Integrated Pest Management
Oak Leaf Blister
Advanced oak leaf blister lesions.
Mild leaf blisters on oak leaves.
Oak Leaf Blister occurs in Utah during wet spring conditions. This disease is caused by the fungus, Taphrina caerulescense, and is known to infect about 50 species of oak. However, it is not known if there is specialization within the species. The most commonly infected oaks in Utah are the scrub oaks, Quercus gambelii.
SYMPTOMS
Initial symptoms are raised or sunken lesions resembling a blister, usually a lighter green than the rest of the leaf. Eventually the lesions become more pronounced and start to turn brown. The lesions range from 1/4"-1/2" in diameter and may appear larger if they merge. The leaf shape may also be distorted. In most cases the infected leaves do not drop prematurely from the tree but may be the earliest to drop in the autumn.
DISEASE CYCLE
The spores of Taphrina are produced on the surface of the leaves and are blown or washed to come into contact with new bud tissue. These spores overwinter in the buds and under bud scales and infect the newly emerging leaves during wet periods in the spring.
This fungus only infects during cool, moist conditions which occur during the spring in Utah. There is only one infection period per year and secondary spread during the season does not occur. Therefore by the time the lesions are observed it is too late to control the disease.
MANAGEMENT
Cultural Controls
- Apply fertilizer to increase tree vigor.
- Rake up leaves to reduce inoculum.
Chemical controls
Chemical controls are not usually recommended since the disease does not cause serious or permanent damage to trees. The disease only occurs during wet springs and is not always a problem. If you anticipate a wet spring and if the tree is considered valuable, a conspicuous specimen or in a nursery you could select one of the following chemicals for control of Oak Leaf Blister.
Apply fungicides just prior to bud break: Daconil 2787, Dithane, Mancozeb