Azalea leaf and flower gall, caused by Exobasidium vaccinii, infects new leaf and flower buds forming swollen galls which may have a white dusting of spores in early infections, later turning brown and hard.
For more information on diagnosis, hosts, and management follow the link to the Online Guide to Plant Disease Control.
Partially galled azalea leaf
More fully formed leaf gall
Single leaf infection
More leaf infections
More pronounced galls
Healthy leaves near galled leaves
Fully formed galls
Partially galled leaves
Older gall with white sporulation