Survey of ‘Candidatus Liberibacter solanacearum’ and Its Potential Psyllid Vectors in Northwestern Italy

Psyllids (Hemiptera: Psylloidea) are the main vectors of various phloem-limited plant pathogens, including '<i>Candidatus</i> Liberibacter' species. '<i>Candidatus</i> Liberibacter solanacearum' (CLso) has been associated with various plant disorders and economic losses in plants from the Solanaceae and Apiaceae families. Recently, it has been reported in Europe, primarily linked to carrots and celery. This situation presents a significant threat, prompting the need for a survey to assess the presence of the bacterium and its potential vectors. Plant and psyllid samples were collected from potato (<i>Solanum tuberosum</i>), carrot (<i>Daucus carota</i>) and other wild weed species in commercial fields and urban areas over two consecutive years (2022 and 2023). DNA was extracted from the samples, followed by conventional PCR and the sequencing of positive samples. The psyllid species <i>Bactericera nigricornis</i> was the dominant species in potato fields, while <i>Bactericera trigonica</i> was the most abundant in carrot fields, followed by <i>Heterotrioza chenopodii</i>, ranking as the second most abundant species in both cases. CLso-positive samples were found in <i>D. carota</i>, <i>B. trigonica</i>, <i>H. chenopodii</i>, <i>B. nigricornis</i>, and <i>Trioza urticae</i>. The sequencing results suggest the detected haplotypes are D and U. These findings raise concerns about the potential spread of CLso and the associated risk of significant economic losses.