We were wrong about spotted lanternflies, research shows. Kill them anyway.

The spotted lanternfly is a Philadelphian’s mortal enemy. Wait. No, that’s the Dallas Cowboys. But still, these bugs give them a run for their money.

A new study, however, reveals that the lanternfly may not be that destructive after all.

In August, researchers in Pennsylvania State University’s Entomology Department published their findings on a four-year study to see if the plant-killing pest is as deadly to local plants as first believed by officials in 2014. At that time, reports from Japan and Korea warned of the invasive species wreaking havoc on fruit and hardwood trees there since the mid-2000s. There was reason to believe that the lanternfly could cause significant destruction to Pennsylvania’s million-dollar grape and billion-dollar timber industries.

But, almost a decade later, scientists are coming to some relieving conclusions about the sap-sucking insect, at least regarding hardwoods used for timber.

Kelli Hoover, an internationally known researcher on pests like the lanternfly and the Penn State entomology professor who authored the study, said lanternflies move around too much to cause enough damage to trees.

“To model what happens in the field after a couple of years of heavy lanternfly feeding, we lightened up the pressure on the tree saplings,” Hoover said, of simulating lanternflies feeding on trees off and on for two years at a time. “When we relieved the pressure, the trees recovered.”

Hoover’s research attempted to simulate the worst-case scenario for trees in the wild by allowing lanternflies to feed on the same trees for four consecutive years, whereas lanternflies in nature commonly only feed for one to two years before hopping to another target. Even with this lanternfly doomsday scenario, Pennsylvania hardwoods were able to rebound, said Hoover.

The study took various trees that lanternflies like to feed on, like red and silver maple, river birch, weeping willow, and — the lanternfly’s favorite food — the invasive tree species, tree of heaven, and set up saplings of each tree in an enclosed environment to let lanternflies go to town on these young trees and measure the impact.

In years one and two of the study, researchers put immense feeding pressure on the tree saplings, which led to a significant reduction in their growth — sometimes by half — with the lanternflies also eating at the energy stores reserved in the tree roots to survive the winter, said Hoover. A potentially fatal one-two punch to trees already under stress from conditions like soggy ground and heavy rain.

However, when researchers reduced the feeding pressure on the saplings in year three, they all recovered despite suffering damage from the first two years of feeding. “Except for the tree of heaven, they did not recover. But who cares? It’s invasive, and we don’t really want it here anyway,” joked Hoover.

Lanternflies, a part of the planthopper family, don’t stick around for long after they deplete sufficient nutrients from their host tree. Once they’re done feeding on a given plant, they hop to the next one for more food. Hoover said lanternflies commonly feed on a tree or target area for one to two years before they’ve had enough, and then they relocate for about one to two more years before returning to that original target.

“The spotted lanternfly is so different than anything I’ve ever worked on because it’s not like you have a cornfield and there are pests in the cornfield, so you treat the cornfield,” Hoover said. “They’re all over the place and moving all the time.”

This means that while lanternflies damage Pennsylvania hardwood trees used for timber, they won’t kill them as long as the trees are strong, healthy, and not under any stress. Excellent news for tree nurseries across the state, said Hoover, but you should still kill lanternflies when you see them.

Grapes in Pennsylvania vineyards are a different story than hardwoods — they’re still in greater danger, said Hoover.

That’s why researchers like Hoover and her Ph.D. student Anne Johnson continue their lanternflies studies to better protect the state’s agriculture. For example, Johnson recently published a study identifying natural predators of lanternflies spanning spiders, birds and even bees. The study also uncovered the lanternfly’s ability to hold toxins in its body to ward off predators that attempt to kill it (similar to monarch butterflies), a trait that may have led to the insect’s success in the States.