bayer tree and shrub.. properly applied .. according to the label instructions ...

will take care of both the scale.. and i am thinking maybe mites or aphids on the new leaves ... [scale probably arent on the new leaves yet .. they dont move that fast ...]

one application.. and you will be done forever ...

the black soot will go away.. once the honeydew is stopped being produced ...

ken

Thanks, Ken. Can you be more specific about which Bayer Tree and Shrub product you recommend? Their "Tree & Shrub" product web page lists 15 options, including
- Insect, Disease & Mite Control
- Insecticidal Soap
- Protect & Feed
- 3-In-1 Insect, Disease & Mite Control
etc.

Here is a link that might be useful: List of Bayer Tree and Shrub products

Schefflera is listed in some places as a poisonous, invasive plant and in Florida it is a banned non native so you may want to rethink what to do with this plant.
The black soot like stuff is most likely excrement from the scales which are usually controlled by horticultural oils. Most all plant problems are often the result of the plant trying to grow in the wrong soil which does not provide the plant with the nutrients it needs to grow strong and healthy.
Perhaps talking with the people at your University of California Cooperative Extension Service will be of some help.