Mardhiansyah, MWidyastuti, SMHarjono2015-03-232015-03-232015-03-23wahyu ari yenihttp://repository.unri.ac.id/xmlui/handle/123456789/6882Ganoderma sp must be controlled with environmental friendy measures, such as Trichoderma spp which Has already been proven in the field. The objectives of this study were to identify interraction betwen isolates of Trichoderma spp. Which were appliled deliberately occurring Trichoderma spp. Isolate in the field. Trichoderma spp isolates T13 dan T62 in pellet form were applied in a ratio of five pellets to each Acacia magium seedling, following which the A. Magium seedling were planted inthe field. At the ages twelve months, the level of attack by Ganoderma sp. Was counted at sampling intensity of 100%, and soil samples were taken from around the plantings intensity 20% in order to identify the presence of isolates T13 dan T62. The results of identification through macroscopic and microcipic observation as well as dual culture test, point back to isolates which appear to be T13 dan T62. In addition, results of the study showed taht for 10 – months old A. Mangium, the use of application of T62 lead to a lower level of attack by ganoderma sp. In plantation of A. Mangium (2,67%) compared to application of T13 (4.83%) and the control (3,83%) and the control (3,83%) in the case of PDA medium, T62 isolate demontrated a better prevention effect against Ganoderma Sp (95,91%) compared to T13 (91,63%). Interaction between Trichoderma spp. Isolate T13 dan T62 and several other isolates of Trichoderma spp. Indicated there was compettition for both nutrition and growing spaceenTrichoderma sppGanoderma spAcacia mangium