Oak leaf blister is favored by cool and moist conditions during budbreak and early stages of leaf development. Infections occur when leaves are emerging. Expanded (older) leaves are not susceptible.
Abnormal growth of leaf includes bulges, depressions, cupping and twisting. Numerous blisters can coalesce to affect entire leaf. Bulges are usually light green, eventually turning to brown as the leaf ages. Defoliation can occur on severely diseased trees. Often leaves remain on tree.
This disease does not seriously affect the overall health of the tree. The aesthetic value of the tree is diminished by diseased leaves that remain on the tree. Chemical controls are usually not recommended. Once infection has occurred, chemical treatments are ineffective. This disease does not seriously affect the overall health of the tree.
Fungicide, such as mancozeb or chlorothalonil, (or any systemic fungicide with PPZ) can be used as protectants. Preventative fungicide should be applied just prior to budbreak and through early leaf development for effective control.