A case control study and a survey on mortalities of honey bee colonies (Apis mellifera) in France during the winter of 2005-6.

SummarySeveral cases of mortality of honey bee colonies (varying from 38 to 100%) were observed in France during the winter of 2005–6. In order to explain the causes of these mortalities, a case control study was conducted on a limited area, together with a larger survey in 18 other apiaries located in 13 sites over the entire country. Both studies included diagnosis of the main honey bee diseases, assessment of the colony management measures taken by beekeepers and the determination of pesticide residues in apicultural matrices. Pollen analysis was carried out on beebread samples to identify which floral species were used for forage before colony death. Poor Varroa destructor treatments together with Nosema disease and brood diseases were frequent in apiaries with high colony mortalities. The absence of any preventive treatment against V. destructorwas the main risk factor.