Spores of Ascosphaera apis contained in wax foundation can infect honeybee brood.

Chalkbrood disease in honeybees (Apis mellifera L.) is caused by an infection with Ascosphaera apis. Disease expression requires the consumption of fungal spores and a predisposing condition in the susceptible brood. A. apis spores within sheets of wax foundation could be a source of inoculum leading to chalkbrood, but it is also possible that these spores remain confined in the wax and do not contribute to disease. We have resolved this topic by chilling susceptible brood within wax combs built on contaminated foundation (using treatments of spores from 1 mummy and spores from 10 mummies) versus uncontaminated foundation. We found significantly higher levels of chalkbrood in brood exposed to the higher dosage. Our results demonstrate that foundation wax contaminated with spores of A. apis spores may be a source of chalkbrood in honeybee colonies.