How Moles Harm Trees

Moles are insectivores that consume grubs, earthworms, spiders, ants and beetles. They do not feed on vegetation, but they can damage trees inadvertently with their burrowing activity. Another small rodent, the vole, is often confused with moles. Voles are capable of causing extensive damage to trees.

Unlike moles, voles do consume plant material. A vole looks very much like a fat field mouse with its rounded nose and long tail. Voles burrow or create 1 1/2 inch wide runs near trees and vegetation around the home. Some species prefer tall grass, while others favor forested environments. Moles have sharply pointed snouts, short tails and webbed front paws that help it "swim" through dirt near the surface.

Mole tunnels are one way these rodents can damage trees, especially young trees. As moles burrow around tree roots, they leave behind air pockets that can dry out tree roots and hinder water absorption. Occasionally, moles will also chew through tap roots as well as lateral roots as they construct their tunnels. This kind of damage to tree roots can kill young trees and invite disease to established trees. Voles will often use mole tunnels for travel and to access vegetation.

Mole damage to tree roots also occurs as the animal girdles the root, gnawing around it as it tunnels. While moles do not attack roots for food, they do find ways to work around the structures, which often results in damage. Voles feed directly on the roots of trees, grasses and other plants. They feed day and night all year and eat roots as a regular part of their diet.

Voles also chew on and consume a tree’s outer bark, whether it’s on seedlings or mature trees. Typically, voles eat bark during the fall and winter. They can girdle the entire tree up to a few inches off the ground, as high as these small animals can reach. Often, the tree suffers extensive damage before signs such as curling leaves and weak branches become evident. The damage also stunts a tree’s growth.