I've had a medium-sized schefflera or 'umbrella' houseplant for about five years now, and it might have been as old when I first got it. Lately, I have noticed black spotting on some of its lower leaves - the leaves higher up don't seem to be affected. The affected leaves are slightly sticky.
My question is twofold. First, is this caused by alternaria? Second, what is the best means for dealing with it? I'm reluctant to use any sort of fungicide or bactericide as I have two cats that are fond of this and other plants. Can it be controlled with removal of the affected foliage, limiting the moisture of the soil, and ensuring that the remaining foliage is kept dry?
As a bonus, I also encountered some small yellowish growths of what appeared to be a fungus on the surface of the soil a few months ago. Whenever I saw it, I would scrape it off and dispose of it, but it kept creeping back. I can't provide a picture, as it now seems to have departed, at least for the time being. Could this be related to the spotting of the leaves, or share a cause (overwatering)?