First records of elm zigzag sawfly (Hymenoptera: Argidae) in the United States

Abstract

The elm zigzag sawfly (EZS), Aproceros leucopoda Takeuchi, was detected in the United States for the first time in Virginia in 2021. In 2022, it was confirmed in 4 additional states: Pennsylvania, North Carolina, Maryland, and New York. These are the first records of this species in the United States and demonstrate a rapid range expansion of an invasive defoliating pest. Native to Asia, EZS feeds exclusively on Ulmus spp. (elms; Ulmaceae). In the United States, feeding damage ranges in severity from minor to severe. Young instars create a zigzag-shaped pattern in leaves as they feed, while older larvae feed more completely on foliage, leaving only the midvein and sometimes thick lateral veins. This more complete feeding often obscures the signature zigzag defoliation of younger instars. Long-term health impacts to host trees are unknown, though aesthetic damage, growth loss, and branch dieback occur in Europe where it is also invasive. Little is known about management options for this pest, and continued expansion of this species’ range in the United States is expected.