Inside honeybee hives: Impact of natural propolis on the ectoparasitic mite Varroa destructor and viruses

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Social immunity is a key factor for honeybee health, including behavioral defense strategies such as the collective use of antimicrobial plant resins (propolis). While laboratory data repeatedly show significant propolis effects, field data are scarce, especially at the colony level. Here, we investigated whether propolis, as naturally deposited in the nests, can protect honeybees against ectoparasitic mites Varroa destructor and associated viruses, which are currently considered the most serious biological threat to European honeybee subspecies, Apis mellifera, globally. Propolis intake of 10 field colonies was manipulated by either reducing or adding freshly collected propolis. Mite infestations, titers of deformed wing virus (DWV) and sacbrood virus (SBV), resin intake, as well as colony strength were recorded monthly from July to September 2013. We additionally examined the effect of raw propolis volatiles on mite survival in laboratory assays. Our results showed no significant effects of adding or removing propolis on mite survival and infestation levels. However, in relation to V. destructor, DWV titers increased significantly less in colonies with added propolis than in propolis-removed colonies, whereas SBV titers were similar. Colonies with added propolis were also significantly stronger than propolis-removed colonies. These findings indicate that propolis may interfere with the dynamics of V. destructor-transmitted viruses, thereby further emphasizing the importance of propolis for honeybee health.

Original languageEnglish
Article number15
Issue number1
Number of pages18
Publication statusPublished - 01.03.2017

Bibliographical note

Funding Information:
Financial support was granted by the Swiss National Science Foundation (SNSF) and the Vinetum Foundation to Peter Neumann and Orlando Yañez, and the Deutsche Forschungsgemeinschaft (DFG project: LE 2750/1-1) to Sara D. Leonhardt. Nora Drescher was supported by the Leuphana University of Lüneburg. Kaspar Roth is greatly acknowledged for technical laboratory support and Manfred Lütke for assistance with practical beekeeping.

Publisher Copyright:
© 2017 by the authors; licensee MDPI, Basel, Switzerland.