Hormiactis cap spotting
Hormiactis, an uncommon fungus which causes a cap spotting disease of mushrooms was recorded for the first time on a commercial mushroom farm in Australia in 2007.
Hormiactis is normally a soil saprophyte but is pathogenic on mushrooms. The spoilage it causes through cap spotting can render mushrooms unsaleable.
Overseas reports suggest that the fungus causes infrequent, localised disease on mushroom farms.
The symptoms caused by Hormiactis sp. are similar to those of cobweb disease (Dactylium dendroides), particularly the dense, white mycelial growth.
Cap spotting most often occurs when the surface of the cap remains wet for a few hours.
Deformities of the mushroom may also result from infection by the fungus.
Information about Hormiactis cap spotting is limited. However, it is considered to behave in a similar way to cobweb disease (Dactylium dendroides), the spores of which are easily released and quickly spread throughout the crop via the air handling system.
Control of Hormiactis cap spotting will most likely be achieved through the use of an evaporating atmosphere. However, a grower relying on relative humidity to control evaporation may not have enough capacity in the air at 18ºC to give sufficient evaporation.
If absolute humidity control is in use, this can be adjusted to give a two degree difference, which at 18ºC will provide more than enough capacity. However, some growers may not have adequate temperature control to use this method.
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T.R Fermor. Hormiactis alba, an uncommon fungal pathogen of the cultivated mushroom Agaricus bisporus. Glasshouse Crops Research Institute Annual Report, University of Warwick UK.