ALABAMA A&M AND AUBURN UNIVERSITIES Leaf Gall on Azalea and Camellia ANR-942

Huge leaf gall on a plum leaf azalea.

Galled leaves on azaleas usually appear light green, while the spore mass of the causal fungus is white.

eaf gall is a common spring Ldisease of azalea, rhododen- dron, and sansaqua camellia. Other plants reported susceptible to this fungal disease include leucothoe, Japanese andromeda, blueberries, and cranberries. The fungus Exobasidium vaccinii infects young Swollen, distorted leaves on sasanqua leaves, blossoms, and sometimes camellia often have light rose-colored young twigs or shoots. Infected highlights. plant tissues typically become may become galled. As azalea and swollen and appear as fleshy, soft, camellia galls age, their surfaces irregularly shaped galls. become white with masses of spores. Symptoms.ARCHIVEIn early spring, Galls of some other hosts may be small, soft, swollen areas form on white or pink. Later on in the spring leaves, flower buds, and sometimes or early summer, old galls turn on new shoots. Typically, the devel- brown, shrivel, and fall to the ground. oping leaf and shoot galls are green On some susceptible rhododendron while blossom galls are the color of cultivars, infected leaves do not the normal blossoms. Galls can be become galled but show yellow or small, or they can develop into creamy white spots that cover the swellings an inch or more in diame- leaf surface. Later, a white spore ter. Whole leaves or parts of leaves layer develops on lower leaf surfaces.

www.aces.edu Persistence and Transmission. ¥ Do not plant extremely suscepti- The white or pinkish spores pro- ble azalea cultivars such as China duced on galled tissues or on lower Seas, Copperman, Herbert, Hinodegiri, surfaces of some rhododendron va- Mother’s Day, Rosebud, or White rieties are spread by wind and Gumpo. The rhododendron cultivars splashing rain to nearby healthy Purple Splendour and Roseum are leaves, shoots, or buds. Initial in- also especially susceptible to leaf gall. fections occur when the spores con- ¥ If possible, plant a leaf gall re- tact susceptible tissues. Galls form sistant cultivar such as Amoena, the following spring. Cool, moist Aphrodite, Coral Bells, Eikan, Faker, weather favors spore development, Formosa, Glacier, Gloria, Hampton dispersal, and infection. The dis- Beauty, Kow-Ko-Ku, Mrs. G. G. ease is often more severe in shaded Gerbing, Nancy, New White, Pride areas with high humidity. of Summerville, R. Poukhanese, Control. Cultural methods pro- Sensation, Thinbegen, Sunglow, vide the most practical control for Treasure, or White Jade. azalea gall in many home landscapes: ¥ Place susceptible varieties in ¥ Hand remove and discard all locations where they will get maxi- galled leaves and yellow or white mum exposure to sun and air spotted leaves on rhododendrons movement. before they become white or pink ¥ Use protective fungicide spray with spores. applications to give some control of ¥ Destroy galls. You can add leaf gall. Apply Bordeaux mixture galled leaves to a hot, properly or Bayleton just before bud break; maintained compost pile. apply a second time 2 to 3 weeks ¥ Prune overhanging branches later. Follow specific label directions. to improve air circulation and sun- Add a spreader-sticker to Bayleton to light penetration. allow for complete spraying coverage. ¥ Allow adequate space between plants. Prune to keep the landscape open to decrease humidity levels. Jacqueline Mullen, Extension Plant Pathologist and Diagnostician, and Austin Hagan, Extension Plant Pathologist, Professor, Entomology and Plant Pathology, both with Auburn University ARCHIVEUse chemicals only according to the directions on the label. Follow all directions, precautions, and restrictions that are listed. For more information, call your county Extension office. Look in your telephone directory under your county’s name to find the number. ANR-942 Issued in furtherance of Cooperative Extension work in agriculture and home economics, Acts of May 8 and June 30, 1914, and other related acts, in cooperation with the U.S. Department of Agriculture. The Alabama Cooperative Extension System (Alabama A&M University and Auburn University) offers educational programs, materials, and equal opportunity employment to all people without regard to race, color, national origin, religion, sex, age, veteran sta- tus, or disability. Web Only, Revised Nov 2003, ANR-942 © 2003 by the Alabama Cooperative Extension System. All rights reserved.