What Does a Zigzag Pattern Chewed Out of a Leaf in New York Mean?

The term Invasive Species is never one you want to hear. Even the most harmless invasive species can be a problem and obviously being named "invasive" tells us right from the start that it is not great that whatever it is has arrived where it's not wanted.

Wanted may not be the correct term to define an invasive species, which by the way can be a plant, an animal, or any other living organism right down to the tiniest microbe. Sadly with the way we travel, it is hard to keep invasive species from traveling from place to place with us.

What Made a Zigzag Pattern on a Leave in New York State

NYS Department of Environmental Conservation - ZigZag Fly

To explain why it is so hard to prevent the infiltration of invasive species we should probably define what one is, Invasive Species are defined by the USDA as a "non-native (or alien) to the ecosystem under consideration and whose introduction causes or is likely to cause economic or environmental harm or harm to human health.

See Also: Invasive Plant That Can Burn You

So in short it is a plant animal or other living organism that has taken root where it doesn't belong. The latest invasive species in New York is affectionately known by the name Zigzag Sawfly. According to a source I found online the Elm zigzag sawfly was first reported in North America in July 2020. By August of 2022, the zigzag sawfly was confirmed to be alive and well in NY.

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Like any other insect they can be hard to spot but what you can spot easily is the zigzag pattern they leave on Elm tree leaves. If you notice that an elm tree has leaves that appear to have been eaten in a zigzag fashion the NYS DEC would like you to report any sighting.

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.

Have You Seen Any of These Invasive Species in New York State?

5 of New York's Most Devastating Invasive Species

Here are 5 species that have invaded New York State and in some cases they must be killed. We are talking about fish that walk on land, plants that cause severe burns and insects that could wipe out a variety of crops that we rely on.

Keep an eye out for these species and you hike, work around the yard or do some fishing this year. Should you locate any of these it is important to report where and when you found them to the New York State DEC.

Gallery Credit: Karolyi