Posted: April 19, 2021

Researchers devise creative ways to defeat a destructive pest.

Photo: GH Photos / Alamy Stock Photo

Photo: GH Photos / Alamy Stock Photo

In the spring of 2018, the staff at Karamoor Estate Vineyard and Winery in Fort Washington, Pennsylvania, noticed a small gathering of spotted lanternfly nymphs coming together on a sycamore tree bordering the 200-acre estate. Staff had been on high alert, keeping a lookout for this pest in years past, but the insect never seemed to create any problems.

What started as a trickle in 2018 turned into a steady stream the following year. Spotted lanternflies that once stayed on trees at the edge of the property spilled into the vineyard, leading owners and staff to engage in an unremitting battle to keep the insects at bay.

"We began to notice vines that were damaged from large numbers of spotted lanternflies feeding on them the previous season," said Joseph Rienzi, the estate's viticulturist. "We started the 2020 season with lower initial crop potential due to the bud death on the heavily fed vines, which reduced our crop this year."

Of equal concern is how spotted lanternfly feeding on the grapevines affected the quality of the fruit harvested. Rienzi said they saw slightly lower Brix levels (sugar content) in some of the grapes, and they also noticed nutrient deficiencies, specifically potassium, in the vines.

For advice, they turned to Heather Leach, who at the time, was the spotted lanternfly extension associate in Penn State's College of Agricultural Sciences. Besides advising on perimeter barriers and insecticide treatments that could hinder the pest's spread, Leach asked if the vineyard could serve as a research site.

"There was not much research done specifically on the spotted lanternfly before being introduced to Pennsylvania," Rienzi said. "Penn State and its associates have done an awesome job of publishing their research findings and providing insight where there was once little information, which is why many people are becoming aware of the spotted lanternfly in general."

Studies such as the one underway at Karamoor yield important insights into controlling the pest in vineyards, fruit farms, nurseries, homes, and recreational areas. More than 25 College of Agricultural Sciences faculty, Penn State Extension educators, research technicians, and graduate students are dedicated to spotted lanternfly studies. These projects run the gamut from basic biology of the pest and economic damage from feeding to its host-plant preferences and the efficacy of biological and chemical control methods.

"Our research objectives regarding the spotted lanternfly are clear--to find sustainable, long-term solutions that are effective and environmentally safe," said Rick Roush, dean of the College of Agricultural Sciences. "Each exploration adds to our strategy in the fight against this destructive pest."

A "Most Pernicious Insect"

Dennis Calvin has seen his fair share of destructive pests during his career as an extension entomologist--the first being the southwestern corn borer, which he researched as a graduate student at Kansas State University in the 1970s.

But when it comes to destruction, he said few insects have sucker-punched Pennsylvania quite like the spotted lanternfly, a planthopper native to parts of China, India, Vietnam, and eastern Asia. First discovered in Berks County, Pennsylvania, in 2014, it is now confirmed in 26 Pennsylvania counties and reported in surrounding states, including New Jersey, Delaware, West Virginia, Virginia, Connecticut, Ohio, New York, and Maryland.

"Most insect pests have a limited number of plants on which they feed, plus they tend to stay in one location," said Calvin, associate dean and director of special programs in the college. "These factors are favorable for an effective integrated pest management program."

The spotted lanternfly, he pointed out, feeds and moves continuously, especially during the nymphal stages. "It has an insatiable appetite for the sap of more than 70 types of fruit and landscape trees, grapevines, and woody ornamental plants. Plus, it's a rolling stone--it never stays in one spot for very long."

To boot, the pest leaves behind a sugary excrement called honeydew, which promotes the growth of sooty mold, further harming the plant while attracting other insects and creating a mess that can render outdoor areas unusable.

Calvin's assessment of the pest's appetite for destruction is spot on, noted Roush, an entomologist recognized globally as a leading authority on resistance management to conventional insecticides, herbicides, and genetically modified crops, and for biological control and integrated pest management.

"Emerald ash borer, the brown marmorated stink bug, and the Asian long-horned beetle are examples of introduced insects that have caused significant harm to crops, native plants, or ecosystems," Roush said. "Now we face potentially the worst invasive pest since the introduction of the gypsy moth nearly 150 years ago: the spotted lanternfly, which one of our veteran Penn State entomologists called 'the weirdest, most pernicious insect' he's ever seen."

If not contained, the spotted lanternfly could potentially drain Pennsylvania's economy by $324 million annually and cause the loss of about 2,800 jobs, according to a study carried out by economists in the college and funded by the Center for Rural Pennsylvania, a legislative agency of the Pennsylvania General Assembly.

Their study places current economic damages due to the pest at more than $50 million per year, with a loss of 484 jobs in the southeastern part of the state. Under a worst-case scenario, in which damage reaches the maximum projected by crop production and forestry experts, these losses could increase to $554 million annually and almost 5,000 jobs.

"Even if the worst-case scenario doesn't come to pass, the spotted lanternfly has already inflicted millions of dollars in damage to our state's agriculture and forestry industries," said Jayson Harper, professor of agricultural economics and director of Penn State's Fruit Research and Extension Center.

"Our findings demonstrate that the vigorous response by the Pennsylvania Department of Agriculture, U.S. Department of Agriculture, Penn State, and industry stakeholders to limit the spread of spotted lanternfly is warranted--our economy depends on it."

That response is being supported, in part, by a $7.3 million grant from the U.S. Department of Agriculture's National Institute of Food and Agriculture. The funding, awarded to Penn State in 2019, supports an interdisciplinary, multi-institutional taskforce that is focused on developing strategies to combat the spotted lanternfly.

The projects draw on the expertise of 37 collaborating researchers and extension educators from Penn State, the USDA Agricultural Research Service, the USDA Animal and Plant Health Inspection Service, Virginia Tech, the University of Delaware, the University of Rhode Island, Temple University, Rutgers University, Cornell University, and the Northeastern IPM Center.

The grant is complemented by more than $5 million in matching investments from growers and landowners who agreed to participate in this work, many of whom are currently working with researchers on spotted lanternfly.

Investigating Biology and Behavior

In its native environment, the spotted lanternfly is kept in check by predators, parasitoids, diseases, and other population-regulation mechanisms, so it seldom is considered a problematic pest in these countries. Therefore, little research has been done, noted Calvin.

"Over evolutionary time, insects, diseases, birds, and mammals in its native region have adapted to use spotted lanternflies as a food resource," he said. "This regulates the insect's population and typically keeps the number below levels that cause issues for humans. In the United States, this is a new insect that has been freed of its natural enemies and other population-regulation mechanisms. To control it, we first must understand it."

Penn State studies have revealed much about the insect's biology and behavior. First, the spotted lanternfly goes through five stages of growth after hatching from eggs in late spring. The first four stages are called nymphs, which are incapable of flight. In mid-summer, they became adults sporting gray wings with black spots and perhaps their most discernable trait: bright red underwings.

Throughout the fall, adult females each lay at least one egg mass, which typically contains an average of 30 to 50 eggs. They deposit their progeny just about anywhere--on trees, lawn furniture, cars, trailers, outdoor grills, and many other surfaces. "While adult spotted lanternflies die off after the first few cold snaps, their egg masses can survive winter weather," Leach said. "The arrival of spring signals the emergence of a new generation."

Finding ways to reduce the number of new births in spotted lanternfly populations is one of the projects Julie Urban, associate research professor of entomology, is spearheading. Specifically, she wants to develop strategies that will disrupt the female's reproductive cycle by blocking the growth of bacteria that the eggs need to mature--in other words, spotted lanternfly birth control.

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In the lab: Julie Urban, associate research professor of entomology, left, and Heather Leach, former spotted lanternfly extension associate, examine images of a female spotted lanternfly's anatomy in Urban's lab in January 2020. Photo: Amy Duke

Another method to prevent the birth of spotted lanternflies was hatched from studies done between February and April in 2018 and 2019. These findings suggest that some insecticides containing paraffinic or mineral oils, which are commonly used in fruit systems to control soft-bodied insects, effectively destroy egg masses.

"Oils, when applied at the correct time and with good coverage, can offer some control of egg masses and have minimal effect on nontarget species," said Greg Krawczyk, a tree fruit extension entomologist and associate research professor. "The use of oils is a safe, environmentally friendly option that provides control of some egg masses that are not accessible for physical removal or smashing."

Despite its name, the spotted lanternfly is not a frequent or strong flyer, a weakness that may hinder its ability to travel long distances, at least by way of flight, according to Thomas Baker, Distinguished Professor of Entomology and Chemical Ecology, whose research group has been studying the pest's flight behaviors and dispersal patterns.

"We wanted to discover if there was any preferred directionality to these flights related to wind, visual landmarks, or anything else," he said. "We believed this information would give state and federal workers insight into where an infestation might spread in the future."

The researchers found that adult spotted lanternflies, both male and female, will crawl to the top of the nearest vertical surface and launch themselves into the wind to create level or gradually descending straight-line flight paths, usually 10 to 30 feet high and averaging 75 feet in length before landing.

The experiments also showed that, during flight, the lanternflies orient strongly to anything they can see nearby, including light poles, garbage cans, and tree trunks, which they gravitate toward. After landing, the pests immediately begin trying to feed, even on nonedible items, which suggests to the researchers that the lanternflies are taking to the skies in search of food.

As for its feeding preferences, scientists know that although Ailanthus altissima, commonly referred to as tree-of-heaven, is a preferred host, the spotted lanternfly can survive, develop, and reproduce without it. And the pest is not a lollygagger when it comes to feeding--once it devours its current meal, it moves on to the next open buffet, wherever that may be.

"We recognize the urgency of the situation and the need to act quickly to stop this pest before it establishes throughout the rest of the Mid-Atlantic and in other parts of the country," Leach said.

Management Techniques

Knowledge gained from research is guiding management strategies used by the state and federal Departments of Agriculture, growers, and nurseries. One of the most recent studies took place this past summer on six secluded acres in the Blue Marsh Lake Recreation Area in Berks County. It was a continuation and expansion of research carried out in 2019 at Norristown Farm Park in Montgomery County.

The overall goal of the Blue Marsh project was to explore the feasibility of controlling spotted lanternfly using areawide spray application techniques while minimizing negative impacts on nontarget organisms in the environment, noted Brian Walsh, an extension educator based in Berks County who, along with Roush, spearheaded the project.

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On the ground: Researchers, extension educators, and volunteers assembled at Blue Marsh Lake National Recreation Area in Berks County last summer to assist with a spotted lanternfly study. Photo: Michael Houtz

The study involved the evaluation of two biopesticides using ground and aerial applications over several weeks compared to a single application early in the season of a synthetic insecticide containing the active ingredient dinotefuran, a systemic insecticide that is taken up by plants.

Preliminary findings indicate that foliar application of an insecticide containing dinotefuran timed to the spring egg-hatch period could help reduce satellite populations of the pest, with minimal impact on nontarget species such as soil insects and pollinators.

The experiments also suggest that the effectiveness of biopesticides containing Beauveria bassiana, a native soilborne fungus that causes disease in insects, could be affected by the life stage of the spotted lanternfly and environmental conditions. These factors will be a focus of future experiments, Roush noted.

Leading up to the Blue Marsh study, researchers tested more than 20 different insecticides for their efficacy and residual activity against nymphs and adults at Peiffer Turf Farm at Penn State Berks. In this experiment, led by Dave Biddinger, research associate and professor of entomology at Penn State's Fruit Research and Extension Center, scientists sprayed plants and then placed field-collected spotted lanternflies in net cages surrounding the trees.

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Ranger Brianna Treichler talks with Nina Jenkins, Penn State senior research associate in entomology, at Blue Marsh Lake National Recreational Area in Berks County. Photo: Michael Houtz

The experiments were replicated across different products, plant hosts, and life stages of the spotted lanternfly, leading to a breadth of understanding on optimal chemicals that destroy the pest. The findings, shared with stakeholders and outlined on the Penn State Extension website, demonstrated that more than 14 insecticides effectively reduced spotted lanternfly populations on various hosts, including grape, peach, tree-of-heaven, and maple trees.

As the scientists continue to test insecticides against spotted lanternfly, they are evaluating slower-acting compounds that may provide better long-term control or are safer to pollinators.

Vineyards at Risk

There is a lot at stake, especially for Pennsylvania's grape and wine industries, which pour an estimated $4.8 billion annually into the state's economy through employment, wine sales, tourism, tax revenue, and related avenues, according to the National Association of American Wineries. There are more than 300 in-state wineries and vineyards.

To understand the pest's potential to cause pandemonium in vineyards, Urban and Leach, along with Erica Smyers and Andrew Harner, doctoral candidates in entomology and plant science, respectively; Michela Centinari, assistant professor of viticulture; and Lauren Briggs, research technician, are among the scientists who have established satellite research sites at vineyards in the spotted lanternfly quarantine zone.

They are documenting how feeding damage caused by the insect affects grapevine health and the quality and quantity of the fruit. They also aim to establish economic thresholds for growers to determine when to take action to protect their crops.

At Karamoor, the research focuses on using tree-of-heaven as a "food truck" to lure the spotted lanternflies away from the grapevines. Potted tree-of-heaven treated with a systemic insecticide were placed around the vineyard. The trick worked. The treated plants killed more than 25,000 spotted lanternflies that otherwise would have fed on the grapevines.

"It was encouraging to see that we can manipulate numbers of spotted lanternfly and their attraction to a given location," Leach said. "The next steps are to optimize placement and add other nonvalued species that they like to feed on."

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In the field: In October 2019, Rep. Chrissy Houlahan, left, tours the Center for the Agricultural Sciences and a Sustainable Environment at Penn State Berks, where researchers are studying methods to stop the spotted lanternfly. With her is Dr. R. Keith Hillkirk, former chancellor of Penn State Berks, and Julie Urban, associate research professor of entomology. Photo: Katie Quinn

Vynecrest Vineyards and Winery, the oldest existing wine vineyard in Lehigh County, is also working with Penn State. Like Karamoor Estate, the pest's arrival at Vynecrest in 2017 was insidious. "Then in 2018 and 2019, we began to see high levels of spotted lanternflies on our plants and laying eggs, as many as 100 spotted lanternflies per grapevine," said John Landis, a partner in the business, which produces 22,000 gallons of wine, or 9,000 cases, a year.

Consequently, about 10 percent of the vineyard's grapevines were killed. The loss of those grapevines, the cost to replace them, and the investment in insecticide applications have been an "expensive burden" on the business, he noted.

In 2020, with help from Penn State, the business saw a decrease in the pest, thanks to scouting and controlled spraying. "We have been growing wine grapes for more than 40 years; the spotted lanternfly has been the greatest threat to our vineyards," Landis said. "Penn State has been very supportive in conducting research and scouting. This pest is spreading to other states. With no natural predators, it will have a big impact on vineyards and orchards."

Animal Allies

Finding predators that already live in the United States would be an excellent biological control option and useful in guiding management practices, contends Kelli Hoover, professor of entomology. She and Anne Johnson, a doctoral candidate in entomology, are investigating the potential for native birds and insects to feed on the spotted lanternfly.

The team, which also includes Margaret Brittingham, professor of wildlife resources, and Allison Cornell, assistant professor of biology at Penn State Altoona, will study spotted lanternfly specimens that have been raised in a quarantined laboratory with tree-of-heaven as their food source. Researchers will analyze the insects for chemical compounds present during each life stage while examining tree-of-heaven sap as the potential source of these chemicals.

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A juvenile eastern bluebird holds a spotted lanternfly in its beak. Photo: Debra Bangasser Waxler

Suet containing ground-up spotted lanternfly adults that have fed on tree-of-heaven, which contains compounds that may create a bitter taste to birds, or grapevines, which are not bitter, will be placed side by side in feeders attached to trees. Video cameras will record birds that visit the feeders and the suet cake they prefer.

The investigators also enlisted the help of bird watchers, who are posting reports, videos, and photos of birds they see feeding on spotted lanternflies. One month into the project, Johnson had already received more than 800 reports.

A second phase of the research will investigate the potential for native insects to suppress spotted lanternfly populations. Hoover said there have been many reports of insects, including praying mantises and assassin bugs, feeding on spotted lanternflies.

Educating Homeowners

Penn State Extension provides a bevy of information on effective management techniques for homeowners struggling to contain spotted lanternfly populations on their properties, with updates provided on the extension website and in printed pieces.

One of the many homeowners who have turned to Penn State Extension for help is Angie Burke of Berks County. "I first noticed them on a maple tree in my front yard in 2018," said Burke, who lives in a residential development with many maple trees. "When walking my dog, I started noticing them on my neighbors' maple trees. I thought to myself, 'This is not good.'"

And it was not. In the years since, the pests have taken up residence in the maple, birch, and willow trees that adorn her property, prompting her to look to Penn State Extension for guidance on the use of sticky bands and systemic insecticides.

"These tactics knock them down, but they come back--there is a second, third, and fourth wave," she said. "Homeowners have to realize this is not like having ants in your kitchen that you can eliminate with a treatment or two. You must keep up with a maintenance program and everyone must do their part. Otherwise, spotted lanternflies will consume everything."

The nuisance factor takes it to a whole other level, she added. "They're everywhere," she said. "i've found them in my pool, in my garage, and on my patio furniture. I have even had them jump on me when entering my basement. It's like being in a haunted house--these things jump out from anywhere at any given time."

Knowledge Gaps

While much has been learned, there are information gaps that need to be filled, noted Urban. Current and future studies are determining how far spotted lanternflies can move to infest vineyards, Christmas tree farms, ornamental nurseries, and backyards, and studying the use of insecticide-treated nets as a control measure.

In the meantime, Penn State Extension educators, staff, faculty, and volunteer Master Gardeners and Master Watershed Stewards regularly engage with the public, government officials, growers, and other industry stakeholders to provide research and management updates. Additionally, extension hosts a website, extension.psu. edu/spotted-lanternfly, and a newsletter, both of which spotlight the pest.

"There are no easy answers when it comes to the spotted lanternfly, and we understand that's hard for people to hear," Urban said. "Good research takes time--and funding--but we are making discoveries every day."

By Amy Duke