First report of <i>Diplodia bulgarica</i> causing black canker on apple (<i>Malus domestica</i>) and pear (<i>Pyrus communis</i>) in Germany

Apple and pear are economically important fruit crops in Germany. Since 2018 many apple trees grown organically Baden-Wuerttemberg (southwestern Germany) developed black cankers on their trunks limbs (Fig. 1). These oval, sunken, brown lesions often next to bark injuries such as cracks, pruning wounds or sun damage. In older cankers, pycnidia sometimes broke through the near canker 2). As infection separated from underlying wood fell ground. The beneath was blackened looked like charcoal 3). Some of were girdled by died. Small pieces tissue containing taken without surface sterilisation margin plated onto potato dextrose agar (PDA). plates incubated at 20°C under constant light for 7 14 days. Newly formed transferred PDA after a few days hyphal tips subcultured same medium. Fungal isolates identified Diplodia spp. according morphology conidia 4). sequences ITS obtained 38 57 more than 99 % identical that D. bulgarica isolate CBS 124254 (GenBank Accession No. MH863355). generated submitted GenBank herbarium samples deposited fungal collections State Museum Natural History Karlsruhe (KR), Germany (Table Pathogenicity tests conducted with three one-year-old (cv. Novembra) Topaz) greenhouse conditions. Agar plugs 10-day-old cultures inoculated into directly intact bark. Sterile used controls. All sealed plastic film prevent desiccation. Stem four weeks inoculation fungus wound. Pycnidia within successfully re-isolated edge lesion fulfilling Koch's postulates. Trees sterile wounding remained symptomless. A.J.L. Phillips, J. Lopes & Bobev first isolated M. sylvestris Bulgaria domestica Iran described new species (Phillips et al., 2012). It threatens industry (Abdollahzadeh, 2015) recently also reported India (Nabi 2020). To our knowledge, this is report causing symptoms pear. survey over two thirds showing canker, dieback twig blight bulgarica. This appears be relevant pathogen pome poses threat authors would thank Ministerium für Ländlichen Raum und Verbraucherschutz Baden-Württemberg financial support.