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Where did Central Pa.’s spotted lanternflies go? 

  • Katie Knol
In this Thursday, Sept. 19, 2019, photo, spotted lanternfly gather on a tree in Kutztown.

 Matt Rourke / AP Photo

In this Thursday, Sept. 19, 2019, photo, spotted lanternfly gather on a tree in Kutztown.

A few summers ago, it looked like Central Pennsylvania was experiencing a biblical plague. 

Plants, trees, and parking lots seemed to be covered in spotted lanternflies — an invasive species native to Southeast Asia. They were first spotted in Berks County, and have since spread throughout Pennsylvania and the Northeastern United States. 

In the commonwealth, 51 counties are under quarantine for the pests, which means people are asked to take extra precautions to prevent the bug from making it into new areas. 

But recently, the summertime bug hasn’t been seen in huge numbers in the midstate. Brian Walsh, a Penn State extension educator who researches spotted lanternflies, said the decline isn’t just your imagination. 

“The population dropping [in Harrisburg] seems to be consistent,” he said. “We have heard of other areas such as out in Allegheny County where the numbers are skyrocketing and picking up like where Harrisburg was just a year or two ago, so really it makes a big difference on where you’re at.” 

He said Eastern Pennsylvania saw large lanternfly populations for several summers, and then the numbers started to decline. The same thing is happening in the central part of the state now. 

Walsh said there are a lot of unanswered questions when it comes to the spotted lanternfly, so continued research is important. Penn State Extension is now looking into population dynamics and the bug’s life cycle. 

More information about how lanternfly populations act could help explain why the bugs haven’t been as common this summer. It could also provide warning for the agriculture industry about what states and crops are at the highest risk. 

But just because the midstate’s  population is declining doesn’t mean the problem is over. 

“As this invasion matures, what we might be looking at in the future is something is some years you have them, some years you don’t, and you can travel just a few miles and see the opposite,” Walsh said. “It doesn’t mean that it’s over — it doesn’t mean that we don’t have to be vigilant anymore. It just means that I think we’re entering a new phase in some of these areas as to what the population dynamics might look like.” 

The species feeds on sap from over 70 different plant species, particularly ones that are important for the state’s economy such as fruit trees, vegetables, herbs, grains and vines. Penn State economics estimate the pests could drain at least $324 million out of Pennsylvania’s economy each year if they aren’t contained. 

He recommends people continue to take precautions to slow the spread of the invasive species — like killing any spotted lanternflies they see and checking cars and outdoor equipment before traveling.

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