Damping off is a fungal disease that can kill or weaken seedlings both before and/or after they germinate. It can affect both beginner and experienced growers when starting seeds and is caused be several strains of fungal organisms including alternia, pythium, rhizoctonia, fusarium, and phytophthora.
Damping off typically occurs when old seed is planted in cold, wet, and poor draining soil. High humidity levels and seeds planted too deep can also encourage the growth of these fungal organisms. Symptoms include a pinched stem right at the soil line, followed by the seedling falling over, withering, and quickly dying. As the seeds start to grow and develop their roots, the fungus attacks the roots. If the roots can’t grow fast enough, the plant will die.
To minimize the chance of damping off affecting your plants, growers should use a sterile potting soil mix and sanitized tools and equipments. The disease can carry over from pots that are reused so a good wash using hot soapy water or a mild bleach solution will minimize the spread of the disease. In addition, good watering practices (i.e. not letting the soil stay too wet for extended periods of time) and good air circulation will help to prevent the disease from taking hold.
Another tip will be getting your seeds to germinate quickly and grow quickly will also minimize the chance of disease. This can be accomplished by providing your plants with adequate light and heat, especially if starting seeds indoors in the winter.
Finally, natural fungicides like can be used such as misting with chamomile tea, misting with clove tea, or a light dusting of cinnamon on the soil surface can be used to protect your seeds and seedlings just as they’re starting to grow. OMAFRA has additional information on the different strains of damping off organisms for additional information.