Field-realistic neonicotinoid exposure has sub-lethal effects on non-Apis bees: A meta-analysis

Exposure to sublethal levels of insecticide-fungicide mixtures affect reproductive success and population growth rates in the solitary bee Osmia cornuta

In agricultural environments, bees are routinely exposed to combinations of pesticides. For the most part, exposure to these pesticide mixtures does not result in acute lethal effects, but we know very little about potential sublethal effects and their consequences on reproductive success and population dynamics. In this study, we orally exposed newly emerged females of the solitary bee Osmia cornuta to environmentally-relevant levels of acetamiprid (a cyano-substituted neonicotinoid insecticide) singly and in combination with tebuconazole (a sterol-biosynthesis inhibitor (SBI) fungicide). The amount of feeding solution consumed during the exposure phase was lowest in bees exposed to the pesticide mixture. Following exposure, females were individually marked and released into oilseed rape field cages to monitor their nesting performance and assess their reproductive success. The nesting performance and reproductive success of bees exposed to the fungicide or the insecticide alone were similar to those of control bees and resulted in a 1.3-1.7 net population increases. By contrast, bees exposed to the pesticide mixture showed lower establishment, shortened nesting period, and reduced fecundity. Together, these effects led to a 0.5-0.6 population decrease. Female establishment and shortened nesting period were the main population bottlenecks. We found no effects of the pesticide mixture on nest provisioning rate, offspring body weight or sex ratio. Our study shows how sublethal pesticide exposure may affect several components of bee reproductive success and, ultimately, population growth. Our results calls for a rethinking of pollinator risk assessment schemes, which should target not only single compounds but also combinations of compounds likely to co-occur in agricultural environments.

Exposure to an insecticide formulation alters chemosensory orientation, but not floral scent detection, in buff-tailed bumblebees (Bombus terrestris)

Although pesticide-free techniques have been developed in agriculture, pesticides are still routinely used against weeds, pests, and pathogens worldwide. These agrochemicals pollute the environment and can negatively impact human health, biodiversity and ecosystem services. Acetamiprid, an approved neonicotinoid pesticide in the EU, may exert sub-lethal effects on pollinators and other organisms. However, our knowledge on the scope and severity of such effects is still incomplete. Our experiments focused on the effects of the insecticide formulation Mospilan (active ingredient: 20% acetamiprid) on the peripheral olfactory detection of a synthetic floral blend and foraging behaviour of buff-tailed bumblebee (Bombus terrestris) workers. We found that the applied treatment did not affect the antennal detection of the floral blend; however, it induced alterations in their foraging behaviour. Pesticide-treated individuals started foraging later, and the probability of finding the floral blend was lower than that of the control bumblebees. However, exposed bumblebees found the scent source faster than the controls. These results suggest that acetamiprid-containing Mospilan may disrupt the activity and orientation of foraging bumblebees. We hypothesize that the observed effects of pesticide exposure on foraging behaviour could be mediated through neurophysiological and endocrine mechanisms. We propose that future investigations should clarify whether such sub-lethal effects can affect pollinators' population dynamics and their ecosystem services.

Flupyradifurone negatively affects survival, physical condition and mobility in the two-spotted lady beetle (Adalia bipunctata)

Lady beetles play a crucial role in natural ecosystems and agricultural settings. Unfortunately, these insects and more specifically the two-spotted lady beetle (Adalia bipunctata) are currently facing a severe decline in populations due to various stressors, with pesticide exposure being a significant threat. Flupyradifurone is a relatively newly introduced insecticide and as existing research is mainly elucidating its effects on bees there remains a limited understanding of its effects on non-hymenopteran insects, including lady beetles. In this study we investigated the impact of acute orally applied flupyradifurone doses on survival and sublethal parameters such as physical condition and mobility on A. bipunctata. Our findings revealed a significant increase in mortality among individuals subjected to flupyradifurone doses of 19 ng/individual (corresponding to >1.5-2.0 ng active substance (a.s.)/mg body weight (bw). The calculated LD50 of flupyradifurone at 48 h was 2.11 ng a.s./mg bw corresponding to an amount of 26.38 ng/individual. Sublethal consequences were observable immediately after pesticide application. Even at doses as low as 2 ng/individual (corresponding to >0.0-0.5 ng a.s./mg bw), flupyradifurone induced trembling and temporary immobility in treated animals. Furthermore, pesticide intoxication led to hypoactivity, with less distance covered and a decline in straightness of locomotion. In conclusion, our study underscores the harmful effects of flupyradifurone on the two-spotted lady beetle at doses notably lower than those affecting bees. These findings stress the importance of additional research to attain a more holistic understanding of pesticide impacts not only on a broader range of non-target arthropods species, but also on various exposure routes as well as lethal and sublethal effects.

Field agrochemical exposure impacts locomotor activity in wild bumblebees

Agricultural intensification has been identified as one of the key causes of global insect biodiversity losses. These losses have been further linked to the widespread use of agrochemicals associated with modern agricultural practices. Many of these chemicals are known to have negative sublethal effects on commercial pollinators, such as managed honeybees and bumblebees, but less is known about the impacts on wild bees. Laboratory-based studies with commercial pollinators have consistently shown that pesticide exposure can impact bee behavior, with cascading effects on foraging performance, reproductive success, and pollination services. However, these studies typically assess only one chemical, neglecting the complexity of real-world exposure to multiple agrochemicals and other stressors. In the summer of 2020, we collected wild-foraging workers of the common eastern bumblebee, Bombus impatiens, from five squash (Cucurbita) agricultural sites (organic and conventional farms), selected to represent a range of agrochemical, including neonicotinoid insecticide, use. For each bee, we measured two behaviors relevant to foraging success and previously shown to be impacted by pesticide exposure: sucrose responsiveness and locomotor activity. Following behavioral testing, we used liquid chromatography-tandem mass spectrometry (LC-MS/MS) chemical analysis to detect and quantify the presence of 92 agrochemicals in each bumblebee. Bees collected from our sites did not vary in pesticide exposure as expected. While we found a limited occurrence of neonicotinoids, two fungicides (azoxystrobin and difenoconazole) were detected at all sites, and the pesticide synergist piperonyl butoxide (PBO) was present in all 123 bees. We found that bumblebees that contained higher levels of PBO were less active, and this effect was stronger for larger bumblebee workers. While PBO is unlikely to be the direct cause of the reduction in bee activity, it could be an indicator of exposure to pyrethroids and/or other insecticides that we were unable to directly quantify, but which PBO is frequently tank-mixed with during pesticide applications on crops. We did not find a relationship between agrochemical exposure and bumblebee sucrose responsiveness. To our knowledge, this is the first evidence of a sublethal behavioral impact of agrochemical exposure on wild-foraging bees.

Novel indices reveal that pollinator exposure to pesticides varies across biological compartments and crop surroundings

Declines in insect pollinators have been linked to a range of causative factors such as disease, loss of habitats, the quality and availability of food, and exposure to pesticides. Here, we analysed an extensive dataset generated from pesticide screening of foraging insects, pollen-nectar stores/beebread, pollen and ingested nectar across three species of bees collected at 128 European sites set in two types of crop. In this paper, we aimed to (i) derive a new index to summarise key aspects of complex pesticide exposure data and (ii) understand the links between pesticide exposures depicted by the different matrices, bee species and apple orchards versus oilseed rape crops. We found that summary indices were highly correlated with the number of pesticides detected in the related matrix but not with which pesticides were present. Matrices collected from apple orchards generally contained a higher number of pesticides (7.6 pesticides per site) than matrices from sites collected from oilseed rape crops (3.5 pesticides), with fungicides being highly represented in apple crops. A greater number of pesticides were found in pollen-nectar stores/beebread and pollen matrices compared with nectar and bee body matrices. Our results show that for a complete assessment of pollinator pesticide exposure, it is necessary to consider several different exposure routes and multiple species of bees across different agricultural systems.

A novel insecticide impairs bumblebee memory and sucrose responsiveness across high and low nutrition

Wild bees are important pollinators of crops and wildflowers but are exposed to a myriad of different anthropogenic stressors, such as pesticides and poor nutrition, as a consequence of intensive agriculture. These stressors do not act in isolation, but interact, and may exacerbate one another. Here, we assessed whether a field-realistic concentration of flupyradifurone, a novel pesticide that has been labelled as 'bee safe' by regulators, influenced bumblebee sucrose responsiveness and long-term memory. In a fully crossed experimental design, we exposed individual bumblebees (Bombus impatiens) to flupyradifurone at high (50% (w/w)) or low (15% (w/w)) sucrose concentrations, replicating diets that are either carbohydrate rich or poor, respectively. We found that flupyradifurone impaired sucrose responsiveness and long-term memory at both sucrose concentrations, indicating that better nutrition did not buffer the negative impact of flupyradifurone. We found no individual impact of sugar deficiency on bee behaviour and no significant interactions between pesticide exposure and poor nutrition. Our results add to a growing body of evidence demonstrating that flupyradifurone has significant negative impacts on pollinators, indicating that this pesticide is not 'bee safe'. This suggests that agrochemical risk assessments are not protecting pollinators from the unintended consequences of pesticide use.

The stingless bee Trigona spinipes (Hymenoptera: Apidae) is at risk from a range of insecticides via direct ingestion and trophallactic exchanges

BACKGROUND

The stingless bee, Trigona spinipes, is an important pollinator of numerous native and cultivated plants. Trigona spinipes populations can be negatively impacted by insecticides commonly used for pest control in crops. However, this species has been neglected in toxicological studies. Here we observed the effects of seven insecticides on the survival of bees that had fed directly on insecticide-contaminated food sources or received insecticides via trophallactic exchanges between nestmates. The effects of insecticides on flight behavior were also determined for the compounds considered to be of low toxicity.

RESULTS

Imidacloprid, spinosad and malathion were categorized as highly toxic to T. spinipes, whereas lambda-cyhalothrin, methomyl and chlorfenapyr were of medium to low toxicity and interfered with two aspects of flight behavior evaluated here. Chlorantraniliprole was the only insecticide tested here that had no significant effect on T. spinipes survival, although it did interfere with one aspect of flight capacity. A single bee that had ingested malathion, spinosad or imidacloprid, could contaminate three, four and nineteen other bees, respectively via trophallaxis, resulting in the death of the recipients.

CONCLUSION

This is the first study to evaluate the ecotoxicology of a range of insecticides that not only negatively affected T. spinipes survival, but also interfered with flight capacity, a very important aspect of pollination behavior. The toxicity of the insecticides was observed following direct ingestion and also via trophallactic exchanges between nestmates, highlighting the possibility of lethal effects of these insecticides spreading throughout the colony, reducing the survival of non-foraging individuals. © 2023 Society of Chemical Industry.

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.

Manipulation of soil mycorrhizal fungi influences floral traits

Most plants form root hyphal relationships with mycorrhizal fungi, especially arbuscular mycorrhizal fungi (AMF). These associations are known to positively impact plant biomass and competitive ability. However, less is known about how mycorrhizas impact other ecological interactions, such as those mediated by pollinators. We performed a meta-regression of studies that manipulated AMF and measured traits related to pollination, including floral display size, rewards, visitation, and reproduction, extracting 63 studies with 423 effects. On average, the presence of mycorrhizas was associated with positive effects on floral traits. Specifically, we found impacts of AMF on floral display size, pollinator visitation and reproduction, and a positive but nonsignificant impact on rewards. Studies manipulating mycorrhizas with fungicide tended to report contrasting results, possibly because fungicide destroys both beneficial and pathogenic microbes. Our study highlights the potential for relationships with mycorrhizal fungi to play an important, yet underrecognized role in plant-pollinator interactions. With heightened awareness of the need for a more sustainable agricultural industry, mycorrhizal fungi may offer the opportunity to reduce reliance on inorganic fertilizers. At the same time, fungicides are now ubiquitous in agricultural systems. Our study demonstrates indirect ways in which plant-belowground fungal partnerships could manifest in plant-pollinator interactions.

Impacts of neonicotinoid insecticides on bumble bee energy metabolism are revealed under nectar starvation

Bumble bees are an important group of insects that provide essential pollination services as a consequence of their foraging behaviors. These pollination services are driven, in part, by energetic exchanges between flowering plants and individual bees. Thus, it is important to examine bumble bee energy metabolism and explore how it might be influenced by external stressors contributing to declines in global pollinator populations. Two stressors that are commonly encountered by bees are insecticides, such as the neonicotinoids, and nutritional stress, resulting from deficits in pollen and nectar availability. Our study uses a metabolomic approach to examine the effects of neonicotinoid insecticide exposure on bumble bee metabolism, both alone and in combination with nutritional stress. We hypothesized that exposure to imidacloprid disrupts bumble bee energy metabolism, leading to changes in key metabolites involved in central carbon metabolism. We tested this by exposing Bombus impatiens workers to imidacloprid according to one of three exposure paradigms designed to explore how chronic versus more acute (early or late) imidacloprid exposure influences energy metabolite levels, then also subjecting them to artificial nectar starvation. The strongest effects of imidacloprid were observed when bees also experienced nectar starvation, suggesting a combinatorial effect of neonicotinoids and nutritional stress on bumble bee energy metabolism. Overall, this study provides important insights into the mechanisms underlying the impact of neonicotinoid insecticides on pollinators, and underscores the need for further investigation into the complex interactions between environmental stressors and energy metabolism.

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.

Monarch Butterflies in Western North America: A Holistic Review of Population Trends, Ecology, Stressors, Resilience and Adaptation

Monarch butterfly populations in western North America suffered a substantial decline, from millions of butterflies overwintering in California in the 1980s to less than 400,000 at the beginning of the 21st century. The introduction of neonicotinoid insecticides in the mid-1990s and their subsequent widespread use appears to be the most likely major factor behind this sudden decline. Habitat loss and unfavorable climates (high temperatures, aridity, and winter storms) have also played important and ongoing roles. These factors kept overwintering populations stable but below 300,000 during 2001-2017. Late winter storm mortality and consequent poor spring reproduction drove winter populations to less than 30,000 butterflies during 2018-2019. Record high temperatures in California during the fall of 2020 appeared to prematurely terminate monarch migration, resulting in the lowest overwintering population (1899) ever recorded. Many migrants formed winter-breeding populations in urban areas. Normal seasonal temperatures in the autumns of 2021 and 2022 enabled overwintering populations to return to around the 300,000 level, characteristic of the previous two decades. Natural enemies (predators, parasitoids, parasites, and pathogens) may be important regional or local drivers at times but they are a consistent and fundamental part of monarch ecology. Human interference (capture, rearing) likely has the least impact on monarch populations. The rearing of monarch caterpillars, particularly by children, is an important human link to nature that has positive ramifications for insect conservation beyond monarch butterflies and should be encouraged.

Imidacloprid increases the prevalence of the intestinal parasite Lotmaria passim in honey bee workers

A challenge in bee protection is to assess the risks of pesticide-pathogen interactions. Lotmaria passim, a ubiquitous unicellular parasite in honey bees, is considered harmful under specific conditions. Imidacloprid causes unpredictable side effects. Research indicates that both L. passim and imidacloprid may affect the physiology, behavior, immunity, microbiome and lifespan of honey bees. We designed cage experiments to test whether the infection of L. passim is affected by a sublethal dose of imidacloprid. Workers collected at the time of emergence were exposed to L. passim and 2.5 μg/L imidacloprid in the coexposure treatment group. First, samples of bees were taken from cages since they were 5 days old and 3 days postinfection, i.e., after finishing an artificial 24 h L. passim infection. Additional bees were collected every two additional days. In addition, bees frozen at the time of emergence and collected from the unexposed group were analyzed. Abdomens were analyzed using qPCR to determine parasite load, while corresponding selected heads were subjected to a label-free proteomic analysis. Our results show that bees are free of L. passim at the time of emergence. Furthermore, imidacloprid considerably increased the prevalence as well as parasite loads in individual bees. This means that imidacloprid facilitates infection, enabling faster parasite spread in a colony and potentially to surrounding colonies. The proteomic analysis of bee heads showed that imidacloprid neutralized the increased transferrin 1 expression by L. passim. Importantly, this promising marker has been previously observed to be upregulated by infections, including gut parasites. This study contributes to understanding the side effects of imidacloprid and demonstrates that a single xenobiotic/pesticide compound can interact with the gut parasite. Our methodology can be used to assess the effects of different compounds on L. passim.

Pesticide pollution associations with riverine invertebrate communities in England

Globally freshwater biodiversity has experienced major decline and chemical pollutants are believed to have played a significant role in this decline, but this has not been well quantified for most riverine invertebrate populations. Here we applied a biogeographically independent trait-based bioindicator, SPEARpesticides across sites across five regions (Northern, Midlands and Western, Anglian, Southeast, and Southwest) in England to investigate for associations specifically between pesticide use/pollution and riverine invertebrate communities over a 55-year period (1965-2019). Both spatially and temporally post-1990, the Anglian and Thames regions consistently showed the lowest SPEARpesticides scores, illustrating the presence of fewer pesticide sensitive species. The Anglian region had the highest pesticide use compared to all other regions from 1990 to 2018 and there were negative relationships between the level of pesticide/insecticide use and the regional SPEARpesticides score. Biochemical Oxygen Demand and ammonia, as measures of general water quality, were also negatively correlated with the SPEARpesticides scores across the regions, but these factors were not the driver for the lower SPEARpesticides scores seen in the Anglian region. Based on SPEARpesticides scores, riverine invertebrate communities in England have been most impacted in the Anglian region and we evidence chronic insecticide exposure is likely a significant factor in shaping the status of those invertebrate communities.

Seed treatment with clothianidin induces changes in plant metabolism and alters pollinator foraging preferences

Neonicotinoids, systemic insecticides that are distributed into all plant tissues and protect against pests, have become a common part of crop production, but can unintentionally also affect non-target organisms, including pollinators. Such effects can be direct effects from insecticide exposure, but neonicotinoids can affect plant physiology, and effects could therefore also be indirectly mediated by changes in plant phenology, attractiveness and nutritional value. Under controlled greenhouse conditions, we tested if seed treatment with the neonicotinoid clothianidin affected oilseed rape's production of flower resources for bees and the content of the secondary plant products glucosinolates that provide defense against herbivores. Additionally, we tested if seed treatment affected the attractiveness of oilseed rape to flower visiting bumblebees, using outdoor mesocosms. Flowers and leaves of clothianidin-treated plants had different profiles of glucosinolates compared with untreated plants. Bumblebees in mesocosms foraged slightly more on untreated plants. Neither flower timing, flower size nor the production of pollen and nectar differed between treatments, and therefore cannot explain any preference for untreated oilseed rape. We instead propose that this small but significant preference for untreated plants was related to the altered glucosinolate profile caused by clothianidin. Thereby, this study contributes to the understanding of the complex relationships between neonicotinoid-treated crops and pollinator foraging choices, by suggesting a potential mechanistic link by which insecticide treatment can affect insect behavior.

Breaking the cycle: Reforming pesticide regulation to protect pollinators

Over decades, pesticide regulations have cycled between approval and implementation, followed by the discovery of negative effects on nontarget organisms that result in new regulations, pesticides, and harmful effects. This relentless pattern undermines the capacity to protect the environment from pesticide hazards and frustrates end users that need pest management tools. Wild pollinating insects are in decline, and managed pollinators such as honey bees are experiencing excessive losses, which threatens sustainable food security and ecosystem function. An increasing number of studies demonstrate the negative effects of field-realistic exposure to pesticides on pollinator health and fitness, which contribute to pollinator declines. Current pesticide approval processes, although they are superior to past practices, clearly continue to fail to protect pollinator health. In the present article, we provide a conceptual framework to reform cyclical pesticide approval processes and better protect pollinators.

Pollination crisis Down-Under: Has Australasia dodged the bullet?

Since mid-1990s, concerns have increased about a human-induced "pollination crisis." Threats have been identified to animals that act as plant pollinators, plants pollinated by these animals, and consequently human well-being. Threatening processes include loss of natural habitat, climate change, pesticide use, pathogen spread, and introduced species. However, concern has mostly been during last 10-15 years and from Europe and North America, with Australasia, known as Down-Under, receiving little attention. So perhaps Australasia has "dodged the bullet"? We systematically reviewed the published literature relating to the "pollination crisis" via Web of Science, focusing on issues amenable to this approach. Across these issues, we found a steep increase in publications over the last few decades and a major geographic bias towards Europe and North America, with relatively little attention in Australasia. While publications from Australasia are underrepresented, factors responsible elsewhere for causing the "pollination crisis" commonly occur in Australasia, so this lack of coverage probably reflects a lack of awareness rather than the absence of a problem. In other words, Australasia has not "dodged the bullet" and should take immediate action to address and mitigate its own "pollination crisis." Sensible steps would include increased taxonomic work on suspected plant pollinators, protection for pollinator populations threatened with extinction, establishing long-term monitoring of plant-pollinator relationships, incorporating pollination into sustainable agriculture, restricting the use of various pesticides, adopting an Integrated Pest and Pollinator Management approach, and developing partnerships with First Nations peoples for research, conservation and management of plants and their pollinators. Appropriate Government policy, funding and regulation could help.

The Impacts of Early-Life Experience on Bee Phenotypes and Fitness

Across diverse animal species, early-life experiences have lifelong impacts on a variety of traits. The scope of these impacts, their implications, and the mechanisms that drive these effects are central research foci for a variety of disciplines in biology, from ecology and evolution to molecular biology and neuroscience. Here, we review the role of early life in shaping adult phenotypes and fitness in bees, emphasizing the possibility that bees are ideal species to investigate variation in early-life experience and its consequences at both individual and population levels. Bee early life includes the larval and pupal stages, critical time periods during which factors like food availability, maternal care, and temperature set the phenotypic trajectory for an individual's lifetime. We discuss how some common traits impacted by these experiences, including development rate and adult body size, influence fitness at the individual level, with possible ramifications at the population level. Finally, we review ways in which human alterations to the landscape may impact bee populations through early-life effects. This review highlights aspects of bees' natural history and behavioral ecology that warrant further investigation with the goal of understanding how environmental disturbances threaten these vulnerable species.

Behavioral and physiological response of the passerine bird Agelaioides badius to seeds coated with imidacloprid

Neonicotinoids are globally used insecticides, and there are increasing evidence on their negative effects on birds. This study is aimed at characterizing the behavioral and physiological effects of the neonicotinoid imidacloprid (IMI) in a songbird. Adults of Agelaioides badius were exposed for 7 days to non-treated peeled millet and to peeled millet treated with nominal concentrations of 75 (IMI1) and 450 (IMI2) mg IMI/kg seed. On days 2 and 6 of the trial, the behavior of each bird was evaluated for 9 min by measuring the time spent on the floor, the perch, or the feeder. Daily millet consumption, initial and final body weight, and physiological, hematological, genotoxic, and biochemical parameters at the end of exposure were also measured. Activity was greatest on the floor, followed by the perch and the feeder. On the second day, birds exposed to IMI1and IMI2 remained mostly on the perch and the feeder, respectively. On the sixth day, a transition occurred to sectors of greater activity, consistent with the disappearance of the intoxication signs: birds from IMI1 and IMI2 increased their time on the floor and the perch, respectively. Control birds always remained most of the time on the floor. IMI2 birds significantly decreased their feed intake by 31% the first 3 days, compared to the other groups, and significantly decreased their body weight at the end of the exposure. From the set of hematological, genotoxic, and biochemical parameters, treated birds exhibited an alteration of glutathione-S-transferase activity (GST) in breast muscle; the minimal effects observed are probably related to the IMI administration regime. These results highlight that the consumption of less than 10% of the bird daily diet as IMI-treated seeds trigger effects at multiple levels that can impair bird survival.

Pesticide residues in nectar and pollen of melon crops: Risk to pollinators and effects of a specific pesticide mixture on Bombus terrestris (Hymenoptera: Apidae) micro-colonies

Residues detected in pollen collected by honey bees are often used to estimate pesticide exposure in ecotoxicological studies. However, for a more accurate assessment of pesticides effect on foraging pollinators, residues found directly on flowers are a more realistic exposure approximation. We conducted a multi-residue analysis of pesticides on pollen and nectar of melon flowers collected from five fields. The cumulative chronic oral exposure Risk Index (RI) was calculated for Apis mellifera, Bombus terrestris and Osmia bicornis to multiple pesticides. However, this index could underestimate the risk since sublethal or synergistic effects are not considered. Therefore, a mixture containing three of the most frequently detected pesticides in our study was tested for synergistic impact on B. terrestris micro-colonies through a chronic oral toxicity test. According to the result, pollen and nectar samples contained numerous pesticide residues, including nine insecticides, nine fungicides, and one herbicide. Eleven of those were not applied by farmers during the crop season, revealing that melon agroecosystems may be pesticide contaminated environments. The primary contributor to the chronic RI was imidacloprid and O. bircornis is at greatest risk for lethality resulting from chronic oral exposure at these sites. In the bumblebee micro-colony bioassay, dietary exposure to acetamiprid, chlorpyrifos and oxamyl at residue level concentration, showed no effects on worker mortality, drone production or drone size and no synergies were detected when pesticide mixtures were evaluated. In conclusion, our findings have significant implications for improving pesticide risk assessment schemes to guarantee pollinator conservation. In particular, bee pesticide risk assessment should not be limited to acute exposure effects to isolated active ingredients in honey bees. Instead, risk assessments should consider the long-term pesticide exposure effects in both pollen and nectar on a range of bees that reflect the diversity of natural ecosystems and the synergistic potential among pesticide formulations.

Sensitivity to imidacloprid insecticide varies among some social and solitary bee species of agricultural value

Pollinator health risks from long-lasting neonicotinoid insecticides like imidacloprid has primarily focused on commercially managed, cavity-nesting bees in the genera Apis, Bombus, and Osmia. We expand these assessments to include 12 species of native and non-native crop pollinators of differing levels of body size, sociality, and floral specialization. Bees were collected throughout 2016 and 2017 from flowering blueberry, squash, pumpkin, sunflower and okra in south Mississippi, USA. Within 30-60 minutes of capture, bees were installed in bioassay cages made from transparent plastic cups and dark amber jars. Bees were fed via dental wicks saturated with 27% (1.25 M) sugar syrup containing a realistic range of sublethal concentrations of imidacloprid (0, 5, 20, or 100 ppb) that are often found in nectar. Bees displayed no visible tremors or convulsions except for a small sweat bee, Halictus ligatus, and only at 100ppb syrup. Imidacloprid shortened the captive longevities of the solitary bees. Tolerant bee species lived ~10 to 12 days in the bioassays and included two social and one solitary species: Halictus ligatus, Apis mellifera and Ptilothrix bombiformis (rose mallow bees), respectively. No other bee species tolerated imidacloprid as well as honey bees did, which exhibited no appreciable mortality and only modest paralysis across concentration. In contrast, native bees either lived shorter lives, experienced longer paralysis, or endured both. Overall, longevity decreased with concentration linearly for social bees and non-linearly for solitary species. The percentage of a bee's captive lifespan spent paralyzed increased logarithmically with concentration for all species, although bumble bees suffered longest. Of greatest concern was comparable debilitation of agriculturally valuable solitary bees at both low and high sublethal rates of imidacloprid.

Potential risk to pollinators from neonicotinoid applications to host trees for management of spotted lanternfly, Lycorma delicatula (Hemiptera: Fulgoridae)

Neonicotinoid insecticides are used to manage spotted lanternfly (Lycorma delicatula (White); hereafter SLF), a recently introduced pest in the United States. Neonicotinoids can harm nontargets, such as pollinators potentially exposed via floral resources of treated plants. We quantified neonicotinoid residues in whole flowers of two SLF host plant species, red maple (Acer rubrum L. [Sapindales: Sapindaceae]) and tree-of-heaven (Ailanthus altissima (Mill.) [Sapindales: Simaroubaceae]), treated with post-bloom imidacloprid or dinotefuran applications that differed in timing and method of application. In red maple flowers, dinotefuran residues from fall applications were significantly higher than summer applications, while imidacloprid residues from fall applications were significantly lower than summer applications. Residues did not differ between application methods or sites. In tree-of-heaven flowers, dinotefuran residues were only detected in one of 28 samples at a very low concentration. To assess acute mortality risk to bees from oral exposure to residues in these flowers, we calculated risk quotients (RQ) using mean and 95% prediction interval residue concentrations from treatments in this study and lethal concentrations obtained from acute oral bioassays for Apis mellifera (L. (Hymenoptera: Apidae)) and Osmia cornifrons (Radoszkowski (Hymenoptera: Megachilidae)), then compared these RQs to a level of concern. For A. mellifera, only one treatment group, applied at 2X maximum label rate, had an RQ that exceeded this level. However, several RQs for O. cornifrons exceeded the level of concern, suggesting potential acute risk to solitary bees. Further studies are recommended for more comprehensive risk assessments to nontargets from neonicotinoid use for SLF management.

Are Botanical Biopesticides Safe for Bees (Hymenoptera, Apoidea)?

The recent global decline in insect populations is of particular concern for pollinators. Wild and managed bees (Hymenoptera, Apoidea) are of primary environmental and economic importance because of their role in pollinating cultivated and wild plants, and synthetic pesticides are among the major factors contributing to their decline. Botanical biopesticides may be a viable alternative to synthetic pesticides in plant defence due to their high selectivity and short environmental persistence. In recent years, scientific progress has been made to improve the development and effectiveness of these products. However, knowledge regarding their adverse effects on the environment and non-target species is still scarce, especially when compared to that of synthetic products. Here, we summarize the studies concerning the toxicity of botanical biopesticides on the different groups of social and solitary bees. We highlight the lethal and sublethal effects of these products on bees, the lack of a uniform protocol to assess the risks of biopesticides on pollinators, and the scarcity of studies on specific groups of bees, such as the large and diverse group of solitary bees. Results show that botanical biopesticides cause lethal effects and a large number of sublethal effects on bees. However, the toxicity is limited when comparing the effects of these compounds with those of synthetic compounds.

Wild bees are exposed to low levels of pesticides in urban grasslands and community gardens

Globally documented wild bee declines threaten sustainable food production and natural ecosystem functioning. Urban environments are often florally abundant, and consequently can contain high levels of pollinator diversity compared with agricultural environments. This has led to the suggestion that urban environments are an increasingly important habitat for pollinators. However, pesticides, such as commercial bug sprays, have a range of lethal and sub-lethal impacts on bees and are widely available for public use, with past work indicating that managed bees (honeybees and bumblebees) are exposed to a range of pesticides in urban environments. Despite this, we still have a poor understanding of (i) whether wild bees foraging in urban environments are exposed to pesticides and (ii) if exposure differs between genera. Here we assessed pesticide exposure in 8 bee genera foraging across multiple urban landscapes. We detected 13 different pesticides, some at concentrations known to have sub-lethal impacts on pollinators. Both the likelihood of pesticides being detected, and the concentrations observed, were higher for larger bees, likely due to their greater foraging ranges. Our results suggest that restricting agrochemical use in urban environments, where the economic benefits are limited, is a simple way to reduce anthropogenic stress on wild bees.

Surrogate species in pesticide risk assessments: Toxicological data of three stingless bees species

Discussions about environmental risk reassessment of pesticides have grown in the last decades, especially in tropical and subtropical regions since the diversity of bee species in these places is quite different. Stingless bees are highly affected by pesticides, and toxicity information is necessary to include them in the regulatory process of countries that hosts a diversity of these species. Therefore, the present study aimed to evaluate the Median Lethal Concentration (LC₅₀), estimate the Median Lethal Dose (LD₅₀) and compared the sensitivity of three species of stingless bees exposed to the commercial formulation of the neonicotinoid thiamethoxam (TMX). The LD₅₀ was estimated based on the LC₅₀ determined in the present study (LC₅₀ = 0.329 ng a.i./μL for Tetragonisca angustula; 0.624 ng a.i./μL for Scaptotrigona postica, and 0.215 ng a.i./μL for Melipona scutellaris). Considering these data, toxicity endpoints were used to fit species sensitive distribution curves (SSD) and determine the sensitivity ratio. The results showed that all the stingless bees tested are more sensitive to TMX than the Apis mellifera, the model organism used in ecotoxicological tests. Regarding the oral LC₅₀, the most susceptible and most tolerant species were M. scutellaris > T. angustula > S. postica > A. mellifera. Following the same evaluated pattern, for the LD₅₀ (considering the weight of the bees - ng a.i./g bee), we have: M. scutellaris > S. postica > T. angustula > A. mellifera, and without the weight considered (ng a.i./bee): T. angustula > M. scutellaris > S. postica > A. mellifera. The different sensitivities among stingless bee species highlight the importance of inserting more than one surrogate species with a variety of sizes in research and protocol development. Additionally, the research suggests the need to investigate patterns regarding the influence of body mass on pesticide sensitivity among stingless bee species.

Pesticide licensing in the EU and protecting pollinators

Intensive agriculture is reliant on pesticides to control crop pests, but these chemicals can have negative environmental consequences. This has resulted in repeated calls for pesticide risk assessments to be modified to better protect ecosystem services such as pollination. However, the pesticide licensing process is complex, and consequently there is often confusion between risk assessments where the environmental impact of pesticide use is considered, and risk management where licensing decisions are made. Using bees as a case study, we provide a roadmap for how pesticides are licensed for use in the European Union. By outlining the regulatory process, we highlight key data gaps that need to be addressed to generate a holistic approach to environmental risk assessment. Such an approach is vital to protect pollinators and wildlife more broadly from the unintended consequences of pesticide use.

Ecological Drivers and Consequences of Bumble Bee Body Size Variation

Body size is arguably one of the most important traits influencing the physiology and ecology of animals. Shifts in animal body size have been observed in response to climate change, including in bumble bees (Bombus spp. [Hymenoptera: Apidae]). Bumble bee size shifts have occurred concurrently with the precipitous population declines of several species, which appear to be related, in part, to their size. Body size variation is central to the ecology of bumble bees, from their social organization to the pollination services they provide to plants. If bumble bee size is shifted or constrained, there may be consequences for the pollination services they provide and for our ability to predict their responses to global change. Yet, there are still many aspects of the breadth and role of bumble bee body size variation that require more study. To this end, we review the current evidence of the ecological drivers of size variation in bumble bees and the consequences of that variation on bumble bee fitness, foraging, and species interactions. In total we review: (1) the proximate determinants and physiological consequences of size variation in bumble bees; (2) the environmental drivers and ecological consequences of size variation; and (3) synthesize our understanding of size variation in predicting how bumble bees will respond to future changes in climate and land use. As global change intensifies, a better understanding of the factors influencing the size distributions of bumble bees, and the consequences of those distributions, will allow us to better predict future responses of these pollinators.

The Insecticide Imidacloprid Decreases Nannotrigona Stingless Bee Survival and Food Consumption and Modulates the Expression of Detoxification and Immune-Related Genes

Stingless bees are ecologically and economically important species in the tropics and subtropics, but there has been little research on the characterization of detoxification systems and immune responses within them. This is critical for understanding their responses to, and defenses against, a variety of environmental stresses, including agrochemicals. Therefore, we studied the detoxification and immune responses of a stingless bee, Nanotrigona perilampoides, which is an important stingless bee that is widely distributed throughout Mexico, including urban areas, and has the potential to be used in commercial pollination. We first determined the LC50 of the neonicotinoid insecticide imidacloprid for foragers of N. perilampoides, then chronically exposed bees for 10 days to imidacloprid at two field-realistic concentrations, LC10 (0.45 ng/µL) or LC20 (0.74 ng/µL), which are respectively 2.7 and 1.3-fold lower than the residues of imidacloprid that have been found in honey (6 ng/g) in central Mexico. We found that exposing N. perilampoides stingless bees to imidacloprid at these concentrations markedly reduced bee survival and food consumption, revealing the great sensitivity of this stingless bee to the insecticide in comparison to honey bees. The expression of detoxification (GSTD1) and immune-related genes (abaecin, defensin1, and hymenopteacin) in N. perilampoides also changed over time in response to imidacloprid. Gene expression was always lower in bees after 8 days of exposure to imidacloprid (LC10 or LC20) than it was after 4 days. Our results demonstrate that N. perilampoides stingless bees are extremely sensitive to imidacloprid, even at low concentrations, and provide greater insight into how stingless bees respond to pesticide toxicity. This is the first study of its kind to look at detoxification systems and immune responses in Mexican stingless bees, an ecologically and economically important taxon.

Nutritional stress exacerbates impact of a novel insecticide on solitary bees' behaviour, reproduction and survival

Pesticide exposure and food stress are major threats to bees, but their potential synergistic impacts under field-realistic conditions remain poorly understood and are not considered in current pesticide risk assessments. We conducted a semi-field experiment to examine the single and interactive effects of the novel insecticide flupyradifurone (FPF) and nutritional stress on fitness proxies in the solitary bee Osmia bicornis. Individually marked bees were released into flight cages with monocultures of buckwheat, wild mustard or purple tansy, which were assigned to an insecticide treatment (FPF or control) in a crossed design. Nutritional stress, which was high in bees foraging on buckwheat, intermediate on wild mustard and low on purple tansy, modulated the impact of insecticide exposure. Within the first day after application of FPF, mortality of bees feeding on buckwheat was 29 times higher compared with control treatments, while mortality of FPF exposed and control bees was similar in the other two plant species. Moreover, we found negative synergistic impacts of FPF and nutritional stress on offspring production, flight activity, flight duration and flower visitation frequency. These results reveal that environmental policies and risk assessment schemes that ignore interactions among anthropogenic stressors will fail to adequately protect bees and the pollination services they provide.

Quantifying exposure of bumblebee (Bombus spp.) queens to pesticide residues when hibernating in agricultural soils

Exposure to pesticides is a major threat to bumblebee (Bombus spp.) health. In temperate regions, queens of many bumblebee species hibernate underground for several months, putting them at potentially high risk of exposure to soil contaminants. The extent to which bumblebees are exposed to residues in agricultural soils during hibernation is currently unknown, which limits our understanding of the full pesticide exposome for bumblebees throughout their lifecycle. To generate field exposure estimates for overwintering bumblebee queens to pesticide residues, we sampled soils from areas corresponding to suitable likely hibernation sites at six apple orchards and 13 diversified farms throughout Southern Ontario (Canada) in fall 2019-2020. Detectable levels of pesticides were found in 65 of 66 soil samples analysed for multi-pesticide residues (UPLC-MS/MS). A total of 53 active ingredients (AIs) were detected in soils, including 27 fungicides, 13 insecticides, and 13 herbicides. Overall, the frequency of detection, residue levels (median = 37.82 vs. 2.20 ng/g), and number of pesticides per sample (mean = 12 vs. 4 AIs) were highest for orchard soils compared to soils from diversified farms. Ninety-one percent of samples contained multiple residues (up to 29 different AIs per sample), including mixtures of insecticides and fungicides that might lead to synergistic effects. Our results suggest that when hibernating in agricultural areas, bumblebee queens are very likely to be exposed to a wide range of pesticide residues in soil, including potentially harmful levels of insecticides (e.g., cyantraniliprole up to 148.82 ng/g). Our study indicates the importance of empirically testing the potential effects of pesticide residues in soils for hibernating bumblebee queens, using field exposure data such as those generated here. The differences in potential exposure that we detected between cropping systems can also be used to better inform regulations that govern the use of agricultural pesticides, notably in apple orchards.

Biopesticides and insect pollinators: Detrimental effects, outdated guidelines, and future directions

As synthetic pesticides play a major role in pollinator decline worldwide, biopesticides have been gaining increased attention to develop more sustainable methods for pest management in agriculture. These biocontrol agents are usually considered as safe for non-target species, such as pollinators. Unfortunately, when it comes to non-target insects, only the acute or chronic effects on survival following exposure to biopesticides are tested. Although international boards have highlighted the need to include also behavioral and morphophysiological traits when assessing risks of plant protection products on pollinators, no substantial concerns have been raised about the risks associated with sublethal exposure to these substances. Here, we provide a comprehensive review of the studies investigating the potential adverse effects of biopesticides on different taxa of pollinators (bees, butterflies, moths, beetles, flies, and wasps). We highlight the fragmentary knowledge on this topic and the lack of a systematic investigation of these negative effects of biopesticides on insect pollinators. We show that all the major classes of biopesticides, besides their direct toxicity, can also cause a plethora of more subtle detrimental effects in both solitary and social species of pollinators. Although research in this field is growing, the current risk assesment approach does not suffice to properly assess all the potential side-effects that these agents of control may have on pollinating insects. Given the urgent need for a sustainable agriculture and wildlife protection, it appears compelling that these so far neglected detrimental effects should be thoroughly assessed before allegedly safe biopesticides can be used in the field and, in this view, we provide a perspective for future directions.

The flavonoid rutin protects against cognitive impairments by imidacloprid and fipronil

The ongoing decline of bee populations and its impact on food security demands integrating multiple strategies. Sublethal impairments associated with exposure to insecticides, affecting the individual and the colony levels, have led to insecticide moratoria and bans. However, legislation alone is not sufficient and remains a temporary solution to an evolving market of insecticides. Here, we asked whether bees can be prophylactically protected against sublethal cognitive effects of two major neurotoxic insecticides, imidacloprid and fipronil, with different mechanisms of action. We evaluated the protective effect of the prophylactic administration of the flavonoid rutin, a secondary plant metabolite, present in nectar and pollen, and known for its neuroprotective properties. Following controlled or ad libitum administration of rutin, foragers of the North American bumble bee Bombus impatiens received oral administration of the insecticides at sublethal realistic dosages. Learning acquisition, memory retention and decision speed were evaluated using olfactory absolute conditioning of the proboscis extension response. We show that the insecticides primarily impair acquisition but not retention or speed of the conditioned proboscis extension response. We further show that the administration of the flavonoid rutin successfully protects the bees against impairments produced by acute and chronic administration of insecticides. Our results suggest a new avenue for the protection of bees against sublethal cognitive effects of insecticides.

Highlighted Article: Prophylactically feeding bumble bees with rutin protects their learning and memory performance against oral exposure to insecticides with different mechanisms of action.

Exposure to the novel insecticide flupyradifurone impairs bumblebee feeding motivation, learning, and memory retention

Bees are vital pollinators of crops and wildflowers and as such, wild bee declines threaten food security and functioning ecosystems. One driver of bee declines is the use of systemic insecticides, such as commonly used neonicotinoids. However, rising pest resistance to neonicotinoids, and restrictions on their use in the EU, has increased the demand for replacement insecticides to control crop pests. Flupyradifurone is a novel systemic insecticide that is thought to be relatively 'bee safe' although it can be present in the nectar and pollen of bee-attractive crops. Bumblebees rely on learning to forage efficiently, and thus detriments to learning performance may have downstream consequences on their ability to forage. While neonicotinoids negatively influence bumblebee learning and memory, whether this is also the case for their replacements is unclear. Here, we exposed bumblebees (Bombus impatiens) to an acute, field-realistic dose of flupyradifurone before training them to learn either an olfactory or colour association. We found that flupyradifurone impaired bumblebees' learning and memory performance in both olfactory and visual modalities. Flupyradifurone-treated bees were also less motivated to feed. Given the similarity between the detriments to cognition found here and those previously reported for neonicotinoids, this implies that these insecticides may have similar sub-lethal effects on bees. Restrictions on neonicotinoid use are therefore unlikely to benefit bees if novel insecticides like flupyradifurone are used as an alternative, highlighting that current agrochemical risk assessments are not protecting bees from the unwanted consequences of pesticide use. Sub-lethal assessments on non-Apis bees should be made mandatory in agrochemical regulation to ensure that novel insecticides are indeed 'bee safe'.

Pollen diet mediates how pesticide exposure impacts brain gene expression in nest-founding bumble bee queens

A primary goal in biology is to understand the effects of multiple, interacting environmental stressors on organisms. Wild and domesticated bees are exposed to a wide variety of interacting biotic and abiotic stressors, with widespread declines in floral resources and agrochemical exposure being two of the most important. In this study, we used examinations of brain gene expression to explore the sublethal consequences of neonicotinoid pesticide exposure and pollen diet composition in nest-founding bumble bee queens. We demonstrate for the first time that pollen diet composition can influence the strength of bumble bee queen responses to pesticide exposure at the molecular level. Specifically, one pollen mixture in our study appeared to buffer bumble bee queens entirely against the effects of pesticide exposure, with respect to brain gene expression. Additionally, we detected unique effects of pollen diet and sustained (versus more temporary) pesticide exposure on queen gene expression. Our findings support the hypothesis that nutritional status can help buffer animals against the harmful effects of other stressors, including pesticides, and highlight the importance of using molecular approaches to explore sublethal consequences of stressors.

Do pesticide and pathogen interactions drive wild bee declines?

There is clear evidence for wild insect declines globally. Habitat loss, climate change, pests, pathogens and environmental pollution have all been shown to cause detrimental effects on insects. However, interactive effects between these stressors may be the key to understanding reported declines. Here, we review the literature on pesticide and pathogen interactions for wild bees, identify knowledge gaps, and suggest avenues for future research fostering mitigation of the observed declines. The limited studies available suggest that effects of pesticides most likely override effects of pathogens. Bees feeding on flowers and building sheltered nests, are likely less adapted to toxins compared to other insects, which potential susceptibility is enhanced by the reduced number of genes encoding detoxifying enzymes compared with other insect species. However, to date all 10 studies using a fully-crossed design have been conducted in the laboratory on social bees using Crithidia spp. or Nosema spp., identifying an urgent need to test solitary bees and other pathogens. Similarly, since laboratory studies do not necessarily reflect field conditions, semi-field and field studies are essential if we are to understand these interactions and their potential effects in the real-world. In conclusion, there is a clear need for empirical (semi-)field studies on a range of pesticides, pathogens, and insect species to better understand the pathways and mechanisms underlying their potential interactions, in particular their relevance for insect fitness and population dynamics. Such data are indispensable to drive forward robust modelling of interactive effects in different environmental settings and foster predictive science. This will enable pesticide and pathogen interactions to be put into the context of other stressors more broadly, evaluating their relative importance in driving the observed declines of wild bees and other insects. Ultimately, this will enable the development of more effective mitigation measures to protect bees and the ecosystem services they supply.

No evidence for impaired solitary bee fitness following pre-flowering sulfoxaflor application alone or in combination with a common fungicide in a semi-field experiment

Pesticide exposure is considered a major driver of pollinator decline and the use of neonicotinoid insecticides has been restricted by regulatory authorities due to their risks for pollinators. Impacts of new alternative sulfoximine-based compounds on solitary bees and their potential interactive effects with other commonly applied pesticides in agriculture remain unclear. Here, we conducted a highly replicated full-factorial semi-field experiment with the solitary bee Osmia bicornis, an important pollinator of crops and wild plants in Europe, and Phacelia tanacetifolia as a model crop. We show that spray applications of the insecticide sulfoxaflor (product Closer) and the fungicide azoxystrobin (product Amistar), both alone and combined, had no significant negative impacts on adult female survival or the production, mortality, sex ratio and body size of offspring when sulfoxaflor was applied five days before crop flowering. Our results indicate that for O. bicornis (1) the risk of adverse impacts of sulfoxaflor (Closer) on fitness is small when applied at least five days before crop flowering and (2) that azoxystrobin (Amistar) has a low potential of exacerbating sulfoxaflor effects under field-realistic conditions.

A Combined LD50 for Agrochemicals and Pathogens in Bumblebees (Bombus terrestris [Hymenoptera: Apidae])

Neonicotinoid insecticides are the most commonly used insecticide in the world and can have significant sub-lethal impacts on beneficial insects, including bumblebees, which are important pollinators of agricultural crops and wild-flowers. This has led to bans on neonicotinoid use in the EU and has resulted in repeated calls for the agrochemical regulatory process to be modified. For example, there is increasing concern about 1) the underrepresentation of wild bees, such as bumblebees, in the regulatory process, and 2) the failure to determine how agrochemicals, such as neonicotinoids, interact with other commonly occurring environmental stressors, such as parasites. Here, we modify an OECD approved lethal dose (LD50) experimental design and coexpose bumblebees (Bombus terrestris) to the neonicotinoid thiamethoxam and the highly prevalent trypanosome parasite Crithidia bombi, in a fully crossed design. We found no difference in the LD50 of thiamethoxam on bumblebees that had or had not been inoculated with the parasite (Crithidia bombi). Furthermore, thiamethoxam dosage did not appear to influence the parasite intensity of surviving bumblebees, and there was no effect of either parasite or insecticide on sucrose consumption. The methodology used demonstrates how existing ring-tested experimental designs can be effectively modified to include other environmental stressors such as parasites. Moving forward, the regulatory process should implement methodologies that assess the interactions between agrochemicals and parasites on non-Apis bees and, in cases when this is not practical, should implement post-regulatory monitoring to better understand the real-world consequences of agrochemical use.

Bee Tracker—an open‐source machine learning‐based video analysis software for the assessment of nesting and foraging performance of cavity‐nesting solitary bees

The foraging and nesting performance of bees can provide important information on bee health and is of interest for risk and impact assessment of environmental stressors. While radiofrequency identification (RFID) technology is an efficient tool increasingly used for the collection of behavioral data in social bee species such as honeybees, behavioral studies on solitary bees still largely depend on direct observations, which is very time‐consuming. Here, we present a novel automated methodological approach of individually and simultaneously tracking and analyzing foraging and nesting behavior of numerous cavity‐nesting solitary bees. The approach consists of monitoring nesting units by video recording and automated analysis of videos by machine learning‐based software. This Bee Tracker software consists of four trained deep learning networks to detect bees that enter or leave their nest and to recognize individual IDs on the bees’ thorax and the IDs of their nests according to their positions in the nesting unit. The software is able to identify each nest of each individual nesting bee, which permits to measure individual‐based measures of reproductive success. Moreover, the software quantifies the number of cavities a female enters until it finds its nest as a proxy of nest recognition, and it provides information on the number and duration of foraging trips. By training the software on 8 videos recording 24 nesting females per video, the software achieved a precision of 96% correct measurements of these parameters. The software could be adapted to various experimental setups by training it according to a set of videos. The presented method allows to efficiently collect large amounts of data on cavity‐nesting solitary bee species and represents a promising new tool for the monitoring and assessment of behavior and reproductive success under laboratory, semi‐field, and field conditions.