They are back again! But I have tried a new and effective way this to get rid of these.
I mixed one part chemical vinegar (you can also use organic vinegar) with ten parts water and sprayed the solution right on to the bunches of whitefly under the leaves and along the stem nodes. You can dilute the solution further if upon spraying you get a strong smell of the vinegar.
Spraying has stopped their further multiplication. You need to spray it daily early in the morning before whiteflies get active.