The box tree moth, Cydalima perspectalis, is a non-native moth that has recently been found in a nursery in South Carolina. Native to eastern Asia, the box tree moth has been present in Canada since November 2018. From August 2020 through May 2021, infested boxwood (Buxus sp.) plants were inadvertently shipped from a grower in Canada to several nurseries in the U.S.; a retail nursery in South Carolina received infested plants in May 2021. As of June 1, 2021, the South Carolina detection is being treated as a regulatory incident, and this pest is not thought to have escaped into the landscape. Clemson’s Department of Plant Industry is investigating plant shipments into and out of the South Carolina nursery to determine if infested material may have been inadvertently sold to homeowners and will be monitoring in and around the nursery to ensure this moth has not escaped. If populations are found, a survey and eradication effort will follow.
Adult moths have white wings with a brown border but occasionally may be the “dark form” that has brown wings. Both color forms have small white comma-shaped spots on the forewing.
Eggs are pale yellow, laid in small groups, and overlap like shingles. Caterpillars primarily feed on boxwood but may also feed on Ilex and Euonymus species. Further, there is some evidence that the caterpillars will feed on Acer sp., Fraxinus sp., Rubus sp., Ligustrum sinense, Eriobotrya japonica, Murraya paniculata, and Smilax excelsa when boxwoods are not readily available. Feeding by young larvae causes leaves to turn brown, but older larvae will consume the entire leaf except for the midvein. While several insects can be pests on boxwoods, the box tree moth is potentially the most impactful as feeding by the caterpillars can cause severe damage and even death to infested plants. Larvae may also produce copious amounts of webbing on infested plants. Caterpillars don’t make distinct cocoons; rather, pupae are found among the webbing and damaged leaves. Several generations may occur in a single year.
There are no official management recommendations for box tree moth because this is the first time it has been found in the U.S. Small caterpillars can be knocked off plants with a strong stream of water, and several readily available horticultural oils and insecticides are likely to provide effective control. Several natural enemies are likely to help control moth populations.
Homeowners are asked to report any potential occurrence of box tree moth to Clemson’s Department of Plant Industry by calling 864-646-2140 or emailing firstname.lastname@example.org. It is extremely important to find any infestations early so they can be quickly eradicated before establishing in the environment.
Authors: David Coyle (Department of Forestry and Environmental Conservation, Clemson University), Twitter and Instagram: @drdavecoyle; Steven Long, Department of Plant Industry, Clemson University