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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 of seedlings
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
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