@RobLaffin, Rob ...
All of my experience is with spider mites on roses, so you may want to experiment to see if my method works on other plants.
Spider mites like hot, dry conditions. Change that, and they disappear quickly.
If I have a rose infested with spider mites, I just wash the rose with a hard stream of water, you can put your hand behind soft growth, making sure I wash both the upper and lower surface of the leaves three days in row to break the breeding cycle.
Washing the rose down creates a more humid environment than spider mites like, so they move on.
On-going care is to wash the roses well at least once or twice a week.
In my garden, I usually spray down my roses every afternoon to slow down the transpiration rate, so I haven't had an infestation in years.
