CONTROLLING DAMPING OFF IN SEEDLINGS
Damping off — a condition where a seemingly healthy seedling suddenly dies, is easily preventable with the following tips and guidelines.
Purchase disease free plants and seeds. If someone gives you seed, disease can be avoided by soaking the seeds for 15 minutes in bleach (one teaspoon per quart of water) prior to sowing.
Use sterile well drained seeding mix. 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. You can acidify a container or growing flat with 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. Try 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 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).
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 harbour fungi than the media itself, like coarse sand, milled sphagnum moss (peat).
Mist seedlings in communal pots or flats once or twice per day with water containing a known anti-fungal agent such as:
- chamomile tea
- clove tea
- a one-time light dusting of powdered cinnamon on the soil surface
- a one-time light dusting of powdered charcoal on the soil surface
These are suggested by sufficient anecdotal evidence to prove the existence of a low level of fungicidal activity and are worth a try 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.
Good results have been documented by using bio-fungicide containing Bacillus subtilis QST 713, a bacteria that suppresses many different types of fungus sprayed on the soil and seedlings.