Landscaping - Insects & Diseases
Leaf and flower galls are commonly found on many flowering woody hosts, most often on azalea and camellia. This disease occurs on plants in the Ericaceae or heath family, as well as on some species in the Empetraceae, Lauraceae, Symplocaceae and Theaceae families; including andromeda, arbutus, azalea, blueberry, camellia, huckleberry, Labrador tea, leatherleaf (Chamaedaphne calyculata), leucothoe, kalmia (mountain laurel) and rhododendron. Azalea leaf and flower gall, caused by the fungus Exobasidium vaccinii can occur on woody ornamentals growing outdoors in landscape plantings and in greenhouses. Disease is more common on plants growing in humid, sheltered areas with little air movement. This allows leaves and flowers to stay wet for long periods of time and favors infection and spread of the disease. After new leaf buds are infected in the spring, leaves and flowers develop fleshy, pale green or whitish galls (swellings) which, while unsightly, usually don't cause severe damage.
"SP277-F-Azalea Leaf and Flower Gall," The University of Tennessee Agricultural Extension Service, SP277F-1M-12/98 (Rep) E12-2015-00-056-99, http://trace.tennessee.edu/utk_agexgard/50