1. Università di Firenze, Istituto di Patologia e Zoologia Forestale e Agraria, P. delle Cascine 28, I‐50144 Firenze, Italy,
2. University of Helsinki, Department of Plant Biology, Plant and Forest Pathology Section, PO Box 28, 00014 Helsinki,
3. Finnish Forest Research Institute, Vantaa Research Centre, PO Box18, 01301 Vantaa; Finland