Damping off

Damping off is the term used for a number of different fungus-caused ailments which can kill seeds or seedlings before or after they germinate.

The term is used most often in horticulture, where seeds are specifically planted to be germinated, especially if in warm, wet conditions which speed growth but are considered conducive to fungal attacks.

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Symptoms

A given seed can become infected with a fungus, often causing it to darken and soften. This can kill it before the seedling emerges, or cause the seedling to be weak, sometimes getting "wet" patches on it which decay until it falls apart.

Likewise, a seedling can be infected after it sprouts, but before it leaves the ground, or even after it appears well-developed, the latter often resulting in the plant mysteriously thinning right where it touches the ground, until its stem at that point rots and it falls over.

Causes

A number of different fungi cause these problems, including:

• Botrytis, also known as "grey mould".
• Macrophomina phaseoli
• Phytophthora
• Pythium
• Rhizoctonia solani
• Sclerotium
• Thielaviopsis

Prevention

Damping off can be prevented in many different ways, including germination in dryer conditions with better air circulation (but this slows germination), starting seedlings in sterilized soil, and/or spraying the soil with an anti-fungal known to work for this purpose, either a commercial one or a homemade solution, such as one made from chamomile tea or garlic.

References

• Damping off of seedlings University of Minnesota Extension Office
• Damping-off disease
• How to prevent damping off] EHow.com