Oak Leaf Blister – Identification
Q: There is something weird on my oak leaves.
A: This is a fine example of oak leaf blister. The disease is favored by cool, moist conditions during budbreak and in the early stages of leaf development.
It doesn’t seem to damage trees permanently. Given a dry spring next year, you may not see it at all.
Be sure to rake and remove leaves in fall.
See Oak Leaf Blister