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Pesticide Biochemistry and Physiology Jun 2021The intense spraying of pesticides to control different arthropod pests has resulted in negative side effects for the management of pests. It was previously discovered...
The intense spraying of pesticides to control different arthropod pests has resulted in negative side effects for the management of pests. It was previously discovered that exposure to non-acaricidal insecticides alone or in a mixture, results in lower efficiency of the acaricide spirodiclofen used for Brevipalpus spp. control. We investigate here whether the induced expression of detoxification enzymes by non-lethal insecticides may antagonize spirodiclofen toxicity. Brevipalpus californicus mites exposed to the insecticide phosmet alone or in combination with spirodiclofen showed increased activity of P450 monooxygenases (P450s). No antagonistic effects in mite mortality were observed by the combination of phosmet and spirodiclofen. On the other hand, mites exposed to the insecticide imidacloprid alone or in combination with spirodiclofen showed an increase in the activity of P450s, carboxylcholinesterases (CCE), and glutathione-S-transferases (GST). An antagonistic effect on mite mortality was observed when mites were exposed to the LC of spirodiclofen combined with the field rate treatment of imidacloprid. The addition of PBO (a P450 monooxygenase inhibitor) to the mixture of spirodiclofen and imidacloprid resulted in a synergistic effect over mite mortality but the addition of DEM (a GST inhibitor) resulted in an antagonist effect. Taken together, this study showed that the combination of imidacloprid with spirodiclofen is antagonistic for the control of B. californicus, and this results from the induction of detoxification enzymes, such as P450s, CCE, and GST. The use of inhibitors highlights the role of these enzymes in the antagonism of the mixture.
Topics: Acaricides; Animals; Insecticide Resistance; Insecticides; Mites; Pesticides
PubMed: 33993973
DOI: 10.1016/j.pestbp.2021.104855 -
EFSA Journal. European Food Safety... Mar 2021The conclusions of the EFSA following the peer review of the initial risk assessments carried out by the competent authorities of the rapporteur Member State, Spain, and... (Review)
Review
The conclusions of the EFSA following the peer review of the initial risk assessments carried out by the competent authorities of the rapporteur Member State, Spain, and co-rapporteur Member State, Greece, for the pesticide active substance phosmet and the assessment of applications for maximum residue levels (MRLs) are reported. The context of the peer review was that required by Commission Implementing Regulation (EU) No 844/2012, as amended by Commission Implementing Regulation (EU) No 2018/1659. The conclusions were reached on the basis of the evaluation of the representative uses of phosmet as an insecticide on citrus fruits, pome fruits, peaches/nectarines and potatoes (field uses). The reliable end points, appropriate for use in regulatory risk assessment, are presented. Missing information identified as being required by the regulatory framework is listed. Concerns are identified.
PubMed: 33747228
DOI: 10.2903/j.efsa.2021.6237 -
PloS One 2021Monitoring pesticide resistance is essential for effective and sustainable agricultural practices. Bioassays are the basis for pesticide-resistance testing, but devising...
Monitoring pesticide resistance is essential for effective and sustainable agricultural practices. Bioassays are the basis for pesticide-resistance testing, but devising a reliable and reproducible method can be challenging because these tests are carried out on living organisms. Here, we investigated five critical parameters and how they affected the evaluation of resistance to the organophosphate phosmet or the pyrethroid lambda-cyhalothrin using a tarsal-contact protocol on Drosophila suzukii, a worldwide invasive pest. Three of the parameters were related to insect biology: (i) sex, (ii) age of the imago (adult stage) and (iii) genetic diversity of the tested population. The two remaining parameters were linked to the experimental setup: (iv) the number of individuals tested per dose and (v) the duration of exposure to the active ingredient. Results showed that response to insecticide differed depending on sex, males being twice as susceptible to phosmet as females. Age principally affected young females' susceptibility to phosmet, because 0-24 hour-old flies were twice as susceptible as 24-48 hour-old and 72-96 hour-old females. Genetic diversity had no observable effect on resistance levels. The precision and accuracy of the median lethal dose (LD50) were greatly affected by the number of individuals tested per dose with a threshold effect. Finally, optimal duration of exposure to the active ingredient was 24 h, as we found an underestimation of mortality when assessed between 1 and 5 h after exposure to lambda-cyhalothrin. None of the main known point mutations on the para sodium channel gene associated with a knockdown effect were observed. Our study demonstrates the importance of calibrating the various parameters of a bioassay to develop a reliable method. It also provides a valuable and transferable protocol for monitoring D. suzukii resistance worldwide.
Topics: Animals; Biological Assay; Drosophila; Female; Genetic Variation; Insect Control; Insecticide Resistance; Insecticides; Introduced Species; Lethal Dose 50; Male; Nitriles; Phosmet; Pyrethrins
PubMed: 33667239
DOI: 10.1371/journal.pone.0247756 -
Food Chemistry Jun 2021This study was undertaken to assess the potential of Tribolium castaneum (Red flour beetle) acetylcholinesterase (Tc-AChE) based electrochemical biosensor integrating...
This study was undertaken to assess the potential of Tribolium castaneum (Red flour beetle) acetylcholinesterase (Tc-AChE) based electrochemical biosensor integrating WO/g-CN nanocomposite modified Pencil graphite electrode to detect an organophosphate insecticide, Phosmet. The WO/g-CN nanocomposite provides a non-toxic, biocompatible surface for binding the enzyme on the electrode surface, attributed to its large surface area, high conductivity, and low ohmic resistance. The proposed biosensor shows a very good analytical performance with LOD 3.6 nM for Phosmet and effectively determined Phosmet in wheat with a 99% recovery rate. Furthermore, molecular docking deciphers the binding interactions of Phosmet with Tc-AChE using a modified AutoDock LGA algorithm and an AMBER03 force field in YASARA. The kinetic parameters strongly suggest the high potency of inhibitor with the enzyme. This study presents an adaptable, rapid, and straightforward approach that opens ways towards real progress in developing commercial biosensors for pesticide detection.
Topics: Acetylcholinesterase; Animals; Biosensing Techniques; Coleoptera; Edible Grain; Electrodes; Food Storage; Graphite; Molecular Docking Simulation; Nanocomposites; Nitriles; Oxides; Pesticides; Phosmet; Tungsten
PubMed: 33422918
DOI: 10.1016/j.foodchem.2020.128894 -
Journal of Economic Entomology Feb 2021The Mediterranean fruit fly Ceratitis capitata (Wiedemann, 1824) (Diptera: Tephritidae) is among the main pests of fruit crops worldwide. Biological control using...
The Mediterranean fruit fly Ceratitis capitata (Wiedemann, 1824) (Diptera: Tephritidae) is among the main pests of fruit crops worldwide. Biological control using entomopathogenic nematodes (EPNs) may be an alternative to suppress populations of this pest. Thus, the aim of this study was to evaluate the pathogenicity and virulence of six EPN isolates (Heterorhabditis bacteriophora HB, H. amazonensis IBCB-n24, Steinernema carpocapsae IBCB-n02, S. rarum PAM-25, S. glaseri IBCB-n47, and S. brazilense IBCB-n06) against C. capitata pupae. The compatibility of EPNs with different chemical insecticides that are registered for management of C. capitata was also assessed. Isolates of H. bacteriophora HB and S. brazilense IBCB-n06 at a concentration of 1,000 infective juveniles (IJ)/ml proved to be most pathogenic to C. capitata (70 and 80% mortality, respectively). In contrast, the isolates H. amazonensis IBCB-n24, Steinernema carpocapsae IBCB-n02, S. rarum PAM-25, S. glaseri IBCB-n47 provided pupal mortality of less than 60%. Bioassays to determine lethal concentrations indicated that concentrations of 600 IJ/ml (H. bacteriophora HB) and 1,000 IJ/ml (S. brazilense IBCB-n06) showed the highest virulence against C. capitata pupae. In contrast, the highest numbers of IJs emerged at concentrations of 1,200 and 200 IJ/ml. In compatibility bioassays, malathion, spinetoram, phosmet, acetamiprid, and novaluron were considered compatible with and harmless (Class 1) to H. bacteriophora HB and S. brazilense IBCB-n06, according to IOBC/WPRS. This information is important for implementing integrated management programs for C. capitata, using biological control with EPNs, whether alone or in combination with chemical insecticides.
Topics: Animals; Ceratitis capitata; Insecticides; Pest Control, Biological; Pupa; Rhabditida; Tephritidae
PubMed: 33399211
DOI: 10.1093/jee/toaa301 -
Advanced Science (Weinheim,... Dec 2020Recently, 2D niobium carbide MXene has drawn vast attention due to its merits of large surface area, good metallic conductivity, and tunable band gap, making it...
Recently, 2D niobium carbide MXene has drawn vast attention due to its merits of large surface area, good metallic conductivity, and tunable band gap, making it desirable for various applications. However, the usage of highly toxic fluoride-containing etchant and quite long etching time in the conventional synthesis route has greatly hindered further exploration of MXene, especially restricting its biomedical application. Herein, novel fluoride-free NbCT nanosheets are prepared by a facile strategy of electrochemical etching (E-etching) exfoliation. Taking advantage of rapid aluminum clearance, excellent chemical stability, and biocompatibility from the MXene by E-etching, fluoride-free NbCT /acetylcholinesterase-based biosensors are constructed for phosmet detection with the limit of detection down to 0.046 ng mL. The fabricated NbCT -based biosensor is superior to the counterpart from hydrofluoric acid-etched NbCT , indicating that fluoride-free MXene can enhance the enzyme activity and electron transfer in the biosensor. The results prove that the fluorine-free MXene shows promise for developing biosensors with high performance of ultrahigh sensitivity and selectivity. It is highly expected that the fluoride-free MXene as a stable and biocompatible nanoplatform has great potential to be expanded to many other biomedical fields.
PubMed: 33344117
DOI: 10.1002/advs.202001546 -
Archives of Toxicology Dec 2020In chemical risk assessment, default uncertainty factors are used to account for interspecies and interindividual differences, and differences in toxicokinetics and... (Comparative Study)
Comparative Study
Acetylcholinesterase inhibition in electric eel and human donor blood: an in vitro approach to investigate interspecies differences and human variability in toxicodynamics.
In chemical risk assessment, default uncertainty factors are used to account for interspecies and interindividual differences, and differences in toxicokinetics and toxicodynamics herein. However, these default factors come with little scientific support. Therefore, our aim was to develop an in vitro method, using acetylcholinesterase (AChE) inhibition as a proof of principle, to assess both interspecies and interindividual differences in toxicodynamics. Electric eel enzyme and human blood of 20 different donors (12 men/8 women) were exposed to eight different compounds (chlorpyrifos, chlorpyrifos-oxon, phosmet, phosmet-oxon, diazinon, diazinon-oxon, pirimicarb, rivastigmine) and inhibition of AChE was measured using the Ellman method. The organophosphate parent compounds, chlorpyrifos, phosmet and diazinon, did not show inhibition of AChE. All other compounds showed concentration-dependent inhibition of AChE, with ICs in human blood ranging from 0.2-29 µM and ICs ranging from 0.1-18 µM, indicating that AChE is inhibited at concentrations relevant to the in vivo human situation. The oxon analogues were more potent inhibitors of electric eel AChE compared to human AChE. The opposite was true for carbamates, pointing towards interspecies differences for AChE inhibition. Human interindividual variability was low and ranged from 5-25%, depending on the concentration. This study provides a reliable in vitro method for assessing human variability in AChE toxicodynamics. The data suggest that the default uncertainty factor of ~ 3.16 may overestimate human variability for this toxicity endpoint, implying that specific toxicodynamic-related adjustment factors can support quantitative in vitro to in vivo extrapolations that link kinetic and dynamic data to improve chemical risk assessment.
Topics: Acetylcholinesterase; Animals; Bayes Theorem; Biological Variation, Population; Cholinesterase Inhibitors; Dose-Response Relationship, Drug; Electrophorus; Female; GPI-Linked Proteins; Humans; Male; Proof of Concept Study; Reproducibility of Results; Risk Assessment; Species Specificity; Toxicity Tests; Toxicokinetics; Uncertainty
PubMed: 33037899
DOI: 10.1007/s00204-020-02927-8 -
A bacteriophage infecting species has a prolate capsid and shows similarities to a family of phages.Canadian Journal of Microbiology Feb 2021phage vB_MloS_Cp1R7A-A1 was isolated from soil planted with chickpea in Saskatchewan. It is dissimilar in sequence and morphology to previously described...
phage vB_MloS_Cp1R7A-A1 was isolated from soil planted with chickpea in Saskatchewan. It is dissimilar in sequence and morphology to previously described rhizobiophages. It is a B3 morphotype virus with a distinct prolate capsid and belongs to the tailed phage family . Its genome has a GC content of 60.3% and 238 predicted genes. Putative functions were predicted for 57 genes, which include 27 tRNA genes with anticodons corresponding to 18 amino acids. This represents the highest number of tRNA genes reported yet in a rhizobiophage. The gene arrangement shows a partially modular organization. Most of the structural genes are found in one module, whereas tRNA genes are in another. Genes for replication, recombination, and nucleotide metabolism form the third module. The arrangement of the replication module resembles the replication module of Enterobacteria phage T5, raising the possibility that it uses a recombination-based replication mechanism, but there is also a suggestion that a T7-like replication mechanism could be used. Phage termini appear to be long direct repeats of just over 12 kb in length. Phylogenetic analysis revealed that Cp1R7A-A1 is more closely related to PhiCbK-like phages and other B3 morphotype phages than to other rhizobiophages sequenced thus far.
Topics: Bacteriophages; Capsid; Caulobacter crescentus; Genes, Viral; Genome, Viral; Mesorhizobium; Phosmet; Phylogeny; Siphoviridae; Species Specificity
PubMed: 32905709
DOI: 10.1139/cjm-2020-0281 -
Journal of Economic Entomology Oct 2020Spotted-wing drosophila (Drosophila suzukii Matsumura) is a major pest of soft-skinned fruit and due to the low infestation tolerance for marketable fruit, growers take...
Spotted-wing drosophila (Drosophila suzukii Matsumura) is a major pest of soft-skinned fruit and due to the low infestation tolerance for marketable fruit, growers take preventive actions to hinder spotted-wing drosophila damages. Insecticides application is one of the measures taken by growers. Although intensive spraying programs have been used to manage spotted-wing drosophila, its early infestation, rapid reproduction, and vast range of host have caused damage to still occur in fruit, including tart cherries, Prunus ceraus (Linnaeus). Therefore, there is a merit for information on insecticide's curative activity to understand whether sprays manage spotted-wing drosophila individuals within infested fruit. Tart cherry fruit were exposed to spotted-wing drosophila adults for 3 d. After this infestation period, insecticides were applied 1 and 3 d later. Small larvae, large larvae, and pupae were counted 9 d after initial infestation. A parallel set of insecticide-treated tart cherries were subjected to residue analysis. Phosmet and spinetoram were able to reduced live spotted-wing drosophila counts compared with the control at all life stages and insecticide application times, whereas zeta-cypermethrin, acetamiprid, and cyantraniliprole were less consistent in reducing spotted-wing drosophila numbers. Chromobacterium subtsugae demonstrated no curative action. Residue analysis demonstrated that zeta-cypermethrin residues mostly remained on fruit surface. Small portions of phosmet, spinetoram, and cyantraniliprole were able to penetrate fruit surfaces and move into subsurface tissues. Acetamiprid was the only compound which >47% penetrated into the fruit subsurface consistently across both years. Curative activity demonstrated in this study can provide additional tactics for spotted-wing drosophila management in tart cherry Integrated Pest Management (IPM) programs.
Topics: Animals; Chromobacterium; Drosophila; Fruit; Insect Control; Insecticides
PubMed: 32869833
DOI: 10.1093/jee/toaa161 -
Spectrochimica Acta. Part A, Molecular... Jan 2021Phosmet exerts its neurotoxicity by inhibiting acetylcholinesterase that catalyzes the degradation of acetylcholine (a neurotransmitter). Serum proteins are known to...
Phosmet exerts its neurotoxicity by inhibiting acetylcholinesterase that catalyzes the degradation of acetylcholine (a neurotransmitter). Serum proteins are known to influence the biodistribution of various endogenous and exogenous compounds. In the present study, the binding interactions of phosmet with bovine serum albumin (BSA) was investigated to determine the free concentration of phosmet for its neurotoxicity. The binding mechanism was studied using fluorescence, UV-Vis absorption spectroscopy, circular dichroism (CD), and molecular docking techniques. UV-Vis absorption data showed an increase in absorbance of BSA upon binding with phosmet with a slight red-shift in the peak around 280 nm. Intrinsic fluorescence of BSA was quenched in the presence of phosmet. The quenching was observed to be inversely correlated to the temperature that indicated the formation of ground state non-fluorescent complex (static quenching). Binding constant values and n values for the binding of phosmet with BSA at three different temperatures confirmed non-covalent binding interactions with a single set of equivalent binding sites. Thermodynamic parameters ∆G (-137.40 ± 3.58 kJ mol); ΔH (-16.33 ± 5.28 kJ mol) and ΔS(-469 ± 12.45 kJ mol) confirmed that the binding was spontaneous and non-covalent interactions like electrostatic, hydrogen bonding and van der Waals forces played an important role in the binding. The CD data indicated the conformational change in BSA upon binding with phosmet which resulted in a change in the melting temperature. Molecular docking presented the binding model for BSA-phosmet complex and displayed that non-covalent interactions played a significant role in the binding mechanism.
Topics: Binding Sites; Circular Dichroism; Molecular Docking Simulation; Phosmet; Protein Binding; Serum Albumin, Bovine; Spectrometry, Fluorescence; Spectrophotometry, Ultraviolet; Thermodynamics; Tissue Distribution
PubMed: 32829155
DOI: 10.1016/j.saa.2020.118803