Abstract: The invention relates to oligopeptides used as elicitors of the natural defences of plants in order to control fungal and/or bacterial and/or viral pathogens and/or crop pests, by means of foliar or root application or by injection. According to the invention, said oligopeptides are characterised in that they are obtained by organic or enzymatic synthesis, in that they are heteropolymers and/or homopolymers of protein and/or non-protein amino acids, and in that said amino acids form sequences of said polymers selected for the capacity thereof to form spiral structures.