I've actually had good luck with the smoke poison. And yes, you can get them in Ca. Imagine that.
Most people don't dig down into the tunnel enough for them to be effective. Do two or three tunnels at a time. Cover them up after lighting so no smoke comes out. It'll work.
Or I'll loan you my Beagle for a month. He'll kill all of them. You won't have any yard to speak of after though. Ask me how I know.
