Spotted lanternfly season is back in Pennsylvania. The polka-dotted, gray-and-red-winged adult insects make their appearance each July and tend to hang around until December. It’s an unwelcome summer ritual that started in 2014 when the invasive pests were first detected in the U.S.

The Conversation U.S. talked to Flor Acevedo, an assistant professor of entomology at Penn State University, about the bugs and her research on how lanternflies are threatening the state’s vineyards and wine industry.

Does Pennsylvania have many vineyards?

Pennsylvania has more than 400 wineries with about 14,000 acres planted in vineyards, according to the Pennsylvania Wine Association. The industry generates about US$7 billion in total economic activity. Erie County, where I live, has about 70% of Pennsylvania’s vineyard acreage, with the rest scattered across the state.

What do lanternflies do to grapevines?

The spotted lanternfly feeds on many plants, but its preferred hosts are the Tree of Heaven, an invasive plant introduced to Philadelphia from China in 1784, and grapevines.

Extensive feeding by these sap-sucking insects can weaken grapevines and, when combined with other stressors such as diseases or frosty winters, can kill the vines. While spotted lanternflies feed on other important crops such as apple trees, they have been lethal only to grapevines and Tree of Heaven plants.

Feeding can also reduce yield and fruit quality, which affects juice and wine quality.

Tell us about your lanternfly experiments

My lab initially investigated whether spotted lanternflies could survive to adulthood and reproduce when feeding exclusively on grapevines. This would help us determine whether the insects could thrive in regions with extensive grapevine cultivation.

We found they do survive, but their fitness is severely reduced. Insects feeding solely on grapevines had high mortality, slower development and laid fewer eggs when compared with those that had access to a mixed diet of Tree of Heaven and grapevines.

Our next question was whether different grapes would be equally suitable for spotted lanternfly survival and reproduction. In the U.S. we grow native grapevines such as Concord and muscadine as well as vines of European origin. We found that spotted lanternflies did not survive to adulthood when they fed only on muscadine grapevines.

We have also partnered with colleagues specialized in plant science, food science and agricultural economics to investigate the effects of spotted lanternfly feeding on grapevine yield and wine and juice quality.

This research group enclosed both red and white grapevines – Cabernet Franc and Chardonnay – in mesh cages in the field and infested them with between 20 and 350 spotted lanternflies per vine. We wanted to determine the effect of constant adult insect feeding on grapevine yield, fruit sugars and phenolics, which are chemical compounds that are important for wine color, flavor and aroma. We also wanted to know the density of infestation that would induce changes in yield and fruit and wine quality.

We found a decrease in sugar content in the fruit within a single season, as well as a decrease in phenolics in red wine. We also found a reduction in yield after the second year of consecutive insect feeding.

These findings suggest that, if not controlled, spotted lanternfly adult feeding could reduce income to growers by reducing yield and could affect the wine industry by reducing the quality of the drink.

How worried are Pennsylvania winemakers and how are they responding?

Perceptions vary depending on whether the winery or vineyard is in an area that has already been infested.

Those that have been dealing with lanternflies for a few years have established protocols for pest monitoring and applying insecticides. But those that haven’t experienced it yet are concerned about the insect’s arrival on their properties.

Owners of organic vineyards are also concerned, but there are few of those in this region.

Wineries are being affected by spotted lanternflies in at least two ways. First, for those that grow grapes, lanternflies have increased their costs due to the extra labor and insecticide applications needed to control them. Second, for wineries that are agrotourism sites, they need to keep outdoor seating spaces neat and free from lanternflies.

As an entomologist, what do you find most fascinating about these creatures?

Most insects that feed on plants lay their eggs close to a food source for the young to feed on when they hatch. But spotted lanternflies lay their eggs on almost anything – car tires, field equipment, rocks, fabrics, old wood, cardboard. This behavior facilitates the insect’s dispersal, as eggs can be easily transported without being noticed. Once the eggs hatch, the nymphs search for young plant shoots or herbaceous plants to eat.

Anything else people in Pennsylvania should know as they see lanternflies again this summer?

I think it’s important for the public to know that, as pretty as some of us may find spotted lanternflies, these insects are invasive, damaging and affecting the state economy. Everybody can help stop the spread of these insects by killing and avoiding transporting them at any living stage.

Spotted lanternflies lay eggs in masses. These masses look like light grayish-brown, mudlike or puttylike patches, typically about an inch long, and they are found on various surfaces. At any life stage the insects can be killed by squishing them, immersing them in hand sanitizer or freezing them for several days.

Read more of our stories about Philadelphia and Pennsylvania.

Flor Acevedo has received funding for her research from the USDA Crop Protection and Pest Management program (2023-70006-40597), the Pennsylvania Department of Agriculture, the Pennsylvania Wine Marketing and Research Board, the New York Wine and Grape Foundation, the Penn State University College of Agriculture, and the John H. and Timothy R. Crouch Endowment Grant for Viticulture, Enology, and Pomology Research.