The veins on my live oak tree leaves are turning a yellow to orange color and then the leaves are shedding. Why is my oak tree losing its leaves?
Based on the description, it would seem that the live oak tree is exhibiting signs of oak wilt. Oak wilt is a vascular disease caused by the fungus Ceratocystis fagacearum. All oaks can be infected with the pathogen; red oaks are the most susceptible, while white oaks are the least susceptible.
The disease is spread through two routes:
1. Through interconnected root systems
2. From oak to oak by a beetle
The accumulation of the oak wilt fungus in the vascular tissue stops the flow of nutrients and water from the roots to the leaves. Death rates can vary from as quick as two weeks in red oaks to two months or a year in live oaks. One method of identification is through veinal necrosis. The interveinal areas on the leaves stay green, while the areas directly adjacent to the veins die. Prior to the brown coloring, the dying area is often bright yellow or orange. To minimize the threat of oak wilt, prune your trees in the winter months of December, January, and February, but prune only if you have to. If you do prune, always paint over any wounds with pruning paint.
Symptoms of oak wilt could be confused with other problems or diseases. A sample should be submitted to a diagnostic lab for proper identification.
Contact your local Cooperative Extension office for more information on pruning and instructions on submitting plant samples to a diagnostic lab.