Plant Problem Diagnosis Key / Pests
Bagworms
Thyridopteryx ephemeraeformis
Caterpillars that build spindle-shaped bags of silk and bits of the plant, and carry them as they feed. Heavy numbers can strip and kill juniper and arborvitae, since evergreens do not regrow needles on bare wood.
Signs
- Bags 1-2½ inches long hanging from twigs, covered in needle or leaf bits.
- Browned, stripped branch tips in summer.
- Bags still hanging in winter hold the next year's eggs.
What favors it
Juniper, arborvitae, spruce and other evergreens. Females cannot fly, so infestations build on the same plants; young larvae drift to nearby plants on silk.
Prevention
- Pick off and destroy bags from fall to early spring, before the eggs inside hatch in late spring.
- Check evergreens in June for tiny new bags about ⅛ inch long.
Crops it shows up on
Evergreens & conifers (pine, spruce, juniper); Shade & ornamental trees; Roses & ornamentals.
Often confused with
Sources
- Bagworm and Its ControlOhio State University Extension
- BagwormsNebraska Extension
Treatment by crop
Cultural, biological and chemical options in the order to use them, and notes written for each crop.
Identification is free. Treatment is on the Home and Pro plans.
Questions in the key that lead here
- Look the plant over, leaf undersides included. Are insects, mites, slugs, eggs, webbing or droppings on it?
Yes, something living or its traces - What is on the plant?
Something chewing - What is doing the chewing?
Silk tents, webs or hanging bags in tree branches - What is in the branches?
Spindle-shaped bags of needle or leaf bits hanging from twigs
Not a match? Start the key or describe what you see.
More photos
More from university Extension: search Extension pages on bagworms, or find a plant diagnostic lab through your state's Extension.
Other pests
- Aphids
- Bark beetles of pine and spruce
- Broad mites and cyclamen mites
- Caterpillars
- Cicada and twig-cutting damage
- Colorado potato beetle
- Cucumber beetles
- Cutworms
- Elm leaf beetle
- Emerald ash borer
- Flea beetles
- Fungus gnats
- Galls on leaves and twigs
- Hemlock woolly adelgid
- Japanese beetles
- Lace bugs
- Leafminers
- Mealybugs
- Pine sawflies
- Root aphids
- Root-knot nematodes
- Russet mites
- Sapsucker damage
- Scale insects
- Shore flies
- Slugs and snails
- Spider mites
- Spongy moth (gypsy moth)
- Spotted lanternfly
- Squash bugs and stink bugs
- Squash vine borer
- Tent caterpillars and fall webworm
- Thrips
- Whiteflies
- Wood borers