DiseaseTrichoderma spp.Reviewed 23 September 2026

Green mould (Trichoderma)

The single biggest reason a first mushroom batch fails — a fast green mould that out-races the mushroom spawn on a poorly pasteurised substrate. No cure once it takes hold, only prevention.

Problem type: Substrate contamination (mould), not a disease of the mushroom plant itself
Attacks: The straw, compost or sawdust substrate before or during spawn run
Worst when: Substrate is under-pasteurised or the growing room is not disinfected between batches
Main risk: A whole bag or bed turning green instead of white — complete loss of that unit

Overview

Green mould, caused by several Trichoderma species, is by far the most common substrate contamination problem in mushroom cultivation across every species grown in India — oyster, button and milky alike. It is an opportunistic mould, meaning it is present in the environment (straw, compost, air, soil) essentially everywhere, and only becomes a problem when conditions let it establish and out-grow the mushroom mycelium.

The substrate is a race: correctly pasteurised or sterilised substrate, freshly and cleanly spawned with vigorous spawn, gives the mushroom mycelium a head start that lets it dominate the block before any surviving mould spores can establish. Under-pasteurisation (too short a time, too low a temperature, or straw packed too densely for heat to penetrate evenly), contaminated straw, weak or old spawn, or a dirty growing room all tip that race in the mould's favour.

Once green mould is visibly established in a bag, there is no way to save that bag — the correct and only response is fast removal and disposal, not treatment, since every hour it is left in the growing room adds to the spore load threatening every other bag around it.

How to identify it

A patch that starts as white, fluffy mycelium-like growth and turns green within a day or two as it produces spores — easy to mistake for healthy mushroom mycelium in its earliest hours.
Green colour usually starts at one point (often where the substrate was packed too tightly, or near a tear in the bag) and spreads outward across the surface.
Bags or beds affected show poor or absent mushroom pinning wherever the green patch has taken hold, even if the rest of the bag looks fine.
A musty, sometimes slightly sour smell distinct from the earthy-mushroomy smell of healthy, well-colonised substrate.

The damage it does

A bag with established green mould gives little to no mushroom yield from the affected area — the mould has simply out-competed the mushroom mycelium for the substrate's food.
Left in the growing room, it releases enormous numbers of airborne spores that can spread to neighbouring bags, turning a single contaminated bag into a room-wide problem within days.
Repeated green mould outbreaks in the same shed usually point to a systemic cause — inadequate pasteurisation equipment, a room that is never properly disinfected, or a spawn source with reliability problems — rather than one unlucky batch.

When to act

Check every bag during the spawn-run week — the earlier a green patch is caught, the less spore load it has released into the room.
Remove and dispose of an affected bag immediately on sighting, rather than waiting to see if it "might still give some mushrooms."
After clearing an affected batch, disinfect the room thoroughly before the next substrate goes in, rather than assuming one clean-looking bag means the room itself is fine.

Organic & cultural control

Give the substrate its full recommended pasteurisation time and temperature — hot-water dipping at about 65–80°C for 45–90 minutes, or a properly run steam pasteurisation, every single batch without shortcuts.
Use only fresh, dry, undamaged straw and buy spawn only from a reliable source such as ICAR-DMR Solan, a state mushroom unit, or another registered spawn lab — never carry spawn over from a previous, possibly contaminated batch.
Whitewash the growing room walls with lime and fumigate or deep-clean it between every batch, since leftover spores from a previous crop are a major source of the next one's contamination.
Spawn with clean, ideally alcohol-wiped hands and tools in as draft-free a space as possible, since a stray contamination introduced at spawning shows up as green mould weeks later.
Remove a contaminated bag from the room immediately, seal it, and dispose of it well away from the growing area — burning or deep burial, not just leaving it outside the shed door.

Chemical control

There is no effective in-bag fungicide treatment once green mould has established — chemical control here means disinfecting the room and equipment between batches, not spraying an infected bag.
A recommended room fumigant or surface disinfectant, applied between batches following the label instructions, reduces the spore load a new batch starts against.

Crops most at risk

Where this problem is called out in our crop guides — open a crop for the full package of practices.

Mushroom

Varieties to consider

Named seed varieties whose resistance or susceptibility to this problem is documented on their own variety page.

Frequently asked questions

My substrate bag turned green after a week — is there any way to save it?

No. Once green mould (Trichoderma) is visibly established, there is no treatment that will let that bag still produce mushrooms — the mould has already out-competed the mushroom mycelium for the substrate's nutrients. Remove and dispose of the bag immediately, well away from the growing area, to stop its spores from spreading to your other bags.

Why does green mould keep coming back in my shed even though I clean the bags?

It is almost never the bags themselves — it is usually the room. Leftover spores from a previous infected batch survive on walls, floors and equipment and infect every new batch from day one. Whitewash the walls with lime and fumigate or deep-clean the entire room between every batch, not just the bags.

Is under-pasteurised straw really the main cause?

Yes, in the great majority of cases. Trichoderma spores are present on straw and in the air almost everywhere — correct pasteurisation (the full recommended time and temperature, straw not packed too densely for heat to reach the centre) kills them before spawning. A rushed pasteurisation is the single most common root cause of a green-mould outbreak, more often than bad spawn or a dirty room.

Symptoms and control measures follow ICAR, KVK and state agricultural-university package-of-practices; any named chemical is a registered use. Always read the product label and confirm the dose for your crop and zone. editorial policy.