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Mason bees (Osmia spp.) are efficient fruit tree pollinators that can be encouraged to occupy and breed in artificial nesting material. In sweet cherry orchards, they are occasionally used as an alternative managed pollinator as a replacement for or in addition to honey bees (Apis mellifera). Yet, the lack of practical guidelines on management practices, for example optimal stocking rates, for both mason bee nesting material and honey bees might compromise pollination service provision. In this study, we assessed the relationship between stocking rates (honey bee hives and mason bee nesting material) and the abundance of honey bees and mason bees in 17 sweet cherry (Prunus avium) orchards in Central Germany. We furthermore performed a pollination experiment to explore the interactive effect of mason bees and honey bees on sweet cherry fruit set. In the orchards, both honey bee and mason bee abundance increased with increasing stocking rates of hives or nesting material, respectively. Honey bee abundance increased linearly with stocking rates. In contrast, mason bee abundance asymptoted at 2–3 nesting boxes per ha, beyond which more boxes resulted in little increase in visitation rate. Our pollination experiment demonstrated that orchards were pollen limited, with only 28% of insect‐pollinated flowers setting fruit versus 39% of optimally hand‐pollinated flowers. Honey bees and mason bees enhanced sweet cherry fruit set, but only when both were present and not when either was present alone in an orchard. Our findings demonstrate that offering nesting material for mason bees and employing honey bee hives can enhance bee abundance in sweet cherry orchards. By increasing honey bee abundance in combination with enhanced mason bee abundance, farmers can substantially boost fruit set and potentially sweet cherry yield. To enhance pollination services, farmers should consider the benefits of increasing pollinator biodiversity as an immediate benefit to improve crop yields. [ABSTRACT FROM AUTHOR]

Urbanization is a global phenomenon that can affect fitness and could challenge the persistence of most species, including wild bee pollinators. Yet, how and which environmental features affect bee health and fitness within the urban ecosystem remain unclear.Here, we placed experimental Bombus terrestris colonies in sites spanning from the edge into a city's core to investigate bumble bee parasitism, foraging behaviour, energetic stress, colony growth and reproductive output. In each site, ambient temperature was recorded, the availability of floral resources was evaluated and landscape heterogeneity was characterized using land‐cover maps.We found that Bombus terrestris parasitism levels increased across the season in line with colony growth but were negatively related to the proportion of impervious surfaces surrounding a site. Bombus terrestris foraging trip duration decreased with increasing ecotones (edge density) but, conversely, increased in sites with honey bee hives present. Energetic stress was evaluated as lowered trehalose titre in the haemolymph of returning foragers; stress increased with the proportion of impervious surfaces. Furthermore, our analyses identified ambient temperature to be a strong predictor of Bombus terrestris colony performance in that high ambient temperature reduced colony growth and indirectly the production of sexual offspring (gynes).Our results highlight the importance of ecotones as well as minimizing the intensity of urbanization and urban honey bee beekeeping for bumble bee colony health and foraging behaviour. They also point to the importance of microclimate (i.e. temperature) for bumble bee colony performance and suggest that increasing temperatures could have a negative impact in slowing colony weight gain, and indirectly in reducing colony reproduction. [ABSTRACT FROM AUTHOR]

The essential ecosystem service of pollination is provided largely by insects, which are considered threatened by diverse biotic and abiotic global change pressures. RNA viruses are one such pressure, and have risen in prominence as a major threat for honey bees ( Apis mellifera ) and global apiculture, as well as a risk factor for other bee species through pathogen spill-over between managed honey bees and sympatric wild pollinator communities. Yet despite their potential role in global bee decline, the prevalence of honey bee-associated RNA viruses in wild bees is poorly known from both geographic and taxonomic perspectives. We screened members of pollinator communities (honey bees, bumble bees and other wild bees belonging to four families) collected from apple orchards in Georgia, Germany and Kyrgyzstan for six common honey bee-associated RNA virus complexes encompassing nine virus targets. The Deformed wing virus complex (DWV genotypes A and B) had the highest prevalence across all localities and host species and was the only virus complex found in wild bee species belonging to all four studied families. Based on amplification of negative-strand viral RNA, we found evidence for viral replication in wild bee species of DWV-A/DWV-B (hosts: Andrena haemorrhoa and several Bombus spp.) and Black queen cell virus (hosts: Anthophora plumipes, several Bombus spp. , Osmia bicornis and Xylocopa spp.). Viral amplicon sequences revealed that DWV-A and DWV-B are regionally distinct but identical in two or more bee species at any one site, suggesting virus is shared amongst sympatric bee taxa. This study demonstrates that honey bee associated RNA viruses are geographically and taxonomically widespread, likely infective in wild bee species, and shared across bee taxa. [ABSTRACT FROM AUTHOR]

Declining populations of bee pollinators are a cause of concern, with major repercussions for biodiversity loss and food security. RNA viruses associated with honeybees represent a potential threat to other insect pollinators, but the extent of this threat is poorly understood., This study aims to attain a detailed understanding of the current and ongoing risk of emerging infectious disease ( EID) transmission between managed and wild pollinator species across a wide range of RNA viruses., Within a structured large-scale national survey across 26 independent sites, we quantify the prevalence and pathogen loads of multiple RNA viruses in co-occurring managed honeybee ( Apis mellifera) and wild bumblebee ( Bombus spp.) populations. We then construct models that compare virus prevalence between wild and managed pollinators., Multiple RNA viruses associated with honeybees are widespread in sympatric wild bumblebee populations. Virus prevalence in honeybees is a significant predictor of virus prevalence in bumblebees, but we remain cautious in speculating over the principle direction of pathogen transmission. We demonstrate species-specific differences in prevalence, indicating significant variation in disease susceptibility or tolerance. Pathogen loads within individual bumblebees may be high and in the case of at least one RNA virus, prevalence is higher in wild bumblebees than in managed honeybee populations., Our findings indicate widespread transmission of RNA viruses between managed and wild bee pollinators, pointing to an interconnected network of potential disease pressures within and among pollinator species. In the context of the biodiversity crisis, our study emphasizes the importance of targeting a wide range of pathogens and defining host associations when considering potential drivers of population decline. [ABSTRACT FROM AUTHOR]

[Display omitted] • Apple orchards were pollen limited. • Honey bees were attracted from apple orchards to co-blooming oilseed rape (OSR). • Wild bee numbers in apple orchards increased with more OSR in the landscape. • No effect of OSR or decreasing honey bee numbers on apple fruit or seed set. • Wild bees might compensate the loss of honey bees. Over the past two decades, the cultivated area of oilseed rape (Brassica napus L. or OSR), a mass-flowering crop, has markedly increased in Europe in response to bioenergy demands. As well as representing a major shift in floral composition across the landscape, mass-flowering OSR may alter pollination services to other simultaneously blooming crops, either decreasing pollination via competition for pollinators or facilitating it via pollinator spill-over. Apple (Malus domestica Borkh.) is an economically important, obligately insect-pollinated fruit crop that co-flowers with OSR. Using twelve independent apple orchards varying in the percentage of OSR in the surrounding landscape, we investigated the effect of OSR on pollinators and pollination of co-blooming apple. We collected bees with pan traps and quantified flower visitors during transect walks in both crops and we experimentally measured pollination service provision to apple as fruit and seed set. We confirm that apples are highly dependent on animal pollination and report pollination limitation in our apple orchards. Honey bees were the numerically dominant visitors of apple flowers observed during transect walks. Though their numbers dropped with an increasing percentage of OSR in the landscape, the number of bumble bees visiting apple flowers remained stable and those of other wild bees rose. The pan trapped Shannon diversity of bees remained constant. We could not detect an effect of OSR in the landscape on apple fruit set or seed set, both of which remained stable. Local wild bee populations might compensate for the loss of honey bees in the provision of pollination services in apple, providing especially effective pollination. Our results underscore not only the dominant role of bees in apple pollination but also the importance of wild bee conservation for providing pollination insurance and stability of apple crop yields under changing agricultural policies and cropping practices. [ABSTRACT FROM AUTHOR]

Nosema ceranae is a widespread obligate intracellular parasite of the ventriculus of many species of honey bee (Apis), including the Western honey bee Apis mellifera, in which it may lead to colony death. It can be controlled in A. mellifera by feeding the antibiotic fumagillin to a colony, though this product is toxic to humans and its use has now been banned in many countries, so in beekeeping, there exists a need for alternative and safe products effective against N. ceranae. Honeybees produce propolis from resinous substances collected from plants and use it to protect their nest from parasites and pathogens; propolis is thought to decrease the microbial load of the hive. We hypothesized that propolis might also reduce N. ceranae infection of individual bees and that they might consume propolis as a form of self-medication. To test these hypotheses, we evaluated the effects of an ethanolic extract of propolis administered orally on the longevity and spore load of experimentally N. ceranae-infected worker bees and also tested whether infected bees were more attracted to, and consumed a greater proportion of, a diet containing propolis in comparison to uninfected bees. Propolis extracts and ethanol (solvent control) increased the lifespan of N. ceranae-infected bees, but only propolis extract significantly reduced spore load. Our propolis extract primarily contained derivatives of caffeic acid, ferulic acid, ellagic acid and quercetin. Choice, scan sampling and food consumption tests did not reveal any preference of N. ceranae-infected bees for commercial candy containing propolis. Our research supports the hypothesis that propolis represents an effective and safe product to control N. ceranae but worker bees seem not to use it to self-medicate when infected with this pathogen. [ABSTRACT FROM AUTHOR]

Deformed wing virus (DWV) is an emerging infectious disease of the honey bee (Apis mellifera) that is considered a major cause of elevated losses of honey bee colonies. DWV comprises two widespread genotypes: the originally described genotype A, and genotype B. In adult honey bees, DWV-B has been shown to be more virulent than DWV-A. However, their comparative effects on earlier host developmental stages are unknown. Here, we experimentally inoculated honey bee pupae and tested for the relative impact of DWV-A versus DWV-B on mortality and wing deformities in eclosing adults. DWV-A and DWV-B caused similar, and only slightly elevated, pupal mortality (mean 18% greater mortality than control). Both genotypes caused similarly high wing deformities in eclosing adults (mean 60% greater wing deformities than control). Viral titer was high in all of the experimentally inoculated eclosing adults, and was independent of wing deformities, suggesting that the phenotype 'deformed wings' is not directly related to viral titer or viral genotype. These viral traits favor the emergence of both genotypes of DWV by not limiting the reproduction of its vector, the ectoparasitic Varroa destructor mite, in infected pupae, and thereby facilitating the spread of DWV in honey bees infested by the mite. [ABSTRACT FROM AUTHOR]

Pathogen spillover is a major threat to biodiversity. Insect pollinators, important providers of the ecosystem service of pollination that are in global decline, are no exception to this threat, with mounting evidence of pathogen spillover from managed into wild bee species in temperate regions. The phenomenon is likely global in scope, though poorly documented, and its consequences for recipient species are largely unknown. To address these knowledge gaps, we investigated viral spillover in the neotropics from the honey bee (Apis mellifera), where it is a managed and invasive species, into native stingless bees, a biodiverse taxon of pollinators. We furthermore exposed stingless bees to honey bee viruses to test for their impact on host survival. High viral prevalence in honey bees and low prevalence of identical viral haplotypes in stingless bees supports ongoing spillover from managed to native species. The survival of native stingless bees was reduced when inoculated with virus by feeding, a plausible route of natural infection. We conclude that viral spillover from managed to wild insect pollinators is likely a global phenomenon and poses a serious threat worldwide to native insect species. If negative impacts are detected in the field, conservation management needs to be developed to reduce spillover, including better control of pathogens in managed species and legislation on their movement. [ABSTRACT FROM AUTHOR]