Osservazioni epidemiologiche sui giallumi della vite nelle province di Modena e Reggio Emilia

Since the year 2000, grapevine Flavescence Dorée (FD) and Bois Noir (BN) phytoplasmas were found in grapevine growing areas of Modena and Reggio Emilia provinces (northern Italy). Epidemiological investigations carried out by the provincial Plant Protection Services throughout a five-year period (2000 to 2004), have highlighted the wide presence of these pathogens in all the grapevine growing areas. The results obtained from molecular analysis (PCR/RFLP) performed throughout the all period on symptomatic plants, have shown the striking prevalence of BN phytoplasmas. Out of 557 samples collected in Reggio Emilia province, 55,7% were positive to BN whereas 14,4% of the tested plants resulted infected by FD. As regard the 463 analyses on samples collected in Modena province, samples positive to BN phytoplasmas were 67,7% and those positive to FD were 10,8%. Moreover the 2,3% of the Reggio Emilia samples appeared positive to both phytoplasmas. A number of symptomatic grapevines were negative: 27,7% in Reggio Emilia and 21% in Modena provinces. Contemporary presence in the territory of the two phytoplasmas has been noticed in the majority of the counties around Reggio Emilia, while very few in the ones around Modena. Incidence data of yellows were related to the cultivar, training systems, and agronomic conduction of the vineyards. Spatial distribution of yellows diseased plants in the vineyards of the two provinces shows with a gradient decreasing from the edges to the inner parts, as was previously reported in other yellows infected vineyards (Credi et al., 2004). Molecular analysis performed on herbaceous plants around and inside the vineyards demonstrated the presence of BN phytoplasmas in some dicotyledons species (Botti et al., this book). Control measures adopted from 2000 against FD spreading allowed to greatly reducing its epidemic spreading in these provinces. This has not occurred for BN that has become eventually the most dangerous grapevine phytoplasma disease in the two provinces. Wide presence of important epidemiological factors such as etiological agent, insect vector (Hyalesthes obsoletus), herbaceous plants in vineyard’s ecosystem, have so far avoided to carry out an efficient control strategy, with the consequent rapid and large spreading of BN in these vineyards.