First report of various Diplodia spp. causing stem cankers of Ulmus sp., Platanus x hispanica, Aesculus hippocastanum, Fagus sylvatica, Sorbus domestica, Carpinus betulus and Crataegus persimilis in central Europe

Abstract This report documents the first identification of Diplodia species on atypical tree hosts, isolated from stem cankers. Diplodia is part of the Botryosphaeriaceae family, which includes plant pathogens that predominantly infect conifer species. However, Diplodia species are expanding their host range and geographic distribution worldwide. Typically associated with tip blight, the fungi described in this study were isolated from stem necroses in urban trees across various German cities, representing distinct geographical regions. Diplodia mutila was identified for the first time on Carpinus betulus , Fagus sylvatica , Crataegus persimilis , and Platanus x hispanica . Additionally, Diplodia juglandis was isolated from Aesculus hippocastanum and Platanus x hispanica , marking a first record for these hosts. Diplodia seriata was detected as a first finding on Aesculus hippocastanum , Crataegus persimilis , Platanus x hispanica , and Ulmus species, while Diplodia malorum was isolated for the first time from Sorbus domestica , and Diplodia sapinea on Ulmus species. The taxonomy of these fungi was verified through sequencing with multiple primers, including ITSu1/4, LSU/LR6, EF1a 526/1567R, Beta-tubulin T1/T22, and species-specific Diplodia primers where applicable. The pathogenicity of these fungi was confirmed by fulfilling Koch’s postulates. Stem infection trials were conducted on the corresponding tree hosts using the isolated fungi, and the resulting symptoms confirmed their pathogenic role. The growing incidence of Diplodia species on non-coniferous hosts in urban environments raises significant concerns not only for forestry but also for urban management. This underscores the need for further research and heightened awareness of these pathogens.