IDENTIFICATION – Damping off can be a problem for gardeners who start seeds inside. It is usually caused by cool, damp soil. The fungi that cause this disease can attack seeds before they germinate, although the most common symptom is seen on seedlings. An otherwise healthy seedling suddenly tips over. If you look closely at the stem near the soil level, you will find a pinched-in area. In a day or two the top part of the seedling will wilt and die. Damping off can kill an entire flat of seedling in just a few days.
CONTROL – It’s easier to prevent damping off than “cure” it. To start, sterilize everything – flats and tools – with a 10-percent bleach and water solution. Be sure to use sterilized seed-starting mix that is fresh. After sowing your seed, keep the flats in a warm area. Once the seedlings are up, slow down the watering. Let the top layer of soil feel dry to the touch before watering again. Also, don’t mist the flat between waterings. You can also turn on a fan to keep the air moving; just don’t aim it directly at the seedlings.
Commercial greenhouses use fungicidal soil drenches to prevent damping off, but home gardeners don’t have access to those chemicals. Good sanitation is the best bet for healthy seedlings.