Abiotic Disorders
1. Agaricus
bisporus a. Storma Stroma or
sectors / sectoring are noticeable agreegations of mushroom mycelium on surface
of spawned compost or the casing. Discrete aerial patches of white mycelium form
a dense tissue layer on the substrate surface. Stroma can easily be peeled from
the surface of compost or casing. Storma appearing on the compost in
small-localized patches can coalesce into larger areas. After casing, stroma may
form on the casing above a patch of compost-borne stroma or on casing where
stroma does not exist in the compost. Stroma on casing develops in advance of
pinning but rapidly putrefies once watering begins. Mushrooms can develop on
stroma, but this is somewhat unusual. Stroma and sectors are related to the
genetic character of the spawn but are sometime induced if spawn is mishandled
or exposed to harmful petroleum based fumes or chemicals or certain detergents
during preparation, storage, transit or at the farm. Production
practices during cropping also affect the appearance of these abnormalities but
specific relationship has not been elucidated. Excessive CO2, with high water
content in the compost and prolonged spawn run period may also result in stroma.
Large patches of stroma of 8 to 12 inches are often removed from the compost or
casing surfaces with the hope that next growth of spawn will be normal and bear
mushrooms. b. Weepers
/ Strinkers / Leakers Mushrooms
described as being ‘Weepers’ typically exude considerable amount of water
from mushroom cap. When small water droplets exude from stem or cap, the
mushrooms are called leakers. These water droplets may be few in number and
relatively isolated from each other or may be sufficiently numerous to cover the
mushrooms. A weeping mushroom can dissolve into white foam. Water collects on
the casing surface beneath a weeper and the area developes a putrid odour
becoming a ‘stinker’. Factors that induce a mushroom to become a weeper are
not known but low-moisture compost (less than 64%) coupled with high moisture
casing is where weepers are frequently seen. The combination of these two
conditions often foster weeper mushrooms prior to and during the first break. In
some strains it may also symbolize the degeneration of the strain. c. Hollow
core and brown pith These two
disorders seem to affect cream strains much more than other strains, although
off-white strains can also have hollow core. When the bottoms of the stems are
trimmed after harvesting, a circular gap is seen in the centre of the stem. This
hole may extend the length of the stipe or it may be shorter. When the hollow
cut end portion is brown in colour the sale price is considerably reduced. This
abnormality seems to be related to watering and water stress. d. Purple
stem / Black leg / Storage bum Cut stems of the
mushrooms develop a deep purple colour within few hours of harvest or after
being in cold storage overnight. At times colour is closer to balck than purple
and it occurs in all strains smooth white, off-white, cream and brown. Generally
mushrooms from 3rd break to the end of the crop are most susceptible. Conditions
that predispose mushrooms to this phenomenon are unknown but the frequency and
the amount of water applied before harvest seems to affect its occurrence. e. Rose
comb As the name
indicates pinkish gills form large lumps and grow on the cap in an abnormal
manner giving the appearance of the comb. These abnormal gills appear at various
places on the fruit body and give it swollen or spongy appearance. Such
mushrooms are not marketable. The abnormality is caused by smoke or gases or
vapours of kerosene oil, petrol, diesel paint or oil products etc. f. Scales or
crocodiles On the top of
the cap, scales arise due to high velocity of air coupled with low RH. Strong
vapours of formaldehyde or pest control products in excess can also cause the
outer layer of the skin to tear off. The scale symptoms reduce the value of the
mushrooms.
Fig. 15. Scaling
in mushrooms
Fig. 16. Long stemmed mushrooms g. Long stemmed
mushrooms Mushroom with long stems and
small caps that may look like drum sticks can indicate virus diseases but it is
often the result of high CO2 concentration. With the improvement of aeration
such conditions can be corrected. h. Brown
discolouration Browning of
small pin heads or half grown mushrooms is very common on On the top of the cap,
scales arise due to high velocity of air coupled with low RH. Strong vapours of
formaldehyde or pest control products in excess can also cause the outer layer
of the skin to tear off. The scale symptoms reduce the value of the mushrooms
seasonal mushroom farms. This may be caused by high temperature, sprinkling
water with high pressure (maximum pressure is 0.4 atm), highly chlorinated or
excessive use of formalin for spray. i. Mass
pinning In many
instances symptoms of mass pinning or pinning below the casing are observed,
especially during seasonal cultivation. Sudden fall in temperature, excessive
aeration or early lowering of CO2 concentration than recommended can lead to
such symptoms. Many of the abiotic disorders are strain specific and some
high yielding strains may be more sensitive. 2. Oyster
mushroom As compared to
white button mushroom, there are few physiological disorders recorded in oyster
mushrooms. Reduced light in the cropping room results in longer and thicker
stipes and pileus is partly reduced. Insufficient ventilation (1-2% carbon
dioxide) and low light exposure induce bunched growth of mushrooms. General
guidelines Initial inoculum
load, density, the rate at which the disease develops/spreads and the time of
infection determines the control measures to be applied. The following
preventive and/or eradicative control measures are adopted for the management of
diseases: ●
Ecological-by
manipulations of environmental factors such as temperature, humidity and
ventilation ●
Biological-by
incorporation of biocontrol agents and organic amendments ●
Chemical-by
use of safe and minimum doses of specific fungicides, antibiotic, etc A close
relationship exists between crop management practices and some endemic disease
problems like dry bubble, brown blotch and truffle. Biological agents are being
increasingly tried throughout the world but with a limited application on
commercial scale. Sanitation and hygienic measures are most essential to manage
the disease particularly under Indian conditions although under certain
situations use of chemicals is inevitable. Sanitation
and hygiene Hygiene covers
all the measures, which are necessary to minimize the possible incidence of the
pests and pathogens. Thus, hygiene and sanitation go hand in hand at all stages
of mushroom growing. Farm hygiene is the best defense for a mushroom grower
against mushroom pests and diseases particularly during the present time, when
use of chemicals on food crops is being discouraged. Based on the critical
observations during all the stages of mushroom production, the following steps
should be adopted as a routine practice for successful mushroom cultivation. ●
The location of mushroom unit
should be away from chemical industries and should be free from toxic fumes or
gases ●
Floor for the preparation of
compost should be cemented/tiled and covered with a roof. ●
Substrates used for compost
preparation should be fresh, protected from rain and mixed in exact proportion. ●
Pasteurization and conditioning of
the compost should be for optimum duration at right temperatures as over/under
pasteurization may produce poor quality compost and invite disease problems. ●
Do not allow free access of
persons working in composting yards to spawning and other cleaner areas without
changing the dress and foot-dip. ●
Spawn should be fresh and free
from all contaminants. ●
Spawning area must be washed and
disinfected with 2% formalin. ●
The fresh air should be filtered
before it enters the growing rooms to exclude all particles of 2 micron and
above. ●
Casing mixture should be properly
sterilized (65°C for 5-6 hours). ●
Casing mixture should be stored in
a clean and disinfected place. All the containers, equipments and machinery used
for casing should be thoroughly washed and disinfected. ●
Picking should start from new or
cleaner crop towards older crops. ●
Waste from picking, trash, stems,
unsaleable mushrooms should be carefully collected not allowing to fall on the
floor and be disposed off carefully. ●
Avoid surface condensation of
water on developing mushrooms. ●
Add bleaching powder (150ppm) at
every watering to manage bacterial disease. ●
Remove heavily infected bags from
the cropping rooms or treat the patches by spot application of 2% formalin or
0.1% Bavistin. ●
Maintain optimum environmental
conditions in the cropping rooms to avoid abiotic disorders. ●
Control insect-pests well in time
to avoid the spread of pathogen by them. ●
At the end of crop, cook out at
70°C for 12 hours is very essential to eliminate all pests and pathogens. Use of
chemicals Some of the most
common fungicides recommended for the control of major fungal pathogens of
mushrooms and used in mushroom industry are: ●
Benomyl (Benlate 50 wp)- For
control of Cladobotryum, Mycogone, Trichoderma, Verticillium, mix 240 g/100 m˛
with casing or dissolve in water at 240 g/200 litres/100 m˛ during first
watering. ●
Carbendazim (Bavistin) same as for
benomyl. ●
Chlorothalonil (Bravo or Repulse)
- to control Mycogone and Verticillium. Apply as spray 2 week after casing and
repeat after 2 weeks later @ 200 ml in 100-200 litre water/100 m2. ●
Prochloroz Manganese (Sporgon)- to
control Mycogone, Verticillium, Cladobotryum, give a single application of
300g/100litres/100m˛, 7-9 days after casing. For double application, use
113g/100litres/100m˛, 7-9 days after casing and repeat again between second and
third flushes. For triple application, use 57g/100litres/100m˛, 7-9 days after
casing and after first and third flushes (presently sporogon is not available in
India). ●
Thiabendazole(Tecto)- to control
Cladobotryum, Mycogone, Verticillium, Apply at the same rate as Benomyl. ●
Zineb- to control Dactylium,
Mycogone, Geotrichum and Verticillium, Use 350 g/ 100 m˛ every week after
casing. For wettable powder, 1 kg/1000 litres @ 5 litre/ 100 m˛ after casing
and between flushes. As a general
practice, cook out of compost, fumigation of cropping rooms after cropping with
formaldehyde and spray with copper fungicides helps in removing primary inoculum.
Similarly it may be appropriate to spray 0.5% formalin or 0.1% bavistin just after casing to
check the primary inoculum. The chances of infection are much higher at these stages as
there is lot of movement of air, materials and persons and all are potential carrier of
diseases.
Besides
the biotic agents, which adversely affect the mushrooms, there are a large
number of abiotic agents which create unfavourable environment for the proper
growth of 170 Mushrooms :
Cultivation, Marketing and Consumption mushrooms
resulting in the quantitative as well as qualitative losses. These abiotic
agents include temperature, relative humidity, low or high moisture in the
substrate, pH, CO2 concentration in the room, wind velocity and fumes. Some of
the most common abnormalitities generally encountered during button mushroom
cultivation are as under.
