Inside Honeybee Hives: Impact of Natural Propolis on the Ectoparasitic Mite Varroa destructor and Viruses.
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 mitesVarroa destructorand 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 toV. 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 ofV. destructor-transmitted viruses, thereby further emphasizing the importance of propolis for honeybee health.
Institute of Ecology, Leuphana University of Lüneburg, Scharnhorststr. 1, Lüneburg D-21335, Germany. nora.drescher@gmx.de.
Nora
N
Drescher
Department of Nature Conservation and Landscape Ecology, University of Freiburg, Tennenbacher Str. 4, Freiburg D-79106, Germany. alexandra.klein@nature.uni-freiburg.de.
Alexandra-Maria
AM
Klein
Institute of Bee Health, Vetsuisse Faculty, University of Bern, Schwarzenburgstrasse 161, Bern CH-3003, Switzerland. peter.neumann@vetsuisse.unibe.ch.|Swiss Bee Research Centre, Agroscope, Bern CH-3003, Switzerland. peter.neumann@vetsuisse.unibe.ch.
Peter
P
Neumann
Institute of Bee Health, Vetsuisse Faculty, University of Bern, Schwarzenburgstrasse 161, Bern CH-3003, Switzerland. orlando.yanez@vetsuisse.unibe.ch.|Swiss Bee Research Centre, Agroscope, Bern CH-3003, Switzerland. orlando.yanez@vetsuisse.unibe.ch.
Orlando
O
Yañez
Department of Animal Department of Ecology and Tropical Biology, University of Würzburg, Biocenter-Am Hubland, Würzburg D-97074, Germany. sara.leonhardt@uni-wuerzburg.de.
Sara D
SD
Leonhardt
Apis mellifera; deformed wing virus; plant-insect interactions; resin; sacbrood virus; social immunity