Boxwoods (Buxus spp.) are some of the most common plants found in Ohio landscapes and they remain a mainstay of our nursery industry. Box Tree Moth (Cydalima perspectalis) caterpillars defoliate boxwoods and will strip bark once they run out of leaves to eat. The moth has multiple generations per year, depending on geographical locations, and sustained high populations are capable of killing boxwoods.
The caterpillars have also been observed feeding on the leaves of burning bush euonymous (Euonymus alatus), Japanese euonymus (E. japonicus), purple holly (Ilex purpurea), and orange jasmine (Murraya paniculate). However, these are considered secondary hosts with impacts on plant health being far less than those observed on boxwoods.
Coming to America
The box tree moth is native to East Asia. It was discovered in southern Germany and the Netherlands in 2007 and is now found in 30 European countries. Its rapid spread in Europe was fueled by the wide distribution of two species of native boxwoods that served as natural bridges for the moths to spread between urban areas. Also, DNA analysis has shown that the moths were introduced multiple times from Asia into Europe.
The moth was found in Canada in 2018 infesting boxwoods in a home landscape in an urban neighborhood in Toronto, Ontario. In 2021, the moth was confirmed in a St. Catharines, Ontario, nursery.
The USDA Animal and Plant Health Inspection Service (APHIS) issued a press release today confirming that the box tree moth has been found in the United States.
According to the press release: “Between August 2020 and April 2021, a nursery in St. Catharines, Ontario shipped boxwood (Buxus species) that may have been infested with box tree moth to locations in six states—25 retail facilities in Connecticut, Massachusetts, Michigan, New York, Ohio, and South Carolina—and a distribution center in Tennessee. At this time, the pest has been identified in three facilities in Michigan, one in Connecticut, and one in South Carolina, and APHIS is working with state plant regulatory officials to determine whether other facilities may be impacted.”
The Ohio Department of Agriculture (ODA) has intercepted and destroyed the vast majority of plants shipped into our state and are rapidly closing in on eradication. They have also deployed pheromone traps to monitor for male moths and will react quickly to eradicate discovered populations.
Communications between Canadian regulatory agencies, the USDA APHIS, and state-based agencies such as our ODA may have allowed us to dodge a bullet; however, it’s still important for us all to remain vigilant. Thankfully, the box tree moth’s lifestyle is unique among boxwood pests.
There are no native defoliating caterpillars or sawfly larvae specific to boxwoods in Ohio and only a small number of caterpillars that may occasionally nip a few leaves. Heavy defoliation by a caterpillar would point towards the box tree moth.
Of course, it’s important to eliminate known boxwood pests and diseases including boxwood leafminer and boxwood blight. These images may be helpful.