Use control measures such as traps or chemical means when all else fails. Voles don't nest in man-made structures as do the mice but do definitely live in yards, especially where grasses are allowed to grow naturally. Vole populations cycle periodically and high populations coupled with heavy snows usually mean damage to bases of shrubs and trees. Voles normally eat grass seeds but will turn to tree bark under the snow line in winter. Fruit trees seem to be special favorites and can be killed if totally girdled.
Damage seems to be more prevalent in untilled areas.
To prevent the loss of trees, they must be protected at the bases before winter sets in. Either purchase pre-fabricated trunk protectors or fashion your own out of some type of metal screening like hardware cloth. Make sure the trunk is protected from the ground to a height of at least six inches. During the winter, they will both girdle bark from trees and also eat tops of young trees within their reach. Protect gardens, trees and other plants by enclosing in wire fence material with a mesh size smaller than two and one- half inches.