Spotted lanternflies have begun reaching their adult stages - the time when they’re most noticeable and capable of doing the most damage.

As a horticulture educator with the Penn State Extension in Northampton and Lehigh counties, Dr. Amy Korman keeps a track on the invasive species.

So, too, does Rob Bergstresser, an environmental education specialist at Beltzville State Park.

The lanternflies are native to China, and were first spotted in Berks County in 2014. Since then, they’ve spread to 51 of Pennsylvania’s 67 counties.

“In our area, the adult stage is generally July through September. Because lanternfly eggs do not all hatch at the same time, we can see nymphs and adults simultaneously in July,” Bergstresser said.

But at this point, Korman said too early to say whether the lanternfly population will be up or down this year.

In south central Pennsylvania, for example, reports of the destructive bug are lower than last year.

Bergstresser said lanternfly populations have been spotty in certain areas, and high in other areas.

“No one is exactly certain why this occurs, but it could be related to food availability. Research is currently ongoing as to why their populations are becoming almost cyclical in nature,” he explained.

Another factor could be weather, Korman added.

“It could be one of a number of factors influencing the lanternfly populations,” she said. “Environmental factors, including the availability of appropriate host plants, the temperature, rainfall, natural enemies - all these things probably influence populations.”

Scientists, she said, don’t have all the details at this point.

“It may be misleading to assume that the population is low because we don’t see a lot of nymphs,” she explained.

Adults should make their presence known soon. Their forewings are gray with black spots, and when they fly, they expose their red and black hind wings.

According to the United States Department of Agriculture, lanternflies feed on the invasive tree of heaven, along with a wide range of crops and plants including grapes, apples, hops, walnuts and hardwood trees.

At Beltzville State Park, Bergstresser said the pests are here and there but seem to favor red maple and black walnut trees.

“We have also continued to remove any Ailanthus trees (tree-of-heaven), which is an invasive tree found in the lanternfly’s native China,” he said. “Ailanthus trees are a ‘magnet’ for the lanternfly, so I always advise people to remove any Ailanthus trees they might find on their property.”

When park employees find the lanternflies, the bugs can number in the hundreds on one single tree.

“If we do see a lot in a certain area, we tend to focus on surveying (in fall and winter) for more egg casings in those areas,” he said.

The lanternflies are dangerous because of the piercing and sucking mouth parts that feed on plant sap.

“They are really problematic for vineyards, quite destructive and costly. Their ferocious feeding can rob the plant of the ‘stored energy’ that the grapevines need to thrive,” Korman said.

Their feeding is considered a plant stressor and may contribute to the weakening of trees over long periods of exposure, she added.

As they feed, they produce a sticky substance called honeydew.

“Honeydew, by the way, that impacts the undergrowth around affected trees and we don’t know what the long term effects will be for wooded areas,” Korman said.

A 2022 study from Penn State’s College of Agricultural Sciences estimated that lanternflies’ direct economic impact on Pennsylvania’s agriculture per year is $42.6 million statewide.

If they continue to spread, the number could grow to $324 million annually and cause the loss of about 2,800 jobs, the study found.

Those in the impacted counties are under a quarantine and are not to move any spotted lanternfly living stage, including egg masses, nymphs, and adults.

The Pennsylvania Department of Agriculture encourages people to kill the bugs.

“It’s strongly advised to kill them immediately,” Bergstresser said. “Just a few lanternflies can spread to other areas, and in the long-run, end-up costing a state millions of dollars.”

He admitted that they can be difficult to kill because they are fast jumpers. Fortunately, he said, they’re not strong flyers.

“I’ve personally found that it’s much easier to squash them after they jump, and land on the ground the first time. It takes them a second or two to regain enough energy to jump a second time,” he noted.

Furthermore, he said, people are urged to report any lanternflies they see, even in areas where they have previously been reported.

“This can help scientists better track their population trends,” Bergstresser said.

Lanternfly sightings can be reported through the Department of Agriculture’s website: https://services.agriculture.pa.gov/SLFReport/ or by calling 1-888-4BADFLY.