High Humidity in the Honey Bee (Apis mellifera L.) Brood Nest Limits Reproduction of the Parasitic Mite Varroa jacobsoni Oud.

Factors influencing reproduction of the parasitic mite Varroa jacobsoni have become a central theme of honey bee pathology. In large parts of the world the mite has made it impossible for colonies of the honey bee Apis mellifera to survive if no measures of treatment are applied [1]. Originally a parasite of the Eastern honey bee A. cerana, the mite was detected in colonies of A. mellifera only less than 4 decades ago [2]. A. cerana colonies are not damaged by V. jacobsoni because several factors prevent the build-up of a large mite population [3]. The most important factor is that in colonies of A. cerana the parasite, which can reproduce only in capped brood cells, reproduces exclusively in drone brood cells while in colonies of A. mellifera it reproduces in worker brood cells as well [4]. In cold, temperate, and Mediterranean climates the mite population grows exponentially until the colony collapses, due mainly to a high percentage of bees damaged by V. jacobsoni during their pupal development [5]