Infection Dynamics of Zarea fungicola and Its Impact on White Button Mushroom Yield

The ascomycetous fungus, Zarea fungicola (syn. Lecanicillium fungicola), is the most common fungal pathogen of the white button mushroom, Agaricus bisporus. The objective of this study was to assess the impact of the timing and concentration of spore inoculation on the development of dry bubble disease, its progression, and the yield of mushrooms. Experiments included two factors: inoculation timing (at casing, three days after casing (4th day), onset of induction (7th day), primordia formation (12th day), and mixing spores with casing soil) and different inoculum concentrations (105 m−2, 106 m−2, and 107 m−2 casing). The first symptoms of dry bubble appeared at the beginning of the first flush (14–16 days of cultivation) in trials where spore inoculum was applied three days after casing and during the induction phase. In contrast, the longest disease latent period (26–28 days) occurred when spores were mixed with the casing soil. A significant interaction was observed between inoculation timing and spore concentration, which influenced disease incidence and yield. Area under the disease progress curve (AUDPC) analysis indicated the fastest disease progression following inoculation three days after casing (4th day) and at induction phase (7th day). Correspondingly, the highest reductions in yield and biological efficiency were observed at these inoculation timings. In addition, an increase in conidial concentration generally led to more severe disease symptoms. The results indicate that the period from casing application up to the induction phase requires strict hygiene measures, as infection during this time causes the most significant reduction in yields. Furthermore, the stage of mushroom development and inoculum concentration critically determines the severity of dry bubble, providing important guidance for disease management in white button mushroom cultivation.