Some ways to exterminate voles in a garden include using poison bait and mouse traps. Using poison of any kind is good for exterminating voles and other pests, but can also be dangerous to pets or children. Keep them out of the garden area when setting out the traps.
Poison bait both lures the voles to the trap and kills them, allowing you to remove the exterminated rodents from the yard. There are a variety of poisons for voles, including products that have phosphide in them. Many poison baits and traps also contain warfarin, which causes hemorrhaging and internal bleeding in rodents. When using poison traps, the safest method is to keep them in the burrow openings where the voles are living. This lowers the likelihood of other wildlife becoming poisoned.
To successfully exterminate the voles, examine the area to locate their paths and burrows. Look for areas of the grass that are bare, since they are likely where the voles are soiling the lawn and killing the grass. There might also be visible feces or urine soiling of the garden area.
Since voles hide in tall and overgrown vegetation, regularly trim bushes, shrubs and grass to keep voles out of the yard.