Test your knowledge about Fuzzy Feet, Leggy Mushrooms, and White Dots on Caps
Take the test to check and improve your knowledge! Learn how to diagnose long stems, fuzzy feet and caps issues. What they mean, what they are, and how to fix them. Explore case studies with photo examples, where you’ll identify whether it’s harmless fuzzy growth or contamination
Learning resources to pass this quiz: Why Mushrooms too Leggy, Fuzzy Feet and White Dots on Caps
Questions covered in this Quiz
First principle - Are leggy stems, fuzzy feet, and white dots on mushroom caps usually contamination?
Possible answers:
- Usually NOT contamination; the main reason is lack of fresh air exchange
- YES, these are classic signs of early Green Mold
- YES, these are classic signs of Cobweb Mold
- NO, these symptoms only happen from “bad genetics”
Gas exchange - Mushrooms and mycelium “breathe” by…
Possible answers:
- Inhaling oxygen (O₂) and exhaling carbon dioxide (CO₂)
- Inhaling carbon dioxide (CO₂) and exhaling oxygen (O₂)
- Inhaling nitrogen (N₂) and exhaling oxygen (O₂)
- They don’t exchange gases at all
Long stems - Why do mushrooms become “too leggy” and usually with small caps?
Possible answers:
- Low oxygen and high CO₂ –> encourages fruit bodies to stretch stems searching for fresh air
- Too much light –> forces the stems to follow the light and elongate
- Highly nutritious bulk substrate –> stimulates the production of long stems
- Long stems are a sign of contamination –> in this way, mushrooms try to save the caps with spores
What is the fuzziness? - What is “fuzzy feet” actually made of?
Possible answers:
- Mushroom mycelium
- Cobweb mold (white-grey, wispy contamination)
- Green mold (bright white powdery texture at the early stage)
- A parasite eating the stems
Fuzzy feet causes - Which two factors are cited as the common causes of fuzzy feet?
Possible answers:
- Lack of fresh air exchange (FAE) in the fruiting chamber
- High relative humidity combined with lack of FAE
- Too much light, especially direct sunlight
- High temperature (over 81°F or 27°C)
- Direct misting on mushroom fruit bodies
- Bacterial contamination in bulk substrate (mycelium tries to heal the affected areas)
Fuzziness vs Contamination - Which type of contamination is commonly confused with fluffy mycelium growth and fuzzy feet?
Possible answers:
- Cobweb mold
- Early green mold (like Trichoderma or Penicillium) before it turns green
- Wet bubble (Mycogone)
- Bacterial blotch
- Black Pin Mold (Mucor & Rhizopus)
- Dry Bubble disease (Verticillium)
Fuzzy feet vs Mold - How to visually distinguish fuzzy mycelium from Cobweb or Pin Mold?
Possible answers:
- Fuzzy feet is snow-white mycelium; mold has thinner threads and a greyish color
- Mold is bright white; fuzzy mycelium is always grey
- Mold always smells like coconut; mycelium never has a smell
- You can’t distinguish them visually
Fluffy growth on mushroom caps - “White dots” or fluffy caps are most often caused by…
Possible answers:
- Poor fresh air exchange (FAE) during fruiting (the cap fuzz is mycelium)
- A nutrient deficiency in the substrate
- Overly low CO₂
- A required stage before mushrooms mature
Problem solution - How to fix fuzzy feet, fuzzy caps and reduce legginess?
Possible answers:
- Increasing fresh air improves the issue within a couple of days
- Once it happens, it can never be improved in the same flush
- The only fix is direct misting on the fluffy areas
- The correct fix is to reduce fresh air even more
CO₂ level - What target CO₂ range is ideal for fruiting period?
Possible answers:
- Up to 1500 ppm
- 3,000–5,000 ppm
- 5,000–10,000 ppm
- CO₂ level is irrelevant to fruiting morphology
Case study - Is it fuzzy feet or mold contamination?
Possible answers:
- Fuzzy feet (fluffy mycelium)
- Cobweb Mold
Case study - Can you identify this? Fuzziness or contamination?
Possible answers:
- Fuzzy feet and fluffy (tomentose) mycelium
- Cobweb mold covered the entire top layer and the base of the stems
Case study - Can you identify this? Fuzziness or contamination?
Possible answers:
- Fluffy (tomentose) mycelium
- Cobweb mold contamination
Case study - Fuzzy base of the stem or contamination?
Possible answers:
- Fuzzy base of the stem
- Cobweb Mold contamination
Case study - Try to identify. Fuzzy cap or cobweb mold contamination?
Possible answers:
- Fuzzy cap (mycelium on the cap)
- Cobweb mold contamination
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