Jeffrey Hahn, Asst. Extension Entomologist
There have been reports of sawflies defoliating azaleas recently. The larvae hatch during May and are active into June. They are smooth, slender and grow to about 3/4 inch long. They are light green which allows them to blend in really well with the azalea leaves, making them difficult to see.
It isn’t unusual for gardeners to overlook azalea sawflies when they first start feeding. Often the first symptom of their presence is chewed leaves or droppings on the foliage. Azalea sawflies start feeding on the edge of leaves and work their way down to the midrib. On heavily defoliated branches, all that remains is just a series of veins sticking out, resembling a skeleton.
Photo 1: Azalea sawfly. Jeff Hahn
It is important to detect azalea sawflies soon after they hatch to minimize their damage to plants. In many cases now, these sawflies are already finishing their feeding making it too late to treat them. However, if most of the sawflies you are finding are still relatively small, there are several options you can consider to manage them. If there are not many larvae present, just remove them by hand, throwing them into a bucket of soapy water to kill them. Particularly inspect partially chewed leaves or leaves next to areas where you find droppings to help find larvae.
You could also consider using an insecticide. If you wish to use a low impact product, try insecticidal soap. To be effective, you need to hit the larvae directly with the spray. Also, there isn't any residual activity so you won't kill sawflies that walk onto treated leaves later. Another effective, low impact product is spinosad. Residual garden insecticides are also available, such as bifenthrin, permethrin, and carbaryl.
Photo 2: Defoliated Azalea. Roger Moon