Prevention of bark scale crape myrtles - Ask Extension
Hello! I have read several articles on the black scale infecting crape Myrtles. I understand all about the life cycle of the insects and eggs. We trea...
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Prevention of bark scale crape myrtles #947586
Asked October 23, 2026, 3:51 PM EDT
Hello! I have read several articles on the black scale infecting crape Myrtles. I understand all about the life cycle of the insects and eggs. We treated the trees with a root drench last year. We have a fairly large population of the trees that have been infected again this year, and they will be treated again .
I have read a few articles that suggest having pollinator flowers near the trees would be helpful to keep the insects from going to the trees. I was wondering if you have seen enough data to promote this . I am the landscape chairperson of our HOA and would love to know if you feel that this practice would be helpful! Thank you for all the guidance you have provided me through the past few years. Kathleen
Howard County Maryland
Expert Response
The scale that infests crapemyrtle is white (actually their body is pink, and their waxy body covering is white), not black, which is the sooty mold that grows on the sugary waste liquid they excrete. If you are seeing black sooty mold but no white scale on the bark, the source of the honeydew that is supporting the growth of the sooty mold could be Crapemyrtle Aphids instead, or Spotted Lanternfly. It's also possible a crapemyrtle could have more than one of those insect types present at once (or in succession).
Planting a diversity of flowering plants near pest-prone plants can help naturally-occurring beneficial insects (which prey on those pests) stick around because it provides them with an alternative/supplemental food source. Examples include various wasps, hoverflies, ladybugs, and lacewings. Many beneficial insects which use scale insects as prey for their young also visit flowers as adults.
However, the presence of those flowering plants alone will not have anything to do with the scale insects themselves "going to the trees" in the sense that such plantings can't prevent the scale from colonizing the tree in the first place. Scale insects are largely immobile for most of their lives, only crawling around as newly-hatched juveniles, and even then, they can't go far unless they happen to hitch a ride on wildlife (bird feet, maybe squirrels, etc.) or blow around from one plant to another over shorter distances. After they settle down, they do not move very far, if at all.
As you might already be aware from your reading, using a systemic like a root drench product on crapemyrtle may make the flowers unsafe for pollinators, as the insecticide moves into the plant's tissues from root absorption and remains in the canopy for a period of time. (More research needs to be done to better understand how much pesticide may make it into nectar and pollen, how long it remains there, what concentrations are damaging to pollinators, and how these details may differ from one ingredient to another and the method and timing of its application. With a variety of pollinators that have different life cycles and behaviors, this is difficult to study.)
Several systemic insecticides are regulated in Maryland, which prohibits their use except by certified pesticide applicators in order to reduce their impacts on pollinators. If you decide to continue using such products, make sure they are not in the neonicotinoid group (common active ingredients in that group include imidacloprid and dinotefuran) unless you are hiring someone to purchase and apply them for you. An alternative is to have a professional apply an insect growth regulator (IGR-class) pesticide instead, which targets juvenile scale and prevents them from maturing and breeding.
We mention this because we discourage the use of systemic insecticides once scale insect populations are under control. At that point, it should not be used as a preventative to resist re-infestation, although it sounds like the trees you're asking about aren't at that point yet. Even so, dead scale do not necessarily look any different than live scale, and they also don't fall off of the plant right away, so what looks like a high continuing population might actually be made up of lots of dead scale. If you are having a professional apply the insecticide drench, have them examine the scale closely next time they come by to verify if enough of them are still alive before treating the tree again. Some of the ladybug species whose juveniles eat scale look nearly identical to them, so it also helps to make sure what looks like scale are not a mix of scale and their predators instead.
Overall, though, yes -- having a mix of species of flowering plants (ideally native, so they are as ecosystem-supporting as possible) is always recommended, both as a remedy for pest outbreaks and a preventative measure against future outbreaks. Pests can become resistant to pesticides, especially if the same chemicals are used repeatedly, but they are not becoming resistant to their predators.
Miri
Planting a diversity of flowering plants near pest-prone plants can help naturally-occurring beneficial insects (which prey on those pests) stick around because it provides them with an alternative/supplemental food source. Examples include various wasps, hoverflies, ladybugs, and lacewings. Many beneficial insects which use scale insects as prey for their young also visit flowers as adults.
However, the presence of those flowering plants alone will not have anything to do with the scale insects themselves "going to the trees" in the sense that such plantings can't prevent the scale from colonizing the tree in the first place. Scale insects are largely immobile for most of their lives, only crawling around as newly-hatched juveniles, and even then, they can't go far unless they happen to hitch a ride on wildlife (bird feet, maybe squirrels, etc.) or blow around from one plant to another over shorter distances. After they settle down, they do not move very far, if at all.
As you might already be aware from your reading, using a systemic like a root drench product on crapemyrtle may make the flowers unsafe for pollinators, as the insecticide moves into the plant's tissues from root absorption and remains in the canopy for a period of time. (More research needs to be done to better understand how much pesticide may make it into nectar and pollen, how long it remains there, what concentrations are damaging to pollinators, and how these details may differ from one ingredient to another and the method and timing of its application. With a variety of pollinators that have different life cycles and behaviors, this is difficult to study.)
Several systemic insecticides are regulated in Maryland, which prohibits their use except by certified pesticide applicators in order to reduce their impacts on pollinators. If you decide to continue using such products, make sure they are not in the neonicotinoid group (common active ingredients in that group include imidacloprid and dinotefuran) unless you are hiring someone to purchase and apply them for you. An alternative is to have a professional apply an insect growth regulator (IGR-class) pesticide instead, which targets juvenile scale and prevents them from maturing and breeding.
We mention this because we discourage the use of systemic insecticides once scale insect populations are under control. At that point, it should not be used as a preventative to resist re-infestation, although it sounds like the trees you're asking about aren't at that point yet. Even so, dead scale do not necessarily look any different than live scale, and they also don't fall off of the plant right away, so what looks like a high continuing population might actually be made up of lots of dead scale. If you are having a professional apply the insecticide drench, have them examine the scale closely next time they come by to verify if enough of them are still alive before treating the tree again. Some of the ladybug species whose juveniles eat scale look nearly identical to them, so it also helps to make sure what looks like scale are not a mix of scale and their predators instead.
Overall, though, yes -- having a mix of species of flowering plants (ideally native, so they are as ecosystem-supporting as possible) is always recommended, both as a remedy for pest outbreaks and a preventative measure against future outbreaks. Pests can become resistant to pesticides, especially if the same chemicals are used repeatedly, but they are not becoming resistant to their predators.
Miri
