Bacterial blotch is one of the most economically important diseases of button mushrooms. Knowledge on mechanisms of disease expression, inoculum thresholds and disease management is limited to the most-well known pathogen, . Recent outbreaks in Western Europe have been attributed to and for ginger and brown blotch, respectively, although information on their identity, infection dynamics and pathogenicity is largely lacking.The disease pressure in an experimental mushroom cultivation facility was evaluated for and over varying inoculation densities, casing soil types, environmental humidity and cultivation cycles. The pathogen population structures in the casing soils were simultaneously tracked across the cropping cycle using highly specific and sensitive TaqmanTM-qPCR assays. caused disease outbreaks at lower inoculum thresholds (10 cfu/g) in the soil than (10 cfu/g). Ginger blotch generically declined in later harvest cycles, although brown blotch did not. Casing soils were differentially suppressive to blotch diseases, based on their composition and supplementation. Endemic pathogen populations increased across the cultivation cycle although the inoculated pathogen populations were consistent between the 1st and 2nd flush. and have unique infection and population dynamics, that vary over soil types. Their endemic populations are also differently abundant in peat-based casing soils. This knowledge is essential to interpret diagnostic results from screening mushroom farms and design localized disease control strategies.