1 Iritis is uncommon, but can be due to trauma, infections, or autoimmune conditions. Symptoms include pain, red eye, and often, decreased vision.  Optic neuritis. The nerve travelling from the back of the eyeball into the brain can become inflamed.
Oak root fungus, or white rot, is a widespread disease that becomes visible just beneath the bark and on roots. What looks like layers of light brown to tan mushrooms form in clusters at the base of the trees.
The mushrooms collect sugars from the tree and, in turn, provide the tree with water and nutrients. The fruiting bodies of mycorrhizal mushrooms do not grow directly on the tree but instead emerge from the soil surrounding the tree; underground, the mycelia of the mushrooms are intertwined with the roots of the tree.