Invasive Moth Could Prove Costly To MD Homeowners: How To Spot It

A pesky moth has prompted state officials to invoke a box tree moth quarantine in Maryland that now includes nine counties.

In March 2026, a quarantine order was put in place for Allegany, Frederick, Garrett, and Washington counties due to their proximity to states with established box tree moth populations and a confirmed positive case recorded in Washington County.

In August 2026, the box tree moth quarantine was expanded into Caroline, Cecil, Kent and Queen Anne’s counties. At that time, the box tree moth had not yet been spotted in Kent County, but its presence has now been confirmed.

In September 2026, the quarantine was expanded to include Harford County.

The box tree moth is a federally regulated insect that is native to East Asia. It was first identified in the United States in 2021 after being confirmed in New York and has spread to Delaware, Massachusetts, Michigan, New Jersey, Ohio, Pennsylvania, Virginia and West Virginia.

The insect poses a threat to the region’s nursery industries as it feeds primarily on boxwoods, an ornamental shrub used in landscaping. Early infestations are often hard to detect because the molting caterpillars generally feed on the undersides of leaves, and multiple generations can live on the shrub, as the box tree moth has a short development time.

This intensive feeding limits shrub recovery, and once it is fully defoliated, or cleared of leaves, the caterpillars will eat the bark, cutting off its supply of water and nutrients, a process called girdling. This will fully kill the shrub.

In the U.S., box tree moth caterpillars have been found feeding only on boxwoods so far, according to the MDA. Applying preventative pesticides to boxwoods will not effectively control the box tree month.

Affected Businesses

The box tree moth spreads through the movement of infested boxwood nursery stock and adult moth flight. One study in Europe suggested adult moths can sustain flights of over 20 miles. Be sure to check for signs of box tree moth on any boxwoods you purchase and on any existing boxwoods in your landscape. If you believe you have seen box tree moth or its damage, send reports and photos to Ask Extension.

Businesses that grow and ship boxwoods must have a certificate of inspection and complete a compliance agreement with the Maryland Department of Agriculture to move regulated items into or out of the quarantine zone.

Nursery owners and residents within the quarantine zone are encouraged to monitor their boxwoods and implement safeguards to limit pest risk. Early detection is key to preventing significant damage and loss, as well as the spread of the box tree moth, according to the MDA.

What To Look For

Caterpillars are lime green with thin black stripes and can be difficult to spot when small. Full-grown caterpillars can grow up to 1.5 inches. Adult box tree moths have white wings with a brown border. They are generally active at night and may be hard to detect.

Injury begins with young caterpillars that chew on the undersides of leaves, removing one layer of leaf tissue. Older caterpillars can defoliate leaves either by consuming the entire leaf or by just leaving behind the leaf edges and/or leaf midvein, according to the University of Maryland Extension.

Extensive feeding can result in "see-through" brown boxwoods and potentially plant death. Box tree moth caterpillars have also been observed chewing boxwood bark, leading to girdling (a circular groove around a woody stem that cuts off the movement of nutrients) and potentially plant death.

What To Do

Residents can take the following steps:

• Monitor boxwoods in your landscape, looking for signs of defoliation, stripped back and/or caterpillar webs.
• If you suspect the presence of box tree moths, report it to MDA through this online form
• Allow state and/or federal agricultural officials to inspect your boxwood plants to place detection traps.
• Prune out localized infestations and cut the tree down to its base, or completely remove the infected shrubs.
• Any infested shrub material should be double-bagged and placed in the trash so the moths do not escape.

Other steps include:

• Confirm the identification of box tree moth by submitting photos through Ask Extension or via the Maryland Department of Agriculture's online reporting form before applying controls. Unnecessary treatments can harm beneficial insects and cause secondary pest outbreaks. Do not apply preventative insecticide applications.

• With small infestations, hand-pick or prune caterpillars off plants and place them in a bucket of soapy water.
• For large infestations, use a horticultural oil or insecticidal soap spray on small caterpillars, following all label instructions. Please note: adequate coverage is needed for effective control, aiming for the underside of leaves (where the young caterpillars feed). A professional pest control company can be contacted for further guidance.
• Heavily infested plants may need to be removed and destroyed to prevent further spread.
• Any infested shrub or plant materials should be double bagged and place in the trash to prevent box tree moth life stages from escaping/spreading.
• Further management options are currently being researched.