Crape myrtles are beautiful trees that showcase their beauty in candy colours every summer. Unfortunately, the trees that brighten our hottest months are under attack by a foreign invader. Have you seen a strange white cottony growth on the trunks of beautiful crape myrtles? If you look closely, you’ll notice that it is alive! Meet the crape myrtle scale. It destroys the bark of crape myrtles causing a lot of damage in a small amount of time. It’s also accompanied by heavy layer of black sooty mold on the branches. Crape myrtle Bark Scale is a small insect that appears as a white or grey felt-like encrustation. They may be found anywhere on crape myrtles, and often appear near pruning sites and branch crotches of more mature wood.
Generally, the first sign of crape myrtle bark scale is the black sooty mold on the tree bark. The scale excretes honeydew that coats leaves and limbs, resulting in a sticky coating from the excess sugars excreted from the insects’ feeding. Sooty mold grows on the honeydew. This results in a black coating that appears on the bark of the branches and trunks of crape myrtles. Additionally, white cases are visible, and they enclose the adult female scales. The tiny pest was first identified in the Dallas area about 10 years ago and is believed to have entered the country from Asia. Since then, it’s been slowly making its way across the South, arriving in Shreveport-Bossier City about four years ago. Infestations have also been verified in Houma, Oklahoma, Arkansas, Tennessee and Georgia.
It was reported that out of the 430 Crape Myrtle trees on the campus of Louisiana State University in Shreveport, 60 percent of these iconic trees are affected by the Bark Scale. Scales can be found on various parts of the tree as oval, white, crusted clusters of insects with a powdery waxy appearance. The insects don’t seem to be fatal to trees, but they are unsightly and weaken trees so they aren’t likely to bloom profusely. The bark scale has been known to stress the tree and make it less healthy. The scale gives these beautiful trees a burnt appearance which makes them look unsightly and weak.
The below article would explain the situation better.
“Pest” Disfiguring Crape Myrtles in McKinney
By Catherine Ross
May 5, 2014
A pest is leaving its mark on one of North Texas’ favorite flowering plants.
In McKinney, the crape myrtle has become an emblem of the city where this year they received congressional recognition as “America’s Crape Myrtle City.”
The plant is native to Southeast Asia but has been cultivated throughout warm climates, including Texas.
“We’re really proud of crape myrtles and our association with crape myrtles,” said Neil Sperry, renowned Texas horticulturalist and a board member of the Crape Myrtle Trails of McKinney.
Sperry said his organization, over the last decade, has helped plant 20,000 crape myrtles within city limits.
However, over the same time, something “unsightly” has also taken root in the plants.
“It’s moved up through Collin County over the years and become a serious problem,” said Dr. Greg Church, the Collin County AgriLife Extension Agent through Texas A&M. “[It's] two different organisms, making the plant look bad.”
Church said little insects feed off the plants, in turn, excreting honey dew. That substance attracts a “sooty mold fungus,” which transforms the bark.
The pest is called “crape myrtle bark scale” and, according to experts, is threatening both the aesthetics and the utility of the plant.
“During drought conditions, which we’ve experienced the past three years, it can weaken the plant,” Church said.
There have been no plant deaths attributed to the bark scale, but the condition is spreading across the American South, specifically in the past two years, though it’s been present in North Texas since 2004.
Church said if the plant is manageably small enough, the bark scale can be cleaned off with water and some light soap.
However, Sperry recommends placing insecticide at the roots of larger crape myrtle and clusters.
Crape myrtle is one of the few trees that bear colourful flower displays through much of the summer, come in a variety of stunning colours, is easy to grow, and until now has been relatively pest free. Unfortunately, the pest-free reputation is changing with the advent of the bark scale. With their extremely high reproduction potential, there could be at least two generations of the bark scale in one year. This can be a difficult pest to control and it may take multiple years of treatment. So, how do we fight this pest? Keep reading!
C Tech Corporation provides a unique non-toxic product called Termirepel™ which is an environmentally safe insect repellent. It can repel more than 500 species of insects on account of it being a broad spectrum anti-insect repellent. The most striking feature of Termirepel™ is that it neither kills the target species, nor the non-target species. It will simply keep the insects away from the application. Termirepel™ in lacquer form can be coated on the trunks of our beloved crape myrtles, which would effectively keep the bark scale from infesting and causing the trees any damage!