommends checking catalpa and Japanese tree lilacs for bloom, then inspecting conifers for small bags.
Spray, then check the trees about two weeks later for live bagworms. If you find any, treat again.
No single spray gets rid of bagworms for good. Remove and destroy the bags from fall through early spring, before the eggs hatch, then spray young larvae in late spring. Check the trees again two weeks after treatment and repeat if you find live worms.
Spray while the larvae are small, which in many areas is late May through June. Extension guidance gives April, May, and June as effective windows, and the eggs usually hatch from late May to mid-June. Check local extension recommendations, since timing varies by region.
None of the sources we used recommends dish soap as a spray. One extension guide does suggest picking bags off isolated trees and drowning them in a bucket of soapy water, which is a hand method, not a spray. For spraying, use a labeled product.
Vinegar does not appear in any of the expert guidance we used. The labeled insecticides in this guide are the products the sources recommend for bagworms. Read the label before using any product on trees.
Bt is the most-recommended choice for young bagworms on evergreens, and the 16 oz Fertilome spray is our top pick. Confirm on the label that the product is approved for arborvitae or your specific evergreen before buying. Spray while the bags are small.
The 16 oz Bt spray is the best overall choice for shade trees, and the spinosad ready-to-spray bottle is a good option if you want a different active ingredient. For tall trees, use a hose-end or pressure sprayer, since a bottle reaches only so far.
Why trust BullseyeBuy
We compared six bagworm sprays, weighing label claims, active ingredients, and the advice in three university extension guides and one reader forum. Every product here was checked for an Amazon listing that is in stock, and each recommendation is tied to what the listing and the sources say.
Our expert team tests products when it is needed and researches online and in interviews. Every guide is fact-checked and edited by a real person.
The BullseyeBuy editorial team · Updated Oct 17, 2026
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