Oak Leaf Blisters...Dangerous
or Just Ugly?
Name: Oak Leaf Blister
Description: Taphrina caerulescens is a fungus that causes the Oak Leaf Blister. This is a common disease affecting many species of oaks. Members of the red oak group are especially susceptible to infection. The disease develops when conditions are cool and wet. Right now, in the Upstate, a majority of our trees are infected causing unsightly leaf deformity! Interestingly, white oaks are rarely infected. While red oaks are easily diseased with oak leaf blisters and their appearance is greatly marred, the blisters rarely endanger the tree health.
Symptoms: Symptoms appear in early summer as blister-like, yellow, circular, raised areas. The blisters can be up to a half of an inch in diameter. They are scattered over the upper leaf surface and have gray depressions on the lower surface. They turn from yellow to reddish brown with pale yellow margins, and then become dull brown with age. Several blisters can merge, causing the leaves to curl.
Action: This disease does not pose a threat to tree health but can greatly mar the tree's appearance. If you want to prevent this unsightly infection, a single pesticide application in early spring just before the buds begin to swell, will effectively manage this disease leaving your oaks strong and beautiful! Fungicides will not be effective if applied after bud break. However, homeowners are strongly discouraged from trying to treat large landscape trees. If treatment of large specimens is required, consider hiring a Schneider Tree Care professional.
Name: Oak Leaf Blister
Description: Taphrina caerulescens is a fungus that causes the Oak Leaf Blister. This is a common disease affecting many species of oaks. Members of the red oak group are especially susceptible to infection. The disease develops when conditions are cool and wet. Right now, in the Upstate, a majority of our trees are infected causing unsightly leaf deformity! Interestingly, white oaks are rarely infected. While red oaks are easily diseased with oak leaf blisters and their appearance is greatly marred, the blisters rarely endanger the tree health.
Symptoms: Symptoms appear in early summer as blister-like, yellow, circular, raised areas. The blisters can be up to a half of an inch in diameter. They are scattered over the upper leaf surface and have gray depressions on the lower surface. They turn from yellow to reddish brown with pale yellow margins, and then become dull brown with age. Several blisters can merge, causing the leaves to curl.
Action: This disease does not pose a threat to tree health but can greatly mar the tree's appearance. If you want to prevent this unsightly infection, a single pesticide application in early spring just before the buds begin to swell, will effectively manage this disease leaving your oaks strong and beautiful! Fungicides will not be effective if applied after bud break. However, homeowners are strongly discouraged from trying to treat large landscape trees. If treatment of large specimens is required, consider hiring a Schneider Tree Care professional.
Figure
1: Oak leaf blister symptoms on upper and lower leaf surfaces.
Figure
2: Oak leaf blister symptoms. 
