Ascosphaera apis is a causative agent of chalkbrood, which is one of the most widespread honey bee diseases. In our experiments, the influence of several artificial media and cultivation under different temperatures was evaluated. Concretely, the radial growth of separated mating types was measured, reproductive structures in a Neubauer hemocytometer chamber were counted simultaneously, and the morphometry of spore cysts and spore balls was assessed. The complex set of experiments determined suitable cultivation conditions. A specific pattern between reproductive structure size and temperature was found. The optimal temperature for both mating types was 30 °C. SDA and YGPSA media are suitable for fast mycelial growth. Moreover, the effect of bee brood on fungus growth and development in vitro was investigated by modification of culture medium. The newly modified medium PDA-BB4 was most effective for the production of the reproductive structures. The result suggests that honey bee brood provides necessary nutrients for proper fungus development during in vitro cultivation. As there is no registered therapeutic agent against chalkbrood in most countries, including the European Union, the assessment of A. apis growth and development in different conditions could help to understand fungus pathogenesis and thus control chalkbrood disease.

Biology Centre of the Czech Academy of Sciences Institute of Entomology 370 05 Ceske Budejovice Czech Republic

Department of Agroecosystems Faculty of Agriculture University of South Bohemia Studentska 1668 370 05 Ceske Budejovice Czech Republic

Department of Crop Production Faculty of Agriculture University of South Bohemia Studentska 1668 370 05 Ceske Budejovice Czech Republic

Department of Genetics and Agricultural Biotechnology Faculty of Agriculture University of South Bohemia Studentska 1668 370 05 Ceske Budejovice Czech Republic

Department of Zoology Fisheries Hydrobiology and Apiculture Faculty of AgriSciences Mendel University in Brno Zemedelska 1 613 00 Brno Czech Republic

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Screening of Honey Bee Pathogens in the Czech Republic and Their Prevalence in Various Habitats