1.4.4. Spore production
Ascosphaera apis spores are the only infective units of chalkbrood. It is essential to have a high quantity and quality of spores for experiments; e.g. for testing antifungal compounds or for breeding experiments. Spores can be retrieved from black mummies or produced in vitro. From a standardization point of view, the use of in vitro spores from reference strains are strongly recommended, but spores retrieved from black mummies might be chosen in certain situations. Ascosphaera apis will mate on various media but the yield of spores is increased on malt yeast with 20 % dextrose agar (MY20) (Ruffinengo et al., 2000). It is recommended that a fresh spore solution be made for every experiment.