Bark scale is infesting D.C.-area crape myrtle bushes. A remedy is elusive
Whereas their leafy cousins parade their fabulous colours this month, the long run for crape myrtles throughout the area — and past — is decidedly grey.
The favored bushes don’t bloom till summer time, however thousands and thousands of them, from Texas to Delaware, are beneath siege from a tiny and relentless enemy: the crape myrtle bark scale, a grayish-whitish bug that sucks the sap and vitamins from the tree and excretes honeydew, a sticky mess that draws flies and bugs and finally coats all the things under the tree in cheesy black. If that weren’t sufficient, the honeydew results in the expansion of sooty mildew, a black fungal an infection that spreads throughout the tree’s trunk, branches and leaves, the place it might impair photosynthesis.
“It’s disgusting,” mentioned Steve Donnelly, who lives in North Arlington together with his spouse and three youngsters and had three sickly crape myrtles in his yard. “At our home, initially, I used to be type of embarrassed by it. I used to be like, ‘I’ve received one thing gross occurring with my bushes.’ There was goo throughout our driveway.”
Donnelly first observed the issue final summer time. “We didn’t even take into consideration these bushes earlier than that. They had been type of indestructible after which it was, ‘Oh my gosh, what is occurring?’”
That have is more and more widespread throughout the area as residents notice the bushes they counted on for his or her lengthy summer time blooms in stunning reds, purples and white had been struggling silently (and messily). Native arborists say the infestation is widespread and rising and never but near peaking.
Matthew Roberts, supervisor of Ginkgo Gardens, on Capitol Hill, the place he has labored for 23 years, mentioned that in 2021 the shop acquired perhaps a dozen calls from clients inquiring about their crape myrtles. Final yr, “there have been lots of.”
“They’re superior bushes. They’re stunning, they bloom in the summertime, they love D.C.,” Roberts mentioned. “However that is fairly dangerous”
Roberts mentioned Ginkgo Gardens has stopped promoting the bushes and bushes till higher therapies for the bug are developed.
The crape myrtle bark scale is a comparatively new pest from Asia that was first observed by entomologists from Texas A&M College on crape myrtles in Texas round 2005 and has moved steadily east and north. Forestry specialists and scientists have been finding out the ravenous bug in hopes of discovering one of the simplest ways to get rid of it or no less than restrict the harm it might trigger. For probably the most half, the pest doesn’t kill the bushes however the related prices, aesthetic and monetary, are taking pictures up.
“It’s a really vital and widespread downside and could be very costly to deal with,” mentioned Yan Chen, professor of medicinal plant physiology at Louisiana State College, the place she has been researching the crape myrtle bark scale since 2013. To date, she mentioned, there have been no magic bullets to deal with the infestation. Some pesticides have proved considerably efficient in killing it off, however there are issues that they are often dangerous to bees and different pollinators.
Crape myrtle bushes are initially from Asia however have been fashionable in North America, particularly all through the south, for a lot of many years. A part of their enchantment was that they had been stunning, comparatively cheap and didn’t require lots of consideration. However this infestation has dramatically modified that.
As a result of the bushes aren’t native to North America, the crape myrtle bark scale doesn’t have a variety of pure predators to assist preserve it beneath management. Girl beetles and lacewings have proven an urge for food for feeding on the dimensions and displayed some efficacy in attacking it, Chen mentioned, however not but in a manner that may halt its unfold. At her Louisiana residence, Chen surveyed the crape myrtle in her yard and determined it needed to go. She changed it with a local magnolia.
Jacob Hender mentioned he first began noticing the crape myrtle bark scale about two years in the past within the Northern Virginia suburb the place he lives. Hender had purpose to be apprehensive. Because the arborist at Smithsonian Gardens, he’s liable for bushes on Smithsonian properties alongside the Nationwide Mall and in a number of different areas. That prime dominion consists of about 65 crape myrtle bushes.
“These bushes are in excessive influence areas so it’s a pest that has the potential to essentially change how our websites look in a short time,” he mentioned. “I moved right here from Montreal and completely love crape myrtle for its decorative traits. It’s one in all our solely bushes that may bloom many of the summer time, in addition to typically being a great, robust, adaptable, resilient, pretty low upkeep tree … till this pest got here alongside.”
Hender is taking a cautious method in coping with the infestation. He mentioned the Smithsonian is specializing in preserving the bushes wholesome and is hesitant to make use of any chemical substances to deal with the issue due to the doable unfavourable impact that may have on bees and butterflies and the native predators feeding on the bug.
Entomologists and arborists within the Washington area have scrambled to search out the very best answer to countering the crape myrtle bark scale, however there are nonetheless extra questions than solutions.
“It’s spreading throughout, and it’s simply rampaging. It’s extremely quick,” mentioned Stanton Gill, a specialist in built-in pest administration on the College of Maryland Extension who has been engaged on efforts to include and deal with the crape myrtle bark scale. When a scale egg hatches, Gill mentioned, the insect goes to a crawler stage and seeks out new development on the tree for meals. As soon as it finds a spot, it settles in and begins extracting fluids from the plant. It then places out a white waxy layer that covers its physique and makes it tougher for predators to search out and eat it. Small white fluffy materials on the stem and trunk of the bushes are one of many indicators that the tree is infested.
Gill mentioned the pest is transported simply from tree to tree by principally wind, but in addition by birds and even squirrels. Close by bushes are significantly susceptible to the unfold. Specialists who’ve studied the unfold say that, in cities and metropolitan areas, infestation charges can attain 80 to 100% of crape myrtle bushes.
For householders preferring a lower-risk method to treating their bushes, Gill recommends spraying the bushes with horticultural oil so long as it’s achieved on the appropriate time. “It gained’t wipe them out, however it’s going to suppress them,” he mentioned. “And that’s in all probability the most secure factor for a home-owner to use.”
In D.C., which has roughly 10,000 crape myrtles on private and non-private property, town has quickly halted planting any new crape myrtles on public land, mentioned Kasey Yturralde, a forest well being and neighborhood outreach specialist with the District’s City Forestry Division.
Yturralde means that householders who have already got the bushes keep away from utilizing chemical substances to deal with the infestation and as an alternative attempt washing the bushes. “Crape myrtles are actually a showy type of charismatic tree and this pest impacts it in a manner that reduces how good it seems to be,” Yturralde mentioned. “And so in case you use a soapy water and a scrub brush, you’ll be able to eliminate the sooty mildew and a few of the scale.”
As extra householders are discovering their crape myrtles are compromised, they’re turning to tree and backyard specialists for recommendation on remedy. Thomas Spencer, the proprietor of the Coronary heart of Wooden Tree Service in Arlington, says calls about crape myrtles with the dimensions are coming in much more usually.
“On 100 that I have a look at, it’s in all probability on 75 or 80 % of them,” mentioned Spencer, who has been working with bushes for nearly 30 years. Spencer mentioned he has had success battling the crape myrtle bark scale by soaking the soil in a trench on the base of the tree with a business insecticide that’s absorbed via the roots. He mentioned he wouldn’t advocate that householders take out a tree with out making an attempt to deal with it first, except it’s lifeless.
Spencer says crape myrtles are in his high 5 of favourite bushes. “Even in winter after they’re naked, there’s one thing stunning to take a look at within the bark,” he mentioned. However as a lot as he likes them, Spencer doesn’t suppose folks ought to plant them this yr.
“It’s in all probability not the very best thought proper now,” he mentioned.