Plant Health Problems
See Rhododendron for a detailed discussion of other common diseases of this host.
Diseases caused by Fungi:
Leaf and flower gall, Exobasidium vaccinii.
Leaf and flower gall is generally not a serious disease of azaleas and rhododendrons but at times can be troubling, especially under moist conditions. The disease is sometimes called pinkster gall, because of the enlarged, apple-like, sometimes pink galls on the leaves of the pinkster flower, Rhododendron nudiflorum. The first indication of the disease is a thickening and fleshy appearance of the infected plant part. Expanding leaf and flower buds as well as young, developing shoots are susceptible to infection. The disease occurs most commonly on the leaves, and part or all of the leaf may be affected. The developing galls range from small individual thickenings on leaves to extensive, shapeless or bladder-like galls up to 2 inches in diameter.
Control may be attained by pruning out and destroying infected leaves. Reducing humidity where possible, increasing aeration, and avoiding moisture on leaves, reduces infection. Some newer varieties of azalea are resistant to leaf and flower gall.