DNA barcoding of Toumeyella parvicornis (Hemiptera: Coccidae)

The pine tortoise scale, Toumeyella parvicornis (Hemiptera: Coccidae), is a sap-sucking pest native to the Nearctic region that affects several Pinus species, whose heavy infestations may contribute to host tree declines. Recently, the scale insect was accidentally introduced to Europe where it was first discovered in Italy in 2014 and later in southern France in 2021. Since its introduction, T. parvicornis has rapidly spread across several regions in Italy and is contributing to pine tree losses, particularly in the areas surrounding Naples and Rome. The infestation caused by the pest is of great concern as it has the potential to significantly impact the local pine forests and cause direct and indirect damage to urban areas. The lack of a reliable system to trace the origins and spread of T. parvicornis infestation limits our capacity to identify the main entry routes of this alien species and to develop effective control measures. In this study, we used the mitochondrial COI and ribosomal 28S-D2 markers to assess the genetic diversity of pine tortoise scale populations and to study its invasive process in Europe. Samples were collected from Italy, France and USA. Alignment of the 28S-D2 sequences revealed a unique haplotype, while COI showed a single haplotype in Europe which differs by five nucleotide substitutions from USA population of T. parvicornis. Moreover, our dataset differs by approximately 10% identity from the only two sequences of T. parvicornis available in GenBank at the moment, suggesting a likely erroneous taxonomic annotation of these samples collected in Canada. These results highlight the importance of morphological identification and haplotype analysis in tracing the origins and spread of invasive pests. Further studies and additional samples from different countries are needed to fully reconstruct the invasive process of T. parvicornis and to implement effective control measures.