Exotic Spawn CC

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General Information

Quick growing oyster mushrooms can be cultivated on a variety of agricultural wastes, including wheat straw, leaves, maize cobs and various pods. They do not need sophisticated machinery and other structures to flourish.  The methods described below are suitable for rural and urban people, growing oyster mushrooms on a small scale for home consumption or a small business.

Oyster mushrooms are fairly resistant to environmental changes, growing at temperatures ranging from 16 - 25 °C and a relative humidity of 60 - 90% of the air.

Oyster mushrooms are easier to grow compared to other cultivated mushroom species.  During favourable seasons they can even be grown in the open, in shaded areas, in forest or between buildings where there is fairly dense vegetation.  It is much better, however, to grow them in protective structures, such as a thatched hut, a climate controlled growing room or even in soil trenches covered by a thatched roof.

 

SUBSTRATES

The medium on which to cultivate the oyster mushroom is called the substrate.

Wheat straw, maize straw, maize cobs and certain veld grasses, such as Hyparrhinia hirta and Eragrotis curvula, are among a number of suitable substrate materials. Sawdust can be used but the mushroom grows poorly on it. Hence, we do not recommend any saw dust as a substrate for the oyster mushroom.

 

SUBSTRATE PREPARATION

The substrate must first be cut into small pieces ( 25 - 50 mm). This can be achieved in different ways from chopping the substrate by hand to the use of a hammer mill.

The next step is to wet the substrate and pasteurise it.  An old oil drum (200 l) would be useful for this purpose. It is vitally important that the drum should be perfectly clean and contain no traces of oil or petrol.

Fit a tap or plug at the lower side of the drum so that it can be drained.  The drum is placed on stones or bricks to raise it above the ground.

The cut substrate is placed into the drum and water is added. The substrate is weighted down by means of stones to completely submerge it. A wire cage fitting into the drum is very handy.

A fire is made under the drum, using materials such as wood, dry dung or coal. The substrate should be kept in the hot water (65 - 75 °C) for at least 4 hours.

 

SPAWNING (Mixing of spawn into the substrate)

After draining off the hot water the pasteurised substrate is allowed to cool down.

The substrate can be spawned while still in the drum. However, this makes proper mixing of spawn and substrate very difficult. Alternatively, the substrate can be spread out on a clean plastic sheet in a protected area for the spawning.

Typically 4-5 % spawn is used, i.e., for every 100 kg of wet, pasteurised substrate, 4-5 kg of spawn is needed. The spawn must first be broken up. This can be done while the spawn is still in the spawn bag. Simply knead the spawn until it is broken up into individual grains.  Mix the spawn thoroughly into the substrate, fill into a growing container made of transparent polythene plastic bags (25 kg).

The spawned substrate should be slightly compressed into the plastic bag. The top of the bag is tried with a string to close it.  One lower corner of the bag is cut off to serve as a drain for excess water.

 

SPAWN RUNNING

The spawned bags are placed in a suitable growing area, such as a grass hut, to allow the mycelium originating from the spawn to colonise the entire substrate (this is called the “spawn run”).

A white cottony growth, the oyster mushroom mycelium, will fill the bags in about 21 days, depending on the temperature. Beware of hot temperatures, above 30 °C, which can kill the entire culture. Temperatures must be monitored carefully during this critical period.

 

GROWING AREA

Oyster mushrooms need a cool (16-25 ^oC), humid environment to grow. In addition some light is necessary as a stimulus for the production of mushrooms. A very simple and relative inexpensive grass structure gave good results.

 

A THATCH GRASS GROWING HUT

Grass has the advantage of being available almost everywhere, being relatively cheap and giving excellent insulation.

Use timber poles and slats to make a frame measuring about 2 x 3 m, depending on available space.  Thatch the frame with grass and secure the grass to the poles with wire and twine.

As oyster mushrooms require some light, an opening must be left in the thatched roof or on one side of the wall.  This opening can be covered with a transparent plastic.

A moveable flap can also be fitted to cover the plastic opening during the heat of the day, particularly during very hot summer months.  Sufficient light enters the hut if the flap is kept open during early morning and late afternoon.

A thatched door must be fitted.

The floor of the hut should be kept wet at all times, thus maintaining the relative humidity of the air at fairly high level.

 

INITIATION OF PINNING

When the mycelium has colonised the substrate fully, it is time to initiate development of mushrooms.

This is done by supplying light, i.e., opening the flap of the roof  opening.

Supplying fresh air by cutting holes in the substrate bag. A hole is cut with a clean knife by making two slits, 20 mm in length, crossing each other at 90° . This produces a hole with four flaps.  Similar holes are made all over the bag , usually  4 - 6 vertical rows , with the holes 100 mm apart .

Light combined with the sudden availability of oxygen, causes many mushroom initials (pins) to form at the holes.

 

HARVESTING AND POST HARVEST HANDLING

The pins grow into mature oyster mushrooms.

They should be harvested when the caps are 5 - 7 cm in diameter.

A sharp knife or a small pair of scissors is best for harvesting; snip individual mushrooms at the stem as they reach the required size. Whole clusters may also be harvested and the mushrooms trimmed off afterwards

Harvested mushrooms can be kept for a day or more, especially if they are kept in a brown paper bag.  A plastic bag should be avoided as it induces bacterial damage and slimy mushrooms.  If the mushrooms are kept in a refrigerator they last even  longer.

 

DISEASE, INSECT PESTS AND HYGIENE

Like any other crop, oyster mushrooms are prone to fungus disease, fungus competitors and insect pests.

Proper pasteurisation, strict hygiene and good management practices can usually overcome most of these problems.

If mushroom flies become a serious problem an aerial insecticide may be sprayed.  It should, however, never be used after the pins have started to form.

The growing mushroom must always be kept very clean and free from any chemicals.

 

WARNING

Oyster mushrooms release millions of dust-like spores into the air.  These spores can cause respiratory mucosa of mushroom handlers and therefore results in asthma and other allergies. Protective measures, like wearing a face masks or wrapping a cloth around the nose and mouth, are strongly advised when working with these mushrooms for long periods of time.  Most spores are released during harvesting and packaging of the mushrooms.