Entomology
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Item Characterizing effectiveness of and obstacles to best beekeeping management practices(2020) Kulhanek, Kelly; vanEngelsdorp, Dennis; Entomology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Honey bees (Apis mellifera, L.) provide critical pollination services to many US crops, but decades of high colony loss rates have strained beekeepers’ ability to provide sufficient colonies for crop production. In a national survey of colony losses for the 2015-2016 season, beekeepers reported losses averaging at 37.4%, and that the parasitic mite Varroa destructor was a leading cause of mortality. Survey results were used to create empirical best management practices (BMPs) to reduce colony loss rates. Best practices were the top four practices which correlated to significant reductions in winter colony loss. This set of BMPs was tested on 140 colonies in 7 locations across the US, compared to average beekeeping practices. At the end of 3 years, apiaries managed according to BMPs exhibited reduced Varroa loads, which resulted in reduced fall viral loads and reduced winter mortality. However, colony loss rates still exceeded rates that beekeepers have deemed acceptable. A prominent factor affecting colony health and mortality in the BMP study was Varroa. After identifying Varroa treatment as a preventative measure, the effects of Varroa management were evaluated in non-experimental apiaries. Citizen scientist beekeepers participating in the Sentinel Apiary Program provided Varroa samples and Varroa management information. Out of 192 Varroa treatments applied to 155 apiaries over 2 years, only 45 treatments resulted in reduced Varroa loads. Common hypotheses of factors affecting Varroa population growth failed to explain the rapid increases in Varroa loads experienced by beekeepers in critical fall months. Finally, a more novel explanation for rapid increases in Varroa load was explored: horizontal transmission of mites between apiaries. Colonies that were visited by non-natal bees experienced larger increases in Varroa loads than unvisited colonies, but not as a result of visitation to or from high mite colonies. High mite colonies in the landscape represent a threat to nearby colonies, and cooperative Varroa management is likely to mediate colony losses resulting from Varroa. This dissertation supports the critical need for proactive, cooperative Varroa management to improve colony health and reduce mortality.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.