Sooty mould

Follows pest outbreaks, worst through the warm months, October to April.

Sooty mould is a black fungus that grows on the sticky honeydew dripped by aphids, scale, whitefly, mealybugs and passionvine hoppers. It does not infect the plant directly but coats leaves and blocks light, so the real fix is to control the sap-sucking pest underneath.

How to identify

• A black sooty film over leaves, stems and fruit
• The film wipes off to reveal healthy green tissue underneath
• Sticky honeydew on the leaves above the mould
• Aphids, scale, whitefly, mealybugs or hoppers on the plant

How to prevent

• Control the sap-sucking pests producing the honeydew
• Keep ants off plants with a sticky barrier, since ants farm the pests
• Prune for airflow and avoid soft over-fed growth that draws pests
• Inspect plants regularly to catch honeydew producers early

How to control organically

• Treat the underlying pest with oil or soap sprays, which is the real fix
• Wipe or hose the mould off leaves once the pest is under control
• Spray a soap solution to help loosen and lift heavy mould
• Prune out badly coated growth to let light back in
• Control ants so predators can clean up the pests