This study was performed in the Tropical Plant Resources Research Center of Korea National Arboretum to assess the effects of natural enemy attack on aphid population feeding on tropical plants. We measured the density of leaf-feeding aphids, Myzus persicae and Aphis gossypii, cohabiting with 5 types of tropical plants at intervals of approximately 2 weeks after introducing their natural enemy, Aphidius colemani. The density of aphids cohabiting with 4 types of tropical plants-Sanchezia parvibracteata, Hibiscus rosa-chinensis, Ficus kurzii, and Aloysia triphylla-started decreasing after 2 weeks of observation and was completely in control after 4 weeks of observation; however, the density of aphids cohabiting with the tropical plant, Hamelia patens, increased during 22 weeks of observation but decreased after the $23^{rd}$ week of observation. We suggest that a banker plant is necessary for the maintenance of A. colemani in tropical greenhouses, and monitoring studies on H. patens, which was weakest against the aphids, should be performed. Our results indicate that biological pest management strategies using their natural enemies were formulated for the construction of new tropical greenhouses.