Oak leaf blister occurs on most species of oaks.
Spots also turn a noticeably lighter green color as young leaves expand.
Leaf tissue cells in the diseased spots multiply more than surrounding cells and result in a raised blister-like buckling of the leaf. As the spots age, their upper surfaces become covered with a buff-white coating of fungal growth that later turns brown. The leaves remain on the tree and do not fall prematurely. In most cases, chemical control is generally not necessary for near-mature and mature trees. Fungicide application is generally not necessary because the trees are seldom severely infected and most leaves do not fall prematurely.