Lycorma delicatula (White) (Hemiptera: Fulgoridae), spotted lanternfly (SLF), is an invasive agricultural pest native to China.1,2 This pest has invaded South Korea, Japan, and the United States, causing serious problems in agricultural and forest landscapes.1,3−6 In South Korea, SLF was first reported in 2004, and the area of infestation increased over 8,000-fold from 2006 to 2010.7–10 In the US, it was first detected in Berks County, Pennsylvania in 2014. Since then, SLF infestation has expanded to three different states including New Jersey, Virginia, and Delaware by 2019.3,6 Furthermore, recent modeling studies predicted that SLF would become a global threat, in which Asia, Oceania, South America, North America, Africa, and Europe might be susceptible to its invasion based on their temperature profiles.1,6
SLF has a broad range of host plants which facilitate the successful establishment of this pest in new areas. It is known to feed on more than 70 plant species including various ornamental and fruit trees such as apples (Malus spp.) (Rosaceae), grapes (Vitis vinifera) (Vitaceae), and peaches (Prunus persica) (Rosaceae), as well as other woody trees such as black locust (Robinia pseudoacacia) (Fabaceae), willow tree (Salix spp.) (Salicaceae), and Korean evodia tree (Evodia danielli) (Rutaceae).4,10 Moreover, in invaded areas including South Korea and the US, SLF is known to switch hosts during its development, with the range of host plants becoming narrower through its univoltine life cycle.10 After emerging from eggs starting in May, its nymphs feed on a variety of host plants from 81 taxa worldwide.11–14 As they start to develop into adults from late July, SLF adults feed on a narrower range of host plants of 47 taxa. Finally, the adults oviposit egg masses on hosts belonging to 28 taxa between late September and November.4,10−12
Among various host plants of SLF, Ailanthus altissima (Simaroubaceae), the tree-of-heaven, is native to Southeast Asia and known as one of the major host plants in China, South Korea, and the US.4,15 Furthermore, A. altissima has already been introduced and established in multiple continents including East Asia, Europe, and North America, making it readily available for SLF even in areas in which the insects have yet to invade.16 Previous studies indicate the importance of A. altissima as a major host plant of SLF. First, A. altissima is known as the most preferred and suitable feeding host of SLF along with V. vinifera. Lee et al.15 observed a high survivorship of SLF nymphs and adults on A. altissima as well as their preference for this plant compared with different ornamental and fruit trees. Second, A. altissima was reported to be one of the most preferred oviposition sites. 4,10 Liu et al.17 found that A. altissima was one of the four oviposition host plants favored by this insect along with black cherry, black birch, and sweet cherry in Pennsylvania, US. Finally, A. altissima contains high concentrations of cytotoxic alkaloids, which SLF may utilize for their own defence against predators.4,12,18
Therefore, it is essential to understand the abundance and distribution of SLF on A. altissima in order to develop effective management programs. Previous studies demonstrated that SLF adults shift host plants from woody and non-herbaceous plants, on which the insects feed as they emerge in July, towards A. altissima between September and November.11,12,17 In addition, SLF adults are known to mate and reproduce during this period utilizing multiple substrates including A. altissima for oviposition.19 However, the dispersal patterns of SLF adults within and among A. altissima patches after their arrival have not yet been investigated. Especially, given that SLF is a univoltine species in the invaded areas, investigating the dispersal patterns of this pest on A. altissima and characterizing their oviposition pattern can provide valuable information for its management.
In our study, we surveyed the abundance and distribution of SLF on A. altissima patches from September to November when SLF adults are known to shift their host plant to A. altissima and lay eggs.12,17 In particular, to investigate the dispersal pattern of SLF within and among different A. altissima patches, we tracked the movement of SLF using a fluorescent marking system (FMS).20,21 Then, in December, we surveyed the location, number, and size of SLF egg masses on A. altissima trees and analyzed the oviposition patterns relative to the traits of A. altissima surveyed.