Development of the First Cytochrome Oxidase I Barcode and Evidence for a Single Haplotype Associated with the Recent United States Invasion of the Pasture Mealybug Heliococcus summervillei (Hemiptera: Pseudococcidae)

Heliococcus summervillei is an emerging invasive mealybug that causes severe dieback in grasses in pastures and turfgrass landscapes. It is widespread in Australia and has recently been detected across the Caribbean, Mexico, and the United States. Accurate mealybug identification is challenging because of cryptic and overlapping diagnostic characters and limited taxonomic expertise and literature, making molecular tools essential for regulatory diagnostics and management. We developed the first Cytochrome Oxidase I (COI) sequences for morphology-based Type A and Type B variants of H. summervillei and used them to examine mitochondrial variation across available populations. COI sequences reveal approximately a 10% mitochondrial split between the Type A and Type B variants. Phylogenetic, haplotype network, and genetic distance analyses show that all Type B populations share a single haplotype associated with a recent invasion of the United States and Australia. Type A in Barbados contains two closely related haplotypes that may represent a historically stable mitochondrial variant corresponding to the holotype's morphological description. Together, these results establish the first COI reference library for H. summervillei, resolve mitochondrial lineage structure, and provide a practical tool for rapid identification and timely regulatory and pest management responses.