It has been the target of an “if you see it, stomp it” campaign in the eastern US for several years. But now the spotted lanternfly – an elegant but invasive insect with distinctive red wings – might be on the decline in some areas.
Harmless to humans, spotted lanternflies can damage trees and fruit crops, and feed on the sap of over 70 different species of host plants. They are now common across the north-east. In New York, red splats, from eager lanternfly stompers, are a frequent sight on sidewalks.
The population is seemingly down in some of the areas where they’ve been established the longest, like south-eastern Pennsylvania. They were first reported there in 2014.
“We think this is the result of exhausting the food supply,” said Kelli Hoover, professor of entomology at Pennsylvania State University. The lanternfly’s food of choice is tree of heaven, a plant that is also invasive.
It has a higher concentration of sugars in its roots compared with trees like red maples, river birches and willows, making it attractive to the insect. “It’s where they get all their energy,” Hoover said. The state is currently on a mission to eradicate the tree.
While lanternfly sightings and surveys in Pennsylvania tallied roughly 9,000 insects in 2017, soaring to 150,000 in 2019, there has been a drastic drop in recent years. Some 61,000 were found in 2021, the latest year for which state data is available.
Scientists are split on the significance of these findings.
Perhaps there is truly a decline, or perhaps the lower numbers simply mean that “folks are tired of letting us know about it”, said Jay Losiewicz, deputy communications director of the Pennsylvania department of agriculture.
“There is really no consensus,” says Julie Urban, professor of entomology at Pennsylvania State University. “There’s evidence that in some areas where it was heavy originally and close to the site of the original introduction, it seems that population there is lower.”
But, she added, “they really move around a lot”. And “as their host plants get depleted, they literally move on to greener pastures”.
Efforts to eliminate host trees in Pennsylvania could be prompting the pest’s spread to other areas where it can find that food supply.
“Without the tree of heaven, the spotted lanternflies are potentially moving further, and dispersing to new areas looking for resources that are out there,” said Matthew Travis, the spotted lanternfly national policy manager for the US Department of Agriculture.
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The invasive pest has spread across at least a dozen states on the east coast and the midwest, including New Jersey, Connecticut, Maryland, Virginia, Indiana and Ohio. Although not the most adept of flying insects, the spotted lanternfly is an excellent hitchhiker and can find its way into machines that humans travel in, like trains, cars, trucks and planes.
Scientists in New Jersey have also noticed lower numbers in 2023.
Experts agree that just because the places that used to be thronged with spotted lanternflies are seemingly having an off-year, it doesn’t mean that they’ve left for good. As plants recover, so could lanternfly populations.
States are also using insecticides in targeted areas to attempt to control the bug. Stomping is still worthwhile, experts said, not least because it can prevent females from reproducing.
“It’s good to do that because every single one of them can lay 30 to 60 eggs,” said Cecilia Sequeira, a spokesperson for the US Department of Agriculture. “And every time you stomp one out that’s one more that isn’t reproducing. Every little bit helps; it is a very prolific pest and we’re probably their biggest natural enemies. It’s pretty important that people do their part.”
Female spotted lanternflies typically start to lay their eggs in late August through November, or until the first frost. While the adults freeze to death in the winter, their egg masses can survive. Spotted lanternflies can lay their eggs on a variety of surfaces, including tree trunks, telephone poles, rocks and the undercarriage of vehicles. They resemble a smudge of clay.
“That’s 50 insects that could be wiped out simply by taking a credit card out of your wallet, scraping that egg mass off and squashing it,” said Travis.