Ganoderma root rot is the most serious disease affecting commercially planted Acacia mangium in plantations in Indonesia.
Numerous Ganoderma spp. have been recorded from diseased trees of this species and to a lesser extent Eucalyptus,
causing confusion regarding the primary cause of the disease. In this study, a large collection of Ganoderma isolates were
obtained from the roots of A. mangium showing early signs of root rot in disease centres in South Sumatra plantations.
Isolates were also collected from Eucalyptus roots at Lake Toba in North Sumatra showing similar symptoms as well as
from sporocarps connected to these samples. Phylogenetic analyses showed that a single Ganoderma sp., identified as
G. philippii, is the major causal agent of Ganoderma root rot on A. mangium. Results from this study also showed that the
isolates obtained for Eucalyptus trees in North Sumatra belong to G. philippii. Isolates from roots and connected fruiting
bodies together with the morphology of the fruiting structures confirmed this identification. Symptoms associated with this
pathogen are obvious and it should not be confused with other diseases. Other Ganoderma spp. found in disease centres are
considered to be of minor importance and management strategies for root rot should be focused on G. philippii.