Signs of Contamination

Signs of Contamination

Contamination can happen at any stage of the process. Knowing what to look for early can save you time and prevent it from spreading.

Common Signs

Unusual colors
Green, black, pink, or orange growth is almost always contamination.

Sour or foul smell
Healthy mycelium smells earthy. Anything sour, sweet, or rotten is a bad sign.

Slimy or wet patches
Excess moisture with a sticky or slimy texture usually means bacterial contamination.

Growth that doesn’t look like mycelium
Healthy mycelium is white and thread-like. Anything powdery, fuzzy in a weird way, or oddly colored is suspect.

When to Be Concerned

• Rapid color changes in the bag
• Wet spots forming without reason
• Growth that looks different from the rest of the mycelium
• Strong or unpleasant odors

What to Do

• Isolate the bag immediately
• Do not open contaminated bags indoors
• Dispose of heavily contaminated bags
• If unsure, give it time—but don’t risk spreading it

Important Notes

• Not all discoloration is contamination, but most of it is
• Early contamination can spread quickly
• Clean technique during inoculation is critical
• Always trust smell and appearance together

Common Mistakes

• Ignoring early signs
• Opening contaminated bags inside
• Confusing bruising with contamination
• Trying to save heavily contaminated grows