Prized for the wood and nuts it produces, a walnut tree can be a great source of value and treasure to those who grow them. The wood is used to make fine furnishings and novelties, and the best of walnut wood is sliced into thin sheets and used as veneer. But before any of these scenarios can play out, the tree must first withstand the pests, diseases and other environmental issues that can pose a problem.
Coddling moth and walnut leaf gall mite are the two most common pests affecting walnut trees. Coddling moth attacks the nuts, staining the shells and kernels. The walnut leaf gall mite does not pose a serious threat to walnut trees. It causes small, raised surfaces to form on a tree's leaves.
The two most common diseases that affect walnut trees are walnut blight and walnut leaf blotch. Walnut blight inflicts widespread damage to the fruit, causing holes and blotches. It also discolors the leaves and produces black spots on the leaves. Young trees are more susceptible to walnut blight, particularly during cold, wet periods. The best way to treat walnut blight is to cut damaged parts and discard them. Leaf blotch discolors a tree's fruit, causing it to turn black and then fall. This disease also causes a large number of leaves to fall. The most effective way to treat leaf blotch is to rake and discard fallen, infected leaves.
Environmental and Site Problems
Natural elements, freezing temperatures in particular, can be a major problem for walnut trees. Damaged branches, and in some cases, a complete ruin of a tree can sometimes be the result of such exposure. Additionally, trees that are damaged in this way are susceptible to an infection by fusarium canker. There are a few measures that can be taken to help minimize this potential injury, including planting the species of tree where it naturally grows, and avoiding pruning the tree during its growing season.