The Elm zigzag sawfly (Aproceros leucopoda) is an invasive insect native to Asia, specifically parts of China and Japan. Its common name comes from the zigzag feeding pattern of its larvae. Elm zigzag sawflies feed exclusively on elm trees; elms in a variety of habitats, including arboretums, botanical gardens, roadside trees, urban plantings, and natural woodlands are threatened by the elm zigzag sawfly (2)(3)(4).

Elm zigzag sawfly larvae are light green with a black band on their head with T-shaped markings above the second and third pair of true legs. Adults are black with yellowish-white colored legs and smoky-brown colored wings. Cocoons are loosely-spun and net-like; they can be found attached to leaves or other objects like fence posts(2)(3)(4).

Above photos were taken from the NC State Extension Publications


Elm zigzag sawfly was first reported in North America in July of 2020 in Sainte-Martine Quebec. The NYS DEC’s Division of Lands and Forest staff began surveying for the pest along the Canadian- U.S. border in 2021. The pathway of introduction to North America, as well as the amount of time it has been present, is currently unknown (1).

In August of 2022, the elm zigzag sawfly was confirmed for the first time in New York State. Three dead A. leucopoda Takeuchi (Argidae) were collected and confirmed present at Wildland in Brasher Falls in St. Lawrence County. Feeding patterns, characteristic of the elm zigzag sawfly, have also been reported at three locations in St. Lawrence County, the Brasher State Forest, Wilson Hill WMA, and the St. Lawrence State Park. At this time, sawfly populations appear to be at low levels and causing only minor damage. Confirmations were made possible through the survey and diagnostic efforts of the New York State Department of Environmental Conservation Forest Health Diagnostic Lab and USDA APHIS. Continued surveys through these organizations and partners will continue throughout the fall to determine the extent of the sawfly’s presence and impact on the region (1).


Young larvae of the elm zigzag sawfly feed on elm leaves in a distinctive zigzag pattern-hence their name, while older larvae feed more broadly on leaf tissue leaving behind only leaf veins. Although the sawfly has not yet been shown to cause tree mortality, the feeding of the larvae can cause significant defoliation, branch dieback, and crown thinning on infested elm trees. Competition between native sawfly species and native elm foilage-feeding species may become a concern. Infested trees are also more vulnerable to other tree pests and pathogens causing a cascading impact on forest ecology, the economy, and societal values (2)(3)(4).

Above photos were taken from the NC State Extension Publications


The elm zigzag sawfly reproduces parthenogenetically, meaning females reproduce without mating. Females can lay up to 60 eggs at a time, with four to six generations a year (2).

The sawfly can be unknowingly spread through the introduction of infested nursery stock. Once introduced, the sawfly can fly up to 56 miles in a year or further when assisted by wind currents(1)


Prevention and early detection are considered to be the best control methods at this time. The NYSDEC encourages the public to report sightings of the elm zigzag sawfly through New York’s invasive species observation database, iMapInvasives.org

The interactive map below features suggested survey sites for EZZS. The sites were provided by regional DEC managers and include public hiking trails in St. Lawrence County that have elm stands and are near the sites in which EZZ-sawfly has been confirmed to be present. As there is concern about the impact EZZ-sawfly will have on urban street trees, survey sites will be expanded to include urban elm trees once we receive information from regional tree managers.

Below is a Google Map with suggested survey sites with known elm tree stands on public trails located near confirmed sightings of elm zigzag sawfly. These sites were provided by the St. Lawrence County DEC Lands Manager and are the same sites listed in the above storymap. Click on the suggested survey sites to get GPS coordinates of known elm stands. 

An informative webinar was held on Monday, October 25th with representatives from the NYS Department of Agriculture and Markets, NYS Department of Environmental Conservation, the Canada Forest Service and SLELO staff. The webinar shared an overview of the EZZ-sawfly, survey efforts in the U.S. and Canada and invited attendees to join the early detection effort and gave a tour of the map featuring suggested survey sites mentioned earlier. The webinar recording can be viewed on our YouTube channel.

To aid early detection efforts in the St. Lawrence Eastern Lake Ontario region, SLELO PRISM has developed an invasive species Volunteer Surveillance Network (VSN) with partners and community members. 

To join this effort please fill out the form below, or contact our Education/Outreach and Communications Coordinator, Megan Pistolese-Shaw at megan.pistolese@tnc.org

Prevent the introduction of invasive species into the SLELO PRISM.

Rapidly detect new and recent invaders and eliminate all individuals within a specific area.

Share resources, including funding personnel, equipment, information, and expertise.

Collect, utilize, and share information regarding surveys, infestations, control methods, monitoring, and research.

Control invasive species infestations by using best management practices, methods and techniques to include: ERADICATION (which is to eliminate all individuals and the seed bank from an area), CONTAINMENT (which is reducing the spread of established infestations from entering an uninfested area) and SUPPRESSION which is to reduce the density but not necessarily the total infested area.

Develop and implement effective restoration methods for areas that have been degraded by invasive species and where suppression or control has taken place.

Increase public awareness and understanding of invasive species.

Develop and implement innovative technologies that help us to better understand, visualize, alleviate or manage invasive species and their impacts or that serve to strengthen ecosystem function and/or processes.

Rob Williams                              rwilliams@tnc.org                     Program Director

Megan Pistolese megan.pistolese@tnc.org
Outreach and Education

Brittney Rogers brittney.rogers@tnc.org 
Aquatic Invasive Species

Robert Smith       robert.l.smith@tnc.org 
Terrestrial Invasive Species

Zachary Simek    zachary.simek@TNC.ORG     Conservation and GIS Analyst

During this time the best way to contact our team is via email.