Just started using Neem 3 days ago on budding plants as I just got infested recently. They already claimed 1 pretty much.
Next time around I am going to do the preventative thing.
Try and look up www.naturescontrol.com/triplethreat I had heard of these a couple of days ago while at a disp. Also ran a thread here asking if anyone had heard of these but apparently no one has. They're to be used once you already have an infestation prob though so not for preventative I guess.
Anyway, good luck to you.

MM