A black coating on tree leaves is almost always sooty mold, a fungus that grows on the sticky honeydew residue left behind by sucking insects like scale, aphids, and mealybugs.

What Is the Black Coating Actually Made Of?

Sooty mold is a surface fungus, not an infection inside the leaf. It grows on top of honeydew, the sweet, sticky substance sucking insects excrete after feeding on plant fluids, rather than feeding on the leaf tissue itself.

Which Insects Produce the Honeydew Behind It?

Sucking insects extract liquid directly from leaves and twigs, and scale is the type most often responsible for the honeydew that leads to sooty mold. The mold shows up wherever that honeydew drips or accumulates, which is often on lower leaves and branches beneath an infested spot.

Can the Black Coating Return After Being Cleaned Off?

Yes, as long as the insects producing the honeydew are still feeding. Rinsing the coating away improves the tree's appearance right away, but new mold will grow back on fresh honeydew until the insect problem itself is treated.

Frequently Asked Questions

Does the black coating mean the tree has a fungal disease?

No. Sooty mold sits on the surface rather than infecting the plant, so it's a cosmetic byproduct of an insect problem rather than a disease in its own right.

Is honeydew visible before the mold forms?

Yes. Honeydew often shows up first as a clear or slightly shiny, sticky film on leaves before the black sooty mold fungus has had time to grow on it.

What treats the insects causing the coating?

The Multi-Insect Killer Tree Injection Kit is injected directly into the trunk and controls scale insects, along with aphids and mealybugs, the main sources of the honeydew behind sooty mold.