EZS North America Detections Map 2025

The elm zigzag sawfly (EZS) is a small (7-8 mm long), invasive, stingless wasp-like fly originally from East Asia. It was first observed in North America in 2020 in Quebec, Ontario, Canada and in the United States in 2021 in Virginia, before further observations in New York, Maryland, and North Carolina. EZS larva are green in color with a black band on their head and develop T-shaped black markings on their second and third pair of legs. EZS larvae defoliate native and nonnative elm (Ulmus) species and create a characteristic zigzag pattern between leaf veins. Large defoliation events can lead to weakened trees and predispose them to other pests and diseases, before leading to tree death if defoliation occurs several years in a row. With EZS being a relatively new pest, not much is known about the ecological and economic impacts it may have, or management techniques for this species.