A regular spray of the soapy water solution is the best preventative measure you can use. Don't make the soap solution too strong, either. Stronger is not better. About 1/2tsp. dish soap to a quart of water is enough. Spray every week or two and be sure to spray up under the leaves, all the stems and even the soil surface and the pot. Juvenile crawlers can be anywhere. A thorough rinse of the whole tree with a warm shower or hose is also a good idea.
The mature bugs have that waxy shell over them so to kill them, alcohol or a horticultural oil spray is preferable. The alcohol is best in hot weather. Use dormant oil spray in the winter.
Vigilance is important for any plant in a pot. Keep looking carefully for these and other little guys to return, because wherever they came from, they probably can still get to your plant if it is outdoors especially. But even indoors, they find what they want to eat.
