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Appetite For Destruction

Penn State researchers and extension educators mobilize against an invasive pest that's taking a bite out of Pennsylvania.
Spotted Lanternfly (GH Photos / Alamy Stock Photo)

Spotted Lanternfly (GH Photos / Alamy Stock Photo)

By virtue of her profession--and her family's farm and produce stand--Emelie Swackhamer long has been connected to the local agricultural community in southeastern Pennsylvania. As autumn approached in 2014, Swackhamer, a Penn State Extension horticulture educator based in Montgomery County, began to hear rumors in farm circles that state officials had discovered a strange, new insect in Berks County, just a few miles from her family's farm.

"People were talking about it, but nobody knew what it was," she recalled.

A public announcement from the Pennsylvania Department of Agriculture in November of that year identified "it" as the spotted lanternfly, which never before had been found in the United States. The discovery of this invasive pest, which likely hitchhiked with shipped goods that originated in the insect's native range in Asia, quickly created a stir among growers and homeowners--and dictated how Swackhamer and colleagues would spend a large portion of their time over the next three-plus years (and counting).

As populations of the spotted lanternfly continue to grow, Penn State Extension educators and College of Agricultural Sciences researchers are looking for solutions and working with federal, state, and local agencies to help stop the insect's spread. Potentially at stake are Pennsylvania agricultural crops and forest products worth nearly $18 billion annually. The pest can also cause damage to high-value ornamentals in home landscapes and affect quality of life for residents.

A Pernicious Problem

After the lanternfly's discovery, the Department of Agriculture imposed a quarantine regulating the movement of plants, plant-based materials, and outdoor household items out of the quarantine area. Originally covering parts of Berks County, the quarantine by April 2018 encompassed all of Berks, Bucks, Chester, Lehigh, Montgomery, Northampton, Carbon, Delaware, Lancaster, Lebanon, Monroe, Philadelphia, and Schuylkill counties.

Swackhamer, her Northampton County-based extension colleague Amy Korman, and other Penn State specialists have spoken at scores of public meetings and industry workshops, authored articles and fact sheets, served as expert sources for news media stories, trained Penn State Extension Master Gardeners and other volunteers, and testified at General Assembly committee hearings.

Officials are worried about the threat the spotted lanternfly poses to the state's grape, treefruit, hardwood, and nursery industries. The pest does not attack fruit. Rather, it uses its piercing-sucking mouthparts to feed on sap from leaf veins or the woody parts of plants, such as grape vines and the trunks and branches of trees. As it feeds, the insect excretes a substance known as honeydew and inflicts wounds that weep with sap. The honeydew and sap can attract bees and other insects and provide a medium for the growth of fungi, such as sooty mold, which covers leaf surfaces and can stunt growth. Plants with heavy infestations may not survive.

The role of Penn State agricultural researchers and extension specialists--as part of the University's land-grant mission--is to bring science-based information to bear in solving emerging issues such as the spotted lanternfly. With a pest that is new to North America, these efforts must start at square one.

"The spotted lanternfly is a fascinating insect," said Korman, who is an entomologist by training. "Everything we learn about it is a new discovery. But the novelty also makes it frustrating, because we don't yet know enough about it to provide all the answers people are seeking."

To develop near-term solutions for managing lanternfly infestations, Korman and Swackhamer have tested the efficacy of various pesticides, both contact insecticides and systemic products that are applied to plants and kill the pests when they feed on the sap. They also have looked at "softer," lower-toxicity products. Although several chemicals showed promise, these experiments need to be replicated to confirm the results, according to Swackhamer.

"What we've found so far is that these insects are not difficult to kill, but we need to conduct more tests before we're comfortable giving formal, research-based recommendations," she said.

Swackhamer has also assisted Erica Smyers, a Penn State doctoral candidate in entomology, in conducting pesticide efficacy trials for use on grapes and apples. Researchers at Penn State's Fruit Research and Extension Center in Adams County are analyzing those data, with an eye toward seeking an emergency exemption from the U.S. Environmental Protection Agency to permit growers to use the most promising of these chemicals on fruit crops.

Biology Basics

Other Penn State scientists are conducting basic research to better understand spotted lanternfly biology and behavior--knowledge that they hope will eventually lead to tactics for managing it.

For instance, with support from the U.S. Department of Agriculture, Julie Urban, senior research associate in entomology, is studying the population genetics of spotted lanternfly in Pennsylvania. She explained that genotyping the insect can help in the effort to more precisely pinpoint the Asian origin of the lanternfly invasion and geographically narrow the search for natural predators and parasitoids.

"Novel genetic markers that are variable within the Pennsylvania population also will help us estimate the effective size of the current population, track population growth and movement, and detect subsequent invasions," she said.

Urban's team is also characterizing bacteria and fungi associated with spotted lanternfly and examining the microbial communities present in a frothy substance found at the base of ailanthus (tree-of-heaven) plants that show heavy lanternfly feeding damage and honeydew deposition.

Tree-of-heaven is one of the spotted lanternfly's highly preferred host plants, and Urban said the froth will be analyzed to determine whether it serves as an attractant to the pest. "We will aim to determine the source of any potentially attractive compounds, which may be helpful in developing spotted lanternfly lures," she said.

Tom Baker, Distinguished Professor of Entomology and Chemical Ecology, has used funding from USDA's Animal and Plant Health Inspection Service to study the mating behavior of spotted lanternfly. His laboratory has also collected data on how far the insects fly, what they orient to, what they land on, and so forth.

"Understanding the natural dispersal behavior could be helpful to state and federal agriculture officials and industry stakeholders in planning for where and in what direction the front edge of an infestation will spread," he said.

It Takes a Village

Until research bears more fruit, Swackhamer and Korman are helping stakeholders and homeowners understand what to look for and what to do if they find the spotted lanternfly or its egg masses.

"When I get calls from residents seeking advice, I talk them through an integrated pest management (IPM) thought process," Swackhamer said. "Start with mechanical approaches, such as scraping and destroying egg masses and swatting or vacuuming nymphs and adults, if practical. If you kill one female that could lay 100 eggs in its lifetime, you can have an impact on next year's population."

She also recommends conserving natural enemies, such as spiders and praying mantids, that prey on lanternflies. "If someone wants to use pesticides, they can try least-toxic options first, and they must take timing into account--not all methods will work on all life stages of the insect."

Korman urges homeowners and others not to let the "good-idea fairy" persuade them to use unconventional--and perhaps illegal--control methods that may be hazardous to themselves or harmful to the environment. "Our goal is to provide research-based recommendations, deliver IPM solutions, and promote pesticide safety. People can draw on Penn State Extension resources to help them address these issues," she said.

As the battle against spotted lanternfly rages on, Penn State Extension and Penn State's Department of Entomology are deploying state and federal funds to add staff members who will enhance extension programming. Entomologists are also seeking additional USDA grants to continue research on spotted lanternfly biology, the development of biocontrols such as natural enemies, and other topics related to this exotic and unusual pest.

But entomology professor Baker, who has studied insects for 40 years, explained that finding long-term solutions will take time and resources. "The spotted lanternfly is the weirdest, most pernicious insect I've ever seen."

Spotted Lanternfly Life Cycle

To manage a spotted lanternfly infestation, it's important to accurately identify the pest, and that means knowing what it looks like during its life stages--including the eggs.

Newly laid spotted lanternfly egg masses (which appear in the fall) have a gray, mudlike covering, which can become dry and cracked over time. Older egg masses may lose their covering and appear as four to seven columns of seedlike eggs, 30-50 eggs in total, approximately one inch long.

Nymphs begin to appear in late April through early May and develop through four stages called instars, all of which are wingless and incapable of flight. The first three nymphal stages are black with white spots. Fourth instars appear in early July and develop red patches on the body and are over a half inch long.

Spotted lanternfly adults appear in late July and are about one inch long and a half inch wide with wings folded. When at rest, they have grayish wings with black spots, and the tips are black with a dense series of lighter gray crossveins.

Diagram showing spotted lanternfly lifecycle timeline, and images of stages

Southeastern Pennsylvania Quarantine

A quarantine is in place to stop the movement of this pest to new areas and to slow its spread within the existing quarantine area. The quarantine affects a variety of plant, wood, and stone products.

Efforts are under way to ensure the spotted lanternfly is not present in other parts of the Commonwealth.

spottedlanternfly-quarentinemap2018.jpg
The 13 counties currently in the quarantine zone are Berks, Bucks, Carbon, Chester, Delaware, Lancaster, Lebanon, Lehigh, Monroe, Montgomery, Northampton, Philadelphia, and Schuylkill.

For more information about the spotted lanternfly and the quarantine, visit the Penn State Extension Spotted Lanternfly or the Pennsylvania Department of Agriculture websites.

The quarantine restricts the movement of certain articles, and may be expanded to new areas as further detections of the spotted lanternfly are reported and confirmed.

-- Chuck Gill