| Summary: | Many forest plantations in Indonesia were built on converted tropical forest. Minimal site preparation was often applied before planting, and the result was that various forest debris, particullarly dead stumps, were still remained in young plantation site. Since some root pathogens use the debris to survive in the absence of host, this might be potential as disease inoculum to the plantation establised. The experiment was aimed to evaluate the response of Acacia and Eucalyptus to root-rot pathogen. infection.
Field study was made in some forest plantations to observe the root disease status. The root-rot pathogens were isolated and their pathogenicity were tested using Crotalaria juncea L. as indicator plant. In laboratory experiment, pieces of root of three species ofAcacia and four species of Eucalyptus were selected for root pathogen colonization test. Selected Ganoderma sp. isolated from A. mangium was inoculated to the root samples using modified soil block test. The attack ofGanodernia, on the root sample was evaluated based on fungal colonization on the root samples.
The results indicated that root-rot disease was found to attack A. mangium and A. auriculifirmis, and 17 different isolates of Ganodernia were known associated with the disease. Laboratory experiment showed that theroot of A. mangium was totally colonized by Ganoderma on day 5 after inoculation, whereas root of A. auriculifirmis was colonized by the pathogen on day 8 after inoculation. On day 37 only 53.28% of the surface area of A. oraria's root sample was colonized by the pathogen. E. pelita, E. alba, E. camaldulensis and E. urophylla were entirely colonized by Ganoderma on day 7, 8, 12 and 37 respectively, although for the last species the colonization was only 90% of total sample surface area.
Key words: Ganoderma, root-rot disease, Eucalyptus, Acacia
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