Aphids may cover the leaves with sticky honeydew. Use sprays of Sevin, rotenone, acephate or malathion. The insects can also be dislodged with high pressure water sprays from the garden hose.
Japanese beetles are particularly fond of the flowers. Use sprays of malathion, rotenone, Sevin or methoxychlor to control the adult beetles. The grubs in the lawn can be controlled with diazinon or milky spore disease.