Damping off is the single term used to describe underground, soil line, or crown rots of seedlings due to unknown causes. The term actually covers several soil borne diseases of plants and seed borne fungi. The fungi which cause root rot are species of Phyium, Phytophthora, Rhizoctonia and Fusarium.

There are two types of damping off: pre-emergence and post- emergence. In pre-emergence damping-off, seeds may rot and seedlings may decay before they emerge. In post-emergence damping off the seedlings emerge then may pale, curl, wilt, and collapse from a rot at the soil line and below. The base of the stem is generally water-soaked at first then turns gray to brown or black then rots.

Vegetable seedlings often do not grow well under humid conditions, particularly if the soil is cold and wet. Damping off fungi flourish in moist, unhygienic conditions. The disease often starts at one end of a seed tray, and quickly spreads to the other end. A fluffy fungal growth may also appear on the soil surface as well as on the dead seedlings.

When preparing to plant be sure that flats, tools, plant containers, and benches are clean. Damping off pathogens can live in these containers. The easiest way to disinfect them is to dip them in a bleach solution for 10 seconds. Use 1 part bleach to 4 parts water. Or use 70 percent rubbing alcohol.

Plant in a light, well drained fertile seedbed. Preferably use sterile soils that have been pasteurized with heat before planting. Maintain a soil pH at the low end of the average scale. A soil of 6.4 pH is less susceptible to root rot than a pH of 7.5. As plants are watered the pH gradually increases. Test often and continue to maintain a lower pH while the plants are still germinating. If necessary use one tablespoon of vinegar to 1 gallon of water to lower a rising pH level.

Plant seeds no deeper than 4 times their own thickness. Keep the seedbed soil on the dry side after planting and allow plenty of bright light but not direct sunlight.

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 which will stop all growth of seedlings. Never water late in the day.

Avoid overcrowding and overfeeding of plants. Do not overfertilize, especially with nitrogen.