Dogwood sawfly feeds on gray dogwood and other species of dogwood. They occur throughout the state, and we've received reports of them migrating to pupate in southern Illinois. Dogwood sawflies appear as curled larvae on the leaf uppersides. They are yellow underneath, but covered above with long, white, waxy strands, making them look like fuzzy styrofoam peanuts. High numbers will strip the foliage from the trees. This late in the season, defoliation is unlikely to harm the plant.
Once the larvae are done feeding, they migrate from the dogwoods to find a place to pupate. Migrating larvae are about one inch long and lose their white fuzz to become solid dark green or dark spotted on top and yellow underneath. They have large black heads and seven pairs of prolegs. These larvae pupate in wood, preferring rotting wood in nature. However, they will also burrow into chipboard and wood siding.
Dogwood sawfly larvae are easily controlled with many chemical insecticides while they are feeding on dogwood. Once they begin migrating, control becomes more difficult. Stepping on them may become the best method, although insecticidal soap may be effective if you hit them with it. In cases where dogwoods are close to houses, you might want to keep an eye out for this insect.