Most specialty mushrooms are grown on sterilized substrates, and once a contaminant gets a foothold, it flourishes in the absence of competition from other contaminants. In nature, complex interactions among hundreds of other fungi, bacteria, nematodes, etc. maintain an ecological equilibrium. In a sterilized medium, the grower provides ideal conditions for the contaminant to prosper. In sawdust bags, contamination usually involves another fungus living off the waste products or on the remains of the cultivated fungus, or sometimes on the living mycelium or fruiting body of the cultivated fungus. The only competition for these contaminants is the cultivated fungus itself.

Wet Spot; Sour Rot - Bacillus sp
Bacterial Blotch – Pseudomonas tolaasii (P. fluorescens)
Cobweb mold or Dactylium Mildew (Hypomyces sp.)
Green Mold - Trichoderma harzianum, T. viride, T. koningii
http://mushgrowinfo.cas.psu.edu/Trichoderma Green Mold.html

Cinnamon Brown Mold – Chromelosporium fulva (Peziza ostrachoderma)

Lipstick Mold – Sporendonema purpurescens (Geotrichum candidium)

Pink Mold; Red Bread Mold – Neurospora

Sepedonium Yellow Mold – Sepedonium spp.

Black Whisker Mold – Doratomyces spp.

Blue-green Molds – Penicillium spp .

Black Mold (also Yellow Mold and others) – Aspergillus sp.

Inky Cap – Coprinus spp.

Oedocephalum (Brown) Mold – Oedocephalum spp.

Olive Green Mold – Chaetomiu m spp.

Pin Molds – Rhizopus spp.

Plaster Molds and Flour Molds – Papulaspora byssina, Thielavia thermophila, Botryotrichum piluiliferum, Trichothecium spp., and others

La France Disease – an isometric virus
http://www.hri.ac.uk/isms/article4.htm

Mummy Disease – Pseudomonas aeruginosa
http://www.shroomery.org/index/par/26841

Wet Bubble – Mycogone perniciosa

Dry Bubble –Verticillium
http://mushgrowinfo.cas.psu.edu/Verticillium Dry Bubble.htm

Fungus gnats (Sciarids) (Lycoriella spp.) and phorids (Megaselia spp.)

Mites

Nematodes – Aphlelenchoides composticola and Ditylenchus myceliophagus

Abnormalities:

Browning – tyrosinase (phenolase);
Flock, hardcap, and open veil; Rosecomb

Scaling

Stroma

Weepers

Literature sources:

• Plant Pathology 40, Edible Mushroom Cultivation Lecture/Lab 8 Pest, Diseases, and Weed Control; Abnormalities, February 26, 1999
  
  
• Mushroom Cultivator : A Practical Guide to Growing Mushrooms at Home, Paul Stamets, J.S. Chilton, 1984
  
  
• www.mold-help.org
  
  
• http://www2.truman.edu/~jherrera/colonies/colonies-genera.html
  
  
  
• http://www.hortips.co.uk/mush_2.htm