LAUSR

Esca is a widespread grapevine trunk disease, and a global increase in esca incidence has been observed in recent decades. Estimates attribute considerable economic losses to esca, and the disease is considered one of the major causes of vine mortality and vineyard dieback. However, accurate quantification of esca incidence is difficult due to symptom inconsistency, and there are very few studies precisely quantifying yield losses and impacts on fruit composition and wine quality. This study carried out an extensive esca surveying program; annually monitoring ~57,000 vines across 12 estates in the Bordeaux region for 9 years. In conjunction with this surveying program we quantified the yield losses of vines with known esca symptom histories and assessed their fruit composition and resulting wine quality. The study revealed that because of year-to-year variation in symptom expression accurate rates of esca can only be obtained through monitoring over many years. We found that yield losses in individual vines exhibiting esca can reach up to 50% but they are rarely unproductive, and when scaled to the parcel scale yield losses are low, never exceeding 1hL/ha. In addition, the quality of the grapes produced is similar to that obtained from vines without symptoms. Finally, the majority of mortality observed in vineyards was not due to esca, with only 40% of dead vines exhibiting an esca history. These results suggest that the impact of esca is likely overestimated and that it is necessary to more broadly investigate other factors contributing to vine mortality and vineyard dieback.