Ceratocystis fimbriata is an important pathogen in duku (Lansium domesticum Corr.) plants that causes stem cancer, tissue rot, and rapid plant death, thereby significantly impacting duku production in South Sumatra. This study aims to evaluate the effectiveness of phosphite acid (K₃PO₃) in inducing duku resistance through in vitro and in vivo testing. The study was conducted using a complet…