Identification and molecular characterization of aphid species damaging hazelnut trees distributed in Artvin

This study aimed to identify aphid species on hazelnut (Corylus avellana) trees in Artvin and then to characterize them at the molecular level. Field surveys conducted in the districts of Borçka, Kemalpaşa, Arhavi, and Hopa revealed that the species Myzocallis coryli was present in all regions at low densities (1–5 individuals), remaining well below the economic damage threshold. Molecular analyses using Neighbour Joining (NJ), Maximum Likelihood (ML), and Bayesian Inference (BI) methods demonstrated that the resulting tree topologies were consistent with one another and that species-level distinctions were clearly resolved. Individuals of Myzocallis coryli collected from different districts in Türkiye were included in the ML analysis together with reference sequences obtained from the GenBank database. Samples from Hopa, Arhavi, and Kemalpaşa clustered within the same clade as the reference sequences with high bootstrap support (99%), confirming that the specimens belong to the species M. coryli in accordance with morphological identifications. The close proximity of the three populations also indicates low intraspecific genetic variation among Turkish populations. The strong bootstrap support for the Myzocallis clade further confirms that this group represents a monophyletic lineage. In conclusion, aphid populations in Artvin were found to pose a low risk to hazelnut production; however, continued monitoring is recommended to prevent potential damage associated with future population increases.