Why are my crepe myrtle leaves sticky and turning black?

The stickiness is honeydew, the sugary waste of sap-sucking pests, usually crepe myrtle aphids on the leaves or crapemyrtle bark scale on the trunk and branches. Black sooty mold then grows on the honeydew. The mold is a symptom: control the insect and the honeydew stops, and the mold weathers away.

How do I tell crepe myrtle aphids from bark scale?

Aphids are soft, pale green to yellow insects clustered on the undersides of leaves, mostly in the warm months. Crapemyrtle bark scale is a white to gray felt-like crust on the bark, branches, and crotches that bleeds pink when crushed, and it stays on the wood year round.

Is it safe to use a systemic insecticide on a flowering crepe myrtle?

Use caution. Crepe myrtles are highly attractive to bees in bloom, and systemic neonicotinoids such as imidacloprid can move into nectar and pollen. Best practice is to avoid soil drenching a blooming or about-to-bloom tree, prefer non-systemic controls, and treat any systemic as a last resort under label and local guidance rather than relying on timing alone, because the chemical can linger in nectar and pollen for months.

There is a herd of little gray bugs moving on my crepe myrtle bark. What are they?

Those are almost certainly bark lice, often called tree cattle. They are harmless psocid insects, not true lice, that move in herds across the bark and graze on surface mold, lichen, and algae. They do not feed on the tree and are considered beneficial, so no treatment is needed. Unlike crapemyrtle bark scale, bark lice are separate insects that move when disturbed and do not bleed pink when crushed.

Crepe Myrtle Care • Central Texas

Sticky Leaves and Black Bark

When a crepe myrtle goes sticky and the bark turns sooty black, two different pests are usually behind it: aphids on the leaves and bark scale on the wood. Both feed the same black mold. Here is how to tell them apart and shut them down without poisoning the bees.

Get an assessment → Call 512-800-3566

Two pestsAphids and bark scale

One messHoneydew and sooty mold

TreatableOnce the honeydew stops

Crepe myrtle trunk crusted with white crapemyrtle bark scale and coated in black sooty mold

Field photo

What's going on

Two bugs, one sticky mess

That shine on the leaves and the patio furniture is honeydew, the sugary waste that sap-sucking insects leave behind. On crepe myrtles it comes from one of two pests, and often both: crepe myrtle aphids feeding on the leaves, and crapemyrtle bark scale encrusting the trunk and branches.

Wherever the honeydew lands, a black fungus called sooty mold grows on it. The mold is the part everyone notices, but it is only a symptom. It does not infect the tree, it just feeds on the sugar. Stop the insect, the honeydew stops, and the mold weathers off on its own.

Tinocallis kahawaluokalani (aphid) • Acanthococcus lagerstroemiae (bark scale)

What it looks like

Sooty mold in the field

The same honeydew story, from the first flecks to a shrub filmed solid black. All Central Texas field photos.

A crepe myrtle shrub with leaves filmed black by sooty mold — Heavy sooty mold coating a whole crepe myrtle. The black is the fungus feeding on honeydew, not a disease of the tree.

A lady beetle on sooty-mold-covered crepe myrtle leaves — A lady beetle working the same sooty leaves. Beneficials like this are exactly why the gentle-first approach pays off.

Early honeydew and dark flecks on the upper surface of crepe myrtle leaves — Early honeydew and dark flecking on the leaves, the first sign before the black sets in.

Tell them apart

Aphids or bark scale

They cause the same sticky, sooty result, but they look nothing alike and they are not handled the same way. Check the leaves and check the bark.

Pale aphids and cast skins on the underside of a crepe myrtle leaf

On the leaves

Crepe myrtle aphids

Tinocallis kahawaluokalani

Soft, pale green to yellow insects, smaller than a pinhead
Cluster on the undersides of the leaves where they feed
Worst in the warm months, and they explode fast in heat
Leaves get sticky, then black, and may yellow and drop

On the bark

Crapemyrtle bark scale

Acanthococcus lagerstroemiae

White to gray felt-like crust on the trunk, branches, and crotches
Bleeds pink when you crush it, a quick confirming test
Stays on the wood year round, not just in summer
Often the cause when the whole trunk goes sooty black, like the photo above

Not every bug is a pest

Bark lice: the look-alike to leave alone

Before you spray anything on the bark, look closer. If the crust is actually a herd of little gray insects moving across the trunk, that is bark lice, and they are on your side, not the tree's enemy.

A herd of gray, banded bark lice clustered on the smooth bark of a crepe myrtle — Bark lice, often called tree cattle, herding on a crepe myrtle trunk. Separate insects that move as a group, not a crust fixed to the wood.

Bark lice gathered in the branch crotch of a crepe myrtle in full leaf — The same herd in a branch crotch. Bark lice graze surface mold, lichen, and algae off the bark and do no harm to the tree.

How to tell it from bark scale

Watch it, then poke it

Bark scale is a white, waxy crust that stays put and bleeds pink when you press it. Bark lice are separate gray insects that move as a herd and do not bleed pink. If the patch scatters when you touch it, it is bark lice, and the right treatment is none. They graze the same sooty mold the scale creates, so left alone they are a beneficial cleanup crew.

Why it spreads

Honeydew, mold, and ants

The three feed each other. Understand the loop and you know where to break it.

The honeydew

Sugar coats everything

Aphids and scale drink more sap than they can use and excrete the excess as a sticky film, onto lower leaves, the bark, and whatever sits beneath the tree, cars and patios included.

The sooty mold

Black film on the sugar

Sooty mold is a harmless-but-ugly fungus that grows on honeydew. A heavy coat blocks light from the leaves, but it does not infect the tree. Clear the pest and it fades.

The ants

Ants farm the pests

Ants love honeydew, so they protect aphids and scale and drive off the ladybugs and lacewings that would eat them. Control the ants and you let the good bugs do free work.

What to do

Break the loop, gently first

Start with the least aggressive tool that works. Most crepe myrtle infestations come down without reaching for a systemic at all.

Do

Blast the foliage with a strong hose stream, hitting the leaf undersides, to knock aphids off without chemicals.
Use insecticidal soap, neem, or horticultural oil when water is not enough, coating both sides of the leaves.
Treat bark scale with horticultural oil on the trunk and branches, ideally in the dormant season, to smother the crust.
Control the ants so ladybugs and lacewings can hold the pests down for you.

Never

Spray oils or soaps in 90°F-plus heat. It burns the leaves. Treat in the cool of the morning.
Soil-drench a blooming tree with a systemic. See the pollinator note below, this one matters.
Expect the black to vanish overnight. Sooty mold weathers off over weeks once the honeydew stops.
Ignore the ants. Leave them and they will undo the rest of your work.

Before you reach for a systemic

Imidacloprid and the bees

A systemic insecticide such as imidacloprid, applied as a soil drench, is effective for stubborn aphids and scale because the plant carries it to every feeding insect. But crepe myrtles are magnets for bees when they bloom, and systemic neonicotinoids move into the nectar and pollen those bees collect.

So the rule on a flowering crepe myrtle is cautious: do not drench a tree that is blooming or about to bloom, and reach for the non-systemic options first. Neonicotinoids can linger in a plant's nectar and pollen for months, sometimes into later seasons, so timing alone does not make them safe on a tree that bees visit. If a systemic is ever truly warranted, treat it as a careful, label-driven decision, ideally one for a licensed applicator.

When to hit it

A Central Texas bark scale calendar

Bark scale is beaten on timing, not brute force. The young crawlers are the soft, exposed stage, so the whole game is hitting them while they are out. These windows follow Texas A&M AgriLife monitoring, not a textbook from another climate.

Late winter · Dec to Feb

Dormant horticultural oil on the trunk, branches, and crotches, smothering the scale that overwinters under the bark. A useful clean-up, not a stand-alone cure.

Mid-March

If a systemic is ever used, this leaf-out window is the entomology timing. But read the bee note above: a neonic applied now can still reach the summer blooms, which is why I treat crawler sprays, not systemics, as the first move.

Mid-April to early May

The main event. The first crawlers are out and exposed. Target the bark with a crawler-timed treatment and repeat every 10 to 14 days while they are active. This is the highest-leverage window of the year.

Late summer into fall

Watch for a second round. Central Texas runs two or more overlapping generations a year, so a late flare-up is common and worth a follow-up if numbers climb.

Field tip: wrap a strip of double-sided sticky tape around an infested branch and check it. When the tiny crawlers start showing up stuck to the tape, the spray window is open. It beats guessing by the calendar alone.

Crepe myrtle dripping sap and going black? Let's sort it

Send me a photo of the leaves and the trunk and I will tell you whether you are dealing with aphids, bark scale, or both, and the safest way to clear it for your tree and the bees.

Request an assessment → Call 512-800-3566

This page is educational and does not diagnose any tree. Pesticide choices, rates, and timing should follow the product label and local conditions, and pollinator protection should always be considered on flowering plants. When in doubt, have the tree evaluated on site before treating.