Post-release genetic structure and parasitism performance of Anastatus orientalis, an egg parasitoid introduced for biological control of Lycorma delicatula in South Korea

Understanding the genetic composition and field performance of introduced biological control agents is critical for assessing long-term effectiveness. Anastatus orientalis Yang and Choi (Hymenoptera: Eupelmidae), an egg parasitoid of the invasive spotted lanternfly, Lycorma delicatula White (Hemiptera: Fulgoridae), was introduced from China and released in South Korea between 2015 and 2019. Yet post-release genetic and ecological evaluations have been limited. Between 2018 and 2024, we conducted broad-scale surveys across South Korea to assess haplotype diversity and parasitism rates. Anastatus orientalis was detected at 43 of 46 sites from which L. delicatula egg masses were collected as well as at two additional sites (Namyangju, Daejeon) via only adult collecting, indicating establishment within the surveyed network. Partial mitochondrial COI analyses of 596 individuals (390 from Korea, 206 from China) revealed two haplotypes in Korea versus seven in China, with Korean haplotypes clustering with northern Chinese lineages. Spatio-temporal variation in haplotype composition suggests possible additional or undocumented introductions, although uneven sampling and spatial demographic processes cannot be excluded. Parasitism rates across 46 sites with quantitative data ranged from 0.0–97.1% (two additional sites yielded adult wasps but lacked egg mass data for parasitism estimation) and were not significantly associated with haplotype composition or distance from the nearest release site, but showed a weak positive association with host availability (number of egg masses per site). These findings provide insights into post-release establishment dynamics and highlight the importance of continued genetic and ecological monitoring in classical biological control programs.