Advice
RHS Help & Advice
Damping off
This is a seedling problem that can be tackled by good hygiene and fungicides
Symptoms
Seedlings keel over, collapse and die. It may be pre-emergent, killing seedlings before they emerge, or post-emergent, once they have pushed through the soil surface. Most seedlings are potentially susceptible, but the problem is most common in seedtrays in the glasshouse.
Cause
Damping off is due to several soil and water-borne fungi (particularly those in the genera Pythium, Phytophthora and Rhizoctonia) that attack the stem base, which becomes thin and brown and a white fluffy fungus may develop. The same fungi may attack below ground causing an apparent failure of seed to germinate (pre-emergence damping off). The disease is encouraged by cool, humid conditions and overwatering.
Prevention
Use clean containers, fresh compost and clean water. Sow seeds thinly. After sowing water with copper fungicide (Cheshunt Compound, Murphy Traditional Copper Fungicide).
If you use home-made compost, sterilise it before use with an electrical soil steriliser. Chemical sterilants are no longer legally available for this purpose.
Control
Remove damaged seedlings and apply a copper fungicide (Cheshunt Compound, Murphy Traditional Copper Fungicide).