Elm Zigzag Sawfly

Pest Alert: Elm Zigzag Sawfly Confirmed for the First Time in MassachusettsThis non-native insect has been detected in a small, forested area of Berkshire and Hampden Counties.

        The elm zigzag sawfly (Aproceros leucopoda) is a non-native insect that originated in eastern Asia (Japan and certain regions of China), and is now invasive in Europe (2003) and North America. The elm zigzag sawfly has been found in Virginia (2021), Maryland, Pennsylvania, North Carolina, New York, and Vermont. In 2023, the elm zigzag sawfly has been detected in a small, forested area of Berkshire and Hampden Counties in Massachusetts: https://www.mass.gov/news/dcr-announces-that-elm-zigzag-sawfly-has-been-confirmed-in-massachusetts. Significant defoliation of elm host plants was seen at the impacted locations. It is currently unclear how widespread the elm zigzag sawfly is in Massachusetts or how the infestation was introduced. Female elm zigzag sawflies cause a tiny amount of damage to the edges of host plant leaves as they lay their eggs. Tiny scars are formed as a result of female egg laying. Eggs hatch and young sawfly caterpillars (the most destructive life stage of the insect) begin their characteristic zig-zag patterned feeding. These zig-zag shaped notches in the leaf can extend 5-10 mm into the leaf from the edge. Multiple caterpillars can feed on a single leaf and entire leaves can be completely stripped, leaving only veins behind. Heavily infested trees can suffer partial or complete defoliation.

        If you suspect you have found elm zigzag sawfly in Massachusetts, please report it to Nicole Keleher (MA Dept. of Conservation and Recreation, Forest Health Program) at Nicole.Keleher@mass.gov, or the MA Department of Agricultural Resources at https://massnrc.org/pests/report.aspx. More images and information about the elm zigzag sawfly, including management options, is now available in this UMass Extension fact sheet.