by Matt Gibson
About Damping Off
Damping off, or seedling disease, is a term used for the sudden death of new plant seedlings. It is usually caused by a fungal disease, most often by one of several root rots or molds. Seedlings that are affected by damping off often fail to emerge, or fall over and die soon after emerging.
Most seedlings that are affected by damping off rarely grow to produce a strong, fruit bearing plant. Once your plants have matured, and have a well developed root system, they are much more capable of resisting the fungus or molds that cause the disease.
There is a period of critical time of growth, between planting and maturity, in which extra special care must be practiced to protect very sensitive seedlings from soil-borne diseases. A wide variety of vegetables and flowers are affected by damping off. The young, underdeveloped leaves, roots, and stems of newly emerged seedlings are prone to succumbing to infections.
Especially in soils with poor drainage, in damp, cool conditions, early on in the growing season, damping off thrives. Generally, damping off is only an issue in areas with poor soil conditions, or where soil is too compacted, but the disease can affect entire fields of crops, causing significant losses.
Causes And Symptoms of Damping Off
Common root rots Pythium and Phytophthora, the fungi, Rhizoctonia spp. and Fusarium spp., and molds such as Botrytis (gray mold) or Sclerotinia (white mold), are often the causes of damping off. Fungi and mold survive well in damp soil and plant debris, and they can be introduced into your garden through pots, tools, and potting media that has been used in previous seasons and is not properly cleaned and sanitized.
Reusing old pots is fine, but be sure to sanitize them with a good soak in a ten percent bleach solution to kill away any pathogens that might cause damping off. Fungal spores can be blown into your garden on the wind or carried in by insects like fungus gnats. The spores can also be splashed onto the seedlings during rains or irrigation. Pythium is often caused by dirty hands or contaminated tools.
Once introduced to a seedling tray, the pathogens easily spread through the soil, or through the irrigation. Garden soil often contains small amounts of the pathogens. If you use garden soil for seedling trays, you may be introducing fungi and mold pathogens to a cool, wet environment, a perfect recipe for damping off.
Damping off symptoms include seedlings that fail to emerge from the soil, seedling stems and first leaves appear water soaked, soft, or mushy, and oftentimes discolored gray or brown. Stems sometimes become very thin, or thread-like where infected. Young leaves begin to wilt, roots are absent, or stunted with sunken gray or brown spots. Sometimes you can even spot a white, web-like fluffy fungal growth near the soil on infected plants.
When young seedlings appear healthy one day and dying the next day, it’s usually a sign of damping off. Damping off affects the stems of seedlings both above and below the soil line. Some affected seedlings will grow and quickly wither, while others will appear to be pinched or broken near the soil line, collapsing with their young healthy-looking leaves still attached. Sometimes, damping off causes a gradual discoloration and wilting, however, most cases of damping off cause a very sudden death of a large group of seedlings.
Treatment and Control of Damping Off
Damping off spreads very quickly. If you happen to notice signs of damping off in your seedling trays, remove all infected seedlings immediately and apply a fungicide to the remaining plants. There is no cure for damping off once it occurs, as the seedlings tend to die off too quickly to respond to treatment, so it is best to prevent damping off from occuring in the first place by practicing the following control methods:
- Use clean pots. If reusing old pots, sterilize thoroughly by cleaning them well and then soaking them in a ten percent bleach solution for at least 30 minutes. Sterilize any garden tools you will be using as well. Store garden tools in a clean location when they are not in use.
- Avoid using garden soil or reusing old potting soil for seedling trays. Instead, use new potting mix, preferably a potting mix that is specifically made for seed starting to fill your starter trays. Make sure that your seed starting mix is light and fast draining.
- Plant your seedlings so that the soil surface is close to the top of the container to promote proper air circulation.
- Plant your seeds at the appropriate depth so that they don’t have to work extra hard to germinate.
- Overcrowding seedlings can lead to more humid conditions, so sow your seeds thinly.
- Seed starting trays which provide water from below are better than overhead watering.
- For indoor seed starting, use a heating pad underneath trays to warm soil to 70-75 degrees F.
- For outdoor planting, wait until the soil has reached optimal temperatures for germination before moving seedlings outdoors. The optimal germination temperature varies depending on the plant.
- Use a potting mix with ample drainage and pots with sufficient drainage holes to help keep soil moist but never soggy.
- Keep garden hose and water heads off of the ground to keep stagnant water well away from your garden soil.
- Never water past noon so that seedlings and soil surface is dry by evening time.
- Use clean, warm water to water your seedlings, preferably between 68-77 degrees F, as cool water, or water 50 degrees F and below increases the likelihood of infection and slows growth significantly.
- Avoid overwatering seedlings. Drain off any excess water if necessary.
- Create a natural breeze by placing a fan nearby and turning it on periodically during the day to combat humidity and help keep your seedlings dry.
- Concoct your own organic fungicide and use it as a preventative treatment. A light dusting of cinnamon on the soil’s surface, a three percent hydrogen peroxide solution (one tablespoon of hydrogen peroxide mixed with one quart of water), or a strong brew of chamomile or cinnamon tea can be used in place of regular water for irrigation.
- Organocide Plant Doctor can be applied as a foliar spray or soil drench to combat a large number of fungal disease issues.
- Add a ¼ strength standard soluble fertilizer once several true leaves have developed. Alternatively, use a potting mix that contains a slow-release fertilizer.
- Light from a window is insufficient for seedling development. Instead, provide 12-16 hours of light from a soft white fluorescent light, or a grow light.
Common Questions and Answers About Damping Off
Can you stop damping off?
No, damping off cannot be stopped once the disease has taken hold of a plant, as it kills seedlings off too quickly for treatments to have any effect. Preventative methods are the only effective way of combating damping off issues.
What does damping off disease look like?
Seedlings affected by damping off fail to emerge from the soil or fall over and die soon after emerging. Stems usually have a discolored and shriveled section near the soil line. Healthy young seedlings look pinched or cut off at the base of the stem. They wilt, droop, wither, and die. A white, mold-like growth sometimes appears near the base of seedlings on the plant and the topsoil around the base of the plant.
Does cinnamon prevent damping off?
Though more research is needed, cinnamon does have antifungal and antimicrobial properties. True cinnamon is more effective than fake cinnamon, essential oils are more effective than other forms of the extract. If you are using a spice to treat damping off, cinnamon is your best bet, and though it probably works to some degree, there is no direct scientific research that proves cinnamon’s effectiveness in treating or preventing damping off in seedlings.
What is damping off in tomatoes?
Damping off is the term for a group of deadly seedling diseases which are fatal for tomato seedlings. Caused by several different fungi, damping off attacks tomato seeds, stems, and roots. Most affected by cold, wet, humid conditions, young seedlings are susceptible to infection, and damping off disease can be devastating to a new tomato crop. Once the infection is underway, it’s hard to save even a handful of your plants. Prevention is the best cure.
How does damping off spread?
Damping off disease thrives in cool wet humid conditions in wet or soggy soils. It is airborne and can spread quickly from one seed tray to the next. Fungal spores take root in your soil and spread quickly and easily across the seed tray and can jump to other nearby trays easily.
Can a plant recover from damping off?
There is no cure for plants that have been affected by damping off. However, the problem can easily be prevented by providing good air circulation and by practicing safe control methods.
What is damping off and how can it be avoided?
Damping off is a horticultural infection caused by several different pathogens that kills or weakens seeds or seedlings before or just after germination. It is most prevalent in wet, cool, humid conditions. It cannot be cured or treated once infection has started, but it can be avoided by practicing preventative control methods. Avoid overwatering, promote proper air circulation, and use sanitized containers and equipment when starting seeds to avoid damping off issues.
Want to learn more about damping off seedling disease?
University of Minnesota Extension covers How to Prevent Seedling Damping Off
University of California covers Damping Off
Planet Natural covers Damping Off
the Spruce covers Damping Off Seedling Disease