Grapevine vigour: A critical factor associated with trunk disease symptom expression

Grapevine trunk diseases (GTDs), especially Esca and Botryosphaeria dieback, cause mortality and production decline in vineyards worldwide. As they are thought to be complex diseases, unravelling the different factors that determine symptom expression is crucial in mitigating the impact on growers. While cultivar, climate, age, and pruning system are known contributors, they do not fully explain the variability in GTD incidence. This study investigates the role of grapevine vigour as a determinant factor in GTD foliar symptom expression. Three vineyard networks were monitored in 2022 and 2023, each consisting of approximately 30 commercial vineyard plots of Grenache noir, uniform in age. To minimise climate variation, the selected vineyards were located within small geographical areas. We evaluated grapevine vigour and its primary drivers including water and nitrogen status, weed cover, production, and vegetation biomass—and correlated them with GTD incidence over the two seasons. Results show that current season vigour is positively correlated with the GTD incidence rate in most of the network*year scenarios. The relationship shape suggests that, while low to moderate vigour is consistently associated with reduced symptom expression, high vigour can be correlated with either high or low expression which implies the involvement of additional factors. In one instance, previous year water stress indicators were the ones most correlated with current year GTD incidence, though vigour was also influential. For the plots where GTD expression was greatest, the previous year’s water stress was combined with the current year’s substantial spring vigour. While these results need to be confirmed over a longer period, in more regions and with other cultivars, they open new perspectives of applications for growers. As correlation with vigour is recurrent but not exclusive, it suggests a wider implication of grapevine physiology.