An eco-friendly water-soluble Cu₂O@His for efficient control of citrus canker

Citrus canker, a bacterial disease caused by Xanthomonas citri subsp. citri (Xcc), is one of the major threats to the citrus industry. Inorganic copper (Cu) formulations such as Bordeaux mixture and Kocide 3000 are currently used to control citrus canker; however, they are poorly water-soluble and have negligible plant transport, making the systemic treatment of citrus canker difficult.

This study synthesized Cu₂O@His by one-pot self-assembly of Cu²⁺ and histidine for controlling citrus canker. The results showed that Cu₂O@His had a uniform size distribution (≈2.7 nm) and good water solubility. It could disrupt the cell membrane of Xcc and enter into the bacterial cells to destroy the DNA, thereby inhibiting the growth (half maximal inhibitory concentration = 7.4 μg mL^-1) and production of virulence factors of Xcc. This was attributed to its excellent dispersibility and reactive oxygen species-inducing ability. The therapeutic efficacy and plant transport of Cu₂O@His were much better than those of Kocide 3000. Additionally, it had remarkable biosafety for citrus plants and earthworms (lethal concentration 50% >> 40 mg kg^-1).

This study provides a new, eco-friendly and more efficient option for citrus canker control. © 2025 Society of Chemical Industry.