Seasonal activity of spotted lanternfly (Hemiptera: Fulgoridae), in Southeast Pennsylvania

The spotted lanternfly, Lycorma delicatula (White, 1845), is an invasive species in the United States. This pest causes damage to vineyards and has the potential to negatively affect other crops and industries. Information describing the seasonal timing of life stages can improve its management. In 2019 and 2020, spotted lanternfly seasonal activity was followed weekly from spring egg hatch to the first hard freeze. Weighted mean timing of activity for each nymphal instar, early adults, late adults, total adults, and egg mass deposition are presented for 2019 and 2020 on Acer rubrum and 2020 on Ailanthus altissima. Logistic equations describing the percentage completion of each activity period on these hosts were fitted using a start date of 1 January to calculate accumulated degree days (ADD). For the adult and egg mass deposition periods, we additionally used a biofix of the date adults were first observed to calculate ADD. ADD from 1 January adequately estimated the timing of nymphal instars but ADD from observation of the first adult better estimated the timing of adult activity and egg mass deposition. Late adult activity and egg mass deposition periods appeared to be influenced by another environmental cue, such as day length. Maps of season-long ADD show that spotted lanternflies are unlikely to reach adulthood in colder regions of the northeast United States, and therefore may not establish there. We also report a strong seasonal trend in sex ratio on A. rubrum, where the population shifted from over 80% male to over 80% female in October.

Dispersion Patterns and Sample Size Estimates for Egg Masses of Spotted Lanternfly (Hemiptera: Fulgoridae)

The spotted lanternfly, Lycorma delicatula (White), is a new invasive pest in the United States. To quantify spotted lanternfly population abundance, one must understand this pest's dispersion pattern, that is, the spatial arrangement of individuals within a population. Spotted lanternflies overwinter in egg masses from late fall to May, making this life stage suitable for population assessments. We measured the dispersion pattern of egg masses at two types of sites: a suburban housing development, where we used individual trees as the sampling unit, and rural woodlots, where we used individual trees and also plots with 5.64 m radius as sampling units. Plots were the same size as those recommended for monitoring the gypsy moth, a well-studied pest with similar egg laying habit to the spotted lanternfly. Egg masses in both sampling units were counted up to a height of 3 m. With trees as the sampling unit, egg masses were aggregated in 12 of 20 rural sampling universes, randomly dispersed at 6, and completely absent at 2. Similar patterns were seen when using the 5.64-m radius rural sampling units and for suburban sampling universes. We calculated sample size requirements for a range of mean densities at a precision of 25 and 30%. Additionally, the vertical distribution of egg masses was characterized on the invasive tree of heaven [Ailanthus altissima (Mill.) Swingle], a preferred host for spotted lanternflies. For small trees, there was a positive relationship between number of egg masses in the bottom 3 m of the tree and the total count.