Use Of Synthetic Insecticides Research Articles

Activity of insecticide detoxification enzymes in Pectinophora gossypiella (Saunders): Implications for insect pest management in cotton crops

The pink bollworm Pectinophora gossypiella is one of the most important endocarpic pests in cotton. In the management of this pest, the intensive use of synthetic insecticides has led to the reduction of its sensitivity to certain active ingredients. It is in this perspective that the study was conducted to determine the enzymes involved in the metabolism of insecticides in P. gossypiella. Insects were collected in five localities (Bouaké, Bouaflé, Vavoua, Sésuéla and Kounahiri) with high pest pressure in the southern cotton zone. The collected insects were ground for the determination of enzymes involved in insecticide metabolism. The analyses showed a significant increase in glutathione-δ-transferase activity in populations of Bouaké compared to the other localities. However, individuals from Séguéla expressed more esterase (alpha and beta) and oxidase activities. Alpha and beta esterase activities were also more expressed in Bouaflé individuals. The high enzymatic activity of esterases and oxidases in individuals from Séguéla and Bouaflé reflects a low sensitivity to insecticides in which esterases and oxidases are involved in the metabolism. On the other hand, in Bouaké, only glutathione- δtransferases are involved in the detoxification of insecticides.

Entomopathogenic fungi-based silver nanoparticles: a potential substitute of synthetic insecticides to counter behavioral and physiological immunity in Aedes aegypti mosquito (Diptera: Culicidae).

Excessive use of synthetic insecticides has resulted in environmental contamination and adverse effects on humans and other non-target organisms. Entomopathogenic fungi offer eco-friendly alternatives; however, their application for pest control requires significant advancement owing to limitations like slow killing time and effectiveness only when applied in higher amounts, whereas exposure to UV radiation, high temperature, and humidity can also reduce their viability and shelf-life. The nanoparticles synthesized using fungal extracellular extracts provide a new approach to use fungal pathogens. Our study focused on the synthesis of Metarhizium anisopliae-based silver nanoparticles (AgNPs) and evaluation of their efficiency on various physiological and behavioral parameters of the mosquito Aedes aegypti. The synthesis, size (27.6 d.nm, PDI = 0.209), zeta potential (- 24.3 mV), and shape of the AgNPs were determined through dynamic light scattering, scanning and transmission electron microscopic, and UV-visual spectroscopic analyses (432 nm). Our results showed significantly reduced survival (100% decrease in case of 3.2 and 1.8 μL/cm2 volumes, and 60% decrease in case of 0.8 μL/cm2 volume), phenoloxidase activity (t = 39.91; p = 0.0001), and gut microbiota, with increased oxidative stress and cell apoptosis in AgNPs-challenged mosquitoes. Furthermore, the AgNPs-exposed mosquitoes presented a concentration-specific decrease in flight locomotor activity (F = 17.312; p < 0.0001), whereas no significant changes in antifungal activity, self-grooming frequencies, or time spent were found. These findings enhance our understanding of mosquito responses to AgNPs exposure, and offer a more efficient mosquito control strategy using entomopathogenic fungi.

Hot air and infrared heating methods as alternative control methods against Tribolium castaneum (Herbst.) and their effect on the physiochemical properties of finger millet (Eleusine corocana) flour

Excessive use of synthetic insecticides has raised widespread environmental concerns. Synthetic fumigants such as methyl bromide and phosphine pose significant hazards causing severe environmental issues like ozone depletion, pollution toxicity to non-target organisms, pesticide residues and non-biodegradable properties. The study aims to employ alternate methods for chemical fumigants to disinfest stored pest, T. castaneum in finger millet flour using Hot air (HA) and Infrared (IR) heating methods. HA treatment at 65 °C for 10 min and IR heating at 1760 W for 9 min resulted in 100% mortality of all the life stages of the pest. The mortality (LT50 and LT99) was determined using probit analysis and the mortality data was subjected to generate a regression equation. Considering the properties of the treated flour, HA showed slight increase in bulk density as the temperature and time increased and IR exhibited significant effect on bulk density, influencing the flowability and compressibility of the flour. SEM images on the surface of HA treated flour was smooth, and IR treated flour with surface irregularities were noticed and the surface of untreated flour was coarse. HA and IR can be used for the disinfestation of millet flour thus maintaining the product quality. This research provides valuable insights for sustainable pest management and environment sustainability.

Genetic architecture of the toxicological response to eucalyptol and citronellal in Drosophila melanogaster

The excessive and indiscriminate use of synthetic insecticides has led to environmental pollution, wildlife destruction, and adverse effects on human health, while simultaneously giving rise to resistance in insect pest populations. This adaptive trait is expressed through various mechanisms, such as changes in the cuticle, heightened activities of detoxifying enzymes, and alterations in the sites of action that reduce their affinity for insecticides. In this context, we associate variation in toxicological response with genomic variation, to identify genetic polymorphisms underlying the different steps of the insect (genotype)-response (phenotype)-insecticide (environment) interaction. Under this framework, our objective was to investigate the genetic factors involved in the toxicological response of D. melanogaster lines when exposed to citronellal and eucalyptol vapors (monoterpenes of plant origin). We quantified KT50 in adult males, representing the time necessary for half of the exposed individuals to be turned upside down (unable to walk or fly). Since the genomes of all lines used are completely sequenced, we perform a Genome Wide Association Study to analyze the genetic underpinnings of the toxicological response. Our investigation enabled the identification of 656 genetic polymorphisms and 316 candidate genes responsible for the overall phenotypic variation. Among these, 162 candidate genes (77.1%) exhibited specificity to citronellal, 45 (21.4%) were specific to eucalyptol, and 3 candidate genes (1.5%, CG34345, robo2, and Ac13E), were implicated in the variation for both monoterpenes. These suggest a widespread adaptability in the response to insecticides, encompassing genes influenced by monoterpenes and those orchestrating resistance to the toxicity of these compounds.

White Mustard, Sweet Alyssum, and Coriander as Insectary Plants in Agricultural Systems: Impacts on Ecosystem Services and Yield of Crops

The main reason for adding plants to accompany the main crop is to protect it from pests and diseases. We reviewed the effectiveness of white mustard (Sinapis alba L.), sweet alyssum (Lobularia maritima L.), and coriander (Coriandrum sativum L.) in this regard. White mustard proximity had a strong positive influence on the occurrence of Syrphidae, parasitoids, Coccinellidae, and Carabidae, as well as on the fertility of Syrphidae and the longevity of parasitoids—all of which are essential for biological pest control. It also reduced many pests and diseases. The influence of S. alba on yield depends on the spacing used and the species of protected plant. Sweet alyssum positively affected the occurrence of Syrphidae, Coccinellidae, Anthocoridae, epigeal, and soil fauna, as well as the longevity of parasitoids and Anthocoridae. Its effect on the crop yield is variable, depending on the references consulted. The sensitivity of L. maritima to Phyllotreta spp. excludes it as a companion plant for hosts of these pests. Coriander positively affected the occurrence of Chrysopidae, Coccinellidae, Staphylinidae, and Aranea, as well as the longevity of parasitoids and the egg-laying of Syrphidae. It also reduced some crop pests. Introduction of the reviewed plants can improve the biodiversity of beneficial entomofauna that can help control pests and reduce diseases, with benefits to crop and yield. The use of synthetic insecticides can thus be greatly reduced, though it is not always possible to avoid them completely.

Bio-efficacy of Xanthium strumarium L. Essential Oil against Castor Semilooper, Achaea janata L. (Lepidoptera: Noctuidae)

Background: Although use of synthetic insecticides causes excellent control of insect pests, it leads to adverse effects on non-target organisms as well as the environment. The present study determining the chemical composition and insecticidal activities of essential oil extracted from the leaves of rough cocklebur, Xanthium strumarium and its bioefficacy against the castor semilooper, Achaea janata shall show a new dimension in formulating an ecofriendly management strategy towards castor crop. Methods: Xanthium strumarium leaf essential oil was isolated through hydro-distillation method using Clevenger apparatus and the chemical composition was analysed using GC-MS. The ovicidal and insecticidal activity of the essential oil was determined by dipping and topical application methods, respectively. Larval feeding deterrence and growth inhibitory properties of the essential oil was evaluated through the diet incorporation method. Result: GC-MS analysis of the X. strumarium essential oil revealed the presence of 14 chemical compounds, of which the majority are the terpenes (94.48%). The LC50 values in terms of ovicidal and insecticidal activities were recorded to be 69.70 µL/mL and 0.30 µL/larvae, respectively. The fifty per cent larval feeding deterrence (DC50) and growth inhibitory properties (EC50) were recorded to be 1.88 µl/cm² and 213.94 µL/mL, respectively.

Laboratory evaluation of a bio-insecticide candidate from tangerine peel extracts against Trialeurodes vaporariorum (Homoptera: Aleyrodidae).

The excessive use of synthetic insecticides in modern agriculture has led to environmental contamination and the development of insect resistance. Also, the prolonged use of chemical insecticides in producing flowers and tomatoes in greenhouses has caused health problems for workers and their offspring. In this study, we analyzed the efficacy of mandarin peel (Citrus reticulata L.) essential oil (EO) as a natural insecticide against greenhouse whitefly (Trieurodes vaporariorum W., Homoptera: Aleyrodidae), a common pest in greenhouse production of different crops. Petroleum ether (PET) and n-hexane (HEX) were used as solvents to extract essential oil (EO) from tangerine peels. The yield of EO was 1.59% and 2.00% (m/m) for PET and HEX, respectively. Additionally, the insect-killing power of EO was tested by checking how many greenhouse whiteflies died at different times. The results showed that PET and HEX extracts of tangerine EO effectively controlled greenhouse whiteflies. Furthermore, with both solvents, a 12.5% (v/v) application was as practical as the commercial insecticide imidacloprid. Further characterization tests with the polarimeter, FTIR, HPLC-RP, and GC-MS showed that the essential oil (EO) contained about 41% (v/v) of d-limonene and that this compound may be responsible for the observed insecticidal properties. Therefore, tangerine peel essential oil is an excellent botanical insecticide candidate for controlling greenhouse whiteflies.

Presence of Multiple Genetic Mutations Related to Insecticide Resistance in Chinese Field Samples of Two Phthorimaea Pest Species.

Potatoes hold the distinction of being the largest non-cereal food crop globally. The application of insecticides has been the most common technology for pest control. The repeated use of synthetic insecticides of the same chemical class and frequent applications have resulted in the emergence of insecticide resistance. Two closely related pests that feed on potato crops are the potato tuber moth, Phthorimaea operculella, and the tomato leafminer, Phthorimaea absoluta (syn. Tuta absoluta). Previous studies indicated the existence of insecticide resistance to various classes of insecticides including organophosphates, carbamates, and pyrethroids in field populations of P. operculella and P. absoluta. However, the exact mechanisms of insecticide resistance in P. operculella and to a lesser extent P. absoluta remain still poorly understood. Detecting resistance genotypes is crucial for the prediction and management of insecticide resistance. In this study, we identified multiple genetic mutations related to insecticide resistance in two species of Phthorimaea. An unexpected genetic divergence on target-site mutations was observed between P. operculella and P. absoluta. Three mutations (A201S, L231V, and F290V) in Ace1 (acetylcholinesterase), four mutations (M918T, L925M, T928I, and L1014F) in VGSC (voltage-gated sodium channel), and one mutation (A301S) in RDL (GABA-gated chloride channel) have been detected with varying frequencies in Chinese P. absoluta field populations. In contrast, P. operculella field populations showed three mutations (F158Y, A201S, and L231V) in Ace1, one mutation (L1014F) in VGSC at a lower frequency, and no mutation in RDL. These findings suggest that pyrethroids, organophosphates, and carbamates are likely to be ineffective in controlling P. absoluta, but not P. operculella. These findings contributed to a deeper understanding of the presence of target-site mutations conferring resistance to commonly used (and cheap) classes of insecticides in two closely related potato pests. It is recommended to consider the resistance status of both pests for the implementation of resistance management strategies in potatoes.

Bioefficacy of Chenopodium ambrosioides L. (Chenopodiaceae) on adult Callosobruchus maculatus F. (Coleoptera: Bruchidae)

The use of synthetic insecticides has become widespread and useful for decades. However, due to not being eco- friendly and development of resistance in these organisms plants natural products essential oil components have shown significant potentials for insect control. Hence, laboratory bioassays were conducted to investigate bio-efficacy of Chenopodium ambrosioides L: (Chenopodiaceae) essential oil on adult Callosobruchus maculatus F. (Coleoptera: Bruchidae). On the basis of 24 hr and 48 hr median lethal toxicity (L50). Essential oil of C. ambrosioides was toxic on C. maculatus adults at 0.50 Mg/m2 and 0.20 Mg /m2 in 24 hr Lc50. Also 48 hr Lc99 values obtained show that essential oil of tested plant was 0.90 Mg/m2 and 0.18 Mg/ m2 toxic on adult C. maculatus. The study shows that essential oil of C. ambrosioides have potentials as fumigants for protecting cowpea from damage of C. maculatus

Metabolomic Approaches in Assessing the Insecticidal Activity of the Extracts from Argemone ochroleuca Sweet (Papaveraceae) Against Three Diverse Crop Pests of Economic Importance.

For years, crop protection from pest attack, has been dominated by the use of synthetic insecticides. However, many of them can cause severe environmental problems and human health. In this context, the use of plant extracts constitutes an alternative to avoid this kind of contaminants. In this work, we investigated the chemical constituents and insecticidal activity of different extracts of leaves and stems of Argemone ochroleuca Sweet (Papaveraceae) against three economically important pests Sitophilos zeamais (Coleoptera:Curculionidae), Galleria mellonella (Lepidoptera:Pyralidae) and Xyleborus ferrugineus (Coleoptera:Scolytidae). A GC-MS analysis mostly revealed the presence benzylisoquinoline alkaloids such as allocryptopine, protopine, among others. For the insecticidal activity, after nine hours of contact, the methanolic leaves extract showed a 100 % of mortality, followed by the dichloromethane stems extract with up to 93 % of mortality. The results suggest that the benzylisoquinoline alkaloids are involved in the insecticidal activity through the octopaminergic system of the tested insects.

Laboratory and simulated semi-field larvicidal efficacy of Aframomum angustifolium (Sonn.) K. Schum and Tagetes patula essential oils against Anopheles gambiae

IntroductionMalaria is a vector-borne, important public health problem spread by mosquitoes in tropical regions. The use of synthetic insecticides for mosquito control has been linked to insecticide resistance and environmental consequences. Thus, there is an urgent need to search for new highly selective and biodegradable insecticides lacking long-term toxicity to humans and mammals which are botanical-based compounds from indigenous plant sources available in local communities. Therefore, this study focused on evaluating the larvicidal activity of Aframomum angustifolium and Tagetes patula essential oils against Anopheles gambiae larvae in laboratory and simulated fields. MethodsThe Eos was extracted by the hydro distillation method, and the chemical composition of the Eos was determined using gas chromatography-mass spectrometry (GC-MS). The WHO protocol was followed for the laboratory and the simulated bioassays. Both laboratory-reared and field-collected larvae, as well as non-targeted organisms (Gambusia affinis), were used in simulated field conditions. The collected data were analyzed using probit analysis, and their means were compared in one-way analysis of variance (ANOVA) using IBM SPSS Statistic version 26. ResultsThe main active ingredients in T. patula Eo were terpinolene (20.75 %) and (Z)-ocimene (17.10 %) and A. angustifolium were cis-pinen-3-ol (58.48 %) β-pinene (31.03 %). The EO of T. patula was the most efficacious in the bioassay. The larvicidal bioassay findings demonstrated that the mortality rate was dose- and exposure-dependent. In the laboratory, the EOs of A. angustifolium and T. patula have larvicidal activity against An. gambiae larvae, with LC50 values of 1.71 and 0.71 ppm after 48 h, respectively. Both binary combinations of the EOs showed synergistic interactions at 24 h but antagonistic interactions at 48 h. In the simulated field trial using laboratory-reared larvae, the mortality rate was higher in the simulated setting compared with the laboratory setting for all the tested concentrations for both EOs. Only A. angustifolium EO was toxic against Gambusia affins at 100 ppm. ConclusionThe findings of this study have shown that T. patula and A. angustifolium oils have good larvicidal activities for An. gambiae. The two plants are potential sources of larvicidal compounds that could be used to control the malaria vector.

Characterization of essential oils of Baeckea frutescen L and Cymbopogon nardus L for development as bioinsecticides

The increase in the world’s human population has implications for efforts to minimize crop production losses due to insect attacks. The use of synthetic insecticides has a negative impact on environmental pollution and human health. There is a need for alternative natural insecticides made from plants that are safe, effective and selective. Baeckea frutescen L and Cymbopogon nardus L are essential oil producing plants. The essential oil components contained in these species need to be analyzed for development as bioinsecticides. In this study, the content of the essential oils of samples were analyzed. The method used was steam distillation and the components of the compounds were analyzed using GC-MS. The results of the essential oil content in C. nardus L included citronella, beta.-citronellol, and trans-geraniol. The constituent components of essential oils in B. frutescen L are alpha-pinene, 2- beta -pinene, eucalyptol, trans-caryophyllene, alpha-humulene, and linalool. Based on the literature, these two plants can be developed as raw materials for bioinsecticides.

Effect of gamal leaves (Gliricidia sepium ) extract against termite (Coptotermes curvignathus)

The World Health Organization (WHO) estimates around 3 million people working in the agricultural sector experience insecticide poisoning, and 18 thousand of them die every year. The massive use of synthetic insecticides can harm non-targeted organisms such as plants and livestock. Moreover, this may lead to ecological imbalance and increase pollution. Thus, there is a need for innovation in making natural insecticides. Indonesia is home to abundant plant diversity; one of those is the Gamal plant (Gliricidia sepium). Previous studies found that Gamal leaves contain secondary metabolites such as flavonoids, alkaloids, tannins, saponins, and steroids. Flavonoids are known to have a toxic effect on mealybugs in the papaya plant, and tannins are antimicrobial and often used as pest control. Based on this, the Gamal plant has potential as a natural insecticide. One of the most critical pests in agriculture and households is termites (Coptotermes curvignathus), which often cause losses by damaging plants and household furniture. Also, there is no research yet on Gamal leaves against termites. Therefore, research is necessary to test the effectiveness of Gamal leaf extract against termites. In this study, experimental research was used with a quantitative approach. The Gamal leaf extract was obtained using ethanol and methanol solvents through a maceration technique. Several termites were acclimatized, and 120 were taken randomly for toxicity testing. Four concentrations (10%, 25%, 50%, and 75%) were applied to each group of ten termites. This treatment was repeated three times, and the termite mortality time was measured. Afterwards, the value of LC50 was determined using a regression line between log concentration and probit mortality. The result shows that the higher the concentration, the shorter the termite death time. The mortality rate reaches 100% within 1 to 2 minutes after treatment. The LC50 value of Gamal leaves extract against termites obtained is 5,1%. This indicates that Gamal leaves are very effective in killing termites, even in the lowest concentration. It is likely caused by secondary metabolites, especially flavonoids, that have insecticidal effects. In brief, the ethanolic and methanolic extract of Gamal leaves has the potential to be a natural insecticide to substitute synthetic insecticide, which is safer, economical, and environmentally friendly.

Botanical biopesticides have an influence on tomato quality through pest control and are cost-effective for farmers in developing countries.

Synthetic insecticides heavily applied to manage agricultural pests are highly hazardous to the environment and non-target organisms. Their overuse through repeated treatments in smallholder farming communities is frequent. Botanical biopesticides are ideal for sustainable pest management in agricultural environments by keeping synthetic insecticide use at a minimum. Here we evaluated a locally prepared neem seed extract (NSE) alongside emamectin benzoate against both lepidopteran pests Helicoverpa armigera (Hübner) and Spodoptera exigua (Hübner) on tomato Lycopersicon esculentum Mill under natural field conditions in Pakistan. We compared pest severity, fruit injury, quality, marketability, and cost:benefit ratio (CBR) between treatments. The concentration of azadirachtin A in the NSE was 26.5 ppm. NSE at 2% (20 mL/L) and the emamectin benzoate at the recommended field rate in Pakistan were sprayed weekly throughout the fruiting stage. The pest larvae were significantly more abundant on fruits than on flowers and leaves. Fruit injury and losses were significantly more important in untreated control compared to NSE and emamectin benzoate treatments. NSE efficacy varied with respect to the cultivars used and the seasons. Cultivar Eden harboured more pests than Adventa, and emamectin benzoate suppressed more pest individuals than NSE. Both the insecticidal treatments were comparable in terms of marketable yield productions as well as unmarketable, uninjured, and recovered fruit yields. NSE generated a higher CBR (1: 9.26) than emamectin benzoate (1: 3.23). NSE suppressed pests by acting as an antifeedant, similar to its synthetic counterpart. Smallholder growers can thus use NSE as a cost-effective solution in tomato pest management in Pakistan.

The differences in the toxicity of jackfruit (Artocarpus heterophyllus lam.) seed extract and cocoa fruit (Theobroma cacao l.) extract on mortality of Culex spp. mosquito larvae: Elephant foot disease vector

Culex spp. mosquitoes are the main vectors of filariasis. According to the East Java Provincial Health Office on 2018, the total number of filariasis (elephantiasis) cases in East Java Province was 134 cases distributed across 38 districts/cities. So far, the control of Culex mosquitoes has been carried out using synthetic insecticides. The use of synthetic insecticides is considered effective, practical, potent, and economically advantageous. However, continuous and repeated use of synthetic insecticides can lead to environmental pollution, the death of various types of living creatures, and resistance. Synthetic insecticides are hazardous to human and domestic animal health, as well as having an impact on other non-target organisms. An alternative that can be pursued is the use of natural insecticides derived from plants. Jackfruit seeds contain secondary metabolites such as tannins, flavonoids, alkaloids, steroids, and saponins. Meanwhile, cocoa fruit husks contain tannins, saponins, alkaloids, and flavonoids. The utilization of compounds present in the extracts of jackfruit seeds (Artocarpus heterophyllus Lam.) and cocoa fruit husks can be used to control the population of Culex spp. mosquitoes, the main vectors of filariasis. The methods employed in this research include extraction, preparation of serial concentrations, colonization of test larvae, preliminary testing, and final testing. The research results reveal the toxicity or LC50 value of jackfruit seed extract (Artocarpus heterophyllus Lam.) towards Culex spp. mosquito larvae are 430.303 ppm, while the toxicity (LC50) value of cocoa fruit husk extract (Theobroma cacao L.) is 306.742 ppm. The conclusion drawn from this research is that the cocoa fruit husk extract (Theobroma cacao L.) is more toxic compared to the jackfruit seed extract (Artocarpus heterophyllus Lam.) towards Culex spp. mosquito larvae.

Larvicidal susceptibility of essential oils from Cinnamodendron dinisii, Callistemon viminalis and Myrcia tomentosa against Culex quinquefasciatus (Say) (Diptera: Culicidae)

Culex quinquefasciatus Say, 1823 (Diptera: Culicidae) is a vector of pathogens and parasites, whose form of control is the use of synthetic insecticides. However, the indiscriminate use of these products has led to the emergence of resistant populations. The objective was to evaluate the susceptibility of C. quinquefasciatus larvae to essential oils (EOs) from leaves of Cinnamodendron dinisii Schwacke (CD), Callistemon viminalis (Sol. ex Gaertn.) G.Don (CV) and Myrcia tomentosa (Aubl.) DC. (MT), and the influence on biochemical parameters, in addition to the in silico potential of the most promising EO for the target acetylcholinesterase (AChE) enzyme. The steam distilled EOs were analysed by gas chromatography/mass spectrometry. The EOs lethal concentration of 50 % (LC50) was estimated using different concentrations and probit analysis. Then, the larvae were exposed for 1 h to the LC75 of the most promising EO, and the biochemical parameters were evaluated in vitro: soluble protein concentration, reduced glutathione content, hydrogen peroxide production, lipid peroxidation levels, and AChE enzyme activity. The AChE molecular docking was also performed. The main chemical constituents in CD were pinenes, sabinene and bicyclogermacrene; in CV were α-pinene and 1,8-cineole and in MT were (E)-caryophyllene and germacrene D. The lowest LC50 (1.43 mg. L−1) was estimated for CD EO, although LC75 reduced all biochemical parameters and inhibited AChE activity. The docking results for the major (bicyclogermacrene) and minor compounds (aromadendrene, α-copaene, drymenol, σ- and β-elemene) present in CD EO have high affinity with AChE. In conclusion the effects indicate the promising potential of the CD EO for the development of larvicide against the C. quinquefasciatus.

Exploring the bioactive potential leaves of Sphaeranthus indicus: Targeting immature stages of Aedes aegypti and Culex quinquefasciatus mosquito vectors through bioassay-guided screening and fraction isolation

Mosquito control is vital for combating mosquito-borne diseases, but concerns exist regarding the use of synthetic insecticides. This study aimed to explore eco-friendly alternatives derived from natural sources. The larvicidal, pupicidal, and ovicidal activities of various fractions obtained from the hexane leaf extract of Sphaeranthus indicus were investigated against two important mosquito vectors, Aedes aegypti and Culex quinquefasciatus. S. indicus leaves were extracted with hexane and column chromatography was performed with hexane, ethyl acetate, methanol, and their mixtures as eluents. Among the ten fractions (F1-F10) evaluated, fraction ‘F-4’ exhibited significant activity against third instar larvae, pupae, and eggs of both mosquito species, closely followed by ‘F-5’ . At a concentration of 10 ppm, ‘F-4’ achieved 100% mortality in larvae and displayed LC50 values of 5.08 ppm and 5.03 ppm for Ae. aegypti and Cx. quinquefasciatus larvae, respectively. The LC50 values for pupae were 6.12 ppm and 5.83 ppm for Ae. aegypti and Cx. quinquefasciatus, respectively. Regarding ovicidal activity, ‘F-4’ demonstrated percentages ranging from 63.2% to 64.8% against Ae. aegypti and Cx. quinquefasciatus eggs, respectively. These findings underscore the potent larvicidal, pupicidal, and ovicidal effects of fraction ‘F-4’ from S. indicus against the targeted mosquito species. Further research is warranted to identify the active compounds responsible for these effects and explore practical applications for sustainable mosquito control strategies.

Synthetic Carvacrol Derivatives for the Management of Solenopsis Ants: Toxicity, Sublethal Effects, and Horizontal Transfer

Ants belonging to the genus Solenopsis are highly significant invasive pests worldwide. The control of these insects has historically relied on the use of synthetic insecticides, which, unfortunately, has led to a range of ecological repercussions. In light of these challenges and the limited availability of registered products for managing these pests, our study set out to synthesize and assess the insecticidal properties of carvacrol derivatives. The lethal and sublethal effects caused by these derivatives were compared to the essential oil of Lippia gracilis (50.7% carvacrol) and to the base molecule—carvacrol. Carvacryl benzoate was the most toxic derivative to Solenopsis sp., with an LD50 of 3.20 μg/ mg. This compound was about 2 and 7.6 times more toxic than carvacrol at the doses needed to kill 50 and 90% of populations, respectively. The workers of Solenopsis sp. showed a rapid reduction in survival when exposed to carvacrol (LT50 = 8.43 h) and carvacryl benzoate (LT50 = 8.87 h). Insects treated with sublethal doses of the compounds did not show significant effects on self-cleaning, allogrooming and aggregation, with the exception of those treated with L. gracilis essential oil. The oil increased self-cleaning and reduced allogrooming and aggregation. Ants treated with carvacrol and carvacryl benzoate travelled greater distances and had higher movement speeds when compared to the control. These compounds exhibited decreased meanders and angular velocities. When live workers were exposed to dead individuals at the LD90 of the compounds, carvacryl benzoate was the derivative that most reduced survival due to horizontal transfer. These findings underscore the considerable potential of carvacrol derivatives, specifically carvacryl benzoate, as an alternative approach to managing ants of the Solenopsis genus.

Evaluation Of Phytochemical Active Ingredients Present In Organic Solvent Extracts And Larvicidal Properties Of Some Selected Plants From Taraba State Against Anopheles Larvae

The Continuous use of synthetic insecticides and its toxicity problems coupled with the incidence of insect resistance calls for the need for alternative insecticide. Plants extracts a rich source of bioactive compounds can provide an alternative source of insecticide which are ecofriendly. The research evaluated the phytochemical active ingredients present in organic solvent extracts and larvicidal effect of some selected plants from Taraba state against Anopheles larvae. World Health Organisation protocol was adopted for the larvicidal bioassay. Twenty group of fourth instar Anopheles larvae were exposed to various concentrations of 200,400,600 and 800ppm, mortality was observed and recorded after 24 hours. The results of preliminary qualitative phytochemical analyses of tested plants revealed the presence of some secondary metabolite that may be responsible for the bio control potentials. Acetone extract of Hyptis suaveoleons against the fourth instant anopheles larval was observed to have the highest percentage mortality among the entire plants extracts than the aqueous. The lowest mortality was observed at 200ppm with 35.0% while the maximum was at 800ppm with 80.0%. Lc50 and Lc90 values were achieved at 438 and 866ppm with the LCL -UCL 340-540 and 722-1151 respectively. While the biological activity of Hyptis suaveolence aqueous extract had its lowest mortality at 200ppm with 36.67% while the maximum was at 800ppm with 80.0%. Lc50 and Lc90 values were achieved at 582 and 1225ppm with the LCL -UCL 449-806 and 942-2636 respectively. Ancova results showed no significance difference at p&gt;0.05 among the mean percentage mortality of the treated doses.&#x0D;  

Determination of insecticide resistence associated insensitive acetylcholinesterase in Culex quinquefasciatus, Say,1823 (Diptera: Culicidae) collected in Yucatán, Mexico

Acetylcholinesterase is an enzyme whose main function is to terminate the transmission of nerve impulses in the cholinergic synapse in insects through the hydrolysis of acetylcholine. However, frequent applications of insecticides can select for individuals with an alteration in the enzyme and functional changes that result in an insensitivity to insecticides. In Mexico, the current strategy to combat insect vectors such as Culex quinquefasciatus is based mainly on the use of synthetic insecticides. The use of these chemicals in health and agricultural practices may also contribute to mosquito insensitivity to several groups of insecticides. Therefore, it is considered necessary to determine if there is any physiological mechanism associated with resistance. For this reason, the objective of this research was to identify if there is insensitivity of acetylcholinesterase to insecticides in Cx. quinquefasciatus populations, collected in urban and rural areas of the State of Yucatán, Mexico. Enzymatic tests were carried out with slight modifications to the established protocols. Areas were identified with mosquito populations showing acetylcholinesterase insensitivity to propoxur, a carbamate insecticide. We consider it important to determine the environmental factors that affect the behavior and response of mosquitoes following exposure to insecticides, and this knowledge could inform the design of efficient strategies in vector control programs.