---
title: What is rhizoctonia and how to fix it
description: Learn how to identify and prevent rhizoctonia, a fungal disease affecting seedlings, with our comprehensive guide on causes, symptoms, and effective solutions.
---

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## ![5 step guide to fixing rhizoctoniaStep 1 Remove affected seedlingsPull out any collapsed or infected plants immediatelyDispose of them dont compostTh](https://www.theonlinegardencenter.com/hs-fs/hubfs/AI-Generated%20Media/Images/5%20step%20guide%20to%20fixing%20rhizoctoniaStep%201%20Remove%20affected%20seedlingsPull%20out%20any%20collapsed%20or%20infected%20plants%20immediatelyDispose%20of%20them%20%20dont%20compostTh.png?width=1024&height=1536&name=5%20step%20guide%20to%20fixing%20rhizoctoniaStep%201%20Remove%20affected%20seedlingsPull%20out%20any%20collapsed%20or%20infected%20plants%20immediatelyDispose%20of%20them%20%20dont%20compostTh.png)

## What is rhizoctonia and how to fix it

Rhizoctonia is a soil-borne fungal disease that attacks seedlings at the base, often causing them to collapse suddenly. It’s one of the main causes behind what people call “damping off.”

It works fast — but it’s also preventable.

## Quick answer: what is rhizoctonia

Rhizoctonia is a fungal disease that damages stems and roots at soil level, causing seedlings to collapse. Control it by improving airflow, reducing moisture, and using clean compost and containers.

## 5 step guide to fixing rhizoctonia

Step 1: Remove affected seedlings

- Pull out any **collapsed or infected plants immediately**
- Dispose of them — don’t compost
- This limits spread

Step 2: Reduce moisture

- Let the surface dry slightly between watering
- Avoid constantly wet soil
- Water from below if possible

Step 3: Improve airflow

- Remove lids or ventilate propagators daily
- Space seedlings out
- Stagnant air encourages fungal growth

Step 4: Switch to clean materials

- Use **fresh, sterile compost**
- Clean trays and tools before reuse
- Avoid reusing infected soil

Step 5: Stabilise conditions

- Keep temperatures steady
- Avoid sudden changes
- Maintain balanced light and moisture

## Best varieties & why (less prone seedlings)

- Zinnia 
    - Fast-growing and less sensitive
- Marigold 
    - More tolerant of variable conditions
- Nasturtium 
    - Hardy and forgiving
- Beans and peas 
    - Larger seeds, stronger early growth

Very fine or slow-growing seedlings are more vulnerable.

## Common issues, pests & diseases

Seedlings collapsing at soil level

- Classic rhizoctonia symptom
- Stems look pinched or rotted

Patchy losses in trays

- Disease spreading through compost

White or grey fungal growth

- Often appears alongside damping off
- If you’re seeing mould as well, click here: [https://www.theonlinegardencenter.com/how-to-garden/why-mould-appears-during-seed-germination](https://www.theonlinegardencenter.com/how-to-garden/why-mould-appears-during-seed-germination?hsLang=en)

Recurring seedling failure

- Usually a setup issue, not bad luck
- Fix the environment, not just the symptom
- This guide will help: [https://www.theonlinegardencenter.com/how-to-garden/how-to-prevent-damping-off-in-seedlings](https://www.theonlinegardencenter.com/how-to-garden/how-to-prevent-damping-off-in-seedlings?hsLang=en)

## Best fertiliser, soil, lighting & growing conditions

- Light 
    - Bright light helps strengthen seedlings
- Soil 
    - Free-draining, sterile seed compost
- Water 
    - Light, controlled watering
    - Avoid waterlogging
- Feeding 
    - Not needed early on

Strong, well-grown seedlings are less vulnerable.

## Time of year

- Most common in **early spring**
- When temperatures are warm but light is still limited
- Indoor sowing increases risk if conditions aren’t balanced

## Climate and regional notes

UK & Ireland

- High risk due to damp conditions
- Airflow and drainage are critical

Europe

- Northern regions similar to UK
- Southern regions less prone if well ventilated

USA

- Indoor setups often the main risk
- Overwatering is the biggest trigger

## Pro tips for prevention

- Don’t overwater — this is the biggest factor
- Ventilate propagators daily
- Sow seeds thinly
- Use fresh compost every time
- Act fast at the first sign of trouble

## 10 frequently asked questions about rhizoctonia

**What is rhizoctonia**  
A fungal disease that causes seedlings to rot at soil level.

**Is it the same as damping off**  
It’s one of the main causes of damping off.

**Can infected seedlings recover**  
No — remove them immediately.

**Why are my seedlings collapsing**  
Usually due to excess moisture and poor airflow.

**Can I reuse soil after infection**  
Not recommended — use fresh compost.

**How do I prevent rhizoctonia**  
Control moisture, improve airflow, and maintain hygiene.

**Does light help prevent it**  
Yes, stronger seedlings are more resistant.

**Can it spread to other trays**  
Yes, especially in humid conditions.

**Is it common**  
Yes, especially in indoor seed starting.

**What’s the best defence**  
Good setup — clean compost, airflow, and careful watering.

## Related guides

- If your seedlings are collapsing, start here: [https://www.theonlinegardencenter.com/how-to-garden/how-to-prevent-damping-off-in-seedlings](https://www.theonlinegardencenter.com/how-to-garden/how-to-prevent-damping-off-in-seedlings?hsLang=en)
- If mould is showing up as well, fix this first: [https://www.theonlinegardencenter.com/how-to-garden/why-mould-appears-during-seed-germination](https://www.theonlinegardencenter.com/how-to-garden/why-mould-appears-during-seed-germination?hsLang=en)
- Watering is usually the root cause — check this: https://www.theonlinegardencenter.com/how-to-garden/how-often-to-water-seeds-during-germination

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