Bioassay Results Research Articles

Novel Evodiamine-Based Sulfonamide Derivatives as Potent Insecticide Candidates Targeting Insect Ryanodine Receptors.

Pests represent an important impediment to efficient agricultural production and pose a threat to global food security. On the basis of our prior research focused on identifying insecticidal leads targeting insect ryanodine receptors (RyRs), we aimed to identify evodiamine scaffold-based novel insecticides. Thus, a variety of evodiamine-based derivatives were designed, synthesized, and assessed for their insecticidal activity against the larvae of Mythimna separata (M. separata) and Plutella xylostella (P. xylostella). The preliminary bioassay results revealed that more than half of the target compounds exhibited superior activity compared to evodiamine, matrine, and rotenone against M. separata. Among these, compound 21m displayed the most potent larvicidal efficiency, with a remarkable mortality rate of 93.3% at 2.5 mg/L, a substantial improvement over evodiamine (10.0% at 10 mg/L), matrine (10.0% at 200 mg/L), and rotenone (30.0% at 200 mg/L). In the case of P. xylostella, compounds 21m and 21o displayed heightened larvicidal activity, boasting LC50 values of 9.37 × 10-2 and 0.13 mg/L, respectively, surpassing that of evodiamine (13.41 mg/L), matrine (291.78 mg/L), and rotenone (18.39 mg/L). A structure-activity relationship analysis unveiled that evodiamine-based derivatives featuring a cyclopropyl sulfonyl group at the nitrogen atom of the B ring and a fluorine atom in the E ring exhibited more potent larvicidal effects. This finding was substantiated by calcium imaging experiments and molecular docking, which suggested that 21m could target insect RyRs, including resistant mutant RyRs of P. xylostella (G4946E and I4790M), with higher affinity than chlorantraniliprole (CHL). Additionally, cytotoxicity assays highlighted that the potent compounds 21i, 21m, and 21o displayed favorable selectivity and low toxicity toward nontarget organisms. Consequently, compound 21m emerges as a promising candidate for further development as an insecticide targeting insect RyRs.

Combining Passive Sampling and Dosing to Unravel the Contribution of Hydrophobic Organic Contaminants to Sediment Ecotoxicity.

Contaminated sediments are ubiquitous repositories of pollutants and cause substantial environmental risks. Results of sediment bioassays remain difficult to interpret, however, as observed effects may be caused by a variety of (un)known stressors. This study aimed therefore to isolate the effects of hydrophobic organic contaminants from other (non)chemical stressors present in contaminated sediments, by employing a newly developed passive sampling-passive dosing (PSPD) test. The results showed that equilibrium partitioning between pesticides or polyaromatic hydrocarbons (PAHs) in contaminated sediments and a silicone rubber (SR) passive sampler was achieved after 1-3 days. Chlorpyrifos concentrations in pore water of spiked sediment matched very well with concentrations released from the SR into an aqueous test medium, showing that SR can serve as a passive dosing device. Subjecting the 96 h PSPD laboratory bioassay with nonbiting midge (Chironomus riparius) larvae to field-collected sediments showed that at two locations, concentrations of the hydrophobic organic contaminant mixtures were high enough to affect the test organisms. In conclusion, the developed PSPD test was able to isolate the effects of hydrophobic organic contaminants and provides a promising simplified building block for a suite of PSPD tests that after further validation could be used to unravel the contribution of hydrophobic organic chemicals to sediment ecotoxicity.

Potential control of Vespula germanica and Polistes dominula (Hymenoptera: Vespidae) using entomopathogens

ABSTRACT The first recordings in South Africa of the invasive social wasps, Vespula germanica and Polistes dominula (Hymenoptera: Vespidae) were in 1974 and again in 2008. These wasps are known to represent a significant threat to the biodiversity of ecosystems and socio-economic activities in countries they invade. Here, the susceptibility of V. germanica and P. dominula larvae to indigenous species of entomopathogenic nematodes (EPNs), namely Heterorhabditis bacteriophora, H. noenieputensis and Steinernema yirgalemense, and entomopathogenic fungus (EPF) Beauveria bassiana was tested both in laboratory bioassays and in situ wasp nests application in the Western Cape province. The bioassay results indicate that both P. dominula and V. germanica larvae are susceptible to all biocontrol agents used. All larvae of both wasp species were dead and infected after exposure to 200 IJ/insect within four days after inoculation. Similar results were obtained seven days after inoculation with B. bassiana. To test in-field pathogenicity against P. dominula, wasp nests were treated with B. bassiana, H. bacteriophora, a mixture of the EPF and EPN species and a control of distilled water. The number of larvae and pupae infected 168 h after application were determined. In both cases, the mixture of EPF/EPN performed best, with a mean percentage of 31.39% ± 4.75% larvae infected, and only 3.42% ± 0.68% of pupae infected. The results obtained suggest that higher concentrations of selected biologicals can be used as inundative biological control agents within an integrated management programme for the control of P. dominula and V. germanica in South Africa. Highlights At 48 h after inoculation, 100% of the wasp larvae treated with EPN were infected After 168 h, 74–98% of EPF-treated larvae showed visual infection of Beauveria bassiana Heterorhabditis bacteriophora outperformed other biocontrol agents tested Combined EPN and EPF in situ nest application achieved larval infection of 31% ± 4.75%.

Do Commercial Insect Repellents Provide Protection against the Tick Amblyomma sculptum (Acari: Ixodidae)?

Amblyomma sculptum is a species of public health interest because it is associated with the transmission of the bacteria that causes Brazilian Spotted Fever (BSF). The use of repellents on humans is a prophylactic measure widely used to provide protection against a series of arthropod vectors, including mosquitoes and ticks. However, in Brazil, the effectiveness of commercial repellents against A. sculptum is little known. Therefore, it is necessary to carry out specific studies to evaluate the repellency of these commercial products, registered for use against mosquitoes, against the star tick. The main goal of the present work was to evaluate the effectiveness of six commercial repellents against A. sculptum. Unfed nymphs, aged between two and eight weeks, were tested against products based on DEET (OFF!® and Repelex®), Icaridin (Exposis® and SBP®), and IR3535 (Johnsons and Henlau). Three bioassays were conducted to evaluate tick behavior: (i) filter paper, (ii) fingertip, and (iii) field. All bases tested showed high repellent activity, differing significantly (p < 0.05) from the control. It was observed the formulation with DEET resulted in the best results in the filter paper bioassay. In the fingertip bioassay, the DEET base repelled a greater number of ticks compared to Icaridin. In the field bioassay, there was no significant difference between the Icaridin base and DEET, and both formulations differed from the control (p < 0.05). The six formulations tested showed significant percentages of repellency against ticks; however, for the fingertip and field bioassays, the products OFF!®, Repelex®, and Exposis® were tested as they showed better performance in the filter paper test. OFF!® showed the best percentage of repellency (100%), followed by Repelex® (96.8%), and Exposis® (93.1%), considering the two-hour period of the bioassay-field-test. Proving the effectiveness of repellents on the market against A. sculptum presented in this study is crucial, since this is the main ectoparasite of humans that can transmit Rickettsia rickettsii when infected. The effectiveness of commercial insect repellents against other tick species that parasitize humans can also be explored.

Avian colibacillosis – current aspects

Colibacillosis is a bacterial disease of humans, animals and birds caused by Escherichia coli, pathogenic gram-negative bacillus. Despite its secondary nature, colibacillosis widely affects poultry farms and causes significant economic losses. The disease spread is closely associated with antibiotic resistance problem because a diseased carrier bird may be a reservoir of antibiotic-resistant Escherichia coli strains. In addition, genes of virulence and resistance have been proven to be transferred from avian Escherichia strains toextra intestinal pathogenic strains that are dangerous to humans. Colibacillosis is transmitted aerogenically, alimentally, rarely transovarially, with droppings, mucus, feed, water, handling tools and operating personnel. Birds are most susceptible attheage of1–14days and at the onset of laying period. The disease may present asacute, subacute and chronic forms and is most often manifested by catarrhal hemorrhagic enteritis with profuse foamy diarrhea, respiratory tract lesions, fibrinous peritonitis and polyserositis, as well as a significant decrease in weight gains, stunting, egg laying decrease or complete cessation. Colibacillosis is diagnosed comprehensively taking into account the epizootic situation, findings of clinical examination and postmortem examination of dead or emergency-slaughtered poultry as well as laboratory test and bioassay results. Bacteriological, serological and molecular genetic methods are used for the disease diagnosis. Colibacillosis prevention includes improvement of poultry keeping practice (control of feed and water quality, disinfection, pest control, microclimate control) as well as timely complex vaccination of all poultry. The disease shall be treated taking into account primary etiological factors and bacteria sensitivity to antimicrobials.

Limonoids from the Branches and Leaves of Aglaia lawii and Their Cytotoxic Activities.

Three undescribed limonoids (1-3), named aglaians G-I, and one new natural product azedaralide (4), together with nine known analogues (5-13) were isolated from the branches and leaves of Aglaia lawii by RP C18 column, silica gel column, Sephadex LH-20 column chromatography and preparative HPLC. The structures of the new compounds were elucidated by IR, HRESIMS, 1D, 2D NMR, electronic circular dichroism (ECD) calculations and X-ray crystallography diffraction analysis. The results of bioassay showed that the compound 12 exhibited potential inhibitory activity against six human tumor cell lines (MDA-MB-231, MCF-7, Ln-cap, A549, HeLa and HepG-2) with IC50 values as 8.0-18.6 μM.

Effective biosorption of Al ions from drinking water by lignocellulosic biomass rice straw

High concentration of aluminum (Al) in drinking water is a major intake source of it and can result in serious diseases. Rice straw (RS) as lignocellulosic biomasses has great potential to peak up metal ions from aqueous environment, however, feasibility of Al3+ removal by RS has not been investigated yet. The present study aimed to evaluate the capacity of RS as a novel biosorbent for Al3+ from drinking water. Biosorption characteristics of RS were surveyed through several biological and physiochemical techniques. Additionally, isotherm, kinetic and thermodynamic studies were evaluated using various common models. BET profiles revealed the presence of textural mesoporosity on heterogeneous surface, which leading to improve the biosorption capacity. SEM-EDS analysis confirmed the morphological changes as irregularly particles of Al3+ on external surface via physical mechanism. The results of bioassays and FTIR analysis showed carboxylic and hydroxyl groups in lignin and pectin as the main Al3+ binding site. The batch experimental results showed the maximum biosorption capacity of 283.09 mg/g and removal efficiency of 94.86% for Al3+ at biosorbent dosage of 0.05 g/100 mL, contact time of 50 min, pH 7.5, and temperature of 30 °C. The Freundlich model has the best match and suggests the biosorption process as a multi-layer. According to the results of free activation energy, biosorption process was also physical. As thermodynamic result, the biosorption behavior was found spontaneous and endothermic. Consequently, results showed RS as an economical biosorbent for reducing Al3+ of drinking water. Meanwhile, it can be considered as one of the most appropriate methods for management of rice paddies waste.

Electrophysiological and behavioural responses of Plutella xylostella L. (Lepidoptera: Plutellidae) to thirteen non-host plant essential oils

The diamondback moth (DBM), Plutella xylostella (L.), is a cosmopolitan obligate pest of cruciferous crops. Currently, DBMs management is largely dependent on broad-spectrum synthetic pesticides, which has led to the adverse effects on the environment, human health, and nontargeted organisms. Thus, alternative control methods are needed. The essential oils (EOs) derived from bioactive species may be developed as effective alternatives for the management of DBMs that is safe and eco-sustainable than conventional pesticides. In this study, we investigated electrophysiological (EAG) and behavioral responses of DBM adults to the thirteen non-host EOs of Acorus calamus, Ageratum conyzoides, Artemisia argyi, Chenopodium ambrosioides, Cymbopogon citratus, Foeniculum vulgare, Ocimum basilicum, Pelargonium hortorum, Perilla frutescens, Pogostemon cablin, Polygonum hydropiper, Rosmarinus officinalis, and Ruta graveolens in order to contribute to the development of low environmental impact management alternatives. EAG recordings revealed all the tested EOs significantly elicited EAG responses of DBM females, and the males were sensitive to the eleven EOs except A. conyzoides and O. basilicum. Meanwhile, EAG recordings of DBMs exhibited dose-dependent responses to these tested EOs in most cases. In Y-tube olfactometer bioassays, the EOs of A. calamus, C. citratus, P. hortorum, P. hydropiper, and R. graveolen demonstrated prominent repellent effects on DBM females at concentrations of 10 μg/μL or higher. The results of oviposition bioassays found the number of eggs on the two plants with the five tested EOs were less than that on the two plants with paraffin oil. And the oviposition indexes of the plants that fixed with the EOs of P. hortorum, R. graveolen, A. calamus, P. hydropiper, C. citratus, and paraffin oil were –71.81%, –59.43%, –57.46%, –51.11%, –35.41%, and 0.09%, respectively. These findings indicate that the five EOs, especially P. hydropiper EO, provide active and safe tools for natural repellents to prevent and control DBMs infestations of cruciferous vegetables.

Chemical Composition and Insecticidal Activities of Blumea balsamifera (Sambong) Essential Oil Against Three Stored Product Insects

Blumea balsamifera (L.) DC. (Asteraceae), also known as sambong, is a perennial herb used in China for medicinal purposes. The essential oil (EO) of B. balsamifera was extracted by hydrodistillation. Thirty chemical components of the EO were analyzed by gas chromatography-mass spectrometry (GC-MS) and GC, accounting for 88.0% (w/w) of the total oil. The EO of B. balsamifera was mainly composed of monoterpenes and sesquiterpenes, in which borneol (23.3%), β-caryophyllene (20.9%) and camphor (11.8%) were the major components. The insecticidal activities of the EO and its three main compounds against Tribolium castaneum, Lasioderma serricorne and Sitophilus oryzae were evaluated. The results of bioassays displayed that the EO of B. balsamifera did not have fumigant toxicity to the three target insects, but exhibited significant contact activity against L. serricorne (LD50 = 12.4 μg/adult) and S. oryzae (LD50 = 44.4 μg/adult). Meanwhile, the EO showed a notable repellent effect on T. castaneum at all testing concentrations and a general repellent effect on S. oryzae at high concentrations (78.63 nL/cm2). β-Caryophyllene showed the best performance in the contact toxicity bioassays against the three insects. The results indicated that B. balsamifera has the potential to be used as a source of botanical insecticides for the control of stored-product insects.

Multivariate Statistical Analysis in Assessing Surface Water Toxicity in the Volga Reservoirs (Based on the Results of Bioassay and Chemical Analysis)

Multivariate Statistical Analysis in Assessing Surface Water Toxicity in the Volga Reservoirs (Based on the Results of Bioassay and Chemical Analysis)

Characterization of anti-drug antibody dynamics using a bivariate mixed hidden-markov model by nonlinear-mixed effects approach

Biological therapies may act as immunogenic triggers leading to the formation of anti-drug antibodies (ADAs). Population pharmacokinetic (PK) models can be used to characterize the relationship between ADA and drug disposition but often rely on the ADA bioassay results, which may not be sufficiently sensitive to inform on this characterization.In this work, a methodology that could help to further elucidate the underlying ADA production and impact on the drug disposition was explored. A mixed hidden-Markov model (MHMM) was developed to characterize the underlying (hidden) formation of ADA against the biologic, using certolizumab pegol (CZP), as a test drug. CZP is a PEGylated Fc free TNF-inhibitor used in the treatment of rheumatoid arthritis and other chronic inflammatory diseases.The bivariate MHMM used information from plasma drug concentrations and ADA measurements, from six clinical studies (n = 845), that were correlated through a bivariate Gaussian function to infer about two hidden states; production and no-production of ADA influencing PK. Estimation of inter-individual variability was not supported in this case. Parameters associated with the observed part of the model were reasonably well estimated while parameters associated with the hidden part were less precise. Individual state sequences obtained using a Viterbi algorithm suggested that the model was able to determine the start of ADA production for each individual, being a more assay-independent methodology than traditional population PK. The model serves as a basis for identification of covariates influencing the ADA formation, and thus has the potential to identify aspects that minimize its impact on PK and/or efficacy.

Plant volatiles mediated the orientation preference of slugs to different plant species.

Slugs mechanically damage plant leaves, resulting in significant economic losses. However, there are limited cost-efficient strategies available in slug management. By studying how slugs utilize plant volatiles to locate host plants, we can gain insights into the design of attractants and repellents. Bioassay results suggest slugs (Agriolimax agrestis) prefer to orientate to lettuce (Lactuca sativa), cabbage (Brassica oleracea L.), and young tobacco seedlings, compared with old tobacco seedlings. We analyzed the volatomics of lettuce, cabbage, young and old tobacco seedlings. 2-(2-butoxyethoxy)-ethanol acetate (2EA) had high abundance while nonanal, decanal, and β-cylocitral had relatively low content in volatiles. Old tobacco seedlings released significantly more hexanal but fewer 1,4-dihydro-4-oxopyridazine (DO). In olfactory tests, hexanal, nonanal, decanal, and β-cylocitral showed strong repellency to slugs, while DO at a dose of 500 ng/μL and 2EA at a dose of 1% were attractive to slugs. The two alkanes, hexadecane and heptadecane, had no effect on slug orientating to host plants. DO and 2EA can thus alleviate the repellency of hexanal, nonanal, decanal and β-cylocitral. The high emission of hexanal in old tobacco seedlings helps repel slugs, while 2EA and DO attract slugs to lettuce and cabbage. These findings suggest that these chemicals can be utilized in the design of repellents and attractants, and contribute to constructing a push-pull system for slug control. © 2023 Society of Chemical Industry.

Viruses Demonstrate Selective Survival During Simulated Anaerobic Digestion of Plant Biomass

Objective. This research aimed at laboratory simulation of anaerobic digestion of plant biomass contaminated by a mixture of viruses with a wide host range to evaluate if viruses can retain their infectivity and pose a biohazard during the use of plant-based reusable resources such as digestate. Methods. Anaerobic digestion was simulated in air-tight desiccators using anaerobic bags and indicator strips to ensure proper conditions, and using fresh biomass of naturallyvirus-infected plants. In one of the variants, a commercial mixture of anaerobic bacteria and enzymes was also added to see if it would be more efficient in terms of plant digestion and virus inactivation. For serological detection of the tomato mosaic virus, cucumber mosaic virus, and potato virus Y, DAS-ELISA was used with commercial diagnostic kits and positive controls. Absorbance values were measured at 405 nm. Total RNA was extracted using a RNeasy Plant Mini kit following the manufacturer’s instructions. Molecular detection of viruses was carried out by two-step RT-PCR using specific oligonucleotide primers available from the literature. To check if the viruses can retain their infectivity after the anaerobic digestion of plant biomass waste, a bioassay was used where Nicotiana rustica plants producing necrotic lesions upon infection with many viruses were mechanically inoculated at the stage of 2 true leaves. For statistical processing of data, the mean and standard error were calculated using Microsoft Excel software. Results. After prolonged anaerobic digestion, tomato mosaic virus was still detected in plant residues, but it is important to note that it was also found in high concentration in the liquid phase. Hence, during the anaerobic digestion, a significant proportion of the virus was successfully eluted from plant residues into the digestate. Interestingly and contrary to tomato mosaic virus, cucumber mosaic virus has not practically eluted to the liquid phase. On the other hand, potato virus Y was supposedly completely decomposed during the anaerobic digestion of plant biomass waste, as it was not detected either by ELISA or by PCR. It is likely that not all of the investigated viruses represent a potential biohazard in the context of the use of renewable resources. RT-PCR outcomes showed the presence of tomato mosaic virus and cucumber mosaic virus both in the solid and the liquid phases, augmenting the ELISA data. Lastly, bioassay results have confirmed that at least tomato mosaic tobamovirus may escape the aggressive process of waste decomposition and remain able to infect host plants raising issues about the safety of reusable plant resources. Conclusions. The survival of plant viruses during plant biomass waste processing was studied in the context of biological safety. The preservation of serological markers and genetic signatures of model viruses in the process of anaerobic digestion has been confirmed. For the first time, it was proven that tomato mosaic virus may preserve its infectivity during long-term incubation of plant biomass waste in anaerobic conditions, which requires further attention when using renewable resources. On the example of PVY, it has been shown that potyviruses do not survive during anaerobic digestion and therefore may not pose an epidemic risk in using processed renewable resources. It has been demonstrated that artificial introduction of anaerobic microorganisms does not have a decisive effect on the stability of the studied model viruses.

Identification of Mid-Polar and Polar AhR Agonists in Cetaceans from Korean Coastal Waters: Application of Effect-Directed Analysis with Full-Scan Screening.

Major aryl hydrocarbon receptor (AhR) agonists were identified in extracts of blubber, liver, and muscle from six long-beaked common dolphins (Delphinus capensis) and one fin whale (Balaenoptera physalus) collected from Korean coastal waters using effect-directed analysis. Results of the H4IIE-luc bioassay indicated that the polar fractions of blubber and liver extracts from the fin whale exhibited relatively high AhR-mediated potencies. Based on full-scan screening with high-resolution mass spectrometry, 37 AhR agonist candidates, spanning four use categories: pharmaceuticals, pesticides, cosmetics, and natural products, were selected. Among these, five polar AhR agonists were newly identified through toxicological confirmation. Concentrations of polar AhR agonists in cetaceans were tissue-specific, with extracts of blubber and liver containing greater concentrations than muscle extracts. Polar AhR agonists with great log KOA values (>5) were found to biomagnify in the marine food chain potentially. Polar AhR agonists contributed 8.9% of the observed AhR-mediated potencies in blubber and 49% in liver. Rutaecarpine and alantolactone contributed significantly to the total AhR-mediated potencies of blubber, whereas hydrocortisone was a major AhR contributor in the liver of the fin whale. This study is the first to identify the tissue-specific accumulation of polar AhR agonists in blubber and liver extracts of cetaceans.

Evaluating cover crop tolerance to corn residual herbicides using field-treated soil in greenhouse bioassay

AbstractMore growers across the U.S. Midwest are considering interseeding or overseeding cover crops into corn for soil health purposes. One challenge of this practice is the potential injury from soil residual herbicides applied preemergence (PRE) for weed control in corn to the interseeded and overseeded cover crop species. Field-treated soil was collected in 2021 and 2022 at Janesville, WI, and Lancaster, WI, to investigate the impact of PRE residual herbicides on establishment of interseeded and overseeded cover crops via greenhouse bioassay. Soil samples (0 to 5 cm depth) were collected from field experiments at 0, 10, 20, 30, 40, 50, 60, and 70 days after treatment (DAT). Treatments consisted of 14 single and multiple sites of action (SOAs) PRE herbicides plus a nontreated check (NTC). Four bioindicator cover crop species were used in the greenhouse bioassay: annual ryegrass, cereal rye, radish, and red clover. Cover crop biomass was collected 28 d after bioassay seeding. Cover crop species responded differently across herbicide treatments. Annual ryegrass and cereal rye were sensitive to treatments containing herbicide Group 15, whereas Groups 2, 4, 5, 14, and 27 had minimal impact on their establishment when field soil was collected at 30 DAT (interseeding scenario) and 70 DAT (overseeding scenario) compared to the NTC. Radish and red clover were sensitive to herbicide Groups 2, 4, and 27, whereas Groups 5, 14, and 15 had minimal impact on their establishment. Annual ryegrass, radish, and red clover were more sensitive to PRE herbicides containing two and three SOAs than to herbicides with a single SOA. On the basis of these greenhouse bioassay results, cover crop species should be carefully selected depending on the soil residual herbicide when interseeded and overseeded into corn. Field studies will be conducted to validate these results and support recommendations to growers interested in this system.

Design and Synthesis of Pyrimidine Amine Containing Isothiazole Coumarins for Fungal Control.

Developing new fungicides is always crucial to protecting crops. A series of 4-(3,4-dichloroisothiazol-5-yl)-7-(2-((5-(5-pyrimidin-4-yl)amino)ethoxy)-8-methyl) coumarin derivatives were designed and synthesized by Williamson ether condensation and substitution reactions. Structure determinations were clarified by 1H NMR, 13C NMR, and HRMS, and compound 4h crystallized by the fusion method for further structural confirmation. The in vitro bioassay results showed that the target compounds displayed good fungicidal activity against Alternaria solani, Botrytis cinerea, Cercospora arachidicola, Fusarium graminearum, Physalospora piricola, Rhizoctonia solani, and Sclerotinia sclerotiorum. Among them, compounds 4b and 4d showed higher inhibitory activity against R. solani, with EC50 values of 11.3 and 13.7 μg/mL, respectively, and they were more active than the positive control diflumetorim with an EC50 value of 19.8 μg/mL. Molecular docking suggested that compound 4b and diflumetorim may have similar interactions with complex I NADH oxidoreductase. Density functional theory calculation and pesticide-likeness analysis studies gave a rational explanation of their fungicidal activity. These results indicated that compounds 4b and 4d deserved further optimization according to the principle of pesticide-likeness.

Uracil hydrazones: design, synthesis, antimicrobial activities, and putative mode of action.

Crop diseases caused by plant pathogenic fungi and bacteria have led to substantial losses in global food production. Chemical pesticides have been widely used as a primary means to mitigate these issues. Nevertheless, the persistent and excessive use of pesticides has resulted in the emergence of microbial resistance. Moreover, the improper application and excessive utilization of pesticides can contribute to environmental pollution and the persistence of pesticide residues. Consequently, the development of novel and highly effective bactericides and fungicides to combat plant pathogens holds immense practical importance. A series of uracil hydrazones IV-B was deliberately designed and evaluated for their antimicrobial efficacy. The results of bioassays indicated that most IV-B exhibited >80% inhibition against the fungal species Monilia fructigena and Sclerotium rolfsii, as well as the bacterial species Clavibacter michiganensis subsp. michiganensis, Xanthomonas oryzae pv. oryzae, and Ralstonia solanacearum, at 50 μg/mL in vitro. In vivo, IV-B20 showed 89.9% of curative and 71.8% of protective activities against C. michiganensis subsp. michiganensis at 100 μg/mL superior to thiodiazole copper and copper hydroxide. IV-B20 also showed excellent protective activity against M. fructigena (96.3% at 200 μg/mL) and S. rolfsii (80.4% at 1000 μg/mL), which were greater than chlorothalonil and equivalent to thifluzamide. Mechanistic studies revealed that IV-B20 induced oxidative damage in pathogenic bacteria and promoted the leakage of cellular contents. This study suggests that IV-B20 with uracil hydrazone skeleton has great potential as an antimicrobial candidate. These findings lay a foundation for practical application in agriculture. © 2023 Society of Chemical Industry.

Efficacy of &lt;em&gt;Eucalyptus citriodora&lt;/em&gt; and &lt;em&gt;Syzygium aromaticum&lt;/em&gt; essential oil as insecticidal, antiovipositant, and fumigant against &lt;em&gt;Callosobruchus maculatus&lt;/em&gt; F (Coleoptera: Bruchidae)

Callosobruchus maculatus is the most pernicious pest of stored grain worldwide. Even though synthetic insecticides are commonly used to eliminate this insect pest, the negative effect of this pest management method on humans and the environment raises concern among people around the world. This study was done to identify the active ingredient of essential oils in Eucalyptus citriodora and Syzygium aromaticum and to evaluate the effectiveness of those essential oils in controlling C. maculatus. The results of gas chromatography/mass spectrometry analysis indicated that the essential oil extracted from the leaves of S. aromaticum are rich in Eugenol and β caryophyllene as much as 81% and 14.65% consecutively, while E. citriodora oil contains 86% of Citronella. According to the bioassay results, increasing the essential oil concentration from 1% to 3% resulted in a significant increase in insect mortality rate, oviposition deterrence, and fumigant toxicity. Additionally, S. aromaticum has significantly shown a higher insecticidal performance compared to E. citriodora. However, there are no synergistic effects observed on the use of essential oil of both plant species on C. maculatus. These results suggest that S. aromaticum and E. citriodora essential oils could be potential candidates as a natural insecticide in managing C. maculatus in stored products.

Adult Diaphorina citri Biocontrol Using Hirsutella citriformis Strains and Gum Formulations.

Hirsutella citriformis Speare is the only entomopathogenic fungus that has been applied to control the hemipteran Diaphorina citri Kuwayama. However, the use of available commercial products under field conditions is limited due to conidia's shelf life and short environmental persistence. We have previously reported the citrus psyllid D. citri adults' biocontrol potential using H. citriformis strains. The aim of the present study was to evaluate different formulations based on H. citriformis (OP-Hir-3, OP-Hir-10, and OP-Hir-12 strains) conidia and gums as additives to improve D. citri adults' biocontrol, under laboratory, greenhouse, and field conditions, using Hirsutella gums as conidia stabilizers to improve their viability under environmental drought conditions and as insecticide. Laboratory bioassay results showed that the highest (p < 0.05) D. citri mortality was achieved using FOP-Hir-10GH (63.5%), followed by the Hirsutella gum control (42.2%). Under greenhouse conditions, adults' mortality reached up to 84.6% with FOP-Hir-12 and 49.0% with Hirsutella gum. In addition, we applied H. citriformis formulations under field conditions in a commercial citrus grove located in Tecomán, Colima, México, at 21.5 °C and 73.3% relative humidity (RH) in March and 25.7 °C and 72.5% RH in October 2022 and observed 67.3% and 94.0% mortality of D. citri adults, respectively. Hirsutella gum alone showed significant insecticidal activity against D. citri adults. In conclusion, this study demonstrated that Hirsutella gum functioned as additive to H. citriformis conidia formulations, improving D. citri adults' mortality and showing potential for this pest biocontrol in citrus orchards.

Assessing the susceptibility and efficacy of traditional neurotoxic (pyrethroid) and new-generation insecticides (chlorfenapyr, clothianidin, and pyriproxyfen), on wild pyrethroid-resistant populations of Anopheles gambiae from southern Benin.

The objective of this study was to determine the susceptibility of wild Anopheles gambiae sensu lato (s.l.) from southern Benin to the new insecticides (chlorfenapyr (CFP), pyriproxyfen (PPF), and clothianidin (CTD)) and assess the efficacy of insecticide-treated bed nets (ITNs) that contain these new products. Wild An. gambiae from the Benin communes of Allada, Ifangni, Akpro-Missérété, and Porto-Novo were tested for their susceptibility to CFP and PPF using the WHO bottle tests, and pyrethroids (alpha-cypermethrin, deltamethrin, and permethrin) and CTD using WHO tube tests. WHO cone tests were used to evaluate the efficacy of Interceptor® (which contains alpha-cypermethrin (ACM) only), Interceptor® G2, (CFP + ACM), and Royal Guard® nets (PPF + ACM). The ovaries of blood-fed An. gambiae from Ifangni exposed to a new PPF net were dissected, and egg development status was examined using Christopher's stages to determine the fertility status of the mosquitoes. Using a standardized protocol, the oviposition rate and oviposition inhibition rate were calculated from live blood-fed An. gambiae placed in oviposition chambers after exposure to PPF. In all four mosquito populations, pyrethroid mortality ranged from 5 to 80%, while chlorfenapyr and clothianidin mortality ranged from 98 to 100%. At Ifangni, all mosquitoes exposed to Royal Guard® nets were infertile (100%) while the majority (74.9%) of mosquitoes exposed to Interceptor® nets had fully developed their eggs to Christopher's stage V. The oviposition inhibition rate after exposure of the mosquitoes to the PPF was 99% for the wild population of An. gambiae s.l. and the susceptible laboratory strain, An. gambiae sensu stricto (Kisumu). The results of this study suggest that pyrethroid-resistant An. gambiae from the selected communes in southern Benin are susceptible to chlorfenapyr, clothianidin, and pyriproxyfen. In addition, based on bioassay results, new and unused Interceptor® G2 and Royal Guard® nets were effective on Ifangni's mosquito populations. Despite the availability of new effective insecticides, continued vigilance is needed in Benin. Therefore, monitoring of resistance to these insecticides will continue to periodically update the Benin national insecticide resistance database and management plan.