Box Tree Moth (Cydalima perspectalis) — identification, habitat & look-alikes

The box tree moth is a moth from East Asia whose caterpillars feed almost entirely on boxwood and can leave a heavily infested shrub brown and stripped within weeks. Most adults have white wings with a brown border. It spread to Europe in 2006 and Canada in 2018, and since 2021 it has turned up in the eastern and Great Lakes United States as an invasive pest.

Appearance

Appearance: Wingspan about 1.5–1.75 in (40–45 mm). Most moths have white wings with a brown border. A few are solid brown, sometimes with a purplish tint. Both forms have a small white comma- or crescent-shaped mark on each forewing.

Look-alikes

Melonworm mothDiaphania hyalinata

Smaller (about 1 in, 2.5 cm across), with a broad, pearly-white area across both wings and no white comma mark. Its caterpillars feed on squash, melon, and cucumber, not boxwood.

Why they get mixed upA white moth with a dark border that shows up in late summer.

Pickleworm mothDiaphania nitidalis

About 1.2 in (3 cm) across, with yellowish markings and a big splotch on the forewings, and a solid brown body behind the head. Its caterpillars eat squash-family plants.

Why they get mixed upSimilar shape and pale wings with dark edges.

Boxwood webwormGalasa nigrinodis

The caterpillar is dingy grayish-brown rather than green and striped, and damage usually stays inside the shrub. The adult is a small reddish-brown moth.

Why they get mixed upIt also webs boxwood leaves together.

Where it lives

Typical habitats: Gardens
Nurseries
Boxwood hedges
Range: Native to China, Taiwan, Korea, and India. In North America it has been found in Ontario since 2018 and in the eastern and Great Lakes US since 2021.
Preferred conditions: Anywhere boxwood is planted.

Behavior

Diet: Caterpillars feed almost entirely on boxwood (Buxus).
Activity: Adults fly at night.
Overwintering: Young caterpillars spend the winter inside a silk shelter made from two boxwood leaves.

Life cycle

Larva: The caterpillar is green to greenish-yellow with black stripes, black spots, and a shiny black head, growing to about 1.5 in (35–40 mm). Young caterpillars scrape the leaf surface; older ones eat whole leaves, leaving curled , messy silk webbing, and piles of green droppings. Heavy feeding can turn a shrub brown and kill it. In Ohio, no native pest strips boxwoods bare like this, so caterpillars eating boxwood bare are a strong sign of this moth.
Caterpillar food plants: Boxwood (Buxus) species. Other plants have been reported only rarely in Asia, and none in Europe.