Box tree moth, lethal to boxwoods, found in one county in Delaware, USDA confirms

Property owners with boxwoods beware! The box tree moth, lethal to the shrubs, has been found in Delaware.

The U.S. Department of Agriculture’s animal and plant health inspection service has confirmed the moth at a private residence in Kent County, according to a July 15 press release from the Delaware Department of Agriculture.

Boxwoods are a popular ornamental evergreen shrub, but box tree moths can damage or kill the plants if left unchecked.

“The aggressive, destructive nature of the caterpillar life stage makes it essential to take quick action as soon as damage is detected because defoliation can occur within 10 days,” said Jessica Munski, plant industries administrator at the Delaware Department of Agriculture.

The state agriculture department is working with the USDA and the University of Delaware Agricultural Extension Service to map the infestation and control the moth at the Kent County residence.

How did the box tree moth get to Delaware?

This confirmed sighting in Kent County may be the first in the state.

“Box tree moth is an unexpected find in Delaware due to the distance from the only known U.S. detections in New York, Michigan, Ohio and Massachusetts, with the original introduction in New York in 2021,” Munski said.

The moth could have flown to Delaware or have been brought into the state.

“This invasive pest is a good flyer, spreading naturally three to six miles a year, but it is suspected that they can fly up to 20 miles,” Munski said.

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Signs of the box tree moth

The box tree moth caterpillars start as lime green with black stripes, white spots, hair and a shiny black head. They can grow to about 1.5 inches and create a large amount of webbing on the plant.

"The caterpillars are ravenous feeders and, in heavy infestations, can completely defoliate host plants," according to the state department of agriculture press release. "After the leaves are gone, they feed on the bark, eventually killing the plant."

The adult box tree moth generally has white wings with a thick brown border. Because it is most active at night, it can be hard to see. The box tree moth is sometimes confused with the melonworm moth.

How to prevent the spread of box tree moths

Munski asked Delawareans to help prevent the spread of box tree moths by monitoring, reporting and controlling infestations.

“If you have boxwoods in your landscape, monitor your shrubs for brown or skeletonized leaves, defoliation and webbing with caterpillars,” she said.

To report sightings, call the Delaware Cooperative Extension Master Gardeners at the garden helpline in New Castle County at 302-831-8862, in Kent County at 302-730-4000 or Sussex County at 302-831-3389.

After a reported sighting, the property owner will be asked to allow state or federal agricultural officials to inspect boxwood plants and possibly place detection traps.

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If boxwood branches are infested, they should be removed. For heavy infestations, cut the boxwood from its base. Your plant should grow back from its roots. All boxwood debris should be double-bagged in plastic and placed in the trash. Property owners should follow the Delaware Cooperative Extension’s pesticide recommendations.

Nursery owners should monitor their boxwoods and implement safeguards to limit pest risk, Munski said. All nursery businesses should report box tree moth detections to the Delaware Department of Agriculture by email at DDA_PlantPests@delaware.gov.

Reach reporter Ben Mace at rmace@gannett.com.

This article originally appeared on Delaware News Journal: Box tree moths, lethal to boxwoods, have been found in Delaware