I bought a schefflera 8 months ago and am now repotting it. The top of the dirt has light green mold on it and the root ball has granular light green (almost white) fungus througout the root system. The trunk has a faint white dusting (presumable mold) on it. Otherwise the plant looks healthy and has the right sunlight conditions. How can I get rid of the mold and support my plant's health?