Fuente: WIPO "organic farming" The method for stimulating the defenses of a plant or tree against an infection of bacterium or fungus comprises the application on the plant or tree of an aqueous extract from at least leaves of a Rocket plant. The application on the plant or tree is achieved by foliar spray. The extract is obtained by grinding the Rocket plants in an aqueous medium, filtering the ground material obtained and recovering the liquid extract of Rocket plants obtained after filtering.