Trap, as fireballsocal has mentioned. We have a real issue here in S. Calif. with pocket gophers. If you struggle setting traps correctly, which is finding the main tunnel, and setting 2 traps back to back, facing out from each other, then call in a professional to get the counts down, and spend some time with the professional, watching how he sets the traps. I use Black Box traps as well as Macabee cinch traps. Here's a link about how to set both types of traps:
Garden Counselor Lawn Care: Gopher Traps

You have to set and trap, set and trap, set and trap, until you no long find gophers in your traps or evidence of tunneling activity. And, you have to get on it, the next spring, before the new ones have more babies.

Patty S.

great advice above...shortcuts do not get it done.

If these are indeed gophers (the bit about the lawn has me confused since gophers don't "kill" lawns) then trapping and exclusion really are best. You have to set the traps properly in tunnels, and it is rather an art form, but it works. It won't ever be complete eradication, but you will have to trap each time the population seems to be problematic. I use trapping combined with chicken wire baskets around roots of newly planted trees/shrubs, as well as chicken wire underneath each row in the vegetable garden.

The only good thing about gophers is that they do the majority of their work from underground, so you don't need to worry about them climbing fences or even feeding on aboveground plant parts (unless they've pulled the entire plant into their burrow, which they do with vegetables). Also, large, established plants are usually not bothered since their root systems are so extensive.

We knew what we were in for when we purchased this property, and everything we have planted has been planted in a gopher wire basket which is a pain, but it allows the tree to get a good start prior to the gopher munching. All the gophers do is root prune which makes for more roots inside the basket. THEN, the trapping and poisons come next. I heard that ammonia soaked rags placed in the tunnels will drive them away. They don't like that smell... nor do I. We have a huge castor plant that we grew for the gophers. They leave it alone, and we do put seeds in their tunnels, but no way to know if the gophers have feasted and died. We also have voles and they actually eat the bark and new shoots. Tabasco and soap mixed with water and sprayed on leaf and trunk surfaces works well to discourage voles.

HD has a tool to deliver poison underground, it looks like a long t. I have used it many times. Yet to fail. May take two applications.

It costs about thirty dollars. Plus poison.

I'd second the suggestion of poison bait placed in their tunnels with a tool. It isn't perfect control, but does seem effective. And it does take several applications. I have had mixed to poor results with trapping. Traps usually work once in an area, and then the gophers avoid them. At least the ones here do.

Best bait to use seems to be the strychnine based ones, but those are also persistent in the food chain. The zinc phosphide ones (like HD sells) have the advantage of not working again if some predator eats a gopher it killed, and seems to work OK.