Damping-off (seedlings)
Seedlings that fail to emerge, or topple and collapse from a water-soaked, pinched rot at soil level — a wet-nursery disease.
- Pathogen
- Fungi (Pythium, Rhizoctonia, Fusarium)
- Spreads by
- Soil- & seed-borne; splashing water
- Favoured by
- Over-watering, poor drainage, crowding
- Main risk
- Seedlings rot and collapse in patches
Overview
Damping-off is the common seedling-killing disease of nurseries, caused by a complex of soil- and seed-borne fungi (mainly Pythium, Rhizoctonia and Fusarium). It comes in two forms: pre-emergence, where the seed or the sprouting seedling rots in the soil and never comes up (patchy, gappy germination), and post-emergence, where an emerged seedling develops a water-soaked, brown, pinched (constricted) rot on the stem at soil level, so it topples over and collapses.
It spreads fast in patches and can wipe out a nursery bed in a few days. It is favoured by everything that keeps the soil wet and airless around the seedling: over-watering, poor drainage, heavy shade, crowded thick sowing, cool cloudy weather and high humidity. Because it is soil- and seed-borne and moisture-driven, control is preventive — a clean, well-drained nursery, treated seed, careful watering and, where needed, a fungicide drench.
How to identify it
- Pre-emergence: patchy, gappy germination where seed or sprouts rot in the soil and never come up.
- Post-emergence: a water-soaked, brown, pinched (constricted) rot on the stem right at soil level.
- Seedlings toppling over and collapsing, usually in spreading patches in the bed.
- Whole patches of a nursery bed lost within a few days in wet, crowded conditions.
What causes it and when
- A complex of soil- and seed-borne fungi (Pythium, Rhizoctonia, Fusarium) that attack the seed and the tender seedling stem.
- Favoured by over-watering, poor drainage, heavy shade, crowded thick sowing and cool, cloudy, humid weather.
- Worst in the first two to three weeks after sowing, while the stem is still soft.
- Spreads by splashing water and through infested nursery soil and containers.
Cultural & organic control
- Raise seedlings on a raised, well-drained nursery bed or clean pro-tray media; never on waterlogged soil.
- Sow thinly, avoid over-watering, and give light and air so the surface dries between waterings.
- Solarise or otherwise treat nursery soil before sowing, and use fresh clean media/containers.
- Treat seed with a bio-agent (e.g. Trichoderma) and enrich the media with it as part of the package.
Chemical control
- Treat seed with a recommended fungicide (e.g. a captan/thiram or metalaxyl-based dressing) before sowing.
- At the first sign of damping-off, drench the affected patch and surroundings with a CIB&RC-registered fungicide (e.g. copper oxychloride or metalaxyl+mancozeb).
- Stop over-watering immediately and improve drainage alongside the drench.
- Confirm the current seed-treatment and drench product for your crop with your local KVK.
Prevent it coming back
- Make raised, well-drained beds, thin sowing and treated seed the routine for every nursery.
- Manage watering so the surface dries between irrigations, and avoid deep shade and crowding.
- Solarise/treat and rotate nursery soil, and keep containers and tools clean between batches.
Crops most at risk
Where this problem is called out in our crop guides — open a crop for the full package of practices.
Frequently asked questions
My nursery seedlings are toppling over and rotting at the base. What is it?
That water-soaked, pinched brown rot at soil level, with seedlings toppling in patches, is damping-off — a soil- and seed-borne fungal disease of nurseries. It thrives in wet, over-watered, crowded beds. Stop over-watering at once, improve drainage, and drench the patch with a registered fungicide (e.g. copper oxychloride or metalaxyl+mancozeb). Next time, use a raised bed, thin sowing and treated seed.
Why does over-watering cause damping-off?
The fungi that cause damping-off — especially Pythium — need wet, airless soil to attack the seed and the soft seedling stem, and splashing water spreads them across the bed. Over-watering and poor drainage keep the soil exactly that wet, so the disease races through the nursery. Watering carefully so the surface dries between irrigations, on a raised well-drained bed, is one of the strongest controls.
How do I raise a nursery that avoids damping-off?
Use a raised, well-drained bed or clean pro-tray media, solarise or treat the nursery soil first, sow thinly, and treat the seed with a fungicide or a bio-agent like Trichoderma. Water carefully so the surface dries between waterings, give light and air, and avoid deep shade and crowding. At the very first sign of collapse, stop over-watering and drench with a registered fungicide.
Symptoms and control measures follow ICAR, KVK and state agricultural-university package-of-practices; any named chemical is a registered use. Always read the product label and confirm the dose for your crop and zone. editorial policy.