Title "Can reduced comb cell size influence varroa infestation and honey production in a mountain environment?"

A small parasitic mite, Varroa destructor, was imported to Europe from the Asiatic honeybee, Apis cerana, about 30 years ago. Today this parasitic mite is the most serious pest of honeybees all over the world and also in South Tyrol. The varroa mite attacks adults and larvae of the Western honey bees (Apis mellifera) sucking their blood and causing a disease called varroatosis. Several chemical treatments have been developed to tread infected colonies, but many acaricides can harm honeybees and/or beekeepers. Moreover, acaricide residuals may pollute the honey and other bee products. Finally, some acaricides are no longer effective because the development of resistance in varroa populations against these pesticides. Therefore, in the last years non-chemical methods of varroa control have been strongly investigated in several research institutes. One method has been recently adopted by some beekeepers, by reducing the worker cell width from the current size of 5.5 mm to 4.9 mm, a cell width that bees had till 100 years ago. During last century cell width was increased, thinking that bigger bees may produce more honey, however it has been proved that colonies where bees are reared in smaller cells have the same honey production that the others. One important advantage of small cell size is that reproductive phase of varroa mites is reduced, because also bee metamorphosis is shorter. Therefore, varroa replicate on pupae in lower speed. In this thesis we aim to compare the dynamic of varroa infestation in two groups of 5 colonies each. In the first group bees will develop in 4.9 mm cells, while in the second group will be kept with the common 5.5 mm cell size. In both gropus we will also investigate the nest cleaning performance and honey production. The apiary with the 10 colonies will be located in a mountain environment at altitude 1.100 m a.s.l.