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Mushrooms
Scientific name:
Agaricus spp. (button mushrooms); Pleurotus spp. (oyster mushrooms)
Order/Family:
Agaricaceae (Agaricus spp.); Pleurotaceae (Pleurotus spp.)
Local names:
Swahili: Uyoga; Luhya: Obwoba; Luo: Obwolo; Kikamba: Makunu; Kikuyu: Makunu; Kalenjin: Bobar
Pests and Diseases:
Bacterial blotch   Green mould   Mites  Mushroom flies  Mycophytic nematodes   Virus diseases  Wet Bubble  Bacterial blotch, die-back disease, dry bubble disease, wet bubble disease, green mould, mites, mycophytic nematodes, phorid fly, sciarid fly  

Bacterial blotch (Pseudomonas tolaasi)

The main source of bacterial blotch in the mushroom farm is the casing soil. The disease is favoured by dampness [high humidity (over RH 85%), high temperatures (over 20°C) and poor ventilation in the growing houses]. It can be spread by the workers´ hands, irrigation water and on the inventory. Mushroom flies and mites also spread the disease. The first disease symptoms appear in areas of caps that have been moist for a longest time and areas where mushroom caps touch. Symptoms include spots that darken becoming chocolate-brown in colour and slimy. It can also cause distortion and splitting of the stipes. When the infection is severe, spots spread throughout the whole mushroom surface. Seriously diseased mushrooms can become deformed and the caps can decay giving a foul (unpleasant) odour. Young pins affected by the disease become brown and do not further develop.

What to do:
  • Maintain strict hygiene and sanitation in mushroom facilities
  • Use properly prepared substrate and casing soil that have been adequately pasteusterized
  • Avoid excessive humidity, high temperatures and poor ventilation in growing rooms
  • Avoid fluctuation of temperatures in the growing rooms which may cause water condensation on mushroom caps
  • Remove diseased mushrooms which can be a source of the disease
  • Control mushroom flies and mites which can spread the bacteria
  • Water mushrooms with chlorinated water (125 ml 10% chlorine solution for 100 l of water per 100 m². Use calcium hypochlorite products since sodium hypochlorite may burn caps) before first break when the pin size is 4-5 mm
  • Remove spent substrate from the farm. It can be used as manure for other crops

Green mould (Trichoderma aggressivum var. aggressivum)

This fungus is soil-borne. There are many species of the fungus but Trichoderma aggressivum var. aggressivum (Trichoderma harzianum biotype 4 (Th4)) is a major problem particularly to button mushrooms. It gains entry to growing rooms primarily through contaminated personnel and equipment. Other sources include poorly composted substrate or carryover in rooms that were not sufficiently steamed off. Once introduced, it rapidly spreads into large disease areas from infection source. Infection of casing soil can result in serious losses. Green mold is characterized by dense white mycelial growth followed by extensive green patches on casing/compost or mushroom caps. The spores of the fungus are sticky and can easily be spread by flies, mites and workers to previously uninfected area. Red pepper mites are often associated with the disease.

What to do:
  • Maintain hygienic conditions at all stages of production
  • Use properly prepared substrate and casing soil that have been adequately pasteusterized
  • Remove contaminated substrate as soon as possible from the farm and dispose of it at a considerable distance nor less than 100 metres
  • Control flies and mites
  • Spread table salt on the compost in affected areas when green mold is first recognized.
  • Filter air to prevent colonization of sterilized compost
  • Disinfest all structures and equipment (including clothing) associated with spawning (use immediately after disinfestation or store where air is filtered).

Mites

Mites belong to the spider family. They are eight-legged compared to insects which are six-legged. They are very small and are usually not noticed until large numbers are present. Many different kinds of mites are encountered during mushroom cultivation process. Some mites feed on fungi and bacteria that exist in great amounts in decaying organic materials used as a substrate in mushroom production. Other members of mites are predators that mainly feed on nematodes and smaller mites. Only a few of them are considered as mushroom pests. These include mushroom mites or tarsonemid mites (Tarsonemus myceliophagus) and red pepper mites (Pygmephorus sellnicki). The mushroom mites are so small, that they are not seen with a naked eye. They are shiny, light brown in colour feeding on the mushroom mycelium and mycelium of many other competing fungi present in the substrate. They gnaw the bases of mushroom stipes (stalks of mushroom) which in result become rounded and obtain a reddish-brown shade. The amount of damage they bring to the growing crop will depend on the time and degree of infestation. If a large population of mites enters the batch at spawning, the damage can be significant.

Red pepper mites got their names from their reddish-brown colour and are often found moving on the mushroom caps or the casing surface. These mites are not regarded as primary pests, their presence is usually an indicator that Trichoderma (green mould) is present in the compost. These mites feed on various weed moulds but not mushrooms, thus their presence indicates that the compost is unsatisfactory. They are yellowish-brown in colour, 0.25 mm in length and have a flattened appearance. They spread spores of Trichoderma from bag to bag. They feed on competing fungi and that is why their presence indicates poorly prepared compost and possible presence of Trichoderma. They reproduce very fast one female can lay up to 160 eggs within 5 days. They cause browning of mushroom heads and promote the spreading of green molds not only in the infected room, but also in the whole farm. When their population is high, they cause discomfort and even allergy to mushroom pickers at work.

What to do:
  • Maintain strict hygiene in the mushroom houses. This includes thorough cleaning of all machinery, equipment and rooms that were used during the spawning process, steaming the rooms in the end of the cultivation cycle at necessary temperature, and using disinfectants such as household bleach (sodium hypochlorite) (e.g. Teepol®) to clean all working surfaces and implements. Workers should wear clean clothes and dip their shoes in a disinfecting solution (sodium hypochlorite) before entering the growing rooms
  • Keep straw and manure away from mushroom growing houses
  • Use properly pasteurized substrate (compost)
  • Control mushroom flies
  • Remove spent compost from the farm. It can be used as manure for other crops

Mushroom flies

Sciarid flies (Lycoriella spp.) and phorid flies (Megaselia spp.) can be a major problem in mushroom production. Adult flies enter mushroom houses through openings and cracks. They are attracted by the smell of substrate (compost) and growing mushrooms. They lay eggs in the substrate, casing layer and mushrooms. Each female can lay up to 170 eggs. At a temperature of 24.5°C development from egg to adult takes about 21 days. Emerging larvae (maggots) feed on the substrate, mushroom mycelium and developing mushrooms. Damaged mycelium results in the formation of pins brown in colour and having a leathery surface. Developing pins and young mushrooms may not survive after larval attack. Infested young mushrooms become hollow and shrink, and may eventually die. Larvae may also tunnel ripe mushrooms forming many passage ways and holes, which makes the mushrooms unsuitable for human consumption. The affected substrate areas turn into swampy masses with a foul odour in which mushroom mycelium will not be able to grow. Adult flies are known to spread mushroom diseases and mites. They are also a nuisance to workers.

What to do:
  • All windows or ventilating vents should be covered with insect proof net
  • Use yellow sticky traps (yellow polythene sheets coated with vegetable oil) to detect and monitor presence of flies in the growing house
  • In India, yellow coloured bulbs of 15 W and yellow polythene sheets coated with vegetable oil (e.g. mustard oil) have been widely adopted and proven very effective in management of mushroom flies without use of synthetic pesticides
  • Remove from growing houses and farm all used substrate (compost). The spent substrate can be used as compost manure for other crops
  • Disinfect growing rooms with household bleach (sodium hypochlorite) (e.g. Teepol®) after harvesting (end of cultivation cycle)
  • Remove weeds and rotting materials near mushroom growing facilities

Mycophytic nematodes (Aphelenchoides composticola and Ditylenchus myceliophagus)

These nematodes (eelworms) are common inhabitants of most agricultural soils. They feed on mushroom mycelium. They gain access to growing rooms in substrate and casing soil. They are spread by insects, personnel and implements. Affected areas become unpleasantly wet and soft with a foul odour because of anaerobic (not needing oxygen to live) bacteria activities. Nematodes affect yield and quality. The degree of crop losses depends on the time and level of the initial infection. Infection at spawning time can have an effect on mycelial growth and thus making cultivation unprofitable. Infection occurring later causes only minor crop losses and goes unnoticed by the mushroom grower. The presence of nematodes on mushroom beds indicates bad cultivation conditions, that is, poor substrate and casing soil preparation and non-observance of sanitation and hygiene.

What to do:
  • Maintain good sanitation and hygiene in growing rooms
  • Use well prepared and pasteurized substrate (compost)
  • Control flies and mites
  • Workers should dip their shoes in a disinfecting solution (sodium hypochlorite) (household bleach) before entering the growing rooms
  • Remove spent substrate from the farm. This can be used as manure for other crops

Die-back disease (Virus)

It causes spots in the casing soil where no mycelial growth occurs. Around these spots, mushrooms of low quality appear with long stems and dirty caps. Sometimes the only indication of a virus infection is low yield. In severe cases, a few deformed mushrooms are produced. The disease can be introduced to the farm by infected spawn. It is spread by spores and mycelium from infected mushrooms. Mushrooms affected with the virus open fast, releasing infected spores. Sometimes, mushrooms that were formed inside the casing layer come out already open. Spores from infected mushrooms are easily carried by wind, insets, on implement, clothes and hands of personnel.

What to do:
  • Observe sanitation and hygiene during growing cycle
  • Cover the beds after spawning with a paper, which must be sprinkled with 2% formalin solution every 3-4 days in order to kill all settling spores
  • Harvest mushrooms in proper time, not allowing them to open
  • Clean and disinfect growing rooms after growth cycle
  • Grow tropical mushroom (Agaricus bitorquis). It is resistant to the virus

Wet bubble (Mycogone perniciosa)

This disease like dry bubble is soil-borne. Infested soil may be primary source of infection. Infection usually occurs at casing. The disease is spread within a house mainly by water splash, on clothing, equipment, flies or mites. Cross-contamination between houses can also take place. Young pin heads infected by Mycogone grow into shapeless lumps cauliflower-like which have a velvety appearance initially and eventually break down producing small amber droplets of liquid on the surface. It can also appear as gray fuzzy growth on gills (a series of radially arranged (from the center) flat surfaces located on the underside of the cap on which spores are formed).

What to do:
  • As for dry bubble disease

General Information and Agronomic Aspects
Cultivated mushrooms are edible fungi that grow on decaying organic matter, known as a substrate. Unlike vegetables they do not rely on sunlight to grow. Mushrooms start as very small spores (reproductive structures like very, very tiny seeds in fungi). The spores will grow in the substrate to produce a network of fine white filaments called mycelium (portion of the mushroom that grows underground). From the mycelium the mushroom fruit is produced. This is the part that is harvested. Mushrooms have a high nutritional value and are high in protein. They are also a good source of vitamins (B-complex and C), essential amino acids, and carbohydrates but are low in fat and fibre and contain no starch. When fresh they have a very high water content of around 90%. Minerals present include phosphorus, potassium, iron, calcium, zinc and copper. They are an ideal diet for diabetics and weight-watchers. Some species are also grown for their medicinal value.
Mushrooms are a valuable source of food and their cultivation can be a viable small-scale business, but investing in a mushroom growing scheme can be risky so a feasibility study looking at potential markets and supply chains should be done before starting. A general understanding of mushroom growing should be obtained through training or literature to ensure the best chance of success. Some expert assistance will help at this stage. The Agricultural Information Resource Centre (AIRC), Ministry of Agriculture, Kenya (email: agriinfocentre@yahoo.com) has published in 2009 a coloured booklet 'Guide to Growing Mushroom'. Short-term training in mushroom production is conducted by several institutions in Kenya including Juja Community Development Centre (JCDC) and Jomo Kenyatta University of Agriculture and Technology (JKUAT).
As well as individual small-scale production, set up options include cooperatives and community groups that can collaborate in set-up costs, production costs, harvesting and marketing. It does not help to work in isolation, but in joint ventures with regional agro-industries and universities as they can assist with linking to market outlets and training. The most popular mushroom species grown in Kenya are button (Agaricus spp.) and oyster (Pleurotus spp.). Button mushrooms are widely cultivated by large scale farmers as their production requires high input technology. Oyster mushrooms are mostly grown by small scale farmers using simple production techniques.
Oyster mushrooms
© Courtesy of AIRC, Nairobi, Kenya
Button mushrooms
© Courtesy of Wikipedia:
Before starting to grow mushrooms, farmers should consider the following:

1) potential markets and supply chains
2) source(s) of high quality spawn ('seeds' of mushrooms)
3) availability of substrate (material on which mushrooms grow)
4) availability of supplements (additional nutrients to the substrate)
5) production plan to ensure continuous production


Nutritive Value per 100 g of edible Portion
Raw or Cooked Vegetable Food
Energy
(Calories / %Daily Value*)		 Carbohydrates
(g / %DV) 		Fat
(g / %DV) 		Protein
(g / %DV) 		Calcium
(g / %DV) 		Phosphorus
(mg / %DV) 		Iron
(mg / %DV) 		Potassium
(mg / %DV) 		Vitamin A
(I.U)		 Vitamin C
(I.U)		 Vitamin B 6
(I.U)		 Vitamin B 12
(I.U)		 Thiamine
(mg / %DV) 		Riboflavin
(mg / %DV) 		Ash
(g / %DV)
Mushroom, oyster raw 43.0 / 2% 6.5 / 2% 0.4 / 1% 3.3 / 7% 3.0 / 0% 120 / 12% 1.3 / 7% 420 / 12% 48 IU / 1% 0.0 / 0% 0.1 / 6% 0.0 / 0% 0.1 / 8% 0.3 / 28% 1.0
*Percent Daily Values are based on a 2000 calorie diet. Your daily values may be higher or lower, depending on your calorie needs.


Markets and marketing
When considering producing mushrooms as a business, check on the following:

1) type and amount in demand by market outlets
2) their price and availability
3) current distributors and possibility of business relationship
4) possibility of value addition
Small scale farmers are, therefore, advised to identify where they can sell their mushrooms, especially to the nearest markets before starting production.

Production plan
Farmers must plan their production in such a way that they produce only the amount they are able to sell. They can divide their production units into four sections such that each section has mushrooms at different growth stages at any one time. This way they will maintain a consistent supply to the market.


Spawn in a bottle
© Courtesy of AIRC, Nairobi, Kenya
Spawn
It is a planting material equivalent of farmers' seed for starting mushroom cultures. It is made from mycelia (plural of mycelium) of mushroom grown on a carrier such as grains and is produced in specialized laboratories under sterile conditions. The amount of spawn needed is equal to 4-6% of the wet weight of the substrate. For example if the wet weight of the substrate is 50 kg, 2-3 kg of spawn is required. One kg of spawn may cost between Kenya shillings 600 and 800.
In Kenya, there are a number of institutions such as JKUAT producing high quality spawn. Farmers who need spawn or training can contact the university at the following address: Business Manager, JKUAT Enterprises Ltd., P.O. Box 62000-00200, Nairobi. Mobile phone: 0722 728812.


Wheat straw
© Courtesy of AIRC, Nairobi, Kenya
Substrate
Substrate is an organic-based material on which mushrooms grow. And a good substrate should be rich in nutrients, have good aeration and water holding capacity. Substrates commonly used in mushroom production include agricultural by-products such as cereal straws (wheat, barley, rice, maize), cotton waste, maize cobs, coffee husks and pulp, sawdust, sugar bagasse, water hyacinth among others. Growing mushrooms on a substrate of water hyacinth was first promoted by the Chinese University of Hong Kong, and has been taken up by the African University of Mutare in Zimbabwe. The advantage of using water hyacinth, which is an unwanted weed that clogs up many waterways in Africa, is that the costs of preparing the substrate can be kept down. However, cereal straws, particularly wheat straw, are usually the best because they are rich in nutrients that mushrooms require and they facilitate quick colonization (the formation of a white mass of mushroom mycelium) of the substrate.
Gypsum is a useful ingredient to be added to the substrate as it provides calcium to the growing mushrooms, regulates the acidity level of the substrate, counters potassium, magnesium and phosphorus concentration and increases water holding capacity thus decreasing the risk of over wetting. It also improves the physical structure of the substrate. Lime may also be added to the substrate to adjust its pH (level of acidity)
It should be noted that different species of mushrooms will require different substrate mixes. The substrate must not be rotten, mouldy and should be kept dry while in storage.


Supplements
These are materials added on the final mix of substrates to increase nitrogen content in order to improve the yields. Commonly used supplements include urea, bran, cotton seed cake, sunflower seed cake, molasses, broiler chicken manure and horse manure among others. However, it should be noted that heavy supplementation may increase the risk of contamination by other micro-organisms which are likely to benefit from extra nutrients added to the substrate.


Mushroom house
Mushroom house should not be sited near dumping sites and livestock pens to reduce the risk of insect infestation and diseases. It should preferably be under shade. The house can be made from locally available materials that can main cool temperatures and high humidity such as clay or bricks. In a small scale farmer scenario, a grass thatched mud walled house is the most ideal. The house should have air vents or small windows on the upper walls for ventilation and required light during fruiting. The vents and door should
have insect screens and be closed. If the temperature inside the house is high, water can be sprayed on the floor using a knapsack sprayer with fine nozzles and vents and door opened at night. Wooden shelves for holding bags or wooden racks for hanging spawned substrate tubes should be constructed at the height of about 1.5 m from the ground and 1 m apart for ease of working in the growing house.
A grass thatched mud mushroom house
© Courtesy of AIRC, Nairobi, Kenya
Wooden shelves holding bags in the house
© Courtesy of AIRC, Nairobi, Kenya


An overview on production of mushrooms
A detailed step by step procedure with coloured photos on cultivation of button and oyster mushrooms is given in the AIRC booklet "Guide to growing mushrooms". Farmers intending to start mushroom production as a business are strongly advised to undertake a hands-on training on growing mushrooms. A number of institutions in Kenya such as JCDC and JKUAT conduct short training courses on mushroom production.

Phases of cultivation of button and oyster mushrooms

Phase Time span and temperature Remarks
Substrate preparation 6-8 hours for soaking shredded straw in water for oyster. Pre-wetting of wheat straw for button is done for 3 days Selection of substrate. Cereal straws are preferred. Wheat straw is ideal for button. In case of oyster it involves shredding, soaking in water to 70% moisture content (1), draining excess water, adding supplements plus lime and packing into polybags.
Composting 18-20 days Oyster does not require composted substrate. Only applicable to button. Involves pre-wetting of wheat straw to 70% moisture content, adding supplements plus lime and gypsum. Good compost is dark brown, 70% moisture content and pH 8.0 - 8.5 (2)
Pasteurization and conditioning 4-6 hours of steam heating at 60°C for oyster and cool polybags to 20-25°C. For button steam for 8 hours and lower the heat for 4-5 days at 45-50°C then cool to 22-25°C Steam heating of oyster polybags is done in water drums but it can also be done in hot water at boiling point for 1 hour. Button steaming is done in special chambers (tunnels). Conditioning is to remove ammonia gas which is poisonous for button. Cooling is in preparation for spawning. The moisture content of the substrate then should be 67-70%
Spawning and incubation 5-10 days incubation for oyster; 15 days for button at 23-25°C Applying spawn to substrate in polybags. The growing room should be kept humid (RH 65-95%) (3) with dim lighting just sufficient to read a newspaper
Casing Sterilize casing soil for 4 hours at 60°C. Casing run (4) is 14-15 days at 25°C This is not applicable in oyster production. Casing is applying a thin layer of red top soil added with murram and lime on top of fully colonized substrate. Casing soil should be kept wet but not waterlogged. Substrate turns white to grayish due to the colour of mycelium. It is now ready for fruiting.
Pinning Oyster 5-10 days in the growing house at 23-25°C. Button 7-10 days but the growing house temperature will depend on variety (5) Pinning is when mycelia start fruiting (formation of very young mushroom known as 'pin heads'). It takes 3-4 days for pin heads to develop into mature mushrooms. RH required is 85-95%.
Harvesting Oyster about 30 days, button 30-40 days from spawning to harvesting Oyster harvesting is done when the mushroom ear is 7.5-10 cm in diameter, turgid and bright in colour. Button is picked at the young stage before opening. Repeated over 7-10 day cycles

(1) When the substrate is squeezed between the fingers it should give 2 to 3 drops of water. If it gives more drops, continue draining and with fewer drops add more water.
(2) pH is a measure of acidity. A pH value of 7 is neutral, lower than 7 is acidic and above 7 is alkaline. It can be determined using a pH meter. pH meters are readily available in shops selling laboratory equipment for schools in urban areas of Kenya.
(3) Relative humidity (RH) is the percentage of moisture in the air compared to the maximal amount that the air can hold at that temperature and pressure. It can be monitored by using a hydrometer which can be bought in shops selling laboratory equipment. If the RH is low, spray clean water on the floor or place pots with water in the room. If the RH is above the required, open windows or vents of the room.
(4) Casing run is the period in which the mycelia is left to grow on the casing soil.
(5) There are varieties grown: white mushroom or 'champignon') (Agaricus bisporus) and tropical mushroom (Agaricus bitorquis). During pinning the temperature in the growing house should be reduced from 25 to 20-22°C for tropical mushroom, and for white mushroom to 12-18°C.


Yield
An average of 33 kg of fresh button mushrooms per square metre of substrate can be obtained. In case of oyster mushrooms yield depends on the type of substrate used. For example wheat straw would convert at 75 to 100% (75-100 kg fresh mushrooms are expected from 75-100 kg of dried wheat straw).


Post-harvest handling
Mushrooms are highly perishable and if possible should be sold the same day of harvest. Under cool conditions their shelf-life is 1-3 days. The shelf-life can be extended to up to 7 days under refrigeration at 10°C. Surplus can be preserved by drying, canning, pickling and grinding dry mushroom into powder for soups.
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General Information on 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 having pest and disease problems. Therefore, it is very important to strictly maintain sanitation and hygiene in the farm (e.g. by sterilizing growing houses, proper disposal of spent substrate etc). Even with care there will be times when a pest or disease problem may occur, so it is useful to be able to identify the particular problem in order that appropriate action can be taken. Record keeping is important to identify where problems arise. Information required includes dates of all phases of production and particularly their parameters (temperatures, moisture levels, pasteurization times etc).


Mushroom abnormalities

The formation of scales or "crocodile skin"
Causes:
  • Very dry air
  • Strong air movement with low relative humidity
  • Shortcomings in the air supply and distribution system
  • Tendency of the strain to form scales
  • Damage done by pesticides


The formation of stroma (dense layer of mycelium without fruiting on casing soil)
Causes:
  • Low-quality degenerating mushroom strain
  • Mycelial growth in a poorly ventilated casing layer, with a high concentration of carbon dioxide, high temperature and low humidity, and a high volume of evaporation
  • Overly long period of mycelial growth in the casing layer
  • Petroleum-based fumes or chemicals


Rosecomb (misshapen cap with gills on the cap)
Causes:
  • Casing layer contaminated by mineral oils
  • Contamination by petroleum-based materials


Outgrowths on mushroom caps - "cock's comb"
Causes:
  • An overdose of pesticides
  • Casing layer contaminated with chemicals
  • Effect of exhaust gases, heating appliances, diesel oil, formalin vapors, dissolvers, paint


Thick stipes, small caps
Cause:
  • Excessively high carbon dioxide level on the initial stage of growth


A small cap on a normal stipe
Causes:
  • Improper climatic conditions for specific strains
  • Susceptibility of some strains
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Information on Diseases

Bacterial blotch (Pseudomonas tolaasi)

The main source of bacterial blotch in the mushroom farm is the casing soil. The disease is favoured by dampness [high humidity (over RH 85%), high temperatures (over 20°C) and poor ventilation in the growing houses]. It can be spread by the workers´ hands, irrigation water and on the inventory. Mushroom flies and mites also spread the disease. The first disease symptoms appear in areas of caps that have been moist for a longest time and areas where mushroom caps touch. Symptoms include spots that darken becoming chocolate-brown in colour and slimy. It can also cause distortion and splitting of the stipes. When the infection is severe, spots spread throughout the whole mushroom surface. Seriously diseased mushrooms can become deformed and the caps can decay giving a foul (unpleasant) odour. Young pins affected by the disease become brown and do not further develop.



What to do:
  • Maintain strict hygiene and sanitation in mushroom facilities
  • Use properly prepared substrate and casing soil that have been adequately pasteusterized
  • Avoid excessive humidity, high temperatures and poor ventilation in growing rooms
  • Avoid fluctuation of temperatures in the growing rooms which may cause water condensation on mushroom caps
  • Remove diseased mushrooms which can be a source of the disease
  • Control mushroom flies and mites which can spread the bacteria
  • Water mushrooms with chlorinated water (125 ml 10% chlorine solution for 100 l of water per 100 m². Use calcium hypochlorite products since sodium hypochlorite may burn caps) before first break when the pin size is 4-5 mm
  • Remove spent substrate from the farm. It can be used as manure for other crops

Green mould (Trichoderma aggressivum var. aggressivum)

This fungus is soil-borne. There are many species of the fungus but Trichoderma aggressivum var. aggressivum (Trichoderma harzianum biotype 4 (Th4)) is a major problem particularly to button mushrooms. It gains entry to growing rooms primarily through contaminated personnel and equipment. Other sources include poorly composted substrate or carryover in rooms that were not sufficiently steamed off. Once introduced, it rapidly spreads into large disease areas from infection source. Infection of casing soil can result in serious losses. Green mold is characterized by dense white mycelial growth followed by extensive green patches on casing/compost or mushroom caps. The spores of the fungus are sticky and can easily be spread by flies, mites and workers to previously uninfected area. Red pepper mites are often associated with the disease.



What to do:
  • Maintain hygienic conditions at all stages of production
  • Use properly prepared substrate and casing soil that have been adequately pasteusterized
  • Remove contaminated substrate as soon as possible from the farm and dispose of it at a considerable distance nor less than 100 metres
  • Control flies and mites
  • Spread table salt on the compost in affected areas when green mold is first recognized.
  • Filter air to prevent colonization of sterilized compost
  • Disinfest all structures and equipment (including clothing) associated with spawning (use immediately after disinfestation or store where air is filtered).

Mycophytic nematodes (Aphelenchoides composticola and Ditylenchus myceliophagus)

These nematodes (eelworms) are common inhabitants of most agricultural soils. They feed on mushroom mycelium. They gain access to growing rooms in substrate and casing soil. They are spread by insects, personnel and implements. Affected areas become unpleasantly wet and soft with a foul odour because of anaerobic (not needing oxygen to live) bacteria activities. Nematodes affect yield and quality. The degree of crop losses depends on the time and level of the initial infection. Infection at spawning time can have an effect on mycelial growth and thus making cultivation unprofitable. Infection occurring later causes only minor crop losses and goes unnoticed by the mushroom grower. The presence of nematodes on mushroom beds indicates bad cultivation conditions, that is, poor substrate and casing soil preparation and non-observance of sanitation and hygiene.




What to do:
  • Maintain good sanitation and hygiene in growing rooms
  • Use well prepared and pasteurized substrate (compost)
  • Control flies and mites
  • Workers should dip their shoes in a disinfecting solution (sodium hypochlorite) (household bleach) before entering the growing rooms
  • Remove spent substrate from the farm. This can be used as manure for other crops

Die-back disease (Virus)

It causes spots in the casing soil where no mycelial growth occurs. Around these spots, mushrooms of low quality appear with long stems and dirty caps. Sometimes the only indication of a virus infection is low yield. In severe cases, a few deformed mushrooms are produced. The disease can be introduced to the farm by infected spawn. It is spread by spores and mycelium from infected mushrooms. Mushrooms affected with the virus open fast, releasing infected spores. Sometimes, mushrooms that were formed inside the casing layer come out already open. Spores from infected mushrooms are easily carried by wind, insets, on implement, clothes and hands of personnel.



What to do:
  • Observe sanitation and hygiene during growing cycle
  • Cover the beds after spawning with a paper, which must be sprinkled with 2% formalin solution every 3-4 days in order to kill all settling spores
  • Harvest mushrooms in proper time, not allowing them to open
  • Clean and disinfect growing rooms after growth cycle
  • Grow tropical mushroom (Agaricus bitorquis). It is resistant to the virus

Wet bubble (Mycogone perniciosa)

This disease like dry bubble is soil-borne. Infested soil may be primary source of infection. Infection usually occurs at casing. The disease is spread within a house mainly by water splash, on clothing, equipment, flies or mites. Cross-contamination between houses can also take place. Young pin heads infected by Mycogone grow into shapeless lumps cauliflower-like which have a velvety appearance initially and eventually break down producing small amber droplets of liquid on the surface. It can also appear as gray fuzzy growth on gills (a series of radially arranged (from the center) flat surfaces located on the underside of the cap on which spores are formed).



What to do:
  • As for dry bubble disease
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Information on Pests

Mites

Mites belong to the spider family. They are eight-legged compared to insects which are six-legged. They are very small and are usually not noticed until large numbers are present. Many different kinds of mites are encountered during mushroom cultivation process. Some mites feed on fungi and bacteria that exist in great amounts in decaying organic materials used as a substrate in mushroom production. Other members of mites are predators that mainly feed on nematodes and smaller mites. Only a few of them are considered as mushroom pests. These include mushroom mites or tarsonemid mites (Tarsonemus myceliophagus) and red pepper mites (Pygmephorus sellnicki). The mushroom mites are so small, that they are not seen with a naked eye. They are shiny, light brown in colour feeding on the mushroom mycelium and mycelium of many other competing fungi present in the substrate. They gnaw the bases of mushroom stipes (stalks of mushroom) which in result become rounded and obtain a reddish-brown shade. The amount of damage they bring to the growing crop will depend on the time and degree of infestation. If a large population of mites enters the batch at spawning, the damage can be significant.

Red pepper mites got their names from their reddish-brown colour and are often found moving on the mushroom caps or the casing surface. These mites are not regarded as primary pests, their presence is usually an indicator that Trichoderma (green mould) is present in the compost. These mites feed on various weed moulds but not mushrooms, thus their presence indicates that the compost is unsatisfactory. They are yellowish-brown in colour, 0.25 mm in length and have a flattened appearance. They spread spores of Trichoderma from bag to bag. They feed on competing fungi and that is why their presence indicates poorly prepared compost and possible presence of Trichoderma. They reproduce very fast one female can lay up to 160 eggs within 5 days. They cause browning of mushroom heads and promote the spreading of green molds not only in the infected room, but also in the whole farm. When their population is high, they cause discomfort and even allergy to mushroom pickers at work.




What to do:
  • Maintain strict hygiene in the mushroom houses. This includes thorough cleaning of all machinery, equipment and rooms that were used during the spawning process, steaming the rooms in the end of the cultivation cycle at necessary temperature, and using disinfectants such as household bleach (sodium hypochlorite) (e.g. Teepol®) to clean all working surfaces and implements. Workers should wear clean clothes and dip their shoes in a disinfecting solution (sodium hypochlorite) before entering the growing rooms
  • Keep straw and manure away from mushroom growing houses
  • Use properly pasteurized substrate (compost)
  • Control mushroom flies
  • Remove spent compost from the farm. It can be used as manure for other crops

Mushroom flies

Sciarid flies (Lycoriella spp.) and phorid flies (Megaselia spp.) can be a major problem in mushroom production. Adult flies enter mushroom houses through openings and cracks. They are attracted by the smell of substrate (compost) and growing mushrooms. They lay eggs in the substrate, casing layer and mushrooms. Each female can lay up to 170 eggs. At a temperature of 24.5°C development from egg to adult takes about 21 days. Emerging larvae (maggots) feed on the substrate, mushroom mycelium and developing mushrooms. Damaged mycelium results in the formation of pins brown in colour and having a leathery surface. Developing pins and young mushrooms may not survive after larval attack. Infested young mushrooms become hollow and shrink, and may eventually die. Larvae may also tunnel ripe mushrooms forming many passage ways and holes, which makes the mushrooms unsuitable for human consumption. The affected substrate areas turn into swampy masses with a foul odour in which mushroom mycelium will not be able to grow. Adult flies are known to spread mushroom diseases and mites. They are also a nuisance to workers.




What to do:
  • All windows or ventilating vents should be covered with insect proof net
  • Use yellow sticky traps (yellow polythene sheets coated with vegetable oil) to detect and monitor presence of flies in the growing house
  • In India, yellow coloured bulbs of 15 W and yellow polythene sheets coated with vegetable oil (e.g. mustard oil) have been widely adopted and proven very effective in management of mushroom flies without use of synthetic pesticides
  • Remove from growing houses and farm all used substrate (compost). The spent substrate can be used as compost manure for other crops
  • Disinfect growing rooms with household bleach (sodium hypochlorite) (e.g. Teepol®) after harvesting (end of cultivation cycle)
  • Remove weeds and rotting materials near mushroom growing facilities
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Information Source Links
  • AIRC (2000). Local and Export Vegetables. Growing Manual. Ministry of Agriculture and Rural Development, Kenya / Japan International Cooperation Agency. Reprinted by the Agricultural Information Centre, Nairobi, Kenya. Email: agriinfocentre@yahoo.com; agrinfodata@yahoo.com
  • AIRC (2009). Guide to Growing Mushrooms. Published by the Agricultural Information Centre, Nairobi, Kenya. Email: agriinfocentre@yahoo.com; agrinfodata@yahoo.com
  • Fungiculture: www.wikipedia.org/
  • Nutrition Data www.nutritiondata.com.
  • Peter Oei (2003). Mushroom Cultivation. 3rd. Edition. Appropriate Technology for Mushroom Growers. Backhuys Publishers, Leiden, The Netherlands. ISBN: 90-5782-137-0
  • Tsarev, A.V. (2003). Mushroom Growing Technology.
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Oyster mushroom
© Courtesy of AIRC, Nairobi, Kenya
Distortion
deformation or malformation
Diameter
Thickness or width.
organic
Refers to the farming system and products described in the IFOAM standard and not to 'organic chemistry'.
Fungi
Occurring worldwide, most fungi are largely invisible to the naked eye, living for the most part in soil, dead matter, and as symbionts of plants, animals, or other fungi. They perform an essential role in all ecosystems in decomposing organic matter and are indispensable in nutrient cycling and exchange. Some fungi become noticeable when fruiting, either as mushrooms or molds.

Fungi are responsible for a range of serious plant diseases such as blight, grey mould, bunts, powdery mildew, and downy mildew. Crops of all kinds often suffer heavy losses.

Fungal plant diseases are usually managed with applications of chemical fungicides or heavy metals. In some cases, conventional breeding has provided fungus resistantcultivars.

Besides combatting yield losses, preventing fungal infection keeps crops free of toxic compounds produced by some pathogenic fungi. These compounds, often referred to as mycotoxins, can affect affect the immune system and disrupt hormone balances. Some mycotoxins are carcinogenic.
Disinfect
To reduce, by physical or chemical means, the number of potentially harmful microorganisms in the environment, to a level that does not compromise food safety and suitability.
Synthetic
Manufactured by chemical and industrial processes. May include products not found in nature, or simulation of products from natural sources (but not extracted from natural raw materials).
Ingredient
is a substance, including a food additive, used in the manufacture or preparation of a food or present in the final although possibly in a modified form.
Fungi
Occurring worldwide, most fungi are largely invisible to the naked eye, living for the most part in soil, dead matter, and as symbionts of plants, animals, or other fungi. They perform an essential role in all ecosystems in decomposing organic matter and are indispensable in nutrient cycling and exchange. Some fungi become noticeable when fruiting, either as mushrooms or molds.

Fungi are responsible for a range of serious plant diseases such as blight, grey mould, bunts, powdery mildew, and downy mildew. Crops of all kinds often suffer heavy losses.

Fungal plant diseases are usually managed with applications of chemical fungicides or heavy metals. In some cases, conventional breeding has provided fungus resistantcultivars.

Besides combatting yield losses, preventing fungal infection keeps crops free of toxic compounds produced by some pathogenic fungi. These compounds, often referred to as mycotoxins, can affect affect the immune system and disrupt hormone balances. Some mycotoxins are carcinogenic.
Contamination
Pollution of organic product or land; or contact with any material that would render the product unsuitable for organic certification.