Entomology
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Item Home sick: impacts of migratory beekeeping on honey bee (Apis mellifera) pests, pathogens, and colony size(PeerJ, 2018-11-02) Alger, Samantha A.; Burnham, P. Alexander; Lamas, Zachary S.; Brody, Alison K.; Richardson, Leif L.Honey bees are important pollinators of agricultural crops and the dramatic losses of honey bee colonies have risen to a level of international concern. Potential contributors to such losses include pesticide exposure, lack of floral resources and parasites and pathogens. The damaging effects of all of these may be exacerbated by apicultural practices. To meet the pollination demand of US crops, bees are transported to areas of high pollination demand throughout the year. Compared to stationary colonies, risk of parasitism and infectious disease may be greater for migratory bees than those that remain in a single location, although this has not been experimentally established. Here, we conducted a manipulative experiment to test whether viral pathogen and parasite loads increase as a result of colonies being transported for pollination of a major US crop, California almonds. We also tested if they subsequently transmit those diseases to stationary colonies upon return to their home apiaries. Colonies started with equivalent numbers of bees, however migratory colonies returned with fewer bees compared to stationary colonies and this difference remained one month later. Migratory colonies returned with higher black queen cell virus loads than stationary colonies, but loads were similar between groups one month later. Colonies exposed to migratory bees experienced a greater increase of deformed wing virus prevalence and load compared to the isolated group. The three groups had similar infestations of Varroa mites upon return of the migratory colonies. However, one month later, mite loads in migratory colonies were significantly lower compared to the other groups, possibly because of lower number of host bees. Our study demonstrates that migratory pollination practices has varying health effects for honey bee colonies. Further research is necessary to clarify how migratory pollination practices influence the disease dynamics of honey bee diseases we describe here.Item NOVEL ADAPTATIONS IN MORPHOLOGY, DEVELOPMENT, AND NUTRIENT AQUISITION FOR HOST EXPLOITATION IN THE MESOSTIGMATID HONEY BEE PARASITE VARROA DESTRUCTOR(2018) Ramsey, Samuel David; vanEngelsdorp, Dennis; Entomology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The parasitic mite Varroa destructor is the most significant single driver of the global honey bee health decline. Better understanding of the association of this parasite and its host is critical to developing sustainable management practices. This work shows that Varroa is not consuming hemolymph as has been the accepted view, but damages host bees by consuming fat body. Feeding wounds in adult bees were imaged for the first time showing that Varroa feed on the underside of the abdomen where fat body is the immediate underlying tissue. Fat body at the wound site showed evidence of external digestion. Hemolymph and fat body in honey bees were then marked with fluorescent biostains. Fluorescence associated with the fat body was consistently detected in the gut of mites fed on these bees while comparatively little fluorescence was detected from the hemolymph biostain. Mites were then fed a diet composed of one or both tissues. Mites fed fat body tissue survived longer and produced more eggs than those fed hemolymph. Mites fed hemolymph showed fitness metrics no different from the starved control group. Collectively, these findings show that Varroa are exploiting the fat body as their primary source of sustenance; a tissue integral to proper immune function, pesticide detoxification, overwinter survival and several other essential processes in healthy adult and immature bees. Additional study was undertaken to better understand how the Varroa accelerates its reproductive rate. Via gel electrophoresis and immunodetection, undigested honey bee vitellogenin was found in Varroa eggs. The presence and identity of these host proteins was confirmed via HPLC MS/MS. This particular cleavage of vitellogenin is found only in the fat body. These findings fundamentally alter our understanding of the etiology of varroosis and underscore a need to revisit our understanding of this parasite and its impacts, both direct and indirect, on honey bee health. Further study of Varroa adaptations focused on expanding knowledge of Varroa morphology with the aim of determining features that can distinguish between Varroa species. Using low temperature scanning electron microscopy, we were able to provide better resolution of key morphological features, detail variability within traits, and provide novel descriptions of certain characters.Item Reducing the risk of honey bee colony loss through beekeeping management practices(2017) Steinhauer, Nathalie Annick; vanEngelsdorp, Dennis; Entomology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)As primary pollinators in agricultural settings, managed honey bee colonies (Apis mellifera L.) are a highly value commodity for which demand is only growing. With high levels of colony loss experienced in the USA and around the world, there is demand for a better understanding of the drivers of colony mortality and identification of suites of management practices which are optimal for colony survivorship. This dissertation responds to these demands by summarizing the state of knowledge on the causes of colony loss (Chapter 1); describing the epidemiological tools used to investigate honey bee colony health (Chapter 2); describing the variability of colony loss across stakeholder typology, regions, seasons and years (Chapters 3 and 4); and investigating the association between management practices and colony mortality (Chapter 5). Honey bee health, and ultimately, colony loss, is affected by multiple stressors acting concomitantly and sometimes interacting. Those stressors include pests and diseases, forage availability and pesticide exposure. Management practices have the potential, when used judiciously, to alleviate some of those stressors. Investigations of sets of management practices have been frustrated by the lack of methodology to handle large complex and incomplete datasets that are typical in observational studies. Using long term observational data obtained from the Bee Informed Partnership monitoring of honey bee colony losses and management practices in the US, we were able to describe the variation in colony loss across years, seasons, States and stakeholder’s types. In parallel, we summarized management information into a quality index, based on experts’ opinion, and confirmed the association between management practices quality and overwintering colony loss. Further, we ranked individual practices based on their associated potential reduction in colony mortality. Because our method accounts for the pre-existing prevalence of practices, we propose that those sets of practices should be prioritized as recommendations, rather than those identified by experts, to derive the highest reduction in risk of colony mortality. The methodology we developed could benefit other Ag or epidemiological systems interested in the summarization of a great number of practices and their prioritization based on highest potential to reduce risk.