Are spotted lanternflies on the decline in Western Pennsylvania?

Spotted lanternflies are still a pest in Western Pennsylvania, but populations are trending lower in certain regions.

Sandy Feather works as a Penn State Extension educator in Pittsburgh. She has noticed a large decrease in spotted lanternflies.

“I bet we don’t have a 10th of the population that we had last year,” she said of her office at the Energy Innovation Center in the Hill District. “You couldn’t walk in the entryway. There were carcasses in the entrance of the building and even in the elevator.”

Feather, who has expertise in integrated pest management and is also part of Penn State Extension’s green industry team, said educators don’t know what to attribute the decrease to. Pittsburgh had a mild winter.

“I don’t think we can blame winter — we barely had winter last year,” she said. “We’ve been very dry, and I think that’s probably had some kind of an impact on them.”

Spotted lanterflies were discovered for the first time in 2014 in Berks County, which is where Brian Walsh, horticulture educator for Penn State Extension, is based. They have since quickly expanded geographically, he said.

In Berks County, Walsh said he’s seen a pretty big decline in spotted lanternflies, with the exception of a couple areas that have seen a resurgence.

“We try not to have too many expectations,” he said. “We’re learning as we go.”

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.

Spotted lanternflies mainly feed on black walnut saplings, tree of heaven and grapevines, according to Feather. Dry areas can take away these potential food sources for the spotted lanternflies, Walsh said.

Despite the decrease Feather has seen at her office, it doesn’t mean spotted lanternflies are totally gone.

Feather said she spoke with a landscaper who said spotted lanternflies were really bad in the Fox Chapel area this year.

“There’s a lot of things about their population dynamics that we don’t really understand,” she said. “Their population really changes and shifts — it’s very hard to predict what they’re going to do.”

Predators of the spotted lanternfly have increased, according to Walsh, like spiders, assassin bugs, soldier bugs, insects and arachnids. There have also been reports of birds eating them, he said.

Spotted lanternflies stick around until cold weather kills them, according to Feather.

“It’s going to take a couple of good, hard frosts,” she said.

However, they will lay eggs right up until the frosts come in. The new eggs will remain protected throughout the winter, she said.

Similar to other pests, Feather said, spotted lanternflies will never be eradicated.

“They are here to stay,” she said. “Their populations fluctuate, depending on predation including humans stomping on them, weather conditions like drought, not getting enough tree sap.”

Does stomping work?

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

Walsh said he believes the Western Pennsylvania region saw its peak last year.

“It’s not as widespread. This will be semi-normal going forward,” he said of the spotted lanternflies statewide. “It’s not that it’s gone completely, but it’s not as evenly distributed as it was.”

Both the Pennsylvania and U.S. departments of agriculture are working to try and manage the populations, according to Feather. They’re especially focused on keeping them out of Erie County due to the high amount of grapes growing there, she said.

“Otherwise, we consider them a plant stressor just like the drought we’re in,” Feather said.

She said apparently people are good at stomping on spotted lanternflies, as she believes both stomping and treatment by landscape professionals on trees have contributed to a dent in the population.

In Eastern Pennsylvania, people started hiring professionals to cut down trees that were hanging over decks or patios due to the honeydew the spotted lanternflies produce, according to Feather.

Others have decided to treat their trees with certain sprays, she said.

“Use EPA-registered insecticides if you’re going to spray,” Feather said. “Homemade spray could cause more harm than lanternflies.”

And stomping actually works.

Walsh said that every spotted lanternfly that is stomped out could result in 30 to 120 fewer eggs for the following year. A female spotted lanternfly can lay three to four egg masses, and there’s an average of 30 eggs per mass, he said.

“Roughly, they look like an inch, inch and a half splotch of mud,” Walsh said. “Underneath can be anywhere between 20 and 50 eggs, but it’s pretty nondescript if you don’t know what you’re looking at.”

Walsh encouraged people to be vigilant in not moving anything that has egg masses attached so as not to spread the population even more. If people notice egg masses, they should scrape them off, he said.

“People will be bringing their campers home when they spend the summer,” he said, as well as trailers and boats. “Make sure they don’t pick up lanternfly eggs in the summer.”