eDNA Sampling Detects Early Colonization of Spotted Lanternfly Lycorma delicatula Better Than In-Person Scouting in an Urban Landscape

Abstract

Spotted lanternfly (SLF), Lycorma delicatula, is an invasive insect species rapidly colonizing the Northeast and Midwest USA. Environmental DNA (eDNA) can provide early detection and insight into the distribution of this new pest. SLF is often found in association with tree-of-heaven (Ailanthus altissima), near rail lines, and in disturbed areas; however, further data is needed to understand how these factors increase the risk of spotted lanternfly detection. Over 2 years, we sampled for spotted lanternfly using two methods: in-person scouting and eDNA sampling over 45 sites in Cleveland, OH during peak SLF activity (May–October). SLF detection at these sites was modeled against expected significant variables for SLF spread, including proximity to rail lines, tree of heaven density, and other landscape attributes. Our results showed eDNA outperformed visual detection by a magnitude of 2× (average of 20.4% scouting samples were positive compared to a mean of 46.3% eDNA samples). Of the factors analyzed, only tree of heaven presence at sites correlated with the likelihood of SLF eDNA detection. Sites with tree of heaven were 1.87 times more likely to test positive for SLF eDNA when compared to sites without tree-of-heaven. The results suggest the spread of SLF depends on host plant availability; however, further evaluation is needed to understand the movement of SLF into different urban ecosystems. The use of eDNA remains promising to pair with visual detection when there are low populations of SLF.