PittsburghIt’s a cool, drizzly Sunday morning in fall 2022, but that hasn’t stopped more than 66,000 fans from showing up to see the Steelers take on the New York Jets. At the stadium entrance, the smell of charcoal briquettes fill the air, while portable speakers blast music from innumerable tailgate parties.
Nearly everyone is wearing black and gold to support the home team—even the entomologist currently scraping putty-like egg masses off a maple tree on a street just outside the stadium.
“Ma’am, that bag is not going to be allowed to go in,” barks a blue-jacketed security official.
Inside the turquoise backpack in question, Duennes has a dozen vials of ethanol, each brimming with euthanized spotted lanternflies captured along her walk to the stadium. As she plucks another handful of bumblebee-size bugs off a branch, Duennes explains that she’s harvesting lanternflies from around the region, including New Jersey and eastern Pennsylvania, to analyze their genetics and determine how they are moving across the United States. Ultimately, each specimen will be entered into the Spotted Lanternfly Invasion Archive.
Native to China, this striking, black-and-red planthopper showed up in the U.S. for the first time in 2014, perhaps stowed away on an international shipment of decorative stone bound for Berks County in eastern Pennsylvania. The species has also been found in South Korea and Japan. (Read how invasive species are taking hold in U.S. national parks.)
Over the last nine years, spotted lanternflies, which use their straw-like mouthparts to slurp the juices out of trees, have colonized 51 counties within the Keystone State and established satellite populations in 14 other states, from Connecticut and North Carolina as far west as Indiana. They’ve also invaded the public consciousness. In 2020, a spotted lanternfly crawled across President Joe Biden’s shoulder at a campaign stop in Wilmington, Delaware. And in October 2022, the species made a guest appearance on Saturday Night Live.
As the insect spreads, it has the potential to wreak havoc on crops and other agriculture, feeding on over 70 different kinds of plants and trees in the U.S. alone. They have a taste for certain species, namely tree of heaven—also an invasive species from Asia—as well as native species, such as black walnut, several species of maple, hops, and grapevines.
While lanternflies do not appear to kill most trees outright, as was initially feared, large aggregations can affect plant health—which is especially concerning to the wine and beer industries. Worst of all, the spotted lanternfly is a skilled hitchhiker, able to cling to surfaces that travel at high speed, such as cars and trains. An egg clutch, which contains between 30 to 50 eggs, can survive months of extreme weather and cold on a variety of surfaces, such as tree bark or the side of a shipping container.
“Just look at these abdomens. They’re super swollen!” says Duennes, holding up a female lanternfly with her outer wings splayed to reveal the vibrant red markings underneath. “They’ve got to be just full of eggs.”
As spectators chant and funnel into the tree-lined stadium, the day starts to warm, which is when spotted lanternflies can be found rising into the air on thermals. Nearby sit tens of thousands of cars with license plates from as far away as Florida, Tennessee, Colorado, and California—all places where lanternflies have not yet taken hold.
Yet if even one egg mass gets laid on a car destined for a faraway state, it could kickstart an entirely new wave of spotted lanternfly invasion, perhaps this time in Napa Valley or the Finger Lakes, where wineries are already on high alert for the vine-sucking insects. The chances are small, but the stakes are enormous.
Fortunately, Duennes is just one of many scientists looking for ways to fight back against this new, prolific invader. To see where things stand, I had to go back to where it all began.
It's a trap!
If the lanternfly invasion were an earthquake, Berks County would be its epicenter. Just short of a two-hour drive from Philadelphia, the people who live here have already seen the worst of it.
“When you see the sky filled with them, it’s like a biblical plague,” says Brian Walsh, a Penn State Extension educator, as he pulls off strips of sticky tape from a stand of tree of heaven near the Bernville Sewage Treatment Plant. (Learn more about the impacts of invasive species.)
Every weekday, Walsh travels across southeastern Pennsylvania to set an ever-evolving array of traps for the spotted lanternfly, experimenting to see which kind are most effective against the insect while also least damaging to native species.
Because lanternflies are drawn to tall objects, where the wind can carry them more easily, the insects climb up everything from tree trunks to telephone poles to skyscrapers—making them highly vulnerable to sticky traps.
“When it comes to the nymphs, just on these 27 to 29 trees here, it’s not uncommon to see over 10,000 caught each week,” says Walsh, who has sandy-brown dreadlocks and a bushy beard.
At a gated agricultural plot on the Penn State Berks Campus, pollinators hum to and fro through rolling fields of aster and goldenrod. But at the foot of a line of telephone poles rising out of the flowers, there is death.
“We call this ‘split wings,’” says Walsh, picking up a spotted lanternfly with its wings spread wide. It’s twitching slightly and clearly immobilized—a result of the way the pesticides being tested here interact with the insect’s nerves.
When injected directly into a tree, he says, the pesticide sometimes moves through the trunk so quickly that you can watch the lanternflies’ wings pop open in real time as the poison travels between plant and insect.
Each telephone pole is capped with a sort of basket wrapped in netting, which contains alpha-cypermethrin, a controlled insecticide that the U.S. government has approved for use on some crops.
In an open area like this field, lanternflies fly to the poles, smash into them, and then climb up to the top. The baskets prevent the bugs from doing so, while the netting exposes them to the poison as they climb. Below, an inverted skirt catches the corpses as they tumble back to earth, where Walsh collects them.
To measure the current configuration’s efficacy, Walsh has dusted wild-caught lanternflies in fluorescent-yellow powder and released them at the base of the poles. Next, he’ll count how many wind up in the baskets over the next few days.
One treatment that used just eight poles and a different insecticide known as deltamethrin killed and captured about 14,000 spotted lanternflies in just a few months, Walsh says. Unfortunately, that insecticide-laced netting, which is also used to control malaria-carrying mosquitoes, is no longer available in the United States. Though pole traps are unlikely to be a magic bullet that wipes out the lanternflies, they may be an effective way to monitor current populations or detect new invasions.
As Walsh packs up his truck to move on to the next site, a soft drizzle glistens in the sunshine streaming through the branches. But it’s not precipitation. It’s honeydew, a sweet substance excreted out of the lanternflies’ anuses as they feed in the canopy above.
Lanternflies are passive feeders, Walsh explains. So when the sun hits the forest canopy, it causes the trees to begin releasing moisture. This makes the sap start to flow, allowing the insects to gorge upon the trees’ nutrient-rich juices and causing them to expel waste products as they fill up.
Where the bugs are thick, lanternfly honeydew can kill the forest’s understory by blanketing it in stickiness, which encourages the growth of sooty mold. Indirectly, sooty mold can damage crops and reduce farmer’s yields, too. It also gives the appearance of scorched earth.
“It looks like you’re in a forest fire with no fire,” says Walsh.
While the mechanics of a spotted lanternfly’s feeding behavior may seem granular, every little kernel of knowledge gleaned during such experiments brings scientists closer to gaining an advantage over the interloper.
For instance, there’s a whole class of insecticides that target the muscles in a sucking insect’s mouthparts, but because spotted lanternflies let the internal pressure of the tree’s circulation do most of the work, such chemicals are mostly useless on them.
As for the insect discharge raining down from above, Walsh says, “You just get used to being sticky.”
Know thy enemy
For instance, lanternflies have an unusual habit of radiating heat while they’re sitting still.
“You can image them with an infrared camera, which means they’re giving off heat,” says Hoover, who is also a professor in Penn State’s entomology department. “That’s not true for most insects.” (Read why many insect species are plummeting.)
Why does this matter? “They’re burning quite a bit of calories in a given amount of time, which explains why they feed so heavily,” she says.
So far, it’s unclear why the animals need so many more nutrients than similar-size insects, but it may be connected to their requirements for reaching full reproductive capacity, says Hoover.
Here’s another puzzle: Out of 12,000-some known species in the planthopper family, Fulgoromorpha, the spotted lanternfly seems to be the only one to turn into an adult after the fourth molt, or what scientists call an instar. All the other planthoppers wait until their fifth instar before transforming. (Learn how metamorphosis works.)
“Evolutionarily, this seems odd,” says Urban in an email. “Why emerge as an adult in July and not mate and lay eggs until September through November?” After all, every day spent as an adult means a greater risk of getting eaten, contracting a disease, or getting stomped by a Pittsburgh Steeler’s fan.
Whatever the case, the scientists suspect that additional time as a winged adult also aids lanternflies’ ability to inhabit new lands. Right now, they estimate the insects’ range can expand by seven to 10 miles each year—and that’s not counting cases where they hop a train.
Frustratingly, lanternflies can also walk far distances. In one study, Hoover dusted nymphs of each life stage with fluorescent powder and then released them into a forest. She and her colleagues then walked transect lines with ultraviolet flashlights that make the powder glow.
“We learned that they keep moving until they find what they’re looking for—an adequate food source.”
In fact, one night, the team discovered a few third instars, which have no wings and are less than an inch long, had crawled almost 215 feet away from where they’d been released.
“Yeah, we didn’t expect them to move that far,” says Hoover.
Within the neatly arranged suburbs of Blandon, Pennsylvania, a grove of young silver maples looks like they’ve dressed up as ghosts for Halloween. But it’s what’s inside the shrouds that’s spooky—rows and rows of lanternflies, huddled together and sipping silently.
Lizz Wagner unzippers the netting that covers a tree from crown to trunk and pokes her head inside. With incredible speed, she counts 78 adult spotted lanternflies, noting it on her clipboard.
“So it looks like we’re down by two,” she says before extracting two dead bugs from the bottom of the netting. Wagner then snatches two new adults off a nearby tree, places them inside the study area, and zips it all back up.
As a technician in Hoover’s lab group, it’s Wagner’s job to check each tree daily to make sure the proper number of insects are inside. As part of an ongoing experiment, one lot of maples will host 80 lanternflies, another gets just 20, and a third control group receives zero.
The netting serves two purposes: To keep the legions of lanternflies nearby from swarming the experiment, and to keep native predators out. After three weeks, the team will take stock of the trees’ health, as well as to look for signs of chemical resistance to the insects’ feeding.
The results show that, so far, the spotted lanternfly has not led to the widescale demise of native trees, including fruit producers such as apple and peach trees. But that doesn’t mean the newcomer is benevolent, either.
After two years of feeding, lanternflies affect tree health by reducing the plant’s ability to photosynthesize and store starch in its roots, says Hoover, who published the findings in the journal Environmental Entomology in 2023. Likewise, tree diameter growth was cut in half when compared with trees protected from the invasive suckers. The good news? Those same trees recovered when the threat was removed.
“Grapes are another matter,” she says. “Lanternflies are very fond of cultivated grape and wild grape.”
By sapping the plant of nutrients, lanternflies can actually kill the vines. But even vines that survive are affected, sometimes producing as little as 10 percent of their normal grape yields in the following year, according to research published in 2022 by Hoover’s colleague, Michela Centinari of Penn State’s Department of Plant Science.
Unfortunately, grapevines aren’t the only alcoholic beverage ingredient on tap for these sap-suckers: Spotted lanternflies also appear to have a penchant for hops, a primary ingredient for making beer.
An invader becomes prey
So far, she’s received more than a thousand pictures and videos of backyard beasties chowing down on lanternflies, such as garter snakes, goldfish, rabbits, and bats. Birds, such as blue jays, cardinals, and chickens; as well as arthropods, such as praying mantises, spiders, yellowjackets, and ants, are the most common predators.
“One person reported that their toddler ate one,” says Johnson, who recently published her findings in the Bulletin of Entomological Research. “Apparently the toddler also spat it out and said it tasted yucky.”
Not so surprising, given that Johnson has also found evidence that spotted lanternflies can sequester foul-tasting compounds called quassinoids from tree of heaven, with which they evolved. She also believes these compounds are linked to the bright red under-wings, which may act as a warning signal to predators.
“Arthropods don’t seem to care though,” she says. “I think they don’t taste them the same way we do.” (Here’s how predators get past the trickiest of defenses.)
By collecting such data, Hoover hopes to determine how much we can rely on native predators to help stop the insects’ expansion.
Meanwhile, scientists are also encouraging the public to kill lanternflies on sight, from egg masses and nymphs to adults.
The enemy of my enemy is my friend
Of course, lanternflies have natural enemies where they come from, too.
In Massachusetts, scientists with the U.S. Department of Agriculture’s Animal and Plant Health Inspection Service (APHIS) are studying the possibility of releasing two species of parasitic wasps known to attack spotted lanternflies in their native range.
One wasp, known as Anastatus orientalis, is about the size of a sesame seed and proven to attack lanternfly eggs. The other, Dryinus sinicus, “hunts down the [spotted lanternfly] nymphs, grabs them and either feeds on them or parasitizes them,” Juli Gould, a laboratory entomologist for APHIS who specializes in forest pests, says in an email.
Walsh and colleagues are also experimenting with using helicopters to treat tree canopies with a naturally occurring fungi, called Beauveria bassiana, which causes a deadly disease in certain insects, including spotted lanternflies.
Yet with such a significant invasion underway, scientists are also exploring the use of systemic pesticides, such as neonicotinoids. Walsh practically winces as he pronounces the word.
Neonicotinoids have garnered a bad reputation in recent years for negatively affecting pollinators, birds, and even mammals. However, the preliminary results from their research suggests that when such substances are used diligently, and with proper regard to timing of when the trees flower, neonicotinoids can be very effective at knocking down lanternflies without damaging native pollinators.
“I’m by no means a spray-everything kind of person,” says Walsh. “It’s more about using the tool the correct way. You wouldn’t go out and throw rat poison around a daycare center because of a rat. You have to be careful about how you use it.”
An uneasy equilibrium
In the end, it will probably require a whole toolbox of control measures to curb the spread of the spotted lanternfly throughout the U.S.
As Berks County nears its 10-year anniversary of the insect’s arrival, an uneasy equilibrium seems to have set in. The bugs are still so plentiful, the trained eye can spot them clinging to the trunks of tree of heaven while driving on the turnpike. But at the same time, the swarms aren’t nearly as intense.
“It looks like as we normalize a bit with this, it’s not going to be as crazy as that first wave,” says Walsh. “At my house, we have very few now, where we had thousands and thousands before.”
Every effort should still be made to stop the infestation from spreading to new regions, of course. Hoover and Urban recently hosted scientists from New Zealand’s Institute for Plant and Food Research in the hopes that what we’ve learned so far can benefit other countries where the lanternflies have not yet landed.
But as for total eradication, well, the experts seem to agree that that ship has sailed—probably with a few dozen egg masses hidden on the side of its hull.
“The best we can hope for,” says Hoover, “is that we can keep it at levels that are tolerable.”