Galled leaves on azaleas usually appear light green, while the spore mass of the causal fungus is white.	Huge leaf gall on a plum leaf azalea.
Swollen, distorted leaves on sasanqua camellia often have light rose-colored highlights.

Leaf gall is a common spring disease of azalea, rhododendron, and sansaqua camellia. Other plants reported susceptible to this fungal disease include leucothoe, Japanese andromeda, blueberries, and cranberries. The fungus Exobasidium vaccinii infects young leaves, blossoms, and sometimes young twigs or shoots. Infected plant tissues typically become swollen and appear as fleshy, soft, irregularly shaped galls.

Symptoms. In early spring, small, soft, swollen areas form on leaves, flower buds, and sometimes on new shoots. Typically, the developing leaf and shoot galls are green while blossom galls are the color of the normal blossoms. Galls can be small, or they can develop into swellings an inch or more in diameter. Whole leaves or parts of leaves may become galled. As azalea and camellia galls age, their surfaces
become white with masses of spores. Galls of some other hosts may be white or pink. Later on in the spring or early summer, old galls turn brown, shrivel, and fall to the ground. On some susceptible rhododendron cultivars, infected leaves do not become galled but show yellow or creamy white spots that cover the leaf surface. Later, a white spore layer develops on lower leaf surfaces.

Persistence and Transmission. The white or pinkish spores produced on galled tissues or on lower surfaces of some rhododendron varieties are spread by wind and splashing rain to nearby healthy leaves, shoots, or buds. Initial infections occur when the spores contact susceptible tissues. Galls form the following spring. Cool, moist weather favors spore development, dispersal, and infection. The disease is often more severe in shaded areas with high humidity.

Control. Cultural methods provide the most practical control for azalea gall in many home landscapes:

Ôø‡’Ä¢ Hand remove and discard all galled leaves and yellow or white spotted leaves on rhododendrons before they become white or pink with spores.

’Ä¢ Ôø‡Destroy galls. You can add galled leaves to a hot, properly maintained compost pile.

’Ä¢ Prune overhanging branches to improve air circulation and sunlight penetration.

Ôø‡’Ä¢ Allow adequate space between plants. Prune to keep the landscape open to decrease humidity levels.

’Ä¢ Do not plant extremely susceptible azalea cultivars such as China Seas, Copperman, Herbert, Hinodegiri, Mother's Day, Rosebud, or White Gumpo. The rhododendron cultivars Purple Splendour and Roseum are also especially susceptible to leaf gall.

Ôø‡ ’Ä¢ If possible, plant a leaf gall resistant cultivar such as Amoena, Aphrodite, Coral Bells, Eikan, Faker, Formosa, Glacier, Gloria, Hampton Beauty, Kow-Ko-Ku, Mrs. G. G. Gerbing, Nancy, New White, Pride of Summerville, R. Poukhanese, Sensation, Thinbegen, Sunglow, Treasure, or White Jade.

Ôø‡’Ä¢ Place susceptible varieties in locations where they will get maximum exposure to sun and air movement.

’Ä¢ Use protective fungicide spray applications to give some control of leaf gall. Apply Bordeaux mixture or Bayleton just before bud break; apply a second time 2 to 3 weeks later. Follow specific label directions. Add a spreader-sticker to Bayleton to allow for complete spraying coverage.

Use 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.

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