Spotted lanternfly eggs have started hatching in the Philadelphia region, with the emergent black-and-white polka-dotted nymphs using their remarkably powerful hind legs to spring from yards to decks to lawn furniture.
When the first spotted lanternflies appeared in the United States in Berks County in 2014, Pennsylvania agricultural officials and other experts hoped they could be eradicated with an all-out effort.
But that battle has proven futile, and the invasive pests are now so numerous that they have spread into dozens of Pennsylvania counties, as well as into New Jersey, and through to Long Island. They first landed in Philadelphia in 2018 and were found in sizable numbers last year in South Jersey.
The bug is able to propel itself three or four miles by hopping or flying. It is known to hitchhike on vehicles and trains, which makes its spread almost impossible to stop.
In other words, the spotted lanternfly is here to stay, says Brian Walsh, of Penn State Extension. But, he said, the plant hoppers haven’t been as destructive to trees and plants as once feared — though they still pose significant threats to vineyards.
“Some of our fears have been allayed at this point,” Walsh said, noting that the bug has not been especially destructive to otherwise healthy ornamental trees and plants. That could be, he said, because “tree fruit growers have kept it in check with spray programs, while vineyards still face a significant challenge and are still seeing losses in production and increased costs with increased spray applications.”
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Why are spotted lanternflies bad?
The spotted lanternfly, however, has proved lethal to its favored host: Ailanthus altissima, an invasive weed tree also known as Tree of Heaven. While that might seem a good thing, Walsh said the pest just picks another favored host to feed on in a neighborhood.
The biggest threat, so far, he said, has been to vineyards as the bug gravitates to grapevines. Early on, it caused a nearly 100% loss to some grape crops in Berks County.
“It’s not been a worst-case scenario that was feared,” Walsh said. “But it’s been more difficult for grape growers. … Once the lanternflies find the vines, they just keep arriving.”
He and others say it’s too early to gauge the size of this year’s infestation.
“We have begun to get reports of hatching,” said Shannon Powers, a spokesperson with the Pennsylvania Department of Agriculture. “But there is no really good way of measuring the extent of the spread this early, since data are collected over the course of the season. Adult insects do not survive the winter, and egg masses have proven to survive consistently colder temperatures than we had this year.”
Walsh said infestations can be remarkably different from neighborhood to neighborhood.
“We still don’t have the whole life cycle figured out,” Walsh said. “It’s a very complex organism, and it moves a lot. It is capable of feeding on so many things from perennials to mature trees.”
Native to Asia, the pest feeds on plant sap and loves maples, black walnut, birch, and willow. Overall, it is known to feed on 70 types of plants and trees. That feeding can stress and damage plants.
How can you stop spotted lanternflies?
But should you still try to kill them? Walsh, who’s written an article on the topic with colleagues, said go ahead and squash them if you see them “because we don’t want them in our environment.”
Though he said a few spotted lanternflies feeding on the sap of a healthy tree are probably not a threat, adults have a bigger appetite and can feed for weeks on a tree, stressing it. The bugs excrete a partially digested sugary sap known as honeydew that allows molds to grow on trees.
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Insecticide might be a solution if they pose a threat to a prized tree. Both the spotted lanternfly nymphs and adults are easy to kill with insecticides, including less toxic ones such as soaps and oils. However, insecticides should be used with caution, as they could make things worse for beneficial insects such as bees, Walsh said. And the bugs can just hop to another tree.
“One person is not going to have an impact on the greater population,” Walsh said when considering treatment. “Eradication is off the table in our region,” he said, stressing that we don’t know all of the impacts that will play out long term.
While it’s too late now, an easy way to destroy spotted lanternflies before they hatch is by scraping their eggs off tree trunks during the winter and placing them in alcohol. In the spring, circle traps can catch the nymphs as they climb trees. They can even be sucked off with a vacuum.
Pennsylvanians can try to prevent the pest from spreading by inspecting their vehicles’ wheel wells, and anything else they are transporting before crossing into other regions, Walsh said.
In fact, the state Department of Agriculture has put 34 of 67 counties under quarantine. Eight of those counties are newly added. The state regulates the movement of anything that might spread nymph and adult spotted lanternflies such as construction waste, firewood, grapevines, pallets, recreational vehicles, tractors, mowers, grills, outdoor furniture, and even tarps. Last year, New Jersey had eight counties under quarantine.
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