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Organism tolerance thresholds for emerging contaminants are vital to the development of water quality criteria. Acute (96-h) and chronic (10-day) effects thresholds for neonicotinoid pesticides clothianidin and thiamethoxam, and the carbamate pesticide methomyl were developed for the midge Chironomus dilutus to support criteria development using the UC Davis Method. Median lethal concentrations (LC50s) were calculated for acute and chronic exposures, and the 25% inhibition concentrations (IC25) were calculated for the chronic exposures based on confirmed chemical concentrations. Clothianidin effect concentrations were 4.89 µg/L, 2.11 µg/L and 1.15 µg/L for 96-h LC50, 10-day LC50 and 10-day IC25, respectively. Similarly, thiamethoxam concentrations were 56.4 µg/L, 32.3 µg/L and 19.6 µg/L, and methomyl concentrations were 244 µg/L, 266 µg/L and 92.1 µg/L. Neonicotinoid effect concentrations compared favorably to previously published 96-h and 14-day LC50 concentrations, and methomyl effect concentrations were within the acute survival range reported for Chironomus species and other organisms.

Few human data on exposure and toxicity are available on neonicotinoids and neonicotinoid-like compounds (NNIs), an important group of insecticides worldwide. Specifically, exposure assessment of humans by biomonitoring remains a challenge due to the lack of appropriate biomarkers. We investigated the human metabolism and metabolite excretion in urine of acetamiprid (ACE), clothianidin (CLO), flupyradifurone (FLUP), imidacloprid (IMI), sulfoxaflor (SULF), thiacloprid (THIAC) and thiamethoxam (THIAM) after single oral dosages at the currently acceptable daily intake levels of the European Food Safety Authority. Consecutive post-dose urine samples were collected up to 48 h. Suspect screening of tentative metabolites was carried out by liquid chromatography–high-resolution mass spectrometry. Screening hits were identified based on their accurate mass, isotope signal masses and ratios, product ion spectra, and excretion kinetics. We found, with the exception of SULF, extensive metabolization of NNIs to specific metabolites which were excreted next to the parent compounds. Overall, 24 metabolites were detected with signal intensities indicative of high metabolic relevance. Phase-I metabolites were predominantly derived by mono-oxidation (such as hydroxy-FLUP, -IMI, and -THIAC) and by oxidative N-desalkylation (such as N-desdifluoroethyl-FLUP and N-desmethyl-ACE, -CLO and -THIAM). IMI-olefin, obtained by dehydration of hydroxylated IMI, was identified as a major metabolite of IMI. SULF was excreted unchanged in urine. Previously reported metabolites of NNIs such as 6-chloronicotinic acid or 2-chlorothiazole-4-carboxylic acid and their glycine derivatives were detected either at low signal intensities or not at all and seem less relevant for human biomonitoring. Our highly controlled approach provides specific insight into the human metabolism of NNIs and suggests suitable biomarkers for future exposure assessment at environmentally relevant exposures.

Bradysia odoriphaga is a major insect pest that infests Chinese chive in northern China. Clothianidin is a second-generation neonicotinoid insecticide that is commonly used against B. odoriphaga. In this study, the effect of sublethal clothianidin concentrations (LC5 and LC10) on key biological characteristics of B. odoriphaga was investigated using an age-stage, two-sex life table method. Bioassays results showed that clothianidin exhibited high toxicity against B. odoriphaga with LC50 of 1.898 mg L−1 following 24 h exposure. The developmental duration of larvae was significantly increased when exposed to the LC5 (0.209 mg L−1) and LC10 (0.340 mg L−1) of clothianidin. No significant effects were observed on the pupal stage, adult pre-oviposition period (APOP), total pre-oviposition period (TPOP), and mean longevities of male and female. The oviposition period and fecundity of B. odoriphaga were reduced in clothianidin-treated groups. Moreover, key demographic parameters, including the intrinsic rate of increase (r), finite rate of increase (λ), and net reproductive rate (R0), were significantly decreased by the LC5 and LC10 of clothianidin, while no effects were noted on mean generation time (T). Overall, this study showed that sublethal concentrations of clothianidin have a detrimental effect on B. odoriphaga developmental period, fecundity, and life table parameters. Therefore, clothianidin has the potential to suppress the population of B. odoriphaga even at sublethal concentrations.

Habitat loss, climate change, environmental contaminants, and parasites and pathogens are among the main factors thought to act singly or together in causing amphibian declines. We tested for combined effects of neonicotinoid pesticides and parasites (versus parasites-only) on mortality, growth, and white blood cell profiles of a model amphibian: the northern leopard frog (Rana pipiens). We first exposed infectious stages of frog trematodes (cercariae of Echinostoma spp.) to low and high concentrations of thiamethoxam or clothianidin versus water-only controls. There were no differences in survival of trematode cercariae between treatments. For the main experiment, we exposed tadpoles to clean water versus high concentrations of clothianidin or thiamethoxam for 2 weeks and added trematode cercariae to all tanks after 1 week. Exposure of tadpoles and parasites to high concentrations of thiamethoxam or clothianidin did not affect parasite infection success. Tadpole survival was not different between treatments before or after parasite addition and there were no significant differences in tadpole snout-to-vent lengths or developmental stages between treatments. Tadpoles exposed to thiamethoxam + parasites had smaller widths than parasite-only tadpoles, whereas tadpoles exposed to clothianidin + parasites had higher eosinophil to leukocyte ratios compared to parasite-only tadpoles. Tadpoles of both neonicotinoid + parasite treatments had significantly lower monocyte to leukocyte ratios relative to parasite-only tadpoles. High concentrations of neonicotinoid combined with parasites appear to influence tadpole immune function important for further defense against parasites and pathogens. This work highlights the need for more holistic approaches to ecotoxicity studies, using multiple stressors.

This research investigated the adverse effects of neonicotinoids on the Northwestern salamander (Ambystoma gracile; NWS) after acute and subchronic exposures during early aquatic life stages via whole organism (i.e., growth, development) and molecular (i.e., gene expression) level endpoints. In a 96-h exposure, NWS larvae were exposed to four imidacloprid concentrations (250, 750, 2250, 6750 µg/L) and a water control treatment, and no effects on survival, body weight, snout-vent length (SVL), and total body length were observed. However, a significant 1.70- and 2.33-fold decrease in thyroid receptor β (TRβ) mRNA expression levels were detected in the larvae exposed to 750 and 2250 µg/L imidacloprid, respectively, compared with the larvae in the water control. In subsequent subchronic experiments, NWS larvae were exposed for 35 days to imidacloprid alone and an equal part mixture of neonicotinoids (imidacloprid, clothianidin, and thiamethoxam (ICT)) at three concentrations (10, 100 and 1000 µg total neonicotinoids/L) and a water control. In these experiments, there were no effects on larval survival, body weight, SVL, and total body length. However, advanced development of larvae in the 100 µg/L imidacloprid treatment was observed compared with the control after 35-day imidacloprid exposure, providing some evidence of disruption of the thyroid endocrine axis at an environmentally relevant concentration. Ultimately, there is a paucity of studies conducted examining the sensitivity of salamanders to pollutants; thus, this study reports novel findings that will contribute to understanding the sensitivity of a Caudate amphibian model to a common environmental pollutant.

The green lacewing, Chrysoperla carnea, Stephens (Neu.: Chrysopidae) is one of the most important predators for insect pests such as whiteflies, thrips, psyllids and aphids that ignificantly decrease their populations. In the current study, lethal (LC50) and sublethal effects (LC30) of three insecticides; clothianidin, tebufenozide and flupyradifurone on first instar larvae of C. carnea (

Insecticides are the most economic and quick tool to control harmful agricultural insect pests which reduce crop productivity. However, these insecticides have a suppressive and negative impact on non-targeted beneficial fauna. The efficiency and mode of action of numerous insecticides are also much diverse. Therefore, we studied the sublethal impact of bifenthrin (pyrethroids) and clothianidin (neonicotinoids) on ladybird beetle Coccinella septempunctata L. (Coleoptera: Coccinellidae), taking these insecticides as the model representative for the insecticide groups. Our results revealed that both insecticides enhanced the life length of male and female adults of ladybird beetle as compared to control treatment. Bifenthrin reduced the survival rate of larvae and adults as compared to clothianidin and control as well as lowered the fecundity rate of C. septempunctata. After control treatment, the developmental period of each larval instar was shorter in clothianidin than bifenthrin. Adult emergence was also less in clothianidin than in the control group. However, clothianidin triggered the fecundity of the female ladybird beetle. Higher fecundity was recorded in clothianidin treatment as compared to bifenthrin and control which means clothianidin is a better option in integrated pest management (IPM) program as compared to bifenthrin involving the ladybird beetle as a natural biocontrol agent.

Water is essential for honey bees (Apis mellifera L.), but contaminated sources of water in agricultural environments represent a risk of exposure to potentially harmful contaminants. Providing clean water to honey bees could be an efficient and cost-effective measure for beekeepers to reduce bee mortality associated with pesticides and improve the health of their colonies. The main goal of this study was to design a waterer prototype to fulfill the water requirements of honey bees and to evaluate the potential of this waterer in improving colonies’ health in agricultural settings, through mitigating the possible impact of an exposure to pesticides from puddle water. We tested the preference of honey bees regarding water composition and waterer prototypes, among which honey bees showed a strong preference for salted water and a poultry-type waterer. Our waterer models were quickly adopted and intensively used through the season in both the context of honey production in field crops and pollination services in cranberry crops. However, in neither context did the use of waterers reduce worker mortality nor increase overall colony weight. Our waterers provided bees with water containing fewer pesticides and were associated with reduced risks of drowning compared to natural sources of water. Our study suggests that the use of waterers fulfills an important requirement for honey bees and represents an interesting and convenient precautionary measure for beekeepers.

A functional pesticide–fertilizer combination is in high demand due to the many potential advantages, including the dual reduction in pesticide and fertilizer inputs, increased crop yield, safe to use, and environmental friendly. To investigate the impact of a pesticide–fertilizer on the soil environment of sugarcane, the effects of clothianidin and/or organic fertilizer treatments on the diversity, structure, and function of the rhizosphere bacterial community were studied using 16S rRNA gene sequencing in 2019 at Guangzhou Sugarcane Research Institute. The bacterial community treated with the pesticide–fertilizer displayed a higher diversity compared with the control treatments (added with pesticide or fertilizer only). The dynamic changes of the bacterial community structure revealed that the pesticide–fertilizer treatment showed a significant variation in the second week. Functional analysis demonstrated that four bacterial genera, including Dyella, Mucilaginibacter, Massilia, and Telmatospirillum, could play an important role in degrading clothianidin and improving soil health. The relative abundance of nitrogen cycle genes showed that the nitrification-related gene pmoA-amoA and denitrification-related genes nirK and norB were increased significantly in the pesticide–fertilizer treatment compared with that of the control treatments. This preliminary study provides a good basis to understand the effect of a pesticide–fertilizer integration on the soil rhizosphere microbiome which would be helpful for the evaluation of its application in the field.

Symbionts participate in various physiological activities of their insect hosts, including detoxification metabolism. Emerging evidence has revealed that the bacterial symbiont Arsenophonus is involved in insecticide detoxification metabolism of Nilaparvata lugens, which harbors diverse symbionts. However, it is still unknown whether other bacterial symbionts have a functional role in this process. This study showed that pretreatment with antibiotics significantly increased N. lugens susceptibility to imidacloprid, chlorpyrifos, and clothianidin, and the detoxifying enzyme activities of the cytochrome P450 enzyme (P450) and glutathione S-transferase (GST) were significantly inhibited. Notably, the P450 genes NlCYP6ER1 and NlCYP4CE1, which are related to imidacloprid metabolism, were dramatically downregulated in ciprofloxacin- and tetracycline-pretreated N. lugens, respectively. Furthermore, the expression levels of various detoxifying genes (GSTs and P450s) were significantly positively correlated with Wolbachia, Arsenophonus, Acinetobacter, and Staphylococcus. These results indicated that bacterial symbionts may affect insecticide metabolism by regulating the expression of the insect host’s GST and P450 genes, and provide a foundation for further study on the mechanism of symbiont-mediated host detoxification metabolism in insect pests.

Neonicotinoids are a group of insecticides that are commonly used in agriculture throughout the world. Despite their widespread use, there are significant knowledge gaps related to the presence and fate of neonicotinoids in groundwater. This research explores the environmental parameters governing the transport of the most commonly found neonicotinoids from surface application to deeper groundwater in two distinct hydrogeologic settings. Both of these research sites are located in Ontario, Canada: one has an unconfined, sandy Quaternary aquifer while the other has a fractured, crystalline bedrock aquifer (Canadian Shield) under a thin layer of soil and till. Groundwater sampling was conducted using 18–26 monitoring intervals at each research site during each sampling round (April 2016, July 2016, August 2016, November 2016, and April 2017). Analysis of six neonicotinoids, two fungicides, two herbicides, and one ryanoid insecticide were conducted using liquid chromatography–mass spectrometry (positive electrospray ionization)–tandem mass spectrometry. During the groundwater sampling period, soil sampling was conducted, and a crop survey completed. Results from groundwater sampling found the neonicotinoids clothianidin, imidacloprid, and thiamethoxam with maximum concentrations and detection frequencies above the level of quantitation of 2.09, 0.7, 0.46 μg/L, and 2.2, 0.9, 1.3%, respectively. Numerical analysis revealed that under similar environmental conditions, clothianidin and thiamethoxam are released in a similar pattern that resembles a pulse. Future research into this subject should include a finer sampling timeframe to confirm theories about the pulsing nature of neonicotinoids in groundwater.

Globally, neonicotinoid contamination in aquatic environments, including estuarine areas, is a prevailing environmental concern. The estuarine resident marine crustacean sand shrimp Crangon uritai was previously found to have a higher tolerance to neonicotinoids than the marine crustaceans kuruma prawn Penaeus japonicus and mysid Americamysis bahia. Based on these findings, we aimed to explore the mechanisms underlying their differences in insecticide sensitivity. We hypothesized that differences in the structures of their nicotinic acetylcholine receptors (nAChRs) and/or the involvement of a metabolizing enzyme may confer sand shrimp resistance to neonicotinoids. No obvious differences were found in the amino acid residue (position 81) of the loop D region of the nAChR β-subunit among the three crustaceans. A synergistic toxicity bioassay was used to explore candidate metabolizing enzymes, esterase, glutathione S-transferase, and oxygenase. The three species were exposed to two neonicotinoids (acetamiprid and clothianidin) at concentrations equivalent to 1/15–1/10 of 96-h LC50 values and synergists (inhibitors of metabolizing enzyme) or combinations of both. Treatments with the oxygenase inhibitor and the neonicotinoids resulted in increased mortality in sand shrimps but not in kuruma prawns or mysids. Consequently, it was determined that oxygenase may explain the higher resistance of the sand shrimp to neonicotinoid insecticides.

The use of pesticides for greenbug, Schizaphis graminum in wheat not only can manage the pest population but also can influence its predator, Coccinella septempunctata. Acute and chronic effects of imidacloprid, clothianidin and sulfoxaflor on S. graminum and its predator, C. septempunctata were investigated. The results showed that LC50 of imidacloprid, clothianidin and sulfoxaflor to S. graminum at 48 h was 9.80, 34.29 and 4.40 ml a.i. L−1, respectively, while LC50 of imidacloprid, clothianidin and sulfoxaflor to C. septempunctata at 48 h was 107.80, 49.52 and 379.26 ml a.i. L−1. Sulfoxaflor and clothianidin were found the most toxic to S. graminum and C. septempunctata, respectively. Tested sublethal doses (LC10 and LC30) of all insecticides had significant effects on percent repellency of both S. graminum and C. septempunctata. Sulfoxaflor and clothianidin proved the most repellent to S. graminum (67.00 ± 2.03% at LC10 and 86.20 ± 1.62% at LC30) and C. septempunctata (50.60 ± 2.81% at LC10 and 60.00 ± 3.26% at LC30), respectively. Sublethal doses also demonstrated significant and the lowest percentage reduction in feeding by C. septempunctata on S. graminum in sulfoxaflor treatment (LC10: 4.13 ± 0.61%; LC30: 5.26 ± 0.69%). Additionally, sublethal doses reduced body-weight of C. septempunctata adults emerged from its treated grubs. These results revealed that sublethal doses of sulfoxaflor, imidacloprid and clothianidin negatively affected the biological activities of S. graminum and C. septempunctata as compared to control. Hence it can be concluded that more attention should be paid towards strategic application of these chemicals as a part of an integrated pest management program for an agro-ecosystem exhibiting maximum activity of coccinelid-predators. Overall, sulfoxaflor proved more appropriate for use against S. graminum in C. septempunctata manipulated agro-ecosystem. However, C. septempunctata compatible integration-strategy for field-application of sulfoxaflor should be devised to enhance its effectiveness against S. graminum and selectivity against C. septempunctata.

We investigate the minimum-energy path for the rotation of formal C=N double bonds in molecules with guanidine-like substructures as present in the chemical class of neonicotinoids. The transitions between the E- and Z-isomers of several neonicotinoids using scans of the torsional potential energy hypersurfaces are quantified at the DFT-level of theory. The validity of using this ansatz is checked by single-point CCSD(T) calculations for model systems like nitroguanidine. A combined approach of theory and experiment permits to unambiguously identify the relevant isomers present at ambient conditions. As an example, MP2-GIAO predictions of the NMR spectra of E- and Z-Clothianidin are experimentally confirmed by low-temperature NMR-experiments identifying for the first time the hitherto unknown Z-Isomer of Clothianidin.

This study measured both nutrient and pesticide concentrations at up to 13 different freshwater stream sites in New Brunswick, Nova Scotia and Prince Edward Island between 2013 and 2018. Up to 62 different pesticides were analysed in 248 discreet samples. A large majority of pesticides were below the detection limit of the laboratory while seven pesticides had at least 20% or more detections throughout the years of this study. The four pesticides that had the highest frequency of detection were the insecticides chlorantraniliprole, clothianidin, imidacloprid, and thiamethoxam of which the last three are categorised as neonicotinoid insecticides.

Clothianidin served as the model pollutant to investigate the performance and mechanism of pollutant removal by dielectric barrier discharge plasma (DBD) combined with the titanium dioxide-reduced graphene oxide (rGO-TiO2) composite catalyst. In this study, different ratios of titanium dioxide-graphene catalysts were loaded onto honeycomb ceramic plates via the sol-gel method, and the modified catalytic ceramic plates were characterized by XRD, SEM, FTIR, DRS, and energy dispersive X-ray. The results suggested that the rGO-TiO2 was well loaded on the surface of the honeycomb ceramic plates. According to the results of the characterization experiments and the degradation of the clothianidin solution with different proportions of the catalyst, 8 wt% rGO-TiO2 was selected as the optimum ratio for degradation. Clothianidin degradation efficiency was significantly influenced by input power, clothianidin concentration, pH value, liquid conductivity, free radical quencher. Finally, six degradation products of clothianidin were identified by HPLC-MS, and the possible transformation pathways of clothianidin degradation were identified.

Bemisia tabaci is the most destructive insect of cotton worldwide. We analysed infestation dynamics of B. tabaci in cotton during summers of 2015–2017, and predicted the factors influencing its abundance. The incidence of B. tabaci on cotton was exceptionally high in 2015 (25.91 ± 2.14 adults/3 leaves) as compared to 2016 (9.53 ± 1.23 adults/3 leaves) and 2017 (8.54 ± 1.12 adults/3 leaves). Minimum temperature, maximum-minimum relative humidity and rainfall influencing the B. tabaci population build-up were predicted using PCRA technique with reasonable accuracy (R2 = 0.87). The results also showed that monitoring/ sampling of B. tabaci in cotton should be done before 10:00 h. Among different cotton cultivars, Ankur 3028 and Bioseed 6588 were most susceptible to B. tabaci infestation. Bemisia tabaci incidence in cotton interferes with the secondary metabolite production in different cultivars. Pesticides tested for management of B. tabaci gave a maximum population reduction ranging from 42.91 to 77.01% 7 days after spray. The efficacy of tested pesticides persisted up to 10 days after spray. Maximum control of B. tabaci was achieved by flonicamid > clothianidin > diafenthiuron > dinotefuran > thiamethoxam, whereas, ethion was found least effective. Pyriproxyfen have nymphicidal action and provided maximum reduction (68.62%) in whitefly population after 10 days of spray.

Frankliniella occidentalis (Thysanoptera: Thripidae) is a notorious pest of horticultural crops, against which the predator Orius sauteri or neonicotinoid insecticides are commonly used in control programmes. Here, we carried out a series of indoor acute toxicity tests and a risk assessment of eight neonicotinoid insecticides (imidacloprid, nitenpyram, acetamiprid, thiacloprid, thiamethoxam, clothianidin, dinotefuran and flupyradifurone) for O. sauteri and F. occidentalis. For O. sauteri, the LC50 values of acetamiprid and flupyradifurone were 12.75 and 9.24 mg a.i. L−1, respectively, and their hazard quotients were ≤ 2. Their toxicities to F. occidentalis were in a similar range. When LC20 of acetamiprid or flupyradifurone was applied to the pest, predator or both, predation ability was slightly reduced with flupyradifurone (37, 59 and 18, respectively) having less impact compared to acetamiprid (18, 21 and 10, respectively). Furthermore, we performed a greenhouse efficacy trial which involved the selected neonicotinoids acetamiprid and flupyradifurone as well as O. sauteri. Our results showed that integrated pest management, i.e. the application of half the amount of O. sauteri together with low doses (LC20) of acetamiprid or flupyradifurone, significantly reduced the pest with 76% and 75%, respectively, during the trial time, similar to the biocontrol treatment and significantly better than for chemical control alone. The cost of the integrated pest control strategy was similar to chemical control alone and lower than for biocontrol, indicating its potential as an economically feasible thrips control strategy, with reduced environmental risks compared to using chemicals only.

A simple, sensitive, and efficient method has been developed for the determination of the seven neonicotinoid insecticides commercially available (imidacloprid, thiacloprid, clothianidin, thiamethoxam, acetamiprid, nitenpyram, and dinotefuran) and the main metabolite 6-chloronicotinic acid. Micellar electrokinetic chromatography (MEKC) mode was applied, using 48.5 cm of total length capillary (50 μm i.d.) with an extended light-path capillary (150 μm). The running electrolyte consisted of 25 mM sodium tetraborate buffer (pH 9.2) containing 120 mM of sodium dodecyl sulfate and 15% of methanol (v/v). A voltage of 27 kV and a temperature of 25 °C were applied. Samples dissolved in deionized water were hydrodynamically injected at 50 mbar for 12 s, achieving the analysis in less than 12 min. Diode array detection (DAD) was performed at 220, 254, and 270 nm, depending on the analyte. Two different methodologies as sample treatments were developed; for water samples, solid-phase extraction was checked using different cartridges (C18, Oasis® HLB, Oasis® HLB Prime, and Strata-X), being the best option Oasis® HLB for preconcentration and cleanup. In the case of soil samples, a simple solid-liquid extraction was applied using a mixture of 1:3 (v/v) acetonitrile/dichloromethane. Satisfactory linearity, trueness, and precision were achieved, with detection limits in the range of 0.1-0.4 μg L-1 for river water and 1.0-2.9 μg kg-1 for soil samples. Recoveries in the range of 80-107% for all of the assayed neonicotinoids in water samples of different origin and 73-92% for soil samples were achieved.

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.

Neonicotinoid insecticides are highly water soluble with relatively long half-lives, which allows them to move into and persist in aquatic ecosystems. However, little is known of the impacts of neonicotinoids on non-target vertebrates, especially at sublethal concentrations. We evaluated the effects of the neonicotinoid clothianidin on the behavior of southern leopard frog tadpoles (Rana sphenocephala) after a 96-h exposure at 6 concentrations, including 0 (control), 0.375, 0.75, 1.5, 3.0, 6.0 µg/L. We quantified total displacement, mean velocity, maximum velocity, and time spent moving of tadpoles for 1 h post-exposure. Total displacement and mean velocity of tadpoles decreased with clothianidin exposure. Maximum velocity decreased linearly with concentration, but there was no relationship between time spent moving and clothianidin concentration. Our results suggest exposure to clothianidin at sublethal concentrations can affect movement behavior of non-target organisms such as tadpoles.

Little information is available on the effects of neonicotinoid insecticides on vertebrates. Previous work using amphibians found chronic exposure to some neonicotinoids had no detrimental effects on fitness-relevant traits. However, there is some evidence of more subtle effects of neonicotinoids on immune traits and evidence that other pesticides can suppress tadpole immunity resulting in elevated levels of parasitism in the exposed tadpoles. The objective of our study was to assess whether neonicotinoid exposure affected tadpole immunometrics and susceptibility to parasitic helminths. We assessed northern leopard frog tadpole (Lithobates pipiens) levels of parasitism and leukocyte profiles following exposure to environmentally relevant concentrations of clothianidin and free-living infective cercariae of a helminth parasite, an Echinostoma sp. trematode. When comparing tadpoles from controls to either 1 or 100 μg/L clothianidin treatments, we found similar measures of parasitism (i.e. prevalence, abundance and intensity of echinostome cysts) and similar leukocyte profiles. We also confirmed that clothianidin was not lethal for cercariae; however, slight reductions in swimming activity were detected at the lowest exposure concentration of 0.23 μg/L. Our results show that exposure to clothianidin during the larval amphibian stage does not affect leukocyte profiles or susceptibility to parasitism by larval trematodes in northern leopard frogs although other aspects such as length of host exposure require further study.

Impacts of neonicotinoid-containing pesticides on pollinators have been heavily debated in recent years. While bees in the field get rarely exposed to lethal concentrations of neonicotinoids applied as seed coating, sublethal levels found in pollen and nectar may affect bee population development. We assessed a realistic and a worst-case scenario of clothianidin exposure to mason bees (Osmia bicornis) and bumblebees (Bombus terrestris) by conducting a small-scale field and semi-field experiment at sites planted with winter oilseed rape. Flight activity, mortality and population development (brood, colony strength and weight) of bumblebees and number of mason bee brood cells were assessed at three locations. We also analysed clothianidin residues in bee-collected pollen and nectar. We detected clothianidin at low concentrations in nectar and pollen; residues in pollen were higher than in nectar but did not exceed a maximum field concentration of 2.7 µg/kg for bumblebees and 4.7 µg/kg for mason bees. Exposure did not result in significant negative impacts on bumblebee colony development and potential reproductive success of mason bees in either semi-field or field setup. During exposure bumblebees in semi-field treatment tunnels were flying less actively than in control tunnels. Bumblebee colonies in treatment tunnels weighed more than control colonies at the end of the experiment. Our findings suggest that field-realistic exposure to oilseed rape grown from clothianidin-treated seeds (10 g clothianidin/kg seeds) poses little risks to mason bees, bumblebees and their population development. However, an impairment of flower visitation under a worst-case scenario may have implications for pollination services and crop production.

We developed an analytical method for quantifying clothianidin residues in green bean, pepper and watermelon crops using dispersive liquid-liquid microextraction (DLLME) and liquid chromatography-tandem mass spectrometry; this method was more rapid, sensitive and simple than QuEChERS sample preparation. Method validation indicated that the recovery for clothianidin was 80.8–93.1%, intra-day and inter-day repeatability ranged from 3.32 to 6.11% and 7.77 to 14.74%, respectively, limits of detection ranged from 0.64 to 0.74 µg/kg, and limits of quantification were 2.13–2.47 µg/kg. Matrix-matched calibration was used to compensate for matrix effects. Following application of the recommended dose in field trials, clothianidin dissipation followed first-order kinetics with half-lives of 1.9, 2.07, and 1.87 days in green bean, pepper, and watermelon crops; respective waiting periods of 5.76, 6.18, and 7.87 days after application are suggested for safe consumption. This study indicates the application of clothianidin presents no significant health risk to Egyptian consumers.

Oxycarenus hyalinipennis Costa is a polyphagous insect pest and can develop insecticide resistance. The resistance of O. hyalinipennis to neonicotinoids (clothianidin and dinotefuran), flonicamid, and conventional insecticides; carbamates (methomyl and carbosulfon), organophosphates (chlorpyrifos and malathion), and pyrethroids (cypermethrin and zeta-cypermethrin) was evaluated. The O. hyalinipennis populations were sampled from four locations in Pakistan and performed bioassays against the insecticides by leaf dip protocol. The O. hyalinipennis' populations showed low resistance to carbosulfan (resistance ratio (RR) = 2.06-6.34) and methomyl (RR = 2.78-7.27), moderate to high resistance to chlorpyrifos (RR = 30-45), malathion (RR = 20.29-88.19), and flonicamid (RR = 14.24-46.97), in comparison with the susceptible strain. Susceptibility to low resistance against cypermethrin (RR = 1.27-2.82), zeta-cypermethrin (RR = 2.62-3.38), and clothianidin (RR = 1.74-3.40), and low to moderate resistance to dinotefuran (RR = 3.84-13.43) in the field populations, was observed compared to the susceptible strain. A rotational usage of carbamates and pyrethroids with an integrated pest management tool should be considered to deal with O. hyalinipennis' insecticide resistance.

The rhizosphere microbial community is important for plant health and is shaped by numerous environmental factors. This study aimed to unravel the effects of a pesticide/fertilizer mixture on the soil rhizosphere microbiome of field-grown sugarcane. A field trial on sugarcane was conducted in Zhanjian City, Guangdong Province, China, and soil samples from the rhizosphere were collected after clothianidin pesticide and/or organic fertilizer treatments. The effects of pesticide and/or organic fertilizer treatments on the composition, diversity, and predictive function of the rhizosphere microbial communities were examined using 16S rRNA gene and ITS1 amplicon sequencing. Compared with the controls (no pesticide or fertilizer used), the microbial community that resulted from treatment with the pesticide/fertilizer mixture (SPF) had a higher relative bacterial diversity and fungal richness, and contributed more beneficial functions to sugarcane, including xenobiotics biodegradation and metabolism of amino acids. The bacterial and fungal compositions at various taxonomic levels were not significantly different in SPF and SP (pesticide only) treatments compared to treatments without the pesticide, suggesting that the clothianidin addition did not cause a detrimental impact on the soil microbiome. Moreover, five bacterial genera, including Dyella, Sphingomonas, Catenulispora, Mucilaginibacter, and Tumebacillus, were significantly more abundant in the SPF and SP treatments, which could be associated with the pesticide addition. With the addition of organic fertilizers in SPF, the abundances of some soil-beneficial bacteria Bacillus, Paenibacillus, and Brevibacillus were highly increased. Our study provides insights into the interactions between the rhizosphere soil microbiome and pesticide-fertilizer integration, which may help improve the application of pesticide-fertilizer to sugarcane fields. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s13205-021-02770-3.

The effects of agricultural pesticide exposure upon honey bee colonies is of increasing interest to beekeepers and researchers, and the impact of neonicotinoid pesticides in particular has come under intense scrutiny. To explore potential colony-level effects of a neonicotinoid pesticide at field-relevant concentrations, honey bee colonies were fed 5- and 20-ppb concentrations of clothianidin in sugar syrup while control colonies were fed unadulterated syrup. Two experiments were conducted in successive years at the same site in southern Arizona, and one in the high rainfall environment of Mississippi. Across all three experiments, adult bee masses were about 21% lower among colonies fed 20-ppb clothianidin than the untreated control group, but no effects of treatment on brood production were observed. Average daily hive weight losses per day in the 5-ppb clothianidin colonies were about 39% lower post-treatment than in the 20-ppb clothianidin colonies, indicating lower consumption and/or better foraging, but the dry weights of newly-emerged adult bees were on average 6–7% lower in the 5-ppb group compared to the other groups, suggesting a nutritional problem in the 5-ppb group. Internal hive CO2 concentration was higher on average in colonies fed 20-ppb clothianidin, which could have resulted from greater CO2 production and/or reduced ventilating activity. Hive temperature average and daily variability were not affected by clothianidin exposure but did differ significantly among trials. Clothianidin was found to be, like imidacloprid, highly stable in honey in the hive environment over several months.

SummaryGlobally, neonicotinoids are still the most used insecticides, despite their well-documented sub-lethal effects on beneficial insects1. Neonicotinoids are agonists at the nicotinic acetylcholine receptors, the main mediator of synaptic transmission in the insect brain2–5, making them highly potent neurotoxins and insecticides6,7. Memory, circadian rhythmicity and sleep are essential for efficient foraging in many pollinating insects, and involve nicotinic acetylcholine receptor signalling2,4,8–10. The effect of field-relevant concentrations of European Union-banned neonicotinoids: imidacloprid, clothianidin and thiamethoxam, as well as the currently unbanned thiacloprid were tested on Drosophila memory, circadian rhythms and sleep. Field-relevant concentrations of imidacloprid, clothianidin and thiamethoxam disrupted learning, behavioural rhythmicity and sleep whilst thiacloprid exposure only affected sleep. Exposure to imidacloprid and clothianidin directly affected neurophysiology, preventing the day/night remodelling and accumulation of pigment dispersing factor neuropeptide in the dorsal terminals of clock neurons. Knockdown of the neonicotinoid susceptible Dα1 and Dβ2 nicotinic acetylcholine receptor subunits in the mushroom bodies or clock neurons recapitulated the neonicotinoid like deficits in memory or circadian/sleep behaviour demonstrating that neonicotinoid effects are likely mediated in the mushroom body and clock circuitry. Disruption to learning, circadian rhythmicity and sleep are likely to have far-reaching detrimental effects on beneficial insects in the field.

Background A new generation of IRS insecticides which can provide improved and prolonged control of pyrethroid-resistant malaria vector populations are being developed. Fludora® Fusion is a new IRS insecticide containing a mixture of deltamethrin and clothianidin, a neonicotinoid. Methods The efficacy of Fludora® Fusion IRS was evaluated over 11–12 months on concrete and mud substrates in laboratory bioassays and experimental huts against wild free-flying pyrethroid-resistant Anopheles gambiae (sensu lato) in Cové, Benin. A comparison was made with the two active ingredients of the mixture; clothianidin and deltamethrin, applied alone. CDC bottle bioassays were also performed to investigate resistance to clothianidin in the wild vector population. Results Fludora® Fusion induced > 80% laboratory cone bioassay mortality with both susceptible and pyrethroid-resistant An. gambiae (s.l.) for 7–9 months on concrete block substrates and 12 months on mud block substrates. The vector population at the experimental hut site was fully susceptible to clothianidin in CDC bottle bioassays. Overall mortality rates of wild free-flying pyrethroid-resistant An. gambiae (s.l.) entering the experimental huts during the 11-month trial were 80%) only declined by 50% after 8 months. Monthly in situ wall cone bioassay mortality of susceptible mosquitoes was > 80% for 9–12 months with Fludora® Fusion and clothianidin alone. Fludora® Fusion induced significantly higher levels of early exiting of mosquitoes compared to clothianidin alone (55–60% vs 37–38%, P Conclusions Indoor residual spraying with Fludora® Fusion induced high and prolonged mortality of wild pyrethroid-resistant malaria vectors for 7–10 months mostly due to the clothianidin component and substantial early exiting of mosquitoes from treated huts due to the pyrethroid component. Fludora® Fusion is an important addition to the current portfolio of IRS insecticides with the potential to significantly reduce transmission of malaria by pyrethroid-resistant mosquito vectors.

Background: Large amounts of insecticide-containing dusts produced from abrasion of the seed dressing can be released into the atmosphere during sowing operations. Neonicotinoid pesticides, introduced in the 1990s for several crops, are the leading products for seed-coating treatments in many countries. Neonicotinoid containing dusts can be efectively intercepted by bees in fight over the sowing feld, inducing lethal acute efects, so that restrictions in the use of the main neonicotinoids have been adopted in the European Union. This led to the consequent introduction of replacement insecticides for seed-coating, i.e. methiocarb and thiacloprid, despite the lack of information on both the toxicity and the exposure scenarios for honeybees. Results: In this study, a laboratory apparatus was developed in order to quantify the toxicity of the dusts produced from the abrasion of the seed coating. This quantifcation is based on (i) an airstream transporting coating particles into an exposure chamber; (ii) exposure of bees to reproducible and measurable concentrations of insecticide, and (iii) direct measurement of the exposure dose on single bees. The method allowed us to perform in vivo experiments of honeybee exposure to provide toxicity data in more realistic exposure conditions. In fact, the formulation rather than the active principle alone can be tested, and the exposure is through dusts rather than a solution so that specifc absorption behavior can be studied in representative environmental conditions. The method was used to quantify the acute toxicity (LD50) of dusts obtained from the abrasion of corn seeds coated with clothianidin, thiacloprid and methiocarb. Conclusions: Our results show that, surprisingly, the replacement insecticide methiocarb has a toxicity (LD50=421– 693 ng/bee) in the same order of magnitude as clothianidin (LD50=113–451 ng/bee) through this specifc exposure route, while thiacloprid (LD50=16.9·103 ng/bee) has a signifcantly lower acute toxicity. Moreover, dusts containing methiocarb and clothianidin show a signifcant increase in toxicity when, after exposure, bees are kept under high humidity conditions. This suggests that the method here presented can be used to obtain complementary toxicity data in the risk assessment procedure for the authorization of new seed-coating insecticides or new formulations. Keywords: Systemic insecticides, Neonicotinoids, Methiocarb, Seed coating, Abrasion dusts, Honeybees, Pollinator insects, Acute toxicity, Exposure measurement

Neonicotinoid insecticides are widely used replacements for organophosphate and carbamate insecticides, but the extent of human exposure is largely unknown. On the other hand, based on urinary concentrations of DEET metabolites, human exposure to N,N-diethyl-m-toluamide (DEET) appears to be widespread. We developed a fast online solid-phase extraction high-performance liquid chromatography-isotope dilution tandem mass spectrometry (HPLC-MS/MS) method to measure in 200 μL of human urine the concentrations of six neonicotinoid biomarkers (acetamiprid, N-desmethyl-acetamiprid, clothianidin, imidacloprid, 5-hydroxy-imidacloprid, thiacloprid), and two DEET biomarkers (3-diethyl-carbamoyl benzoic acid, 3-ethyl-carbamoyl benzoic acid). Limits of detection ranged from 0.01 to 0.1 μg/L, depending on the biomarker. Accuracy ranged from 91 to 116% and precision ranged from 3.7 to 10 %RSD. The presented method can be used to increase our understanding of exposure to neonicotinoid insecticides and DEET, and to evaluate the potential health effects from such exposures.

Neonicotinoid insecticides have been reported to occur widely in surface waters, including those of wetlands within the Prairie Pothole Region (PPR). In the US portion of the PPR, the US Fish and Wildlife Service has established Waterfowl Production Areas (WPAs) in an effort to enhance waterfowl production. Most WPAs have an area of protected upland surrounding wetlands that can act as a buffer to reduce the transport of contaminants, including pesticides. We assessed the extent that neonicotinoid insecticides occurred in the ponded water of wetlands within WPAs located along a gradient of agricultural influence throughout west-central Minnesota. Of the five neonicotinoids we tested for, two were not detected. However, at least one of the other three, imidacloprid, clothianidin and thiamethoxam, were detected in 29% of our wetland water samples. Additionally, both the occurrence and total concentrations of neonicotinoids were higher in sites with higher surrounding crop use. Neonicotinoid insecticides, if persistent for long periods of time, have the potential to affect aquatic-invertebrate communities within PPR wetlands. Our research indicates that areas often perceived as protected may still be at risk to neonicotinoid contamination, emphasizing the importance of maintaining effective grassland buffers around wetlands.

In this study, quick, easy, cheap, effective, rugged, and safe (QuEChERS) method coupled with liquid chromatography-tandem mass spectrometry (LC-MS/MS) was applied and optimized in determination of 34 commonly used pesticides in black pepper. Two cleanup approaches including dispersive solid-phase extraction (d-SPE) and dispersive solid liquid extraction (d-SLE) were investigated and compared. The results showed that for d-SPE method, 26 target pesticides met the analytical recovery and RSD requirements (recoveries 60–120%, RSDs 2–28%) and LODs were 0.5–1 μg/kg, while for d-SLE method, 19 target pesticides met the analytical requirements (recoveries 60–117%, RSDs 3–24%) and the LODs were 0.5–2.5 μg/kg. Cleanup by d-SLE showed lower matrix effects and lower sensitivity due to the dilution factor, while d-SPE method could be applicable to more pesticides due to better sensitivity. It was therefore decided that d-SPE cleanup would be used in the final method for multi-residue analysis in black pepper. The method was developed and validated to determine the residues of 34 pesticides in 15 black pepper market samples collected from 11 different provinces in China. Four pesticides were detected, including clothianidin (0.02 mg/kg) that was detected in one sample and acetamiprid (

In this study, the effect of the four different insecticides Karate Zeon (a.i. lambda-cyhalothrin), Elado (clothianidin + beta-cyfluthrin), Fortenza Force (cyantraniliprole + tefluthrin) (only 2015), and Lumiposa (cyantraniliprole) (only 2016 and 2017) on the insect autumn pests Delia radicum, Psylliodes chrysocephala, and aphids (mainly Myzus persicae) and Turnip Yellows Virus in winter oilseed rape was investigated in 3 years of field trials. The results showed that the effects of the Elado seed treatment on P. chrysocephala depend on the time of migration of adults. Due to delayed immigration of beetles into the field in 2015/2016 and 2017/2018, there was no clear effect of the seed treatment on the number of larvae per plant. In contrast in 2016/2017, the beetles colonized the crop in early September, and the number of larvae was significantly reduced by Elado. Cyantraniliprole and clothianidin seed treatments seem to support crop emergence independent of insect pests assessed. Spraying of the pyrethroid Karate Zeon in autumn significantly decreased the number of larvae in all years. Also the number of next-generation beetles was significantly reduced only by Karate Zeon. In all years, the aphid infestation was significantly reduced only by Elado seed treatment. The infection rate by TuYV was very high in all years and only slightly reduced by Elado seed treatment. There was only minimal occurrence of Delia radicum in all years. Cyantraniliprole products did not show any influence on the assessed insect pests in all years. There was no significant effect of any treatment on yield, but in 2015/2016 and 2016/2017, the highest yield was obtained in the Elado seed treatment.

China is ranked first by greenhouse area in the world; pesticide application using knapsack electric sprayers is the main tool used in these settings to prevent and control plant diseases and insect pests. This is the first report of an exposure assessment for 60 greenhouse operators to the insecticide clothianidin when applied with knapsack electric sprayers. The commercial clothianidin formulation used in the field trials was a 20% suspension concentrate. The assessment was based on the whole-body dosimetry method and a personal air sampler fitted with an XAD-2 resin tube located in the operator’s breathing zone to monitor dermal and inhalation exposure, respectively. During application, the total dermal unit exposure was 598.71 mg/kg. The leg was the largest exposure area, accounting for about 53% of total dermal exposure. Meanwhile, inhalation exposure was only 0.50 mg/kg. The margin of exposure was much greater than 100 in all cases, indicating that the risk is controllable with the use of protection equipment and comparable to that of the manual application of treated soil.

The use of neonicotinoid insecticides in agriculture is now recognized for the health risks it poses to non-target wildlife, with associated honey bee mortality especially concerning. Research directed toward the presence and effects of these pesticides on terrestrial vertebrates that consume neonicotinoid-coated seeds, such as wild turkeys (Meleagris gallopavo silvestris), is lacking. This study used liquid chromatography attached to a tandem mass spectrometer to assess the liver from 40 wild turkeys for neonicotinoid and other pesticide residues and compared detected levels of these contaminants across the southern Ontario, Canada. Nine (22.5%) wild turkeys had detectible levels of neonicotinoid residues-clothianidin in eight, and thiamethoxam in three. Two (5.0%) of these turkeys had detectable levels of both clothianidin and thiamethoxam. Fuberidazole was detected in two (5.0%) wild turkeys. The highest level of thiamethoxam detected was 0.16 ppm, while clothianidin was detected at 0.12 ppm, and fuberidazole at 0.0094 ppm. Knowledge of exposure in free-ranging wildlife is critical for better understanding the effects of neonicotinoids on wildlife health; thus, these data help establish baseline data for southern Ontario wild turkeys and provide context for reference values in future analyses.

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.

A study was initiated to investigate a fast and reliable method for the determination of selected systemic insecticides in water matrixes and to evaluate potential sources of bias in their analysis. Acetamiprid, clothianidin, desnitro-imidacloprid, dinotefuran, fipronil, imidacloprid, nitenpyram, thiacloprid, and thiamethoxam were amenable to analysis via on-line sample enrichment hyphenated to ultra-high-performance liquid chromatography tandem mass spectrometry. The selection of on-line solid-phase extraction parameters was dictated by a multicriterion desirability approach. A 2-mL on-line injection volume with a 1500 μL min−1 loading flow rate met the objectives sought in terms of chromatographic requirements, extraction efficiency, sensitivity, and precision. A total analysis time of 8 min per sample was obtained with method limits of detection in the range of 0.1–5 ng L−1 for the scope of targeted analytes. Automation at the sample concentration step yielded intraday and interday precisions in the range of 1–23 and 2–26%, respectively. Factors that could affect the whole method accuracy were further evaluated in matrix-specific experiments. The impact of the initial filtration step on analyte recovery was evaluated in ultra-pure water, tap water, and surface water. Out of the nine membranes tested, glass fiber filters and polyester filters appeared as the most appropriate materials. Sample storage stability was also investigated across the three matrix types; the targeted analytes displayed suitable stability during 28 days at either 4 °C or − 20 °C, with little deviations (± 10%) with respect to the initial T0 concentration. Method applicability was demonstrated in a range of tap water and surface water samples from the province of Quebec, Canada. Results from the present survey indicated a predominance of thiamethoxam (

Clothianidin is a widely used insecticide under Indian subtropical condition. The objective of this study was to generate residue data which aims to understand leaching potential of clothianidin [(E)-1-(2-chloro-1,3-thiazol-5-ylmethyl)-3-methyl-2- nitroguanidine] through packed soil column. The maximum amount of clothianidin was recovered at 0-5 cm soil depth in both Manipur (67.15%) and Delhi soil (52.0%) under continuous flow condition. Manipur and Delhi soil concentrated maximum residue with or without farm yard manure (FYM) in 0-20 cm soil depth. The effect of varying the amount of water enhanced the distribution of residues in the first 0-5 cm layer. Among the tested soils, residue was detected in the leachate from Delhi soil (0.04 µg/mL). Clothianidin leaching was minimized in soil of Manipur compared to Delhi after incorporation of FYM. As the volume of water increased upto 160 mL, mobility increased and residues moved to lower depth. Clothianidin did not leach out of the 25 cm long soil columns even after percolating water equivalent to 415.42 mm rainfall. Clothianidin is mobile in soil system and mobility can be reduced by organic amendment application.

Surface waters are sometimes contaminated with neonicotinoids: a widespread, persistent, systemic class of insecticide with leaching potential. Previous ecotoxicological investigations of this chemical class in aquatic ecosystems have largely focused on the impacts of the neonicotinoid imidacloprid; few empirical, manipulative studies have investigated the effect on invertebrate abundances of two other neonicotinoids which are now more widely used: clothianidin and thiamethoxam. In this study, we employ a simple microcosm semi-field design, incorporating a one-off contamination event, to investigate the effect of these pesticides at field-realistic levels (ranging from 0 to 15 ppb) on invertebrate colonisation and survival in small ephemeral ponds. In line with previous research on neonicotinoid impacts on aquatic invertebrates, significant negative effects of both neonicotinoids were found. There were clear differences between the two chemicals, with thiamethoxam generally producing stronger negative effects than clothianidin. Populations of Chironomids (Diptera) and Ostracoda were negatively affected by both chemicals, while Culicidae appeared to be unaffected by clothianidin at the doses used. Our data demonstrate that field-realistic concentrations of neonicotinoids are likely to reduce populations of invertebrates found in ephemeral ponds, which may have knock on effects up the food chain. We highlight the importance of developing pesticide monitoring schemes for European surface waters.

There is a great concern about the decline of pollinators, and neonicotinoids emerging bee disorders are assumed to play a significant role. Since changes in learning ability has been observed in honey bees exposed to some acetylcholine esterase (AChE) inhibitors, we therefore, tested in vitro the effect of four neonicotinoids on purified eel AChE. AChE activity was inhibited in a concentration-dependent manner, and calculated IC50 values for thiamethoxam (IC50 = 414 μM) and clothianidin (IC50 = 160 μM) were found to be much higher compared to acetamiprid (IC50 = 75.2 μM) and thiacloprid (IC50 = 87.8 μM). The Lineweaver-Burk reciprocal plots for acetamiprid shows unchanged Vmax and increased Km values with inhibitor concentrations, while analysis of Michaelis-Menten plots shows predominantly competitive mechanism. The inhibition constant value (Ki = 24.3 μM) indicates strong binding of the acetamiprid complex to AChE. Finally, the four tested neonicotinoids are not a uniform group regarding their blocking ability. Our results suggest a previously not established, direct AChE blocking mechanism of neonicotinoids tested, thus the neuronal AChE enzyme is likely among the direct targets of the neonicotinoid insecticides. We conclude, that these AChE inhibitory effects may also contribute to toxic effects on the whole exposed animal.

A robust analytical method for simultaneously determining five neonicotinoid insecticides (clothianidin, dinotefuran, imidacloprid, thiacloprid, and thiamethoxam) in commonly consumed edible fungi (Agaricus bisporus, Flammulina velutipes, Hypsizygus marmoreus, Lentinus edodes, and Pleurotus eryngii) was provided in the present study. Samples were pretreated using a modified QuEChERS (quick, easy, cheap, efficient, rugged, and safe) method with the detection of neonicotinoids by ultrahigh-performance liquid chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS). A number of optimizations performed to sample pretreatment and detection conditions were discussed. Limits of detection (LODs) for all analytes in edible fungi were between 0.03 and 0.7 μg kg−1, while limits of quantitation (LOQs) ranged from 0.1 to 2 μg kg−1. Mean recoveries for clothianidin, dinotefuran, imidacloprid, thiacloprid, and thiamethoxam were in the range of 100.5–118.0, 73.9–89.5, 88.6–117.8, 72.9–121.8, and 98.9–117.2%, respectively, with RSDs less than 8.1%. This method could be used for fast screen of the five neonicotinoid insecticides in edible fungi for risk assessing aims.

A new method has been developed and validated to determine potential differences in thiamethoxam and its metabolite (clothianidin) contents in treated rapeseed samples, which were stored under different conditions of light exposure and temperature (protected at 20 and 30 °C; unprotected at 30 °C), using liquid chromatography coupled to a diode array detector. An efficient extraction procedure has also been proposed (average analytes recoveries were between 82 and 104%); this involved a solvent extraction using a mixture of acetonitrile and sodium chloride (60:40, v/v), centrifugation, and a concentration step in a rotary evaporator. The chromatographic analysis of the compounds was achieved using a core-shell technology-based column (Kinetex C18, 150 × 4.6 mm, 2.6 μm, 100 A). The mobile phase consisted of 0.1% formic acid in water and 0.1% of formic acid in acetonitrile (25:75, v/v), with a flow rate of 0.5 mL/min in isocratic elution mode. The method was fully validated in terms of selectivity, limits of detection, and quantification, as well as matrix effect, linearity, precision, and trueness. Finally, the developed methodology was applied to determine thiamethoxam and clothianidin content in rapeseed samples, which were stored under different conditions of light exposure and temperature during 100 days. The results showed that rapeseeds should be stored at 20 °C and protected from light exposure, and that the loss of thiamethoxam was directly related to the formation of clothianidin.

Polyphagous shot hole borer (PSHB) has recently invaded southern California. This beetle attacks more than 200 host tree species, including avocado (Persea americana Mill.) and many important native, urban landscape and nursery stock trees including sycamore (Platanus racemosa Nutt.), and box elder (Acer negundo L.). The beetle, along with its associated fungi, causes branch dieback and tree mortality in a large variety of tree species. Due to the severity of the impact of PSHB, short-term management tools must include chemical control options for the industry and private landowners to protect trees. We assessed the effectiveness of systemic and contact insecticides for control of PSHB in laboratory tests using fresh-cut castor bean (Ricinus communis L.) branches. Castor bean was chosen because, as a weedy species, it is widely available, and it is a preferred host for the beetles. We conducted field tests using mature, weedy, infested field-grown castor bean. We also surveyed infested coral trees (Erythrina corallodendron L.) in an established residential landscape. For field-grown infested castor bean, beetle activity was lowest for plants treated with bifenthrin, imidacloprid and dinotefuran. Bifenthrin was the most effective insecticide for reducing beetle attacks and gallery formation in castor bean branches in laboratory experiments with cut branches. Dinotefuran was more variable in effectiveness in laboratory trials. Fenpropathrin, clothianidin and orange oil extracts did not differ from untreated controls in beetle attacks and gallery formation. Based on these results, bifenthrin and imidacloprid were selected for further testing in combination with fungicides for control of PSHB.

A new DP AdSV method was developed for the determination of the pesticide clothianidin (Clo) based on its nitro group reduction at the in situ renovated bismuth bulk annular band working electrode (BiABE). Crucial point of the proposed procedure is simple and fast regeneration of the BiABE’s surface in the presence of testing solution, by application of the activation potential (E act = −1.5 V) and next short accumulation potential (E acc = −0.6 V). The voltammetric behaviour of clothianidin has been investigated by cyclic voltammetry (CV). The experimental variables such as; potential and time of activation or accumulation, pH, concentration of the supporting electrolyte, DP mode parameters and influence of possible interferences on the Clo signal response, were tested. In the optimized conditions, the peak current was proportional to the concentration of Clo over the range from 0.2 to 23.4 μmol L−1 (0.050 to 5.84 mg L−1) with R = 0.9996. The calculated value of LOD was 0.047 μmol L−1 (0.012 mg L−1) (at S/N = 3), and sensitivity was 0.094 μA/μmol L−1, for 5 s of the accumulation time. The relative standard deviation for 2 μmol L−1 of Clo was 4.2% (n = 5). The presented results were obtained without any pre-concentration time. Finally, the proposed method was successfully applied for determination of Clo in the spiked tap and river waters samples with the recovery test.

Insecticide exposure is an environmental factor of concern relating to pollinator health. Recent increases in use of systemic insecticides, particularly neonicotinoids, have led to considerable research into the potential impacts for bees of exposure to these insecticide residues via the nectar and pollen of treated crops or contaminated wild flowers. However, although the majority of bee species are ground-nesting, the risk of exposure to insecticides in soil has not yet been evaluated. Here we use the hoary squash bee (Peponapis pruinosa) as a model system to provide the first evaluation of the risk of exposure to insecticide residues in soil to ground-nesting solitary bee species. The evaluation assessed agrochemical residues from the nectar, pollen and soil from Cucurbita-crops (e.g. squash and pumpkin) grown in southern Ontario in 2016, and soil insecticide residue data collected from field crops by the Ontario government. Systemic insecticide residues were rarely detected in the nectar and pollen of Cucurbita-crops in 2016, and hazard assessment deemed these potential routes of exposure to be non-hazardous for honey bee lethal dose endpoints. In contrast, quantifiable pesticide residues were frequently detected in soil suggesting this route of exposure to be hazardous for honey bee lethal dose endpoints, leading to further assessment using probabilistic risk assessments. Concentrations of clothianidin, imidacloprid, thiamethoxam (neonicotinoid insecticides) and chlorantraniliprole (an anthranilic diamide insecticide) in soil samples were plotted to produce an environmental exposure distribution for each insecticide. A honey bee LC50 and a solitary bee LC50 endpoint were converted to exposure endpoints using the amount of soil excavated by hoary squash bees during nest construction, for both acute and chronic exposure scenarios. The probability of exceedance of each exposure endpoint was calculated and compared to an acceptable risk threshold (i.e. 5% exceedance). In the acute exposure scenario, risk to hoary squash bees was below acceptable threshold levels for all residues evaluated using the honey bee LC50, but exceeded the threshold for clothianidin and imidacloprid using the solitary bee LC50. In the chronic exposure scenario, risk from exposure to clothianidin and imidacloprid exceeded the threshold for both the honey bee and solitary bee LC50s, and for chlorantraniliprole risk only exceeded the threshold for the solitary bee LC50. Using the hoary squash bee as a model, the wider implications for other ground-nesting bees that pollinate crops was explored using insecticide residues from soil samples taken from Ontario field crops. Probabilistic risk assessments suggest that risk to ground-nesting bees is high from clothianidin residues in soils, even when exposure is acute, and substantial for both thiamethoxam and imidacloprid under chronic exposure scenarios. These results demonstrate the urgent need to consider direct exposure to pesticides in soil for ground-nesting bees as part of risk assessments and provides a potential model for evaluating risk from this type of exposure.

Background In 2017, more than 5 million house structures were sprayed through the U.S. President’s Malaria Initiative, protecting more than 21 million people in sub-Saharan Africa. New IRS formulations, SumiShield™ 50WG and Fludora Fusion™ WP-SB, became World Health Organization (WHO) prequalified vector control products in 2017 and 2018, respectively. Both formulations contain the neonicotinoid active ingredient, clothianidin. The target site of neonicotinoids represents a novel mode of action for vector control, meaning that cross-resistance through existing mechanisms is less likely. In preparation for rollout of clothianidin formulations as part of national IRS rotation strategies, baseline susceptibility testing was conducted in 16 countries in sub-Saharan Africa. Methods While work coordinated by the WHO is ongoing to develop a suitable bottle bioassay procedure, there was no published guidance regarding clothianidin susceptibility procedures or diagnostic concentrations. Therefore, a protocol was developed for impregnating filter papers with 2% w/v SumiShield™ 50WG dissolved in distilled water. Susceptibility tests were conducted using insectary-reared reference Anopheles and wild collected malaria vector species. All tests were conducted within 24 h of treating papers, with mortality recorded daily for 7 days, due to the slow-acting nature of clothianidin against mosquitoes. Anopheles gambiae sensu lato (s.l.) adults from wild collected larvae were tested in 14 countries, with wild collected F0 Anopheles funestus s.l. tested in Mozambique and Zambia. Results One-hundred percent mortality was reached with all susceptible insectary strains and with wild An. gambiae s.l. from all sites in 11 countries. However, tests in at least one location from 5 countries produced mortality below 98%. While this could potentially be a sign of clothianidin resistance, it is more likely that the diagnostic dose or protocol requires further optimization. Repeat testing in 3 sites in Ghana and Zambia, where possible resistance was detected, subsequently produced 100% mortality. Results showed susceptibility to clothianidin in 38 of the 43 sites in sub-Saharan Africa, including malaria vectors with multiple resistance mechanisms to pyrethroids, carbamates and organophosphates. Conclusions This study provides an interim diagnostic dose of 2% w/v clothianidin on filter papers which can be utilized by National Malaria Control Programmes and research organizations until the WHO concludes multi-centre studies and provides further guidance. Electronic supplementary material The online version of this article (10.1186/s12936-019-2888-6) contains supplementary material, which is available to authorized users.

Background The wetlands used for some agricultural activities constitute productive breeding sites for many mosquito species. Thus, the agricultural use of insecticide targeting other pests may select for insecticide resistance in malaria mosquitoes. The purpose of this study is to clarify some knowledge gaps on the role of agrochemicals in the development of insecticide resistance in malaria vectors is of utmost importance for vector control. Methods Using the CDC bottle test and the log-probit analysis, we investigated for the first time the resistance levels of Anopheles coluzzii mosquitoes to neonicotinoids, insecticides used exclusively for crop protection in Côte d’Ivoire. The study was conducted in two agricultural regions (Tiassale and Gagnoa) and one non-agricultural region (Vitre) between June and August 2017 using clothianidin, acetamiprid and imidacloprid. Results Mosquito populations from Tiassale and Gagnoa (agricultural settings) were determined to be resistant to acetamiprid with mortality rates being

Background Neonicotinoids are a class of systemic insecticides widely used on food crops globally. These pesticides may be found in “off-target” food items and persist in the environment. Despite the potential for extensive human exposure, there are limited studies regarding the prevalence of neonicotinoid residues in foods sold and consumed in the United States. Methods Residue data for seven neonicotinoid pesticides collected between 1999 and 2015 by the US Department of Agriculture’s Pesticide Data Program (PDP) were collated and summarized by year across various food commodities, including fruit, vegetable, meat, dairy, grain, honey, and baby food, as well as water to qualitatively describe and examine trends in contamination frequency and residue concentrations. Results The highest detection frequencies (DFs) for neonicotinoids by year on all commodities were generally below 20%. Average DFs over the entire study period, 1999–2015, for domestic and imported commodities were similar at 4.5%. For all the samples (both domestic and imported) imidacloprid was the neonicotinoid with the highest overall detection frequency at 12.0%. However, higher DFs were observed for specific food commodity-neonicotinoid combinations such as: cherries (45.9%), apples (29.5%), pears (24.1%) and strawberries (21.3%) for acetamiprid; and cauliflower (57.5%), celery (20.9%), cherries (26.3%), cilantro (30.6%), grapes (28.9%), collard greens (24.9%), kale (31.4%), lettuce (45.6%), potatoes (31.2%) and spinach (38.7%) for imidacloprid. Neonicotinoids were also detected in organic commodities, (DF