Larry, if you don't have a lot of plants, just removing the scales by hand works for me. Then spray with a soapy remedy of some kind.
Scales are protected by their little 'shells' from a lot of the soapy insecticides, but the nymphs (young 'uns) don't have shells yet so they can be killed by insecticidal soap. You may need to repeat the soap application a few times to take care of new hatchlings.
On a larger scale (no pun intended
) a horticultural oil spray is recommended, as it will virtually smother both the adult scales with shells and the nymphs. But don't let your plant be in the sun if it has an oil spray on the leaves, or the leaves can burn. Keep it in the shade until you wash the oil off (wait a few days for it to work, of course). If you wash it off with a soapy spray that will again reinforce the treatment, to kill off newly hatched bugs.
I have completely given up on using any systemic insecticides, as it seems the bugs get resistant to them very quickly. Just like antibiotics, we've over-used them to the point that they are nearly useless now. It just takes a few bugs to survive the initial application, and when they breed, the resistance is passed on to all the new generation bugs. Some bugs' generations are counted in weeks!
