Portland panel warns of threat from new invasive insect

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A Portland committee tasked with pesticide management is warning of a new invasive insect potentially making its way to Maine.

Jesse O’Brien, a soil and crop management expert and member of the city’s Pesticide Management Advisory Committee, said in an April 6 meeting that the potential threat is from the spotted lanternfly, a relatively new insect in the United States. Although its origin is in China, Taiwan, and Vietnam, the plant-hopping insect was first discovered in this country in Pennsylvania in 2014.

The adult spotted lanternfly. (Courtesy PennState Extension/Dalton Ludwick)

Since then, it has been classified as an invasive species in parts of Delaware, Maryland, Pennsylvania, New Jersey, New York, Virginia, and Ohio.

“It will be important on all of us to make sure we see these insects and spot these insects so they don’t become a problem,” O’Brien said.

The insect, which grows to about an inch long, attacks crops like grapes around harvest time. Their presence also leads to a mold on trees where they nest, which weakens the trees.

The Pennsylvania State University Extension has classified the insect as a “serious invasive pest with a healthy appetite.” It said the pest feeds on plant sap of many different species, including grapevines, maples, black walnut, birch, willow, and others. The university group estimated the insect would potentially drain the Pennsylvania economy of at least $324 million, given its preference for economically important plants.

O’Brien said the spotted lanternfly is coming dangerously close to Maine. He said there’s no rhyme or reason to where they lay their eggs: they will breed on several different kinds of trees, and even objects like park benches. And the eggs are difficult to spot because they often blend in with their surroundings.

He also said there have been imported trees in towns including Yarmouth and Freeport that contained egg masses, but they were caught in time.

A particular tree that O’Brien said is a well-known host for the spotted lanternfly is the tree of heaven, which itself is an invasive plant species in the area. O’Brien called it “invasive beyond invasive.”

“Even before invasive plants became important to us,” he said, “this was considered invasive.”

Jeff Tarling, the city’s arborist, said he doesn’t believe there are any trees of heaven in Portland, although they look like many other native trees and are often misidentified. He also said the spotted lanternfly will feed on many other local trees.

“There’s no question there is a food source here,” Tarling said.

Like many non-native insects, he said, there aren’t many natural predators for the pest. He said there is a track record of invasive pests finding their way to Maine, noting the browntail moth as an example.

“It’s definitely a concern,” Tarling said. “These things can spread different ways. People may be in an infested area and come to Maine to go camping, and (the insects) fall off a vehicle or a camper.”

As for the browntail moth, Tarling said the city is beginning to target nests, particularly in Deering Oaks Park. Pesticide spraying in the park is planned for mid-May, which will require the park to be closed for about six weeks.