Impacts of short-term feeding by spotted lanternfly (Lycorma delicatula) on ecophysiology of young hardwood trees in a common garden

Effects of long-term feeding by spotted lanternfly (Hemiptera: Fulgoridae) on ecophysiology of common hardwood host trees

While the invasive spotted lanternfly, Lycorma delicatula (White) [Hemiptera: Fulgoridae], continues to expand its range in the United States, there remains a knowledge gap regarding the economic threat that this pest presents to forest ecosystems and production nurseries. L. delicatula uses several common hardwood trees as hosts and a previous study found that short-term feeding can reduce growth of young maple saplings. Herein, long-term feeding over 4 consecutive seasons significantly reduced diameter growth and below-ground starch storage in roots of young silver maples (Acer saccharinum L.), weeping willows (Salix babylonica L.), river birches (Betula nigra L.), and trees of heaven (Ailanthus altissima [Mill.] Swingle) in response to L. delicatula feeding pressure in a density-dependent manner. In Year 3 when feeding pressure was the lowest, silver maple and willow recovered with greater diameter growth than in Year 2. Nutrients essential for photosynthesis and growth (iron, sulfur, and phosphorus) were reduced in leaves of all tree species compared to controls in the second year. This 4-yr study represents a worst-case scenario in which L. delicatula fed on the same trees for 4 consecutive growing seasons. In the wild, population numbers can vary greatly from year to year on individual trees and they move frequently among hosts (until autumn when they settle on A. altissima or other late-season hosts that have not yet senesced). Thus, we would not expect negative impacts of unconfined L. delicatula in natural settings on forest or ornamental trees to be as marked as reported here.

Using community science to identify predators of spotted lanternfly, Lycorma delicatula (Hemiptera: Fulgoridae), in North America

Spotted lanternfly, Lycorma delicatula (Hemiptera: Fulgoridae), is an invasive insect that was first detected in the United States in 2014 and feeds on a wide variety of plants, with economic impacts on the agricultural, ornamental, and timber industries. Part of what likely contributes to the success of L. delicatula in its invaded range is that it appears to be chemically defended by sequestering toxins from its host plant(s), which may deter predators in the introduced range. To determine the identity and behavior of North American predators that feed on spotted lanternfly, we performed a community science study in which we asked members of the public to contribute reports of animals feeding on spotted lanternfly through a Facebook page. The largest group of reported predators was arthropods followed by birds. Araneae was the arthropod order with the most reports and Phasianidae was the most frequently reported bird family. Using Pearson's χ2 tests, we also identified significant relationships between predator behavior and (1) taxonomic group of the predator, (2) L. delicatula life stage, and (3) host plant L. delicatula was observed on. These results can help to guide future research on predator host shifting to spotted lanternfly and potential for biocontrol as a management tactic.

Dendrochronology reveals different effects among host tree species from feeding by Lycorma delicatula (White)

The spotted lanternfly, Lycorma delicatula (White) (Hemiptera: Fulgoridae), was first detected in the United States in Berks County, Pennsylvania, in 2014. Native to China, this phloem-feeding planthopper threatens agricultural, ornamental, nursery, and timber industries in its invaded range through quarantine restrictions on shipments, as well as impacts on plants themselves. The long-term impacts of L. delicatula feeding on tree species have not been well studied in North America. Using standard dendrochronological methods on cores taken from trees with differing levels of L. delicatula infestation and systemic insecticidal control, we quantified the impact of L. delicatula feeding on the annual growth of four tree species in Pennsylvania: Ailanthus altissima, Juglans nigra, Liriodendron tulipifera, and Acer rubrum. The results suggest that L. delicatula feeding is associated with the diminished growth of A. altissima, but no change was observed in any other tree species tested. The results also suggest that systemic insecticides mitigate the impact of L. delicatula feeding on A. altissima growth.

Approach to surveying egg masses of the invasive spotted lanternfly (Hemiptera: Fulgoridae)

For the invasive planthopper Lycorma delicatula, eggs are an attractive target for surveys and management because they can persist from September through May before hatching, and remnants may be retained for years after hatching. Efforts to control this invasive species, though, are hampered by imperfect detection, which impedes early detection and rapid response, obscures management impacts, and reduces the fraction of egg masses that can be managed. To estimate egg mass detectability, we conducted 75 duplicate surveys of 20 × 5 m plots located in forest edges and disturbed areas frequently used by L. delicatula. We fit binomial mixture models and investigated the effects of weather, height (above or below 3 m), season (winter or spring), and basal area of trees within plots, finding no evidence that these factors affected detection rate, which averaged 52.2%. We additionally estimated the fraction of L. delicatula eggs that were laid above 3 m, putting them outside of easy reach for management by scraping or targeted ovicide application. This proportion varied with basal area of trees within plots, and the estimated mean was greater than 50% across the range of basal areas in study plots. Finally, we found that counts of old egg masses correlated with counts of new egg masses laid the year prior, but the ability to infer prior years' egg mass counts was limited. Together, these findings inform managers delimiting L. delicatula populations in mixed habitats and those treating egg masses to slow population growth and spread of this pest.