The method for preparing a novel elicitor or agent stimulating the defenses of plants against pathogens is applied to agronomically useful plants in order to control pathogens. The elicitor is prepared without extraction by a liquid from a dry product made of Trigonella foenum graecum seeds. The inventive method preferably includes the following steps: separating the germ fraction and cotyledon of the seed; grinding the fraction so as to obtain a powder; and solubilizing the powder in water, whereupon the obtained solution is sprayed onto the plant/s that is/are to be treated.