INFECTIVITY AND SURVIVAL OF THE CHALKBROOD PATHOGEN, ASCOSPHAERA APIS, IN COLONIES OF HONEY BEES, APIS MELLIFERA

Abstract

To gain insight into the recurring nature of chalkbrood disease in honey bee colonies, suspensions of Ascosphaera apis prepared from sporulated chalkbrood mummies were sprayed triweekly on the brood combs and the bees around the brood of colonies for four months beginning in August. For nine months, mummies were collected from dead bee traps and bottom boards and were counted in comb cells. For seven months, bees, brood, and hive products were tested for A, apis by microbiological plating procedures. Two major periods of infection occurred. The first was one week after spray inoculation began, and the second took place in November and seemed related to nutritional stress. Susceptibility of the inoculated colonies to the disease varied from nil to high. Five months were required after the last spray before most substrates in the colonies were free of A. apis, although low level contamination still persisted in bee bread, honey, and the interior of larvae from capped cells. The pathogen can survive in bee colonies without causing overt disease.