How to protect moonbeam flower and hibiscus plants from insects

Hi All,
I am expecting a good solution from ILites. I am very much interested in gardening. Very recently with the help of a gardener I cleansed my garden and bought several hibiscus flowers. Earlier I had hibiscus and moonbeam plants which use to give many flowers. But nowadays often these plants are affected by insects and entire leaves are falling off. Please suggest something to get rid of these insects