FAQ - Answer
I’m not aware of any fungicide that could be used as a topical treatment. The bark loss is most likely related to an infection by oak root fungus (Armillaria mellea) and there are no fungicides effective in the treatment of this pathogen. The general recommendation is to expose the root crown (trunk base) to air - to allow it to dry. This is done in pear orchards where infections have occurred and it has had a beneficial effect. The pathogen is not killed, but its development slows substantially. It is believed that the same effect occurs with oaks.