Elm tree pest found in St. Lawrence County

Elm zigzag sawfly
Elm zigzag sawfly(Herbert A. 'Joe' Pase III, Texas A&M Forest Service, Bugwood.org)
Published: Sep. 26, 2022 at 1:10 PM EDT
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ALBANY, New York (WWNY) - An invasive species harmful to elm trees has been found in St. Lawrence County.

The state Department f Environmental Conservation says the elm zigzag sawfly has been detected at Wilson Hill Wildlife Management Area, Brasher State Forest, and Lost Nation State Forest.

It’s the first time the pest, which was first detected in southern Quebec in 2020, has been found in New York State.

The fly feeds exclusively on elm trees and can cause severe deforestation, branch dieback, and crown thinning.

Why the sawfly isn’t known to kill trees, it can add stress to those already under assault from Dutch elm disease.

The elm zigzag sawfly is native to East Asia. Once it’s in an area, it’s capable of flying up to 56 miles a year and can also be transported accidentally on infested nursery stock.

The fly can quickly establish itself in a new area, the DEC says, because each female can lay up to 60 eggs at a time and there are four to six generations a year.

The larvae make a distinctive zigzag pattern, for which the insect is named, as they feed on the leaves. At this time, the DEC says, sawfly population levels appear to be low and are causing only minor damage.

Invasive species like the elm zigzag sawfly can reported through the state’s online reporting system.

Elm zigzag sawfly
Elm zigzag sawfly(NCDA & CS)