When are the spotted lanternflies coming, and should I still be trying to crush the bejesus out of them?

TL;DR: Soon, and yes.

Spotted Lanternfly Pennsylvania
Matt Rourke / AP Photo
ashaprihar-headshot

Philly knows them all too well: The big, actually-kinda-pretty bugs with red bodies and polka dot wings. The goop they leave behind on trees (which is actually poop). The splotches on the pavement that come after someone who’s been paying attention to the news crushes the life out of one of them.

Spotted lanternfly eggs are getting ready to hatch any day now. After that, it’s only a matter of time before they transform into giant hopping insects.

As a reminder, the bug is native to China. It was first documented in the U.S. in 2014, in Berks County, and reached Philly three years later. Since then, the invasive species has reached at least 45 of Pennsylvania’s counties and spread to 11 states over its eight years in the U.S. Why is that a problem? Its poop attracts mold that’s harmful to plant life.

Over the past few years, Philadelphians have internalized a popular directive: Squish spotted lanternflies on sight. But there’s a school of thought that asks whether that’s really effective or necessary.

There’s still plenty researchers are trying to find out, but here’s the latest on spotted lanternflies and what you should do if they’re pestering you or your plants.

Why were there fewer in the Philly area last year? Is it because I stomped the living daylights out of them?

Lanternfly sightings were down in Philly last year, and the exact reasons for their disappearance aren’t clear.

Many invasive insects experience population changes in cycles, said Emelie Swackhamer, a horticulture educator with Penn State Extension Montgomery County.

One factor could be a lack of host plants to feed on, she said. One of spotted lanternflies’ favorites is the giant-leafed weed called Tree of Heaven, a fellow invasive species, and some localized efforts to remove it have been successful in reducing the insect populations too.

Natural enemies like spiders, praying mantises, and fungi can also have an impact, as can weather conditions. Also, spreading to new areas like NYC could have thinned the local hordes.

“We don’t understand all of these different factors completely,”  Swackhamer said, “but we have a good idea of some of the factors that might be important in these population fluctuations.”

What about the valiant squishing and egg-scraping efforts of years’ past?

The bugs move quickly, which makes it challenging for researchers to conduct any sort of controlled count, Swackhamer said. But it makes sense that killing them limits their spread.

“Each female has the potential to lay about 70 or more eggs. We think they probably lay two egg masses in their life cycle … you can really do the math and get some big numbers,” she said.

“So intuitively, we think destroying lanternflies [is] helping, but we don’t have a way to measure that impact.”

Spotted lanternfly nymphs

Spotted lanternfly nymphs

Courtesy Penn State Extension Montgomery County

Are they gonna be back, even if I barely saw any last year?

The bugs weren’t totally gone last year. Across Pennsylvania, they tended to show up intensely in some spots, but not at all in others, according to Pa. Secretary of Agriculture Russell Redding, who spoke about them at a press conference last week.

So don’t be surprised if you see them again.

“You may have seen a reduced population in your neighborhood in 2021,” added Swackhamer, the PSU educator. “We believe in the future, you may see high populations, and we don’t have a way to predict that yet. But we don’t want people to be surprised that we have high populations in some years and low in others. It’s kind of to be expected.”

OK… so when will they show up?

Hatching doesn’t happen all at once, and there’s not a super exact timeframe on it, but you’ll probably start to see it in the next couple of weeks.

They start out as small nymphs, which are small and black with bright white spots, then they’ll grow bigger and turn red before eventually growing into full, adult lanternflies around late July.

In 2020 and 2021, Philly-area lanternfly hatching began in the third week of April, according to Shannon Powers, Dept. of Agriculture press secretary. The earliest recorded egg hatch in Pa. last year was on March 31 in the Philly area.

It won’t be clear how prevalent the bugs will be until hatching starts, but you can tell now how infested a specific spot might become by seeing how many eggs are around.

Getting rid of the eggs can mitigate the number of bugs you’ll see. Every mass that’s removed “is 30-60 pests that won’t infest your property in a few weeks,” Powers said.

You get rid of the eggs by using something with a hard edge (like a credit card) to scrape any masses you see into a plastic bag with rubbing alcohol or hand sanitizer.

Lanternfly eggs on a tree

Lanternfly eggs on a tree

Courtesy Penn State Extension Montgomery County

What are they doing to local plants?

Spotted lanternflies aren’t directly responsible for killing most plants, researchers have found.

“We have not seen lanternflies kill trees in landscapes,” PSU’s Swackhamer said. “It’s important for people to realize that and not panic.”

They’re specifically harmful to a few specific plants, like grapevines and the Tree of Heaven (an invasive species on its own). So the impact on grape-growers and vineyards can be huge.

Aside from that, the bugs can make landscape and forest trees more vulnerable to other stressors by hindering photosynthesis and plants’ abilities to store carbohydrates, she said. But they’re ultimately not the sole culprit for plant death — that’s caused by other factors.

If you suspect that lanternflies are indeed killing off a typical landscape tree in their own right, Swackhamer asked that you notify your county’s Penn State Extension office, so the people there can look into the situation.

“If it’s happening, we want to know about it,” she said.

Once they hatch, how tf do I get rid of them?

If there are a bunch of lanternflies plaguing your home or business, Swackhamer advised that you should choose the method you use to get rid of them based on the level of risk. Consider whether it’s a new area (that should be reported), and the likelihood of impact on plants.

There are a couple of tiers of response, starting with “cultural control” (removing favored hosts, like the Tree of Heaven) as a first step and landing on “chemical control” (using EPA-registered chemicals) only when other options have been exhausted.

Solutions in the middle include:

  • Using circle traps (learn how to make one here)
  • Providing a habitat for natural enemies like spiders and mantises
  • Using recommended, reduced-toxicity chemicals like insecticidal soaps, horticultural oil sprays, botanical oils, or pyrethrum, according to Swackhamer (you can find more guidance on using chemical treatments here)

Some things to avoid, per Swackhamer: home remedies you find on the internet (some of which are toxic to plants and humans), untrained/non-professional application of toxic chemicals, going overboard (e.g. getting up on a ladder just to scrape some egg masses from a tree).

“Kill them if you can, but be safe,” Swackhamer said. “Use safe methods, and don’t react out of fear and do dangerous things. But try to kill them, yeah.”

A spotted lanternfly swarm

A spotted lanternfly swarm

Courtesy Penn State Extension Montgomery County

So I’ve got the green light to keep stomping?

Yep. But don’t go too crazy — it’s important to understand why you’re doing it, and to “recognize beneficial insects and preserve the good guy,” Swackhamer said.

“We don’t want to be teaching people that we just want to indiscriminately kill insects,” she said. “We want people to understand why we’re concerned about this insect, and why we’re trying to destroy spotted lanternflies specifically.”

Take a moment to report them, too. The state agriculture department is still working with the USDA to follow up on new infestations as much as possible and welcomes the reports, per spokesperson Powers. And researchers are always looking for more places or bugs to study, Swackhamer said.

Penn State Extension maintains a website where you can make a report. You can also call 1-888-4BAD-FLY.

Scrape, squish, and stomp away, folks.

Let the news come to you

Billy Penn’s free morning newsletter brings you the latest Philly news that everyone will be talking about in your Slack channel.

Nice to see you (instead of a paywall)

Billy Penn’s mission is to provide free, quality information to Philadelphians through our articles and daily newsletter. If you believe local journalism is key to a healthy community, join us!

Did you hear that?

That was the sound of you being informed after reading another BP article. If you believe local information should be free and accessible to all Philadelphians, will you support Billy Penn today?

Informing Philadelphians, one story at a time

Your generous donation brought this article to life. Become a sustaining member today to continue Billy Penn’s work.

Bring a friend into the Billy Penn-verse

Thanks for reading another story! Know a fellow Philadelphian that would appreciate BP? Tell them about our newsletter.