The population dynamics and biology of the gall-inducing insect, Crotonothrips polyalthiae Mound & Nasruddin, and its damage to Polyalthia longifolia Sonn, were studied in Makassar, South Sulawesi, Indonesia, from 15 Aug 2010 to 25 Jul 2011. The average number of thrips per gall, young leaves per plant, and bi-weekly rainfall peaked 3 times during the survey. The average number of living thrips per gall peaked about 4 wk after the peak in the number of young leaves per plant, and this occurred 2 to 4 wk after each rainfall peak. The thrips development time ranged from 17 to 25 d with an average of 20.8 d. Average adult longevity for female and male were 24.3 and 12.2 d, respectively. The number of eggs laid by a female ranged from 11 to 74 with an average of 41.5 eggs. An average of 94.9% of those eggs successfully hatched. One year after the initiation of the experiment, the thrips reduced the plant height and stem circumference by 49 and 37%, respectively, in comparison with the plants that were kept thrips-uninfested by using insecticides. This appears to be the first experimental account of a gall-inducing thrips impeding the growth of a tree or woody plant.