The present invention relates to a method for stimulating the resistance of plants to biotic stress by radiation exposure of at least one spot of a plant characterized in that the radiation exposure is performed by UV-C rays alone or UV-B rays alone or a combination thereof with an exposure duration being less or equal to one second and the radiation exposure being repeated at least once with an interval of time between one hour and one month.The invention will find an application for stimulating natural defenses of plants to biotic stress as pests, bacteria, fungus or virus. The invention could be used directly on plants growing in fields for agriculture and the food industry.