How Do You Treat Black Sooty Mold On Crepe Myrtles

You treat black sooty mold on crepe myrtles by first controlling the underlying pest infestation, then washing the mold off the tree, and finally taking steps to prevent it from returning.
 
Black sooty mold on crepe myrtles is a frustrating sight, but the good news is that the mold itself isn’t attacking your tree.
 
It’s actually a fungus that grows on the sticky honeydew left behind by sap-sucking insects like aphids and crape myrtle bark scale.
 
So if you’re wondering how to treat black sooty mold on crepe myrtles, the real answer starts with getting rid of those pests, because without them, the mold won’t have anything to feed on.
 
In this post, we’ll walk you through exactly how to treat black sooty mold on crepe myrtles, from identifying the culprit pests to washing the black residue away and keeping your tree clean all season long.
 
Let’s dig in and get your crepe myrtle looking beautiful again.
 

Why Black Sooty Mold On Crepe Myrtles Appears In The First Place

To effectively treat black sooty mold on crepe myrtles, you have to understand the chain reaction that causes it.
 
The mold doesn’t just appear out of nowhere; it’s always a sign that there’s another problem happening on your tree.
 
Here’s how the whole process starts.
 

1. The Pest Problem That Starts It All

The most common culprits behind black sooty mold on crepe myrtles are aphids and crape myrtle bark scale.
 
These tiny insects feed by piercing the leaves and stems of your crepe myrtle and sucking out the sugary sap.
 
As they feed, they excrete a sticky, sweet substance called honeydew, which drips down onto the leaves and branches below.
 
This honeydew is basically a feast for the sooty mold fungus, and where there’s honeydew, black sooty mold on crepe myrtles is sure to follow.
 

2. The Fungus That Takes Advantage

Once the honeydew is present, the spores of the sooty mold fungus land on it and begin to grow.
 
The fungus forms a black, powdery layer that covers the leaf surfaces and stems.
 
While black sooty mold on crepe myrtles looks scary, it’s actually superficial and doesn’t penetrate the tree’s tissue.
 
The real harm comes when the mold covers enough leaf surface to block sunlight, which can reduce the tree’s ability to photosynthesize.
 

3. Why It Gets Worse Over Time

If you leave black sooty mold on crepe myrtles untreated, the mold will continue to spread as long as the pests are active.
 
And since the honeydew keeps coming, the mold keeps growing, turning your beautiful tree into a black, sooty mess.
 
That’s why quick action is so important when you’re learning how to treat black sooty mold on crepe myrtles.
 

How To Treat Black Sooty Mold On Crepe Myrtles: Step-By-Step

Now that you know what causes it, let’s talk about the actual treatment process.
 
Following these steps will help you treat black sooty mold on crepe myrtles effectively and stop it from coming back.
 

1. First, Knock Out The Insect Pests

You can’t treat black sooty mold on crepe myrtles without dealing with the insects that produce the honeydew.
 
Start by inspecting your tree for signs of aphids or crape myrtle bark scale, which look like small, whitish-gray felt-like patches on the bark.
 
You can spray the tree with a strong jet of water from your hose to knock off many of the soft-bodied aphids.
 
For heavier infestations, apply a horticultural oil or insecticidal soap, making sure to cover the undersides of the leaves and the branches thoroughly.
 
For crape myrtle bark scale, dormant oil applications in late winter are highly effective at smothering the overwintering eggs.
 

2. Wash The Black Sooty Mold Off The Crepe Myrtles

Once the pests are under control, you can physically remove the black sooty mold on crepe myrtles with water.
 
The mold is not deeply rooted, so a good rinse can wash much of it away.
 
Use a garden hose with a spray nozzle and thoroughly rinse the leaves, stems, and branches.
 
For stubborn patches, you can gently scrub the leaves with a soft cloth dipped in soapy water, but be careful not to damage the foliage.
 
With heavy buildup, you might need to repeat the washing a few times over a couple of weeks to fully clean the tree.
 

3. Encourage Natural Predators

One of the best long-term strategies to treat black sooty mold on crepe myrtles is to bring in the good guys.
 
Ladybugs, lacewings, and parasitic wasps are natural predators of aphids and can significantly reduce their numbers.
 
You can attract these beneficial insects to your garden by planting a variety of flowering plants that provide nectar and pollen.
 
Avoid using broad-spectrum insecticides that kill these beneficial bugs, as you’ll just make the pest problem worse in the long run.
 

4. Keep Your Crepe Myrtle Healthy

A healthy, vigorous crepe myrtle is less susceptible to pest infestations and can bounce back faster from black sooty mold.
 
Make sure your tree gets adequate water during dry spells, but avoid overwatering, which can stress the roots.
 
Fertilize your crepe myrtle in early spring with a balanced fertilizer to promote strong new growth.
 
Proper pruning to improve air circulation can also help reduce humidity around the leaves, making it less inviting for both pests and fungus.
 

Preventing Black Sooty Mold On Crepe Myrtles Going Forward

Treating the current problem is only half the battle; you also want to prevent black sooty mold on crepe myrtles from making a comeback.
 
Prevention is all about staying one step ahead of both the pests and the conditions that favor the fungus.
 

1. Monitor Your Tree Regularly

Get into the habit of checking your crepe myrtle’s leaves and bark every week, especially in the spring and early summer.
 
Look for the first signs of aphids, sticky leaves, or tiny scale insects on the bark.
 
Catching an infestation early makes it much easier to treat black sooty mold on crepe myrtles before it spreads.
 

2. Control Ants Which Protect The Aphids

Ants actually farm aphids for their honeydew and will fiercely protect them from predators.
 
If you see ants crawling up and down your crepe myrtle, they’re likely shielding an aphid colony.
 
Use sticky tree barriers or ant baits around the base of the tree to disrupt their movement and allow the natural predators to take over.
 
Without the ants’ protection, aphids are much more vulnerable to being eaten by ladybugs and other beneficial insects.
 

3. Avoid Over-Fertilizing With Nitrogen

While you want to keep your crepe myrtle healthy, too much nitrogen can cause a flush of soft, succulent new growth.
 
Aphids absolutely love this tender new growth, so you’d be essentially rolling out the red carpet for them.
 
Use a slow-release fertilizer and avoid heavy nitrogen applications, especially mid-season, to keep your tree less attractive to pests.
 

So, How Do You Treat Black Sooty Mold On Crepe Myrtles?

You treat black sooty mold on crepe myrtles by getting rid of the sap-sucking insects first, then washing the mold off the leaves and branches.
 
The whole process starts with controlling aphids and crape myrtle bark scale, and once you stop the honeydew production, the black sooty mold on crepe myrtles will naturally stop spreading.
 
A simple combination of horticultural oils, a good hose-down, and encouraging beneficial predators will solve your problem.
 
And with regular monitoring and a few simple prevention tactics, you can keep your crepe myrtle clean, healthy, and free from that ugly black coating for years to come.
 
Hope this clears up how to treat black sooty mold on crepe myrtles, and you’re ready to tackle this issue head-on in your garden.