Contamination identification
Reference
What the thing in your jar is, whether it is recoverable, and what caused it. Most cultivation failures are one of six organisms, and telling them apart is mostly colour, texture and smell.
What you need
- Good light
- Nose, but never open a suspect container indoors to smell it
Procedure
- 01
Do not open it indoors
A contaminated container is a spore bomb. Opening it in the room where you grow reseeds every surface and every subsequent batch. Take it outside, or bag it sealed and bin it.
Watch out: This is the mistake that turns one failed jar into six months of failed jars.
- 02
Check colour before texture
Healthy mycelium is white, sometimes with blue-green bruising where it has been knocked, and yellow-amber metabolite droplets. Any other colour on the substrate is a problem. Blue is bruising and is fine; forest green is Trichoderma and is not.
- 03
Check growth rate
Contaminants generally grow faster than mycelium. Something that visibly advanced overnight is not your culture.
- 04
Decide recoverable or not
Cobweb mould caught early is recoverable. Trichoderma, bacterial wet spot and black bread mould are not. The correct response to the unrecoverable set is to dispose of it immediately rather than to attempt heroics, because every day it sits there it is releasing spores.
Troubleshooting
| What you see | What it is | What to do |
|---|---|---|
| Forest-green patches, white at the leading edge, powdery | Trichoderma, green mould. The most common and most aggressive contaminant. | Not recoverable. Bag sealed and remove from the building. Review sterilisation time and still-air technique. |
| Grey, wispy, fast-growing fuzz that looks like cotton wool | Cobweb mould (Dactylium). Grows across the surface visibly faster than mycelium, and is grey rather than white. | Recoverable. Mist directly with 3% hydrogen peroxide and increase fresh air exchange substantially. It indicates stagnant, over-humid air. |
| Wet, slimy, grey-brown patches with a sour, sweet or foul smell | Bacterial wet spot (Bacillus). Almost always substrate above field capacity, or under-sterilised grain. | Not recoverable. Reduce moisture and extend grain sterilisation to 90 minutes at 15 psi. |
| White fluff that turns black with visible pinhead spore heads | Black bread mould (Rhizopus). Fast and prolific. | Not recoverable. Remove immediately, the spore heads burst and travel. |
| Powdery blue-green or grey-green with a musty smell | Penicillium. | Not recoverable in bulk. Usually indicates airborne contamination at inoculation. |
| Pink, orange or salmon patches | Neurospora, or a pink Trichoderma variant. Rare and extremely aggressive. | Not recoverable. Remove from the building immediately; Neurospora spores are exceptionally mobile. |
| Yellow or amber droplets sitting on healthy white mycelium | Metabolite exudate. NOT contamination. | Nothing required. Heavy exudate suggests low fresh air exchange. |
| Blue or blue-green staining where the mycelium was knocked | Bruising, oxidation of psilocin. NOT contamination. | Nothing. It is the same reaction that identifies the mushrooms in the field. |
Sources
- [1]Shroomery cultivation archives
- [2]Stamets & Chilton, The Mushroom Cultivator (1983)