Most greenhouse diseases share one root cause: warm, humid, stagnant air. Get airflow, watering and hygiene right and you prevent the majority of problems before they start. This guide covers the usual suspects and the prevention that works across all of them.
The common greenhouse diseases
- Botrytis (grey mould)“>Botrytis (grey mould) — the classic greenhouse disease; fuzzy grey growth on stems, leaves and fruit in cool, humid, still air.
- Downy mildew“>Downy mildew — needs leaf wetness and humidity; yellow patches with growth underneath.
- Powdery mildew“>Powdery mildew — white powder on upper leaves in warm, humid-but-dry conditions.
- Damping off — seedlings collapse at soil level in wet, crowded propagation trays.
- Root rot“>Root rot — from overwatering and poor drainage.
- Anthracnose“>Anthracnose and leaf spots“>leaf spots on susceptible crops.
Prevention that works across the board
- Airflow — ventilate and run a circulation fan“>circulation fan; still, humid air is the enemy. See ventilation“>ventilation.
- Manage humidity — keep it out of the danger zone; see greenhouse humidity“>greenhouse humidity.
- Water at the base, in the morning — dry foliage resists disease (see watering“>watering).
- Space plants and stay hygienic — remove dead leaves and debris; don’t crowd.
- Clean up — disinfect the greenhouse and pots between seasons.
Damping off in propagation
Prevent it with clean trays, fresh sterile seed mix, not sowing too thickly, good airflow and careful watering (avoid waterlogging). See seed germination“>seed germination and propagation equipment“>propagation equipment.
Quick questions
How do I prevent disease in a greenhouse? Keep air moving, manage humidity, water at the base in the morning, space plants and stay hygienic — humidity and stagnant air cause most greenhouse disease.
Related guides
- Botrytis“>Botrytis · powdery mildew“>powdery mildew · downy mildew“>downy mildew · humidity“>humidity · pest control“>pest control
