Bagworms & Evergreens

Bagworms, or Thyridopteryx ephemeraeformis, are insect pests that mainly attack evergreen trees, but they also attack deciduous trees and shrubs on occasion. Approximately 128 different plant species are at risk of injury from bagworm infestations.

Features

Bagworms commonly attack fir, hemlock, spruce, juniper and pine, among other evergreen species. Adult male bagworms are clear-winged moths with black bodies and an approximately 1-inch wingspan, while females are eyeless, legless and wingless. Female bagworms spend their lives inside small cone-shaped bags created from silk and evergreen tree parts. After mating, the females lay between 500 and 1,000 eggs inside the bag and then die. The eggs spend the winter in the bag and hatch during the spring.

Effects

Bagworm eggs hatch in late spring or early summer. The young larvae, which are approximately .18 inches long but grow to around 2 inches long, build bags that they carry with them as they move around and feed on evergreen foliage. They strip evergreens of their needles, causing extensive defoliation. Repeated infestations can cause death in stressed evergreen trees.

Prevention/Solution

Chemical insecticides can be applied to trees when bagworm larvae are small; older and larger worms are more difficult to kill. Recommended insecticides include Bacillus thuringiensis, a bacterium that sickens and kills bagworm larvae, as well as carbaryl or acephate. Homeowners can also handpick and destroy bags in smaller evergreen trees.

References

• University of Tennessee Extension: The Bagworm and Its Control
• Alabama Cooperative Extension System: Controlling Bagworms on Ornamentals
• North Carolina State University Cooperative Extension: Bagworms