Be Aware of Box Tree Moth, A New Pest of Boxwood
Boxwoods, Buxus spp, are an important and widely used ornamental landscape plant. Boxwoods are frequently used in hedges, foundation plantings and in formal gardens. Box tree moth, Cydalima perspectalis, is a non-native insect pest that feeds on boxwood and left unmanaged can kill boxwood.
Box tree moth was discovered in Barnstable County in 2023 causing damage to boxwood. Since the discovery, box tree moth has been found in several towns of the Upper and Mid Cape region where damage to some boxwood has been severe. Boxwoods in the landscape and nursery should be scouted regularly to avoid damage which can happen very quickly.
Box tree moth was first discovered in the United States in New York in 2021 and has since been found in Michigan, Ohio, Massachusetts and most recently in Delaware. Box tree moth is a federally regulated pest and United States Department of Agriculture (USDA) Animal and Plant Health Inspection Services (APHIS) is working with state agricultural authorities to limit the impacts and spread of box tree moth. Box tree moth is native to temperate and subtropical areas in Asia.
The caterpillar has a destructive appetite for boxwood. Caterpillars initially feed on the interior portions of the shrub remaining somewhat unnoticed. Peering into the thick foliage of boxwood may reveal silk, frass, and damaged leaves caused by the feeding caterpillars. As the caterpillars continue to feed damage becomes noticeable in all portions of the shrubs and includes silk, frass, brown leaves and leaves in which only the margin remains. Feeding continues until there is no live foliage left on the plant.
The insect overwinters as a caterpillar and begins feeding on boxwood around forsythia bloom. Caterpillars are green with a black head and black and white longitudinal stripes. Mature caterpillars reach a size of about 1.25 inches. Caterpillars pupate on boxwood or neighboring plants and structures. Adult moths have white wings with a brown border or brown wings with a white fleck and are about 1.5 inches long. Adults lay eggs on the undersides of boxwood leaves. Box tree moth is active all growing season with multiple generations.
Be aware of box tree moth and scout boxwoods frequently for this pest. Infestations in areas not previously found should be reported. When box tree moth is present and untreated; boxwoods are frequently killed. Heavily damaged or infested shrubs should be removed and destroyed by burial or chipping. Infested boxwood may also be placed in large plastic bags and left in sun to kill and prevent escape of the insect. Control options are limited, hand removal of caterpillars is typically not feasible. Insecticides including organophosphates, pyrethroids and spinosyns provide effective treatment. Biological insecticides such as Bacillus thuringensis Bt are effective at controlling younger larvae. Because there are multiple generations repeated treatments are likely necessary.
Where boxwood have been heavily damaged or destroyed consider replacing with other species including inkberry holly (Ilex glabra), Japanese holly (Ilex crenata), bayberry (Myrica pennsylvanica) or plum yew (Cephalotaxus harringtonia).
If you think your boxwoods might be infected or spot signs of trouble, reach out to a Master Gardener through our Hort Clinic webpage at www.capecod.gov/hortclinic. For more information about box tree moth identification and management please check out these resources.
UMass box tree moth fact sheet
Massachusetts Introduced Pest Outreach Box Tree Moth & Reporting
