# Damping-off

> The collapse of seedlings or cuttings when soil-borne pathogens such as Pythium, Rhizoctonia solani and Fusarium rot the stem at the soil line.

- Canonical: https://genetixbay.com/knowledge/glossary/damping-off.html
- Also written: damping off, dampening off, seedling rot, pre-emergence damping-off, Rhizoctonia solani
- Glossary category: Pests and diseases · Evidence: Established
- Status: Draft: awaiting expert review · Updated: 2026-10-31
- Licence: CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0/), attribute "GenetixBay cannabis glossary"

Damping-off is a disease syndrome, not one pathogen. [Seedlings](https://genetixbay.com/knowledge/glossary/seedling.md) either rot before they emerge, or they emerge and then collapse as the stem at the soil line turns brown, thin and water-soaked. The usual culprits are *[Pythium](https://genetixbay.com/knowledge/glossary/pythium.md)* species, *Rhizoctonia solani*, *[Fusarium](https://genetixbay.com/knowledge/glossary/fusarium-wilt.md)* species and sometimes *[Botrytis cinerea](https://genetixbay.com/knowledge/glossary/botrytis.md)*. Fresh cuttings can suffer the same rot at the base.

## In practice

The textbook sign is a seedling that [looks](https://genetixbay.com/knowledge/glossary/bag-appeal.md) fine in the morning and has toppled by evening, with a pinched "wire stem" at the base. Cold, [waterlogged](https://genetixbay.com/knowledge/glossary/overwatering.md) media, high humidity under domes, reused trays and unsterilised compost all raise the risk. [Prevention](https://genetixbay.com/knowledge/glossary/cultural-control.md) is clean or new starter media, washed trays, warm (around 22-25 °C / 72-77 °F) but not soggy conditions, a gentle fan once seedlings are up, and no heavy feeding before [true leaves](https://genetixbay.com/knowledge/glossary/true-leaves.md). A collapsed seedling cannot be saved, so remove it and its plug to protect its neighbours.

## Don't confuse with

- **Cutworms**: chew stems clean through at night.
- **Stretching**: tall, thin stems from low light, but firm and green.
- **Drowning**: limp but not pinched or brown at the base.

## Related terms

[Pythium](https://genetixbay.com/knowledge/glossary/pythium.md), [Fusarium wilt](https://genetixbay.com/knowledge/glossary/fusarium-wilt.md), [Cutworm](https://genetixbay.com/knowledge/glossary/cutworm.md), [Sanitation](https://genetixbay.com/knowledge/glossary/sanitation.md), [Root rot](https://genetixbay.com/knowledge/glossary/root-rot.md)

## Read more

- [Damping-off: why seedlings collapse at the soil line](https://genetixbay.com/knowledge/germination/damping-off.md)

## Sources

1. NC State Extension. Damping-off in flower and vegetable seedlings. https://content.ces.ncsu.edu/damping-off-in-flower-and-vegetable-seedlings
2. University of Minnesota Extension. How to prevent seedling damping off. https://extension.umn.edu/solve-problem/how-prevent-seedling-damping