Some Observations on the Relationship of Manifest and Hidden Esca to Rainfall

Abstract

This paper reports observations on the relationship between the yearly incidence of manifest esca (i.e.
diseased plants which show foliar symptoms), hidden esca (that which remains asymptomatic throughout a growing
season) and rainfall. Data from three vineyards (two in Tuscany and one in Emilia-Romagna, Italy) showed that
rainfall in May–July or only in July was inversely related with hidden esca. For two vineyards, TB in Emilia-Romagna
and CAR-3 in Tuscany, the spatial pattern of diseased vines in the first year of appearance of the foliar esca symptoms
was also determined. The maps of the vines in these vineyards indicated that diseased plants mostly occurred
alone. This suggests that the disease had its origin in infected rooted cuttings or was triggered by inoculum aerially
dispersed from distant sources and/or occurring, at least in hypothesis, in the soil.