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Spotted lanternflies arrived in Pa. 10 years ago. Here’s what experts have learned

A spotted lanternfly creeps on the ground during a baseball game in Pittsburgh in 2021.
Keith Srakocic
A spotted lanternfly creeps on the ground during a baseball game in Pittsburgh in 2021.

Spotted lanternflies showed up in Pennsylvania 10 years ago.

It’s not an anniversary to celebrate. This invasive pest spread to Chicago and Nashville, stressing trees and killing grapevines. By this time of year, if you haven’t seen the tiny black pest with white dots, wait a few weeks. They become much easier to spot as they morph into red, black and white dice on the move. Research continues to help understand and control spotted lanternflies.

Agriculture educators, entomologists and others in Pennsylvania’s spotted lanternfly program recently discussed the pest in an online talk for Penn State Extension. Here are a few highlights.

Why are spotted lanternflies a problem?

Spotted lanternflies are native to China. They have spread through much of Pennsylvania (including Lancaster County) and beyond, where there aren’t many natural predators.

Lanternflies feed on more than 70 species of plants and trees and can kill grapevines and small tree saplings. They can stress trees, leaving them vulnerable to more stressors, says Emelie Swackhamer, horticulture extension educator in Montgomery County.

How many spotted lanternflies are in Pennsylvania this year?

Looking at numbers before September only shows part of the story, says Brian Walsh, horticulture educator in Berks County. The population shifts through the season and year to year.

One may spot groups of lanternflies as they hatch. Then they spread out to feed. By late July, lanternflies reach adulthood. As they gather in September to lay eggs, the population explodes.

Populations have fluctuated in the past decade as lanternflies move into new areas.

“Generally, we can say we see an expansion of the populations for three to five years in a new area,” he says. “And it can get to a point where it looks like a biblical plague and then we do see a fall-off. It doesn’t mean that they’re gone. But the population is definitely decreased.”

What do we know about spotted lanternflies and grapes?

While lanternflies eat dozens of species of plants, grapes are a particular concern.

Researchers are studying when it makes sense for grape growers to take extra steps to manage spotted lanternflies. They looked into things like spotted lanternflies’ effect on grape yield and grape juice chemistry.

Preliminary results for a two-year study show vineyards infested with spotted lanternflies have lower yield and lower juice quality, measuring things like sugars and tannins, says Flor Acevedo, assistant professor of entomology and arthropod ecology at the Lake Erie Regional Grape Research and Extension Center.

What they eat matters in development and the next generation. Lanternflies only eating grapevines can grow and lay eggs but they aren’t as healthy as those with a diverse diet, including tree of heaven. The lanternflies feeding only cab franc grapes or only concord grapes, for example, laid no eggs.

Ways to manage this pest in vineyards include removing plants like tree of heaven. Adding nets around grapevines keeps lanternflies away as well and don’t damage the fruit.

What else have we learned about this pest?

After hearing spotted lanternflies may be attracted to the buzz of electrical wires, researchers set up their own sound studio. In their controlled setting, lanternfly nymphs and adults moved toward the vibration.

Vibration is important because there isn’t a good lure for spotted lanternflies, says Julie Urban, director of the department of entomology at Penn State.

Planthoppers such as lanternflies don’t rely on chemical signals so the search is on to find how to attract them. Tremors also have been used to disrupt the mating of glassy-wing sharpshooter, a pest feeding on California vineyards.

Outside of the lab, traps were added to poles in the Port of Philadelphia, including some connected to power lines. However, the poles connected to the vibrating power lines didn’t attract more lanternflies. There’s more work to be done to learn if the lab study can be translated outdoors, Urban says.

Other research shows lanternflies can significantly reduce growth of hardwood trees like silver maple, weeping willow and river birch. These trees can recover when the insects move along.

And a field study in Berks County was used to develop a model to estimate how much time lanternflies need in warm temperatures to complete their life cycle. As the pest spreads, the model can show what regions have the right climate for adults to emerge. A related and upcoming model will show which areas stay warm long enough for females to lay eggs.

How can you kill spotted lanternflies?

“Everybody would like to have a silver bullet that just takes care of this insect but we just don’t have one,” says Amy Korman, horticulture extension educator for Penn State Extension in Northampton and Lehigh counties.

So, in lieu of a magic wand, experts recommend the following:

  • Destroy egg masses before nymphs hatch, usually in May.
  • Once the nymphs emerge, trap them in circle traps and bug barrier traps.
  • Don’t use home remedies like dish soap, vinegar or bleach. These can be unsafe for people, pets and plants.
  • For pesticides approved for spotted lanternflies, weigh the risks against how many pests are around and whether your plants or trees are vulnerable.

Read more from our partners, LNP | LancasterOnline.