An alarming mortality of honeybee colonies (Apis Mellifera) has been reported in many countries since early 2000. In the recent European Epilobee project, the honeybee colonies mortality in Belgium was the highest among the participating countries in 2012-2014. Our Veterinary epidemiology service provides epidemiologic support to the Belgian Federal Agency for the Security of the Food Chain in a recurrent survey of bee mortality. In this project, we describe and monitor the honeybee colony mortality and its spatio-temporal variation across Belgium.
In this project we describe the honeybee colony mortality monitoring in Belgium and its variation in time (between three visits) for 2017-2018.
According to European Union regulations and using a 2-stage random sampling strategy, 20 apiaries in each Belgian Province and up to 6 hives by apiary were selected among the 6.000 beekeepers officially recorded in Belgium.
Within 174 apiaries (out of 200 selected apiaries), 3 visits were conducted:
- the first one in Fall 2017, when the colonies were preparing for winter
- the second in Spring 2018, after bees started foraging
- the third during the Summer 2018, the active season.
The field survey included direct observations, interviews and measurements performed by trained FASFC inspectors. The questionnaire provided information regarding:
- colony attributes: such as colony mortality, demography, and detection of Varroa Destructor mites
- beekeeping management practices: such as beekeepers experience, number of managed colonies, Varroa Destructor management.
The over winter weighted colony mortality in 2017-2018 was estimated at 23.8% (95% Confidence interval (95%CI): 21.7%-26.1%) for Belgium.
Further risk factors analysis and ranking is now ongoing to check if risk factors and ranking are identical to those identified during previous (2016-2017) winter mortality estimations (29.3%; 95%CI: 23.2%-36.0%). In this study based on Random Forest modelling, risk factors were identified and ranked (by decreasing order) using the Gini impurity criterion:
- Varroa Destructor level of infection
- density of beekeepers in the municipality
- location of the apiary (municipality)
- apiary size (count of hives)
- demographical indicator before winter (vitality)
- bees subspecies
- beekeeper experience.
As a partner in a continuous improvement process, our Veterinary epidemiology service is now supporting the FASFC to refine and adapt the surveillance inquiry form which will be proposed to the beekeepers during the coming surveys.