Lecanicillium fungicola: causal agent of dry bubble disease in white‐button mushroom

Lecanicillium fungicola causes dry bubble disease in commercially cultivated mushroom. This review summarizes current knowledge on the biology of the pathogen and the interaction between the pathogen and its most important host, the white‐button mushroom, Agaricus bisporus. The ecology of the pathogen is discussed with emphasis on host range, dispersal and primary source of infection. In addition, current knowledge on mushroom defence mechanisms is reviewed. Taxonomy: Lecanicillium fungicola (Preuss) Zare and Gams: Kingdom Fungi; Phylum Ascomycota; Subphylum Pezizomycotina; Class Sordariomycetes; Subclass Hypocreales; Order Hypocreomycetidae; Family Cordycipitaceae; genus Lecanicillium. Host range: Agaricus bisporus, Agaricus bitorquis and Pleurotus ostreatus. Although its pathogenicity for other species has not been established, it has been isolated from numerous other basidiomycetes. Disease symptoms: Disease symptoms vary from small necrotic lesions on the caps of the fruiting bodies to partially deformed fruiting bodies, called stipe blow‐out, or totally deformed and undifferentiated masses of mushroom tissue, called dry bubble. The disease symptoms and severity depend on the time point of infection. Small necrotic lesions result from late infections on the fruiting bodies, whereas stipe blow‐out and dry bubble are the result of interactions between the pathogen and the host in the casing layer. Economic importance: Lecanicillium fungicola is a devastating pathogen in the mushroom industry and causes significant losses in the commercial production of its main host, Agaricus bisporus. Annual costs for mushroom growers are estimated at 2–4% of total revenue. Reports on the disease originate mainly from North America and Europe. Although China is the main producer of white‐button mushrooms in the world, little is known in the international literature about the impact of dry bubble disease in this region. Control: The control of L. fungicola relies on strict hygiene and the use of fungicides. Few chemicals can be used for the control of dry bubble because the host is also sensitive to fungicides. Notably, the development of resistance of L. fungicola has been reported against the fungicides that are used to control dry bubble disease. In addition, some of these fungicides may be banned in the near future. Useful websites: http://www.mycobank.org ; http://www.isms.biz ; http://www.cbs.knaw.nl