Effect of chitosan nano-encapsulated Vitex agnus-castus phenolic extract on biological aspects of Ephestia cautella

Abstract

Stored product pests such as Ephestia cautella threaten global food security and storage systems. Recently, plant-based nanotechnology has emerged as an eco-friendly, more effective alternative to conventional pesticides with lower environmental impact. The present study, therefore, investigated the physicochemical characterization and insecticidal efficacy of Vitex agnus-castus leaf extract nano-capsules against different life stages of Ephestia cautella. Fourier Transform Infrared Spectroscopy (FTIR) analysis revealed key functional groups, including hydroxyl groups (~3414 cm⁻¹), aliphatic C-H stretches (~2923 cm⁻¹), and aromatic or carbonyl-related bands (1619–1401 cm⁻¹), along with C-O stretching (1300–1000 cm⁻¹), and metal-oxygen bonds in the fingerprint region (800–400 cm⁻¹), indicating the formation of an organic-inorganic nanocomposite. Scanning Electron Microscopy (SEM) showed that the nano-capsules were semi-spherical with minimal aggregation, averaging 43.77 nm in diameter. Dynamic Light Scattering (DLS) analysis further confirmed a consistent average particle size of 227.1 nm. The bioassay results demonstrated significant toxicity of the nano-capsules against E. cautella eggs, larvae, and pupae. At 2000 ppm, egg mortality peaked at 60.96%, while lower concentrations (1000, 500, and 250 ppm) resulted in 50.52%, 37.04%, and 25.93% mortality, respectively. Larval mortality increased with both dose and exposure time, reaching 66% at 2000 ppm after 72 hours. Similarly, pupal mortality reached 57.69% at 2000 ppm, with lower but notable mortality at 1000 ppm (50%). Minimal effect was observed at 500 and 250 ppm. These findings suggest that V. agnus-castus nano-capsules possess promising insecticidal properties and could serve as an eco-friendly biopesticide for controlling E. cautella infestations.