When apparently healthy seedlings die suddenly soon after germination the likely cause is “damping-off.
Symptoms and Diagnosis
Damping-off is caused by a number of soil fungi in several genera including: Rhizoctonia, Pythium, Botrytis, Phtyophthora, and Fusarium and is often accompanied by low rates of germination. Stem tissue on the seedlings may appear to look “burned” and water soaked lesions appear at the soil line and girdle the stem. Occasionally, white/pink/gray cottony fungus may appear at the base of the stem.
Life Cycle
The fungi that cause damping-off are ubiquitous and can multiply and readily infect seedling when conditions favor their development. There is no recommended cure for damping off. Survivors are generally weak and non-productive. However, there are actions which can reduce the likelihood of the condition reoccurring. These include elimination of pathogens and control of environmental conditions.
Integrated Pest Management Strategies
1. Sanitation. Dispose of all plants and soil in the affected containers and washing all containers and tools with soapy water and soak/rinse with a 10:1 bleach solution.
2. Start clean. When starting seeds always use a sterile soil-less growing mix. Do not use garden soil or reuse contaminated soil.
3. Use seeds treated with a fungicide, if available.
4. Provide an environment that is not conducive to the development of the disease. After seeds germinate place plants in an area with good air circulation. Remove plastic or glass coverings after half of the seeds have germinated. Bottom water seedlings and do not overwater. Thin out and fertilize seedlings after the first true leaves have developed. | 
