The first generation of crawlers of arrowhead scale Unaspis yanonensis (Kuwana) occur in citrus orchards from early May to late July. Insecticide application is generally carried out to control U. yanonensis during the peak days of larval occurrence in June. We demonstrated that a high synergistic effect in controlling U. yanonensis was observed with the combined application of petroleum oil (9.7 g/L) and buprofezin (0.2 g/L) at the adult stage in late April.However, independent application of each insecticide during this time was less effective in controlling U. yanonensis.