Damping-off affects seeds and seedlings, and is most often seen where seedlings are growing too close together, and in cool, humid conditions. The seedlings collapse and die as their roots darken and rot off, or occasionally, the lower stem shrivels and blackens leaving the stunted plants standing and alive for a while. This is known as wirestem, as the blackened section looks like a twisted piece of wire. This disease often starts at one end of a seed tray and then rapidly spreads to the rest, and is accompanied by a fluffy, fungal growth on the compost and the dead seedlings.

Control

Unfortunately, once established, there is no cure for damping-off, and so measures must be taken to prevent it from occurring in the first place. The fungus thrives in moist, unhygienic conditions so maintain strict hygiene, water sparingly and carefully, use sterilised seed composts that drain quickly, sow thinly and improve ventilation around seedlings. Seedlings should also be watered occasionally with a copper-based fungicide.