Antimicrobial Zn-Based "TSOL" for Citrus Greening Management: Insights from Spectroscopy and Molecular Simulation

Huanglongbing (HLB), also known as citrus greening, is a bacterial disease that poses a devastating threat to the citrus industry worldwide. To manage this disease efficiently, we developed and characterized a ternary aqueous solution (TSOL) that contains zinc nitrate, urea, and hydrogen peroxide. We report that TSOL exhibits better antimicrobial activity than commercial bactericides for growers. X-ray fluorescence analysis demonstrates that zinc is delivered to citrus leaves, where the bacteria reside. FTIR and Raman spectroscopy, molecular dynamics simulations, and density functional theory calculations elucidate the solution structure of TSOL and reveal a water-mediated interaction between Zn²⁺ and H₂O₂, which may facilitate the generation of highly reactive hydroxyl radicals contributing to superior antimicrobial activity of TSOL. Our results not only suggest TSOL as a potent antimicrobial agent to suppress bacterial growth in HLB-infected trees, but also provide a structure-property relationship that explains the superior performance of TSOL.