Effect of Esca on the Quality of Berries, Musts and Wines

Abstract

Variations in the composition of berries, musts and wines in three groups of vines: 1. vines with foliar esca symptoms; 2. asymptomatic esca diseased vines; and 3. healthy vines, were studied in 2001 and 2002 in two “Trebbiano d’Abruzzo” vineyards in the Abruzzi region, Italy, to determine the effect of esca. Vines were grouped by foliar symptoms that had been recorded in annual inspections for 10 years: symptomatic vines by definition showed foliar symptoms in the sampling years (2001 and 2002); asymptomatic esca diseased vines showed no symptoms during the sampling years though they were known to be diseased because they had had foliar symptoms in at least one previous annual inspections; healthy vines were those with no symptoms at any time during the 10-year survey. The quality of berries, musts and wines obtained from vines with trunk renewal that had been restored, and of healthy unrenewed vines was compared in another vineyard of the same cultivar. Fairly similar results were obtained over the two sampling years, with a strong reduction in sugar levels of the must from symptomatic vines, leading to a lower ethanol content in the wine made from that must. These findings confirmed those of the preliminary investigation carried out in 2000. The yield pressed from symptomatic vines also had significantly higher levels of malic acid (causing higher total acidity), and of total nitrogen, potassium and total polyphenols. Berries from symptomatic vines had much higher levels of trans-resveratrol, possibly because of the spots on the leaves and berries. Small and non-significant differences between the yields of healthy vines and asymptomatic diseased vines were found, suggesting a slight loss in the quality of musts and wines from asymptomatic diseased vines. The yield of trunk-renewed vines was similar to that of healthy unrenewed vines, despite an increase of trans-resveratrol in the berries and of total nitrogen in the must of the trunk-renewed vines.