Crepe Myrtle Bark Scale is a relatively new nonnative scale that was first detected in the U.S. in 2004. Slowly over the last 13 years it has moved northward and is now a serious threat to Crepe Myrtles in Hampton Roads.
Crepe Myrtle Bark Scale (or CMBS) is relatively easy to identify in heavy infestations, but can be difficult to notice in its early stages on Crepe Myrtles. CMBS has only infested Crepe Myrtles in the U.S. so far, but in other parts of the world it has infested other species of plants that we do plant in our area. This is why it is so important to identify and control this insect now before it begins to spread to other plant species in the future.
Heavily infested crepe myrtles will have large almost completely encrusted sections of the bark or twigs covered in white scale. CMBS produce large quantities of honeydew, a sticky substance that gets on the leaves and branches and trunks of the plant and then will usually encourage the development of sooty mold, which will turn dark brown to black over a short amount of time. Smaller infestations are much more difficult to identify, in the nymph stage they are very small and usually pink, gray or brown. The adults create a white covering making them easier to spot. CMBS will mainly eat off the twigs, branches and trunks. Most infestations begin in the smaller branches and twigs at the top of the tree, making larger specimens harder to initially identify until the bark scale moves lower down the tree. One adult can lay up to 300 eggs, making this scale one of the fastest to spread in short time frame.
Treatment of Crepe Myrtle Bark Scale has to be done in stages and the time of the year will dictate what you should treat with. The late fall to early spring time frame is an easier time to identify whether or not you have a problem, as there are no leaves and blooms to hide the infestations.
Treat in late fall to early spring with a high quality oil spray like Fertilome Horticultural Oil Spray. With 80% mineral oil this product works as a suffocant and will kill the scale and the sooty mold. The mold and the scale both need to be coated in the Horticultural Oil in order to be controlled effectively, so spray the branches, twigs and trunks liberally until dripping. Spray nearby Crepe Myrtles as well, as newly or slightly infested plants may be unnoticeable. Repeat applications every 2-3 weeks or as needed, and always read label and instructions before using any control.
The Crepe Myrtle Bark Scale that dies will discolor and fall off the tree over time. The sooty mold will eventually wash off naturally, but can be washed off gently with soap and water on the main trunks and branches where applicable and noticeable.
Treatments will need to be made in the late spring to early fall time to completely control the Crepe Myrtle Bark Scale. In a future blog we will discuss the importance of treating CMBS with Systemic Insecticides which are much stronger during the growing season to really control the scale, and other effective fungicides to control the sooty mold as well. These products listed below will be discussed in detail then:
•Fertilome Systemic Insect Drench
•Hi Yield Systemic Insect Spray
•Fertilome Broad Spectrum Fungicide
•Fertilome F-Stop Fungicide
Crepe Myrtle Bark Scale is a serious insect issue to one of our beloved trees in Hampton Roads and with proper identification and control methods together we can control this issue. Please stay tuned to our blogs for future information and control methods for the Crepe Myrtle Bark Scale. Please visit any of our year round locations to talk with a Garden Pharmacy employee to help identify and control any issues you may be having in your garden or landscape.