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Life History
Box tree moth primarily targets boxwoods (Buxus sp.). Although there is a possibility for certain Ilex, Euonymous and Murraya species to act as host plants, it HAS NOT been documented in North America as of now. Box tree moth also has a fast development time. Under lab conditions, the time between egg hatch to adulthood took at little more than a month. Although the number of generations per year in Maryland is unknown, it is expected to have multiple overlapping generations. Similarly, BTM's phenology is unknown in MD so the time its various life stages appear throughout the year are estimates.
Larvae
BTM overwinter as caterpillars, primarily as 3rd or even 4th instars, in a protective silk covering called a hibernaculum. As the weather warms around March, they will begin to feed again.
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Figure 2: Hibernaculum (Credit: Joe Boggs, OSU Extension)
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.
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Figure 3: Early instar larvae (Credit: Hannah Nadel, USDA)
| .jpg) Figure 4: Late instar larvae (Credit: Hannah Nadel, USDA)
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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.
.jpg) Figure 5: Pupae (Credit: Hannah Nadel, USDA) |
Adults
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 marking. There is also a much rarer brown form which has the same crescent marking.
The adults are nocturnal so daytime sightings are less likely. the overwintering generation generally emerge between May to July and live for about two weeks.
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Figure 6: Adult (Credit: Szabolcs Sáfián, University of West Hungary, Bugwood.org)
| .jpg) Figure 7: Rare dark morph (Credit: Szabolcs Sáfián, University of West Hungary, Bugwood.org)
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Eggs
Eggs are laid on the leaves in clusters of 5-20, with females laying up to 42 egg masses in their lifetime.
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Figure 8: Eggs (Credit: Hannah Nadel, USDA) |
A Generalized Timeline Can Be Seen Here
What to Look For
Identifying Boxwood
There are typically three boxwood species planted as ornamentals: Buxus sempervirens, B. sinica, and B. microphylla, and plus their many cultivars. Boxwoods are identified by their opposite leaf arrangement, a white midrib on the underside of the leaves, and the pungent odor they emit.
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Figure 9: White midrib (Credit: Clark Bacwaden, MDA)
| .jpeg) Figure 10: Opposite leaf arrangement (Credit: Clark Bacwaden, MDA)
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Signs of Infestation
Early detection may not always be possible because the caterpillars will generally hide within the shrub and early instar caterpillars will typically eat the underside of the leaf. In contrast, the late instar caterpillars will eat the entire leaf, leaving the midrib or the outline (skeletonized leaves). It is not until sufficient feeding damage by late instar caterpillars will infestations be more noticeable. As the caterpillars eat, they also produce a silk webbing around the branches and between leaves. The webbed leaves act as protective coverings while they eat or as an overwintering structure. Webbing may also be produced by nesting spiders so that alone is not as good of an indicator. Green-black frass is also another indicator which can be found on top of the webbing or on the crook of the branches.
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Figure 11: Early instar feeding (Credit: Clark Bacwaden, MDA)
| .jpg) Figure 12: Late instar feeding damage (Credit: Clark Bacwaden, MDA)
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Figure 13: More signs (Credit: Clark Bacwaden, MDA)
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Figure 14: Larvae hidden within boxwood (Credit: Clark Bacwaden, MDA)
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.jpeg) Figure 15: Spider web (Credit: Clark Bacwaden, MDA)
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Longterm Damage
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Figure 16: Heavy feeding damage (Credit: Ferenc Lakatos, University of Sopron, Bugwood.org)
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Once the shrub is completely defoliated, the caterpillars begin to feed on the bark. This can girdle the shrub, potentially killing it.
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Figure 17: Stripped bark (Credit: Aaron Shurtleff, MDA)
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Figure 18: Dead boxwood (Credit: Aaron Shurtleff, MDA) |
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Figure 19: Row of dead boxwoods (Credit: Aaron Shurtleff, MDA)
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%20and%20Mafalda%20Weldon%20(r),%20USDA).jpg) Figure 20: Healthy vs. Infested (Credit: Ignacio Baez (l) and Mafalda Weldon (r), USDA) |
Lookalikes
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Figure 21: Melonworm moth (Credit: Mark Dreiling, Bugwood.org)
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Diaphania hyalinata or the melonworm moth is a lookalike of box tree moth. However, it does not have the crescent markings on its forewings. It is also primarily feeds on cucurbits not boxwoods so it is likely to not be seen together with box tree moth.
There are other pests and disease that can cause a boxwood to look sickly and bare but they generally do not involve whole skeletonized leaves. The University of Maryland Extension has a helpful quide in identifying and managing common boxwood problems which can be found here.
Management
The Maryland Department of Agriculture does not have the resources to do residential treatments. Below are methods that can help manage infestations. But make sure you are certain it is box tree moth before applying control measures to your boxwoods. Also if you are moving or buying boxwoods please inspect them first for any signs of box tree moth to help prevent its further spread.
Manual removal of box tree moth and any of its life stages on the plant is an easy option, though labor-intensive depending on the infestation level.
If it is heavily infested, either pruning infested branches, or cutting the whole boxwood down to its base is recommended. However, caterpillars are able to pupate and overwinter outside the plant, so the debris around the ground should also be removed. Any infested clippings, parts or debris should be double-bagged for disposal to prevent further spread.
There are currently no pesticides that exclusively kill box tree moth and preventative sprays on boxwoods are not recommended. Some pesticides also require pesticide license to be applied and should only be used by professionals. Chemical treatments need adequate coverage to penetrate the interior of the boxwoods and the caterpillar webbing. Improper use of pesticides may also cause secondary pest outbreaks like mites and other non-target effects on beneficial insects and the environment.
For information about your chemical options, you can contact your local Extension office for recommendations and further actions. Additionally, Cornell Extension and Penn State Extension provide some additional management options and both list chemical options for homeowner and commericial use. However these are state specific and the active ingredients listed might not be available or legal to use in Maryland.
Quarantine
As of March 2026, four counties are under a quarantine for BTM: Allegany, Frederick, Garrett, and Washington county. Although the quarantine is in northwestern MD, the surrounding states also have positive counties for BTM and have a quarantine in place. So, it is still a good idea to be on the lookout for BTM across MD not just the northwestern counties.
The Quarantine Order prohibits the movement of Regulated Articles from and within the quarantine zone. Businesses involved with growing and shipping boxwoods must sign a Compliance Agreement with the Department and then obtain a certificate of inspection to ship boxwoods.
Regulated Articles include:
- Any life stage of Box Tree Moth (Cydalima perspectalis) dead or alive.
- The Buxus genus including: cultivars, varieties, plant parts and debris.
- Any other articles, with reasonable doubt, that may present the risk of spread or is susceptible to infestation.
Persons found to have violated the order are liable for civil penalties. If you have any questions about the quarantine contact us at [email protected]
