Distribution of Eutypella Canker in Sycamore Is Driven by Proximity to Infected Forest Sites, High Precipitation and Moderate Temperatures

ABSTRACT Eutypella parasitica , the causal agent of Eutypella canker on maple species, is an invasive forest pathogen recently introduced to Europe. Due to the wide distribution of susceptible Acer species, further spread across European forests is expected. To better understand factors driving the spread of this emerging forest disease, we aimed to identify the key environmental and spatial drivers of Eutypella canker occurrence focusing on Acer pseudoplatanus . For this purpose, we surveyed the presence and absence of Eutypella canker at 232 forest sites in southeastern Germany and analysed climatic, site‐related and spatial factors using a binomial generalised linear model (GLM). Eutypella canker was detected at 57 sites, while 175 forest sites showed no symptoms. The probability of disease occurrence increased with higher precipitation and moderate temperatures during the vegetation period from May to September. In addition, forests located in close proximity to water bodies such as rivers and lakes exhibited a significantly higher probability of infection. Spatial proximity to already infected forest sites emerged as the strongest predictor of disease occurrence, indicating pronounced spatial clustering and suggesting active spatial spread processes. Our results demonstrate that both climatic suitability and spatial connectivity are key determinants of Eutypella canker establishment. These findings provide an important basis for risk assessment and targeted monitoring of this emerging invasive forest disease in Europe.