What causes leaf gall on azaleas?

Leaf gall on azaleas is primarily caused by a type of gall-forming insect, such as the azalea leaf gall midge (Asphondylia spp.). These insects lay eggs in the leaves, and as the larvae develop, they stimulate abnormal growth, resulting in swollen, distorted leaf structures known as galls. Environmental stressors, such as excessive moisture or nutrient imbalances, can also contribute to the occurrence of galls. While galls can be unsightly, they typically do not harm the overall health of the azalea.