Have you tried using those electronic gopher deterrents? We've used them and while they don't go away entirely, they seem to keep away from those stakes. They make a solar version, but the ones that use batteries seem to work better.
http://www.harborfreight.com/s...
Here's an article about the little pests from the Washington DFW:
http://wdfw.wa.gov/living/goph...
