Putting the Damper on Damping-off

Melanie Mathieson

Wednesday, Apr 8, 2020
When starting seeds indoors, you must be concerned with a disease called damping-off as it can quickly turn your young seedlings into a complete crop failure almost overnight, setting your gardening schedule back by weeks.

Damping-off can be caused by any one of the many types of soil fungus. Pre-emergence damping-off occurs when the sprouted seeds rot in the soil, shortly after they germinate. The seedling never emerges from the soil and the gardener doesn’t know what happened and just chocks it up to poor seed quality.

Post-emergence damping-off occurs either as the seedlings emerge or shortly after they emerge from the soil and show signs of wilt or a rot-infested spot on the stem. The seedling then wilts, collapses and quickly dies because the fungus has girdled the stem with infection, preventing the seedlings from being able to draw the required nutrients and water it needs to grow. Damping-off can affect almost any seedlings but is most common with lettuce varieties, spinach, beans and other vine plants (cucumber, squash, etc.) cabbage, eggplant, peppers, tomatoes, onions, corn, beets, carrots and flowers like petunias and snapdragons.

Using a high quality sterilized soil or soil-less mix is one of the best ways to prevent damping-off as well as using seed that has been treated with a fungicide. If the seed has been treated it will be indicated on the seed package and the seed will have a coloured coating on it which is very poisonous.

Make sure all of your pots, planting trays and containers are clean and sanitized if being reused, by using a bleach solution (60 milliliters of bleach per four litres of warm water). Use only plump, healthy and crack-free seed. Do not over water or fertilize the seedlings excessively, especially when they are first emerging from the seed and soil. Adding water to the bottom of the tray or a fine sprinkling of watering on the surface can help you control the amount of water added. Also, don’t let the condensation get too thick on the clear cover of the planting tray or container. If you see mould or an over abundance of condensation developing, remove the cover and wipe dry before replacing.

Make sure seedlings receive adequate light, good air circulation and are never overcrowded. Seedlings that receive too much heat or light can grow quickly and become leggy, while not enough light makes a pale and weak seedling, making the seedling more susceptible to damping-off. You can improve air circulation by using a fan on low near the seedlings. Just don’t put the fan so close that you create a strong wind for fragile seedlings.

Now that you understand what damping-off is and how it can be prevented, you can certainly proceed with confidence and get those seedlings started. I may have even solved the mysteries of some of your past crop failures. Now you won’t have to let damping-off put a damper on your gardening experience.

Melanie Mathieson – Gardening Guru