Damping-off diseases can be prevented:
* Purchase disease free plants and seeds. Know your supplier. Do not be afraid of fungicidal coatings on seeds which will be direct sown out doors in cold soils, such as corn and peas. Seed borne disease can also be avoided by soaking the seeds for 15 minutes in a bleach soak (one teaspoon per quart of water) prior to sowing.
* Use sterile well drained soil mediums. See article on soil mixes. Try to maintain a soil mix pH at the low end of the average scale, i.e. 6.4 pH is less susceptible to root rot than a pH of 7.5. Commercially prepared germination mixes usually have a pH around 5.5. As you water the seed pots and your seedlings with tap water (which in many municipalities is quite alkaline), the pH in your pots gradually increases as does the susceptibility to damping-off diseases. Know the pH of your tap water, and condition it if necessary to maintain a lower pH while the plants are still in the germination room. I prefer the use of vinegar at the rate of one tablespoon per gallon of water.
* Plants must not have their crowns below the soil line. Seeds must not be covered more than 4 times the thickness of the seed.
* Use plant containers with drainage holes, water from the bottom only, and avoid excess watering. Do not allow pots to stand in water as excess water cannot drain and the roots will be starved for oxygen bringing all growth to a halt.
* Avoid overcrowding and overfeeding of plants. It is important to maintain constant levels of growth through proper lighting and complete control of the growing environment.
* Avoid working with plants (taking cuttings or transplanting) when the soil is wet. Do not use water from ditches or drainage ponds or rain barrels in the germination room.
* Avoid spreading soil from infested areas or tools which have been used out of doors. Disinfect tools and containers with one part bleach in four parts water or with 70 percent rubbing alcohol (isopropyl).
* In the germination room, sow all your seeds on the surface of the media, then cover the seeds to necessary depth with a material which is less likely to harbor fungi than the media itself. Use one or more of the following seed toppings instead of soil mix:
o milled sphagnum moss
o chick grit
o course sand or fine aquarium gravel
o composted hardwood bark (steamed)
* In the germination room, mist seedlings in communal pots or flats once or twice per day with water containing a known anti-fungal agent such as:
o Captan (or other approved fungicide) especially if walls or floors are damp, or
o Cheshunt compound, a copper/aluminum formulation, or
o chamomile tea, or
o clove tea, or
o a one-time light dusting of powdered cinnamon on the soil surface, or
o a one-time light dusting of powdered charcoal on the soil surface, or
o if stinging nettle is endemic in your area, make a fermented infusion to use like clove tea.
These last five actions are suggested by sufficient anecdotal evidence to prove the existence of a low level of fungicidal activity. I would not hesitate to use them in germination environments which have no history of damping-off diseases.
* Rotate plantings on a 2 to 3 year schedule using plants from different families in order to starve out existing pathogens.
* Provide constant air movement not tied in with the light timer. Air should move freely 24 hours per day, but not directly aimed at the plants. This helps the seedlings to aspirate, and excess soil moisture to wick. If you do everything else right but do not provide plenty of air movement, you will still get damping-off.