In Greece, sudden deaths, unusual b

In Greece, sudden deaths, unusual behaviour and declines of adult honey bee populations were reported in summer 2009 by the beekeepers in the region of Peloponnese, Greece (Bacandritsos et al. 2010). A preliminary study was carried out to investigate these unexplained phenomena in this region and samples were collected from the affected colonies. The clinical symptoms of selected colonies were noted and 37 bee samples were collected from fifive different apiaries suffering similar symptoms. Symptomatic adult honey bees tested positive for Varroa destructor, Nosemaceranae, chronic bee paralysis virus (CBPV), acute paralysis virus (ABPV), deformed wing virus (DWV), sacbrood virus (SBV) and black queen cell virus (BQCV). Chemical analysis revealed that amitraz, thiamethoxam, clothianidin and acetamiprid were all absent although imidacloprid was present in three out of the fifive apiaries sampled. Residue levels were detected at an average concentration of 27 µg/kg tissue which is equivalent to a dose of about 3 ng/bee. This residue level is close to the lower threshold of the calculated acute oral LD50 dose which range between 3.7 and 40.9 ng/bee (Schmuck et al. 2001). However, the presence of multiple pathogens and pesticides made it impossible to associate a single specifific cause to the depopulation phenomena observed in Greece. The authors identifified fifive possible factors: (i) multiple virus infection by fifive different viruses along with infection by N. ceranae,(ii) imidacloprid residues in bee tissues, (iii) stress induced by transportation, (iv) temperature and humidity flfluctuations and (v) the collection of fifir honeydew (low water content).