azaleas - Knowledgebase Question

Monroe, Ge
Question by patgreen
May 13, 2009
I pruned my azaleas this morning and discovered they are infested with something I've never seen before. Some kind of fungus/bug/larvae is attaching to and eating holes in the new leaves.
Starting as small green pimple size and as large as a thumbnail as it turns to white. It is only on azaleas but in several different locations in the garden. What is it and what's the cure? Thank you.

Answer from NGA
May 13, 2009


What you describe sounds like azalea leaf gall. Exobasidium vaccinii causes leaves and flowers to become swollen, curled, waxy and fleshy. The swollen plant tissues or "galls" are made up of abnormal plant tissue. Infected leaf tissue is usually pale green in color during the early stages of the disease; infected flowers are usually pinkish. Later in the season, a white spore layer covers the infected plant parts. Galls eventually turn brown and harden as the season progresses.

The occurrence and intensity of the disease depends on weather conditions and on the source of the causal fungus. Spores produced in the whitish mold on the surface of galls in late spring to early summer are blown and washed to leaf and flower buds where they cause new infections. Galls form the following spring. Cool, wet weather favors dispersal of the spores.

The disease is easily controlled by hand picking the galls or pruning them off and removing the debris from the garden. Fungicide control is generally not warranted. Since you've already pruned off the problems, your azaleas should be fine next spring. If you see more developing, prune them off.

Best wishes with your azaleas!

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