LANSING, Mich. - The Michigan Department of Agriculture and Rural Development (MDARD) has confirmed the state's first detection of elm zigzag sawfly (Aproceros leucopoda) in St. Clair County. The invasive insect was identified by the U.S. Department of Agriculture's Animal and Plant Health Inspection Service (USDA APHIS) following a report submitted by an arborist through the Midwest Invasive Species Information Network (MISIN) online reporting tool.

"While this is the first detection of the invasive elm zigzag sawfly in Michigan, it's important to emphasize the insect does not pose a significant threat to Michigan's people, anmials, agriculture or natural resources," said MDARD Director Tim Boring. "The elm trees this invasive pest feeds on can typically recover from defoliation by producing new foliage. We encourage residents to be aware of this pest and report suspected sightings to help track its distribution in Michigan."

Elm zigzag sawfly feeds on the leaves of elm trees (Ulmaceae) and can defoliate several elm species. Young larvae create distinctive, meandering "zigzag" patterns starting at the leaf edges as they feed. Older larvae consume a greater amount of leaf material, creating large notches. While repeated defoliation can stress trees, healthy elms can recover from feedings and produce new leaves.

Elm zigzag sawfly is native to Asia. It was initially detected in Canada in 2020 and was first identified in the United States in Virginia in 2021. Since then, it has been reported in several eastern and midwestern states. Elm zigzag sawfly can spread quickly because adults are capable fliers and the species reproduces rapidly.

Most people are likely to encounter elm zigzag sawfly in its larval stage, when the yellow-green caterpillar-like larvae feed actively on elm leaves. These larvae grow to about 10-11 millimeters long and can be recognized by a brown band on the head and dark T-shaped markings on the hind legs.

Adult sawflies are less commonly noticed; they are small, about 7-8 millimeters long with shiny black bodies, smoky wings, pale yellow to whitish legs and distinctive three-segmented antennae, with the final segment much longer than the first two.

MDARD encourages the public to help track the spread of elm zigzag sawfly in Michigan. Suspected infestations can be reported by using the Midwest Invasive Species Information Network (MISIN) online reporting tool or downloading the MISIN smartphone app and reporting from your phone. Be prepared to report the location of infested trees and to take one or two pictures of infested branches to help confirm identification.

Members of the public can also help prevent the spread of invasive species by inspecting vehicles, outdoor equipment and recreational gear after traveling; by removing plant debris and soil from vehicles and outdoor equipment; and by not moving firewood and other potentially infested materials.

For more information on elm zigzag sawfly, see the USDA pest alert. To learn about other invasive species in Michigan, and to find out what you can do to help prevent their spread, visit Michigan.gov/Invasives.

Photo of adult elm zigzag sawfly on leaf. Photo credit: Gyorgy Scosa Hungary, Forest Research Institute, Bugwood.org

Elm zigzag sawfly larva feeding on leaf. Photo credit: Gyorgy Scosa Hungary, Forest Research Institute, Bugwood.org

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