Epidemiology of Flaveseence doree in vineyards in northwestern Italy

A serious outbreak of Flavescence dorée was reported in Piemonte, North-Western Italy, in 1998 and since then the disease has compromized the economy of this traditional wine-growing area, even following the application of compulsory insecticide treatments to control Scaphoideus titanus, vector of the causal phytoplasma. Affected vines show severe symptoms, varying according to cultivar, and are rogued to reduce disease spread. Following winter and pruning, a previously affected vine may appear symptomless (recovered) and free of phytoplasmas in both its aerial as well as root system, even by nested PCR assays. Since 1998 homogenous data on the incidence of newly infected, healthy or recovered plants, productivity, presence of vectors and treatment schedules have been collected in seven severely affected vineyards of Southern Piemonte for 5 years (1999 – 2003). Infectivity and recovery rates were also calculated each year. From 1999 to 2003 the average number of healthy plants decreased and numbers of recovered plants and those with symptoms increased. Productivity of recovered vines was always higher than that of vines with symptoms, and was not influenced by the time elapsed from date of recovery. The relationships between the ln-transformed number of vectors trapped in the vineyards the previous year and the infection and the recovery rates were fitted by an exponential (R2 = 0.95) and an asymptotic (R2= 0.93) model, respectively. Recovery as a possible management of FD in grapevine is discussed.