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1. Neonicotinoids are now the most widely used insecticides in the world. They act systemically, travelling through plant tissues and protecting all parts of the crop, and are widely applied as seed dressings. As neurotoxins with high toxicity to most arthropods, they provide effective pest control and have numerous uses in arable farming and horticulture. 2. However, the prophylactic use of broad-spectrum pesticides goes against the long-established principles of integrated pest management (IPM), leading to environmental concerns. 3. It has recently emerged that neonicotinoids can persist and accumulate in soils. They are water soluble and prone to leaching into waterways. Being systemic, they are found in nectar and pollen of treated crops. Reported levels in soils, waterways, field margin plants and floral resources overlap substantially with concentrations that are sufficient to control pests in crops, and commonly exceed the LC₅₀ (the concentration which kills 50% of individuals) for beneficial organisms. Concentrations in nectar and pollen in crops are sufficient to impact substantially on colony reproduction in bumblebees. 4. Although vertebrates are less susceptible than arthropods, consumption of small numbers of dressed seeds offers a route to direct mortality in birds and mammals. 5. Synthesis and applications. Major knowledge gaps remain, but current use of neonicotinoids is likely to be impacting on a broad range of non-target taxa including pollinators and soil and aquatic invertebrates and hence threatens a range of ecosystem services.

Summary Neonicotinoids are now the most widely used insecticides in the world. They act systemically, travelling through plant tissues and protecting all parts of the crop, and are widely applied as seed dressings. As neurotoxins with high toxicity to most arthropods, they provide effective pest control and have numerous uses in arable farming and horticulture. However, the prophylactic use of broad‐spectrum pesticides goes against the long‐established principles of integrated pest management (IPM), leading to environmental concerns. It has recently emerged that neonicotinoids can persist and accumulate in soils. They are water soluble and prone to leaching into waterways. Being systemic, they are found in nectar and pollen of treated crops. Reported levels in soils, waterways, field margin plants and floral resources overlap substantially with concentrations that are sufficient to control pests in crops, and commonly exceed the LC50 (the concentration which kills 50% of individuals) for beneficial organisms. Concentrations in nectar and pollen in crops are sufficient to impact substantially on colony reproduction in bumblebees. Although vertebrates are less susceptible than arthropods, consumption of small numbers of dressed seeds offers a route to direct mortality in birds and mammals. Synthesis and applications. Major knowledge gaps remain, but current use of neonicotinoids is likely to be impacting on a broad range of non‐target taxa including pollinators and soil and aquatic invertebrates and hence threatens a range of ecosystem services. Major knowledge gaps remain, but current use of neonicotinoids is likely to be impacting on a broad range of non‐target taxa including pollinators and soil and aquatic invertebrates and hence threatens a range of ecosystem services.

Background The residual activity of a clothianidin + deltamethrin mixture and clothianidin alone in IRS covered more than the period of malaria transmission in northern Benin. The aim of this study was to show whether the prolonged residual efficacy of clothianidin-based products resulted in a greater reduction in vector populations and subsequent malaria transmission compared with the shorter residual efficacy of pirimiphos-methyl. Methods Human bait mosquito collections by local volunteers and pyrethrum spray collections were used in 6 communes under IRS monitoring and evaluation from 2019 to 2021. ELISA/CSP and species PCR tests were performed on Anopheles gambiae sensu lato ( s.l .) to determine the infectivity rate and subspecies by commune and year. The decrease in biting rate, entomological inoculation rate, incidence, inhibition of blood feeding, resting density of An. gambiae s.l. were studied and compared between insecticides per commune. Results The An . gambiae complex was the major vector throughout the study area, acounting for 98.71% (19,660/19,917) of all Anopheles mosquitoes collected. Anopheles gambiae s.l. collected was lower inside treated houses (45.19%: 4,630/10,245) than outside (54.73%: 5,607/10,245) after IRS (p < 0.001). A significant decrease (p < 0.001) in the biting rate was observed after IRS in all departments except Donga in 2021 after IRS with clothianidin 50 WG. The impact of insecticides on EIR reduction was most noticeable with pirimiphos-methyl 300 CS, followed by the clothianidin + deltamethrin mixture and finally clothianidin 50 WG. A reduction in new cases of malaria was observed in 2020, the year of mass distribution of LLINs and IRS, as well as individual and collective protection measures linked to COVID-19. Anopheles gambiae s.l. blood-feeding rates and parous were high and similar for all insecticides in treated houses. Conclusion To achieve the goal of zero malaria, the optimal choice of vector control tools plays an important role. Compared with pirimiphos-methyl, clothianidin-based insecticides induced a lower reductions in entomological indicators of malaria transmission.

The honey bee is a major pollinator whose health is of global concern. Declines in bee health are related to multiple factors, including resource quality and pesticide contamination. Intensive agricultural areas with crop monocultures potentially reduce the quality and quantity of available nutrients and expose bee foragers to pesticides. However, there is, to date, no evidence for synergistic effects between pesticides and nutritional stress in animals. The neonicotinoids clothianidin (CLO) and thiamethoxam (TMX) are common systemic pesticides that are used worldwide and found in nectar and pollen. We therefore tested if nutritional stress (limited access to nectar and access to nectar with low-sugar concentrations) and sublethal, field-realistic acute exposures to two neonicotinoids (CLO and TMX at 1/5 and 1/25 of LD50) could alter bee survival, food consumption and haemolymph sugar levels. Bee survival was synergistically reduced by the combination of poor nutrition and pesticide exposure (−50%). Nutritional and pesticide stressors reduced also food consumption (−48%) and haemolymph levels of glucose (−60%) and trehalose (−27%). Our results provide the first demonstration that field-realistic nutritional stress and pesticide exposure can synergistically interact and cause significant harm to animal survival. These findings have implications for current pesticide risk assessment and pollinator protection.

Neonicotinoid pesticides were first introduced in the mid-1990s, and since then, their use has grown rapidly. They are now the most widely used class of insecticides in the world, with the majority of applications coming from seed dressings. Neonicotinoids are water-soluble, and so can be taken up by a developing plant and can be found inside vascular tissues and foliage, providing protection against herbivorous insects. However, only approximately 5% of the neonicotinoid active ingredient is taken up by crop plants and most instead disperses into the wider environment. Since the mid-2000s, several studies raised concerns that neonicotinoids may be having a negative effect on non-target organisms, in particular on honeybees and bumblebees. In response to these studies, the European Food Safety Authority (EFSA) was commissioned to produce risk assessments for the use of clothianidin, imidacloprid and thiamethoxam and their impact on bees. These risk assessments concluded that the use of these compounds on certain flowering crops poses a high risk to bees. On the basis of these findings, the European Union adopted a partial ban on these substances in May 2013. The purpose of the present paper is to collate and summarise scientific evidence published since 2013 that investigates the impact of neonicotinoids on non-target organisms. Whilst much of the recent work has focused on the impact of neonicotinoids on bees, a growing body of evidence demonstrates that persistent, low levels of neonicotinoids can have negative impacts on a wide range of free-living organisms.

Large-scale losses of honey bee colonies represent a poorly understood problem of global importance. Both biotic and abiotic factors are involved in this phenomenon that is often associated with high loads of parasites and pathogens. A stronger impact of pathogens in honey bees exposed to neonicotinoid insecticides has been reported, but the causal link between insecticide exposure and the possible immune alteration of honey bees remains elusive. Here, we demonstrate that the neonicotinoid insecticide clothianidin negatively modulates NF-κB immune signaling in insects and adversely affects honey bee antiviral defenses controlled by this transcription factor. We have identified in insects a negative modulator of NF-κB activation, which is a leucine-rich repeat protein. Exposure to clothianidin, by enhancing the transcription of the gene encoding this inhibitor, reduces immune defenses and promotes the replication of the deformed wing virus in honey bees bearing covert infections. This honey bee immunosuppression is similarly induced by a different neonicotinoid, imidacloprid, but not by the organophosphate chlorpyriphos, which does not affect NF-κB signaling. The occurrence at sublethal doses of this insecticide-induced viral proliferation suggests that the studied neonicotinoids might have a negative effect at the field level. Our experiments uncover a further level of regulation of the immune response in insects and set the stage for studies on neural modulation of immunity in animals. Furthermore, this study has implications for the conservation of bees, as it will contribute to the definition of more appropriate guidelines for testing chronic or sublethal effects of pesticides used in agriculture.

1. Neonicotinoids are the most widely used insecticides world-wide, but their fate in the environment remains unclear, as does their potential to influence non-target species and the roles they play in agroecosystems. 2. We investigated in laboratory and field studies the influence of the neonicotinoid thiamethoxam, applied as a coating to soya bean seeds, on interactions among soya beans, nontarget molluscan herbivores and their insect predators. 3. In the laboratory, the pest slug Deroceras reticulatum was unaffected by thiamethoxam, but transmitted the toxin to predaceous beetles (Chlaenius tricolor), impairing or killing >60%. 4. In the field, thiamethoxam-based seed treatments depressed activity-density of arthropod predators, thereby relaxing prédation of slugs and reducing soya bean densities by 19% and yield by 5%. 5. Neonicotinoid residue analyses revealed that insecticide concentrations declined through the food chain, but levels in field-collected slugs (up to 500 ng g⁻¹) were still high enough to harm insect predators. 6. Synthesis and applications. Our findings reveal a previously unconsidered ecological pathway through which neonicotinoid use can unintentionally reduce biological control and crop yield. Trophic transfer of neonicotinoids challenges the notion that seed-applied toxins precisely target herbivorous pests and highlights the need to consider predatory arthropods and soil communities in neonicotinoid risk assessment and stewardship.

Neonicotinoids are the most widely used class of insecticides globally. However, the link between farming practices and the extent of contamination of soils and crops by neonicotinoid insecticides, as well as the extent of such contamination in organic fields and ecological focus areas (EFAs) are currently unclear. We measured the concentrations of five neonicotinoid insecticides (imidacloprid, clothianidin, thiamethoxam, thiacloprid, acetamiprid) in 702 soil and plant samples in 169 cultivated fields and EFAs from 62 conventional, integrated production and organic farms distributed over the entire lowland of Switzerland. We detected neonicotinoids in 93% of organic soils and crops, and more than 80% of EFA soils and plants—two types of arable land supposedly free of insecticides. We also tested 16 samples of organic seeds, of which 14 were positive for neonicotinoids. Finally, we calculated hazard quotients (HQs) and potentially affected fractions for 72 beneficial and 12 pest species. Under a field‐realistic scenario, we found that between 5.3%–8.6% of above‐ground invertebrate species may be exposed to lethal concentrations of clothianidin, and 31.6%–41.2% to sublethal concentrations, in “integrated production” and conventional fields. We also found that 1.3%–6.8% (up to 12.5% based on HQs) of the beneficial invertebrate species may be exposed to sublethal concentrations of neonicotinoids in EFAs and organic fields. In contrast, no pest species would be exposed to lethal concentrations, even under a worst‐case scenario. Synthesis and applications. Our study suggests that diffuse contamination by neonicotinoids may harm a significant fraction of non‐target beneficial species. The use of neonicotinoids on crops may threaten biodiversity in refuge areas, while also potentially jeopardizing the practice of organic farming by impeding the biological control of pests. On the basis of our results, we call for a reduction in the dispersion and overuse of neonicotinoid insecticides in order to prevent any detrimental effects on biodiversity and ecosystem services associated with agroecosystems. ZUSAMMENFASSUNG Neonicotinoide sind weltweit die am meisten verbreitete Gruppe von Insektiziden. Es ist jedoch unklar inwiefern ein Zusammenhang zwischen den landwirtschaftlichen Praktiken und dem Ausmass der Kontimination von Böden und Erntegut durch Neonicotinoide besteht. Über das Ausmass einer solchen Kontamination auf biologischen Feldern und Ökologischen Ausgleichsflächen (ÖAF) ist ebenfall wenig bekannt. Wir haben die Konzentrationen von fünf Neonicotinoid Insektiziden (Imidacloprid, Clothianidin, Thiamethoxam, Thiacloprid, Acetamiprid) in 702 Boden‐ und Pflanzenproben von 169 Ackerflächen und ÖAF von 62 konventionellen, IP (Integrierter Landbau) und biologischen Landwirtschaftsbetrieben im schweizer Mittelland gemessen. Auf 93% der Böden und des Ernteguts der biologischen Betriebe als auch auf über 80% der Böden und Pflanzen der ÖAF haben wir Neonicotinoide festgestellt—zwei Arten von landwirtschaftlichen Flächen, welche vermeintlich frei von Insektiziden sein sollten. Wir haben ebenfalls 16 Proben von biologischem Saatgut untersucht, von denen 14 Neonicotinoide enthielten. Schliesslich haben wir den Gefahrenquotienten (GQ) und den potentiel betroffenen Anteil von 72 Nützlingen und 12 Schädlingen berechnet. In einem feldrealistischen Szenario haben wir festgestellt, dass zwischen 5,3 bis 8,6% der oberirdischen Wirbellosenarten tödlichen Konzentrationen von Clothianidin und 31,6 bis 41,2% subletalen Konzentrationen in der IP‐ und konventionellen Feldern ausgesetzt sein können. Wir haben ebefalls festgestellt, dass 1,3 bis 6,8% (bis zu 12,5% basierend auf GQ) der Nützlinge subletalen Konzentrationen von Neonicotinoiden in ÖAF und biologischen Feldern ausgesetzt sein können. Im Gegensatz dazu würden Schädlinge selbst im schlimmsten Szenario keiner tödlichen Konzentration ausgesetzt sein. Synthese und Anwendungen. Unsere Studie deutet darauf hin, dass eine diffuse Kontamination durch Neonicotinoide einen erheblichen Teil der nicht zu den Zielgruppen gehörenden Nützlingen schädigen kann. Die Verwendung von Neonicotinoiden auf Ackerflächen kann die biologische Vielfalt in Rückzugsgebieten bedrohen und gleichzeitig den biologischen Landbau gefährden, indem sie die biologische Schädlingsbekämpfung behindert. Auf Grundlage unserer Ergebnisse fordern wir eine Verringerung der Verbreitung und des übermäßigen Einsatzes von Neonicotinoid‐Insektiziden, um schädliche Auswirkungen auf die Biodiversität und die mit Agrarökosystemen verbundenen Ökosystemleistungen zu vermeiden. Our study suggests that diffuse contamination by neonicotinoids may harm a significant fraction of non‐target beneficial species. The use of neonicotinoids on crops may threaten biodiversity in refuge areas, while also potentially jeopardizing the practice of organic farming by impeding the biological control of pests. On the basis of our results, we call for a reduction in the dispersion and overuse of neonicotinoid insecticides in order to prevent any detrimental effects on biodiversity and ecosystem services associated with agroecosystems. Editor's Choice

Concerns over the role of pesticides affecting vertebrate wildlife populations have recently focussed on systemic products which exert broad-spectrum toxicity. Given that the neonicotinoids have become the fastest-growing class of insecticides globally, we review here 150 studies of their direct (toxic) and indirect (e.g. food chain) effects on vertebrate wildlife—mammals, birds, fish, amphibians and reptiles. We focus on two neonicotinoids, imidacloprid and clothianidin, and a third insecticide, fipronil, which also acts in the same systemic manner. Imidacloprid and fipronil were found to be toxic to many birds and most fish, respectively. All three insecticides exert sub-lethal effects, ranging from genotoxic and cytotoxic effects, and impaired immune function, to reduced growth and reproductive success, often at concentrations well below those associated with mortality. Use of imidacloprid and clothianidin as seed treatments on some crops poses risks to small birds, and ingestion of even a few treated seeds could cause mortality or reproductive impairment to sensitive bird species. In contrast, environmental concentrations of imidacloprid and clothianidin appear to be at levels below those which will cause mortality to freshwater vertebrates, although sub-lethal effects may occur. Some recorded environmental concentrations of fipronil, however, may be sufficiently high to harm fish. Indirect effects are rarely considered in risk assessment processes and there is a paucity of data, despite the potential to exert population-level effects. Our research revealed two field case studies of indirect effects. In one, reductions in invertebrate prey from both imidacloprid and fipronil uses led to impaired growth in a fish species, and in another, reductions in populations in two lizard species were linked to effects of fipronil on termite prey. Evidence presented here suggests that the systemic insecticides, neonicotinoids and fipronil, are capable of exerting direct and indirect effects on terrestrial and aquatic vertebrate wildlife, thus warranting further review of their environmental safety.

Evaluating the effects of neonicotinoids on forager bees in conditions as near as possible to those in nature presents a considerable challenge. Tackling this challenge is, however, necessary to establish their negative side effects on these pollinators. For instance, it is still under debate the mechanism by which bees seem to recognize low-level contaminations of neonicotinoid insecticides in nectar and pollen of the flowers they visit and limit collection to protect themselves and their hive from a possible intoxication. In this study, we propose an experimental system that involves the use of foragers in free flight foraging repeatedly on artificial feeders containing a sucrose solution contaminated with clothianidin, as well as foragers feeding at adjacent control feeders, allowing us to observe changes in their foraging activity. The progressive disappearance of foragers from the contaminated feeders became increasingly clear and rapid with the increase in clothianidin concentration. The lowest concentration at which we observed an effect was around 10 µg/L, which corresponds to the maximum residual concentration (10 ng/g) observed in pollen and nectar of flowers close to open fields sown with seeds coated with insecticides. At the highest concentrations tested (80 µg/L), there was an almost total abandonment of the feeders. The estimated quantity of contaminated sucrose solution collected by foragers showed an almost linear relationship inversely proportional to clothianidin concentration, whilst the estimated quantity of insecticide collected by a forager increased and then stabilised at the highest concentrations tested of 40 and 80 µg/L. Irregular mortality was not observed in front of the hives, furthermore, foragers did not show evident memory of the position of the treated units in the trials on the 2 consecutive days. The decrease in foraging activity in the presence of a few µg/L of insecticide in the sucrose solution appears to limit the introduction of elevated amounts of toxic substances into the hives, which would have serious consequences for the young bees and the brood. At the same time, in the absence of an alternative energy source, even reduced feeding of the hive can compromise colony health.