Join the RHS today and support our charity
Free personalised gardening advice
RHS members get reduced ticket prices
RHS members get free access to RHS Gardens
Reduced prices on RHS Garden courses and workshops
020 3176 5800
Mon – Fri | 9am – 5pm
Help us achieve our goals
Make a donation
I have forgotten my password
Keep me signed in
Register for free to receive our newsletters, add comments to blogs/articles and to save content.
See what events are on near you and browse your bookmarked pages.
Inspiring days out and so much more
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 is caused by several soil-borne fungi and fungus-like organisms including Pythium, Phytophthora, Rhizoctonia and Fusarium, which infect seedlings and cause them to ‘damp off’ or collapse and decay.
Damping off can affect most seedlings, particularly under levels of high humidity, poor air circulation and if seed is sown too thickly. It is mainly a problem when sowing early indoors or under glass, but can affect seedlings sown outdoors in situ.
Damping off is especially damaging in spring when light levels and temperatures are low and seedlings grow slowly, but may occur at any time of year.
You may see the following symptoms:
These measures are very important, particularly given the current lack of fungicides for the control of damping off.
No fungicides are available to gardeners for the control of damping off.
Species of the fungus-like organisms Phytophthora and Pythium are widespread in soil. Species of the true fungi Rhizoctonia and Fusarium are also common in soil.
All of these organisms, and some others, can infect the delicate tissues of young seedlings and kill them. Infection of the seed can occur before emergence (pre-emergence damping off), leading to patchy emergence. Infection can also occur after emergence, particularly where the seedlings are crowded and where humidity is high, leading to a rapid collapse. The fungi are often visible as a whitish growth of mould on the rotting plants.
Grey mouldDisposing of diseased materialSeed: sowing indoorsSeed: sowing outdoorsVegetable seeds: sowing
the RHS today and get 12 months for the price of 9
RHS members can get exclusive individual advice from the RHS Gardening Advice team.
Register for the site or sign in to share your experiences on this topic and seek advice from our community of gardeners.
We're a UK charity established to share the best in gardening. We want to enrich everyone's life through plants, and make the UK a greener and more beautiful place.
Join the RHS today and get 12 months for the price of 9