Neonicotinoid Insecticides and Their Impacts on Bees: A Systematic Review of Research Approaches and Identification of Knowledge Gaps

Imidacloprid impairs performance on a model flower handling task in bumblebees (Bombus impatiens)

Bumblebees exposed to neonicotinoid pesticides collect less pollen on foraging trips. Exposed bumblebees are also slower to learn to handle flowers, which may account for reduced pollen collection. It is unclear, however, why neonicotinoid exposure slows learning to handle flowers. We investigated the effect of imidacloprid, a neonicotinoid pesticide, on bumblebee motor learning using a lab model of flower handling. Bumblebees learned to invert inside a narrow tube and lift a petal-shaped barrier to reach a reward chamber. Imidacloprid-exposed bumblebees showed a dose-dependent delay to solve the task, which resulted from reduced switching between behavioural strategies and a subsequent delay in use of the successful strategy. This effect was consistent in colonies exposed at 10 but not 2.6 ppb, suggesting a variable effect on individuals at lower doses. These results help to explain why exposed bumblebees are slow to learn to handle flowers and collect less pollen on foraging trips.

Lethal and sublethal effects of toxicants on bumble bee populations: a modelling approach

Pollinator decline worldwide is well-documented; globally, chemical pesticides (especially the class of pesticides known as neonicotinoids) have been implicated in hymenopteran decline, but the mechanics and drivers of population trends and dynamics of wild bees is poorly understood. Declines and shifts in community composition of bumble bees (Bombus spp.) have been documented in North America and Europe, with a suite of lethal and sub-lethal effects of pesticides on bumble bee populations documented. We employ a mathematical model parameterized with values taken from the literature that uses differential equations to track bumble bee populations through time in order to attain a better understanding of toxicant effects on a developing colony of bumble bees. We use a delay differential equation (DDE) model, which requires fewer parameter estimations than agent-based models while affording us the ability to explicitly describe the effect of larval incubation and colony history on population outcomes. We explore how both lethal and sublethal effects such as reduced foraging ability may combine to affect population outcomes, and discuss the implications for the protection and conservation of ecosystem services.

Can Costs of Pesticide Exposure for Bumblebees Be Balanced by Benefits from a Mass-Flowering Crop?

Mass-flowering crops provide forage for bees but also contain pesticides. Such pesticide exposure can harm bees, but our understanding of how this cost is balanced by forage benefits is limited. To provide insights into benefits and costs, we placed bumblebee colonies in 18 landscapes with conventional red clover fields treated with the neonicotinoid thiacloprid (flowers + pesticide), untreated organic red clover fields (flowers), or landscapes lacking clover fields (controls). Colonies grew heavier near thiacloprid-treated clover compared to controls lacking clover, while colonies near untreated clover did not differ from colonies in neither of the other landscape types. Thiacloprid treatment effectively controlled pests and increased bumblebee crop visitation. However, colony production of queens and males did not differ among landscape types. In conclusion, thiacloprid application in clover appears to be of low risk for bumblebees. More generally, neonicotinoids may not be equally harmful when used in flowering crops and effective low-risk pest control in such crops could potentially benefit bumblebees and crop pollination.

Fungicides, herbicides and bees: A systematic review of existing research and methods

Bees and the pollination services they deliver are beneficial to both food crop production, and for reproduction of many wild plant species. Bee decline has stimulated widespread interest in assessing hazards and risks to bees from the environment in which they live. While there is increasing knowledge on how the use of broad-spectrum insecticides in agricultural systems may impact bees, little is known about effects of other pesticides (or plant protection products; PPPs) such as herbicides and fungicides, which are used more widely than insecticides at a global scale. We adopted a systematic approach to review existing research on the potential impacts of fungicides and herbicides on bees, with the aim of identifying research approaches and determining knowledge gaps. While acknowledging that herbicide use can affect forage availability for bees, this review focussed on the potential impacts these compounds could have directly on bees themselves. We found that most studies have been carried out in Europe and the USA, and investigated effects on honeybees. Furthermore, certain effects, such as those on mortality, are well represented in the literature in comparison to others, such as sub-lethal effects. More studies have been carried out in the lab than in the field, and the impacts of oral exposure to herbicides and fungicides have been investigated more frequently than contact exposure. We suggest a number of areas for further research to improve the knowledge base on potential effects. This will allow better assessment of risks to bees from herbicides and fungicides, which is important to inform future management decisions around the sustainable use of PPPs.

A holistic study of neonicotinoids neuroactive insecticides-properties, applications, occurrence, and analysis

Among pesticides and foliar sprays involved in the treatment of seed, soil, and grass, also to crops, an important group is neonicotinoids. Neonicotinoid pesticides present similar properties with nicotine, but the mentioned compounds are less harmful for humans. Nevertheless, neonicotinoids are poisonous to insects and some invertebrates, which can act against insects' central nervous system, leading to their death. Moreover, neonicotinoids can affect the reproduction, foraging, and flying ability of honeybee and other insects including pollinators. In the present study, some neonicotinoids, such as imidacloprid, acetamiprid, clothianidin, thiacloprid, and thiamethoxam together with their toxic effects, have been presented. The Environmental Protection Agency (EPA) classifies these neonicotinoids as II and III class toxicity agents. Due to accumulation of these pesticides into the pollen of treated plants, especially due to their toxic effects against pollinators, the consequences of the occurrence of these insecticides have been discussed. Analytical aspects and methods involved in the isolation and determination of this class of pesticides have been presented in this contribution.

tau-Fluvalinate and other pesticide residues in honey bees before overwintering

BACKGROUND

Pesticides have often been linked to honey bee colony losses, which occur mainly over winter. In this study, we investigated residues in nine colonies at a model agricultural research site during the period before wintering. Moreover, we applied the acaricide tau-fluvalinate to the colonies via a strip formulation. The pesticide content was determined by UHPLC-QqQ-MS/MS in bees from brood comb initially collected in mid-September immediately prior to the start of tau-fluvalinate treatment and 30 later at the time of tau-fluvalinate strip removal.

RESULTS

In addition to commonly analyzed pesticides, we detected two plant growth regulators, chlormequat and metazachlor, in the bee colonies. Whereas thiacloprid, chlormequat and acetamiprid decreased after 30 days and contributed considerably to differences between sample time points, other pesticides appeared to be rather stable. Interestingly, we identified diazinon, which has been banned in the European Union since 2007. The residues of methiocarb sulfoxide and imidacloprid-urea in the absence of their parent compounds indicate historical environmental contamination that can be identified by the detection of residues in a bee colony. tau-Fluvalinate was detected only after the 30-day treatment at an average (± SD) concentration of 1.29 ± 1.93 ng/bee, ranging from 0.06 to 7.13 ng/bee.

CONCLUSION

The multidimensional behavior of pesticides in a bee colony was indicated. Although the research area is used for agriculture, the measured pesticide level was relatively low. The recorded concentrations of tau-fluvalinate should not be dangerous to bees, as the values were ∼ 200-5000-fold lower than the reported median lethal dose (LD₅₀ ) values. © 2019 Society of Chemical Industry.

Comparative ecotoxicity of neonicotinoid insecticides to three species of Trichogramma parasitoid wasps (Hymenoptera: Trichogrammatidae)

Compatibility of neonicotinoid insecticides with the natural enemies has been concerned for decades. This study aims to evaluate and compare the acute and sublethal toxicity effects of neonicotinoid insecticides on three species of Trichogramma parasitoid wasps (i.e. Trichogramma dendrolimi, T. ostriniae and T. confusum) with broad distribution and great relevance to integrated pest management (IPM) strategies. A residual contact bioassay demonstrated that nitenpyram had the greatest intrinsic toxicity to T. dendrolimi and T. ostriniae with LC₅₀ values of 0.060 (0.056-0.065) and 0.066 (0.050-0.087) mg a.i. L^-1, respectively. But for T. confusum, the most toxic neonicotinoid insecticide is dinotefuran with a LC₅₀ value of 0.065 (0.055-0.078) mg a.i. L^-1. Furthermore, based on the risk quotient estimation, acetamiprid was considered to be the only safe neonicotinoid insecticide (Class 1, RQ＜50). A dipped egg contact bioassay showed that neonicotinoid insecticides induced significant toxic effects on the parasitism of three Trichogramma spp. at low-lethal concentrations. Additionally, emergence probability of the unexposed offspring was also significantly reduced by neonicotinoids. According to the estimated EC₅₀ values, acetamiprid possessed the least toxicity to the parasitism and emergence of T. dendrolimi and T. ostriniae, and for T. confusum, the least toxic neonicotinoid insecticide was thiacloprid. Overall, among the test neonicotinoid insecticides, acetamiprid and thiacloprid may exhibit the less ecotoxicity to the test Trichogramma species.

Biopesticide spinosad induces transcriptional alterations in genes associated with energy production in honey bees (Apis mellifera) at sublethal concentrations

Bees experience substantial colony losses, which are often associated with pesticides. Besides synthetic insecticides biological compounds such as spinosad are used in agriculture and organic farming against insect pests. However, potential adverse effect at sublethal concentrations to pollinators are poorly known. Here we aim to determine potential adverse outcome pathways of spinosad and to identify molecular effects by investigating transcriptional alterations in the brain of honey bees. We experimentally exposed bees to three sublethal concentrations of 0.05, 0.5 and 5 ng spinosad/bee, and assessed transcriptional alterations of target genes. Additionally, we evaluated whether spinosad-induced transcriptional alterations were influenced by the time of the year. In April, alterations were most pronounced after 24 h exposure, while in June alterations occurred mostly after 48 h. In July, expressional alterations were often lower but the pattern was more similar to that in June than that in April. Down-regulation of genes encoding acetylcholine receptors, enzymes involved in oxidative phosphorylation (cox5a, ndufb7 and cox17), cytochrome P450 dependent monooxygenases (cyp9q1, cyp9q2 and cyp9q3) and insulin-like peptide-1 were among the most significant transcriptional alterations. This suggests adverse effects of spinosad to energy production and metabolism and thus negative consequences on foraging. Together, our study indicates that spinosad causes adverse effects at environmentally realistic concentrations, which may pose a risk to bee populations.

Fungicides chlorothanolin, azoxystrobin and folpet induce transcriptional alterations in genes encoding enzymes involved in oxidative phosphorylation and metabolism in honey bees (Apis mellifera) at sublethal concentrations

Fungicides are highly used for plant protection but their molecular and chronic effects are poorly known. Here, we analyse transcriptional effects in the brain of honey bees of three frequently applied fungicides, azoxystrobin, chlorothanolin and folpet, after oral exposure for 24, 48 and 72 h. Among transcripts assessed were genes encoding proteins for immune and hormone system regulation, oxidative phosphorylation, metabolism, and acetylcholine receptor alpha 1. Azoxystrobin and folpet induced minor alterations, including down-regulation of hbg-3 by azoxystrobin and induction of ndufb-7 by folpet. Chlorothanolin induced strong transcriptional down-regulation of genes encoding enzymes related to oxidative phosphorylation and metabolism, including cyp9q1, cyp9q2 and cyp9q3, acetylcholine receptor alpha 1 and hbg-3 and ilp-1, which are linked to hormonal regulation and behavioural transition of honey bees. Exposures to chlorothanolin in different seasonal times showed different responsiveness; responses were faster and often stronger in April than in June. Chlorothanolin caused the strongest effects and affected transcriptional abundance of genes related to energy production, metabolism and the endocrine system. Disturbed energy production may reduce foraging activity and hormonal dysregulation, such as the transition of nurse bees to foragers. Further analyses are needed to further substantiate potential adverse effects of chlorothanolin in bees on the physiological level.

Comprehensive Survey of Area-Wide Agricultural Pesticide Use in Southern United States Row Crops and Potential Impact on Honey Bee Colonies

Honey bees forage across a large area, continually scouting the local landscape for ephemeral food resources. Beekeepers often rely on flowering plants in and around irrigated farmland to maintain their colonies during dry seasons, despite the potential risk of pesticide exposure. Recent declines in pollinator abundance and diversity have focused attention on the role of pesticides and their effects on honey bee health. This investigation examined two types of landscapes within a two-mile (3.2 km) radius of honey bee colonies: an intensive agricultural setting and a rural setting without intensive agriculture. More than 10,000 acres of agricultural land was surveyed to quantify the area of cultivated crops and the area treated with pesticides, including seed treatments and foliar applications of insecticides. Samples of honey, bee bread (stored pollen), beeswax, and adult bees were collected from hives in both landscape types and screened for pesticide residues to determine if foraging bees were transporting pesticides to hives. Some samples of bee bread and honey did contain pesticide residues, but these were below known lethal dose (LD₅₀) levels for honey bees. Beeswax samples contained the highest levels of contamination, but most were still relatively low. Samples were screened for 174 common agricultural pesticides and metabolites, but only 26 compounds were detected during the two-year study. These included one defoliant, one insect growth regulator, five herbicides, six fungicides, six insecticides never used in beekeeping, and five insecticides/miticides and their metabolites, which are used in beekeeping and for various other agricultural purposes, as well as two miticides exclusively used by beekeepers to control Varroa destructor. Bee colonies foraging in agricultural landscapes are potentially exposed to numerous pesticide applications. While the residues detected in this study did not pose an acute lethal risk to adult honey bees, this study did not measure sublethal effects on bee colony health or performance, which merit further investigation.

Effect of Sub-lethal Doses of Imidacloprid on Learning and Memory Formation of Indigenous Arabian Bee (Apis mellifera jemenitica Ruttner) Adult Foragers

The indigenous bee race Apis mellifera jemenitica Ruttner of Saudi Arabia can learn and retain memories established by the classical conditioning of proboscis extension response (PER). The insecticide imidacloprid has shown a drastic effect on the olfactory behavior of A. m. jemenitica in the harsh arid climatic conditions of central Saudi Arabia. The oral feeding of single imidacloprid sub-lethal doses (1.0 ng, 0.5 ng, or 0.1 ng) under laboratory conditions significantly impaired associative learning during the 2nd and 3rd conditioning trials compared to control bees (0 ng). The memory tests also revealed significant impairment in memory formation at 1 h, 2 h, and 24 h after conditioning compared to control bees. Even the lowest dose (0.1 ng/bee) can significantly impair the bees' ability to learn and memorize. This impairment effect was dose dependent and increased with increasing doses. The higher dose (1.0 ng) completely impaired the learning but still showed a little memory and reflected the potential recovery of bees from insecticide-induced impairment with the passage of time. To our knowledge, this is the first study in A. m. jemenitica that demonstrated the drastic effect of neonicotinoids on associative learning in indigenous bees. This study further expresses the possible severity of insecticidal exposure to bees in actual field conditions and its effect on the neural functions used in important behavior involved in the foraging of bees.

A review of the factors that influence pesticide residues in pollen and nectar: Future research requirements for optimising the estimation of pollinator exposure

In recent years, the impact of Plant Protection Products (PPPs) on insect pollinator decline has stimulated significant amounts of research, as well as political and public interest. PPP residues have been found in various bee-related matrices, resulting in governmental bodies worldwide releasing guidance documents on methods for the assessment of the overall risk of PPPs to different bee species. An essential part of these risk assessments are PPP residues found in pollen and nectar, as they represent a key route of exposure. However, PPP residue values in these matrices exhibit large variations and are not available for many PPPs and crop species combinations, which results in inaccurate estimations and uncertainties in risk evaluation. Additionally, residue studies on pollen and nectar are expensive and practically challenging. An extrapolation between different cropping scenarios and PPPs is not yet justified, as the behaviour of PPPs in pollen and nectar is poorly understood. Therefore, this review aims to contribute to a better knowledge and understanding of the fate of PPP residues in pollen and nectar and to outline knowledge gaps and future research needs. The literature suggests that four primary factors, the crop type, the application method, the physicochemical properties of a compound and the environmental conditions have the greatest influence on PPP residues in pollen and nectar. However, these factors consist of many sub-factors and initial effects may be disguised by different sampling methodologies, impeding their exact characterisation. Moreover, knowledge about these factors is ambiguous and restricted to a few compounds and plant species. We propose that future research should concentrate on identifying relationships and common features amongst various PPP applications and crops, as well as an overall quantification of the described parameters; in order to enable a reliable estimation of PPP residues in pollen, nectar and other bee matrices.

The impact of four widely used neonicotinoid insecticides on Tetragonisca angustula (Latreille) (Hymenoptera: Apidae)

Application of neonicotinoid insecticides on crops can reduce the pollination services and population levels of the stingless bee Tetragonisca angustula (Latreille) (Hymenoptera: Apidae) in Neotropical agroecosystems. However, the impact of these insecticides on this bee has not been fully investigated. This study assessed the susceptibility levels of T. angustula to four neonicotinoid insecticides (acetamiprid, imidacloprid, thiacloprid and thiamethoxam), widely used to manage pests on different crops, and their effects on locomotion of the bee. Neonicotinoids with the cyano radical caused lower bee mortality (assessed by mean lethal concentration, LC₅₀), while those compounds with the nitro radical were highly harmful to T. angustula. Locomotion activity was strongly impaired in bees treated with thiacloprid and imidacloprid, while acetamiprid did not affect the locomotion activity, which was similar to the control. Application of thiamethoxam caused hyperactivity, as observed by increases of ∼4.5 and 5.0-fold in mean speed and distance traveled, respectively. These results suggest that applications of neonicotinoid insecticides can negatively affect the pollination activity of T. angustula. These results can also help to develop strategies to conserve these pollinators in agroecosystems.

Pesticide exposure affects flight dynamics and reduces flight endurance in bumblebees

The emergence of agricultural land use change creates a number of challenges that insect pollinators, such as eusocial bees, must overcome. Resultant fragmentation and loss of suitable foraging habitats, combined with pesticide exposure, may increase demands on foraging, specifically the ability to collect or reach sufficient resources under such stress. Understanding effects that pesticides have on flight performance is therefore vital if we are to assess colony success in these changing landscapes. Neonicotinoids are one of the most widely used classes of pesticide across the globe, and exposure to bees has been associated with reduced foraging efficiency and homing ability. One explanation for these effects could be that elements of flight are being affected, but apart from a couple of studies on the honeybee (Apis mellifera), this has scarcely been tested. Here, we used flight mills to investigate how exposure to a field realistic (10 ppb) acute dose of imidacloprid affected flight performance of a wild insect pollinator-the bumblebee, Bombus terrestris audax. Intriguingly, observations showed exposed workers flew at a significantly higher velocity over the first ¾ km of flight. This apparent hyperactivity, however, may have a cost because exposed workers showed reduced flight distance and duration to around a third of what control workers were capable of achieving. Given that bumblebees are central place foragers, impairment to flight endurance could translate to a decline in potential forage area, decreasing the abundance, diversity, and nutritional quality of available food, while potentially diminishing pollination service capabilities.

Chronic toxicity and biochemical response of Apis cerana cerana (Hymenoptera: Apidae) exposed to acetamiprid and propiconazole alone or combined

Acetamiprid and ergosterol-inhibiting fungicide (EBI) are frequently applied to many flowering plants, while honey bees are pollinating agents or pollinators of the flowers. Hence honey bees are often exposed to these pesticides. But until now, the effects of theses combinations at field-realistic doses on honey bee health have been poorly investigated. In this study, we explore the synergistic mortality and some physiological effects in surviving honey bees after chronic oral exposure to acetamiprid and/or propiconazole in the laboratory. The results indicated that chronic combined exposure to acetamiprid and propiconazole produced a significant synergistic effect on mortality both for newly emerged bees (50% mortality in 7.2 days) and forager bees (50% mortality in 4.8 days). Honey bee weight of newly emerged bees was decreased after feeding food with a field concentration of acetamiprid and propiconazole, alone or combined for 10 days. Combination of acetamiprid and propiconazole also modulated the activities of P450s, GST and CAT in newly emerged bees and forager bees than either alone, but neither pesticide affected the activity of AChE. These results show that chronic combined exposure to pesticides of relatively low toxicity may caused severely physiological disruptions that could be potentially damaging for the honey bees.

Chronic contact with realistic soil concentrations of imidacloprid affects the mass, immature development speed, and adult longevity of solitary bees

The non-target effects of pesticides are an area of growing concern, particularly for ecologically and economically important organisms such as bees. Much of the previous research on the effects of neonicotinoids, a class of insecticide that has gained attention for non-target effects, on bees focused on the consumption of contaminated food resources by a limited number of eusocial species. However, neonicotinoids are known to accumulate and persist in soils at concentrations 2 to 60 times greater than in food resources, and may represent an important route of exposure for diverse and ecologically important ground-nesting bees. This study aimed to assess the effect of chronic contact exposure to realistic soil concentrations of imidacloprid, the most widely used neonicotinoid pesticide, on bee longevity, development speed, and body mass. Cohorts of Osmia lignaria and Megachile rotundata were used as proxies for ground-nesting species. We observed species- and sex-specific changes to adult longevity, development speed, and mass in response to increasing concentrations of imidacloprid. These results suggest that chronic exposure to nesting substrates contaminated with neonicotinoids may represent an important route of exposure that could have considerable physiological and ecological consequences for bees and plant-pollinator interactions.

Chronic contact with realistic soil concentrations of imidacloprid affects the mass, immature development speed, and adult longevity of solitary bees

The non-target effects of pesticides are an area of growing concern, particularly for ecologically and economically important organisms such as bees. Much of the previous research on the effects of neonicotinoids, a class of insecticide that has gained attention for non-target effects, on bees focused on the consumption of contaminated food resources by a limited number of eusocial species. However, neonicotinoids are known to accumulate and persist in soils at concentrations 2 to 60 times greater than in food resources, and may represent an important route of exposure for diverse and ecologically important ground-nesting bees. This study aimed to assess the effect of chronic contact exposure to realistic soil concentrations of imidacloprid, the most widely used neonicotinoid pesticide, on bee longevity, development speed, and body mass. Cohorts of Osmia lignaria and Megachile rotundata were used as proxies for ground-nesting species. We observed species- and sex-specific changes to adult longevity, development speed, and mass in response to increasing concentrations of imidacloprid. These results suggest that chronic exposure to nesting substrates contaminated with neonicotinoids may represent an important route of exposure that could have considerable physiological and ecological consequences for bees and plant-pollinator interactions.

Compound and Dose-Dependent Effects of Two Neonicotinoid Pesticides on Honey Bee (Apis mellifera) Metabolic Physiology

Use of neonicotinoid pesticides is now ubiquitous, and consequently non-targeted arthropods are exposed to their residues at sub-lethal doses. Exposure to these neurotoxins may be a major contributor to poor honey bee colony health. Few studies have explored how sub lethal exposure to neonicotinoids affects honey bee metabolic physiology, including nutritional and energetic homeostasis, both of which are important for maintaining colony health. Reported here are results from a study of chronic oral exposure of honey bees to two sub lethal concentrations of clothianidin and imidacloprid. Neonicotinoids altered important aspects of honey bee nutritional and metabolic physiology in a compound and dose-dependent manner; both compounds at low doses reduced honey bee body weight. Low-dose clothianidin exposure resulted in bees having protein, lipids, carbohydrates, and glycogen levels similar to newly emerged bees. High-dose clothianidin exposure lowered lipids and glycogen content of bees. High-dose imidacloprid exposure resulted in bees having depressed metabolic rate. Low-dose imidacloprid exposure resulted in bees consuming low and high levels of protein and carbohydrate rich foods, respectively. Results suggest neonicotinoids interfere with honey bee endocrine neurophysiological pathways. Compound and dose-dependent effects might represent respective chemical structural differences determining an observed effect, and thresholds of compound effects on honey bee physiology.

Queen bee acceptance under threat: Neurotoxic insecticides provoke deep damage in queen-worker relationships

Virgin queens (gynes) exhibit a range of behaviors in order to be accepted as the leader of colony. However, environmental neurotoxic insecticides as neonicotinoids may affect the social performance of the bees. Here, we evaluated the sublethal effects of neonicotinoid imidacloprid on the larval food of queens from Plebeia droryana, a species of neotropical stingless bee. Several behaviors were analyzed as multivariate response variables in a Hotelling test, as well as generalized additive mixed models. Our findings demonstrate that treated queens perform less wing vibration and trophallaxis with their workers. Furthermore, the treated gynes encounter more harassment (aggression) from their workers, suggesting that workers can differentiate nontreated queens from treated queens most likely by chemical signals. Our data indicate that the behavioral repertoire underlying the queen selection process by the stingless bee P. droryana may be seriously affected by residual doses of imidacloprid in larval food. As a result, such queens are rather undernourished and aggressed by workers, which most likely compromises the viability and permanence of colonies in the long term.

Relationship of Landscape Type on Neonicotinoid Insecticide Exposure Risks to Honey Bee Colonies: A Statewide Survey

Neonicotinoid insecticide use has been suggested as a cause of honey bee colony decline; however, detection rates and concentrations of neonicotinoid insecticide residues in field-collected honey bees have been low. We collected honey bee and beebread samples from apiaries in agricultural, developed, and undeveloped areas during 2 years in Virginia to assess whether landscape type or county pesticide use was predictive of honey bee colony exposure to neonicotinoid insecticides. Trace concentrations of the neonicotinoid imidacloprid were detected in honey bees (3 of 84 samples, 2.02-3.97 ng/g), whereas higher concentrations were detected in beebread (5 of 84 samples, 4.68-11.5 ng/g) and pollen (three of five pollen trap samples, 7.86-12.6 ng/g). Imidacloprid was only detected in samples collected during July and August and was not detected in honey bees from hives where neonicotinoids were detected in pollen or beebread. The number of hives sampled at a site, county pesticide use, and landscape characteristics were not predictive of neonicotinoid detections in honey bees or beebread (all P > 0.05). Field surveys may underestimate honey bee exposure to field-realistic levels of pesticides or the risk of exposure in different landscapes because of low detection rates. Undetectably low levels of exposure or high levels of exposure that go undetected raise questions with regard to potential threats to honey bees and other pollinators.

Imidacloprid alters ant sociobehavioral traits at environmentally relevant concentrations

Much research has focused on the effects of neonicotinoids on honey bees, however, relatively few studies have investigated their effects on ants, a taxonomically-related eusocial insect of high ecological importance. This study quantified how dietary exposures to environmentally-relevant levels of a neonicotinoid insecticide (imidacloprid) affected foraging and nest building of the western harvester ant over 14 days. Using a replicated design, statistically-significant reductions in ant foraging success (50% or greater) occurred at concentrations as low as 50 ppb compared to controls. Both the number of ants entering the maze and the percentage of foraging ants able to locate food were impacted by imidacloprid exposure. Ants exposed to 50 ppb also took three times longer than controls to find food in a test maze. This concentration is among the lowest levels of imidacloprid reported to affect ants and is well within the range of concentrations found in pollen and nectar of imidacloprid-treated plants. Ant foraging success was also impaired at comparable levels as those reported for the honey bee. Although more refinement and research are needed, results from this study suggest that the western harvester ant may be useful for screening the effects of neurotoxic chemicals on their navigation and foraging, two behaviors which are critical to maintaining colony health of ants and the ecological services they provide.

The development of honey bee colonies assessed using a new semi-automated brood counting method: CombCount

Precise, objective data on brood and honey levels in honey bee colonies can be obtained through the analysis of hive frame photographs. However, accurate analysis of all the frame photographs from medium- to large-scale experiments is time-consuming. This limits the number of hives than can be practically included in honeybee studies. Faster estimation methods exist but they significantly decrease precision and their use requires a larger sample size to maintain statistical power. To resolve this issue, we created 'CombCount' a python program that automatically detects uncapped cells to speed up measurements of capped brood and capped honey on photos of frames. CombCount does not require programming skills, it was designed to facilitate colony-level research in honeybees and to provide a fast, free, and accurate alternative to older methods based on visual estimations. Six observers measured the same photos of thirty different frames both with CombCount and by manually outlining the entire capped areas with ImageJ. The results obtained were highly similar between both the observers and the two methods, but measurements with CombCount were 3.2 times faster than with ImageJ (4 and 13 min per side of the frame, respectively) and all observers were faster when using CombCount rather than ImageJ. CombCount was used to measure the proportions of capped brood and capped honey on each frame of 16 hives over a year as they developed from packages to full-size colonies over about 60 days. Our data describe the formation of brood and honey stores during the establishment of a new colony.

RETRACTED:Insecticide exposure affects DNA and antioxidant enzymes activity in honey bee species Apis florea and A. dorsata: Evidence from Punjab, Pakistan

This article has been retracted: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/about/our-business/policies/article-withdrawal). After a thorough investigation, the Editors have concluded that the acceptance of this article was partly based upon the positive advice of two illegitimate reviewer reports. The reports were submitted from email accounts which were provided by the corresponding author Christos A. Damalas as suggested reviewers during the submission of the article. Although purportedly real reviewer accounts, the Editors have concluded that these were not of appropriate, independent reviewers. This manipulation of the peer-review process represents a clear violation of the fundamentals of peer review, our publishing policies, and publishing ethics standards. Apologies are offered to the reviewers whose identity was assumed and to the readers of the journal that this deception was not detected during the submission process.

Foraging bumblebees acquire a preference for neonicotinoid-treated food with prolonged exposure

Social bees represent an important group of pollinating insects that can be exposed to potentially harmful pesticides when foraging on treated or contaminated flowering plants. To investigate if such exposure is detrimental to bees, many studies have exclusively fed individuals with pesticide-spiked food, informing us about the hazard but not necessarily the risk of exposure. While such studies are important to establish the physiological and behavioural effects on individuals, they do not consider the possibility that the risk of exposure may change over time. For example, many pesticide assays exclude potential behavioural adaptations to novel toxins, such as rejection of harmful compounds by choosing to feed on an uncontaminated food source, thus behaviourally lowering the risk of exposure. In this paper, we conducted an experiment over 10 days in which bumblebees could forage on an array of sucrose feeders containing 0, 2 and 11 parts per billion of the neonicotinoid pesticide thiamethoxam. This more closely mimics pesticide exposure in the wild by allowing foraging bees to (i) experience a field realistic range of pesticide concentrations across a chronic exposure period, (ii) have repeated interactions with the pesticide in their environment, and (iii) retain the social cues associated with foraging by using whole colonies. We found that the proportion of visits to pesticide-laced feeders increased over time, resulting in greater consumption of pesticide-laced sucrose relative to untreated sucrose. After changing the spatial position of each feeder, foragers continued to preferentially visit the pesticide-laced feeders which indicates that workers can detect thiamethoxam and alter their behaviour to continue feeding on it. The increasing preference for consuming the neonicotinoid-treated food therefore increases the risk of exposure for the colony during prolonged pesticide exposure. Our results highlight the need to incorporate attractiveness of pesticides to foraging bees (and potentially other insect pollinators) in addition to simply considering the proportion of pesticide-contaminated floral resources within the foraging landscape.

Combined exposure to sublethal concentrations of an insecticide and a fungicide affect feeding, ovary development and longevity in a solitary bee

Pollinators in agroecosystems are often exposed to pesticide mixtures. Even at low concentrations, the effects of these mixtures on bee populations are difficult to predict due to potential synergistic interactions. In this paper, we orally exposed newly emerged females of the solitary bee Osmia bicornis to environmentally realistic levels of clothianidin (neonicotinoid insecticide) and propiconazole (fungicide), singly and in combination. The amount of feeding solution consumed was highest in bees exposed to the neonicotinoid, and lowest in bees exposed to the pesticide mixture. Ovary maturation and longevity of bees of the neonicotinoid and the fungicide treatments did not differ from those of control bees. By contrast, bees exposed to the pesticide mixture showed slow ovary maturation and decreased longevity. We found a synergistic interaction between the neonicotinoid and the fungicide on survival probability. We also found an interaction between treatment and emergence time (an indicator of physiological condition) on longevity. Longevity was negatively correlated to physiological condition only in the fungicide and the mixture treatments. Delayed ovary maturation and premature death imply a shortened nesting period (highly correlated to fecundity in Osmia). Our findings provide a mechanism to explain the observed dynamics of solitary bee populations exposed to multiple chemical residues in agricultural environments.

Investigating the role of landscape composition on honey bee colony winter mortality: A long-term analysis

The health of honey bee colonies is, amongst others, affected by the amount, quality and diversity of available melliferous plants. Since landscape is highly diverse throughout Austria regarding the availability of nutritional resources, we used data from annual surveys on honey bee colony losses ranging over six years to analyse a possible relationship with land use. The data set comprises reports from a total of 6,655 beekeepers and 129,428 wintered honey bee colonies. Regions surrounding the beekeeping operations were assigned to one of six clusters according to their composition of land use categories by use of a hierarchical cluster analysis, allowing a rough distinction between urban regions, regions predominated by semi-natural areas and pastures, and mainly agricultural environments. We ran a Generalised Linear Mixed Model and found winter colony mortality significantly affected by operation size, year, and cluster membership, but also by the interaction of year and cluster membership. Honey bee colonies in regions composed predominantly of semi-natural areas, coniferous forests and pastures had the lowest loss probability in four out of six years, and loss probabilities within these regions were significantly lower in five out of six years compared to those within regions composed predominantly of artificial surfaces, broad-leaved and coniferous forest.

Low dose of neonicotinoid insecticide reduces foraging motivation of bumblebees

Widespread use of neonicotinoid insecticides, such as imidacloprid, is often associated with diminishing populations of bees; this loss of pollinators presents a concern for food security and may cause unpredictable changes in ecological networks. However, little is known about the potential behavioural mechanisms behind the neonicotinoid-associated pollinator decline. We quantified the effects of low-dose (1 ppb) imidacloprid exposure on the foraging behaviour of bumblebees (Bombus terrestris). Individual bumblebees were released into a flight arena containing three patches of robotic flowers whose colour (yellow, orange, blue) indicated whether the flower delivered a reward (sugar solution). Exposure to imidacloprid had no significant effect on measures of bumblebee physical performance (such as flight speed) or learning (identifying rewarding flowers). However, pesticide-treated bumblebees had reduced foraging motivation compared with the control bumblebees, as they visited fewer robotic flowers, were slower to start foraging and did not visit all three flower colours as often. Neonicotinoid concentrations of 1 ppb, often reported in plant nectar near agricultural lands, can thus affect the foraging behaviour of bumblebees. Even without a notable impact on flight performance and learning, a reduction in foraging motivation could explain the poor performance of colonies of bumblebees exposed to neonicotinoids.

The dilemma of agricultural pollination in Brazil: Beekeeping growth and insecticide use

Pollination by bees improves agricultural crop yields and improves the financial outlook of beekeepers because it increases honey production and hive rental revenues. However, in Brazil, with a few exceptions, these benefits have been neglected in recent years because beekeepers are more interested in honey production than in agricultural pollination. The excessive and indiscriminate use of insecticides on agricultural fields in Brazil appears to be one of the principal obstacles preventing partnership between farmers and beekeepers. The goal of this study was therefore to evaluate the most recent situation in Brazil in relation to the use of insecticides, agriculture and to honey production in comparison with other countries. Our results show that Brazil is the largest consumer of insecticides in the world and that consumption has increased by > 150% over 15 years. While countries with a high Human Development Index (i.e., a measure that can also be used to question national policy choices) are reducing their levels of insecticide use in agriculture, Brazil is going in the opposite direction. It is highly likely the increase seen in other countries is a result of alternative methods for pest control rather than a result of the amount of area under agricultural cultivation and their capability to shift their economies from agriculture to other sectors. The number of hives (23%) and the volume of honey production (72%) in Brazil have, however, increased over the same period, raising Brazil to the ninth highest honey producer in the world. Although the data on apiculture are promising, the growth in use of insecticides in Brazil is a cause for concern because they leave residuals on bee products, on crops, and in the environment. Civil society and government in Brazil should encourage reductions in insecticide use and better relations between agricultural farmers and beekeepers.

Neonicotinoid insecticides negatively affect performance measures of non-target terrestrial arthropods: a meta-analysis

Neonicotinoid insecticides are currently the fastest-growing and most widely used insecticide class worldwide. Valued for their versatility in application, these insecticides may cause deleterious effects in a range of non-target (beneficial) arthropods. However, it remains unclear whether strong patterns exist in terms of their major effects, if broad measures of arthropod performance are negatively affected, or whether different functional groups are equally vulnerable. Here, we present a meta-analysis of 372 observations from 44 field and laboratory studies that describe neonicotinoid effects on 14 arthropod orders across five broad performance measures: abundance, behavior, condition, reproductive success, and survival. Across studies, neonicotinoids negatively affected all performance metrics evaluated; however, magnitude of the effects varied. Arthropod behavior and survival were the most negatively affected and abundance was the least negatively affected. Effects on arthropod functional groups were inconsistent. Pollinator condition, reproductive success, and survival were significantly lower in neonicotinoid treatments compared to untreated controls; whereas, neonicotinoid effects on detritivores were not significant. Although magnitude of arthropod response to neonicotinoids varied among performance measures and functional groups, we documented a consistent negative relationship between exposure to neonicotinoid insecticides in published studies and beneficial arthropod performance.

Viability of honeybee colonies exposed to sunflowers grown from seeds treated with the neonicotinoids thiamethoxam and clothianidin

In this study, honeybee colonies were monitored in a field study conducted on sunflowers grown from seeds treated with the systemic neonicotinoids thiamethoxam or clothianidin. This field trial was carried out in different representative growing areas in Spain over a beekeeping season. The health and development of the colonies was assessed by measuring factors that have a significant influence on their strength and overwintering ability. The parameters assessed were: colony strength (adult bees), brood development, amount of pollen and honey stores and presence and status of the queen. The concentration of residues (clothianidin and thiamethoxam) in samples of beebread and in adult bees was at the level of ng.g^-1; in the ranges of 0.10-2.89 ng g^-1 and 0.05-0.12 ng g^-1; 0.10-0.37 ng g^-1 and 0.01-0.05 ng g^-1, respectively. Multivariate models were applied to evaluate the interaction among factors. No significant differences were found between the honeybee colonies of the different treatment groups, either exposed or not to the neonicotinoids. The seasonal development of the colonies was affected by the environmental conditions which, together with the initial strength of the bee colonies and the characteristics of the plots, had a significant effect on the different variables studied.

Sublethal effects of clothianidin and Nosema spp. on the longevity and foraging activity of free flying honey bees

Neonicotinoids alone or in combination with pathogens are considered to be involved in the worldwide weakening of honey bees. We here present a new approach for testing sublethal and/or synergistic effects in free flying colonies. In our experiment individually marked honey bees were kept in free flying mini-hives and chronically exposed to sublethal doses of the neonicotinoid clothianidin. Additional groups of bees were challenged with Nosema infections or with combinations of the pesticide and pathogens. Longevity and flight activity of the differentially treated bees were monitored for a period of 18 days. In contrast to previous laboratory studies, no effect of the neonicotinoid treatment on mortality or flight activity could be observed. Although the lifespan of Nosema infected bees were significantly reduced compared to non-infected bees a combination of pesticide and pathogen did not reveal any synergistic effect. Our results indicate that individual bees are less impaired by neonicotinoids if kept within the social environment of the colony. The effect of such a "social buffering" should be considered in future risk assessments.

Exposure of Honey Bee (Apis mellifera L.) Colonies to Pesticides in Pollen, A Statewide Assessment in Maine

In 2015, we conducted a statewide assessment of honey bee exposure to pesticides with assistance of volunteer beekeepers. Pollen trapping was conducted at 32 sites in the spring, summer, and early fall. Apiary locations ranged from unmanaged natural landscapes to managed agricultural or urban landscapes. Pollen samples at each site were aggregated over the collection dates and chemical residue analysis was conducted on each pollen sample for 190 pesticides and metabolites using HPLC/MS. Twenty-five different residues were detected for an average of 2.9 detections per site. Detections were dominated by fungicides, but risk, calculated as: ppb residue concentration/LD50, was mostly due to insecticides. Beekeeper perceived land-use in the vicinity of each apiary was associated with significant differences in the number of detections and residue concentrations, agricultural landscapes greater than nonagricultural. However, there was no significant difference in oral or contact risk quotients due to land-use type. The landscape composition surrounding apiaries, derived with GIS, determined pesticide exposure for honey bees when total detections, log pesticide residue concentration, and log contact risk quotients were used as measures. Partial least squares explained 43.9% of the variance in pesticide exposure due to landscape composition. The best predictors describing pesticide exposure were: area (ha) of blueberry, coniferous forest, and urban/developed land cover types. Maine is the most forested state in the United States (as determined by % land area forested, 93%) and a negative exponential decay was observed between land area in conifer forest and the number of pesticide detections per apiary.

Effects of Field-Relevant Concentrations of Clothianidin on Larval Development of the Butterfly Polyommatus icarus (Lepidoptera, Lycaenidae)

Arable field margins are often sown with wildflowers to encourage pollinators and other beneficial or desirable insects such as bees and butterflies. Concern has been raised that these margins may be contaminated with systemic pesticides such as neonicotinoids used on the adjacent crop, and that this may negatively impact beneficial insects. The use of neonicotinoids has been linked to butterfly declines, and species such as the common blue butterfly ( Polyommatus icarus) that feed upon legumes commonly sown in arable field margins, may be exposed to such toxins. Here, we demonstrate that the larval food plants of P. icarus growing in an arable field margin adjacent to a wheat crop treated with the neonicotinoid clothianidin not only contain the pesticide at concentrations comparable to and sometimes higher than those found in foliage of treated crops (range 0.2-48 ppb) but also remain detectable at these levels for up to 21 months after sowing of the crop. Overall, our study demonstrates that nontarget herbivorous organisms in arable field margins are likely to be chronically exposed to neonicotinoids. Under laboratory conditions, exposure to clothianidin at 15 ppb (a field-realistic dose) or above reduced larval growth for the first 9 days of the experiment. Although there was evidence of clothianidin inducing mortality in larvae, with highest survival in control groups, the dose-response relationship was unclear. Our study suggests that larvae of this butterfly exhibit some deleterious sublethal and sometimes lethal impacts of exposure to clothianidin, but many larvae survive to adulthood even when exposed to high doses.

Seasonal Effects and the Impact of In-Hive Pesticide Treatments on Parasite, Pathogens, and Health of Honey Bees

Honey bee, Apis mellifera (L.; Hymenoptera: Apidae), populations are in decline and their losses pose a serious threat for crop pollination and food production. The specific causes of these losses are believed to be multifactorial. Pesticides, parasites and pathogens, and nutritional deficiencies have been implicated in the losses due to their ability to exert energetic stress on bees. While our understanding of the role of these factors in honey bee colony losses has improved, there is still a lack of knowledge of how they impact the immune system of the honey bee. In this study, honey bee colonies were exposed to Fumagilin-B, Apistan (tau-fluvalinate), and chlorothalonil at field realistic levels. No significant effects of the antibiotic and two pesticides were observed on the levels of varroa mite, Nosema ceranae (Fries; Microsporidia: Nosematidae), black queen cell virus, deformed wing virus, or immunity as measured by phenoloxidase and glucose oxidase activity. Any effects on the parasites, pathogens, and immunity we observed appear to be due mainly to seasonal changes within the honey bee colonies. The results suggest that Fumagilin-B, Apistan, and chlorothalonil do not significantly impact the health of honey bee colonies, based on the factors analyzed and the concentration of chemicals tested.

Toxicity and effects of the neonicotinoid thiamethoxam on Scaptotrigona bipunctata lepeletier, 1836 (Hymenoptera: Apidae)

The neonicotinoid thiamethoxam is widely used in different agricultural crops, and it has a spectrum of action against insects, affecting both pests and pollinators, such as bees. In this study, the effects of exposure to sublethal concentrations of thiamethoxam on stingless bees Scaptotrigona bipunctata were evaluated. Foragers bees were exposed to the insecticide and subjected to genetic biochemical, histochemical, and morphological analyses after 24, 48, and 72 h of ingestion. Analysis of isoenzyme esterases revealed significant alterations in the relative activity of EST-4, a type II cholinesterase. Evaluation of the S. bipunctata brain revealed changes in the state of chromatin condensation according to the exposure time and concentration of neonicotinoid compared with the control. Morphological changes were observed in the midgut of this species at all concentrations and exposure times, which may interfere with various physiological processes of these insects. We can conclude that, although thiamethoxam at the concentrations evaluated did not cause high mortality, it induced concentration-dependent changes in bees by activating enzymes related with the protection for xenobiotic, internal morphology and probably these changes may lead to alterations in the activity of bees.

Effects of exposure to winter oilseed rape grown from thiamethoxam-treated seed on the red mason bee Osmia bicornis

There has been increasing interest in the effects of neonicotinoid insecticides on wild bees. In solitary bee species the direct link between each individual female and reproductive success offers the opportunity to evaluate effects on individuals. The present study investigated effects of exposure to winter oilseed rape grown from thiamethoxam-treated seed on reproductive behavior and output of solitary red mason bees (Osmia bicornis) released in 6 pairs of fields over a 2-yr period and confined to tunnels in a single year. After adjustment to the number of females released, there was significantly lower production of cells and cocoons/female in tunnels than in open field conditions. This difference may be because of the lack of alternative forage within the tunnels. Under open field conditions, palynology of the pollen provisions within the nests demonstrated a maximum average of 31% oilseed rape pollen at any site, with Quercus (oak) contributing up to 86% of the pollen. There were no significant effects from exposure to oilseed rape grown from thiamethoxam-treated seed from nest establishment through cell production to emergence under tunnel or field conditions. Environ Toxicol Chem 2018;37:1071-1083. © 2017 SETAC.

Environmental Risks and Challenges Associated with Neonicotinoid Insecticides

Neonicotinoid use has increased rapidly in recent years, with a global shift toward insecticide applications as seed coatings rather than aerial spraying. While the use of seed coatings can lessen the amount of overspray and drift, the near universal and prophylactic use of neonicotinoid seed coatings on major agricultural crops has led to widespread detections in the environment (pollen, soil, water, honey). Pollinators and aquatic insects appear to be especially susceptible to the effects of neonicotinoids with current research suggesting that chronic sublethal effects are more prevalent than acute toxicity. Meanwhile, evidence of clear and consistent yield benefits from the use of neonicotinoids remains elusive for most crops. Future decisions on neonicotinoid use will benefit from weighing crop yield benefits versus environmental impacts to nontarget organisms and considering whether there are more environmentally benign alternatives.

Exposure assessment of honeybees through study of hive matrices: analysis of selected pesticide residues in honeybees, beebread, and beeswax from French beehives by LC-MS/MS

Apiculture and pollination services are seriously threatened by bee weakening and losses phenomena. In this context, a survey was performed on samples from beehives across French areas during the 2012-2016 growing seasons, primarily taken from symptomatic colonies. A total of 488 honeybees, beebread, and wax were analyzed for the presence of pesticide residues. A total of 13 analytes including neonicotinoids and pyrethroids insecticides together with some of their metabolites and the fungicide boscalid were screened within samples. Methodologies based on efficient modified quick, easy, cheap, effective, rugged, and safe extractions followed by an LC-MS/MS quantification were implemented for each matrix. Thirty-eight percent of the 125 bee samples, 61% of the 87 wax samples, and 77% of the 276 beebread samples contained at least one of the targeted pesticides. Beebread was the most contaminated matrix with an average of two pesticide detections by positive sample and a maximum of seven compounds for a sample. Neonicotinoids and boscalid were the most often detected pesticides, whatever the matrix. The comparison of neonicotinoid detections in samples collected before and after the partial neonicotinoid ban in France displays a decrease in the frequency of detections for contamination levels lower than 1 ng/g in beebread. For higher levels and other matrices, no tendency can be drawn.

Imidacloprid slows the development of preference for rewarding food sources in bumblebees (Bombus impatiens)

Bee pollination is economically and ecologically vital and recent declines in bee populations are therefore a concern. One possible cause of bee declines is pesticide use. Bumblebees exposed to imidacloprid, a neonicotinoid pesticide, have been shown to be less efficient foragers and collect less pollen on foraging trips than unexposed bees. We investigated whether bumblebees (Bombus impatiens) chronically exposed to imidacloprid at field-realistic levels of 2.6 and 10 ppb showed learning deficits that could affect foraging. Bumblebees were tested for their ability to associate flower colour with reward value in a simulated foraging environment. Bumblebees completed 10 foraging trips in which they collected sucrose solution from artificial flowers that varied in sucrose concentration. The reward quality of each artificial flower was predicted by corolla colour. Unexposed bumblebees acquired a preference for feeding on the most rewarding flower colour on the second foraging trip, while bumblebees exposed at 2.6 and 10 ppb did not until their third and fifth trip, respectively. The delay in preference acquisition in exposed bumblebees may be due to reduced flower sampling and shorter foraging trips. These results show that bumblebees exposed to imidacloprid are slow to learn the reward value of flowers and this may explain previously observed foraging inefficiencies associated with pesticide exposure.

Interactions between immunotoxicants and parasite stress: Implications for host health

Many organisms face a wide variety of biotic and abiotic stressors which reduce individual survival, interacting to further reduce fitness. Here we studied the effects of two such interacting stressors: immunotoxicant exposure and parasite infection. We model the dynamics of a within-host infection and the associated immune response of an individual. We consider both the indirect sub-lethal effects on immunosuppression and the direct effects on health and mortality of individuals exposed to toxicants. We demonstrate that sub-lethal exposure to toxicants can promote infection through the suppression of the immune system. This happens through the depletion of the immune response which causes rapid proliferation in parasite load. We predict that the within-host parasite density is maximised by an intermediate toxicant exposure, rather than continuing to increase with toxicant exposure. In addition, high toxicant exposure can alter cellular regulation and cause the breakdown of normal healthy tissue, from which we infer higher mortality risk of the host. We classify this breakdown into three phases of increasing toxicant stress, and demonstrate the range of conditions under which toxicant exposure causes failure at the within-host level. These phases are determined by the relationship between the immunity status, overall cellular health and the level of toxicant exposure. We discuss the implications of our model in the context of individual bee health. Our model provides an assessment of how pesticide stress and infection interact to cause the breakdown of the within-host dynamics of individual bees.

Effects of neonicotinoid imidacloprid exposure on bumble bee (Hymenoptera: Apidae) queen survival and nest initiation

Neonicotinoids are highly toxic to insects and may systemically translocate to nectar and pollen of plants where foraging bees may become exposed. Exposure to neonicotinoids can induce detrimental sublethal effects on individual and colonies of bees and may have long-term impacts, such as impaired foraging, reduced longevity, and reduced brood care or production. Less well-studied are the potential effects on queen bumble bees that may become exposed while foraging in the spring during colony initiation. This study assessed queen survival and nest founding in caged bumble bees [Bombus impatiens (Cresson) (Hymenoptera: Apidae)] after chronic (18-d) dietary exposure of imidacloprid in syrup (1, 5, 10, and 25 ppb) and pollen (0.3, 1.7, 3.3, and 8.3 ppb), paired respectively. Here we show some mortality in queens exposed at all doses even as low as 1 ppb, and, compared with untreated queens, significantly reduced survival of treated queens at the two highest doses. Queens that survived initial imidacloprid exposure commenced nest initiation; however, they exhibited dose-dependent delay in egg-laying and emergence of worker brood. Furthermore, imidacloprid treatment affected other parameters such as nest and queen weight. This study is the first to show direct impacts of imidacloprid at field-relevant levels on individual B. impatiens queen survival and nest founding, indicating that bumble bee queens are particularly sensitive to neonicotinoids when directly exposed. This study also helps focus pesticide risk mitigation efforts and highlights the importance of reducing exposure rates in the early spring when bumble bee queens, and other wild bees are foraging and initiating nests.

Increased survival of honeybees in the laboratory after simultaneous exposure to low doses of pesticides and bacteria

Recent studies of honeybees and bumblebees have examined combinatory effects of different stressors, as insect pollinators are naturally exposed to multiple stressors. At the same time the potential influences of simultaneously occurring agricultural agents on insect pollinator health remain largely unknown. Due to different farming methods, and the drift of applied agents and manure, pollinators are most probably exposed to insecticides but also bacteria from organic fertilizers at the same time. We orally exposed honeybee workers to sub-lethal doses of the insecticide thiacloprid and two strains of the bacterium Enterococcus faecalis, which can occur in manure from farming animals. Our results show that under laboratory conditions the bees simultaneously exposed to the a bacterium and the pesticide thiacloprid thiacloprid had significant higher survival rates 11 days post exposure than the controls, which surprisingly showed the lowest survival. Bees that were exposed to diet containing thiacloprid showed decreased food intake. General antibacterial activity is increased by the insecticide and the bacteria, resulting in a higher immune response observed in treated individuals compared to control individuals. We thus propose that caloric restriction through behavioural and physiological adaptations may have mediated an improved survival and stress resistance in our tests. However, the decreased food consumption could in long-term also result in possible negative effects at colony level. Our study does not show an additive negative impact of sub-lethal insecticide and bacteria doses, when tested under laboratory conditions. In contrast, we report seemingly beneficial effects of simultaneous exposure of bees to agricultural agents, which might demonstrate a surprising biological capacity for coping with stressors, possibly through hormetic regulation.

Comparative chronic toxicity of three neonicotinoids on New Zealand packaged honey bees

BACKGROUND

Thiamethoxam, clothianidin, and imidacloprid are the most commonly used neonicotinoid insecticides on the Canadian prairies. There is widespread contamination of nectar and pollen with neonicotinoids, at concentrations which are sublethal for honey bees (Apis mellifera Linnaeus).

OBJECTIVE

We compared the effects of chronic, sublethal exposure to the three most commonly used neonicotinoids on honey bee colonies established from New Zealand packaged bees using colony weight gain, brood area, and population size as measures of colony performance.

METHODS

From May 7 to July 29, 2016 (12 weeks), sixty-eight colonies received weekly feedings of sugar syrup and pollen patties containing 0 nM, 20 nM (median environmental dose), or 80 nM (high environmental dose) of one of three neonicotinoids (thiamethoxam, clothianidin, and imidacloprid). Colonies were weighed at three-week intervals. Brood area and population size were determined from digital images of colonies at week 12. Statistical analyses were performed by ANOVA and mixed models.

RESULTS

There was a significant negative effect (-30%, p<0.01) on colony weight gain (honey production) after 9 and 12 weeks of exposure to 80 nM of thiamethoxam, clothianidin, or imidacloprid and on bee cluster size (-21%, p<0.05) after 12 weeks. Analysis of brood area and number of adult bees lacked adequate (>80%) statistical power to detect an effect.

CONCLUSIONS

Chronic exposure of honey bees to high environmental doses of neonicotinoids has negative effects on honey production. Brood area appears to be less sensitive to detect sublethal effects of neonicotinoids.

The impact of restrictions on neonicotinoid and fipronil insecticides on pest management in maize, oilseed rape and sunflower in eight European Union regions

BACKGROUND

In 2013, the European Commission restricted the use of three neonicotinoids (clothianidin, imidacloprid and thiamethoxam) and the pyrazole fipronil, which are widely used to control early-season pests. Here, we used original farm survey data to examine the impact of the restrictions on pest management practices in eight regional case studies including maize, oilseed rape and sunflower in seven European Union (EU) countries.

RESULTS

In four case studies, farmers switched to using untreated seeds as no alternative seed treatments were available. In three case studies, farmers switched to using unrestricted neonicotinoid- or pyrethroid-treated seeds. In five case studies, farmers increased the use of soil or foliar treatments, with pyrethroids as the principal insecticide class. Other changes in pest management practices ranged from increased sowing density to more frequent scouting for pests. Many farmers perceived that the time, cost and amount of insecticides required to protect crops increased, along with pest pressure. Alternative seed treatments were mostly perceived as being less effective than the restricted seed treatments.

CONCLUSION

Farmers generally relied on alternative seed treatments or more soil/foliar treatments in the first growing season after the restrictions took effect. Further study is required to assess the effectiveness and sustainability of these alternatives compared with the restricted insecticides. © 2017 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

The pesticide flupyradifurone impairs olfactory learning in Asian honey bees (Apis cerana) exposed as larvae or as adults

Relatively little attention has focused on how pesticides may affect Asian honey bees, which provide vital crop pollination services and are key native pollinators. We therefore studied the effects of a relatively new pesticide, flupyradifurone (FLU), which has been developed, in part, because it appears safer for honey bees than neonicotinoids. We tested the effects of FLU on Apis cerana olfactory learning in larvae (lower dose of 0.033 µg/larvae/day over 6 days) and, in a separate experiment, adults (lower dose of 0.066 µg/adult bee/day) at sublethal, field-realistic doses given over 3 days. A worst-case field-realistic dose is 0.44 µg/bee/day. Learning was tested in adult bees. The lower larval dose did not increase mortality, but the lower adult dose resulted in 20% mortality. The lower FLU doses decreased average olfactory learning by 74% (larval treatment) and 48% (adult treatment) and reduced average memory by 48% (larval treatment) and 22% (adult treatment) as compared to controls. FLU at higher doses resulted in similar learning impairments. The effects of FLU, a pesticide that is reported to be safer than neonicotinoids for honey bees, thus deserve greater attention.

Effects of Thiamethoxam-Treated Seed on Mexican Bean Beetle (Coleoptera: Coccinellidae), Nontarget Arthropods, and Crop Performance in Southwestern Virginia Snap Beans

Thiamethoxam is a neonicotinoid insecticide commonly applied directly to the seeds (seed-treatment) of commercial snap beans, Phaseolus vulgaris L. While previous studies have examined target and nontarget effects of thiamethoxam seed-treatments in snap beans and other crops, to our knowledge, none have been conducted in agroecosystems predominated by the pest Mexican bean beetle, Epilachna varivestis Mulsant (Coleoptera: Coccinellidae). This study examined the effects of thiamethoxam-treated snap beans on E. varivestis, other arthropods, and crop performance in southwestern Virginia. Greenhouse experiments were conducted to evaluate residual toxicity of treated snap beans to E. varivestis and a key predator, Podisus maculiventris (Say) (Hemiptera: Pentatomidae). Treated plants were highly toxic to E. varivestis at 13 d, moderately toxic from 16 to 20 d, and minimally toxic at 24 d. P. maculiventris was unaffected by exposure to treated plants or by feeding on E. varivestis that consumed treated plants. Small plot field experiments in 2014 and 2015 showed no significant effects of thiamethoxam seed-treatments on E. varivestis densities, other arthropods, crop injury, or yield. In 2016, planting was delayed by persistent rain, resulting in early E. varivestis colonization. In this year, thiamethoxam-treated plants had significantly lower densities and feeding injury from E. varivestis, followed by significantly higher yields. Natural enemies were unaffected by seed-treatments in all field experiments. These experiments demonstrated that thiamethoxam seed-treatments provide control of E. varivestis when beetles infest fields within 2 to 3 wk after planting; but otherwise provide negligible advantages. Negative effects from thiamethoxam seed-treatments on nontarget arthropods appear minimal for snap beans in this region.