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Aedes aegypti L. is the primary vector associated with transmission of globally concerned diseases; Zika, yellow fever, dengue and Chikungunya. Present study investigates an efficient, alternative and comparative approach for mosquito control which is safe to environment and non-target organisms. The silver nano-composites ( AgNCs) were synthesized from the aqueous stem extract of Achyranthes aspera (AASE) using different concentration of aqueous silver nitrate (AgNO 3 ). The synthesis was tracked by UV-vis spectrophotometer and particle size analyser (DLS). The evaluation of their larvicidal potential against early fourth instars of Ae. aegypti showed significant potency, the toxicity increasing with the concentration of silver nitrate. The 24, 48 and 72 h bioassays resulted in respective LC 50 values of 26.693, 1.113 and 0.610 μg/mL (3 mM AASE-AgNO 3 ) 9.119, 0.420 and 0.407 μg/mL (4 mM AASE-AgNO 3 ) and that of 4.283, 0.3 and 0.248 μg/mL (5 mM AASE-AgNO 3 ). Keeping in view the significantly high larvicidal efficiency at lower concentration of silver nitrate, the 4 mM nano-composites were selected over 5 mM composites for further biophysical characterization carried out by X-ray Diffraction (XRD), Fourier transform infrared spectrometer (FTIR), Scanning electron microscopy (SEM), Energy dispersive X-ray (EDX) spectroscopy and Transmission electron microscopy (TEM). SEM and TEM confirmed the synthesis of spherical poly-dispersed AgNCs with average size ranging from 1–30 nm. Characterization through XRD showed the crystalline face-centered-cubic (fcc) structure of AgNCs with the highest intense peak obtained at 2θ value of 31.82°. FT-IR data suggests complex nature of AgNCs showing clearly defined peaks in different ranges. The present investigations recommend AgNCs of A. aspera stems as a low-cost and eco-friendly alternative to chemical insecticides for mosquito control.

Background and Objectives. Aedes aegypti, dengue fever mosquito, is primarily associated with the transmission of dengue and chikungunya in tropical and subtropical regions of the world. The present investigations were carried out to assess the larvicidal efficiency of five indigenous weeds against Ae. aegypti. Methods. The 1,000 ppm hexane and ethanol extracts prepared from the leaves and stem of five plants (Achyranthes aspera, Cassia occidentalis, Catharanthus roseus, Lantana camara, and Xanthium strumarium) were screened for their larvicidal activity against early fourth instars of dengue vector. The extracts which could cause 80–100% mortality were further investigated for their efficacy. Results. The preliminary screening established the efficacy of hexane extracts as compared to the ethanol extracts. Further investigations revealed the highest larvicidal potential of A. aspera extracts exhibiting LC50 value of 82.555 ppm and 68.133 ppm, respectively. Further, their leaf extracts showed 5–85.9% higher larvicidal activity and stem extracts exhibited 0.23- to 0.85-fold more efficiency than the other four extracts. Conclusion. The present investigations suggest the possible use of A. aspera as an ideal ecofriendly, larvicidal agent for the control of dengue vector, Ae. aegypti. Future studies are, however, required to explore and identify the bioactive component involved and its mode of action.

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Helicoverpa armigera is a global agricultural pest of serious concern. Continued use of chemical insecticides as control measures has raised grave health and environment concerns, necessitating a search for botanicals as safe alternatives. The current study investigates the effects of ?-sitosterol, a bioactive phytocomponent in Thevetia neriifolia, on the growth and development, as well as on midgut enzymes of H. armigera. Dietary ?-sitosterol produced dose-dependent systemic toxicity and growth inhibitory effects in H. armigera; the most significant effects were obtained with 10 ?g/mL dietary ?-sitosterol. Higher prepupal and pupal mortality in comparison to larval mortality and a comparatively greater reduction in average weight gained by later instars point to cumulative effects of ?-sitosterol. The delayed effects were ascertained by the 82.05%-57.89% reduction in adult emergence in comparison to 95.02% emergence in controls. Dose-dependent effects of ?-sitosterol were observed as significantly decreased enzyme activities of alanine aminotransaminase (ALT), aspartate aminotransaminase (AST) and alkaline phosphatase (ALP) in the larval midgut. Suppression of enzyme activity was obtained in the order ALT>AST>ALP. Impaired activity of gut enzymes possibly lowered the energy reserves and affected nutrient transport through the gut epithelium, affecting the growth and development of H. armigera. Our study points to a promising use of ?-sitosterol against H. armigera, although further examination and field studies are needed to ascertain its possible use in control programs.

Current studies investigated the anti-mosquito potential of against the dengue vector, The stems and leaves of were extracted in hexane and evaluated for their toxicity against early fourth instars of. The larvicidal efficacy of the extract was validated as per WHO protocol. The mortality counts were made after 24 h and LC values were calculated at different levels. The adverse impact of extracts was also explored on the larval genomic DNA. The larvae were exposed to extracts at LC levels and the alterations in -DNA was evaluated through RAPD-PCR technique using three random primers; MA-09, MA-12 and MA-26. Our investigations ascertained the larvicidal efficacy of both the leaf and stem extracts of resulting in respective LC values of 0.068 and 0.082 mg/mL. The extracts also caused variable genotoxic effects with significant changes in the RAPD profiles. The results showed appreciable modifications in larval -DNA with loss of certain bands and gain of unique bands with 82.35% DNA polymorphism. These alterations suggest the probable DNA damage and mutations in the larval-DNA caused by certain phytocomponents which could be the possible reason of larval mortality. Our studies evidenced the anti-mosquito potential of extracts against causing appreciable larval mortality and significant changes in -DNA. The extracts are suggested as efficient and eco-friendly control agent against , yet further investigations are needed to identify the bioactive constituent and ascertain its effectiveness in the field conditions.

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Background: Aedes aegypti L.; one of the most important insect vectors in the world; transmits several diseases of concern; Zika, yellow fever, Chikungunya, dengue and dengue haemorrhagic fever. Despite multifarious problems on humans, non-targets and environment; caused by synthetic chemical insecticides; these are still the prime and preferred control measures against dengue vector. Alternative control strategies using eco-friendly and bio-degradable plant products are being explored. Objective: The present study investigates the toxic potential of the hexane extract of the leaf and stem of Achyranthes aspera against Ae. aegypti. Methods: The larvicidal potential of extracts was evaluated against dengue larvae as per WHO protocol. Subsequent concentration and time-dependent studies assessed their effects on the larval midgut histo-architecture using microtomy techniques. Results: Larvicidal bioassays with A. aspera extracts revealed their appreciable larvicidal potential. Hexane extract of the leaf resulted in respective LC30, LC50 and LC90 values of 67, 83 and 140 ppm while exposure to hexane extract of the stem showed respective values of 55, 68 and 115 ppm. Extract-exposed larvae at various lethal levels exhibited significant damage, shrinkage, distortion and vacuolization of gut tissues and peritrophic membrane. The disintegration of epithelial cells and cytoplasmic organelles evidenced stomach poison potential of the extracts. The extent of toxicity and damage was concentration and time-dependent; the stem extract imparted more deleterious effects as compared to the leaf extract. Conclusion: Present findings suggest the utilization of A. aspera as an alternate control strategy against Ae. aegypti; though further studies against non-targets are needed to ascertain its use in the fields.