Epidemiological survey on 'Candidatus Phytoplasma solani' and putative vectors in Western Sicily

Bois noir (BN) associated with ‘Candidatus Phytoplasma solani’ is an important grapevine yellows disease widespread in Europe and Mediterranean regions. During a two years survey (2014-15) carried out in a 10-year-old vineyard located in San Giuseppe Jato (PA), symptoms of Bois noir were observed on cvs Chardonnay, Pinot Noir and Nero d’ Avola. Incidence of the disease increased over the two years, reaching values of about 34 % on cv Chardonnay. Ca. ‘P. solani’ was detected on symptomatic leaf samples from all cultivars with the highest percentage on cv Chardonnay followed by Pinot noir and Nero d’Avola. Further surveys were performed in order to highlight the epidemiology of the disease by monitoring wild herbaceous species and potential vectors and by molecular characterization of Bois noir phytoplasma isolates. Herbaceous weed samples were collected within and at the border of the vineyard, whereas plant- and leafhoppers individuals were monitored from June to August of each year, using yellow sticky traps replaced at weekly intervals. Eleven weed species and about 2000 insect specimens were collected and identified at species or genus level by morphological feature. No Hyalesthes obsoletus was found. ‘Ca P. solani’ was detected in 5 weed species and nine out twenty-two taxa of the different insect specimens: Anaceratagallia laevis, Empoasca decipiens, E. vitis, Empoasca/Zigina sp., Hauptipia provincialis, Neoaliturus fenestratus, Selachina apicalis, Zygina rhamni and Z. serpentine. RLFP analysis of the tuf gene of phytoplasma isolates recovered from symptomatic grapes, weeds and insect specimens revealed the presence of only Ca P. solani’ tuf type-b.