Mix peppermint oil, garlic, urine, dawn soap with some water and spray it everywhere they go and all in their tunnels and get some of those solar powered yard spikes that vibrate to further disrupt them from digging tunnels. Also, you don't have to use urine in the mixture but I would just to show them you mean business and this is your lawn.
Everytime I gotta piss I run down there and piss down one of their holes. It seems I've only got 1 gopher left for now
Bigsmokeharold: 7
Gophers : 1
Notable loot drops : one gopher had a white patch under its chin the rest did not