Answer: I suspect a fungal disease called oak leaf blister. Oak species such as pin oak and Shumard oak are resistant to leaf blister and are rarely affected, but rarely does not mean never. I'm basing my suspicion on your description of the foliage. Although the following publication is from Illinois, it has good photos of affected leaves: http://web.aces.uiuc.edu/vista/pdf_pubs/663.PDF
If the photos match, then read on:
The fungus which causes leaf blister attacks only the leaves, and does no damage to other parts of the tree. While landscape trees with affected foliage may appear unsightly, oak leaf blister causes little damage and will not cause any long term tree health problems.
Since this disease is much more unsightly than harmful to oak trees, no control measures are usually suggested.
Collecting and composting or burning the leaves as they drop may be of some benefit in reducing the inoculum for the following spring. A single dormant fungicide spray, applied before the buds begin to swell in early spring, will control the disease but is not commonly recommended. Fungicide sprays applied after budbreak are ineffective.
So, rake and remove the fallen leaves and spray your tree with a fungicide just as the new leaves are beginning to emerge. This should offer protection to next year's foliage.
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