hizotrons allow the monitoring of Ganoderma infection, through a clearwalled chamber, after inoculation of germinated seeds with pre-infected substrate. This tool was developed for direct observation in vivo of (i) the development of Ganoderma isolates on different substrate sources (rubber wood block, rubber sawdust…), (ii) the effect of several treatments (bio-agents, fungicides…) on the pre-infected or infectious substrates tested and (iii) the sampling and analysis of roots at very early stages of infection. Two germinated seeds were inoculated per rhizotron and the seedlings were observed until 6 months after inoculation. The first root symptoms appear two months after inoculation (using preinfected rubber wood blocks, RWB) while the leaf symptoms are not detected until 4 months after inoculation. The observation of the penetration point demonstrates that a very close contact between roots with pre-infected RWB is required. Penetration of Ganoderma mycelium to host tissues seems related to the development of stromatic-like structures surrounding the root on the RWB surface. The induction of stromatic-like structures was also observed without the presence of root contact leading to the hypothesis that there is no strong chemotaxis developed by the fungus. No stromatic-like structure is observed after inoculation using pre-infected rubber sawdust and no infected seedling was obtained. The development of the stromatic-like structures by Ganoderma seems to require a solid substrate.