Do not plug the hole. The light and air will attract the pocket gopher. When the gopher tries to plug the hole he will get caught. Check the traps daily and leave them in place for a day or two after you catch a pocket gopher. If a trap is not sprung within 48 hours, move it to a new location.
Traps are available from hardware and garden supply stores.
In flower gardens or other areas where landscape disturbance is not desirable, some success has been achieved by flooding pocket gophers out with a garden hose. Insert the hose into the lateral tunnel and pour water into the tunnel system until the gopher is flushed out. This method can only be used in new tunnel systems, and only where other damage from the water will not be a factor. These methods could result in serious explosions or the placement of toxic fumes in undesirable areas. Although in many cases the damage caused by pocket gophers is the overriding factor, the benefits of pocket gophers should be recognized.