More counties in Maryland have been put on notice about an invasive moth that can quickly kill one of the most popular plants in the D.C. region. The box tree moth loves, not surprisingly, based on its name, boxwoods, and it’s been spotted in Maryland, Virginia and Delaware.
“The current quarantine notice is quite disturbing. We now have something like six to eight counties here in Maryland that are now quarantined for this rascal,” said the “Bug Guy” Mike Raupp, an entomologist and professor emeritus at the University of Maryland. “That indicates to me it’s spreading very rapidly and we’re getting better at detecting where exactly this very noxious pest is here in Maryland.”
The latest confirmed detections in Maryland’s Eastern Shore counties have led to quarantines being declared in Caroline, Cecil, Kent and Queen Anne’s counties. State agriculture officials said the moth was confirmed in Caroline, Cecil and Queen Anne’s counties, while Kent County was added because of its proximity to the affected areas and Delaware.
This comes after quarantines were put in place for Allegany, Frederick, Garrett and Washington counties. In December, Virginia declared a quarantine for the bug in Clarke and Frederick counties and the city of Winchester.
“This boxwood tree moth can actually be a killer of these boxwoods in a very, very rapid period of time,” Raupp said.
The quarantine zones are meant to slow the spread of the box tree moth by restricting the movement of boxwoods and related plant material out of areas where the pest has been found. The idea is to keep people from accidentally transporting the moth to new areas, even though the insect can also spread on its own by flying.
Raupp has been among those investigating the spread, and he said homeowners need to act quickly if their plants become infested. Boxwoods are common in residential landscaping throughout the region, but they’re also part of iconic landscapes, including Mount Vernon, Dumbarton Oaks and the National Arboretum.
“We’ve found that people who have discovered box tree moth, perhaps a month ago, come back to that plant and see that it’s 100% dead within the span of, let’s say, a month or two months,” Raupp said.
He added people not in quarantine zones should not ignore reports of the moths because they don’t stay within declared zones and they are “great fliers.”
“Don’t be at all surprised if it can jump great distances here,” Raupp said.
He recommends homeowners examine their plants frequently. Raupp said there is no preventive treatment available if your boxwoods aren’t infested, making early detection critical.
He said one telltale sign of the moth’s arrival is a change in your plant’s appearance.
“If you start to see browning in the canopy, dig a little bit deeper, see if you see silk,” Raupp said.
He said to next search the browning boxwood for silk webbing and dark green caterpillars with black and yellow stripes. If you suspect they’ve arrived at your home, take a picture of what you’ve found and report it to Virginia or Maryland’s agriculture departments.
If you’ve caught the infestation early enough, light infestations can often be treated with caterpillar-targeting insecticides, including Bt (Bacillus thuringiensis), while heavily infested plants may need to be removed and destroyed to help prevent the pest from spreading.
If a plant is too far gone, it should be removed, and Maryland officials urge that the remains of the plant to be double-bagged and placed in the trash.
While Raupp said the spread is concerning, he stressed homeowners who catch an infestation early still have a chance to save their plants.
“If you’ve got boxwoods, look at those boxwoods right now. If you have box tree moths, and it hasn’t killed your boxwood, there’s redemption here. You can shut that thing down,” he said.
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