Plant pests and diseases are considered as one of the problems in agricultural production, including oil palm. Oil palm leaf-eating caterpillars are a class of pests often found in oil palm plantations throughout Indonesia. The bagworm is one of the leaf eaters classified as voracious insect pest and difficult to control because these pests hide in their bags. Pest control needs to be done from young (immature) plants so that yield loss during production can be prevented and cause no economic losses. This study aims to know the attack of bagworm C. tertia on immature oil palm on different locations and different treatments and determine the factors causing the death of bagworm in the Plantation of PT Inti Indosawit Subur, Pangkalan Kerinci, Pelalawan Regency, Riau. This study was conducted by direct observation of the bagworm in Block A and Block K. From each block, two observation sites were determined, and 25 sample plants were selected from each observation site. The dead bagworms were collected to determine the cause of death. The research results showed that the bagworm dead in Block A was higher than in Block K due to pest control such as trunk injection (TI) were implemented in Block A. In Block A, the highest percentage of deaths due to insecticides occurred in the second observation, and decreased at each observation time. The death of the bagworm in Block K was mostly caused by the role of predators.