Comparative mosquitocidal activity of Pisonia alba extracts and green-synthesized silver nanoparticles against Aedes aegypti and Culex quinquefasciatus

Mosquito-borne diseases remain a major public health challenge, necessitating effective and sustainable mosquito control strategies. This study comparatively evaluated the mosquitocidal activity of aqueous and methanolic extracts and green-synthesized silver nanoparticles (AgNPs) derived from Pisonia alba leaves against Aedes aegypti and Culex quinquefasciatus. The synthesized AgNPs were characterized using UV-Visible spectroscopy, FTIR, XRD, and SEM. A surface plasmon resonance peak at 434 nm confirmed AgNP formation, while FTIR indicated plant-derived functional groups associated with nanoparticle reduction and stabilization. XRD confirmed a face-centered cubic crystalline structure, while SEM analysis revealed predominantly spherical to semi-spherical nanoparticles. Re-evaluation of the SEM micrograph using ImageJ showed a mean particle size of 30.42 ± 13.03 nm, based on measurements of 13 randomly selected, clearly distinguishable nanoparticles, with sizes ranging from 19.26 to 60.69 nm. AgNPs exhibited markedly higher larvicidal and pupicidal activity than the crude extracts, with LC₅₀ values of 6.95 and 16.38 ppm against Ae. aegypti larvae and pupae, respectively, and 10.73 and 20.06 ppm against Cx. quinquefasciatus, respectively. AgNP treatment also caused significant growth disruption and developmental abnormalities, along with marked histopathological alterations in the larval midgut, including epithelial disruption, cytoplasmic vacuolation, microvillar degradation, peritrophic membrane fragmentation, and pyknotic nuclei. These findings demonstrate the superior mosquitocidal activity of P. alba-mediated AgNPs and their potential for laboratory-based mosquito vector management. Further studies on non-target toxicity, environmental persistence, and field efficacy are required before practical application.