Seasonal dynamics of Cryptostroma corticale conidial spread

Cryptostroma corticale, the causal agent of sooty bark disease (SBD) in maples, is a typical tree pathogen that emerged as a result of climate change. In Central Europe, it primarily affects sycamore maple, with airborne conidia infecting fresh bark wounds, allowing the fungus to penetrate the wood. C. corticale may survive in an endophytic phase until the tree is stressed by drought and/or long periods of above-average temperatures. After such periods, it begins to develop stromata under the bark. When the covering layer of bark is peeled off, infective airborne conidia are spread over distances of up to hundreds of kilometers. Apart from infecting trees, these conidia can also cause hypersensitive pneumonitis in humans. To describe the seasonal spore dispersal pattern of C. corticale, an automatic volumetric spore trap was installed from March to November 2022 in an SBD-affected locality close to Brno, Czech Republic. Samples were analyzed by qPCR, and a logistic regression model was fitted to express the spore occurrence probability based on meteorological variables. The model revealed a positive effect of wind speed on spore abundance and a negative impact of temperature and surface moisture. The highest abundance of spores was recorded in spring. Negligible numbers of conidia were observed during the summer, followed by a slight increase in the early autumn and a subsequent drop after the end of October. Practitioners are advised to avoid any bark or wood damage during windy and dry weather throughout the growing season. Arboriculture care should be planned for winter or windless, hot, and wetter days throughout the growing season when spore concentrations are lowest, thereby reducing the risk of spreading the disease and provoking allergic reactions in humans.