Invasive pest Elm zigzag sawfly found in Massachusetts

BECKET, Mass. (WWLP) – An invasive insect that damages elm trees has been found in Massachusetts for the first time.

The Department of Conservation and Recreation (DCR) reports that the elm zigzag sawfly (Aproceros leucopoda) has been identified in western Massachusetts.

DCR Forest Health staff investigated defoliated elm trees in Becket and determined the damage was caused by elm zigzag sawfly. Since the original detection, more have been found in Berkshire and Hampden Counties. Foresters haven’t determined how the species was introduced into the state and are working to identify how widespread the infestation may be.

The elm zigzag sawfly is native to Asia and was first reported in North America in July 2020 in Sainte-Martine, Quebec, Canada. Since then, it has been confirmed in seven U.S. states: Virginia, Pennsylvania, New York, Massachusetts, North Carolina, Maryland, and Vermont.

The larvae are small, pale green, and caterpillar-like insects that feed upon elm trees (Ulmus spp.) and can be identified by a zig-zag pattern damage. Once mature, they will spin a net-like cocoon on the elm leaves to pupate, eventually emerging as a winged adult sawfly.  

Residents should report elm zigzag sawfly activity to the DCR Forest Health Program and contact a certified arborist to discuss treatment options for their elm trees. To learn more about elm zigzag sawfly and other forest health threats visit the Massachusetts DCR Forest Health Program (arcgis.com).