The role of honey hydrogen peroxide (H2O2) as a natural defense mechanism and colony stress indictor

Previous work from our lab supports that honey hydrogen peroxide (H₂O₂) effects small hive beetle (SHB, Aethina tumida) survival and may be regulated within colonies. Given that glucose oxidase controls honey H₂O₂, whether honeybee worker castes regulate the addition of this enzyme to nectar or genetically regulate it's expression could be connected to honeybee SHB resistance and overall colony health. Our results show enhanced SHB survival in the absence of H₂O₂ (added catalase) with a 20-50% decreased SHB survival with additions of H₂O₂ to fed honey. Within healthy colonies, honey H₂O₂ varies with location (brood, honey, or uncapped nectar frames) as well as in sugar-water fed colonies (75% reduced content). H₂O₂ content was measured with a colormetric microplate assay. Work in progress at the UGA Bee Laboratory (Athens, GA) expands on these observations. First, we are testing whether supplemental feeding with sucrose versus HFCS (standard beekeeping practices to strengthen colonies) alters honey H₂O₂ levels. Secondly, the longitudinal effects of experimental colony infection with SHB or Varroa mite (VM, V. destructor) on honey H₂O₂ will be examined. Finally, we will determine whether glucose oxidase activity in the hypopharyngeal gland of different worker castes (nurse, receiver, forager) varies with feeding methods. Thus, these experiments in progress, will further solidify the importance of honey H₂O₂ as a natural, and potentially regulated, honeybee defense mechanism. In so far as artificial bee feeds dramatically reduce the H₂O₂ content of stored nectar, this customary beekeeping practice may have inadvertent detrimental actions on overall colony health.