This document summarizes mushroom diseases and disorders caused by biotic and abiotic factors. Biotic diseases are caused by fungi, bacteria, and insects. Major fungal diseases described are olive green mould, inky caps, brown plaster mould, green mould, false truffle, and white plaster mould. Bacterial diseases include bacterial blotch. Abiotic disorders discussed are rose comb, stroma, hollow core/stem, long stem/stipe, brown discoloration, scales or crocodiles, and purple stem. Causes, symptoms, and management strategies are provided for each disease and disorder.

1. MUSHROOM DISEASES AND DISORDERS
Diseases and disorders of button mushroom (Agaricus bisporus) are caused by two
factors viz., biotic and abiotic. Biotic includes parasitic and antagonistic fungi, bacteria and
insect pests. The abiotic causes of various diseases include temperature, relative humidity,
carbon dioxide concentration in the air, moisture level in compost and casing and presence of
toxic chemicals in atmosphere, compost or casing.
Biotic causes:
Olive Green Mould (Chaetomium spp.)
Symptoms
The early symptoms of fungus consists of appearance of inconspicuous greyish white fine
mycelium in the compost ten days after spawning that delays spawn growth. Fruiting structures of
the fungus look like grey-green, cockle-burns that develop on the straw in isolated spots of the
affected compost. The infected compost gives a musty odour. The fungus grows in compost that
remains too wet and is not properly prepared. This can be attributed to ammonia left in the
compost after peak heating or due to under-composting.
Management
 The fermentation period of the compost should not be too short.
 Avoid too wet compost mixture and the mixture should not be pressed too hard during
composting.
 Sufficient oxygen should be provided during pasteurization.
 In severe cases, respawning of the compost should be done to get good yield.
Inky Caps (Coprinus spp.)
Symptoms
Inky caps appear in the compost during spawn run or newly cased beds and in the
compost pile during composting. These are slender, bell-shaped, cream coloured mushrooms later
turning bluish black which ultimately decay and produce blackish slimy mass resembling inky
fluid. It depletes the food material from the compost and hampers spawn run and yield.

2. Management
 Rogue out young fruit bodies of the weed fungus to avoid further spread.
 Properly pasteurize the compost.
 Compost mixture should not be pressed too hard during composting.
 Add sufficient gypsum in the compost.
Brown Plaster Mould (Papulaspora byssina)
Symptoms
The fungus is characterized by production of large and dense white patches initially on the
compost and then upon casing surface, later turning brown and powdery with time. No mushroom
grows on places where plaster mould occurs.
Management:
 Localized treatment of infected spots with 2% formalin or carbendazim (0.05%) in initial
stages after the removal of affected portions.
 Prepare compost from fresh materials.
 Regulate compost moisture between 62-65%.
Green Mould (Trichoderma spp.)
Symptoms:
The fungus appears in spawn bottles, compost, casing soil and on grains after spawning.
A dense, pure white growth of mycelium appears on casing surface or in compost which resemble
mushroom mycelium. Later the mycelium turns to green colour due to heavy sporulation, which
is the characteristic symptom of the disease. Sometime the fungus develops on the newly formed
primordia and also grows around dead butts of the mushroom. In severe cases, there is complete
crop failure. The fungus also causes dry sunken brown spots on stem and cap.
Management:
 Maintain proper hygienic conditions in and around the growing house.
 Proper pasteurization and conditioning of the compost.
 Lower down the temperature in the growing room to 15-180
C.

3.  Treat the affected patches with formalin 2% or carbendazim 0.05%
 Destroy the infected bags.
False Truffle (Diehliomyces microsporus)
Symptoms
The disease is also known as calve’s brains as it grows with a creamy white mycelium
resembling mushroom mycelium in the initial stage. This may appear mostly at the juncture of
compost layer and the casing mixture. Initially, the fungal fruiting body appear like small pin
heads of mushroom and later turning to thick, bold, yellowish, grayish wrinkled mass resembling
brain like structures. At maturity, fruit bodies emit chlorine like odour and spreads fast on the
compost and on casing soil. It usually appears when the temperature of the growing room exceeds
250
C.
Management:
 Prepare compost on a concrete floor.
 Avoid temperature above 250
C during spawn run and after casing.
 Lower down the temperature to 15-180
C in the growing room during cropping.
 Formalin 2% or carbendazim (0.05%) should be used to check the initial infection by
treating the infected patches.
White Plaster Mould (Scopulariopsis fimicola)
Symptoms
The disease appear as dense white patches of mycelium on compost or casing soil giving
floor like appearance. The fungus does not change its colour with age as in case of brown plaster
mould. Spawn run is hampered and yield is reduced. It occurs when compost pH is more than 8.0.
Management
 Maintain compost pH less than 8.0.
 Spot touch of formalin 2% or carbendazim (0.05%) after scrapping the fungal mat.
 Proper composting and use of adequate gypsum in compost preparation reduces growth
of mould.

4. Dry Bubble (Verticillium fungicola)
Symptoms
Whitish mycelial growth is initially noticed on the casing soil which turns grayish yellow.
If infection takes place in early stage, typical onion shape mushrooms are produced. Infection at
later stage leads to malformed mushrooms with distorted shaggy swollen stipes and tilted caps. In
severe form, it produces light brown depressed necrotic spots on fully developed sporophores. In
the later stages, these become irregular swollen masses of leathery tissues.
Management
 Use properly sterilized casing soil.
 Proper disposal of spent compost.
 Dithane M-45 0.2% or carbendazim 0.05% treatment at 10-day interval is effective in
controlling dry bubble.
Wet Bubble (Mycogone perniciosa)
Symptoms
Infection takes place early before differentiation of stipe and pileus resulting in
sclerodermoid like masses. If infection takes place after differentiation, mushrooms with
thickened stipe and deformed gills develop. In severe cases, there is putrefaction of fruiting
bodies giving unpleasant smell. The infected pinheads decay with brown to umber colour liquid
ooze.
Management:
 Cover the infected spots with common salt and plastic caps to prevent the spread of
infection.
 Maintain proper hygienic conditions
 Spray Dithane M-45 (0.2%) at 7 day interval in severe cases.

5. Cobweb (Dactylium dendroides)
Symptoms
It produces conspicuous cottony grayish to rose red mycelial patches on casing soil. Later it
engulfs the developing pin heads and buttons which results in their rottage.
Management:
 Avoid excessive humidity during cropping.
 Treat infected portion with 0.15% calcium hypochlorite solution or spray with 0.2%
Dithane M-45.
(B) Bacterial diseases
Bacterial Blotch (Pseudomonas tolassii)
Symptoms
The diseased mushroom shows yellowish brown patches on cap and stipe. In severe cases
whole mushroom turns brown in colour. Sometimes brown sunken pits are also seen on
mushrooms. The young pinheads turns brown in colour and die prematurely. The disease spreads
rapidly when mushrooms stay wet for long.
Management
 Avoid spraying water directly on developing pinheads.
 Keep fans on or doors and windows open after water spray to allow quick drying of
mushrooms.
 Remove diseased mushrooms and spray bleaching powder at 0.05% at seven day interval.
 Avoid temperature above 180
C and humidity more than 85 % during cropping.
 Streptomycin 200 ppm or oxytetracycline 300 ppm is also effective in controlling the
disease.
ABIOTIC CAUSES
a) Rose comb
b) Stoma
c) Hollow core/stem

6. d) Long stem/stipe
e) Brown discoloration
f) Scales or crocodiles
g) Purple stem
Rose Comb
Causes:
 The deformity occurs due to contamination by hydrocarbons (diesel or kerosene)
 Contaminated casing soil with heavy overdose of pesticide
Symptoms:
 Pink gill tissues with porous appearance develop on the surface of the mushroom cap
giving comb like appearance
 Mushrooms are distorted and unsalable.
Management:
 The use of diesel/ kerosene for heating the growing rooms should be avoided.
 Heat the growing room with steam and the vapours will also maintain the humidity.
 Use of pesticides in the casing soil should be limited.
Stroma: It is due to high carbon dioxide concentration, high relative humidity and high
temperature in the growing room.
Symptoms: Mycelium after penetrating the casing soil do not form pinheads but continue to
grow to form thick mycelial mat above the casing layer.
Management:
 Ruffle the affected casing layer and recase.
 Maintain the carbon dioxide concentration below 300ppm. Bring down the temperature
below 150
C in the growing room.
Hollow Stem: This abnormality arises due to low humidity, excess of dry air and less moisture
in the casing.

7. Symptoms
 Stems are not solid, instead they are hollow.
 Stipe begins to split and forms scale on stipe and pileus.
Management:
 Avoid low humidity in the growing room
 Keep the casing soil moist.
Long stipe:
High carbon dioxide concentration in the growing room during cropping.
Symptoms:
 Excessive elongation of stipes, sometimes giving drumstick like appearance
 Mushrooms open prematurely
Management
 Provide proper ventilation during cropping to bring down carbon dioxide concentration
below 300ppm.
Brown Discoloration:
Cause
 High temperature
 Sprinkling water at higher pressure
 High chlorine concentration in the water. Incorrect use of formalin
Symptoms: Browning of small pinheads or half growing mushrooms
Management
 Bring down the temperature of the growing room to 13-180
C.
 Sprinkle water on the pinheads at low pressure.
 If needed, apply chlorine water at the rate of 500ml/100 lit. Water/100m2 area.
Scales or Crocodiles
Cause
 Too much drying of mushroom beds or too great air velocity in the growing room

8.  Strong vapours of formaldehyde or use of pest control products in excess can also cause
the outer layer of skin of half growing mushrooms to tear.
Symptoms: The scale arises throughout the surface tissues which fail to grow while caps
develop further.
Purple Stem
Cause
 Polyphenoloxidase enzyme increases in later breaks and this enzyme influences pigment
formation.
 Conditions that predispose mushroom to this phenomenon are unknown but the
frequency and the amount of water applied before harvest seems to affect its occurrence.
Symptoms: Cut stems of mushrooms develop a deep purple colour within few hours of harvest
or being in cold storage overnight.
Management
 Never spray water before harvest of the crop.
 Do not steep cut mushrooms in water for too long.
 Do not rub mushrooms vigorously while washing.