Contamination Types Guide
Visual reference to identify and understand common contaminations in mushroom growing
Quick Identification Tips
🚨 Immediate Disposal
- • Green mold (Trichoderma)
- • Black pin mold
- • Orange/red bread mold
- • Black mold (Aspergillus)
⚠️ Treatable (Sometimes)
- • Cobweb mold
- • Blue/green Penicillium
- • Early bacterial spots
- • Minor yeast
💡 Key Signs
- • Unusual colors
- • Strange smells
- • Faster growth than mycelium
- • Different texture
Common Contamination Types
Green Mold (Trichoderma)
Identification
- • Starts as bright white aggressive growth
- • Yellowing appears before sporulation
- • Emerald to forest green spores
- • Powdery texture when mature
- • Circular growth pattern
Common Causes
- • Non-sterile technique
- • Contaminated spawn
- • Poor sterilization
- • Excessive moisture
Prevention
Proper sterile technique, correct moisture levels
Treatment
Immediate disposal recommended, isolation critical
Cobweb Mold (Dactylium)
Identification
- • Gray, wispy appearance like cobwebs
- • Grows above substrate surface
- • Much faster than mycelium
- • Less dense than mycelium
- • Responds to air movement
Common Causes
- • High humidity
- • Poor air circulation
- • Contaminated casing layer
- • Stagnant conditions
Prevention
Increase air exchange, reduce humidity
Treatment
Hydrogen peroxide spray, increase FAE
Black Pin Mold (Rhizopus)
Identification
- • Black pinhead structures on stalks
- • Starts as white/gray fuzz
- • Develops black spore heads
- • Very fast growth rate
- • Spreads rapidly when disturbed
Common Causes
- • High temperatures
- • Excessive moisture
- • Poor sterilization
- • Contaminated grains
Prevention
Lower temperature, proper moisture content
Treatment
Disposal required, highly aggressive
Orange/Red Bread Mold (Neurospora)
Identification
- • Bright orange to pink coloration
- • Powdery spore masses
- • Extremely fast growth
- • Can grow through filter patches
- • Heat resistant
Common Causes
- • Contaminated grains
- • Survives poor sterilization
- • Common in bakeries/kitchens
- • Heat-resistant spores
Prevention
Extended sterilization times, avoid kitchen areas
Treatment
Immediate disposal, deep clean required
Bacterial Contamination (Bacillus)
Identification
- • Slimy, wet appearance
- • Sour or rotten smell
- • Yellow to brown discoloration
- • Grains look melted
- • No fuzzy growth
Common Causes
- • Over-hydration
- • Insufficient sterilization
- • Damaged grains
- • Anaerobic conditions
Prevention
Proper moisture content, adequate sterilization
Treatment
Usually requires disposal, sometimes recoverable if caught early
Blue/Green Penicillium
Identification
- • Blue-green to gray-green color
- • Velvety texture
- • Slower than Trichoderma
- • Musty smell
- • Often in circular colonies
Common Causes
- • Cool, damp conditions
- • Poor air circulation
- • Contaminated substrate
- • Old spawn
Prevention
Maintain proper temperatures, fresh spawn
Treatment
Early removal possible, monitor closely
Black Mold (Aspergillus niger)
Identification
- • Black powdery spores
- • Starts as white/yellow
- • Develops black coloration
- • Can be toxic to humans
- • Dusty when disturbed
Common Causes
- • High temperatures
- • Poor ventilation
- • Contaminated materials
- • Humid conditions
Prevention
Temperature control, proper ventilation
Treatment
Disposal with safety precautions (wear mask)
Yeast Contamination
Identification
- • Creamy white to beige
- • Smooth, paste-like
- • Sweet or beer-like smell
- • Bubbling may occur
- • No fuzzy growth
Common Causes
- • High sugar content
- • Excessive moisture
- • Fermentation conditions
- • Contaminated LC
Prevention
Proper nutrient balance, avoid excess sugars
Treatment
May coexist with mycelium, monitor growth
Contamination vs Normal Growth
✓ Normal Mycelium
- ✓ White, thread-like growth
- ✓ Ropey or rhizomorphic patterns
- ✓ Fresh mushroom smell
- ✓ Steady, even colonization
- ✓ May bruise blue (some species)
- ✓ Dense, cottony appearance
✗ Contamination Signs
- ✗ Any color other than white
- ✗ Slimy, wet appearance
- ✗ Sour, sweet, or rotten smell
- ✗ Faster growth than mycelium
- ✗ Powdery or dusty texture
- ✗ Circular growth patterns
If You Find Contamination
- 1
Don't Panic
Contamination happens to everyone. Stay calm and assess the situation.
- 2
Isolate Immediately
Move contaminated items away from clean grows to prevent spread.
- 3
Identify the Type
Use this guide to determine what you're dealing with.
- 4
Decide: Treat or Toss
Based on severity and type, either attempt treatment or dispose safely.
- 5
Clean and Prevent
Deep clean your space and review your procedures to prevent recurrence.