Basal stem rot (BSR) caused by Ganoderma boninense is a major oil palm (OP) disease. However, the effective treatment that is practicable in the field as a recommendation remains elusive. This study aimed to assess the effectiveness of the combinations that consisted of organic fungicide (OF), biofungicide (BF), endophytic bacteria (EN), and biostimulant (BS) applied to 20-year old (TM 20) and 14-year old (TM 14) OP with a mild, moderate, and severe level of infection. Results revealed that TM 20 palm recovery response is slower for all infection levels. The effective treatments for mild infection of TM 20 were BF, EN, and BS, meanwhile, for moderate infection, the treatments included OF, BF, EN, and BS. The effective treatment for both mild and moderate infections for TM 14 was the treatment which comprises BF, EN, and BS. It seems that there is no need for BS in this mature palm for both mild and moderate Ganoderma sp. infection since it has rapid recovery. However, the most effective treatment for severe Ganoderma infection in both OP groups was a complete treatment consisting of OF, BF, EN, and BS. We found that severe BSR symptoms could be reduced by providing the complete treatment several times, both holistically and progressively.