Summary of Winter Honey Bee Colony Losses in Slovakia Between the Years 2009 and 2015

Between the seasons 2009/2010 and 2014/2015 was evaluated 1305 questionnaires in total, received from Slovak beekeepers. Standard questionnaires of COST working group COLOSS were used with sets of questions related to overwintering of bee colonies and possible reasons of its losses. In season 2009/2010 winter losses in Slovakia reached 7.10 %, subsequently in 2010/2011 - 5.96 %, 2011/2012 - 9.70 %, 2012/2013 - 9.50 %, 2013/2014 - 8.84 %, 2014/2015 - 10.00 %. Expected causes of winter mortality (starvation, poor queen´s quality, parasitism, robbery) were evaluated in the study to detect the presence of depopulation syndrome of bee colonies - CCD (colony collapse disorder) reported from some North American and European areas. As acceptable level of winter losses is generally considered level 10 %, which was not exceeded in any season, thereby Slovakia ranks among countries with the lowest winter mortality of bee colonies worldwide. Possible reason of this situation is most probably multiple Varroa treatment throughout the year, but other reasons are discussed as well in the study.