Description and Injury
    Mice, rabbits, and other small mammals gnaw on the stems of young trees, usually during winter, and remove patches of bark. Teeth marks are usually visible at the base of the tree.

    Squirrels are a common problem in black walnut. Walnuts are a favorite food of squirrels, which feed on green nuts still hanging on the tree or mature nuts after they have fallen. Squirrels also dig up planted walnut seeds, sometimes destroying entire plantations seeded directly with nuts.

Control
    Wire screening around the base of young walnut trees will prevent small rodents from eating the bark.

    Commercial animal repellents seem to have little or no effect on squirrels. The most effective control known to date is to place fresh cow manure on top of each newly planted nut.