Last week, I was out for a walk and came to a quick stop when I noticed a crape myrtle with black leaves and trunks. At closer inspection, I found hundreds of scaly, white things all along the trunks and branches. These scale insects are Crape Myrtle Bark Scale.
Late summer seems to be the time that damage from CMBS really stands out. They have had all spring and summer to reproduce and feed on the host plants, and now the honeydew and sooty mold are evident from a distance.
CMBS is a small, white, sap-feeding insect that lives on the bark of crape myrtle trees. The adult females look like tiny pieces of popcorn attached near pruning wounds or in the branch crotches. They are usually 2mm in length. If you squish the scale, it has bright pink insides. CMBS does not kill the tree, but it can cause reduced flowering and the scale secretes a honeydew that causes sooty mold.
Crape Myrtle Bark Scale has found new hosts in Texas. Boxwood, pomegranate, cleyera, hackberry, persimmon, soybean, figs, Ligustrum, apple, and beautyberry have all been confirmed as hosts for Crape Myrtle Bark Scale. The pest continues to spread in Texas, and it can be an expensive pest to commercial landscapers, nurseries, and homeowners.
The good news about CMBS is that we have several treatment options! If you just spot a few, you can squish them. You can also use soapy water and a brush or a power washer to remove infestations from your plants. Washing your tree can also help remove sooty mold. Ladybeetles are a natural enemy of CMBS, if you prefer to use a biological control option. Preliminary research from the Dallas AgriLife Research Center suggests that ladybeetles can provide 75% suppression of scale insects in the landscape.
If you have a heavy infestation, AgriLife Specialists recommend a systemic insecticide application to be made in March – May. Chemical controls need to be applied early to prevent the formation of new adults. Once adults (the white spots), they are challenging to remove because they do not feed on the tree and are covered with a waxy later for protection. Imidacloprid and dinotefuran are two systemic insecticides that you can apply as a soil drench. Both chemicals have been shown to be highly effective at managing scale populations when they are applied in early spring (March-May).
Texas A&M AgriLife Extension continues to monitor the spread of this economically important pest, as well as research control options. If you have found CMBS in your landscape, you can report it to the research team at https://stopcmbs.com/report/.
For more information about CMBS or other lawn and garden questions, contact Kate Whitney, Horticulture Extension Agent, at 512-943-3300.
