ABSTRACT This study aims to determine the effectiveness of chitosan compounds in controlling Ceratocystis disease in langsat plants (Lansium domesticum Corr.) through in vitro and in vivo approaches. The study used a Completely Randomized Design (CRD) with six chitosan concentration treatments and included two controls (0; 0 mg/L + 0.1% acetic acid; 0.5; 5; 50; and 500 mg/L) with 10 replication…