Key points
- The euonymus caterpillar is an introduced pest of Euonymus.
- Species attacked include European Euonymus (Euonymus europaea) (the tree form); Spreading Euonymus (E. kiautschovicus); Winged Euonymus (E. alatus) and Japanese Euonymus (E. japonicus).
- The larvae (caterpillars) appear in central Maryland in early to mid-Mary. The young larvae are gregarious (feed in groups).
- They web the foliage together and feed on new growth. Webs increase in size as the larvae grow, eventually enveloping large branches.
- Feeding lasts for about 3 weeks before pupating in June.
- Mature caterpillars are about 20mm long. They are creamy-gray color, with black spots and black heads.
- Moths are small (wingspan: 24mm) and white with black spots. They emerge in mid-June and lay eggs on twigs, branches, and axils of buds.
- The eggs hatch by early August, but instead of feeding, the larvae immediately prepare for overwintering.
- No further activity is seen until the following spring.
Management
- Since there is only one generation and the feeding occurs early in the season, control is seldom warranted.
- Euonymus outgrows the damage by the end of summer.
- Bt (Bacillus thuringiensis) may be used on young caterpillars if damage is unacceptable.
Rev. 2020