Statistical Analysis of Grapevine Mortality Associated with Esca or Eutypa Dieback Foliar Expression

Esca and Eutypa dieback are the two main wood diseases in France. Their widespread distribution in vineyards leads to grapevine decline and to a loss of productivity. However, little is known about the temporal dynamics of these diseases on plant scale and equally, the relationships between foliar expression of the diseases and vine death is relatively unknown too. To investigate these relationships, we surveyed the vines of six vineyards cv. Cabernet Sauvignon in the Bordeaux region, by recording foliar symptoms, dead arms and dead plants from 2004 to 2010. In 2008, 2009 and 2010, about five percent of the asymptomatic vines died but the rate of dead vines, which had previously expressed Esca foliar symptoms, was higher and varied also depending on the vineyards. Whether the vines expressed foliar symptoms or not, a logistic regression statistical model was used to select the previous years of symptomatic expression associated with mortality. The mortality of Esca is always associated with the foliar symptom expression of the year preceding vine death. One or two other earlier years of expression were frequently additional risk factors. Eutypa dieback symptom was also a risk factor for death, superior or equal to that of Esca. The study of the internal necroses of vines expressing Esca or Eutypa dieback is discussed in the light of these statistical results