AbstractXanthomonas euvesicatoria (Xe) is of the genera Xanthomonas, which causes a bacterial spot disease that affects tomato and pepper plants, resulting in significant economic losses. Commonly used bactericides lead to pathogen resistance, environmental contamination and a current risk to human health. Herein, a nanocomposite consisting of Cu and Ag loaded onto reduced graphene oxide (rGO) was synthesized, characterized and tested. After confirmation of the antibacterial properties in vitro, nanocomposites at concentrations of 50 and 500 µg mL⁻¹ were applied to protect tomato and pepper plants under controlled greenhouse conditions. The tomato and pepper plants indicated significantly lower disease severity when treated with the nanocomposite (15.6 and 16.7%, respectively) than when treated with the commercial copper-based bactericide Kocide® 2000. The nanocomposite was demonstrated as a high-efficiency biocide and has the potential for crop disease management with no phytotoxic effect. Graphical Abstract