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When something's wrong

Contamination ID

Telling trich, cobweb, bacteria and other moulds apart from bruising, metabolites and hyphal knots, and what to do about each.

Signs this guide is for you

  • There is a patch of color on your substrate, grain or fruits.
  • Something smells sour, sweet or musty instead of earthy.
  • Part of a jar or tub has stopped growing.

First, three checks

  • Texture: mould sits on top of the surface as powder, fuzz or whiskers. Bruising is a stain inside the tissue. A swab tells you: pigment that wipes off is spores.
  • Smell: earthy or mushroomy is normal. Sour, rotten or dirty-sock is bacteria. Sweet and beery is yeast. Musty is mould.
  • Time: real mould grows between checks. Condensation, glare and bruises do not spread.

When in doubt, keep a suspect jar or tub closed and away from the others. Do not open a green or black-spotted container indoors. A badly contaminated jar can be pressure-cooked again before opening so its spores are dead (Bible, p. 252); a tub gets bagged and taken outside.

Contaminants

  • : dense, raised white patch that turns forest green from the centre, often with a white rimUsually: Trichoderma; starts white, so it hides early, then covers everything in green and attacks fruits (Bible, p. 250)Do: Throw out. Bag it closed, take it outside, do not fan it
  • : grey, see-through, wispy fluff standing off the surface, spreading fastUsually: Cobweb mould: greyer and finer than mycelium, never rope-like; can take a jar in about a day (Bible, p. 250)Do: Isolate. Some growers treat a tiny early patch with 3% hydrogen peroxide; the Bible advises throwing out instead (p. 249). Add fresh air
  • : grain looks wet, greasy or grey, growth stalls at a lineUsually: Bacillus bacteria whose spores can survive a short cook; grey ooze on bare grain and a rotten-fruit smell (Bible, p. 253)Do: Throw out. Never spawn, dunk or dry it
  • Grey whiskers with black dots on topUsually: Black pin mould (Rhizopus or Mucor); grows in hoursDo: Throw out unopened
  • Blue-green or grey-green powder in round coloniesUsually: Penicillium (felt-like, usually green) or Aspergillus (black, yellow or green) (Bible, p. 249–251)Do: Throw out. Wear a dust mask to dispose of it (Bible, p. 251)
  • : white film or small balls turning pink to redUsually: Lipstick mould; slow and uncommon, a sign sterilizing fell short (Bible, p. 252)Do: Throw out
  • Fast orange or salmon fluff, often in grain bagsUsually: Neurospora; very fast and grows through filter discs into other jars (Bible, p. 263)Do: Remove unopened; clean the area
  • Small white spots everywhere, greasy shine, beer-sweet smellUsually: Yeast, often after grain-to-grain transfers (Bible, p. 255–256)Do: Throw out
  • : yellow-tan to brown sunken spots on capsUsually: Pseudomonas bacteria on caps that stay wet or sit in stale air; starts near the cap edge (Bible, p. 253–254)Do: Pick affected fruits, stop wetting caps, add air

Look-alikes that are fine

  • Blue, blue-green or near-black staining where touchedUsually: , a reaction inside the tissueDo: Leave it. It does not wipe off or grow in circles. Spreading blue with powder is different
  • Tiny dense white specks on the surfaceUsually: , the start of pinsDo: Good news. Keep conditions steady
  • Clear to amber droplets on white myceliumUsually: Do: Fine in small amounts; lots, with yellowing and a sour smell, points to bacteria
  • Bright white fuzz only on stem basesUsually: , high CO₂Do: Add fresh air. Not cobweb, which is greyer and spreads across the surface
  • Thick, flat white matUsually: Do: Add fresh air. Raised white circles that later green are trich, not overlay
  • Flat purple-black dust under capsUsually: Spore dropDo: Harvest earlier. It follows cap outlines and has no texture
  • Small dark pins among healthy onesUsually: Do: Pick them so they do not rot
  • Fluffy, cottony white areasUsually: myceliumDo: Normal. Watch that it stays white

The white-before-green trap

Trichoderma starts out white. It is usually denser, fluffier and more raised than the mycelium around it, and forms a rounder patch. A day or two later the centre greys and turns green. If a white patch looks different from the rest of the surface, mark it and check again in 12–24 hours before you soak, case or disturb anything.

Pests

Fungus gnats eat mycelium and mushrooms and carry rot; they often come from houseplant soil. Use sticky traps and move houseplants away, and never use insecticide on a grow (Bible, p. 254–255). Mites mostly arrive on straw or manure and carry mould spores between jars; standing jars on sticky paper stops them crossing (Bible, p. 255).

Preventing the next one

  • Most tub contamination starts in the spawn. Use only clean, sweet-smelling, fully colonized grain.
  • Keep substrate at field capacity, not wetter; bacteria thrive in pooled water.
  • Remove stubs, aborts and dead pins, where mould starts first.
  • Give enough fresh air: still, wet, warm air favours cobweb and trich.
  • Harvest before heavy spore drop, which feeds moulds and hides them.

Common mistakes

  • Fanning or opening a green tub indoors.
  • Cutting out a patch of trich and hoping.
  • Dunking a cake that smells sour.
  • Throwing out a healthy tub because of bruising or metabolites.

What to do next

  • If it was climate, not contamination: troubleshooting.
  • To lose fewer jars: clean work, agar and liquid culture.

Seen something different in your own tub? Add your grow report on the strain you grew. Reports are how these pages get better.

What it looks like

Real photos, credited below each one.

Sources

  1. Psilocybin Mushroom Bible (Haze & Mandrake, 2016), molds, bacteria and yeast described, p. 249–256
  2. Psilocybin Mushroom Bible (Haze & Mandrake, 2016), pests, p. 254–255
  3. Psilocybin Mushroom Bible (Haze & Mandrake, 2016), pink bread mould in grain, p. 263
  4. Psilocybin Mushroom Bible (Haze & Mandrake, 2016), bruising versus spreading color on cakes, p. 120
  5. The Mushroom Cultivator (Stamets & Chilton, 1983), bacterial blotch on cubensis, p. 252–253
  6. The Mushroom Cultivator (Stamets & Chilton, 1983), cobweb mould, p. 275
  7. The Mushroom Cultivator (Stamets & Chilton, 1983), green mould, p. 311
  8. Shroomery forum: recognizing and dealing with contamination
  9. Shroomery forum: how it should and shouldn't look

Written for this site in our own words from the books and threads above. Where growers disagree, both sides are given. Nothing here is advice about anything other than growing.