The research was carried out in the Educational Forest Area of the Department of Forestry, Universitas Pattimura, Ambon, Maluku in January 2018 - July 2018. The study aimed to inventory the types of pests that infest the Tusam tree (Pinus merkusii Jung et De Vriese), diagnose the symptoms of pest infestations and calculate the magnitude of the outbreak and the extent of the infestation due to Tusam pest infestations. The study used a survey method on an area of 5 ha by making ten observation lanes measuring 100 m × 10 m with 10 sample trees per path. Observations were made on the roots, stems, and leaves with the system of the compass direction. The types of pests found were Tusam Leaf Snail (Mollusca sp), Brown Fire Caterpillar (Thosea sp), Brown Butterfly (Papilio sp), Pine Woolly Aphid and Termite Queen (Mactotermes gilvus hagen). The intensity of damage due to pest infestations were Brown Fire Caterpillars (38.13%), Tusam Brown Butterflies (37, 9%), Pine Woolly Aphid (30.4%) and Termite Queen (60.53%) respectively. The extent of infestation due to the outbreak of brown fire caterpillar pests by 30.38% was classified as moderate criteria, Tusam Brown Butterflies by 29.04% was classified as reasonable criteria, Pine Woolly Aphid by 42.4% was classified as average criteria, and Termite Queen by 68% was classified as severe criteria.