Everything you need to learn about controlling diseases and pests of mushroom!
1. Dry Bubble:
Mycelia white in growth turning grayish yellow in casing soil. The early infection shows typical onion shaped mushrooms are produced. Sometimes they appear as small undifferentiated masses of tissue up to 2 cm in diameter. When a part of the cap is affected hare-lip symptom is noticed. Affected mushrooms are grayish in colour. If the infection occurs at the latter stage, grey mouldy fuzz can be seen on the mushrooms.
Sometimes little pustules or lumps appear on the cap. On fully developed mushroom, it produces localized light brown depressed spots. The adjacent spots coalesce and form irregular brown blotches. Diseased caps shrink in blotched area, turn leathery, dry and show cracks. Infected fruit bodies are malformed; onion shaped and become irregular and swollen mass of dry leathery tissue.
Several species of Verticillium have been reported to cause dry bubble disease which is abundant in soil but V. fungicola, V. malthousei and V. psalliotae are important. All the species of Verticillium numerous one celled thin walled, oblong to cylindrical, hyaline conidia, 3.5-15.9 X 1.5-5 μ on lateral or terminal, vertically branched conidiophores (200-800 X 1.5-5.0 μ). Conidiophores are relatively slender and tall. Conidia accumulate in clusters surrounded by a sticky mucilage.
Physical Methods:
Follow strict sanitation practices to prevent introduction of the disease, including use of clean or pasteurized casing media and properly maintained air filtering system. Control the fly populations. Dry bubble is effectively kept in check on many farms by cropping for only three breaks.
Resistant Cultivars – None.
Chemical Methods:
Water early infection centres with formaldehyde (COM) SN drench. For protective measure, use benomyl (COM) WP; zineb (COM) DU. Apply chlorothalonil (COM) SU at casing or mix into casing material at 254 ml formulation per 100 m2 of production surface and pinning at 128 ml2 formulation per 100 m2.
A minimum of 100 L water per 100m2 is necessary to achieve good coverage of the casing. The applicator must wear a full respirator and protective clothing during all activities. No more than two applications are permitted per crop. The treated area is not to be re-entered for 48 hours.
However, short-term tasks, not involving handling the treated casing, are permitted 4 hours after application. This individual must wear long sleeved shirt, hat and chemical-resistant gloves.
Limitations:
Pre-harvest interval – 2 days (benomyl); 1 day (zineb); 7 days (Chlorothalonil).
Note:
1. Careful use of the Vineland Verticillium Medium will aid the grower in detecting the weak link in the sanitation program or source of the infection.
2. Verticillium is generally resistant to benomyl. Repeated use (greater than 2 times per crop) may increase Verticillium’s tolerance to benomyl.
3. Although zineb is allowed for use on mushrooms in Canada for domestic consumption, it is not recommended for mushrooms that will be exported to the U.S.A.
2. Wet Bubble:
There are two main symptom types, infected sporophores (infection after differentiation resulted in the production of thickened stipe with deformation of the gills) and sclerodermoid (when infection took place before the differentiation of stipe and pileus) masses which is result of infection of Mycogone perniciosa at different stages in the development of the sporophores. The white mouldy growth on the mushroom leading to their putrefaction (giving foul odour) with a golden brown liquid exudates.
The infected sporophores may be recognized by the two symptoms, one is tumorous form, infected from pin-heads, and other is malformation, infected at last stage. Both types of infections may exude water drops on the surface of infected sporophores. This water drops later change into amber colour. Cross section of deformed sporophores without cottony growth showed black circular area just beneath the upper layer.
Causal Organism:
Mycogone perniciosa is the perfect stage of Hypomyces perniciosa. The mycelium of the pathogen is a white, compact, and felt-like. Hyphae branched interwoven septate, hyaline, hyaline, 3.5 μ broad. It produces conidia and chlamydospores. Chlamydospores short, slender, branched, hyaline, measuring 200 x 3.5 μ and having sub-verticillate to verticillate branches which bear thin walled, one celled conidia measuring 5-10 x 4-5 μ. Long two celled chlamydospores present upper cell warty, thick walled, globose, bright coloured measuring 15-30 x 10-20 μ, lower cell hyaline, smooth and measure 5-10 x 4-5 μ.
Control Measures:
Physical methods – Strict sanitation procedures must be followed.
Resistant Cultivars – None.
Chemical Methods:
Eradicate early infection centers with formaldehyde (COM) SN drench. If the casing is contaminated control can be achieved by treating it with 1 percent formalin. Alternatively spray of 0.8 percent formalin on the casing surface, immediately after casing can be effective. When bringing casing layer to full moisture capacity, apply benomyl at 0.5-4 g/m2 (COM) WP through the irrigation water very effective.
Zineb (COM) DU, WP may be applied as a protective dust to the casing surface. Basamid (Dazomet) and Vapam (Metham sodium) applied @ 100ppm to casing has also been reported very effective. Application of carbendazim, benomyl, chlorothalonil, TBZ, prochloraz manganese complex (Sportak 50 wp) into casing mixture have been reported very effective for management of wet bubble.
Limitations:
Preharvest interval – 2 days before first pinning (benomyl); 1 day (zineb) – 2 days in Ontario.
3. Cobweb:
Cobweb appears first as small white patches on the casing soil which then spreads to the nearest mushroom by a fine gray white mycelium. A floccose white mycelium covers the stipe, pileus and gills, eventually resulting in decomposition of entire fruit body.
As infection develops, mycelium becomes pigmented eventually turning a delicate pink cover. In severe attack, a dense white mould develops over casing and mushroom change from fully a cobweb to a dense mat of mycelium. The white colour can turn pink or even red with age.
One symptom which can appear and which is generally not associated with the disease is cap spotting. The spots can be brown or pinkish brown. On inoculation fruit bodies, characteristic symptoms appeared within 24 hours of inoculation when mycelial + spore suspension were applied, 4-12 days after infestation.
Younger mushrooms are more susceptible than fully developed ones. Tufts of conidiophores develop on all sides of the web and growth of engulfed mushroom is arrested. On removal of mycelial felt from affected mushroom, drops of dark brown coloured fluids exudes emitting bitter foul smell.
Causal Organism:
Cladobotryum dendroides (= Dactylium dendroides) imperfect of Hypomyces rosellus. Sterile hyphae form a turf and are prostrate, branched, septate and hyaline with approximately opposite branches, which divide above into usually three pointed branchlets. Conidiophores are erect, similar or branched in many whorls.
Conidia single, elongate pointed at the base, 2-3 septate, slightly constricted at the septa and measure 20-30 x 10-12.5 μ. It produces sexual stage belonging to Hypomyces rosellus, which has been observed on decaying dried fruit bodies of wild in HP.
Physical Methods:
Good sanitation is essential. Disease is favored above 18°C and R.H. > 90%. Pasteurize casing material. Spread a wet paper towel over the spot and then cover the towel with salt, lime or gypsum and lime mix, especially before crop irrigation. The spores are easily airborne.
Through disinfection of casing soil with live steam of casing mixture at 50°C for 4 hours effectively eliminates the pathogen.
Regular cleaning, removal of cut mushroom stems and young dead half mushrooms after each break and controlling temperature and humidity helps in controlling the disease.
Resistant Cultivars – None.
Chemical Methods:
Eradicate early infection centres with formaldehyde (COM) SN as a drench. Apply zineb (COM) DU between breaks as required.
Terraclor (pentachloronitrobenzene) can eradicate Dactylium mildew even after the well establishment of the disease.
Chemical:
Limitations – Preharvest interval -1 day (zineb).
4. Green Moulds:
The different species of Trichoderma are associated with green mould symptoms in spawn bottle, casing soil and in compost. A dense, pure white growth of the mycelium may appear on the casing surface or in compost which resembles to mushroom mycelium.
Later on mycelial mat turns to green colour because of heavy sporulation of causal organism which is a characteristic symptom of the disease. The mould creeps on the surface of the casing layer and infects new parts and develop newly borne primordial.
Mushroom developing in or near this mycelium are brown, may crack and distort and the stipe peels in a similar way to mushroom attacked by Verticillum fugicola causing dry bubble disease. Some species induce brownish lesion/spots on caps which may cover the entire cap surface under congenial conditions.
Causal Organism:
The association of several species Trichoderma with A. bisporus is the basic reason of green mould disease. The species recorded are Trichoderma koningi, T. viride, and T. harzianum.
Chemical Measures:
Physical Methods:
Trichoderma koningi and T. viride flourish in compost as indicator moulds when excess carbohydrates are available or when the compost is not supplemented with sufficient nitrogen. Adequate compost formulation and schedules will prevent the problem. In addition, supplements added at spawning should be evenly mixed throughout the compost. T. harzianwn appearance is similar to the other green moulds.
However, this species is able to aggressively attack and colonize mushroom compost and casing, devastating production. Manage the infection pressure through a thorough sanitation and hygiene programme, especially targeting post crop steam off and it’s clean up, cool down, spawning and early spawn run.
Cover spots with sodium hypochlorite solution, salt, lime or gypsum and lime mix. Good insect and mite control and personnel traffic patterns further reduce the spread of the disease. Optimize the compost preparation and horticultural conditions for a healthy vigorous growth of the mushroom fungus.
Chemical Methods:
Benomyl (COM) WP may reduce growth in the casing soil. Neither benomyl nor chlorothalonil are effective against an established infection of Trichoderma harzianum. Benomyl (COM) WP may be applied to the spawn grains as a ‘seed coat’ at 0.25 g (a.i.) per 22 gypsum per 1 kg spawn as a preventative against Trichoderma aggressivum. Spraying with 0.05 per cent benlate checks the disease.
Limitations:
Pre harvest interval – 2 days (benomyl); 7 days (chlorothalonil).
5. Bacterial Diseases Bacterial Blotch:
Brown spots or blotches on stipes and pilei. The appearance of circular or irregular yellowish spots starts from margins of the cap which enlarges rapidly and coalesce to form rich chocolate brown spots (1-3mm) depression. The caps may splits where the blotch symptoms appear.
Pseudomonas fluorescens (biotype G)
Control Measures:
Physical Methods: Cultural:
Air temperature should not be allowed to rise above bed temperature. If heating is required, provide only a small amount of heat at any one time. Maintenance of a stable difference between wet and dry bulb reading of 1 to 1.5 C will significantly reduce the occurrence of bacterial blotch. Do not water mushrooms less than two days before harvest. After watering, surface of mushrooms must be dried in 2-4 hours by ventilating and heating.
Resistant Cultivars – None.
Chemical Methods:
Sodium hypochlorite at 160-320 ml ai/ 1,000 litres of water is used as a drench by growers to control this disease although it is not registered for use. Household bleaches generally contain 5.25-6% sodium hypochlorite. A slight acidification of the water-chlorine solution increases the effectiveness of chlorine.
Precaution:
Hazards have been noted when sodium hypochlorite solutions combine with acids. Toxic chlorine gas is emitted. Both mixing tank and solutions should be in well ventilated areas. Calcium chloride (food grade) at 0.3% (ai) is applied in the irrigation water from early pinning to the end of the crop to enhance drying and reduce the browning reactions.
6. Mummy Disease:
Patches development occurrence after spawn spread/run. The early opening and grayish white to brown colour of fruit bodies develops. The pin heads remain stunted in the casing soil. The base of stem get thickened and covered with mycelium. At latter stage mushroom becomes tough, spongy or leathery dry (Mummy). The cut end of infected stem shows reddish brown colouration.
Causal Organism – Pseudomonas spp.
Control Measures:
Physical Methods:
Where mummy disease is present, remove 20 cm wide section of compost across the beds and 1.5 m from either side of the infection. The exposed netting and shelving should be thoroughly treated with formalin solution and the surface of the infected area covered with plastic. Thoroughly clean up and disinfect the production room before refilling to prevent re infection. If plastic is used to cover the compost during spawn- run, remove two days before casing to permit water on compost surface to dry.
Resistant Cultivars – None.
Chemical – None.
7. Ginger Blotch:
The disease is closely related to bacterial blotch. It was firstly reported in England. The ginger colour does not change as in bacterial blotch. The blotch diameter is 1-2 mm in diameter. The disease spread through spawning material.
Causal organism – Pseudomonas gingeri.
Control measures – Similar to bacterial blotch.
8. Weed Moulds:
Causal Organism:
Chaetomium olivaceum (olive-green mould); Coprinus fimetarius (ink cap); Sporendonema purpurescens (lipstick mould); Chromelasporium sp. (cinnamon brown mould); Papulaspora byssina (brown plaster mould); Scopulariopsis fimicola (white plaster mould); Trichoderma viride (green mould); Doratomyces stermonites (black whisker mould).
Physical Methods:
Good pasteurization and sanitation practices are always essential. Lack of oxygen during the conditioning phase of indoor pasteurization promotes olive green mould. Ink cap mould appears when compost contains excess ammonia due to poor conditioning of compost during Phase II. Lipstick mould is reported to be associated with chicken manure in compost formula or wet compost, and occasionally where virus is present.
Cinnamon brown mould is an opportunistic fungus growing on casing that has been overly pasteurized, where strong formalin solution has been used, or where virus has killed the mycelium in the casing. White and brown plaster moulds are stimulated by amines in the mushroom compost.
Modifications of composting practices (Phase I and Phase II) to improve compost quality will reduce the occurrence. Both green mould and black whisker mould develop under conditions where compost has been under composted, the C: N ratio was too high, or where the compost has over heated during the spawn run period.
Resistant Cultivars – None.
Chemical Methods:
Eradicate early infection centres with formaldehyde (COM) SN as a drench. Apply zineb (COM) DU between breaks as required.
Limitations:
Preharvest interval -1 day (zineb).
9. Other Diseases:
Aphanocladium Cap Spotting (Aphanocladium album)
Gill Mildew (Cephalosporium spp.)
Hormiactis Cap Spot (Hormiactis Alba).
Mat Or Confetti Disease (Chrysoporium luteum and C. medarian)
Shaggy Stipe (Mortierella bainieri)
Truffle Disease (Diehlioinyces microsporia)
10. Viral Diseases:
Mushrooms appear only in dense clusters, maturing too early. The delayed appearance of the pinheads of the first flush is an important indication of the disease and formation of fruiting primordial below the surface of casing layer. Development of abnormal mycelial growth and mushroom; slow pinhead development and dwarfing. Sporophores with elongated stem; small caps; quick brown on cutting with small early maturing pileus.
Thickened elongated bent, barrel-shaped and spongy stipes. Pilei are small and fat. Veils are abnormal or absent area and hard gills are common. Specific musty smell perceived in growing room infested with the disease. Volvariella is without any significant symptoms.
Causal Organism:
Virus recorded on different mushrooms shows different shape and sizes. Button mushrooms infecting vims like particles measuring 29 nm and 35 nm in diameter have reported. The club-shaped and rod-shaped particles have been reported in A. bisporus from different parts of the world.
Transmission:
Mycelium:
The diseased mycelium may remain in trays and other content after a crop which would mix with new healthy mycelium of next crop and thus transmit the virus.
Spores:
Spores can infect the compost at any stage before or after spawning. The mycelium from infected spores and healthy mycelium gets intermingled thereby resulting in vims transmission.
Vectors:
Some flies and mites are important carriers which carry mushroom spores from one place to another within a tray or from tray to tray, which resulting in introduction of vims inoculum. There is no any vector as such involved in transmission of vims.
Mechanical:
The diseased fragments of mycelium and spores can be transmitted through contaminated shelves, trays, equipment and workers cloths and new crop can be damaged.
Physical Methods:
Once the disease is established it is impossible to control without complete sterilization of the production facilities, tools, and all materials previously used in production.
The following measures must be taken to prevent establishment of viruses:
All rooms should have high efficiency filters in the fresh air system; discourage visits from other growers and do not visit other mushroom farms where virus is suspect or known to be present; do not employ workers who visit or do part-time work on a farm where virus is present; and immediately disinfest any shipping bins that are returned to the farm to avoid contamination.
Mushrooms should be picked before the veil opens to prevent liberation of spores that carry the virus. Cover spawned compost with plastic so diseased spores cannot land on the surface. Routinely between crops, clean and steam all shelving material and nets, which can harbor diseased mycelium.
Resistant Cultivars – None.
Chemical Methods:
The wood is immersed in 4% sodium pentachlorophenate solution in which 0.5-1 % sodium carbonate has been added.
Notes:
A routine rotation of different mushroom strains in each production room will help in preventing the establishment of virus disease.
11. Abiotic Disorders:
During cultivation of the commercial mushroom, there frequently occur a number of abnormalities that are not caused by any living organism. These conditions are described by the following names – stroma, rose comb, hardgill, open veil, weepers, hollow case, purple stem, saggy socks. Although these conditions are rare, they can disturb growers.
Arthropods:
A variety of small fly and midge species are pests of mushrooms. The larvae feed on the fungal mycelium in the compost, but may also tunnel into the fruiting bodies.
A range of mite species may affect the mushroom crop. Some directly damage the fruiting bodies, some may attack the mycelium and some mites are predatory on other mites, fly eggs, nematodes or bacteria.
Mite damage on the fruiting bodies often shows up as small cavities in the stem and cap similar in appearance to bacterial pit disease. Mycelium-eating mites can cause high yield losses. Mites are very small and easily transported on clothing and tools.
Springtails are commonly associated with compost, and can damage the crop if present in high enough numbers. Slaters and millipedes may also cause damage to the fruiting bodies.
Nematodes will cause a loss in yield and brown, watery mushrooms, and in extreme cases soggy, smelly compost. Peat is a common source for nematodes and should be treated before use.
Management:
Maintaining high levels of hygiene will assist any pest management program by reducing the number of problems that are likely to occur. If an outbreak does occur, ensure that the pest or disease is correctly identified before taking any action.
There are several chemicals registered for use on mushrooms – contact your local chemical reseller.