CMBS control - Ask Extension
Unfortunately, I deleted all good photos from last year but I am certain CMBS is the issue complete with ants climbing on the tree and all foliage und...
Knowledgebase
CMBS control #932494
Asked May 21, 2026, 12:08 PM EDT
Unfortunately, I deleted all good photos from last year but I am certain CMBS is the issue complete with ants climbing on the tree and all foliage under the tree turned black from honeydew.
I had a very heavy infestation with most upper limbs and branches completely white.
I sprayed several times with neem oil and agricultural oil: No help
I sprayed with SEVEN, no help.
After the trees lost leaves in the fall, I washed all visible scale from the tree with a high pressure water hose. In many cases the bark came off as well leaving a reddish trunk and whitish branches. The white branches appear to be colorization only, not biological. It appears that the scale has been successfully washed off.
So, I'm waiting for return of the critters as I am certain that the washdown was probably not sufficient. Since oils and insecticides had little impact last year, do you have any other silver bullets? I don't want to lose another tree just 12 feet away.
Thank you!
Jonas Gottlieb
Baltimore County Maryland
Expert Response
It would help us to see photos of the current state of the infestation (or lack thereof) and the tree overall. The only other approaches using pesticide may require the hiring of a certified pesticide applicator, due to either practical application issues (not having the right equipment or easy access to certain insecticides) or due to legal restrictions (some systemic insecticides are not legal for unlicensed persons to buy and apply). (Many arborists and landscape companies have people with this license.) Pesticide options beyond horticultural oil (neem oil is one kind of horticultural oil) is an insect growth regulator (IGR), which prevents the insects from maturing and breeding, or a systemic, which is absorbed into the plant's tissues and kills the scale as they feed. Systemic applications for this situation are usually applied as a root drench or injection into the trunk(s). How long any of those treatments last greatly depend on the chemical used and how it's applied, but more than one application per year is likely needed. Neither a systemic nor an IGR is useful before the pests are present (or return), and since IGR-class chemicals may need to be applied directly to the pest (as opposed to the pest ingesting them as they feed), this too may need to wait until a scale population has build up a bit again.
You may find that you don't need to break out the heavier-duty insecticides, though, since several beneficial predators eat Crapemyrtle Bark Scale. On the linked page, you can see a pictured example of a common ladybug larva (which looks nearly identical to the scale until you look closely) that we've found eating enough scale that we can't even do control experiments on the trial plants one of our researchers is working on. They may be effective enough on their own to keep another scale outbreak at bay, as low numbers of this type of scale do not cause serious damage to crapemyrtles. However, using broad-spectrum topical pesticide sprays like Sevin can kill those beneficials, so we do not recommend using it any more.
Dead scale insects do not often fall off of their host plant right away. Therefore, an infestation that looks heavy may actually be comprised of mostly dead scale, some that succumbed to pesticide or which were eaten by predators like that ladybug larva. Scrubbing can certainly remove them faster (both live and dead scale), but be cautious about cutting into the bark, since crapemyrtle bark is very thin, and open wounds could be entry points for wood decay.
White insects on the bark are almost certainly Crapemyrtle Bark Scale (and/or the ladybug larvae, so check closely), but ants can also be present with Crapemyrtle Aphids, another common (but not very damaging) pest of crapemyrtles. Depending on the insecticide used, some applications made for the scale may also simultaneously suppress the aphids.
Miri
You may find that you don't need to break out the heavier-duty insecticides, though, since several beneficial predators eat Crapemyrtle Bark Scale. On the linked page, you can see a pictured example of a common ladybug larva (which looks nearly identical to the scale until you look closely) that we've found eating enough scale that we can't even do control experiments on the trial plants one of our researchers is working on. They may be effective enough on their own to keep another scale outbreak at bay, as low numbers of this type of scale do not cause serious damage to crapemyrtles. However, using broad-spectrum topical pesticide sprays like Sevin can kill those beneficials, so we do not recommend using it any more.
Dead scale insects do not often fall off of their host plant right away. Therefore, an infestation that looks heavy may actually be comprised of mostly dead scale, some that succumbed to pesticide or which were eaten by predators like that ladybug larva. Scrubbing can certainly remove them faster (both live and dead scale), but be cautious about cutting into the bark, since crapemyrtle bark is very thin, and open wounds could be entry points for wood decay.
White insects on the bark are almost certainly Crapemyrtle Bark Scale (and/or the ladybug larvae, so check closely), but ants can also be present with Crapemyrtle Aphids, another common (but not very damaging) pest of crapemyrtles. Depending on the insecticide used, some applications made for the scale may also simultaneously suppress the aphids.
Miri
