The elm zigzag sawfly (Aproceros leucopoda) is an insect that only eats elm leaves and can cause severe defoliation (leaf loss) that threatens tree health.
They get their name from the easily recognizable “zigzag” feeding pattern larvae create as they chew through leaves. However, when most of the tree’s leaves have been eaten, the zigzag pattern may not always be as clear because larvae will eat all the leaf tissue down to the vein.
To learn more about the elm zigzag sawfly, visit the St. Lawrence Lake Ontario for Regional Invasive Species Management website.
Photo: Elm zigzag sawfly (by Gyorgy Csoka, Hungary Forest Research Institute, Bugwood.org).