David Hofer
Bachelor student (2011-12)
Now scientific collaborator at the Museum of Nature South Tyrol
Title "Evaluation of the fungal pathogen Metharizium anisopliae as control agents of Varroa destructor in South Tyrol"
Apis mellifera is the most important pollinator worldwide. About 80% of plant species are dependent on cross pollination and out of this, again 80% of the pollination is done through A. mellifera. In economic measures, bees generate more than 150 billion Euros per year for agriculture and other sectors. Therefore it is the third most important livestock animal right behind cattle and pigs. Moreover, honeybees provide humans with honey, wax, propolis, pollen and royal jelly.
In the last years an alarming decrease in A. mellifera populations can be observed all over the world. Several causes are proposed to explain the so-called “Colony Collapse Disorder” or CCD. The reasons for this devastating phenomenon are not clear, but hypotheses involve the decrease of natural habitats, viruses, insecticides and the bee ectoparasite Varroa destructor. Other scientists suspected also genetically-modified crops and the microsporidian Nosema ceranae as infection agents of CCD as well as of bee colony losses. However, many aspects are still unclear about these mechanisms. For instance V. destructor also acts as a vector and activator of other pathogens, viruses in particular, and seems to play a central role in increasing bee mortality rate.
The aim of this thesis is to evaluate the use of entomopathogen fungus Metarhizium anisopliae, strain “Bipesco 5”, as a possible biological control agent of V. destructor. Therefore, tests in laboratory under controlled conditions and field trials will be done. Firstly, the potential toxicity or adverse effects of the spore of M. anisopliae on live honey bees will be tested in laboratory, although previous experiments suggested that the M. anisopliae treatments are safe for bees. Then, field trials will be performed. Beehives will be treated with dry M. anisopliae spore powder and confronted with untreated beehives under similar environmental conditions. Particular attention will be given to ensure that all beehives start with a similar bee population and mite infestation rate. Moreover, queens will be of the same year and genetically related. Varroa population will be monitored in all beehives before and after the treatments with two different methodologies: counting the number of mites falling down into the inspection bottom board and using the ice-sugar method to estimante the number of mites present on adult bees. Both methods will be conducted on a weekly sampling program. At the end of the testing period each colony will be treated with oxalic acid, in order to have a better estimation of the residual mite population. Each test will be analyzed statistically.