Resin foraging dynamics in Varroa destructor‐infested hives: a case of medication of kin?

Abstract

Social insects have evolved colony behavioral, physiological, and organizational adaptations (social immunity) to reduce the risks of parasitization and/or disease transmission. The collection of resin from various plants and its use in the hive as propolis is a clear example of behavioral defense. For Apis mellifera, an increased propolis content in the hive may correspond to variations in the microbial load of the colony and to a downregulation of an individual bee's immune response. However, many aspects of such antimicrobial mechanism still need to be clarified. Assuming that bacterial and fungal infection mechanisms differ from the action of a parasite, we studied the resin collection dynamics in Varroa destructor-infested honeybee colonies. Comparative experiments involving hives with different mite infestation levels were conducted in order to assess the amount of resin collected and propolis quality within the hive, over a 2-year period (2014 and 2015). Our study demonstrates that when A. mellifera colonies are under stress because of Varroa infestation, an increase in the number of resin foragers is recorded, even if a general intensification of the foraging activity is not observed. A reduction in the total polyphenolic content in propolis produced in infested versus uninfested hives was also noticed. Considering that different propolis types show varying levels of inhibition against a variety of honey bee pathogens in vitro, it would be very important to study the effects against Varroa of two diverse types of propolis: from Varroa-free and from Varroa-infested hives.

Propolis Consumption Reduces Nosema ceranae Infection of European Honey Bees (Apis mellifera)

“…The lack of significant differences observed between infected and uninfected honey bees in our choice, scan and food consumption tests did not support the hypothesis that bees therapeutically use propolis in self-medication. In contrast to our findings, Simone-Finstrom and Spivak [46] and Pusceddu et al [47] suggest propolis may be used by honey bees in self-mediation. However, these two latter studies addressed the role of propolis not against N. ceranae but against two other hive enemies (A. apis and V. destructor) and were conducted in an apiary rather than in the laboratory.…”

“…In contrast, our study dealt with self-medication by bees for the benefit of the individual bee, and it is very likely that the mechanisms that regulate the response of an infected individual are different from those that regulate the response of uninfected individuals (resin foragers) to the infection of their nestmates. Propolis may therefore be used in colony-level self-medication against some pathogens and pests [46,47] but not in individual-level self-medication against Nosema. We note, though, that Gherman et al [49] did observe individual self-medication by N. ceranae-infected honey bees, though different honeys as opposed to propolis were preferred by bees in those experiments.…”

Total Brood Removal and Other Biotechniques for the Sustainable Control of Varroa Mites in Honey Bee Colonies: Economic Impact in Beekeeping Farm Case Studies in Northwestern Italy

“…However, Sustainability 2020, 12, 2302 3 of 16 the appearance of acaricide resistance and the risk of contamination of the bee product have led to increased interest in alternative control strategies against Varroa [20][21][22]. In recent years, great attention has focused on the use of environmentally safe chemicals (such as organic acids), essential oils, and biotechnical methods, and integrated management is recommended [23][24][25][26][27].…”

The Strong Anti-Kinetoplastid Properties of Bee Propolis: Composition and Identification of the Active Agents and Their Biochemical Targets

“…Furthermore, ethanolic extracts of German propolis were highly toxic to Varroa destructor, with a 10% w/v solution being lethal at 5 s contact [90], and Pusceddu et al observed that raw propolis highly significantly increased the lifespan of Varroa-infected bees, almost completely reversing Varroa-associated mortality [91]. Moreover, the addition of natural propolis to hives reduced the titer of Varroa-transmitted deformed wing virus (DWV) [92] and Varroa-infected colonies specifically increased resin foraging [93]. It is not yet clear which chemical agents in propolis reduce the impact of Varroa infestation, but it was reported that the total polyphenolic content of propolis correlated with levels of Varroa infection in experimental hives in Sardinia [91].…”