Toxin sequestration by spotted lanternfly (Lycorma delicatula) and its effects on predator-prey interactions

The invasive planthopper, spotted lanternfly (SLF), has established populations in 15 states in the U.S. since 2014 and represents a major economic threat to the grape, hops, and ornamentals industries. Among its host plants, SLF shows a strong preference for tree of heaven (Ailanthus altissima). A. altissima produces several toxins, including quassinoids (degraded triterpene lactones of the Simaroubaceae plant family) which have a bitter taste and confer insecticidal, herbicidal, and anticancer properties. Using quassinoid standards isolated from A. altissima, we quantified six of these compounds in different life stages and specific tissues of SLF to document the phenology of sequestration across the lifecycle and specific storage locations within the insect. Quassinoid concentrations were highest in adults and eggs; in the adults, concentrations were highest in the gut and salivary glands, followed by the ovaries and cuticle. Through > 1,000 field reports from a community science project and several predator-prey interaction experiments, we found that birds preferred SLF that fed on grapevines or other host trees compared with those fed on A. altissima, while arthropod predators showed no preference. Birds were more likely to pull the wings off SLF adults before consuming them, possibly in response to the high toxin concentrations in the cuticle. Sequestration of quassinoids and perhaps of other toxins (e.g., alkaloids) from tree of heaven can act as an effective defense against vertebrate predators.