Molecular Identification of Two Vector Species, Cacopsylla melanoneura and Cacopsylla picta (Hemiptera: Psyllidae), of Apple Proliferation Disease and Further Common Psyllids of Northern Italy.

The psyllid species Cacopsylla melanoneura (Förster) and Cacopsylla picta (Förster) are vectors of 'Candidatus Phytoplasma mali', the causal agent of apple proliferation, one of the economically most important apple diseases in Europe. Both vectors are present in apple orchards of South Tyrol and Trentino provinces in Northern Italy. As no direct treatment of the disease is possible, monitoring of the psyllids provides information about the vector presence in the orchards and enables targeted control. Thus, fast and reliable identification of the various psyllids occurring in the apple orchards is required. Morphological differentiation is problematic due to extensive resemblance of some psyllid species especially among females and is error-prone for nymphs. Here we present a rapid and cost-effective polymerase chain reaction-restriction fragment length polymorphism method based on the cytochrome c oxidase subunit I region for the molecular identification of the vector species as well as eight further Cacopsylla species present in the orchards. This method was verified through 98.9% consensus with morphologically identified males, through sequencing and subsequent phylogenetic analysis. In case of doubtful morphological identification of females, the method was able to provide a refined species assignment and could also remarkably facilitate the identification of nymphs.