Keith S. Delaplane

Standard methods for varroa research

Summary Very rapidly after Varroa destructor invaded apiaries of Apis mellifera, the devastating effect of this mite prompted an active research effort to understand and control this parasite. Over a few decades, varroa has spread to most countries exploiting A. mellifera. As a consequence, a large number of teams have worked with this organism, developing a diversity of research methods. Often different approaches have been followed to achieve the same goal. The diversity of methods made the results difficult to compare, thus hindering our understanding of this parasite. In this paper, we provide easy to use protocols for the collection, identification, diagnosis, rearing, breeding, marking and measurement of infestation rates and fertility of V. destructor. We also describe experimental protocols to study orientation and feeding of the mite, to infest colonies or cells and measure the mites susceptibility to acaricides. Where relevant, we describe which mite should be used for bioassays since their behaviour is influenced by their physiological state. We also give a method to determine the damage threshold above which varroa damages colonies. This tool is fundamental to be able to implement integrated control concepts. We have described pros and cons for all methods for the user to know which method to use under which circumstances. These methods could be embraced as standards by the community when designing and performing research on V. destructor.

Colony Collapse Disorder in context

Although most of humanity relies upon foods that do not require animal pollination 1, production of 39 of the worlds 57 most important monoculture crops still benefits from this ecosystem service 2. Western honey bees (Apis mellifera) are undoubtedly the single-most valuable animal pollinators to agriculture because they can be easily maintained and transported to pollinator-dependent crops. Yet, despite an almost 50% increase in world honey bee stocks over the last century, beekeepers have not kept pace with the >300% increase in pollinator-dependent crops 3. This has led to great uncertainty surrounding the recent large-scale die-offs of honey bees around the world, and has sparked enormous interest from both scientists and the general public.

Varroa destructor : research avenues towards sustainable control

Summary Pollination by honey bees plays a key role in the functioning of ecosystems and optimisation of agricultural yields. Severe honey bee colony losses worldwide have raised concerns about the sustainability of these pollination services. In many cases, bee mortality appears to be the product of many interacting factors, but there is a growing consensus that the ectoparasitic mite Varroa destructor plays the role of the major predisposing liability. We argue that the fight against this mite should be a priority for future honey bee health research. We highlight the lack of efficient control methods currently available against the parasite and discuss the need for new approaches. Gaps in our knowledge of the biology and epidemiology of the mite are identified and a research road map towards sustainable control is drawn. Innovative and challenging approaches are suggested in order to stimulate research efforts and ensure that honey bees will be able to sustainably fulfil their role in the ecosystem.

Coordinated responses to honey bee decline in the USA

In response to successive years of high honey bee mortality, the United States Congress mandated the US Department of Agriculture (USDA) to increase funding for research and education directed at reducing honey bee decline. The funding follows two administrative streams within USDA — one through the USDA Agricultural Research Service (ARS) and another through the USDA National Institute for Food and Agriculture (NIFA). ARS is funding an Areawide Project operated by the four ARS honey bee labs, and NIFA is funding through a competitive grant process a Coordinated Agricultural Project (CAP) operated by scientists and educators heavily represented by state colleges of agriculture. Each project — Areawide and CAP — is characterized as a consortium of investigators working in a coordinated manner to reduce institutional redundancy and optimize the discovery and delivery of sustainable bee management practices to client beekeepers.ZusammenfassungDaten über imkerlich gehaltene Bienenvölker vom US amerikanischen Landwirtschaftsministerium (US Department of Agriculture, USDA) zeigen eine kontinuierliche Abnahme der Bienenvölker vom Spitzenwert von 6 Mio. in den 1940er Jahren auf 2,3 Mio. im Jahr 2008 (Abb. 1). Die vermutlichen Ursachen für diesen Rückgang sind vielfältig. Sie beinhalten trans-globale Pathogene und Parasiten und sozio-ökonomische Trends, die Imker aus ihrer Praxis drängen, was in ganz Europa der Fall ist. Zusätzlich sind unter den toten Völkern aus der jüngsten Vergangenheit eine Gruppe mit abgegrenzten Symptomen, die als „colony collapse disorder (CCD)“ bezeichnet wurden. Die Hauptsymptome des CCD sind Schwund oder nahezu vollständiger Verlust adulter Bienen und ein geringer Anteil von Adultbienen zu Brut. Die generelle Abnahme der Völkerzahlen, zusammen mit einer erhöhten Mortalität aufgrund von CCD und anderen Faktoren, führte zu einer Verteuerung der Bestäubungsprämie für Mandeln und anderen Nutzpflanzen. In den Vereinigten Staaten wird der Anstieg der bestäubungsabhängigen Nutzpflanzen von einer Abnahme des nationalen Bienenvölkervorrats begleitet, eine ernste Situation für die landwirtschaftliche Bestäubung.Als Reaktion auf die hohe Honigbienensterblichkeit der vergangenen Jahre beauftragte der US Congress das US Landwirtschaftsministerium damit, solche Forschungs- und Bildungsförderung zu steigern, die auf eine Reduktion der Honigbienenabnahme gerichtet sind. Der Landwirtschaftliche Forschungsdienst der USA (USDA-ARS) fördert ein von vier ARS Laboratorien durchgeführtes, sogenanntes Areawide Projekt. Das USDA National Institute for Food and Agriculture fördert ein koordiniertes Landwirtschaftsprojekt (CAP), welches vornehmlich von Wissenschaftlern und Pädagogen aus staatlichen landwirtschaftlichen Colleges betrieben wird. Beide Projekte, Areawide und CAP, sind durch ein Konsortium von Forschern charakterisiert, die koordiniert zusammenarbeiten, um institutionelle Redundanz zu reduzieren und die Entdeckung und Verbreitung einer nachhaltigen Imkerei zu optimieren.Das übergeordnete Ziel des USDA-ARS Areawide Programms ist es, das Überleben der Völker und die Verfügbarkeit für Bestäubung zu erhöhen. Der CAP-Ansatz geht davon aus, dass die Bienenabnahme ein Produkt zahlreicher interagierender Faktoren ist: synthetische und organische. Daraus sollen Versuche um die spezifischen Faktoren der Völkerverluste entwickelt werden. Der Technologie- und Wissenstransfer vom Areawide Programm und CAP Programmen wird ein Gruppenaufwand mit Unterstützung des Verbandes der amerikanischen Berufssimker (American Association of Professional Apiculturists: AAPA) sein. Die auffälligste bereits lancierte Partnerschaft ist die Webseite der Gemeinschaft zur Bienengesundheit und Praxis (Bee Health Community of Practice, http://www.extension. org/bee_health). Es ist eine Kollaboration zwischen dem Areawide Programm und allen oben genannten Programmen. Beide Projekte, Areawide und CAP werden daran arbeiten, die Gesundheit der Bienenvölker zu verbessern und wissenschaftlich fundierte Lösungen anzubieten um die Bienenhaltung und das Überleben der Bienen zu verbessern.

Encuesta nacional sobre la pérdida anual de colmenas de abejas manejadas durante 2014–2015 en los EEUU

Declines of pollinators and high mortality rates of honey bee colonies are a major concern, both in the USA and globally. Long-term data on summer, winter, and annual colony losses improve our understanding of forces shaping the viability of the pollination industry. Since the mass die-offs of colonies in the USA during the winter of 2006–2007, generally termed “Colony Collapse Disorder” (CCD), annual colony loss surveys have been conducted. These surveys gage colony losses among beekeepers of all operation sizes, recruited to participate via regional beekeeping organizations, phone calls, and postal mail. In the last three years, these surveys include summer and annual losses in addition to winter losses. Winter losses in this most recent survey include 5,937 valid participants (5,690 backyard, 169 sideline, and 78 commercial beekeepers), collectively managing 414,267 colonies on 1 October 2014 and constituting 15.1% of the estimated 2.74 million managed colonies in the USA. Annual losses are typically higher than either winter or summer losses, as they calculate losses over the entire year. Total reported losses were 25.3% [95% CI 24.7–25.9%] over the summer, 22.3% [95% CI 21.9–22.8%] over the winter, and 40.6% [95% CI 40.0–41.2%] for the entire 2014–2015 beekeeping year. Average losses were 14.7% [95% CI 14.0–15.3%] over the summer, 43.7% [95% CI 42.8–44.6%] over the winter, and 49.0% [95% CI 48.1–50.0%] over the entire year. While total winter losses were lower in 2014–2015 than in previous years, summer losses remained high, resulting in total annual colony losses of more than 40% during the survey period. This was the first year that total losses were higher in the summer than in the winter, explained in large part by commercial beekeepers reporting losses of 26.2% of their managed colonies during summer, compared to 20.5% during winter. Self-identified causes of overwintering mortality differed by operation size, with smaller backyard beekeepers generally indicating colony management issues (e.g., starvation, weak colony in the fall), in contrast to commercial beekeepers who typically emphasize parasites or factors outside their control (e.g., varroa, nosema, queen failure). More than two-thirds of all beekeepers (67.3%) had higher colony losses than they deemed acceptable.

Israeli acute paralysis virus: epidemiology, pathogenesis and implications for honey bee health

Israeli acute paralysis virus (IAPV) is a widespread RNA virus of honey bees that has been linked with colony losses. Here we describe the transmission, prevalence, and genetic traits of this virus, along with host transcriptional responses to infections. Further, we present RNAi-based strategies for limiting an important mechanism used by IAPV to subvert host defenses. Our study shows that IAPV is established as a persistent infection in honey bee populations, likely enabled by both horizontal and vertical transmission pathways. The phenotypic differences in pathology among different strains of IAPV found globally may be due to high levels of standing genetic variation. Microarray profiles of host responses to IAPV infection revealed that mitochondrial function is the most significantly affected biological process, suggesting that viral infection causes significant disturbance in energy-related host processes. The expression of genes involved in immune pathways in adult bees indicates that IAPV infection triggers active immune responses. The evidence that silencing an IAPV-encoded putative suppressor of RNAi reduces IAPV replication suggests a functional assignment for a particular genomic region of IAPV and closely related viruses from the Family Dicistroviridae, and indicates a novel therapeutic strategy for limiting multiple honey bee viruses simultaneously and reducing colony losses due to viral diseases. We believe that the knowledge and insights gained from this study will provide a new platform for continuing studies of the IAPV–host interactions and have positive implications for disease management that will lead to mitigation of escalating honey bee colony losses worldwide.

Standard methods for pollination research with Apis mellifera

Summary In this chapter we present a synthesis of recommendations for conducting field experiments with honey bees in the context of agricultural pollination. We begin with an overview of methods for determining the mating system requirements of plants and the efficacy of specific pollinators. We describe methods for evaluating the pollen-vectoring capacity of bees at the level of individuals or colonies and follow with methods for determining optimum colony field stocking densities. We include sections for determining post-harvest effects of pollination, the effects of colony management (including glasshouse enclosure) on bee pollination performance, and a brief section on considerations about pesticides and their impact on pollinator performance. A final section gives guidance on determining the economic valuation of honey bee colony inputs at the scale of the farm or region.

Effects of delayed acaricide treatment in honey bee colonies parasitized by Varroa jacobsoni and a late-season treatment threshold for the south-eastern USA

SUMMARYWe set up 72 colonies of honey bees (Apis mellifera) in the piedmont region of Georgia and South Carolina, USA (2 states × 6 apiaries per state × 6 colonies per apiary) in April 1995. Colonies were individually housed in single-chamber Langstroth hive bodies and one honey super, started with standard mail-order 0.9 kg (2lb) packages of bees containing small incipient populations of the parasitic mite Varroa jacobsoni, and managed optimally as for honey production. Within each state, each apiary was assigned one of the following treatments: (1) treatment with Apistan acaricide in June, (2) treatment in August, (3) treatment in October, or (4) no treatment By December, colony bee populations were optimum in August-treated apiaries. Month of treatment did not affect bee body weight. There were treatment by state interactions for number of sealed brood cells, colony mite populations, and percentage of brood cells with disease-like symptoms. Our data suggest that late-season acaricide treatments in firs...

Integrated pest management against Varroa destructor reduces colony mite levels and delays treatment threshold

SUMMARY Two independent, long-term (17 months and 87 weeks) studies were done to appraise the effects of published integrated pest management (IPM) practices on colony varroa mite levels, length of time before onset of treatment threshold, and other measures of colony productivity. Screen hive floors tended to reduce colony mite levels (24-h sticky sheet counts), sometimes significantly. Likewise, mite-resistant queens tended to cause a numeric and sometimes significant reduction in mite levels; number of mites on sticky sheets decreased as the percentage expression of hygienic behaviour in a colony increased, and on the majority of sampling episodes the number of mites retrieved on sticky sheets was numerically lower in colonies with queens expressing suppressed mite reproduction (SMR). In six of eight cases when IPM components were found to interact they did so in a manner favourable to mite control. Time until achieving treatment threshold was significantly delayed in colonies with SMR queens (c. 72 weeks) compared to non-selected queens (59). In one experiment, stored honey was significantly reduced in colonies with screens (3.8 frames) compared to solid floors (5.1); likewise, stored pollen was lower in screen colonies (0.9 frames) than on solid floors (1.3). SMR queens tended to have reduced brood production.

Net energetic advantage drives honey bees ( Apis mellifera L) to nectar larceny in Vaccinium ashei Reade

Carpenter bees (Xylocopa spp.) act as primary nectar thieves in rabbiteye blueberry (Vaccinium ashei Reade), piercing corollas laterally to imbibe nectar at basal nectaries. Honey bees (Apis mellifera L) learn to visit these perforations and thus become secondary nectar thieves. We tested the hypothesis that honey bees make this behavioral switch in response to an energetic advantage realized by nectar-robbing flower visits. Nectar volume and sugar quantity were higher in intact than perforated flowers, but bees (robbers) visiting perforated flowers were able to extract a higher percentage of available nectar and sugar so that absolute amount of sugar (mg) removed by one bee visit is the same for each flower type. However, because perforated flowers facilitate higher rates of bee flower visitation and the same or higher rates of nectar ingestion, they are rendered more profitable than intact flowers in temporal terms. Accordingly, net energy (J) gain per second flower handling time was higher for robbers on most days sampled. We conclude that the majority evidence indicates an energetic advantage for honey bees that engage in secondary nectar thievery in V. ashei.