Winter rodent damage to newly planted trees and shrubs can be severe, but taking steps in the fall can help eliminate the problem. In most home landscapes, the principle culprits are rabbits and voles. Most homeowners are familiar with cottontail rabbits but are not as well acquainted with voles, a short-tailed relative of the common mouse. Voles have compact, stocky bodies with small eyes and ears that are partially hidden by their gray or brown fur.
Rabbits most often damage landscape plantings by clipping off small twigs, branches or buds, but they will resort to stripping the bark from young trees if limited food sources are available. Voles, unable to find seeds to feed on in winter, may turn to trees or shrubs less than 2 years old because the bark is still thin and easy to chew through. This feeding may be confined to one side of the tree or occur in patches around the tree. When the bark is chewed off around the entire trunk, the tree's vascular system (the tissues that move water and carbohydrates up and down the plant) is destroyed and the tree is killed. This type of injury is called 'girdling'.
Vole damage to a young tree.
Minnesota Department of Natural Resources Archive, Minnesota Department of Natural Resources, Bugwood.org
In some cases, particularly with rabbit feeding, the top of the plant may be completely detached from the trunk. This type of injury can be disastrous to a young tree. An evergreen chewed off below its lowest branch will never grow back. A deciduous tree that is chewed off will usually send forth a new shoot the next season, and a new leader may be established.
Prevention is the only way to protect trees and shrubs from rodent injury since very little can be done to salvage plants once the damage has occurred. Constructing a physical barrier around new plants is the most effective control, but it can be expensive and time consuming. Make a cyclinder of hardware cloth, ΒΌ inch mesh or less in size. Bury the wire 6 inches in the soil to prevent voles from tunneling under it, and make it tall enough to stand at least two feet above the anticipated snowline so that rabbits will not jump over it. PVC pipe or black plastic draintile can also be slit to fit around tree trunks, and applied in the same manner as the hardware cloth. The most economically effective technique for large plantings of windbreak seedlings is to mow grass and weeds near the tree so the growth doesn't become a winter cover for rodents. Also pull mulches back from the trunk of new plants, to eliminate this source of winter protection for foraging voles.
Close and frequent inspections are recommended during the late fall and winter to discover and solve any rodent problems as soon as possible.
