A historical review of managed honey bee populations in Europe and the United States and the factors that may affect them

Distribution of honey bee mitochondrial DNA haplotypes in an Italian region where a legislative act is protecting the Apis mellifera ligustica subspecies

The conservation of the genetic integrity of Apis mellifera subspecies has emerged as an important objective. In 2019, the Emilia-Romagna region became the first Italian regional authority to issue a law specifically addressing the protection of the native Apis mellifera ligustica subspecies. In this study we analysed a highly informative portion of the mitochondrial DNA (mtDNA), widely used for assessing genetic diversity of honey bee populations. By analysing 1143 honey bees sampled after the introduction of this law, we provided a snapshot of the distribution of mtDNA haplotypes in this region. The two most frequent mtDNA haplotypes were C1 (characteristic of A. m. ligustica) and C2 (characteristic of A. m. carnica), reported in 86.5% and 11.0% of the analysed bees, respectively. About 1.3% and 1.1% of the analysed bees carried mtDNA haplotypes of the A and M lineages (haplotypes A1a, A1e, A4, A26, A65 and two novel ones, A2w and A6a; M3, M3a, M4 and M79). Continued genetic monitoring will be important to assess the impact of this regional law over the coming years. Based on the obtained results, we recommend a more stringent policy to prevent the erosion of the genetic integrity of the native subspecies A. m. ligustica.

Diagnostic study on major honeybee disease, pests and predators in North Western Ethiopia

BACKGROUND

The study was conducted in Pawe district from Benishangul-Gumuz and Jawi and Fagita Lekoma districts from the Amhara region to investigate major honeybee pests, predators and diseases.

METHODS

Using a purposive sampling technique, 183 households were interviewed, and 240 samples were collected for laboratory analysis of bee disease; data were analysed using descriptive statistics.

RESULTS

The share of hive types owned by sampled respondents was 88.6%; overall, 1.1% and 10.3% were traditional, transitional and modern beehives, respectively. About 92% of the sample respondents acquired their base colonies by catching swarm bees on the apex of trees. The majority of beekeepers executed external inspections of their colony, whereas only 50% carried out internal inspections. Based on the responses of beekeepers, around 48.9%, 56.3% and 23.1% of colonies absconded every year from Pawe, Jawi and Fagita Lekoma districts, respectively. Ants, wax moths, bee lice, beetles, spiders, birds, monkeys and honey badgers were the major honeybee pests and predators discovered in study areas in decreasing order. Concerning the incidence of Varroa mites, Nosema apis and amoeba disease, 27.5%, 60% and 71.6% of samples showed positive results in study locations, respectively.

CONCLUSIONS

From this result, we observed that ants, wax moths, bee lice, beetles, spiders, birds, monkeys and honey badgers were the major honeybee pests and predators. The prevalence of amoeba disease was comparatively higher in highland areas and in the summer season. This finding suggests the need for the alertness of beekeepers in controlling bee disease and pests and strengthening bee colonies through seasonal colony management. There should be a strict quarantine, and check-up undertaken when a new colony is purchased from one region to another is essential.

Impact of copper and zinc oral chronic exposure on Carniolan honey bee survival and feeding preference

Honey bees are important plant pollinators and honey producers. Contamination of the environment with metals can lead to a decline in honey bee populations. Copper (Cu) and zinc (Zn) salts are commonly used as fungicides and foliar fertilizers. In this study, we investigated the effects of 10-day chronic oral exposure to different concentrations of Cu (CuSO4) and Zn (ZnCl2) on survival and feeding rates of Carniolan honey bees in laboratory conditions. We found that mortality in honey bee workers increased in a concentration-dependent manner and that Cu (lethal concentration [LC50] = 66 mg/l) was more toxic than Zn (LC50 = 144 mg/l). There was no difference in the feeding rate of Cu-treated bees for the different concentrations tested, but the feeding rate decreased with the increase in Zn concentration. To determine feeding preference or avoidance for Cu and Zn, we conducted 2-choice 24-h feeding experiments. We demonstrated that honey bees preferred Zn-containing solutions compared to the control diet. A two-choice experiment with Cu showed a tendency for honey bees to be deterred by Cu at high concentrations; however, it was not statistically significant. In summary, our results suggest that honey bee workers may suffer adverse effects when exposed to ecologically relevant concentrations of Cu and Zn.

Detection and characterization of Deformed Wing Virus (DWV) in apiaries with stationary and migratory management in the province of Entre Ríos, Argentina

In Argentina, migratory activity in search of floral diversity has become a common approach to maximizing honey production. The Entre Ríos province possesses a floral diversity that allows beekeepers to perform migratory or stationary management. Beyond the impact caused by transhumance, migratory colonies in this province start and end the season in monoculture areas. To study the effect of these practices on viral infection, we assayed for the presence, abundance and genetic characterization of the Deformed Wing Virus (DWV) in honey bees from apiaries with both types of management. In migratory apiaries, DWV was detectable in 86.2% of the colonies at the beginning of the season (September 2018), and 66% at the end of the season (March 2019). On the other hand, DWV was detected in 44.11% and 53.12% of stationary samples, at the beginning and the end of the season, respectively. Sequence analysis from migratory and stationary colonies revealed that all samples belonged to DWV-A type. The highest viral loads were detected in migratory samples collected in September. Higher DWV presence and abundance were associated with migratory management and the sampling time. Based on our findings we propose that the benefit of migration to wild flowering areas can be dissipated when the bee colonies end the season with monoculture.

Dancing with danger-how honeybees are getting affected in the web of microplastics-a review

Anthropogenic activities have negatively impacted the ecosystem dramatically over the last few decades. The environment is becoming more contaminated with heavy metals, pesticides, and microplastics (MPs) as a result of the swift rise in industrialization and urbanisation. These contaminants are present everywhere in the ecosystem, affecting every living creature, from aquatic to terrestrial to aerial. Recently, the widespread of microplastics in the environment has raised serious concerns about the contamination of honey bees by these tiny particles of plastic. Honeybees are the major pollinators which contributes in the pollination of about 70% food that we consume. This review summarizes current research findings on the presence, uptake, and possible effects of microplastics on honey bees. Findings revealed the presence of microplastics in various honey bee matrices, such as honey, pollen, beeswax, and bee bodies, highlighting the potential routes of exposure for these vital pollinators. Additionally, evidence suggests that microplastics can accumulate in honey bee tissues (brain, midgut, Malpighian tubules, trachea, and haemolymph) potentially leading to adverse effects on honey bee health, behaviour, and colony dynamics. Additionally, MPs has a synergistic impact on immune system as well. Change in cuticle profile, reduction in body weight, and changes in eating frequency can regulate overall success rate of their survival. However, significant knowledge gaps remain regarding the long-term consequences for honey bee populations and ecosystem health, which cannot unveil the ultimate degree of future threats. Future research efforts should focus on investigating the interactions between microplastics and other stressors, such as pesticides and pathogens, and assessing the broader ecological implications of honey bee contamination with microplastics. Addressing these knowledge gaps is essential for developing effective mitigation strategies to minimize the impact of microplastics on honey bee populations and safeguarding their vital role in ecosystem functioning and food security.

Estimates of the vitality and performances of Apis mellifera mellifera and hybrid honey bee colonies in Siberia: a 13-year study

Honeybees display a great range of biological, behavioral, and economic traits, depending on their genetic origin and environmental factors. The high diversity of honeybees is the result of natural selection of specific phenotypes adapted to the local environment. Of particular interest is adaptation of local and non-local bee colonies to environmental conditions. To study the importance of genotype-environment interactions on the viability and productivity of local and non-local bee colonies, we analyzed the long-term dynamics of the main traits in dark forest bees (Apis mellifera mellifera) and hybrid colonies. From 2010 to 2022, a total of 64 colonies living in an apiary in Siberia, Russia, were monitored and tested to assess their biological, behavioral, and economic traits in a temperate continental climate. We detected significant correlations between the studied biological and behavioral indicators of the bee colony such as colony strength, overwintering ability, infection of colonies with diseases, hygienic behavior, and others. No relationships between the biological and economic (honey productivity) traits of bee colonies are shown. The overall result of our study is that local dark forest bee, A.m.mellifera, showed higher values for all analyzed traits than hybrid colonies. Compared to hybrids, dark forest bee colonies showed more gentleness, productivity, and survivorship. The results from our study indicate a specific local adaptation of the A.m.mellifera subspecies in a temperate continental climate. Siberia represents a unique region for the conservation of the dark forest bee. The creation of conservation areas is one way to protect local bee populations, well adapted to local environmental conditions, from uncontrolled importation of bee breeds from different regions.

Haplotype Diversity in mtDNA of Honeybee in the Czech Republic Confirms Complete Replacement of Autochthonous Population with the C Lineage

The study aimed to analyze the genetic diversity in the Czech population of Apis mellifera using mitochondrial DNA markers, tRNAleu-cox2 intergenic region and cox1 gene. A total of 308 samples of bees were collected from the entire Czech Republic (from colonies and flowers in 13 different regions). Following sequencing, several polymorphisms and haplotypes were identified. Analysis of tRNAleu-cox2 sequences revealed three DraI haplotypes (C, A1, and A4). The tRNAleu-cox2 region yielded 10 C lineage haplotypes, one of which is a newly described variant. Three A lineage haplotypes were identified, two of which were novel. A similar analysis of cox1 sequences yielded 16 distinct haplotypes (7 new) within the population. The most prevalent tRNAleu-cox2 haplotype identified was C1a, followed by C2a, C2c, C2l, and C2d. For the cox1 locus, the most frequent haplotypes were HpB02, HpB01, HpB03, and HpB04. The haplotype and nucleotide diversity indices were high in both loci, in tRNAleu-cox2 with values of 0.682 and 0.00172, respectively, and in cox1 0.789 and 0.00203, respectively. The Tajima's D values were negative and lower in tRNAleu-cox2 than in cox1. The most frequent haplotypes were uniformly distributed across all regions of the Czech Republic. No haplotype of the indigenous M lineage was identified. High diversity and the occurrence of rare haplotypes indicate population expansion and continuous import of tribal material of the C lineage.

Allele Frequencies of Genetic Variants Associated with Varroa Drone Brood Resistance (DBR) in Apis mellifera Subspecies across the European Continent

Implementation of marker-assisted selection (MAS) in modern beekeeping would improve sustainability, especially in breeding programs aiming for resilience against the parasitic mite Varroa destructor. Selecting honey bee colonies for natural resistance traits, such as brood-intrinsic suppression of varroa mite reproduction, reduces the use of chemical acaricides while respecting local adaptation. In 2019, eight genomic variants associated with varroa non-reproduction in drone brood were discovered in a single colony from the Amsterdam Water Dune population in the Netherlands. Recently, a new study tested the applicability of these eight genetic variants for the same phenotype on a population-wide scale in Flanders, Belgium. As the properties of some variants varied between the two studies, one hypothesized that the difference in genetic ancestry of the sampled colonies may underly these contribution shifts. In order to frame this, we determined the allele frequencies of the eight genetic variants in more than 360 Apis mellifera colonies across the European continent and found that variant type allele frequencies of these variants are primarily related to the A. mellifera subspecies or phylogenetic honey bee lineage. Our results confirm that population-specific genetic markers should always be evaluated in a new population prior to using them in MAS programs.

Comprehensive Approach to Phenotype Varroa destructor Reproduction in Honey Bee Drone Brood and Its Correlation with Decreased Mite Reproduction (DMR)

The mechanisms of action behind decreased mite reproduction (DMR) are still unknown, but current hypotheses state that DMR is the result of brood-intrinsic and/or external disturbances in the V. destructor-honey bee pupa signal interactions. For accurate and precise DMR phenotyping, sufficient single infested honey bee brood cells are required (e.g., 35), which requires extensive labor and time and may exclude many samples not reaching the threshold. We defined a new comprehensive trait called the 'mean V. destructor reproduction rate' (mVR), which describes the mean number of offspring mites per infested cell in the sample while compensating for the reduced number of offspring with increasing multiple infested cells. We found a significant correlation between mVR and DMR, allowing for an estimation of DMR based on the mVR only. When the mVR was calculated with 10 infested cells, we found an average variation in mVR of 16.8%. For the same variation in DMR determination, 40 single infested cells are required. This broader look at V. destructor resistance phenotyping can improve the applicability and effectiveness of traits related to V. destructor reproduction in honey bee breeding programs.

Winter Hive Debris Analysis Is Significant for Assessing the Health Status of Honeybee Colonies (Apis mellifera)

Honeybee diseases are one of the most significant and most common causes of honeybee colonies' weakness and death. An early diagnosis of subclinical infections is necessary to implement precautionary and control measures. Sampling debris from hive bottom boards is simple, non-invasive, and cheap. In this study, we collected winter debris samples in apiaries located in the continental part of Croatia. We used molecular methods, PCR and qPCR, for the first time to analyze those samples. Laboratory results were compared with the health condition and strength of honeybee colonies at an apiary in spring. Our study successfully identified the presence and quantity of various pathogens, including the presence of Vairimorpha spp. (Nosema spp.), quintefied Paenibacillus larvae, Acute Bee Paralysis Virus (ABPV), Black Queen Cell Virus (BQCV), Deformed Wing Virus (DWV), and Sacbrood Virus (SBV). However, our analysis did not detect Melissococcus plutonius, Crithidia mellificae, Lotmaria passim, and Aethina tumida. Samples of winter debris were also examined for the presence and quantification of the V. destructor mites, and their natural mite fall was observed in spring. Honeybee colonies were simultaneously infected by an average of four to six pathogens. Some observed honeybee colonies developed characteristic symptoms, while others did not survive the winter.

Neonicotinoid exposure increases Varroa destructor (Mesostigmata: Varroidae) mite parasitism severity in honey bee colonies and is not mitigated by increased colony genetic diversity

Agrochemical exposure is a major contributor to ecological declines worldwide, including the loss of crucial pollinator species. In addition to direct toxicity, field-relevant doses of pesticides can increase species' vulnerabilities to other stressors, including parasites. Experimental field demonstrations of potential interactive effects of pesticides and additional stressors are rare, as are tests of mechanisms via which pollinators tolerate pesticides. Here, we controlled honey bee colony exposure to field-relevant concentrations of 2 neonicotinoid insecticides (clothianidin and thiamethoxam) in pollen and simultaneously manipulated intracolony genetic heterogeneity. We showed that exposure increased rates of Varroa destructor (Anderson and Trueman) parasitism and that while increased genetic heterogeneity overall improved survivability, it did not reduce the negative effect size of neonicotinoid exposure. This study is, to our knowledge, the first experimental field demonstration of how neonicotinoid exposure can increase V. destructor populations in honey bees and also demonstrates that colony genetic diversity cannot mitigate the effects of neonicotinoid pesticides.

Eggs sampling as an effective tool for identifying the incidence of viruses in honey bees involved in artificial queen rearing

The Carniolan honey bee (Apis mellifera carnica) plays an essential role in crop pollination, environment diversity, and the production of honey bee products. However, the health of individual honey bees and their colonies is under pressure due to multiple stressors, including viruses as a significant threat to bees. Monitoring various virus infections could be a crucial selection tool during queen rearing. In the present study, samples from all developmental stages (eggs, larvae, pupae, and queens) were screened for the incidence of seven viruses during queen rearing in Slovenia. The screening of a total of 108 samples from five queen breeders was performed by the RT-qPCR assays. The results showed that the highest incidence was observed for black queen cell virus (BQCV), Lake Sinai virus 3 (LSV3), deformed wing virus B (DWV-B), and sacbrood virus (SBV). The highest viral load was detected in queens (6.07 log10 copies/queen) and larvae (5.50 log10 copies/larva) for BQCV, followed by SBV in larvae (5.47 log10 copies/larva). When comparing all the honey bee developmental stages, the eggs exhibited general screening for virus incidence and load in queen mother colonies. The results suggest that analyzing eggs is a good indicator of resilience to virus infection during queen development.

Evaluating the role of social context and environmental factors in mediating overwintering physiology in honey bees (Apis mellifera)

In temperate climates, honey bees show strong phenotypic plasticity associated with seasonal changes. In summer, worker bees typically only survive for about a month and can be further classified as young nurse bees (which feed the developing brood) and older forager bees. In winter, brood production and foraging halt and the worker bees live for several months. These differences in task and longevity are reflected in their physiology, with summer nurses and long-lived winter bees typically having large fat bodies, high expression levels of vitellogenin (a longevity-, nutrition- and immune-related gene), and large provisioning glands in their head. The environmental factors (both within the colony and within the surrounding environment) that trigger this transition to long-lived winter bees are poorly understood. One theory is that winter bees are an extended nurse bee state, brought on by a reduction in nursing duties in autumn (i.e. lower brood area). We examined that theory here by assessing nurse bee physiology in both the summer and autumn, in colonies with varying levels of brood. We found that season is a better predictor of nurse bee physiology than brood area. This suggests that seasonal factors beyond brood area, such as pollen availability and colony demography, may be necessary for inducing the winter bee phenotype. This finding furthers our understanding of winter bee biology, which could have important implications for colony management for winter, a critical period for colony survival.

Foraging Activity of Honey Bees (Apis mellifera L., 1758) and Exposure to Cadmium: a Review

Honey bees are commonly exposed to a broad spectrum of xenobiotics, including heavy metals. Heavy metal toxicity is of concern in the context of global pollinator declines, especially since honey bees seem to be particularly susceptible to xenobiotics in general. Here we summarize current knowledge on the interplay between cadmium, one of the most toxic and mobile elements in the environment, and honey bees, the primary managed pollinator species worldwide. Overall, cadmium pollution has been shown to be ubiquitous, affecting industrial, urban and rural areas alike. Uptake of this heavy metal by plants serves as the primary route of exposure for bees (through pollen and nectar). Reported cadmium toxicity consists of lethal and sublethal effects (reduced development and growth) in both adult and larval stages, as well as various molecular responses related to detoxification and cellular antioxidant defence systems. Other effects of cadmium in honey bees include the disruption of synaptic signalling, calcium metabolism and muscle function.

Effects of feeding with a protein liquid supplement on productivity, mortality and health of Apis mellifera hives in southwestern Spain

Colony collapse disorder (CCD) has affected bees worldwide in recent decades, with southwestern Spain being no exception. This disorder is one of the main causes of Apis mellifera mortality and is believed to be caused by environmental, social and sanitary conditions. Dietary supplementation can help to improve some parameters of the general status and sanitary condition of bees, such as infestation by certain recurrent pathogens, including Varroa destructor and Nosema ceranae, by enhancing immune and social response. Thus, the aim of this study was to test a liquid hydrolysed protein supplement on the health and general status of the hive in several apiaries with access to the same natural food and under similar climatic conditions. We selected two groups of ten hives (supplemented by either placebo or protein) from five apiaries where the number of adult bees, amount of brood (open and operculated), honey and pollen reserves, infestation by V. destructor, N. ceranae, deformed wing virus (DWV) and chronic bee paralysis virus (CBPV) were measured. Additionally, we assess the expression of four immune system-related genes and a gene encoding vitellogenin. At the end of this work, treated hives showed a significant increase in open brood and a decrease in V. destructor infestation. Also, these hives showed a significant decrease in the mortality rate after the cold season. Therefore, supplementation with this product improved the health of the hive and could be a promising tool against bee colony loss.

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.

Ecology and Management of African Honey Bees (Apis mellifera L.)

In Africa, humans evolved as honey hunters of honey bee subspecies adapted to diverse geographical regions. Beekeeping today is practiced much as it was when Africans moved from honey hunting to beekeeping nearly 5,000 years ago, with beekeepers relying on seasonally available wild bees. Research suggests that populations are resilient, able to resist diseases and novel parasites. Distinct biomes, as well as environmental pressures, shaped the behavior and biology of these bees and in turn influenced how indigenous beekeeping developed. It appears that passive beekeeping practices that enabled free-living populations contributed to the overall resilience and health of the bee. There is clearly a need for research aimed at a deeper understanding of bee biology and the ecosystems from which they benefit and on which humans depend, as well as a growing realization that the management of these bees requires an indigenous approach that reflects a broader knowledge base and the economics of local communities and markets.

Impacts of the insecticide thiamethoxam on the native stingless bee Plebeia catamarcensis (Hymenoptera, Apidae, Meliponini)

Agricultural production and the indiscriminate use of insecticides such as thiamethoxam have put at risk the biodiversity and ecosystem services provided by bees, including native stingless species. Since most of the native species do not present economic importance, they may suffer "silent extinction", due to lack of monitoring of their colonies. Therefore, this study aimed to determine the lethal and sublethal concentrations of the insecticide thiamethoxam, with evaluation of its sublethal effects on mobility, in the stingless bee Plebeia catamarcensis (Holmberg, 1903). Foraging bees were collected and exposed to thiamethoxam to determine lethal (LC50) and sublethal concentrations. The 24 h LC50 was 0.408 ng a.i./μL, a value demonstrating that this species may be as sensitive as other stingless bees already studied. Sublethal concentrations influenced the locomotion abilities of the bees, making them hyperactive when exposed to LC50/10 and lethargic when exposed to LC50/100. The effects of sublethal concentrations on individuals may have collective consequences, especially in colonies with few individuals, as is the case of P. catamarcensis. The findings reinforce the hypothesis that thiamethoxam may contribute to the decline of native stingless bees, which can be significantly impacted when chronically exposed to agricultural production systems that use this insecticide, consequently affecting the ecosystem services provided by these bees.

Greater wax moth control in apiaries can be improved by combining Bacillus thuringiensis and entrapments

The greater wax moth (GWM), Galleria mellonella (Lepidoptera: Pyralidae), is a major bee pest that causes significant damage to beehives and results in economic losses. Bacillus thuringiensis (Bt) appears as a potential sustainable solution to control this pest. Here, we develop a novel Bt strain (designated BiotGm) that exhibits insecticidal activity against GWM larvae with a LC50 value lower than 2 μg/g, and low toxicity levels to honey bee with a LC50 = 20598.78 μg/mL for larvae and no observed adverse effect concentration = 100 μg/mL for adults. We design an entrapment method consisting of a lure for GWM larvae, BiotGm, and a trapping device that prevents bees from contacting the lure. We find that this method reduces the population of GWM larvae in both laboratory and field trials. Overall, these results provide a promising direction for the application of Bt-based biological control of GWM in beehives, although further optimization remain necessary.

Effects of Virgin Coconut Oil-Enriched Diet on Immune and Antioxidant Enzymatic Activity, Fat and Vitellogenin Contents in Newly Emerged and Forager Bees (Apis mellifera L.) Reared in Cages

Searching for artificial diets positively affecting the survival, immune and antioxidant systems of honey bees is one of main challenges occurring in beekeeping. Among nutrients, lipids play a significant role in insect nutrition as structural components in cell membranes, energy sources and reserves, and are involved in many physiological processes. In this context, the aim of this work was to investigate the effect of 0.5% and 1% coconut oil-enriched diet administration on newly emerged and forager bees survival rate, feed intake, immune system, antioxidant system and both fat and vitellogenin content. In newly emerged bees, supplementation with 1% coconut oil determined a decrease in feed consumption, an increase in survival rate from the 3rd to 14th day of feeding, a short-term decrease in phenoloxidase activity, an increase in body fat and no differences in vitellogenin content. Conversely, supplementation with 0.5% coconut oil determined an increase in survival rate from the 3rd to 15th day of feeding and an increase in fat content in the long term (i.e., 20 days). Regarding the forager bee diet, enrichment with 0.5% and 1% coconut oil only determined an increase in fat content. Therefore, supplementation with coconut oil in honey bee diets at low percentages (0.5 and 1%) determines fat gain. Further investigations to evaluate the use of such supplement foods to prevent the fat loss of weak families during winter are desirable.

Biotechnical Control of Varroa in Honey Bee Colonies: A Trade-Off between Sustainable Beekeeping and Profitability?

Beekeeping faces several challenges, such as the Varroa mite. Few studies have measured the economic performance of farms in relation to the practices used for Varroa control. Our study analyzed various biotechniques (total brood removal, TBR; queen caging, QC; royal cell insertion, CI) and other methods (chemical treatments, CT; thymol use, THY) adopted by Italian beekeepers to show whether the adoption of biotechniques leads to farm profitability or a necessary trade-off between sustainability and profitability. Beekeepers were interviewed about the methods and operations conducted on their farms. The net incomes (NIs) of the farms were calculated and inter- and intrafarm comparisons were performed. A detailed schema of each practice was designed. The net income derived from TBR was the highest in eight out of the nine case studies, followed by CI and then QC. The NI calculated for farms using CT was lower than that for farms using other methods in two of the case studies. We also analyzed different biotechniques applied by the same farm and found that the NI resulting from TBR was higher than that achieved from the use of QC and CI. Our study suggests that use of biotechniques represents a long-term sustainable solution for reducing the level of Varroa infestation, which affects farm net income.

Generalized Stressors on Hive and Forager Bee Colonies

Hive-forming bees play an integral role in promoting agricultural sustainability and ecosystem preservation. The recent worldwide decline of several species of bees, and in particular, the honeybee in the United States, highlights the value in understanding possible causes. Over the past decade, numerous mathematical models and empirical experiments have worked to understand the causes of colony stress, with a particular focus on colony collapse disorder. We integrate and enhance major mathematical models of the past decade to create a single, analytically tractable model using a traditional disease modeling framework that incorporates both lethal and sublethal stressors. On top of this synthesis, a major innovation of our model is the generalization of stressor attributes including their transmissibility, impairment level, lethality, duration, and temporal-occurrence. Our model is validated against numerous emergent, biological characteristics and demonstrates that precocious foraging and labor destabilization can produce colony collapse disorder. The thresholds for these phenomena to occur depend on the characteristics and timing of the stressor, thus motivating further empirical and theoretical studies into stressor characteristics.

Gut microbiota-driven regulation of queen bee ovarian metabolism

With the global prevalence of Varroa mites, more and more beekeepers resort to confining the queen bee in a queen cage to control mite infestation or to breed superior and robust queen bees. However, the impact of such practices on the queen bee remains largely unknown. Therefore, we subjected the queen bees to a 21-day egg-laying restriction treatment (from the egg stage to the emergence of adult worker bees) and analyzed the queen bees' ovarian metabolites and gut microbiota after 21 days, aiming to assess the queen bees' quality and assist beekeepers in better hive management. Our findings revealed a significant reduction in the relative expression levels of Vg and Hex110 genes in the ovaries of egg laying-restricted queen bees compared to unrestricted egg-laying queens. The diversity of gut microbiota in the queen bee exhibited a notable decrease, accompanied by corresponding changes in the core bacteria of the microbial community, the relative abundance of Lactobacillus and Bifidobacterium increased from 22.34% to 53.14% (P = 0.01) and from 0.053% to 0.580% (P = 0.04), respectively. The relative abundance of Bombella decreased from 25.85% to 1.720% (P = 0.002). Following egg-laying restriction, the activity of the queen bee's ovaries decreased, while the metabolism of glycerophospholipids remained or stored more lipid molecules, awaiting environmental changes for the queen bee to resume egg laying promptly. Furthermore, we observed that Bombella in the queen bee's gut may regulate the queen's ovarian metabolism through tryptophan metabolism. These findings provide novel insights into the interplay among queen egg laying, gut microbiota, and ovarian metabolism. IMPORTANCE With Varroa mite infestation, beekeepers often confine the queen bee in cages for control or breeding. However, the impact on the queen bee is largely unknown. We evaluated queen bee quality by restricting egg laying and analyzing ovarian metabolites and gut microbiota. In this study, we provided a comprehensive explanation of the expression of ovarian genes, the diversity of gut microbiota, and changes in ovarian metabolism in the queen bee. Through integrated analysis of the queen bee's gut microbiota and ovarian metabolism, we discovered that the gut microbiota can regulate the queen bee's ovarian metabolism. These findings provide valuable insights into the interplay among egg laying, gut microbiota, and the reproductive health of the queen bee. Understanding these relationships can contribute to the development of better strategies for Varroa mite control and queen bee breeding.

Phenotypic and genetic characterization of Africanized Apis mellifera colonies with natural tolerance to Varroa destructor and contrasting defensive behavior

Africanized Apis mellifera colonies with promising characteristics for beekeeping have been detected in northern Argentina (subtropical climate) and are considered of interest for breeding programs. Integral evaluation of this feral material revealed high colony strength and resistance/tolerance to brood diseases. However, these Africanized honeybees (AHB) also showed variable negative behavioral traits for beekeeping, such as defensiveness, tendency to swarm and avoidance behavior. We developed a protocol for the selection of AHB stocks based on defensive behavior and characterized contrasting colonies for this trait using NGS technologies. For this purpose, population and behavioral parameters were surveyed throughout a beekeeping season in nine daughter colonies obtained from a mother colony (A1 mitochondrial haplotype) with valuable characteristics (tolerance to the mite Varroa destructor, high colony strength and low defensiveness). A Defensive Behavior Index was developed and tested in the colonies under study. Mother and two daughter colonies displaying contrasting defensive behavior were analyzed by ddRADseq. High-quality DNA samples were obtained from 16 workers of each colony. Six pooled samples, including two replicates of each of the three colonies, were processed. A total of 12,971 SNPs were detected against the reference genome of A. mellifera, 142 of which showed significant differences between colonies. We detected SNPs in coding regions, lncRNA, miRNA, rRNA, tRNA, among others. From the original data set, we also identified 647 SNPs located in protein-coding regions, 128 of which are related to 21 genes previously associated with defensive behavior, such as dop3 and dopR2, CaMKII and ADAR, obp9 and obp10, and members of the 5-HT family. We discuss the obtained results by considering the influence of polyandry and paternal lineages on the defensive behavior in AHB and provide baseline information to use this innovative molecular approach, ddRADseq, to assist in the selection and evaluation of honey bee stocks showing low defensive behavior for commercial uses.

Comprehensive Investigation of Fluoroquinolone Residues in Apis mellifera and Apis cerana Honey and Potential Risks to Consumers: A Five-Year Study (2014-2018) in Zhejiang Province, China

As a group of antibiotics largely used in China's animal husbandry, fluoroquinolone (FQ) residues in honey may pose potential threats to human health. This study performed a five-year investigation on the occurrence of FQ residues in honey in 521 Apis mellifera and 160 Apis cerana honey samples collected from Zhejiang Province, China and compared FQ residue profiles in honey with a subgroup of various factors. Deterministic and probabilistic risk assessments of exposure to FQ residues in honey were further conducted. Overall, four FQs were detected in 6.9% (47/681) of analyzed samples; banned norfloxacin with the highest level (7890 μg·kg-1) and detection frequency (4.9%) was the primary safety risk factor associated with honeybees raised in China. FQ detection frequency and concentration of rape honey was highest among four of the largest and most stable honeys (rape, acacia, chaste, and linden) in China. Processed honey from commercial sale channels had a significantly higher detection frequency of FQ residues than raw honey from apiaries. Deterministic assessment showed that the noncarcinogenic hazard quotient (HQ) value of the dietary intake of FQs by the local population was between 4.75 × 10-6 and 1.18 × 10-3, less than 1.0, indicating that FQ residues in honey posed a low risk for consumers. The order of the HQ value was ciprofloxacin > norfloxacin > enrofloxacin > ofloxacin. Probabilistic assessment showed that at P95, the HQ of FQs for the age groups of children, adolescents, adults, and older adults over 65 years ranged from 2.39 × 10-5 to 0.217, less than 1, and the exposure risk for adults was higher than for children and adolescents. Sensitivity analysis showed that FQ concentrations were the major contributors to health risks. Although a low risk was found, a strict hive management is needed for beekeepers regarding troubles of food safety, international trade, and human bacterial resistance.

Blue orchard bee (Hymenoptera: Megachilidae) origin and orchard growing region affect female retention at artificial nest sites in cherry orchards

The blue orchard bee, Osmia lignaria Say (Hymenoptera: Megachilidae), is a solitary, cavity-nesting species used for pollinating spring blooming crops. Commercial stocks are sourced from a few locations in the western United States but are sold across the country. However, the existence of local adaptations of these bees is unknown, such as the propensity to nest in nearby provided materials or to disperse broadly beyond release sites. In spring 2019, California- and Utah-sourced blue orchard bees were introduced into cherry orchards in both source and reciprocal states. Nest boxes were placed near (within 78 m) and far (500 m-1 km) from central bee release points. Paint-marked bees were released when floral resources were available. Observations of marked bees at nest boxes were used to evaluate female retention and dispersal pattern. Nesting bee counts in March-blooming California orchards revealed a significant difference in female retention by population source; over twice as many UT bees established nests than did CA bees. Few females were found at far nest sites. In May-blooming Utah orchards, counts of CA and UT bees were similar at near and far nest sites; neither female retention nor dispersal was significantly affected by bee origin. It is concerning that CA females were less likely to be retained in California orchards because the demand for commercial pollination is high for early-blooming California almond and cherry. Our results highlight the need to understand potential consequences of bee origin and their management on pollinator performance and reproduction in target crops.

Extracts of Talaromyces purpureogenus Strains from Apis mellifera Bee Bread Inhibit the Growth of Paenibacillus spp. In Vitro

Honey bees coexist with fungi that colonize hive surfaces and pollen. Some of these fungi are opportunistic pathogens, but many are beneficial species that produce antimicrobial compounds for pollen conservation and the regulation of pathogen populations. In this study, we tested the in vitro antimicrobial activity of Talaromyces purpureogenus strains isolated from bee bread against Paenibacillus alvei (associated with European foulbrood disease) and three Aspergillus species that cause stonebrood disease. We found that methanol extracts of T. purpureogenus strains B18 and B195 inhibited the growth of P. alvei at a concentration of 0.39 mg/mL. Bioactivity-guided dereplication revealed that the activity of the crude extracts correlated with the presence of diketopiperazines, a siderophore, and three unknown compounds. We propose that non-pathogenic fungi such as Talaromyces spp. and their metabolites in bee bread could be an important requirement to prevent disease. Agricultural practices involving the use of fungicides can disrupt the fungal community and thus negatively affect the health of bee colonies.

Individual and social defenses in Apis mellifera: a playground to fight against synergistic stressor interactions

The honeybee is an important species for the agri-food and pharmaceutical industries through bee products and crop pollination services. However, honeybee health is a major concern, because beekeepers in many countries are experiencing significant colony losses. This phenomenon has been linked to the exposure of bees to multiple stresses in their environment. Indeed, several biotic and abiotic stressors interact with bees in a synergistic or antagonistic way. Synergistic stressors often act through a disruption of their defense systems (immune response or detoxification). Antagonistic interactions are most often caused by interactions between biotic stressors or disruptive activation of bee defenses. Honeybees have developed behavioral defense strategies and produce antimicrobial compounds to prevent exposure to various pathogens and chemicals. Expanding our knowledge about these processes could be used to develop strategies to shield bees from exposure. This review aims to describe current knowledge about the exposure of honeybees to multiple stresses and the defense mechanisms they have developed to protect themselves. The effect of multi-stress exposure is mainly due to a disruption of the immune response, detoxification, or an excessive defense response by the bee itself. In addition, bees have developed defenses against stressors, some behavioral, others involving the production of antimicrobials, or exploiting beneficial external factors.

A systematic review of honey bee (Apis mellifera, Linnaeus, 1758) infections and available treatment options

BACKGROUND

Honey bees and honeycomb bees are very valuable for wild flowering plants and economically important crops due to their role as pollinators. However, these insects confront many disease threats (viruses, parasites, bacteria and fungi) and large pesticide concentrations in the environment. Varroa destructor is the most prevalent disease that has had the most negative effects on the fitness and survival of different honey bees (Apis mellifera and A. cerana). Moreover, honey bees are social insects and this ectoparasite can be easily transmitted within and across bee colonies.

OBJECTIVE

This review aims to provide a survey of the diversity and distribution of important bee infections and possible management and treatment options, so that honey bee colony health can be maintained.

METHODS

We used PRISMA guidelines throughout article selection, published between January 1960 and December 2020. PubMed, Google Scholar, Scopus, Cochrane Library, Web of Science and Ovid databases were searched.

RESULTS

We have collected 132 articles and retained 106 articles for this study. The data obtained revealed that V. destructor and Nosema spp. were found to be the major pathogens of honey bees worldwide. The impact of these infections can result in the incapacity of forager bees to fly, disorientation, paralysis, and death of many individuals in the colony. We find that both hygienic and chemical pest management strategies must be implemented to prevent, reduce the parasite loads and transmission of pathogens. The use of an effective miticide (fluvalinate-tau, coumaphos and amitraz) now seems to be an essential and common practice required to minimise the impact of Varroa mites and other pathogens on bee colonies. New, alternative biofriendly control methods, are on the rise, and could be critical for maintaining honey bee hive health and improving honey productivity.

CONCLUSIONS

We suggest that critical health control methods be adopted globally and that an international monitoring system be implemented to determine honey bee colony safety, regularly identify parasite prevalence, as well as potential risk factors, so that the impact of pathogens on bee health can be recognised and quantified on a global scale.

Overlapping exposure effects of pathogen and dimethoate on honeybee (Apis mellifera Linnaeus) metabolic rate and longevity

Introduction: Declines in honeybee abundance have been observed worldwide during last decades. This is partly due to plant protection agents used in intensive farming, landscaping and infrastructure maintenance. Another type of factors negatively affecting honeybees is the spread of diseases caused by different pathogens and pests. Lately, more focus has been paid to the interactions between different overlapping stressors affecting honeybee health, the combination of these often being more detrimental compared to individual stressors. The most widely used stress-evaluating methods take into account lethal- or motorial changes of the individuals or colonies. Comparatively little honeybee research has examined changes in initial recovery potential and physiological symptoms of toxification. The aim of this study was to examine the combined effect of Nosema apis and N. ceranae (according to a newer classification Vairimorpha apis and V. ceranae), the common causes of nosemosis in the honeybee Apis mellifera L., with the insecticide dimethoate. Methods: In this study, honeybee mortality and metabolic rate were used to assess the combined effects interactions of Nosema ssp. and dimethoate. Results: Our results showed that exposure to the low concentration of either dimethoate, either one or both species of Nosema ssp as single factors or in the combination had no significant effect on honeybee metabolic rate. The mortality increased with the two Nosema spp., as well as with infection by N. ceranae alone. The effect of dimethoate was observed only in combination with N. apis infection, which alone had no effect on individual honeybee mortality. Conclusion: This study demonstrates that the overlapping exposure to a non-lethal concentration of a pesticide and a pathogen can be hidden by stronger stressor but become observable with milder stressors.

The Ascosphaera apis Infection (Chalkbrood Disease) Alters the Gut Bacteriome Composition of the Honeybee

The declining honeybee populations are a significant risk to the productivity and security of agriculture worldwide. Although there are many causes of these declines, parasites are a significant one. Disease glitches in honeybees have been identified in recent years and increasing attention has been paid to addressing the issue. Between 30% and 40% of all managed honeybee colonies in the USA have perished annually over the past few years. American foulbrood (AFB) and European foulbrood (EFB) have been reported as bacterial diseases, Nosema as a protozoan disease, and Chalkbrood and Stonebrood as fungal diseases. The study aims to compare the bacterial community related to the Nosema ceranae and Ascosphaera apis infection on the gut of the honeybee and compare it with the weakly active honeybees. The Nosema-infected honeybees contain the phyla Proteobacteria as the significantly dominant bacterial phyla, similar to the weakly active honeybees. In contrast, the Ascosphaera (Chalkbrood) infected honeybee contains large amounts of Firmicutes rather than Proteobacteria.

First molecular detection of the presence of honey bee viruses in insects, Varroa destructor mites, and pollinated plants in an isolated region of Armenia

Background and Aim

Recently, viral diseases of honey bees (Apis mellifera) have presented an increasing threat to beekeeping. This study aimed to examine the presence of honey bee viruses in Apis and non-Apis bee species, the mite Varroa destructor, and pollinated plants in Armenia.

Materials and Methods

Sampling was performed in Tavush Province, in the northeast of the Republic of Armenia, from August to November 2019. Overall, 200 A. mellifera bees, 50 V. destructor mites, and 20 wasps were collected (corresponding to three bees, five mites, and 2-11 wasps in each investigated sample) and homogenized for RNA isolation and detection of viruses. Ten pollinated plants were taken from each plant, and 2 g of each sample was used for homogenization. In each investigated case Apis mellifera, Varroa destructor, Vespula germanica and plants received percentages of the virus presence.

Results

Six important honey bee viruses (acute bee paralysis virus [ABPV], deformed wing virus [DWV], A. mellifera norovirus [ANV], Lake Sinai virus-2 [LSV-2], Big Sioux River virus [BSRV], and A. mellifera filamentous virus [AmFV]) were detected in samples by polymerase chain reaction. Our results showed that DWV, ANV, and ABPV were the most common viruses in honey bees. All viruses were detected in wasps, but LSV-2 and ANV were present in almost all samples.

Conclusion

Our results showed that almost all viruses were present in V. destructor. Although ANV is very common in honey bees, it did not appear in any mite samples. Our study indicates that viruses typically associated with honey bees were also actively infecting wasps. Our data suggest that the survival of viruses in plants can be an important source of seasonal transmission of viruses to bees. In addition, pollinated plants can potentially serve as reservoirs for honey bee viruses.

When One's Not Enough: Colony Pool-Seq Outperforms Individual-Based Methods for Assessing Introgression in Apis mellifera mellifera

The human management of honey bees (Apis mellifera) has resulted in the widespread introduction of subspecies outside of their native ranges. One well known example of this is Apis mellifera mellifera, native to Northern Europe, which has now been significantly introgressed by the introduction of C lineage honey bees. Introgression has consequences for species in terms of future adaptive potential and long-term viability. However, estimating introgression in colony-living haplodiploid species is challenging. Previous studies have estimated introgression using individual workers, individual drones, multiple drones, and pooled workers. Here, we compare introgression estimates via three genetic approaches: SNP array, individual RAD-seq, and pooled colony RAD-seq. We also compare two statistical approaches: a maximum likelihood cluster program (ADMIXTURE) and an incomplete lineage sorting model (ABBA BABA). Overall, individual approaches resulted in lower introgression estimates than pooled colonies when using ADMIXTURE. However, the pooled colony ABBA BABA approach resulted in generally lower introgression estimates than all three ADMIXTURE estimates. These results highlight that sometimes one individual is not enough to assess colony-level introgression, and future studies that do use colony pools should not be solely dependent on clustering programs for introgression estimates.

Evaluating the Impact of Commonly Used Pesticides on Honeybees (Apis mellifera) in North Gonder of Amhara Region, Ethiopia

Global honeybee losses and colony decline are becoming continuous threat to the apicultural industry, as well as, for food security and environmental stability. Although the putative causes are still unclear, extensive exposure of bees to pesticides could be the possible factor for worldwide colony losses. This study was aimed at evaluating the impact of nine commonly used pesticide incidents on adult worker honeybees (A. mellifera) under the laboratory condition, in North Gonder of Amhara region, Ethiopia. Feeding test, contact test, and fumigation tests were carried out for each pesticide following the standard procedures, and each pesticide toxicity was compared to the standard toxic chemical, dimethoate 40% EC (positive control), and to 50% honey solution (negative control). The results revealed that all the tested pesticides caused significant deaths of the experimental bees ( $P<0.05$ ) in all the tests when compared to the negative control. Diazinon 60% EC, endosulfan 35% EC, and malathion 50% EC were appeared highly toxic causing 100% mortality of bees, while chlorsulfuron 75% WG killed 90% of the experimental bees as tested via feeding. On the other hand, agro-2, 4-D and its mixture with glycel 41% EC are moderately toxic, and mancozeb 80% WP and glycel 41% EC were slightly toxic to honeybees as compared to the positive control (dimethoate 40% EC). Suddenly, diazinon 60% EC and malathion 50% EC triggered 100% mortality of bees, while endosulfan 35% EC and chlorsulfuron 75% WG caused 63.63% and 90.82% of bee mortality, respectively, when evaluated via contact test. The fumigation test also showed that chlorsulfuron 75% WG, diazinon 60% EC, and endosulfan 35% EC caused 100%, 86.7%, and 65.6% mortality rate of bees. Our result also highlighted that tested LD50 of all pesticide incidents were significantly lower than the manufacturer-based LD50. This shows that local honeybees A. m. jemenetica are extremely sensitive to commonly used agricultural pesticides, which may affect the colony level due to the intensive application of these pesticides in Ethiopia.

Honey bee (Apis mellifera) wing images: a tool for identification and conservation

BACKGROUND

The honey bee (Apis mellifera) is an ecologically and economically important species that provides pollination services to natural and agricultural systems. The biodiversity of the honey bee in parts of its native range is endangered by migratory beekeeping and commercial breeding. In consequence, some honey bee populations that are well adapted to the local environment are threatened with extinction. A crucial step for the protection of honey bee biodiversity is reliable differentiation between native and nonnative bees. One of the methods that can be used for this is the geometric morphometrics of wings. This method is fast, is low cost, and does not require expensive equipment. Therefore, it can be easily used by both scientists and beekeepers. However, wing geometric morphometrics is challenging due to the lack of reference data that can be reliably used for comparisons between different geographic regions.

FINDINGS

Here, we provide an unprecedented collection of 26,481 honey bee wing images representing 1,725 samples from 13 European countries. The wing images are accompanied by the coordinates of 19 landmarks and the geographic coordinates of the sampling locations. We present an R script that describes the workflow for analyzing the data and identifying an unknown sample. We compared the data with available reference samples for lineage and found general agreement with them.

CONCLUSIONS

The extensive collection of wing images available on the Zenodo website can be used to identify the geographic origin of unknown samples and therefore assist in the monitoring and conservation of honey bee biodiversity in Europe.

Spermidine dietary supplementation and polyamines level in reference to survival and lifespan of honey bees

Honey bee health has been an important and ongoing topic in recent years. Honey bee is also an important model organism for aging studies. Polyamines, putrescine, spermidine and spermine, are ubiquitous polycations, involved in a wide range of cellular processes such as cell growth, gene regulation, immunity, and regulation of lifespan. Spermidine, named longevity elixir, has been most analysed in the context of aging. One of the several proposed mechanisms behind spermidine actions is antioxidative activity. In present study we showed that dietary spermidine supplementation: (a) improved survival, (b) increased the average lifespan, (c) influenced the content of endogenous polyamines by increasing the level of putrescine and spermidine and decreasing the level of spermine, (d) reduced oxidative stress (MDA level), (e) increased the antioxidant capacity of the organism (FRAP), (f) increased relative gene expression of five genes involved in polyamine metabolism, and (g) upregulated vitellogenin gene in honey bees. To our knowledge, this is the first study on honey bee polyamine levels in reference to their longevity. These results provide important information on possible strategies for improving honey bee health by introducing spermidine into their diet. Here, we offer spermidine concentrations that could be considered for that purpose.

Greenhouse Gas (GHG) Emissions from Honey Production: Two-Year Survey in Italian Beekeeping Farms

The objective of this study was to quantify the climate change (CC) impact of the honey supply chain in different beekeeping systems and farms, over two consecutive years. The CC impact category is quantified as kg CO₂ equivalent and it evaluates the GHG emissions, mainly CO₂, N₂O, and CH₄. The results ranged from 0.44 to 3.18 (p = 0.039) kg CO₂e/kg honey with higher values in 2021 than 2020. The main contributors to climate change of the honey supply chain are represented by transport and supplemental feeding inputs. The beekeeping system (migratory or stationary) influenced CC: the contribution to CC for stationary farms was estimated at 0.58 kg CO₂e/kg honey and 2.48 for migratory ones (p < 0.001). Given the close connection between honey yield and LCA results due to the unit of measurement of impact, i.e., kg of honey produced, an index was developed (wildflower honey climate index) as a simple benchmark tool for prediction of honey yield in the survey context. Using the data from the present study, we found that the index is positively related to honey yield (r = 0.504; p < 0.05) but negatively related to supplemental feeding (r = -0.918; p < 0.01) and overall carbon footprint (r = -0.657; p < 0.05). Further studies are needed to better explain the effects of weather on honey production, as well as environmental impact.

Mixture effects of thiamethoxam and seven pesticides with different modes of action on honey bees (Aplis mellifera)

Even though honey bees in the field are routinely exposed to a complex mixture of many different agrochemicals, few studies have surveyed toxic effects of pesticide mixtures on bees. To elucidate the interactive actions of pesticides on crop pollinators, we determined the individual and joint toxicities of thiamethoxam (THI) and other seven pesticides [dimethoate (DIM), methomyl (MET), zeta-cypermethrin (ZCY), cyfluthrin (CYF), permethrin (PER), esfenvalerate (ESF) and tetraconazole (TET)] to honey bees (Aplis mellifera) with feeding toxicity test. Results from the 7-days toxicity test implied that THI elicited the highest toxicity with a LC₅₀ data of 0.25 (0.20-0.29) μg mL^-1, followed by MET and DIM with LC₅₀ data of 4.19 (3.58-4.88) and 5.30 (4.65-6.03) μg mL^-1, respectively. By comparison, pyrethroids and TET possessed relatively low toxicities with their LC₅₀ data from the range of 33.78 (29.12-38.39) to 1125 (922.4-1,442) μg mL^-1. Among 98 evaluated THI-containing binary to octonary mixtures, 29.59% of combinations exhibited synergistic effects. In contrast, 18.37% of combinations exhibited antagonistic effects on A. mellifera. Moreover, 54.8% pesticide combinations incorporating THI and TET displayed synergistic toxicities to the insects. Our findings emphasized that the coexistence of several pesticides might induce enhanced toxicity to honey bees. Overall, our results afforded worthful toxicological information on the combined actions of neonicotinoids and current-use pesticides on honey bees, which could accelerate farther comprehend on the possible detriments of other pesticide mixtures in agro-environment.

Sunflower-Associated Reductions in Varroa Mite Infestation of Honey Bee Colonies

Landscapes can affect parasite epidemiology in wild and agricultural animals. Honey bees are threatened by loss of floral resources and by parasites, principally the mite Varroa destructor and the viruses it vectors. Existing mite control relies heavily on chemical treatments that can adversely affect bees. Alternative, pesticide-free control methods are needed to mitigate infestation with these ectoparasites. Many flowering plants provide nectar and pollen that confer resistance to parasites. Enrichment of landscapes with antiparasitic floral resources could therefore provide a sustainable means of parasite control in pollinators. Floral rewards of Asteraceae plants can reduce parasitic infection in diverse bee species, including honey and bumble bees. Here, we tested the effects of sunflower (Helianthus annuus) cropland and pollen supplementation on honey bee resistance to macro- and microparasites. Although sunflower had nonsignificant effects on microparasites, We found that increased sunflower pollen availability correlated with reduced Varroa mite infestation in landscapes and pollen-supplemented colonies. At the landscape level, each doubling of sunflower crop area was associated with a 28% reduction in mite infestation. In field trials, late-summer supplementation of colonies with sunflower pollen reduced mite infestation by 2.75-fold relative to artificial pollen. United States sunflower crop acreage has declined by 2% per year since 1980, however, suggesting reduced availability of this floral resource. Although further research is needed to determine whether the observed effects represent direct inhibition of mite fecundity or mite-limiting reductions in honey bee brood-rearing, our findings suggest the potential for sunflower plantings or pollen supplements to counteract a major driver of honey bee losses worldwide.

Preliminary Survey of Pathogens in the Asian Honey Bee (Apis cerana) in Thailand

Widespread parasites, along with emerging threats, globalization, and climate change, have greatly affected honey bees' health, leading to colony losses worldwide. In this study, we investigated the detection of biotic stressors (i.e., viruses, microsporidian, bacteria, and fungi) in Apis cerana by surveying the colonies across different regions of Thailand (Chiang Mai in the north, Nong Khai and Khon Kaen in the northeast, and Chumphon and Surat Thani in the south, in addition to the Samui and Pha-ngan islands). In this study, we detected ABPV, BQCV, LSV, and Nosema ceranae in A. cerana samples through RT-PCR. ABPV was only detected from the samples of Chiang Mai, whereas we found BQCV only in those from Chumphon. LSV was detected only in the samples from the Samui and Pha-ngan islands, where historically no managed bees are known. Nosema ceranae was found in all of the regions except for Nong Khai and Khon Kaen in northeastern Thailand. Paenibacillus larvae and Ascosphaera apis were not detected in any of the A. cerana samples in this survey. The phylogenetic tree analysis of the pathogens provided insights into the pathogens' movements and their distribution ranges across different landscapes, indicating the flow of pathogens among the honey bees. Here, we describe the presence of emerging pathogens in the Asian honey bee as a valuable step in our understanding of these pathogens in terms of the decline in eastern honey bee populations.

The adverse impact on lifespan, immunity, and forage behavior of worker bees (Apis mellifera Linnaeus 1758) after exposure to flumethrin

Several pyrethroids (such as flumethrin and fluvalinate) with low toxicity to honey bees and comparable high toxicity to mites are used worldwide as acaricides. However, flumethrin has been used for a long time in colonies to control Varroa destructor and the honey bees might be exposed to flumethrin cumulatively, which could affect the health of honey bee colonies. This study evaluated the potential adverse effects of direct flumethrin exposure on worker bees under laboratory and colony conditions. Under laboratory conditions, downregulation of genes related to immune was observed when worker bees were exposed to flumethrin above 1/16 LD₅₀; at levels above 1/8 LD₅₀, olfactory learning was impaired, and genes related to learning memory were downregulated; and at >1/4 LD₅₀, their lifespan was shortened. Monitoring with radio frequency identification (RFID) revealed that worker bees in a colony exposed to flumethrin above 1/8 LD₅₀ had a shortened lifespan and reduced foraging ability. When worker bees are exposed to >1/4 LD₅₀ of flumethrin, it can lead to excessive rest day behavior. These results indicate that applying flumethrin in colonies may pose a severe health risk to honey bees and reveal the urgent need to develop non-toxic and highly effective acaricides.

Strategies and techniques to mitigate the negative impacts of pesticide exposure to honey bees

In order to support food, fiber, and fuel production around the world, billions of kilograms of pesticides are applied to crop fields every year to suppress pests, plant diseases and weeds. These fields are often home to the most important commercial pollinators, honey bees (Apis spp.), which improve yield and quality of many agricultural products. The pesticides applied to support crop health can be detrimental to honey bee health. The conflict of pesticide use and reliance on honey bees contributes to significant honey bee colony losses across the world. Recommendations for reducing impact on honey bees are generally suggested in literature, pesticide regulations, and by crop consultants, but without a considerable discussion of the realistic limitations of protecting honey bees. New techniques in farming and beekeeping can reduce pesticide exposure through reduction in bee exposure, reduced toxicity of pesticides, and remedies that can be in response to exposure. However, lack of assessment of those new techniques under a systematical, comprehensive framework may overestimate or underestimate these techniques' potential to protect honey bees from pesticide damage. In this review, we summarize the current and arising strategies and techniques with the goal to inspire the development and adoption of pesticide mitigation practices for both agriculture and apiculture.

A GABA Receptor Modulator and Semiochemical Compounds Evidenced Using Volatolomics as Candidate Markers of Chronic Exposure to Fipronil in Apis mellifera

Among the various "omics" approaches that can be used in toxicology, volatolomics is in full development. A volatolomic study was carried out on soil bacteria to validate the proof of concept, and this approach was implemented in a new model organism: the honeybee Apis mellifera. Emerging bees raised in the laboratory in pain-type cages were used. Volatolomics analysis was performed on cuticles, fat bodies, and adhering tissues (abdomens without the digestive tract), after 14 and 21 days of chronic exposure to 0.5 and 1 µg/L of fipronil, corresponding to sublethal doses. The VOCs analysis was processed using an HS-SPME/GC-MS method. A total of 281 features were extracted and tentatively identified. No significant effect of fipronil on the volatolome could be observed after 14 days of chronic exposure. Mainly after 21 days of exposure, a volatolome deviation appeared. The study of this deviation highlighted 11 VOCs whose signal abundances evolved during the experiment. Interestingly, the volatolomics approach revealed a VOC (2,6-dimethylcyclohexanol) that could act on GABA receptor activity (the fipronil target) and VOCs associated with semiochemical activities (pheromones, repellent agents, and compounds related to the Nasonov gland) leading to a potential impact on bee behavior.

Long-term spatiotemporal patterns in the number of colonies and honey production in Mexico

Honey bee decline is currently one of the world's most serious environmental issues, and scientists, governments, and producers have generated interest in understanding its causes and consequences in honey production and food supply. Mexico is one of the world's top honey producers, however, the honey bee population's status has not been documented to date. Based on 32 years of data from beekeeping, we make a country-level assessment of honey bee colony trends in Mexico. We use generalized additive mixed models to measure the associations between the percent change in honey bee hives and the percent change in honey yield per hive in relation to land-use, climate, and socioeconomic conditions. Despite the fact that the average annual yield per hive increased from 1980 to 2012, we detected a significant decline in the percent change in the number of honey bee hives across the time period studied. We also found a relationship between climatic conditions and agricultural land use, with agriculture increases and high temperatures producing a decrease in the percent change in honey yield. We found a relationship between a reduction in the temperature range (the difference between maximum and minimum temperatures) and a decrease in the percent change in the number of hives, while socioeconomic factors related to poverty levels have an impact on the number of hives and honey yields. Although long-term declines in hive numbers are not correlated with poverty levels, socioeconomic factors in states with high and medium poverty levels limit the increase in honey yield per hive. These results provide evidence that land-use changes, unfavorable climatic conditions, political, and socioeconomic factors are partially responsible for the reductions in the percent change in honey bee hives in Mexico.

The Role of Honey Bee Derived Aliphatic Esters in the Host-Finding Behavior of Varroa destructor

Varroa destructor is an obligate ectoparasite of honey bees and shifted from its original host Apis cerana to the new host Apis mellifera in the first half of the twentieth century. The host shift has resulted in a great threat to the health and survival of A. mellifera colonies worldwide. Chemical signals play a crucial role in all aspects of the Varroa life cycle, including host finding. However, the chemical cues that affect the host finding behavior of Varroa mites are still not fully understood. In this study, we systematically profiled the headspace volatiles of both worker and drone larvae of the two honey bee species by using solid phase micro-extraction coupled to gas chromatography-mass spectrometry (SPME-GC-MS), and then used electrophysiological recording and Y-tube olfactometer bioassay to study the potential roles of the selected compounds. The chemical profiling showed that there were four aliphatic esters, ethyl myristate (EM), methyl palmitate (MP), ethyl palmitate (EP), and ethyl oleate (EO) commonly detected from all four types of larval hosts. Among them, EM was a new substance identified from honey bee headspace volatiles. Results from electrophysiological recordings indicated that all the aliphatic esters could elicit significant responses of Varroa pit organs on its forelegs. Moreover, behavioral analyses revealed that EM could significantly attract V. destructor at a medium dosage (10 µg), while MP had no observable effect on the mites and both EP and EO were able to repel the parasites. Our findings suggest an important role of host-derived aliphatic esters in Varroa host finding, and provide new chemicals for Varroa monitoring and control.

Uptrend in global managed honey bee colonies and production based on a six-decade viewpoint, 1961-2017

We conducted a retrospective study to examine the long-term trends for the global honey bee population and its two main products: honey and beeswax. Our analysis was based on the data collected by the Food and Agriculture Organization of the United Nations from 1961 to 2017. During this period, there were increases in the number of managed honey bee colonies (85.0%), honey production (181.0%) and beeswax production (116.0%). The amount of honey produced per colony increased by 45.0%, signifying improvements in the efficiency for producing honey. Concurrently, the human population grew by 144.0%. Whilst the absolute number of managed colonies increased globally, the number per capita declined by 19.9% from 13.6 colonies per 1000 population in 1961 to 10.9 colonies per 1000 population in 2017. Beeswax had a similar trend as the global production per capita reduced by 8.5% from 8.2 to 7.5 kg per 1000 population. In contrast, the global honey production per capita increased by 42.9% at the global level. The global human population growth outpaced that of managed honey bee colonies. Continuation of this trend raises the possibility of having a shortfall of pollinators to meet the increasing consumer demand for pollinated crops. To mitigate these challenges locally driven solutions will be key as influencing factors differed geographically.

Honey bee colony loss linked to parasites, pesticides and extreme weather across the United States

Honey bee (Apis mellifera) colony loss is a widespread phenomenon with important economic and biological implications, whose drivers are still an open matter of investigation. We contribute to this line of research through a large-scale, multi-variable study combining multiple publicly accessible data sources. Specifically, we analyzed quarterly data covering the contiguous United States for the years 2015-2021, and combined open data on honey bee colony status and stressors, weather data, and land use. The different spatio-temporal resolutions of these data are addressed through an up-scaling approach that generates additional statistical features which capture more complex distributional characteristics and significantly improve modeling performance. Treating this expanded feature set with state-of-the-art feature selection methods, we obtained findings that, nation-wide, are in line with the current knowledge on the aggravating roles of Varroa destructor and pesticides in colony loss. Moreover, we found that extreme temperature and precipitation events, even when controlling for other factors, significantly impact colony loss. Overall, our results reveal the complexity of biotic and abiotic factors affecting managed honey bee colonies across the United States.

Genomic architecture and sexually dimorphic expression underlying immunity in the red mason bee, Osmia bicornis

Insect pollinators provide crucial ecosystem services yet face increasing environmental pressures. The challenges posed by novel and reemerging pathogens on bee health means we need to improve our understanding of the immune system, an important barrier to infections and disease. Despite the importance of solitary bees, which are ecologically relevant, our understanding of the genomic basis and molecular mechanisms underlying their immune potential, and how intrinsic and extrinsic factors may influence it is limited. To improve our understanding of the genomic architecture underlying immunity of a key solitary bee pollinator, we characterized putative immune genes of the red mason bee, Osmia bicornis. In addition, we used publicly available RNA-seq datasets to determine how sexes differ in immune gene expression and splicing but also how pesticide exposure may affect immune gene expression in females. Through comparative genomics, we reveal an evolutionarily conserved set of more than 500 putative immune-related genes. We found genome-wide patterns of sex-biased gene expression, with greater enrichment of immune-related processes among genes with higher constitutive expression in males than females. Our results also suggest an up-regulation of immune-related genes in response to exposure to two common neonicotinoids, thiacloprid and imidacloprid. Collectively, our study provides important insights into the gene repertoire, regulation and expression differences in the sexes of O. bicornis, as well as providing additional support for how neonicotinoids can affect immune gene expression, which may affect the capacity of solitary bees to respond to pathogenic threats.

Honeybee (Apis mellifera) resistance to deltamethrin exposure by Modulating the gut microbiota and improving immunity

Honeybees (Apis mellifera) are important economic insects and play important roles in pollination and maintenance of ecological balance. However, the use of pesticides has posed a substantial threat to bees in recent years, with the more widely used deltamethrin being the most harmful. In this study, we found that deltamethrin exposure significantly reduced bee survival in a dose-dependent manner (p = 0.025). In addition, metagenomic sequencing further revealed that DM exposure significantly reduced the diversity of the bee gut microbiota (Chao1, p < 0.0001; Shannon, p < 0.0001; Simpson, p < 0.0001) and decreased the relative abundance of core species of the gut microbiota. Importantly, in studies of GF-bees, we found that the colonization of important gut bacteria such as Gilliamella apicola and Lactobacillus kunkeei significantly increased bee resistance to DM (survival rate increased from 16.7 to 66.7%). Interestingly, we found that the immunity-genes Defensin-2 and Toll were significantly upregulated in bees after the colonization of gut bacteria. These results suggest that gut bacteria may protect against DM stress by improving host immunity. Our findings provide an important rationale for protecting honeybees from pollutants from the perspective of gut microbes.