Assuming regular care and maintainance and
with strictly a judicial application, i've had very good success with Marathon 1% Granular, including specimen fukien. It is quite expensive, but a little bit will go a long way. I'm also noticing that the active ingredient in marathon is finding its way into insecticide products which are more affordable. depending on the hatching cycle of the criters, a repeated application may be necessary.
http://greenhouse.ucdavis.edu/safety/msds/Marathon.PDF
As a general fungicide, i use Immunox made by Spectracide, which is readily found in most nursery areas and Lowes. When a copper sulphate formula is required, especially for my prized acers,crab apples etc. I use Phyton 27, which again is quite expensive but will go a long long way.
In a lot of ways, the use of these is a no win battle in that the more you use these, the greater the tolerance being built up by the critter population. Also its very easy to get lulled into a false sense of security in thinking that a systemic is a proverbial 'silver bullet'. But then i don't think anybody stays in bonsai for the pure ease and comfort of it all.......