Title "A new biological control method of Varroa destructor and its economic impact assessment"

The western honey bee Apis mellifera is the most important pollinator worldwide, being responsible for ca. 80% of the pollination of insect-pollinated crops. Beside its importance as pollinator of economically important crops honey bees are of major importance for the conservation of plant diversity in mountain environments. In the last years an alarming decrease in A. mellifera populations was observed all over the world. One of the main factors of this Colony Collapse Disorder (CCD) is the vampire mite Varroa destructor. This external parasitic mite is native in Asia where it infects the Asiatic honey bee Apis cerana. Varroa was introduced in Europe and the USA in the 1980s where it infests Apis mellifera. Today V. destructor is responsible for annual losses of untreated colonies up to 50-80% and is a vector for several honeybee viruses. V. destructor populations are currently controlled by synthetic acaricides and organic acids, while biological methods are lacking. The aim of this project is the evaluation of a new biological control method of V. destructor by using the fungal pathogen Metharizium anisopliae. Preliminary tests indicated that specific strains of M. anisopliae are able to infest and kill the mite without harmful effects on honeybees. Considering the drift of workers and drones between colonies, it is suggested that the fungus is able to spread in an apiary. Therefore, the application of M. anisopliae could represent a new low-cost, environmental friendly control of V. destructor.