seedling damping off

Damping off Disease of Seedlings

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Damping off is a term used for the sudden death of new plant seedlings.   It can be caused by any of a handful of fungal diseases, including several root rots (Pythium, Phytophthora) and molds (Sclerotinia or white mold, Botrytis or gray mold).


When young seedlings seem to be growing healthy one day and dying the next, it is probably being caused by damping off. Damping off can affect the stems of seedlings both below the soil line and above.   Some seedlings may start to grow and suddenly whither. Others will have stems that appear pinched or broken, causing them to collapse while they still have their cotyledons attached. You may see some gradual discoloring or it may happen very suddenly. Often it appears the seedling has been pinched off at the soil line.

Seedlings with root rot can appear to be wilting, even when kept watered. Even poor germination may be attributable to damping off. If your seedlings were growing along fine and suddenly wilt and die, it’s a good bet they have succumbed to some form of damping off disease.

What to Do If Your Seedlings Get Damping Off

There is no cure for damping off, once it occurs. The tiny seedlings die so quickly, you probably would not have time to help them if you could. That’s why it is important to try and avoid the problem altogether, with the following prevention practices.

Damping off spreads rapidly.   If you should spot signs of damping off, remove those seedlings immediately and apply one of the homemade fungicides described below, to all remaining seedlings.

Prevention Tips

  • Use a sterile potting mix, rather than soil from your garden. The funguses and molds that cause damping off can live in the soil and outdoor garden soil can harbor all kinds of fungus spores.
  • Start with clean pots. Even the small amount of soil clinging to plant pots is enough to provide a safe harbor for fungal spores. If reusing pots, sterilize in 1 part bleach to 10 parts water.
  • Plant your seeds at the proper depth so they don’t have to work so hard to germinate. Don’t bury the plant’s crown.
  • Don’t crowd your seedlings. Be sure to leave room between them for air circulation. Fungal diseases and mold favor damp conditions.
  • Water seedlings from the bottom, by placing the container in a tray of water. This keeps the seedling itself dry and less susceptible.
  • Add a thin coating of sand or gravel on top of the potting soil, to keep the surface relatively dry. The soil underneath will remain moist, even if the sand or gravel dries out.
  • Don’t overwater your seedlings or leave them sitting in water. Drain off any excess.
  • If possible, create a breeze by placing a small fan nearby and turning it on periodically each day. This will prevent humidity from settling on your seedlings.
  • Give your seedlings plenty of heat and light, so they germinate and grow quickly. Damping off only affects seedlings. If you can get them past the seedling stage, they’re safe.


Remove any affected plants or trays of plants immediately. Damping off will quickly spread to nearby plants.

Protection Tips

  • Sterilize your own soil: Sterilize small quantities of soil by heating it.   Doing this in the oven gives off an unpleasant odor, but microwaves don’t seem to produce the same problem. Place dampened potting mix in a microwave-safe container and cover loosely. Microwave on high for 8-10 minutes, until you see condensation under the lid. Close the lid and let the potting mix cool on its own. Caution, it can get surprisingly hot.
  • Make your own organic fungicide: You can use any of these three homemade concoctions as a preventative. They will not cure damping off once it has started, but they will give you an edge to prevent it from taking hold.
    • Prepare a strong brew of chamomile or cinnamon tea and use it to water and/or mist your seedlings.
    • Mix a splash (1 T.) of 3 percent solution of hydrogen peroxide/quart of water and mist the seedling with it.
    • Apply a light dusting of cinnamon on the soil surface.

A strong, commercial fungicide is a last resort for controlling damping-off and will probably be applied too late to be effective. Sadly, sometimes you have to be prepared to start over. If so, be prepared to take precautions ahead of time.

Damping off is a term used for seedling death caused by any of a handful of fungal diseases. There is no cure, but here are some tips to prevent it.

How to prevent seedling damping off

Quick facts

Damping off is a disease of seedlings

Seedlings infected by damping off rarely survive to produce a vigorous plant. Quite often a large section or an entire tray of seedlings is killed.

Once plants have mature leaves and a well developed root system, they are better able to naturally resist the fungus or mold that causes damping off. There is a critical period of growth between planting and maturity when special care needs to be taken to protect sensitive seedlings.

A wide variety of vegetables and flowers can be affected by damping off. Young leaves, roots and stems of newly emerged seedlings are highly susceptible to infection. Under certain environmental conditions, damping off pathogens can cause root rot or crown rot in mature plants.

The fungi, Rhizoctonia spp. and Fusarium spp., along with the water mold Pythiumspp. are the most common pathogens responsible for damping off.

Identifying damping off symptoms

  • Seedlings fail to emerge from the soil.
  • Cotyledons (the first leaves produced by a seedling) and seedling stems are water soaked, soft, mushy and may be discolored gray to brown.
  • Seedling stems become water soaked and thin, almost thread like, where infected.
  • Young leaves wilt and turn green-gray to brown.
  • Roots are absent, stunted or have grayish-brown sunken spots.
  • Fluffy white cobweb-like growth on infected plant parts under high humidity.

What causes damping off

All of the pathogens (fungi and molds) responsible for damping off survive well in soil and plant debris.

The pathogens can be introduced into the seedling tray in several ways.

  • Pots, tools, and potting media that have been used in previous seasons and are not properly cleaned can harbor the pathogens.
  • Spores of Fusarium spp. can be blown in and carried by insects like fungus gnats, or move in splashing irrigation water.
  • Pythium spp. is often introduced on dirty hands, contaminated tools or by hose ends that have been in contact with dirt and debris.

Once introduced to a seedling tray, the damping off pathogens easily move from plant to plant by growing through the potting media or in shared irrigation water.

Garden soil often contains small amounts of the damping off pathogens. If you use garden soil to fill seedling trays, you could introduce the damping off pathogens that cause the disease into the warm wet conditions best for seed growth.

Seeds planted directly into the garden can also suffer from damping off. Disease is particularly severe when seeds are planted in soils that are too cool for optimal germination or when weather turns cool and wet after planting resulting in slow germination and growth.

The damping off pathogens thrive in cool wet conditions. And any condition that slows plant growth will increase damping off. Low light, overwatering, high salts from over fertilizing and cool soil temperatures are all associated with increased damping off.

Seedlings infected by damping off rarely survive to produce a vigorous plant. Find out how to recognize and prevent damping off.