Exploring Chemically Mediated Interactions Between Spotted Lanternfly, Lycorma delicatula, and Its Host Plants in the Mid-Atlantic Region of the United States

Abstract

Spotted lanternfly, Lycorma delicatula (Hemiptera: Fulgoridae), is a polyphagous phloem feeding planthopper introduced to the United States in 2014. Now established in 19 states, its aggregations, persistent feeding, and honeydew threaten specialty crops, especially wine grapes. Management often relies on insecticides and removal of tree-of-heaven (Ailanthus altissima), a preferred host from which L. delicatula sequesters quassinoids for chemical defense. Yet how volatile semiochemicals and sequestration dynamics shape behavior and inform management remains unresolved. This dissertation integrates behavioral ecology, analytical chemistry, and transcriptomics to connect mechanisms with management. Chapter I reviews invasion biology, crop risk, and host phytochemistry-based hypotheses. Chapter II evaluates plant-derived semiochemicals as repellents: vineyard assays showed lavender essential oil repelled adults in early fall, with efficacy contingent on temperature, dose, and vine phenology. Chapter III investigates sequestration of the quassinoid ailanthone using in situ sampling of A. altissima phloem, actively feeding adults, and honeydew. Subsequent LC-MS/MS analysis revealed that ailanthone levels in the insect body exceed those in phloem sap and honeydew. A more polar, earlier-eluting feature consistent with glycosylated ailanthone also appeared in some honeydew, indicating conjugation as a route to excretion during high ailanthone ingestion. In host-transfer trials, adults retained ailanthone up to 14 days without A. altissima. Chapter IV develops a host-free liquid-diet to deliver allelochemicals such as ailanthone. Third and fourth instar nymphs survived longer on a mixed-sugar diet than on a sucrose diet with amino acids and vitamins. Administration of ailanthone increased third-instar consumption without affecting survival, suggesting the compound acts as a feeding stimulant. Chapter V investigates host-dependent and sex-biased gene expression profiles of L. delicatula. Differential gene expression was substantially increased in males over females when fed on grapevine and A. altissima, with transporter and detoxification genes being upregulated on A. altissima. Chapter VI proposes a model of how L. delicatula may acquire and transport ailanthone, and how the compound could be compartmentalized and retained across host shifts. Together, these results clarify SLF-host chemical ecology and support behaviorally and biochemically informed integrated pest management.