I have found one thing that sort of works. Forget all the commecial insecticide sprays that claim on the label to work on white flies. They don't. Not for more than a day or two and you have to poison everything in sight. But you can get relief by thoroughly soaking the tops and bottoms of ALL leaves on the infected plant(s) with a spray of liquid Spinosad D (Fertilome, Bionide and Green Light all make liquid concentrates of Spinosad D and a tablespoon makes a gallon of spray). Spinosad is a realtively safe organic compound that only attacks certain bugs and doesn't harm beneficial insects (although like anything you have to keep it away from water and bees). You can use it on fruits and vegetables up to 3 or 4 days before harvest. A thorough spray of it will make the tiny white creeps completely disappear for like maybe 4 or 5 days. Then a few will begin to reappear. It takes them about another week for the next generation to building up in large numbers -- at which time you can hit them with the Spinosad again. This is the best thing I've found, but who knows how long it will be before they develop an immunity to the Spinosad?
The other option is ladybugs and lacewings. They love to chow down on white flies. If you've got a bad infestation (and there doesn't seem to be any other kind), it might be worth purchasing a box or two of ladybugs and sending them out to do battle. Unfortunately for me, we have such strong continual breezes around here that the ladybugs I release don't stay around for long.
Side note: A spray of Spinosad D also will also completely eliminate the hard-to-kill citrus leaf miners... works far better than anything else (and far safer as well).
I organically co-exist with most garden pests, but I gotta say if I found a nuclear option that worked on these damn white flies I wouldn't hesitate. I have noticed several people mention that they got them on their poinsettias and I believe that's how they entered my greenhouse as well (and then spread outside to the rest of the garden). I attempted to rescue two abandoned poinsettias last Christmas and that's when the trouble started.