Pesticide residues in daily bee pollen samples (April-July) from an intensive agricultural region in Southern Germany

Residues of agrochemicals in beebread as an indicator of landscape management

The agricultural intensification represents a major threat to biodiversity, with negative effects on the ecosystem. In particular, habitat loss and degradation, along with pesticide use have been recognised as primary factors contributing to the actual global decline of pollinators. Here we investigated the quality of agroecosystems in the Emilia-Romagna region (Northern Italy) within the national monitoring project BeeNet. We analysed pesticide residues in 100 samples of beebread collected in 25 BeeNet stations in March and June 2021 and 2022. We evaluated diversity and concentration of these chemicals, their risk (TWC) to honey bees, and their correlation with land use. Overall, in 84 % of the samples we found 63 out of 373 different pesticide residues, >90 % of them belonging to fungicides and insecticides. The TWC exceeded the risk threshold in seven samples (TWCmix), mostly due to only one or two compounds. We also found 15 compounds not approved in the EU as plant protection products (PPPs), raising concerns about illegal use or contamination through beeswax recycling. Samples collected in 2021 and in June presented a significantly higher number of active ingredients and TWC than those collected in 2022 and in March. The TWC calculated on single compounds (TWCcom) exceeded the risk threshold in case of four insecticides, namely carbaryl, fipronil, imidacloprid and thiamethoxam (although each detected in only one sample). Finally, both TWC and number of active ingredients were moderately or highly positively correlated with the percentage of area covered by orchards. Considering that we found on average more than five different molecules per sample, and that we ignored potential synergistic effects, the results of this work highlight the alarming situation regarding pesticide treatments and toxicity risk for bees linked to the current agricultural practices, and the need for implementing sustainable and pollinator-friendly strategies.

Honey bees for pesticide monitoring in the landscape: which bee matrices should be used?

Among bee species, the western honey bee (Apis mellifera) is preferred in monitoring studies performed in the agricultural landscape, while bee matrices, pollen, and honey are mostly a subject of these studies due to their unique composition. A justified question about the relevance of other bee matrices, like larvae, foragers, beebread, and/or wax, has been raised. The ability of different bee matrices (wax, pollen grains, bee bread, foragers, larvae, nectar, and honey) to absorb pesticide residues is subjected in this study. All samples were collected during a crop flowering season (oilseed rape) on intensively managed agricultural land in Slovakia and Germany. The observed high variability in residue levels, profile, and number of detections among studied matrices from Germany, west, and east Slovakia gave us an assumption of the use of different agricultural practices between these two countries. Fungicides clearly dominated across all samples in all sampling regions. The increased pesticide profile positively correlated with the oilseed rape pollen grains in pollen pellets and/or bee bread. Bee wax, pollen, and bee bread showed a high number of detected active substances and total residue concentrations among matrices, indicating their high ability to absorb pesticide residues in the surrounding hive environment.

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.

Cytotoxic and genotoxic effects of a pendimethalin-based herbicide in Apis mellifera

Public concern about the effects of pesticides on non-target organisms has increased in the recent years. Nevertheless, there is a limited number of studies that address the actual toxic effects of herbicides on insects. This study investigated the side effects of herbicides on non-target organisms inhabiting agroecosystems and performing essential ecological and economic functions such as crop pollination. We analysed morphological alterations in the gut, Malpighian tubules and circulating haemocytes of Apis mellifera workers as markers of exposure effects. A commercial formulation of a pendimethalin-based herbicide (PND) was administered orally under laboratory conditions at a realistic concentration admitted in the field (330gL-1 of active ingredient., 4 L ha-1 for cereal and vegetable crops). The worker bees were exposed to a single application of PND for a period of one week, to simulate the exposure that can occur when foraging bees accidentally drink drops of contaminated water upon treatments. Histopathological analyses of the midgut, ileum and Malpighian tubules showed alterations over time (from 24 to 72 h after the beginning of exposure) such as loss of epithelial organisation, cellular vacuolisation and altered pyknotic nuclei as well as disruption of the peritrophic membrane over time. Semiquantitative analyses of the midgut showed a significant increase in the organ injury index 24 and 72 h after the initial exposure in PND-exposed bees compared to control bees. In addition, a change in positivity to Gram staining was observed in the midgut histological sections. A recovery of cytotoxic effects was observed one week after the initial exposure, which was favoured by the periodic renewal of the intestinal epithelium and the herbicide dissipation time. Cytochemical staining with Giemsa of haemocytes from PND-treated workers over 24 and 72 h showed significant nuclear alterations such as lobed or polymorphic nuclei and micronuclei compared to bees in the control group. These results show that the dose of PND used to protect crops from weeds can lead to significant cytotoxic and genotoxic effects in non-target organisms such as honey bees. In croplands, the sublethal effects on cell morphology can impair vital physiological processes such as nutrition, osmoregulation, and resistance to pathogens, contributing to the decline in biodiversity and abundance of species that play a prominent ecological role, such as pollinators.

Effects of chronic oral exposure to insecticide teflubenzuron on the midgut of the honey bee Apis mellifera workers: histopathological insights into pesticide toxicity

The honey bee Apis mellifera plays a significant role as a pollinator of native and cultivated plants, by increasing the productivity of several cultures, preserving the flora, and producing forest seeds. However, bee populations are declining worldwide, including A. mellifera, due to Colony Collapse Disorder, mainly resulting from the constant use of pesticides in the crops. Teflubenzuron is a physiological insecticide that belongs to the benzoylurea group, which inhibits chitin synthesis, the main component of the insect integument classified as safe for non-target insects, including bees. However, its effect on non-target organs of insects remains unknown. The midgut is the main organ of the digestive tract, which works in digestion and absorption and may be exposed to pesticides that contaminate food resources. The present work aimed to verify if the insecticide teflubenzuron is toxic and has histopathological effects on the midgut of A. mellifera adult workers. Workers exposed orally and chronically to the field-realistic concentration of teflubenzuron present 81.54% mortality. The epithelium of the midgut of these bees presents high vacuolization, spherocrystals, cell fragments released to the organ lumen, apocrine secretion, nuclear pyknosis, loss of cell-cell contact, and damage to regenerative cell nests and to the peritrophic matrix. These results indicate that the chitin synthesis-inhibiting insecticide teflubenzuron is toxic to A. mellifera after chronic oral exposure, at realistic field concentration, although it is classified as non-toxic to adult and non-target insects.

Exposure of honey bees to mixtures of microbial biopesticides and their effects on bee survival under laboratory conditions

Biopesticides, having as active ingredients viruses, bacteria, or fungi, are developed to substitute or reduce the use of chemical plant protection products in different agrosystems. Though the application of mixtures containing several products is a common practice, interactions between microbial biopesticides and related effects on bees as non-target organisms have not been studied yet. In the current study, we exposed winter bees to five different microbial-based products and their combinations at the maximum recommended application rate to assess their responses. Laboratory oral exposure tests (acute/chronic) to single or binary products were conducted. Survival and food consumption of the tested bees were evaluated over the experimental duration. Our results show that some product combinations have potential additive or synergistic effects on bees, whereas others did not affect the bee's survival compared to the control. Exposure of tested bees to the most critical combination of products containing Bacillus thuringiensis aizawai ABTS-1857 and B. amyloliquefaciens QST 713 strongly resulted in a median lifespan of 4.5 days compared to 8.0 and 8.5 days after exposure to the solo products, respectively. The exposure to inactivated microorganisms by autoclaving them did not differ from their respective uncontaminated negative controls, indicating effects on bee mortality might originate in the treatment with the different microorganisms or their metabolites. Further investigations should be conducted under field conditions to prove the magnitude of observed effects on bee colonies and other bee species.

Impact of landscape composition on honey bee pollen contamination by pesticides: A multi-residue analysis

The honey bee is the most common and important managed pollinator of crops. In recent years, honey bee colonies faced high mortality for multiple causes, including land-use change and the use of plant protection products (hereafter pesticides). This work aimed to explore how contamination by pesticides of pollen collected by honey bees was modulated by landscape composition and seasonality. We placed two honey bee colonies in 13 locations in Northern Italy in contrasting landscapes, from which we collected pollen samples monthly during the whole flowering season in 2019 and 2020. We searched for almost 400 compounds, including fungicides, herbicides, insecticides, and acaricides. We then calculated for each pollen sample the Pollen Hazard Quotient (PHQ), an index that provides a measure of multi-residue toxicity of contaminated pollen. Almost all pollen samples were contaminated by at least one compound. We detected 97 compounds, mainly fungicides, but insecticides and acaricides showed the highest toxicity. Fifteen % of the pollen samples had medium-high or high levels of PHQ, which could pose serious threats to honey bees. Fungicides showed a nearly constant PHQ throughout the season, while herbicides and insecticides and acaricides showed higher PHQ values in spring and early summer. Also, PHQ increased with increasing cover of agricultural and urban areas from April to July, while it was low and independent of landscape composition at the end of the season. The cover of perennial crops, i.e., fruit trees and vineyards, but not of annual crops, increased PHQ of pollen samples. Our work highlighted that the potential toxicity of pollen collected by honey bees was modulated by complex interactions among pesticide category, seasonality, and landscape composition. Due to the large number of compounds detected, our study should be complemented with additional experimental research on the potential interactive effects of multiple compounds on honey bee health.

Fungicides and insecticides can alter the microbial community on the cuticle of honey bees

Honey bees are crucial for our ecosystems as pollinators, but the intensive use of plant protection products (PPPs) in agriculture poses a risk for them. PPPs do not only affect target organisms but also affect non-targets, such as the honey bee Apis mellifera and their microbiome. This study is the first of its kind, aiming to characterize the effect of PPPs on the microbiome of the cuticle of honey bees. We chose PPPs, which have frequently been detected in bee bread, and studied their effects on the cuticular microbial community and function of the bees. The effects of the fungicide Difcor® (difenoconazole), the insecticide Steward® (indoxacarb), the combination of both (mix A) and the fungicide Cantus® Gold (boscalid and dimoxystrobin), the insecticide Mospilan® (acetamiprid), and the combination of both (mix B) were tested. Bacterial 16S rRNA gene and fungal transcribed spacer region gene-based amplicon sequencing and quantification of gene copy numbers were carried out after nucleic acid extraction from the cuticle of honey bees. The treatment with Steward® significantly affected fungal community composition and function. The fungal gene copy numbers were lower on the cuticle of bees treated with Difcor®, Steward®, and PPP mix A in comparison with the controls. However, bacterial and fungal gene copy numbers were increased in bees treated with Cantus® Gold, Mospilan®, or PPP mix B compared to the controls. The bacterial cuticular community composition of bees treated with Cantus® Gold, Mospilan®, and PPP mix B differed significantly from the control. In addition, Mospilan® on its own significantly changed the bacterial functional community composition. Cantus® Gold significantly affected fungal gene copy numbers, community, and functional composition. Our results demonstrate that PPPs show adverse effects on the cuticular microbiome of honey bees and suggest that PPP mixtures can cause stronger effects on the cuticular community than a PPP alone. The cuticular community composition was more diverse after the PPP mix treatments. This may have far-reaching consequences for the health of honey bees.

Analysis of Pesticide Levels in Honey and Pollen from Irish Honey Bee Colonies Using a Modified Dutch Mini-Luke Method with Gas and Liquid Chromatography-Tandem Mass Spectrometry Detection

Determining the levels of agrochemicals, such as pesticides, that honey bees are exposed to is critical for understanding what stress factors may be contributing to colony declines. Although several pesticide detection methods are available for honey, limited work has been conducted to adapt these methods for pollen. Here, we address this gap by modifying the Dutch mini-Luke extraction method (NL method) for pesticide analysis in honey and pollen from throughout the island of Ireland. The NL method was modified to enable detection in small-sized samples and validated for both pollen and honey matrices. The modified NL method combined with liquid and gas chromatography-tandem mass spectrometry gave consistent results in terms of accuracy and precision measured by recovery experiments and was successfully applied in the analysis of a range of pesticide residues. The modified NL method developed here provides a key tool for detecting pesticides in honey bee colony resources and the environment more broadly.

Digestion dynamics of acetamiprid during royal jelly formation and exposure risk assessment to honeybee larva based on processing factor

Previous studies to the exposure effects of acetamiprid on honeybees were based on the analysis of bee pollen and honey sacs from field trials or of beebread and honey in the hive, which overestimate or underestimate the risk of exposure to pesticide residues. It was believed that the processing factor (PF) is an important variable to determine the final pesticide residue during royal jelly formation and the actual risk to honeybee larva. Hence, a QuEChERS method to determine acetamiprid contents in honeybee samples was established in this study. Then, the PFs for acetamiprid in beebread fermentation, honey brewing, and royal jelly formation were determined to be 0.85, 0.76, and 0.16, respectively. The PF for royal jelly formation was 0.04 when acetamiprid was detected in beebread alone, and it was 0.12 when acetamiprid was only detected in honey. Finally, the predicted exposure concentration of acetamiprid in royal jelly was calculated to be 2.05 µg/kg using the PF without significant difference with the 90th percentile value (3.64 µg/kg) in the actual sample. However, the value was 16.62 µg/kg without considering the PF. This study establishes a methodology for the correct evaluation of the risk to bee larva of acetamiprid residues in bee pollen and honey sac contents and the residual levels in royal jelly.

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.

Ecological threat caused by malathion and its chiral metabolite in a honey bee-rape system: Stereoselective exposure risk and the mechanism revealed by proteome

Honey bees play an important role in the ecological environment. Regrettably, a decline in honey bee colonies caused by chemical insecticides has occurred throughout the world. Potential stereoselective toxicity of chiral insecticides may be a hidden source of danger to bee colonies. In this study, the stereoselective exposure risk and mechanism of malathion and its chiral metabolite malaoxon were investigated. The absolute configurations were identified using an electron circular dichroism (ECD) model. Ultrahigh-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was used for chiral separation. In pollen, the initial residues of malathion and malaoxon enantiomers were 3571-3619 and 397-402 μg/kg, respectively, and R-malathion degraded relatively slowly. The oral LD₅₀ values of R-malathion and S-malathion were 0.187 and 0.912 μg/bee with 5 times difference, respectively, and the malaoxon values were 0.633 and 0.766 μg/bee. The Pollen Hazard Quotient (PHQ) was used to evaluate exposure risk. R-malathion showed a higher risk. An analysis of the proteome, including Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), and subcellular localization, indicated that energy metabolism and neurotransmitter transport were the main affected pathways. Our results provide a new scheme for the evaluation of the stereoselective exposure risk of chiral pesticides to honey bees.

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.

Abamectin and difenoconazole monitoring in strawberry flowers and pollen sampled from Tetragonisca angustula (Latreille) (Hymenoptera: Apidae) hives located in crop vicinities

The increase in agricultural productivity associated with the emergence and the extensive use of pesticides is undeniable. However, strong evidence indicates that this continuous demand is causing serious environmental impacts and bringing toxic effects to associated biota as pollinating insects. The present work aims the determination of the insecticide abamectin (ABA) and the fungicide difenoconazole (DIF) in strawberry flowers (Fragaria x ananassa DUCH.) and pollen sampled from beehives of the stingless bee Tetragonisca angustula Latreille (Hymenoptera: Apidae) located nearby strawberry fields. For analysis, QuEChERS method was optimized, and the analytical performance of those two pesticides was verified. Then, the method was applied to strawberry flowers and the pollen was sampled during three field campaigns. While abamectin was not detected, the systemic fungicide difenoconazole was determined in almost all flowers and pollen samples, demonstrating the major persistence of this pesticide in investigated matrices. The results were then discussed about the difenoconazole application rate and transport to colonies to estimate a preliminary environmental risk assessment for stingless native bees. All calculations were proceeded considering exposure rates and toxicity data from the literature, adapted from Apis mellifera studies. In this sense, the determination, application, and discussion about risk assessment figure out as an important tool to the knowledge about the preliminary risks of native bees exposed to pesticides.

Quantitation of pesticides in bee bread collected from honey bee colonies in an agricultural environment in Switzerland

Pesticide contamination of bee products is a widespread phenomenon. Due to its composition, bee bread is affected by both lipophilic and hydrophilic substances. As proof of concept of a monitoring campaign and to better understand the extent of contamination, we developed an analytical method based on a modified QuEChERS extraction, with subsequent separation by liquid chromatography and detection by mass spectrometry. This allowed for the quantitation of 51 agricultural- or beekeeping-associated pesticides in bee bread. The workflow was applied to 60 samples taken biweekly throughout spring to autumn 2022 from five colonies at a Swiss apiary in an agricultural area. In total, 30 pesticides were identified (> LOD), among which 26 pesticides were quantitated. The total number of pesticides detected per colony ranged from 11 to 19. The most prevalent substances (> LOQ) were two neonicotinoid insecticides, acetamiprid and thiacloprid (max. 16 μg/kg and 37 μg/kg, respectively); seven fungicides, azoxystrobin (max. 72 μg/kg), boscalid (max. 50 μg/kg), cyprodinil (max. 1965 μg/kg), difenoconazole (max. 73 μg/kg), mandipropamid (max. 33 μg/kg), pyraclostrobin (max. 8 μg/kg) and trifloxystrobin (max. 38 μg/kg); and two herbicides, prosulfocarb (max. 38 μg/kg) and terbuthylazine (max. 26 μg/kg). The study revealed strong variability in pesticide occurrence and concentrations among colonies sampled at the same site and date. The applied biweekly sampling of bee bread from March to August was shown to be reliable in capturing peak contaminations and revealing the onset of certain pesticides in bee bread. The study provides an adequate practical approach for pesticide monitoring campaigns.

Decision-making criteria for pesticide spraying considering the bees’ presence on crops to reduce their exposure risk

The risk of poisoning bees by sprayed pesticides depends on the attractiveness of plants and environmental and climatic factors. Thus, to protect bees from pesticide intoxication, an usual exemption to pesticide regulations allows for spraying on blooming flowers with insecticides or acaricides when no bees are foraging on crops. Nevertheless, decision-making criteria for farmers to assess the absence of bees on their crops remain under debate. To fill this gap, we present here a review of the literature and an analysis of weather conditions and environmental factors that affect the presence of bees on flowering crops that may be treated with pesticides, with the objective of proposing to farmers a series of decision-making criteria on how and when to treat. We conclude that the criteria commonly considered, such as ambient temperature, crop attractiveness, or distance from field edges, cannot guarantee the absence of forager exposure during pesticide sprays. Nocturnal sprays of pesticides on crops would be the most effective action to help farmers avoid unintentional acute poisoning of bees.

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.

The role of AccCDK20 and AccCDKN1 from Apis cerana cerana in development and response to pesticide and heavy metal toxicity

Apis cerana cerana is a native bee species in China and plays a key role in agricultural production and ecological balance. However, the growth and development of Apis cerana cerana has not been smooth, and pesticide and heavy metal stress are key factors that have forced a dramatic decline in population size. This study was performed with the objective of investigating the role of AccCDK20 and AccCDKN1 in honey bee resistance to pesticide and heavy metal stress. RT-qPCR analysis revealed that AccCDK20 transcript levels were highest in brown-eyed pupae and AccCDKN1 transcript levels were highest in 1-day-old worker bees. In different tissues and body parts of adult bees, AccCDK20 transcript levels were highest in the head, and AccCDKN1 transcript levels were highest in the thorax. It was further observed that environmental stress can affect the transcript levels of the AccCDK20 and AccCDKN1 genes. Silencing of the AccCDK20 and AccCDKN1 genes resulted in altered activities of antioxidant-related genes and antioxidant-related enzymes. AccCDK20 and AccCDKN1 transcript levels were upregulated under glyphosate stress, and silencing of the genes resulted in reduced resistance to glyphosate and greatly increased mortality in Apis cerana cerana. In addition, gene function was verified by in vitro repression assays. Overexpression of the AccCDK20 and AccCDKN1 proteins in E. coli cells increased the resistance to ROS damage induced by CHP. In conclusion, AccCDK20 and AccCDKN1 play an indispensable role in honey bee resistance to pesticide and heavy metal stress.

Binding and Detoxification of Insecticides by Potentially Probiotic Lactic Acid Bacteria Isolated from Honeybee (Apis mellifera L.) Environment-An In Vitro Study

Lactic acid bacteria (LAB) naturally inhabiting the digestive tract of honeybees are known for their ability to detoxify xenobiotics. The effect of chlorpyrifos, coumaphos, and imidacloprid on the growth of LAB strains was tested. All strains showed high resistance to these insecticides. Subsequently, the insecticide binding ability of LAB was investigated. Coumaphos and chlorpyrifos were bound to the greatest extent (up to approx. 64%), and imidacloprid to a much weaker extent (up to approx. 36%). The insecticides were detected in extra- and intracellular extracts of the bacterial cell wall. The ability of selected LAB to reduce the cyto- and genotoxicity of insecticides was tested on two normal (ovarian insect Sf-9 and rat intestinal IEC-6) cell lines and one cancer (human intestinal Caco-2) cell line. All strains exhibited various levels of reduction in the cyto- and genotoxicity of tested insecticides. It seems that coumaphos was detoxified most potently. The detoxification abilities depended on the insecticide, LAB strain, and cell line. The detoxification of insecticides in the organisms of honeybees may reduce the likelihood of the penetration of these toxins into honeybee products consumed by humans and may contribute to the improvement of the condition in apiaries and honeybee health.

The Value of Hazard Quotients in Honey Bee (Apis mellifera) Ecotoxicology: A Review

Estimates of pesticide application hazards have grown to be one of the most common methodologies for evaluating the impact of pest management practices on honey bees. Typically, hazards are estimated by calculating a Hazard Quotient (HQ), which is based on acute toxicity data for different pesticides and the quantity of those pesticides applied to a field or detected on bees and matrices associated with their hive (honey, wax, pollen, and/or bee bread). Although use of HQ is widespread, there have been few reviews of this methodology, particularly with focus on how effective this method is at predicting effects of pesticides on hives. We evaluated 36 relevant papers, containing calculations of HQ to estimate hazards to honey bees. We observed that HQ was primarily calculated using two different approaches: (1) from the concentration of pesticides in the food, hive, or tissues of honey bees or (2) using the field application rate of the active ingredient as the estimation of pesticide hazard. Within and between HQ calculation methods, thresholds vary widely with some HQ thresholds set below 1 and others set at 10,000. Based on our review we identify key weakness with current HQ methodology and how studies relate HQ to honey bee health endpoints. First, HQ thresholds from studies of pesticides in hives are not based on the same pesticide consumption models from the EPA, potentially overestimating the risk of impacts to colonies. Conversely, HQ estimates calculated from field application rates are not based on eco-toxicological estimates of field exposure, resulting in an overestimation of pesticide reaching colonies. We suggest it is for these reasons that there is poor correspondence between HQ and field-level honey bee health endpoints. Considering these challenges, HQ calculations should be used cautiously in future studies and more research should be dedicated to field level exposure models.

Pesticide risk to managed bees during blueberry pollination is primarily driven by off-farm exposures

When managed bee colonies are brought to farms for crop pollination, they can be exposed to pesticide residues. Quantifying the risk posed by these exposures can indicate which pesticides are of the greatest concern and helps focus efforts to reduce the most harmful exposures. To estimate the risk from pesticides to bees while they are pollinating blueberry fields, we sampled blueberry flowers, foraging bees, pollen collected by returning honey bee and bumble bee foragers at colonies, and wax from honey bee hives in blooming blueberry farms in southwest Michigan. We screened the samples for 261 active ingredients using a modified QuEChERS method. The most abundant pesticides were those applied by blueberry growers during blueberry bloom (e.g., fenbuconazole and methoxyfenozide). However, we also detected highly toxic pesticides not used in this crop during bloom (or other times of the season) including the insecticides chlorpyrifos, clothianidin, avermectin, thiamethoxam, and imidacloprid. Using LD₅₀ values for contact and oral exposure to honey bees and bumble bees, we calculated the Risk Quotient (RQ) for each individual pesticide and the average sample RQ for each farm. RQ values were considered in relation to the U.S. Environmental Protection Agency acute contact level of concern (LOC, 0.4), the European Food Safety Authority (EFSA) acute contact LOC (0.2) and the EFSA chronic oral LOC (0.03). Pollen samples were most likely to exceed LOC values, with the percent of samples above EFSA’s chronic oral LOC being 0% for flowers, 3.4% for whole honey bees, 0% for whole bumble bees, 72.4% for honey bee pollen in 2018, 45.4% of honey bee pollen in 2019, 46.7% of bumble bee pollen in 2019, and 3.5% of honey bee wax samples. Average pollen sample RQ values were above the EFSA chronic LOC in 92.9% of farms in 2018 and 42.9% of farms in 2019 for honey bee collected pollen, and 46.7% of farms for bumble bee collected pollen in 2019. Landscape analyses indicated that sample RQ was positively correlated with the abundance of apple and cherry orchards located within the flight range of the bees, though this varied between bee species and landscape scale. There was no correlation with abundance of blueberry production. Our results highlight the need to mitigate pesticide risk to bees across agricultural landscapes, in addition to focusing on the impact of applications on the farms where they are applied.

High abundance of pyrrolizidine alkaloids in bee pollen collected in July 2019 from Southern Germany

Pyrrolizidine alkaloids (PA) are secondary plant defense compounds and known pre-toxins when containing a 1,2-double bond. They are commonly produced by various plants and may thus be present in bee pollen which may be consumed by humans as food supplements. In this study, PA were determined in bee pollen samples from 57 locations in Southern Germany sampled by means of pollen traps in July 2019. Samples were analyzed by using palynological methodology and solid-phase extraction (SPE) followed by LC-MS/MS. In total, 52 pollen samples featured total pyrrolizidine alkaloids (ΣPA) with concentrations up to 48,000 ng/g bee pollen, while the N-oxides (NO) echinatine-NO and rinderine-NO clearly dominated. In contrast, the palynological analysis only detected 33 samples with pollen from PA-producing plants. Accordingly, the results showed that palynological analysis is not sufficient to determine PA in pollen. In addition, a risk assessment was followed to estimate the risk of the detected PA concentrations to humans.

Determination of Pesticides in Bee Pollen: Validation of a Multiresidue High-Performance Liquid Chromatography-Mass Spectrometry/Mass Spectrometry Method and Testing Pollen Samples of Selected Botanical Origin

Pollen is a source of nutrients for honeybees (Apis mellifera L.) and suitable for human consumption as well. In our research, a multiresidue method for pesticide determination was developed and validated for the bee pollen matrix. 247 components met the validation criteria for limit of detection, limit of quantification, linearity, and interday repeatability. Average recoveries varied between 70 and 120% except for 14 analytes, which were corrected during on-going validation. The matrix effect was strong for certain analytes, which required the use of matrix-matched calibration. The pesticide residue profiles of 21 pollen samples of different botanical origins were identified by the developed method. The most common active substances were chlorpyrifos, thiacloprid, and acetamiprid. Some products contained pesticides that are already banned. According to our estimates, the tested samples do not pose an acute risk on honeybees, although the combination of pesticides may cause synergistic toxicity.

Direct pesticide exposure of insects in nature conservation areas in Germany

In Germany, the decline of insect biomass was observed in nature conservation areas in agricultural landscapes. One of the main causal factors discussed is the use of synthetic pesticides in conventional agriculture. In a Germany-wide field study, we collected flying insects using Malaise traps in nature conservation areas adjacent to agricultural land. We used a multi-component chemical trace element analysis to detect 92 common agricultural pesticides in ethanol from insect traps sampled in May and August 2020. In total, residues of 47 current use pesticides were detected, and insect samples were on average contaminated with 16.7 pesticides. Residues of the herbicides metolachlor-S, prosulfocarb and terbuthylazine, and the fungicides azoxystrobin and fluopyram were recorded at all sites. The neonicotinoid thiacloprid was detected in 16 of 21 nature conservation areas, most likely due to final use before an EU-wide ban. A change in residue mixture composition was noticeable due to higher herbicide use in spring and increasing fungicide applications in summer. The number of substances of recorded residues is related to the proportion of agricultural production area in a radius of 2000 m. Therefore, a drastic pesticide reduction in large buffers around nature conservation areas is necessary to avoid contamination of their insect fauna.

Review of harmful chemical pollutants of environmental origin in honey and bee products

Honey is a natural food with many pro-health properties, which comprises a wide variety of valuable ingredients. It can also be the source of chemical contaminants of environmental origin, including POPs that can contribute to adverse health effects to human. Monitoring the degree of pollution of honey/bee products with hazardous chemicals is important from a nutraceutical point of view. In the present work, overview of recent literature data on chemical pollutants in honey/bee products originating from the environment was performed. Their MLs, MRLs and EDI were discussed. It can be concluded that huge amount of research concerned on the presence of TMs and pesticides in honey. Most of the studies have shown that honey/bee products sampled from urban and industrialized areas were more contaminated than these sampled from ecological and rural locations. More pollutants were usually detected in propolis and bee pollen than in honey. Based on their research and regulations, authors stated, that most of the toxic pollutants of environmental origin in honey/bee products are at levels that do not pose a threat to the health of the potential consumer. The greatest concern relates to pesticides and TMs, because in some research MLs in individual samples were highly exceeded.

The use of the Hazard Quotient approach to assess the potential risk to honeybees (Apis mellifera) posed by pesticide residues detected in bee-relevant matrices is not appropriate

BACKGROUND

Pesticide residue data for pollen and nectar are valuable for characterizing realistic exposure of pollinators, e.g. from agricultural crops, flowering margins. Interpretation of residues relies on comparing exposure with toxicity and the Hazard Quotient (HQ) is widely utilized. However, the HQ (threshold of concern 50) was only validated for foliar sprays, based on application rate as a proxy for exposure, not measured residues in bee-relevant matrices.

RESULTS

A review of the literature showed a range of HQ approaches and thresholds of concern used to assess non-foliar applications and residues detected in bee-relevant matrices, mostly pollen. The use of the HQ thresholds to assess risks associated with residue data or non-foliar spray application methods is not validated, does not reflect realistic exposure and the conclusions reached differ substantially from current risk assessment approaches. Re-evaluation of residue data from the first published use of the concentration-based HQ (2013) and a recent paper (2021) reduced the proportion of pesticides where a conclusion of potential risk was reached from 30 to 7% and 28% to 3-6%, respectively.

CONCLUSIONS

An understanding of the applicability of the selected risk assessment approach to the available residue data is needed to enable robust conclusions to be drawn on the potential risk to bees. Use of the HQ approach to assess the risk posed by application methods other than foliar sprays or residues in nectar and pollen is likely to result in unreliable conclusions. An alternative approach should be used to assess the significance of measured residues.

Changes of microorganism composition in fresh and stored bee pollen from Southern Germany

Analysis of plant pollen can provide valuable insights into the existing spectrum of microorganisms in the environment. When harvesting bee-collected pollen as a dietary supplement for human consumption, timely preservation of the freshly collected pollen is fundamental for product quality. Environmental microorganisms contained in freshly collected pollen can lead to spoilage by degradation of pollen components. In this study, freshly collected bee pollen was sampled at different locations and stored under various storage conditions to examine the hypothesis that storage conditions may have an effect on the composition of microorganisms in pollen samples. The samples were analyzed using 16S and 18S amplicon sequencing and characterized by palynological analysis. Interestingly, the bacterial communities between pollen samples from different locations varied only slightly, whereas for fungal community compositions, this effect was substantially increased. Further, we noticed that fungal communities in pollen are particularly sensitive to storage conditions. The fungal genera proportion Cladosporium and Mycosphaerella decreased, while Zygosaccharomyces and Aspergillus increased during storage. Aspergillus and Zygosaccharomyces fractions increased during storage at 30 °C, which could negatively impact the pollen quality if it is used as a dietary supplement.

Identities, concentrations, and sources of pesticide exposure in pollen collected by managed bees during blueberry pollination

Bees are critical for crop pollination, but there is limited information on levels and sources of pesticide exposure in commercial agriculture. We collected pollen from foraging honey bees and bumble bees returning to colonies placed in blooming blueberry fields with different management approaches (conventional, organic, unmanaged) and located across different landscape settings to determine how these factors affect pesticide exposure. We also identified the pollen and analyzed whether pesticide exposure was correlated with corbicular load composition. Across 188 samples collected in 2 years, we detected 80 of the 259 pesticide active ingredients (AIs) screened for using a modified QuEChERS method. Detections included 28 fungicides, 26 insecticides, and 21 herbicides. All samples contained pesticides (mean = 22 AIs per pollen sample), with pollen collected from bees on conventional fields having significantly higher average concentrations (2019 mean = 882.0 ppb) than those on unmanaged fields (2019 mean = 279.6 ppb). Pollen collected by honey bees had more AIs than pollen collected by bumble bees (mean = 35 vs. 19 AIs detected at each farm, respectively), whereas samples from bumble bees had higher average concentrations, likely reflecting differences in foraging behavior. Blueberry pollen was more common in pollen samples collected by bumble bees (25.9% per sample) than honey bees (1.8%), though pesticide concentrations were only correlated with blueberry pollen for honey bees. Pollen collected at farms with more blueberry in the surrounding landscape had higher pesticide concentrations, mostly AIs applied for control of blueberry pathogens and pests during bloom. However, for honey bees, the majority of AIs detected at each farm are not registered for use on blueberry at any time (55.2% of AIs detected), including several highly toxic insecticides. These AIs therefore came from outside the fields and farms they are expected to pollinate. For bumble bees, the majority of AIs detected in their pollen are registered for use on blueberry during bloom (56.9% of AIs detected), though far fewer AIs were sprayed at the focal farm (16.7%). Our results highlight the need for integrated farm and landscape-scale stewardship of pesticides to reduce exposure to pollinators during crop pollination.

Future of Insecticide Seed Treatment

Seed treatment as a method of local application of pesticides in precise agriculture reduces the amount of pesticides used per unit area and is considered to be the safest, cheapest and most ecologically acceptable method of protecting seeds and young plants from pests in the early stages of their development. With the introduction of insecticides from the neonicotinoid group in the mid-1990s, the frequency of seed treatment increased. Due to suspected negative effects on pollinators, most of these insecticides are banned in the European Union. The ban has therefore led to a reduction in the number of active substances approved for seed treatment and to an increased re-use of active substances from the group of pyrethroids as well as other organophosphorus insecticides, which pose potentially very serious risks, perhaps even greater than those of the banned neonicotinoids. The objective of this review is to analyze the advantages and disadvantages of seed treatment and the potential role of insecticide seed treatment in reducing the negative impact of pesticides on the environment. The main disadvantage of this method is that it has been widely accepted and has become a prophylactic protective measure applied to almost all fields. This is contrary to the principles of integrated pest management and leads to an increased input of insecticides into the environment, by treating a larger number of hectares with a lower amount of active ingredient, and a negative impact on beneficial entomofauna. In addition, studies show that due to the prophylactic approach, the economic and technical justification of this method is often questionable. Extremely important for a quality implementation are the correct processing and implementation of the treatment procedure as well as the selection of appropriate insecticides, which have proven to be problematic in the case of neonicotinoids. The ban on neonicotinoids and the withdrawal of seed treatments in oilseed rape and sugar beet has led to increased problems with a range of pests affecting these crops at an early stage of growth. The results of the present studies indicate good efficacy of active ingredients belonging to the group of anthranilic diamides, cyantraniliprole and chlorantraniliprole in the treatment of maize, soybean, sugar beet and rice seeds on pests of the above-ground part of the plant, but not on wireworms. Good efficacy in controlling wireworms in maize is shown by an insecticide in the naturalites group, spinosad, but it is currently used to treat seeds of vegetable crops, mainly onions, to control onion flies and flies on other vegetable crops. Seed treatment as a method only fits in with the principles of integrated pest management when treated seeds are sown on land where there is a positive prognosis for pest infestation.

Field cross-fostering and in vitro rearing demonstrate negative effects of both larval and adult exposure to a widely used fungicide in honey bees (Apis mellifera)

Pollinators and other insects are experiencing an ongoing worldwide decline. While various environmental stressors have been implicated, including pesticide exposure, the causes of these declines are complex and highly debated. Fungicides may constitute a particularly prevalent threat to pollinator health due to their application on many crops during bloom, and because pollinators such as bees may consume fungicide-tainted pollen or nectar. In a previous study, consumption of pollen containing the fungicide Pristine® at field-relevant concentrations by honey bee colonies increased pollen foraging, caused earlier foraging, lowered worker survival, and reduced colony population size. Because most pollen is consumed by young adults, we hypothesized that Pristine® (25.2% boscalid, 12.8% pyraclostrobin) in pollen exerts its negative effects on honey bee colonies primarily on the adult stage. To rigorously test this hypothesis, we used a cross-fostering experimental design, with bees reared in colonies provided Pristine® incorporated into pollen patties at a supra-field concentration (230 mg/kg), only in the larvae, only in the adult, or both stages. In contrast to our predictions, exposure to Pristine® in either the larval or adult stage reduced survival relative to control bees not exposed to Pristine®, and exposure to the fungicide at both larval and adult stages further reduced survival. Adult exposure caused precocious foraging, while larval exposure increased the tendency to forage for pollen. These results demonstrate that pollen containing Pristine® can induce significant negative effects on both larvae and adults in a hive, though the magnitude of such effects may be smaller at field-realistic doses. To further test the potential negative effects of direct consumption of Pristine® on larvae, we reared them in vitro on food containing Pristine® at a range of concentrations. Consumption of Pristine® reduced survival rates of larvae at all concentrations tested. Larval and adult weights were only reduced at a supra-field concentration. We conclude that consumption of pollen containing Pristine® by field honey bee colonies likely exerts impacts on colony population size and foraging behavior by affecting both larvae and adults.