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June 16, 2017

Evergreen Bagworm? Not Forever True.

Cliff Sadof, Department of Entomology, Purdue University

The evergreen bagworm, as its name implies, is well known for its ability to defoliate evergreen trees and shrubs like spruce, arborvitae, fir, junipers and pine. When given a chance, it will also feed on deciduous trees like maples, honeylocust, and crabapples. In late May and early June bagworms hatch from eggs that overwinter in the bag of their mother.  Soon after they begin feeding, they cover themselves with leaf tissue. When young bagworms begin feeding on broadleaved plants the caterpillars are too small to feed all the way through, so they leave circular patterns of skeletonization.  Bagworms can be easily controlled with a spray application of spinosad (Conserve, or Fertilome borer and bagworm killer), or Bacillus thuringiensis (Dipel).   More details are available on the Purdue Tree Doctor App, or our Bulletin https://extension.entm.purdue.edu/publications/E-27.pdf


Evergreen Bagworm  Lepidoptera: Psychidae, Thyridopteryx ephemeraeformis

​Click image to enlarge

 

Figure 1.   Circular spots of skeletonization caused by young bagworms feeding on sugar maple 

 

Figure 2.   Young bagworm covering itself with bits freshly cut green leaves

 

Figure 3.   Overwintering bagworm on maple next leaf injured by young bagworms.