Nothing is quite as frustrating for home gardeners than the joy of seeing newly planted seeds begin to sprout and flourish one day, and then discovering them collapsed and wilted the next. Damping off is a fungal disease that makes seemingly healthy seedlings suddenly topple and die, or at times, never emerge at all. Although damping off is usually fatal, it is preventable. With a little attention to detail combined with good planting practices, your young seedlings will continue to grow into the healthy plants you want them to be.
A number of pathogens live in the soil, just waiting for the right conditions to occur before they step forward. The common fungi that cause damping off are Pythium, Phytophthora and Rhizoctonia. Each are microscopic organisms that, when they come in contact with a root or stem system will penetrate the plant and disrupt the normal growth and cell development process of the plant. These pathogens all grow and thrive in poor soil and less-than-ideal environmental conditions.
Use a good quality, soilless potting mix to start your seeds. Fresh potting soils are usually free from harmful organisms and the nature of the mix provides good drainage, another important factor in reducing the risk of damping off. Soggy soil encourages fungal growth. Keep open bags of soil away from floors and any unclean surfaces that could transfer contaminates into the clean seeding medium. When planting, also be sure to plant the seeds at the soil depth as indicated by the seed package. Planting seeds deeper than recommended in any soil could slow (or stop) their germination process and ultimately damage the seeds or young plants.
Good air circulation and room ventilation are other key factors in reducing humidity buildup that promotes pathogen growth; do not crowd pots, flats, or the seeds when planting. If you do have multiple seeds in a pot, as they begin to grow thin the seedlings by removing the weakest looking and keeping those that are growing the strongest. Thinning helps to keep the air adequately flowing around the seedlings, which reduces the amount of moisture on the plants. When thinning, snip or gently pull out crowded seedlings, referring to the seed package for the right spacing for the plant being grown.
Temperature and Water
Cool soil temperatures before the seeds begin to germinate promotes the risk of damping off. Help ensure healthy seed germination by keeping the soil at a consistent 20-24 degrees Centigrade (70-75 Fahrenheit) during the seeds’ early growth period. Keep the soil evenly moist but not waterlogged until the risk of frost passes and weather conditions are favourable to move the growing plants into an outdoor garden area.
Many pathogens, including those that cause damping off are transferred to new plantings via garden tools. Before working with plants and soil, or after contact with any diseased growth, rinse your tools in a week solution of one part bleach to nine parts water. Leave the solution on the tools for at least 15 minutes, rinse them off and allow the tools to air-dry. Planting seeds in new pots and flats as often as possible also helps prevent contamination. If, however, using new pots and flats each year isn’t practical, sterilize the containers along with your tools to provide the optimum environment for new seeds. And always remember to wear eye protection and gloves when cleaning pots and tools.