It’s Pa.’s spotted lanternfly season. Here’s what researchers know and want you to do

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The invasive spotted lanternflies have just begun to hatch in Pennsylvania, New Jersey and Delaware, sending the black beetle-like nymphs with white spots crawling, and more often hopping, from one juicy plant to the next. The planthopper, as it is known in the entomology world, first arrived from Asia in 2014, likely hitching a ride on a shipping container and landing in Berks County, Pa.

Since then, the pest has spread to 18 states, and almost every county in Pennsylvania is under a quarantine for the bug — meaning businesses transporting equipment need to have obtained a permit that includes training on how to spot egg sacs and infestations. A 2019 report by Penn State found that lanternfly damage to the state’s agriculture could cost an estimated loss of $50.1 million per year, along with 484 jobs.

The state and federal government have spent millions researching the invader to understand how to keep it from spreading and damaging crops, specifically grapevines. And while the spotted lanternfly is not a picky eater, its favorite meal is another invader that was brought to the U.S. in 1784 by the wealthy West Philadelphia gardener William Hamilton — the now ubiquitous tree of heaven.

Turns out there may be a good reason for that. When the lanternfly feeds on the tree of heaven, it becomes bitter tasting to a lot of predators.

What eats the spotted lanternfly?

When the lanternfly first arrived, scientists worried that it had no natural predator. But a decade since its arrival, researchers are discovering that more and more native species are munching on the bug.

Penn State professor of entomology Kelli Hoover did a citizen science survey during the COVID-19 lockdowns, when a lot of people were out in nature, smashing as many of the lanternflies as they could find. Hoover wanted to know if anything was actually eating them.

“We had almost 2000 reports of animals feeding on spotted lanternfly in nature,” Hoover said.

“And it was incredible how many different species there were, and there were lots of reports of arthropods, spiders, ants, lots and lots of insects, birds, many, many, many, different types of birds were feeding on them.”

People reported seeing raccoons, chipmunks, frogs, and even fish eat lanternflies on occasion. What Hoover discovered in her experiments is that when lanternflies don’t feed from the tree of heaven, they seem more palatable to vertebrates like birds. It’s not that animals won’t feed on those that have munched on tree of heaven sap, but they much prefer those that don’t.

Arthropods on the other hand — spiders, ants, praying mantis — really don’t seem to care what the spotted lanternfly has eaten.

“Our star predator is something called the spined soldier bug, it’s a predatory stink bug,” Hoover said. “They are small, and they mass attack as a group and dig their beaks into it and suck all the juices out.”

Hoover said she has also found increasing numbers of eggs from the Carolina Mantis and the Chinese mantis, soldier bugs and wheel bugs, in areas of heavy lanternfly infestation. “They’re all just kind of hanging out, and when the lantern flies start hatching and they move right over and go after them.”

Hoover’s current research is looking to see if the spined soldier bug could control the spotted lanternfly population naturally.

“Do they increase their rate of predation when the lanternfly populations increase? Because if they do… they could be released to help boost populations of those things, like in a vineyard.”

Impact of lanternflies on vineyards

Vineyards are the most vulnerable to lanternfly infestations, and have suffered the most economic damage, said Flor Acevedo, assistant professor of entomology at Penn State. Acevedo said that while lanternflies do feed on fruit trees, those don’t seem to suffer as much damage as some grapevines. Acevedo said the damage could occur over time and include other stressors.

“The lanternflies do weaken grapevines a lot, but if there are additional stressors such as diseases or very cold environmental conditions, then altogether, the vines are not able to respond to these stressors and end up dying,” Acevedo said.

Acevedo recently looked at how well the insect reproduces on diets limited to specific grapes. Some of the insects were fed on a diet that included tree of heaven and a grape variety, while others were fed simply on a grape vine. Acevedo found that the insect thrives when fed a variety of food, in this case, a grape along with tree of heaven sap.

“They really need that mixture of diets to be able to thrive, to be able to survive more, to be able to develop faster and to be able to lay more eggs,” Acevedo said.

The most resilient vine, meaning the lanternflies did not do well by feeding on it, was the native muscadine grape.

“That is what I consider the most important finding of this study because it opens possibilities of perhaps finding some traits of resistance that could be helpful,” Acevedo said.

She said she has spoken to vineyard owners who use the tree of heaven as a trap, injecting it with a chemical that would kill the lanternflies that feed on it. Others, she said, have removed the tree of heaven from the surrounding area, but it’s unclear to what extent, if any, either of those methods are useful.

Where have all the lanternflies gone?

Some have reported seeing little to no spotted lanternflies a few years after massive, bothersome infestations.

But both Hoover and Acevedo say they are still thriving.

“They just moved,” Acevedo said. “They will probably be back.”

They likely migrated after exhausting their food source, and while they eat a varied diet, they still seek out the best sap. So, although they may not have killed a tree, they may have sucked all the good nutrients out, according to Hoover.

“They’re like, ‘I want my favorite food. I’m leaving so I can find it,’” Hoover said.

But researchers like Hoover caution the bug could return to areas it had previously seemed to abandon.

In terms of natural predation, so far, nothing has done enough damage to the spotted lanternfly to control it. But Hoover said that could change with time.

“Remember when we had the brown marmorated stink bug come into Pennsylvania, and it was really a serious problem for many, many crops,” Hoover said. “But after about 10 years, there were natural enemies that were feeding on other things that switched over to going after those brown marmorated stink bugs, and they started really reducing numbers, and they’re now managed pretty well.”

In the meantime, Hoover advises to keep scraping the egg sacs and stomping the bug dead.