Wet Rot and Bacterial Blotch: Identifying, Preventing, and Treating Sour-Smelling Substrates

While molds are highly visible, bacterial contamination is often insidious, ruining grain spawn before mycelium can take hold. The most common culprit is Bacillus species, causing what cultivators call "Wet Rot."

Identifying Wet Rot

1. The Smell Test: The most reliable indicator of bacterial contamination is odor. Healthy mycelium smells earthy, like fresh forest soil. Bacterial rot smells sour, fermented, like rotting apples or dirty gym socks. 2. Visual Cues: Look for "slime" or grains pressing tightly against the glass in a wet, mushy clump. Mycelium will often avoid colonizing the infected grain, creating stark lines of uncolonized territory.

Prevention is the Only Cure

Unlike molds, bacteria cannot be easily excised. Once a jar has wet rot, it must be discarded. Prevention hinges on two factors:

1. Proper Hydration: Grains must be dry on the outside before jarring. If water pools at the bottom of the jar, it creates an anaerobic environment where endospores thrive. 2. Adequate Sterilization: Ensure your pressure cooker hits a true 15 PSI for a full 90 minutes.

Using professional-grade substrates, such as a Magic Bag grow bag, guarantees perfectly hydrated and sterile grain, eliminating the risk of wet rot entirely.

Research Citation: Fletcher, J. T., & Gaze, R. H. (2007). Mushroom Pest and Disease Control: A Color Handbook. Academic Press.