Contamination identification guide — what are you actually looking at?

Green (Trichoderma): The most common and most aggressive grain contamination. Often starts as a small white spot that goes green within 24-48 hours. Trichoderma produces antibiotics that kill your mycelium — if you see any green on grain jars, seal the bag and discard. Do not open inside your growing space. No salvage.

Black/dark green (Aspergillus or mold): Usually from wet grain or insufficient sterilization time. Aspergillus niger produces aflatoxins — health hazard, discard immediately. If it's just surface mold (not penetrating the grain) you might salvage by removing affected sections in a flow hood, but this is advanced technique and the risk is usually not worth it for beginners.

Orange/reddish spots: Often bacterial contamination, sometimes wet rot from Bacillus species. Smells bad (sour, sometimes sulfurous). Grain will be mushy at the site. Cause is usually insufficient sterilization or wet grain — pressure cook longer and ensure grain is field capacity dry before loading jars. Discard affected jars.