The green “worms” are the larvae of the azalea sawfly. The larvae are green, smooth, and up to one inch long. They feed along the edges of the azalea leaves. After feeding, oftentimes only the midvein of the leaf and leaf petiole remain. The larvae of the azalea sawfly are typically present in May in Iowa. There is one generation per year.
Small numbers of azalea sawflies can be controlled by handpicking. They can also be controlled with insecticides, such as Sevin (carbaryl).