Box Tree Moth

The box tree moth, Cydalima perspectalis, is an invasive species in the order Lepidoptera that feeds on boxwood trees. This insect pest is native to East Asia and was detected in New York in 2021. In West Virginia, positive cases of this pest were reported in Morgan and Berkeley counties in 2025. It also has been detected in Delaware, Massachusetts, Michigan, Ohio, Pennsylvania, and Virginia. The caterpillars are green with black, yellow, and white stripes. Depending on the age, caterpillars will be 0.25 to 1.5 inches long. Adult moths are typically white and have a brown margin on their wings, with a wingspan of 1.5 inches. Occasionally, an adult might be melanated with darkened wings. Feeding damage can be quite severe, and heavy infestations can defoliate the plant. 

Life Cycle

Box tree moths will probably have 2 to 4 generations annually in West Virginia, depending on the temperature throughout the year. They overwinter in the larval stage, which can tolerate low temperatures, at least to -22 F. Feeding begins in early to mid-spring as temperatures hit around 50 F. This is interrupted by a resting period when day length reaches 13.5 hours and feeding resumes 6 to 8 weeks later. Caterpillars will begin to pupate among the leaves of the host plant after about 14 days of feeding. It takes another 2 weeks for the adult moths to emerge from their cocoons. Adult moths live for a month, and females will lay eggs in clusters of 5 to 20 on the leaves of boxwood trees. Eggs are overlapping, pale yellow, and will develop in 3 days. Adults are strong fliers and can disperse over several miles. They appear similar to the melon worm moth, which may migrate northward each year, and can be distinguished by white comma markings in the wing margin and a white prothorax behind the head. 

Damage

Boxwoods, Buxus species, are the only known hosts of box tree moths. Young larvae feed on the underside of the leaves, which gives them a “peeled” appearance. Older caterpillars will consume entire leaves, except for the midrib. 

Caterpillars also create webbing between leaves with their silk. Infested plants will have patchy defoliation with webbing in a light infestation and greater defoliation in heavy infestations. 

If the larvae consume all available leaves, they may begin to feed on the bark. Severe infestations can leave the plant browned. Green-black frass, or droppings, can be used to detect the presence of larvae as well.

Report

Any suspicion activity of the box tree moths or boxwoods damaged by this pest should be reported to the West Virginia Department of Agriculture at (304) 558-2212 or bugbusters@wvda.us. 

Do not ship live samples of the pest anywhere, including the West Virginia Department of Agriculture or WVU Extension diagnostic clinic. 

To kill specimens, eggs, larvae, pupae, and adults can be placed in alcohol. Adults also can be killed by placing them in a container in the freezer for 24 hours.

Cultural Control

The optimal method to manage this invasive species is to stop or reduce its spread by prioritizing prevention, early discovery, and rapid response. Nurseries and landscape companies should purchase plants only from propagators that have been certified as free of the box tree moth. Also, nurseries and landscape companies should also inspect their boxwood plants weekly looking for insects or damage caused by this pest. They should consider the use of pheromone traps since they are commercially available. Homeowners should buy boxwood plants only within the same city or county. If insects are found in residential or nurseries in shrubs, plants and insects should be destroyed and reported to the West Virginia Department of Agriculture. Small infestations can be pruned and infested material should be destroyed. After infested plant removal, homeowners and landscape companies should consider other plant species for replacement.

Biological Control

Several natural enemy species have been reported for attacking the box tree moth in its native range. Some of those species are naturally present in the Mid-Atlantic, but they are not commercially available, except for the parasitic wasp, Trichogramma. However, the most successful control with a Trichogramma species achieved 40% mortality in China, but the efficacy of parasitoids differed by species. 

Chemical Control

In West Virginia, the target pest does not have to appear on the pesticide label. Pesticide applicators can legally use any insecticide to control the box tree moth if the product has the site of application (boxwood plant or ornamental plants) listed on the label. Due to its recent establishment, there are only 6 insecticides labeled to control box tree moths, but they all have Bacillus thuringiensis (BT) as active ingredients. BT is a biopesticide that has high effectiveness against lepidopterans, including the box tree moth. Caterpillars have shown an increase in tolerance to BT with age. Another biopesticide that has shown high efficacy against caterpillars is Spinosad. Horticultural oils, insecticidal soaps, and chlorantraniliprole are reduced-risk insecticides that also should be effective on caterpillars. Last, there are several broad-spectrum insecticides, such as pyrethroids, labeled for control of other caterpillars on ornamentals that should also provide control. However, these products should be avoided because they are more toxic to beneficial insects and can cause outbreaks of secondary pests. 

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