A study of the spotted lanternfly led by master’s student Benjamin Rohr may shed light on ways to control this emerging threat.
Benjamin Rohr, a graduate student in environmental studies, is studying the invasive spotted lanternfly at The Woodlands, a large cemetery a stone’s throw from Penn’s campus. The pest was first spotted there last year, in the wilder portions of the property’s periphery, where SEPTA and Amtrak trains pass regularly.
By the chain link fence lining the southern border of The Woodlands Cemetery property, Benjamin Rohr attempts to avoid brushing against poison ivy as he approaches a large black walnut tree. “Oh good, it’s still up!” he says, assessing a wide, sticky band encircling the trunk, now covered with the bodies of dozens of small insects. “No SLFs I don’t think,” he observes, using a shorthand for spotted lanternfly, an exotic bug that is poised to wreak havoc on farms, wineries, and forests in the mid-Atlantic states.
Rohr, a student in Penn’s Master of Environmental Studies program, is embarking on his capstone project to culminate his degree. The premise of his experiment is straightforward: to determine the types of trees the lanternfly prefers beyond its known affinity for ailanthus, commonly known as tree of heaven, dozens of which sprout enthusiastically in several groves at The Woodlands and elsewhere around the region.
First discovered in the U.S. in Berks County, Pennsylvania, five years ago, the spotted lanternfly has quickly spread. Though they can’t fly, the insects can hop 20 meters or more. (Photo: Pennsylvania Department of Agriculture)
“Maybe they prefer cherry over ash or maple instead of willow,” says Rohr. “If we find these finer-grain preferences, and land managers on Penn’s campus or with the Natural Lands Trust are replanting, maybe they wouldn’t choose as many of those species that are lanternfly attractors.”
The stories of the ailanthus and spotted lanternfly (Lycorma delicatula) run in parallel, albeit a few centuries apart. Ailanthus, a tree species native to China and Taiwan, was introduced to the United States in 1784 by William Hamilton, an avid plant collector who inherited a sprawling estate along the Schuylkill River: The Woodlands. The species spread rapidly, outcompeting native species. They’re now widely considered “trash trees,” often targeted for removal.
Meanwhile, the spotted lanternfly’s introduction into the U.S. appears to have been accidental. The bugs, which can fly but more often hop, up to 20 meters or more in a go, were first seen in 2014 in Berks County, Pennsylvania, and quickly extended their range. They’re known to feed on 70 species of tree and vine, 30 of which occur in Pennsylvania. Using their piercing mouthparts, they feed on tree sap, leaving plants weak and vulnerable to secondary infections. Currently, 13 counties in Pennsylvania are under quarantine for the lanternfly, and the U.S. Department of Agriculture’s Animal Plant Health Inspection Service (USDA APHIS), in partnership with Penn State Extension and the Pennsylvania Department of Agriculture, have kicked into high gear to keep the species under control.
For Rohr, who just finished his first year in the MES program, the lanternfly wasn’t on his radar until the spring semester, when he took a course in urban forestry taught by Sally Willig and Lara Roman. When an alternative capstone project didn’t pan out, Willig invited him to attend a meeting headed by Penn’s Facilities and Real Estate Services department focused on urban forest management. The Woodlands’ Facilities and Landscape Manager Robin Rick was also attending, and mentioned that she was working with USDA APHIS to manage what appeared to be an emerging infestation in parts of the property.
Rather than counting insects in the field, Rohr is taking a photo of each of the sticky bands when he removes them from the trees to evaluate later.
“I knew about the threat of the spotted lanternfly from reading different publications from Penn State and hearing about it in different horticultural forums,” says Rick. “I started to keep an eye out. And around the same time, we were approached by the USDA as a property owner in the city to participate in their efforts to control and stop the spread of the lanternfly. So that really raised our awareness.”
Following the FRES meeting, Rohr reached out to Rick, who was enthusiastic about a project on The Woodlands property. Together they formulated the experiment. At four different areas where ailanthus grow at The Woodlands, Rohr is affixing wide, sticky bands—in essence, big pieces of sturdy tape placed stick-side out—on one ailanthus tree. Then, within the 20-meter hopping range of the lanternfly, Rohr and Rick identified another tree species that the insects are known to feed on, and will monitor those trees as well.
To avoid catching birds, Rohr overlays the sticky band with chicken wire. The Woodlands will also post signage to inform visitors about the project. Rohr will switch out the bands once a week until the species goes dormant, likely around December, and count the lanternflies he catches on each tree.
Once his data collection and analysis is complete, Rohr hopes to offer up his findings as a guide for land managers aiming to mitigate the impact of the lanternfly.
The USDA has visited The Woodlands to note the location of ailanthus trees on the property and set up a treatment plan. The survey, Rick says, identified 274 saplings under 1 inch in diameter, 36 trees between 1 and 6 inches in diameter, and 45 larger trees greater than 6 inches in diameter. A couple are in the heart of the cemetery, but most sit along the fence line, bordering the Amtrak and SEPTA rail lines or the VA hospital. Rick says the first signs of lanternfly came from near the train tracks.
In Rohr’s first time out checking the bands, he found only five lanternflies—unsurprising since late May is when the nymphs generally emerge.
Once the season revs up, Rohr expects to find many more, and he’ll be tracking what happens after USDA treatment later this summer—herbicide for the smaller trees and pesticide applications on the larger ones.
“There are a lot of really old mature trees at The Woodlands, some have been there for centuries,” says Rohr. “These massive maples or black walnuts could drop branches if they get sick. So just from a safety perspective, it will be interesting to get a sense of how much this pest could damage The Woodlands, and how Robin, the USDA, and others might mitigate this.”
Eventually, Rohr would like to pull together his findings into a user-friendly format to serve as a guide for other land managers. And Rick hopes to spread the word to the West Philadelphia community that lives near or recreates in The Woodlands.
“Learning more about this bug is going to rely on collaboration,” Rick says. “Large institutions like Penn and SEPTA will need to work together with smaller ones like us as well as community members to understand how [the lanternflies] are moving through the area and take efforts to slow and stop them.”
At four areas around The Woodlands, Rohr will be checking weekly to see how many lanternflies he finds. The insect prefers ailanthus trees, but also feeds on dozens of other species.
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