Publication: Synthesis of green pest repellent from multiple plants and evaluation of agronomic performance
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Date
2025-08-04
Authors
Heong, Kar Yhean
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Abstract
The increasing demand for sustainable agriculture has driven the development of eco-friendly pest control alternatives. This study developed a broad-spectrum green pest repellent from five medicinal plants: Justicia adhatoda, Ocimum basilicum, Azadirachta indica, Carica papaya, and Ficus carica. Ultrasound-Assisted Extraction (UAE) was optimized using ethanol-water mixtures to efficiently recover bioactive compounds. Spectroscopic analyses including Ultraviolet-Visible (UV-Vis), Fourier Transform Infrared (FTIR), and Gas Chromatography-Mass Spectrometry (GC-MS), confirmed the presence of phenolics, flavonoids, alkaloids, and terpenoids, which are associated with insecticidal and antimicrobial properties. Although individual extractions yielded slightly higher Total Phenolic Content (TPC) and Total Flavonoid Content (TFC), the grouped extraction method was selected for its simplicity and efficiency with minimal compromise in bioactivity. The extracts were formulated into nano-emulsions and evaluated for stability. The best formulation (0.8% w/w extract, 8 minutes sonication) exhibited excellent characteristics, with a droplet size of 128.9 nm, polydispersity index (PDI) of 0.096, and zeta potential of −31.3 mV, as measured by Dynamic Light Scattering (DLS) at 1:30 dilution. Transmission Electron Microscopy (TEM) confirmed uniform, spherical droplets. Bio-efficacy tests on Brassica juncea showed that 2X and 3X dosages significantly reduced pest populations and leaf damage. The improved performance was attributed to the nano droplet size, enhanced surface adhesion, and controlled release, leading to longer-lasting protection. Overall, this green nano-emulsion offers a scalable, sustainable, and effective alternative to synthetic pesticides