There are three sawfly species that commonly attack azaleas, two in the spring and one in the summer. We are apparently currently seeing Amauronematus azaleae. There is one generation per year with the adults emerging to lay eggs on expanding leaves in the spring. The larvae are feeding at this time in central Illinois and apparently prefer hybrid azaleas, which are deciduous. Nearby evergreen azaleas are not attacked.
The larvae are green with tan heads, blending in very well with the expanding foliage of the host plant. They are about three-fourths inch long when full grown. They feed on the leaf margins down to the mid-vein, defoliating the plants if not controlled. When fully grown, they drop to the soil to pupate.
Handpicking can be effective on these shrubby azaleas, but the larvae are difficult to see. An application of spinosad (Conserve) or labeled pyrethroid provides effective control.
Photo Credit Phil Nixon