Potential larvicidal bioefficacy of copper sulfide-based hybrid nanoemulsions of eucalyptus oil against Aedes aegypti (Linnaeus)

Background & objectives: Nanotechnology, an emerging field, has acquired considerable attention for the control of vectors. The present study aimed to synthesize, characterize copper sulfide- and eucalyptus oil-based hybrid nanoemulsions and investigate their larvicidal potential against Aedes aegypti by studying larvicidal bioassay, morphological aberrations, histopathological alterations, biochemical analysis and evaluation of risk assessment in non-target organisms. Methods: Hybrid nanoemulsions were prepared by mixing aqueous copper sulfide nanoparticles (CuSNPs) with non-polar eucalyptus oil in five ratios (1:1, 1:2, 1:3, 1:4 and 1:5) by sonication, screened and characterized using Transmission electron microscopy (TEM). Larvicidal activity was recorded and toxicity values were calculated by log-probit method. Morphological, histological and biochemical changes were examined in Aedes aegypti larvae after treatment. Nanohybrids were also tested under simulated conditions and against non-target organism. Results: The nanohybrid ratio of 1:5 was found to be stable after thermodynamic stability tests. TEM studies revealed average size of 90±7.90 nm with globular shape. LC50 and LC90 toxicity values of prepared CuSNPs were calculated out to be 5.00 and 5.81ppm after 24 hours treatment. Effective concentration of prepared nanohybrid (6.5ppm) tested under simulated conditions showed maximum larvicidal mortality after 48 hours of exposure. No toxicity towards the Mesocyclops spp. was observed after treatment of these nanohybrids even up to 21 days. Interpretation & conclusion: Copper sulfide based hybrid nanoemulsions were found to show efficient larvicidal property which can be used for the formulation of ecofriendly bio-larvicide against Aedes aegypti.

Atividade larvicida contra aedes aegypti e toxicidade preliminar contra artemia salina l. de extratos e frações de monteverdia evonymoides (reissek) biral / Larvicidal activity against aedes aegypti and preliminary toxicity against artemia salina l. of extracts and fractions of monteverdia evonymoides (reissek) biral. / Actividad larvicida contra aedes aegypti y toxicidad preli- minar contra artemia salina l. de extractos y fracciones de monteverdia evonymoides (reissek) biral.

Aedes aegypti (Diptera: Culicidae) é o principal vetor das arboviroses dengue, zika, chikungunya e febre amarela. A busca por inseticidas naturais para combater o mosquito ganha destaque nos países de clima tropical. Considerando a atividade larvicida presente no gênero Monteverdia o objetivo do estudo foi avaliar o potencial larvicida dos extratos e frações da espécie Monteverdia evonymoides (Reissek) Biral. O material vegetal (folhas e galhos) foi seco a temperatura ambiente, foi moído e submetido a extração em Soxhlet modificado. A toxicidade foi avaliada por meio do bioensaio com Artemia salina L. As larvas de Aedes aegypti foram expostas nas concentrações 10, 100, 500 e 1000 µg.mL⁻¹. Após 24H foi realizada a leitura da mortalidade (CL50) e submetido método estatístico Probit. As amostras não apresentaram toxicidade frente a Artemia salina L. (>1000 µg.mL⁻¹) e apresentaram potencial larvida no controle de larvas de terceiro estádio, com CL50 >200 µg.mL⁻¹. Os extratos de M. Evonymoides são seguros e apresentaram potencial larvicida contra larvas do mosquito.

Aedes aegypti (Diptera: Culicidae) is the main vector of arboviruses den- gue, zika, chikungunya and yellow fever. The search for natural insecticides to combat the mosquito is highlighted in countries with a tropical climate. Considering the larvicidal activity present in the genus Monteverdia, the objective of the study was to evaluate the larvicidal potential of extracts and fractions of the species Monteverdia evonymoides (Reissek) Biral. The plant material (leaves and branches) was dried at room temperature, ground and subjected to extraction in modified Soxhlet. Toxicity was evaluated by bio- assay with Artemia salina L. Aedes aegypti larvae were exposed to concentrations of 10, 100, 500 and 1000 µg.mL⁻¹. After 24 hours, the mortality reading (CL50) was performed and the Probit statistical method was submitted. The samples did not show toxicity against Artemia salina L. (>1000 µg.mL⁻¹) and showed potential larval life in the control of third- stage larvae, with CL50 >200 µg.mL⁻¹. M. Evonymoides extracts are safe and showed lar- vicidal potential against mosquito larvae.

Aedes aegypti (Diptera: Culicidae) es el principal vector de los arbovirus dengue, zika, chikungunya y fiebre amarilla. Se destaca la búsqueda de insecticidas natu- rales para combatir el mosquito en países con clima tropical. Considerando la actividad larvicida presente en el género Monteverdia, el objetivo del estudio fue evaluar el poten- cial larvicida de extractos y fracciones de la especie Monteverdia evonymoides (Reissek) Biral. El material vegetal (hojas y ramas) fue secado a temperatura ambiente, molido y sometido a extracción en Soxhlet modificado. La toxicidad se evaluó mediante el bioen- sayo con Artemia salina L. Se expusieron larvas de Aedes aegypti a concentraciones de 10, 100, 500 y 1000 µg.mL⁻¹. A las 24 horas se realizó la lectura de mortalidad (CL50) y se sometió al método estadístico Probit. Las muestras no presentaron toxicidad contra Artemia salina L. (>1000 µg.mL⁻¹) y mostraron potencial de vida larvaria en el control de larvas de tercer estadio, con CL50 >200 µg.mL⁻¹. Los extractos de M. Evonymoides son seguros y mostraron potencial larvicida contra las larvas de mosquitos.

Larvicidal potential and residual activity effect of kinnow peel oil against Aedes aegypti L.

Background & objectives: Transmission of dengue virus by Aedes aegypti mosquito is one of the major global health concerns. The present study was aimed to explore the larvicidal potential of oil extracted from kinnow peel waste to be used as an efficient, economic and safe agent against Ae. aegypti. Methods: Kinnow peel oil was extracted and its five concentrations at 40, 50, 60, 70 and 80 ppm were tested against 4th instar larvae of Ae. aegypti. Larval mortality (%) and LC50 and LC90 values of toxicity were determined followed by evaluation of the residual activity effect of its leftover effective concentration on larval mortality, development and emergence. Effect of storage (2, 4 and 6 months) on larvicidal potential of kinnow peel oil was also determined. Results: Out of the tested concentrations, 70 ppm of kinnow peel oil was found to be the effective concentration against 4th instar larvae of Ae. aegypti. LC50 and LC90 toxicity values were 47.26 and 61.56 ppm, respectively. No residual activity effect in terms of larval mortality was found, however a significant delay in development (L4 to adult) was observed after placing new larvae in the leftover effective oil concentration. No effect of storage on larvicidal potential of 2, 4 and 6 months old kinnow peel oil in comparison to freshly extracted oil was observed. Interpretation & conclusion: Kinnow peel oil proved to have a good potential as a biolarvicide against Ae. aegypti and could be used as an effective and eco-friendly mosquito control agent in the future.

Preliminary evaluation of the larvicidal activity of extracts and fractions from Ocotea nutans (Nees) Mez against Aedes aegypti

Abstract INTRODUCTION: Aedes aegypti is the main vector of dengue and yellow fever. Recently, the use of plant-sourced larvicides has gained momentum. METHODS: The hydroethanolic extracts and fractions ofOcotea nutansleaves and stems were bioassayed to determine the larvicidal efficacy of these samples. RESULTS: S-HEX (hexane fraction from the crude stem extract) demonstrated high potential for controlling third-stage larvae, with an LC50 of 14.14 µg.mL-1 (concentration required to inhibit 50% of the treated larvae). CONCLUSIONS Extracts from O. nutans were effective against third-stage larvae ofA. aegyptiafter 24 h of exposure.

Screening of plant extracts and fractions on Aedes aegypti larvae found in the state of Mato Grosso do Sul (linnaeus, 1762) (culicidae)

ABSTRACT The constant use of chemical insecticides for Aedes aegypti control has caused resistance in the mosquito populations. Thus, the objective of this study was to analyze the larvicidal potential of extracts and fractions of plants on A. aegypti larvae. The analysis included sixty one extracts and twenty five fractions of fifty botanical species at concentrations of 0.25; 0.12; 0.06 to 0.03 mg mL-1; 4 replications and one negative control of dechlorinate water and 1% DMSO; and a positive control with rotenone. The toxicity index in descending order with LC50 for the most active of the extracts selected were ethanol extract of Ormosea arborea (0.111 mg mL-1) seeds and ethanol extracts of leaves such as Piper hispidum (0.169 mg mL-1), Solanum variabile (0.188 mg mL-1), O. arborea (0.238 mg mL-1), Turnera umifolia (0.242 mg mL-1) and Piper hispidum (0.567 mg mL-1). For plant fractions, the most active were chloroform (0.192 mg mL-1) and hexane (0.342 mg mL-1) P. aduncum leaves, hexane fraction (0.415 mg mL-1) and methanol extract (0.625 mg mL-1) of Spermacocea latifolia leaves. Regarding the extract of T. umifolia single species, there is no bibliographic report on their degree of efficiency as an insecticide.

Comparative larvicidal potential of different plant parts of Withania somnifera against vector mosquitoes in the semi-arid region of Rajasthan.

Larvicidal potential of the extracts from different parts viz. green and red fruits, seeds, fruit without seeds, leaves and roots of Withania somnifera in different solvents was evaluated against larvae of Anopheles stephensi, Aedes aegypti and Culex quinquefasciatus, the important disease vectors prevalent in the semi-arid region. Experiments were carried out on late 3rd or early 4th instar larvae of these mosquitoes using standard WHO technique. 24 and 48 hr LC 50 values along with their 95% confidence limits, regression equation, chi-square (c2)/ heterogeneity of the response have been determined by log probit regression analysis. The 24 hr LC50 values as observed for whole green fruits in water, methanol and petroleum ether were 350.9, 372.4, 576.9; 115.0, 197.1, 554.6; 154.9, 312.0, 1085.0 while corresponding values for red fruits were 473.5, 406.4, 445.2; 94.7, 94.5, 1013.0; 241.8, 535.0, 893.3 mg l-1 for An. stephensi, Ae. aegypti and Cx. quinquefasciatus respectively showing that methanol extracts were more effective against anophelines as compared to culicines when whole fruits were taken. The 24 hr LC50 values as observed for seeds in acetone, methanol and petroleum ether were 188.1, 777.5, 822.5; 245.5, 769.0, 1169.0; 140.3, 822.9, 778.4 and for fruit without seeds were 80.2, 97.6, 146.6; 88.4, 404.4, 1030.0; 30.0, 44.5, 54.2 mg l-1 for the above mosquito species respectively showing that extract of fruit without seeds were most effective in petroleum ether followed by acetone and methanol extracts. However, experiments conducted with methanol extracts of leaves and roots of this plant species did not show any appreciable larvicidal activity and a 20-40% mortality was observed up to 500 mg l-1 of the extracts. Overall larvae of anophelines were found more susceptible as compared to culicines to all the extracts tested. Petroleum ether extract of fruit without seeds was found most effective against all the mosquito species showing that active ingredient might be present in this part of the plant species. The study would be of great importance while planning vector control strategy based on alternative plant derived insecticides.

Bioefficacy ofMentha piperita essential oil against dengue fever mosquito Aedes aegypti L

Objective:To assess the larvicidal and repellent potential of the essential oil extracted from the leaves of peppermint plant,Mentha piperita (M. piperita) against the larval and adult stages of Aedes aegypti (Ae. Aegypti).Methods: The larvicidal potential of peppermint oil was evaluated against early fourth instar larvae ofAe. aegypti usingWHO protocol. The mortality counts were made after 24 and48 h, and LC50 and LC90values were calculated. The efficacy of peppermint oil as mosquito repellent was assessed using the human-bait technique. The measured area of one arm of a human volunteer was applied with the oil and the other arm was applied with ethanol. The mosquito bites on both the arms were recorded for3 min after every15 min. The experiment continued for 3 h and the percent protection was calculated.Results:The essential oil extracted fromM. piperita possessed excellent larvicidal efficiency against dengue vector. The bioassays showed an LC50 and LC90 value of111.9 and295.18 ppm, respectively after24 h of exposure. The toxicity of the oil increased11.8% when the larvae were exposed to the oil for48 h. The remarkable repellent properties ofM. piperita essential oil were established against adults Ae. aegypti. The application of oil resulted in100% protection till150 min. After next30min, only1-2 bites were recorded as compared with8-9 bites on the control arm.Conclusions:The peppermint essential oil is proved to be efficient larvicide and repellent against dengue vector. Further studies are needed to identify the possible role of oil as adulticide, oviposition deterrent and ovicidal agent. The isolation of active ingredient from the oil could help in formulating strategies for mosquito control.

Bioefficacy of Mentha piperita essential oil against dengue fever mosquito Aedes aegypti L

<p><b>OBJECTIVE</b>To assess the larvicidal and repellent potential of the essential oil extracted from the leaves of peppermint plant, Mentha piperita (M. piperita) against the larval and adult stages of Aedes aegypti (Ae. Aegypti).</p><p><b>METHODS</b>The larvicidal potential of peppermint oil was evaluated against early fourth instar larvae of Ae. aegypti using WHO protocol. The mortality counts were made after 24 and 48 h, and LC50 and LC90 values were calculated. The efficacy of peppermint oil as mosquito repellent was assessed using the human-bait technique. The measured area of one arm of a human volunteer was applied with the oil and the other arm was applied with ethanol. The mosquito bites on both the arms were recorded for 3 min after every 15 min. The experiment continued for 3 h and the percent protection was calculated.</p><p><b>RESULTS</b>The essential oil extracted from M. piperita possessed excellent larvicidal efficiency against dengue vector. The bioassays showed an LC50 and LC90 value of 111.9 and 295.18 ppm, respectively after 24 h of exposure. The toxicity of the oil increased 11.8% when the larvae were exposed to the oil for 48 h. The remarkable repellent properties of M. piperita essential oil were established against adults Ae. aegypti. The application of oil resulted in 100% protection till 150 min. After next 30 min, only 1-2 bites were recorded as compared with 8-9 bites on the control arm.</p><p><b>CONCLUSIONS</b>The peppermint essential oil is proved to be efficient larvicide and repellent against dengue vector. Further studies are needed to identify the possible role of oil as adulticide, oviposition deterrent and ovicidal agent. The isolation of active ingredient from the oil could help in formulating strategies for mosquito control.</p>