Jeffrey Hahn, Asst. Extension Entomologist
Adults are active any time from late May through July. After the larvae first hatch, they are covered in a whitish material which some entomologists believe helps the sawflies resemble bird droppings, protecting them from predation. The young larvae skeletonize leaves, i.e. feed between the veins. Older larvae consume the entire leaf except for the midrib. As mature larvae, dogwood sawflies are about one inch long. Also, the whitish material comes off, revealing their greenish - yellowish, conspicuously spotted bodies.When they are done feeding, they wander off looking for places to pupate, preferring rotted wood. Dogwood sawflies have also been known to bore into homes to pupate. They remain as pupae through the winter and in the following spring There is one generation of dogwood sawflies each year.
If you find your shrubs are being defoliated now, there is not a lot that you can do as dogwood sawfly feeding is either done or is nearly finished. However, if you did have a problem with them this year, watch for them next year starting in June and treat if they are abundant. There are a variety insecticides than can be used if you catch them while they are small, including insecticidal soap, spinosad, horticultural oil, permethrin, bifenthrin, and other pyrethroids. Safari (dinotefuran) and imidacloprid, both systemics, are also effective but need some time to be taken up by the shrubs.