The box tree moth (Cydalima perspectalis) sometimes called boxwood moth, is a relatively new pest that has been causing significant damage to boxwood plants across Europe and North America. This article will provide an overview of the box tree moth, its life cycle, and how to protect your garden from this destructive pest.
The box tree moth is a species of moth that originates from East Asia. It was first reported in Europe in 2007 and has since spread rapidly across the continent. The moth has also been found in North America, where it is causing significant damage to boxwood plants.
The adult box tree moth is a striking creature, with white wings that have a dark brown border. The larvae, however, are the real problem. They are voracious eaters and can quickly defoliate a boxwood plant, leaving it bare and susceptible to disease.
First detected in the Greater Toronto Area in 2019, this pest has spread to surrounding areas. Active populations can be found on our beloved boxwoods in a large are that spans from Oshawa to Cookstown to Kitchener and down in Niagara. There are two generations of box tree moth in southern Ontario.
When temperatures become warm in late-April/May, usually >15C, overwintered early-instar larvae will venture out of their winter cocoon to feed on the surface tissue of the leaves. Larvae are green with black striping and black heads. Note how young larvae feed on just the leaf surface, as they have small chewing mouthparts. Chewed leaf tissue becomes desiccated and will turn light brown after a few weeks. Also note the webbing and excrement amongst the chewed foliage and twigs. A second generation of larvae can be found hatching in July and August.
As larvae mature, they shed their skins (molt) in order to increase their body size. With each molt, larvae acquire a larger set of mandibles and will eventually consume entire portions of leaves, quite often leaving just the margin of the leaf behind. Note the webbing and excrement amongst the chewed foliage and twigs.
Box tree moths are small insects with a wingspan of about 4 cm. The adults have white wings with a distinctive brown border and brownish-black markings. They have a characteristic silvery sheen when they fly. The larvae, or caterpillars, of the box tree moth are bright green with black heads and yellowish stripes along their bodies. They can grow up to 4 cm in length. The larvae are voracious eaters and can cause significant damage to boxwood plants by defoliating the leaves. It is important to identify and manage box tree moth infestations promptly to prevent widespread damage to boxwood plants.
Box tree moth larvae can be effectively managed with the biological insecticide Bt, a naturally occurring bacterium found in the soil that is also registered for organic food production. Bt is the same biological insecticide that is applied by air over the City of Toronto to combat spongy moth larvae during epidemic years. Bt works best when sprayed thoroughly on foliage with adequate pressure to penetrate the dense canopy and webby larval colonies. When Bt is sprayed on the foliage, leaf-munching box tree moth larvae consume it. Within an hour of ingesting the B.t. residue, the larvae stop feeding and then expire within 48-72 hours. We find that 2 or 3 applications of Bt per season can be very effective at reducing box tree moth populations. ing, invasive insect species. Contact Beautiful Trees today for all your tree and shrub pest management needs. Don’t let box tree moth damage ruin your green space, trust the professional arborists with the knowledge and experience you need.
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