Houseplant pests

[Zippy]

I've got a well-established bay tree in my garden that seems to act as a host for all kinds of pests. Much of the new growth is curled and black and whenever you brush past it a cloud of tiny white flies fly up. I've tried spraying with both insecticide and fungicide but neither seems to have worked. Does anyone know what's causing the problems and suggest what I can do about it?