Go to hd or lowes and hit the traps section. I have used the smoke bombs, traps with lil success. I am using a castor oil product this week and I can see new gopher holes on the perimeter of my garden like they are moving out. Supposedly they hate the smell.
You can also cut the bottom out of your continer and bury it. It totally thwarts the gophers. A small animal fence usually keeps them out. I haven't lost a plant in a few years using a combination of these methods.
Regular old road flares may be cheaper than the commercial smoke bombs.
It's the sulphur smoke that kills the rodents.
Take a flare, cut it into 4 or 5 pieces, depending if you get the 10 minute or 20 minute ones. It doesn't take much, just 3" or so, so thqat you can hold one end and light it with a propane torch.
I use these bombs made for agriculture use. I killed 14 last year with traps and water hoses and this year we only got 2. also next year prep out and make rings out of chicken wire and line your holes.
they make poison bait worms, you poke a hole in the tunnel and slip them in. You could also buy a 22. calb. rifle and a twelve pack a PBR and sit there all day till u see em' get em son!!!!