Sooty Mold 🦠
At a glance
- Cause: Fungi growing on sticky honeydew, not usually an infection inside the leaf
- Tell-tale sign: Black soot-like coating that appears with sticky residue or sap-sucking insects
- Severity: Moderate — mostly blocks light and signals another pest problem
How to identify
Sooty mold looks like a black, dusty or felty film on leaves, stems, fruit, furniture, or pavement below a plant. The key clue is honeydew: sticky residue from Aphids, Whiteflies, Mealybugs, or Scale Insects. If the black film wipes partly off, then returns, the honeydew source is still active.
What causes it
Sooty mold fungi grow on sugary honeydew excreted by sap-sucking insects. The mold itself is usually superficial, but it can block sunlight and make leaves less efficient.
Treatment & management
Following Integrated Pest Management:
- Find and control the honeydew insect first: aphids, whiteflies, mealybugs, or scale.
- Wash leaves gently with water and a soft cloth once the insect source is under control.
- Control ants outdoors because they protect honeydew insects.
- Improve airflow and plant vigor so the plant can recover clean foliage.
Prevention
Monitor for sticky leaves, ants, and sap-sucking insects early. Treating the insect source prevents the mold from coming back.
Affects (in this guide)
Any plant with honeydew insects; common on houseplants, citrus, oaks, and landscape ornamentals