Honey bee toxicology

Honeybee toxicity of pesticides used in United States maize and soybean production, 1998-2020

Pesticides are widely used around the world and have demonstrated benefits to crop production. However, pesticides have also been associated with negative impacts to nontarget organisms, including pollinators. Here, we combined pesticide usage and toxicity data to create a toxicity index, which shows that pesticide hazard to honeybees (Apis mellifera) has changed substantially in U.S. maize (Zea mays) and soybean (Glycine max) production between 1998 and 2020. To reduce potential risks to honeybees and increase the eco-efficiency of crop production, efforts should be made to refine management strategies for pests that contribute most to the honeybee toxicity index. In maize, Coleoptera and Lepidoptera pests drive pesticide usage most responsible for hazard to honeybees, although the relative hazard from targeting those pests has decreased over time. In soybean, hemipteran pests were the largest relative contributor to insecticide honeybee hazard. Specific pests that contributed to honeybee toxicity hazard included corn rootworm species (Diabrotica spp.), silk-eating insects, and cutworms in maize, and stink bugs (family Pentatomidae) and aphid species (Family Aphididae) in soybean. We combined crop yield data with the toxicity index to quantify the eco-efficiency, a measure of crop yield per unit of toxicity hazard. While crop yield for both maize and soybean increased steadily throughout the study period, eco-efficiency decreased in both crops between 2012 and 2020, suggesting increases in crop yield have failed to keep pace with increases in insecticide hazard to honeybees.

Impact of a lambda-cyhalothrin formulation residues on larval Apis mellifera: examining midgut and fat body morphological response to insecticide chronic exposure

Pollination by honey bees (Apis mellifera) is crucial for maintaining biodiversity and crop yields. However, the widespread use of pesticides may threaten bees' survival by contaminating their resources. Lambda-cyhalothrin, a neurotoxic insecticide commonly used in agricultural pest control, poses particular risks. In insects, the midgut and fat body serve as primary barriers against xenobiotics, and exposure to these chemicals during larval development can impact adult bees. This study aimed to assess whether the residual concentration of lambda-cyhalothrin in pollen grains affects the midgut and fat body of larval A. mellifera workers after chronic exposure. The midgut epithelium of larvae exposed to a lambda-cyhalothrin-based insecticide (λ-CBI) exhibited autophagic vacuoles, apical cell protrusions, apocrine secretion, nuclear pyknosis, and high levels of polysaccharides and glycoconjugates in the cytoplasm, with smaller amounts in the brush border. Histochemical analysis revealed areas of vacuolation and damage to cell integrity in the midgut. In fat body cells, the insecticide increased polysaccharide storage and decreased lipid droplet diameter. Despite the histopathological damage, no effects were found in the larval development and adult emergence. These findings suggest the occurrence of apoptosis and autophagy in midgut cells and alterations in nutrient storage in the fat body of A. mellifera larvae exposed to the λ-CBI, potentially impacting the physiology and development of this pollinator with possible effects on adult workers.

Short-term persistence of foliar insecticides and fungicides in pumpkin plants and their pollinators

To minimize the risk to bees and other beneficial insects, plant protection chemicals are typically applied to pollinator-dependent crop plants when flowers are absent or unopened. However, this approach does not entirely remove the risk of pollinator exposure. Much research has focused on negative effects of systemic insecticides (e.g., seed treatments) on pollinators, but less is known about the level of hazard posed by translocation of non-systemic foliar-applied pesticides to pollen and nectar that bees consume. In this study we assess the frequency and persistence of six foliar-applied pesticides in pumpkin (Cucurbita pepo) tissues and in their bee visitors. We analyzed residues of three insecticides (carbaryl, lambda-cyhalothrin, permethrin) and three fungicides (chlorothalonil, quinoxyfen, triflumizole) in pumpkin leaves, pollen, and nectar collected from five farms in the north-central USA, one day before a spray event, and one, three, and seven days after. Bees foraging on pumpkin flowers were collected one day before and one day after spray and screened for the same pesticides. Overall, insecticides were present in 56% of leaf samples. Compared to leaves, fewer pollen (insecticide detected in 16%, fungicide in 16%) and nectar samples (14%, 0%) contained pesticides. We detected one insecticide (carbaryl) in two out of 69 samples of foraging bees, and only in male squash bees (not in bumble or honey bees), which have life history traits that bring them into prolonged close contact with the sprayed crop plants. The persistence of some agrochemicals in leaves, pollen, and nectar up to a week following application merits consideration when managing pollinator-dependent crops. Even pesticides that are traditionally considered contact-based and applied when flowers are unopened can reach pollen and nectar and produce measurable risk to bees.

Lactic Acid Bacteria: A Probiotic to Mitigate Pesticide Stress in Honey Bee

Using probiotics, especially those containing lactic acid bacteria (LAB), to support honey bee health and alleviate the negative effects of pesticides represents a promising approach for sustainable beekeeping. Probiotics have shown their ability to boost honey bee immune systems, counteract pesticide impacts, and lower disease rates. Bacteria like Lactobacillus and Bifidobacterium have demonstrated their ability to degrade organophosphorus pesticides using phosphatase enzymes. Additionally, these bacteria are resistant to the harmful effects of pesticides and aid in detoxification. Furthermore, supplementing with LAB positively affects colony growth, resulting in increased honey production, improved pollen storage, and higher brood counts. Various methods of delivering probiotics, such as powdered supplements, sucrose syrup, and pollen patties, have been explored, each with its own set of challenges and considerations. Despite making significant progress, further study is still required to fully comprehend the precise interactions between probiotics and the physiology of honey bees, to improve delivery strategies, and to evaluate the wider ecological effects on hive microbiomes. By implementing probiotic strategies in beekeeping practices, we can create stronger and more resilient honey bee colonies that can thrive amidst environmental challenges, thus promoting the sustainability of pollination services.

Sub-lethal exposure to 2,4-Dichlorophenoxyacetic acid disrupts nursing and foraging behaviors in honey bees

A popular herbicide from the chlorophenoxy group, 2,4-Dichlorophenoxyacetic acid (2,4-D) effectively controls broadleaf weeds in agricultural environments. However, its application threatens honey bee habitats and has been implicated in colony collapse disorder (CCD) due to its toxic effects. While the general hazards of 2,4-D to honey bees are recognized, its specific impact on nursing and foraging behaviors remains poorly understood. This study quantified the lethal dose (LD50) of 2,4-D for honey bees across developmental stages, finding LD50 values of 104.1 μg/bee for newly emerged bees, 456.6 μg/bee for nurse bees, and 221.6 μg/bee for foragers. We further investigated sub-lethal effects on nursing and foraging, observing that exposure led to significant reductions in hypopharyngeal gland (HG) acini size, essential for brood care, and decreased expression of AmGr10, an amino acid receptor gene linked to nursing behavior. For foragers, sub-lethal 2,4-D exposure impaired gustatory responsiveness to key feeding stimuli, such as sucrose and glucose. This impairment corresponded with a decrease in AmGr1 expression, a taste receptor gene critical for resource detection. Additionally, affected foragers showed reduced olfactory learning and memory, likely due to decreased expression of the octopamine receptor AmOA1, essential for associative learning processes. These findings provide compelling evidence that sub-lethal abdominal exposure to 2,4-D disrupts both nursing and foraging behaviors by impairing physiological and cognitive functions, ultimately jeopardizing colony health and resilience.

Unveiling Molecular Mechanisms Mediating Coumaphos Tolerance in Western Honey Bees (Apis mellifera)

Honey bees (Apis mellifera) are managed pollinators playing a critical role in global agriculture. Among factors linked to bee decline, the ectoparasitic varroa mite (Varroa destructor) is a major stressor. Coumaphos is an organophosphate pro-insecticide known for its selectivity toward honey bees, rendering it an effective in-hive treatment against varroa mites. This study investigated the molecular mechanisms underlying coumaphos tolerance in honey bees. Coumaphos-oxon inhibition studies with recombinantly expressed acetylcholinesterases of bees and mites precluded toxicodynamic reasons for the observed selectivity. Synergist bioassays and biochemical studies confirmed that honey bee CYP9Q2 is a key enzyme involved in coumaphos detoxification, particularly by its catalytic capacity to hydroxylate coumaphos-oxon. Bioassays with transgenic Drosophila expressing CYP9Q2 validated our molecular findings. Enzyme inhibition studies revealed suicide substrate properties for coumaphos leading to the inactivation of P450s during coumaphos oxidation. This study demonstrated the complexity of P450-mediated coumaphos activation and inactivation driving honey bee selectivity.

Azoxystrobin hides the respiratory failure of low dose sulfoxaflor in bumble bees

Pollinators are exposed to multiple pesticides during their lifetime. Various pesticides are used in agriculture and thus not all mixtures have been tested against each other and little is known about them. In this article, we investigate the impact of sulfoxaflor, a novel sulfoximine insecticide, and azoxystrobin, a widely used strobilurin fungicide, on bumble bee Bombus terrestris worker survival and physiological functions. The dosages used in this experiment are selected from dose response experiments based on LD50 data. Due to variable interactive effects on survival, our findings reveal distinct effects on bumble bee metabolic rate and respiratory patterns induced by sulfoxaflor in combination with azoxystrobin, shedding light on previously unexplored aspects of its physiological impact. Notably, we observed noteworthy differences between oral and contact treatments, emphasizing the importance of considering distinct application methods when evaluating pesticide effects and interactions. Specifically, our results indicate that azoxystrobin can mitigate the impact of sulfoxaflor, suggesting dose-dependent antagonistic interaction between these pesticides in contact exposure. In oral exposure, however, Amistar tended to potentiate the sulfoxaflor effect. This study contributes valuable insights into the multifaceted dynamics of pesticide exposure and interactions, paving the way for a more nuanced understanding of their implications on pollinator health.

Metals in honey from bees as a proxy for environmental contamination in the United States

This is the first large bio-surveillance study examining the contents and geographic variation of metals of public health concern-arsenic (As), lead (Pb), cadmium (Cd), nickel (Ni), chromium (Cr), and cobalt (Co)-in honey samples collected across the United States. Metal concentrations were measured using ICP-MS, and the spatial distribution pattern of these contaminants was evaluated using statistical and GIS tools. The mean (highest) values (in μg/kg) were 3.8 (170) for As, 8.0 (451) for Pb, and 0.75 (8.1) for Cd. These values, as well as the mean (highest) concentrations of 29.5 (516) for Ni, 14.3 (166) for Co, and 19.6 (11) for Cr, were markedly lower than global averages reported in other countries. The study identified distinct geographic patterns of honey contamination; particularly high As levels were found in northwestern states, while high Co was measured in the southeast. Health risk calculations based on the hazard quotient (HQ) and hazard index (HI) were below 1 for a daily tablespoon (21g) of honey consumption, indicating no adverse health concerns for children and adults, and all samples fell below the 1.0 × 10-6 threshold for carcinogenic risk from As. The variation in metal concentrations found in samples from different states may reflect the influence of air, water, or soil pollution, as well as differential accumulation across plant species, and the distinct geographic clustering of As and Co warrants further investigation to determine the sources of these metals and to assess public health risks, particularly for As, a well-known carcinogen. In sum, this initial study provides baseline values of metal concentrations in honey that can be useful for monitoring future pollution trends, identifying target areas where reductions of emissions or remediation efforts are most critical, and facilitating discovery in environmental exposures (the exposome) and health research, including on cancer and cardiovascular diseases.

Impact of chlorantraniliprole on honey bees: Differential sensitivity and biological responses in Apis mellifera and Apis cerana

Chlorantraniliprole (CAP), a diamide insecticide, is extensively applied to combat pests in various crops. However, the widespread use of insecticides has raised concerns about their potential impact on pollinators. In the present study, we explored the toxic effects of CAP in two important honey bee species, Apis mellifera and Apis cerana. The 48 h LC50 values of CAP for A. mellifera and A. cerana was 256.052 mg/L and 109.709 mg/L, implying that A. cerana is more sensitive to CAP. Prolonged exposure to 40 mg/L CAP significantly impaired sucrose responsiveness and climbing activity in both bee species. Both species showed a decrease in GR activity and GSH content with increasing CAP concentration. By contrast, the activities of GST, CAT, P450 and NAD-MDH were increased in both A. mellifera and A. cerana, but the differences between the 10 mg/L and 40 mg/L treatments were less pronounced in A. mellifera. Moreover, the immune related genes exhibited differential responses to CAP when comparing the two species. Low CAP concentrations led to down-regulation in expression of toll but up-regulation in expression of apideacin and hymeopatecin in A. mellifera, whereas A. cerana exhibited minimal changes in these genes. Additionally, CAP significantly inhibited the expression of ER stress response genes gp-93 and P58 in A. mellifera, while 10 mg/L of CAP promoted P58 expression in A. cerana. Our results highlight species-specific effects with the possible, distinct detoxification mechanisms and immune responses between A. mellifera and A. cerana. These findings serve as a foundation for further evaluating the safety of CAP for honey bee species and offer insights into the scientific use of pesticides.

Artificial intelligence-driven tool for spectral analysis: identifying pesticide contamination in bees from reflectance profiling

Pesticide poisoning constantly threatens bees as they forage for resources in pesticide-treated crops. This poisoning requires thorough investigation to identify its causes, underscoring the importance of reliable pesticide detection methods for bee monitoring. Infrared spectroscopy provides reflectance data across hundreds of spectral bands (hyperspectral reflectance), presumably enabling the efficient classification of pesticide contamination in bee carcasses using artificial intelligence (AI) models, such as machine learning. In this study, bee contamination by commercial formulations of three insecticides-dimethoate (organophosphate), fipronil (phenylpyrazole), and imidacloprid (neonicotinoid)-as well as glyphosate, the most widely used herbicide globally, was detected using machine learning models. These models classified the hyperspectral reflectance profiles of the body surfaces of contaminated bees. The best-performing model, the linear discriminant analysis, achieved 98 % accuracy in discriminating contamination across species Apis mellifera, Melipona mondury, and Partamona helleri, with prediction speeds of 0.27 s. Our pioneering study introduced an effective method for discerning multiple classes of bees contaminated with pesticides using hyperspectral reflectance. An AI-driven spectral data analysis tool (https://github.com/bernardesrodrigoc/MACSS) was developed for the purpose of identifying and characterizing new samples through their spectral characteristics. This platform aids efforts to monitor and conserve bee populations and holds potential importance in environmental monitoring, agricultural research, and industrial quality control.

Molecular Impact of Sublethal Spinetoram Exposure on Honeybee (Apis mellifera) Larval and Adult Transcriptomes

Pesticide toxicity is a global concern for honeybee populations, and understanding these effects at the molecular level is critical. This study analyzed the transcriptome of honeybees at larval and adult stages after chronic exposure to a sublethal dose (0.0017 µg a.i./larva) of spinetoram (SPI) during the larval phase. Four groups were used: acetone-treated honeybee larvae (ATL), acetone-treated honeybee adults (ATAs), SPI-treated honeybee larvae (STL), and SPI-treated honeybee adults (STAs). In total, 5719 differentially expressed genes (DEGs) were identified for ATL vs. ATAs, 5754 for STL vs. STAs, 273 for ATL vs. STL, and 203 for ATAs vs. STAs (FC ≤ 1.5, p < 0.05). In response to SPI, 29 unique DEGs were identified in larvae and 42 in adults, with 23 overlapping between comparisons, suggesting genes linked to SPI toxicity. Gene ontology analysis showed that SPI affected metabolism-related genes in larvae and lipid-transport-associated genes in adults. KEGG pathway analysis revealed an enrichment of pathways predominantly associated with metabolism, hormone biosynthesis, and motor proteins in STL. The transcriptomic data were validated by qPCR. These findings demonstrated that SPI disrupts essential molecular processes, potentially harming honeybee development and behavior, underscoring the need for safer agricultural practices.

The neonicotinoid acetamiprid reduces larval and adult survival in honeybees (Apis mellifera) and interacts with a fungicide mixture

Plant protection products (PPPs), which are frequently used in agriculture, can be major stressors for honeybees. They have been found abundantly in the beehive, particularly in pollen. Few studies have analysed effects on honeybee larvae, and little is known about effects of insecticide-fungicide-mixtures, although this is a highly realistic exposure scenario. We asked whether the combination of a frequently used insecticide and fungicides would affect developing bees. Honeybee larvae (Apis mellifera carnica) were reared in vitro on larval diets containing different PPPs at two concentrations, derived from residues found in pollen. We used the neonicotinoid acetamiprid, the combined fungicides boscalid/dimoxystrobin and the mixture of all three substances. Mortality was assessed at larval, pupal, and adult stages, and the size and weight of newly emerged bees were measured. The insecticide treatment in higher concentrations significantly reduced larval and adult survival. Interestingly, survival was not affected by the high concentrated insecticide-fungicides-mixture. However, negative synergistic effects on adult survival were caused by the low concentrated insecticide-fungicides-mixture, which had no effect when applied alone. The lower concentrated combined fungicides led to significantly lighter adult bees, although the survival was unaffected. Our results suggest that environmental relevant concentrations can be harmful to honeybees. To fully understand the interaction of different PPPs, more combinations and concentrations should be studied in social and solitary bees with possibly different sensitivities.

Physiological responses of the stingless bee Partamona helleri to oral exposure to three agrochemicals: impact on antioxidant enzymes and hemocyte count

Agrochemicals pose significant threats to the survival of bees, yet the physiological impacts of sublethal doses on stingless bees remain poorly understood. This study investigated the effects of acute oral exposure to three commercial formulations of agrochemicals [CuSO4 (leaf fertilizer), glyphosate (herbicide), and spinosad (bioinsecticide)] on antioxidant enzymes, malondialdehyde content (MDA), nitric oxide (NO) levels, and total hemocyte count (THC) in the stingless bee Partamona helleri. Foragers were exposed to lethal concentrations aimed to kill 5% (LC5) of CuSO4 (120 μg mL-1) or spinosad (0.85 μg mL-1) over a 24-h period. Glyphosate-exposed bees received the recommended label concentration (7400 μg mL-1), as they exhibited 100% survival after exposure. Ingestion of CuSO4 or glyphosate-treated diets by bees was reduced. Levels of NO and catalase (CAT) remained unaffected at 0 h or 24 h post-exposure. Superoxide dismutase (SOD) activity was higher at 0 h compared to 24 h, although insignificantly so when compared to the control. Exposure to CuSO4 reduced glutathione S-transferase (GST) activity at 0 h but increased it after 24 h, for both CuSO4 and glyphosate. MDA levels decreased after 0 h exposure to CuSO4 or spinosad but increased after 24 h exposure to all tested agrochemicals. THC showed no difference among glyphosate or spinosad compared to the control or across time. However, CuSO4 exposure significantly increased THC. These findings shed light on the physiological responses of stingless bees to agrochemicals, crucial for understanding their overall health.

Airborne metofluthrin, a pyrethroid repellent, does not impact foraging honey bees

Outdoor spatial mosquito repellents, such as mosquito coils or heating devices, release pyrethroid insecticides into the air to provide protection from mosquitoes within a defined area. This broadcast discharge of pyrethroids into the environment raises concern about the effect on non-target organisms. A previous study found that prallethrin discharged from a heating device did not affect honey bee (Apis mellifera L.) [Hymenoptera: Apidae] foraging or recruitment. In this second study, there was no significant difference in foraging frequency (our primary outcome), waggle dance propensity, or persistency in honey bees collecting sucrose solution between those exposed to metofluthrin from a different heating device and bees exposed to a non-metofluthrin control. One measure, waggle dance frequency, was higher in the metofluthrin treatment than the control but this outcome was likely a spurious result due to the small sample size. The small particle size of the emissions, averaging 4.43 µm, from the heated spatial repellent products, which remain airborne with little settling, may play an important role in the lack of effect found on honey bee foraging.

Advancing ecotoxicity assessment: Leveraging pre-trained model for bee toxicity and compound degradability prediction

The prediction of ecological toxicity plays an increasingly important role in modern society. However, the existing models often suffer from poor performance and limited predictive capabilities. In this study, we propose a novel approach for ecological toxicity assessment based on pre-trained models. By leveraging pre-training techniques and graph neural network models, we establish a highperformance predictive model. Furthermore, we incorporate a variational autoencoder to optimize the model, enabling simultaneous discrimination of toxicity to bees and molecular degradability. Additionally, despite the low similarity between the endogenous hormones in bees and the compounds in our dataset, our model confidently predicts that these hormones are non-toxic to bees, which further strengthens the credibility and accuracy of our model. We also discovered the negative correlation between the degradation and bee toxicity of compounds. In summary, this study presents an ecological toxicity assessment model with outstanding performance. The proposed model accurately predicts the toxicity of chemicals to bees and their degradability capabilities, offering valuable technical support to relevant fields.

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.

Acute toxicity of the fungicide captan to honey bees and mixed evidence for synergism with the insecticide thiamethoxam

Honey bees are commonly co-exposed to pesticides during crop pollination, including the fungicide captan and neonicotinoid insecticide thiamethoxam. We assessed the impact of exposure to these two pesticides individually and in combination, at a range of field-realistic doses. In laboratory assays, mortality of larvae treated with captan was 80-90% greater than controls, dose-independent, and similar to mortality from the lowest dose of thiamethoxam. There was evidence of synergism (i.e., a non-additive response) from captan-thiamethoxam co-exposure at the highest dose of thiamethoxam, but not at lower doses. In the field, we exposed whole colonies to the lowest doses used in the laboratory. Exposure to captan and thiamethoxam individually and in combination resulted in minimal impacts on population growth or colony mortality, and there was no evidence of synergism or antagonism. These results suggest captan and thiamethoxam are each acutely toxic to immature honey bees, but whole colonies can potentially compensate for detrimental effects, at least at the low doses used in our field trial, or that methodological differences of the field experiment impacted results (e.g., dilution of treatments with natural pollen). If compensation occurred, further work is needed to assess how it occurred, potentially via increased queen egg laying, and whether short-term compensation leads to long-term costs. Further work is also needed for other crop pollinators that lack the social detoxification capabilities of honey bee colonies and may be less resilient to pesticides.

Interaction of acetamiprid, Varroa destructor, and Nosema ceranae in honey bees

Health of honey bees is threatened by a variety of stressors, including pesticides and parasites. Here, we investigated effects of acetamiprid, Varroa destructor, and Nosema ceranae, which act either alone or in combination. Our results suggested that interaction between the three factors was additive, with survival risk increasing as the number of stressors increased. Although exposure to 150 μg/L acetamiprid alone did not negatively impact honey bee survival, it caused severe damage to midgut tissue. Among the three stressors, V. destructor posed the greatest threat to honey bee survival, and N. ceranae exacerbated intestinal damage and increased thickness of the midgut wall. Transcriptomic analysis indicated that different combinations of stressors elicited specific gene expression responses in honey bees, and genes involved in energy metabolism, immunity, and detoxification were altered in response to multiple stressor combinations. Additionally, genes associated with Toll and Imd signalling, tyrosine metabolism, and phototransduction pathway were significantly suppressed in response to different combinations of multiple stressors. This study enhances our understanding of the adaptation mechanisms to multiple stressors and aids in development of suitable protective measures for honey bees. ENVIRONMENTAL IMPLICATION: We believe our study is environmentally relevant for the following reasons: This study investigates combined effects of pesticide, Varroa destructor, and Nosema ceranae. These stressors are known to pose a threat to long-term survival of honey bees (Apis mellifera) and stability of the ecosystems. The research provides valuable insights into the adaptive mechanisms of honey bees in response to multiple stressors and developing effective conservation strategies. Further research can identify traits that promote honey bee survival in the face of future challenges from multiple stressors to maintain the overall stability of environment.

Impact of chronic exposure to field level glyphosate on the food consumption, survival, gene expression, gut microbiota, and metabolomic profiles of honeybees

Glyphosate (GLY) is among the most widely used pesticides in the world. However, there are a lot of unknowns about chronic exposure to GLY's effects on Honeybee (HB) behavior and physiology. To address this, we carried out five experiments to study the impact of chronic exposure to 5 mg/kg GLY on sugar consumption, survival, gene expression, gut microbiota, and metabolites of HB workers. Our results find a significant decrease in sugar consumption and survival probability of HB after chronic exposure to GLY. Further, genes associated with immune response, energy metabolism, and longevity were conspicuously altered. In addition, a total of seven metabolites were found to be differentially expressed in the metabolomic profiles, mainly related the sucrose metabolism. There was no significant difference in the gut microbiota. Results suggest that chronic exposure to field-level GLY altered the health of HB and the intricate toxic mechanisms. Our data provided insights into the chronic effects of GLY on HB behavior in food intake and health, which represents the field conditions where HB are exposed to pesticides over extended periods.

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.

Bumblebees are resilient to neonicotinoid-fungicide combinations

Bumblebees are among the most important wild bees for pollination of crops and securing wildflower diversity. However, their abundance and diversity have been on a steady decrease in the last decades. One of the most important factors leading to their decline is the frequent use of plant protection products (PPPs) in agriculture, which spread into forests and natural reserves. Mixtures of different PPPs pose a particular threat because of possible synergistic effects. While there is a comparatively large body of studies on the effects of PPPs on honeybees, we still lack data on wild bees. We here investigated the influence of the frequent fungicide Cantus® Gold (boscalid/dimoxystrobin), the neonicotinoid insecticide Mospilan® (acetamiprid) and their combination on bumblebees. Cognitive performance and foraging flights of bumblebees were studied. They are essential for the provisioning and survival of the colony. We introduce a novel method for testing four treatments simultaneously on the same colony, minimizing inter-colony differences. For this, we successfully quartered the colony and moved the queen daily between compartments. Bumblebees appeared astonishingly resilient to the PPPs tested or they have developed mechanisms for detoxification. Neither learning capacity nor flight activity were inhibited by treatment with the single PPPs or their combination.

Insecticide resistance in social insects: assumptions, realities, and possibilities

Insecticide resistance is an evolved ability to survive insecticide exposure. Compared with nonsocial insects, eusocial insects have lower numbers of documented cases of resistance. Eusocial insects include beneficial and pest species that can be incidentally or purposely targeted with insecticides. The central goal of this review is to explore factors that either limit resistance or the ability to detect it in eusocial insects. We surveyed the literature and found that resistance has been documented in bees, but in other pest groups such as ants and termites, the evidence is more sparse. We suggest the path forward for better understanding eusocial resistance should include more tractable experimental models, comprehensive geographic sampling, and targeted testing of the impacts of social, symbiont, genetic, and ecological factors.

Exploring honey bee toxicological data as a proxy for assessing dimethoate sensitivity in stingless bees

The high diversity and distinctive characteristics of stingless bees pose challenges in utilizing toxicity test results for agrochemical registrations. Toxicity assessments were performed on 15 stingless bee species, along with the honey bee, using the insecticide dimethoate, following adapted OECD protocols. Median lethal doses over 24 h (24 h-LD50) were determined for exposure routes (acute oral or contact) and species. Species sensitivity distribution (SSD) curves were constructed and the 5% hazard doses (HD5) were estimated based on 24 h-LD50 values. The SSD curve was adjusted as the body weight and dimethoate response were correlated. Lighter bees (<10 mg) had lower 24 h-LD50 values. Contact exposure for adjusted HD5 suggested insufficient protection for Melipona mondury, whereas the oral exposure HD5 indicated no risks for the other 14 species. Comprehensive risk assessments are crucial for understanding the agrochemical impact on stingless bees, emphasizing the need for a broader species range in formulating conservation strategies.

Chronic cadmium exposure impairs flight behavior by dampening flight muscle carbon metabolism in bumblebees

Cadmium pollution affects the global ecosystem because cadmium can be transferred up the food chain. The bumblebee, Bombus terrestris, is an important insect pollinator. Their foraging activity on flowers exposes them to harmful heavy metals, which damages their health and leads to massive population declines. However, the effects of chronic exposure to heavy metals on the flight performance of bumblebees have not yet been characterized. Here, we studied variation in the flight capacity of bumblebees induced by chronic cadmium exposure at field-realistic concentrations using behavioral, physiological, and molecular approaches. Chronic cadmium exposure caused a significant reduction in the duration, distance, and mean velocity of bumblebee flight. Transcriptome analysis showed that the impairment of carbon metabolism and mitochondrial dysfunction in the flight muscle were the primary causes. Physiological, biochemical, and metabolomic analyses validated disruptions in energy metabolism, and impairments in mitochondrial respiratory chain complexes activities. Histological analysis revealed muscle fiber damage and mitochondrial loss. Exogenous decanoic acid or citric acid partially restored sustained flight ability of bumblebees by mitigating muscle fiber damage and increasing energy generation. These findings provide insights into how long-term cadmium stress affects the flight ability of insects and will aid human muscle or exercise-related disease research.

Enhancing knowledge of chemical exposures and fate in honey bee hives: Insights from colony structure and interactions

Honey bees are unintentionally exposed to a wide range of chemicals through various routes in their natural environment, yet research on the cumulative effects of multi-chemical and sublethal exposures on important caste members, including the queen bee and brood, is still in its infancy. The hive's social structure and food-sharing (trophallaxis) practices are important aspects to consider when identifying primary and secondary exposure pathways for residential hive members and possible chemical reservoirs within the colony. Secondary exposures may also occur through chemical transfer (maternal offloading) to the brood and by contact through possible chemical diffusion from wax cells to all hive members. The lack of research on peer-to-peer exposures to contaminants and their metabolites may be in part due to the limitations in sensitive analytical techniques for monitoring chemical fate and dispersion. Combined application of automated honey bee monitoring and modern chemical trace analysis techniques could offer rapid progress in quantifying chemical transfer and accumulation within the hive environment and developing effective mitigation strategies for toxic chemical co-exposures. To enhance the understanding of chemical fate and toxicity within the entire colony, it is crucial to consider both the intricate interactions among hive members and the potential synergistic effects arising from combinations of chemical and their metabolites.

The molecular determinants of pesticide sensitivity in bee pollinators

Bees carry out vital ecosystem services by pollinating both wild and economically important crop plants. However, while performing this function, bee pollinators may encounter potentially harmful xenobiotics in the environment such as pesticides (fungicides, herbicides and insecticides). Understanding the key factors that influence the toxicological outcomes of bee exposure to these chemicals, in isolation or combination, is essential to safeguard their health and the ecosystem services they provide. In this regard, recent work using toxicogenomic and phylogenetic approaches has begun to identify, at the molecular level, key determinants of pesticide sensitivity in bee pollinators. These include detoxification systems that convert pesticides to less toxic forms and key residues in insecticide target-sites that underlie species-specific insecticide selectivity. Here we review this emerging body of research and summarise the state of knowledge of the molecular determinants of pesticide sensitivity in bee pollinators. We identify gaps in our knowledge for future research and examine how an understanding of the genetic basis of bee sensitivity to pesticides can be leveraged to, a) predict and avoid negative bee-pesticide interactions and facilitate the future development of pest-selective bee-safe insecticides, and b) inform traditional effect assessment approaches in bee pesticide risk assessment and address issues of ecotoxicological concern.

Determination of bisphenols in beeswax based on sugaring out-assisted liquid-liquid extraction: Method development and application in survey, recycling and degradation studies

The methodology of sugaring out-assisted liquid-liquid extraction (SULLE) coupled with high-performance liquid chromatography-fluorescence detection was devised for quantifying bisphenol A (BPA) and bisphenol B (BPB) in beeswax. The effectiveness of SULLE was methodically explored and proved superior to the salting out-assisted liquid-liquid extraction approach for beeswax sample preparation. The analytical performance underwent comprehensive validation, revealing detection limits of 10 μg/kg for BPA and 20 μg/kg for BPB. The method developed was employed to analyse commercial beeswax (n = 15), beeswax foundation (n = 15) and wild-build comb wax (n = 26) samples. The analysis revealed BPA presence in four commercial beeswax samples and three beeswax foundation samples, with the highest detected residue content being 88 ± 7 μg/kg. For BPB, two beeswax foundation samples were positive, with concentrations below the limits of quantification and 85 ± 4 μg/kg, respectively. No bisphenols were detected in wild-build comb wax. Furthermore, the bisphenol removal efficacy of two recycling methods-boiling in water and methanol extraction-was assessed. The findings indicated that after four recycling cycles using water boiling, 9.6% of BPA and 29.2% of BPB remained in the beeswax. Whereas methanol extraction resulted in approximately 7% residual after one recycling process. A long-term study over 210 days revealed the slow degradation of bisphenols in comb beeswax. This degradation fitted well with a first-order model, indicating half-lives (DT50) of 139 days for BPA and 151 days for BPB, respectively. This research provides the first report on bisphenol contamination in beeswax. The low removal rate during the recycling process and the gradual degradation in beeswax underscore the significance of bisphenol contamination and migration in bee hives along with their potential risk to pollinators warranting concern. Furthermore, the developed SULLE method shows promise in preparing beeswax samples to analyse other analytes.

Preliminary data on glyphosate, glufosinate, and metabolite contamination in Italian honey samples

Glyphosate and glufosinate are among the most widely used pesticides in agriculture worldwide. Their extensive use leads to the presence of their residues on crops and in the surrounding environment. Beehives, bees, and apiculture products can represent potential sources for the accumulation of these substances and their metabolites, and the consequences for bee health, as well as the level of risk to human health from consuming contaminated food, are still unclear. Furthermore, information on the contamination levels of honey and other beehive products by these compounds remains poorly documented. This study is part of a broader research effort aimed at developing specific analytical methods for monitoring the level of these contaminants in bee products. The methodology employed enabled the acquisition of preliminary information concerning the levels of glyphosate and glufosinate contamination in honey samples obtained from various retailers in Italy to assess compliance with the limits established by Regulation 293/2013. The liquid chromatography tandem mass spectrometry analysis of the 30 honey samples revealed quantifiable levels of glyphosate in eight samples, with contamination ranging from 5.4 to 138.5 ng/g. Notably, one sample of the wild-flower type showed residue levels nearly three times the maximum residue limit. Additionally, trace levels of glyphosate contamination were detected in another ten samples. It is noteworthy that glufosinate and its metabolites were not detected in any of the analyzed samples within the established method's detection ranges.

Architecture and potential roles of a delta-class glutathione S-transferase in protecting honey bee from agrochemicals

The European honey bee, Apis mellifera, serves as the principle managed pollinator species globally. In recent decades, honey bee populations have been facing serious health threats from combined biotic and abiotic stressors, including diseases, limited nutrition, and agrochemical exposure. Understanding the molecular mechanisms underlying xenobiotic adaptation of A. mellifera is critical, considering its extensive exposure to phytochemicals and agrochemicals present in the environment. In this study, we conducted a comprehensive structural and functional characterization of AmGSTD1, a delta class glutathione S-transferase (GST), to unravel its roles in agrochemical detoxification and antioxidative stress responses. We determined the 3-dimensional (3D) structure of a honey bee GST using protein crystallography for the first time, providing new insights into its molecular structure. Our investigations revealed that AmGSTD1 metabolizes model substrates, including 1-chloro-2,4-dinitrobenzene (CDNB), p-nitrophenyl acetate (PNA), phenylethyl isothiocyanate (PEITC), propyl isothiocyanate (PITC), and the oxidation byproduct 4-hydroxynonenal (HNE). Moreover, we discovered that AmGSTD1 exhibits binding affinity with the fluorophore 8-Anilinonaphthalene-1-sulfonic acid (ANS), which can be inhibited with various herbicides, fungicides, insecticides, and their metabolites. These findings highlight the potential contribution of AmGSTD1 in safeguarding honey bee health against various agrochemicals, while also mitigating oxidative stress resulting from exposure to these substances.

Variation in the physiological response of adult worker bees of different ages (Apis mellifera L.) to pyraclostrobin stress

The social division of labor within the honeybee colony is closely related to the age of the bees, and the age structure is essential to the development and survival of the colony. Differences in tolerance to pesticides and other external stresses among worker bees of different ages may be related to their social division of labor and corresponding physiological states. Pyraclostrobin was widely used to control the fungal diseases of nectar and pollen plants, though it was not friend to honey bees and other pollinators. This work aimed to determine the effects of field recommended concentrations of pyraclostrobin on the activities of protective and detoxifying enzymes, on the expression of genes involved in nutrient metabolism, and immune response in worker bees of different ages determined to investigate the physiological and biochemical differences in sensitivity to pyraclostrobin among different age of worker bees. The result demonstrates that the tolerance of adult worker bees to pyraclostrobin was negatively correlated with their age, and the significantly reduced survival rate of forager bees (21 day-old) with continued fungicide exposure. The activities of protective enzymes (CAT and SOD) and detoxifying enzymes (CarE, GSTs and CYP450) in different ages of adult worker bees were significantly altered, indicating the physiological response and the regulatory capacity of worker bees of different ages to fungicide stress was variation. Compared with 1 and 8 day-old worker bees, the expression of nutrient-related genes (ilp1 and ilp2) and immunity-related genes (apidaecin and defensin1) in forager bees (21 day-old) was gradually downregulated with increasing pyraclostrobin concentrations. Moreover, the expression of vitellogenin and hymenoptaecin in forager bees (21 day-old) was also decreased in high concentration treatment groups (250 and 313 mg/L). The present study confirmed the findings of the chronic toxicity of pyraclostrobin on the physiology and biochemistry of worker bees of different ages, especially to forager bees (21 day-old). These results would provide important physiological and biochemical insight for better understanding the potential risks of pyraclostrobin on honeybees and other non-target pollinators.

Biomarker responses and lethal dietary doses of tau-fluvalinate and coumaphos in honey bees: Implications for chronic acaricide toxicity

Evidence suggests that acaricide residues, such as tau-fluvalinate and coumaphos, are very prevalent in honey bee colonies worldwide. However, the endpoints and effects of chronic oral exposure to these compounds remain poorly understood. In this study, we calculated LC50 and LDD50 endpoints for coumaphos and tau-fluvalinate, and then evaluated in vivo and in vitro effects on honey bees using different biomarkers. The LDD50 values for coumaphos were 0.539, and for tau-fluvalinate, they were 12.742 in the spring trial and 8.844 in the autumn trial. Chronic exposure to tau-fluvalinate and coumaphos resulted in significant changes in key biomarkers, indicating potential neurotoxicity, xenobiotic biotransformation, and oxidative stress. The Integrated Biomarker Response was stronger for coumaphos than for tau-fluvalinate, supporting their relative lethality. This study highlights the chronic toxicity of these acaricides and presents the first LDD50 values for tau-fluvalinate and coumaphos in honey bees, providing insights into the risks faced by colonies.

A critical review on the accumulation of neonicotinoid insecticides in pollen and nectar: Influencing factors and implications for pollinator exposure

Neonicotinoids are a class of neuro-active insecticides widely used to protect major crops, primarily because of their broad-spectrum insecticidal activity and low vertebrate toxicity. Owing to their systemic nature, plants readily take up neonicotinoids and translocate them through roots, leaves, and other tissues to flowers (pollen and nectar) that serve as a critical point of exposure to pollinators foraging on treated plants. The growing evidence for potential adverse effects on non-target species, especially pollinators, and persistence has raised serious concerns, as these pesticides are increasingly prevalent in terrestrial and aquatic systems. Despite increasing research efforts, our understanding of the potential toxicity of neonicotinoids and the risks they pose to non-target species remains limited. Therefore, this critical review provides a succinct evaluation of the uptake, translocation, and accumulation processes of neonicotinoids in plants and the factors that may affect the eventual build-up of neonicotinoids in pollen and nectar. The role of plant species, as well as the physicochemical properties and application methods of neonicotinoids is discussed. Potential knowledge gaps are identified, and questions meriting future research are suggested for improving our understanding of the relationship between neonicotinoid residues in plants and exposure to pollinators.

'Inert' co-formulants of a fungicide mediate acute effects on honey bee learning performance

Managed honey bees have experienced high rates of colony loss recently, with pesticide exposure as a major cause. While pesticides can be lethal at high doses, lower doses can produce sublethal effects, which may substantially weaken colonies. Impaired learning performance is a behavioral sublethal effect, and is often present in bees exposed to insecticides. However, the effects of other pesticides (such as fungicides) on honey bee learning are understudied, as are the effects of pesticide formulations versus active ingredients. Here, we investigated the effects of acute exposure to the fungicide formulation Pristine (active ingredients: 25.2% boscalid, 12.8% pyraclostrobin) on honey bee olfactory learning performance in the proboscis extension reflex (PER) assay. We also exposed a subset of bees to only the active ingredients to test which formulation component(s) were driving the learning effects. We found that the formulation produced negative effects on memory, but this effect was not present in bees fed only boscalid and pyraclostrobin. This suggests that the trade secret "other ingredients" in the formulation mediated the learning effects, either through exerting their own toxic effects or by increasing the toxicities of the active ingredients. These results show that pesticide co-formulants should not be assumed inert and should instead be included when assessing pesticide risks.

The role of the veterinary diagnostic toxicologist in apiary health

Susceptibility of individuals and groups to toxicants depends on complex interactions involving the host, environment, and other exposures. Apiary diagnostic investigation and honey bee health are truly population medicine: the colony is the patient. Here we provide basic information on the application of toxicology to the testing of domestic honey bees, and, in light of recent research, expand on some of the challenges of interpreting analytical chemistry findings as they pertain to hive health. The hive is an efficiently organized system of wax cells used to store brood, honey, and bee bread, and is protected by the bee-procured antimicrobial compound propolis. Toxicants can affect individual workers outside or inside the hive, with disease processes that range from acute to chronic and subclinical to lethal. Toxicants can impact brood and contaminate honey, bee bread, and structural wax. We provide an overview of important natural and synthetic toxicants to which honey bees are exposed; behavioral, husbandry, and external environmental factors influencing exposure; short- and long-term impacts of toxicant exposure on individual bee and colony health; and the convergent impacts of stress, nutrition, infectious disease, and toxicant exposures on colony health. Current and potential future toxicology testing options are included. Common contaminants in apiary products consumed or used by humans (honey, wax, pollen), their sources, and the potential need for product testing are also noted.

Composition, functional properties and safety of honey: a review

Honey has been used not only as a food source but also for medicinal purposes. Recent studies have indicated that honey exhibits antioxidant, hepatoprotective, hypolipidemic, hypoglycemic and anti-obesity properties, as well as anticancer, anti-atherosclerotic, hypotensive, neuroprotective and immunomodulatory activities. These health benefits of honey could be attributed to its wide range of nutritional components, including polysaccharides and polyphenols, which have been proven to possess various beneficial properties. It is notable that the composition of honey can also be affected by nectar, season, geography and storage condition. Moreover, the safety of honey requires caution to avoid any potential safety incidents. Therefore, this review aims to provide recent research regarding the chemical composition, biological activities and safety of honey, which might be attributed to comprehensive utilization of honey. © 2023 Society of Chemical Industry.

Contamination of Honeybee (Apis mellifera L.) Royal Jelly by Pesticides and Sample Preparation Methods for Its Determination: A Critical Appraisal

Pesticides can easily enter the food chain, harming bee populations and ecosystems. Exposure of beehive products to various contaminants has been identified as one of the factors contributing to the decline in bee populations, and multiple food alerts have been reported. Despite this fact, royal jelly, a valuable bee product with nutritional and functional properties, has received less attention in this context. Pesticide residues of different chemical class can contaminate royal jelly when foraging bees collect pollen or nectar from pesticide-treated flowers, or in some cases, due to its frequent and inappropriate use in the treatment of mites in beehives. To monitor this issue and also make it more reliable, it is crucial to develop effective sample preparation methods for extracting pesticides from royal jelly for subsequent analysis. In this context, this review provides information about sample preparation methods (solid-phase extraction, solvent extraction, and QuEChERS-quick, easy, cheap, effective, rugged and safe) and analytical methods that have been validated or improved to extract and analyze pesticides, respectively, in royal jelly samples of different origins. Finally, future perspectives are discussed. With this background, we aim to provide data that can guide future research related to this topic.

Sublethal doses of glyphosate modulates mitochondria and oxidative stress in honeybees by direct feeding

Honeybees are essential for the ecosystem maintenance and for plant production in agriculture. Glyphosate is a broad-spectrum systemic herbicide widely used in crops to control weeds and could affect honeybees' health in sublethal doses. Our aim was to study how sublethal doses of glyphosate affects to oxidative stress and mitochondrial homeostasis in honeybees. We exposed honeybees to glyphosate at 5 and 10 mg·l-1 for 2 and 10 h for the gene expression analysis by reverse transcription polymerase chain reaction and for 48 and 72 h for the antioxidant enzymes activity and lipid peroxidation determination. We observed a general increase in antioxidant- and mitochondrial-related genes expression in honeybees after 2 h of exposition to glyphosate, as well as a rise in catalase and superoxide dismutase enzymatic activity after 48 h and an increment in lipid peroxidation adducts generation after 72 h. These results suggest a direct effect of glyphosate on honeybees' health, with an insufficient response of the antioxidant system to the generated oxidative stress, resulting in an increase in lipid peroxidation and, therefore, oxidative damage. Altogether, results obtained in this work demonstrate that sublethal treatments of glyphosate could directly affect honeybee individuals under laboratory conditions. Therefore, it is necessary to investigate alternatives to glyphosate to determine if they are less harmful to non-target organisms.

Functional analysis of AccCDK2-like and AccCINP-like genes in Apis cerana cerana under pesticide and heavy metal stress

Heavy metals and pesticides represent prominent sources of pollution in the natural habitat of Apis cerana cerana, potentially endangering their health through the induction of oxidative stress reactions. This study aimed to address this issue by isolating AccCDK2-like and AccCINP-like proteins from Apis cerana cerana and investigating their functional roles in honey bee resistance against pesticide and heavy metal stresses. Bioinformatics analysis revealed significant homology of these proteins with those found in other species. Functional studies confirmed their participation in interaction with each other, alongside demonstrating distinct patterns of expression and localization. Specifically, AccCDK2-like exhibited higher expression levels in prepupae and muscle tissues, while AccCINP-like showed maximal expression in brown pupae and abdomen. Furthermore, the expression levels of these proteins were found to be modulated in response to pesticide and heavy metal stresses. Notably, overexpression of AccCDK2-like and AccCINP-like led to a noticeable alteration in E. coli's ability to withstand external stresses. Additionally, silencing of the AccCDK2-like and AccCINP-like genes resulted in a significant reduction in antioxidant enzyme activity and the expression levels of genes related to antioxidant function. Consequently, the mortality rate of Apis cerana cerana under pesticide and heavy metal stresses conspicuously increased. Hence, our findings suggest that AccCDK2-like and AccCINP-like proteins potentially play a crucial role in the response of Apis cerana cerana to pesticide and heavy metal stress, likely by modulating the antioxidant pathway.

Acute and chronic effects of sublethal neonicotinoid thiacloprid to Asian honey bee (Apis cerana cerana)

Pesticide pollution is one of the most important factors for global bee declines. Despite many studies have revealed that the most important Chinese indigenous species，Apis cerana, is presenting a high risk on exposure to neonicotinoids, the toxicology information on Apis cerana remain limited. This study was aimed to determine the acute and chronic toxic effects of thiacloprid (IUPAC name: {(2Z)-3-[(6-Chloro-3-pyridinyl)methyl]-1,3-thiazolidin-2-ylidene}cyanamide) on behavioral and physiological performance as well as genome-wide transcriptome in A. cerana. We found the 1/5 LC50 of thiacloprid significantly impaired learning and memory abilities after both acute and chronic exposure, nevertheless, has no effects on the sucrose responsiveness and phototaxis climbing ability of A. cerana. Moreover, activities of detoxification enzyme P450 monooxygenases and CarE were increased by short-term exposure to thiacloprid, while prolonged exposure caused suppression of CarE activity. Neither acute nor chronic exposure to thiacloprid altered honey bee AChE activities. To further study the potential defense molecular mechanisms in Asian honey bee under pesticide stress, we analyzed the transcriptomes of honeybees in response to thiacloprid stress. The transcriptomic profiles revealed consistent upregulation of immune- and stress-related genes by both acute or chronic treatments. Our results suggest that the chronic exposure to thiacloprid produced greater toxic effects than a single administration to A. cerana. Altogether, our study deepens the understanding of the toxicological characteristic of A. cerana against thiacloprid, and could be used to further investigate the complex molecular mechanisms in Asian honey bee under pesticide stress.

Pesticide mixtures detected in crop and non-target wild plant pollen and nectar

Cultivation of mass flowering entomophilous crops benefits from the presence of managed and wild pollinators, who visit flowers to forage on pollen and nectar. However, management of these crops typically includes application of pesticides, the presence of which may pose a hazard for pollinators foraging in an agricultural environment. To determine the levels of potential exposure to pesticides, their presence and concentration in pollen and nectar need assessing, both within and beyond the target crop plants. We selected ten pesticide compounds and one metabolite and analysed their occurrence in a crop (Brassica napus) and a wild plant (Rubus fruticosus agg.), which was flowering in field edges. Nectar and pollen from both plants were collected from five spring and five winter sown B. napus fields in Ireland, and were tested for pesticide residues, using QuEChERS and Liquid Chromatography tandem mass spectrometry (LC-MS/MS). Pesticide residues were detected in plant pollen and nectar of both plants. Most detections were from fields with no recorded application of the respective compounds in that year, but higher concentrations were observed in recently treated fields. Overall, more residues were detected in B. napus pollen and nectar than in the wild plant, and B. napus pollen had the highest mean concentration of residues. All matrices were contaminated with at least three compounds, and the most frequently detected compounds were fungicides. The most common compound mixture was comprised of the fungicides azoxystrobin, boscalid, and the neonicotinoid insecticide clothianidin, which was not recently applied on the fields. Our results indicate that persistent compounds like the neonicotinoids, should be continuously monitored for their presence and fate in the field environment. The toxicological evaluation of the compound mixtures identified in the present study should be performed, to determine their impacts on foraging insects that may be exposed to them.

Effect of fluvalinate on the expression profile of circular RNA in brain tissue of Apis mellifera ligustica workers

Fluvalinate is widely used in apiculture as an acaricide for removing Varroa mites, but there have been growing concerns about the negative effects of fluvalinate on honeybees in recent years. Previous research revealed changes in the miRNA and mRNA expression profiles of Apis mellifera ligustica brain tissues during fluvalinate exposure, as well as key genes and pathways. The role of circRNAs in this process, however, is unknown. The goal of this study was to discover the fluvalinate-induced changes in circular RNA (circRNA) expression profiles of brain tissue of A. mellifera ligustica workers. A total of 10,780 circRNAs were detected in A. mellifera ligustica brain tissue, of which eight were differentially expressed between at least two of the four time periods before and after fluvalinate administration, and six circRNAs were experimentally verified to be structurally correct, and their expression patterns were consistent with transcriptome sequencing results. Furthermore, ceRNA analysis revealed that five differentially expressed circRNAs (DECs) (novel_circ_012139, novel_circ_011690, novel_circ_002628, novel_circ_004765, and novel_circ_010008) were primarily involved in apoptosis-related functions by competitive binding with miRNAs. This study discovered changes in the circRNA expression profile of A. mellifera ligustica brain tissue caused by fluvalinate exposure, and it provides a useful reference for the biological function study of circRNAs in A. mellifera ligustica.

Expression profile of the entire detoxification gene inventory of the western honeybee, Apis mellifera across life stages

The western honeybee, Apis mellifera, is a managed pollinator of many crops and potentially exposed to a wide range of foreign compounds, including pesticides throughout its life cycle. Honeybees as well as other insects recruit molecular defense mechanisms to facilitate the detoxification of xenobiotic compounds. The inventory of detoxification genes (DETOXome) is comprised of five protein superfamilies: cytochrome P450 monooxygenases (P450), carboxylesterases, glutathione S-transferases (GST), UDP-glycosyl transferases (UGT) and ATP-binding cassette (ABC) transporters. Here we characterized the gene expression profile of the entire honeybee DETOXome by analyzing 47 transcriptomes across the honeybee life cycle, including different larval instars, pupae, and adults. All life stages were well separated by principal component analysis, and K-means clustering revealed distinct temporal patterns of gene expression. Indeed, >50% of the honeybee detoxification gene inventory is found in one cluster and follows strikingly similar expression profiles, i.e., increased expression during larval development, followed by a sharp decline after pupation and a steep increase again in adults. This cluster includes 29 P450 genes dominated by CYP3 and CYP4 clan members, 15 ABC transporter genes mostly belonging to the ABCC subfamily and 13 carboxylesterase genes including almost all members involved in dietary/detox and hormone/semiochemical processing. RT-qPCR analysis of selected detoxification genes from all families revealed high expression levels in various tissues, especially Malpighian tubules, fatbody and midgut, supporting the view that these tissues are essential for metabolic clearance of environmental toxins and pollutants in honeybees. Our study is meant to spark further research on the molecular basis of detoxification in this critical pollinator to better understand and evaluate negative impacts from potentially toxic substances. Additionally, the entire gene set of 47 transcriptomes collected and analyzed provides a valuable resource for future honeybee research across different disciplines.

Fox transcription factor AccGRF1 in response to glyphosate stress in Apis cerana cerana

Glyphosate is an herbicide commonly used in agriculture, and its widespread use has adversely affected the survival of nontarget organisms. Among these organisms, bees in particular are important pollinators, and declining bee populations have severely affected crop yields around the world. However, the molecular mechanism by which glyphosate harms bees remains unclear. In our experiment, we screened and cloned a glyphosate-induced gene in Apis cerana cerana (A. c. cerana) and named glyphosate response factor 1 (AccGRF1). Sequence analysis showed that AccGRF1 contains a winged-helix DNA binding domain, which suggests that it belongs to the Forkhead box (Fox) protein family. qRT-PCR and heterologous expression in Escherichia coli and yeast showed that AccGRF1 can respond to glyphosate and oxidative stress. After AccGRF1 knockdown by means of RNA interference (RNAi), the resistance of A. c. cerana to glyphosate stress improved. The results suggested that AccGRF1 is involved in A. c. cerana glyphosate stress tolerance. This study reveals the functions of Fox transcription factors in response to glyphosate stress and provides molecular insights into the regulation of glyphosate responses in honeybees.

Fungicide Exposure in Honey Bee Hives Varies By Time, Worker Role, and Proximity to Orchards in Spring

Fungicides are commonly applied to prevent diseases in eastern North American cherry orchards at the same time that honey bees (Apis mellifera L. (Hymenoptera: Apidae)) are rented for pollination services. Fungicide exposure in honey bees can cause negative health effects. To measure fungicide exposure, we sampled commercial honey bee colonies during orchard bloom at two commercial tart cherry orchards and one holding yard in northern Michigan over two seasons. Nurse bees, foragers, larvae, pollen, bee bread, and wax were screened for captan, chlorothalonil, and thiophanate-methyl. We also looked at the composition of pollens collected by foragers during spring bloom. We found differences in fungicide residue levels between nurse bees and foragers, with higher captan levels in nurse bees. We also found that residue levels of chlorothalonil in workers were significantly increased during tart cherry bloom, and that nurse bees from hives adjacent to orchards had significantly higher chlorothalonil residues than nurse bees from hives kept in a holding yard. Our results suggest that fungicide exposure of individual honey bees depends greatly on hive location in relation to mass-flowering crops, and worker role (life stage) at the time of collection. In some pollen samples, captan and chlorothalonil were detected at levels known to cause negative health effects for honey bees. This study increases our understanding of exposure risk for bees under current bloom time orchard management in this region. Further research is needed to balance crop disease management requirements with necessary pollination services and long-term pollinator health.

Glyphosate and Glufosinate Residues in Honey and Other Hive Products

Hive products have numerous beneficial properties; however, the hive’s health is affected by the surrounding environment. The widespread use of herbicides in agriculture, such as glyphosate and glufosinate, has raised alarm among consumers, beekeepers, and environmentalists due to their potential to harm bees and humans through the consumption of bee products. This review aims to provide a comprehensive overview of the presence of glyphosate, glufosinate, and their metabolites in hive products, collecting and comparing available data from peer-reviewed research and surveys conducted across several countries. Moreover, it analyzes and discusses the potential impacts of these substances on human and bee health, analytical aspects, and recent regulatory developments. The data has revealed that these substances can be present in the different matrices tested, but the concentrations found are usually lower than the maximum residue limits set. However, the use of different methodologies with non-uniform analytical performances, together with an incomplete search for regulated analytes, leads to heterogeneity and makes comparisons challenging. In addition to the completion of studies on the toxicology of herbicide active ingredients, further monitoring actions are necessary, harmonizing analytical methodologies and data management procedures.

Pesticide exposure and forage shortage in rice cropping system prevents honey bee colony establishment

As one of the key stable crops to feed half of the world's population, how rice cropping system affects honey bee health regarding pesticide exposure and forage availability is under investigated. We predicted honey bees were stressed by high pesticide exposure and forage dearth in monoculture rice systems. Providing access to natural habitats is a typical approach to mitigate the negative impact of intensive agriculture on honey bees. We aimed to determine if bee colonies located in landscapes with more cover of forest habitat would collect more forage and be exposed to less pesticides. We selected beekeeping locations in rice dominated landscapes (as control), mosaic landscapes of rice and medium woodland (MW) cover, and landscapes of high woodland (HW) cover, respectively, in July when rice starts bloom and pesticides are commonly used. Colonies were inspected at a biweekly frequency from July to October with population growth and forage (nectar and pollen) availability estimated. Pollen and bees were collected in middle August for pesticide exposure analysis. We did not observe enhancement in forage availability and reduction in pesticide exposure in landscapes with increased forest habitat (i.e., MW or HW cover), and all colonies failed in the end. Other natural habitats that can supplement flower shortage periods in forest can be considered for supporting bee health. Our results suggest that forest should be carefully assessed for being incorporated into beekeeping management or pollinator conservation when forest phenology can be a factor to affect its impact as a natural habitat.

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.

Exposure of chlorothalonil and acetamiprid reduce the survival and cause multiple internal disturbances in Apis mellifera larvae reared in vitro

Background: Chlorothalonil and acetamiprid are chemical pesticides commonly used in agricultural production and have been shown to have negative effects on bee's fitness. Despite many studies have revealed that honey bee (Apis mellifera L.) larvae are posting a high risk on exposure to pesticides, but the toxicology information of chlorothalonil and acetamiprid on bee larvae remain limited. Results: The no observed adverse effect concentration (NOAEC) of chlorothalonil and acetamiprid for honey bee larvae were 4 μg/mL and 2 μg/mL, respectively. Except for CarE, the enzymic activities of GST and P450 were not influenced by chlorothalonil at NOAEC, while chronic exposure to acetamiprid slightly increased the activities of the three tested enzymes at NOAEC. Further, the exposed larvae showed significantly higher expression of genes involved in a series of different toxicologically relevant process following, including caste development (Tor (GB44905), InR-2 (GB55425), Hr4 (GB47037), Ac3 (GB11637) and ILP-2 (GB10174)), immune system response (abaecin (GB18323), defensin-1 (GB19392), toll-X4 (GB50418)), and oxidative stress response (P450, GSH, GST, CarE). Conclusion: Our results suggest that the exposure to chlorothalonil and acetamiprid, even at concentrations below the NOAEC, showed potentially effects on bee larvae's fitness, and more important synergistic and behavioral effects that can affect larvae fitness should be explored in the further.

Nutritional resources modulate the responses of three bee species to pesticide exposure

The response of bee species to various stressors is assumed to depend on the availability of sufficient nutrients in their environment. We compare the response of three bee species (Apis mellifera, Bombus terrestris, Osmia bicornis) under laboratory conditions. Survival, physiology, and sensitivity, after exposure to the fungicide prochloraz, the insecticide chlorantraniliprole, and their mixture with different nutritional resources (sugar only, sugar with amino acids or pollen) were observed. Prochloraz reduced the bee survival of A. mellifera and O. bicornis fed with pollen, but not with other diets. Chlorantraniliprole impaired the survival of A. mellifera fed with sugar or pollen diet, but not with amino acid diet. The mixture impaired survival of A. mellifera and O. bicornis in association with every diet. B. terrestris was only affected by chlorantraniliprole and its mixture with prochloraz fed with sugar diet. The activity of P450 reductase was higher in A. mellifera fed with amino acids in all treatments, whereas no effect emerged in O. bicornis and B. terrestris. Our results indicate that the sensitivity of bee species after exposure to agrochemicals is affected by diet. Thus, balanced and species-dependent nutrition ameliorated the effects. Further field studies are necessary to evaluate the potential effects of such mixtures on bee populations.

In Vitro and Predictive Computational Toxicology Methods for the Neurotoxic Pesticide Amitraz and Its Metabolites

The Varroa destructor parasite is responsible for varroasis in honeybees worldwide, the most destructive disease among parasitic diseases. Thus, different insecticides/acaricides have been widely used within beehives to control these parasitic diseases. Namely, amitraz is the most used acaricide due to its high efficacy shown against Varroa destructor. However, pesticides used for beehive treatments could be incorporated into the honey and accumulate in other hive products. Hence, honeybee health and the impairment of the quality of honey caused by pesticides have gained more attention. Amitraz and its main metabolites, N-(2,4-dimethylphenyl) formamide (2,4-DMF) and 2,4-dimethylaniline (2,4-DMA), are known to be potent neurotoxicants. In this research, the cytotoxicity of amitraz and its metabolites has been assessed by MTT and PC assays in HepG2 cells. In addition, possible target receptors by in silico strategies have been surveyed. Results showed that amitraz was more cytotoxic than its metabolites. According to the in silico ADMEt assays, amitraz and its metabolites were predicted to be compounds that are able to pass the blood-brain barrier (BBB) and induce toxicity in the central and peripheral nervous systems. The main target class predicted for amitraz was the family of A G protein-coupled receptors that comprises responses to hormones and neurotransmitters. This affects, among other things, reproduction, development, locomotion, and feeding. Furthermore, amitraz and its metabolites were predicted as active compounds interacting with diverse receptors of the Tox21-nuclear receptor signaling and stress response pathways.