Sticky Leaves & Sooty Mould
A tacky residue on leaves, sometimes followed by a black, sooty coating, is a two-stage problem that starts with sap-sucking pests rather than a disease on its own.
Common causes
Honeydew from sap-sucking pests
Aphids, scale, mealybugs, and whiteflies excrete a sugary waste called honeydew as they feed. Treat the underlying pest first, then wipe leaves clean with a damp cloth.
Sooty mould growing on honeydew
A black, powdery fungal growth colonises leftover honeydew rather than infecting the plant directly. Once the pest source is gone, gently wash the mould away — it doesn’t need fungicide.
Ants farming the pests
Ants protect and even relocate honeydew-producing pests between plants to keep the food source going. Dealing with an ant trail nearby often reveals the real source of a recurring infestation.