MushroomFarming / disease

Button Mushroom diseases

Move from observation to differential diagnosis, containment and prevention without unsafe treatment shortcuts.

Practical explanation + detailed referenceSources & review ↓

Real cultivation photograph. Read its source for location and context; it is not a universal operating specification.I. G. Safonov (IGSafonov) · CC BY-SA 3.0View full photograph ↗

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Read this in the full guide: Run a Button mushroom crop from receipt to room reset →

Understand the topic

What you need to know.

Many button mushroom diseases and disorders look alike, and no single sign or photograph can name them. This page works symptom first: what the common diseases look like, what else can cause the same sign, the conditions ICAR-DMR links to each, what to contain on the first day, and which compost or casing step a mould points back to. It gives no fungicide doses.

Teaching revised 2026-09-24. Source-linked editorial synthesis; this date does not imply independent technical review.

Part 01

Describe the pattern before you name a disease

The same sign can come from a fungus, a pest or the room itself. The ICAR-DMR manual gives examples. Long-stemmed mushrooms with small caps can indicate virus disease, but are often the result of high carbon dioxide. Onion-shaped mushrooms follow early dry bubble infection, and also high carbon dioxide at pinning. Pins that stop growing and die can be the work of sciarid larvae feeding inside them.

So record before you conclude. Note where the problem is and where it is not, how many mushrooms or bags are affected, which flush is running, and what changed on the farm in the days before. A problem that spreads outward from a point suggests an infection or a moving pest. A sign spread evenly across a room points first to a condition such as temperature, gas or water, or to one lot of compost or casing.

Keep a photograph of healthy growth for comparison. Healthy mycelium is white, and so is the early growth of several moulds.

Source: ICAR-DMR manual, 2011

From a sign to a working diagnosis

DescribeWhat it looks like, how many are affected, since when.
MapWhere it is, and where it is not.
ListEvery cause that could give the same sign: fungus, pest or room.
TestRun the cheapest check first and cross off what it rules out.

Part 02

Signs on the crop, and what else can cause each one

Each line gives a sign as the manual describes it, the disease it is often linked to, and a look-alike to rule out. Treat each as a lead to check, not an answer.

Shapeless swollen masses, or thick stems with deformed gills, later rotting with a foul smell and golden-brown drops: typical of wet bubble. Dry bubble also deforms mushrooms, but leaves them dry and leathery.
Onion-shaped mushrooms, or small lumps of tissue up to 2 cm across, after whitish growth on the casing: early dry bubble. High carbon dioxide at pinning also gives onion shapes, without growth on the casing.
Light-brown sunken spots on mature caps that join into irregular blotches, with the cap shrinking, turning leathery and cracking: later dry bubble.
Dark brown, slimy spots on caps, worst where water sits: bacterial blotch. Bruising and fungal spotting also brown the cap, so check the watering record.
Fine grey-white growth spreading from the casing to the nearest mushrooms and covering stem, cap and gills, turning pink with age: cobweb.
Dense white growth on casing or compost that later turns green: green mould. The manual lists Trichoderma species and also Penicillium and Aspergillus under this name, so the colour does not identify the fungus.
White to cream wrinkled masses like small brains, 0.5 to 3 cm across, in compost or casing: false truffle. At maturity they break down into a powder with a chlorine-like smell.
Late pins in the first flush, pins forming under the casing, dense clusters, watery or brown stems: possible dieback virus. The symptoms vary widely, and symptoms alone are unreliable.

Source: ICAR-DMR manual, 2011

White button mushrooms in the corner of the frame with white thread-like mycelium running through dark growing medium. — Young button mushrooms beside the healthy white mycelium strands that feed them. Early cobweb and green mould also start white, so compare any white growth with a healthy patch. Photo: Ірина Бучнєва, CC BY 4.0. Source

Part 03

Conditions the manual links to each disease

These values explain why a disease appears in one room or season and not another. Most of them can be measured today.

Dry bubble develops best at20 °CDistortion shows about 10 days after infection, cap spots after 3 to 4 days. Favoured above 16 °C with high humidity, poor air circulation and delayed picking.

Time for uncontrolled dry bubble to destroy a crop2 to 3 weeks

Wet bubble resting spores survive in casing soil forup to 3 yearsCasing soil is the main route in.

Blotch spots on caps grow larger from20 °C or aboveOnly with a water film on the cap; worst when the film lasts more than 3 hours. Avoid humidity above 85 percent with temperature above 20 °C.

Cobweb losses are greatest at19 to 22 °CWith high humidity.

False truffle appears above23 °CFebruary or early March in the north Indian plains; summer in the hills.

Sources: ICAR-DMR manual, 2011 · NHB DPR model, 2018

Part 04

Contain first, then get the problem identified

Containment needs no diagnosis and costs little. Do it the same day, then gather the evidence an adviser needs.

Mark it and leave itMark the affected patch. Do not brush, blow or splash it, and keep watering away from it.
Cover wet bubble mushroomsThe manual suggests covering mushrooms that show wet bubble with plastic pots or cups during cropping, to prevent spread.
Take out heavily affected bagsRemove them from the room without carrying them over healthy beds.
Change the order of workVisit and pick the affected room last, and wash hands and tools afterwards.
Record the evidencePhotograph the patch and a healthy patch, and note bed positions, flush, casing lot, watering and room readings.
Ask for identificationSend the record to ICAR-DMR, a KVK or an agricultural university; ICAR-DMR lists crop protection diagnosis among its services. Ask how to collect a sample before sending one.
Keep chemicals behind a gateThe manual documents fungicide use, but no doses are given here. Any product needs current label approval for mushrooms in India.

Sources: ICAR-DMR manual, 2011 · ICAR-Directorate of Mushroom Research: Technical and diagnostic services

The first day after a sign appears

MarkFlag the patch; do not touch or splash it.
ContainCover, remove, pick that room last.
RecordPhotographs, positions, flush, casing lot, readings.
AskSend the record for identification before any treatment.

Part 05

When a mould appears, check the step it points back to

The manual's table of competitor moulds reads like a checklist of compost and casing steps. A mould is often a message about the last few weeks of work.

IfGreen mould: ThenCheck compost pH, since low pH favours it, and whether the spawn was immature. The manual also links it to carbohydrate-rich, nitrogen-poor compost and frequent formalin use, and names mites and sciarid flies as carriers.
IfWhite plaster mould: ThenCheck for high compost pH and an ammonia smell. The manual links it to under- or over-composting with pH above 8.0.
IfInk caps: ThenCheck for ammonia left in the compost, too much nitrogen, old straw or very wet compost. The manual wants ammonia below 10 ppm at spawning.
IfOlive green mould: ThenLook at Phase II: lack of aeration, or temperatures above 60 °C during pasteurisation.
IfBrown plaster mould: ThenCheck for old straw, wet compost, too little or poor gypsum, and high temperature.
IfCinnamon mould: ThenCheck whether the casing was too wet or too strongly disinfected with formaldehyde.

Source: ICAR-DMR manual, 2011

Close view of two plastic substrate bags; one is streaked dark green and grey, the other is brown with pale growth. — Two sawdust substrate bags at a farm in Malaysia, not a button crop. The left bag is covered in a dark green mould of unidentified species; its colour alone cannot tell which fungus it is. Photo: Arne Müseler, CC BY-SA 3.0 DE. Source

Part 06

Mistakes that let one disease become a crop loss

Common mistakeNaming a disease from one sign or one photograph.

Do this insteadRecord where it is and is not, and whether it spreads, before choosing a name.

Common mistakeBrushing, splashing or walking through an affected patch while picking or watering.

Do this insteadMark it, work around it, and do that room last.

Common mistakeUsing casing that was not pasteurised, or storing it near the rooms.

Do this insteadPasteurise casing and store it clean. The manual names casing soil as the main route in for both wet bubble and dry bubble.

Common mistakeChoosing a fungicide from an old list or a neighbour's advice.

Do this insteadCheck current label approval for mushrooms in India. Approvals change after a document is printed.

Source: ICAR-DMR manual, 2011

Go deeper

Technical reference, records and tools.

Detailed crop-stage information, parameters, diagrams and specialist tools are kept together below. This material retains its source conditions and review limits.

Open the complete technical reference

Button Mushroom · disease

Button Mushroom diseases

Agaricus bisporus

Move from observation to differential diagnosis, containment and prevention without unsafe treatment shortcuts.

Publication: Public editorial page
External review: Not yet recorded · needed from Button Mushroom technical reviewer
Updated: 2026-08-22
Evidence records: 3

From symptom to cause

A first look, not a diagnosis. Most signs have more than one possible cause. Source: ICAR-DMR manual 2011.

What you see	One common cause	First step
Long stems, small caps	CO₂ building up around the crop; poor air movement	Correct the air circulation; cropping CO₂ 800 to 1,000 ppm
Green patches on compost	Green mould; low compost pH, immature spawn	Isolate, remove; check the next batch
No pins after casing	Room not aired and cooled	Air at 15 to 17 °C, RH 85%, ventilate
Brown sunken spots on caps	Bacterial blotch; a water film on the caps	Manage humidity, temperature and air movement so caps dry
White wet lumps	Wet bubble; spores survive in casing soil	Cover with plastic cups; treat the next casing
Small flies	Sciarid or phorid flies	Screens, light traps, hygiene

Picture → explanation → field task

Keep clean and suspect work separate

AI-generated educational illustrations. Not actual farm photographs, diagnostic evidence or construction specifications.

Generated illustration of dedicated work footwear and a handwashing basin at a farm entrance.

Make clean entry a routine

Clean entry has a place and a repeatable sequence. Footwear, hands and movement between areas are part of farm hygiene. The illustration does not demonstrate a validated disinfection process.

Try this on your farm

Assign the entry routine, provide suitable facilities and check that visitors and workers follow it.

Generated illustration of raw straw separated from closed cultivation bags on a different bench.

Protect prepared material

Raw inputs and protected prepared material are separated. Treatment does not protect a substrate indefinitely. Handling afterwards can introduce contamination.

Try this on your farm

Keep work areas, tools and movement routes separated. Label batches so a later problem can be traced to its preparation history.

Generated illustration of two closed cultivation bags in a washable tray with dedicated tools.

Keep suspect bags closed

A separate tray helps identify material being held for investigation. The bags are illustrative and not diagnosed. Opening, shaking or smelling suspect material is not a confirmation method.

Try this on your farm

Mark the batch, limit movement and seek qualified advice on sampling or disposal. Do not return dedicated tools to clean work without the appropriate procedure.

Generated illustration of a covered waste tub leaving a separate area away from covered harvest crates.

Plan the spent-material route

Used material and saleable harvest follow different handling paths. A disposal route can undo clean-work separation if it crosses incoming materials or harvest handling.

Try this on your farm

Map the exit route and cleaning responsibility. Check the actual workflow during a busy room turnaround, not only on a drawing.

Button mushroom · Photo reference and management

See the symptom. Check the cause. Act carefully.

Real research photographs with practical, nonchemical first steps. These examples come from published studies, not MushroomWale farms. Resemblance is a clue, not confirmation of disease in your crop.

01Observe the crop and record the pattern
02Limit transfer to clean areas
03Check the diagnosis and follow a response plan
04Review the next crop for recurrence

Dry bubble

Look for malformed mushrooms, split stems or wart-like growths. Later infection can appear as grey-brown cap spots; the appearance changes with crop stage.

What to do first: Mark the patch and do not pick out or handle dry bubbles. Avoid splashing exposed affected tissue. Have a trained supervisor contain the patch using the linked extension procedure.
Reduce the chance of recurrence: Keep casing, casing equipment and clean tools protected from contaminated dust and debris. Check fly control and movement of people between rooms.
What can look similar?: Wet bubble and other causes of spotting can look similar. A photograph cannot identify the pathogen; ask for specialist examination when the pattern is unclear.
What to record: Record when the first affected mushrooms appeared, their bed positions, watering history and whether new spots developed nearby.

Read the full condition guide →AHDB: dry bubble recognition and containment ↗Undated archived guidance; accessed 17 September 2026. International guidance: adapt with a qualified adviser for your Indian farm.

Wet bubble

Irregular swollen tissue, severely distorted mushrooms and amber droplets are useful clues. Decay can develop as affected tissue deteriorates.

What to do first: Mark the area and avoid splashing it. Once wet bubble is identified, trained staff can carefully enclose local affected material in a disposable bag, seal it and follow the farm's containment and disposal procedure.
Reduce the chance of recurrence: Protect casing and water supplies from soil, dust and crop debris. Keep clean equipment away from contaminated floors and spent material.
What can look similar?: Do not apply this removal approach to an unidentified bubble: dry bubble handling differs. Ask a crop-health specialist to distinguish them.
What to record: Record the casing lot, first affected location, water source, spread after watering and photographs before intervention.

Read the full condition guide →AHDB: wet bubble recognition and containment ↗Undated archived guidance; accessed 17 September 2026. International guidance: adapt with a qualified adviser for your Indian farm.

Research reference: white cottony growth spreading across mushrooms and casing, captioned as cobweb in Gea et al. Figure 1b. — **Published research photograph**Panel 1b, lower photograph. Display cropped; no symptom retouching.Gea, Navarro, Santos, Diánez & Carrasco (2021), Figure 1, Microorganisms 9:585 CC BY 4.0The publication identifies crop symptoms in the lower row; the upper row contains cultures. Only the crop photograph is shown here.

Cobweb disease

Watch for an expanding cottony surface growth across casing and mushrooms. Older growth may become powdery, with spotting or a pinkish tinge.

What to do first: Mark the patch before routine watering. Do not brush, blow or spray exposed growth. Arrange gentle containment by trained staff, following the extension procedure and the room's crop-management plan.
Reduce the chance of recurrence: Inspect before watering, control dust and crop debris, and clean equipment between rooms. Review how air movement and watering could carry material from an affected patch.
What can look similar?: Normal mushroom mycelium and other moulds may look white. Rate of spread, location and examination of samples matter more than colour alone.
What to record: Photograph the same marked area over time. Note nearby spotting, recent watering and which rooms shared tools or staff.

Read the full condition guide →AHDB: cobweb recognition and containment ↗Undated archived guidance; accessed 17 September 2026. International guidance: adapt with a qualified adviser for your Indian farm.

Research reference: green-sporulating growth in a Button mushroom crop, captioned as green mould in Gea et al. Figure 1d. — **Published research photograph**Panel 1d, lower photograph. Display cropped; no symptom retouching.Gea, Navarro, Santos, Diánez & Carrasco (2021), Figure 1, Microorganisms 9:585 CC BY 4.0The publication identifies crop symptoms in the lower row; the upper row contains cultures. Only the crop photograph is shown here.

Green mould observation

A dense white patch may later become green as spores form. Poor cropping can accompany the affected area, but colour does not identify a mould species.

What to do first: Flag the batch and restrict movement of affected material, tools and staff into clean areas. Do not shake bags or brush spores off beds. Obtain advice on containment and whether the crop should continue.
Reduce the chance of recurrence: Review compost preparation, spawning hygiene and batch history together. Check cleaning and the validated end-of-crop treatment before loading another crop.
What can look similar?: Several moulds can appear green. Laboratory identification may be needed to establish whether Trichoderma is involved and which species it is.
What to record: Record whether growth is in compost, casing or surface debris, which input lots are shared, and whether other rooms from the same batch are affected.

Read the full condition guide →Penn State Extension: green mold of mushrooms ↗Updated 23 December 2025; accessed 17 September 2026. International guidance: adapt with a qualified adviser for your Indian farm.

Research reference: brown surface blotching on a naturally affected mature Button mushroom, Huang et al. Figure 1b. — **Published research photograph**Panel 1b, natural symptoms. Display cropped; no symptom retouching.Huang, Huang, Nie & Liu (2024), Figure 1b, Phytopathology Research 6:21 CC BY 4.0Panel b shows naturally affected mature Button mushrooms from the study in Guangxi, China, not an Indian farm or an inoculation experiment.

Bacterial blotch

Yellow-brown to dark brown superficial patches may occur on caps, including places where mushrooms touch or surfaces remain wet.

What to do first: Check actual cap wetness after watering and look for condensation. Correct water timing and air distribution with the crop supervisor so surfaces can dry without desiccating the crop.
Reduce the chance of recurrence: Avoid persistent wet surfaces, uncontrolled temperature swings and splash transfer. Clean handling equipment and compare conditions across the room, not only at the wall sensor.
What can look similar?: Bruising, fungal spots and other bacteria can produce browning. The photographed study found more than one bacterial cause; matching a picture is not a species diagnosis.
What to record: Note when spotting appears relative to watering, picking and packing. Record wetness, condensation and affected positions before changing settings.

Read the full condition guide →Penn State Extension: bacterial blotch disease ↗Updated 23 December 2025; accessed 17 September 2026. International guidance: adapt with a qualified adviser for your Indian farm.

Quick orientation

A disease page should help a grower record and differentiate a problem. It should not turn a photograph into certainty or publish chemical use without current legal, label and safety review.

System role

Disease investigation connects symptoms, spatial pattern, crop stage, material traceability, hygiene and laboratory support.

What to observe

Build a record before making a change.

First location and spread
Morphology and tissue signs
Water and handling pathways
Crop and room history

Decision framework

Use the observation to narrow a decision, then verify the response.

Contain movement
Build a differential diagnosis
Collect qualified evidence
Use only authorised management under competent supervision

Dependencies and handoffs

This topic cannot be interpreted in isolation.

Rapid reporting
Clean sampling
Diagnostic support
Biosecurity procedure
Current regulation

Practical layer

Start in the room with first location and spread and morphology and tissue signs. Record location, stage and recent events before changing the process.

Technical layer

The technical model joins rapid reporting, clean sampling, diagnostic support. Any operating value must be attached to a registered parameter, measurement location and applicable condition.

Evidence boundary

This page is grounded in: Technical Bulletins; Technical and diagnostic services; Crop Advisory, August 2026. Source provenance does not remove the need to check stage, system, date and local applicability.

Progressive depth

Go deeper without losing the field question.

PracticalWhat to notice in the room

First location and spread
Morphology and tissue signs
Water and handling pathways
Crop and room history

TechnicalHow the interacting system is interpreted

Rapid reporting
Clean sampling
Diagnostic support
Biosecurity procedure
Current regulation

ResearchWhich evidence records govern this page

ICAR-DMR-TECH-BULLETINS
ICAR-DMR-SERVICES
ICAR-DMR-ADVISORY-2026-08

Diagnostic relationships

Related observations and differentials.

disease · under review

Dry bubble

Observe

Abnormal tissue or malformed fruit bodies require expert differentiation
Distribution and progression matter
Water injury and other disorders may be confused with disease

Checks and prevention

Discriminating checks

Isolate representative observations
Record the first affected locations and movement pattern
Use qualified diagnosis or laboratory support
Review hygiene, picking and water pathways

Prevention principles

Clean-to-dirty work sequence
Tool and personnel hygiene
Rapid removal under an approved farm procedure
Verified casing and room sanitation systems

disease · under review

Green mould complex

Observe

Green sporulation is a late visual clue, not a complete species diagnosis
The point of first appearance may indicate a process pathway
Affected patches can follow material, water or handling routes

Checks and prevention

Discriminating checks

Record colour change before disturbance
Map affected zones and batch links
Retain traceability for compost, spawn and casing
Seek laboratory identification when action depends on species

Prevention principles

Process verification
Clean material handling
Room emptying and sanitation
Batch-level traceability

Evidence and review record3 mapped sources

Sources support the page architecture and conceptual guidance. Technical values remain governed separately in the Button registry.

Tier A · institutional

Technical Bulletins

Official index for crop protection, post-harvest, farm design, spawn and developed technologies.

Accessed: 2026-08-22
Publisher: ICAR-Directorate of Mushroom Research

Open original source

Tier A · institutional

Technical and diagnostic services

Official scope for compost and casing tests, crop protection diagnosis, farm design and crop-management support.

Accessed: 2026-08-22
Publisher: ICAR-Directorate of Mushroom Research

Open original source

Tier A · advisory

Crop Advisory, August 2026

Time-bounded Indian crop observations and seasonal alerts. Does not overwrite foundational guidance.

Accessed: 2026-08-22
Publisher: ICAR-Directorate of Mushroom Research

Open original source

Read the evidence

Sources & review.

Editorial update: 2026-08-22. Independent technical review is not recorded for this entry.

Technical Bulletins ↗
ICAR-Directorate of Mushroom Research
Technical and diagnostic services ↗
ICAR-Directorate of Mushroom Research
Crop Advisory, August 2026 ↗
ICAR-Directorate of Mushroom Research · 2026 · Date-specific advisory. Chemical recommendations are not reproduced without current label, jurisdiction and safety verification.

Reading a source is not the same as applying its instructions to every farm. Confirm species, strain, crop stage, system, region and publication date. Old chemical recommendations are not current-use instructions.

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