It’s been a decade since the lanternfly landed in Pennsylvania. Is it as bad as we feared?

When lanternflies were first discovered in Berks County in 2014, panic set in among the country and region’s top scientists. They feared the insect would devastate Pennsylvania’s robust farming, lumber, and grape industries. A 2019 study projected the annual costs of damage could reach $324 million and result in the loss of 2,800 jobs across agricultural industries.

Researchers from Pennsylvania State University’s College of Agricultural Sciences used an economic assessment software program to estimate potential damage and said that in the worst-case scenario the damage could climb to half a billion dollars annually.

According to Brian Walsh, a Penn State lanternfly researcher, these concerns stemmed from the fact that the lanternfly had zero natural predators in the U.S., that their affinity for fruit and timber trees could jeopardize billions of dollars in economic activity, and that they could easily spread by hitching a ride on cargo and vehicles.

“I mean, look, it made it to Pennsylvania from China in one shot,” Walsh said. Lanternflies came to the U.S. attached to a stone shipment sent to a local landscaping company.

The concern was enough to turn Philly residents into a unified band of bug stompers. But did it work?

Ten years later, we have a clearer picture of what lanternflies have wrought. And so far, it’s not as bad as we feared.

“The reality is that some of those assumptions have not played out as predicted. Far and away, lanternflies are not the fire and brimstone, doom and gloom situation that they were originally feared to be,” Walsh said. “Except for grapes — it’s been worse than expected for grapes.”

That doesn’t mean there aren’t real risks — or that things could have been much worse if we hadn’t taken action, Walsh said. As scientists continue to study the pest as it spreads through the U.S., much is still unknown.

Here’s what we do know.

A major concern when lanternflies landed in Berks County was that they had no natural predators to control them. Ten years later, scientists have found that lanternflies do have predators like birds, spiders, and praying mantids, so-called “generalist” predators, that snack on a wide range of insects.

U.S. Department of Agriculture (USDA) scientists are currently studying the possibility of bringing in parasitoid wasps, native to China, that lay eggs inside lanternfly egg masses and nymphs, eventually killing the insects, Walsh said. But these observations take years because one miscalculation can lead to devastating effects to beneficial native species.

“First off, lanternflies are difficult to keep alive in the lab, they’re not easy to colonize, don’t thrive well in captivity, and must be wild-caught, which limits when you can research,” Walsh said. “Now they have to introduce the wasps to lanternflies and other native insects to see if they stay on target or go after other natives.”

Identifying and possibly introducing a predator as a natural control is part of the equation, Walsh said, but lanternfly management most likely won’t come from a single predator.

Early fears of lanternflies destroying crops weren’t unwarranted. However, research has shown that lanternflies aren’t as destructive as initially thought.

While extremely disruptive to the wine and grape industry, the spotted lanternfly is not as damaging to hardwood trees used for timber as previously thought, according to 2023 research from Penn State’s Entomology Department. This is a major win for the forest products industry, which rakes in $39 billion per year for the state.

Penn State researchers simulated lanternfly feeding habits on a variety of hardwoods, such as red and silver maple, river birch, weeping willow, and the invasive tree of heaven, to observe how the trees recover over time. In the worst-case scenario, scientists allowed lanternflies to feast on tree samplings for four consecutive years. In nature, lanternflies typically only feed for one to two years before hopping to the next target.

Tree growth was significantly reduced after lanternfly feeding, sometimes by half, which could be a fatal blow if other outside stressors harm the tree. However, even in the doomsday scenario of continuous feeding, all hardwoods recovered despite suffering damage.

“While long-term damage to trees is not fully understood, we don’t see many trees dying outright from spotted lanternfly,” Walsh said.

On the other hand, nature doesn’t afford grapes the same recovery as hardwoods. Grape growers and vineyards, which account for $1.8 billion of Pennsylvania’s yearly economic activity, are especially vulnerable because lanternfly feeding can kill grapevines entirely.

“The vineyards that were first hit where nobody knew what to do yet had such bad swarms that they actually did kill the vines,” said Carley Razzi, president of Penns Woods Winery in Chadds Ford. “We were fortunate enough to not have any plants die outright from lanternflies.”

According to Penn State researchers, the heaviest hit vineyards lost up to 90% of their grapevines.

Penns Woods’ lead winemaker and vineyard manager, Davide Creato, said that due to the slim margins of the wine industry, lanternflies have been a devastating blow for some, between dying grapevines and the cost of protecting vineyards.

“I think for every acre, and we have 40 acres of vineyard, we sprayed about $7 to $17 worth of pesticide, and that’s not including the costs of the labor, the equipment, and the rest of the expenses that come with it,” Creato said, who during the worst of the lanternfly invasion invested $10,000 in a high-end insecticide air cannon that could spray inside the vineyard and around its perimeter.

In 2022, the owner of Lehigh-based Stony Run Winery outside of Allentown told CNBC that at one point, lanternflies destroyed 15% of the winery’s crops, translating to a loss of over a half-million dollars. Even when crops don’t die, the costs of insecticides, reduced crop yield, and safely transporting and inspecting goods can add up.

Grape growers can’t just immediately replace a grapevine. Creato said it takes up to three years for grapevines to bear fruit and five to seven years to be ready for wine.

When lanternflies first arrived in the Philly region in 2018 through 2020, residents couldn’t walk a city block without seeing hundreds of lanternflies covering trees, the sides of buildings, and sidewalks. Only recently did Philly start to see a decline.

“The first year we had lanternflies we sprayed the vineyard three to four times. By 2022, their numbers were already going down. Last year, we didn’t spray for lanternflies at all and we haven’t had to spray this year either,” Creato said of Penns Woods Winery.

Walsh said there is a trend of lanternflies arriving in an area, growing in numbers rapidly for a few years, and then declining for another few years. “But in that sigh of relief, the question is then, ‘Why?’” he said.

Predators and parasites could affect lanternfly numbers, as well as a lack of diverse vegetation in Philly’s urban setting, and exhausting their food resources after years of feeding could all play roles in the insect’s diminished numbers in the city.

The stomping didn’t stop the spread of the lanternfly — the insects have spread to a total of 17 states, from Massachusetts to Tennessee and as far west as Illinois, threatening more than 70 host plants, including fruit trees, vegetables, herbs, and, most devastatingly, grapevines.

But stomping the bugs wasn’t in vain.

“It’s a complex bug that still has lots of secrets that we’re slowly working out,” Walsh said. “Everyday citizens reporting back information and doing the ‘lanternfly stomp’ as they went about their daily travels absolutely had a positive effect in slowing the spread.”