i have a beautiful 15 year old Tiger Bark Ficus bonsai. The problem is that is has been plagued with honey dew the last two years and is experiencing a lot of leaf drop. I've tried washing it with the hose, spraying it with neem oil, spraying it with home made insecticidal soap and even resorted to spraying it with commercial insecticide. Nothing has gotten rid of the honey dew. I cannot actually see the insect that is causing this problem. Does anyone have any ideas?