Invasion dynamics of the mealy fennel aphid Dysaphis foeniculus in South Korea: evidence for a novel host association with Heracleum moellendorffii

Abstract The mealy fennel aphid Dysaphis ( Dysaphis ) foeniculus (Theobald, 1923) is a globally distributed aphid associated with economically and ecologically important Apiaceae and is increasingly recognized as an invasive pest. Here, we document its occurrence in South Korea and provide evidence for a previously unrecognized host association with Heracleum moellendorffii Hance (Apiaceae), a widely used edible and medicinal plant in East Asia. Species identity was validated using an integrative taxonomic framework combining detailed morphological assessment of apterous viviparae with COI-based DNA barcoding and haplotype analysis. Morphological features were consistent with the diagnosis of D. foeniculus and neighbor-joining analysis recovered the Korean specimens within a strongly supported clade (Clade A; BS = 99%). Among 28 COI sequences analysed, 12 haplotypes were identified, which included one outgroup species, 11 Dysaphys spp., of which three were D . foeniculus . The most prevalent haplotype (Hap_1) was shared among populations in Australia, Egypt, Italy, Pakistan, South Korea, and the USA. Although the haplotype network represents an exploratory analysis due to limited sample size, it supports the phylogenetic evidence for cryptic dispersal pattern. Overall, these findings emphasize the importance of combining morphological and molecular diagnostics to detect early-stage aphid invasions, uncover novel host associations, and enhance biosecurity surveillance strategies.