Urban London plane tree dieback linked to fungi in the Botryosphaeriaceae

74–83

e-journal

200211293

Urban Forestry & Urban Greening ; Jrg. 22 (2017) , 74–83

tSince the first report of the stain canker agent Ceratocystis platani in 2001 in Geneva, dieback of Lon-don plane trees (Platanus × acerifolia) has focused greater attention and an epidemiological monitoringhas been implemented, as part of a compelling state directive for stain canker management. Geneticidentification was carried out in order to ascertain the presence or absence of C. platani. We report hereobservations recorded between 2011 and 2013, of samplings from a total of 6 plane trees in 4 locations.Identification of bacteria and fungi was performed by sequencing of the rDNA ITS region for fungi, andof the 16S rRNA gene for bacteria. Fungi belonging to the Botryosphaeriaceae species occurred in almostevery sampling, whereas Ceratocystis platani was only isolated in 2 trees. The 4 botryosphaeriaceousspecies, Diplodia mutila, Dothiorella sp., Diplodia seratia and Neofusicoccum parvum, could be responsiblefor the observed plane cankers, while other fungi could participate in the dieback symptoms. Since thesespecies have been reported as canker agents on other tree species in Europe, artificial infections werecarried out with pure cultures of Dothiorella sp., Diplodia mutila and Neofusicoccum parvum on youngplane trees. Only Neofusicoccum parvum managed to provoke cork canker symptoms after a few months,but D. mutila and N. parvum were found in internal necrotic tissues. This is the first report of Dothiorellasp., Diplodia mutila and Neofusicoccum parvum associated with plane tree dieback in Switzerland and thefirst report of pathogenicity of Neofusicoccum parvum in plane trees. This survey showed that most casesof plane tree dieback in the Geneva region were not caused by C. platani and that other fungi could beresponsible for similar symptoms.
Keywords: Botryosphaeriaceae, Ceratocystis platani, Dieback Plane tree canker, Platanus acerifoliaa