Honey bee colony winter loss rates for 35 countries participating in the COLOSS survey for winter 2018–2019, and the effects of a new queen on the risk of colony winter loss

Abstract

This article presents managed honey bee colony loss rates over winter 2018/19 resulting from using the standardised COLOSS questionnaire in 35 countries (31 in Europe). In total, 28,629 beekeepers supplying valid loss data wintered 738,233 colonies, and reported 29,912 (4.1%, 95% confidence interval (CI) 4.0–4.1%) colonies with unsolvable queen problems, 79,146 (10.7%, 95% CI 10.5–10.9%) dead colonies after winter and 13,895 colonies (1.9%, 95% CI 1.8–2.0%) lost through natural disaster. This gave an overall colony winter loss rate of 16.7% (95% CI 16.4–16.9%), varying greatly between countries, from 5.8% to 32.0%. We modelled the risk of loss as a dead/empty colony or from unresolvable queen problems, and found that, overall, larger beekeeping operations with more than 150 colonies experienced significantly lower losses (p < 0.001), consistent with earlier studies. Additionally, beekeepers included in this survey who did not migrate their colonies at least once in 2018 had significantly lower losses than those migrating (p < 0.001). The percentage of new queens from 2018 in wintered colonies was also examined as a potential risk factor. The percentage of colonies going into winter with a new queen was estimated as 55.0% over all countries. Higher percentages of young queens corresponded to lower overall losses (excluding losses from natural disaster), but also lower losses from unresolvable queen problems, and lower losses from winter mortality (p < 0.001). Detailed results for each country and overall are given in a table, and a map shows relative risks of winter loss at regional level.

Keywords:

• Apis mellifera
• mortality
• colony winter losses
• queens
• queen replacement
• monitoring surveys
• beekeeping
• citizen science

Acknowledgements

The colony loss monitoring group which carried out this study is a core project of the COLOSS research association (prevention of honey bee colony losses), which supports regular workshops facilitating research discussions and collaboration between group members. COLOSS is supported by the Ricola Foundation – Nature and Culture and Véto-pharma. The authors thank very much all the beekeepers who gave their time to complete the COLOSS questionnaire providing the data for this work, and the additional COLOSS members who contributed to survey organisation, data collection and/or data processing. The authors are also grateful to various national funding sources for their support of some of the monitoring surveys, including, in the Republic of Serbia, MPNTR-RS, through Grant No. III46002, Slovenian Research Program P1-0164, and “Zukunft Biene 2” (grant number 101295/2) in Austria. In Macedonia, the technical support was provided by the MacBee association (www.macbee.mk) and its member Miroljub Golubovski. The authors acknowledge the financial support by the University of Graz for open access.

Disclosure statement

No potential conflict of interest was reported by the authors.