Common crops affected
- Citrus
- Tree fruit
- Vines
- Ornamentals
What is it?
Sooty mould fungi don't infect the plant — they grow on the sugary honeydew that sucking insects deposit on leaves and fruit. So sooty mould is a symptom of an insect problem; control the insect and the mould stops.
How to identify it
- Black, dry, soot-like coating on leaf surfaces, stems and fruit that can be rubbed off.
- Sticky honeydew underneath, and colonies of aphids, whiteflies, scale or mealybugs nearby (often with ants).
- Reduced light reaching leaves; fruit blemished and downgraded.
- Decline in vigour where heavy coating blocks photosynthesis.
Life cycle & spread
The mould grows whenever honeydew is present and stops producing new growth once the honeydew source (the insects) is removed; old coating weathers and flakes off over time.
Conditions that favour it
Active populations of aphids, whiteflies, scale or mealybugs; ant activity that protects those insects; still, humid conditions.
Damage and how it spreads
Blocks light and reduces photosynthesis; blemishes and downgrades fruit and ornamentals; indicates an underlying sucking-pest infestation that is itself damaging the crop.
Monitoring & scouting
Trace sooty mould back to the honeydew producer; scout for aphids, whiteflies, scale and mealybugs and for ant trails; target the insect, not the mould.
How to control it
- Control the honeydew-producing insects (the root cause);
- manage ants that protect them;
- once the insects are controlled, the mould stops growing and weathers off, and washing/rain speeds removal.
Recommended Vegalab solution: Spider Mite Control
Spider Mite Control — all-natural contact product (geraniol with peppermint, cottonseed and rosemary oils) to control the aphids, whiteflies, scale and mealybugs that produce the honeydew; once they're controlled, sooty mould stops growing.
| Role | Product | Use |
|---|---|---|
| Primary control | Spider Mite Control |
Preventing it next season
Keep honeydew-producing pests in check, manage ants, and maintain airflow; preventing the insect prevents the mould.
Claims and product availability vary by jurisdiction. Always read and follow the product label.