Box Tree Moth

Untitled design (60).png Box tree moth (Cydalima perspectalis) is a boxwood defoliator native to East Asia. It was first identified in the US in New York in 2021, and has since been detected in Delaware, Massachusetts, Michigan, Ohio, Pennsylvania, and, as of 2025, in Maryland, Virginia, and West Virginia.

The only sightings so far in Maryland are Washington County.

A Generalized Timeline Can Be Seen Here

Life History

Box tree moth has a fast developmental time. Although the number of generations per year in Maryland is unknown, it is expected to have multiple overlapping generations. Currently, little is known about its phenology, so the appearances of its life stages are estimates.

Larvae

Untitled design (62).png BTM overwinter as caterpillars (of any instar) and begin to feed as the weather warms around March.

Early Instar Larvae: Indistinct green caterpillars that are around 0.5 inches with black head capsules.

Late Instar Larvae: As they mature, they develop black and white stripes with black dots. They are typically around 1.6 inches long.

Pupae

The caterpillars pupate from April to May, with a coloration similar to the larvae, developing in a silk cocoon among the leaves and webbing. The pupae are around 0.7 inches long.

Adults

Untitled design (64).png Adults are around 1.7 inches in wingspan and wings are typically white with a thick brown border, and a brown head and abdomen. The front brown border of their forewing has small white crescent-shaped markings. There is also a much rarer brown form which has the same crescent marking.

Untitled design (65).png The adults are nocturnal and generally emerge between April and July, living for about two weeks.

Eggs

Untitled design (66).png Eggs are laid on the leaves in clusters of 5-20, with females laying up to 42 egg masses in their lifetime.

What to Look For

Identifying Boxwood

There are typically three boxwood species planted as ornamentals, Buxus sempervirens, B. sinica, and B. microphylla, and their many cultivars. Boxwoods are identified by their opposite leaf arrangement, a white midrib on the underside of the leaves, and the pungent aroma they emit.

Signs of Infestation

Caterpillars hide within the plants, so signs may not be immediately noticeable until sufficient feeding damages leaves. As the caterpillars eat, they produce a silk webbing around the branches and leave behind green-black grass. A similar webbing may also be produced by nesting spiders.

Damage

Box tree moth primarily targets boxwoods (Buxus sp.). Once the shrub is completely defoliated, the caterpillars begin to feed on the bark. This can girdle the shrub, potentially killing it.

Figure 19: Healthy vs. Infested (Credit: Ignacio Baez (l) and Mafalda Weldon (r), USDA) unnamed (16).jpg

Management

Manual removal of box tree moth life stages on the plant is an option, although it could be labor-intensive, depending on the infestation level.

Pruning infested branches, or cutting the whole boxwood down to its base if heavily damaged are also recommended, but infested clippings/parts should be double-bagged for disposal to prevent further spread.