Mushroom Culture

Diseases and mould problems in mushroom cultivation and their management

A. FUNGAL COMPETITORS OR INDICATOR MOULDS OR WEED FUNGI:

• While some fungi, bacteria and viruses directly attack mushroom fruit bodies causing pathogenic diseases, a large number of harmful fungi are encountered in compost and casing which may not be directly pathogenic , but may cause harm to the crop during spawn run and cropping stages. These are known as Competitor moulds as they compete for food with mushroom mycelium or " Indicator moulds " as presence of each mould indicates some deficiency or fault in compost or casing and also called as " Weed fungi " because of their undesirable occurrence.

The following are some of the established vectors of contamination :

• Air
• The mycelium or spawn
• The substrate or the compost
• Casing materials
• Growers or workers hands
  
• Equipments, containers and tools
• Water
• Insects and animals.

Fig. Occurrence of competitor moulds on mushroom bed:

(1) Conidiophores and conidia of Aspergillus sp
(2) Torula sp
(3) that occurs frequently in mushroom compost

1) GREENMOULD:

• It is the most common mould and found in beds of every type of mushroom cultivated. Mainly three types of fungi Trichoderma , Penicillium and Aspergillus have been found to be associated.

Symptomatology:

• Green patches appear in compost , spawn , on casing surface and also sometime on the mushroom surface, engulfing the fruit bodies with its white and greenish mycelium causing Trichoderma blotch disease.. The pathogenic species of Trichoderma like Trichoderma harzianum, infect the fruit body, otherwise green moulds try to spread rapidly and cover entire compost structure depending upon the quality of compost and environmental conditions .The appearance of green mould indicates poor quality compost, unhygienic cropping conditions and low compost pH .
• 
  

Causal organism:

• The most common species of Trichoderma appearing in mushroom beds are Trichoderma viride , T. koningi , T. harzianum . T. hamatum and several species of Aspergillus and Penicillium. Rifai in 1969 revised and has proposed nine different species of Trichoderma .Trichoderma viride is the most commonly occurring weed mould whereas ,T. koningi and T. harzianum have been reported to be competitors as well as pathogenic to button mushroom producing blotch symptoms on fruit bodies.

Fig. Showing the (1) Green mould infection in mushroom bags
(2) Petri dish culture of Trichoderma viride, (3) microscopic observation of fungus Trichoderma sp

Epidemiology:

• The fungus mainly enters spawn laboratory or the cropping room through air, dust particles, contaminated overall or hands, infected spawn, contaminated equipments and machinery; vectors like mites , mushroom flies etc. The compost quality mainly determines the establishment and growth of this mould. Poor quality compost prepared under unhygienic conditions, high moisture conten , use of straw having short texture for composting, highly pressed compost heap during composting, low pH of compost, high humidity etc; are the predisposing factors for the growth and development of the fungus.

Control methods or management:

• There should be complete hygiene inside and around the mushroom farm, compost ingredients should never come in contact with the soil particles; proper turnings, conditioning and pasteurization of compost is a must, use of foot dips at the doors of cropping rooms, lesser use of formalin sprays, proper cleaning of equipments and tools, use of clean and washed clothes, early removal of infected bags etc; are some of the recommended methods of control.Spray of some fungicides like 0.1 % carbendazim, thiabendazole ,mancozeb ( 0.2 % ) etc. on cropping beds have been found effective in controlling the mould.

2) OLIVE GREEN MOULD:

• During spawn run stage, small military green coloured cockle burrs appear sometimes in the compost which is easily recognizable and that affect the yield . The occurrence of these moulds were first reported in India by Gupta et al ,1975 and Thapa et al, 1979.

Symptoms:

• The initial signs of fungus consists of appearance of greyish - white aerial mycelial growth in the compost just after spawning confused with the growth of mushroom mycelium . These mycelial structures later on give rise to small, round , military green or grey green cockle burr ( 1 / 16 inch diameter ) structure in the compost strictly adhering to the straw.

Fig. 13.10 & 13.11 Chaetomium infection in straw of compost, (b) Ascus and ascospores of Chaetomium olivaceum

Causal Organism:

• Mainly two fungi Chaetomium olivaceum and C. globosum have been observed occurring in mushroom beds.

Epidemiology:

• The spores of Chaetomium are already present in the compost or they may come through air and casing materials . It has been found that during compost pasteurization process , mainly at peak heat or kill stage ( 59-60 º c ) , it should never be processed in the absence of fresh air or Oxygen . Absence of aeration during peak heat or kill may lead to compost damage which favours the appearance and development of these fungi.

Control Methods:

• In case of pasteurization process , the peak heat or kill should be done at 58 – 59 ºC for 3-4 hours in the presence of fresh air or aerated steam . Carbendazim ( 0,05 % ) and Dithane Z-78 (.2 % ) have been found to be effective in controlling the mould only in case of minor damage of the compost.

3) BROWN PLASTER MOULD:

• The mould appears as white mycelial growth on the surface of compost during spawn run stage and also on the casing surface slowly changing colour from white to light brown to cinnamon brown and finally changed to rusty in appearance.

Causal Organism:

• Papulospora byssina is the fungus responsible for causing brown plaster mould . The mycelium is initially white which later turns brownish , septate , producing clusters of brown coloured , spherical bulbils.

Fig. 13.12 & 13.13 Shows (a) Brown plaster mould on the mushroom bed surface, (b) the mycelial structure and bulbils of Papulospora byssina , the causal fungus

Epidemiology:

• The fungus mainly enters through air, spent compost, casing material or the containers as well as the workers’ hands. But a wet, soggy and improperly pasteurized , bad quality compost favours its rapid growth . It commonly occurs on compost prepared by long method of composting .A greasy and wet compost is vulnerable to infection.

Control methods:

• Good hygiene and preparation of good quality compost removes the chances of its appearance and further development . Addition of good quality gypsum is recommended and proper turning of compost with attentive pasteurization procedures help in preventing this mould. Sometimes spray of some fungicides like carbendazim , TPM , TBZ ( 0.05 % ) and Dithane Z-78 or Dithane M-45 ( .025 % ) have been recommended for its control .