Bee Populations Research Articles

Exposure of the stingless bee Melipona scutellaris to imidacloprid, pyraclostrobin, and glyphosate, alone and in combination, impair its walking activity and fat body morphology and physiology

The stingless bee Melipona scutellaris performs buzz pollination, effectively pollinating several wild plants and crops with economic relevance. However, most research has focused on honeybees, leaving a significant gap in studies concerning native species, particularly regarding the impacts of pesticide combinations on these pollinators. Thus, this study aimed to evaluate the sublethal effects of imidacloprid (IMD), pyraclostrobin (PYR), and glyphosate (GLY) on the behavior and fat body cell morphology and physiology of M. scutellaris. Foragers were orally exposed to the different pesticides alone and in combination for 48 h. Bees fed with contaminated solution walked less, moved slower, presented morphological changes in the fat body, including vacuolization, altered cell shape and nuclei morphology, and exhibited a higher count of altered oenocytes and trophocytes. In all exposed groups, alone and in combination, the number of cells expressing caspase-3 increased, but the TLR4 number of cells expressing decreased compared to the control groups. The intensity of HSP70 immunolabeling increased compared to the control groups. However, the intensity of the immunolabeling of HSP90 decreased in the IMD, GLY, and I + G (IMD + GLY) groups but increased in I + P-exposed bees (IMD + PYR). Alternatively, exposure to PYR and P + G (PYR + GLY) did not affect the immunolabeling intensity. Our findings demonstrate the hazardous effects and environmental consequences of isolated and combined pesticides on a vital neotropical pollinator. Understanding how pesticides impact the fat body can provide crucial insights into the overall health and survival of native bee populations, which can help develop more environmentally friendly approaches to agricultural practices.

Bees and their interactions with flowering plants in disturbed and semi-natural settings

A knowledge of bee populations is scarce, particularly in sub-Saharan Africa, where human-induced changes appear to have a considerable negative effect on wild bees. The goal of the study was to assess the abundance, diversity, and richness of bees and their interactions (or visitation) with flowering plants in disturbed and semi-natural habitats in Tanzania. Bees were sampled using sweep nets and pan traps whereas bee-plant interaction and floral abundance were visually assessed. We show that semi-natural habitats are crucial places for bees to forage and nest, as their richness, diversity, and species composition were higher than disturbed habitats. The study areas in semi-natural habitats also had a higher number of bee visits compared to the disturbed habitats. The lower number of bees found in disturbed habitats implies that human-caused alterations have a negative impact on foraging resources and bee communities. Furthermore, we recorded more than 400 bee-plant interactions and high floral abundance in semi-natural habitats compared to disturbed habitats. However, in both disturbed and semi-natural habitats, there was a positive relationship between floral abundance and bee abundance. This reveals that floral resources have a significant impact on bee abundance and their visitation. Our findings demonstrate further that, if natural environments are disturbed and floral resources are depleted, bee populations may decline. Therefore, habitat management, whether disturbed or semi-natural, is critical for the survival of bees.

Discovery and characterization of novel DNA viruses in Apis mellifera: expanding the honey bee virome through metagenomic analysis.

To date, many viruses have been discovered to infect honey bees. In this study, we used high-throughput sequencing to expand the known virome of the honey bee, Apis mellifera, by identifying several novel DNA viruses. While the majority of previously identified bee viruses are RNA, our study reveals nine new genomes from the Parvoviridae family, tentatively named Bee densoviruses 1 to 9. In addition, we characterized a large DNA virus, Apis mellifera filamentous-like virus (AmFLV), which shares limited protein identities with the known Apis mellifera filamentous virus. The complete sequence of AmFLV, obtained by a combination of laboratory techniques and bioinformatics, spans 152,678 bp. Linear dsDNA genome encodes for 112 proteins, of which 49 are annotated. Another large virus we discovered is Apis mellifera nudivirus, which belongs to a group of Alphanudivirus. The virus has a length of 129,467 bp and a circular dsDNA genome, and has 106 protein encoding genes. The virus contains most of the core genes of the family Nudiviridae. This research demonstrates the effectiveness of viral binning in identifying viruses in honey bee virology, showcasing its initial application in this field.IMPORTANCEHoney bees contribute significantly to food security by providing pollination services. Understanding the virome of honey bees is crucial for the health and conservation of bee populations and also for the stability of the ecosystems and economies for which they are indispensable. This study unveils previously unknown DNA viruses in the honey bee virome, expanding our knowledge of potential threats to bee health. The use of the viral binning approach we employed in this study offers a promising method to uncovering and understanding the vast viral diversity in these essential pollinators.

The dark European honey bee Apis mellifera mellifera in Lithuania: data on mitotype diversity of native bee population

In Europe, the population of the dark European honey bee Apis mellifera mellifera L. has been significantly affected by the introduction and propagation of non-indigenous subspecies of honey bees. For a long time, the status of the native Lithuanian A. m. mellifera bees was unknown. Thus, the aim of this study was to determine the current distribution of the subspecies population in Lithuania and the diversity of its mitotypes. A total of 598 honey bee colonies from traditionally managed apiaries were studied to determine their maternal ancestry using the COI–COII intergenic spacer sequences of mtDNA. The results revealed that 52% of the maternal lines investigated belonged to A. m. mellifera. They represented 20 unique COI–COII intergenic spacer mitotypes, 11 of which were detected for the first time. We hypothesised that a small proportion of ancestral A lineage mitotypes among the dominant M lineage mitotypes could be the relict of the maternal line.

Local floral abundance influences bumble bee occupancy more than urban‐agricultural landscape context

Abstract Loss of natural habitat due to increases in agricultural extent raises the question of whether human‐dominated landscape types can support biodiversity, particularly for declining insect pollinators. Compared to more rural agricultural landscapes, urban areas may confer benefits for bumble bee populations by providing stable and diverse floral resources. However, disentangling the effects of local‐ and landscape‐scale characteristics on bumble bee populations in human‐modified landscapes is challenging. Here, we assessed bumble bee occupancy using a repeated transect sampling design conducted during the summers of 2019 and 2020 within the metropolitan area of Madison, WI, and the surrounding agricultural landscape. We fit hierarchical occupancy models to estimate the detection (p) and occupancy () probabilities relative to local habitat quality (floral abundance and floral richness) and landscape (agricultural‐urban gradient) features for eight bumble bee species. We hypothesised that bumble bees were more likely to occupy urban areas, serving as refugia, relative to agricultural sites. We found that the detection probability of all bumble bee species was seasonal and influenced by maximum floral abundance at survey sites, independent of the surrounding land cover type. After accounting for species‐specific detection probabilities, the effect of urbanisation on bee occupancy was weak, and no species were less likely to occupy urban than rural agricultural areas. Our findings suggest that bumble bee occupancy is associated with a ‘honeypot effect’ where local resource availability, in the form of higher floral abundance, is most important in limiting the occupancy of bumble bees across urban and agricultural landscapes.

Ecological and social factors influence interspecific pathogens occurrence among bees

The interspecific transmission of pathogens can occur frequently in the environment. Among wild bees, the main spillover cases are caused by pathogens associated with Apis mellifera, whose colonies can act as reservoirs. Due to the limited availability of data in Italy, it is challenging to accurately assess the impact and implications of this phenomenon on the wild bee populations. In this study, a total of 3372 bees were sampled from 11 Italian regions within the BeeNet project, evaluating the prevalence and the abundance of the major honey bee pathogens (DWV, BQCV, ABPV, CBPV, KBV, Nosema ceranae, Ascosphaera apis, Crithidia mellificae, Lotmaria passim, Crithidia bombi). The 68.4% of samples were positive for at least one pathogen. DWV, BQCV, N. ceranae and CBPV showed the highest prevalence and abundance values, confirming them as the most prevalent pathogens spread in the environment. For these pathogens, Andrena, Bombus, Eucera and Seladonia showed the highest mean prevalence and abundance values. Generally, time trends showed a prevalence and abundance decrease from April to July. In order to predict the risk of infection among wild bees, statistical models were developed. A low influence of apiary density on pathogen occurrence was observed, while meteorological conditions and agricultural management showed a greater impact on pathogen persistence in the environment. Social and biological traits of wild bees also contributed to defining a higher risk of infection for bivoltine, communal, mining and oligolectic bees. Out of all the samples tested, 40.5% were co-infected with two or more pathogens. In some cases, individuals were simultaneously infected with up to five different pathogens. It is essential to increase knowledge about the transmission of pathogens among wild bees to understand dynamics, impact and effects on pollinator populations. Implementing concrete plans for the conservation of wild bee species is important to ensure the health of wild and human-managed bees within a One-Health perspective.

Route of exposure to veterinary products in bees: Unraveling pasture's impact on avermectin exposure and tolerance in stingless bees.

Deforestation rapidly increases in tropical regions, primarily driven by converting natural habitats into pastures for extensive cattle ranching. This landscape transformation, coupled with pesticide use, are key drivers of bee population decline. Here, we investigate the impact of pasture-dominated landscapes on colony performance, pesticide exposure, and insecticide sensitivity of the stingless bee Tetragonisca angustula. We monitored 16 colonies located in landscapes with varying proportions of pasture. We collected bee bread for pesticide and palynological analysis. We found a positive correlation between pollen diversity and colony growth, with no effect of the proportion of pasture in the landscape. In contrast, we detected prevalent and hazardous concentrations of the insecticide abamectin (9.6-1,856 µg/kg) in bee bread, which significantly increased with a higher proportion of pasture. Despite the abamectin exposure, the bee colonies displayed no adverse effects on their growth, indicating a potential tolerance response. Further investigations revealed that bees from sites with higher proportions of pasture showed significantly reduced mortality when exposed to a lethal concentration of abamectin (0.021 µg/µL) after 48 h. Since abamectin is scarcely used in the study area, we designed an experiment to track ivermectin, a closely related antiparasitic drug used in cattle. Our findings uncovered a new exposure route of bees to pesticides, wherein ivermectin excreted by cattle is absorbed and biotransformed into abamectin within flowering plants in the pastures. These results highlight that unexplained exposure routes of bees to pesticides remain to be described while also revealing that bees adapt to changing landscapes.

Obtaining morphometric standards of drone wings of separate populations of honey bees (Apis mellifera) in Ukraine

Today, there are no systematic studies on the wing phenotypes of drone populations of the honeybee widespread in Ukraine. Considering that drone genomes are haploid, this allows one to establish the correspondence between the phenotype and the drone genome, thereby roughly determining the queen's genome in the part responsible for the wing phenotype. This partially compensates for the lack of resources among domestic scientists to conduct genetic research on bees. The aim of the study was to examine the wings of drones from several apiaries in the Kharkiv, Sumy, Poltava, and Zhytomyr regions, identify typical phenotypes, and attempt their taxonomic identification. Using discriminant analysis, 4640 drone wings were classified into three clusters. A two-step scheme for forming significantly different phenotype clusters of wings was proposed. Initially, based on the similarity of Euclidean distances and Mahalanobis distances (<2.6) between clusters, three groups were obtained, which, for refinement, underwent a second classification. As a result, average values and confidence intervals of eight morphometric traits were established: Ci, Dbi, Disc.sh, Pci, Ri, Ci.3, Ci.2.1, Ci.2.2 for the three wing groups. It is suggested to accept the trait values of these groups as reference data: one as a local population of the A. m. carnica subspecies, and the other two as regional standards for Ukrainian bees. Based on the obtained standards, a significant presence of A. m. carnica subspecies bees was established in all studied apiaries, except for the apiary with the status of a breeding ground for Ukrainian steppe bees (Kuzemin village, Sumy region), where such presence is minimal. This fact indicates the need for special measures to reproduce and expand the ranges of existence of local populations of Ukrainian steppe bees. The example of creating local and regional morphometric standards provided in this work is specifically designed to address this issue.

Risk assessment of veterinary treatments in bee brood and adult honey bees

Amitraz and tau-fluvalinate are veterinary treatments administered for the control of Varroa destructor in honey bee colonies. These treatments can generate harmful residues for bees. This field study addresses the issue under two scenarios: 1) administration according to the posology and 2) placing contaminated wax containing the treatments. Tau-fluvalinate (Apistan®) residues were detected in larval stages from 25.34 to 84.72 ng g−1 in scenario 1 and from 29.63 to 173.97 ng g−1 in scenario 2. In addition, it was detected in bee bread in scenario 2 from 55.72 to 573.79 ng g−1. In scenario 1, DMPF + DMF (amitraz metabolites) were found from 37.09 to 171.58 ng g−1 (Amicel®) and from 36.74 to 42.64 ng g−1 (Apivar®) in bee bread. In honey, DMPF + DMF ranged from 19.96 to 145.30 ng g−1 (Amicel®) and from 32.20 to 78.43 ng g−1 from (Apivar®). With these treatments, a significant reduction in the population of Varroa mites (mean ± s.d.) was observed between 95.15 ± 2.56% and 98.29 ± 1.97%. There were significant positive correlations between Amicel®, the population of adult bees and the population of brood during evaluation 2 showing a higher effectiveness. According to both RQ (Risk Quotient) and SRA (Standard Risk Approach) values for adult bees and larvae, there is no risk when considering exposure by contact or by ingestion of bee bread or honey. In scenario 2, there is no risk for most of the larval stages, except in two bee hives treated with tau-fluvalinate, where the SRA values were 1.73 and 1.29%, indicating a moderate risk due to acute oral exposure.

How seasonality, semi-natural habitat cover and compositional landscape heterogeneity affect pollen collection and development of Apis mellifera colonies in Mediterranean agro-sylvo-pastoral systems

ContextThe reduction in the abundance and diversity of flowering plant species, mainly due to landscape alteration and consequent habitat loss, negatively affects honey bee populations and is the main driver of their decline. To safeguard pollination service and food security, we need to know how landscape characteristics affect the availability of pollen sources and consequently colony performance across seasons.ObjectivesWe therefore here explore how seasonality, percentage of semi-natural habitat cover and compositional landscape heterogeneity affect the abundance, richness, diversity and composition of pollen collected by honey bees and the development of their colonies in a Mediterranean area where agro-sylvo-pastoral systems are widely spread.MethodsFor the purpose of our study, pollen samples were collected over a year from colonies of Apis mellifera placed in four sampling sites selected across a gradient of landscape heterogeneity and where semi-natural habitats were predominant at various levels within an agro-sylvo-pastoral zone. Simultaneously, the extension of the sealed brood of the same colonies was periodically evaluated.ResultsWe found that the amount of pollen collected by honey bees was positively correlated with the percentage of semi-natural habitat cover and that increasing habitat diversity at the landscape level had a significant positive effect on the richness and diversity of pollen collected by honey bees. In addition, season significantly affected the amount, diversity and composition of pollen collected by honey bees. Furthermore, bee colony growth was positively correlated with richness, diversity and amount of pollen collected by honey bees.ConclusionOur study highlights the importance of an abundant and diverse pollen diet for honey bee colony development, which in agro-sylvo-pastoral systems seems to be ensured by a heterogeneous landscape dominated by different types of semi-natural habitats.

Fewer bowl traps and more hand netting can increase effective number of bee species and reduce excessive captures.

Reports increasingly point to substantial declines in wild bee abundance and diversity, yet there is uncertainty about how best to measure these attributes in wild bee populations. Two commonly used methods are passive trapping with bee bowls or active netting of bees on flowers, but each of these has drawbacks. Comparing the outcomes of the two methods is complicated by their uncomparable units of effort. The abundance distribution of bee species is also typically highly skewed, making it difficult to accurately assess diversity when rarer species are unlikely to be caught. The effective number of species, or Hill numbers, provides a way forward by basing the response metric on the number of equally abundant species. Our goal is to compare the effective number of bee species captured between hand netting and bowl trapping in wheatgrass prairie in South Dakota and tallgrass prairie in Minnesota, USA. Species overlap between the two methods ranged from ~40% to ~60%. Emphasis placed on rare species was important, so that 95% confidence limits overlapped between the two methods for species richness but netting exceeded trapping for Shannon's and Simpson's diversities. Netting always captured more bee species with fewer bee individuals than trapping. In most cases, the number of bees captured in bowl traps indicated substantial over-sampling, with little increase in bee species detected. Correlations between bee and floral abundance, richness, and diversity differed between netted and trapped samples. We conclude that netting and trapping together produce a more complete account of species richness, but shifting sampling emphasis from trapping to netting will result in fewer bees, but more bee species captured. Due to the different relationships between bee and floral diversities that depended on sampling method, it is unwise to compare habitat associations determined by netting with those determined by trapping.

Microbial ensemble in the hives: deciphering the intricate gut ecosystem of hive and forager bees of Apis mellifera.

The gut microbiome of honey bees significantly influences vital traits and metabolic processes, including digestion, detoxification, nutrient provision, development, and immunity. However, there is a limited information is available on the gut bacterial diversity of western honey bee populations in India. This study addresses the critical knowledge gap and outcome of which would benefit the beekeepers in India. This study investigates the gut bacterial diversity in forager and hive bees of Indian Apis mellifera, employing both culture-based and culture-independent methods. In the culturable study, a distinct difference in gut bacterial alpha and beta diversity between forager and hive bees emerges. Firmicutes, Proteobacteria, and Actinobacteria dominate, with hive bees exhibiting a Firmicutes-rich gut (65%), while foragers showcase a higher proportion of Proteobacteria (37%). Lactobacillus in the hive bee foregut aligns with the findings by other researchers. Bacterial amplicon sequencing analysisreveals a more intricate bacterial composition with 18 identified phyla, expanding our understanding compared to culturable methods. Hive bees exhibit higher community richness and diversity, likely due to diverse diets and increased social interactions. The core microbiota includes Snodgrassella alvi, Gilliamella apicola, and Bombilactobacillus mellis and Lactobacillus helsingborgensis, crucial for digestion, metabolism, and pathogen resistance. The study emphasises bacteria's role in pollen and nectar digestion, with specific groups like Lactobacillus and Bifidobobacterium spp. associated with carbohydrate metabolism and polysaccharide breakdown. These microbes aid in starch and sucrose digestion, releasing beneficial short-chain fatty acids. This research highlights the intricate relationship between honey bees and their gut microbiota, showcasing how the diverse and complex microbiome helps bees overcome dietary challenges and enhances overall host health. Understanding these interactions contributes to bee ecology knowledge and has implications for honey bee health management, emphasising the need for further exploration and conservation efforts.

Optimizing coffee production: Increased floral visitation and bean quality at plantation edges with wild pollinators and natural vegetation

Abstract Animal pollination is important for more than 75% of agricultural crops, including coffee, whose productivity can increase with adequate pollination. Bees, including many solitary species, are diverse pollinators, with around 85% of them considered more effective than honeybees in pollen transfer. We assessed the coffee plantation and its surrounding vegetation for solitary bee nesting throughout the coffee flowering season and measured their impact on coffee productivity. We installed collection stations with trap nests inside a coffee plantation, on the border and inside the native vegetation in a farm in Diamantina, MG, Brazil. We used 10 weekly monitored replicates at least 1 km apart. We evaluated fruiting by autogamy in relation to natural pollination and used the increase in fruit set from pollinators to calculate the farmer's monetary gain. We recorded bee visits to the exposed flowers during coffee flowering considering both on the edge and inside the coffee plantation. Ripe fruits were dried, counted and weighed. We discovered 132 solitary bee nests outside the plantation, with 54% containing coffee pollen grains, indicating coffee as an essential resource for bees even outside the crop area. More bee visits occurred at the coffee plantation's edge, resulting in increased fruit production, denser fruits, and rounder fruits in that area. Bagged flowers produced consistent seeds in all locations. The farmer could earn an extra US$1736.37 per hectare if the entire area received the same level of pollination contribution from bees as observed at the coffee border. Synthesis and applications. Our study emphasises the key role of pollinators in coffee production and their impact on fruit and seed characteristics. Bee visits were more frequent on border areas, emphasising their reliance on natural nesting sites. Bee‐mediated pollination positively affected fruit traits and self‐pollinated fruits in plantation borders had reduced mass. Solitary bee nesting was primarily observed in native vegetation, underlining its importance for bee populations. Pollen composition in nests varied with proximity to coffee plantations, indicating landscape vegetation influences pollinator foraging. These findings support optimising coffee plantation design by preserving native vegetation to increase coffee yields and conserve biodiversity.

Thinking inside the box: Restoring the propolis envelope facilitates honey bee social immunity.

When wild honey bee colonies (Apis mellifera) nest in hollow tree cavities, they coat the rough cavity walls with a continuous layer of propolis, a substance comprised primarily of plant resins. Studies have shown that the resulting "propolis envelope" leads to both individual- and colony-level health benefits. Unfortunately, the smooth wooden boxes most commonly used in beekeeping do little to stimulate propolis collection. As a result, most managed bees live in hives that are propolis-poor. In this study, we assessed different surface texture treatments (rough wood boxes, boxes outfitted with propolis traps, and standard, smooth wood boxes) in terms of their ability to stimulate propolis collection, and we examined the effect of propolis on colony health, pathogen loads, immune gene expression, bacterial gene expression, survivorship, and honey production in both stationary and migratory beekeeping contexts. We found that rough wood boxes are the most effective box type for stimulating propolis deposition. Although the use of rough wood boxes did not improve colony survivorship overall, Melissococcus plutonius detections via gene expression were significantly lower in rough wood boxes, and viral loads for multiple viruses tended to decrease as propolis deposition increased. By the end of year one, honey bee populations in migratory rough box colonies were also significantly larger than those in migratory control colonies. The use of rough wood boxes did correspond with decreased honey production in year one migratory colonies but had no effect during year two. Finally, in both stationary and migratory operations, propolis deposition was correlated with a seasonal decrease and/or stabilization in the expression of multiple immune and bacterial genes, suggesting that propolis-rich environments contribute to hive homeostasis. These findings provide support for the practical implementation of rough box hives as a means to enhance propolis collection and colony health in multiple beekeeping contexts.

Comparison of pure caucasian, carniolan and native anatolian ecotype honey bee (Apis mellifera L.) colonies in the eastern anatolia region with reciprocal F1 hybrids

The aim of this study was to compare specific physiological and behavioral characteristics of A. m. caucasica, A. m. carnica, and native honeybees, as well as reciprocal crosses, within the ecological conditions of East Anatolia (Van province), Turkey. The findings revealed that native honeybees exhibited the highest average sealed brood area and the highest average number of frames with bees. In contrast, the highest average honey yield was observed in the crossbreeding of Carniolan bees with native bees. Significant differences were identified among the groups concerning brood area, the number of bee frames, aggression tendency, and honey yield. The study concluded that Carniolan and Caucasian bees exhibited suboptimal performance outside their native habitats. Nevertheless, Carniolan bees were identified as a viable option for mitigating aggression tendencies and enhancing honey yield in native bee populations.

Assessment of Efficacy of Algerian Propolis against the Parasitic Mite Varroa destructor and Safety for Honey Bees by Spray Treatment.

Varroa destructor is an ectoparasitic mite and is considered one of the most important causes of honey bee population loss. In the last years, substances of botanical origin have emerged as natural alternatives to diminish the mite population levels. Propolis is a natural product and is used by honey bees for multiple tasks, including protection from pathogens and parasites, and varroacidal activity of propolis extracts has been shown. In this study, we investigated the potential of propolis, collected by native Algerian honey bee subspecies (Apis mellifera intermissa and A. m. sahariensis) in different locations in Algeria and extracted by ultrasound, to control mites of V. destructor and tested the safety for the honey bees. The most important results were that the best propolis extracts at 10% killed 100% of the Varroa mites within 3-4 h in a Petri dish assay. In addition, when we sprayed A. m. intermissa bees infested with Varroa mites with a 10% concentration in a mini-hive setup, we scored a high mite mortality of 85-87% with the best propolis extracts, and importantly, there was no mortality in the bees. Our data demonstrated that propolis extracts in Algeria could be used in honey bee colonies by spraying against Varroa mite infestations, which may develop as an easy method for local beekeepers to control Varroa in their hives. Further research should investigate the mechanism of action.

Atmospheric non-thermal plasma inactivation of Ascosphaera apis, the causative agent of chalkbrood disease in honeybee

Ascosphaera apis is a worldwide pathogenic fungi of honeybees that can cause a decline in bee populations. In this study, we investigated the antifungal activity of non-thermal plasma on fungal growth. Spore inactivation after exposure to gas plasma by liquid phase and plasma activated water (PAW) and pathogenicity of A. apis in vivo were also examined. The results demonstrated that the mycelial growth of fungi was completely inhibited after argon plasma treatment. Both gas plasma and PAW exposures resulted in a significant decrease of A. apis spore numbers, maximum reduction of 1.71 and 3.18-fold, respectively. Germinated fungal spores on potato dextrose agar were also reduced after plasma treatment. SEM analysis revealed a disruption in the morphological structure of the fungal spores. The pathogenicity of A. apis on honeybee larvae was decreased after spores treated by gas plasma and PAW with a disease inhibition of 63.61 ± 7.28% and 58.27 ± 5.87%, respectively after 7 days of cultivation. Chalkbrood in honey bees have limited control options and our findings are encouraging. Here, we demonstrate a possible alternative control method using non-thermal plasma for chalkbrood disease in honeybees.

Improving wild bee monitoring, sampling methods, and conservation

Bees are the most important group of insect pollinators, but their populations are declining. To gain a better understanding of wild bee responses to different stressors (e.g. land-use change) and conservation measures, regional and national monitoring schemes are currently being established in Germany, which is used here as a model region, and in many other countries. We offer perspectives on how to best design future bee monitoring programs with a focus on evaluating the implementation of conservation measures. We discuss different traditional and novel sampling methods, their efficacy depending on research questions and the life-history traits of target species, and how greater standardization of wild bee sampling and monitoring methods can make data more comparable, contributing to the identification of general trends and mechanisms driving bee populations. Furthermore, the potential impact of bee sampling itself on bee populations is discussed.

Combined pesticides in field doses weaken honey bee (Apis cerana F.) flight ability and analyses of transcriptomics and metabolomics

Imidacloprid, chlorpyrifos, and glyphosate rank among the most extensively employed pesticides worldwide. The effects of these pesticides and their combined on the flight capability of Apis cerana, and the potential underlying mechanisms remain uncertain. To investigate these effects, we carried out flight mill, transcriptome, and metabolome experiments. Our findings reveal that individual acute oral treatments with pesticides, specifically 20 μL of 10 ng/g imidacloprid (0.2 ng per bee), 30 ng/g chlorpyrifos (0.6 ng per bee), and 60 ng/g glyphosate (1.2 ng per bee), did not impact the flight capability of the bees. However, when bees were exposed to a combination of two or three pesticides, a notable reduction in flight duration and distance was observed. In the transcriptomic and metabolomic analyses, we identified 307 transcripts and 17 metabolites that exhibited differential expression following exposure to combined pesticides, primarily associated with metabolic pathways involved in energy regulation. Our results illuminate the intricate effects and potential hazards posed by combined pesticide exposures on bee behavior. These findings offer valuable insights into the synergistic potential of pesticide combinations and their capacity to impair bee behavior. Understanding these complex interactions is essential for comprehending the broader consequences of pesticide formulations on honey bee populations.

Prevalence and distribution of Varroa destructor and Nosema spp. in symptomatic honey bee colonies across the USA from 2015 to 2022

USDA-ARS Bee Research Laboratory received symptomatic honey bee (Apis mellifera L.) samples across the United States for disease diagnosis. Here, we present a retrospective study and cartography of ectoparasite Varroa destructor and intracellular microsporidia parasite Nosema spp. These two major parasites were identified in the diseased honey bee samples between 2015 and 2022. Varroa infestation level (VIL) was examined by a wash technique (Mites/100 bees) and calculated as a percentage, while Nosema infection was quantified by microscopical spore count (Million Spores/Bee). Data were analyzed by month, year, state, and by nine geographical climate regions described in the U.S. Of adult bee samples (n = 4039) that were analyzed for Varroa mite infestation, the overall VIL in the U.S. ranged between 0.4 and 30.85%, with an overall national VIL and Varroa prevalence of 8.21% and 85.14%, respectively. Overall monthly data showed VIL constantly exceeded the critical level of 4% except from June to September and reached a maximum of 15% in January and December. Nationwide, VIL significantly (p < 0.001) increased from 2015 to 2018 (1.1–4.7%), plateaued from 2018 to 2021 (4.7–4.5%), followed by a significant decrease in 2022 (3.6%). Significant VIL differences (p < 0.001) were recorded among climate regions, with the highest mite infestation levels in the Upper Midwest region (13.9%) and the lowest in the West region (5.1%). Of adult bee samples (n = 2,994) that were analyzed for Nosema infection, Nosema spore count ranged between (1–16.8) million spores per bee among states, with a national average of 6.8 and a prevalence of 99.7%. The lowest and highest Nosema loads were respectively recorded in the South region (3.1) and Upper Midwest (10.5), a significant difference (p < 0.001). No statistical differences were recorded among the six other climate regions. Overall, VIL and Nosema infection correlated significantly (p < 0.001) with a regression coefficient of (R2 = 0.6). Our data, which originated from ailing bee colonies, showed significantly higher rates of maladies compared to data from healthy colonies obtained by the USDA-APHIS National Honey Bee Survey, demonstrating the role of bee diseases caused by Varroa mite and Nosema in honey bee population declines.