Last fall, end of summer, we noticed that our azaleas were attacked. Massive loss of leaves, like something ate them. I have moved three times with these azaleas, had them over 12 years and nothing happened to them before. They have been transplanted out of their pots, other than that, I can't think what happened to them. I love these plants and would love to bring them back.
Azaleas can be attacked by several insects and even diseases can cause flower and foliage loss.
This article will help you.
Neem oil is great treatment for most insects.