Plant peptides represent a novel molecular tool in crop science due to their essential regulatory roles in plant growth, development, and responses to biotic and abiotic stresses. Although numerous bioactive plant peptides have been identified, a major gap remains in translating these discoveries into practical strategies for crop protection. Synthetic peptides are increasingly recognized as promising biological agents for enhancing crop productivity and protection in an environmentally sustainable manner. In this study, we demonstrate that the potato elicitor peptide StPep1, applied as a foliar spray at nanomolar concentrations (10–100 nM), strongly enhances resistance to the oomycete pathogen Phytophthora infestans in Solanum tuberosum cv. Gala under controlled climate chamber conditions. Preventive treatment 24 h prior to inoculation markedly reduced disease symptoms, with treated plants exhibiting a phenotype comparable to uninoculated controls. These findings highlight the potential of low-dose StPep1 as an environmentally friendly and cost-effective bioprotective agent, providing a foundation for future translational research and small-scale agricultural applications.