Experts predict high spotted lanternfly numbers in Western Pennsylvania this year

Spotted lanternflies are back this summer — and experts are predicting Southwestern Pennsylvania will once again see significant numbers of the invasive insect.

Brian Walsh, spotted lanternfly researcher and horticulture educator for Penn State Extension, said though it’s difficult to measure the population since they are constantly in motion, experts are able to “guesstimate.”

“It’ll probably be fairly high population in most of the same areas this year,” he said.

Though they present no danger to humans, similar to previous seasons, Walsh still encouraged people to squish the spotted lanternflies when possible.

“The insect turned out to be more complicated than (we) originally thought that it was,” he said.

Southwestern Pennsylvania saw high numbers of spotted lanternflies the last couple years, according to Julie Urban, associate research professor in the department of entomology at Penn State University Park.

“I know it was really high last year,” Urban said, but in specific areas, numbers can fluctuate. “You can have an area where it’s really heavily infested … but a few blocks over, you really don’t have anything.”

She also said she expects there to be a significant presence this year.

Areas where there are heavy infestations of spotted lanternflies can then drop off in numbers in subsequent years, according to Urban.

“It’s really hard right now to tell where Pittsburgh is in that cycle,” she said, as researcher is ongoing. “We don’t really understand what drives that cycle.”

Walsh said if this region follows the trend of other areas with high spotted lanternfly numbers, there should be a drop off eventually.

“We don’t have a crystal ball — we can’t tell you when it’s going to start quieting down,” he said. “At some point … it’ll get better.”

Spotted lanterflies were discovered for the first time in 2014 in Berks County, which is where Walsh’s research is based. Since then, they have quickly expanded geographically, he said.

“They’re very good at hitchhiking rides on human transportation,” Walsh said, which is likely how they arrived to Pennsylvania initially.

Walsh said it is believed that the spottern lanternflies originated somewhere in Asia, but Berks County was the first introduction point to the Western Hemisphere.

In the last two or three years, he said the Berks County area has seen declining populations.

“They’re not gone,” he said, “but they’re not at the peak that they were at several years ago.”

Walsh said he and other researchers still have “no idea” why this occurs in areas where there used to be higher populations of the bug.

“That’s part of our research work — trying to figure out what is driving this,” he said of the fluctuation.

Spotted lanternfly populations are currently in 17 states, according to the U.S. Department of Agriculture’s Animal and Plant Health Inspection Service, and several states have quarantine areas in place to prevent spread.

According to Penn State Extension’s online quarantine map, spotted lanternflies are currently found in 51 of the 67 counties statewide — all of which are under a state-imposed quarantine. Allegheny and Westmoreland counties, as well as all of the counties in Southwestern Pennsylvania are included.

“The quarantine affects vehicles and other conveyances, plant, wood, stone products and outdoor household items,” Penn State Extension said.

Urban said she hopes the region will be on the downswing soon.

“Pittsburgh’s seen it kind of bad the last couple of years,” she said. “But, at least in terms of where we’ve seen egg masses, it’s still likely to be high in some areas.”

Recently, Urban came to Pittsburgh to collect egg masses to take back for experiments at Penn State, and she said it was similar to what she’s seen in the past — in the limited areas her team looked.

As of now in their life cycle, the spotted lanternflies have hatched and they’re out feeding on anything herbaceous, she said, but they’re hard to spot until they emerge as adults starting around the end of July.

The spotted lanternflies will then gather in higher numbers on host plants starting around September and feed heavily to become mature and reproduce, according to Urban.

“That’s when they’re constantly moving … and that’s when everybody freaks out,” she said of the first few weeks of September.

Walsh said any non-coniferous plants can be host plants.

In Southwestern Pennsylvania, Urban said spotted lanternflies mostly feed on tree of heaven and abundant wild grapevine. Other foods include poison ivy and bittersweet, as well as weedy and invasive plants.

“The wild grapevine is the one that really, really stands out,” she said.