Some kind of sucking insect, such as aphids or scale, probably. I've found spray products containing imidacloprid to be most effective, since they will kill even the bugs you don't spray directly, through systemic action. The same chemical applied as a soil drench will also kill them, and has the advantage of lasting about a year, though it is slow acting that way. Either way, hose off as much of the sticky stuff and mold as you can, to help maintain some of the plant's health.