Field Identification
Black, powdery fungal growth on leaf surfaces fed by honeydew from aphids, scales, whiteflies, or psyllids—not a primary pathogen but a billboard advertising sap feeders. Blocks light and can reduce vigor on heavily coated evergreens.
Soot can be wiped to expose green tissue underneath; no fungal lesions penetrate—if leaves are yellowing with no honeydew source, suspect something else. Often follows ant-tended hemipterans.
How to Deal With It
Organic Control Methods
Horticultural oil or soap aimed at the honeydew producers; light potassium bicarbonate or soap rinses can wash film on small plants—repeat as sap insects return.
Parasitoids and predators that collapse scale and aphid populations indirectly clear sooty mold; ants must be excluded or baited so natural enemies can work.
Prune dense interior branches to improve coverage when spraying; reduce nitrogen that prolongs soft aphid-prone growth.
Soft brush and water on ornamentals; pressure wash sturdy foliage where it will not strip bark.
Monitor sticky traps and new flush for the first whiteflies or aphids; band trees for ants where appropriate.
Let Nature Handle It
Natural Enemies
- Parasitic Wasps
- Lady Beetles
- Lacewings