First report of Cryptostroma corticale on Aesculus hippocastanum causing sooty bark disease in Germany

Cryptostroma corticale is the causal agent of sooty bark disease, which was first described in the middle of the last century and has developed in recent years to a relevant threat for Acer spp. trees in Central Europe. Triggered by extreme heat and drought, this tree disease is becoming more and more important in the course of climate change. Acer pseudoplatanus is a particularly affected tree species, but the disease has also been observed on other Acer spp., and there is some indication that there are suitable hosts outside the Acer genus. In literature, Aesculus hippocastanum was mentioned twice to be a host, however, without any proof or details. With this study, we verify the assumption that A. hippocastanum is a host of C. corticale by morphological and phylogenetic analyses based on a case in Germany. Furthermore, we provide microscope pictures of microtome sections of the specimens, showing the spore production of C. corticale on A. hippocastanum.