| Summary: | The susceptibility of bee larvae to Ascosphaera apis infestation and the hygienic behaviour of worker bees in relation to A. apis infected and freeze-killed brood were evaluated in three races of bees: Apis mellifera carnica, Apis mellifera caucasica, and Apis mellifera mellifera. Experimental bee colonies were evaluated in field conditions during the three beekeeping seasons. The lowest percentage of infected larvae was observed in car GR1 and mel A colonies (8.5% and 15%, respectively) and the highest in car Mr and cau P colonies (21% and 24.3%, respectively). Bees in the car GR1 and mel A colonies removed mummified brood in a shorter period of time (6.5 and 7.1 days on average, respectively) than car Mr and cau P colonies (above 8 days). Bees in the mel A and car GR1 colonies cleaned significantly more cells with freeze-killed brood within 24 and 48 hours (above 70% and 80% on average, respectively) than car Mr and cau P colonies (on average 10 - 20% lower cleaning rate). A low correlation coefficient was found for the susceptibility of larvae to A. apis infection and hygienic behaviour.
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