Epidemiology of esca in some vineyards in Tuscany (Italy)

The incidence of esca in 5 vineyards (SCFI, GTFI, CBSI-1, 2, 3) in Tuscany was monitored from 1992 to 1994 in SCFI, from 1993 to 1998 in GTFI, and from 1995 to 1998 in CBSI-1, 2 and 3. Disease incidence varied from vineyard to vineyard and from year to year. SCFI was the vineyard most affected with an incidence of 63% in 1993, 20% in 1994, and 46% in 1992. However, symptom expression in individual plants was characterized by very marked discontinuity from year to year. As a result, only 8% of diseased plants in SCFI had foliar symptoms in all 3 years of the survey period. The percentage of consistently diseased plants went down to less than 1% in GTFI and CBSI-3 and was nil in CBSI-1 and 2. The cumulative disease incidence, calculated by counting all the plants that showed foliar symptoms at least once in the years surveyed, was 82, 50, 19, 12, and 10% in SCFI, GTFI, CBSI-3, 1 and 2 respectively. An examination of rainfall and air temperature parameters in relation to esca incidence did not detect any weather conditions especially conducive to esca. However, it seemed that a fresh, rainy summer is more favorable to the chronic form of esca while a hot, dry summer is more conducive to the acute form.