Recording the proportion of damaged Varroa jacobsoni Oud. in the debris of honey bee colonies (Apis mellifera)

The proportion of damaged mites in natural mite fall is considered a useful criterion in the breeding of Varroa-tolerant bees. This study, observing about 16 000 mites, tested several modifications of recording this trait. The effects of a predator-proof hive, coating the bottom boards with grease, and the time intervals between recordings were examined. Studies were also conducted to determine the extent of damage by bees to already dead mites, and the influence of storage conditions of the dead mites. The type and the amount of damage to immature and adult mites differed considerably. Protection of the bottom board against predators significantly reduced the extent of damaged mites. Mites should not remain on the bottom board for longer than 2 days, because the extent of damage increases significantly after that, especially when wax moth larvae are present. Conditions under which the mites are stored significantly affect the extent of the damage. Quantity and quality of damage in natural mortality indicate that a proportion of mites died due to specific defensive behaviour of the bees. (C) Inra/DIB/AGIB/Elsevier, Paris.