how do you exterminate moles from the yard?

traps are the only thing that reliably works. the sonic spikes and castor oil stuff is mostly hope. stamp down a few runs, see which one is raised again the next day - that's an active tunnel - and set a scissor or harpoon trap in it, wearing gloves so it doesn't smell of you. check your local rules first though, some places restrict mole trapping. or get a pest controller in if you'd rather not deal with it.