When I was a kid my neighbor took the rubber watchamacallit out of an old type writer the hard black rubber thing the paper rest on when the type hits it. He cut the rubber off the steal rod that goes through the center about half way.
Then he taped one side on an extension cord to the top of the rod sticking out the other end.
and taped up the other wire. when you pluged it in we would stick it in the ground and slowly pull it out if you could not feel it vibrating we would unplug the cord and flip it over and plug it back in ( back before the days of one side of a plug being bigger then the other )
Then just wait. in no time everyworm in a 6' to 8' radius would shoot out of the ground after picking them all up we would move over and do again. it wasn't long before we did not have any more worms in our yard ;\)
I need to find me an old type writer and make me one again.