Puckered, circular areas, up to ½ inch in diameter, appear on the leaves in the spring. The blisterlike spots are yellowish green at first, and later die and turn brown. The leaves usually remain attached to the tree.
Puckered, circular areas, up to ½ inch in diameter, appear on the leaves in the spring. The blisterlike spots are yellowish green at first, and later die and turn brown. The leaves usually remain attached to the tree.
Leaf blister is caused by a fungus (Taphrina caerulescens) that is unsightly but rarely harmful to the tree. It is a problem on various species of oak, particularly red, black, scarlet, and live oaks. The fungus spends the winter in the bud scales on the tree. During cool, wet spring weather, it enters the developing leaves. Green blisters form where the fungus enters the tissue. The infected tissue eventually dies and turns brown. In the fall, the fungus produces the overwintering spores. If the following spring is cool and wet, the cycle begins again.
If leaf blister was a problem the previous year and the weather this spring is cool and wet, spray the tree with a fungicide containing chlorothalonil 1 or 2 weeks before the leaves appear. Cover the entire tree thoroughly with the spray.
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