Surveys as a tool to record winter losses of honey bee colonies: a two year case study in Austria and South Tyrol

Alarmed by reports of high losses of honey bee colonies in other countries, and with no field data available for Austria, a mixed media survey on winter mortality of honey bee colonies was carried out in Austria for the overwintering periods of 2007-8 and 2008-9. In addition, the survey was extended to South Tyrol (Italy) in 2007-8. Data presented for 2007-8 were gathered at eight beekeeping conventions in Austria (374 beekeepers; 16,217 colonies, representing 1.7% of beekeepers and 5.8% of colonies, respectively) and one convention in South Tyrol (115 beekeepers; 3,999 colonies, representing 3.7% of beekeepers and 10.6% of colonies, respectively). During the overwintering period of 2007-8 we calculated a total loss of 13.3% of colonies in Austria, ranging from 9.2 to 17.1% in different regions. Overwintering mortality in South Tyrol was 12.3%. In 2009, data were collected at nine beekeeping conventions in Austria and from some respondents who returned the questionnaire which was also published in the Austrian beekeeping journal and on our website (575 beekeepers; 18,141 colonies, representing 2.6% of beekeepers and 6.5% of colonies, respectively). Total colony losses were calculated as 9.3%, ranging from 6.0% to 17.8% in different provinces of Austria. Respondents attributed Varroa destructor as a key factor in the occurrence of high colony losses during overwintering in our area of investigation, followed by queen loss and starvation. We analyzed the impact of hive management (operation size, date of carbohydrate feeding, type of carbohydrates fed before winter, V destructor treatment and migratory beekeeping) on colony loss. We also reported observed biases due to different survey methods in the second year.