Expert issues stark warning about dangerous invasive pest found across the US: 'Rapidly spreading'

Invasive species are a major problem in the U.S. Non-native fish or insects can have a devastating effect on local ecosystems and agriculture. 

One example is the elm zigzag sawfly, which has now spread to 14 states and four Canadian provinces after just six years on the continent.

What's happening?

According to Entomology Today, research on the elm zigzag sawfly documented the growing threat to trees in the U.S., calling it "a rapidly spreading invasive defoliator." 

Not only does this insect larva feed on and damage elm trees, but it has now found a new early food source: Japanese zelkova, which gets its leaves earlier in the season.

As lead author Kelly Oten told the publication, "Like most invasive species, the elm zigzag sawfly probably isn't [spreading] on its own. While adult sawflies are estimated to spread 28 to 56 miles (45 to 90 kilometers) a year on their own, human activity likely speeds things along."

The study, published in the Journal of Integrated Pest Management, documented this insect being attached to vehicles and wood products that could be transported long distances. 

It also noted that the bug winters underground and could be carried in gardening soil and potted plants as these products are transported for sale.

Why is this invasive insect concerning?

Invasive species can be extremely destructive. As Oten noted, the larva of this sawfly munches a zigzag pattern into tree leaves. Get too many larvae in one tree, and they can eat up all the leaves, causing branches to die back and weakening the tree as they feed on it over multiple years. 

She also pointed out that the bug's new food source, the zelkova, is an extremely popular tree for public landscaping in cities across the country. As this bug spreads, it could take out many green spaces in urban areas, reducing tree coverage and increasing the heat island effect.

What's being done about the elm zigzag sawfly?

Oten encouraged readers to keep an eye out for that zigzag pattern in the leaves of susceptible trees. If you spot it, report it to the local extension office or state forestry agency. They can help track the spread of this invasive species and potentially take measures to exterminate it.

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