Damping off

Damping off is a disease of seedlings caused by several different fungi and fungus-like organisms. This disease causes emerging seedlings to collapse, often submerged in a mass of white fungal growth. It is particularly a problem when sowing seed indoors or under glass.

Damping off can affect most seedlings, particularly under conditions of high humidity, poor air circulation and if seed is sown too thickly, and is especially damaging in spring when light levels and temperatures are low and seedlings grow slowly, but may occur at any time of year.


Non-chemical control

These measures are very important, particularly given the current lack of fungicides for the control of damping off.

  • Raise seedlings in commercial growing compost, which is usually free of damping off organisms. If home-produced compost must be used, consider steam sterilisation to destroy pathogens
  • Ideally, use new pots and trays whenever raising seedlings. If they must be re-used, brush off soil, wash and preferably also treat them with a disinfectant such as Jeyes Fluid. Dry before storage. Never reuse pots and trays in which damping off has been a problem
  • Sow seedlings thinly to avoid crowding
  • Use mains water if possible when irrigating seedlings grown in pots and trays. If using rainwater, ensure that the water butt is covered to prevent the entry of leaves and other organic debris that could harbour some of the damping off pathogens
  • Do not overwater
  • Keep seedlings well ventilated to reduce humidity
  • Ensure that both greenhouses and water butts are cleaned regularly. After thoroughly cleaning and refilling rainwater tanks or water butts, add a proprietary water butt cleaner to help prevent problems from both damping off and algae

Chemical control

No fungicides are available to gardeners for the control of damping off.