The Amino Acid Transporter PtCAT7 and Ammonium Nutrition Enhance the Uptake of Thiamethoxam in Citrus Rootstock Seedlings.

Thiamethoxam (THX), when applied to the soil, can be taken up by citrus roots and subsequently transported to the leaves, providing effective protection of plants against the Asian citrus psyllid (Diaphorina citri Kuwayama). In this study, the field experiments showed that the coapplication of THX and nitrogen fertilizer (AN) did not affect THX uptake in six-year-old citrus plants. However, their coapplication promoted THX uptake in three-year-old Potassium trifoliate rootstocks and relieved the inhibition of AN at a higher level on plant growth characteristics, including biomass and growth of root and stem. RNA-seq analysis found that THX induced upregulation of a cationic amino acid transporter (PtCAT7) in citrus leaves. PtCAT7 facilitated THX uptake in the yeast strain to inhibit its growth, and the PtCAT7 protein was localized on the plasma membrane. Our results demonstrate that THX and N fertilizer can be coapplied and PtCAT7 may be involved in THX uptake in citrus.

Hormetic effects of thiamethoxam on Schizaphis graminum: demographics and feeding behavior.

In agroecosystems, insects contend with chemical insecticides often encountered at sublethal concentrations. Insects' exposure to these mild stresses may induce hormetic effects, which has consequences for managing insect pests. In this study, we used an electrical penetration graph (EPG) technique to investigate the feeding behavior and an age-stage, two-sex life table approach to estimate the sublethal effects of thiamethoxam on greenbug, Schizaphis graminum. The LC5 and LC10 of thiamethoxam significantly decreased longevity and fecundity of directly exposed adult aphids (F0). However, the adult longevity, fecundity, and reproductive days (RPd)-indicating the number of days in which the females produce offspring - in the progeny generation (F1) exhibited significant increase when parental aphids (F0) were treated with LC5 of the active ingredient. Subsequently, key demographic parameters such as intrinsic rate of increase (r) and net reproductive rate (R0) significantly increased at LC5 treatment. EPG recordings showed that total durations of non-probing (Np), intercellular stylet pathway (C), and salivary secretion into the sieve element (E1) were significantly increased, while mean duration of probing (Pr) and total duration of phloem sap ingestion and concurrent salivation (E2) were decreased in F0 adults exposed to LC5 and LC10. Interestingly, in the F1 generation, total duration of Np was significantly decreased while total duration of E2 was increased in LC5 treatment. Taken together, our results showed that an LC5 of thiamethoxam induces intergenerational hormetic effects on the demographic parameters and feeding behavior of F1 individuals of S. graminum. These findings have important implications on chemical control against S. graminum and highlight the need for a deeper understanding of the ecological consequences of such exposures within pest management strategies across the agricultural landscapes.

Heterologous antigen selection of chicken single-chain variable fragments against thiamethoxam.

Single-chain variable fragments (scFvs) are valuable in the development of immunoassays for pesticide detection. In this study, scFvs specific to thiamethoxam (Thi) were successfully isolated from a library generated by chicken immunization through heterologous coating selection. These scFvs were subsequently expressed with fusion with an Avi tag and alkaline phosphatase. After combination and optimization, a scFv-biotin based enzyme linked immunosorbent assay (ELISA) was developed for the detection of Thi, demonstrating an impressive half-maximum signal inhibition concentration (IC50) of 30 ng mL-1 and a limit of detection (LOD) of 1.8 ng mL-1. The immunoassay exhibited minimal cross-reactivity with other neonicotinoid insecticides, except for 7.5% for imidacloprid and 6.7% for imidaclothiz. The accuracy of the assay was confirmed by testing spiked samples of apple, pear, cabbage, and cucumber, which resulted in average recoveries ranging between 82% and 119%, closely aligning with the results obtained through high-performance liquid chromatography. Therefore, the chicken scFv-biotin based assay showed promise as a high-throughput screening tool for Thi in agricultural samples.

Investigation of dissipation kinetics and half-lives of fipronil and thiamethoxam in soil under various conditions using experimental modeling design by Minitab software.

To determine the extent of pesticide buildup and their environmental contamination, the environmental half-lives of pesticides are examined. The influence of the factors affecting the half-lives of fipronil and thiamethoxam including soil type, sterilization, temperature, and time and their interactions was studied using experimental modeling design by Minitab software. Based on the dissipation kinetics data, fipronil concentrations reduced gradually over 60 days while thiamethoxam concentrations decreased strongly. Also, fipronil and thiamethoxam dissipated more rapidly in calcareous soil than in alluvial soil. Thiamethoxam, however, disappeared more rapidly than fipronil in all treatments. Incubation at 50 °C leads to rapid the pesticide degradation. For prediction of the dissipation rate, model 5 was found to be the best fit, Residue of insecticide (%) = 15.466 - 11.793 Pesticide - 1.579 Soil type + 0.566 Sterilization - 3.120 Temperature, R2 = 0.94 and s = 3.80. Also, the predicted DT50 values were calculated by a model, DT50 (day) = 20.20 - 0.30 Pesticide - 7.97 Soil Type + 0.07 Sterilization - 2.04 Temperature. The shortest experimental and predicted DT50 values were obtained from treatment of thiamethoxam at 50 °C in calcareous soil either sterilized (7.36 and 9.96 days) or non-sterilized (5.92 and 9.82 days), respectively. The experimental DT50 values of fipronil and thiamethoxam ranged from 5.92 to 59.95 days while, the modeled values ranged from 9.82 to 30.58 days. According to the contour plot and response surface plot, temperature and sterilization were the main factors affecting the half-lives of fipronil and thiamethoxam. The DT50 values of fipronil and thiamethoxam increased in alluvial soil and soil with low temperature. In general, there is a high agreement between the experimental results and the modeled results.

Combined neurotoxicity of aged microplastics and thiamethoxam in the early developmental stages of zebrafish (Daniorerio).

Microplastics (MPs) pollution, together with its consequential effect on aquatic biota, represent a burgeoning environmental concern that has garnered significant scholarly attention. Thiamethoxam (TMX), a prevalently utilized neonicotinoid insecticide, is renowned for its neurotoxic impact and selective action against targeted pests. The aquatic environment serves as a receptacle for numerous pollutants, such as MPs and neonicotinoid insecticides. However, there is currently a lack of comprehensive understanding regarding the toxic effects of co-exposure to aged MPs and neonicotinoid insecticides in aquatic organisms. Therefore, we endeavor to elucidate the deleterious impacts of aged polystyrene (PS) and TMX on zebrafish (Danio rerio) larvae when present at environmentally relevant concentrations, and to reveal the underlying molecular mechanisms driving these effects. Our study showed that exposure to aged PS, TMX, or their combination notably inhibited the heart rate and locomotion of zebrafish larvae, with a pronounced effect observed under combined exposure. Aged PS and TMX were found to diminish the activity of antioxidative enzymes (SOD, CAT, and GST), elevate MDA levels, and disrupt neurotransmitter homeostasis (5-HT, GABA and ACh). Notably, the mixtures exhibited synergistic effects. Moreover, gene expression related to oxidative stress (e.g., gstr1, gpx1a, sod1, cat1, p38a, ho-1, and nrf2b) and neurotransmission (e.g., ache, ChAT, gat1, gabra1, 5ht1b, and 5ht1aa) was significantly altered upon co-exposure to aged PS and TMX in larval zebrafish. In summary, our findings support the harmful effects of aged MPs and the neonicotinoid insecticides they carry on aquatic organisms. Results from this study enhance our understanding of the biological risks of MPs and insecticides, as well as help fill existing knowledge gaps on neonicotinoid insecticides and MPs coexistence toxicity in aquatic environment.

Non-acute exposure of neonicotinoids, health risk assessment, and evidence integration: a systematic review.

Neonicotinoid pesticides are utilized against an extensive range of insects. A growing body of evidence supports that these neuro-active insecticides are classified as toxicants in invertebrates. However, there is limited published data regarding their toxicity in vertebrates and mammals. the current systematic review is focused on the up-to-date knowledge available for several neonicotinoid pesticides and their non-acute toxicity on rodents and human physiology. Oral lethal dose 50 (LD50) of seven neonicotinoids (i.e. imidacloprid, acetamiprid, clothianidin, dinotefuran, thiamethoxam, thiacloprid, and nitenpyram) was initially identified. Subsequently, a screening of the literature was conducted to collect information about non-acute exposure to these insecticides. 99 studies were included and assessed for their risk of bias and level of evidence according to the Office of Health and Translation (OHAT) framework. All the 99 included papers indicate evidence of reproductive toxicity, hepatotoxicity, nephrotoxicity, neurotoxicity, immunotoxicity, and oxidative stress induction with a high level of evidence in the health effect of rodents and a moderate level of evidence for human health. The most studied type of these insecticides among 99 papers was imidacloprid (55 papers), followed by acetamiprid (22 papers), clothianidin (21 papers), and thiacloprid (11 papers). While 10 of 99 papers assessed the relationship between clothianidin, thiamethoxam, dinotefuran, and nitenpyram, showing evidence of liver injury, dysfunctions of oxidative stress markers in the reproductive system, and intestinal toxicity. This systematic review provides a comprehensive overview of the potential risks caused by neonicotinoid insecticides to humans and rodents with salient health effects. However, further research is needed to better emphasize and understand the patho-physiological mechanisms of these insecticides, taking into account various factors that can influence their toxicity.

Distribution and risk assessment of pesticide pollution in small streams adjoining paddy fields.

The present investigation was planned to bridge the knowledge gap on spatiotemporal variations of pesticide pollution in small streams adjacent to paddy fields, and to visualize the associated risks in the aquatic ecosystems. We screened 106 pesticides using GCMSMS and LCMSMS from 10 small streams (n = 212, surface water samples) adjacent to paddy fields over seven months. Fifty-five pesticides were detected across different streams and months. The highest mean concentration was detected for fenobucarb (272 ng L-1), followed by thiamethoxam (199 ng L-1). The highest maximum concentration was detected for thiamethoxam ( 13,264 ng L-1), followed by triflumezopyrim ( 11,505 ng L-1). The highest detection frequency was recorded for fenobucarb (80.00%), followed by pretilachlor (79.00%). Out of the ten streams, Attabira stream had the highest mean number of pesticides detected in each sample. Maximum number of pesticides were detected in October followed by September. Pesticides namely, hexaconazole, pretilachlor, tricyclazole, fenobucarb and thiamethoxam were consistently detected across all streams. The risk assessment against the fishes, micro-invertebrates and algae were measured by risk quotient index (RQ). Twenty-five pesticides out of the detected pesticides (n = 55) had risk quotient values greater than 1. The highest RQmax values were observed in case of fenpropathrin followed by cyfluthrin-3. The highest RQmean value was observed in case of cyfluthrin, indicating its higher toxicity to fishes. The present study reveals that small streams are polluted with pesticides and there is a need to develop strategies and policy interventions in regularizing the pesticide uses for reducing the pesticide pollution in aquatic systems.

Greenhouse cultivation enhances pesticide bioaccumulation in cowpeas following repeated spraying.

Understanding pesticide residue patterns in crops is important for ensuring human health. However, data on residue accumulation and distribution in cowpeas grown in the greenhouse and open field are lacking. Our results suggest that acetamiprid, chlorantraniliprole, cyromazine, and thiamethoxam residues in greenhouse cowpeas were 1.03-15.32 times higher than those in open field cowpeas. Moreover, repeated spraying contributed to the accumulation of pesticide residues in cowpeas. Clothianidin, a thiamethoxam metabolite, was detected at 1.04-86.00 µg/kg in cowpeas. Pesticide residues in old cowpeas were higher than those in tender cowpeas, and the lower half of the plants had higher pesticide residues than did the upper half. Moreover, pesticide residues differed between the upper and lower halves of the same cowpea pod. Chronic and acute dietary risk assessments indicated that the human health risk was within acceptable levels of cowpea consumption. Given their high residue levels and potential accumulation, pesticides in cowpeas should be continuously assessed.

[Determination of 118 pesticide residues in urine by ultra-high performance liquid chromatography-tandem mass spectrometry].

Pesticide residues in food and their hazardous effects have attracted much attention given the increased and widespread use of pesticides. The long-term consumption of food containing pesticide residues is an important pathway for the gradual accumulation of pesticides in the human body. Urine is often monitored as a biological sample for low-dose exposure to pesticides, and urine collection is a relatively convenient sampling technique in general population research. In order to effectively monitor residual levels of multiple pesticides in human urine and provide an important technological approach for health risk assessment, a rapid screening and confirmatory detection method for 118 pesticides in urine was established using QuEChERS method as a pretreatment combined with ultra-high performance liquid chromatography-triple quadrupole mass spectrometry (UHPLC-MS/MS). The 118 pesticides analyzed included organophosphorus, carbamate, neonicotinoid, and strobilurin fungicides and other widely used pesticides. Following systematic optimization of the pretreatment process, LC separation conditions, and MS/MS parameters, 118 pesticides were extracted from urine samples and analyzed within 2 h. In brief, the target analytes in 5 mL urine samples were extracted with 10 mL of acetonitrile and added with 5 g of anhydrous MgSO4 and 1 g of NaCl as water-removal and salting-out agents, respectively. After centrifugation, 6 mL of the supernatant was cleaned using the QuEChERS method with 300 mg of C18, 300 mg of primary secondary amine (PSA) and 900 mg of anhydrous MgSO4 as the purification adsorbent. After nitrogen blowing and solubilization, the 118 target analytes were separated on a ZORBAX Eclipse Plus C18 analytical chromatographic column (100 mm×2.1 mm, 1.8 µm) with gradient elution using (A) 0.01% formic acid aqueous solution (containing 2 mmol/L ammonium formate) and (B) 0.01% formic acid methanol solution (containing 2 mmol/L ammonium formate) as mobile phases. The gradient elution program was as follows: 0-0.5 min, 5%B; 0.5-1.5 min, 5%B-20%B; 1.5-2.5 min, 20%B-50%B; 2.5-8.0 min, 50%B-80%B; 8.0-9.0 min, 80%B-98%B; 9.0-11.0 min, 98%B; 11.0-11.5 min, 98%B-5%B; 11.5-15.0 min, 5%B. The analytes were then determined by UHPLC-MS/MS with positive/negative ion switching in dynamic multiple-reaction monitoring mode and quantified using the external standard method. The results indicated that the proposed method can determine 118 pesticides in urine simultaneously and rapidly. The limits of detection and limits of quantification were 0.10 and 0.50 µg/L, respectively, and the matrix effects were less than 20%for all targeted compounds. The recoveries of the 118 pesticides in urine were between 70.2% and 104% at three spiked levels of 0.50, 1.00, and 5.00 µg/L, and the relative standard deviations ranged from 2.8% to 9.3%. The method was applied to 10 actual urine samples, and the results revealed the presence of six pesticides, including thiamethoxam, clothianidin, acetamiprid, dinotefuran, isoproturon, and dimethomorph, with contents ranging from

A study of the pesticide residues in rapeseeds in China: Levels, distribution and health risk assessment.

The aim of this survey was to evaluate the residue levels, distribution and exposure risk of the 38 most commonly used pesticides in rapeseed samples collected from the main production areas in China over a two-year period. The sampling area covered 12 provinces, including Guizhou, Shaanxi, Yunnan, Hunan, Jiangxi, Sichuan, Chongqing, Anhui, Henan, Hubei, Zhejiang, and Jiangsu provinces. The pesticide residues were determined using a QuEChERS (Quick Easy Cheap Effective Rugged and Safe) method coupled with gas chromatography-tandem mass spectrometry and liquid chromatography-tandem mass spectrometry. 8.4% of the rapeseed samples contained pesticides with a residue level ranging from 0.001 to 0.634 mg/kg. The detected analytes were imidacloprid, quizalofop-P-ethyl, thiamethoxam, paclobutrazol, prochloraz, tebuconazole, difenoconazole, s-metolachlor, carbofuran, and carbendazim. The concentrations of four analytes, including thiamethoxam, difenoconazole, carbendazim and prochloraz, exceeded the maximum residue level set by the Chinese government for rapeseed, with exceedance rates of 0.1%, 0.1%, 0.1%, and 1.1%, respectively. Based on the index of quality for residues (IqR) values, 91.6% of the total rapeseed samples had an IqR category of Excellent (IqR = 0). Only 1.5% of the tested samples were of inadequate quality. Furthermore, the assessment of chronic and acute exposure, as well as health risks associated with pesticide residues in rapeseed, was conducted for different age groups within the Chinese population, including adults (6-14 years), children (15-49 years), and the elderly (50-74 years). The results of this assessment indicated that pesticide residues in rapeseed cultivated in China are not expected to be of short- or long-term risks to the Chinese customers.

Persistence of foliar applied and pre-storage seed-treated insecticides in rice and its processed products.

A field study was conducted to investigate the persistence of foliar-applied thiamethoxam 25% WG at a rate of 25 g ai ha-1 and chlorantraniliprole 18.5% SC at 30 g ai ha-1 in various parts of rice plants, including whole grain rice, brown rice, bran, husk, straw, and cooked rice. Liquid Chromatography-Mass spectrometry/Mass spectrometry was used for sample analysis. Chlorantraniliprole residues were found to persist in whole grains, bran, husk, and straw at the time of harvest, while thiamethoxam residue was not detected in harvested grains, processed products, or straw. The study concluded that foliar-applied chlorantraniliprole and thiamethoxam did not pose any dietary risk in cooked rice. In a pre-storage seed treatment study, thiamethoxam 30% FS at 3 mL kg-1 was evaluated against Angoumois grain moth infestation during storage. The seeds remained unharmed for nine months and exhibited significantly less moth damage (2.0%) even after twelve months of storage. Thiamethoxam residues persisted for more than one year in whole rice grain, brown rice, bran, and husk with seed treatment, with higher residue levels observed in bran and husk. Parboiling and cooking led to the degradation of thiamethoxam residues.

Physiological responses of oxidative damage, genotoxicity and hematological parameters of the toxic effect of neonicotinoid-thiamethoxam in Oreochromis niloticus.

The purpose of investigation assessed the impacts of neonicotinoid thiamethoxam (TMX) at sublethal concentrations in hematological profile and renal function of Oreochromis niloticus. In the experiment, fish were exposed to TMX in four groups (0, 50, 100 and 150 ppm) for 7 days. At the end of the experiment, biochemical analysis of blood samples showed that the parameters indicating renal function showed a significant increase in serum enzymes ALT, AST, ALP and metabolites (BUN, urea, uric acid, creatinine and cortisol) concentrations, while albumin concentration decreased in a dose-dependent manner compared to the control group. In parallel with the decrease in Na+, K+ and Ca+2 in blood ion levels, there was a significant decrease in the activity of Na+/K+ ATPase, Ca+2 ATPase and AChE enzyme, levels of GSH and HSP70 in kidney tissue in TMX groups compared to the control group. It was determined that the toxic effect of TMX caused a significant increase in TBARS, PC, 8-OHdG levels, respectively. In conclusion, our study shows that TMX causes dose-dependent toxic effects, with knock-on effects on physiological processes regarding the hematological profile and renal function of O. niloticus.

Toxicant Responses and Culturing Characteristics of Long-Term Laboratory-Reared and Field Populations of Ceriodaphnia dubia.

Ceriodaphnia dubia is a standardized test organism for regulatory toxicity testing of surface waters and commercial chemicals because of its simplicity to culture and responsiveness to toxicants. For testing convenience, C. dubia is often cultured for extended periods in the laboratory with little knowledge of the impact on subsequent generations. Extended laboratory rearing could impact how they respond to stressors and decrease the accuracy of test results. The present study investigated if C. dubia cultured for an extended period were representative of three recently collected field populations by comparing their culturing characteristics and sensitivities to toxicants. For culturing characteristics, the field cultures were more challenging because they had shorter body lengths, fewer neonates, and higher mortality rates than the laboratory culture. Comparative chronic toxicity tests with sodium chloride and the neonicotinoid insecticide thiamethoxam indicated that the laboratory and field organisms did not differ much in their toxicological responses but did differ in the variability of responses (percentage of coefficient of variation). The differences between the laboratory and field cultures found in the present study highlight the challenges of addressing discrepancies between laboratory and field applications in existing standardized methodologies. Environ Toxicol Chem 2024;43:159-169. © 2023 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Urinary neonicotinoids and metabolites are associated with obesity risk in Chinese school children.

BACKGROUND: Neonicotinoids are the most widely used insecticides. Laboratory studies have suggested that neonicotinoids are one potential obesogen, but relevant data are limited in human. OBJECTIVE: To examine the association between exposure to neonicotinoids and childhood obesity. METHODS: We investigated 442 children in Shanghai, East China and measured eight neonicotinoids (thiamethoxam, clothianidin, acetamiprid, imidacloprid, thiacloprid, nitenpyram, dinotefuran, and imidaclothiz) and four metabolites (N-desmethyl-thiamethoxam, N-desmethyl-clothianidin, N-desmethyl-acetamiprid, and 5-OH-imidacloprid) in urine. Body mass index (BMI) and waist circumference (WC) were used to identify general overweight/obesity and central obesity, respectively. Linear and logistic regression models based on generalized estimating equations were used to investigate the associations of urinary neonicotinoids and metabolites with BMI z-score, WC z-score, general overweight/obesity, and central obesity. RESULTS: Children with a positive detection of clothianidin and its metabolite had a marginally higher BMI z-score (regression coefficient (ß): 0.08, 95% confidence interval (95% CI): 0.01, 0.14) after adjusted for relevant covariates. After creatinine-adjusted concentration was trichotomized, compared to children with a negative detection, children in the high urinary concentration of acetamiprid and its metabolite had a low BMI z-score (ß: -0.19, 95%CI: -0.30, -0.08), children in the medium urinary concentration of neonicotinoids and metabolites other than thiamethoxam, clothianidin, acetamiprid, and their metabolites had a marginally higher BMI z-score (ß: 0.25, 95%CI: 0.03, 0.46), a higher WC z-score (ß: 0.24, 95%CI: 0.14, 0.33), and a higher odds of central obesity (odds ratio (OR): 2.16, 95% CI: 1.28, 3.63), and children in the medium urinary concentration of all neonicotinoids and metabolites had a higher odds of central obesity (OR: 1.55, 95%CI: 1.04, 2.33). Some associations showed sex- and age- related differences. CONCLUSION: Urinary neonicotinoids and metabolites were found to be differently associated with obesity-related indexes, which suggested that exposure to neonicotinoids might have a mixed effect on childhood obesity.

Source and health risk of urinary neonicotinoids in Tibetan pregnant women.

High altitude could influence the level of exposure to neonicotinoids, but relevant data remain limited for people living in Tibet. We investigated 476 Tibetan pregnant women from Lhasa of Tibet, China in 2021 and measured eight neonicotinoids and four metabolites in urine. Food consumption was investigated by a food frequency questionnaire. Health risk was assessed by using hazard quotient (HQ) and hazard index (HI) based on acceptable daily dose or chronic reference dose. Neonicotinoids and metabolites were overall detected in 56.5% of urine samples with a median concentration being 0.73 µg g-1 creatinine. Four neonicotinoids or metabolites were detected in more than 10% of urine samples, including N-desmethyl-acetamiprid (47.5%), clothianidin (15.5%), thiamethoxam (16.0%), and imidacloprid (10.5%). Annual household income, family smoking, and pre-pregnancy body mass index were associated with the detection frequencies of neonicotinoids. Pregnant women with a higher consumption frequency of wheat, rice, fresh vegetable, fresh fruit, beef and mutton, fresh milk, yoghourt, candy and chocolate, or carbonated drinks had a higher detection frequency of neonicotinoids. Both HQ and HI were less than one. There was an evident exposure to neonicotinoids in Tibetan pregnant women with both plant- and animal-derived food items as exposure sources, but a low health risk was found based on current safety thresholds.

Dynamic monitoring of the insecticide resistance status of Bemisia tabaci across China from 2019-2021.

BACKGROUND: Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) is a major agricultural insect pest that causes severe economic losses worldwide. Several insecticides have been applied to effectively control this key pest. However, owing to the indiscriminate use of chemical insecticides, B. tabaci has developed resistance against these chemical compounds over the past several years. RESULTS: From 2019 to 2021, 23 field samples of B. tabaci were collected across China. Twenty species were identified as the Mediterranean 'Q' type (MED) and three were identified as MED/ Middle East-Asia Minor 1 mixtures. Subsequently, resistance of the selected populations to different insecticides was evaluated. The results showed that 13 populations developed low levels of resistance to abamectin. An overall upward trend in B. tabaci resistance toward spirotetramat, cyantraniliprole and pyriproxyfen was observed. In addition, resistance to thiamethoxam remained low-to-moderate in the 23 field populations. CONCLUSION: These findings suggest that the overall resistance of the field-collected B. tabaci populations has shown an upward trend over the years in China. We believe our study can provide basic data to support integrated pest management and insecticide resistance management of field B. tabaci in China. © 2023 Society of Chemical Industry.

CYP4CS5-mediated thiamethoxam and clothianidin resistance is accompanied by fitness cost in the whitefly Bemisia tabaci.

BACKGROUND: Understanding the trade-offs between insecticide resistance and the associated fitness is of particular importance to sustainable pest control. One of the most devastating pest worldwide, the whitefly Bemisia tabaci, has developed resistance to various insecticides, especially the neonicotinoid group. Although neonicotinoid resistance often is conferred by P450s-mediated metabolic resistance, the relationship between such resistance and the associated fitness phenotype remains largely elusive. By gene cloning, quantitative reverse transcription (qRT)-PCR, RNA interference (RNAi), transgenic Drosophila melanogaster, metabolism capacity in vitro and 'two sex-age stage' life table study, this study aims to explore the molecular role of a P450 gene CYP4CS5 in neonicotinoid resistance and to investigate whether such resistance mechanism carries fitness costs in the whitefly. RESULTS: Our bioassay tests showed that a total of 13 field-collected populations of B. tabaci MED biotype displayed low-to-moderate resistance to thiamethoxam and clothianidin. Compared to the laboratory susceptible strain, we then found that an important P450 CYP4CS5 was remarkably upregulated in the field resistant populations. Such overexpression of CYP4CS5 had a good match with the resistance level among the whitefly samples. Further exposure to the two neonicotinoids resulted in an increase in CYP4CS5 expression. These results implicate that overexpression of CYP4CS5 is closely correlated with thiamethoxam and clothianidin resistance. RNAi knockdown of CYP4CS5 increased mortality of the resistant and susceptible populations after treatment with thiamethoxam and clothianidin in bioassay, but obtained an opposite result when using a transgenic line of D. melanogaster expressing CYP4CS5. Metabolic assays in vitro revealed that CYP4CS5 exhibited certain capacity of metabolizing thiamethoxam and clothianidin. These in vivo and in vitro assays indicate an essential role of CYP4CS5 in conferring thiamethoxam and clothianidin resistance in whitefly. Additionally, our life-table analysis demonstrate that the field resistant whitefly exhibited a prolonged development time, shortened longevity and reduced fecundity compared to the susceptible, suggesting an existing fitness cost as a result of the resistance. CONCLUSION: Collectively, in addition to the important role of CYP4CS5 in conferring thiamethoxam and clothianidin resistance, this resistance mechanism is associated with fitness costs in the whitefly. These findings not only contribute to the development of neonicotinoids resistance management strategies, but also provide a new target for sustainable whitefly control. © 2023 Society of Chemical Industry.

Modulatory role ulexit against thiamethoxam-induced hematotoxicity/hepatotoxicity oxidative stress and immunotoxicity in Oncorhynchusmykiss.

Contamination of the aquatic environment with different insecticides is a major concern in the aquatic ecosystem today. For this reason, in the designed study, Thiamethoxam (TMX) for which there is limited information on its negative effects on Oncorhynchus mykiss was investigated, its effects on hematotoxicity, oxidative status, cytotoxicity, DNA damage and apoptotic status indicators in blood/liver tissue. However, the antitoxic potential of ulexite (UX) supplementation in the elimination of TMX-mediated toxicity has been determined. LC50-96h value determined for TMX 0.73 mg/L has been determined. As a result of hematology profile, TMX application, RBC, Hgb and Hct values showed a temporal decrease compared to the control group, while increases were determined in MCV, MCH and MCHC values. It was determined that the inhibition/induction of hematological parameters was slowed down by adding UX to the medium. During the trial (48th and 96th hours), it was noted that TMX induced cortisol level, while UX supplementation slowed this induction at 48th hour. Antioxidant enzyme activities were significantly inhibited by TMX application, and MDA and MPO values increased as a result of the stimulation of ROS. It was determined that UX added to the medium showed activity in favor of antioxidants and tried to inhibit MDA and MPO levels. When Nrf-2, one of the inflammation parameters, was compared with the administration and control groups, it was determined that it inhibited depending on time, TNF-α, IL-6, DNA damage and apoptosis were induced, and UX suppressed this situation. The results obtained were evaluated as statistically meaningful. Briefly, it was determined that TMX induced oxidative damage in all tissues at 48th - 96th hours, whereas UX mitigated this situation. The results provide possible in vivo evidence that UX supplements can reduce TMX-mediated oxidative stress and tissues damage in O. mykiss blood and liver tissues.

Microbial degradation mechanism and pathway of the insecticide thiamethoxam by isolated Bacillus Cereus from activated sludge.

The high water solubility and ecotoxicity of thiamethoxam (TMX) is a potential hazard to ecosystems and human health. Here, a strain of Bacillus cereus with high TMX degradation activity was isolated from the sediment of the A2O process in the wastewater treatment plant and was able to utilize TMX as its sole carbon source. Under different environmental conditions, the degradation efficiency of TMX by Bacillus cereus-S1 (strain S1) ranged from 41.0% to 68.9% after 216 h. The optimum degradation conditions were DO = 3.5 mg/L and pH 9.0. The addition of an appropriate carbon-to-nitrogen ratio could accelerate the degradation of TMX. A plausible biodegradation pathway has been proposed based on the identified metabolites and their corresponding degradation pathways. TMX can be directly converted into Clothianidin (CLO), TMX-dm-hydroxyl and TMX-Urea by a series of reactions such as demethylation, oxadiazine ring cleavage and C=N substitution by hydroxy group. The main products were TMX-dm-hydroxyl and TMX-Urea, the amount of CLO production is relatively small. This study aims to provide a new approach for efficient degradation of TMX; furthermore, strain S1 is a promising biological source for in situ remediation of TMX contamination.

Thiamethoxam dynamics in pepper plants: Deciphering deposition and dissipation pattern across diverse planting modes and regions.

To reduce the application dosage of thiamethoxam (TMX), we investigated the deposition and dissipation patterns in a pepper-planted ecosystem under different planting modes across four regions in China, namely Hainan (HN), Zhejiang (ZJ), Anhui (AH) and Hebei (HB). This study focused on the deposition and dissipation of TMX at concentrations of 63.00, 47.25, 31.50, 23.63 and 15.75 g a.i.hm-2. As the application dose increased, the deposition amount of TMX initially increased in the plants and cultivated soil, showing obvious geographic differences in four cultivation areas. Surprisingly, the initial amount of TMX deposited the pepper-cultivated greenhouse of ZJ and AH was 1.1-2.1-fold and 1.0-3.6-fold higher than that in the open field system at the same application dose, respectively. In pepper leaves, stems, fruits and soil, the dissipation exhibited rapid growth and then slowed. However, the residual concentration showed an increasing trend, followed by a subsequent decrease in the pepper roots. In different planting regions, the dissipation rate of TMX followed the order HN > ZJ > AH > HB in pepper plants and cultivated soil. In comparison to the open field, the total TMX retention rate in greenhouse was higher, indicating overall greater persistence in the greenhouse conditions. These findings reveal the deposition and dissipation characteristics of TMX within the pepper-field ecosystem, offering a significant contribution to the risk assessment of pesticides.