winter bees

[cam bishop]

Interesting study on winter bees/virus issues and survival:

Dainatn, B., J.D. Evansg, Y.P. Cheng, L. Gauthiern & P. Neumannn,o – DEAD OR ALIVE? PATHOGENS AND LIFE SPAN OF WINTER HONEY BEES - Honey bees, Apis mellifera, suffer numerous biotic and abiotic stresses and have recently faced large repeated losses. Although the scientific community agrees that losses may result from several factors acting synergistically, it is not clear yet what causes this phenomenon. It has
been proposed that pathogens are involved in winter losses. We hypothesized that pathogens may reduce the life expectancy of individual winter bees to a point that the critical size threshold of a cluster to survive winter would be reached leading to the collapse of the colony. To test this hypothesis, a monitoring experiment on 29 colonies has been performed in winter 2007/2008 in Switzerland where levels of three pathogens including Deformed wing virus (DWV), Acute bee paralysis virus (ABPV) and Nosema ceranae, Varroa destructor (Vd) infestation, and life expectancy of individuals workers were measured. The results show that neither ABPV nor Nosema ceranae could be incriminated as a deadly factor in this study. Conversely, both DWV and Vd, in this order, reduced significantly life expectancy of winter workers. Furthermore, the number of DWV-infected bees in colonies, which didn`t survive winter, was significantly higher than in colonies which survived. The data of this study are in contrast with the intriguing Colony Collapse Disorder in the U.S, for which Varroa destructor and DWV were poor correlates with CCD risk. Finally, the results suggest that reduced life expectancy of individual bees is one proximate mechanism of colony winter losses and Varroa destructor remains one of the main culprits.