Environmentally acquired gut-associated bacteria are not critical for growth and survival in a solitary bee, Megachile rotundata.

Social bees have been extensively studied for their gut microbial functions, but the significance of the gut microbiota in solitary bees remains less explored. Solitary bee, Megachile rotundata females provision their offspring with pollen from various plant species, harboring a diverse microbial community that colonizes larvae guts. The Apilactobacillus is the most abundant microbe, but evidence concerning the effects of Apilactobacillus and other provision microbes on growth and survival are lacking. We hypothesized that the presence of Apilactobacillus in abundance would enhance larval and prepupal development, weight, and survival, while the absence of intact microbial communities was expected to have a negative impact on bee fitness. We reared larvae on pollen provisions with naturally collected microbial communities (Natural pollen) or devoid of microbial communities (Sterile pollen). We also assessed the impact of introducing Apilactobacillus micheneri by adding it to both types of pollen provisions. Feeding larvae with sterile pollen + A. micheneri led to the highest mortality rate, followed by natural pollen + A. micheneri, and sterile pollen. Larval development was significantly delayed in groups fed with sterile pollen. Interestingly, larval and prepupal weights did not significantly differ across treatments compared to natural pollen-fed larvae. 16S rRNA gene sequencing found a dominance of Sodalis, when A. micheneri was introduced to natural pollen. The presence of Sodalis with abundant A. micheneri suggests potential crosstalk between both, shaping bee nutrition and health. Hence, this study highlights that the reliance on nonhost-specific environmental bacteria may not impact fitness of M. rotundata.IMPORTANCEThis study investigates the impact of environmentally acquired gut microbes of solitary bee fitness with insights into the microbial ecology of bee and their health. While the symbiotic microbiome is well-studied in social bees, the role of environmental acquired microbiota in solitary bees remains unclear. Assessing this relationship in a solitary pollinator, the leaf-cutting bee, Megachile rotundata, we discovered that this bee species does not depend on the diverse environmental bacteria found in pollen for either its larval growth or survival. Surprisingly, high concentrations of the most abundant pollen bacteria, Apilactobacillus micheneri did not consistently benefit bee fitness, but caused larval mortality. Our findings also suggest an interaction between Apilactobacillus and the Sodalis and perhaps their role in bee nutrition. Hence, this study provides significant insights that contribute to understanding the fitness, conservation, and pollination ecology of other solitary bee species in the future.

Larval Exposure to Parasitic Varroa destructor Mites Triggers Specific Immune Responses in Different Honey Bee Castes and Species.

Innate immune systems are key defenses of animals and particularly important in species that lack the sophisticated adaptive immune systems as found in vertebrates. Here, we were interested to quantify variation in innate immune responses of insects in hosts that differ in their parasite susceptibility. To do this, we studied immune responses in honey bees, which can host a remarkable number of different parasites, which are major contributors of declining bee health and colony losses. The most significant parasite of honey bees is the mite Varroa destructor, which has infested the majority of global honey bee populations, and its control remains a major challenge for beekeepers. However, a number of nonmanaged honey bees seem able to control Varroa infections, for example, the Eastern honey bee Apis ceranacerana or the African honey bee Apis mellifera scutellata. These bees therefore make interesting study subjects to identify underlaying resistance traits, for example, by comparing them to more susceptible bee genotypes such as Western honey bees (A. melliferaligustica). We conducted a series of interlinked experiments and started with behavioral assays to compare the attractiveness of bee larvae to mites using different honey bee genotypes and castes. We found that 6-day-old larvae are always most attractive to mites, independently of genotype or castes. In a next step, we compared volatile profiles of the most attractive larvae to test whether they could be used by mites for host selection. We found that the abundance of volatile compounds differed between larval ages, but we also found significant differences between genotypes and castes. To further study the expected underlaying physiological differences between potentially resistant and susceptible host larvae, we compared the larval hemolymph proteomes of the three honey bee genotypes and two castes in response to mite exposure. We identified consistent upregulation of immune and stress-related genes in Varroa-exposed larvae, which differed between genotypes and castes. Tolerant honey bee castes and genotypes were characterized by stronger or more distinct immune esponses. In summary, we provide first insights into the complex involvement of the innate immune system of tolerant honey bees against mite infestations, which could be used for future breeding purposes.

Long-term monitoring of Paenibacillus larvae, causative agent of American Foulbrood, in Uruguay.

Paenibacillus larvae is the causative agent of American Foulbrood (AFB), the most severe bacterial disease affecting honey bee (Apis mellifera) larvae. It was first reported in Uruguay in 1999. Here, we summarize the monitoring strategy carried out from 2001 to date, based on nationwide surveys sampling honey from colonies (2001/2002, 2011, 2021) or from honey storage tanks (2014-2019). We also discuss the actions carried out for the prevention of AFB outbreaks. Uruguay's experience in managing AFB for nearly 25 years without antibiotic use, might provide some helpful ideas for other countries working on AFB control programs.

Inactivation of Nosema spp. with zinc phthalocyanine.

Most honey bee pathogens, such as Vairimorpha (Nosema), cannot be rapidly and definitively diagnosed in a natural setting, consequently there is typically the spread of these diseases through shared and re-use of beekeeping equipment. Furthermore, there are no viable treatment options available for Nosema spores to aid in managing the spread of this bee disease. We therefore aimed to develop a new method using novel Zinc Phthalocyanine (ZnPc) as a photosensitizer for the photodynamic inactivation of Nosema spores that could be used for the decontamination of beekeeping equipment. Nosema spores were propagated for in vitro testing using four caged Apis mellifera honey bees. The ZnPc treatment was characterized, encapsulated with a liposome, and then used as either a 10 or 100 µM treatment for the freshly harvested Nosema spores, for either a 30 and or 60-minute time period, under either light or dark conditions, in-vitro, in 96-well plates. In the dark treatment, after 30-min, the ZnPc 100 µM treatment, caused a 30 % Nosema mortality, while this increased to 80 % at the same concentration after the light treatment. The high rate of anti-spore effects, in a short period of time, supports the notion that this could be an effective treatment for managing honey bee Nosema infections in the future. Our results also suggest that the photo activation of the treatment could be applied in the field setting and this would increase the sterilization of beekeeping equipment against Nosema.

Volatile Organic Compounds from Offspring of Stingless Bee Sacrificed in Hygienic Behavior Test.

This study shows the profile of volatile organic compounds (VOCs) from pupae and larvae of Melipona quadrifasciata anthidioides Lepeletier subjected to three death induction techniques for hygienic behavior (HB) studies: freezing in liquid nitrogen (LN2), freezing in a freezer (FRZ) and piercing of offspring with an entomological pin (PIN). The VOCs from larvae and pupae were obtained through headspace solid-phase microextraction and characterized using gas chromatography coupled to mass spectrometry. In addition, an HB test was performed on the colonies. The main classes of VOCs were hydrocarbons, terpenes and alcohols. Multivariate analysis was applied and showed that there was a separation in the compound profiles between the different treatments. The HB test in the colonies showed that 24 hours after the application of the techniques, the bees removed more dead larvae in LN2 treatment (83.5 %), while after 48 hours more larvae were removed in the LN2 and FRZ treatments (92.3 %). When compared to pupae removal, larvae removal was significantly faster in LN2.

Unraveling the Bombus terrestris Hemolymph, an Indicator of the Immune Response to Microbial Infections, through Complementary Mass Spectrometry Approaches.

Pollinators, including Bombus terrestris, are crucial for maintaining biodiversity in ecosystems and for agriculture. Deciphering their immune response under stress conditions is a key issue for protecting these populations. To assess this metric, we analyzed the B. terrestris hemolymph as an indicator of their immune status. Hemolymph analysis was carried out using mass spectrometry, MALDI molecular mass fingerprinting was used for its effectiveness in assessing the immune status, and high-resolution mass spectrometry was used to measure the impact of experimental bacterial infections on the "hemoproteome". By infecting with three different types of bacteria, we observed that B. terrestris reacts in a specific way to bacterial attacks. Indeed, bacteria impact survival and stimulate an immune response in infected individuals, visible through changes in the molecular composition of their hemolymph. The characterization and label-free quantification of proteins involved in specific signaling pathways in bumble bees by bottom-up proteomics revealed differences in protein expression between the non-experimentally infected and the infected bees. Our results highlight the alteration of pathways involved in immune and defense reactions, stress, and energetic metabolism. Lastly, we developed molecular signatures reflecting the health status of B. terrestris to pave the way for diagnosis/prognosis tools in response to environmental stress.

Nutritional stress exacerbates impact of a novel insecticide on solitary bees' behaviour, reproduction and survival.

Pesticide exposure and food stress are major threats to bees, but their potential synergistic impacts under field-realistic conditions remain poorly understood and are not considered in current pesticide risk assessments. We conducted a semi-field experiment to examine the single and interactive effects of the novel insecticide flupyradifurone (FPF) and nutritional stress on fitness proxies in the solitary bee Osmia bicornis. Individually marked bees were released into flight cages with monocultures of buckwheat, wild mustard or purple tansy, which were assigned to an insecticide treatment (FPF or control) in a crossed design. Nutritional stress, which was high in bees foraging on buckwheat, intermediate on wild mustard and low on purple tansy, modulated the impact of insecticide exposure. Within the first day after application of FPF, mortality of bees feeding on buckwheat was 29 times higher compared with control treatments, while mortality of FPF exposed and control bees was similar in the other two plant species. Moreover, we found negative synergistic impacts of FPF and nutritional stress on offspring production, flight activity, flight duration and flower visitation frequency. These results reveal that environmental policies and risk assessment schemes that ignore interactions among anthropogenic stressors will fail to adequately protect bees and the pollination services they provide.

Factors affecting virus prevalence in honey bees in the Pacific-Northwest, USA.

Global efforts to assess honey bee health show viruses are major stressors that undermine colony performance. Identifying factors that affect virus incidence, such as management practices and landscape context, could aid in slowing virus transmission. Here we surveyed viruses in honey bees from 86 sites in the Pacific Northwest, USA, and tested effects of regional bee density, movement associated with commercial pollination, julian date, and hive management on virus prevalence. We also explored patterns of virus co-occurrence and spatial autocorrelation to identify whether local transmission was a primary driver of pathogen distribution. Our surveys found widespread prevalence of Deformed wing virus (DWV), Sacbrood virus (SBV), and Black queen cell virus (BQCV). BQCV and SBV were most prolific in commercial apiaries, while Chronic bee paralysis virus (CPBV) was more common in hobbyist apiaries than commercial apiaries. DWV was most common in urban landscapes and was best predicted by mite prevalence and julian date, while the incidence of both SBV and BQCV were best predicted by regional apiary density. We did not find evidence of additional spatial autocorrelation for any viruses, although high co-occurrence suggests parallel transmission patterns. Our results support the importance of mite management in slowing virus spread and suggest that greater bee density increases transmission. Our study provides support that viruses are widespread in honey bees and connects known mechanisms of virus transmission to the distribution of pathogens observed across the Pacific Northwest.

The World Organisation for Animal Health - current and potential roles in safe international trade of bees and other insects.

The World Organisation for Animal Health (WOAH, founded as OIE) is the recognised intergovernmental standard-setting organisation for animal health and welfare. The WOAH mandate is to support its members in the prevention of the spread of animal diseases of concern, as listed in the Terrestrial Animal Health Code (Terrestrial Code). Once a disease, infection or infestation is listed, national Veterinary Authorities have the obligation regularly to notify WOAH of the presence or absence of the listed disease. In regard to insects, the scope of the Terrestrial Code limits its recommendations to preserving the health of bees (species of the genus Apis, extended to the genus Bombus and to the stingless bees for one disease). However, it does not include standards to mitigate the potential animal health risks associated with the international trade of other insects. A description of the standard-setting process and a review of the history of the standards for bee health highlight the resources and requirements to expand the scope of the Terrestrial Code to include recommendations for animal health risk mitigation measures for the safety of international trade in insects. Any initiative to develop guidance on insect trade should include WOAH in its role as the sole global standard-setting organisation on animal health and welfare matters. This aligns with the WOAH commitment to a One Health approach.

L'Organisation mondiale de la santé animale (OMSA, fondée en tant qu'OIE) est l'organisation inter-gouvernementale reconnue pour l'élaboration de normes relatives à la santé et au bien-être des animaux. L'OMSA a pour mandat d'apporter un soutien à ses Membres afin de prévenir la propagation des maladies animales d'importance majeure listées dans le Code sanitaire pour les animaux terrestres (Code terrestre). Dès lors qu'une maladie, une infection ou une infestation figure sur cette liste, les Autorités vétérinaires ont l'obligation de notifier régulièrement à l'OMSA la présence ou l'absence de cette maladie sur leur territoire. S'agissant des insectes, le champ d'application du Code terrestre limite ses recommandations à la préservation de la santé des abeilles (espèces du genre Apis, avec l'inclusion du genre Bombus et des abeilles sans dard pour une maladie). Néanmoins, le Code terrestre ne contient pas de normes visant à atténuer les risques pour la santé animale associés aux échanges internationaux d'autres insectes. La description faite par les auteurs du processus d'élaboration des normes et leur aperçu rétrospectif de la mise au point des normes relatives à la santé des abeilles font ressortir les ressources et les conditions nécessaires pour élargir le champ d'application du Code terrestre afin d'y inclure des recommandations portant sur les mesures d'atténuation des risques pour la santé animale applicables à la sécurité sanitaire des échanges internationaux d'insectes. Toute initiative visant à fournir des orientations sur les échanges d'insectes devrait inclure l'OMSA dans son rôle d'unique organisation chargée de l'élaboration des normes internationales relatives à la santé animale et au bien-être des animaux. Cette exigence est en cohérence avec l'engagement de l'OMSA en faveur de l'approche Une seule santé.

La Organización Mundial de Sanidad Animal (OMSA, fundada como OIE) es la organización intergubernamental facultada para ejercer funciones normativas en materia de sanidad y bienestar de los animales. La OMSA tiene por mandato ayudar a sus miembros a prevenir la propagación de una serie de enfermedades animales de importancia, recogidas en el Código Sanitario para los Animales Terrestres (Código Terrestre) de la OMSA. La inclusión de una enfermedad, infección o infestación en la lista de la OMSA obliga a las autoridades veterinarias nacionales a dar cuenta periódicamente a la OMSA de la presencia o ausencia de esa patología en su territorio. Por lo que respecta a los insectos, en el Código Terrestre solo se formulan una serie de recomendaciones para proteger la salud de las abejas (categoría que corresponde a las especies del género Apis, extensible también al género Bombus y, en el caso de una enfermedad, a las abejas sin aguijón). El Código Terrestre, sin embargo, no contiene norma alguna destinada a mitigar los posibles riesgos zoosanitarios ligados al comercio internacional de otros insectos. Los autores describen el proceso normativo y repasan la historia de las normas relativas a la sanidad de las abejas, con lo que ponen de relieve los recursos y demás elementos necesarios para conferir mayor alcance al Código Terrestre incluyendo en él recomendaciones sobre medidas de mitigación del riesgo zoosanitario para un comercio seguro de insectos a escala internacional. Toda iniciativa encaminada a marcar pautas sobre el comercio de insectos debería incluir a la OMSA, única organización con potestad normativa mundial sobre temas de sanidad y bienestar de los animales, lo que además se encuadra en el compromiso de la OMSA con los planteamientos de «Una sola salud¼.

Honey Bees and Industrial Agriculture: What Researchers are Missing, and Why it's a Problem.

Industrial agriculture is the root cause of many health problems that honey bees (Apis mellifera Linneaus, 1758) face, but honey bee researchers seldom call attention to this fact. We often discuss the stressors that contribute to colony loss (e.g., pathogens, pesticides, poor nutrition), but we rarely talk about where those stressors come from. This is a problem because we cannot resolve honey bee health issues unless we confront the systems that cause them harm. In this forum article, I unpack the relationship between honey bee health and industrial agriculture. I propose steps we can take to reframe our research to account for the impacts of this destructive system, and I discuss the uncomfortable questions that surface when we engage in this process. The goal of this article is to encourage conversation within the honey bee research community around the impacts of industrial agriculture, so that we can fully engage in the transformative change needed to support honey bee health.

Field-realistic neonicotinoid exposure has sub-lethal effects on non-Apis bees: A meta-analysis.

Neonicotinoid insecticides can have sub-lethal effects on bees which has led to calls from conservationists for a global ban. In contrast, agrochemical companies argue that neonicotinoids do not harm honeybees at field-realistic levels. However, the focus on honeybees neglects the potential impact on other bee species. We conducted a meta-analysis to assess whether field-realistic neonicotinoid exposure has sub-lethal effects on non-Apis bees. We extracted data from 53 papers (212 effects sizes) and found that it largely consisted of two genera: bumblebees (Bombus) and mason bees (Osmia), highlighting a substantial taxonomic knowledge gap. Neonicotinoid exposure negatively affected reproductive output across all bees and impaired bumblebee colony growth and foraging. Neonicotinoids also reduced Bombus, but not Osmia, individual development (growth and body size). Our results suggest that restrictions on neonicotinoids should benefit bee populations and highlight that the current regulatory process does not safeguard pollinators from the unwanted consequences of insecticide use.

Simulated vector transmission differentially influences dynamics of two viral variants of deformed wing virus in honey bees (Apis mellifera).

Understanding how vectors alter the interactions between viruses and their hosts is a fundamental question in virology and disease ecology. In honey bees, transmission of deformed wing virus (DWV) by parasitic Varroa mites has been associated with elevated disease and host mortality, and Varroa transmission has been hypothesized to lead to increased viral titres or select for more virulent variants. Here, we mimicked Varroa transmission by serially passaging a mixed population of two DWV variants, A and B, by injection through in vitro reared honey bee pupae and tracking these viral populations through five passages. The DWV-A and DWV-B variant proportions shifted dynamically through passaging, with DWV-B outcompeting DWV-A after one passage, but levels of both variants becoming equivalent by Passage 5. Sequencing analysis revealed a dominant, recombinant DWV-B strain (DWV-A derived 5' IRES region with the rest of the genome DWV-B), with low nucleotide diversity that decreased through passaging. DWV-A populations had higher nucleotide diversity compared to DWV-B, but this also decreased through passaging. Selection signatures were found across functional regions of the DWV-A and DWV-B genomes, including amino acid mutations in the putative capsid protein region. Simulated vector transmission differentially impacted two closely related viral variants which could influence viral interactions with the host, demonstrating surprising plasticity in vector-host-viral dynamics.

Effects of pollen and nectar inoculation by yeasts, bacteria or both on bumblebee colony development.

It is increasingly recognized that gut microbiota have a major effect on the physiology, biology, ecology and evolution of their animal hosts. Because in social insects, the gut microbiota is acquired through the diet and by contact with nest provisions, it can be hypothesized that regular supplementation of microorganisms to the diet will have an impact on the fitness of the consumer and on the development of the whole colony. To test this hypothesis, we investigated how supplementation of bacteria, yeasts, and combinations of the two to either pollen or nectar affected colony development in the social bumblebee Bombus terrestris. Three yeasts and three bacterial species that live at the flower-insect interface were used in the experiments and the development of bumblebee colonies was monitored over a period of 10 weeks. The results showed that administration of microbes via pollen had a stronger positive impact on colony development than when provided via sugar water. Supplementation of bacteria led, in general, to a faster egg laying, higher brood size and increased production of workers during the first weeks, whereas yeasts or a combination of yeasts and bacteria had less impact on colony development. However, the results differed between microbial species, with Wickerhamiella bombiphila and Rosenbergiella nectarea showing the strongest increase in colony development. Torulaspora delbrueckii induced early male production, which is likely a fitness cost. We conclude that the tested bacteria-yeast consortia did not result in better colony development than the interacting species alone.

Fipronil pesticide as a suspect in historical mass mortalities of honey bees.

Mass mortalities of honey bees occurred in France in the 1990s coincident with the introduction of two agricultural insecticides, imidacloprid and fipronil. Imidacloprid, a neonicotinoid, was widely blamed, but the differential potency of imidacloprid and fipronil has been unclear because of uncertainty over their capacity to bioaccumulate during sustained exposure to trace dietary residues and, thereby, cause time-reinforced toxicity (TRT). We experimentally quantified the toxicity of fipronil and imidacloprid to honey bees and incorporated the observed mortality rates into a demographic simulation of a honey bee colony in an environmentally realistic scenario. Additionally, we evaluated two bioassays from new international guidance for agrochemical regulation, which aim to detect TRT. Finally, we used analytical chemistry (GC-MS) to test for bioaccumulation of fipronil. We found in demographic simulations that only fipronil produced mass mortality in honey bees. In the bioassays, only fipronil caused TRT. GC-MS analysis revealed that virtually all of the fipronil ingested by a honey bee in a single meal was present 6 d later, which suggests that bioaccumulation is the basis of TRT in sustained dietary exposures. We therefore postulate that fipronil, not imidacloprid, caused the mass mortalities of honey bees in France during the 1990s because it is lethal to honey bees in even trace doses due to its capacity to bioaccumulate and generate TRT. Our results provide evidence that recently proposed laboratory bioassays can discriminate harmful bioaccumulative substances and, thereby, address evident shortcomings in a regulatory system that had formerly approved fipronil for agricultural use.

Visual Diagnosis of the Varroa Destructor Parasitic Mite in Honeybees Using Object Detector Techniques.

The Varroa destructor mite is one of the most dangerous Honey Bee (Apis mellifera) parasites worldwide and the bee colonies have to be regularly monitored in order to control its spread. In this paper we present an object detector based method for health state monitoring of bee colonies. This method has the potential for online measurement and processing. In our experiment, we compare the YOLO and SSD object detectors along with the Deep SVDD anomaly detector. Based on the custom dataset with 600 ground-truth images of healthy and infected bees in various scenes, the detectors reached the highest F1 score up to 0.874 in the infected bee detection and up to 0.714 in the detection of the Varroa destructor mite itself. The results demonstrate the potential of this approach, which will be later used in the real-time computer vision based honey bee inspection system. To the best of our knowledge, this study is the first one using object detectors for the Varroa destructor mite detection on a honey bee. We expect that performance of those object detectors will enable us to inspect the health status of the honey bee colonies in real time.

Structural diversity and functional variability of gut microbial communities associated with honey bees.

Microbial consortia accompanied to all eukaryotes can be inherited from ancestors, environment, and/or from various food source. Gut microbiota study is an emerging discipline of biological sciences that expands our understanding of the ecological and functional dynamics of gut environments. Microorganisms associated with honey bees play an important role in food digestion, colony performance, immunity, pollination, antagonistic effect against different pathogens, amelioration of food and many more. Although, many repots about honey bee gut microbiota are well documented, microbiome with other key components of honey bees such as larvae, adults, their food (pollen, beebread, and honey), honey combs, and floral nectar are poorly understood. Mutual interactions and extent of the roles of microbial communities associated with honey bees are still unclear and demand for more research on the nutritional physiology and health benefits of this ecologically and economically important group. Here in this study, we highlighted all the honey bee microbiome that harbored from different life stages and other relevant components. The anatomical parts of honey bee (larvae, adults), food source (pollen, beebread, and honey), honey combs, and floral nectar were highly flourished by numerous microorganisms like bacteria (Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria, Actinobacteria, Actinomycetes, Bacilli, Bacteroidetes, Cocci, Clostridia, Coliforms, Firmicutes, Flavobacteriia, Mollicutes) and fungi (Dothideomycetes, Eurotiomycetes, Mucormycotina, Saccharomycetes, Zygomycetes, Yeasts, Molds). Some distinctive microbial communities of a taxonomically constrained species have coevolved with social bees. This contribution is to enhance the understanding of honey bee gut microbiota, to accelerate bee microbiota and microbiome research in general and to aid design of future experiments in this growing field.

MALDI-MS Profiling to Address Honey Bee Health Status under Bacterial Challenge through Computational Modeling.

Honey bees play a critical role in the maintenance of plant biodiversity and sustainability of food webs. In the past few decades, bees have been subjected to biotic and abiotic threats causing various colony disorders. Therefore, monitoring solutions to help beekeepers to improve bee health are necessary. Matrix-assisted laser desorption ionization-mass spectrometry (MALDI-MS) profiling has emerged within this decade as a powerful tool to identify in routine micro-organisms and is currently used in real-time clinical diagnosis. MALDI BeeTyping is developed to monitor significant hemolymph molecular changes in honey bees upon infection with a series of entomopathogenic Gram-positive and -negative bacteria. A Serratia marcescens strain isolated from one naturally infected honey bee collected from the field is also considered. A series of hemolymph molecular mass fingerprints is individually recorded and to the authors' knowledge, the first computational model harboring a predictive score of 97.92% and made of nine molecular signatures that discriminate and classify the honey bees' systemic response to the bacteria is built. Hence, the model is challenged by classifying a training set of hemolymphs and an overall recognition of 91.93% is obtained. Through this work, a novel, time and cost saving high-throughput strategy that addresses honey bee health on an individual scale is introduced.

Synergistic effects of pathogen and pesticide exposure on honey bee (Apis mellifera) survival and immunity.

Declines in native insect pollinator populations and substantial losses in managed honey bees have been reported on a global scale and become a widespread concern because of the importance of these insects for human food production and ecosystem stability. Several potential factors have been studied as possible causes of declining pollinator health, such as parasites and pathogens, exposure to agricultural pesticides, habitat loss and/or climate change. More recently, a combination of these factors rather than a single cause have been blamed for observed pollinator losses, but field studies of such interactions are challenging, especially in the presence of confounding environmental stressors. We therefore examined the impact of single and combined stressors on the honey bee (Apis mellifera) in a generally healthy Australian population. We exposed workers during their larval development and drones until they reached sexual maturity to the neonicotinoid pesticide Thiamethoxam, at concentrations more than 20 times lower than we initially measured in the field, the microsporidian gut pathogen Nosema apis or both stressors at the same time. We found that simultaneous exposure significantly reduced bee health. We observed a substantial increase in mortality and a reduction of immunocompetence in workers exposed to both the pathogen and the pesticide. We conclude that the exposure of generally healthy bees to multiple environmental stressors results in synergistic effects where the effects are expected to negatively impact performance and could be sufficient to trigger colony collapse. We found that the vast majority of males did not survive to sexual maturity after exposure to very low levels of Thiamethoxam. This would not only reduce the reproductive success of individual colonies, but can also impact gene flow and genetic diversity at the population level, which are both known as key components of honey bee health.

Gamma irradiation inactivates honey bee fungal, microsporidian, and viral pathogens and parasites.

Managed honey bee (Apis mellifera) populations are currently facing unsustainable losses due to a variety of factors. Colonies are challenged with brood pathogens, such as the fungal agent of chalkbrood disease, the microsporidian gut parasite Nosema spp., and several viruses. These pathogens may be transmitted horizontally from worker to worker, vertically from queen to egg and via vectors like the parasitic mite, Varroa destructor. Despite the fact that these pathogens are widespread and often harbored in wax comb that is reused from year to year and transferred across beekeeping operations, few, if any, universal treatments exist for their control. In order to mitigate some of these biological threats to honey bees and to allow for more sustainable reuse of equipment, investigations into techniques for the sterilization of hive equipment and comb are of particular significance. Here, we investigated the potential of gamma irradiation for inactivation of the fungal pathogen Ascosphaera apis, the microsporidian Nosema ceranae and three honey bee viruses (Deformed wing virus [DWV], Black queen cell virus [BQCV], and Chronic bee paralysis virus [CBPV]), focusing on the infectivity of these pathogens post-irradiation. Results indicate that gamma irradiation can effectively inactivate A. apis, N. ceranae, and DWV. Partial inactivation was noted for BQCV and CBPV, but this did not reduce effects on mortality at the tested, relatively high doses. These findings highlight the importance of studying infection rate and symptom development post-treatment and not simply rate or quantity detected. These findings suggest that gamma irradiation may function as a broad treatment to help mitigate colony losses and the spread of pathogens through the exchange of comb across colonies, but raises the question why some viruses appear to be unaffected. These results provide the basis for subsequent studies on benefits of irradiation of used comb for colony health and productivity.

Neonicotinoid pesticides and nutritional stress synergistically reduce survival in honey bees.

The honey bee is a major pollinator whose health is of global concern. Declines in bee health are related to multiple factors, including resource quality and pesticide contamination. Intensive agricultural areas with crop monocultures potentially reduce the quality and quantity of available nutrients and expose bee foragers to pesticides. However, there is, to date, no evidence for synergistic effects between pesticides and nutritional stress in animals. The neonicotinoids clothianidin (CLO) and thiamethoxam (TMX) are common systemic pesticides that are used worldwide and found in nectar and pollen. We therefore tested if nutritional stress (limited access to nectar and access to nectar with low-sugar concentrations) and sublethal, field-realistic acute exposures to two neonicotinoids (CLO and TMX at 1/5 and 1/25 of LD50) could alter bee survival, food consumption and haemolymph sugar levels. Bee survival was synergistically reduced by the combination of poor nutrition and pesticide exposure (-50%). Nutritional and pesticide stressors reduced also food consumption (-48%) and haemolymph levels of glucose (-60%) and trehalose (-27%). Our results provide the first demonstration that field-realistic nutritional stress and pesticide exposure can synergistically interact and cause significant harm to animal survival. These findings have implications for current pesticide risk assessment and pollinator protection.