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  • Writer's pictureW. H. Perron


The damping-off of seedlings is caused either by different species of fungi present in the soil and also the growing region.

In Quebec, damping-off of seedlings is often due to Pythium fungi such as Pythium debaryanum, P.irregulare, and P.ultimum, resulting in Pythian rot. Damping-off can also be caused by the bacteria Rhizoctonia solani or the common rhizoctonia.


1. Root rot before germination: the seeds rot before germination or the seedlings die before lifting.

2. Root rot after germination: rotting of stem and roots tissues at the soil surface.

Seedling damping-off is often observed in cold and wet soil, in open-field or breeding ground. Stagnant humidity is also a factor that will help develop the disease.

This disease will attack seedlings and can appear soon after planting or at the plantlet stage. The tomato, for example, will no longer be at risk after the 2 or 3 leaves stage.


When 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 discolouring 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.

* All means of controlling seedling damping are preventive, rather than curative.


  • Use a sterile potting mix, rather than soil from your garden. The fungi and moulds that cause damping off can live in the soil and outdoor garden soil can harbour 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 harbour for fungal spores. If reusing pots, sterilize in 1 part bleach to 9 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 mould favour 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.


* Sterilization

Sterilization of the soil (potting soil) is a sure way to control the disease, however, as it is always to be started again; it is not a long-term solution.

But that is recommended if you reuse the soil from other seedlings or a plant.

Put potting soil in a glass or metal dish, no more than 10 cm thick at a time.

Cover with aluminum foil.

Heat in the oven for 30 minutes at 80 ° C to 95 °C.

* Disinfection of tools and containers

A. Boil tools and containers in water at 70 °C for 30 minutes.


B. Bathe them in a solution comprising one (1) part of household bleach for nine (9) parts of water.

* Make your own organic fungicide

You can’t use any of these homemade concoctions as prevention. They will not cure damping off once it has started, but they will give you to prevent it from taking hold.

* Chamomile tea

Put 50 g of dried chamomile flowers in boiling water and leave to infuse for 24 hours.


Water and mist your seedlings. Chamomile can be used for prevention, but also after the appearance of the first symptoms to stop the development of the disease. It is not worth saving excessively weakened plants.

* Garlic tea

1. Finely chop 100 g of garlic

2. Place garlic in one (1) litre container with a lid.

3. Cover with boiling water and close.

4. Then place in a warm or sunny place for three days.


Water, the soil with the garlic tea at the time of sowing and each time it is watered. Avoid overwatering.

* Horsetail decoction

1. Dip dried horsetail, 50 g/litre of water and leave to macerate for 24 hours.

2. Boil everything for 20 minutes, cover and let cool.


Put the seed in the horsetail decoction for 10 to 15 minutes.

Dry the seed out of direct sunlight.

Sow the seeds within the next two days.

Water, the seedlings during germination with the decoction.

Spray the decoction of horsetail on the ground.

* Horseradish extracts

1. Finely chop and place in a blender 100 g of horseradish leaves and roots.

2. Put in a litre of water and let stand 24 hours.

3. Extract the liquid using a fine cloth while pressing.


Put 10 drops of extract in one (1) litre of water and stir for 15 minutes.

Deposit the seed in the decoction from 10 minutes to 15 minutes.

Then dry out of direct sunlight.

Sow the seeds within the next two days.

* Broad-leaved dock (Rumex obtusifolius)

1. Harvest flowers that have just hatched.

2. Cut, moisten and pass them through the blender.

3. Extract the liquid using a fine cloth while pressing.


Put 10 drops of extract in one litre of water and stir for 15 minutes.

Put the seed in the decoction from 10 minutes to 15 minutes.

Dry out of direct sunlight. Sow the seeds within the next 2 days.

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