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Azalea leaf & flower gall

Azalea gall is caused by a fungus

By: Sandy Feather 2009
Penn State Extension


Q. I have a lovely white azalea that has always been healthy and that flowered profusely every spring. It did not have as many flowers this spring, and I have noticed something wrong with the leaves. They appear yellow and curled; some have pale green swellings on them, but it looks white on others. Can you tell me what this is and how to get rid of it?

A. Azalea leaf and flower gall is caused by a fungus, Exobasidium vaccinii. Young leaves become swollen and fleshy, with a pale green color. These become white when they begin to form spores. Once the spores are released, the galls become hard and brown. The spores produced will not cause new infection until next spring when your azalea begins to put on new growth. New growth is more susceptible to infection than older growth that has hardened off. Wet, humid weather creates a favorable environment for this disease to develop.

White azalea
White Azalea in full blossom

 

Pruning off and destroying the galls before they turn white is one of the primary controls for this disease. Send them out with the trash or burn them, rather than attempting to compost them. This removes the spores that would overwinter on twigs and buds to cause infection the following spring. I imagine most of the galls on your azalea have already turned white; pruning the galls off may not be enough to protect it next spring. As new growth starts next spring, make repeated applications of mancozeb (Dithane) to protect it. Applications can cease once the leaves have reached their full size. Be sure to read and follow label directions as to application rate and intervals between applications.


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