Oak Leaf Blister or Taphrina caerulescens is a fungus, that causes lesions and blisters on trees from the Quercus family (Oak trees). Infestation takes place early spring through spores overwintering in bark crevasses and bud scales infecting the young leaves. The disease reduces the effectiveness of photosynthesis, but is not considered significantly harmful for the trees and mainly an esthetic issue. The disease is closely related to Peach Leaf Curl (Taphrina deformans), which causes similar symptoms with Peach trees.
Which of my trees should be inspected for Oak Leaf Blister?
Oak Leaf Blister can infect all species from the Oak family. In Calgary it is mostly seen on Bur Oaks (Quercus macrocarpa).
Oak Leaf Blister is very easily to recognize from the blisters it creates on leaves. In later stages yellowing/browning can be seen on the infected leaves, leading to premature leaf drop.
Following pictures can help you determine if your tree is infected with Oak Leaf Blister.
Can Oak Leaf Blister be treated?
Oak Leaf Blister can be controlled by both mechanical and chemical measures, but can seldom be fully cured due to the high contamination chances.