I know Pathfinder moved away from ghosts being from the ethereal plan like D&D. But force damage affects ghosts and ethereal creatures just the same, and there are at least haunts (if not ghosts) that inflict force damage.
But even if you had a haunt that deals force damage, I'm not sure it could detect, target, or trigger from a character using Ethereal Jaunt, for example. Ghosts certainly don't have a special sense listed that indicates they could. Neither do haunts, but then again we don't know how they sense creatures on the material plane either.
There's a chance I'm going to run into this scenario soon, and I would like to decide how it should work.
Ethereal and Incorporeal are listed as two different Traits in the Bestiary, and and I can't find anything linking them, so I'd say no. Ether Spiders would work. Or give the Ghosts Ethereal Jaunt as an Innate ability if you want them to be able to do that.
It seems that creatures on the Ethereal Plane can see into the Material Plane, but not interact with it, but Creatures on the Material Plane cannot see into the Ethereal Plane.