Chalkbrood development in honeybee brood under controlled conditionsF. Puerta, J.M. Flores, M. Bustos, F. Padilla and F. Campano
Departamento de Biología Animal, Cátedra de Biología Aplicada, Sección de Apicultura, Facultad de Veterinaria, Universidad de Córdoba, 14005 Córdoba, Spain
Abstract - 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 contents removed from 4 stages of brood development. The inocula (5 x 105 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 cooling stress (22 ± 2°C, for 24 h). When chilling was applied 24 h before or after operculation, mummification occurred in the majority of larvae (59.6 and 65.5%, respectively). Chilling of older brood (spinning larvae or pupa) produced a much lower incidence of chalkbrood. This confirms the need for predisposing conditions over a short period of brood development for the development of this disease.
Key words: chalkbrood / Apis mellifera / Ascosphaera apis / predisposing conditions / stress / brood chilling