Answer: You're describing a fungal disease called Azalea Leaf Gall. Eventually the swollen leaves will develop a powdery white coating. These are the maturing fungal spores, so to prevent spread of the disease, prune off the affected leaves now and get them out of the garden. Prune your plants to increase air circulation and pinch or prune off any suspect leaves. Some azalea's are prone to leaf gall and others seem to resist the problem. Plants under stress are more susceptible to disease problems. Once you've pruned to provide air circulation your azalea will regain its health and become more resistant to fungal diseases.
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