The best results I have had is with a product called "distance". It will be very difficult for just anyone to find, you almost have to know a professional grower to get this product. Although it is very safe to use. It is a growth regulator, similar to enstar. Orthene is effective but is more effective if you pot water with it, once a week, for three weeks. With products such as malathion, diazinon, which are commonly oil based, you need to be careful not to apply when it is very hot, this can burn your plants. Also when you do kill the scale, there will be scaring from where the scale was, pay close attention, this could turn into a secondary disease such as "black rot", it will appear as a black area on your plant which will, for one appear to be soft to the touch and also will notice it spreading, there is no cure for this except to cut it out. Don't ask me how I know all this, I have learned the "hard way"....lol.