The owner of the company I work for also happens to own a small vineyard that has a gopher problem. He has a device he lovingly refers to as his "gopher getter". Basically it consists of a 20 lb. propane tank w/ a length of hose on it, attached to a pipe w/ an ingniter on the end of it. He fills the tunnel w/ propane, ignites it, and then giggles for the next 15 minutes. I don't know that this has solved his gopher problem, but it sure is a lot of fun.
edit: btw....the propane in the tunnel will explode, so use a little common sense here, or you may end up breaking a picture window (like the owner of the company i work for
)
