Many gardeners have experienced the disappointment of sowing seeds, watching them germinate, and carefully tending the tiny, apparently healthy seedlings only to find them one morning keeled over dead and rotting. The cause is an attack of damping-off fungi. These pathogens can kill seedlings even before they emerge from the soil.
Damping-off fungi are present in most gardens, and virtually every kind of seedling is vulnerable; no resistant cultivars have been developed.
Nevertheless, the disease can be prevented if you take a few simple precautions. The most important step, is to minimize the risk of exposure to the fungus itself. It is also important to avoid high nitrogen levels and excess moisture in the soil and to ensure adequate light, whether natural or artificial. Poor light results in spindly seedlings that are more likely to infection.
Tips for starting healthy seedlings:
Seeding Indoors. Use either a new container or if using used containers, disinfect with a 10 percent bleach solution. Dry. Fill planting containers with a sterile seedling mix. Do not use compost or garden garden soil, since it may contain damping-off fungi. Sow seeds, cover to depth suggested by the seed pack with vermiculite or perlite, both of which are free of pathogens and drain quickly. Water, but do not let containers soak in water. Before watering again, be sure soil is not already moist. If the soil is to wet , it can and likely will encourage damping-off fungi. Keep soil slightly moist, but let the surface dry out slightly before watering. Air circulation will encourage healthier growth. Using a fan works well. Keep seeds away from cold drafts such as a window at night when temperatures are cooler. Windows are great to put your seedling in for the sunlight during the day, but remove from the window sill at night, as windows can be cold at night time. Do not fertilize with nitrogen until the seedlings begin to produce true leaves- these follow the first growth of leaves to sprout.
It’s so satisfying starting your own selected seeds at home. Not only do you have a larger selection when choosing from seeds, but its more rewarding. Kids love to start seeds indoors too!
Out Standing In The Garden 
Damping off is why I REALLY do not like to start seedlings inside. Because our warm growing season is so long and starts so early, there is no need to start anything inside, although many of us do. I find that those sown directly grow so efficiently that they catch up and pass the seedlings. However, there are a few that get started inside, mainly those that are likely to get eaten by snails if sown directly. (Larger seedlings are less likely to get eaten.) Damping off is a serious problem in nursery production!