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.
Varieties to consider
Named seed varieties whose resistance or susceptibility to this problem is documented on their own variety page.
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.