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Damping off
Pythium spp. / Phytophthora spp.
Fungal diseaseHigh impact
Young seedlings collapse at or just below soil level, caused by fungal pathogens that thrive in overwatered, poorly ventilated growing conditions. Can spread rapidly through a seed tray.
Outside typical active season.
Key facts
- Type
- Fungal disease
- Active season
- Feb - Jun
- Peak season
- Mar - May
- Vulnerable stages
- Sown · Transplanted
- Spread rate
- fast
- If confirmed
- Act now
Signs & symptoms
- -seedlings collapsing and shrivelling at the base of the stem
- -thin, pinched-looking stem bases turning dark or translucent
- -patches of lost seedlings that spread outward through a tray or row
- -white fluffy mould sometimes visible on soil surface in humid conditions
Management
Do now
- -Remove affected seedlings immediately to limit spread
- -Reduce watering and allow the soil surface to dry between waterings
- -Improve ventilation and airflow around the tray or growing area
- -Separate healthy seedlings from affected trays
Prevention
- -Use fresh, sterile growing medium - reused compost harbours more pathogens
- -Sow at the recommended depth - too deep is a common cause of failure
- -Use clean, rinsed trays and pots for seedling raising
- -Water from below where possible to keep the surface drier
Further reading
- -Damping off is caused by overwatering combined with poor ventilation - the pathogen needs consistently moist conditions near the stem base to take hold
- -Spreading through a tray is rapid; removing affected seedlings early is the key to limiting losses