Grapevine trunk diseases (GTDs) are major constraints to vineyard longevity and productivity worldwide, and pruning wounds are recognized as key infection courts for their causal fungi. However, the dynamics of natural infection after pruning under field conditions remain insufficiently defined. This study evaluated natural infection of grapevine pruning wounds by GTD pathogens in three commercial vineyards in Spain and France over two growing seasons. At each site, vines were pruned in the dormant season either early (November-December) or late (February), and wounds were sampled weekly for 8 weeks. Recovery-based disease severity was quantified using the percentage of wood pieces yielding GTD pathogens after isolation. A total of 11,230 fungal isolates were recovered, of which Botryosphaeriaceae accounted for 54.4%, followed by Diaporthe spp. (34.2%) and Cytospora spp. (11.4%). The dominant species identified was D. seriata. Recovery-based disease severity varied significantly over time in all site-disease combinations, and temporal trajectories differed with pruning time and season. Late pruning resulted in significantly greater recovery-based disease severity than early pruning in 6 of 9 site-disease combinations. The strongest effect was observed in Pyrénées-Atlantiques for Botryosphaeria dieback, where late pruning increased severity by 18.8%; Cytospora canker at the same site increased by 7.2%. Climatic analyses revealed site-specific associations, with relative humidity showing the strongest association with recovery-based disease severity in Pyrénées-Atlantiques and rainfall in Pyrénées-Orientales. These results indicate that GTD pathogens can be recovered from pruning wounds for at least 8 weeks after pruning and that the effect of pruning time is strongly site- and pathogen-dependent.
Ashley et al. (Mon,) studied this question.