The leaves are likely to be infected with Exobasidium vacinii, a fungus that produces galls on young leaves, blossoms, and sometimes young twigs and shoots. Humid conditions, cool temperatures in spring, and shady conditions favor gall production. The disease causes the leaves to become swollen and curled. Galls appear fleshy, pale green to whitish or pink in color, turning brown and hard with age. Infected flowers have thickened petals and appear waxy.
Control by hand pruning and disposing of gall-affected tissue. To prevent galls, allow adequate space between plants to improve circulation and sunlight penetration. If possible, plant resistant cultivars. Protective fungicide sprays give some control of leaf call. Contact your local Extension office for specific fungicide recommendations.
