By Ann Hazelrigg
Extension Plant Pathologist
University of Vermont
The apple harvest is over, but there are still some important pest management practices to follow to ensure healthy trees in the spring. The pests we need to manage are not the little ones we typically see in the summer but are larger and fluffier and include rabbits, mice and voles.
Occasionally, voles will burrow in the soil and damage roots, resulting in weakened trees. Moles do not cause damage to the tree bark since they are meat eaters looking for grubs and earthworms.
Maintaining vegetation-free zones under tree canopies extending at least two feet from the trunk will discourage voles from living near the bases of trees where they cause the most damage. Rabbits, mice and voles have plenty to eat in the summer but once the temperatures drop and snow covers the ground, food sources become scarce.
These animals often prefer young apple tree bark because it is tender, thin and easier to chew, so be prepared to protect these in addition to young crabapples. I also have seen girdling in young maples and other trees and shrubs, but this not as common as the damage in apples and crabapples.
The furry pests will nibble the bark at the base of your tree or higher when the animal stands on top of deep snow. If the damage is small and located on only one side of the tree, the tree can often repair itself over time.
However, if the feeding damage totally encircles the trunk, the tree is “girdled” and will not survive unless you intervene with bridge grafting, a dying art that connects the two portions of the tree with grafted strips of the same type of tree. Without this bridge, the tree will die due to the interruption of the water-conducting system that transports nutrients and water from the roots to the foliage at the top of the tree.
To protect your tree, be sure the barrier you choose covers the trunk from the soil line up to at least two feet or higher depending on snow depth. I usually try to protect the tree up to the first set of branches. You can use 1/4-inch hardware mesh and, if possible, set it 4 to 6 inches into the ground to prevent vole burrowing.
The hardware cloth or screening can stay on year-round and, if sealed at the top, can protect against apple borers. Create a large enough diameter to allow for five years of growth. You can also use 24-inch white, spiral plastic tree wraps to protect your fruit trees, but the wraps should be removed in the spring since they can harbor pests in the summer.