A couple of things.
Interplant with French marigold....whitefly can't stand them
Under glass.....shake the plants to get them airborn...suck them up with a Hoover. Repeat 3 times once every 10 days. Their life cycle is just 10 days..so in theory you should get them all!!.
More seriously....buy Incarsia Formosa....they are natural predators of whitefly. You should be able to get them on line.