Bagworms feed on many types of landscape plants, but they're especially damaging to evergreens, which rely on their leaves or needles to stay from year to year. Male bagworms mature into transparent-winged moths, but plant damage comes from the pest's wormlike caterpillar phase. Bagworms often go unnoticed until it's too late. Timely, proactive treatment is essential to save plants from these pests.
Identification: Newly hatched bagworms are barely visible to the eye, but the black or tan larvae grow up to 2 inches long as they feed heavily through the growing season. Positive I.D. often comes once the pests form protective, spindle-shaped bags that hang down from leaves and branches. The foliage-covered bags measure 2 inches or more and blend into the affected plant, looking like miniature pinecones or nearly normal growth on evergreens.
Signs/Damage: Sudden, dramatic changes in evergreens signal bagworm damage. Trees become sickly, pale and dying in a matter of weeks over summer months. Trees and shrubs turn brown and leaves or needles drop, as though deprived of water, but irrigation and fertilization won't help. Closer inspection reveals the protective bags hanging like small ornaments on a Christmas tree. Larvae come and go from the bags until late summer, when it's egg-laying time.
Control: Effective bagworm control requires reaching unprotected larvae. They typically hatch in late spring and early summer, but don't form bags right away. Proactive treatment during this vulnerable time yields the best results. GardenTech® brand offers highly effective controls that kill feeding bagworms by contact and keep protecting foliage for up to three months.
- Sevin® Insect Killer Concentrate provides an easy, economical way to provide extensive coverage of small trees and shrubs. Use with a pump-style sprayer, and cover all plant surfaces thoroughly.
- Sevin® Insect Killer Ready to Spray attaches to a common garden hose and does the mixing and measuring as you work, providing thorough coverage for evergreens or ornamentals.
Tip: Remove bagworm bags from trees and shrubs during winter or early spring, before worms hatch from eggs inside. Always destroy the bags. Each one can contain hundreds of eggs.
Always read product labels and follow the instructions carefully.
GardenTech is a registered trademark of Gulfstream Home and Garden, Inc.
Sevin is a registered trademark of Tessenderlo Kerley, Inc.
- "Evergreen Bagworm - Thyridopteryx ephemeraeformis, Woodbridge" by Judy Gallagherdit: licensed under CC BY 2.0
- "Thyridopteryx ephemeraeformis – Evergreen Bagworm Moth" by Andy Reago & Chrissy McClarren licensed under CC BY 2.0