Diversity of the sooty blotch and flyspeck complex on apple in Germany

Sooty blotch and flyspeck (SBFS) is a complex of more than 80 fungal species in 24 genera, mostly belonging to the order Capnodiales within the Dothideomycetes. Colonies of these epiphytes become visible on the surface of apples in mid- to late summer. Several species of SBFS fungi have been previously identified from apples in Germany, but little is known about species diversity, prevalence patterns, or relationship to orchard management practices. To address these questions, apple orchards were surveyed during the 2008 to 2011 seasons in the two largest German apple-growing regions along the Lower Elbe river (northern Germany) and Lake Constance (southern Germany). Using a combination of approaches based on morphology and ITS sequence data, 19 known or putative SBFS species were found, of which 10 belonged to Capnodiales. Abandoned orchards harboured a higher species diversity than organically managed orchards, and no SBFS disease was seen in orchards under integrated pest management. Peltaster cerophilus was the most common SBFS fungus, being associated with 96 and 84 % of SBFS-affected apples sampled from northern and southern German organic orchards, respectively. Microcyclosporella mali and Cyphellophora sessilis were the next most commonly found SBFS species in northern and southern Germany, respectively. Schizothyrium pomi was the only cause of the flyspeck mycelial type of SBFS disease in Germany.