Diagnosing and Treating Crepe Myrtle Bark Scale - Ask Extension
I have a Natchez Crepe Myrtle that has small white fuzzy spots over many of the trunks. The tree was installed 3 years ago, and is about 12 feet tall ...
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Diagnosing and Treating Crepe Myrtle Bark Scale #897320
Asked April 14, 2025, 5:19 PM EDT
I have a Natchez Crepe Myrtle that has small white fuzzy spots over many of the trunks. The tree was installed 3 years ago, and is about 12 feet tall now. Last year was the first year I noticed this problem. I've looked online and the closest pest that seems to match what I'm seeing is bark scale. I think the remnants of the pest are now dead - there is no red when I pinch them, and I don't see anything that's alive.
1. With the photos below, can you tell if this is bark scale?
2. I see online recommendations for bark scale to first brush the bark with soapy water to remove the scale. What kind of soap, and how dilute? Brand recommendations? Could rushing harm the bark?
3. Online recommendations for bark scale also include treating the soil with a systemic insecticide. Do you recommend this as well? What type or brand? Would an application harm Vinca minor at the base of the Crape Myrtle?
Thanks! Bruce
Montgomery County Maryland
Expert Response
You can explore our Crapemyrtle Bark Scale web page for management tips; we agree that seems to be what is pictured on the bark, and it's generally the only cause of white masses on the trunk. There are some insect predators of scale, including this species, which might have helped to reduce the population since it began, and if they are keeping scale numbers low, intervention is not necessary, as the insect rarely causes significant damage to crapemyrtle. Removal with a gentle scrubbing is sufficient without needing to use soap, especially since household soaps and detergents are not formulated for landscape use and might damage plants. If anything is sprayed on the trunk, horticultural oil (instead of insecticidal soap) will help to "smother" and kill the scale, especially if a disturbance manually damages their protective waxy "shell" first. Any brush that won't scrape into the live wood below the bark is fine to use; a soft dish brush, old toothbrush, etc. Scale insects of this type are easy to remove.
Use of a systemic insecticide, addressed in our Introduction to Scale Insects page's management section, is the last resort for suppressing a large scale population; it should not be needed for a population that looks as low as it does in the photos. Systemic insecticides are absorbed by the plant (through roots, trunk injections, or more rarely, foliage) and move into tissues that are not treated directly, which may include blooms. The risk of pollinator exposure is the main reason why this should be the approach of last resort. Some systemic products are in the chemical class called neonicotinoids, and these are legally regulated in Maryland so that only certified pesticide applicators can use them on outdoor plants. Therefore, if it were called for here, you'd need to hire a professional. For root zone applications (like a "soil drench"), yes, any plant sharing that space could potentially absorb the pesticide as well, affecting pollinators or other non-pest insects or wildlife that utilize that plant.
That said, Vinca minor is an invasive species, so we encourage gardeners to remove it and use other groundcover species instead. It also has very little wildlife value, so from that perspective, at least any pollinator impacts of exposure via that route should be low.
Miri
Use of a systemic insecticide, addressed in our Introduction to Scale Insects page's management section, is the last resort for suppressing a large scale population; it should not be needed for a population that looks as low as it does in the photos. Systemic insecticides are absorbed by the plant (through roots, trunk injections, or more rarely, foliage) and move into tissues that are not treated directly, which may include blooms. The risk of pollinator exposure is the main reason why this should be the approach of last resort. Some systemic products are in the chemical class called neonicotinoids, and these are legally regulated in Maryland so that only certified pesticide applicators can use them on outdoor plants. Therefore, if it were called for here, you'd need to hire a professional. For root zone applications (like a "soil drench"), yes, any plant sharing that space could potentially absorb the pesticide as well, affecting pollinators or other non-pest insects or wildlife that utilize that plant.
That said, Vinca minor is an invasive species, so we encourage gardeners to remove it and use other groundcover species instead. It also has very little wildlife value, so from that perspective, at least any pollinator impacts of exposure via that route should be low.
Miri
You're welcome!
