Common crops affected
What is it?
Leaf mold is caused by the fungus Passalora fulva (formerly Cladosporium fulvum). It thrives in high humidity and moderate temperatures, which is why it is especially common in protected culture. The fungus infects leaves and produces spores on the undersides that spread on air currents and splashing water.
How to identify it
- Pale green to yellow blotches on the upper leaf surface
- Olive-green, gray, or brown velvety fuzz on the corresponding underside
- Yellowing, curling, and drop of affected leaves
- Worse in high humidity and poorly ventilated greenhouses and tunnels
Damage and how it spreads
By blotching and killing leaves, leaf mold reduces photosynthesis, weakens plants, and lowers yield — and in humid protected culture it can defoliate a crop. Because high humidity drives it, it recurs wherever air is still and moist. Ventilation plus protective treatment is the reliable combination.
How to control it
- Reduce humidity and increase ventilation, especially in greenhouses and tunnels.
- Space and prune plants for airflow; avoid overhead watering and wet foliage.
- Remove and destroy infected leaves and end-of-season debris.
- Apply a protective natural fungicide at first sign and through humid periods.
Recommended Vegalab solution: Spore Control
Vegalab Spore Control (Thymol) protects against leaf mold by forming a cuticle film and inhibiting spore germination and mycelium proliferation. Apply as a foliar spray at first sign of disease, diluted 1:1,000 (1 mL/L), covering leaf undersides where the fungus sporulates, and keep up coverage during humid spells. Humidity control makes the program far more effective.
| Role | Product | Use |
|---|---|---|
| Primary control | Spore Control | Broad-spectrum protective fungicide |
| Companion / broader pressure | Armour Boost | Silica for tissue resilience |
Preventing it next season
Manage humidity and ventilation aggressively in protected culture, space and prune for airflow, avoid wet foliage, remove debris, and protect preventively in humid weather. Resilient foliage helps — support it with Armour Boost.
Claims and product availability vary by jurisdiction. Always read and follow the product label.