At this time it is unknown whether the fungus was recently introduced into California or if it is a native and has only recently increased in importance as a tree-killer. The fruiting bodies of the Hypoxylon thouarsianum fungus may also be present. They are small, black domes. Touching them with your finger may break the thin crust revealing a khaki-green, powdery surface below. Older fruiting bodies develop a rough surface and become dull black.
Oaks are highly resilient trees, but they are also host to many plant pathogens and insect pests.
Avoid stressing the tree. For more details on tree care see Natural Tree Pest Control Steps Specific treatments Start spraying with the mixture below. Spray leaves and soak trunk, as well as soak ground around tree. Use this mixture first to help raise energy level of tree. The formula is suggested, you may substitute products which you feel are close or similar to the products I suggest.