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Exposure to pesticides is one potential factor contributing to the recent loss of pollinators and pollinator diversity. Few studies have specifically focused on the relationship between pesticide management during ornamental plant production and contamination of nectar. We evaluated contamination of nectar in Salvia 'Indigo Spires' (Salvia longispicata M. Martens & Galeotti × S. farinacea Benth.) associated with applications of the systemic insecticide thiamethoxam, and the nonsystemic fungicides boscalid and pyraclostrobin. Applications were made at the labeled rates for the commercially available products, and we compared the influence of application method (drench vs. spray), timing (relative to flowering), and rate (low vs. high) for each pesticide. Nectar was sampled using 50‐µL microcapillary tubes and analyzed by liquid chromatography–tandem mass spectrometry. The results indicate that concentrations from the spray application resulted in the least contamination of nectar with the systemic thiamethoxam, with lower concentrations occurring when thiamethoxam was applied before blooming at the lowest rate. Concentrations of thiamethoxam and its metabolite clothianidin were detected in nectar in all treatments (regardless of the method, timing, or rate of application), and ranged from 3.6 ± 0.5 ng/mL (spray‐applied before blooming, low rate) to 1720.0 ± 80.9 ng/mL (drench‐applied after blooming, high rate). Residues of clothianidin in nectar ranged from below quantification limits (spray‐applied before blooming, low rate) to 81.2 ± 4.6 ng/mL (drench‐applied after blooming, high rate). Drench applications resulted in the highest levels of nectar contamination with thiamethoxam, and exceeded published median lethal concentrations (LC50s/median lethal doses for native bees and/or honeybees in all cases). Spray treatments resulted in nectar concentrations exceeding published LC50s for some bee species. In comparison, all nonsystemic treatments resulted in concentrations much lower than the published no‐observable‐effect doses and sublethal toxicity values, indicating low risks of toxicity. Environ Toxicol Chem 2024;43:2616–2627. © 2024 SETAC [ABSTRACT FROM AUTHOR]

Data from prior research indicate the prepupal stage of the monarch butterfly life cycle is more sensitive to clothianidin exposure than the larval stage. A set of experiments was conducted to determine if the dietary clothianidin exposures that cause prepupal mortality are environmentally relevant. Monarch larvae were raised from egg to pupae on clothianidin‐contaminated swamp milkweed plants (Asclepias incarnata). Larval growth as well as larval and prepupal survival were monitored throughout the experiments, in which the exposures ranged from 1.4 to 2793.1 ng/g leaf. Exposures of 5.4 to 46.9 ng/g leaf resulted primarily in prepupal mortality, whereas higher exposures of 1042.4 to 2793.1 ng/g leaf resulted exclusively in larval mortality, indicating the prepupal stage is more sensitive to clothianidin exposure than the larval stage. A median lethal concentration and a 10% lethal concentration of 37 and 6 ng/g leaf, respectively, were estimated for prepupal mortality. Both effect concentrations are within the range of clothianidin concentrations reported in leaves collected from wild milkweed plants, indicating prepupal mortality is an environmentally relevant effect. Environ Toxicol Chem 2024;43:2039–2044. © 2024 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC. [ABSTRACT FROM AUTHOR]

Neonicotinoids have been among the most widely and abundantly used insecticides for most of the current century. The effects of these substances on nontarget terrestrial and aquatic organisms have resulted in a significant decrease in their use in many parts of the world. In response, the application of several novel classes of insecticides including diamides, ketoenols, pyridines, and butenolides has significantly increased. The hexapod subclass Collembola is an ecologically significant and widely distributed group of soil invertebrates often found in leaf litter and in surficial soils. We exposed the parthenogenic collembolan species Folsomia candida to six insecticides in a sandy loam soil for 28 days, including two neonicotinoids (thiamethoxam and clothianidin), a diamide (cyantraniliprole), a ketoenol (spirotetramat), a pyridine (flonicamid), and a butanolide (flupyradifurone) to assess the effect of each insecticide on survival and reproduction. Clothianidin, thiamethoxam, and cyantraniliprole (median effective concentration [EC50] values for reproduction: 0.19, 0.38, and 0.49 mg/kg soil, respectively) had a greater effect on survival and reproduction of F. candida than flupyradifurone, spirotetramat, and flonicamid (EC50 values for reproduction: 0.73, >3.08, and 5.20 mg/kg soil, respectively). All significant impacts found in our study were observed at concentrations below concentrations of the active ingredients that would be expected in agricultural soils. Environ Toxicol Chem 2023;42:1516–1528. © 2023 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC. [ABSTRACT FROM AUTHOR]

In 2018 the European Union (EU) banned the three neonicotinoid insecticides imidacloprid, clothianidin (CLO), and thiamethoxam (TMX), but they can still be used if an EU Member State issues an emergency approval. Such an approval went into effect in 2021 for TMX‐coated sugar beet seeds in Germany. Usually, this crop is harvested before flowering without exposing non‐target organisms to the active ingredient or its metabolites. In addition to the approval, strict mitigation measures were imposed by the EU and the German federal states. One of the measures was to monitor the drilling of sugar beet and its impact on the environment. Hence we took residue samples from different bee and plant matrices and at different dates to fully map beet growth in the German states of Lower Saxony, Bavaria, and Baden‐Württemberg. A total of four treated and three untreated plots were surveyed, resulting in 189 samples. Residue data were evaluated using the US Environmental Protection Agency BeeREX model to assess acute and chronic risk to honey bees from the samples, because oral toxicity data are widely available for both TMX and CLO. Within treated plots, we found no residues either in pools of nectar and honey crop samples (n = 24) or dead bee samples (n = 21). Although 13% of beebread and pollen samples and 88% of weed and sugar beet shoot samples were positive, the BeeREX model found no evidence of acute or chronic risk. We also detected neonicotinoid residues in the nesting material of the solitary bee Osmia bicornis, probably from contaminated soil of a treated plot. All control plots were free of residues. Currently, there are insufficient data on wild bee species to allow for an individual risk assessment. In terms of the future use of these highly potent insecticides, therefore, it must be ensured that all regulatory requirements are complied with to mitigate any unintentional exposure. Environ Toxicol Chem 2023;42:1167–1177. © 2023 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC. [ABSTRACT FROM AUTHOR]

Recently, the high toxicity of neonicotinoids to the survival and reproduction of adult earthworms has become apparent in standard 56‐day toxicity tests. The persistence of some neonicotinoids and/or their repeated application may lead to long‐term exposure, possibly also affecting other parts of the life cycle of earthworms. The present study aimed at providing insight into the sublethal effects of imidacloprid, thiacloprid, and clothianidin on juvenile Eisenia andrei exposed for 16 weeks in Lufa 2.2 soil. Significant effects on growth and maturation were observed for all compounds. Exposure to 0.125 mg imidacloprid/kg dry soil and 0.03125 and 0.0625 mg thiacloprid/kg dry soil significantly affected the growth of the earthworms, while significant maturation effects were observed at 0.03125 mg/kg dry soil for imidacloprid and thiacloprid and 0.25 mg clothianidin/kg dry soil. The 16‐week no‐observed‐effect concentrations (NOECs) found in the present study were lower than previously reported NOECs for effects on earthworm reproduction. Predicted environmental concentrations after a single application exceeded the observed NOECs for effects on earthworm maturation in the case of imidacloprid and thiacloprid and for effects on earthworm growth in the case of thiacloprid and clothianidin. Environ Toxicol Chem 2022;41:1686–1695. © 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC. [ABSTRACT FROM AUTHOR]

Polar organic chemical integrative sampler (POCIS) devices have been suggested for measuring time‐weighted averages (TWAs) of contaminant concentrations resulting from chemical leak accidents in aquatic environments. However, the response of the POCIS device in the emergency condition in natural water remains unclear. The response of the POCIS device to contaminant fluctuation was investigated using a chamber test with tap water and a channel test with natural water. The fluctuation in the chamber and the channel simulated the condition of river water under a chemical leak scenario (maximum concentration: 1–10 μg L–1, half‐life: 1 day). The target chemicals were neonicotinoid pesticides (dinotefuran, clothianidin, thiamethoxam, imidacloprid, acetamiprid, and thiacloprid) and bisphenol A. The ratio of the POCIS measured value to the TWA values of grab samplings (POCIS/TWA) for the channel test (temperature: 15 °C, flow velocity: 15 cm s–1) ranged from 61% (clothianidin) to 133% (thiacloprid). The results indicated that the POCIS device could be effectively used as a monitoring device in an aquatic environment under the chemical leak scenario over a time period of more than14 days. In addition, the POCIS/TWA ratios obtained from the chamber test and the channel test were in the range of 50–150%. Thus, the chamber test could be used to evaluate the POCIS device at a low cost. Environ Toxicol Chem 2021;40:3010–3018. © 2021 SETAC [ABSTRACT FROM AUTHOR]

Bumblebees can be exposed to neonicotinoid pesticides through nectar and pollen collected from treated crops, which can cause lethal and sublethal effects in these nontarget pollinators. However, the body distribution of the compound after exposure to neonicotinoids in bumblebees is not well studied. Bumblebee colonies (Bombus terrestris, n = 20) were exposed to field‐realistic concentrations of clothianidin through artificial nectar (3.6–13 µg/L) for 9 d. Comparison of the nominal with the measured exposure in nectar indicated good compliance, confirming the applicability of the method. When quantified, clothianidin showed a concentration‐dependent occurrence in the head and body of workers (head: <0.2–2.17 µg/kg; body: <0.2–3.17 µg/kg), and in the body of queens (<0.2–2.49 µg/kg), although concentrations were below those measured in the nectar (bioaccumulation factor = 0.2). Exposure to clothianidin did not affect mortality nor brood production, nor did it have a statistically significant effect on nectar consumption and size of food storage. However, visual inspection suggests higher nectar consumption of nectar with low clothianidin content compared with nectar with no or high clothianidin content. Our results show that dietary clothianidin is taken up in bumblebees, but does not bioaccumulate to elevated levels compared with exposure. Still, clothianidin may elicit responses that affect feeding behavior of the pollinator B. terrestris, although our endpoints were not significantly affected. Environ Toxicol Chem 2021;40:2781–2790. © 2021 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC. [ABSTRACT FROM AUTHOR]

Neonicotinoid insecticides (NNIs) are now popular in many agricultural systems across Africa; however, the extent of human exposures to NNIs in African countries is scarcely reported. The present study evaluates neonicotinoid exposures in the consumer population of Kumasi, a cosmopolitan city in Ghana. A total of 75 human urine samples were collected from healthy volunteers (nonfarmers, aged 13–80 yr) and analyzed with a liquid chromatography electrospray ionization tandem mass spectrometry system. Seven NNIs and 3 NNI metabolites were detected in the following pattern (frequency, median concentration, maximum concentration): N‐dm‐acetamiprid (94.7%, 0.41 µg/L, 8.79 µg/L) > imidacloprid (70.7%, 0.15 µg/L, 211.62 µg/L) > N‐(6‐chloro‐3‐pyridylmethyl)‐N‐ethyl‐N′‐methylformamidine (62.2%, 0.43 µg/L, 53.85 µg/L) > 2‐[N‐(6‐chloro‐3‐pyridylmethyl)‐N‐ethylamino]‐2‐(methylimino)acetic acid (56.8%, 0.10 µg/L, 3.53 µg/L) > clothianidin (40%, >limit of quantification [LOQ], 0.45 µg/L) > nitenpyram (18.7%, >LOQ, 0.14 µg/L) ≈ thiamethoxam (18.7%, >LOQ, 0.21 µg/L) > dinotefuran (12.0%, >LOQ, 1.01 µg/L) > acetamiprid (2.7%, >LOQ, 0.08 µg/L) ≈ thiacloprid (2.7%, >LOQ, 0.14 µg/L). Approximately 92% of the subjects were found to be exposed to multiple neonicotinoids simultaneously. The mean, median, and maximum imidacloprid equivalent of the relative potency factor of NNIs were found to be 1.6, 0.5, and 22.52, respectively. The median estimated daily intakes of acetamiprid, imidacloprid, and nitenpyram were 0.47, 1.27, and 0.02 µg/kg/d for females and 0.91, 0.66, and 0.08 µg/kg/d for males, respectively. The maximum daily intakes of all the NNIs were <1% of their chronic reference doses (cRfDs), except for imidacloprid and thiacloprid which recorded maximum daily intakes corresponding to 17.97 and 8.28% of cRfDs, respectively. To the best of our knowledge, the present study is the first biomonitoring report on neonicotinoid insecticides in Africa. Environ Toxicol Chem 2021;40:2306–2318. © 2021 SETAC [ABSTRACT FROM AUTHOR]

Most corn (Zea mays) seeds planted in the United States in recent years are coated with a seed treatment containing neonicotinoid insecticides. Abrasion of the seed coating generates insecticide‐laden planter dust that disperses through the landscape during corn planting and has resulted in many "bee‐kill" incidents in North America and Europe. We investigated the linkage between corn planting and honey bee colony success in a region dominated by corn agriculture. Over 3 yr we consistently observed an increased presence of corn seed treatment insecticides in bee‐collected pollen and elevated worker bee mortality during corn planting. Residues of seed treatment neonicotinoids, clothianidin and thiamethoxam, detected in pollen positively correlated with cornfield area surrounding the apiaries. Elevated worker mortality was also observed in experimental colonies fed field‐collected pollen containing known concentrations of corn seed treatment insecticides. We monitored colony growth throughout the subsequent year in 2015 and found that colonies exposed to higher insecticide concentrations exhibited slower population growth during the month of corn planting but demonstrated more rapid growth in the month following, though this difference may be related to forage availability. Exposure to seed treatment neonicotinoids during corn planting has clear short‐term detrimental effects on honey bee colonies and may affect the viability of beekeeping operations that are dependent on maximizing colony size in the springtime. Environ Toxicol Chem 2021;40:1212–1221. © 2020 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC. [ABSTRACT FROM AUTHOR]

The dispersion of clothianidin from treated seeds was studied in a commercial winter canola field. During planting, using a John Deere 1890 single disk air seeder, a proportion, an estimated 14.2 ± 2.9% (mean ± standard error), of the clothianidin that was applied to the seed escaped into the atmosphere from the seeder's exhaust. We suggest that this source of environmental contamination may be the main contributor that explains the off‐target detection of neonicotinoid residues in soils and water near canola plantings better than movement from seed after it is placed in the soil, which is often proposed in the literature. Environ Toxicol Chem 2020;39:2420–2423. © 2020 SETAC [ABSTRACT FROM AUTHOR]

Neonicotinoid insecticides have been shown to have high chronic toxicity relative to acute toxicity, and therefore short‐term toxicity tests ≤96 h in duration may underestimate their environmental risks. Among nontarget aquatic invertebrates, insects of the orders Diptera and Ephemeroptera have been found to be the most sensitive to neonicotinoids. To undertake a more accurate assessment of the risks posed by neonicotinoids to freshwater ecosystems, more data are needed from long‐term tests employing the most sensitive taxa. Using nymphs of the common New Zealand mayfly genus Deleatidium spp., we performed 28‐d static‐renewal exposures with the widely used neonicotinoids imidacloprid, clothianidin, and thiamethoxam. We monitored survival, immobility, impairment, and mayfly moulting propensity at varying time points throughout the experiment. Imidacloprid and clothianidin exerted strong chronic toxicity effects on Deleatidium nymphs, with 28‐d median lethal concentrations (LC50s) of 0.28 and 1.36 µg/L, respectively, whereas thiamethoxam was the least toxic, with a 28‐d LC50 > 4 µg/L (highest concentration tested). Mayfly moulting propensity was also negatively affected by clothianidin (during 3 of 4 wk), imidacloprid (2 of 4 wk), and thiamethoxam (1 of 4 wk). Comparisons with published neonicotinoid chronic toxicity data for other mayfly taxa and larvae of the midge genus Chironomus showed similar sensitivities for mayflies and midges, suggesting that experiments using these taxa provide reliable assessments of the threats of neonicotinoids to the most vulnerable freshwater species. Environ Toxicol Chem 2019;38:2459–2471. © 2019 SETAC [ABSTRACT FROM AUTHOR]

The use of neonicotinoids in agriculture is a critical environmental protection issue. Although there has been considerable research on pollinator exposure and aquatic toxicological effects, few studies have investigated the chronic impacts on soil‐dwelling species. Given the application of neonicotinoids into soil systems, there is the potential for risk to soil invertebrates. The toxicity of 2 commercial formulations containing the active ingredients (a.i.) thiamethoxam (Actara® 240SC) or clothianidin (Titan™) was investigated using 3 soil invertebrate species: Oppia nitens, Eisenia andrei, and Folsomia candida. No adverse effects were observed for O. nitens at the highest tested concentrations (≥92 mg a.i./kg dry soil) after a 28‐d exposure. Exposure to clothianidin resulted in a 28‐d median inhibitory concentration (IC50) of 0.069 (95% confidence limits: 0.039–0.12) mg/kg dry soil for F. candida, and a 56‐d IC50 of 0.26 (0.22–3.2) mg a.i./kg dry soil for E. andrei. Exposure to thiamethoxam was less toxic, with IC50s of 0.36 (0.19–0.66) and 3.0 (2.2–4.0) mg a.i./kg dry soil for F. candida and E. andrei reproduction, respectively. The observed toxicity for F. candida adult survival and reproduction and for E. andrei reproduction occurred at environmentally relevant concentrations. However, because clothianidin is a degradation product of thiamethoxam, and detection of clothianidin rose to levels of concern in the thiamethoxam‐amended soils over time, the observed toxicity may be partly attributed to the presence of clothianidin. Environ Toxicol Chem 2019;38:2111–2120. © 2019 Crown in the right of Canada. Published by Wiley Periodicals Inc. on behalf of SETAC. [ABSTRACT FROM AUTHOR]

Neonicotinoid insecticides are used extensively in agriculture and, as a consequence, are now detectable in nearby aquatic environments. Few studies have evaluated the effects of neonicotinoids on amphibians in these aquatic environments. In the present study, we examined the effects of 2 commercial formulations of neonicotinoids (active ingredients clothianidin and thiamethoxam) on survival and life‐history traits of wood frogs (Lithobates sylvaticus) and northern leopard frogs (Lithobates pipiens). We used artificial pond mesocosms to assess the effects of these neonicotinoids, at nominal concentrations of 2.5 and 250 µg/L, on amphibian larval development through metamorphosis. We found no differences between controls and neonicotinoid exposure for any of the endpoints assessed for either wood frogs or leopard frogs. The present study suggests that concentrations meeting or exceeding observed levels of clothianidin and thiamethoxam in surface waters will not directly affect metamorphosis in 2 amphibians. Environ Toxicol Chem 2019;38:1967–1977. © 2019 SETAC. [ABSTRACT FROM AUTHOR]

Neonicotinoids are widely used insecticides that are detectable in agricultural waterways. These insecticides are of concern due to their potential impacts on nontarget organisms. Pesticides can affect development of amphibians and suppress the immune system, which could impact disease susceptibility and tolerance. No previous studies on amphibians have examined the effects of these insecticides on differential blood cell proportions or concentrations of corticosterone (a general stress hormone). We investigated the effects of chronic exposure to 2 neonicotinoids, thiamethoxam and clothianidin, on immunometrics of wood frogs (Lithobates sylvaticus). Frogs were exposed to single, chronic treatments of 2.5 or 250 µg/L of clothianidin or thiamethoxam for 7 wk from Gosner stages 25 to 46. The juvenile frogs were then maintained for 3 wk post metamorphosis without exposure to neonicotinoids. We measured water‐borne corticosterone twice: at 6 d and 8 wk after exposure in larval and juvenile frogs, respectively. We assessed differential blood cell profiles from juvenile frogs. Corticosterone was significantly lower in tadpoles exposed to 250 µg/L of thiamethoxam compared with other tadpole treatments, but no significant differences in corticosterone concentrations were found in treatments using juvenile frogs. Anemia was detected in all treatments compared with controls with the exception of tadpoles exposed to 2.5 µg/L of clothianidin. Neutrophil‐to‐leukocyte and neutrophil‐to‐lymphocyte ratios were elevated in frogs exposed to 250 µg/L of thiamethoxam. Collectively, these results indicate that chronic exposure to neonicotinoids has varied impacts on blood cell profiles and corticosterone concentrations of developing wood frogs, which are indicative of stress. Future studies should investigate whether exposure to neonicotinoids increases susceptibility to infection by parasites in both larval and adult wood frogs. Environ Toxicol Chem 2019;38:1273–1284. © 2019 Crown in the right of Canada. Published by Wiley Periodicals Inc. on behalf of SETAC. [ABSTRACT FROM AUTHOR]

The insect yolk precursor vitellogenin is a lipoglycoprotein synthesized and stored in the fat body and secreted into the hemolymph. In honey bees, vitellogenin displays crucial functions in hormone signaling, behavioral transition of nurse bees to foragers, stress resistance, and longevity in workers. Plant protection products such as neonicotinoids, pyrethroids, and organophosphates alter the transcriptional expression of vitellogenin. To assess plant protection product‐induced alterations on the protein level, we developed a rabbit polyclonal vitellogenin antibody. After characterization, we assessed its specificity and vitellogenin levels in different tissues of worker bees. The vitellogenin antibody recognized full‐length 180‐kDa vitellogenin and the lighter fragment of 150 kDa in fat body, hemolymph, and brain. In hemolymph, a band of approximately 75 kDa was detected. Subsequent mass spectrometric analysis (liquid chromatography–mass spectrometry) confirmed the 180‐ and 150‐kDa bands as vitellogenin. Subsequently, we evaluated vitellogenin expression in brain, fat body, and hemolymph on 24‐h exposure of bees to 3 ng/bee to the neonicotinoid clothianidin. Full‐length vitellogenin was upregulated 3‐fold in the fat body, and the 150‐kDa fragment was upregulated in the brain of exposed honey bees, whereas no alteration occurred in the hemolymph. Upregulation of the vitellogenin protein by the neonicotinoid clothianidin is in line with the previously shown induction of its transcript. We conclude that vitellogenin might serve as a potential biomarker for neonicotinoid and other pesticide exposure in bees. Environ Toxicol Chem 2019;00:1–10. © 2019 SETAC [ABSTRACT FROM AUTHOR]

Discerning potential effects of insecticides on honey bee colonies in field studies conducted under realistic conditions can be challenging because of concurrent interactions with other environmental conditions. Honey bee colony models can control exposures and other environmental factors, as well as assess links among pollen and nectar residues in the landscape, their influx into the colony, and the resulting exposures and effects on bees at different developmental stages. We extended the colony model BEEHAVE to represent exposure to the insecticide clothianidin via residues in pollen from treated cornfields set in real agricultural landscapes in the US Midwest. We assessed their potential risks to honey bee colonies over a 1‐yr cycle. Clothianidin effects on colony strength were only observed if unrealistically high residue levels in the pollen were simulated. The landscape composition significantly impacted the collection of pollen (residue exposure) from the cornfields, resulting in higher colony‐level effects in landscapes with lower proportions of semi‐natural land. The application of the extended BEEHAVE model with a pollen exposure‐effects module provides a case study for the application of a mechanistic honey bee colony model in pesticide risk assessment integrating the impact of a range of landscape compositions. Environ Toxicol Chem 2019;38:423–435. © 2018 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals, Inc. on behalf of SETAC. Overview of pollen exposure‐effects module added to BEEHAVE. [ABSTRACT FROM AUTHOR]

Freshwater mussels contribute important ecological functions to aquatic systems. The water filtered by mussel assemblages can improve water quality, and the mixing of sediments by burrowing mussels can improve oxygen content and release nutrients. However, nearly 70% of North American freshwater mussel species are listed as either endangered, threatened, or in decline. In Ontario, 28 species are in decline or in need of protection. Even though freshwater mussels have a heightened sensitivity to some contaminants, few studies have investigated the risks that various pesticide classes pose to one freshwater mussel species or among life stages. Lampsilis siliquoidea and Villosa iris were the focus of the present study, with the latter currently listed as of "special concern" in Canada. A potential risk to the recovery of freshwater mussel species is the presence and persistence of pesticides in Ontario surface waters. Acute (48 h) toxicity tests were performed with V. iris glochidia to determine the effect on viability (surrogate for survival) following exposure to 4 fungicides (azoxystrobin, boscalid, metalaxyl, and myclobutanil), 3 neonicotinoids (clothianidin, imidacloprid, and thiamethoxam), 2 carbamates (carbaryl and malathion), 1 organophosphate (chlorpyrifos), and 1 butenolide (flupyradifurone). Juvenile and adult L. siliquoidea were also exposed to azoxystrobin, clothianidin, imidacloprid (juvenile only), and carbaryl (adult only). Our study found in general that all life stages were insensitive to the pesticides tested, with median effect and lethal concentrations >161 µg/L. The pesticides tested likely represent a minimal risk (hazard quotients <5.4 × 10−3) to freshwater mussel viability and survival in acute (48 h) and subchronic (28 d) exposures, respectively, in Ontario streams where pesticide concentrations were considerably lower than those tested in the present study. Environ Toxicol Chem 2018;37:2871–2880. © 2018 SETAC [ABSTRACT FROM AUTHOR]

Extensive agricultural use of neonicotinoid insecticide products has resulted in the presence of neonicotinoid mixtures in surface waters worldwide. Although many aquatic insect species are known to be sensitive to neonicotinoids, the impact of neonicotinoid mixtures is poorly understood. In the present study, the cumulative toxicities of binary and ternary mixtures of select neonicotinoids (imidacloprid, clothianidin, and thiamethoxam) were characterized under acute (96-h) exposure scenarios using the larval midge Chironomus dilutus as a representative aquatic insect species. Using the MIXTOX approach, predictive parametric models were fitted and statistically compared with observed toxicity in subsequent mixture tests. Single-compound toxicity tests yielded median lethal concentration (LC50) values of 4.63, 5.93, and 55.34 μg/L for imidacloprid, clothianidin, and thiamethoxam, respectively. Because of the similar modes of action of neonicotinoids, concentration-additive cumulative mixture toxicity was the predicted model. However, we found that imidacloprid-clothianidin mixtures demonstrated response-additive dose-level-dependent synergism, clothianidin-thiamethoxam mixtures demonstrated concentration-additive synergism, and imidacloprid-thiamethoxam mixtures demonstrated response-additive dose-ratio-dependent synergism, with toxicity shifting from antagonism to synergism as the relative concentration of thiamethoxam increased. Imidacloprid-clothianidin-thiamethoxam ternary mixtures demonstrated response-additive synergism. These results indicate that, under acute exposure scenarios, the toxicity of neonicotinoid mixtures to C. dilutus cannot be predicted using the common assumption of additive joint activity. Indeed, the overarching trend of synergistic deviation emphasizes the need for further research into the ecotoxicological effects of neonicotinoid insecticide mixtures in field settings, the development of better toxicity models for neonicotinoid mixture exposures, and the consideration of mixture effects when setting water quality guidelines for this class of pesticides. Environ Toxicol Chem 2017;36:3091-3101. © 2017 SETAC [ABSTRACT FROM AUTHOR]

Limited data are available on the fate of clothianidin under realistic agricultural production conditions. The present study is the first large-scale assessment of clothianidin residues in soil and bee-relevant matrices from corn and canola fields after multiple years of seed-treatment use. The average soil concentration from 50 Midwest US corn fields with 2 yr to 11 yr of planting clothianidin-treated seeds was 7.0 ng/g, similar to predicted concentrations from a single planting of Poncho 250-treated corn seeds (6.3 ng/g). The water-extractable (i.e., plant-bioavailable) clothianidin residues in soil were only 10% of total residues. Clothianidin concentrations in soil reached a plateau concentration (amount applied equals amount dissipated) in fields with 4 or more application years. Concentrations in corn pollen from these fields were low (mean: 1.8 ng/g) with no correlation to total years of use or soil concentrations. For canola, soil concentrations from 27 Canadian fields with 2 yr to 4 yr of seed treatment use (mean = 5.7 ng/g) were not correlated with use history, and plant bioavailability was 6% of clothianidin soil residues. Average canola nectar concentrations were 0.6 ng/g and not correlated to use history or soil concentrations. Under typical cropping practices, therefore, clothianidin residues are not accumulating significantly in soil, plant bioavailability of residues in soil is limited, and exposure to pollinators will not increase over time in fields receiving multiple applications of clothianidin. Environ Toxicol Chem 2016;35:311-321. © 2015 The Authors. Published by Wiley Periodicals, Inc. on behalf of SETAC. [ABSTRACT FROM AUTHOR]

Neonicotinoid insecticides, especially as seed treatments, have raised concerns about environmental loading and impacts on pollinators, biodiversity, and ecosystems. The authors measured concentrations of neonicotinoid residues in the top 5 cm of soil before planting of maize (corn) in 18 commercial fields with a history of neonicotinoid seed treatment use in southwestern Ontario in 2013 and 2014 using liquid chromatography-tandem mass spectrometry with electrospray ionization. A simple calculator based on first-order kinetics, incorporating crop rotation, planting date, and seed treatment history from the subject fields, was used to estimate dissipation rate from the seed zone. The estimated half-life (the time taken for 50% of the insecticide to have dissipated by all mechanisms) based on 8 yr of crop history was 0.64 (range, 0.25-1.59) yr and 0.57 (range, 0.24-2.12) yr for 2013 and 2014, respectively. In fields where neonicotinoid residues were measured in both years, the estimated mean half-life between 2013 and 2014 was 0.4 (range, 0.27-0.6) yr. If clothianidin and thiamethoxam were used annually as a seed treatment in a typical crop rotation of maize, soybean, and winter wheat over several years, residues would plateau rather than continue to accumulate. Residues of neonicotinoid insecticides after 3 yr to 4 yr of repeated annual use tend to plateau to a mean concentration of less than 6 ng/g in agricultural soils in southwestern Ontario. Environ Toxicol Chem 2016;35:295-302. © 2015 SETAC [ABSTRACT FROM AUTHOR]

Using neonicotinoid insecticides as seed treatments is a common practice in field crop production. Exposure of nontarget organisms to neonicotinoids present in various environmental matrices is debated. In the present study, concentrations of neonicotinoid residues were measured in the top 5 cm of soil and overlying soil surface dust before planting in 25 commercial fields with a history of neonicotinoid seed treatment use in southwestern Ontario in 2013 and 2014 using liquid chromatography-electrospray ionization tandem mass spectrometry. The mean total concentrations were 3.05 ng/g and 47.84 ng/g in 2013 and 5.59 ng/g and 71.17 ng/g in 2014 for parent soil and soil surface dust, respectively. When surface and parent soil residues were compared the mean concentration in surface dust was 15.6-fold and 12.7-fold higher than that in parent soil in 2013 and 2014, respectively. Pooled over years, the surface dust to parent soil ratio was 13.7, with mean concentrations of 4.36 ng/g and 59.86 ng/g for parent soil and surface dust, respectively. The present study's results will contribute important knowledge about the role these residues may play in the overall risk assessment currently under way for the source, transport, and impact of neonicotinoid insecticide residues in a maize ecosystem. Environ Toxicol Chem 2016;35:303-310. © 2015 SETAC [ABSTRACT FROM AUTHOR]

Despite the extensive use of the neonicotinoid insecticide clothianidin, and its known toxicity to beneficial insects such as pollinators, little attention has been given to its fate under agricultural field conditions. The present study investigated the fate and toxicity of clothianidin applied every other year as a corn seed-coating at 2 different rates, 0.25 mg/seed and 0.50 mg/seed, in an agricultural field undergoing a corn-soybean annual rotation, and conservation tillage. Concentrations were measured in soil, surface runoff, infiltration, and groundwater from 2011 to 2013. Clothianidin was detected at low concentrations in soil and water throughout the 2-yr corn and soybean rotation. Low and no-tillage had little or no effect on clothianidin concentrations. Laboratory toxicity bioassays were performed on nontarget species, including Daphnia magna, Hyalella azteca, Chironomus dilutus, Pimephales promelas and Eisenia fetida. Risk quotients were calculated from clothianidin concentrations measured in the field and compared with the laboratory toxicity bioassay results to assess the environmental risk of the insecticide. The risk quotient was found to be lower than the level of concern for C. dilutus, which was the most sensitive species tested; therefore, no short-term environmental risk was expected for the species investigated in the present study. Environ Toxicol Chem 2014;9999:1-8. © 2014 SETAC [ABSTRACT FROM AUTHOR]