Electrolyzed fertilizer solution (EFS) was produced by passing an irrigation solution through an electrolization chamber in order to suppress fungal disease caused by Fusarium oxysporum f. sp. cubense race 4 (Foc4) infecting banana plantlets. In the laboratory, EFS was prepared by electrolyzing solutions containing different amounts of potassium chloride and potassium nitrate. The results indicated a significant reduction in the conidial densities of Foc4 which was from 106 spores · ml^–1 to a maximum of 10 1.3 spores · ml^–1 and depended on the concentration of components in the input flow. Eventually the EFS produced from the lowest one was chosen to treat banana plantlets. Greenhouse experiments gave contra- dictory results of inoculated plantlets irrigated with or without EFS. The untreated banana plantlets virtually showed symptoms of infection such as discoloration of cross-cut corms, rapid wilting and dying within 60 days, while the treated ones kept their shapes and grew normally. The drastic fall in the microbial population in the rhizosphere of treated plants confirmed the activity of oxidation agents which is the major mechanism of disease sup- pression. The results suggest that further studies of EFS in the field as a potential technique in fighting Panama wilt in the banana industry are necessary.