CHALKBROOD DEVELOPMENT IN HONEYBEE BROOD UNDER CONTROLLED CONDITIONS

Third instar larvae from a honeybee colony were fed with high doses of spores of Ascosphaera apis, the causative agent of chalkbrood disease . Optimal survival of spores was detected during a short period after sealing the cell and before larval spinning by culture of the gut cont ents removed from 4 stages of brood development. The inocula (5 x 10(5 ) spores/larva) did not induce the disease and were not present in the digestive tract before pupation. In a second experiment, third instar larvae, fed with the same amounts of spores as before, received a coo ling stress (22 +/- 2-degrees-C, for 24 h). When chilling was applied 24 h before or after operculation, mummification occurred in the major ity of larvae (59.6 and 65.5%, respectively). Chilling of older brood (spinning larvae or pupa) produced a much lower incidence of chalkbroo d. This confirms the need for predisposing conditions over a short per iod of brood development for the development of this disease.