Dealing with gophers and moles can be a difficult and frustrating problem. There are a number of treatment types to address gopher problems (e.g. traps, sprays, mechanical barriers, noise deterrents, toxic baits). What is the best way to proceed to eliminate gophers from the garden?

We are currently working on a project where we are going to install a mechanical barrier (gopher wire and gopher baskets) for all lawn and planted areas. This is an expensive solution for large areas, and it isn’t bulletproof, but it helps insure there aren’t problems with gophers harming newly planted areas.

The University of California Integrated Pest Management Program, has a good general guide to dealing with gophers and the different treatment types available. An important highlight:

No repellents currently available will successfully protect gardens or other
plantings from pocket gophers. Plants such as gopher purge (Euphorbia
lathyrus), castor bean (Ricinus communis), and garlic have
been suggested as repellents but these claims have not been substantiated
by research. Although there are many frightening devices commercially
available to use on pocket gophers (vibrating stakes, ultrasonic devices,
wind-powered pinwheels, etc.), pocket gophers do not frighten easily, probably
because of their repeated exposure to noise and vibrations from sprinklers,
lawnmowers, vehicles, and people moving about. Consequently, frightening devices
have not proven to be effective. Another ineffective control method is placing
chewing gum or laxatives in burrows in hopes of killing gophers.

This leaves trapping, baiting, or barriers as the best ways to deal with gophers in the garden.

For More:

Information from Colorado State
Another Guide From Iowa State
Iowa State Information on Moles