Fenusa pumila
Pest description and damage The adults are a small (0.125 to 0.375 inch in length) black sawfly. Mature larvae are flattened and up to 0.5 inch long. The larvae feed between the leaf surfaces, leaving blotch-shaped or winding brown mines. Severe infestations over consecutive seasons may result in decline of trees. Vigorous gray, white, and paper birches are attacked most. In some years, infestations are heavy.
