Neonicotinoid Residues in Wildflowers, a Potential Route of Chronic Exposure for Bees

Insecticide and pathogens co-exposure induces histomorphology changes in midgut and energy metabolism disorders on Apis mellifera

Honey bees in agroecosystems face increasingly exposure to multiple stressors, such as pesticides and pathogens, making it crucial to assess their combined impacts rather than focusing on individual factors alone. This study examined the adverse effects of single exposure acetamiprid, Varroa destructor, and Nosema ceranae, both individually and in combination, on honey bee survival, midgut integrity and transcriptomic changes to understand the molecular mechanisms involved. The findings revealed that combination of acetamiprid and N. ceranae induced significant energetic stress, as evidenced by disruptions in energy metabolism. The synergistic effects of V. destructor and N. ceranae led to severe alterations in midgut histomorphology, particularly damaging the midgut epithelium. Concurrent exposure to acetamiprid and V. destructor inhibited the immune response and energy metabolism of honey bees, thereby exacerbating the vulnerability to pathogens and destabilizing their physiological equilibrium. The combination of all three stressors caused the most dramatic damage, disrupting midgut structure as well as aromatic amino acids and lipid metabolism. Our study underscored the complexity and unpredictability of stressor interactions, emphasizing the need to consider environmental context when assessing the risks of honey bee health.

Evaluating the Safety Profile of Cycloxaprid for Seed Treatment: Insights from Plant Uptake, Translocation, and Metabolism

The use of neonicotinoids in agricultural seed treatments faces increased scrutiny due to their adverse effects such as induced pollinator decline. Cycloxaprid is a promising alternative to traditional neonicotinoids with higher efficiency and improved safety profiles. This study systematically investigated the uptake, translocation, and metabolism of cycloxaprid in rice, maize, and water spinach after seed treatment, using 14C isotope tracing and high-resolution mass spectrometry. Results indicated that less than 11% of cycloxaprid was absorbed by the seedlings, with over 85% released into soils. Cycloxaprid predominantly accumulated in the roots and lower leaves, with minimal translocation to upper leaves or edible parts. Subcellular analysis revealed that cycloxaprid and its metabolites predominantly bonded with internal plant matrix molecules, limiting their transport within the plants. Additionally, seven metabolites of cycloxaprid were identified, and a preliminary metabolic pathway in plants was proposed. Compared to conventional neonicotinoids, cycloxaprid displayed lower potential for plant uptake and vertical translocation, thereby reducing risks to nontarget species like pollinators. These findings provide important theoretical support for the promotion of cycloxaprid as a safe seed treatment agent and offer new perspectives for the sustainable use and risk management of neonicotinoid pesticides.

Differential effects of clothianidin exposure on metabolic rates across life stages of Danaus plexippus (Lepidoptera: Nymphalidae)

The restoration of milkweed to agricultural landscapes is thought to be essential for bolstering declining monarch butterfly (Danaus plexippus) populations. However, the rise of neonicotinoid seed treatments in recent decades has severely increased the toxicity of these landscapes for insects. It is therefore crucial that we understand how monarchs utilize neonicotinoid-contaminated plants and their impacts on monarch health to better inform conservation efforts. We monitored monarch usage of milkweed (Asclepias syriaca) plantings adjacent to clothianidin-treated and untreated cornfields and found both were utilized with equal frequency. We then examined how plant-mediated larval clothianidin exposure affected monarch development, morphology, and energetics by tracking mortality rates, development times, body metrics, and metabolic rates across life stages. We found no difference in mortality rates or body metrics between the 2 treatment groups. Larvae feeding on clothianidin-treated plants required less time to reach pupation than those feeding on control plants, but there was no difference in the time between pupation and eclosion. Larval clothianidin exposure did not affect the resting metabolic rates of monarchs at any life stage; however, it lowered both the average and peak flight metabolic rates of adults, with the effects being stronger in males than females. These findings suggest that larval exposure to clothianidin-contaminated plants can have carry-over sublethal effects in adulthood, which may adversely affect flight capacity, particularly in males. Further studies are needed to elucidate the possible impacts on crucial aspects of monarch ecology, including their foraging, migratory, and reproductive potential.

Neonicotinoid insecticides in non-target organisms: Occurrence, exposure, toxicity, and human health risks

Pesticides have consistently portrayed a crucial role in the history of modern agricultural production. Neonicotinoid insecticides are classified as the fourth generation of pesticides, following organophosphorus, pyrethroids, and carbamates. Due to their broad-spectrum insecticidal activity, unique neurotoxic mode of action, and versatility of application methods, neonicotinoids have been widely used worldwide since their introduction. Recent studies have shown that neonicotinoids are frequently detected in a variety of food and environmental media around the world, posing considerable safety risks to human health and ecosystems, and therefore have become an emerging contaminant. However, the toxic effects and exposure risks of neonicotinoids to non-target organisms, including humans, have not received sufficient attention. Therefore, based on previous studies, this critical review concisely evaluates the occurrence and exposure levels of neonicotinoids in the environment and the associated risks to human health. The toxic effects of neonicotinoids on non-target organisms are systematically reviewed, including the aspects of acute toxicity, reproductive development, nervous system, immune function, genetics, and others. The potential toxic mechanism of these pesticides is discussed. The existing knowledge gaps are identified, and future prospects for neonicotinoids are proposed to provide scientific guidance for the safe and rational use of neonicotinoids and future research directions.

Romance in peril: A common pesticide impairs mating behaviours and male fertility of solitary bees (Osmiabicornis)

Mating behaviour and fertility are strong selective forces, driving the reproductive trends of animals. Mating disorders may therefore contribute to the recent decline in insect and pollinators health worldwide. While the impact of pesticides on pollinators is widely considered as a driving factor for reducing pollinators health, their effect on mating behaviour and male fertility remains widely overlooked. Here, we assessed the effects of field-realistic exposure to a common pesticide used as a neonicotinoid substitute worldwide, sulfoxaflor, on the behaviour and male physiology of the solitary bee, Osmia bicornis. We measured a variety of parameters focusing on behaviours occurring before, and during mating, as well as sperm quantity. For the first time, we demonstrate that short-term chronic, field-realistic exposure to a common pesticide reduced pre-copulatory display (-36 %) and sounds (-27 %), increased the number of copulations (+110 %) and the mating duration (+166 %), while finally reducing sperm quantity (-25 %) and mating success (-43 %). Our research raises considerable concern on the impact of field-realistic, low sublethal pesticide levels on the fertility and reproductive success of pollinators. Assessing the impact of pesticides on fitness parameters and implementing more sustainable agricultural solutions would allow mitigating the ongoing threat of pesticide pollution on wild insect populations and the broader environment.

Pesticide residues in honey: Agricultural landscapes and commercial wax foundation sheets as potential routes of chronic exposure for honey bees

Pesticides pose significant threats to pollinators, and honey bees are frequently exposed through foraging and beekeeping practices. We assessed honey bee pesticide exposure by analyzing 92 pesticide residues in honey from 30 hobbyist apiaries across Massachusetts, along with store-bought honey and commercial wax foundation. For all samples, we calculated the risk of multiresidue toxicity to honey bees and assessed the role of landscape composition in predicting pesticides in local honey. Both honey and wax contained multiple pesticides, particularly neonicotinoids and piperonyl butoxide. Store-bought honey accumulated at least two times more residues than local, but did not differ significantly in toxicity. Overall, honey toxicity levels remained below thresholds of concern for bees and human consumption. Although our study had low agricultural land (∼6 %), croplands were positively correlated with pesticides in honey, while wetlands (∼ 15 %) were negatively correlated. Additionally, our study suggests that commercial wax exacerbates pesticide exposure.

Acute and chronic pesticide exposure trigger fundamentally different molecular responses in bumble bee brains

BACKGROUND

Beneficial insects, including pollinators, encounter various pesticide exposure conditions, from brief high-concentration acute exposure to continuous low-level chronic exposure. To effectively assess the environmental risks of pesticides, it is critical to understand how different exposure schemes influence their effects. Unfortunately, this knowledge remains limited. To clarify whether different exposure schemes disrupt the physiology of pollinators in a similar manner, we exposed bumble bees to acute or chronic treatments of three different pesticides: acetamiprid, clothianidin, or sulfoxaflor. Genome-wide gene expression profiling enabled us to compare the effects of these treatments on the brain in a high-resolution manner.

RESULTS

There were two main findings: First, acute and chronic exposure schemes largely affected non-overlapping sets of genes. Second, different pesticides under the same exposure scheme showed more comparable effects than the same pesticide under different exposure schemes. Each exposure scheme induced a distinct gene expression profile. Acute exposure mainly caused upregulation of genes linked to the stress response mechanisms, like peroxidase and detoxification genes, while chronic exposure predominantly affected immunity and energy metabolism.

CONCLUSIONS

Our findings show that the mode of exposure is critical in determining the molecular effects of pesticides. These results signal the need for safety testing practices to better consider mode-of-exposure dependent effects and suggest that transcriptomics can support such improvements.

Impacts of neonicotinoids on biodiversity: a critical review

Neonicotinoids are the most widely used class of insecticides in the world, but they have raised numerous concerns regarding their effects on biodiversity. Thus, the objective of this work was to do a critical review of the contamination of the environment (soil, water, air, biota) by neonicotinoids (acetamiprid, clothianidin, imidacloprid, thiacloprid, thiamethoxam) and of their impacts on terrestrial and aquatic biodiversity. Neonicotinoids are very frequently detected in soils and in freshwater, and they are also found in the air. They have only been recently monitored in coastal and marine environments, but some studies already reported the presence of imidacloprid and thiamethoxam in transitional or semi-enclosed ecosystems (lagoons, bays, and estuaries). The contamination of the environment leads to the exposure and to the contamination of non-target organisms and to negative effects on biodiversity. Direct impacts of neonicotinoids are mainly reported on terrestrial invertebrates (e.g., pollinators, natural enemies, earthworms) and vertebrates (e.g., birds) and on aquatic invertebrates (e.g., arthropods). Impacts on aquatic vertebrate populations and communities, as well as on microorganisms, are less documented. In addition to their toxicity to directly exposed organisms, neonicotinoid induce indirect effects via trophic cascades as demonstrated in several species (terrestrial and aquatic invertebrates). However, more data are needed to reach firmer conclusions and to get a clearer picture of such indirect effects. Finally, we identified specific knowledge gaps that need to be filled to better understand the effects of neonicotinoids on terrestrial, freshwater, and marine organisms, as well as on ecosystem services associated with these biotas.

Comparative temporal response of toxicity for the neonicotinoid clothianidin and organophosphate dimethoate insecticides in two species of solitary bee (Osmia bicornis and Osmia cornuta)

Solitary bees provide essential pollination services. Concerns for the decline of these wild bee species have led to calls for their inclusion in pesticide risk assessment. Solitary bees differ from honey bees in their physiology and ecology and this may affect how they respond to pesticide exposure. Here we investigate the life-time toxicity of two insecticides, the organophosphate dimethoate and neonicotinoid clothianidin, for two mason bee species, Osmia bicornis and O. cornuta using a toxicokinetic/toxicodynamic stochastic death model taken from Dynamic Energy Budget (DEBtox) theory. Both species showed concentration and exposure duration dependent effects for each chemical. LC50 values estimated from the model parameters at 48 h were ≥ 14 fold and 6 fold those at 480 h for dimethoate and clothianidin respectively. Survival modelling indicated greater sensitivity in O. bicornis than for O. cornuta to dimethoate, whilst for clothianidin, O. cornuta females but not males, were more sensitive than both sexes of O. bicornis. These sensitivity differences were not related to body size. Toxicokinetic and toxicodynamic traits derived from modelling indicated lower elimination rates in O. bicornis and higher killing rates for O. cornuta females for dimethoate and lower elimination rates for clothianidin in O. cornuta females that were related to sensitivity. This study shows the near life-time testing is possible for solitary bees and that combining adult life-time toxicity tests with toxicokinetic/toxicodynamic modelling provides a more mechanistic understanding of pesticide effects in solitary bee species.

Binary Mixture of Neonicotinoid-Pyrethroid Insecticide: Impact on Survival, Cognitive Learning, and Memory in Apis mellifera jemenitica

The impact of agrochemicals on pollinators, especially honey bees, has drawn significant attention due to its critical implications for worldwide food stability and ecosystems. Given the potential threat of insecticides to honey bees, bees may encounter multiple insecticides simultaneously during foraging. This study investigated the toxic effect of an insecticide mixture (IM) containing acetamiprid (neonicotinoid) and deltamethrin (pyrethroid) on the survival and cognitive appetitive performance of Apis mellifera jemenitica, a vital native pollinator in arid regions of Saudi Arabia. The lethal concentration (LC50) was determined by assessing bees' mortality rates following exposure to IM through topical and oral routes. Significant bee mortality occurred at 4-48 h post treatment with IM through both exposure routes, showing a trend of increased mortality with higher IM concentrations compared to the control bees. Throughout all tested times, topical exposure proved relatively more effective, resulting in significantly greater bee mortality compared to oral exposure to IM. Food intake declined progressively with rising IM concentrations during oral exposure. The LC50 values of IM at 24 h after treatment were 12.24 ppm for topical and 10.45 ppm for oral exposure. The corresponding LC10, LC20, and LC30 values were 3.75 ppm, 5.63 ppm, and 7.54 ppm for topical exposure and 2.45 ppm, 4.04 ppm, and 5.78 ppm for oral exposure, respectively. The combination index (CI) revealed a synergistic effect (0.43) for topical exposure and antagonistic effects (1.43) for oral exposure, highlighting differential toxicity dynamics. IM exposure significantly impaired cognitive acquisition and memory reinforcement in honey bees, as demonstrated through behavioral assays, indicating potential neurotoxic effects. Learning and memory formation significantly declined at 2, 12, and 24 h after exposure to sublethal concentrations of IM through both topical and oral routes. Thus, evaluating the interactive impact of multiple pesticides on bees' health and cognitive function is essential, particularly in regions where diverse agrochemicals are routinely utilized.

Sub-lethal pesticide exposure interferes with honey bee memory of learnt colours

Neonicotinoid pesticide use has increased around the world despite accumulating evidence of their potential detrimental sub-lethal effects on the behaviour and physiology of bees, and its contribution to the global decline in bee health. Whilst flower colour is considered as one of the most important signals for foraging honey bees (Apis mellifera), the effects of pesticides on colour vision and memory retention in a natural setting remain unknown. We trained free flying honey bee foragers by presenting artificial yellow flower feeder, to an unscented artificial flower patch with 6 different flower colours to investigate if sub-lethal levels of imidacloprid would disrupt the acquired association made between the yellow flower colour from the feeder and food reward. We found that for doses higher than 4 % of LD50 value, the foraging honey bees no longer preferentially visited the yellow flowers within the flower patch and instead, we suspect, reverted back to baseline foraging preferences, with a complete loss of the yellow preference. Our honey bee colour vision modelling indicates that discriminating the yellow colour from the rest should have been easy cognitive task. Pesticide exposure also resulted in a significant increase in Lop1, UVop, and Blop, and a decrease in CaMKII and CREB gene expression. Our results suggest that memory loss is the most plausible mechanism to explain the alteration of bee foraging colour preference. Across bees, colour vision is highly conserved and is essential for efficient pollination services. Therefore, our findings have important implications for ecosystem health and agricultural services world-wide.

Chronic oral toxicity protocol for adult solitary bees (Osmia bicornis L.): Reduced survival under long-term exposure to a "bee-safe" insecticide

Pollinators are essential for crop productivity. Yet, in agricultural areas, they may be threatened by pesticide exposure. Current pesticide risk assessments predominantly focus on honey bees, with a lack of standardized protocols for solitary bees. This study addresses this gap by developing a long-term oral exposure protocol tailored for O. bicornis. We conducted initial trials to determine optimal container sizes and feeding methods, ensuring high survival rates and accurate syrup consumption measurements. A validation test involving five laboratories was then conducted with the insecticide Flupyradifurone (FPF). Control mortality thresholds were set at ≤ 15% at 10 days. Three laboratories achieved ≤10%, demonstrating the protocol's effectiveness in maintaining healthy test populations. The seasonal timing of experiments influenced control mortality, underscoring the importance of aligning tests with the natural flight period of the population used. Our findings revealed dose-dependent effects of FPF on syrup consumption, showing stimulatory effects at lower concentrations and inhibitory effects at higher ones. The 10-day median lethal daily dose (LDD50) of FPF for O. bicornis (531.92 ng/bee/day) was 3.4-fold lower than that reported for Apis mellifera (1830 ng/bee/day), indicating Osmia's higher susceptibility. Unlike other insecticides, FPF did not exhibit time-reinforced toxicity. This study introduces a robust protocol for chronic pesticide exposure in solitary bees, addressing a critical gap in current risk assessment. Based on its low risk to honey bees and bumblebees, FPF is approved for application during flowering. However, our results suggest that it may threaten Osmia populations under realistic field conditions. Our findings underscore the need for comparative toxicity studies to ensure comprehensive protection of all pollinators and the importance of accounting for long term exposure scenarios in risk assessment. By enhancing our understanding of chronic pesticide effects in solitary bees, our study should contribute to the development of more effective conservation strategies and sustainable agricultural practices.

Life stage dependent effects of neonicotinoid exposure on honey bee hypopharyngeal gland development

Functional Apis mellifera honey bee colonies rely on collaborative brood care typically performed by nurse bees with well-developed hypopharyngeal glands (HPGs). Neonicotinoids, widely used insecticides, have been shown to negatively affect HPG development when worker bees were exposed to field-realistic concentrations either as brood or adults. To date, it is unknown whether timing of neonicotinoid exposure influences the severity of these observed negative effects on HPGs. To address this, we conducted a fully-crossed field experiment assessing potential effects of a neonicotinoid blend (clothianidin and thiamethoxam combined) on worker HPGs when exposed during different life stages. We found that neonicotinoid exposure during the brood stage, but not the adult stage, significantly influenced subsequent HPG development. Since HPG morphogenesis begins during the brood stage, neonicotinoid-induced stress possibly impaired this process, resulting in smaller glands once these individuals became adult nurses. Because HPG productivity is correlated to their size, smaller glands as a result of neonicotinoid exposure could negatively affect colony functionality.

Invisible hazards: Exploring neonicotinoid contamination and its environmental risks in urban parks across China

Neonicotinoids (NEOs) are commonly used pesticides in agriculture. Urban parks containing numerous green plants and flowers also require NEOs for pest control. However, information on the distribution patterns and environmental risks of NEOs and their metabolites in urban park soils has yet to be discovered, which seriously limits the comprehensive evaluation of the potential hazards of NEOs. Our study explored the occurrence and distribution patterns of ten NEOs and five major metabolites in park soils from Guangzhou, Shijiazhuang, and Urumqi of China. At least three NEOs were detected in 95 % of soil samples, with the sum of all NEOs (∑10NEOs) ranging from 2.21 to 204 ng/g. Guangzhou has the highest levels of ∑10NEOs (median: 52.1 ng/g), followed by Urumqi (49.3 ng/g) and Shijiazhuang (21.7 ng/g). The top three most common NEOs in all three cities are imidacloprid, acetamiprid, and thiacloprid, which together account for 67 % to 70 % of ∑10NEOs. The levels of the metabolites of NEOs show a significant positive correlation with their corresponding parent NEOs. These NEOs pose detrimental effects to non-targeted invertebrates in the soil. Our findings raise concern about the environmental risks posed by NEO exposure to humans and other organisms in urban parks.

Sequential pesticide exposure: Concentration addition at high concentrations - Inhibition of hormesis at ultra-low concentrations

Sequential pesticide exposure is a common scenario in both aquatic and terrestrial agricultural ecosystems. Predicting the effects of such exposures is therefore highly relevant for improving risk assessment. However, there is currently no information available for predicting the effects of sequential exposure to the same toxicant at both high and low concentrations. Here we exposed one-week-old individuals of Daphnia magna to the pyrethroid Esfenvalerate for 24 h and compared the effects with individuals treated twice with half the concentration after 7 and 14 days. We showed that at the concentrations close to the LC50, both the survival and population growth rate from the two half-pulses were consistent with the concentration addition approach. At low (1/10th to 1/100th of the LC50) and ultra-low concentrations (1/100th to 1/1000th of the LC50), survival was around 100 %, while the population growth rate showed a hormetic increase following the one-pulse exposure but not for the two-pulse exposure. We hypothesize that this hormetic effect is due to lower systemic stress (SyS) after pesticide exposure in combination with only one rebound stress pulse. Our study suggests that while the lethal effects of sequential exposure are according to the concentration addition model, the sublethal effects at low and ultra-low concentrations need to consider hormetic effects.

Milkweed in agricultural field margins - A neonicotinoid exposure route for pollinators at multiple life stages

Neonicotinoid insecticides move from targeted crops to wildflowers located in adjacent field margins, acting as a potential exposure source for wild pollinators and insect species of conservation concern, including monarch butterflies. Monarchs rely on milkweed over multiple life stages, including as a host plant for eggs and a food source for both larvae (leaves) and adults (flowers). Milkweeds, which are closely associated with field margins, can contain neonicotinoid residues, but previous assessments are constrained to a single plant tissue type. In 2017 and 2018, we sampled milkweeds from 95 field margins adjacent to crop fields (corn, soybean, hay, wheat, and barley) in agricultural landscapes of eastern Ontario, Canada. Milkweeds were sampled during the flower blooming period and leaves and flower tissues were analysed. The neonicotinoids acetamiprid, clothianidin, thiamethoxam, and thiacloprid were detected. Maximum concentrations in leaf samples included 10.30 ng/g of clothianidin in 2017, and 24.4 ng/g of thiamethoxam in 2018. Clothianidin and thiamethoxam percent detections in flowers (72 % and 61 %, respectively) were significantly higher than detections in leaves (24 % and 31 %, respectively). Thiamethoxam concentrations were significantly higher in paired flower samples than leaf samples (median 0.33 ng/g vs <0.07 ng/g) while clothianidin concentrations also trended higher in flowers (median 0.18-0.55 ng/g vs <0.18 ng/g). Only thiamethoxam showed significant differences between years, and we found no effect of crop type, with hay, soybean and corn fields all yielding 50-56 % detections in leaves. We found significantly higher concentrations in older milkweed flowers than young flowers or leaves (medians 0.87 ng/g vs <0.18 ng/g and 0.45 ng/g vs <0.07 ng/g for clothianidin and thiamethoxam, respectively). Our results highlight the importance of considering variation in milkweed tissue type and age of flowers in neonicotinoid exposure risk assessments. Efforts to increase milkweed availability in agricultural landscapes should consider how exposure to neonicotinoids can be mitigated.

Sublethal pesticide exposure in non-target terrestrial ecosystems: From known effects on individuals to potential consequences on trophic interactions and network functioning

Over the last decades, the intensification of agriculture has resulted in an increasing use of pesticides, which has led to widespread contamination of non-target ecosystems in agricultural landscapes. Plants and arthropods inhabiting these systems are therefore chronically exposed to, at least, low levels of pesticides through direct pesticide drift, but also through the contamination of their nutrient sources (e.g. soil water or host/prey tissues). Pesticides (herbicides, acaricides/insecticides and fungicides) are chemical substances used to control pests, such as weeds, phytophagous arthropods and pathogenic microorganisms. These molecules are designed to disturb specific physiological mechanisms and induce mortality in targeted organisms. However, under sublethal exposure, pesticides also affect biological processes including metabolism, development, reproduction or inter-specific interactions even in organisms that do not possess the molecular target of the pesticide. Despite the broad current knowledge on sublethal effects of pesticides on organisms, their adverse effects on trophic interactions are less investigated, especially within terrestrial trophic networks. In this review, we provide an overview of the effects, both target and non-target, of sublethal exposures to pesticides on traits involved in trophic interactions between plants, phytophagous insects and their natural enemies. We also discuss how these effects may impact ecosystem functioning by analyzing studies investigating the responses of Plant-Phytophage-Natural enemy trophic networks to pesticides. Finally, we highlight the current challenges and research prospects in the understanding of the effects of pesticides on trophic interactions and networks in non-target terrestrial ecosystems.

The impact of landscape structure on pesticide exposure to honey bees

Pesticides may have serious negative impacts on bee populations. The pesticide exposure of bees could depend on the surrounding landscapes in which they forage. In this study, we assess pesticide exposure across various land-use categories, while targeting the Japanese honey bee, Apis cerana japonica, a native subspecies of the eastern honey bee. In a project involving public participation, we measured the concentrations of major pesticides in honey and beeswax collected from 175 Japanese honey bee colonies across Japan and quantitatively analyzed the relationships between pesticide presence/absence or pesticide concentration and land-use categories around the colonies. Our findings revealed that the surrounding environment in which bees live strongly influences pesticide residues in beehive materials, whether the pesticides are systemic or not, with a clear trend for each land-use category. Agricultural lands, particularly paddy fields and orchards, and urban areas resulted in higher pesticide exposure, whereas forests presented a lower risk of exposure. To effectively control pesticide exposure levels in bees, it is essential to understand pesticide usage patterns and to develop appropriate regulatory systems in non-agricultural lands, similar to those in agricultural lands.

Pesticides and pollinator brain: How do neonicotinoids affect the central nervous system of bees?

Neonicotinoids represent over a quarter of the global pesticide market. Research on their environmental impact has revealed their adverse effect on the cognitive functions of pollinators, in particular of bees. Cognitive impairments, mostly revealed by behavioural studies, are the phenotypic expression of an alteration in the underlying neural circuits, a matter deserving greater attention. Here, we reviewed studies on the impact of field-relevant doses of neonicotinoids on the neurophysiology and neurodevelopment of bees. In particular, we focus on their olfactory system as much knowledge has been gained on the different brain areas that participate in odour processing. Recent studies have revealed the detrimental effects of neonicotinoids at multiple levels of the olfactory system, including modulation of odorant-induced activity in olfactory sensory neurons, diminished neural responses in the antennal lobe (the first olfactory processing centre) and abnormal development of the neural connectivity within the mushroom bodies (central neuropils involved in multisensory integration, learning and memory storage, among others). Given the importance of olfactory perception for multiple aspects of bee biology, the reported disruption of the olfactory circuit, which can occur even upon exposure to sublethal doses of neonicotinoids, has severe consequences at both individual and colony levels. Moreover, the effects reported for a multimodal structure such as the mushroom bodies indicate that neonicotinoids' impact translates to other sensory domains. Assessing the impact of field-relevant doses of pesticides on bee neurophysiology is crucial for understanding how neonicotinoids influence their behaviour in ecological contexts and for defining effective and sustainable agricultural practices.

Novel fungicide and neonicotinoid insecticide impair flight behavior in pollen foraging honey bees, Apis mellifera

Bees are often exposed to pesticides affecting physiological functions and molecular mechanisms. Studies showed a potential link between altered expression of energy metabolism related transcripts and increased homing flight time of foragers exposed to pesticides. In this study, we investigated the effects of thiamethoxam and pyraclostrobin on longevity, flight behavior, and expression of transcripts involved in endocrine regulation (hbg-3, buffy, vitellogenin) and energy metabolism (cox5a, cox5b, cox17) using radio frequency identification (RFID) technology and quantitative polymerase chain reaction. Parallel, a laboratory study was conducted investigating whether pesticide exposure alone without the influence of flight activity caused similar expression patterns as in the RFID experiment. No significant effect on survival, homing flight duration, or return rate of exposed bees was detected. The overall time foragers spent outside the hive was significantly reduced post-exposure. Irrespective of the treatment group, a correlation was observed between cox5a, cox5b, cox17 and hbg-3 expression and prolonged homing flight duration. Our results suggest that flight behavior can impact gene expression and exposure to pesticides adversely affects the expression of genes that are important for maintaining optimal flight capacity. Our laboratory-based experiment showed significantly altered expression levels of cox5a, cox6c, and cox17. However, further work is needed to identify transcriptional profiles responsible for prolonged homing flight duration.

The power to (detect) change: Can honey bee collected pollen be used to monitor pesticide residues in the landscape?

Analysis of trapped honey bee pollen for pesticide residues is the most widely used method of monitoring the amount of pesticide entering colonies and its change over time. In this study, we collected and analyzed pollen from 70 sites across four bee-pollinated crops over two years to characterize the variation in pesticide detection across sites, crops and at different periods during bloom. Hazard Quotient, HQ, is the most common way that pesticide residues are aggregated into a single pesticide hazard value in the current literature. Therefore, change in pesticide hazard (HQ) was quantified in composite pollen samples collected from pollen traps and in pollen color subsamples separated into pollen from the target crop being pollinated and pollen from other plant species. We used our estimates of the variation in HQ to calculate the number of sample location sites needed to detect a 5% annual change in HQ across all crops or within specific crops over a 5-year period. The number of sites required to be sampled varied by crop and year and ranged between 139 and 7194 sites, costing an estimated $129,548 and $3.35 million, respectively. The HQ values detectable for this cost would be 575 and 154. We identified additional factors that complicate the interpretation of the results as a way to evaluate changes in pest management practices at a state level. First, in all but one crop (meadowfoam), the pollen collected from outside the crop honey bee colonies were pollinating comprised a major percentage of the total pollen catch. Moreover, we found that when the overall quantity of pollen from different pollen sources was taken into account, differences in HQ among crops widened. We also found that while HQ estimates remain consistent across the bloom period for some crops, such as cherry, we observed large differences in other crops, notably meadowfoam. Overall, our results suggest the current practice of interpreting pesticides levels in pollen may come with limitations for agencies charged with improving pesticide stewardship due to the high variation associated with HQ values over time and across crops. Despite the limitations of HQ for detecting change in pesticide hazard, there remains a potential for HQ to provide feedback to regulators and scientists on field-realistic pesticide hazard within a landscape.

Cocktail effects of clothianidin and imidacloprid in zebrafish embryonic development, with high and low concentrations of mixtures

There is growing concern that sprayed neonicotinoid pesticides (neonics) persist in mixed forms in the environmental soil and water systems, and these concerns stem from reports of increase in both the detection frequency and concentration of these pollutants. To confirm the toxic effects of neonics, we conducted toxicity tests on two neonics, clothianidin (CLO) and imidacloprid (IMD), in embryos of zebrafish. Toxicity tests were performed with two different types of mixtures: potential mixture compounds and realistic mixture compounds. Potential mixtures of CLO and IMD exhibited synergistic effects, in a dose-dependent manner, in zebrafish embryonic toxicity. Realistic mixture toxicity tests that are reflecting the toxic effects of mixture in the aquatic environment were conducted with zebrafish embryos. The toxicity of the CLO and IMD mixture at environmentally-relevant concentrations was confirmed by the alteration of the transcriptional levels of target genes, such as cell damage linked to oxidative stress response and thyroid hormone synthesis related to zebrafish embryonic development. Consequently, the findings of this study can be considered a strategy for examining mixture toxicity in the range of detected environmental concentrations. In particular, our results will be useful in explaining the mode of toxic action of chemical mixtures following short-term exposure. Finally, the toxicity information of CLO and IMD mixtures will be applied for the agricultural environment, as a part of chemical regulation guideline for the use and production of pesticides.

Potential acetylcholine-based communication in honeybee haemocytes and its modulation by a neonicotinoid insecticide

There is growing concern that some managed and wild insect pollinator populations are in decline, potentially threatening biodiversity and sustainable food production on a global scale. In recent years, there has been increasing evidence that sub-lethal exposure to neurotoxic, neonicotinoid pesticides can negatively affect pollinator immunocompetence and could amplify the effects of diseases, likely contributing to pollinator declines. However, a direct pathway connecting neonicotinoids and immune functions remains elusive. In this study we show that haemocytes and non-neural tissues of the honeybee Apis mellifera express the building blocks of the nicotinic acetylcholine receptors that are the target of neonicotinoids. In addition, we demonstrate that the haemocytes, which form the cellular arm of the innate immune system, actively express choline acetyltransferase, a key enzyme necessary to synthesize acetylcholine. In a last step, we show that the expression of this key enzyme is affected by field-realistic doses of clothianidin, a widely used neonicotinoid. These results support a potential mechanistic framework to explain the effects of sub-lethal doses of neonicotinoids on the immune function of pollinators.

Fluctuating Asymmetry Spotted Wing Drosophila (Diptera: Drosophilidae) Exposed to Sublethal Doses of Acetamiprid and Nicotine

Long-term exposure to low concentrations of toxic substances can cause several adverse consequences ranging from molecular to morphological. Sublethal doses may also lead to increased tolerance in the offspring of surviving individuals. One of the consequences of such stress is deviations from the ideal body symmetry during development, reflected by increased levels of fluctuating asymmetry (FA). This research aimed to verify FA in the wing veins of insects belonging to the Drosophilidae family-Drosophila suzukii, a fruit pest controlled by the insecticide acetamiprid, a neonicotinoid. To determine whether FA varied depending on insecticides present in the diet, multigenerational cultures of D. suzukii were carried out on media supplemented with different concentrations (below the LC50) of two insecticides. Nicotine was used as a positive control. Fecundity decreased, the number of insects decreased, and breeding did not continue beyond the tenth generation. However, the FA level at different concentrations was similar, and high FA values were observed even at lower acetamiprid concentrations. We did not see significant changes in FA levels in subsequent generations. D. suzukii proved extremely sensitive to acetamiprid, and FA is a good index of this sensitivity.

Associations between neonicotinoid insecticide levels in follicular fluid and serum and reproductive outcomes among women undergoing assisted reproductive technology: An observational study

Neonicotinoid insecticides (NEOs) are a widely used type of insecticide found globally, leading to broad human exposure. However, there is limited research on how internal exposure levels of NEOs and their metabolites impact in vitro fertilization/intracytoplasmic sperm injection (IVF/ICSI) outcomes. A study was conducted at the Sixth Affiliated Hospital of Sun Yat-sen University between 2017 and 2020 involving 436 women undergoing IVF/ICSI treatment. Data on demographics and clinical history were collected from medical records. The concentrations of 11 NEOs and 4 NEO metabolites in follicular fluid and serum were measured using a salting-out assisted liquid-liquid extraction method and liquid chromatography-tandem mass spectrometry. Our findings indicated that NEOs were prevalent in women with infertility. One NEO metabolite, N-dm-ACE, was detected in all samples with median concentrations of 0.221 ng/mL in follicular fluid and 0.228 ng/mL in serum. The study showed a decrease in the number of retrieved oocytes, mature oocytes, 2 PN zygotes, and high-quality embryos as the number of exposed NEOs in follicular fluid increased. Women in the highest tertile of N-dm-ACE exposure had fewer mature oocytes, 2 PN zygotes, and lower oocyte maturity rates compared to those in the lowest tertile. The findings suggest that exposure to NEOs may negatively impact reproductive outcomes in IVF/ICSI pregnancies, particularly affecting oocyte retrieval and embryo quality. This study highlights the potential adverse effects of environmental NEO exposure on IVF/ICSI outcomes, emphasizing the importance of considering such exposures in preconception care.

Potential exposure of honey bees to neonicotinoid seed treatments in US rice

Neonicotinoid insecticide seed treatments are commonly used in rice (Oryza sativa) production to control rice water weevil (Lisorhoptrus oryzophilus). With the use of neonicotinoid seed treatments, there is potential that honey bees (Apis mellifera) could be exposed to neonicotinoids through translocation to the pollen. Studies were conducted in 2015 and 2016 to determine the level of neonicotinoids present in flag leaves, pollen, and grain of rice. Thiamethoxam was applied as a seed treatment and foliar prior to flooding. Clothianidin was applied as a seed treatment and as a foliar at a preflood and postflood timing. Subsamples of flag leaves, pollen, and grain were analyzed for positive neonicotinoid detections and abundance. Thiamethoxam was detected in 8.9% of samples and clothianidin was detected in 1.4% of samples. For both thiamethoxam and clothianidin, more positive samples were observed in flag leaf samples than in pollen or grain. An average of 4.30 ng/g of thiamethoxam was detected in flag leaves from seed-applied thiamethoxam. An average of 1.25 ng/g of clothianidin was found in flag leaves from a preflood application of clothianidin. A survey of honey bees present in rice fields was conducted in Mississippi and Arkansas to determine the abundance of honey bees present in rice fields based on the time of day. Honey bee densities were low in rice, with less than 5% and 3% positive detections observed in Mississippi and Arkansas, respectively. More positive detections and higher densities of honey bees were observed for mid-day sampling than for morning or evening sampling.

Unveiling the Contamination Patterns of Neonicotinoid Insecticides: Detection, Distribution, and Risk Assessment in Panax notoginseng across Plant Parts

This study analyzed neonicotinoid insecticides (NEOs) and metabolite (m-NEOs) residues in 136 Panax notoginseng samples via ultra-performance liquid chromatography-tandem mass spectrometry. Imidacloprid was the most detected NEO (88.24% of samples), ranging from 1.50 to 2850 μg/kg. To the best of our knowledge, some novel NEOs were detected in P. notoginseng for the first time. NEO clustering patterns varied among plant parts, with higher contamination in leaves and flowers. Fourteen NEO/m-NEOs, including cycloxaprid and acetamiprid, showed site-specific behavior, indicating the possibility of using multiple NEOs simultaneously during planting, resulting in formation of distinct metabolites in different plant parts. Transfer rates in decoction and infusion ranged from 10.06 to 32.33%, reducing residues postprocessing. Dietary risk assessment showed low hazard quotients (HQa: 7.05 × 10-7 to 2.09 × 10-2; HQc: 3.74 × 10-7 to 2.38 × 10-3), but risk-ranking scores indicated potential hazards with imidacloprid and acetamiprid in flowers and leaves. The findings are expected to promote safety assessment and distribution research of NEOs in plants.

Characterization of near-field temporal and spatial variations of pesticide residues using honeybee specimens as bio-sensing matrices

This study was prompted by recent reports of the ubiquity of neonicotinoids (neonics) in environment and the likelihood of exposures and health hazards to non-target organisms. We aimed to quantify neonics levels in time- and location-match pollen and nectar samples foraged by honeybees (Apis mellifera) and characterized the temporal and spatial variations using a relative potency factor method to determine the total neonic levels, expressed as the imidacloprid-adjusted total neonics, IMIRPF (ng/g). Six pairs of pollen and nectar samples, a total of twelve samples, were collected from each of the thirty-two experimental hives during the active foraging months of March, April, and June and analyzed for eight neonics. We found 59% and 64% of pollen and nectar contained at least one neonic, respectively. Among those neonic-detected pollen and nectar samples, 45% and 77% of them contained more than one neonic, respectively. Imidacloprid and acetamiprid in pollen and clothianidin and thiamethoxam in nectar accounted for 60% and 83% detection, respectively. The highest 3-month average of IMIRPF in pollen (6.56 ng/g) and nectar (11.19 ng/g) were detected in a location with the predominant production of citrus fruit. The temporal and spatial variations of IMIRPF levels demonstrated the robustness of using paired pollen and nectar data as the bio-sensing matrices to facilitate the assessment of near-field exposure to total neonics and the delineation of risks.

Following Regulation, Imidacloprid Persists and Flupyradifurone Increases in Nontarget Wildlife

After regulation of pesticides, determination of their persistence in the environment is an important indicator of effectiveness of these measures. We quantified concentrations of two types of systemic insecticides, neonicotinoids (imidacloprid, acetamiprid, clothianidin, thiacloprid, and thiamethoxam) and butenolides (flupyradifurone), in off-crop nontarget media of hummingbird cloacal fluid, honey bee (Apis mellifera) nectar and honey, and wildflowers before and after regulation of imidacloprid on highbush blueberries in Canada in April 2021. We found that mean total pesticide load increased in hummingbird cloacal fluid, nectar, and flower samples following imidacloprid regulation. On average, we did not find evidence of a decrease in imidacloprid concentrations after regulation. However, there were some decreases, some increases, and other cases with no changes in imidacloprid levels depending on the specific media, time point of sampling, and site type. At the same time, we found an overall increase in flupyradifurone, acetamiprid, thiamethoxam, and thiacloprid but no change in clothianidin concentrations. In particular, flupyradifurone concentrations observed in biota sampled near agricultural areas increased twofold in honey bee nectar, sevenfold in hummingbird cloacal fluid, and eightfold in flowers after the 2021 imidacloprid regulation. The highest residue detected was flupyradifurone at 665 ng/mL (parts per billion [ppb]) in honey bee nectar. Mean total pesticide loads were highest in honey samples (84 ± 10 ppb), followed by nectar (56 ± 7 ppb), then hummingbird cloacal fluid (1.8 ± 0.5 ppb), and least, flowers (0.51 ± 0.06 ppb). Our results highlight that limited regulation of imidacloprid does not immediately reduce residue concentrations, while other systemic insecticides, possibly replacement compounds, concurrently increase in wildlife. Environ Toxicol Chem 2024;43:1497-1508. © 2024 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Chronic sub-lethal exposure to clothianidin triggers organismal and sub-organismal-level health hazards in a non-target organism, Drosophila melanogaster

Neonicotinoids are among the most widely used systemic pesticides across the world. These chemicals have gathered significant attention for their potential adverse impacts on non-target organisms. Clothianidin is a novel neonicotinoid pesticide, employed globally to control sucking and chewing types of pests. In nature, various non-target organisms can be exposed to this chemical through contaminated food, water, and air. Nonetheless, extensive investigations demonstrating the sub-lethal impacts of clothianidin on non-target entities are limited. Hence, the present study was aimed to unravel the chronic sub-lethal impacts (LC50 0.74 μg/mL) of clothianidin on a non-target organism, Drosophila melanogaster. The study parameters involved multiple tiers of life ranging from organismal level to the sub-cellular level. 1st instar larvae were exposed to the six sub-lethal concentrations viz. 0.05, 0.06, 0.07, 0.08, 0.09, and 0.1 μg/mL of clothianidin till their 3rd larval instar. Investigations involving organismal level have revealed clothianidin-induced significant reduction in the developmental duration, life span, phototaxis, and physical activities of the treated individuals. Interestingly, the tested compound has also altered the compound eye morphology of treated flies. Study was extended to the tissue and cellular levels where reduced cell viability in gut, brain, and fat body was apparent. Additionally, increased ROS production, nuclear disorganization, and higher lipid deposition were evident in gut of exposed individuals. Study was further extended to the sub-cellular level where chronic exposure to clothianidin up-regulated the major oxidative stress markers such as lipid peroxidation, protein carbonylation, HSP-70, SOD, catalase, GSH, and thioredoxin reductase. Furthermore, the activities of detoxifying enzymes such as CYP4501A1 and GST were also altered. Chronic exposure to clothianidin also triggered DNA fragmentation in treated larvae. In essence, results of this multi-level study depict the ROS-mediated toxicity of clothianidin on a non-target organism, D. melanogaster.

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.

Environmental ameliorations and politics in support of pollinators. Experiences from Europe: A review

At least 87% of angiosperm species require animal vectors for their reproduction, while more than two-thirds of major global food crops depend on zoogamous pollination. Pollinator insects are a wide variety of organisms that require diverse biotic and abiotic resources. Many factors have contributed to a serious decrease in the abundance of populations and diversity of pollinator species over the years. This decline is alarming, and the European Union has taken several actions aimed at counteracting it by issuing new conservation policies and standardizing the actions of member countries. In 2019, the European Green Deal was presented, aiming to restore 100% of Europe's degraded land by 2050 through financial and legislative instruments. Moreover, the Common Agricultural Policies have entailed greening measures for the conservation of habitats and beneficial species for more than 10 years. The new CAP (CAP 23-27) reinforces conservation objectives through strategic plans based on eco-schemes defined at the national level by the member countries, and some states have specifically defined eco-schemes for pollinator conservation. Here, we review the framework of EU policies, directives, and regulations, which include measures aimed at protecting pollinators in agricultural, urban, and peri-urban environments. Moreover, we reviewed the literature reporting experimental works on the environmental amelioration for pollinators, particularly those where CAP measures were implemented and evaluated, as well as studies conducted in urban areas. Among CAP measures, several experimental works have considered the sowing and management of entomophilous plants and reported results important for environmental ameliorations. Some urban, peri-urban and wasteland areas have been reported to host a considerable number of pollinators, especially wild bees, and despite the lack of specific directives, their potential to contribute to pollinator conservation could be enhanced through targeted actions, as highlighted by some studies.

Engineering Gut Symbionts: A Way to Promote Bee Growth?

Bees play a crucial role as pollinators, contributing significantly to ecosystems. However, the honeybee population faces challenges such as global warming, pesticide use, and pathogenic microorganisms. Promoting bee growth using several approaches is therefore crucial for maintaining their roles. To this end, the bacterial microbiota is well-known for its native role in supporting bee growth in several respects. Maximizing the capabilities of these microorganisms holds the theoretical potential to promote the growth of bees. Recent advancements have made it feasible to achieve this enhancement through the application of genetic engineering. In this review, we present the roles of gut symbionts in promoting bee growth and collectively summarize the engineering approaches that would be needed for future applications. Particularly, as the engineering of bee gut symbionts has not been advanced, the dominant gut symbiotic bacteria Snodgrassella alvi and Gilliamella apicola are the main focus of the paper, along with other dominant species. Moreover, we propose engineering strategies that will allow for the improvement in bee growth with listed gene targets for modification to further encourage the use of engineered gut symbionts to promote bee growth.

Effects of common co-occurring pesticides (a neonicotinoid and fungicide) on honey bee colony health in a semi-field study

Multiple stressors are linked to declines of insects and important pollinators, such as bees. Recently, interactive effects of multiple agrochemicals on bees have been highlighted, including fungicides, which increase toxicity of neonicotinoid insecticides. Here, we use a semi-field study across two seasons in controlled foraging tunnels to test the effects of a field application of a commercial fungicide product with two active ingredients (pyraclostrobin and metconazole) applied at label rates. We also examine its interactive effects with the neonicotinoid insecticide clothianidin, at a conservative field-realistic dose of 2.23 ppb, on 48 honey bee colonies. We found combined effects of pesticide exposure, including additive 2.93-fold increases in mortality, and an additional effect of increased infestation levels of the ectoparasitic mite, Varroa destructor. Pesticide treatments also reduced colony activity, reduced colony weight, and increased sugar consumption of whole colonies. These findings indicate that typical sublethal exposure levels to common, co-occurring agrochemicals in the field significantly affect the health of whole honey bee colonies, highlighting an unintended consequence of increasing pesticide applications.

Contaminant dynamics in honey bees and hive products of apiaries from environmentally contrasting Argentinean regions

Argentina is a leading honey producer and honey bees are also critical for pollination services and wild plants. At the same time, it is a major crop producer with significant use of insecticides, posing risks to bees. Therefore, the presence of the highly toxic insecticide chlorpyrifos, and forbidden contaminants (organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs)) was investigated in honey bee, beebread, wax and honey samples in apiaries from three contrasting regions of Argentina. Chlorpyrifos was detected in all samples with higher levels during period 1 (spring) in contrast to period 2 (fall), agreeing with its season-wise use in different crops, reaching 3.05 ng/g in honey bees. A subsequent first-tier pesticide hazard analysis revealed that it was relevant to honey bee health, mainly due to the high concentrations found in wax samples from two sites, reaching 132.4 ng/g. In addition, wax was found to be the most contaminated matrix with a prevalence of OCPs (∑OCPs 58.23-172.99 ng/g). Beebread samples showed the highest concentrations and diversity of pesticide residues during period 1 (higher temperatures). A predominance of the endosulfan group was registered in most samples, consistent with its intensive past use, especially in Central Patagonia before its prohibition. Among the industrial compounds, lighter PCB congeners dominated, suggesting the importance of atmospheric transport. The spatio-temporal distribution of pesticides shows a congruence with the environmental characteristics of the areas where the fields are located (i.e., land use, type of productive activities and climatic conditions). Sustained monitoring of different pollutants in beekeeping matrices is recommended to characterize chemical risks, assess the health status of honey bee hives and the pollution levels of different agroecosystems. This knowledge will set a precedent for South America and be helpful for actions focused on the conservation of pollination services, apiculture and ecosystems in Argentina.

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.

High pesticide exposure and risk to bees in pollinator plantings adjacent to conventionally managed blueberry fields

Wildflower plantings adjacent to agricultural fields provide diverse floral resources and nesting sites for wild bees. However, their proximity to pest control activities in the crop may result in pesticide exposure if pesticides drift into pollinator plantings. To quantify pesticide residues in pollinator plantings, we sampled flowers and soil from pollinator plantings and compared them to samples from unenhanced field margins and crop row middles. At conventionally managed farms, flowers from pollinator plantings had similar exposure profiles to those from unenhanced field margins or crop row middles, with multiple pesticides and high and similar risk quotient (RQ) values (with pollinator planting RQ: 3.9; without pollinator planting RQ: 4.0). Whereas samples from unsprayed sites had significantly lower risk (RQ: 0.005). Soil samples had overall low risk to bees. Additionally, we placed bumble bee colonies (Bombus impatiens) in field margins of crop fields with and without pollinator plantings and measured residues in bee-collected pollen. Pesticide exposure was similar in pollen from sites with or without pollinator plantings, and risk was generally high (with pollinator planting RQ: 0.5; without pollinator planting RQ: 1.1) and not significant between the two field types. Risk was lower at sites where there was no pesticide activity (RQ: 0.3), but again there was no significant difference between management types. The insecticide phosmet, which is used on blueberry farms for control of Drosophila suzukii, accounted for the majority of elevated risk. Additionally, analysis of pollen collected by bumble bees found no significant difference in floral species richness between sites with or without pollinator plantings. Our results suggest that pollinator plantings do not reduce pesticide risk and do not increase pollen diversity collected by B. impatiens, further highlighting the need to reduce exposure through enhanced IPM adoption, drift mitigation, and removal of attractive flowering weeds prior to insecticide applications.

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.

Mitochondrial dynamics disruption: Unraveling Dinotefuran's impact on cardiotoxicity

Exposure to pesticides has been associated with several cardiovascular complications in animal models. Neonicotinoids are now the most widely used insecticide globally, while the impact of neonicotinoids on cardiovascular function and the role of mitochondrial dynamics in neonicotinoids-induced cardiotoxicity is unclear. In the present study, Xenopus laevis tadpoles were exposed to environmental related concentrations (0, 5, and 50 μg/L) of typical neonicotinoid dinotefuran, with two enantiomers, for 21 days. We evaluated the changes in heart rate and cardiomyocyte apoptosis in exposed tadpoles. Then, we performed the transcriptome, metabolomics, transmission electron microscopy (TEM), and protein immunoblot to investigate the potential adverse impact of two enantiomers of dinotefuran on cardiotoxicity associated with mitochondrial dynamics. We observed changes in heart rate and increased cardiomyocyte apoptosis in exposed tadpoles, indicating that dinotefuran had a cardiotoxic effect. We further found that the cardiac contractile function pathway was significantly enriched, while the glucose metabolism-related pathways were also disturbed significantly. TEM observation revealed that the mitochondrial morphology of cardiomyocytes in exposed tadpoles was swollen, and mitophagy was increased. Mitochondria fusion was excessively manifested in the enhanced mitochondrial fusion protein. The mitochondrial respiratory chain was also disturbed, which led to an increase in ROS production and a decrease in ATP content. Therefore, our results suggested that dinotefuran exposure can induce cardiac disease associated mitochondrial disorders by interfering with the functionality and dynamics of mitochondria. In addition, both two enantiomers of dinotefuran have certain toxicity to tadpole cardiomyocytes, while R-dinotefuran exhibited higher toxicity than S-enantiomer, which may be attributed to disparities in the activation capacities of the respiratory chain.

Pesticide Exposure and Effects on Non-Apis Bees

Bees are essential pollinators of many crops and wild plants, and pesticide exposure is one of the key environmental stressors affecting their health in anthropogenically modified landscapes. Until recently, almost all information on routes and impacts of pesticide exposure came from honey bees, at least partially because they were the only model species required for environmental risk assessments (ERAs) for insect pollinators. Recently, there has been a surge in research activity focusing on pesticide exposure and effects for non-Apis bees, including other social bees (bumble bees and stingless bees) and solitary bees. These taxa vary substantially from honey bees and one another in several important ecological traits, including spatial and temporal activity patterns, foraging and nesting requirements, and degree of sociality. In this article, we review the current evidence base about pesticide exposure pathways and the consequences of exposure for non-Apis bees. We find that the insights into non-Apis bee pesticide exposure and resulting impacts across biological organizations, landscapes, mixtures, and multiple stressors are still in their infancy. The good news is that there are many promising approaches that could be used to advance our understanding, with priority given to informing exposure pathways, extrapolating effects, and determining how well our current insights (limited to very few species and mostly neonicotinoid insecticides under unrealistic conditions) can be generalized to the diversity of species and lifestyles in the global bee community. We conclude that future research to expand our knowledge would also be beneficial for ERAs and wider policy decisions concerning pollinator conservation and pesticide regulation.

Sublethal effects of imidacloprid-contaminated honey stores on colony performance, queens, and worker activities in fall and early winter colonies

Neonicotinoid-contaminated sugar stores can have both near term and long term effects on honey bees due to their persistence in honey stores. Effects of imidacloprid food stores contaminants were examined in subtropical colonies that experience reduced brood rearing and foraging during overwintering. Colonies were given treatment sugar syrup containing 0 ppb (control), 20 ppb (field relevant), or 100 ppb (above field relevant) imidacloprid over six weeks to simulate contaminated fall nectar. Colonies were evaluated immediately (post-treatment) and 10 weeks (mid-winter) after treatment to compare proximal and latent effects. Post-treatment 0 ppb and 20 ppb colonies had more workers than 100 ppb colonies while 0 ppb colonies more brood than 20 ppb or 100 ppb colonies. Mid-winter 0 ppb and 20 ppb colonies had more workers than 100 ppb colonies and 0 ppb colonies more brood than 100 ppb colonies. Colonies experienced seasonal declines in stored pollen but no treatment effects. Lower 100 ppb colony performance was associated with reduced effort rather than lifespan. RFID (Radio Frequency Identification) tracking revealed that workers had similar adult lifespans across treatments; however, 100 ppb workers engaged in activities outside the colony for less time than 0 ppb workers. Imidacloprid exposure affected queen but not worker nutritional physiology. Nurses retained well-developed hypopharyngeal glands (as indicated by head protein) across treatments. Mid-winter queens from 0 ppb colonies had marginally higher ovary protein than queens from 100 ppb colonies and more ovary lipids than queens from 20 ppb colonies. However, queen nutrient stores in non-reproductive tissues (fat bodies) did not differ across treatments. Queens from different treatments were attended by comparable numbers of retinue workers and had similar gland contents of four QMP (Queen Mandibular Pheromone) components essential to queen care. High levels of imidacloprid in sugar stores can negatively affect colony performance months after initial storage.

Olfactory Learning Behavior and Mortality of the Honey Bee Apis mellifera jemenitica in Response to Pyrethroid Insecticide (Deltamethrin)

Honey bees are constantly threatened due to the wide use of pesticides. This study presents the effects of deltamethrin on the mortality, olfactory learning, and memory formation of the native Saudi bee Apis mellifera jemenitica. Topical and oral application of realistic field and serial dilutions of deltamethrin (250, 125, 62.5, and 25 ppm) caused significant mortality at 4, 12, 24, and 48 h posttreatment. Bee mortality increased with the increasing concentration of insecticide at all tested posttreatment times. Highest mortality was observed at 24 h and 48 h after both exposure routes. Food consumption gradually decreased with increasing concentration of deltamethrin during oral exposure. The LC50 of deltamethrin was determined at 12, 24, and 48 h for topical (86.28 ppm, 36.16 ppm, and 29.19 ppm, respectively) and oral (35.77 ppm, 32.53 ppm, and 30.78 ppm, respectively) exposure. Oral exposure led to significantly higher bee mortality than topical exposure of deltamethrin at 4 h and 12 h, but both exposure routes were equally toxic to bees at 24 h and 48 h. The sublethal concentrations (LC10, LC20, and LC30) of deltamethrin significantly impaired the learning during conditioning trials, as well as the memory formation of bees at 2, 12, and 24 h after topical and oral exposure. Thus, deltamethrin inhibits learning, and bees were unable to memorize the learned task.

Winter is coming: Interactions of multiple stressors in winter and implications for the natural world

Winter is a key driver of ecological processes in freshwater, marine and terrestrial ecosystems, particularly in higher latitudes. Species have evolved various adaptive strategies to cope with food limitations and the cold and dark wintertime. However, human-induced climate change and other anthropogenic stressors are impacting organisms in winter in unpredictable ways. In this paper, we show that global change experiments investigating multiple stressors have predominantly been conducted during summer months. However, effects of anthropogenic stressors sometimes differ between winter and other seasons, necessitating comprehensive investigations. Here, we outline a framework for understanding the different effects of anthropogenic stressors in winter compared to other seasons and discuss the primary mechanisms that will alter ecological responses of organisms (microbes, animals and plants). For instance, while the magnitude of some anthropogenic stressors can be greater in winter than in other seasons (e.g. some pollutants), others may alleviate natural winter stress (e.g. warmer temperatures). These changes can have immediate, delayed or carry-over effects on organisms during winter or later seasons. Interactions between stressors may also vary with season. We call for a renewed research direction focusing on multiple stressor effects on winter ecology and evolution to fully understand, and predict, how ecosystems will fare under changing winters. We also argue the importance of incorporating the interactions of anthropogenic stressors with winter into ecological risk assessments, management and conservation efforts.

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.

Wild bee and pollen microbiomes across an urban-rural divide

Wild pollinators and their microbiota are sensitive to land use changes from anthropogenic activities that disrupt landscape and environmental features. As urbanization and agriculture affect bee habitats, human-led disturbances are driving changes in bee microbiomes, potentially leading to dysbiosis detrimental to bee fitness. This study examines the bacterial, fungal, and plant compositions of the small carpenter bee, Ceratina calcarata, and its pollen provisions across an urban-rural divide. We performed metabarcoding of C. calcarata and provisions in Toronto by targeting the 16S rRNA, ITS, and rbcL regions. Despite similar plant composition and diversity across bees and their provisions, there was a greater microbial diversity in pollen provisions than in bees. By characterizing the differences in land use, climate, and pesticide residues that differentiate urban and rural landscapes, we find that urban areas support elevated levels of microbial diversity and more complex networks between microbes and plants than rural areas. However, urban areas may lead to lower relative abundances of known beneficial symbionts and increased levels of pathogens, such as Ascosphaera and Alternaria fungi. Further, rural pollen provisions indicate elevated pesticide residues that may dysregulate symbiosis. As anthropogenic activities continue to alter land use, ever changing environments threaten microbiota crucial in maintaining bee health.

Honey bees and bumble bees may be exposed to pesticides differently when foraging on agricultural areas

In an agricultural environment, where crops are treated with pesticides, bees are likely to be exposed to a range of chemical compounds in a variety of ways. The extent to which different bee species are affected by these chemicals, largely depends on the concentrations and type of exposure. We quantified the presence of selected pesticide compounds in the pollen of two different entomophilous crops; oilseed rape (Brassica napus) and broad bean (Vicia faba). Sampling was performed in 12 sites in Ireland and our results were compared with the pollen loads of honey bees and bumble bees actively foraging on those crops in those same sites. Detections were compound specific, and the timing of pesticide application in relation to sampling likely influenced the final residue contamination levels. Most detections originated from compounds that were not recently applied on the fields, and samples from B. napus fields were more contaminated compared to those from V. faba fields. Crop pollen was contaminated only with fungicides, honey bee pollen loads contained mainly fungicides, while more insecticides were detected in bumble bee pollen loads. The highest number of compounds and most detections were observed in bumble bee pollen loads, where notably, all five neonicotinoids assessed (acetamiprid, clothianidin, imidacloprid, thiacloprid, and thiamethoxam) were detected despite the no recent application of these compounds on the fields where samples were collected. The concentrations of neonicotinoid insecticides were positively correlated with the number of wild plant species present in the bumble bee-collected pollen samples, but this relationship could not be verified for honey bees. The compounds azoxystrobin, boscalid and thiamethoxam formed the most common pesticide combination in pollen. Our results raise concerns about potential long-term bee exposure to multiple residues and question whether honey bees are suitable surrogates for pesticide risk assessments for all bee species.

Moving past neonicotinoids and honeybees: A systematic review of existing research on other insecticides and bees

Synthetic pesticides (e.g. herbicides, fungicides and insecticides) are used widely in agriculture to protect crops from pests, weeds and disease. However, their use also comes with a range of environmental concerns. One key concern is the effect of insecticides on non-target organisms such as bees, who provide pollination services for crops and wild plants. This systematic literature review quantifies the existing research on bees and insecticides broadly, and then focuses more specifically on non-neonicotinoid insecticides and non-honeybees. We find that articles on honeybees (Apis sp.) and insecticides account for 80% of all research, with all other bees combined making up 20%. Neonicotinoids were studied in 34% of articles across all bees and were the most widely studied insecticide class for non-honeybees overall, with almost three times as many studies than the second most studied class. Of non-neonicotinoid insecticide classes and non-honeybees, the most studied were pyrethroids and organophosphates followed by carbamates, and the most widely represented bee taxa were bumblebees (Bombus), followed by leaf-cutter bees (Megachile) and mason bees (Osmia). Research has taken place across several countries, with the highest numbers of articles from Brazil and the US, and with notable gaps from countries in Asia, Africa and Oceania. Mortality was the most studied effect type, while sub-lethal effects such as on behaviour were less studied. Few studies tested how the effect of insecticides were influenced by multiple pressures, such as climate change and co-occurring pesticides (cocktail effects). As anthropogenic pressures do not occur in isolation, we suggest that future research also addresses these knowledge gaps. Given the changing global patterns in insecticide use, and the increasing inclusion of both non-honeybees and sub-lethal effects in pesticide risk assessment, there is a need for expanding research beyond its current state to ensure a strong scientific evidence base for the development of risk assessment and associated policy.

Environmental Effects on Bee Microbiota

Anthropogenic activities and increased land use, which include industrialization, agriculture and urbanization, directly affect pollinators by changing habitats and floral availability, and indirectly by influencing their microbial composition and diversity. Bees form vital symbioses with their microbiota, relying on microorganisms to perform physiological functions and aid in immunity. As altered environments and climate threaten bees and their microbiota, characterizing the microbiome and its complex relationships with its host offers insights into understanding bee health. This review summarizes the role of sociality in microbiota establishment, as well as examines if such factors result in increased susceptibility to altered microbiota due to environmental changes. We characterize the role of geographic distribution, temperature, precipitation, floral resources, agriculture, and urbanization on bee microbiota. Bee microbiota are affected by altered surroundings regardless of sociality. Solitary bees that predominantly acquire their microbiota through the environment are particularly sensitive to such effects. However, the microbiota of obligately eusocial bees are also impacted by environmental changes despite typically well conserved and socially inherited microbiota. We provide an overview of the role of microbiota in plant-pollinator relationships and how bee microbiota play a larger role in urban ecology, offering microbial connections between animals, humans, and the environment. Understanding bee microbiota presents opportunities for sustainable land use restoration and aiding in wildlife conservation.

Effects of thiamethoxam on brain structure of Bombus terrestris (Hymenoptera: Apidae) workers

Neonicotinoids are the most widely used pesticide compared to other major insecticide classes known worldwide and have the fastest growing market share. Many studies showed that neonicotinoid pesticides harm honeybee learning and farming activities, negatively affect colony adaptation and reduce pollination abilities. Bumblebees are heavily preferred species all over the world in order to ensure pollination in plant production. In this study, sublethal effects of the neonicotinoid insecticide thiamethoxam on the brain of Bombus terrestris workers were analyzed. Suspensions (1/1000, 1/100, 1/10) of the maximum recommended dose of thiamethoxam were applied to the workers. 48 h after spraying, morphological effects on the brains of workers were studied. According to area measurements of ICC's of Kenyon cells, there was a significant difference between 1/10 dose and all groups. On the other hand, areas of INC's of Kenyon cells showed a significant difference between the control group and all dose groups. Neuropil disorganization in the calyces increased gradually and differed significantly between the groups and was mostly detected at the highest dose (1/10). Apart from optic lobes, pycnotic nuclei were also observed in the middle region of calyces of mushroom bodies in the high dose group. Also, the width of the lamina, medulla and lobula parts of the optic lobes of each group and the areas of the antennal lobes were measured and significant differences were determined between the groups. The results of the study revealed that sublethal doses of thiamethoxam caused some negative impacts on brain morphology of B. terrestris workers.

Description and validation of an improved method to feed solitary bees (Osmia spp.) known amounts of pesticides

Pesticide exposure is an important driver of bee declines. Laboratory toxicity tests provide baseline information on the potential effects of pesticides on bees, but current risk assessment schemes rely on one species, the highly social honey bee, Apis mellifera, and there is uncertainty regarding the extent to which this species is a suitable surrogate for other pollinators. For this reason, Osmia cornuta and Osmia bicornis have been proposed as model solitary bee species in the EU risk assessment scheme. The use of solitary bees in risk assessment requires the development of new methodologies adjusted to the biology of these species. For example, oral dosing methods used with honey bees cannot be readily applied to solitary bees due to differences in feeding behaviour and social interactions. In this study, we describe the "petal method", a laboratory feeding method, and validate its use in acute and chronic exposure oral tests with Osmia spp. We conducted five experiments in which we compared the performance of several artificial flowers combining visual and olfactory cues against the petal method, or in which variations of the petal method were confronted. We then use the results of these experiments to optimize the feeding arenas and propose standardized methods for both acute and chronic exposure tests. The petal method provides high levels of feeding success, thus reducing the number of bees needed. It works with a wide variety of petal species and with both female and male Osmia spp., thus ensuring reproducibility across studies. To validate the use of the petal method in ecotoxicology tests, we assess the toxicity of a standard reference insecticide, dimethoate, in O. cornuta adults and determine LD50 values for this species. The petal method should facilitate the inclusion of solitary bees in risk assessment schemes therefore increasing the protection coverage of pesticide regulation.