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Your crepe myrtles look black because of a common fungal issue called sooty mold.
This black coating isn’t a disease attacking the tree itself, but rather a symptom of a bigger problem hiding underneath.
When you see that black, powdery, or sticky film on the leaves and branches, it’s usually sooty mold growing on honeydew.
Honeydew is a sugary, sticky substance excreted by sap-sucking pests like aphids, scale, and whiteflies.
So, if you’ve been wondering “why do my crepe myrtles look black,” the short answer is that you likely have a pest infestation feeding on your tree.
In this post, we’ll dig deep into why your crepe myrtles look black, how to identify the culprit, and the best ways to clean it up for good.
Let’s get to the bottom of this black mess together.
Why Do My Crepe Myrtles Look Black: The Real Culprit
Your crepe myrtles look black because of the combination of sap-feeding insects and the sooty mold that follows their activity.
First, the insects puncture the leaves and stems to drink the sap.
Second, they excrete the excess sugar as honeydew, which lands on the foliage.
Third, that honeydew becomes a perfect breeding ground for sooty mold spores floating in the air.
The mold doesn’t invade the plant tissue, it just grows on the surface, giving your crepe myrtles that unmistakable black appearance.
1. Aphids Are the Most Common Reason Your Crepe Myrtles Look Black
Aphids are tiny, soft-bodied insects that love to feast on new growth.
They cluster on the undersides of leaves and along tender stems, sucking out the plant’s juices.
As they feed, they produce copious amounts of honeydew.
That’s why you often notice a sticky residue on your car or patio furniture under the tree, and then the black mold follows.
Aphids reproduce quickly, so a small population can become a full-blown infestation in just a couple of weeks.
If your crepe myrtles look black and you see clusters of tiny green, yellow, or black bugs, aphids are your answer.
2. Crape Myrtle Bark Scale Is Another Reason Your Crepe Myrtles Look Black
Crape myrtle bark scale is a relatively new pest that also causes black sooty mold.
These scale insects look like small, white or gray felt-like spots on the bark.
They don’t just feed on the leaves, they attack the bark itself.
As they suck sap from the branches, they excrete honeydew that coats everything below.
You’ll often see blackened trunks and branches, not just leaves.
If you notice white, crusty patches on the bark along with the black, then crape myrtle bark scale is likely why your crepe myrtles look black.
3. Whiteflies and Other Sap-Suckers Can Make Your Crepe Myrtles Look Black
Whiteflies are another sap-sucking pest that contributes to the black mess.
They look like tiny white moths that flutter up in a cloud when you shake a branch.
Their nymphs stay on the leaf undersides and produce honeydew just like aphids do.
Lace bugs, although they don’t produce as much honeydew, can also stress the tree and create conditions for mold.
The key here is that any piercing-sucking insect can start the chain reaction that leads to your crepe myrtles look black.
4. Sooty Mold Itself Is What Makes the Leaves Look Black
Sooty mold is the actual black substance you see.
It’s a fungus that doesn’t infect the plant but grows on the honeydew surface.
The mold appears as a thin, black, crusty layer that can be rubbed off with your finger.
It can cover leaves, stems, and even the trunk, blocking sunlight from reaching the leaf surface.
While it doesn’t kill the tree directly, it weakens photosynthesis, which can lead to yellowing leaves and reduced vigor.
So when you ask “why do my crepe myrtles look black,” the sooty mold is the cosmetic culprit, but the pests are the real root cause.
How to Fix It When Your Crepe Myrtles Look Black
Once you know why your crepe myrtles look black, you can take action to clean them up.
The goal is twofold: remove the sooty mold and get rid of the pests producing the honeydew.
Here’s the best way to tackle both problems.
1. Wash the Black Off Your Crepe Myrtles
Start with a strong blast of water from your garden hose.
Aim at the leaves, especially the undersides where pests hide.
The water pressure will knock off adult aphids and whiteflies, and it will also wash away a lot of the honeydew and loose sooty mold.
For a more thorough cleaning, mix a few drops of mild dish soap in a spray bottle with water.
Spray the affected areas and then rinse with plain water.
This won’t completely eliminate the mold but it will make the tree look much better almost immediately.
2. Apply Horticultural Oil or Insecticidal Soap
To control the pests that cause the black, apply a horticultural oil or insecticidal soap.
These products suffocate the soft-bodied insects without harming beneficial predators when used correctly.
Spray thoroughly, covering all leaf surfaces, especially the undersides.
You’ll likely need to repeat this treatment every 7 to 14 days until the pest population is under control.
Once the pests are gone, no new honeydew is produced, and the sooty mold will eventually dry up and flake off.
3. Promote Natural Predators to Keep Your Crepe Myrtles From Looking Black
Ladybugs, lacewings, and parasitic wasps are natural enemies of aphids and scale.
Avoid using broad-spectrum insecticides that kill these helpful insects.
You can even buy ladybugs from garden centers and release them at dusk near the affected tree.
Encouraging these predators will help keep the pest numbers low, so your crepe myrtles don’t look black again next season.
4. Prune Heavily Infested Branches
If certain branches are absolutely coated in black mold and pests, prune them off.
Make clean cuts back to a main stem or branch junction.
Dispose of the trimmings in a sealed bag so the pests don’t spread.
This also improves air circulation in the canopy, which helps the tree dry out faster and makes the environment less inviting for mold.
5. Fertilize and Water to Help Your Crepe Myrtles Recover
A stressed tree is more susceptible to pests and mold.
Water deeply once a week during dry spells, especially in the first few years.
Apply a balanced, slow-release fertilizer in early spring to promote healthy new growth.
But don’t over-fertilize with nitrogen, as that can encourage a flush of tender new leaves that pests love even more.
A healthy crepe myrtle that is growing vigorously will shed old, moldy leaves and push out clean growth more quickly.
Prevent Your Crepe Myrtles From Looking Black in the Future
Now that you know why your crepe myrtles look black, let’s talk about prevention.
It’s always easier to stop the problem before it starts than to clean up a huge mess.
Here are a few habits that will keep your tree clean and green all summer.
1. Monitor Early in the Season
Check your crepe myrtles every few weeks starting in late spring.
Look for the first signs of honeydew, which is a sticky sheen on the leaves.
If you catch aphids or scale when they’re few in number, a simple water blast might be enough.
The earlier you act, the less likely your crepe myrtles will look black later on.
2. Avoid Overhead Watering
Water at the base of the tree instead of from above.
Overhead watering keeps the foliage wet for extended periods, which encourages fungal growth.
And while sooty mold needs honeydew to grow, other fungal diseases also love wet leaves.
Drip irrigation or a soaker hose is ideal for crepe myrtles.
3. Thin the Canopy Yearly
Prune your crepe myrtles each winter or early spring to remove crossing branches and open up the center.
Good airflow means leaves dry out quickly after rain or dew.
Dry leaves are less hospitable to mold spores and also make it harder for pests to thrive.
Just don’t commit “crepe murder” by topping the tree, stick to selective thinning.
So, Why Do My Crepe Myrtles Look Black?
Your crepe myrtles look black due to sooty mold that grows on the honeydew left behind by sap-sucking pests.
That’s the straightforward answer to why your crepe myrtles look black.
Aphids, crape myrtle bark scale, and whiteflies are the primary culprits that start the whole chain reaction.
By controlling these pests and washing off the mold, you can restore your tree’s natural beauty.
Remember, the black mold won’t permanently harm your crepe myrtles, but the underlying pest infestation can weaken them over time.
So roll up your sleeves, give that tree a good wash, and treat the pests.
With a little effort, your crepe myrtles will look lush and vibrant again, without that ugly black coating.