Voles

Voles, or field mice, can be very destructive. There are 23 species of voles in the United States and they can be identified by a shorter tail then house mice. They like to eat roots and can cause damage to ornamentals and trees. They can kill trees by eating the bark of the tree near the ground which girdles the tree. Control is best achieved by rodenticides like zinc phosphide and anticoagulants. These baits can also affect non-target species and pets and children so care should be used. Voles reproduce quickly having 1-5 litters per year in the wild. Each litter usually 3-6 voles. Because of this their population can increase quickly. Natural predators are not effective at controlling voles because of their reproduction speed.

The publication Mike referred to is "Voles" in Prevention and Control of Wildlife Damage

Related Resources:
Voles
Controlling Voles in Horticulture Plantings and Orchards in Missouri
Voles