Esca of grapevine and training practices in France: results of a 10-year survey
Esca is a widespread and damaging grapevine trunk disease in France. A survey was undertaken to identify relevant cultural factors that may influence symptom severity. Preliminary observations in the Aquitaine region confirmed the complex interactions among cultivar, vine training system, and climate, so the study was expanded to the national level to help account for esca in different wine growing regions. Twenty-five vineyard plots were examined. The plots were comparable by pairs, with the same cultivar (or cultivar with similar levels of susceptibility in a few cases), with the same age and similar soil and climatic environments, but with different training or pruning systems. Esca was the predominant trunk disease and prevalence was assessed by visible symptoms on leaves and on wood. Training systems with long arms (or cordons) were generally less affected by the disease than those with short or no arms. Pruning also played a major role, with a trend of less severe symptoms associated with less pruning. The study confirmed that foliar symptoms reveal the presence of the disease, but cannot be considered a reliable indicator of the disease impact in all situations. This study also confirmed: i) that vine training and pruning options may greatly influence the severity of esca, ii) that increasing the length of cordons may minimize the consequences of the wood necroses, and, iii) that simplifications of the woody vine structure (resulting from adoption of modern training and pruning options) may have favoured the development of esca.
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