De novo synthesis of a novel hapten and development of a monoclonal antibody-based immunoassay for the detection of dichlorvos and trichlorfon.

The absence of high-affinity antibodies has hindered the development of satisfactory immunoassays for dichlorvos (DDVP) and trichlorfon (TCP), two highly toxic organophosphorus pesticides. Herein, the de novo synthesis of a novel anti-DDVP hapten was introduced. Subsequently, a specific anti-DDVP monoclonal antibody (Mab) was produced with satisfying affinity to DDVP (IC50: 12.4 ng mL-1). This Mab was highly specific to DDVP, and TCP could readily convert into DDVP under mild alkaline conditions. Leveraging this insight, an indirect competitive ELISA was successfully developed for simultaneous detection of DDVP and TCP. The limit of detection in rice, cabbage and apple for DDVP /TCP was found to be 12.1/14.6 µg kg-1, 7.3/8.8 µg kg-1 and 6.9/8.3 µg kg-1, respectively. This study not only provides an effective strategy for producing a high-quality anti-DDVP Mab but also affords a reliable and cost-effective tool suitable for high-throughput detection of DDVP and TCP in food samples.

Ecological risk assessment for typical organophosphorus pesticides in surface water of China based on a species sensitivity distribution model.

The ecological risks posed by widespread organophosphorus pesticide (OPs) pollution in the surface waters of China remain unclear. In this study, species sensitivity distribution (SSD) parametric statistical approaches were coupled with fully acute and chronic toxicity data to fit the sensitivity distributions of different aquatic species to five typical OPs: dimethoate, malathion, parathion-methyl, trichlorfon, and dichlorvos. Crustaceans exhibit the highest sensitivity to OPs, whereas algae are the least sensitive. The acute hazardous concentrations that affected 5 % of the species (HC5) were 0.112, 0.001, 0.001, 0.001, and 0.001 mg/L for dimethoate, malathion, parathion-methyl, trichlorfon, and dichlorvos, respectively, whereas their chronic HC5 values were 0.004, 0.004, 0.053, 0.001, and 0.0005 mg/L, respectively. Hence, dichlorvos is highly toxic and poses greater risk to non-target aquatic species. The evaluation data revealed varying geographical distribution characteristics of the ecological risks from OPs in 15 freshwater aquatic systems across different regions of China. Dichlorvos posed the highest risk in the basins of Zhejiang and Guangdong Provinces, with the highest chronic Risk Quotient (RQ) and Hazard Index (HI) at 9.34 and 9.92, respectively. This is much higher than what was collected and evaluated for foreign rivers (the highest chronic RQ and HI in foreign rivers were 1.65 and 2.24, respectively). Thus, dichlorvos in the surface waters of China poses a substantial ecological risk to aquatic organisms, and may endanger human health.

Phytoremediation of cadmium-trichlorfon co-contaminated water by Indian mustard (Brassica juncea): growth and physiological responses.

In this study, the morphological and physiological responses of Brassica juncea to the stresses of Cadmium (Cd) and trichlorfon (TCF), and the phytoremediation potential of B. juncea to Cd and TCF were investigated under hydroponics. Results showed that Cd exhibited strong inhibition on biomass and root morphology of B. juncea as Cd concentration increased. The chlorophyll a fluorescence intensity and chlorophyll content of B. juncea decreased with the increased Cd concentration, whereas the malondialdehyde and soluble protein contents and superoxide dismutase activity increased. TCF with different concentrations showed no significant influence on these morphological and physiological features of B. juncea. The biomass and physiological status of B. juncea were predominantly regulated by Cd level under the co-exposure of Cd and TCF. B. juncea could accumulate Cd in different plant parts, as well as showed efficient TCF degradation performance. A mutual inhibitory removal of Cd and TCF was observed under their co-system. The present study clearly signified the physiological responses and phytoremediation potential of B. juncea toward Cd and TCF, and these results suggest that B. juncea can be used as an effective phytoremediation agent for the Cd-TCF co-contamination in water.

Combined pollution of heavy metals and pesticides in agricultural water systems is a common phenomenon. In previous phytoremediation studies, limited information is available on the co-contamination of heavy metals and pesticides. In this study, we aimed to investigate the concentration-dependent morphological and physiological characteristics of B. juncea under single and co-stress of Cd and trichlorfon (TCF), and the phytoremediation ability of B. juncea to remove Cd and TCF through hydroponic experiment. B. juncea exhibited efficient removal performance of Cd and TCF alone and simultaneous exposure of both pollutants, indicating that B. juncea is an effective phytoremediation agent for the Cd-TCF co-contaminated water.

Assessing the effect of ß-glucan diets on innate immune response of tilapia macrophages against trichlorfon exposure: an in vitro study.

The widespread use of pesticides in some areas where fish species such as tilapia are farmed may cause damage to the environment and affect commercial fish and therefore, human health. Water leaching with the pesticide trichlorfon, during the fumigation season in the field, can affect water quality in fish farms and consequently affect fish health. At the same time, the use of immunomodulatory compounds such as ß-glucan supplied in the diet has become widespread in fish farms as it has been shown that improves the overall immune response. The present research examines the immunomodulatory impacts observed in macrophages of Nile tilapia (Oreochromis niloticus) after being fed a diet supplemented with ß-glucan for 15 days, followed by their in vitro exposure to trichlorfon, an organophosphate pesticide, at concentrations of 100 and 500 µg mL-1 for 24 h. The results showed that ß-glucan diet improved the viability of cells exposed to trichlorfon and their antioxidant capacity. However, ß-glucan did not counteract the effects of the pesticide as for the ability to protect against bacterial infection. From the present results, it can be concluded that ß-glucan feeding exerted a protective role against oxidative damage in cells, but it was not enough to reduce the deleterious effects of trichlorfon on the microbicidal capacity of macrophages exposed to this pesticide.

Study on the acute toxicity of trichlorfon and its breakdown product dichlorvos to goldfish (Carassius auratus) based on 1H NMR metabonomics.

Trichlorfon, one of the most widely used organophosphate insecticides, is commonly employed in aquaculture and agriculture to combat parasitic infestations. However, its inherent instability leads to rapid decomposition into dichlorvos (DDVP), increasing its toxicity by eightfold. Therefore, the environmental effects of trichlorfon in real-world scenarios involve the combined effects of trichlorfon and its degradation product, DDVP. In this study, we systematically investigated the degradation of trichlorfon in tap water over time using HPLC and LC-MS/MS analysis. Subsequently, an experiment was conducted to assess the acute toxicity of trichlorfon and DDVP on goldfish (Carassius auratus), employing a 1H NMR-based metabolic approach in conjunction with serum biochemistry, histopathological inspection, and correlation network analysis. Exposure to trichlorfon and its degradation product DDVP leads to increased lipid peroxidation, reduced antioxidant activity, and severe hepatotoxicity and nephrotoxicity in goldfish. Based on the observed pathological changes and metabolite alterations, short-term exposure to trichlorfon significantly affected the liver and kidney functions of goldfish, while exerting minimal influence on the brain, potentially due to the presence of the blood-brain barrier. The changes in the metabolic profile indicated that trichlorfon and DDVP influenced several pathways, including oxidative stress, protein synthesis, energy metabolism, and nucleic acid metabolism. This study demonstrated the applicability and potential of 1H NMR-based metabonomics in pesticide environmental risk assessment, providing a feasible method for the comprehensive study of pesticide toxicity in water environments.

Detection of insecticides by Tetronarce californica acetylcholinesterase via expression and in silico analysis.

The acetylcholinesterase (AChE) is involved in termination of synaptic transmission at cholinergic synapses and plays a vital role in the insecticide detection and inhibitor screening. Here, we report the heterologous expression of an AChE from Tetronarce californica (TcA) in Escherichia coli (E. coli) as a soluble active protein. TcA was immobilized in calcium alginate beads; the morphology, biochemical properties, and insecticide detection performance of free and immobilized TcA were characterized. Moreover, we used sequence, structure-based approaches, and molecular docking to investigate structural and functional characterization of TcA. The results showed that TcA exhibited a specific activity of 102 U/mg, with optimal activity at pH 8.0 and 30 °C. Immobilized TcA demonstrated superior thermal stability, pH stability, and storage stability compared to the free enzyme. The highest sensitivity of free TcA was observed with trichlorfon, whereas immobilized TcA showed reduced IC50 values towards tested insecticides by 3 to 180-fold. Molecular docking analysis revealed the interaction of trichlorfon, acephate, isoprocarb, λ-cyhalothrin, and fenpropathrin in the active site gorge of TcA, particularly mediated through the formation of hydrogen bonds and π-π stacking. Therefore, TcA expressed heterologously in E. coli is a promising candidate for applications in food safety and environmental analysis. KEY POINTS: • T. californica AChE was expressed solubly in prokaryotic system. • The biochemical properties of free/immobilized enzyme were characterized. • The sensitivity of enzyme to insecticides was evaluated in vitro and in silico.

A colorimetric analytical method based on a TCPP-CuCo2O4-like peroxidase for the detection of trichlorfon.

In this work, a highly sensitive colorimetric sensing platform was designed for the detection of trichlorfon based on inhibiting thiocholine (TCh)-induced redox reaction. 5,10,15,20-Tetracarboxyphenylporphyrin (TCPP) functionalized CuCo2O4 (TCPP-CuCo2O4) was synthesized to construct a colorimetric sensing platform for trichlorfon. In the presence of H2O2, TCPP-CuCo2O4 can oxidize colorless 3,3',5,5'-tetramethylbenzidine (TMB) into blue ox-TMB, accompanied by a strong absorption peak at 652 nm, while acetylcholinesterase (AChE) can specifically hydrolyze acetylthiocholine (ATCh) into TCh, which can reduce ox-TMB back into colorless TMB, resulting in a lower absorbance at 652 nm. Trichlorfon can irreversibly inhibit the activity of AChE and thus recover the absorption peak. Under the optimized conditions, detection of trichlorfon has a wide linear range of 40-4000 ng mL-1 with a linear correlation coefficient of 0.9904. The proposed method can be applied to the detection of trichlorfon in vegetables and has good application prospects.

Developmental Neurotoxicity of Trichlorfon in Zebrafish Larvae.

Trichlorfon is an organophosphorus pesticide widely used in aquaculture and has potential neurotoxicity, but the underlying mechanism remains unclear. In the present study, zebrafish embryos were exposed to trichlorfon at concentrations (0, 0.1, 2 and 5 mg/L) used in aquaculture from 2 to 144 h post fertilization. Trichlorfon exposure reduced the survival rate, hatching rate, heartbeat and body length and increased the malformation rate of zebrafish larvae. The locomotor activity of larvae was significantly reduced. The results of molecular docking revealed that trichlorfon could bind to acetylcholinesterase (AChE). Furthermore, trichlorfon significantly inhibited AChE activity, accompanied by decreased acetylcholine, dopamine and serotonin content in larvae. The transcription patterns of genes related to acetylcholine (e.g., ache, chrna7, chata, hact and vacht), dopamine (e.g., drd4a and drd4b) and serotonin systems (e.g., tph1, tph2, tphr, serta, sertb, htrlaa and htrlab) were consistent with the changes in acetylcholine, dopamine, serotonin content and AChE activity. The genes related to the central nervous system (CNS) (e.g., a1-tubulin, mbp, syn2a, shha and gap-43) were downregulated. Our results indicate that the developmental neurotoxicity of trichlorfon might be attributed to disorders of cholinergic, dopaminergic and serotonergic signaling and the development of the CNS.

The Combined Use of Copper Sulfate and Trichlorfon Exerts Stronger Toxicity on the Liver of Zebrafish.

In aquaculture, copper sulphate and trichlorfon are commonly used as disinfectants and insecticide, sometimes in combination. However, improper use can result in biotoxicity and increased ecological risks. The liver plays a crucial role in detoxification, lipid metabolism, nutrient storage, and immune function in fish. Selecting the liver as the main target organ for research helps to gain an in-depth understanding of various aspects of fish physiology, health, and adaptability. In the present study, zebrafish were exposed to Cu (0.5 mg/L) and Tri (0.5 mg/L) alone and in combination for 21 days. The results demonstrate that both Cu and Tri caused hepatocyte structure damage in zebrafish after 21 days of exposure, with the combination showing an even greater toxicity. Additionally, the antioxidant and immune enzyme activities in zebrafish liver were significantly induced on both day 7 and day 21. A transcriptome analysis revealed that Cu and Tri, alone and in combination, impacted various physiological activities differently, including metabolism, growth, and immunity. Overall, Cu and Tri, either individually or in combination, can induce tissue damage by generating oxidative stress in the body, and the longer the exposure duration, the stronger the toxic effects. Moreover, the combined exposure to Cu and Tri exhibits enhanced toxicity. This study provides a theoretical foundation for the combined use of heavy metal disinfectants and other drugs.

Trichlorfon blocks androgen synthesis and metabolism in rat immature Leydig cells.

Trichlorfon is a widely used organophosphorus insecticide. It has been reported that it has reproductive toxicity to animal models. However, whether trichlorfon affects testosterone biosynthesis and metabolism remains unclear. In this study, we explored the effects of trichlorfon on the steroidogenesis and the expression of genes in androgen biosynthetic and metabolic cascades in immature Leydig cells isolated from pubertal male rats. Immature Leydig cells were treated with trichlorfon (0.5-50 µM) for 3 h. Trichlorfon significantly inhibited total androgen output under basal condition at 5 and 50 µM, and under LH- and cAMP-stimulated conditions at 50 µM. Trichlorfon also downregulated the expression of Star, Sod2, and Gpx1 and their proteins at 5 and 50 µM and the expression of Cyp11a1, Hsd3b1, Cyp17a1, and Srd5a1 at 50 µM. Trichlorfon significantly inhibited total androgen output at 50 µM, which was partially reversed by 400 µg/ml vitamin E, which alone had no effects on androgen output. In conclusion, trichlorfon downregulates the expression of steroidogenesis-related genes and antioxidants, which leads to a decrease in androgen production in rat immature Leydig cells.

Cytochrome P450 superfamily in spotted sea bass: Genome-wide identification and expression profiles under trichlorfon and environmental stresses.

Cytochrome P450s (CYPs), as one of the most diverse enzyme superfamilies in nature, play critical functions in antioxidant reactions against endogenous and exogenous compounds. In this study, we performed genome-wide characterization of CYP superfamily members and analyzed their expression patterns under several abiotic stresses in spotted sea bass, which is known as an economically important fish species in the Chinese aquaculture industry. A total of 55 CYP genes were identified and divided into 17 families within 10 clans. The analysis of phylogeny, gene structure, and syntenic relationships provided evidence for the evolution of CYP genes and confirmed their annotation and orthology. The expression of CYP genes was examined in the liver during trichlorfon stress using quantitative real-time PCR. The results showed that 20 tested CYP genes displayed significant mRNA expression changes, indicating that they may play crucial roles in the metabolism of trichlorfon and can be potential biomarkers for trichlorfon pollution. Moreover, by screening transcriptomic databases, 10, 3 and 19 CYP genes exhibited differential expression patterns in response to hypoxia, alkalinity and heat stress, respectively. Taken together, this study provided insights into the regulation of CYP genes by toxicological and environmental stresses, laid basis for extensive functional studies of the CYP superfamily in spotted sea bass and other teleost species.

Dynamics of dominant rhizospheric microbial communities responsible for trichlorfon absorption and translocation in maize seedlings.

In this study, the available phosphorus (AP) and TCF concentrations in soils and maize (Zea mays) seedling tissues were measured in response to escalating TCF concentrations during 216 hr of culture. Maize seedlings growth considerably enhanced soil TCF degradation, reaching the highest of 73.2% and 87.4% at 216 hr in 50 and 200 mg/kg TCF treatments, respectively, and increased AP contents in all the seedling tissues. Soil TCF was majorly accumulated in seedling roots, reaching maximum concentration of 0.017 and 0.076 mg/kg in TCF-50 and TCF-200, respectively. The hydrophilicity of TCF might hinder its translocation to the aboveground shoot and leaf. Using bacterial 16 S rRNA gene sequencing, we found that TCF addition drastically lessened bacterial community interactions and hindered the complexity of their biotic networks in rhizosphere than in bulk soils, leading to the homogeneity of bacterial communities that were resistant or prone to TCF biodegradation. Mantel test and redundancy analysis suggested a significant enrichment of dominant species Massilia belonging to Proteobacteria phyla, which in turn affecting TCF translocation and accumulation in maize seedling tissues. This study provided new insight into the biogeochemical fate of TCF in maize seedling and the responsible rhizobacterial community in soil TCF absorption and translocation.

Efficacy of chlorine, sodium chloride and trichlorfon baths against monogenean Dawestrema cycloancistrium parasite of pirarucu Arapaima gigas.

This study investigated the efficacy of sodium chloride (SC) and trichlorfon (T) against Dawestrema cycloancistrium and its physiological effects on Arapaima gigas. The efficacy of chlorine (C) as a prophylactic disinfectant was also evaluated. In vitro test with 15 treatments were: SC 4, 8, 10, 12, 14 g/L, T0.1, 0.4, 0.8, 1.6, 3.2 mg/L, and C500, 1000, 3000, 6000 mg/L. Scanning electron microscopy was performed to evaluate parasite damage. The in vivo test was as follows: control, 4 h short baths, once a day, for four consecutive days (SC12 g/L, T5 mg/L); 24 h long baths, for 2 days in 24 h intervals (SC10 g/L, T5 mg/L). In vitro exposure to SC12 and 14 g/L caused 100% mortality of monogeneans at 45 and 60 min, while at T3.2 and 1.6 mg/L 100% of monogeneans died at 30 and 60 min, respectively. In vitro exposure to C resulted in complete mortality after 2-5 min exposure. The SC and T LD50-96 h were 9.9 g/L and 9.73 mg/L, respectively. All in vivo treatments presented efficacy above or close to 90%, with low survival in the long baths. C, starting at 500 mg/L for 5 min, can be used as a disinfectant. Short baths with SC12 g/L and T5 mg/L are recommended for D. cycloancistrium infestations in Arapaima.

In vitro and in vivo action of turmeric oil (Curcuma longa L.) against Argulus spp. in goldfish (Carassius auratus).

Background: Argulus is a common and widespread ectoparasite that causes major parasitic diseases and is a virus and bacteria carrier in the ornamental fish trade. Aim: The purpose of this study is to determine what types of phytochemicals are present in the essential oil extracted from turmeric rhizome (Curcuma longa L.) and to assess the efficacy of turmeric oil in eliminating Argulus spp. infestations in goldfish (Carassius auratus). Methods: The chemical composition and quantity of the major substances in essential oils from fresh turmeric rhizome were detected by gas chromatography/mass spectrometry (GC-MS). The antiparasitic effect of turmeric oils on Argulus spp. was tested at 12.5, 25, 50, 100, and 200 ppm and compared to 0.25 ppm Neguvon® (the positive control). The percentage of Argulus spp. killed, the percentage of the mean mortality rate, and the effectiveness of each test were evaluated. Results: By using GC-MS analysis, it was possible to identify the primary phytochemical component of turmeric essential oil as b-turmerone. The results obtained from the in vitro test indicated that there was a correlation between the concentration of turmeric essential oil and the average mortality rate of fish lice. The mean mortality of fish louse exposed to 200 ppm turmeric essential oil was higher than the mean mortality of fish louse exposed to Neguvon® (p < 0.05). In an in vivo study, the effectiveness of 12.5 ppm turmeric essential oil against parasites was 44.44%, 55.46%, and 62.83% at 24, 48, and 72 hours, respectively. Conclusion: In summary, the efficacy of turmeric essential oil against fish louse has been shown both in vitro and in vivo studies.

Effects of isolated and combined exposures of Boana curupi (Anura: Hylidae) tadpoles to environmental doses of trichlorfon and ultraviolet radiation.

The biodiversity collapse strongly affects the amphibian group and many factors have been pointed out as catalytic agents. It is estimated that several events in the amphibian population decline worldwide may have been caused by the interaction of multiple drivers. Thus, this study aimed to evaluate the stressful effects of the exposure to environmental doses of trichlorfon (TCF) pesticide (0.5 µg/L; and an additional 100-fold concentration of 50 µg/L) and ultraviolet radiation (UV) (184.0 kJ/m² of UVA and 3.4 kJ/m² of UVB, which correspond to 5% of the daily dose) in tadpoles of the Boana curupi species (Anura: Hylidae). The isolated and combined exposures to TCF happened within 24 h of acute treatments under laboratory-controlled conditions. In the combined treatments, we adopted three different moments (M) of tadpole irradiation from the beginning of the exposures to TCF (0 h - M1; 12 h - M2; and 24 h - M3). Then, we evaluated tadpole survival, change in morphological characters, induction of apoptotic cells, lipid peroxidation (LPO), protein carbonyl content (PCC), glutathione S-transferase (GST), non-protein thiols (NPSH), and acetylcholinesterase (AChE), as well as the induction of genomic DNA (gDNA) damage. UVB treatment alone resulted in high mortality, along with a high level of apoptosis induction. Both UVA, UVB, and TCF increased LPO, PC, and AChE, while decreased GST activity. Regarding co-exposures, the most striking effect was observed in the interaction between UVB and TCF, which surprisingly decreased UVB-induced tadpole mortality, apoptosis, and gDNA damage. These results reinforce the B. curupi sensitivity to solar UVB radiation and indicate a complex response in face of UVB interaction with TCF, which may be related to activation of DNA repair pathways and/or inhibition of apoptosis, decreasing UVB-induced tadpole mortality.

Colorimetric assay based on peroxidase-like activity of dodecyl trimethylammonium bromide-tetramethyl zinc (4-pyridinyl) porphyrin for detection of organophosphorus pesticides.

A simple and sensitive colorimetric assay for detecting organophosphorus pesticides (OPs) was developed based on 3,3',5,5'-tetramethylbenzidine (TMB)/hydrogen peroxide (H2O2)/dodecyl trimethylammonium bromide (DTAB)-tetramethyl zinc (4-pyridinyl) porphyrin (ZnTPyP). In this system, based on the peroxidase-like activity of DTAB-ZnTPyP, H2O2 decomposes to produce hydroxyl radicals, which oxidize TMB, resulting in blue oxidation products. The OPs (trichlorfon, dichlorvos, and thimet) were first combined with DTAB-ZnTPyP through electrostatic interactions. The OPs caused a decrease in the peroxidase-like activity of DTAB-ZnTPyP due to spatial site blocking. At the same time, π-interactions occurred between them, and these interactions also inhibited the oxidation of TMB (652 nm), thus making the detection of OPs possible. The limits of detection for trichlorfon, dichlorvos, and thimet were 0.25, 1.02, and 0.66 µg/L, respectively, and the corresponding linear ranges were 1-35, 5-45, and 1-40 µg/L, respectively. Moreover, the assay was successfully used to determine OPs in cabbage, apple, soil, and traditional Chinese medicine samples (the recovery ratios were 91.8-109.8%), showing a great promising potential for detecting OPs also in other complex samples.

Determination of trichlorfon using a molecularly imprinted electrochemiluminescence sensor on multi-walled carbon nanotubes decorated with silver nanoparticles.

Considering the limitations associated with existing methods for the detection of trace amounts of trichlorfon, this paper proposes a novel molecularly imprinted electrochemiluminescence (ECL) sensor for the detection of trichlorfon by utilizing the double enhancement effect of trichlorfon and Ag nanoparticles supported by multi-walled carbon nanotubes (MWCNTs/Ag NPs) in a luminol-H2O2 ECL system. Here, trichlorfon was electropolymerized on the surface of the MWCNT/Ag NP-modified gold nanoelectrode with o-phenylenediamine to prepare the molecularly imprinted polymer-based sensor. After eluting the trichlorfon, imprinted holes for the identification of trichlorfon were retained on the sensor, which were used as signal switches to obtain different ECL intensities through the adsorption of different concentrations of trichlorfon. The ECL signal of the sensitized luminol-H2O2 was doubly enhanced by the MWCNTs/Ag and trichlorfon, improving the sensitivity of the sensor. The trichlorfon concentration was positively correlated with the enhanced ECL intensity of the sensor in the range 5.0 × 10-8-5.0 × 10-11 mol L-1, and the detection limit of trichlorfon was 3.9 × 10-12 mol L-1. Moreover, the proposed sensor was successfully applied to the detection of trichlorfon residues in real samples, and the recovery ranged between 91.8 and 109%. A molecularly imprinted electrochemiluminescence sensor for trichlorfon detection by utilizing the double enhancement effect of trichlorfon and Ag nanoparticles supported by multi-walled carbon nanotubes in a luminol-H2O2 ECL system. The dual enhancement of the ECL signal improved the sensitivity of the sensor.

Effects of Sublethal Concentrations of Insecticides on Survival and Reproduction of Two Bactrocera Species (Diptera: Tephritidae).

The melon fruit fly, Bactrocera cucurbitae (Coquillett) and the pumpkin fruit fly, Bactrocera tau (Walker) (Diptera: Tephritidae), are important invasive pests on Cucurbitaceous hosts. The acute toxicity of five insecticides to females of these two fruit fly species was bio-assayed by membrane method, and effects of their sublethal concentration on the survival, reproduction, and ovary development of females were evaluated in the laboratory. Results showed that based on the LC50 values, both B. cucurbitae and B. tau were the most susceptible to trichlorfon. After treatment with sublethal concentration (LC30) of trichlorfon, abamectin+ß-cypermethrin, spinetoram, and lambda-cyhalothrin, the female survival days of the two Bactrocera species were significantly shortened compared with the control. Moreover, the fecundity of two Bactrocera species was remarkably decreased, after exposure to abamectin+ß-cypermethrin and trichlorfon LC30. However, the sublethal concentration (LC30) of insecticides had no significant influence on the egg hatchability of the fruit flies. Furthermore, after treatment with abamectin+ß-cypermethrin LC30, the ovary length, width, and egg load of B. cucurbitae were significantly lower than that of the control; however, only the ovarian length and egg load of B. tau were significantly decreased on the 16th and 20th day. In conclusion, abamectin+ß-cypermethrin has an excellent insecticidal activity against B. cucurbitae and B. tau.

Acaricide resistance in Boophilus microplus ticks collected from two ecological Zones of Khyber Pakhtunkhwa, Pakistan.

Boophilus microplus is a major cattle tick specie causing great economic loss to the dairy industry throughout the globe including Pakistan. Trichlorfon and Deltamethrin are used to control bovine ticks, and their sprays are also used in other pest control programs that exert pressure on ticks to gain resistance. This study is aimed to examine the resistance level of Rhipiciphalus microplus against trichlorfon and deltamethrin. The engorged ticks were collected from two ecological regions of Khyber Pakhtunkhwa, KPK Pakistan i.e., Swat & Dir (zone-1), and Charsadda & Nowshera (zone-2). Four concentrations of acaricides in two-fold and ten-fold ppm with three replicates for each were used in both bioassays. Egg hatch assay and adult immersion tests were used to assess the resistance status. The probit analysis of egg hatch assay showed the highest hatching percentage in zone 1 on both dilutions (67-76% on two-fold and 68-88% on ten-fold dilution) while lethal concentration (LC95) was found to be 2.187 ppm and discriminating dose (DD) as 4.374 ppm for trichlorfon. In zone 2, hatching percentage was 73-84 on two-fold and 72-91% on ten-fold dilution while LC95 was recorded as 0.599 ppm and DD as 1.198 ppm. The same parameters were studied for deltamethrin and in zone 1 the hatching percentage was found as 38-56% on two-fold dilution and 37-80% on ten-fold dilution while LC95 was recorded as 0.001 ppm and DD as 0.002 ppm. In zone 2, the hatchability was recorded as 42-58% on two-fold and 43-85% on ten-fold dilution. The values for LC95 was recorded as 0.001 ppm and DD as 0.002 ppm. Further, analysis of adult immersion test against trichlorfon revealed the values of LC50 as 2.85 ppm and LC95 as 4.71 ppm in zone 1 and in zone 2 as 3.14 ppm and 5.28 ppm, respectively. Similarly, LC50 and LC95 against deltamethrin was recorded as 0.79 ppm & 1.71 ppm in zone 1 and 0.45 ppm & 4.325 ppm in zone 2, respectively. Based on the findings of this study, the isolated Rhipicephalus microplus was found to be more resistant to the widely used acaricides i.e., trichlorfon than deltamethrin. In order to maintain the efficacy of acaricides at country level, the study recommends continuous monitoring of resistance.

Correlation of bacterial community with phosphorus fraction drives discovery of Actinobacteria involved soil phosphorus transformation during the trichlorfon degradation.

Trichlorfon (TCF) is a broad-spectrum phosphorus (P)-containing pesticide, yet its effects on soil P fraction transformation and bacterial communities during the TCF degradation in soils is unknown. In this study, we investigated soil TCF degradation behavior at different contents of 50, 100 and 200 mg/kg, and analyzed residual TCF contents and metabolites by gas chromatography mass spectrometry after 216-h incubation. Our results suggested that TCF was gradually degraded in soils and was be initially hydrolyzed to dichlorvos via P-C bond cleavage and then other P-containing metabolites. By analyzing different P fractions and soil microbial community composition, we found significant increases of soil available phosphorus contents from 2.76 mg/kg (control) to 3.23 mg/kg (TCF-50), 5.12 mg/kg (TCF-100) and 5.72 mg/kg (TCF-200), respectively. Inorganic CaCl2-P was easily and instantly transformed to primary mineral inorganic P (Pi) forms of HCl-P and citrate-P, while the proportion of enzyme-P (a labile organic P) fluctuated throughout TCF degradation process. Soil available P contents and Pi fractions were significantly correlated with the relative abundance of Actinobacteria. These results highlighted that Actinobacteria is the dominant soil species utilizing TCF as P sources to increase its community richness, and subsequently affect the transformation of P fractions to regulate soil P cycle. Our study gives new understanding on the microorganisms can involve soil P transformation during organophosphorus pesticides degradation in soils, highlighting the importance of bacteria in P transformation and pesticides soil decontamination.