Feeding habits of spotted lanternflies in a forest of eastern Pennsylvania

Student research blog by Jon Krupnick, Earth & Environmental Science Major, Lehigh University.

Photo: Jon Krupnick

The spotted lanternfly (Lycorma delicatula) is an invasive species in the Fulgoridae family of insects. Native to eastern China, India, and Vietnam, it invaded eastern Pennsylvania in 2014 (Liu et al., 2017). Spotted lanternflies feed on sap from a range of plant species and pose a significant threat to agriculture and native ecological communities (Liu et al., 2017). Much research has focused on agricultural impacts; however, little is known about their potential effects on forested ecosystems. While spotted lanternflies are known to prefer the tree of heaven (Ailanthus altissima), a species from their native range, they have also been observed feeding on at least 70 other species (Kim et al., 2011; Dara et al., 2015). 

Observing spotted lanternflies.

To help anticipate potential impacts of this new invasive species, I collected baseline ecological data assessing the lanternfly’s feeding preferences in the forest of South Mountain near Bethlehem, Pennsylvania. Specifically, I assessed 1) whether different life stages of the spotted lanternfly feed on different species and 2) whether their feeding reflected the abundance and availability of plant species in the surrounding forest or real preference for particular plant species.

To do this, I conducted repeated surveys of ~75-acres of forest (Figure 1) from early July through the end of August 2020, recording the density of spotted lanternflies on trees, vines, and shrubs. Host plant species were marked and numbered with flagging tape, coordinates were recorded using Gaia GPS, and locations were plotted in Arcmap (Figure 2). Each day a subset of the affected plants were visited, and changes in the number of spotted lanternflies of different life stages were recorded. To assess whether spotted lanternflies were targeting particular plant species at greater rates than their abundance in the surrounding forest, I also identified the three nearest, non-affected plant species at each of the trees, shrubs, and vines used by the lanternflies.

Figure 1. Location of the 75 acres of forest on South Mountain near Lehigh University where this study was performed. The entire area was hiked weekly during summer of 2020, focusing on a different subsection each day.
Figure 2. Location of plant species used by spotted lanterflies on South Mountain in the summer of 2020.

Lanternflies were observed feeding on a total of 186 individual plants (Figure 2) representing 21 different plant species. Results indicate clear feeding preferences, with substantial differences across life stages (Figure 3). Earlier life stages fed on a broad range of species, but as the lanternfly progressed through its life stages it increasingly focused on tree of heaven, with a small portion of adults feeding on black walnut and grape (Figure 3).

Figure 3. Relative abundance of spotted lanternflies of different life stages using different plant species on South Mountain in summer 2020.

More detailed information on the shifting trends of feeding preference, and actual numbers of spotted lanternflies, can be found in Figure 4. Decreasing trends of spotted lanternfly use were observed during the late summer for grape, silverbell, bittersweet, and devil’s walking stick. The use of black walnut by spotted lanternflies peaked during mid August when the 4th instar nymphs were at their maximum abundance. The vast majority of adult lanternflies used tree of heaven. 

Figure 4. Actual numbers of spotted lanternflies feeding on native and invasive plant species on South Mountain over 8 weeks from July until late August.

Plant species targeted at higher rates than what would be expected given their availability in the forest included grape (Vitis sp.), tree of heaven, black walnut (Juglans nigra), devil’s walking stick (Aralia spinosa), and oriental bittersweet (Celastrus orbiculatus) (Figure 5). Some species, including grape and tree of heaven, were clearly used at higher rates than their abundance in the forest, suggesting real preferences for these food sources by the spotted lanternfly. Other trees like oak were found to host lanternflies but at much lower rates than their availability in the forest would suggest, suggesting that the insects tend to avoid these.

Recent research has demonstrated that spotted lanternflies sequester toxins from tree of heaven as a defense against predation (Song et al. 2018). Several targeted plant species on South Mountain, like black walnut, oriental bittersweet, and devil’s walking stick also contain toxic chemical compounds, and perhaps spotted lanternfly are using them in a similar way. Additional research is needed to better understand spotted lanternfly feeding preferences and to determine potential relationships with the chemical content of host plant species.

Figure 5. The plot on the left shoes an estimate of the relative abundance of potential plant species that could be used by spotted lanternflies in the study area, as indicated by identifying woody plants nearby those used by spotted lanternflies, in addition to those actually used by the insects. The plot to the right shows woody species targeted at greater and lower frequencies than would be expected based on their abundance alone. Spotted lanternflies are clearly selecting some species and avoiding others. Cyan colors indicate tree species where spotted lanternflies were never observed.
Photo: Jon Krupnick

References 

Dara, S. K., L. Barringer, and S. P. Arthurs (2015), Lycorma delicatula(Hemiptera: Fulgoridae): A New Invasive Pest in the United States, Journal of Integrated Pest Management6(1), 20, doi:10.1093/jipm/pmv021.

Kang, C., H. Moon, T. N. Sherratt, S.-I. Lee, and P. G. Jablonski (2016), Multiple lines of anti-predator defence in the spotted lanternfly,Lycorma delicatula(Hemiptera: Fulgoridae), Biological Journal of the Linnean Society120(1), 115–124, doi:10.1111/bij.12847.

Kim, J. G., E.-H. Lee, Y.-M. Seo, and N.-Y. Kim (2011), Cyclic Behavior of Lycorma delicatula (Insecta: Hemiptera: Fulgoridae) on Host Plants, Journal of Insect Behavior24(6), 423–435, doi:10.1007/s10905-011-9266-8.

Lee, D.-H., Y.-L. Park, and T. C. Leskey (2019), A review of biology and management of Lycorma delicatula (Hemiptera: Fulgoridae), an emerging global invasive species, Journal of Asia-Pacific Entomology22(2), 589–596, doi:10.1016/j.aspen.2019.03.004.

Liu, H. (2017), Biology and natural enemies of the spotted lanternfly,Lycorma delicatula,in North America, 2016 International Congress of Entomology, 30–32, doi:10.1603/ice.2016.109022.

Malek, R., J. M. Kaser, H. J. Broadley, J. Gould, M. Ciolli, G. Anfora, and K. A. Hoelmer (2019), Footprints and Ootheca of Lycorma delicatula Influence Host-Searching and -Acceptance of the Egg-Parasitoid Anastatus orientalis, Environmental Entomology48(6), 1270–1276, doi:10.1093/ee/nvz110.

Song, S., S. Kim, S. W. Kwon, S.-I. Lee, and P. G. Jablonski (2018), Defense sequestration associated with narrowing of diet and ontogenetic change to aposematic colours in the spotted lanternfly, Scientific Reports8(1), doi:10.1038/s41598-018-34946-y.

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