Mushroom growing
Practical Action
The Chakohwa Voluntary Mothers Group grow their mushrooms in plastic bags that are
suspended in darkened rooms. Slits are made in the bags to allow the mushrooms to grow.
This approach requires very little space and by growing in bags contamination can be can
reduced as the plastic will protect the substrate.
It is important to prevent cavities forming within these bags. Any gaps that are left after the
filling process can be eliminated by dropping the bag from a low height onto a firm surface a
few times. The bags are then hung from the rafters of the growing shed and the colonisation
of the substrate by the mycelium begins. This takes about 10 days. Deformed mushrooms
appearing under the plastic indicate that the substrate was not compacted enough and the
mushrooms are growing in the cavities.
There should be air circulating between the sacks so that the temperature can be regulated.
There should also be sufficient humidity to prevent the mushrooms from drying out.
If the substrate in the plastic bags is green or pink in any part and only partly showing signs
of white mycelium growth then the ambient temperature may be too high. This may result in
competitor moulds growing in place of the desired mushroom crop. If the mycelium has not
grown to any extent but there are no signs of growth by other moulds then the temperature
may be too low.
If the mycelium has not grown in the bottom of the bag then this indicates that the substrate
is too wet. This can happen if the bag has not been drained properly after the fermentation
stage so that water remains trapped at the bottom.
If the mushrooms are wrinkled and brown at the edges then it has been too dry during
growing and more moisture should have been provided during the growing stage. They need to
be sprayed with water on a regular basis.
Equipment options
For small scale production there are limited equipment requirements. For larger operations a
steam unit can be used for pasteurising the substrate. These can be made from modified 200
litre drums.
Regulating the temperature is the other main concern – heating and cooling the mushroom
house can be controlled with additional equipment. For example; an electric fire could be
used to maintain an even temperature if electricity is available; cooling could be assisted by
using a table fan blowing over a container of water. Humidity within the growing house can be
increased by watering the floor.
Pests and Diseases
There are a whole range of pests and diseases that can attack mushrooms. The longer
mushrooms are grown in one location the greater the chance of infection from pests and
disease. Therefore it is important to sterilise the growing room and the preparation areas on a
regular basis. Even with care there will be times when an infection occurs, so it is useful to be
able in identifying the particular problem so that appropriate action can be taken. Record
keeping is important to identify where problems arise. Information required includes dates of
stages of compost preparation, nitrogen analysis, temperatures, moisture, pasteurisation
times, opening and closing times of ventilation etc.
Some of the most likely problems are:
Thread like worms or nematodes can infest substrates and eat the mycelium. They
can appear in substrates that have not been pasteurised properly.
Mushroom flies. The most common in Zimbabwe is the Sciarid fly. Again
pasteurisation kills off the fly’s larvae but the flies can enter the growing room if
there are holes in the screens. Cleaning between crops is important and sterilising
equipment helps to prevent contamination.
Mites can survive pasteurisation if it is not done for long enough.
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