My Oak Tree Wilts

Oak Wilt

• A gardener who notices that the leaves of his oak tree wilt has identified the symptoms of the appropriately named oak wilt, a disease caused by the pathogen Ceratocystis fagacearum. This disorder affects all species of oak but is especially virulent in the red oak family and is capable of leading to the death of the tree within one year, although some survive into a second year. Trees in the white oak family are less susceptible and may live with the disease for several years.

Symptoms

• Upon infection, the oak begins to show signs of distress from the top downward. The green leaves see their color dull and the leaves begin to wilt, drooping and taking on a bronze or tan color at their edges. The disease progresses further down the tree and leaves begin to yellow and fall from the oak, often accompanied by even healthier green leaves. Although it cannot be seen by the naked eye, brown streaks develop in the sapwood.

Root Grafts

• Oak wilt spreads rapidly among the roots of trees that are grafted together, or intertwined. Therefore, it is imperative that these roots be separated to prevent the spread of the disease to healthy trees. This can be done either chemically or mechanically, but chemical measures take some time to be effective and oak wilt may spread before the chemical is able to work. Mechanical separation of the root graft is the most effective technique, yet also the most expensive and labor-intensive.

Control

• No fungicide exists to counter the effects of oak wilt. Infected trees should be immediately separated, removed and destroyed. All gardening devices, such as pruning shears and shovels, that have touched the roots, soil or tree are likely to carry the fungus, so they must be sterilized, either with simple chlorine bleach or alcohol. Keep in mind that animals -- especially squirrels -- also transfer the disease from tree to tree, so simply separating the infected tree from others will not suffice.