The box tree moth (Cydalima perspectalis) is native to temperate and sub-tropical regions in Asia. It was first reported in Europe in 2007, after which it spread rapidly across Europe into Western Asia and Northern Africa. In 2018, it was documented in Canada, and now has been confirmed in the US. The box tree moth can significantly damage and potentially kill boxwood plants if left unchecked.
From left to right: box tree moth egg mass, larvae, and adult. Images courtesy of Walter Schön, www.schmetterling-raupe.de/art/perspectalis.htm, and Courtesy of Matteo Maspero and Andrea Tantardini, Centro MiRT - Fondazione Minoprio
Identification & Lifecycle
Two to five generations may occur per year.
Females lay pale yellow eggs singly or in egg masses, and typically hatch within 4 to 6 days.
Box tree moths overwinter as larvae, and typically begin feeding in March, continuing until they pupate in late April to early May. These caterpillars are green and yellow with white, yellow, and black stripes and black spots.
Larvae of the next generation hatch in May or June and immediately begin feeding on boxwood leaves. As they develop, they spin webs to hold leaves together and create protected areas to feed. Larvae remain active through the summer until early autumn.
Green pupae with brown stripes will typically first appear in April or May and will be present continuously through the summer and into the fall.
Adult box tree moths are white with a brown border and may be confused for melon worm moths (Diaphania hyalinata). Adult moths are highly mobile and are typically active at dusk and throughout the night. They usually live for two weeks after emergence; first emerging from the overwintering generation between April and July. Subsequent generations are active between June and October.
If you suspect a box tree moth infestation, at any life stage, please report the finding to the ODA Plant Pest Control (email@example.com), your local OSU Extension specialist, or submit your findings using the Great Lakes Early Detection Network.
On May 26, 2021, USDA APHIS issued a Federal Order to halt the importation of host plants from Canada, including boxwood (Buxus spp.), Euonymus (Euonymus spp.), and holly (Ilex spp.). ODA will continue trapping and visual inspection for the box tree moth throughout the growing season.
Damage and Impact
The caterpillars feed mostly on boxwood and heavy infestations can defoliate host plants. Once the leaves are gone, larvae consume the bark, leading to girdling and plant death.
There are currently no official recommendations for controlling box tree moth in large areas. Removing larvae manually or via water-spraying has been recommended for spot control on ornamental box trees.