Mushroom Contamination Checker
Answer a few questions about what you can see on a gourmet or culinary grow, and get a cautious view of what the pattern may be consistent with, plus safe next steps.
Learn the method behind this calculatorWhere is the problem?
What this checker does
This is a symptom-based triage tool for legal gourmet and culinary mushroom grows. You describe what you can actually see — colour, texture, where it started, how fast it spread, whether there is a smell or free liquid — and it maps that pattern against the contamination types home growers most often meet: green mould of the Trichoderma type, cobweb-like fungal growth, bacterial blotch, and overly wet substrate. It also recognises the very common case where the growth described is simply healthy mycelium.
It deliberately gives a cautious, hedged answer rather than a diagnosis. Contamination identification from a description is inherently uncertain, so every result is framed as "consistent with" a pattern and paired with safe next steps you can take without needing to be sure.
When to use it
- When a grain jar, bag or bulk tub develops a colour or texture you did not expect.
- When colonisation stalls and you want to know whether something is competing with your culture.
- When a smell, sliminess or standing water appears in a block or tub.
- When you are unsure whether dense white fluff is aerial mycelium or something else.
A practical example
A lion's mane block that was fully white last week now has a coin-sized patch that started white and has turned green in the centre, spreading outwards a little each day. Working through the checker, that pattern is consistent with a Trichoderma-type mould: the white-then-green sequence is the coloniser sporulating, and the point-source spread is characteristic. The cautious response is not to open the bag indoors — seal it, move it outside, dispose of it under local waste practice, and then clean the shelf and equipment nearby before starting the next block.
Contrast that with a bulk tub showing fast, wispy grey growth across the surface overnight with no colour change: that is more consistent with cobweb-type growth, which behaves and looks quite different. Logging both events against the grow makes the pattern easy to compare next season.
Common mistakes
- Opening a suspected mouldy container indoors, which spreads spores through your grow space.
- Treating every patch of white fluff as contamination — aerial mycelium and early pins are normal.
- Judging colour under warm artificial light, where early green mould reads as cream.
- Misting a bacterial or wet-substrate problem, which usually makes it worse rather than better.
- Not photographing the same spot 12 to 24 hours apart, which is the single most useful diagnostic step.
FAQ
How can I tell green mould from healthy mycelium?
Healthy mycelium is white and fibrous and does not develop colour. Green, blue-green or grey powdery patches that spread from a point are typical of mould contamination, and colour usually appears once the coloniser has begun to sporulate.
Can I save a contaminated grow?
Sometimes a small surface issue on a bulk substrate can be cut out and the grow continued, but a visibly mouldy grain jar or bag is not worth rescuing. The cautious answer is to isolate anything you are unsure about rather than opening it indoors.
Is white fuzzy growth on the substrate always contamination?
No. Dense white aerial mycelium and small white pins are normal at certain stages, and cobweb-type growth is faster, greyer and more diffuse. Photographing the same spot 12 to 24 hours apart usually makes the difference obvious.
How do I dispose of a contaminated grow safely?
Keep the container sealed, move it outdoors before opening or bagging it, dispose of it under local waste practice, and clean the surfaces and equipment it touched. Opening a mouldy bag indoors spreads spores through the space you grow in.
Related guides and tools
- Mushroom contamination guide — each pattern explained in depth, with prevention.
- Grain spawn beginner guide — where most contamination is won or lost.
- Substrate hydration calculator — avoid the wet substrate that invites bacterial problems.
- Equipment checklist — the clean-work kit that prevents most of these issues.
Log this contamination against the grow
Hyphae Fidelity is a free grow tracker for gourmet cultivation — log every batch, check, harvest and contamination, and see what actually works in your setup.