What’s Going on with Your Crape Myrtle?

What’s Going On With My Crape Myrtle?

What’s all the white gunk on the trunk and branches — and why are my leaves black?

The White “Bumps” Explained

The white bumps on the trunk and stems are an insect called Crape Myrtle Scale. They moved into North Carolina a couple of years ago, and because we have so many crape myrtles in the area, they’ve found a very comfortable home.

There are several different types of scale insects. These, however, are specific to crape myrtles. If you see similar insects on other plants, it’s likely a different type of scale, but the treatment approach is the same.

How Scale Damages the Tree

Scale insects attach themselves to stems and branches, pierce the bark, and suck nutrients from the layer beneath. While feeding, they secrete a waxy coating that protects them and prevents most spray chemicals from reaching the insect itself.

For years, the standard treatment was dormant or horticultural oil, which works by coating the insect and essentially suffocating it. The downside is coverage — if you only spray what you can reach, scale higher up in the tree survives, spreads, and reinfests the tree.

Is the Tree Hopeless?

Absolutely not.

The Most Effective Treatment

The most effective control method is Imidacloprid, a systemic insecticide.

Applied as a soil drench around the base of the tree
Absorbed by the roots and transported throughout the entire tree
Scale insects ingest the chemical while feeding

Before treatment, you can mash the scale — it will squish and bleed. About two weeks after applying Imidacloprid, the scale will begin to flake off easily with a light scrape of a fingernail.

And What About the Black Leaves?

Black leaves are caused by an aphid infestation.

Aphids (and scale) secrete a sticky substance known as honeydew. Dirt and dust in the air stick to this residue, creating the black appearance on the leaves.

The Imidacloprid drench will also control aphids
The black residue takes time to loosen and fall off naturally

To speed up cleanup:

Spray the leaves with warm, soapy water
Let it sit for about 30 minutes
Rinse the tree thoroughly with a hose

This won’t remove everything, but it will noticeably improve appearance.

The Bottom Line

Treat heavy infestations as soon as possible
Re-treat in mid to late March — eggs laid in late summer will return
Imidacloprid remains active for about 90 days
Reapply every 2–3 months to prevent reinfestation

Consistent treatment keeps scale and aphids from settling back in and turning your crape myrtles into their next happy home.