Deer, squirrels, mice, rabbits, and beaver are the most common and destructive. Types of damage caused include nipped buds, gnawed or shredded bark, girdled stems, reduced nut crop, and stolen nuts that had been planted for trees. Loss of growth, severe forking, or death are the final results of mammal damage.

DEER DAMAGE

Description and Injury
    Buck deer rub against young black walnut trees in the fall to remove the velvet from their antlers, often shredding the bark and leaving it hanging in strips. Larger trees, more resistant to bending, are usually not affected.

    Deer may also nip the buds of smaller trees, causing forking of the main stem. In areas of high deer populations, tree growth may be stunted because terminal buds are eaten by deer every year.

Control
    An effective, but expensive, means of preventing deer damage is to erect a tall fence around the entire plantation.

    Another suggested but not proven means of control is to hang cloth bags containing tankage (dead animal residues, obtainable from slaughter houses) on every second or third tree around the periphery of the plantation.

RODENT DAMAGE

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.