I've used lots of white fly traps in the past with reasonable success. Yellow sticky traps work surprisingly well and easy to make your own too.. Got something bright yellow? stick it on the growbed, come back a couple of hours later and it will have loads of white fly on it. Now coat it in something really sticky and try it again..
Though if your infestation is really bad I'd look at removing susceptible plants, replant with things they don't like and run a trapping program as above. Once you break the infestation through lack of feed and constant trapping you may be ok.