We examined the residual effects of the granular insecticides applied on sweet pepper plants on the survival of the green peach aphid, Myzus persicae. Sweet pepper seedlings were transplanted in a green house after applying imidacloprid or nitenpyram granules at the recommended dosage of 2 g ⁄ plant. Then, an upper leaf and a lower leaf were taken from each plant at 5, 12, 19 and 26 days after the insecticide treatment and were examined. Each test leaf was set in a Munger cell into which 10 adult female green peach aphids were released. The survival of the aphids and the number of nymphs laid by these insects were determined after 48 hours. The leaves from the plants treated with imidacloprid exhibited high insecticidal activity and suppressed the production of nymphs at 5 and 12 days after the insecticide treatment. The lower leaves retained a high residual effect for 19 days, but the residual effect in the upper leaf was considerably reduced after the same period. The effect of imidacloprid application disappeared at 26 days. The leaves treated with nitenpyram exhibited high insecticidal effect and suppressed the production of nymphs at 5 and 12 days, although the mortality rate of aphids on the upper leaves started to decrease on the 12th day after the insecticide treatment. The effect of nitenpyram application almost disappeared with some residual effect on nymph production on the 19th day. Therefore, it is necessary to initiate other control methods for transplanted seedlings when the effectiveness of the initial treatment is diminished.