Efficacy of Green‐Synthesized Silver and Copper Oxide Nanoparticles Against Phytoplasma‐Associated Little Leaf Disease in Brinjal

Phytoplasma‐associated little leaf disease is an important constraint to brinjal ( Solanum melongena L.) production, while effective and sustainable options for its management remain limited. This study evaluated, under pot conditions over two consecutive years, the potential of green‐synthesized silver nanoparticles (AgNPs) and copper oxide nanoparticles (CuONPs) produced using Curcuma longa leaf extract for managing phytoplasma‐associated little leaf disease. The use of turmeric leaves, an underutilized agricultural biomass, as a reducing and capping source and the evaluation of the resulting nanoparticles against a phytoplasma‐associated disease represent the principal focus of this study. The synthesized nanoparticles were characterized using UV–vis spectroscopy, FTIR, SEM, TEM, and X‐ray diffraction (XRD). UV–vis absorption maxima were observed at 380 nm for AgNPs and 390 nm for CuONPs, while TEM indicated predominantly spherical to quasispherical particles within the nanoscale range. XRD analysis indicated crystalline Ag and monoclinic CuO phases, with estimated crystallite sizes of approximately 24 and 36 nm, respectively. The foliar spray of AgNPs 100 ppm was found to be effective in reducing the disease severity (19.26%) as compared to untreated control (65.58%), with 70.63% reduction in disease severity and increased plant height (59.20 cm), number of primary branches (12.20), and fruits per plant (11.00). Treatment effects were significant at the 5% level. In nanoparticle‐treated plants, TaqMan‐based real‐time PCR showed delayed amplification of phytoplasma‐associated signals compared with untreated infected control, but these observations do not confirm a direct antimicrobial mechanism. To summarize, the results indicate the potential of C. longa‐mediated AgNPs, especially at 100 ppm, for reducing the little leaf disease under controlled pot conditions. Further studies on field validation, quantitative assessment of phytoplasma titer, nanoparticle uptake and persistence, residue analysis, phytotoxicity, and nontarget effects are required before practical agricultural application.