Damping off, a seedling disease caused by several different fungi, can hit at any time of year but is most likely to strike in spring, when light levels and temperatures are low. While it can take hold on seedlings outside, it is more likely to occur with seeds sown indoors under high humidity.
The signs are obvious, seedlings seemingly collapse and wither and are occasionally covered in white fluffy mould. It can be very localised – one half of a seed tray may remain unaffected, while the other is lost to the disease.
There are no specific chemical controls for the problem, so prevention is better than cure.
Always use a quality compost such as Gro-Sure Seed & Cutting Compost when sowing seed, and where possible use new seed trays for each sowing you make. If you do need to re-use containers wash them well and disinfect them. Throw away any containers where damping off has been a problem.
Keep seedlings well ventilated to improve air circulation and reduce humidity and avoid sowing seed too thickly to avoid overcrowding.
Use tap water rather than stored rain water, which is more likely to harbour the pathogens that cause the problem.
Always buy quality seed. Varieties in the Unwins Gro-sure seed range have been selected for their pest and disease resistance, and many are pre-treated to further boost their ability to fight off disease problems.