New pest damaging elms in WNY is spreading rapidly; please help

damage on leaf by elm zigzag sawfly
The jagged trail created as the insect eats gives the elm zigzag sawfly its name. Photo courtesy Gyorgy Csoka, Hungary Forest Research Institute,

The elm zigzag sawfly (Aproceros leucopoda), an exotic insect pest, has been found this summer in Allegany County and is spreading rapidly through New York State.

The elm zigzag sawfly is an insect that eats only elm leaves and can cause severe defoliation (leaf loss) that threatens tree health.

It was first detected in August 2022 in St. Lawrence County in the northern part of New York State. This summer it has been found in Allegany, Ontario, Madison, Ulster, Schenectady, Albany, Saratoga, Warren and Clinton counties, with new counties being confirmed weekly, according to the New York State Department of Environmental Conservation (DEC).

The elm zigzag sawfly (EZS) can most easily be identified by its unique zigzag feeding pattern. Learn more about EZS and how to identify it.

What can you do to help?

Keep an eye out and report sightings to iMap Invasives. Because this pest is being detected in new counties weekly, reports are incredibly valuable right now to help the DEC understand the full range of this pest.

How is EZS impacting our forests?

As a newly introduced species, the impact of EZS on our forests is not yet clear. Most reported defoliation has been minor, with only 2–5 percent of leaves showing damage. However, one resident in Niskayuna in Schenectady County reported several Siberian elms in their yard that were severely defoliated. Potentially, urban forests could endure the worst of EZS damage, as various elm cultivars are widely planted in ornamental landscapes. Open-grown elms with large canopies provide abundant foliage to support multiple generations of EZS within a growing season.

What is DEC doing about elm zigzag sawfly?

The DEC has partnered with the SUNY College of Environmental Science and Forestry to conduct research on the phenology, damage severity, and associated insect community of EZS. This research will help the DEC better understand how EZS interacts with our environment and what, if any, natural controls might be present. The DEC also participates with a working group of practitioners and researchers from all states with EZS present in order to stay up to date on current research and best management practices.

Learn more about the elm zigzag sawfly here on the St. Lawrence Lake Ontario for Regional Invasive Species Management website.

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