Neonicotinoid Insecticides Research Articles

Neonicotinoid Insecticides and Their Metabolites Can Pass through the Human Placenta Unimpeded.

Studies on neonicotinoid (NEO) exposure in pregnant women and fetuses are scarce, and transplacental transfer of these insecticides is unknown. In this study, parent NEOs (p-NEOs) and their metabolites (m-NEOs) were determined in 95 paired maternal (MS) and cord serum (CS) samples collected in southern China. Imidacloprid was the predominant p-NEO in both CS and MS samples, found at median concentrations of 1.84 and 0.79 ng/mL, respectively, whereas N-desmethyl-acetamiprid was the most abundant m-NEO in CS (median: 0.083 ng/mL) and MS (0.13 ng/mL). The median transplacental transfer efficiencies (TTEs) of p-NEOs and m-NEOs were high, ranging from 0.81 (thiamethoxam, THM) to 1.61 (olefin-imidacloprid, of-IMI), indicating efficient placental transfer of these insecticides. Moreover, transplacental transport of NEOs appears to be passive and structure-dependent: cyanoamidine NEOs such as acetamiprid and thiacloprid had higher TTE values than the nitroguanidine NEOs, namely, clothianidin and THM. Multilinear regression analysis revealed that the concentrations of several NEOs in MS were associated significantly with hematological parameters related to hepatotoxicity and renal toxicity. To our knowledge, this is the first analysis of the occurrence and distribution of NEOs in paired maternal-fetal serum samples.

Toxicity of the neonicotinoid insecticides thiamethoxam and imidacloprid to tadpoles of three species of South American amphibians and effects of thiamethoxam on the metamorphosis of Rhinella arenarum

ABSTRACT The present study examined the acute and chronic toxicity of the neonicotinoid insecticides imidacloprid (IMI) and thiamethoxam (TIA) on the neotropical amphibian species Rhinella arenarum, Rhinella fernandezae and Scinax granulatus. The median lethal concentration after 96 hr exposure (96 hr-LC50) ranged between 11.28 and >71.2 mg/L amongst all species and development stages tested, indicating that these pesticides are not likely to produce acute toxicity in the wild. The subchronic toxicity was also low, with 21 day-LC50 values ranging between 27.15 and >71.2 mg/L. However, tadpoles of Rhinella arenarum exposed to thiamethoxam from stage 27 until completion of metamorphosis presented a significantly lower metamorphic success rate together with a smaller size at metamorphosis, starting from the lowest concentration tested. Although a number of studies previously examined the effects of neonicotinoids on amphibian tadpoles, these investigations focused on the time to metamorphosis and reported a variety of results including retardation, acceleration or lack of effect. Here, data demonstrated that thiamethoxam predominantly impacts metamorphosis through reduction of the transformation success and body weight, rather than by affecting the timings of metamorphosis. By closely monitoring progression of tadpoles through the different stages, impairment of metamorphosis was demonstrated to occur during the transition from stage 39 to 42, suggesting an effect on the thyroid system. An asymmetry in the length of the arms was also observed in metamorphs treated with thiamethoxam. Overall, these results indicate that thiamethoxam, and conceivably other neonicotinoids, have the potential to significantly impair metamorphosis of amphibians and diminish their performance and survival in the wild.

Biodegradation and Metabolic Pathway of the Neonicotinoid Insecticide Thiamethoxam by Labrys portucalensis F11.

Thiamethoxam (TMX) is an effective neonicotinoid insecticide. However, its widespread use is detrimental to non-targeted organisms and water systems. This study investigates the biodegradation of this insecticide by Labrys portucalensis F11. After 30 days of incubation in mineral salt medium, L. portucalensis F11 was able to remove 41%, 35% and 100% of a supplied amount of TMX (10.8 mg L-1) provided as the sole carbon and nitrogen source, the sole carbon and sulfur source and as the sole carbon source, respectively. Periodic feeding with sodium acetate as the supplementary carbon source resulted in faster degradation of TMX (10.8 mg L-1); more than 90% was removed in 3 days. The detection and identification of biodegradation intermediates was performed by UPLC-QTOF/MS/MS. The chemical structure of 12 metabolites is proposed. Nitro reduction, oxadiazine ring cleavage and dechlorination are the main degradation pathways proposed. After biodegradation, toxicity was removed as indicated using Aliivibrio fischeri and by assessing the synthesis of an inducible β-galactosidase by an E. coli mutant (Toxi-Chromo test). L. portucalensis F11 was able to degrade TMX under different conditions and could be effective in bioremediation strategies.

Sub-lethal doses of imidacloprid alter food selection in the invasive garden ant Lasius neglectus

Despite several restrictions to their use, neonicotinoid insecticides are still widely employed worldwide. Residual sub-lethal amounts of these chemicals can have detrimental effects on the behavior of non-target insects. Toxic effects on economically important species such as bees have been widely documented, but less is known about their toxic action on other social insects, such as ants. In this study, we assessed the effect of different sub-lethal doses of the neonicotinoid imidacloprid on the ability of colonies of the invasive ant Lasius neglectus to select the most profitable resource. We used Y-shaped mazes having an imidacloprid-polluted or an unpolluted sucrose solution on the two branches. Two sucrose (0.1 M, 0.5 M) and two imidacloprid (1 μg/ml, 10 μg/ml) concentrations were used. In parallel, we evaluated the marking activity of foragers who fed on the same solutions. We found that the 0.1 M sugar solution polluted with 1 μg/ml imidacloprid was significantly more frequently selected in binary choices experiments than the unpolluted resource. Moreover, the ingestion of the same combination of sugar and imidacloprid significantly increased the marking rate of foragers. The higher concentration of the pollutant had lower effects, probably because of the hormesis phenomenon. Results suggest that the lower sub-lethal dose of imidacloprid can lead ants to select again the polluted resource. This “active” selection of the pollutant may magnify the negative effects on the colonies. Due to their ecological role, any impairment of ant survival or behavior may have detrimental cascade effects on the whole ecosystem.

Field-realistic concentrations of a neonicotinoid insecticide influence socially regulated brood development in a bumblebee.

The systemic neonicotinoid insecticides are considered as one of the key culprits contributing to ongoing declines in pollinator health and abundance. Bumblebees are among the most important pollinators of temperate zone plants, making their susceptibility to neonicotinoid exposure of great concern. We report that bumblebee (Bombus terrestris) colonies exposed to field-realistic concentrations of the commonly used neonicotinoid Imidacloprid grew slower, consumed less food, and produced fewer workers, males and gynes, but unexpectedly produced larger workers compared to control colonies. Behavioural observations show that queens in pesticide-treated colonies spend more time inactive and less time caring for the brood. We suggest that the observed effects on brood body size are driven by a decreased queen ability to manipulate the larva developmental programme. These findings reveal an intricate and previously unknown effect of insecticides on the social interactions controlling brood development in social insect colonies. Insecticide influences on the social mechanisms regulating larval development are potentially detrimental for bumblebees, in which body size strongly influences both caste differentiation and the division of labour among workers, two organization principles of insect societies.

Imidacloprid: Comparative toxicity, DNA damage, ROS production and risk assessment for aquatic non-target organisms

Imidacloprid is a neonicotinoid systemic insecticide used worldwide. Despite its hazardous impact on non-target organisms, few studies have been conducted concerning the potential eco-genotoxic effects in invertebrates of surface waters where this pesticide is detected from units of ng/L to tens of μg/L. The aim of the present work was to determine the acute, the sub-chronic and the chronic toxicity of imidacloprid in producers and primary consumers of the freshwater trophic chain. The organisms under investigation were the green alga Raphidocelis subcapitata, the rotifer Brachionus calyciflorus, the cladoceran crustacean Ceriodaphnia dubia and the benthic ostracod Heterocypris incongruens. In addition, potential DNA damage and ROS production were evaluated in C. dubia.Furthermore, in accordance with European guidelines, toxicological risk assessment of imidacloprid was performed for all continents considering its global occurrence in surface waters. In addition, we assessed the genotoxicological risk and median inhibition of reproduction was observed at units of mg/L for rotifers and daphnids. Algae showed the lowest level of sensitivity to the pesticide with effective concentrations from units to hundreds of mg/L. DNA lesions were marked from 7 μg/L with a significant increase in damage as concentrations increased. Chronic toxicity risk quotient values were generally below to a threshold value of 1, with no consequential environmental concern other than for the Canadian areas. On the contrary, the genotoxicological risk quotient values were found higher than the threshold value in all continents.

Biochemical responses, feeding and survival in the solitary bee Osmia bicornis following exposure to an insecticide and a fungicide alone and in combination

In agricultural ecosystems, bees are exposed to combinations of pesticides that may have been applied at different times. For example, bees visiting a flowering crop may be chronically exposed to low concentrations of systemic insecticides applied before bloom and then to a pulse of fungicide, considered safe for bees, applied during bloom. In this study, we simulate this scenario under laboratory conditions with females of the solitary bee, Osmia bicornis L. We studied the effects of chronic exposure to the neonicotinoid insecticide, Confidor® (imidacloprid) at a realistic concentration, and of a pulse (1 day) exposure of the fungicide Folicur® SE (tebuconazole) at field application rate. Syrup consumption, survival, and four biomarkers: acetylcholinesterase (AChE), carboxylesterase (CaE), glutathione S-transferase (GST), and alkaline phosphatase (ALP) were evaluated at two different time points. An integrated biological response (IBRv2) index was elaborated with the biomarker results. The fungicide pulse had no impact on survival but temporarily reduced syrup consumption and increased the IBRv2 index, indicating potential molecular alterations. The neonicotinoid significantly reduced syrup consumption, survival, and the neurological activity of the enzymes. The co-exposure neonicotinoid-fungicide did not increase toxicity at the tested concentrations. AChE proved to be an efficient biomarker for the detection of early effects for both the insecticide and the fungicide. Our results highlight the importance of assessing individual and sub-individual endpoints to better understand pesticide effects on bees.

Melatonin ameliorates imidacloprid-induced intestinal injury by negatively regulating the PGN/P38MAPK pathway in the common carp (Cyprinuscarpio)

Imidacloprid (IMI), one of the most frequently used neonicotinoid insecticides in agriculture, is resided in surface water worldwide and poses a threat to aquatic organisms. Melatonin (MT) provides effective protection against insecticide-induced toxicity, nevertheless, the toxic effects and whether MT attenuates intestinal injury caused by IMI exposure in the common carps remains poorly explored. Previous studies have reported adverse effects of IMI exposure on intestinal health status. Therefore, we first demonstrated that IMI altered the composition and function of the intestinal microbiota, destroying the integrity of intestinal ultrastructure, increasing intestinal permeability. Meanwhile, metagenomic sequencing and ELISA kits results hypothesized that peptidoglycan (PGN) is an IMI-triggered intestinal microbial metabolite. Subsequently, we thus further elucidated that IMI induced an increase in intestinal tight junction permeability by inducing PGN secretion in vitro model. MT addition dramatically attenuated IMI-induced intestinal toxicity by remitting PGN synthesis and thus resecuring tight junction permeability, thereby reducing intestinal injury. SB203580 was supplied as a P38MAPK inhibitor to alleviate the increased permeability of tight junctions induced by IMI/PGN. Therefore, these findings confirmed that MT protects against IMI-induced intestinal injury by negatively regulating PGN/P38MAPK pathway to antagonize the increased tight junction permeability.

Sublethal Effects of Thiamethoxam on Biological Traits and Detoxification Enzyme Activities in the Small Brown Planthopper, Laodelphax striatellus (Fallén).

The small brown planthopper (Laodelphax striatellus (Fallén), Hemiptera: Delphacidae), is an important agricultural pest of rice, and neonicotinoid insecticides are commonly used for controlling L. striatellus. However, the sublethal effects of thiamethoxam on L. striatellus remain relatively unknown. In this study, an age-stage life table procedure was used to evaluate the sublethal effects of thiamethoxam on the biological parameters of L. striatellus. Additionally, activities of carboxylesterase, glutathione S-transferase, and cytochrome P450 monooxygenase in the third instar nymphs were analyzed. The results indicated that the survival time of F0 adults and the fecundity of female adults decreased significantly after the third instar nymphs were treated with sublethal concentrations of thiamethoxam (LC15 0.428 mg/liter and LC30 0.820 mg/liter). The developmental duration, adult preoviposition period, total preoviposition period, and mean generation time of the F1 generation increased significantly, whereas the fecundity of the female adults, intrinsic rate of increase (ri), and finite rate of increase (λ) decreased significantly. The oviposition period was significantly shorter for the insects treated with LC30 than for the control insects. Neither sublethal concentrations had significant effects on the adult longevity, net reproduction rate (R0), or gross reproduction rate (GRR) of the F1 generation. The activities of carboxylesterase, glutathione-S-transferase, and cytochrome P450 monooxygenase increased significantly after the thiamethoxam treatments. These results indicate that sublethal concentrations of thiamethoxam can inhibit L. striatellus population growth and enhance detoxification enzyme activities.

Chronic toxicity of three formulations of neonicotinoid insecticides and their mixture on two daphniid species: Daphnia magna and Ceriodaphnia dubia

Neonicotinoid insecticides represent nearly a quarter of the global insecticide market and are widely used in agriculture but also for lawn, garden care, and pest control. They are highly water-soluble, persistent in soil, may enter the aquatic compartment via spray drift, runoff, or leaching, and contribute to downstream aquatic toxicity. Although insects appear to be the most sensitive group to neonicotinoids, other groups, such as crustaceans, may also be affected. Furthermore, most studies focus on single-insecticide exposure and very little is known concerning the impact of neonicotinoid mixtures on aquatic invertebrates. The present study was designed to test potential toxicological effects of an environmentally relevant mixture of imidacloprid, clothianidin, and thiamethoxam on populations of Ceriodaphnia dubia and Daphnia magna under controlled conditions. Chronic toxicity tests were conducted in the laboratory, and survival and reproduction were measured for both species under environmentally relevant, ‘worst-case’ concentrations for each compound separately and in combination as pesticides are often detected as mixtures in aquatic environments. The neonicotinoids did not appear to affect the survival of C. dubia and D. magna. Reproduction of C. dubia was affected by the mixture whereas all three individual insecticides as well as the mixture caused a significant reduction in the reproduction of D. magna. Our results highlight the complexity of pesticide toxicity and show that traditional toxicological approaches such as, acute mortality studies and tests with single compounds can underestimate negative impacts that occur in the environment.

Preparation of magnetic molybdenum disulfide for the extraction of neonicotinoid insecticides from environmental water samples

In this study, magnetic molybdenum disulfide hybrid composites (Fe3O4/MoS2) were successfully synthesized by in situ fabrication method and firstly applied as magnetic adsorbent for extracting neonicotinoid insecticides from environmental water samples. The Fe3O4/MoS2 composites were characterized in detail by scanning electron microscope, fourier transform infrared, X-ray diffraction and vibrating sample magnetometer, and possessed the faster adsorption capacity towards neonicotinoid insecticides (only 10 min). The parameters (solution pH, amounts of adsorbents, adsorption time, elution conditions and sample volume) effecting the performance of magnetic solid-phase extraction were carefully investigated. Under the optimal conditions, the magnetic solid-phase extraction-high performance liquid chromatography method based on Fe3O4/MoS2 composites for enriching and detecting neonicotinoid insecticides in environmental water samples was established. The good linearity (0.01–10 μg/mL) with correlation coefficients between 0.9949 and 0.9999 was obtained. The limits of detection and the limits of quantifications were 0.48–0.67 ng/mL and 1.44–2.02 ng/mL, respectively. With spiked at three different concentration levels (50, 100,500 ng/mL), the recovery was 66.0–91.3 % with relative standard deviations from 1.4 % to 8.3 %. These data demonstrated that the developed method was highly sensitive, repeatable and easily operated. Also, this study provided new adsorbents for other trace pollutants in the environment.

Effect of thiamethoxam on the behavioral profile alteration and toxicity of adult zebrafish at environmentally relevant concentrations

Thiamethoxam (THM) is a commercial neonicotinoid insecticide with broad-spectrum insecticidal activity. It has been widely detected in the aquatic environment, but its behavioral toxicity on aquatic organisms received limited attention. In this study, adult zebrafish were exposed to THM at three levels (0.1, 10, and 1000 μg/L) for 45 days to investigate its effect on their ecological behavior, histopathology, bioaccumulation, and stress response. The bioconcentration factor in zebrafish brain was significantly higher (p < 0.05) at low concentration of THM (0.1 μg/L) than in other treatment groups. In terms of individual behavior, the locomotor activity, aggregation, and social activity of fish were enhanced after THM exposure, but the memory of the food zone was disturbed and abnormal swimming behavior was observed. THM exposure caused brain tissue necrosis, erythrocyte infiltration, cloudy swelling, and other pathological changes in brain tissue and affected the concentrations of acetylcholinesterase and cortisol related to neurotoxicity. The condition factor and organ coefficients (brain, heart, and intestine) of zebrafish were markedly impacted by THM treatment at 0.1 and 1000 μg/L, respectively. This finding showed that THM was more harmful to fish behavior than lethality, reproduction, and growth, and a behavioral study can be a useful tool for ecological risk assessment.

Resistance to dinotefuran in Bemisia tabaci in China: status and characteristics.

Bemisia tabaci (Gennadius) is a serious agricultural pest worldwide. Neonicotinoids are the most important new class of synthetic insecticides used in the management of B. tabaci. However, B. tabaci populations have developed resistance to various active ingredients in neonicotinoids following long-term and widespread application. Dinotefuran exhibited high toxicity against most B. tabaci field populations. One population (Din-R) with a high level of resistance to dinotefuran (255.6-fold) was first identified in the field. The Din-R population exhibited medium to high levels of resistance to all the tested neonicotinoid insecticides and a high level of resistance to spinetoram. Genetic inheritance analysis revealed that resistance to dinotefuran was incompletely recessive and polygenic. The synergist piperonyl butoxide significantly increased the toxicity of dinotefuran to Din-R. P450 activity in the Din-R population was 2.19-fold higher than in the susceptible population. RNA-sequencing analysis showed that 12 P450 genes were significantly upregulated in the Din-R population, of which CYP6DW5, CYP6JM1 and CYP306A1 were found to exhibit more than 3.00-fold higher expression in Din-R when using a reverse transcription quantitative real-time polymerase chain reaction. Expression of eight P450 genes was obviously induced by dinotefuran, and CYP6DW5 showed the highest expression level. After knockdown of CYP6DW5 in Din-R, the toxicity of dinotefuran increased significantly. P450 had a crucial role in dinotefuran resistance in B. tabaci, and CYP6DW5 was involved in the resistance. These results provide important information for the management of resistance in B. tabaci and improve our understanding of the resistance mechanism of dinotefuran. © 2022 Society of Chemical Industry.

Residue status and risk assessment of neonicotinoids under real field conditions: Based on a two-year survey of cotton fields throughout China

There is considerable controversy regarding the harm caused by neonicotinoids to pollinators. Oilseed rape, corn and wild flowers, but not cotton, have been identified as important for toxicity risk of neonicotinoids to pollinators. To this end, 396 stamens and maternal flowers from major cotton areas across China were analyzed, 97.3% (2020) and 100% (2021) of samples contained at least one neonicotinoid pesticide. The probability of multiple residues was greater than that of a single neonicotinoid residue, and there was no significant difference between stamen and maternal flowers. The median total concentration of neonicotinoids ranged from 3.73 to 638 ng g −1 . Acetamiprid (detection rate ratio (DRR): 14.3%; concentration ratio (CR): 53.1%), dinotefuran (DRR: 23.3%; CR: 19.9%), and clothianidin (DRR: 21.1%; CR: 6.49%) were the most frequently detected neonicotinoids. Based on the Hazard Quotient (HQ) assessment, acetamiprid, clothianidin and dinotefuran (median HQ value > 1,000) reached the risk level; while the Risk Quotient (RQ) assessment indicated that they have not yet reached the degree of risk concern (median RQ value < 0.4). This research provides the first overview of neonicotinoid residues in cotton field, and supplements the data of cotton field planting for international risk assessment of neonicotinoids. • Neonicotinoid insecticides were detected in 98.6% of cotton flowers. • Multiple neonicotinoid residues have a higher detection rate than single residues. • The number of neonicotinoids detected mostly ranged from 3–5. • The risk of neonicotinoids to honeybees was assessed using HQ and RQ models. • Acetamiprid, clothianidin, and dinotefuran are the most common and potentially risky neonicotinoids.

Development of a new rotating photocatalytic reactor for the degradation of hazardous pollutants

Abstract The aim of this study was to develop a new rotating photocatalytic reactor operating in recirculation mode with light sources placed outside the photoreactor vessel. The photoreactor with cylindrical geometry was equipped with four artificial lamps used to simulate solar irradiation (2.4% UVB and 12% UVA; 300–700 nm). The photocatalyst was immobilized on abrasive material used as a support and placed on the central (inner) photoreactor tube, which was connected to a power-driven shaft that allowed rotation at a desired speed. A suitable modification of the commercial TiO2 P25 photocatalyst was carried out to reduce its band gap energy and electron-hole recombination and to extend the visible light response range of TiO2. The main task of this research was to apply the basic principles of process intensification methodology, i.e. to explore the influence of rotational hydrodynamics, which allows good access of reactants to the photocatalyst surface, good irradiation of the photocatalytic surface and reduction of mass transfer resistance, leading to increased process efficiency. The homemade photoreactor was used for the photocatalytic degradation of one of the major types of neonicotinoid insecticides, acetamiprid. The influence of various working conditions, such as initial solution pH, rotation speed, recirculation flow rate and initial concentration of acetamiprid on the photocatalytic degradation process was investigated. The optimum degradation conditions were found at a recirculation flow rate of 200 cm3 min−1 and a rotation speed of 200 rpm, indicating that the mass transfer process strongly contributes to the photocatalytic degradation rate at the conditions used in this study. The results obtained during the photocatalytic degradation of acetamiprid in a rotating photoreactor were compared with those obtained under similar operating conditions in a flat-plate photoreactor, and the corresponding conclusions were drawn based on the performed kinetic analysis.

Impact of Imidacloprid Resistance on the Demographic Traits and Expressions of Associated Genes in Aphis gossypii Glover.

Imidacloprid is one of the most widely used neonicotinoid insecticides to control sap-sucking insect pests, including Aphis gossypii. The intensive application of chemical insecticides to A. gossypii led to the development of resistance against several insecticides, including imidacloprid. Therefore, it is crucial to understand the association between imidacloprid resistance and the fitness of A. gossypii to limit the spread of the resistant population under field contexts. In this study, we used the age-stage, two-sex life table method to comprehensively investigate the fitness of imidacloprid resistant (ImR) and susceptible strains (SS) of melon aphids. Results showed that ImR aphids have prolonged developmental stages and decreased longevity, fecundity, and reproductive days. The key demographic parameters (r, λ, and R0) were significantly reduced in ImR strain compared to SS aphids. Additionally, the molecular mechanism for fitness costs was investigated by comparing the expression profile of juvenile hormone-binding protein (JHBP), juvenile hormone epoxide hydrolase (JHEH), juvenile hormone acid O-methyltransferase (JHAMT), Vitellogenin (Vg), ecdysone receptor (EcR), and ultraspiracle protein (USP) supposed to be associated with development and reproduction in insects. The results of RT-qPCR showed that EcR, JHBP, JHAMT, JHEH, and Vg genes were downregulated, while USP was statistically the same in ImR A. gossypii compared to the SS strain. Together, these results provide in-depth information about the occurrence and magnitude of fitness costs against imidacloprid resistance that could help manage the evolution and spread of A. gossypii resistance in field populations.

Sample Preparation Approach by In Situ Formation of Supramolecular Solvent Microextraction for Enrichment of Neonicotinoid Insecticide Residues

Sample Preparation Approach by In Situ Formation of Supramolecular Solvent Microextraction for Enrichment of Neonicotinoid Insecticide Residues

Toxicity of nitenpyram to silkworm (Bombyx mori L.) and its potential mechanisms

Silkworm (Bombyx mori L.), as an economic insect, occupies a certain position in the development of China's economy. The neonicotinoid insecticide nitenpyram is commonly used in farmland to control planthoppers and aphids. In China, mulberry orchards are often planted adjacent to fields or commercial crops, and mist drifts occur during application, which may affect the production safety of Bombyx mori. In this study, a risk assessment of nitenpyram was carried out, and the results showed that there were risks in spraying nitenpyram around the periphery and subperipheries of mulberry fields. However, few studies have reported the mechanism underlying nitenpyram's toxic effect on silkworms. Here, we validated 25 differentially expressed (DE) miRNAs in the nitenpyram treatment group of silkworms, and the significantly enriched mTOR signaling pathway, oxidative phosphorylation and FoxO signaling pathway were verified. Among them, bmo-miR-2766-5P was up-regulated by 2.122-fold, and the expression of its regulated target gene 101,741,287 was up-regulated. After the injection of bmo-miR-2766-5P inhibitor, the Log2FC value of 101,741,287 was changed from 1.26 to −2.19. Bmo-miR-3326, bmo-miR-3378-5P and bmo-miR-2761-3P were down-regulated by 2.386-fold, 1.158-fold and 2.359-fold, respectively. After injecting miRNA mimics into silkworms, the Log2FC values of the target genes 100,302,609, 101,740,730 and 101,746,319 were changed from 1.24 to −11.94, −1.12 changed to 2.84 and 1.93 changed to −0.37, respectively. In addition, nitenpyram induced oxidative damage in silkworms, and the degree of DNA damage increased with the increase of concentration and time. Meanwhile Imd was significantly up-regulated in IMD-related pathways (38.7-fold, p < 0.01). The results indicated that nitenpyram could affect the growth and development process of silkworms, and these DE-miRNAs may have an important impact on the stress response of silkworms to nitenpyram.

Uptake kinetics and subcellular distribution of three classes of typical pesticides in rice plants

Food safety problems caused by pesticide residues have always been a concern for many people. In this study, we investigated the uptake, translocation and subcellular distribution of neonicotinoid insecticides, triazole fungicides, and sulfonylurea herbicides in rice plants (Oryza sativa L.). The time-dependent uptake kinetics of the three categories of pesticides with different molecular structures fit a first-order one-compartment kinetic model. The neonicotinoids (log Kow −0.66–0.8) were mainly concentrated in the leaves, and the triazoles (log Kow 3.72–4.4) were mainly concentrated in the roots. Neonicotinoid pesticides in the roots were preferentially transported across the membrane through the symplastic pathway; triazole pesticides except for triadimefon and myclobutanil preferentially passed through the symplastic pathway; and sulfonylurea pesticides (log Kow 0.034–2.89) were first transported upward through the apoplastic pathway. In the roots, neonicotinoids, triazoles, and sulfonylurea herbicides were mainly concentrated in the soluble fractions, cell wall and apoplast fractions, respectively. In addition, there was a high positive correlation between the subcellular distribution of pesticides in the roots, stems and leaves. Molecular weight and log Kow jointly affected the enrichment of triazole pesticides in the roots, stems and leaves and the transfer from stems to leaves, while water solubility and log Kow commonly affected neonicotinoids. There was a correlation between pesticide absorption and the molecular structures of pesticides. To develop pesticides with strong uptake and transport capabilities, it is necessary to consider that the electronegativity of some atoms is stronger, the sum of the topological indices of heteroatoms can be large, and the van der Waals volume increases accordingly.

Residual efficacy of the neonicotinoid insecticide clothianidin against pyrethroid-resistant Aedes aegypti.

Here we report the residual efficacy of the neonicotinoid insecticide clothianidin against pyrethroid-resistant Aedes aegypti. We first conducted a range-finding evaluation of clothianidin on three different substrates (wall, wood, cloth) using three doses (100, 300 and 600 mg a.i.m-2 ) and conducting World Health Organization (WHO) cone bioassays to assess acute (24 h) and delayed (up to 7 days) mortality. In experimental houses located in Merida (Mexico) and using free-flying pyrethroid-resistant Ae. aegypti females, we quantified the acute and delayed mortality after a 24-h exposure to the targeted indoor residual spraying (TIRS) of two clothianidin doses (100 and 300 mg a.i.m-2 ). Range-finding studies with WHO cones showed low (<50%) acute mortality for all surfaces, doses and times post spraying. Delayed mortality was higher, with average values above or close to the 60% mark (and 95% confidence interval estimates crossing 80% for the 600 mg a.i.m-2 dose). In experimental houses, a similar low acute mortality was quantified (range of mortality across 12 months was 2-44% for 100 mg a.i.m-2 and 8-61% for 300 mg a.i/m2 ). However, delayed mortality showed a strong effect of clothianidin on free-flying Ae. aegypti, with values above 80% up to 7months post-TIRS. Novel residual insecticide molecules have a promising outlook for Ae. aegypti control and can contribute to the expansion and adoption of TIRS in urban areas. clothianidin can contribute to the control of resistant Ae. aegypti and provide residual control for up to 7 months after application. © 2022 Society of Chemical Industry.