I have mealy bugs. Yuck! The good thing is that, with the exception of a few spider mites here and there, they are my ONLY pest.
My trees are too big to drown (50 or so 5-10 ft trees in pots), and are in my greenhouse with about a dozen tropical birds loose in there, so this has been a big issue for me. I did not have much luck with neem oil, and in the winter when I can't ventilate, the smell would get really bad. I use Bayer systemic (imidicloprid), but I really can't see much progress. I keep with it though, just in case.
My latest tactic has been 50% rubbing alcohol in a spray bottle, mixed with the appropriate amount (about 1 tsp per pint) pyrethrin. The rubbing alcohol gives a fast kill and the pyrethrin holds them back for a while. The smell isn't too bad and it dissipates very quickly, unlike the neem oil. It seems to work really well and the plants don't mind it at all.
With the birds out there, I can't use anything stronger than pyrethrin or neem, and even with that, I can't just start spraying at random. I go tree-by-tree. I go leaf-by-leaf in the case of my kukui, which are always the hardest hit.
The big thing for me is that I just have to keep on it, and never let my guard down. I have a fanciful vision of the future where I have actually eliminated all the squishy white critters!
They are expensive, but this spring I am going to order some mealy bug destroyers (Cryptolaemus Montrouzieri). Hopefully they can do the trick. I would like to raise my own beetles and keep them on hand when I need them, so I am doing a bit of research into what else I can feed them if I am lucky enough to run out of mealy bugs!
Carolyn