Distribution, Biology and Management of a Fast-Moving Invader

Photo 1. Adult box tree moths have white bodies with brown heads. Wing markings are variable, often with large white central patches bordered by brown margins on both fore and hind wings. The brown border of each fore wing often has a small white patch. Photo courtesy of Bernard DuPont from France, CC BY-SA 2.0.

A pattern often seen with invasive pests in a newly colonized land is a lag time between the first detection of the foreign pest in a new location and its widespread geographic distribution, which in some instances can occur rapidly (Simberloff 2013). Such is the case with several important pests of woody trees and shrubs making their destructive presence known in the United States. In this article, we meet the box tree moth (BTM, Cydalima perspectalis, Lepidoptera: Crambidae), a native to eastern Asia, including China, Taiwan, Japan, South Korea, India, Pakistan and eastern Russia.

Where is BTM now – and likely to be in the future?
BTM was first reported as an invader to Europe in 2007, in Germany and the Netherlands, and has now spread to more than three-dozen countries in Europe, western Asia and Africa in less than two decades (Seehausen 2024). BTM debuted in the United Kingdom in 2008, and it became a major pest in private gardens in a few short years. Closer to home and a decade later, in 2018, BTM was discovered in a residential landscape by a community scientist in Toronto, Canada. Just three years later, in July of 2021, the New York State Department of Agriculture and Markets (AGM) detected adult BTM in Niagara County, about 30 miles south of Toronto. Officials with New York AGM suggest that adult BTM may have been carried by wind or flown from Canada to New York (AGM 2021).

In merely four years since the border in Canada was breached, as of September 2025, BTM has been found some 500 miles away from Toronto in Kentucky. BTM is now also confirmed in Delaware, Maryland, Massachusetts, Michigan, Ohio, Pennsylvania, Virginia and West Virginia, according to the U.S. Department of Agriculture (USDA 2025).

How far will BTM spread?
A recent climatic study predicts that BTM will survive throughout much of Europe, from Scotland and Sweden in the North to countries in the south lining the Mediterranean Sea, including those in Europe, Africa and Asia (Seehausen 2024). The study by Seehausen et al. predicts that most regions of North America, except Alaska and northern Canada, will provide suitable climates for establishment of BTM. However, some areas in the United States may dodge BTM infestations due to conditions unsuitable for boxwood (Buxus sempervirens) or BTM survival.

Extremes of heat and cold affect the growth and survival of BTM as well as boxwoods, and regions may simply be too hot or cold for either BTM or their hosts to survive. Parts of the southwestern United States with limited rainfall may simply be too dry for boxwoods to survive without irrigation. Of course, managed landscapes with irrigation that support boxwoods may be at risk of infestation if BTM find their way into the landscape.

Photo 2. Older larvae are greenish yellow with broad black stripes and thinner white stripes running the length of the body, and their heads are shiny and jet black. They can reach a length of 40 mm (1.6 inches) when fully grown. Photo courtesy of Paula M. Shrewsbury, University of Maryland.

How has BTM spread so rapidly?
The rapid spread of BTM through Europe and Asia is due in part to the abundance of boxwoods in natural and managed landscapes. Natural, short-
distance dispersal by adult moths is estimated to range from three to six miles; however, one study suggests that natural dispersal might be as much as 20 miles (Cook et al. 2022). Abetting relatively short-distance natural dispersal events are long-distance human-assisted movements of BTM. Transfer of infested ornamental plants from eastern China likely transported BTM thousands of miles to Europe. Ongoing transit of infested plants contributes to the rapid spread of BTM among countries in Europe, Asia and Africa (Bras et al. 2019).

BTM description and life cycle
BTM adults are active at night. Their bodies are white and their heads are brown. Wing markings are variable, often with large white central patches bordered by brown margins on both fore and hind wings. The brown border of each fore wing often has a small white patch. (Photo 1) Less common are adults with brown wings bearing small white streaks.

With respect to the lifecycle of BTM, new generations begin when female moths deposit eggs in clusters of five to 20 light-yellow eggs that slightly overlap in a gelatinous sheet on the underside of boxwood leaves. Caterpillars have six to seven instars. Young larvae are light green with black heads. Older larvae are greenish yellow with broad black stripes and thinner white stripes running the length of the body, and their heads are shiny and jet black. The larvae attain a length of 40 mm (1.6 inches) when fully grown. (Photo 2)

BTM has an obligatory winter resting period called diapause. Cook et al. (2022) report that all larval stages can overwinter. Larvae spin silken cocoons between boxwood leaves to pass the winter. While timing differs depending on geographic temperatures, typically as weather warms, larval development resumes and caterpillars continue feeding in March and pupate in April and May. Pupation occurs in leaf-borne white silken cocoons on plants or on fallen leaves near infested plants. Larvae of a second generation hatch from eggs in May and June, and feeding continues into late summer and early autumn.

While two generations are likely to occur throughout much of the United States, North America and parts of Europe, three to five generations occur in warmer parts of the globe. In North America, climatic models predict that in the northernmost parts of boxwood’s range, only a single generation is likely to occur, while in southern locations where boxwoods can be grown, multiple generations are expected (Cook et al. 2022, Coyle et al. 2022).

Photo 3. Discolored leaves of these boxwoods could be due to several biotic factors such as Volutella or boxwood blight, or abiotic factors such as mechanical or winter damage. A closer investigation would reveal the telltale presence of caterpillars. Photo courtesy of Paula M. Shrewsbury, UMD.

BTM damage symptoms, signs and hosts
Damage by BTM is dramatic, quick and often lethal. Damage on newly infested boxwoods may be mistaken for other biotic or abiotic problems that appear as isolated discolored leaves on scattered branches of boxwoods. Young larvae enclose leaves in a loose web in which they feed. (Photo 3) Early instars remove green tissues from one side of the leaf surface in a type of defoliation called etching. Within these leaf shelters, larvae are not readily seen, but bundled leaves turn brown. Older larvae defoliate leaves, usually at their margins, but at high densities, only curly leaf tissue may remain. Caterpillars web leaves, and these webs become littered with frass and shed skins. When caterpillars are abundant, boxwoods may be completely defoliated, and caterpillars consume bark as well as leaves. (Photo 4) Tree death can be rapid, occurring in a year or two. Regularly inspect your boxwoods for signs and damage symptoms of BTM.

Photo 4. A close inspection of symptomatic boxwoods reveals etched and defoliated leaves, webbing, frass and caterpillars. Photo courtesy of Paula M. Shrewsbury, UMD.

In several European countries, boxwoods are native and thrive in natural areas. BTM has killed large areas (greater than 150 acres) of native boxwoods (Buxus sempervirens) in natural forests in Switzerland (Leuthardt and Ramin 2011, Schumacher 2013) and Russia (Gninenko et al. 2014). The loss of natural stands of boxwood has cascading environmental impacts ranging from increased soil erosion to disruption of food webs. Coyle et al. (2022) list several primary hosts of BTM, including these popular species: little leaf boxwood (Buxus microphylla), common boxwood (Buxus sempervirens) and Korean boxwood (Buxus sinica). Additional hosts recorded in the native range of BTM include species of Euonymus, holly (Ilex), ash (Fraxinus), mock orange (Murraya), brambles (Rubus), maple (Acer) and greenbrier (Smilax). (Photo 5) Some good news is that, to date, BTM has only been found feeding on boxwood in North America.

Photo 5. If left untreated, box tree moths can remove green tissue from leaves and girdle branches, leading to the death of small or large boxwoods and even entire hedges in a single season or two. Photo courtesy of Jeff Semler, UMD.

BTM management
As with most newly invasive species, management includes slowing the spread and reducing damage through early detection and response, and involves government agencies, commercial providers of plant health care and the general public. Increasing awareness and continuing information sharing and education are key elements in managing BTM. Since the movement of infested boxwood plants is the most likely avenue for rapid long-distance movement of BTM, informing and educating plant-industry professionals and hobbyists on inspecting boxwoods and identifying BTM is critical to early detection and slowing the spread of this invader.

Fortunately, pheromone traps have been developed to capture male BTM and can be used to help detect and track local populations of BTM in landscapes. USDA has a sophisticated program for delimiting BTM populations in infested areas. Eradication of some invasives like Asian longhorned beetle can succeed; however, no successful eradication programs for BTM have been reported in infested lands to date. Nonetheless, USDA considers eradication possible in small patches of managed boxwoods if infestations are detected early and interventions are made quickly (Cook et al. 2022).

Photo 6. Counties with federal quarantines for the Box Tree Moth as of September 2025. Map courtesy of the USDA Animal and Plant Health Inspection Service.

Once established, a multifaceted
integrated-pest-management (IPM) and plant-health-care (PHC) approach is the best bet to reduce populations of BTM and mitigate their damage. Heavily infested boxwoods should be removed and burned, buried or chipped on site if possible. If transportation off site is necessary, plants should be tightly sealed in containers or bags during transit to avoid spreading the pest. Black plastic bags placed in direct sunlight may become lethally hot to caterpillars inside, and infested plants can be dealt with in place.

Biological control is one of the cornerstones of IPM programs. In Europe and Asia, there are reports of several species of parasitic wasps and tachinid flies attacking immature stages of BTM (Cook et al. 2022, Coyle et al. 2022). Several species of birds attack and consume BTM caterpillars (Bird et al. 2020). To date, little is known about the likelihood of these natural enemies providing substantial, widespread biological control of BTM in managed or natural settings.

On the local scale of individual plants or plantings in landscapes and nurseries, formulated microbials and synthetic insecticides can be highly effective. Some products with active ingredients labeled for use in organic food production (OMRI listed), including Bacillus thuringiensis kurstaki (Btk), entomopathogenic nematodes, neem oil and spinosad, work well against BTM caterpillars (Cook et al. 2022, Coyle et al. 2022). Btk products work best on early instar caterpillars.

The active ingredients emamectin benzoate and abamectin, which in some formulations are listed as “reduced risk” by the EPA, should also be effective. Several synthetic pyrethroids and chlorantraniliprole provided 95%-99% control of BTM caterpillars (Cook et al. 2022). Due to multiple generations of BTM, in some cases applications may need to be repeated.

Mechanical control by physically removing larvae from boxwoods can work on isolated low-density infestations or on smaller plants, but removal by hand is likely too labor intensive for larger plantings. Many garden managers are removing and replacing boxwood with alternative plants or not replanting at all to reduce the economic impact of BTM (Kenis et al. 2013). Coyle et al. (2022) provided a nice list of possible replacements for Buxus in regions infested with BTM that includes species and cultivars of Ilex, Taxus and Thuja.

Conclusion
BTM is a federally regulated invasive species. If you find BTM, report the finding to your state Department of Agriculture or your University Extension Service. Early detection, timely mitigation and comprehensive IPM and PHC interventions can help stop the spread and reduce the loss of boxwood to this noxious, fast-moving invader. (Photo 6)

Michael J. Raupp is a professor emeritus and extension specialist at the University of Maryland in College Park, Maryland. His writing, research and scientific outreach have received a dozen national and international awards. He is a regular guest on television and radio. His most recent book, “26 Things that Bug Me,” introduces youngsters to the wonders of insects and natural history, while “Managing Insects and Mites on Woody Plants,” published by the Tree Care Industry Association, is a standard for the arboricultural industry.

Paula M. Shrewsbury is a professor and extension specialist of entomology at the University of Maryland in College Park, Maryland. Her research and extension-program focus is to create sustainable landscapes, nurseries and turf systems with an emphasis on biological control, conservation of beneficial arthropods and management of invasive species. She has won several awards for excellence in research and extension, including the National Award for Extension presented by the Entomological Society of America (ESA) and an ESA Fellow Award. She also is a co-founder and long-time principal contributor to the University of Maryland Extension Landscape and Nursery IPM Alert newsletter.

Article resources and references
AGM 2021. NYS Department of Agriculture Confirms Box Tree Moth Found in Western New York. New York State Department of Agriculture and Markets. August 2021.

Bird, S., C. Raper, N. Dale-Skey, and A. Salsbury. 2020. First records of two natural enemies of box tree moth, Cydalima perspectalis (Lepidoptera: Crambidae), in Britain. BR. J. Ent. Nat. Hist., 33: 67-70.

Bras, A., D. N. Avtzis, M. Kenis, H. Li, G. Vétek, A. Bernard, C. Courtin, J. Rousselet, A. Roques, and M-A. Auger‑Rozenberg. 2019. A complex invasion story underlies the fast spread of the invasive box tree moth (Cydalima perspectalis) across Europe. Journal of Pest Science 92(3):1187-1202.

Cook, J. C., T. C. Thomas Culliney, C. F. Funaro, and J. B. van Kretschmar. 2022. New Pest Response Guidelines, Cydalima perspectalis, Box tree moth. USDA Animal and Plant Health Inspection Service.

Coyle, D. R., J. Adams, E. Bullas-Appleton, J. Llewellyn, A. Rimmer, M. J. Skvarla, S. M. Smith, and J.-H. Chong. 2022. Identification and Management of Cydalima perspectalis (Lepidoptera: Crambidae) in North America. Journal of Integrated Pest Management, 13(1): 24; 1–8.

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Leuthardt F.L.G., W. Billen, B. Baur. 2010. Spread of the box-tree pyralid Diaphania perspectalis (Lepidoptera: Pyralidae) in the region of Basel – a pest species new for Switzerland. Entomo Helvetica, No.3:51-57.

Schumacher J. R., 2013. Der Buchsbaum-Zünsler (Cydalima perspectalis) im Grenzach-Wyhlener Buchswald – Invasionschronik und Monitoringergebnisse. (Der Buchsbaum-Zünsler (Cydalima perspectalis) im Grenzach-Wyhlener Buchswald – Invasionschronik und Monitoringergebnisse.) Gesunde Pflanzen, 65:1-6.

Seehausen, M.L., A. Rimmer, A. Wiesner, M. Kenis, C. Scott-Dupree, and S. M. Smith. 2024. Modelling potential distribution of the invasive box tree moth across Asia, Europe, and North America. PLoS ONE 19(4): e0302259.

Simberloff, D. 2013. Invasive Species: What Everyone Needs to Know, Oxford University Press. 352 pp.

USDA 2025. Animal and Plant Health Inspection Service. Box Tree Moth. September 2025.