Mortality of Varroa destructor in honey bee (Apis mellifera) colonies during winter

Abstract

The change in infestation levels of the mite Varroa destructor Anderson and Trueman on adult bees during periods with little or no brood rearing (late October/early November to early February) was investigated in 10 colonies for two consecutive years in a Swedish climate (N57°06'E18°16'). The results do not support the hypothesis that mites become concentrated on the remaining bees as bees die off from the winter cluster. When the number of all mites recovered from dead bees or from debris was used to calculate mites per dead bee, the level of infestation per bee was not significantly different between samples of live bee and dead bees. For modelling purposes, we presently find no reason to differentiate the mortality rates of bees and mites during periods when there is no or limited amounts of brood in the colonies, although the connection between bee mortality and mite mortality may not be as direct as previously assumed.