Voltage-gated sodium channel gene mutation and P450 gene expression are associated with the resistance of Aphis spiraecola Patch (Hemiptera: Aphididae) to lambda-cyhalothrin.

Aphis spiraecola Patch is one of the most economically important tree fruit pests worldwide. The pyrethroid insecticide lambda-cyhalothrin is commonly used to control A. spiraecola. In this 2-year study, we quantified the resistance level of A. spiraecola to lambda-cyhalothrin in different regions of the Shaanxi province, China. The results showed that A. spiraecola had reached extremely high resistance levels with a 174-fold resistance ratio (RR) found in the Xunyi region. In addition, we compared the enzymatic activity and expression level of P450 genes among eight A. spiraecola populations. The P450 activity of A. spiraecola was significantly increased in five regions (Xunyi, Liquan, Fengxiang, Luochuan, and Xinping) compared to susceptible strain (SS). The expression levels of CYP6CY7, CYP6CY14, CYP6CY22, P4504C1-like, P4506a13, CYP4CZ1, CYP380C47, and CYP4CJ2 genes were significantly increased under lambda-cyhalothrin treatment and in the resistant field populations. A L1014F mutation in the sodium channel gene was found and the mutation rate was positively correlated with the LC50 of lambda-cyhalothrin. In conclusion, the levels of lambda-cyhalothrin resistance of A. spiraecola field populations were associated with P450s and L1014F mutations. Our combined findings provide evidence on the resistance mechanism of A. spiraecola to lambda-cyhalothrin and give a theoretical basis for rational and effective control of this pest species.

Combined toxic effects of polyethylene microplastics and lambda-cyhalothrin on gut of zebrafish (Danio rerio).

Microplastics (MPs), which are prevalent and increasingly accumulating in aquatic environments. Other pollutants coexist with MPs in the water, such as pesticides, and may be carried or transferred to aquatic organisms, posing unpredictable ecological risks. This study sought to assess the adsorption of lambda-cyhalothrin (LCT) by virgin and aged polyethylene MPs (VPE and APE, respectively), and to examine their influence on LCT's toxicity in zebrafish, specifically regarding acute toxicity, oxidative stress, gut microbiota and immunity. The adsorption results showed that VPE and APE could adsorb LCT, with adsorption capacities of 34.4 mg∙g-1 and 39.0 mg∙g-1, respectively. Compared with LCT exposure alone, VPE and APE increased the acute toxicity of LCT to zebrafish. Additionally, exposure to LCT and PE-MPs alone can induce oxidative stress in the zebrafish gut, while combined exposure can exacerbate the oxidative stress response and intensify intestinal lipid peroxidation. Moreover, exposure to LCT or PE-MPs alone promotes inflammation, and combined exposure leads to downregulation of the myd88-nf-κb related gene expression, thus impacting intestinal immunity. Furthermore, exposure to APE increased LCT toxicity to zebrafish more than VPE. Meanwhile, exposure to PE-MPs and LCT alone or in combination has the potential to affect gut microbiota function and alter the abundance and diversity of the zebrafish gut flora. Collectively, the presence of PE-MPs may affect the toxicity of pesticides in zebrafish. The findings emphasize the importance of studying the interaction between MPs and pesticides in the aquatic environment.

Investigation of lambda-cyhalothrin resistance in Spodoptera frugiperda: Heritability, cross-resistance, and mechanisms.

Lambda-cyhalothrin, a representative pyrethroid insecticide widely used for Spodoptera frugiperda control in China, poses challenges due to the development of resistance. This study investigates the realized heritability, inheritance pattern, cross-resistance, and resistance mechanisms to lambda-cyhalothrin. After 21 generations of selection, the lambda-cyhalothrin-resistant strain (G21) developed a 171.11-fold resistance compared to a relatively susceptible strain (RS-G9), with a realized heritability (h2) of 0.11. Cross-resistance assays revealed that lambda-cyhalothrin-resistant strains showed no significant cross-resistance to the majority of tested insecticides. Genetic analysis indicated that lambda-cyhalothrin resistance in S. frugiperda was autosomal, incompletely dominant, and polygenic inheritance. The P450 enzyme inhibitor PBO significantly enhanced lambda-cyhalothrin toxicity in the resistant strains. Compared with the RS-G9 strain, the P450 enzyme activity was significantly increased and multiple P450 genes were significantly up-regulated in the lambda-cyhalothrin-resistant strains. RNAi targeting the most overexpressed P450 genes (CYP337B5 and CYP321B1) significantly increased the susceptibility of resistant S. frugiperda larvae to lambda-cyhalothrin. This study provides comprehensive insights into lambda-cyhalothrin resistance in S. frugiperda, and the results are helpful for developing effective resistance management strategies of this pest.

Molecular insights into the functional analysis of P450 CYP321A7 gene in the involvement of detoxification of lambda-cyhalothrin in Spodoptera frugiperda.

Fall armyworm, Spodoptera frugiperda (J. E. Smith), is a widely recognized global agricultural pest that has significantly reduced crop yields all over the world. S. frugiperda has developed resistance to various insecticides. Insect cytochrome P450 monooxygenases (CYPs or P450s) play an important role in detoxifying insecticides, leading to increased resistance in insect populations. However, the function of the specific P450 gene for lambda-cyhalothrin resistance in S. frugiperda was unclear. Herein, the expression patterns of 40 P450 genes in the susceptible and lambda-cyhalothrin-resistant populations were analyzed. Among them, CYP321A7 was found to be overexpressed in the resistant population, specifically LRS (resistance ratio = 25.38-fold) derived from a lambda-cyhalothrin-susceptible (SS) population and FLRS (a population caught from a field, resistance ratio = 63.80-fold). Elevated enzyme activity of cytochrome P450 monooxygenases (P450s) was observed for LRS (2.76-fold) and the FLRS (4.88-fold) as compared to SS, while no significant differences were observed in the activities of glutathione S-transferases and esterases. Furthermore, the knockdown of CYP321A7 gene by RNA interference significantly increased the susceptibility to lambda-cyhalothrin. Remarkably, the knockdown of CYP321A7 reduced the enzymatic activity of P450 by 43.7%, 31.9%, and 22.5% in SS, LRS, and FLRS populations, respectively. Interestingly, fourth-instar larvae treated with lambda-cyhalothrin at the LC30 dosage had a greater mortality rate due to RNA interference-induced suppression of CYP321A7 (with increases of 61.1%, 50.0%, and 45.6% for SS, LRS, and FLRS populations, respectively). These findings suggest a link between lambda-cyhalothrin resistance and continual overexpression of CYP321A7 in S. frugiperda larvae, emphasizing the possible importance of CYP321A7 in lambda-cyhalothrin detoxification in S. frugiperda.

Micro-algal astaxanthin improves lambda-cyhalothrin-induced necroptosis and inflammatory responses via the ROS-mediated NF-κB signaling in lymphocytes of carp (Cyprinus carpio L.).

Lambda-cyhalothrin (LCY) is a widely used toxic pesticide that causes harmful effects on the immune organs of fish and aquatic species. Micro-algal astaxanthin (MAA), a heme pigment found in haematococcus pluvialis, has been shown to benefit antioxidants and immunity in aquaculture. To investigate how MAA protects carp lymphocytes from LCY-induced immunotoxicity, a model of fish lymphocytes treated with LCY and/or MAA was established. Lymphocytes from carp (Cyprinus carpio L.) were given LCY (80 µM) and/or MAA (50 µM) as a treatment for a period of 24 h. Firstly, LCY exposure resulted in excessive ROS and malondialdehyde production and reduces antioxidant enzymes (SOD and CAT), indicating a reduced capacity of the antioxidant system. Secondly, the results of flow cytometry and AO/EB labeling proved that lymphocytes treated with LCY have a larger ratio of necroptosis. In addition, LCY upregulated the levels of necroptosis-related regulatory factors (RIP1, RIP3 and MLKL) via the ROS-mediated NF-κB signaling pathway in lymphocytes. Thirdly, LCY treatment caused increased secretion of inflammatory genes (IL-6, INF-γ, IL-4, IL-1ß and TNF-α), leading to immune dysfunction in lymphocytes. Surprisingly, LCY-induced immunotoxicity was inhibited by MAA treatment, indicating that it effectively attenuated the LCY-induced changes described above. Overall, we concluded that MAA treatment could ameliorate LCY-induced necroptosis and immune dysfunction by inhibiting the ROS-mediated NF-κB signaling in lymphocytes. It provides insights into the protection of farmed fish from agrobiological threats in fish under LCY and the value of MAA applications in aquaculture.

New insights into Microalgal astaxanthin's effect on Lambda-cyhalothrin-induced lymphocytes immunotoxicity in Cyprinus carpio: Involving miRNA-194-5p-FoxO1-mediated-mitophagy and pyroptosis.

Lambda-cyhalothrin (LC), a pyrethroid insecticide widely used in agriculture, causes immunotoxicity to aquatic organisms in the aquatic environment. Microalgal astaxanthin (MA) is a natural carotenoid that enhances viability of a variety of fish. To investigate the immunotoxicity of LC and the improvement effect of MA in lymphocytes (Cyprinus carpio), lymphocytes were treated with LC (80 M) and/or MA (50 M) for 24 h. Firstly, CCK8 combined with PI staining results showed that MA significantly attenuated the LC-induced lymphocyte death rate. Secondly, LC exposure resulted in excessively damaged mitochondrial and mtROS, diminished mitochondrial membrane potential and ATP content, which could be improved by MA. Thirdly, MA upregulated the levels of mitophagy-related regulatory factors (Beclin1, LC3, ATG5, Tom20 and Lamp2) induced by LC. Importantly, MA decreased the levels of pyroptosis-related genes treated with LC, including NLRP3, Cas-4, GSDMD and active Cas-1. Further study indicated that LC treatment caused excessive miRNA-194-5p and reduced levels of FoxO1, PINK1 and Parkin, which was inhibited by MA treatment. Overall, we concluded that MA could enhance damaged mitochondrial elimination by promoting the miRNA-194-5p-FoxO1-PINK1/Parkin-mitophagy in lymphocytes, which reduced mtROS accumulation and alleviated pyroptosis. It offers insights into the importance of MA application in aquaculture as well as the defense of farmed fish against agrobiological hazards in fish under LC.

Development of Copper Nanoclusters-Based Turn-Off Nanosensor for Fluorescence Detection of Two Pyrethroid Pesticides (Cypermethrin and Lambda-Cyhalothrin).

Fluorescent copper nanoclusters (Cu NCs) were synthesized by using Withania somnifera (W. somnifera) plant extract as a biotemplate. Aqueous dispersion of W. somnifera-Cu NCs displays intense emission peak at 458 nm upon excitation at 350 nm. This fluorescence emission was utilized for the detection of two pyrethroid pesticides (cypermethrin and lambda-cyhalothrin) via "turn-off" mechanism. Upon the addition of two pyrethiod pesticides independently, the fluorescence emission of W. somnifera-Cu NCs was gradually decreased with increasing concentrations of both pesticides. It was noticed that the decrease in emission intensity at 458 nm was linearly dependent on the logarithm of both pesticides concentrations in the ranges of 0.01-100 µM and of 0.05-100 µM for cypermethrin and lambda-cyhalothrin, respectively. Consequently, the limits of detection were found to be 27.06 and 23.28 nM for cypermethrin and lambda-cyhalothrin, respectively. The as-fabricated W. somnifera-Cu NCs acted as a facile sensor for the analyses of cypermethrin and lambda-cyhalothrin in vegetables (tomato and bottle gourd), which demonstrates that it could be used as portable sensing platform for assaying of two pyrethroid pesticides in food samples.

Rapid response of midgut bacteria in Bactrocera tau (Walker) (Diptera: Tephritidae) to lambda-cyhalothrin- and spinosad-induced stress.

In recent decades, the increasingly widespread application of chemical pesticides has exacerbated the emergence of insecticide resistance among insect pests. In this study, we examined the rapid response of bacteria in the midgut of the fruit fly Bactrocera tau (Walker) (Diptera: Tephritidae) to stress induced by the insecticides lambda-cyhalothrin and spinosad by analyzing the bacterial community structure and diversity in the midguts of 4-day-old B. tau. The results revealed that 4-day-old B. tau females were more resistant to lambda-cyhalothrin and spinosad than their 4-day-old male counterparts. Alpha- and beta-diversity analyses revealed no significant differences between male and female B. tau with respect to the diversity and richness of gut bacteria in response to the same treatments. In response to treatment with lambda-cyhalothrin and spinosad at lethal concentration 50 (LC50), we detected significant changes in the structure and diversity of the bacterial community in the midguts of both male and female B. tau. Particularly among the dominant bacterial genera, there were decreases in the relative abundances of Citrobacter, Enterobacter, Klebsiella, and Pectobacterium. Increases were observed in the relative abundances of Dysgonomonas, Erwinia, and Providencia. Our findings provide a theoretical basis for gaining a better understanding of the relationships between midgut bacteria and the insecticide resistance of B. tau.

Identification of 14 glutathione S-transferase genes from Lasioderma serricorne and characterization of LsGSTe1 involved in lambda-cyhalothrin detoxification.

In insects, glutathione S-transferases (GSTs) play a pivotal role in the detoxification of a wide range of pesticides. The cigarette beetle, Lasioderma serricorne, is an economically important pest insect of stored products. Recently, pyrethroid insecticides have been used to control this pest. However, little is known concerning the responses and functions of GSTs in L. serricorne under pyrethroid exposure. In this study, transcriptome sequencing was performed on L. serricorne, and a total of 14 GSTs were identified by retrieving the unigene dataset. Of these, 13 predicted GSTs fell into six cytosolic classes, namely, delta, epsilon, omega, sigma, theta, and zeta, and one was assigned to an "unclassified" group. The GST genes were differentially expressed in various larval tissues and at different developmental stages. Exposure to the pyrethroid insecticide lambda-cyhalothrin (LCT) caused oxidative stress in L. serricorne larvae and led to significantly elevated expression levels of six genes, among which LsGSTe1 was the most upregulated. Recombinant LsGSTE1 protein displayed LCT-metabolizing activity. Furthermore, LsGSTE1 protects cells against oxidative stress. Moreover, knockdown of LsGSTe1 by RNA interference dramatically increased the susceptibility of L. serricorne larvae to LCT treatment. The results from this study provide sequence resources and expression data for GST genes in L. serricorne. Our findings indicate that LsGSTE1 plays a dual role in LCT detoxification by metabolizing the pesticide and by preventing LCT-induced oxidative stress. Thus, the LsGSTe1 gene could be used as a potential target for sustainable management of the cigarette beetle.

UGT2B13 and UGT2C1 are involved in lambda-cyhalothrin resistance in Rhopalosiphum padi.

Uridine diphosphate-glucuronosyltransferases (UGTs) are major multifunctional detoxification phase II enzymes involved in the metabolic detoxification of xenobiotics. However, their roles in insecticides resistance are still unclear. In this study, we identified two UGTs genes (UGT2B13 and UGT2C1) in Rhopalosiphum padi, a serious insect pest of wheat worldwide. Bioassays results showed that the resistance ratio of R. padi resistance strain (LC-R) to lambda-cyhalothrin (LC) was 2963.8 fold. The roles of UGT2B13 and UGT2C1 in lambda-cyhalothrin resistance were evaluated. Results indicated that the UGTs contents were significantly increased in the LC resistant strain of R. padi. UGT2B13 and UGT2C1 were significantly overexpressed in the LC-R strain. Transcription levels of UGT2B13 and UGT2C1 were relatively higher in the gut of LC-R strain. RNA interference (RNAi) of UGT2B13 or UGT2C1 significantly decreased the UGTs contents of the LC-R aphids and increased mortality of R. padi exposure to the LC50 concentration of LC. This study provides a new view that UGTs are involved in LC resistance of R. padi. The findings will promote further work to detailed the functions of UGTs in the metabolism resistance of insects to insecticides.

Carvacrol protects against λ-Cyhalothrin-induced hepatotoxicity and nephrotoxicity by modulating oxidative stress, inflammation, apoptosis, endoplasmic reticulum stress, and autophagy.

λ-Cyhalothrin, a type II synthetic pyrethroid, has been widely used in households, agriculture, public health, and gardening to control insect pests. Despite its widespread usage, it is known to induce a variety of adverse effects, including hepatotoxicity and nephrotoxicity. The goal of this study was to investigate the protective effect of carvacrol, which has antioxidant, anti-inflammatory, anti-apoptotic, and some other properties, on λ-Cyhalothrin-induced hepatotoxicity and nephrotoxicity 35 male Sprague-Dawley rats were randomly divided into five groups for this purpose: I-Control group: II-CRV group (50 mg/kg carvacrol), III-LCT group (6.23 mg/kg LCT), IV-LCT + CRV 25 group (6.23 mg/kg LCT + 25 mg/kg carvacrol), and V-LCT + CRV 50 group (6.23 mg/kg LCT + 50 mg/kg carvacrol). Using biochemical, real-time PCR, and western blotting methods, the collected tissues were analyzed. While λ-Cyhalothrin treatment increased MDA levels, which are indicated of lipid peroxidation, but reduced SOD, CAT, GPx activities, and GSH levels. After receiving carvacrol therapy, the degree of oxidative stress reduced as the values of these parameters approached those of the control group. Increased inflammation, apoptosis, endoplasmic reticulum stress, and autophagy with λ-Cyhalothrin administration reduced with carvacrol co-administration, and liver and kidney tissues were protected from damage, depending on the degree of oxidative stress. After considering all of these data, it was discovered that λ-Cyhalothrin-induced oxidative stress, inflammation, apoptosis, endoplasmic reticulum stress, and autophagy in the liver and kidneys; however, carvacrol protected the tissues from damage. Our findings indicate that carvacrol may be a promising protective agent in λ-Cyhalothrin-induced hepatotoxicity and nephrotoxicity.

Persistence and dissipation kinetics of novaluron 9.45% + lambda-cyhalothrin 1.9% ZC insecticides in tomato crop under semi-arid region.

In recent decades, fate studies of pesticides have been a topic of interest worldwide due to human health concerns tomato, contain abundant nutritional phytochemicals and lycopene which is known for antioxidant. Tomato is susceptible to many pest, so to overcome from these pests many insecticides are used, leaving residual effects on the crop. So to find out the persistence, the present study was carried out to investigate the residual levels and dissipation behaviour of novaluron 9.45% + lambda-cyhalothrin 1.9% ZC in tomato crop during Rabi session of 2017-18 in randomized block design. The first spray of insecticide was done at fruit formation stage and second spray at 10-day interval at recommended dose @43.31 g a.i. ha-1 and double of recommended dose @86.62 g a.i. ha-1. The residue of novaluron determined by HPLC (high-performance liquid chromatography) on 0 day (two hours after spraying) was 0.154 ppm at lower dose and 0.234 ppm at higher dose. The residue of lambda-cyhalothrin determined by GC ECD (gas chromatography electron capture detector) at 0 day (two hours after spraying) was 0.451 ppm at lower dose and 0.849 ppm at higher dose. The deposition of novaluron 9.45% + lambda-cyhalothrin 1.9% ZC was gradually decreased with increasing days after spraying (DAS). The mean initial deposition of the pesticide novaluron and lambda-cyhalothrin was recorded as 0.154 mg/kg, 0.451 mg/kg, respectively, at the recommended dose @43.31 g a.i. ha-1 while at double of recommended dose @86.62 g a.i. ha-1 novaluron and lambda-cyhalothrin, the mean initial deposition of 0.234 mg/kg and 0.849 mg/kg was recorded, respectively. The residue of the novaluron and lambda-cyhalothrin was at BDL (below determination level) (0.01 and 0.05 ppm) on 5th and 7th day, respectively, at lower dose (x), whereas at higher dose (2x) it was below determination level on 7th and 10th day, respectively. In soil samples, the residue levels were at below the determination level (0.01 mg/kg) for novaluron and (0.05 mg/kg) for lambda-cyhalothrin at both doses. The half-life DT50 of novaluron and lambda-cyhalothrin in the tomato fruit was found to be 2 days at recommended dose (X) @43.31 g a.i. ha-1 for both the pesticide and at double of the recommended dose @86.62 g a.i. ha-1 it was 3 and 2 days, respectively.

Residues of pyrethroids and triazoles pesticides in water and sediment of certain Egyptian watercourses: assessing their influence on fungal diversity.

Contamination of water and sediment with pyrethroids and triazoles residues can affect fungal diversity, and hence the aquatic system functioning. The aim of the present study is to investigate the effect of water and sediment contamination with pyrethroids and triazoles on fungal diversity. Water and sediment samples were seasonally collected along 2019 from water bodies representing Gharbeya and Qualubeya governorates. Concentrations of pyrethroids and triazoles were determined, and fungal species in water and sediment samples were molecularly identified. The results indicated that temperature and pH varied according to the season. Permethrin, deltamethrin, lambda-cyhalothrin and esfenvalerate showed the highest pyrethroids concentrations, whereas tetraconazole, tebuconazole and difenconazole were of the highest triazoles concentrations. Aspergillus niger was one of the most frequent species, in addition to Trichoderma capillare, Fusarium oxysporum, Penicillium commune and Penicillium polonicum. Principal component analysis indicated a positive correlation between temperature and different Aspergillus spp., and between pH and each of pyrethroids and triazoles. Moreover, a negative correlation was observed between triazoles and Trichoderma asperellum, Penicillium griseofulvum and Aspergillus fumigatus. In conclusion, contamination of water with pesticides affected fungal diversity. This disturbance in fungal assemblages might result in a reduction of some key organisms, or an increase and emergence of new pathogens.

Excretion time courses of lambda-cyhalothrin metabolites in the urine of strawberry farmworkers and effect of coexposure with captan.

There are limited literature data on the impact of coexposure on the toxicokinetics of pesticides in agricultural workers. Using the largely employed pyrethroid lambda-cyhalothrin (LCT) and fungicide captan as sentinel pesticides, we compared individual temporal profiles of biomarkers of exposure to LCT in strawberry field workers following an application episode of LCT alone or in coexposure with captan. Participants provided all urine voided over a 3-day period after an application of a pesticide formulation containing LCT alone (E1) or LCT mixed with captan (E2), and in some cases following re-entry in treated field (E3). Pyrethroid metabolites were measured in all urine samples, in particular 3-(2-chloro-3,3,3-trifluoroprop-1-en-1-yl)-2,2-dimethyl-cyclopropanecarboxylic acid (CFMP), 3-phenoxybenzoic acid (3-PBA), and 4-hydroxy-3-phenoxybenzoic acid (4-OH3PBA). There were no obvious differences in individual concentration-time profiles and cumulative excretion of metabolites (CFMP, 3-PBA, 4-OH3BPA) after exposure to LCT alone or in combination with captan. For most workers and exposure scenarios, CFMP was the main metabolite excreted, but time courses of CFMP in urine did not always follow that of 3-PBA and 4-OH3BPA. Given that the latter metabolites are common to other pyrethroids, this suggests that some workers were coexposed to pyrethroids other than LCT. For several workers and exposure scenarios E1 and E2, values of CFMP increased in the hours following spraying. However, for many pesticide operators, other peaks of CFMP were observed at later times, indicating that tasks other than spraying of LCT-containing formulations contributed to this increased exposure. These tasks were mainly handling/cleaning of equipment used for spraying (tractor or sprayer) or work/inspection in LCT-treated field according to questionnaire responses. Overall, this study provided novel excretion time course data for LCT metabolites valuable for interpretation of biomonitoring data in workers, but also showed that coexposure was not a major determinant of variability in exposure biomarker levels. Our analysis also pointed out the importance of measuring specific metabolites.

Comparative transcriptome and RNA interference reveal CYP6DC1 and CYP380C47 related to lambda-cyhalothrin resistance in Rhopalosiphum padi.

The bird-cherry-oat aphid, Rhopalosiphum padi, is a serious agricultural pest of Triticeae crops, and pyrethroids are the most widely used chemical pesticides for the control of the aphid. Our previous studies found that some R. padi field populations have developed resistance against pyrethroids; an M918L target-site mutation of the voltage gated sodium channel was present in the pyrethroid resistant individuals, while the high-level resistance to lambda-cyhalothrin revealed the presence of other mechanisms in the pest. Here, we conducted genome-wide transcriptional analysis for the lambda-cyhalothrin susceptible (SS) and resistant (LC-RR) strains of R. padi. Results indicated that 2457 genes were differently expressed between the SS and LC-RR strains. In the LC-RR, a total of 1265 and 1192 genes were up- and down-regulated, respectively. KEGG analysis implicated enrichment of P450 involved in insecticide metabolic pathways in the resistant transcriptome. qRT-PCR results confirmed that two P450 genes (CYP6DC1 and CYP380C47) were significantly overexpressed in the LC-RR individuals. Furthermore, RNA interference (RNAi) of CYP6DC1 or CYP380C47 significantly increased mortality of R. padi exposure to lambda-cyhalothrin. These results suggest that the overexpression of CYP6DC1 and CYP380C47 contributed to the lambda-cyhalothrin resistance in the pest. This study provides knowledge for further analyzing the molecular mechanism of resistance to pyrethroids in R. padi.

A heat shock protein protects against oxidative stress induced by lambda-cyhalothrin in the green peach aphid Myzus persicae.

Lambda-cyhalothrin (LCT) is a pyrethroid insecticide widely used to control insect pests. Insect exposure to LCT may cause abnormal accumulation of reactive oxygen species (ROS) and result in oxidative damage. Heat shock proteins (HSPs) may help protect against oxidative stress. However, little is known about the role of HSPs in response to LCT in the green peach aphid, Myzus persicae. This insect is an important agricultural pest causing severe yield losses in crops. In this study, we characterized a cDNA sequence (MpHsp70) encoding a member of the HSP70 family in M. persicae. MpHsp70 encoded a 623 amino acid protein putatively localized in the cytosol. The highest expression level of MpHsp70 occurred in fourth-instar nymphs. Treatment of M. persicae with LCT resulted in oxidative stress and significantly increased H2O2 and malondialdehyde levels. This led to an elevated transcription level of MpHsp70. Injection of H2O2 into M. persicae also upregulated the MpHsp70 expression level, suggesting that MpHsp70 is responsive to ROS, particularly H2O2, induced by LCT. Recombinant MpHSP70 protein was expressed in Escherichia coli. E. coli cells overexpressing MpHSP70 exhibited significant tolerance to H2O2 and the ROS generators, cumene hydroperoxide and paraquat. This indicated that MpHSP70 protects against oxidative stress. Furthermore, knockdown of MpHsp70 by RNA interference resulted in increased susceptibility in apterous adults of M. persicae to LCT. These findings indicate that MpHsp70 plays an important role in defense against LCT-induced oxidative stress and insecticide susceptibility in M. persicae.

Construction and Characterization of Novel Hydrophilic Nanospheres Loaded with Lambda-Cyhalothrin via Ultrasonic Emulsification-Solvent Evaporation.

Safe and efficient pesticide formulations have attracted great attention for the prevention and control of diseases and pests. In recent years, improving the effectiveness and duration of pesticides through nanotechnology has become a research hotspot in the field of pesticide formulations. Here, we develop a novel hydrophilic lambda-cyhalothrin nanospheres encapsulated with poly(styrene-co-maleic anhydride) (PSMA) via the ultrasonic emulsification-solvent evaporation method, which exhibited better particle size uniformity and dispersion in comparison with the traditional method. The effects of PSMA content, oil phase/water phase ratio and phacoemulsification time on the particle size and morphology of nanoparticles were investigated to optimize preparation process parameters. Meanwhile, the wettability and adhesion behavior on the leaf surface, the release properties, and the storage stability of nanoparticles were characterized to evaluate the performance of the novel nano-formulation. This work not only establishes a facile and promising method for the applicable of insoluble pesticides, but also develops an innovative nano-formulation with hydrophilicity and high leaf adhesion, which opens a new direction in plant protection and residue reduction.

The Binary Mixtures of Lambda-Cyhalothrin, Chlorfenapyr, and Abamectin, against the House Fly Larvae, Musca domestica L.

The house fly Musca domestica L. is one of the medical and veterinary pests that can develop resistance to different insecticides. Mixing insecticides is a new strategy for accelerating pest control; furthermore, it can overcome insect resistance to insecticides. This study aims to evaluate three insecticides, chlorfenapyr, abamectin, and lambda-cyhalothrin, individually and their binary mixtures against 2nd instar larvae of M. domestica laboratory strain. Chlorfenapyr exhibited the most toxic effect on larvae, followed by abamectin then the lambda-cyhalothrin. The half-lethal concentrations (LC50) values were 3.65, 30.6, and 94.89 ppm, respectively. These results revealed that the high potentiation effect was the mixture of abamectin/chlorfenapyr in all the mixing ratios. In contrast, the tested combination of lambda-cyhalothrin/abamectin showed an antagonism effect at all mixing ratios against house fly larvae. The total protein, esterases, glutathione-S-transferase (GST), and cytochrome P-450 activity were also measured in the current investigation in the larvae treated with chlorfenapyr. Our results indicate that GST may play a role in detoxifying chlorfenapyr in M. domestica larvae. The highest activity of glutathione-S-transferase was achieved in treated larvae with chlorfenapyr, and an increase in cytochrome P-450 activity in the larvae was observed post-treatment with Abamectin/chlorfenapyr.

Effectiveness of a long-lasting insecticide treatment kit (ICON® Maxx) for polyester nets over three years of household use: a WHO phase III trial in Tanzania.

BACKGROUND: ICON® Maxx (Syngenta) is an insecticide treatment kit of pyrethroid and binding agent for long-lasting treatment of mosquito nets. Interim recommendation for use on nets was granted by the World Health Organization (WHO) after successful evaluation in experimental huts following multiple washes. A full WHO recommendation is contingent upon demonstration of continued bio-efficacy after 3 years of use. METHODS: A household-randomized prospective study design was used to assess ICON Maxx-treated nets over 3 years in north-eastern Tanzania. Conventional treated nets (with lambda-cyhalothrin, but without binder) served as a positive control. At 6-monthly intervals, cross-sectional household surveys monitored net use and physical integrity, while cone and tunnel tests assessed insecticidal efficacy. Pyrethroid content was determined after 12 and 36 months. A parallel cohort of nets was monitored annually for evidence of net deterioration and attrition. RESULTS: After 12 months' use, 97% of ICON Maxx-treated nets but only 67% of CTN passed the WHO efficacy threshold for insecticidal durability (> 80% mortality in cone or tunnel or 90% feeding inhibition in tunnel). After 24- and 36-months use, 67% and 26% of ICON Maxx treated nets met the cone criteria, respectively, and over 90% met the combined cone and tunnel criteria. Lambda-cyhalothrin content after 36 months was 17% (15.8 ± 4.3 mg/m2) of initial content. ICON Maxx nets were used year-round and washed approximately 4 times per year. In cross-sectional survey after 36 months the average number of holes was 20 and hole index was 740 cm2 per net. Cohort nets had fewer holes and smaller hole index than cross-sectional nets. However, only 15% (40/264) of cohort nets were not lost to follow-up or not worn out after 36 months. CONCLUSIONS: Because more than 80% of nets met the WHO efficacy criteria after 36 months use, ICON Maxx was granted WHO full recommendation. Cross-sectional and cohort surveys were complementary and gave a fuller understanding of net durability. To improve net usage and retention, stronger incentives and health messaging should be introduced in WHO LLIN longitudinal trials. Untreated polyester nets may be made long-lastingly insecticidal in Africa through simple household treatment using ICON Maxx pyrethroid-binder kits.

Bio-efficacy and wash-fastness of a lambda-cyhalothrin long-lasting insecticide treatment kit (ICON® Maxx) against mosquitoes on various polymer materials.

BACKGROUND: Long-lasting efficacy of insecticide-treated nets is a balance between adhesion, retention and migration of insecticide to the surface of netting fibres. ICON® Maxx is a twin-sachet 'home-treatment kit' of pyrethroid plus binding agent, recommended by the World Health Organization (WHO) for long-lasting, wash-fast treatment of polyester nets. While knitted polyester netting is widely used, fine woven polyethylene netting is increasingly available and nets made of cotton and nylon are common in Africa and Asia. It is important to investigate whether ICON Maxx is able to fulfill the WHO criteria of long-lasting treatment on a range of domestic fabrics to widen the scope for malaria protection. METHODS: This study was a controlled comparison of the bio-efficacy and wash-fastness of lambda-cyhalothrin CS, with or without binder, on nets made of cotton, polyethylene, nylon, dyed and undyed polyester. Evaluation compared an array of bioassays: WHO cone and cylinder, median time to knockdown and WHO tunnel tests using Anopheles mosquitoes. Chemical assay revealed further insight. RESULTS: ICON Maxx treated polyethylene and polyester netting met the WHO cone and tunnel test bio-efficacy criteria for LLIN after 20 standardized washes. Although nylon and cotton netting failed to meet the WHO cone and cylinder criteria, both materials passed the WHO tunnel test criterion of 80% mortality after 20 washes. All materials treated with standard lambda-cyhalothrin CS without binder failed to meet any of the WHO bio-efficacy criteria within 5 washes. CONCLUSION: The bio-efficacy of ICON Maxx against mosquitoes on netting washed up to 20 times demonstrated wash durability on a range of synthetic polymer and natural fibres: polyester, polyethylene, nylon and cotton. This raises the prospect of making insecticide-binder kits into an effective approach for turning untreated nets, curtains, military clothing, blankets-and tents and tarpaulins as used in disasters and humanitarian emergencies-into effective malaria prevention products. It may provide a solution to the problem of reduced LLIN coverage between campaigns by converting commercially sourced untreated nets into LLINs through community or home treatment. It may also open the door to binding of non-pyrethroid insecticides to nets and textiles for control of pyrethroid resistant vectors.