Damping Off
Pythium spp., Rhizoctonia solani
A complex of soil fungi that kill seedlings before or shortly after emergence. Cold wet seed-raising mix is the classic trigger.
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Identify from a photoBackground
Damping off refers to the sudden death of seedlings, caused by several soil-borne fungi and oomycetes. Pre-emergence damping off rots seed in the soil; post-emergence damping off causes seedlings to topple over with a pinched, water-soaked stem at soil level. The problem is almost always a combination of pathogen presence, overly wet mix and poor airflow.
How to identify
- Patchy failure of germination. Seed rots before emergence
- Emerged seedlings topple with pinched watery stem at soil level
- Fine white or greyish fungal threads sometimes visible in the mix
- Roots brown and sloughed
Life cycle
Pathogens persist in soil and unsterilised seed-raising mix. Wet mix, cool temperatures and poor airflow trigger rapid infection. Life cycles are fast. Whole seed trays can fail overnight.
Weather triggers
- Temperature: 8-22°C
- Humidity: >90%
- Cool wet conditions with poor airflow. Indoor propagation in winter is high risk.
Peak season (southern hemisphere)
Red = active season · Dark red outlined = this month
Affected vegetables & crops
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Climate zones at risk
Organic & low-impact control
- Use sterile seed-raising mix (commercial bagged mix is typically heat-treated)
- Sprinkle a light layer of fine vermiculite on the surface to keep crown dry
- Water from below or with a fine sprayer
- Add a handful of mature worm-castings or compost for suppressive microbes
Chemical control
- Fungicide drenches (such as propamocarb) are used in commercial propagation; not generally available or needed for home gardens
Always read product labels. Registrations change.
Prevention
- Never reuse old potting mix for seed raising
- Disinfect trays and pots between uses
- Avoid overcrowding. Thin early
- Provide airflow with a small fan in propagation areas
Companion planting
Not applicable at seedling stage.
Biosecurity
No quarantine concern. Ubiquitous soil organisms.
Know when Damping Off is actually about
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