What does Bacterial Blotch look like?
Yellow to dark brown sticky, slimy spots on mushroom caps. Affected areas become soft and discolored. Can cover entire cap surface in severe cases.
- Color
- Yellow
- Texture
- Slimy, sticky spots
- Smell
- None to slight
- Growth speed
- Moderate
Why does Bacterial Blotch show up?
Excessive moisture on caps, poor air circulation, high humidity, overhead watering, water droplets sitting on mushroom surfaces.
What do I do if I find Bacterial Blotch in my grow?
- Reduce humidity and watering.
- Increase air circulation.
- Harvest affected mushrooms quickly — they are still edible if symptoms are mild.
- Apply chlorinated water (150 ppm) as a preventive spray.
- Avoid overhead watering.
How do I prevent Bacterial Blotch?
- Reduce watering frequency.
- Ensure good air circulation over mushroom beds.
- Avoid water sitting on caps.
- Maintain proper temperature.
- Allow caps to dry slightly between watering.
At which stage does Bacterial Blotch appear?
| Stage | Risk | What happens | How to prevent it |
|---|---|---|---|
| Preparation | No risk | — | — |
| Inoculation | No risk | — | — |
| Colonization | No risk | — | — |
| Fruiting | High | Disease appears on mushroom caps during fruiting. Wet conditions favor bacteria. | Avoid water on caps. Good air circulation. Harvest before symptoms worsen. |
| Harvest | Moderate | Can spread from affected caps to healthy ones during harvest. | Harvest affected mushrooms first. Clean hands between batches. |
Updated: February 24, 2026
This guide is for orientation. A reliable diagnosis needs a lab. If in doubt, ask an experienced mycologist.
