Crapemyrtles, Lagerstroemia ssp., are a staple of the Southern landscape in the US. The breeding efforts of US National Arboretum, USDA and keen horticulturists brought diversity and interest into the group in the 70’s and 80’s; following the 1950’s expedition that brought the famous Lagertstroemia fauriei ‘Fantasy’ to what is now called the JC Raulston Arboretum. Now, there is a crapemyrtle of every size, shape and color for every niche you might have in your yard. Yet, there is danger in the overutilization of the same species or group of plants: susceptibility to pests and diseases. The time has come for crapemyrtles to meet their match.

Crapemyrtle Bark Scale

Crapemyrtle Bark Scale (CMBS) is a species of Asian scale insect, Acanthococcus lagerstromiae, first found in the United States in Dallas, TX, in 2004. It is suspected that it was here prior to being identified, but it is hard to confirm how it exactly entered the US (most likely on nursery stock imported). Scale insects have piercing/sucking mouthparts, like little, hard, straws, that help the insects suck sugars from plants. CBMS attacks the bark specifically, and can congregate and procreate at alarming rates (two to three generations a year!). The scale insects themselves are small and can blend in with the bark at their early stages and become more obvious as they mature to their egg-laying stage. As infestations get aggressive, the bark can turn black from sooty mold growing on the insects’ sugary excretions. This mold turns the trunks of infested crapemyrtles black and unsightly. The combination of scale insect feeding and sooty mold growth can cause trees to decline and even die.

What to Do If You See It

I have not seen much CMBS in Lee County, as of March 2024, but I have had a few reports come in from residents wondering what is going on with their trees. I have seen bad infestations in Wake county though, especially on already-stressed crapemyrtles in parking lots. If you suspect your crapemyrtles have CMBS, send a picture to your county N.C. Cooperative Extension office for confirmation. There are a lot of insects that can be confused with them, especially early in an infestation.

Once the infestation is confirmed, there are some options for homeowners. Chemical options have been the most effective in the case of heavy infestations. Studies have shown the following to be effective: Imidacloprid (as a drench); Dinotefuran (as a drench or bark spray); Pyriproxyfen (as a bark spray); Buprofezin (as a bark spray); Bifenthrin (variable results, as a bark spray). You should always read the entire label of a chemical before applying it to a plant, and it is recommended that you look for a landscaper who is a licensed pesticide applicator to make chemical applications easier and more effective. Some of these chemicals can also be harmful to non-target organisms, including the natural predators of CMBS and pollinators.

What Can You Do to Prevent It

Healthy, unstressed plants are less susceptible to insect infestations and diseases, so adopt good cultural practices to help your crapemyrtle be as healthy as it can be. Do not apply too much mulch, but apply mulch annually. Do a soil test and apply appropriate fertility as directed by a soil test report. Do not park directly on the roots of the plants. Do not heavily prune crapemyrtles (crape-murder), especially during the wrong season.

Monitoring is always the first step of prevention. Inspect your plants before you buy them, making sure to look for any tell-tale white puffy blobs on the stems. Buy your plants from a reputable dealer, as well. A good nursery inspects plants themselves before they offer them to you! If you have crapemyrtles in your landscape, keep an eye out for CMBS. You can keep your prized plants protected!

Amanda Wilkins is the Horticulture Agent for North Carolina Cooperative Extension in Lee County.