While their leafy cousins parade their fabulous colors this month, the future for crape myrtles across the region — and beyond — is decidedly gray.
The popular trees don’t bloom until summer, but millions of them, from Texas to Delaware, are under siege from a tiny and relentless enemy: the crape myrtle bark scale, a grayish-whitish bug that sucks the sap and nutrients from the tree and excretes honeydew, a sticky mess that attracts flies and bugs and eventually coats everything below the tree in tacky black. If that weren’t enough, the honeydew leads to the growth of sooty mold, a black fungal infection that spreads across the tree’s trunk, branches and leaves, where it can impair photosynthesis.
“It’s disgusting,” said Steve Donnelly, who lives in North Arlington with his wife and three children and had three sickly crape myrtles in his yard. “At our house, initially, I was kind of embarrassed by it. I was like, ‘I’ve got something gross going on with my trees.’ There was goo all over our driveway.”
Donnelly first noticed the problem last summer. “We didn’t even think about these trees before that. They were kind of indestructible and then it was, ‘Oh my gosh, what is happening?’”
That experience is increasingly common across the region as residents realize the trees they counted on for their long summer blooms in beautiful reds, purples and white were suffering silently (and messily). Local arborists say the infestation is widespread and growing and not yet close to peaking.
Matthew Roberts, manager of Ginkgo Gardens, on Capitol Hill, where he has worked for 23 years, said that in 2021 the store received maybe a dozen calls from customers inquiring about their crape myrtles. Last year, “there were hundreds.”
“They’re awesome trees. They’re beautiful, they bloom in the summer, they love D.C.,” Roberts said. “But this is pretty bad”
Roberts said Ginkgo Gardens has stopped selling the trees and bushes until better treatments for the bug are developed.
The crape myrtle bark scale is a relatively new pest from Asia that was first noticed by entomologists from Texas A&M University on crape myrtles in Texas around 2005 and has moved steadily east and north. Forestry experts and scientists have been studying the ravenous bug in hopes of finding the best way to eliminate it or at least limit the damage it can cause. For the most part, the pest doesn’t kill the trees but the associated costs, aesthetic and financial, are shooting up.
“It’s a very significant and widespread problem and can be very expensive to treat,” said Yan Chen, professor of medicinal plant physiology at Louisiana State University, where she has been researching the crape myrtle bark scale since 2013. So far, she said, there have been no magic bullets to treat the infestation. Some pesticides have proved somewhat effective in killing it off, but there are concerns that they can be harmful to bees and other pollinators.
Crape myrtle trees are originally from Asia but have been popular in North America, especially throughout the south, for many decades. Part of their appeal was that they were beautiful, relatively inexpensive and didn’t require a lot of attention. But this infestation has dramatically changed that.
Because the trees are not native to North America, the crape myrtle bark scale doesn’t have a wide range of natural predators to help keep it under control. Lady beetles and lacewings have shown an appetite for feeding on the scale and displayed some efficacy in attacking it, Chen said, but not yet in a way that can halt its spread. At her Louisiana home, Chen surveyed the crape myrtle in her yard and decided it had to go. She replaced it with a native magnolia.
Jacob Hender said he first started noticing the crape myrtle bark scale about two years ago in the Northern Virginia suburb where he lives. Hender had reason to be worried. As the arborist at Smithsonian Gardens, he is responsible for trees on Smithsonian properties along the National Mall and in several other locations. That prime dominion includes about 65 crape myrtle trees.
“These trees are in high impact locations so it’s a pest that has the potential to really change how our sites look very quickly,” he said. “I moved here from Montreal and absolutely love crape myrtle for its ornamental characteristics. It’s one of our only trees that will bloom most of the summer, as well as generally being a good, strong, adaptable, resilient, fairly low maintenance tree … until this pest came along.”
Hender is taking a cautious approach in dealing with the infestation. He said the Smithsonian is focusing on keeping the trees healthy and is hesitant to use any chemicals to address the problem because of the possible negative effect that will have on bees and butterflies and the native predators feeding on the bug.
Entomologists and arborists in the Washington region have scrambled to find the best solution to countering the crape myrtle bark scale, but there are still more questions than answers.
“It’s spreading all over, and it’s just rampaging. It’s incredibly fast,” said Stanton Gill, a specialist in integrated pest management at the University of Maryland Extension who has been working on efforts to contain and treat the crape myrtle bark scale. When a scale egg hatches, Gill said, the insect goes to a crawler stage and seeks out new growth on the tree for food. Once it finds a spot, it settles in and starts extracting fluids from the plant. It then puts out a white waxy layer that covers its body and makes it harder for predators to find and eat it. Small white fluffy material on the stem and trunk of the trees are one of the signs that the tree is infested.
Gill said the pest is transported easily from tree to tree by mostly wind, but also by birds and even squirrels. Nearby trees are particularly vulnerable to the spread. Experts who have studied the spread say that, in towns and metropolitan areas, infestation rates can reach 80 to 100 percent of crape myrtle trees.
For homeowners who prefer a lower-risk approach to treating their trees, Gill recommends spraying the trees with horticultural oil as long as it is done at the correct time. “It won’t wipe them out, but it will suppress them,” he said. “And that’s probably the safest thing for a homeowner to apply.”
In D.C., which has approximately 10,000 crape myrtles on public and private property, the city has temporarily halted planting any new crape myrtles on public land, said Kasey Yturralde, a forest health and community outreach specialist with the District’s Urban Forestry Division.
Yturralde suggests that homeowners who already have the trees avoid using chemicals to treat the infestation and instead try washing the trees. “Crape myrtles are really a showy kind of charismatic tree and this pest impacts it in a way that reduces how good it looks,” Yturralde said. “And so if you use a soapy water and a scrub brush, you can get rid of the sooty mold and some of the scale.”
As more homeowners are discovering their crape myrtles are compromised, they’re turning to tree and garden experts for advice on treatment. Thomas Spencer, the owner of the Heart of Wood Tree Service in Arlington, says calls about crape myrtles with the scale are coming in a lot more often.
“On a hundred that I look at, it’s probably on 75 or 80 percent of them,” said Spencer, who has been working with trees for almost 30 years. Spencer said he has had success battling the crape myrtle bark scale by soaking the soil in a trench at the base of the tree with a commercial insecticide that is absorbed through the roots. He said he wouldn’t recommend that homeowners take out a tree without trying to treat it first, unless it’s dead.
Spencer says crape myrtles are in his top five of favorite trees. “Even in winter when they’re bare, there’s something beautiful to look at in the bark,” he said. But as much as he likes them, Spencer doesn’t think people should plant them this year.
“It’s probably not the best idea right now,” he said.