Invasive Insect Elm Zigzag Sawfly Found for First Time in Minnesota

Residents are asked to report any suspected finds

St. Paul, MN: The elm zigzag sawfly, an invasive insect new to Minnesota, was recently discovered. The elm zigzag sawfly was reported by a citizen on iNaturalist, and later spotted on the platform by an out-of-state college student working on the insect.

Minnesota state officials were notified of the discovery, which was on the University of Minnesota Twin Cities campus. Officials collected larvae and the identification was confirmed by the Smithsonian Institute Museum of Natural History.

The elm zigzag sawfly is an invasive insect that feeds on the leaves of elm trees. The young larvae create a distinctive zigzag pattern through the elm leaves while feeding. The larvae are green with a black band on their head. They have T-shaped brown or black markings on the top of their second and third pair of legs.

The easiest way to identify elm zigzag sawfly is by the distinct zigzag pattern that the larvae create in elm leaves while feeding. Photo by Nathan W. Siegert United States Forest Service.

Download photo here

Native to East Asia, elm zigzag sawfly was first confirmed in the United States in 2021. It has been confirmed in several eastern states and now Minnesota. The potential impacts of the elm zigzag sawfly are unknown because of the short period of time it has been present in the United States. Although the insect causes defoliation of elm trees, most defoliated trees can recover from a defoliation event.

Best management practices are also unknown. However, since most trees can recover, management may not be necessary. Currently, there is research being done at North Carolina State on insecticide applications.

More information on the elm zigzag sawfly is available on the North Carolina State website.

Since the elm zigzag sawfly is newly discovered in Minnesota, the Minnesota Department of Agriculture (MDA) would like to better understand where this insect may be in the state. Residents can report suspected sightings of the insect to the MDA’s Report a Pest line or call 1-888-545-6684. Please include clear photos when submitting a report online.

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