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Life History
Box tree moth (BTM) primarily targets boxwoods (Buxus sp.). Although there is a possibility for certain Ilex, Euonymous and Murraya species to act as host plants under lab conditions, it has NOT yet been seen to do so in field conditions in North America. Box tree moth also has a fast development time. In lab conditions, the time between egg hatch to adulthood takes a 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.
Figure 2: Hibernaculum (Credit: Joe Boggs, OSU Extension)
Early Instar Larvae: Plain 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.
Figure 3: Early instar larvae (Credit: Hannah Nadel, USDA)
|  Figure 4: Late instar larvae (Credit: Hannah Nadel, USDA)
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Pupae
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.
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 first generation of adults emerges generally between May to July and then live for about two weeks.
Figure 6: Adult (Credit: Szabolcs Sáfián, University of West Hungary, Bugwood.org)
|  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.
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, with many cultivars. Boxwoods are evergreen shrubs and can be identified by their opposite leaf arrangement, a white midrib on the underside of the leaves, smooth leaf margins and a distinct scent.
 
Figure 9: White midrib (Credit: Clark Bacwaden, MDA)
| Figure 10: Opposite leaf arrangement (Credit: Clark Bacwaden, MDA)
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Boxwood Looklikes
Common Name
| General Description
| Evergreen vs. Deciduous
| Hollies (Ilex sp.)
| - Alternate leaf arrangement
- Toothed leaf margins
| Evergreen
| Euonymus (Euonymus sp.)
| - Opposite leaf arrangement
- Toothed leaf margins
- Prominent lateral leaf
| Both
| Privets (Ligustrum sp.)
| - Opposite leaf arrangement
- Smooth leaf margins
- Produces a cluster of white flowers
| Both
| Japanese Barberry
(Berberis thunbergii)
| - Alternate leaf arrangement
- Smooth leaf margins
- Thorny stem
| Deciduous
| Azaleas (Rhododendron sp.)
| - Alternate leaf arrangement
- Smooth leaf margins
| Both
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Figure 11: Ilex spp. (Credit: Clark Bacwaden, MDA)
| Figure 12: Euonymus spp. (Credit: Clark Bacwaden, MDA)
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Figure 13: Ligustrum sinense (Credit: Karan A. Rawlins, University of Georgia, Bugwood.org)
| Figure 14: Berberis thunbergii (Credit: Richard Gardner, Bugwood.org)
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Figure 15: Azalea (Rhododendron spp.) (Credit: Clark Bacwaden, MDA)
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Signs of Infestation
Early instar caterpillars typically eat one side of the leaf creating “windowpanes”. In contrast, late instar caterpillar damage is much more noticeable since they eat the entire leaf, often leaving the midrib or the outline (skeletonized leaves). As they eat, they produce a silk webbing around the branches and between leaves. However, webbing may also be produced by nesting spiders, so it is not a good indicator by itself. Green-black frass is also another sign which can be found on top of the webbing or on the crook of the branches. Early detection may not always be possible, as the caterpillars spin leaves together to create cover and will generally hide within the shrub.
Figure 16: Early instar feeding (Credit: Clark Bacwaden, MDA)
|  Figure 17: Late instar feeding damage (Credit: Clark Bacwaden, MDA)
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Figure 18: More signs (Credit: Clark Bacwaden, MDA)
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Figure 19: Larvae hidden within boxwood (Credit: Clark Bacwaden, MDA)
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 Figure 20: Spider web (Credit: Clark Bacwaden, MDA)
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Longterm Damage
Repeated and continuos infestations reduce the shrub’s chances of recovery. Once the plant is completely defoliated, the caterpillars begin to feed on the bark, which can girdle and potentially kill the shrub.
 
Figure 21: Stripped bark (Credit: Aaron Shurtleff, MDA)
| Figure 22: Heavy feeding damage (Credit: Ferenc Lakatos, University of Sopron, Bugwood.org)
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Figure 23: Dead boxwood (Credit: Aaron Shurtleff, MDA)
| Figure 24: Row of dead boxwoods (Credit: Aaron Shurtleff, MDA)
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Figure 25: Healthy vs. Infested (Credit: Ignacio Baez (l) and Mafalda Weldon (r), USDA) |
Box Tree Moth Lookalikes
Figure 26: Melonworm moth (Credit: Mark Dreiling, Bugwood.org)
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Adults of the melonworm moth (Diaphania hyalinata), appear similar to BTM adults. However, it does not have the crescent markings on its forewings. It also primarily feeds on cucurbits, not boxwoods.
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Figure 27: Euonymus leaf notcher (Credit: Eric R. Day, Virginia Polytechnic Institute and State University, Bugwood.org)
| Figure 28: Euonymus caterpillar (Credit: Dawn Dailey O'Brien, Cornell University, Bugwood.org)
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Caterpillars of the euonymus leaf notcher (Pryeria sinica) and euonymus caterpillar (Yponomeuta cagnagella) have similar markings, and show feeding damage similar to box tree moth caterpillars. Another similarity is that they gregariously defoliate leaves while leaving webbing and frass on the stems of the shrubs. However, the caterpillars are generally only active during the springtime and feed on euonymus (burning bush, spindle tree etc..) NOT on boxwoods.
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 BTM and any of its life stages is an easy option, though laborious, depending on the infestation level. Make sure to check the interior of the boxwood and the underside of leaves for any hidden caterpillars.
- Hand pick caterpillars
- Spray the shrub with a strong jet of water to knock off caterpillars
If it is heavily infested, pruning infested branches, or cutting the whole plant down to its base is recommended. However, caterpillars are able to pupate and overwinter outside the plant, so the debris should also be removed. Any infested clippings, parts or debris should be double-bagged for disposal, to prevent further spread.
Since BTM has multiple generations per year, it is important to keep monitoring the shrub after the intial infestation and treatment to prevent re-infestation. Moths from other infested boxwoods could also re-infest the shrub and any missed caterpillars/eggs can restart the cycle. Further reinfestations can stress the shrub and reduce it’s vigor and potentially even kill it.
Unfortunately, there are currently no pesticides that exclusively kill box tree moth and preventative sprays on boxwoods are not recommended. Some pesticides also require a 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’s webbing. Improper use of pesticides may also cause secondary pest outbreaks like mites and harmful 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 August 2026, eight counties are under a quarantine for BTM: Allegany, Caroline, Cecil, Frederick, Garrett, Kent, Queen Anne's 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]
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