Damping off disease is a common term for deadly soil-borne fungi that attack seeds, stems, and roots of seedlings. Phytophthorathat, pythium, fusarium, and rhizoctonia fungi live in the soil and water and thrive in humid conditions, with cold wet soil. Pythium is the most common culprit. The fungi spores are spread through the air and affect nearby plants in your seed trays or garden rows.
Types of Damping Off Disease
Pre-emergent damping off: They seeds will rot under the soil before they ever emerge
Post-emergent damping off: The seeds sprout, sometimes can be very healthy but as the fungi set in they will wilt or collapse to the soil line. The stem looks mushy and will turn black or a dark color. It will disintegrate and the plant will die.
Identifying Damping Off Disease:
The affected plants will look like they have been cut at the base. They will be wilted, falling over, and dying. The stems can be brown and look like they are rotting near the soil. Sometimes you may see a white mold-like growth on the soils surface.
Prevention of Damping Off Disease:
Pots & Soil:
Start with potting containers that are sterile. If you are re-using pots, rinse them in a bleach solution (1 part bleach to 9 parts water) before planting.
Use sterile potting mix. Soil-less mix is the healthiest as rich potting soils can encourage fungi growth. If unsure about your potting mix you can bake it in the oven at 200°F for 30 minutes to sterilize it.
Make sure your soil level is near the top of the pot or tray to help air circulate over it.
Make sure to have good soil drainage and plant your seeds at the recommended depth.
Sow seeds thinly so airflow is not reduced from overcrowding.
Placing a thin layer of perlite, peat moss, or even sand on the surface of the potting mix will discourage the fungi and bacteria.
Once your seedlings have become big and strong you can move them to a good rich potting soil. Plants produce a secondary stem tissue as they become older which forms a protective barrier that limits fungi from penetrating the stem. Older plants are seldom killed by damping off disease.
Air & Temperature:
Maintain an even warm temperature with good air circulation. Run a fan if needed. Make sure the conditions are not damp and cool as fungi will thrive. If you have seed starting trays with a lid, crack the lid open just a bit so air can flow through.
If you are using seed starting trays water from the bottom. If you must water from the top water only the soil not the leaves and stems.
If available use rain water as it has a lower ph than tap water. A high ph level increases the susceptibility to damping off.
Water early in the day to ensure the surface of the soil and plants are dry by evening. Be careful to not overwater.
Garden tools can transport the fungi. Be sure to also disinfect your tools with a bleach solution before reusing.
Fungicide and beneficial bacterium prevention options:
Spraying or drenching the soil with a recommended anti-fungal treatment helps suppress the disease. Many options including organic can be found at your local store.
A homemade preventative is a garlic and water mix. 10 cloves of garlic combined with one pint of water in a blender. Strain completely and spray onto plants and soil weekly. This is also a good pest preventative.¹
Infected plants with damping off disease:
There is not a cure for infected plants. Upon discovering your plants have dampening disease remove them from the area immediately. Damping disease can spread very quickly from one plant or tray to another. Dispose of the infected plants and soil. Do not place in your compost pile. The disease will spread to your plants next year when you use the compost. If you keep the container your plant was in, be sure to disinfect it with the bleach solution.
Infected plants with damping off disease:
There is not a cure for infected plants. Upon discovering your plants have dampening disease remove them from the area immediately. Damping disease can spread very quickly from one plant or tray to another. Dispose of the infected plants and soil. Do not place in your compost pile. The disease will spread to your plants next year when you use the compost. If you keep the container your plant was in be sure to disinfect it with the bleach solution.