Posted: 17/11/2013 at 18:22
This is what I use:
Get a pint jelly jar and fill it 2/3 full with vegetable oil. Add 4 drops dish soap, then fill with water and shake until it's emulsified. Then, get yourself a spray bottle and add about 1/3 of the mixture to the spray bottle. Fill with warmish water and again, shake until the entire mixture looks white.
Bring your affected plant to an area where you have some newspaper spread out. Spray the entire plant, topside of leaves and undersides, then stems. Leave 24 hours, then get a cloth and wipe the (by now smothered) scale off the plant. If it's summertime you can then give the plant a bit of a bath to remove the oil.
I've used this with calamondin oranges, limes, and lemons and it's very effective.