It is found throughout the United States and has two generations per year in NC. The birch sawfly has only one generation per year. A sawfly is a primitive wasp-like insect. As its name suggests, the dusky birch sawfly feeds primarily on birch trees, most commonly river birch in North Carolina landscapes. Right now they are in the larval stage of their second generation. This species has at times caused serious defoliation of birch in Nova Scotia and in British Columbia. No intervention is required because the infestations are short-lived. Insecticides can control the pest or small populations can be removed by hand and destroyed. In Quebec, infestations have been very localized and sporadic. Thank you for reviewing this information. Action: The dusky birch sawfly’s primary host is River birch, but sometimes grey, black, red paper and yellow birch are also attacked. The dusky birch sawfly is an occasional pest of birch trees, particularly river birch. The river birch “caterpillars” are not caterpillars at all. Sawflies are stingless wasps whose larvae are plant feeders. They are sawfly larvae. They LOOK like caterpillars to the uneducated eye but they are not.