Ash dieback is an important tree disease induced by Hymenoscyphus fraxineus, an invasive fungus. We studied the influence of climate and local environment on the ability of H. fraxineus to infect, be transmitted and cause damage on its host. We showed that healthy carrier, i.e. individuals showing no dieback but carrying H. fraxineus, exists and may play a significant role in ash dieback epidemiology.  While the ability of H. fraxineus to establish and to reproduce on leaves mainly depended on summer rainfall, the damages it cause to the host depend on other parameters (high summer temperature in July-August, tree cover). As a consequence, in many situations, ash trees are infected and enable H. fraxineus transmission while showing limited or even no damage. The dataset contains data on several step of the disease on a network of 20 plots over France from 2013 to 2022. About 20s sapling are rated anually for 1–6 years depending on the sites. Most of the data are collected at the tree level (dieback status, part of data on the ability of H. fraxineus to produce apothecia on rachises collected at leaf fall) or at the shoot level (frequency of leaf necrosis and shoot mortality). However, data on the ability of H. fraxineus to produce apothecia on rachises collected at leaf fall are partly collected at the plot level. Climatic data are not part of the dataset.

Data collected by visual observation in the field (dieback score, leaf necrosis, shoot mortality)

Data from DNA extraction / qPCR with specific primers for detection of Hymenoscyphus fraxineus in infected tissues

Data on the ability of H. fraxineus to produce apothecia on rachises collected at leaf fall. Rachises that were just shed were collected in autumn and placed outdoors for overwintering in common gardens on the soil in a forest situation. They were retrieved in spring and placed in humid chamber to assess the ability of Hymenoscyphus fraxineus to produce apothecia on them. The part producing / not producing apothecia were separated and the proportion of rachises-producing apothecia were computed