Oak leaf blister

Natural History
Close-up of oak leaf blisters
Photo credit: R. L. Anderson - USDA Forest Service

Oak leaf blister is a common leaf disease among oaks in Florida and is caused by the fungus Taphrina caerulescens. Although infected trees may have unsightly leaves, serious damage is uncommon.

Spores of the pathogen infect young oak leaves. As the pathogen develops within the leaf, it causes a disruption of normal development of leaf cells. The infected tissues appear swollen or blister-like. Severe infections can cause the leaf to become curled or twisted. Over time the infected tissues die, leaving gray-brown areas scattered within the given leaf.


Identifying Characteristics

Identifying the disease: Leaf blisters first appear on the underside of leaves as small, slightly depressed gray areas. Over time the infection causes the leaf to become deformed, forming a blister. The blisters can grow to be 1/3" or larger and can be seen on both sides of the leaf. Mature blisters are gray or brown in color. There may be several blisters on a leaf and if blisters occur near the edge, leaf curl may result. Oak leaf blister is not usually noticed until many leaves have become very blistered or excessive leaf fall occurs.
Susceptible trees: Any oak can be infected. Live oak, water oaks, and laurel oak are preferred hosts.



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