The decline of grapevines due to esca and Botryosphaeria dieback (Bot. dieback) is a serious problem in the Alsace region of France. A survey of 82 vineyards over 8 years showed that among a set of agronomical and cultural variables, esca and Bot. dieback prevalence correlated to the harvest dates, especially late harvest dates for the production of sweet wines. The interpretation of this finding that points to the carbon balance of the vine and its reserves status as possible causation is discussed. Under this hypothesis the data also point to climatic variables as factors in the disease epidemiology, with a lag phase of about one year.