Sublethal neonicotinoid insecticide exposure reduces solitary bee reproductive success

1.Pollinating insects provide crucial and economically important ecosystem services to crops and wild plants, but pollinators, particularly bees, are globally declining as a result of various driving factors, including the prevalent use of pesticides for crop protection. Sublethal pesticide exposure negatively impacts numerous pollinator life-history traits, but its influence on reproductive success remains largely unknown. Such information is pivotal, however, to our understanding of the long-term effects on population dynamics. 2.We investigated the influence of field-realistic trace residues of the routinely used neonicotinoid insecticides thiamethoxam and clothianidin in nectar substitutes on the entire life-time fitness performance of the red mason bee Osmia bicornis. 3.We show that chronic, dietary neonicotinoid exposure has severe detrimental effects on solitary bee reproductive output. Neonicotinoids did not affect adult bee mortality; however, monitoring of fully controlled experimental populations revealed that sublethal exposure resulted in almost 50% reduced total offspring production and a significantly male-biased offspring sex ratio. 4.Our data add to the accumulating evidence indicating that sublethal neonicotinoid effects on non-Apis pollinators are expressed most strongly in a rather complex, fitness-related context. Consequently, to fully mitigate long-term impacts on pollinator population dynamics, present pesticide risk assessments need to be expanded to include whole life-cycle fitness estimates, as demonstrated in the present study using O. bicornis as a model.

Wild pollinators enhance fruit set of crops regardless of honey bee abundance.

The diversity and abundance of wild insect pollinators have declined in many agricultural landscapes. Whether such declines reduce crop yields, or are mitigated by managed pollinators such as honey bees, is unclear. We found universally positive associations of fruit set with flower visitation by wild insects in 41 crop systems worldwide. In contrast, fruit set increased significantly with flower visitation by honey bees in only 14% of the systems surveyed. Overall, wild insects pollinated crops more effectively; an increase in wild insect visitation enhanced fruit set by twice as much as an equivalent increase in honey bee visitation. Visitation by wild insects and honey bees promoted fruit set independently, so pollination by managed honey bees supplemented, rather than substituted for, pollination by wild insects. Our results suggest that new practices for integrated management of both honey bees and diverse wild insect assemblages will enhance global crop yields.

Evaluation of Cage Designs and Feeding Regimes for Honey Bee (Hymenoptera: Apidae) Laboratory Experiments

The aim of this study was to improve cage systems for maintaining adult honey bee (Apis mellifera L.) workers under in vitro laboratory conditions. To achieve this goal, we experimentally evaluated the impact of different cages, developed by scientists of the international research network COLOSS (Prevention of honey bee COlony LOSSes), on the physiology and survival of honey bees. We identified three cages that promoted good survival of honey bees. The bees from cages that exhibited greater survival had relatively lower titers of deformed wing virus, suggesting that deformed wing virus is a significant marker reflecting stress level and health status of the host. We also determined that a leak- and drip-proof feeder was an integral part of a cage system and a feeder modified from a 20-ml plastic syringe displayed the best result in providing steady food supply to bees. Finally, we also demonstrated that the addition of protein to the bees' diet could significantly increase the level ofvitellogenin gene expression and improve bees' survival. This international collaborative study represents a critical step toward improvement of cage designs and feeding regimes for honey bee laboratory experiments.

Honey Bee Apis mellifera Parasites in the Absence of Nosema ceranae Fungi and Varroa destructor Mites

Few areas of the world have western honey bee (Apis mellifera) colonies that are free of invasive parasites Nosema ceranae (fungi) and Varroa destructor (mites). Particularly detrimental is V. destructor; in addition to feeding on host haemolymph, these mites are important vectors of several viruses that are further implicated as contributors to honey bee mortality around the world. Thus, the biogeography and attendant consequences of viral communities in the absence of V. destructor are of significant interest. The island of Newfoundland, Province of Newfoundland and Labrador, Canada, is free of V. destructor; the absence of N. ceranae has not been confirmed. Of 55 Newfoundland colonies inspected visually for their strength and six signs of disease, only K-wing had prevalence above 5% (40/55 colonies = 72.7%). Similar to an earlier study, screenings again confirmed the absence of V. destructor, small hive beetles Aethina tumida (Murray), tracheal mites Acarapis woodi (Rennie), and Tropilaelaps spp. ectoparasitic mites. Of a subset of 23 colonies screened molecularly for viruses, none had Israeli acute paralysis virus, Kashmir bee virus, or sacbrood virus. Sixteen of 23 colonies (70.0%) were positive for black queen cell virus, and 21 (91.3%) had some evidence for deformed wing virus. No N. ceranae was detected in molecular screens of 55 colonies, although it is possible extremely low intensity infections exist; the more familiar N. apis was found in 53 colonies (96.4%). Under these conditions, K-wing was associated (positively) with colony strength; however, viruses and N. apis were not. Furthermore, black queen cell virus was positively and negatively associated with K-wing and deformed wing virus, respectively. Newfoundland honey bee colonies are thus free of several invasive parasites that plague operations in other parts of the world, and they provide a unique research arena to study independent pathology of the parasites that are present.

Infra-Population and -Community Dynamics of the Parasites Nosema apis and Nosema ceranae, and Consequences for Honey Bee (Apis mellifera) Hosts

Nosema spp. fungal gut parasites are among myriad possible explanations for contemporary increased mortality of western honey bees (Apis mellifera, hereafter honey bee) in many regions of the world. Invasive Nosema ceranae is particularly worrisome because some evidence suggests it has greater virulence than its congener N. apis. N. ceranae appears to have recently switched hosts from Asian honey bees (Apis cerana) and now has a nearly global distribution in honey bees, apparently displacing N. apis. We examined parasite reproduction and effects of N. apis, N. ceranae, and mixed Nosema infections on honey bee hosts in laboratory experiments. Both infection intensity and honey bee mortality were significantly greater for N. ceranae than for N. apis or mixed infections; mixed infection resulted in mortality similar to N. apis parasitism and reduced spore intensity, possibly due to inter-specific competition. This is the first long-term laboratory study to demonstrate lethal consequences of N. apis and N. ceranae and mixed Nosema parasitism in honey bees, and suggests that differences in reproduction and intra-host competition may explain apparent heterogeneous exclusion of the historic parasite by the invasive species

The Honey Bee Pathosphere of Mongolia: European Viruses in Central Asia

Parasites and pathogens are apparent key factors for the detrimental health of managed European honey bee subspecies, Apis mellifera. Apicultural trade is arguably the main factor for the almost global distribution of most honey bee diseases, thereby increasing chances for multiple infestations/infections of regions, apiaries, colonies and even individual bees. This imposes difficulties to evaluate the effects of pathogens in isolation, thereby creating demand to survey remote areas. Here, we conducted the first comprehensive survey for 14 honey bee pathogens in Mongolia (N = 3 regions, N = 9 locations, N = 151 colonies), where honey bee colonies depend on humans to overwinter. In Mongolia, honey bees, Apis spp., are not native and colonies of European A. mellifera subspecies have been introduced ~60 years ago. Despite the high detection power and large sample size across Mongolian regions with beekeeping, the mite Acarapis woodi, the bacteria Melissococcus plutonius and Paenibacillus larvae, the microsporidian Nosema apis, Acute bee paralysis virus, Kashmir bee virus, Israeli acute paralysis virus and Lake Sinai virus strain 2 were not detected, suggesting that they are either very rare or absent. The mite Varroa destructor, Nosema ceranae and four viruses (Sacbrood virus, Black queen cell virus, Deformed wing virus (DWV) and Chronic bee paralysis virus) were found with different prevalence. Despite the positive correlation between the prevalence of V. destructor mites and DWV, some areas had only mites, but not DWV, which is most likely due to the exceptional isolation of apiaries (up to 600 km). Phylogenetic analyses of the detected viruses reveal their clustering and European origin, thereby supporting the role of trade for pathogen spread and the isolation of Mongolia from South-Asian countries. In conclusion, this survey reveals the distinctive honey bee pathosphere of Mongolia, which offers opportunities for exciting future research.

Neonicotinoid insecticides severely affect honey bee queens

Queen health is crucial to colony survival of social bees. Recently, queen failure has been proposed to be a major driver of managed honey bee colony losses, yet few data exist concerning effects of environmental stressors on queens. Here we demonstrate for the first time that exposure to field realistic concentrations of neonicotinoid pesticides during development can severely affect queens of western honey bees (Apis mellifera). In pesticide-exposed queens, reproductive anatomy (ovaries) and physiology (spermathecal-stored sperm quality and quantity), rather than flight behaviour, were compromised and likely corresponded to reduced queen success (alive and producing worker offspring). This study highlights the detriments of neonicotinoids to queens of environmentally and economically important social bees, and further strengthens the need for stringent risk assessments to safeguard biodiversity and ecosystem services that are vulnerable to these substances.

Differential diagnosis of the honey bee trypanosomatids Crithidia mellificae and Lotmaria passim

Trypanosomatids infecting honey bees have been poorly studied with molecular methods until recently. After the description of Crithidia mellificae (Langridge and McGhee, 1967) it took about forty years until molecular data for honey bee trypanosomatids became available and were used to identify and describe a new trypanosomatid species from honey bees, Lotmaria passim (Evans and Schwarz, 2014). However, an easy method to distinguish them without sequencing is not yet available. Research on the related bumble bee parasites Crithidia bombi and Crithidia expoeki revealed a fragment length polymorphism in the internal transcribed spacer 1 (ITS1), which enabled species discrimination. In search of fragment length polymorphisms for differential diagnostics in honey bee trypanosomatids, we studied honey bee trypanosomatid cell cultures of C. mellificae and L. passim. This research resulted in the identification of fragment length polymorphisms in ITS1 and ITS1-2 markers, which enabled us to develop a diagnostic method to differentiate both honey bee trypanosomatid species without the need for sequencing. However, the amplification success of the ITS1 marker depends probably on the trypanosomatid infection level. Further investigation confirmed that L. passim is the dominant species in Belgium, Japan and Switzerland. We found C. mellificae only rarely in Belgian honey bee samples, but not in honey bee samples from other countries. C. mellificae was also detected in mason bees (Osmia bicornis and Osmia cornuta) besides in honey bees. Further, the characterization and comparison of additional markers from L. passim strain SF (published as C. mellificae strain SF) and a Belgian honey bee sample revealed very low divergence in the 18S rRNA, ITS1-2, 28S rRNA and cytochrome b sequences. Nevertheless, a variable stretch was observed in the gp63 virulence factor.

Effects of Nosema apis, N. ceranae, and coinfections on honey bee (Apis mellifera) learning and memory

Western honey bees (Apis mellifera) face an increasing number of challenges that in recent years have led to significant economic effects on apiculture, with attendant consequences for agriculture. Nosemosis is a fungal infection of honey bees caused by either Nosema apis or N. ceranae. The putative greater virulence of N. ceranae has spurred interest in understanding how it differs from N. apis. Little is known of effects of N. apis or N. ceranae on honey bee learning and memory. Following a Pavlovian model that relies on the proboscis extension reflex, we compared acquisition learning and long-term memory recall of uninfected (control) honey bees versus those inoculated with N. apis, N. ceranae, or both. We also tested whether spore intensity was associated with variation in learning and memory. Neither learning nor memory differed among treatments. There was no evidence of a relationship between spore intensity and learning, and only limited evidence of a negative effect on memory; this occurred only in the co-inoculation treatment. Our results suggest that if Nosema spp. are contributing to unusually high colony losses in recent years, the mechanism by which they may affect honey bees is probably not related to effects on learning or memory, at least as assessed by the proboscis extension reflex.

Effects, but no interactions, of ubiquitous pesticide and parasite stressors on honey bee (Apis mellifera) lifespan and behaviour in a colony environment

Interactions between pesticides and parasites are believed to be responsible for increased mortality of honey bee (Apis mellifera) colonies in the northern hemisphere. Previous efforts have employed experimental approaches using small groups under laboratory conditions to investigate influence of these stressors on honey bee physiology and behaviour, although both the colony level and field conditions play a key role for eusocial honey bees. Here, we challenged honey bee workers under in vivo colony conditions with sublethal doses of the neonicotinoid thiacloprid, the miticide tau-fluvalinate and the endoparasite Nosema ceranae, to investigate potential effects on longevity and behaviour using observation hives. In contrast to previous laboratory studies, our results do not suggest interactions among stressors, but rather lone effects of pesticides and the parasite on mortality and behaviour, respectively. These effects appear to be weak due to different outcomes at the two study sites, thereby suggesting that the role of thiacloprid, tau-fluvalinate and N. ceranae and interactions among them may have been overemphasized. In the future, investigations into the effects of honey bee stressors should prioritize the use of colonies maintained under a variety of environmental conditions in order to obtain more biologically relevant data.

Quo vadis Aethina tumida? Biology and control of small hive beetles

Small hive beetles (SHBs) are generalists native to sub-Saharan Africa and reproduce in association with honeybees, bumblebees, stingless bees, fruits and meat. The SHB has recently become an invasive species, and introductions have been recorded from America, Australia, Europe and Asia since 1996. hile SHBs are usually considered a minor pest in Africa, they can cause significant damage to social bee colonies in their new ranges. Potential reasons for differential impact include differences in bee behaviour, climate and release from natural enemies. Here, we provide an overview on biology, distribution, pest status, diagnosis, control and prevention to foster adequate mitigation and stimulate future research. SHBs have become a global threat to both apiculture and wild bee populations, but our knowledge of this pest is still limited, reating demand for more research in all areas of its biology.

The ectoparasitic mite Tropilaelaps mercedesae reduces western honey bee, Apis mellifera, longevity and emergence weight, and promotes Deformed wing virus infections

Historically an ectoparasite of the native Giant honey bee Apis dorsata, the mite Tropilaelaps mercedesae has switched hosts to the introduced western honey bee Apis mellifera throughout much of Asia. Few data regarding lethal and sub-lethal effects of T. mercedesae on A. mellifera exist, despite its similarity to the devastating mite Varroa destructor. Here we artificially infested worker brood of A. mellifera with T. mercedesae to investigate lethal (longevity) and sub-lethal (emergence weight, Deformed wing virus (DWV) levels and clinical symptoms of DWV) effects of the mite on its new host. The data show that T. mercedesae infestation significantly reduced host longevity and emergence weight, and promoted both DWV levels and associated clinical symptoms. Our results suggest that T. mercedesae is a potentially important parasite to the economically important A. mellifera honey bee.

Susceptibility of Aethina tumida (Coleoptera: Nitidulidae) Larvae and Pupae to Entomopathogenic Nematodes

In this study, we evaluated the potential use of entomopathogenic nematodes as a control for the beetle Aethina tumida Murray (Coleoptera: Nitidulidae). In particular, we conducted 1) four screening bioassays to determine nematode (seven species, 10 total strains tested) and application level effects on A. tumida larvae and pupae, 2) a generational persistence bioassay to determine whether single inoculations with nematodes would control multiple generations of A. tumida larvae in treated soil, and 3) a field bioassay to determine whether the nematodes would remain efficacious in the field. In the screening bioassays, nematode efficacy varied significantly by tested nematode and the infective juvenile (IJ) level at which they were applied. Although nematode virulence was moderate in screening bioassays 1-3 (0 - 68% A. tumida mortality), A. tumida mortality approached higher levels in screening bioassay 4 (nearly 100% after 39 d) that suggest suitable applicability of some of the test nematodes as field controls for A. tumida. In the generational persistence bioassay, Steinernema Hobrave Cabanillas, Poinar & Raulston 7-12 strain and Heterorhabditis indica Poinar, Karunaka & David provided adequate A. tumida control for 19 wk after a single soil inoculation (76-94% mortality in A. tumida pupae). In the field bioassay, the same two nematode species also showed high virulence toward pupating A. tumida (88-100%) mortality. Our data suggest that nematode use may be an integral component of an integrated pest management scheme aimed at reducing A. tumida populations in bee colonies to tolerable levels.

Worldwide Diaspora of Aethina tumida (Coleoptera: Nitidulidae), a Nest Parasite of Honey Bees

Native to sub-Saharan Africa, Aethina tumida Murray (Coleoptera: Nitidulidae) is now an invasive pest of honey bee, Apis mellifera L., colonies in Australia and North America. Knowledge about the introduction (s) of this beetle from Africa into and among the current ranges will elucidate pest populations and invasion pathways and contribute to knowledge of how a parasite expands in new populations. We examined genetic variation in adult beetle samples from the United States, Australia, Canada, and Africa by sequencing a 912-base pair region of the mitochondrial DNA cytochrome c oxidase subunit I gene and screening 10 informative microsatellite loci. One Canadian introduction of small hive beetles can be traced to Australia, whereas the second introduction seems to have come from the United States. Beetles now resident in Australia were of a different African origin than were beetles in North America. North American beetles did not show covariance between two mitochondrial haplotypes and their microsatellite frequencies, suggesting that these beetles have a shared source despite having initial genetic structure within their introduced range. Excellent dispersal of beetles, aided in some cases by migratory beekeeping and the bee trade, seems to lead to panmixis in the introduced populations as well as in Africa.